Vachaspati, Tanmay; Steer, Daniele
2015-01-01
This article, written for Scolarpedia, provides a brief introduction into the subject of cosmic strings, together with a review of their main properties, cosmological evolution and observational signatures.
Supermassive cosmic string compactifications
Energy Technology Data Exchange (ETDEWEB)
Blanco-Pillado, Jose J.; Reina, Borja; Sousa, Kepa; Urrestilla, Jon, E-mail: josejuan.blanco@ehu.es, E-mail: borja.reina@ehu.es, E-mail: kepa.sousa@ehu.es, E-mail: jon.urrestilla@ehu.es [Department of Theoretical Physics and History of Science, University of the Basque Country UPV/EHU, 48080 Bilbao (Spain)
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.
Supermassive Cosmic String Compactifications
Blanco-Pillado, Jose J; Sousa, Kepa; Urrestilla, Jon
2014-01-01
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.
A disintegrating cosmic string
Griffiths, J B
2002-01-01
We present a simple sandwich gravitational wave of the Robinson-Trautman family. This is interpreted as representing a shock wave with a spherical wavefront which propagates into a Minkowski background minus a wedge. (i.e. the background contains a cosmic string.) The deficit angle (the tension) of the string decreases through the gravitational wave, which then ceases. This leaves an expanding spherical region of Minkowski space behind it. The decay of the cosmic string over a finite interval of retarded time may be considered to generate the gravitational wave.
Sjodin, K R P; Vickers, J A
2001-01-01
The field equations for a time dependent cylindrical cosmic string coupled togravity are reformulated in terms of geometrical variables defined on a2+1-dimensional spacetime by using the method of Geroch decomposition. Unlikethe 4-dimensional spacetime the reduced case is asymptotically flat. Anumerical method for solving the field equations which involves conformallycompactifying the space and including null infinity as part of the grid isdescribed. It is shown that the code reproduces the results of a number ofvacuum solutions with one or two degrees of freedom. In the final section theinteraction between the cosmic string and a pulse of gravitational radiation isbriefly described. This will be fully analysed in the sequel.
Vanchurin, V
2005-01-01
We investigate the evolution of finite loops and infinite strings as a part of a complete cosmic string network. We give dynamical arguments showing that the structures on infinite strings should obey a scaling law. We perform a simulation of the network which uses functional forms for the string position and thus is exact to the limits of computer arithmetic. The effective box size of our simulation is at least two orders of magnitude larger than what was previously reached. Our results confirm that the wiggles on the strings obey a scaling law described by universal power spectrum. The average distance between long strings also scales accurately with the time. Production functions of string loops do not show scaling. With low intercommutation probability p the true scaling régime is not reached until very late cosmic times, which makes it difficult to simulate such evolutions. Via the expansion of the box technique, we were able to reach scaling with a wide range of p. The physical correlation ...
Blanco-Pillado, Jose J; Shlaer, Benjamin
2015-01-01
We analyze the shapes of cosmic string loops found in large-scale simulations of an expanding-universe string network. The simulation does not include gravitational back reaction, but we model that process by smoothing the loop using Lorentzian convolution. We find that loops at formation consist of generally straight segments separated by kinks. We do not see cusps or any cusp-like structure at the scale of the entire loop, although we do see very small regions of string that move with large Lorentz boosts. However, smoothing of the string almost always introduces two cusps on each loop. The smoothing process does not lead to any significant fragmentation of loops that were in non-self-intersecting trajectories before smoothing.
Cosmic Strings and Quintessence
Institute of Scientific and Technical Information of China (English)
段一士; 任继荣; 杨捷
2003-01-01
Using torsion two-form we present a new Lorentz gauge invariant U (1) topological field theory in Riemann-Cartan space-time manifold U4. By virtue of the decomposition theory of U(1) gauge potential and the φ-mapping topological current theory, it is proven that the U(1) complex scalar field φ(x) can be looked upon as the order parameter field in our Universe, and a set of zero points of φ(x) create the cosmic strings as the space-time defects in the early Universe. In the standard cosmology, this complex scalar order parameter field possesses negative pressure, provides an accelerating expansion of Universe, and be able to explain the inflation in the early Universe. Therefore this complex scalar field is not only the order parameter field created the cosmic strings in the early universe, but also reasonably behaves as the quintessence, the dark energy.
