Pure connection action principle for general relativity.
Krasnov, Kirill
2011-06-24
It has already been known for two decades that general relativity can be reformulated as a certain gauge theory, so that the only dynamical field is an SO(3) connection and the spacetime metric appears as a derived object. However, no simple action principle realizing these ideas has been available. A new elegant action principle for such a "pure connection" formulation of GR is described.
Gauge connection formulations for general relativity
NASA Astrophysics Data System (ADS)
González, Diego; Montesinos, Merced
2015-01-01
We report a new class of S O (3 ,C ) and diffeomorphism invariant formulations for general relativity with either a vanishing or a nonvanishing cosmological constant, which depends functionally on a S O (3 ,C ) gauge connection and a complex-valued 4-form via a holomorphic function of the trace of a symmetric 3 ×3 matrix that is constructed from these variables. We present two members of this class, one of which results from the implementation of a method for obtaining action principles belonging to the class. For the case of a nonvanishing cosmological constant, we solve for the complex-valued 4-form and get pure connection action principles. We perform the canonical analysis of the class. The analysis shows that only the Hamiltonian constraint is modified with respect to the Ashtekar formulation and that the members of the class have two physical degrees of freedom per space point.
Connection between Newtonian simulations and general relativity
Chisari, Nora Elisa; Zaldarriaga, Matias
2011-06-15
On large scales, comparable to the horizon, the observable clustering properties of galaxies are affected by various general relativistic effects. To calculate these effects one needs to consistently solve for the metric, densities, and velocities in a specific coordinate system or gauge. The method of choice for simulating large-scale structure is numerical N-body simulations which are performed in the Newtonian limit. Even though one might worry that the use of the Newtonian approximation would make it impossible to use these simulations to compute properties on very large scales, we show that the simulations are still solving the dynamics correctly even for long modes and we give formulas to obtain the position of particles in the conformal Newtonian gauge given the positions computed in the simulation. We also give formulas to convert from the output coordinates of N-body simulations to the observable coordinates of the particles.
Regular connections among generalized connections
NASA Astrophysics Data System (ADS)
Fleischhack, Christian
2003-09-01
The properties of the space A of regular connections as a subset of the space Ā of generalized connections in the Ashtekar framework are studied. For every choice of compact structure group and smoothness category for the paths, it is determined whether A is dense in Ā or not. Moreover, it is proven that A has Ashtekar-Lewandowski measure zero for every non-trivial structure group and every smoothness category. The analogous results hold for gauge orbits instead of connections.
Extended theory of harmonic maps connects general relativity to chaos and quantum mechanism
NASA Astrophysics Data System (ADS)
Ren, Gang; Duan, Yi-Shi
2017-10-01
General relativity and quantum mechanism are two separate rules of modern physics explaining how nature works. Both theories are accurate, but the direct connection between two theories was not yet clarified. Recently, researchers blur the line between classical and quantum physics by connecting chaos and entanglement. Here, we showed the early reported extended HM theory that included the general relativity can also be used to recover the classic chaos equations and even the Schrodinger equation in quantum physics, suggesting the extended theory of harmonic maps may act as a universal theory of physics.
Teleparallelism as a universal connection on null hypersurfaces in general relativity
NASA Technical Reports Server (NTRS)
Mazur, P. O.; Sokolowski, L. M.
1986-01-01
It is shown that a close relationship between the inner geometry of a null hypersurface N3 and the Newman-Penrose (NP) (1962, 1963) spin coefficient formalism exists. Projecting the null complex NP tetrad onto N3, two triads of basis vectors in N3 are obtained. The inner geometry of N3 is based on the assumption that these vectors are parallelly transported along the surface; this gives rise to the teleparallel connection as a metric nonsymmetric affine connection. The gauge freedom for the choice of the basis triads is given by the isotropy subgroup of the local Lorentz group leaving invariant the direction of the null generators of N3, and teleparallelism is determined by the equivalence class of the basis triads with respect to the global gauge group. Nine of the twelve NP coefficients are identified as the triad components of the torsion and the second fundamental form of N3. The resulting generalized Gauss-Codazzi equations are identical to nine of the NP equations, i.e., to the half of the Ricci identities. This result gives a geometrical meaning to the entire formalism. Finally a general proof of Penrose's theorem that the shear of the null generators of N3 is the only initial null datum for a gravitational field on N3 is presented.
Teleparallelism as a universal connection on null hypersurfaces in general relativity
NASA Technical Reports Server (NTRS)
Mazur, P. O.; Sokolowski, L. M.
1986-01-01
It is shown that a close relationship between the inner geometry of a null hypersurface N3 and the Newman-Penrose (NP) (1962, 1963) spin coefficient formalism exists. Projecting the null complex NP tetrad onto N3, two triads of basis vectors in N3 are obtained. The inner geometry of N3 is based on the assumption that these vectors are parallelly transported along the surface; this gives rise to the teleparallel connection as a metric nonsymmetric affine connection. The gauge freedom for the choice of the basis triads is given by the isotropy subgroup of the local Lorentz group leaving invariant the direction of the null generators of N3, and teleparallelism is determined by the equivalence class of the basis triads with respect to the global gauge group. Nine of the twelve NP coefficients are identified as the triad components of the torsion and the second fundamental form of N3. The resulting generalized Gauss-Codazzi equations are identical to nine of the NP equations, i.e., to the half of the Ricci identities. This result gives a geometrical meaning to the entire formalism. Finally a general proof of Penrose's theorem that the shear of the null generators of N3 is the only initial null datum for a gravitational field on N3 is presented.
Generalized magnetofluid connections in pair plasmas
Asenjo, Felipe A.; Comisso, Luca; Mahajan, Swadesh M.
2015-12-15
We extend the magnetic connection theorem of ideal magnetohydrodynamics to nonideal relativistic pair plasmas. Adopting a generalized Ohm's law, we prove the existence of generalized magnetofluid connections that are preserved by the plasma dynamics. We show that these connections are related to a general antisymmetric tensor that unifies the electromagnetic and fluid fields. The generalized magnetofluid connections set important constraints on the plasma dynamics by forbidding transitions between configurations with different magnetofluid connectivity. An approximated solution is explicitly shown where the corrections due to current inertial effects are found.
Generalized magnetofluid connections in pair plasmas
NASA Astrophysics Data System (ADS)
Asenjo, Felipe A.; Comisso, Luca; Mahajan, Swadesh M.
2015-12-01
We extend the magnetic connection theorem of ideal magnetohydrodynamics to nonideal relativistic pair plasmas. Adopting a generalized Ohm's law, we prove the existence of generalized magnetofluid connections that are preserved by the plasma dynamics. We show that these connections are related to a general antisymmetric tensor that unifies the electromagnetic and fluid fields. The generalized magnetofluid connections set important constraints on the plasma dynamics by forbidding transitions between configurations with different magnetofluid connectivity. An approximated solution is explicitly shown where the corrections due to current inertial effects are found.
Sandberg, Chaleece W.; Bohland, Jason W.; Kiran, Swathi
2015-01-01
The neural mechanisms that underlie generalization of treatment-induced improvements in word finding in persons with aphasia (PWA) are currently poorly understood. This study aimed to shed light on changes in functional network connectivity underlying generalization in aphasia. To this end, we used fMRI and graph theoretic analyses to examine changes in functional connectivity after a theoretically-based word-finding treatment in which abstract words were used as training items with the goal of promoting generalization to concrete words. Ten right-handed native English-speaking PWA (7 male, 3 female) ranging in age from 47 to 75 (mean = 59) participated in this study. Direct training effects coincided with increased functional connectivity for regions involved in abstract word processing. Generalization effects coincided with increased functional connectivity for regions involved in concrete word processing. Importantly, similarities between training and generalization effects were noted as were differences between participants who generalized and those who did not. PMID:26398158
General relativity and cosmology
NASA Astrophysics Data System (ADS)
Bucher, Martin; Ni, Wei-Tou
2015-10-01
This year marks the 100th anniversary of Einstein’s 1915 landmark paper “Die Feldgleichungen der Gravitation” in which the field equations of general relativity were correctly formulated for the first time, thus rendering general relativity a complete theory. Over the subsequent hundred years, physicists and astronomers have struggled with uncovering the consequences and applications of these equations. This paper, which was written as an introduction to six chapters dealing with the connection between general relativity and cosmology that will appear in the two-volume book One Hundred Years of General Relativity: From Genesis and Empirical Foundations to Gravitational Waves, Cosmology and Quantum Gravity, endeavors to provide a historical overview of the connection between general relativity and cosmology, two areas whose development has been closely intertwined.
Yuan, Minlan; Zhu, Hongru; Qiu, Changjian; Meng, Yajing; Zhang, Yan; Shang, Jing; Nie, Xiaojing; Ren, Zhengjia; Gong, Qiyong; Zhang, Wei; Lui, Su
2016-06-13
Amygdala is considered as the core pathogenesis of generalized social anxiety disorder (GSAD). However, it is still unclear whether effective group cognitive behavioral therapy (CBT) could modulate the function of amygdala-related network. We aimed to examine the resting-state functional connectivity (rsFC) of the amygdala before and after group CBT. Fifteen patients with GSAD were scanned on a 3T MR system before and after 8 weeks of group CBT. For comparison, nineteen healthy control participants also underwent baseline fMRI scanning. We used bilateral amygdala as seed regions and the rsFC maps of the right and left amygdala were created separately in a voxel-wise way. Clusters survived two-tailed Gaussian Random Field (GRF) correction at p <0.05 (voxel z value >2.3). Compared with baseline, patients with CBT showed significantly decreased connectivity of the left amygdala with the right putamen, the left dorsal medial prefrontal cortex (dmPFC) and the right dorsal anterior cingulate cortex (dACC). Especially, the changes of the connectivity between the left amygdala and the dACC positively correlated with changes of the anxiety symptom in patients. Furthermore, in relative to controls, patients showed higher connectivity of left amygdala with dmPFC and dACC at baseline, while normal after CBT. Short-term group CBT could down-regulate the abnormal higher connectivity of prefrontal-amygdala network, along with clinical improvement. This may provide a potential biomarker to monitor the treatment effect of CBT in GSAD patients.
Connection with dynamics: General introduction
NASA Technical Reports Server (NTRS)
Shandarin, Sergei F.
1993-01-01
This is a brief nontechnical introduction to a few theoretical issues to the density-velocity relation. The aim of this introduction is not an exhaustive analysis of the current theoretical situation but rather setting a stage for the following talks. The selection of topics has been determined by the sequel program.
Finsler Connection for General Lagrangian Systems
NASA Astrophysics Data System (ADS)
Kozma, László; Ootsuka, Takayoshi
2016-10-01
We give a new simplified definition of a nonlinear connection of Finsler geometry which could be applied not only for regular cases but also for singular ones. For the regular case, it corresponds to the nonlinear part of the Berwald connection, but our connection is expressed not in the line element space but in the point-Finsler space. From this point of view we recognize a Finsler metric L(x, dx) as a "nonlinear form", which could be regarded as a generalization of the original expression of Riemannian metric, √{gμυ (x) dxμ dxυ } . Furthermore our formulae are easy to calculate compared to the conventional methods, which encourages applications to physics. This definition can be used in the case where the Finsler metric is singular, which corresponds to gauge constrained systems in mechanics. Some nontrivial examples of constrained systems are introduced for exposition of applicability of the connection.
General anesthesia and human brain connectivity.
Hudetz, Anthony G
2012-01-01
General anesthesia consists of amnesia, hypnosis, analgesia, and areflexia. Of these, the mechanism of hypnosis, or loss of consciousness, has been the most elusive, yet a fascinating problem. How anesthetic agents suppress human consciousness has been investigated with neuroimaging for two decades. Anesthetics substantially reduce the global cerebral metabolic rate and blood flow with a degree of regional heterogeneity characteristic to the anesthetic agent. The thalamus appears to be a common site of modulation by several anesthetics, but this may be secondary to cortical effects. Stimulus-dependent brain activation is preserved in primary sensory areas, suggesting that unconsciousness cannot be explained by cortical deafferentation or a diminution of cortical sensory reactivity. The effect of general anesthetics in functional and effective connectivity is varied depending on the agent, dose, and network studied. At an anesthetic depth characterized by the subjects' unresponsiveness, a partial, but not complete, reduction in connectivity is generally observed. Functional connectivity of the frontoparietal association cortex is often reduced, but a causal role of this change for the loss of consciousness remains uncertain. Functional connectivity of the nonspecific (intralaminar) thalamic nuclei is preferentially reduced by propofol. Higher-order thalamocortical connectivity is also reduced with certain anesthetics. The changes in functional connectivity during anesthesia induction and emergence do not mirror each other; the recovery from anesthesia may involve increases in functional connectivity above the normal wakeful baseline. Anesthetic loss of consciousness is not a block of corticofugal information transfer, but a disruption of higher-order cortical information integration. The prime candidates for functional networks of the forebrain that play a critical role in maintaining the state of consciousness are those based on the posterior parietal
General Anesthesia and Human Brain Connectivity
2012-01-01
Abstract General anesthesia consists of amnesia, hypnosis, analgesia, and areflexia. Of these, the mechanism of hypnosis, or loss of consciousness, has been the most elusive, yet a fascinating problem. How anesthetic agents suppress human consciousness has been investigated with neuroimaging for two decades. Anesthetics substantially reduce the global cerebral metabolic rate and blood flow with a degree of regional heterogeneity characteristic to the anesthetic agent. The thalamus appears to be a common site of modulation by several anesthetics, but this may be secondary to cortical effects. Stimulus-dependent brain activation is preserved in primary sensory areas, suggesting that unconsciousness cannot be explained by cortical deafferentation or a diminution of cortical sensory reactivity. The effect of general anesthetics in functional and effective connectivity is varied depending on the agent, dose, and network studied. At an anesthetic depth characterized by the subjects' unresponsiveness, a partial, but not complete, reduction in connectivity is generally observed. Functional connectivity of the frontoparietal association cortex is often reduced, but a causal role of this change for the loss of consciousness remains uncertain. Functional connectivity of the nonspecific (intralaminar) thalamic nuclei is preferentially reduced by propofol. Higher-order thalamocortical connectivity is also reduced with certain anesthetics. The changes in functional connectivity during anesthesia induction and emergence do not mirror each other; the recovery from anesthesia may involve increases in functional connectivity above the normal wakeful baseline. Anesthetic loss of consciousness is not a block of corticofugal information transfer, but a disruption of higher-order cortical information integration. The prime candidates for functional networks of the forebrain that play a critical role in maintaining the state of consciousness are those based on the posterior parietal
ERIC Educational Resources Information Center
Ridgely, Charles T.
2010-01-01
Many textbooks dealing with general relativity do not demonstrate the derivation of forces in enough detail. The analyses presented herein demonstrate straightforward methods for computing forces by way of general relativity. Covariant divergence of the stress-energy-momentum tensor is used to derive a general expression of the force experienced…
ERIC Educational Resources Information Center
Ridgely, Charles T.
2010-01-01
Many textbooks dealing with general relativity do not demonstrate the derivation of forces in enough detail. The analyses presented herein demonstrate straightforward methods for computing forces by way of general relativity. Covariant divergence of the stress-energy-momentum tensor is used to derive a general expression of the force experienced…
ERIC Educational Resources Information Center
Jackson, A. T.
1973-01-01
Reviews theoretical and experimental fundamentals of Einstein's theory of general relativity. Indicates that recent development of the theory of the continually expanding universe may lead to revision of the space-time continuum of the finite and unbounded universe. (CC)
ERIC Educational Resources Information Center
Jackson, A. T.
1973-01-01
Reviews theoretical and experimental fundamentals of Einstein's theory of general relativity. Indicates that recent development of the theory of the continually expanding universe may lead to revision of the space-time continuum of the finite and unbounded universe. (CC)
NASA Technical Reports Server (NTRS)
Ray, J. R.
1982-01-01
Two theories of matter in general relativity, the fluid theory and the kinetic theory, were studied. Results include: (1) a discussion of various methods of completing the fluid equations; (2) a method of constructing charged general relativistic solutions in kinetic theory; and (3) a proof and discussion of the incompatibility of perfect fluid solutions in anisotropic cosmologies. Interpretations of NASA gravitational experiments using the above mentioned results were started. Two papers were prepared for publications based on this work.
NASA Technical Reports Server (NTRS)
Ray, J. R.
1982-01-01
Two theories of matter in general relativity, the fluid theory and the kinetic theory, were studied. Results include: (1) a discussion of various methods of completing the fluid equations; (2) a method of constructing charged general relativistic solutions in kinetic theory; and (3) a proof and discussion of the incompatibility of perfect fluid solutions in anisotropic cosmologies. Interpretations of NASA gravitational experiments using the above mentioned results were started. Two papers were prepared for publications based on this work.
Connecting Related Rates and Differential Equations
ERIC Educational Resources Information Center
Brandt, Keith
2012-01-01
This article points out a simple connection between related rates and differential equations. The connection can be used for in-class examples or homework exercises, and it is accessible to students who are familiar with separation of variables.
Connecting Related Rates and Differential Equations
ERIC Educational Resources Information Center
Brandt, Keith
2012-01-01
This article points out a simple connection between related rates and differential equations. The connection can be used for in-class examples or homework exercises, and it is accessible to students who are familiar with separation of variables.
Generalized uncertainty relations
NASA Astrophysics Data System (ADS)
Herdegen, Andrzej; Ziobro, Piotr
2017-04-01
The standard uncertainty relations (UR) in quantum mechanics are typically used for unbounded operators (like the canonical pair). This implies the need for the control of the domain problems. On the other hand, the use of (possibly bounded) functions of basic observables usually leads to more complex and less readily interpretable relations. In addition, UR may turn trivial for certain states if the commutator of observables is not proportional to a positive operator. In this letter we consider a generalization of standard UR resulting from the use of two, instead of one, vector states. The possibility to link these states to each other in various ways adds additional flexibility to UR, which may compensate some of the above-mentioned drawbacks. We discuss applications of the general scheme, leading not only to technical improvements, but also to interesting new insight.
Kramer, Michael
2011-09-22
The last years have seen continuing activities in the exploration of our understanding of gravity, motivated by results from precision cosmology and new precision astrophysical experiments. At the centre of attention lies the question as to whether general relativity is the correct theory of gravity. In answering this question, we work not only towards correctly interpreting the phenomenon of 'dark energy' but also towards the goal of achieving a quantum theory of gravity. In these efforts, the observations of pulsars, especially those in binary systems, play an important role. Pulsars do not only provide the only evidence for the existence of gravitational waves so far, but they also provide precision tests of general relativity and alternative theories of gravity. This talk summarizes the current state-of-art in these experiments and looks into the future.
General Relativity and Gravitation
NASA Astrophysics Data System (ADS)
Ashtekar, Abhay; Berger, Beverly; Isenberg, James; MacCallum, Malcolm
2015-07-01
Part I. Einstein's Triumph: 1. 100 years of general relativity George F. R. Ellis; 2. Was Einstein right? Clifford M. Will; 3. Cosmology David Wands, Misao Sasaki, Eiichiro Komatsu, Roy Maartens and Malcolm A. H. MacCallum; 4. Relativistic astrophysics Peter Schneider, Ramesh Narayan, Jeffrey E. McClintock, Peter Mészáros and Martin J. Rees; Part II. New Window on the Universe: 5. Receiving gravitational waves Beverly K. Berger, Karsten Danzmann, Gabriela Gonzalez, Andrea Lommen, Guido Mueller, Albrecht Rüdiger and William Joseph Weber; 6. Sources of gravitational waves. Theory and observations Alessandra Buonanno and B. S. Sathyaprakash; Part III. Gravity is Geometry, After All: 7. Probing strong field gravity through numerical simulations Frans Pretorius, Matthew W. Choptuik and Luis Lehner; 8. The initial value problem of general relativity and its implications Gregory J. Galloway, Pengzi Miao and Richard Schoen; 9. Global behavior of solutions to Einstein's equations Stefanos Aretakis, James Isenberg, Vincent Moncrief and Igor Rodnianski; Part IV. Beyond Einstein: 10. Quantum fields in curved space-times Stefan Hollands and Robert M. Wald; 11. From general relativity to quantum gravity Abhay Ashtekar, Martin Reuter and Carlo Rovelli; 12. Quantum gravity via unification Henriette Elvang and Gary T. Horowitz.
Modern Canonical Quantum General Relativity
NASA Astrophysics Data System (ADS)
Thiemann, Thomas
2007-09-01
Preface; Notation and conventions; Introduction; Part I. Classical Foundations, Interpretation and the Canonical Quantisation Programme: 1. Classical Hamiltonian formulation of general relativity; 2. The problem of time, locality and the interpretation of quantum mechanics; 3. The programme of canonical quantisation; 4. The new canonical variables of Ashtekar for general relativity; Part II. Foundations of Modern Canonical Quantum General Relativity: 5. Introduction; 6. Step I: the holonomy-flux algebra [P]; 7. Step II: quantum-algebra; 8. Step III: representation theory of [A]; 9. Step IV: 1. Implementation and solution of the kinematical constraints; 10. Step V: 2. Implementation and solution of the Hamiltonian constraint; 11. Step VI: semiclassical analysis; Part III. Physical Applications: 12. Extension to standard matter; 13. Kinematical geometrical operators; 14. Spin foam models; 15. Quantum black hole physics; 16. Applications to particle physics and quantum cosmology; 17. Loop quantum gravity phenomenology; Part IV. Mathematical Tools and their Connection to Physics: 18. Tools from general topology; 19. Differential, Riemannian, symplectic and complex geometry; 20. Semianalytical category; 21. Elements of fibre bundle theory; 22. Holonomies on non-trivial fibre bundles; 23. Geometric quantisation; 24. The Dirac algorithm for field theories with constraints; 25. Tools from measure theory; 26. Elementary introduction to Gel'fand theory for Abelean C* algebras; 27. Bohr compactification of the real line; 28. Operatir -algebras and spectral theorem; 29. Refined algebraic quantisation (RAQ) and direct integral decomposition (DID); 30. Basics of harmonic analysis on compact Lie groups; 31. Spin network functions for SU(2); 32. + Functional analytical description of classical connection dynamics; Bibliography; Index.
Modern Canonical Quantum General Relativity
NASA Astrophysics Data System (ADS)
Thiemann, Thomas
2008-11-01
Preface; Notation and conventions; Introduction; Part I. Classical Foundations, Interpretation and the Canonical Quantisation Programme: 1. Classical Hamiltonian formulation of general relativity; 2. The problem of time, locality and the interpretation of quantum mechanics; 3. The programme of canonical quantisation; 4. The new canonical variables of Ashtekar for general relativity; Part II. Foundations of Modern Canonical Quantum General Relativity: 5. Introduction; 6. Step I: the holonomy-flux algebra [P]; 7. Step II: quantum-algebra; 8. Step III: representation theory of [A]; 9. Step IV: 1. Implementation and solution of the kinematical constraints; 10. Step V: 2. Implementation and solution of the Hamiltonian constraint; 11. Step VI: semiclassical analysis; Part III. Physical Applications: 12. Extension to standard matter; 13. Kinematical geometrical operators; 14. Spin foam models; 15. Quantum black hole physics; 16. Applications to particle physics and quantum cosmology; 17. Loop quantum gravity phenomenology; Part IV. Mathematical Tools and their Connection to Physics: 18. Tools from general topology; 19. Differential, Riemannian, symplectic and complex geometry; 20. Semianalytical category; 21. Elements of fibre bundle theory; 22. Holonomies on non-trivial fibre bundles; 23. Geometric quantisation; 24. The Dirac algorithm for field theories with constraints; 25. Tools from measure theory; 26. Elementary introduction to Gel'fand theory for Abelean C* algebras; 27. Bohr compactification of the real line; 28. Operatir -algebras and spectral theorem; 29. Refined algebraic quantisation (RAQ) and direct integral decomposition (DID); 30. Basics of harmonic analysis on compact Lie groups; 31. Spin network functions for SU(2); 32. + Functional analytical description of classical connection dynamics; Bibliography; Index.
Tachyons in general relativity
Schwartz, Charles
2011-05-15
We consider the motion of tachyons (faster-than-light particles) in the framework of general relativity. An important feature is the large contribution of low energy tachyons to the energy-momentum tensor. We also calculate the gravitational field produced by tachyons in particular geometric arrangements; and it appears that there could be self-cohering bundles of such matter. This leads us to suggest that such theoretical ideas might be relevant to major problems (dark matter and dark energy) in current cosmological models.
Beyond Einstein's General Relativity
NASA Astrophysics Data System (ADS)
Lobo, Francisco S. N.
2015-04-01
Modern astrophysical and cosmological models are plagued with two severe theoretical difficulties, namely, the dark energy and the dark matter problems. Relative to the former, high-precision observational data have confirmed with startling evidence that the Universe is undergoing a phase of accelerated expansion. This phase, one of the most important and challenging current problems in cosmology, represents a new imbalance in the governing gravitational equations. Several candidates, responsible for this expansion, have been proposed in the literature, in particular, dark energy models and modified gravity, amongst others. Outstanding questions are related to the nature of this so-called “dark energy” that is driving the acceleration of the universe, and whether it is due to the vacuum energy or a dynamical field. On the other hand, the late-time cosmic acceleration may be due to modifications of General Relativity, which introduce new degrees of freedom to the gravitational sector itself. We analyze some of the modified theories of gravity that address these intriguing and exciting problems facing modern physics, and explore the foundations of gravitation theory, essential for the construction of modified theories of gravity.
NASA Astrophysics Data System (ADS)
Dadhich, Naresh; Pons, Josep M.
2012-09-01
In the framework of the Einstein-Palatini formalism, even though the projective transformation connecting the arbitrary connection with the Levi-Civita connection has been floating in the literature for a long time and perhaps the result was implicitly known in the affine gravity community, yet as far as we know Julia and Silva were the first to realise its gauge character. We rederive this result by using the Rosenfeld-Dirac-Bergmann approach to constrained Hamiltonian systems and do a comprehensive self contained analysis establishing the equivalence of the Einstein-Palatini and the metric formulations without having to impose the gauge choice that the connection is symmetric. We also make contact with the the Einstein-Cartan theory when the matter Lagrangian has fermions.
Directions in General Relativity
NASA Astrophysics Data System (ADS)
Hu, B. L.; Ryan, M. P., Jr.; Vishveshwara, C. V.
2005-10-01
Preface; Dieter Brill: a spacetime perspective; 1. Thawing the frozen formalism: the difference between observables and what we observe A. Anderson; 2. Jacobi's action and the density of states J. D. Brown and J. W. York; 3. Decoherence of correlation histories E. Calzetta and B. L. Hu; 4. The initial value problem in light of Ashtekar's variables R. Capovilla, J. Dell and T. Jacobson; 5. Status report on an axiomatic basis for functional integration P. Cartier and C. DeWitt-Morette; 6. Solution of the coupled Einstein constraints on asymptotically Euclidean manifolds Y. Choquet-Bruhat; 7. Compact Cauchy horizons and Cauchy surfaces P. Chrusciel and J. Isenberg; 8. The classical electron J. M. Cohen and E. Mustafa; 9. Gauge (in)variance, mass and parity in D=3 revisited S. Deser; 10. Triality, exceptional Lie groups and Dirac operators F. Flaherty; 11. The reduction of the state vector and limitations on measurement in the quantum mechanics of closed systems J. B. Hartle; 12 Quantum linearization instabilities of de Sitter spacetime A. Higuchi; 13. What is the true description of charged black holes? G. T. Horowitz; 14. Limits on the adiabatic index in static stellar models L. Lindblom and A. K. M. Masood-ul-Alam; 15. On the relativity of rotation B. Mashhoon; 16. Recent progress and open problems in linearization stability V. E. Moncrief; 17. Brill waves N. Ó Murchadha; 18. You can't get there from here: constraints on topology change K. Schleich and D. M. Witt; 19. Time, measurement and information loss in quantum cosmology L. Smolin; 20. Impossible measurements on quantum fields R. Sorkin; 21. A new condition implying the existence of a constant mean curvature foliation F. J. Tipler; 22. Maximal slices in stationary spacetimes with ergoregions R. M. Wald; 23. (1 + 1) - Dimensional methods for general relativity J. H. Yoon; 24. Coalescence of primal gravity waves to make cosmological mass without matter D. E. Holz, W. A. Miller, M. Wakano and J. A. Wheeler.
Milestones of general relativity
NASA Astrophysics Data System (ADS)
Pullin, Jorge
2017-02-01
We present a summary for non-specialists of the special issue of the journal Classical and Quantum Gravity on ‘Milestones of general relativity’, commemorating the 100th anniversary of the theory.
Lowe, Mark J; Koenig, Katherine A; Beall, Erik B; Sakaie, Ken A; Stone, Lael; Bermel, Robert; Phillips, Michael D
2014-09-01
This work presents a pathway-dependent anatomic and functional connectivity analysis in 19 patients with relapse-remitting multiple sclerosis (MS) and 16 age-, education-, and gender-matched controls. An MS population is used in this study as a model for anatomic connectivity, permitting us to observe relationships between anatomic and functional connectivity more easily. A combined resting-state functional magnetic resonance imaging (fMRI) and whole-brain, high angular resolution diffusion imaging analysis is performed in three independent, monosynaptic pathways. The pathways chosen were transcallosal pathway connecting the bilateral primary sensorimotor regions, right and left posterior portion of the Papez circuit, connecting the posterior cingulate cortex and hippocampus. The Papez circuit is known to be involved in memory function, one of the most frequently impacted cognitive domains in patients with MS. We show that anatomic connectivity, as measured with diffusion-weighted imaging, and functional connectivity, as measured with resting-state fMRI, are significantly reduced in patients as compared with controls for at least some of the pathways considered. In addition when all pathway measures are combined, anatomic and functional connectivity are significantly correlated in patients with MS as well as healthy controls. We suggest that anatomic and functional connectivity are related for monosynaptic pathways and that radial diffusivity, as a diffusion-tensor-based measure of white matter integrity, is a robust measure of anatomic connectivity in the general population.
NASA Astrophysics Data System (ADS)
Mashhoon, Bahram
2014-12-01
A brief account of the present status of the recent nonlocal generalization of Einstein's theory of gravitation is presented. The main physical assumptions that underlie this theory are described. We clarify the physical meaning and significance of Weitzenbock's torsion and emphasize its intimate relationship with the gravitational field, characterized by the Riemannian curvature of spacetime. In this theory, nonlocality can simulate dark matter; in fact, in the Newtonian regime, we recover the phenomenological Tohline-Kuhn approach to modified gravity. To account for the observational data regarding dark matter, nonlocality is associated with a characteristic length scale of order 1 kpc. The confrontation of nonlocal gravity with observation is briefly discussed.
18. General view of truss geometry and connections at west ...
18. General view of truss geometry and connections at west portal end of swing span, looking southeast - New Bedford-Fairhaven Middle Bridge, Spanning Acushnet River on U.S. Highway 6, New Bedford, Bristol County, MA
SECONDARY GENERAL MOTORS DIESEL ENGINE WITH CONNECTION TO REDUCTION GEAR ...
SECONDARY GENERAL MOTORS DIESEL ENGINE WITH CONNECTION TO REDUCTION GEAR BELT DRIVE SYSTEM, LOOKING SOUTH. - Mad River Glen, Single Chair Ski Lift, 62 Mad River Glen Resort Road, Fayston, Washington County, VT
39. GENERAL VIEW OF VIVIANNA WORKS CONDENSING CHANNEL CONNECTING TO ...
39. GENERAL VIEW OF VIVIANNA WORKS CONDENSING CHANNEL CONNECTING TO MARISCAL WORKS STACK BEING REUSED AS FINAL CONDENSER LOOKING EAST, NORTHEAST. STONE STRUCTURE IN FOREGROUND UNKNOWN. - Mariscal Quicksilver Mine & Reduction Works, Terlingua, Brewster County, TX
ERIC Educational Resources Information Center
Stauffer, Frederic R.
1984-01-01
Proposes novel methods of solving mechanics and dynamics problems by changing frames of reference. Uses these ideas to pursue Einstein's notions of inertial and uniformly rotating reference frames, gravitational and inertial mass, and the gravitational bending of light in relation to the simple original problem. (JM)
Do well-connected landscapes promote road-related mortality?
Grilo, C.; Ascensao, F.; Santos-Reis, M.; Bissonette, J.A.
2011-01-01
Cost surface (CS) models have emerged as a useful tool to examine the interactions between landscapes patterns and wildlife at large-scale extents. This approach is particularly relevant to guide conservation planning for species that show vulnerability to road networks in human-dominated landscapes. In this study, we measured the functional connectivity of the landscape in southern Portugal and examined how it may be related to stone marten road mortality risk. We addressed three questions: (1) How different levels of landscape connectivity influence stone marten occurrence in montado patches? (2) Is there any relation between montado patches connectivity and stone marten road mortality risk? (3) If so, which road-related features might be responsible for the species' high road mortality? We developed a series of connectivity models using CS scenarios with different resistance values given to each vegetation cover type to reflect different resistance to species movement. Our models showed that the likelihood of occurrence of stone marten decreased with distance to source areas, meaning continuous montado. Open areas and riparian areas within open area matrices entailed increased costs. We found higher stone marten mortality on roads in well-connected areas. Road sinuosity was an important factor influencing the mortality in those areas. This result challenges the way that connectivity and its relation to mortality has been generally regarded. Clearly, landscape connectivity and road-related mortality are not independent. ?? 2010 Springer-Verlag.
Discovering relations between indirectly connected biomedical concepts.
Weissenborn, Dirk; Schroeder, Michael; Tsatsaronis, George
2015-01-01
The complexity and scale of the knowledge in the biomedical domain has motivated research work towards mining heterogeneous data from both structured and unstructured knowledge bases. Towards this direction, it is necessary to combine facts in order to formulate hypotheses or draw conclusions about the domain concepts. This work addresses this problem by using indirect knowledge connecting two concepts in a knowledge graph to discover hidden relations between them. The graph represents concepts as vertices and relations as edges, stemming from structured (ontologies) and unstructured (textual) data. In this graph, path patterns, i.e. sequences of relations, are mined using distant supervision that potentially characterize a biomedical relation. It is possible to identify characteristic path patterns of biomedical relations from this representation using machine learning. For experimental evaluation two frequent biomedical relations, namely "has target", and "may treat", are chosen. Results suggest that relation discovery using indirect knowledge is possible, with an AUC that can reach up to 0.8, a result which is a great improvement compared to the random classification, and which shows that good predictions can be prioritized by following the suggested approach. Analysis of the results indicates that the models can successfully learn expressive path patterns for the examined relations. Furthermore, this work demonstrates that the constructed graph allows for the easy integration of heterogeneous information and discovery of indirect connections between biomedical concepts.
49 CFR 192.367 - Service lines: General requirements for connections to main piping.
Code of Federal Regulations, 2010 CFR
2010-10-01
... connections to main piping. 192.367 Section 192.367 Transportation Other Regulations Relating to... STANDARDS Customer Meters, Service Regulators, and Service Lines § 192.367 Service lines: General... main connection must: (1) Be designed and installed to effectively sustain the longitudinal pull-out or...
Spinning fluids in general relativity
NASA Technical Reports Server (NTRS)
Ray, J. R.; Smalley, L. L.
1982-01-01
General relativity field equations are employed to examine a continuous medium with internal spin. A variational principle formerly applied in the special relativity case is extended to the general relativity case, using a tetrad to express the spin density and the four-velocity of the fluid. An energy-momentum tensor is subsequently defined for a spinning fluid. The equations of motion of the fluid are suggested to be useful in analytical studies of galaxies, for anisotropic Bianchi universes, and for turbulent eddies.
Spinning fluids in general relativity
NASA Technical Reports Server (NTRS)
Ray, J. R.; Smalley, L. L.
1982-01-01
General relativity field equations are employed to examine a continuous medium with internal spin. A variational principle formerly applied in the special relativity case is extended to the general relativity case, using a tetrad to express the spin density and the four-velocity of the fluid. An energy-momentum tensor is subsequently defined for a spinning fluid. The equations of motion of the fluid are suggested to be useful in analytical studies of galaxies, for anisotropic Bianchi universes, and for turbulent eddies.
Connecting instances to promote children’s relational reasoning
Son, Ji Y.; Smith, Linda B.; Goldstone, Robert L.
2010-01-01
The practice of learning from multiple instances seems to allow children to learn about relational structure. The experiments reported here have focused on two issues regarding relational learning from multiple instances: (1) what kind of perceptual situations foster such learning and (2) how particular object properties, such as complexity or similarity, interact with relational learning. Two kinds of perceptual situations were of interest here: simultaneous view, where instances are viewed at once, and sequential view, instances are viewed one at a time, one right after the other. We examine the influence of particular perceptual situations and object properties using two tests of relational reasoning: a common match-to-sample task (where new instances are compared to a common sample) and a variable match-to-sample task (where new instances are compared to a sample that varies on each trial). Experiments 1 and 2 indicate that simultaneous presentation of even highly dissimilar instances, one simple and one complex, effectively connects them together and improves relational generalization in both match-to-sample tasks. Experiment 3 showed simple samples are more effective than complex ones in the common match-to-sample task. However, when one instance is not used a common sample and various pairs of instances are simply compared (Experiment 4), simple and rich instances are equally effective at promoting relational learning. These results bear on our understanding of how children connect instances and how those initial connections affect learning and generalization. PMID:20926099
Projective structure and holonomy in general relativity
NASA Astrophysics Data System (ADS)
Hall, G. S.; Lonie, D. P.
2011-04-01
This review presents a study of the situation when two spacetimes admit the same (unparametrized) geodesics, that is, when they are projectively related. The solution is based on the curvature class and the holonomy type of a spacetime and it transpires that all holonomy possibilities can be solved except the most general one and that the consequence of two spacetimes being projectively related leads, in many cases, to their associated Levi-Civita connections being identical. Some results are also given regarding the general case. It is also shown that the holonomy types of projectively related spacetimes are very closely related. The theory is then applied, with Einstein's principle of equivalence in mind, to 'generic' spacetimes.
Quasilocal Hamiltonians in general relativity
Anderson, Michael T.
2010-10-15
We analyze the definition of quasilocal energy in general relativity based on a Hamiltonian analysis of the Einstein-Hilbert action initiated by Brown-York. The role of the constraint equations, in particular, the Hamiltonian constraint on the timelike boundary, neglected in previous studies, is emphasized here. We argue that a consistent definition of quasilocal energy in general relativity requires, at a minimum, a framework based on the (currently unknown) geometric well-posedness of the initial boundary value problem for the Einstein equations.
Dimensional Analysis and General Relativity
ERIC Educational Resources Information Center
Lovatt, Ian
2009-01-01
Newton's law of gravitation is a central topic in the first-year physics curriculum. A lecturer can go beyond the physical details and use the history of gravitation to discuss the development of scientific ideas; unfortunately, the most recent chapter in this history, general relativity, is not covered in first-year courses. This paper discusses…
Dimensional Analysis and General Relativity
ERIC Educational Resources Information Center
Lovatt, Ian
2009-01-01
Newton's law of gravitation is a central topic in the first-year physics curriculum. A lecturer can go beyond the physical details and use the history of gravitation to discuss the development of scientific ideas; unfortunately, the most recent chapter in this history, general relativity, is not covered in first-year courses. This paper discusses…
General Relativity: Geometry Meets Physics
ERIC Educational Resources Information Center
Thomsen, Dietrick E.
1975-01-01
Observing the relationship of general relativity and the geometry of space-time, the author questions whether the rest of physics has geometrical explanations. As a partial answer he discusses current research on subatomic particles employing geometric transformations, and cites the existence of geometrical definitions of physical quantities such…
General Relativity: Geometry Meets Physics
ERIC Educational Resources Information Center
Thomsen, Dietrick E.
1975-01-01
Observing the relationship of general relativity and the geometry of space-time, the author questions whether the rest of physics has geometrical explanations. As a partial answer he discusses current research on subatomic particles employing geometric transformations, and cites the existence of geometrical definitions of physical quantities such…
Some Properties of Generalized Connections in Quantum Gravity
NASA Astrophysics Data System (ADS)
Velhinho, J. M.
2002-12-01
Theories of connections play an important role in fundamental interactions, including Yang-Mills theories and gravity in the Ashtekar formulation. Typically in such cases, the classical configuration space {A}/ {G} of connections modulo gauge transformations is an infinite dimensional non-linear space of great complexity. Having in mind a rigorous quantization procedure, methods of functional calculus in an extension of {A}/ {G} have been developed. For a compact gauge group G, the compact space /line { {A}{ {/}} {G}} ( ⊃ {A}/ {G}) introduced by Ashtekar and Isham using C*-algebraic methods is a natural candidate to replace {A}/ {G} in the quantum context, 1 allowing the construction of diffeomorphism invariant measures. 2,3,4 Equally important is the space of generalized connections bar {A} introduced in a similar way by Baez. 5 bar {A} is particularly useful for the definition of vector fields in /line { {A}{ {/}} {G}} , fundamental in the construction of quantum observables. 6 These works crucially depend on the use of (generalized) Wilson variables associated to certain types of curves. We will consider the case of piecewise analytic curves, 1,2,5 althought most of the arguments apply equally to the piecewise smooth case. 7,8...
Testing general relativity on accelerators
Kalaydzhyan, Tigran
2015-09-07
Within the general theory of relativity, the curvature of spacetime is related to the energy and momentum of the present matter and radiation. One of the more specific predictions of general relativity is the deflection of light and particle trajectories in the gravitational field of massive objects. Bending angles for electromagnetic waves and light in particular were measured with a high precision. However, the effect of gravity on relativistic massive particles was never studied experimentally. Here we propose and analyze experiments devoted to that purpose. We demonstrate a high sensitivity of the laser Compton scattering at high energy accelerators tomore » the effects of gravity. The main observable – maximal energy of the scattered photons – would experience a significant shift in the ambient gravitational field even for otherwise negligible violation of the equivalence principle. In conclusion, we confirm predictions of general relativity for ultrarelativistic electrons of energy of tens of GeV at a current level of resolution and expect our work to be a starting point of further high-precision studies on current and future accelerators, such as PETRA, European XFEL and ILC.« less
"imprinting" in General Relativity Tests?
NASA Astrophysics Data System (ADS)
Iorio, Lorenzo
We investigate possible a priori "imprinting" of general relativity itself on spaceraft-based tests of it. We deal with some performed or proposed time-delay ranging experiments in the Sun's gravitational field. The "imprint" of general relativity on the Astronomical Unit and the solar gravitational constant GM⊙, not solved for in the spacecraft-based time-delay test performed so far, may induce an a priori bias of the order of 10-6 in typical solar system ranging experiments aimed to measuring the space curvature PPN parameter γ. It is too small by one order of magnitude to be of concern for the performed Cassini experiment, but it would affect future planned or proposed tests aiming to reach a 10-7-10-9 accuracy in determining γ.
General Relativity and Spacetime Relationism.
NASA Astrophysics Data System (ADS)
Hoefer, Carl
1992-01-01
This dissertation takes up the project of showing that, in the context of the general theory of relativity (GTR), spacetime relationism is not a refuted or hopeless view, as many in the recent literature have maintained (John Earman, Michael Friedman, and others). Most of the challenges to the relationist view in General Relativity can be satisfactorily answered; in addition, the opposing absolutist and substantivalist views of spacetime can be shown to be problematic. The crucial burden for relationists concerned with GTR is to show that the realistic cosmological models, i.e. those that may be roughly accurate representations of our universe, satisfy Mach's ideas about the origin of inertia. This dissertation clears the way for and begins such a demonstration. After a brief discussion of the problem of the nature of spacetime and its history in the Introduction, chapters 2 and 3 provide conceptual analysis and criticism of contemporary philosophical arguments about relationism, absolutism, and particularly substantivalism. The current best arguments in favor of substantivalism are shown to be flawed, with the exception of the argument from inertial and metrical structure; and on this issue, it is shown that both relationism and substantivalism need to argue for modifications of GTR (restriction of its models to those with certain features) in order to have a non-trivial explanation of inertial and metrical structure. For relationists, a Machian account of the origin of inertia in some models of GTR is required. Chapter 4 demonstrates that such a Machian account is equivalent to the demand for a truly general relativity of motion. Chapter 5 explores the history of Einstein's commitment to Mach's ideas in his work on GTR. Through an examination of the history of Einstein's attempts to impose Machian constraints on the models of General Relativity, further insight into the nature of this problem is obtained, as are reasons to believe that the project is by no means
Bubble collisions in general relativity
NASA Astrophysics Data System (ADS)
Sikos, S. T. C.; Wu, Z. C.
The collision of two bubbles of true vacuum in a background of false vacuum is considered in the context of General Relativity. It is found that in the thin wall approximation, the problem can be solved exactly. The region to the future of the collision is described by the pseudo-Schwarzschild de Sitter metric. The parameters in this metric are found by solving the junction conditions at each collision.
NASA Astrophysics Data System (ADS)
Johannsen, Tim
2016-06-01
General relativity has been widely tested in weak gravitational fields but still stands largely untested in the strong-field regime. According to the no-hair theorem, black holes in general relativity depend only on their masses and spins and are described by the Kerr metric. Mass and spin are the first two multipole moments of the Kerr spacetime and completely determine all higher-order moments. The no-hair theorem and, hence, general relativity can be tested by measuring potential deviations from the Kerr metric affecting such higher-order moments. Sagittarius A* (Sgr A*), the supermassive black hole at the center of the Milky Way, is a prime target for precision tests of general relativity with several experiments across the electromagnetic spectrum. First, near-infrared (NIR) monitoring of stars orbiting around Sgr A* with current and new instruments is expected to resolve their orbital precessions. Second, timing observations of radio pulsars near the Galactic center may detect characteristic residuals induced by the spin and quadrupole moment of Sgr A*. Third, the event horizon telescope, a global network of mm and sub-mm telescopes, aims to study Sgr A* on horizon scales and to image the silhouette of its shadow cast against the surrounding accretion flow using very-long baseline interferometric (VLBI) techniques. Both NIR and VLBI observations may also detect quasiperiodic variability of the emission from the accretion flow of Sgr A*. In this review, I discuss our current understanding of the spacetime of Sgr A* and the prospects of NIR, timing, and VLBI observations to test its Kerr nature in the near future.
Results from Numerical General Relativity
NASA Technical Reports Server (NTRS)
Baker, John G.
2011-01-01
For several years numerical simulations have been revealing the details of general relativity's predictions for the dynamical interactions of merging black holes. I will review what has been learned of the rich phenomenology of these mergers and the resulting gravitational wave signatures. These wave forms provide a potentially observable record of the powerful astronomical events, a central target of gravitational wave astronomy. Asymmetric radiation can produce a thrust on the system which may accelerate the single black hole resulting from the merger to high relative velocity.
Gravitation. [Book on general relativity
NASA Technical Reports Server (NTRS)
Misner, C. W.; Thorne, K. S.; Wheeler, J. A.
1973-01-01
This textbook on gravitation physics (Einstein's general relativity or geometrodynamics) is designed for a rigorous full-year course at the graduate level. The material is presented in two parallel tracks in an attempt to divide key physical ideas from more complex enrichment material to be selected at the discretion of the reader or teacher. The full book is intended to provide competence relative to the laws of physics in flat space-time, Einstein's geometric framework for physics, applications with pulsars and neutron stars, cosmology, the Schwarzschild geometry and gravitational collapse, gravitational waves, experimental tests of Einstein's theory, and mathematical concepts of differential geometry.
Gravitation. [Book on general relativity
NASA Technical Reports Server (NTRS)
Misner, C. W.; Thorne, K. S.; Wheeler, J. A.
1973-01-01
This textbook on gravitation physics (Einstein's general relativity or geometrodynamics) is designed for a rigorous full-year course at the graduate level. The material is presented in two parallel tracks in an attempt to divide key physical ideas from more complex enrichment material to be selected at the discretion of the reader or teacher. The full book is intended to provide competence relative to the laws of physics in flat space-time, Einstein's geometric framework for physics, applications with pulsars and neutron stars, cosmology, the Schwarzschild geometry and gravitational collapse, gravitational waves, experimental tests of Einstein's theory, and mathematical concepts of differential geometry.
Universality of affine formulation in general relativity
NASA Astrophysics Data System (ADS)
Kijowski, Jerzy; Werpachowski, Roman
2007-02-01
The affine variational principle for general relativity, proposed in 1978 by one of us, is a good remedy for the nonuniversal properties of the standard, metric formulation, arising when the matter Lagrangian depends upon the metric derivatives. The affine version of the theory cures the standard drawback of the metric version, where the leading (second-order) term of the field equations depends upon the matter fields and its causal structure violates the light cone structure of the metric. Choosing the affine connection (and not the metric one) as the gravitational configuration, simplifies considerably the canonical structure of the theory and is more suitable for the purposes of its quantization along the lines of Ashtekar and Lewandowski. We show how the affine formulation provides a simple method to handle boundary integrals in general relativity theory.
Age-Related Difference in Functional Brain Connectivity of Mastication
Lin, Chia-shu; Wu, Ching-yi; Wu, Shih-yun; Lin, Hsiao-Han; Cheng, Dong-hui; Lo, Wen-liang
2017-01-01
The age-related decline in motor function is associated with changes in intrinsic brain signatures. Here, we investigated the functional connectivity (FC) associated with masticatory performance, a clinical index evaluating general masticatory function. Twenty-six older adults (OA) and 26 younger (YA) healthy adults were recruited and assessed using the masticatory performance index (MPI) and resting-state functional magnetic resonance imaging (rs-fMRI). We analyzed the rs-fMRI FC network related to mastication, which was constructed based on 12 bilateral mastication-related brain regions according to the literature. For the OA and the YA group, we identified the mastication-related hubs, i.e., the nodes for which the degree centrality (DC) was positively correlated with the MPI. For each pair of nodes, we identified the inter-nodal link for which the FC was positively correlated with the MPI. The network analysis revealed that, in the YA group, the FC between the sensorimotor cortex, the thalamus (THA) and the cerebellum was positively correlated with the MPI. Consistently, the cerebellum nodes were defined as the mastication-related hubs. In contrast, in the OA group, we found a sparser connection within the sensorimotor regions and cerebellum and a denser connection across distributed regions, including the FC between the superior parietal lobe (SPL), the anterior insula (aINS) and the dorsal anterior cingulate cortex (dACC). Compared to the YA group, the network of the OA group also comprised more mastication-related hubs, which were spatially distributed outside the sensorimotor regions, including the right SPL, the right aINS, and the bilateral dACC. In general, the findings supported the hypothesis that in OA, higher masticatory performance is associated with a widespread pattern of mastication-related hubs. Such a widespread engagement of multiple brain regions associated with the MPI may reflect an increased demand in sensorimotor integration, attentional
Limiting values and general relativity
NASA Astrophysics Data System (ADS)
Pyrohova, U. V.; Golubov, O. A.
2015-10-01
From the general theory of relativity it is known that the force of gravitational interaction never exceeds the value Fmax=c2/4G. In this paper we try to make the notion of the force limit intuitively understandable, and illustrate it with thought experiments with such exotic objects as black holes. It was found that maximum limits of force, power, and flow of mass exist in nature. These limits are physically equivalent. All the maximum values could be seen only on a black hole surface. Moreover, maximum limits of force, power, and mass flow are inevitable consequences of properties of the event horizon of a black hole. And vice versa, the existence of black holes could be deduced from the principle of the maximum force. So, these three principles also could be considered as features of a black hole. The role played by the maximum force in general relativity is similar to the role played by speed of light in special relativity.
Internal connectivity of meandering rivers: Statistical generalization of channel hydraulic geometry
NASA Astrophysics Data System (ADS)
Czapiga, M. J.; Smith, V. B.; Nittrouer, J. A.; Mohrig, D.; Parker, G.
2015-09-01
The geometry of rivers has been characterized in terms of downstream and at-a-station hydraulic geometry, based on individual cross sections. Such analyses do not, however, provide insight as to how these cross sections are connected. We generalize the concept of hydraulic geometry, using data on bathymetry from four reaches of meandering rivers that include at least five bends. We quantify connectivity in terms of the probability that a connected path exists such that a given attribute remains within specified bounds along it. While the concept is general, here we apply it to vessel navigability. We develop a predictor for navigability in meandering rivers, which requires only the following, relatively easily obtained input: vessel draft, vessel width, bankfull depth, bankfull width, relative difference between current and bankfull water surface elevation, and length of desired navigation path. The predictor is applicable to both bankfull and below-bankfull stage. A key input parameter is the standard deviation of the probability distribution of depth. This parameter, in and of itself, yields no information on connectivity as it does not capture the spatial orientation of depth variation. We find, however, that (a) the probability function for connectivity does depend on this parameter, and (b) its use allows for an approximate similarity collapse of the probability function, so providing a quasi-universal predictive relation applying to all four reaches. The results also suggest potential application to more complex forms for connectivity that involve other or multiple in-stream physical variables.
Aberrant pulvinar effective connectivity in generalized social anxiety disorder
Tadayonnejad, Reza; Klumpp, Heide; Ajilore, Olusola; Leow, Alex; Phan, Kinh Luan
2016-01-01
Abstract Recent neuroimaging findings in general social anxiety disorder (gSAD) have extended our understanding of the neural mechanisms of gSAD beyond an amygdala-centric fear-based hyperactivity model to include other brain regions and networks relevant to salient cues. In particular, higher order areas compromising visual networks that process emotional and social information have been implicated. The pulvinar anchors this network and is a key regulatory node that mediates complex sensory inputs and the integration between limbic and frontal brain systems. However, the role of the pulvinar and specifically alteration of its effective connectivity with the rest of the brain has not been examined in the pathophysiology of gSAD, a disorder characterized by aberrant socio-emotional processing. The main aim of this study was to examine the pulvinar network effective connectivity in gSAD. In this study, we recruited 21 individuals with gSAD and 19 demographically matched healthy controls (HC), who performed an emotional face processing task while brain activity was recorded using functional magnetic resonance imaging (fMRI). To examine pulvinar-based network dynamics, Granger causality (GC) based effective connectivity (EC) analysis was applied on fMRI data to compare gSAD and HC. The EC analysis revealed heightened casual influential dynamics between pulvinar in higher order visual and frontal regions in gSAD. In conclusion, these preliminary data suggest a novel network-based cortico-pulvino-cortical neural mechanism in the pathophysiology of gSAD. PMID:27828859
A Generalized Detailed Balance Relation
NASA Astrophysics Data System (ADS)
Ruelle, David
2016-08-01
Given a system M in a thermal bath we obtain a generalized detailed balance relation for the ratio r=π _τ (K→ J)/π _τ (J→ K) of the transition probabilities M:J→ K and M:K→ J in time τ . We assume an active bath, containing solute molecules in metastable states. These molecules may react with M and the transition J→ K occurs through different channels α involving different reactions with the bath. We find that r=sum p^α r^α , where p^α is the probability that channel α occurs, and r^α depends on the amount of heat (more precisely enthalpy) released to the bath in channel α.
Spacecraft Tests of General Relativity
NASA Technical Reports Server (NTRS)
Anderson, John D.
1997-01-01
Current spacecraft tests of general relativity depend on coherent radio tracking referred to atomic frequency standards at the ground stations. This paper addresses the possibility of improved tests using essentially the current system, but with the added possibility of a space-borne atomic clock. Outside of the obvious measurement of the gravitational frequency shift of the spacecraft clock, a successor to the suborbital flight of a Scout D rocket in 1976 (GP-A Project), other metric tests would benefit most directly by a possible improved sensitivity for the reduced coherent data. For purposes of illustration, two possible missions are discussed. The first is a highly eccentric Earth orbiter, and the second a solar-conjunction experiment to measure the Shapiro time delay using coherent Doppler data instead of the conventional ranging modulation.
Spacecraft Tests of General Relativity
NASA Technical Reports Server (NTRS)
Anderson, John D.
1997-01-01
Current spacecraft tests of general relativity depend on coherent radio tracking referred to atomic frequency standards at the ground stations. This paper addresses the possibility of improved tests using essentially the current system, but with the added possibility of a space-borne atomic clock. Outside of the obvious measurement of the gravitational frequency shift of the spacecraft clock, a successor to the suborbital flight of a Scout D rocket in 1976 (GP-A Project), other metric tests would benefit most directly by a possible improved sensitivity for the reduced coherent data. For purposes of illustration, two possible missions are discussed. The first is a highly eccentric Earth orbiter, and the second a solar-conjunction experiment to measure the Shapiro time delay using coherent Doppler data instead of the conventional ranging modulation.
Generalized Optoelectronic Model of Series-Connected Multijunction Solar Cells
Geisz, John F.; Steiner, Myles A.; Garcia, Ivan; France, Ryan M.; McMahon, William E.; Osterwald, Carl R.; Friedman, Daniel J.
2015-10-02
The emission of light from each junction in a series-connected multijunction solar cell, we found, both complicates and elucidates the understanding of its performance under arbitrary conditions. Bringing together many recent advances in this understanding, we present a general 1-D model to describe luminescent coupling that arises from both voltage-driven electroluminescence and voltage-independent photoluminescence in nonideal junctions that include effects such as Sah-Noyce-Shockley (SNS) recombination with n ≠ 2, Auger recombination, shunt resistance, reverse-bias breakdown, series resistance, and significant dark area losses. The individual junction voltages and currents are experimentally determined from measured optical and electrical inputs and outputs of the device within the context of the model to fit parameters that describe the devices performance under arbitrary input conditions. Furthermore, our techniques to experimentally fit the model are demonstrated for a four-junction inverted metamorphic solar cell, and the predictions of the model are compared with concentrator flash measurements.
Young, C B; Chen, T; Nusslock, R; Keller, J; Schatzberg, A F; Menon, V
2016-01-01
Anhedonia, the reduced ability to experience pleasure in response to otherwise rewarding stimuli, is a core symptom of major depressive disorder (MDD). Although the posterior ventromedial prefrontal cortex (pVMPFC) and its functional connections have been consistently implicated in MDD, their roles in anhedonia remain poorly understood. Furthermore, it is unknown whether anhedonia is primarily associated with intrinsic ‘resting-state' pVMPFC functional connectivity or an inability to modulate connectivity in a context-specific manner. To address these gaps, a pVMPFC region of interest was first identified using activation likelihood estimation meta-analysis. pVMPFC connectivity was then examined in relation to anhedonia and general distress symptoms of depression, using both resting-state and task-based functional magnetic resonance imaging involving pleasant music, in current MDD and healthy control groups. In MDD, pVMPFC connectivity was negatively correlated with anhedonia but not general distress during music listening in key reward- and emotion-processing regions, including nucleus accumbens, ventral tegmental area/substantia nigra, orbitofrontal cortex and insula, as well as fronto-temporal regions involved in tracking complex sound sequences, including middle temporal gyrus and inferior frontal gyrus. No such dissociations were observed in the healthy controls, and resting-state pVMPFC connectivity did not dissociate anhedonia from general distress in either group. Our findings demonstrate that anhedonia in MDD is associated with context-specific deficits in pVMPFC connectivity with the mesolimbic reward system when encountering pleasurable stimuli, rather than a static deficit in intrinsic resting-state connectivity. Critically, identification of functional circuits associated with anhedonia better characterizes MDD heterogeneity and may help track of one of its core symptoms. PMID:27187232
Young, C B; Chen, T; Nusslock, R; Keller, J; Schatzberg, A F; Menon, V
2016-05-17
Anhedonia, the reduced ability to experience pleasure in response to otherwise rewarding stimuli, is a core symptom of major depressive disorder (MDD). Although the posterior ventromedial prefrontal cortex (pVMPFC) and its functional connections have been consistently implicated in MDD, their roles in anhedonia remain poorly understood. Furthermore, it is unknown whether anhedonia is primarily associated with intrinsic 'resting-state' pVMPFC functional connectivity or an inability to modulate connectivity in a context-specific manner. To address these gaps, a pVMPFC region of interest was first identified using activation likelihood estimation meta-analysis. pVMPFC connectivity was then examined in relation to anhedonia and general distress symptoms of depression, using both resting-state and task-based functional magnetic resonance imaging involving pleasant music, in current MDD and healthy control groups. In MDD, pVMPFC connectivity was negatively correlated with anhedonia but not general distress during music listening in key reward- and emotion-processing regions, including nucleus accumbens, ventral tegmental area/substantia nigra, orbitofrontal cortex and insula, as well as fronto-temporal regions involved in tracking complex sound sequences, including middle temporal gyrus and inferior frontal gyrus. No such dissociations were observed in the healthy controls, and resting-state pVMPFC connectivity did not dissociate anhedonia from general distress in either group. Our findings demonstrate that anhedonia in MDD is associated with context-specific deficits in pVMPFC connectivity with the mesolimbic reward system when encountering pleasurable stimuli, rather than a static deficit in intrinsic resting-state connectivity. Critically, identification of functional circuits associated with anhedonia better characterizes MDD heterogeneity and may help track of one of its core symptoms.
Generalized Anxiety Disorder: Connections with Self-Reported Attachment
ERIC Educational Resources Information Center
Cassidy, Jude; Lichtenstein-Phelps, June; Sibrava, Nicholas J.; Thomas, Charles L., Jr.; Borkovec, Thomas D.
2009-01-01
Even though generalized anxiety disorder (GAD) is one of the most common of the anxiety disorders, relatively little is known about its precursors. Bowlby's attachment theory provides a framework within which these precursors can be considered. According to Bowlby, adult anxiety may be rooted in childhood experiences that leave a child uncertain…
Generalized Anxiety Disorder: Connections with Self-Reported Attachment
ERIC Educational Resources Information Center
Cassidy, Jude; Lichtenstein-Phelps, June; Sibrava, Nicholas J.; Thomas, Charles L., Jr.; Borkovec, Thomas D.
