NASA Technical Reports Server (NTRS)
Bennett, David P.
1988-01-01
Cosmic strings are linear topological defects which are predicted by some grand unified theories to form during a spontaneous symmetry breaking phase transition in the early universe. They are the basis for the only theories of galaxy formation aside from quantum fluctuations from inflation based on fundamental physics. In contrast to inflation, they can also be observed directly through gravitational lensing and their characterisitc microwave background anisotropy. It was recently discovered that details of cosmic string evolution are very differnt from the so-called standard model that was assumed in most of the string-induced galaxy formation calculations. Therefore, the details of galaxy formation in the cosmic string models are currently very uncertain.
Cosmic strings and superconducting cosmic strings
NASA Technical Reports Server (NTRS)
Copeland, Edmund
1988-01-01
The possible consequences of forming cosmic strings and superconducting cosmic strings in the early universe are discussed. Lecture 1 describes the group theoretic reasons for and the field theoretic reasons why cosmic strings can form in spontaneously broken gauge theories. Lecture 2 discusses the accretion of matter onto string loops, emphasizing the scenario with a cold dark matter dominated universe. In lecture 3 superconducting cosmic strings are discussed, as is a mechanism which leads to the formation of structure from such strings.
Steer, Daniele A.; Vachaspati, Tanmay
2011-02-15
The time-dependent metric of a cosmic string leads to an effective interaction between the string and photons--the ''gravitational Aharonov-Bohm'' effect--and causes cosmic strings to emit light. We evaluate the radiation of pairs of photons from cosmic strings and find that the emission from cusps, kinks and kink-kink collisions occurs with a flat spectrum at all frequencies up to the string scale. Further, cusps emit a beam of photons, kinks emit along a curve, and the emission at a kink-kink collision is in all directions. The emission of light from cosmic strings could provide an important new observational signature of cosmic strings that is within reach of current experiments for a range of string tensions.
Supermassive cosmic string compactifications
Blanco-Pillado, Jose J.; Reina, Borja; Sousa, Kepa; Urrestilla, Jon E-mail: borja.reina@ehu.es E-mail: jon.urrestilla@ehu.es
2014-06-01
The space-time dimensions transverse to a static straight cosmic string with a sufficiently large tension (supermassive cosmic strings) are compact and typically have a singularity at a finite distance form the core. In this paper, we discuss how the presence of multiple supermassive cosmic strings in the 4d Abelian-Higgs model can induce the spontaneous compactification of the transverse space and explicitly construct solutions where the gravitational background becomes regular everywhere. We discuss the embedding of this model in N = 1 supergravity and show that some of these solutions are half-BPS, in the sense that they leave unbroken half of the supersymmetries of the model.
NASA Technical Reports Server (NTRS)
Gregory, Ruth
1988-01-01
The effect of an infinite cosmic string on a cosmological background is investigated. It is found that the metric is approximately a scaled version of the empty space string metric, i.e., conical in nature. Results are used to place bounds on the amount of cylindrical gravitational radiation currently emitted by such a string. The gravitational radiation equations are then analyzed explicitly and it is shown that even initially large disturbances are rapidly damped as the expansion proceeds. The implications of the gravitational radiation background and the limitations of the quadrupole formula are discussed.
Inflation, string theory and cosmic strings
NASA Astrophysics Data System (ADS)
Chernoff, David F.; Tye, S.-H. Henry
2015-02-01
At its very beginning, the universe is believed to have grown exponentially in size via the mechanism of inflation. The almost scale-invariant density perturbation spectrum predicted by inflation is strongly supported by cosmological observations, in particular the cosmic microwave background (MB) radiation. However, the universe's precise inflationary scenario remains a profound problem for cosmology and for fundamental physics. String theory, the most-studied theory as the final physical theory of nature, should provide an answer to this question. Some of the proposals on how inflation is realized in string theory are reviewed. Since everything is made of strings, some string loops of cosmological sizes are likely to survive in the hot big bang that followed inflation. They appear as cosmic strings, which can have intricate properties. Because of the warped geometry in flux compactification of the extra spatial dimensions in string theory, some of the cosmic strings may have tensions substantially below the Planck or string scale. Such strings cluster in a manner similar to dark matter leading to hugely enhanced densities. As a result, numerous fossil remnants of the low tension cosmic strings may exist within the galaxy. They can be revealed through the optical lensing of background stars in the near future and studied in detail through gravitational wave emission. We anticipate that these cosmic strings will permit us to address central questions about the properties of string theory as well as the birth of our universe.
Cosmic strings and galaxy formation
NASA Technical Reports Server (NTRS)
Bertschinger, Edmund
1989-01-01
The cosmogonical model proposed by Zel'dovich and Vilenkin (1981), in which superconducting cosmic strings act as seeds for the origin of structure in the universe, is discussed, summarizing the results of recent theoretical investigations. Consideration is given to the formation of cosmic strings, the microscopic structure of strings, gravitational effects, cosmic string evolution, and the formation of galaxies and large-scale structure. Simulation results are presented in graphs, and several outstanding issues are listed and briefly characterized.
Slagter, R. J.
2010-06-23
We present a cosmic string solution in Einstein-Yang-Mills Gauss-Bonnet theory on a warped 5 dimensional space-time conform the Randall-Sundrum-2 theory. In a simplipied model, we find an exact solutions with exponential decreasing or periodic warp function. In a more general setting, where the metric- and Yang-Mills components depend on both scales and one of the YM components resides in the bulk, we find a time dependent numerical solution.
Reionization from cosmic string loops
Olum, Ken D.; Vilenkin, Alexander
2006-09-15
Loops formed from a cosmic string network at early times would act as seeds for early formation of halos, which would form galaxies and lead to early reionization. With reasonable guesses about astrophysical and string parameters, the cosmic string scale G{mu} must be no more than about 3x10{sup -8} to avoid conflict with the reionization redshift found by WMAP. The bound is much stronger for superstring models with a small string reconnection probability. For values near the bound, cosmic string loops may explain the discrepancy between the WMAP value and theoretical expectations.
Evolution of cosmic string networks
NASA Technical Reports Server (NTRS)
Albrecht, Andreas; Turok, Neil
1989-01-01
Results on cosmic strings are summarized including: (1) the application of non-equilibrium statistical mechanics to cosmic string evolution; (2) a simple one scale model for the long strings which has a great deal of predictive power; (3) results from large scale numerical simulations; and (4) a discussion of the observational consequences of our results. An upper bound on G mu of approximately 10(-7) emerges from the millisecond pulsar gravity wave bound. How numerical uncertainties affect this are discussed. Any changes which weaken the bound would probably also give the long strings the dominant role in producing observational consequences.
Evolution of cosmic string networks
NASA Technical Reports Server (NTRS)
Albrecht, Andreas; Turok, Neil
1989-01-01
A discussion of the evolution and observable consequences of a network of cosmic strings is given. A simple model for the evolution of the string network is presented, and related to the statistical mechanics of string networks. The model predicts the long string density throughout the history of the universe from a single parameter, which researchers calculate in radiation era simulations. The statistical mechanics arguments indicate a particular thermal form for the spectrum of loops chopped off the network. Detailed numerical simulations of string networks in expanding backgrounds are performed to test the model. Consequences for large scale structure, the microwave and gravity wave backgrounds, nucleosynthesis and gravitational lensing are calculated.
Cosmic necklaces from string theory
Leblond, Louis; Wyman, Mark
2007-06-15
We present the properties of a cosmic superstring network in the scenario of flux compactification. An infinite family of strings, the (p,q) strings, are allowed to exist. The flux compactification leads to a string tension that is periodic in p. Monopoles, appearing here as beads on a string, are formed in certain interactions in such networks. This allows bare strings to become cosmic necklaces. We study network evolution in this scenario, outlining what conditions are necessary to reach a cosmologically viable scaling solution. We also analyze the physics of the beads on a cosmic necklace, and present general conditions for which they will be cosmologically safe, leaving the network's scaling undisturbed. In particular, we find that a large average loop size is sufficient for the beads to be cosmologically safe. Finally, we argue that loop formation will promote a scaling solution for the interbead distance in some situations.
Fireballs from superconducting cosmic strings
NASA Astrophysics Data System (ADS)
Gruzinov, Andrei; Vilenkin, Alexander
2017-01-01
Thermalized fireballs should be created by cusp events on superconducting cosmic strings. This simple notion allows to reliably estimate particle emission from the cusps in a given background magnetic field. With plausible assumptions about intergalactic magnetic fields, the cusp events can produce observable fluxes of high-energy photons and neutrinos with unique signatures.
Cosmic string catalysis of skyrmion decay
NASA Technical Reports Server (NTRS)
Gregory, Ruth; Davis, Anne-Christine; Brandenberger, Robert
1988-01-01
The Callan-Witten picture is developed for monopole catalyzed skyrmion decay in order to analyze the corresponding cosmic string scenario. It is discovered that cosmic strings (both ordinary and superconducting) can catalyze proton decay, but that this catalysis only occurs on the scale of the core of the string. In order to do this we have to develop a vortex model for the superconducting string. An argument is also given for the difference in the enhancement factors for monopoles and strings.
CMB constraints on cosmic strings and superstrings
NASA Astrophysics Data System (ADS)
Charnock, Tom; Avgoustidis, Anastasios; Copeland, Edmund J.; Moss, Adam
2016-06-01
We present the first complete Markov chain Monte Carlo analysis of cosmological models with evolving cosmic (super)string networks, using the unconnected segment model in the unequal-time correlator formalism. For ordinary cosmic string networks, we derive joint constraints on Λ cold dark matter (CDM) and string network parameters, namely the string tension G μ , the loop-chopping efficiency cr, and the string wiggliness α . For cosmic superstrings, we obtain joint constraints on the fundamental string tension G μF, the string coupling gs, the self-interaction coefficient cs, and the volume of compact extra dimensions w . This constitutes the most comprehensive CMB analysis of Λ CDM cosmology+strings to date. For ordinary cosmic string networks our updated constraint on the string tension, obtained using Planck2015 temperature and polarization data, is G μ <1.1 ×10-7 in relativistic units, while for cosmic superstrings our constraint on the fundamental string tension after marginalizing over gs, cs, and w is G μF<2.8 ×10-8.
Brane Inflation: From Superstring to Cosmic Strings
Tye, S.-H. Henry
2004-12-10
Brane inflation, where branes move towards each other in the brane world, has been shown to be quite natural in superstring theory. Inflation ends when branes collide and heat the universe, initiating the hot big bang. Cosmic strings (but not domain walls or monopoles) are copiously produced during the brane collision. Using the COBE data on the temperature anisotropy in the cosmic microwave background, the cosmic string tension {mu} is estimated to be around 10 -6 > G{mu} > 10-11, while the present observational bound is 7 x 10 -7 > G{mu}. This implies that the anisotropy that seeds structure formation comes mostly from inflation, but with a small component (< 10%) from cosmic string effects. This cosmic string effect should be testable in the near future via gravitational lensing, the cosmic microwave background radiation, and/or gravitational wave detectors like LIGO II/VIRGO.
Cosmic strings - A problem or a solution?
NASA Technical Reports Server (NTRS)
Bennett, David P.; Bouchet, Francois R.
1988-01-01
The most fundamental issue in the theory of cosmic strings is addressed by means of Numerical Simulations: the existence of a scaling solution. The resolution of this question will determine whether cosmic strings can form the basis of an attractive theory of galaxy formation or prove to be a cosmological disaster like magnetic monopoles or domain walls. After a brief discussion of our numerical technique, results are presented which, though still preliminary, offer the best support to date of this scaling hypothesis.
Cosmic microwave anisotropies from BPS semilocal strings
Urrestilla, Jon; Bevis, Neil; Hindmarsh, Mark; Kunz, Martin; Liddle, Andrew R E-mail: n.bevis@imperial.ac.uk E-mail: martin.kunz@physics.unige.ch
2008-07-15
We present the first ever calculation of cosmic microwave background (CMB) anisotropy power spectra from semilocal cosmic strings, obtained via simulations of a classical field theory. Semilocal strings are a type of non-topological defect arising in some models of inflation motivated by fundamental physics, and are thought to relax the constraints on the symmetry breaking scale as compared to models with (topological) cosmic strings. We derive constraints on the model parameters, including the string tension parameter {mu}, from fits to cosmological data, and find that in this regard Bogomol'nyi-Prasad-Sommerfield (BPS) semilocal strings resemble global textures more than topological strings. The observed microwave anisotropy at l=10 is reproduced if G{mu} = 5.3 Multiplication-Sign 10{sup -6} (G is Newton's constant). However as with other defects the spectral shape does not match observations, and in models with inflationary perturbations plus semilocal strings the 95% confidence level upper bound is G{mu}<2.0 Multiplication-Sign 10{sup -6} when CMB, Hubble key project and big bang nucleosynthesis data are used (cf G{mu}<0.9 Multiplication-Sign 10{sup -6} for cosmic strings). We additionally carry out a Bayesian model comparison of several models with and without defects, showing that models with defects are neither conclusively favoured nor disfavoured at present.
Cosmic Strings Stabilized by Quantum Fluctuations
NASA Astrophysics Data System (ADS)
Weigel, H.
2017-03-01
Fermion quantum corrections to the energy of cosmic strings are computed. A number of rather technical tools are needed to formulate this correction, and isospin and gauge invariance are employed to verify consistency of these tools. These corrections must also be included when computing the energy of strings that are charged by populating fermion bound states in its background. It is found that charged strings are dynamically stabilized in theories similar to the standard model of particle physics.
Constraints on cosmic strings due to black holes formed from collapsed cosmic string loops
NASA Technical Reports Server (NTRS)
Caldwell, R. R.; Gates, Evalyn
1993-01-01
The cosmological features of primordial black holes formed from collapsed cosmic string loops are studied. Observational restrictions on a population of primordial black holes are used to restrict f, the fraction of cosmic string loops which collapse to form black holes, and mu, the cosmic string mass-per-unit length. Using a realistic model of cosmic strings, we find the strongest restriction on the parameters f and mu is due to the energy density in 100MeV photons radiated by the black holes. We also find that inert black hole remnants cannot serve as the dark matter. If earlier, crude estimates of f are reliable, our results severely restrict mu, and therefore limit the viability of the cosmic string large-scale structure scenario.
Cosmic Microwave Background spectral distortions from cosmic string loops
Anthonisen, Madeleine; Brandenberger, Robert; Laguë, Alex; Morrison, Ian A.; Xia, Daixi E-mail: rhb@physics.mcgill.ca E-mail: imorrison@physics.mcgill.ca
2016-02-01
Cosmic string loops contain cusps which decay by emitting bursts of particles. A significant fraction of the released energy is in the form of photons. These photons are injected non-thermally and can hence cause spectral distortions of the Cosmic Microwave Background (CMB). Under the assumption that cusps are robust against gravitational back-reaction, we compute the fractional energy density released as photons in the redshift interval where such non-thermal photon injection causes CMB spectral distortions. Whereas current constraints on such spectral distortions are not strong enough to constrain the string tension, future missions such as the PIXIE experiment will be able to provide limits which rule out a range of string tensions between G μ ∼ 10{sup −15} and G μ ∼ 10{sup −12}, thus ruling out particle physics models yielding these kind of intermediate-scale cosmic strings.
Cosmic string with a light massive neutrino
NASA Technical Reports Server (NTRS)
Albrecht, Andreas; Stebbins, Albert
1992-01-01
We have estimated the power spectra of density fluctuations produced by cosmic strings with neutrino hot dark matter (HDM). Normalizing at 8/h Mpc, we find that the spectrum has more power on small scales than HDM + inflation, less than cold dark matter (CDM) + inflation, and significantly less the CDM + strings. With HDM, large wakes give significant contribution to the power on the galaxy scale and may give rise to large sheets of galaxies.
Cosmic strings: Gravitation without local curvature
Helliwell, T.M.; Konkowski, D.A.
1987-05-01
Cosmic strings are very long, thin structures which might stretch over vast reaches of the universe. If they exist, they would have been formed during phase transitions in the very early universe. The space-time surrounding a straight cosmic string is flat but nontrivial: A two-dimensional spatial section is a cone rather than a plane. This feature leads to unique gravitational effects. The flatness of the cone means that many of the gravitational effects can be understood with no mathematics beyond trigonometry. This includes the observational predictions of the double imaging of quasars and the truncation of the images of galaxies.
Cosmic strings: A problem or a solution
Bennett, D.P.; Bouchet, F.R.
1987-10-01
The most fundamental issue in the theory of cosmic strings is addressed by means of Numerical Simulations: the existence of a scaling solution. The resolution of this question will determine whether cosmic strings can form the basis of an attractive theory of galaxy formation or prove to be a cosmological disaster like magnetic monopoles or domain walls. After a brief discussion of our numerical technique, results are presented which, though still preliminary, offer the best support to date of this scaling hypothesis. 6 refs., 2 figs.
Thin shells joining local cosmic string geometries
NASA Astrophysics Data System (ADS)
Eiroa, Ernesto F.; Rubín de Celis, Emilio; Simeone, Claudio
2016-10-01
In this article we present a theoretical construction of spacetimes with a thin shell that joins two different local cosmic string geometries. We study two types of global manifolds, one representing spacetimes with a thin shell surrounding a cosmic string or an empty region with Minkowski metric, and the other corresponding to wormholes which are not symmetric across the throat located at the shell. We analyze the stability of the static configurations under perturbations preserving the cylindrical symmetry. For both types of geometries we find that the static configurations can be stable for suitable values of the parameters.
Small scale structure on cosmic strings
Albrecht, A.
1989-10-30
I discuss our current understanding of cosmic string evolution, and focus on the question of small scale structure on strings, where most of the disagreements lie. I present a physical picture designed to put the role of the small scale structure into more intuitive terms. In this picture one can see how the small scale structure can feed back in a major way on the overall scaling solution. I also argue that it is easy for small scale numerical errors to feed back in just such a way. The intuitive discussion presented here may form the basis for an analytic treatment of the small structure, which I argue in any case would be extremely valuable in filling the gaps in our resent understanding of cosmic string evolution. 24 refs., 8 figs.
Small scale structure on cosmic strings
NASA Technical Reports Server (NTRS)
Albrecht, Andreas
1989-01-01
The current understanding of cosmic string evolution is discussed, and the focus placed on the question of small scale structure on strings, where most of the disagreements lie. A physical picture designed to put the role of the small scale structure into more intuitive terms is presented. In this picture it can be seen how the small scale structure can feed back in a major way on the overall scaling solution. It is also argued that it is easy for small scale numerical errors to feed back in just such a way. The intuitive discussion presented here may form the basis for an analytic treatment of the small scale structure, which argued in any case would be extremely valuable in filling the gaps in the present understanding of cosmic string evolution.
Search for cosmic strings at MITO.
NASA Astrophysics Data System (ADS)
de Petris, M.; Melchiorri, B.; Melchiorri, F.; Signore, M.
MITO (Millimetric and Infrared Testagrigia Observatory) is a 3 meter telescope dedicated to the study of Cosmic Background Anisotropies. It is located at 3500 m above sea level at Plateau Rosa', Cervinia. The authors describe the Observatory and discuss two ongoing research programs: a cleaning procedure in order to remove galactic dust signals from cosmological data and a search for cosmic strings toward double lensed quasars. Both the programs will be carried out by means of an He-3 photometer operating at the frequencies of 5, 10, 12, 30 cm-1.
Zipping and unzipping of cosmic string loops in collision
Firouzjahi, H.; Karouby, J.; Khosravi, S.; Brandenberger, R.
2009-10-15
In this paper the collision of two cosmic string loops is studied. After collision junctions are formed and the loops are entangled. We show that after their formation the junctions start to unzip and the loops disentangle. This analysis provides a theoretical understanding of the unzipping effect observed in numerical simulations of a network of cosmic strings with more than one type of cosmic strings. The unzipping phenomena have important effects in the evolution of cosmic string networks when junctions are formed upon collision, such as in a network of cosmic superstrings.
Cosmic strings and ultra-high energy cosmic rays
NASA Technical Reports Server (NTRS)
Bhattacharjee, Pijushpani
1989-01-01
The flux is calculated of ultrahigh energy protons due to the process of cusp evaporation from cosmic string loops. For the standard value of the dimensionless cosmic string parameter epsilon is identical to G(sub mu) approx. = 10(exp -6), the flux is several orders of magnitude below the observed cosmic ray flux of ultrahigh energy protons. However, the flux at any energy initially increases as the value of epsilon is decreased. This at first suggests that there may be a lower limit on the value of epsilon, which would imply a lower limit on the temperature of a cosmic string forming phase transition in the early universe. However, the calculation shows that this is not the case -- the particle flux at any energy reaches its highest value at epsilon approx. = 10(exp -15) and it then decreases for further decrease of the value of epsilon. This is due to the fact that for too small values of epsilon (less than 10(exp -15)), the energy loss of the loops through the cusp evaporation process itself (rather than gravitational energy loss of the loops) becomes the dominant factor that controls the behavior of the number density of the loops at the relevant times of emission of the particles. The highest flux at any energy remains at least four orders of magnitude below the observed flux. There is thus no lower limit on epsilon.
Fragmentation of cosmic-string loops
NASA Technical Reports Server (NTRS)
York, Thomas
1989-01-01
The fragmentation of cosmic string loops is discussed, and the results of a simulation of this process are presented. The simulation can evolve any of a large class of loops essentially exactly, including allowing fragments that collide to join together. Such reconnection enhances the production of small fragments, but not drastically. With or without reconnections, the fragmentation process produces a collection of nonself-intersecting loops whose typical length is on the order of the persistence length of the initial loop.
Cosmic strings and baryon decay catalysis
NASA Technical Reports Server (NTRS)
Gregory, Ruth; Perkins, W. B.; Davis, A.-C.; Brandenberger, R. H.
1989-01-01
Cosmic strings, like monopoles, can catalyze proton decay. For integer charged fermions, the cross section for catalysis is not amplified, unlike in the case of monopoles. The catalysis processes are reviewed both in the free quark and skyrmion pictures and the implications for baryogenesis are discussed. A computation of the cross section for monopole catalyzed skyrmion decay is presented using classical physics. Also discussed are some effects which can screen catalysis processes.
The Hubble Web: The Dark Matter Problem and Cosmic Strings
Alexander, Stephon
2009-07-06
I propose a reinterpretation of cosmic dark matter in which a rigid network of cosmic strings formed at the end of inflation. The cosmic strings fulfill three functions: At recombination they provide an accretion mechanism for virializing baryonic and warm dark matter into disks. These cosmic strings survive as configurations which thread spiral and elliptical galaxies leading to the observed flatness of rotation curves and the Tully-Fisher relation. We find a relationship between the rotational velocity of the galaxy and the string tension and discuss the testability of this model.
Ultrahigh-energy particles from cosmic strings
Bhattacharjee, P. . Astronomy and Astrophysics Center Fermi National Accelerator Lab., Batavia, IL )
1991-02-01
The idea of production of ultrahigh-energy particles in the present universe due to annihilation or collapse of topological defects is discussed. Topological defects, formed in symmetry-breaking phase transitions in the early universe, can survive till today owing to their topological stability. However, under certain circumstances, topological defects may be physically destroyed. When topological defects are destroyed, the energy contained in the defects can be released in the form of massive gauge- and Higgs bosons of the underlying spontaneously broken gauge theory. Subsequent decay of these massive particles can give rise to energetic particles ranging up to an energy on the order of the mass of the original particles released from the defects. This may give us a natural'' mechanism of production of extremely energetic cosmic ray particles in the universe today, without the need for any acceleration mechanism. To illustrate this idea, I describe in detail the calculation of the expected ultrahigh-energy proton spectrum due to a specific process which involves collapse or multiple self-intersections of a class of closed cosmic string loops formed in a phase transition at a grand unification energy scale. I discuss the possibility that some of the highest-energy cosmic ray particles are of this origin. By comparing with the observational results on the ultrahigh-energy cosmic rays, we derive an upper limit to the average fraction of the total energy in all primary'' cosmic string loops that may be released in the form of particles due to collapse or multiple self-intersections of these loops. No nuclei such as {alpha}'s or Fe's are in the spectrum. 43 refs., 3 figs.
Gravitating non-Abelian cosmic strings
NASA Astrophysics Data System (ADS)
de Pádua Santos, Antônio; Bezerra de Mello, Eugênio R.
2015-08-01
In this paper, we study regular cosmic string solutions of the non-Abelian Higgs model coupled with gravity. In order to develop this analysis, we constructed a set of coupled non-linear differential equations. Because there is no closed solution for this set of equations, we solve it numerically. The solutions we are interested in asymptote to a flat spacetime with a planar angle deficit. The model under consideration presents two bosonic sectors, besides the non-Abelian gauge field. The two bosonic sectors may present a direct coupling, so we investigate the relevance of this coupling on the system, specifically in the linear energy density of the string and on the planar angle deficit. We also analyze the behaviors of these quantities as a function of the energy scale where the gauge symmetry is spontaneously broken.
Conservation law for linked cosmic string loops
NASA Astrophysics Data System (ADS)
Bekenstein, Jacob D.
1992-05-01
Taking a cue from the connection between fluid helicity and the linkage between closed vortices in ordinary turbulent flow, we examine topological restrictions on the linkage of cosmic string loops (or superfluid quantum vortex rings). The analog of helicity in these cases vanishes, but loops (and vortex rings) can link together, the extent of linkage (knotting included) being related to the contorsion of the loops or rings by a topological conservation law. This law is respected by intercommunication. One consequence is that total loop contorsion is quantized in integers.
The minimal SUSY B - L model: simultaneous Wilson lines and string thresholds
NASA Astrophysics Data System (ADS)
Deen, Rehan; Ovrut, Burt A.; Purves, Austin
2016-07-01
In previous work, we presented a statistical scan over the soft supersymmetry breaking parameters of the minimal SUSY B - L model. For specificity of calculation, unification of the gauge parameters was enforced by allowing the two Z_3× Z_3 Wilson lines to have mass scales separated by approximately an order of magnitude. This introduced an additional "left-right" sector below the unification scale. In this paper, for three important reasons, we modify our previous analysis by demanding that the mass scales of the two Wilson lines be simultaneous and equal to an "average unification" mass < M U >. The present analysis is 1) more "natural" than the previous calculations, which were only valid in a very specific region of the Calabi-Yau moduli space, 2) the theory is conceptually simpler in that the left-right sector has been removed and 3) in the present analysis the lack of gauge unification is due to threshold effects — particularly heavy string thresholds, which we calculate statistically in detail. As in our previous work, the theory is renormalization group evolved from < M U > to the electroweak scale — being subjected, sequentially, to the requirement of radiative B - L and electroweak symmetry breaking, the present experimental lower bounds on the B - L vector boson and sparticle masses, as well as the lightest neutral Higgs mass of ˜125 GeV. The subspace of soft supersymmetry breaking masses that satisfies all such constraints is presented and shown to be substantial.
Patterns of the cosmic microwave background from evolving string networks
NASA Technical Reports Server (NTRS)
Bouchet, Francois R.; Bennett, David P.; Stebbins, Albert
1988-01-01
A network of cosmic strings generated in the early universe may still exist today. As the strings move across the sky, they produce, by gravitational lensing, a characteristic pattern of anisotropies in the temperature of the cosmic microwave background. The observed absence of such anisotropies places constraints on theories in which galaxy formation is seeded by strings, but it is anticipated that the next generation of experiments will detect them.
On the Bispectrum of Cosmic String Seeded CMB Fluctuations
NASA Astrophysics Data System (ADS)
Landriau, M.
2013-07-01
I compute the bispectrum of maps of cosmic microwave background (CMB) fluctuations seeded by cosmic strings from large to 30 arcminute scales. Examining the distribution of triangle configurations and comparing with Gaussian realizations with the same power spectrum, I conclude that the CMB bispectrum cannot pick up the mild non-Gaussianity present in the maps and thus that it cannot characterize cosmic string induced non-Gaussianity produced in the regimes probed by these maps.
The bispectrum of cosmic string temperature fluctuations including recombination effects
Regan, Donough; Hindmarsh, Mark E-mail: m.b.hindmarsh@sussex.ac.uk
2015-10-01
We calculate the cosmic microwave background temperature bispectrum from cosmic strings, including the contributions from the last scattering surface, using a well-established Gaussian model for the string energy-momentum correlation functions, and a simplified model for the cosmic fluid. We check our approximation for the integrated Sachs-Wolfe (ISW) contribution against the bispectrum obtained from the full sky map of the cosmic string ISW signal used by the Planck team, obtaining good agreement. We validate our model for the last scattering surface contribution by comparing the predicted temperature power spectrum with that obtained from a full Boltzmann code treatment applied to the Unconnected Segment Model of a string network. We find that including the last scattering contribution has only a small impact on the upper limit on the string tension resulting from the bispectrum at Planck resolutions, and argue that the bispectrum is unlikely to be competitive with the power spectrum at any resolution.
Cosmic strings in hidden sectors: 2. Cosmological and astrophysical signatures
Long, Andrew J.; Vachaspati, Tanmay E-mail: tvachasp@asu.edu
2014-12-01
Cosmic strings can arise in hidden sector models with a spontaneously broken Abelian symmetry group. We have studied the couplings of the Standard Model fields to these so-called dark strings in the companion paper. Here we survey the cosmological and astrophysical observables that could be associated with the presence of dark strings in our universe with an emphasis on low-scale models, perhaps TeV . Specifically, we consider constraints from nucleosynthesis and CMB spectral distortions, and we calculate the predicted fluxes of diffuse gamma ray cascade photons and cosmic rays. For strings as light as TeV, we find that the predicted level of these signatures is well below the sensitivity of the current experiments, and therefore low scale cosmic strings in hidden sectors remain unconstrained. Heavier strings with a mass scale in the range 10{sup 13} GeV to 10{sup 15} GeV are at tension with nucleosynthesis constraints.
Cosmic strings in hidden sectors: 2. Cosmological and astrophysical signatures
Long, Andrew J.; Vachaspati, Tanmay
2014-12-18
Cosmic strings can arise in hidden sector models with a spontaneously broken Abelian symmetry group. We have studied the couplings of the Standard Model fields to these so-called dark strings in the companion paper. Here we survey the cosmological and astrophysical observables that could be associated with the presence of dark strings in our universe with an emphasis on low-scale models, perhaps TeV. Specifically, we consider constraints from nucleosynthesis and CMB spectral distortions, and we calculate the predicted fluxes of diffuse gamma ray cascade photons and cosmic rays. For strings as light as TeV, we find that the predicted level of these signatures is well below the sensitivity of the current experiments, and therefore low scale cosmic strings in hidden sectors remain unconstrained. Heavier strings with a mass scale in the range 10{sup 13} GeV to 10{sup 15} GeV are at tension with nucleosynthesis constraints.
Scattering of Cosmic Strings by Black Holes:. Loop Formation
NASA Astrophysics Data System (ADS)
Dubath, Florian; Sakellariadou, Mairi; Viallet, Claude Michel
We study the deformation of a long cosmic string by a nearby rotating black hole. We examine whether the deformation of a cosmic string, induced by the gravitational field of a Kerr black hole, may lead to the formation of a string loop. The segment of the string which enters the ergo-sphere of a rotating black hole gets deformed and, if it is sufficiently twisted, it can self-intersect, chopping off a loop. We find that the formation of a loop, via such a mechanism, is a rare event. It will only arise in a small region of the collision phase space, which depends on the string velocity, the impact parameter and the black hole angular momentum. We conclude that, generically, a long cosmic string is simply scattered, or captured, by a nearby rotating black hole.
Extremely high energy neutrinos from cosmic strings
Berezinsky, Veniamin; Sabancilar, Eray; Vilenkin, Alexander
2011-10-15
Superstring theory and other supersymmetric theories predict the existence of relatively light, weakly interacting scalar particles, called moduli, with a universal form of coupling to matter. Such particles can be emitted from cusps of cosmic strings, where extremely large Lorentz factors are achieved momentarily. Highly boosted modulus bursts emanating from cusps subsequently decay into gluons; they generate parton cascades which in turn produce large numbers of pions and then neutrinos. Because of very large Lorentz factors, extremely high energy neutrinos, up to the Planck scale and above, are produced. For some model parameters, the predicted flux of neutrinos with energies > or approx. 10{sup 21} eV is observable by JEM-EUSO and by the future large radio detectors LOFAR and SKA.
Large-scale structure from wiggly cosmic strings
NASA Astrophysics Data System (ADS)
Vachaspati, Tanmay; Vilenkin, Alexander
1991-08-01
Recent simulations of the evolution of cosmic strings indicate the presence of small-scale structure on the strings. It is shown that wakes produced by such 'wiggly' cosmic strings can result in the efficient formation of large-scale structure and large streaming velocities in the universe without significantly affecting the microwave-background isotropy. It is also argued that the motion of strings will lead to the generation of a primordial magnetic field. The most promising version of this scenario appears to be the one in which the universe is dominated by light neutrinos.
The bispectrum of matter perturbations from cosmic strings
Regan, Donough; Hindmarsh, Mark E-mail: m.b.hindmarsh@sussex.ac.uk
2015-03-01
We present the first calculation of the bispectrum of the matter perturbations induced by cosmic strings. The calculation is performed in two different ways: the first uses the unequal time correlators (UETCs) of the string network - computed using a Gaussian model previously employed for cosmic string power spectra. The second approach uses the wake model, where string density perturbations are concentrated in sheet-like structures whose surface density grows with time. The qualitative and quantitative agreement of the two gives confidence to the results. An essential ingredient in the UETC approach is the inclusion of compensation factors in the integration with the Green's function of the matter and radiation fluids, and we show that these compensation factors must be included in the wake model also. We also present a comparison of the UETCs computed in the Gaussian model, and those computed in the unconnected segment model (USM) used by the standard cosmic string perturbation package CMBACT. We compare numerical estimates for the bispectrum of cosmic strings to those produced by perturbations from an inflationary era, and discover that, despite the intrinsically non-Gaussian nature of string-induced perturbations, the matter bispectrum is unlikely to produce competitive constraints on a population of cosmic strings.
Will cosmic strings be discovered using the Space Telescope?
NASA Technical Reports Server (NTRS)
Pacynski, B.
1986-01-01
Cosmic strings are topologically stable defects in the vacuum of space which may be produced by a phase transition in the early universe. Here, it is suggested that observations of very distant galaxies are a more useful means of discovering strings than quasar observations. It is argued that if there is only one string out to redshift z - about 1 the probability that it crosses a random image obtained using the Wide Field Camera (WFC) of the Space Telescope is about 0.0001. In order to discover a cosmic string the Space Telescope WFC will be required to operate almost continuously in primary and serendipity modes, and a cosmic string, if it exists, may be discovered within the first few years of operation.
Effect of a cosmic string on spin dynamics
NASA Astrophysics Data System (ADS)
Chowdhury, Debashree; Basu, B.
2014-12-01
In the present paper, we have investigated the role of the cosmic string on spin current and Hall electric field. Due to the background cosmic string, the modified electric field of the system generates renormalized spin-orbit coupling, which induces a modified non-Abelian gauge field. The defect causes a change in the Aharonov-Bohm and Aharonov-Casher phases appearing due to the modified electromagnetic field. In addition, for a time varying electric field we perform explicit analytic calculations to derive the exact form of spin electric field and spin current, which is defect parameter dependent and of oscillating type. Furthermore, in an asymmetric crystal within the Drude model approach we investigate the dependence of the cosmic string parameters on cosmic string induced Hall electric field.
CMB ISW-lensing bispectrum from cosmic strings
Yamauchi, Daisuke; Sendouda, Yuuiti; Takahashi, Keitaro E-mail: sendouda@cc.hirosaki-u.ac.jp
2014-02-01
We study the effect of weak lensing by cosmic (super-)strings on the higher-order statistics of the cosmic microwave background (CMB). A cosmic string segment is expected to cause weak lensing as well as an integrated Sachs-Wolfe (ISW) effect, the so-called Gott-Kaiser-Stebbins (GKS) effect, to the CMB temperature fluctuation, which are thus naturally cross-correlated. We point out that, in the presence of such a correlation, yet another kind of the post-recombination CMB temperature bispectra, the ISW-lensing bispectra, will arise in the form of products of the auto- and cross-power spectra. We first present an analytic method to calculate the autocorrelation of the temperature fluctuations induced by the strings, and the cross-correlation between the temperature fluctuation and the lensing potential both due to the string network. In our formulation, the evolution of the string network is assumed to be characterized by the simple analytic model, the velocity-dependent one scale model, and the intercommutation probability is properly incorporated in order to characterize the possible superstringy nature. Furthermore, the obtained power spectra are dominated by the Poisson-distributed string segments, whose correlations are assumed to satisfy the simple relations. We then estimate the signal-to-noise ratios of the string-induced ISW-lensing bispectra and discuss the detectability of such CMB signals from the cosmic string network. It is found that in the case of the smaller string tension, Gμ << 10{sup -7}, the ISW-lensing bispectrum induced by a cosmic string network can constrain the string-model parameters even more tightly than the purely GKS-induced bispectrum in the ongoing and future CMB observations on small scales.
Perturbations from cosmic strings in cold dark matter
NASA Technical Reports Server (NTRS)
Albrecht, Andreas; Stebbins, Albert
1992-01-01
A systematic linear analysis of the perturbations induced by cosmic strings in cold dark matter is presented. The power spectrum is calculated and it is found that the strings produce a great deal of power on small scales. It is shown that the perturbations on interesting scales are the result of many uncorrelated string motions, which indicates a much more Gaussian distribution than was previously supposed.
Perturbations from cosmic strings in cold dark matter
NASA Technical Reports Server (NTRS)
Albrecht, Andreas; Stebbins, Albert
1991-01-01
A systematic linear analysis of the perturbations induced by cosmic strings in cold dark matter is presented. The power spectrum is calculated and it is found that the strings produce a great deal of power on small scales. It is shown that the perturbations on interesting scales are the result of many uncorrelated string motions, which indicates a much more Gaussian distribution than was previously supposed.
Cosmic (Super)String Constraints from 21 cm Radiation
Khatri, Rishi; Wandelt, Benjamin D.
2008-03-07
We calculate the contribution of cosmic strings arising from a phase transition in the early Universe, or cosmic superstrings arising from brane inflation, to the cosmic 21 cm power spectrum at redshifts z{>=}30. Future experiments can exploit this effect to constrain the cosmic string tension G{mu} and probe virtually the entire brane inflation model space allowed by current observations. Although current experiments with a collecting area of {approx}1 km{sup 2} will not provide any useful constraints, future experiments with a collecting area of 10{sup 4}-10{sup 6} km{sup 2} covering the cleanest 10% of the sky can, in principle, constrain cosmic strings with tension G{mu} > or approx. 10{sup -10}-10{sup -12} (superstring/phase transition mass scale >10{sup 13} GeV)
Cosmic strings and the origin of globular clusters
Barton, Alistair; Brandenberger, Robert H.; Lin, Ling E-mail: rhb@physics.mcgill.ca
2015-06-01
We hypothesize that cosmic string loops are the seeds about which globular clusters accrete. Fixing the cosmic string tension by demanding that the peak in the distribution of masses of objects accreting onto string loops agrees with the peak in the observed mass distribution of globular clusters in our Milky Way galaxy, we then compute the expected number density and mass function of globular clusters, and compare with observations. Our hypothesis naturally explains why globular clusters are the oldest and most dense objects in a galaxy, and why they are found in the halo of the galaxy.
Evidence for a scaling solution in cosmic-string evolution
NASA Technical Reports Server (NTRS)
Bennett, David P.; Bouchet, Francois R.
1988-01-01
Numerical simulations are used to study the most fundamental issue of cosmic-string evolution: the existence of a scaling solution. Strong evidence is found that a scaling solution does indeed exist. This justifies the main assumption on which the cosmic-string theories of galaxy formation is based. The main conclusion coincides with that of Albrecht and Turok (1985) but the results are not consistent with theirs. In fact, the results indicate that the details of string evolution are very different from the standard dogma.
Formation of black holes from collapsed cosmic string loops
NASA Astrophysics Data System (ADS)
Caldwell, R. R.; Casper, Paul
1996-03-01
The fraction of cosmic string loops which collapse to form black holes is estimated using a set of realistic loops generated by loop fragmentation. The smallest radius sphere into which each cosmic string loop may fit is obtained by monitoring the loop through one period of oscillation. For a loop with invariant length L which contracts to within a sphere of radius R, the minimum mass per unit length μmin necessary for the cosmic string loop to form a black hole according to the hoop conjecture is μmin=R/(2GL). Analyzing 25 576 loops, we obtain the empirical estimate f BH=104.9+/-0.2(Gμ)4.1+/-0.1 for the fraction of cosmic string loops which collapse to form black holes as a function of the mass per unit length μ in the range 10-3<~Gμ<~3×10-2. We use this power law to extrapolate to Gμ~10-6, obtaining the fraction fBH of cosmologically interesting string loops which collapse to form black holes within one oscillation period of formation. Comparing this fraction with the observational bounds on a population of evaporating black holes, we obtain the limit Gμ<=3.1(+/-0.7)×10-6 on the cosmic string mass per unit length. This limit is consistent with all other observational bounds.
Quantum vacuum interaction between two cosmic strings revisited
NASA Astrophysics Data System (ADS)
Muñoz-Castañeda, J. M.; Bordag, M.
2014-03-01
We reconsider the quantum vacuum interaction energy between two straight parallel cosmic strings. This problem was discussed several times in an approach treating both strings perturbatively and treating only one perturbatively. Here we point out that a simplifying assumption made by Bordag [Ann. Phys. (Berlin) 47, 93 (1990).] can be justified and show that, despite the global character of the background, the perturbative approach delivers a correct result. We consider the applicability of the scattering methods, developed in the past decade for the Casimir effect, for the cosmic string and find it not applicable. We calculate the scattering T-operator on one string. Finally, we consider the vacuum interaction of two strings when each carries a two-dimensional delta function potential.
Stochastic gravitational wave background from light cosmic strings
DePies, Matthew R.; Hogan, Craig J.
2007-06-15
Spectra of the stochastic gravitational wave backgrounds from cosmic strings are calculated and compared with present and future experimental limits. Motivated by theoretical expectations of light cosmic strings in superstring cosmology, improvements in experimental sensitivity, and recent demonstrations of large, stable loop formation from a primordial network, this study explores a new range of string parameters with masses lighter than previously investigated. A standard 'one-scale' model for string loop formation is assumed. Background spectra are calculated numerically for dimensionless string tensions G{mu}/c{sup 2} between 10{sup -7} and 10{sup -18}, and initial loop sizes as a fraction of the Hubble radius {alpha} from 0.1 to 10{sup -6}. The spectra show a low frequency power-law tail, a broad spectral peak due to loops decaying at the present epoch (including frequencies higher than their fundamental mode, and radiation associated with cusps), and a flat (constant energy density) spectrum at high frequencies due to radiation from loops that decayed during the radiation-dominated era. The string spectrum is distinctive and unlike any other known source. The peak of the spectrum for light strings appears at high frequencies, significantly affecting predicted signals. The spectra of the cosmic string backgrounds are compared with current millisecond pulsar limits and Laser Interferometer Space Antenna (LISA) sensitivity curves. For models with large stable loops ({alpha}=0.1), current pulsar-timing limits exclude G{mu}/c{sup 2}>10{sup -9}, a much tighter limit on string tension than achievable with other techniques, and within the range of current models based on brane inflation. LISA may detect a background from strings as light as G{mu}/c{sup 2}{approx_equal}10{sup -16}, corresponding to field theory strings formed at roughly 10{sup 11} GeV.
Cosmic super-strings and Kaluza-Klein modes
Dufaux, Jean-François
2012-09-01
Cosmic super-strings interact generically with a tower of relatively light and/or strongly coupled Kaluza-Klein (KK) modes associated with the geometry of the internal space. In this paper, we study the production of spin-2 KK particles by cusps on loops of cosmic F- and D-strings. We consider cosmic super-strings localized either at the bottom of a warped throat or in a flat internal space with large volume. The total energy emitted by cusps in KK modes is comparable in both cases, although the number of produced KK modes may differ significantly. We then show that KK emission is constrained by the photo-dissociation of light elements and by observations of the diffuse gamma ray background. We show that this rules out regions of the parameter space of cosmic super-strings that are complementary to the regions that can be probed by current and upcoming gravitational wave experiments. KK modes are also expected to play an important role in the friction-dominated epoch of cosmic super-string evolution.
Cosmological constraints on cosmic-string gravitational radiation
NASA Astrophysics Data System (ADS)
Caldwell, R. R.; Allen, B.
1992-05-01
The primordial nucleosynthesis and pulsar timing noise constraints on cosmic-string gravitational radiation are computed. The computation consists of a numerical integration of the Friedmann-Robertson-Walker Einstein equations which describe a universe containing radiation, dust, and a ``one-scale''-model cosmic-string component. The procedure takes into account the effects of the annihilations of massive particle species on the equation of state of the cosmological fluid. An expression for the power emitted per mode of oscillation by a cosmic-string loop, suggested by both analytic calculations and recent numerical simulations, is used. The results of the computation are spectra of the cosmic-string gravitational radiation at nucleosynthesis and at present. Comparison of these spectra with the observed bounds on pulsar timing noise, and the observed bound on the effective number of light neutrino species permitted by the model of nucleosynthesis, allows one to exclude a range of values of μ, the cosmic-string linear mass density, for certain values of α, the size of a newly formed loop as a fraction of the particle horizon radius. We find constraints to μ which are more restrictive than any previous limit.
Landau quantization in the spinning cosmic string spacetime
Muniz, C.R.; Bezerra, V.B.; Cunha, M.S.
2014-11-15
We analyze the quantum phenomenon arising from the interaction of a spinless charged particle with a rotating cosmic string, under the action of a static and uniform magnetic field parallel to the string. We calculate the energy levels of the particle in the non-relativistic approach, showing how these energies depend on the parameters involved in the problem. In order to do this, we solve the time independent Schrödinger equation in the geometry of the spinning cosmic string, taking into account that the coupling between the rotation of the spacetime and the angular momentum of the particle is very weak, such that makes sense to apply the Schrödinger equation in a curved background whose metric has an off diagonal term which involves time and space. It is also assumed that the particle orbits sufficiently far from the boundary of the region of closed timelike curves which exist around this topological defect. Finally, we find the Landau levels of the particle in the presence of a spinning cosmic string endowed with internal structure, i.e., having a finite width and uniformly filled with both material and vacuum energies. - Highlights: • Solution of the wave equation characterizing the problem. • Energy levels of the particle in spacetime of the structureless string. • Expression for an analogous of the quadratic Zeeman effect. • Energy levels of the particle in spacetime of the string with internal structure. • Evidence of the string structure by the internal existence of the vacuum energy.
Quantum fluctuations of the superconducting cosmic string
NASA Technical Reports Server (NTRS)
Zhang, Shoucheng
1987-01-01
Quantum fluctuations of the proposed superconducting string with Bose charge carriers are studied in terms of the vortices on the string world sheet. In the thermodynamical limit, it is found that they appear in the form of free vortices rather than as bound pairs. This fluctuation mode violates the topological conservation law on which superconductivity is based. However, this limit may not be reached. The critical size of the superconducting string is estimated as a function of the coupling constants involved.
Movahed, M. Sadegh; Khosravi, Shahram E-mail: khosravi@ipm.ir
2011-03-01
In this paper we study the footprint of cosmic string as the topological defects in the very early universe on the cosmic microwave background radiation. We develop the method of level crossing analysis in the context of the well-known Kaiser-Stebbins phenomenon for exploring the signature of cosmic strings. We simulate a Gaussian map by using the best fit parameter given by WMAP-7 and then superimpose cosmic strings effects on it as an incoherent and active fluctuations. In order to investigate the capability of our method to detect the cosmic strings for the various values of tension, Gμ, a simulated pure Gaussian map is compared with that of including cosmic strings. Based on the level crossing analysis, the superimposed cosmic string with Gμ∼>4 × 10{sup −9} in the simulated map without instrumental noise and the resolution R = 1' could be detected. In the presence of anticipated instrumental noise the lower bound increases just up to Gμ∼>5.8 × 10{sup −9}.
Light-cone fluctuations in the cosmic string spacetime
NASA Astrophysics Data System (ADS)
Mota, H. F.; Bezerra de Mello, E. R.; Bessa, C. H. G.; Bezerra, V. B.
2016-07-01
In this paper we consider light-cone fluctuations arising as a consequence of the nontrivial topology of the locally flat cosmic string spacetime. By setting the light-cone along the z -direction we are able to develop a full analysis to calculate the renormalized graviton two-point function, as well as the mean square fluctuation in the geodesic interval function and the time delay (or advance) in the propagation of a light pulse. We found that all these expressions depend upon the parameter characterizing the conical topology of the cosmic string spacetime and vanish in the absence of it. We also point out that at large distances from the cosmic string the mean square fluctuation in the geodesic interval function is extremely small while in the opposite limit it logarithmically increases.
Cosmic-string-induced hot dark matter perturbations
NASA Technical Reports Server (NTRS)
Van Dalen, Anthony
1990-01-01
This paper investigates the evolution of initially relativistic matter, radiation, and baryons around cosmic string seed perturbations. A detailed analysis of the linear evolution of spherical perturbations in a universe is carried out, and this formalism is used to study the evolution of perturbations around a sphere of uniform density and fixed radius, approximating a loop of cosmic string. It was found that, on scales less than a few megaparsec, the results agree with the nonrelativistic calculation of previous authors. On greater scales, there is a deviation approaching a factor of 2-3 in the perturbation mass. It is shown that a scenario with cosmic strings, hot dark matter, and a Hubble constant greater than 75 km/sec per Mpc can generally produce structure on the observed mass scales and at the appropriate time: 1 + z = about 4 for galaxies and 1 + z = about 1.5 for Abell clusters.
Cosmic superstring gravitational lensing phenomena: Predictions for networks of (p,q) strings
Shlaer, Benjamin; Wyman, Mark
2005-12-15
The unique, conical space-time created by cosmic strings brings about distinctive gravitational lensing phenomena. The variety of these distinctive phenomena is increased when the strings have nontrivial mutual interactions. In particular, when strings bind and create junctions, rather than intercommute, the resulting configurations can lead to novel gravitational lensing patterns. In this brief note, we use exact solutions to characterize these phenomena, the detection of which would be strong evidence for the existence of complex cosmic string networks of the kind predicted by string theory-motivated cosmic string models. We also correct some common errors in the lensing phenomenology of straight cosmic strings.
Cosmic strings and the microwave sky. I - Anisotropy from moving strings
NASA Technical Reports Server (NTRS)
Stebbins, Albert
1988-01-01
A method is developed for calculating the component of the microwave anisotropy around cosmic string loops due to their rapidly changing gravitational fields. The method is only valid for impact parameters from the string much smaller than the horizon size at the time the photon passes the string. The method makes it possible to calculate the temperature pattern around arbitrary string configurations numerically in terms of one-dimensional integrals. This method is applied to temperature jump across a string, confirming and extending previous work. It is also applied to cusps and kinks on strings, and to determining the temperature pattern far from a strong loop. The temperature pattern around a few loop configurations is explicitly calculated. Comparisons with the work of Brandenberger et al. (1986) indicates that they have overestimated the MBR anisotropy from gravitational radiation emitted from loops.
Using cosmic strings to relate local geometry to spatial topology
NASA Astrophysics Data System (ADS)
Duston, Christopher Levi
In this paper, we will discuss how cosmic strings can be used to bridge the gap between the local geometry of our spacetime model and the global topology. The primary tool is the theory of foliations and surfaces, and together with observational constraints, we can isolate several possibilities for the topology of the spatial section of the observable universe. This implies that the discovery of cosmic strings would not just be significant for an understanding of structure formation in the early universe, but also for the global properties of the spacetime model.
Bosonic condensates in realistic supersymmetric GUT cosmic strings
Allys, Erwan
2016-04-01
We study the realistic structure of F-term Nambu-Goto cosmic strings forming in a general supersymmetric Grand Unified Theory implementation, assuming standard hybrid inflation. Examining the symmetry breaking of the unification gauge group down to the Standard Model, we discuss the minimal field content necessary to describe abelian cosmic strings appearing at the end of inflation. We find that several fields will condense in most theories, questioning the plausible occurrence of associated currents (bosonic and fermionic). We perturbatively evaluate the modification of their energy per unit length due to the condensates. We provide a criterion for comparing the usual abelian Higgs approximation used in cosmology to realistic situations.
The solutions of cosmic string loop equation in expanding universe
NASA Astrophysics Data System (ADS)
Li, Xinzhou; Zhang, Jianzu
1992-09-01
The cosmic string loop equation is studied analytically during the radiation-dominated era in the Robertson-Walker universe. If the loops expand with Hubble flow at the time of formation of loops, the cosmic string loops occur always collapsing. We also discuss the initial radii Rs(t*) dependence of the lifetime taus without considering the oscillations, as a first approximation, where t* denotes the time of formation of loops. We find that the lifetime factor gamma = c taus/Rs(t*) is (pi)/2 in the little initial radius limit.