Racetrack Inflation and Cosmic Strings
Brax, Philippe; Davis, Anne-Christine; Davis, Stephen C; Jeannerot, Rachel; Postma, Marieke
2008-01-01
We consider the coupling of racetrack inflation to matter fields as realised in the D3/D7 brane system. In particular, we investigate the possibility of cosmic string formation in this system. We find that string formation before or at the onset of racetrack inflation is possible, but they are then inflated away. Furthermore, string formation at the end of inflation is prevented by the presence of the moduli sector. As a consequence, no strings survive racetrack inflation.
Reconnection of Colliding Cosmic Strings
Hanany, A; Hanany, Amihay; Hashimoto, Koji
2005-01-01
For vortex strings in the Abelian Higgs model and D-strings in superstring theory, both of which can be regarded as cosmic strings, we give analytical study of reconnection (recombination, inter-commutation) when they collide, by using effective field theories on the strings. First, for the vortex strings, via a string sigma model, we verify analytically that the reconnection is classically inevitable for small collision velocity and small relative angle. Evolution of the shape of the reconnected strings provides an upper bound on the collision velocity in order for the reconnection to occur. These analytical results are in agreement with previous numerical results. On the other hand, reconnection of the D-strings is not classical but probabilistic. We show that a quantum calculation of the reconnection probability using a D-string action reproduces the nonperturbative nature of the worldsheet results by Jackson, Jones and Polchinski. The difference on the reconnection -- classically inevitable for the vortex...
Test particle trajectories near cosmic strings
Indian Academy of Sciences (India)
Farook Rahaman; Subenoy Chakraborty; K Maity
2002-01-01
We present a detailed analysis of the motion of test particle in the gravitational ﬁeld of cosmic strings in different situations using the Hamilton–Jacobi (H–J) formalism. We have discussed the trajectories near static cosmic string, cosmic string in Brans–Dicke theory and cosmic string in dilaton gravity.
Cosmic Strings with Small Tension
Halyo, Edi
2009-01-01
We describe cosmic F--term strings with exponentially small tension which are D3 branes wrapped on deformed $A_3$ singularities. We show that brane instanton effects which can be calculated after a geometric transition give rise to an exponentially small volume for the node on which the D3 branes wrap leading to a string with small tension. We generalize our description to the case of non--Abelian cosmic strings and argue that these strings are stable against monopole--anti monopole pair creation.
Dynamic Cosmic Strings Numerical evolution of excited Cosmic Strings
Sperhake, U; Vickers, J A
2001-01-01
An implicit, fully characteristic, numerical scheme for solving the field equations of a cosmic string coupled to gravity is described. The inclusion of null infinity as part of the numerical grid allows us to apply suitable boundary conditions on the metric and matter fields to suppress unphysical divergent solutions. The code is tested by comparing the results with exact solutions, checking that static cosmic string initial data remain constant when evolved and undertaking a time dependent convergence analysis of the code. It is shown that the code is accurate, stable and exhibits clear second order convergence. The code is used to analyse the interaction between a Weber--Wheeler pulse of gravitational radiation with the string. The interaction causes the string to oscillate at frequencies inversely proportional to the masses of the scalar and vector fields of the string. After the pulse has largely radiated away the string continues to ring but the oscillations slowly decay and eventually the variables ret...