2009-01-01
Even though generalized anxiety disorder (GAD) is one of the most common of the anxiety disorders, relatively little is known about its precursors. Bowlby's attachment theory provides a framework within which these precursors can be considered. According to Bowlby, adult anxiety may be rooted in childhood experiences that leave a child uncertain…
General Relativity and Gravitation, 1989
NASA Astrophysics Data System (ADS)
Ashby, Neil; Bartlett, David F.; Wyss, Walker
2005-10-01
Part I. Classical Relativity and Gravitation Theory: 1. Global properties of exact solutions H. Friedrich; 2. Numerical relativity T. Nakamura; 3. How fast can a pulsar spin? J. L. Friedman; 4. Colliding waves in general relativity V. Ferrari; Part II. Relativistic Astrophysics, Early Universe, and Classical Cosmology: 5. Observations of cosmic microwave radiation R. B. Partridge; 6. Cosmic microwave background radiation (theory) M. Panek; 7. Inflation and quantum cosmology A. D. Linde; 8. Observations of lensing B. Fort; 9. Gravitational lenses: theory and interpretation R. Blandford; Part III. Experimental Gravitation and Gravitational Waves: 10. Solar system tests of GR: recent results and present plans I. Shapiro; 11. Laser interferometer detectors R. Weiss; 12. Resonant bar gravitational wave experiments G. Pizzella; 13. A non-inverse square law test E. Adelberger; Part IV. Quantum Gravity, Superstrings, Quantum Cosmology: 14. Cosmic strings B. Unruh; 15. String theory as a quantum theory of gravity G. Horowitz; 16. Progress in quantum cosmology J. B. Hartle; 17. Self-duality, quantum gravity, Wilson loops and all that A. V. Ashtekar; Part V. Summary Talk: 18. GR-12 Conference summary J. Ehlers II; Part VI. Reports on Workshops/Symposia: 19. Exact solutions and exact properties of Einstein equations V. Moncrieff; 20. Spinors, twistors and complex methods N. Woodhouse; 21. Alternative gravity theories M. Francaviglia; 22. Asymptotia, singularities and global structure B. G. Schmidt; 23. Radiative spacetimes and approximation methods T. Damour; 24. Algebraic computing M. MacCallum; 25. Numerical relativity J. Centrella; 26. Mathematical cosmology J. Wainwright; 27. The early universe M. Turner; 28. Relativistic astrophysics M. Abramowitz; 29. Astrophysical and observational cosmology B. Carr; 30. Solar system and pulsar tests of gravitation R. Hellings; 31. Earth-based gravitational experiments J. Faller; 32. Resonant bar and microwave gravitational wave
General Relativity and Gravitation, 1989
NASA Astrophysics Data System (ADS)
Ashby, Neil; Bartlett, David F.; Wyss, Walker
1990-11-01
Part I. Classical Relativity and Gravitation Theory: 1. Global properties of exact solutions H. Friedrich; 2. Numerical relativity T. Nakamura; 3. How fast can a pulsar spin? J. L. Friedman; 4. Colliding waves in general relativity V. Ferrari; Part II. Relativistic Astrophysics, Early Universe, and Classical Cosmology: 5. Observations of cosmic microwave radiation R. B. Partridge; 6. Cosmic microwave background radiation (theory) M. Panek; 7. Inflation and quantum cosmology A. D. Linde; 8. Observations of lensing B. Fort; 9. Gravitational lenses: theory and interpretation R. Blandford; Part III. Experimental Gravitation and Gravitational Waves: 10. Solar system tests of GR: recent results and present plans I. Shapiro; 11. Laser interferometer detectors R. Weiss; 12. Resonant bar gravitational wave experiments G. Pizzella; 13. A non-inverse square law test E. Adelberger; Part IV. Quantum Gravity, Superstrings, Quantum Cosmology: 14. Cosmic strings B. Unruh; 15. String theory as a quantum theory of gravity G. Horowitz; 16. Progress in quantum cosmology J. B. Hartle; 17. Self-duality, quantum gravity, Wilson loops and all that A. V. Ashtekar; Part V. Summary Talk: 18. GR-12 Conference summary J. Ehlers II; Part VI. Reports on Workshops/Symposia: 19. Exact solutions and exact properties of Einstein equations V. Moncrieff; 20. Spinors, twistors and complex methods N. Woodhouse; 21. Alternative gravity theories M. Francaviglia; 22. Asymptotia, singularities and global structure B. G. Schmidt; 23. Radiative spacetimes and approximation methods T. Damour; 24. Algebraic computing M. MacCallum; 25. Numerical relativity J. Centrella; 26. Mathematical cosmology J. Wainwright; 27. The early universe M. Turner; 28. Relativistic astrophysics M. Abramowitz; 29. Astrophysical and observational cosmology B. Carr; 30. Solar system and pulsar tests of gravitation R. Hellings; 31. Earth-based gravitational experiments J. Faller; 32. Resonant bar and microwave gravitational wave
Ideal stars and General Relativity
NASA Astrophysics Data System (ADS)
Frønsdal, Christian
2007-12-01
We study a system of differential equations that governs the distribution of matter in the theory of General Relativity. The new element in this paper is the use of a dynamical action principle that includes all the degrees of freedom, matter as well as metric. The matter lagrangian defines a relativistic version of non-viscous, isentropic hydrodynamics. The matter fields are a scalar density and a velocity potential; the conventional, four-vector velocity field is replaced by the gradient of the potential and its scale is fixed by one of the Eulerian equations of motion, an innovation that significantly affects the imposition of boundary conditions. If the density is integrable at infinity, then the metric approaches the Schwarzschild metric at large distances. There are stars without boundary and with finite total mass; the metric shows rapid variation in the neighbourhood of the Schwarzschild radius and there is a very small core where a singularity indicates that the gas laws break down. For stars with boundary there emerges a new, critical relation between the radius and the gravitational mass, a consequence of the stronger boundary conditions. Tentative applications are suggested, to certain Red Giants, and to neutron stars, but the investigation reported here was limited to homogeneous polytropes. Comparison with the results of Oppenheimer and Volkoff on neutron cores shows a close agreement of numerical results. However, in the model the boundary of the star is fixed uniquely by the required matching of the interior metric to the external Schwarzschild metric, which is not the case in the traditional approach. There are solutions for which the metric is very close to the Schwarzshild metric everywhere outside the horizon, where the source is concentrated. The Schwarzschild metric is interpreted as the metric of an ideal, limiting configuration of matter, not as the metric of empty space.
[Marfan syndrome and related connective tissue disorders].
Steindl, Katharina
2013-11-27
Marfan syndrome is an autosomal dominantly inherited connective tissue disorder with a prevalence of approximately 1:5000 people. Typical manifestations affect the cardiovascular system, eyes, skeleton, lungs, skin and dura mater. Most patients have a so-called marfanoid habitus with tall stature, long and narrow limbs, a long and narrow head shape and other skeletal abnormalities. Of particular medical importance are the possible complications such as severe scoliosis or pectus excavatum, spontaneous pneumothorax, retinal detachment, or an acute glaucoma evoked by lens luxation. However, the most dangerous complication is acute dissection of the ascending aorta, which is usually the result of a slowly progressive aortic dilatation. With the introduction of therapies the average life expectancy of previously just 32 years could be raised to above 60 years.
Generalized Optoelectronic Model of Series-Connected Multijunction Solar Cells
Geisz, John F.; Steiner, Myles A.; Garcia, Ivan; ...
2015-10-02
The emission of light from each junction in a series-connected multijunction solar cell, we found, both complicates and elucidates the understanding of its performance under arbitrary conditions. Bringing together many recent advances in this understanding, we present a general 1-D model to describe luminescent coupling that arises from both voltage-driven electroluminescence and voltage-independent photoluminescence in nonideal junctions that include effects such as Sah-Noyce-Shockley (SNS) recombination with n ≠ 2, Auger recombination, shunt resistance, reverse-bias breakdown, series resistance, and significant dark area losses. The individual junction voltages and currents are experimentally determined from measured optical and electrical inputs and outputs ofmore » the device within the context of the model to fit parameters that describe the devices performance under arbitrary input conditions. Furthermore, our techniques to experimentally fit the model are demonstrated for a four-junction inverted metamorphic solar cell, and the predictions of the model are compared with concentrator flash measurements.« less
Connection: Schwartz Center Rounds at Massachusetts General Hospital Cancer Center
Schapira, Lidia; Mack, Sally; Stanzler, Marjorie; Lynch, Thomas J.
2010-01-01
Shortly before his death in 1995, Kenneth B. Schwartz, a cancer patient at Massachusetts General Hospital, founded the Kenneth B. Schwartz Center®, a nonprofit organization dedicated to supporting and advancing compassionate health care. The Center sponsors Schwartz Rounds®, a multidisciplinary forum in which doctors, nurses, chaplains, social workers, and other staff reflect on important psychosocial issues that arise in caring for patients. Attendees participate in an interactive discussion about issues anchored in a case presentation and share their experiences, thoughts, and feelings. The patient narratives may center on wonderful events and transcendent experiences or tragic stories, during which staff can only bear witness to the suffering. The Rounds focus on caregivers' experiences, and encourage staff to share insights, own their vulnerabilities, and support each other. The primary objective is to foster healing relationships and provide support to professional caregivers, enhance communication among caregivers, and improve the connection between patients and caregivers. Currently, >50,000 clinicians attend monthly Schwartz Rounds at 195 sites in 31 states, numbers that are rapidly growing. In this article we explore the reasons that contribute to the success of this model of multidisciplinary reflection. PMID:20584809
On superpotentials in general relativity
NASA Astrophysics Data System (ADS)
Stolín, Oldřich; Novotný, Jan
2001-10-01
It is shown that the Einstein—Freud, Landau—Lifshitz and Møller tetrad super-potentials represent special cases of a more general construction. The tetrad version of the Landau—Lifshitz superpotential is derived.
Connecting Instances to Promote Children's Relational Reasoning
ERIC Educational Resources Information Center
Son, Ji Y.; Smith, Linda B.; Goldstone, Robert L.
2011-01-01
The practice of learning from multiple instances seems to allow children to learn about relational structure. The experiments reported here focused on two issues regarding relational learning from multiple instances: (a) what kind of perceptual situations foster such learning and (b) how particular object properties, such as complexity and…
Action principle for the generalized harmonic formulation of general relativity
Brown, J. David
2011-10-15
An action principle for the generalized harmonic formulation of general relativity is presented. The action is a functional of the spacetime metric and the gauge source vector. An action principle for the Z4 formulation of general relativity has been proposed recently by Bona, Bona-Casas, and Palenzuela. The relationship between the generalized harmonic action and the Bona, Bona-Casas, and Palenzuela action is discussed in detail.
Pace-Schott, Edward F; Zimmerman, Jared P; Bottary, Ryan M; Lee, Erik G; Milad, Mohammed R; Camprodon, Joan A
2017-07-30
Sleep abnormalities are extremely common in anxiety disorders and may contribute to their development and persistence. Their shared pathophysiological mechanisms could thus serve as biomarkers or targets for novel therapeutics. Individuals with Primary Insomnia were age- and sex-matched to controls and to persons with Generalized Anxiety Disorder. All underwent fMRI resting-state scans at 3-T. In Primary Insomnia and controls, sleep was recorded for 2 weeks using diaries and actigraphy. All participants completed state-anxiety and neuroticism inventories. Whole-brain connectivity of 6 fear- and extinction-related seeds were compared between the 3 groups using ANOVA. The only significant between-group main effect was seen for connectivity between the left amygdala seed and a bilateral cluster in the rostral anterior cingulate cortex. The latter is believed to exert top-down control over amygdala activity and their interaction may thus constitute an emotion regulatory circuit. This connectivity was significantly greatest in controls while Primary Insomnia was intermediate between that of controls and Generalized Anxiety Disorder. Across Primary Insomnia and control subjects, mean connectivity decreased with poorer sleep. Across all 3 groups, connectivity decreased with greater neuroticism and pre-scan anxiety. Decreased top-down control of the amygdala may increase risk of developing an anxiety disorder with preexisting Primary Insomnia. Copyright © 2017 Elsevier Ireland Ltd. All rights reserved.
Liu, Feng; Wang, Yifeng; Li, Meiling; Wang, Wenqin; Li, Rong; Zhang, Zhiqiang; Lu, Guangming; Chen, Huafu
2017-02-01
Idiopathic generalized epilepsy (IGE) has been linked with disrupted intra-network connectivity of multiple resting-state networks (RSNs); however, whether impairment is present in inter-network interactions between RSNs, remains largely unclear. Here, 50 patients with IGE characterized by generalized tonic-clonic seizures (GTCS) and 50 demographically matched healthy controls underwent resting-state fMRI scans. A dynamic method was implemented to investigate functional network connectivity (FNC) in patients with IGE-GTCS. Specifically, independent component analysis was first carried out to extract RSNs, and then sliding window correlation approach was employed to obtain dynamic FNC patterns. Finally, k-mean clustering was performed to characterize six discrete functional connectivity states, and state analysis was conducted to explore the potential alterations in FNC and other dynamic metrics. Our results revealed that state-specific FNC disruptions were observed in IGE-GTCS and the majority of aberrant functional connectivity manifested itself in default mode network. In addition, temporal metrics derived from state transition vectors were altered in patients including the total number of transitions across states and the mean dwell time, the fraction of time spent and the number of subjects in specific FNC state. Furthermore, the alterations were significantly correlated with disease duration and seizure frequency. It was also found that dynamic FNC could distinguish patients with IGE-GTCS from controls with an accuracy of 77.91% (P < 0.001). Taken together, this study not only provided novel insights into the pathophysiological mechanisms of IGE-GTCS but also suggested that the dynamic FNC analysis was a promising avenue to deepen our understanding of this disease. Hum Brain Mapp 38:957-973, 2017. © 2016 Wiley Periodicals, Inc.
Uniform acceleration in general relativity
NASA Astrophysics Data System (ADS)
Friedman, Yaakov; Scarr, Tzvi
2015-10-01
We extend de la Fuente and Romero's (Gen Relativ Gravit 47:33, 2015) defining equation for uniform acceleration in a general curved spacetime from linear acceleration to the full Lorentz covariant uniform acceleration. In a flat spacetime background, we have explicit solutions. We use generalized Fermi-Walker transport to parallel transport the Frenet basis along the trajectory. In flat spacetime, we obtain velocity and acceleration transformations from a uniformly accelerated system to an inertial system. We obtain the time dilation between accelerated clocks. We apply our acceleration transformations to the motion of a charged particle in a constant electromagnetic field and recover the Lorentz-Abraham-Dirac equation.
Measuring Experiences of Interest-Related Pursuits in Connected Learning
ERIC Educational Resources Information Center
Maul, Andrew; Penuel, William R.; Dadey, Nathan; Gallagher, Lawrence P.; Podkul, Timothy; Price, Emily
2017-01-01
This paper describes an effort to develop a survey instrument capable of measuring important aspects of adolescents' experiences of interest-related pursuits that are supported by technology. The measure focuses on youths' experiences of "connected learning" (Ito et al. in Connected learning: an agenda for research and design. Digital…
Measuring Experiences of Interest-Related Pursuits in Connected Learning
ERIC Educational Resources Information Center
Maul, Andrew; Penuel, William R.; Dadey, Nathan; Gallagher, Lawrence P.; Podkul, Timothy; Price, Emily
2017-01-01
This paper describes an effort to develop a survey instrument capable of measuring important aspects of adolescents' experiences of interest-related pursuits that are supported by technology. The measure focuses on youths' experiences of "connected learning" (Ito et al. in Connected learning: an agenda for research and design. Digital…
Hamiltonian formulation of general relativity.
NASA Astrophysics Data System (ADS)
Teitelboim, Claudio
The following sections are included: * INTRODUCTION * HAMILTONIAN FORMULATION OF GAUGE THEORIES (PRE-BRST) * BRST HAMILTONIAN FORMULATION OF GAUGE THEORIES * DYNAMICS OF GRAVITATIONAL FIELD * DOES THE HAMILTONIAN VANISH? GENERAL COVARIANCE AS AN "ORDINARY" GAUGE INVARIANCE * GENERALLY COVARIANT SYSTEMS * TIME AS A CANONICAL VARIABLE. ZERO HAMILTONIAN * Parametrized Systems * Zero Hamiltonian * Parametrization and Explicit Time Dependence * TIME REPARAMETRIZATION INVARIANCE * Form of Gauge Transformations * Must the Hamiltonian be Zero for a Generally Covariant System? * Simple Example of a Generally Covariant System with a Nonzero Hamiltonian * "TRUE DYNAMICS" VERSUS GAUGE TRANSFORMATIONS * Interpretation of the Formalism * Reduced Phase Space * MUST TIME FLOW? * GAUGE INDEPENDENCE OF PATH INTEGRAL FOR A PARAMETRIZED SYSTEM ILLUSTRATED. EQUIVALENCE OF THE GAUGES t = τ AND t = 0 * Reduced Phase Space Transition Amplitude as a Reduced Phase Space Path Integral * Canonical Gauge Conditions * Gauge
Numerical Hydrodynamics in General Relativity.
Font, José A
2000-01-01
The current status of numerical solutions for the equations of ideal general relativistic hydrodynamics is reviewed. Different formulations of the equations are presented, with special mention of conservative and hyperbolic formulations well-adapted to advanced numerical methods. A representative sample of available numerical schemes is discussed and particular emphasis is paid to solution procedures based on schemes exploiting the characteristic structure of the equations through linearized Riemann solvers. A comprehensive summary of relevant astrophysical simulations in strong gravitational fields, including gravitational collapse, accretion onto black holes and evolution of neutron stars, is also presented.
BASCO: a toolbox for task-related functional connectivity
Göttlich, Martin; Beyer, Frederike; Krämer, Ulrike M.
2015-01-01
BASCO (BetA Series COrrelation) is a user-friendly MATLAB toolbox with a graphical user interface (GUI) which allows investigating functional connectivity in event-related functional magnetic resonance imaging (fMRI) data. Connectivity analyses extend and compliment univariate activation analyses since the actual interaction between brain regions involved in a task can be explored. BASCO supports seed-based functional connectivity as well as brain network analyses. Although there are a multitude of advanced toolboxes for investigating resting-state functional connectivity, BASCO is the first toolbox for evaluating task-related whole-brain functional connectivity employing a large number of network nodes. Thus, BASCO allows investigating task-specific rather than resting-state networks. Here, we summarize the main features of the toolbox and describe the methods and algorithms. PMID:26441558
Multimodal Connectivity of Motor Learning-Related Dorsal Premotor Cortex
Hardwick, Robert M.; Lesage, Elise; Eickhoff, Claudia R; Clos, Mareike; Fox, Peter; Eickhoff, Simon B.
2015-01-01
The dorsal premotor cortex (dPMC) is a key region for motor learning and sensorimotor integration, yet we have limited understanding of its functional interactions with other regions. Previous work has started to examine functional connectivity in several brain areas using resting state functional connectivity (RSFC) and meta-analytical connectivity modelling (MACM). More recently, structural covariance (SC) has also been proposed as a technique that may also allow delineation of functional connectivity. Here we applied these three approaches to provide a comprehensive characterization of functional connectivity with a seed in the left dPMC that a previous meta-analysis of functional neuroimaging studies has identified as playing a key role in motor learning. Using data from two sources (the Rockland sample, containing resting state data and anatomical scans from 132 participants, and the BrainMap database, which contains peak activation foci from over 10,000 experiments), we conducted independent whole-brain functional connectivity mapping analyses of a dPMC seed. RSFC and MACM revealed similar connectivity maps spanning prefrontal, premotor and parietal regions, while the SC map identified more widespread frontal regions. Analyses indicated a relatively consistent pattern of functional connectivity between RSFC and MACM that was distinct from that identified by SC. Notably, results indicate the seed is functionally connected to areas involved in visuomotor control and executive functions, suggesting the dPMC acts as an interface between motor control and cognition. PMID:26282855
General relativity and satellite orbits
NASA Technical Reports Server (NTRS)
Rubincam, D. P.
1975-01-01
The general relativistic correction to the position of a satellite is found by retaining Newtonian physics for an observer on the satellite and introducing a potential. The potential is expanded in terms of the Keplerian elements of the orbit and substituted in Lagrange's equations. Integration of the equations shows that a typical earth satellite with small orbital eccentricity is displaced by about 17 cm. from its unperturbed position after a single orbit, while the periodic displacement over the orbit reaches a maximum of about 3 cm. The moon is displaced by about the same amounts. Application of the equations to Mercury gives a total displacement of about 58 km. after one orbit and a maximum periodic displacement of about 12 km.
Holonomy groups in general relativity
Hall, G.S.; Kay, W.
1988-02-01
The infinitesimal holonomy group structure of space-time is discussed and related to the Petrov type of the Weyl tensor and the algebraic (Segre) type of the energy-momentum tensor. The number of covariant derivatives of the curvature tensor required to determine the infinitesimal holonomy group is determined in each case and the complete classification scheme is tabulated. Some special cases of physical interest are investigated in more detail. A geometrical approach is followed throughout.
Developmental changes in effective connectivity associated with relational reasoning.
Bazargani, Narges; Hillebrandt, Hauke; Christoff, Kalina; Dumontheil, Iroise
2014-07-01
Rostrolateral prefrontal cortex (RLPFC) is part of a frontoparietal network of regions involved in relational reasoning, the mental process of working with relationships between multiple mental representations. RLPFC has shown functional and structural changes with age, with increasing specificity of left RLPFC activation for relational integration during development. Here, we used dynamic causal modeling (DCM) to investigate changes in effective connectivity during a relational reasoning task through the transition from adolescence into adulthood. We examined fMRI data of 37 healthy female participants (11–30 years old) performing a relational reasoning paradigm. Comparing relational integration to the manipulation of single relations revealed activation in five regions: the RLPFC, anterior insula, dorsolateral PFC, inferior parietal lobe, and medial superior frontal gyrus. We used a new exhaustive search approach and identified a full DCM model, which included all reciprocal connections between the five clusters in the left hemisphere, as the optimal model. In line with previous resting state fMRI results, we showed distinct developmental effects on the strength of long-range frontoparietal versus frontoinsular short-range fixed connections. The modulatory connections associated with relational integration increased with age. Gray matter volume in left RLPFC, which decreased with age, partly accounted for changes in fixed PFC connectivity. Finally, improvements in relational integration performance were associated with greater modulatory and weaker fixed PFC connectivity. This pattern provides further evidence of increasing specificity of left PFC function for relational integration compared to the manipulation of single relations, and demonstrates an association between effective connectivity and performance during development.
Pulsar timing and general relativity
NASA Technical Reports Server (NTRS)
Backer, D. C.; Hellings, R. W.
1986-01-01
Techniques are described for accounting for relativistic effects in the analysis of pulsar signals. Design features of instrumentation used to achieve millisecond accuracy in the signal measurements are discussed. The accuracy of the data permits modeling the pulsar physical characteristics from the natural glitches in the emissions. Relativistic corrections are defined for adjusting for differences between the pulsar motion in its spacetime coordinate system relative to the terrestrial coordinate system, the earth's motion, and the gravitational potentials of solar system bodies. Modifications of the model to allow for a binary pulsar system are outlined, including treatment of the system as a point mass. Finally, a quadrupole model is presented for gravitational radiation and techniques are defined for using pulsars in the search for gravitational waves.
Pulsar timing and general relativity
NASA Technical Reports Server (NTRS)
Backer, D. C.; Hellings, R. W.
1986-01-01
Techniques are described for accounting for relativistic effects in the analysis of pulsar signals. Design features of instrumentation used to achieve millisecond accuracy in the signal measurements are discussed. The accuracy of the data permits modeling the pulsar physical characteristics from the natural glitches in the emissions. Relativistic corrections are defined for adjusting for differences between the pulsar motion in its spacetime coordinate system relative to the terrestrial coordinate system, the earth's motion, and the gravitational potentials of solar system bodies. Modifications of the model to allow for a binary pulsar system are outlined, including treatment of the system as a point mass. Finally, a quadrupole model is presented for gravitational radiation and techniques are defined for using pulsars in the search for gravitational waves.
Separate universes beyond general relativity
NASA Astrophysics Data System (ADS)
Hu, Wayne; Joyce, Austin
2017-02-01
We establish purely geometric or metric-based criteria for the validity of the separate universe ansatz, under which the evolution of small-scale observables in a long-wavelength perturbation is indistinguishable from a separate Friedmann-Robertson-Walker cosmology in their angle average. In order to be able to identify the local volume expansion and curvature in a long-wavelength perturbation with those of the separate universe, we show that the lapse perturbation must be much smaller in amplitude than the curvature potential on a time slicing that comoves with the Einstein tensor. Interpreting the Einstein tensor as an effective stress-energy tensor, the condition is that the effective stress energy comoves with freely falling synchronous observers who establish the local expansion, so that the local curvature is conserved. By matching the expansion history of these synchronous observers in cosmological simulations, one can establish and test consistency relations even in the nonlinear regime of modified gravity theories.
Connections between Generalizing and Justifying: Students' Reasoning with Linear Relationships
ERIC Educational Resources Information Center
Ellis, Amy B.
2007-01-01
Research investigating algebra students' abilities to generalize and justify suggests that they experience difficulty in creating and using appropriate generalizations and proofs. Although the field has documented students' errors, less is known about what students do understand to be general and convincing. This study examines the ways in which…
Altered resting brain connectivity in persistent cancer related fatigue
Hampson, Johnson P.; Zick, Suzanna M.; Khabir, Tohfa; Wright, Benjamin D.; Harris, Richard E.
2015-01-01
There is an estimated 3 million women in the US living as breast cancer survivors and persistent cancer related fatigue (PCRF) disrupts the lives of an estimated 30% of these women. PCRF is associated with decreased quality of life, decreased sleep quality, impaired cognition and depression. The mechanisms of cancer related fatigue are not well understood; however, preliminary findings indicate dysfunctional activity in the brain as a potential factor. Here we investigate the relationship between PCRF on intrinsic resting state connectivity in this population. Twenty-three age matched breast cancer survivors (15 fatigued and 8 non-fatigued) who completed all cancer-related treatments at least 12 weeks prior to the study, were recruited to undergo functional connectivity magnetic resonance imaging (fcMRI). Intrinsic resting state networks were examined with both seed based and independent component analysis methods. Comparisons of brain connectivity patterns between groups as well as correlations with self-reported fatigue symptoms were performed. Fatigued patients displayed greater left inferior parietal lobule to superior frontal gyrus connectivity as compared to non-fatigued patients (P < 0.05 FDR corrected). This enhanced connectivity was associated with increased physical fatigue (P = 0.04, r = 0.52) and poor sleep quality (P = 0.04, r = 0.52) in the fatigued group. In contrast greater connectivity in the non-fatigued group was found between the right precuneus to the periaqueductal gray as well as the left IPL to subgenual cortex (P < 0.05 FDR corrected). Mental fatigue scores were associated with greater default mode network (DMN) connectivity to the superior frontal gyrus (P = 0.05 FDR corrected) among fatigued subjects (r = 0.82) and less connectivity in the non-fatigued group (r = −0.88). These findings indicate that there is enhanced intrinsic DMN connectivity to the frontal gyrus in breast cancer survivors with persistent fatigue. As
Altered resting brain connectivity in persistent cancer related fatigue.
Hampson, Johnson P; Zick, Suzanna M; Khabir, Tohfa; Wright, Benjamin D; Harris, Richard E
2015-01-01
There is an estimated 3 million women in the US living as breast cancer survivors and persistent cancer related fatigue (PCRF) disrupts the lives of an estimated 30% of these women. PCRF is associated with decreased quality of life, decreased sleep quality, impaired cognition and depression. The mechanisms of cancer related fatigue are not well understood; however, preliminary findings indicate dysfunctional activity in the brain as a potential factor. Here we investigate the relationship between PCRF on intrinsic resting state connectivity in this population. Twenty-three age matched breast cancer survivors (15 fatigued and 8 non-fatigued) who completed all cancer-related treatments at least 12 weeks prior to the study, were recruited to undergo functional connectivity magnetic resonance imaging (fcMRI). Intrinsic resting state networks were examined with both seed based and independent component analysis methods. Comparisons of brain connectivity patterns between groups as well as correlations with self-reported fatigue symptoms were performed. Fatigued patients displayed greater left inferior parietal lobule to superior frontal gyrus connectivity as compared to non-fatigued patients (P < 0.05 FDR corrected). This enhanced connectivity was associated with increased physical fatigue (P = 0.04, r = 0.52) and poor sleep quality (P = 0.04, r = 0.52) in the fatigued group. In contrast greater connectivity in the non-fatigued group was found between the right precuneus to the periaqueductal gray as well as the left IPL to subgenual cortex (P < 0.05 FDR corrected). Mental fatigue scores were associated with greater default mode network (DMN) connectivity to the superior frontal gyrus (P = 0.05 FDR corrected) among fatigued subjects (r = 0.82) and less connectivity in the non-fatigued group (r = -0.88). These findings indicate that there is enhanced intrinsic DMN connectivity to the frontal gyrus in breast cancer survivors with persistent fatigue. As
"The Chemicals Project": Connecting General Chemistry to Students' Lives
NASA Astrophysics Data System (ADS)
Stout, Roland
2000-10-01
"The Chemicals Project" described here strives to bring freshman chemistry alive for students by emphasizing its connection to the real world and to their own lives and experiences. Its major assignments deal with chemical phobias, recognizing the chemicals found in everyday life and chemical hazards (using Material Data Safety Sheets). The project is described in a cooperative learning format, employs portfolio grading, and includes a significant writing component. Ways of linking this project with the course lecture and student evaluations of the project are described. The bottom line: pre- and post-testing shows that it works. The Chemicals Project brings chemistry alive for students.
NASA Astrophysics Data System (ADS)
Rosenstock, Sarita; Weatherall, James Owen
2016-10-01
A classic result in the foundations of Yang-Mills theory, due to Barrett [Int. J. Theor. Phys. 30, 1171-1215 (1991)], establishes that given a "generalized" holonomy map from the space of piece-wise smooth, closed curves based at some point of a manifold to a Lie group, there exists a principal bundle with that group as structure group and a principal connection on that bundle such that the holonomy map corresponds to the holonomies of that connection. Barrett also provided one sense in which this "recovery theorem" yields a unique bundle, up to isomorphism. Here we show that something stronger is true: with an appropriate definition of isomorphism between generalized holonomy maps, there is an equivalence of categories between the category whose objects are generalized holonomy maps on a smooth, connected manifold and whose arrows are holonomy isomorphisms, and the category whose objects are principal connections on principal bundles over a smooth, connected manifold. This result clarifies, and somewhat improves upon, the sense of "unique recovery" in Barrett's theorems; it also makes precise a sense in which there is no loss of structure involved in moving from a principal bundle formulation of Yang-Mills theory to a holonomy, or "loop," formulation.
General Relativity in (1 + 1) Dimensions
ERIC Educational Resources Information Center
Boozer, A. D.
2008-01-01
We describe a theory of gravity in (1 + 1) dimensions that can be thought of as a toy model of general relativity. The theory should be a useful pedagogical tool, because it is mathematically much simpler than general relativity but shares much of the same conceptual structure; in particular, it gives a simple illustration of how gravity arises…
General Relativity in (1 + 1) Dimensions
ERIC Educational Resources Information Center
Boozer, A. D.
2008-01-01
We describe a theory of gravity in (1 + 1) dimensions that can be thought of as a toy model of general relativity. The theory should be a useful pedagogical tool, because it is mathematically much simpler than general relativity but shares much of the same conceptual structure; in particular, it gives a simple illustration of how gravity arises…
Testing general relativity with current cosmological data
Daniel, Scott F.; Linder, Eric V.; Smith, Tristan L.; Caldwell, Robert R.; Cooray, Asantha; Leauthaud, Alexie; Lombriser, Lucas
2010-06-15
Deviations from general relativity, such as could be responsible for the cosmic acceleration, would influence the growth of large-scale structure and the deflection of light by that structure. We clarify the relations between several different model-independent approaches to deviations from general relativity appearing in the literature, devising a translation table. We examine current constraints on such deviations, using weak gravitational lensing data of the CFHTLS and COSMOS surveys, cosmic microwave background radiation data of WMAP5, and supernova distance data of Union2. A Markov chain Monte Carlo likelihood analysis of the parameters over various redshift ranges yields consistency with general relativity at the 95% confidence level.
Connecting Achievement Motivation to Performance in General Chemistry
ERIC Educational Resources Information Center
Ferrell, Brent; Phillips, Michael M.; Barbera, Jack
2016-01-01
Student success in chemistry is inherently tied to motivational and other affective processes. We investigated three distinct constructs tied to motivation: self-efficacy, interest, and effort beliefs. These variables were measured twice over the course of a semester in three sections of a first-semester general chemistry course (n = 170). We…
Connecting Achievement Motivation to Performance in General Chemistry
ERIC Educational Resources Information Center
Ferrell, Brent; Phillips, Michael M.; Barbera, Jack
2016-01-01
Student success in chemistry is inherently tied to motivational and other affective processes. We investigated three distinct constructs tied to motivation: self-efficacy, interest, and effort beliefs. These variables were measured twice over the course of a semester in three sections of a first-semester general chemistry course (n = 170). We…
Particle Pair Production in Cosmological General Relativity
NASA Astrophysics Data System (ADS)
Oliveira, Firmin J.
2012-12-01
The Cosmological General Relativity (CGR) of Carmeli, a 5-dimensional (5-D) theory of time, space and velocity, predicts the existence of an acceleration a 0= c/ τ due to the expansion of the universe, where c is the speed of light in vacuum, τ=1/ h is the Hubble-Carmeli time constant, where h is the Hubble constant at zero distance and no gravity. The Carmeli force on a particle of mass m is F c = ma 0, a fifth force in nature. In CGR, the effective mass density ρ eff = ρ- ρ c , where ρ is the matter density and ρ c is the critical mass density which we identify with the vacuum mass density ρ vac =- ρ c . The fields resulting from the weak field solution of the Einstein field equations in 5-D CGR and the Carmeli force are used to hypothesize the production of a pair of particles. The mass of each particle is found to be m= τc 3/4 G, where G is Newton's constant. The vacuum mass density derived from the physics is ρ vac =- ρ c =-3/8 πGτ 2. We make a connection between the cosmological constant of the Friedmann-Robertson-Walker model and the vacuum mass density of CGR by the relation Λ=-8 πGρ vac =3/ τ 2. Each black hole particle defines its own volume of space enclosed by the event horizon, forming a sub-universe. The cosmic microwave background (CMB) black body radiation at the temperature T o =2.72548 K which fills that volume is found to have a relationship to the ionization energy of the Hydrogen atom. Define the radiation energy ɛ γ =(1- g) mc 2/ N γ , where (1- g) is the fraction of the initial energy mc 2 which converts to photons, g is a function of the baryon density parameter Ω b and N γ is the total number of photons in the CMB radiation field. We make the connection with the ionization energy of the first quantum level of the Hydrogen atom by the hypothesis ɛ_{γ} = ( 1 - g ) m c^2 / N_{γ } = α^2 μ c^2/2, where α is the fine-structure constant and μ= m p f/(1+ f), where f= m e / m p with m e the electron mass and m p the
BOOK REVIEW: Modern Canonical Quantum General Relativity
NASA Astrophysics Data System (ADS)
Kiefer, Claus
2008-06-01
The open problem of constructing a consistent and experimentally tested quantum theory of the gravitational field has its place at the heart of fundamental physics. The main approaches can be roughly divided into two classes: either one seeks a unified quantum framework of all interactions or one starts with a direct quantization of general relativity. In the first class, string theory (M-theory) is the only known example. In the second class, one can make an additional methodological distinction: while covariant approaches such as path-integral quantization use the four-dimensional metric as an essential ingredient of their formalism, canonical approaches start with a foliation of spacetime into spacelike hypersurfaces in order to arrive at a Hamiltonian formulation. The present book is devoted to one of the canonical approaches—loop quantum gravity. It is named modern canonical quantum general relativity by the author because it uses connections and holonomies as central variables, which are analogous to the variables used in Yang Mills theories. In fact, the canonically conjugate variables are a holonomy of a connection and the flux of a non-Abelian electric field. This has to be contrasted with the older geometrodynamical approach in which the metric of three-dimensional space and the second fundamental form are the fundamental entities, an approach which is still actively being pursued. It is the author's ambition to present loop quantum gravity in a way in which every step is formulated in a mathematically rigorous form. In his own words: 'loop quantum gravity is an attempt to construct a mathematically rigorous, background-independent, non-perturbative quantum field theory of Lorentzian general relativity and all known matter in four spacetime dimensions, not more and not less'. The formal Leitmotiv of loop quantum gravity is background independence. Non-gravitational theories are usually quantized on a given non-dynamical background. In contrast, due to
The Confrontation between General Relativity and Experiment.
Will, Clifford M
2006-01-01
The status of experimental tests of general relativity and of theoretical frameworks for analyzing them is reviewed. Einstein's equivalence principle (EEP) is well supported by experiments such as the Eötvös experiment, tests of special relativity, and the gravitational redshift experiment. Ongoing tests of EEP and of the inverse square law are searching for new interactions arising from unification or quantum gravity. Tests of general relativity at the post-Newtonian level have reached high precision, including the light deflection, the Shapiro time delay, the perihelion advance of Mercury, and the Nordtvedt effect in lunar motion. Gravitational wave damping has been detected in an amount that agrees with general relativity to better than half a percent using the Hulse-Taylor binary pulsar, and other binary pulsar systems have yielded other tests, especially of strong-field effects. When direct observation of gravitational radiation from astrophysical sources begins, new tests of general relativity will be possible.
The Confrontation between General Relativity and Experiment.
Will, Clifford M
2001-01-01
The status of experimental tests of general relativity and of theoretical frameworks for analysing them are reviewed. Einstein's equivalence principle (EEP) is well supported by experiments such as the Eötvös experiment, tests of special relativity, and the gravitational redshift experiment. Future tests of EEP and of the inverse square law will search for new interactions arising from unification or quantum gravity. Tests of general relativity at the post-Newtonian level have reached high precision, including the light defl ection the Shapiro time delay, the perihelion advance of Mercury, and the Nordtvedt effect in lunar motion. Gravitational wave damping has been detected in an amount that agrees with general relativity to half a percent using the Hulse-Taylor binary pulsar, and new binary pulsar systems may yield further improvements. When direct observation of gravitational radiation from astrophysical sources begins, new tests of general relativity will be possible.
A General Framework for Relative Impact Indicators.
ERIC Educational Resources Information Center
Egghe, Leo; Rousseau, Ronald
2003-01-01
Discussion of the assessment and comparison of scientific journals, bibliometrics, and types of impact factors focuses on a general framework for the relative comparison of journal impact. Highlights include the relative impact of a journal within a set of journals, or meta-journal; and mathematical explorations of relative indicators. (Author/LRW)
Integrated Science General Education Program (ISGE): Bioastronomy Connections
NASA Astrophysics Data System (ADS)
Troncale, Len
2004-06-01
A new, NSF-supported, General Education (GE) science curriculum, synthesizes and unifies the key theories and evidence of seven natural sciences using natural systems processes as Integrative Themes. The considerably reformulated subject matter is completely built on interdisciplinary concepts and methods fundamental to newly emerging cross-disciplinary fields like bioastronomy. The year of ISGE study incorporates 15 built-in computer based multimedia features and 10 special learning features to help non-science students learn more science, faster, and with better understanding. Results from seven test course offerings are reported. ISGE intends to be an initial example of the ``living, evolving'' knowledge bases needed for a space-faring species.
Einstein and General Relativity: Historical Perspectives.
ERIC Educational Resources Information Center
Chandrasekhar, S.
1979-01-01
This paper presented in the 1978 Oppenheimer Memorial Lecture at Los Alamos Scientific Laboratories on August 17, 1978, discusses Einstein's contributions to physics, in particular, his discovery of the general theory of relativity. (HM)
Einstein and General Relativity: Historical Perspectives.
ERIC Educational Resources Information Center
Chandrasekhar, S.
1979-01-01
This paper presented in the 1978 Oppenheimer Memorial Lecture at Los Alamos Scientific Laboratories on August 17, 1978, discusses Einstein's contributions to physics, in particular, his discovery of the general theory of relativity. (HM)
The General Fishbone Like Dispersion Relation
NASA Astrophysics Data System (ADS)
Zonca, Fulvio
2015-12-01
The following sections are included: * Introduction * Motivation and outline * Fundamental equations * The collisionless gyrokinetic equation * Vorticity equation * Quasi-neutrality condition * Perpendicular Ampère's law * Studying collective modes in burning plasmas * Ideal plasma equilibrium in the low-β limit * Approximations for the energetic population * Characteristic frequencies of particle motions * Alfvén wave frequency and wavelength orderings * Applications of the general theoretical framework * The general fishbone like dispersion relation * Properties of the fishbone like dispersion relation * Derivation of the fishbone like dispersion relation * Special cases of the fishbone like dispersion relation * Toroidal Alfvén Eigenmodes (TAE) * Alfvén Cascades * Summary and discussions * Acknowledgments * References
A golden age of general relativity? Some remarks on the history of general relativity
NASA Astrophysics Data System (ADS)
Goenner, Hubert
2017-03-01
This article deals with the concepts "renaissance" and "low water mark between 1925 and 1955" of general relativity suggested in the literature. By empirical data, it is shown that no such period did exist. Research on general relativity continued continuously since the 1920s interrupted only by the second world war. On a broad scale, research on general relativity started only after 1945.
Anisotropic Generalized Ghost Pilgrim Dark Energy Model in General Relativity
NASA Astrophysics Data System (ADS)
Santhi, M. Vijaya; Rao, V. U. M.; Aditya, Y.
2017-02-01
A spatially homogeneous and anisotropic locally rotationally symmetric (LRS) Bianchi type- I Universe filled with matter and generalized ghost pilgrim dark energy (GGPDE) has been studied in general theory of relativity. To obtain determinate solution of the field equations we have used scalar expansion proportional to the shear scalar which leads to a relation between the metric potentials. Some well-known cosmological parameters (equation of state (EoS) parameter ( ω Λ), deceleration parameter ( q) and squared speed of sound {vs2}) and planes (ω _{Λ }-dot {ω }_{Λ } and statefinder) are constructed for obtained model. The discussion and significance of these parameters is totally done through pilgrim dark energy parameter ( β) and cosmic time ( t).
Black hole based tests of general relativity
NASA Astrophysics Data System (ADS)
Yagi, Kent; Stein, Leo C.
2016-03-01
General relativity has passed all solar system experiments and neutron star based tests, such as binary pulsar observations, with flying colors. A more exotic arena for testing general relativity is in systems that contain one or more black holes. Black holes are the most compact objects in the Universe, providing probes of the strongest-possible gravitational fields. We are motivated to study strong-field gravity since many theories give large deviations from general relativity only at large field strengths, while recovering the weak-field behavior. In this article, we review how one can probe general relativity and various alternative theories of gravity by using electromagnetic waves from a black hole with an accretion disk, and gravitational waves from black hole binaries. We first review model-independent ways of testing gravity with electromagnetic/gravitational waves from a black hole system. We then focus on selected examples of theories that extend general relativity in rather simple ways. Some important characteristics of general relativity include (but are not limited to) (i) only tensor gravitational degrees of freedom, (ii) the graviton is massless, (iii) no quadratic or higher curvatures in the action, and (iv) the theory is four-dimensional. Altering a characteristic leads to a different extension of general relativity: (i) scalar-tensor theories, (ii) massive gravity theories, (iii) quadratic gravity, and (iv) theories with large extra dimensions. Within each theory, we describe black hole solutions, their properties, and current and projected constraints on each theory using black hole based tests of gravity. We close this review by listing some of the open problems in model-independent tests and within each specific theory.
Teaching General Relativity to the Layperson
ERIC Educational Resources Information Center
Egdall, Mark
2009-01-01
This paper describes a lay course on general relativity (GR) given at the Osher Lifelong Learning Institute at Florida International University. It is presented in six hour-and-a-half weekly sessions. Other courses offered by the author include special relativity (which precedes the course described here), quantum theory, and cosmology. Students…
Teaching General Relativity to the Layperson
ERIC Educational Resources Information Center
Egdall, Mark
2009-01-01
This paper describes a lay course on general relativity (GR) given at the Osher Lifelong Learning Institute at Florida International University. It is presented in six hour-and-a-half weekly sessions. Other courses offered by the author include special relativity (which precedes the course described here), quantum theory, and cosmology. Students…
Wei, Huilin; An, Jie; Shen, Hui; Zeng, Ling-Li; Qiu, Shijun; Hu, Dewen
2016-01-01
Idiopathic generalized epilepsy (IGE) patients with generalized tonic-clonic seizures (GTCS) suffer long-term cognitive impairments, and present a higher incidence of psychosocial and psychiatric disturbances than healthy people. It is possible that the cognitive dysfunctions and higher psychopathological risk in IGE-GTCS derive from disturbed causal relationship among core neurocognitive brain networks. To test this hypothesis, we examined the effective connectivity across the salience network (SN), default mode network (DMN), and central executive network (CEN) using resting-state functional magnetic resonance imaging (fMRI) data collected from 27 IGE-GTCS patients and 29 healthy controls. In the study, a combination framework of time domain and frequency domain multivariate Granger causality analysis was firstly proposed, and proved to be valid and accurate by simulation experiments. Using this method, we then observed significant differences in the effective connectivity graphs between the patient and control groups. Specifically, between-group statistical analysis revealed that relative to the healthy controls, the patients established significantly enhanced Granger causal influence from the dorsolateral prefrontal cortex to the dorsal anterior cingulate cortex, which is coherent both in the time and frequency domains analyses. Meanwhile, time domain analysis also revealed decreased Granger causal influence from the right fronto-insular cortex to the posterior cingulate cortex in the patients. These findings may provide new evidence for functional brain organization disruption underlying cognitive dysfunctions and psychopathological risk in IGE-GTCS. PMID:27656137
General very special relativity in Finsler cosmology
Kouretsis, A. P.; Stathakopoulos, M.; Stavrinos, P. C.
2009-05-15
General very special relativity (GVSR) is the curved space-time of very special relativity (VSR) proposed by Cohen and Glashow. The geometry of general very special relativity possesses a line element of Finsler geometry introduced by Bogoslovsky. We calculate the Einstein field equations and derive a modified Friedmann-Robertson-Walker cosmology for an osculating Riemannian space. The Friedmann equation of motion leads to an explanation of the cosmological acceleration in terms of an alternative non-Lorentz invariant theory. A first order approach for a primordial-spurionic vector field introduced into the metric gives back an estimation of the energy evolution and inflation.
General very special relativity in Finsler cosmology
NASA Astrophysics Data System (ADS)
Kouretsis, A. P.; Stathakopoulos, M.; Stavrinos, P. C.
2009-05-01
General very special relativity (GVSR) is the curved space-time of very special relativity (VSR) proposed by Cohen and Glashow. The geometry of general very special relativity possesses a line element of Finsler geometry introduced by Bogoslovsky. We calculate the Einstein field equations and derive a modified Friedmann-Robertson-Walker cosmology for an osculating Riemannian space. The Friedmann equation of motion leads to an explanation of the cosmological acceleration in terms of an alternative non-Lorentz invariant theory. A first order approach for a primordial-spurionic vector field introduced into the metric gives back an estimation of the energy evolution and inflation.
The Confrontation between General Relativity and Experiment.
Will, Clifford M
2014-01-01
The status of experimental tests of general relativity and of theoretical frameworks for analyzing them is reviewed and updated. Einstein's equivalence principle (EEP) is well supported by experiments such as the Eötvös experiment, tests of local Lorentz invariance and clock experiments. Ongoing tests of EEP and of the inverse square law are searching for new interactions arising from unification or quantum gravity. Tests of general relativity at the post-Newtonian level have reached high precision, including the light deflection, the Shapiro time delay, the perihelion advance of Mercury, the Nordtvedt effect in lunar motion, and frame-dragging. Gravitational wave damping has been detected in an amount that agrees with general relativity to better than half a percent using the Hulse-Taylor binary pulsar, and a growing family of other binary pulsar systems is yielding new tests, especially of strong-field effects. Current and future tests of relativity will center on strong gravity and gravitational waves.
[The Marfan syndrome and related connective tissue disorders].
Siepe, Matthias; Löffelbein, Florian
2009-06-01
The Marfan syndrome is an inherited disorder of the connective tissue which is mainly caused by a mutation in the fibrillin-1 gene. The defect in the connective tissue protein can lead to several organ dysfunctions. For the life expectancy, the cardiovascular aspect is of paramount importance. Patients with Marfan syndrome may develop aortic aneurysms and valvular heart defects. The risk of aortic aneurysms consists in the development of aortic dissection or rupture with their fatal consequences. Besides the cardiovascular manifestation, the skeletal and ocular system can also be affected. The skeletal manifestation is often characterised by long limbs, arachnodactyly, and abnormal joint flexibility along with other signs. Patients may also have dislocated lenses, ectasia of the dural sac, stretch marks, spontaneous pneumothorax, recurrent hernia, or a family history suspicious for Marfan. During the past years, other related connective tissue disorders with analogous organ manifestation have been described (e.g., Loeys-Dietz syndrome). In this article we present the basic knowledge about these connective tissue disorders, and we mention new insights in the recently explored pathophysiology of the disorder which is a possible target for future medical treatment options. Furthermore, recent new concepts for the prophylactic treatment of the aortic manifestation are explained.
Assessing connectivity related injury burden in diffuse traumatic brain injury.
Solmaz, Berkan; Tunç, Birkan; Parker, Drew; Whyte, John; Hart, Tessa; Rabinowitz, Amanda; Rohrbach, Morgan; Kim, Junghoon; Verma, Ragini
2017-03-15
Many of the clinical and behavioral manifestations of traumatic brain injury (TBI) are thought to arise from disruption to the structural network of the brain due to diffuse axonal injury (DAI). However, a principled way of summarizing diffuse connectivity alterations to quantify injury burden is lacking. In this study, we developed a connectome injury score, Disruption Index of the Structural Connectome (DISC), which summarizes the cumulative effects of TBI-induced connectivity abnormalities across the entire brain. Forty patients with moderate-to-severe TBI examined at 3 months postinjury and 35 uninjured healthy controls underwent magnetic resonance imaging with diffusion tensor imaging, and completed behavioral assessment including global clinical outcome measures and neuropsychological tests. TBI patients were selected to maximize the likelihood of DAI in the absence of large focal brain lesions. We found that hub-like regions, with high betweenness centrality, were most likely to be impaired as a result of diffuse TBI. Clustering of participants revealed a subgroup of TBI patients with similar connectivity abnormality profiles who exhibited relatively poor cognitive performance. Among TBI patients, DISC was significantly correlated with post-traumatic amnesia, verbal learning, executive function, and processing speed. Our experiments jointly demonstrated that assessing structural connectivity alterations may be useful in development of patient-oriented diagnostic and prognostic tools. Hum Brain Mapp, 2017. © 2017 Wiley Periodicals, Inc.
Enhanced economic connectivity to foster heat stress-related losses.
Wenz, Leonie; Levermann, Anders
2016-06-01
Assessing global impacts of unexpected meteorological events in an increasingly connected world economy is important for estimating the costs of climate change. We show that since the beginning of the 21st century, the structural evolution of the global supply network has been such as to foster an increase of climate-related production losses. We compute first- and higher-order losses from heat stress-induced reductions in productivity under changing economic and climatic conditions between 1991 and 2011. Since 2001, the economic connectivity has augmented in such a way as to facilitate the cascading of production loss. The influence of this structural change has dominated over the effect of the comparably weak climate warming during this decade. Thus, particularly under future warming, the intensification of international trade has the potential to amplify climate losses if no adaptation measures are taken.
Enhanced economic connectivity to foster heat stress–related losses
Wenz, Leonie; Levermann, Anders
2016-01-01
Assessing global impacts of unexpected meteorological events in an increasingly connected world economy is important for estimating the costs of climate change. We show that since the beginning of the 21st century, the structural evolution of the global supply network has been such as to foster an increase of climate-related production losses. We compute first- and higher-order losses from heat stress–induced reductions in productivity under changing economic and climatic conditions between 1991 and 2011. Since 2001, the economic connectivity has augmented in such a way as to facilitate the cascading of production loss. The influence of this structural change has dominated over the effect of the comparably weak climate warming during this decade. Thus, particularly under future warming, the intensification of international trade has the potential to amplify climate losses if no adaptation measures are taken. PMID:27386555
Generalized entropies and logarithms and their duality relations
Hanel, Rudolf; Thurner, Stefan; Gell-Mann, Murray
2012-01-01
For statistical systems that violate one of the four Shannon–Khinchin axioms, entropy takes a more general form than the Boltzmann–Gibbs entropy. The framework of superstatistics allows one to formulate a maximum entropy principle with these generalized entropies, making them useful for understanding distribution functions of non-Markovian or nonergodic complex systems. For such systems where the composability axiom is violated there exist only two ways to implement the maximum entropy principle, one using escort probabilities, the other not. The two ways are connected through a duality. Here we show that this duality fixes a unique escort probability, which allows us to derive a complete theory of the generalized logarithms that naturally arise from the violation of this axiom. We then show how the functional forms of these generalized logarithms are related to the asymptotic scaling behavior of the entropy. PMID:23129618
Affine generalization of the Komar complex of general relativity
NASA Astrophysics Data System (ADS)
Mielke, Eckehard W.
2001-02-01
On the basis of the ``on shell'' Noether identities of the metric-affine gauge approach of gravity, an affine superpotential is derived which comprises the energy- and angular-momentum content of exact solutions. In the special case of general relativity (GR) or its teleparallel equivalent, the Komar or Freud complex, respectively, are recovered. Applying this to the spontaneously broken anti-de Sitter gauge model of McDowell and Mansouri with an induced Euler term automatically yields the correct mass and spin of the Kerr-AdS solution of GR with a (induced) cosmological constant without the factor two discrepancy of the Komar formula.
Gökdeniz, Erinç; Özgür, Arzucan; Canbeyli, Reşit
2016-01-01
Identifying the relations among different regions of the brain is vital for a better understanding of how the brain functions. While a large number of studies have investigated the neuroanatomical and neurochemical connections among brain structures, their specific findings are found in publications scattered over a large number of years and different types of publications. Text mining techniques have provided the means to extract specific types of information from a large number of publications with the aim of presenting a larger, if not necessarily an exhaustive picture. By using natural language processing techniques, the present paper aims to identify connectivity relations among brain regions in general and relations relevant to the paraventricular nucleus of the thalamus (PVT) in particular. We introduce a linguistically motivated approach based on patterns defined over the constituency and dependency parse trees of sentences. Besides the presence of a relation between a pair of brain regions, the proposed method also identifies the directionality of the relation, which enables the creation and analysis of a directional brain region connectivity graph. The approach is evaluated over the manually annotated data sets of the WhiteText Project. In addition, as a case study, the method is applied to extract and analyze the connectivity graph of PVT, which is an important brain region that is considered to influence many functions ranging from arousal, motivation, and drug-seeking behavior to attention. The results of the PVT connectivity graph show that PVT may be a new target of research in mood assessment. PMID:27708573
Tests of general relativity using pulsars
NASA Technical Reports Server (NTRS)
Reichley, P. E.
1971-01-01
The arrival times of the pulses from each pulsar are measured by a cesium clock. The observations are all made at a frequency of 2388 MHz (12.5 cm wavelength) on a 26 m dish antenna. The effect of interstellar charged particles is a random one that increases the noise level on the arrival time measurements. The variation in clock rate is shown consisting of two effects: the time dilation effect of special relativity and the red shift effect of general relativity.
Tests of General Relativity with GW150914
NASA Astrophysics Data System (ADS)
Abbott, B. P.; Abbott, R.; Abbott, T. D.; Abernathy, M. R.; Acernese, F.; Ackley, K.; Adams, C.; Adams, T.; Addesso, P.; Adhikari, R. X.; Adya, V. B.; Affeldt, C.; Agathos, M.; Agatsuma, K.; Aggarwal, N.; Aguiar, O. D.; Aiello, L.; Ain, A.; Ajith, P.; Allen, B.; Allocca, A.; Altin, P. A.; Anderson, S. B.; Anderson, W. G.; Arai, K.; Araya, M. C.; Arceneaux, C. C.; Areeda, J. S.; Arnaud, N.; Arun, K. G.; Ascenzi, S.; Ashton, G.; Ast, M.; Aston, S. M.; Astone, P.; Aufmuth, P.; Aulbert, C.; Babak, S.; Bacon, P.; Bader, M. K. M.; Baker, P. T.; Baldaccini, F.; Ballardin, G.; Ballmer, S. W.; Barayoga, J. C.; Barclay, S. E.; Barish, B. C.; Barker, D.; Barone, F.; Barr, B.; Barsotti, L.; Barsuglia, M.; Barta, D.; Bartlett, J.; Bartos, I.; Bassiri, R.; Basti, A.; Batch, J. C.; Baune, C.; Bavigadda, V.; Bazzan, M.; Behnke, B.; Bejger, M.; Bell, A. S.; Bell, C. J.; Berger, B. K.; Bergman, J.; Bergmann, G.; Berry, C. P. L.; Bersanetti, D.; Bertolini, A.; Betzwieser, J.; Bhagwat, S.; Bhandare, R.; Bilenko, I. A.; Billingsley, G.; Birch, J.; Birney, R.; Birnholtz, O.; Biscans, S.; Bisht, A.; Bitossi, M.; Biwer, C.; Bizouard, M. A.; Blackburn, J. K.; Blair, C. D.; Blair, D. G.; Blair, R. M.; Bloemen, S.; Bock, O.; Bodiya, T. P.; Boer, M.; Bogaert, G.; Bogan, C.; Bohe, A.; Bojtos, P.; Bond, C.; Bondu, F.; Bonnand, R.; Boom, B. A.; Bork, R.; Boschi, V.; Bose, S.; Bouffanais, Y.; Bozzi, A.; Bradaschia, C.; Brady, P. R.; Braginsky, V. B.; Branchesi, M.; Brau, J. E.; Briant, T.; Brillet, A.; Brinkmann, M.; Brisson, V.; Brockill, P.; Brooks, A. F.; Brown, D. A.; Brown, D. D.; Brown, N. M.; Buchanan, C. C.; Buikema, A.; Bulik, T.; Bulten, H. J.; Buonanno, A.; Buskulic, D.; Buy, C.; Byer, R. L.; Cadonati, L.; Cagnoli, G.; Cahillane, C.; Calderón Bustillo, J.; Callister, T.; Calloni, E.; Camp, J. B.; Cannon, K. C.; Cao, J.; Capano, C. D.; Capocasa, E.; Carbognani, F.; Caride, S.; Casanueva Diaz, J.; Casentini, C.; Caudill, S.; Cavaglià, M.; Cavalier, F.; Cavalieri, R.; Cella, G.; Cepeda, C. B.; Cerboni Baiardi, L.; Cerretani, G.; Cesarini, E.; Chakraborty, R.; Chalermsongsak, T.; Chamberlin, S. J.; Chan, M.; Chao, S.; Charlton, P.; Chassande-Mottin, E.; Chen, H. Y.; Chen, Y.; Cheng, C.; Chincarini, A.; Chiummo, A.; Cho, H. S.; Cho, M.; Chow, J. H.; Christensen, N.; Chu, Q.; Chua, S.; Chung, S.; Ciani, G.; Clara, F.; Clark, J. A.; Cleva, F.; Coccia, E.; Cohadon, P.-F.; Colla, A.; Collette, C. G.; Cominsky, L.; Constancio, M.; Conte, A.; Conti, L.; Cook, D.; Corbitt, T. R.; Cornish, N.; Corsi, A.; Cortese, S.; Costa, C. A.; Coughlin, M. W.; Coughlin, S. B.; Coulon, J.-P.; Countryman, S. T.; Couvares, P.; Cowan, E. E.; Coward, D. M.; Cowart, M. J.; Coyne, D. C.; Coyne, R.; Craig, K.; Creighton, J. D. E.; Cripe, J.; Crowder, S. G.; Cumming, A.; Cunningham, L.; Cuoco, E.; Dal Canton, T.; Danilishin, S. L.; D'Antonio, S.; Danzmann, K.; Darman, N. S.; Dattilo, V.; Dave, I.; Daveloza, H. P.; Davier, M.; Davies, G. S.; Daw, E. J.; Day, R.; DeBra, D.; Debreczeni, G.; Degallaix, J.; De Laurentis, M.; Deléglise, S.; Del Pozzo, W.; Denker, T.; Dent, T.; Dereli, H.; Dergachev, V.; De Rosa, R.; DeRosa, R. T.; DeSalvo, R.; Dhurandhar, S.; Díaz, M. C.; Di Fiore, L.; Di Giovanni, M.; Di Lieto, A.; Di Pace, S.; Di Palma, I.; Di Virgilio, A.; Dojcinoski, G.; Dolique, V.; Donovan, F.; Dooley, K. L.; Doravari, S.; Douglas, R.; Downes, T. P.; Drago, M.; Drever, R. W. P.; Driggers, J. C.; Du, Z.; Ducrot, M.; Dwyer, S. E.; Edo, T. B.; Edwards, M. C.; Effler, A.; Eggenstein, H.-B.; Ehrens, P.; Eichholz, J.; Eikenberry, S. S.; Engels, W.; Essick, R. C.; Etzel, T.; Evans, M.; Evans, T. M.; Everett, R.; Factourovich, M.; Fafone, V.; Fair, H.; Fairhurst, S.; Fan, X.; Fang, Q.; Farinon, S.; Farr, B.; Farr, W. M.; Favata, M.; Fays, M.; Fehrmann, H.; Fejer, M. M.; Ferrante, I.; Ferreira, E. C.; Ferrini, F.; Fidecaro, F.; Fiori, I.; Fiorucci, D.; Fisher, R. P.; Flaminio, R.; Fletcher, M.; Fournier, J.-D.; Franco, S.; Frasca, S.; Frasconi, F.; Frei, Z.; Freise, A.; Frey, R.; Frey, V.; Fricke, T. T.; Fritschel, P.; Frolov, V. V.; Fulda, P.; Fyffe, M.; Gabbard, H. A. G.; Gair, J. R.; Gammaitoni, L.; Gaonkar, S. G.; Garufi, F.; Gatto, A.; Gaur, G.; Gehrels, N.; Gemme, G.; Gendre, B.; Genin, E.; Gennai, A.; George, J.; Gergely, L.; Germain, V.; Ghosh, Abhirup; Ghosh, Archisman; Ghosh, S.; Giaime, J. A.; Giardina, K. D.; Giazotto, A.; Gill, K.; Glaefke, A.; Goetz, E.; Goetz, R.; Gondan, L.; González, G.; Gonzalez Castro, J. M.; Gopakumar, A.; Gordon, N. A.; Gorodetsky, M. L.; Gossan, S. E.; Gosselin, M.; Gouaty, R.; Graef, C.; Graff, P. B.; Granata, M.; Grant, A.; Gras, S.; Gray, C.; Greco, G.; Green, A. C.; Groot, P.; Grote, H.; Grunewald, S.; Guidi, G. M.; Guo, X.; Gupta, A.; Gupta, M. K.; Gushwa, K. E.; Gustafson, E. K.; Gustafson, R.; Hacker, J. J.; Hall, B. R.; Hall, E. D.; Hammond, G.; Haney, M.; Hanke, M. M.; Hanks, J.; Hanna, C.; Hannam, M. D.; Hanson, J.; Hardwick, T.; Harms, J.; Harry, G. M.; Harry, I. W.; Hart, M. J.; Hartman, M. T.; Haster, C.-J.; Haughian, K.; Healy, J.; Heidmann, A.; Heintze, M. C.; Heitmann, H.; Hello, P.; Hemming, G.; Hendry, M.; Heng, I. S.; Hennig, J.; Heptonstall, A. W.; Heurs, M.; Hild, S.; Hoak, D.; Hodge, K. A.; Hofman, D.; Hollitt, S. E.; Holt, K.; Holz, D. E.; Hopkins, P.; Hosken, D. J.; Hough, J.; Houston, E. A.; Howell, E. J.; Hu, Y. M.; Huang, S.; Huerta, E. A.; Huet, D.; Hughey, B.; Husa, S.; Huttner, S. H.; Huynh-Dinh, T.; Idrisy, A.; Indik, N.; Ingram, D. R.; Inta, R.; Isa, H. N.; Isac, J.-M.; Isi, M.; Islas, G.; Isogai, T.; Iyer, B. R.; Izumi, K.; Jacqmin, T.; Jang, H.; Jani, K.; Jaranowski, P.; Jawahar, S.; Jiménez-Forteza, F.; Johnson, W. W.; Johnson-McDaniel, N. K.; Jones, D. I.; Jones, R.; Jonker, R. J. G.; Ju, L.; Haris, M. K.; Kalaghatgi, C. V.; Kalogera, V.; Kandhasamy, S.; Kang, G.; Kanner, J. B.; Karki, S.; Kasprzack, M.; Katsavounidis, E.; Katzman, W.; Kaufer, S.; Kaur, T.; Kawabe, K.; Kawazoe, F.; Kéfélian, F.; Kehl, M. S.; Keitel, D.; Kelley, D. B.; Kells, W.; Kennedy, R.; Key, J. S.; Khalaidovski, A.; Khalili, F. Y.; Khan, I.; Khan, S.; Khan, Z.; Khazanov, E. A.; Kijbunchoo, N.; Kim, C.; Kim, J.; Kim, K.; Kim, Nam-Gyu; Kim, Namjun; Kim, Y.-M.; King, E. J.; King, P. J.; Kinzel, D. L.; Kissel, J. S.; Kleybolte, L.; Klimenko, S.; Koehlenbeck, S. M.; Kokeyama, K.; Koley, S.; Kondrashov, V.; Kontos, A.; Korobko, M.; Korth, W. Z.; Kowalska, I.; Kozak, D. B.; Kringel, V.; Krishnan, B.; Królak, A.; Krueger, C.; Kuehn, G.; Kumar, P.; Kuo, L.; Kutynia, A.; Lackey, B. D.; Landry, M.; Lange, J.; Lantz, B.; Lasky, P. D.; Lazzarini, A.; Lazzaro, C.; Leaci, P.; Leavey, S.; Lebigot, E. O.; Lee, C. H.; Lee, H. K.; Lee, H. M.; Lee, K.; Lenon, A.; Leonardi, M.; Leong, J. R.; Leroy, N.; Letendre, N.; Levin, Y.; Levine, B. M.; Li, T. G. F.; Libson, A.; Littenberg, T. B.; Lockerbie, N. A.; Logue, J.; Lombardi, A. L.; London, L. T.; Lord, J. E.; Lorenzini, M.; Loriette, V.; Lormand, M.; Losurdo, G.; Lough, J. D.; Lousto, C. O.; Lovelace, G.; Lück, H.; Lundgren, A. P.; Luo, J.; Lynch, R.; Ma, Y.; MacDonald, T.; Machenschalk, B.; MacInnis, M.; Macleod, D. M.; Magaña-Sandoval, F.; Magee, R. M.; Mageswaran, M.; Majorana, E.; Maksimovic, I.; Malvezzi, V.; Man, N.; Mandel, I.; Mandic, V.; Mangano, V.; Mansell, G. L.; Manske, M.; Mantovani, M.; Marchesoni, F.; Marion, F.; Márka, S.; Márka, Z.; Markosyan, A. S.; Maros, E.; Martelli, F.; Martellini, L.; Martin, I. W.; Martin, R. M.; Martynov, D. V.; Marx, J. N.; Mason, K.; Masserot, A.; Massinger, T. J.; Masso-Reid, M.; Matichard, F.; Matone, L.; Mavalvala, N.; Mazumder, N.; Mazzolo, G.; McCarthy, R.; McClelland, D. E.; McCormick, S.; McGuire, S. C.; McIntyre, G.; McIver, J.; McManus, D. J.; McWilliams, S. T.; Meacher, D.; Meadors, G. D.; Meidam, J.; Melatos, A.; Mendell, G.; Mendoza-Gandara, D.; Mercer, R. A.; Merilh, E.; Merzougui, M.; Meshkov, S.; Messenger, C.; Messick, C.; Meyers, P. M.; Mezzani, F.; Miao, H.; Michel, C.; Middleton, H.; Mikhailov, E. E.; Milano, L.; Miller, J.; Millhouse, M.; Minenkov, Y.; Ming, J.; Mirshekari, S.; Mishra, C.; Mitra, S.; Mitrofanov, V. P.; Mitselmakher, G.; Mittleman, R.; Moggi, A.; Mohan, M.; Mohapatra, S. R. P.; Montani, M.; Moore, B. C.; Moore, C. J.; Moraru, D.; Moreno, G.; Morriss, S. R.; Mossavi, K.; Mours, B.; Mow-Lowry, C. M.; Mueller, C. L.; Mueller, G.; Muir, A. W.; Mukherjee, Arunava; Mukherjee, D.; Mukherjee, S.; Mukund, N.; Mullavey, A.; Munch, J.; Murphy, D. J.; Murray, P. G.; Mytidis, A.; Nardecchia, I.; Naticchioni, L.; Nayak, R. K.; Necula, V.; Nedkova, K.; Nelemans, G.; Neri, M.; Neunzert, A.; Newton, G.; Nguyen, T. T.; Nielsen, A. B.; Nissanke, S.; Nitz, A.; Nocera, F.; Nolting, D.; Normandin, M. E.; Nuttall, L. K.; Oberling, J.; Ochsner, E.; O'Dell, J.; Oelker, E.; Ogin, G. H.; Oh, J. J.; Oh, S. H.; Ohme, F.; Oliver, M.; Oppermann, P.; Oram, Richard J.; O'Reilly, B.; O'Shaughnessy, R.; Ottaway, D. J.; Ottens, R. S.; Overmier, H.; Owen, B. J.; Pai, A.; Pai, S. A.; Palamos, J. R.; Palashov, O.; Palomba, C.; Pal-Singh, A.; Pan, H.; Pan, Y.; Pankow, C.; Pannarale, F.; Pant, B. C.; Paoletti, F.; Paoli, A.; Papa, M. A.; Paris, H. R.; Parker, W.; Pascucci, D.; Pasqualetti, A.; Passaquieti, R.; Passuello, D.; Patricelli, B.; Patrick, Z.; Pearlstone, B. L.; Pedraza, M.; Pedurand, R.; Pekowsky, L.; Pele, A.; Penn, S.; Perreca, A.; Pfeiffer, H. P.; Phelps, M.; Piccinni, O.; Pichot, M.; Piergiovanni, F.; Pierro, V.; Pillant, G.; Pinard, L.; Pinto, I. M.; Pitkin, M.; Poggiani, R.; Popolizio, P.; Post, A.; Powell, J.; Prasad, J.; Predoi, V.; Premachandra, S. S.; Prestegard, T.; Price, L. R.; Prijatelj, M.; Principe, M.; Privitera, S.; Prix, R.; Prodi, G. A.; Prokhorov, L.; Puncken, O.; Punturo, M.; Puppo, P.; Pürrer, M.; Qi, H.; Qin, J.; Quetschke, V.; Quintero, E. 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L.; Warner, J.; Was, M.; Weaver, B.; Wei, L.-W.; Weinert, M.; Weinstein, A. J.; Weiss, R.; Welborn, T.; Wen, L.; Weßels, P.; Westphal, T.; Wette, K.; Whelan, J. T.; White, D. J.; Whiting, B. F.; Williams, D.; Williams, R. D.; Williamson, A. R.; Willis, J. L.; Willke, B.; Wimmer, M. H.; Winkler, W.; Wipf, C. C.; Wittel, H.; Woan, G.; Worden, J.; Wright, J. L.; Wu, G.; Yablon, J.; Yam, W.; Yamamoto, H.; Yancey, C. C.; Yap, M. J.; Yu, H.; Yvert, M.; ZadroŻny, A.; Zangrando, L.; Zanolin, M.; Zendri, J.-P.; Zevin, M.; Zhang, F.; Zhang, L.; Zhang, M.; Zhang, Y.; Zhao, C.; Zhou, M.; Zhou, Z.; Zhu, X. J.; Zucker, M. E.; Zuraw, S. E.; Zweizig, J.; Boyle, M.; Campanelli, M.; Hemberger, D. A.; Kidder, L. E.; Ossokine, S.; Scheel, M. A.; Szilagyi, B.; Teukolsky, S.; Zlochower, Y.; LIGO Scientific; Virgo Collaborations
2016-06-01
The LIGO detection of GW150914 provides an unprecedented opportunity to study the two-body motion of a compact-object binary in the large-velocity, highly nonlinear regime, and to witness the final merger of the binary and the excitation of uniquely relativistic modes of the gravitational field. We carry out several investigations to determine whether GW150914 is consistent with a binary black-hole merger in general relativity. We find that the final remnant's mass and spin, as determined from the low-frequency (inspiral) and high-frequency (postinspiral) phases of the signal, are mutually consistent with the binary black-hole solution in general relativity. Furthermore, the data following the peak of GW150914 are consistent with the least-damped quasinormal mode inferred from the mass and spin of the remnant black hole. By using waveform models that allow for parametrized general-relativity violations during the inspiral and merger phases, we perform quantitative tests on the gravitational-wave phase in the dynamical regime and we determine the first empirical bounds on several high-order post-Newtonian coefficients. We constrain the graviton Compton wavelength, assuming that gravitons are dispersed in vacuum in the same way as particles with mass, obtaining a 90%-confidence lower bound of 1013 km . In conclusion, within our statistical uncertainties, we find no evidence for violations of general relativity in the genuinely strong-field regime of gravity.