Effects of ordinary and superconducting cosmic strings on primordial nucleosynthesis
NASA Technical Reports Server (NTRS)
Hodges, Hardy M.; Turner, Michael S.
1988-01-01
A precise calculation is done of the primordial nucleosynthesis constraint on the energy per length of ordinary and superconducting cosmic strings. A general formula is provided for the constraint on the string tension for ordinary strings. Using the current values for the various parameters that describe the evolution of loops, the constraint for ordinary strings is G mu less than 2.2 x 10 to the minus 5 power. Our constraint is weaker than previously quoted limits by a factor of approximately 5. For superconducting loops, with currents generated by primordial magnetic fields, the constraint can be less or more stringent than this limit, depending on the strength of the magnetic field. It is also found in this case that there is a negligible amount of entropy production if the electromagnetic radiation from strings thermalizes with the radiation background.
Black strings, low viscosity fluids, and violation of cosmic censorship.
Lehner, Luis; Pretorius, Frans
2010-09-03
We describe the behavior of 5-dimensional black strings, subject to the Gregory-Laflamme instability. Beyond the linear level, the evolving strings exhibit a rich dynamics, where at intermediate stages the horizon can be described as a sequence of 3-dimensional spherical black holes joined by black string segments. These segments are themselves subject to a Gregory-Laflamme instability, resulting in a self-similar cascade, where ever-smaller satellite black holes form connected by ever-thinner string segments. This behavior is akin to satellite formation in low-viscosity fluid streams subject to the Rayleigh-Plateau instability. The simulation results imply that the string segments will reach zero radius in finite asymptotic time, whence the classical space-time terminates in a naked singularity. Since no fine-tuning is required to excite the instability, this constitutes a generic violation of cosmic censorship.
Probabilistic estimates of the number of cosmic strings
Sazhina, O. S.
2013-01-15
The dependences of the mean expected number of cosmic strings on their redshift up to the surface of last scattering have been derived. The calculations are based on the geometric probability of a straight string segment crossing a given field and on information about the absence of strings when they are searched for via their gravitational lensing effects in optical catalogs. It is shown that there are no strings for redshifts 0 < z < 1.954, but the expected number of strings for 0 < z < 5 can be no more than 2.1 Multiplication-Sign 10{sup 3} at the 95% confidence level. The expected number of strings for redshifts up to z = 1100 can be no more than 2.4 Multiplication-Sign 10{sup 4} at the 95% confidence level. The latter estimate is sensitive to a priori information about the absence of cosmic strings in the redshift range 0 < z < 1.954 in a field of 4.48 square degrees in optical catalogs; it is smaller than the estimate without allowance for this information by 6%.
Axions from cosmic string and wall decay
Hagmann, C A
2010-03-10
If inflation occurred with a reheat temperature > T{sub PQ}, axions from the decay of global axion strings and domain walls would make an important contribution to the cosmological energy density, comparable to that from vacuum misalignment. Several groups have numerically studied the evolution of axion strings and walls in the past, however substantial uncertainties remain in their contribution to the present density {Omega}{sub a,string+wall} {approx} 1-100 (f{sub a}/10{sup 12} GeV){sup 7/6}, where f{sub a} is the axion decay constant. I will describe the numerical methods used in our simulations and show results for several string and wall configurations.
Strings matter: Dynamics and evolution of cosmic string networks in flat spacetime
NASA Astrophysics Data System (ADS)
Sakellariadou, Maria
1990-12-01
This research inquires into the dynamics and evolution of cosmic string networks in flat spacetime. It involves the study of the statistical properties of string networks and the dynamics of long strings, including the scaling density; the fractal nature of string substructure; and the effectiveness of the gravitational damping mechanism, regarding the long strings' wiggles. Methodologically, it employs both numerical (within the framework of an exact soluble model in flat spacetime) and analytical analyses. The central propositions of this research are a follows: (1) for a string network in equilibrium, when the energy density of the network is low, the dominant part of the string is in the form of closed loops of the smallest allowed size, and a certain critical density the system undergoes a phase transition characterized by formation of very long strings; (2) for an evolving network, the typical curvature radius of long strings, and the characteristic distance between them, are both comparable to the evolution time, and at the same time, long strings possess a significant small-scale structure, which plays an important role in the energy distribution of the produced loops: and (3) gravitational radiation is rather effective in damping the small-scale structure, but only for large amplitude waves.
Strings matter: Dynamics and evolution of cosmic string networks in flat spacetime
Sakellariadou, M.
1990-01-01
This research inquires into the dynamics and evolution of cosmic string networks in flat spacetime. It involves the study of the statistical properties of string networks and the dynamics of long strings, including the scaling density; the fractal nature of string substructure; and the effectiveness of the gravitational damping mechanism, regarding the long strings' wiggles. Methodologically, it employs both numerical (within the framework of an exact soluble model in flat spacetime) and analytical analyses. The central propositions of this research are a follows: (1) for a string network in equilibrium, when the energy density of the network is low, the dominant part of the string is in the form of closed loops of the smallest allowed size, and a certain critical density the system undergoes a phase transition characterized by formation of very long strings; (2) for an evolving network, the typical curvature radius of long strings, and the characteristic distance between them, are both comparable to the evolution time, and at the same time, long strings possess a significant small-scale structure, which plays an important role in the energy distribution of the produced loops: and (3) gravitational radiation is rather effective in damping the small-scale structure, but only for large amplitude waves.
THE FLOW AROUND A COSMIC STRING. I. HYDRODYNAMIC SOLUTION
Beresnyak, Andrey
2015-05-10
Cosmic strings are linear topological defects which are hypothesized to be produced during inflation. Most searches for strings have relied on the string’s lensing of background galaxies or the cosmic microwave background. In this paper, I obtained a solution for the supersonic flow of collisional gas past the cosmic string which has two planar shocks with a shock compression ratio that depends on the angle defect of the string and its speed. The shocks result in the compression and heating of the gas and, given favorable conditions, particle acceleration. Gas heating and over-density in an unusual wedge shape can be detected by observing the Hi line at high redshifts. Particle acceleration can occur in the present-day universe when the string crosses the hot gas contained in galaxy clusters and, since the consequences of such a collision persist for cosmological timescales, could be located by looking at unusual large-scale radio sources situated on a single spatial plane.
Large scale CMB anomalies from thawing cosmic strings
Ringeval, Christophe; Yamauchi, Daisuke; Yokoyama, Jun'ichi; Bouchet, François R. E-mail: yamauchi@resceu.s.u-tokyo.ac.jp E-mail: bouchet@iap.fr
2016-02-01
Cosmic strings formed during inflation are expected to be either diluted over super-Hubble distances, i.e., invisible today, or to have crossed our past light cone very recently. We discuss the latter situation in which a few strings imprint their signature in the Cosmic Microwave Background (CMB) Anisotropies after recombination. Being almost frozen in the Hubble flow, these strings are quasi static and evade almost all of the previously derived constraints on their tension while being able to source large scale anisotropies in the CMB sky. Using a local variance estimator on thousand of numerically simulated Nambu-Goto all sky maps, we compute the expected signal and show that it can mimic a dipole modulation at large angular scales while being negligible at small angles. Interestingly, such a scenario generically produces one cold spot from the thawing of a cosmic string loop. Mixed with anisotropies of inflationary origin, we find that a few strings of tension GU = O(1) × 10{sup −6} match the amplitude of the dipole modulation reported in the Planck satellite measurements and could be at the origin of other large scale anomalies.
New Solutions for Non-Abelian Cosmic Strings
NASA Astrophysics Data System (ADS)
Hindmarsh, Mark; Rummukainen, Kari; Weir, David J.
2016-12-01
We study the properties of classical vortex solutions in a non-Abelian gauge theory. A system of two adjoint Higgs fields breaks the SU(2) gauge symmetry to Z2 , producing 't Hooft-Polyakov monopoles trapped on cosmic strings, termed beads; there are two charges of monopole and two degenerate string solutions. The strings break an accidental discrete Z2 symmetry of the theory, explaining the degeneracy of the ground state. Further symmetries of the model, not previously appreciated, emerge when the masses of the two adjoint Higgs fields are degenerate. The breaking of the enlarged discrete symmetry gives rise to additional string solutions and splits the monopoles into four types of "semipole": kink solutions that interpolate between the string solutions, classified by a complex gauge-invariant magnetic flux and a Z4 charge. At special values of the Higgs self-couplings, the accidental symmetry broken by the string is continuous, giving rise to supercurrents on the strings. The SU(2) theory can be embedded in a wide class of grand unified theories (GUTs), including SO(10). We argue that semipoles and supercurrents are generic on GUT strings.
Urrestilla, Jon; Bevis, Neil; Hindmarsh, Mark; Kunz, Martin E-mail: n.bevis@imperial.ac.uk E-mail: martin.kunz@physics.unige.ch
2011-12-01
We present a significant update of the constraints on the Abelian Higgs cosmic string tension by cosmic microwave background (CMB) data, enabled both by the use of new high-resolution CMB data from suborbital experiments as well as the latest results of the WMAP satellite, and by improved predictions for the impact of Abelian Higgs cosmic strings on the CMB power spectra. The new cosmic string spectra [1] were improved especially for small angular scales, through the use of larger Abelian Higgs string simulations and careful extrapolation. If Abelian Higgs strings are present then we find improved bounds on their contribution to the CMB anisotropies, fd{sup AH} < 0.095, and on their tension, Gμ{sub AH} < 0.57 × 10{sup −6}, both at 95% confidence level using WMAP7 data; and fd{sup AH} < 0.048 and Gμ{sub AH} < 0.42 × 10{sup −6} using all the CMB data. We also find that using all the CMB data, a scale invariant initial perturbation spectrum, n{sub s} = 1, is now disfavoured at 2.4σ even if strings are present. A Bayesian model selection analysis no longer indicates a preference for strings.
Brane cosmic string compactification in Brans-Dicke theory
Abdalla, M. C. B.; Hoff da Silva, J. M.; Guimaraes, M. E. X.
2007-04-15
We investigate an alternative compactification of extra dimensions using local cosmic string in the Brans-Dicke gravity framework. In the context of dynamical systems it is possible to show that there exist a stable field configuration for the Einstein-Brans-Dicke equations. We explore the analogies between this particular model and the Randall-Sundrum scenario.
More about thin-shell wormholes associated to cosmic strings
Richarte, Martin G.; Simeone, Claudio
2009-06-15
Previous analysis about thin-shell wormholes associated to cosmic strings are extended. More evidence is found supporting the conjecture that, under reasonable assumptions about the equations of state of matter on the shell, the configurations are not stable under radial velocity perturbations.
Thin-shell wormholes associated with global cosmic strings
Bejarano, Cecilia; Eiroa, Ernesto F.; Simeone, Claudio
2007-01-15
In this article we construct cylindrical thin-shell wormholes in the context of global cosmic strings. We study the stability of static configurations under perturbations preserving the symmetry and we find that the throat tends to collapse or expand, depending only on the direction of the velocity perturbation.
Topological Casimir effect in compactified cosmic string spacetime
NASA Astrophysics Data System (ADS)
Bezerra de Mello, E. R.; Saharian, A. A.
2012-02-01
We investigate the Wightman function, the vacuum expectation values of the field squared and the energy-momentum tensor for a massive scalar field with general curvature coupling in the generalized cosmic string geometry with a compact dimension along its axis. The boundary condition along the compactified dimension is taken in general form with an arbitrary phase. The vacuum expectation values are decomposed into two parts. The first one corresponds to the uncompactified cosmic string geometry and the second one is the correction induced by the compactification. The asymptotic behavior of the vacuum expectation values of the field squared, energy density and stresses is investigated near the string and at large distances. We show that the nontrivial topology due to the cosmic string enhances the vacuum polarization effects induced by the compactness of spatial dimension for both the field squared and the vacuum energy density. A simple formula is given for the part of the integrated topological Casimir energy induced by the planar angle deficit. The results are generalized for a charged scalar field in the presence of a constant gauge field. In this case, the vacuum expectation values are periodic functions of the component of the vector potential along the compact dimension.
Landau quantization in the spinning cosmic string spacetime
NASA Astrophysics Data System (ADS)
Muniz, C. R.; Bezerra, V. B.; Cunha, M. S.
2014-11-01
We analyze the quantum phenomenon arising from the interaction of a spinless charged particle with a rotating cosmic string, under the action of a static and uniform magnetic field parallel to the string. We calculate the energy levels of the particle in the non-relativistic approach, showing how these energies depend on the parameters involved in the problem. In order to do this, we solve the time independent Schrödinger equation in the geometry of the spinning cosmic string, taking into account that the coupling between the rotation of the spacetime and the angular momentum of the particle is very weak, such that makes sense to apply the Schrödinger equation in a curved background whose metric has an off diagonal term which involves time and space. It is also assumed that the particle orbits sufficiently far from the boundary of the region of closed timelike curves which exist around this topological defect. Finally, we find the Landau levels of the particle in the presence of a spinning cosmic string endowed with internal structure, i.e., having a finite width and uniformly filled with both material and vacuum energies.
Gravitational Smoothing of Kinks on Cosmic String Loops
NASA Astrophysics Data System (ADS)
Wachter, Jeremy M.; Olum, Ken D.
2017-02-01
We analyze the effect of gravitational backreaction on cosmic string loops with kinks, which is an important determinant of the shape, and thus the potential observability, of string loops which may exist in the Universe today. Kinks are not rounded off, but may be straightened out. This means that backreaction will only cause loops with kinks to develop cusps after some potentially large fraction of their lifetimes. In some loops, symmetries prevent even this process, so that the loop evaporates in a self-similar fashion and the kinks are unchanged. As an example, we discuss backreaction on the rectangular Garfinkle-Vachaspati loop.
Gravitational Smoothing of Kinks on Cosmic String Loops.
Wachter, Jeremy M; Olum, Ken D
2017-02-03
We analyze the effect of gravitational backreaction on cosmic string loops with kinks, which is an important determinant of the shape, and thus the potential observability, of string loops which may exist in the Universe today. Kinks are not rounded off, but may be straightened out. This means that backreaction will only cause loops with kinks to develop cusps after some potentially large fraction of their lifetimes. In some loops, symmetries prevent even this process, so that the loop evaporates in a self-similar fashion and the kinks are unchanged. As an example, we discuss backreaction on the rectangular Garfinkle-Vachaspati loop.
Dynamics of cosmic strings with higher-dimensional windings
Yamauchi, Daisuke; Lake, Matthew J. E-mail: matthewj@nu.ac.th
2015-06-01
We consider F-strings with arbitrary configurations in the Minkowski directions of a higher-dimensional spacetime, which also wrap and spin around S{sup 1} subcycles of constant radius in an arbitrary internal manifold, and determine the relation between the higher-dimensional and the effective four-dimensional quantities that govern the string dynamics. We show that, for any such configuration, the motion of the windings in the compact space may render the string effectively tensionless from a four-dimensional perspective, so that it remains static with respect to the large dimensions. Such a critical configuration occurs when (locally) exactly half the square of the string length lies in the large dimensions and half lies in the compact space. The critical solution is then seen to arise as a special case, in which the wavelength of the windings is equal to their circumference. As examples, long straight strings and circular loops are considered in detail, and the solutions to the equations of motion that satisfy the tensionless condition are presented. These solutions are then generalized to planar loops and arbitrary three-dimensional configurations. Under the process of dimensional reduction, in which higher-dimensional motion is equivalent to an effective worldsheet current (giving rise to a conserved charge), this phenomenon may be seen as the analogue of the tensionless condition which arises for superconducting and chiral-current carrying cosmic strings.
Dynamics of cosmic strings with higher-dimensional windings
Yamauchi, Daisuke; Lake, Matthew J.
2015-06-11
We consider F-strings with arbitrary configurations in the Minkowski directions of a higher-dimensional spacetime, which also wrap and spin around S{sup 1} subcycles of constant radius in an arbitrary internal manifold, and determine the relation between the higher-dimensional and the effective four-dimensional quantities that govern the string dynamics. We show that, for any such configuration, the motion of the windings in the compact space may render the string effectively tensionless from a four-dimensional perspective, so that it remains static with respect to the large dimensions. Such a critical configuration occurs when (locally) exactly half the square of the string length lies in the large dimensions and half lies in the compact space. The critical solution is then seen to arise as a special case, in which the wavelength of the windings is equal to their circumference. As examples, long straight strings and circular loops are considered in detail, and the solutions to the equations of motion that satisfy the tensionless condition are presented. These solutions are then generalized to planar loops and arbitrary three-dimensional configurations. Under the process of dimensional reduction, in which higher-dimensional motion is equivalent to an effective worldsheet current (giving rise to a conserved charge), this phenomenon may be seen as the analogue of the tensionless condition which arises for superconducting and chiral-current carrying cosmic strings.
Is it Really Naked? On Cosmic Censorship in String Theory
Frolov, A
2004-09-30
We investigate the possibility of cosmic censorship violation in string theory using a characteristic double-null code, which penetrates horizons and is capable of resolving the spacetime all the way to the singularity. We perform high-resolution numerical simulations of the evolution of negative mass initial scalar field profiles, which were argued to provide a counter example to cosmic censorship conjecture for AdS-asymptotic spacetimes in five-dimensional supergravity. In no instances formation of naked singularity is seen. Instead, numerical evidence indicates that black holes form in the collapse. Our results are consistent with earlier numerical studies, and explicitly show where the ''no black hole'' argument breaks.
Is it really naked? On cosmic censorship in string theory
Frolov, Andrei V.
2004-11-15
We investigate the possibility of cosmic censorship violation in string theory using a characteristic double-null code, which penetrates horizons and is capable of resolving the spacetime all the way to the singularity. We perform high-resolution numerical simulations of the evolution of negative mass initial scalar field profiles, which were argued to provide a counterexample to cosmic censorship conjecture for AdS-asymptotic spacetimes in five-dimensional supergravity. In no instances formation of naked singularity is seen. Instead, numerical evidence indicates that black holes form in the collapse. Our results are consistent with earlier numerical studies, and explicitly show where the 'no black hole' argument breaks.
Stability of false vacuum in supersymmetric theories with cosmic strings
Kumar, Brijesh; Yajnik, Urjit A.
2009-03-15
We study the stability of supersymmetry breaking vacuum in the presence of cosmic strings arising in the messenger sector. For certain ranges of the couplings, the desired supersymmetry breaking vacua become unstable against decay into phenomenologically unacceptable vacua. This sets constraints on the range of allowed values of the coupling constants appearing in the models and more generally on the chosen dynamics of gauge symmetry breaking.
Induced vacuum bosonic current in a compactified cosmic string spacetime
NASA Astrophysics Data System (ADS)
Bragança, E. A. F.; Santana Mota, H. F.; de Mello, E. R. Bezerra
2016-03-01
We analyze the bosonic current densities induced by a magnetic flux running along an idealized cosmic string considering that the coordinate along its axis is compactified. We also consider the presence of a magnetic flux enclosed by the compactificatified axis. To develop this analysis, we calculate the complete set of normalized bosonic wave functions obeying a quasiperiodicity condition along the compactified dimension. We show that in this context only the azimuthal and axial currents take place.
The COBE cosmic 3 K anisotropy experiment: A gravity wave and cosmic string probe
NASA Technical Reports Server (NTRS)
Bennett, Charles L.; Smoot, George F.
1989-01-01
Among the experiments to be carried into orbit next year, by the COBE satellite, are differential microwave radiometers. They will make sensitive all-sky maps of the temperature of the cosmic microwave background radiation at three frequencies, giving dipole, quadrupole, and higher order multipole measurements of the background radiation. The experiment will either detect, or place significant constraints on, the existence of cosmic strings and long wavelength gravity waves.
Constraints on Cosmic Strings from the LIGO-Virgo Gravitational-Wave Detectors
NASA Astrophysics Data System (ADS)
Aasi, J.; Abadie, J.; Abbott, B. P.; Abbott, R.; Abbott, T.; Abernathy, M. R.; Accadia, T.; Acernese, F.; Adams, C.; Adams, T.; Adhikari, R. X.; Affeldt, C.; Agathos, M.; Aggarwal, N.; Aguiar, O. D.; Ajith, P.; Allen, B.; Allocca, A.; Amador Ceron, E.; Amariutei, D.; Anderson, R. A.; Anderson, S. B.; Anderson, W. G.; Arai, K.; Araya, M. C.; Arceneaux, C.; Areeda, J.; Ast, S.; Aston, S. M.; Astone, P.; Aufmuth, P.; Aulbert, C.; Austin, L.; Aylott, B. E.; Babak, S.; Baker, P. T.; Ballardin, G.; Ballmer, S. W.; Barayoga, J. C.; Barker, D.; Barnum, S. H.; Barone, F.; Barr, B.; Barsotti, L.; Barsuglia, M.; Barton, M. A.; Bartos, I.; Bassiri, R.; Basti, A.; Batch, J.; Bauchrowitz, J.; Bauer, Th. S.; Bebronne, M.; Behnke, B.; Bejger, M.; Beker, M. G.; Bell, A. S.; Bell, C.; Belopolski, I.; Bergmann, G.; Berliner, J. M.; Bersanetti, D.; Bertolini, A.; Bessis, D.; Betzwieser, J.; Beyersdorf, P. T.; Bhadbhade, T.; Bilenko, I. A.; Billingsley, G.; Birch, J.; Bitossi, M.; Bizouard, M. A.; Black, E.; Blackburn, J. K.; Blackburn, L.; Blair, D.; Blom, M.; Bock, O.; Bodiya, T. P.; Boer, M.; Bogan, C.; Bond, C.; Bondu, F.; Bonelli, L.; Bonnand, R.; Bork, R.; Born, M.; Boschi, V.; Bose, S.; Bosi, L.; Bowers, J.; Bradaschia, C.; Brady, P. R.; Braginsky, V. B.; Branchesi, M.; Brannen, C. A.; Brau, J. E.; Breyer, J.; Briant, T.; Bridges, D. O.; Brillet, A.; Brinkmann, M.; Brisson, V.; Britzger, M.; Brooks, A. F.; Brown, D. A.; Brown, D. D.; Brückner, F.; Bulik, T.; Bulten, H. J.; Buonanno, A.; Buskulic, D.; Buy, C.; Byer, R. L.; Cadonati, L.; Cagnoli, G.; Calderón Bustillo, J.; Calloni, E.; Camp, J. B.; Campsie, P.; Cannon, K. C.; Canuel, B.; Cao, J.; Capano, C. D.; Carbognani, F.; Carbone, L.; Caride, S.; Castiglia, A.; Caudill, S.; Cavaglià, M.; Cavalier, F.; Cavalieri, R.; Cella, G.; Cepeda, C.; Cesarini, E.; Chakraborty, R.; Chalermsongsak, T.; Chao, S.; Charlton, P.; Chassande-Mottin, E.; Chen, X.; Chen, Y.; Chincarini, A.; Chiummo, A.; Cho, H. S.; Chow, J.; Christensen, N.; Chu, Q.; Chua, S. S. Y.; Chung, S.; Ciani, G.; Clara, F.; Clark, D. E.; Clark, J. A.; Cleva, F.; Coccia, E.; Cohadon, P.-F.; Colla, A.; Colombini, M.; Constancio, M.; Conte, A.; Conte, R.; Cook, D.; Corbitt, T. R.; Cordier, M.; Cornish, N.; Corsi, A.; Costa, C. A.; Coughlin, M. W.; Coulon, J.-P.; Countryman, S.; Couvares, P.; Coward, D. M.; Cowart, M.; Coyne, D. C.; Craig, K.; Creighton, J. D. E.; Creighton, T. D.; Crowder, S. G.; Cumming, A.; Cunningham, L.; Cuoco, E.; Dahl, K.; Canton, T. Dal; Damjanic, M.; Danilishin, S. L.; D'Antonio, S.; Danzmann, K.; Dattilo, V.; Daudert, B.; Daveloza, H.; Davier, M.; Davies, G. S.; Daw, E. J.; Day, R.; Dayanga, T.; De Rosa, R.; Debreczeni, G.; Degallaix, J.; Del Pozzo, W.; Deleeuw, E.; Deléglise, S.; Denker, T.; Dent, T.; Dereli, H.; Dergachev, V.; DeRosa, R.; DeSalvo, R.; Dhurandhar, S.; Di Fiore, L.; Di Lieto, A.; Di Palma, I.; Di Virgilio, A.; Díaz, M.; Dietz, A.; Dmitry, K.; Donovan, F.; Dooley, K. L.; Doravari, S.; Drago, M.; Drever, R. W. P.; Driggers, J. C.; Du, Z.; Dumas, J.-C.; Dwyer, S.; Eberle, T.; Edwards, M.; Effler, A.; Ehrens, P.; Eichholz, J.; Eikenberry, S. S.; Endrőczi, G.; Essick, R.; Etzel, T.; Evans, K.; Evans, M.; Evans, T.; Factourovich, M.; Fafone, V.; Fairhurst, S.; Fang, Q.; Farinon, S.; Farr, B.; Farr, W.; Favata, M.; Fazi, D.; Fehrmann, H.; Feldbaum, D.; Ferrante, I.; Ferrini, F.; Fidecaro, F.; Finn, L. S.; Fiori, I.; Fisher, R.; Flaminio, R.; Foley, E.; Foley, S.; Forsi, E.; Fotopoulos, N.; Fournier, J.-D.; Franco, S.; Frasca, S.; Frasconi, F.; Frede, M.; Frei, M.; Frei, Z.; Freise, A.; Frey, R.; Fricke, T. T.; Fritschel, P.; Frolov, V. V.; Fujimoto, M.-K.; Fulda, P.; Fyffe, M.; Gair, J.; Gammaitoni, L.; Garcia, J.; Garufi, F.; Gehrels, N.; Gemme, G.; Genin, E.; Gennai, A.; Gergely, L.; Ghosh, S.; Giaime, J. A.; Giampanis, S.; Giardina, K. D.; Giazotto, A.; Gil-Casanova, S.; Gill, C.; Gleason, J.; Goetz, E.; Goetz, R.; Gondan, L.; González, G.; Gordon, N.; Gorodetsky, M. L.; Gossan, S.; Goßler, S.; Gouaty, R.; Graef, C.; Graff, P. B.; Granata, M.; Grant, A.; Gras, S.; Gray, C.; Greenhalgh, R. J. S.; Gretarsson, A. M.; Griffo, C.; Groot, P.; Grote, H.; Grover, K.; Grunewald, S.; Guidi, G. M.; Guido, C.; Gushwa, K. E.; Gustafson, E. K.; Gustafson, R.; Hall, B.; Hall, E.; Hammer, D.; Hammond, G.; Hanke, M.; Hanks, J.; Hanna, C.; Hanson, J.; Harms, J.; Harry, G. M.; Harry, I. W.; Harstad, E. D.; Hartman, M. T.; Haughian, K.; Hayama, K.; Heefner, J.; Heidmann, A.; Heintze, M.; Heitmann, H.; Hello, P.; Hemming, G.; Hendry, M.; Heng, I. S.; Heptonstall, A. W.; Heurs, M.; Hild, S.; Hoak, D.; Hodge, K. A.; Holt, K.; Holtrop, M.; Hong, T.; Hooper, S.; Horrom, T.; Hosken, D. J.; Hough, J.; Howell, E. J.; Hu, Y.; Hua, Z.; Huang, V.; Huerta, E. A.; Hughey, B.; Husa, S.; Huttner, S. H.; Huynh, M.; Huynh-Dinh, T.; Iafrate, J.; Ingram, D. R.; Inta, R.; Isogai, T.; Ivanov, A.; Iyer, B. R.; Izumi, K.; Jacobson, M.; James, E.; Jang, H.; Jang, Y. J.; Jaranowski, P.; Jiménez-Forteza, F.; Johnson, W. W.; Jones, D.; Jones, D. I.; Jones, R.; Jonker, R. J. G.; Ju, L.; Haris, K.; Kalmus, P.; Kalogera, V.; Kandhasamy, S.; Kang, G.; Kanner, J. B.; Kasprzack, M.; Kasturi, R.; Katsavounidis, E.; Katzman, W.; Kaufer, H.; Kaufman, K.; Kawabe, K.; Kawamura, S.; Kawazoe, F.; Kéfélian, F.; Keitel, D.; Kelley, D. B.; Kells, W.; Keppel, D. G.; Khalaidovski, A.; Khalili, F. Y.; Khazanov, E. A.; Kim, B. K.; Kim, C.; Kim, K.; Kim, N.; Kim, W.; Kim, Y.-M.; King, E. J.; King, P. J.; Kinzel, D. L.; Kissel, J. S.; Klimenko, S.; Kline, J.; Koehlenbeck, S.; Kokeyama, K.; Kondrashov, V.; Koranda, S.; Korth, W. Z.; Kowalska, I.; Kozak, D.; Kremin, A.; Kringel, V.; Królak, A.; Kucharczyk, C.; Kudla, S.; Kuehn, G.; Kumar, A.; Kumar, P.; Kumar, R.; Kurdyumov, R.; Kwee, P.; Landry, M.; Lantz, B.; Larson, S.; Lasky, P. D.; Lawrie, C.; Lazzarini, A.; Le Roux, A.; Leaci, P.; Lebigot, E. O.; Lee, C.-H.; Lee, H. K.; Lee, H. M.; Lee, J.; Lee, J.; Leonardi, M.; Leong, J. R.; Leroy, N.; Letendre, N.; Levine, B.; Lewis, J. B.; Lhuillier, V.; Li, T. G. F.; Lin, A. C.; Littenberg, T. B.; Litvine, V.; Liu, F.; Liu, H.; Liu, Y.; Liu, Z.; Lloyd, D.; Lockerbie, N. A.; Lockett, V.; Lodhia, D.; Loew, K.; Logue, J.; Lombardi, A. L.; Lorenzini, M.; Loriette, V.; Lormand, M.; Losurdo, G.; Lough, J.; Luan, J.; Lubinski, M. J.; Lück, H.; Lundgren, A. P.; Macarthur, J.; Macdonald, E.; Machenschalk, B.; MacInnis, M.; Macleod, D. M.; Magana-Sandoval, F.; Mageswaran, M.; Mailand, K.; Majorana, E.; Maksimovic, I.; Malvezzi, V.; Man, N.; Manca, G. M.; Mandel, I.; Mandic, V.; Mangano, V.; Mantovani, M.; Marchesoni, F.; Marion, F.; Márka, S.; Márka, Z.; Markosyan, A.; Maros, E.; Marque, J.; Martelli, F.; Martin, I. W.; Martin, R. M.; Martinelli, L.; Martynov, D.; Marx, J. N.; Mason, K.; Masserot, A.; Massinger, T. J.; Matichard, F.; Matone, L.; Matzner, R. A.; Mavalvala, N.; May, G.; Mazumder, N.; Mazzolo, G.; McCarthy, R.; McClelland, D. E.; McGuire, S. C.; McIntyre, G.; McIver, J.; Meacher, D.; Meadors, G. D.; Mehmet, M.; Meidam, J.; Meier, T.; Melatos, A.; Mendell, G.; Mercer, R. A.; Meshkov, S.; Messenger, C.; Meyer, M. S.; Miao, H.; Michel, C.; Mikhailov, E. E.; Milano, L.; Miller, J.; Minenkov, Y.; Mingarelli, C. M. F.; Mitra, S.; Mitrofanov, V. P.; Mitselmakher, G.; Mittleman, R.; Moe, B.; Mohan, M.; Mohapatra, S. R. P.; Mokler, F.; Moraru, D.; Moreno, G.; Morgado, N.; Mori, T.; Morriss, S. R.; Mossavi, K.; Mours, B.; Mow-Lowry, C. M.; Mueller, C. L.; Mueller, G.; Mukherjee, S.; Mullavey, A.; Munch, J.; Murphy, D.; Murray, P. G.; Mytidis, A.; Nagy, M. F.; Nanda Kumar, D.; Nardecchia, I.; Nash, T.; Naticchioni, L.; Nayak, R.; Necula, V.; Nelemans, G.; Neri, I.; Neri, M.; Newton, G.; Nguyen, T.; Nishida, E.; Nishizawa, A.; Nitz, A.; Nocera, F.; Nolting, D.; Normandin, M. E.; Nuttall, L. K.; Ochsner, E.; O'Dell, J.; Oelker, E.; Ogin, G. H.; Oh, J. J.; Oh, S. H.; Ohme, F.; Oppermann, P.; O'Reilly, B.; Ortega Larcher, W.; O'Shaughnessy, R.; Osthelder, C.; Ott, C. D.; Ottaway, D. J.; Ottens, R. S.; Ou, J.; Overmier, H.; Owen, B. J.; Padilla, C.; Pai, A.; Palomba, C.; Pan, Y.; Pankow, C.; Paoletti, F.; Paoletti, R.; Papa, M. A.; Paris, H.; Pasqualetti, A.; Passaquieti, R.; Passuello, D.; Pedraza, M.; Peiris, P.; Penn, S.; Perreca, A.; Phelps, M.; Pichot, M.; Pickenpack, M.; Piergiovanni, F.; Pierro, V.; Pinard, L.; Pindor, B.; Pinto, I. M.; Pitkin, M.; Poeld, J.; Poggiani, R.; Poole, V.; Poux, C.; Predoi, V.; Prestegard, T.; Price, L. R.; Prijatelj, M.; Principe, M.; Privitera, S.; Prix, R.; Prodi, G. A.; Prokhorov, L.; Puncken, O.; Punturo, M.; Puppo, P.; Quetschke, V.; Quintero, E.; Quitzow-James, R.; Raab, F. J.; Rabeling, D. S.; Rácz, I.; Radkins, H.; Raffai, P.; Raja, S.; Rajalakshmi, G.; Rakhmanov, M.; Ramet, C.; Rapagnani, P.; Raymond, V.; Re, V.; Reed, C. M.; Reed, T.; Regimbau, T.; Reid, S.; Reitze, D. H.; Ricci, F.; Riesen, R.; Riles, K.; Robertson, N. A.; Robinet, F.; Rocchi, A.; Roddy, S.; Rodriguez, C.; Rodruck, M.; Roever, C.; Rolland, L.; Rollins, J. G.; Romano, R.; Romanov, G.; Romie, J. H.; Rosińska, D.; Rowan, S.; Rüdiger, A.; Ruggi, P.; Ryan, K.; Salemi, F.; Sammut, L.; Sandberg, V.; Sanders, J.; Sannibale, V.; Santiago-Prieto, I.; Saracco, E.; Sassolas, B.; Sathyaprakash, B. S.; Saulson, P. R.; Savage, R.; Schilling, R.; Schnabel, R.; Schofield, R. M. S.; Schreiber, E.; Schuette, D.; Schulz, B.; Schutz, B. F.; Schwinberg, P.; Scott, J.; Scott, S. M.; Seifert, F.; Sellers, D.; Sengupta, A. S.; Sentenac, D.; Sergeev, A.; Shaddock, D.; Shah, S.; Shahriar, M. S.; Shaltev, M.; Shapiro, B.; Shawhan, P.; Shoemaker, D. H.; Sidery, T. L.; Siellez, K.; Siemens, X.; Sigg, D.; Simakov, D.; Singer, A.; Singer, L.; Sintes, A. M.; Skelton, G. R.; Slagmolen, B. J. J.; Slutsky, J.; Smith, J. R.; Smith, M. R.; Smith, R. J. E.; Smith-Lefebvre, N. D.; Soden, K.; Son, E. J.; Sorazu, B.; Souradeep, T.; Sperandio, L.; Staley, A.; Steinert, E.; Steinlechner, J.; Steinlechner, S.; Steplewski, S.; Stevens, D.; Stochino, A.; Stone, R.; Strain, K. A.; Straniero, N.; Strigin, S.; Stroeer, A. S.; Sturani, R.; Stuver, A. L.; Summerscales, T. Z.; Susmithan, S.; Sutton, P. J.; Swinkels, B.; Szeifert, G.; Tacca, M.; Talukder, D.; Tang, L.; Tanner, D. B.; Tarabrin, S. P.; Taylor, R.; ter Braack, A. P. M.; Thirugnanasambandam, M. P.; Thomas, M.; Thomas, P.; Thorne, K. A.; Thorne, K. S.; Thrane, E.; Tiwari, V.; Tokmakov, K. V.; Tomlinson, C.; Toncelli, A.; Tonelli, M.; Torre, O.; Torres, C. V.; Torrie, C. I.; Travasso, F.; Traylor, G.; Tse, M.; Ugolini, D.; Unnikrishnan, C. S.; Vahlbruch, H.; Vajente, G.; Vallisneri, M.; van den Brand, J. F. J.; Van Den Broeck, C.; van der Putten, S.; van der Sluys, M. V.; van Heijningen, J.; van Veggel, A. A.; Vass, S.; Vasúth, M.; Vaulin, R.; Vecchio, A.; Vedovato, G.; Veitch, J.; Veitch, P. J.; Venkateswara, K.; Verkindt, D.; Verma, S.; Vetrano, F.; Viceré, A.; Vincent-Finley, R.; Vinet, J.-Y.; Vitale, S.; Vlcek, B.; Vo, T.; Vocca, H.; Vorvick, C.; Vousden, W. D.; Vrinceanu, D.; Vyachanin, S. P.; Wade, A.; Wade, L.; Wade, M.; Waldman, S. J.; Walker, M.; Wallace, L.; Wan, Y.; Wang, J.; Wang, M.; Wang, X.; Wanner, A.; Ward, R. L.; Was, M.; Weaver, B.; Wei, L.-W.; Weinert, M.; Weinstein, A. J.; Weiss, R.; Welborn, T.; Wen, L.; Wessels, P.; West, M.; Westphal, T.; Wette, K.; Whelan, J. T.; Whitcomb, S. E.; White, D. J.; Whiting, B. F.; Wibowo, S.; Wiesner, K.; Wilkinson, C.; Williams, L.; Williams, R.; Williams, T.; Willis, J. L.; Willke, B.; Wimmer, M.; Winkelmann, L.; Winkler, W.; Wipf, C. C.; Wittel, H.; Woan, G.; Worden, J.; Yablon, J.; Yakushin, I.; Yamamoto, H.; Yancey, C. C.; Yang, H.; Yeaton-Massey, D.; Yoshida, S.; Yum, H.; Yvert, M.; ZadroŻny, A.; Zanolin, M.; Zendri, J.-P.; Zhang, F.; Zhang, L.; Zhao, C.; Zhu, H.; Zhu, X. J.; Zotov, N.; Zucker, M. E.; Zweizig, J.; LIGO Scientific Collaboration; Virgo Collaboration
2014-04-01
Cosmic strings can give rise to a large variety of interesting astrophysical phenomena. Among them, powerful bursts of gravitational waves (GWs) produced by cusps are a promising observational signature. In this Letter we present a search for GWs from cosmic string cusps in data collected by the LIGO and Virgo gravitational wave detectors between 2005 and 2010, with over 625 days of live time. We find no evidence of GW signals from cosmic strings. From this result, we derive new constraints on cosmic string parameters, which complement and improve existing limits from previous searches for a stochastic background of GWs from cosmic microwave background measurements and pulsar timing data. In particular, if the size of loops is given by the gravitational backreaction scale, we place upper limits on the string tension Gμ below 10-8 in some regions of the cosmic string parameter space.
Constraints on cosmic strings from the LIGO-Virgo gravitational-wave detectors.
Aasi, J; Abadie, J; Abbott, B P; Abbott, R; Abbott, T; Abernathy, M R; Accadia, T; Acernese, F; Adams, C; Adams, T; Adhikari, R X; Affeldt, C; Agathos, M; Aggarwal, N; Aguiar, O D; Ajith, P; Allen, B; Allocca, A; Amador Ceron, E; Amariutei, D; Anderson, R A; Anderson, S B; Anderson, W G; Arai, K; Araya, M C; Arceneaux, C; Areeda, J; Ast, S; Aston, S M; Astone, P; Aufmuth, P; Aulbert, C; Austin, L; Aylott, B E; Babak, S; Baker, P T; Ballardin, G; Ballmer, S W; Barayoga, J C; Barker, D; Barnum, S H; Barone, F; Barr, B; Barsotti, L; Barsuglia, M; Barton, M A; Bartos, I; Bassiri, R; Basti, A; Batch, J; Bauchrowitz, J; Bauer, Th S; Bebronne, M; Behnke, B; Bejger, M; Beker, M G; Bell, A S; Bell, C; Belopolski, I; Bergmann, G; Berliner, J M; Bersanetti, D; Bertolini, A; Bessis, D; Betzwieser, J; Beyersdorf, P T; Bhadbhade, T; Bilenko, I A; Billingsley, G; Birch, J; Bitossi, M; Bizouard, M A; Black, E; Blackburn, J K; Blackburn, L; Blair, D; Blom, M; Bock, O; Bodiya, T P; Boer, M; Bogan, C; Bond, C; Bondu, F; Bonelli, L; Bonnand, R; Bork, R; Born, M; Boschi, V; Bose, S; Bosi, L; Bowers, J; Bradaschia, C; Brady, P R; Braginsky, V B; Branchesi, M; Brannen, C A; Brau, J E; Breyer, J; Briant, T; Bridges, D O; Brillet, A; Brinkmann, M; Brisson, V; Britzger, M; Brooks, A F; Brown, D A; Brown, D D; Brückner, F; Bulik, T; Bulten, H J; Buonanno, A; Buskulic, D; Buy, C; Byer, R L; Cadonati, L; Cagnoli, G; Calderón Bustillo, J; Calloni, E; Camp, J B; Campsie, P; Cannon, K C; Canuel, B; Cao, J; Capano, C D; Carbognani, F; Carbone, L; Caride, S; Castiglia, A; Caudill, S; Cavaglià, M; Cavalier, F; Cavalieri, R; Cella, G; Cepeda, C; Cesarini, E; Chakraborty, R; Chalermsongsak, T; Chao, S; Charlton, P; Chassande-Mottin, E; Chen, X; Chen, Y; Chincarini, A; Chiummo, A; Cho, H S; Chow, J; Christensen, N; Chu, Q; Chua, S S Y; Chung, S; Ciani, G; Clara, F; Clark, D E; Clark, J A; Cleva, F; Coccia, E; Cohadon, P-F; Colla, A; Colombini, M; Constancio, M; Conte, A; Conte, R; Cook, D; Corbitt, T R; Cordier, M; Cornish, N; Corsi, A; Costa, C A; Coughlin, M W; Coulon, J-P; Countryman, S; Couvares, P; Coward, D M; Cowart, M; Coyne, D C; Craig, K; Creighton, J D E; Creighton, T D; Crowder, S G; Cumming, A; Cunningham, L; Cuoco, E; Dahl, K; Dal Canton, T; Damjanic, M; Danilishin, S L; D'Antonio, S; Danzmann, K; Dattilo, V; Daudert, B; Daveloza, H; Davier, M; Davies, G S; Daw, E J; Day, R; Dayanga, T; De Rosa, R; Debreczeni, G; Degallaix, J; Del Pozzo, W; Deleeuw, E; Deléglise, S; Denker, T; Dent, T; Dereli, H; Dergachev, V; DeRosa, R; DeSalvo, R; Dhurandhar, S; Di Fiore, L; Di Lieto, A; Di Palma, I; Di Virgilio, A; Díaz, M; Dietz, A; Dmitry, K; Donovan, F; Dooley, K L; Doravari, S; Drago, M; Drever, R W P; Driggers, J C; Du, Z; Dumas, J-C; Dwyer, S; Eberle, T; Edwards, M; Effler, A; Ehrens, P; Eichholz, J; Eikenberry, S S; Endrőczi, G; Essick, R; Etzel, T; Evans, K; Evans, M; Evans, T; Factourovich, M; Fafone, V; Fairhurst, S; Fang, Q; Farinon, S; Farr, B; Farr, W; Favata, M; Fazi, D; Fehrmann, H; Feldbaum, D; Ferrante, I; Ferrini, F; Fidecaro, F; Finn, L S; Fiori, I; Fisher, R; Flaminio, R; Foley, E; Foley, S; Forsi, E; Fotopoulos, N; Fournier, J-D; Franco, S; Frasca, S; Frasconi, F; Frede, M; Frei, M; Frei, Z; Freise, A; Frey, R; Fricke, T T; Fritschel, P; Frolov, V V; Fujimoto, M-K; Fulda, P; Fyffe, M; Gair, J; Gammaitoni, L; Garcia, J; Garufi, F; Gehrels, N; Gemme, G; Genin, E; Gennai, A; Gergely, L; Ghosh, S; Giaime, J A; Giampanis, S; Giardina, K D; Giazotto, A; Gil-Casanova, S; Gill, C; Gleason, J; Goetz, E; Goetz, R; Gondan, L; González, G; Gordon, N; Gorodetsky, M L; Gossan, S; Goßler, S; Gouaty, R; Graef, C; Graff, P B; Granata, M; Grant, A; Gras, S; Gray, C; Greenhalgh, R J S; Gretarsson, A M; Griffo, C; Groot, P; Grote, H; Grover, K; Grunewald, S; Guidi, G M; Guido, C; Gushwa, K E; Gustafson, E K; Gustafson, R; Hall, B; Hall, E; Hammer, D; Hammond, G; Hanke, M; Hanks, J; Hanna, C; Hanson, J; Harms, J; Harry, G M; Harry, I W; Harstad, E D; Hartman, M T; Haughian, K; Hayama, K; Heefner, J; Heidmann, A; Heintze, M; Heitmann, H; Hello, P; Hemming, G; Hendry, M; Heng, I S; Heptonstall, A W; Heurs, M; Hild, S; Hoak, D; Hodge, K A; Holt, K; Holtrop, M; Hong, T; Hooper, S; Horrom, T; Hosken, D J; Hough, J; Howell, E J; Hu, Y; Hua, Z; Huang, V; Huerta, E A; Hughey, B; Husa, S; Huttner, S H; Huynh, M; Huynh-Dinh, T; Iafrate, J; Ingram, D R; Inta, R; Isogai, T; Ivanov, A; Iyer, B R; Izumi, K; Jacobson, M; James, E; Jang, H; Jang, Y J; Jaranowski, P; Jiménez-Forteza, F; Johnson, W W; Jones, D; Jones, D I; Jones, R; Jonker, R J G; Ju, L; K, Haris; Kalmus, P; Kalogera, V; Kandhasamy, S; Kang, G; Kanner, J B; Kasprzack, M; Kasturi, R; Katsavounidis, E; Katzman, W; Kaufer, H; Kaufman, K; Kawabe, K; Kawamura, S; Kawazoe, F; Kéfélian, F; Keitel, D; Kelley, D B; Kells, W; Keppel, D G; Khalaidovski, A; Khalili, F Y; Khazanov, E A; Kim, B K; Kim, C; Kim, K; Kim, N; Kim, W; Kim, Y-M; King, E J; King, P J; Kinzel, D L; Kissel, J S; Klimenko, S; Kline, J; Koehlenbeck, S; Kokeyama, K; Kondrashov, V; Koranda, S; Korth, W Z; Kowalska, I; Kozak, D; Kremin, A; Kringel, V; Królak, A; Kucharczyk, C; Kudla, S; Kuehn, G; Kumar, A; Kumar, P; Kumar, R; Kurdyumov, R; Kwee, P; Landry, M; Lantz, B; Larson, S; Lasky, P D; Lawrie, C; Lazzarini, A; Le Roux, A; Leaci, P; Lebigot, E O; Lee, C-H; Lee, H K; Lee, H M; Lee, J; Lee, J; Leonardi, M; Leong, J R; Leroy, N; Letendre, N; Levine, B; Lewis, J B; Lhuillier, V; Li, T G F; Lin, A C; Littenberg, T B; Litvine, V; Liu, F; Liu, H; Liu, Y; Liu, Z; Lloyd, D; Lockerbie, N A; Lockett, V; Lodhia, D; Loew, K; Logue, J; Lombardi, A L; Lorenzini, M; Loriette, V; Lormand, M; Losurdo, G; Lough, J; Luan, J; Lubinski, M J; Lück, H; Lundgren, A P; Macarthur, J; Macdonald, E; Machenschalk, B; MacInnis, M; Macleod, D M; Magana-Sandoval, F; Mageswaran, M; Mailand, K; Majorana, E; Maksimovic, I; Malvezzi, V; Man, N; Manca, G M; Mandel, I; Mandic, V; Mangano, V; Mantovani, M; Marchesoni, F; Marion, F; Márka, S; Márka, Z; Markosyan, A; Maros, E; Marque, J; Martelli, F; Martin, I W; Martin, R M; Martinelli, L; Martynov, D; Marx, J N; Mason, K; Masserot, A; Massinger, T J; Matichard, F; Matone, L; Matzner, R A; Mavalvala, N; May, G; Mazumder, N; Mazzolo, G; McCarthy, R; McClelland, D E; McGuire, S C; McIntyre, G; McIver, J; Meacher, D; Meadors, G D; Mehmet, M; Meidam, J; Meier, T; Melatos, A; Mendell, G; Mercer, R A; Meshkov, S; Messenger, C; Meyer, M S; Miao, H; Michel, C; Mikhailov, E E; Milano, L; Miller, J; Minenkov, Y; Mingarelli, C M F; Mitra, S; Mitrofanov, V P; Mitselmakher, G; Mittleman, R; Moe, B; Mohan, M; Mohapatra, S R P; Mokler, F; Moraru, D; Moreno, G; Morgado, N; Mori, T; Morriss, S R; Mossavi, K; Mours, B; Mow-Lowry, C M; Mueller, C L; Mueller, G; Mukherjee, S; Mullavey, A; Munch, J; Murphy, D; Murray, P G; Mytidis, A; Nagy, M F; Nanda Kumar, D; Nardecchia, I; Nash, T; Naticchioni, L; Nayak, R; Necula, V; Nelemans, G; Neri, I; Neri, M; Newton, G; Nguyen, T; Nishida, E; Nishizawa, A; Nitz, A; Nocera, F; Nolting, D; Normandin, M E; Nuttall, L K; Ochsner, E; O'Dell, J; Oelker, E; Ogin, G H; Oh, J J; Oh, S H; Ohme, F; Oppermann, P; O'Reilly, B; Ortega Larcher, W; O'Shaughnessy, R; Osthelder, C; Ott, C D; Ottaway, D J; Ottens, R S; Ou, J; Overmier, H; Owen, B J; Padilla, C; Pai, A; Palomba, C; Pan, Y; Pankow, C; Paoletti, F; Paoletti, R; Papa, M A; Paris, H; Pasqualetti, A; Passaquieti, R; Passuello, D; Pedraza, M; Peiris, P; Penn, S; Perreca, A; Phelps, M; Pichot, M; Pickenpack, M; Piergiovanni, F; Pierro, V; Pinard, L; Pindor, B; Pinto, I M; Pitkin, M; Poeld, J; Poggiani, R; Poole, V; Poux, C; Predoi, V; Prestegard, T; Price, L R; Prijatelj, M; Principe, M; Privitera, S; Prix, R; Prodi, G A; Prokhorov, L; Puncken, O; Punturo, M; Puppo, P; Quetschke, V; Quintero, E; Quitzow-James, R; Raab, F J; Rabeling, D S; Rácz, I; Radkins, H; Raffai, P; Raja, S; Rajalakshmi, G; Rakhmanov, M; Ramet, C; Rapagnani, P; Raymond, V; Re, V; Reed, C M; Reed, T; Regimbau, T; Reid, S; Reitze, D H; Ricci, F; Riesen, R; Riles, K; Robertson, N A; Robinet, F; Rocchi, A; Roddy, S; Rodriguez, C; Rodruck, M; Roever, C; Rolland, L; Rollins, J G; Romano, R; Romanov, G; Romie, J H; Rosińska, D; Rowan, S; Rüdiger, A; Ruggi, P; Ryan, K; Salemi, F; Sammut, L; Sandberg, V; Sanders, J; Sannibale, V; Santiago-Prieto, I; Saracco, E; Sassolas, B; Sathyaprakash, B S; Saulson, P R; Savage, R; Schilling, R; Schnabel, R; Schofield, R M S; Schreiber, E; Schuette, D; Schulz, B; Schutz, B F; Schwinberg, P; Scott, J; Scott, S M; Seifert, F; Sellers, D; Sengupta, A S; Sentenac, D; Sergeev, A; Shaddock, D; Shah, S; Shahriar, M S; Shaltev, M; Shapiro, B; Shawhan, P; Shoemaker, D H; Sidery, T L; Siellez, K; Siemens, X; Sigg, D; Simakov, D; Singer, A; Singer, L; Sintes, A M; Skelton, G R; Slagmolen, B J J; Slutsky, J; Smith, J R; Smith, M R; Smith, R J E; Smith-Lefebvre, N D; Soden, K; Son, E J; Sorazu, B; Souradeep, T; Sperandio, L; Staley, A; Steinert, E; Steinlechner, J; Steinlechner, S; Steplewski, S; Stevens, D; Stochino, A; Stone, R; Strain, K A; Straniero, N; Strigin, S; Stroeer, A S; Sturani, R; Stuver, A L; Summerscales, T Z; Susmithan, S; Sutton, P J; Swinkels, B; Szeifert, G; Tacca, M; Talukder, D; Tang, L; Tanner, D B; Tarabrin, S P; Taylor, R; ter Braack, A P M; Thirugnanasambandam, M P; Thomas, M; Thomas, P; Thorne, K A; Thorne, K S; Thrane, E; Tiwari, V; Tokmakov, K V; Tomlinson, C; Toncelli, A; Tonelli, M; Torre, O; Torres, C V; Torrie, C I; Travasso, F; Traylor, G; Tse, M; Ugolini, D; Unnikrishnan, C S; Vahlbruch, H; Vajente, G; Vallisneri, M; van den Brand, J F J; Van Den Broeck, C; van der Putten, S; van der Sluys, M V; van Heijningen, J; van Veggel, A A; Vass, S; Vasúth, M; Vaulin, R; Vecchio, A; Vedovato, G; Veitch, J; Veitch, P J; Venkateswara, K; Verkindt, D; Verma, S; Vetrano, F; Viceré, A; Vincent-Finley, R; Vinet, J-Y; Vitale, S; Vlcek, B; Vo, T; Vocca, H; Vorvick, C; Vousden, W D; Vrinceanu, D; Vyachanin, S P; Wade, A; Wade, L; Wade, M; Waldman, S J; Walker, M; Wallace, L; Wan, Y; Wang, J; Wang, M; Wang, X; Wanner, A; Ward, R L; Was, M; Weaver, B; Wei, L-W; Weinert, M; Weinstein, A J; Weiss, R; Welborn, T; Wen, L; Wessels, P; West, M; Westphal, T; Wette, K; Whelan, J T; Whitcomb, S E; White, D J; Whiting, B F; Wibowo, S; Wiesner, K; Wilkinson, C; Williams, L; Williams, R; Williams, T; Willis, J L; Willke, B; Wimmer, M; Winkelmann, L; Winkler, W; Wipf, C C; Wittel, H; Woan, G; Worden, J; Yablon, J; Yakushin, I; Yamamoto, H; Yancey, C C; Yang, H; Yeaton-Massey, D; Yoshida, S; Yum, H; Yvert, M; Zadrożny, A; Zanolin, M; Zendri, J-P; Zhang, F; Zhang, L; Zhao, C; Zhu, H; Zhu, X J; Zotov, N; Zucker, M E; Zweizig, J
2014-04-04
Cosmic strings can give rise to a large variety of interesting astrophysical phenomena. Among them, powerful bursts of gravitational waves (GWs) produced by cusps are a promising observational signature. In this Letter we present a search for GWs from cosmic string cusps in data collected by the LIGO and Virgo gravitational wave detectors between 2005 and 2010, with over 625 days of live time. We find no evidence of GW signals from cosmic strings. From this result, we derive new constraints on cosmic string parameters, which complement and improve existing limits from previous searches for a stochastic background of GWs from cosmic microwave background measurements and pulsar timing data. In particular, if the size of loops is given by the gravitational backreaction scale, we place upper limits on the string tension Gμ below 10(-8) in some regions of the cosmic string parameter space.
