2004-05-01
change under the various nui- sances of image formation and viewing geometry was appealing; it held potential for application to recognition...Springer, 1990. 29. S. Z. Li. Shape matching based on invariants. In O. M. Omidvar (ed.), editor, Progress in Neural Networks : Shape Recognition, volume 6
Shape Invariance in Deformation Quantization
NASA Astrophysics Data System (ADS)
Rasinariu, Constantin
2013-03-01
Shape invariance is a powerful solvability condition, that allows for complete knowledge of the energy spectrum, and eigenfunctions of a system. After a short introduction into the deformation quantization formalism, this work explores the implications of the supersymmetric quantum mechanics and shape invariance techniques to the phase space formalism. We show that shape invariance induces a new set of relations between the Wigner functions of the system, that allows for their direct calculation, once we know one of them. The simple harmonic oscillator and the Morse potential are presented as examples. I would like to acknowledge a sabbatical leave and grant from Columbia College Chicago that made this work possible.
Spectral dimension with deformed spacetime signature
NASA Astrophysics Data System (ADS)
Mielczarek, Jakub; Trześniewski, Tomasz
2017-07-01
Studies of the effective regime of loop quantum gravity (LQG) revealed that, in the limit of Planckian curvature scales, spacetime may undergo a transition from the Lorentzian to Euclidean signature. This effect is a consequence of quantum modifications of the hypersurface deformation algebra, which in the linearized case is equivalent to a deformed version of the Poincaré algebra. In this paper the latter relation is explored for the LQG-inspired hypersurface deformation algebra that is characterized by the above mentioned signature change. While the exact form of the deformed Poincaré algebra is not uniquely determined, the algebra under consideration is representative enough to capture a number of qualitative features. In particular, the analysis reveals that the signature change can be associated with two symmetric invariant energy scales, which separate three physically disconnected momentum subspaces. Furthermore, the invariant measure on momentum space is derived, which allows to properly define the average return probability, characterizing a fictitious diffusion process on spacetime. The diffusion is subsequently studied in the momentum representation for all possible variants of the model. Finally, the spectral dimension of spacetime is calculated in each case as a function of the scale parameter. In the most interesting situation the deformation is of the asymptotically ultralocal type and the spectral dimension reduces to dS=1 in the UV limit.
Twist deformation of rotationally invariant quantum mechanics
Chakraborty, B.; Kuznetsova, Z.; Toppan, F.
2010-11-15
Noncommutative quantum mechanics in 3D is investigated in the framework of an abelian Drinfeld twist which deforms a given Hopf algebra structure. Composite operators (of coordinates and momenta) entering the Hamiltonian have to be reinterpreted as primitive elements of a dynamical Lie algebra which could be either finite (for the harmonic oscillator) or infinite (in the general case). The deformed brackets of the deformed angular momenta close the so(3) algebra. On the other hand, undeformed rotationally invariant operators can become, under deformation, anomalous (the anomaly vanishes when the deformation parameter goes to zero). The deformed operators, Taylor-expanded in the deformation parameter, can be selected to minimize the anomaly. We present the deformations (and their anomalies) of undeformed rotationally invariant operators corresponding to the harmonic oscillator (quadratic potential), the anharmonic oscillator (quartic potential), and the Coulomb potential.
The Superluminal Neutrinos from Deformed Lorentz Invariance
NASA Astrophysics Data System (ADS)
Huo, Yunjie; Li, Tianjun; Liao, Yi; Nanopoulos, Dimitri V.; Qi, Yonghui; Wang, Fei
2012-10-01
We study two superluminal neutrino scenarios where δ v≡ (v-c)/(c) is a constant. To be consistent with the OPERA, Borexino and ICARUS experiments and with the SN1987a observations, we assume that δvν on the Earth is about three-order larger than that on the interstellar scale. To explain the theoretical challenges from the Bremsstrahlung effects and pion decays, we consider the deformed Lorentz invariance, and show that the superluminal neutrino dispersion relations can be realized properly while the modifications to the dispersion relations of the other Standard Model particles can be negligible. In addition, we propose the deformed energy and momentum conservation laws for a generic physical process. In Scenario I the momentum conservation law is preserved while the energy conservation law is deformed. In Scenario II the energy conservation law is preserved while the momentum conservation law is deformed. We present the energy and momentum conservation laws in terms of neutrino momentum in Scenario I and in terms of neutrino energy in Scenario II. In such formats, the energy and momentum conservation laws are exactly the same as those in the traditional quantum field theory with Lorentz symmetry. Thus, all the above theoretical challenges can be automatically solved. We show explicitly that the Bremsstrahlung processes are forbidden and there is no problem for pion decays.
Feature-aided tracking using invariant features of HRR signatures
NASA Astrophysics Data System (ADS)
Gross, David C.; Oppenheimer, Michael W.; Schmitz, James L.; Sturtz, Kirk
2001-08-01
The present era of limited warfare demands that warfighters have the capability for timely acquisition and precision strikes against enemy ground targets with minimum collateral damage. As a result, automatic target recognition (ATR) and Feature Aided Tracking (FAT) of moving ground vehicles using High Range Resolution (HRR) radar has received increased interest in the community. HRR radar is an excellent sensor for potentially identifying moving targets under all-weather, day/night, long-standoff conditions. This paper presents preliminary results of a Veridian Engineering Internal Research and Development effort to determine the feasibility of using invariant HRR signature features to assist a FAT algorithm. The presented method of invariant analysis makes use of Lie mathematics to determine geometric and system invariants contained within an Object/Image (O/I) relationship. The fundamental O/I relationship expresses a geometric relationship (constraint) between a 3-D object (scattering center) and its image (a 1-D HRR profile). The HRR radar sensor model is defined, and then the O/I relationship for invariant features is derived. Although constructing invariants is not a trivial task, once an invariant is determined, it is computationally simple to implement into a FAT algorithm.
Deformation and signature splitting in 74Br
NASA Astrophysics Data System (ADS)
Holcomb, J. W.; Johnson, T. D.; Womble, P. C.; Cottle, P. D.; Tabor, S. L.; Durham, F. E.; Buccino, S. G.
1991-02-01
The high-spin states of 74Br were studied via the 48Ti(32S,αpn)74Br and the 58Ni(19F,2pn)74Br fusion-evaporation reactions at energies of 105 and 62 MeV, respectively, using the Florida State University Tandem LINAC. γ-γ coincidence arrays were produced using four Compton-suppressed Ge detectors. Two independent groups of γ rays were studied-one of positive parity and one of negative parity, both of which appear to be based on an isomeric 4(+) state. Lifetimes were measured using both the Doppler-shift attenuation and recoil-distance methods. A cranking-model analysis of the bands shows that the kinematic and dynamic moments of inertia for the bands are rather similar and fairly constant for high spins with values of (20-23)ħ2/MeV. A phase reversal occurs in the signature splitting in the yrast band around spin 9 which is related to the quasiparticle alignments. The lifetimes imply an average axial quadrupole deformation of 0.37 in the yrast band and 0.34 in the negative-parity band. These deformations are close to those predicted by Hartree-Fock-Bogolyubov cranking calculations.
Isomonodromic deformations and SU 2-invariant instantons on S4
NASA Astrophysics Data System (ADS)
Manasliski, Richard Muñiz
2009-07-01
Anti-self-dual (ASD) solutions to the Yang-Mills equation (or instantons) over an anti-self-dual 4-manifold, which are invariant under an appropriate action of a three-dimensional Lie group, give rise, via twistor construction, to isomonodromic deformations of connections on CP having four simple singularities. As is well known, such deformations are governed by the sixth Painlevé equation P VI(α,β,γ,δ). We work out the particular case of the SU-action on S4, obtained from the irreducible representation on R5. In particular, we express the parameters (α,β,γ,δ) in terms of the instanton number. The present paper contains the proof of the result announced in [Richard Muñiz Manasliski, Painlevé VI equation from invariant instantons, in: Geometric and Topological Methods for Quantum field theory, Contemp. Math., vol. 434, Amer. Math. Soc., Providence, RI, 2007, pp. 215-222].
Brst-Invariant Deformations of Geometric Structures in Sigma Models
NASA Astrophysics Data System (ADS)
Bytsenko, A. A.
The closed string correlators can be constructed from the open ones using topological string theories as a model. The space of physical closed string states is isomorphic to the Hochschild cohomology of (A,Q) (operator Q of ghost number one), - this statement has been verified by means of computation of the Hochschild cohomology of the category of D-branes. We study a Lie algebra of formal vector fields Wn with its application to the perturbative deformed holomorphic symplectic structure in the A-model, and a Calabi-Yau manifold with boundaries in the B-model. We show that equivalent classes of deformations are describing by a Hochschild cohomology theory of the DG-algebra, {A} = (A, Q), Q = bar ∂ + {∂ {deform}}, which is defined to be the cohomology of (-1)nQ+dHoch. Here bar ∂ is the initial non-deformed BRST operator while ∂deform is the deformed part whose algebra is a Lie algebra of linear vector fields gln. We assume that if in the theory exists a single D-brane then all the information associated with deformations is encoded in an associative algebra A equipped with a differential Q = bar ∂ + {∂ {deform}}. In addition equivalence classes of deformations of these data are described by a Hochschild cohomology of (A,Q), an important geometric invariant of the (anti)holomorphic structure on X. We also discuss the identification of the harmonic structure (HT•(X) HΩ•(X)) of affine space X and the group {Ext}Xn ({ {O}_Δ }, { {O}Δ }) (the HKR isomorphism), and bulk-boundary deformation pairing.
Brst-Invariant Deformations of Geometric Structures in Sigma Models
NASA Astrophysics Data System (ADS)
Bytsenko, A. A.
2011-06-01
The closed string correlators can be constructed from the open ones using topological string theories as a model. The space of physical closed string states is isomorphic to the Hochschild cohomology of (A, Q) (operator Q of ghost number one), - this statement has been verified by means of computation of the Hochschild cohomology of the category of D-branes. We study a Lie algebra of formal vector fields Wn with its application to the perturbative deformed holomorphic symplectic structure in the A-model, and a Calabi-Yau manifold with boundaries in the B-model. We show that equivalent classes of deformations are describing by a Hochschild cohomology theory of the DG-algebra {A} = (A, Q), Q = /line{\\part} + \\part { deform}, which is defined to be the cohomology of (-1)n Q + dHoch. Here /line{\\part} is the initial non-deformed BRST operator while \\partdeform is the deformed part whose algebra is a Lie algebra of linear vector fields gln. We assume that if in the theory exists a single D-brane then all the information associated with deformations is encoded in an associative algebra A equipped with a differential Q = /line{\\part}+\\part { deform}. In addition equivalence classes of deformations of these data are described by a Hochschild cohomology of (A, Q), an important geometric invariant of the (anti)holomorphic structure on X. We also discuss the identification of the harmonic structure (HT•(X); HΩ•(X)) of affine space X and the group ExtXn({O}\\triangle , {O}\\triangle ) (the HKR isomorphism), and bulk-boundary deformation pairing.
Analysis of Unresolved Spectral Infrared Signature for the Extraction of Invariant Features
2010-09-01
satellite is illuminated continuously and is operating under steady-state conditions, its solar panel and body reach a thermal equilibrium with its...environment such that the thermal energy emitted by the solar panel and the body remain constant . Thus the signature is a function of entities that...remain constant (or, are invariant) and entities that are varying. The invariant entities are the spectral radiance values (i.e., the thermal energy
Mechanics and seismic signature of brittle deformation of serpentinites
NASA Astrophysics Data System (ADS)
David, Emmanuel C.; Brantut, Nicolas; Hansen, Lars N.; Mitchell, Thomas M.
2017-04-01
It is well recognised that serpentinites play a major role in subduction zone processes, such as tectonic evolution of the oceanic lithosphere, earthquake nucleation, or recycling of water in the upper mantle. However, it is not yet clearly known how and by which micromechanical process serpentinites deform, and what is their signature on seismic properties. Deformation experiments were conducted on 90%-rich antigorite polycrystalline serpentinite in the brittle field, under varying conditions of confining pressure, with simultaneous measurements of axial and radial strains, and P and S-wave velocities at various directions with respect to the applied stress. Failure, controlled-failure, and cyclic-loading tests were performed to investigate the strength, dissipation of mechanical energy, seismic signature and resulting microstructures of a suite of antigorite specimens. The brittle deformation of antigorite is mostly non-dilatant and accommodated by shear microcracks localised over a very narrow zone near the failure plane - as confirmed by microstructural observations. Antigorite serpentinites display a failure strength as high as for crystalline rocks, and a yield point occurring close to failure. Another untypical feature observed during deformation of the antigorite specimens is the spectacular absence of any wave velocity evolution, and any stress-induced anisotropy, during axial compression. Such results may have strong implications for the understanding of subduction zone dynamics, which remain to be complemented by mechanical tests conducted in the ductile regime.
A properly invariant theory of infinitesimal deformations of an elastic Cosserat point
NASA Astrophysics Data System (ADS)
O'Reilly, Oliver M.
1996-03-01
In the context of a mechanical theory of a Cosserat point developed by Green and Naghdi [1=Quart. J. Mech. and Appl. Math., 44, 335 355 (1991)], this paper establishes a properly invariant theory for infinitesimal deformations. The invariant theory is valid for an elastic Cosserat point with an arbitrary number of directors. Its construction is based on a method developed by Casey and Naghdi [2=Arch. Rational Mech. Anal., 76, 355 391 (1981)] for unconstrained non-polar elastic bodies.
Tzagkarakis, George; Beferull-Lozano, Baltasar; Tsakalides, Panagiotis
2008-07-01
This paper addresses the construction of a novel efficient rotation-invariant texture retrieval method that is based on the alignment in angle of signatures obtained via a steerable sub-Gaussian model. In our proposed scheme, we first construct a steerable multivariate sub-Gaussian model, where the fractional lower-order moments of a given image are associated with those of its rotated versions. The feature extraction step consists of estimating the so-called covariations between the orientation subbands of the corresponding steerable pyramid at the same or at adjacent decomposition levels and building an appropriate signature that can be rotated directly without the need of rotating the image and recalculating the signature. The similarity measurement between two images is performed using a matrix-based norm that includes a signature alignment in angle between the images being compared, achieving in this way the desired rotation-invariance property. Our experimental results show how this retrieval scheme achieves a lower average retrieval error, as compared to previously proposed methods having a similar computational complexity, while at the same time being competitive with the best currently known state-of-the-art retrieval system. In conclusion, our retrieval method provides the best compromise between complexity and average retrieval performance.
Analysis on volume invariability of metal circular shaft in torsion deformation
NASA Astrophysics Data System (ADS)
Yang, Li-Hong; Zou, Guang-Ping; He, Yun-Zeng; Wang, Hui
2009-12-01
Volume invariability of metal circular shaft in the case of small strain torsion deformation and large strain torsion deformation was, respectively, discussed experimentally and theoretically in this study. In accordance with the elastoplastic theory, it was given that the shear stress did not cause the change of volume in the large strain range. By utilizing torsion experiment with the solid shaft of low carbon steel, it was proved that metal can meet the conditions of the volume invariability in torsion deformation while the cumulative damage was not very serious. Volumetric deformation was analyzed in torsion of circular shaft in the perspective of micromechanics. Finally, Swift effect of solid circular shaft and tubular shaft of brass material were interpreted by using the formulae of elastoplastic critic load obtained from double-limb bar model test presented by Shanley.
Analysis on volume invariability of metal circular shaft in torsion deformation
NASA Astrophysics Data System (ADS)
Yang, Li-Hong; Zou, Guang-Ping; He, Yun-Zeng; Wang, Hui
2010-03-01
Volume invariability of metal circular shaft in the case of small strain torsion deformation and large strain torsion deformation was, respectively, discussed experimentally and theoretically in this study. In accordance with the elastoplastic theory, it was given that the shear stress did not cause the change of volume in the large strain range. By utilizing torsion experiment with the solid shaft of low carbon steel, it was proved that metal can meet the conditions of the volume invariability in torsion deformation while the cumulative damage was not very serious. Volumetric deformation was analyzed in torsion of circular shaft in the perspective of micromechanics. Finally, Swift effect of solid circular shaft and tubular shaft of brass material were interpreted by using the formulae of elastoplastic critic load obtained from double-limb bar model test presented by Shanley.
Scale invariance of shallow seismicity and the prognostic signatures of earthquakes
NASA Astrophysics Data System (ADS)
Stakhovsky, I. R.
2017-08-01
The results of seismic investigations based on methods of the theory of nonequilibrium processes and self-similarity theory have shown that a shallow earthquake can be treated as a critical transition that occurs during the evolution of a non-equilibrium seismogenic system and is preceded by phenomena such as the scale invariance of spatiotemporal seismic structures. The implication is that seismicity can be interpreted as a purely multifractal process. Modeling the focal domain as a fractal cluster of microcracks allows formulating the prognostic signatures of earthquakes actually observed in seismic data. Seismic scaling permits monitoring the state of a seismogenic system as it approaches instability.
Gauge-invariant observables and marginal deformations in open string field theory
NASA Astrophysics Data System (ADS)
Kudrna, Matěj; Masuda, Toru; Okawa, Yuji; Schnabl, Martin; Yoshida, Kenichiro
2013-01-01
The level-truncation analysis of open string field theory for a class of periodic marginal deformations indicates that a branch of solutions in Siegel gauge exists only for a finite range of values of the marginal field. The periodicity in the deformation parameter is thus obscure. We use the relation between gauge-invariant observables and the closed string tadpole on a disk conjectured by Ellwood to construct a map between the deformation parameter of the boundary conformal field theory and the parameter labeling classical solutions of open string field theory. We evaluate the gauge-invariant observables for the numerical solutions in Siegel gauge up to level 12 and find that our results qualitatively agree with the analysis by Sen using the energy-momentum tensor and are consistent with the picture that the finite range of the branch covers one fundamental domain of the periodic moduli space.
Signatures of time-reversal-invariant topological superconductivity in the Josephson effect
NASA Astrophysics Data System (ADS)
Mellars, Ehren; Béri, Benjamin
2016-11-01
For Josephson junctions based on s -wave superconductors, time-reversal symmetry is known to allow for powerful relations between the normal-state junction properties, the excitation spectrum, and the Josephson current. Here we provide analogous relations for Josephson junctions involving one-dimensional time-reversal-invariant topological superconductors supporting Majorana-Kramers pairs, considering both topological-topological and s -wave-topological junctions. Working in the regime where the junction is much shorter than the superconducting coherence length, we obtain a number of analytical and numerical results that hold for arbitrary normal-state conductance and the most general forms of spin-orbit coupling. The signatures of topological superconductivity we find include the fractional ac Josephson effect, which arises in topological-topological junctions provided that the energy relaxation is sufficiently slow. We also show, for both junction types, that robust signatures of topological superconductivity arise in the dc Josephson effect in the form of switches in the Josephson current due to zero-energy crossings of Andreev levels. The junction spin-orbit coupling enters the Josephson current only in the topological-topological case and in a manner determined by the switch locations, thereby allowing quantitative predictions for experiments with the normal-state conductance, the induced gaps, and the switch locations as inputs.
NASA Astrophysics Data System (ADS)
Deng, Zhipeng; Lei, Lin; Zhou, Shilin
2015-10-01
Automatic image registration is a vital yet challenging task, particularly for non-rigid deformation images which are more complicated and common in remote sensing images, such as distorted UAV (unmanned aerial vehicle) images or scanning imaging images caused by flutter. Traditional non-rigid image registration methods are based on the correctly matched corresponding landmarks, which usually needs artificial markers. It is a rather challenging task to locate the accurate position of the points and get accurate homonymy point sets. In this paper, we proposed an automatic non-rigid image registration algorithm which mainly consists of three steps: To begin with, we introduce an automatic feature point extraction method based on non-linear scale space and uniform distribution strategy to extract the points which are uniform distributed along the edge of the image. Next, we propose a hybrid point matching algorithm using DaLI (Deformation and Light Invariant) descriptor and local affine invariant geometric constraint based on triangulation which is constructed by K-nearest neighbor algorithm. Based on the accurate homonymy point sets, the two images are registrated by the model of TPS (Thin Plate Spline). Our method is demonstrated by three deliberately designed experiments. The first two experiments are designed to evaluate the distribution of point set and the correctly matching rate on synthetic data and real data respectively. The last experiment is designed on the non-rigid deformation remote sensing images and the three experimental results demonstrate the accuracy, robustness, and efficiency of the proposed algorithm compared with other traditional methods.
Structural Signature of Plastic Deformation in Metallic Glasses
NASA Astrophysics Data System (ADS)
Peng, H. L.; Li, M. Z.; Wang, W. H.
2011-04-01
The structure feature of a model CuZr metallic glass during deformation is investigated by molecular dynamics simulations. A spatially heterogeneous irreversible rearrangement is observed in terms of nonaffine displacement. We find that regions with smaller nonaffine displacement have more Voronoi pentagons, while in those with larger nonaffine displacement other types of faces are more populated. We use the degree of local fivefold symmetry (LFFS) as the structural indicator to predict plastic deformation of local structures and find that the plastic events prefer to be initiated in regions with a lower degree of LFFS and propagate toward regions with a higher degree of LFFS.
Xu, Xuemiao; Jin, Qiang; Zhou, Le; Qin, Jing; Wong, Tien-Tsin; Han, Guoqiang
2015-02-12
We propose a novel biometric recognition method that identifies the inner knuckle print (IKP). It is robust enough to confront uncontrolled lighting conditions, pose variations and low imaging quality. Such robustness is crucial for its application on portable devices equipped with consumer-level cameras. We achieve this robustness by two means. First, we propose a novel feature extraction scheme that highlights the salient structure and suppresses incorrect and/or unwanted features. The extracted IKP features retain simple geometry and morphology and reduce the interference of illumination. Second, to counteract the deformation induced by different hand orientations, we propose a novel structure-context descriptor based on local statistics. To our best knowledge, we are the first to simultaneously consider the illumination invariance and deformation tolerance for appearance-based low-resolution hand biometrics. Settings in previous works are more restrictive. They made strong assumptions either about the illumination condition or the restrictive hand orientation. Extensive experiments demonstrate that our method outperforms the state-of-the-art methods in terms of recognition accuracy, especially under uncontrolled lighting conditions and the flexible hand orientation requirement.
Search for a proposed signature of Lorentz-invariant spacetime granularity
NASA Astrophysics Data System (ADS)
Terrano, W. A.; Heckel, B. R.; Adelberger, E. G.
2011-07-01
We used a rotating torsion pendulum containing ≈1023 polarized electrons placed in an orientable quadrupole source to constrain Bonder and Sudarsky's quantum-gravity effect based on a Lorentz-invariant spacetime granularity model proposed by Corichi and Sudarsky. Our null results constrain the model's free parameters 13 orders of magnitude more tightly than those Bonder and Sudarsky obtained by reinterpreting the data from a previous polarized neutron experiment that was designed to test Lorentz invariance.
Age and gender-invariant features of handwritten signatures for verification systems
NASA Astrophysics Data System (ADS)
AbdAli, Sura; Putz-Leszczynska, Joanna
2014-11-01
Handwritten signature is one of the most natural biometrics, the study of human physiological and behavioral patterns. Behavioral biometrics includes signatures that may be different due to its owner gender or age because of intrinsic or extrinsic factors. This paper presents the results of the author's research on age and gender influence on verification factors. The experiments in this research were conducted using a database that contains signatures and their associated metadata. The used algorithm is based on the universal forgery feature idea, where the global classifier is able to classify a signature as a genuine one or, as a forgery, without the actual knowledge of the signature template and its owner. Additionally, the reduction of the dimensionality with the MRMR method is discussed.
Two signatures of implicit intergroup attitudes: developmental invariance and early enculturation.
Dunham, Yarrow; Chen, Eva E; Banaji, Mahzarin R
2013-06-01
Long traditions in the social sciences have emphasized the gradual internalization of intergroup attitudes and the putatively more basic tendency to prefer the groups to which one belongs. In four experiments (N = 883) spanning two cultures and two status groups within one of those cultures, we obtained new evidence that implicit intergroup attitudes emerge in young children in a form indistinguishable from adult attitudes. Strikingly, this invariance from childhood to adulthood holds for members of socially dominant majorities, who consistently favor their in-group, as well as for members of a disadvantaged minority, who, from the early moments of race-based categorization, do not show a preference for their in-group. Far from requiring a protracted period of internalization, implicit intergroup attitudes are characterized by early enculturation and developmental invariance.
Del Gado, Emanuela; Ilg, Patrick; Kröger, Martin; Ottinger, Hans Christian
2008-08-29
We unveil the existence of nonaffinely rearranging regions in the inherent structures (IS) of supercooled liquids by numerical simulations of model glass formers subject to static shear deformations combined with local energy minimizations. In the liquid state IS, we find a broad distribution of large rearrangements which are correlated only over small distances. At low temperatures, the onset of the cooperative dynamics corresponds to much smaller displacements correlated over larger distances. This finding indicates the presence of nonaffinely rearranging domains of relevant size in the IS deformation, which can be seen as the static counterpart of the cooperatively rearranging regions in the dynamics. This idea provides new insight into possible structural signatures of slow cooperative dynamics of supercooled liquids and supports the connections with elastic heterogeneities found in amorphous solids.
The geometry and invariance properties for certain classes of metrics with neutral signature
NASA Astrophysics Data System (ADS)
Bashingwa, Jean J. H.; Bokhari, Ashfaque H.; Kara, A. H.; Zaman, F. D.
2016-04-01
In this paper, we study anti-self dual manifolds endowed with metrics of neutral signature. Since the metrics depend on solutions of, in some cases, well-known partial differential equations (PDEs), we determine exact solutions using Lie group methods. This concludes specific forms of the metrics. We then determine the isometries and the variational symmetries of the underlying metrics and corresponding Euler-Lagrange (geodesic) equations, respectively, and establish relationships between the resultant Lie algebras. In some cases, we construct conservation laws via these symmetries or the “multiplier approach”.
NASA Astrophysics Data System (ADS)
Paganelli, Chiara; Peroni, Marta; Riboldi, Marco; Sharp, Gregory C.; Ciardo, Delia; Alterio, Daniela; Orecchia, Roberto; Baroni, Guido
2013-01-01
Adaptive radiation therapy (ART) aims at compensating for anatomic and pathological changes to improve delivery along a treatment fraction sequence. Current ART protocols require time-consuming manual updating of all volumes of interest on the images acquired during treatment. Deformable image registration (DIR) and contour propagation stand as a state of the ART method to automate the process, but the lack of DIR quality control methods hinder an introduction into clinical practice. We investigated the scale invariant feature transform (SIFT) method as a quantitative automated tool (1) for DIR evaluation and (2) for re-planning decision-making in the framework of ART treatments. As a preliminary test, SIFT invariance properties at shape-preserving and deformable transformations were studied on a computational phantom, granting residual matching errors below the voxel dimension. Then a clinical dataset composed of 19 head and neck ART patients was used to quantify the performance in ART treatments. For the goal (1) results demonstrated SIFT potential as an operator-independent DIR quality assessment metric. We measured DIR group systematic residual errors up to 0.66 mm against 1.35 mm provided by rigid registration. The group systematic errors of both bony and all other structures were also analyzed, attesting the presence of anatomical deformations. The correct automated identification of 18 patients who might benefit from ART out of the total 22 cases using SIFT demonstrated its capabilities toward goal (2) achievement.
Non-Contact Acousto-Thermal Signatures of Plastic Deformation in TI-6AL-4V
NASA Astrophysics Data System (ADS)
Welter, J. T.; Malott, G.; Schehl, N.; Sathish, S.; Jata, K. V.; Blodgett, M. P.
2010-02-01
Plastic deformation introduces changes in a material which include increases in: dislocations, strains, residual stress, and yield stress. However, these changes have a very small impact on the material properties such as elastic modulus, conductivity and ultrasonic wave speed. This is due to the fact that interatomic forces govern these properties, and they are not affected by plastic deformation to any large degree. This is evident from the fact that the changes in electrical resistance and ultrasonic velocity in plastically deformed and virgin samples are very small and can only be determined by highly controlled experiments. Except for X-ray diffraction, there are no direct nondestructive methods for measuring strain and the residual stress. This paper presents an application of the non-contact acousto-thermal signature (NCATS) NDE methodology to detect plastic deformation in flat dog bone Ti-6Al-4V samples. Results of the NCATS measurements on samples subjected to incremental amounts of plastic deformation are presented. The maximum temperature attained by the sample due to acoustic excitation is found to be sensitive to the amount of plastic strain. It is observed that the temperature induced by acoustic excitation increases to a peak followed by a decrease to failure. The maximum temperature peak occurs at plastic strains of 12-14%. It is observed that there is a correlation between the peak in maximum temperature rise and the strain at the experimentally determined ultimate tensile strength. A microstructural based explanation for this will be presented. The results are discussed in reference to utilizing this technique for detection and evaluation of plastic deformation.
NON-CONTACT ACOUSTO-THERMAL SIGNATURES OF PLASTIC DEFORMATION IN TI-6AL-4V
Welter, J. T.; Jata, K. V.; Blodgett, M. P.; Malott, G.; Schehl, N.; Sathish, S.
2010-02-22
Plastic deformation introduces changes in a material which include increases in: dislocations, strains, residual stress, and yield stress. However, these changes have a very small impact on the material properties such as elastic modulus, conductivity and ultrasonic wave speed. This is due to the fact that interatomic forces govern these properties, and they are not affected by plastic deformation to any large degree. This is evident from the fact that the changes in electrical resistance and ultrasonic velocity in plastically deformed and virgin samples are very small and can only be determined by highly controlled experiments. Except for X-ray diffraction, there are no direct nondestructive methods for measuring strain and the residual stress. This paper presents an application of the non-contact acousto-thermal signature (NCATS) NDE methodology to detect plastic deformation in flat dog bone Ti-6Al-4V samples. Results of the NCATS measurements on samples subjected to incremental amounts of plastic deformation are presented. The maximum temperature attained by the sample due to acoustic excitation is found to be sensitive to the amount of plastic strain. It is observed that the temperature induced by acoustic excitation increases to a peak followed by a decrease to failure. The maximum temperature peak occurs at plastic strains of 12-14%. It is observed that there is a correlation between the peak in maximum temperature rise and the strain at the experimentally determined ultimate tensile strength. A microstructural based explanation for this will be presented. The results are discussed in reference to utilizing this technique for detection and evaluation of plastic deformation.
Second order gauge invariant measure of a tidally deformed black hole
Ahmadi, Nahid
2012-08-01
In this paper, a Lagrangian perturbation theory for the second order treatment of small disturbances of the event horizon in Schwarzchild black holes is introduced. The issue of gauge invariance in the context of general relativistic theory is also discussed. The developments of this paper is a logical continuation of the calculations presented in [1], in which the first order coordinate dependance of the intrinsic and exterinsic geometry of the horizon is examined and the first order gauge invariance of the intrinsic geometry of the horizon is shown. In context of second order perturbation theory, It is shown that the rate of the expansion of the congruence of the horizon generators is invariant under a second order reparametrization; so it can be considered as a measure of tidal perturbation. A generally non-vanishing expression for this observable, which accomodates tidal perturbations and implies nonlinear response of the horizon, is also presented.
Gabor frame sets of invariance: a Hamiltonian approach to Gabor frame deformations.
Faulhuber, Markus
In this work we study families of pairs of window functions and lattices which lead to Gabor frames which all possess the same frame bounds. To be more precise, for every generalized Gaussian g, we will construct an uncountable family of lattices [Formula: see text] such that each pairing of g with some [Formula: see text] yields a Gabor frame, and all pairings yield the same frame bounds. On the other hand, for each lattice we will find a countable family of generalized Gaussians [Formula: see text] such that each pairing leaves the frame bounds invariant. Therefore, we are tempted to speak about Gabor Frame Sets of Invariance.
Brst-Invariant Deformations of Geometric Structures in Topological Field Theories
NASA Astrophysics Data System (ADS)
Bytsenko, A. A.; Chaichian, M.; Tureanu, A.; Williams, F. L.
2013-06-01
We study a Lie algebra of formal vector fields Wn with its application to the perturbative deformed holomorphic symplectic structure in the A-model, and a Calabi-Yau manifold with boundaries in the B-model. A relevant concept in the vertex operator algebra and the BRST cohomology is that of the elliptic genera (the one-loop string partition function). We show that the elliptic genera can be written in terms of spectral functions of the hyperbolic three-geometry (which inherits the cohomology structure of BRST-like operator). We show that equivalence classes of deformations are described by a Hochschild cohomology theory of the DG-algebra {A} = (A, Q), Q = \\bar {∂ } + ∂ deform, which is defined to be the cohomology of (-1)n Q + dHoch. Here, \\bar {∂ } is the initial nondeformed BRST operator while ∂deform is the deformed part whose algebra is a Lie algebra of linear vector fields gln. We discuss the identification of the harmonic structure (HT•(X);HΩ•(X)) of affine space X and the group {Ext}Xn({{O}}\\triangle, {{O}}\\triangle ) (the HKR isomorphism), and bulk-boundary deformation pairing.
Bi, Lei; Yang, Ping
2013-05-01
The invariant imbedding T-matrix method (II-TM) is employed to simulate the optical properties of normal biconcave and deformed red blood cells (RBCs). The phase matrix elements of a RBC model computed with the II-TM are compared with their counterparts computed with the discrete-dipole approximation (DDA) method. As expected, the DDA results approach the II-TM results with an increase in the number of dipoles per incident wavelength. Computationally, the II-TM is faster than the DDA when multiple RBC orientations are considered. For a single orientation, the DDA is comparable with or even faster than the II-TM because the DDA efficiently converges for optically soft particles; however, the DDA method demands significantly more computer memory than the II-TM. After the applicability of the II-TM is numerically confirmed, a comparison is conducted of the optical properties of oxygenated and deoxygenated RBCs and of normal and deformed RBCs. The spectral variations of RBCs' optical properties are investigated in the wavelength range from 0.25 to 1.0 μm. Furthermore, the statistically averaged phase matrix of spheres and biconcave RBCs are compared. Conducted numerical simulations suggest the applicability of the II-TM for the inverse light scattering analysis and radiative transfer simulations in blood.
Signature of magmatic processes in ground deformation signals from Phlegraean Fields (Italy)
NASA Astrophysics Data System (ADS)
Bagagli, Matteo; Montagna, Chiara Paola; Longo, Antonella; Papale, Paolo
2016-04-01
Ground deformation signals such as dilatometric and tiltmetric ones, are nowadays well studied from the vulcanological community all over the world. These signals can be used to retrieve information on volcanoes state and to study the magma dynamics in their plumbing system. We compared synthetic signals in the Very Long Period (VLP, 10-2 - 10-1 Hz) and Ultra Long Period (ULP, 10-4 - 10-2 Hz) bands obtained from the simulation of magma mixing in shallow reservoirs ([3],[4]) with real data obtained from the dilatometers and tiltmeters network situated in the Phlegraean Fields near Naples (Italy), in order to define and constrain the relationships between them. Analyses of data from the October 2006 seismic swarm in the area show that the frequency spectrum of the synthetics is remarkably similar to the transient present in the real signals. In depth studies with accurated techniques for spectral analysis (i.e wavelet transform) and application of this method to other time windows have identified in the bandwidth around 10-4Hz (between 1h30m and 2h45m) peaks that are fairly stable and independent from the processing carried out on the full-band signal. These peaks could be the signature of ongoing convection at depth. It is well known that re-injection of juvenile magmas can reactivate the eruption dynamics ([1],[2]), thus being able to define mixing markers and detect them in the ground deformation signals is a relevant topic in order to understand the dynamics of active and quiescent vulcanoes and to eventually improve early-warning methods for impending eruptions. [1] Arienzo, I. et al. (2010). "The feeding system of Agnano-Monte Spina eruption (Campi Flegrei, Italy): dragging the past into present activity and future scenarios". In: Chemical Geology 270.1, pp. 135-147. [2] Bachmann, Olivier and George Bergantz (2008). "The magma reservoirs that feed supereruptions". In: Elements 4.1, pp. 17-21. [3] Longo, Antonella et al. (2012). "Magma convection and mixing
NASA Astrophysics Data System (ADS)
Uma, V. S.; Goel, Alpana
2015-06-01
Several signature partner pairs in super-deformed rotational bands in the A = 190 mass region have exhibited ΔI = 1 staggering effects in its transition energies. A total of twenty signature partner pairs of super-deformed (SD) rotational bands in the A = 190 mass region were investigated in this study. The intrinsic structure and the band head moment of inertia J 0 of these signature partner pairs were found to be identical. The band head spin I 0 and the band head moment of inertia J 0 of these pairs were assigned by using the VMI (variable moment of inertia) equation. The ΔI = 1 staggering was also examined through the staggering index S( I) formula, where interlinking transition energies between signature partner pairs were experimentally known. A large amplitude staggering was observed in these signature partner pairs. The paper indicates the possibility of a high signature splitting property and will be useful for further studies.
Stratigraphic signature of lithospheric deformation style in post-rift passive margin basins
NASA Astrophysics Data System (ADS)
Rouby, Delphine; Huismans, Ritske; Robin, Cecile; Braun, Jean; Granjeon, Didier
2016-04-01
We revise commonly accepted models explaining long-term stratigraphic trends along Atlantic-type passive margins by including the impact of complex lithosphere deformation at depth and it's coupling with surface processes. To achieve this, we simulated the evolution of a passive margin basin using a cascade of three modeling tools: a thermo-mechanical model of the syn-rift stretching of the lithosphere, a flexural and thermal model of the post-rift stage that includes coupling with surface processes and, finally, a stratigraphic model of the associated sedimentary basin architecture. We compare two necking styles that lead to different margin geometries: wide and narrow margins that form by heterogeneous stretching. Wide margins, forming thinner and wider sedimentary wedges, show significantly larger aggradation component and longer preservation duration, in more continental/proximal depositional facies. Narrow margins are characterized by enhanced erosion and by-pass during transgression. Through a parametric analysis we constrain the relative contribution of lithosphere deformation and surface processes on the stratigraphic trends and show that both may contribute equally to the stratigraphic architecture. For example, enhanced erosion in narrow margins impacts the volume of sediments delivered to the basin, which, in turn, significantly increases the subsidence. Our simulations also underline the importance of the assumed sediment transport length, which controls whether the main depocentres remain in the necking zone or reach the more distal parts of the margin.
Invariants of polarization transformations.
Sadjadi, Firooz A
2007-05-20
The use of polarization-sensitive sensors is being explored in a variety of applications. Polarization diversity has been shown to improve the performance of the automatic target detection and recognition in a significant way. However, it also brings out the problems associated with processing and storing more data and the problem of polarization distortion during transmission. We present a technique for extracting attributes that are invariant under polarization transformations. The polarimetric signatures are represented in terms of the components of the Stokes vectors. Invariant algebra is then used to extract a set of signature-related attributes that are invariant under linear transformation of the Stokes vectors. Experimental results using polarimetric infrared signatures of a number of manmade and natural objects undergoing systematic linear transformations support the invariancy of these attributes.
Deformation signature from the Gamow-Teller decay of N=Z nuclei
Miehe, Ch.; Dessagne, Ph.; Huck, A.; Knipper, A.; Marguier, G.; Longour, C.; Rauch, V.; Giovinazzo, J.; Borge, M. J. G.; Piqueras, I.; Tengblad, O.; Jokinen, A.; Ramdhane, M.
1998-12-21
The {sup 76}Sr (N=Z=38) and the {sup 72}Kr (N=Z=36) {beta}{sup +} EC decay have been studied at the CERN/ISOLDE PSB facility where their beta-gamma and delayed particle decay modes have been investigated. The established decay schemes yield new information on the Gamow-Teller (GT) strength spread over the J{sup {pi}}=1{sup +} states in the daughter nuclei. The delayed proton emission of an N=Z nucleus is observed for the first time in the case of {sup 76}Sr. The experimental GT strength intensities and distributions are discussed in the light of the theoretical estimates for oblate and prolate deformations.
The Teton fault, Wyoming: Topographic signature, neotectonics, and mechanisms of deformation
NASA Technical Reports Server (NTRS)
Byrd, John O. D.; Smith, Robert B.; Geissman, John W.
1994-01-01
We integrated geophysical and geological methods to evalute the structural evolution of the active Teton normal fault, Wyoming, and its role in the development of the dramatic topography of Teton Range and Jackson Hole. Comparison of variations in surface offsets with the topographic expression of the Teton range crest and drainage divide, and the overall structure of the range, suggests that the effects ofpostglacial faulting cannot be discriminated from the influence of pre-extensional structures and differential; erosion on the footwall topography. In contrast, the effects of multiple scarp-forming normal faulting earthquakes are expressed by the anomalous drainage pattern and westward tilt of the hanging wall, Jackson Hole, toward the Teton fault. Kinematic boundary element fault models suggest that the westward tilt of the valley floor is the product of 110-125 m of displacement on a 45 deg-75 deg E dipping Teton fault in the past 25,000-75,000 years. Comparisons with historic normal faulting earthquake displacements imply that this range of displacement corresponds to 10-50, M greater than 7 scarp-forming earthquakes. A total throw of 2.5 to 3.5 km across the Teton fault is suggested by inverse ray-tracing and forward gravity models. These models also suggest that Laramide age structures have been offset across the Teton fault and obscure its geophysical signature but also continue to influence the structural and topographic expression of the footwall and hanging wall blocks. Paleomagnetic analyses of the approximately 2.0 Ma Huckelberry Ridge Tuff suggest that the overall westward tilt of the Teton Range is a result ofabout 10 deg of west side down tilt across the Teton fault since tuff emplacement. This suggests that much if not all of the throw across the Teton fault has accumulated in the past 2 m.y. Complex demagnetization and rock magnetic behavior and local emplacement of the Huckleberry Ridge Tuff on preexisting topogrpahy preclude determination of
Temporal shape analysis via the spectral signature.
Bernardis, Elena; Konukoglu, Ender; Ou, Yangming; Metaxas, Dimitris N; Desjardins, Benoit; Pohl, Kilian M
2012-01-01
In this paper, we adapt spectral signatures for capturing morphological changes over time. Advanced techniques for capturing temporal shape changes frequently rely on first registering the sequence of shapes and then analyzing the corresponding set of high dimensional deformation maps. Instead, we propose a simple encoding motivated by the observation that small shape deformations lead to minor refinements in the spectral signature composed of the eigenvalues of the Laplace operator. The proposed encoding does not require registration, since spectral signatures are invariant to pose changes. We apply our representation to the shapes of the ventricles extracted from 22 cine MR scans of healthy controls and Tetralogy of Fallot patients. We then measure the accuracy score of our encoding by training a linear classifier, which outperforms the same classifier based on volumetric measurements.
NASA Astrophysics Data System (ADS)
Chatzinikos, Miltiadis; Dermanis, Athanasios
2017-04-01
By considering a deformable geodetic network, deforming in a linear-in-time mode, according to a coordinate-invariant model, it becomes possible to get an insight into the rank deficiency of the stacking procedure, which is the standard method for estimating initial station coordinates and constant velocities, from coordinate time series. Comparing any two out of the infinitely many least squares estimates of stacking unknowns (initial station coordinates, velocity components and transformation parameters for the reference system in each data epoch), it is proven that the two solutions differ only by a linear-in-time trend in the transformation parameters. These pass over to the initial coordinates (the constant term) and to the velocity estimates (the time coefficient part). While the difference in initial coordinates is equivalent to a change of the reference system at the initial epoch, the differences in velocity components do not comply with those predicted by the same change of reference system for all epochs. Consequently, the different velocity component estimates, obtained by introducing different sets of minimal constraints, correspond to physically different station velocities, which are therefore non-estimable quantities. The theoretical findings are numerically verified for a global, a regional and a local network, by obtaining solutions based on four different types of minimal constraints, three usual algebraic ones (inner or partial inner) and the lately introduced kinematic constraints. Finally, by resorting to the basic ideas of Felix Tisserand, it is explained why the station velocities are non-estimable quantities in a very natural way. The problem of the optimal choice of minimal constraints and, hence, of the corresponding spatio-temporal reference system is shortly discussed.
NASA Astrophysics Data System (ADS)
Chatzinikos, Miltiadis; Dermanis, Athanasios
2016-11-01
By considering a deformable geodetic network, deforming in a linear-in-time mode, according to a coordinate-invariant model, it becomes possible to get an insight into the rank deficiency of the stacking procedure, which is the standard method for estimating initial station coordinates and constant velocities, from coordinate time series. Comparing any two out of the infinitely many least squares estimates of stacking unknowns (initial station coordinates, velocity components and transformation parameters for the reference system in each data epoch), it is proven that the two solutions differ only by a linear-in-time trend in the transformation parameters. These pass over to the initial coordinates (the constant term) and to the velocity estimates (the time coefficient part). While the difference in initial coordinates is equivalent to a change of the reference system at the initial epoch, the differences in velocity components do not comply with those predicted by the same change of reference system for all epochs. Consequently, the different velocity component estimates, obtained by introducing different sets of minimal constraints, correspond to physically different station velocities, which are therefore non-estimable quantities. The theoretical findings are numerically verified for a global, a regional and a local network, by obtaining solutions based on four different types of minimal constraints, three usual algebraic ones (inner or partial inner) and the lately introduced kinematic constraints. Finally, by resorting to the basic ideas of Felix Tisserand, it is explained why the station velocities are non-estimable quantities in a very natural way. The problem of the optimal choice of minimal constraints and, hence, of the corresponding spatio-temporal reference system is shortly discussed.
Scale invariance vs conformal invariance
NASA Astrophysics Data System (ADS)
Nakayama, Yu
2015-03-01
In this review article, we discuss the distinction and possible equivalence between scale invariance and conformal invariance in relativistic quantum field theories. Under some technical assumptions, we can prove that scale invariant quantum field theories in d = 2 space-time dimensions necessarily possess the enhanced conformal symmetry. The use of the conformal symmetry is well appreciated in the literature, but the fact that all the scale invariant phenomena in d = 2 space-time dimensions enjoy the conformal property relies on the deep structure of the renormalization group. The outstanding question is whether this feature is specific to d = 2 space-time dimensions or it holds in higher dimensions, too. As of January 2014, our consensus is that there is no known example of scale invariant but non-conformal field theories in d = 4 space-time dimensions under the assumptions of (1) unitarity, (2) Poincaré invariance (causality), (3) discrete spectrum in scaling dimensions, (4) existence of scale current and (5) unbroken scale invariance in the vacuum. We have a perturbative proof of the enhancement of conformal invariance from scale invariance based on the higher dimensional analogue of Zamolodchikov's c-theorem, but the non-perturbative proof is yet to come. As a reference we have tried to collect as many interesting examples of scale invariance in relativistic quantum field theories as possible in this article. We give a complementary holographic argument based on the energy-condition of the gravitational system and the space-time diffeomorphism in order to support the claim of the symmetry enhancement. We believe that the possible enhancement of conformal invariance from scale invariance reveals the sublime nature of the renormalization group and space-time with holography. This review is based on a lecture note on scale invariance vs conformal invariance, on which the author gave lectures at Taiwan Central University for the 5th Taiwan School on Strings and
Multiparameter deformation theory for quantum confined systems
Aleixo, A. N. F.; Balantekin, A. B.
2009-11-15
We introduce a generalized multiparameter deformation theory applicable to all supersymmetric and shape-invariant systems. Taking particular choices for the deformation factors used in the construction of the deformed ladder operators, we show that we can generalize the one-parameter quantum-deformed harmonic oscillator models and build alternative multiparameter deformed models that are also shape invariant like the primary undeformed system.
NASA Astrophysics Data System (ADS)
Vilaseca, Géraud; Deplus, Christine; Escartin, Javier; Ballu, Valérie; Nomikou, Paraskevi; Mével, Catherine; Andreani, Muriel
2016-04-01
Bottom pressure, tilt and seawater physical-properties were monitored for a year using two instruments within the immerged Santorini caldera (Greece). Piggy-backed on the CALDERA2012 cruise, this geodetic experiment was designed to monitor evolution of the 2011-2012 Santorini unrest. Conducted during a quiescent period, it allowed us to study oceanographic and atmospheric signal in our data series. We observe periodic oceanographic signals associated with tides, and seiches that are likely linked to both the caldera and Cretan basin geometries. In winter, the caldera witnesses sudden cooling events that tilt an instrument towards the Southeast, indicating cold-water influx likely originating from the north-western passage between Thirasia and Oia. We do not obtain evidence of long-term vertical seafloor deformation from the pressure signal, although it may be masked by instrumental drift. However, tilt data suggests a local seafloor tilt event ~1 year after the end of the unrest period which could be consistent with inflation under or near Nea Kameni. In addition, we illustrate that tilt sensor can roughly record seismic induced ground motion which in our case led to a shift in sensors attitude for one seismic event. Seafloor geodetic data recorded at the bottom of the Santorini caldera illustrates that the oceanographic signature is an important part of the signal, which needs to be considered for monitoring volcanic or geological seafloor deformation in shallow-water and/or nearshore areas.
NASA Astrophysics Data System (ADS)
Gomez, F. G.; Johnson, H. E., III; LeWinter, A. L.; Finnegan, D. C.; Sandvol, E. A.; Nayak, A.; Hurwitz, S.
2014-12-01
Geysers are important subjects for studying processes involved with multi-phase eruptions. As part of a larger field effort, this study applies imaging geodesy and seismology to study eruptive cycles of the Lone Star Geyser in Yellowstone National Park. Lone Star Geyser is an ideal candidate for such study, as it erupts with a nearly regular period of approximately 3 hours. The geyser includes a 5 m diameter cone that rises 2 meters above the sinter terrace, and the entire system can be viewed from a nearby hillside. Fieldwork was accomplished during April 2014. Ground-based interferometric radar (GBIR) and terrestrial laser scanning (TLS) were used to image possible surface deformations associated with Lone Star Geyer's eruption cycles. Additional observations were provided by global positioning system (GPS) measurements and six broad-band seismometers deployed in the immediate vicinity of the geyser. The GBIR and TLS were deployed approximately 65 meters from the sinter cone of the geyser. The GBIR involves a ku-band radar (1.7 cm wavelength) that is sensitive to approximately half-millimeter changes in the line-of-sight distance. Radar images were acquired every minute for 3 or more eruptions per day. Temporally redundant, overlapping interferograms were used to improve the sensitivity and interpolate a minute-wise time series of line-of-sight displacement, and efforts were made to account for possible path-delay effects resulting from water vapor around the geyser cone. Repeat (every minute) high-speed TLS scans were acquired for multiple eruption cycles over the course of two-days. Resulting measurement point spacing on the sinter cone was ~3cm. The TLS point-clouds were geo-referenced using static surveyed reflectors and scanner positions. In addition to measuring ground deformation, filtering and classification of the TLS point cloud was used to construct a mask that allows radar interferometry to exclude non-ground areas (vegetation, snow, sensors
Biswas, Tora; Pawale, Vijaykumar S; Choudhury, Devapriya; Roy, Rajendra P
2014-04-22
Transpeptidase sortase catalyzes the covalent anchoring of surface proteins to the cell wall in Gram-positive bacteria. Sortase A (SrtA) of Staphylococcus aureus is a prototype enzyme and considered a bona fide drug target because several substrate proteins are virulence-related and implicated in pathogenesis. Besides, SrtA also works as a versatile tool in protein engineering. Surface proteins destined for cell wall anchoring contain a LPXTG sequence located in their C-terminus which serves as a substrate recognition motif for SrtA. Recent studies have implicated substrate-induced conformational dynamics in SrtA. In the present work, we have explored the roles of invariant Leu and Pro residues of the substrate in modulating the enzyme dynamics with a view to understand the selection process of a catalytically competent substrate. Overall results of molecular dynamics simulations and experiments carried out with noncanonical substrates and site-directed mutagenesis reveal that the kinked conformation due to Pro in LPXTG is obligatory for productive binding but does not per se control the enzyme dynamics. The Leu residue of the substrate appears to play the crucial role of an anchor to the beta6-beta7 loop directing the conformational transition of the enzyme from an "open" to a "closed" state subsequent to which the Pro residue facilitates the consummation of binding through predominant engagement of the loop and catalytic motif residues in hydrophobic interactions. Collectively, our study provides insights about specificity, tolerance, and conformational sorting of substrate by SrtA. These results have important implications in designing newer substrates and inhibitors for this multifaceted enzyme.
NASA Astrophysics Data System (ADS)
Long, Maureen D.; Jackson, Kenneth G.; McNamara, John F.
2016-01-01
Seismic anisotropy in the upper mantle beneath continental interiors is generally complicated, with contributions from both the lithosphere and the asthenosphere. Previous studies of SKS splitting beneath the eastern United States have yielded evidence for complex and laterally variable anisotropy, but until the recent arrival of the USArray Transportable Array (TA) the station coverage has been sparse. Here we present SKS splitting measurements at TA stations in eastern North America and compare the measured fast directions with indicators such as absolute plate motion, surface geology, and magnetic lineations. We find few correlations between fast directions and absolute plate motion, except in the northeastern U.S. and southern Canada, where some stations exhibit variations in apparent splitting with backazimuth that would suggest multiple layers of anisotropy. A region of the southeastern U.S. is dominated by null SKS arrivals over a range of backazimuths, consistent with previous work. We document a pattern of fast directions parallel to the Appalachian mountain chain, suggesting a contribution from lithospheric deformation associated with Appalachian orogenesis. Overall, our measurements suggest that upper mantle anisotropy beneath the eastern United States is complex, with likely contributions from both asthenospheric and lithospheric anisotropy in many regions.
NASA Astrophysics Data System (ADS)
Agliardi, F.; Vinciguerra, S.; Dobbs, M. R.; Zanchetta, S.
2014-12-01
Fabric anisotropy is a key control of rock behavior in different geological settings and over different timescales. However, the effect of tectonically folded fabrics on the brittle strength and failure mode of metamorphic rocks is poorly understood. Recent data, obtained from uniaxial compression experiments on folded gneiss (Agliardi et al., 2014), demonstrated that their brittle failure modes depend upon the arrangement of two anisotropies (i.e. foliation and fold axial planes) and that rock strength correlates with failure mode. Since lithostatic pressure may significantly affect this rock behavior, we investigated its effect in triaxial compression experiments. We tested the Monte Canale Gneiss (Italian Alps), characterized by low phyllosilicate content and compositional layering folded at the cm-scale. We used a servo-controlled hydraulic loading system to test 19 air-dry cylindrical specimens (ø = 54 mm) that were characterized both in terms of fold geometry and orientation of foliation and fold axial planes to the axial load direction. The specimens were instrumented with direct contact axial and circumferential strain gauges. Acoustic emissions and P- and S-wave velocities were measured by piezoelectric transducers mounted in the compression platens. The tests were performed at confining pressures of 40 MPa and axial strain rates of 5*10-6 s-1. Post-failure study of fracture mechanisms and related microfabric controls was undertaken using X-ray CT, optical microscopy and SEM. Samples failed in three distinct brittle modes produced by different combinations of fractures parallel to foliation, fractures parallel to fold axial planes, or mm-scale shear bands. The failure modes, consistent with those described in uniaxial compression experiments, were found to be associated with distinct stress-strain and acoustic emission signatures. Failure modes involving quartz-dominated axial plane anisotropy correspond to higher peak strength and axial strain, less
Frank, Steven A
2016-01-01
In nematodes, environmental or physiological perturbations alter death's scaling of time. In human cancer, genetic perturbations alter death's curvature of time. Those changes in scale and curvature follow the constraining contours of death's invariant geometry. I show that the constraints arise from a fundamental extension to the theories of randomness, invariance and scale. A generalized Gompertz law follows. The constraints imposed by the invariant Gompertz geometry explain the tendency of perturbations to stretch or bend death's scaling of time. Variability in death rate arises from a combination of constraining universal laws and particular biological processes.