Cooperative Education General Related Instructional Units.
ERIC Educational Resources Information Center
Arizona State Dept. of Vocational Education, Phoenix.
Resulting from the efforts of teacher-coordinators in a 3-week workshop, this study guide was designed to help student-trainees adjust to the many factors of the world of work. Including material useful in a general related class, the study guide is arranged in the following 10 units: (1) Introduction To Cooperative Education, (2) Youth Clubs and…
Does Physics Need Special and General Relativity?
NASA Astrophysics Data System (ADS)
Dunning-Davies, Jeremy
Here it is intended to reconsider briefly some of the objections which have arisen over the years to both the Special and General Theories of Relativity before raising the question of whether or not either of these two theories is actually required by modern physics.
General Relativity theory: tests through time
NASA Astrophysics Data System (ADS)
Yatskiv, Ya. S.; Alexandrov, A. N.; Vavilova, I. B.; Zhdanov, V. I.; Kudrya, Yu. N.; Parnovsky, S. L.; Fedorova, O. V.; Khmil, S. V.
2005-09-01
Theoretical basis of General relativity Theory, its experimental tests as well as GRT applications are briefly summarized taking into account the results of the last decade. The monograph addresses scientists, post-graduated students, and students specialized in the natural sciences as well as everyone who takes a great interest in GRT.
Tests of General Relativity with GW150914.
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Gordon, N A; Gorodetsky, M L; Gossan, S E; Gosselin, M; Gouaty, R; Graef, C; Graff, P B; Granata, M; Grant, A; Gras, S; Gray, C; Greco, G; Green, A C; Groot, P; Grote, H; Grunewald, S; Guidi, G M; Guo, X; Gupta, A; Gupta, M K; Gushwa, K E; Gustafson, E K; Gustafson, R; Hacker, J J; Hall, B R; Hall, E D; Hammond, G; Haney, M; Hanke, M M; Hanks, J; Hanna, C; Hannam, M D; Hanson, J; Hardwick, T; Harms, J; Harry, G M; Harry, I W; Hart, M J; Hartman, M T; Haster, C-J; Haughian, K; Healy, J; Heidmann, A; Heintze, M C; Heitmann, H; Hello, P; Hemming, G; Hendry, M; Heng, I S; Hennig, J; Heptonstall, A W; Heurs, M; Hild, S; Hoak, D; Hodge, K A; Hofman, D; Hollitt, S E; Holt, K; Holz, D E; Hopkins, P; Hosken, D J; Hough, J; Houston, E A; Howell, E J; Hu, Y M; Huang, S; Huerta, E A; Huet, D; Hughey, B; Husa, S; Huttner, S H; Huynh-Dinh, T; Idrisy, A; Indik, N; Ingram, D R; Inta, R; Isa, H N; Isac, J-M; Isi, M; Islas, G; Isogai, T; Iyer, B R; Izumi, K; Jacqmin, T; Jang, H; Jani, K; Jaranowski, P; Jawahar, S; Jiménez-Forteza, F; Johnson, W W; Johnson-McDaniel, N K; Jones, D I; Jones, R; Jonker, R J G; Ju, L; Haris, M K; Kalaghatgi, C V; Kalogera, V; Kandhasamy, S; Kang, G; Kanner, J B; Karki, S; Kasprzack, M; Katsavounidis, E; Katzman, W; Kaufer, S; Kaur, T; Kawabe, K; Kawazoe, F; Kéfélian, F; Kehl, M S; Keitel, D; Kelley, D B; Kells, W; Kennedy, R; Key, J S; Khalaidovski, A; Khalili, F Y; Khan, I; Khan, S; Khan, Z; Khazanov, E A; Kijbunchoo, N; Kim, C; Kim, J; Kim, K; Kim, Nam-Gyu; Kim, Namjun; Kim, Y-M; King, E J; King, P J; Kinzel, D L; Kissel, J S; Kleybolte, L; Klimenko, S; Koehlenbeck, S M; Kokeyama, K; Koley, S; Kondrashov, V; Kontos, A; Korobko, M; Korth, W Z; Kowalska, I; Kozak, D B; Kringel, V; Krishnan, B; Królak, A; Krueger, C; Kuehn, G; Kumar, P; Kuo, L; Kutynia, A; Lackey, B D; Landry, M; Lange, J; Lantz, B; Lasky, P D; Lazzarini, A; Lazzaro, C; Leaci, P; Leavey, S; Lebigot, E O; Lee, C H; Lee, H K; Lee, H M; Lee, K; Lenon, A; Leonardi, M; Leong, J R; Leroy, N; Letendre, N; Levin, Y; Levine, B M; Li, T G F; Libson, A; Littenberg, T B; Lockerbie, N A; Logue, J; Lombardi, A L; London, L T; Lord, J E; Lorenzini, M; Loriette, V; Lormand, M; Losurdo, G; Lough, J D; Lousto, C O; Lovelace, G; Lück, H; Lundgren, A P; Luo, J; Lynch, R; Ma, Y; MacDonald, T; Machenschalk, B; MacInnis, M; Macleod, D M; Magaña-Sandoval, F; Magee, R M; Mageswaran, M; Majorana, E; Maksimovic, I; Malvezzi, V; Man, N; Mandel, I; Mandic, V; Mangano, V; Mansell, G L; Manske, M; Mantovani, M; Marchesoni, F; Marion, F; Márka, S; Márka, Z; Markosyan, A S; Maros, E; Martelli, F; Martellini, L; Martin, I W; Martin, R M; Martynov, D V; Marx, J N; Mason, K; Masserot, A; Massinger, T J; Masso-Reid, M; Matichard, F; Matone, L; Mavalvala, N; Mazumder, N; Mazzolo, G; McCarthy, R; McClelland, D E; McCormick, S; McGuire, S C; McIntyre, G; McIver, J; McManus, D J; McWilliams, S T; Meacher, D; Meadors, G D; Meidam, J; Melatos, A; Mendell, G; Mendoza-Gandara, D; Mercer, R A; Merilh, E; Merzougui, M; Meshkov, S; Messenger, C; Messick, C; Meyers, P M; Mezzani, F; Miao, H; Michel, C; Middleton, H; Mikhailov, E E; Milano, L; Miller, J; Millhouse, M; Minenkov, Y; Ming, J; Mirshekari, S; Mishra, C; Mitra, S; Mitrofanov, V P; Mitselmakher, G; Mittleman, R; Moggi, A; Mohan, M; Mohapatra, S R P; Montani, M; Moore, B C; Moore, C J; Moraru, D; Moreno, G; Morriss, S R; Mossavi, K; Mours, B; Mow-Lowry, C M; Mueller, C L; Mueller, G; Muir, A W; Mukherjee, Arunava; Mukherjee, D; Mukherjee, S; Mukund, N; Mullavey, A; Munch, J; Murphy, D J; Murray, P G; Mytidis, A; Nardecchia, I; Naticchioni, L; Nayak, R K; Necula, V; Nedkova, K; Nelemans, G; Neri, M; Neunzert, A; Newton, G; Nguyen, T T; Nielsen, A B; Nissanke, S; Nitz, A; Nocera, F; Nolting, D; Normandin, M E; Nuttall, L K; Oberling, J; Ochsner, E; O'Dell, J; Oelker, E; Ogin, G H; Oh, J J; Oh, S H; Ohme, F; Oliver, M; Oppermann, P; Oram, Richard J; O'Reilly, B; O'Shaughnessy, R; Ottaway, D J; Ottens, R S; Overmier, H; Owen, B J; Pai, A; Pai, S A; Palamos, J R; Palashov, O; Palomba, C; Pal-Singh, A; Pan, H; Pan, Y; Pankow, C; Pannarale, F; Pant, B C; Paoletti, F; Paoli, A; Papa, M A; Paris, H R; Parker, W; Pascucci, D; Pasqualetti, A; Passaquieti, R; Passuello, D; Patricelli, B; Patrick, Z; Pearlstone, B L; Pedraza, M; Pedurand, R; Pekowsky, L; Pele, A; Penn, S; Perreca, A; Pfeiffer, H P; Phelps, M; Piccinni, O; Pichot, M; Piergiovanni, F; Pierro, V; Pillant, G; Pinard, L; Pinto, I M; Pitkin, M; Poggiani, R; Popolizio, P; Post, A; Powell, J; Prasad, J; Predoi, V; Premachandra, S S; Prestegard, T; Price, L R; Prijatelj, M; Principe, M; Privitera, S; Prix, R; Prodi, G A; Prokhorov, L; Puncken, O; Punturo, M; Puppo, P; Pürrer, M; Qi, H; Qin, J; Quetschke, V; Quintero, E A; Quitzow-James, R; Raab, F J; Rabeling, D S; Radkins, H; Raffai, P; Raja, S; Rakhmanov, M; Rapagnani, P; Raymond, V; Razzano, M; Re, V; Read, J; Reed, C M; Regimbau, T; Rei, L; Reid, S; Reitze, D H; Rew, H; Reyes, S D; Ricci, F; Riles, K; Robertson, N A; Robie, R; Robinet, F; Rocchi, A; Rolland, L; Rollins, J G; Roma, V J; Romano, R; Romanov, G; Romie, J H; Rosińska, D; Rowan, S; Rüdiger, A; Ruggi, P; Ryan, K; Sachdev, S; Sadecki, T; Sadeghian, L; Salconi, L; Saleem, M; Salemi, F; Samajdar, A; Sammut, L; Sanchez, E J; Sandberg, V; Sandeen, B; Sanders, J R; Sassolas, B; Sathyaprakash, B S; Saulson, P R; Sauter, O; Savage, R L; Sawadsky, A; Schale, P; Schilling, R; Schmidt, J; Schmidt, P; Schnabel, R; Schofield, R M S; Schönbeck, A; Schreiber, E; Schuette, D; Schutz, B F; Scott, J; Scott, S M; Sellers, D; Sengupta, A S; Sentenac, D; Sequino, V; Sergeev, A; Serna, G; Setyawati, Y; Sevigny, A; Shaddock, D A; Shah, S; Shahriar, M S; Shaltev, M; Shao, Z; Shapiro, B; Shawhan, P; Sheperd, A; Shoemaker, D H; Shoemaker, D M; Siellez, K; Siemens, X; Sigg, D; Silva, A D; Simakov, D; Singer, A; Singer, L P; Singh, A; Singh, R; Singhal, A; Sintes, A M; Slagmolen, B J J; Smith, J R; Smith, N D; Smith, R J E; Son, E J; Sorazu, B; Sorrentino, F; Souradeep, T; Srivastava, A K; Staley, A; Steinke, M; Steinlechner, J; Steinlechner, S; Steinmeyer, D; Stephens, B C; Stone, R; Strain, K A; Straniero, N; Stratta, G; Strauss, N A; Strigin, S; Sturani, R; Stuver, A L; Summerscales, T Z; Sun, L; Sutton, P J; Swinkels, B L; Szczepańczyk, M J; Tacca, M; Talukder, D; Tanner, D B; Tápai, M; Tarabrin, S P; Taracchini, A; Taylor, R; Theeg, T; Thirugnanasambandam, M P; Thomas, E G; Thomas, M; Thomas, P; Thorne, K A; Thorne, K S; Thrane, E; Tiwari, S; Tiwari, V; Tokmakov, K V; Tomlinson, C; Tonelli, M; Torres, C V; Torrie, C I; Töyrä, D; Travasso, F; Traylor, G; Trifirò, D; Tringali, M C; Trozzo, L; Tse, M; Turconi, M; Tuyenbayev, D; Ugolini, D; Unnikrishnan, C S; Urban, A L; Usman, S A; Vahlbruch, H; Vajente, G; Valdes, G; Vallisneri, M; van Bakel, N; van Beuzekom, M; van den Brand, J F J; Van Den Broeck, C; Vander-Hyde, D C; van der Schaaf, L; van Heijningen, J V; van Veggel, A A; Vardaro, M; Vass, S; Vasúth, M; Vaulin, R; Vecchio, A; Vedovato, G; Veitch, J; Veitch, P J; Venkateswara, K; Verkindt, D; Vetrano, F; Viceré, A; Vinciguerra, S; Vine, D J; Vinet, J-Y; Vitale, S; Vo, T; Vocca, H; Vorvick, C; Voss, D; Vousden, W D; Vyatchanin, S P; Wade, A R; Wade, L E; Wade, M; Walker, M; Wallace, L; Walsh, S; Wang, G; Wang, H; Wang, M; Wang, X; Wang, Y; Ward, R L; Warner, J; Was, M; Weaver, B; Wei, L-W; Weinert, M; Weinstein, A J; Weiss, R; Welborn, T; Wen, L; Weßels, P; Westphal, T; Wette, K; Whelan, J T; White, D J; Whiting, B F; Williams, D; Williams, R D; Williamson, A R; Willis, J L; Willke, B; Wimmer, M H; Winkler, W; Wipf, C C; Wittel, H; Woan, G; Worden, J; Wright, J L; Wu, G; Yablon, J; Yam, W; Yamamoto, H; Yancey, C C; Yap, M J; Yu, H; Yvert, M; Zadrożny, A; Zangrando, L; Zanolin, M; Zendri, J-P; Zevin, M; Zhang, F; Zhang, L; Zhang, M; Zhang, Y; Zhao, C; Zhou, M; Zhou, Z; Zhu, X J; Zucker, M E; Zuraw, S E; Zweizig, J; Boyle, M; Campanelli, M; Hemberger, D A; Kidder, L E; Ossokine, S; Scheel, M A; Szilagyi, B; Teukolsky, S; Zlochower, Y
2016-06-03
The LIGO detection of GW150914 provides an unprecedented opportunity to study the two-body motion of a compact-object binary in the large-velocity, highly nonlinear regime, and to witness the final merger of the binary and the excitation of uniquely relativistic modes of the gravitational field. We carry out several investigations to determine whether GW150914 is consistent with a binary black-hole merger in general relativity. We find that the final remnant's mass and spin, as determined from the low-frequency (inspiral) and high-frequency (postinspiral) phases of the signal, are mutually consistent with the binary black-hole solution in general relativity. Furthermore, the data following the peak of GW150914 are consistent with the least-damped quasinormal mode inferred from the mass and spin of the remnant black hole. By using waveform models that allow for parametrized general-relativity violations during the inspiral and merger phases, we perform quantitative tests on the gravitational-wave phase in the dynamical regime and we determine the first empirical bounds on several high-order post-Newtonian coefficients. We constrain the graviton Compton wavelength, assuming that gravitons are dispersed in vacuum in the same way as particles with mass, obtaining a 90%-confidence lower bound of 10^{13} km. In conclusion, within our statistical uncertainties, we find no evidence for violations of general relativity in the genuinely strong-field regime of gravity.
General Relativity in the Undergraduate Physics Curriculum
NASA Astrophysics Data System (ADS)
Hartle, James
2005-04-01
Einstein's theory of gravitation --- general relativity--- will shortly be a century old. At is core is one of the most beautiful and revolutionary conceptions of modern science --- the idea that gravity is the geometry of four-dimensional curved spacetime. Together with quantum theory, general relativity is one of the two most profound developments of twentieth century physics. General relativity underlies our understanding of the universe on the largest distance scales, and is central to the the explanation of such frontier astrophysical phenomena gravitational collapse,black holes, X-ray sources, neutron stars, active galactic nuclei, gravitational waves, and the big bang. General relativity is the intellectual origin of many ideas in contemporary elementary particle physics such as string theory. This talk will make the case that an introduction to general relativity is naturally a part education of every undergraduate physics major, and describe a `physics first' approach to teaching at that level. The simplest physically relevant solutions of the Einstein equation, such as those representing black holes, simple cosmologies, and gravitational waves, are presented first without derivation. Their observational consequences are explored by the study of the motion of test particles and light rays in them.This brings the student to the physical phenomena as quickly aspossible. It is the part of the subject most directly connectedto classical mechanics, and requires the minimum of new mathematical ideas. The Einstein equation is introduced later to show where these geometries originate. A course for junior or senior level physics students based on theseprinciples has been part of the undergraduate curriculum at the University of California, Santa Barbara for several decades. It works.
BOOK REVIEW: Advanced Mechanics and General Relativity Advanced Mechanics and General Relativity
NASA Astrophysics Data System (ADS)
Louko, Jorma
2011-04-01
Joel Franklin's textbook `Advanced Mechanics and General Relativity' comprises two partially overlapping, partially complementary introductory paths into general relativity at advanced undergraduate level. Path I starts with the Lagrangian and Hamiltonian formulations of Newtonian point particle motion, emphasising the action principle and the connection between symmetries and conservation laws. The concepts are then adapted to point particle motion in Minkowski space, introducing Lorentz transformations as symmetries of the action. There follows a focused development of tensor calculus, parallel transport and curvature, using examples from Newtonian mechanics and special relativity, culminating in the field equations of general relativity. The Schwarzschild solution is analysed, including a detailed discussion of the tidal forces on a radially infalling observer. Basics of gravitational radiation are examined, highlighting the similarities to and differences from electromagnetic radiation. The final topics in Path I are equatorial geodesics in Kerr and the motion of a relativistic string in Minkowski space. Path II starts by introducing scalar field theory on Minkowski space as a limit of point masses connected by springs, emphasising the action principle, conservation laws and the energy-momentum tensor. The action principle for electromagnetism is introduced, and the coupling of electromagnetism to a complex scalar field is developed in a detailed and pedagogical fashion. A free symmetric second-rank tensor field on Minkowski space is introduced, and the action principle of general relativity is recovered from coupling the second-rank tensor to its own energy-momentum tensor. Path II then merges with Path I and, supplanted with judicious early selections from Path I, can proceed to the Schwarzschild solution. The choice of material in each path is logical and focused. A notable example in Path I is that Lorentz transformations in Minkowki space are introduced
Leibnizian relationalism for general relativistic physics
NASA Astrophysics Data System (ADS)
Vassallo, Antonio; Esfeld, Michael
2016-08-01
An ontology of Leibnizian relationalism, consisting in distance relations among sparse matter points and their change only, is well recognized as a serious option in the context of classical mechanics. In this paper, we investigate how this ontology fares when it comes to general relativistic physics. Using a Humean strategy, we regard the gravitational field as a means to represent the overall change in the distance relations among point particles in a way that achieves the best combination of being simple and being informative.
O'Brien, G.M.; Tchrakian, D.H.
1988-05-01
In every even dimension, a modification of the generalized Yang--Mills systems (modGYM) is introduced. It is shown that spin-connection modGYM fields, which are self-dual on a double-self-dual background of generalized Einstein--Cartan (GEC) gravity, can be constructed: this generalizes the constructions of Charap and Duff (Phys. Lett. B 69, 445 (1977)) in four dimensions, to all even dimensions. Additional duality constraints are also given that must be satisfied by the gravitational fields, if these constructions are to apply also to the full GYM systems. Applications to compactification, as well as relevant physical criteria, are briefly discussed.
Spin-connection generalized Yang-Mills fields on double-dual generalized Einstein-Cartan backgrounds
NASA Astrophysics Data System (ADS)
O'Brien, G. M.; Tchrakian, D. H.
1988-05-01
In every even dimension, a modification of the generalized Yang-Mills systems (modGYM) is introduced. It is shown that spin-connection modGYM fields, which are self-dual on a double-self-dual background of generalized Einstein-Cartan (GEC) gravity, can be constructed—this generalizes the constructions of Charap and Duff [Phys. Lett. B 69, 445 (1977)] in four dimensions, to all even dimensions. Additional duality constraints are also given that must be satisfied by the gravitational fields, if these constructions are to apply also to the full GYM systems. Applications to compactification, as well as relevant physical criteria, are briefly discussed.
ERIC Educational Resources Information Center
Grush, Mary, Ed.
2006-01-01
Connectivity has dramatically changed the landscape of higher education IT. From "on-demand" services for net-gen students and advanced eLearning systems for faculty, to high-performance computing grid resources for researchers, IT now provides more networked services than ever to connect campus constituents to each other and to the world.…
Generalized Tests for Eight GRB Luminosity Relations
NASA Astrophysics Data System (ADS)
Schaefer, Bradley E.; Collazzi, Andrew C.
2007-02-01
Long-duration gamma-ray bursts (GRBs) have eight luminosity relations where observable burst properties can yield the burst luminosity and hence distance. This turns GRBs into useful tools of cosmology. Recently, two tests have been proposed (by Nakar & Piran and by Li) for which one of the eight relations is claimed to have significant problems. In this Letter, we generalize these tests and apply them to all eight GRB luminosity relations. (1) All eight relations pass the Nakar & Piran test after accounting for the uncertainties on the data and the dispersions of the correlations. (2) All eight relations are good when the GRB redshifts are known, for example, for calibration of the relations and for GRB Hubble diagram purposes. (3) We confirm the earlier results that the Eγ,iso-Epeak Amati relation must produce very large error bars whenever an unknown redshift being sought is >~1.4. (4) The Eγ-Epeak relation of Ghirlanda et al. must produce very large error bars whenever an unknown redshift being sought is >~3.4. (55) The other six relations have no problem at all from the ambiguity test of Li.
Yang, Zhiliang; Dienes, Zoltan
2013-01-01
People can implicitly learn a connection between linguistic forms and meanings, for example between specific determiners (e.g. this, that…) and the type of nouns to which they apply. Li et al (2013) recently found that transfer of form-meaning connections from a concrete domain (height) to an abstract domain (power) was achieved in a metaphor-consistent way without awareness, showing that unconscious knowledge can be abstract and flexibly deployed. The current study aims to determine whether people transfer knowledge of form-meaning connections not only from a concrete domain to an abstract one, but also vice versa, consistent with metaphor representation being bi-directional. With a similar paradigm as used by Li et al, participants learnt form- meaning connections of different domains (concrete vs. abstract) and then were tested on two kinds of generalizations (same and different domain generalization). As predicted, transfer of form-meaning connections occurred bidirectionally when structural knowledge was unconscious. Moreover, the present study also revealed that more transfer occurred between metaphorically related domains when judgment knowledge was conscious (intuition) rather than unconscious (guess). Conscious and unconscious judgment knowledge may have different functional properties. PMID:23844159
Probing the Higgs vacuum with general relativity
NASA Technical Reports Server (NTRS)
Mannheim, Philip D.; Kazanas, Demosthenes
1991-01-01
It is shown that the structure of the Higgs vacuum can be revealed in gravitational experiments which probe the Schwarzschild geometry to only one order in MG/r beyond that needed for the classical tests of general relativity. The possibility that deviations from the conventional geometry are at least theoretically conceivable is explored. The deviations obtained provide a diagnostic test for searching for the existence of macroscopic scalar fields and open up the possiblity for further exploring the Higgs mechanism.
Probing the Higgs vacuum with general relativity
NASA Technical Reports Server (NTRS)
Mannheim, Philip D.; Kazanas, Demosthenes
1991-01-01
It is shown that the structure of the Higgs vacuum can be revealed in gravitational experiments which probe the Schwarzschild geometry to only one order in MG/r beyond that needed for the classical tests of general relativity. The possibility that deviations from the conventional geometry are at least theoretically conceivable is explored. The deviations obtained provide a diagnostic test for searching for the existence of macroscopic scalar fields and open up the possiblity for further exploring the Higgs mechanism.
Teaching General Relativity to the Layperson
NASA Astrophysics Data System (ADS)
Egdall, Mark
2009-11-01
This paper describes a lay course on general relativity (GR) given at the Osher Lifelong Learning Institute at Florida International University. It is presented in six hour-and-a-half weekly sessions. Other courses offered by the author include special relativity (which precedes the course described here), quantum theory, and cosmology. Students are people 50 and older, mostly retired or semi-retired like me. They come from all walks of life, including medical doctors, ballet directors, educators, cruise line executives, and poets. Most are college educated, but with little or no formal physics education. A few have technical backgrounds, e.g., chemistry or physics.
Tests of General Theory of Relativity
NASA Astrophysics Data System (ADS)
Brynjolfsson, Ari
2002-04-01
Einstein’s theory of general relativity and experiments proving it are all in the domain of classical physics. These include experiments by Pound, Rebka, and Snider of the gravitational redshift of 14.4 keV photons; the rocket experiments by Vessot et al.; the Galileo redshift experiments by Krisher et al.; the gravitational deflection of light experiments by Riveros and Vucetich; and delay of echoes of radar signals passing close to Sun as observed by Shapiro et al. Bohr’s correspondence principle assures that the quantum mechanical theory of general relativity agrees with Einstein’s classical theory when frequency and gravitational field gradient approach zero, or when photons cannot interact with the gravitational field. Quantum theory invalidates some of the assumption made by Einstein. His argument that equally many crests of waves must arrive on Earth as leave Sun is correct in classical physics, but impermissible in quantum mechanics. We will show that solar redshift experiments contradict the classical theory and support a quantum mechanically modified theory of general relativity. This changes drastically the entire theory, including the equivalence principle.
Macrostate equivalence of two general ensembles and specific relative entropies
NASA Astrophysics Data System (ADS)
Mori, Takashi
2016-08-01
The two criteria of ensemble equivalence, i.e., macrostate equivalence and measure equivalence, are investigated for a general pair of states. Macrostate equivalence implies the two ensembles are indistinguishable by the measurement of macroscopic quantities obeying the large-deviation principle, and measure equivalence means that the specific relative entropy of these two states vanishes in the thermodynamic limit. It is shown that measure equivalence implies a macrostate equivalence for a general pair of states by deriving an inequality connecting the large-deviation rate functions to the specific relative Renyi entropies. The result is applicable to both quantum and classical systems. As applications, a sufficient condition for thermalization, the time scale of quantum dynamics of macrovariables, and the second law with strict irreversibility in a quantum quench are discussed.
Towards the quasi-localization of canonical general relativity
NASA Astrophysics Data System (ADS)
Szabados, László B.
2009-06-01
A general framework for a systematic quasi-localization of canonical general relativity and a new ingredient, the requirement of the gauge invariance of the boundary terms appearing in the calculation of Poisson brackets, are given. As a consequence of this it is shown, in particular, that the generator vector fields (built from the lapse and shift) of the quasi-local quantities must be divergence free with respect to a Sen-type connection, and the volume form induced from the spatial metric on the boundary surface must be fixed. Talk given at the Conference on Recent Results in Mathematical Relativity, The Erwin Schrödinger Institute, Vienna, 20-21 August 2008, and dedicated to Bobby Beig on the occasion of his 60th birthday.
Facilitating NCAR Data Discovery by Connecting Related Resources
NASA Astrophysics Data System (ADS)
Rosati, A.
2012-12-01
Linking datasets, creators, and users by employing the proper standards helps to increase the impact of funded research. In order for users to find a dataset, it must first be named. Data citations play the important role of giving datasets a persistent presence by assigning a formal "name" and location. This project focuses on the next step of the "name-find-use" sequence: enhancing discoverability of NCAR data by connecting related resources on the web. By examining metadata schemas that document datasets, I examined how Semantic Web approaches can help to ensure the widest possible range of data users. The focus was to move from search engine optimization (SEO) to information connectivity. Two main markup types are very visible in the Semantic Web and applicable to scientific dataset discovery: The Open Archives Initiative-Object Reuse and Exchange (OAI-ORE - www.openarchives.org) and Microdata (HTML5 and www.schema.org). My project creates pilot aggregations of related resources using both markup types for three case studies: The North American Regional Climate Change Assessment Program (NARCCAP) dataset and related publications, the Palmer Drought Severity Index (PSDI) animation and image files from NCAR's Visualization Lab (VisLab), and the multidisciplinary data types and formats from the Advanced Cooperative Arctic Data and Information Service (ACADIS). This project documents the differences between these markups and how each creates connectedness on the web. My recommendations point toward the most efficient and effective markup schema for aggregating resources within the three case studies based on the following assessment criteria: ease of use, current state of support and adoption of technology, integration with typical web tools, available vocabularies and geoinformatic standards, interoperability with current repositories and access portals (e.g. ESG, Java), and relation to data citation tools and methods.
Duarte-Carvajalino, Julio M.; Jahanshad, Neda; Lenglet, Christophe; McMahon, Katie L.; de Zubicaray, Greig I.; Martin, Nicholas G.; Wright, Margaret J.; Thompson, Paul M.
2012-01-01
Modern non-invasive brain imaging technologies, such as diffusion weighted magnetic resonance imaging (DWI), enable the mapping of neural fiber tracts in the white matter, providing a basis to reconstruct a detailed map of brain structural connectivity networks. Brain connectivity networks differ from random networks in their topology, which can be measured using small worldness, modularity, and high-degree nodes (hubs). Still, little is known about how individual differences in structural brain network properties relate to age, sex, or genetic differences. Recently, some groups have reported brain network biomarkers that enable differentiation among individuals, pairs of individuals, and groups of individuals. In addition to studying new topological features, here we provide a unifying general method to investigate topological brain networks and connectivity differences between individuals, pairs of individuals, and groups of individuals at several levels of the data hierarchy, while appropriately controlling false discovery rate (FDR) errors. We apply our new method to a large dataset of high quality brain connectivity networks obtained from High Angular Resolution Diffusion Imaging (HARDI) tractography in 303 young adult twins, siblings, and unrelated people. Our proposed approach can accurately classify brain connectivity networks based on sex (93% accuracy) and kinship (88.5% accuracy). We find statistically significant differences associated with sex and kinship both in the brain connectivity networks and in derived topological metrics, such as the clustering coefficient and the communicability matrix. PMID:22108644
On solar system dynamics in general relativity
NASA Astrophysics Data System (ADS)
Battista, Emmanuele; Esposito, Giampiero; di Fiore, Luciano; Dell'Agnello, Simone; Simo, Jules; Grado, Aniello
Recent work in the literature has advocated using the Earth-Moon-planetoid Lagrangian points as observables, in order to test general relativity and effective field theories of gravity in the solar system. However, since the three-body problem of classical celestial mechanics is just an approximation of a much more complicated setting, where all celestial bodies in the solar system are subject to their mutual gravitational interactions, while solar radiation pressure and other sources of nongravitational perturbations also affect the dynamics, it is conceptually desirable to improve the current understanding of solar system dynamics in general relativity, as a first step towards a more accurate theoretical study of orbital motion in the weak-gravity regime. For this purpose, starting from the Einstein equations in the de Donder-Lanczos gauge, this paper arrives first at the Levi-Civita Lagrangian for the geodesic motion of planets, showing in detail under which conditions the effects of internal structure and finite extension get canceled in general relativity to first post-Newtonian order. The resulting nonlinear ordinary differential equations for the motion of planets and satellites are solved for the Earth’s orbit about the Sun, written down in detail for the Sun-Earth-Moon system, and investigated for the case of planar motion of a body immersed in the gravitational field produced by the other bodies (e.g. planets with their satellites). At this stage, we prove an exact property, according to which the fourth-order time derivative of the original system leads to a linear system of ordinary differential equations. This opens an interesting perspective on forthcoming research on planetary motions in general relativity within the solar system, although the resulting equations remain a challenge for numerical and qualitative studies. Last, the evaluation of quantum corrections to location of collinear and noncollinear Lagrangian points for the planar restricted
NASA Astrophysics Data System (ADS)
Cao, Meng
The goal of this dissertation is to develop a generally covariant Hamiltonian approach to the generalized harmonic formulation of general relativity. As en route investigations, an important class of coordinate transformations in the context of the 3 + 1 decomposition, foliation preserving transformations, is defined; transformation rules of various 3 + 1 decomposition variables under this change of coordinates are investigated; the notion of covariant time derivative under foliation preserving transformations is defined; gauge conditions of various numerical relativity formulations are rewritten in generally covariant form. The Hamiltonian formulation of the generalized harmonic system is defined in the latter part of this dissertation. With the knowledge of covariant time derivative, the Hamiltonian formulation is extended to achieve general covariance. The Hamiltonian formulation is further proved to be symmetric hyperbolic.
[Relation between autoimmune thyroid diseases and connective tissue diseases].
Barragán-Garfias, Jorge Alberto; Zárate, Arturo
2013-01-01
The main physiological function of the immune system consists in the defense against infectious micro-organisms. Sometimes there is a loss of immunological tolerance with the consequence of ignorance of self-antibodies. Some thyroid diseases are related to autoimmune diseases associated with the most common exocrine glands between them. There are also the autoimmune thyroid organ specific diseases, such as Graves-Basedow and the Hashimoto thyroiditis. It has been shown that there is a higher prevalence of autoimmune thyroid diseases in patients with connective tissue diseases (systemic autoimmune) such as Sjögren syndrome, rheumatoid arthritis, systemic lupus erithmatosis and systemic myopathic diseases. In the same way a higher prevalence of antinuclear antibodies against antigens extracted from the nucleus in patients with a thyroid autoimmune disease has been identified. There is a high percentage of patients with subclinical thyroid diseases, and it is recommended for patients with connective tissue diseases with hypo- or hyperthyroidism to have thyroid globulin and peroxide antibodies measured.
2013-01-01
Background The dimensional approach to autism spectrum disorder (ASD) considers ASD as the extreme of a dimension traversing through the entire population. We explored the potential utility of electroencephalography (EEG) functional connectivity as a biomarker. We hypothesized that individual differences in autistic traits of typical subjects would involve a long-range connectivity diminution within the delta band. Methods Resting-state EEG functional connectivity was measured for 74 neurotypical subjects. All participants also provided a questionnaire (Social Responsiveness Scale, SRS) that was completed by an informant who knows the participant in social settings. We conducted multivariate regression between the SRS score and functional connectivity in all EEG frequency bands. We explored modulations of network graph metrics characterizing the optimality of a network using the SRS score. Results Our results show a decay in functional connectivity mainly within the delta and theta bands (the lower part of the EEG spectrum) associated with an increasing number of autistic traits. When inspecting the impact of autistic traits on the global organization of the functional network, we found that the optimal properties of the network are inversely related to the number of autistic traits, suggesting that the autistic dimension, throughout the entire population, modulates the efficiency of functional brain networks. Conclusions EEG functional connectivity at low frequencies and its associated network properties may be associated with some autistic traits in the general population. PMID:23806204
Complexifier coherent states for quantum general relativity
NASA Astrophysics Data System (ADS)
Thiemann, T.
2006-03-01
Recently, substantial amount of activity in quantum general relativity (QGR) has focused on the semiclassical analysis of the theory. In this paper, we want to comment on two such developments: (1) polymer-like states for Maxwell theory and linearized gravity constructed by Varadarajan which use much of the Hilbert space machinery that has proved useful in QGR, and (2) coherent states for QGR, based on the general complexifier method, with built-in semiclassical properties. We show the following. (A) Varadarajan's states are complexifier coherent states. This unifies all states constructed so far under the general complexifier principle. (B) Ashtekar and Lewandowski suggested a non-Abelian generalization of Varadarajan's states to QGR which, however, are no longer of the complexifier type. We construct a new class of non-Abelian complexifiers which come close to that underlying Varadarajan's construction. (C) Non-Abelian complexifiers close to Varadarajan's induce new types of Hilbert spaces which do not support the operator algebra of QGR. The analysis suggests that if one sticks to the present kinematical framework of QGR and if kinematical coherent states are at all useful, then normalizable, graph-dependent states must be used which are produced by the complexifier method as well. (D) Present proposals for states with mildened graph dependence, obtained by performing a graph average, do not approximate well coordinate-dependent observables. However, graph-dependent states, whether averaged or not, seem to be well suited for the semiclassical analysis of QGR with respect to coordinate-independent operators.
Strongly magnetized rotating dipole in general relativity
NASA Astrophysics Data System (ADS)
Pétri, J.
2016-10-01
Context. Electromagnetic waves arise in many areas of physics. Solutions are difficult to find in the general case. Aims: We numerically integrate Maxwell equations in a 3D spherical polar coordinate system. Methods: Straightforward finite difference methods would lead to a coordinate singularity along the polar axis. Spectral methods are better suited for such artificial singularities that are related to the choice of a coordinate system. When the radiating object rotates like a star, for example, special classes of solutions to Maxwell equations are worthwhile to study, such as quasi-stationary regimes. Moreover, in high-energy astrophysics, strong gravitational and magnetic fields are present especially around rotating neutron stars. Results: To study such systems, we designed an algorithm to solve the time-dependent Maxwell equations in spherical polar coordinates including general relativity and quantum electrodynamical corrections to leading order. As a diagnostic, we computed the spin-down luminosity expected for these stars and compared it to the classical or non-relativistic and non-quantum mechanical results. Conclusions: Quantum electrodynamics leads to an irrelevant change in the spin-down luminosity even for a magnetic field of about the critical value of 4.4 × 109 T. Therefore the braking index remains close to its value for a point dipole in vacuum, namely n = 3. The same conclusion holds for a general-relativistic quantum electrodynamically corrected force-free magnetosphere.
Resting-state functional connectivity in the Baboon Model of Genetic Generalized Epilepsy
Salinas, Felipe S.; Szabó, C. Ákos
2015-01-01
Objective The baboon provides a natural model of genetic generalized epilepsy. This study compares the intrinsic connectivity networks of epileptic and healthy control baboons using resting-state fMRI and data-driven functional connectivity mapping. Methods Twenty baboons, matched for gender, age, and weight were classified into two groups (10 epileptic, 10 control) on the basis of scalp EEG findings. Each animal underwent one MRI session which acquired one 5-minute resting state fMRI scan and one anatomical MRI scan—used for registration and spatial normalization. Using independent component analysis, we identified 14 unique components/networks, which were then used to characterize each group’s functional connectivity maps of each brain network. Results The epileptic group demonstrated network-specific differences in functional connectivity when compared to the control animals. The sensitivity and specificity of the two groups’ functional connectivity maps were significantly different in the visual, motor, amygdala, insular, and default mode networks. Significant increases were found in the occipital gyri of the epileptic group’s functional connectivity map for the default mode, cingulate, intraparietal, motor, visual, amygdala, and thalamic regions. Significance This is the first study using resting-state fMRI to demonstrate intrinsic functional connectivity differences between epileptic and control non-human primates. These results are consistent with seed-based genetic generalized epilepsy studies in humans; however, our use of a data-driven approach expands the scope of functional connectivity mapping to include brain regions/networks comprising the whole brain. PMID:26290449
On the Geodesic Hypothesis in General Relativity
NASA Astrophysics Data System (ADS)
Yang, Shiwu
2014-02-01
In this paper, we give a rigorous derivation of Einstein's geodesic hypothesis in general relativity. We use small material bodies governed by the nonlinear Klein-Gordon equations to approximate the test particle. Given a vacuum spacetime , we consider the initial value problem for the Einstein-scalar field system. For all sufficiently small ɛ and δ ≤ ɛ q , q > 1, where δ, ɛ are the amplitude and size of the particle, we show the existence of the solution to the Einstein-scalar field system with the property that the energy of the particle is concentrated along a timelike geodesic. Moreover, the gravitational field produced by is negligibly small in C 1, that is, the spacetime metric g is C 1 close to the given vacuum metric h. These results generalize those obtained by Stuart in (Ann Sci École Norm Sup (4) 37(2):312-362, 2004, J Math Pures Appl (9) 83(5):541-587, 2004).
Numerical Hydrodynamics and Magnetohydrodynamics in General Relativity.
Font, José A
2008-01-01
This article presents a comprehensive overview of numerical hydrodynamics and magneto-hydrodynamics (MHD) in general relativity. Some significant additions have been incorporated with respect to the previous two versions of this review (2000, 2003), most notably the coverage of general-relativistic MHD, a field in which remarkable activity and progress has occurred in the last few years. Correspondingly, the discussion of astrophysical simulations in general-relativistic hydrodynamics is enlarged to account for recent relevant advances, while those dealing with general-relativistic MHD are amply covered in this review for the first time. The basic outline of this article is nevertheless similar to its earlier versions, save for the addition of MHD-related issues throughout. Hence, different formulations of both the hydrodynamics and MHD equations are presented, with special mention of conservative and hyperbolic formulations well adapted to advanced numerical methods. A large sample of numerical approaches for solving such hyperbolic systems of equations is discussed, paying particular attention to solution procedures based on schemes exploiting the characteristic structure of the equations through linearized Riemann solvers. As previously stated, a comprehensive summary of astrophysical simulations in strong gravitational fields is also presented. These are detailed in three basic sections, namely gravitational collapse, black-hole accretion, and neutron-star evolutions; despite the boundaries, these sections may (and in fact do) overlap throughout the discussion. The material contained in these sections highlights the numerical challenges of various representative simulations. It also follows, to some extent, the chronological development of the field, concerning advances in the formulation of the gravitational field, hydrodynamics and MHD equations and the numerical methodology designed to solve them. To keep the length of this article reasonable, an effort has
Bf and Anti-Bf Theories in the Generalized Connection Formalism
NASA Astrophysics Data System (ADS)
Aidaoui, A.; Doebner, H.-D.; Tahiri, M.
We present a generalized connection formalism to explicitly determine an off-shell BRST-anti-BRST algebra for BF theories. This results in the construction of anti-BF theories based on an anti-BRST exact quantum action. These are not fundamentally different from BF theories, since they are in complete duality with respect to a mirror symmetry of the ghost numbers.
Generating fractal-like surfaces on general purpose mesh-connected computers
NASA Technical Reports Server (NTRS)
Wainer, Michael
1988-01-01
Realistic images of natural surfaces are often generated using computationally expensive stochastic modeling techniques. Here a parallel procedure to generate such models is presented. The target machines are general-purpose mesh-connected computers. The complexity of the procedure is similar to that of a proposed special-purpose parallel fractal generator.
Cosmological graviton production in general relativity and related gravity theories
NASA Astrophysics Data System (ADS)
de Garcia Maia, Márcio R.; Barrow, John D.
1994-11-01
A unified description of graviton creation is given for isotropic cosmological models in general relativity, Brans-Dicke theory, and higher-order gravity theories. The Bogolubov coefficents are derived in general and may be specialized to each of the possible gravity theories. The power spectrum and energy density of relic gravitons surviving a variety of early cosmological scenarios are calculated. The possibility of a nonvacuum initial state is allowed for and the problems of imposing an ultraviolet cutoff are analyzed. We distinguish carefully the effects of gravity waves on super- and subhorizon scales. The associated infrared cutoff, or the ``Allen effect,'' is discussed in detail in order to evaluate the dependence of the graviton energy density on the expansion scale factor. It is found that the nonadiabatic evolution of the graviton energy density can occur even during the radiation era when long-wavelength primoridal gravitational waves enter the horizon. Detailed, multistage, cosmological models are set up involving a sequence of changes in the equation of state for general relativity and Brans-Dicke theories. These examples include models with an inflationary phase. The resulting gravitational-wave background is calculated analytically over the whole frequency range in all cases. The limits imposed by nucleosynthesis of helium-4 are found for general relativity. We also investigate the effects of the presence of a thermal sea of gravitons in the initial state prior to gravitational-wave amplification by the expansion and calculate the effects of the small horizon size upon the thermal distributions.
New Area Law in General Relativity.
Bousso, Raphael; Engelhardt, Netta
2015-08-21
We report a new area law in general relativity. A future holographic screen is a hypersurface foliated by marginally trapped surfaces. We show that their area increases monotonically along the foliation. Future holographic screens can easily be found in collapsing stars and near a big crunch. Past holographic screens exist in any expanding universe and obey a similar theorem, yielding the first rigorous area law in big bang cosmology. Unlike event horizons, these objects can be identified at finite time and without reference to an asymptotic boundary. The Bousso bound is not used, but it naturally suggests a thermodynamic interpretation of our result.
Testing General Relativity with Atomic Clocks
NASA Astrophysics Data System (ADS)
Reynaud, S.; Salomon, C.; Wolf, P.
2009-12-01
We discuss perspectives for new tests of general relativity which are based on recent technological developments as well as new ideas. We focus our attention on tests performed with atomic clocks and do not repeat arguments present in the other contributions to the present issue (Space Sci. Rev. 2009, This Issue). In particular, we present the scientific motivations of the space projects ACES (Salomon et al. in CR Acad. Sci. IV-2:1313, 2001) and SAGAS (Wolf et al. in Exp. Astron. 23:651, 2009).
New Area Law in General Relativity
NASA Astrophysics Data System (ADS)
Bousso, Raphael; Engelhardt, Netta
2015-08-01
We report a new area law in general relativity. A future holographic screen is a hypersurface foliated by marginally trapped surfaces. We show that their area increases monotonically along the foliation. Future holographic screens can easily be found in collapsing stars and near a big crunch. Past holographic screens exist in any expanding universe and obey a similar theorem, yielding the first rigorous area law in big bang cosmology. Unlike event horizons, these objects can be identified at finite time and without reference to an asymptotic boundary. The Bousso bound is not used, but it naturally suggests a thermodynamic interpretation of our result.
Republication of: On the general relativity theory
NASA Astrophysics Data System (ADS)
Weyl, H.
2009-07-01
This English translation of the paper by H. Weyl, "Zur allgemeinen Relativitätstheorie", Physikalische Zeitschrift 24, 230-232 (1923), in which he formulated the geometrical foundations of a model of an expanding Universe, has been selected by the Editors of General Relativity and Gravitation for publication in the Golden Oldies series of the journal. The paper is accompanied by an editorial note written by Juergen Ehlers and by Weyl's brief biography compiled by Andrzej Krasiński from internet sources, with corrections provided by Weyl's son and grandson.
Solving the Vlasov equation in general relativity
NASA Astrophysics Data System (ADS)
Rasio, Frederic A.; Shapiro, Stuart L.; Teukolsky, Saul A.
1989-09-01
A new numerical method for determining the dynamical evolution of a collisionless system in full general relativity is developed. The method exploits Liouville's theorem to determine the evolution of the distribution function of matter in phase space directly. The distribution function is governed by the collisionless Boltzmann (Vlasov) equation coupled to Einstein's equations for the gravitational field. The method accurately tracks the increasingly complicated fine-grained structure developed by the distribution function due to phase mixing. It can be used to study Newtonian as well as fully relativistic systems. Applications include violent relaxation, the stability of relativistic star clusters, and the collapse of unstable relativistic star clusters to black holes.
A Machian approach to general relativity
NASA Astrophysics Data System (ADS)
Vishwakarma, Ram Gopal
2015-08-01
Mach's principle is surely one of those tantalizingly beautiful concepts in physics which remain elusive. Though general Relativity (GR) was conceived in the spirit of realizing it, the theory failed to fulfill this expectation. Here a study on the implications of imposing Mach's principle on GR with an insight that spacetime has no independent existence without a material background, is presented. This inclusion of the principle in GR turns out to be unexpectedly rewarding. The resulting theory solves many mysteries and averts lingering problems of the conventional forms of GR and cosmology.
A Machian approach to general relativity
NASA Astrophysics Data System (ADS)
Vishwakarma, Ram Gopal
2015-08-01
Mach's principle is surely one of those tantalizingly beautiful concepts in physics which remain elusive. Though general Relativity (GR) was conceived in the spirit of realizing it, the theory failed to fulfill this expectation. Here a study on the implications of imposing Mach.s principle on GR with an insight that spacetime has no independent existence without a material background, is presented. This inclusion of the principle in GR turns out to be unexpectedly rewarding. The resulting theory solves many mysteries and averts lingering problems of the conventional forms of GR and cosmology
Linear derivative Cartan formulation of general relativity
NASA Astrophysics Data System (ADS)
Kummer, W.; Schütz, H.
2005-07-01
Beside diffeomorphism invariance also manifest SO(3,1) local Lorentz invariance is implemented in a formulation of Einstein gravity (with or without cosmological term) in terms of initially completely independent vielbein and spin connection variables and auxiliary two-form fields. In the systematic study of all possible embeddings of Einstein gravity into that formulation with auxiliary fields, the introduction of a “bi-complex” algebra possesses crucial technical advantages. Certain components of the new two-form fields directly provide canonical momenta for spatial components of all Cartan variables, whereas the remaining ones act as Lagrange multipliers for a large number of constraints, some of which have been proposed already in different, less radical approaches. The time-like components of the Cartan variables play that role for the Lorentz constraints and others associated to the vierbein fields. Although also some ternary ones appear, we show that relations exist between these constraints, and how the Lagrange multipliers are to be determined to take care of second class ones. We believe that our formulation of standard Einstein gravity as a gauge theory with consistent local Poincaré algebra is superior to earlier similar attempts.
Uncertainty relations for general unitary operators
NASA Astrophysics Data System (ADS)
Bagchi, Shrobona; Pati, Arun Kumar
2016-10-01
We derive several uncertainty relations for two arbitrary unitary operators acting on physical states of a Hilbert space. We show that our bounds are tighter in various cases than the ones existing in the current literature. Using the uncertainty relation for the unitary operators, we obtain the tight state-independent lower bound for the uncertainty of two Pauli observables and anticommuting observables in higher dimensions. With regard to the minimum-uncertainty states, we derive the minimum-uncertainty state equation by the analytic method and relate this to the ground-state problem of the Harper Hamiltonian. Furthermore, the higher-dimensional limit of the uncertainty relations and minimum-uncertainty states are explored. From an operational point of view, we show that the uncertainty in the unitary operator is directly related to the visibility of quantum interference in an interferometer where one arm of the interferometer is affected by a unitary operator. This shows a principle of preparation uncertainty, i.e., for any quantum system, the amount of visibility for two general noncommuting unitary operators is nontrivially upper bounded.
The generalized scheme-independent Crewther relation in QCD
NASA Astrophysics Data System (ADS)
Shen, Jian-Ming; Wu, Xing-Gang; Ma, Yang; Brodsky, Stanley J.
2017-07-01
The Principle of Maximal Conformality (PMC) provides a systematic way to set the renormalization scales order-by-order for any perturbative QCD calculable processes. The resulting predictions are independent of the choice of renormalization scheme, a requirement of renormalization group invariance. The Crewther relation, which was originally derived as a consequence of conformally invariant field theory, provides a remarkable connection between two observables when the β function vanishes: one can show that the product of the Bjorken sum rule for spin-dependent deep inelastic lepton-nucleon scattering times the Adler function, defined from the cross section for electron-positron annihilation into hadrons, has no pQCD radiative corrections. The ;Generalized Crewther Relation; relates these two observables for physical QCD with nonzero β function; specifically, it connects the non-singlet Adler function (Dns) to the Bjorken sum rule coefficient for polarized deep-inelastic electron scattering (CBjp) at leading twist. A scheme-dependent ΔCSB-term appears in the analysis in order to compensate for the conformal symmetry breaking (CSB) terms from perturbative QCD. In conventional analyses, this normally leads to unphysical dependence in both the choice of the renormalization scheme and the choice of the initial scale at any finite order. However, by applying PMC scale-setting, we can fix the scales of the QCD coupling unambiguously at every order of pQCD. The result is that both Dns and the inverse coefficient CBjp-1 have identical pQCD coefficients, which also exactly match the coefficients of the corresponding conformal theory. Thus one obtains a new generalized Crewther relation for QCD which connects two effective charges, αˆd (Q) =∑i≥1 αˆg1 i (Qi), at their respective physical scales. This identity is independent of the choice of the renormalization scheme at any finite order, and the dependence on the choice of the initial scale is negligible. Similar
Drawing Connections Across Conceptually Related Visual Representations in Science
NASA Astrophysics Data System (ADS)
Hansen, Janice
with support for structure mapping led to a lessened reliance on surface features, and a better understanding of the science concepts presented. These findings suggest that presenting diagrams serially in an effort to reduce cognitive load may not be preferable for learning if making connections across representations, and by extension across science concepts, is desired. Instead, providing simultaneous diagrams with structure mapping support may result in greater attention to the salient relationships between related visual representations as well as between the representations and the science concepts they depict.
Generalized nonholonomic mechanics, servomechanisms and related brackets
NASA Astrophysics Data System (ADS)
Cendra, H.; Grillo, S.
2006-02-01
It is well known that nonholonomic systems obeying D'Alembert's principle are described on the Hamiltonian side, after using the Legendre transformation, by the so-called almost-Poisson brackets. In this paper we define the Lagrangian and Hamiltonian sides of a class of generalized nonholonomic systems (GNHS), obeying a generalized version of D'Alembert's principle, such as rubber wheels (like some simplified models of pneumatic tires) and certain servomechanisms (like the controlled inverted pendulum), and show that corresponding equations of motion can also be described in terms of a bracket. We present essentially all possible brackets in terms of which the mentioned equations can be written down, which include the brackets that appear in the literature, and point out those (if any) that are naturally related to each system. In particular, we show there always exists a Leibniz bracket related to a GNHS, and conversely, that every Leibniz system is a GNHS. The control of the inverted pendulum on a cart is studied as an illustrative example.
Generalized trace-distance measure connecting quantum and classical non-Markovianity
NASA Astrophysics Data System (ADS)
Wißmann, Steffen; Breuer, Heinz-Peter; Vacchini, Bassano
2015-10-01
We establish a direct connection of quantum Markovianity of an open system to its classical counterpart by generalizing the criterion based on the information flow. Here the flow is characterized by the time evolution of Helstrom matrices, given by the weighted difference of statistical operators, under the action of the quantum dynamical map. It turns out that the introduced criterion is equivalent to P divisibility of a quantum process, namely, divisibility in terms of positive maps, which provides a direct connection to classical Markovian stochastic processes. Moreover, it is shown that mathematical representations similar to those found for the original trace-distance-based measure hold true for the associated generalized measure for quantum non-Markovianity. That is, we prove orthogonality of optimal states showing a maximal information backflow and establish a local and universal representation of the measure. We illustrate some properties of the generalized criterion by means of examples.
The generalized scheme-independent Crewther relation in QCD
Shen, Jian-Ming; Wu, Xing-Gang; Ma, Yang; ...
2017-05-10
The Principle of Maximal Conformality (PMC) provides a systematic way to set the renormalization scales order-by-order for any perturbative QCD calculable processes. The resulting predictions are independent of the choice of renormalization scheme, a requirement of renormalization group invariance. The Crewther relation, which was originally derived as a consequence of conformally invariant field theory, provides a remarkable connection between two observables when the β function vanishes: one can show that the product of the Bjorken sum rule for spin-dependent deep inelastic lepton–nucleon scattering times the Adler function, defined from the cross section for electron–positron annihilation into hadrons, has no pQCD radiative corrections. The “Generalized Crewther Relation” relates these two observables for physical QCD with nonzero β function; specifically, it connects the non-singlet Adler function (Dns) to the Bjorken sum rule coefficient for polarized deep-inelastic electron scattering (CBjp) at leading twist. A scheme-dependent ΔCSB-term appears in the analysis in order to compensate for the conformal symmetry breaking (CSB) terms from perturbative QCD. In conventional analyses, this normally leads to unphysical dependence in both the choice of the renormalization scheme and the choice of the initial scale at any finite order. However, by applying PMC scale-setting, we can fix the scales of the QCD coupling unambiguously at every order of pQCD. The result is that both Dns and the inverse coefficient Cmore » $$-1\\atop{Bjp}$$ have identical pQCD coefficients, which also exactly match the coefficients of the corresponding conformal theory. Thus one obtains a new generalized Crewther relation for QCD which connects two effective charges, $$\\hat{α}$$d(Q)=Σi≥1$$\\hat{α}^i\\atop{g1}$$(Qi), at their respective physical scales. This identity is independent of the choice of the renormalization scheme at any finite order, and the dependence on the
Von Neumann's quantization of general relativity
NASA Astrophysics Data System (ADS)
Arbuzov, A. B.; Cherny, A. Yu.; Cirilo-Lombardo, D. J.; Nazmitdinov, R. G.; Han, Nguyen Suan; Pavlov, A. E.; Pervushin, V. N.; Zakharov, A. F.
2017-05-01
Von Neumann's procedure is applied to quantizing general relativity. Initial data for dynamical variables in the Planck epoch, where the Hubble parameter value coincided with the Planck mass are quantized. These initial data are defined in terms of the Fock orthogonal simplex in the tangent Minkowski spacetime and the Dirac conformal interval. The Einstein cosmological principle is used to average the logarithm of the determinant of the spatial metric over the spatial volume of the visible Universe. The splitting of general coordinate transformations into diffeomorphisms and transformations of the initial data is introduced. In accordance with von Neumann's procedure, the vacuum state is treated is a quantum ensemble that is degenerate in quantum numbers of nonvacuum states. The distribution of the vacuum state leads to the Casimir effect in gravidynamics in just the same way as in electrodynamics. The generating functional for perturbation theory in gravidynamics is found by solving the quantum energy constraint. The applicability range of gravidynamics is discussed along with the possibility of employing this theory to interpret modern observational data.
Motivations for antigravity in General Relativity
NASA Astrophysics Data System (ADS)
Chardin, G.