Constraints on Cosmic Strings from the LIGO-Virgo Gravitational-Wave Detectors
NASA Technical Reports Server (NTRS)
Aasi, J.; Abadie, J.; Abbott, B.P.; Abbott, R.; Abbott, T.; Abernathy, M.R.; Accadia, T.; Adams, C.; Adams, T.; Adhikari, R.X.; Affeldt, C.; Agathos, M.; Aggarwal, N.; Aguiar, O.D.; Ajith, P.; Allen, B.; Allocca, A.; Ceron, E.A.; Amariutei, D.; Anderson, S.B.; Blackburn, L.; Camp, J.B.; Gehrels, N.; Graff, P.B.; Kanner, J.B.
2014-01-01
Cosmic strings can give rise to a large variety of interesting astrophysical phenomena. Among them, powerful bursts of gravitational waves (GWs) produced by cusps are a promising observational signature. In this Letter we present a search for GWs from cosmic string cusps in data collected by the LIGO and Virgo gravitational wave detectors between 2005 and 2010, with over 625 days of live time. We find no evidence of GW signals from cosmic strings. From this result, we derive new constraints on cosmic string parameters, which complement and improve existing limits from previous searches for a stochastic background of GWs from cosmic microwave background measurements and pulsar timing data. In particular, if the size of loops is given by the gravitational backreaction scale, we place upper limits on the string tension (Newton's Constant x mass per unit length) below 10(exp -8) in some regions of the cosmic string parameter space.
CMB polarization power spectra contributions from a network of cosmic strings
Bevis, Neil; Hindmarsh, Mark; Urrestilla, Jon; Kunz, Martin
2007-08-15
We present the first calculation of the possible (local) cosmic string contribution to the cosmic microwave background polarization spectra from simulations of a string network (rather than a stochastic collection of unconnected string segments). We use field-theory simulations of the Abelian Higgs model to represent local U(1) strings, including their radiative decay and microphysics. Relative to previous estimates, our calculations show a shift in power to larger angular scales, making the chance of a future cosmic string detection from the B-mode polarization slightly greater. We explore a future ground-based polarization detector, taking the CLOVER project as our example. In the null hypothesis (that cosmic strings make a zero contribution) we find that CLOVER should limit the string tension {mu} to G{mu}<0.12x10{sup -6} (where G is the gravitational constant), above which it is likely that a detection would be possible.
The implications of the COBE diffuse microwave radiation results for cosmic strings
NASA Technical Reports Server (NTRS)
Bennett, David P.; Stebbins, Albert; Bouchet, Francois R.
1992-01-01
We compare the anisotropies in the cosmic microwave background radiation measured by the COBE experiment to those predicted by cosmic string theories. We use an analytic model for the Delta T/T power spectrum that is based on our previous numerical simulations of strings, under the assumption that cosmic strings are the sole source of the measured anisotropy. This implies a value for the string mass per unit length of 1.5 +/- 0.5 x 10 exp -6 C-squared/G. This is within the range of values required for cosmic strings to successfully seed the formation of large-scale structures in the universe. These results clearly encourage further studies of Delta T/T and large-scale structure in the cosmic string model.
Closed timelike curves produced by pairs of moving cosmic strings - Exact solutions
NASA Technical Reports Server (NTRS)
Gott, J. Richard, III
1991-01-01
Exact solutions of Einstein's field equations are presented for the general case of two moving straight cosmic strings that do not intersect. The solutions for parallel cosmic strings moving in opposite directions show closed timelike curves (CTCs) that circle the two strings as they pass, allowing observers to visit their own past. Similar results occur for nonparallel strings, and for masses in (2+1)-dimensional spacetime. For finite string loops the possibility that black-hole formation may prevent the formation of CTCs is discussed.
Imprints of cosmic strings on the cosmological gravitational wave background
Kleidis, K; Papadopoulos, D B; Vlahos, L; Verdaguer, E
2008-07-15
The equation which governs the temporal evolution of a gravitational wave (GW) in curved space-time can be treated as the Schroedinger equation for a particle moving in the presence of an effective potential. When GWs propagate in an expanding universe with constant effective potential, there is a critical value (k{sub c}) of the comoving wave number which discriminates the metric perturbations into oscillating (k>k{sub c}) and nonoscillating (k
Nonlinear dynamics of cosmic strings with nonscaling loops
Vanchurin, Vitaly
2010-09-15
At early stages the dynamics of cosmic string networks is expected to be influenced by an excessive production of small loops at the scales of initial conditions l{sub min}. To understand the late time behavior we propose a very simple analytical model of strings with a nonscaling population of loops. The complicated nonlinear dynamics is described by only a single parameter N{approx}2/(1-C(l{sub min})) where C(l) is a correlation function of the string tangent vectors. The model predicts an appearance of two new length scales: the coherence length {xi}{approx}t/N{sup 2} and the cross-correlation length {chi}{approx}t/N. At the onset of evolution N{approx}10 and at late times N is expected to grow logarithmically due to cosmological stretching and emission of small loops. The very late time evolution might be modified further when the gravitational back-reaction scale grows larger than l{sub min}.
Anisotropies in the gravitational wave background as a probe of the cosmic string network
NASA Astrophysics Data System (ADS)
Kuroyanagi, Sachiko; Takahashi, Keitaro; Yonemaru, Naoyuki; Kumamoto, Hiroki
2017-02-01
Pulsar timing arrays are powerful tools to test the existence of cosmic strings by searching for the gravitational wave (GW) background. The amplitude of the background connects to information on cosmic strings such as the tension and string network properties. In addition, one may be able to extract more information on the properties of cosmic strings by measuring anisotropies in the GW background. In this paper, we provide estimates of the level of anisotropy expected in the GW background generated by cusps on cosmic strings. We find that the anisotropy level strongly depends on the initial loop size α , and thus we may be able to put constraints on α by measuring the anisotropy of the GW background. We also find that certain regions of the parameter space can be probed by shifting the observation frequency of GWs.
Gravitational backreaction on piecewise linear cosmic string loops
NASA Astrophysics Data System (ADS)
Wachter, Jeremy M.; Olum, Ken D.
2017-01-01
We calculate the metric and affine connection due to a piecewise linear cosmic string loop, and the effect of gravitational backreaction for the Garfinkle-Vachaspati loop with four straight segments. As expected, backreaction reduces the size of the loop, in accord with the energy going into gravitational waves. The "square" (maximally symmetric) loop evaporates without changing shape, but for all other loops in this class, the kinks become less sharp and segments between kinks become curved. If the loop is close to the square case, it will evaporate before its kinks are significantly changed; if it is far from square, the opening out of the kinks is much faster than evaporation of the loop.
Urrestilla, Jon; Mukherjee, Pia; Liddle, Andrew R.; Hindmarsh, Mark; Kunz, Martin; Bevis, Neil
2008-06-15
While observations indicate that the predominant source of cosmic inhomogeneities are adiabatic perturbations, there are a variety of candidates to provide auxiliary trace effects, including inflation-generated primordial tensors and cosmic defects which both produce B-mode cosmic microwave background polarization. We investigate whether future experiments may suffer confusion as to the true origin of such effects, focusing on the ability of Planck to distinguish tensors from cosmic strings, and show that there is no significant degeneracy.
Self-force on an electric dipole in the spacetime of a cosmic string
Muniz, C.R.; Bezerra, V.B.
2014-01-15
We calculate the electrostatic self-force on an electric dipole in the spacetime generated by a static, thin, infinite and straight cosmic string. The electric dipole is held fixed in different configurations, namely, parallel, perpendicular to the cosmic string and oriented along the azimuthal direction around this topological defect, which is stretched along the z axis. We show that the self-force is equivalent to an interaction of the electric dipole with an effective dipole moment which depends on the linear mass density of the cosmic string and on the configuration. The plots of the self-forces as functions of the parameter which determines the angular deficit of the cosmic string are shown for those different configurations. -- Highlights: •Review of regularized Green’s function applied to the problem. •Self-force on an electric dipole in the string spacetime for some orientations. •Representation via graphs of the self-forces versus angular parameter of the cosmic string. •Self-force induced by the string seen as an interaction between two dipoles. •Discussion about the superposition principle in this non-trivial background.
NASA Astrophysics Data System (ADS)
Yuzurihara, Hirotaka; Kanda, Nobuyuki
Cosmic string is one dimensional topological defects which might be formed at the phase transition in the early universe. Gravitational Wave (GW) waveform and its power spectrum from structure in closed cosmic string loop that is called as "cusp" are theoretically predicted. Cosmic string is thought to be described with two characteristic parameters: string tension μ and initial loop size α. We demonstrate numerical simulation for GWs from closed comic string loops to study detectability and parameter decision with ground-based detectors, such as KAGRA, advanced LIGO, advanced Virgo and LIGO-India. We employ characteristic parameters 10 - 13 < Gμ < 10 - 7 and 10 - 16 < α < 10 - 1, assuming uniform distribution of cosmic string in isotropic direction, at time epochs of loop forming and GW emission according to the universe model. We calculate waveform numerically in time domain of each GW from these distributed cosmic strings, and superpose waveforms to generate continuously observational signal on the ground-based GW detectors, including detector responses. We consider data analysis for stochastic background type gravitational wave signatures in the observation.
Wedges, cones, cosmic strings and their vacuum energy
NASA Astrophysics Data System (ADS)
Fulling, S. A.; Trendafilova, C. S.; Truong, P. N.; Wagner, J.
2012-09-01
One of J Stuart Dowker’s most significant achievements has been to observe that the theory of diffraction by wedges developed a century ago by Sommerfeld and others provided the key to solving two problems of great interest in general-relativistic quantum field theory during the last quarter of the 20th century: the vacuum energy associated with an infinitely thin, straight cosmic string, and (after an interchange of time with a space coordinate) the apparent vacuum energy of empty space as viewed by an accelerating observer. In a sense the string problem is more elementary than the wedge, since Sommerfeld’s technique was to relate the wedge problem to that of a conical manifold by the method of images. Indeed, Minkowski space, as well as all cone and wedge problems, are related by images to an infinitely sheeted master manifold, which we call Dowker space. We review the research in this area and exhibit in detail the vacuum expectation values of the energy density and pressure of a scalar field in Dowker space and the cone and wedge spaces that result from it. We point out that the (vanishing) vacuum energy of Minkowski space results, from the point of view of Dowker space, from the quantization of angular modes, in precisely the way that the Casimir energy of a toroidal closed universe results from the quantization of Fourier modes; we hope that this understanding dispels any lingering doubts about the reality of cosmological vacuum energy. This article is part of a special issue of Journal of Physics A: Mathematical and Theoretical in honour of Stuart Dowker’s 75th birthday devoted to ‘Applications of zeta functions and other spectral functions in mathematics and physics’.
Weak lensing generated by vector perturbations and detectability of cosmic strings
Yamauchi, Daisuke; Namikawa, Toshiya; Taruya, Atsushi E-mail: namikawa@utap.phys.s.u-tokyo.ac.jp
2012-10-01
We study the observational signature of vector metric perturbations through the effect of weak gravitational lensing. In the presence of vector perturbations, the non-vanishing signals for B-mode cosmic shear and curl-mode deflection angle, which have never appeared in the case of scalar metric perturbations, naturally arise. Solving the geodesic and geodesic deviation equations, we drive the full-sky formulas for angular power spectra of weak lensing signals, and give the explicit expressions for E-/B-mode cosmic shear and gradient-/curl-mode deflection angle. As a possible source for seeding vector perturbations, we then consider a cosmic string network, and discuss its detectability from upcoming weak lensing and CMB measurements. Based on the formulas and a simple model for cosmic string network, we calculate the angular power spectra and expected signal-to-noise ratios for the B-mode cosmic shear and curl-mode deflection angle. We find that the weak lensing signals are enhanced for a smaller intercommuting probability of the string network, P, and they are potentially detectable from the upcoming cosmic shear and CMB lensing observations. For P ∼ 10{sup −1}, the minimum detectable tension of the cosmic string will be down to Gμ ∼ 5 × 10{sup −8}. With a theoretically inferred smallest value P ∼ 10{sup −3}, we could even detect the string with Gμ ∼ 5 × 10{sup −10}.
High redshift signatures in the 21 cm forest due to cosmic string wakes
Tashiro, Hiroyuki; Sekiguchi, Toyokazu; Silk, Joseph E-mail: toyokazu.sekiguchi@nagoya-u.jp
2014-01-01
Cosmic strings induce minihalo formation in the early universe. The resultant minihalos cluster in string wakes and create a ''21 cm forest'' against the cosmic microwave background (CMB) spectrum. Such a 21 cm forest can contribute to angular fluctuations of redshifted 21 cm signals integrated along the line of sight. We calculate the root-mean-square amplitude of the 21 cm fluctuations due to strings and show that these fluctuations can dominate signals from minihalos due to primordial density fluctuations at high redshift (z∼>10), even if the string tension is below the current upper bound, Gμ < 1.5 × 10{sup −7}. Our results also predict that the Square Kilometre Array (SKA) can potentially detect the 21 cm fluctuations due to strings with Gμ ≈ 7.5 × 10{sup −8} for the single frequency band case and 4.0 × 10{sup −8} for the multi-frequency band case.
Cosmic string configuration in a five dimensional Brans-Dicke theory
Bezerra, V. B.; Ferreira, C. N.; Marques, G. de A
2010-01-15
We consider a scalar field interacting with a cosmic string configuration. The origin of the scalar field is given by a compactification mechanism in the context of a five-dimensional Brans-Dicke theory. We analyze the behavior of a charged cosmic string given by the Maxwell-Chern-Simons term on the 3-brane. The Cosmic Microwave Background Radiation constraint is used to analyze the possibility of optical activity effect in connection with the Brans-Dicke parameter {omega}. We show that the dilatons produced by a cosmic string can decay into gauge bosons with masses given by the compactification modes. The Brans-Dicke parameter {omega} imposes stringent constraints on the mass of the dilaton and help us to understand the energy scales. In this scenario the lifetime of the dilaton which decays into light gauge bosons as well as the dependence of this phenomenon with the Brans-Dicke parameter are estimated.
Induced fermionic currents in de Sitter spacetime in the presence of a compactified cosmic string
NASA Astrophysics Data System (ADS)
Mohammadi, A.; Bezerra de Mello, E. R.; Saharian, A. A.
2015-07-01
We investigate the vacuum fermionic currents in the geometry of a compactified cosmic string on the background of de Sitter (dS) spacetime. The currents are induced by magnetic fluxes running along the cosmic string and enclosed by the compact dimension. We show that the vacuum charge and the radial component of the current density vanish. By using the Abel-Plana summation formula, the azimuthal and axial currents are explicitly decomposed into two parts: the first one corresponds to the geometry of a straight cosmic string, and the second one is induced by the compactification of the string along its axis. For the axial current the first part vanishes and the corresponding topological part is an even periodic function of the magnetic flux along the string axis and an odd periodic function of the flux enclosed by the compact dimension with the periods equal to the flux quantum. The azimuthal current density is an odd periodic function of the flux along the string axis and an even periodic function of the flux enclosed by the compact dimension with the same period. Depending on the magnetic fluxes, the planar angle deficit can either enhance or reduce the azimuthal and axial currents. The influence of the background gravitational field on the vacuum currents is crucial at distances from the string larger than the dS curvature radius. In particular, for the geometry of a straight cosmic string and for a massive fermionic field, we show that the decay of the azimuthal current density is damping oscillatory with the amplitude inversely proportional to the fourth power of the distance from the string. This behavior is in clear contrast with the case of the string in Minkowski bulk, where the current density is exponentially suppressed at large distances.
Analytical model for CMB temperature angular power spectrum from cosmic (super-)strings
Yamauchi, Daisuke; Yoo, Chul-Moon; Sasaki, Misao; Takahashi, Keitaro; Sendouda, Yuuiti
2010-09-15
We present a new analytical method to calculate the small angle cosmic microwave background (CMB) temperature angular power spectrum due to cosmic (super-)string segments. In particular, using our method, we clarify the dependence on the intercommuting probability P. We find that the power spectrum is dominated by Poisson-distributed string segments. The power spectrum for a general value of P has a plateau on large angular scales and shows a power-law decrease on small angular scales. The resulting spectrum in the case of conventional cosmic strings is in very good agreement with the numerical result obtained by Fraisse et al.. Then we estimate the upper bound on the dimensionless tension of the string for various values of P by assuming that the fraction of the CMB power spectrum due to cosmic (super-)strings is less than ten percent at various angular scales up to l=2000. We find that the amplitude of the spectrum increases as the intercommuting probability. As a consequence, strings with smaller intercommuting probabilities are found to be more tightly constrained.
On the large-scale structures formed by wakes of open cosmic strings
NASA Technical Reports Server (NTRS)
Hara, Tetsuya; Morioka, Shoji; Miyoshi, Shigeru
1990-01-01
Large-scale structures of the universe have been variously described as sheetlike, filamentary, cellular, bubbles or spongelike. Recently cosmic strings became one of viable candidates for a galaxy formation scenario, and some of the large-scale structures seem to be simply explained by the open cosmic strings. According to this scenario, sheets are wakes which are traces of moving open cosmic strings where dark matter and baryonic matter have accumulated. Filaments are intersections of such wakes and high density regions are places where three wakes intersect almost orthogonally. The wakes formed at t sub eq become the largest surface density among all wakes, where t sub eq is the epoch when matter density equals to radiation density. If we assume that there is one open cosmic string per each horizon, then it can be explained that the typical distances among wakes, filaments and clusters are also approx. 10(exp 2) Mpc. This model does not exclude a much more large scale structure. Open cosmic string may move even now and accumulate cold dark matter after its traces. However, the surface density is much smaller than the ones formed at t sub eq. From this model, it is expected that the typical high density region will have extended features such as six filaments and three sheets and be surrounded by eight empty regions (voids). Here, the authors are mainly concerned with such structures and have made numerical simulations for the formation of such large scale structures.
On the motion of a quantum particle in the spinning cosmic string space–time
Hassanabadi, H.; Afshardoost, A.; Zarrinkamar, S.
2015-05-15
We analyze the energy spectrum and the wave function of a particle subjected to magnetic field in the spinning cosmic string space–time and investigate the influence of the spinning reference frame and topological defect on the system. To do this we solve Schrödinger equation in the spinning cosmic string background. In our work, instead of using an approximation in the calculations, we use the quasi-exact ansatz approach which gives the exact solutions for some primary levels. - Highlights: • Solving the Schrödinger equation in the spinning cosmic string space time. • Proposing a quasi-exact analytical solution to the general form of the corresponding equation. • Generalizing the previous works.
The 21 cm signature of shock heated and diffuse cosmic string wakes
Hernández, Oscar F.; Brandenberger, Robert H. E-mail: rhb@physics.mcgill.ca
2012-07-01
The analysis of the 21 cm signature of cosmic string wakes is extended in several ways. First we consider the constraints on Gμ from the absorption signal of shock heated wakes laid down much later than matter radiation equality. Secondly we analyze the signal of diffuse wake, that is those wakes in which there is a baryon overdensity but which have not shock heated. Finally we compare the size of these signals to the expected thermal noise per pixel which dominates over the background cosmic gas brightness temperature and find that the cosmic string signal will exceed the thermal noise of an individual pixel in the Square Kilometre Array for string tensions Gμ > 2.5 × 10{sup −8}.
Sanidas, Sotirios A.; Battye, Richard A.; Stappers, Benjamin W. E-mail: rbattye@jb.man.ac.uk
2013-02-10
We present projected constraints on the cosmic string tension, G{mu}/c {sup 2}, that could be achieved by future gravitational wave detection experiments and express our results as semi-analytic relations of the form G{mu}({Omega}{sub gw} h {sup 2})/c {sup 2}, to allow for direct computation of the tension constraints for future experiments. These results can be applied to new constraints on {Omega}{sub gw} h {sup 2} as they are imposed. Experiments operating in different frequency bands probe different parts of the gravitational wave spectrum of a cosmic string network and are sensitive to different uncertainties in the underlying cosmic string model parameters. We compute the gravitational wave spectra of cosmic string networks based on the one-scale model, covering all the parameter space accessed by each experiment that is strongly dependent on the birth scale of loops relative to the horizon, {alpha}. The upper limits on the string tension avoid any assumptions on the model parameters. We perform this investigation for Pulsar Timing Array experiments of different durations, as well as ground-based and space-borne interferometric detectors.
Battle of the bulge: Decay of the thin, false cosmic string
NASA Astrophysics Data System (ADS)
Lee, Bum-Hoon; Lee, Wonwoo; MacKenzie, Richard; Paranjape, M. B.; Yajnik, U. A.; Yeom, Dong-han
2013-11-01
We consider the decay of cosmic strings that are trapped in the false vacuum in a theory of scalar electrodynamics in 3+1 dimensions. This paper is the 3+1-dimensional generalization of the 2+1-dimensional decay of false vortices which we have recently completed . We restrict our analysis to the case of thin-walled cosmic strings which occur when large magnetic flux is trapped inside the string. Thus the string looks like a tube of fixed radius, at which it is classically stable. The core of the string contains magnetic flux in the true vacuum, while outside the string, separated by a thin wall, is the false vacuum. The string decays by tunneling to a configuration which is represented by a bulge, where the region of true vacuum within is ostensibly enlarged. The bulge can be described as the meeting of a kink soliton-antisoliton pair along the length of the string. It can be described as a bulge appearing in the initial string, starting from the string of small, classically stable radius, expanding to a fat string of large, classically unstable (to expansion) radius and then returning back to the string of small radius along its length. This configuration is the bounce point of a corresponding O(2) symmetric instanton, which we can determine numerically. Once the bulge appears it explodes in real time. The paired soliton and antisoliton recede from each other along the length of the string with a velocity that quickly approaches the speed of light, leaving behind a fat tube. At the same time the radius of the fat tube that is being formed expands (transversely) as it is no longer classically stable, converting false vacuum to the true vacuum with ever-diluting magnetic field within. The rate of this expansion is determined by the energy difference between the true vacuum and the false vacuum. Our analysis could be applied to a network of cosmic strings formed in the very early Universe or vortex lines in a superheated superconductor.
Cosmic string loops as the seeds of super-massive black holes
Bramberger, Sebastian F.; Brandenberger, Robert H.; Jreidini, Paul; Quintin, Jerome E-mail: rhb@physics.mcgill.ca E-mail: jquintin@physics.mcgill.ca
2015-06-01
Recent discoveries of super-massive black holes at high redshifts indicate a possible tension with the standard ΛCDM paradigm of early universe cosmology which has difficulties in explaining the origin of the required nonlinear compact seeds which trigger the formation of these super-massive black holes. Here we show that cosmic string loops which result from a scaling solution of strings formed during a phase transition in the very early universe lead to an additional source of compact seeds. The number density of string-induced seeds dominates at high redshifts and can help trigger the formation of the observed super-massive black holes.
Effects of cosmic string velocities and the origin of globular clusters
Lin, Ling; Yamanouchi, Shoma; Brandenberger, Robert E-mail: shoma.yamanouchi@mail.mcgill.ca
2015-12-01
With the hypothesis that cosmic string loops act as seeds for globular clusters in mind, we study the role that velocities of these strings will play in determining the mass distribution of globular clusters. Loops with high enough velocities will not form compact and roughly spherical objects and can hence not be the seeds for globular clusters. We compute the expected number density and mass function of globular clusters as a function of both the string tension and the peak loop velocity, and compare the results with the observational data on the mass distribution of globular clusters in our Milky Way. We determine the critical peak string loop velocity above which the agreement between the string loop model for the origin of globular clusters (neglecting loop velocities) and observational data is lost.
Cosmic strings in hidden sectors: 1. Radiation of standard model particles
Long, Andrew J.; Hyde, Jeffrey M.; Vachaspati, Tanmay E-mail: jmhyde@asu.edu
2014-09-01
In hidden sector models with an extra U(1) gauge group, new fields can interact with the Standard Model only through gauge kinetic mixing and the Higgs portal. After the U(1) is spontaneously broken, these interactions couple the resultant cosmic strings to Standard Model particles. We calculate the spectrum of radiation emitted by these ''dark strings'' in the form of Higgs bosons, Z bosons, and Standard Model fermions assuming that string tension is above the TeV scale. We also calculate the scattering cross sections of Standard Model fermions on dark strings due to the Aharonov-Bohm interaction. These radiation and scattering calculations will be applied in a subsequent paper to study the cosmological evolution and observational signatures of dark strings.
The gravitational wave spectrum from cosmological B-L breaking
Buchmüller, W.; Domcke, V.; Kamada, K.; Schmitz, K. E-mail: valerie.domcke@desy.de E-mail: kai.schmitz@ipmu.jp
2013-10-01
Cosmological B-L breaking is a natural and testable mechanism to generate the initial conditions of the hot early universe. If B-L is broken at the grand unification scale, the false vacuum phase drives hybrid inflation, ending in tachyonic preheating. The decays of heavy B-L Higgs bosons and heavy neutrinos generate entropy, baryon asymmetry and dark matter and also control the reheating temperature. The different phases in the transition from inflation to the radiation dominated phase produce a characteristic spectrum of gravitational waves. We calculate the complete gravitational wave spectrum due to inflation, preheating and cosmic strings, which turns out to have several features. The production of gravitational waves from cosmic strings has large uncertainties, with lower and upper bounds provided by Abelian Higgs strings and Nambu-Goto strings, implying Ω{sub GW}h{sup 2} ∼ 10{sup −13}–10{sup −8}, much larger than the spectral amplitude predicted by inflation. Forthcoming gravitational wave detectors such as eLISA, advanced LIGO, ET, BBO and DECIGO will reach the sensitivity needed to test the predictions from cosmological B-L breaking.
The gravitational wave spectrum from cosmological B-L breaking
NASA Astrophysics Data System (ADS)
Buchmüller, W.; Domcke, V.; Kamada, K.; Schmitz, K.
2013-10-01
Cosmological B-L breaking is a natural and testable mechanism to generate the initial conditions of the hot early universe. If B-L is broken at the grand unification scale, the false vacuum phase drives hybrid inflation, ending in tachyonic preheating. The decays of heavy B-L Higgs bosons and heavy neutrinos generate entropy, baryon asymmetry and dark matter and also control the reheating temperature. The different phases in the transition from inflation to the radiation dominated phase produce a characteristic spectrum of gravitational waves. We calculate the complete gravitational wave spectrum due to inflation, preheating and cosmic strings, which turns out to have several features. The production of gravitational waves from cosmic strings has large uncertainties, with lower and upper bounds provided by Abelian Higgs strings and Nambu-Goto strings, implying ΩGWh2 ~ 10-13-10-8, much larger than the spectral amplitude predicted by inflation. Forthcoming gravitational wave detectors such as eLISA, advanced LIGO, ET, BBO and DECIGO will reach the sensitivity needed to test the predictions from cosmological B-L breaking.
Quantum field theory in the space-time of a cosmic string
Linet, B.
1987-01-15
For a massive scalar field in the static cylindrically symmetric space-time describing a cosmic string, we determine explicitly the Euclidean Green's function. We obtain also an alternative local form which allows us to calculate the vacuum energy-momentum tensor. In the case of a conformal scalar field, we carry out completely the calculations.
Equatorial geodesics of dyonic Kerr-Newman black hole pierced by a cosmic string
NASA Astrophysics Data System (ADS)
Sharif, M.; Iftikhar, Sehrish
2016-12-01
This paper is devoted to study the circular geodesics of the dyonic Kerr-Newman black hole with a cosmic string passing through it. We investigate circular geodesics of null and timelike particle. In this context, we find the circular photon orbit as well as the innermost stable circular orbit. The angular velocity and time period for the timelike particle are calculated. The effect of electric and magnetic charge as well as of the cosmic string parameter on the effective potential is analyzed numerically. Finally, we discuss the role of these parameters on the energy extraction by the Penrose process. We conclude that the string parameter does not affect the gain energy of the particle but it decreases with respect to charge.
Search for cosmic strings in the Great Observatories Origins Deep Survey
Christiansen, J. L.; Albin, E.; James, K. A.; Goldman, J.; Maruyama, D.; Smoot, G. F.
2008-06-15
We search Hubble Space Telescope Treasury Program images collected as part of the Great Observatories Origins Deep Survey for pairs of galaxies consistent with the gravitational lensing signature of a cosmic string. Our technique includes estimates of the efficiency for finding the lensed galaxy pair. In the north (south) survey field we find no evidence out to a redshift of greater than 0.5 (0.3) for cosmic strings to a mass per unit length limit of G{mu}/c{sup 2}<3.0x10{sup -7} at 95% confidence limits (C.L.). In the combined 314.9 arcmin{sup 2} of the north and south survey fields this corresponds to a global limit on {omega}{sub strings}<0.02. Our limit on G{mu}/c{sup 2} is more than an order of magnitude lower than searches for individual strings in cosmic microwave background (CMB) data. Our limit is higher than other CMB and gravitational wave searches, however, we note that it is less model dependent than these other searches.
Rotation of galaxies as a signature of cosmic strings in weak lensing surveys.
Thomas, Daniel B; Contaldi, Carlo R; Magueijo, João
2009-10-30
Vector perturbations sourced by topological defects can generate rotations in the lensing of background galaxies. This is a potential smoking gun for the existence of defects since rotation generates a curl-like component in the weak lensing signal which is not generated by standard density perturbations at linear order. This rotation signal is calculated as generated by cosmic strings. Future large scale weak lensing surveys should be able to detect this signal even for string tensions an order of magnitude lower than current constraints.
MITO: a procedure for CBA measurements and a search for cosmic strings.
NASA Astrophysics Data System (ADS)
de Petris, M.; Melchiorri, B.; Melchiorri, F.; Signore, M.
1995-06-01
MITO (Millimetric and Infrared Testa Grigia Observatory) is a 3-m telescope dedicated to the study of the cosmic background anisotropies. It is located at 3500 m above sea-level at Plateau Rosa, Cervinia, Italy. The authors describe the observatory and discuss two on-going research programs: a cleaning procedure in order to remove Galactic dust signals from cosmological data and a search for cosmic strings toward double-lensed quasars. Both programs will be carried out by means of a He-3 photometer operating at the frequencies of 5, 10, 12, and 30 cm-1.
Effect of Extra Dimensions on Gravitational Waves from Cosmic Strings
O'Callaghan, Eimear; Chadburn, Sarah; Geshnizjani, Ghazal; Gregory, Ruth; Zavala, Ivonne
2010-08-20
We show how the motion of cosmic superstrings in extra dimensions can modify the gravitational wave signal from cusps. Additional dimensions both round off cusps, as well as reducing the probability of their formation, and thus give a significant dimension dependent damping of the gravitational waves. We look at the implication of this effect for LIGO and LISA, as well as commenting on more general frequency bands.
Resurrecting hot dark matter - Large-scale structure from cosmic strings and massive neutrinos
NASA Technical Reports Server (NTRS)
Scherrer, Robert J.
1988-01-01
These are the results of a numerical simulation of the formation of large-scale structure from cosmic-string loops in a universe dominated by massive neutrinos (hot dark matter). This model has several desirable features. The final matter distribution contains isolated density peaks embedded in a smooth background, producing a natural bias in the distribution of luminous matter. Because baryons can accrete onto the cosmic strings before the neutrinos, the galaxies will have baryon cores and dark neutrino halos. Galaxy formation in this model begins much earlier than in random-phase models. On large scales the distribution of clustered matter visually resembles the CfA survey, with large voids and filaments.
Formation of large-scale structure from cosmic strings and massive neutrinos
NASA Technical Reports Server (NTRS)
Scherrer, Robert J.; Melott, Adrian L.; Bertschinger, Edmund
1989-01-01
Numerical simulations of large-scale structure formation from cosmic strings and massive neutrinos are described. The linear power spectrum in this model resembles the cold-dark-matter power spectrum. Galaxy formation begins early, and the final distribution consists of isolated density peaks embedded in a smooth background, leading to a natural bias in the distribution of luminous matter. The distribution of clustered matter has a filamentary appearance with large voids.
CMB power spectra from cosmic strings: Predictions for the Planck satellite and beyond
Bevis, Neil; Hindmarsh, Mark; Kunz, Martin; Urrestilla, Jon
2010-09-15
We present a significant improvement over our previous calculations of the cosmic string contribution to cosmic microwave background (CMB) power spectra, with particular focus on sub-WMAP angular scales. These smaller scales are relevant for the now-operational Planck satellite and additional suborbital CMB projects that have even finer resolutions. We employ larger Abelian Higgs string simulations than before and we additionally model and extrapolate the statistical measures from our simulations to smaller length scales. We then use an efficient means of including the extrapolations into our Einstein-Boltzmann calculations in order to yield accurate results over the multipole range 2{<=}l{<=}4000. Our results suggest that power-law behavior cuts in for l > or approx. 3000 in the case of the temperature power spectrum, which then allows cautious extrapolation to even smaller scales. We find that a string contribution to the temperature power spectrum making up 10% of power at l=10 would be larger than the Silk-damped primary adiabatic contribution for l > or approx. 3500. Astrophysical contributions such as the Sunyaev-Zeldovich effect also become important at these scales and will reduce the sensitivity to strings, but these are potentially distinguishable by their frequency-dependence.
Proliferation of sharp kinks on cosmic (super)string loops with junctions
Binetruy, P.; Bohe, A.; Hertog, T.; Steer, D. A.
2010-10-15
Motivated by their effect on the gravitational wave signal emitted by cosmic strings, we study the dynamics of kinks on strings of different tensions meeting at junctions. The propagation of a kink through a Y junction leads to the formation of three 'daughter' kinks. Assuming a uniform distribution of the incoming wave vectors at the junction, we find there is a significant region of configuration space in which the sharpness of at least one of the daughter kinks is enhanced relative to the sharpness of the initial kink. For closed loops with junctions we show this leads to an exponential growth in time of very sharp kinks. Using numerical simulations of realistic, evolving cosmic string loops with junctions to calculate the distribution of kink amplitudes as a function of time, we show that loops of this kind typically develop several orders of magnitude of very sharp kinks before the two junctions collide. This collision, or other effects such as gravitational backreaction, may end the proliferation.
Propagation of cosmic rays through the atmosphere in the quark-gluon strings model
NASA Technical Reports Server (NTRS)
Erlykin, A. D.; Krutikova, N. P.; Shabelski, Y. M.
1985-01-01
The quark-gluon strings model succeeds in the description of multiple hadron production in the central rapidity region of nucleon-nucleon interctions. This model was developed for hadron-nucleus interactions and used for calculation of the cosmic ray propagation through the atmosphere. It is shown that at energies 10 to the 11th power to the 12th power eV, this model gives a satisfactory description of experimental data. But with the increase of the energy up to approximately 10 to the 14th power eV, results of calculations and of experiments begin to differ and this difference rises with the energy. It may indicate that the scaling violation in the fragmentation region of inclusive spectra for hadron-nucleus interactions is stronger than in the quark-gluon strings model.
Towards a hybrid compactification with a scalar-tensor global cosmic string
Abdalla, M C B; Hoff da Silva, J M; Guimaraes, M E X E-mail: emilia@if.uff.br
2008-09-15
We derive a solution of the gravitational equations which leads to a braneworld scenario in six dimensions, using a global cosmic string solution in a low energy effective string theory framework. The final spacetime is composed by one warped brane with R{sup (3,1)} Multiplication-Sign S{sup 1} topology and a power law warp factor, and one non-compact extra dimension transverse to the brane; by looking at the current experimental bounds, we find a range of parameters in which, if the on-brane dimension has an acceptable size, it does not solve the hierarchy problem. In another example, this problem is smoothed by means of the Brans-Dicke parameter.
Formation of large-scale structure from cosmic-string loops and cold dark matter
NASA Technical Reports Server (NTRS)
Melott, Adrian L.; Scherrer, Robert J.
1987-01-01
Some results from a numerical simulation of the formation of large-scale structure from cosmic-string loops are presented. It is found that even though G x mu is required to be lower than 2 x 10 to the -6th (where mu is the mass per unit length of the string) to give a low enough autocorrelation amplitude, there is excessive power on smaller scales, so that galaxies would be more dense than observed. The large-scale structure does not include a filamentary or connected appearance and shares with more conventional models based on Gaussian perturbations the lack of cluster-cluster correlation at the mean cluster separation scale as well as excessively small bulk velocities at these scales.
Comment on high resolution simulations of cosmic strings. 1: Network evoloution
NASA Technical Reports Server (NTRS)
Turok, Neil; Albrecht, Andreas
1990-01-01
Comments are made on recent claims (Albrecht and Turok, 1989) regarding simulations of cosmic string evolution. Specially, it was claimed that results were dominated by a numerical artifact which rounds out kinks on a scale of the order of the correlation length on the network. This claim was based on an approximate analysis of an interpolation equation which is solved herein. The typical rounding scale is actually less than one fifth of the correlation length, and comparable with other numerical cutoffs. Results confirm previous estimates of numerical uncertainties, and show that the approximations poorly represent the real solutions to the interpolation equation.
Topics in Cosmic String Physics and Vacuum Stability of Field Theories
NASA Astrophysics Data System (ADS)
Dasgupta, Indranil
1998-01-01
In this thesis I examine aspects of the vacuum state of quantum field theories. Namely, I study topological defects in the vacuum which appear as localized regions of non-zero energy density if the model system is unable to relax to a homogeneous and isotropic ground state because of topological constraints. I also examine the stability of the so called false vacua in theories that have multiple vacuum states with different energy densities. I first consider topological defects in the form of strings and independently the decay of false vacua in models of particle physics where the presence of either defects or of false vacua leads to interesting phenomenology. Then I describe a situation in which the defects arising from topological properties of the vacuum in turn affect the stability of the vacuum itself. In the first part of this work (chapters 2 and 3), I explore the phenomenology of cosmic strings. I introduce new string-like topological defects that resemble pairs of strings bound together. I give an existence proof of these 'binary strings' and then develop their cosmological properties in detail. I then propose a simple extension of the Standard Model in which cosmic strings may form and then decay through baryon number violating interactions leading to baryogenesis. I show that the model has distinct and testable signatures. In the second part of this work (chapters 4 and 5), I examine the vacua of several proposed models of gauge mediated dynamical supersymmetry breaking and show that the viable vacua are often unstable. I develop a rigorous theory for approximating vacuum tunneling rates in multi-scalar field theories and by computing bounds on the decay rate of the vacua in these models obtain useful constraints on the parameter space. In the final part of this work (chapter 6), I develop a theory of vacuum tunneling induced by topological defects. I show that defects can speed up vacuum tunneling rates by seeding new kinds of bubbles during a first
Test particle motion in the space-time of a Kerr black hole pierced by a cosmic string
Hackmann, Eva; Hartmann, Betti; Sirimachan, Parinya; Laemmerzahl, Claus
2010-08-15
We study the geodesic equation in the space-time of a Kerr black hole pierced by an infinitely thin cosmic string and give the complete set of analytical solutions of this equation for massive and massless particles in terms of Mino time that allows one to decouple the r and {theta} components of the geodesic equation. The solutions of the geodesic equation can be classified according to the particle's energy and angular momentum, the mass and angular momentum per mass of the black hole. We give examples of orbits showing the influence of the cosmic string. We also discuss the perihelion shift and the Lense-Thirring effect for bound orbits and show that the presence of a cosmic string enhances both effects. Comparing our results with experimental data from the LAGEOS satellites we find an upper bound on the energy per unit length of a string piercing the earth which is approximately 10{sup 16} kg/m. Our work has also applications to the recently suggested explanation of the alignment of the polarization vector of quasars using remnants of cosmic string decay in the form of primordial magnetic field loops.
NASA Astrophysics Data System (ADS)
Bakke, K.; Furtado, C.; Belich, H.
2016-09-01
From the modified Maxwell theory coupled to gravity, we establish a possible scenario of the violation of the Lorentz symmetry and write an effective metric for the cosmic string spacetime. Then, we investigate the arising of an analogue of the Anandan quantum phase for a relativistic Dirac neutral particle with a permanent magnetic dipole moment in the cosmic string spacetime under Lorentz symmetry breaking effects. Besides, we analyse the influence of the effects of the Lorentz symmetry violation and the topology of the defect on the Aharonov-Casher geometric quantum phase in the nonrelativistic limit.
On the gravitational, dilatonic, and axionic radiative damping of cosmic strings
NASA Astrophysics Data System (ADS)
Buonanno, Alessandra; Damour, Thibault
1999-07-01
We study the radiation reaction on cosmic strings due to the emission of dilatonic, gravitational and axionic waves. After verifying the (on average) conservative nature of the time-symmetric self-interactions, we concentrate on the finite radiation damping force associated with the half-retarded minus half-advanced ``reactive'' fields. We reexamine a recent proposal of using a ``local back reaction approximation'' for the reactive fields. Using dimensional continuation as a convenient technical tool, we find, contrary to previous claims, that this proposal leads to antidamping in the case of the axionic field, and to zero (integrated) damping in the case of the gravitational field. One gets normal positive damping only in the case of the dilatonic field. We propose to use a suitably modified version of the local dilatonic radiation reaction as a substitute for the exact (nonlocal) gravitational radiation reaction. The incorporation of such a local approximation to gravitational radiation reaction should allow one to complete, in a computationally nonintensive way, string network simulations and to give better estimates of the amount and spectrum of gravitational radiation emitted by a cosmologically evolving network of massive strings.
Bevis, Neil; Hindmarsh, Mark; Kunz, Martin; Urrestilla, Jon
2007-03-15
We present the first field-theoretic calculations of the contribution made by cosmic strings to the temperature power spectrum of the cosmic microwave background (CMB). Unlike previous work, in which strings were modeled as idealized one-dimensional objects, we evolve the simplest example of an underlying field theory containing local U(1) strings, the Abelian Higgs model. Limitations imposed by finite computational volumes are overcome using the scaling property of string networks and a further extrapolation related to the lessening of the string width in comoving coordinates. The strings and their decay products, which are automatically included in the field theory approach, source metric perturbations via their energy-momentum tensor, the unequal-time correlation functions of which are used as input into the CMB calculation phase. These calculations involve the use of a modified version of CMBEASY, with results provided over the full range of relevant scales. We find that the string tension {mu} required to normalize to the WMAP 3-year data at multipole l=10 is G{mu}=[2.04{+-}0.06(stat.){+-}0.12(sys.)]x10{sup -6}, where we have quoted statistical and systematic errors separately, and G is Newton's constant. This is a factor 2-3 higher than values in current circulation.
Induced fermionic current by a magnetic flux in a cosmic string spacetime at finite temperature
NASA Astrophysics Data System (ADS)
Bezerra de Mello, Eugênio R.; Saharian, Aram A.; Mohammadi, Azadeh
2016-01-01
Here we analyze the finite temperature expectation values of the charge and current densities for a massive fermionic quantum field with nonzero chemical potential μ, induced by a magnetic flux running along the axis of an idealized cosmic string. These densities are decomposed into the vacuum expectation values and contributions coming from the particles and antiparticles. Specifically the charge density is an even periodic function of the magnetic flux with the period equal to the quantum flux and an odd function of the chemical potential. The only nonzero component of the current density corresponds to the azimuthal current and it is an odd periodic function of the magnetic flux and an even function of the chemical potential. Both analyzed are developed for the cases where |μ| is smaller than the mass of the field quanta m.
Gravitating Vortices, Cosmic Strings, and the Kähler-Yang-Mills Equations
NASA Astrophysics Data System (ADS)
Álvarez-Cónsul, Luis; Garcia-Fernandez, Mario; García-Prada, Oscar
2017-04-01
In this paper we construct new solutions of the Kähler-Yang-Mills equations, by applying dimensional reduction methods to the product of the complex projective line with a compact Riemann surface. The resulting equations, which we call gravitating vortex equations, describe abelian vortices on the Riemann surface with back reaction of the metric. As a particular case of these gravitating vortices on the Riemann sphere we find solutions of the Einstein-Bogomol'nyi equations, which physically correspond to Nielsen-Olesen cosmic strings in the Bogomol'nyi phase. We use this to provide a Geometric Invariant Theory interpretation of an existence result by Y. Yang for the Einstein-Bogomol'nyi equations, applying a criterion due to G. Székelyhidi.
NASA Technical Reports Server (NTRS)
Borden, David; Ostriker, Jeremiah P.; Weinberg, David H.
1989-01-01
If galaxies form on shells, then clusters of galaxies should form at the vertices where three shells intersect. Weinberg, Ostriker, and Dekel (WOD, 1989) studied this picture quantitatively and found that an intersecting spherical shell model reproduces many of the properties of the observed distribution of galaxy clusters, but that too much superclustering is produced. In this paper, the WOD analysis is repeated with prolate spheroids that could be created by superconducting cosmic strings. It is found that most of the attractive features of the WOD model are maintained in the more general case and there is slight improvement in some aspects, but that the overall problem of excessive superclustering is not really alleviated.
Fermionic vacuum polarization by an Abelian magnetic tube in the cosmic string spacetime
NASA Astrophysics Data System (ADS)
Maior de Sousa, M. S.; Ribeiro, R. F.; Bezerra de Mello, E. R.
2017-02-01
In this paper, we consider a charged massive fermionic quantum field in the idealized cosmic string spacetime and in the presence of a magnetic field confined in a cylindrical tube of finite radius. Three distinct configurations for the magnetic fields are taken into account: (i) a cylindrical shell of radius a , (ii) a magnetic field proportional to 1 /r , and (iii) a constant magnetic field. In these three cases, the axis of the infinitely long tube of radius a coincides with the cosmic string. Our main objectives in this paper are to analyze the fermionic condensate (FC) and the vacuum expectation value (VEV) of the fermionic energy-momentum tensor. In order to do that, we explicitly construct the complete set of normalized wave functions for each configuration of the magnetic field. We show that in the region outside the tube, the FC and the VEV of the energy-momentum tensor are decomposed into two parts: The first ones correspond to the zero-thickness magnetic flux contributions, and the second ones are induced by the nontrivial structure of the magnetic field, named core-induced contributions. The latter present specific forms depending on the magnetic field configuration considered. We also show that the VEV of the energy-momentum tensor is diagonal and obeys the conservation condition, and its trace is expressed in terms of the fermionic condensate. The zero-thickness contributions to the FC and VEV of the energy-momentum tensor depend only on the fractional part of the ration of the magnetic flux inside the tube by the quantum one. As to the core-induced contributions, they depend on the total magnetic flux inside the tube and, consequently, in general, are not a periodic function of the magnetic flux.
Gasparini, Maria Alice; Marshall, Phil; Treu, Tommaso; Morganson, Eric; Dubath, Florian; /Santa Barbara, KITP
2007-11-14
We use current theoretical estimates for the density of long cosmic strings to predict the number of strong gravitational lensing events in astronomical imaging surveys as a function of angular resolution and survey area. We show that angular resolution is the single most important factor, and that interesting limits on the dimensionless string tension G{mu}/c{sup 2} can be obtained by existing and planned surveys. At the resolution of the Hubble Space Telescope (0'.14), it is sufficient to survey of order a square degree -- well within reach of the current HST archive -- to probe the regime G{mu}/c{sup 2} {approx} 10{sup -8}. If lensing by cosmic strings is not detected, such a survey would improve the limit on the string tension by an order of magnitude on that available from the cosmic microwave background. At the resolution (0'.028) attainable with the next generation of large ground based instruments, both in the radio and the infra-red with adaptive optics, surveying a sky area of order ten square degrees will allow us to probe the G{mu}/c{sup 2} {approx} 10{sup -9} regime. These limits will not be improved significantly by increasing the solid angle of the survey.
Topological defects in alternative theories to cosmic inflation and string cosmology
NASA Astrophysics Data System (ADS)
Alexander, Stephon H. S.
The physics of the Early Universe is described in terms of the inflationary paradigm, which is based on a marriage between Einstein's general theory of relativity minimally coupled to quantum field theory. Inflation was posed to solve some of the outstanding problems of the Standard Big Bang Cosmology (SBB) such as the horizon, formation of structure and monopole problems. Despite its observational and theoretical successes, inflation is plagued with fine tuning and initial singularity problems. On the other hand, superstring/M theory, a theory of quantum gravity, possesses symmetries which naturally avoid space-time singularities. This thesis investigates alternative theories to cosmic inflation for solving the initial singularity, horizon and monopole problems, making use of topological defects. It was proposed by Dvali, Liu and Vaschaspati that the monopole problem can be solved without inflation if domain walls "sweep" up the monopoles in the early universe, thus reducing their number density significantly. Necessary for this mechanism to work is the presence of an attractive force between the monopole and the domain wall as well as a channel for the monopole's unwinding. We show numerically and analytically in two field theory models that for global defects the attraction is a universal result but the unwinding is model specific. The second part of this thesis investigates a string/M theory inspired model for solving the horizon problem. It was proposed by Moffat, Albrecht and Magueijo that the horizon problem is solved with a "phase transition" associated with a varying speed of light before the surface of last scattering. We provide a string/M theory mechanism based on assuming that our space-time is a D-3 brane probing a bulk supergravity black hole bulk background. This mechanism provides the necessary time variation of the velocity of light to solve the horizon problem. We suggest a mechanism which stablilizes the speed of light on the D-3 brane. We
Vieira, H.S.; Bezerra, V.B.; Silva, G.V.