Frank, Steven A.
2016-01-01
In nematodes, environmental or physiological perturbations alter death’s scaling of time. In human cancer, genetic perturbations alter death’s curvature of time. Those changes in scale and curvature follow the constraining contours of death’s invariant geometry. I show that the constraints arise from a fundamental extension to the theories of randomness, invariance and scale. A generalized Gompertz law follows. The constraints imposed by the invariant Gompertz geometry explain the tendency of perturbations to stretch or bend death’s scaling of time. Variability in death rate arises from a combination of constraining universal laws and particular biological processes. PMID:27785361
NASA Astrophysics Data System (ADS)
Chitea, F.; Mitrofan, H.; Marin, C.; Anghelache, M. A.; Tudorache, A.
2009-04-01
recorded one of the main crustal events (3.3≤Mw≤4.4) of the Marasesti-Galati lineament. The above-indicated time-lags provided obvious evidence that the considered crustal earthquakes were neither foreshocks, nor aftershocks of the strong intermediate-depth events. Instead, each succession of "Vrancioaia crustal - strong subcrustal - Marasesti-Galati crustal" events appeared to define a major lithospheric deformation episode. In the case of the last recorded episode ("centered" on the strong subcrustal earthquake of 27 October 2004), corroborating evidence that some kind of long-range lithospheric deformation indeed took place has been provided by Na-K-Mg geothermometry anomalies recorded at a deep-origin groundwater discharge (Slanic Moldova): while the corresponding "forerunning" crustal earthquake of Vrancioaia region had occurred on 10 February 2003, the hydrogeochemically anomalous behavior has been continuously manifest from April 2003 until October 2004. The previously-discussed results revealed that some kind of long-range interdependence seemed to exist between various phenomena (subcrustal and crustal seismicity, groundwater chemistry fluctuations) that occurred in a broad region associated to the Vrancea "nest" of strong earthquakes. Integrated monitoring of the indicated phenomena might further provide precursor signatures of impending catastrophic Vrancea earthquakes. At the same time, there can be assessed possible influences that major lithospheric deformation episodes, related to Vrancea zone, might exert on the seismicity of apparently remote areas (that of the major city of Galati, for instance).
2010-01-01
principle’s application to many common devices from jar wrenches to rock-climbing cams. 1 Introduction What principles should guide the design of...this paper we explore the possible role of the fingers in adapting to variations in object shape and pose. One common design approach is to adapt to...several fingers, the job of gracefully adapting to shape and pose variations may fall on the finger form. This work explores grasp invariance over shape and
View Invariant Gait Recognition
NASA Astrophysics Data System (ADS)
Seely, Richard D.; Goffredo, Michela; Carter, John N.; Nixon, Mark S.
Recognition by gait is of particular interest since it is the biometric that is available at the lowest resolution, or when other biometrics are (intentionally) obscured. Gait as a biometric has now shown increasing recognition capability. There are many approaches and these show that recognition can achieve excellent performance on current large databases. The majority of these approaches are planar 2D, largely since the early large databases featured subjects walking in a plane normal to the camera view. To extend deployment capability, we need viewpoint invariant gait biometrics. We describe approaches where viewpoint invariance is achieved by 3D approaches or in 2D. In the first group, the identification relies on parameters extracted from the 3D body deformation during walking. These methods use several video cameras and the 3D reconstruction is achieved after a camera calibration process. On the other hand, the 2D gait biometric approaches use a single camera, usually positioned perpendicular to the subject’s walking direction. Because in real surveillance scenarios a system that operates in an unconstrained environment is necessary, many of the recent gait analysis approaches are orientated toward view-invariant gait recognition.
Geometry-invariant resonant cavities
NASA Astrophysics Data System (ADS)
Liberal, I.; Mahmoud, A. M.; Engheta, N.
2016-03-01
Resonant cavities are one of the basic building blocks in various disciplines of science and technology, with numerous applications ranging from abstract theoretical modelling to everyday life devices. The eigenfrequencies of conventional cavities are a function of their geometry, and, thus, the size and shape of a resonant cavity is selected to operate at a specific frequency. Here we demonstrate theoretically the existence of geometry-invariant resonant cavities, that is, resonators whose eigenfrequencies are invariant with respect to geometrical deformations of their external boundaries. This effect is obtained by exploiting the unusual properties of zero-index metamaterials, such as epsilon-near-zero media, which enable decoupling of the temporal and spatial field variations in the lossless limit. This new class of resonators may inspire alternative design concepts, and it might lead to the first generation of deformable resonant devices.
Geometry-invariant resonant cavities
Liberal, I.; Mahmoud, A. M.; Engheta, N.
2016-01-01
Resonant cavities are one of the basic building blocks in various disciplines of science and technology, with numerous applications ranging from abstract theoretical modelling to everyday life devices. The eigenfrequencies of conventional cavities are a function of their geometry, and, thus, the size and shape of a resonant cavity is selected to operate at a specific frequency. Here we demonstrate theoretically the existence of geometry-invariant resonant cavities, that is, resonators whose eigenfrequencies are invariant with respect to geometrical deformations of their external boundaries. This effect is obtained by exploiting the unusual properties of zero-index metamaterials, such as epsilon-near-zero media, which enable decoupling of the temporal and spatial field variations in the lossless limit. This new class of resonators may inspire alternative design concepts, and it might lead to the first generation of deformable resonant devices. PMID:27010103
Neutrinos as Probes of Lorentz Invariance
Díaz, Jorge S.
2014-01-01
Neutrinos can be used to search for deviations from exact Lorentz invariance. The worldwide experimental program in neutrino physics makes these particles a remarkable tool to search for a variety of signals that could reveal minute relativity violations. This paper reviews the generic experimental signatures of the breakdown of Lorentz symmetry in the neutrino sector.
Invariant variational structures on fibered manifolds
NASA Astrophysics Data System (ADS)
Krupka, Demeter
2015-12-01
The aim of this paper is to present a relatively complete theory of invariance of global, higher-order integral variational functionals in fibered spaces, as developed during a few past decades. We unify and extend recent results of the geometric invariance theory; new results on deformations of extremals are also included. We show that the theory can be developed by means of the general concept of invariance of a differential form in geometry, which does not require different ad hoc modifications. The concept applies to invariance of Lagrangians, source forms and Euler-Lagrange forms, as well as to extremals of the given variational functional. Equations for generators of invariance transformations of the Lagrangians and the Euler-Lagrange forms are characterized in terms of Lie derivatives. As a consequence of invariance, we derive the global Noether's theorem on existence of conserved currents along extremals, and discuss the meaning of conservation equations. We prove a theorem describing extremals, whose deformations by a vector field are again extremals. The general settings and structures we use admit extension of the global invariance theory to variational principles in physics, especially in field theory.
Generalizing twisted gauge invariance
Duenas-Vidal, Alvaro; Vazquez-Mozo, Miguel A.
2009-05-01
We discuss the twisting of gauge symmetry in noncommutative gauge theories and show how this can be generalized to a whole continuous family of twisted gauge invariances. The physical relevance of these twisted invariances is discussed.
NASA Astrophysics Data System (ADS)
Nakayama, Yu
2017-02-01
We show that 11-dimensional supergravity in Euclidean signature admits an exact classical solution with isometry corresponding to a three-dimensional scale-invariant field theory without conformal invariance. We also construct the holographic renormalization group flow that connects the known UV conformal fixed point and the new scale-invariant but not conformal fixed point. In view of holography, the existence of such classical solutions suggests that the topologically twisted M2-brane gauge theory possesses a scale-invariant but not conformal phase.
NASA Astrophysics Data System (ADS)
Kaur, Jasmeet; Bansal, Neeraj; Bhati, A. K.; Kumar, R.; Sharma, Vijay R.; Kapoor, K.; Kumar, V.; Kaur, Navneet
2017-02-01
The g-factor and the static quadrupole moment of a magnetic rotational band head 21/2- at 2121 keV in 131La have been determined by means of the time-differential perturbed angular distribution technique. The measured value of the g-factor, + 1.060 (4), is in agreement with the theoretical value for a three quasi-proton, π3 {11/2- [ 505 ] ⊗5/2+ [ 422 ] ⊗5/2+ [ 413 ] } Nilsson configuration assignment. The observed spectroscopic quadrupole moment ratio, Qs (21/2- ,131 La)/Qs (19/2- ,137 La) = 0.457 (4), supports the collective oblate shape (γ ∼ - 60 °) with quadrupole deformation β2 < 0.07. The half-life of the 21/2- state, 37.2(1) ns, is re-measured with better accuracy.
Conformal Invariance of Graphene Sheets
Giordanelli, I.; Posé, N.; Mendoza, M.; Herrmann, H. J.
2016-01-01
Suspended graphene sheets exhibit correlated random deformations that can be studied under the framework of rough surfaces with a Hurst (roughness) exponent 0.72 ± 0.01. Here, we show that, independent of the temperature, the iso-height lines at the percolation threshold have a well-defined fractal dimension and are conformally invariant, sharing the same statistical properties as Schramm-Loewner evolution (SLEκ) curves with κ = 2.24 ± 0.07. Interestingly, iso-height lines of other rough surfaces are not necessarily conformally invariant even if they have the same Hurst exponent, e.g. random Gaussian surfaces. We have found that the distribution of the modulus of the Fourier coefficients plays an important role on this property. Our results not only introduce a new universality class and place the study of suspended graphene membranes within the theory of critical phenomena, but also provide hints on the long-standing question about the origin of conformal invariance in iso-height lines of rough surfaces. PMID:26961723
NASA Astrophysics Data System (ADS)
Pyati, Vittal P.
The reduction of vehicle radar signature is accomplished by means of vehicle shaping, the use of microwave frequencies-absorbent materials, and either passive or active cancellation techniques; such techniques are also useful in the reduction of propulsion system-associated IR emissions. In some anticipated scenarios, the objective is not signature-reduction but signature control, for deception, via decoy vehicles that mimic the signature characteristics of actual weapons systems. As the stealthiness of airframes and missiles increases, their propulsion systems' exhaust plumes assume a more important role in detection by an adversary.
Gravity as the breakdown of conformal invariance
NASA Astrophysics Data System (ADS)
Amelino-Camelia, Giovanni; Arzano, Michele; Gubitosi, Giulia; Magueijo, João
2015-06-01
In this paper, we propose that at the beginning of the universe gravity existed in a limbo either because it was switched off or because it was only conformally coupled to all particles. This picture can be reverse-engineered from the requirement that the cosmological perturbations be (nearly) scale-invariant without the need for inflation. It also finds support in recent results in quantum gravity suggesting that spacetime becomes two-dimensional at super-Planckian energies. We advocate a novel top-down approach to cosmology based on the idea that gravity and the Big Bang Universe are relics from the mechanism responsible for breaking the fundamental conformal invariance. Such a mechanism should leave clear signatures in departures from scale-invariance in the primordial power spectrum and the level of gravity waves generated.
Rainbow gravity and scale-invariant fluctuations
NASA Astrophysics Data System (ADS)
Amelino-Camelia, Giovanni; Arzano, Michele; Gubitosi, Giulia; Magueijo, João
2013-08-01
We reexamine a recently proposed scenario where the deformed dispersion relations associated with a flow of the spectral dimension to a UV value of 2 leads to a scale-invariant spectrum of cosmological fluctuations, without the need for inflation. In that scenario Einstein gravity was assumed. The theory displays a wavelength-dependent speed of light but by transforming to a suitable “rainbow frame” this feature can be removed, at the expense of modifying gravity. We find that the ensuing rainbow gravity theory is such that gravity switches off at high energy (or at least leads to a universal conformal coupling). This explains why the fluctuations are scale invariant on all scales: there is no horizon scale as such. For dispersion relations that do not lead to exact scale invariance we find instead esoteric inflation in the rainbow frame. We argue that these results shed light on the behavior of gravity under the phenomenon of dimensional reduction.
Conformal differential invariants
NASA Astrophysics Data System (ADS)
Kruglikov, Boris
2017-03-01
We compute the Hilbert polynomial and the Poincaré function counting the number of fixed jet-order differential invariants of conformal metric structures modulo local diffeomorphisms, and we describe the field of rational differential invariants separating generic orbits of the diffeomorphism pseudogroup action. This resolves the local recognition problem for conformal structures.
Geometry and Radiometry Invariant Matched Manifold Detection.
Sharon, Ran; Francos, Joseph M; Hagege, Rami R
2017-09-01
Consider a set of deformable objects undergoing geometric and radiometric transformations. As a result of the action of these transformations, the set of different realizations of each object is generally a manifold in the space of observations. Assuming the geometric deformations an object undergoes, belong to some finite dimensional family, it has been shown that the universal manifold embedding (UME) provides a set of nonlinear operators that universally maps each of the different manifolds, where each manifold is generated by the set all of possible appearances of a single object, into a distinct linear subspace of an Euclidean space. In this paper, we generalize this framework to the case where the observed object undergoes both an affine geometric transformation, and a monotonic radiometric transformation, and present a novel framework for the detection and recognition of the deformable objects. Applying to each of the observations an operator that makes it invariant to monotonic amplitude transformations, but is geometry-covariant with the affine transformation, the set of all possible observations on that object is mapped by the UME into a single linear subspace-invariant with respect to both the geometric and radiometric transformations. The embedding of the space of observations is independent of the specific observed object; hence it is universal. The invariant representation of the object is the basis of a matched manifold detection and tracking framework of objects that undergo complex geometric and radiometric deformations: the observed surface is tessellated into a set of tiles such that the deformation of each one is well approximated by an affine geometric transformation and a monotonic transformation of the measured intensities. Since each tile is mapped by the radiometry invariant UME to a distinct linear subspace, the detection and tracking problems are solved by evaluating distances between linear subspaces. Classification in this context
Cosmological disformal invariance
Domènech, Guillem; Sasaki, Misao; Naruko, Atsushi E-mail: naruko@th.phys.titech.ac.jp
2015-10-01
The invariance of physical observables under disformal transformations is considered. It is known that conformal transformations leave physical observables invariant. However, whether it is true for disformal transformations is still an open question. In this paper, it is shown that a pure disformal transformation without any conformal factor is equivalent to rescaling the time coordinate. Since this rescaling applies equally to all the physical quantities, physics must be invariant under a disformal transformation, that is, neither causal structure, propagation speed nor any other property of the fields are affected by a disformal transformation itself. This fact is presented at the action level for gravitational and matter fields and it is illustrated with some examples of observable quantities. We also find the physical invariance for cosmological perturbations at linear and high orders in perturbation, extending previous studies. Finally, a comparison with Horndeski and beyond Horndeski theories under a disformal transformation is made.
Cosmological disformal invariance
NASA Astrophysics Data System (ADS)
Domènech, Guillem; Naruko, Atsushi; Sasaki, Misao
2015-10-01
The invariance of physical observables under disformal transformations is considered. It is known that conformal transformations leave physical observables invariant. However, whether it is true for disformal transformations is still an open question. In this paper, it is shown that a pure disformal transformation without any conformal factor is equivalent to rescaling the time coordinate. Since this rescaling applies equally to all the physical quantities, physics must be invariant under a disformal transformation, that is, neither causal structure, propagation speed nor any other property of the fields are affected by a disformal transformation itself. This fact is presented at the action level for gravitational and matter fields and it is illustrated with some examples of observable quantities. We also find the physical invariance for cosmological perturbations at linear and high orders in perturbation, extending previous studies. Finally, a comparison with Horndeski and beyond Horndeski theories under a disformal transformation is made.
Explicit Krawtchouk moment invariants for invariant image recognition
NASA Astrophysics Data System (ADS)
Xiao, Bin; Zhang, Yanhong; Li, Linping; Li, Weisheng; Wang, Guoyin
2016-03-01
The existing Krawtchouk moment invariants are derived by a linear combination of geometric moment invariants. This indirect method cannot achieve perfect performance in rotation, scale, and translation (RST) invariant image recognition since the derivation of these invariants are not built on Krawtchouk polynomials. A direct method to derive RST invariants from Krawtchouk moments, named explicit Krawtchouk moment invariants, is proposed. The proposed method drives Krawtchouk moment invariants by algebraically eliminating the distorted (i.e., rotated, scaled, and translated) factor contained in the Krawtchouk moments of distorted image. Experimental results show that, compared with the indirect methods, the proposed approach can significantly improve the performance in terms of recognition accuracy and noise robustness.
Discrete scale invariant quantum dynamics and universal quantum beats in Bose gases
NASA Astrophysics Data System (ADS)
Maki, J.; Jiang, S. J.; Zhou, F.
2017-06-01
We study the signature of classical scale invariance in the far-from-equilibrium quantum dynamics of two-dimensional Bose gases. We show that the density profile displays a scale invariant logarithmic singularity near the center. In addition, the density oscillates due to quantum beats with universal structures. Namely, the frequencies of the beats can be connected with one another by a universal discrete scale transformation induced by the classical scale invariance. The experimental applicability of these results is then discussed.
Möbius Invariants of Shapes and Images
NASA Astrophysics Data System (ADS)
Marsland, Stephen; McLachlan, Robert I.
2016-08-01
Identifying when different images are of the same object despite changes caused by imaging technologies, or processes such as growth, has many applications in fields such as computer vision and biological image analysis. One approach to this problem is to identify the group of possible transformations of the object and to find invariants to the action of that group, meaning that the object has the same values of the invariants despite the action of the group. In this paper we study the invariants of planar shapes and images under the Möbius group PSL(2,C), which arises in the conformal camera model of vision and may also correspond to neurological aspects of vision, such as grouping of lines and circles. We survey properties of invariants that are important in applications, and the known Möbius invariants, and then develop an algorithm by which shapes can be recognised that is Möbius- and reparametrization-invariant, numerically stable, and robust to noise. We demonstrate the efficacy of this new invariant approach on sets of curves, and then develop a Möbius-invariant signature of grey-scale images.
Invariants of Boundary Link Cobordism
NASA Astrophysics Data System (ADS)
Sheiham, Desmond
2001-10-01
An n-dimensional μ-component boundary link is a codimension 2 embedding of spheres L=bigsqcup_{μ}S^n subset S^{n+2} such that there exist μ disjoint oriented embedded (n+1)-manifolds which span the components of L. An F_μ-link is a boundary link together with a cobordism class of such spanning manifolds. The F_μ-link cobordism group C_n(F_μ) is known to be trivial when n is even but not finitely generated when n is odd. Our main result is an algorithm to decide whether two odd-dimensional F_μ-links represent the same cobordism class in C_{2q-1}(F_μ) assuming q>1. We proceed to compute the isomorphism class of C_{2q-1}(F_μ), generalizing Levine's computation of the knot cobordism group C_{2q-1}(F_1). Our starting point is the algebraic formulation of Levine, Ko and Mio who identify C_{2q-1}(F_μ) with a surgery obstruction group, the Witt group G^{(-1)^q,μ}(Z) of μ-component Seifert matrices. We obtain a complete set of torsion-free invariants by passing from integer coefficients to complex coefficients and by applying the algebraic machinery of Quebbemann, Scharlau and Schulte. Signatures correspond to `algebraically integral' simple self-dual representations of a certain quiver (directed graph with loops). These representations, in turn, correspond to algebraic integers on an infinite disjoint union of real affine varieties. To distinguish torsion classes, we consider rational coefficients in place of complex coefficients, expressing G^{(-1)^q,μ}(Q) as an infinite direct sum of Witt groups of finite-dimensional division Q-algebras with involution. Numerical invariants of such Witt groups are available in the literature.
NASA Astrophysics Data System (ADS)
Li, Youning; Han, Muxin; Grassl, Markus; Zeng, Bei
2017-06-01
Invariant tensors are states in the SU(2) tensor product representation that are invariant under SU(2) action. They play an important role in the study of loop quantum gravity. On the other hand, perfect tensors are highly entangled many-body quantum states with local density matrices maximally mixed. Recently, the notion of perfect tensors has attracted a lot of attention in the fields of quantum information theory, condensed matter theory, and quantum gravity. In this work, we introduce the concept of an invariant perfect tensor (IPT), which is an n-valent tensor that is both invariant and perfect. We discuss the existence and construction of IPTs. For bivalent tensors, the IPT is the unique singlet state for each local dimension. The trivalent IPT also exists and is uniquely given by Wigner’s 3j symbol. However, we show that, surprisingly, 4-valent IPTs do not exist for any identical local dimension d. On the contrary, when the dimension is large, almost all invariant tensors are asymptotically perfect, which is a consequence of the phenomenon of the concentration of measure for multipartite quantum states.
Yang-Baxter invariance of the Nappi-Witten model
NASA Astrophysics Data System (ADS)
Kyono, Hideki; Yoshida, Kentaroh
2016-04-01
We study Yang-Baxter deformations of the Nappi-Witten model with a prescription invented by Delduc, Magro and Vicedo. The deformations are specified by skew-symmetric classical r-matrices satisfying (modified) classical Yang-Baxter equations. We show that the sigma-model metric is invariant under arbitrary deformations (while the coefficient of B-field is changed) by utilizing the most general classical r-matrix. Furthermore, the coefficient of B-field is determined to be the original value from the requirement that the one-loop β-function should vanish. After all, the Nappi-Witten model is the unique conformal theory within the class of the Yang-Baxter deformations preserving the conformal invariance.
Funabashi, Masatoshi
2015-05-01
This study applies information geometry of normal distribution to model Japanese vowels on the basis of the first and second formants. The distribution of Kullback-Leibler (KL) divergence and its decomposed components were investigated to reveal the statistical invariance in the vowel system. The results suggest that although significant variability exists in individual KL divergence distributions, the population distribution tends to converge into a specific log-normal distribution. This distribution can be considered as an invariant distribution for the standard-Japanese speaking population. Furthermore, it was revealed that the mean and variance components of KL divergence are linearly related in the population distribution. The significance of these invariant features is discussed.
Janse Van Rensburg, E.J.
1996-12-31
The geometry of polygonal knots in the cubic lattice may be used to define some knot invariants. One such invariant is the minimal edge number, which is the minimum number of edges necessary (and sufficient) to construct a lattice knot of given type. In addition, one may also define the minimal (unfolded) surface number, and the minimal (unfolded) boundary number; these are the minimum number of 2-cells necessary to construct an unfolded lattice Seifert surface of a given knot type in the lattice, and the minimum number of edges necessary in a lattice knot to guarantee the existence of an unfolded lattice Seifert surface. In addition, I derive some relations amongst these invariants. 8 refs., 5 figs., 2 tabs.
Reparametrization invariant collinear operators
Marcantonini, Claudio; Stewart, Iain W.
2009-03-15
In constructing collinear operators, which describe the production of energetic jets or energetic hadrons, important constraints are provided by reparametrization invariance (RPI). RPI encodes Lorentz invariance in a power expansion about a collinear direction, and connects the Wilson coefficients of operators at different orders in this expansion to all orders in {alpha}{sub s}. We construct reparametrization invariant collinear objects. The expansion of operators built from these objects provides an efficient way of deriving RPI relations and finding a minimal basis of operators, particularly when one has an observable with multiple collinear directions and/or soft particles. Complete basis of operators is constructed for pure glue currents at twist-4, and for operators with multiple collinear directions, including those appearing in e{sup +}e{sup -}{yields}3 jets, and for pp{yields}2 jets initiated via gluon fusion.
Generalized scale invariant theories
NASA Astrophysics Data System (ADS)
Padilla, Antonio; Stefanyszyn, David; Tsoukalas, Minas
2014-03-01
We present the most general actions of a single scalar field and two scalar fields coupled to gravity, consistent with second-order field equations in four dimensions, possessing local scale invariance. We apply two different methods to arrive at our results. One method, Ricci gauging, was known to the literature and we find this to produce the same result for the case of one scalar field as a more efficient method presented here. However, we also find our more efficient method to be much more general when we consider two scalar fields. Locally scale invariant actions are also presented for theories with more than two scalar fields coupled to gravity and we explain how one could construct the most general actions for any number of scalar fields. Our generalized scale invariant actions have obvious applications to early Universe cosmology and include, for example, the Bezrukov-Shaposhnikov action as a subset.
Supersymmetric invariant theories
NASA Astrophysics Data System (ADS)
Esipova, S. R.; Lavrov, P. M.; Radchenko, O. V.
2014-04-01
We study field models for which a quantum action (i.e. the action appearing in the generating functional of Green functions) is invariant under supersymmetric transformations. We derive the Ward identity which is a direct consequence of this invariance. We consider a change of variables in functional integral connected with supersymmetric transformations when its parameter is replaced by a nilpotent functional of fields. Exact form of the corresponding Jacobian is found. We find restrictions on generators of supersymmetric transformations when a consistent quantum description of given field theories exists.
Discussion on Lorentz invariance violation of noncommutative field theory and neutrino oscillation
NASA Astrophysics Data System (ADS)
Luo, Cui-Bai; Shi, Song; Du, Yi-Lun; Wang, Yong-Long; Zong, Hong-Shi
2017-03-01
Depending on deformed canonical anticommutation relations, massless neutrino oscillation based on Lorentz invariance violation in noncommutative field theory is discussed. It is found that the previous studies about massless neutrino oscillation within deformed canonical anticommutation relations should satisfy the condition of new Moyal product and new nonstandard commutation relations. Furthermore, comparing the Lorentz invariant violation parameters A in the previous studies with new Moyal product and new nonstandard commutation relations, we find that the orders of magnitude of noncommutative parameters (Lorentz invariant violation parameters A) is not self-consistent. This inconsistency means that the previous studies of Lorentz invariance violation in noncommutative field theory may not naturally explain massless neutrino oscillation. In other words, it should be impossible to explain neutrino oscillation by Lorentz invariance violation in noncommutative field theory. This conclusion is supported by the latest atmospheric neutrinos experimental results from the super-Kamiokande Collaboration, which show that no evidence of Lorentz invariance violation on atmospheric neutrinos was observed.
Pokhozhaev, Stanislav I
2011-06-30
The notion of Riemann quasi-invariants is introduced and their applications to several conservation laws are considered. The case of nonisentropic flow of an ideal polytropic gas is analysed in detail. Sufficient conditions for gradient catastrophes are obtained. Bibliography: 16 titles.
Kobayashi, Tatsuo; Nitta, Daisuke; Urakawa, Yuko
2016-08-08
Modular invariance is a striking symmetry in string theory, which may keep stringy corrections under control. In this paper, we investigate a phenomenological consequence of the modular invariance, assuming that this symmetry is preserved as well as in a four dimensional (4D) low energy effective field theory. As a concrete setup, we consider a modulus field T whose contribution in the 4D effective field theory remains invariant under the modular transformation and study inflation drived by T. The modular invariance restricts a possible form of the scalar potenntial. As a result, large field models of inflation are hardly realized. Meanwhile, a small field model of inflation can be still accomodated in this restricted setup. The scalar potential traced during the slow-roll inflation mimics the hilltop potential V{sub ht}, but it also has a non-negligible deviation from V{sub ht}. Detecting the primordial gravitational waves predicted in this model is rather challenging. Yet, we argue that it may be still possible to falsify this model by combining the information in the reheating process which can be determined self-completely in this setup.
Modular invariant gaugino condensation
Gaillard, M.K.
1991-05-09
The construction of effective supergravity lagrangians for gaugino condensation is reviewed and recent results are presented that are consistent with modular invariance and yield a positive definite potential of the noscale type. Possible implications for phenomenology are briefly discussed. 29 refs.
NASA Astrophysics Data System (ADS)
Kobayashi, Tatsuo; Nitta, Daisuke; Urakawa, Yuko
2016-08-01
Modular invariance is a striking symmetry in string theory, which may keep stringy corrections under control. In this paper, we investigate a phenomenological consequence of the modular invariance, assuming that this symmetry is preserved as well as in a four dimensional (4D) low energy effective field theory. As a concrete setup, we consider a modulus field T whose contribution in the 4D effective field theory remains invariant under the modular transformation and study inflation drived by T. The modular invariance restricts a possible form of the scalar potenntial. As a result, large field models of inflation are hardly realized. Meanwhile, a small field model of inflation can be still accomodated in this restricted setup. The scalar potential traced during the slow-roll inflation mimics the hilltop potential Vht, but it also has a non-negligible deviation from Vht. Detecting the primordial gravitational waves predicted in this model is rather challenging. Yet, we argue that it may be still possible to falsify this model by combining the information in the reheating process which can be determined self-completely in this setup.
Idiographic Measurement Invariance?
ERIC Educational Resources Information Center
Willoughby, Michael T.; Sideris, John
2007-01-01
In this article, the authors comment on Nesselroade, Gerstorf, Hardy, and Ram's efforts (this issue) to grapple with the challenge of accommodating idiographic assessment as it pertains to measurement invariance (MI). Although the authors are in complete agreement with the motivation for Nesselroade et al.'s work, the authors have concerns about…
Cheng, Miranda C. N.; Duncan, John F. R.; Harrison, Sarah M.; Kachru, Shamit
2017-01-01
In this note, we describe a connection between the enumerative geometry of curves in K3 surfaces and the chiral ring of an auxiliary superconformal field theory. We consider the invariants calculated by Yau–Zaslow (capturing the Euler characters of the moduli spaces of D2-branes on curves of given genus), together with their refinements to carry additional quantum numbers by Katz–Klemm–Vafa (KKV), and Katz–Klemm–Pandharipande (KKP). We show that these invariants can be reproduced by studying the Ramond ground states of an auxiliary chiral superconformal field theory which has recently been observed to give rise to mock modular moonshine for a variety of sporadic simple groups that are subgroups of Conway’s group. We also study equivariant versions of these invariants. A K3 sigma model is specified by a choice of 4-plane in the K3 D-brane charge lattice. Symmetries of K3 sigma models are naturally identified with 4-plane preserving subgroups of the Conway group, according to the work of Gaberdiel–Hohenegger–Volpato, and one may consider corresponding equivariant refined K3 Gopakumar–Vafa invariants. The same symmetries naturally arise in the auxiliary CFT state space, affording a suggestive alternative view of the same computation. We comment on a lift of this story to the generating function of elliptic genera of symmetric products of K3 surfaces.
Cheng, Miranda C. N.; Duncan, John F. R.; Harrison, Sarah M.; ...
2017-01-01
In this note, we describe a connection between the enumerative geometry of curves in K3 surfaces and the chiral ring of an auxiliary superconformal field theory. We consider the invariants calculated by Yau–Zaslow (capturing the Euler characters of the moduli spaces of D2-branes on curves of given genus), together with their refinements to carry additional quantum numbers by Katz–Klemm–Vafa (KKV), and Katz–Klemm–Pandharipande (KKP). We show that these invariants can be reproduced by studying the Ramond ground states of an auxiliary chiral superconformal field theory which has recently been observed to give rise to mock modular moonshine for a variety ofmore » sporadic simple groups that are subgroups of Conway’s group. We also study equivariant versions of these invariants. A K3 sigma model is specified by a choice of 4-plane in the K3 D-brane charge lattice. Symmetries of K3 sigma models are naturally identified with 4-plane preserving subgroups of the Conway group, according to the work of Gaberdiel–Hohenegger–Volpato, and one may consider corresponding equivariant refined K3 Gopakumar–Vafa invariants. The same symmetries naturally arise in the auxiliary CFT state space, affording a suggestive alternative view of the same computation. We comment on a lift of this story to the generating function of elliptic genera of symmetric products of K3 surfaces.« less
NASA Astrophysics Data System (ADS)
Chung, Won Sang; Kim, Jae Yoon
In this paper, the q-deformed circular unit and hyperbolic imaginary unit are studied. With a help of these units, the invariant q-deformed length is defined. As applications, the q-deformed rotation in two dimension and q-deformed special relativity in 1 + 1 dimension are also investigated.
Measurement Invariance versus Selection Invariance: Is Fair Selection Possible?
ERIC Educational Resources Information Center
Borsman, Denny; Romeijn, Jan-Willem; Wicherts, Jelte M.
2008-01-01
This article shows that measurement invariance (defined in terms of an invariant measurement model in different groups) is generally inconsistent with selection invariance (defined in terms of equal sensitivity and specificity across groups). In particular, when a unidimensional measurement instrument is used and group differences are present in…
Measurement Invariance versus Selection Invariance: Is Fair Selection Possible?
ERIC Educational Resources Information Center
Borsman, Denny; Romeijn, Jan-Willem; Wicherts, Jelte M.
2008-01-01
This article shows that measurement invariance (defined in terms of an invariant measurement model in different groups) is generally inconsistent with selection invariance (defined in terms of equal sensitivity and specificity across groups). In particular, when a unidimensional measurement instrument is used and group differences are present in…
Are there p-adic knot invariants?
NASA Astrophysics Data System (ADS)
Morozov, A. Yu.
2016-04-01
We suggest using the Hall-Littlewood version of the Rosso-Jones formula to define the germs of p-adic HOMFLY-PT polynomials for torus knots [ m, n] as coefficients of superpolynomials in a q-expansion. In this form, they have at least the [ m, n] ↔ [ n, m] topological invariance. This opens a new possibility to interpret superpolynomials as p-adic deformations of HOMFLY polynomials and poses a question of generalizing to other knot families, which is a substantial problem for several branches of modern theory.
Markov invariants, plethysms, and phylogenetics.
Sumner, J G; Charleston, M A; Jermiin, L S; Jarvis, P D
2008-08-07
We explore model-based techniques of phylogenetic tree inference exercising Markov invariants. Markov invariants are group invariant polynomials and are distinct from what is known in the literature as phylogenetic invariants, although we establish a commonality in some special cases. We show that the simplest Markov invariant forms the foundation of the Log-Det distance measure. We take as our primary tool group representation theory, and show that it provides a general framework for analyzing Markov processes on trees. From this algebraic perspective, the inherent symmetries of these processes become apparent, and focusing on plethysms, we are able to define Markov invariants and give existence proofs. We give an explicit technique for constructing the invariants, valid for any number of character states and taxa. For phylogenetic trees with three and four leaves, we demonstrate that the corresponding Markov invariants can be fruitfully exploited in applied phylogenetic studies.
NASA Astrophysics Data System (ADS)
Vollmer, Gerhard
2010-10-01
Scientific knowledge should not only be true, it should be as objective as possible. It should refer to a reality independent of any subject. What can we use as a criterion of objectivity? Intersubjectivity (i.e., intersubjective understandability and intersubjective testability) is necessary, but not sufficient. Other criteria are: independence of reference system, independence of method, non-conventionality. Is there some common trait? Yes, there is: invariance under some specified transformations. Thus, we say: A proposition is objective only if its truth is invariant against a change in the conditions under which it was formulated. We give illustrations from geometry, perception, neurobiology, relativity theory, and quantum theory. Such an objectivist position has many advantages.
2010-12-02
evaluating the function ΘP (A) for any fixed A,P is equivalent to solving the so-called Quadratic Assignment Problem ( QAP ), and thus we can employ various...tractable linear programming, spectral, and SDP relaxations of QAP [40, 11, 33]. In particular we discuss recent work [14] on exploiting group...symmetry in SDP relaxations of QAP , which is useful for approximately computing elementary convex graph invariants in many interesting cases. Finally in
Kozin, Scott H; Zlotolow, Dan A
2015-10-01
Madelung deformity of the wrist is more common in females and is often associated with Leri Weill dyschondrosteosis, a mesomelic form of dwarfism. Patients with Madelung deformity often report wrist deformity resulting from the prominence of the relatively long ulna. The typical Madelung deformity is associated with a Vickers ligament that creates a tether across the volar-ulnar radial physis that restricts growth across this segment. The distal radius deforms in the coronal (increasing radial inclination) and the sagittal (increasing volar tilt) planes. There is lunate subsidence and the proximal carpal row adapts to the deformity by forming an upside-down pyramid shape or triangle. Treatment depends on the age at presentation, degree of deformity, and magnitude of symptoms. Mild asymptomatic deformity warrants a period of nonsurgical management with serial x-ray examinations because the natural history is unpredictable. Many patients never require surgical intervention. Progressive deformity in the young child with considerable growth potential remaining requires release of Vickers ligament and radial physiolysis to prevent ongoing deterioration Concomitant ulnar epiphysiodesis may be necessary. Advanced asymptomatic deformity in older children with an unacceptable-appearing wrist or symptomatic deformity are indications for surgery. A dome osteotomy of the radius allows 3-dimensional correction of the deformity. Positive radiographic and clinical results after dome osteotomy have been reported. Copyright © 2015 American Society for Surgery of the Hand. Published by Elsevier Inc. All rights reserved.
Perspective Projection Invariants,
1986-02-01
ORGANIZATION NAME ANC ADDRESS 10. PROGRAM ELEMENT. PROJECT. TASK Artificial Inteligence Laboratory AREA & WORK UNIT NUMBERSO 545 Technology Square dCambridge...AD-AI67 793 PERSPECTIVE PROJECTION INVARIANTS(U) MASSACHUSETTS INST 1/1~ OF TECH CAMBRIDGE ARTIFICIAL INTELLIGENCE LAB VERRI ET AL, FEB 86 AI-M-832...0R020I4 661 SEC R TVC PAGE fjSr .W IlIII UI A 8 gT@OFTNS21 07 1 MASSACHUSETTS INSTITUTE OF TECHNOLOGY ARTIFICIAL INTELLIGENCE LABORATORY and CENTER
Brain Morphometry on Congenital Hand Deformities based on Teichmüller Space Theory.
Peng, Hao; Wang, Xu; Duan, Ye; Frey, Scott H; Gu, Xianfeng
2015-01-01
Congenital Hand Deformities (CHD) are usually occurred between fourth and eighth week after the embryo is formed. Failure of the transformation from arm bud cells to upper limb can lead to an abnormal appearing/functioning upper extremity which is presented at birth. Some causes are linked to genetics while others are affected by the environment, and the rest have remained unknown. CHD patients develop prehension through the use of their hands, which affect the brain as time passes. In recent years, CHD have gain increasing attention and researches have been conducted on CHD, both surgically and psychologically. However, the impacts of CHD on brain structure are not well-understood so far. Here, we propose a novel approach to apply Teichmüller space theory and conformal welding method to study brain morphometry in CHD patients. Conformal welding signature reflects the geometric relations among different functional areas on the cortex surface, which is intrinsic to the Riemannian metric, invariant under conformal deformation, and encodes complete information of the functional area boundaries. The computational algorithm is based on discrete surface Ricci flow, which has theoretic guarantees for the existence and uniqueness of the solutions. In practice, discrete Ricci flow is equivalent to a convex optimization problem, therefore has high numerically stability. In this paper, we compute the signatures of contours on general 3D surfaces with surface Ricci flow method, which encodes both global and local surface contour information. Then we evaluated the signatures of pre-central and post-central gyrus on healthy control and CHD subjects for analyzing brain cortical morphometry. Preliminary experimental results from 3D MRI data of CHD/control data demonstrate the effectiveness of our method. The statistical comparison between left and right brain gives us a better understanding on brain morphometry of subjects with Congenital Hand Deformities, in particular, missing
Brain Morphometry on Congenital Hand Deformities based on Teichmüller Space Theory
Peng, Hao; Wang, Xu; Duan, Ye; Frey, Scott H.; Gu, Xianfeng
2016-01-01
Congenital Hand Deformities (CHD) are usually occurred between fourth and eighth week after the embryo is formed. Failure of the transformation from arm bud cells to upper limb can lead to an abnormal appearing/functioning upper extremity which is presented at birth. Some causes are linked to genetics while others are affected by the environment, and the rest have remained unknown. CHD patients develop prehension through the use of their hands, which affect the brain as time passes. In recent years, CHD have gain increasing attention and researches have been conducted on CHD, both surgically and psychologically. However, the impacts of CHD on brain structure are not well-understood so far. Here, we propose a novel approach to apply Teichmüller space theory and conformal welding method to study brain morphometry in CHD patients. Conformal welding signature reflects the geometric relations among different functional areas on the cortex surface, which is intrinsic to the Riemannian metric, invariant under conformal deformation, and encodes complete information of the functional area boundaries. The computational algorithm is based on discrete surface Ricci flow, which has theoretic guarantees for the existence and uniqueness of the solutions. In practice, discrete Ricci flow is equivalent to a convex optimization problem, therefore has high numerically stability. In this paper, we compute the signatures of contours on general 3D surfaces with surface Ricci flow method, which encodes both global and local surface contour information. Then we evaluated the signatures of pre-central and post-central gyrus on healthy control and CHD subjects for analyzing brain cortical morphometry. Preliminary experimental results from 3D MRI data of CHD/control data demonstrate the effectiveness of our method. The statistical comparison between left and right brain gives us a better understanding on brain morphometry of subjects with Congenital Hand Deformities, in particular, missing
On the new translational shape-invariant potentials
NASA Astrophysics Data System (ADS)
Ramos, Arturo
2011-08-01
Recently, several authors have found new translational shape-invariant potentials not present in classic classifications like those of Infeld and Hull. For example, Quesne on the one hand and Bougie, Gangopadhyaya and Mallow on the other have provided examples of them, consisting on deformations of the classical ones. We analyze the basic properties of the new examples and observe a compatibility equation which has to be satisfied by them. We study particular cases of such an equation and give more examples of new translational shape-invariant potentials.
Lorentz-invariant formulation of Cherenkov radiation by tachyons
NASA Technical Reports Server (NTRS)
Jones, F. C.
1972-01-01
Previous treatments of Cherenkov radiation, electromagnetic and gravitational, by tachyons were in error because the prescription employed to cut off the divergent integral over frequency is not a Lorentz invariant procedure. The resulting equation of motion for the tachyon is therefore not covariant. The proper procedure requires an extended, deformable distribution of charge or mass and yields a particularly simple form for the tachyon's world line, one that could be deduced from simple invariance considerations. It is shown that Cherenkov radiation by tachyons implys their ultimate annihilation with an antitachyon and demonstrates a disturbing property of tachyons, namely the impossibility of specifying arbitrary Cauchy data even in a purely classical theory.
Entanglement, Invariants, and Phylogenetics
NASA Astrophysics Data System (ADS)
Sumner, J. G.
2007-10-01
This thesis develops and expands upon known techniques of mathematical physics relevant to the analysis of the popular Markov model of phylogenetic trees required in biology to reconstruct the evolutionary relationships of taxonomic units from biomolecular sequence data. The techniques of mathematical physics are plethora and have been developed for some time. The Markov model of phylogenetics and its analysis is a relatively new technique where most progress to date has been achieved by using discrete mathematics. This thesis takes a group theoretical approach to the problem by beginning with a remarkable mathematical parallel to the process of scattering in particle physics. This is shown to equate to branching events in the evolutionary history of molecular units. The major technical result of this thesis is the derivation of existence proofs and computational techniques for calculating polynomial group invariant functions on a multi-linear space where the group action is that relevant to a Markovian time evolution. The practical results of this thesis are an extended analysis of the use of invariant functions in distance based methods and the presentation of a new reconstruction technique for quartet trees which is consistent with the most general Markov model of sequence evolution.
Invariants from classical field theory
Diaz, Rafael; Leal, Lorenzo
2008-06-15
We introduce a method that generates invariant functions from perturbative classical field theories depending on external parameters. By applying our methods to several field theories such as Abelian BF, Chern-Simons, and two-dimensional Yang-Mills theory, we obtain, respectively, the linking number for embedded submanifolds in compact varieties, the Gauss' and the second Milnor's invariant for links in S{sup 3}, and invariants under area-preserving diffeomorphisms for configurations of immersed planar curves.
Tractors, mass, and Weyl invariance
NASA Astrophysics Data System (ADS)
Gover, A. R.; Shaukat, A.; Waldron, A.
2009-05-01
Deser and Nepomechie established a relationship between masslessness and rigid conformal invariance by coupling to a background metric and demanding local Weyl invariance, a method which applies neither to massive theories nor theories which rely upon gauge invariances for masslessness. We extend this method to describe massive and gauge invariant theories using Weyl invariance. The key idea is to introduce a new scalar field which is constant when evaluated at the scale corresponding to the metric of physical interest. This technique relies on being able to efficiently construct Weyl invariant theories. This is achieved using tractor calculus—a mathematical machinery designed for the study of conformal geometry. From a physics standpoint, this amounts to arranging fields in multiplets with respect to the conformal group but with novel Weyl transformation laws. Our approach gives a mechanism for generating masses from Weyl weights. Breitenlohner-Freedman stability bounds for Anti-de Sitter theories arise naturally as do direct derivations of the novel Weyl invariant theories given by Deser and Nepomechie. In constant curvature spaces, partially massless theories—which rely on the interplay between mass and gauge invariance—are also generated by our method. Another simple consequence is conformal invariance of the maximal depth partially massless theories. Detailed examples for spins s⩽2 are given including tractor and component actions, on-shell and off-shell approaches and gauge invariances. For all spins s⩾2 we give tractor equations of motion unifying massive, massless, and partially massless theories.
Kahler stabilized, modular invariant heterotic string models
Gaillard, Mary K.; Gaillard, Mary K.; Nelson, Brent D.
2007-03-19
We review the theory and phenomenology of effective supergravity theories based on orbifold compactifications of the weakly-coupled heterotic string. In particular, we consider theories in which the four-dimensional theory displays target space modular invariance and where the dilatonic mode undergoes Kahler stabilization. A self-contained exposition of effective Lagrangian approaches to gaugino condensation and heterotic string theory is presented, leading to the development of the models of Binétruy, Gaillard and Wu. Various aspects of the phenomenology of this class of models are considered. These include issues of supersymmetry breaking and superpartner spectra, the role of anomalous U(1) factors, issues of flavor and R-parity conservation, collider signatures, axion physics, and early universe cosmology. For the vast majority of phenomenological considerations the theories reviewed here compare quite favorably to other string-derived models in the literature. Theoretical objections to the framework and directions for further research are identified and discussed.
Integrable amplitude deformations for N =4 super Yang-Mills and ABJM theory
NASA Astrophysics Data System (ADS)
Bargheer, Till; Huang, Yu-Tin; Loebbert, Florian; Yamazaki, Masahito
2015-01-01
We study Yangian-invariant deformations of scattering amplitudes in 4d N =4 super Yang-Mills theory and 3d N =6 Aharony-Bergman-Jafferis-Maldacena (ABJM) theory. In particular, we obtain the deformed Graßmannian integral for 4d N =4 supersymmetric Yang-Mills theory, both in momentum and momentum-twistor space. For 3d ABJM theory, we initiate the study of deformed scattering amplitudes. We investigate general deformations of on-shell diagrams, and find the deformed Graßmannian integral for this theory. We furthermore introduce the algebraic R-matrix construction of deformed Yangian invariants for ABJM theory.
The scale invariant generator technique for quantifying anisotropic scale invariance
NASA Astrophysics Data System (ADS)
Lewis, G. M.; Lovejoy, S.; Schertzer, D.; Pecknold, S.
1999-11-01
Scale invariance is rapidly becoming a new paradigm for geophysics. However, little attention has been paid to the anisotropy that is invariably present in geophysical fields in the form of differential stratification and rotation, texture and morphology. In order to account for scaling anisotropy, the formalism of generalized scale invariance (GSI) was developed. Until now there has existed only a single fairly ad hoc GSI analysis technique valid for studying differential rotation. In this paper, we use a two-dimensional representation of the linear approximation to generalized scale invariance, to obtain a much improved technique for quantifying anisotropic scale invariance called the scale invariant generator technique (SIG). The accuracy of the technique is tested using anisotropic multifractal simulations and error estimates are provided for the geophysically relevant range of parameters. It is found that the technique yields reasonable estimates for simulations with a diversity of anisotropic and statistical characteristics. The scale invariant generator technique can profitably be applied to the scale invariant study of vertical/horizontal and space/time cross-sections of geophysical fields as well as to the study of the texture/morphology of fields.
Bifurcation from an invariant to a non-invariant attractor
NASA Astrophysics Data System (ADS)
Mandal, D.
2016-12-01
Switching dynamical systems are very common in many areas of physics and engineering. We consider a piecewise linear map that periodically switches between more than one different functional forms. We show that in such systems it is possible to have a border collision bifurcation where the system transits from an invariant attractor to a non-invariant attractor.
NASA Astrophysics Data System (ADS)
Ben-Arie, Jezekiel; Wang, Zhiqian; Rao, Raghunath K.
1996-02-01
This paper describes an approach for affine-invariant object recognition by iconic recognition of image patches that correspond to object surfaces that are roughly planar. Each surface is recognized separately invariant to its 3D pose, employing novel affine-invariant spectral signatures (AISSs). The 3D-pose invariant recognition is achieved by convolving the image with a novel configuration of Gaussian kernels and extracting local spectral signatures. The local spectral signature of each image patch is then matched against a set of iconic models using multi-dimensional indexing (MDI) in the frequency domain. Affine-invariance of the signatures is achieved by a new configuration of Gaussian kernels with modulation in two orthogonal axes. The proposed configuration of kernels is Cartesian with varying aspect ratios in two orthogonal directions. The kernels are organized in subsets where each subset has a distinct orientation. Each subset spans the entire frequency domain and provides invariance to slant, scale and limited translation. The union of differently oriented subsets is utilized to achieve invariance in two additional degrees of freedom, i.e. rotation and tilt. Hence, complete affine-invariance is achieved by the proposed set of kernels. The indexing method provides robustness in partial distortion, background clutter, noise, illumination effects and lower image resolution. The localized nature of the Gaussian kernels allows independent recognition of adjacent shapes that correspond to object parts which could have different poses. The method has yielded high recognition rates in experiments over a wide range of slant, scale, rotation, and tilt with a library of 26 gray-level and infra-red models, in the presence of noise, clutter and other degradations.
mathcal{PT} Invariant Complex E 8 Root Spaces
NASA Astrophysics Data System (ADS)
Fring, Andreas; Smith, Monique
2011-04-01
We provide a construction procedure for complex root spaces invariant under antilinear transformations, which may be applied to any Coxeter group. The procedure is based on the factorisation of a chosen element of the Coxeter group into two factors. Each of the factors constitutes an involution and may therefore be deformed in an antilinear fashion. Having the importance of the E 8-Coxeter group in mind, such as underlying a particular perturbation of the Ising model and the fact that for it no solution could be found previously, we exemplify the procedure for this particular case. As a concrete application of this construction we propose new generalisations of Calogero-Moser-Sutherland models and affine Toda field theories based on the invariant complex root spaces and deformed complex simple roots, respectively.
Invariant Measures for Cherry Flows
NASA Astrophysics Data System (ADS)
Saghin, Radu; Vargas, Edson
2013-01-01
We investigate the invariant probability measures for Cherry flows, i.e. flows on the two-torus which have a saddle, a source, and no other fixed points, closed orbits or homoclinic orbits. In the case when the saddle is dissipative or conservative we show that the only invariant probability measures are the Dirac measures at the two fixed points, and the Dirac measure at the saddle is the physical measure. In the other case we prove that there exists also an invariant probability measure supported on the quasi-minimal set, we discuss some situations when this other invariant measure is the physical measure, and conjecture that this is always the case. The main techniques used are the study of the integrability of the return time with respect to the invariant measure of the return map to a closed transversal to the flow, and the study of the close returns near the saddle.
Rotation, scale and translation invariant pattern recognition system for color images
NASA Astrophysics Data System (ADS)
Barajas-García, Carolina; Solorza-Calderón, Selene; Álvarez-Borrego, Josué
2016-12-01
This work presents a color image pattern recognition system invariant to rotation, scale and translation. The system works with three 1D signatures, one for each RGB color channel. The signatures are constructed based on Fourier transform, analytic Fourier-Mellin transform and Hilbert binary rings mask. According with the statistical theory of box-plots, the pattern recognition system has a confidence level at least of 95.4%.
Physical Invariants of Intelligence
NASA Technical Reports Server (NTRS)
Zak, Michail
2010-01-01
A program of research is dedicated to development of a mathematical formalism that could provide, among other things, means by which living systems could be distinguished from non-living ones. A major issue that arises in this research is the following question: What invariants of mathematical models of the physics of systems are (1) characteristic of the behaviors of intelligent living systems and (2) do not depend on specific features of material compositions heretofore considered to be characteristic of life? This research at earlier stages has been reported, albeit from different perspectives, in numerous previous NASA Tech Briefs articles. To recapitulate: One of the main underlying ideas is to extend the application of physical first principles to the behaviors of living systems. Mathematical models of motor dynamics are used to simulate the observable physical behaviors of systems or objects of interest, and models of mental dynamics are used to represent the evolution of the corresponding knowledge bases. For a given system, the knowledge base is modeled in the form of probability distributions and the mental dynamics is represented by models of the evolution of the probability densities or, equivalently, models of flows of information. At the time of reporting the information for this article, the focus of this research was upon the following aspects of the formalism: Intelligence is considered to be a means by which a living system preserves itself and improves its ability to survive and is further considered to manifest itself in feedback from the mental dynamics to the motor dynamics. Because of the feedback from the mental dynamics, the motor dynamics attains quantum-like properties: The trajectory of the physical aspect of the system in the space of dynamical variables splits into a family of different trajectories, and each of those trajectories can be chosen with a probability prescribed by the mental dynamics. From a slightly different perspective
Lifshitz as a deformation of Anti-de Sitter
NASA Astrophysics Data System (ADS)
Korovin, Yegor; Skenderis, Kostas; Taylor, Marika
2013-08-01
We consider holography for Lifshitz spacetimes with dynamical exponent z = 1+ɛ2, where ɛ is small. We show that the holographically dual field theory is a specific deformation of the relativistic CFT, corresponding to the z = 1 theory. Treating ɛ as a small expansion parameter we set up the holographic dictionary for Einstein-Proca models up to order ɛ2 in three and four bulk dimensions. We explain how renormalization turns the relativistic conformal invariance into non-relativistic Lifshitz invariance with dynamical exponent z = 1 + ɛ2. We compute the two-point function of the conserved spin two current for the dual two-dimensional field theory and verify that it is Lifshitz invariant. Using only QFT arguments, we show that a particular class of deformations of CFTs generically leads to Lifshitz scaling invariance and we construct examples of such deformations.