1997-08-01
We present arguments showing that it is natural to interpret the negative mass part of the Kerr solution as representing the geometry experienced by antimatter. The C, P and T discrete transformations are considered for this geometry. The C and T properties of the proposed identification are found to be in agreement with the usual representation of antimatter. In addition, we conjecture a property of perfect stigmatism through Kerr wormholes which allows General Relativity to mimic antigravity. Kerr wormholes would then act as “supermirrors” reversing the C, P and T images of an object seen through it. This interpretation is subject to several experimental tests and able to provide an explanation, without any free parameter, of the “CP” violation observed in the neutral kaon system.
Rapidly rotating polytropes in general relativity
NASA Technical Reports Server (NTRS)
Cook, Gregory B.; Shapiro, Stuart L.; Teukolsky, Saul A.
1994-01-01
We construct an extensive set of equilibrium sequences of rotating polytropes in general relativity. We determine a number of important physical parameters of such stars, including maximum mass and maximum spin rate. The stability of the configurations against quasi-radial perturbations is diagnosed. Two classes of evolutionary sequences of fixed rest mass and entropy are explored: normal sequences which behave very much like Newtonian evolutionary sequences, and supramassive sequences which exist solely because of relativistic effects. Dissipation leading to loss of angular momentum causes a star to evolve in a quasi-stationary fashion along an evolutionary sequence. Supramassive sequences evolve towards eventual catastrophic collapse to a black hole. Prior to collapse, the star must spin up as it loses angular momentum, an effect which may provide an observational precursor to gravitational collapse to a black hole.
On thick domain walls in general relativity
NASA Technical Reports Server (NTRS)
Goetz, Guenter; Noetzold, Dirk
1989-01-01
Planar scalar field configurations in general relativity differ considerably from those in flat space. It is shown that static domain walls of finite thickness in curved space-time do not possess a reflection symmetry. At infinity, the space-time tends to the Taub vacuum on one side of the wall and to the Minkowski vacuum (Rindler space-time) on the other. Massive test particles are always accelerated towards the Minkowski side, i.e., domain walls are attractive on the Taub side, but repulsive on the Minkowski side (Taub-vacuum cleaner). It is also proved that the pressure in all directions is always negative. Finally, a brief comment is made concerning the possibility of infinite, i.e., bigger than horizon size, domain walls in our universe. All of the results are independent of the form of the potential V(phi) greater than or equal to 0 of the scalar field phi.
Symplectic time integrators for numerical general relativity
Richter, Ronny
2009-05-01
We describe how we use symplectic time integrators in numerical general relativity. Of particular interest is the free symplectic Stoermer-Verlet method and its application to the dynamical part of ADM-like equations.The behavior of this scheme is illustrated on an effectively 1+1-dimensional version of Einstein's equations that we apply to a perturbed Minkowski problem. We discuss differences between symplectic and non-symplectic integrators, showing favorable evolution properties of the symplectic Stoermer-Verlet method in this example.To handle the constraint part of the equations with a symplectic integrator one can use a partially constrained scheme that applies the RATTLE method, a modification of the Stoermer-Verlet method for holonomic constraints.
Black hole mergers: beyond general relativity
NASA Astrophysics Data System (ADS)
Stein, Leo; Okounkova, Maria
2017-01-01
One hundred years after the birth of general relativity, advanced LIGO has finally directly detected gravitational waves. The source: two black holes merging into one. Advanced LIGO will soon provide the opportunity to test GR, using gravitational waves, in the dynamical strong-field regime-a setting where GR has not yet been tested. GR has passed all weak-field tests with flying colors. Yet it should eventually break down, so we must look to the strong-field. To perform strong-field tests of GR, we need waveform models from theories beyond GR. To date there are no numerical simulations of black hole mergers in theories which differ from GR. The main obstacle is the mathematical one of well-posedness. I will explain how to overcome this obstacle, and demonstrate the success of this approach by presenting the first numerical simulations of black hole mergers in a theory beyond GR.
Rapidly rotating polytropes in general relativity
NASA Technical Reports Server (NTRS)
Cook, Gregory B.; Shapiro, Stuart L.; Teukolsky, Saul A.
1994-01-01
We construct an extensive set of equilibrium sequences of rotating polytropes in general relativity. We determine a number of important physical parameters of such stars, including maximum mass and maximum spin rate. The stability of the configurations against quasi-radial perturbations is diagnosed. Two classes of evolutionary sequences of fixed rest mass and entropy are explored: normal sequences which behave very much like Newtonian evolutionary sequences, and supramassive sequences which exist solely because of relativistic effects. Dissipation leading to loss of angular momentum causes a star to evolve in a quasi-stationary fashion along an evolutionary sequence. Supramassive sequences evolve towards eventual catastrophic collapse to a black hole. Prior to collapse, the star must spin up as it loses angular momentum, an effect which may provide an observational precursor to gravitational collapse to a black hole.
The confrontation between general relativity and experiment
NASA Technical Reports Server (NTRS)
Will, C. M.
1980-01-01
Experiments that test the foundations of gravitation theory in terms of the Einstein equivalence principle are discussed along with solar system tests of general relativity at the post-Newtonian level. These include classical (light-deflection, time delay and perihelion shift) tests as well as tests of the strong equivalence principle. The binary pulsar is discussed as an extra-solar-system gravitational testing ground, and attention is given to the multipolarity of the waves and the amount of radiation damping. The mass function, periastron shift, redshift-Doppler parameter and rate of change of the orbit period (Pb) of the binary pulsar are also considered, and it is suggested that the measurement of Pb represents the first observation of the effects of gravitational radiation.
Language Generativity, Response Generalization, and Derived Relational Responding
Stewart, Ian; McElwee, John; Ming, Siri
2013-01-01
Language generativity can be described as the ability to produce sentences never before said, and to understand sentences never before heard. One process often cited as underlying language generativity is response generalization. However, though the latter seems to promise a technical understanding of the former at a process level, an investigation of definitions and approaches to the term “response generalization” that appear in the literature suggests that it does not do so. We argue that a more promising candidate for the role of key process underlying language generativity is derived relational responding. We introduce the latter concept and describe empirical research showing its connection with language. We subsequently present a relational frame theory (RFT) conceptualization of derived relations as contextually controlled generalized relational responding. We then review a series of recent studies on derived manding in developmentally delayed children and adults that arguably demonstrate the applied utility of a derived relations-based approach with respect to the phenomenon of generative language. PMID:23814374
Elshahabi, Adham; Klamer, Silke; Sahib, Ashish Kaul; Lerche, Holger; Braun, Christoph; Focke, Niels K.
2015-01-01
Idiopathic/genetic generalized epilepsy (IGE/GGE) is characterized by seizures, which start and rapidly engage widely distributed networks, and result in symptoms such as absences, generalized myoclonic and primary generalized tonic-clonic seizures. Although routine magnetic resonance imaging is apparently normal, many studies have reported structural alterations in IGE/GGE patients using diffusion tensor imaging and voxel-based morphometry. Changes have also been reported in functional networks during generalized spike wave discharges. However, network function in the resting-state without epileptiforme discharges has been less well studied. We hypothesize that resting-state networks are more representative of the underlying pathophysiology and abnormal network synchrony. We studied functional network connectivity derived from whole-brain magnetoencephalography recordings in thirteen IGE/GGE and nineteen healthy controls. Using graph theoretical network analysis, we found a widespread increase in connectivity in patients compared to controls. These changes were most pronounced in the motor network, the mesio-frontal and temporal cortex. We did not, however, find any significant difference between the normalized clustering coefficients, indicating preserved gross network architecture. Our findings suggest that increased resting state connectivity could be an important factor for seizure spread and/or generation in IGE/GGE, and could serve as a biomarker for the disease. PMID:26368933
Analysis of nonlocal neural fields for both general and gamma-distributed connectivities
NASA Astrophysics Data System (ADS)
Hutt, Axel; Atay, Fatihcan M.
2005-04-01
This work studies the stability of equilibria in spatially extended neuronal ensembles. We first derive the model equation from statistical properties of the neuron population. The obtained integro-differential equation includes synaptic and space-dependent transmission delay for both general and gamma-distributed synaptic connectivities. The latter connectivity type reveals infinite, finite, and vanishing self-connectivities. The work derives conditions for stationary and nonstationary instabilities for both kernel types. In addition, a nonlinear analysis for general kernels yields the order parameter equation of the Turing instability. To compare the results to findings for partial differential equations (PDEs), two typical PDE-types are derived from the examined model equation, namely the general reaction-diffusion equation and the Swift-Hohenberg equation. Hence, the discussed integro-differential equation generalizes these PDEs. In the case of the gamma-distributed kernels, the stability conditions are formulated in terms of the mean excitatory and inhibitory interaction ranges. As a novel finding, we obtain Turing instabilities in fields with local inhibition-lateral excitation, while wave instabilities occur in fields with local excitation and lateral inhibition. Numerical simulations support the analytical results.
Hellmann–Feynman connection for the relative Fisher information
Venkatesan, R.C.; Plastino, A.
2015-08-15
The (i) reciprocity relations for the relative Fisher information (RFI, hereafter) and (ii) a generalized RFI–Euler theorem are self-consistently derived from the Hellmann–Feynman theorem. These new reciprocity relations generalize the RFI–Euler theorem and constitute the basis for building up a mathematical Legendre transform structure (LTS, hereafter), akin to that of thermodynamics, that underlies the RFI scenario. This demonstrates the possibility of translating the entire mathematical structure of thermodynamics into a RFI-based theoretical framework. Virial theorems play a prominent role in this endeavor, as a Schrödinger-like equation can be associated to the RFI. Lagrange multipliers are determined invoking the RFI–LTS link and the quantum mechanical virial theorem. An appropriate ansatz allows for the inference of probability density functions (pdf’s, hereafter) and energy-eigenvalues of the above mentioned Schrödinger-like equation. The energy-eigenvalues obtained here via inference are benchmarked against established theoretical and numerical results. A principled theoretical basis to reconstruct the RFI-framework from the FIM framework is established. Numerical examples for exemplary cases are provided. - Highlights: • Legendre transform structure for the RFI is obtained with the Hellmann–Feynman theorem. • Inference of the energy-eigenvalues of the SWE-like equation for the RFI is accomplished. • Basis for reconstruction of the RFI framework from the FIM-case is established. • Substantial qualitative and quantitative distinctions with prior studies are discussed.
Cui, Huiru; Zhang, Jie; Liu, Yicen; Li, Qingwei; Li, Hui; Zhang, Lanlan; Hu, Qiang; Cheng, Wei; Luo, Qiang; Li, Jianqi; Li, Wei; Wang, Jijun; Feng, Jianfeng; Li, Chunbo; Northoff, Georg
2016-04-01
Generalized anxiety disorder (GAD) and panic disorder (PD) are most common anxiety disorders with high lifetime prevalence while the pathophysiology and disease-specific alterations still remain largely unclear. Few studies have taken a whole-brain perspective in the functional connectivity (FC) analysis of these two disorders in resting state. It limits the ability to identify regionally and psychopathologically specific network abnormalities with their subsequent use as diagnostic marker and novel treatment strategy. The whole brain FC using a novel FC metric was compared, that is, scaled correlation, which they demonstrated to be a reliable FC statistics, but have higher statistical power in two-sample t-test of whole brain FC analysis. About 21 GAD and 18 PD patients were compared with 22 matched control subjects during resting-state, respectively. It was found that GAD patients demonstrated increased FC between hippocampus/parahippocampus and fusiform gyrus among the most significantly changed FC, while PD was mainly associated with greater FC between somatosensory cortex and thalamus. Besides such regional specificity, it was observed that psychopathological specificity in that the disrupted FC pattern in PD and GAD correlated with their respective symptom severity. The findings suggested that the increased FC between hippocampus/parahippocampus and fusiform gyrus in GAD were mainly associated with a fear generalization related neural circuit, while the greater FC between somatosensory cortex and thalamus in PD were more likely linked to interoceptive processing. Due to the observed regional and psychopathological specificity, their findings bear important clinical implications for the potential treatment strategy. © 2016 Wiley Periodicals, Inc.
An Introduction to General Relativity and Cosmology
NASA Astrophysics Data System (ADS)
Plebanski, Jerzy; Krasinski, Andrzej
2012-09-01
1. How the theory of relativity came into being (a brief historical sketch); Part I. Elements of Differential Geometry: 2. A short sketch of two-dimensional differential geometries; 3. Tensors, tensor densities; 4. Covariant derivatives; 5. Parallel transport and geodesic lines; 6. Curvature of a manifold: flat manifolds; 7. Riemannian geometry; 8. Symmetries of Rieman spaces, invariance of tensors; 9. Methods to calculate the curvature quickly - Cartan forms and algebraic computer programs; 10. The spatially homogeneous Bianchi-type spacetimes; 11. The Petrov classification by the spinor method; Part II. The Gravitation Theory: 12. The Einstein equations and the sources of a gravitational field; 13. The Maxwell and Einstein-Maxwell equations and the Kaluza-Klein theory; 14. Spherically symmetric gravitational field of isolated objects; 15. Relativistic hydrodynamics and thermodynamics; 16. Relativistic cosmology I: general geometry; 17. Relativistic cosmology II: the Robertson-Walker geometry; 18. Relativistic cosmology III: the Lemaître-Tolman geometry; 19. Relativistic cosmology IV: generalisations of L-T and related geometries; 20. The Kerr solution; 21. Subjects omitted in this book; References.
An Introduction to General Relativity and Cosmology
NASA Astrophysics Data System (ADS)
Plebanski, Jerzy; Krasinski, Andrzej
2006-08-01
1. How the theory of relativity came into being (a brief historical sketch); Part I. Elements of Differential Geometry: 2. A short sketch of two-dimensional differential geometries; 3. Tensors, tensor densities; 4. Covariant derivatives; 5. Parallel transport and geodesic lines; 6. Curvature of a manifold: flat manifolds; 7. Riemannian geometry; 8. Symmetries of Rieman spaces, invariance of tensors; 9. Methods to calculate the curvature quickly - Cartan forms and algebraic computer programs; 10. The spatially homogeneous Bianchi-type spacetimes; 11. The Petrov classification by the spinor method; Part II. The Gravitation Theory: 12. The Einstein equations and the sources of a gravitational field; 13. The Maxwell and Einstein-Maxwell equations and the Kaluza-Klein theory; 14. Spherically symmetric gravitational field of isolated objects; 15. Relativistic hydrodynamics and thermodynamics; 16. Relativistic cosmology I: general geometry; 17. Relativistic cosmology II: the Robertson-Walker geometry; 18. Relativistic cosmology III: the Lemaître-Tolman geometry; 19. Relativistic cosmology IV: generalisations of L-T and related geometries; 20. The Kerr solution; 21. Subjects omitted in this book; References.
BOOK REVIEW: Equations of Motion in General Relativity Equations of Motion in General Relativity
NASA Astrophysics Data System (ADS)
Schäfer, Gerhard
2012-03-01
-like signals in gravitational fields of binary systems is treated, which is important for a precise interpretation of pulsar observation measurements. Based on original research by the authors, a detailed presentation is given of a mathematical scheme which makes feasible the treatment of small black holes in background space-times. Using that approach, the equations of motion of small charged black holes are derived in vacuum Einstein-Maxwell space-times without encountering infinities, showing up electromagnetic radiation reaction, background field, and tail forces. At this stage, the book defines various issues to be tackled in future research within the given formalism, such as a physical understanding of the very structure of the tail contribution or a more detailed calculation of the motion of a small Schwarzschild black hole in an external vacuum gravitational field. A unique chapter is devoted to the choreographic three-body solution of the 1PNA dynamics, also mentioning the 2PNA dynamics, in the form of figure-eight configurations. The emitted gravitational waves are shown, and a discussion of their observability in future gravitational wave astronomy is given. Four appendices support and complement the main part of the book. Here, the far zone non-contribution to the equations of motion at 3PNA is carefully investigated, forces resulting from the extendedness of objects are presented in analytic form, null geodesic congruences with their optical scalars are discussed, and the perturbed vacuum Einstein-Maxwell field equations are given. The book delivers a very readable account of the problem of motion in general relativity. It covers the state of the art up to the years 2006/8 and presents a plethora of interesting and important topics and results. Whenever appropriate, connection with observation is made. A reader with good post-introductory knowledge of the theory of general relativity should find easy access to the book, and will surely benefit from the
Generalized Entropic Uncertainty Relations with Tsallis' Entropy
NASA Technical Reports Server (NTRS)
Portesi, M.; Plastino, A.
1996-01-01
A generalization of the entropic formulation of the Uncertainty Principle of Quantum Mechanics is considered with the introduction of the q-entropies recently proposed by Tsallis. The concomitant generalized measure is illustrated for the case of phase and number operators in quantum optics. Interesting results are obtained when making use of q-entropies as the basis for constructing generalized entropic uncertainty measures.
49 CFR 192.367 - Service lines: General requirements for connections to main piping.
Code of Federal Regulations, 2011 CFR
2011-10-01
... connections to main piping. 192.367 Section 192.367 Transportation Other Regulations Relating to Transportation (Continued) PIPELINE AND HAZARDOUS MATERIALS SAFETY ADMINISTRATION, DEPARTMENT OF TRANSPORTATION (CONTINUED) PIPELINE SAFETY TRANSPORTATION OF NATURAL AND OTHER GAS BY PIPELINE: MINIMUM FEDERAL SAFETY...
49 CFR 192.367 - Service lines: General requirements for connections to main piping.
Code of Federal Regulations, 2013 CFR
2013-10-01
... connections to main piping. 192.367 Section 192.367 Transportation Other Regulations Relating to Transportation (Continued) PIPELINE AND HAZARDOUS MATERIALS SAFETY ADMINISTRATION, DEPARTMENT OF TRANSPORTATION (CONTINUED) PIPELINE SAFETY TRANSPORTATION OF NATURAL AND OTHER GAS BY PIPELINE: MINIMUM FEDERAL SAFETY...
Directions in General Relativity, Vol. 2
NASA Astrophysics Data System (ADS)
Hu, B. L.; Jacobson, T. A.
2005-10-01
Preface; Dieter Brill: a spacetime perspective; 1. Thawing the frozen formalism: the difference between observables and what we observe A. Anderson; 2. Jacobi's action and the density of states J. D. Brown and J. W. York; 3. Decoherence of correlation histories E. Calzetta and B. L. Hu; 4. The initial value problem in light of Ashtekar's variables R. Capovilla, J. Dell and T. Jacobson; 5. Status report on an axiomatic basis for functional integration P. Cartier and C. DeWitt-Morette; 6. Solution of the coupled Einstein constraints on asymptotically Euclidean manifolds Y. Choquet-Bruhat; 7. Compact Cauchy horizons and Cauchy surfaces P. Chrusciel and J. Isenberg; 8. The classical electron J. M. Cohen and E. Mustafa; 9. Gauge (in)variance, mass and parity in D=3 revisited S. Deser; 10. Triality, exceptional Lie groups and Dirac operators F. Flaherty; 11. The reduction of the state vector and limitations on measurement in the quantum mechanics of closed systems J. B. Hartle; 12 Quantum linearization instabilities of de Sitter spacetime A. Higuchi; 13. What is the true description of charged black holes? G. T. Horowitz; 14. Limits on the adiabatic index in static stellar models L. Lindblom and A. K. M. Masood-ul-Alam; 15. On the relativity of rotation B. Mashhoon; 16. Recent progress and open problems in linearization stability V. E. Moncrief; 17. Brill waves N. Murchadha; 18. You can't get there from here: constraints on topology change K. Schleich and D. M. Witt; 19. Time, measurement and information loss in quantum cosmology L. Smolin; 20. Impossible measurements on quantum fields R. Sorkin; 21. A new condition implying the existence of a constant mean curvature foliation F. J. Tipler; 22. Maximal slices in stationary spacetimes with ergoregions R. M. Wald; 23. (1 + 1) - Dimensional methods for general relativity J. H. Yoon; 24. Coalescence of primal gravity waves to make cosmological mass without matter D. E. Holz, W. A. Miller, M. Wakano and J. A. Wheeler
Harmonizing General Relativity with Quantum Mechanics
NASA Astrophysics Data System (ADS)
Alfonso-Faus, Antonio
2007-04-01
Gravitation is the common underlying texture between General Relativity and Quantum Mechanics. We take gravitation as the link that can make possible the marriage between these two sciences. We use here the duality of Nature for gravitation: A continuous warped space, wave-like, and a discrete quantum gas, particle-like, both coexistent and producing an equilibrium state in the Universe. The result is a static, non expanding, spherical, unlimited and finite Universe, with no cosmological constant and no dark energy. Macht's Principle is reproduced here by the convergence of the two cosmological equations of Einstein. From this a Mass Boom concept is born given by M = t, M the mass of the Universe and t its age. Also a decreasing speed of light is the consequence of the Mass Boom, c = 1/t, which explains the Supernovae Type Ia observations without the need of expansion (nor, of course, accelerated expansion). Our Mass Boom model completely wipes out the problems and paradoxes built in the Big Bang model, like the horizon, monopole, entropy, flatness, fine tuning, etc. It also eliminates the need for inflation.
Exotic differentiable structures and general relativity
NASA Astrophysics Data System (ADS)
Brans, Carl H.; Randall, Duane
1993-02-01
We review recent developments in differential topology with special concern for their possible significance to physical theories, especially general relativity. In particular we are concerned here with the discovery of the existence of non-standard (“fake” or “exotic”) differentiable structures on topologically simple manifolds such asS 7, ℝ4 andS 3 X ℝ1. Because of the technical difficulties involved in the smooth case, we begin with an easily understood toy example looking at the role which the choice of complex structures plays in the formulation of two-dimensional vacuum electrostatics. We then briefly review the mathematical formalisms involved with differentiable structures on topological manifolds, diffeomorphisms and their significance for physics. We summarize the important work of Milnor, Freedman, Donaldson, and others in developing exotic differentiable structures on well known topological manifolds. Finally, we discuss some of the geometric implications of these results and propose some conjectures on possible physical implications of these new manifolds which have never before been considered as physical models.
Inflation and bubbles in general relativity
NASA Astrophysics Data System (ADS)
Laguna-Castillo, Pablo; Matzner, Richard A.
1986-11-01
Following Israel's study of singular hypersurfaces and thin shells in general relativity, the complete set of Einstein's field equations in the presence of a bubble boundary SIGMA is reviewed for all spherically symmetric embedding four-geometries M+/-. The mapping that identifies points between the boundaries Σ+ and Σ- is obtained explicitly when the regions M+ and M- are described by a de Sitter and a Minkowski metric, respectively. In addition, the evolution of a bubble with vanishing surface energy density is studied in a spatially flat Robertson-Walker space-time, for region M- radiation dominated with a vanishing cosmological constant, and an energy equation in M+ determined by the matching. It is found that this type of bubble leads to a ``worm-hole'' matching; that is, an infinite extent exterior of a sphere is joined across the wall to another infinite extent exterior of a sphere. Interior-interior matches are also possible. Under this model, solutions for a bubble following a Hubble law are analyzed. Numerical solutions for bubbles with constant tension are also obtained.
Giménez, Mónica; Pujol, Jesús; Ortiz, Hector; Soriano-Mas, Carles; López-Solà, Marina; Farré, Magí; Deus, Joan; Merlo-Pich, Emilio; Martín-Santos, Rocio
2012-06-30
Although the fear of being scrutinized by others in a social context is a key symptom in social anxiety disorder (SAD), the neural processes underlying the perception of scrutiny have not previously been studied by functional magnetic resonance imaging (fMRI). We used fMRI to map brain activation during a perception-of-scrutiny task in 20 SAD patients and 20 controls. A multi-dimensional analytic approach was used. Scrutiny perception was mediated by activation of the medial frontal cortex, insula-operculum region and cerebellum, and the additional recruitment of visual areas and the thalamus in patients. Between-group comparison demonstrated significantly enhanced brain activation in patients in the primary visual cortex and cerebellum. Functional connectivity mapping demonstrated an abnormal connectivity between regions underlying general arousal and attention. SAD patients showed significantly greater task-induced functional connectivity in the thalamo-cortical and the fronto-striatal circuits. A statistically significant increase in task-induced functional connectivity between the anterior cingulate cortex and scrutiny-perception-related regions was observed in the SAD patients, suggesting the existence of enhanced behavior-inhibitory control. The presented data indicate that scrutiny perception in SAD enhances brain activity in arousal-attention systems, suggesting that fMRI may be a useful tool to explore such a behavioral dimension.
Lateral frontal pole and relational processing: Activation patterns and connectivity profile.
Hartogsveld, Bart; Bramson, Bob; Vijayakumar, Suhas; van Campen, A Dilene; Marques, José P; Roelofs, Karin; Toni, Ivan; Bekkering, Harold; Mars, Rogier B
2017-08-12
The functional contribution of the lateral frontal cortex to behavior has been discussed with reference to several higher-order cognitive domains. In a separate line of research, recent studies have focused on the anatomical organization of this part of the brain. These different approaches are rarely combined. Here, we combine previous work using anatomical connectivity that identified a lateral subdivision of the human frontal pole and work that suggested a general role for rostrolateral prefrontal cortex in processing higher-order relations, irrespective of the type of information. We asked healthy human volunteers to judge the relationship between pairs of stimuli, a task previously suggested to engage the lateral frontal pole. Presenting both shape and face stimuli, we indeed observed overlapping activation of the lateral prefrontal cortex when subjects judged relations between pairs. Using resting state functional MRI, we confirmed that the activated region's whole-brain connectivity most strongly resembles that of the lateral frontal pole. Using diffusion MRI, we showed that the pattern of connections of this region with the main association fibers again is most similar to that of the lateral frontal pole, consistent with the observation that it is this anatomical region that is involved in relational processing. Copyright © 2017 The Authors. Published by Elsevier B.V. All rights reserved.
Price, Gavin R; Yeo, Darren J; Wilkey, Eric D; Cutting, Laurie E
2017-02-22
The present study investigates the relation between resting-state functional connectivity (rsFC) of cytoarchitectonically defined subdivisions of the parietal cortex at the end of 1st grade and arithmetic performance at the end of 2nd grade. Results revealed a dissociable pattern of relations between rsFC and arithmetic competence among subdivisions of intraparietal sulcus (IPS) and angular gyrus (AG). rsFC between right hemisphere IPS subdivisions and contralateral IPS subdivisions positively correlated with arithmetic competence. In contrast, rsFC between the left hIP1 and the right medial temporal lobe, and rsFC between the left AG and left superior frontal gyrus, were negatively correlated with arithmetic competence. These results suggest that strong inter-hemispheric IPS connectivity is important for math development, reflecting either neurocognitive mechanisms specific to arithmetic processing, domain-general mechanisms that are particularly relevant to arithmetic competence, or structural 'cortical maturity'. Stronger connectivity between IPS, and AG, subdivisions and frontal and temporal cortices, however, appears to be negatively associated with math development, possibly reflecting the ability to disengage suboptimal problem-solving strategies during mathematical processing, or to flexibly reorient task-based networks. Importantly, the reported results pertain even when controlling for reading, spatial attention, and working memory, suggesting that the observed rsFC-behavior relations are specific to arithmetic competence. Copyright © 2017 The Authors. Published by Elsevier Ltd.. All rights reserved.
Cortico-Cerebellar Structural Connectivity Is Related to Residual Motor Output in Chronic Stroke.
Schulz, Robert; Frey, Benedikt M; Koch, Philipp; Zimerman, Maximo; Bönstrup, Marlene; Feldheim, Jan; Timmermann, Jan E; Schön, Gerhard; Cheng, Bastian; Thomalla, Götz; Gerloff, Christian; Hummel, Friedhelm C
2015-10-27
Functional imaging studies have argued that interactions between cortical motor areas and the cerebellum are relevant for motor output and recovery processes after stroke. However, the impact of the underlying structural connections is poorly understood. To investigate this, diffusion-weighted brain imaging was conducted in 26 well-characterized chronic stroke patients (aged 63 ± 1.9 years, 18 males) with supratentorial ischemic lesions and 26 healthy participants. Probabilistic tractography was used to reconstruct reciprocal cortico-cerebellar tracts and to relate their microstructural integrity to residual motor functioning applying linear regression modeling. The main finding was a significant association between cortico-cerebellar structural connectivity and residual motor function, independent from the level of damage to the cortico-spinal tract. Specifically, white matter integrity of the cerebellar outflow tract, the dentato-thalamo-cortical tract, was positively related to both general motor output and fine motor skills. Additionally, the integrity of the descending cortico-ponto-cerebellar tract contributed to rather fine motor skills. A comparable structure-function relationship was not evident in the controls. The present study provides first tract-related structural data demonstrating a critical importance of distinct cortico-cerebellar connections for motor output after stroke.
Makovac, Elena; Watson, David R.; Meeten, Frances; Garfinkel, Sarah N.; Cercignani, Mara; Critchley, Hugo D.
2016-01-01
Generalized anxiety disorder (GAD) is characterized by excessive worry, autonomic dysregulation and functional amygdala dysconnectivity, yet these illness markers have rarely been considered together, nor their interrelationship tested longitudinally. We hypothesized that an individual’s capacity for emotion regulation predicts longer-term changes in amygdala functional connectivity, supporting the modification of GAD core symptoms. Sixteen patients with GAD (14 women) and individually matched controls were studied at two time points separated by 1 year. Resting-state fMRI data and concurrent measurement of vagally mediated heart rate variability were obtained before and after the induction of perseverative cognition. A greater rise in levels of worry following the induction predicted a stronger reduction in connectivity between right amygdala and ventromedial prefrontal cortex, and enhanced coupling between left amygdala and ventral tegmental area at follow-up. Similarly, amplified physiological responses to the induction predicted increased connectivity between right amygdala and thalamus. Longitudinal shifts in a distinct set of functional connectivity scores were associated with concomitant changes in GAD symptomatology over the course of the year. Results highlight the prognostic value of indices of emotional dysregulation and emphasize the integral role of the amygdala as a critical hub in functional neural circuitry underlying the progression of GAD symptomatology. PMID:27369066
The Concept of General Relativity is not Related to Reality
NASA Astrophysics Data System (ADS)
Kotas, Ronald
2015-04-01
The concept of general relativity is not related to reality. It is not real or factual Science. GR cannot account for objects falling to earth or for the weight of objects sitting on the earth. The Cavendish demonstration showing the attraction between two masses at right angles to earth's gravity, is not explained by GR. No one can prove the existence of ``space fabric.'' The concept of ``space time'' effects causing gravitational attraction between masses is wrong. Conservation law of energy - momentum does not exist in GR. LIGO fails in detecting ``gravity waves'' because there is no ``space fabric'' to transmit them. The Gravity B Probe data manipulated to show some effects, is not proof of ``space fabric.'' It is Nuclear Quantum Gravitation that provides clear definitive explanation of Gravity and Gravitation. It is harmonious with Newtonian and Quantum Mechanics, and Scientific Logic. Nuclear Quantum Gravitation has 10 clear, Scientific proofs and 21 more good indications. With this theory the Physical Forces are Unified. See: OBSCURANTISM ON EINSTEIN GRAVITATION? http://www.santilli-foundation.org/inconsistencies-gravitation.php and Einstein's Theory of Relativity versus Classical Mechanics, by Paul Marmet http://www.newtonphysics.on.ca/einstein/
Gamma and Related Functions Generalized for Sequences
ERIC Educational Resources Information Center
Ollerton, R. L.
2008-01-01
Given a sequence g[subscript k] greater than 0, the "g-factorial" product [big product][superscript k] [subscript i=1] g[subscript i] is extended from integer k to real x by generalizing properties of the gamma function [Gamma](x). The Euler-Mascheroni constant [gamma] and the beta and zeta functions are also generalized. Specific examples include…
Gamma and Related Functions Generalized for Sequences
ERIC Educational Resources Information Center
Ollerton, R. L.
2008-01-01
Given a sequence g[subscript k] greater than 0, the "g-factorial" product [big product][superscript k] [subscript i=1] g[subscript i] is extended from integer k to real x by generalizing properties of the gamma function [Gamma](x). The Euler-Mascheroni constant [gamma] and the beta and zeta functions are also generalized. Specific examples include…
Gravitational Wave in Linear General Relativity
NASA Astrophysics Data System (ADS)
Cubillos, D. J.
2017-07-01
General relativity is the best theory currently available to describe the interaction due to gravity. Within Albert Einstein's field equations this interaction is described by means of the spatiotemporal curvature generated by the matter-energy content in the universe. Weyl worked on the existence of perturbations of the curvature of space-time that propagate at the speed of light, which are known as Gravitational Waves, obtained to a first approximation through the linearization of the field equations of Einstein. Weyl's solution consists of taking the field equations in a vacuum and disturbing the metric, using the Minkowski metric slightly perturbed by a factor ɛ greater than zero but much smaller than one. If the feedback effect of the field is neglected, it can be considered as a weak field solution. After introducing the disturbed metric and ignoring ɛ terms of order greater than one, we can find the linearized field equations in terms of the perturbation, which can then be expressed in terms of the Dalambertian operator of the perturbation equalized to zero. This is analogous to the linear wave equation in classical mechanics, which can be interpreted by saying that gravitational effects propagate as waves at the speed of light. In addition to this, by studying the motion of a particle affected by this perturbation through the geodesic equation can show the transversal character of the gravitational wave and its two possible states of polarization. It can be shown that the energy carried by the wave is of the order of 1/c5 where c is the speed of light, which explains that its effects on matter are very small and very difficult to detect.
Gorka, Stephanie M; Fitzgerald, Daniel A; Labuschagne, Izelle; Hosanagar, Avinash; Wood, Amanda G; Nathan, Pradeep J; Phan, K Luan
2015-01-01
The neuropeptide oxytocin (OXT) is thought to attenuate anxiety by dampening amygdala reactivity to threat in individuals with generalized social anxiety disorder (GSAD). Because the brain is organized into networks of interconnected areas, it is likely that OXT impacts functional coupling between the amygdala and other socio-emotional areas of the brain. Therefore, the aim of the current study was to examine the effects of OXT on amygdala functional connectivity during the processing of fearful faces in GSAD subjects and healthy controls (HCs). In a randomized, double-blind, placebo (PBO)-controlled, within-subjects design, 18 HCs and 17 GSAD subjects performed a functional magnetic resonance imaging task designed to probe amygdala response to fearful faces following acute intranasal administration of PBO or OXT. Functional connectivity between the amygdala and the rest of the brain was compared between OXT and PBO sessions using generalized psychophysiological interaction analyses. Results indicated that within individuals with GSAD, but not HCs, OXT enhanced functional connectivity between the amygdala and the bilateral insula and middle cingulate/dorsal anterior cingulate gyrus during the processing of fearful faces. These findings suggest that OXT may have broad pro-social implications such as enhancing the integration and modulation of social responses.
A Time Domain Waveform for Testing General Relativity
NASA Astrophysics Data System (ADS)
Huwyler, Cédric; Porter, Edward K.; Jetzer, Philippe
2015-05-01
Gravitational-wave parameter estimation is only as good as the theory the waveform generation models are based upon. It is therefore crucial to test General Relativity (GR) once data becomes available. Many previous works, such as studies connected with the ppE framework by Yunes and Pretorius, rely on the stationary phase approximation (SPA) to model deviations from GR in the frequency domain. As Fast Fourier Transform algorithms have become considerably faster and in order to circumvent possible problems with the SPA, we test GR with corrected time domain waveforms instead of SPA waveforms. Since a considerable amount of work has been done already in the field using SPA waveforms, we establish a connection between leading-order-corrected waveforms in time and frequency domain, concentrating on phase-only corrected terms. In a Markov Chain Monte Carlo study, whose results are preliminary and will only be available later, we will assess the ability of the eLISA detector to measure deviations from GR for signals coming from supermassive black hole inspirals using these corrected waveforms.
A General Purpose Connections type CTI Server Based on SIP Protocol and Its Implementation
NASA Astrophysics Data System (ADS)
Watanabe, Toru; Koizumi, Hisao
In this paper, we propose a general purpose connections type CTI (Computer Telephony Integration) server that provides various CTI services such as voice logging where the CTI server communicates with IP-PBX using the SIP (Session Initiation Protocol), and accumulates voice packets of external line telephone call flowing between an IP telephone for extension and a VoIP gateway connected to outside line networks. The CTI server realizes CTI services such as voice logging, telephone conference, or IVR (interactive voice response) with accumulating and processing voice packets sampled. Furthermore, the CTI server incorporates a web server function which can provide various CTI services such as a Web telephone directory via a Web browser to PCs, cellular telephones or smart-phones in mobile environments.
Improving Cancer-Related Outcomes with Connected Health - Objective 4
The full benefits of connected health cannot be achieved unless everyone in the United States who wants to participate and the organizations that support health and deliver healthcare have adequate access to high-speed Internet service. Access depends both on the availability of broadband service and the resources needed to obtain and maintain service.
The equivalence principle as a stepping stone from special to general relativity: A Socratic dialog
NASA Astrophysics Data System (ADS)
Drake, S. P.
2006-01-01
We show how students can be led to an understanding of the connection between special relativity and general relativity by considering the time dilation effect of clocks placed on the surface of the Earth. This paper is written as a Socratic dialog between a lecturer and a student.
Matrix general relativity: a new look at old problems
NASA Astrophysics Data System (ADS)
Avramidi, Ivan G.
2004-01-01
We develop a novel approach to gravity that we call 'matrix general relativity' (MGR) or 'gravitational chromodynamics' (GCD or GQCD for the quantum version). Gravity is described in this approach not by one Riemannian metric (i.e. a symmetric two-tensor field) but by a multiplet of such fields, or by a matrix-valued symmetric two-tensor field that satisfies certain conditions. We define the matrix extensions of standard constructions of differential geometry including connections and curvatures, and finally, an invariant functional of the new field that reduces to the standard Einstein action functional in the commutative (diagonal) case. Our main idea is the analogy with Yang Mills theory (QCD and the standard model). We call the new degrees of freedom of gravity associated with the matrix structure 'gravitational colour' or simply 'gravicolour' and introduce a new gauge symmetry associated with this degree of freedom. As in the standard model there are two possibilities. First of all, it is possible that at high energies (say at the Planckian scale) this symmetry is exact (symmetric phase), but at low energies it is badly broken, so that one tensor field remains massless (and gives general relativity) and the other ones become massive with masses of Planckian scale. The second possibility is that the additional degrees of freedom of the gravitational field are confined to the Planckian scale. What one sees at large distances are singlets (invariants) of the new gauge symmetry.
Making Connections to Students' Lives and Careers Throughout a General Education Science Course
NASA Astrophysics Data System (ADS)
LaDue, D. S.
2014-12-01
The University of Oklahoma's general education lecture course Severe & Unusual Weather, taught in two sections each fall and spring, covers about nine topics. The sections are taught by different instructors, each of whom has flexibility to employ a variety of instructional strategies and choose specific topics to cover while meeting the requirement that general education courses in the natural sciences help students understand the importance of the science for appreciating the world around them. Students enrolled have been approximately 6-10% returning adult students, some of whom were veterans or active duty military, and about 10% members of racial or ethnic groups. Their majors are mostly in the humanities (theater, photography) and social sciences (education, English, journalism, sociology), with some natural science majors (psychology, aviation). For the past two years, Section 001 has been designed with adult and active learning concepts in mind, using deliberate connections between course content and students' lives and careers to motivate meaningful learning. Students were grouped in teams according to similar majors and assigned group presentations connecting course content to topics that should interest them, such as economic impacts of weather, societal and personal impacts of severe weather, risks to aviation, media coverage of weather, and psychological and sociological responses to weather risks. Students learn about the peer review process for scientific papers while also exploring a connection of course content to their future career or life interests through papers that are run through a mock peer review process. Public policy is discussed in several sections of the course, such as hurricane building codes, wind-resistant construction in tornado alley, and the disproportionate impacts of weather and climate on certain socioeconomic groups. Most students deeply appreciate the opportunity to explore how course content intersects with their lives
Generalized Squashing Factors for Covariant Description of Magnetic Connectivity in the Solar Corona
NASA Technical Reports Server (NTRS)
Titov, V. S.
2007-01-01
The study of magnetic connectivity in the solar corona reveals a need to generalize the field line mapping technique to arbitrary geometry of the boundaries and systems of coordinates. Indeed, the global description of the connectivity in the corona requires the use of the photospheric and solar wind boundaries. Both are closed surfaces and therefore do not admit a global regular system of coordinates. At least two overlapping regular systems of coordinates for each of the boundaries are necessary in this case to avoid spherical-pole-like singularities in the coordinates of the footpoints. This implies that the basic characteristic of magnetic connectivity-the squashing degree or factor Q of elemental flux tubes, according to Titov and coworkers-must be rewritten in covariant form. Such a covariant expression of Q is derived in this work. The derived expression is very flexible and highly efficient for describing the global magnetic connectivity in the solar corona. In addition, a general expression for a new characteristic Q1, which defines a squashing of the flux tubes in the directions perpendicular to the field lines, is determined. This new quantity makes it possible to filter out the quasi-separatrix layers whose large values of Q are caused by a projection effect at the field lines nearly touching the photosphere. Thus, the value Q1 provides a much more precise description of the volumetric properties of the magnetic field structure. The difference between Q and Q1 is illustrated by comparing their distributions for two configurations, one of which is the Titov-Demoulin model of a twisted magnetic field.
Generalized Squashing Factors for Covariant Description of Magnetic Connectivity in the Solar Corona
NASA Technical Reports Server (NTRS)
Titov, V. S.
2007-01-01
The study of magnetic connectivity in the solar corona reveals a need to generalize the field line mapping technique to arbitrary geometry of the boundaries and systems of coordinates. Indeed, the global description of the connectivity in the corona requires the use of the photospheric and solar wind boundaries. Both are closed surfaces and therefore do not admit a global regular system of coordinates. At least two overlapping regular systems of coordinates for each of the boundaries are necessary in this case to avoid spherical-pole-like singularities in the coordinates of the footpoints. This implies that the basic characteristic of magnetic connectivity-the squashing degree or factor Q of elemental flux tubes, according to Titov and coworkers-must be rewritten in covariant form. Such a covariant expression of Q is derived in this work. The derived expression is very flexible and highly efficient for describing the global magnetic connectivity in the solar corona. In addition, a general expression for a new characteristic Q1, which defines a squashing of the flux tubes in the directions perpendicular to the field lines, is determined. This new quantity makes it possible to filter out the quasi-separatrix layers whose large values of Q are caused by a projection effect at the field lines nearly touching the photosphere. Thus, the value Q1 provides a much more precise description of the volumetric properties of the magnetic field structure. The difference between Q and Q1 is illustrated by comparing their distributions for two configurations, one of which is the Titov-Demoulin model of a twisted magnetic field.
The connections between general and reproductive senescence and the evolutionary basis of menopause.
Kirkwood, Thomas B L; Shanley, Daryl P
2010-08-01
We consider the relationship between the factors responsible for the general biology of aging and those that specifically influence the aging of the reproductive system. To understand this relationship it is necessary to be clear about the evolutionary forces acting on both sets of factors. Only in this way can the correct causal connections be established. Of particular significance is the existence in some species of a distinct period of postreproductive life. This is most striking in the case of the human menopause, for which a particular combination of biological and sociobiological factors appear to be responsible.
NASA Astrophysics Data System (ADS)
Aspon, Siti Zulaiha; Murid, Ali Hassan Mohamed; Rahmat, Hamisan
2014-07-01
This research is about computing the Green's functions on unbounded doubly connected regions by using the method of boundary integral equation. The method depends on solving an exterior Dirichlet problem. The Dirichlet problem is then solved using a uniquely solvable Fredholm integral equation on the boundary of the region. The kernel of this integral equation is the generalized Neumann kernel. The method for solving this integral equation is by using the Nyström method with trapezoidal rule to discretize it to a linear system. The linear system is then solved by the Gaussian elimination method. Mathematica plots of Green's functions for several test regions are also presented.
Improving Cancer-Related Outcomes with Connected Health - Acknowledgements
The President’s Cancer Panel is grateful to all participants who invested their time to take part in the series of workshops on connected health and cancer. A complete list of participants is in Series Information. The Panel is especially appreciative to the series co-chairs who graciously contributed their time and knowledge on this topic, providing valuable guidance during workshop planning and extensive input on this report.
Superspace and global stability in general relativity
NASA Astrophysics Data System (ADS)
Gurzadyan, A. V.; Kocharyan, A. A.
A framework is developed enabling the global analysis of the stability of cosmological models using the local geometric characteristics of the infinite-dimensional superspace, i.e. using the generalized Jacobi equation reformulated for pseudo-Riemannian manifolds. We give a direct formalism for dynamical analysis in the superspace, the requisite equation pertinent for stability analysis of the universe by means of generalized covariant and Fermi derivative is derived. Then, the relevant definitions and formulae are retrieved for cosmological models with a scalar field.
Makovac, Elena; Meeten, Frances; Watson, David R; Herman, Aleksandra; Garfinkel, Sarah N; D Critchley, Hugo; Ottaviani, Cristina
2016-11-15
Generalized anxiety disorder (GAD) is characterized by the core symptom of uncontrollable worry. Functional magnetic resonance imaging studies link this symptom to aberrant functional connectivity between the amygdala and prefrontal cortex. Patients with GAD also display a characteristic pattern of autonomic dysregulation. Although frontolimbic circuitry is implicated in the regulation of autonomic arousal, no previous study to our knowledge combined functional magnetic resonance imaging with peripheral physiologic monitoring in these patients to test the hypothesis that core symptoms of worry and autonomic dysregulation in GAD arise from a shared underlying neural mechanism. We used resting-state functional magnetic resonance imaging and the measurement of parasympathetic autonomic function (heart rate variability) in 19 patients with GAD and 21 control subjects to define neural correlates of autonomic and cognitive responses before and after induction of perseverative cognition. Seed-based analyses were conducted to quantify brain changes in functional connectivity with the right and left amygdala. Before induction, patients showed relatively lower connectivity between the right amygdala and right superior frontal gyrus, right paracingulate/anterior cingulate cortex, and right supramarginal gyrus than control subjects. After induction, such connectivity patterns increased in patients with GAD and decreased in control subjects, and these changes tracked increases in state perseverative cognition. Moreover, decreases in functional connectivity between the left amygdala and subgenual cingulate cortex and between the right amygdala and caudate nucleus predicted the magnitude of reduction in heart rate variability after induction. Our results link functional brain mechanisms underlying worry and rumination to autonomic dyscontrol, highlighting overlapping neural substrates associated with cognitive and autonomic responses to the induction of perseverative cognitions
Sensory Discrimination as Related to General Intelligence.
ERIC Educational Resources Information Center
Acton, G. Scott; Schroeder, David H.
2001-01-01
Attempted to replicate the pitch discrimination findings of previous research and expand them to the modality of color discrimination in a sample of 899 teenagers and adults by correlating 2 sensory discrimination measures with the general factor from a battery of 13 cognitive ability tests. Results suggest that sensory discrimination is…
An Elementary Formalism for General Relativity.
ERIC Educational Resources Information Center
diSessa, Andrea A.
1981-01-01
An elementary formalism is developed for representing curved space-time which allows transparent qualitative explanation of general relativistic effects and is used to make a conceptual analysis of Einstein's principle of equivalence. A final section outlines a number of student activities. (Author/SK)
An Elementary Formalism for General Relativity.
ERIC Educational Resources Information Center
diSessa, Andrea A.
1981-01-01
An elementary formalism is developed for representing curved space-time which allows transparent qualitative explanation of general relativistic effects and is used to make a conceptual analysis of Einstein's principle of equivalence. A final section outlines a number of student activities. (Author/SK)
Wiech, K; Jbabdi, S; Lin, C S; Andersson, J; Tracey, I
2014-10-01
Functional neuroimaging studies suggest that the anterior, mid, and posterior division of the insula subserve different functions in the perception of pain. The anterior insula (AI) has predominantly been associated with cognitive-affective aspects of pain, while the mid and posterior divisions have been implicated in sensory-discriminative processing. We examined whether this functional segregation is paralleled by differences in (1) structural and (2) resting state connectivity and (3) in correlations with pain-relevant psychological traits. Analyses were restricted to the 3 insular subdivisions and other pain-related brain regions. Both type of analyses revealed largely overlapping results. The AI division was predominantly connected to the ventrolateral prefrontal cortex (structural and resting state connectivity) and orbitofrontal cortex (structural connectivity). In contrast, the posterior insula showed strong connections to the primary somatosensory cortex (SI; structural connectivity) and secondary somatosensory cortex (SII; structural and resting state connectivity). The mid insula displayed a hybrid connectivity pattern with strong connections with the ventrolateral prefrontal cortex, SII (structural and resting state connectivity) and SI (structural connectivity). Moreover, resting state connectivity revealed strong connectivity of all 3 subdivisions with the thalamus. On the behavioural level, AI structural connectivity was related to the individual degree of pain vigilance and awareness that showed a positive correlation with AI-amygdala connectivity and a negative correlation with AI-rostral anterior cingulate cortex connectivity. In sum, our findings show a differential structural and resting state connectivity for the anterior, mid, and posterior insula with other pain-relevant brain regions, which might at least partly explain their different functional profiles in pain processing.
Yang, Yuan; Solis-Escalante, Teodoro; Yao, Jun; Daffertshofer, Andreas; Schouten, Alfred C; van der Helm, Frans C T
2016-02-01
Interaction between distant neuronal populations is essential for communication within the nervous system and can occur as a highly nonlinear process. To better understand the functional role of neural interactions, it is important to quantify the nonlinear connectivity in the nervous system. We introduce a general approach to measure nonlinear connectivity through phase coupling: the multi-spectral phase coherence (MSPC). Using simulated data, we compare MSPC with existing phase coupling measures, namely n : m synchronization index and bi-phase locking value. MSPC provides a system description, including (i) the order of the nonlinearity, (ii) the direction of interaction, (iii) the time delay in the system, and both (iv) harmonic and (v) intermodulation coupling beyond the second order; which are only partly revealed by other methods. We apply MSPC to analyze data from a motor control experiment, where subjects performed isotonic wrist flexions while receiving movement perturbations. MSPC between the perturbation, EEG and EMG was calculated. Our results reveal directional nonlinear connectivity in the afferent and efferent pathways, as well as the time delay (43 ± 8 ms) between the perturbation and the brain response. In conclusion, MSPC is a novel approach capable to assess high-order nonlinear interaction and timing in the nervous system.
Generating matter inhomogeneities in general relativity.
Coley, A A; Lim, W C
2012-05-11
In this Letter we discuss a natural general relativistic mechanism that causes inhomogeneities and hence generates matter perturbations in the early Universe. We concentrate on spikes, both incomplete spikes and recurring spikes, that naturally occur in the initial oscillatory regime of general cosmological models. In particular, we explicitly show that spikes occurring in a class of G2 models lead to inhomogeneities that, due to gravitational instability, leave small residual imprints on matter in the form of matter perturbations. The residual matter overdensities from recurring spikes are not local but form on surfaces. We discuss the potential physical consequences of the residual matter imprints and their possible effect on the subsequent formation of large-scale structure.
A General Paradigm for Public Relations Research.
ERIC Educational Resources Information Center
Whitcomb, Debra
Grunig's decision-situation model is proposed as a comprehensive framework under which various public-relations-related theories may be subsumed. The decision-situation model postulates three dimensions which, taken together, may predict the course of communication behavior: level of involvement, problem recognition, and structural constraints.…
Aberrant long-range functional connectivity density in generalized tonic-clonic seizures.
Zhu, Ling; Li, Yibo; Wang, Yifeng; Li, Rong; Zhang, Zhiqiang; Lu, Guangming; Chen, Huafu
2016-06-01
Studies in generalized tonic-clonic seizures (GTCS) have reported both structural and functional alterations in the brain. However, changes in spontaneous neuronal functional organization in GTCS remain largely unknown.In this study, 70 patients with idiopathic generalized epilepsy characterized by tonic-clonic seizures and 70 age- and sex-matched healthy controls were recruited. Here, functional connectivity density (FCD) mapping, an ultrafast data-driven method based on functional magnetic resonance imaging (fMRI), was applied for the first time to investigate the changes of spontaneous functional brain activity caused by epilepsy.The results showed significantly decreased long-range FCD in the middle and inferior temporal, prefrontal, and inferior parietal cortices as well as increased long-range FCD in the cerebellum anterior lobe and sensorimotor areas. Negative correlation between duration of disease and reduced long-range FCD was found. In addition, most regions with reduced long-range FCD showed decreased resting-state functional connectivity (rsFC) within default mode network.Negative correlation between duration of disease and long-range FCD may reflect an adverse consequence eventually from original. Furthermore, the observed FCD and rsFC alterations have been speculated to be associated with the social-cognitive impairments as well as motor control. Our study provided novel evidences to look into neuro-pathophysiological mechanisms underlying GTCS.
Ke, Ming; Jin, Bixia; Liu, Guangyao; Yang, Xiaoping
2017-01-01
). The results of the ROI3 (left middle cingulum) revealed the significantly decreased functional connectivity in the parietal lobe and frontal lobe. Seeding at the ROI4 (right middle cingulum), decreased functional connectivity showed in the occipital lobe, temporal lobe, frontal lobe. Seeding at the ROI5 (left posterior cingulum), decreased functional connectivity showed in the temporal lobe and frontal lobe. Seeding at the ROI6 (right posterior cingulum), decreased functional connectivity showed in the cuneus and frontal lobe. We did not find any increased functional connectivity of the posterior cingulated cortex (ROI3-ROI6) for the generalized tonic-clonic seizure patients in comparison to the controls (p<0.001). Our findings demonstrated that the abnormalities of the functional connectivity were likely to be related to the decreased gray matter volume in the cingulated cortex.
Uncertainty relations for general phase spaces
NASA Astrophysics Data System (ADS)
Werner, Reinhard F.
2016-04-01
We describe a setup for obtaining uncertainty relations for arbitrary pairs of observables related by a Fourier transform. The physical examples discussed here are the standard position and momentum, number and angle, finite qudit systems, and strings of qubits for quantum information applications. The uncertainty relations allow for an arbitrary choice of metric for the outcome distance, and the choice of an exponent distinguishing, e.g., absolute and root mean square deviations. The emphasis of this article is on developing a unified treatment, in which one observable takes on values in an arbitrary locally compact Abelian group and the other in the dual group. In all cases, the phase space symmetry implies the equality of measurement and preparation uncertainty bounds. There is also a straightforward method for determining the optimal bounds.
Altered task-related modulation of long-range connectivity in children with autism.
Pillai, Ajay S; McAuliffe, Danielle; Lakshmanan, Balaji M; Mostofsky, Stewart H; Crone, Nathan E; Ewen, Joshua B
2017-09-12
Functional connectivity differences between children with autism spectrum disorder (ASD) and typically developing children have been described in multiple datasets. However, few studies examine the task-related changes in connectivity in disorder-relevant behavioral paradigms. In this paper, we examined the task-related changes in functional connectivity using EEG and a movement-based paradigm that has behavioral relevance to ASD. Resting-state studies motivated our hypothesis that children with ASD would show a decreased magnitude of functional connectivity during the performance of a motor-control task. Contrary to our initial hypothesis, however, we observed that task-related modulation of functional connectivity in children with ASD was in the direction opposite to that of TDs. The task-related connectivity changes were correlated with clinical symptom scores. Our results suggest that children with ASD may have differences in cortical segregation/integration during the performance of a task, and that part of the differences in connectivity modulation may serve as a compensatory mechanism. Autism Res 2017. © 2017 International Society for Autism Research, Wiley Periodicals, Inc. Decreased connectivity between brain regions is thought to cause the symptoms of autism. Because most of our knowledge comes from data in which children are at rest, we do not know how connectivity changes directly lead to autistic behaviors, such as impaired gestures. When typically developing children produced complex movements, connectivity decreased between brain regions. In children with autism, connectivity increased. It may be that behavior-related changes in brain connectivity are more important than absolute differences in connectivity in autism. © 2017 International Society for Autism Research, Wiley Periodicals, Inc.
Conroy, Paul; Sage, Karen; Ralph, Matt Lambon
2009-01-01
Naming accuracy for nouns and verbs in aphasia can vary across different elicitation contexts, for example, simple picture naming, composite picture description, narratives, and conversation. For some people with aphasia, naming may be more accurate to simple pictures as opposed to naming in spontaneous, connected speech; for others, the opposite pattern may be evident. These differences have, in some instances, been related to word class (for example, noun or verb) as well as aphasia subtype. Given that the aim of picture-naming therapies is to improve word-finding in general, these differences in naming accuracy across contexts may have important implications for the potential functional benefits of picture-naming therapies. This study aimed to explore single-word therapy for both nouns and verbs, and to answer the following questions. (1) To what extent does an increase in naming accuracy after picture-naming therapy (for both nouns and verbs) predict accurate naming of the same items in less constrained spontaneous connected speech tasks such as composite picture description and retelling of a narrative? (2) Does the word class targeted in therapy (verb or noun) dictate whether there is 'carry-over' of the therapy item to connected speech tasks? (3) Does the speed at which the picture is named after therapy predict whether it will also be used appropriately in connected speech tasks? Seven participants with aphasia of varying degrees of severity and subtype took part in ten therapy sessions over five weeks. A set of potentially useful items was collected from control participant accounts of the Cookie Theft Picture Description and the Cinderella Story from the Quantitative Production Analysis. Twenty-four of these words (twelve verbs and twelve nouns) were collated for each participant, on the basis that they had failed to name them in either simple picture naming or connected speech tasks (picture-supported narrative and unsupported retelling of a narrative
Depression-Related Brain Connectivity Analyzed by EEG Event-Related Phase Synchrony Measure
Li, Yuezhi; Kang, Cheng; Qu, Xingda; Zhou, Yunfei; Wang, Wuyi; Hu, Yong
2016-01-01
This study is to examine changes of functional connectivity in patients with depressive disorder using synchronous brain activity. Event-related potentials (ERPs) were acquired during a visual oddball task in 14 patients with depressive disorder and 19 healthy controls. Electroencephalogram (EEG) recordings were analyzed using event-related phase coherence (ERPCOH) to obtain the functional network. Alteration of the phase synchronization index (PSI) of the functional network was investigated. Patients with depression showed a decreased number of significant electrode pairs in delta phase synchronization, and an increased number of significant electrode pairs in theta, alpha and beta phase synchronization, compared with controls. Patients with depression showed lower target-dependent PSI increment in the frontal-parietal/temporal/occipital electrode pairs in delta-phase synchronization than healthy participants. However, patients with depression showed higher target-dependent PSI increments in theta band in the prefrontal/frontal and frontal-temporal electrode pairs, higher PSI increments in alpha band in the prefrontal pairs and higher increments of beta PSI in the central and right frontal-parietal pairs than controls. It implied that the decrease in delta PSI activity in major depression may indicate impairment of the connection between the frontal and parietal/temporal/occipital regions. The increase in theta, alpha and beta PSI in the frontal/prefrontal sites might reflect the compensatory mechanism to maintain normal cognitive performance. These findings may provide a foundation for a new approach to evaluate the effectiveness of therapeutic strategies for depression. PMID:27725797
Pang, Lijuan; Kennedy, David; Wei, Qinling; Lv, Luxian; Gao, Jinsong; Li, Hong; Quan, Meina; Li, Xue; Yang, Yongfeng; Fan, Xiaoduo; Song, Xueqin
2017-01-01
Background This study was to examine the insular cortical functional connectivity in drug naïve patients with first episode schizophrenia and to explore the relationship between the connectivity and the severity of clinical symptoms. Methods Thirty-seven drug naïve patients with schizophrenia and 25 healthy controls were enrolled in this study. A seed-based approach was used to analyze the resting-state functional imaging data. Insular cortical connectivity maps were bilaterally extracted for group comparison and validated by voxel-based morphometry (VBM) analysis. Clinical symptoms were measured using the Positive and Negative Syndrome Scale (PANSS). Results There were significant reductions in the right insular cortical connectivity with the Heschl’s gyrus, anterior cingulate cortex (ACC), and caudate (p’s<0.001) in the patient group compared with the healthy control (HC) group. Reduced right insular cortical connectivity with the Heschl’s gyrus was further confirmed in the VBM analysis (FDR corrected p<0.05). Within the patient group, there was a significant positive relationship between the right insula-Heschl’s connectivity and PANSS general psychopathology scores (r = 0.384, p = 0.019). Conclusion Reduced insula-Heschl’s functional connectivity is present in drug naïve patients with first episode schizophrenia, which might be related to the manifestation of clinical symptoms. PMID:28107346
Sexual disclosures: connections to relational satisfaction and closeness.
Coffelt, Tina A; Hess, Jon A
2014-01-01
This study examines sexual communication by describing the content of sexual disclosures within marital relationships and assessing the association between sexual disclosures and relational outcomes, specifically relational satisfaction and closeness. A survey administered to 293 married individuals (58% female) who had an average age of 40 years (range = 20-73), 13.7 years of marriage (range = 1 month to 54 years), and who reported high levels of relational satisfaction assessed the relation between the content of sexual disclosures and satisfaction and closeness. While sexual disclosures are made infrequently, positive affect and sexual preferences are disclosed more than negative topics and disclosing sexual information is positively related to relationship satisfaction, rρ(280) =.26, p <.001; and closeness, rs(280) =.475, p <.01. Therapists can use these findings to show clients the positive relation between revealing sexual information and relationship satisfaction and closeness, as reported by individuals experiencing relationship satisfaction.
Connections between the Sznajd model with general confidence rules and graph theory.
Timpanaro, André M; Prado, Carmen P C
2012-10-01
The Sznajd model is a sociophysics model that is used to model opinion propagation and consensus formation in societies. Its main feature is that its rules favor bigger groups of agreeing people. In a previous work, we generalized the bounded confidence rule in order to model biases and prejudices in discrete opinion models. In that work, we applied this modification to the Sznajd model and presented some preliminary results. The present work extends what we did in that paper. We present results linking many of the properties of the mean-field fixed points, with only a few qualitative aspects of the confidence rule (the biases and prejudices modeled), finding an interesting connection with graph theory problems. More precisely, we link the existence of fixed points with the notion of strongly connected graphs and the stability of fixed points with the problem of finding the maximal independent sets of a graph. We state these results and present comparisons between the mean field and simulations in Barabási-Albert networks, followed by the main mathematical ideas and appendices with the rigorous proofs of our claims and some graph theory concepts, together with examples. We also show that there is no qualitative difference in the mean-field results if we require that a group of size q>2, instead of a pair, of agreeing agents be formed before they attempt to convince other sites (for the mean field, this would coincide with the q-voter model).
Ramabhadran, Raghunath O; Raghavachari, Krishnan
2011-07-12
A generalized, unique thermochemical hierarchy applicable for all closed shell organic molecules is developed in this paper. In this chemically intuitive, structure-based approach, the connectivity of the atoms in an organic molecule is used to construct our hierarchy called "connectivity-based hierarchy" (CBH). The hierarchy has several rungs and ascending up the hierarchy increasingly balances the reaction energy. It requires no prior knowledge of the types of molecules and hybridizations for the appropriate balancing of the bond types and the bonding environments of the atoms. The rungs can be generated by an automated computer program for any closed shell organic molecule, and the first three rungs generate the simplest reactions for the widely used isodesmic, hypohomodesmotic, and hyperhomodesmotic schemes. The generated reaction schemes are unique for each rung and are derived in a simpler manner than previous approaches, avoiding potential errors. This work also suggests that for closed shell organic molecules, the previously well-studied homodesmotic scheme does not have a fundamental structure-based origin. In a preliminary application of CBH, density functional theory has been used to calculate accurate enthalpies of formation for a test set of 20 organic molecules. The performance of the hierarchy suggests that it will be useful to predict accurate thermodynamic properties of larger organic molecules.
Connections between the Sznajd model with general confidence rules and graph theory
NASA Astrophysics Data System (ADS)
Timpanaro, André M.; Prado, Carmen P. C.