2015-11-15
Charged massive scalar fields are considered in the gravitational and electromagnetic field produced by a dyonic black hole with a cosmic string along its axis of symmetry. Exact solutions of both angular and radial parts of the covariant Klein–Gordon equation in this background are obtained, and are given in terms of the confluent Heun functions. The role of the presence of the cosmic string in these solutions is showed up. From the radial solution, we obtain the exact wave solutions near the exterior horizon of the black hole, and discuss the Hawking radiation spectrum and the energy flux. -- Highlights: •A cosmic string is introduced along the axis of symmetry of the dyonic black hole. •The covariant Klein–Gordon equation for a charged massive scalar field in this background is analyzed. •Both angular and radial parts are transformed to a confluent Heun equation. •The resulting Hawking radiation spectrum and the energy flux are obtained.
String mediated phase transitions
NASA Technical Reports Server (NTRS)
Copeland, ED; Haws, D.; Rivers, R.; Holbraad, S.
1988-01-01
It is demonstrated from first principles how the existence of string-like structures can cause a system to undergo a phase transition. In particular, the role of topologically stable cosmic string in the restoration of spontaneously broken symmetries is emphasized. How the thermodynamic properties of strings alter when stiffness and nearest neighbor string-string interactions are included is discussed.
NASA Astrophysics Data System (ADS)
Bakke, K.
2015-07-01
The behaviour of the Landau-Aharonov-Casher system is discussed by showing a case where the external electric field cannot yield the Landau-Aharonov-Casher quantization under the influence of rotating effects in the cosmic string spacetime, but it can yield bound states solutions to the Schrödinger-Pauli equation analogous to having the Landau-Aharonov-Casher system confined to a hard-wall confining potential under the influence of rotating effects and the topology of the cosmic string spacetime (by assuming ω ρ≪1 and neglecting the effects of a gravitational self-force on the particle).
Kinematic constraints on formation of bound states of cosmic strings: Field theoretical approach
Salmi, P.; Achucarro, A.; Copeland, E. J.; Kibble, T. W. B.; Putter, R. de; Steer, D. A.
2008-02-15
Superstring theory predicts the potential formation of string networks with bound states ending in junctions. Kinematic constraints for junction formation have been derived within the Nambu-Goto thin string approximation. Here we test these constraints numerically in the framework of the Abelian-Higgs model in the Type-I regime and report on good agreement with the analytical predictions. We also demonstrate that strings can effectively pass through each other when they meet at speeds slightly above the critical velocity permitting bound-state formation. This is due to reconnection effects that are beyond the scope of the Nambu-Goto approximation.
Field Theoretical Approach to the Formation of Junctions of Cosmic Strings
Salmi, Petja
2007-11-20
Superstring theory predicts the potential formation of string networks with junctions. Kinematic constraints for junction formation were derived in [1], based on Nambu-Goto action. Here we test these constraints numerically within the framework of Abelian-Higgs model and report on good agreement with the analytical predictions.
Vachaspati, Tanmay
2009-09-15
Recent astrophysical observations have motivated novel theoretical models of the dark matter sector. A class of such models predicts the existence of GeV scale cosmic strings that communicate with the standard model sector by Aharonov-Bohm interactions with electrically charged particles. We discuss the cosmology of these 'dark strings' and investigate possible observational signatures. More elaborate dark sector models are argued to contain hybrid topological defects that may also have observational signatures.
Interactions of cosmic superstrings
Jackson, Mark G.; /Fermilab
2007-06-01
We develop methods by which cosmic superstring interactions can be studied in detail. These include the reconnection probability and emission of radiation such as gravitons or small string loops. Loop corrections to these are discussed, as well as relationships to (p; q)-strings. These tools should allow a phenomenological study of string models in anticipation of upcoming experiments sensitive to cosmic string radiation.
Rotating Space Elevator: Classical and Statistical Mechanics of cosmic scale spinning strings
NASA Astrophysics Data System (ADS)
Knudsen, Steven; Golubovic, Leonardo
2009-03-01
We introduce a novel and unique nonlinear dynamical system, the Rotating Space Elevator (RSE). The RSE is a multiply rotating system of cables (strings) reaching beyond the Earth geo-synchronous satellite orbit. Strikingly, objects sliding along the RSE cable do not require internal engines or propulsion to be transported far away from the Earth's surface. The RSE action employs, in a very fundamental way, basic natural phenomena -- gravitation and inertial forces. The RSE exhibits interesting nonlinear dynamics and statistical physics phenomena. Its kinetic phase diagram involves both chaotic and quasi-periodic states of motion separated by a morphological phase transition that occurs with changing the RSE angular frequency.
Ultra high energy cosmic rays and possible signature of black strings
Anjos, Rita C. dos; Coimbra-Araújo, Carlos H.; Rocha, Roldão da; De Souza, Vitor E-mail: carlos.coimbra@ufpr.br E-mail: vitor@ifsc.usp.br
2016-03-01
Ultra high energy cosmic rays (UHECRs) probably originate in extreme conditions in which extra dimension effects might be important. In this paper we calculate the correction in black hole accretion mechanisms due to extra dimension effects in the static and rotating cases. A parametrization of the external Kerr horizons in both cases is presented and analysed. We use previous calculations of upper limits on the UHECR flux to set limits on the UHECR production efficiency of nine sources. The upper limit on the UHECR luminosity calculation is based on GeV-TeV gamma-ray measurements. The total luminosity due to the accretion mechanism is compared to the upper limit on UHECRs. The dependence of the UHECR production efficiency upper limit on black hole mass is also presented and discussed.
Sakellariadou, Mairi
2008-08-28
Cosmic superstrings are expected to be formed at the end of brane inflation, within the context of brane-world cosmological models inspired from string theory. By studying the properties of cosmic superstring networks and comparing their phenomenological consequences against observational data, we aim to pin down the successful and natural inflationary model and get an insight into the stringy description of our Universe.
Smolyaninov, Igor I; Smolyaninova, Vera N; Smolyaninov, Alexei I
2015-08-28
In the presence of an external magnetic field, cobalt nanoparticle-based ferrofluid forms a self-assembled hyperbolic metamaterial. The wave equation, which describes propagation of extraordinary light inside the ferrofluid, exhibits 2+1 dimensional Lorentz symmetry. The role of time in the corresponding effective three-dimensional Minkowski space-time is played by the spatial coordinate directed along the periodic nanoparticle chains aligned by the magnetic field. Here, we present a microscopic study of point, linear, planar and volume defects of the nanoparticle chain structure and demonstrate that they may exhibit strong similarities with such Minkowski space-time defects as magnetic monopoles, cosmic strings and the recently proposed space-time cloaks. Experimental observations of such defects are described.
Smolyaninov, Igor I.; Smolyaninova, Vera N.; Smolyaninov, Alexei I.
2015-01-01
In the presence of an external magnetic field, cobalt nanoparticle-based ferrofluid forms a self-assembled hyperbolic metamaterial. The wave equation, which describes propagation of extraordinary light inside the ferrofluid, exhibits 2+1 dimensional Lorentz symmetry. The role of time in the corresponding effective three-dimensional Minkowski space–time is played by the spatial coordinate directed along the periodic nanoparticle chains aligned by the magnetic field. Here, we present a microscopic study of point, linear, planar and volume defects of the nanoparticle chain structure and demonstrate that they may exhibit strong similarities with such Minkowski space–time defects as magnetic monopoles, cosmic strings and the recently proposed space–time cloaks. Experimental observations of such defects are described. PMID:26217055
Perturbations from strings don't look like strings!
NASA Technical Reports Server (NTRS)
Albrecht, Andreas; Stebbins, Albert
1991-01-01
A systematic analysis is challenging popular ideas about perturbation from cosmic strings. One way in which the picture has changed is reviewed. It is concluded that, while the scaling properties of cosmic strings figure significantly in the analysis, care must be taken when thinking in terms of single time snapshots. The process of seeding density perturbations is not fundamentally localized in time, and this fact can wash out many of the details which appear in a single snapshot.
Balanced metrics and phenomenological aspects of heterotic string compactifications
NASA Astrophysics Data System (ADS)
Brelidze, Tamaz
compactifications with the MSSM spectrum. These vacua have the SU(3) C x SU(2)L x U(1)Y gauge group of the standard model augmented by additional an U(1) B-L. The B-L symmetry is spontaneously broken by a vacuum expectation value of one of the right-handed sneutrinos, which leads to U(1)B-L cosmic string solutions. We present a numerical analysis that demonstrates that boson condensates can, in principle, form for theories of this type. However, the weak Yukawa and gauge couplings of the right-handed sneutrino suggests that bosonic superconductivity will not occur in the simplest vacua in this context. Fermion superconductivity is also disallowed by the electroweak phase transition, although bound state fermion currents can exist.
Collisions of Strings with Y Junctions
Copeland, E. J.; Kibble, T. W. B.; Steer, D. A.
2006-07-14
We study the dynamics of Nambu-Goto strings with junctions at which three strings meet. In particular, we exhibit one simple exact solution and examine the process of intercommuting of two straight strings in which they exchange partners but become joined by a third string. We show that there are important kinematical constraints on this process. The exchange cannot occur if the strings meet with very large relative velocity. This may have important implications for the evolution of cosmic superstring networks and non-Abelian string networks.
Static, cylindrically symmetric strings in general relativity with cosmological constant
Linet, B.
1986-07-01
The static, cylindrically symmetric solutions to Einstein's equations with a cosmological term describing cosmic strings are determined. The discussion depends on the sign of the cosmological constant.
Cusps on cosmic superstrings with junctions
Davis, Anne-Christine; Rajamanoharan, Senthooran; Nelson, William; Sakellariadou, Mairi E-mail: william.nelson@kcl.ac.uk E-mail: mairi.sakellariadou@kcl.ac.uk
2008-11-15
The existence of cusps on non-periodic strings ending on D-branes is demonstrated and the conditions for which such cusps are generic are derived. The dynamics of F-strings, D-strings and FD-string junctions are investigated. It is shown that pairs of FD-string junctions, such as would form after intercommutations of F-strings and D-strings, generically contain cusps. This new feature of cosmic superstrings opens up the possibility of extra channels of energy loss from a string network. The phenomenology of cusps on such cosmic superstring networks is compared to that of cusps formed on networks of their field theory analogues, the standard cosmic strings.
NASA Astrophysics Data System (ADS)
Niedermann, Florian; Schneider, Robert; Hofmann, Stefan; Khoury, Justin
2015-01-01
The cosmology of brane-induced gravity in six infinite dimensions is investigated. It is shown that a brane with Friedmann-Robertson-Walker symmetries necessarily acts as a source of cylindrically symmetric gravitational waves, so-called Einstein-Rosen waves. Their existence essentially distinguishes this model from its codimension-one counterpart and necessitates solving the nonlinear system of bulk and brane-matching equations. A numerical analysis is performed and two qualitatively different and dynamically separated classes of cosmologies are derived: Degravitating solutions for which the Hubble parameter settles to zero despite the presence of a novanishing energy density on the brane, and superaccelerating solutions for which Hubble grows unbounded. The parameter space of both the stable and unstable regime is derived and observational consequences are discussed: It is argued that the degravitating regime does not allow for a phenomenologically viable cosmology. On the other hand, the superaccelerating solutions are potentially viable; however, their unstable behavior questions their physical relevance.
Instability of colliding metastable strings
NASA Astrophysics Data System (ADS)
Hiramatsu, Takashi; Eto, Minoru; Kamada, Kohei; Kobayashi, Tatsuo; Ookouchi, Yutaka
2014-01-01
The breaking of U(1) R symmetry plays a crucial role in modeling the breaking of supersymmetry (SUSY). In the models that possess both SUSY preserving and SUSY breaking vacua, tube-like cosmic strings called R-tubes, whose surfaces are constituted by domain walls interpolating a false and a true vacuum with some winding numbers, can exist. Their (in)stability can strongly constrain SUSY breaking models theirselves. In the present study, we investigate the dynamical (in)stability of two colliding metastable tube-like strings by field-theoretic simulations. From them, we find that the strings become unstable, depending on the relative collision angle and speed of two strings, and the false vacuum is eventually filled out by the true vacuum owing to rapid expansion of the strings or unstable bubbles created as remnants of the collision.
NASA Astrophysics Data System (ADS)
Rossing, Thomas D.
In the next three chapters we consider the science of hammered string instruments. In this chapter, we present a brief discussion of vibrating strings excited by a hard or soft hammer. Chapter 20 discusses the most important hammered string instrument, the piano - probably the most versatile and popular of all musical instruments. Chapter 21 discusses hammered dulcimers, especially the American folk dulcimer.
NASA Astrophysics Data System (ADS)
Rossing, Thomas D.; Hanson, Roger J.
In the next eight chapters, we consider some aspects of the science of bowed string instruments, old and new. In this chapter, we present a brief discussion of bowed strings, a subject that will be developed much more thoroughly in Chap. 16. Chapters 13-15 discuss the violin, the cello, and the double bass. Chapter 17 discusses viols and other historic string instruments, and Chap. 18 discusses the Hutchins-Schelleng violin octet.
Searching for signatures of cosmic superstrings in the CMB
Danos, Rebecca J.; Brandenberger, Robert H. E-mail: rhb@physics.mcgill.ca
2010-02-01
Because cosmic superstrings generically form junctions and gauge theoretic strings typically do not, junctions may provide a signature to distinguish between cosmic superstrings and gauge theoretic cosmic strings. In cosmic microwave background anisotropy maps, cosmic strings lead to distinctive line discontinuities. String junctions lead to junctions in these line discontinuities. In turn, edge detection algorithms such as the Canny algorithm can be used to search for signatures of strings in anisotropy maps. We apply the Canny algorithm to simulated maps which contain the effects of cosmic strings with and without string junctions. The Canny algorithm produces edge maps. To distinguish between edge maps from string simulations with and without junctions, we examine the density distribution of edges and pixels crossed by edges. We find that in string simulations without Gaussian noise (such as produced by the dominant inflationary fluctuations) our analysis of the output data from the Canny algorithm can clearly distinguish between simulations with and without string junctions. In the presence of Gaussian noise at the level expected from the current bounds on the contribution of cosmic strings to the total power spectrum of density fluctuations, the distinction between models with and without junctions is more difficult. However, by carefully analyzing the data the models can still be differentiated.
String theory in the early universe
NASA Astrophysics Data System (ADS)
Gwyn, Rhiannon
String theory is a rich and elegant framework which many believe furnishes a UV-complete unified theory of the fundamental interactions, including gravity. However, if true, it holds at energy scales out of the reach of any terrestrial particle accelerator. While we cannot observe the string regime directly, we live in a universe which has been evolving from the string scale since shortly after the Big Bang. It is possible that string theory underlies cosmological processes like inflation, and that cosmology could confirm or constrain stringy physics in the early universe. This makes the intersection of string theory with the early universe a potential window into otherwise inaccessible physics. The results of three papers at this intersection are presented in this thesis. First, we address a longstanding problem: the apparent incompatibility of the experimentally constrained axion decay constant with most string theoretic realisations of the axion. Using warped compactifications in heterotic string theory, we show that the axion decay constant can be lowered to acceptable values by the warp factor. Next, we move to the subject of cosmic strings: linelike topological defects formed during phase transitions in the early universe. It was realised recently that cosmic superstrings are produced in many models of brane inflation, and that cosmic superstrings are stable and can have tensions within the observational bounds. Although they are now known not to be the primary generators of primordial density perturbations leading to structure formation, the evolution of cosmic string networks could have important consequences for astrophysics and cosmology. In particular, there are quantitative differences between cosmic superstring networks and GUT cosmic string networks. We investigate the properties of cosmic superstring networks in warped backgrounds, where they are expected to be produced at the end of brane inflation. We give the tension and properties of three-string
The mass spectra, hierarchy and cosmology of B-L MSSM heterotic compactifications
Ambroso, Michael; Ovrut, Burt A.
2011-04-10
The matter spectrum of the MSSM, including three right-handed neutrino supermultiplets and one pair of Higgs-Higgs conjugate superfields, can be obtained by compactifying the E₈ x E₈ heterotic string and M-theory on Calabi-Yau manifolds with specific SU(4) vector bundles. These theories have the standard model gauge group augmented by an additional gauged U(1)_{B-L}. Their minimal content requires that the B-L gauge symmetry be spontaneously broken by a vacuum expectation value of at least one right-handed neutrino. In previous papers, we presented the results of a quasi-analytic renormalization group analysis showing that B-L gauge symmetry is indeed radiatively broken with an appropriate B-L/electroweak hierarchy. In this paper, we extend these results by 1) enlarging the initial parameter space and 2) explicitly calculating all renormalization group equations numerically. The regions of the initial parameter space leading to realistic vacua are presented and the B-L/electroweak hierarchy computed over these regimes. At representative points, the mass spectrum for all particles and Higgs fields is calculated and shown to be consistent with present experimental bounds. Some fundamental phenomenological signatures of a non-zero right-handed neutrino expectation value are discussed, particularly the cosmology and proton lifetime arising from induced lepton and baryon number violating interactions.
The mass spectra, hierarchy and cosmology of B-L MSSM heterotic compactifications
Ambroso, Michael; Ovrut, Burt A.
2011-04-10
The matter spectrum of the MSSM, including three right-handed neutrino supermultiplets and one pair of Higgs-Higgs conjugate superfields, can be obtained by compactifying the E₈ x E₈ heterotic string and M-theory on Calabi-Yau manifolds with specific SU(4) vector bundles. These theories have the standard model gauge group augmented by an additional gauged U(1)B-L. Their minimal content requires that the B-L gauge symmetry be spontaneously broken by a vacuum expectation value of at least one right-handed neutrino. In previous papers, we presented the results of a quasi-analytic renormalization group analysis showing that B-L gauge symmetry is indeed radiatively broken with anmore » appropriate B-L/electroweak hierarchy. In this paper, we extend these results by 1) enlarging the initial parameter space and 2) explicitly calculating all renormalization group equations numerically. The regions of the initial parameter space leading to realistic vacua are presented and the B-L/electroweak hierarchy computed over these regimes. At representative points, the mass spectrum for all particles and Higgs fields is calculated and shown to be consistent with present experimental bounds. Some fundamental phenomenological signatures of a non-zero right-handed neutrino expectation value are discussed, particularly the cosmology and proton lifetime arising from induced lepton and baryon number violating interactions.« less
Inflection-point B -L Higgs inflation
NASA Astrophysics Data System (ADS)
Okada, Nobuchika; Raut, Digesh
2017-02-01
Inflection-point inflation is an interesting possibility to realize a successful slow-roll inflation when inflation is driven by a single scalar field with its initial value below the Planck mass (ϕI≲MPl). In order for a renormalization group (RG) improved effective λ ϕ4 potential to develop an inflection point, the quartic coupling λ (ϕ ) must exhibit a minimum with an almost vanishing value in its RG evolution, namely λ (ϕI)≃0 and βλ(ϕI)≃0 , where βλ is the beta function of the quartic coupling. As an example, we consider the minimal gauged B -L extended Standard Model at the TeV scale, where we identify the B -L Higgs field as the inflaton field. For a successful inflection-point inflation, which is consistent with the current cosmological observations, the mass ratios among the Z' gauge boson, the right-handed neutrinos and the B -L Higgs boson are fixed. Our scenario can be tested in the future collider experiments such as the high-luminosity LHC and the SHiP experiments. In addition, the inflection-point inflation provides a unique prediction for the running of the spectral index α ≃-2.7 ×10-3(60/N) 2 (N is the e -folding number), which can be tested in the near future.
ERIC Educational Resources Information Center
New York State Education Dept., Albany. Bureau of Secondary Curriculum Development.
Intended primarily for use by instrumental music teachers who do not have a major concentration in strings, this guide provides pertinent basic resources, materials, teaching--learning expectation, and a general overall guide to achievement levels at various stages of development. Discussions are presented of Choosing the Proper Method Book,…
NASA Astrophysics Data System (ADS)
Wheeler, J. Craig
2000-07-01
In this tour de force of the ultimate and extreme in astrophysics, renowned astrophysicist and author J. Craig Wheeler takes us on a breathtaking journey to supernovae, black holes, gamma-ray bursts and adventures in hyperspace. This is no far-fetched science fiction tale, but an enthusiastic exploration of ideas at the cutting edge of current astrophysics. Wheeler follows the tortuous life of a star from birth to evolution and death, and goes on to consider the complete collapse of a star into a black hole, worm-hole time machines, the possible birth of baby bubble universes, and the prospect of a revolutionary view of space and time in a ten-dimensional string theory. Along the way he offers evidence that suggests the Universe is accelerating and describes recent developments in understanding gamma-ray bursts--perhaps the most catastrophic cosmic events of all. With the use of lucid analogies, simple language and crystal-clear cartoons, Cosmic Catastrophes makes accessible some of the most exciting and mind-bending objects and ideas in the Universe. J. Craig Wheeler is currently Samuel T. and Fern Yanagisawa Regents Professor of Astronomy at the University of Texas at Austin and Vice President of the American Astronomical Society as of 1999.
The dynamics of domain walls and strings
NASA Technical Reports Server (NTRS)
Gregory, Ruth; Haws, David; Garfinkle, David
1989-01-01
The leading order finite-width corrections to the equation of motion describing the motion of a domain wall are derived. The regime in which this equation of motion is invalid is discussed. Spherically and cylindrically symmetric solutions to this equation of motion are found. A misconception that has arisen in recent years regarding the rigidity (or otherwise) of cosmic strings is also clarified.
ERIC Educational Resources Information Center
Hoover, Todd F.
2010-01-01
The "Magic" String is a discrepant event that includes a canister with what appears to be the end of two strings protruding from opposite sides of it. Due to the way the strings are attached inside the canister, it appears as if the strings can magically switch the way they are connected. When one string end is pulled, the observer's expectation…
Mirage in the sky: Nonthermal dark matter, gravitino problem, and cosmic ray anomalies
Dutta, Bhaskar; Sinha, Kuver; Leblond, Louis
2009-08-01
Recent anomalies in cosmic rays could be due to dark matter annihilation in our galaxy. In order to get the required large cross section to explain the data while still obtaining the right relic density, we rely on a nonstandard thermal history between dark matter freeze out and big-bang nucleosynthesis. We show that through a reheating phase from the decay of a heavy moduli or even the gravitino, we can produce the right relic density of dark matter if its self-annihilation cross section is large enough. In addition to fitting the recent data, this scenario solves the cosmological moduli and gravitino problems. We illustrate this mechanism with a specific example in the context of U(1){sub B-L} extended minimal supersymmetric standard model where supersymmetry is broken via mirage mediation. These string motivated models naturally contain heavy moduli decaying to the gravitino, whose subsequent decay to the LSP can reheat the Universe at a low temperature. The right-handed sneutrino and the B-L gaugino can both be viable dark matter candidates with a large cross section. They are leptophilic because of B-L charges. We also show that it is possible to distinguish the nonthermal from the thermal scenario (using Sommerfeld enhancement) in direct detection experiments for certain regions of parameter space.
Scaling of multitension cosmic superstring networks
Tye, S.-H. Henry; Wasserman, Ira; Wyman, Mark
2005-05-15
Brane inflation in superstring theory ends when branes collide, initiating the hot big bang. Cosmic superstrings are produced during the brane collision. The cosmic superstrings produced in a D3-brane-antibrane inflationary scenario have a spectrum: (p,q) bound states of p fundamental (F) strings and q D-strings, where p and q are coprime. By extending the velocity-dependent one-scale network evolution equations for Abelian Higgs cosmic strings to allow a spectrum of string tensions, we construct a coupled (infinite) set of equations for strings that interact through binding and self-interactions. We apply this model to a network of (p,q) superstrings. Our numerical solutions show that (p,q) networks rapidly approach a stable scaling solution. We also extract the relative densities of each string type from our solutions. Typically, only a small number of the lowest tension states are populated substantially once scaling is reached. The model we study also has an interesting new feature: the energy released in (p,q) string binding is by itself adequate to allow the network to reach scaling. This result suggests that the scaling solution is robust. To demonstrate that this result is not trivial, we show that choosing a different form for string interactions can lead to network frustration.
Towards a kinetic theory of strings
Vanchurin, Vitaly
2011-05-15
We study the dynamics of strings by means of a distribution function f(A,B,x,t), defined on a 9+1D phase space, where A and B are the correlation vectors of right- and left-moving waves. We derive a transport equation (analogous to a Boltzmann transport equation for particles) that governs the evolution of long strings with Nambu-Goto dynamics, as well as reconnections taken into account. We also derive a system of coupled transport equations (analogous to a Bogoliubov-Born-Green-Kirkwood-Yvon hierarchy for particles) which can simultaneously describe long strings f-tilde(A,B,x,t) as well as simple loops f(convolution sign)(A,B,x,t) made out of four correlation vectors. The formalism can be used to study nonlinear dynamics of fundamental strings, D-brane strings, or field theory strings. For example, the complicated semiscaling behavior of cosmic strings translates into a simple solution of the transport system at small energy densities.
Highly excited strings I: Generating function
NASA Astrophysics Data System (ADS)
Skliros, Dimitri P.; Copeland, Edmund J.; Saffin, Paul M.
2017-03-01
This is the first of a series of detailed papers on string amplitudes with highly excited strings (HES). In the present paper we construct a generating function for string amplitudes with generic HES vertex operators using a fixed-loop momentum formalism. We generalise the proof of the chiral splitting theorem of D'Hoker and Phong to string amplitudes with arbitrary HES vertex operators (with generic KK and winding charges, polarisation tensors and oscillators) in general toroidal compactifications E =R D - 1 , 1 ×T Dcr - D (with generic constant Kähler and complex structure target space moduli, background Kaluza-Klein (KK) gauge fields and torsion). We adopt a novel approach that does not rely on a ;reverse engineering; method to make explicit the loop momenta, thus avoiding a certain ambiguity pointed out in a recent paper by Sen, while also keeping the genus of the worldsheet generic. This approach will also be useful in discussions of quantum gravity and in particular in relation to black holes in string theory, non-locality and breakdown of local effective field theory, as well as in discussions of cosmic superstrings and their phenomenological relevance. We also discuss the manifestation of wave/particle (or rather wave/string) duality in string theory.
Gravitational wave bursts from cosmic superstrings with Y-junctions
Binetruy, P.; Bohe, A.; Hertog, T.; Steer, D. A.
2009-12-15
Cosmic superstring loops generically contain strings of different tensions that meet at Y-junctions. These loops evolve nonperiodically in time, and have cusps and kinks that interact with the junctions. We study the effect of junctions on the gravitational wave signal emanating from cosmic string cusps and kinks. We find that earlier results on the strength of individual bursts from cusps and kinks on strings without junctions remain largely unchanged, but junctions give rise to additional contributions to the gravitational wave signal coming from strings expanding at the speed of light at a junction and kinks passing through a junction.
Constraint Reasoning Over Strings
NASA Technical Reports Server (NTRS)
Koga, Dennis (Technical Monitor); Golden, Keith; Pang, Wanlin
2003-01-01
This paper discusses an approach to representing and reasoning about constraints over strings. We discuss how many string domains can often be concisely represented using regular languages, and how constraints over strings, and domain operations on sets of strings, can be carried out using this representation.
Self-similar motion of a Nambu-Goto string
NASA Astrophysics Data System (ADS)
Igata, Takahisa; Houri, Tsuyoshi; Harada, Tomohiro
2016-09-01
We study the self-similar motion of a string in a self-similar spacetime by introducing the concept of a self-similar string, which is defined as the world sheet to which a homothetic vector field is tangent. It is shown that in Nambu-Goto theory, the equations of motion for a self-similar string reduce to those for a particle. Moreover, under certain conditions such as the hypersurface orthogonality of the homothetic vector field, the equations of motion for a self-similar string simplify to the geodesic equations on a (pseudo)Riemannian space. As a concrete example, we investigate a self-similar Nambu-Goto string in a spatially flat Friedmann-Lemaître-Robertson-Walker expanding universe with self-similarity and obtain solutions of open and closed strings, which have various nontrivial configurations depending on the rate of the cosmic expansion. For instance, we obtain a circular solution that evolves linearly in the cosmic time while keeping its configuration by the balance between the effects of the cosmic expansion and string tension. We also show the instability for linear radial perturbation of the circular solutions.
Turok, N.
1987-11-01
It is argued that, in fundamental string theories, as one traces the universe back in time a point is reached when the expansion rate is so fast that the rate of string creation due to quantum effects balances the dilution of the string density due to the expansion. One is therefore led into a phase of constant string density and an exponentially expanding universe. Fundamental strings therefore seem to lead naturally to inflation. 17 refs., 1 fig.
NASA Technical Reports Server (NTRS)
Turok, Neil
1988-01-01
It is argued that, in fundamental string theories, as one traces the universe back in time a point is reached when the expansion rate is so fast that the rate of string creation due to quantum effects balances the dilution of the string density due to the expansion. One is therefore led into a phase of constant string density and an exponentially expanding universe. Fundamental strings therefore seem to lead naturally to inflation.
Sneutrino inflation in supersymmetric B - L with inverse seesaw
Khalil, Shaaban; Sil, Arunansu
2012-07-27
We have shown that inflation in the supersymmetric B - L extension of the Standard Model can be realized where one of the associated right-handed sneutrinos can provide a non-trivial inflationary trajectory at tree level (hence breaking B - L during inflation). As soon as the inflation ends, the right-handed sneutrino falls into the supersymmetric vacuum, with a vanishing vacuum expectation value, so that B - L symmetry is restored. The B - L gauge symmetry will be radiatively broken at a TeV scale and light neutrino masses are generated through the inverse seesaw mechanism.
Specifications for Managed Strings
2006-05-01
string_m 3.1.3.1 The strcreate_m Function Synopsis #include <string_m.h> errno_t strcreate_m(string_m *s, const char * cstr , const rsize_t maxlen...strcreate_m function creates a managed string, referenced by s, given a conven- tional string cstr (which may be null or empty). maxlen specifies the...characters to be those in the null-terminated byte string cstr (which may be empty). If charset is a null pointer, no restricted character set is
Spin-string interaction in QCD strings
Vyas, Vikram
2008-08-15
I consider the question of the interaction between a QCD string and the spin of a quark or an antiquark on whose worldline the string terminates. The problem is analyzed from the point of view of a string representation for the expectation value of a Wilson loop for a spin-half particle. A string representation of the super Wilson loop is obtained starting from an effective string representation of a Wilson Loop. The action obtained in this manner is invariant under a worldline supersymmetry and has a boundary term which contains the spin-string interaction. For rectangular loops the spin-string interaction vanishes and there is no spin-spin term in the resulting heavy quark potential. On the other hand if an allowance is made for the finite intrinsic thickness of the flux tube by assuming that the spin-string interaction takes place not just at the boundary of the string world sheet but extends to a distance of the order of the intrinsic thickness of the flux tube then we do obtain a spin-spin interaction which falls as the fifth power of the distance. Such a term was previously suggested by Kogut and Parisi in the context of a flux-tube model of confinement.
Vacuum polarization in gravitational and electromagnetic fields around a superconducting string
Mankiewicz, L. ); Misiak, M.
1989-09-15
We have calculated the polarization current induced in the physical vacuum around a superconducting cosmic string taking into account the gravitational field of the string. The current can be calculated as an expansion in powers of the inverse of the electron mass. In the region far from the string, where it is justified to keep only the lowest term of this expansion, the polarization current turns out to screen the original current in the string, but the effect is very weak. A direct calculation of terms due to the presence of the gravitational field shows that they are dominated, for realistic string parameters, by the purely electromagnetic contribution.
Primordial magnetic fields from the string network
NASA Astrophysics Data System (ADS)
Horiguchi, Kouichirou; Ichiki, Kiyotomo; Sugiyama, Naoshi
2016-08-01
Cosmic strings are a type of cosmic defect formed by a symmetry-breaking phase transition in the early universe. Individual strings would have gathered to build a network, and their dynamical motion would induce scalar-, vector-, and tensor-type perturbations. In this paper, we focus on the vector mode perturbations arising from the string network based on the one scale model and calculate the time evolution and the power spectrum of the associated magnetic fields. We show that the relative velocity between photon and baryon fluids induced by the string network can generate magnetic fields over a wide range of scales based on standard cosmology. We obtain the magnetic field spectrum before recombination as aB(k,z)~4×10Gμ/1k)3.5 gauss on super-horizon scales, and aB(k,z)~2.4×10Gμ/1k)2.5 gauss on sub-horizon scales in co-moving coordinates. This magnetic field grows up to the end of recombination, and has a final amplitude of approximately B~10Gμ gauss at the k~1 Mpc scale today. This field might serve as a seed for cosmological magnetic fields.
NASA Technical Reports Server (NTRS)
Hall, A. Daniel (Inventor); Davies, Francis J. (Inventor)
2007-01-01
Method and system are disclosed for determining individual string resistance in a network of strings when the current through a parallel connected string is unknown and when the voltage across a series connected string is unknown. The method/system of the invention involves connecting one or more frequency-varying impedance components with known electrical characteristics to each string and applying a frequency-varying input signal to the network of strings. The frequency-varying impedance components may be one or more capacitors, inductors, or both, and are selected so that each string is uniquely identifiable in the output signal resulting from the frequency-varying input signal. Numerical methods, such as non-linear regression, may then be used to resolve the resistance associated with each string.
Effect of kinematic constraints on multitension string network evolution
Avgoustidis, Anastasios; Copeland, Edmund J.
2010-03-15
We consider the evolution of a network of strings in an expanding Universe, allowing for the formation of junctions between strings of different tensions. By explicitly including, in the velocity-dependent evolution equations for the network, kinematic constraints associated with the formation of Y-shaped string junctions, we show how they lead to scaling solutions in regimes where they would not otherwise be found, thereby extending the range of parameters which lead to scaling. By incorporating these constraints we are able to study their general behavior for networks with cosmic superstring interaction rules, and predict the scaling densities expected by these networks.
[The string of Einthoven's string galvanometer].
Wyers, P J
1996-01-01
The Dutch physiologist Willem Einthoven (1860-1927) published in 1901 his construction of a string galvanometer. With this apparatus he opened the era for electrocardiography. As the quality of his instrument largely depended on the string of the string galvanometer it is surprising to note that in his publications Einthoven never mentioned the exact way of producing the string. However, Einthoven's hand written laboratory notes are preserved at the Museum Boerhaave in Leiden. From these notes it comes clear what problems Einthoven had with the string. To get a very thin thread of quarts he first used the method of shooting the thread as was described by Boys (1887), later the blowing method of Nichols (1894). The silvering of the thread was done first chemically, later by cathode spray. In all cases premature breaking of the thread was a nuisance. Because of these failures Einthoven might have decided not to publish any details.
NASA Astrophysics Data System (ADS)
Cardona, Biel; Gomis, Joaquim; Pons, Josep M.
2016-07-01
We construct the canonical action of a Carroll string doing the Carroll limit of a canonical relativistic string. We also study the Killing symmetries of the Carroll string, which close under an infinite dimensional algebra. The tensionless limit and the Carroll p-brane action are also discussed.
Jorgensen, Douglas K.; Kuhns, Douglass J.; Wiersholm, Otto; Miller, Timothy A.
1993-01-01
The drill string enclosure consists of six component parts, including; a top bracket, an upper acrylic cylinder, an acrylic drill casing guide, a lower acrylic cylinder, a bottom bracket, and three flexible ducts. The upper acrylic cylinder is optional based upon the drill string length. The drill string enclosure allows for an efficient drill and sight operation at a hazardous waste site.
Jorgensen, D.K.; Kuhns, D.J.; Wiersholm, O.; Miller, T.A.
1993-03-02
The drill string enclosure consists of six component parts, including; a top bracket, an upper acrylic cylinder, an acrylic drill casing guide, a lower acrylic cylinder, a bottom bracket, and three flexible ducts. The upper acrylic cylinder is optional based upon the drill string length. The drill string enclosure allows for an efficient drill and sight operation at a hazardous waste site.
Dark matter in B-L extended MSSM models
Khalil, S.; Okada, H.
2009-04-15
We analyze the dark matter problem in the context of the supersymmetric U(1){sub B-L} model. In this model, the lightest neutralino can be the B-L gaugino Z-tilde{sub B-L} or the extra Higgsinos {chi}-tilde{sub 1,2} dominated. We compute the thermal relic abundance of these particles and show that, unlike the lightest neutralino in the MSSM, they can account for the observed relic abundance with no conflict with other phenomenological constraints. The prospects for their direct detection, if they are part of our galactic halo, are also discussed.
Straight strings and Friedmann-Robertson-Walker spacetimes
NASA Astrophysics Data System (ADS)
Unruh, W. G.
1992-10-01
The embeddability of a straight cosmic string in a Friedmann-Robertson-Walker (FRW) universe is examined. Although previous suggestions that an exact embedding for a string with longitudinal tension equal to energy density is impossible are substantiated, it is shown that the deviations of either the external metric from the exact FRW metric or of the internal structure of the string from the exact tension equals energy density are expected to be very small, of the order of the square of the ratio of the string diameter (or the evacuated shell around the string) to the Hubble radius. Thus the lack of an exact mathematical embedding leads to negligible physical consequences. The problem with solving for an exact embedding of a string in the manner of the Swiss-cheese model is examined in detail, and it is shown that the metric in the evacuated region around the string is unique. That metric is determined to lowest order in the ratio of the evacuated region over the Hubble radius. The implications of this uniqueness for the Swiss-cheese embedding of a string are discussed.
A cosmic book. [of physics of early universe
NASA Technical Reports Server (NTRS)
Peebles, P. J. E.; Silk, Joseph
1988-01-01
A system of assigning odds to the basic elements of cosmological theories is proposed in order to evaluate the strengths and weaknesses of the theories. A figure of merit for the theories is obtained by counting and weighing the plausibility of each of the basic elements that is not substantially supported by observation or mature fundamental theory. The magnetized strong model is found to be the most probable. In order of decreasing probability, the ranking for the rest of the models is: (1) the magnetized string model with no exotic matter and the baryon adiabatic model; (2) the hot dark matter model and the model of cosmic string loops; (3) the canonical cold dark matter model, the cosmic string loops model with hot dark matter, and the baryonic isocurvature model; and (4) the cosmic string loops model with no exotic matter.
String Theory, String Model-Building, and String Phenomenology — A Practical Introduction
NASA Astrophysics Data System (ADS)
Dienes, Keith R.
This is the written version of an introductory self-contained course on string model-building and string phenomenology given at the 2006 TASI summer school. No prior knowledge of string theory is assumed. The goal is to provide a practical, "how-to" manual on string theory, string model-building, and string phenomenology with a minimum of mathematics. These notes cover the construction of bosonic strings, super-strings, and heterotic strings prior to compactification. These notes also develop the ten-dimensional free-fermionic construction. A final lecture discusses general features of heterotic string models, Type I (open) string models, and recent trends of string phenomenology. and general features of low-energy string phenomenology.
NASA Astrophysics Data System (ADS)
Clancy, Dominic; Feinstein, Alexander; Lidsey, James E.; Tavakol, Reza
1999-04-01
Global symmetries of the string effective action are employed to generate tilted, homogeneous Bianchi type VIh string cosmologies from a previously known stiff perfect fluid solution to Einstein gravity. The dilaton field is not constant on the surfaces of homogeneity. The future asymptotic state of the models is interpreted as a plane wave and is itself an exact solution to the string equations of motion to all orders in the inverse string tension. An inhomogeneous generalization of the Bianchi type III model is also found.
Probing cosmic superstrings with gravitational waves
NASA Astrophysics Data System (ADS)
Sousa, L.; Avelino, P. P.
2016-09-01
We compute the stochastic gravitational wave background generated by cosmic superstrings using a semianalytical velocity-dependent model to describe their dynamics. We show that heavier string types may leave distinctive signatures on the stochastic gravitational wave background spectrum within the reach of present and upcoming gravitational wave detectors. We examine the physically motivated scenario in which the physical size of loops is determined by the gravitational backreaction scale and use NANOGrav data to derive a conservative constraint of G μF<3.2 ×10-9 on the tension of fundamental strings. We demonstrate that approximating the gravitational wave spectrum generated by cosmic superstring networks using the spectrum generated by ordinary cosmic strings with reduced intercommuting probability (which is often done in the literature) leads, in general, to weaker observational constraints on G μF. We show that the inclusion of heavier string types is required for a more accurate characterization of the region of the (gs,G μF) parameter space that may be probed using direct gravitational wave detectors. In particular, we consider the observational constraints that result from NANOGrav data and show that heavier strings generate a secondary exclusion region of parameter space.
Scaling configurations of cosmic superstring networks and their cosmological implications
Pourtsidou, A.; Avgoustidis, A.; Copeland, E. J.; Pogosian, L.; Steer, D. A.
2011-03-15
We study the cosmic microwave background temperature and polarization spectra sourced by multitension cosmic-superstring networks. First, we obtain solutions for the characteristic length scales and velocities associated with the evolution of a network of F-D strings, allowing for the formation of junctions between strings of different tensions. We find two distinct regimes describing the resulting scaling distributions for the relative densities of the different types of strings, depending on the magnitude of the fundamental string coupling g{sub s}. In one of them, corresponding to the value of the coupling being of order unity, the network's stress-energy power spectrum is dominated by populous light F and D strings, while the other regime, at smaller values of g{sub s}, has the spectrum dominated by rare heavy D strings. These regimes are seen in the cosmic microwave background (CMB) anisotropies associated with the network. We focus on the dependence of the shape of the B-mode polarization spectrum on g{sub s} and show that measuring the peak position of the B-mode spectrum can point to a particular value of the string coupling. Finally, we assess how this result, along with pulsar bounds on the production of gravitational waves from strings, can be used to constrain a combination of g{sub s} and the fundamental string tension {mu}{sub F}. Since CMB and pulsar bounds constrain different combinations of the string tensions and densities, they result in distinct shapes of bounding contours in the ({mu}{sub F},g{sub s}) parameter plane, thus providing complementary constraints on the properties of cosmic superstrings.
Classically conformal radiative neutrino model with gauged B - L symmetry
NASA Astrophysics Data System (ADS)
Okada, Hiroshi; Orikasa, Yuta
2016-09-01
We propose a classically conformal model in a minimal radiative seesaw, in which we employ a gauged B - L symmetry in the standard model that is essential in order to work the Coleman-Weinberg mechanism well that induces the B - L symmetry breaking. As a result, nonzero Majorana mass term and electroweak symmetry breaking simultaneously occur. In this framework, we show a benchmark point to satisfy several theoretical and experimental constraints. Here theoretical constraints represent inert conditions and Coleman-Weinberg condition. Experimental bounds come from lepton flavor violations (especially μ → eγ), the current bound on the Z‧ mass at the CERN Large Hadron Collider, and neutrino oscillations.
Space-Time Variable Superstring Vacua Calabi-Yau Cosmic Yarn)
NASA Astrophysics Data System (ADS)
Green, Paul S.; Hübsch, Tristan
In a general superstring vacuum configuration, the “internal” space (sector) varies in space-time. When this variation is nontrivial only in two spacelike dimensions, the vacuum contains static cosmic strings with finite energy per unit length and which is, up to interactions with matter, an easily computed topological invariant. The total space-time is smooth although the “internal” space is singular at the center of each cosmic string. In a similar analysis of the Wick-rotated Euclidean model, these cosmic strings acquire expected self-interactions. Also, a possibility emerges to define a global time in order to rotate back to the Lorentzian case.
NASA Astrophysics Data System (ADS)
Maldacena, Juan Martín
D-Branes on Calabi-Yau manifolds / Paul S. Aspinwall -- Lectures on AdS/CFT / Juan M. Maldacena -- Tachyon dynamics in open string theory / Ashoke Sen -- TASI/PITP/ISS lectures on moduli and microphysics / Eva Silverstein -- The duality cascade / Matthew J. Strassler -- Perturbative computations in string field theory / Washington Taylor -- Student seminars -- Student participants -- Lecturers, directors, and local organizing committee.
Probing a classically conformal B -L model with gravitational waves
NASA Astrophysics Data System (ADS)
Jinno, Ryusuke; Takimoto, Masahiro
2017-01-01
We study the cosmological history of the classical conformal B -L gauge extension of the standard model, in which the physical scales are generated via the Coleman-Weinberg-type symmetry breaking. In particular, we consider the thermal phase transition of the U (1 )B -L symmetry in the early Universe and resulting gravitational wave production. Due to the classical conformal invariance, the phase transition tends to be a first-order one with ultra-supercooling, which enhances the strength of the produced gravitational waves. We show that, requiring (1) U (1 )B -L is broken after the reheating, (2) the B -L gauge coupling does not blow up below the Planck scale, and (3) the thermal phase transition completes in almost all the patches in the Universe, the gravitational wave spectrum can be as large as ΩGW˜10-8 at the frequency f ˜0.01 - 1 Hz for some model parameters, and a vast parameter region can be tested by future interferometer experiments.
Gravitational lensing effects of vacuum strings - Exact solutions
NASA Technical Reports Server (NTRS)
Gott, J. R., III
1985-01-01
Exact interior and exterior solutions to Einstein's field equations are derived for vacuum strings. The exterior solution for a uniform density vacuum string corresponds to a conical space while the interior solution is that of a spherical cap. For Mu equals 0-1/4 the external metric is ds-squared = -dt-squared + dr-squared + (1-4 Mu)-squared r-squared dphi-squared + dz-squared, where Mu is the mass per unit length in the string in Planck masses per Planck length. A maximum mass per unit length for a string is 6.73 x 10 to the 27th g/cm. It is shown that strings cause temperature fluctuations in the cosmic microwave background and produce equal brightness double QSO images separated by up to several minutes of arc. Formulae for lensing probabilities, image splittings, and time delays are derived for strings in a realistic cosmological setting. String searches using ST, the VLA, and the COBE satellite are discussed.
Universality and string theory
NASA Astrophysics Data System (ADS)
Bachlechner, Thomas Christian
The first run at the Large Hadron Collider has deeply challenged conventional notions of naturalness, and CMB polarization experiments are about to open a new window to early universe cosmology. As a compelling candidate for the ultraviolet completion of the standard model, string theory provides a prime opportunity to study both early universe cosmology and particle physics. However, relating low energy observations to ultraviolet physics requires knowledge of the metastable states of string theory through the study of vacua. While it is difficult to directly obtain infrared data from explicit string theory constructions, string theory imposes constraints on low energy physics. The study of ensembles of low energy theories consistent with ultra-violet constraints provides insight on generic features we might expect to occur in string compactifications. In this thesis we present a statistical treatment of vacuum stability and vacuum properties in the context of random supergravity theories motivated by string theory. Early universe cosmology provides another avenue to high energy physics. From the low energy perspective large field inflation is typically considered highly unnatural: the scale relevant for the diameter of flat regions in moduli space is sub-Planckian in regions of perturbative control. To approach this problem, we consider generic Calabi-Yau compactifications of string theory and find that super-Planckian diameters of axion fundamental domains in fact arise generically. We further demonstrate that such super-Planckian flat regions are plausibly consistent with theWeak Gravity Conjecture.
Supersymmetry and String Theory
NASA Astrophysics Data System (ADS)
Dine, Michael
2016-01-01
Preface to the first edition; Preface to the second edition; A note on choice of metric; Text website; Part I. Effective Field Theory: The Standard Model, Supersymmetry, Unification: 1. Before the Standard Model; 2. The Standard Model; 3. Phenomenology of the Standard Model; 4. The Standard Model as an effective field theory; 5. Anomalies, instantons and the strong CP problem; 6. Grand unification; 7. Magnetic monopoles and solitons; 8. Technicolor: a first attempt to explain hierarchies; Part II. Supersymmetry: 9. Supersymmetry; 10. A first look at supersymmetry breaking; 11. The Minimal Supersymmetric Standard Model; 12. Supersymmetric grand unification; 13. Supersymmetric dynamics; 14. Dynamical supersymmetry breaking; 15. Theories with more than four conserved supercharges; 16. More supersymmetric dynamics; 17. An introduction to general relativity; 18. Cosmology; 19. Astroparticle physics and inflation; Part III. String Theory: 20. Introduction; 21. The bosonic string; 22. The superstring; 23. The heterotic string; 24. Effective actions in ten dimensions; 25. Compactification of string theory I. Tori and orbifolds; 26. Compactification of string theory II. Calabi-Yau compactifications; 27. Dynamics of string theory at weak coupling; 28. Beyond weak coupling: non-perturbative string theory; 29. Large and warped extra dimensions; 30. The landscape: a challenge to the naturalness principle; 31. Coda: where are we headed?; Part IV. The Appendices: Appendix A. Two-component spinors; Appendix B. Goldstone's theorem and the pi mesons; Appendix C. Some practice with the path integral in field theory; Appendix D. The beta function in supersymmetric Yang-Mills theory; References; Index.
Swiftly Computing Center Strings
2011-01-01
Background The center string (or closest string) problem is a classic computer science problem with important applications in computational biology. Given k input strings and a distance threshold d, we search for a string within Hamming distance at most d to each input string. This problem is NP complete. Results In this paper, we focus on exact methods for the problem that are also swift in application. We first introduce data reduction techniques that allow us to infer that certain instances have no solution, or that a center string must satisfy certain conditions. We describe how to use this information to speed up two previously published search tree algorithms. Then, we describe a novel iterative search strategy that is effecient in practice, where some of our reduction techniques can also be applied. Finally, we present results of an evaluation study for two different data sets from a biological application. Conclusions We find that the running time for computing the optimal center string is dominated by the subroutine calls for d = dopt -1 and d = dopt. Our data reduction is very effective for both, either rejecting unsolvable instances or solving trivial positions. We find that this speeds up computations considerably. PMID:21504573
Witten, Edward
2015-10-21
The Strings 2014 meeting was held at Princeton University June 23-27, 2014, co-sponsored by Princeton University and the Institute for Advanced Study. The goal of the meeting was to provide a stimulating and up-to-date overview of research in string theory and its relations to other areas of physics and mathematics, ranging from geometry to quantum field theory, condensed matter physics, and more. This brief report lists committee members and speakers but contains no scientific information. Note that the talks at Strings 2014 were videotaped and are available on the conference website: http://physics.princeton.edustrings2014/Talk_titles.shtml.
Reheating for closed string inflation
Cicoli, Michele; Mazumdar, Anupam E-mail: a.mazumdar@lancaster.ac.uk
2010-09-01
We point out some of the outstanding challenges for embedding inflationary cosmology within string theory studying the process of reheating for models where the inflaton is a closed string mode parameterising the size of an internal cycle of the compactification manifold. A realistic model of inflation must explain the tiny perturbations in the cosmic microwave background radiation and also how to excite the ordinary matter degrees of freedom after inflation, required for the success of Big Bang Nucleosynthesis. We study these issues focusing on two promising inflationary models embedded in LARGE volume type IIB flux compactifications. We show that phenomenological requirements and consistency of the effective field theory treatment imply the presence at low energies of a hidden sector together with a visible sector, where the Minimal Supersymmetric Standard Model fields are residing. A detailed calculation of the inflaton coupling to the fields of the hidden sector, visible sector, and moduli sector, reveals that the inflaton fails to excite primarily the visible sector fields, instead hidden sector fields are excited copiously after the end of inflation. This sets severe constraints on hidden sector model building where the most promising scenario emerges as a pure N = 1 SYM theory, forbidding the kinematical decay of the inflaton to the hidden sector. In this case it is possible to reheat the Universe with the visible degrees of freedom even though in some cases we discover a new tension between TeV scale SUSY and reheating on top of the well-known tension between TeV scale SUSY and inflation.
Casper, William L.; Clark, Don T.; Grover, Blair K.; Mathewson, Rodney O.; Seymour, Craig A.
2008-10-07
A drill string comprises a first drill string member having a male end; and a second drill string member having a female end configured to be joined to the male end of the first drill string member, the male end having a threaded portion including generally square threads, the male end having a non-threaded extension portion coaxial with the threaded portion, and the male end further having a bearing surface, the female end having a female threaded portion having corresponding female threads, the female end having a non-threaded extension portion coaxial with the female threaded portion, and the female end having a bearing surface. Installation methods, including methods of installing instrumented probes are also provided.
Arago C. de; Bazeia, D.; Eboli, O.J.P.; Marques, G.C.
1985-12-15
We obtain a semiclassical evaluation of the temperature for which the free energy of the strings of spontaneously broken scalar electrodynamics vanishes. We argue that, above this temperature, these objects should play a significant physical role.
Universality in string interactions
NASA Astrophysics Data System (ADS)
Huang, Yu-tin; Schlotterer, Oliver; Wen, Congkao
2016-09-01
In this note, we provide evidence for universality in the low-energy expansion of tree-level string interactions. More precisely, in the α'-expansion of tree-level scattering amplitudes, we conjecture that the leading transcendental coefficient at each order in α' is universal for all perturbative string theories. We have checked this universality up to seven points and trace its origin to the ability to restructure the disk integrals of open bosonic string into those of the superstring. The accompanying kinematic functions have the same low-energy limit and do not introduce any transcendental numbers in their α'-corrections. Universality in the closed-string sector then follows from KLT-relations.