On Lorentz Transformations in Symplectic Deformations
Cuesta, R.; Sabido, M.; Guzman, W.
2010-07-12
In this paper we study noncommutative Lorentz transformations using symplectic deformations. In this framework we define an infinitesimal line element that is invariant under this noncommutative Lorentz transformations. Using the symplectic geometry formalism, we find that noncommutative Lorentz transformations intertwine the canonical momentums with canonical position coordinates.
Does the nontrivially deformed field-antifield formalism exist?
NASA Astrophysics Data System (ADS)
Batalin, Igor A.; Lavrov, Peter M.
2015-06-01
We reformulate the Lagrange deformed field-antifield BV-formalism suggested, in terms of the general Euler vector field N generated by the antisymplectic potential. That N generalizes, in a natural anticanonically-invariant manner, the usual power-counting operator. We provide for the "usual" gauge-fixing mechanism as applied to the deformed BV-formalism.
Shape invariance through Crum transformation
Organista, Jose Orlando; Nowakowski, Marek; Rosu, H. C.
2006-12-15
We show in a rigorous way that Crum's result regarding the equal eigenvalue spectrum of Sturm-Liouville problems can be obtained iteratively by successive Darboux transformations. Furthermore, it can be shown that all neighboring Darboux-transformed potentials of higher order, u{sub k} and u{sub k+1}, satisfy the condition of shape invariance provided the original potential u does so. Based on this result, we prove that under the condition of shape invariance, the nth iteration of the original Sturm-Liouville problem defined solely through the shape invariance is equal to the nth Crum transformation.
Bayesian tests of measurement invariance.
Verhagen, A J; Fox, J P
2013-11-01
Random item effects models provide a natural framework for the exploration of violations of measurement invariance without the need for anchor items. Within the random item effects modelling framework, Bayesian tests (Bayes factor, deviance information criterion) are proposed which enable multiple marginal invariance hypotheses to be tested simultaneously. The performance of the tests is evaluated with a simulation study which shows that the tests have high power and low Type I error rate. Data from the European Social Survey are used to test for measurement invariance of attitude towards immigrant items and to show that background information can be used to explain cross-national variation in item functioning.
Quadratic Generalized Scale Invariance
NASA Astrophysics Data System (ADS)
Lovejoy, S.; Schertzer, D.; Addor, J. B.
Nearly twenty years ago, two of us argued that in order to account for the scaling strat- ification of the atmosphere, that an anisotropic "unified scaling model" of the atmo- sphere was required with elliptical dimension 23/9=2.555... "in between" the standard 3-D (small scale) and 2-D large scale model. This model was based on the formal- ism of generalized scale invariance (GSI). Physically, GSI is justified by arguing that various conserved fluxes (energy, buoyancy force variance etc.) should define the ap- propriate notion of scale. In a recent large scale satellite cloud image analysis, we directly confirmed this model by studying the isotropic (angle averaged) horizontal cloud statistics. Mathematically, GSI is based on a a group of scale changing opera- tors and their generators but to date, both analyses (primarily of cloud images) and nu- merical (multifractal) simulations, have been limited to the special case of linear GSI. This has shown that cloud texture can plausibly be associated with local linearizations. However realistic morphologies involve spatially avarying textures; the full non linear GSI is clearly necessary. In this talk, we first show that the observed angle averaged (multi)scaling statistics only give a realtively weak constraint on the nonlinear gner- ator: that the latter can be expressed by self-similar (isotropic) part, and a deviatoric part described (in two dimensions) by an arbitrary scalar potential which contains all the information about the cloud morphology. We then show (using a theorem due to Poincaré) how to reduce nonlinear GSI to linear GSI plus a nonlinear coordinate trans- formation numerically, using this to take multifractal GSI modelling to the next level of approximation: quadratic GSI. We show many examples of the coresponding simu- lations which include transitions from various morphologies (including cyclones) and we discuss the results in relation to satellite cloud images.
... deformity is often called “pump bump” because the rigid backs of pump-style shoes can create pressure ... when walking. In fact, any shoes with a rigid back, such as ice skates, men’s dress shoes ...
Deformity - contracture ... Contracture can be caused by any of the following: Brain and nervous system disorders, such as cerebral ... Follow your health care provider's instructions for treating contracture at home. Treatments may include: Doing exercises and ...
Bunnell, W P
1986-12-01
Spinal deformity is a relatively common disorder, particularly in teenage girls. Early detection is possible by a simple, quick visual inspection that should be a standard part of the routine examination of all preteen and teenage patients. Follow-up observation will reveal those curvatures that are progressive and permit orthotic treatment to prevent further increase in the deformity. Spinal fusion offers correction and stabilization of more severe degrees of scoliosis.
Invariant measures in brain dynamics
NASA Astrophysics Data System (ADS)
Boyarsky, Abraham; Góra, Paweł
2006-10-01
This note concerns brain activity at the level of neural ensembles and uses ideas from ergodic dynamical systems to model and characterize chaotic patterns among these ensembles during conscious mental activity. Central to our model is the definition of a space of neural ensembles and the assumption of discrete time ensemble dynamics. We argue that continuous invariant measures draw the attention of deeper brain processes, engendering emergent properties such as consciousness. Invariant measures supported on a finite set of ensembles reflect periodic behavior, whereas the existence of continuous invariant measures reflect the dynamics of nonrepeating ensemble patterns that elicit the interest of deeper mental processes. We shall consider two different ways to achieve continuous invariant measures on the space of neural ensembles: (1) via quantum jitters, and (2) via sensory input accompanied by inner thought processes which engender a “folding” property on the space of ensembles.
NASA Astrophysics Data System (ADS)
Hawley, Chadwick T.
2009-05-01
The Signatures Support Program (SSP) leverages the full spectrum of signature-related activities (collections, processing, development, storage, maintenance, and dissemination) within the Department of Defense (DOD), the intelligence community (IC), other Federal agencies, and civil institutions. The Enterprise encompasses acoustic, seismic, radio frequency, infrared, radar, nuclear radiation, and electro-optical signatures. The SSP serves the war fighter, the IC, and civil institutions by supporting military operations, intelligence operations, homeland defense, disaster relief, acquisitions, and research and development. Data centers host and maintain signature holdings, collectively forming the national signatures pool. The geographically distributed organizations are the authoritative sources and repositories for signature data; the centers are responsible for data content and quality. The SSP proactively engages DOD, IC, other Federal entities, academia, and industry to locate signatures for inclusion in the distributed national signatures pool and provides world-wide 24/7 access via the SSP application.
Lesson 6: Signature Validation
Checklist items 13 through 17 are grouped under the Signature Validation Process, and represent CROMERR requirements that the system must satisfy as part of ensuring that electronic signatures it receives are valid.
Jordanian deformation of the open sℓ(2) Gaudin model
NASA Astrophysics Data System (ADS)
António, N. Cirilo; Manojlović, N.; Nagy, Z.
2014-04-01
We derive a deformed sℓ( 2) Gaudin model with integrable boundaries. Starting from the Jordanian deformation of the SL( 2)-invariant Yang R-matrix and generic solutions of the associated reflection equation and the dual reflection equation, we obtain the corresponding inhomogeneous spin- 1/2 XXX chain. The semiclassical expansion of the transfer matrix yields the deformed sℓ( 2) Gaudin Hamiltonians with boundary terms.
Orthosymplectically invariant functions in superspace
NASA Astrophysics Data System (ADS)
Coulembier, K.; De Bie, H.; Sommen, F.
2010-08-01
The notion of spherically symmetric superfunctions as functions invariant under the orthosymplectic group is introduced. This leads to dimensional reduction theorems for differentiation and integration in superspace. These spherically symmetric functions can be used to solve orthosymplectically invariant Schrödinger equations in superspace, such as the (an)harmonic oscillator or the Kepler problem. Finally, the obtained machinery is used to prove the Funk-Hecke theorem and Bochner's relations in superspace.
Hidden scale invariance of metals
NASA Astrophysics Data System (ADS)
Hummel, Felix; Kresse, Georg; Dyre, Jeppe C.; Pedersen, Ulf R.
2015-11-01
Density functional theory (DFT) calculations of 58 liquid elements at their triple point show that most metals exhibit near proportionality between the thermal fluctuations of the virial and the potential energy in the isochoric ensemble. This demonstrates a general "hidden" scale invariance of metals making the condensed part of the thermodynamic phase diagram effectively one dimensional with respect to structure and dynamics. DFT computed density scaling exponents, related to the Grüneisen parameter, are in good agreement with experimental values for the 16 elements where reliable data were available. Hidden scale invariance is demonstrated in detail for magnesium by showing invariance of structure and dynamics. Computed melting curves of period three metals follow curves with invariance (isomorphs). The experimental structure factor of magnesium is predicted by assuming scale invariant inverse power-law (IPL) pair interactions. However, crystal packings of several transition metals (V, Cr, Mn, Fe, Nb, Mo, Ta, W, and Hg), most post-transition metals (Ga, In, Sn, and Tl), and the metalloids Si and Ge cannot be explained by the IPL assumption. The virial-energy correlation coefficients of iron and phosphorous are shown to increase at elevated pressures. Finally, we discuss how scale invariance explains the Grüneisen equation of state and a number of well-known empirical melting and freezing rules.
Imaka: a Lagrange invariant of ELTs
NASA Astrophysics Data System (ADS)
Lai, Olivier; Chun, Mark R.; Pazder, John; Véran, Jean-Pierre; Jolissaint, Laurent; Andersen, David; Salmon, Derrick; Cuillandre, Jean-Charles
2010-07-01
The IMAKA project is a ground layer corrected wide field visible imager proposed for CFHT. It consists of three processes or components: The dome and local turbulence will be controlled by ventilation; the remaining ground layer turbulence will be corrected by a GLAO system and the free atmosphere seeing will be locally reduced by using an Orthogonal Transfer CCD to correct for tip-tilt within the isokinetic angle of field stars. In designing the AO system, whether based on an adaptive secondary mirror or using pupil relay optics, it becomes apparent that the conjugation of the deformable mirror is a difficult constraint to achieve given the large field. It turns out this problem is not isolated to IMAKA, because the Lagrange Invariant for our project is in the same range as that of EAGLE on the E-ELT for example. The effects of tilting the deformable mirror with respect to the pupil or compensating for misconjugation of an adaptive secondary mirror using a tomographic reconstructor have been investigated using Monte-Carlo simulation codes, including our code developed specifically for GLAO simulations. We report on quantitative results from IMAKA simulations for a variety of realistic turbulence conditions for each topical scheme, and allude to how these results are applicable to ELTs' adaptive optics.
Exposing local symmetries in distorted driven lattices via time-averaged invariants
NASA Astrophysics Data System (ADS)
Wulf, T.; Morfonios, C. V.; Diakonos, F. K.; Schmelcher, P.
2016-05-01
Time-averaged two-point currents are derived and shown to be spatially invariant within domains of local translation or inversion symmetry for arbitrary time-periodic quantum systems in one dimension. These currents are shown to provide a valuable tool for detecting deformations of a spatial symmetry in static and driven lattices. In the static case the invariance of the two-point currents is related to the presence of time-reversal invariance and/or probability current conservation. The obtained insights into the wave functions are further exploited for a symmetry-based convergence check which is applicable for globally broken but locally retained potential symmetries.
Weyl invariance with a nontrivial mass scale
Álvarez, Enrique; González-Martín, Sergio
2016-09-07
A theory with a mass scale and yet Weyl invariant is presented. The theory is not invariant under all diffeomorphisms but only under transverse ones. This is the reason why Weyl invariance does not imply scale invariance in a free falling frame. Physical implications of this framework are discussed.
CPT violation implies violation of Lorentz invariance.
Greenberg, O W
2002-12-02
A interacting theory that violates CPT invariance necessarily violates Lorentz invariance. On the other hand, CPT invariance is not sufficient for out-of-cone Lorentz invariance. Theories that violate CPT by having different particle and antiparticle masses must be nonlocal.
Brown, R.D. Jr.
1990-01-01
Displaced or deformed rock units and landforms record the past 2 m.y. of faulting, folding, uplift, and subsidence in California. Properly interpreted, such evidence provides a quantitative basis for predicting future earthquake activity and for relating many diverse structures and landforms to the 5 cm/yr of horizontal motion at the boundary between the North American and Pacific plates. Modern techniques of geologic dating and expanded research on earthquake hazards have greatly improved our knowledge of the San Andreas fault system. Much of this new knowledge has been gained since 1965, and that part which concerns crustal deformation during the past 2 m.y. is briefly summarized here.
Scale invariance and invariant scaling in a mixed hierarchical system.
Shnirman, M G; Blanter, E M
1999-11-01
We consider a mixed hierarchical model with heterogeneous and monotone conditions of destruction. We investigate how scaling properties of defects in the model are related with heterogeneity of rules of destruction, determined by concentration of the mixture. The system demonstrates different kinds of criticality as a general form of system behavior. The following forms of critical behavior are obtained: stability, catastrophe, scale invariance, and invariant scaling. Different slopes of the magnitude-frequency relation are realized in areas of critical stability and catastrophe. A simple relation between the slope of magnitude-frequency relation and parameters of the mixture is established.
Machine learning strategies for systems with invariance properties
Ling, Julia; Jones, Reese E.; Templeton, Jeremy Alan
2016-05-06
Here, in many scientific fields, empirical models are employed to facilitate computational simulations of engineering systems. For example, in fluid mechanics, empirical Reynolds stress closures enable computationally-efficient Reynolds-Averaged Navier-Stokes simulations. Likewise, in solid mechanics, constitutive relations between the stress and strain in a material are required in deformation analysis. Traditional methods for developing and tuning empirical models usually combine physical intuition with simple regression techniques on limited data sets. The rise of high-performance computing has led to a growing availability of high-fidelity simulation data, which open up the possibility of using machine learning algorithms, such as random forests or neuralmore » networks, to develop more accurate and general empirical models. A key question when using data-driven algorithms to develop these models is how domain knowledge should be incorporated into the machine learning process. This paper will specifically address physical systems that possess symmetry or invariance properties. Two different methods for teaching a machine learning model an invariance property are compared. In the first , a basis of invariant inputs is constructed, and the machine learning model is trained upon this basis, thereby embedding the invariance into the model. In the second method, the algorithm is trained on multiple transformations of the raw input data until the model learns invariance to that transformation. Results are discussed for two case studies: one in turbulence modeling and one in crystal elasticity. It is shown that in both cases embedding the invariance property into the input features yields higher performance with significantly reduced computational training costs.« less
Machine learning strategies for systems with invariance properties
NASA Astrophysics Data System (ADS)
Ling, Julia; Jones, Reese; Templeton, Jeremy
2016-08-01
In many scientific fields, empirical models are employed to facilitate computational simulations of engineering systems. For example, in fluid mechanics, empirical Reynolds stress closures enable computationally-efficient Reynolds Averaged Navier Stokes simulations. Likewise, in solid mechanics, constitutive relations between the stress and strain in a material are required in deformation analysis. Traditional methods for developing and tuning empirical models usually combine physical intuition with simple regression techniques on limited data sets. The rise of high performance computing has led to a growing availability of high fidelity simulation data. These data open up the possibility of using machine learning algorithms, such as random forests or neural networks, to develop more accurate and general empirical models. A key question when using data-driven algorithms to develop these empirical models is how domain knowledge should be incorporated into the machine learning process. This paper will specifically address physical systems that possess symmetry or invariance properties. Two different methods for teaching a machine learning model an invariance property are compared. In the first method, a basis of invariant inputs is constructed, and the machine learning model is trained upon this basis, thereby embedding the invariance into the model. In the second method, the algorithm is trained on multiple transformations of the raw input data until the model learns invariance to that transformation. Results are discussed for two case studies: one in turbulence modeling and one in crystal elasticity. It is shown that in both cases embedding the invariance property into the input features yields higher performance at significantly reduced computational training costs.
Machine learning strategies for systems with invariance properties
Ling, Julia; Jones, Reese E.; Templeton, Jeremy Alan
2016-05-06
Here, in many scientific fields, empirical models are employed to facilitate computational simulations of engineering systems. For example, in fluid mechanics, empirical Reynolds stress closures enable computationally-efficient Reynolds-Averaged Navier-Stokes simulations. Likewise, in solid mechanics, constitutive relations between the stress and strain in a material are required in deformation analysis. Traditional methods for developing and tuning empirical models usually combine physical intuition with simple regression techniques on limited data sets. The rise of high-performance computing has led to a growing availability of high-fidelity simulation data, which open up the possibility of using machine learning algorithms, such as random forests or neural networks, to develop more accurate and general empirical models. A key question when using data-driven algorithms to develop these models is how domain knowledge should be incorporated into the machine learning process. This paper will specifically address physical systems that possess symmetry or invariance properties. Two different methods for teaching a machine learning model an invariance property are compared. In the first , a basis of invariant inputs is constructed, and the machine learning model is trained upon this basis, thereby embedding the invariance into the model. In the second method, the algorithm is trained on multiple transformations of the raw input data until the model learns invariance to that transformation. Results are discussed for two case studies: one in turbulence modeling and one in crystal elasticity. It is shown that in both cases embedding the invariance property into the input features yields higher performance with significantly reduced computational training costs.
Machine learning strategies for systems with invariance properties
Ling, Julia; Jones, Reese E.; Templeton, Jeremy Alan
2016-05-06
Here, in many scientific fields, empirical models are employed to facilitate computational simulations of engineering systems. For example, in fluid mechanics, empirical Reynolds stress closures enable computationally-efficient Reynolds-Averaged Navier-Stokes simulations. Likewise, in solid mechanics, constitutive relations between the stress and strain in a material are required in deformation analysis. Traditional methods for developing and tuning empirical models usually combine physical intuition with simple regression techniques on limited data sets. The rise of high-performance computing has led to a growing availability of high-fidelity simulation data, which open up the possibility of using machine learning algorithms, such as random forests or neural networks, to develop more accurate and general empirical models. A key question when using data-driven algorithms to develop these models is how domain knowledge should be incorporated into the machine learning process. This paper will specifically address physical systems that possess symmetry or invariance properties. Two different methods for teaching a machine learning model an invariance property are compared. In the first , a basis of invariant inputs is constructed, and the machine learning model is trained upon this basis, thereby embedding the invariance into the model. In the second method, the algorithm is trained on multiple transformations of the raw input data until the model learns invariance to that transformation. Results are discussed for two case studies: one in turbulence modeling and one in crystal elasticity. It is shown that in both cases embedding the invariance property into the input features yields higher performance with significantly reduced computational training costs.
Testing Lorentz invariance of dark matter with satellite galaxies
NASA Astrophysics Data System (ADS)
Bettoni, Dario; Nusser, Adi; Blas, Diego; Sibiryakov, Sergey
2017-05-01
We develop the framework for testing Lorentz invariance in the dark matter sector using galactic dynamics. We consider a Lorentz violating (LV) vector field acting on the dark matter component of a satellite galaxy orbiting in a host halo. We introduce a numerical model for the dynamics of satellites in a galactic halo and for a galaxy in a rich cluster to explore observational consequences of such an LV field. The orbital motion of a satellite excites a time dependent LV force which greatly affects its internal dynamics. Our analysis points out key observational signatures which serve as probes of LV forces. These include modifications to the line of sight velocity dispersion, mass profiles and shapes of satellites. With future data and a more detailed modeling these signatures can be exploited to constrain a new region of the parameter space describing the LV in the dark matter sector.
Uncertainty in hydrological signatures
NASA Astrophysics Data System (ADS)
Westerberg, I. K.; McMillan, H. K.
2015-09-01
Information about rainfall-runoff processes is essential for hydrological analyses, modelling and water-management applications. A hydrological, or diagnostic, signature quantifies such information from observed data as an index value. Signatures are widely used, e.g. for catchment classification, model calibration and change detection. Uncertainties in the observed data - including measurement inaccuracy and representativeness as well as errors relating to data management - propagate to the signature values and reduce their information content. Subjective choices in the calculation method are a further source of uncertainty. We review the uncertainties relevant to different signatures based on rainfall and flow data. We propose a generally applicable method to calculate these uncertainties based on Monte Carlo sampling and demonstrate it in two catchments for common signatures including rainfall-runoff thresholds, recession analysis and basic descriptive signatures of flow distribution and dynamics. Our intention is to contribute to awareness and knowledge of signature uncertainty, including typical sources, magnitude and methods for its assessment. We found that the uncertainties were often large (i.e. typical intervals of ±10-40 % relative uncertainty) and highly variable between signatures. There was greater uncertainty in signatures that use high-frequency responses, small data subsets, or subsets prone to measurement errors. There was lower uncertainty in signatures that use spatial or temporal averages. Some signatures were sensitive to particular uncertainty types such as rating-curve form. We found that signatures can be designed to be robust to some uncertainty sources. Signature uncertainties of the magnitudes we found have the potential to change the conclusions of hydrological and ecohydrological analyses, such as cross-catchment comparisons or inferences about dominant processes.
Abelian link invariants and homology
Guadagnini, Enore; Mancarella, Francesco
2010-06-15
We consider the link invariants defined by the quantum Chern-Simons field theory with compact gauge group U(1) in a closed oriented 3-manifold M. The relation of the Abelian link invariants with the homology group of the complement of the links is discussed. We prove that, when M is a homology sphere or when a link--in a generic manifold M--is homologically trivial, the associated observables coincide with the observables of the sphere S{sup 3}. Finally, we show that the U(1) Reshetikhin-Turaev surgery invariant of the manifold M is not a function of the homology group only, nor a function of the homotopy type of M alone.
Invariance concepts in spectral analysis
NASA Astrophysics Data System (ADS)
Schaum, Alan
2017-05-01
Methods are developed for insuring robust discrimination performance in detection problems with epistemic unknowns. The problem is first solved for the class of problems exhibiting some symmetry, as expressed by invariances to some group of feature space transformations. The determination of whether a problem admits a uniformly most powerful invariant (UMPI) solution (and how to derive it) is solved with a new and simple procedure. This motivates an approach for solving problems where a symmetry is gracefully broken, which leads in turn to a general approach for producing robust detectors. This introduces a new category of detector, the UMPIC (UMPI constrained). Finally, principles of UMPIC construction are shown to apply to problems exhibiting no invariances.
Test of charge conjugation invariance.
Nefkens, B M K; Prakhov, S; Gårdestig, A; Allgower, C E; Bekrenev, V; Briscoe, W J; Clajus, M; Comfort, J R; Craig, K; Grosnick, D; Isenhower, D; Knecht, N; Koetke, D; Koulbardis, A; Kozlenko, N; Kruglov, S; Lolos, G; Lopatin, I; Manley, D M; Manweiler, R; Marusić, A; McDonald, S; Olmsted, J; Papandreou, Z; Peaslee, D; Phaisangittisakul, N; Price, J W; Ramirez, A F; Sadler, M; Shafi, A; Spinka, H; Stanislaus, T D S; Starostin, A; Staudenmaier, H M; Supek, I; Tippens, W B
2005-02-04
We report on the first determination of upper limits on the branching ratio (BR) of eta decay to pi0pi0gamma and to pi0pi0pi0gamma. Both decay modes are strictly forbidden by charge conjugation (C) invariance. Using the Crystal Ball multiphoton detector, we obtained BR(eta-->pi0pi0gamma)<5 x 10(-4) at the 90% confidence level, in support of C invariance of isoscalar electromagnetic interactions of the light quarks. We have also measured BR(eta-->pi0pi0pi0gamma)<6 x 10(-5) at the 90% confidence level, in support of C invariance of isovector electromagnetic interactions.
Energy Invariance in Capillary Systems.
Ruiz-Gutiérrez, Élfego; Guan, Jian H; Xu, Ben; McHale, Glen; Wells, Gary G; Ledesma-Aguilar, Rodrigo
2017-05-26
We demonstrate the continuous translational invariance of the energy of a capillary surface in contact with reconfigurable solid boundaries. We present a theoretical approach to find the energy-invariant equilibria of spherical capillary surfaces in contact with solid boundaries of arbitrary shape and examine the implications of dynamic frictional forces upon a reconfiguration of the boundaries. Experimentally, we realize our ideas by manipulating the position of a droplet in a wedge geometry using lubricant-impregnated solid surfaces, which eliminate the contact-angle hysteresis and provide a test bed for quantifying dissipative losses out of equilibrium. Our experiments show that dissipative energy losses for an otherwise energy-invariant reconfiguration are relatively small, provided that the actuation time scale is longer than the typical relaxation time scale of the capillary surface. We discuss the wider applicability of our ideas as a pathway for liquid manipulation at no potential energy cost in low-pinning, low-friction situations.
Energy Invariance in Capillary Systems
NASA Astrophysics Data System (ADS)
Ruiz-Gutiérrez, Élfego; Guan, Jian H.; Xu, Ben; McHale, Glen; Wells, Gary G.; Ledesma-Aguilar, Rodrigo
2017-05-01
We demonstrate the continuous translational invariance of the energy of a capillary surface in contact with reconfigurable solid boundaries. We present a theoretical approach to find the energy-invariant equilibria of spherical capillary surfaces in contact with solid boundaries of arbitrary shape and examine the implications of dynamic frictional forces upon a reconfiguration of the boundaries. Experimentally, we realize our ideas by manipulating the position of a droplet in a wedge geometry using lubricant-impregnated solid surfaces, which eliminate the contact-angle hysteresis and provide a test bed for quantifying dissipative losses out of equilibrium. Our experiments show that dissipative energy losses for an otherwise energy-invariant reconfiguration are relatively small, provided that the actuation time scale is longer than the typical relaxation time scale of the capillary surface. We discuss the wider applicability of our ideas as a pathway for liquid manipulation at no potential energy cost in low-pinning, low-friction situations.
Lorentz Invariance:. Present Experimental Status
NASA Astrophysics Data System (ADS)
Lämmerzahl, Claus
2006-02-01
Being one of the pillars of modern physics, Lorentz invariance has to be tested as precisely as possible. We review the present status of laboratory tests of Lorentz invariance. This includes the tests of properties of light propagation which are covered by the famous Michelson-Morley, Kennedy-Thorndike, and Ives-Stilwell experiments, as well as tests on dynamical properties of matter as, e.g., tests exploring the maximum velocity of massive particles or tests of the isotropy of quantum particles in Hughes-Drever experiments.
A generalization of gauge invariance
NASA Astrophysics Data System (ADS)
Grigore, Dan-Radu
2017-08-01
We consider perturbative quantum field theory in the causal framework. Gauge invariance is, in this framework, an identity involving chronological products of the interaction Lagrangian; it expresses the fact that the scattering matrix must leave invariant the sub-space of physical states. We are interested in generalizations of such identity involving Wick sub-monomials of the interaction Lagrangian. The analysis can be performed by direct computation in the lower orders of perturbation theory; guided by these computations, we conjecture a generalization for arbitrary orders.
Invariants of broken discrete symmetries.
Kalozoumis, P A; Morfonios, C; Diakonos, F K; Schmelcher, P
2014-08-01
The parity and Bloch theorems are generalized to the case of broken global symmetry. Local inversion or translation symmetries in one dimension are shown to yield invariant currents that characterize wave propagation. These currents map the wave function from an arbitrary spatial domain to any symmetry-related domain. Our approach addresses any combination of local symmetries, thus applying, in particular, to acoustic, optical, and matter waves. Nonvanishing values of the invariant currents provide a systematic pathway to the breaking of discrete global symmetries.
Invariants of Broken Discrete Symmetries
NASA Astrophysics Data System (ADS)
Kalozoumis, P. A.; Morfonios, C.; Diakonos, F. K.; Schmelcher, P.
2014-08-01
The parity and Bloch theorems are generalized to the case of broken global symmetry. Local inversion or translation symmetries in one dimension are shown to yield invariant currents that characterize wave propagation. These currents map the wave function from an arbitrary spatial domain to any symmetry-related domain. Our approach addresses any combination of local symmetries, thus applying, in particular, to acoustic, optical, and matter waves. Nonvanishing values of the invariant currents provide a systematic pathway to the breaking of discrete global symmetries.
Preferred orientation in experimentally deformed stishovite: implications for deformation mechanisms
NASA Astrophysics Data System (ADS)
Kaercher, P. M.; Zepeda-Alarcon, E.; Prakapenka, V.; Kanitpanyacharoen, W.; Smith, J.; Sinogeikin, S. V.; Wenk, H. R.
2014-12-01
The crystal structure of the high pressure SiO2 polymorph stishovite has been studied in detail, yet little is known about its deformation mechanisms. Information about how stishovite deforms under stress is important for understanding subduction of quartz-bearing crustal rocks into the mantle. Particularly, stishovite is elastically anisotropic and thus development of crystallographic preferred orientation (CPO) during deformation may contribute to seismic anomalies in the mantle. We converted a natural sample of flint to stishovite in a laser heated diamond anvil cell and compressed the stishovite aggregate up to 38 GPa. Diffraction patterns were collected in situ in radial geometry at the Advanced Light Source (ALS) and the Advanced Photon Source (APS) to examine development of CPO during deformation. We find that (001) poles preferentially align with the compression direction and infer deformation mechanisms leading to the observed CPO with visco-plastic self consistent (VPSC) polycrystal plasticity models. Our results show pyramidal and basal slip are most likely active at high pressure and ambient temperature, in agreement with transmission electron microscopy (TEM) studies of rutile (TiO2) and paratellurite (TeO2), which are isostructural to stishovite. Conversely other TEM studies of stishovite done at higher temperature suggest dominant prismatic slip. This indicates that a variety of slip systems may be active in stishovite, depending on conditions. As a result, stishovite's contribution to the seismic signature in the mantle may vary as a function of pressure and temperature and thus depth.
Background Independence and Duality Invariance in String Theory.
Hohm, Olaf
2017-03-31
Closed string theory exhibits an O(D,D) duality symmetry on tori, which in double field theory is manifest before compactification. I prove that to first order in α^{'} there is no manifestly background independent and duality invariant formulation of bosonic string theory in terms of a metric, b field, and dilaton. To this end I use O(D,D) invariant second order perturbation theory around flat space to show that the unique background independent candidate expression for the gauge algebra at order α^{'} is inconsistent with the Jacobi identity. A background independent formulation exists instead for frame variables subject to α^{'}-deformed frame transformations (generalized Green-Schwarz transformations). Potential applications for curved backgrounds, as in cosmology, are discussed.
Background Independence and Duality Invariance in String Theory
NASA Astrophysics Data System (ADS)
Hohm, Olaf
2017-03-01
Closed string theory exhibits an O (D ,D ) duality symmetry on tori, which in double field theory is manifest before compactification. I prove that to first order in α' there is no manifestly background independent and duality invariant formulation of bosonic string theory in terms of a metric, b field, and dilaton. To this end I use O (D ,D ) invariant second order perturbation theory around flat space to show that the unique background independent candidate expression for the gauge algebra at order α' is inconsistent with the Jacobi identity. A background independent formulation exists instead for frame variables subject to α'-deformed frame transformations (generalized Green-Schwarz transformations). Potential applications for curved backgrounds, as in cosmology, are discussed.
Thomas, Anthony W.
2008-10-13
We discuss recent theoretical progress in understanding the distribution of spin and orbital angular momentum in the proton. Particular attention is devoted to the effect of QCD evolution and to the distinction between 'chiral' and 'invariant' spin. This is particularly significant with respect to the possible presence of polarized strange quarks.
Algebraic invariants for homotopy types
NASA Astrophysics Data System (ADS)
Blanc, David
1999-11-01
We define a sequence of purely algebraic invariants - namely, classes in the Quillen cohomology of the [Pi]-algebra [pi][low asterisk]X - for distinguishing between different homotopy types of spaces. Another sequence of such cohomology classes allows one to decide whether a given abstract [Pi]-algebra can be realized as the homotopy [Pi]-algebra of a space.
Galilean invariance in Lagrangian mechanics
NASA Astrophysics Data System (ADS)
Mohallem, J. R.
2015-10-01
The troublesome topic of Galilean invariance in Lagrangian mechanics is discussed in two situations: (i) A particular case involving a rheonomic constraint in uniform motion and (ii) the general translation of an entire system and the constants of motion involved. A widespread impropriety in most textbooks is corrected, concerning a condition for the equality h = E to hold.
Conformal invariant vacuum nonlinear electrodynamics
NASA Astrophysics Data System (ADS)
Denisov, V. I.; Dolgaya, E. E.; Sokolov, V. A.; Denisova, I. P.
2017-08-01
In this paper, a general case of conformal invariant vacuum nonlinear electrodynamics is studied. We analyze the consistency of this electrodynamics model with fundamental principles such as causality, unitarity, and the Ellis-Hawking dominant energy condition. Certain features of the electromagnetic waves in this model are investigated.
Boundary state from Ellwood invariants
NASA Astrophysics Data System (ADS)
Kudrna, Matěj; Maccaferri, Carlo; Schnabl, Martin
2013-07-01
Boundary states are given by appropriate linear combinations of Ishibashi states. Starting from any open string field theory solution and assuming Ellwood conjecture we show that every coefficient of such a linear combination is given by an Ellwood invariant, computed in a slightly modified theory where it does not trivially vanish by the on-shell condition. Unlike the previous construction of Kiermaier, Okawa and Zwiebach, ours is linear in the string field, it is manifestly gauge invariant and it is also suitable for solutions known only numerically. The correct boundary state is readily reproduced in the case of known analytic solutions and, as an example, we compute the energy momentum tensor of the rolling tachyon from the generalized invariants of the corresponding solution. We also compute the energy density profile of Siegel-gauge multiple lump solutions and show that, as the level increases, it correctly approaches a sum of delta functions. This provides a gauge invariant way of computing the separations between the lower dimensional D-branes.
Time-scale invariance as an emergent property in a perceptron with realistic, noisy neurons
Buhusi, Catalin V.; Oprisan, Sorinel A.
2013-01-01
In most species, interval timing is time-scale invariant: errors in time estimation scale up linearly with the estimated duration. In mammals, time-scale invariance is ubiquitous over behavioral, lesion, and pharmacological manipulations. For example, dopaminergic drugs induce an immediate, whereas cholinergic drugs induce a gradual, scalar change in timing. Behavioral theories posit that time-scale invariance derives from particular computations, rules, or coding schemes. In contrast, we discuss a simple neural circuit, the perceptron, whose output neurons fire in a clockwise fashion (interval timing) based on the pattern of coincidental activation of its input neurons. We show numerically that time-scale invariance emerges spontaneously in a perceptron with realistic neurons, in the presence of noise. Under the assumption that dopaminergic drugs modulate the firing of input neurons, and that cholinergic drugs modulate the memory representation of the criterion time, we show that a perceptron with realistic neurons reproduces the pharmacological clock and memory patterns, and their time-scale invariance, in the presence of noise. These results suggest that rather than being a signature of higher-order cognitive processes or specific computations related to timing, time-scale invariance may spontaneously emerge in a massively-connected brain from the intrinsic noise of neurons and circuits, thus providing the simplest explanation for the ubiquity of scale invariance of interval timing. PMID:23518297
Time-scale invariance as an emergent property in a perceptron with realistic, noisy neurons.
Buhusi, Catalin V; Oprisan, Sorinel A
2013-05-01
In most species, interval timing is time-scale invariant: errors in time estimation scale up linearly with the estimated duration. In mammals, time-scale invariance is ubiquitous over behavioral, lesion, and pharmacological manipulations. For example, dopaminergic drugs induce an immediate, whereas cholinergic drugs induce a gradual, scalar change in timing. Behavioral theories posit that time-scale invariance derives from particular computations, rules, or coding schemes. In contrast, we discuss a simple neural circuit, the perceptron, whose output neurons fire in a clockwise fashion based on the pattern of coincidental activation of its input neurons. We show numerically that time-scale invariance emerges spontaneously in a perceptron with realistic neurons, in the presence of noise. Under the assumption that dopaminergic drugs modulate the firing of input neurons, and that cholinergic drugs modulate the memory representation of the criterion time, we show that a perceptron with realistic neurons reproduces the pharmacological clock and memory patterns, and their time-scale invariance, in the presence of noise. These results suggest that rather than being a signature of higher order cognitive processes or specific computations related to timing, time-scale invariance may spontaneously emerge in a massively connected brain from the intrinsic noise of neurons and circuits, thus providing the simplest explanation for the ubiquity of scale invariance of interval timing. Copyright © 2013 Elsevier B.V. All rights reserved.
NASA Astrophysics Data System (ADS)
Larson, Kristine M.
1995-07-01
Geodetic measurements of crustal deformation provide direct tests of geophysical models which are used to describe the dynamics of the Earth. Although geodetic observations have been made throughout history, only in the last several hundred years have they been sufficiently precise for geophysical studies. In the 19th century, these techniques included leveling and triangulation. Approximately 25 years ago, trilateration measurements were initiated by the USGS (United States Geological Survey) to monitor active faults in the United States. Several years later, NASA (National Aeronautics and Space Administration) begin an effort to measure plate tectonic motions on a global scale, using space geodetic techniques, VLBI (Very Long Baseline Interferometry) and SLR (Satellite Laser Ranging). The period covered by this report to the IUGG, 1991-1994, was a transition period in the field of crustal deformation. Trilateration measurements (previously the backbone of measurements across plate boundaries in the western United States and Alaska) have been abandoned. This system was labor-intensive, involved highly trained crews to carry out the observations, and only measured the length between sites. In addition, NASA drastically cut the budgets for VLBI and SLR during this period. Fixed site VLBI systems are still operational, but mobile VLBI measurements in North America have ceased. SLR measurements continue on a global scale, but the remaining crustal deformation measurements are now being made with the Global Positioning System (GPS). Nonetheless, because of the time scales involved, older geodetic data (including leveling, triangulation, and trilateration) continue to be important for many geophysical studies.
Perception of Invariance Over Perspective Transformations in Five Month Old Infants.
ERIC Educational Resources Information Center
Gibson, Eleanor; And Others
This experiment asked whether infants at 5 months perceived an invariant over four types of rigid motion (perspective transformations), and thereby differentiated rigid motion from deformation. Four perspective transformations of a sponge rubber object (rotation around the vertical axis, rotation around the horizontal axis, rotation in the frontal…
Identification of the Origin of Monojet Signatures at the LHC
Rizzo, Thomas G.; /SLAC
2008-05-13
Several new physics scenarios can lead to monojet signatures at the LHC. If such events are observed above the Standard Model background it will be important to identify their origin. In this paper we compare and contrast these signatures as produced in two very different pictures: vector or scalar unparticle production in the scale-invariant/conformal regime and graviton emission in the Arkani-Hamed, Dimopoulos and Dvali extra-dimensional model. We demonstrate that these two scenarios can be distinguished at the LHC for a reasonable range of model parameters through the shape of their respective monojet and/or missing E{sub T} distributions.
ERIC Educational Resources Information Center
Hassler, Vesna; Biely, Helmut
1999-01-01
Describes the Digital Signature Project that was developed in Austria to establish an infrastructure for applying smart card-based digital signatures in banking and electronic-commerce applications. Discusses the need to conform to international standards, an international certification infrastructure, and security features for a public directory…
ERIC Educational Resources Information Center
Hassler, Vesna; Biely, Helmut
1999-01-01
Describes the Digital Signature Project that was developed in Austria to establish an infrastructure for applying smart card-based digital signatures in banking and electronic-commerce applications. Discusses the need to conform to international standards, an international certification infrastructure, and security features for a public directory…
Invariance of visual operations at the level of receptive fields
Lindeberg, Tony
2013-01-01
The brain is able to maintain a stable perception although the visual stimuli vary substantially on the retina due to geometric transformations and lighting variations in the environment. This paper presents a theory for achieving basic invariance properties already at the level of receptive fields. Specifically, the presented framework comprises (i) local scaling transformations caused by objects of different size and at different distances to the observer, (ii) locally linearized image deformations caused by variations in the viewing direction in relation to the object, (iii) locally linearized relative motions between the object and the observer and (iv) local multiplicative intensity transformations caused by illumination variations. The receptive field model can be derived by necessity from symmetry properties of the environment and leads to predictions about receptive field profiles in good agreement with receptive field profiles measured by cell recordings in mammalian vision. Indeed, the receptive field profiles in the retina, LGN and V1 are close to ideal to what is motivated by the idealized requirements. By complementing receptive field measurements with selection mechanisms over the parameters in the receptive field families, it is shown how true invariance of receptive field responses can be obtained under scaling transformations, affine transformations and Galilean transformations. Thereby, the framework provides a mathematically well-founded and biologically plausible model for how basic invariance properties can be achieved already at the level of receptive fields and support invariant recognition of objects and events under variations in viewpoint, retinal size, object motion and illumination. The theory can explain the different shapes of receptive field profiles found in biological vision, which are tuned to different sizes and orientations in the image domain as well as to different image velocities in space-time, from a requirement that the
Cohomological invariants of central simple algebras
NASA Astrophysics Data System (ADS)
Merkurjev, A. S.
2016-10-01
We determine the indecomposable degree 3 cohomological invariants of tuples of central simple algebras with linear relations. Equivalently, we determine the degree 3 reductive cohomological invariants of all split semisimple groups of type A.
Measurement invariance versus selection invariance: is fair selection possible?
Borsboom, Denny; Romeijn, Jan-Willem; Wicherts, Jelte M
2008-06-01
This article shows that measurement invariance (defined in terms of an invariant measurement model in different groups) is generally inconsistent with selection invariance (defined in terms of equal sensitivity and specificity across groups). In particular, when a unidimensional measurement instrument is used and group differences are present in the location but not in the variance of the latent distribution, sensitivity and positive predictive value will be higher in the group at the higher end of the latent dimension, whereas specificity and negative predictive value will be higher in the group at the lower end of the latent dimension. When latent variances are unequal, the differences in these quantities depend on the size of group differences in variances relative to the size of group differences in means. The effect originates as a special case of Simpson's paradox, which arises because the observed score distribution is collapsed into an accept-reject dichotomy. Simulations show the effect can be substantial in realistic situations. It is suggested that the effect may be partly responsible for overprediction in minority groups as typically found in empirical studies on differential academic performance. A methodological solution to the problem is suggested, and social policy implications are discussed. (PsycINFO Database Record (c) 2008 APA, all rights reserved).
Gauge invariance, current conservation, and GIAO's
NASA Technical Reports Server (NTRS)
Epstein, S. T.
1972-01-01
The well known relationship between gauge invariance and current conservation is exhibited within the usual quantum mechanical formalism. It is then shown that the use of gauge-invariant atomic orbitals (GIAO) does not necessarily lead to the expected current conservation. The reason is found to lie in the constrained nature of the gauge invariance which is provided by the use of GIAO's. It is concluded that this invariance is, of itself, no argument in favor of their use.
Signature detection and matching for document image retrieval.
Zhu, Guangyu; Zheng, Yefeng; Doermann, David; Jaeger, Stefan
2009-11-01
As one of the most pervasive methods of individual identification and document authentication, signatures present convincing evidence and provide an important form of indexing for effective document image processing and retrieval in a broad range of applications. However, detection and segmentation of free-form objects such as signatures from clustered background is currently an open document analysis problem. In this paper, we focus on two fundamental problems in signature-based document image retrieval. First, we propose a novel multiscale approach to jointly detecting and segmenting signatures from document images. Rather than focusing on local features that typically have large variations, our approach captures the structural saliency using a signature production model and computes the dynamic curvature of 2D contour fragments over multiple scales. This detection framework is general and computationally tractable. Second, we treat the problem of signature retrieval in the unconstrained setting of translation, scale, and rotation invariant nonrigid shape matching. We propose two novel measures of shape dissimilarity based on anisotropic scaling and registration residual error and present a supervised learning framework for combining complementary shape information from different dissimilarity metrics using LDA. We quantitatively study state-of-the-art shape representations, shape matching algorithms, measures of dissimilarity, and the use of multiple instances as query in document image retrieval. We further demonstrate our matching techniques in offline signature verification. Extensive experiments using large real-world collections of English and Arabic machine-printed and handwritten documents demonstrate the excellent performance of our approaches.
Invariance in Measurement and Prediction Revisited
ERIC Educational Resources Information Center
Millsap, Roger E.
2007-01-01
Borsboom (Psychometrika, 71:425-440, 2006) noted that recent work on measurement invariance (MI) and predictive invariance (PI) has had little impact on the practice of measurement in psychology. To understand this contention, the definitions of MI and PI are reviewed, followed by results on the consistency between the two forms of invariance in…
Measuring Scale Invariance between and within Subjects.
ERIC Educational Resources Information Center
Benson, Jeri; Hocevar, Dennis
The present paper represents a demonstration of how LISREL V can be used to investigate scale invariance (1) across time (its relationship to test-retest reliability), and (2) across groups. Five criteria were established to test scale invariance across time and four criteria were established to test scale invariance across groups. Using the…
Scalar Field Theory on κ-MINKOWSKI Space-Time and Translation and Lorentz Invariance
NASA Astrophysics Data System (ADS)
Meljanac, S.; Samsarov, A.
We investigate the properties of κ-Minkowski space-time by using representations of the corresponding deformed algebra in terms of undeformed Heisenberg-Weyl algebra. The deformed algebra consists of κ-Poincaré algebra extended with the generators of the deformed Weyl algebra. The part of deformed algebra, generated by rotation, boost and momentum generators, is described by the Hopf algebra structure. The approach used in our considerations is completely Lorentz covariant. We further use an advantage of this approach to consistently construct a star product, which has a property that under integration sign, it can be replaced by a standard pointwise multiplication, a property that was since known to hold for Moyal but not for κ-Minkowski space-time. This star product also has generalized trace and cyclic properties, and the construction alone is accomplished by considering a classical Dirac operator representation of deformed algebra and requiring it to be Hermitian. We find that the obtained star product is not translationally invariant, leading to a conclusion that the classical Dirac operator representation is the one where translation invariance cannot simultaneously be implemented along with hermiticity. However, due to the integral property satisfied by the star product, noncommutative free scalar field theory does not have a problem with translation symmetry breaking and can be shown to reduce to an ordinary free scalar field theory without nonlocal features and tachyonic modes and basically of the very same form. The issue of Lorentz invariance of the theory is also discussed.
Anisotropic invariance in minisuperspace models
NASA Astrophysics Data System (ADS)
Chagoya, Javier; Sabido, Miguel
2016-06-01
In this paper we introduce invariance under anisotropic transformations to cosmology. This invariance is one of the key ingredients of the theory of quantum gravity at a Lifshitz point put forward by Hořava. We find that this new symmetry in the minisuperspace introduces characteristics to the model that can be relevant in the ultraviolet regime. For example, by canonical quantization we find a Schrödinger-type equation which avoids the problem of frozen time in quantum cosmology. For simple cases we obtain solutions to this quantum equation in a Kantowski-Sachs (KS) minisuperspace. At the classical level, we study KS and Friedmann-Robertson-Walker cosmologies, obtaining modifications to the solutions of general relativity that can be relevant in the early Universe.
Proton spin: A topological invariant
NASA Astrophysics Data System (ADS)
Tiwari, S. C.
2016-11-01
Proton spin problem is given a new perspective with the proposition that spin is a topological invariant represented by a de Rham 3-period. The idea is developed generalizing Finkelstein-Rubinstein theory for Skyrmions/kinks to topological defects, and using non-Abelian de Rham theorems. Two kinds of de Rham theorems are discussed applicable to matrix-valued differential forms, and traces. Physical and mathematical interpretations of de Rham periods are presented. It is suggested that Wilson lines and loop operators probe the local properties of the topology, and spin as a topological invariant in pDIS measurements could appear with any value from 0 to ℏ 2, i.e. proton spin decomposition has no meaning in this approach.
Conformal invariance for Wilson actions
NASA Astrophysics Data System (ADS)
Sonoda, H.
2017-08-01
We discuss the realization of conformal invariance for Wilson actions using the formalism of the exact renormalization group. This subject has been studied extensively in the recent works of O. J. Rosten. The main purpose of this paper is to reformulate Rosten's formulas for conformal transformations using a method developed earlier for the realization of any continuous symmetry in the exact renormalization group formalism. The merit of the reformulation is simplicity and transparency via the consistent use of equation-of-motion operators. We derive equations that imply the invariance of the Wilson action under infinitesimal conformal transformations which are non-linearly realized but form a closed conformal algebra. The best effort has been made to make the paper self-contained; ample background on the formalism is provided.
Emerging universe from scale invariance
Del Campo, Sergio; Herrera, Ramón; Guendelman, Eduardo I.; Labraña, Pedro E-mail: guendel@bgu.ac.il E-mail: plabrana@ubiobio.cl
2010-06-01
We consider a scale invariant model which includes a R{sup 2} term in action and show that a stable ''emerging universe'' scenario is possible. The model belongs to the general class of theories, where an integration measure independent of the metric is introduced. To implement scale invariance (S.I.), a dilaton field is introduced. The integration of the equations of motion associated with the new measure gives rise to the spontaneous symmetry breaking (S.S.B) of S.I. After S.S.B. of S.I. in the model with the R{sup 2} term (and first order formalism applied), it is found that a non trivial potential for the dilaton is generated. The dynamics of the scalar field becomes non linear and these non linearities are instrumental in the stability of some of the emerging universe solutions, which exists for a parameter range of the theory.
Invariant Foliation of Dynamical Spacetimes
NASA Astrophysics Data System (ADS)
Tiemblo, A.; Tresguerres, R.
1998-02-01
We present a gauge-theoretical derivation of the Frobenius foliation condition. It is based on a nonlinear coset realization of the Poincaré group, implying the time component ϑ0 of the coframe to be invariant. By means of the unitary gauge fixing of the boosts, three Goldstone-like degrees of freedom of ϑ0 are eliminated. The remaining Higgs-like boson, satisfying the foliation condition, plays the role of time.
Invariant amplitudes for pion electroproduction
NASA Astrophysics Data System (ADS)
Pasquini, B.; Drechsel, D.; Tiator, L.
2007-12-01
The invariant amplitudes for pion electroproduction on the nucleon are evaluated by dispersion relations at constant t with MAID as input for the imaginary parts of these amplitudes. In the threshold region these amplitudes are confronted with the predictions of several low-energy theorems derived in the soft-pion limit. In general agreement with chiral perturbation theory, the dispersive approach yields large corrections to these theorems because of the finite pion mass.
Holographic multiverse and conformal invariance
Garriga, Jaume; Vilenkin, Alexander E-mail: vilenkin@cosmos.phy.tufts.edu
2009-11-01
We consider a holographic description of the inflationary multiverse, according to which the wave function of the universe is interpreted as the generating functional for a lower dimensional Euclidean theory. We analyze a simple model where transitions between inflationary vacua occur through bubble nucleation, and the inflating part of spacetime consists of de Sitter regions separated by thin bubble walls. In this model, we present some evidence that the dual theory is conformally invariant in the UV.
[Invariants of the anthropometrical proportions].
Smolianinov, V V
2012-01-01
In this work a general interpretation of a modulor as scales of segments proportions of anthropometrical modules (extremities and a body) is made. The objects of this study were: 1) to reason the idea of the growth modulor; 2) using the modern empirical data, to prove the validity of a principle of linear similarity for anthropometrical segments; 3) to specify the system of invariants for constitutional anthropometrics.
Shift and Scale Invariant Preprocessor.
1981-12-01
1982 THESIS D V SHIFT AND SCALE INVARIANT ?PREPROCESSOR by Norman E. Huston, Jr. December 1981 0 Thesis Advisor: L. A. Wilson Approved for public...SCHOOL December 1981 Author: - . 4 ,/ A pp ro0ved by: rYY. ( Thesis Advisor Co-Ad isor Chairman, De artment of 4n n eing Dean of Science and...large range of problems/disciplines. Fields where it is particularly common include optical imagery, acoustic signal processing , radiology, radio
Knot Invariants and Cellular Automata
1993-05-04
lattice gases. Since our approach equates the spacetime evolution of a dynamical system with an equilibrium configuration of a statistical mechanics...model in one higher dimension, a model of ’t Hooft for two dimensional spacetime with discrete local coordinate invariance was a natural inspiration [5...thermodynamic equilibrium, as well as demonstrating the efficacy of constructing and analyzing lattice gas automata according to ( spacetime ) symmetry principles
Invariance of the Noether charge
NASA Astrophysics Data System (ADS)
Silagadze, Z. K.
2016-01-01
Surprisingly, an interesting property of the Noether charge that it is by itself invariant under the corresponding symmetry transformation is never discussed in quantum field theory or classical mechanics textbooks we have checked. This property is also almost never mentioned in articles devoted to Noether’s theorem. Nevertheless, to prove this property in the context of Lagrangian formalism is not quite trivial and the proof, outlined in this article, can constitute an useful and interesting exercise for students.
Scale invariance implies conformal invariance for the three-dimensional Ising model.
Delamotte, Bertrand; Tissier, Matthieu; Wschebor, Nicolás
2016-01-01
Using the Wilson renormalization group, we show that if no integrated vector operator of scaling dimension -1 exists, then scale invariance implies conformal invariance. By using the Lebowitz inequalities, we prove that this necessary condition is fulfilled in all dimensions for the Ising universality class. This shows, in particular, that scale invariance implies conformal invariance for the three-dimensional Ising model.
Inflationary quasiscale-invariant attractors
NASA Astrophysics Data System (ADS)
Rinaldi, Massimiliano; Vanzo, Luciano; Zerbini, Sergio; Venturi, Giovanni
2016-01-01
In a series of recent papers Kallosh, Linde, and collaborators provide a unified description of single-field inflation with several types of potentials ranging from power law to supergravity, in terms of just one parameter α . These so-called α attractors predict a spectral index ns and a tensor-to-scalar ratio r , which are fully compatible with the latest Planck data. The only common feature of all α attractors is a noncanonical kinetic term with a pole, and a potential analytic around the pole. In this paper, starting from the same Einstein frame with a noncanonical scalar kinetic energy, we explore the case of nonanalytic potentials. We find the functional form that corresponds to quasiscale-invariant gravitational models in the Jordan frame characterized by a universal relation between r and ns that fits the observational data but is clearly distinct from the one of the α attractors. It is known that the breaking of the exact classical scale invariance in the Jordan frame can be attributed to one-loop corrections. Therefore we conclude that there exists a class of nonanalytic potentials in the noncanonical Einstein frame that is physically equivalent to a class of models in the Jordan frame, with scale invariance softly broken by one-loop quantum corrections.
Similarity, invariance, and musical variation.