Improving cosmic string network simulations
Hindmarsh, Mark; Tenkanen, Tuomas V I; Weir, David J
2014-01-01
In real-time lattice simulations of cosmic strings in the Abelian Higgs model, the broken translational invariance introduces lattice artefacts; relativistic strings therefore decelerate and radiate. We introduce two different methods to construct a moving string on the lattice, and study in detail the lattice effects on moving strings. We find that there are two types of lattice artefact: there is an effective maximum speed with which a moving string can be placed on the lattice, and a moving string also slows down, with the deceleration approximately proportional to the exponential of the velocity. To mitigate this, we introduce and study an improved discretisation, based on the tree-level L\\"{u}scher-Weisz action, which is found to reduce the deceleration by an order of magnitude, and to increase the string speed limit by an amount equivalent to halving the lattice spacing. The improved algorithm is expected to be very useful for 3D simulations of cosmic strings in the early universe, where one wishes to s...
Improving cosmic string network simulations
Hindmarsh, Mark; Rummukainen, Kari; Tenkanen, Tuomas V. I.; Weir, David J.
2014-08-01
In real-time lattice simulations of cosmic strings in the Abelian Higgs model, the broken translational invariance introduces lattice artifacts; relativistic strings therefore decelerate and radiate. We introduce two different methods to construct a moving string on the lattice, and study in detail the lattice effects on moving strings. We find that there are two types of lattice artifact: there is an effective maximum speed with which a moving string can be placed on the lattice, and a moving string also slows down, with the deceleration approximately proportional to the exponential of the velocity. To mitigate this, we introduce and study an improved discretization, based on the tree-level Lüscher-Weisz action, which is found to reduce the deceleration by an order of magnitude, and to increase the string speed limit by an amount equivalent to halving the lattice spacing. The improved algorithm is expected to be very useful for 3D simulations of cosmic strings in the early Universe, where one wishes to simulate as large a volume as possible.
Lake, Matthew J
2015-01-01
We outline a model of abelian-Higgs strings with variable scalar and vector core radii. In general, the functions determining the time and position-dependent core widths may be expressed as arbitrary left or right movers, of which the usual constant values are a particular solution. In this case the string may carry momentum, even if the embedding of its central axis remains fixed, and the resulting objects resemble "necklaces". Some possible astrophysical applications of lumpy strings, including as potential engines for anomalous gamma ray bursts, are also discussed.
Fireballs from Superconducting Cosmic Strings
Gruzinov, Andrei
2016-01-01
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.
Fireballs from superconducting cosmic strings
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.
CMB Constraints on Cosmic Strings and Superstrings
Charnock, Tom; Copeland, Edmund J; Moss, Adam
2016-01-01
We present the first complete MCMC 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 {\\Lambda}CDM and string network parameters, namely the string tension G{\\mu}, the loop-chopping efficiency c_r and the string wiggliness {\\alpha}. For cosmic superstrings, we obtain joint constraints on the fundamental string tension G{\\mu}_F, the string coupling g_s, the self-interaction coefficient c_s, and the volume of compact extra dimensions w. This constitutes the most comprehensive CMB analysis of {\\Lambda}CDM cosmology + strings to date. For ordinary cosmic string networks our updated constraint on the string tension is, in relativistic units, G{\\mu}<1.1x10^-7, while for cosmic superstrings our constraint on the fundamental string tension is G{\\mu}_F<2.8x10^-8, both obtained using Planck2015 temperature and polarisation data.
Radiation from cosmic string standing waves
Olum; Blanco-Pillado
2000-05-01
We have simulated large-amplitude standing waves on an Abelian-Higgs cosmic string in classical lattice field theory. The radiation rate falls exponentially with wavelength, as one would expect from the field profile around a gauge string. Our results agree with those of Moore and Shellard, but not with those of Vincent, Antunes, and Hindmarsh. The radiation rate falls too rapidly to sustain a scaling solution via direct radiation of particles from string length. There is thus reason to doubt claims of strong constraints on cosmic string theories from cosmic ray observations.
CMB distortions from superconducting cosmic strings
Tashiro, Hiroyuki; Sabancilar, Eray; Vachaspati, Tanmay
2012-05-01
We reconsider the effect of electromagnetic radiation from superconducting strings on cosmic microwave background μ and y distortions and derive present (COBE-FIRAS) and future (PIXIE) constraints on the string tension, μs, and electric current, I. We show that absence of distortions of the cosmic microwave background in PIXIE will impose strong constraints on μs and I, leaving the possibility of light strings (Gμs≲10-18) or relatively weak currents (I≲10TeV).