NASA Astrophysics Data System (ADS)
Frampton, Paul H.
2016-04-01
In this note, I recollect a two-week period in September 1968 when I factorized the Veneziano model using string variables in Chicago. Professor Yoichiro Nambu went on to calculate the N-particle dual resonance model and then to factorize it on an exponential degeneracy of states. That was in 1968 and the following year 1969 he discovered the string action. I also include some other reminiscences of Nambu who passed away on July 5, 2015.
NASA Astrophysics Data System (ADS)
Frampton, Paul H.
In this note, I recollect a two-week period in September 1968 when I factorized the Veneziano model using string variables in Chicago. Professor Yoichiro Nambu went on to calculate the N-particle dual resonance model and then to factorize it on an exponential degeneracy of states. That was in 1968 and the following year 1969 he discovered the string action. I also include some other reminiscences of Nambu who passed away on July 5, 2015.
NASA Astrophysics Data System (ADS)
Trzetrzelewski, Maciej
2016-11-01
Starting with a Nambu-Goto action, a Dirac-like equation can be constructed by taking the square-root of the momentum constraint. The eigenvalues of the resulting Hamiltonian are real and correspond to masses of the excited string. In particular there are no tachyons. A special case of radial oscillations of a closed string in Minkowski space-time admits exact solutions in terms of wave functions of the harmonic oscillator.
Ahlén, Olof
2015-12-17
These proceedings from the second Caesar Lattes meeting in Rio de Janeiro 2015 are a brief introduction to how automorphic forms appear in the low energy effective action of maximally supersymmetric string theory. The explicit example of the R{sup 4}-interaction of type IIB string theory in ten dimensions is discussed. Its Fourier expansion is interpreted in terms of perturbative and non-perturbative contributions to the four graviton amplitude.
Hydroball string sensing system
Hurwitz, Michael J.; Ekeroth, Douglas E.; Squarer, David
1991-01-01
A hydroball string sensing system for a nuclear reactor that includes stainless tubes positioned to guide hydroball strings into and out of the nuclear reactor core. A sensor such as an ultrasonic transducer transmitter and receiver is positioned outside of the nuclear reactor core and adjacent to the tube. The presence of an object such a bullet member positioned at an end a hydroball string, or any one of the hydroballs interrupts the transmission of ultrasound from the transmitter to the receiver. Alternatively, if the bullet member and hydroballs include a ferritic material, either a Hall effect sensor or other magnetic field sensors such as a magnetic field rate of change sensor can be used to detect the location and position of a hydroball string. Placing two sensors along the tube with a known distance between the sensors enables the velocity of a hydroball string to be determined. This determined velocity can be used to control the flow rate of a fluid within the tube so as to control the velocity of the hydroball string.
Power suppression at large scales in string inflation
Cicoli, Michele; Downes, Sean; Dutta, Bhaskar E-mail: sddownes@physics.tamu.edu
2013-12-01
We study a possible origin of the anomalous suppression of the power spectrum at large angular scales in the cosmic microwave background within the framework of explicit string inflationary models where inflation is driven by a closed string modulus parameterizing the size of the extra dimensions. In this class of models the apparent power loss at large scales is caused by the background dynamics which involves a sharp transition from a fast-roll power law phase to a period of Starobinsky-like slow-roll inflation. An interesting feature of this class of string inflationary models is that the number of e-foldings of inflation is inversely proportional to the string coupling to a positive power. Therefore once the string coupling is tuned to small values in order to trust string perturbation theory, enough e-foldings of inflation are automatically obtained without the need of extra tuning. Moreover, in the less tuned cases the sharp transition responsible for the power loss takes place just before the last 50-60 e-foldings of inflation. We illustrate these general claims in the case of Fibre Inflation where we study the strength of this transition in terms of the attractor dynamics, finding that it induces a pivot from a blue to a redshifted power spectrum which can explain the apparent large scale power loss. We compute the effects of this pivot for example cases and demonstrate how magnitude and duration of this effect depend on model parameters.
String melting in a photon bath
Karouby, Johanna
2013-10-01
We compute the decay rate of a metastable cosmic string in contact with a thermal bath by finding the instanton solution. The new feature is that this decay rate is found in the context of non thermal scalar fields in contact with a thermal bath of photons. In general, to make topologically unstable strings stable, one can couple them to such a bath. The resulting plasma effect creates metastable configurations which can decay from the false vacuum to the true vacuum. In our specific set-up, the instanton computation is realized for the case of two out-of-equilibrium complex scalar fields: one is charged and coupled to the photon field, and the other is neutral. New effects coming from the thermal bath of photons make the radius of the nucleated bubble and most of the relevant physical quantities temperature-dependent. However, the temperature appears in a different way than in the purely thermal case, where all scalar fields are in thermal equilibrium. As a result of the tunneling, the core of the initial string melts while bubbles of true vacuum expand at the speed of light.
Chaotic hybrid inflation with a gauged B -L
NASA Astrophysics Data System (ADS)
Carpenter, Linda M.; Raby, Stuart
2014-11-01
In this paper we present a novel formulation of chaotic hybrid inflation in supergravity. The model includes a waterfall field which spontaneously breaks a gauged U1 (B- L) at a GUT scale. This allows for the possibility of future model building which includes the standard formulation of baryogenesis via leptogenesis with the waterfall field decaying into right-handed neutrinos. We have not considered the following issues in this short paper, i.e. supersymmetry breaking, dark matter or the gravitino or moduli problems. Our focus is on showing the compatibility of the present model with Planck, WMAP and Bicep2 data.
Amore, Paolo; Fernández, Francisco M.; Garcia, Javier; Gutierrez, German
2014-04-15
We study both analytically and numerically the spectrum of inhomogeneous strings with PT-symmetric density. We discuss an exactly solvable model of PT-symmetric string which is isospectral to the uniform string; for more general strings, we calculate exactly the sum rules Z(p)≡∑{sub n=1}{sup ∞}1/E{sub n}{sup p}, with p=1,2,… and find explicit expressions which can be used to obtain bounds on the lowest eigenvalue. A detailed numerical calculation is carried out for two non-solvable models depending on a parameter, obtaining precise estimates of the critical values where pair of real eigenvalues become complex. -- Highlights: •PT-symmetric Hamiltonians exhibit real eigenvalues when PT symmetry is unbroken. •We study PT-symmetric strings with complex density. •They exhibit regions of unbroken PT symmetry. •We calculate the critical parameters at the boundaries of those regions. •There are exact real sum rules for some particular complex densities.
Electromagnetic backreaction from currents on a straight string
NASA Astrophysics Data System (ADS)
Wachter, Jeremy M.; Olum, Ken D.
2014-07-01
Charge carriers moving at the speed of light along a straight, superconducting cosmic string carry with them a logarithmically divergent slab of electromagnetic field energy. Thus, no finite local input can induce a current that travels unimpeded to infinity. Rather, electromagnetic backreaction must damp this current asymptotically to nothing. We compute this backreaction and find that the electromagnetic fields and currents decline exactly as rapidly as necessary to prevent a divergence. We briefly discuss the corresponding gravitational situation.
Energy radiation by cosmic superstrings in brane inflation
Firouzjahi, Hassan
2008-01-15
The dominant method of energy loss by a loop of cosmic D-strings in models of warped brane inflation is studied. It is shown that the energy loss via Ramond-Ramond field radiation can dominate by many orders of magnitude over the energy radiation via gravitational wave emission. The ratio of these two energy loss mechanisms depends on the energy scale of inflation, the mass scale of string theory, and whether it is a single-throat or a multithroat inflationary scenario. This can have important consequences for the detection of cosmic superstrings in the near future. It is argued that the bounds from cosmic microwave background anisotropies and big bang nucleosynthesis are the dominant cosmological sources to constrain the physical parameters of the network of cosmic superstrings, whereas the role of the gravitational wave-based experiments may be secondary.
NASA Astrophysics Data System (ADS)
Kawamoto, Noboru; Kugo, Taichiro
String theories seem to have created a breakthrough in theoretical physics. At long last a unified theory of all the fundamental interactions, including gravity, looks possible. This, according to theorist Stephen Hawking, will mark the end of theoretical physics as we have known it, since we will then have a single consistent theory within which to explain all natural phenomena from elementary particles to galactic superclusters. Strings themselves are extremely tiny entities, smaller than the Planck scale, which form loops whose vibrational harmonics can be used to model all the standard elementary particles. Of course the mathematical complexities of the theory are daunting, and physicists are still at a very early stage in understanding how strings and their theoretical cousins superstrings can be used. This proceedings volume gives an overview of the intense recent work in the field and reports latest developments.
Battye, R.A.; Shellard, E.P. |
1995-12-01
We discuss radiative backreaction for global strings described by the Kalb-Ramond action with an analogous derivation to that for the point electron in classical electrodynamics. We show how local corrections to the equations of motion allow one to separate the self-field of the string from that of the radiation field. Modifications to this {open_quote}{open_quote}local backreaction approximation{close_quote}{close_quote} circumvent the runaway solutions, allowing these corrections to be used to evolve string trajectories numerically. Comparisons are made with analytic and numerical radiation calculations from previous work and the merits and limitations of this approach are discussed. {copyright} {ital 1995 The American Physical Society.}
Strings in strong gravitational fields
NASA Astrophysics Data System (ADS)
De Vega, H. J.; Nicolaidis, A.
1992-12-01
We study string propagation in curved space-time. In such a problem, the equations of motion and the string constraints are nonlinear and difficult to solve. We propose here a systematic expansion in c, the world-sheet speed of light, to solve the string dynamics. Since c is proportional to the string tension, this amounts to a large α' expansion. To zeroth order each point of the string moves along a null geodesic (null string), while the first order correction incorporates the string dynamics. As an illustration we apply our formalism to the Robertson-Walker geometry. In this case, it turns out that the string expands or contracts at the same rate as the whole universe.
Keith Dienes
2009-12-01
We are currently in the throes of a potentially huge paradigm shift in physics. Motivated by recent developments in string theory and the discovery of the so-called "string landscape", physicists are beginning to question the uniqueness of fundamental theories of physics and the methods by which such theories might be understood and investigated. In this colloquium, I will give a non-technical introduction to the nature of this paradigm shift and how it developed. I will also discuss some of the questions to which it has led, and the nature of the controversies it has spawned.
NASA Astrophysics Data System (ADS)
Jejjala, Vishnu; Minic, Djordje; Ng, Y. Jack; Tze, Chia-Hsiung
We propose a string theory of turbulence that explains the Kolmogorov scaling in 3+1 dimensions and the Kraichnan and Kolmogorov scalings in 2+1 dimensions. This string theory of turbulence should be understood in light of the AdS/CFT dictionary. Our argument is crucially based on the use of Migdal's loop variables and the self-consistent solutions of Migdal's loop equations for turbulence. In particular, there is an area law for turbulence in 2+1 dimensions related to the Kraichnan scaling.
Keith Dienes
2016-07-12
We are currently in the throes of a potentially huge paradigm shift in physics. Motivated by recent developments in string theory and the discovery of the so-called "string landscape", physicists are beginning to question the uniqueness of fundamental theories of physics and the methods by which such theories might be understood and investigated. In this colloquium, I will give a non-technical introduction to the nature of this paradigm shift and how it developed. I will also discuss some of the questions to which it has led, and the nature of the controversies it has spawned.
Bianchi type-VIh string cloud cosmological models with bulk viscosity
NASA Astrophysics Data System (ADS)
Tripathy, Sunil K.; Behera, Dipanjali
2010-11-01
String cloud cosmological models are studied using spatially homogeneous and anisotropic Bianchi type VIh metric in the frame work of general relativity. The field equations are solved for massive string cloud in presence of bulk viscosity. A general linear equation of state of the cosmic string tension density with the proper energy density of the universe is considered. The physical and kinematical properties of the models have been discussed in detail and the limits of the anisotropic parameter responsible for different phases of the universe are explored.
Constraints on cosmic superstrings from Kaluza-Klein emission.
Dufaux, Jean-François
2012-07-06
Cosmic superstrings interact generically with a tower of light and/or strongly coupled Kaluza-Klein (KK) modes associated with the geometry of the internal space. We study the production of KK particles by cosmic superstring loops, and show that it is constrained by big bang nucleosynthesis. We study the resulting constraints in the parameter space of the underlying string theory model and highlight their complementarity with the regions that can be probed by current and upcoming gravitational wave experiments.
String Theory and Gauge Theories
Maldacena, Juan
2009-02-20
We will see how gauge theories, in the limit that the number of colors is large, give string theories. We will discuss some examples of particular gauge theories where the corresponding string theory is known precisely, starting with the case of the maximally supersymmetric theory in four dimensions which corresponds to ten dimensional string theory. We will discuss recent developments in this area.
Music: Instrumental Techniques, Strings.
ERIC Educational Resources Information Center
Ryan, Philip
A course in music which emphasizes harmony is presented. The approach used is a laboratory one in which pupils will develop skill in playing orchestral string instruments, sing, listen to, read and compose music with emphasis on elementary concepts of harmony. Course objectives include: (1) The student will select the title of a familiar melody…
McAllister, Liam P.; Silverstein, Eva
2007-10-22
We give an overview of the status of string cosmology. We explain the motivation for the subject, outline the main problems, and assess some of the proposed solutions. Our focus is on those aspects of cosmology that benefit from the structure of an ultraviolet-complete theory.
NASA Astrophysics Data System (ADS)
Ortín, Tomás
2015-03-01
1. Differential geometry; 2. Symmetries and Noether's theorems; 3. A perturbative introduction to general relativity; 4. Action principles for gravity; 5. Pure N=1,2,d=4 supergravities; 6. Matter-coupled N=1,d=4 supergravity; 7. Matter-coupled N=2,d=4 supergravity; 8. A generic description of all the N>2,d=4 SUEGRAS; 9. Matter-coupled N=1,d=5 supergravity; 10. Conserved charges in general relativity; 11. The Schwarzschild black hole; 12. The Reissner-Nordström black hole; 13. The Taub-NUT solution; 14. Gravitational pp-waves; 15. The Kaluza-Klein black hole; 16. Dilaton and dilaton/axion black holes; 17. Unbroken supersymmetry I: supersymmetric vacua; 18. Unbroken supersymmetry II: partially supersymmetric solutions; 19. Supersymmetric black holes from supergravity; 20. String theory; 21. The string effective action and T duality; 22. From eleven to four dimensions; 23. The type-IIB superstring and type-II T duality; 24. Extended objects; 25. The extended objects of string theory; 26. String black holes in four and five dimensions; 27. The FGK formalism for (single, static) black holes and branes; Appendices: A.1 Lie groups, symmetric spaces, and Yang-Mills fields; A.2 The irreducible, non-symmetric Riemannian spaces of special holonomy; A.3 Miscellanea on the symplectic group; A.4 Gamma matrices and spinors; A.5 Kähler geometry; A.6 Special Kähler geometry; A.7 Quaternionic-Kähler geometry.
ERIC Educational Resources Information Center
Music Educators Journal, 1979
1979-01-01
Seven string educators respond to questions about repertoire sources for novice players, the teaching of improvisation, weaknesses in current instructional materials, ensemble size, the integration of Suzuki's methods into traditional programs, the problems of a violinist teaching other instruments, and coordination of school and other youth…
Casalbuoni, Roberto; Gomis, Joaquim; Longhi, Giorgio
2007-12-15
We construct a classical nonrelativistic string model in 3+1 dimensions. The model contains a spurion tensor field that is responsible for the noncommutative structure of the model. Under double-dimensional reduction the model reduces to the exotic nonrelativistic particle in 2+1 dimensions.
Experimenting with Guitar Strings
ERIC Educational Resources Information Center
LoPresto, Michael C.
2006-01-01
What follows is a description of a simple experiment developed in a non-mathematical general education science course on sound and light for fine arts students in which a guitar is used with data collection hardware and software to verify the properties of standing waves on a string.
NASA Astrophysics Data System (ADS)
Aragone, C.
1986-12-01
An action is presented for the free bosonic string on external flat space in terms of an antisymmetric second-rank string background tensor which is classically equivalent to the Nambu-Goto action. Both action and field equations are entirely described in terms of 2D world-sheet forms, without any reference to a 2D metric tensor background. The analysis of its canonical formulation shows how the quadratic Virasoro constraints are generated in this case and what their connection with the Bianchi identities are. Since in the orthonormal gauge the reduced action coincides with the standard one, it has the same critical dimension D = 26. The existence of an interaction term of a purely geometric structure stemming in the extrinsic curvature is pointed out. Its action and the new string field equations are then derived. This polynomial antisymmetric string action is uniformly generalized in order to describe d < D-dimensional extended objects in D-dimensional flat space. On leave of absence from Departamento de Física, Universidad Simon Bolívar, Apartado 80659, Caracas 1080A, Venezuela.
ERIC Educational Resources Information Center
Tsutsumanova, Gichka; Russev, Stoyan
2013-01-01
A simple experiment demonstrating the excitation of a standing wave in a metal string is presented here. Several tasks using the set-up are considered, which help the students to better understand the standing waves, the interaction between electric current and magnetic field and the resonance phenomena. This can serve also as a good lecture…
Predictions from String Theory
NASA Astrophysics Data System (ADS)
Kuflik, Eric
String theory is the leading candidate for an underlying theory of nature, as it provides a framework through which to address critical questions left unanswered by the Standard Model and Supersymmetry. A number of predictions of string constructions can be empirically tested at the Large Hadron Collider (LHC) and dark matter experiments. In this work I aim to make generic predictions of string theory, while combining bottom-up approaches to fill in the gaps in our understanding of string theory to make predictions for current and upcoming experiments. First I study moduli masses and claim that moduli dominated the energy density of the universe prior to big bang nucleosynthesis. We argue that in any string theory with stabilized moduli there will be at least one modulus field whose mass is of order the gravitino mass. Cosmology then generically requires the gravitino mass to be greater than 30 TeV and the early cosmological history of the Universe be non-thermal. We are then led to believe that the best-motivated channel for early LHC discovery is gluino pair-production events decaying into a high multiplicity of third generation quarks. We analyze signals and background at the LHC for 7 TeV center of mass energy for 1 fb -1 integrated luminosity, suggesting a reach for gluinos for masses about 650 GeV. Second, I seek to construct a Grand Unified Theory (GUT) within different branches of string theory. One promising GUT, developed outside of string theory, is Flipped-SU(5), which I show has serious phenomenological difficulties. I demonstrate both that Flipped-SU(5) requires an R-symmetry to solve the mu-problem, and that no R-symmetries exist in F-theory. Thus Flipped-SU(5) cannot serve as a GUT within F-theory. Similarly, I seek to construct a GUT within M-theory. My study is based upon the discrete symmetry proposed by Witten that forbids the mu-term and solves the doublet-triplet splitting problem, but does not address how the symmetry might be broken. I find
Current balancing for battery strings
Galloway, James H.
1985-01-01
A battery plant is described which features magnetic circuit means for balancing the electrical current flow through a pluraliircuitbattery strings which are connected electrically in parallel. The magnetic circuit means is associated with the battery strings such that the conductors carrying the electrical current flow through each of the battery strings pass through the magnetic circuit means in directions which cause the electromagnetic fields of at least one predetermined pair of the conductors to oppose each other. In an alternative embodiment, a low voltage converter is associated with each of the battery strings for balancing the electrical current flow through the battery strings.
NASA Astrophysics Data System (ADS)
Berenstein, David
2014-10-01
This review discusses the status of string physics where the string tension is around the TeV scale. It covers model-building basics for perturbative strings, based on D-brane configurations. The effective low-energy physics description of such string constructions is analyzed: how anomaly cancellation is implemented, how fast proton decay is avoided, and how D-brane models lead to additional Z' particles. This review also discusses direct search bounds for strings at the TeV scale, as well as theoretical issues with model building related to flavor physics and axions.
New string theory vacua with suppressed proton decay
NASA Astrophysics Data System (ADS)
Reinbacher, Rene
In this thesis we construct new heterotic superstring vacua with suppressed proton decay. More concretely, we construct Calabi-Yau threefolds Z with fundamental group Z2xZ2 . These threefolds carry Ricci flat hermitian metrics [48] which we use to solve the gravitational part of the string theory equation of motions. Furthermore, these Calabi-Yau threefolds allow the existence of Z2xZ2 Wilson loops. On these threefolds Z we construct stable, holomorphic vector bundles with SU(4) structure group. It follows from a famous theorem by Donaldson [20], Uhlenbeck and Yau [47] that these vector bundles correspond to gauge field configurations whose fields strength obey the hermitian Yang-Mills equations. Therefore, in constructing these vector bundles, we solve the gauge theoretic part of the string theory equations of motion. These vacuum solutions of heterotic string theory give, in conjunction with Z2xZ2 Wilson loops, consistent four dimensional N = 1 supersymmetric vacua with three families of quarks and leptons. The four dimensional gauge group is the standard-model-like group SU3Cx SU2WxU 1YxU1 B-L. The additional gauge symmetry U(1) B--L is used to suppress the most egregious proton decay modes. In addition, we calculate in this thesis the moduli space of SU(n) x SU( m) vector bundles on simply connected Calabi-Yau spaces X. Such gauge configurations can arise in strongly coupled heterotic string theory in certain phase transitions [42], called small instanton transitions [52].
Device for balancing parallel strings
Mashikian, Matthew S.
1985-01-01
A battery plant is described which features magnetic circuit means in association with each of the battery strings in the battery plant for balancing the electrical current flow through the battery strings by equalizing the voltage across each of the battery strings. Each of the magnetic circuit means generally comprises means for sensing the electrical current flow through one of the battery strings, and a saturable reactor having a main winding connected electrically in series with the battery string, a bias winding connected to a source of alternating current and a control winding connected to a variable source of direct current controlled by the sensing means. Each of the battery strings is formed by a plurality of batteries connected electrically in series, and these battery strings are connected electrically in parallel across common bus conductors.
ERIC Educational Resources Information Center
El Abed, Mohamed
2014-01-01
A team of French high-school students sent a weather balloon into the upper atmosphere to recreate Viktor Hess's historical experiment that demonstrated the existence of ionizing radiation from the sky--later called cosmic radiation. This discovery earned him the Nobel Prize for Physics in 1936.
Dark energy from the string axiverse.
Kamionkowski, Marc; Pradler, Josef; Walker, Devin G E
2014-12-19
String theories suggest the existence of a plethora of axionlike fields with masses spread over a huge number of decades. Here, we show that these ideas lend themselves to a model of quintessence with no super-Planckian field excursions and in which all dimensionless numbers are order unity. The scenario addresses the "Why now?" problem-i.e., Why has accelerated expansion begun only recently?-by suggesting that the onset of dark-energy domination occurs randomly with a slowly decreasing probability per unit logarithmic interval in cosmic time. The standard axion potential requires us to postulate a rapid decay of most of the axion fields that do not become dark energy. The need for these decays is averted, though, with the introduction of a slightly modified axion potential. In either case, a universe like ours arises in roughly 1 in 100 universes. The scenario may have a host of observable consequences.
Svrcek, Peter; Witten, Edward; /Princeton, Inst. Advanced Study
2006-06-09
In the context of string theory, axions appear to provide the most plausible solution of the strong CP problem. However, as has been known for a long time, in many string-based models, the axion coupling parameter Fa is several orders of magnitude higher than the standard cosmological bounds. We re-examine this problem in a variety of models, showing that Fa is close to the GUT scale or above in many models that have GUT-like phenomenology, as well as some that do not. On the other hand, in some models with Standard Model gauge fields supported on vanishing cycles, it is possible for Fa to be well below the GUT scale.
Real topological string amplitudes
NASA Astrophysics Data System (ADS)
Narain, K. S.; Piazzalunga, N.; Tanzini, A.
2017-03-01
We discuss the physical superstring correlation functions in type I theory (or equivalently type II with orientifold) that compute real topological string amplitudes. We consider the correlator corresponding to holomorphic derivative of the real topological amplitude G_{χ } , at fixed worldsheet Euler characteristic χ. This corresponds in the low-energy effective action to N=2 Weyl multiplet, appropriately reduced to the orientifold invariant part, and raised to the power g' = -χ + 1. We show that the physical string correlator gives precisely the holomorphic derivative of topological amplitude. Finally, we apply this method to the standard closed oriented case as well, and prove a similar statement for the topological amplitude F_g.
Effective string theory revisited
NASA Astrophysics Data System (ADS)
Dubovsky, Sergei; Flauger, Raphael; Gorbenko, Victor
2012-09-01
We revisit the effective field theory of long relativistic strings such as confining flux tubes in QCD. We derive the Polchinski-Strominger interaction by a calculation in static gauge. This interaction implies that a non-critical string which initially oscillates in one direction gets excited in orthogonal directions as well. In static gauge no additional term in the effective action is needed to obtain this effect. It results from a one-loop calculation using the Nambu-Goto action. Non-linearly realized Lorentz symmetry is manifest at all stages in dimensional regularization. We also explain that independent of the number of dimensions non-covariant counterterms have to be added to the action in the commonly used zeta-function regularization.
Mezincescu, Luca; Townsend, Paul K.
2010-11-05
The Nambu-Goto string in a three-dimensional (3D) Minkowski spacetime is quantized preserving Lorentz invariance and parity. The spectrum of massive states contains anyons. An ambiguity in the ground state energy is resolved by the 3D N=1 Green-Schwarz superstring, which has massless ground states describing a dilaton and dilatino, and first-excited states of spin 1/4.
ERIC Educational Resources Information Center
Fitzgerald, Mike; Brand, Lance
2004-01-01
In this article, the authors present an activity that shows students how flight occurs. The "wing on a string" is a simple teacher-made frame that consists of PVC pipe, fishing line, and rubber bands--all readily available hardware store items. The only other materials/tools involved are a sheet of paper, some pieces of a soda straw, a stapler,…
Thermodynamical string fragmentation
NASA Astrophysics Data System (ADS)
Fischer, Nadine; Sjöstrand, Torbjörn
2017-01-01
The observation of heavy-ion-like behaviour in pp collisions at the LHC suggests that more physics mechanisms are at play than traditionally assumed. The introduction e.g. of quark-gluon plasma or colour rope formation can describe several of the observations, but as of yet there is no established paradigm. In this article we study a few possible modifications to the Pythia event generator, which describes a wealth of data but fails for a number of recent observations. Firstly, we present a new model for generating the transverse momentum of hadrons during the string fragmentation process, inspired by thermodynamics, where heavier hadrons naturally are suppressed in rate but obtain a higher average transverse momentum. Secondly, close-packing of strings is taken into account by making the temperature or string tension environment-dependent. Thirdly, a simple model for hadron rescattering is added. The effect of these modifications is studied, individually and taken together, and compared with data mainly from the LHC. While some improvements can be noted, it turns out to be nontrivial to obtain effects as big as required, and further work is called for.
Coulomb string tension, asymptotic string tension, and the gluon chain
Greensite, Jeff; Szczepaniak, Adam P.
2015-02-01
We compute, via numerical simulations, the non-perturbative Coulomb potential and position-space ghost propagator in pure SU(3) gauge theory in Coulomb gauge. We find that that the Coulomb potential scales nicely in accordance with asymptotic freedom, that the Coulomb potential is linear in the infrared, and that the Coulomb string tension is about four times larger than the asymptotic string tension. We explain how it is possible that the asymptotic string tension can be lower than the Coulomb string tension by a factor of four.
Stationary rotating strings as relativistic particle mechanics
Ogawa, Kouji; Ishihara, Hideki; Saito, Shinya; Kozaki, Hiroshi; Nakano, Hiroyuki
2008-07-15
Stationary rotating strings can be viewed as geodesic motions in appropriate metrics in two-dimensional space. We obtain all solutions describing stationary rotating strings in flat spacetime as an application. These rotating strings have infinite length with various wiggly shapes. Averaged value of the string energy, the angular momentum, and the linear momentum along the string are discussed.
Brane-world cosmology with black strings
NASA Astrophysics Data System (ADS)
Gergely, László Á.
2006-07-01
We consider the simplest scenario when black strings/cigars penetrate the cosmological brane. As a result, the brane has a Swiss-cheese structure, with Schwarzschild black holes immersed in a Friedmann-Lemaître-Robertson-Walker brane. There is no dark radiation in the model, the cosmological regions of the brane are characterized by a cosmological constant Λ and flat spatial sections. Regardless of the value of Λ, these brane-world universes forever expand and forever decelerate. The totality of source terms in the modified Einstein equation sum up to a dust, establishing a formal equivalence with the general relativistic Einstein-Straus model. However in this brane-world scenario with black strings the evolution of the cosmological fluid strongly depends on Λ. For Λ≤0 it has positive energy density ρ and negative pressure p and at late times it behaves as in the Einstein-Straus model. For (not too high) positive values of Λ the cosmological evolution begins with positive ρ and negative p, but this is followed by an epoch with both ρ and p positive. Eventually, ρ becomes negative, while p stays positive. A similar evolution is present for high positive values of Λ, however in this case the evolution ends in a pressure singularity, accompanied by a regular behavior of the cosmic acceleration. This is a novel type of singularity appearing in brane-worlds.
Factorization of chiral string amplitudes
NASA Astrophysics Data System (ADS)
Huang, Yu-tin; Siegel, Warren; Yuan, Ellis Ye
2016-09-01
We re-examine a closed-string model defined by altering the boundary conditions for one handedness of two-dimensional propagators in otherwise-standard string theory. We evaluate the amplitudes using Kawai-Lewellen-Tye factorization into open-string amplitudes. The only modification to standard string theory is effectively that the spacetime Minkowski metric changes overall sign in one open-string factor. This cancels all but a finite number of states: as found in earlier approaches, with enough supersymmetry (e.g., type II) the tree amplitudes reproduce those of the massless truncation of ordinary string theory. However, we now find for the other cases that additional fields, formerly thought to be auxiliary, describe new spin-2 states at the two adjacent mass levels (tachyonic and tardyonic). The tachyon is always a ghost, but can be avoided in the heterotic case.
Classical theory of radiating strings
NASA Technical Reports Server (NTRS)
Copeland, Edmund J.; Haws, D.; Hindmarsh, M.
1990-01-01
The divergent part of the self force of a radiating string coupled to gravity, an antisymmetric tensor and a dilaton in four dimensions are calculated to first order in classical perturbation theory. While this divergence can be absorbed into a renormalization of the string tension, demanding that both it and the divergence in the energy momentum tensor vanish forces the string to have the couplings of compactified N = 1 D = 10 supergravity. In effect, supersymmetry cures the classical infinities.
Renormalization constants from string theory.
NASA Astrophysics Data System (ADS)
di Vecchia, P.; Magnea, L.; Lerda, A.; Russo, R.; Marotta, R.
The authors review some recent results on the calculation of renormalization constants in Yang-Mills theory using open bosonic strings. The technology of string amplitudes, supplemented with an appropriate continuation off the mass shell, can be used to compute the ultraviolet divergences of dimensionally regularized gauge theories. The results show that the infinite tension limit of string amplitudes corresponds to the background field method in field theory.
Experimenting with string musical instruments
NASA Astrophysics Data System (ADS)
LoPresto, Michael C.
2012-03-01
What follows are several investigations involving string musical instruments developed for and used in a Science of Sound & Light course. The experiments make use of a guitar, orchestral string instruments and data collection and graphing software. They are designed to provide students with concrete examples of how mathematical formulae, when used in physics, represent reality that can actually be observed, in this case, the operation of string musical instruments.
NASA Technical Reports Server (NTRS)
Rees, M. J.
1986-01-01
The evidence that active galactic nuclei produce collimated plasma jets is summarised. The strongest radio galaxies are probably energised by relativistic plasma jets generated by spinning black holes interacting with magnetic fields attached to infalling matter. Such objects can produce e(+)-e(-) plasma, and may be relevant to the acceleration of the highest-energy cosmic ray primaries. Small-scale counterparts of the jet phenomenon within our own galaxy are briefly reviewed.
Complex geometry and string theory
NASA Astrophysics Data System (ADS)
Morozov, A. Y.; Perelomov, A. M.
1990-06-01
The analytic properties of string theory are reviewed. It is demonstrated that the theory of strings is connected with contemporary fields of complex geometry. A massless classical point-like particle which moves in Minkowski space of D dimensions is considered. The formulation used to develop string theory is based on the Polyakov approach. In order to find the quantum scattering amplitude in the Polyakov approach, the functional integral over all Riemannian surfaces is calculated. The simplest case of the amplitude of vacuum-vacuum transitions Z of a closed string is considered. The description of linear bundles in the divisor terms is given.
Advances in String Theory in Curved Backgrounds
NASA Astrophysics Data System (ADS)
Sanchez, N. G.
A synthetic report of the advances in the study of classical and quantum string dynamics in curved backgrounds is provided, namely : the new feature of Multistring solutions; the mass spectrum of Strings in Curved backgrounds; The effect of a Cosmological Constant and of Spacial Curvature on Classical and Quantum Strings; Classical splitting of Fundamental Strings; The General String Evolution in constant Curvature Spacetimes; The Conformal Invariance Effects; Strings on plane fronted and gravitational shock waves, string falling on spacetime singularities and its spectrum. New Developments in String Gravity and String Cosmology are reported: String driven cosmology and its Predictions; The primordial gravitational wave background; Non-singular string cosmologies from Exact Conformal Field Theories; Quantum Field Theory, String Temperature and the String Phase of de Sitter space-time Hawking Radiation in String Theory and the String Phase of Black Holes; New Dual Relation between Quantum Field Theory regime and String regime and the "QFT/String Tango" New Coherent String States and Minimal Uncertainty Principle in string theory.
Non-Riemannian Cosmic Walls as Boundaries of Spinning Matter with Torsion
NASA Astrophysics Data System (ADS)
Garcia de Andrade, L. C.
An example of a plane topological defect solution of linearized Einstein-Cartan (EC) field equation representing a cosmic wall boundary of spinning matter is given. The source of Cartan torsion is composed of two orthogonal lines of static polarized spins bounded by the cosmic plane wall. The Kopczyński-Obukhov-Tresguerres (KOT) spin fluid stress-energy current coincides with thin planar matter current in the static case. Our solution is similar to the Letelier solution of Einstein equation for multiple cosmic strings. Due to this fact we suggest that the lines of spinning matter could be analogous to multiple cosmic spinning string solution in EC theory of gravity. When torsion is turned off, a pure Riemannian cosmic wall is obtained.
Cosmic impacts, cosmic catastrophes. II
NASA Technical Reports Server (NTRS)
Chapman, Clark R.; Morrison, David
1990-01-01
The role of extraterrestrial impacts in shaping the earth's history is discussed, arguing that cosmic impacts represent just one example of a general shift in thinking that has made the idea of catastrophes respectable in science. The origins of this view are presented and current catastrophic theory is discussed in the context of modern debate on the geological formation of the earth. Various conflicting theories are reviewed and prominent participants in the ongoing scientific controversy concerning catastrophism are introduced.
Dark Matter in Supersymmetric U(1){sub B-L} Model
Khalil, S.; Okada, H.
2009-04-17
We analyze the dark matter problem in the context of supersymmetric, U(1){sub B-L} model. In this model, the lightest neutalino can be B-L gaugino Z-tilde{sub B-L} or Higgsinos {chi}-tilde{sub 1,2} dominated. We examine the thermal relic abundance of these particles and discuss the prospects for their direct detection if they form part of our galactic halo.
Axially symmetric anisotropic string cosmological models in Saez-Ballester theory of gravitation
NASA Astrophysics Data System (ADS)
Kanakavalli, T.; Rao, G. Ananda; Reddy, D. R. K.
2017-02-01
Field equations of a scalar-tensor theory of gravitation proposed by Saez and Ballester (Phys. Lett. A 113:467, 1986) are derived with the help of a spatially homogeneous axially symmetric anisotropic Bianchi type metric in the presence of cosmic string source. To obtain determinate solutions of the field equations we have used the fact that the scalar expansion is proportional to shear scalar and the equations of state which correspond to geometric, Takabayasi and massive strings. It is found that geometric and massive strings do not coexist with the Saez-Ballester Scalar field. However, Takabayasi string which survives has been determined. Also, physical discussion of the dynamical parameters of the model is presented.
Kachru, Shamit; McAllister, Liam; Sundrum, Raman
2007-04-04
We study sequestering, a prerequisite for flavor-blind supersymmetry breaking in several high-scale mediation mechanisms, in compactifications of type IIB string theory. We find that although sequestering is typically absent in unwarped backgrounds, strongly warped compactifications do readily sequester. The AdS/CFT dual description in terms of conformal sequestering plays an important role in our analysis, and we establish how sequestering works both on the gravity side and on the gauge theory side. We pay special attention to subtle compactification effects that can disrupt sequestering. Our result is a step toward realizing an appealing pattern of soft terms in a KKLT compactification.
NASA Astrophysics Data System (ADS)
Güijosa, Alberto
2016-10-01
In the nearly 20 years that have elapsed since its discovery, the gauge-gravity correspondence has become established as an efficient tool to explore the physics of a large class of strongly-coupled field theories. A brief overview is given here of its formulation and a few of its applications, emphasizing attempts to emulate aspects of the strong-coupling regime of quantum chromodynamics (QCD). To the extent possible, the presentation is self-contained, and does not presuppose knowledge of string theory.
NASA Astrophysics Data System (ADS)
Hashimoto, Koji; Morita, Takeshi
2011-08-01
In generic holographic QCD, we find that baryons are bound to form a nucleus, and that its radius obeys the empirically-known mass-number (A) dependence r∝A1/3 for large A. Our result is robust, since we use only a generic property of D-brane actions in string theory. We also show that nucleons are bound completely in a finite volume. Furthermore, employing a concrete holographic model (derived by Hashimoto, Iizuka, and Yi, describing a multibaryon system in the Sakai-Sugimoto model), the nuclear radius is evaluated as O(1)×A1/3[fm], which is consistent with experiments.
Dynamical behavior and Jacobi stability analysis of wound strings
NASA Astrophysics Data System (ADS)
Lake, Matthew J.; Harko, Tiberiu
2016-06-01
We numerically solve the equations of motion (EOM) for two models of circular cosmic string loops with windings in a simply connected internal space. Since the windings cannot be topologically stabilized, stability must be achieved (if at all) dynamically. As toy models for realistic compactifications, we consider windings on a small section of mathbb {R}^2, which is valid as an approximation to any simply connected internal manifold if the winding radius is sufficiently small, and windings on an S^2 of constant radius mathcal {R}. We then use Kosambi-Cartan-Chern (KCC) theory to analyze the Jacobi stability of the string equations and determine bounds on the physical parameters that ensure dynamical stability of the windings. We find that, for the same initial conditions, the curvature and topology of the internal space have nontrivial effects on the microscopic behavior of the string in the higher dimensions, but that the macroscopic behavior is remarkably insensitive to the details of the motion in the compact space. This suggests that higher-dimensional signatures may be extremely difficult to detect in the effective (3+1)-dimensional dynamics of strings compactified on an internal space, even if configurations with nontrivial windings persist over long time periods.
Open string fields as matrices
NASA Astrophysics Data System (ADS)
Kishimoto, Isao; Masuda, Toru; Takahashi, Tomohiko; Takemoto, Shoko
2015-03-01
We show that the action expanded around Erler-Maccaferri's N D-brane solution describes the N+1 D-brane system where one D-brane disappears due to tachyon condensation. String fields on multi-branes can be regarded as block matrices of a string field on a single D-brane in the same way as matrix theories.
NASA Technical Reports Server (NTRS)
Frasch, W.; Ciavola, S.
1982-01-01
String-conveyor portion of solar-array assembly line holds silicon solar cells while assembled into strings and tested. Cells are transported collector-side-down, while uniform cell spacing and registration are maintained. Microprocessor on machine controls indexing of cells.
French String Grammar. Final Report.
ERIC Educational Resources Information Center
New York Univ., NY. Linguistic String Project.
This work reports on an initial study of the possibility of providing a suitable framework for the teaching of a foreign language grammar through string analysis, using French as the target language. Analysis of a string word list (word-class sequences) yields an overall view of the grammar. Details are furnished in a set of restrictions which…
ERIC Educational Resources Information Center
Schaffer, Karl
2012-01-01
The use of traditional string figures by the Dr. Schaffer and Mr. Stern Dance Ensemble led to experimentation with polyhedral string constructions. This article presents a series of polyhedra made with six loops of three colors which sequence through all the Platonic Solids.
ERIC Educational Resources Information Center
Ng, Chiu-king
2010-01-01
When one end of a taut horizontal elastic string is shaken repeatedly up and down, a transverse wave (assume sine waveform) will be produced and travel along it. College students know this type of wave motion well. They know when the wave passes by, each element of the string will perform an oscillating up-down motion, which in mechanics is termed…
Experimenting with String Musical Instruments
ERIC Educational Resources Information Center
LoPresto, Michael C.
2012-01-01
What follows are several investigations involving string musical instruments developed for and used in a "Science of Sound & Light" course. The experiments make use of a guitar, orchestral string instruments and data collection and graphing software. They are designed to provide students with concrete examples of how mathematical formulae, when…
String Mining in Bioinformatics
NASA Astrophysics Data System (ADS)
Abouelhoda, Mohamed; Ghanem, Moustafa
Sequence analysis is a major area in bioinformatics encompassing the methods and techniques for studying the biological sequences, DNA, RNA, and proteins, on the linear structure level. The focus of this area is generally on the identification of intra- and inter-molecular similarities. Identifying intra-molecular similarities boils down to detecting repeated segments within a given sequence, while identifying inter-molecular similarities amounts to spotting common segments among two or multiple sequences. From a data mining point of view, sequence analysis is nothing but string- or pattern mining specific to biological strings. For a long time, this point of view, however, has not been explicitly embraced neither in the data mining nor in the sequence analysis text books, which may be attributed to the co-evolution of the two apparently independent fields. In other words, although the word "data-mining" is almost missing in the sequence analysis literature, its basic concepts have been implicitly applied. Interestingly, recent research in biological sequence analysis introduced efficient solutions to many problems in data mining, such as querying and analyzing time series [49,53], extracting information from web pages [20], fighting spam mails [50], detecting plagiarism [22], and spotting duplications in software systems [14].
String Mining in Bioinformatics
NASA Astrophysics Data System (ADS)
Abouelhoda, Mohamed; Ghanem, Moustafa
Sequence analysis is a major area in bioinformatics encompassing the methods and techniques for studying the biological sequences, DNA, RNA, and proteins, on the linear structure level. The focus of this area is generally on the identification of intra- and inter-molecular similarities. Identifying intra-molecular similarities boils down to detecting repeated segments within a given sequence, while identifying inter-molecular similarities amounts to spotting common segments among two or multiple sequences. From a data mining point of view, sequence analysis is nothing but string- or pattern mining specific to biological strings. For a long time, this point of view, however, has not been explicitly embraced neither in the data mining nor in the sequence analysis text books, which may be attributed to the co-evolution of the two apparently independent fields. In other words, although the word “data-mining” is almost missing in the sequence analysis literature, its basic concepts have been implicitly applied. Interestingly, recent research in biological sequence analysis introduced efficient solutions to many problems in data mining, such as querying and analyzing time series [49,53], extracting information from web pages [20], fighting spam mails [50], detecting plagiarism [22], and spotting duplications in software systems [14].
NASA Astrophysics Data System (ADS)
't Hooft, Gerardus
QCD was proposed as a theory for the strong interactions long before we had any idea as to how it could be that its fundamental constituents, the quarks, are never seen as physical particles. Massless gluons also do not exist as free particles. How can this be explained? The first indication that this question had to be considered in connection with the topological structure of a gauge theory came when Nielsen and Olesen observed the occurrence of stable magnetic vortex structures [1] in the Abelian Higgs model. Expanding on such ideas, the magnetic monopole solution was found [2]. Other roundabout attempts to understand confinement involve instantons. Today, we have better interpretations of these topological structures, including a general picture of the way they do lead to unbound potentials confining quarks. It is clear that these unbound potentials can be ascribed to a string-like structure of the vortices formed by the QCD field lines. Can string theory be used to analyze QCD? Many researchers think so. The leading expert on this is Sacha Polyakov. In his instructive account he adds how he experienced the course of events in Gauge Theory, emphasizing the fact that quite a few discoveries often ascribed to researchers from the West, actually were made independently by scientists from the Soviet Union…
NASA Astrophysics Data System (ADS)
de Boer, Jan; de Medeiros, Paul; El-Showk, Sheer; Sinkovics, Annamaria
2008-02-01
We consider an open string version of the topological twist previously proposed for sigma-models with G2 target spaces. We determine the cohomology of open strings states and relate these to geometric deformations of calibrated submanifolds and to flat or anti-self-dual connections on such submanifolds. On associative three-cycles we show that the worldvolume theory is a gauge-fixed Chern-Simons theory coupled to normal deformations of the cycle. For coassociative four-cycles we find a functional that extremizes on anti-self-dual gauge fields. A brane wrapping the whole G2 induces a seven-dimensional associative Chern-Simons theory on the manifold. This theory has already been proposed by Donaldson and Thomas as the higher-dimensional generalization of real Chern-Simons theory. When the G2 manifold has the structure of a Calabi-Yau times a circle, these theories reduce to a combination of the open A-model on special Lagrangians and the open B + B-bar-model on holomorphic submanifolds. We also comment on possible applications of our results.
Surface operators from M -strings
NASA Astrophysics Data System (ADS)
Mori, Hironori; Sugimoto, Yuji
2017-01-01
It has been found that surface operators have a significant role in Alday-Gaiotto-Tachikawa (AGT) relation. This duality is an outstanding consequence of M -theory, but it is actually encoded into the brane web for which the topological string can work. From this viewpoint, the surface defect in AGT relation is geometrically engineered as a toric brane realization. Also, there is a class of the brane configuration in M -theory called M -strings which can be translated into the language of the topological string. In this work, we propose a new M -string configuration which can realize AGT relation in the presence of the surface defect by utilizing the geometric transition in the refined topological string.
String fields and their interactions
NASA Astrophysics Data System (ADS)
Erler, Theodore George, IV
2005-07-01
In this thesis is devoted to illuminating the underlying structure of Witten's star product, which defines the interactions of open strings in cubic bosonic string field theory [3]. We give an in depth analysis of the product from the perspective of noncommutative geometry, specifically using the split string [19] and Moyal formalisms [20, 22]. We identify some fundamental algebraic features of the star product originating from the singular structure of the overlap conditions at the string midpoint. Finally, we use some of these insights to construct a consistent and nonsingular initial value formulation of the theory in lightcone time. Such a general formalism seems prerequisite to address questions of time, causality, and cosmology in string theory.
Summing Planar Bosonic Open Strings
Bardakci, Korkut
2006-02-16
In earlier work, planar graphs of massless {phi}{sup 3} theory were summed with the help of the light cone world sheet picture and the mean field approximation. In the present article, the same methods are applied to the problem of summing planar bosonic open strings. They find that in the ground state of the system, string boundaries form a condensate on the world sheet, and a new string emerges from this summation. Its slope is always greater than the initial slope, and it remains non-zero even when the initial slope is set equal to zero. If they assume the initial string tends to a field a theory in the zero slope limit, this result provides evidence for string formation in field theory.
Subcritical string and large N QCD
Thorn, Charles B.
2008-10-15
We pursue the possibility of using subcritical string theory in 4 spacetime dimensions to establish a string dual for large N QCD. In particular we study the even G-parity sector of the 4 dimensional Neveu-Schwarz dual resonance model as the natural candidate for this string theory. Our point of view is that the open string dynamics given by this model will determine the appropriate subcritical closed string theory, a tree level background of which should describe the sum of planar multiloop open string diagrams. We examine the one-loop open string diagram, which contains information about the closed string spectrum at weak coupling. Higher loop open string diagrams will be needed to determine closed string interactions. We also analyze the field theory limit of the one-loop open string diagram and recover the correct running coupling behavior of the limiting gauge theory.
Effective String Theory and Integrability
NASA Astrophysics Data System (ADS)
Mohsen, Ali
In this dissertation several applications are collected were one deduces properties of UV complete string theories by examining low energy interactions on the world sheet of effective strings. As a first application, a UV complete asymptotically fragile theory is presented, which provides a very special theory in regards to the standard connection between causality and analyticity, and positivity conditions. Continuing with this approach, and exploiting the interplay between hidden symmetries and integrability, a no go theorem for the bosonic string is proved and the connection between double softness of branon amplitudes and integrability is elucidated. This theorem suggests considering supersymmetric strings and more generally Lorentz invariant fermionic strings. Analyzing the integrability of the former at tree level singles out critical dimensions where kappa-symmetry can exist, and unveils a hidden supersymmetry for GS-like actions. Whereas the analysis of the latter necessitates the use of the CCWZ machinery and results in the complete classification of Lorentz invariant fermionic strings, including among unexplored possibilities the GS, RNS and Heterotic superstrings in D=10. Finally, Zamolodchikov's method of integrable deformations of fixed point CFTs is applied for the bosonic string, which provides higher spin currents perturbatively and singles out the critical dimension in yet another paradigm.
String bit models for superstring
Bergman, O.; Thorn, C.B.
1995-12-31
The authors extend the model of string as a polymer of string bits to the case of superstring. They mainly concentrate on type II-B superstring, with some discussion of the obstacles presented by not II-B superstring, together with possible strategies for surmounting them. As with previous work on bosonic string work within the light-cone gauge. The bit model possesses a good deal less symmetry than the continuous string theory. For one thing, the bit model is formulated as a Galilei invariant theory in (D {minus} 2) + 1 dimensional space-time. This means that Poincare invariance is reduced to the Galilei subgroup in D {minus} 2 space dimensions. Naturally the supersymmetry present in the bit model is likewise dramatically reduced. Continuous string can arise in the bit models with the formation of infinitely long polymers of string bits. Under the right circumstances (at the critical dimension) these polymers can behave as string moving in D dimensional space-time enjoying the full N = 2 Poincare supersymmetric dynamics of type II-B superstring.
String bit models for superstring
Bergman, O.; Thorn, C.B.
1995-11-15
We extend the model of string as a polymer of string bits to the case of superstring. We mainly concentrate on type II-B superstring, with some discussion of the obstacles presented by not II-B superstring, together with possible strategies for surmounting them. As with previous work on bosonic string we work within the light-cone gauge. The bit model possesses a good deal less symmetry than the continuous string theory. For one thing, the bit model is formulated as a Galilei-invariant theory in [({ital D}{minus}2)+1]-dimensional space-time. This means that Poincare invariance is reduced to the Galilei subgroup in {ital D}{minus}2 space dimensions. Naturally the supersymmetry present in the bit model is likewise dramatically reduced. Continuous string can arise in the bit models with the formation of infinitely long polymers of string bits. Under the right circumstances (at the critical dimension) these polymers can behave as string moving in {ital D}-dimensional space-time enjoying the full {ital N}=2 Poincare supersymmetric dynamics of type II-B superstring.
NASA Technical Reports Server (NTRS)
Enison, R. L.
1971-01-01
A computer program called Character String Scanner (CSS), is presented. It is designed to search a data set for any specified group of characters and then to flag this group. The output of the CSS program is a listing of the data set being searched with the specified group of characters being flagged by asterisks. Therefore, one may readily identify specific keywords, groups of keywords or specified lines of code internal to a computer program, in a program output, or in any other specific data set. Possible applications of this program include the automatic scan of an output data set for pertinent keyword data, the editing of a program to change the appearance of a certain word or group of words, and the conversion of a set of code to a different set of code.
Bergshoeff, E.A. ); Kallosh, R.; Ortin, T. )
1993-06-15
We present plane-wave-type solutions of the lowest-order superstring effective action which have unbroken space-time supersymmetries. They are given by a stringy generalization of the Brinkmann metric, dialton, axion, and gauge fields. Some conspiracy between the metric and the axion field is required. The [alpha][prime] stringy corrections to the effective on-shell action, to the equations of motion (and therefore to the solutions themselves), and to the supersymmetry transformations are shown to vanish for a special class of these solutions that we call supersymmetric string waves (SSW's). In the SSW solutions, there exists a conspiracy not only between the metric and the axion field, but also between the gauge fields and the metric, since the embedding of the spin connection in the gauge group is required.
String Formatting Considered Harmful for Novice Programmers
ERIC Educational Resources Information Center
Hughes, Michael C.; Jadud, Matthew C.; Rodrigo, Ma. Mercedes T.
2010-01-01
In Java, "System.out.printf" and "String.format" consume a specialised kind of string commonly known as a format string. In our study of first-year students at the Ateneo de Manila University, we discovered that format strings present a substantial challenge for novice programmers. Focusing on their first laboratory we found…
NASA Technical Reports Server (NTRS)
Alfven, H.