McAdams, S; Matzkin, D
2001-06-01
Perceptual similarity underlies a number of important psychological properties of musical materials, including perceptual invariance under transformation, categorization, recognition, and the sense of familiarity. Mental processes involved in the perception of musical similarity may be an integral part of the functional logic of music composition and thus underly important aspects of musical experience. How much and in what ways can musical materials be varied and still be considered as perceptually related or as belonging to the same category? The notions of musical material, musical variation, perceptual similarity and invariance, and form-bearing dimensions are considered in this light. Recent work on similarity perception has demonstrated that the transformation space for a given musical material is limited by several factors ranging from degree of match of the values of auditory attributes of the events composing the sequences to their relations of various levels of abstraction and to the degree that the transformation respects the grammar of the musical system within which the material was composed. These notions and results are considered in the light of future directions of research, particularly concerning the role of similarity and invariance in the understanding of musical form during listening.
Disformal invariance of curvature perturbation
Motohashi, Hayato; White, Jonathan E-mail: jwhite@post.kek.jp
2016-02-01
We show that under a general disformal transformation the linear comoving curvature perturbation is not identically invariant, but is invariant on superhorizon scales for any theory that is disformally related to Horndeski's theory. The difference between disformally related curvature perturbations is found to be given in terms of the comoving density perturbation associated with a single canonical scalar field. In General Relativity it is well-known that this quantity vanishes on superhorizon scales through the Poisson equation that is obtained on combining the Hamiltonian and momentum constraints, and we confirm that a similar result holds for any theory that is disformally related to Horndeski's scalar-tensor theory so long as the invertibility condition for the disformal transformation is satisfied. We also consider the curvature perturbation at full nonlinear order in the unitary gauge, and find that it is invariant under a general disformal transformation if we assume that an attractor regime has been reached. Finally, we also discuss the counting of degrees of freedom in theories disformally related to Horndeski's.
Hierarchies of invariant spin models
NASA Astrophysics Data System (ADS)
Carbone, Gaspare; Carfora, Mauro; Marzuoli, Annalisa
2001-02-01
In this paper we present classes of state sum models based on the recoupling theory of angular momenta of SU(2) (and of its q-counterpart U q(sl(2)) , q a root of unity). Such classes are arranged in hierarchies depending on the dimension d, and include all known closed models, i.e., the Ponzano-Regge state sum and the Turaev-Viro invariant in dimension d=3, the Crane-Yetter invariant in d=4. In general, the recoupling coefficient associated with a d-simplex turns out to be a {3(d-2)(d+1)/2}j symbol, or its q-analog. Each of the state sums can be further extended to compact triangulations (T d,∂T d) of a PL-pair (M d,∂M d) , where the triangulation of the boundary manifold is not kept fixed. In both cases we find out the algebraic identities which translate complete sets of topological moves, thus showing that all state sums are actually independent of the particular triangulation chosen. Then, owing to Pachner's theorems, it turns out that classes of PL-invariant models can be defined in any dimension d.
Twin Signature Schemes, Revisited
NASA Astrophysics Data System (ADS)
Schäge, Sven
In this paper, we revisit the twin signature scheme by Naccache, Pointcheval and Stern from CCS 2001 that is secure under the Strong RSA (SRSA) assumption and improve its efficiency in several ways. First, we present a new twin signature scheme that is based on the Strong Diffie-Hellman (SDH) assumption in bilinear groups and allows for very short signatures and key material. A big advantage of this scheme is that, in contrast to the original scheme, it does not require a computationally expensive function for mapping messages to primes. We prove this new scheme secure under adaptive chosen message attacks. Second, we present a modification that allows to significantly increase efficiency when signing long messages. This construction uses collision-resistant hash functions as its basis. As a result, our improvements make the signature length independent of the message size. Our construction deviates from the standard hash-and-sign approach in which the hash value of the message is signed in place of the message itself. We show that in the case of twin signatures, one can exploit the properties of the hash function as an integral part of the signature scheme. This improvement can be applied to both the SRSA based and SDH based twin signature scheme.
NASA Astrophysics Data System (ADS)
Fujisaki, Eiichiro; Suzuki, Koutarou
The ring signature allows a signer to leak secrets anonymously, without the risk of identity escrow. At the same time, the ring signature provides great flexibility: No group manager, no special setup, and the dynamics of group choice. The ring signature is, however, vulnerable to malicious or irresponsible signers in some applications, because of its anonymity. In this paper, we propose a traceable ring signature scheme. A traceable ring scheme is a ring signature except that it can restrict “excessive” anonymity. The traceable ring signature has a tag that consists of a list of ring members and an issue that refers to, for instance, a social affair or an election. A ring member can make any signed but anonymous opinion regarding the issue, but only once (per tag). If the member submits another signed opinion, possibly pretending to be another person who supports the first opinion, the identity of the member is immediately revealed. If the member submits the same opinion, for instance, voting “yes” regarding the same issue twice, everyone can see that these two are linked. The traceable ring signature can suit to many applications, such as an anonymous voting on a BBS. We formalize the security definitions for this primitive and show an efficient and simple construction in the random oracle model.
NASA Technical Reports Server (NTRS)
Graham, D. E.; Overbeek, R.; Olsen, G. J.; Woese, C. R.
2000-01-01
Comparisons of complete genome sequences allow the most objective and comprehensive descriptions possible of a lineage's evolution. This communication uses the completed genomes from four major euryarchaeal taxa to define a genomic signature for the Euryarchaeota and, by extension, the Archaea as a whole. The signature is defined in terms of the set of protein-encoding genes found in at least two diverse members of the euryarchaeal taxa that function uniquely within the Archaea; most signature proteins have no recognizable bacterial or eukaryal homologs. By this definition, 351 clusters of signature proteins have been identified. Functions of most proteins in this signature set are currently unknown. At least 70% of the clusters that contain proteins from all the euryarchaeal genomes also have crenarchaeal homologs. This conservative set, which appears refractory to horizontal gene transfer to the Bacteria or the Eukarya, would seem to reflect the significant innovations that were unique and fundamental to the archaeal "design fabric." Genomic protein signature analysis methods may be extended to characterize the evolution of any phylogenetically defined lineage. The complete set of protein clusters for the archaeal genomic signature is presented as supplementary material (see the PNAS web site, www.pnas.org).
An archaeal genomic signature.
Graham, D E; Overbeek, R; Olsen, G J; Woese, C R
2000-03-28
Comparisons of complete genome sequences allow the most objective and comprehensive descriptions possible of a lineage's evolution. This communication uses the completed genomes from four major euryarchaeal taxa to define a genomic signature for the Euryarchaeota and, by extension, the Archaea as a whole. The signature is defined in terms of the set of protein-encoding genes found in at least two diverse members of the euryarchaeal taxa that function uniquely within the Archaea; most signature proteins have no recognizable bacterial or eukaryal homologs. By this definition, 351 clusters of signature proteins have been identified. Functions of most proteins in this signature set are currently unknown. At least 70% of the clusters that contain proteins from all the euryarchaeal genomes also have crenarchaeal homologs. This conservative set, which appears refractory to horizontal gene transfer to the Bacteria or the Eukarya, would seem to reflect the significant innovations that were unique and fundamental to the archaeal "design fabric." Genomic protein signature analysis methods may be extended to characterize the evolution of any phylogenetically defined lineage. The complete set of protein clusters for the archaeal genomic signature is presented as supplementary material (see the PNAS web site, www.pnas.org).
Graham, David E.; Overbeek, Ross; Olsen, Gary J.; Woese, Carl R.
2000-01-01
Comparisons of complete genome sequences allow the most objective and comprehensive descriptions possible of a lineage's evolution. This communication uses the completed genomes from four major euryarchaeal taxa to define a genomic signature for the Euryarchaeota and, by extension, the Archaea as a whole. The signature is defined in terms of the set of protein-encoding genes found in at least two diverse members of the euryarchaeal taxa that function uniquely within the Archaea; most signature proteins have no recognizable bacterial or eukaryal homologs. By this definition, 351 clusters of signature proteins have been identified. Functions of most proteins in this signature set are currently unknown. At least 70% of the clusters that contain proteins from all the euryarchaeal genomes also have crenarchaeal homologs. This conservative set, which appears refractory to horizontal gene transfer to the Bacteria or the Eukarya, would seem to reflect the significant innovations that were unique and fundamental to the archaeal “design fabric.” Genomic protein signature analysis methods may be extended to characterize the evolution of any phylogenetically defined lineage. The complete set of protein clusters for the archaeal genomic signature is presented as supplementary material (see the PNAS web site, www.pnas.org). PMID:10716711
2014-01-01
Sequencing complete tumor genomes and exomes has sparked the cancer field's interest in mutation signatures for identifying the tumor's carcinogen. This review and meta-analysis discusses signatures and their proper use. We first distinguish between a mutagen's canonical mutations – deviations from a random distribution of base changes to create a pattern typical of that mutagen – and the subset of signature mutations, which are unique to that mutagen and permit inference backward from mutations to mutagen. To verify UV signature mutations, we assembled literature datasets on cells exposed to UVC, UVB, UVA, or solar simulator light (SSL) and tested canonical UV mutation features as criteria for clustering datasets. A confirmed UV signature was: ≥60% of mutations are C→T at a dipyrimidine site, with ≥5% CC→TT. Other canonical features such as a bias for mutations on the non-transcribed strand or at the 3' pyrimidine had limited application. The most robust classifier combined these features with criteria for the rarity of non-UV canonical mutations. In addition, several signatures proposed for specific UV wavelengths were limited to specific genes or species; non-signature mutations induced by UV may cause melanoma BRAF mutations; and the mutagen for sunlight-related skin neoplasms may vary between continents. PMID:25354245
NASA Technical Reports Server (NTRS)
Graham, D. E.; Overbeek, R.; Olsen, G. J.; Woese, C. R.
2000-01-01
Comparisons of complete genome sequences allow the most objective and comprehensive descriptions possible of a lineage's evolution. This communication uses the completed genomes from four major euryarchaeal taxa to define a genomic signature for the Euryarchaeota and, by extension, the Archaea as a whole. The signature is defined in terms of the set of protein-encoding genes found in at least two diverse members of the euryarchaeal taxa that function uniquely within the Archaea; most signature proteins have no recognizable bacterial or eukaryal homologs. By this definition, 351 clusters of signature proteins have been identified. Functions of most proteins in this signature set are currently unknown. At least 70% of the clusters that contain proteins from all the euryarchaeal genomes also have crenarchaeal homologs. This conservative set, which appears refractory to horizontal gene transfer to the Bacteria or the Eukarya, would seem to reflect the significant innovations that were unique and fundamental to the archaeal "design fabric." Genomic protein signature analysis methods may be extended to characterize the evolution of any phylogenetically defined lineage. The complete set of protein clusters for the archaeal genomic signature is presented as supplementary material (see the PNAS web site, www.pnas.org).
Chronometric Invariance and String Theory
NASA Astrophysics Data System (ADS)
Pollock, M. D.
The Einstein-Hilbert Lagrangian R is expressed in terms of the chronometrically invariant quantities introduced by Zel'manov for an arbitrary four-dimensional metric gij. The chronometrically invariant three-space is the physical space γαβ = -gαβ+e2ϕ γαγβ, where e2ϕ = g00 and γα = g0α/g00, and whose determinant is h. The momentum canonically conjugate to γαβ is π α β =-√ {h}(Kα β -γ α β K), where Kα β =½ ∂ tγ α β and ∂t≡e-ϕ∂0 is the chronometrically invariant derivative with respect to time. The Wheeler-DeWitt equation for the wave function Ψ is derived. For a stationary space-time, such as the Kerr metric, παβ vanishes, implying that there is then no dynamics. The most symmetric, chronometrically-invariant space, obtained after setting ϕ = γα = 0, is Rα β =-λ (t)δ α β , where δαβ is constant and has curvature k. From the Friedmann and Raychaudhuri equations, we find that λ is constant only if k=1 and the source is a perfect fluid of energy-density ρ and pressure p=(γ-1)ρ, with adiabatic index γ=2/3, which is the value for a random ensemble of strings, thus yielding a three-dimensional de Sitter space embedded in four-dimensional space-time. Furthermore, Ψ is only invariant under the time-reversal operator {T} if γ=2/(2n-1), where n is a positive integer, the first two values n=1,2 defining the high-temperature and low-temperature limits ρ T±2, respectively, of the heterotic superstring theory, which are thus dual to one another in the sense T↔1/2π2α‧T.
Blur invariants constructed from arbitrary moments.
Kautsky, Jaroslav; Flusser, Jan
2011-12-01
This paper deals with moment invariants with respect to image blurring. It is mainly a reaction to the works of Zhang and Chen , recently published in these Transactions. We present a general method on how to construct blur invariants from arbitrary moments and show that it is no longer necessary to separately derive the invariants for each polynomial basis. We show how to discard dependent terms in blur invariants definition and discuss a proper implementation of the invariants in orthogonal bases using recurrent relations. An example for Legendre moments is given. © 2011 IEEE
Shape invariant potentials in higher dimensions
Sandhya, R.; Sree Ranjani, S.; Kapoor, A.K.
2015-08-15
In this paper we investigate the shape invariance property of a potential in one dimension. We show that a simple ansatz allows us to reconstruct all the known shape invariant potentials in one dimension. This ansatz can be easily extended to arrive at a large class of new shape invariant potentials in arbitrary dimensions. A reformulation of the shape invariance property and possible generalizations are proposed. These may lead to an important extension of the shape invariance property to Hamiltonians that are related to standard potential problems via space time transformations, which are found useful in path integral formulation of quantum mechanics.
Jordanian deformation of the open XXX spin chain
NASA Astrophysics Data System (ADS)
Kulish, P. P.; Manojlović, N.; Nagy, Z.
2010-05-01
We find the general solution of the reflection equation associated with the Jordanian deformation of the SL(2)-invariant Yang R-matrix. A special scaling limit of the XXZ model with general boundary conditions leads to the same K-matrix. Following the Sklyanin formalism, we derive the Hamiltonian with the boundary terms in explicit form. We also discuss the structure of the spectrum of the deformed XXX model and its dependence on the boundary conditions.
On asymptotically lacunary invariant statistical equivalent set sequences
NASA Astrophysics Data System (ADS)
Pancaroglu, Nimet; Nuray, Fatih; Savas, Ekrem
2013-10-01
In this paper, we define asymptotically invariant equivalence, strongly asymptotically invariant equivalence, asymptotically invariant statistical equivalence, asymptotically lacunary invariant statistical equivalence, strongly asymptotically lacunary invariant equivalence, asymptotically lacunary invariant equivalence (Wijsman sense) for sequences of sets. Also we investigate some relations between asymptotically lacunary invariant statistical equivalence and asymptotically invariant statistical equivalence for sequences of sets. We introduce some notions and theorems as follows, asymptotically lacunary invariant statistical equivalence, strongly asymptotically lacunary invariant equivalence, asymptotically lacunary invariant equivalence (Wijsman sense) for sequences of sets.
Cohen, Bruce E; Nicholson, Christopher W
2007-05-01
The bunionette, or tailor's bunion, is a lateral prominence of the fifth metatarsal head. Most commonly, bunionettes are the result of a widened 4-5 intermetatarsal angle with associated varus of the metatarsophalangeal joint. When symptomatic, these deformities often respond to nonsurgical treatment methods, such as wider shoes and padding techniques. When these methods are unsuccessful, surgical treatment is based on preoperative radiographs and associated lesions, such as hyperkeratoses. In rare situations, a simple lateral eminence resection is appropriate; however, the risk of recurrence or overresection is high with this technique. Patients with a lateral bow to the fifth metatarsal are treated with a distal chevron-type osteotomy. A widened 4-5 intermetatarsal angle often requires a diaphyseal osteotomy for correction.
Are there molecular signatures?
Bennett, W.P.
1995-10-01
This report describes molecular signatures and mutational spectrum analysis. The mutation spectrum is defined as the type and location of DNA base change. There are currently about five well documented cases. Mutations and radon-associated tumors are discussed.
President Signature Onboard Curiosity
2012-09-21
This view of Curiosity deck shows a plaque bearing several signatures of US officials, including that of President Obama and Vice President Biden. The image was taken by the rover Mars Hand Lens Imager MAHLI.
Automated transformation-invariant shape recognition through wavelet multiresolution
NASA Astrophysics Data System (ADS)
Brault, Patrice; Mounier, Hugues
2001-12-01
We present here new results in Wavelet Multi-Resolution Analysis (W-MRA) applied to shape recognition in automatic vehicle driving applications. Different types of shapes have to be recognized in this framework. They pertain to most of the objects entering the sensors field of a car. These objects can be road signs, lane separation lines, moving or static obstacles, other automotive vehicles, or visual beacons. The recognition process must be invariant to global, affine or not, transformations which are : rotation, translation and scaling. It also has to be invariant to more local, elastic, deformations like the perspective (in particular with wide angle camera lenses), and also like deformations due to environmental conditions (weather : rain, mist, light reverberation) or optical and electrical signal noises. To demonstrate our method, an initial shape, with a known contour, is compared to the same contour altered by rotation, translation, scaling and perspective. The curvature computed for each contour point is used as a main criterion in the shape matching process. The original part of this work is to use wavelet descriptors, generated with a fast orthonormal W-MRA, rather than Fourier descriptors, in order to provide a multi-resolution description of the contour to be analyzed. In such way, the intrinsic spatial localization property of wavelet descriptors can be used and the recognition process can be speeded up. The most important part of this work is to demonstrate the potential performance of Wavelet-MRA in this application of shape recognition.
Scale Invariant Gabor Descriptor-Based Noncooperative Iris Recognition
NASA Astrophysics Data System (ADS)
Du, Yingzi; Belcher, Craig; Zhou, Zhi
2010-12-01
A new noncooperative iris recognition method is proposed. In this method, the iris features are extracted using a Gabor descriptor. The feature extraction and comparison are scale, deformation, rotation, and contrast-invariant. It works with off-angle and low-resolution iris images. The Gabor wavelet is incorporated with scale-invariant feature transformation (SIFT) for feature extraction to better extract the iris features. Both the phase and magnitude of the Gabor wavelet outputs were used in a novel way for local feature point description. Two feature region maps were designed to locally and globally register the feature points and each subregion in the map is locally adjusted to the dilation/contraction/deformation. We also developed a video-based non-cooperative iris recognition system by integrating video-based non-cooperative segmentation, segmentation evaluation, and score fusion units. The proposed method shows good performance for frontal and off-angle iris matching. Video-based recognition methods can improve non-cooperative iris recognition accuracy.
Meteor signature interpretation
Canavan, G.H.
1997-01-01
Meteor signatures contain information about the constituents of space debris and present potential false alarms to early warnings systems. Better models could both extract the maximum scientific information possible and reduce their danger. Accurate predictions can be produced by models of modest complexity, which can be inverted to predict the sizes, compositions, and trajectories of object from their signatures for most objects of interest and concern.
NASA Astrophysics Data System (ADS)
Dai, Wei-Ming; Guo, Zong-Kuan; Cai, Rong-Gen; Zhang, Yuan-Zhong
2017-06-01
We investigate constraints on Lorentz invariance violation in the neutrino sector from a joint analysis of big bang nucleosynthesis and the cosmic microwave background. The effect of Lorentz invariance violation during the epoch of big bang nucleosynthesis changes the predicted helium-4 abundance, which influences the power spectrum of the cosmic microwave background at the recombination epoch. In combination with the latest measurement of the primordial helium-4 abundance, the Planck 2015 data of the cosmic microwave background anisotropies give a strong constraint on the deformation parameter since adding the primordial helium measurement breaks the degeneracy between the deformation parameter and the physical dark matter density.
De Sitter Invariant Special Relativity
NASA Astrophysics Data System (ADS)
Yan, Mu-Lin
2015-06-01
Einstein's Special Relativity is one of the cornerstones of modern physics. There is one universal parameter c (i.e., speed of light) in the Einstein's Special Relativity (E-SR), which serves as the maximal velocity of physics. One might be curious about whether there is another universal parameter R that serves as the maximal length in physics besides the universal maximal velocity limit c. The answer is yes. This book intends to describe a special theory of relativity with two universal parameters c and R. Such a theory is called the de Sitter Invariant Special Relativity, or the Special Relativity with Cosmology Constant...
A Characterization of Invariant Connections
NASA Astrophysics Data System (ADS)
Hanusch, Maximilian
2014-03-01
Given a principal fibre bundle with structure group S and a fibre transitive Lie group G of automorphisms thereon, Wang's theorem identifies the invariant connections with certain linear maps ψ\\colon {g}→ {s}. In the present paper we prove an extension of this theorem that applies to the general situation where G acts non-transitively on the base manifold. We consider several special cases of the general theorem including the result of Harnad, Shnider and Vinet which applies to the situation where G admits only one orbit type. Along the way we give applications to loop quantum gravity.
Invariant Quantities in Shear Flow
NASA Astrophysics Data System (ADS)
Baule, A.; Evans, R. M. L.
2008-12-01
The dynamics of systems out of thermal equilibrium is usually treated on a case-by-case basis without knowledge of fundamental and universal principles. We address this problem for a class of driven steady states, namely, those mechanically driven at the boundaries such as complex fluids under shear. From a nonequilibrium counterpart to detailed balance (NCDB) we derive a remarkably simple set of invariant quantities which remain unchanged when the system is driven. These new nonequilibrium relations are both exact and valid arbitrarily far from equilibrium. Furthermore, they enable the systematic calculation of transition rates in driven systems with state spaces of arbitrary connectivity.
More on lattice BRST invariance
NASA Astrophysics Data System (ADS)
Bock, Wolfgang; Golterman, Maarten F. L.; Shamir, Yigal
1998-11-01
In the gauge-fixing approach to (chiral) lattice gauge theories, the action in the U(1) case implicitly contains a free ghost term, in accordance with the continuum Abelian theory. On the lattice there is no BRST symmetry and, without fermions, the partition function is strictly positive. Recently, Neuberger pointed out, Phys. Rev. D 58, 057502 (1998), that a different choice of the ghost term would lead to a BRST-invariant lattice model, which is ill defined nonperturbatively. We show that such a lattice model is inconsistent already in perturbation theory, and clearly different from the gauge-fixing approach.
Parallel computation of invariant measures
Ding, J.; Liu, Y.
1995-12-01
A parallel numerical algorithm for computing invariant measures is presented. Let I{sup N} {triple_bond} [0,1]{sup N} be the unit N-cube in R N and let S : I{sup N}{r_arrow} I{sup N} be a nonsingular transformation, that is, S is Borel-measurable and m(A) = 0 implies m(S{sup -1}(A)) = 0, where m is the Lebesgue measure. The motivation of this study is the parallel computation of an absolutely continuous invariant measure {mu} under S, that is, {mu} {much_lt} m and {mu}(A) = {mu}(S{sup -1}(A)) for all Borel sets A {contained_in} I{sup N}. It is well-known that an absolutely continuous finite invariant measure {mu} can be obtained by computing a fixed density of the Frobenius-Perron operator Ps: L{sup 1} (I{sup N}) {r_arrow} L{sup 1}(I{sup N}) associated with S which is defined by (1) {integral}{sub A} P{sub S}fdm = {integral}{sub s-1(A)} fdm, {forall}f {element_of} L{sup 1} (I{sup N}). Using any suitable discretization scheme, the infinite dimensional eigenvector problem P{sub S}f = f in L{sup 1}(I{sup N}) can be approximated by an algebraic eigenvector problem P{sub l}f{sub l} = f{sub l} in {gradient}{sub l}, where P{sub l} is a finite approximation of P{sub s} associated with a finite element subspace {gradient}{sub l} of L{sup l} (I{sup N}) {intersection} L{sup {infinity}} (I{sup N}). It has been shown that for P{sub l} arising from Galerkin`s projection principle or the Markov finite approximation principle, there always exists a eigenvector f{sub l} to P{sub l}, and that a sequence of normalized eigenvectors (f{sub l}) converges to the density of an absolutely continuous probability invariant measure {mu} for a class of piecewise C{sup 2} expanding maps of I{sup N} under which the existence of {mu} is guaranteed by Gora-Boyarsky`s theorem which is reduced to Lasota-Yorke`s thoerem when N = 1.
Prognostic value of a 92-probe signature in breast cancer.
Akter, Salima; Choi, Tae Gyu; Nguyen, Minh Nam; Matondo, Abel; Kim, Jin-Hwan; Jo, Yong Hwa; Jo, Ara; Shahid, Muhammad; Jun, Dae Young; Yoo, Ji Youn; Nguyen, Ngoc Ngo Yen; Seo, Seong-Wook; Ali, Liaquat; Lee, Ju-Seog; Yoon, Kyung-Sik; Choe, Wonchae; Kang, Insug; Ha, Joohun; Kim, Jayoung; Kim, Sung Soo
2015-06-20
Clinical applications of gene expression signatures in breast cancer prognosis still remain limited due to poor predictive strength of single training datasets and appropriate invariable platforms. We proposed a gene expression signature by reducing baseline differences and analyzing common probes among three recent Affymetrix U133 plus 2 microarray data sets. Using a newly developed supervised method, a 92-probe signature found in this study was associated with overall survival. It was robustly validated in four independent data sets and then repeated on three subgroups by incorporating 17 breast cancer microarray datasets. The signature was an independent predictor of patients' survival in univariate analysis [(HR) 1.927, 95% CI (1.237-3.002); p < 0.01] as well as multivariate analysis after adjustment of clinical variables [(HR) 7.125, 95% CI (2.462-20.618); p < 0.001]. Consistent predictive performance was found in different multivariate models in increased patient population (p = 0.002). The survival signature predicted a late metastatic feature through 5-year disease free survival (p = 0.006). We identified subtypes within the lymph node positive (p < 0.001) and ER positive (p = 0.01) patients that best reflected the invasive breast cancer biology. In conclusion using the Common Probe Approach, we present a novel prognostic signature as a predictor in breast cancer late recurrences.
Invisibly Sanitizable Signature without Pairings
NASA Astrophysics Data System (ADS)
Yum, Dae Hyun; Lee, Pil Joong
Sanitizable signatures allow sanitizers to delete some pre-determined parts of a signed document without invalidating the signature. While ordinary sanitizable signatures allow verifiers to know how many subdocuments have been sanitized, invisibly sanitizable signatures do not leave any clue to the sanitized subdocuments; verifiers do not know whether or not sanitizing has been performed. Previous invisibly sanitizable signature scheme was constructed based on aggregate signature with pairings. In this article, we present the first invisibly sanitizable signature without using pairings. Our proposed scheme is secure under the RSA assumption.
NASA Astrophysics Data System (ADS)
Lahamy, H.; Lichti, D.
2012-07-01
The automatic interpretation of human gestures can be used for a natural interaction with computers without the use of mechanical devices such as keyboards and mice. The recognition of hand postures have been studied for many years. However, most of the literature in this area has considered 2D images which cannot provide a full description of the hand gestures. In addition, a rotation-invariant identification remains an unsolved problem even with the use of 2D images. The objective of the current study is to design a rotation-invariant recognition process while using a 3D signature for classifying hand postures. An heuristic and voxelbased signature has been designed and implemented. The tracking of the hand motion is achieved with the Kalman filter. A unique training image per posture is used in the supervised classification. The designed recognition process and the tracking procedure have been successfully evaluated. This study has demonstrated the efficiency of the proposed rotation invariant 3D hand posture signature which leads to 98.24% recognition rate after testing 12723 samples of 12 gestures taken from the alphabet of the American Sign Language.
A new affine-invariant image matching method based on SIFT
NASA Astrophysics Data System (ADS)
Wang, Peng-cheng; Chen, Qian; Chen, Hai-xin; Cheng, Hong-chang; Gong, Zhen-fei
2013-09-01
Local invariant feature extraction, as one of the main problems in the field of computer vision, has been widely applied to image matching, splicing and target recognition etc. Lowe's scale invariant feature transform (known as SIFT) algorithm has attracted much attention due to its invariance to scale, rotation and illumination. However, SIFT is not robust to affine deformations, because it is based on the DoG detector which extracts keypoints in a circle region. Besides, the feature descriptor is represented by a 128-dimensional vector, which means that the algorithm complexity is extremely large especially when there is a great quantity of keypoints in the image. In this paper, a new feature descriptor, which is robust to affine deformations, is proposed. Considering that circles turn to be ellipses after affine deformations, some improvements have been made. Firstly, the Gaussian image pyramids are constructed by convoluting the source image and the elliptical Gaussian kernel with two volatile parameters, orientation and eccentricity. In addition, the two parameters are discretely selected in order to imitate the possibilities of the affine deformation, which can make sure that anisotropic regions are transformed into isotropic ones. Next, all extreme points can be extracted as the candidates for the affine-invariant keypoints in the image pyramids. After accurate keypoints localization is performed, the secondary moment of the keypoints' neighborhood is calculated to identify the elliptical region which is affineinvariant, the same as SIFT, the main orientation of the keypoints can be determined and the feature descriptor is generated based on the histogram constructed in this region. At last, the PCA method for the 128-dimensional descriptor's reduction is used to improve the computer calculating efficiency. The experiments show that this new algorithm inherits all SIFT's original advantages, and has a good resistance to affine deformations; what's more, it
Interacting scale invariant but nonconformal field theories
NASA Astrophysics Data System (ADS)
Nakayama, Yu
2017-03-01
There is a dilemma in constructing interacting scale invariant Euclidean field theories that are not conformal invariant. On one hand, scale invariance without conformal invariance seems more generic by requiring only a smaller symmetry. On the other hand, the existence of a nonconserved current with exact scaling dimension d -1 in d dimensions seems to require extra fine-tuning. To understand the competition better, we explore some examples without the reflection positivity. We show that a theory of elasticity (also known as Riva-Cardy theory) coupled with massless fermions in d =4 -ɛ dimensions does not possess an interacting scale invariant fixed point except for an unstable (and unphysical) one with an infinite coefficient of compression. We do, however, find interacting scale invariant but nonconformal field theories in gauge fixed versions of the Banks-Zaks fixed points in d =4 dimensions.
Galilei invariant technique for quantum system description
Kamuntavičius, Gintautas P.
2014-04-15
Problems with quantum systems models, violating Galilei invariance are examined. The method for arbitrary non-relativistic quantum system Galilei invariant wave function construction, applying a modified basis where center-of-mass excitations have been removed before Hamiltonian matrix diagonalization, is developed. For identical fermion system, the Galilei invariant wave function can be obtained while applying conventional antisymmetrization methods of wave functions, dependent on single particle spatial variables.
Uncertainty in hydrological signatures
NASA Astrophysics Data System (ADS)
McMillan, Hilary; Westerberg, Ida
2015-04-01
Information that summarises the hydrological behaviour or flow regime of a catchment is essential for comparing responses of different catchments to understand catchment organisation and similarity, and for many other modelling and water-management applications. Such information types derived as an index value from observed data are known as hydrological signatures, and can include descriptors of high flows (e.g. mean annual flood), low flows (e.g. mean annual low flow, recession shape), the flow variability, flow duration curve, and runoff ratio. Because the hydrological signatures are calculated from observed data such as rainfall and flow records, they are affected by uncertainty in those data. Subjective choices in the method used to calculate the signatures create a further source of uncertainty. Uncertainties in the signatures may affect our ability to compare different locations, to detect changes, or to compare future water resource management scenarios. The aim of this study was to contribute to the hydrological community's awareness and knowledge of data uncertainty in hydrological signatures, including typical sources, magnitude and methods for its assessment. We proposed a generally applicable method to calculate these uncertainties based on Monte Carlo sampling and demonstrated it for a variety of commonly used signatures. The study was made for two data rich catchments, the 50 km2 Mahurangi catchment in New Zealand and the 135 km2 Brue catchment in the UK. For rainfall data the uncertainty sources included point measurement uncertainty, the number of gauges used in calculation of the catchment spatial average, and uncertainties relating to lack of quality control. For flow data the uncertainty sources included uncertainties in stage/discharge measurement and in the approximation of the true stage-discharge relation by a rating curve. The resulting uncertainties were compared across the different signatures and catchments, to quantify uncertainty
Practical quantum digital signature
NASA Astrophysics Data System (ADS)
Yin, Hua-Lei; Fu, Yao; Chen, Zeng-Bing
2016-03-01
Guaranteeing nonrepudiation, unforgeability as well as transferability of a signature is one of the most vital safeguards in today's e-commerce era. Based on fundamental laws of quantum physics, quantum digital signature (QDS) aims to provide information-theoretic security for this cryptographic task. However, up to date, the previously proposed QDS protocols are impractical due to various challenging problems and most importantly, the requirement of authenticated (secure) quantum channels between participants. Here, we present the first quantum digital signature protocol that removes the assumption of authenticated quantum channels while remaining secure against the collective attacks. Besides, our QDS protocol can be practically implemented over more than 100 km under current mature technology as used in quantum key distribution.
Quantum gravity signatures in the Unruh effect
NASA Astrophysics Data System (ADS)
Alkofer, Natalia; D'Odorico, Giulio; Saueressig, Frank; Versteegen, Fleur
2016-11-01
We study quantum gravity signatures emerging from phenomenologically motivated multiscale models, spectral actions, and causal set theory within the detector approach to the Unruh effect. We show that while the Unruh temperature is unaffected, Lorentz-invariant corrections to the two-point function leave a characteristic fingerprint in the induced emission rate of the accelerated detector. Generically, quantum gravity models exhibiting dynamical dimensional reduction exhibit a suppression of the Unruh rate at high energy while the rate is enhanced in Kaluza-Klein theories with compact extra dimensions. We quantify this behavior by introducing the "Unruh dimension" as the effective spacetime dimension seen by the Unruh effect and show that it is related, though not identical, to the spectral dimension used to characterize spacetime in quantum gravity. We comment on the physical origins of these effects and their relevance for black hole evaporation.
Scale Invariance & Emergent Behavior in Spontaneous Activity of Heart Cells
NASA Astrophysics Data System (ADS)
Cohen, Netta; Rotstein, Horacio G.; Braun, Erez
2004-03-01
Cultured heart cells from newborn rat ventricles have the capacity to beat spontaneously. Long-term noninvasive recordings of beating activity reveal a rich repertoire of behavior that is characterized by variable interspike intervals, sudden rate changes and long intermissions. Statistical analysis of the recorded time series is presented. In particular, scale-invariant fluctuations in the interspike intervals are found both in single cells and in extended networks. A model of single-cell activity in the vicinity of an infinite-period bifurcation captures the main statistical and qualitative features of activity and successfully links single-cell dynamics to emergent network properties. Simulations of nonlinear oscillators and instructive `cartoon models' are presented. Simulations of coupled oscillators are shown to reproduce qualitative signatures of the dynamics in small groups of cells as well as in extended networks. N Cohen, PhD Thesis, Technion, Haifa (2001).
Deforming the Maxwell-Sim algebra
Gibbons, G. W.; Gomis, Joaquim; Pope, C. N.
2010-09-15
The Maxwell algebra is a noncentral extension of the Poincare algebra, in which the momentum generators no longer commute, but satisfy [P{sub {mu}},P{sub {nu}}]=Z{sub {mu}{nu}}. The charges Z{sub {mu}{nu}} commute with the momenta, and transform tensorially under the action of the angular momentum generators. If one constructs an action for a massive particle, invariant under these symmetries, one finds that it satisfies the equations of motion of a charged particle interacting with a constant electromagnetic field via the Lorentz force. In this paper, we explore the analogous constructions where one starts instead with the ISim subalgebra of Poincare, this being the symmetry algebra of very special relativity. It admits an analogous noncentral extension, and we find that a particle action invariant under this Maxwell-Sim algebra again describes a particle subject to the ordinary Lorentz force. One can also deform the ISim algebra to DISim{sub b}, where b is a nontrivial dimensionless parameter. We find that the motion described by an action invariant under the corresponding Maxwell-DISim algebra is that of a particle interacting via a Finslerian modification of the Lorentz force. In an appendix is it shown that the DISim{sub b} algebra is isomorphic to the extended Schroedinger algebra with its standard deformation parameter z, when b=(1/1-z).
Factor models for cancer signatures
NASA Astrophysics Data System (ADS)
Kakushadze, Zura; Yu, Willie
2016-11-01
We present a novel method for extracting cancer signatures by applying statistical risk models (http://ssrn.com/abstract=2732453) from quantitative finance to cancer genome data. Using 1389 whole genome sequenced samples from 14 cancers, we identify an ;overall; mode of somatic mutational noise. We give a prescription for factoring out this noise and source code for fixing the number of signatures. We apply nonnegative matrix factorization (NMF) to genome data aggregated by cancer subtype and filtered using our method. The resultant signatures have substantially lower variability than those from unfiltered data. Also, the computational cost of signature extraction is cut by about a factor of 10. We find 3 novel cancer signatures, including a liver cancer dominant signature (96% contribution) and a renal cell carcinoma signature (70% contribution). Our method accelerates finding new cancer signatures and improves their overall stability. Reciprocally, the methods for extracting cancer signatures could have interesting applications in quantitative finance.
NASA Technical Reports Server (NTRS)
Perotti, Jose M. (Inventor); Lucena, Angel (Inventor); Ihlefeld, Curtis (Inventor); Burns, Bradley (Inventor); Bassignani, Karin E. (Inventor)
2005-01-01
A solenoid health monitoring system uses a signal conditioner and controller assembly in one embodiment that includes analog circuitry and a DSP controller. The analog circuitry provides signal conditioning to the low-level raw signal coming from a signal acquisition assembly. Software running in a DSP analyzes the incoming data (recorded current signature) and determines the state of the solenoid whether it is energized, de-energized, or in a transitioning state. In one embodiment, the software identifies key features in the current signature during the transition phase and is able to determine the health of the solenoid.
NASA Technical Reports Server (NTRS)
Perotti, Jose M. (Inventor); Lucena, Angel (Inventor); Ihlefeld, Curtis (Inventor); Burns, Bradley (Inventor); Bassignani, Mario (Inventor); Bassignani, Karin E. (Inventor)
2005-01-01
A solenoid health monitoring system uses a signal conditioner and controller assembly in one embodiment that includes analog circuitry and a DSP controller. The analog circuitry provides signal conditioning to the low-level raw signal coming from a signal acquisition assembly. Software running in a DSP analyzes the incoming data (recorded current signature) and determines the state of the solenoid whether it is energized, de-energized, or in a transitioning state. In one embodiment, the software identifies key features in the current signature during the transition phase and is able to determine the health of the solenoid.
Soft phononic crystals with deformation-independent band gaps
2017-01-01
Soft phononic crystals have the advantages over their stiff counterparts of being flexible and reconfigurable. Normally, the band gaps of soft phononic crystals will be modified after deformation due to both geometric and constitutive nonlinearity. Indeed these are important properties that can be exploited to tune the dynamic properties of the material. However, in some instances, it may be that one wishes to deform the medium while retaining the band gap structure. A special class of soft phononic crystals is described here with band gaps that are independent or almost-independent of the imposed mechanical deformation, which enables the design of phononic crystals with robust performance. This remarkable behaviour originates from transformation elasticity theory, which leaves the wave equation and the eigenfrequencies invariant after deformation. The necessary condition to achieve such a property is that the Lagrangian elasticity tensor of the hyperelastic material should be constant, i.e. independent of deformation. It is demonstrated that incompressible neo-Hookean materials exhibit such a unique property. Semilinear materials also possess this property under special loading conditions. Phononic crystals composed of these two materials are studied theoretically and the predictions of invariance, or the manner in which the response deviates from invariance, are confirmed via numerical simulation. PMID:28484331
Soft phononic crystals with deformation-independent band gaps
NASA Astrophysics Data System (ADS)
Zhang, Pu; Parnell, William J.
2017-04-01
Soft phononic crystals have the advantages over their stiff counterparts of being flexible and reconfigurable. Normally, the band gaps of soft phononic crystals will be modified after deformation due to both geometric and constitutive nonlinearity. Indeed these are important properties that can be exploited to tune the dynamic properties of the material. However, in some instances, it may be that one wishes to deform the medium while retaining the band gap structure. A special class of soft phononic crystals is described here with band gaps that are independent or almost-independent of the imposed mechanical deformation, which enables the design of phononic crystals with robust performance. This remarkable behaviour originates from transformation elasticity theory, which leaves the wave equation and the eigenfrequencies invariant after deformation. The necessary condition to achieve such a property is that the Lagrangian elasticity tensor of the hyperelastic material should be constant, i.e. independent of deformation. It is demonstrated that incompressible neo-Hookean materials exhibit such a unique property. Semilinear materials also possess this property under special loading conditions. Phononic crystals composed of these two materials are studied theoretically and the predictions of invariance, or the manner in which the response deviates from invariance, are confirmed via numerical simulation.
A Note on Invariant Observables
NASA Astrophysics Data System (ADS)
Lendelová, Katarína
2006-05-01
The ergodic theory and particularly the individual ergodic theorem were studied in many structures. Recently the individual ergodic theorem has been proved for MV-algebras of fuzzy sets (Riečan, 2000; Riečan and Neubrunn, 1997) and even in general MV-algebras (Jurečková, 2000). The notion of almost everywhere equality of observables was introduced by B. Riečan and M. Jurečková in Riečan and Jurečková (2005). They proved that the limit of Cesaro means is an invariant observable for P-observables. In this paper show that the assumption of P-observable can be omitted.
Rotationally Invariant Holographic Tracking System
NASA Astrophysics Data System (ADS)
Lambert, James L.; Chao, Tien-Hsin; Gheen, Gregory; Johnston, Alan R.; Liu, Hua-Kuang
1989-06-01
A multi-channel holographic correlator has been constructed which can identify and track objects of a given shape across the input field independent of their in-plane rotation. This system, derived from the classic Vander Lugt correlator, incorporates a hololens to store an array of matched spatial filters (MSFs) on thermoplastic film. Each member of the MSF array is generated from a different incrementally rotated version of the training object. Rotational invariant tracking is achieved through superposition of the corresponding array of the correlations in the output plane. Real time tracking is accomplished by utilizing a liquid crystal light valve (LCLV) illuminated with a CRT to process video input signals. The system can be programmed to recognize different objects by recording the MSF array on re-usable thermoplastic film. Discussion of the system architecture and laboratory results are presented.
Baire classes of Lyapunov invariants
NASA Astrophysics Data System (ADS)
Bykov, V. V.
2017-05-01
It is shown that no relations exist (apart from inherent ones) between Baire classes of Lyapunov transformation invariants in the compact- open and uniform topologies on the space of linear differential systems. It is established that if a functional on the space of linear differential systems with the compact-open topology is the repeated limit of a multisequence of continuous functionals, then these can be chosen to be determined by the values of system coefficients on a finite interval of the half-line (one for each functional). It is proved that the Lyapunov exponents cannot be represented as the limit of a sequence of (not necessarily continuous) functionals such that each of these depends only on the restriction of the system to a finite interval of the half-line. Bibliography: 28 titles.
Invariant Coordinates in Breakup Reactions
NASA Astrophysics Data System (ADS)
Skwira-Chalot, I.; Ciepał, I.; Kistryn, St.; Kozela, A.; Parol, W.; Stephan, E.
2017-03-01
Systematic experimental studies of few-nucleon systems expose various dynamical ingredients which play an important role in correct description of observables, such as three-nucleon force, Coulomb force and relativistic effects. A large set of existing experimental data for ^1H(d, p p)n reaction allows for systematic investigations of these dynamical effects, which vary with energy and appear with different strength in certain observables and phase space regions. Moreover, systematic comparisons with exact theoretical calculations, done in variables related to the system dynamics in a possibly direct ways is a very important tool to verify and improve the existing description of the nucleon interaction. Examples of experimental data for a breakup reaction, transformed to the variables based on Lorentz-invariants are compared with modern theoretical calculations.
Asymptotic invariants of homotopy groups
NASA Astrophysics Data System (ADS)
Manin, Fedor
We study the homotopy groups of a finite CW complex X via constraints on the geometry of representatives of their elements. For example, one can measure the "size" of alpha ∈ pi n (X) by the optimal Lipschitz constant or volume of a representative. By comparing the geometrical structure thus obtained with the algebraic structure of the group, one can define functions such as growth and distortion in pin(X), analogously to the way that such functions are studied in asymptotic geometric group theory. We provide a number of examples and techniques for studying these invariants, with a special focus on spaces with few rational homotopy groups. Our main theorem characterizes those X in which all non-torsion homotopy classes are undistorted, that is, their volume distortion functions, and hence also their Lipschitz distortion functions, are linear.
Scale invariance in road networks
NASA Astrophysics Data System (ADS)
Kalapala, Vamsi; Sanwalani, Vishal; Clauset, Aaron; Moore, Cristopher
2006-02-01
We study the topological and geographic structure of the national road networks of the United States, England, and Denmark. By transforming these networks into their dual representation, where roads are vertices and an edge connects two vertices if the corresponding roads ever intersect, we show that they exhibit both topological and geographic scale invariance. That is, we show that for sufficiently large geographic areas, the dual degree distribution follows a power law with exponent 2.2⩽α⩽2.4 , and that journeys, regardless of their length, have a largely identical structure. To explain these properties, we introduce and analyze a simple fractal model of road placement that reproduces the observed structure, and suggests a testable connection between the scaling exponent α and the fractal dimensions governing the placement of roads and intersections.
Quantum groups with invariant integrals
Van Daele, Alfons
2000-01-01
Quantum groups have been studied intensively for the last two decades from various points of view. The underlying mathematical structure is that of an algebra with a coproduct. Compact quantum groups admit Haar measures. However, if we want to have a Haar measure also in the noncompact case, we are forced to work with algebras without identity, and the notion of a coproduct has to be adapted. These considerations lead to the theory of multiplier Hopf algebras, which provides the mathematical tool for studying noncompact quantum groups with Haar measures. I will concentrate on the *-algebra case and assume positivity of the invariant integral. Doing so, I create an algebraic framework that serves as a model for the operator algebra approach to quantum groups. Indeed, the theory of locally compact quantum groups can be seen as the topological version of the theory of quantum groups as they are developed here in a purely algebraic context. PMID:10639115
Real-time pose invariant logo and pattern detection
NASA Astrophysics Data System (ADS)
Sidla, Oliver; Kottmann, Michal; Benesova, Wanda
2011-01-01
The detection of pose invariant planar patterns has many practical applications in computer vision and surveillance systems. The recognition of company logos is used in market studies to examine the visibility and frequency of logos in advertisement. Danger signs on vehicles could be detected to trigger warning systems in tunnels, or brand detection on transport vehicles can be used to count company-specific traffic. We present the results of a study on planar pattern detection which is based on keypoint detection and matching of distortion invariant 2d feature descriptors. Specifically we look at the keypoint detectors of type: i) Lowe's DoG approximation from the SURF algorithm, ii) the Harris Corner Detector, iii) the FAST Corner Detector and iv) Lepetit's keypoint detector. Our study then compares the feature descriptors SURF and compact signatures based on Random Ferns: we use 3 sets of sample images to detect and match 3 logos of different structure to find out which combinations of keypoint detector/feature descriptors work well. A real-world test tries to detect vehicles with a distinctive logo in an outdoor environment under realistic lighting and weather conditions: a camera was mounted on a suitable location for observing the entrance to a parking area so that incoming vehicles could be monitored. In this 2 hour long recording we can successfully detect a specific company logo without false positives.
Distortion-invariant ID tags for object identification
NASA Astrophysics Data System (ADS)
Perez-Cabre, Elisabet; Javidi, Bahram
2004-11-01
Active and passive optical identification (ID) tags and readers for remote identification and verification of objects are described. We focus our attention on the design of passive ID tags to achieve distortion-invariant authentication of the information included in the optical tag. A passive ID tag will consist of an optical phase code which can be placed in a visible part of an object for remote detection. We aim to authenticate the object even if the reader captures a distorted version of the code due to in-plane rotations. Distortion-invariance is achieved by both multiplexing the information included in the ID tag and the topology of the tag. For security purposes, double-phase encryption has already been shown as an appropriate technique to encode information. By using double-phase encryption, a signature is hidden in a phase-encoded ID tag not visible by visual inspection. Once the ID tag is captured by the reader and is decrypted, a correlation-based processor verifies the decoded information with a previously stored reference signal. The proposed system may have broad applications in transportation, homeland security, and inventory control.
Structural assessment of glycyl mutations in invariantly conserved motifs.
Prakash, Tulika; Sandhu, Kuljeet Singh; Singh, Nitin Kumar; Bhasin, Yasha; Ramakrishnan, C; Brahmachari, Samir K
2007-11-15
Motifs that are evolutionarily conserved in proteins are crucial to their structure and function. In one of our earlier studies, we demonstrated that the conserved motifs occurring invariantly across several organisms could act as structural determinants of the proteins. We observed the abundance of glycyl residues in these invariantly conserved motifs. The role of glycyl residues in highly conserved motifs has not been studied extensively. Thus, it would be interesting to examine the structural perturbations induced by mutation in these conserved glycyl sites. In this work, we selected a representative set of invariant signature (IS) peptides for which both the PDB structure and mutation information was available. We thoroughly analyzed the conformational features of the glycyl sites and their local interactions with the surrounding residues. Using Ramachandran angles, we showed that the glycyl residues occurring in these IS peptides, which have undergone mutation, occurred more often in the L-disallowed as compared with the L-allowed region of the Ramachandran plot. Short range contacts around the mutation site were analyzed to study the steric effects. With the results obtained from our analysis, we hypothesize that any change of activity arising because of such mutations must be attributed to the long-range interaction(s) of the new residue if the glycyl residue in the IS peptide occurred in the L-allowed region of the Ramachandran plot. However, the mutation of those conserved glycyl residues that occurred in the L-disallowed region of the Ramachandran plot might lead to an altered activity of the protein as a result of an altered conformation of the backbone in the immediate vicinity of the glycyl residue, in addition to long range effects arising from the long side chains of the new residue. Thus, the loss of activity because of mutation in the conserved glycyl site might either relate to long range interactions or to local perturbations around the site
Online signature recognition using principal component analysis and artificial neural network
NASA Astrophysics Data System (ADS)
Hwang, Seung-Jun; Park, Seung-Je; Baek, Joong-Hwan
2016-12-01
In this paper, we propose an algorithm for on-line signature recognition using fingertip point in the air from the depth image acquired by Kinect. We extract 10 statistical features from X, Y, Z axis, which are invariant to changes in shifting and scaling of the signature trajectories in three-dimensional space. Artificial neural network is adopted to solve the complex signature classification problem. 30 dimensional features are converted into 10 principal components using principal component analysis, which is 99.02% of total variances. We implement the proposed algorithm and test to actual on-line signatures. In experiment, we verify the proposed method is successful to classify 15 different on-line signatures. Experimental result shows 98.47% of recognition rate when using only 10 feature vectors.
ERIC Educational Resources Information Center
Smiles, Robin V.
2005-01-01
This article discusses Dr. Amalia Amaki and her approach to art as her signature style by turning everyday items into fine art. Amaki is an assistant professor of art, art history, and Black American studies at the University of Delaware. She loves taking unexpected an object and redefining it in the context of art--like a button, a fan, a faded…
ERIC Educational Resources Information Center
Smiles, Robin V.
2005-01-01
This article discusses Dr. Amalia Amaki and her approach to art as her signature style by turning everyday items into fine art. Amaki is an assistant professor of art, art history, and Black American studies at the University of Delaware. She loves taking unexpected an object and redefining it in the context of art--like a button, a fan, a faded…
Multipartite invariant states. I. Unitary symmetry
Chruscinski, Dariusz; Kossakowski, Andrzej
2006-06-15
We propose a natural generalization of bipartite Werner and isotropic states to multipartite systems consisting of an arbitrary even number of d-dimensional subsystems (qudits). These generalized states are invariant under the action of local unitary operations. We study basic properties of multipartite invariant states and present necessary and sufficient separability criteria.
Lorentz invariance in loop quantum gravity
NASA Astrophysics Data System (ADS)
Pullin, Jorge; Rastgoo, Saeed; Gambini, Rodolfo
2011-04-01
We reconsider the argument of Collins, Perez, Sudarsky, Urrutia and Vucetich concerning violations of Lorentz invariance in the context of loop quantum gravity. We show that even if one introduces a lattice that violates Lorentz invariance at the Planck scale, this does not translate itself into large violations that would conflict with experiment.
Rotation-invariant of Quantum Gross Laplacian
Horrigue, Samah; Ouerdiane, Habib
2010-05-04
In this paper, we prove that the quantum Gross Laplacian denoted DELTA{sub QG} is a rotation-invariant operator. For this purpose, we use the Schwartz-Grothendieck kernel theorem and the characterization theorem of rotation-invariant distributions and operators.
Invariance or Noninvariance, that Is the Question
ERIC Educational Resources Information Center
Widaman, Keith F.; Grimm, Kevin J.
2009-01-01
Nesselroade, Gerstorf, Hardy, and Ram developed a new and interesting way to enforce invariance at the second-order level in P-technique models, while allowing first-order structure to stray from invariance. We discuss our concerns with this approach under the headings of falsifiability, the nature of manifest variables included in models, and…
Rejoinder: Continuing the Dialogue on Invariant Measurement
ERIC Educational Resources Information Center
Engelhard, George, Jr.
2008-01-01
The major purpose of my focus article was to stimulate discussion regarding the concept of invariant measurement. My intent was to provide a historical lens for considering how our views of invariant measurement have evolved over time through the work of three key measurement theorists: Guttman, Rasch, and Mokken. The commentators have offered a…
Discernment of Invariants in Dynamic Geometry Environments
ERIC Educational Resources Information Center
Leung, Allen; Baccaglini-Frank, Anna; Mariotti, Maria Alessandra
2013-01-01
In this paper, we discuss discernment of invariants in dynamic geometry environments (DGE) based on a combined perspective that puts together the lens of variation and the maintaining dragging strategy developed previously by the authors. We interpret and describe a model of discerning invariants in DGE through types of variation awareness and…
Cross-National Invariance of Children's Temperament
ERIC Educational Resources Information Center
Benson, Nicholas; Oakland, Thomas; Shermis, Mark
2009-01-01
Measurement of temperament is an important endeavor with international appeal; however, cross-national invariance (i.e., equivalence of test scores across countries as established by empirical comparisons) of temperament tests has not been established in published research. This study examines the cross-national invariance of school-aged…
Rejoinder: Continuing the Dialogue on Invariant Measurement
ERIC Educational Resources Information Center
Engelhard, George, Jr.