Supermassive screwed cosmic string in dilaton gravity
Energy Technology Data Exchange (ETDEWEB)
Bezerra, V B [Departamento de Fisica, Universidade Federal da ParaIba, 58059-970, Joao Pessoa, PB (Brazil); Ferreira, Cristine N [Nucleo de Fisica, Centro Federal de Educacao Tecnologica de Campos, Rua Dr Siqueira, 273-Parque Dom Bosco, 28030-130, Campos dos Goytacazes, RJ (Brazil); Cuesta, H J Mosquera [Instituto de Cosmologia, Relatividade e AstrofIsica (ICRA-BR), Centro Brasileiro de Pesquisas Fisicas, Rua Dr Xavier Sigaud 150, Urca 22290-180, Rio de Janeiro, RJ (Brazil)
2006-06-21
The early universe might have undergone phase transitions at energy scales much higher than the one corresponding to the grand unified theories (GUT) scales. At these higher energy scales, the transition at which gravity separated from all other interactions, the so-called Planck era, more massive strings called supermassive cosmic strings could have been produced, with energy of about 10{sup 19} GeV. The dynamics of strings formed with this energy scale cannot be described by means of the weak-field approximation, as in the standard procedure for ordinary GUT cosmic strings. As suggested by string theories, at this extreme energy, gravity may be transmitted by some kind of scalar field (usually called the dilaton) in addition to the tensor field of Einstein's theory of gravity. It is then permissible to tackle the issue regarding the dynamics of supermassive cosmic strings within this framework. With this aim, we obtain the gravitational field of a supermassive screwed cosmic string in a scalar-tensor theory of gravity. We show that for the supermassive configuration, exact solutions of scalar-tensor screwed cosmic strings can be found in connection with the Bogomol'nyi limit. We show that the generalization of Bogomol'nyi arguments to the Brans-Dicke theory is possible when torsion is present and we obtain an exact solution in this supermassive regime, with the dilaton solution obtained by consistency with internal constraints.
Cosmic R-string in thermal history
Energy Technology Data Exchange (ETDEWEB)
Kamada, Kohei [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Kobayashi, Tatsuo [Kyoto Univ. (Japan). Dept. of Physics; Ohashi, Keisuke [Osaka City Univ. (Japan). Dept. of Mathematics and Physics; Ookouchi, Yutaka [Kyoto Univ. (Japan). Dept. of Physics; Kyoto Univ. (Japan). The Hakubi Center for Advanced Research
2013-03-15
We study stabilization of an unstable cosmic string associated with spontaneously broken U(1){sub R} symmetry, which otherwise causes a dangerous roll-over process. We demonstrate that in a gauge mediation model, messengers can receive enough corrections from the thermal plasma of the supersymmetric standard model particles to stabilize the unstable modes of the string.
Cosmic Strings Stabilized by Quantum Fluctuations
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.
Cosmic Strings Stabilized by Quantum Fluctuations
Weigel, H
2016-01-01
We compute fermion quantum corrections to the energy of cosmic strings. A number of rather technical tools is needed to formulate this correction and we employ isospin and gauge invariance 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. We find that charged strings are dynamically stabilized in theories similar to the standard model of particle physics.
Wave diffraction by a cosmic string
Fernández-Núñez, Isabel
2016-01-01
We show that if a cosmic string exists, it may be identified through characteristic diffraction pattern in the energy spectrum of the observed signal. In particular, if the string is on the line of sight, the wave field is shown to fit the Cornu spiral. We suggest a simple procedure, based on Keller's geometrical theory of diffraction, which allows to explain wave effects in conical spacetime of a cosmic string in terms of interference of four characteristic rays. Our results are supposed to be valid for scalar massless waves, including gravitational waves, electromagnetic waves, or even sound in case of condensed matter systems with analogous topological defects.