1981-01-01
Attention is given to experimental and theoretical approaches to plasma physics, plasma phenomena in laboratory and space, field and particle aspects of plasmas, the present state of the classical theory, boundary conditions and circuit dependence, and cosmology. Electric currents in space plasmas are considered, taking into account dualism in physics, particle-related phenomena in plasma physics, magnetic field lines, filaments, local plasma properties and the circuit, electric double layers, field-aligned currents as 'cables', an expanding circuit, different types of plasma regions, the cellular structure of space, and the fine structure of active plasma regions. Other topics discussed are related to circuits, the theory of cosmic plasmas, the origin of the solar system, the coexistence of matter and antimatter, annihilation as a source of energy, the Hubble expansion in a Euclidean space, and a model for the evolution of the Metagalaxy.
Geometry, topology, and string theory
Varadarajan, Uday
2003-01-01
A variety of scenarios are considered which shed light upon the uses and limitations of classical geometric and topological notions in string theory. The primary focus is on situations in which D-brane or string probes of a given classical space-time see the geometry quite differently than one might naively expect. In particular, situations in which extra dimensions, non-commutative geometries as well as other non-local structures emerge are explored in detail. Further, a preliminary exploration of such issues in Lorentzian space-times with non-trivial causal structures within string theory is initiated.
Worldsheet geometries of ambitwistor string
NASA Astrophysics Data System (ADS)
Ohmori, Kantaro
2015-06-01
Mason and Skinner proposed the ambitwistor string theory which directly reproduces the formulas for the amplitudes of massless particles proposed by Cachazo, He and Yuan. In this paper we discuss geometries of the moduli space of worldsheets associated to the bosonic or the RNS ambitwistor string. Further, we investigate the factorization properties of the amplitudes when an internal momentum is near on-shell in the abstract CFT language. Along the way, we propose the existence of the ambitwistor strings with three or four fermionic worldsheet currents.
Semisuperfluid strings in high density QCD
Balachandran, A.P.; Digal, S.; Matsuura, T.
2006-04-01
We show that topological semisuperfluid strings exist in the color-flavor locked (CFL) phase of color superconductors. These semisuperfluid strings carry quantized flux of ordinary and color magnetic fields. Away from the core the behavior of the string is that of a superfluid string. Using a Ginzburg-Landau free energy we find the configurations of these strings. These strings can form during the transition from the normal phase to the CFL phase at the core of very dense stars. We discuss an interesting scenario for a network of strings and its evolution at the core of dense stars.
Charting the landscape of supercritical string theory.
Hellerman, Simeon; Swanson, Ian
2007-10-26
Special solutions of string theory in supercritical dimensions can interpolate in time between theories with different numbers of spacetime dimensions and different amounts of world sheet supersymmetry. These solutions connect supercritical string theories to the more familiar string duality web in ten dimensions and provide a precise link between supersymmetric and purely bosonic string theories. Dimension quenching and c duality appear to be natural concepts in string theory, giving rise to large networks of interconnected theories.
Classification of cohomogeneity-one strings
Ishihara, Hideki; Kozaki, Hiroshi
2005-09-15
We define the cohomogeneity one string, string with continuous symmetries, as its world surface is tangent to a Killing vector field of a target space. We classify the Killing vector fields by an equivalence relation using isometries of the target space. We find that the equivalence classes of Killing vectors in Minkowski spacetime are partitioned into seven families. It is clarified that there exist seven types of strings with spacelike symmetries and four types of strings with timelike symmetries, stationary strings.
String and Sticky Tape Experiments.
ERIC Educational Resources Information Center
Edge, R. D., Ed.
1979-01-01
Explains how to demonstrate the fundamentals of one dimensional kinematics such as Newton's third law of motion, and collision between bodies, using simple materials of marbles, strings, sticky tape, drinking straws, and rubber bands. (GA)
Spin chains and string theory.
Kruczenski, Martin
2004-10-15
Recently, an important test of the anti de Sitter/conformal field theory correspondence has been done using rotating strings with two angular momenta. We show that such a test can be described more generally as the agreement between two actions: one a low energy description of a spin chain appearing in the field theory side, and the other a limit of the string action in AdS5xS5. This gives a map between the mean value of the spin in the boundary theory and the position of the string in the bulk, and shows how a string action can emerge from a gauge theory in the large-N limit.
Nuclear Force from String Theory
NASA Astrophysics Data System (ADS)
Hashimoto, Koji
2010-04-01
Recent "technology" called holography, or gauge/string duality (AdS/CFT correspondence) found in string theory, makes it possible to compute various quantities of strongly coupled gauge theories. This technology was applied to QCD, and it was found that it describes surprisingly well important properties of low energy QCD, the hadron physics. We apply it further to nuclear physics. In this talk, I review a part of the developments of the holographic QCD, and show a computation of nuclear force at short distance, derived using the holographic QCD, which was done in collaboration with T. Sakai and S. Sugimoto [K. Hashimoto, T. Sakai, and S. Sugimoto, "Holographic Baryons: Static Properties and Form Factors from Gauge/String Duality," Prog. Theor. Phys. 120 (2008) 1093-1137, arXiv:0806.3122 [hep-th]; K. Hashimoto, T. Sakai, and S. Sugimoto, "Nuclear Force from String Theory," arXiv:0901.4449 [hep-th
Aspects of topological string theory
NASA Astrophysics Data System (ADS)
Cook, Paul L. H.
Two aspects of the topological string and its applications are considered in this thesis. Firstly, non-perturbative contributions to the OSV conjecture relating four-dimensional extremal black holes and the closed topological string partition function are studied. A new technique is formulated for encapsulating these contributions for the case of a Calabi-Yau manifold constructed by fibering two line bundle over a torus, with the unexpected property that the resulting non-perturbative completion of the topological string partition function is such that the black hole partition function is equal to a product of a chiral and an anti-chiral function. This new approach is considered both in the context of the requirement of background independence for the topological string, and for more general Calabi-Yau manifolds. Secondly, this thesis provides a microscopic derivation of the open topological string holomorphic anomaly equations proposed by Walcher in arXiv:0705.4098 under the assumption that open string moduli do not contribute. In doing so, however, new anomalies are found for compact Calabi-Yau manifolds when the disk one-point functions (string to boundary amplitudes) are non-zero. These new anomalies introduce coupling to wrong moduli (complex structure moduli in A-model and Kahler moduli in B-model), and spoil the recursive structure of the holomorphic anomaly equations. For vanishing disk one-point functions, the open string holomorphic anomaly equations can be integrated to solve for amplitudes recursively, using a Feynman diagram approach, for which a proof is presented.
TeV-scale gauged B-L symmetry with inverse seesaw mechanism
Khalil, Shaaban
2010-10-01
We propose a modified version of the TeV-scale B-L extension of the standard model, where neutrino masses are generated through the inverse seesaw mechanism. We show that heavy neutrinos in this model can be accessible via clean signals at the LHC. The search for the extra gauge boson Z{sub B-L}{sup '} through the decay into dileptons or two dileptons plus missing energy is studied. We also show that the B-L extra Higgs boson can be directly probed at the LHC via a clean dilepton and missing energy signal.
Evolution of segmented strings
NASA Astrophysics Data System (ADS)
Gubser, Steven S.
2016-11-01
I explain how to evolve segmented strings in de Sitter and anti-de Sitter spaces of any dimension in terms of forward-directed null displacements. The evolution is described entirely in terms of discrete hops which do not require a continuum spacetime. Moreover, the evolution rule is purely algebraic, so it can be defined not only on ordinary real de Sitter and anti-de Sitter but also on the rational points of the quadratic equations that define these spaces. For three-dimensional anti-de Sitter space, a simpler evolution rule is possible that descends from the Wess-Zumino-Witten equations of motion. In this case, one may replace three-dimensional anti-de Sitter space by a noncompact discrete subgroup of S L (2 ,R ) whose structure is related to the Pell equation. A discrete version of the Bañados-Teitelboim-Zanelli (BTZ) black hole can be constructed as a quotient of this subgroup. This discrete black hole avoids the firewall paradox by a curious mechanism: even for large black holes, there are no points inside the horizon until one reaches the singularity.
Dirac or Inverse Seesaw Neutrino Masses from Gauged B - L Symmetry
NASA Astrophysics Data System (ADS)
Ma, Ernest; Srivastava, Rahul
The gauged B - L symmetry is one of the simplest and well studied extension of standard model. In the conventional case, addition of three singlet right-handed neutrinos each transforming as -1 under the B - L symmetry renders it anomaly free. It is usually assumed that the B - L symmetry is spontaneously broken by a singlet scalar having two units of B - L charge, resulting in a natural implementation of Majorana seesaw mechanism for neutrinos. However, as we discuss in this proceeding, there is another simple anomaly free solution which leads to Dirac or inverse seesaw masses for neutrinos. These new possibilities are explored along with an application to neutrino mixing with S3 flavour symmetry.
Right-handed neutrino dark matter under the B - L gauge interaction
NASA Astrophysics Data System (ADS)
Kaneta, Kunio; Kang, Zhaofeng; Lee, Hye-Sung
2017-02-01
We study the right-handed neutrino (RHN) dark matter candidate in the minimal U(1) B-L gauge extension of the standard model. The U(1) B-L gauge symmetry offers three RHNs which can address the origin of the neutrino mass, the relic dark matter, and the matter-antimatter asymmetry of the universe. The lightest among the three is taken as the dark matter candidate, which is under the B - L gauge interaction. We investigate various scenarios for this dark matter candidate with the correct relic density by means of the freeze-out or freeze-in mechanism. A viable RHN dark matter mass lies in a wide range including keV to TeV scale. We emphasize the sub-electroweak scale light B - L gauge boson case, and identify the parameter region motivated from the dark matter physics, which can be tested with the planned experiments including the CERN SHiP experiment.
Fundamental string solutions in open string field theories
Michishita, Yoji
2006-02-15
In Witten's open cubic bosonic string field theory and Berkovits' superstring field theory we investigate solutions of the equations of motion with appropriate source terms, which correspond to Callan-Maldacena solution in Born-Infeld theory representing fundamental strings ending on the D-branes. The solutions are given in order by order manner, and we show some full order properties in the sense of {alpha}{sup '} expansion. In superstring case we show that the solution is 1/2 BPS in full order.
Note on the stability of axionic D-term s-strings
Achucarro, Ana; Sousa, Kepa
2006-10-15
We investigate the stability of a new class of BPS cosmic strings in N=1 supergravity with D-terms recently proposed by Blanco-Pillado, Dvali and Redi. These have been conjectured to be the low energy manifestation of D-strings that might form from tachyon condensation after D- anti-D-brane annihilation in type IIB superstring theory. There are three one-parameter families of cylindrically symmetric one-vortex solutions to the BPS equations (tachyonic, axionic and hybrid). We find evidence that the zero mode in the axionic case, or s-strings, can be excited. Its evolution leads to the decompactification of four-dimensional spacetime at late times, with a rate that decreases with decreasing brane tension.
NASA Astrophysics Data System (ADS)
2008-01-01
An image based on data taken with ESO's Very Large Telescope reveals a triplet of galaxies intertwined in a cosmic dance. ESO PR Photo 02/08 ESO PR Photo 02/08 NGC 7173, 7174, and 7176 The three galaxies, catalogued as NGC 7173 (top), 7174 (bottom right) and 7176 (bottom left), are located 106 million light-years away towards the constellation of Piscis Austrinus (the 'Southern Fish'). NGC 7173 and 7176 are elliptical galaxies, while NGC 7174 is a spiral galaxy with quite disturbed dust lanes and a long, twisted tail. This seems to indicate that the two bottom galaxies - whose combined shape bears some resemblance to that of a sleeping baby - are currently interacting, with NGC 7176 providing fresh material to NGC 7174. Matter present in great quantity around the triplet's members also points to the fact that NGC 7176 and NGC 7173 have interacted in the past. Astronomers have suggested that the three galaxies will finally merge into a giant 'island universe', tens to hundreds of times as massive as our own Milky Way. ESO PR Photo 02/08 ESO PR Photo 02b/08 NGC 7173, 7174, and 7176 The triplet is part of a so-called 'Compact Group', as compiled by Canadian astronomer Paul Hickson in the early 1980s. The group, which is the 90th entry in the catalogue and is therefore known as HCG 90, actually contains four major members. One of them - NGC 7192 - lies above the trio, outside of this image, and is another peculiar spiral galaxy. Compact groups are small, relatively isolated, systems of typically four to ten galaxies in close proximity to one another. Another striking example is Robert's Quartet. Compact groups are excellent laboratories for the study of galaxy interactions and their effects, in particular the formation of stars. As the striking image reveals, there are many other galaxies in the field. Some are distant ones, while others seem to be part of the family. Studies made with other telescopes have indeed revealed that the HCG 90 group contains 16 members
Ambitwistor Strings in Four Dimensions
NASA Astrophysics Data System (ADS)
Geyer, Yvonne; Lipstein, Arthur E.; Mason, Lionel
2014-08-01
We develop ambitwistor string theories for four dimensions to obtain new formulas for tree-level gauge and gravity amplitudes with arbitrary amounts of supersymmetry. Ambitwistor space is the space of complex null geodesics in complexified Minkowski space, and in contrast to earlier ambitwistor strings, we use twistors rather than vectors to represent this space. Although superficially similar to the original twistor string theories of Witten, Berkovits, and Skinner, these theories differ in the assignment of world sheet spins of the fields, rely on both twistor and dual twistor representatives for the vertex operators, and use the ambitwistor procedure for calculating correlation functions. Our models are much more flexible, no longer requiring maximal supersymmetry, and the resulting formulas for amplitudes are simpler, having substantially reduced moduli. These are supported on the solutions to the scattering equations refined according to helicity and can be checked by comparison with corresponding formulas of Witten and of Cachazo and Skinner.
Cooperative strings and glassy interfaces.
Salez, Thomas; Salez, Justin; Dalnoki-Veress, Kari; Raphaël, Elie; Forrest, James A
2015-07-07
We introduce a minimal theory of glass formation based on the ideas of molecular crowding and resultant string-like cooperative rearrangement, and address the effects of free interfaces. In the bulk case, we obtain a scaling expression for the number of particles taking part in cooperative strings, and we recover the Adam-Gibbs description of glassy dynamics. Then, by including thermal dilatation, the Vogel-Fulcher-Tammann relation is derived. Moreover, the random and string-like characters of the cooperative rearrangement allow us to predict a temperature-dependent expression for the cooperative length ξ of bulk relaxation. Finally, we explore the influence of sample boundaries when the system size becomes comparable to ξ. The theory is in agreement with measurements of the glass-transition temperature of thin polymer films, and allows quantification of the temperature-dependent thickness hm of the interfacial mobile layer.
Electroweak vacuum stability in classically conformal B-L extension of the standard model
NASA Astrophysics Data System (ADS)
Das, Arindam; Okada, Nobuchika; Papapietro, Nathan
2017-02-01
We consider the minimal U(1)_{B-L} extension of the standard model (SM) with the classically conformal invariance, where an anomaly-free U(1)_{B-L} gauge symmetry is introduced along with three generations of right-handed neutrinos and a U(1)_{B-L} Higgs field. Because of the classically conformal symmetry, all dimensional parameters are forbidden. The B-L gauge symmetry is radiatively broken through the Coleman-Weinberg mechanism, generating the mass for the U(1)_{B-L} gauge boson (Z^' boson) and the right-handed neutrinos. Through a small negative coupling between the SM Higgs doublet and the B-L Higgs field, the negative mass term for the SM Higgs doublet is generated and the electroweak symmetry is broken. In this model context, we investigate the electroweak vacuum instability problem in the SM. It is well known that in the classically conformal U(1)_{B-L} extension of the SM, the electroweak vacuum remains unstable in the renormalization group analysis at the one-loop level. In this paper, we extend the analysis to the two-loop level, and perform parameter scans. We identify a parameter region which not only solve the vacuum instability problem, but also satisfy the recent ATLAS and CMS bounds from search for Z^' boson resonance at the LHC Run-2. Considering self-energy corrections to the SM Higgs doublet through the right-handed neutrinos and the Z^' boson, we derive the naturalness bound on the model parameters to realize the electroweak scale without fine-tunings.
Constraints on the Fundamental String Coupling from B-Mode Experiments
Avgoustidis, A.; Copeland, E. J.; Moss, A.; Pogosian, L.; Pourtsidou, A.; Steer, Daniele A.
2011-09-16
We study signatures of cosmic superstring networks containing strings of multiple tensions and Y junctions, on the cosmic microwave background (CMB) temperature and polarization spectra. Focusing on the crucial role of the string coupling constant g{sub s}, we show that the number density and energy density of the scaling network are dominated by different types of string in the g{sub s}{approx}1 and g{sub s}<<1 limits. This can lead to an observable shift in the position of the B-mode peak--a distinct signal leading to a direct constraint on g{sub s}. We forecast the joint bounds on g{sub s} and the fundamental string tension {mu}{sub F} from upcoming and future CMB polarization experiments, as well as the signal to noise in detecting the difference between B-mode signals in the limiting cases of large and small g{sub s}. We show that such a detectable shift is within reach of planned experiments.
Safety First When Stringing Holiday Lights
... fullstory_162645.html Safety First When Stringing Holiday Lights Putting lights on a metallic tree is an electrical hazard, ... TUESDAY, Dec. 20, 2016 (HealthDay News) -- Stringing up lights is a holiday tradition for many families, but ...
Energy and Momentum Transport in String Waves
ERIC Educational Resources Information Center
Juenker, D. W.
1976-01-01
Formulas are derived for the energy, momentum, and angular momentum transmitted by waves of arbitrary shape in an inextensible string by pure transverse waves in a string using Tait's procedure. (Author/CP)
Geometry independence of three-string vertices
NASA Astrophysics Data System (ADS)
Maeno, Masahiro
1989-01-01
The geometry independence of three-string vertices in both HIKKO's and Witten's string field theories is examined. A careful regularization shows that the anomaly which has been reported by Morris and Mañes vanishes.
Acoustic data transmission through a drill string
Drumheller, D.S.
1988-04-21
Acoustical signals are transmitted through a drill string by canceling upward moving acoustical noise and by preconditioning the data in recognition of the comb filter impedance characteristics of the drill string. 5 figs.
NASA Astrophysics Data System (ADS)
Jejjala, Vishnumohan
2002-01-01
This Thesis explores aspects of superstring theory on orbifold spaces and applies some of the intuition gleaned from the study of the non-commutative geometry of space-time to understanding the fractional quantum Hall effect. The moduli space of vacua of marginal and relevant deformations of N = 4 super-Yang-Mills gauge theory in four dimensions is interpreted in terms of non-commutative geometry. A formalism for thinking about the algebraic geometry of the moduli space is developed. Within this framework, the representation theory of the algebras studied provides a natural exposition of D-brane fractionation. The non-commutative moduli space of deformations preserving N = 1 supersymmetry is examined in detail through various examples. In string theory, by the AdS/CFT correspondence, deformations of the N = 4 field theory are dual to the near-horizon geometries of D-branes on orbifolds of AdS5 x S 5. The physics of D-branes on the dual AdS backgrounds is explored. Quivers encapsulate the matter content of supersymmetric field theories on the worldvolumes of D-branes at orbifold singularities. New techniques for constructing quivers are presented here. When N is a normal subgroup of a finite group G, the quiver corresponding to fixed points of the orbifold M/G is computed from a G/N action on the quiver corresponding to M/G . These techniques prove useful for constructing non-Abelian quivers and for examining discrete torsion orbifolds. Quivers obtained through our constructions contain interesting low-energy phenomenology. The matter content on a brane at an isolated singularity of the Delta27 orbifold embeds the Standard Model. The symmetries of the quiver require exactly three generations of fields in the particle spectrum. Lepton masses are suppressed relative to quark masses because lepton Yukawa couplings do not appear in the superpotential. Lepton masses are generated through the Kahler potential and are related to the supersymmetry breaking scale. The model
String theory in electromagnetic fields
NASA Astrophysics Data System (ADS)
Ambjørn, Jan; Makeenko, Yuri M.; Semenoff, Gordon W.; Szabo, Richard J.
2003-02-01
A review of various aspects of superstrings in background electromagnetic fields is presented. Topics covered include the Born-Infeld action, spectrum of open strings in background gauge fields, the Schwinger mechanism, finite-temperature formalism and Hagedorn behaviour in external fields, Debye screening, D-brane scattering, thermodynamics of D-branes, and noncommutative field and string theories on D-branes. The electric field instabilities are emphasized throughout and contrasted with the case of magnetic fields. A new derivation of the velocity-dependent potential between moving D-branes is presented, as is a new result for the velocity corrections to the one-loop thermal effective potential.
Twenty-five questions for string theorists
Binetruy, Pierre; Kane, G.L.; Lykken, Joseph D.; Nelson, Brent D.; /Pennsylvania U.
2005-09-01
In an effort to promote communication between the formal and phenomenological branches of the high-energy theory community, we provide a description of some important issues in supersymmetric and string phenomenology. We describe each within the context of string constructions, illustrating them with specific examples where applicable. Each topic culminates in a set of questions that we believe are amenable to direct consideration by string theorists, and whose answers we think could help connect string theory and phenomenology.
NASA Technical Reports Server (NTRS)
2006-01-01
Something appears to be peering through a shiny red mask, in this new false-colored image from NASA's Spitzer Space Telescope. The mysterious blue eyes are actually starlight from the cores of two merging galaxies, called NGC 2207 and IC 2163. The mask is the galaxies' dusty spiral arms.
NGC 2207 and IC 2163 recently met and began a sort of gravitational tango about 40 million years ago. The two galaxies are tugging at each other, stimulating new stars to form. Eventually, this cosmic ball will come to an end, when the galaxies meld into one. The dancing duo is located 140 million light-years away in the Canis Major constellation.
The Spitzer image reveals that the galactic mask is adorned with strings of pearl-like beads. These dusty clusters of newborn stars, called 'beads on a string' by astronomers, appear as white balls throughout the arms of both galaxies. They were formed when the galaxies first interacted, forcing dust and gas to clump together into colonies of stars.
This type of beading has been seen before in other galaxies, but it took Spitzer's infrared eyes to identify them in NGC 2207 and IC 2163. Spitzer was able to see the beads because the stars inside heat up surrounding dust, which then radiates with infrared light.
The biggest bead lighting up the left side of the mask is also the densest. In fact, some of its central stars might have merged to form a black hole. (Now, that would be quite the Mardi Gras mask!)
This picture, taken by Spitzer's infrared array camera, is a four-channel composite. It shows light with wavelengths of 3.6 microns (blue); 4.5 microns (green); and 5.8 and 8.0 microns (red). The contribution from starlight (measured at 3.6 microns) has been subtracted from the 5.8- and 8-micron channels to enhance the visibility of the dust features.
The vacuum interaction of magnetic strings
Bordag, M. )
1991-03-01
The author investigates the interaction of two parallel magnetic strings which is due to the perturbation of the vacuum state of a scalar massive field. The Green function with one string is studied in detail and the influence of the second string is found in perturbation theory. The Casimir is expressed in terms of Bessel functions.
Transverse structure of the QCD string
Meyer, Harvey B.
2010-11-15
The characterization of the transverse structure of the QCD string is discussed. We formulate a conjecture as to how the stress-energy tensor of the underlying gauge theory couples to the string degrees of freedom. A consequence of the conjecture is that the energy density and the longitudinal-stress operators measure the distribution of the transverse position of the string, to leading order in the string fluctuations, whereas the transverse-stress operator does not. We interpret recent numerical measurements of the transverse size of the confining string and show that the difference of the energy and longitudinal-stress operators is a particularly natural probe at next-to-leading order. Second, we derive the constraints imposed by open-closed string duality on the transverse structure of the string. We show that a total of three independent ''gravitational'' form factors characterize the transverse profile of the closed string, and obtain the interpretation of recent effective string theory calculations: the square radius of a closed string of length {beta} defined from the slope of its gravitational form factor, is given by (d-1/2{pi}{sigma})log({beta}/4r{sub 0}) in d space dimensions. This is to be compared with the well-known result that the width of the open string at midpoint grows as (d-1/2{pi}{sigma})log(r/r{sub 0}). We also obtain predictions for transition form factors among closed-string states.
String duality and novel theories without gravity
Kachru, Shamit
1998-01-15
We describe some of the novel 6d quantum field theories which have been discovered in studies of string duality. The role these theories (and their 4d descendants) may play in alleviating the vacuum degeneracy problem in string theory is reviewed. The DLCQ of these field theories is presented as one concrete way of formulating them, independent of string theory.
The Physics of "String Passing through Ice"
ERIC Educational Resources Information Center
Mohazzabi, Pirooz
2011-01-01
One of the oldest yet interesting experiments related to heat and thermodynamics is placing a string on a block of ice and hanging two masses from the ends of the string. Sometime later, it is discovered that the string has passed through the ice without cutting it in half. A simple explanation of this effect is that the pressure caused by the…
p-Adic Strings and Their Applications
Freund, Peter G. O.
2006-03-29
The theory of p-adic strings is reviewed along with some of their applications, foremost among them to the tachyon condensation problem in string theory. Some open problems are discussed, in particular that of the superstring in 10 dimensions as the end-stage of the 26-dimensional closed bosonic string's tachyon condensation.
Cosmic electrons. [literature review
NASA Technical Reports Server (NTRS)
Ramaty, R.
1974-01-01
The published literature on cosmic electrons is summarized. The primary and secondary sources of cosmic electrons are discussed, and the propagation of the electrons in the interstellar medium is studied with respect to energy loss mechanisms, age distributions, and spectral modifications during flight. Various portions of the electron and positron spectra are then considered in relation to problems of astrophysics. New information is presented on such topics as the origin of low-energy positrons, the decay kinematics of the pi-mu-e process, the application of age distributions for nuclear cosmic rays to cosmic electrons, and the possibility of nonidentical sources for cosmic electrons and protons.
NASA Technical Reports Server (NTRS)
Mather, John C.
2012-01-01
neutrons, liberating a little energy and creating complexity. Then, the expanding universe cooled some more, and neutrons and protons, no longer kept apart by immense temperatures, found themselves unstable and formed helium nuclei. Then, a little more cooling, and atomic nuclei and electrons were no longer kept apart, and the universe became transparent. Then a little more cooling, and the next instability began: gravitation pulled matter together across cosmic distances to form stars and galaxies. This instability is described as a "negative heat capadty" in which extracting energy from a gravitating system makes it hotter -- clearly the 2nd law of thermodynamics does not apply here! (This is the physicist's part of the answer to e e cummings' question: what is the wonder that's keeping the stars apart?) Then, the next instability is that hydrogen and helium nuclei can fuse together to release energy and make stars burn for billions of years. And then at the end of the fuel source, stars become unstable and explode and liberate the chemical elements back into space. And because of that, on planets like Earth, sustained energy flows support the development of additional instabilities and all kinds of complex patterns. Gravitational instability pulls the densest materials into the core of the Earth, leaving a thin skin of water and air, and makes the interior churn incessantly as heat flows outwards. And the heat from the sun, received mostly near the equator and flowing towards the poles, supports the complex atmospheric and oceanic circulations. And because or that, the physical Earth is full of natural chemical laboratories, concentrating elements here, mixing them there, raising and lowering temperatures, ceaselessly experimenting with uncountable events where new instabilities can arise. At least one of them was the new experiment called life. Now that we know that there are at least as many planets as there are stars, it is hard to imagine that nature's ceasess
NASA Technical Reports Server (NTRS)
Mather, John C.
2012-01-01
neutrons, liberating a little energy and creating complexity. Then, the expanding universe cooled some more, and neutrons and protons, no longer kept apart by immense temperatures, found themselves unstable and formed helium nuclei. Then, a little more cooling, and atomic nuclei and electrons were no longer kept apart, and the universe became transparent. Then a little more cooling, and the next instability began: gravitation pulled matter together across cosmic distances to form stars and galaxies. This instability is described as a "negative heat capadty" in which extracting energy from a gravitating system makes it hotter -- clearly the 2nd law of thermodynamics does not apply here! (This is the physicist's part of the answer to e e cummings' question: what is the wonder that's keeping the stars apart?) Then, the next instability is that hydrogen and helium nuclei can fuse together to release energy and make stars burn for billions of years. And then at the end of the fuel source, stars become unstable and explode and liberate the chemical elements back into space. And because of that, on planets like Earth, sustained energy flows support the development of additional instabilities and all kinds of complex patterns. Gravitational instability pulls the densest materials into the core of the Earth, leaving a thin skin of water and air, and makes the interior churn incessantly as heat flows outwards. And the heat from the sun, received mostly near the equator and flowing towards the poles, supports the complex atmospheric and oceanic circulations. And because or that, the physical Earth is full of natural chemical laboratories, concentrating elements here, mixing them there, raising and lowering temperatures, ceaselessly experimenting with uncountable events where new instabilities can arise. At least one of them was the new experiment called life. Now that we know that there are at least as many planets as there are stars, it is hard to imagine that nature's ceasess
New Possibilities: Strings Are Strolling.
ERIC Educational Resources Information Center
Gillespie, Robert
1992-01-01
Describes a high school music program in which students form strolling performance groups. Explains that violinists, violists, and even cellists play as they stroll through audiences. Suggests that strolling strings programs benefit both students and teachers by providing opportunities for creativity and enhancing musical skills. Provides a list…
New Approaches to String Instruction.
ERIC Educational Resources Information Center
Teaching Music, 1994
1994-01-01
Maintains that use of the Suzuki, Orff, and Dalcroze methods have assisted string teachers in helping music students achieve mastery from the beginning of instruction. Describes how these methods are used by five music teachers. Includes addresses of organizations that provide information about these music teaching methods. CFR)
Localized gravity in string theory.
Karch, A; Randall, L
2001-08-06
We propose a string realization of the AdS4 brane in AdS5 that is known to localize gravity. Our theory is M D5 branes in the near horizon geometry of N D3 branes, where M and N are appropriately tuned.
String universality in ten dimensions.
Adams, Allan; Taylor, Washington; Dewolfe, Oliver
2010-08-13
We show that the N=1 supergravity theories in ten dimensions with gauge groups U(1){496} and E{8}×U(1){248} are not consistent quantum theories. Cancellation of anomalies cannot be made compatible with supersymmetry and Abelian gauge invariance. Thus, in ten dimensions all supersymmetric theories of gravity without known inconsistencies are realized in string theory.
Probing the string winding sector
NASA Astrophysics Data System (ADS)
Aldazabal, Gerardo; Mayo, Martín; Nuñez, Carmen
2017-03-01
We probe a slice of the massive winding sector of bosonic string theory from toroidal compactifications of Double Field Theory (DFT). This string subsector corresponds to states containing one left and one right moving oscillators. We perform a generalized Kaluza Klein compactification of DFT on generic 2 n-dimensional toroidal constant backgrounds and show that, up to third order in fluctuations, the theory coincides with the corresponding effective theory of the bosonic string compactified on n-dimensional toroidal constant backgrounds, obtained from three-point amplitudes. The comparison between both theories is facilitated by noticing that generalized diffeomorphisms in DFT allow to fix generalized harmonic gauge conditions that help in identifying the physical degrees of freedom. These conditions manifest as conformal anomaly cancellation requirements on the string theory side. The explicit expression for the gauge invariant effective action containing the physical massless sector (gravity+antisymmetric+gauge+ scalar fields) coupled to towers of generalized Kaluza Klein massive states (corresponding to compact momentum and winding modes) is found. The action acquires a very compact form when written in terms of fields carrying O( n, n) indices, and is explicitly T-duality invariant. The global algebra associated to the generalized Kaluza Klein compactification is discussed.
NASA Astrophysics Data System (ADS)
Boels, Rutger H.; Hansen, Tobias
2014-06-01
It is argued that the complete S-matrix of string theory at tree level in a flat background can be obtained from a small set of target space properties, without recourse to the worldsheet description. The main non-standard inputs are (generalised) Britto-Cachazo-Feng-Witten shifts, as well as the monodromy relations for open string theory and the Kawai-Lewellen-Tye relations for closed string theory. The roots of the scattering amplitudes and especially their appearance in the residues at the kinematic poles are central to the story. These residues determine the amplitudes through on-shell recursion relations. Several checks of the formalism are presented, including a computation of the Koba-Nielsen amplitude in the bosonic string. Furthermore the question of target space unitarity is (re-)investigated. For the Veneziano amplitude this question is reduced by Poincaré invariance, unitarity and locality to that of positivity of a particular numerical sum. Interestingly, this analysis produces the main conditions of the no-ghost theorem on dimension and intercept from the first three poles of this amplitude.
Testing parity-violating physics from cosmic rotation power reconstruction
NASA Astrophysics Data System (ADS)
Namikawa, Toshiya
2017-02-01
We study the reconstruction of the cosmic rotation power spectrum produced by parity-violating physics, with an eye to ongoing and near future cosmic microwave background (CMB) experiments such as BICEP Array, CMBS4, LiteBIRD and Simons Observatory. In addition to the inflationary gravitational waves and gravitational lensing, measurements of other various effects on CMB polarization open new window into the early Universe. One of these is anisotropies of the cosmic polarization rotation which probes the Chern-Simons term generally predicted by string theory. The anisotropies of the cosmic rotation are also generated by the primordial magnetism and in the Standard Model extention framework. The cosmic rotation anisotropies can be reconstructed as quadratic in CMB anisotropies. However, the power of the reconstructed cosmic rotation is a CMB four-point correlation and is not directly related to the cosmic-rotation power spectrum. Understanding all contributions in the four-point correlation is required to extract the cosmic rotation signal. Assuming inflationary motivated cosmic-rotation models, we employ simulation to quantify each contribution to the four-point correlation and find that (1) a secondary contraction of the trispectrum increases the total signal-to-noise, (2) a bias from the lensing-induced trispectrum is significant compared to the statistical errors in, e.g., LiteBIRD and CMBS4-like experiments, (3) the use of a realization-dependent estimator decreases the statistical errors by 10%-20%, depending on experimental specifications, and (4) other higher-order contributions are negligible at least for near future experiments.
Ultrasensitive string-based temperature sensors
NASA Astrophysics Data System (ADS)
Larsen, T.; Schmid, S.; Grönberg, L.; Niskanen, A. O.; Hassel, J.; Dohn, S.; Boisen, A.
2011-03-01
Resonant strings are a promising concept for ultra sensitive temperature detection. We present an analytical model for the sensitivity with which we optimize the temperature response of resonant strings by varying geometry and material. The temperature sensitivity of silicon nitride and aluminum microstrings was measured. The relative change in resonant frequency per temperature change of -1.74±0.04%/°C of the aluminum strings is more than one order of magnitude higher than of the silicon nitride strings and of comparable state-of-the-art AuPd strings.
Growth and characterization of string ribbon
Hanoka, J.I.; Behnin, B.; Michel, J.; Symko, M.; Sopori, B.L.
1995-08-01
Evergreen Solar, a new photovoltaics company, makes solar cells and modules based on String Ribbon. String Ribbon is a silicon sheet growth method wherein two high temperature strings are pulled through a shallow melt of silicon and a crystalline silicon sheet then grows between the two strings. The strings serve to stabilize the edges of the growing silicon sheet. The growth process is primarily meniscus controlled and, compared to other silicon ribbon growth methods such as d-web and EFG, relatively insensitive to temperature fluctuations as great as {+-}10{degrees}C. Growth speed is about 2 cm/minute.
Cosmic ray antiprotons from nearby cosmic accelerators
NASA Astrophysics Data System (ADS)
Joshi, Jagdish C.; Gupta, Nayantara
2015-05-01
The antiproton flux measured by PAMELA experiment might have originated from Galactic sources of cosmic rays. These antiprotons are expected to be produced in the interactions of cosmic ray protons and nuclei with cold protons. Gamma rays are also produced in similar interactions inside some of the cosmic accelerators. We consider a few nearby supernova remnants observed by Fermi LAT. Many of them are associated with molecular clouds. Gamma rays have been detected from these sources which most likely originate in decay of neutral pions produced in hadronic interactions. The observed gamma ray fluxes from these SNRs are used to find out their contributions to the observed diffuse cosmic ray antiproton flux near the earth.
Chemical composition of primary cosmic rays with IceCube
NASA Astrophysics Data System (ADS)
Xu, Chen
Ground detector arrays have been used to measure high energy cosmic rays for decades to overcome their very low rate. IceCube is a special case with its 3D deployment and unique location---the South Pole. Although all 86 strings and 81 stations of IceCube were completed in 2011, IceCube began to take data in 2006, after the completion of the first 9 strings. In this thesis, experimental data taken in 2009 with 59 strings are used for composition analysis albeit some techniques are illustrated with the 40-string data. Simulation is essential in the composition work. Simulated data must be compared against the experimental data to find the right mix of cosmic ray components. However, because of limited computing resources and complexities of cosmic rays, the simulation in IceCube is well behind the experiment. The lower and upper bounds of primary energy in simulation for events that go through IceTop and the deep arrays of IceCube are 1014 eV and 1017 eV. However, since IceCube has a threshold energy about several hundred TeV, and an upper limit of 10 18 eV, the full energy range cannot be explored in this thesis. The approach taken to the composition problem in this thesis is a 2D Bayesian unfolding. It takes account of the measured IceTop and InIce energy spectrum and outputs the expected primary energy spectrum of different mass components. Studies of the uncertainties in the results are not complete because of limited simulation and understanding of the new detector and South Pole environment.
Dynamical AdS strings across horizons
Ishii, Takaaki; Murata, Keiju
2016-03-01
We examine the nonlinear classical dynamics of a fundamental string in anti-deSitter spacetime. The string is dual to the flux tube between an external quark-antiquark pair in $N = 4$ super Yang-Mills theory. We perturb the string by shaking the endpoints and compute its time evolution numerically. We find that with sufficiently strong perturbations the string continues extending and plunges into the Poincare´ horizon. In the evolution, effective horizons are also dynamically created on the string worldsheet. The quark and antiquark are thus causally disconnected, and the string transitions to two straight strings. The forces acting on the endpoints vanish with a power law whose slope depends on the perturbations. Lastly, the condition for this transition to occur is that energy injection exceeds the static energy between the quark-antiquark pair.
Dynamical AdS strings across horizons
Ishii, Takaaki; Murata, Keiju
2016-03-01
We examine the nonlinear classical dynamics of a fundamental string in anti-deSitter spacetime. The string is dual to the flux tube between an external quark-antiquark pair in $N = 4$ super Yang-Mills theory. We perturb the string by shaking the endpoints and compute its time evolution numerically. We find that with sufficiently strong perturbations the string continues extending and plunges into the Poincare´ horizon. In the evolution, effective horizons are also dynamically created on the string worldsheet. The quark and antiquark are thus causally disconnected, and the string transitions to two straight strings. The forces acting on the endpoints vanishmore » with a power law whose slope depends on the perturbations. Lastly, the condition for this transition to occur is that energy injection exceeds the static energy between the quark-antiquark pair.« less
String formatting considered harmful for novice programmers
NASA Astrophysics Data System (ADS)
Hughes, Michael C.; Jadud, Matthew C.; Rodrigo, Ma. Mercedes T.
2010-09-01
In Java, System.out.printf and String.format consume a specialised kind of string commonly known as a format string. In our study of first-year students at the Ateneo de Manila University, we discovered that format strings present a substantial challenge for novice programmers. Focusing on their first laboratory we found that 8% of all the compilation errors and 100% of the exceptional, run-time behaviour they encountered were due to the improper construction of format strings. Format strings are a language unto themselves embedded within Java, and they are difficult for novice programmers to master when learning to program. In this article, we present exemplars of students' problematic interactions with the Java compiler and run-time environment when dealing with format strings, discuss these interactions, and recommend possible instructional interventions based on our observations.
String theory as a Lilliputian world
NASA Astrophysics Data System (ADS)
Ambjørn, J.; Makeenko, Y.
2016-05-01
Lattice regularizations of the bosonic string do not allow us to probe the tachyon. This has often been viewed as the reason why these theories have never managed to make any contact to standard continuum string theories when the dimension of spacetime is larger than two. We study the continuum string theory in large spacetime dimensions where simple mean field theory is reliable. By keeping carefully the cutoff we show that precisely the existence of a tachyon makes it possible to take a scaling limit which reproduces the lattice-string results. We compare this scaling limit with another scaling limit which reproduces standard continuum-string results. If the people working with lattice regularizations of string theories are akin to Gulliver they will view the standard string-world as a Lilliputian world no larger than a few lattice spacings.
Bianchi type-V bulk viscous string cosmological model in a self-creation theory of gravitation
NASA Astrophysics Data System (ADS)
Bhaskara Rao, M. P. V. V.; Reddy, D. R. K.; Sobhan Babu, K.
2015-10-01
A spatially homogenous and anisotropic Bianchi type space-time is considered in the frame work of second self-creation theory of gravitation proposed by Barber (Gen. Relativ. Gravit. 14:117, 1982) in the presence of bulk viscous fluid containing one dimensional cosmic strings. Solving the field equations of this theory an exact cosmological model is obtained using some physically plausible conditions. It is observed that strings in this model do not survive. Some physical and kinematical properties of the model are also discussed.
NASA Astrophysics Data System (ADS)
2015-09-01
Despite the title, this blog has nothing (or at least very little) to do with string theory, and you can put away your looms and knitting needles, too: the “yarns” on this site are of the storytelling variety.
Tree-level unitarity bounds for the minimal B-L model
Basso, L.; Belyaev, A.; Moretti, S.; Pruna, G. M.
2010-05-01
We have derived the unitarity bounds in the high energy limit for the minimal B-L extension of the standard model by analyzing the full class of Higgs and would-be Goldstone boson two-to-two scatterings at tree level. Moreover, we have investigated how these limits could vary at some lower critical value of the energy.
Unification and mass spectrum in a B-L extended MSSM
Hernandez-Pinto, R. J.; Perez-Lorenzana, A.
2009-04-20
The simplest B-L extension of the minimum supersymmetric standard model (MSSM) may change some of the conceptions about the path for gauge unification as well as to affect the predicted spectrum of the supersymmetric particles at low energy. We present our results for the running of gauge coupling constants and mass parameter in this context.
Closed String S-matrix Elements in Open String Field Theory
NASA Astrophysics Data System (ADS)
Garousi, Mohammad R.; Maktabdaran, G. R.
2005-03-01
We study the S-matrix elements of the gauge invariant operators corresponding to on-shell closed strings, in open string field theory. In particular, we calculate the tree level S-matrix element of two arbitrary closed strings, and the S-matrix element of one closed string and two open strings. By mapping the world-sheet of these amplitudes to the upper half z-plane, and by evaluating explicitly the correlators in the ghost part, we show that these S-matrix elements are exactly identical to the corresponding disk level S-matrix elements in perturbative string theory.
The Cosmic Background Explorer.
ERIC Educational Resources Information Center
Gulkis, Samuel; And Others
1990-01-01
Outlines the Cosmic Background Explorer (COBE) mission to measure celestial radiation. Describes the instruments used and experiments involving differential microwave radiometers, and a far infrared absolute spectrophotometer. (YP)
The cosmic neutrino background
NASA Technical Reports Server (NTRS)
Dar, Arnon
1991-01-01
The cosmic neutrino background is expected to consist of relic neutrinos from the big bang, of neutrinos produced during nuclear burning in stars, of neutrinos released by gravitational stellar collapse, and of neutrinos produced by cosmic ray interactions with matter and radiation in the interstellar and intergalactic medium. Formation of baryonic dark matter in the early universe, matter-antimatter annihilation in a baryonic symmetric universe, and dark matter annihilation could have also contributed significantly to the cosmic neutrino background. The purpose of this paper is to review the properties of these cosmic neutrino backgrounds, the indirect evidence for their existence, and the prospects for their detection.
NASA Astrophysics Data System (ADS)
Schulz, Marc Daniel; Dusuel, Sébastien; Vidal, Julien
2016-11-01
We discuss the emergence of bound states in the low-energy spectrum of the string-net Hamiltonian in the presence of a string tension. In the ladder geometry, we show that a single bound state arises either for a finite tension or in the zero-tension limit depending on the theory considered. In the latter case, we perturbatively compute the binding energy as a function of the total quantum dimension. We also address this issue in the honeycomb lattice where the number of bound states in the topological phase depends on the total quantum dimension. Finally, the internal structure of these bound states is analyzed in the zero-tension limit.
Loop Variables in String Theory
NASA Astrophysics Data System (ADS)
Sathiapalan, B.
The loop variable approach is a proposal for a gauge-invariant generalization of the sigma-model renormalization group method of obtaining equations of motion in string theory. The basic guiding principle is space-time gauge invariance rather than world sheet properties. In essence it is a version of Wilson's exact renormalization group equation for the world sheet theory. It involves all the massive modes and is defined with a finite world sheet cutoff, which allows one to go off the mass-shell. On shell the tree amplitudes of string theory are reproduced. The equations are gauge-invariant off shell also. This paper is a self-contained discussion of the loop variable approach as well as its connection with the Wilsonian RG.
Hall, David R.; Pixton, David S.; Briscoe, Michael; McPherson, James
2007-12-04
A filter for a drill string comprises a perforated receptacle having an open end and a perforated end and first and second mounting surfaces are adjacent the open end. A transmission element is disposed within each of the first and second mounting surfaces. A capacitor may modify electrical characteristics of an LC circuit that comprises the transmission elements. The respective transmission elements are in communication with each other and with a transmission network integrated into the drill string. The transmission elements may be inductive couplers, direct electrical contacts, or optical couplers. In some embodiments of the present invention, the filter comprises an electronic component. The electronic component may be selected from the group consisting of a sensor, a router, a power source, a clock source, a repeater, and an amplifier.
Macroscopic constraints on string unification
Taylor, T.R.
1989-03-01
The comparison of sting theory with experiment requires a huge extrapolation from the microscopic distances, of order of the Planck length, up to the macroscopic laboratory distances. The quantum effects give rise to large corrections to the macroscopic predictions of sting unification. I discus the model-independent constraints on the gravitational sector of string theory due to the inevitable existence of universal Fradkin-Tseytlin dilatons. 9 refs.
Acoustical properties of drill strings
Drumheller, D.S.
1988-08-01
The recovery of petrochemical and geothermal resources requires extensive drilling of wells to increasingly greater depths. Real-time collection and telemetry of data about the drilling process while it occurs thousands of feet below the surface is an effective way of improving the efficiency of drilling operations. Unfortunately, due to hostile down-hole environments, telemetry of this data is an extremely difficult problem. Currently, commercial systems transmit data to the surface by producing pressure pulses within the portion of the drilling mud enclosed in the hollow steel drill string. Transmission rates are between two and four data bits per second. Any system capable of raising data rates without increasing the complexity of the drilling process will have significant economic impact. One alternative system is based upon acoustical carrier waves generated within the drill string itself. If developed, this method would accommodate data rates up to 100 bits per second. Unfortunately, the drill string is a periodic structure of pipe and threaded tool joints, the transmission characteristics are very complex and exhibit a banded and dispersive structure. Over the past forty years, attempts to field systems based upon this transmission method have resulted in little success. This paper examines this acoustical transmission problem in great detail. The basic principles of acoustic wave propagation in the periodic structure of the drill string are examined through theory, laboratory experiment, and field test. The results indicate the existence of frequency bands which are virtually free of attenuation and suitable for data transmission at high bit rates. 9 refs., 38 figs., 2 tabs.
On the null origin of the ambitwistor string
NASA Astrophysics Data System (ADS)
Casali, Eduardo; Tourkine, Piotr
2016-11-01
In this paper we present the null string origin of the ambitwistor string. Classically, the null string is the tensionless limit of string theory, and so too is the ambitwistor string. Both have as constraint algebra the Galilean Conformal Algebra in two dimensions. But something interesting happens in the quantum theory since there is an ambiguity in quantizing the null string. We show that, given a particular choice of quantization scheme and a particular gauge, the null string coincides with the ambitwistor string both classically and quantum mechanically. We also show that the same holds for the spinning versions of the null string and ambitwistor string. With these results we clarify the relationship between the ambitwistor string, the null string, the usual string and the Hohm-Siegel-Zwiebach theory.
NASA Astrophysics Data System (ADS)
Desmond, Timothy
In this dissertation I discern what Carl Jung calls the mandala image of the ultimate archetype of unity underlying and structuring cosmos and psyche by pointing out parallels between his transpersonal psychology and Stanford physicist Leonard Susskind's string theory. Despite his atheistic, materialistically reductionist interpretation of it, I demonstrate how Susskind's string theory of holographic information conservation at the event horizons of black holes, and the cosmic horizon of the universe, corroborates the following four topics about which Jung wrote: (1) his near-death experience of the cosmic horizon after a heart attack in 1944; ( 2) his equation relating psychic energy to mass, "Psyche=highest intensity in the smallest space" (1997, 162), which I translate into the equation, Psyche=Singularity; (3) his theory that the mandala, a circle or sphere with a central point, is the symbolic image of the ultimate archetype of unity through the union of opposites, which structures both cosmos and psyche, and which rises spontaneously from the collective unconscious to compensate a conscious mind torn by irreconcilable demands (1989, 334-335, 396-397); and (4) his theory of synchronicity. I argue that Susskind's inside-out black hole model of our Big Bang universe forms a geometrically perfect mandala: a central Singularity encompassed by a two-dimensional sphere which serves as a universal memory bank. Moreover, in precise fulfillment of Jung's theory, Susskind used that mandala to reconcile the notoriously incommensurable paradigms of general relativity and quantum mechanics, providing in the process a mathematically plausible explanation for Jung's near-death experience of his past, present, and future life simultaneously at the cosmic horizon. Finally, Susskind's theory also provides a plausible cosmological model to explain Jung's theory of synchronicity--meaningful coincidences may be tied together by strings at the cosmic horizon, from which they
Maria Montessori's Cosmic Vision, Cosmic Plan, and Cosmic Education
ERIC Educational Resources Information Center
Grazzini, Camillo
2013-01-01
This classic position of the breadth of Cosmic Education begins with a way of seeing the human's interaction with the world, continues on to the grandeur in scale of time and space of that vision, then brings the interdependency of life where each growing human becomes a participating adult. Mr. Grazzini confronts the laws of human nature in…
Informing New String Programmes: Lessons Learned from an Australian Experience
ERIC Educational Resources Information Center
Murphy, Fintan; Rickard, Nikki; Gill, Anneliese; Grimmett, Helen
2011-01-01
Although there are many examples of notable string programmes there has been relatively little comparative analysis of these programmes. This paper examines three benchmark string programmes (The University of Illinois String Project, The Tower Hamlets String Teaching Project and Colourstrings) alongside Music4All, an innovative string programme…
Large-spin expansions of GKP strings
NASA Astrophysics Data System (ADS)
Floratos, Emmanuel; Georgiou, George; Linardopoulos, Georgios
2014-03-01
We demonstrate that the large-spin expansion of the energy of Gubser-Klebanov-Polyakov (GKP) strings that rotate in ℝ × S2 and AdS3 can be expressed in terms of Lambert's W-function. We compute the leading, subleading and next-to-subleading series of exponential corrections to the infinite-volume dispersion relation of GKP strings that rotate in ℝ × S2. These strings are dual to the long = 4 SYM operators +… and provide their scaling dimensions at strong coupling. We also show that the strings obey a short-long (strings) duality. For the folded GKP strings that spin inside AdS3 and are dual to twist-2 operators, we confirm the known formulas for the leading and next-to-leading coefficients of their anomalous dimensions and derive the corresponding expressions for the next-to-next-to-leading coefficients.
NASA Astrophysics Data System (ADS)
Lai, Sheng-Hong; Lee, Jen-Chi; Yang, Yi
2016-05-01
We review and extend high energy four point string BCJ relations in both the fixed angle and Regge regimes. We then give an explicit proof of four point string BCJ relations for all energy. This calculation provides an alternative proof of the one based on monodromy of integration in string amplitude calculation. In addition, we calculate both s- t and t- u channel nonrelativistic low energy string scattering amplitudes of three tachyons and one higher spin string state at arbitrary mass levels. We discover that the mass and spin dependent nonrelativistic string BCJ relations can be expressed in terms of Gauss hypergeometry functions. As an application, for each fixed mass level N, we derive extended recurrence relations among nonrelativistic low energy string scattering amplitudes of string states with different spins and different channels.
Specifications for Managed Strings, Second Edition
2010-05-01
const char * cstr , const size_t maxsize, const char *charset); 10 | CMU/SEI-2010-TR-018 Runtime-Constraints s shall not be a null pointer...strcreate_m function creates a managed string, referenced by s, given a conventional string cstr (which may be null or empty). maxsize specifies the...characters to those in the null-terminated byte string cstr (which may be empty). If charset is a null pointer, no restricted character set is defined. If
Orbifold SUSY GUT from the Heterotic String
Kyae, Bumseok
2008-11-23
From the string partition function, we discuss the mass-shell and GSO projection conditions valid for Kaluza-Klein (KK) as well as massless states in the heterotic string theory compactifled on a nonprime orbifold. Using the obtained conditions we construct a 4D string standard model, which is embedded in a 6D SUSY GUT by including KK states above the compactiflcation scale. We discuss the stringy threshold corrections to gauge couplings, including the Wilson line effects.