2008-01-01
The major purpose of my focus article was to stimulate discussion regarding the concept of invariant measurement. My intent was to provide a historical lens for considering how our views of invariant measurement have evolved over time through the work of three key measurement theorists: Guttman, Rasch, and Mokken. The commentators have offered a…
Discernment of Invariants in Dynamic Geometry Environments
ERIC Educational Resources Information Center
Leung, Allen; Baccaglini-Frank, Anna; Mariotti, Maria Alessandra
2013-01-01
In this paper, we discuss discernment of invariants in dynamic geometry environments (DGE) based on a combined perspective that puts together the lens of variation and the maintaining dragging strategy developed previously by the authors. We interpret and describe a model of discerning invariants in DGE through types of variation awareness and…
Invariant Ordering of Item-Total Regressions
ERIC Educational Resources Information Center
Tijmstra, Jesper; Hessen, David J.; van der Heijden, Peter G. M.; Sijtsma, Klaas
2011-01-01
A new observable consequence of the property of invariant item ordering is presented, which holds under Mokken's double monotonicity model for dichotomous data. The observable consequence is an invariant ordering of the item-total regressions. Kendall's measure of concordance "W" and a weighted version of this measure are proposed as measures for…
Cross-National Invariance of Children's Temperament
ERIC Educational Resources Information Center
Benson, Nicholas; Oakland, Thomas; Shermis, Mark
2009-01-01
Measurement of temperament is an important endeavor with international appeal; however, cross-national invariance (i.e., equivalence of test scores across countries as established by empirical comparisons) of temperament tests has not been established in published research. This study examines the cross-national invariance of school-aged…
Invariance or Noninvariance, that Is the Question
ERIC Educational Resources Information Center
Widaman, Keith F.; Grimm, Kevin J.
2009-01-01
Nesselroade, Gerstorf, Hardy, and Ram developed a new and interesting way to enforce invariance at the second-order level in P-technique models, while allowing first-order structure to stray from invariance. We discuss our concerns with this approach under the headings of falsifiability, the nature of manifest variables included in models, and…
On jordanian deformations of AdS5 and supergravity
NASA Astrophysics Data System (ADS)
Hoare, Ben; van Tongeren, Stijn J.
2016-10-01
We consider various homogeneous Yang-Baxter deformations of the {{AdS}}5× {{{S}}}5 superstring that can be obtained from the η-deformed superstring and related models by singular boosts. The jordanian deformations we obtain in this way behave similarly to the η-deformed model with regard to supergravity: T dualizing the classical sigma model it is possible to find corresponding solutions of supergravity, which, however, have dilatons that prevent T dualizing back. Hence the backgrounds of these jordanian deformations are not solutions of supergravity. Still, they do satisfy a set of recently found modified supergravity equations which implies that the corresponding sigma models are scale invariant. The abelian models that we obtain by singular boosts do directly correspond to solutions of supergravity. In addition to our main results we consider contraction limits of our main example, which do correspond to supergravity solutions.
Dynamic Signature Verification System Based on One Real Signature.
Diaz, Moises; Fischer, Andreas; Ferrer, Miguel A; Plamondon, Rejean
2016-12-06
The dynamic signature is a biometric trait widely used and accepted for verifying a person's identity. Current automatic signature-based biometric systems typically require five, ten, or even more specimens of a person's signature to learn intrapersonal variability sufficient to provide an accurate verification of the individual's identity. To mitigate this drawback, this paper proposes a procedure for training with only a single reference signature. Our strategy consists of duplicating the given signature a number of times and training an automatic signature verifier with each of the resulting signatures. The duplication scheme is based on a sigma lognormal decomposition of the reference signature. Two methods are presented to create human-like duplicated signatures: the first varies the strokes' lognormal parameters (stroke-wise) whereas the second modifies their virtual target points (target-wise). A challenging benchmark, assessed with multiple state-of-the-art automatic signature verifiers and multiple databases, proves the robustness of the system. Experimental results suggest that our system, with a single reference signature, is capable of achieving a similar performance to standard verifiers trained with up to five signature specimens.
2007-12-20
shoe was that? The use of computerised image database to assist in identification”. Forensic Science International , 82(1):7–20, 9/15 1996. 3. Bay...biometric systems”. Forensic science international , 155(2-3):126–140, 2005. 7. Haibin Ling; Jacobs, D.W. “Deformation invariant image matching”. Computer...Image match- ing algorithms for breech face marks and firing pins in a database of spent car- tridge cases of firearms”. Forensic science international , 2001
A Gaussian Distribution for Refined DT Invariants and 3D Partitions
NASA Astrophysics Data System (ADS)
Morrison, Andrew
2014-11-01
We show that the refined Donaldson-Thomas invariants of , suitably normalized, have a Gaussian distribution as limit law. Combinatorially, these numbers are given by weighted counts of 3D partitions. Our technique is to use the Hardy-Littlewood circle method to analyze the bivariate asymptotics of a q-deformation of MacMahon's function. The proof is based on that of E.M. Wright, who explored the single variable case.
Pose-Invariant Face Recognition via RGB-D Images
Sang, Gaoli; Li, Jing; Zhao, Qijun
2016-01-01
Three-dimensional (3D) face models can intrinsically handle large pose face recognition problem. In this paper, we propose a novel pose-invariant face recognition method via RGB-D images. By employing depth, our method is able to handle self-occlusion and deformation, both of which are challenging problems in two-dimensional (2D) face recognition. Texture images in the gallery can be rendered to the same view as the probe via depth. Meanwhile, depth is also used for similarity measure via frontalization and symmetric filling. Finally, both texture and depth contribute to the final identity estimation. Experiments on Bosphorus, CurtinFaces, Eurecom, and Kiwi databases demonstrate that the additional depth information has improved the performance of face recognition with large pose variations and under even more challenging conditions. PMID:26819581
A FRAME-INVARIANT FORMULATION OF FUNG ELASTICITY
ATESHIAN, GERARD A.; COSTA, KEVIN D.
2011-01-01
Fung elasticity refers to the hyperelasticity constitutive relation proposed by Y.C. Fung and co-workers for describing the pseudo-elastic behavior of biological soft tissues undergoing finite deformation. A frame-invariant formulation of Fung elasticity is provided for material symmetries ranging from orthotropy to isotropy, which uses Lamé-like material constants. In the orthotropic case, three orthonormal vectors are used to defined mutually orthogonal planes of symmetry and associated texture tensors. The strain energy density is then formulated as an isotropic function of the Lagrangian strain and texture tensors. The cases of isotropy and transverse isotropy are derived from the orthotropic case. Formulations are provided for both material and spatial frames. These formulations are suitable for implementation into finite element codes. It is also shown that the strain energy function can be naturally uncoupled into a dilatational and a distortional part, to facilitate the computational implementation of incompressibility. PMID:19281991
A frame-invariant formulation of Fung elasticity.
Ateshian, Gerard A; Costa, Kevin D
2009-04-16
Fung elasticity refers to the hyperelasticity constitutive relation proposed by Fung and co-workers for describing the pseudo-elastic behavior of biological soft tissues undergoing finite deformation. A frame-invariant formulation of Fung elasticity is provided for material symmetries ranging from orthotropy to isotropy, which uses Lamé-like material constants. In the orthotropic case, three orthonormal vectors are used to define mutually orthogonal planes of symmetry and associated texture tensors. The strain energy density is then formulated as an isotropic function of the Lagrangian strain and texture tensors. The cases of isotropy and transverse isotropy are derived from the orthotropic case. Formulations are provided for both material and spatial frames. These formulations are suitable for implementation into finite element codes. It is also shown that the strain energy function can be naturally uncoupled into a dilatational and a distortional part, to facilitate the computational implementation of incompressibility.
South Pole Lorentz Invariance Test
NASA Astrophysics Data System (ADS)
Hedges, Morgan; Smiciklas, Marc; Romalis, Michael
2015-05-01
Searches for Lorentz and CPT violation play an important role in testing current theories of space-time. To test one of the consequences of local Lorentz invariance we have performed a precision test of spatial isotropy at the Amundsen-Scott station near the geographic South Pole. This location provides the most isotropic environment available on Earth. The experiment is a rotating atomic-spin co-magnetometer which compares energy levels of 21Ne and Rubidium atoms as a function of direction. The experimental sensitivity obtained is more than an order of magnitude better than in previous such measurements, known as Hughes-Drever experiments. By operating the experiment at the Pole we are able to eliminate background signals due to the gyroscopic interactions of spins with Earth's rotation as well as diurnal environmental effects. Here we will present final results from the experiment's 2-year data collection period. This is the first precision atomic physics experiment performed at the Pole, and we will discuss the potential for future such measurements.
Stereo Correspondence Using Moment Invariants
NASA Astrophysics Data System (ADS)
Premaratne, Prashan; Safaei, Farzad
Autonomous navigation is seen as a vital tool in harnessing the enormous potential of Unmanned Aerial Vehicles (UAV) and small robotic vehicles for both military and civilian use. Even though, laser based scanning solutions for Simultaneous Location And Mapping (SLAM) is considered as the most reliable for depth estimation, they are not feasible for use in UAV and land-based small vehicles due to their physical size and weight. Stereovision is considered as the best approach for any autonomous navigation solution as stereo rigs are considered to be lightweight and inexpensive. However, stereoscopy which estimates the depth information through pairs of stereo images can still be computationally expensive and unreliable. This is mainly due to some of the algorithms used in successful stereovision solutions require high computational requirements that cannot be met by small robotic vehicles. In our research, we implement a feature-based stereovision solution using moment invariants as a metric to find corresponding regions in image pairs that will reduce the computational complexity and improve the accuracy of the disparity measures that will be significant for the use in UAVs and in small robotic vehicles.
South Pole Lorentz Invariance Test
NASA Astrophysics Data System (ADS)
Hedges, Morgan; Smiciklas, Marc; Romalis, Michael
2015-04-01
Tests of Lorentz and CPT symmetries are important because they form a cornerstone of quantum field theory and general relativity. To test one of the consequences of local Lorentz invariance we have performed a precision test of spatial isotropy at the Amundsen-Scott station near the geographic South Pole. This location provides the most isotropic environment available on Earth. We use an atomic spin co-magnetometer to compare energy levels in 21 Ne and Rubidium atoms as the apparatus rotates with respect to the cosmos. Our experimental sensitivity is more than an order of magnitude greater than in previous such measurements, known as Hughes-Drever experiments. By operating at the South Pole we eliminate background signals due to the gyroscopic interactions of spins with Earth's rotation as well as diurnal environmental effects. The experiment has finished a 2-year data collection period and we expect to present the final results at the meeting. This is the first precision atomic physics experiment performed at the Pole and we will discuss the potential for future such measurements.
Rotational Invariant Dimensionality Reduction Algorithms.
Lai, Zhihui; Xu, Yong; Yang, Jian; Shen, Linlin; Zhang, David
2016-06-30
A common intrinsic limitation of the traditional subspace learning methods is the sensitivity to the outliers and the image variations of the object since they use the L₂ norm as the metric. In this paper, a series of methods based on the L₂,₁-norm are proposed for linear dimensionality reduction. Since the L₂,₁-norm based objective function is robust to the image variations, the proposed algorithms can perform robust image feature extraction for classification. We use different ideas to design different algorithms and obtain a unified rotational invariant (RI) dimensionality reduction framework, which extends the well-known graph embedding algorithm framework to a more generalized form. We provide the comprehensive analyses to show the essential properties of the proposed algorithm framework. This paper indicates that the optimization problems have global optimal solutions when all the orthogonal projections of the data space are computed and used. Experimental results on popular image datasets indicate that the proposed RI dimensionality reduction algorithms can obtain competitive performance compared with the previous L₂ norm based subspace learning algorithms.
Maximum likelihood signature estimation
NASA Technical Reports Server (NTRS)
Walker, H. F.
1975-01-01
Maximum-likelihood estimates are discussed which are based on an unlabeled sample of observations, of unknown parameters in a mixture of normal distributions. Several successive approximation procedures for obtaining such maximum-likelihood estimates are described. These procedures, which are theoretically justified by the local contractibility of certain maps, are designed to take advantage of good initial estimates of the unknown parameters. They can be applied to the signature extension problem, in which good initial estimates of the unknown parameters are obtained from segments which are geographically near the segments from which the unlabeled samples are taken. Additional problems to which these methods are applicable include: estimation of proportions and adaptive classification (estimation of mean signatures and covariances).
NASA Astrophysics Data System (ADS)
Spedding, Geoffrey R.
2014-01-01
An accumulated body of quantitative evidence shows that bluff-body wakes in stably stratified environments have an unusual degree of coherence and organization, so characteristic geometries such as arrays of alternating-signed vortices have very long lifetimes, as measured in units of buoyancy timescales, or in the downstream distance scaled by a body length. The combination of pattern geometry and persistence renders the detection of these wakes possible in principle. It now appears that identifiable signatures can be found from many disparate sources: Islands, fish, and plankton all have been noted to generate features that can be detected by climate modelers, hopeful navigators in open oceans, or hungry predators. The various types of wakes are reviewed with notes on why their signatures are important and to whom. A general theory of wake pattern formation is lacking and would have to span many orders of magnitude in Reynolds number.
Feedback-Driven Dynamic Invariant Discovery
NASA Technical Reports Server (NTRS)
Zhang, Lingming; Yang, Guowei; Rungta, Neha S.; Person, Suzette; Khurshid, Sarfraz
2014-01-01
Program invariants can help software developers identify program properties that must be preserved as the software evolves, however, formulating correct invariants can be challenging. In this work, we introduce iDiscovery, a technique which leverages symbolic execution to improve the quality of dynamically discovered invariants computed by Daikon. Candidate invariants generated by Daikon are synthesized into assertions and instrumented onto the program. The instrumented code is executed symbolically to generate new test cases that are fed back to Daikon to help further re ne the set of candidate invariants. This feedback loop is executed until a x-point is reached. To mitigate the cost of symbolic execution, we present optimizations to prune the symbolic state space and to reduce the complexity of the generated path conditions. We also leverage recent advances in constraint solution reuse techniques to avoid computing results for the same constraints across iterations. Experimental results show that iDiscovery converges to a set of higher quality invariants compared to the initial set of candidate invariants in a small number of iterations.
Characterization of cerebral aneurysms using 3D moment invariants
NASA Astrophysics Data System (ADS)
Millan, Raul D.; Hernandez, Monica; Gallardo, Daniel; Cebral, Juan R.; Putman, Christopher; Dempere-Marco, Laura; Frangi, Alejandro F.
2005-04-01
The rupture mechanism of intracranial aneurysms is still not fully understood. Although the size of the aneurysm is the shape index most commonly used to predict rupture, some controversy still exists about its adequateness as an aneurysm rupture predictor. In this work, an automatic method to geometrically characterize the shape of cerebral saccular aneurysms using 3D moment invariants is proposed. Geometric moments are efficiently computed via application of the Divergence Theorem over the aneurysm surface using a non-structured mesh. 3D models of the aneurysm and its connected parent vessels have been reconstructed from segmentations of both 3DRA and CTA images. Two alternative approaches have been used for segmentation, the first one based on isosurface deformable models, and the second one based on the level set method. Several experiments were also conducted to both assess the influence of pre-processing steps in the stability of the aneurysm shape descriptors, and to know the robustness of the proposed method. Moment invariants have proved to be a robust technique while providing a reliable way to discriminate between ruptured and unruptured aneurysms (Sensitivity=0.83, Specificity=0.74) on a data set containing 55 aneurysms. Further investigation over larger databases is necessary to establish their adequateness as reliable predictors of rupture risk.
Holography beyond conformal invariance and AdS isometry?
Barvinsky, A. O.
2015-03-15
We suggest that the principle of holographic duality be extended beyond conformal invariance and AdS isometry. Such an extension is based on a special relation between functional determinants of the operators acting in the bulk and on its boundary, provided that the boundary operator represents the inverse propagators of the theory induced on the boundary by the Dirichlet boundary value problem in the bulk spacetime. This relation holds for operators of a general spin-tensor structure on generic manifolds with boundaries irrespective of their background geometry and conformal invariance, and it apparently underlies numerous O(N{sup 0}) tests of the AdS/CFT correspondence, based on direct calculation of the bulk and boundary partition functions, Casimir energies, and conformal anomalies. The generalized holographic duality is discussed within the concept of the “double-trace” deformation of the boundary theory, which is responsible in the case of large-N CFT coupled to the tower of higher-spin gauge fields for the renormalization group flow between infrared and ultraviolet fixed points. Potential extension of this method beyond the one-loop order is also briefly discussed.
NASA Astrophysics Data System (ADS)
Chä, Seok-Yeong; Fischer, Uwe R.
2017-03-01
We consider an analogue de Sitter cosmos in an expanding quasi-two-dimensional Bose-Einstein condensate with dominant dipole-dipole interactions between the atoms or molecules in the ultracold gas. It is demonstrated that a hallmark signature of inflationary cosmology, the scale invariance of the power spectrum of inflaton field correlations, experiences strong modifications when, at the initial stage of expansion, the excitation spectrum displays a roton minimum. Dipolar quantum gases thus furnish a viable laboratory tool to experimentally investigate, with well-defined and controllable initial conditions, whether primordial oscillation spectra deviating from Lorentz invariance at trans-Planckian momenta violate standard predictions of inflationary cosmology.
1974-10-01
were generally inversely proportional to the size assesments of the flash and smoke . Table 26 shows the percent of change in average judgments of...Average Time of Gunner’s View Obscuration by Smoke During Firings From the Wood Line .. .. ..... ..... ...... ..... .. 18 7. Average Obscuration Times...of Gunner’s View Obscuration by Smoke - Grass Line 19 8. Normalized Comparisons of the Relative Grades Assigned to Systems Signature Components
Quantum cosmology and conformal invariance.
Pioline, B; Waldron, A
2003-01-24
According to Belinsky, Khalatnikov, and Lifshitz, gravity near a spacelike singularity reduces to a set of decoupled one-dimensional mechanical models at each point in space. We point out that these models fall into a class of conformal mechanical models first introduced by de Alfaro, Fubini, and Furlan (DFF). The deformation used by DFF to render the spectrum discrete corresponds to a negative cosmological constant. The wave function of the Universe is the zero-energy eigenmode of the Hamiltonian, or the spherical vector of the representation of the conformal group SO(1,2). A new class of conformal quantum mechanical models with enhanced ADE symmetry is constructed, based on the quantization of nilpotent coadjoint orbits.
Advances in Rotation-Invariant Texture Analysis
NASA Astrophysics Data System (ADS)
Estudillo-Romero, Alfonso; Escalante-Ramirez, Boris
Robust rotation invariance has been a matter of great interest in many applications which use low-level features such as textures. In this paper, we propose a method to analyze and capture visual patterns from textures regardless their orientation. In order to achieve rotation invariance, visual texture patterns are locally described as one-dimensional patterns by appropriately steering the Cartesian Hermite coefficients. Experiments with two datasets from the Brodatz album were performed to evaluate orientation invariance. High average precision and recall rates were achieved by the proposed method.
Invariance kernel of biological regulatory networks.
Ahmad, Jamil; Roux, Olivier
2010-01-01
The analysis of Biological Regulatory Network (BRN) leads to the computing of the set of the possible behaviours of the biological components. These behaviours are seen as trajectories and we are specifically interested in cyclic trajectories since they stand for stability. The set of cycles is given by the so-called invariance kernel of a BRN. This paper presents a method for deriving symbolic formulae for the length, volume and diameter of a cylindrical invariance kernel. These formulae are expressed in terms of delay parameters expressions and give the existence of an invariance kernel and a hint of the number of cyclic trajectories.
Invariant extreme physical information and fuzzy clustering
NASA Astrophysics Data System (ADS)
Venkatesan, Ravi C.
2004-04-01
A principled formulation for knowledge acquisition from discrete data based on a continuum-free invariance preserving extension of the Extreme Physical Information (EPI) theory of Frieden is presented. A systematic invariance preserving methodology to formulate and minimize lattice EPI fuzzy clustering objective functions, and, determine the concomitant constraints is suggested. Equivalence between invariant EPI (IEPI) fuzzy clustering, described within a discrete time-independent Schrodinger-like framework, and robust Possibilistic c-Means (PcM) clustering is exemplified. The constraints are shown to be consistent with Heisenberg's uncertainty principle. Numerical examples for exemplary cases are provided for multiple potential wells, without a-priori knowledge of the number of clusters.
Knowledge Signatures for Information Integration
Thomson, Judi; Cowell, Andrew J.; Paulson, Patrick R.; Butner, R. Scott; Whiting, Mark A.
2003-10-25
This paper introduces the notion of a knowledge signature: a concise, ontologically-driven representation of the semantic characteristics of data. Knowledge signatures provide programmatic access to data semantics while allowing comparisons to be made across different types of data such as text, images or video, enabling efficient, automated information integration. Through observation, which determines the degree of association between data and ontological concepts, and refinement, which uses the axioms and structure of the domain ontology to place the signature more accurately within the context of the domain, knowledge signatures can be created. A comparison of such signatures for two different pieces of data results in a measure of their semantic separation. This paper discusses the definition of knowledge signatures along with the design and prototype implementation of a knowledge signature generator.
Invarient patterns in articulatory movements
NASA Astrophysics Data System (ADS)
Bonaventura, Patrizia
2004-04-01
The purpose of the reported study is to discover an effective method of characterizing movement patterns of the crucial articulator as the function of an abstract syllable magnitude and the adjacent boundary, and at the same time to investigate effects of prosodic control on utterance organization. In particular, the speed of movement when a flesh point on the tongue blade or the lower lip crosses a selected position relative to the occlusion plane is examined. The time of such crossing provides an effective measure of syllable timing and syllable duration according to previous work. In the present work, using a very limited vocabulary with only a few consonants and one vowel as the key speech materials, effects of contrastive emphasis on demisyllabic movement patterns were studied. The theoretical framework for this analysis is the C/D model of speech production in relation to the concept of an invariant part of selected articulatory movements. The results show evidence in favor of the existence of ``iceberg'' patterns, but a linear dependence of slope on the total excursion of the demisyllabic movement, instead of the approximate constancy of the threshold crossing speed as suggested in the original proposal of the iceberg, has been found. Accordingly, a revision of the original concept of iceberg, seems necessary. This refinement is consistent with the C/D model assumption on ``prominence control'' that the syllable magnitude determines the movement amplitude, accompanying directly related syllable duration change. In this assumption, the movement of a consonantal component should also be proportional to syllable magnitude. The results suggests, however, systematic outliers deviating from the linear dependence of movement speed on excursion. This deviation may be caused by the effect of the immediately following boundary, often referred to as phrase-final elongation. Thesis advisor: Osamu Fujimura Copies of this thesis written in English can be obtained from
Injuries to law enforcement officers: the backface signature injury.
Wilhelm, Marianne; Bir, Cynthia
2008-01-15
In today's law enforcement community, one of the most vital tools an officer can possess is personal body armor. However, a recent Department of Justice investigation has raised important questions regarding the protection actually afforded officers through the use of personal body armor, and the current test methods used to assess the armor. Test results show that most Zylon-containing vests showed deformations in excess of the 0101.04 Standard's 44 mm backface signature limit. Such increased deformation can lead to serious injuries, including backface signature injuries, which have occurred in the field. Although the vest is successful in containing the round, it is not effectively dissipating the energy enough to prevent large amounts of vest deformation at the area of impact. Therefore, open, penetrating wounds occur even though the bullet did not penetrate the vest. The objective of the current study was to further define the backface signature injury through the use of case studies and laboratory experiments. Following the case study investigation, backface signature testing was conducted using a clay medium based on the NIJ 0101.04 Standard. The final component of this research involved the use of post-mortem human specimens (PMHS) for further investigation of the backface signature injury. Although the underlying cause of backface signature injuries is unknown, energy density is likely to play a role in the mechanism. Energy density (E/a) is defined as the energy per unit area and has been previously used in less lethal skin penetration research. Further research into the underlying causes of backface signature injuries is necessary. In addition to armor testing, the study of law enforcement personnel who have been shot while wearing soft body armor is also a valuable tool for determining the effectiveness of certification standards. Finally, it is important for medical personnel to recognize the backface signature injury and document this as a type of
Invariance in the isoheptanes of petroleum
Mango, F.D.
1987-07-31
Four isoheptanes in petroleum display a remarkable invariance in a ratio of sums of concentrations. The isoheptanes are not at thermodynamic equilibrium, nor are they fixed to some constant composition. The four isomers display coherent change in relative amounts but maintain invariance in the ratio of sums. Within sets of genetically related petroleum samples, invariance reaches levels that approach the limits of their analytical precision. The invariance is inconsistent with a chemical origin that involves the thermal fragmentation of natural products or their derivatives. It suggests a reaction process at steady state, in which relative rates of product formation are constant. A mechanism is proposed in which the four isoheptanes are formed pairwise and sequentially through two intermediates in a catalytic process that operates at steady state. 13 references, 3 figures, 1 table.
Testing Lorentz invariance of dark matter
Blas, Diego; Ivanov, Mikhail M.; Sibiryakov, Sergey E-mail: mm.ivanov@physics.msu.ru
2012-10-01
We study the possibility to constrain deviations from Lorentz invariance in dark matter (DM) with cosmological observations. Breaking of Lorentz invariance generically introduces new light gravitational degrees of freedom, which we represent through a dynamical timelike vector field. If DM does not obey Lorentz invariance, it couples to this vector field. We find that this coupling affects the inertial mass of small DM halos which no longer satisfy the equivalence principle. For large enough lumps of DM we identify a (chameleon) mechanism that restores the inertial mass to its standard value. As a consequence, the dynamics of gravitational clustering are modified. Two prominent effects are a scale dependent enhancement in the growth of large scale structure and a scale dependent bias between DM and baryon density perturbations. The comparison with the measured linear matter power spectrum in principle allows to bound the departure from Lorentz invariance of DM at the per cent level.
Topological invariants and renormalization of Lorenz maps
NASA Astrophysics Data System (ADS)
Silva, Luis; Sousa Ramos, J.
2002-02-01
We prove that the invariants of the topological semiconjugation of Lorenz maps with β-transformations remains constant on the renormalization archipelagoes and analyze how the dynamics on the archipelagoes depends on its structure.
Numerical considerations in computing invariant subspaces
Dongarra, J.J. . Dept. of Computer Science Oak Ridge National Lab., TN ); Hammarling, S. ); Wilkinson, J.H. )
1990-11-01
This paper describes two methods for computing the invariant subspace of a matrix. The first involves using transformations to interchange the eigenvalues; the second involves direct computation of the vectors. 10 refs.
Convecting reference frames and invariant numerical models
NASA Astrophysics Data System (ADS)
Bihlo, Alexander; Nave, Jean-Christophe
2014-09-01
In the recent paper by Bernardini et al. [1] the discrepancy in the performance of finite difference and spectral models for simulations of flows with a preferential direction of propagation was studied. In a simplified investigation carried out using the viscous Burgers equation the authors attributed the poorer numerical results of finite difference models to a violation of Galilean invariance in the discretization and propose to carry out the computations in a reference frame moving with the bulk velocity of the flow. Here we further discuss this problem and relate it to known results on invariant discretization schemes. Non-invariant and invariant finite difference discretizations of Burgers equation are proposed and compared with the discretization using the remedy proposed by Bernardini et al.
Position, rotation, and intensity invariant recognizing method
Ochoa, Ellen; Schils, George F.; Sweeney, Donald W.
1989-01-01
A method for recognizing the presence of a particular target in a field of view which is target position, rotation, and intensity invariant includes the preparing of a target-specific invariant filter from a combination of all eigen-modes of a pattern of the particular target. Coherent radiation from the field of view is then imaged into an optical correlator in which the invariant filter is located. The invariant filter is rotated in the frequency plane of the optical correlator in order to produce a constant-amplitude rotational response in a correlation output plane when the particular target is present in the field of view. Any constant response is thus detected in the output The U.S. Government has rights in this invention pursuant to Contract No. DE-AC04-76DP00789 between the U.S. Department of Energy and AT&T Technologies, Inc.
Preimpact porosity controls the gravity signature of lunar craters
NASA Astrophysics Data System (ADS)
Milbury, C.; Johnson, B. C.; Melosh, H. J.; Collins, G. S.; Blair, D. M.; Soderblom, J. M.; Nimmo, F.; Bierson, C. J.; Phillips, R. J.; Zuber, M. T.
2015-11-01
We model the formation of lunar complex craters and investigate the effect of preimpact porosity on their gravity signatures. We find that while preimpact target porosities less than ~7% produce negative residual Bouguer anomalies (BAs), porosities greater than ~7% produce positive anomalies whose magnitude is greater for impacted surfaces with higher initial porosity. Negative anomalies result from pore space creation due to fracturing and dilatant bulking, and positive anomalies result from destruction of pore space due to shock wave compression. The central BA of craters larger than ~215 km in diameter, however, are invariably positive because of an underlying central mantle uplift. We conclude that the striking differences between the gravity signatures of craters on the Earth and Moon are the result of the higher average porosity and variable porosity of the lunar crust.
Rephasing invariant parametrization of flavor mixing
NASA Astrophysics Data System (ADS)
Lee, Tae-Hun
A new rephasing invariant parametrization for the 3 x 3 CKM matrix, called (x, y) parametrization, is introduced and the properties and applications of the parametrization are discussed. The overall phase condition leads this parametrization to have only six rephsing invariant parameters and two constraints. Its simplicity and regularity become apparent when it is applied to the one-loop RGE (renormalization group equations) for the Yukawa couplings. The implications of this parametrization for unification of the Yukawa couplings are also explored.
From scale invariance to Lorentz symmetry.
Sibiryakov, Sergey
2014-06-20
It is shown that a unitary translationally invariant field theory in 1+1 dimensions, satisfying isotropic scale invariance, standard assumptions about the spectrum of states and operators, and the requirement that signals propagate with finite velocity, possesses an infinite dimensional symmetry given by one or a product of several copies of conformal algebra. In particular, this implies the presence of one or several Lorentz groups acting on the operator algebra of the theory.
'Breaking' position-invariant object recognition.
Cox, David D; Meier, Philip; Oertelt, Nadja; DiCarlo, James J
2005-09-01
While it is often assumed that objects can be recognized irrespective of where they fall on the retina, little is known about the mechanisms underlying this ability. By exposing human subjects to an altered world where some objects systematically changed identity during the transient blindness that accompanies eye movements, we induced predictable object confusions across retinal positions, effectively 'breaking' position invariance. Thus, position invariance is not a rigid property of vision but is constantly adapting to the statistics of the environment.
Invariant distributions on compact homogeneous spaces
Gorbatsevich, V V
2013-12-31
In this paper, we study distributions on compact homogeneous spaces, including invariant distributions and also distributions admitting a sub-Riemannian structure. We first consider distributions of dimension 1 and 2 on compact homogeneous spaces. After this, we study the cases of compact homogeneous spaces of dimension 2, 3, and 4 in detail. Invariant distributions on simply connected compact homogeneous spaces are also treated. Bibliography: 18 titles.
Invariants of Fokker-Planck equations
NASA Astrophysics Data System (ADS)
Abe, Sumiyoshi
2017-02-01
A weak invariant of a stochastic system is defined in such a way that its expectation value with respect to the distribution function as a solution of the associated Fokker-Planck equation is constant in time. A general formula is given for time evolution of the fluctuations of the invariant. An application to the problem of share price in finance is illustrated. It is shown how this theory makes it possible to reduce the growth rate of the fluctuations.
Recognizing 3D Object Using Photometric Invariant.
1995-02-01
model and the data space coordinates, using centroid invariance of corresponding groups of feature positions. Tests are given to show the stability and...positions in the model and the data space coordinates, using centroid invariance of corresponding groups of feature positions. Tests are given to show the...ognizing 3D objects. In our testing , it took only 0.2 seconds to derive corresponding positions in the model and the image for natural pictures. 2
A Hydrodynamic Invariant of Polymeric Molecules
NASA Astrophysics Data System (ADS)
Tsvetkov, V. N.; Lavrenko, P. N.; Bushin, S. V.
1982-10-01
Theories of the hydrodynamic properties of macromolecules in solution are examined, from which the invariant relation A0 = kη0(M[η]/100)1/3f can be obtained between the intrinsic viscosity [η] , the molecular mass M, and the coefficient of sliding friction of the molecule f. Analysis of the experimental results will indicate the most probable values of the invariant A0 for various classes of polymers. A list of 314 references is included.
On Lorentz invariants in relativistic magnetic reconnection
Yang, Shu-Di; Wang, Xiao-Gang
2016-08-15
Lorentz invariants whose nonrelativistic correspondences play important roles in magnetic reconnection are discussed in this paper. Particularly, the relativistic invariant of the magnetic reconnection rate is defined and investigated in a covariant two-fluid model. Certain Lorentz covariant representations for energy conversion and magnetic structures in reconnection processes are also investigated. Furthermore, relativistic measures for topological features of reconnection sites, particularly magnetic nulls and separatrices, are analyzed.
Computer calculation of Witten's 3-manifold invariant
NASA Astrophysics Data System (ADS)
Freed, Daniel S.; Gompf, Robert E.
1991-10-01
Witten's 2+1 dimensional Chern-Simons theory is exactly solvable. We compute the partition function, a topological invariant of 3-manifolds, on generalized Seifert spaces. Thus we test the path integral using the theory of 3-manifolds. In particular, we compare the exact solution with the asymptotic formula predicted by perturbation theory. We conclude that this path integral works as advertised and gives an effective topological invariant.
NASA Technical Reports Server (NTRS)
Clark, T. A.; Thomsen, P.
1988-01-01
A study is presented of deformations in antennas with the emphasis on their influence on VLBI measurements. The GIFTS structural analysis program has been used to model the VLBI antenna in Fairbanks (Alaska). The report identifies key deformations and studies the effect of gravity, wind, and temperature. Estimates of expected deformations are given.
Molecular signatures of ribosomal evolution.
Roberts, Elijah; Sethi, Anurag; Montoya, Jonathan; Woese, Carl R; Luthey-Schulten, Zaida
2008-09-16
Ribosomal signatures, idiosyncrasies in the ribosomal RNA (rRNA) and/or proteins, are characteristic of the individual domains of life. As such, insight into the early evolution of the domains can be gained from a comparative analysis of their respective signatures in the translational apparatus. In this work, we identify signatures in both the sequence and structure of the rRNA and analyze their contributions to the universal phylogenetic tree using both sequence- and structure-based methods. Domain-specific ribosomal proteins can be considered signatures in their own right. Although it is commonly assumed that they developed after the universal ribosomal proteins, we present evidence that at least one may have been present before the divergence of the organismal lineages. We find correlations between the rRNA signatures and signatures in the ribosomal proteins showing that the rRNA signatures coevolved with both domain-specific and universal ribosomal proteins. Finally, we show that the genomic organization of the universal ribosomal components contains these signatures as well. From these studies, we propose the ribosomal signatures are remnants of an evolutionary-phase transition that occurred as the cell lineages began to coalesce and so should be reflected in corresponding signatures throughout the fabric of the cell and its genome.
Molecular signatures of ribosomal evolution
Roberts, Elijah; Sethi, Anurag; Montoya, Jonathan; Woese, Carl R.; Luthey-Schulten, Zaida
2008-01-01
Ribosomal signatures, idiosyncrasies in the ribosomal RNA (rRNA) and/or proteins, are characteristic of the individual domains of life. As such, insight into the early evolution of the domains can be gained from a comparative analysis of their respective signatures in the translational apparatus. In this work, we identify signatures in both the sequence and structure of the rRNA and analyze their contributions to the universal phylogenetic tree using both sequence- and structure-based methods. Domain-specific ribosomal proteins can be considered signatures in their own right. Although it is commonly assumed that they developed after the universal ribosomal proteins, we present evidence that at least one may have been present before the divergence of the organismal lineages. We find correlations between the rRNA signatures and signatures in the ribosomal proteins showing that the rRNA signatures coevolved with both domain-specific and universal ribosomal proteins. Finally, we show that the genomic organization of the universal ribosomal components contains these signatures as well. From these studies, we propose the ribosomal signatures are remnants of an evolutionary-phase transition that occurred as the cell lineages began to coalesce and so should be reflected in corresponding signatures throughout the fabric of the cell and its genome. PMID:18768810
Four motional invariants in axisymmetric tori equilibria
A ring gren, O.; Moiseenko, V.E.
2006-05-15
In addition to the standard set ({epsilon},{mu},p{sub {phi}}) of three invariants in axisymmetric tori, there exists a fourth independent radial drift invariant I{sub r}. For confined particles, the net radial drift has to be zero, whereby the drift orbit average I{sub r}=
The invariances of power law size distributions.
Frank, Steven A
2016-01-01
Size varies. Small things are typically more frequent than large things. The logarithm of frequency often declines linearly with the logarithm of size. That power law relation forms one of the common patterns of nature. Why does the complexity of nature reduce to such a simple pattern? Why do things as different as tree size and enzyme rate follow similarly simple patterns? Here I analyze such patterns by their invariant properties. For example, a common pattern should not change when adding a constant value to all observations. That shift is essentially the renumbering of the points on a ruler without changing the metric information provided by the ruler. A ruler is shift invariant only when its scale is properly calibrated to the pattern being measured. Stretch invariance corresponds to the conservation of the total amount of something, such as the total biomass and consequently the average size. Rotational invariance corresponds to pattern that does not depend on the order in which underlying processes occur, for example, a scale that additively combines the component processes leading to observed values. I use tree size as an example to illustrate how the key invariances shape pattern. A simple interpretation of common pattern follows. That simple interpretation connects the normal distribution to a wide variety of other common patterns through the transformations of scale set by the fundamental invariances.
The invariances of power law size distributions
Frank, Steven A.
2016-01-01
Size varies. Small things are typically more frequent than large things. The logarithm of frequency often declines linearly with the logarithm of size. That power law relation forms one of the common patterns of nature. Why does the complexity of nature reduce to such a simple pattern? Why do things as different as tree size and enzyme rate follow similarly simple patterns? Here I analyze such patterns by their invariant properties. For example, a common pattern should not change when adding a constant value to all observations. That shift is essentially the renumbering of the points on a ruler without changing the metric information provided by the ruler. A ruler is shift invariant only when its scale is properly calibrated to the pattern being measured. Stretch invariance corresponds to the conservation of the total amount of something, such as the total biomass and consequently the average size. Rotational invariance corresponds to pattern that does not depend on the order in which underlying processes occur, for example, a scale that additively combines the component processes leading to observed values. I use tree size as an example to illustrate how the key invariances shape pattern. A simple interpretation of common pattern follows. That simple interpretation connects the normal distribution to a wide variety of other common patterns through the transformations of scale set by the fundamental invariances. PMID:27928497
Anisotropic Cosmology and Curvature Invariants.
NASA Astrophysics Data System (ADS)
Skea, James E. F.
greater when non-axisymmetric cosmologies are considered. In the limit where the particle production is switched on at the Planck time (t _{rm Pl}), isotropisation is found to occur at _{Omega } 10^5 t_ {rm Pl}, compatible with restrictions on anistropy at that time. Particle production is not found to isotropise Bianchi VIII and IX cosmologies. In Part 3, we study the structure of various curvature invariants and, following a suggestion by Karlhede, we investigate their relationship to horizons in particular space-times. (Abstract shortened by UMI.).
1982-10-01
RADC-TR-82-269 A. A 9 q _ ___ ___ __ 4. TITLE (and Subtitle) S . TYPE or REPORT & PERIOD COVERED] Final Technical Report MODEM SIGNATURE ANALYSIS Sep 80...Nov 81 a. PERFORMING 011G. REPORT NME N/A 7. AUTI4OR( s ) 4. CONTRACT DOR GRANT oMumEalr) Thomas V. Edwards Dr. Robert J. Dick Dr. James W. Modestino...3-7 3-2 Second NSA Data Collection System . ....... ... 3-8 3-3 Time Plot Paradyne MP-96 AGN 20 dB S /N ..... .... 3-11 3-4 Power Spectral Density
Signatures of nonthermal melting
Zier, Tobias; Zijlstra, Eeuwe S.; Kalitsov, Alan; Theodonis, Ioannis; Garcia, Martin E.
2015-01-01
Intense ultrashort laser pulses can melt crystals in less than a picosecond but, in spite of over thirty years of active research, for many materials it is not known to what extent thermal and nonthermal microscopic processes cause this ultrafast phenomenon. Here, we perform ab-initio molecular-dynamics simulations of silicon on a laser-excited potential-energy surface, exclusively revealing nonthermal signatures of laser-induced melting. From our simulated atomic trajectories, we compute the decay of five structure factors and the time-dependent structure function. We demonstrate how these quantities provide criteria to distinguish predominantly nonthermal from thermal melting. PMID:26798822
2006-01-24
Le DG W.Jentschke souhaite la bienvenue à l'assemblée et aux invités pour la signature du protocole entre le Cern et l'URSS qui est un événement important. C'est en 1955 que 55 visiteurs soviétiques ont visité le Cern pour la première fois. Le premier DG au Cern, F.Bloch, et Mons.Amaldi sont aussi présents. Tandis que le discours anglais de W.Jentschke est traduit en russe, le discours russe de Mons.Morozov est traduit en anglais.
Spatial Signature Estimation with an Uncalibrated Uniform Linear Array †
Cao, Xiang; Xin, Jingmin; Nishio, Yoshifumi; Zheng, Nanning
2015-01-01
In this paper, the problem of spatial signature estimation using a uniform linear array (ULA) with unknown sensor gain and phase errors is considered. As is well known, the directions-of-arrival (DOAs) can only be determined within an unknown rotational angle in this array model. However, the phase ambiguity has no impact on the identification of the spatial signature. Two auto-calibration methods are presented for spatial signature estimation. In our methods, the rotational DOAs and model error parameters are firstly obtained, and the spatial signature is subsequently calculated. The first method extracts two subarrays from the ULA to construct an estimator, and the elements of the array can be used several times in one subarray. The other fully exploits multiple invariances in the interior of the sensor array, and a multidimensional nonlinear problem is formulated. A Gauss–Newton iterative algorithm is applied for solving it. The first method can provide excellent initial inputs for the second one. The effectiveness of the proposed algorithms is demonstrated by several simulation results. PMID:26076405
Finite elasto-plastic deformation. I - Theory and numerical examples
NASA Technical Reports Server (NTRS)
Osias, J. R.; Swedlow, J. L.
1974-01-01
It is demonstrated that the problem of elasto-plastic finite deformation is governed by a quasi-linear model irrespective of deformation magnitude. This feature follows from the adoption of a rate viewpoint toward finite deformation analysis in an Eulerian reference frame. Objectivity of the formulation is preserved by introduction of a frame-invariant stress rate. Equations for piece-wise linear incremental finite element analysis are developed by application of the Galerkin method to the instantaneously linear governing differential equations of the quasi-linear model. Numerical solution capability has been established for problems of plane strain and plane stress. The accuracy of the numerical analysis is demonstrated by consideration of a number of problems of homogeneous finite deformation admitting comparative analytic solution. It is shown that accurate, objective numerical solutions can be obtained for problems involving dimensional changes of an order of magnitude and rotations of a full radian.
Modified Lorentz transformations in deformed special relativity
NASA Astrophysics Data System (ADS)
Salesi, G.; Greselin, M.; Deleidi, L.; Peruzza, R. A.
2017-05-01
We have extended a recent approach to Deformed Special Relativity based on deformed dispersion laws, entailing modified Lorentz transformations and, at the same time, noncommutative geometry and intrinsically discrete space-time. In so doing we have obtained the explicit form of the modified Lorentz transformations for a special class of modified momentum-energy relations often found in literature and arising from quantum gravity and elementary particle physics. Actually, our theory looks as a very simple and natural extension of special relativity to include a momentum cutoff at the Planck scale. In particular, the new Lorentz transformations do imply that for high boost speed (V ˜ c) the deformed Lorentz factor does not diverge as in ordinary relativity, but results to be upper bounded by a large finite value of the order of the ratio between the Planck mass and the particle mass. We have also predicted that a generic boost leaves unchanged Planck energy and momentum, which result invariant with respect to any reference frame. Finally, through matrix deformation functions, we have extended our theory to more general cases with dispersion laws containing momentum-energy mixed terms.
Gauge theory in deformed mathcal{N} = (1, 1) superspace
NASA Astrophysics Data System (ADS)
Buchbinder, I. L.; Ivanov, E. A.; Lechtenfeld, O.; Samsonov, I. B.; Zupnik, B. M.
2008-09-01
We review the non-anticommutative Q-deformations of mathcal{N} = (1, 1) supersymmetric theories in four-dimensional Euclidean harmonic superspace. These deformations preserve chirality and harmonic Grassmann analyticity. The associated field theories arise as a low-energy limit of string theory in specific backgrounds and generalize the Moyal-deformed supersymmetric field theories. A characteristic feature of the Q-deformed theories is the half-breaking of supersymmetry in the chiral sector of the Euclidean superspace. Our main focus is on the chiral singlet Q-deformation, which is distinguished by preserving the SO(4) ˜ Spin(4) “Lorentz” symmetry and the SU(2) R-symmetry. We present the superfield and component structures of the deformed mathcal{N} = (1, 0) supersymmetric gauge theory as well as of hypermultiplets coupled to a gauge superfield: invariant actions, deformed transformation rules, and so on. We discuss quantum aspects of these models and prove their renormalizability in the Abelian case. For the charged hypermultiplet in an Abelian gauge superfield background we construct the deformed holomorphic effective action.
Signature change in loop quantum gravity: Two-dimensional midisuperspace models and dilaton gravity
NASA Astrophysics Data System (ADS)
Bojowald, Martin; Brahma, Suddhasattwa
2017-06-01
Models of loop quantum gravity based on real connections have a deformed notion of general covariance, which leads to the phenomenon of signature change. This result is confirmed here in a general analysis of all midisuperspace models without local degrees of freedom. As a subclass of models, two-dimensional theories of dilaton gravity appear, but a larger set of examples is possible based only on the condition of anomaly freedom. While the classical dilaton gravity models are the only such systems without deformed covariance, they do give rise to signature change when holonomy modifications are included.
Deformable Nanolaminate Optics
Olivier, S S; Papavasiliou, A P; Barbee, T W; Miles, R R; Walton, C C; Cohn, M B; Chang, K
2006-05-12
We are developing a new class of deformable optic based on electrostatic actuation of nanolaminate foils. These foils are engineered at the atomic level to provide optimal opto-mechanical properties, including surface quality, strength and stiffness, for a wide range of deformable optics. We are combining these foils, developed at Lawrence Livermore National Laboratory (LLNL), with commercial metal processing techniques to produce prototype deformable optics with aperture sizes up to 10 cm and actuator spacing from 1 mm to 1 cm and with a range of surface deformation designed to be as much as 10 microns. The existing capability for producing nanolaminate foils at LLNL, coupled with the commercial metal processing techniques being used, enable the potential production of these deformable optics with aperture sizes of over 1 m, and much larger deformable optics could potentially be produced by tiling multiple deformable segments. In addition, based on the fabrication processes being used, deformable nanolaminate optics could potentially be produced with areal densities of less than 1 kg per square m for applications in which lightweight deformable optics are desirable, and deformable nanolaminate optics could potentially be fabricated with intrinsically curved surfaces, including aspheric shapes. We will describe the basic principles of these devices, and we will present details of the design, fabrication and characterization of the prototype deformable nanolaminate optics that have been developed to date. We will also discuss the possibilities for future work on scaling these devices to larger sizes and developing both devices with lower areal densities and devices with curved surfaces.
NASA Astrophysics Data System (ADS)
Milton, Graeme Walter
2013-07-01
A complete characterization is given of the possible macroscopic deformations of periodic non-linear affine unimode metamaterials constructed from rigid bars and pivots. The materials are affine in the sense that their macroscopic deformations can only be affine deformations: on a local level the deformation may vary from cell to cell. Unimode means that macroscopically the material can only deform along a one dimensional trajectory in the six dimensional space of invariants describing the deformation (excluding translations and rotations). We show by explicit construction that any continuous trajectory is realizable to an arbitrarily high degree of approximation provided at all points along the trajectory the geometry does not collapse to a lower dimensional one. In particular, we present two and three dimensional dilational materials having an arbitrarily large flexibility window. These are perfect auxetic materials for which a dilation is the only easy mode of deformation. They are free to dilate to arbitrarily large strain with zero bulk modulus.
Bohr Hamiltonian with a deformation-dependent mass term for the Davidson potential
Bonatsos, Dennis; Georgoudis, P. E.; Lenis, D.; Minkov, N.; Quesne, C.
2011-04-15
Analytical expressions for spectra and wave functions are derived for a Bohr Hamiltonian, describing the collective motion of deformed nuclei, in which the mass is allowed to depend on the nuclear deformation. Solutions are obtained for separable potentials consisting of a Davidson potential in the {beta} variable, in the cases of {gamma}-unstable nuclei, axially symmetric prolate deformed nuclei, and triaxial nuclei, implementing the usual approximations in each case. The solution, called the deformation-dependent mass (DDM) Davidson model, is achieved by using techniques of supersymmetric quantum mechanics (SUSYQM), involving a deformed shape invariance condition. Spectra and B(E2) transition rates are compared to experimental data. The dependence of the mass on the deformation, dictated by SUSYQM for the potential used, reduces the rate of increase of the moment of inertia with deformation, removing a main drawback of the model.
Advanced spectral signature discrimination algorithm
NASA Astrophysics Data System (ADS)
Chakravarty, Sumit; Cao, Wenjie; Samat, Alim
2013-05-01
This paper presents a novel approach to the task of hyperspectral signature analysis. Hyperspectral signature analysis has been studied a lot in literature and there has been a lot of different algorithms developed which endeavors to discriminate between hyperspectral signatures. There are many approaches for performing the task of hyperspectral signature analysis. Binary coding approaches like SPAM and SFBC use basic statistical thresholding operations to binarize a signature which are then compared using Hamming distance. This framework has been extended to techniques like SDFC wherein a set of primate structures are used to characterize local variations in a signature together with the overall statistical measures like mean. As we see such structures harness only local variations and do not exploit any covariation of spectrally distinct parts of the signature. The approach of this research is to harvest such information by the use of a technique similar to circular convolution. In the approach we consider the signature as cyclic by appending the two ends of it. We then create two copies of the spectral signature. These three signatures can be placed next to each other like the rotating discs of a combination lock. We then find local structures at different circular shifts between the three cyclic spectral signatures. Texture features like in SDFC can be used to study the local structural variation for each circular shift. We can then create different measure by creating histogram from the shifts and thereafter using different techniques for information extraction from the histograms. Depending on the technique used different variant of the proposed algorithm are obtained. Experiments using the proposed technique show the viability of the proposed methods and their performances as compared to current binary signature coding techniques.
Noncommutative oscillators from a Hopf algebra twist deformation. A first principles derivation
Castro, P. G.; Kullock, R.; Toppan, F.
2011-03-15
Noncommutative oscillators are first-quantized through an abelian Drinfel'd twist deformation of a Hopf algebra and its action on a module. Several important and subtle issues making the quantization possible are solved. The spectrum of the single-particle Hamiltonians is computed. The multiparticle Hamiltonians are fixed, unambiguously, by the Hopf algebra coproduct. The symmetry under particle exchange is guaranteed. In d= 2 dimensions the rotational invariance is preserved, while in d= 3 the so(3) rotational invariance is broken down to an so(2) invariance.
High Energy Astrophysics Tests of Lorentz Invariance and Quantum Gravity Models
NASA Technical Reports Server (NTRS)
Stecker, Floyd W.
2011-01-01
High-energy astrophysics observations provide the best possibilities to detect a very small violation of Lorentz invariance such as may be related to the structure of space-time near the Planck scale of approximately 10-35 m. I will discuss here the possible signatures of Lorentz invariance violation (LIV) from observations of the spectra, polarization, and timing of gamma-rays from active galactic nuclei and gamma-ray bursts. Other sensitive tests are provided by observations ofthe spectra of ultrahigh energy cosmic rays and neutrinos. Using the latest data from the Pierre Auger Observatory one can already derive an upper limit of 4.5 x 10(exp -23) to the amount of LIV at a proton Lorentz factor of -2 x 10(exp 11). This result has fundamental implications for quantum gravity models. I will also discuss the possibilities of using more sensitive space based detection techniques to improve searches for LIV in the future.
Gamma-Ray, Cosmic Ray and Neutrino Tests of Lorentz Invariance and Quantum Gravity Models
NASA Technical Reports Server (NTRS)
Stecker, Floyd
2011-01-01
High-energy astrophysics observations provide the best possibilities to detect a very small violation of Lorentz invariance such as may be related to the structure of space-time near the Planck scale of approximately 10(exp -35) m. I will discuss here the possible signatures of Lorentz invariance violation (LIV) from observations of the spectra, polarization, and timing of gamma-rays from active galactic nuclei and gamma-ray bursts. Other sensitive tests are provided by observations of the spectra of ultrahigh energy cosmic rays and neutrinos. Using the latest data from the Pierre Auger Observatory one can already derive an upper limit of 4.5 x 10(exp -23) to the amount of LIV of at a proton Lorentz factor of approximately 2 x 10(exp 11). This result has fundamental implications for quantum gravity models. I will also discuss the possibilities of using more sensitive space based detection techniques to improve searches for LIV in the future.
NASA Astrophysics Data System (ADS)
Nag, Amit; Sau, Jay
The observed zero bias peak in tunneling conductance experiments on semiconductor Rashba nanowire is a signature of presence of Majorana zero modes. Characteristics of zero bias conductance peak (ZBCP) namely, height, width and peak splitting, are a function of microscopic parameters. Zero modes have finite splitting as a result of finiteness of the nanowire rendering the ground state only approximately topological i.e. zero modes are only approximately Majoranas. We calculate the scattering matrix topological invariant to quantify the quality of approximate Majorana modes and study its relation to observed characteristics of ZBCP. Furthermore we study the effect of dephasing on the topological invariant. Finally, we draw connection between the characteristics of the ZBCP and probability of observing non-Abelian statistics in proposed future experiments involving braiding of Majorana modes. Work is done in collaboration with Sankar Das Sarma and supported by LPS-MPO-CMTC, Microsoft Q, Univ. of Maryland startup grants and JQI-NSF-PFC.
Neural Representations that Support Invariant Object Recognition
Goris, Robbe L. T.; Op de Beeck, Hans P.
2008-01-01
Neural mechanisms underlying invariant behaviour such as object recognition are not well understood. For brain regions critical for object recognition, such as inferior temporal cortex (ITC), there is now ample evidence indicating that single cells code for many stimulus aspects, implying that only a moderate degree of invariance is present. However, recent theoretical and empirical work seems to suggest that integrating responses of multiple non-invariant units may produce invariant representations at population level. We provide an explicit test for the hypothesis that a linear read-out mechanism of a pool of units resembling ITC neurons may achieve invariant performance in an identification task. A linear classifier was trained to decode a particular value in a 2-D stimulus space using as input the response pattern across a population of units. Only one dimension was relevant for the task, and the stimulus location on the irrelevant dimension (ID) was kept constant during training. In a series of identification tests, the stimulus location on the relevant dimension (RD) and ID was manipulated, yielding estimates for both the level of sensitivity and tolerance reached by the network. We studied the effects of several single-cell characteristics as well as population characteristics typically considered in the literature, but found little support for the hypothesis. While the classifier averages out effects of idiosyncratic tuning properties and inter-unit variability, its invariance is very much determined by the (hypothetical) ‘average’ neuron. Consequently, even at population level there exists a fundamental trade-off between selectivity and tolerance, and invariant behaviour does not emerge spontaneously. PMID:19242556
Invariant object recognition based on extended fragments.