Wave diffraction by a cosmic string
Fernández-Núñez, Isabel; Bulashenko, Oleg
2016-08-01
We show that if a cosmic string exists, it may be identified through characteristic diffraction pattern in the energy spectrum of the observed signal. In particular, if the string is on the line of sight, the wave field is shown to fit the Cornu spiral. We suggest a simple procedure, based on Keller's geometrical theory of diffraction, which allows to explain wave effects in conical spacetime of a cosmic string in terms of interference of four characteristic rays. Our results are supposed to be valid for scalar massless waves, including gravitational waves, electromagnetic waves, or even sound in case of condensed matter systems with analogous topological defects.
Cosmic Acceleration and the String Coupling
Ellis, Jonathan Richard; Nanopoulos, Dimitri V; Ellis, John
2005-01-01
In the context of a cosmological string model describing the propagation of strings in a time-dependent Robertson-Walker background space-time, we show that the asymptotic acceleration of the Universe can be identified with the square of the string coupling. This allows for a direct measurement of the ten-dimensional string coupling using cosmological data. We conjecture that this is a generic feature of a class of non-critical string models that approach asymptotically a conformal (critical) sigma model whose target space is a four-dimensional space-time with a dilaton background that is linear in sigma-model time. The relation between the cosmic acceleration and the string coupling does not apply in critical strings with constant dilaton fields in four dimensions.
Wave diffraction by a cosmic string
Energy Technology Data Exchange (ETDEWEB)
Fernández-Núñez, Isabel [Departament de Física Quàntica i Astrofísica, Facultat de Física, Universitat de Barcelona, Martí i Franquès 1, E-08028 Barcelona (Spain); Institut de Ciències del Cosmos (ICCUB), Facultat de Física, Universitat de Barcelona, Martí i Franquès 1, E-08028 Barcelona (Spain); Bulashenko, Oleg, E-mail: oleg.bulashenko@ub.edu [Departament de Física Quàntica i Astrofísica, Facultat de Física, Universitat de Barcelona, Martí i Franquès 1, E-08028 Barcelona (Spain)
2016-08-26
We show that if a cosmic string exists, it may be identified through characteristic diffraction pattern in the energy spectrum of the observed signal. In particular, if the string is on the line of sight, the wave field is shown to fit the Cornu spiral. We suggest a simple procedure, based on Keller's geometrical theory of diffraction, which allows to explain wave effects in conical spacetime of a cosmic string in terms of interference of four characteristic rays. Our results are supposed to be valid for scalar massless waves, including gravitational waves, electromagnetic waves, or even sound in case of condensed matter systems with analogous topological defects. - Highlights: • Gravitational waves could help us to reveal cosmic strings – topological defects of early Universe. • Wave diffraction in conical spacetime of a cosmic string is solved analytically. • The Cornu spiral is shown to appear when the string is on the line of sight. • For a string located within our galaxy, the highest amplification would occur at a frequency range of LIGO detector.
Gravitational Waves and Light Cosmic Strings
Depies, Matthew R
2009-01-01
Gravitational wave signatures from cosmic strings are analyzed numerically. Cosmic string networks form during phase transistions in the early universe and these networks of long cosmic strings break into loops that radiate energy in the form of gravitational waves until they decay. The gravitational waves come in the form of harmonic modes from individual string loops, a "confusion noise" from galactic loops, and a stochastic background of gravitational waves from a network of loops. In this study string loops of larger size $\\alpha$ and lower string tensions $G\\mu$ (where $\\mu$ is the mass per unit length of the string) are investigated than in previous studies. Several detectors are currently searching for gravitational waves and a space based satellite, the Laser Interferometer Space Antenna (LISA), is in the final stages of pre-flight. The results for large loop sizes ($\\alpha=0.1$) put an upper limit of about $G\\mu<10^{-9}$ and indicate that gravitational waves from string loops down to $G\\mu \\approx...