String Fragmentation Model in Space Radiation Problems
NASA Technical Reports Server (NTRS)
Tang, Alfred; Johnson, Eloise (Editor); Norbury, John W.; Tripathi, R. K.
2002-01-01
String fragmentation models such as the Lund Model fit experimental particle production cross sections very well in the high-energy limit. This paper gives an introduction of the massless relativistic string in the Lund Model and shows how it can be modified with a simple assumption to produce formulas for meson production cross sections for space radiation research. The results of the string model are compared with inclusive pion production data from proton-proton collision experiments.
Exact solutions and singularities in string theory
Horowitz, G.T. ); Tseytlin, A.A. )
1994-10-15
We construct two new classes of exact solutions to string theory which are not of the standard plane wave of gauged WZW type. Many of these solutions have curvature singularities. The first class includes the fundamental string solution, for which the string coupling vanishes near the singularity. This suggests that the singularity may not be removed by quantum corrections. The second class consists of hybrids of plane wave and gauged WZW solutions. We discuss a four-dimensional example in detail.
Relation between strings and ribbon knots
NASA Astrophysics Data System (ADS)
Ahmed, E.; El-Rifai, E. A.; Abdellatif, R. A.
1991-02-01
A ribbon knot can be represented as the propagation of an open string in (Euclidean) space-time. By imposing physical conditions plus an ansatz on the string scattering amplitude, we get invariant polynomials of ribbon knots which correspond to Jones and Wadati et al. polynomials for ordinary knots. Motivated by the string scattering vertices, we derive an algebra which is a generalization of Hecke and Murakami-Birman-Wenzel (BMW) algebras of knots.
NASA Technical Reports Server (NTRS)
Stone, E. C.
1973-01-01
The isotopic composition of cosmic rays is studied in order to develop the relationship between cosmic rays and stellar processes. Cross section and model calculations are reported on isotopes of H, He, Be, Al and Fe. Satellite instrument measuring techniques separate only the isotopes of the lighter elements.
ERIC Educational Resources Information Center
Leonard, Gerard
2013-01-01
This article is a special blend of research, theory, and practice, with clear insight into the origins of Cosmic Education and cosmic task, while recalling memories of student explorations in botany, in particular, episodes from Mr. Leonard's teaching. Mr. Leonard speaks of a storytelling curriculum that eloquently puts perspective into dimensions…
p-adic string theories provide lattice Discretization to the ordinary string worldsheet.
Ghoshal, Debashis
2006-10-13
A class of models called p-adic strings is useful in understanding the tachyonic instability of string theory. These are found to be empirically related to the ordinary strings in the p-->1 limit. We propose that these models provide discretization for the string worldsheet and argue that the limit is naturally thought of as a continuum limit in the sense of the renormalization group.
Kahane, Guy
2014-01-01
The universe that surrounds us is vast, and we are so very small. When we reflect on the vastness of the universe, our humdrum cosmic location, and the inevitable future demise of humanity, our lives can seem utterly insignificant. Many philosophers assume that such worries about our significance reflect a banal metaethical confusion. They dismiss the very idea of cosmic significance. This, I argue, is a mistake. Worries about cosmic insignificance do not express metaethical worries about objectivity or nihilism, and we can make good sense of the idea of cosmic significance and its absence. It is also possible to explain why the vastness of the universe can make us feel insignificant. This impression does turn out to be mistaken, but not for the reasons typically assumed. In fact, we might be of immense cosmic significance—though we cannot, at this point, tell whether this is the case. PMID:25729095
Problems with Chaos in String Cosmology
NASA Astrophysics Data System (ADS)
Dąbrowski, Mariusz P.
I review the main ideas of the pre-big-bang cosmology scenario emphasizing the role of different boundary conditions in comparison to the standard ones which appear in quantum cosmology. My main issue is duality symmetry - a very general feature of string theory - and its role in suppressing chaos in Bianchi type IX "Mixmaster" universes within the framework of the tree-level low-energy-effectiveactions for strings. Finally, I discuss the ways to possibly `generate' chaos in string cosmology by admitting dilaton potential/massive string modes, more spacetime dimensions or nonlinear Yang-Mills-Lorentz-Chern-Simons terms into the action.
Gauge invariant actions for string models
Banks, T.
1986-06-01
String models of unified interactions are elegant sets of Feynman rules for the scattering of gravitons, gauge bosons, and a host of massive excitations. The purpose of these lectures is to describe the progress towards a nonperturbative formulation of the theory. Such a formulation should make the geometrical meaning of string theory manifest and explain the many ''miracles'' exhibited by the string Feynman rules. There are some new results on gauge invariant observables, on the cosmological constant, and on the symmetries of interacting string field theory. 49 refs.
Bell's Inequalities, Superquantum Correlations, and String Theory
Chang, Lay Nam; Lewis, Zachary; Minic, Djordje; ...
2011-01-01
We offermore » an interpretation of superquantum correlations in terms of a “doubly” quantum theory. We argue that string theory, viewed as a quantum theory with two deformation parameters, the string tension α ' , and the string coupling constant g s , is such a superquantum theory that transgresses the usual quantum violations of Bell's inequalities. We also discuss the ℏ → ∞ limit of quantum mechanics in this context. As a superquantum theory, string theory should display distinct experimentally observable supercorrelations of entangled stringy states.« less
Spontaneous knotting of an agitated string.
Raymer, Dorian M; Smith, Douglas E
2007-10-16
It is well known that a jostled string tends to become knotted; yet the factors governing the "spontaneous" formation of various knots are unclear. We performed experiments in which a string was tumbled inside a box and found that complex knots often form within seconds. We used mathematical knot theory to analyze the knots. Above a critical string length, the probability P of knotting at first increased sharply with length but then saturated below 100%. This behavior differs from that of mathematical self-avoiding random walks, where P has been proven to approach 100%. Finite agitation time and jamming of the string due to its stiffness result in lower probability, but P approaches 100% with long, flexible strings. We analyzed the knots by calculating their Jones polynomials via computer analysis of digital photos of the string. Remarkably, almost all were identified as prime knots: 120 different types, having minimum crossing numbers up to 11, were observed in 3,415 trials. All prime knots with up to seven crossings were observed. The relative probability of forming a knot decreased exponentially with minimum crossing number and Möbius energy, mathematical measures of knot complexity. Based on the observation that long, stiff strings tend to form a coiled structure when confined, we propose a simple model to describe the knot formation based on random "braid moves" of the string end. Our model can qualitatively account for the observed distribution of knots and dependence on agitation time and string length.
The physics of guitar string vibrations
NASA Astrophysics Data System (ADS)
Perov, Polievkt; Johnson, Walter; Perova-Mello, Nataliia
2016-01-01
We describe laboratory experiments to study the harmonic content of standing waves in guitar strings. The experimental data were taken by using the magnetic pickup from a guitar and a digital oscilloscope with a Fast Fourier transform capability. The amplitudes of the harmonics in the measured signal depend on the location where the string is plucked, resulting in a different timbre of the sound. The relative amplitudes of transverse standing waves in a string were determined from the experimental data and also predicted from the wave equation with the boundary and initial conditions corresponding to the initial shape of the string.
Interacting quintessence, the coincidence problem, and cosmic acceleration
NASA Astrophysics Data System (ADS)
Huey, Greg; Wandelt, Benjamin D.
2006-07-01
Faced by recent evidence for a flat universe dominated by dark energy, cosmologists grapple with deep cosmic enigmas such as the cosmological constant problem, extreme fine-tuning and the cosmic coincidence problem. The extent to which we observe the dimming of distant supernovae suggests that the cosmic acceleration is as least as severe as in cosmological constant models. Extrapolating this to our cosmic future implies terrifying visions of either a cold and empty universe or an explosive demise in a “Big Rip.” We construct a class of dynamical scalar field models of dark energy and dark matter. Within this class we can explain why supernovae imply a cosmic equation of state w≲-1, address fine-tuning issues, protect the universe from premature acceleration and predict a constant fraction of dark energy to dark matter in the future (thus solving the coincidence problem), satisfy the dominant energy condition, and ensure that gravitationally bound objects remain so forever (avoid a Big Rip). This is achieved with a string theory inspired Lagrangian containing standard kinetic terms, exponential potentials and couplings, and parameters of order unity.
Finding Optimal Alignment and Consensus of Circular Strings
NASA Astrophysics Data System (ADS)
Lee, Taehyung; Na, Joong Chae; Park, Heejin; Park, Kunsoo; Sim, Jeong Seop
We consider the problem of finding the optimal alignment and consensus (string) of circular strings. Circular strings are different from linear strings in that the first (leftmost) symbol of a circular string is wrapped around next to the last (rightmost) symbol. In nature, for example, bacterial and mitochondrial DNAs typically form circular strings. The consensus string problem is finding a representative string (consensus) of a given set of strings, and it has been studied on linear strings extensively. However, only a few efforts have been made for the consensus problem for circular strings, even though circular strings are biologically important. In this paper, we introduce the consensus problem for circular strings and present novel algorithms to find the optimal alignment and consensus of circular strings under the Hamming distance metric. They are O(n 2logn)-time algorithms for three circular strings and an O(n 3logn)-time algorithm for four circular strings. Our algorithms are O(n/ logn) times faster than the naïve algorithm directly using the solutions for the linear consensus problems, which takes O(n 3) time for three circular strings and O(n 4) time for four circular strings. We achieved this speedup by adopting a convolution and a system of linear equations into our algorithms to reflect the characteristics of circular strings that we found.
B-L violating proton decay modes and new baryogenesis scenario in SO(10).
Babu, K S; Mohapatra, R N
2012-08-31
We show that grand unified theories based on SO(10) generate quite naturally baryon number violating dimension seven operators that violate B-L, and lead to novel nucleon decay modes such as n→e(-)K(+), e(-)π(+) and p→νπ(+). We find that in two-step breaking schemes of nonsupersymmetric SO(10), the partial lifetimes for these modes can be within reach of experiments. The interactions responsible for these decay modes also provide a new way to understand the origin of matter in the Universe via the decays of grand unified theory (GUT) scale scalar bosons of SO(10). Their (B-L)-violating nature guarantees that the GUT scale induced baryon asymmetry is not washed out by the electroweak sphaleron interactions. In minimal SO(10) models this asymmetry is closely tied to the masses of quarks, leptons and the neutrinos.
Resonant leptogenesis in the minimal B-L extended standard model at TeV
Iso, Satoshi; Orikasa, Yuta; Okada, Nobuchika
2011-05-01
We investigate the resonant leptogenesis scenario in the minimal B-L extended standard model with the B-L symmetry breaking at the TeV scale. Through detailed analysis of the Boltzmann equations, we show how much the resultant baryon asymmetry via leptogenesis is enhanced or suppressed, depending on the model parameters, in particular, the neutrino Dirac-Yukawa couplings and the TeV scale Majorana masses of heavy degenerate neutrinos. In order to consider a realistic case, we impose a simple ansatz for the model parameters and analyze the neutrino oscillation parameters and the baryon asymmetry via leptogenesis as a function of only a single CP phase. We find that for a fixed CP phase all neutrino oscillation data and the observed baryon asymmetry of the present Universe can be simultaneously reproduced.
Muon anomalous magnetic moment in SUSY B - L model with inverse seesaw
NASA Astrophysics Data System (ADS)
Khalil, Shaaban; Ün, Cem Salih
2016-12-01
Motivated by the tension between the Higgs mass and muon g - 2 in minimal supersymmetric standard model (MSSM), we analyze the muon g - 2 in supersymmetric B - L extension of the standard model (BLSSM) with inverse seesaw mechanism. In this model, the Higgs mass receives extra important radiative corrections proportional to large neutrino Yukawa coupling. We point out that muon g - 2 also gets significant contribution, due to the constructive interferences of light neutralino effects. The light neutralinos are typically the MSSM Bino like and the supersymmetric partner of U(1) B - L gauge boson (B˜‧-ino). We show that with universal soft supersymmetry breaking terms, the muon g - 2 resides within 2σ of the measured value, namely ∼ 20 ×10-10, with Higgs mass equal to 125 GeV.
Irreversible inhibition of human cathepsins B, L, S and K by hypervalent tellurium compounds.
Cunha, Rodrigo L O R; Gouvêa, Iuri E; Feitosa, Geovana P V; Alves, Márcio F M; Brömme, Dieter; Comasseto, João V; Tersariol, Ivarne L S; Juliano, Luiz
2009-11-01
The inhibition of human cysteine cathepsins B, L, S and K was evaluated by a set of hypervalent tellurium compounds (telluranes) comprising both organic and inorganic derivatives. All telluranes studied showed a time- and concentration-dependent irreversible inhibition of the cathepsins, and their second-order inactivation rate constants were determined. The organic derivatives were potent inhibitors of the cathepsins and clear specificities were detected, which were parallel to their known substrate specificities. In all cases, the activity of the tellurane-inhibited cathepsins was recovered by treatment of the inactivated enzymes with reducing agents. The maximum stoichiometry of the reaction between cysteine residues and telluranes were also determined. The presented data indicate that it is possible to design organic compounds with a tellurium(IV) moiety as a novel warhead that covalently modifies the catalytic cysteine, and which also form strong interactions with subsites of cathepsins B, L, S and K, resulting in more specific inhibition.
Search for mono-Higgs signals at the LHC in the B -L supersymmetric standard model
NASA Astrophysics Data System (ADS)
Abdallah, W.; Hammad, A.; Khalil, S.; Moretti, S.
2017-03-01
We study mono-Higgs signatures emerging in the B -L supersymmetric standard model induced by new channels not present in the minimal supersymmetric standard model, i.e., via topologies in which the mediator is either a heavy Z', with mass of O (2 TeV ) , or an intermediate h' (the lightest C P -even Higgs state of B -L origin), with a mass of O (0.2 TeV ) . The mono-Higgs probe considered is the standard model-like Higgs state recently discovered at the Large Hadron Collider, so as to enforce its mass reconstruction for background reduction purposes. With this in mind, its two cleanest signatures are selected: γ γ and Z Z*→4 l (l =e , μ ). We show how both of these can be accessed with foreseen energy and luminosity options using a dedicated kinematic analysis performed in the presence of partonic, showering, hadronization and detector effects.
Minimal flavor violation in the minimal U(1)B-L model and resonant leptogenesis
NASA Astrophysics Data System (ADS)
Okada, Nobuchika; Orikasa, Yuta; Yamada, Toshifumi
2012-10-01
We investigate the resonant leptogenesis scenario in the minimally U(1)B-L extended standard model with minimal flavor violation. In our model, the U(1)B-L gauge symmetry is broken at the TeV scale and standard model singlet neutrinos gain Majorana masses of order TeV. In addition, we introduce a flavor symmetry on the singlet neutrinos at a scale higher than TeV. The flavor symmetry is explicitly broken by the neutrino Dirac Yukawa coupling, which induces splittings in the singlet neutrino Majorana masses at lower scales through renormalization group evolutions. We call this setup minimal flavor violation. The mass splittings are proportional to the tiny Dirac Yukawa coupling, and hence they automatically enhance the CP asymmetry parameter necessary for the resonant leptogenesis mechanism. In this paper, we calculate the baryon number yield by solving the Boltzmann equations, including the effects of U(1)B-L gauge boson that also has TeV scale mass and causes washing-out of the singlet neutrinos in the course of thermal leptogenesis. The Dirac Yukawa coupling for neutrinos is fixed in terms of neutrino oscillation data and an arbitrary 3×3 complex-valued orthogonal matrix. We show that the right amount of baryon number asymmetry can be achieved through thermal leptogenesis in the context of the minimal flavor violation with singlet neutrinos and U(1)B-L gauge boson at the TeV scale. These particles can be discovered at the LHC in the near future.
Singularities and Closed String Tachyons
Silverstein, Eva; /SLAC /Stanford U., Phys. Dept.
2006-03-17
A basic problem in gravitational physics is the resolution of spacetime singularities where general relativity breaks down. The simplest such singularities are conical singularities arising from orbifold identifications of flat space, and the most challenging are spacelike singularities inside black holes (and in cosmology). Topology changing processes also require evolution through classically singular spacetimes. I briefly review how a phase of closed string tachyon condensate replaces, and helps to resolve, basic singularities of each of these types. Finally I discuss some interesting features of singularities arising in the small volume limit of compact negatively curved spaces and the emerging zoology of spacelike singularities.
NASA Astrophysics Data System (ADS)
Dijkgraaf, Robbert; Verlinde, Herman; Verlinde, Erik
1991-03-01
We calculate correlation functions in minimal topological field theories. These twisted versions of N = 2 minimal models have recently been proposed to describe d < 1 matrix models, once coupled to topological gravity. In our calculation we make use of the Landau-Ginzburg formulation of the N = 2 models, and we find a direct relation between the Landau-Ginzburg superpotential and the KdV differential operator. Using this correspondence we show that the minimal topological models are in perfect agreement with the matrix models as solved in terms of the KdV hierarchy. This proves the equivalence at tree-level of topological and ordinary string thoery in d < 1.
String inflation after Planck 2013
Burgess, C.P.; Cicoli, M.; Quevedo, F. E-mail: mcicoli@ictp.it
2013-11-01
We briefly summarize the impact of the recent Planck measurements for string inflationary models, and outline what might be expected to be learned in the near future from the expected improvement in sensitivity to the primordial tensor-to-scalar ratio. We comment on whether these models provide sufficient added value to compensate for their complexity, and ask how they fare in the face of the new constraints on non-gaussianity and dark radiation. We argue that as a group the predictions made before Planck agree well with what has been seen, and draw conclusions from this about what is likely to mean as sensitivity to primordial gravitational waves improves.
Extraordinary vacuum black string solutions
Kim, Hyeong-Chan; Lee, Jungjai
2008-01-15
In addition to the boosted static solution there are two other classes of stationary stringlike solutions of the vacuum Einstein equation in (4+1) dimensions. Each class is characterized by three parameters of mass, tension, and momentum flow along the fifth coordinate. We analyze the metric properties of one of the two classes, which was previously assumed to be naked singular, and show that the solution spectrum contains black string and wormhole in addition to the known naked singularity as the momentum flow to mass ratio increases. Interestingly, there does not exist new zero momentum solution in these cases.
NASA Astrophysics Data System (ADS)
Bena, Iosif; El-Showk, Sheer; Vercnocke, Bert
These lectures notes provide a fast-track introduction to modern developments in black hole physics within string theory, including microscopic computations of the black hole entropy as well as construction and quantization of microstates using supergravity. These notes are largely self-contained and should be accessible to students at an early PhD or Masters level. Topics covered include the black holes in supergravity, D-branes, Strominger-Vafa's computation of the black hole entropy via D-branes, AdS-CFT and its applications to black hole phyisics, multicenter solutions, and the geometric quantization of the latter.
Martins, R. A.
2007-08-15
The recent extension of the standard model to include massive neutrinos in the framework of noncommutative geometry and the spectral action principle involves new scalar fields and their interactions with the usual complex scalar doublet. After ensuring that they bring no unphysical consequences, we address the question of how these fields affect the physics predicted in the Weinberg-Salam theory, particularly in the context of the electroweak phase transition. Applying the Dolan-Jackiw procedure, we calculate the finite temperature corrections, and find that the phase transition is first order. The new scalar interactions significantly improve the stability of the electroweak Z string, through the 'bag' phenomenon described by Vachaspati and Watkins ['Bound states can stabilize electroweak strings', Phys. Lett. B 318, 163-168 (1993)]. (Recently, cosmic strings have climbed back into interest due to a new evidence.) Sourced by static embedded strings, an internal space analogy of Cartan's torsion is drawn, and a possible Higgs-force-like 'gravitational' effect of this nonpropagating torsion on the fermion masses is described. We also check that the field generating the Majorana mass for the {nu}{sub R} is nonzero in the physical vacuum.
Indriolo, Nick; McCall, Benjamin J
2013-10-07
Gas-phase chemistry in the interstellar medium is driven by fast ion-molecule reactions. This, of course, demands a mechanism for ionization, and cosmic rays are the ideal candidate as they can operate throughout the majority of both diffuse and dense interstellar clouds. Aside from driving interstellar chemistry via ionization, cosmic rays also interact with the interstellar medium in ways that heat the ambient gas, produce gamma rays, and produce light element isotopes. In this paper we review the observables generated by cosmic-ray interactions with the interstellar medium, focusing primarily on the relevance to astrochemistry.
Plucked String on a Shoestring Budget
ERIC Educational Resources Information Center
Gluck, Paul
2009-01-01
The physics of the plucked string has been treated in many articles and books. For our 12th-grade high school physics laboratory, we have built a cheap, simple sonometer apparatus for each pair of students on which they may investigate some interesting phenomena that arise when a string is plucked. Among these are the generation of harmonics…
Melt dumping in string stabilized ribbon growth
Sachs, Emanuel M.
1986-12-09
A method and apparatus for stabilizing the edge positions of a ribbon drawn from a melt includes the use of wettable strings drawn in parallel up through the melt surface, the ribbon being grown between the strings. A furnace and various features of the crucible used therein permit continuous automatic growth of flat ribbons without close temperature control or the need for visual inspection.
From surface roughening to QCD string theory
Keisuke Jimmy Juge et al.
2001-05-23
Surface critical phenomena and the related onset of Goldstone modes represent fundamental properties of the confining flux in Quantum Chromodynamics. New ideas on surface roughening and their implications for lattice studies of quark confinement and string formation are presented. Problems with a simple string description of the large Wilson surface are discussed.
Hydromonochord: Visualizing String Vibration by Water Swirls
ERIC Educational Resources Information Center
Sommer, Wilfried; Meier-Boke, Ralf; Meinzer, Nicholas
2010-01-01
The hydromonochord is a horizontal vibrating string that just makes contact with the surface of a water bath. The motion of the string sets up a pattern of swirls on the surface of the water, thus complementing the usual pattern of nodes and antinodes. The device is based on the traditional monochord. A water basin (Fig. 1) has two slits in the…
Topological string theory revisited I: The stage
NASA Astrophysics Data System (ADS)
Jia, Bei
2016-08-01
In this paper, we reformulate topological string theory using supermanifolds and supermoduli spaces, following the approach worked out by Witten (Superstring perturbation theory revisited, arXiv:1209.5461). We intend to make the construction geometrical in nature, by using supergeometry techniques extensively. The goal is to establish the foundation of studying topological string amplitudes in terms of integration over appropriate supermoduli spaces.
The Fate of Massive Closed Strings
Chen Bin; Li Miao; She Jianhuang
2005-12-02
We calculate the semi-inclusive decay rate of an average string state with toroidal compactification in the the superstring theory. We also apply this calculation to a brane-inflation model in a warped geometry and find that the decay rate is greatly suppressed if the final strings are both massive and enhanced for massless radiation.
A Computer String-Grammar of English.
ERIC Educational Resources Information Center
Sager, Naomi
This volume is the fourth in a series of detailed reports on a working computer program for the syntactic analysis of English sentences into their component strings. The report (1) records the considerations involved in various decisions among alternative grammatical formulations and presents the word-subclasses, the linguistic strings, etc., for…
String Theory: Big Problem for Small Size
ERIC Educational Resources Information Center
Sahoo, S.
2009-01-01
String theory is the most promising candidate theory for a unified description of all the fundamental forces that exist in nature. It provides a mathematical framework that combines quantum theory with Einstein's general theory of relativity. The typical size of a string is of the order of 10[superscript -33] cm, called the Planck length. But due…
Density fluctuations from strings and galaxy formation
NASA Technical Reports Server (NTRS)
Vilenkin, A.; Shafi, Q.
1983-01-01
The spectra of density fluctuations caused by strings in a universe dominated either by baryons, neutrinos, or axions are presented. Realistic scenarios for galaxy formation seem possible in all three cases. Examples of grand unified theories which lead to strings with the desired mass scales are given.
No-scale supergravity inflation: A bridge between string theory and particle physics?
NASA Astrophysics Data System (ADS)
Ellis, John
The plethora of recent and forthcoming data on the cosmic microwave background (CMB) data are stimulating a new wave of inflationary model-building. Naturalness suggests that the appropriate framework for models of inflation is supersymmetry. This should be combined with gravity in a supergravity theory, whose specific no-scale version has much to commend it, e.g. its derivation from string theory and the flat directions in its effective potential. Simple no-scale supergravity models yield predictions similar to those of the Starobinsky R + R2 model, though some string-motivated versions make alternative predictions. Data are beginning to provide interesting constraints on the rate of inflaton decay into Standard Model particles. In parallel, LHC and other data provide significant constraints on no-scale supergravity models, which suggest that some sparticles might have masses close to present experimental limits.
Planckian axions in string theory
NASA Astrophysics Data System (ADS)
Bachlechner, Thomas C.; Long, Cody; McAllister, Liam
2015-12-01
We argue that super-Planckian diameters of axion fundamental domains can arise in Calabi-Yau compactifications of string theory. In a theory with N axions θ i , the fundamental domain is a polytope defined by the periodicities of the axions, via constraints of the form - π < Q i j θ j < π. We compute the diameter of the fundamental domain in terms of the eigenvalues f 1 2 ≤ … ≤ f N 2 of the metric on field space, and also, crucially, the largest eigenvalue of ( QQ ⊤)-1. At large N, QQ ⊤ approaches a Wishart matrix, due to universality, and we show that the diameter is at least Nf N , exceeding the naive Pythagorean range by a factor > √{N} . This result is robust in the presence of P > N constraints, while for P = N the diameter is further enhanced by eigenvector delocalization to N 3/2 f N . We directly verify our results in explicit Calabi-Yau compactifications of type IIB string theory. In the classic example with h 1,1 = 51 where parametrically controlled moduli stabilization was demonstrated by Denef et al. in [1], the largest metric eigenvalue obeys f N ≈ 0.013 M pl. The random matrix analysis then predicts, and we exhibit, axion diameters ≈ M pl for the precise vacuum parameters found in [1]. Our results provide a framework for pursuing large-field axion inflation in well-understood flux vacua.
Statistical inference and string theory
NASA Astrophysics Data System (ADS)
Heckman, Jonathan J.
2015-09-01
In this paper, we expose some surprising connections between string theory and statistical inference. We consider a large collective of agents sweeping out a family of nearby statistical models for an M-dimensional manifold of statistical fitting parameters. When the agents making nearby inferences align along a d-dimensional grid, we find that the pooled probability that the collective reaches a correct inference is the partition function of a nonlinear sigma model in d dimensions. Stability under perturbations to the original inference scheme requires the agents of the collective to distribute along two dimensions. Conformal invariance of the sigma model corresponds to the condition of a stable inference scheme, directly leading to the Einstein field equations for classical gravity. By summing over all possible arrangements of the agents in the collective, we reach a string theory. We also use this perspective to quantify how much an observer can hope to learn about the internal geometry of a superstring compactification. Finally, we present some brief speculative remarks on applications to the AdS/CFT correspondence and Lorentzian signature space-times.
Natural quintessence in string theory
Cicoli, Michele; Pedro, Francisco G.; Tasinato, Gianmassimo E-mail: f.pedro1@physics.ox.ac.uk
2012-07-01
We introduce a natural model of quintessence in string theory where the light rolling scalar is radiatively stable and couples to Standard Model matter with weaker-than-Planckian strength. The model is embedded in an anisotropic type IIB compactification with two exponentially large extra dimensions and TeV-scale gravity. The bulk turns out to be nearly supersymmetric since the scale of the gravitino mass is of the order of the observed value of the cosmological constant. The quintessence field is a modulus parameterising the size of an internal four-cycle which naturally develops a potential of the order (gravitino mass){sup 4}, leading to a small dark energy scale without tunings. The mass of the quintessence field is also radiatively stable since it is protected by supersymmetry in the bulk. Moreover, this light scalar couples to ordinary matter via its mixing with the volume mode. Due to the fact that the quintessence field is a flat direction at leading order, this mixing is very small, resulting in a suppressed coupling to Standard Model particles which avoids stringent fifth-force constraints. On the other hand, if dark matter is realised in terms of Kaluza-Klein states, unsuppressed couplings between dark energy and dark matter can emerge, leading to a scenario of coupled quintessence within string theory. We study the dynamics of quintessence in our set-up, showing that its main features make it compatible with observations.
Bose-Einstein condensate strings
NASA Astrophysics Data System (ADS)
Harko, Tiberiu; Lake, Matthew J.
2015-02-01
We consider the possible existence of gravitationally bound general relativistic strings consisting of Bose-Einstein condensate (BEC) matter which is described, in the Newtonian limit, by the zero temperature time-dependent nonlinear Schrödinger equation (the Gross-Pitaevskii equation), with repulsive interparticle interactions. In the Madelung representation of the wave function, the quantum dynamics of the condensate can be formulated in terms of the classical continuity equation and the hydrodynamic Euler equations. In the case of a condensate with quartic nonlinearity, the condensates can be described as a gas with two pressure terms, the interaction pressure, which is proportional to the square of the matter density, and the quantum pressure, which is without any classical analogue, though, when the number of particles in the system is high enough, the latter may be neglected. Assuming cylindrical symmetry, we analyze the physical properties of the BEC strings in both the interaction pressure and quantum pressure dominated limits, by numerically integrating the gravitational field equations. In this way we obtain a large class of stable stringlike astrophysical objects, whose basic parameters (mass density and radius) depend sensitively on the mass and scattering length of the condensate particle, as well as on the quantum pressure of the Bose-Einstein gas.
NASA Astrophysics Data System (ADS)
Ketov, Sergei V.; Lechtenfeld, Olaf; Parkes, Andrew J.
1995-03-01
The most general homogeneous monodromy conditions in N=2 string theory are classified in terms of the conjugacy classes of the global symmetry group U(1,1)⊗openZ2. For classes which generate a discrete subgroup Γ, the corresponding target space backgrounds openC1,1/Γ include half spaces, complex orbifolds, and tori. We propose a generalization of the intercept formula to matrix-valued twists, but find massless physical states only for Γ=open1 (untwisted) and Γ=openZ2 (in the manner of Mathur and Mukhi), as well as for Γ being a parabolic element of U(1,1). In particular, the 16 openZ2-twisted sectors of the N=2 string are investigated, and the corresponding ground states are identified via bosonization and BRST cohomology. We find enough room for an extended multiplet of ``spacetime'' supersymmetry, with the number of supersymmetries being dependent on global ``spacetime'' topology. However, world-sheet locality for the chiral vertex operators does not permit interactions among all massless ``spacetime'' fermions.
Paraquantum strings in noncommutative space-time
NASA Astrophysics Data System (ADS)
Seridi, M. A.; Belaloui, N.
2015-10-01
A parabosonic string is assumed to propagate in a total noncommutative target phase space. Three models are investigated: open strings, open strings between two parallel Dp-Dq branes and closed ones. This leads to a generalization of the oscillators algebra of the string and the corresponding Virasoro algebra. The mass operator is no more diagonal in the ordinary Fock space, a redefinition of this later will modify the mass spectrum, so that, neither massless vector state nor massless tensor state are present. The restoration of the photon and the graviton imposes specific forms of the noncommutativity parameter matrices, partially removes the mass degeneracy and gives new additional ones. In particular, for the D-branes, one can have a tachyon free model with a photon state when more strict conditions on these parameters are imposed, while, the match level condition of the closed string model induces the reduction of the spectrum.
Plucked String on a Shoestring Budget
NASA Astrophysics Data System (ADS)
Gluck, Paul
2009-01-01
The physics of the plucked string has been treated in many articles and books.1-4 For our 12th-grade high school physics laboratory, we have built a cheap, simple sonometer apparatus for each pair of students on which they may investigate some interesting phenomena that arise when a string is plucked. Among these are the generation of harmonics (overtones) and the way their number depends on the length of a string and on where one plucks, the relation between the frequencies of the fundamental and those of the harmonics, and the way these are affected by changes in the length and the tension in the string. Such an experiment will help students appreciate the working of stringed musical instruments and, in particular, the contribution of overtones to the richness of sound produced.
String theory of the Regge intercept.
Hellerman, S; Swanson, I
2015-03-20
Using the Polchinski-Strominger effective string theory in the covariant gauge, we compute the mass of a rotating string in D dimensions with large angular momenta J, in one or two planes, in fixed ratio, up to and including first subleading order in the large J expansion. This constitutes a first-principles calculation of the value for the order-J(0) contribution to the mass squared of a meson on the leading Regge trajectory in planar QCD with bosonic quarks. For open strings with Neumann boundary conditions, and for closed strings in D≥5, the order-J(0) term in the mass squared is exactly calculated by the semiclassical approximation. This term in the expansion is universal and independent of the details of the theory, assuming only D-dimensional Poincaré invariance and the absence of other infinite-range excitations on the string world volume, beyond the Nambu-Goldstone bosons.
Using cosmic rays to monitor large scintillator arrays
Knauer, J.P.; Kremens, R.L.; Russotto, M.A.; Tudman, S. )
1995-01-01
Large arrays of scintillator-photomultiplier detectors are becoming the technique of choice to measure neutron spectrum from ICF implosions. A 32[times]30 array of detectors is currently under construction at LLE (MEDUSA). This array is at an angle of 26[degree] relative to vertical and thus cosmic rays can be used to monitor individual channel performance. We will present: an analysis of the expected count rates and expected signal levels for single scintillator-photomultiplier detectors; a comparison of the above analysis to a test string of 30 detectors mounted in the MEDUSA frame; and the triggering scheme used to acquire data for routine operation of the instrument.
NASA Technical Reports Server (NTRS)
Mccammon, Dan; Cox, D. P.; Kraushaar, W. L.; Sanders, W. T.
1990-01-01
The annual progress report on Cosmic X Ray Physics is presented. Topics studied include: the soft x ray background, proportional counter and filter calibrations, the new sounding rocket payload: X Ray Calorimeter, and theoretical studies.
NASA Technical Reports Server (NTRS)
Mccammon, Dan; Cox, D. P.; Kraushaar, W. L.; Sanders, W. T.
1991-01-01
The annual progress report on Cosmic X Ray Physics for the period 1 Jan. to 31 Dec. 1990 is presented. Topics studied include: soft x ray background, new sounding rocket payload: x ray calorimeter, and theoretical studies.
Astrophysics: Cosmic jet engines
NASA Astrophysics Data System (ADS)
Young, Andy
2010-02-01
In some galaxies, matter falling onto a supermassive black hole is ejected in narrow jets moving at close to the speed of light. New observations provide insight into the workings of these cosmic accelerators.
NASA Technical Reports Server (NTRS)
Wu, S. T.
2000-01-01
The cosmic ray division participation in the cooperative agreement was activated in the second year. The scientific goals will be analysis of cosmic ray data from the Japanese-American Cooperative Emulsion Experiments (JACEE). Measurements of primary cosmic rays in the JACEE emulsion chambers will be made to derive for each detected particle the deposited energy in the chamber and the primary charge (atomic number). The data will be corrected to the primary flux above the atmosphere, and the composition and energy spectra will be derived. The spectra of the individual elements will be interpreted in context with the supernova shock and other models of cosmic ray acceleration. Additional information is contained in the original extended abstract.
COSMIC monthly progress report
NASA Technical Reports Server (NTRS)
1994-01-01
Activities of the Computer Software Management and Information Center (COSMIC) are summarized for the month of January 1994. Tables showing the current inventory of programs available from COSMIC are presented and program processing and evaluation activities are discussed. Marketing and customer service activities in this period are presented as is the progress report of NASTRAN maintenance and support. Tables of disseminations and budget summary conclude the report.
NASA Astrophysics Data System (ADS)
Atkinson, M.
2011-06-01
This paper discusses the intertwined relationship between the terrestrial and celestial using the labyrinth as a metaphor referencing sources from art, gardens and Australian Indigenous culture. Including the Morning Star with the labyrinthine mortuary ritual in Arnhem Land, the cosmic plan garden at Auschwitz and Marea Atkinson's art project undertaken at the Villa Garzoni garden in Italy to create The Cosmic Labyrinth installation exhibited at Palazzo Franchetti, Venice, during the sixth conference on the Inspiration of Astronomical Phenomena.
The strings connection: MSSM-like models from strings
NASA Astrophysics Data System (ADS)
Nilles, Hans Peter
2014-05-01
String theory constructions towards the MSSM allow us to identify some general properties that could be relevant for tests at the LHC. They originate from the geometric structure of compactification and the location of fields in extra-dimensional space. Within the framework of the heterotic MiniLandscape we extract some generic lessons for supersymmetric model building. Among them is a specific pattern of SUSY breakdown based on mirage mediation and remnants of extended supersymmetry. This leads to a split spectrum with heavy scalars of the first two families of quarks and leptons and suppressed masses for gauginos, top partners and Higgs bosons. The models exhibit some specific form of hidden supersymmetry consistent with the high mass of the Higgs boson and all presently available experimental constraints. The most compelling picture is based on precision gauge coupling unification that might be in the kinematic reach of the LHC.
NASA Astrophysics Data System (ADS)
Isenberg, James
2017-01-01
The Hawking-Penrose theorems tell us that solutions of Einstein's equations are generally singular, in the sense of the incompleteness of causal geodesics (the paths of physical observers). These singularities might be marked by the blowup of curvature and therefore crushing tidal forces, or by the breakdown of physical determinism. Penrose has conjectured (in his `Strong Cosmic Censorship Conjecture`) that it is generically unbounded curvature that causes singularities, rather than causal breakdown. The verification that ``AVTD behavior'' (marked by the domination of time derivatives over space derivatives) is generically present in a family of solutions has proven to be a useful tool for studying model versions of Strong Cosmic Censorship in that family. I discuss some of the history of Strong Cosmic Censorship, and then discuss what is known about AVTD behavior and Strong Cosmic Censorship in families of solutions defined by varying degrees of isometry, and discuss recent results which we believe will extend this knowledge and provide new support for Strong Cosmic Censorship. I also comment on some of the recent work on ``Weak Null Singularities'', and how this relates to Strong Cosmic Censorship.
Systematic U(1 ) B - L extensions of loop-induced neutrino mass models with dark matter
NASA Astrophysics Data System (ADS)
Ho, Shu-Yu; Toma, Takashi; Tsumura, Koji
2016-08-01
We study the gauged U(1 ) B - L extensions of the models for neutrino masses and dark matter. In this class of models, tiny neutrino masses are radiatively induced through the loop diagrams, while the origin of the dark matter stability is guaranteed by the remnant of the gauge symmetry. Depending on how the lepton number conservation is violated, these models are systematically classified. We present complete lists for the one-loop Z2 and the two-loop Z3 radiative seesaw models as examples of the classification. The anomaly cancellation conditions in these models are also discussed.
Phenomenology of the minimal B-L extension of the standard model: The Higgs sector
Basso, Lorenzo; Moretti, Stefano; Pruna, Giovanni Marco
2011-03-01
We investigate the phenomenology of the Higgs sector of the minimal B-L extension of the standard model. We present results for both the foreseen energy stages of the Large Hadron Collider ({radical}(s)=7 and 14 TeV). We show that in such a scenario several novel production and decay channels involving the two physical Higgs states could be accessed at such a machine. Amongst these, several Higgs signatures have very distinctive features with respect to those of other models with an enlarged Higgs sector, as they involve interactions of Higgs bosons between themselves, with Z{sup '} bosons as well as with heavy neutrinos.
Gauged B-L symmetry and baryogenesis via leptogenesis at TeV scale
Sahu, Narendra; Yajnik, Urjit A.
2005-01-15
It is shown that the requirement of preservation of baryon asymmetry does not rule out a scale for leptogenesis as low as 10 TeV. The conclusions are compatible with see-saw mechanism if, for example, the pivot mass scale for neutrinos is {approx_equal}10{sup -2} that of the charged leptons. We explore the parameter space m-tilde{sub 1}- M{sub 1} of relevant light and heavy neutrino masses by solving Boltzmann equations. A viable scenario for obtaining baryogenesis in this way is presented in the context of gauged B-L symmetry.
Inflation in string theory: A graceful exit to the real world
Cicoli, Michele; Mazumdar, Anupam
2011-03-15
The most important criteria for a successful inflation are: explaining the observed temperature anisotropy in the cosmic microwave background radiation, and exiting inflation in a vacuum where it can excite the standard model quarks and leptons required for the success of big bang nucleosynthesis. In this paper, we provide the first ever closed-string model of inflation where the inflaton couplings to hidden sector, moduli sector, and visible sector fields can be computed, showing that inflation can lead to reheating the standard model degrees of freedom before the electro-weak scale.
Worldsheet factorization for twistor-strings
NASA Astrophysics Data System (ADS)
Adamo, Tim
2014-04-01
We study the multiparticle factorization properties of two worldsheet theories which — at tree-level — describe the scattering of massless particles in four dimensions: the Berkovits-Witten twistor-string for = 4 super-Yang-Mills coupled to = 4 conformal supergravity, and the Skinner twistor-string for = 8 supergravity. By considering these string-like theories, we can study factorization at the level of the worldsheet before any Wick contractions or integrals have been performed; this is much simpler than considering the factorization properties of the amplitudes themselves. In Skinner's twistor-string this entails the addition of worldsheet gravity as well as a formalism that represents all external states in a manifestly symmetric way, which we develop explicitly at genus zero. We confirm that the scattering amplitudes of Skinner's theory, as well as the gauge theory amplitudes for the planar sector of the Berkovits-Witten theory, factorize appropriately at genus zero. In the non-planar sector, we find behavior indicative of conformal gravity in the Berkovits-Witten twistor-string. We contrast factorization in twistor-strings with the story in ordinary string theory, and also make some remarks on higher genus factorization and disconnected prescriptions.
Effects of overlapping strings in pp collisions
Bierlich, Christian; Gustafson, Gösta; Lönnblad, Leif; ...
2015-03-26
In models for hadron collisions based on string hadronization, the strings are usually treated as independent, allowing no interaction between the confined colour fields. In studies of nucleus collisions it has been suggested that strings close in space can fuse to form "colour ropes." Such ropes are expected to give more strange particles and baryons, which also has been suggested as a signal for plasma formation. Overlapping strings can also be expected in pp collisions, where usually no phase transition is expected. In particular at the high LHC energies the expected density of strings is quite high. To investigate possiblemore » effects of rope formation, we present a model in which strings are allowed to combine into higher multiplets, giving rise to increased production of baryons and strangeness, or recombine into singlet structures and vanish. Also a crude model for strings recombining into junction structures is considered, again giving rise to increased baryon production. The models are implemented in the DIPSY MC event generator, using PYTHIA8 for hadronization, and comparison to pp minimum bias data, reveals improvement in the description of identified particle spectra.« less
Effects of overlapping strings in pp collisions
Bierlich, Christian; Gustafson, Gösta; Lönnblad, Leif; Tarasov, Andrey
2015-03-26
In models for hadron collisions based on string hadronization, the strings are usually treated as independent, allowing no interaction between the confined colour fields. In studies of nucleus collisions it has been suggested that strings close in space can fuse to form "colour ropes." Such ropes are expected to give more strange particles and baryons, which also has been suggested as a signal for plasma formation. Overlapping strings can also be expected in pp collisions, where usually no phase transition is expected. In particular at the high LHC energies the expected density of strings is quite high. To investigate possible effects of rope formation, we present a model in which strings are allowed to combine into higher multiplets, giving rise to increased production of baryons and strangeness, or recombine into singlet structures and vanish. Also a crude model for strings recombining into junction structures is considered, again giving rise to increased baryon production. The models are implemented in the DIPSY MC event generator, using PYTHIA8 for hadronization, and comparison to pp minimum bias data, reveals improvement in the description of identified particle spectra.
Hall, David R.; Dahlgren, Scott; Hall, Jr., Tracy H.; Fox, Joe; Pixton, David S.
2007-07-17
An apparatus in a drill string comprises an internally upset drill pipe. The drill pipe comprises a first end, a second end, and an elongate tube intermediate the first and second ends. The elongate tube and the ends comprising a continuous an inside surface with a plurality of diameters. A conformable spirally welded metal tube is disposed within the drill pipe intermediate the ends thereof and terminating adjacent to the ends of the drill pipe. The conformable metal tube substantially conforms to the continuous inside surface of the metal tube. The metal tube may comprise a non-uniform section which is expanded to conform to the inside surface of the drill pipe. The non-uniform section may comprise protrusions selected from the group consisting of convolutions, corrugations, flutes, and dimples. The non-uniform section extends generally longitudinally along the length of the tube.
Stabilizing semilocal strings by polarization
NASA Astrophysics Data System (ADS)
Eto, Minoru; Nitta, Muneto; Sakurai, Kohei
2016-10-01
Semilocal strings are vortices in the extended Abelian-Higgs model with two complex Higgs scalar fields among which a global SU(2) symmetry acts. They are known to be stable (unstable against expansion) in type-I (II) superconductors, in which gauge field is heavier (lighter) than the Higgs scalar field. In this paper, we find that vortices can be stabilized in the whole parameter region including the type-II region by adding a potential term breaking the SU(2) symmetry. We construct numerical solutions in various parameters and determine the vortex phase diagram consisting of six phases. In two phases, a vortex is polarized, that is, split into two half-quantized vortices with a certain distance, to form a vortex molecule, while in the rests a vortex is identical to the conventional Abrikosov-Nielsen-Olesen vortex.
Hubeny, Veronika; Maloney, Alexander; Rangamani, Mukund
2005-02-07
We investigate the geometry of four dimensional black hole solutions in the presence of stringy higher curvature corrections to the low energy effective action. For certain supersymmetric two charge black holes these corrections drastically alter the causal structure of the solution, converting seemingly pathological null singularities into timelike singularities hidden behind a finite area horizon. We establish, analytically and numerically, that the string-corrected two-charge black hole metric has the same Penrose diagram as the extremal four-charge black hole. The higher derivative terms lead to another dramatic effect -- the gravitational force exerted by a black hole on an inertial observer is no longer purely attractive! The magnitude of this effect is related to the size of the compactification manifold.
Charged rotating dilaton black strings
Dehghani, M.H.; Farhangkhah, N.
2005-02-15
In this paper we, first, present a class of charged rotating solutions in four-dimensional Einstein-Maxwell-dilaton gravity with zero and Liouville-type potentials. We find that these solutions can present a black hole/string with two regular horizons, an extreme black hole or a naked singularity provided the parameters of the solutions are chosen suitable. We also compute the conserved and thermodynamic quantities, and show that they satisfy the first law of thermodynamics. Second, we obtain the (n+1)-dimensional rotating solutions in Einstein-dilaton gravity with Liouville-type potential. We find that these solutions can present black branes, naked singularities or spacetimes with cosmological horizon if one chooses the parameters of the solutions correctly. Again, we find that the thermodynamic quantities of these solutions satisfy the first law of thermodynamics.
Whiteheadian Actual Entitities and String Theory
NASA Astrophysics Data System (ADS)
Bracken, Joseph A.
2012-06-01
In the philosophy of Alfred North Whitehead, the ultimate units of reality are actual entities, momentary self-constituting subjects of experience which are too small to be sensibly perceived. Their combination into "societies" with a "common element of form" produces the organisms and inanimate things of ordinary sense experience. According to the proponents of string theory, tiny vibrating strings are the ultimate constituents of physical reality which in harmonious combination yield perceptible entities at the macroscopic level of physical reality. Given that the number of Whiteheadian actual entities and of individual strings within string theory are beyond reckoning at any given moment, could they be two ways to describe the same non-verifiable foundational reality? For example, if one could establish that the "superject" or objective pattern of self- constitution of an actual entity vibrates at a specific frequency, its affinity with the individual strings of string theory would be striking. Likewise, if one were to claim that the size and complexity of Whiteheadian 'societies" require different space-time parameters for the dynamic interrelationship of constituent actual entities, would that at least partially account for the assumption of 10 or even 26 instead of just 3 dimensions within string theory? The overall conclusion of this article is that, if a suitably revised understanding of Whiteheadian metaphysics were seen as compatible with the philosophical implications of string theory, their combination into a single world view would strengthen the plausibility of both schemes taken separately. Key words: actual entities, subject/superjects, vibrating strings, structured fields of activity, multi-dimensional physical reality.
A heterotic standard model with B - L symmetry and a stable proton
NASA Astrophysics Data System (ADS)
Buchbinder, Evgeny I.; Constantin, Andrei; Lukas, Andre
2014-06-01
We consider heterotic Calabi-Yau compactifications with S(U(4) × U(1)) background gauge fields. These models lead to gauge groups with an additional U(1) factor which, under certain conditions, can combine with hypercharge to a B - L symmetry. The associated gauge boson is automatically super-massive and, hence, does not constitute a phenomenological problem. We illustrate this class of compactifications with a model based on the monad construction, which leads to a supersymmetric standard model with three families of quarks and leptons, one pair of Higgs doublets, three right-handed neutrinos and no exotics charged under the standard model group. The presence of the B - L symmetry means that the model is safe from proton decay induced by dimension four operators. Due to the presence of a special locus in moduli space where the bundle structure group is Abelian and the low-energy symmetry enhances we can also show the absence of dimension five proton-decay inducing operators.
Viols and Other Historic Bowed String Instruments
NASA Astrophysics Data System (ADS)
Campbell, Murray; Campbell, Patsy
While plucked strings have been used for musical purposes since at least the third millennium BCE, the idea of sounding a string by bowing it is a much more recent development. Bowed string instruments seem to have originated in Asia toward the end of the first millennium CE, and were in widespread use in Western Europe by the end of the eleventh century. For the next three centuries many different types of bowed instrument, with a bewildering variety of names, were in common use throughout Europe.
Observation of Motion of Bowed Strings and Resonant Strings in Violin Performances
NASA Astrophysics Data System (ADS)
Matsutani, Akihiro
2013-10-01
The motion of a bowed string and a resonant string of a violin were simultaneously observed for the first time. The results of the direct observation of string motion in double stops and harmonics are also presented. The importance of the resonance was experimentally demonstrated from these observations. It is suggested that players should take account of the resonance and ideal Helmholtz motion in violin performances.
Cosmic questions: an introduction.
Primack, J R; Abrams, N E
2001-12-01
This introductory talk at the Cosmic Questions conference sponsored by the AAAS summarizes some earlier pictures of the universe and some pictures based on modern physics and cosmology. The uroboros (snake swallowing its tail) is an example of a traditional picture. The Biblical flat-earth picture was very different from the Greek spherical earth-centered picture, which was the standard view until the end of the Middle Ages. Many people incorrectly assume that the Newtonian picture of stars scattered through otherwise empty space is still the prevailing view. Seeing Earth from space shows the power of a new picture. The Hubble Space Telescope can see all the bright galaxies, all the way to the cosmic Dark Ages. We are at the center of cosmic spheres of time: looking outward is looking backward in time. All the matter and energy in the universe can be represented as a cosmic density pyramid. The laws of physics only allow the material objects in the universe to occupy a wedge-shaped region on a diagram of mass versus size. All sizes--from the smallest size scale, the Planck scale, to the entire visible universe--can be represented on the Cosmic Uroboros. There are interesting connections across this diagram, and the human scale lies in the middle.
Open-closed string duality at tree level.
Sen, Ashoke
2003-10-31
We study the decay of unstable D-branes in string theory in the presence of an electric field, and show that the classical open string theory results for various properties of the final state agree with the properties of closed string states into which the system is expected to decay. This suggests a duality between tree level open string theory on unstable D-branes and closed strings at high density.
Introduction to string and superstring theory II
Peskin, M.E.
1987-03-01
Conformal field theory is reviewed, then conformal invariance is used to rederive the basic results on the embedding dimensionality for bosonic and fermionic strings. The spectrum of the bosonic and the computation of scattering amplitudes are discussed. The formalism used is extended to clarify the origin of Yang-Mills gauge invariance in the open bosonic string theory. The question of the general-coordinate gauge invariance of string theory is addressed, presenting two disparate viewpoints on this question. A brief introduction is then given of the reduction from the idealized string theory in 10 extended dimensions to more realistic solutions in which all but 4 of these dimensions are compactified. The state of knowledge about the space-time supersymmetry of the superstring from the covariant viewpoint is outlined. An approach for identifying possible 6-dimensional spaces which might represent the form of the compact dimensions is discussed, and the orbifold scheme of compactification is presented. 77 refs., 18 figs. (LEW)
Beads + String = Atoms You Can See.
ERIC Educational Resources Information Center
Hermann, Christine K. F.