Bart, Evgeniy; Hegdé, Jay
2012-01-01
Visual appearance of natural objects is profoundly affected by viewing conditions such as viewpoint and illumination. Human subjects can nevertheless compensate well for variations in these viewing conditions. The strategies that the visual system uses to accomplish this are largely unclear. Previous computational studies have suggested that in principle, certain types of object fragments (rather than whole objects) can be used for invariant recognition. However, whether the human visual system is actually capable of using this strategy remains unknown. Here, we show that human observers can achieve illumination invariance by using object fragments that carry the relevant information. To determine this, we have used novel, but naturalistic, 3-D visual objects called "digital embryos." Using novel instances of whole embryos, not fragments, we trained subjects to recognize individual embryos across illuminations. We then tested the illumination-invariant object recognition performance of subjects using fragments. We found that the performance was strongly correlated with the mutual information (MI) of the fragments, provided that MI value took variations in illumination into consideration. This correlation was not attributable to any systematic differences in task difficulty between different fragments. These results reveal two important principles of invariant object recognition. First, the subjects can achieve invariance at least in part by compensating for the changes in the appearance of small local features, rather than of whole objects. Second, the subjects do not always rely on generic or pre-existing invariance of features (i.e., features whose appearance remains largely unchanged by variations in illumination), and are capable of using learning to compensate for appearance changes when necessary. These psychophysical results closely fit the predictions of earlier computational studies of fragment-based invariant object recognition.
Optical signature modeling at FOI
NASA Astrophysics Data System (ADS)
Nelsson, C.; Hermansson, P.; Nyberg, S.; Persson, A.; Persson, R.; Sjökvist, S.; Winzell, T.
2006-09-01
Computer programs for prediction of optical signatures of targets and backgrounds are valuable tools for signature assessment and signature management. Simulations make it possible to study optical signatures from targets and backgrounds under conditions where measured signatures are missing or incomplete. Several applications may be identified: Increase understanding, Design and assessment of low signature concepts, Assessment of tactics, Design and assessment of sensor systems, Duel simulations of EW, and Signature awareness. FOI (the Swedish Defence Research Agency) study several methods and modeling programs for detailed physically based prediction of the optical signature of targets in backgrounds. The most important commercial optical signature prediction programs available at FOI are CAMEO-SIM, RadThermIR, and McCavity. The main tasks of the work have been: Assembly of a database of input data, Gain experience of different computer programs, In-house development of complementary algorithms and programs, and Validation and assessment of the simulation results. This paper summarizes the activities and the results obtained. Some application examples will be given as well as results from validations. The test object chosen is the MTLB which is a tracked armored vehicle. It has been used previously at FOI for research purposes and therefore measurement data is available.
Multimodal signature modeling of humans
NASA Astrophysics Data System (ADS)
Cathcart, J. Michael; Kocher, Brian; Prussing, Keith; Lane, Sarah; Thomas, Alan
2010-04-01
Georgia Tech been investigating method for the detection of covert personnel in traditionally difficult environments (e.g., urban, caves). This program focuses on a detailed phenomenological analysis of human physiology and signatures with the subsequent identification and characterization of potential observables. Both aspects are needed to support the development of personnel detection and tracking algorithms. The difficult nature of these personnel-related problems dictates a multimodal sensing approach. Human signature data of sufficient and accurate quality and quantity do not exist, thus the development of an accurate signature model for a human is needed. This model should also simulate various human activities to allow motion-based observables to be exploited. This paper will describe a multimodal signature modeling approach that incorporates human physiological aspects, thermoregulation, and dynamics into the signature calculation. This approach permits both passive and active signatures to be modeled. The focus of the current effort involved the computation of signatures in urban environments. This paper will discuss the development of a human motion model for use in simulating both electro-optical signatures and radar-based signatures. Video sequences of humans in a simulated urban environment will also be presented; results using these sequences for personnel tracking will be presented.
Conformal field theories from deformations of theories with Wn symmetry
NASA Astrophysics Data System (ADS)
Babaro, Juan Pablo; Giribet, Gaston; Ranjbar, Arash
2016-10-01
We construct a set of nonrational conformal field theories that consist of deformations of Toda field theory for s l (n ). In addition to preserving conformal invariance, the theories may still exhibit a remnant infinite-dimensional affine symmetry. The case n =3 is used to illustrate this phenomenon, together with further deformations that yield enhanced Kac-Moody symmetry algebras. For generic n we compute N -point correlation functions on the Riemann sphere and show that these can be expressed in terms of s l (n ) Toda field theory ((N -2 )n +2 ) -point correlation functions.
Lahamy, Hervé; Lichti, Derek D
2012-10-29
The automatic interpretation of human gestures can be used for a natural interaction with computers while getting rid of mechanical devices such as keyboards and mice. In order to achieve this objective, the recognition of hand postures has been studied for many years. However, most of the literature in this area has considered 2D images which cannot provide a full description of the hand gestures. In addition, a rotation-invariant identification remains an unsolved problem, even with the use of 2D images. The objective of the current study was to design a rotation-invariant recognition process while using a 3D signature for classifying hand postures. A heuristic and voxel-based signature has been designed and implemented. The tracking of the hand motion is achieved with the Kalman filter. A unique training image per posture is used in the supervised classification. The designed recognition process, the tracking procedure and the segmentation algorithm have been successfully evaluated. This study has demonstrated the efficiency of the proposed rotation invariant 3D hand posture signature which leads to 93.88% recognition rate after testing 14,732 samples of 12 postures taken from the alphabet of the American Sign Language.
Lahamy, Hervé; Lichti, Derek D.
2012-01-01
The automatic interpretation of human gestures can be used for a natural interaction with computers while getting rid of mechanical devices such as keyboards and mice. In order to achieve this objective, the recognition of hand postures has been studied for many years. However, most of the literature in this area has considered 2D images which cannot provide a full description of the hand gestures. In addition, a rotation-invariant identification remains an unsolved problem, even with the use of 2D images. The objective of the current study was to design a rotation-invariant recognition process while using a 3D signature for classifying hand postures. A heuristic and voxel-based signature has been designed and implemented. The tracking of the hand motion is achieved with the Kalman filter. A unique training image per posture is used in the supervised classification. The designed recognition process, the tracking procedure and the segmentation algorithm have been successfully evaluated. This study has demonstrated the efficiency of the proposed rotation invariant 3D hand posture signature which leads to 93.88% recognition rate after testing 14,732 samples of 12 postures taken from the alphabet of the American Sign Language. PMID:23202168
Signature effects in 2qp bands of doubly even rare-earth nuclei
NASA Astrophysics Data System (ADS)
Kalra, Kawalpreet; Goel, Alpana; Jain, A. K.
2016-12-01
The two-quasiparticle rotational bands in deformed doubly even nuclei in the rare-earth region have been studied in detail. A number of interesting features like odd-even staggering and signature inversion have been observed. The phenomenon of signature inversion/reversal is observed experimentally in 162 66Dy, 170 0Yb and 170 74W in even-even nuclei. Two quasiparticle plus rotor model (TQPRM) calculations are carried out to explain the reverse pattern of signature in 170 74W for the rotational band having configuration {(h_{11/2})p ⊗ (d_{5/2})p}.
κ-Deformations and Extended κ-Minkowski Spacetimes
NASA Astrophysics Data System (ADS)
Borowiec, Andrzej; Pachoł, Anna
2014-11-01
We extend our previous study of Hopf-algebraic κ-deformations of all inhomogeneous orthogonal Lie algebras iso(g) as written in a tensorial and unified form. Such deformations are determined by a vector τ which for Lorentzian signature can be taken time-, light- or space-like. We focus on some mathematical aspects related to this subject. Firstly, we describe real forms with connection to the metric's signatures and their compatibility with the reality condition for the corresponding κ-Minkowski (Hopf) module algebras. Secondly, h-adic vs q-analog (polynomial) versions of deformed algebras including specialization of the formal deformation parameter &kappa to some numerical value are considered. In the latter the general covariance is lost and one deals with an orthogonal decomposition. The last topic treated in this paper concerns twisted extensions of κ-deformations as well as the description of resulting noncommutative spacetime algebras in terms of solvable Lie algebras. We found that if the type of the algebra does not depend on deformation parameters then specialization is possible.
Local and gauge invariant observables in gravity
NASA Astrophysics Data System (ADS)
Khavkine, Igor
2015-09-01
It is well known that general relativity (GR) does not possess any non-trivial local (in a precise standard sense) and diffeomorphism invariant observable. We propose a generalized notion of local observables, which retain the most important properties that follow from the standard definition of locality, yet is flexible enough to admit a large class of diffeomorphism invariant observables in GR. The generalization comes at a small price—that the domain of definition of a generalized local observable may not cover the entire phase space of GR and two such observables may have distinct domains. However, the subset of metrics on which generalized local observables can be defined is in a sense generic (its open interior is non-empty in the Whitney strong topology). Moreover, generalized local gauge invariant observables are sufficient to separate diffeomorphism orbits on this admissible subset of the phase space. Connecting the construction with the notion of differential invariants gives a general scheme for defining generalized local gauge invariant observables in arbitrary gauge theories, which happens to agree with well-known results for Maxwell and Yang-Mills theories.
Dimensional Analysis Using Toric Ideals: Primitive Invariants
Atherton, Mark A.; Bates, Ronald A.; Wynn, Henry P.
2014-01-01
Classical dimensional analysis in its original form starts by expressing the units for derived quantities, such as force, in terms of power products of basic units etc. This suggests the use of toric ideal theory from algebraic geometry. Within this the Graver basis provides a unique primitive basis in a well-defined sense, which typically has more terms than the standard Buckingham approach. Some textbook examples are revisited and the full set of primitive invariants found. First, a worked example based on convection is introduced to recall the Buckingham method, but using computer algebra to obtain an integer matrix from the initial integer matrix holding the exponents for the derived quantities. The matrix defines the dimensionless variables. But, rather than this integer linear algebra approach it is shown how, by staying with the power product representation, the full set of invariants (dimensionless groups) is obtained directly from the toric ideal defined by . One candidate for the set of invariants is a simple basis of the toric ideal. This, although larger than the rank of , is typically not unique. However, the alternative Graver basis is unique and defines a maximal set of invariants, which are primitive in a simple sense. In addition to the running example four examples are taken from: a windmill, convection, electrodynamics and the hydrogen atom. The method reveals some named invariants. A selection of computer algebra packages is used to show the considerable ease with which both a simple basis and a Graver basis can be found. PMID:25436774
Invariants for time-dependent Hamiltonian systems.
Struckmeier, J; Riedel, C
2001-08-01
An exact invariant is derived for n-degree-of-freedom Hamiltonian systems with general time-dependent potentials. The invariant is worked out in two equivalent ways. In the first approach, we define a special Ansatz for the invariant and determine its time-dependent coefficients. In the second approach, we perform a two-step canonical transformation of the initially time-dependent Hamiltonian to a time-independent one. The invariant is found to contain a function of time f(2)(t), defined as a solution of a linear third-order differential equation whose coefficients depend in general on the explicitly known configuration space trajectory that follows from the system's time evolution. It is shown that the invariant can be interpreted as the time integral of an energy balance equation. Our result is applied to a one-dimensional, time-dependent, damped non-linear oscillator, and to a three-dimensional system of Coulomb-interacting particles that are confined in a time-dependent quadratic external potential. We finally show that our results can be used to assess the accuracy of numerical simulations of time-dependent Hamiltonian systems.
Defending the beauty of the Invariance Principle
NASA Astrophysics Data System (ADS)
Barkana, Itzhak
2014-01-01
Customary stability analysis methods for nonlinear nonautonomous systems seem to require a strict condition of uniform continuity. Although extensions of LaSalle's Invariance Principle to nonautonomous systems that mitigate this condition have been available for a long time, they have remained surprisingly unknown or open to misinterpretations. The large scope of the Principle might have misled the prospective users and its application to Control problems has been received with amazing yet clear uneasiness. Counterexamples have been used in order to claim that the Invariance Principle cannot be applied to nonlinear nonautonomous systems. Because the original formulation of the Invariance Principle still imposes conditions that are not necessarily needed, this paper presents a new Invariance Principle that further mitigates previous conditions and thus further expands the scope of stability analysis. A brief comparative review of various alternatives to stability analysis of nonautonomous nonlinear systems and their implications is also presented in order to illustrate that thorough analysis of same examples may actually confirm the efficiency of the Invariance Principle approach when dealing with stability of nonautonomous nonlinear systems problems that may look difficult or even unsolvable otherwise.
Graef, L.L.; Brandenberger, R. E-mail: rhb@physics.mcgill.ca
2015-10-01
Standard inflationary models yield a characteristic signature of a primordial power spectrum with a red tensor and scalar tilt. Nevertheless, Cannone et al. [1] recently suggested that, by breaking the assumption of spatial diffeomorphism invariance in the context of the effective field theory of inflation, a blue tensor spectrum can be achieved without violating the Null Energy Condition. In this context, we explore in which cases the inflationary model of [2] can yield a blue tilt of the tensor modes along with a red tilt in the scalar spectrum. Ultimately, we analyze under which conditions the model of [3] can reproduce the specific consistency relation of String Gas Cosmology.
Forgoston, Eric; Billings, Lora; Yecko, Philip; Schwartz, Ira B.
2011-01-01
We consider the problem of stochastic prediction and control in a time-dependent stochastic environment, such as the ocean, where escape from an almost invariant region occurs due to random fluctuations. We determine high-probability control-actuation sets by computing regions of uncertainty, almost invariant sets, and Lagrangian coherent structures. The combination of geometric and probabilistic methods allows us to design regions of control, which provide an increase in loitering time while minimizing the amount of control actuation. We show how the loitering time in almost invariant sets scales exponentially with respect to the control actuation, causing an exponential increase in loitering times with only small changes in actuation force. The result is that the control actuation makes almost invariant sets more invariant. PMID:21456830
Techni-Dilaton Signatures at LHC
NASA Astrophysics Data System (ADS)
Matsuzaki, S.; Yamawaki, K.
2012-02-01
We explore discovery signatures of techni-dilaton (TD) at LHC. The TD was predicted long ago as a composite pseudo Nambu-Goldstone boson (pNGB) associated with the spontaneous breaking of the approximate scale symmetry in the walking technicolor (WTC) (initially dubbed ``scale-invariant technicolor''). Being pNGB, whose mass arises from the explicit scale-symmetry breaking due to the spontaneous breaking itself (dynamical mass generation), the TD as a composite scalar should have a mass M_{TD} lighter than other techni-hadrons, say M_{TD} ≃ 600 GeV for the typical WTC model, which is well in the discovery range of the ongoing LHC experiment. We develop a spurion method of nonlinear realization to calculate the TD couplings to the standard model (SM) particles and explicitly evaluate the TD LHC production cross sections at √{s} = 7 TeV times the branching ratios in terms of M_{TD} as an input parameter for the region 200 GeV < M_{TD} < 1000 GeV in the typical WTC models. It turns out that the TD signatures are quite different from those of the SM Higgs: In the one-doublet model (1DM) all the cross sections including the WW/ZZ mode are suppressed compared to those of the SM Higgs due to the suppressed TD couplings, while in the one-family model (1FM) all those cross sections get highly enhanced because of the presence of extra colored fermion (techni-quark) contributions. We compare the {TD} → WW/ZZ signature with the recent ATLAS and CMS bounds and find that in the case of 1DM the signature is consistent over the whole mass range 200 GeV < M_{TD} < 1000 GeV due to the large suppression of TD couplings, and by the same token the signal is too tiny for the TD to be visible through this channel at LHC. As for the 1FMs, on the other hand, a severe constraint is given on the TD mass to exclude the TD with mass ≲ 600 GeV, which, however, would imply an emergence of somewhat dramatic excess as the TD signature at 600 GeV ≲ M_{TD} < 1000 GeV in the near future. We
Landsat Signature Development Program
NASA Technical Reports Server (NTRS)
Hall, R. N.; Mcguire, K. G.; Bland, R. A.
1976-01-01
The Landsat Signature Development Program, LSDP, is designed to produce an unsupervised classification of a scene from a Landsat tape. This classification is based on the clustering tendencies of the multispectral scanner data processed from the scene. The program will generate a character map that, by identifying each of the general classes of surface features extracted from the scene data with a specific line printer symbol, indicates the approximate locations and distributions of these general classes within the scene. Also provided with the character map are a number of tables each of which describes either some aspect of the spectral properties of the resultant classes, some inter-class relationship, the incidence of picture elements assigned to the various classes in the character map classification of the scene, or some significant intermediate stage in the development of the final classes.
Drell, S.; Jeanloz, R.; Cornwall, J.; Dyson, F.; Eardley, D.
1998-03-18
This study is a follow-on to the review made by JASON during its 1997 Summer Study of what is known about the aging of critical constituents, particularly the high explosives, metals (Pu, U), and polymers in the enduring stockpile. The JASON report (JSR-97-320) that summarized the findings was based on briefings by the three weapons labs (LANL, LLNL, SNL). They presented excellent technical analyses covering a broad range of scientific and engineering problems pertaining to determining signatures of aging. But the report also noted: `Missing, however, from the briefings and the written documents made available to us by the labs and DOE, was evidence of an adequately sharp focus and high priorities on a number of essential near-term needs of maintaining weapons in the stockpile.
None
2016-07-12
Le DG W.Jentschke souhaite la bienvenue Ã l'assemblÃ©e et aux invitÃ©s pour la signature du protocole entre le Cern et l'URSS qui est un Ã©vÃ©nement important. C'est en 1955 que 55 visiteurs soviÃ©tiques ont visitÃ© le Cern pour la premiÃ¨re fois. Le premier DG au Cern, F.Bloch, et Mons.Amaldi sont aussi prÃ©sents. Tandis que le discours anglais de W.Jentschke est traduit en russe, le discours russe de Mons.Morozov est traduit en anglais.
NASA Astrophysics Data System (ADS)
Bethencourt, John; Shi, Elaine; Song, Dawn
Reputation systems have become an increasingly important tool for highlighting quality information and filtering spam within online forums. However, the dependence of a user's reputation on their history of activities seems to preclude any possibility of anonymity. We show that useful reputation information can, in fact, coexist with strong privacy guarantees. We introduce and formalize a novel cryptographic primitive we call signatures of reputation which supports monotonic measures of reputation in a completely anonymous setting. In our system, a user can express trust in others by voting for them, collect votes to build up her own reputation, and attach a proof of her reputation to any data she publishes, all while maintaining the unlinkability of her actions.
NASA Astrophysics Data System (ADS)
Baltz, Edward Anthony
It is well known that most of the mass in the universe remains unobserved save for its gravitational effect on luminous matter. The nature of this ``dark matter'' remains a mystery. From measurements of the primordial deuterium abundance, the theory of big bang nucleosynthesis predicts that there are not enough baryons to account for the amount of dark matter observed, thus the missing mass must take an exotic form. Several promising candidates have been proposed. In this work I will describe my research along two main lines of inquiry into the dark matter puzzle. The first possibility is that the dark matter is exotic massive particles, such as those predicted by supersymmetric extensions to the standard model of particle physics. Such particles are generically called WIMPs, for weakly interacting massive particles. Focusing on the so-called neutralino in supersymmetric models, I discuss the possible signatures of such particles, including their direct detection via nuclear recoil experiments and their indirect detection via annihilations in the halos of galaxies, producing high energy antiprotons, positrons and gamma rays. I also discuss signatures of the possible slow decays of such particles. The second possibility is that there is a population of black holes formed in the early universe. Any dark objects in galactic halos, black holes included, are called MACHOs, for massive compact halo objects. Such objects can be detected by their gravitational microlensing effects. Several possibilities for sources of baryonic dark matter are also interesting for gravitational microlensing. These include brown dwarf stars and old, cool white dwarf stars. I discuss the theory of gravitational microlensing, focusing on the technique of pixel microlensing. I make predictions for several planned microlensing experiments with ground based and space based telescopes. Furthermore, I discuss binary lenses in the context of pixel microlensing. Finally, I develop a new technique for
Multisensors signature prediction workbench
NASA Astrophysics Data System (ADS)
Latger, Jean; Cathala, Thierry
2015-10-01
Guidance of weapon systems relies on sensors to analyze targets signature. Defense weapon systems also need to detect then identify threats also using sensors. The sensors performance is very dependent on conditions e.g. time of day, atmospheric propagation, background ... Visible camera are very efficient for diurnal fine weather conditions, long wave infrared sensors for night vision, radar systems very efficient for seeing through atmosphere and/or foliage ... Besides, multi sensors systems, combining several collocated sensors with associated algorithms of fusion, provide better efficiency (typically for Enhanced Vision Systems). But these sophisticated systems are all the more difficult to conceive, assess and qualify. In that frame, multi sensors simulation is highly required. This paper focuses on multi sensors simulation tools. A first part makes a state of the Art of such simulation workbenches with a special focus on SE-Workbench. SEWorkbench is described with regards to infrared/EO sensors, millimeter waves sensors, active EO sensors and GNSS sensors. Then a general overview of simulation of targets and backgrounds signature objectives is presented, depending on the type of simulation required (parametric studies, open loop simulation, closed loop simulation, hybridization of SW simulation and HW ...). After the objective review, the paper presents some basic requirements for simulation implementation such as the deterministic behavior of simulation, mandatory to repeat it many times for parametric studies... Several technical topics are then discussed, such as the rendering technique (ray tracing vs. rasterization), the implementation (CPU vs. GP GPU) and the tradeoff between physical accuracy and performance of computation. Examples of results using SE-Workbench are showed and commented.
NASA Astrophysics Data System (ADS)
Wylezalek, D.; Zakamska, N.
2016-06-01
Feedback from active galactic nuclei (AGN) is widely considered to be the main driver in regulating the growth of massive galaxies. It operates by either heating or driving the gas that would otherwise be available for star formation out of the galaxy, preventing further increase in stellar mass. Observational proof for this scenario has, however, been hard to come by. We have assembled a large sample of 133 radio-quiet type-2 and red AGN at 0.1
Learning invariant face recognition from examples.
Müller, Marco K; Tremer, Michael; Bodenstein, Christian; Würtz, Rolf P
2013-05-01
Autonomous learning is demonstrated by living beings that learn visual invariances during their visual experience. Standard neural network models do not show this sort of learning. On the example of face recognition in different situations we propose a learning process that separates learning of the invariance proper from learning new instances of individuals. The invariance is learned by a set of examples called model, which contains instances of all situations. New instances are compared with these on the basis of rank lists, which allow generalization across situations. The result is also implemented as a spike-time-based neural network, which is shown to be robust against disturbances. The learning capability is demonstrated by recognition experiments on a set of standard face databases.
Blurred image recognition by legendre moment invariants
Zhang, Hui; Shu, Huazhong; Han, Guo-Niu; Coatrieux, Gouenou; Luo, Limin; Coatrieux, Jean-Louis
2010-01-01
Processing blurred images is a key problem in many image applications. Existing methods to obtain blur invariants which are invariant with respect to centrally symmetric blur are based on geometric moments or complex moments. In this paper, we propose a new method to construct a set of blur invariants using the orthogonal Legendre moments. Some important properties of Legendre moments for the blurred image are presented and proved. The performance of the proposed descriptors is evaluated with various point-spread functions and different image noises. The comparison of the present approach with previous methods in terms of pattern recognition accuracy is also provided. The experimental results show that the proposed descriptors are more robust to noise and have better discriminative power than the methods based on geometric or complex moments. PMID:19933003
Scale Invariant Gravity - a Simple Formulation
NASA Astrophysics Data System (ADS)
Wesson, P. S.
1981-09-01
Using the Cosmological Principle as justification, it is suggested that the scale-invariant theory of gravity be based on a Conspiracy Hypothesis (CH). The CH says: The matter parameters of a system (mass, density, pressure, etc.), the "constants" of physics and the coordinates occur together in dimensionless combinations (η-numbers) in which the components may vary but in such a manner that the variations conspire to keep the -numbers constant. This hypothesis yields a formulation of the scale-invariant theory that is simpler than other versions of it in which the Newtonian gravitational parameter G is treated as a field variable (Dirac, Hoyle/Narlikar, Canuto et al.). This simple formulation of scale-invariant gravity agrees with a recent reformulation of the (Perfect) Cosmological Principle. It also agrees with observations that have been made to date, and the equations suggest several new tests that can possibly be carried out.
Rotationally invariant correlation filtering for multiple images
Schils, G.F.; Sweeney, D.W.
1986-07-01
A method is presented for designing translation-invariant optical correlation filters that have a specified rotational response for each of several input images. The correlation filter is postulated to have the form of an infinite linear combination of the angular Fourier harmonics of the input images. The corresponding response of the optical system too rotations of the multiple input images is described by a vector-matrix convolution equation. The solution of this equation for the unknown correlation filter is presented in terms of Fourier series. Use of one term in the Fourier series gives the multiple circular-harmonic filter that provides a specified rotationally invariant response for each of the multiple input images. Applications to rotationally invariant discrimination are described, and examples are given.
Gauge-Invariant Formulation of Circular Dichroism.
Raimbault, Nathaniel; de Boeij, Paul L; Romaniello, Pina; Berger, J A
2016-07-12
Standard formulations of magnetic response properties, such as circular dichroism spectra, are plagued by gauge dependencies, which can lead to unphysical results. In this work, we present a general gauge-invariant and numerically efficient approach for the calculation of circular dichroism spectra from the current density. First we show that in this formulation the optical rotation tensor, the response function from which circular dichroism spectra can be obtained, is independent of the origin of the coordinate system. We then demonstrate that its trace is independent of the gauge origin of the vector potential. We also show how gauge invariance can be retained in practical calculations with finite basis sets. As an example, we explain how our method can be applied to time-dependent current-density-functional theory. Finally, we report gauge-invariant circular dichroism spectra obtained using the adiabatic local-density approximation. The circular dichroism spectra we thus obtain are in good agreement with experiment.
Renormalization group invariant of lepton Yukawa couplings
NASA Astrophysics Data System (ADS)
Tsuyuki, Takanao
2015-04-01
By using quark Yukawa matrices only, we can construct renormalization invariants that are exact at the one-loop level in the standard model. One of them, Iq, is accidentally consistent with unity, even though quark masses are strongly hierarchical. We calculate a lepton version of the invariant Il for Dirac and Majorana neutrino cases and find that Il can also be close to unity. For the Dirac neutrino and inverted hierarchy case, if the lightest neutrino mass is 3.0 meV to 8.8 meV, an equality Iq=Il can be satisfied. These invariants are not changed even if new particles couple to the standard model particles, as long as those couplings are generation independent.
Standard model with partial gauge invariance
NASA Astrophysics Data System (ADS)
Chkareuli, J. L.; Kepuladze, Z.
2012-03-01
We argue that an exact gauge invariance may disable some generic features of the Standard Model which could otherwise manifest themselves at high energies. One of them might be related to the spontaneous Lorentz invariance violation (SLIV), which could provide an alternative dynamical approach to QED and Yang-Mills theories with photon and non-Abelian gauge fields appearing as massless Nambu-Goldstone bosons. To see some key features of the new physics expected we propose partial rather than exact gauge invariance in an extended SM framework. This principle applied, in some minimal form, to the weak hypercharge gauge field B μ and its interactions, leads to SLIV with B field components appearing as the massless Nambu-Goldstone modes, and provides a number of distinctive Lorentz breaking effects. Being naturally suppressed at low energies they may become detectable in high energy physics and astrophysics. Some of the most interesting SLIV processes are considered in significant detail.
Lorentz invariance in chiral kinetic theory.
Chen, Jing-Yuan; Son, Dam T; Stephanov, Mikhail A; Yee, Ho-Ung; Yin, Yi
2014-10-31
We show that Lorentz invariance is realized nontrivially in the classical action of a massless spin-1/2 particle with definite helicity. We find that the ordinary Lorentz transformation is modified by a shift orthogonal to the boost vector and the particle momentum. The shift ensures angular momentum conservation in particle collisions and implies a nonlocality of the collision term in the Lorentz-invariant kinetic theory due to side jumps. We show that 2/3 of the chiral-vortical effect for a uniformly rotating particle distribution can be attributed to the magnetic moment coupling required by the Lorentz invariance. We also show how the classical action can be obtained by taking the classical limit of the path integral for a Weyl particle.
Feedback network with space invariant coupling.
Häusler, G; Lange, E
1990-11-10
Processing images by a neural network means performing a repeated sequence of operations on the images. The sequence consists of a general linear transformation and a nonlinear mapping of pixel intensities. The general (shift variant) linear transformation is time consuming for large images if done with a serial computer. A shift invariant linear transformation can be implemented much easier by fast Fourier transform or optically, but the shift invariant transform has fewer degrees of freedom because the coupling matrix is Toeplitz. We present a neural convolution network with shift invariant coupling that nevertheless exhibits autoassociative restoration of distorted images. Besides the simple implementation, the network has one more advantage: associative recall does not depend on object position.
Making texture descriptors invariant to blur.
Gadermayr, Michael; Uhl, Andreas
Besides a high distinctiveness, robustness (or invariance) to image degradations is very desirable for texture feature extraction methods in real-world applications. In this paper, focus is on making arbitrary texture descriptors invariant to blur which is often prevalent in real image data. From previous work, we know that most state-of-the-art texture feature extraction methods are unable to cope even with minor blur degradations if the classifier's training stage is based on idealistic data. However, if the training set suffers similarly from the degradations, the obtained accuracies are significantly higher. Exploiting that knowledge, in this approach the level of blur of each image is increased to a certain threshold, based on the estimation of a blur measure. Experiments with synthetically degraded data show that the method is able to generate a high degree of blur invariance without loosing too much distinctiveness. Finally, we show that our method is not limited to ideal Gaussian blur.
Scale-invariant fluctuations from Galilean genesis
Wang, Yi; Brandenberger, Robert E-mail: rhb@physics.mcgill.ca
2012-10-01
We study the spectrum of cosmological fluctuations in scenarios such as Galilean Genesis \\cite(Nicolis) in which a spectator scalar field acquires a scale-invariant spectrum of perturbations during an early phase which asymptotes in the far past to Minkowski space-time. In the case of minimal coupling to gravity and standard scalar field Lagrangian, the induced curvature fluctuations depend quadratically on the spectator field and are hence non-scale-invariant and highly non-Gaussian. We show that if higher dimensional operators (the same operators that lead to the η-problem for inflation) are considered, a linear coupling between background and spectator field fluctuations is induced which leads to scale-invariant and Gaussian curvature fluctuations.
The Grassmannian origin of dual superconformal invariance
NASA Astrophysics Data System (ADS)
Arkani-Hamed, Nima; Cachazo, Freddy; Cheung, Clifford
2010-03-01
A dual formulation of the S Matrix for mathcal {N} = 4 SYM has recently been presented, where all leading singularities of n-particle N k-2MHV amplitudes are given as an integral over the Grassmannian G( k, n), with cyclic symmetry, parity and superconformal invariance manifest. In this short note we show that the dual superconformal invariance of this object is also manifest. The geometry naturally suggests a partial integration and simple change of variable to an integral over G( k - 2, n). This change of variable precisely corresponds to the mapping between usual momentum variables and the “momentum twistors” introduced by Hodges, and yields an elementary derivation of the momentumtwistor space formula very recently presented by Mason and Skinner, which is manifestly dual superconformal invariant. Thus the G( k, n) Grassmannian formulation allows a direct understanding of all the important symmetries of mathcal {N} = 4 SYM scattering amplitudes.
Cell short circuit, preshort signature
NASA Technical Reports Server (NTRS)
Lurie, C.
1980-01-01
Short-circuit events observed in ground test simulations of DSCS-3 battery in-orbit operations are analyzed. Voltage signatures appearing in the data preceding the short-circuit event are evaluated. The ground test simulation is briefly described along with performance during reconditioning discharges. Results suggest that a characteristic signature develops prior to a shorting event.
Index of Spectrum Signature Data
1985-05-01
Frederick Research Corporation. Alexandria. VA 163 AN/APG-030 Radar Receiver Heasureaents Electromagnetic Coapatibilitv Analysis Center, US Navv Marine ... Electromagnetic Compatibility Characteristics of the W 86 Gun Fire Control Svstem. Naval HEapons Lab, Dahlgren, VA 501 Partial Spectrum Signature...ECAC-I-IO-(SS) DEPARTMENT OF DEFENSE Electromagnetic Compatibility Analysis Center Annapolis, Maryland 21402 INDEX OF SPECTRUM SIGNATURE DATA
Deformations of superconformal theories
NASA Astrophysics Data System (ADS)
Córdova, Clay; Dumitrescu, Thomas T.; Intriligator, Kenneth
2016-11-01
We classify possible supersymmetry-preserving relevant, marginal, and irrelevant deformations of unitary superconformal theories in d ≥ 3 dimensions. Our method only relies on symmetries and unitarity. Hence, the results are model independent and do not require a Lagrangian description. Two unifying themes emerge: first, many theories admit deformations that reside in multiplets together with conserved currents. Such deformations can lead to modifications of the supersymmetry algebra by central and non-central charges. Second, many theories with a sufficient amount of supersymmetry do not admit relevant or marginal deformations, and some admit neither. The classification is complicated by the fact that short superconformal multiplets display a rich variety of sporadic phenomena, including supersymmetric deformations that reside in the middle of a multiplet. We illustrate our results with examples in diverse dimensions. In particular, we explain how the classification of irrelevant supersymmetric deformations can be used to derive known and new constraints on moduli-space effective actions.
Deformations of superconformal theories
Córdova, Clay; Dumitrescu, Thomas T.; Intriligator, Kenneth
2016-11-22
Here, we classify possible supersymmetry-preserving relevant, marginal, and irrelevant deformations of unitary superconformal theories in d ≥ 3 dimensions. Our method only relies on symmetries and unitarity. Hence, the results are model independent and do not require a Lagrangian description. Two unifying themes emerge: first, many theories admit deformations that reside in multiplets together with conserved currents. Such deformations can lead to modifications of the supersymmetry algebra by central and noncentral charges. Second, many theories with a sufficient amount of supersymmetry do not admit relevant or marginal deformations, and some admit neither. The classification is complicated by the fact that short superconformal multiplets display a rich variety of sporadic phenomena, including supersymmetric deformations that reside in the middle of a multiplet. We illustrate our results with examples in diverse dimensions. In particular, we explain how the classification of irrelevant supersymmetric deformations can be used to derive known and new constraints on moduli-space effective actions.
Totonchi, Ali; Guyuron, Bahman
2016-01-01
The alar rim plays an important role in nasal harmony. Alar rim flaws are common following the initial rhinoplasty. Classification of the deformities helps with diagnosis and successful surgical correction. Diagnosis of the deformity requires careful observation of the computerized or life-sized photographs. Techniques for treatment of these deformities can easily be learned with attention to detail. Copyright © 2016 Elsevier Inc. All rights reserved.
Weak associativity and deformation quantization
NASA Astrophysics Data System (ADS)
Kupriyanov, V. G.
2016-09-01
Non-commutativity and non-associativity are quite natural in string theory. For open strings it appears due to the presence of non-vanishing background two-form in the world volume of Dirichlet brane, while in closed string theory the flux compactifications with non-vanishing three-form also lead to non-geometric backgrounds. In this paper, working in the framework of deformation quantization, we study the violation of associativity imposing the condition that the associator of three elements should vanish whenever each two of them are equal. The corresponding star products are called alternative and satisfy important for physical applications properties like the Moufang identities, alternative identities, Artin's theorem, etc. The condition of alternativity is invariant under the gauge transformations, just like it happens in the associative case. The price to pay is the restriction on the non-associative algebra which can be represented by the alternative star product, it should satisfy the Malcev identity. The example of nontrivial Malcev algebra is the algebra of imaginary octonions. For this case we construct an explicit expression of the non-associative and alternative star product. We also discuss the quantization of Malcev-Poisson algebras of general form, study its properties and provide the lower order expression for the alternative star product. To conclude we define the integration on the algebra of the alternative star products and show that the integrated associator vanishes.
Approaching Moons from Resonance via Invariant Manifolds
NASA Technical Reports Server (NTRS)
Anderson, Rodney L.
2012-01-01
In this work, the approach phase from the final resonance of the endgame scenario in a tour design is examined within the context of invariant manifolds. Previous analyses have typically solved this problem either by using numerical techniques or by computing a catalog of suitable trajectories. The invariant manifolds of a selected set of libration orbits and unstable resonant orbits are computed here to serve as guides for desirable approach trajectories. The analysis focuses on designing an approach phase that may be tied into the final resonance in the endgame sequence while also targeting desired conditions at the moon.
Galilean invariant resummation schemes of cosmological perturbations
NASA Astrophysics Data System (ADS)
Peloso, Marco; Pietroni, Massimo
2017-01-01
Many of the methods proposed so far to go beyond Standard Perturbation Theory break invariance under time-dependent boosts (denoted here as extended Galilean Invariance, or GI). This gives rise to spurious large scale effects which spoil the small scale predictions of these approximation schemes. By using consistency relations we derive fully non-perturbative constraints that GI imposes on correlation functions. We then introduce a method to quantify the amount of GI breaking of a given scheme, and to correct it by properly tailored counterterms. Finally, we formulate resummation schemes which are manifestly GI, discuss their general features, and implement them in the so called Time-Flow, or TRG, equations.
Some cosmological consequences of Weyl invariance
Alvarez, Enrique; González-Martín, Sergio; Herrero-Valea, Mario E-mail: sergio.gonzalez.martin@csic.es
2015-03-01
We examine some Weyl invariant cosmological models in the framework of generalized dilaton gravity, in which the action is made of a set of N conformally coupled scalar fields. It will be shown that when the FRW ansatz for the spacetime metric is assumed, the Ward identity for conformal invariance guarantees that the gravitational equations hold whenever the scalar fields EM do so. It follows that any scale factor can solve the theory provided a non-trivial profile for a dilaton field. In particular, accelerated expansion is a natural solution to the full set of equations.
Cosmological constant in scale-invariant theories
Foot, Robert; Kobakhidze, Archil; Volkas, Raymond R.
2011-10-01
The incorporation of a small cosmological constant within radiatively broken scale-invariant models is discussed. We show that phenomenologically consistent scale-invariant models can be constructed which allow a small positive cosmological constant, providing certain relation between the particle masses is satisfied. As a result, the mass of the dilaton is generated at two-loop level. Another interesting consequence is that the electroweak symmetry-breaking vacuum in such models is necessarily a metastable ''false'' vacuum which, fortunately, is not expected to decay on cosmological time scales.
On adiabatic invariant in generalized Galileon theories
Ema, Yohei; Jinno, Ryusuke; Nakayama, Kazunori; Mukaida, Kyohei E-mail: jinno@hep-th.phys.s.u-tokyo.ac.jp E-mail: kazunori@hep-th.phys.s.u-tokyo.ac.jp
2015-10-01
We consider background dynamics of generalized Galileon theories in the context of inflation, where gravity and inflaton are non-minimally coupled to each other. In the inflaton oscillation regime, the Hubble parameter and energy density oscillate violently in many cases, in contrast to the Einstein gravity with minimally coupled inflaton. However, we find that there is an adiabatic invariant in the inflaton oscillation regime in any generalized Galileon theory. This adiabatic invariant is useful in estimating the expansion law of the universe and also the particle production rate due to the oscillation of the Hubble parameter.
Two Invariants of Human-Swarm Interaction
2017-08-15
persisitence, fan-out 1. Introduction In the first sentence of his great paper Invariants of Human Behavior, Herbert Simon wrote, “The fundamental goal of...as general nor as ”invariant” as these classical laws” ( Simon , 1990)[page 1]. In other words, science is built on invariants, concepts or properties...direction of travel to the desired heading. In a follow-on paper, we conducted a user study in which we allowed humans to control flocks of Couzin-like
Symmetric form-invariant dual Pearcey beams.
Ren, Zhijun; Fan, Changjiang; Shi, Yile; Chen, Bo
2016-08-01
We introduce another type of Pearcey beam, namely, dual Pearcey (DP) beams, based on the Pearcey function of catastrophe theory. DP beams are experimentally generated by applying Fresnel diffraction of bright elliptic rings. Form-invariant Bessel distribution beams can be regarded as a special case of DP beams. Subsequently, the basic propagation characteristics of DP beams are identified. DP beams are the result of the interference of two half DP beams instead of two classical Pearcey beams. Moreover, we also verified that half DP beams (including special-case parabolic-like beams) generated by half elliptical rings (circular rings) are a new member of the family of form-invariant beams.
Affine Invariant Character Recognition by Progressive Removing
NASA Astrophysics Data System (ADS)
Iwamura, Masakazu; Horimatsu, Akira; Niwa, Ryo; Kise, Koichi; Uchida, Seiichi; Omachi, Shinichiro
Recognizing characters in scene images suffering from perspective distortion is a challenge. Although there are some methods to overcome this difficulty, they are time-consuming. In this paper, we propose a set of affine invariant features and a new recognition scheme called “progressive removing” that can help reduce the processing time. Progressive removing gradually removes less feasible categories and skew angles by using multiple classifiers. We observed that progressive removing and the use of the affine invariant features reduced the processing time by about 60% in comparison to a trivial one without decreasing the recognition rate.
An invariance theorem in acoustic scattering theory
NASA Astrophysics Data System (ADS)
Ha-Duong, T.
1996-10-01
Karp's theorem states that if the far-field pattern corresponding to the scattering of a time-harmonic acoustic plane wave by a sound-soft obstacle is invariant under the group of orthogonal transformations in 0266-5611/12/5/007/img1 (rotations in 0266-5611/12/5/007/img2), then the scatterer is a sphere (circle). The theorem is generalized to the case where the invariant group of the far field pattern is only a subgroup of the orthogonal group, and for a class of mixed boundary conditions.
Invariant measures on multimode quantum Gaussian states
Lupo, C.; Mancini, S.; De Pasquale, A.; Facchi, P.; Florio, G.; Pascazio, S.
2012-12-15
We derive the invariant measure on the manifold of multimode quantum Gaussian states, induced by the Haar measure on the group of Gaussian unitary transformations. To this end, by introducing a bipartition of the system in two disjoint subsystems, we use a parameterization highlighting the role of nonlocal degrees of freedom-the symplectic eigenvalues-which characterize quantum entanglement across the given bipartition. A finite measure is then obtained by imposing a physically motivated energy constraint. By averaging over the local degrees of freedom we finally derive the invariant distribution of the symplectic eigenvalues in some cases of particular interest for applications in quantum optics and quantum information.
On black hole spectroscopy via adiabatic invariance
NASA Astrophysics Data System (ADS)
Jiang, Qing-Quan; Han, Yan
2012-12-01
In this Letter, we obtain the black hole spectroscopy by combining the black hole property of adiabaticity and the oscillating velocity of the black hole horizon. This velocity is obtained in the tunneling framework. In particular, we declare, if requiring canonical invariance, the adiabatic invariant quantity should be of the covariant form Iadia = ∮pi dqi. Using it, the horizon area of a Schwarzschild black hole is quantized independently of the choice of coordinates, with an equally spaced spectroscopy always given by ΔA = 8 π lp2 in the Schwarzschild and Painlevé coordinates.
Invariant measures on multimode quantum Gaussian states
NASA Astrophysics Data System (ADS)
Lupo, C.; Mancini, S.; De Pasquale, A.; Facchi, P.; Florio, G.; Pascazio, S.
2012-12-01
We derive the invariant measure on the manifold of multimode quantum Gaussian states, induced by the Haar measure on the group of Gaussian unitary transformations. To this end, by introducing a bipartition of the system in two disjoint subsystems, we use a parameterization highlighting the role of nonlocal degrees of freedom—the symplectic eigenvalues—which characterize quantum entanglement across the given bipartition. A finite measure is then obtained by imposing a physically motivated energy constraint. By averaging over the local degrees of freedom we finally derive the invariant distribution of the symplectic eigenvalues in some cases of particular interest for applications in quantum optics and quantum information.
Temperature invariant energy value in LED spectra
NASA Astrophysics Data System (ADS)
Baumgartner, Hans; Vaskuri, Anna; Kärhä, Petri; Ikonen, Erkki
2016-12-01
Relative emission spectra of light-emitting diodes (LEDs) depend on the junction temperature. The high-energy region of the emission spectrum can be modelled with Maxwell-Boltzmann distribution as a function of energy and junction temperature. We show that according to the model and our experiments, the normalized emission spectra at different junction temperatures intersect at a unique energy value. The invariant intersection energy exists for many types of LEDs and can be used to determine the alloy composition of the material. Furthermore, the wavelength determined by the intersection energy can be used as a temperature invariant wavelength reference in spectral measurements.
Some cosmological consequences of Weyl invariance
Alvarez, Enrique; González-Martín, Sergio; Herrero-Valea, Mario
2015-03-19
We examine some Weyl invariant cosmological models in the framework of generalized dilaton gravity, in which the action is made of a set of N conformally coupled scalar fields. It will be shown that when the FRW ansatz for the spacetime metric is assumed, the Ward identity for conformal invariance guarantees that the gravitational equations hold whenever the scalar fields EM do so. It follows that any scale factor can solve the theory provided a non-trivial profile for a dilaton field. In particular, accelerated expansion is a natural solution to the full set of equations.
Approaching Moons from Resonance via Invariant Manifolds
NASA Technical Reports Server (NTRS)
Anderson, Rodney L.
2012-01-01
In this work, the approach phase from the final resonance of the endgame scenario in a tour design is examined within the context of invariant manifolds. Previous analyses have typically solved this problem either by using numerical techniques or by computing a catalog of suitable trajectories. The invariant manifolds of a selected set of libration orbits and unstable resonant orbits are computed here to serve as guides for desirable approach trajectories. The analysis focuses on designing an approach phase that may be tied into the final resonance in the endgame sequence while also targeting desired conditions at the moon.
Tracking visual objects using pyramidal rotation invariant features
NASA Astrophysics Data System (ADS)
Paheding, Sidike; Essa, Almabrok; Krieger, Evan; Asari, Vijayan
2016-02-01
Challenges in object tracking such as object deformation, occlusion, and background variations require a robust tracker to ensure accurate object location estimation. To address these issues, we present a Pyramidal Rotation Invariant Features (PRIF) that integrates Gaussian Ringlet Intensity Distribution (GRID) and Fourier Magnitude of Histogram of Oriented Gradients (FMHOG) methods for tracking objects from videos in challenging environments. In this model, we initially partition a reference object region into increasingly fine rectangular grid regions to construct a pyramid. Histograms of local features are then extracted for each level of pyramid. This allows the appearance of a local patch to be captured at multiple levels of detail to make the algorithm insensitive to partial occlusion. Then GRID and magnitude of discrete Fourier transform of the oriented gradient are utilized to achieve a robust rotation invariant feature. The GRID feature creates a weighting scheme to emphasize the object center. In the tracking stage, a Kalman filter is employed to estimate the center of the object search regions in successive frames. Within the search regions, we use a sliding window technique to extract the PRIF of candidate objects, and then Earth Mover's Distance (EMD) is used to classify the best matched candidate features with respect to the reference. Our PRIF object tracking algorithm is tested on two challenging Wide Area Motion Imagery (WAMI) datasets, namely Columbus Large Image Format (CLIF) and Large Area Image Recorder (LAIR), to evaluate its robustness. Experimental results show that the proposed PRIF approach yields superior results compared to state-of-the-art feature based object trackers.
Invariant Discretization Schemes Using Evolution-Projection Techniques
NASA Astrophysics Data System (ADS)
Bihlo, Alexander; Nave, Jean-Christophe
2013-08-01
Finite difference discretization schemes preserving a subgroup of the maximal Lie invariance group of the one-dimensional linear heat equation are determined. These invariant schemes are constructed using the invariantization procedure for non-invariant schemes of the heat equation in computational coordinates. We propose a new methodology for handling moving discretization grids which are generally indispensable for invariant numerical schemes. The idea is to use the invariant grid equation, which determines the locations of the grid point at the next time level only for a single integration step and then to project the obtained solution to the regular grid using invariant interpolation schemes. This guarantees that the scheme is invariant and allows one to work on the simpler stationary grids. The discretization errors of the invariant schemes are established and their convergence rates are estimated. Numerical tests are carried out to shed some light on the numerical p! roperties of invariant discretization schemes using the proposed evolution-projection strategy.
Disambiguating seesaw models using invariant mass variables at hadron colliders
Dev, P. S. Bhupal; Kim, Doojin; Mohapatra, Rabindra N.
2016-01-19
Here, we propose ways to distinguish between different mechanisms behind the collider signals of TeV-scale seesaw models for neutrino masses using kinematic endpoints of invariant mass variables. We particularly focus on two classes of such models widely discussed in literature: (i) Standard Model extended by the addition of singlet neutrinos and (ii) Left-Right Symmetric Models. Relevant scenarios involving the same "smoking-gun" collider signature of dilepton plus dijet with no missing transverse energy differ from one another by their event topology, resulting in distinctive relationships among the kinematic endpoints to be used for discerning them at hadron colliders. Furthermore, these kinematic endpoints are readily translated to the mass parameters of the on-shell particles through simple analytic expressions which can be used for measuring the masses of the new particles. We also conducted a Monte Carlo simulation with detector effects in order to test the viability of the proposed strategy in a realistic environment. Finally, we discuss the future prospects of testing these scenarios at the $\\sqrt{s}$ = 14 and 100TeV hadron colliders.
Disambiguating seesaw models using invariant mass variables at hadron colliders
Dev, P. S. Bhupal; Kim, Doojin; Mohapatra, Rabindra N.
2016-01-19
Here, we propose ways to distinguish between different mechanisms behind the collider signals of TeV-scale seesaw models for neutrino masses using kinematic endpoints of invariant mass variables. We particularly focus on two classes of such models widely discussed in literature: (i) Standard Model extended by the addition of singlet neutrinos and (ii) Left-Right Symmetric Models. Relevant scenarios involving the same "smoking-gun" collider signature of dilepton plus dijet with no missing transverse energy differ from one another by their event topology, resulting in distinctive relationships among the kinematic endpoints to be used for discerning them at hadron colliders. Furthermore, these kinematic endpoints are readily translated to the mass parameters of the on-shell particles through simple analytic expressions which can be used for measuring the masses of the new particles. We also conducted a Monte Carlo simulation with detector effects in order to test the viability of the proposed strategy in a realistic environment. Finally, we discuss the future prospects of testing these scenarios at themore » $$\\sqrt{s}$$ = 14 and 100TeV hadron colliders.« less
Disambiguating seesaw models using invariant mass variables at hadron colliders
NASA Astrophysics Data System (ADS)
Dev, P. S. Bhupal; Kim, Doojin; Mohapatra, Rabindra N.
2016-01-01
We propose ways to distinguish between different mechanisms behind the collider signals of TeV-scale seesaw models for neutrino masses using kinematic endpoints of invariant mass variables. We particularly focus on two classes of such models widely discussed in literature: (i) Standard Model extended by the addition of singlet neutrinos and (ii) Left-Right Symmetric Models. Relevant scenarios involving the same "smoking-gun" collider signature of dilepton plus dijet with no missing transverse energy differ from one another by their event topology, resulting in distinctive relationships among the kinematic endpoints to be used for discerning them at hadron colliders. These kinematic endpoints are readily translated to the mass parameters of the on-shell particles through simple analytic expressions which can be used for measuring the masses of the new particles. A Monte Carlo simulation with detector effects is conducted to test the viability of the proposed strategy in a realistic environment. Finally, we discuss the future prospects of testing these scenarios at the √{s}=14 and 100 TeV hadron colliders.
Meng, Xianjing; Yin, Yilong; Yang, Gongping; Xi, Xiaoming
2013-01-01
Retinal identification based on retinal vasculatures in the retina provides the most secure and accurate means of authentication among biometrics and has primarily been used in combination with access control systems at high security facilities. Recently, there has been much interest in retina identification. As digital retina images always suffer from deformations, the Scale Invariant Feature Transform (SIFT), which is known for its distinctiveness and invariance for scale and rotation, has been introduced to retinal based identification. However, some shortcomings like the difficulty of feature extraction and mismatching exist in SIFT-based identification. To solve these problems, a novel preprocessing method based on the Improved Circular Gabor Transform (ICGF) is proposed. After further processing by the iterated spatial anisotropic smooth method, the number of uninformative SIFT keypoints is decreased dramatically. Tested on the VARIA and eight simulated retina databases combining rotation and scaling, the developed method presents promising results and shows robustness to rotations and scale changes. PMID:23873409
Conformal invariance and new exact solutions of the elastostatics equations
NASA Astrophysics Data System (ADS)
Chirkunov, Yu. A.
2017-03-01
We fulfilled a group foliation of the system of n-dimensional (n ≥ 2) Lame equations of the classical static theory of elasticity with respect to the infinite subgroup contained in normal subgroup of main group of this system. It permitted us to move from the Lame equations to the equivalent unification of two first-order systems: automorphic and resolving. We obtained a general solution of the automorphic system. This solution is an n-dimensional analogue of the Kolosov-Muskhelishvili formula. We found the main Lie group of transformations of the resolving system of this group foliation. It turned out that in the two-dimensional and three-dimensional cases, which have a physical meaning, this system is conformally invariant, while the Lame equations admit only a group of similarities of the Euclidean space. This is a big success, since in the method of group foliation, resolving equations usually inherit Lie symmetries subgroup of the full symmetry group that was not used for the foliation. In the three-dimensional case for the solutions of the resolving system, we found the general form of the transformations similar to the Kelvin transformation. These transformations are the consequence of the conformal invariance of the resolving system. In the three-dimensional case with a help of the complex dependent and independent variables, the resolving system is written as a simple complex system. This allowed us to find non-trivial exact solutions of the Lame equations, which direct for the Lame equations practically impossible to obtain. For this complex system, all the essentially distinct invariant solutions of the maximal rank we have found in explicit form, or we reduced the finding of those solutions to the solving of the classical one-dimensional equations of the mathematical physics: the heat equation, the telegraph equation, the Tricomi equation, the generalized Darboux equation, and other equations. For the resolving system, we obtained double wave of a
NASA Astrophysics Data System (ADS)
Ollongren, Alexander
2010-12-01
Suppose the international SETI effort yields the discovery of some signal of evidently non-natural origin. Could it contain linguistic information formulated in some kind of Lingua Cosmica? One way to get insight into this matter is to consider what specific (bio) linguistic signature( s) could be attached to a cosmic language for interstellar communication—designed by humans or an alien society having reached a level of intelligence (and technology) comparable to or surpassing ours. For this purpose, we consider in the present paper the logico-linguistic system LINCOS for ( A)CETI, developed during a number of years by the author in several papers and a monograph [1]. The system has a two-fold signature, which distinguishes it significantly from natural languages. In fact abstract and concrete signatures can be distinguished. That an abstract kind occurs is due to the manner in which abstractions of reality are represented in LINCOS-texts. They can take compound forms because the system is multi-expressive—partly due to the availability of inductive (recursive) entities. On the other hand, the concrete signature of LINCOS is related to the distribution of delimiters and predefined tokens in texts. Assigning measures to concrete signatures will be discussed elsewhere. The present contribution concentrates on the abstract signature of the language. At the same time, it is realized that an alien Lingua Cosmica might, but not necessarily needs to have this kind of signatures.