Effects of Cosmic Strings on Free Streaming
Takahashi, T; Takahashi, Tomo; Yamaguchi, Masahide
2006-01-01
We study the effect of free streaming in a universe with cosmic strings with time-varying tension as well as with constant tension. Although current cosmological observations suggest that fluctuation seeded by cosmic strings cannot be the primary source of cosmic density fluctuation, some contributions from them are still allowed. Since cosmic strings actively produce isocurvature fluctuation, the damping of small scale structure via free streaming by dark matter particles with large velocity dispersion at the epoch of radiation-matter equality is less efficient than that in models with conventional adiabatic fluctuation. We discuss its implications to the constraints on the properties of particles such as massive neutrinos and warm dark matter.
The thin string limit of Cosmic Strings coupled to gravity
Sjodin, K R P
2001-01-01
The thin string limit of Cosmic Strings is investigated using a description in terms of Colombeau's theory of nonlinear generalised functions. It is shown that in this description the energy-momentum tensor has a well defined thin string limit. Furthermore the deficit angle of the conical spacetime that one obtains in the limit may be given in terms of the distributional energy-momentum tensor. On the other hand it is only in the special case of critical coupling that the energy-momentum tensor defined in the Colombeau algebra is associated to a conventional distribution. The asymptotics of both the matter and gravitational field are investigated in the thin string limit and it is shown how this leads to the `conical approximation' which is valid outside the inner core of the string.
Closed timelike geodesics in a gas of cosmic strings
Grøn, Ø; Gron, Oyvind; Johannesen, Steinar
2007-01-01
We find a class of solutions of Einstein's field equations representing spacetime outside a spinning cosmic string surrounded by a gas of non-spinning cosmic strings, and show that there exist closed timelike geodesics in this spacetime.
Tangled up in Spinning Cosmic Strings
Slagter, Reinoud Jan
2015-01-01
It is known for a long time that the space time around a spinning cylindrical symmetric compact object such as the cosmic string, show un-physical behavior, i.e., they would possess closed time like curves (CTC). This controversy with Hawking's chronology protection conjecture is unpleasant but can be understood if one solves the coupled scalar-gauge field equations and the matching conditions at the core of the string. A new interior numerical solution is found of a self gravitating spinning cosmic string with a U(1) scalar gauge field and the matching on the exterior space time is revealed. It is conjectured that the experience of CTC's close to the core of the string is exceedingly unlikely. It occurs when the causality breaking boundary, $r_\\mu$, approaches the boundary of the cosmic string, $r_{CS}$. Then the metric components become singular and the proper time on the core of the string stops flowing. Further, we expect that the angular momentum $J$ will decrease due to the emission of gravitational ene...
Thin shells joining local cosmic string geometries
Energy Technology Data Exchange (ETDEWEB)
Eiroa, Ernesto F. [Universidad de Buenos Aires, Ciudad Universitaria Pabellon I, Departamento de Fisica, Facultad de Ciencias Exactas y Naturales, Buenos Aires (Argentina); Instituto de Astronomia y Fisica del Espacio (IAFE, CONICET-UBA), Buenos Aires (Argentina); Rubin de Celis, Emilio; Simeone, Claudio [Universidad de Buenos Aires, Ciudad Universitaria Pabellon I, Departamento de Fisica, Facultad de Ciencias Exactas y Naturales, Buenos Aires (Argentina); Ciudad Universitaria Pabellon I, IFIBA-CONICET, Buenos Aires (Argentina)
2016-10-15
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. (orig.)
CMB Distortions from Superconducting Cosmic Strings
Tashiro, Hiroyuki; Vachaspati, Tanmay
2012-01-01
We reconsider the effect of electromagnetic radiation from superconducting strings on cosmic microwave background (CMB) mu- and y-distortions and derive present (COBE-FIRAS) and future (PIXIE) constraints on the string tension, mu_s, and electric current, I. We show that absence of distortions of the CMB in PIXIE will impose strong constraints on mu_s and I, leaving the possibility of light strings (G mu_s < 10^{-18}) or relatively weak currents (I < 10 TeV).