1998-01-01
Presents hands-on activities that give students a head start in learning the vocabulary and basic theory involved in understanding atomic structure. Uses beads to represent protons, neutrons, and electrons and string to represent orbitals. (DDR)
Towards a theory of the QCD string
NASA Astrophysics Data System (ADS)
Dubovsky, Sergei; Gorbenko, Victor
2016-02-01
We construct a new model of four-dimensional relativistic strings with integrable dynamics on the worldsheet. In addition to translational modes this model contains a single massless pseudoscalar worldsheet field — the worldsheet axion. The axion couples to a topological density which counts the self-intersection number of a string. The corresponding coupling is fixed by integrability to Q=√{7/16π }≈ 0.37 . We argue that this model is a member of a larger family of relativistic non-critical integrable string models. This family includes and extends conventional non-critical strings described by the linear dilaton CFT. Intriguingly, recent lattice data in SU(3) and SU(5) gluodynamics reveals the presence of a massive pseudoscalar axion on the worldsheet of confining flux tubes. The value of the corresponding coupling, as determined from the lattice data, is equal to Q L ≈ 0 .38 ± 0 .04.
NASA Astrophysics Data System (ADS)
Furlanetto, Steven
The following sections are included: * A Brief History of Our Universe: From Soup to Galaxies * The Hidden Cosmic Dawn * The Solution: Flipping Spins * The Spin-Flip Transition as an Astronomical Tool * Foiled!: Early Cosmology with the Spin-Flip Transition * Spin-Flip Radiation Holds the Key to Observing the Cosmic Dawn * The Spin-Flip Background: The First Stars * The Spin-Flip Background: The First Black Holes * The Spin-Flip Background: The Epoch of Reionization * FM Radio Antennae as Cosmic Observatories * Piles and Tiles of Antennae: Mapping the Spin-Flip Background * Mountains to Scale: Challenges to Observing the Spin-Flip Background * Sound and Fury, Signifying Statistics * An Explosion of Telescopes * Dreams for the Future * An Unfinished Story
Inhomogeneous Einstein-Rosen string cosmology
NASA Astrophysics Data System (ADS)
Clancy, Dominic; Feinstein, Alexander; Lidsey, James E.; Tavakol, Reza
1999-08-01
Families of anisotropic and inhomogeneous string cosmologies containing non-trivial dilaton and axion fields are derived by applying the global symmetries of the string effective action to a generalized Einstein-Rosen metric. The models exhibit a two-dimensional group of Abelian isometries. In particular, two classes of exact solutions are found that represent inhomogeneous generalizations of the Bianchi type VIh cosmology. The asymptotic behavior of the solutions is investigated and further applications are briefly discussed.
String perturbation theory and effective Lagrangians
Klebanov, I.
1987-09-01
We isolate logarithmic divergences from bosonic string amplitudes on a disc. These divergences are compared with 'tadpole' divergences in the effective field theory with a cosmological term, which also contains an effective potential for the dilation. Also, corrections to ..beta..-functions are compared with variations of the effective action. In both cases we find an inconsistency between the two. This is a serious problem which could undermine our ability to remove divergences from the bosonic string.
Effective string description of confining flux tubes
NASA Astrophysics Data System (ADS)
Brandt, Bastian B.; Meineri, Marco
2016-08-01
We review the current knowledge about the theoretical foundations of the effective string theory for confining flux tubes and the comparison of the predictions to pure gauge lattice data. A concise presentation of the effective string theory is provided, incorporating recent developments. We summarize the predictions for the spectrum and the profile/width of the flux tube and their comparison to lattice data. The review closes with a short summary of open questions for future research.
Moduli Stabilization Using Open String Fluxes
NASA Astrophysics Data System (ADS)
Kumar, Alok
2007-04-01
In this talk we discuss how by turning on gauge fluxes which couple to the end-points of open strings one can obtain stabilization of closed string moduli. This is done by analyzing supersymmetry constraints and RR tadpole conditions. Stabilization of complex and Kahler moduli is studied in a T6/Z2 orientifold.
Mirage pattern from the heterotic string
Loewen, Valeri; Nilles, Hans Peter
2008-05-15
We provide a simple example of dilaton stabilization in the framework of heterotic string theory. It requires a gaugino condensate and an uplifting sector similar to the one postulated in type IIB string theory. Its signature is a hybrid mediation of supersymmetry breakdown with a variant of a mirage pattern for the soft breaking terms. The setup is suited for the discussion of heterotic minimal supersymmetric standard model candidates.
Electron string phenomenon: physics and use
NASA Astrophysics Data System (ADS)
Donets, Evgeny D.
2004-01-01
Electron string phenomenon arises as a result of phase transition of a state of multiply reflected electron beam to this new discovered state of one component electron plasma and can be easily observed in the reflex mode of EBIS operation. The transition goes via a strong instability, which causes considerable electron energy spread, which in its turn suppresses the instability. Electron string state is a stationary state of hot pure electron plasma, which is heated by injected electron beam and cooled because of electron loses. Electron string is quiet in broad regions of experimental parameters, so that it is used for confinement and ionization of positive ions by electron impact to highly charge states similar to electron beams in EBIS. Application of electron strings instead of electron beams for ion production allows to save about 99% of electric power of electron beam and simultaneously to improve reliability of an ion source considerably. The JINR EBIS `Krion-2' in the string mode of operation is used for production of N7+, Ar16+ and Fe24+ ion beams and their acceleration to relativistic energies on the facility of the JINR super conducting one turn injection synchrotron `Nuklotron'. The tubular electron string possibly can exist and it is under study now theoretically and experiments are prepared now. Estimations show that a Tubular Electron String Ion Source (TESIS) could have up to three orders of magnitude higher ion output then a Linear one (LESIS). In frames of nuclear astrophysics electron strings can be used for research of fusion nuclear reactions at low energies in conditions when both beam and target nuclei do not carry orbital electrons. The project NARITA — Nuclear Astrophysics Researches in an Ion Trap Apparatus is proposed. Polarization effects also can be studied.
Hamiltonian formulation of string field theory
NASA Astrophysics Data System (ADS)
Siopsis, George
1987-09-01
Witten's string field theory is quantized in the hamiltonian formalism. The constraints are solved and the hamiltonian is expressed in terms of only physical degrees of freedom. Thus, no Faddeev-Popov ghosts are introduced. Instead, the action contains terms of arbitrarily high order in the string functionals. Agreement with the standard results is demonstrated by an explicit calculation of the residues of the first few poles of the four-tachyon tree amplitude.
NASA Technical Reports Server (NTRS)
Wefel, J. P.
1981-01-01
A general overview of supernova astronomy is presented, followed by a discussion of the relationship between SN and galactic cosmic rays. Pre-supernova evolution is traced to core collapse, explosion, and mass ejection. The two types of SN light curves are discussed in terms of their causes, and the different nucleosynthetic processes inside SNs are reviewed. Physical events in SN remnants are discussed. The three main connections between cosmic rays and SNs, the energy requirement, the acceleration mechanism, and the detailed composition of CR, are detailed.
Unwinding the von Willebrand factor strings puzzle.
De Ceunynck, Karen; De Meyer, Simon F; Vanhoorelbeke, Karen
2013-01-10
von Willebrand factor (VWF) is amongst others synthesized by endothelial cells and stored as ultra-large (UL) VWF multimers in Weibel-Palade bodies. Although UL-VWF is proteolysed by ADAMTS13 (a disintegrin-like and metalloprotease domain with thrombospondin type-1 motif, number 13) on secretion from endothelial cells, in vitro experiments in the absence of ADAMTS13 have demonstrated that a proportion of these UL-VWF multimers remain anchored to the activated endothelium. These multimers unravel, bind platelets, and wave in the direction of the flow. These so-called VWF "strings" have also been visualized in vivo, lining the lumen of activated mesenteric veins of Adamts13(-/-) mice. Various studies have demonstrated the extraordinary length of these VWF strings, the availability of their platelet binding and ADAMTS13 cleavage sites, and the possible nature of their endothelial attachment. VWF strings are also capable of tethering leukocytes and parasite-infected red blood cells. However, the majority of studies have been performed in the absence of ADAMTS13, a condition only experienced in thrombotic thrombocytopenic purpura. A normal functional role of VWF strings in healthy persons or in other disease pathologies remains unclear. In this review, we discuss some of the puzzling characteristics of VWF strings, and we debate whether the properties of VWF strings in the absence of ADAMTS13 might be relevant for understanding (patho)physiologic mechanisms.
NASA Astrophysics Data System (ADS)
Callebaut, Nele; Gubser, Steven S.; Samberg, Andreas; Toldo, Chiara
2015-11-01
We study segmented strings in flat space and in AdS 3. In flat space, these well known classical motions describe strings which at any instant of time are piecewise linear. In AdS 3, the worldsheet is composed of faces each of which is a region bounded by null geodesics in an AdS 2 subspace of AdS 3. The time evolution can be described by specifying the null geodesic motion of kinks in the string at which two segments are joined. The outcome of collisions of kinks on the worldsheet can be worked out essentially using considerations of causality. We study several examples of closed segmented strings in AdS 3 and find an unexpected quasi-periodic behavior. We also work out a WKB analysis of quantum states of yo-yo strings in AdS 5 and find a logarithmic term reminiscent of the logarithmic twist of string states on the leading Regge trajectory.
The Higgs sector of the minimal B- L model at future Linear Colliders
NASA Astrophysics Data System (ADS)
Basso, Lorenzo; Moretti, Stefano; Pruna, Giovanni Marco
2011-08-01
We investigate the phenomenology of the Higgs sector of the minimal B- L extension of the Standard Model at a future e + e - Linear Collider. We consider the discovery potential of both a sub-TeV and a multi-TeV machine. We show that, within such a theoretical scenario, several novel production and decay channels involving the two physical Higgs states, precluded at the LHC, could experimentally be accessed at such machines. Amongst these, several Higgs signatures have very distinctive features with respect to those of other models with enlarged Higgs sector, as they involve interactions of Higgs bosons between themselves, with Z' bosons as well as with heavy neutrinos. In particular, we present the scope of the Z' strahlung process for single and double Higgs production, the only suitable mechanism enabling one to access an almost decoupled heavy scalar state (therefore outside the LHC range).
B →XSl+l- in the minimal gauged (B -L ) supersymmetry
NASA Astrophysics Data System (ADS)
Feng, Tai-Fu; Yang, Jin-Lei; Zhang, Hai-Bin; Zhao, Shu-Min; Zhu, Rong-Fei
2016-12-01
Applying the effective Hamilton for b →s l+l- , (l =e ,μ ) in the framework of the minimal supersymmetric extension of the standard model with local B -L gauge symmetry, we investigate branching ratios and forward-backward asymmetries of rare decay B →XSl+l- in low and high q2 regions, respectively. In addition, we also study the C P asymmetries depending on new C P phases from soft breaking terms in low and high q2 regions. Assuming that the soft breaking terms of the model induce new sources for flavor-changing neutral currents and CP violations, the numerical analyses of the supersymmetric contributions to the branching ratios, forward-backward and C P asymmetries of B →XSl+l- are presented in low and high q2 regions, respectively.
Cosmic Needles versus Cosmic Microwave Background Radiation
NASA Astrophysics Data System (ADS)
Li, Aigen
2003-02-01
It has been suggested by a number of authors that the 2.7 K cosmic microwave background (CMB) radiation might have arisen from the radiation of ``Population III'' objects thermalized by conducting cosmic graphite/iron needle-shaped dust. Due to a lack of an accurate solution to the absorption properties of exceedingly elongated grains, in existing literature which studies the CMB thermalizing process they are generally modeled as (1) needle-like spheroids in terms of the Rayleigh approximation, (2) infinite cylinders, and (3) antennae. We show here that the Rayleigh approximation is not valid since the Rayleigh criterion is not satisfied for highly conducting needles. We also show that the available intergalactic iron dust, if modeled as infinite cylinders, is not sufficient to supply the required opacity at long wavelengths to obtain the observed isotropy and Planckian nature of the CMB. If appealing to the antenna theory, conducting iron needles with exceedingly large elongations ( >104) appear able to provide sufficient opacity to thermalize the CMB within the iron density limit. But the applicability of the antenna theory to exceedingly thin needles of nanometer/micrometer thickness has not yet been verified.
Galactic cosmic rays and nucleosynthesis
Kiener, Juergen
2010-03-01
The nucleosynthesis of the light elements Li, Be and B by galactic cosmic rays is presented. Observations of cosmic rays and the nuclear reactions responsible for Li, Be and B nucleosynthesis are described, followed by some words on propagation. At the end, some open questions concerning galactic cosmic rays are discussed.
Magnetoresistive sensors for string instruments
NASA Astrophysics Data System (ADS)
Lenssen, K.-M. H.; Somers, G. H. J.; van Zon, J. B. A. D.
2002-05-01
Pickup elements for string instruments, in particular for electric guitars, represent a new application area for magnetoresistive sensors. Recently we developed a sensor configuration with permanent magnets for this purpose. For the first experiments we used commercial anisotropic magnetoresistance sensors (Philips KMZ10) mounted on small ferrite bias magnets. Recently we equipped an electric guitar with prototypes comprising giant magnetoresistance (GMR) sensors. These prototype MR pickup elements showed several clear advantages compared to the presently commonly used inductive pickup units. They are much less sensitive to disturbing electromagnetic fields (>1000×at 5 kHz), mainly because their active sensor area is several orders of magnitude smaller (a few mm2 instead of cm2). Also the larger freedom in the choice of the permanent magnets (due to the larger sensitivity of the GMR elements) is advantageous: employing smaller magnets reduces the damping and thus significantly improves the sustain, the magnets can be less expensive and more stable magnet materials can be chosen so that aging effects are eliminated.
Robust Inflation from fibrous strings
Burgess, C.P.; Cicoli, M.; Alwis, S. de; Quevedo, F.
2016-05-13
Successful inflationary models should (i) describe the data well; (ii) arise generically from sensible UV completions; (iii) be insensitive to detailed fine-tunings of parameters and (iv) make interesting new predictions. We argue that a class of models with these properties is characterized by relatively simple potentials with a constant term and negative exponentials. We here continue earlier work exploring UV completions for these models — including the key (though often ignored) issue of modulus stabilisation — to assess the robustness of their predictions. We show that string models where the inflaton is a fibration modulus seem to be robust due to an effective rescaling symmetry, and fairly generic since most known Calabi-Yau manifolds are fibrations. This class of models is characterized by a generic relation between the tensor-to-scalar ratio r and the spectral index n{sub s} of the form r∝(n{sub s}−1){sup 2} where the proportionality constant depends on the nature of the effects used to develop the inflationary potential and the topology of the internal space. In particular we find that the largest values of the tensor-to-scalar ratio that can be obtained by generalizing the original set-up are of order r≲0.01. We contrast this general picture with specific popular models, such as the Starobinsky scenario and α-attractors. Finally, we argue the self consistency of large-field inflationary models can strongly constrain non-supersymmetric inflationary mechanisms.
Experimental String Physics through UV/IR mixing
NASA Astrophysics Data System (ADS)
Soli, George
2004-05-01
Two-meter wavelength photons, tunneling through a water mirror, are used to produce superluminal group velocity for probing sidereal physics as the one-way group velocity of light. We discover that photon energy is not sidereal but that photon group velocity is sidereal and minimum for tunneling into the cosmic microwave background Doppler redshift direction. The electromagnetic energy pulse is formed into a wavepacket by allowing only frequencies between ω_min and ω_max to survive averaging over time, bandlimiting the energy pulse to the energy range Δ E. The string physics AdS5 radial coordinate is defined here as r = surd (ω_min/ω_max). The measured metric tensor g_tt = (1+r^2)/(1-r^2) = 137.2 ± 0.8 equals the S-dual inverse fine structure constant after renormalization group flow from the boundary-UV electromagnetic field to the bulk-IR dilaton caustic. At the dilaton caustic, (GΔ E/c^4) x (Nyquist sample spacing) = (Planck length)^2. The Nyquist sample spacing hbar c/Δ E is an internal component of the dilaton metric and GΔ E/c^4 is the axion matter field. If the IR-dilaton metric is interpreted as a semiclassical wormhole when photon tunneling is into the cosmic microwave background Doppler redshift direction, then the UV-axion can carry photon energy at the vacuum speed of light through the wormhole. We conjecture that this definition of close enables summing over all multiply connected 3-dimensional topologies.
DSP: a protein shape string and its profile prediction server
Sun, Jiangming; Tang, Shengnan; Xiong, Wenwei; Cong, Peisheng; Li, Tonghua
2012-01-01
Many studies have demonstrated that shape string is an extremely important structure representation, since it is more complete than the classical secondary structure. The shape string provides detailed information also in the regions denoted random coil. But few services are provided for systematic analysis of protein shape string. To fill this gap, we have developed an accurate shape string predictor based on two innovative technologies: a knowledge-driven sequence alignment and a sequence shape string profile method. The performance on blind test data demonstrates that the proposed method can be used for accurate prediction of protein shape string. The DSP server provides both predicted shape string and sequence shape string profile for each query sequence. Using this information, the users can compare protein structure or display protein evolution in shape string space. The DSP server is available at both http://cheminfo.tongji.edu.cn/dsp/ and its main mirror http://chemcenter.tongji.edu.cn/dsp/. PMID:22553364
DSP: a protein shape string and its profile prediction server.
Sun, Jiangming; Tang, Shengnan; Xiong, Wenwei; Cong, Peisheng; Li, Tonghua
2012-07-01
Many studies have demonstrated that shape string is an extremely important structure representation, since it is more complete than the classical secondary structure. The shape string provides detailed information also in the regions denoted random coil. But few services are provided for systematic analysis of protein shape string. To fill this gap, we have developed an accurate shape string predictor based on two innovative technologies: a knowledge-driven sequence alignment and a sequence shape string profile method. The performance on blind test data demonstrates that the proposed method can be used for accurate prediction of protein shape string. The DSP server provides both predicted shape string and sequence shape string profile for each query sequence. Using this information, the users can compare protein structure or display protein evolution in shape string space. The DSP server is available at both http://cheminfo.tongji.edu.cn/dsp/ and its main mirror http://chemcenter.tongji.edu.cn/dsp/.
ERIC Educational Resources Information Center
Young, Donna L.
2005-01-01
To help students understand the connection that Earth and the solar system have with the cosmic cycles of stellar evolution, and to give students an appreciation of the beauty and elegance of celestial phenomena, the Chandra X-Ray Center (CXC) educational website contains a stellar evolution module that is available free to teachers. In this…
Bajan Birds Pull Strings: Two Wild Antillean Species Enter the Select Club of String-Pullers
Ducatez, Simon; Lefebvre, Louis
2016-01-01
String-pulling is one of the most popular tests in animal cognition because of its apparent complexity, and of its potential to be applied to very different taxa. In birds, the basic procedure involves a food reward, suspended from a perch by a string, which can be reached by a series of coordinated pulling actions with the beak and holding actions of the pulled lengths of string with the foot. The taxonomic distribution of species that pass the test includes several corvids, parrots and parids, but in other families, data are much spottier and the number of individuals per species that succeed is often low. To date, the association between string-pulling ability and other cognitive traits was never tested. It is generally assumed that string-pulling is a complex form of problem-solving, suggesting that performance on string-pulling and other problem-solving tasks should be correlated. Here, we show that individuals of two innovative species from Barbados, the bullfinch Loxigilla barbadensis and the Carib grackle Quiscalus lugubris fortirostris, pass the string-pulling test. Eighteen of the 42 bullfinches tested succeeded, allowing us to correlate performance on this test to that on several other behavioral measurements. Surprisingly, string-pulling in bullfinches was unrelated to shyness, neophobia, problem-solving, discrimination and reversal learning performance. Only two of 31 grackles tested succeeded, precluding correlational analyses with other measures but still, the two successful birds largely differed in their other behavioral traits. PMID:27533282
NASA Astrophysics Data System (ADS)
Grieder, P. K. F.
In 1912 Victor Franz Hess made the revolutionary discovery that ionizing radiation is incident upon the Earth from outer space. He showed with ground-based and balloon-borne detectors that the intensity of the radiation did not change significantly between day and night. Consequently, the sun could not be regarded as the sources of this radiation and the question of its origin remained unanswered. Today, almost one hundred years later the question of the origin of the cosmic radiation still remains a mystery. Hess' discovery has given an enormous impetus to large areas of science, in particular to physics, and has played a major role in the formation of our current understanding of universal evolution. For example, the development of new fields of research such as elementary particle physics, modern astrophysics and cosmology are direct consequences of this discovery. Over the years the field of cosmic ray research has evolved in various directions: Firstly, the field of particle physics that was initiated by the discovery of many so-called elementary particles in the cosmic radiation. There is a strong trend from the accelerator physics community to reenter the field of cosmic ray physics, now under the name of astroparticle physics. Secondly, an important branch of cosmic ray physics that has rapidly evolved in conjunction with space exploration concerns the low energy portion of the cosmic ray spectrum. Thirdly, the branch of research that is concerned with the origin, acceleration and propagation of the cosmic radiation represents a great challenge for astrophysics, astronomy and cosmology. Presently very popular fields of research have rapidly evolved, such as high-energy gamma ray and neutrino astronomy. In addition, high-energy neutrino astronomy may soon initiate as a likely spin-off neutrino tomography of the Earth and thus open a unique new branch of geophysical research of the interior of the Earth. Finally, of considerable interest are the biological
Cosmic Rays: "A Thin Rain of Charged Particles."
ERIC Educational Resources Information Center
Friedlander, Michael
1990-01-01
Discussed are balloons and electroscopes, understanding cosmic rays, cosmic ray paths, isotopes and cosmic-ray travel, sources of cosmic rays, and accelerating cosmic rays. Some of the history of the discovery and study of cosmic rays is presented. (CW)
NASA Astrophysics Data System (ADS)
Trautmann, L.; Rabenstein, R.
2004-12-01
The functional transformation method (FTM) is a well-established mathematical method for accurate simulations of multidimensional physical systems from various fields of science, including optics, heat and mass transfer, electrical engineering, and acoustics. This paper applies the FTM to real-time simulations of transversal vibrating strings. First, a physical model of a transversal vibrating lossy and dispersive string is derived. Afterwards, this model is solved with the FTM for two cases: the ideally linearly vibrating string and the string interacting nonlinearly with the frets. It is shown that accurate and stable simulations can be achieved with the discretization of the continuous solution at audio rate. Both simulations can also be performed with a multirate approach with only minor degradations of the simulation accuracy but with preservation of stability. This saves almost 80% of the computational cost for the simulation of a six-string guitar and therefore it is in the range of the computational cost for digital waveguide simulations.
Formation of electron strings in narrow band polar semiconductors
Kusmartsev
2000-01-17
We show that linear electron strings may arise in polar semiconductors. A single string consists of M spinless fermions trapped by an extended polarization well of a cigar shape. Inside the string the particles are free although they interact with each other via Coulomb forces. The strings arise as a result of an electronic phase separation associated with an instability of small adiabatic polarons. We have found the length of the string which depends on dielectric constants of semiconductors. The appearance of these electron strings may have an impact on the effect of stripe formation observed in a variety of high- T(c) experiments.
NASA Astrophysics Data System (ADS)
Andriyash, Evgeny
In this thesis we discuss a number of interesting and important properties of BPS states in string theory. We study wall-crossing behavior of BPS states at large volume limit and implications of it for the OSV conjecture. We find that the weak topological coupling OSV conjecture can be true at most in a special chamber of the Kahler cone. We also clarify an interesting puzzle arising in the description of BPS states on the Higgs branch of supersymmetic quantum mechanics. Using methods of toric geometry we compute Hilbert spaces of BPS states on the compactified Higgs branch and arrive at completely consistent picture of spatial Spin(3) structure of those spaces. We introduce new kinds of walls, called Bound State Transformation(BST) walls, in the moduli space across which the nature of BPS bound states changes but the index remains continuous. These walls are necessary to explain the continuity of BPS index. BPS states can undergo recombination, conjugation or hybrids of the two when crossing a BST wall. Conjugation phenomenon happens near singularities in the moduli space and we relate massless spectra of BPS states at such singularities to monodromies around them. In cases when massless vector BPS particles are present we find new constraints on the spectrum and in particular predict the existence of magnetic monopoles becoming massless at such singularities. We give a simple physical derivation of the Kontsevich-Soibelman wall-crossing formula. Considering galaxy-like configurations of BPS particles with a central supermassive black hole with a number of stellar BPS systems around it we derive a consistency requirement on the partition function of such BPS galaxies. This requirement turns out to be nothing but Kontsevich-Soibelman wall-crossing formula. Our approach gives a generalization of the formula for the case when massless BPS particles are present.
Noyes, H.P.
1990-01-29
We construct discrete space-time coordinates separated by the Lorentz-invariant intervals h/mc in space and h/mc{sup 2} in time using discrimination (XOR) between pairs of independently generated bit-strings; we prove that if this space is homogeneous and isotropic, it can have only 1, 2 or 3 spacial dimensions once we have related time to a global ordering operator. On this space we construct exact combinatorial expressions for free particle wave functions taking proper account of the interference between indistinguishable alternative paths created by the construction. Because the end-points of the paths are fixed, they specify completed processes; our wave functions are born collapsed''. A convenient way to represent this model is in terms of complex amplitudes whose squares give the probability for a particular set of observable processes to be completed. For distances much greater than h/mc and times much greater than h/mc{sup 2} our wave functions can be approximated by solutions of the free particle Dirac and Klein-Gordon equations. Using a eight-counter paradigm we relate this construction to scattering experiments involving four distinguishable particles, and indicate how this can be used to calculate electromagnetic and weak scattering processes. We derive a non-perturbative formula relating relativistic bound and resonant state energies to mass ratios and coupling constants, equivalent to our earlier derivation of the Bohr relativistic formula for hydrogen. Using the Fermi-Yang model of the pion as a relativistic bound state containing a nucleon-antinucleon pair, we find that (G{sub {pi}N}{sup 2}){sup 2} = (2m{sub N}/m{sub {pi}}){sup 2} {minus} 1. 21 refs., 1 fig.
BOOK REVIEW: String Theory in a Nutshell
NASA Astrophysics Data System (ADS)
Skenderis, Kostas
2007-11-01
The book 'String Theory in a Nutshell' by Elias Kiritsis provides a comprehensive introduction to modern string theory. String theory is the leading candidate for a theory that successfully unifies all fundamental forces of nature, including gravity. The subject has been continuously developing since the early 1970s, with classic textbooks on the subject being those of Green, Schwarz and Witten (1987) and Polchinski (1998). Since the latter was published there have been substantial developments, in particular in understanding black holes and gravity/gauge theory dualities. A textbook treatment of this important material is clearly needed, both by students and researchers in string theory and by mathematicians and physicists working in related fields. This book has a good selection of material, starting from basics and moving into classic and modern topics. In particular, Kiritsis' presentation of the basic material is complementary to that of the earlier textbooks and he includes a number of topics which are not easily found or covered adequately elsewhere, for example, loop corrections to string effective couplings. Overall the book nicely covers the major advances of the last ten years, including (non-perturbative) string dualities, black hole physics, AdS/CFT and matrix models. It provides a concise but fairly complete introduction to these subjects which can be used both by students and by researchers. Moreover the emphasis is on results that are reasonably established, as is appropriate for a textbook; concise summaries are given for subjects which are still in flux, with references to relevant reviews and papers. A positive feature of the book is that the bibliography sections at the end of each chapter provide a comprehensive guide to the literature. The bibliographies point to reviews and pedagogical papers on subjects covered in this book as well as those that were omitted. It is rare for a textbook to contain such a self-contained and detailed guide to
Low-ℓ CMB from string-scale SUSY breaking?
NASA Astrophysics Data System (ADS)
Sagnotti, A.
2017-01-01
Models of inflation are instructive playgrounds for supersymmetry (SUSY) breaking in Supergravity and String Theory. In particular, combinations of branes and orientifolds that are not mutually BPS can lead to brane SUSY breaking, a phenomenon where nonlinear realizations are accompanied, in tachyon-free vacua, by the emergence of steep exponential potentials. When combined with milder terms, these exponentials can lead to slow-roll after a fast ascent and a turning point. This leaves behind distinctive patterns of scalar perturbations, where pre-inflationary peaks can lie well apart from an almost scale invariant profile. I review recent attempts to connect these power spectra to the low-ℓ cosmic microwave background (CMB), and a corresponding one-parameter extension of Lambda cold dark matter (ΛCDM) with a low-frequency cut Δ. A detailed likelihood analysis led to Δ = (0.351 ± 0.114) × 10-3Mpc-1, at 99.4% confidence level, in an extended Galactic mask with fsky = 39%, to be compared with a nearby value at 88.5% in the standard Planck 2015 mask with fsky = 94%. In these scenarios, one would be confronted, in the CMB, with relics of an epoch of deceleration that preceded the onset of slow-roll.
Resummation of semiclassical short folded string
NASA Astrophysics Data System (ADS)
Beccaria, Matteo; Macorini, Guido
2012-02-01
We reconsider semiclassical quantization of folded string spinning in AdS3 part of AdS5 × S5 using integrability-based (algebraic curve) method. We focus on the "short string" (small spin S) limit with the angular momentum J in S 5 scaled down according to {mathcal J} = ρ sqrt {S} in terms of the variables {mathcal J} = J/ sqrt {λ } , S = S/ sqrt {λ } . The semi-classical string energy in this particular scaling limit admits the double expansion E = {sum {_{{n = 0}}^{infty }sum {_{{p = 0}}^{infty }left( {sqrt {λ } } right)} }^{{1 - n}}}{a_{{n,p}}}left( ρ right){S^{{P + 1/2}}} . It behaves smoothly as J → 0 and partially resums recent results by Gromov and Valatka. We explicitly compute various one-loop coefficients a1, p ( ρ) by summing over the fluctuation frequencies for integrable perturbations around the classical solution. For the simple folded string, the result agrees with what could be derived exploiting a recent conjecture of Basso. However, the method can be extended to more general situations. As an example, we consider the m-folded string where Basso's conjecture fails. For this classical solution, we present the exact values of a 1,0( ρ) and a 1,1( ρ) for m = 2, 3, 4, 5 and explain how to work out the general case.
Twistor-strings and gravity tree amplitudes
NASA Astrophysics Data System (ADS)
Adamo, Tim; Mason, Lionel
2013-04-01
Recently we discussed how Einstein supergravity tree amplitudes might be obtained from the original Witten and Berkovits twistor-string theory when external conformal gravitons are restricted to be Einstein gravitons. Here we obtain a more systematic understanding of the relationship between conformal and Einstein gravity amplitudes in that twistor-string theory. We show that although it does not in general yield Einstein amplitudes, we can nevertheless obtain some partial twistor-string interpretation of the remarkable formulae recently been found by Hodges and generalized to all tree amplitudes by Cachazo and Skinner. The Hodges matrix and its higher degree generalizations encode the world sheet correlators of the twistor string. These matrices control both Einstein amplitudes and those of the conformal gravity arising from the Witten and Berkovits twistor-string. Amplitudes in the latter case arise from products of the diagonal elements of the generalized Hodges matrices and reduced determinants give the former. The reduced determinants arise if the contractions in the worldsheet correlator are restricted to form connected trees at MHV. The (generalized) Hodges matrices arise as weighted Laplacian matrices for the graph of possible contractions in the correlators and the reduced determinants of these weighted Laplacian matrices give the sum of the connected tree contributions by an extension of the matrix-tree theorem.
Supergravity Duals of Matrix String Theory
NASA Astrophysics Data System (ADS)
Morales, Jose F.; Samtleben, Henning
2002-08-01
We study holographic duals of type II and heterotic matrix string theories described by warped AdS3 supergravities. By explicitly solving the linearized equations of motion around near horizon D-string geometries, we determine the spectrum of Kaluza-Klein primaries for type I, II supergravities on warped AdS3 × S7. The results match those coming from the dual two-dimensional gauge theories living on the D-string worldvolumes. We briefly discuss the connections with the Script N = (8,8), Script N = (8,0) orbifold superconformal field theories to which type IIB/heterotic matrix strings flow in the infrared. In particular, we associate the dimension (h,bar h) = (3/2,3/2) twisted operator which brings the matrix string theories out from the conformal point (Bbb R8)N/SN with the dilaton profile in the supergravity background. The familiar dictionary between masses and ``scaling'' dimensions of field and operators are modified by the presence of non-trivial warp factors and running dilatons. These modifications are worked out for the general case of domain wall/QFT correspondences between supergravities on warped AdSd+1 × Sq geometries and super Yang-Mills theories with 16 supercharges.
String Theory - The Physics of String-Bending and Other Electric Guitar Techniques
Grimes, David Robert
2014-01-01
Electric guitar playing is ubiquitous in practically all modern music genres. In the hands of an experienced player, electric guitars can sound as expressive and distinct as a human voice. Unlike other more quantised instruments where pitch is a discrete function, guitarists can incorporate micro-tonality and, as a result, vibrato and sting-bending are idiosyncratic hallmarks of a player. Similarly, a wide variety of techniques unique to the electric guitar have emerged. While the mechano-acoustics of stringed instruments and vibrating strings are well studied, there has been comparatively little work dedicated to the underlying physics of unique electric guitar techniques and strings, nor the mechanical factors influencing vibrato, string-bending, fretting force and whammy-bar dynamics. In this work, models for these processes are derived and the implications for guitar and string design discussed. The string-bending model is experimentally validated using a variety of strings and vibrato dynamics are simulated. The implications of these findings on the configuration and design of guitars is also discussed. PMID:25054880
String theory--the physics of string-bending and other electric guitar techniques.
Grimes, David Robert
2014-01-01
Electric guitar playing is ubiquitous in practically all modern music genres. In the hands of an experienced player, electric guitars can sound as expressive and distinct as a human voice. Unlike other more quantised instruments where pitch is a discrete function, guitarists can incorporate micro-tonality and, as a result, vibrato and sting-bending are idiosyncratic hallmarks of a player. Similarly, a wide variety of techniques unique to the electric guitar have emerged. While the mechano-acoustics of stringed instruments and vibrating strings are well studied, there has been comparatively little work dedicated to the underlying physics of unique electric guitar techniques and strings, nor the mechanical factors influencing vibrato, string-bending, fretting force and whammy-bar dynamics. In this work, models for these processes are derived and the implications for guitar and string design discussed. The string-bending model is experimentally validated using a variety of strings and vibrato dynamics are simulated. The implications of these findings on the configuration and design of guitars is also discussed.
Sterile neutrino portal to Dark Matter I: the U(1) B- L case
NASA Astrophysics Data System (ADS)
Escudero, Miguel; Rius, Nuria; Sanz, Verónica
2017-02-01
In this paper we explore the possibility that the sterile neutrino and Dark Matter sectors in the Universe have a common origin. We study the consequences of this assumption in the simple case of coupling the dark sector to the Standard Model via a global U(1) B-L , broken down spontaneously by a dark scalar. This dark scalar provides masses to the dark fermions and communicates with the Higgs via a Higgs portal coupling. We find an interesting interplay between Dark Matter annihilation to dark scalars — the CP-even that mixes with the Higgs and the CP-odd which becomes a Goldstone boson, the Majoron — and heavy neutrinos, as well as collider probes via the coupling to the Higgs. Moreover, Dark Matter annihilation into sterile neutrinos and its subsequent decay to gauge bosons and quarks, charged leptons or neutrinos lead to indirect detection signatures which are close to current bounds on the gamma ray flux from the galactic center and dwarf galaxies.
The context-tree kernel for strings.
Cuturi, Marco; Vert, Jean-Philippe
2005-10-01
We propose a new kernel for strings which borrows ideas and techniques from information theory and data compression. This kernel can be used in combination with any kernel method, in particular Support Vector Machines for string classification, with notable applications in proteomics. By using a Bayesian averaging framework with conjugate priors on a class of Markovian models known as probabilistic suffix trees or context-trees, we compute the value of this kernel in linear time and space while only using the information contained in the spectrum of the considered strings. This is ensured through an adaptation of a compression method known as the context-tree weighting algorithm. Encouraging classification results are reported on a standard protein homology detection experiment, showing that the context-tree kernel performs well with respect to other state-of-the-art methods while using no biological prior knowledge.
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.
New vacua for type II string theory
NASA Astrophysics Data System (ADS)
Polchinski, Joseph; Strominger, Andrew
1996-02-01
Lorentz-invariant expectation values for antisymmetric tensor field strengths in Calabi-Yau compactification of IIA string theory are considered. These are found to impart magnetic and/or electric charges to the dilation hypermultiplet. This results in a potential which can have supersymmetric minima at zero coupling or at conifold points in the moduli space. The latter occurs whenever the dilaton charge is aligned with that of the light black hole at the conifold. It is shown that there is a flat direction extending from the conifold along which there is a black hole condensate whose strength is of order the string coupling gs. It is speculated that these new vacua correspond to string compactification on generalized Calabi-Yau spaces which have c1 = 0 but are not Kahler.
String-merging of meso- viscoelastic droplets
NASA Astrophysics Data System (ADS)
Xu, Yuanze; Xu, Jianmao
2007-03-01
Great challenge exists in the multi-scale rheological modeling of immiscible polyblends with non-linear morphology changes, including viscoelastic drop break-up and collapse. A new type mechanism of merging and coalescence, called string-merging of meso- viscoelastic droplets was described and analyzed. By iterative stretching and relaxation in a four-roll mill rheometer, one droplet containing high molar mass PIB (polyisobutene), was separated into two droplets connected by a string in a dumbbell shape suspending in polydimethylsiloxane (PDMS) medium. In quiescent state, the string pulled the two spheres merging closer and collapsed into one spherical drop finally. The process exhibits interesting features, different from capillary breakup mechanism. By adding the viscoelasticity of the systems to the force balance of Laplace force and viscous drag, the phenomenon may be well analyzed. The necessity to involve the microscopic consideration of the highly oriented entangled state are discussed.
Tensor modes on the string theory landscape
NASA Astrophysics Data System (ADS)
Westphal, Alexander
2013-04-01
We attempt an estimate for the distribution of the tensor mode fraction r over the landscape of vacua in string theory. The dynamics of eternal inflation and quantum tunneling lead to a kind of democracy on the landscape, providing no bias towards large-field or small-field inflation regardless of the class of measure. The tensor mode fraction then follows the number frequency distributions of inflationary mechanisms of string theory over the landscape. We show that an estimate of the relative number frequencies for small-field vs large-field inflation, while unattainable on the whole landscape, may be within reach as a regional answer for warped Calabi-Yau flux compactifications of type IIB string theory.
Hadronic density of states from string theory.
Pando Zayas, Leopoldo A; Vaman, Diana
2003-09-12
We present an exact calculation of the finite temperature partition function for the hadronic states corresponding to a Penrose-Güven limit of the Maldacena-Nùñez embedding of the N=1 super Yang-Mills (SYM) into string theory. It is established that the theory exhibits a Hagedorn density of states. We propose a semiclassical string approximation to the finite temperature partition function for confining gauge theories admitting a supergravity dual, by performing an expansion around classical solutions characterized by temporal windings. This semiclassical approximation reveals a hadronic energy density of states of a Hagedorn type, with the coefficient determined by the gauge theory string tension as expected for confining theories. We argue that our proposal captures primarily information about states of pure N=1 SYM theory, given that this semiclassical approximation does not entail a projection onto states of large U(1) charge.
Aspects of String Phenomenology and New Physics
NASA Astrophysics Data System (ADS)
Antoniadis, I.
I discuss possible connections between several scales in particle physics and cosmology, such the the electroweak, ination, dark energy and Planck scales. In particular, I discuss the physics of extra dimensions and low scale gravity that are motivated from the problem of mass hierarchy, providing an alternative to low energy supersymmetry. I describe their realization in type I string theory with D-branes and I present the main experimental predictions in particle accelerators and their implications in cosmology. I also show that low-mass-scale string compactifications, with a generic D-brane configuration that realizes the Standard Model by open strings, can explain the relatively broad peak in the diphoton invariant mass spectrum at 750 GeV recently reported by the ATLAS and CMS collaborations.
Exotic geometry in string theory and cosmology
NASA Astrophysics Data System (ADS)
Haque, Sheikh Shajid
One of the main features expected of a quantum theory of gravity is non-locality. Implementing non-locality in quantum field theories turns out to be already challenging both conceptually and technically and requires the use of several techniques, such as string dualities and twists in order to construct and understand the effects of non-locality. This thesis explored these concepts in the construction of quantum field theories with a particular type of non- locality, non-commutative geometry, as an opportunity to study non-locality in a broader context. Another important challenge of theoretical physics is to connect the microscopic structure of spacetime implied by string theory to the empirical fact that the cosmological constant is positive and that the universe is asymptotically de Sitter. Constructing de Sitter space from string theory has proven to be extremely difficult over the years. In this thesis, I will discuss recent work in these areas.
Phase transitions in QCD and string theory
NASA Astrophysics Data System (ADS)
Campell, Bruce A.; Ellis, John; Kalara, S.; Nanopoulos, D. V.; Olive, Keith A.
1991-02-01
We develop a unified effective field theory approach to the high-temperature phase transitions in QCD and string theory, incorporating winding modes (time-like Polyakov loops, vortices) as well as low-mass states (pseudoscalar mesons and glueballs, matter and dilaton supermultiplets). Anomalous scale invariance and the Z3 structure of the centre of SU(3) decree a first-order phase transition with simultaneous deconfinement and Polyakov loop condensation in QCD, whereas string vortex condensation is a second-order phase transition breaking a Z2 symmetry. We argue that vortex condensation is accompanied by a dilaton phase transition to a strong coupling regime, and comment on the possible role of soliton degrees of freedom in the high-temperature string phase. On leave of absence from the School of Physics & Astronomy, University of Minnesota, Minneapolis, Minnesota, USA.
NASA Technical Reports Server (NTRS)
Bertschinger, Edumund
1994-01-01
This article reviews the prevailing paradigm for how galaxies and larger structures formed in the universe: gravitational instability. Basic observational facts are summarized to motivate the standard cosmological framework underlying most detailed investigations of structure formation. The observed univers approaches spatial uniformity on scales larger than about 10(exp 26) cm. On these scales gravitational dynamics is almost linear and therefore relatively easy to relate to observations of large-scale structure. On smaller scales cosmic structure is complicated not only by nonlinear gravitational clustering but also by nonlinear nongravitational gas dynamical processes. The complexity of these phenomena makes galaxy formation one of the grand challenge problems of the physical sciences. No fully satisfactory theory can presently account in detail for the observed cosmic structure. However, as this article summarizes, significant progress has been made during the last few years.
COSMIC monthly progress report
NASA Technical Reports Server (NTRS)
1994-01-01
Activities of the Computer Software Management and Information Center (COSMIC) are summarized for the month of April 1994. Tables showing the current inventory of programs available from COSMIC are presented and program processing and evaluation activities are summarized. Five articles were prepared for publication in the NASA Tech Brief Journal. These articles (included in this report) describe the following software items: GAP 1.0 - Groove Analysis Program, Version 1.0; SUBTRANS - Subband/Transform MATLAB Functions for Image Processing; CSDM - COLD-SAT Dynamic Model; CASRE - Computer Aided Software Reliability Estimation; and XOPPS - OEL Project Planner/Scheduler Tool. Activities in the areas of marketing, customer service, benefits identification, maintenance and support, and disseminations are also described along with a budget summary.
NASA Astrophysics Data System (ADS)
Calogero, Francesco
An estimate is presented of the angular momentum associated with the stochastic cosmic tremor, which has been hypothesized to be caused by universal gravitation and by the granularity of matter, and to be itself the cause of quantization ("cosmic origin of quantization"). If that universal tremor has the spatial coherence which is instrumental in order that the estimated action associated with it have the order of magnitude of Planck's constant h, then the estimated order of magnitude of the angular momentum associated with it also has the same value. We moreover indicate how these findings (originally based on a simplified model of the Universe, as being made up only of particles having the nucleon mass) are affected (in fact, essentially unaffected) by the possible presence in the mass of the Universe of a large component made up of particles much lighter than nucleons ("dark", or "missing", mass).
NASA Astrophysics Data System (ADS)
Tipler, F. J.
1985-05-01
A number of recent theorems by Krolak (1983) and Newman (1983) purport to prove cosmic censorship by showing that strong-curvature singularities must be hidden behind horizons. It is shown that the 'null strong-curvature' condition which Newman imposes on certain classes of null geodesics to restrict curvature growth in the space-time does not hold in many physically realistic space-times: it is not satisfied by any null geodesic in the relevant class in any open Friedmann cosmological model, nor does it hold for any null geodesic in the relevant class in maximal Schwarzschild space. More generally it is argued that the singularity predicted by the Penrose singularity theorem is unlikely to be of the type eliminated by Newman. Thus the Newman theorems are probably without physical significance. The Krolak theorems, although based on a physically significant definition of strong curvature singularity, are mathematically invalid, and this approach cannot be used to obtain a cosmic-censorship theorem.
Computer Center: BASIC String Models of Genetic Information Transfer.
ERIC Educational Resources Information Center
Spain, James D., Ed.
1984-01-01
Discusses some of the major genetic information processes which may be modeled by computer program string manipulation, focusing on replication and transcription. Also discusses instructional applications of using string models. (JN)
Galactic cosmic ray composition
NASA Technical Reports Server (NTRS)
Meyer, J. P.
1986-01-01
An assessment is given of the galactic cosmic ray source (GCRS) elemental composition and its correlation with first ionization potential. The isotopic composition of heavy nuclei; spallation cross sections; energy spectra of primary nuclei; electrons; positrons; local galactic reference abundances; comparison of solar energetic particles and solar coronal compositions; the hydrogen; lead; nitrogen; helium; and germanium deficiency problems; and the excess of elements are among the topics covered.
NASA Astrophysics Data System (ADS)
2009-03-01
What is it? Cosmic Diary brings together a smorgasbord of blogging astronomers from around the world, with more than 50 contributors commenting on new discoveries and long-standing questions in astronomy - as well as offering insights into their ordinary working lives and outside interests. The site is sponsored by the International Astronomical Union and UNESCO, and it is one of 11 "cornerstone projects" of the International Year of Astronomy 2009 (IYA2009).
Carl Sagan's Cosmic Connection
NASA Astrophysics Data System (ADS)
Sagan, Carl; Agel, Jerome
2000-08-01
Foreword Freeman Dyson; Personal reflections Ann Druyan; Preface; Part I. Cosmic Perspective: 1. A transitional animal; 2. The Unicorn of Cetus; 3. A message from earth; 4. A message to earth; 5. Experiments in utopias; 6. Chauvinism; 7. Space exploration as a human enterprise I. The scientific interest; 8. Space exploration as a human enterprise II. The public interest; 9. Space exploration as a human enterprise III. The historical interest; Part II. The Solar System: 10. On teaching the first grade; 11. 'The ancient and legendary Gods of old'; 12. The Venus detective story; 13. Venus is hell; 14. Science and 'intelligence'; 15. The moons of Barsoom; 16. The mountains of Mars I. Observations from earth; 17. The mountains of Mars II. Observations from space; 18. The canals of Mars; 19. The lost pictures of Mars; 20. The Ice Age and the cauldron; 21. Beginnings and ends of the Earth; 22. Terraforming the plants; 23. The exploration and utlization of the solar system; Part III. Beyond the Solar System: 24. Some of my best friends are dolphins; 25. 'Hello, central casting? Send me twenty extraterrestrials'; 26. The cosmic connection; 27. Extraterrestrial life: an idea whose time has come; 28. Has the Earth been visited?; 29. A search strategy for detecting extraterrestrial intelligence; 30. If we succeed 31. Cables, drums, and seashells; 32. The night freight to the stars; 33. Astroengineering; 34. Twenty questions: a classification of cosmic civilisations; 35. Galactic cultural exchanges; 36. A passage to elsewhere; 37. Starfolk I. A Fable; 38. Starfolk II. A future; 39. Starfolk III. The cosmic Cheshire cats; Epilog David Morrison; Index.
NASA Astrophysics Data System (ADS)
Buitink, Stijn; Scholten, Olaf; van den Berg, Ad; Ebert, Ute
2013-04-01
Cosmic Rays in Thunderstorms Cosmic rays are protons and heavier nuclei that constantly bombard the Earth's atmosphere with energies spanning a vast range from 109 to 1021 eV. At typical altitudes up to 10-20 km they initiate large particle cascades, called extensive air showers, that contain millions to billions of secondary particles depending on their initial energy. These particles include electrons, positrons, hadrons and muons, and are concentrated in a compact particle front that propagates at relativistic speed. In addition, the shower leaves behind a trail of lower energy electrons from ionization of air molecules. Under thunderstorm conditions these electrons contribute to the electrical and ionization processes in the cloud. When the local electric field is strong enough the secondary electrons can create relativistic electron run-away avalanches [1] or even non-relativistic avalanches. Cosmic rays could even trigger lightning inception. Conversely, strong electric fields also influence the development of the air shower [2]. Extensive air showers emit a short (tens of nanoseconds) radio pulse due to deflection of the shower particles in the Earth's magnetic field [3]. Antenna arrays, such as AERA, LOFAR and LOPES detect these pulses in a frequency window of roughly 10-100 MHz. These systems are also sensitive to the radiation from discharges associated to thunderstorms, and provide a means to study the interaction of cosmic ray air showers and the electrical processes in thunderstorms [4]. In this presentation we discuss the involved radiation mechanisms and present analyses of thunderstorm data from air shower arrays [1] A. Gurevich et al., Phys. Lett. A 165, 463 (1992) [2] S. Buitink et al., Astropart. Phys. 33, 1 (2010) [3] H. Falcke et al., Nature 435, 313 (2005) [4] S. Buitink et al., Astron. & Astrophys. 467, 385 (2007)
The cosmic background explorer
Gulkis, G. ); Lubin, P.M. ); Meyer, S.S. ); Silverberg, R.F.
1990-01-01
Late last year the National Aeronautics and Space Administration launched its first satellite dedicated to the study of phenomena related to the origins of the universe. The satellite, called the Cosmic Background Explorer (COBE), carries three complementary detectors that will make fundamental measurements of the celestial radiation. Part of that radiation is believed to have originated in processes that occurred at the very dawn of the universe. By measuring the remnant radiation at wavelengths from one micrometer to one centimeter across the entire sky, scientists hope to be able to solve many mysteries regarding the origin and evolution of the early universe. Unfortunately, these radiative relics of the early universe are weak and veiled by local astrophysical and terrestrial sources of radiation. The wavelengths of the various cosmic components may also overlap, thereby making the understanding of the diffuse celestial radiation a challenge. Nevertheless, the COBE instruments, with their full-sky coverage, high sensitivity to a wide range of wavelengths and freedom from interference from the earth's atmosphere, will constitute for astrophysicists an observatory of unprecedented sensitivity and scope. The interesting cosmic signals will then be separated from one another and from noncosmic radiation sources by a comprehensive analysis of the data.
Diffractive Scattering and Gauge/String Duality
Tan, Chung-I [Brown University, Providence, Rhode Island, United States
2016-07-12
High-energy diffractive scattering will be discussed based on Gauge/String duality. As shown by Brower, Polchinski, Strassler and Tan, the ubiquitous Pomeron emerges naturally in gauge theories with string-theoretical descriptions. Its existence is intimately tied to gluons, and also to the energy-momentum tensor. With a confining dual background metric, the Pomeron can be interpreted as a 'massive graviton'. In a single unified step, both its infrared and ultraviolet properties are dealt with, reflecting confinement and conformal symmetry respectively. An effective field theory for high-energy scattering can be constructed. Applications based on this approach will also be described.
String breaking in four dimensional lattice QCD
Duncan, A.; Eichten, E.; Thacker, H.
2001-06-01
Virtual quark pair screening leads to breaking of the string between fundamental representation quarks in QCD. For unquenched four dimensional lattice QCD, this (so far elusive) phenomenon is studied using the recently developed truncated determinant algorithm (TDA). The dynamical configurations were generated on a 650 MHz PC. Quark eigenmodes up to 420 MeV are included exactly in these TDA studies performed at low quark mass on large coarse [but O(a{sup 2}) improved] lattices. A study of Wilson line correlators in Coulomb gauge extracted from an ensemble of 1000 two-flavor dynamical configurations reveals evidence for flattening of the string tension at distances R{approx}>1 fm.
Blackfolds in supergravity and string theory
NASA Astrophysics Data System (ADS)
Emparan, Roberto; Harmark, Troels; Niarchos, Vasilis; Obers, Niels A.
2011-08-01
We develop the effective worldvolume theory for the dynamics of black branes with charges of the kind that arise in many supergravities and low-energy limits of string theory. Using this theory, we construct numerous new rotating blackholes with charges and dipoles of D-branes, fundamental strings and other branes. In some instances, the black holes can be dynamically stable close enough to extremality. Some of these black holes, such as those based on the D1-D5-P system, have extremal, non-supersymmetric limits with regular horizons of finite area and a wide variety of horizon topologies and geometries.