NASA Astrophysics Data System (ADS)
Sidike, Paheding; Aspiras, Theus; Asari, Vijayan K.; Alam, Mohammad S.
2014-04-01
A new rotation-invariant pattern recognition technique, based on spectral fringe-adjusted joint transform correlator (SFJTC) and histogram representation, is proposed. Synthetic discriminant function (SDF) based joint transform correlation (JTC) techniques have shown attractive performance in rotation-invariant pattern recognition applications. However, when the targets present in a complex scene, SDF-based JTC techniques may produce false detections due to inaccurate estimation of rotation angle of the object. Therefore, we herein propose an efficient rotation-invariant JTC scheme which does not require a priori rotation training of the reference image. In the proposed technique, a Vectorized Gaussian Ringlet Intensity Distribution (VGRID) descriptor is also proposed to obtain rotation-invariant features from the reference image. In this step, we divide the reference image into multiple Gaussian ringlets and extract histogram distribution of each ringlet, and then concatenate them into a vector as a target signature. Similarly, an unknown input scene is also represented by the VGRID which produces a multidimensional input image. Finally, the concept of the SFJTC is incorporated and utilized for target detection in the input scene. The classical SFJTC was proposed for detecting very small objects involving only few pixels in hyperspectral imagery. However, in our proposed algorithm, the SFJTC is applied for a two-dimensional image without limitation of the size of objects and most importantly it achieves rotation-invariant target discriminability. Simulation results verify that the proposed scheme performs satisfactorily in detecting targets in the input scene irrespective of rotation of the object.
Constitutive laws, tensorial invariance and chocolate cake
NASA Astrophysics Data System (ADS)
Rundle, John B.; Passman, S. L.
1982-04-01
Although constitutive modeling is a well-established branch of mathematics which has found wide industrial application, geophysicists often do not take full advantage of its known results. We present a synopsis of the theory of constitutive modeling, couched in terms of the ‘simple material’, which has been extensively studied and is complex enough to include most of the correct models proposed to describe the behavior of geological materials. Critical in the development of the theory are various invariance requirements, the principal ones being coordinate invariance, peer group invariance (isotropy), and frame-indifference. Each places distinet restrictions on constitutive equations. A noncomprehensive list of properly invariant and commonly used constitutive equations is given. To exemplify use of the equations, we consider two problems in detail: steady extension, which models the commonly performed constant strain rate triaxial test, and simple shearing. We note that each test is so restricted kinematically that only the most trivial aspects of material behavior are manifested in these tests, no matter how complex the material. Furthermore, the results of one test do not generally determine the results of the other.
Multipartite invariant states. II. Orthogonal symmetry
Chruscinski, Dariusz; Kossakowski, Andrzej
2006-06-15
We construct a class of multipartite states possessing orthogonal symmetry. This new class contains multipartite states which are invariant under the action of local unitary operations introduced in our preceding paper [Phys. Rev. A 73, 062314 (2006)]. We study basic properties of multipartite symmetric states: separability criteria and multi-PPT conditions.
Invariance Properties for General Diagnostic Classification Models
ERIC Educational Resources Information Center
Bradshaw, Laine P.; Madison, Matthew J.
2016-01-01
In item response theory (IRT), the invariance property states that item parameter estimates are independent of the examinee sample, and examinee ability estimates are independent of the test items. While this property has long been established and understood by the measurement community for IRT models, the same cannot be said for diagnostic…
Position, rotation, and intensity invariant recognizing method
Ochoa, E.; Schils, G.F.; Sweeney, D.W.
1987-09-15
A method for recognizing the presence of a particular target in a field of view which is target position, rotation, and intensity invariant includes the preparing of a target-specific invariant filter from a combination of all eigen-modes of a pattern of the particular target. Coherent radiation from the field of view is then imaged into an optical correlator in which the invariant filter is located. The invariant filter is rotated in the frequency plane of the optical correlator in order to produce a constant-amplitude rotational response in a correlation output plane when the particular target is present in the field of view. Any constant response is thus detected in the output plane to determine whether a particular target is present in the field of view. Preferably, a temporal pattern is imaged in the output plane with a optical detector having a plurality of pixels and a correlation coefficient for each pixel is determined by accumulating the intensity and intensity-square of each pixel. The orbiting of the constant response caused by the filter rotation is also preferably eliminated either by the use of two orthogonal mirrors pivoted correspondingly to the rotation of the filter or the attaching of a refracting wedge to the filter to remove the offset angle. Detection is preferably performed of the temporal pattern in the output plane at a plurality of different angles with angular separation sufficient to decorrelate successive frames. 1 fig.
Broken Scale Invariance and Anomalous Dimensions
DOE R&D Accomplishments Database
Wilson, K. G.
1970-05-01
Mack and Kastrup have proposed that broken scale invariance is a symmetry of strong interactions. There is evidence from the Thirring model and perturbation theory that the dimensions of fields defined by scale transformations will be changed by the interaction from their canonical values. We review these ideas and their consequences for strong interactions.
Scale invariant density perturbations from cyclic cosmology
NASA Astrophysics Data System (ADS)
Frampton, Paul Howard
2016-04-01
It is shown how quantum fluctuations of the radiation during the contraction era of a comes back empty (CBE) cyclic cosmology can provide density fluctuations which re-enter the horizon during the subsequent expansion era and at lowest order are scale invariant, in a Harrison-Zel’dovich-Peebles sense. It is necessary to be consistent with observations of large scale structure.
Scale Invariant Feature Transform Plus Hue Feature
NASA Astrophysics Data System (ADS)
Daneshvar, M. B.
2017-08-01
This paper presents an enhanced method for extracting invariant features from images based on Scale Invariant Feature Transform (SIFT). Although SIFT features are invariant to image scale and rotation, additive noise, and changes in illumination but we think this algorithm suffers from excess keypoints. Besides, by adding the hue feature, which is extracted from combination of hue and illumination values in HSI colour space version of the target image, the proposed algorithm can speed up the matching phase. Therefore, we proposed the Scale Invariant Feature Transform plus Hue (SIFTH) that can remove the excess keypoints based on their Euclidean distances and adding hue to feature vector to speed up the matching process which is the aim of feature extraction. In this paper we use the difference of hue features and the Mean Square Error (MSE) of orientation histograms to find the most similar keypoint to the under processing keypoint. The keypoint matching method can identify correct keypoint among clutter and occlusion robustly while achieving real-time performance and it will result a similarity factor of two keypoints. Moreover removing excess keypoint by SIFTH algorithm helps the matching algorithm to achieve this goal.
Boundary cue invariance in cortical orientation maps.
Zhan, Chang'an A; Baker, Curtis L
2006-06-01
We effortlessly perceive oriented boundaries defined by either luminance changes ('first-order' cues) or texture variations ('second-order' cues). Many neurons in mammalian visual cortex show orientation preference to both types of boundaries, but it is uncertain how they contribute to perceptual orientation cue-invariance at the neuronal population level. Using optical imaging in cat A 18, we observed highly similar orientation preference maps to first-order and a variety of second-order visual stimuli. Thus the neuronal representation of coarse-scale boundary orientation appears to be invariant to the characteristics (including local orientation) of the fine-scale textures by which those boundaries are defined. A common feature of second-order visual stimuli is that modulation shifts their Fourier energy for boundary orientation to the higher spatial frequencies of their constituent textures - our results suggest a common neural mechanism (demodulation) mediating visual processing of many kinds of texture boundary. The similarity between orientation maps to different stimuli implies that second-order responsive neurons are homogeneously distributed across the cortical surface. Such homogeneously cue-invariant orientation representation could provide a neural substrate for perceptual form-cue invariance, and reflect an optimal organization for encoding orientation information in natural scenes.
Understanding Parameter Invariance in Unidimensional IRT Models
ERIC Educational Resources Information Center
Rupp, Andre A.; Zumbo, Bruno D.
2006-01-01
One theoretical feature that makes item response theory (IRT) models those of choice for many psychometric data analysts is parameter invariance, the equality of item and examinee parameters from different examinee populations or measurement conditions. In this article, using the well-known fact that item and examinee parameters are identical only…
A Sim(2) invariant dimensional regularization
NASA Astrophysics Data System (ADS)
Alfaro, J.
2017-09-01
We introduce a Sim (2) invariant dimensional regularization of loop integrals. Then we can compute the one loop quantum corrections to the photon self energy, electron self energy and vertex in the Electrodynamics sector of the Very Special Relativity Standard Model (VSRSM).
Gauge-invariant hydrogen-atom Hamiltonian
Sun Weimin; Wang Fan; Chen Xiangsong; Lue Xiaofu
2010-07-15
For quantum mechanics of a charged particle in a classical external electromagnetic field, there is an apparent puzzle that the matrix element of the canonical momentum and Hamiltonian operators is gauge dependent. A resolution to this puzzle was recently provided by us [X.-S. Chen et al., Phys. Rev. Lett. 100, 232002 (2008)]. Based on the separation of the electromagnetic potential into pure-gauge and gauge-invariant parts, we have proposed a new set of momentum and Hamiltonian operators which satisfy both the requirement of gauge invariance and the relevant commutation relations. In this paper we report a check for the case of the hydrogen-atom problem: Starting from the Hamiltonian of the coupled electron, proton, and electromagnetic field, under the infinite proton mass approximation, we derive the gauge-invariant hydrogen-atom Hamiltonian and verify explicitly that this Hamiltonian is different from the Dirac Hamiltonian, which is the time translation generator of the system. The gauge-invariant Hamiltonian is the energy operator, whose eigenvalue is the energy of the hydrogen atom. It is generally time dependent. In this case, one can solve the energy eigenvalue equation at any specific instant of time. It is shown that the energy eigenvalues are gauge independent, and by suitably choosing the phase factor of the time-dependent eigenfunction, one can ensure that the time-dependent eigenfunction satisfies the Dirac equation.
Invariance Properties for General Diagnostic Classification Models
ERIC Educational Resources Information Center
Bradshaw, Laine P.; Madison, Matthew J.
2016-01-01
In item response theory (IRT), the invariance property states that item parameter estimates are independent of the examinee sample, and examinee ability estimates are independent of the test items. While this property has long been established and understood by the measurement community for IRT models, the same cannot be said for diagnostic…
A Discussion of Population Invariance of Equating
ERIC Educational Resources Information Center
Petersen, Nancy S.
2008-01-01
This article discusses the five studies included in this issue. Each article addressed the same topic, population invariance of equating. They all used data from major standardized testing programs, and they all used essentially the same statistics to evaluate their results, namely, the root mean square difference and root expected mean square…
Invariant of dynamical systems: A generalized entropy
Meson, A.M.; Vericat, F. |
1996-09-01
In this work the concept of entropy of a dynamical system, as given by Kolmogorov, is generalized in the sense of Tsallis. It is shown that this entropy is an isomorphism invariant, being complete for Bernoulli schemes. {copyright} {ital 1996 American Institute of Physics.}
Scale invariance, conformality, and generalized free fields
Dymarsky, Anatoly; Farnsworth, Kara; Komargodski, Zohar; ...
2016-02-16
This paper addresses the question of whether there are 4D Lorentz invariant unitary quantum fi eld theories with scale invariance but not conformal invariance. We present an important loophole in the arguments of Luty-Polchinski-Rattazzi and Dymarsky-Komargodski-Schwimmer-Theisen that is the trace of the energy-momentum tensor T could be a generalized free field. In this paper we rule out this possibility. The key ingredient is the observation that a unitary theory with scale but not conformal invariance necessarily has a non-vanishing anomaly for global scale transformations. We show that this anomaly cannot be reproduced if T is a generalized free field unlessmore » the theory also contains a dimension-2 scalar operator. In the special case where such an operator is present it can be used to redefine ("improve") the energy-momentum tensor, and we show that there is at least one energy-momentum tensor that is not a generalized free field. In addition, we emphasize that, in general, large momentum limits of correlation functions cannot be understood from the leading terms of the coordinate space OPE. This invalidates a recent argument by Farnsworth-Luty-Prilepina (FLP). Finally, despite the invalidity of the general argument of FLP, some of the techniques turn out to be useful in the present context.« less
Scale invariance, conformality, and generalized free fields
Dymarsky, Anatoly; Farnsworth, Kara; Komargodski, Zohar; Luty, Markus A.; Prilepina, Valentina
2016-02-16
This paper addresses the question of whether there are 4D Lorentz invariant unitary quantum fi eld theories with scale invariance but not conformal invariance. We present an important loophole in the arguments of Luty-Polchinski-Rattazzi and Dymarsky-Komargodski-Schwimmer-Theisen that is the trace of the energy-momentum tensor T could be a generalized free field. In this paper we rule out this possibility. The key ingredient is the observation that a unitary theory with scale but not conformal invariance necessarily has a non-vanishing anomaly for global scale transformations. We show that this anomaly cannot be reproduced if T is a generalized free field unless the theory also contains a dimension-2 scalar operator. In the special case where such an operator is present it can be used to redefine ("improve") the energy-momentum tensor, and we show that there is at least one energy-momentum tensor that is not a generalized free field. In addition, we emphasize that, in general, large momentum limits of correlation functions cannot be understood from the leading terms of the coordinate space OPE. This invalidates a recent argument by Farnsworth-Luty-Prilepina (FLP). Finally, despite the invalidity of the general argument of FLP, some of the techniques turn out to be useful in the present context.
Permutation centralizer algebras and multimatrix invariants
NASA Astrophysics Data System (ADS)
Mattioli, Paolo; Ramgoolam, Sanjaye
2016-03-01
We introduce a class of permutation centralizer algebras which underly the combinatorics of multimatrix gauge-invariant observables. One family of such noncommutative algebras is parametrized by two integers. Its Wedderburn-Artin decomposition explains the counting of restricted Schur operators, which were introduced in the physics literature to describe open strings attached to giant gravitons and were subsequently used to diagonalize the Gaussian inner product for gauge invariants of two-matrix models. The structure of the algebra, notably its dimension, its center and its maximally commuting subalgebra, is related to Littlewood-Richardson numbers for composing Young diagrams. It gives a precise characterization of the minimal set of charges needed to distinguish arbitrary matrix gauge invariants, which are related to enhanced symmetries in gauge theory. The algebra also gives a star product for matrix invariants. The center of the algebra allows efficient computation of a sector of multimatrix correlators. These generate the counting of a certain class of bicoloured ribbon graphs with arbitrary genus.
Volume-preserving maps with an invariant.
Gomez, A.; Meiss, J. D.
2002-06-01
Several families of volume-preserving maps on R(3) that have an integral are constructed using techniques due to Suris. We study the dynamics of these maps as the topology of the two-dimensional level sets of the invariant changes. (c) 2002 American Institute of Physics.
Invariant functionals in higher-spin theory
NASA Astrophysics Data System (ADS)
Vasiliev, M. A.
2017-03-01
A new construction for gauge invariant functionals in the nonlinear higher-spin theory is proposed. Being supported by differential forms closed by virtue of the higher-spin equations, invariant functionals are associated with central elements of the higher-spin algebra. In the on-shell AdS4 higher-spin theory we identify a four-form conjectured to represent the generating functional for 3d boundary correlators and a two-form argued to support charges for black hole solutions. Two actions for 3d boundary conformal higher-spin theory are associated with the two parity-invariant higher-spin models in AdS4. The peculiarity of the spinorial formulation of the on-shell AdS3 higher-spin theory, where the invariant functional is supported by a two-form, is conjectured to be related to the holomorphic factorization at the boundary. The nonlinear part of the star-product function F* (B (x)) in the higher-spin equations is argued to lead to divergencies in the boundary limit representing singularities at coinciding boundary space-time points of the factors of B (x), which can be regularized by the point splitting. An interpretation of the RG flow in terms of proposed construction is briefly discussed.
NASA Astrophysics Data System (ADS)
Wylezalek, Dominika; Zakamska, Nadia L.; MaNGA-GMOS Team
2017-01-01
Feedback from actively accreting SMBHs (Active Galactic Nuclei, AGN) is now widely considered to be the main driver in regulating the growth of massive galaxies. Observational proof for this scenario has, however, been hard to come by. Many attempts at finding a conclusive observational proof that AGN may be able to quench star formation and regulate the host galaxies' growth have shown that this problem is highly complex.I will present results from several projects that focus on understanding the power, reach and impact of feedback processes exerted by AGN. I will describe recent efforts in our group of relating feedback signatures to the specific star formation rate in their host galaxies, where our results are consistent with the AGN having a `negative' impact through feedback on the galaxies' star formation history (Wylezalek+2016a,b). Furthermore, I will show that powerful AGN-driven winds can be easily hidden and not be apparent in the integrated spectrum of the galaxy. This implies that large IFU surveys, such as the SDSS-IV MaNGA survey, might uncover many previously unknown AGN and outflows that are potentially very relevant for understanding the role of AGN in galaxy evolution (Wylezalek+2016c)!
Statistical clumped isotope signatures
Röckmann, T.; Popa, M. E.; Krol, M. C.; Hofmann, M. E. G.
2016-01-01
High precision measurements of molecules containing more than one heavy isotope may provide novel constraints on element cycles in nature. These so-called clumped isotope signatures are reported relative to the random (stochastic) distribution of heavy isotopes over all available isotopocules of a molecule, which is the conventional reference. When multiple indistinguishable atoms of the same element are present in a molecule, this reference is calculated from the bulk (≈average) isotopic composition of the involved atoms. We show here that this referencing convention leads to apparent negative clumped isotope anomalies (anti-clumping) when the indistinguishable atoms originate from isotopically different populations. Such statistical clumped isotope anomalies must occur in any system where two or more indistinguishable atoms of the same element, but with different isotopic composition, combine in a molecule. The size of the anti-clumping signal is closely related to the difference of the initial isotope ratios of the indistinguishable atoms that have combined. Therefore, a measured statistical clumped isotope anomaly, relative to an expected (e.g. thermodynamical) clumped isotope composition, may allow assessment of the heterogeneity of the isotopic pools of atoms that are the substrate for formation of molecules. PMID:27535168
Statistical clumped isotope signatures
NASA Astrophysics Data System (ADS)
Röckmann, Thomas; Popa, Maria Elena; Krol, Maarten; Hofmann, Magdalena
2016-04-01
High precision measurements of molecules containing more than one heavy isotope in environmental samples are becoming available with new instrumentation and may provide novel constraints on element cycles in nature. These so-called clumped isotope signatures are reported relative to the random (stochastic) distribution of heavy isotopes over all available isotopocules of a molecule, which is the conventional reference. When multiple indistinguishable atoms of the same element are present in a molecule, this reference is calculated from the bulk isotopic composition of the molecule, which for rare heavy isotopes is approximated by the arithmetic average of the isotope ratios of single substituted atoms. We show here that this referencing convention leads to apparent negative clumped isotope anomalies when the indistinguishable atoms are from isotopically different populations. Such statistical clumped isotope anomalies must occur in any system where two or more indistinguishable atoms of the same element, but with different isotopic composition, combine in a molecule and these anomalies have to be taken into account in data interpretation. The size of the signal is closely related to the relative standard deviation of the initial isotope ratios of the indistinguishable atoms that have combined. Therefore, a measured statistical clumped isotope anomaly may allow assessment of the heterogeneity of the isotopic pools of atoms that are the substrate for formation of molecules.
Statistical clumped isotope signatures
NASA Astrophysics Data System (ADS)
Röckmann, T.; Popa, M. E.; Krol, M. C.; Hofmann, M. E. G.
2016-08-01
High precision measurements of molecules containing more than one heavy isotope may provide novel constraints on element cycles in nature. These so-called clumped isotope signatures are reported relative to the random (stochastic) distribution of heavy isotopes over all available isotopocules of a molecule, which is the conventional reference. When multiple indistinguishable atoms of the same element are present in a molecule, this reference is calculated from the bulk (≈average) isotopic composition of the involved atoms. We show here that this referencing convention leads to apparent negative clumped isotope anomalies (anti-clumping) when the indistinguishable atoms originate from isotopically different populations. Such statistical clumped isotope anomalies must occur in any system where two or more indistinguishable atoms of the same element, but with different isotopic composition, combine in a molecule. The size of the anti-clumping signal is closely related to the difference of the initial isotope ratios of the indistinguishable atoms that have combined. Therefore, a measured statistical clumped isotope anomaly, relative to an expected (e.g. thermodynamical) clumped isotope composition, may allow assessment of the heterogeneity of the isotopic pools of atoms that are the substrate for formation of molecules.
Resurgent deformation quantisation
Garay, Mauricio; Goursac, Axel de; Straten, Duco van
2014-03-15
We construct a version of the complex Heisenberg algebra based on the idea of endless analytic continuation. The algebra would be large enough to capture quantum effects that escape ordinary formal deformation quantisation. -- Highlights: •We construct resurgent deformation quantisation. •We give integral formulæ. •We compute examples which show that hypergeometric functions appear naturally in quantum computations.
Three dimensional quantum geometry and deformed symmetry
NASA Astrophysics Data System (ADS)
Joung, E.; Mourad, J.; Noui, K.
2009-05-01
We study a three dimensional noncommutative space emerging in the context of three dimensional Euclidean quantum gravity. Our starting point is the assumption that the isometry group is deformed to the Drinfeld double D(SU(2)). We generalize to the deformed case the construction of E3 as the quotient of its isometry group ISU(2) by SU(2). We show that the algebra of functions on E3 becomes the noncommutative algebra of SU(2) distributions, C(SU(2))∗, endowed with the convolution product. This construction gives the action of ISU(2) on the algebra and allows the determination of plane waves and coordinate functions. In particular, we show the following: (i) plane waves have bounded momenta; (ii) to a given momentum are associated several SU(2) elements leading to an effective description of ϕ ɛC(SU(2))∗ in terms of several physical scalar fields on E3; (iii) their product leads to a deformed addition rule of momenta consistent with the bound on the spectrum. We generalize to the noncommutative setting the "local" action for a scalar field. Finally, we obtain, using harmonic analysis, another useful description of the algebra as the direct sum of the algebra of matrices. The algebra of matrices inherits the action of ISU(2): rotations leave the order of the matrices invariant, whereas translations change the order in a way we explicitly determine.
Dimensional analysis using toric ideals: primitive invariants.
Atherton, Mark A; Bates, Ronald A; Wynn, Henry P
2014-01-01
Classical dimensional analysis in its original form starts by expressing the units for derived quantities, such as force, in terms of power products of basic units [Formula: see text] etc. This suggests the use of toric ideal theory from algebraic geometry. Within this the Graver basis provides a unique primitive basis in a well-defined sense, which typically has more terms than the standard Buckingham approach. Some textbook examples are revisited and the full set of primitive invariants found. First, a worked example based on convection is introduced to recall the Buckingham method, but using computer algebra to obtain an integer [Formula: see text] matrix from the initial integer [Formula: see text] matrix holding the exponents for the derived quantities. The [Formula: see text] matrix defines the dimensionless variables. But, rather than this integer linear algebra approach it is shown how, by staying with the power product representation, the full set of invariants (dimensionless groups) is obtained directly from the toric ideal defined by [Formula: see text]. One candidate for the set of invariants is a simple basis of the toric ideal. This, although larger than the rank of [Formula: see text], is typically not unique. However, the alternative Graver basis is unique and defines a maximal set of invariants, which are primitive in a simple sense. In addition to the running example four examples are taken from: a windmill, convection, electrodynamics and the hydrogen atom. The method reveals some named invariants. A selection of computer algebra packages is used to show the considerable ease with which both a simple basis and a Graver basis can be found.
Deformation mechanisms in experimentally deformed Boom Clay
NASA Astrophysics Data System (ADS)
Desbois, Guillaume; Schuck, Bernhard; Urai, Janos
2016-04-01
Bulk mechanical and transport properties of reference claystones for deep disposal of radioactive waste have been investigated since many years but little is known about microscale deformation mechanisms because accessing the relevant microstructure in these soft, very fine-grained, low permeable and low porous materials remains difficult. Recent development of ion beam polishing methods to prepare high quality damage free surfaces for scanning electron microscope (SEM) is opening new fields of microstructural investigation in claystones towards a better understanding of the deformation behavior transitional between rocks and soils. We present results of Boom Clay deformed in a triaxial cell in a consolidated - undrained test at a confining pressure of 0.375 MPa (i.e. close to natural value), with σ1 perpendicular to the bedding. Experiments stopped at 20 % strain. As a first approximation, the plasticity of the sample can be described by a Mohr-Coulomb type failure envelope with a coefficient of cohesion C = 0.117 MPa and an internal friction angle ϕ = 18.7°. After deformation test, the bulk sample shows a shear zone at an angle of about 35° from the vertical with an offset of about 5 mm. We used the "Lamipeel" method that allows producing a permanent absolutely plane and large size etched micro relief-replica in order to localize and to document the shear zone at the scale of the deformed core. High-resolution imaging of microstructures was mostly done by using the BIB-SEM method on key-regions identified after the "Lamipeel" method. Detailed BIB-SEM investigations of shear zones show the following: the boundaries between the shear zone and the host rock are sharp, clay aggregates and clastic grains are strongly reoriented parallel to the shear direction, and the porosity is significantly reduced in the shear zone and the grain size is smaller in the shear zone than in the host rock but there is no evidence for broken grains. Comparison of microstructures
An Invariant-Preserving ALE Method for Solids under Extreme Conditions
Sambasivan, Shiv Kumar; Christon, Mark A
2012-07-17
We are proposing a fundamentally new approach to ALE methods for solids undergoing large deformation due to extreme loading conditions. Our approach is based on a physically-motivated and mathematically rigorous construction of the underlying Lagrangian method, vector/tensor reconstruction, remapping, and interface reconstruction. It is transformational because it deviates dramatically from traditionally accepted ALE methods and provides the following set of unique attributes: (1) a three-dimensional, finite volume, cell-centered ALE framework with advanced hypo-/hyper-elasto-plastic constitutive theories for solids; (2) a new physically and mathematically consistent reconstruction method for vector/tensor fields; (3) advanced invariant-preserving remapping algorithm for vector/tensor quantities; (4) moment-of-fluid (MoF) interface reconstruction technique for multi-material problems with solids undergoing large deformations. This work brings together many new concepts, that in combination with emergent cell-centered Lagrangian hydrodynamics methods will produce a cutting-edge ALE capability and define a new state-of-the-art. Many ideas in this work are new, completely unexplored, and hence high risk. The proposed research and the resulting algorithms will be of immediate use in Eulerian, Lagrangian and ALE codes under the ASC program at the lab. In addition, the research on invariant preserving reconstruction/remap of tensor quantities is of direct interest to ongoing CASL and climate modeling efforts at LANL. The application space impacted by this work includes Inertial Confinement Fusion (ICF), Z-pinch, munition-target interactions, geological impact dynamics, shock processing of powders and shaped charges. The ALE framework will also provide a suitable test-bed for rapid development and assessment of hypo-/hyper-elasto-plastic constitutive theories. Today, there are no invariant-preserving ALE algorithms for treating solids with large deformations. Therefore
''Electron Conic'' Signatures observed in the nightside auroral zone and over the polar cap
Menietti, J.D.; Burch, J.L.
1985-06-01
A preliminary search of the Dynamics Explorer 1 high-altitude plasma instrument data base has yielded examples of ''electron conic'' signatures. The three example passes show an association with regions of downward electron acceleration and upward ion beams, but this is not true of all the electron conic events. The electron conic signatures are clearly discernible on energy-flux-versus-time color spectrograms as pairs of discrete vertical bands which are symmetric about a pitch angle of approximately 180/sup 0/. One of the examples is a polar cap pass with electron conic signatures observed at invariant latitudes from 84/sup 0/ to 75/sup 0/. The other two cases are nightside auroral zone passes in which the regions of detectable electron conics are spatially more confined, covering only about 1/sup 0/ in invariant latitude. The conic signatures have been found at energies that range from 50 eV
General coordinate invariance and conformal invariance in nonrelativistic physics: Unitary Fermi gas
Son, D.T.; Wingate, M. . E-mail: wingate@phys.washington.edu
2006-01-15
We show that the Lagrangian for interacting nonrelativistic particles can be coupled to an external gauge field and metric tensor in a way that exhibits a nonrelativistic version of general coordinate invariance. We explore the consequences of this invariance on the example of the degenerate Fermi gas at infinite scattering length, where conformal invariance also plays an important role. We find the most general effective Lagrangian consistent with both general coordinate and conformal invariance to leading and next-to-leading orders in the momentum expansion. At the leading order the Lagrangian contains one phenomenological constant and reproduces the results of the Thomas-Fermi theory and superfluid hydrodynamics. At the next-to-leading order there are two additional constants. We express various physical quantities through these constants.
NASA Astrophysics Data System (ADS)
Bazhenov, V. A.; Sakharov, A. S.; Maksimyuk, Yu. V.; Shkryl', A. A.
2016-03-01
Numerical experiments are performed to analyze the invariance and reliability of the results of evaluation of the J-integral by the modified method of reactions in problems of mixed fracture. Bodies with cracks undergoing elastoplastic deformation under static loading are considered. To demonstrate the universality of the method to finite-element schemes, prismatic bodies are considered. This allows using not only conventional finite-element schemes, but also the semi-analytical finite-element method
Geoid, topography, and convection-driven crustal deformation on Venus
NASA Technical Reports Server (NTRS)
Simons, Mark; Hager, Bradford H.; Solomon, Sean C.
1992-01-01
High-resolution Magellan images and altimetry of Venus reveal a wide range of styles and scales of surface deformation that cannot readily be explained within the classical terrestrial plate tectonic paradigm. The high correlation of long-wavelength topography and gravity and the large apparent depths of compensation suggest that Venus lacks an upper-mantle low-viscosity zone. A key difference between Earth and Venus may be the degree of coupling between the convecting mantle and the overlying lithosphere. Mantle flow should then have recognizable signatures in the relationships between surface topography, crustal deformation, and the observed gravity field.
NASA Astrophysics Data System (ADS)
Aleixo, A. N. F.; Balantekin, A. B.
2014-08-01
We consider the minimal bosonization realization of supersymmetric shape-invariant systems where generalized supercharge operators are constructed using the partner supersymmetric operators, the parameter potential translation formalism and the reflection operator. We obtain the solution of the eigenvalue equation and study the quantum dynamics of the supersymmetric system including terms in the Hamiltonian which are constructed using the combination of the bosonized supercharge operators. The connections between the bosonized supersymmetric formalism, the Bose-Fermi transformation and the generalization of the R-deformed Heisenberg algebra are discussed. As an illustration, we apply the generalized formalism for the case of the trigonometric Rosen-Morse potential.
Left-invariant metrics for diffeomorphic image registration with spatially-varying regularisation.
Schmah, Tanya; Risser, Laurent; Vialard, François-Xavier
2013-01-01
We present a new framework for diffeomorphic image registration which supports natural interpretations of spatially-varying metrics. This framework is based on left-invariant diffeomorphic metrics (LIDM) and is closely related to the now standard large deformation diffeomorphic metric mapping (LDDMM). We discuss the relationship between LIDM and LDDMM and introduce a computationally convenient class of spatially-varying metrics appropriate for both frameworks. Finally, we demonstrate the effectiveness of our method on a 2D toy example and on the 40 3D brain images of the LPBA40 dataset.
Intrusion detection using secure signatures
Nelson, Trent Darnel; Haile, Jedediah
2014-09-30
A method and device for intrusion detection using secure signatures comprising capturing network data. A search hash value, value employing at least one one-way function, is generated from the captured network data using a first hash function. The presence of a search hash value match in a secure signature table comprising search hash values and an encrypted rule is determined. After determining a search hash value match, a decryption key is generated from the captured network data using a second hash function, a hash function different form the first hash function. One or more of the encrypted rules of the secure signatures table having a hash value equal to the generated search hash value are then decrypted using the generated decryption key. The one or more decrypted secure signature rules are then processed for a match and one or more user notifications are deployed if a match is identified.
Retail applications of signature verification
NASA Astrophysics Data System (ADS)
Zimmerman, Thomas G.; Russell, Gregory F.; Heilper, Andre; Smith, Barton A.; Hu, Jianying; Markman, Dmitry; Graham, Jon E.; Drews, Clemens
2004-08-01
The dramatic rise in identity theft, the ever pressing need to provide convenience in checkout services to attract and retain loyal customers, and the growing use of multi-function signature captures devices in the retail sector provides favorable conditions for the deployment of dynamic signature verification (DSV) in retail settings. We report on the development of a DSV system to meet the needs of the retail sector. We currently have a database of approximately 10,000 signatures collected from 600 subjects and forgers. Previous work at IBM on DSV has been merged and extended to achieve robust performance on pen position data available from commercial point of sale hardware, achieving equal error rates on skilled forgeries and authentic signatures of 1.5% to 4%.
De Roover, Kim; Timmerman, Marieke E.; De Leersnyder, Jozefien; Mesquita, Batja; Ceulemans, Eva
2014-01-01
The issue of measurement invariance is ubiquitous in the behavioral sciences nowadays as more and more studies yield multivariate multigroup data. When measurement invariance cannot be established across groups, this is often due to different loadings on only a few items. Within the multigroup CFA framework, methods have been proposed to trace such non-invariant items, but these methods have some disadvantages in that they require researchers to run a multitude of analyses and in that they imply assumptions that are often questionable. In this paper, we propose an alternative strategy which builds on clusterwise simultaneous component analysis (SCA). Clusterwise SCA, being an exploratory technique, assigns the groups under study to a few clusters based on differences and similarities in the component structure of the items, and thus based on the covariance matrices. Non-invariant items can then be traced by comparing the cluster-specific component loadings via congruence coefficients, which is far more parsimonious than comparing the component structure of all separate groups. In this paper we present a heuristic for this procedure. Afterwards, one can return to the multigroup CFA framework and check whether removing the non-invariant items or removing some of the equality restrictions for these items, yields satisfactory invariance test results. An empirical application concerning cross-cultural emotion data is used to demonstrate that this novel approach is useful and can co-exist with the traditional CFA approaches. PMID:24999335
Adaptive Aft Signature Shaping of a Low-Boom Supersonic Aircraft Using Off-Body Pressures
NASA Technical Reports Server (NTRS)
Ordaz, Irian; Li, Wu
2012-01-01
The design and optimization of a low-boom supersonic aircraft using the state-of-the- art o -body aerodynamics and sonic boom analysis has long been a challenging problem. The focus of this paper is to demonstrate an e ective geometry parameterization scheme and a numerical optimization approach for the aft shaping of a low-boom supersonic aircraft using o -body pressure calculations. A gradient-based numerical optimization algorithm that models the objective and constraints as response surface equations is used to drive the aft ground signature toward a ramp shape. The design objective is the minimization of the variation between the ground signature and the target signature subject to several geometric and signature constraints. The target signature is computed by using a least-squares regression of the aft portion of the ground signature. The parameterization and the deformation of the geometry is performed with a NASA in- house shaping tool. The optimization algorithm uses the shaping tool to drive the geometric deformation of a horizontal tail with a parameterization scheme that consists of seven camber design variables and an additional design variable that describes the spanwise location of the midspan section. The demonstration cases show that numerical optimization using the state-of-the-art o -body aerodynamic calculations is not only feasible and repeatable but also allows the exploration of complex design spaces for which a knowledge-based design method becomes less effective.
Ballastic signature identification systems study
NASA Technical Reports Server (NTRS)
Reich, A.; Hine, T. L.
1976-01-01
The results are described of an attempt to establish a uniform procedure for documenting (recording) expended bullet signatures as effortlessly as possible and to build a comprehensive library of these signatures in a form that will permit the automated comparison of a new suspect bullet with the prestored library. The ultimate objective is to achieve a standardized format that will permit nationwide interaction between police departments, crime laboratories, and other interested law enforcement agencies.
Color signatures in Amorsolo paintings
NASA Astrophysics Data System (ADS)
Soriano, Maricor N.; Palomero, Cherry May; Cruz, Larry; Yambao, Clod Marlan Krister; Dado, Julie Mae; Salvador-Campaner, Janice May
2010-02-01
We present the results of a two-year project aimed at capturing quantifiable color signatures of oil paintings of Fernando Amorsolo, the Philippine's first National Artists. Color signatures are found by comparing CIE xy measurements of skin color in portraits and ground, sky and foliage in landscapes. The results are compared with results of visual examination and art historical data as well as works done by Amorsolo's contemporaries and mentors.
Lorentzian and signature changing branes
Mars, Marc; Senovilla, Jose M. M.; Vera, Rauel
2007-08-15
General hypersurface layers are considered in order to describe braneworlds and shell cosmologies. No restriction is placed on the causal character of the hypersurface which may thus have internal changes of signature. Strengthening the results in our previous paper [M. Mars, J. M. M. Senovilla, and R. Vera, Phys. Rev. Lett. 86, 4219 (2001).], we confirm that a good, regular, and consistent description of signature change is achieved in these brane/shells scenarios, while keeping the hypersurface and the bulk completely regular. Our formalism allows for a unified description of the traditional timelike branes/shells together with the signature changing, or pure null, ones. This allows for a detailed comparison of the results in both situations. An application to the case of hypersurface layers in static bulks is presented, leading to the general Robertson-Walker geometry on the layer--with a possible signature change. Explicit examples on anti-de Sitter bulks are then studied. The permitted behaviors in different settings (Z{sub 2}-mirror branes, asymmetric shells, signature changing branes) are analyzed in detail. We show, in particular, that (i) in asymmetric shells there is an upper bound for the energy density, and (ii) that the energy density within the brane vanishes when approaching a change of signature. The description of a signature change as a ''singularity'' seen from within the brane is considered. We also find new relations between the fundamental constants in the brane/shell, its tension, and the cosmological and gravitational constants of the bulk, independently of the existence or not of a change of signature.
Supports of invariant measures for piecewise deterministic Markov processes
NASA Astrophysics Data System (ADS)
Benaïm, M.; Colonius, F.; Lettau, R.
2017-09-01
For a class of piecewise deterministic Markov processes, the supports of the invariant measures are characterized. This is based on the analysis of controllability properties of an associated deterministic control system. Its invariant control sets determine the supports.
The Invariance Hypothesis Implies Domain-Specific Regions in Visual Cortex
Leibo, Joel Z.; Liao, Qianli; Anselmi, Fabio; Poggio, Tomaso
2015-01-01
Is visual cortex made up of general-purpose information processing machinery, or does it consist of a collection of specialized modules? If prior knowledge, acquired from learning a set of objects is only transferable to new objects that share properties with the old, then the recognition system’s optimal organization must be one containing specialized modules for different object classes. Our analysis starts from a premise we call the invariance hypothesis: that the computational goal of the ventral stream is to compute an invariant-to-transformations and discriminative signature for recognition. The key condition enabling approximate transfer of invariance without sacrificing discriminability turns out to be that the learned and novel objects transform similarly. This implies that the optimal recognition system must contain subsystems trained only with data from similarly-transforming objects and suggests a novel interpretation of domain-specific regions like the fusiform face area (FFA). Furthermore, we can define an index of transformation-compatibility, computable from videos, that can be combined with information about the statistics of natural vision to yield predictions for which object categories ought to have domain-specific regions in agreement with the available data. The result is a unifying account linking the large literature on view-based recognition with the wealth of experimental evidence concerning domain-specific regions. PMID:26496457
Evidence of Discrete Scale Invariance in DLA and Time-to-Failure by Canonical Averaging
NASA Astrophysics Data System (ADS)
Johansen, A.; Sornette, D.
Discrete scale invariance, which corresponds to a partial breaking of the scaling symmetry, is reflected in the existence of a hierarchy of characteristic scales l0,l0λ,l0λ2,…, where λ is a preferred scaling ratio and l0 a microscopic cut-off. Signatures of discrete scale invariance have recently been found in a variety of systems ranging from rupture, earthquakes, Laplacian growth phenomena, "animals" in percolation to financial market crashes. We believe it to be a quite general, albeit subtle phenomenon. Indeed, the practical problem in uncovering an underlying discrete scale invariance is that standard ensemble averaging procedures destroy it as if it was pure noise. This is due to the fact, that while λ only depends on the underlying physics, l0 on the contrary is realization-dependent. Here, we adapt and implement a novel so-called "canonical" averaging scheme which re-sets the l0 of different realizations to approximately the same value. The method is based on the determination of a realization-dependent effective critical point obtained from, e.g., a maximum susceptibility criterion. We demonstrate the method on diffusion limited aggregation and a model of rupture.
Perturbative and gauge invariant treatment of gravitational wave memory
NASA Astrophysics Data System (ADS)
Bieri, Lydia; Garfinkle, David
2014-04-01
We present a perturbative treatment of gravitational wave memory. The coordinate invariance of Einstein's equations leads to a type of gauge invariance in perturbation theory. As with any gauge invariant theory, results are more clear when expressed in terms of manifestly gauge invariant quantities. Therefore we derive all our results from the perturbed Weyl tensor rather than the perturbed metric. We derive gravitational wave memory for the Einstein equations coupled to a general energy-momentum tensor that reaches null infinity.
Evans, D
1975-08-01
A discussion of the essential deformity in calcaneo-valgus feet develops a theme originally put forward in 1961 on the relapsed club foot (Evans 1961). Whereas in the normal foot the medial and lateral columns are about equal in length, in talipes equino-varus the lateral column is longer and in calcaneo-valgus shorter than the medial column. The suggestion is that in the treatment of both deformities the length of the columns be made equal. A method is described of treating calcaneo-valgus deformity by inserting cortical bone grafts taken from the tibia to elongate the anterior end of the calcaneus.
Deformations, moduli stabilisation and gauge couplings at one-loop
NASA Astrophysics Data System (ADS)
Honecker, Gabriele; Koltermann, Isabel; Staessens, Wieland
2017-04-01
We investigate deformations of Z_2 orbifold singularities on the toroidal orbifold {T}^6/(Z_2× Z_6) with discrete torsion in the framework of Type IIA orientifold model building with intersecting D6-branes wrapping special Lagrangian cycles. To this aim, we employ the hypersurface formalism developed previously for the orbifold {T}^6/(Z_2× Z_6) with discrete torsion and adapt it to the (Z_2× Z_6× Ω R) point group by modding out the remaining Z_3 subsymmetry and the orientifold projection Ω R. We first study the local behaviour of the Z_3× Ω R invariant deformation orbits under non-zero deformation and then develop methods to assess the deformation effects on the fractional three-cycle volumes globally. We confirm that D6-branes supporting USp(2 N) or SO(2 N) gauge groups do not constrain any deformation, while deformation parameters associated to cycles wrapped by D6-branes with U( N) gauge groups are constrained by D-term supersymmetry breaking. These features are exposed in global prototype MSSM, Left-Right symmetric and Pati-Salam models first constructed in [1, 2], for which we here count the number of stabilised moduli and study flat directions changing the values of some gauge couplings.
Permutation-invariant codes encoding more than one qubit
NASA Astrophysics Data System (ADS)
Ouyang, Yingkai; Fitzsimons, Joseph
2016-04-01
A permutation-invariant code on m qubits is a subspace of the symmetric subspace of the m qubits. We derive permutation-invariant codes that can encode an increasing amount of quantum information while suppressing leading-order spontaneous decay errors. To prove the result, we use elementary number theory with prior theory on permutation-invariant codes and quantum error correction.
Possible universal quantum algorithms for generalized Turaev-Viro invariants
NASA Astrophysics Data System (ADS)
Vélez, Mario; Ospina, Juan
2011-05-01
An emergent trend in quantum computation is the topological quantum computation (TQC). Briefly, TQC results from the application of quantum computation with the aim to solve the problems of quantum topology such as topological invariants for knots and links (Jones polynomials, HOMFLY polynomials, Khovanov polynomials); topological invariants for graphs (Tutte polynomial and Bollobás-Riordan polynomial); topological invariants for 3-manifolds (Reshetiskin-Turaev, Turaev-Viro and Turaer-Viro-Ocneanu invariants) and topological invariants for 4-manifolds( Crane-Yetter invariants). In a few words, TQC is concerned with the formulation of quantum algorithms for the computation of these topological invariants in quantum topology. Given that one of the fundamental achievements of quantum topology was the discovery of strong connections between monoidal categories and 3-dimensional manifolds, in TQC is possible and necessary to exploit such connections with the purpose to formulate universal quantum algorithms for topological invariants of 3-manifolds. In the present work we make an exploration of such possibilities. Specifically we search for universal quantum algorithms for generalized Turaev-Viro invariants of 3-manifolds such as the Turaev-Viro-Ocneanu invariants, the Kashaev-Baseilhac-Benedetti invariants of 3-manifolds with links and the Geer-Kashaev-Turaev invariants of 3-manifolds with a link and a principal bundle. We also look for physical systems (three dimensional topological insulators and three-dimensional gravity) over which implement the resulting universal topological quantum algorithms.
Multigroup Confirmatory Factor Analysis: Locating the Invariant Referent Sets
ERIC Educational Resources Information Center
French, Brian F.; Finch, W. Holmes
2008-01-01
Multigroup confirmatory factor analysis (MCFA) is a popular method for the examination of measurement invariance and specifically, factor invariance. Recent research has begun to focus on using MCFA to detect invariance for test items. MCFA requires certain parameters (e.g., factor loadings) to be constrained for model identification, which are…
Testing Factorial Invariance in Multilevel Data: A Monte Carlo Study
ERIC Educational Resources Information Center
Kim, Eun Sook; Kwok, Oi-man; Yoon, Myeongsun
2012-01-01
Testing factorial invariance has recently gained more attention in different social science disciplines. Nevertheless, when examining factorial invariance, it is generally assumed that the observations are independent of each other, which might not be always true. In this study, we examined the impact of testing factorial invariance in multilevel…
Large stable deformation of dielectric elastomers driven on mode of steady electric field
NASA Astrophysics Data System (ADS)
Zhang, Junshi; Zhao, Jianwen; Wang, Shu; Chen, Hualing; Li, Dichen
2017-05-01
Dielectric elastomers (DEs) are capable of large deformation under the actuation of applied voltage and sprayed charge. Actuation of DE under voltage control is prone to electromechanical instabilities, while the DE under charge control always survives from instabilities with sacrificing a large deformation. In this article, a novel actuation mode of steady electric field is proposed. By tuning applied voltage and sprayed charge during viscoelastic creep, an invariable electric field is generated. Such an actuation method can both avoid the occurrence of electromechanical instabilities and guarantee a large deformation in DE actuation.
Remarks on holography with broken Lorentz invariance
NASA Astrophysics Data System (ADS)
Gordeli, Ivan; Koroteev, Peter
2009-12-01
Recently a family of solutions of Einstein equations in backgrounds with broken Lorentz invariance was found. We show that the gravitational solution recently obtained by Kachru et al. is a part of the former solution which was derived earlier in the framework of extra-dimensional theories. We show how the energy-momentum and Einstein tensors are related and establish a correspondence between parameters which govern Lorentz invariance violation. Then we demonstrate that scaling behavior of two point correlation functions of local operators in scalar field theory is reproduced correctly for two cases with critical values of scaling parameters. Therefore, we complete the dictionary of “tree-level” duality for all known solutions of the bulk theory. In the end we speculate on relations between renormalization group flow of a boundary theory and asymptotic behavior of gravitational solutions in the bulk.
Hidden invariance of the free classical particle
Garcia, S. )
1994-06-01
A formalism describing the dynamics of classical and quantum systems from a group theoretical point of view is presented. We apply it to the simple example of the classical free particle. The Galileo group [ital G] is the symmetry group of the free equations of motion. Consideration of the free particle Lagrangian semi-invariance under [ital G] leads to a larger symmetry group, which is a central extension of the Galileo group by the real numbers. We study the dynamics associated with this group, and characterize quantities like Noether invariants and evolution equations in terms of group geometric objects. An extension of the Galileo group by [ital U](1) leads to quantum mechanics.
Testing CPT Invariance with Antiprotonic Helium Atoms
Horvath, Dezso
2008-08-08
The structure of matter is related to symmetries at every level of study. CPT symmetry is one of the most important laws of field theory: it states the invariance of physical properties when one simultaneously changes the signs of the charge and of the spatial and time coordinates of free elementary particles. Although in general opinion CPT symmetry is not violated in Nature, there are theoretical attempts to develop CPT-violating models. The Antiproton Decelerator at CERN has been built to test CPT invariance. The ASACUSA experiment compares the properties of particles and antiparticles by studying the antiprotonic helium atom via laser spectroscopy and measuring the mass, charge and magnetic moment of the antiproton as compared to those of the proton.
Gauge-invariant approach to quark dynamics
NASA Astrophysics Data System (ADS)
Sazdjian, H.
2016-02-01
The main aspects of a gauge-invariant approach to the description of quark dynamics in the nonperturbative regime of quantum chromodynamics (QCD) are first reviewed. The role of the parallel transport operation in constructing gauge-invariant Green's functions is then presented, and the relevance of Wilson loops for the representation of the interaction is emphasized. Recent developments, based on the use of polygonal lines for the parallel transport operation, are presented. An integro-differential equation, obtained for the quark Green's function defined with a phase factor along a single, straight line segment, is solved exactly and analytically in the case of two-dimensional QCD in the large- N c limit. The solution displays the dynamical mass generation phenomenon for quarks, with an infinite number of branch-cut singularities that are stronger than simple poles.
Fast forward to the classical adiabatic invariant
NASA Astrophysics Data System (ADS)
Jarzynski, Christopher; Deffner, Sebastian; Patra, Ayoti; Subaşı, Yiǧit
2017-03-01
We show how the classical action, an adiabatic invariant, can be preserved under nonadiabatic conditions. Specifically, for a time-dependent Hamiltonian H =p2/2 m +U (q ,t ) in one degree of freedom, and for an arbitrary choice of action I0, we construct a so-called fast-forward potential energy function VFF(q ,t ) that, when added to H , guides all trajectories with initial action I0 to end with the same value of action. We use this result to construct a local dynamical invariant J (q ,p ,t ) whose value remains constant along these trajectories. We illustrate our results with numerical simulations. Finally, we sketch how our classical results may be used to design approximate quantum shortcuts to adiabaticity.
Gauge invariance in the cloudy bag model
Koepf, W.; Henley, E.M.
1993-10-01
We investigate the question, whether the conventional analysis of the electromagnetic form factors, calculated in the frame-work of the cloudy bag model (CBM), is gauge invariant. In order to address that point, we first formulate the model in a way that resembles the technique of loop integrals. Evaluating the self energy and the electromagnetic form factors in that manner and comparing with the standard analysis where non-relativistic perturbation theory is used, allows us to show, that our approach is appropriate, and to point out, what approximations are made in the usual derivation of the CBM. From the form of the loop integrals, we then show whether a seagull correction is needed to preserve gauge invariance, and we discuss corresponding corrections for various models.
Adiabatic invariance with first integrals of motion.
Adib, Artur B
2002-10-01
The construction of a microthermodynamic formalism for isolated systems based on the concept of adiabatic invariance is an old but seldom appreciated effort in the literature, dating back at least to P. Hertz [Ann. Phys. (Leipzig) 33, 225 (1910)]. An apparently independent extension of such formalism for systems bearing additional first integrals of motion was recently proposed by Hans H. Rugh [Phys. Rev. E 64, 055101 (2001)], establishing the concept of adiabatic invariance even in such singular cases. After some remarks in connection with the formalism pioneered by Hertz, it will be suggested that such an extension can incidentally explain the success of a dynamical method for computing the entropy of classical interacting fluids, at least in some potential applications where the presence of additional first integrals cannot be ignored.
Odor Concentration Invariance by Chemical Ratio Coding
Uchida, Naoshige; Mainen, Zachary F.
2007-01-01
Many animal species rely on chemical signals to extract ecologically important information from the environment. Yet in natural conditions chemical signals will frequently undergo concentration changes that produce differences in both level and pattern of activation of olfactory receptor neurons. Thus, a central problem in olfactory processing is how the system is able to recognize the same stimulus across different concentrations. To signal species identity for mate recognition, some insects use the ratio of two components in a binary chemical mixture to produce a code that is invariant to dilution. Here, using psychophysical methods, we show that rats also classify binary odor mixtures according to the molar ratios of their components, spontaneously generalizing over at least a tenfold concentration range. These results indicate that extracting chemical ratio information is not restricted to pheromone signaling and suggest a general solution for concentration-invariant odor recognition by the mammalian olfactory system. PMID:18958244
Elastic wave invariants for acoustic emission
NASA Astrophysics Data System (ADS)
Pardee, W. J.
1981-07-01
It is shown that there are four conserved properties of an elastic wave in an infinite isotropic plate: the energy, the two components of wave momentum parallel to the surface, and wave angular momentum normal to the surface. All four invariants are volume integrals of quadratic functions of the spatial (Eulerian) coordinates. The canonical energy-momentum density tensor and the orbital, spin, and total angular momentum density tensors are constructed and sufficient conditions for their conservation are demonstrated. A procedure for measuring the wave momentum of a surface wave is proposed. It is argued that these invariants are likely to be particularly useful characterizations of acoustic emission, e.g., from a growing crack. Experimental tests are proposed, and possible applications to practical monitoring problems described.
Invariant metrics, contractions and nonlinear matrix equations
NASA Astrophysics Data System (ADS)
Lee, Hosoo; Lim, Yongdo
2008-04-01
In this paper we consider the semigroup generated by the self-maps on the open convex cone of positive definite matrices of translations, congruence transformations and matrix inversion that includes symplectic Hamiltonians and show that every member of the semigroup contracts any invariant metric distance inherited from a symmetric gauge function. This extends the results of Bougerol for the Riemannian metric and of Liverani-Wojtkowski for the Thompson part metric. A uniform upper bound of the Lipschitz contraction constant for a member of the semigroup is given in terms of the minimum eigenvalues of its determining matrices. We apply this result to a variety of nonlinear equations including Stein and Riccati equations for uniqueness and existence of positive definite solutions and find a new convergence analysis of iterative algorithms for the positive definite solution depending only on the least contraction coefficient for the invariant metric from the spectral norm.
A framework for mining signatures from event sequences and its applications in healthcare data.