2012-10-01
The Sznajd model is a sociophysics model that is used to model opinion propagation and consensus formation in societies. Its main feature is that its rules favor bigger groups of agreeing people. In a previous work, we generalized the bounded confidence rule in order to model biases and prejudices in discrete opinion models. In that work, we applied this modification to the Sznajd model and presented some preliminary results. The present work extends what we did in that paper. We present results linking many of the properties of the mean-field fixed points, with only a few qualitative aspects of the confidence rule (the biases and prejudices modeled), finding an interesting connection with graph theory problems. More precisely, we link the existence of fixed points with the notion of strongly connected graphs and the stability of fixed points with the problem of finding the maximal independent sets of a graph. We state these results and present comparisons between the mean field and simulations in Barabási-Albert networks, followed by the main mathematical ideas and appendices with the rigorous proofs of our claims and some graph theory concepts, together with examples. We also show that there is no qualitative difference in the mean-field results if we require that a group of size q>2, instead of a pair, of agreeing agents be formed before they attempt to convince other sites (for the mean field, this would coincide with the q-voter model).
Lange, Adrian W; Herbert, John M
2012-11-13
A previous analytical investigation of the generalized Born (GB) implicit solvation model is extended to solvents of nonzero ionic strength. The GB model with salt effects (GB-SE) is shown to resemble the Debye-Hückel-like screening model (DESMO), a polarizable continuum model (PCM) that we have recently developed for salty solutions. DESMO may be regarded either as a generalization of the conductor-like PCM (C-PCM) that extends C-PCM to electrolyte solutions or alternatively as a generalization of Debye-Hückel theory to arbitrary cavity shapes. The connection between GB-SE and DESMO suggests how the former can be modified to account for the exclusion of mobile ions from the cavity interior, an effect that is typically absent in GB-SE models. We propose two simple GB-SE models that are exact for a point charge in a spherical cavity and that introduce the ability to account, albeit approximately, for the finite size of the mobile ions. The accuracy of these new models is demonstrated by applications to both model systems and real proteins. These tests also demonstrate the accuracy of the DESMO approach, as compared to more sophisticated PCMs developed for electrolyte solutions.
Generalization of the Schwarz–Christoffel mapping to multiply connected polygonal domains
Vasconcelos, Giovani L.
2014-01-01
A generalization of the Schwarz–Christoffel mapping to multiply connected polygonal domains is obtained by making a combined use of two preimage domains, namely, a rectilinear slit domain and a bounded circular domain. The conformal mapping from the circular domain to the polygonal region is written as an indefinite integral whose integrand consists of a product of powers of the Schottky-Klein prime functions, which is the same irrespective of the preimage slit domain, and a prefactor function that depends on the choice of the rectilinear slit domain. A detailed derivation of the mapping formula is given for the case where the preimage slit domain is the upper half-plane with radial slits. Representation formulae for other canonical slit domains are also obtained but they are more cumbersome in that the prefactor function contains arbitrary parameters in the interior of the circular domain. PMID:24910523
Generalization of the Schwarz-Christoffel mapping to multiply connected polygonal domains.
Vasconcelos, Giovani L
2014-06-08
A generalization of the Schwarz-Christoffel mapping to multiply connected polygonal domains is obtained by making a combined use of two preimage domains, namely, a rectilinear slit domain and a bounded circular domain. The conformal mapping from the circular domain to the polygonal region is written as an indefinite integral whose integrand consists of a product of powers of the Schottky-Klein prime functions, which is the same irrespective of the preimage slit domain, and a prefactor function that depends on the choice of the rectilinear slit domain. A detailed derivation of the mapping formula is given for the case where the preimage slit domain is the upper half-plane with radial slits. Representation formulae for other canonical slit domains are also obtained but they are more cumbersome in that the prefactor function contains arbitrary parameters in the interior of the circular domain.
Jung, Kwanghee; Takane, Yoshio; Hwang, Heungsun; Woodward, Todd S
2016-06-01
We extend dynamic generalized structured component analysis (GSCA) to enhance its data-analytic capability in structural equation modeling of multi-subject time series data. Time series data of multiple subjects are typically hierarchically structured, where time points are nested within subjects who are in turn nested within a group. The proposed approach, named multilevel dynamic GSCA, accommodates the nested structure in time series data. Explicitly taking the nested structure into account, the proposed method allows investigating subject-wise variability of the loadings and path coefficients by looking at the variance estimates of the corresponding random effects, as well as fixed loadings between observed and latent variables and fixed path coefficients between latent variables. We demonstrate the effectiveness of the proposed approach by applying the method to the multi-subject functional neuroimaging data for brain connectivity analysis, where time series data-level measurements are nested within subjects.
Making Connections through Math-Related Book Pairs
ERIC Educational Resources Information Center
Whitin, Phyllis; Whitin, David J.
2006-01-01
Students can be provided opportunities to build both English and mathematical proficiency through reading, discussing and extending mathematics-related books. The experience of a teacher through which she expanded her instructional use of mathematics-related literature is described, which was equally valuable for English Language Learners and…
Large-scale tides in general relativity
NASA Astrophysics Data System (ADS)
Ip, Hiu Yan; Schmidt, Fabian
2017-02-01
Density perturbations in cosmology, i.e. spherically symmetric adiabatic perturbations of a Friedmann-Lemaȋtre-Robertson-Walker (FLRW) spacetime, are locally exactly equivalent to a different FLRW solution, as long as their wavelength is much larger than the sound horizon of all fluid components. This fact is known as the "separate universe" paradigm. However, no such relation is known for anisotropic adiabatic perturbations, which correspond to an FLRW spacetime with large-scale tidal fields. Here, we provide a closed, fully relativistic set of evolutionary equations for the nonlinear evolution of such modes, based on the conformal Fermi (CFC) frame. We show explicitly that the tidal effects are encoded by the Weyl tensor, and are hence entirely different from an anisotropic Bianchi I spacetime, where the anisotropy is sourced by the Ricci tensor. In order to close the system, certain higher derivative terms have to be dropped. We show that this approximation is equivalent to the local tidal approximation of Hui and Bertschinger [1]. We also show that this very simple set of equations matches the exact evolution of the density field at second order, but fails at third and higher order. This provides a useful, easy-to-use framework for computing the fully relativistic growth of structure at second order.
Derived relations and generalized alteration of preferences.
Valdivia-Salas, Sonsoles; Dougher, Michael J; Luciano, Carmen
2013-06-01
The present study examined the role of derived relations in the generalizability of the evaluative conditioning effect. Healthy university students participated. Four geometrical shapes were first established as discriminative stimuli for the contingent presentation of pictograms (B1, B2, C1, and C2, respectively). We then assessed the reinforcing properties of B1 versus B2, and C1 versus C2 by using simultaneous discrimination tasks: at baseline (baseline assessment), after pairing B1 with aversive slides plus noise and B2 with pleasant slides (test I), and after employing equivalence training and testing to establish B1 as equivalent to C1 and B2 as equivalent to C2 (test II). Most participants (82%) in the experimental condition, as compared with the control conditions (17% and 10%), selected the discriminative shapes for B2 (test I) and C2 (test II) on most trials, replicating and extending previous findings. Subsequently, the geometrical shapes were established as equivalent to the letters X, Y, W, and Z, respectively, which then served as antecedent stimuli in simultaneous discrimination tasks as before (test III). As was expected, only participants in the experimental condition showed preference for the novel letters that were established as equivalent to B2-producing and C2-producing shapes. These findings suggest that the evaluative conditioning effect may extend far beyond the stimulus being de/valuated and narrow the behavioral repertoire.
Connection between energy relations of solids and molecules
NASA Technical Reports Server (NTRS)
Smith, John R.; Schlosser, Herbert; Leaf, William; Ferrante, John; Rose, James H.
1989-01-01
The universal energy relation, discovered for metallic and covalent solids as well as nuclear matter, is tested for diatomic molecules. It is found that it applies well to covalent diatomic bonds, but that ionic diatomic bonds are in a distinct class. A simple extension of the universal binding energy relation that includes the effects of ionicity ensues. It yields accurate prediction of spectroscopic data for both ionic and covalent bonds in 150 molecules. The form of the covalent part is given by the universal relation, suggesting an intimate relationship between the energetics of solids and diatomic molecules.
Connection between energy relations of solids and molecules
NASA Technical Reports Server (NTRS)
Smith, John R.; Schlosser, Herbert; Leaf, William; Ferrante, John; Rose, James H.
1989-01-01
The universal energy relation, discovered for metallic and covalent solids as well as nuclear matter, is tested for diatomic molecules. It is found that it applies well to covalent diatomic bonds, but that ionic diatomic bonds are in a distinct class. A simple extension of the universal binding energy relation that includes the effects of ionicity ensues. It yields accurate prediction of spectroscopic data for both ionic and covalent bonds in 150 molecules. The form of the covalent part is given by the universal relation, suggesting an intimate relationship between the energetics of solids and diatomic molecules.
Laboratory Connections: Gas Monitoring Transducers: Relative Humidity Sensors.
ERIC Educational Resources Information Center
Powers, Michael H.; Hull, Stacey E.
1988-01-01
Explains the operation of five relative humidity sensors: psychrometer, hair hygrometer, resistance hygrometer, capacitance hygrometer, and resistance-capacitance hygrometer. Outlines the theory behind the electronic sensors and gives computer interfacing information. Lists sensor responses for calibration. (MVL)
Laboratory Connections: Gas Monitoring Transducers: Relative Humidity Sensors.
ERIC Educational Resources Information Center
Powers, Michael H.; Hull, Stacey E.
1988-01-01
Explains the operation of five relative humidity sensors: psychrometer, hair hygrometer, resistance hygrometer, capacitance hygrometer, and resistance-capacitance hygrometer. Outlines the theory behind the electronic sensors and gives computer interfacing information. Lists sensor responses for calibration. (MVL)
Directions in General Relativity, Vol. 1
NASA Astrophysics Data System (ADS)
Hu, B. L.; Ryan, M. P., Jr.; Vishveshwara, C. V.
2005-10-01
1. Remarks concerning the geometrics of gravity, gauge fields and quantum theory J. S. Anandan; 2. Gravity and the unification of fundamental interactions R. L. Arnowitt and P. Nath; 3. Minisuperspaces: symmetrics and quantization A. Ashtekar, R. S. Tate and C. Uggla; 4. Quantum cosmology B. K. Berger; 5. A pictorial history of some gravitational instanton D. Brill and K.- T. Pirk; 6. No time machines from lightlike sources in 2+1 gravity S. Deser and A. R. Steif; 7. Inhomogeneity and anisotropy genertation in FRW cosmologies G. F. R. Ellis and D. R. Matravers; 8. Misner, kinks and Black Holes D. Finkelstein; 9. The quantum mechanics of closed systems J. B. Hartle; 10. Cosmological vacuum open system W. A. Hiscock and D. A. Samuel; 11. Minisuperspace as a quantum open system B. L. Hu, J. P. Paz and S. Sinha; 12. Ricci flow on minisuperspaces and the geometry-topology problem J. Isenberg and M. Jackson; 13. Classical and quantum dynamics of Black Hole interiors W. Israel; 14. Matter time in canonical quantum gravity K. V. Kuchar; 15. The isotropy and homogeneity of the universe R. A. Matzner; 16. Recent advances in ADM reduction V. Moncrief; 17. Some progress in classical canonical gravity J. M. Nester; 18. Harmonic map formulation of colliding electrovac place waves Y. Nutku; 19. Geometry, the renormalization groups and gravity D. J. O'Connor and C. R. Stephens; 20. An example of the indeterminacy of the already-unified theory R. Penrose; 21. Nonstatic metric of Hiscock-Gott type A. K. Raychaudhuri; 22. Non-standard phase space variables, quantization and path-integrals, or little ado about much M. P. Ryan, Jr. and Sergio Hojmann; 23. The present status of the decaying neutrino theory D. W. Sciama; 24. Exploiting the computer to investigate Black Holes and cosmic censorship S. L. Shapiro and S. A. Teukolsky; 25. Misner space as a prototype for almost any pathology K. S. Thorne; 26. Relativity and rotation C. V. Vishveshwara; 27. The first law of Black Hole
Drawing Connections across Conceptually Related Visual Representations in Science
ERIC Educational Resources Information Center
Hansen, Janice
2013-01-01
This dissertation explored beliefs about learning from multiple related visual representations in science, and compared beliefs to learning outcomes. Three research questions were explored: 1) What beliefs do pre-service teachers, non-educators and children have about learning from visual representations? 2) What format of presenting those…
Age-related differences of neural connectivity during mental rotation.
Thomas, Monika
2016-03-01
The purpose of the present study was to investigate age-related effects on functional brain networks during a mental rotation task. At behavioral level age-related cognitive deficits have been shown. Cognitive deficits in older adults are associated with structural decline, especially in frontal and parietal areas and in the corpus callosum. In consequence, functional networks are affected by old age as well. To this end, a graph theoretical approach was taken, which quantifies the global and local efficiency as well as the cost efficiency of frontal and parietal intrahemispheric and interhemispheric networks. Main results indicate that intrahemispheric and interhemispheric networks are differently affected by older age: in the left frontal and the left and right parietal intrahemispheric networks global and local efficiency was reduced, whereas in frontal and parietal interhemispheric networks cost efficiency was decreased. Copyright © 2016. Published by Elsevier B.V.
Do age-related word retrieval difficulties appear (or disappear) in connected speech?
Kavé, Gitit; Goral, Mira
2017-09-01
We conducted a comprehensive literature review of studies of word retrieval in connected speech in healthy aging and reviewed relevant aphasia research that could shed light on the aging literature. Four main hypotheses guided the review: (1) Significant retrieval difficulties would lead to reduced output in connected speech. (2) Significant retrieval difficulties would lead to a more limited lexical variety in connected speech. (3) Significant retrieval difficulties would lead to an increase in word substitution errors and in pronoun use as well as to greater dysfluency and hesitation in connected speech. (4) Retrieval difficulties on tests of single-word production would be associated with measures of word retrieval in connected speech. Studies on aging did not confirm these four hypotheses, unlike studies on aphasia that generally did. The review suggests that future research should investigate how context facilitates word production in old age.
Multifractal analysis of visibility graph-based Ito-related connectivity time series.
Czechowski, Zbigniew; Lovallo, Michele; Telesca, Luciano
2016-02-01
In this study, we investigate multifractal properties of connectivity time series resulting from the visibility graph applied to normally distributed time series generated by the Ito equations with multiplicative power-law noise. We show that multifractality of the connectivity time series (i.e., the series of numbers of links outgoing any node) increases with the exponent of the power-law noise. The multifractality of the connectivity time series could be due to the width of connectivity degree distribution that can be related to the exit time of the associated Ito time series. Furthermore, the connectivity time series are characterized by persistence, although the original Ito time series are random; this is due to the procedure of visibility graph that, connecting the values of the time series, generates persistence but destroys most of the nonlinear correlations. Moreover, the visibility graph is sensitive for detecting wide "depressions" in input time series.
NASA Astrophysics Data System (ADS)
Abd-Elhameed, W. M.
2017-07-01
In this paper, a new formula relating Jacobi polynomials of arbitrary parameters with the squares of certain fractional Jacobi functions is derived. The derived formula is expressed in terms of a certain terminating hypergeometric function of the type _4F3(1) . With the aid of some standard reduction formulae such as Pfaff-Saalschütz's and Watson's identities, the derived formula can be reduced in simple forms which are free of any hypergeometric functions for certain choices of the involved parameters of the Jacobi polynomials and the Jacobi functions. Some other simplified formulae are obtained via employing some computer algebra algorithms such as the algorithms of Zeilberger, Petkovsek and van Hoeij. Some connection formulae between some Jacobi polynomials are deduced. From these connection formulae, some other linearization formulae of Chebyshev polynomials are obtained. As an application to some of the introduced formulae, a numerical algorithm for solving nonlinear Riccati differential equation is presented and implemented by applying a suitable spectral method.
29 CFR 778.5 - Relation to other laws generally.
Code of Federal Regulations, 2010 CFR
2010-07-01
... POLICY OR INTERPRETATION NOT DIRECTLY RELATED TO REGULATIONS OVERTIME COMPENSATION General Considerations..., and the payment of overtime compensation computed on bases different from those set forth in the...
NASA Astrophysics Data System (ADS)
Ness, H.; Genina, A.; Stella, L.; Lorenz, C. D.; Kantorovich, L.
2016-05-01
We extend the generalized Langevin equation (GLE) method [L. Stella, C. D. Lorenz, and L. Kantorovich, Phys. Rev. B 89, 134303 (2014), 10.1103/PhysRevB.89.134303] to model a central classical region connected to two realistic thermal baths at two different temperatures. In such nonequilibrium conditions a heat flow is established, via the central system, in between the two baths. The GLE-2B (GLE two baths) scheme permits us to have a realistic description of both the dissipative central system and its surrounding baths. Following the original GLE approach, the extended Langevin dynamics scheme is modified to take into account two sets of auxiliary degrees of freedom corresponding to the mapping of the vibrational properties of each bath. These auxiliary variables are then used to solve the non-Markovian dissipative dynamics of the central region. The resulting algorithm is used to study a model of a short Al nanowire connected to two baths. The results of the simulations using the GLE-2B approach are compared to the results of other simulations that were carried out using standard thermostatting approaches (based on Markovian Langevin and Nosé-Hoover thermostats). We concentrate on the steady-state regime and study the establishment of a local temperature profile within the system. The conditions for obtaining a flat profile or a temperature gradient are examined in detail, in agreement with earlier studies. The results show that the GLE-2B approach is able to treat, within a single scheme, two widely different thermal transport regimes, i.e., ballistic systems, with no temperature gradient, and diffusive systems with a temperature gradient.
Origins and development of the Cauchy problem in general relativity
NASA Astrophysics Data System (ADS)
Ringström, Hans
2015-06-01
The seminal work of Yvonne Choquet-Bruhat published in 1952 demonstrates that it is possible to formulate Einstein's equations as an initial value problem. The purpose of this article is to describe the background to and impact of this achievement, as well as the result itself. In some respects, the idea of viewing the field equations of general relativity as a system of evolution equations goes back to Einstein himself; in an argument justifying that gravitational waves propagate at the speed of light, Einstein used a special choice of coordinates to derive a system of wave equations for the linear perturbations on a Minkowski background. Over the following decades, Hilbert, de Donder, Lanczos, Darmois and many others worked to put Einstein's ideas on a more solid footing. In fact, the issue of local uniqueness (giving a rigorous justification for the statement that the speed of propagation of the gravitational field is bounded by that of light) was already settled in the 1930s by the work of Stellmacher. However, the first person to demonstrate both local existence and uniqueness in a setting in which the notion of finite speed of propagation makes sense was Yvonne Choquet-Bruhat. In this sense, her work lays the foundation for the formulation of Einstein's equations as an initial value problem. Following a description of the results of Choquet-Bruhat, we discuss the development of three research topics that have their origin in her work. The first one is local existence. One reason for addressing it is that it is at the heart of the original paper. Moreover, it is still an active and important research field, connected to the problem of characterizing the asymptotic behaviour of solutions that blow up in finite time. As a second topic, we turn to the questions of global uniqueness and strong cosmic censorship. These questions are of fundamental importance to anyone interested in justifying that the Cauchy problem makes sense globally. They are also closely
Microscopic diagonal entropy and its connection to basic thermodynamic relations
Polkovnikov, Anatoli
2011-02-15
We define a diagonal entropy (d-entropy) for an arbitrary Hamiltonian system as S{sub d}=-{Sigma}{sub n{rho}nn}ln{rho}{sub nn} with the sum taken over the basis of instantaneous energy states. In equilibrium this entropy coincides with the conventional von Neumann entropy S{sub n} = -Tr{rho} ln {rho}. However, in contrast to S{sub n}, the d-entropy is not conserved in time in closed Hamiltonian systems. If the system is initially in stationary state then in accord with the second law of thermodynamics the d-entropy can only increase or stay the same. We also show that the d-entropy can be expressed through the energy distribution function and thus it is measurable, at least in principle. Under very generic assumptions of the locality of the Hamiltonian and non-integrability the d-entropy becomes a unique function of the average energy in large systems and automatically satisfies the fundamental thermodynamic relation. This relation reduces to the first law of thermodynamics for quasi-static processes. The d-entropy is also automatically conserved for adiabatic processes. We illustrate our results with explicit examples and show that S{sub d} behaves consistently with expectations from thermodynamics.
Are hypnosis and dissociation related? New evidence for a connection.
Cleveland, Jonathan M; Korman, Brandon M; Gold, Steven N
2015-01-01
The authors revisit the question of the existence of a relationship between hypnotizability and dissociative capacity. In the present study, the State Scale of Dissociation (SSD) replaced the commonly employed Dissociative Experiences Scale (DES) as a measure of dissociation, due to the latter capturing primarily pathological aspects of dissociation. Relationships between the Harvard Scale of Hypnotic Susceptibility, Form A (HGSHS:A), the SSD, and the Phenomenology of Consciousness Inventory (PCI) were assessed in the context of hypnosis. Robust results were found when comparing pre- to post-SSD scores, suggesting heightened nonpathological forms of dissociation are indeed related to hypnotizability. The appropriateness of the DES and similar trait-based measures for evaluating hypnotic phenomena is discussed as well as the relationships between PCI and SSD subscales.
Thomas, Sarah A.; Hoste, Renee Rienecke; Le Grange, Daniel
2012-01-01
Objective To examine the relation between observed familial connection and individuation and adolescent bulimia nervosa (BN) symptoms. Method As part of a treatment study for adolescent BN, adolescents (n = 54) and their parents participated in a videotaped semi-structured interview. Participants were rated on observed connection and individuation from these interviews using the Scale of Intergenerational Relationship Quality and two measures of connection. Results There was a significant negative relation between individuation from parents and adolescent BN symptoms. Connection both to and from mothers and adolescents was negatively associated with BN symptoms. Increased eating concern was significantly associated with a greater likelihood of expressing a desire for more connection with the family. Discussion Investigating and understanding family factors present at the time of adolescent BN may assist in providing treatment specific to the needs of the family to best aid the adolescent’s recovery process. PMID:22593023
Generalized Orthogonality Relations and SU(1,1)-Quantum Tomography
NASA Astrophysics Data System (ADS)
Carmeli, C.; Cassinelli, G.; Zizzi, F.
2009-06-01
We present a mathematically precise derivation of some generalized orthogonality relations for the discrete series representations of SU(1,1). These orthogonality relations are applied to derive tomographical reconstruction formulas. Their physical interpretation is also discussed.
Englot, Dario J; Konrad, Peter E; Morgan, Victoria L
2016-10-01
Epilepsy is among the most common brain network disorders, and it is associated with substantial morbidity and increased mortality. Although focal epilepsy was traditionally considered a regional brain disorder, growing evidence has demonstrated widespread network alterations in this disorder that extend beyond the epileptogenic zone from which seizures originate. The goal of this review is to summarize recent investigations examining functional and structural connectivity alterations in focal epilepsy, including neuroimaging and electrophysiologic studies utilizing model-based or data-driven analytic methods. A significant subset of studies in both mesial temporal lobe epilepsy and focal neocortical epilepsy have demonstrated patterns of increased connectivity related to the epileptogenic zone, coupled with decreased connectivity in widespread distal networks. Connectivity patterns appear to be related to the duration and severity of disease, suggesting progressive connectivity reorganization in the setting of recurrent seizures over time. Global resting-state connectivity disturbances in focal epilepsy have been linked to neurocognitive problems, including memory and language disturbances. Although it is possible that increased connectivity in a particular brain region may enhance the propensity for seizure generation, it is not clear if global reductions in connectivity represent the damaging consequences of recurrent seizures, or an adaptive mechanism to prevent seizure propagation away from the epileptogenic zone. Overall, studying the connectome in focal epilepsy is a critical endeavor that may lead to improved strategies for epileptogenic-zone localization, surgical outcome prediction, and a better understanding of the neuropsychological implications of recurrent seizures.
NASA Astrophysics Data System (ADS)
Maute, Astrid
2017-04-01
The NASA Ionospheric Connection explorer (ICON) will study the coupling between the thermosphere and ionosphere at low- and mid-latitudes by measuring the key parameters. The ICON mission will also employ numerical modeling to support the interpretation of the observations, and examine the importance of different vertical coupling mechanisms by conducting numerical experiments. One of these models is the Thermosphere-Ionosphere-Electrodynamics General Circulation Model-ICON (TIEGCM-ICON) which will be driven by tidal perturbations derived from ICON observations using the Hough Mode Extension method (HME) and at high latitude by ion convection and auroral particle precipitation patterns from the Assimilative Mapping of Ionospheric Electrodynamics (AMIE). The TIEGCM-ICON will simulate the thermosphere-ionosphere (TI) system during the period of the ICON mission. In this report the TIEGCM-ICON is introduced, and the focus is on examining the effect of the lower boundary on the TI-system to provide some guidance for interpreting future ICON model results.
Prefrontal-limbic connectivity during worry in older adults with generalized anxiety disorder.
Mohlman, Jan; Eldreth, Dana A; Price, Rebecca B; Staples, Alison M; Hanson, Catherine
2017-04-01
Although generalized anxiety disorder (GAD) is one of the most prevalent anxiety disorders in older adults, very little is known about the neurobiology of worry, the hallmark symptom of GAD in adults over the age of 60. This study investigated the neurobiology and neural circuitry of worry in older GAD patients and controls. Twenty older GAD patients and 16 age-matched controls (mean age = 67.88) were compared on clinical measures and neural activity during worry using functional magnetic resonance imaging. As expected, worry elicited activation in frontal regions, amygdala, and insula within the GAD group, with a similar but less prominent frontal pattern was observed in controls. Effective connectivity analyses revealed a positive directional circuit in the GAD group extending from ventromedial through dorsolateral prefrontal cortices, converging on the amygdala. A less complex circuit was observed in controls with only dorsolateral prefrontal regions converging on the amygdala; however, a separate circuit passing through the orbitofrontal cortex converged on the insula. Results elucidate a different neurobiology of pathological versus normal worry in later life. A limited resource model is implicated wherein worry in GAD competes for the same neural resources (e.g. prefrontal cortical areas) that are involved in the adaptive regulation of emotion through cognitive and behavioral strategies.
A generalized Brownian motion model for turbulent relative particle dispersion
NASA Astrophysics Data System (ADS)
Shivamoggi, B. K.
2016-08-01
There is speculation that the difficulty in obtaining an extended range with Richardson-Obukhov scaling in both laboratory experiments and numerical simulations is due to the finiteness of the flow Reynolds number Re in these situations. In this paper, a generalized Brownian motion model has been applied to describe the relative particle dispersion problem in more realistic turbulent flows and to shed some light on this issue. The fluctuating pressure forces acting on a fluid particle are taken to be a colored noise and follow a stationary process and are described by the Uhlenbeck-Ornstein model while it appears plausible to take their correlation time to have a power-law dependence on Re, thus introducing a bridge between the Lagrangian quantities and the Eulerian parameters for this problem. This ansatz is in qualitative agreement with the possibility of a connection speculated earlier by Corrsin [26] between the white-noise representation for the fluctuating pressure forces and the large-Re assumption in the Kolmogorov [4] theory for the 3D fully developed turbulence (FDT) as well as a similar argument of Monin and Yaglom [23] and a similar result of Sawford [13] and Borgas and Sawford [24]. It also provides an insight into the result that the Richardson-Obukhov scaling holds only in the infinite-Re limit and disappears otherwise. This ansatz further provides a determination of the Richardson-Obukhov constant g as a function of Re, with an asymptotic constant value in the infinite-Re limit. It is shown to lead to full agreement, in the small-Re limit as well, with the Batchelor-Townsend [27] scaling for the rate of change of the mean square interparticle separation in 3D FDT, hence validating its soundness further.
A Generalization of Onsager's Reciprocity Relations to Gradient Flows with Nonlinear Mobility
NASA Astrophysics Data System (ADS)
Mielke, Alexander; Renger, D. R. Michiel; Peletier, Mark A.
2016-04-01
Onsager's 1931 "reciprocity relations" result connects microscopic time reversibility with a symmetry property of corresponding macroscopic evolution equations. Among the many consequences is a variational characterization of the macroscopic evolution equation as a gradient-flow, steepest ascent, or maximal entropy production equation. Onsager's original theorem is limited to close-to-equilibrium situations, with a Gaussian-invariant measure and a linear macroscopic evolution. In this paper, we generalize this result beyond these limitations and show how the microscopic time reversibility leads to natural generalized symmetry conditions, which take the form of generalized gradient flows.
Geodesic Motion in General Relativity:. Lares in Earth's Gravity
NASA Astrophysics Data System (ADS)
Ciufolini, I.; Gurzadyan, V. G.; Penrose, R.; Paolozzi, A.
2013-11-01
According to General Relativity, as distinct from Newtonian gravity, motion under gravity is treated by a theory that deals, initially, only with test particles. At the same time, satellite measurements deal with extended bodies. We discuss the correspondence between geodesic motion in General Relativity and the motion of an extended body by means of the Ehlers-Geroch theorem, and in the context of the recently launched LAser RElativity Satellite (LARES). Being possibly the highest mean density orbiting body in the Solar system, this satellite provides the best realization of a test particle ever reached experimentally and provides a unique possibility for testing the predictions of General Relativity.
Driesen, Naomi R; McCarthy, Gregory; Bhagwagar, Zubin; Bloch, Michael H; Calhoun, Vincent D; D'Souza, Deepak C; Gueorguieva, Ralitza; He, George; Leung, Hoi-Chung; Ramani, Ramachandran; Anticevic, Alan; Suckow, Raymond F; Morgan, Peter T; Krystal, John H
2013-01-01
Preclinical research suggests that N-methyl-D-aspartate glutamate receptors (NMDA-Rs) have a crucial role in working memory (WM). In this study, we investigated the role of NMDA-Rs in the brain activation and connectivity that subserve WM. Because of its importance in WM, the lateral prefrontal cortex, particularly the dorsolateral prefrontal cortex and its connections, were the focus of analyses. Healthy participants (n=22) participated in a single functional magnetic resonance imaging session. They received saline and then the NMDA-R antagonist ketamine while performing a spatial WM task. Time-course analysis was used to compare lateral prefrontal activation during saline and ketamine administration. Seed-based functional connectivity analysis was used to compare dorsolateral prefrontal connectivity during the two conditions and global-based connectivity was used to test for laterality in these effects. Ketamine reduced accuracy on the spatial WM task and brain activation during the encoding and early maintenance (EEM) period of task trials. Decrements in task-related activation during EEM were related to performance deficits. Ketamine reduced connectivity in the DPFC network bilaterally, and region-specific reductions in connectivity were related to performance. These results support the hypothesis that NMDA-Rs are critical for WM. The knowledge gained may be helpful in understanding disorders that might involve glutamatergic deficits such as schizophrenia and developing better treatments. PMID:23856634
Driesen, Naomi R; McCarthy, Gregory; Bhagwagar, Zubin; Bloch, Michael H; Calhoun, Vincent D; D'Souza, Deepak C; Gueorguieva, Ralitza; He, George; Leung, Hoi-Chung; Ramani, Ramachandran; Anticevic, Alan; Suckow, Raymond F; Morgan, Peter T; Krystal, John H
2013-12-01
Preclinical research suggests that N-methyl-D-aspartate glutamate receptors (NMDA-Rs) have a crucial role in working memory (WM). In this study, we investigated the role of NMDA-Rs in the brain activation and connectivity that subserve WM. Because of its importance in WM, the lateral prefrontal cortex, particularly the dorsolateral prefrontal cortex and its connections, were the focus of analyses. Healthy participants (n=22) participated in a single functional magnetic resonance imaging session. They received saline and then the NMDA-R antagonist ketamine while performing a spatial WM task. Time-course analysis was used to compare lateral prefrontal activation during saline and ketamine administration. Seed-based functional connectivity analysis was used to compare dorsolateral prefrontal connectivity during the two conditions and global-based connectivity was used to test for laterality in these effects. Ketamine reduced accuracy on the spatial WM task and brain activation during the encoding and early maintenance (EEM) period of task trials. Decrements in task-related activation during EEM were related to performance deficits. Ketamine reduced connectivity in the DPFC network bilaterally, and region-specific reductions in connectivity were related to performance. These results support the hypothesis that NMDA-Rs are critical for WM. The knowledge gained may be helpful in understanding disorders that might involve glutamatergic deficits such as schizophrenia and developing better treatments.
NASA Astrophysics Data System (ADS)
D'Souza, Adora M.; Abidin, Anas Zainul; Nagarajan, Mahesh B.; Wismüller, Axel
2016-03-01
We investigate the applicability of a computational framework, called mutual connectivity analysis (MCA), for directed functional connectivity analysis in both synthetic and resting-state functional MRI data. This framework comprises of first evaluating non-linear cross-predictability between every pair of time series prior to recovering the underlying network structure using community detection algorithms. We obtain the non-linear cross-prediction score between time series using Generalized Radial Basis Functions (GRBF) neural networks. These cross-prediction scores characterize the underlying functionally connected networks within the resting brain, which can be extracted using non-metric clustering approaches, such as the Louvain method. We first test our approach on synthetic models with known directional influence and network structure. Our method is able to capture the directional relationships between time series (with an area under the ROC curve = 0.92 +/- 0.037) as well as the underlying network structure (Rand index = 0.87 +/- 0.063) with high accuracy. Furthermore, we test this method for network recovery on resting-state fMRI data, where results are compared to the motor cortex network recovered from a motor stimulation sequence, resulting in a strong agreement between the two (Dice coefficient = 0.45). We conclude that our MCA approach is effective in analyzing non-linear directed functional connectivity and in revealing underlying functional network structure in complex systems.
ERIC Educational Resources Information Center
Stevenson, Rosemary; Knott, Alistair; Oberlander, Jon; McDonald, Sharon
2000-01-01
Investigates the relationship between focusing and coherence relations in pronoun comprehension. Examines a function of connectives: that of signaling coherence relations between two clauses. In three studies, coherence relations between sentence fragments ending in pronouns and participants' continuations to the fragments were identified.…
Torsional Newton–Cartan gravity from the large c expansion of general relativity
NASA Astrophysics Data System (ADS)
Van den Bleeken, Dieter
2017-09-01
We revisit the manifestly covariant large c expansion of general relativity, c being the speed of light. Assuming the relativistic connection has no pole in c-2 , this expansion is known to reproduce Newton–Cartan gravity and a covariant version of post-Newtonian corrections to it. We show that relaxing this assumption leads to the inclusion of twistless torsion in the effective non-relativistic theory. We argue that the resulting twistless torsion Newton–Cartan theory is an effective description of a non-relativistic regime of general relativity that extends Newtonian physics by including strong gravitational time dilation.
Hess, Jon A; Coffelt, Tina A
2012-01-01
This study examined the vocabulary husbands and wives use for talking to each other about sex, and connections between language use and relational qualities. Married people (n = 293) responded to a questionnaire about their use of common sex-related terms and about several characteristics of their marriage: sexual communication satisfaction, relational satisfaction, and relational closeness. Cluster analysis based on reported use revealed that sexual terms fell into clusters characterized as clinical terms, slang, or standard English. Results showed an association between use of sexual terms, particularly slang terms, and both satisfaction and closeness. This connection was stronger for women than for men. The findings offer insight into sexual talk and marital relationships.
NASA Astrophysics Data System (ADS)
Tang, Zhenchao; Liu, Zhenyu; Li, Ruili; Cui, Xinwei; Li, Hongjun; Dong, Enqing; Tian, Jie
2017-03-01
It's widely known that HIV infection would cause white matter integrity impairments. Nevertheless, it is still unclear that how the white matter anatomical structural connections are affected by HIV infection. In the current study, we employed a multivariate pattern analysis to explore the HIV-related white matter connections alterations. Forty antiretroviraltherapy- naïve HIV patients and thirty healthy controls were enrolled. Firstly, an Automatic Anatomical Label (AAL) atlas based white matter structural network, a 90 × 90 FA-weighted matrix, was constructed for each subject. Then, the white matter connections deprived from the structural network were entered into a lasso-logistic regression model to perform HIV-control group classification. Using leave one out cross validation, a classification accuracy (ACC) of 90% (P=0.002) and areas under the receiver operating characteristic curve (AUC) of 0.96 was obtained by the classification model. This result indicated that the white matter anatomical structural connections contributed greatly to HIV-control group classification, providing solid evidence that the white matter connections were affected by HIV infection. Specially, 11 white matter connections were selected in the classification model, mainly crossing the regions of frontal lobe, Cingulum, Hippocampus, and Thalamus, which were reported to be damaged in previous HIV studies. This might suggest that the white matter connections adjacent to the HIV-related impaired regions were prone to be damaged.
Discover the network mechanisms underlying the connections between aging and age-related diseases
Yang, Jialiang; Huang, Tao; Song, Won-min; Petralia, Francesca; Mobbs, Charles V.; Zhang, Bin; Zhao, Yong; Schadt, Eric E.; Zhu, Jun; Tu, Zhidong
2016-01-01
Although our knowledge of aging has greatly expanded in the past decades, it remains elusive why and how aging contributes to the development of age-related diseases (ARDs). In particular, a global mechanistic understanding of the connections between aging and ARDs is yet to be established. We rely on a network modelling named “GeroNet” to study the connections between aging and more than a hundred diseases. By evaluating topological connections between aging genes and disease genes in over three thousand subnetworks corresponding to various biological processes, we show that aging has stronger connections with ARD genes compared to non-ARD genes in subnetworks corresponding to “response to decreased oxygen levels”, “insulin signalling pathway”, “cell cycle”, etc. Based on subnetwork connectivity, we can correctly “predict” if a disease is age-related and prioritize the biological processes that are involved in connecting to multiple ARDs. Using Alzheimer’s disease (AD) as an example, GeroNet identifies meaningful genes that may play key roles in connecting aging and ARDs. The top modules identified by GeroNet in AD significantly overlap with modules identified from a large scale AD brain gene expression experiment, supporting that GeroNet indeed reveals the underlying biological processes involved in the disease. PMID:27582315
Cousijn, Janna; Zanolie, Kiki; Munsters, Robbert J. M.; Kleibeuker, Sietske W.; Crone, Eveline A.
2014-01-01
An important component of creativity is divergent thinking, which involves the ability to generate novel and useful problem solutions. In this study, we tested the relation between resting-state functional connectivity of brain areas activated during a divergent thinking task (i.e., supramarginal gyrus, middle temporal gyrus, medial frontal gyrus) and the effect of practice in 32 adolescents aged 15–16. Over a period of two weeks, an experimental group (n = 16) conducted an 8-session Alternative Uses Task (AUT) training and an active control group (n = 16) conducted an 8-session rule switching training. Resting-state functional connectivity was measured before (pre-test) and after (post-test) training. Across groups at pre-test, stronger connectivity between the middle temporal gyrus and bilateral postcentral gyrus was associated with better divergent thinking performance. The AUT-training, however, did not significantly change functional connectivity. Post hoc analyses showed that change in divergent thinking performance over time was predicted by connectivity between left supramarginal gyrus and right occipital cortex. These results provide evidence for a relation between divergent thinking and resting-state functional connectivity in a task-positive network, taking an important step towards understanding creative cognition and functional brain connectivity. PMID:25188416
Connecting and Collaborating: How Content-Related Instruction Increases Students' Speaking Abilities
ERIC Educational Resources Information Center
Harkins, Sherri
2010-01-01
Young students come to world language classrooms with genuine excitement about the possibility of being able to speak a language other than their own. When world language teachers connect second language instruction to students' general education curriculum content, the opportunity presents itself to potentially increase students' ability to speak…
Connecting and Collaborating: How Content-Related Instruction Increases Students' Speaking Abilities
ERIC Educational Resources Information Center
Harkins, Sherri
2010-01-01
Young students come to world language classrooms with genuine excitement about the possibility of being able to speak a language other than their own. When world language teachers connect second language instruction to students' general education curriculum content, the opportunity presents itself to potentially increase students' ability to speak…
Kay, Benjamin P; Holland, Scott K; Privitera, Michael D; Szaflarski, Jerzy P
2014-01-01
Summary Objective Patients with genetic generalized epilepsy (GGE) frequently continue to suffer from seizures despite appropriate clinical management. GGE is associated with changes in the resting-state networks modulated by clinical factors such as duration of disease and response to treatment. However, the effect of GSWDs and/or seizures on resting-state functional connectivity (RSFC) is not well understood. Methods We investigated the effects of GSWD frequency (in GGE patients), GGE (patients vs. healthy controls), and seizures (uncontrolled vs. controlled) on RSFC using seed-based voxel correlation in simultaneous EEG and resting-state fMRI (EEG/fMRI) data from 72 GGE patients (23 w/uncontrolled seizures) and 38 healthy controls. We used seeds in paracingulate cortex, thalamus, cerebellum, and posterior cingulate cortex to examine changes in cortical-subcortical resting-state networks and the default mode network (DMN). We excluded from analyses time points surrounding GSWDs to avoid possible contamination of the resting state. Results (1) Higher frequency of GSWDs was associated with an increase in seed-based voxel correlation with cortical and subcortical brain regions associated with executive function, attention, and the DMN, (2) RSFC in patients with GGE, when compared to healthy controls, was increased between paracingulate cortex and anterior, but not posterior, thalamus, and (3) GGE patients with uncontrolled seizures exhibited decreased cereballar RSFC. Significance Our findings in this large sample of patients with GGE (1) demonstrate an effect of interictal GSWDs on resting-state networks, (2) provide evidence that different thalamic nuclei may be affected differently by GGE, and (3) suggest that cerebellum is a modulator of ictogenic circuits. PMID:24447031
General Relativity Theory - Well Proven and Also Incomplete: Further Arguments
NASA Astrophysics Data System (ADS)
Brandes, Jürgen
In the former article "General Relativity Theory - well proven and also incomplete?" with a few arguments it was proven that general relativity (GRT) makes contradictory predictions about the total energy of a particle resting in the gravitational field. With a few further arguments it was proven that this contradiction is resolved by expanding general relativity. General relativity is contradictious in energy questions since on one side the total energy of a particle resting in the gravitational field is lower than its rest mass (there is energy needed to pull out the particle from the gravitational field) while on the other side it is equal to its rest mass (this is a consequence of the equivalence principle). In the following article these considerations are generalized to a moving particle. A particle moving in the gravitational field has a total energy less than its rest mass times the relativistic γ-factor since there is energy needed to pull the particle out without changing its velocity. On the other side total energy of a moving particle is equal to its rest mass times the relativistic γ-factor (this is a consequence of the equivalence principle, too). This contradiction is resolved by expanding general relativity in the same manner as above. The other fact: Though it is not the aim of the author to reject general relativity but to expand it, he is treated as some uncritical anti-relativist - since the start of his considerations and meanwhile for more than 20 years.
The relation between structural and functional connectivity depends on age and on task goals
Ford, Jaclyn H.; Kensinger, Elizabeth A.
2014-01-01
The last decade has seen an increase in neuroimaging studies examining structural (i.e., structural integrity of white matter tracts) and functional connectivity (e.g., correlations in neural activity throughout the brain). Although structural and functional connectivity changes have often been measured independently, examining the relation between these two measures is critical to understanding the specific function of neural networks and the ways they may differ across tasks and individuals. The current study addressed this question by examining the effect of age (treated as a continuous variable) and emotional valence on the relation between functional and structural connectivity. As prior studies have suggested that prefrontal regions may guide and regulate emotional memory search via functional connections with the amygdala, the current analysis focused on functional connectivity between the left amygdala and the left prefrontal cortex, and structural integrity of the uncinate fasciculus, a white matter tract connecting prefrontal and temporal regions. Participants took part in a scanned retrieval task in which they recalled positive, negative, and neutral images associated with neutral titles. Aging was associated with a significant increase in the relation between measures of structural integrity (specifically, fractional anisotropy, or FA) along the uncinate fasciculus and functional connectivity between the left ventral prefrontal cortex and amygdala during positive event retrieval, but not negative or neutral retrieval. Notably, during negative event retrieval, age was linked to stronger structure-function relations between the amygdala and the dorsal anterior cingulate cortex, such that increased structural integrity predicted stronger negative functional connectivity in older adults only. These findings suggest that young and older adults may utilize a structural pathway to engage different retrieval and regulatory strategies, even when structural
2011-10-01
Genetic influences on brain asymmetry : A dti study of 374 twins and1468 siblings. Neuroimage 52 (2), 455–469.1469 Jensen, D. D., Cohen, P. R., 2000...HIERARCHICAL TOPOLOGICAL NETWORK ANALYSIS OF ANATOMICAL HUMAN BRAIN CONNECTIVITY AND DIFFERENCES RELATED TO SEX AND KINSHIP By Julio M. Duarte...COVERED 00-00-2011 to 00-00-2011 4. TITLE AND SUBTITLE Hierarchical Topological Network Analysis of Anatomical Human Brain Connectivity and
Contradictory character of general relativity. The relativistic theory of gravitation
Logunov, A.A.; Loskutov, Y.M.
1986-11-01
It is shown that in its general form general relativity is unsatisfactory. In particular, its predictions for the gravitational time delay of a radio signal and the period of revolution of a satellite are ambiguous. At the same time, it is shown that the relativistic theory of gravitation is free of such shortcomings and agrees with all reliably established experimental facts.
2. GENERAL VIEW SOUTHEAST DEPICTING THE RELATION (LEFT TO RIGHT) ...
2. GENERAL VIEW SOUTHEAST DEPICTING THE RELATION (LEFT TO RIGHT) OF 25, 35, 119 AND 125 CONTRA COSTA ST. - Point Richmond Historic District, Hillside & Contra Costa Streets, Richmond, Contra Costa County, CA
Relativistic theory of gravitation and criticism of general relativity
Logunov, A.A.; Loskutov, Yu.M.; Mestvirishvili, M.A.
1988-05-01
Two questions are discussed: (1) the invalidity of the general theory of relativity as a physical theory of gravitation and (2) the construction of a relativistic theory of gravitation possessing all attributes of field theories.
Conservative form of Boltzmann's equation in general relativity
NASA Astrophysics Data System (ADS)
Shibata, Masaru; Nagakura, Hiroki; Sekiguchi, Yuichiro; Yamada, Shoichi
2014-04-01
We derive a conservative form of Boltzmann's equation in general relativity, which is concisely written. Several explicit forms of this equation are written for black-hole spacetime with several coordinate conditions in real spacetime and momentum-space coordinates.
2. GENERAL VIEW SHOWING RELATION OF BRIDGE TO THE TOPOGRAPHY ...
2. GENERAL VIEW SHOWING RELATION OF BRIDGE TO THE TOPOGRAPHY OF THE APPROACH ROAD. - Speicher Bridge, Church Road over Tulpehocken Creek between Penn & North Heidelberg Townships, Bernville, Berks County, PA
Chinook salmon use of spawning patches: Relative roles of habitat quality, size, and connectivity
Isaak, D.J.; Thurow, R.F.; Rieman, B.E.; Dunham, J.B.
2007-01-01
Declines in many native fish populations have led to reassessments of management goals and shifted priorities from consumptive uses to species preservation. As management has shifted, relevant environmental characteristics have evolved from traditional metrics that described local habitat quality to characterizations of habitat size and connectivity. Despite the implications this shift has for how habitats may be prioritized for conservation, it has been rare to assess the relative importance of these habitat components. We used an information-theoretic approach to select the best models from sets of logistic regressions that linked habitat quality, size, and connectivity to the occurrence of chinook salmon (Oncorhynchus tshawytscha) nests. Spawning distributions were censused annually from 1995 to 2004, and data were complemented with field measurements that described habitat quality in 43 suitable spawning patches across a stream network that drained 1150 km 2 in central Idaho. Results indicated that the most plausible models were dominated by measures of habitat size and connectivity, whereas habitat quality was of minor importance. Connectivity was the strongest predictor of nest occurrence, but connectivity interacted with habitat size, which became relatively more important when populations were reduced. Comparison of observed nest distributions to null model predictions confirmed that the habitat size association was driven by a biological mechanism when populations were small, but this association may have been an area-related sampling artifact at higher abundances. The implications for habitat management are that the size and connectivity of existing habitat networks should be maintained whenever possible. In situations where habitat restoration is occurring, expansion of existing areas or creation of new habitats in key areas that increase connectivity may be beneficial. Information about habitat size and connectivity also could be used to strategically
Latency-Related Development of Functional Connections in Cultured Cortical Networks
le Feber, J.; van Pelt, J.; Rutten, W.L.C.
2009-01-01
Abstract To study plasticity, we cultured cortical networks on multielectrode arrays, enabling simultaneous recording from multiple neurons. We used conditional firing probabilities to describe functional network connections by their strength and latency. These are abstract representations of neuronal pathways and may arise from direct pathways between two neurons or from a common input. Functional connections based on direct pathways should reflect synaptic properties. Therefore, we searched for long-term potentiation (this mechanism occurs in vivo when presynaptic action potentials precede postsynaptic ones with interspike intervals up to ∼20 ms) in vitro. To investigate if the strength of functional connections showed a similar latency-related development, we selected periods of monotonously increasing or decreasing strength. We observed increased incidence of short latencies (5–30 ms) during strengthening, whereas these rarely occurred during weakening. Furthermore, we saw an increased incidence of 40–65 ms latencies during weakening. Conversely, functional connections tended to strengthen in periods with short latency, whereas strengthening was significantly less than average during long latency. Our data suggest that functional connections contain information about synaptic connections, that conditional firing probability analysis is sensitive enough to detect it and that a substantial fraction of all functional connections is based on direct pathways. PMID:19383487
Exploring the Connection between Age and Strategies for Learning New Technology Related Tasks
ERIC Educational Resources Information Center
Meiselwitz, Gabriele; Chakraborty, Suranjan
2011-01-01
This paper discusses the connection between age and strategies for learning new technology related tasks. Many users have to learn about new devices and applications on a frequent basis and use a variety of strategies to accomplish this learning process. Approaches to learning new technology related tasks vary and can contribute to a user's…
General Relativity Without General Relativity: Self-Gravitating Systems and Effective Geometries
NASA Astrophysics Data System (ADS)
Bini, Donato; Cherubini, Christian; Filippi, Simonetta; Geralico, Andrea
Perturbations of Newtonian self-gravitating barotropic perfect fluid systems can be studied via an extension of the "effective geometry" formalism. The case of polytropic spherical stars described by the Lane-Emden equation has been studied in the past in the known cases of existing explicit solutions relevant for both stellar and galactic dynamics. Applications of the formalism in the case of rotating configurations found via William's "matching method" and possible generalizations are here discussed. The present formulation represents another natural scenario, in addition with the usual one of quantum condensates in laboratories, in which the acoustic analogy has physical relevance.
Implications of a positive cosmological constant for general relativity.
Ashtekar, Abhay
2017-10-01
Most of the literature on general relativity over the last century assumes that the cosmological constant [Formula: see text] is zero. However, by now independent observations have led to a consensus that the dynamics of the universe is best described by Einstein's equations with a small but positive [Formula: see text]. Interestingly, this requires a drastic revision of conceptual frameworks commonly used in general relativity, no matter how small [Formula: see text] is. We first explain why, and then summarize the current status of generalizations of these frameworks to include a positive [Formula: see text], focusing on gravitational waves.
Implications of a positive cosmological constant for general relativity
NASA Astrophysics Data System (ADS)
Ashtekar, Abhay
2017-10-01
Most of the literature on general relativity over the last century assumes that the cosmological constant Λ is zero. However, by now independent observations have led to a consensus that the dynamics of the universe is best described by Einstein’s equations with a small but positive Λ . Interestingly, this requires a drastic revision of conceptual frameworks commonly used in general relativity, no matter how small Λ is. We first explain why, and then summarize the current status of generalizations of these frameworks to include a positive Λ , focusing on gravitational waves.
Learning-Related Shifts in Generalization Gradients for Complex Sounds
Wisniewski, Matthew G.; Church, Barbara A.; Mercado, Eduardo
2010-01-01
Learning to discriminate stimuli can alter how one distinguishes related stimuli. For instance, training an individual to differentiate between two stimuli along a single dimension can alter how that individual generalizes learned responses. In this study, we examined the persistence of shifts in generalization gradients after training with sounds. University students were trained to differentiate two sounds that varied along a complex acoustic dimension. Students subsequently were tested on their ability to recognize a sound they experienced during training when it was presented among several novel sounds varying along this same dimension. Peak shift was observed in Experiment 1 when generalization tests immediately followed training, and in Experiment 2 when tests were delayed by 24 hours. These findings further support the universality of generalization processes across species, modalities, and levels of stimulus complexity. They also raise new questions about the mechanisms underlying learning-related shifts in generalization gradients. PMID:19815929
Miyazono, S.; Aycock, J.N.; Miranda, L.E.; Tietjen, T.E.
2010-01-01
We evaluated the influences of habitat connectivity and local environmental factors on the distribution and abundance patterns of fish functional groups in 17 floodplain lakes in the Yazoo River Basin, USA. The results of univariate and multivariate analyses showed that species-environmental relationships varied with the functional groups. Species richness and assemblage structure of periodic strategists showed strong and positive correlations with habitat connectivity. Densities of most equilibrium and opportunistic strategists decreased with habitat connectivity. Densities of certain equilibrium and opportunistic strategists increased with turbidity. Forested wetlands around the lakes were positively related to the densities of periodic and equilibrium strategists. These results suggest that decreases in habitat connectivity, forested wetland buffers and water quality resulting from environmental manipulations may cause local extinction of certain fish taxa and accelerate the dominance of tolerant fishes in floodplain lakes. ?? 2010 John Wiley & Sons A/S.
The general class of the vacuum spherically symmetric equations of the general relativity theory
Karbanovski, V. V. Sorokin, O. M.; Nesterova, M. I.; Bolotnyaya, V. A.; Markov, V. N. Kairov, T. V.; Lyash, A. A.; Tarasyuk, O. R.
2012-08-15
The system of the spherical-symmetric vacuum equations of the General Relativity Theory is considered. The general solution to a problem representing two classes of line elements with arbitrary functions g{sub 00} and g{sub 22} is obtained. The properties of the found solutions are analyzed.
Wu, Chinglin; Zhong, Suyu; Chen, Hsuehchih
2016-01-01
Remote association is a core ability that influences creative output. In contrast to close association, remote association is commonly agreed to be connected with more original and unique concepts. However, although existing studies have discovered that creativity is closely related to the white-matter structure of the brain, there are no studies that examine the relevance between the connectivity efficiencies and creativity of the brain regions from the perspective of networks. Consequently, this study constructed a brain white matter network structure that consisted of cerebral tissues and nerve fibers and used graph theory to analyze the connection efficiencies among the network nodes, further illuminating the differences between remote and close association in relation to the connectivity of the brain network. Researchers analyzed correlations between the scores of 35 healthy adults with regard to remote and close associations and the connectivity efficiencies of the white-matter network of the brain. Controlling for gender, age, and verbal intelligence, the remote association positively correlated with the global efficiency and negatively correlated with the levels of small-world. A close association negatively correlated with the global efficiency. Notably, the node efficiency in the middle temporal gyrus (MTG) positively correlated with remote association and negatively correlated with close association. To summarize, remote and close associations work differently as patterns in the brain network. Remote association requires efficient and convenient mutual connections between different brain regions, while close association emphasizes the limited connections that exist in a local region. These results are consistent with previous results, which indicate that creativity is based on the efficient integration and connection between different regions of the brain and that temporal lobes are the key regions for discriminating remote and close associations. PMID
Chen, Zhe; Putrino, David F; Ba, Demba E; Ghosh, Soumya; Barbieri, Riccardo; Brown, Emery N
2009-01-01
Identification of multiple simultaneously recorded neural spike train recordings is an important task in understanding neuronal dependency, functional connectivity, and temporal causality in neural systems. An assessment of the functional connectivity in a group of ensemble cells was performed using a regularized point process generalized linear model (GLM) that incorporates temporal smoothness or contiguity of the solution. An efficient convex optimization algorithm was then developed for the regularized solution. The point process model was applied to an ensemble of neurons recorded from the cat motor cortex during a skilled reaching task. The implications of this analysis to the coding of skilled movement in primary motor cortex is discussed.
The relation between structural and functional connectivity patterns in complex brain networks.
Stam, C J; van Straaten, E C W; Van Dellen, E; Tewarie, P; Gong, G; Hillebrand, A; Meier, J; Van Mieghem, P
2016-05-01
An important problem in systems neuroscience is the relation between complex structural and functional brain networks. Here we use simulations of a simple dynamic process based upon the susceptible-infected-susceptible (SIS) model of infection dynamics on an empirical structural brain network to investigate the extent to which the functional interactions between any two brain areas depend upon (i) the presence of a direct structural connection; and (ii) the degree product of the two areas in the structural network. For the structural brain network, we used a 78×78 matrix representing known anatomical connections between brain regions at the level of the AAL atlas (Gong et al., 2009). On this structural network we simulated brain dynamics using a model derived from the study of epidemic processes on networks. Analogous to the SIS model, each vertex/brain region could be in one of two states (inactive/active) with two parameters β and δ determining the transition probabilities. First, the phase transition between the fully inactive and partially active state was investigated as a function of β and δ. Second, the statistical interdependencies between time series of node states were determined (close to and far away from the critical state) with two measures: (i) functional connectivity based upon the correlation coefficient of integrated activation time series; and (ii) effective connectivity based upon conditional co-activation at different time intervals. We find a phase transition between an inactive and a partially active state for a critical ratio τ=β/δ of the transition rates in agreement with the theory of SIS models. Slightly above the critical threshold, node activity increases with degree, also in line with epidemic theory. The functional, but not the effective connectivity matrix closely resembled the underlying structural matrix. Both functional connectivity and, to a lesser extent, effective connectivity were higher for connected as compared to
NASA Astrophysics Data System (ADS)
Borzov, V. V.; Damaskinsky, E. V.
2017-02-01
We consider the families of polynomials P = { P n ( x)} n=0 ∞ and Q = { Q n ( x)} n=0 ∞ orthogonal on the real line with respect to the respective probability measures μ and ν. We assume that { Q n ( x)} n=0 ∞ and { P n ( x)} n=0 ∞ are connected by linear relations. In the case k = 2, we describe all pairs (P,Q) for which the algebras A P and A Q of generalized oscillators generated by { Qn(x)} n=0 ∞ and { Pn(x)} n=0 ∞ coincide. We construct generalized oscillators corresponding to pairs (P,Q) for arbitrary k ≥ 1.
Lynn, Andrew C; Padmanabhan, Aarthi; Simmonds, Daniel; Foran, William; Hallquist, Michael N; Luna, Beatriz; O'Hearn, Kirsten
2016-10-16
Face recognition abilities improve between adolescence and adulthood over typical development (TD), but plateau in autism, leading to increasing face recognition deficits in autism later in life. Developmental differences between autism and TD may reflect changes between neural systems involved in the development of face encoding and recognition. Here, we focused on whole-brain connectivity with the fusiform face area (FFA), a well-established face-preferential brain region. Older children, adolescents, and adults with and without autism completed the Cambridge Face Memory Test, and a matched car memory test, during fMRI scanning. We then examined task-based functional connectivity between the FFA and the rest of the brain, comparing autism and TD groups during encoding and recognition of face and car stimuli. The autism group exhibited underconnectivity, relative to the TD group, between the FFA and frontal and primary visual cortices, independent of age. Underconnectivity with the medial and rostral lateral prefrontal cortex was face-specific during encoding and recognition, respectively. Conversely, underconnectivity with the L orbitofrontal cortex was evident for both face and car encoding. Atypical age-related changes in connectivity emerged between the FFA and the R temporoparietal junction, and R dorsal striatum for face stimuli only. Similar differences in age-related changes in autism emerged for FFA connectivity with the amygdala across both face and car recognition. Thus, underconnectivity and atypical development of functional connectivity may lead to a less optimal face-processing network in the context of increasing general and social cognitive deficits in autism.
2013-01-01
Background Autism Spectrum Conditions (ASC) are a set of pervasive neurodevelopmental conditions characterized by a wide range of lifelong signs and symptoms. Recent explanatory models of autism propose abnormal neural connectivity and are supported by studies showing decreased interhemispheric coherence in individuals with ASC. The first aim of this study was to test the hypothesis of reduced interhemispheric coherence in ASC, and secondly to investigate specific effects of task performance on interhemispheric coherence in ASC. Methods We analyzed electroencephalography (EEG) data from 15 participants with ASC and 15 typical controls, using Wavelet Transform Coherence (WTC) to calculate interhemispheric coherence during face and chair matching tasks, for EEG frequencies from 5 to 40 Hz and during the first 400 ms post-stimulus onset. Results Results demonstrate a reduction of interhemispheric coherence in the ASC group, relative to the control group, in both tasks and for all electrode pairs studied. For both tasks, group differences were generally observed after around 150 ms and at frequencies lower than 13 Hz. Regarding within-group task comparisons, while the control group presented differences in interhemispheric coherence between faces and chairs tasks at various electrode pairs (FT7-FT8, TP7-TP8, P7-P8), such differences were only seen for one electrode pair in the ASC group (T7-T8). No significant differences in EEG power spectra were observed between groups. Conclusions Interhemispheric coherence is reduced in people with ASC, in a time and frequency specific manner, during visual perception and categorization of both social and inanimate stimuli and this reduction in coherence is widely dispersed across the brain. Results of within-group task comparisons may reflect an impairment in task differentiation in people with ASC relative to typically developing individuals. Overall, the results of this research support the value of WTC in examining the time
Stevens, W. Dale; Tessler, Michael Henry; Peng, Cynthia S.; Martin, Alex
2015-01-01
One of the most robust and oft-replicated findings in cognitive neuroscience is that several spatially distinct, functionally dissociable ventral occipitotemporal cortex (VOTC) regions respond preferentially to different categories of concrete entities. However, the determinants of this category-related organization remain to be fully determined. One recent proposal is that privileged connectivity of these VOTC regions with other regions that store and/or process category-relevant properties may be a major contributing factor. To test this hypothesis, we used a multi-category functional MRI localizer to individually define category-related brain regions of interest (ROIs) in a large group of subjects (n=33). We then used these ROIs in resting-state functional connectivity MRI analyses to explore spontaneous functional connectivity among these regions. We demonstrate that during rest, distinct category-preferential VOTC regions show differentially stronger functional connectivity with other regions that have congruent category-preference, as defined by the functional localizer. Importantly, a ‘tool’-preferential region in the left medial fusiform gyrus showed differentially stronger functional connectivity with other left lateralized cortical regions associated with perceiving and knowing about common tools – posterior middle temporal gyrus (involved in perception of non-biological motion), lateral parietal cortex (critical for reaching, grasping, manipulating), and ventral premotor cortex (involved in storing/executing motor programs) – relative to other category-related regions in VOTC of both the right and left hemisphere. Our findings support the claim that privileged connectivity with other cortical regions that store and/or process category-relevant properties constrains the category-related organization of VOTC. PMID:25704493
NASA Astrophysics Data System (ADS)
Chen, Yong-Zhou; Fu, Chun-Hua; Chang, Hui; Li, Nan; He, Da-Ren
2008-10-01
In this paper, an empirical investigation is presented, which focuses on unveiling the universality of connectivity correlations in three spaces (the route space, the stop geographical space and bus-transferring space) of urban bus-transport networks (BTNs) in four major cities of China. The underlying features of the connectivity correlations are shown in two statistical ways. One is the correlation between the (weighted) average degree of all the nearest neighbouring vertices with degree k, (Knnw (k)) Knn(k), and k, and the other is the correlations between the assortativity coefficient r and, respectively, the network size N, the network diameter D, the averaged clustering coefficient C, and the averaged distance
A general design algorithm for low optical loss adiabatic connections in waveguides.
Chen, Tong; Lee, Hansuek; Li, Jiang; Vahala, Kerry J
2012-09-24
Single-mode waveguide designs frequently support higher order transverse modes, usually as a consequence of process limitations such as lithography. In these systems, it is important to minimize coupling to higher-order modes so that the system nonetheless behaves single mode. We propose a variational approach to design adiabatic waveguide connections with minimal intermodal coupling. An application of this algorithm in designing the "S-bend" of a whispering-gallery spiral waveguide is demonstrated with approximately 0.05 dB insertion loss. Compared to other approaches, our algorithm requires less fabrication resolution and is able to minimize the transition loss over a broadband spectrum. The method can be applied to a wide range of turns and connections and has the advantage of handling connections with arbitrary boundary conditions.
Generalization of Pain-Related Fear Based on Conceptual Knowledge.
Meulders, Ann; Vandael, Kristof; Vlaeyen, Johan W S
2017-05-01
Increasing evidence suggests that pain-related fear is key to the transition from acute to chronic pain. Previous research has shown that perceptual similarity with a pain-associated movement fosters the generalization of fear to novel movements. Perceptual generalization of pain-related fear is adaptive as it enables individuals to extrapolate the threat value of one movement to another without the necessity to learn anew. However, excessive spreading of fear to safe movements may become maladaptive and may lead to sustained anxiety, dysfunctional avoidance behaviors, and severe disability. A hallmark of human cognition is the ability to extract conceptual knowledge from a learning episode as well. Although this conceptual pathway may be important to understand fear generalization in chronic pain, research on this topic is lacking. We investigated acquisition and generalization of concept-based pain-related fear. During acquisition, unique exemplars of one action category (CS+; e.g., opening boxes) were followed by pain, whereas exemplars of another action category (CS-; e.g., closing boxes) were not. Subsequently, spreading of pain-related fear to novel exemplars of both action categories was tested. Participants learned to expect the pain to occur and reported more pain-related fear to the exemplars of the CS+ category compared with those of the CS- category. During generalization, fear and expectancy generalized to novel exemplars of the CS+ category, but not to the CS- category. This pattern was not corroborated in the eyeblink startle measures. This is the first study that demonstrates that pain-related fear can be acquired and generalized based on conceptual knowledge. Copyright © 2016. Published by Elsevier Ltd.
Network-Based Analysis Reveals Functional Connectivity Related to Internet Addiction Tendency.
Wen, Tanya; Hsieh, Shulan
2016-01-01
Preoccupation and compulsive use of the internet can have negative psychological effects, such that it is increasingly being recognized as a mental disorder. The present study employed network-based statistics to explore how whole-brain functional connections at rest is related to the extent of individual's level of internet addiction, indexed by a self-rated questionnaire. We identified two topologically significant networks, one with connections that are positively correlated with internet addiction tendency, and one with connections negatively correlated with internet addiction tendency. The two networks are interconnected mostly at frontal regions, which might reflect alterations in the frontal region for different aspects of cognitive control (i.e., for control of internet usage and gaming skills). Next, we categorized the brain into several large regional subgroupings, and found that the majority of proportions of connections in the two networks correspond to the cerebellar model of addiction which encompasses the four-circuit model. Lastly, we observed that the brain regions with the most inter-regional connections associated with internet addiction tendency replicate those often seen in addiction literature, and is corroborated by our meta-analysis of internet addiction studies. This research provides a better understanding of large-scale networks involved in internet addiction tendency and shows that pre-clinical levels of internet addiction are associated with similar regions and connections as clinical cases of addiction.
Network-Based Analysis Reveals Functional Connectivity Related to Internet Addiction Tendency
Wen, Tanya; Hsieh, Shulan
2016-01-01
Preoccupation and compulsive use of the internet can have negative psychological effects, such that it is increasingly being recognized as a mental disorder. The present study employed network-based statistics to explore how whole-brain functional connections at rest is related to the extent of individual’s level of internet addiction, indexed by a self-rated questionnaire. We identified two topologically significant networks, one with connections that are positively correlated with internet addiction tendency, and one with connections negatively correlated with internet addiction tendency. The two networks are interconnected mostly at frontal regions, which might reflect alterations in the frontal region for different aspects of cognitive control (i.e., for control of internet usage and gaming skills). Next, we categorized the brain into several large regional subgroupings, and found that the majority of proportions of connections in the two networks correspond to the cerebellar model of addiction which encompasses the four-circuit model. Lastly, we observed that the brain regions with the most inter-regional connections associated with internet addiction tendency replicate those often seen in addiction literature, and is corroborated by our meta-analysis of internet addiction studies. This research provides a better understanding of large-scale networks involved in internet addiction tendency and shows that pre-clinical levels of internet addiction are associated with similar regions and connections as clinical cases of addiction. PMID:26869896
General Relativity Theory -- Well Proven and Also Incomplete?
NASA Astrophysics Data System (ADS)
Brandes, Jürgen
2013-09-01
With a few arguments (half a page) it is proven that general relativity (GRT) makes contradictory predictions about the total energy of a particle resting in the gravitational field. With a few further arguments (one page) it is proven that these contradictions are resolved by expanding general relativity. The other situation: Though it is not the aim of the author to reject general relativity but to expand it, he is treated as some uncritical anti-relativist - since the start of his considerations and meanwhile for more than 20 years. My public question: Are relativists - on account of their many famous results - unable to admit imperfections of general relativity? General relativity is contradictious in energy questions since on one side the total energy of a particle resting in the gravitational field is lower than its rest mass (there is energy needed to pull out the particle from the gravitational field) while on the other side it is equal to its rest mass (this is a consequence of the equivalence principle).
Gerraty, Raphael T; Davidow, Juliet Y; Wimmer, G Elliott; Kahn, Itamar; Shohamy, Daphna
2014-08-20
An important aspect of adaptive learning is the ability to flexibly use past experiences to guide new decisions. When facing a new decision, some people automatically leverage previously learned associations, while others do not. This variability in transfer of learning across individuals has been demonstrated repeatedly and has important implications for understanding adaptive behavior, yet the source of these individual differences remains poorly understood. In particular, it is unknown why such variability in transfer emerges even among homogeneous groups of young healthy participants who do not vary on other learning-related measures. Here we hypothesized that individual differences in the transfer of learning could be related to relatively stable differences in intrinsic brain connectivity, which could constrain how individuals learn. To test this, we obtained a behavioral measure of memory-based transfer outside of the scanner and on a separate day acquired resting-state functional MRI images in 42 participants. We then analyzed connectivity across independent component analysis-derived brain networks during rest, and tested whether intrinsic connectivity in learning-related networks was associated with transfer. We found that individual differences in transfer were related to intrinsic connectivity between the hippocampus and the ventromedial prefrontal cortex, and between these regions and large-scale functional brain networks. Together, the findings demonstrate a novel role for intrinsic brain dynamics in flexible learning-guided behavior, both within a set of functionally specific regions known to be important for learning, as well as between these regions and the default and frontoparietal networks, which are thought to serve more general cognitive functions. Copyright © 2014 the authors 0270-6474/14/3411297-07$15.00/0.
Gerraty, Raphael T.; Davidow, Juliet Y.; Wimmer, G. Elliott; Kahn, Itamar
2014-01-01
An important aspect of adaptive learning is the ability to flexibly use past experiences to guide new decisions. When facing a new decision, some people automatically leverage previously learned associations, while others do not. This variability in transfer of learning across individuals has been demonstrated repeatedly and has important implications for understanding adaptive behavior, yet the source of these individual differences remains poorly understood. In particular, it is unknown why such variability in transfer emerges even among homogeneous groups of young healthy participants who do not vary on other learning-related measures. Here we hypothesized that individual differences in the transfer of learning could be related to relatively stable differences in intrinsic brain connectivity, which could constrain how individuals learn. To test this, we obtained a behavioral measure of memory-based transfer outside of the scanner and on a separate day acquired resting-state functional MRI images in 42 participants. We then analyzed connectivity across independent component analysis-derived brain networks during rest, and tested whether intrinsic connectivity in learning-related networks was associated with transfer. We found that individual differences in transfer were related to intrinsic connectivity between the hippocampus and the ventromedial prefrontal cortex, and between these regions and large-scale functional brain networks. Together, the findings demonstrate a novel role for intrinsic brain dynamics in flexible learning-guided behavior, both within a set of functionally specific regions known to be important for learning, as well as between these regions and the default and frontoparietal networks, which are thought to serve more general cognitive functions. PMID:25143610
Galaxy bias and gauges at second order in general relativity
NASA Astrophysics Data System (ADS)
Bertacca, Daniele; Bartolo, Nicola; Bruni, Marco; Koyama, Kazuya; Maartens, Roy; Matarrese, Sabino; Sasaki, Misao; Wands, David
2015-09-01
We discuss the question of gauge choice when analysing relativistic density perturbations at second order. We compare Newtonian and general relativistic approaches. Some misconceptions in the recent literature are addressed. We show that the comoving-synchronous gauge is the unique gauge in general relativity that corresponds to the Lagrangian frame and is entirely appropriate to describe the matter overdensity at second order. The comoving-synchronous gauge is the simplest gauge in which to describe Lagrangian bias at second order.
Euler Equations Related to the Generalized Neveu-Schwarz Algebra
NASA Astrophysics Data System (ADS)
Zuo, Dafeng
2013-06-01
In this paper, we study supersymmetric or bi-superhamiltonian Euler equations related to the generalized Neveu-Schwarz algebra. As an application, we obtain several supersymmetric or bi-superhamiltonian generalizations of some well-known integrable systems including the coupled KdV equation, the 2-component Camassa-Holm equation and the 2-component Hunter-Saxton equation. To our knowledge, most of them are new.
Construction of regular black holes in general relativity
NASA Astrophysics Data System (ADS)
Fan, Zhong-Ying; Wang, Xiaobao
2016-12-01
We present a general procedure for constructing exact black hole solutions with electric or magnetic charges in general relativity coupled to a nonlinear electrodynamics. We obtain a variety of two-parameter family spherically symmetric black hole solutions. In particular, the singularity at the center of the space-time can be canceled in the parameter space and the black hole solutions become regular everywhere in space-time. We study the global properties of the solutions and derive the first law of thermodynamics. We also generalize the procedure to include a cosmological constant and construct regular black hole solutions that are asymptotic to anti-de Sitter space-time.
33 CFR 162.130 - Connecting waters from Lake Huron to Lake Erie; general rules.
Code of Federal Regulations, 2013 CFR
2013-07-01
... Light to the lakeward limits of the improved navigation channels at the head of Lake Erie. District... vessel. River Rouge means the waters of the Short Cut Canal and the River Rouge from Detroit Edison Cell Light 1 to the head of navigation. St. Clair River means the connecting waters from the lakeward...
ERIC Educational Resources Information Center
Cacciatore, Kristen L.; Amado, Jose; Evans, Jason J.; Sevian, Hannah
2008-01-01
We present a novel first-year chemistry laboratory experiment that connects solubility, equilibrium, and chemical periodicity concepts. It employs a unique format that asks students to replicate experiments described in different sample lab reports, each lacking some essential information, rather than follow a scripted procedure. This structure is…
ERIC Educational Resources Information Center
Cacciatore, Kristen L.; Amado, Jose; Evans, Jason J.; Sevian, Hannah
2008-01-01
We present a novel first-year chemistry laboratory experiment that connects solubility, equilibrium, and chemical periodicity concepts. It employs a unique format that asks students to replicate experiments described in different sample lab reports, each lacking some essential information, rather than follow a scripted procedure. This structure is…
Quaternionic quantization principle in general relativity and supergravity
NASA Astrophysics Data System (ADS)
Kober, Martin
2016-01-01
A generalized quantization principle is considered, which incorporates nontrivial commutation relations of the components of the variables of the quantized theory with the components of the corresponding canonical conjugated momenta referring to other space-time directions. The corresponding commutation relations are formulated by using quaternions. At the beginning, this extended quantization concept is applied to the variables of quantum mechanics. The resulting Dirac equation and the corresponding generalized expression for plane waves are formulated and some consequences for quantum field theory are considered. Later, the quaternionic quantization principle is transferred to canonical quantum gravity. Within quantum geometrodynamics as well as the Ashtekar formalism, the generalized algebraic properties of the operators describing the gravitational observables and the corresponding quantum constraints implied by the generalized representations of these operators are determined. The generalized algebra also induces commutation relations of the several components of the quantized variables with each other. Finally, the quaternionic quantization procedure is also transferred to 𝒩 = 1 supergravity. Accordingly, the quantization principle has to be generalized to be compatible with Dirac brackets, which appear in canonical quantum supergravity.
Li, Yujie; Li, Chunlin; Wu, Qiong; Xu, Zhihan; Kurata, Tomoko; Ohno, Seiichiro; Kanazawa, Susumu; Abe, Koji; Wu, Jinglong
2015-06-15
Advanced aging is accompanied by a decline in visuospatial attention. Previous neuroimaging and electrophysiological studies have demonstrated dysfunction in specific brain areas related to visuospatial attention. However, it is still unclear how the functional connectivity between brain regions causes the decline of visuospatial attention. Here, we combined task and rest functional magnetic resonance imaging (fMRI) to investigate the age-dependent alterations of resting-state functional connectivity within the task-related network. Twenty-three young subjects and nineteen elderly subjects participated in this study, and a modified Posner paradigm was used to define the region of interest (ROI). Our results showed that a marked reduction in the number of connections occurred with age, but this effect was not uniform throughout the brain: while there was a significant loss of communication in the anterior portion of the brain and between the anterior and posterior cerebral cortices, communication in the posterior portion of the brain was preserved. Moreover, the older adults exhibited weakened resting-state functional connectivity between the supplementary motor area and left anterior insular cortex. These findings suggest that, the disrupted functional connectivity of the brain network for visuospatial attention that occurs during normal aging may underlie the decline in cognitive performance.
Ziaei, Maryam; Salami, Alireza; Persson, Jonas
2017-01-08
Previous findings indicate age-related differences in frontal-amygdala connectivity during emotional processing. However, direct evidence for age differences in brain functional activation and connectivity during emotional processing and concomitant behavioral implications is lacking. In the present study, we examined the impact of aging on the neural signature of selective attention to emotional information during working memory (WM) encoding. Participants completed an emotional WM task in which they were asked to attend to emotional targets and ignore irrelevant distractors. Despite an overall reduction in accuracy for older relative to younger adults, no behavioral age effect was observed as a function of emotional valence. The functional connectivity patterns of left ventrolateral prefrontal cortex showed that younger adults recruited one network for encoding of both positive and negative emotional targets and this network contributed to higher memory accuracy in this cohort. Older adults, on the other hand, engaged two distinct networks for encoding of positive and negative targets. The functional connectivity analysis using left amygdala further demonstrated that older adults recruited one single network during encoding of positive as well as negative targets whereas younger adults recruited this network only for encoding of negative items. The engagement of amygdala functional network also contributed to higher memory performance and faster response times in older adults. Our findings provide novel insights into the differential roles of functional brain networks connected to the medial PFC and amygdala during encoding of emotionally-valenced items with advancing age. Copyright © 2016 Elsevier Ltd. All rights reserved.
Liu, Wen-jing; Yin, Da-zhi; Cheng, Wen-hong; Fan, Ming-xia; You, Mei-na; Men, Wei-wei; Zang, Li-li; Shi, Dian-hong; Zhang, Fang
2015-02-12
We aimed to investigate the disruptions of functional connectivity of amygdala-based networks in adolescents with untreated generalized anxiety disorder (GAD). A total of 26 adolescents with first-episode GAD and 20 normal age-matched volunteers underwent resting-state and T1 functional magnetic resonance imaging (fMRI). We analyzed the correlation of fMRI signal fluctuation between the amygdala and other brain regions. The variation of amygdala-based functional connectivity and its correlation with anxiety severity were investigated. Decreased functional connectivity was found between the left amygdala and left dorsolateral prefrontal cortex. An increased right amygdala functional connectivity with right posterior and anterior lobes of the cerebellum, insula, superior temporal gyrus, putamen, and right amygdala were found in our study. Negative correlations between GAD scores and functional connectivity of the right amygdala with the cerebellum were also observed in the GAD adolescents. Adolescents with GAD have abnormalities in brain regions associated with the emotional processing pathways.
Connecting between School and Work: A Case Study in Customer Relations.
ERIC Educational Resources Information Center
Hohberg, Tonian J.
1985-01-01
This article shares some of the strategies and activities that the author believes will improve the connections between independent career education and the world of work. These activities concern school business cooperation, student motivation, student involvement, staff involvement, community and government relations, and career planning and…
Canonical quantization of general relativity in discrete space-times.
Gambini, Rodolfo; Pullin, Jorge
2003-01-17
It has long been recognized that lattice gauge theory formulations, when applied to general relativity, conflict with the invariance of the theory under diffeomorphisms. We analyze discrete lattice general relativity and develop a canonical formalism that allows one to treat constrained theories in Lorentzian signature space-times. The presence of the lattice introduces a "dynamical gauge" fixing that makes the quantization of the theories conceptually clear, albeit computationally involved. The problem of a consistent algebra of constraints is automatically solved in our approach. The approach works successfully in other field theories as well, including topological theories. A simple cosmological application exhibits quantum elimination of the singularity at the big bang.
Using Algebraic Computing To Teach General Relativity And Cosmology
NASA Astrophysics Data System (ADS)
Vulcanov, Dumitru N.; Boată, Remus-Ştefan Ş.
2012-12-01
The article presents some new aspects and experience on the use of computer in teaching general relativity and cosmology for undergraduate students (and not only) with some experience in computer manipulation. Some years ago certain results were reported [1] using old fashioned computer algebra platforms but the growing popularity of graphical platforms as Maple and Mathematica forced us to adapt and reconsider our methods and programs. We will describe some simple algebraic programming procedures (in Maple with GrTensorII package) for obtaining and the study of some exact solutions of the Einstein equations in order to convince a dedicated student in general relativity about the utility of a computer algebra system.
The Mø ller Energy Complexes of Various Wormholes in General Relativity and Teleparallel Gravity
NASA Astrophysics Data System (ADS)
Aygün, Melis; Yilmaz, Ihsan
2007-08-01
This study is aimed to elaborate the energy problem of general wormhole space-times in two different approaches of gravity such as general relativity and teleparallel gravity. In this connection, the energy for well-known wormhole space-times is evaluated using Møller energy-momentum prescription in these different approximations. We obtained that energy distributions of Møller definition give the same results for various wormhole space-times in general relativity (GR) and teleparallel gravity (TG). The results strengthen the importance of Møller energy-momentum definitions in given space-times and viewpoint of Lessner that Møller energy-momentum complex is a powerful concept for energy and momentum.
NASA Astrophysics Data System (ADS)
Parry, A. O.; Boulter, C. J.
1995-02-01
We study the pair correlation function for an inhomogeneous fluid or Ising-type spin system near a wall with particular attention to the complete wetting phase transition. We show that one can unify a generalized interfacial Hamiltonian theory with a mean-field treatment of correlations provided we follow a systematic scheme for reconstructing order-parameter fluctuations. Near a complete wetting transition it is necessary to use a model effective Hamiltonian HI(2) [ l1, l2] which is a functional of two collective coordinates in order to properly describe the coupling between fluctuations near the wall and the depinning fluid (αβ) interface. This gives an accurate description of the Ornstein-Zernike-like fluctuations of particles located near the αβ interface and the non-Ornstein-Zernike behavior of correlations near the wall. We show that the off-diagonal elements of the stiffness matrix characterizing HI(2) [ l1, l2] are related to singular behaviour of the free-energy.
Musical expertise is related to altered functional connectivity during audiovisual integration
Paraskevopoulos, Evangelos; Kraneburg, Anja; Herholz, Sibylle Cornelia; Bamidis, Panagiotis D.; Pantev, Christo
2015-01-01
The present study investigated the cortical large-scale functional network underpinning audiovisual integration via magnetoencephalographic recordings. The reorganization of this network related to long-term musical training was investigated by comparing musicians to nonmusicians. Connectivity was calculated on the basis of the estimated mutual information of the sources’ activity, and the corresponding networks were statistically compared. Nonmusicians’ results indicated that the cortical network associated with audiovisual integration supports visuospatial processing and attentional shifting, whereas a sparser network, related to spatial awareness supports the identification of audiovisual incongruences. In contrast, musicians’ results showed enhanced connectivity in regions related to the identification of auditory pattern violations. Hence, nonmusicians rely on the processing of visual clues for the integration of audiovisual information, whereas musicians rely mostly on the corresponding auditory information. The large-scale cortical network underpinning multisensory integration is reorganized due to expertise in a cognitive domain that largely involves audiovisual integration, indicating long-term training-related neuroplasticity. PMID:26371305
Musical expertise is related to altered functional connectivity during audiovisual integration.
Paraskevopoulos, Evangelos; Kraneburg, Anja; Herholz, Sibylle Cornelia; Bamidis, Panagiotis D; Pantev, Christo
2015-10-06
The present study investigated the cortical large-scale functional network underpinning audiovisual integration via magnetoencephalographic recordings. The reorganization of this network related to long-term musical training was investigated by comparing musicians to nonmusicians. Connectivity was calculated on the basis of the estimated mutual information of the sources' activity, and the corresponding networks were statistically compared. Nonmusicians' results indicated that the cortical network associated with audiovisual integration supports visuospatial processing and attentional shifting, whereas a sparser network, related to spatial awareness supports the identification of audiovisual incongruences. In contrast, musicians' results showed enhanced connectivity in regions related to the identification of auditory pattern violations. Hence, nonmusicians rely on the processing of visual clues for the integration of audiovisual information, whereas musicians rely mostly on the corresponding auditory information. The large-scale cortical network underpinning multisensory integration is reorganized due to expertise in a cognitive domain that largely involves audiovisual integration, indicating long-term training-related neuroplasticity.
Age-Related Changes in Inter-Network Connectivity by Component Analysis
La, Christian; Mossahebi, Pouria; Nair, Veena A.; Bendlin, Barbara B.; Birn, Rasmus; Meyerand, Mary E.; Prabhakaran, Vivek
2015-01-01
Healthy aging is associated with brain changes that reflect an alteration to a functional unit in response to the available resources and architecture. Even before the onset of noticeable cognitive decline, the neural scaffolds underlying cognitive function undergo considerable change. Prior studies have suggested a disruption of the connectivity pattern within the “default-mode” network (DMN), and more specifically a disruption of the anterio-posterior connectivity. In this study, we explored the effects of aging on within-network connectivity of three DMN subnetworks: a posterior DMN (pDMN), an anterior DMN (aDMN), and a ventral DMN (vDMN); as well as between-network connectivity during resting-state. Using groupICA on 43 young and 43 older healthy adults, we showed a reduction of network co-activation in two of the DMN subnetworks (pDMN and aDMN) and demonstrated a difference in between-component connectivity levels. The older group exhibited more numerous high-correlation pairs (Pearson's rho > 0.3, Number of comp-pairs = 46) in comparison to the young group (Number of comp-pairs = 34), suggesting a more connected/less segregated cortical system. Moreover, three component-pairs exhibited statistically significant differences between the two populations. Visual areas V2–V1 and V2–V4 were more correlated in the older adults, while aDMN–pDMN correlation decreased with aging. The increase in the number of high-correlation component-pairs and the elevated correlation in the visual areas are consistent with the prior hypothesis that aging is associated with a reduction of functional segregation. However, the aDMN-pDMN dis-connectivity may be occurring under a different mechanism, a mechanism more related to a breakdown of structural integrity along the anterio-posterior axis. PMID:26733864
Exoplanet predictions based on the generalized Titius-Bode relation
NASA Astrophysics Data System (ADS)
Bovaird, Timothy; Lineweaver, Charles H.
2013-10-01
We evaluate the extent to which newly detected exoplanetary systems containing at least four planets adhere to a generalized Titius-Bode (TB) relation. We find that the majority of exoplanet systems in our sample adhere to the TB relation to a greater extent than the Solar system does, particularly those detected by the Kepler mission. We use a generalized TB relation to make a list of predictions for the existence of 141 additional exoplanets in 68 multiple-exoplanet systems: 73 candidates from interpolation, 68 candidates from extrapolation. We predict the existence of a low-radius (R < 2.5R⊕) exoplanet within the habitable zone of KOI-812 and that the average number of planets in the habitable zone of a star is 1-2. The usefulness of the TB relation and its validation as a tool for predicting planets will be partially tested by upcoming Kepler data releases.
Cosmological tests of general relativity with future tomographic surveys.
Zhao, Gong-Bo; Pogosian, Levon; Silvestri, Alessandra; Zylberberg, Joel
2009-12-11
Future weak lensing surveys will map the evolution of matter perturbations and gravitational potentials, yielding a new test of general relativity on cosmic scales. They will probe the relations between matter overdensities, local curvature, and the Newtonian potential. These relations can be modified in alternative gravity theories or by the effects of massive neutrinos or exotic dark energy fluids. We introduce two functions of time and scale which account for any such modifications in the linear regime. We use a principal component analysis to find the eigenmodes of these functions that cosmological data will constrain. The number of constrained modes gives a model-independent forecast of how many parameters describing deviations from general relativity could be constrained, along with w(z). The modes' scale and time dependence tell us which theoretical models will be better tested.
General relativity at 75: how right was einstein?
Will, C M
1990-11-09
The status of experimental tests of general relativity is reviewed on the occasion of its 75th anniversary. Einstein's equivalence principle is well supported by experiments such as the Eötvös experiment, tests of special relativity, and the gravitational redshift experiment. Tests of general relativity have reached high precision, including the light deflection and the perihelion advance of Mercury, proposed by Einstein 75 years ago, and new tests such as the Shapiro time delay and the Nordtvedt effect in lunar motion. Gravitational wave damping has been detected to an accuracy of 1 percent on the basis of measurements of the binary pulsar. The status of the "fifth force" is discussed, along with the frontiers of experimental relativity, including proposals for testing relativistic gravity with advanced technology and spacecraft.
Doppler frequency in interplanetary radar and general relativity
NASA Technical Reports Server (NTRS)
Mcvittie, G. C.
1972-01-01
The change of frequency of an interplanetary radar signal sent from the earth to another planet or to a space probe is worked out according to general relativity. The Schwarzschild spacetime is employed and its null geodesics control the motion of the signals. Exact Doppler frequency formulas are derived for one-way and two-way radar in terms of an arbitrary Schwarzschild radial coordinate. A reduction to the special relativity case is used to interpret the formulas in terms of the relative radial velocity of emitter and target. The general relativity corrections are worked out approximately for each of three possible Schwarzschild radial coordinates, and a numerical example is given. The amount of the correction is different according as one or the other of the Schwarzschild coordinates is identified with the radius vector deduced from classical celestial mechanics. The identification problem is discussed.
Cosmological perturbations in a family of deformations of general relativity
Krasnov, Kirill; Shtanov, Yuri E-mail: shtanov@bitp.kiev.ua
2010-06-01
We study linear cosmological perturbations in a previously introduced family of deformations of general relativity characterized by the absence of new degrees of freedom. The homogeneous and isotropic background in this class of theories is unmodified and is described by the usual Friedmann equations. The theory of cosmological perturbations is modified and the relevant deformation parameter has the dimension of length. Gravitational perturbations of the scalar type can be described by a certain relativistic potential related to the matter perturbations just as in general relativity. A system of differential equations describing the evolution of this potential and of the stress-energy density perturbations is obtained. We find that the evolution of scalar perturbations proceeds with a modified effective time-dependent speed of sound, which, contrary to the case of general relativity, does not vanish even at the matter-dominated stage. In a broad range of values of the length parameter controlling the deformation, a specific transition from the regime of modified gravity to the regime of general relativity in the evolution of scalar perturbations takes place during the radiation domination. In this case, the resulting power spectrum of perturbations in radiation and dark matter is suppressed on the comoving spatial scales that enter the Hubble radius before this transition. We estimate the bounds on the deformation parameter for which this suppression does not lead to observable consequences. Evolution of scalar perturbations at the inflationary stage is modified but very slightly and the primordial spectrum generated during inflation is not noticeably different from the one obtained in general relativity.
Madsen, Martin Korsbak; Mc Mahon, Brenda; Andersen, Sofie Bech; Siebner, Hartwig Roman; Knudsen, Gitte Moos; Fisher, Patrick MacDonald
2016-01-01
Communication between the amygdala and other brain regions critically regulates sensitivity to threat, which has been associated with risk for mood and affective disorders. The extent to which these neural pathways are genetically determined or correlate with risk-related personality measures is not fully understood. Using functional magnetic resonance imaging, we evaluated independent and interactive effects of the 5-HTTLPR genotype and neuroticism on amygdala functional connectivity during an emotional faces paradigm in 76 healthy individuals. Functional connectivity between left amygdala and medial prefrontal cortex (mPFC) and between both amygdalae and a cluster including posterior cingulate cortex, precuneus and visual cortex was significantly increased in 5-HTTLPR S' allele carriers relative to L(A)L(A) individuals. Neuroticism was negatively correlated with functional connectivity between right amygdala and mPFC and visual cortex, and between both amygdalae and left lateral orbitofrontal (lOFC) and ventrolateral prefrontal cortex (vlPFC). Notably, 5-HTTLPR moderated the association between neuroticism and functional connectivity between both amygdalae and left lOFC/vlPFC, such that S' carriers exhibited a more negative association relative to L(A)L(A) individuals. These findings provide novel evidence for both independent and interactive effects of 5-HTTLPR genotype and neuroticism on amygdala communication, which may mediate effects on risk for mood and affective disorders.
Tóth, Brigitta; Kardos, Zsófia; File, Bálint; Boha, Roland; Stam, Cornelis Jan; Molnár, Márk
2014-10-01
Representations in working memory (WM) are temporary, but can be refreshed for longer periods of time through maintenance mechanisms, thereby establishing their availability for subsequent memory tests. Frontal brain regions supporting WM maintenance operations undergo anatomical and functional changes with advancing age, leading to age related decline of memory functions. The present study focused on age-related functional connectivity changes of the frontal midline (FM) cortex in the theta band (4-8 Hz), related to WM maintenance. In the visual delayed-match-to-sample WM task young (18-26 years, N=20) and elderly (60-71 years N=16) adults had to memorize sample stimuli consisting of 3 or 5 items while 33 channel EEG recording was performed. The phase lag index was used to quantify connectivity strength between cortical regions. The low and high memory demanding WM maintenance periods were classified based on whether they were successfully maintained (remembered) or unsuccessfully maintained (unrecognized later). In the elderly reduced connectivity strength of FM brain region and decreased performance were observed. The connectivity strength between FM and posterior sensory cortices was shown to be sensitive to both increased memory demands and memory performance regardless of age. The coupling of frontal regions (midline and lateral) and FM-temporal cortices characterized successfully maintained trials and declined with advancing age. The findings provide evidence that a FM neural circuit of theta oscillations that serves a possible basis of active maintenance process is especially vulnerable to aging.
Factors Affecting the Relative Efficiency of General Acid Catalysis
ERIC Educational Resources Information Center
Kwan, Eugene E.
2005-01-01
A simple framework for evaluating experimental kinetic data to provide support for Specific Acid Catalysis (SAC) and General Acid Catalysis (GAC) is described based on the factors affecting their relative efficiency. Observations reveal that increasing the SAC-to-GAC rate constant ratio reduces the effective pH range for GAC.
Spinning fluids in general relativity. II - Self-consistent formulation
NASA Technical Reports Server (NTRS)
Ray, John R.; Smalley, Larry, L.; Krisch, Jean P.
1987-01-01
Methods used earlier to derive the equations of motion for a spinning fluid in the Einstein-Cartan theory are specialized to the case of general relativity. The main idea is to include the spin as a thermodynamic variable in the theory.
Testing general relativity: from local to cosmological scales.
Uzan, Jean-Philippe
2011-12-28
I summarize various tests of general relativity on astrophysical scales, based on the large-scale structure of the universe but also on other systems, in particular the constants of physics. I emphasize the importance of hypotheses on the geometric structures of our universe while performing such tests and discuss their complementarity as well as their possible extensions.
Probing Students' Understanding of Some Conceptual Themes in General Relativity
ERIC Educational Resources Information Center
Bandyopadhyay, Atanu; Kumar, Arvind
2010-01-01
This work is an attempt to see how physics undergraduates view the basic ideas of general relativity when they are exposed to the topic in a standard introductory course. Since the subject is conceptually and technically difficult, we adopted a "case studies" approach, focusing in depth on about six students who had just finished a one semester…
Related General-Vocabulary Knowledge Transfers to Learning Technical Terms
ERIC Educational Resources Information Center
Balch, William R.
2015-01-01
In a classroom experiment during the first week of an introductory psychology course, randomly assigned students received a pretest and then a brief training on the definitions of general-vocabulary words either related (e.g., "facilitation") or unrelated (e.g., "rendition") to 16 technical terms (e.g., "social…
Spinning fluids in general relativity. II - Self-consistent formulation
NASA Technical Reports Server (NTRS)
Ray, John R.; Smalley, Larry, L.; Krisch, Jean P.
1987-01-01
Methods used earlier to derive the equations of motion for a spinning fluid in the Einstein-Cartan theory are specialized to the case of general relativity. The main idea is to include the spin as a thermodynamic variable in the theory.
Related General-Vocabulary Knowledge Transfers to Learning Technical Terms
ERIC Educational Resources Information Center
Balch, William R.
2015-01-01
In a classroom experiment during the first week of an introductory psychology course, randomly assigned students received a pretest and then a brief training on the definitions of general-vocabulary words either related (e.g., "facilitation") or unrelated (e.g., "rendition") to 16 technical terms (e.g., "social…
Factors Affecting the Relative Efficiency of General Acid Catalysis
ERIC Educational Resources Information Center
Kwan, Eugene E.
2005-01-01
A simple framework for evaluating experimental kinetic data to provide support for Specific Acid Catalysis (SAC) and General Acid Catalysis (GAC) is described based on the factors affecting their relative efficiency. Observations reveal that increasing the SAC-to-GAC rate constant ratio reduces the effective pH range for GAC.
Probing Students' Understanding of Some Conceptual Themes in General Relativity
ERIC Educational Resources Information Center
Bandyopadhyay, Atanu; Kumar, Arvind
2010-01-01
This work is an attempt to see how physics undergraduates view the basic ideas of general relativity when they are exposed to the topic in a standard introductory course. Since the subject is conceptually and technically difficult, we adopted a "case studies" approach, focusing in depth on about six students who had just finished a one semester…
Costa Dias, Taciana G.; Wilson, Vanessa B.; Bathula, Deepti R.; Iyer, Swathi P.; Mills, Kathryn L.; Thurlow, Bria L.; Stevens, Corinne A.; Musser, Erica D.; Carpenter, Samuel D.; Grayson, David S.; Mitchell, Suzanne H.; Nigg, Joel T.; Fair, Damien A.
2012-01-01
Attention-deficit/hyperactivity disorder (ADHD) is a prevalent psychiatric disorder that has poor long-term outcomes and remains a major public health concern. Recent theories have proposed that ADHD arises from alterations in multiple neural pathways. Alterations in reward circuits are hypothesized as one core dysfunction, leading to altered processing of anticipated rewards. The nucleus accumbens (NAcc) is particularly important for reward processes; task-based fMRI studies have found atypical activation of this region while the participants performed a reward task. Understanding how reward circuits are involved with ADHD may be further enhanced by considering how the NAcc interacts with other brain regions. Here we used the technique of resting-state functional connectivity MRI (rs-fcMRI) to examine the alterations in the NAcc interactions and how they relate to impulsive decision making in ADHD. Using rs-fcMRI, this study: examined differences in functional connectivity of the NAcc between children with ADHD and control children; correlated the functional connectivity of NAcc with impulsivity, as measured by a delay discounting task; and combined these two initial segments to identify the atypical NAcc connections that were associated with impulsive decision making in ADHD. We found that functional connectivity of NAcc was atypical in children with ADHD and the ADHD-related increased connectivity between NAcc and the prefrontal cortex was associated with greater impulsivity (steeper delayed-reward discounting). These findings are consistent with the hypothesis that atypical signaling of the NAcc to the prefrontal cortex in ADHD may lead to excessive approach and failure in estimating future consequences; thus, leading to impulsive behavior. PMID:23206930
Li, Karl; Laird, Angela R.; Price, Larry R.; McKay, D. Reese; Blangero, John; Glahn, David C.; Fox, Peter T.
2016-01-01
The default mode network (DMN) is a set of regions that is tonically engaged during the resting state and exhibits task-related deactivation that is readily reproducible across a wide range of paradigms and modalities. The DMN has been implicated in numerous disorders of cognition and, in particular, in disorders exhibiting age-related cognitive decline. Despite these observations, investigations of the DMN in normal aging are scant. Here, we used blood oxygen level dependent (BOLD) functional magnetic resonance imaging (fMRI) acquired during rest to investigate age-related changes in functional connectivity of the DMN in 120 healthy normal volunteers comprising six, 20-subject, decade cohorts (from 20–29 to 70–79). Structural equation modeling (SEM) was used to assess age-related changes in inter-regional connectivity within the DMN. SEM was applied both using a previously published, meta-analytically derived, node-and-edge model, and using exploratory modeling searching for connections that optimized model fit improvement. Although the two models were highly similar (only 3 of 13 paths differed), the sample demonstrated significantly better fit with the exploratory model. For this reason, the exploratory model was used to assess age-related changes across the decade cohorts. Progressive, highly significant changes in path weights were found in 8 (of 13) paths: four rising, and four falling (most changes were significant by the third or fourth decade). In all cases, rising paths and falling paths projected in pairs onto the same nodes, suggesting compensatory increases associated with age-related decreases. This study demonstrates that age-related changes in DMN physiology (inter-regional connectivity) are bidirectional, progressive, of early onset and part of normal aging. PMID:27378909
Li, Karl; Laird, Angela R; Price, Larry R; McKay, D Reese; Blangero, John; Glahn, David C; Fox, Peter T
2016-01-01
The default mode network (DMN) is a set of regions that is tonically engaged during the resting state and exhibits task-related deactivation that is readily reproducible across a wide range of paradigms and modalities. The DMN has been implicated in numerous disorders of cognition and, in particular, in disorders exhibiting age-related cognitive decline. Despite these observations, investigations of the DMN in normal aging are scant. Here, we used blood oxygen level dependent (BOLD) functional magnetic resonance imaging (fMRI) acquired during rest to investigate age-related changes in functional connectivity of the DMN in 120 healthy normal volunteers comprising six, 20-subject, decade cohorts (from 20-29 to 70-79). Structural equation modeling (SEM) was used to assess age-related changes in inter-regional connectivity within the DMN. SEM was applied both using a previously published, meta-analytically derived, node-and-edge model, and using exploratory modeling searching for connections that optimized model fit improvement. Although the two models were highly similar (only 3 of 13 paths differed), the sample demonstrated significantly better fit with the exploratory model. For this reason, the exploratory model was used to assess age-related changes across the decade cohorts. Progressive, highly significant changes in path weights were found in 8 (of 13) paths: four rising, and four falling (most changes were significant by the third or fourth decade). In all cases, rising paths and falling paths projected in pairs onto the same nodes, suggesting compensatory increases associated with age-related decreases. This study demonstrates that age-related changes in DMN physiology (inter-regional connectivity) are bidirectional, progressive, of early onset and part of normal aging.
ERIC Educational Resources Information Center
Littlefield, Robert S.; Rick, Jessica M.; Currie-Mueller, Jenna L.
2016-01-01
This study explored the intersection between service learning and general education outcomes through the self-reported perceptions of 382 college students participating in an intercultural communication course that satisfied the general education requirement at a midsized Upper Plains research university for studying cultural diversity. The data…
1980-11-01
generalized nodel described by Eykhoff [1, 2], Astrom and Eykhoff [3], and on pages 209-220 of Eykhoff [4]. The origin of the general- ized model can be...aspects of process-parameter estimation," IEEE Trans. Auto. Control, October 1963, pp. 347-357. 3. K. J. Astrom and P. Eykhoff, "System
ERIC Educational Resources Information Center
Littlefield, Robert S.; Rick, Jessica M.; Currie-Mueller, Jenna L.
2016-01-01
This study explored the intersection between service learning and general education outcomes through the self-reported perceptions of 382 college students participating in an intercultural communication course that satisfied the general education requirement at a midsized Upper Plains research university for studying cultural diversity. The data…
Radulescu, Eugenia; Minati, Ludovico; Ganeshan, Balaji; Harrison, Neil A.; Gray, Marcus A.; Beacher, Felix D.C.C.; Chatwin, Chris; Young, Rupert C.D.; Critchley, Hugo D.
2013-01-01
Asperger syndrome (AS) is an Autism Spectrum Disorder (ASD) characterised by qualitative impairment in the development of emotional and social skills with relative preservation of general intellectual abilities, including verbal language. People with AS may nevertheless show atypical language, including rate and frequency of speech production. We previously observed that abnormalities in grey matter homogeneity (measured with texture analysis of structural MR images) in AS individuals when compared with controls are also correlated with the volume of caudate nucleus. Here, we tested a prediction that these distributed abnormalities in grey matter compromise the functional integrity of brain networks supporting verbal communication skills. We therefore measured the functional connectivity between caudate nucleus and cortex during a functional neuroimaging study of language generation (verbal fluency), applying psycho-physiological interaction (PPI) methods to test specifically for differences attributable to grey matter heterogeneity in AS participants. Furthermore, we used dynamic causal modelling (DCM) to characterise the causal directionality of these differences in interregional connectivity during word production. Our results revealed a diagnosis-dependent influence of grey matter heterogeneity on the functional connectivity of the caudate nuclei with right insula/inferior frontal gyrus and anterior cingulate, respectively with the left superior frontal gyrus and right precuneus. Moreover, causal modelling of interactions between inferior frontal gyri, caudate and precuneus, revealed a reliance on bottom-up (stimulus-driven) connections in AS participants that contrasted with a dominance of top-down (cognitive control) connections from prefrontal cortex observed in control participants. These results provide detailed support for previously hypothesised central disconnectivity in ASD and specify discrete brain network targets for diagnosis and therapy in ASD
Finite-time generalization of the thermodynamic uncertainty relation
NASA Astrophysics Data System (ADS)
Pietzonka, Patrick; Ritort, Felix; Seifert, Udo
2017-07-01
For fluctuating currents in nonequilibrium steady states, the recently discovered thermodynamic uncertainty relation expresses a fundamental relation between their variance and the overall entropic cost associated with the driving. We show that this relation holds not only for the long-time limit of fluctuations, as described by large deviation theory, but also for fluctuations on arbitrary finite time scales. This generalization facilitates applying the thermodynamic uncertainty relation to single molecule experiments, for which infinite time scales are not accessible. Importantly, often this finite-time variant of the relation allows inferring a bound on the entropy production that is even stronger than the one obtained from the long-time limit. We illustrate the relation for the fluctuating work that is performed by a stochastically switching laser tweezer on a trapped colloidal particle.
Gong, Diankun; He, Hui; Liu, Dongbo; Ma, Weiyi; Dong, Li; Luo, Cheng; Yao, Dezhong
2015-01-01
Research has shown that distinct insular subregions are associated with particular neural networks (e.g., attentional and sensorimotor networks). Based on the evidence that playing action video games (AVGs) facilitates attentional and sensorimotor functions, this study examined the relation between AVG experience and the plasticity of insular subregions and the functional networks therein that are related to attentional and sensorimotor functions. By comparing AVG experts and amateurs, we found that AVG experts had enhanced functional connectivity and grey matter volume in insular subregions. Furthermore, AVG experts exhibited increased functional connectivity between the attentional and sensorimotor networks, and the experience-related enhancement was predominantly evident in the left insula, an understudied brain area. Thus, AVG playing may enhance functional integration of insular subregions and the pertinent networks therein. PMID:25880157
Gong, Diankun; He, Hui; Liu, Dongbo; Ma, Weiyi; Dong, Li; Luo, Cheng; Yao, Dezhong
2015-04-16
Research has shown that distinct insular subregions are associated with particular neural networks (e.g., attentional and sensorimotor networks). Based on the evidence that playing action video games (AVGs) facilitates attentional and sensorimotor functions, this study examined the relation between AVG experience and the plasticity of insular subregions and the functional networks therein that are related to attentional and sensorimotor functions. By comparing AVG experts and amateurs, we found that AVG experts had enhanced functional connectivity and grey matter volume in insular subregions. Furthermore, AVG experts exhibited increased functional connectivity between the attentional and sensorimotor networks, and the experience-related enhancement was predominantly evident in the left insula, an understudied brain area. Thus, AVG playing may enhance functional integration of insular subregions and the pertinent networks therein.
Einstein's First Steps Toward General Relativity: Gedanken Experiments and Axiomatics
NASA Astrophysics Data System (ADS)
Miller, A. I.
1999-03-01
Albert Einstein's 1907 Jahrbuch paper is an extraordinary document because it contains his first steps toward generalizing the 1905 relativity theory to include gravitation. Ignoring the apparent experimental disconfirmation of the 1905 relativity theory and his unsuccessful attempts to generalize the mass-energy equivalence, Einstein boldly raises the mass-energy equivalence to an axiom, invokes equality between gravitational and inertial masses, and then postulates the equivalence between a uniform gravitational field and an oppositely directed constant acceleration, the equivalence principle. How did this come about? What is at issue is scientific creativity. This necessitates broadening historical analysis to include aspects of cognitive science such as the role of visual imagery in Einstein's thinking, and the relation between conscious and unconscious modes of thought in problem solving. This method reveals the catalysts that sparked a Gedanken experiment that occurred to Einstein while working on the Jahrbuch paper. A mental model is presented to further explore Einstein's profound scientific discovery.
Lyksborg, Mark; Siebner, Hartwig R; Sørensen, Per S; Blinkenberg, Morten; Parker, Geoff J M; Dogonowski, Anne-Marie; Garde, Ellen; Larsen, Rasmus; Dyrby, Tim B
2014-01-01
Multiple sclerosis (MS) damages central white matter pathways which has considerable impact on disease-related disability. To identify disease-related alterations in anatomical connectivity, 34 patients (19 with relapsing remitting MS (RR-MS), 15 with secondary progressive MS (SP-MS) and 20 healthy subjects underwent diffusion magnetic resonance imaging (dMRI) of the brain. Based on the dMRI, anatomical connectivity mapping (ACM) yielded a voxel-based metric reflecting the connectivity shared between each individual voxel and all other brain voxels. To avoid biases caused by inter-individual brain-shape differences, they were estimated in a spatially normalized space. Voxel-based statistical analyses using ACM were compared with analyses based on the localized microstructural indices of fractional anisotropy (FA). In both RR-MS and SP-MS patients, considerable portions of the motor-related white matter revealed decreases in ACM and FA when compared with healthy subjects. Patients with SP-MS exhibited reduced ACM values relative to RR-MS in the motor-related tracts, whereas there were no consistent decreases in FA between SP-MS and RR-MS patients. Regional ACM statistics exhibited moderate correlation with clinical disability as reflected by the expanded disability status scale (EDSS). The correlation between these statistics and EDSS was either similar to or stronger than the correlation between FA statistics and the EDSS. Together, the results reveal an improved relationship between ACM, the clinical phenotype, and impairment. This highlights the potential of the ACM connectivity indices to be used as a marker which can identify disease related-alterations due to MS which may not be seen using localized microstructural indices.
Lyksborg, Mark; Siebner, Hartwig R.; Sørensen, Per S.; Blinkenberg, Morten; Parker, Geoff J. M.; Dogonowski, Anne-Marie; Garde, Ellen; Larsen, Rasmus; Dyrby, Tim B.
2014-01-01
Multiple sclerosis (MS) damages central white matter pathways which has considerable impact on disease-related disability. To identify disease-related alterations in anatomical connectivity, 34 patients (19 with relapsing remitting MS (RR-MS), 15 with secondary progressive MS (SP-MS) and 20 healthy subjects underwent diffusion magnetic resonance imaging (dMRI) of the brain. Based on the dMRI, anatomical connectivity mapping (ACM) yielded a voxel-based metric reflecting the connectivity shared between each individual voxel and all other brain voxels. To avoid biases caused by inter-individual brain-shape differences, they were estimated in a spatially normalized space. Voxel-based statistical analyses using ACM were compared with analyses based on the localized microstructural indices of fractional anisotropy (FA). In both RR-MS and SP-MS patients, considerable portions of the motor-related white matter revealed decreases in ACM and FA when compared with healthy subjects. Patients with SP-MS exhibited reduced ACM values relative to RR-MS in the motor-related tracts, whereas there were no consistent decreases in FA between SP-MS and RR-MS patients. Regional ACM statistics exhibited moderate correlation with clinical disability as reflected by the expanded disability status scale (EDSS). The correlation between these statistics and EDSS was either similar to or stronger than the correlation between FA statistics and the EDSS. Together, the results reveal an improved relationship between ACM, the clinical phenotype, and impairment. This highlights the potential of the ACM connectivity indices to be used as a marker which can identify disease related-alterations due to MS which may not be seen using localized microstructural indices. PMID:24748023
BOOK REVIEW: Partial Differential Equations in General Relativity
NASA Astrophysics Data System (ADS)
Choquet-Bruhat, Yvonne
2008-09-01
General relativity is a physical theory basic in the modeling of the universe at the large and small scales. Its mathematical formulation, the Einstein partial differential equations, are geometrically simple, but intricate for the analyst, involving both hyperbolic and elliptic PDE, with local and global problems. Many problems remain open though remarkable progress has been made recently towards their solutions. Alan Rendall's book states, in a down-to-earth form, fundamental results used to solve different types of equations. In each case he gives applications to special models as well as to general properties of Einsteinian spacetimes. A chapter on ODE contains, in particular, a detailed discussion of Bianchi spacetimes. A chapter entitled 'Elliptic systems' treats the Einstein constraints. A chapter entitled 'Hyperbolic systems' is followed by a chapter on the Cauchy problem and a chapter 'Global results' which contains recently proved theorems. A chapter is dedicated to the Einstein Vlasov system, of which the author is a specialist. On the whole, the book surveys, in a concise though precise way, many essential results of recent interest in mathematical general relativity, and it is very clearly written. Each chapter is followed by an up to date bibliography. In conclusion, this book will be a valuable asset to relativists who wish to learn clearly-stated mathematical results and to mathematicians who want to penetrate into the subtleties of general relativity, as a mathematical and physical theory.
General Relativity as AN ÆTHER Theory
NASA Astrophysics Data System (ADS)
Dupré, Maurice J.; Tipler, Frank J.
Most early twentieth century relativists — Lorentz, Einstein, Eddington, for examples — claimed that general relativity was merely a theory of the æther. We shall confirm this claim by deriving the Einstein equations using æther theory. We shall use a combination of Lorentz's and Kelvin's conception of the æther. Our derivation of the Einstein equations will not use the vanishing of the covariant divergence of the stress-energy tensor, but instead equate the Ricci tensor to the sum of the usual stress-energy tensor and a stress-energy tensor for the æther, a tensor based on Kelvin's æther theory. A crucial first step is generalizing the Cartan formalism of Newtonian gravity to allow spatial curvature, as conjectured by Gauss and Riemann. In essence, we shall show that the Einstein equations are a special case of Newtonian gravity coupled to a particular type of luminiferous æther. Our derivation of general relativity is simple, and it emphasizes how inevitable general relativity is, given the truth of Newtonian gravity and the Maxwell equations.
Reformulation of the symmetries of first-order general relativity
NASA Astrophysics Data System (ADS)
Montesinos, Merced; González, Diego; Celada, Mariano; Díaz, Bogar
2017-10-01
We report a new internal gauge symmetry of the n-dimensional Palatini action with cosmological term (n>3 ) that is the generalization of three-dimensional local translations. This symmetry is obtained through the direct application of the converse of Noether’s second theorem on the theory under consideration. We show that diffeomorphisms can be expressed as linear combinations of it and local Lorentz transformations with field-dependent parameters up to terms involving the variational derivatives of the action. As a result, the new internal symmetry together with local Lorentz transformations can be adopted as the fundamental gauge symmetries of general relativity. Although their gauge algebra is open in general, it allows us to recover, without resorting to the equations of motion, the very well-known Lie algebra satisfied by translations and Lorentz transformations in three dimensions. We also report the analog of the new gauge symmetry for the Holst action with cosmological term, finding that it explicitly depends on the Immirzi parameter. The same result concerning its relation to diffeomorphisms and the open character of the gauge algebra also hold in this case. Finally, we consider the non-minimal coupling of a scalar field to gravity in n dimensions and establish that the new gauge symmetry is affected by this matter field. Our results indicate that general relativity in dimension greater than three can be thought of as a gauge theory.
Phonemic Fluency and Brain Connectivity in Age-Related Macular Degeneration: A Pilot Study
Chou, Ying-hui; Potter, Guy G.; Diaz, Michele T.; Chen, Nan-kuei; Lad, Eleonora M.; Johnson, Micah A.; Cousins, Scott W.; Zhuang, Jie; Madden, David J.
2015-01-01
Abstract Age-related macular degeneration (AMD), the leading cause of blindness in developed nations, has been associated with poor performance on tests of phonemic fluency. This pilot study sought to (1) characterize the relationship between phonemic fluency and resting-state functional brain connectivity in AMD patients and (2) determine whether regional connections associated with phonemic fluency in AMD patients were similarly linked to phonemic fluency in healthy participants. Behavior-based connectivity analysis was applied to resting-state, functional magnetic resonance imaging data from seven patients (mean age=79.9±7.5 years) with bilateral AMD who completed fluency tasks prior to imaging. Phonemic fluency was inversely related to the strength of functional connectivity (FC) among six pairs of brain regions, representing eight nodes: left opercular portion of inferior frontal gyrus (which includes Broca's area), left superior temporal gyrus (which includes part of Wernicke's area), inferior parietal lobe (bilaterally), right superior parietal lobe, right supramarginal gyrus, right supplementary motor area, and right precentral gyrus. The FC of these reference links was not related to phonemic fluency among 32 healthy individuals (16 younger adults, mean age=23.5±4.6 years and 16 older adults, mean age=68.3±3.4 years). Compared with healthy individuals, AMD patients exhibited higher mean connectivity within the reference links and within the default mode network, possibly reflecting compensatory changes to support performance in the setting of reduced vision. These findings are consistent with the hypothesis that phonemic fluency deficits in AMD reflect underlying brain changes that develop in the context of AMD. PMID:25313954
Pu, Weidan; Rolls, Edmund T.; Guo, Shuixia; Liu, Haihong; Yu, Yun; Xue, Zhimin; Feng, Jianfeng; Liu, Zhening
2014-01-01
In order to analyze functional connectivity in untreated and treated patients with schizophrenia, resting-state fMRI data were obtained for whole-brain functional connectivity analysis from 22 first-episode neuroleptic-naïve schizophrenia (NNS), 61 first-episode neuroleptic-treated schizophrenia (NTS) patients, and 60 healthy controls (HC). Reductions were found in untreated and treated patients in the functional connectivity between the posterior cingulate gyrus and precuneus, and this was correlated with the reduction in volition from the Positive and Negative Symptoms Scale (PANSS), that is in the willful initiation, sustenance, and control of thoughts, behavior, movements, and speech, and with the general and negative symptoms. In addition in both patient groups interhemispheric functional connectivity was weaker between the orbitofrontal cortex, amygdala and temporal pole. These functional connectivity changes and the related symptoms were not treated by the neuroleptics. Differences between the patient groups were that there were more strong functional connectivity links in the NNS patients (including in hippocampal, frontal, and striatal circuits) than in the NTS patients. These findings with a whole brain analysis in untreated and treated patients with schizophrenia provide evidence on some of the brain regions implicated in the volitional, other general, and negative symptoms, of schizophrenia that are not treated by neuroleptics so have implications for the development of other treatments; and provide evidence on some brain systems in which neuroleptics do alter the functional connectivity. PMID:25389520
Nyrén, O.; Yin, L.; Josefsson, S.; McLaughlin, J. K.; Blot, W. J.; Engqvist, M.; Hakelius, L.; Boice, J. D.; Adami, H. O.
1998-01-01
OBJECTIVE: To examine the relation between connective tissue disease and related conditions and breast implants. DESIGN: Retrospective cohort study of all women in the Swedish national inpatient registry who underwent breast augmentation surgery with artificial implants during 1964-93, compared with women who underwent breast reduction surgery during the same period. SETTING: Sweden. SUBJECTS: 7442 women with implants for cosmetic reasons or for reconstruction after breast cancer surgery and 3353 women with breast reduction surgery. MAIN OUTCOME MEASURES: Subsequent hospitalisation for definite connective tissue diseases (rheumatoid arthritis, systemic lupus erythematosus, systemic sclerosis, dermatomyositis, and Sjögren's syndrome) or related disorders. RESULTS: 29 women with implants were hospitalised for definite connective tissue disease compared with 25.5 expected based on general population rates (standardised hospitalisation ratio 1.1 (95% confidence interval 0.8 to 1.6)). There were no diagnoses of systemic sclerosis, and no significant excess in risk for polymyalgia rheumatica, fibromyalgia, and several related disorders. Among women who underwent breast reduction surgery, 14 were hospitalised for definite connective tissue disease compared with 10.5 expected (standardised hospitalisation ratio 1.3 (0.7 to 2.2)). Compared with the breast reduction group, women with breast implants showed a slight reduction for all definite connective tissue disease (relative risk 0.8 (95% confidence interval 0.5 to 1.4)). CONCLUSIONS: This large nationwide cohort study shows no evidence of association between breast implants and connective tissue disease. PMID:9492663
Projective equivalence of Einstein spaces in general relativity
NASA Astrophysics Data System (ADS)
Hall, G. S.; Lonie, D. P.
2009-06-01
There has been some recent interest in the relation between two spacetimes which have the same geodesic paths, that is, spacetimes which are projectively equivalent (sometimes called geodesically equivalent). This paper presents a short and accessible proof of the theorem that if two spacetimes have the same geodesic paths and one of them is an Einstein space then (either each is of constant curvature or) their Lévi-Civitá connections are identical. It also clarifies the relationship between their associated metrics. The results are extended to include the signatures (+ + + +) and (- - + +), and some examples and discussion are given in the case of dimension n > 4. Some remarks are also made which show how these results may be useful in the study of projective symmetry.
Resting-state frontostriatal functional connectivity in Parkinson's disease-related apathy.
Baggio, Hugo Cesar; Segura, Bàrbara; Garrido-Millan, Jose Luis; Marti, Maria-José; Compta, Yaroslau; Valldeoriola, Francesc; Tolosa, Eduardo; Junque, Carme
2015-04-15
One of the most common neuropsychiatric symptoms in Parkinson's disease (PD) is apathy, affecting between 23% and 70% of patients and thought to be related to frontostriatal dopamine deficits. In the current study, we assessed functional resting-state frontostriatal connectivity and structural changes associated with the presence of apathy in a large sample of PD subjects and healthy controls, while controlling for the presence of comorbid depression and cognitive decline. Thirty-one healthy controls (HC) and 62 age-, sex-, and education-matched PD patients underwent resting-state functional magnetic resonance imaging (MRI). Apathy symptoms were evaluated with the Apathy Scale (AS). The 11 Beck Depression Inventory-II items that measure dysphoric mood symptoms as well as relevant neuropsychological scores were used as nuisance factors in connectivity analyses. Voxel-wise analyses of functional connectivity between frontal lobes (limbic, executive, rostral motor, and caudal motor regions), striata (limbic, executive, sensorimotor regions), and thalami were performed. Subcortical volumetry/shape analysis and fronto-subcortical voxel-based morphometry were performed to assess associated structural changes. Twenty-five PD patients were classified as apathetic (AS > 13). Apathetic PD patients showed functional connectivity reductions compared with HC and with non-apathetic patients, mainly in left-sided circuits, and predominantly involving limbic striatal and frontal territories. Similarly, severity of apathy negatively correlated with connectivity in these circuits. No significant effects were found in structural analyses. Our results indicate that the presence of apathy in PD is associated with functional connectivity reductions in frontostriatal circuits, predominating in the left hemisphere and mainly involving its limbic components.
Albert, Anastasia; Eksteen, J Johannes; Isaksson, Johan; Sengee, Myagmarsuren; Hansen, Terkel; Vasskog, Terje
2016-10-04
Within the field of bioprospecting, disulfide-rich peptides are a promising group of compounds that has the potential to produce important leads for new pharmaceuticals. The disulfide bridges stabilize the tertiary structure of the peptides and often make them superior drug candidates to linear peptides. However, determination of disulfide connectivity in peptides with many disulfide bridges has proven to be laborious and general methods are lacking. This study presents a general approach for structure elucidation of disulfide-rich peptides. The method features sequential reduction and alkylation of a peptide on solid phase combined with sequencing of the fully alkylated peptide by tandem mass spectrometry. Subsequently, the disulfide connectivity is assigned on the basis of the determined alkylation pattern. The presented method is especially suitable for peptides that are prone to disulfide scrambling or are unstable in solution with partly reduced bridges. Additionally, the use of small amounts of peptide in the lowest nmol range makes the method ideal for structure elucidation of unknown peptides from the bioprospecting process. This study successfully demonstrates the new method for seven different peptides with two to four disulfide bridges. Two peptides with previous contradicting publications, μ-conotoxin KIIA and hepcidin-25, are included, and their disulfide connectivity is confirmed in accordance with the latest published results.
Race matters: the relation between race and general campus climate.
Reid, Landon D; Radhakrishnan, Phanikiran
2003-08-01
This study examined students' perceptions of racial and academic climate as possible mediators of racial differences in the perception of the university's general campus climate (GCC). African American (n = 182), Latino (n = 212), Asian American (n = 358), and White (n = 671) students evaluated their perception of racial, academic, and general campus climates. As expected, racial minority students, particularly African Americans, perceived more negative general campus, racial, and academic climates than White students. Somewhat contrary to prediction, results indicated that racial differences in the perception of GCC were more closely related to perceptions of the academic than racial climate for members of all racial groups at all educational levels. Students' academic and racial experiences were the best predictors of their perception of GCC.
Early Age-Related Functional Connectivity Decline in High-Order Cognitive Networks
Siman-Tov, Tali; Bosak, Noam; Sprecher, Elliot; Paz, Rotem; Eran, Ayelet; Aharon-Peretz, Judith; Kahn, Itamar
2017-01-01
As the world ages, it becomes urgent to unravel the mechanisms underlying brain aging and find ways of intervening with them. While for decades cognitive aging has been related to localized brain changes, growing attention is now being paid to alterations in distributed brain networks. Functional connectivity magnetic resonance imaging (fcMRI) has become a particularly useful tool to explore large-scale brain networks; yet, the temporal course of connectivity lifetime changes has not been established. Here, an extensive cross-sectional sample (21–85 years old, N = 887) from a public fcMRI database was used to characterize adult lifespan connectivity dynamics within and between seven brain networks: the default mode, salience, dorsal attention, fronto-parietal control, auditory, visual and motor networks. The entire cohort was divided into young (21–40 years, mean ± SD: 25.5 ± 4.8, n = 543); middle-aged (41–60 years, 50.6 ± 5.4, n = 238); and old (61 years and above, 69.0 ± 6.3, n = 106) subgroups. Correlation matrices as well as a mixed model analysis of covariance indicated that within high-order cognitive networks a considerable connectivity decline is already evident by middle adulthood. In contrast, a motor network shows increased connectivity in middle adulthood and a subsequent decline. Additionally, alterations in inter-network interactions are noticeable primarily in the transition between young and middle adulthood. These results provide evidence that aging-related neural changes start early in adult life. PMID:28119599
A century of general relativity: astrophysics and cosmology.
Blandford, R D
2015-03-06
One hundred years after its birth, general relativity has become a highly successful physical theory in the sense that it has passed a large number of experimental and observational tests and finds extensive application to a wide variety of cosmic phenomena. It remains an active area of research as new tests are on the way, epitomized by the exciting prospect of detecting gravitational waves from merging black holes. General relativity is the essential foundation of the standard model of cosmology and underlies our description of the black holes and neutron stars that are ultimately responsible for the most powerful and dramatic cosmic sources. Its interface with physics on the smallest and largest scales will continue to provide fertile areas of investigation in its next century. Copyright © 2015, American Association for the Advancement of Science.
Testing General Relativity with the Shadow Size of Sgr A*
NASA Astrophysics Data System (ADS)
Johannsen, Tim; Broderick, Avery E.; Plewa, Philipp M.; Chatzopoulos, Sotiris; Doeleman, Sheperd S.; Eisenhauer, Frank; Fish, Vincent L.; Genzel, Reinhard; Gerhard, Ortwin; Johnson, Michael D.