Wang, Fei; Lee, Noah; Hu, Jianying; Sun, Jimeng; Ebadollahi, Shahram; Laine, Andrew F
2013-02-01
This paper proposes a novel temporal knowledge representation and learning framework to perform large-scale temporal signature mining of longitudinal heterogeneous event data. The framework enables the representation, extraction, and mining of high-order latent event structure and relationships within single and multiple event sequences. The proposed knowledge representation maps the heterogeneous event sequences to a geometric image by encoding events as a structured spatial-temporal shape process. We present a doubly constrained convolutional sparse coding framework that learns interpretable and shift-invariant latent temporal event signatures. We show how to cope with the sparsity in the data as well as in the latent factor model by inducing a double sparsity constraint on the β-divergence to learn an overcomplete sparse latent factor model. A novel stochastic optimization scheme performs large-scale incremental learning of group-specific temporal event signatures. We validate the framework on synthetic data and on an electronic health record dataset.
Blockwise Binary Pattern: a Robust and AN Efficient Approach for Offline Signature Verification
NASA Astrophysics Data System (ADS)
Shekar, B. H.; Pilar, B.; Sunil, K. D. S.
2017-05-01
This paper presents a variant of local binary pattern called Blockwise Binary Pattern (BBP) for the offline signature verification. The proposed approach has three major phases : Preprocessing, Feature extraction and Classification. In the feature extraction phase, the signature is divided into 3 x 3 neighborhood blocks. A BBP value for central pixel of each block is computed by considering its 8 neighboring pixels and the 3 x 3 block is replaced by this central pixel. To compute BBP value for each block, a binary sequence is formed by considering 8 neighbors of the central pixel, by following the pixels in a anti-clockwise direction. Then the minimum decimal equivalent of this binary sequence is computed and this value is assigned to the central pixel. The central pixel is merged with the neighboring 8 pixels representing the 3 X 3 neighborhood block. This method is found to be invariant to rotation, scaling and shift of the signature. The features are stored in the form of normalized histogram. The SVM classifier is used for the signature verification. Experiments have been performed on standard signature datasets namely CEDAR and GPDS which are publicly available English signature datasets and on MUKOS, a regional language (Kannada) dataset and compared with the well-known approaches to exhibit the performance of the proposed approach.
Arctic sea ice microwave signature and geophysical processes study
NASA Technical Reports Server (NTRS)
Onstott, Robert G.; Shuchman, Robert A.
1993-01-01
Studies on the validation and utilization of ERS-1 SAR (Synthetic Aperture Radar) derived liquid and solid ocean information and the study of the interregional, regional, and temporal variation of the microwave signatures of sea ice and snow, are reported. Initial interests are focused on the accuracy of the estimates of ice type, ice form, deformation state, or thickness, and the ability to retrieve ice physical property information. Two in situ campaigns were conducted for the purpose of 'truth' ERS-1 SAR products and to gather data in support of the above science studies.
Quantum messages with signatures forgeable in arbitrated quantum signature schemes
NASA Astrophysics Data System (ADS)
Kim, Taewan; Choi, Jeong Woon; Jho, Nam-Su; Lee, Soojoon
2015-02-01
Even though a method to perfectly sign quantum messages has not been known, the arbitrated quantum signature scheme has been considered as one of the good candidates. However, its forgery problem has been an obstacle to the scheme becoming a successful method. In this paper, we consider one situation, which is slightly different from the forgery problem, that we use to check whether at least one quantum message with signature can be forged in a given scheme, although all the messages cannot be forged. If there are only a finite number of forgeable quantum messages in the scheme, then the scheme can be secured against the forgery attack by not sending forgeable quantum messages, and so our situation does not directly imply that we check whether the scheme is secure against the attack. However, if users run a given scheme without any consideration of forgeable quantum messages, then a sender might transmit such forgeable messages to a receiver and in such a case an attacker can forge the messages if the attacker knows them. Thus it is important and necessary to look into forgeable quantum messages. We show here that there always exists such a forgeable quantum message-signature pair for every known scheme with quantum encryption and rotation, and numerically show that there are no forgeable quantum message-signature pairs that exist in an arbitrated quantum signature scheme.
Simulating realistic predator signatures in quantitative fatty acid signature analysis
Bromaghin, Jeffrey F.
2015-01-01
Diet estimation is an important field within quantitative ecology, providing critical insights into many aspects of ecology and community dynamics. Quantitative fatty acid signature analysis (QFASA) is a prominent method of diet estimation, particularly for marine mammal and bird species. Investigators using QFASA commonly use computer simulation to evaluate statistical characteristics of diet estimators for the populations they study. Similar computer simulations have been used to explore and compare the performance of different variations of the original QFASA diet estimator. In both cases, computer simulations involve bootstrap sampling prey signature data to construct pseudo-predator signatures with known properties. However, bootstrap sample sizes have been selected arbitrarily and pseudo-predator signatures therefore may not have realistic properties. I develop an algorithm to objectively establish bootstrap sample sizes that generates pseudo-predator signatures with realistic properties, thereby enhancing the utility of computer simulation for assessing QFASA estimator performance. The algorithm also appears to be computationally efficient, resulting in bootstrap sample sizes that are smaller than those commonly used. I illustrate the algorithm with an example using data from Chukchi Sea polar bears (Ursus maritimus) and their marine mammal prey. The concepts underlying the approach may have value in other areas of quantitative ecology in which bootstrap samples are post-processed prior to their use.
Switched Systems With Multiple Invariant Sets
2015-05-06
system. The resulting construction is slightly more complicated, as we consider V̇ in order to isolate the invariant sets rather than using the Lyapunov ...switched systems literature are both Lyapunov -based, and we will make use of Lyapunov functions to define all the relevant sets. The benefit to relying on... Lyapunov functions is that this requires no special structure on the subsystems’ entire vector fields. The tradeoff is that we fail to exploit any
Liquids: Surface tension, compressibility, and invariants
NASA Astrophysics Data System (ADS)
Sanchez, Isaac C.
1983-07-01
A new equation has been dervied which relates the surface tension (σ) to a liquid's isothermal compressibility (κ) and mass density (ρ). The derivation is based on a generalized square-gradient approximation for the free energy density of a nonuniform fluid. The equation is σ(κ/ρ)1/2=A1/20=constant in the normal liquid range. Except for water, A0 is temperature independent for a variety of inorganic, organic, and polymer liquids. Among 50 nonpolar and polar organic liquids, including hydrogen bonding liquids, A1/20 appears to be an invariant with a value of 2.78±0.13×10-4 (erg cm2/g)1/2. Among the diatomic elements (except hydrogen), A1/20 is an invariant with a value of 1.8×10-4. Among the heavy noble elements, A1/20 is an invariant with a value of 1.36×10-4. For the quantum noble elements helium and neon, A1/20=1.0×10-4. The constant A0 is shown to be proportional to a second moment of a direct correlation function. A semiempirical formula has been derived for A0 relating it to the parameters ɛ0 and σ0 that characterize the pair interaction potential. For a Lennard-Jones 6-12 potential, it is shown that A1/20=0.26(ɛ0σ20/M)1/2, where M is molecular weight. This result combined with the experimental evaluations of A0 implies that the parameter combination (ɛ0σ20/M) is an invariant for certain classes of molecules. It appears that this surprising observation has never been made before; its physical implications remain unclear.
Invariant measures for singular hyperbolic attractors
Sataev, Evgueni A
2010-05-11
This paper continues the author's previous paper, where strong unstable spaces were constructed for a singular hyperbolic attractor. In this paper the existence of local strongly unstable manifolds and invariant measures of Sinai-Bowen-Ruelle type is established. The properties of such measures are studied. It is proved that the number of ergodic components is finite and the set of periodic trajectories is dense. Bibliography: 34 titles.
OSRI: a rotationally invariant binary descriptor.
Xu, Xianwei; Tian, Lu; Feng, Jianjiang; Zhou, Jie
2014-07-01
Binary descriptors are becoming widely used in computer vision field because of their high matching efficiency and low memory requirements. Since conventional approaches, which first compute a floating-point descriptor then binarize it, are computationally expensive, some recent efforts have focused on directly computing binary descriptors from local image patches. Although these binary descriptors enable a significant speedup in processing time, their performances usually drop a lot due to orientation estimation errors and limited description abilities. To address these issues, we propose a novel binary descriptor based on the ordinal and spatial information of regional invariants (OSRIs) over a rotation invariant sampling pattern. Our main contributions are twofold: 1) each bit in OSRI is computed based on difference tests of regional invariants over pairwise sampling-regions instead of difference tests of pixel intensities commonly used in existing binary descriptors, which can significantly enhance the discriminative ability and 2) rotation and illumination changes are handled well by ordering pixels according to their intensities and gradient orientations, meanwhile, which is also more reliable than those methods that resort to a reference orientation for rotation invariance. Besides, a statistical analysis of discriminative abilities of different parts in the descriptor is conducted to design a cascade filter which can reject nonmatching descriptors at early stages by comparing just a small portion of the whole descriptor, further reducing the matching time. Extensive experiments on four challenging data sets (Oxford, 53 Objects, ZuBuD, and Kentucky) show that OSRI significantly outperforms two state-of-the-art binary descriptors (FREAK and ORB). The matching performance of OSRI with only 512 bits is also better than the well-known floating-point descriptor SIFT (4K bits) and is comparable with the state-of-the-art floating-point descriptor MROGH (6K bits
Invariant solutions for the static vacuum equation
NASA Astrophysics Data System (ADS)
Leandro, Benedito; Pina, Romildo
2017-07-01
We consider the static vacuum Einstein space-time when the spatial factor (or, base) is conformal to a pseudo-Euclidean space, which is invariant under the action of a translation group. We characterize all such solitons. Moreover, we give examples of static vacuum Einstein solutions for Einstein's field equation. Applications provide an explicit example of a complete static vacuum Einstein space-time.
Tests of Lorentz invariance using hydrogen molecules
Mueller, Holger; Herrmann, Sven; Saenz, Alejandro; Peters, Achim; Laemmerzahl, Claus
2004-10-01
We discuss the consequences of Lorentz violation (as expressed within the Lorentz-violating extension of the standard model) for the hydrogen molecule, which represents a generic model of a molecular binding. Lorentz-violating shifts of electronic, vibrational and rotational energy levels, and of the internuclear distance are calculated. This offers the possibility of obtaining improved bounds on Lorentz invariance by experiments using molecules.
Testing local Lorentz invariance with gravitational waves
Kostelecký, V. Alan; Mewes, Matthew
2016-04-20
The effects of local Lorentz violation on dispersion and birefringence of gravitational waves are investigated. The covariant dispersion relation for gravitational waves involving gauge-invariant Lorentz violating operators of arbitrary mass dimension is constructed. The chirp signal from the gravitational wave event GW150914 is used to place numerous first constraints on gravitational Lorentz violation. (C) 2016 The Authors. Published by Elsevier B.V.
Neutrino velocity and local Lorentz invariance
NASA Astrophysics Data System (ADS)
Cardone, Fabio; Mignani, Roberto; Petrucci, Andrea
2015-09-01
We discuss the possible violation of local Lorentz invariance (LLI) arising from a faster-than-light neutrino speed. A toy calculation of the LLI violation parameter δ, based on the (disclaimed) OPERA data, suggests that the values of δ are determined by the interaction involved, and not by the energy range. This hypothesis is further corroborated by the analysis of the more recent results of the BOREXINO, LVD and ICARUS experiments.
Yudovich, A. ); Chin, L.Y. ); Morgan, D.R. )
1989-07-01
Casing deformation resulting from reservoir compaction occurred in the Ekofisk field operated by Phillips Petroleum Co. Norway and is a serious problem in three of the fields. This study established a relationship between reservoir compaction and casing failure by statistical analyses, finite-element modeling (FEM), and the analyses of deformed casing and logs run through collapsed casings. Ekofisk casing deformation is related primarily to the near well incremental strain, well inclination, and casing diameter. Useful correlations to estimate future probabilities of casing deformation as a function of reservoir variables and well parameters were also obtained. The authors concluded that casing failure induced by reservoir compaction can be minimized through a pressure-maintenance program to reduce strain by drilling with the highest practical angle and by using the largest possible casing in the well.
NASA Astrophysics Data System (ADS)
Green, Harry
The Third Rock Deformation Colloquium was held December 4, 1989, at the AGU Fall Meeting in San Francisco. Steve Kirby of the U.S. Geological Survey, Menlo Park, Calif., reported on actions taken by the rock deformation steering committee. Brian Wernicke of Harvard University, Cambridge, Mass., talked on the structural geology of the Great Basin.The steering committee voted for “Committee on Deformation of Earth Materials” as the name for the AGU technical committee on rock deformation, Kirby said. Considerable discussion has occurred in the steering committee over our relationship to the AGU Mineral Physics Committee. Indeed, Kirby will become chairman of that committee in 1990, underlining the overlap of the two groups. It was agreed that we will pursue closer association with Mineral Physics.
Wrist deformities after fracture.
Vanheest, Ann
2006-02-01
Wrist deformities can occur after fracture because of malunion of the fracture or injury to the growth plate leading to imbalance of growth. Prevention of malunion is paramount by early recognition with proper reduction and casting or fixation with casting. If a mal-union occurs, an osteotomy may be necessary if anticipated growth will not correct the deformity. Injury of the growth plate may lead to wrist deformity in two ways: angular growth or growth arrest. Angular growth deformities are corrected most commonly by osteotomy. Growth arrest of the radius or the ulna leads to an ulnar-positive or an ulnar-negative variance at the wrist. If the ulnar variance is symptomatic, treatment is centered on achieving a level joint. Options for joint leveling procedures include epiphysiodesis or physeal stapling of the longer bone, lengthening osteotomy of the shorter bone, or shortening osteotomy of the longer bone.
Against relative timing invariance in movement kinematics.
Burgess-Limerick, R; Neal, R J; Abernethy, B
1992-05-01
The kinematics of stair climbing were examined to test the assertion that relative timing is an invariant feature of human gait. Six male and four female subjects were video-recorded (at 60 Hz) while they climbed a flight of stairs 10 times at each of three speeds. Each gait cycle was divided into three segments by the maximum and minimum angular displacement of the left knee and left foot contact. Gentner's (1987) analysis methods were applied to the individual subject data to determine whether the duration of the segments remained a fixed proportion of gait cycle duration across changes in stair-climbing speed. A similar analysis was performed using knee velocity maxima to partition the gait cycle. Regardless of how the gait cycle was divided, relative timing was not found to remain strictly invariant across changes in speed. This conclusion is contrary to previous studies of relative timing that involved less conservative analysis but is consistent with the wider gait literature. Strict invariant relative timing may not be a fundamental feature of movement kinematics.
Invariance algorithms for processing NDE signals
NASA Astrophysics Data System (ADS)
Mandayam, Shreekanth; Udpa, Lalita; Udpa, Satish S.; Lord, William
1996-11-01
Signals that are obtained in a variety of nondestructive evaluation (NDE) processes capture information not only about the characteristics of the flaw, but also reflect variations in the specimen's material properties. Such signal changes may be viewed as anomalies that could obscure defect related information. An example of this situation occurs during in-line inspection of gas transmission pipelines. The magnetic flux leakage (MFL) method is used to conduct noninvasive measurements of the integrity of the pipe-wall. The MFL signals contain information both about the permeability of the pipe-wall and the dimensions of the flaw. Similar operational effects can be found in other NDE processes. This paper presents algorithms to render NDE signals invariant to selected test parameters, while retaining defect related information. Wavelet transform based neural network techniques are employed to develop the invariance algorithms. The invariance transformation is shown to be a necessary pre-processing step for subsequent defect characterization and visualization schemes. Results demonstrating the successful application of the method are presented.
On local invariants of singular symplectic forms
NASA Astrophysics Data System (ADS)
Domitrz, Wojciech
2017-04-01
We find a complete set of local invariants of singular symplectic forms with the structurally stable Martinet hypersurface on a 2 n-dimensional manifold. In the C-analytic category this set consists of the Martinet hypersurface Σ2, the restriction of the singular symplectic form ω to TΣ2 and the kernel of ω n - 1 at the point p ∈Σ2. In the R-analytic and smooth categories this set contains one more invariant: the canonical orientation of Σ2. We find the conditions to determine the kernel of ω n - 1 at p by the other invariants. In dimension 4 we find sufficient conditions to determine the equivalence class of a singular symplectic form-germ with the structurally smooth Martinet hypersurface by the Martinet hypersurface and the restriction of the singular symplectic form to it. We also study the singular symplectic forms with singular Martinet hypersurfaces. We prove that the equivalence class of such singular symplectic form-germ is determined by the Martinet hypersurface, the canonical orientation of its regular part and the restriction of the singular symplectic form to its regular part if the Martinet hypersurface is a quasi-homogeneous hypersurface with an isolated singularity.
Data series embedding and scale invariant statistics.
Michieli, I; Medved, B; Ristov, S
2010-06-01
Data sequences acquired from bio-systems such as human gait data, heart rate interbeat data, or DNA sequences exhibit complex dynamics that is frequently described by a long-memory or power-law decay of autocorrelation function. One way of characterizing that dynamics is through scale invariant statistics or "fractal-like" behavior. For quantifying scale invariant parameters of physiological signals several methods have been proposed. Among them the most common are detrended fluctuation analysis, sample mean variance analyses, power spectral density analysis, R/S analysis, and recently in the realm of the multifractal approach, wavelet analysis. In this paper it is demonstrated that embedding the time series data in the high-dimensional pseudo-phase space reveals scale invariant statistics in the simple fashion. The procedure is applied on different stride interval data sets from human gait measurements time series (Physio-Bank data library). Results show that introduced mapping adequately separates long-memory from random behavior. Smaller gait data sets were analyzed and scale-free trends for limited scale intervals were successfully detected. The method was verified on artificially produced time series with known scaling behavior and with the varying content of noise. The possibility for the method to falsely detect long-range dependence in the artificially generated short range dependence series was investigated.
Time-warp-invariant neuronal processing.
Gütig, Robert; Sompolinsky, Haim
2009-07-01
Fluctuations in the temporal durations of sensory signals constitute a major source of variability within natural stimulus ensembles. The neuronal mechanisms through which sensory systems can stabilize perception against such fluctuations are largely unknown. An intriguing instantiation of such robustness occurs in human speech perception, which relies critically on temporal acoustic cues that are embedded in signals with highly variable duration. Across different instances of natural speech, auditory cues can undergo temporal warping that ranges from 2-fold compression to 2-fold dilation without significant perceptual impairment. Here, we report that time-warp-invariant neuronal processing can be subserved by the shunting action of synaptic conductances that automatically rescales the effective integration time of postsynaptic neurons. We propose a novel spike-based learning rule for synaptic conductances that adjusts the degree of synaptic shunting to the temporal processing requirements of a given task. Applying this general biophysical mechanism to the example of speech processing, we propose a neuronal network model for time-warp-invariant word discrimination and demonstrate its excellent performance on a standard benchmark speech-recognition task. Our results demonstrate the important functional role of synaptic conductances in spike-based neuronal information processing and learning. The biophysics of temporal integration at neuronal membranes can endow sensory pathways with powerful time-warp-invariant computational capabilities.
Global invariants in ideal magnetohydrodynamic turbulence
Shebalin, John V.
2013-10-15
Magnetohydrodynamic (MHD) turbulence is an important though incompletely understood factor affecting the dynamics of many astrophysical, geophysical, and technological plasmas. As an approximation, viscosity and resistivity may be ignored, and ideal MHD turbulence may be investigated by statistical methods. Incompressibility is also assumed and finite Fourier series are used to represent the turbulent velocity and magnetic field. The resulting model dynamical system consists of a set of independent Fourier coefficients that form a canonical ensemble described by a Gaussian probability density function (PDF). This PDF is similar in form to that of Boltzmann, except that its argument may contain not just the energy multiplied by an inverse temperature, but also two other invariant integrals, the cross helicity and magnetic helicity, each multiplied by its own inverse temperature. However, the cross and magnetic helicities, as usually defined, are not invariant in the presence of overall rotation or a mean magnetic field, respectively. Although the generalized form of the magnetic helicity is known, a generalized cross helicity may also be found, by adding terms that are linear in the mean magnetic field and angular rotation vectors, respectively. These general forms are invariant even in the presence of overall rotation and a mean magnetic field. We derive these general forms, explore their properties, examine how they extend the statistical theory of ideal MHD turbulence, and discuss how our results may be affected by dissipation and forcing.
Permutation-invariant distance between atomic configurations.
Ferré, Grégoire; Maillet, Jean-Bernard; Stoltz, Gabriel
2015-09-14
We present a permutation-invariant distance between atomic configurations, defined through a functional representation of atomic positions. This distance enables us to directly compare different atomic environments with an arbitrary number of particles, without going through a space of reduced dimensionality (i.e., fingerprints) as an intermediate step. Moreover, this distance is naturally invariant through permutations of atoms, avoiding the time consuming associated minimization required by other common criteria (like the root mean square distance). Finally, the invariance through global rotations is accounted for by a minimization procedure in the space of rotations solved by Monte Carlo simulated annealing. A formal framework is also introduced, showing that the distance we propose verifies the property of a metric on the space of atomic configurations. Two examples of applications are proposed. The first one consists in evaluating faithfulness of some fingerprints (or descriptors), i.e., their capacity to represent the structural information of a configuration. The second application concerns structural analysis, where our distance proves to be efficient in discriminating different local structures and even classifying their degree of similarity.
Time-Warp–Invariant Neuronal Processing
Gütig, Robert; Sompolinsky, Haim
2009-01-01
Fluctuations in the temporal durations of sensory signals constitute a major source of variability within natural stimulus ensembles. The neuronal mechanisms through which sensory systems can stabilize perception against such fluctuations are largely unknown. An intriguing instantiation of such robustness occurs in human speech perception, which relies critically on temporal acoustic cues that are embedded in signals with highly variable duration. Across different instances of natural speech, auditory cues can undergo temporal warping that ranges from 2-fold compression to 2-fold dilation without significant perceptual impairment. Here, we report that time-warp–invariant neuronal processing can be subserved by the shunting action of synaptic conductances that automatically rescales the effective integration time of postsynaptic neurons. We propose a novel spike-based learning rule for synaptic conductances that adjusts the degree of synaptic shunting to the temporal processing requirements of a given task. Applying this general biophysical mechanism to the example of speech processing, we propose a neuronal network model for time-warp–invariant word discrimination and demonstrate its excellent performance on a standard benchmark speech-recognition task. Our results demonstrate the important functional role of synaptic conductances in spike-based neuronal information processing and learning. The biophysics of temporal integration at neuronal membranes can endow sensory pathways with powerful time-warp–invariant computational capabilities. PMID:19582146
Scale Invariant Relationships for Snow Avalanches
NASA Astrophysics Data System (ADS)
Landry, C. C.; Birkeland, K. W.
2002-12-01
Snow avalanches have been described as the most common form of lethal mass wasting in the mountains of the western United States and result in more than 30 fatalities per winter. In this poster, we investigate scale-invariant relationships associated with snow avalanches to better understand some of the complex interactions of the snow avalanche system. This work utilizes over 20 years of data from a number of ski areas and other avalanche-prone locations in the western United States. Our results reveal power-law relationships between avalanche frequency and size for several groups of avalanche paths. Further, following some recent work by others, we also demonstrate a power law between avalanche frequency and the estimated fracture depth of the avalanches for groups of avalanche paths in several different snow climates. Interestingly, the relationships explored are valid both for datasets consisting largely of avalanches artificially triggered with explosives as well as for datasets consisting entirely of natural avalanches. Recent research by others also demonstrates scale invariance in the fracture and fragmentation of ice. Our work suggests that scale invariance may also exist in the complicated fracture processes within seasonal snowpacks that result in the release of slab avalanches.
Astroparticle Physics Tests of Lorentz Invariance Violation
NASA Astrophysics Data System (ADS)
Lang, R. G.; de Souza, V.
2017-06-01
Testing Lorentz invariance is essential as it is one of the pillars of modern physics. Moreover, its violation is foreseen in several popular Quantum Gravity models. Several authors study the effects of Lorentz invariance violation (LIV) in the propagation of ultra-high energy cosmic rays. These particles are the most energetic events ever detected and therefore represent a promising framework to test LIV. In this work we present an analytic calculation of the inelasticity for any a + b → c + d interaction using first order perturbation in the dispersion relation that violates Lorentz invariance. The inelasticity can be calculated by solving a third-order polynomial equation containing: a) the kinematics of the interaction, b) the LIV term for each particle and c) the geometry of the interaction. We use the inelasticity we calculate to investigate the proton propagation in the intergalactic media. The photopion production of the proton interaction with the CMB is taken into account using the inelasticity and the attenuation length in different LIV scenarios. We show how the allowed phase space for the photopion production changes when LIV is considered for the interaction. The calculations presented here are going to be extended in order to calculated the modified ultra-high energy cosmic rays spectrum and compare it to the data.
Global invariants in ideal magnetohydrodynamic turbulence
NASA Astrophysics Data System (ADS)
Shebalin, John V.
2013-10-01
Magnetohydrodynamic (MHD) turbulence is an important though incompletely understood factor affecting the dynamics of many astrophysical, geophysical, and technological plasmas. As an approximation, viscosity and resistivity may be ignored, and ideal MHD turbulence may be investigated by statistical methods. Incompressibility is also assumed and finite Fourier series are used to represent the turbulent velocity and magnetic field. The resulting model dynamical system consists of a set of independent Fourier coefficients that form a canonical ensemble described by a Gaussian probability density function (PDF). This PDF is similar in form to that of Boltzmann, except that its argument may contain not just the energy multiplied by an inverse temperature, but also two other invariant integrals, the cross helicity and magnetic helicity, each multiplied by its own inverse temperature. However, the cross and magnetic helicities, as usually defined, are not invariant in the presence of overall rotation or a mean magnetic field, respectively. Although the generalized form of the magnetic helicity is known, a generalized cross helicity may also be found, by adding terms that are linear in the mean magnetic field and angular rotation vectors, respectively. These general forms are invariant even in the presence of overall rotation and a mean magnetic field. We derive these general forms, explore their properties, examine how they extend the statistical theory of ideal MHD turbulence, and discuss how our results may be affected by dissipation and forcing.
Permutation-invariant distance between atomic configurations
Ferré, Grégoire; Maillet, Jean-Bernard; Stoltz, Gabriel
2015-09-14
We present a permutation-invariant distance between atomic configurations, defined through a functional representation of atomic positions. This distance enables us to directly compare different atomic environments with an arbitrary number of particles, without going through a space of reduced dimensionality (i.e., fingerprints) as an intermediate step. Moreover, this distance is naturally invariant through permutations of atoms, avoiding the time consuming associated minimization required by other common criteria (like the root mean square distance). Finally, the invariance through global rotations is accounted for by a minimization procedure in the space of rotations solved by Monte Carlo simulated annealing. A formal framework is also introduced, showing that the distance we propose verifies the property of a metric on the space of atomic configurations. Two examples of applications are proposed. The first one consists in evaluating faithfulness of some fingerprints (or descriptors), i.e., their capacity to represent the structural information of a configuration. The second application concerns structural analysis, where our distance proves to be efficient in discriminating different local structures and even classifying their degree of similarity.
Significance Analysis of Prognostic Signatures
Beck, Andrew H.; Knoblauch, Nicholas W.; Hefti, Marco M.; Kaplan, Jennifer; Schnitt, Stuart J.; Culhane, Aedin C.; Schroeder, Markus S.; Risch, Thomas; Quackenbush, John; Haibe-Kains, Benjamin
2013-01-01
A major goal in translational cancer research is to identify biological signatures driving cancer progression and metastasis. A common technique applied in genomics research is to cluster patients using gene expression data from a candidate prognostic gene set, and if the resulting clusters show statistically significant outcome stratification, to associate the gene set with prognosis, suggesting its biological and clinical importance. Recent work has questioned the validity of this approach by showing in several breast cancer data sets that “random” gene sets tend to cluster patients into prognostically variable subgroups. This work suggests that new rigorous statistical methods are needed to identify biologically informative prognostic gene sets. To address this problem, we developed Significance Analysis of Prognostic Signatures (SAPS) which integrates standard prognostic tests with a new prognostic significance test based on stratifying patients into prognostic subtypes with random gene sets. SAPS ensures that a significant gene set is not only able to stratify patients into prognostically variable groups, but is also enriched for genes showing strong univariate associations with patient prognosis, and performs significantly better than random gene sets. We use SAPS to perform a large meta-analysis (the largest completed to date) of prognostic pathways in breast and ovarian cancer and their molecular subtypes. Our analyses show that only a small subset of the gene sets found statistically significant using standard measures achieve significance by SAPS. We identify new prognostic signatures in breast and ovarian cancer and their corresponding molecular subtypes, and we show that prognostic signatures in ER negative breast cancer are more similar to prognostic signatures in ovarian cancer than to prognostic signatures in ER positive breast cancer. SAPS is a powerful new method for deriving robust prognostic biological signatures from clinically annotated
Principles of rock deformation
Nicolas, A.
1987-01-01
This text focuses on the recent achievements in the analysis of rock deformation. It gives an analytical presentation of the essential structures in terms of kinetic and dynamic interpretation. The physical properties underlying the interpretation of rock structures are exposed in simple terms. Emphasized in the book are: the role of fluids in rock fracturing; the kinematic analysis of magnetic flow structures; the application of crystalline plasticity to the kinematic and dynamic analysis of the large deformation imprinted in many metamorphic rocks.
Signature effects in some [ital N]=90 odd-[ital Z] rare-earth nuclei
Rath, A.K.; Praharaj, C.R.; Khadkikar, S.B. Institute of Physics, Bhubaneswar 751005 )
1993-05-01
Using axially symmetric deformed configuration mixing and angular momentum projection techniques, we have studied the signature effects in the [pi][ital h][sub 11/2] bands of [sup 147]La, [sup 149]Pr, and [sup 151]Pm nuclei. Effects of rotation alignment on the signature splitting in energy and signature inversion in the [ital B]([ital E]2,[ital I][r arrow][ital I][minus]1) values are discussed. We find that transition from a strongly rotation-aligned limit to a weakly rotation-aligned (or more regular rotational behavior) regime or vice versa leads to signature inversion of the [ital B]([ital E]2) values.
NASA Astrophysics Data System (ADS)
Antonellini, Marco; Mollema, Pauline Nella
2015-12-01
We report for the first time the occurrence of polygonal faults in sandstone, which is compelling given that layer-bound polygonal fault systems have been observed so far only in fine-grained sediments such as clay and chalk. The polygonal faults are shear deformation bands that developed under shallow burial conditions via strain hardening in dm-wide zones. The edges of the polygons are 1-5 m long. The shear deformation bands are organized as conjugate faults along each edge of the polygon and form characteristic horst-like structures. The individual deformation bands have slip magnitudes ranging from a few mm to 1.5 cm; the cumulative average slip magnitude in a zone is up to 10 cm. The deformation bands heaves, in aggregate form, accommodate a small isotropic horizontal extension (strain <0.005). The individual shear deformation bands show abutting T-junctions, veering, curving, and merging where they mechanically interact. Crosscutting relationships are rare. The interactions of the deformation bands are similar to those of mode I opening fractures. The documented fault networks have important implications for evaluating the geometry of km-scale polygonal fault systems in the subsurface, top seal integrity, as well as constraining paleo-tectonic stress regimes.
Deformations of superconformal theories
Córdova, Clay; Dumitrescu, Thomas T.; Intriligator, Kenneth
2016-11-22
Here, we classify possible supersymmetry-preserving relevant, marginal, and irrelevant deformations of unitary superconformal theories in d ≥ 3 dimensions. Our method only relies on symmetries and unitarity. Hence, the results are model independent and do not require a Lagrangian description. Two unifying themes emerge: first, many theories admit deformations that reside in multiplets together with conserved currents. Such deformations can lead to modifications of the supersymmetry algebra by central and noncentral charges. Second, many theories with a sufficient amount of supersymmetry do not admit relevant or marginal deformations, and some admit neither. The classification is complicated by the fact thatmore » short superconformal multiplets display a rich variety of sporadic phenomena, including supersymmetric deformations that reside in the middle of a multiplet. We illustrate our results with examples in diverse dimensions. In particular, we explain how the classification of irrelevant supersymmetric deformations can be used to derive known and new constraints on moduli-space effective actions.« less
A Graph Based Methodology for Temporal Signature Identification from HER.
Wang, Fei; Liu, Chuanren; Wang, Yajuan; Hu, Jianying; Yu, Guoqiang
2015-01-01
Data driven technology is believed to be a promising technique for transforming the current status of healthcare. Electronic Health Records (EHR) is one of the main carriers for conducting the data driven healthcare research, where the goal is to derive insights from healthcare data and utilize such insights to improve the quality of care delivery. Due to the progression nature of human disease, one important aspect for analyzing healthcare data is temporality, which suggests the temporal relationships among different healthcare events and how their values evolve over time. Sequential pattern mining is a popular tool to extract time-invariant patterns from discrete sequences and has been applied in analyzing EHR before. However, due to the complexity of EHR, those approaches usually suffers from the pattern explosion problem, which means that a huge number of patterns will be detected with improper setting of the support threshold. To address this challenge, in this paper, we develop a novel representation, namely the temporal graph, for event sequences like EHR, wherein the nodes are medical events and the edges indicate the temporal relationships among those events in patient EHRs. Based on the temporal graph representation, we further develop an approach for temporal signature identification to identify the most significant and interpretable graph bases as temporal signatures, and the expressing coefficients can be treated as the embeddings of the patients in such temporal signature space. Our temporal signature identification framework is also flexible to incorporate semi-supervised/supervised information. We validate our framework on two real-world tasks. One is predicting the onset risk of heart failure. The other is predicting the risk of heart failure related hospitalization for patients with COPD pre-condition. Our results show that the prediction performance in both tasks can be improved by the proposed approaches.
A Graph Based Methodology for Temporal Signature Identification from EHR
Wang, Fei; Liu, Chuanren; Wang, Yajuan; Hu, Jianying; Yu, Guoqiang
2015-01-01
Data driven technology is believed to be a promising technique for transforming the current status of healthcare. Electronic Health Records (EHR) is one of the main carriers for conducting the data driven healthcare research, where the goal is to derive insights from healthcare data and utilize such insights to improve the quality of care delivery. Due to the progression nature of human disease, one important aspect for analyzing healthcare data is temporality, which suggests the temporal relationships among different healthcare events and how their values evolve over time. Sequential pattern mining is a popular tool to extract time-invariant patterns from discrete sequences and has been applied in analyzing EHR before. However, due to the complexity of EHR, those approaches usually suffers from the pattern explosion problem, which means that a huge number of patterns will be detected with improper setting of the support threshold. To address this challenge, in this paper, we develop a novel representation, namely the temporal graph, for event sequences like EHR, wherein the nodes are medical events and the edges indicate the temporal relationships among those events in patient EHRs. Based on the temporal graph representation, we further develop an approach for temporal signature identification to identify the most significant and interpretable graph bases as temporal signatures, and the expressing coefficients can be treated as the embeddings of the patients in such temporal signature space. Our temporal signature identification framework is also flexible to incorporate semi-supervised/supervised information. We validate our framework on two real-world tasks. One is predicting the onset risk of heart failure. The other is predicting the risk of heart failure related hospitalization for patients with COPD pre-condition. Our results show that the prediction performance in both tasks can be improved by the proposed approaches. PMID:26958267
Finite-size effect of η-deformed AdS5 × S5 at strong coupling
NASA Astrophysics Data System (ADS)
Ahn, Changrim
2017-04-01
We compute Lüscher corrections for a giant magnon in the η-deformed (AdS5×S5)η using the su(2 | 2) q-invariant S-matrix at strong coupling and compare with the finite-size effect of the corresponding string state, derived previously. We find that these two results match and confirm that the su(2 | 2) q-invariant S-matrix is describing world-sheet excitations of the η-deformed background.
Appraisal of transport and deformation in shale reservoirs using natural noble gas tracers
Heath, Jason E.; Kuhlman, Kristopher L.; Robinson, David G.; Bauer, Stephen J.; Gardner, William Payton
2015-09-01
This report presents efforts to develop the use of in situ naturally-occurring noble gas tracers to evaluate transport mechanisms and deformation in shale hydrocarbon reservoirs. Noble gases are promising as shale reservoir diagnostic tools due to their sensitivity of transport to: shale pore structure; phase partitioning between groundwater, liquid, and gaseous hydrocarbons; and deformation from hydraulic fracturing. Approximately 1.5-year time-series of wellhead fluid samples were collected from two hydraulically-fractured wells. The noble gas compositions and isotopes suggest a strong signature of atmospheric contribution to the noble gases that mix with deep, old reservoir fluids. Complex mixing and transport of fracturing fluid and reservoir fluids occurs during production. Real-time laboratory measurements were performed on triaxially-deforming shale samples to link deformation behavior, transport, and gas tracer signatures. Finally, we present improved methods for production forecasts that borrow statistical strength from production data of nearby wells to reduce uncertainty in the forecasts.
Scope and applications of translation invariant wavelets to image registration
NASA Technical Reports Server (NTRS)
Chettri, Samir; LeMoigne, Jacqueline; Campbell, William
1997-01-01
The first part of this article introduces the notion of translation invariance in wavelets and discusses several wavelets that have this property. The second part discusses the possible applications of such wavelets to image registration. In the case of registration of affinely transformed images, we would conclude that the notion of translation invariance is not really necessary. What is needed is affine invariance and one way to do this is via the method of moment invariants. Wavelets or, in general, pyramid processing can then be combined with the method of moment invariants to reduce the computational load.
Signature molecular descriptor : advanced applications.
Visco, Donald Patrick, Jr.
2010-04-01
In this work we report on the development of the Signature Molecular Descriptor (or Signature) for use in the solution of inverse design problems as well as in highthroughput screening applications. The ultimate goal of using Signature is to identify novel and non-intuitive chemical structures with optimal predicted properties for a given application. We demonstrate this in three studies: green solvent design, glucocorticoid receptor ligand design and the design of inhibitors for Factor XIa. In many areas of engineering, compounds are designed and/or modified in incremental ways which rely upon heuristics or institutional knowledge. Often multiple experiments are performed and the optimal compound is identified in this brute-force fashion. Perhaps a traditional chemical scaffold is identified and movement of a substituent group around a ring constitutes the whole of the design process. Also notably, a chemical being evaluated in one area might demonstrate properties very attractive in another area and serendipity was the mechanism for solution. In contrast to such approaches, computer-aided molecular design (CAMD) looks to encompass both experimental and heuristic-based knowledge into a strategy that will design a molecule on a computer to meet a given target. Depending on the algorithm employed, the molecule which is designed might be quite novel (re: no CAS registration number) and/or non-intuitive relative to what is known about the problem at hand. While CAMD is a fairly recent strategy (dating to the early 1980s), it contains a variety of bottlenecks and limitations which have prevented the technique from garnering more attention in the academic, governmental and industrial institutions. A main reason for this is how the molecules are described in the computer. This step can control how models are developed for the properties of interest on a given problem as well as how to go from an output of the algorithm to an actual chemical structure. This report
Invariance of bipartite separability and PPT-probabilities over Casimir invariants of reduced states
NASA Astrophysics Data System (ADS)
Slater, Paul B.
2016-09-01
Milz and Strunz (J Phys A 48:035306, 2015) recently studied the probabilities that two-qubit and qubit-qutrit states, randomly generated with respect to Hilbert-Schmidt (Euclidean/flat) measure, are separable. They concluded that in both cases, the separability probabilities (apparently exactly 8/33 in the two-qubit scenario) hold constant over the Bloch radii ( r) of the single-qubit subsystems, jumping to 1 at the pure state boundaries (r=1). Here, firstly, we present evidence that in the qubit-qutrit case, the separability probability is uniformly distributed, as well, over the generalized Bloch radius ( R) of the qutrit subsystem. While the qubit (standard) Bloch vector is positioned in three-dimensional space, the qutrit generalized Bloch vector lives in eight-dimensional space. The radii variables r and R themselves are the lengths/norms (being square roots of quadratic Casimir invariants) of these ("coherence") vectors. Additionally, we find that not only are the qubit-qutrit separability probabilities invariant over the quadratic Casimir invariant of the qutrit subsystem, but apparently also over the cubic one—and similarly the case, more generally, with the use of random induced measure. We also investigate two-qutrit (3 × 3) and qubit- qudit (2 × 4) systems—with seemingly analogous positive partial transpose-probability invariances holding over what has been termed by Altafini the partial Casimir invariants of these systems.
Temperature effects on airgun signatures
Langhammer, J.; Landroe, M. )
1993-08-01
Experiments in an 850 liter water tank were performed in order to study temperature effects on airgun signatures, and to achieve a better understanding of the physical processes that influence an airgun signature. The source was a bolt airgun with a chamber volume of 1.6 cu. in. The pressure used was 100 bar and the gun depth was 0.5 m. The water temperature in the tank was varied between 5 C and 45 C. Near-field signatures were recorded at different water temperatures. Typical signature characteristics such as the primary-to-bubble ratio and the bubble time period increased with increasing water temperature. For comparison and in order to check whether this is valid for larger guns, computer modeling of airguns with chamber volumes of 1.6 and 40 cu. in. was performed. In modeling the same behavior of the signatures with increasing water temperature can be observed. The increase in the primary-to-bubble ratio and the bubble time period with increasing water temperature can be explained by an increased mass transfer across the bubble wall.
Watson-Crick pairing, the Heisenberg group and Milnor invariants.
Gadgil, Siddhartha
2009-07-01
We study the secondary structure of RNA determined by Watson-Crick pairing without pseudo-knots using Milnor invariants of links. We focus on the first non-trivial invariant, which we call the Heisenberg invariant. The Heisenberg invariant, which is an integer, can be interpreted in terms of the Heisenberg group as well as in terms of lattice paths. We show that the Heisenberg invariant gives a lower bound on the number of unpaired bases in an RNA secondary structure. We also show that the Heisenberg invariant can predict allosteric structures for RNA. Namely, if the Heisenberg invariant is large, then there are widely separated local maxima (i.e., allosteric structures) for the number of Watson-Crick pairs found.
Invariant performance of a volume holographic wavelet correlation processor
NASA Astrophysics Data System (ADS)
Feng, Wenyi; Yan, Yingbai; Jin, Guofan; Wu, Minxian; He, Qingsheng
2000-04-01
A multichannel optical correlation processor based on volume holographic associative memory in a photorefractive crystal and wavelet transform is proposed for human face recognition. Distortions due to shift, rotation, scale, and partial hiding are studied to understand invariant performance of the processor. Our results show that shift-invariance and rotation-invariance are key problems for practical applications of the processor to human face recognition. Theoretical analysis and simulation conclude that the focal length of the Fourier transform lens is the main factor to affect shift-invariance of the processor. Shift-invariance would be improved if the focal length were enlarged. With regard to rotation-invariance, a novel mechanism to recognize human faces with any rotation angle is proposed and testified by experiments. The processor is more practical with the improvement of invariance.
A Balanced Comparison of Object Invariances in Monkey IT Neurons
2017-01-01
Abstract Our ability to recognize objects across variations in size, position, or rotation is based on invariant object representations in higher visual cortex. However, we know little about how these invariances are related. Are some invariances harder than others? Do some invariances arise faster than others? These comparisons can be made only upon equating image changes across transformations. Here, we targeted invariant neural representations in the monkey inferotemporal (IT) cortex using object images with balanced changes in size, position, and rotation. Across the recorded population, IT neurons generalized across size and position both stronger and faster than to rotations in the image plane as well as in depth. We obtained a similar ordering of invariances in deep neural networks but not in low-level visual representations. Thus, invariant neural representations dynamically evolve in a temporal order reflective of their underlying computational complexity. PMID:28413827
Renormalization group invariants in the MSSM and its extensions
NASA Astrophysics Data System (ADS)
Demir, Durmus A.
2005-11-01
We derive one-loop renormalization group (RG) invariant observables and analyze their phenomenological implications in the MSSM and its μ problem solving extensions, U(1)' model and NMSSM. We show that there exist several RG invariants in the gauge, Yukawa and soft-breaking sectors of each model. In general, RG invariants are highly useful for projecting experimental data to messenger scale, for revealing correlations among the model parameters, and for probing the mechanism that breaks supersymmetry. The Yukawa couplings and trilinear soft terms in U(1)' model and NMSSM do not form RG invariants though there exist approximate invariants in low tan β domain. In the NMSSM, there are no invariants that contain the Higgs mass-squareds. We provide a comparative analysis of RG invariants in all three models and analyze their model-building and phenomenological implications by a number of case studies.
Ben Ayed, Ismail; Punithakumar, Kumaradevan; Garvin, Gregory; Romano, Walter; Li, Shuo
2011-01-01
This study investigates novel object-interaction priors for graph cut image segmentation with application to intervertebral disc delineation in magnetic resonance (MR) lumbar spine images. The algorithm optimizes an original cost function which constrains the solution with learned prior knowledge about the geometric interactions between different objects in the image. Based on a global measure of similarity between distributions, the proposed priors are intrinsically invariant with respect to translation and rotation. We further introduce a scale variable from which we derive an original fixed-point equation (FPE), thereby achieving scale-invariance with only few fast computations. The proposed priors relax the need of costly pose estimation (or registration) procedures and large training sets (we used a single subject for training), and can tolerate shape deformations, unlike template-based priors. Our formulation leads to an NP-hard problem which does not afford a form directly amenable to graph cut optimization. We proceeded to a relaxation of the problem via an auxiliary function, thereby obtaining a nearly real-time solution with few graph cuts. Quantitative evaluations over 60 intervertebral discs acquired from 10 subjects demonstrated that the proposed algorithm yields a high correlation with independent manual segmentations by an expert. We further demonstrate experimentally the invariance of the proposed geometric attributes. This supports the fact that a single subject is sufficient for training our algorithm, and confirms the relevance of the proposed priors to disc segmentation.
Experimental Deformation of Magnetite
NASA Astrophysics Data System (ADS)
Till, J. L.; Rybacki, E.; Morales, L. F. G.
2015-12-01
Magnetite is an important iron ore mineral and the most prominent Fe-oxide phase in the Earth's crust. The systematic occurrence of magnetite in zones of intense deformation in oceanic core complexes suggests that it may play a role in strain localization in some silicate rocks. We performed a series of high-temperature deformation experiments on synthetic magnetite aggregates and natural single crystals to characterize the rheological behavior of magnetite. As starting material, we used fine-grained magnetite powder that was hot isostatically pressed at 1100°C for several hours, resulting in polycrystalline material with a mean grain size of around 40 μm and containing 3-5% porosity. Samples were deformed to 15-20% axial strain under constant load (approximating constant stress) conditions in a Paterson-type gas apparatus for triaxial deformation at temperatures between 900 and 1100°C and 300 MPa confining pressure. The aggregates exhibit typical power-law creep behavior. At high stresses, samples deformed by dislocation creep exhibit stress exponents close to 3, revealing a transition to near-Newtonian creep with stress exponents around 1.3 at lower stresses. Natural magnetite single crystals deformed at 1 atm pressure and temperatures between 950°C and 1150 °C also exhibit stress exponents close to 3, but with lower flow stresses and a lower apparent activation energy than the aggregates. Such behavior may result from the different oxygen fugacity buffers used. Crystallographic-preferred orientations in all polycrystalline samples are very weak and corroborate numerical models of CPO development, suggesting that texture development in magnetite may be inherently slow compared with lower symmetry phases. Comparison of our results with experimental deformation data for various silicate minerals suggests that magnetite should be weaker than most silicates during ductile creep in dry igneous rocks.
Graph Analytics for Signature Discovery
Hogan, Emilie A.; Johnson, John R.; Halappanavar, Mahantesh; Lo, Chaomei
2013-06-01
Within large amounts of seemingly unstructured data it can be diffcult to find signatures of events. In our work we transform unstructured data into a graph representation. By doing this we expose underlying structure in the data and can take advantage of existing graph analytics capabilities, as well as develop new capabilities. Currently we focus on applications in cybersecurity and communication domains. Within cybersecurity we aim to find signatures for perpetrators using the pass-the-hash attack, and in communications we look for emails or phone calls going up or down a chain of command. In both of these areas, and in many others, the signature we look for is a path with certain temporal properties. In this paper we discuss our methodology for finding these temporal paths within large graphs.
Measurement of sniper infrared signatures
NASA Astrophysics Data System (ADS)
Kastek, M.; Dulski, R.; Trzaskawka, P.; Bieszczad, G.
2009-09-01
The paper presents some practical aspects of sniper IR signature measurements. Description of particular signatures for sniper and background in typical scenarios has been presented. We take into consideration sniper activities in open area as well as in urban environment. The measurements were made at field test ground. High precision laboratory measurements were also performed. Several infrared cameras were used during measurements to cover all measurement assumptions. Some of the cameras are measurement class devices with high accuracy and speed. The others are microbolometer cameras with FPA detector similar to those used in real commercial counter-sniper systems. The registration was made in SWIR and LWIR spectral bands simultaneously. An ultra fast visual camera was also used for visible spectra registration. Exemplary sniper IR signatures for typical situation were presented.
Signature Visualization of Software Binaries
Panas, T
2008-07-01
In this paper we present work on the visualization of software binaries. In particular, we utilize ROSE, an open source compiler infrastructure, to pre-process software binaries, and we apply a landscape metaphor to visualize the signature of each binary (malware). We define the signature of a binary as a metric-based layout of the functions contained in the binary. In our initial experiment, we visualize the signatures of a series of computer worms that all originate from the same line. These visualizations are useful for a number of reasons. First, the images reveal how the archetype has evolved over a series of versions of one worm. Second, one can see the distinct changes between version. This allows the viewer to form conclusions about the development cycle of a particular worm.
Multidimensional signatures in antimicrobial peptides
Yount, Nannette Y.; Yeaman, Michael R.
2004-01-01
Conventional analyses distinguish between antimicrobial peptides by differences in amino acid sequence. Yet structural paradigms common to broader classes of these molecules have not been established. The current analyses examined the potential conservation of structural themes in antimicrobial peptides from evolutionarily diverse organisms. Using proteomics, an antimicrobial peptide signature was discovered to integrate stereospecific sequence patterns and a hallmark three-dimensional motif. This striking multidimensional signature is conserved among disulfide-containing antimicrobial peptides spanning biological kingdoms, and it transcends motifs previously limited to defined peptide subclasses. Experimental data validating this model enabled the identification of previously unrecognized antimicrobial activity in peptides of known identity. The multidimensional signature model provides a unifying structural theme in broad classes of antimicrobial peptides, will facilitate discovery of antimicrobial peptides as yet unknown, and offers insights into the evolution of molecular determinants in these and related host defense effector molecules. PMID:15118082
Deformations of anti-de Sitter black holes
NASA Astrophysics Data System (ADS)
Detournay, Stephane
2006-11-01
This PhD thesis mainly deals with deformations of locally anti-de Sitter black holes, focusing in particular on BTZ black holes. We first study the generic rotating and (extended) non-rotating BTZ black holes within a pseudo-Riemannian symmetric spaces framework, emphasize on the role played by solvable subgroups of SL(2,R) in the black hole structure and derive their global geometry in a group-theoretical way. We analyse how these observations are transposed in the case of higher-dimensional locally AdS black holes. We then show that there exists, in SL(2,R), a family of twisted conjugacy classes which give rise to winding symmetric WZW D1-branes in a BTZ black hole background. The term "deformation" is then considered in two distinct ways. On the one hand, we deform the algebra of functions on the branes in the sense of (strict) deformation quantization, giving rise to a "noncommutative black hole". In the same context, we investigate the question of invariant deformations of the hyperbolic plane and present explicit formulae. On the other hand, we explore the moduli space of the (orbifolded) SL(2,R) WZW model by studying its marginal deformations, yielding namely a new class of exact black string solutions in string theory. These deformations also allow us to relate the D1-branes in BTZ black holes to D0-branes in the 2D black hole. A fair proportion of this thesis consists of (hopefully) pedagogical short introductions to various subjects: deformation quantization, string theory, WZW models, symmetric spaces, symplectic and Poisson geometry.
Do scale-invariant fluctuations imply the breaking of de Sitter invariance?
NASA Astrophysics Data System (ADS)
Youssef, A.
2013-01-01
The quantization of the massless minimally coupled (mmc) scalar field in de Sitter spacetime is known to be a non-trivial problem due to the appearance of strong infrared (IR) effects. In particular, the scale-invariance of the CMB power-spectrum - certainly one of the most successful predictions of modern cosmology - is widely believed to be inconsistent with a de Sitter invariant mmc two-point function. Using a Cesaro-summability technique to properly define an otherwise divergent Fourier transform, we show in this Letter that de Sitter symmetry breaking is not a necessary consequence of the scale-invariant fluctuation spectrum. We also generalize our result to the tachyonic scalar fields, i.e. the discrete series of representations of the de Sitter group, that suffer from similar strong IR effects.
Mousavi Kahaki, Seyed Mostafa; Nordin, Md Jan; Ashtari, Amir H.; J. Zahra, Sophia
2016-01-01
An invariant feature matching method is proposed as a spatially invariant feature matching approach. Deformation effects, such as affine and homography, change the local information within the image and can result in ambiguous local information pertaining to image points. New method based on dissimilarity values, which measures the dissimilarity of the features through the path based on Eigenvector properties, is proposed. Evidence shows that existing matching techniques using similarity metrics—such as normalized cross-correlation, squared sum of intensity differences and correlation coefficient—are insufficient for achieving adequate results under different image deformations. Thus, new descriptor’s similarity metrics based on normalized Eigenvector correlation and signal directional differences, which are robust under local variation of the image information, are proposed to establish an efficient feature matching technique. The method proposed in this study measures the dissimilarity in the signal frequency along the path between two features. Moreover, these dissimilarity values are accumulated in a 2D dissimilarity space, allowing accurate corresponding features to be extracted based on the cumulative space using a voting strategy. This method can be used in image registration applications, as it overcomes the limitations of the existing approaches. The output results demonstrate that the proposed technique outperforms the other methods when evaluated using a standard dataset, in terms of precision-recall and corner correspondence. PMID:26985996
Generic dark matter signature for gamma-ray telescopes
NASA Astrophysics Data System (ADS)
Barger, V.; Gao, Y.; Keung, W.-Y.; Marfatia, D.
2009-09-01
We describe a characteristic signature of dark matter (DM) annihilation or decay into gamma rays. We show that if the total angular momentum of the initial DM particle(s) vanishes, and helicity suppression operates to prevent annihilation/decay into light fermion pairs, then the amplitude for the dominant 3-body final state f+f-γ has a unique form dictated by gauge invariance. This amplitude and the corresponding energy spectra hold for annihilation of DM Majorana fermions or self-conjugate scalars, and for decay of DM scalars, thus encompassing a variety of possibilities. Within this scenario, we analyze Fermi LAT, PAMELA, and HESS data, and predict a hint in future Fermi gamma-ray data that portends a striking signal at atmospheric Cherenkov telescopes.