2016-01-01
In general relativity, the angular radius of the shadow of a black hole is primarily determined by its mass-to-distance ratio and depends only weakly on its spin and inclination. If general relativity is violated, however, the shadow size may also depend strongly on parametric deviations from the Kerr metric. Based on a reconstructed image of Sagittarius A* (Sgr A* ) from a simulated one-day observing run of a seven-station Event Horizon Telescope (EHT) array, we employ a Markov chain Monte Carlo algorithm to demonstrate that such an observation can measure the angular radius of the shadow of Sgr A* with an uncertainty of ˜1.5 μ as (6%). We show that existing mass and distance measurements can be improved significantly when combined with upcoming EHT measurements of the shadow size and that tight constraints on potential deviations from the Kerr metric can be obtained.
Testing General Relativity with the Shadow Size of Sgr A(*).
Johannsen, Tim; Broderick, Avery E; Plewa, Philipp M; Chatzopoulos, Sotiris; Doeleman, Sheperd S; Eisenhauer, Frank; Fish, Vincent L; Genzel, Reinhard; Gerhard, Ortwin; Johnson, Michael D
2016-01-22
In general relativity, the angular radius of the shadow of a black hole is primarily determined by its mass-to-distance ratio and depends only weakly on its spin and inclination. If general relativity is violated, however, the shadow size may also depend strongly on parametric deviations from the Kerr metric. Based on a reconstructed image of Sagittarius A^{*} (Sgr A^{*}) from a simulated one-day observing run of a seven-station Event Horizon Telescope (EHT) array, we employ a Markov chain Monte Carlo algorithm to demonstrate that such an observation can measure the angular radius of the shadow of Sgr A^{*} with an uncertainty of ∼1.5 μas (6%). We show that existing mass and distance measurements can be improved significantly when combined with upcoming EHT measurements of the shadow size and that tight constraints on potential deviations from the Kerr metric can be obtained.
General Theory of Relativity: Will It Survive the Next Decade?
NASA Technical Reports Server (NTRS)
Bertolami, Orfeu; Paramos, Jorge; Turyshev, Slava G.
2006-01-01
The nature of gravity is fundamental to our understanding of our own solar system, the galaxy and the structure and evolution of the Universe. Einstein's general theory of relativity is the standard model that is used for almost ninety years to describe gravitational phenomena on these various scales. We review the foundations of general relativity, discuss the recent progress in the tests of relativistic gravity, and present motivations for high-accuracy gravitational experiments in space. We also summarize the science objectives and technology needs for the laboratory experiments in space with laboratory being the entire solar system. We discuss the advances in our understanding of fundamental physics anticipated in the near future and evaluate discovery potential for the recently proposed gravitational experiments.
General Theory of Relativity: Will It Survive the Next Decade?
NASA Technical Reports Server (NTRS)
Bertolami, Orfeu; Paramos, Jorge; Turyshev, Slava G.
2006-01-01
The nature of gravity is fundamental to our understanding of our own solar system, the galaxy and the structure and evolution of the Universe. Einstein's general theory of relativity is the standard model that is used for almost ninety years to describe gravitational phenomena on these various scales. We review the foundations of general relativity, discuss the recent progress in the tests of relativistic gravity, and present motivations for high-accuracy gravitational experiments in space. We also summarize the science objectives and technology needs for the laboratory experiments in space with laboratory being the entire solar system. We discuss the advances in our understanding of fundamental physics anticipated in the near future and evaluate discovery potential for the recently proposed gravitational experiments.
Towards a general solution of the Hamiltonian constraints of General Relativity
NASA Astrophysics Data System (ADS)
Tiemblo, A.; Tresguerres, R.
2006-12-01
The present work has a double aim. On the one hand, we call attention on the relationship existing between the Ashtekar formalism and other gauge-theoretical approaches to gravity, in particular the Poincaré Gauge Theory. On the other hand, we study two kinds of solutions for the constraints of General Relativity, consisting of two mutually independent parts, namely a general three-metric-dependent contribution to the extrinsic curvature K ab in terms of the Cotton York tensor, and besides it further metric independent contributions, which we analyze in particular in the presence of isotropic three-metrics.
General characteristics of relative dispersion in the ocean.
Corrado, Raffaele; Lacorata, Guglielmo; Palatella, Luigi; Santoleri, Rosalia; Zambianchi, Enrico
2017-04-11
The multi-scale and nonlinear nature of the ocean dynamics dramatically affects the spreading of matter, like pollutants, marine litter, etc., of physical and chemical seawater properties, and the biological connectivity inside and among different basins. Based on the Finite-Scale Lyapunov Exponent analysis of the largest available near-surface Lagrangian data set from the Global Drifter Program, our results show that, despite the large variety of flow features, relative dispersion can ultimately be described by a few parameters common to all ocean sub-basins, at least in terms of order of magnitude. This provides valuable information to undertake Lagrangian dispersion studies by means of models and/or of observational data. Moreover, our results show that the relative dispersion rates measured at submesoscale are significantly higher than for large-scale dynamics. Auxiliary analysis of high resolution GPS-tracked drifter hourly data as well as of the drogued/undrogued status of the buoys is provided in support of our conclusions. A possible application of our study, concerning reverse drifter motion and error growth analysis, is proposed relatively to the case of the missing Malaysia Airlines MH370 aircraft.
General characteristics of relative dispersion in the ocean
Corrado, Raffaele; Lacorata, Guglielmo; Palatella, Luigi; Santoleri, Rosalia; Zambianchi, Enrico
2017-01-01
The multi-scale and nonlinear nature of the ocean dynamics dramatically affects the spreading of matter, like pollutants, marine litter, etc., of physical and chemical seawater properties, and the biological connectivity inside and among different basins. Based on the Finite-Scale Lyapunov Exponent analysis of the largest available near-surface Lagrangian data set from the Global Drifter Program, our results show that, despite the large variety of flow features, relative dispersion can ultimately be described by a few parameters common to all ocean sub-basins, at least in terms of order of magnitude. This provides valuable information to undertake Lagrangian dispersion studies by means of models and/or of observational data. Moreover, our results show that the relative dispersion rates measured at submesoscale are significantly higher than for large-scale dynamics. Auxiliary analysis of high resolution GPS-tracked drifter hourly data as well as of the drogued/undrogued status of the buoys is provided in support of our conclusions. A possible application of our study, concerning reverse drifter motion and error growth analysis, is proposed relatively to the case of the missing Malaysia Airlines MH370 aircraft. PMID:28397797
General characteristics of relative dispersion in the ocean
NASA Astrophysics Data System (ADS)
Corrado, Raffaele; Lacorata, Guglielmo; Palatella, Luigi; Santoleri, Rosalia; Zambianchi, Enrico
2017-04-01
The multi-scale and nonlinear nature of the ocean dynamics dramatically affects the spreading of matter, like pollutants, marine litter, etc., of physical and chemical seawater properties, and the biological connectivity inside and among different basins. Based on the Finite-Scale Lyapunov Exponent analysis of the largest available near-surface Lagrangian data set from the Global Drifter Program, our results show that, despite the large variety of flow features, relative dispersion can ultimately be described by a few parameters common to all ocean sub-basins, at least in terms of order of magnitude. This provides valuable information to undertake Lagrangian dispersion studies by means of models and/or of observational data. Moreover, our results show that the relative dispersion rates measured at submesoscale are significantly higher than for large-scale dynamics. Auxiliary analysis of high resolution GPS-tracked drifter hourly data as well as of the drogued/undrogued status of the buoys is provided in support of our conclusions. A possible application of our study, concerning reverse drifter motion and error growth analysis, is proposed relatively to the case of the missing Malaysia Airlines MH370 aircraft.
Relations between urban bird and plant communities and human well-being and connection to nature.
Luck, Gary W; Davidson, Penny; Boxall, Dianne; Smallbone, Lisa
2011-08-01
By 2050, 70% of the world's population will live in urban areas. In many cases urbanization reduces the richness and abundance of native species. Living in highly modified environments with fewer opportunities to interact directly with a diversity of native species may adversely affect residents' personal well-being and emotional connection to nature. We assessed the personal well-being, neighborhood well-being (a measure of a person's satisfaction with their neighborhood), and level of connection to nature of over 1000 residents in 36 residential neighborhoods in southeastern Australia. We modeled these response variables as a function of natural features of each neighborhood (e.g., species richness and abundance of birds, density of plants, and amount of vegetation cover) and demographic characteristics of surveyed residents. Vegetation cover had the strongest positive relations with personal well-being, whereas residents' level of connection to nature was weakly related to variation in species richness and abundance of birds and density of plants. Demographic characteristics such as age and level of activity explained the greatest proportion of variance in well-being and connection to nature. Nevertheless, when controlling for variation in demographic characteristics (examples were provided above), neighborhood well-being was positively related to a range of natural features, including species richness and abundance of birds, and vegetation cover. Demographic characteristics and how well-being was quantified strongly influenced our results, and we suggest demography and metrics of well-being must be considered when attempting to determine relations between the urban environment and human well-being. © 2011 Society for Conservation Biology.
Normalized general relativity: Nonclosed universe and a zero cosmological constant
NASA Astrophysics Data System (ADS)
Davidson, Aharon; Rubin, Shimon
2014-01-01
We discuss the cosmological constant problem, at the minisuperspace level, within the framework of the so-called normalized general relativity. We prove that the Universe cannot be closed, and reassure that the accompanying cosmological constant Λ generically vanishes, at least classically. The theory does allow, however, for a special class of Λ ≠0 solutions which are associated with static closed Einstein universe and with Eddington-Lemaître universe.
Sensor failure detection using generalized parity relations for flexible structures
NASA Technical Reports Server (NTRS)
Mercadal, Mathieu
1989-01-01
Analytical redundancy may be preferable to hardware redundancy in failure detection/isolation tasks for such large-scale systems as space structures. Generalized single-sensor parity relations are presently applied to this problem; they are noted to yield a very simple isolation logic, and their generation is found to be extremely rapid, even in the case of extremely complex systems, provided only that the eigenstructure of the system be known. Their implementation is, however, extremely sensitive to modeling errors and noise.
Revisiting the classical electron model in general relativity
NASA Astrophysics Data System (ADS)
Rahaman, Farook; Jamil, Mubasher; Chakraborty, Kaushik
2011-01-01
Motivated by earlier studies (Tiwari et al. in Astrophys. Space Sci. 182:105, 1984; Herrera and Varela in Phys. Lett. 189:11, 1994), we model electron as a spherically symmetric charged perfect fluid distribution of matter. The existing model is extended assuming a matter source that is characterized by quadratic equation of state in the context of general theory of relativity. For the suitable choices of the parameters, our charged fluid models almost satisfy the physical properties of electron.
Testing general relativity with laser accelerated electron beams
Gergely, L. A.; Harko, T.
2012-07-09
Electron accelerations of the order of 10{sup 21} g obtained by laser fields open up the possibility of experimentally testing one of the cornerstones of general relativity, the weak equivalence principle, which states that the local effects of a gravitational field are indistinguishable from those sensed by a properly accelerated observer in flat space-time. We illustrate how this can be done by solving the Einstein equations in vacuum and integrating the geodesic equations of motion for a uniformly accelerated particle.
Ries, Michele L; McLaren, Donald G; Bendlin, Barbara B; Guofanxu; Rowley, Howard A; Birn, Rasmus; Kastman, Erik K; Sager, Mark A; Asthana, Sanjay; Johnson, Sterling C
2012-04-01
It is tentatively estimated that 25% of people with early Alzheimer's disease (AD) show impaired awareness of disease-related changes in their own cognition. Research examining both normative self-awareness and altered awareness resulting from brain disease or injury points to the central role of the medial prefrontal cortex (MPFC) in generating accurate self-appraisals. The current project builds on this work - examining changes in MPFC functional connectivity that correspond to impaired self-appraisal accuracy early in the AD time course. Our behavioral focus was self-appraisal accuracy for everyday memory function, and this was measured using the Memory Function Scale of the Memory Awareness Rating Scale - an instrument psychometrically validated for this purpose. Using regression analysis of data from people with healthy memory (n=12) and people with impaired memory due to amnestic mild cognitive impairment or early AD (n=12), we tested the hypothesis that altered MPFC functional connectivity - particularly with other cortical midline structures and dorsolateral prefrontal cortex - explains variation in memory self-appraisal accuracy. We spatially constrained (i.e., explicitly masked) our regression analyses to those regions that work in conjunction with the MPFC to evoke self-appraisals in a normative group. This empirically derived explicit mask was generated from the result of a psychophysiological interaction analysis of fMRI self-appraisal task data in a separate, large group of cognitively healthy individuals. Results of our primary analysis (i.e., the regression of memory self-appraisal accuracy on MPFC functional connectivity) were generally consistent with our hypothesis: people who were less accurate in making memory self-appraisals showed attenuated functional connectivity between the MPFC seed region and proximal areas within the MPFC (including subgenual anterior cingulate cortex), bilateral dorsolateral prefrontal cortex, bilateral caudate, and
The effects of general relativity on near-earth satellites
NASA Technical Reports Server (NTRS)
Ries, J. C.; Watkins, M. M.; Tapley, B. D.; Huang, C.
1990-01-01
Whether one uses a solar system barycentric frame or a geocentric frame when including the general theory of relativity in orbit determination for near-earth satellites, the results should be equivalent to some limiting accuracy. The purpose of this paper is to clarify the effects of relativity in each frame and to demonstrate their equivalence through the analysis of three years of laser tracking data taken on the Lageos satellite. It is demonstrated that the simpler formulation in the geocentric frame is adequate for the purpose of near-earth satellite orbit determination. A correction to the conventional barycentric equations of motion is shown to be required.
The effects of general relativity on near-earth satellites
NASA Technical Reports Server (NTRS)
Ries, J. C.; Watkins, M. M.; Tapley, B. D.; Huang, C.
1990-01-01
Whether one uses a solar system barycentric frame or a geocentric frame when including the general theory of relativity in orbit determination for near-earth satellites, the results should be equivalent to some limiting accuracy. The purpose of this paper is to clarify the effects of relativity in each frame and to demonstrate their equivalence through the analysis of three years of laser tracking data taken on the Lageos satellite. It is demonstrated that the simpler formulation in the geocentric frame is adequate for the purpose of near-earth satellite orbit determination. A correction to the conventional barycentric equations of motion is shown to be required.
General relativity from three-forms in seven dimensions
NASA Astrophysics Data System (ADS)
Krasnov, Kirill
2017-09-01
We consider a certain theory of 3-forms in 7 dimensions, and study its dimensional reduction to 4D, compactifying the 7-dimensional manifold on the 3-sphere of a fixed radius. We show that the resulting 4D theory is (Riemannian) General Relativity (GR) in Plebanski formulation, modulo corrections that are negligible for curvatures smaller than Planckian. Possibly the most interesting point of this construction is that the dimensionally reduced theory is GR with a non-zero cosmological constant, and the value of the cosmological constant is directly related to the size of S3. Realistic values of Λ correspond to S3 of Planck size.
Spacetime and geometry. An introduction to general relativity
NASA Astrophysics Data System (ADS)
Carroll, Sean M.
This book provides a lucid and thoroughly modern introduction to general relativity for advanced readers. It introduces modern techniques and an accessible and lively writing style to what can often be a formal and intimidating subject. Readers are led from physics of flat spacetime (special relativity), through the intricacies of differential geometry and Einstein's equations, and on to exciting applications such as black holes, gravitational radiation, and cosmology. Subtle points are illuminated throughout the text by careful and entertaining exposition. A straightforward and lucid approach, balancing mathematical rigor and physical insight, are hallmarks of this important text.
Exploring the transition from special to general relativity
NASA Astrophysics Data System (ADS)
Semon, Mark D.; Malin, Shimon; Wortel, Stephanie
2009-05-01
In a previous paper we discussed two examples of circular motion which are especially useful in relativity courses because they lead to predictions verified by experiments with macroscopic objects. We analyzed these examples by considering motion around an N-gon and then taking the limit as N →∞ and the N-gon becomes a circle. In this paper we use the same approach to illustrate how generalizing special relativity to a theory that includes non-inertial frames can lead to a non-Euclidean geometry. We also derive two properties of clocks at rest in a reference frame traveling on a circular path.
Tests of general relativity from timing the double pulsar.
Kramer, M; Stairs, I H; Manchester, R N; McLaughlin, M A; Lyne, A G; Ferdman, R D; Burgay, M; Lorimer, D R; Possenti, A; D'Amico, N; Sarkissian, J M; Hobbs, G B; Reynolds, J E; Freire, P C C; Camilo, F
2006-10-06
The double pulsar system PSR J0737-3039A/B is unique in that both neutron stars are detectable as radio pulsars. They are also known to have much higher mean orbital velocities and accelerations than those of other binary pulsars. The system is therefore a good candidate for testing Einstein's theory of general relativity and alternative theories of gravity in the strong-field regime. We report on precision timing observations taken over the 2.5 years since its discovery and present four independent strong-field tests of general relativity. These tests use the theory-independent mass ratio of the two stars. By measuring relativistic corrections to the Keplerian description of the orbital motion, we find that the "post-Keplerian" parameter s agrees with the value predicted by general relativity within an uncertainty of 0.05%, the most precise test yet obtained. We also show that the transverse velocity of the system's center of mass is extremely small. Combined with the system's location near the Sun, this result suggests that future tests of gravitational theories with the double pulsar will supersede the best current solar system tests. It also implies that the second-born pulsar may not have formed through the core collapse of a helium star, as is usually assumed.
Explanatory and illustrative visualization of special and general relativity.
Weiskopf, Daniel; Borchers, Marc; Ertl, Thomas; Falk, Martin; Fechtig, Oliver; Frank, Regine; Grave, Frank; King, Andreas; Kraus, Ute; Müller, Thomas; Nollert, Hans-Peter; Rica Mendez, Isabel; Ruder, Hanns; Schafhitzel, Tobias; Schär, Sonja; Zahn, Corvin; Zatloukal, Michael
2006-01-01
This paper describes methods for explanatory and illustrative visualizations used to communicate aspects of Einstein's theories of special and general relativity, their geometric structure, and of the related fields of cosmology and astrophysics. Our illustrations target a general audience of laypersons interested in relativity. We discuss visualization strategies, motivated by physics education and the didactics of mathematics, and describe what kind of visualization methods have proven to be useful for different types of media, such as still images in popular science magazines, film contributions to TV shows, oral presentations, or interactive museum installations. Our primary approach is to adopt an egocentric point of view: The recipients of a visualization participate in a visually enriched thought experiment that allows them to experience or explore a relativistic scenario. In addition, we often combine egocentric visualizations with more abstract illustrations based on an outside view in order to provide several presentations of the same phenomenon. Although our visualization tools often build upon existing methods and implementations, the underlying techniques have been improved by several novel technical contributions like image-based special relativistic rendering on GPUs, special relativistic 4D ray tracing for accelerating scene objects, an extension of general relativistic ray tracing to manifolds described by multiple charts, GPU-based interactive visualization of gravitational light deflection, as well as planetary terrain rendering. The usefulness and effectiveness of our visualizations are demonstrated by reporting on experiences with, and feedback from, recipients of visualizations and collaborators.
Gravitation experiments at Stanford. [using general relativity theory
NASA Technical Reports Server (NTRS)
Lipa, J. A.
1980-01-01
The experimental situation in post-Newtonian gravitation is briefly reviewed in order to reexamine the extent to which experiment supports or refutes general relativity. A description is given of the equivalence principle project, the gyroscope experiment, and the search for gravity waves. It is noted that even though some doubt has been cast on the value of the perihelion advance and the gravitational redshift as precise tests of general relativity in the past few years, many competing theories have been ruled out; in particular, the results from the Viking mission significantly reduce the credibility of the Brans-Dicke theory (Brans and Dicke, 1961). The dimensionless constant omega in this theory is now forced to exceed 50, while the value originally proposed was 6 (omega being infinity in general relativity). It is noted that the gyro experiment described is capable of putting much tighter limits on this parameter, and together with the other experiments in progress will help place gravitational theory on a firmer experimental footing.
Gravitation experiments at Stanford. [using general relativity theory
NASA Technical Reports Server (NTRS)
Lipa, J. A.
1980-01-01
The experimental situation in post-Newtonian gravitation is briefly reviewed in order to reexamine the extent to which experiment supports or refutes general relativity. A description is given of the equivalence principle project, the gyroscope experiment, and the search for gravity waves. It is noted that even though some doubt has been cast on the value of the perihelion advance and the gravitational redshift as precise tests of general relativity in the past few years, many competing theories have been ruled out; in particular, the results from the Viking mission significantly reduce the credibility of the Brans-Dicke theory (Brans and Dicke, 1961). The dimensionless constant omega in this theory is now forced to exceed 50, while the value originally proposed was 6 (omega being infinity in general relativity). It is noted that the gyro experiment described is capable of putting much tighter limits on this parameter, and together with the other experiments in progress will help place gravitational theory on a firmer experimental footing.
Wang, Lei; Alpert, Kathryn I.; Calhoun, Vince D.; Cobia, Derin J.; Keator, David B.; King, Margaret D.; Kogan, Alexandr; Landis, Drew; Tallis, Marcelo; Turner, Matthew D.; Potkin, Steven G.; Turner, Jessica A.; Ambite, Jose Luis
2015-01-01
SchizConnect (www.schizconnect.org) is built to address the issues of multiple data repositories in schizophrenia neuroimaging studies. It includes a level of mediation—translating across data sources—so that the user can place one query, e.g. for diffusion images from male individuals with schizophrenia, and find out from across participating data sources how many datasets there are, as well as downloading the imaging and related data. The current version handles the Data Usage Agreements across different studies, as well as interpreting database-specific terminologies into a common framework. New data repositories can also be mediated to bring immediate access to existing datasets. Compared with centralized, upload data sharing models, SchizConnect is a unique, virtual database with a focus on schizophrenia and related disorders that can mediate live data as information are being updated at each data source. It is our hope that SchizConnect can facilitate testing new hypotheses through aggregated datasets, promoting discovery related to the mechanisms underlying schizophrenic dysfunction. PMID:26142271
Fluctuation-dissipation theorem in general relativity and the cosmological constant
Mottola, E.
1992-01-01
Vacuum fluctuations are an essential feature of quantum field theory. Yet, the smallness of the scalar curvature of our universe suggests that the zero-point energy associated with these fluctuations does not curve spacetime. A possible way out of this paradox is suggested by the fact that microscopic fluctuations are generally accompanied by dissipative behavior in macroscopic systems. The intimate relation between the two is expressed by a fluctuation-dissipation theorem which extends to general relativity. The connection between quantum fluctuations and dissipation suggests a mechanism for the conversion of coherent stresses in the curvature of space into ordinary matter or radiation, thereby relaxing the effective cosmological constant'' to zero over time. The expansion of the universe may be the effect of this time-asymmetric relaxation process.
Fluctuation-dissipation theorem in general relativity and the cosmological constant
Mottola, E.
1992-06-01
Vacuum fluctuations are an essential feature of quantum field theory. Yet, the smallness of the scalar curvature of our universe suggests that the zero-point energy associated with these fluctuations does not curve spacetime. A possible way out of this paradox is suggested by the fact that microscopic fluctuations are generally accompanied by dissipative behavior in macroscopic systems. The intimate relation between the two is expressed by a fluctuation-dissipation theorem which extends to general relativity. The connection between quantum fluctuations and dissipation suggests a mechanism for the conversion of coherent stresses in the curvature of space into ordinary matter or radiation, thereby relaxing the effective cosmological ``constant`` to zero over time. The expansion of the universe may be the effect of this time-asymmetric relaxation process.
Cosmological Theories of Special and General Relativity - I
NASA Astrophysics Data System (ADS)
Moshe, Carmeli
In the standard cosmological theory one uses the Einstein concepts of space and time as were originally introduced for the special theory of relativity and the general relativity theory. According to this approach all physical quantities are described in terms of the continuum spatial coordinates and time. Using general relativity theory a great progress has been made in understanding the evolution of the Universe. Cosmologists usually measure spatial distances and redshitfs of faraway galaxies as expressed by the Hubble expansion. In recent years this fact was undertaken to develop new theories in terms of distances and velocities (redshift). While in Einstein's relativity the propagation of light plays the major role, in the new theory it is the expansion of the Universe that takes that role and appears at the outset. The cosmic time becomes crucial in these recent theories, which in the standard theory is considered to be absolute but here it is relative. In this lecture this new approach to cosmology is presented.
Wilcox, Claire E.; Mayer, Andrew R.; Teshiba, Terri M.; Ling, Josef; Smith, Bruce W.; Wilcox, George L.; Mullins, Paul G.
2015-01-01
Objective Previous work suggests that the perception of pain is subjective and dependent on individual differences in physiological, emotional and cognitive states. Functional magnetic resonance imaging (FMRI) studies have utilized both stimulus-related (nociceptive properties) and percept-related (subjective experience of pain) models to identify the brain networks associated with pain. Our objective was to identify the network involved in processing subjective pain during cold stimuli. Methods The current FMRI study directly contrasted a stimulus-related model with a percept-related model during blocks of cold pain stimuli in healthy adults. Specifically, neuronal activation was modelled as a function of changes in stimulus intensity versus as a function of increasing/decreasing levels of subjective pain corresponding to changes in pain ratings. In addition, functional connectivity analyses were conducted to examine intrinsic correlations between three proposed sub-networks (sensory/discriminative, affective/motivational, and cognitive/evaluative) involved in pain processing. Results The percept-related model captured more extensive activation than the stimulus-related model and demonstrated an association between higher subjective pain and activation in expected cortical (DLPFC, VLPFC, insula, ACC extending into preSMA) and subcortical (thalamus, striatum) areas. Moreover, connectivity results supported the posited roles of dACC and insula as key relay sites during neural processing of subjective pain. In particular, anterior insula appeared to link sensory/discriminative regions with regions in the other sub-networks, and dACC appeared to serve as a hub for affective/motivational, cognitive/evaluative, and motor sub-networks. Conclusions Using a percept-related model, brain regions involved in the processing of subjective pain during the application of cold stimuli were identified. Connectivity analyses identified linkages between key sub-networks involved in
ERIC Educational Resources Information Center
Roy, Amy K.; Fudge, Julie L.; Kelly, Clare; Perry, Justin S. A.; Daniele, Teresa; Carlisi, Christina; Benson, Brenda; Castellanos, F. Xavier; Milham, Michael P.; Pine, Daniel S.; Ernst, Monique
2013-01-01
Objective: Generalized anxiety disorder (GAD) typically begins during adolescence and can persist into adulthood. The pathophysiological mechanisms underlying this disorder remain unclear. Recent evidence from resting state functional magnetic resonance imaging (R-fMRI) studies in adults suggests disruptions in amygdala-based circuitry; the…
ERIC Educational Resources Information Center
Roy, Amy K.; Fudge, Julie L.; Kelly, Clare; Perry, Justin S. A.; Daniele, Teresa; Carlisi, Christina; Benson, Brenda; Castellanos, F. Xavier; Milham, Michael P.; Pine, Daniel S.; Ernst, Monique
2013-01-01
Objective: Generalized anxiety disorder (GAD) typically begins during adolescence and can persist into adulthood. The pathophysiological mechanisms underlying this disorder remain unclear. Recent evidence from resting state functional magnetic resonance imaging (R-fMRI) studies in adults suggests disruptions in amygdala-based circuitry; the…
ERIC Educational Resources Information Center
Goetz, Lori; O'Farrell, Nora
1999-01-01
This article describes a three-component package to facilitate social supports for students who are deaf-blind in general education classes. The components are: ongoing provision of information, provision of interactive, multiple communication media, and facilitation of social interactions. Case studies of four students with deaf-blindness…
A Jubilant Connection: General Jubal Early's Troops and the Golden Ratio
ERIC Educational Resources Information Center
Bolte, Linda A.; Noon, Tim R., Jr.
2012-01-01
The golden ratio, one of the most beautiful numbers in all of mathematics, arises in some surprising places. At first glance, we might expect that a General checking his troops' progress would be nothing more than a basic distance-rate-time problem. However, further exploration reveals a multi-faceted problem, one in which the ratio of rates…
Alterations in conflict monitoring are related to functional connectivity in Parkinson's disease.
Rosenberg-Katz, Keren; Maidan, Inbal; Jacob, Yael; Giladi, Nir; Mirelman, Anat; Hausdorff, Jeffrey M
2016-09-01
Patients with Parkinson's disease (PD) have difficulties in executive functions including conflict monitoring. The neural mechanisms underlying these difficulties are not yet fully understood. In order to examine the neural mechanisms related to conflict monitoring in PD, we evaluated 35 patients with PD and 20 healthy older adults while they performed a word-color Stroop paradigm in the MRI. Specifically, we focused on changes between the groups in task-related functional connectivity using psycho-physiological interaction (PPI) analysis. The anterior cingulate cortex (ACC), which is a brain node previously associated with the Stroop paradigm, was selected as the seed region for this analysis. Patients with PD, as compared to healthy controls, had reduced task-related functional connectivity between the ACC and parietal regions including the precuneus and inferior parietal lobe. This was seen only in the incongruent Stroop condition. A higher level of connectivity between the ACC and precuneus was correlated with a lower error rate in the conflicting, incongruent Stroop condition in the healthy controls, but not in the patients with PD. Furthermore, the patients also had reduced functional connectivity between the ACC and the superior frontal gyrus which was present in both the incongruent and congruent task condition. The present findings shed light on brain mechanisms that are apparently associated with specific cognitive difficulties in patients with PD. Among patients with PD, impaired conflict monitoring processing within the ACC-based fronto-parietal network may contribute to difficulties under increased executive demands. Copyright © 2016 Elsevier Ltd. All rights reserved.
Meshi, Dar; Mamerow, Loreen; Kirilina, Evgeniya; Morawetz, Carmen; Margulies, Daniel S.; Heekeren, Hauke R.
2016-01-01
Human beings are social animals and they vary in the degree to which they share information about themselves with others. Although brain networks involved in self-related cognition have been identified, especially via the use of resting-state experiments, the neural circuitry underlying individual differences in the sharing of self-related information is currently unknown. Therefore, we investigated the intrinsic functional organization of the brain with respect to participants’ degree of self-related information sharing using resting state functional magnetic resonance imaging and self-reported social media use. We conducted seed-based correlation analyses in cortical midline regions previously shown in meta-analyses to be involved in self-referential cognition: the medial prefrontal cortex (MPFC), central precuneus (CP), and caudal anterior cingulate cortex (CACC). We examined whether and how functional connectivity between these regions and the rest of the brain was associated with participants’ degree of self-related information sharing. Analyses revealed associations between the MPFC and right dorsolateral prefrontal cortex (DLPFC), as well as the CP with the right DLPFC, the left lateral orbitofrontal cortex and left anterior temporal pole. These findings extend our present knowledge of functional brain connectivity, specifically demonstrating how the brain’s intrinsic functional organization relates to individual differences in the sharing of self-related information. PMID:26948055
Thomason, Moriah E.; Grove, Lauren E.; Lozon, Tim A.; Vila, Angela M.; Ye, Yongquan; Nye, Matthew J.; Manning, Janessa H.; Pappas, Athina; Hernandez-Andrade, Edgar; Yeo, Lami; Mody, Swati; Berman, Susan; Hassan, Sonia S.; Romero, Roberto
2015-01-01
Formation of operational neural networks is one of the most significant accomplishments of human fetal brain growth. Recent advances in functional magnetic resonance imaging (fMRI) have made it possible to obtain information about brain function during fetal development. Specifically, resting-state fMRI and novel signal covariation approaches have opened up a new avenue for non-invasive assessment of neural functional connectivity (FC) before birth. Early studies in this area have unearthed new insights about principles of prenatal brain function. However, very little is known about the emergence and maturation of neural networks during fetal life. Here, we obtained cross-sectional rs-fMRI data from 39 fetuses between 24 and 38 weeks postconceptual age to examine patterns of connectivity across ten neural FC networks. We identified primitive forms of motor, visual, default mode, thalamic, and temporal networks in the human fetal brain. We discovered the first evidence of increased long-range, cerebral-cerebellar, cortical-subcortical, and intra-hemispheric FC with advancing fetal age. Continued aggregation of data about fundamental neural connectivity systems in utero is essential to establishing principles of connectomics at the beginning of human life. Normative data provides a vital context against which to compare instances of abnormal neurobiological development. PMID:25284273
Thomason, Moriah E; Grove, Lauren E; Lozon, Tim A; Vila, Angela M; Ye, Yongquan; Nye, Matthew J; Manning, Janessa H; Pappas, Athina; Hernandez-Andrade, Edgar; Yeo, Lami; Mody, Swati; Berman, Susan; Hassan, Sonia S; Romero, Roberto
2015-02-01
Formation of operational neural networks is one of the most significant accomplishments of human fetal brain growth. Recent advances in functional magnetic resonance imaging (fMRI) have made it possible to obtain information about brain function during fetal development. Specifically, resting-state fMRI and novel signal covariation approaches have opened up a new avenue for non-invasive assessment of neural functional connectivity (FC) before birth. Early studies in this area have unearthed new insights about principles of prenatal brain function. However, very little is known about the emergence and maturation of neural networks during fetal life. Here, we obtained cross-sectional rs-fMRI data from 39 fetuses between 24 and 38 weeks postconceptual age to examine patterns of connectivity across ten neural FC networks. We identified primitive forms of motor, visual, default mode, thalamic, and temporal networks in the human fetal brain. We discovered the first evidence of increased long-range, cerebral-cerebellar, cortical-subcortical, and intra-hemispheric FC with advancing fetal age. Continued aggregation of data about fundamental neural connectivity systems in utero is essential to establishing principles of connectomics at the beginning of human life. Normative data provides a vital context against which to compare instances of abnormal neurobiological development.
A New Generalization of von Neumann Relative Entropy
NASA Astrophysics Data System (ADS)
Li, Jing; Cao, Huaixin
2017-08-01
In quantum information, von Neumann relative entropy has a great applications and operational interpretations in diverse fields, and von Neumann entropy is an important tool for describing the uncertainty of a quantum state. In this paper, we generalize the classical von Neumann relative entropy S(ρ||σ) and von Neumann entropy S(ρ) to f-von Neumann relative entropy \\widetilde {S}f(ρ ||σ ) and f-von Neumann entropy \\widetilde {S}f(ρ ) induced by a logarithm-like function f, respectively, and explore their properties. We prove that \\widetilde {S}f(ρ ||σ ) is nonnegative and then prove that \\widetilde {S}f(ρ ) has nonnegativity, boundedness, concavity, subadditivity and so on. Later, we show the stability and continuity of the \\widetilde {S}f(ρ ) with respect to the trace distance. In the case that f(x) = -log x, the resulted entropies reduce the classical von Neumann relative entropy and von Neumann entropy, respectively. This means that our results extend the usual results to a more general setting and then have some potential applications in quantum information.
General regular charged space-times in teleparallel equivalent of general relativity
NASA Astrophysics Data System (ADS)
Nashed, G. G. L.
2007-07-01
Using a non-linear version of electrodynamics coupled to the teleparallel equivalent of general relativity (TEGR), we obtain new regular exact solutions. The non-linear theory reduces to the Maxwell one in the weak limit with the tetrad fields corresponding to a charged space-time. We then apply the energy-momentum tensor of the gravitational field, established in the Hamiltonian structure of the TEGR, to the solutions obtained.
ERIC Educational Resources Information Center
Stieha, Vicki
2010-01-01
Using relational and action oriented qualitative modes of inquiry (Cochran-Smith & Lytle, 2009; Gilligan, Spencer, Weinberg, & Bertsch, 2003; Raider-Roth, 2005), this research explores the trajectory of five veteran teachers' practice over two years. The participants were part of a group of teachers involved in an intensive Summer Teachers…
Mimicking static anisotropic fluid spheres in general relativity
NASA Astrophysics Data System (ADS)
Boonserm, Petarpa; Ngampitipan, Tritos; Visser, Matt
2016-11-01
We argue that an arbitrary general relativistic static anisotropic fluid sphere, (static and spherically symmetric but with transverse pressure not equal to radial pressure), can nevertheless be successfully mimicked by suitable linear combinations of theoretically attractive and quite simple classical matter: a classical (charged) isotropic perfect fluid, a classical electromagnetic field and a classical (minimally coupled) scalar field. While the most general decomposition is not unique, a preferred minimal decomposition can be constructed that is unique. We show how the classical energy conditions for the anisotropic fluid sphere can be related to energy conditions for the isotropic perfect fluid, electromagnetic field, and scalar field components of the model. Furthermore, we show how this decomposition relates to the distribution of both electric charge density and scalar charge density throughout the model. The generalized TOV equation implies that the perfect fluid component in this model is automatically in internal equilibrium, with pressure forces, electric forces, and scalar forces balancing the gravitational pseudo-force. Consequently, we can build theoretically attractive matter models that can be used to mimic almost any static spherically symmetric spacetime.
Understanding non-Gaussianity signatures in general relativity
NASA Astrophysics Data System (ADS)
Dai, Liang
2016-03-01
Possible departure from Gaussian statistics in cosmological perturbations can shed much light on the physics of their generation in the primordial Universe. Many of the forthcoming surveys of the large-scale structure with unprecedented survey volume aim at detecting these signatures. However, ignoring the ``gauge artifacts'' in general relativity that arise from the freedom to choose arbitrary space-time coordinates to describe the perturbed Universe can lead to incorrect interpretation on the observational consequences of these non-Gaussian signatures. I present two important examples of non-Gaussianity signatures. I show that in the ``separate universes'' formalism it can be clarified that they are strictly forbidden in canonical inflation scenarios involving only one scalar degree of freedom. One is a quadrupolar direction-dependence in the power spectrum of matter density, which is naively expected from a non-Gaussian correlation between a primordial gravitational wave of super-horizon wavelength and two density perturbations of shorter wavelengths. The other is a galaxy biasing that grows toward large scales, which is naively expected from nonlinearity in general relativity that couples a long-wavelength gravitational potential with two short-wavelength density fluctuations. Conversely, general models of single-field inflation can be falsified if it turns out that either of those signatures is actually observed.
Standard general relativity from Chern-Simons gravity
NASA Astrophysics Data System (ADS)
Izaurieta, F.; Minning, P.; Perez, A.; Rodriguez, E.; Salgado, P.
2009-07-01
Chern-Simons models for gravity are interesting because they provide a truly gauge-invariant action principle in the fiber-bundle sense. So far, their main drawback has largely been its perceived remoteness from standard General Relativity, based on the presence of higher powers of the curvature in the Lagrangian (except, remarkably, for three-dimensional spacetime). Here we report on a simple model that suggests a mechanism by which standard General Relativity in five-dimensional spacetime may indeed emerge at a special critical point in the space of couplings, where additional degrees of freedom and corresponding “anomalous” Gauss-Bonnet constraints drop out from the Chern-Simons action. To achieve this goal, both the Lie algebra g and the symmetric g-invariant tensor that define the Chern-Simons Lagrangian are constructed by means of the Lie algebra S-expansion method with a suitable finite Abelian semigroup S. The results are generalized to arbitrary odd dimensions, and the possible extension to the case of eleven-dimensional supergravity is briefly discussed.
Clewett, David; Bachman, Shelby; Mather, Mara
2014-01-01
Objective A current neuroanatomical model of anxiety posits that greater structural connectivity between the amygdala and ventral prefrontal cortex (vPFC) facilitates regulatory control over the amygdala and helps reduce anxiety. However, some neuroimaging studies have reported contradictory findings, demonstrating a positive rather than negative association between trait anxiety and amygdala-vPFC white matter integrity. To help reconcile these findings, we tested the regulatory hypothesis of anxiety circuitry using aging as a model of white matter decline in the amygdala-vPFC pathway. Methods We used probabilistic tractography to trace connections between the amygdala and vPFC in 21 younger, 18 middle-aged, and 15 healthy older adults. The resulting tract estimates were used to extract three indices of white-matter integrity: fractional anisotropy (FA), radial diffusivity (RD) and axial diffusivity (AD). The relationship between these amygdala-vPFC structural connectivity measures and age and State-Trait Anxiety Inventory (STAI) scores were assessed. Results The tractography results revealed age-related decline in the FA (p = .005) and radial diffusivity (p = .002) of the amygdala-vPFC pathway. Contrary to the regulatory hypothesis, we found a positive rather than negative association between trait anxiety and right amygdala-vPFC FA (p = .01). Conclusion These findings argue against the notion that greater amygdala-vPFC structural integrity facilitates better anxiety outcomes in healthy adults. Instead, our results suggest that white matter degeneration in this network relates to lower anxiety in older adults. PMID:24635708
Skeide, Michael A; Kirsten, Holger; Kraft, Indra; Schaadt, Gesa; Müller, Bent; Neef, Nicole; Brauer, Jens; Wilcke, Arndt; Emmrich, Frank; Boltze, Johannes; Friederici, Angela D
2015-09-01
Phonological awareness is the best-validated predictor of reading and spelling skill and therefore highly relevant for developmental dyslexia. Prior imaging genetics studies link several dyslexia risk genes to either brain-functional or brain-structural factors of phonological deficits. However, coherent evidence for genetic associations with both functional and structural neural phenotypes underlying variation in phonological awareness has not yet been provided. Here we demonstrate that rs11100040, a reported modifier of SLC2A3, is related to the functional connectivity of left fronto-temporal phonological processing areas at resting state in a sample of 9- to 12-year-old children. Furthermore, we provide evidence that rs11100040 is related to the fractional anisotropy of the arcuate fasciculus, which forms the structural connection between these areas. This structural connectivity phenotype is associated with phonological awareness, which is in turn associated with the individual retrospective risk scores in an early dyslexia screening as well as to spelling. These results suggest a link between a dyslexia risk genotype and a functional as well as a structural neural phenotype, which is associated with a phonological awareness phenotype. The present study goes beyond previous work by integrating genetic, brain-functional and brain-structural aspects of phonological awareness within a single approach. These combined findings might be another step towards a multimodal biomarker for developmental dyslexia.
State space modeling of time-varying contemporaneous and lagged relations in connectivity maps.
Molenaar, Peter C M; Beltz, Adriene M; Gates, Kathleen M; Wilson, Stephen J
2016-01-15
Most connectivity mapping techniques for neuroimaging data assume stationarity (i.e., network parameters are constant across time), but this assumption does not always hold true. The authors provide a description of a new approach for simultaneously detecting time-varying (or dynamic) contemporaneous and lagged relations in brain connectivity maps. Specifically, they use a novel raw data likelihood estimation technique (involving a second-order extended Kalman filter/smoother embedded in a nonlinear optimizer) to determine the variances of the random walks associated with state space model parameters and their autoregressive components. The authors illustrate their approach with simulated and blood oxygen level-dependent functional magnetic resonance imaging data from 30 daily cigarette smokers performing a verbal working memory task, focusing on seven regions of interest (ROIs). Twelve participants had dynamic directed functional connectivity maps: Eleven had one or more time-varying contemporaneous ROI state loadings, and one had a time-varying autoregressive parameter. Compared to smokers without dynamic maps, smokers with dynamic maps performed the task with greater accuracy. Thus, accurate detection of dynamic brain processes is meaningfully related to behavior in a clinical sample. Published by Elsevier Inc.
Relating anatomical and social connectivity: white matter microstructure predicts emotional empathy.
Parkinson, Carolyn; Wheatley, Thalia
2014-03-01
Understanding cues to the internal states of others involves a widely distributed network of brain regions. Although white matter (WM) connections are likely crucial for communication between these regions, the role of anatomical connectivity in empathic processing remains unexplored. The present study tested for a relationship between anatomical connectivity and empathy by assessing the WM microstructural correlates of affective empathy, which promotes interpersonal understanding through emotional reactions, and cognitive empathy, which does so via perspective taking. Associations between fractional anisotropy (FA) and the emotional (empathic concern, EC) and cognitive (perspective taking, PT) dimensions of empathy as assessed by the Interpersonal Reactivity Index were examined. EC was positively associated with FA in tracts providing communicative pathways within the limbic system, between perception and action-related regions, and between perception and affect-related regions, independently of individual differences in age, gender, and other dimensions of interpersonal reactivity. These findings provide a neuroanatomical basis for the rapid, privileged processing of emotional sensory information and the automatic elicitation of responses to the affective displays of others.
State Space Modeling of Time-Varying Contemporaneous and Lagged Relations in Connectivity Maps
Molenaar, Peter C. M.; Beltz, Adriene M.; Gates, Kathleen M.; Wilson, Stephen J.
2017-01-01
Most connectivity mapping techniques for neuroimaging data assume stationarity (i.e., network parameters are constant across time), but this assumption does not always hold true. The authors provide a description of a new approach for simultaneously detecting time-varying (or dynamic) contemporaneous and lagged relations in brain connectivity maps. Specifically, they use a novel raw data likelihood estimation technique (involving a second-order extended Kalman filter/smoother embedded in a nonlinear optimizer) to determine the variances of the random walks associated with state space model parameters and their autoregressive components. The authors illustrate their approach with simulated and blood oxygen level-dependent functional magnetic resonance imaging data from 30 daily cigarette smokers performing a verbal working memory task, focusing on seven regions of interest (ROIs). Twelve participants had dynamic directed functional connectivity maps: Eleven had one or more time-varying contemporaneous ROI state loadings, and one had a time-varying autoregressive parameter. Compared to smokers without dynamic maps, smokers with dynamic maps performed the task with greater accuracy. Thus, accurate detection of dynamic brain processes is meaningfully related to behavior in a clinical sample. PMID:26546863
Wang, Wei; Hou, Jingming; Qian, Shaowen; Liu, Kai; Li, Bo; Li, Min; Peng, Zhaohui; Xin, Kuolin; Sun, Gang
2016-06-15
The purpose of this study was to investigate the neural activity and functional connectivity in generalized anxiety disorder (GAD) during resting state, and how these alterations correlate to patients' symptoms. Twenty-eight GAD patients and 28 matched healthy controls underwent resting-state functional magnetic resonance (fMRI) scans. Amplitude of low-frequency fluctuation (ALFF) and seed-based resting-state functional connectivity (RSFC) were computed to explore regional activity and functional integration, and were compared between the two groups using the voxel-based two-sample t test. Pearson's correlation analyses were performed to examine the neural relationships with demographics and clinical symptoms scores. Compared to controls, GAD patients showed functional abnormalities: higher ALFF in the bilateral dorsomedial prefrontal cortex, bilateral dorsolateral prefrontal cortex and left precuneus/posterior cingulate cortex; lower connectivity in prefrontal gyrus; lower in prefrontal-limbic and cingulate RSFC and higher prefrontal-hippocampus RSFC were correlated with clinical symptoms severity, but these associations were unable to withstand correction for multiple testing. These findings may help facilitate further understanding of the potential neural substrate of GAD.
Family connections: a program for relatives of persons with borderline personality disorder.
Hoffman, Perry D; Fruzzetti, Alan E; Buteau, Ellie; Neiditch, Emily R; Penney, Dixianne; Bruce, Martha L; Hellman, Frederic; Struening, Elmer
2005-06-01
This study assessed changes in family members who participated in Family Connections, a 12-week manualized education program for relatives of persons with borderline personality disorder (BPD). Family Connections, led by trained family members, is based on the strategies of standard Dialectical Behavior Therapy (DBT) and DBT for families. The program provides (a) current information and research on BPD, (b) coping skills, (c) family skills, and (d) opportunities to build a support network for family members. Forty-four participants representing 34 families completed the pre-, post-, and 6-month postbaseline self-report questionnaires. Analyses employing hierarchical linear modeling strategies showed significant reductions in grief and burden, and a significant increase in mastery from pre- to post-group assessment. Changes were maintained at 6 months post baseline.
Characteristics of alcohol-related fatal general aviation crashes.
Li, Guohua; Baker, Susan P; Lamb, Margaret W; Qiang, Yandong; McCarthy, Melissa L
2005-01-01
The effects of alcohol on piloting performance have been studied extensively. Information describing alcohol-related aviation crashes, however, is scant. We developed a data system for fatally injured pilots in Maryland, New Mexico, and North Carolina by linking autopsy data from the state medical examiner offices and crash investigation reports from the National Transportation Safety Board. Alcohol-related crashes are defined as those in which the pilot had a blood alcohol concentration of 20 mg/dL or greater. Differences between alcohol- and non-alcohol-related crashes were assessed with regard to pilot characteristics, crash circumstances, and human factors. The National Transportation Safety Board recorded 313 general aviation crashes fatal to the pilot in the three states between 1985 and 2000. Of these crashes, 255 (81%) were matched successfully with medical examiner records. Alcohol testing results were available for 233 of the fatally injured pilots. Of those tested for alcohol, 25 (11%) had blood alcohol concentrations > or =20 mg/dL (mean=75 +/- 64 mg/dL). The majority of alcohol-related crashes (52%) occurred at night (7p.m. to 6a.m.), compared with 28% of other crashes (P < 0.01). Alcohol-related crashes were significantly more likely than other crashes to have involved continued flight under visual flight rules (VFR) into instrument meteorological conditions (IMC) (32% versus 12%, P < 0.01), and flawed decisions (64% versus 41%, P = 0.03). Distinctive epidemiological patterns are exhibited in alcohol-related fatal general aviation crashes. Alcohol appears to play a particularly important role in crashes involving flight under VFR into IMC.
AB INITIO PULSAR MAGNETOSPHERE: THE ROLE OF GENERAL RELATIVITY
Philippov, Alexander A.; Cerutti, Benoit; Spitkovsky, Anatoly; Tchekhovskoy, Alexander
2015-12-20
It has recently been demonstrated that self-consistent particle-in-cell simulations of low-obliquity pulsar magnetospheres in flat spacetime show weak particle acceleration and no pair production near the poles. We investigate the validity of this conclusion in a more realistic spacetime geometry via general-relativistic particle-in-cell simulations of the aligned pulsar magnetosphere with pair formation. We find that the addition of the frame-dragging effect makes the local current density along the magnetic field larger than the Goldreich–Julian value, which leads to unscreened parallel electric fields and the ignition of a pair cascade. When pair production is active, we observe field oscillations in the open field bundle, which could be related to pulsar radio emission. We conclude that general-relativistic effects are essential for the existence of the pulsar mechanism in low-obliquity rotators.
Boundary and corner terms in the action for general relativity
NASA Astrophysics Data System (ADS)
Jubb, Ian; Samuel, Joseph; Sorkin, Rafael D.; Surya, Sumati
2017-03-01
We revisit the action principle for general relativity, motivated by the path integral approach to quantum gravity. We consider a spacetime region whose boundary has piecewise C 2 components, each of which can be spacelike, timelike or null and consider metric variations in which only the pullback of the metric to the boundary is held fixed. Allowing all such metric variations we present a unified treatment of the spacelike, timelike and null boundary components using Cartan’s tetrad formalism. Apart from its computational simplicity, this formalism gives us a simple way of identifying corner terms. We also discuss ‘creases’ which occur when the boundary is the event horizon of a black hole. Our treatment is geometric and intrinsic and we present our results both in the computationally simpler tetrad formalism as well as the more familiar metric formalism. We recover known results from a simpler and more general point of view and find some new ones.
Guidelines for composite materials research related to general aviation aircraft
NASA Technical Reports Server (NTRS)
Dow, N. F.; Humphreys, E. A.; Rosen, B. W.
1983-01-01
Guidelines for research on composite materials directed toward the improvement of all aspects of their applicability for general aviation aircraft were developed from extensive studies of their performance, manufacturability, and cost effectiveness. Specific areas for research and for manufacturing development were identified and evaluated. Inputs developed from visits to manufacturers were used in part to guide these evaluations, particularly in the area of cost effectiveness. Throughout the emphasis was to direct the research toward the requirements of general aviation aircraft, for which relatively low load intensities are encountered, economy of production is a prime requirement, and yet performance still commands a premium. A number of implications regarding further directions for developments in composites to meet these requirements also emerged from the studies. Chief among these is the need for an integrated (computer program) aerodynamic/structures approach to aircraft design.
Structures of general relativity in dilaton-Maxwell electrodynamics
NASA Astrophysics Data System (ADS)
Kechkin, O. V.; Mosharev, P. A.
2016-08-01
It is shown that electro (magneto) static sector of Maxwell’s electrodynamics coupled to the dilaton field in a string theory form possesses the symmetry group of the stationary General Relativity in vacuum. Performing the Ernst formalism, we develope a technique for generation of exact solutions in this modified electrodynamics on the base of the normalized Ehlers symmetry transformation. In the electrostatic case, we construct and study a general class of spherically symmetric solutions that describes a pointlike source of the Coulomb type. It is demonstrated that this source is characterized by finite and singularity-free interaction at short distances. Also it is established that the total electrostatic energy of this source is finite and inversely proportional to the dilaton-Maxwell coupling constant.
Quasi-Local Conservation Equations in General Relativity
NASA Astrophysics Data System (ADS)
Yoon, J. H.
2002-12-01
A complete set of quasi-local conservation equations is derived from the Einstein's equations using the first-order (2,2)-formalism of general relativity. These equations are interpreted as quasi-local energy, momentum, and angular momentum conservation equations. In the asymptotic region of asymptotically flat space-times, the quasi-local energy and energy-flux integral agrees with the standard Bondi energy and Bondi energy-flux, respectively. In spherically symmetric space-times, the quasi-local energy becomes the Misner-Sharp energy. Moreover, on the event horizon of a general dynamical black hole, it is shown that the quasi-local energy conservation equation coincides with the conservation equation studied by Thome et al.
Quasi-local conservation equations in general relativity
NASA Astrophysics Data System (ADS)
Yoon, Jong Hyuk
2001-12-01
A set of exact quasi-local conservation equations is derived from the Einstein's equations using the first-order Kaluza-Klein formalism of general relativity in the (2,2)-splitting of 4-dimensional spacetime. These equations are interpreted as quasi-local energy, momentum, and angular momentum conservation equations. In the asymptotic region of asymptotically flat spacetimes, it is shown that the quasi-local energy and energy-flux integral reduce to the Bondi energy and energy-flux, respectively. In spherically symmetric spacetimes, the quasi-local energy becomes the Misner-Sharp energy. Moreover, on the event horizon of a general dynamical black hole, the quasi-local energy conservation equation coincides with the conservation equation studied by Thorne et al. We discuss the remaining quasi-local conservation equations briefly.
Visual Working Memory Load-Related Changes in Neural Activity and Functional Connectivity
Li, Ling; Zhang, Jin-Xiang; Jiang, Tao
2011-01-01
Background Visual working memory (VWM) helps us store visual information to prepare for subsequent behavior. The neuronal mechanisms for sustaining coherent visual information and the mechanisms for limited VWM capacity have remained uncharacterized. Although numerous studies have utilized behavioral accuracy, neural activity, and connectivity to explore the mechanism of VWM retention, little is known about the load-related changes in functional connectivity for hemi-field VWM retention. Methodology/Principal Findings In this study, we recorded electroencephalography (EEG) from 14 normal young adults while they performed a bilateral visual field memory task. Subjects had more rapid and accurate responses to the left visual field (LVF) memory condition. The difference in mean amplitude between the ipsilateral and contralateral event-related potential (ERP) at parietal-occipital electrodes in retention interval period was obtained with six different memory loads. Functional connectivity between 128 scalp regions was measured by EEG phase synchronization in the theta- (4–8 Hz), alpha- (8–12 Hz), beta- (12–32 Hz), and gamma- (32–40 Hz) frequency bands. The resulting matrices were converted to graphs, and mean degree, clustering coefficient and shortest path length was computed as a function of memory load. The results showed that brain networks of theta-, alpha-, beta-, and gamma- frequency bands were load-dependent and visual-field dependent. The networks of theta- and alpha- bands phase synchrony were most predominant in retention period for right visual field (RVF) WM than for LVF WM. Furthermore, only for RVF memory condition, brain network density of theta-band during the retention interval were linked to the delay of behavior reaction time, and the topological property of alpha-band network was negative correlation with behavior accuracy. Conclusions/Significance We suggest that the differences in theta- and alpha- bands between LVF and RVF conditions in
Septal complex of the telencephalon of lizards: III. Efferent connections and general discussion.
Font, C; Lanuza, E; Martinez-Marcos, A; Hoogland, P V; Martinez-Garcia, F
1998-11-30
The projections of the septum of the lizard Podarcis hispanica (Lacertidae) were studied by combining retrograde and anterograde neuroanatomical tracing. The results confirm the classification of septal nuclei into three main divisions. The nuclei composing the central septal division (anterior, lateral, medial, dorsolateral, and ventrolateral nuclei) displayed differential projections to the basal telencephalon, preoptic and anterior hypothalamus, lateral hypothalamic area, dorsal hypothalamus, mammillary complex, dorsomedial anterior thalamus, ventral tegmental area, interpeduncular nucleus, raphe nucleus, torus semicircularis pars laminaris, reptilian A8 nucleus/substantia nigra and central gray. For instance, only the medial septal nucleus projected substantially to the thalamus whereas the anterior septum was the only nucleus projecting to the caudal midbrain including the central gray. The anterior and lateral septal nuclei also differ in the way in which their projection to the preoptic hypothalamus terminated. The midline septal division is composed of the dorsal septal nucleus, nucleus septalis impar and nucleus of the posterior pallial commissure. The latter two nuclei projected to the lateral habenula and, at least the nucleus of the posterior pallial commissure, to the mammillary complex. The dorsal septal nucleus projected to the preoptic and periventricular hypothalamus and the anterior thalamus, but its central part seemed to project to the caudal midbrain (up to the midbrain central gray). Finally, the ventromedial septal division (ventromedial septal nucleus) showed a massive projection to the anterior and the lateral tuberomammillary hypothalamus. Data on the connections of the septum of P. hispanica and Gecko gekko are discussed from a comparative point of view and used for better understanding of the functional anatomy of the tetrapodian septum.
Li, Duan; Hambrecht-Wiedbusch, Viviane S.; Mashour, George A.
2017-01-01
Recent data from our laboratory demonstrate that high-frequency gamma connectivity across the cortex is present during consciousness and depressed during unconsciousness. However, these data were derived from static and well-defined states of arousal rather than during transitions that would suggest functional relevance. We also recently found that subanesthetic ketamine administered during isoflurane anesthesia accelerates recovery upon discontinuation of the primary anesthetic and increases gamma power during emergence. In the current study we re-analyzed electroencephalogram (EEG) data to test the hypothesis that functional cortical connectivity between anterior and posterior cortical regions would be increased during accelerated recovery induced by ketamine when compared to saline-treated controls. Rodents were instrumented with intracranial EEG electrodes and general anesthesia was induced with isoflurane anesthesia. After 37.5 min of continuous isoflurane anesthesia, a subanesthetic dose of ketamine (25 mg/kg intraperitoneal) was administered, with evidence of a 44% reduction in emergence time. In this study, we analyzed gamma and theta coherence (measure of undirected functional connectivity) and normalized symbolic transfer entropy (measure of directed functional connectivity) between frontal and parietal cortices during various levels of consciousness, with a focus on emergence from isoflurane anesthesia. During accelerated emergence in the ketamine-treated group, there was increased frontal-parietal coherence {p = 0.005, 0.05–0.23 [95% confidence interval (CI)]} and normalized symbolic transfer entropy [frontal to parietal: p < 0.001, 0.010–0.026 (95% CI); parietal to frontal: p < 0.001, 0.009–0.025 (95% CI)] in high-frequency gamma bandwidth as compared with the saline-treated group. Surrogates of cortical information exchange in high-frequency gamma are increased in association with accelerated recovery from anesthesia. This finding adds evidence
Meda, Shashwath A.; Gill, Adrienne; Stevens, Michael C.; Lorenzoni, Raymond P.; Glahn, David C.; Calhoun, Vince D.; Sweeney, John A.; Tamminga, Carol A.; Keshavan, Matcheri S.; Thaker, Gunvant; Pearlson, Godfrey D.
2013-01-01
Background Schizophrenia and bipolar disorder share overlapping symptoms and genetic etiology. Functional brain dysconnectivity is seen in both disorders. Methods We compared 70 schizophrenia and 64 psychotic bipolar probands, their respective unaffected first-degree relatives (N= 70 and 52) and 118 healthy subjects, all group age-, sex- and ethnicity-matched. We used functional network connectivity (FNC) analysis to measure differential connectivity among 16 fMRI RSNs. First, we examined connectivity differences between probands and controls. Next, we probed these dysfunctional connections in relatives for potential endophenotypes. Network connectivity was then correlated with PANSS scores to reveal clinical relationships. Results Three different network pairs were differentially connected in probands (FDR-corrected q<0.05) involving 5 individual resting-state networks: (A) Fronto/Occipital, (B) anterior Default Mode/Prefrontal, (C) Meso/Paralimbic, (D) Fronto-Temporal/Paralimbic & (E) Sensory-motor. One abnormal pair was unique to schizophrenia, (C-E), one unique to bipolar, (C-D) and one (A-B) shared. Two of these 3 combinations (A-B, C-E) were also abnormal in bipolar relatives, but none in schizophrenia relatives (non-significant trend for C-E). The Paralimbic circuit (C-D), that uniquely distinguished bipolar probands, contained multiple mood-relevant regions. Network relationship C-D correlated significantly with PANSS negative scores in bipolar probands and A-B was correlated to PANSS positive and general scores in schizophrenia. Conclusions Schizophrenia and psychotic bipolar probands share several abnormal RSN connections, but there are also unique neural network underpinnings between disorders. We identified specific connections and clinical relationships that may also be candidate psychosis endophenotypes, although these do not segregate straightforwardly with conventional diagnoses. PMID:22401986
South, Susan C.; Krueger, Robert F.; Iacono, William G.
2011-01-01
Marital distress is linked to many types of mental disorders; however, no study to date has examined this link in the context of empirically-based hierarchical models of psychopathology. There may be general associations between low levels of marital quality and broad groups of comorbid psychiatric disorders as well as links between marital adjustment and specific types of mental disorders. The authors examined this issue in a sample (N=929 couples) of currently married couples from the Minnesota Twin Family Study who completed self-report measures of relationship adjustment and were also assessed for common mental disorders. Structural equation modeling indicated that a) higher standing on latent factors of internalizing (INT) and externalizing (EXT) psychopathology was associated with lower standing on latent factors of general marital adjustment for both husbands and wives, b) the magnitude of these effects was similar across husbands and wives, and c) there were no residual associations between any specific mental disorder and overall relationship adjustment after controlling for the INT and EXT factors. These findings point to the utility of hierarchical models in understanding psychopathology and its correlates. Much of the link between mental disorder and marital distress operated at the level of broad spectrums of psychopathological variation (i.e., higher levels of marital distress were associated with disorder comorbidity), suggesting that the temperamental core of these spectrums contributes not only to symptoms of mental illness but to the behaviors that lead to impaired marital quality in adulthood. PMID:21942335
Entanglement Entropy from Surface Terms in General Relativity
NASA Astrophysics Data System (ADS)
Bhattacharyya, Arpan; Sinha, Aninda
2013-10-01
Entanglement entropy in local quantum field theories is typically ultraviolet divergent due to short distance effects in the neighborhood of the entangling region. In the context of gauge/gravity duality, we show that surface terms in general relativity are able to capture this entanglement entropy. In particular, we demonstrate that for 1 + 1-dimensional (1 + 1d) conformal field theories (CFTs) at finite temperature whose gravity dual is Banados-Teitelboim-Zanelli (BTZ) black hole, the Gibbons-Hawking-York term precisely reproduces the entanglement entropy which can be computed independently in the field theory.
Testing general relativity in space-borne and astronomical laboratories
NASA Technical Reports Server (NTRS)
Will, Clifford M.
1989-01-01
The current status of space-based experiments and astronomical observations designed to test the theory of general relativity is surveyed. Consideration is given to tests of post-Newtonian gravity, searches for feeble short-range forces and gravitomagnetism, improved measurements of parameterized post-Newtonian parameter values, explorations of post-Newtonian physics, tests of the Einstein equivalence principle, observational tests of post-Newtonian orbital effects, and efforts to detect quadrupole and dipole radiation damping. Recent numerical results are presented in tables.
Tests of general relativity using Starprobe radio metric tracking data
NASA Technical Reports Server (NTRS)
Mease, K. D.; Anderson, J. D.; Wood, L. J.; White, L. K.
1982-01-01
The potential of a proposed spacecraft mission, called Starprobe, for testing general relativity and providing information on the interior structure and dynamics of the sun is investigated. Parametric, gravitational perturbation terms are derived which represent relativistic effects and effects due to spatial and temporal variations in the solar potential at a given radial distance. A covariance analysis based on Kalman filtering theory predicts the accuracies with which the free parameters in the perturbation terms can be estimated with radio metric tracking data through the process of trajectory reconstruction. It is concluded that Starprobe can contribute significant information on both the nature of gravitation and the structure and dynamics of the solar interior.
Minimum length from quantum mechanics and classical general relativity.
Calmet, Xavier; Graesser, Michael; Hsu, Stephen D H
2004-11-19
We derive fundamental limits on measurements of position, arising from quantum mechanics and classical general relativity. First, we show that any primitive probe or target used in an experiment must be larger than the Planck length lP. This suggests a Planck-size minimum ball of uncertainty in any measurement. Next, we study interferometers (such as LIGO) whose precision is much finer than the size of any individual components and hence are not obviously limited by the minimum ball. Nevertheless, we deduce a fundamental limit on their accuracy of order lP. Our results imply a device independent limit on possible position measurements.
Testing General Relativity with Spherical Resonant Mass Detectors
NASA Astrophysics Data System (ADS)
Sylvester, Alex J.
2015-08-01
Gravitational waves in f(R) gravity excite monopole and m = 0+/-2 quadrupole resonance modes of a spherical detector. This document reviews the basic ideas of general relativity and gravitational waves, and then applies those concepts to an f( R) gravitational wave. The acoustic response of a GW incident with a spherical detector is reviewed in detail, and the absorption cross section for an f(R) GW impinging on the spherical detector is calculated. Minimum detectable scalar wave amplitudes are explored for the Mario Schenberg detector. The mass of the scalar mode affects its detectability.
Testing general relativity in space-borne and astronomical laboratories
NASA Technical Reports Server (NTRS)
Will, Clifford M.
1989-01-01
The current status of space-based experiments and astronomical observations designed to test the theory of general relativity is surveyed. Consideration is given to tests of post-Newtonian gravity, searches for feeble short-range forces and gravitomagnetism, improved measurements of parameterized post-Newtonian parameter values, explorations of post-Newtonian physics, tests of the Einstein equivalence principle, observational tests of post-Newtonian orbital effects, and efforts to detect quadrupole and dipole radiation damping. Recent numerical results are presented in tables.
General relativity as a two-dimensional CFT
NASA Astrophysics Data System (ADS)
Adamo, Tim
2015-11-01
The tree-level scattering amplitudes of general relativity (GR) encode the full nonlinearity of the Einstein field equations. Yet remarkably compact expressions for these amplitudes have been found which seem unrelated to a perturbative expansion of the Einstein-Hilbert action. This suggests an entirely different description of GR which makes this on-shell simplicity manifest. Taking our cue from the tree-level amplitudes, we discuss how such a description can be found. The result is a formulation of GR in terms of a solvable two-dimensional conformal field theory (CFT), with the Einstein equations emerging as quantum consistency conditions.
A superconducting gyroscope to test Einstein's general theory of relativity
NASA Technical Reports Server (NTRS)
Everitt, C. W. F.
1978-01-01
Schiff (1960) proposed a new test of general relativity based on measuring the precessions of the spin axes of gyroscopes in earth orbit. Since 1963 a Stanford research team has been developing an experiment to measure the two effects calculated by Schiff. The gyroscope consists of a uniform sphere of fused quartz 38 mm in diameter, coated with superconductor, electrically suspended and spinning at about 170 Hz in vacuum. The paper describes the proposed flight apparatus and the current state of development of the gyroscope, including techniques for manufacturing and measuring the gyro rotor and housing, generating ultralow magnetic fields, and mechanizing the readout.
Vector order parameter in general relativity: Covariant equations
NASA Astrophysics Data System (ADS)
Meierovich, Boris E.
2010-07-01
Phase transitions with spontaneous symmetry breaking and vector order parameter are considered in multidimensional theory of general relativity. Covariant equations, describing the gravitational properties of topological defects, are derived. The topological defects are classified in accordance with the symmetry of the covariant derivative of the vector order parameter. The abilities of the derived equations are demonstrated in application to the braneworld concept. New solutions of the Einstein equations with a transverse vector order parameter are presented. In the vicinity of phase transition, the solutions are found analytically.
Rotating black holes in the teleparallel equivalent of general relativity
NASA Astrophysics Data System (ADS)
Nashed, Gamal G. L.
2016-05-01
We derive set of solutions with flat transverse sections in the framework of a teleparallel equivalent of general relativity which describes rotating black holes. The singularities supported from the invariants of torsion and curvature are explained. We investigate that there appear more singularities in the torsion scalars than in the curvature ones. The conserved quantities are discussed using Einstein-Cartan geometry. The physics of the constants of integration is explained through the calculations of conserved quantities. These calculations show that there is a unique solution that may describe true physical black hole.
Vector order parameter in general relativity: Covariant equations
Meierovich, Boris E.
2010-07-15
Phase transitions with spontaneous symmetry breaking and vector order parameter are considered in multidimensional theory of general relativity. Covariant equations, describing the gravitational properties of topological defects, are derived. The topological defects are classified in accordance with the symmetry of the covariant derivative of the vector order parameter. The abilities of the derived equations are demonstrated in application to the braneworld concept. New solutions of the Einstein equations with a transverse vector order parameter are presented. In the vicinity of phase transition, the solutions are found analytically.
Tests of general relativity using Starprobe radio metric tracking data
NASA Technical Reports Server (NTRS)
Mease, K. D.; Anderson, J. D.; Wood, L. J.; White, L. K.
1982-01-01
The potential of a proposed spacecraft mission, called Starprobe, for testing general relativity and providing information on the interior structure and dynamics of the sun is investigated. Parametric, gravitational perturbation terms are derived which represent relativistic effects and effects due to spatial and temporal variations in the solar potential at a given radial distance. A covariance analysis based on Kalman filtering theory predicts the accuracies with which the free parameters in the perturbation terms can be estimated with radio metric tracking data through the process of trajectory reconstruction. It is concluded that Starprobe can contribute significant information on both the nature of gravitation and the structure and dynamics of the solar interior.
Point particles in 2+1 dimensions: general relativity and loop gravity descriptions
NASA Astrophysics Data System (ADS)
Ziprick, Jonathan
2015-02-01
We develop a Hamiltonian description of point particles in (2+1)-dimensions using connection and frame-field variables for general relativity. The topology of each spatial hypersurface is that of a punctured two-sphere with particles residing at the punctures. We describe this topology with a CW complex (a collection of two cells glued together along the edges), and use this to fix a gauge and reduce the Hamiltonian. The equations of motion for the fields describe a dynamical triangulation where each vertex moves according to the equation of motion for a free relativistic particle. The evolution is continuous except for when triangles collapse (i.e. the edges become parallel) causing discrete, topological changes in the underlying CW complex. We then introduce the loop gravity phase space parameterized by holonomy-flux variables on a graph (a network of one-dimensional links). By embedding a graph within the CW complex, we find a description of this system in terms of loop variables. The resulting equations of motion describe the same dynamical triangulation as the connection and frame-field variables. In this framework, the collapse of a triangle causes a discrete change in the underlying graph, giving a concrete realization of the graph-changing moves that many expect to feature in full loop quantum gravity. The main result is a dynamical model of loop gravity that agrees with general relativity and is well-suited for quantization using existing methods.
Gyroscope precession in special and general relativity from basic principles
NASA Astrophysics Data System (ADS)
Jonsson, Rickard M.
2007-05-01
In special relativity a gyroscope that is suspended in a torque-free manner will precess as it is moved along a curved path relative to an inertial frame S. We explain this effect, which is known as Thomas precession, by considering a real grid that moves along with the gyroscope, and that by definition is not rotating as observed from its own momentary inertial rest frame. From the basic properties of the Lorentz transformation we deduce how the form and rotation of the grid (and hence the gyroscope) will evolve relative to S. As an intermediate step we consider how the grid would appear if it were not length contracted along the direction of motion. We show that the uncontracted grid obeys a simple law of rotation. This law simplifies the analysis of spin precession compared to more traditional approaches based on Fermi transport. We also consider gyroscope precession relative to an accelerated reference frame and show that there are extra precession effects that can be explained in a way analogous to the Thomas precession. Although fully relativistically correct, the entire analysis is carried out using three-vectors. By using the equivalence principle the formalism can also be applied to static spacetimes in general relativity. As an example, we calculate the precession of a gyroscope orbiting a static black hole.
Algebraic generalization of the Ginsparg-Wilson relation
NASA Astrophysics Data System (ADS)
Fujikawa, Kazuo
2000-11-01
A specific algebraic realization of the Ginsparg-Wilson relation in the form γ 5(γ 5D)+(γ 5D)γ 5=2a 2k+1(γ 5D) 2k+2 is discussed, where k stands for a non-negative integer and k=0 corresponds to the commonly discussed Ginsparg-Wilson relation. From a view point of algebra, a characteristic property of our proposal is that we have a closed algebraic relation for one unknown operator D, although this relation itself is obtained from the original proposal of Ginsparg and Wilson, γ 5D+Dγ 5=2aDγ 5αD , by choosing α as an operator containing D (and thus Dirac matrices). In this paper, it is shown that we can construct the operator D explicitly for any value of k. We first show that the instanton-related index of all these operators is identical. We then illustrate in detail a generalization of Neuberger's overlap Dirac operator to the case k=1. On the basis of explicit construction, it is shown that the chiral symmetry breaking term becomes more irrelevant for larger k in the sense of Wilsonian renormalization group. We thus have an infinite tower of new lattice Dirac operators which are topologically proper, but a large enough lattice is required to accommodate a Dirac operator with a large value of k.
NASA Astrophysics Data System (ADS)
Poisson, Eric
2010-05-01
A few years ago, in my review of Sean Carroll's book in Classical and Quantum Gravity [1], I wrote that while the 1970s was the decade of Weinberg [2] and Misner, Thorne and Wheeler [3], and while the eighties was the decade of Schutz [4] and Wald [5], the 2000s was clearly the decade of Hartle [6] and Carroll [7]. In my opinion, these books continue to stand out in the surprisingly dense crowd of introductory textbooks on general relativity. At the dawn of this new decade I look forward to see what fresh pedagogical insights will be produced next, and who will be revealed as the winners of the 2010s. It is, of course, much too early to tell, but Schutz is back, and he will set the standard just as he did back in 1985. This is the long-awaited second edition of his `First Course', a short, accessible, and very successful introduction to general relativity. The changes from the first edition are modest: Schutz wisely refrained from bloating the text with new topics, and limited himself to updating his discussion of gravitational-wave sources and detectors, neutron-star and black-hole astrophysics, and suggestions for further reading. Most importantly, he completely rewrote the chapter on cosmology, a topic that has evolved enormously since the first edition. The book begins in chapter 1 with a beautiful review of special relativity that emphasizes spacetime geometry and stays away from an algebraic approach based on the Lorentz transformation, which appears only later in the chapter. This is followed up in chapters 2 and 3 with an introduction to vector and tensor analysis in flat spacetime. The point of view is modern (tensors are defined as linear mapping of vectors and one-forms into real numbers) but the presentation is very accessible and avoids an overload of mathematical fine print. In chapter 4 the book introduces the spacetime description of fluids; it is here that the energy-momentum tensor makes its first appearance. The move to curved spacetime is
Social media connecting ocean sciences and the general public: the @OceanSeaIceNPI experiment
NASA Astrophysics Data System (ADS)
Pavlov, A. K.; Granskog, M. A.; Gerland, S.; Meyer, A.; Hudson, S. R.; Rösel, A.; King, J.; Itkin, P.; Cohen, L.; Dodd, P. A.; de Steur, L.
2016-02-01
As researchers we are constantly being encouraged by funding agencies, policy-makers and journalists to conduct effective outreach and to communicate our latest research findings. As environmental scientists we also understand the necessity of communicating our research to the general public. Many of us wish to become better science communicators but have little time and limited funding available to do so. How can we expend our science communication past project-based efforts that have a limited lifetime? Most critically, how can a small research groups do it without additional resources such as funds and communication officers? Social media is one answer, and has become a powerful and inexpensive tool for communicating science to different target audiences. Many research institutions and researchers are exploring the full breadth of possibilities brought by social media for reaching out to the general public, journalists, policy-makers, stake-holders, and research community. However, smaller research groups and labs are still underrepresented in social media. When it comes to practice, some essential difficulties can be encountered: identifying key target groups, defining the framework for sharing responsibilities and interaction within the research group, and finally, choosing a currently up-to-date social medium as a technical solution for communicating your research. Here, a group of oceanography and sea ice researchers (@OceanSeaIceNPI) share the positive experience of developing and maintaining for more than one year a researcher-driven outreach effort currently implemented through Instagram, Twitter and Facebook. We will present potential pitfalls and challenges that small research groups could face, and how to better overcome them. This will hopefully inspire and help other research groups and labs to conduct their own effective ocean science communication.
A new family of gauges in linearized general relativity
NASA Astrophysics Data System (ADS)
Esposito, Giampiero; Stornaiolo, Cosimo
2000-05-01
For vacuum Maxwell theory in four dimensions, a supplementary condition exists (due to Eastwood and Singer) which is invariant under conformal rescalings of the metric, in agreement with the conformal symmetry of the Maxwell equations. Thus, starting from the de Donder gauge, which is not conformally invariant but is the gravitational counterpart of the Lorenz gauge, one can consider, led by formal analogy, a new family of gauges in general relativity, which involve fifth-order covariant derivatives of metric perturbations. The admissibility of such gauges in the classical theory is first proven in the cases of linearized theory about flat Euclidean space or flat Minkowski spacetime. In the former, the general solution of the equation for the fulfillment of the gauge condition after infinitesimal diffeomorphisms involves a 3-harmonic 1-form and an inverse Fourier transform. In the latter, one needs instead the kernel of powers of the wave operator, and a contour integral. The analysis is also used to put restrictions on the dimensionless parameter occurring in the DeWitt supermetric, while the proof of admissibility is generalized to a suitable class of curved Riemannian backgrounds. Eventually, a non-local construction of the tensor field is obtained which makes it possible to achieve conformal invariance of the above gauges.
Steinmann, Saskia; Leicht, Gregor; Mulert, Christoph
2014-01-01
Auditory verbal hallucinations (AVH) are one of the most common and most distressing symptoms of schizophrenia. Despite fundamental research, the underlying neurocognitive and neurobiological mechanisms are still a matter of debate. Previous studies suggested that "hearing voices" is associated with a number of factors including local deficits in the left auditory cortex and a disturbed connectivity of frontal and temporoparietal language-related areas. In addition, it is hypothesized that the interhemispheric pathways connecting right and left auditory cortices might be involved in the pathogenesis of AVH. Findings based on Diffusion-Tensor-Imaging (DTI) measurements revealed a remarkable interindividual variability in size and shape of the interhemispheric auditory pathways. Interestingly, schizophrenia patients suffering from AVH exhibited increased fractional anisotropy (FA) in the interhemispheric fibers than non-hallucinating patients. Thus, higher FA-values indicate an increased severity of AVH. Moreover, a dichotic listening (DL) task showed that the interindividual variability in the interhemispheric auditory pathways was reflected in the behavioral outcome: stronger pathways supported a better information transfer and consequently improved speech perception. This detection indicates a specific structure-function relationship, which seems to be interindividually variable. This review focuses on recent findings concerning the structure-function relationship of the interhemispheric pathways in controls, hallucinating and non-hallucinating schizophrenia patients and concludes that changes in the structural and functional connectivity of auditory areas are involved in the pathophysiology of AVH.
Steinmann, Saskia; Leicht, Gregor; Mulert, Christoph
2014-01-01
Auditory verbal hallucinations (AVH) are one of the most common and most distressing symptoms of schizophrenia. Despite fundamental research, the underlying neurocognitive and neurobiological mechanisms are still a matter of debate. Previous studies suggested that “hearing voices” is associated with a number of factors including local deficits in the left auditory cortex and a disturbed connectivity of frontal and temporoparietal language-related areas. In addition, it is hypothesized that the interhemispheric pathways connecting right and left auditory cortices might be involved in the pathogenesis of AVH. Findings based on Diffusion-Tensor-Imaging (DTI) measurements revealed a remarkable interindividual variability in size and shape of the interhemispheric auditory pathways. Interestingly, schizophrenia patients suffering from AVH exhibited increased fractional anisotropy (FA) in the interhemispheric fibers than non-hallucinating patients. Thus, higher FA-values indicate an increased severity of AVH. Moreover, a dichotic listening (DL) task showed that the interindividual variability in the interhemispheric auditory pathways was reflected in the behavioral outcome: stronger pathways supported a better information transfer and consequently improved speech perception. This detection indicates a specific structure-function relationship, which seems to be interindividually variable. This review focuses on recent findings concerning the structure-function relationship of the interhemispheric pathways in controls, hallucinating and non-hallucinating schizophrenia patients and concludes that changes in the structural and functional connectivity of auditory areas are involved in the pathophysiology of AVH. PMID:24574995
Rombouts, Serge A.R.B.; Winkler, Anderson M.; van Gorsel, Helene C.; van der Grond, Jeroen; van Gerven, Joop M.A.
2016-01-01
Abstract Psychopharmacological research, if properly designed, may offer insight into both timing and area of effect, increasing our understanding of the brain's neurotransmitter systems. For that purpose, the acute influence of the selective serotonin reuptake inhibitor citalopram (30 mg) and the acetylcholinesterase inhibitor galantamine (8 mg) was repeatedly measured in 12 healthy young volunteers with resting state functional magnetic resonance imaging (RS‐fMRI). Eighteen RS‐fMRI scans were acquired per subject during this randomized, double blind, placebo‐controlled, crossover study. Within‐group comparisons of voxelwise functional connectivity with 10 functional networks were examined (P < 0.05, FWE‐corrected) using a non‐parametric multivariate approach with cerebrospinal fluid, white matter, heart rate, and baseline measurements as covariates. Although both compounds did not change cognitive performance on several tests, significant effects were found on connectivity with multiple resting state networks. Serotonergic stimulation primarily reduced connectivity with the sensorimotor network and structures that are related to self‐referential mechanisms, whereas galantamine affected networks and regions that are more involved in learning, memory, and visual perception and processing. These results are consistent with the serotonergic and cholinergic trajectories and their functional relevance. In addition, this study demonstrates the power of using repeated measures after drug administration, which offers the chance to explore both combined and time specific effects. Hum Brain Mapp 38:308–325, 2017. © 2016 Wiley Periodicals, Inc. PMID:27622387
Dynamic changes of resting state connectivity related to the acquisition of a lexico-semantic skill.
Schlaffke, L; Schweizer, L; Rüther, N N; Luerding, R; Tegenthoff, M; Bellebaum, C; Schmidt-Wilcke, T
2017-02-01
The brain undergoes adaptive changes during learning. Spontaneous neural activity has been proposed to play an important role in acquiring new information and/or improve the interaction of task related brain regions. A promising approach is the investigation of resting state functional connectivity (rs-fc) and resting state networks, which rely on the detection of interregional correlations of spontaneous BOLD fluctuations. Using Morse Code (MC) as a model to investigate neural correlates of lexico-semantic learning we sought to identify patterns in rs-fc that predict learning success and/or undergo dynamic changes during a 10-day training period. Thirty-five participants were trained to decode twelve letters of MC. Rs-fMRI data were collected before and after the training period and rs-fc analyses were performed using a group independent component analysis. Baseline connectivity between the language-network (LANG) and the anterior-salience-network (ASN) predicted learning success and learning was associated with an increase in LANG - ASN connectivity. Furthermore, a disconnection between the default mode network (DMN) and the ASN as well as the left fusiform gyrus, which is critically involved in MC deciphering, was observed. Our findings demonstrate that rs-fc can undergo behaviorally relevant changes within 10 training days, reflecting a learning dependent modulation of interference between task specific networks. Copyright © 2016 The Authors. Published by Elsevier Inc. All rights reserved.
van de Vijver, Irene; Ridderinkhof, K Richard; Harsay, Helga; Reneman, Liesbeth; Cavanagh, James F; Buitenweg, Jessika I V; Cohen, Michael X
2016-10-01
Reinforcement learning (RL) is supported by a network of striatal and frontal cortical structures that are connected through white-matter fiber bundles. With age, the integrity of these white-matter connections declines. The role of structural frontostriatal connectivity in individual and age-related differences in RL is unclear, although local white-matter density and diffusivity have been linked to individual differences in RL. Here we show that frontostriatal tract counts in young human adults (aged 18-28), as assessed noninvasively with diffusion-weighted magnetic resonance imaging and probabilistic tractography, positively predicted individual differences in RL when learning was difficult (70% valid feedback). In older adults (aged 63-87), in contrast, learning under both easy (90% valid feedback) and difficult conditions was predicted by tract counts in the same frontostriatal network. Furthermore, network-level analyses showed a double dissociation between the task-relevant networks in young and older adults, suggesting that older adults relied on different frontostriatal networks than young adults to obtain the same task performance. These results highlight the importance of successful information integration across striatal and frontal regions during RL, especially with variable outcomes.
Villarreal Santiago, María; Tumilty, Steve; Mącznik, Aleksandra; Mani, Ramakrishnan
2016-08-01
Acupuncture has been studied for several decades to establish evidence-based clinical practice. This systematic review aims to evaluate evidence for the effectiveness of acupuncture in influencing the functional connectivity of the central nervous system in patients with musculoskeletal pain. A systematic search of the literature was conducted to identify studies in which the central response of acupuncture in patients with musculoskeletal pain was evaluated by neuroimaging techniques. Databases searched were AMED, CINAHL, Cochrane Library, EMBASE, MEDLINE, PEDro, Pubmed, SCOPUS, SPORTDiscuss, and Web of Science. Included studies were assessed by two independent reviewers for their methodological quality by using the Downs and Black questionnaire and for their levels of completeness and transparency in reporting acupuncture interventions by using Standards for Reporting Interventions in Clinical Trials of Acupuncture (STRICTA) criteria. Seven studies met the inclusion criteria. Three studies were randomized controlled trials (RCTs) and four studies were nonrandomized controlled trials (NRCTs). The neuroimaging techniques used were functional magnetic resonance imaging (fMRI) and positron emission tomography (PET). Positive effects on the functional connectivity of the central nervous system more consistently occurred during long-term acupuncture treatment. The results were heterogeneous from a descriptive perspective; however, the key findings support acupuncture's ability to alter pain-related functional connectivity in the central nervous system in patients with musculoskeletal pain.
Correlated quadratures of resonance fluorescence and the generalized uncertainty relation
NASA Technical Reports Server (NTRS)
Arnoldus, Henk F.; George, Thomas F.; Gross, Rolf W. F.
1994-01-01
Resonance fluorescence from a two-state atom has been predicted to exhibit quadrature squeezing below the Heisenberg uncertainty limit, provided that the optical parameters (Rabi frequency, detuning, laser linewidth, etc.) are chosen carefully. When the correlation between two quadratures of the radiation field does not vanish, however, the Heisenberg limit for quantum fluctuations might be an unrealistic lower bound. A generalized uncertainty relation, due to Schroedinger, takes into account the possible correlation between the quadrature components of the radiation, and it suggests a modified definition of squeezing. We show that the coherence between the two levels of a laser-driven atom is responsible for the correlation between the quadrature components of the emitted fluorescence, and that the Schrodinger uncertainty limit increases monotonically with the coherence. On the other hand, the fluctuations in the quadrature field diminish with an increasing coherence, and can disappear completely when the coherence reaches 1/2, provided that certain phase relations hold.
Testing general relativity with Landers on the Martian satellite Phobos
NASA Technical Reports Server (NTRS)
Anderson, J. D.; Borderies, N. J.; Campbell, J. K.; Dunne, J. A.; Ellis, J.
1989-01-01
A planned experiment to obtain range and Doppler data with the Phobos 2 Lander on the surface of the Martian satellite Phobos is described. With the successful insertion on January 29, 1989 of Phobos 2 into Mars orbit, it is anticipated that the Lander will be placed on the surface of Phobos in April 1989. Depending on the longevity of the Lander, range and Doppler data for a period of from one to several years are expected. Because these data are of value in performing solar-system tests of general relativity, the current accuracy of the relevant relativity tests using Deep Space Network data from the Mariner-9 orbiter of Mars in 1971 and from the Viking Landers in 1976-1982 is reviewed. The expected improvement from data anticipated during the Phobos 2 Lander Mission is also discussed; most important will be an improved sensitivity to any time variation in the gravitational 'constant' as measured in atomic units.
Testing general relativity with Landers on the Martian satellite Phobos
NASA Technical Reports Server (NTRS)
Anderson, J. D.; Borderies, N. J.; Campbell, J. K.; Dunne, J. A.; Ellis, J.
1989-01-01
A planned experiment to obtain range and Doppler data with the Phobos 2 Lander on the surface of the Martian satellite Phobos is described. With the successful insertion on January 29, 1989 of Phobos 2 into Mars orbit, it is anticipated that the Lander will be placed on the surface of Phobos in April 1989. Depending on the longevity of the Lander, range and Doppler data for a period of from one to several years are expected. Because these data are of value in performing solar-system tests of general relativity, the current accuracy of the relevant relativity tests using Deep Space Network data from the Mariner-9 orbiter of Mars in 1971 and from the Viking Landers in 1976-1982 is reviewed. The expected improvement from data anticipated during the Phobos 2 Lander Mission is also discussed; most important will be an improved sensitivity to any time variation in the gravitational 'constant' as measured in atomic units.
Thin-shell wormholes in d-dimensional general relativity: Solutions, properties, and stability
Dias, Goncalo A. S.; Lemos, Jose P. S.
2010-10-15
We construct thin-shell electrically charged wormholes in d-dimensional general relativity with a cosmological constant. The wormholes constructed can have different throat geometries, namely, spherical, planar, and hyperbolic. Unlike the spherical geometry, the planar and hyperbolic geometries allow for different topologies and in addition can be interpreted as higher-dimensional domain walls or branes connecting two universes. In the construction we use the cut-and-paste procedure by joining together two identical vacuum spacetime solutions. Properties such as the null energy condition and geodesics are studied. A linear stability analysis around the static solutions is carried out. A general result for stability is obtained from which previous results are recovered.
Very special relativity as relativity of dark matter: the Elko connection
NASA Astrophysics Data System (ADS)
Ahluwalia, D. V.; Horvath, S. P.
2010-11-01
In the very special relativity (VSR) proposal by Cohen and Glashow, it was pointed out that invariance under HOM (2) is both necessary and sufficient to explain the null result of the Michelson-Morely experiment. It is the quantum field theoretic demand of locality, or the requirement of P, T, CP, or CT invariance, that makes invariance under the Lorentz group a necessity. Originally it was conjectured that VSR operates at the Planck scale; we propose that the natural arena for VSR is at energies similar to the standard model, but in the dark sector. To this end we provide an ab initio spinor representation invariant under the SIM (2) avatar of VSR and construct a mass dimension one fermionic quantum field of spin one half. This field turns out to be a very close sibling of Elko and it exhibits the same striking property of intrinsic darkness with respect to the standard model fields. In the new construct, the tension between Elko and Lorentz symmetries is fully resolved. We thus entertain the possibility that the symmetries underlying the standard model matter and gauge fields are those of Lorentz, while the event space underlying the dark matter and the dark gauge fields supports the algebraic structure underlying VSR.
Gao, Qing; Xu, Fei; Jiang, Cui; Chen, Zhifeng; Chen, Huafu; Liao, Huaqiang; Zhao, Ling
2016-02-01
Migraine is one of the most prevalent neurological disorders which is suggested to be associated with dysfunctions of the central nervous system. The purpose of the present study was to detect the altered functional connectivity architecture in the large-scale network of the whole brain in migraine without aura (MWoA). Meanwhile, the brain functional hubs which are targeted by MWoA could be identified. A new voxel-based method named functional connectivity density (FCD) mapping was applied to resting-state functional magnetic resonance imaging data of 55 female MWoA patients and 44 age-matched female healthy controls (HC). Comparing to HC, MWoA patients showed abnormal short-range FCD values in bilateral hippocampus, bilateral insula, right amygdale, right anterior cingulate cortex, bilateral putamen, bilateral caudate nucleus and the prefrontal cortex. The results suggested decreased intraregional connectivity of these pain-related brain regions in female MWoA. In addition, short-range FCD values in left prefrontal cortex, putamen and caudate nucleus were significantly negatively correlated with duration of disease in MWoA group, implying the repeated migraine attacks over time may consistently affect the resting-state functional connectivity architecture of these brain hubs. Our findings revealed the dysfunction of brain hubs in female MWoA, and suggested the left prefrontal cortex, putamen and caudate nucleus served as sensitive neuroimaging markers for reflecting the disease duration of female MWoA. This may provide us new insights into the changes in the organization of the large-scale brain network in MWoA. Copyright © 2015 Elsevier B.V. All rights reserved.
Integrated measures for rough sets based on general binary relations.
Teng, Shuhua; Liao, Fan; He, Mi; Lu, Min; Nian, Yongjian
2016-01-01
Uncertainty measures are important for knowledge discovery and data mining. Rough set theory (RST) is an important tool for measuring and processing uncertain information. Although many RST-based methods for measuring system uncertainty have been investigated, the existing measures cannot adequately characterise the imprecision of a rough set. Moreover, these methods are suitable only for complete information systems, and it is difficult to generalise methods for complete information systems to incomplete information systems. To overcome these shortcomings, we present new uncertainty measures, integrated accuracy and integrated roughness, that are based on general binary relations, and we study important properties of these measures. A theoretical analysis and examples show that the proposed integrated measures are more precise than existing uncertainty measures, they are suitable for both complete and incomplete information systems, and they are logically consistent. Therefore, integrated accuracy and integrated roughness overcome the limitations of existing measures. This research not only develops the theory of uncertainty, it also expands the application domain of uncertainty measures and provides a theoretical basis for knowledge acquisition in information systems based on general binary relations.
Elliptical galaxies kinematics within general relativity with renormalization group effects
Rodrigues, Davi C.
2012-09-01
The renormalization group framework can be applied to Quantum Field Theory on curved space-time, but there is no proof whether the beta-function of the gravitational coupling indeed goes to zero in the far infrared or not. In a recent paper [1] we have shown that the amount of dark matter inside spiral galaxies may be negligible if a small running of the General Relativity coupling G is present (δG/G{sub 0}∼<10{sup −7} across a galaxy). Here we extend the proposed model to elliptical galaxies and present a detailed analysis on the modeling of NGC 4494 (an ordinary elliptical) and NGC 4374 (a giant elliptical). In order to compare our results to a well known alternative model to the standard dark matter picture, we also evaluate NGC 4374 with MOND. In this galaxy MOND leads to a significative discrepancy with the observed velocity dispersion curve and has a significative tendency towards tangential anisotropy. On the other hand, the approach based on the renormalization group and general relativity (RGGR) could be applied with good results to these elliptical galaxies and is compatible with lower mass-to-light ratios (of about the Kroupa IMF type)
New Probe of Departures from General Relativity Using Minkowski Functionals.
Fang, Wenjuan; Li, Baojiu; Zhao, Gong-Bo
2017-05-05
The morphological properties of the large scale structure of the Universe can be fully described by four Minkowski functionals (MFs), which provide important complementary information to other statistical observables such as the widely used 2-point statistics in configuration and Fourier spaces. In this work, for the first time, we present the differences in the morphology of the large scale structure caused by modifications to general relativity (to address the cosmic acceleration problem), by measuring the MFs from N-body simulations of modified gravity and general relativity. We find strong statistical power when using the MFs to constrain modified theories of gravity: with a galaxy survey that has survey volume ∼0.125(h^{-1} Gpc)^{3} and galaxy number density ∼1/(h^{-1} Mpc)^{3}, the two normal-branch Dvali-Gabadadze-Porrati models and the F5 f(R) model that we simulated can be discriminated from the ΛCDM model at a significance level ≳5σ with an individual MF measurement. Therefore, the MF of the large scale structure is potentially a powerful probe of gravity, and its application to real data deserves active exploration.
New Probe of Departures from General Relativity Using Minkowski Functionals
NASA Astrophysics Data System (ADS)
Fang, Wenjuan; Li, Baojiu; Zhao, Gong-Bo
2017-05-01
The morphological properties of the large scale structure of the Universe can be fully described by four Minkowski functionals (MFs), which provide important complementary information to other statistical observables such as the widely used 2-point statistics in configuration and Fourier spaces. In this work, for the first time, we present the differences in the morphology of the large scale structure caused by modifications to general relativity (to address the cosmic acceleration problem), by measuring the MFs from N -body simulations of modified gravity and general relativity. We find strong statistical power when using the MFs to constrain modified theories of gravity: with a galaxy survey that has survey volume ˜0.125 (h-1 Gpc )3 and galaxy number density ˜1 /(h-1 Mpc )3 , the two normal-branch Dvali-Gabadadze-Porrati models and the F5 f (R ) model that we simulated can be discriminated from the Λ CDM model at a significance level ≳5 σ with an individual MF measurement. Therefore, the MF of the large scale structure is potentially a powerful probe of gravity, and its application to real data deserves active exploration.
White-Matter Structural Connectivity Underlying Human Laughter-Related Traits Processing
Wu, Ching-Lin; Zhong, Suyu; Chan, Yu-Chen; Chen, Hsueh-Chih; Gong, Gaolang; He, Yong; Li, Ping
2016-01-01
Most research into the neural mechanisms of humor has not explicitly focused on the association between emotion and humor on the brain white matter networks mediating this connection. However, this connection is especially salient in gelotophobia (the fear of being laughed at), which is regarded as the presentation of humorlessness, and two related traits, gelotophilia (the enjoyment of being laughed at) and katagelasticism (the enjoyment of laughing at others). Here, we explored whether the topological properties of white matter networks can account for the individual differences in the laughter-related traits of 31 healthy adults. We observed a significant negative correlation between gelotophobia scores and the clustering coefficient, local efficiency and global efficiency, but a positive association between gelotophobia scores and path length in the brain's white matter network. Moreover, the current study revealed that with increasing individual fear of being laughed at, the linking efficiencies in superior frontal gyrus, anterior cingulate cortex, parahippocampal gyrus, and middle temporal gyrus decreased. However, there were no significant correlations between either gelotophilia or katagelasticism scores or the topological properties of the brain white matter network. These findings suggest that the fear of being laughed at is directly related to the level of local and global information processing of the brain network, which might provide new insights into the neural mechanisms of the humor information processing. PMID:27833572
De Vico Fallani, Fabrizio; Clausi, Silvia; Leggio, Maria; Chavez, Mario; Valencia, Miguel; Maglione, Anton Giulio; Babiloni, Fabio; Cincotti, Febo; Mattia, Donatella; Molinari, Marco
2017-04-01
Although cerebellar-cortical interactions have been studied extensively in animal models and humans using modern neuroimaging techniques, the effects of cerebellar stroke and focal lesions on cerebral cortical processing remain unknown. In the present study, we analyzed the large-scale functional connectivity at the cortical level by combining high-density electroencephalography (EEG) and source imaging techniques to evaluate and quantify the compensatory reorganization of brain networks after cerebellar damage. The experimental protocol comprised a repetitive finger extension task by 10 patients with unilateral focal cerebellar lesions and 10 matched healthy controls. A graph theoretical approach was used to investigate the functional reorganization of cortical networks. Our patients, compared with controls, exhibited significant differences at global and local topological level of their brain networks. An abnormal rise in small-world network efficiency was observed in the gamma band (30-40 Hz) during execution of the task, paralleled by increased long-range connectivity between cortical hemispheres. Our findings show that a pervasive reorganization of the brain network is associated with cerebellar focal damage and support the idea that the cerebellum boosts or refines cortical functions. Clinically, these results suggest that cortical changes after cerebellar damage are achieved through an increase in the interactions between remote cortical areas and that rehabilitation should aim to reshape functional activation patterns. Future studies should determine whether these hypotheses are limited to motor tasks or if they also apply to cerebro-cerebellar dysfunction in general.
NASA Astrophysics Data System (ADS)
Sekiguchi, Yuichiro
2010-06-01
Performing fully general relativistic simulations taking account of microphysical processes (e.g. weak interactions and neutrino cooling) is one of the long-standing problems in numerical relativity. One of main difficulties in implementation of weak interactions in the general relativistic framework lies in the fact that the characteristic timescale of weak interaction processes (the WP timescale, t_wp \\sim \\vert Y_{e}/\\dot{Y}_{e} \\vert) in hot dense matters is much shorter than the dynamical timescale (tdyn). Numerically this means that stiff source terms appear in the equations so that an implicit scheme is in general necessary to stably solve the relevant equations. Otherwise a very short timestep (Δt < twp Lt tdyn) will be required to solve them explicitly, which is unrealistic in the present computational resources. Furthermore, in the relativistic framework, the Lorentz factor is coupled with the rest mass density and the energy density. The specific enthalpy is also coupled with the momentum. Due to these couplings, it is very complicated to recover the primitive variables and the Lorentz factor from conserved quantities. Consequently, it is very difficult to solve the equations implicitly in the fully general relativistic framework. At the current status, no implicit procedure has been proposed except for the case of the spherical symmetry. Therefore, an approximate explicit procedure is developed in the fully general relativistic framework in this paper as a first implementation of the microphysics toward a more realistic sophisticated model. The procedure is based on the so-called neutrino leakage schemes which are based on the property that the characteristic timescale in which neutrinos leak out of the system (the leakage timescale, tleak) is much longer than the WP timescale. In the previous leakage schemes, however, the problems of the stiff source terms are avoided in an artificial manner. In this paper, I present a detailed neutrino leakage
van Tol, Marie-José; Veer, Ilya M.; van der Wee, Nic J.A.; Aleman, André; van Buchem, Mark A.; Rombouts, Serge A.R.B.; Zitman, Frans G.; Veltman, Dick J.; Johnstone, Tom
2013-01-01
Major Depressive Disorder (MDD) has been associated with biased processing and abnormal regulation of negative and positive information, which may result from compromised coordinated activity of prefrontal and subcortical brain regions involved in evaluating emotional information. We tested whether patients with MDD show distributed changes in functional connectivity with a set of independently derived brain networks that have shown high correspondence with different task demands, including stimulus salience and emotional processing. We further explored if connectivity during emotional word processing related to the tendency to engage in positive or negative emotional states. In this study, 25 medication-free MDD patients without current or past comorbidity and matched controls (n = 25) performed an emotional word-evaluation task during functional MRI. Using a dual regression approach, individual spatial connectivity maps representing each subject's connectivity with each standard network were used to evaluate between-group differences and effects of positive and negative emotionality (extraversion and neuroticism, respectively, as measured with the NEO-FFI). Results showed decreased functional connectivity of the medial prefrontal cortex, ventrolateral prefrontal cortex, and ventral striatum with the fronto-opercular salience network in MDD patients compared to controls. In patients, abnormal connectivity was related to extraversion, but not neuroticism. These results confirm the hypothesis of a relative (para)limbic–cortical decoupling that may explain dysregulated affect in MDD. As connectivity of these regions with the salience network was related to extraversion, but not to general depression severity or negative emotionality, dysfunction of this network may be responsible for the failure to sustain engagement in rewarding behavior. PMID:24179829
The effects of general relativity on core collapse supernovae
De Nisco, K.R.; Bruenn, S.W.; Mezzacappa, A.
1997-12-01
The effects of general relativity (GR) on the hydrodynamics and neutrino transport are examined during the critical shock reheating phase of core collapse supernovae. The authors find that core collapse computed with GR hydrodynamics results in a substantially more compact core structure out to the shock, the shock radius at stagnation being reduced by a factor of 2. The inflow speed of material behind the shock is also increased by a factor of 2 throughout most of the evolution. They have developed a code for general relativistic multigroup flux-limited diffusion (MGFLD) in static spacetimes and compared the steady-state neutrino distributions for selected time slices of post-bounce models with those computed with Newtonian MGFLD. The GR transport calculations show the expected reductions in neutrino luminosities and rms energies from redshift and curvature effects. Although the effects of GR on the hydrodynamics and neutrino transport seem to work against shock revival, the core configurations are sufficiently different that no firm conclusions can be drawn, except that simulations of core collapse supernovae using Newtonian hydrodynamics and transport are not realistic.
Aging-related gains and losses associated with word production in connected speech.
Dennis, Paul A; Hess, Thomas M
2016-11-01
Older adults have been observed to use more nonnormative, or atypical, words than younger adults in connected speech. We examined whether aging-related losses in word-finding abilities or gains in language expertise underlie these age differences. Sixty younger and 60 older adults described two neutral photographs. These descriptions were processed into word types, and textual analysis was used to identify interrupted speech (e.g., pauses), reflecting word-finding difficulty. Word types were assessed for normativeness, with nonnormative word types defined as those used by six (5%) or fewer participants to describe a particular picture. Accuracy and precision ratings were provided by another sample of 48 high-vocabulary younger and older adults. Older adults produced more interrupted and, as predicted, nonnormative words than younger adults. Older adults were more likely than younger adults to use nonnormative language via interrupted speech, suggesting a compensatory process. However, older adults' nonnormative words were more precise and trended for having higher accuracy, reflecting expertise. In tasks offering response flexibility, like connected speech, older adults may be able to offset instances of aging-related deficits by maximizing their expertise in other instances.
Elfmarková, Nela; Gajdoš, Martin; Mračková, Martina; Mekyska, Jiří; Mikl, Michal; Rektorová, Irena
2016-01-01
Impaired speech prosody is common in Parkinson's disease (PD). We assessed the impact of PD and levodopa on MRI resting-state functional connectivity (rs-FC) underlying speech prosody control. We studied 19 PD patients in the OFF and ON dopaminergic conditions and 15 age-matched healthy controls using functional MRI and seed partial least squares correlation (PLSC) analysis. In the PD group, we also correlated levodopa-induced rs-FC changes with the results of acoustic analysis. The PLCS analysis revealed a significant impact of PD but not of medication on the rs-FC strength of spatial correlation maps seeded by the anterior cingulate (p = 0.006), the right orofacial primary sensorimotor cortex (OF_SM1; p = 0.025) and the right caudate head (CN; p = 0.047). In the PD group, levodopa-induced changes in the CN and OF_SM1 connectivity strengths were related to changes in speech prosody. We demonstrated an impact of PD but not of levodopa on rs-FC within the brain networks related to speech prosody control. When only the PD patients were taken into account, the association between treatment-induced changes in speech prosody and changes in rs-FC within the associative striato-prefrontal and motor speech networks was found. Copyright © 2015 Elsevier Ltd. All rights reserved.
Chuang, Ching-Cheng; Sun, Chia-Wei
2014-01-01
The prefrontal cortex (PFC) is thought to play an important role in “higher” brain functions such as personality and emotion that may associated with several gender-related mental disorders. In this study, the gender effects of functional connectivity, cortical lateralization and significantly differences in the PFC were investigated by using resting-state functional optical tomography (fOT) measurement. A total of forty subjects including twenty healthy male and twenty healthy female adults were recruited for this study. In the results, the hemoglobin responses are higher in the male group. Additionally, male group exhibited the stronger connectivity in the PFC regions. In the result of lateralization, leftward dominant was observed in the male group but bilateral dominance in the female group. Finally, the 11 channels of the inferior PFC regions (corresponding to the region of Brodmann area 45) are significant different with spectrum analysis. Our findings suggest that the resting-state fOT method can provide high potential to apply to clinical neuroscience for several gender-related mental disorders diagnosis. PMID:25136481
Gravitational Wave Tests of General Relativity with Future Detectors
NASA Astrophysics Data System (ADS)
Chamberlain, Katie; Yunes, Nicolas
2017-01-01
Gravitational Wave detections with aLIGO have given us unrivalled insight into the extreme gravity regime, in which the gravitational field is strong and dynamical, but where will these types of detections be in 20 years? In this talk, we will explore how the construction of future generations of gravitational wave detectors influences our ability to test General Relativity in extreme gravity. In particular, using the noise spectra for aLIGO, A+, Voyager, CE, and ET-B, as well as the eLISA configurations N2A1, N2A2, and N2A5, we will compare the constraints that eLISA will provide to those that future generations of aLIGO will provide. These studies should produce useful information about instrument design to help guide design of future detectors for tests of gravity. Supported by the Montana Space Grant Consortium.
Remarks on the consistency of minimal deviations from general relativity
Pons, Josep M.; Talavera, Pere
2010-08-15
We study the consequences of some possible modifications of the phase space structure of general relativity imposed by breaking, in the simplest manner, the full diffeomorphism invariance but retaining the time foliation preserving diffeomorphisms. We examine the different sectors in phase space that satisfy the new structure of constraints. For some sectors we find an infinite tower of constraints. In spite of that, we also show that these sectors allow for solutions, among them some well-known families of black hole and cosmologies which fulfill all the constraints. We raise some physical concerns on the consequences of an absolute Galilean time, on the thermodynamical pathologies of such models, and on their unusual vacuum structure.
Simulating extreme-mass-ratio systems in full general relativity
NASA Astrophysics Data System (ADS)
East, William E.; Pretorius, Frans
2013-05-01
We introduce a new method for numerically evolving the full Einstein field equations in situations where the spacetime is dominated by a known background solution. The technique leverages the knowledge of the background solution to subtract off its contribution to the truncation error, thereby more efficiently achieving a desired level of accuracy. We demonstrate the method by applying it to the radial infall of a solar-type star into supermassive black holes with mass ratios ≥106. The self-gravity of the star is thus consistently modeled within the context of general relativity, and the star’s interaction with the black hole computed with moderate computational cost, despite the over five orders of magnitude difference in gravitational potential (as defined by the ratio of mass to radius). We compute the tidal deformation of the star during infall, and the gravitational wave emission, finding the latter is close to the prediction of the point-particle limit.
Singular Harmonic Maps and Applications to General Relativity
NASA Astrophysics Data System (ADS)
Nguyen, Luc
2011-01-01
The study of axially symmetric stationary multi-black-hole configurations and the force between co-axially rotating black holes involves, as a first step, an analysis on the "boundary regularity" of the so-called reduced singular harmonic maps. We carry out this analysis by considering those harmonic maps as solutions to some homogeneous divergence systems of partial differential equations with singular coefficients. Our results extend previous works by Weinstein (Comm Pure Appl Math 43:903-948, 1990; Comm Pure Appl Math 45:1183-1203, 1992) and by Li and Tian (Manu Math 73(1):83-89, 1991; Commun Math Phys 149:1-30, 1992; Differential geometry: PDE on manifolds, vol 54, pp. 317-326, 1993). This paper is based on the Ph.D. thesis of the author (Singular harmonic maps into hyperbolic spaces and applications to general relativity, PhD thesis, The State University of New Jersey, Rutgers, 2009).
General Relativity and Cosmology: Unsolved Questions and Future Directions
NASA Astrophysics Data System (ADS)
Debono, Ivan; Smoot, George F.
2016-09-01
For the last 100 years, General Relativity (GR) has taken over the gravitational theory mantle held by Newtonian Gravity for the previous 200 years. This article reviews the status of GR in terms of its self-consistency, completeness, and the evidence provided by observations, which have allowed GR to remain the champion of gravitational theories against several other classes of competing theories. We pay particular attention to the role of GR and gravity in cosmology, one of the areas in which one gravity dominates and new phenomena and effects challenge the orthodoxy. We also review other areas where there are likely conflicts pointing to the need to replace or revise GR to represent correctly observations and consistent theoretical framework. Observations have long been key both to the theoretical liveliness and viability of GR.We conclude with a discussion of the likely developments over the next 100 years.
Numerical performance of the parabolized ADM formulation of general relativity
Paschalidis, Vasileios; Hansen, Jakob; Khokhlov, Alexei
2008-09-15
In a recent paper [Vasileios Paschalidis, Phys. Rev. D 78, 024002 (2008).], the first coauthor presented a new parabolic extension (PADM) of the standard 3+1 Arnowitt, Deser, Misner (ADM) formulation of the equations of general relativity. By parabolizing first-order ADM in a certain way, the PADM formulation turns it into a well-posed system which resembles the structure of mixed hyperbolic-second-order parabolic partial differential equations. The surface of constraints of PADM becomes a local attractor for all solutions and all possible well-posed gauge conditions. This paper describes a numerical implementation of PADM and studies its accuracy and stability in a series of standard numerical tests. Numerical properties of PADM are compared with those of standard ADM and its hyperbolic Kidder, Scheel, Teukolsky (KST) extension. The PADM scheme is numerically stable, convergent, and second-order accurate. The new formulation has better control of the constraint-violating modes than ADM and KST.
A stellar model with diffusion in general relativity
NASA Astrophysics Data System (ADS)
Alho, A.; Calogero, S.
2017-10-01
We consider a spherically symmetric stellar model in general relativity whose interior consists of a pressureless fluid undergoing microscopic velocity diffusion in a cosmological scalar field. We show that the diffusion dynamics compel the interior to be spatially homogeneous, by which one can infer immediately that within our model, and in contrast to the diffusion-free case, no naked singularities can form in the gravitational collapse. We then study the problem of matching an exterior Bondi type metric to the surface of the star and find that the exterior can be chosen to be a modified Vaidya metric with variable cosmological constant. Finally, we study in detail the causal structure of an explicit, self-similar solution.
Fixed mesh refinement in the characteristic formulation of general relativity
NASA Astrophysics Data System (ADS)
Barreto, W.; de Oliveira, H. P.; Rodriguez-Mueller, B.
2017-08-01
We implement a spatially fixed mesh refinement under spherical symmetry for the characteristic formulation of General Relativity. The Courant-Friedrich-Levy condition lets us deploy an adaptive resolution in (retarded-like) time, even for the nonlinear regime. As test cases, we replicate the main features of the gravitational critical behavior and the spacetime structure at null infinity using the Bondi mass and the News function. Additionally, we obtain the global energy conservation for an extreme situation, i.e. in the threshold of the black hole formation. In principle, the calibrated code can be used in conjunction with an ADM 3+1 code to confirm the critical behavior recently reported in the gravitational collapse of a massless scalar field in an asymptotic anti-de Sitter spacetime. For the scenarios studied, the fixed mesh refinement offers improved runtime and results comparable to code without mesh refinement.
Spontaneous symmetry breaking in general relativity. Vector order parameter
Meierovich, B. E.
2009-07-15
Gravitational properties of a hedgehog-type topological defect in two extra dimensions are considered in general relativity using a vector as the order parameter. All previous considerations were done using the order parameter in the form of a multiplet in the target space of scalar fields. The difference of these two approaches is analyzed and demonstrated in detail. Regular solutions to the Einstein equations are studied analytically and numerically. It is shown that the existence of a negative cosmological constant is sufficient for the spontaneous symmetry breaking of the initially flat bulk. Regular configurations have an increasing gravitational potential and are able to trap the matter on the brane. If the energy of spontaneous symmetry breaking is high, the gravitational potential has several minimum points. Spinless particles that are identical in the uniform bulk, being trapped at separate minima, acquire different masses and appear to the observer on the brane as different particles with integer spins.
Collapse of magnetized hypermassive neutron stars in general relativity.
Duez, Matthew D; Liu, Yuk Tung; Shapiro, Stuart L; Shibata, Masaru; Stephens, Branson C
2006-01-27
Hypermassive neutron stars (HMNSs)--equilibrium configurations supported against collapse by rapid differential rotation--are possible transient remnants of binary neutron-star mergers. Using newly developed codes for magnetohydrodynamic simulations in dynamical spacetimes, we are able to track the evolution of a magnetized HMNS in full general relativity for the first time. We find that secular angular momentum transport due to magnetic braking and the magnetorotational instability results in the collapse of an HMNS to a rotating black hole, accompanied by a gravitational wave burst. The nascent black hole is surrounded by a hot, massive torus undergoing quasistationary accretion and a collimated magnetic field. This scenario suggests that HMNS collapse is a possible candidate for the central engine of short gamma-ray bursts.
The Gravity Probe B test of general relativity
NASA Astrophysics Data System (ADS)
Everitt, C. W. F.; Muhlfelder, B.; DeBra, D. B.; Parkinson, B. W.; Turneaure, J. P.; Silbergleit, A. S.; Acworth, E. B.; Adams, M.; Adler, R.; Bencze, W. J.; Berberian, J. E.; Bernier, R. J.; Bower, K. A.; Brumley, R. W.; Buchman, S.; Burns, K.; Clarke, B.; Conklin, J. W.; Eglington, M. L.; Green, G.; Gutt, G.; Gwo, D. H.; Hanuschak, G.; He, X.; Heifetz, M. I.; Hipkins, D. N.; Holmes, T. J.; Kahn, R. A.; Keiser, G. M.; Kozaczuk, J. A.; Langenstein, T.; Li, J.; Lipa, J. A.; Lockhart, J. M.; Luo, M.; Mandel, I.; Marcelja, F.; Mester, J. C.; Ndili, A.; Ohshima, Y.; Overduin, J.; Salomon, M.; Santiago, D. I.; Shestople, P.; Solomonik, V. G.; Stahl, K.; Taber, M.; Van Patten, R. A.; Wang, S.; Wade, J. R.; Worden, P. W., Jr.; Bartel, N.; Herman, L.; Lebach, D. E.; Ratner, M.; Ransom, R. R.; Shapiro, I. I.; Small, H.; Stroozas, B.; Geveden, R.; Goebel, J. H.; Horack, J.; Kolodziejczak, J.; Lyons, A. J.; Olivier, J.; Peters, P.; Smith, M.; Till, W.; Wooten, L.; Reeve, W.; Anderson, M.; Bennett, N. R.; Burns, K.; Dougherty, H.; Dulgov, P.; Frank, D.; Huff, L. W.; Katz, R.; Kirschenbaum, J.; Mason, G.; Murray, D.; Parmley, R.; Ratner, M. I.; Reynolds, G.; Rittmuller, P.; Schweiger, P. F.; Shehata, S.; Triebes, K.; VandenBeukel, J.; Vassar, R.; Al-Saud, T.; Al-Jadaan, A.; Al-Jibreen, H.; Al-Meshari, M.; Al-Suwaidan, B.
2015-11-01
The Gravity Probe B mission provided two new quantitative tests of Einstein’s theory of gravity, general relativity (GR), by cryogenic gyroscopes in Earth’s orbit. Data from four gyroscopes gave a geodetic drift-rate of -6601.8 ± 18.3 marc-s yr-1 and a frame-dragging of -37.2 ± 7.2 marc-s yr-1, to be compared with GR predictions of -6606.1 and -39.2 marc-s yr-1 (1 marc-s = 4.848 × 10-9 radians). The present paper introduces the science, engineering, data analysis, and heritage of Gravity Probe B, detailed in the accompanying 20 CQG papers.
Commutative deformations of general relativity: nonlocality, causality, and dark matter
NASA Astrophysics Data System (ADS)
de Vegvar, P. G. N.
2017-01-01
Hopf algebra methods are applied to study Drinfeld twists of (3+1)-diffeomorphisms and deformed general relativity on commutative manifolds. A classical nonlocality length scale is produced above which microcausality emerges. Matter fields are utilized to generate self-consistent Abelian Drinfeld twists in a background independent manner and their continuous and discrete symmetries are examined. There is negligible experimental effect on the standard model of particles. While baryonic twist producing matter would begin to behave acausally for rest masses above {˜ }1-10 TeV, other possibilities are viable dark matter candidates or a right-handed neutrino. First order deformed Maxwell equations are derived and yield immeasurably small cosmological dispersion and produce a propagation horizon only for photons at or above Planck energies. This model incorporates dark matter without any appeal to extra dimensions, supersymmetry, strings, grand unified theories, mirror worlds, or modifications of Newtonian dynamics.
CPT symmetry and antimatter gravity in general relativity
NASA Astrophysics Data System (ADS)
Villata, M.
2011-04-01
The gravitational behavior of antimatter is still unknown. While we may be confident that antimatter is self-attractive, the interaction between matter and antimatter might be either attractive or repulsive. We investigate this issue on theoretical grounds. Starting from the CPT invariance of physical laws, we transform matter into antimatter in the equations of both electrodynamics and gravitation. In the former case, the result is the well-known change of sign of the electric charge. In the latter, we find that the gravitational interaction between matter and antimatter is a mutual repulsion, i.e. antigravity appears as a prediction of general relativity when CPT is applied. This result supports cosmological models attempting to explain the Universe accelerated expansion in terms of a matter-antimatter repulsive interaction.
Sengupta, Arkajyoti; Ramabhadran, Raghunath O; Raghavachari, Krishnan
2014-08-14
In this study we have used the connectivity-based hierarchy (CBH) method to derive accurate heats of formation of a range of biomolecules, 18 amino acids and 10 barbituric acid/uracil derivatives. The hierarchy is based on the connectivity of the different atoms in a large molecule. It results in error-cancellation reaction schemes that are automated, general, and can be readily used for a broad range of organic molecules and biomolecules. Herein, we first locate stable conformational and tautomeric forms of these biomolecules using an accurate level of theory (viz. CCSD(T)/6-311++G(3df,2p)). Subsequently, the heats of formation of the amino acids are evaluated using the CBH-1 and CBH-2 schemes and routinely employed density functionals or wave function-based methods. The calculated heats of formation obtained herein using modest levels of theory and are in very good agreement with those obtained using more expensive W1-F12 and W2-F12 methods on amino acids and G3 results on barbituric acid derivatives. Overall, the present study (a) highlights the small effect of including multiple conformers in determining the heats of formation of biomolecules and (b) in concurrence with previous CBH studies, proves that use of the more effective error-cancelling isoatomic scheme (CBH-2) results in more accurate heats of formation with modestly sized basis sets along with common density functionals or wave function-based methods.
Towards the Proof of AGT Relations with the Help of the Generalized Jack Polynomials
NASA Astrophysics Data System (ADS)
Morozov, Alexei; Smirnov, Andrey
2014-05-01
Original proofs of the AGT relations with the help of the Hubbard-Stratanovich duality of the modified Dotsenko-Fateev matrix model did not work for β ≠ 1, because Nekrasov functions were not properly reproduced by Selberg-Kadell integrals of Jack polynomials. We demonstrate that if the generalized Jack polynomials, depending on the N-ples of Young diagrams from the very beginning, are used instead of the N-linear combinations of ordinary Jacks, this resolves the problem. Such polynomials naturally arise as special elements in the equivariant cohomologies of the GL( N)-instanton moduli spaces, and this also establishes connection to alternative ABBFLT approach to the AGT relations, studying the action of chiral algebras on the instanton moduli spaces. In this paper, we describe a complete proof of AGT in the simple case of GL(2) ( N = 2) Yang-Mills theory, i.e., the 4-point spherical conformal block of the Virasoro algebra.
Charroud, Céline; Le Bars, Emmanuelle; Deverdun, Jérémy; Steffener, Jason; Molino, François; Abdennour, Meriem; Portet, Florence; Bonafe, Alain; Stern, Yaakov; Ritchie, Karen; Akbaraly, Tasnime N; Menjot de Champfleur, Nicolas
2016-07-01
Characterization of normal age-related changes in resting state brain networks associated with working memory performance is a major prerequisite for studying neurodegenerative diseases. The aim of this study was to investigate the relationship between performing a working memory task (under MRI) and resting-state brain networks in a large cohort of healthy elderly subjects (n=337). Functional connectivity and interactions between networks were assessed within the default mode (DMN), salience (SN), and right and left central executive (CEN) networks in two groups of subjects classed by their performance (low and high). The low performance group showed lower functional connectivity in both the DMN and SN, and higher functional connectivity in the right and left CEN compared to the high performance group. Overall the functional connectivity within the DMN and the CEN were correlated. The lower functional connectivity within the DMN and SN in the low performance group is suggestive of altered attentional and memory processes and/or altered motivation. The higher functional connectivity within the CEN could be related to compensatory mechanisms, without which the subjects would have even lower performances. The correlation between the DMN and CEN suggests a modulation between the lower functional connectivity within the DMN and the higher functional connectivity within the CEN when performance is reduced. Finally, this study suggests that performance modifications in healthy elderly subjects are associated with reorganization of functional connectivity within the DMN, SN, and CEN.
Coyne, Sarah M; Nelson, David A; Graham-Kevan, Nicola; Tew, Emily; Meng, K Nathan; Olsen, Joseph A
2011-01-01
Various studies have found that viewing physical or relational aggression in the media can impact subsequent engagement in aggressive behavior. However, this has rarely been examined in the context of relationships. Accordingly, the aim of this study was to examine the connection between viewing various types of aggression in the media and perpetration of aggression against a romantic partner. A total of 369 young adults completed a variety of questionnaires asking for their perpetration of various forms of relationship aggression. Participants' exposure to both physical and relational aggression in the media was also assessed. As a whole, we found a relationship between viewing aggression in the media and perpetration of aggression; however, this depended on the sex of the participant and the type of aggression measured. Specifically, exposure to physical violence in the media was related to engagement in physical aggression against their partner only for men. However, exposure to relational aggression in the media was related to romantic relational aggression for both men and women.
Casanova, Ramon; Hayasaka, Satoru; Saldana, Santiago; Bryan, Nick R; Demos, Kathryn E; Desiderio, Lisa; Erickson, Kirk I; Espeland, Mark A; Nasrallah, Ilya M; Wadden, Thomas; Laurienti, Paul J
2016-12-01
A number of studies have reported that type 2 diabetes mellitus (T2DM) is associated with alterations in resting-state activity and connectivity in the brain. There is also evidence that interventions involving physical activity and weight loss may affect brain functional connectivity. In this study, we examined the effects of nearly 10 years of an intensive lifestyle intervention (ILI), designed to induce and sustain weight loss through lower caloric intake and increased physical activity, on resting-state networks in adults with T2DM. We performed a cross-sectional comparison of global and local characteristics from functional brain networks between individuals who had been randomly assigned to ILI or a control condition of health education and support. Upon examining brain networks from 312 participants (average age: 68.8 for ILI and 67.9 for controls), we found that ILI participants (N=160) had attenuated local efficiency at the network-level compared with controls (N=152). Although there was no group difference in the network-level global efficiency, we found that, among ILI participants, nodal global efficiency was elevated in left fusiform gyrus, right middle frontal gyrus, and pars opercularis of right inferior frontal gyrus. These effects were age-dependent, with more pronounced effects for older participants. Overall these results indicate that the individuals assigned to the ILI had brain networks with less regional and more global connectivity, particularly involving frontal lobes. Such patterns would support greater distributed information processing. Future studies are needed to determine if these differences are associated with age-related compensatory function in the ILI group or worse pathology in the control group. Copyright © 2016 Elsevier Ltd. All rights reserved.
General scaling relations for locomotion in granular media.
Slonaker, James; Motley, D Carrington; Zhang, Qiong; Townsend, Stephen; Senatore, Carmine; Iagnemma, Karl; Kamrin, Ken
2017-05-01
Inspired by dynamic similarity in fluid systems, we have derived a general dimensionless form for locomotion in granular materials, which is validated in experiments and discrete element method (DEM) simulations. The form instructs how to scale size, mass, and driving parameters in order to relate dynamic behaviors of different locomotors in the same granular media. The scaling can be derived by assuming intrusion forces arise from resistive force theory or equivalently by assuming the granular material behaves as a continuum obeying a frictional yield criterion. The scalings are experimentally confirmed using pairs of wheels of various shapes and sizes under many driving conditions in a common sand bed. We discuss why the two models provide such a robust set of scaling laws even though they neglect a number of the complexities of granular rheology. Motivated by potential extraplanetary applications, the dimensionless form also implies a way to predict wheel performance in one ambient gravity based on tests in a different ambient gravity. We confirm this using DEM simulations, which show that scaling relations are satisfied over an array of driving modes even when gravity differs between scaled tests.