Current discontinuities on superconducting cosmic strings
Energy Technology Data Exchange (ETDEWEB)
Troyan, E., E-mail: et@iaaru.astronautiko.org; Vlasov, Yu. V. [Moscow Institute of Physics and Technology (Russian Federation)
2011-07-15
The propagation of current perturbations on superconducting cosmic strings is considered. The conditions for the existence of discontinuities similar to shock waves have been found. The formulas relating the string parameters and the discontinuity propagation speed are derived. The current growth law in a shock wave is deduced. The propagation speeds of shock waves with arbitrary amplitudes are calculated. The reason why there are no shock waves in the case of time-like currents (in the 'electric' regime) is explained; this is attributable to the shock wave instability with respect to perturbations of the string world sheet.
Cosmic strings in axionic-dilatonic gravity
Santos, Caroline
2001-05-01
We first consider local cosmic strings in dilaton-axion gravity and show that they are singular solutions. Then we take a supermassive Higgs limit and present expressions for the fields at far distances from the core by applying a Pecci-Quinn and a duality transformation to the dilatonic Melvin's magnetic universe.
Cosmic strings in axionic-dilatonic gravity
Santos, C
2001-01-01
We first consider local cosmic strings in dilaton-axion gravity and show that they are singular solutions. Then we take a supermassive Higgs limit and present expressions for the fields at far distances from the core by applying a Pecci-Quinn and a duality transformation to the dilatonic Melvin's magnetic universe.
Cosmic String Detection via Microlensing of Stars
Chernoff, David F
2007-01-01
Cosmic superstrings are produced towards the end of the brane inflation. If the string tension is low enough, loops tend to be relatively long-lived. The resultant string network is expected to contain many loops which are smaller than typical Galactic scales. Cosmic expansion damps the center of mass motion of the loops which then cluster like cold dark matter. Loops will lens stars within the galaxy and local group. We explore microlensing of stars as a tool to detect and to characterize some of the fundamental string and string network properties, including the dimensionless string tension $G \\mu/c^2$ and the density of string loops within the Galaxy. As $G \\mu \\to 0$ the intrinsic microlensing rate diverges as $1/\\sqrt{G \\mu}$ but experimental detection will be limited by shortness of the lensing timescale and/or smallness of the bending angle which each vary $\\propto G \\mu$. We find that detection is feasible for a range of tensions. As an illustration, the planned optical astrometric survey mission, Gai...
Non static cosmic strings in Lyra geometry
Rahaman, Farook
2007-01-01
The gravitational field of both local and global non static cosmic strings in the context of Lyra geometry are investigated. Local strings are characterized by having an energy momentum tensor whose only non null components are $T_{tt} = T_{zz}$ . As linearized Einstein equations are formally analogous to the Maxwell equations, the exterior solution does not depend on the radial distribution of the source and hence a Dirac d function was used to approximate the radial distribution of the energy momentum tensor for a local cosmic string along the z-axis: $T_{ab} = \\delta(x) \\delta(y)diag (\\sigma, 0, 0, \\sigma) $, $\\sigma $being the energy density of the string [A.Vilenkin. Phys.Rep.(1985)121,263]. For a global string, the energy momentum tensor components are calculated from the action density for a complex scalar field y along with a Maxican hat potential. The gravitational field of the global string is shown to be attractive in nature.
Scattering off an SO(10) cosmic string
Davis, A C; Davis, A C; Jeannerot, R
1995-01-01
The scattering of fermions from the abelian string arising during the phase transition SO(10) \\rightarrow SU(5) \\times Z_2 induced by the Higgs in the 126 representation is studied. Elastic cross-sections and baryon number violating cross-sections due to the coupling to gauge fields in the core of the string are computed by both a first quantised method and a perturbative second quantised method. The elastic cross-sections are found to be Aharonov-Bohm type. However, there is a marked asymmetry between the scattering cross-sections for left and right handed fields. The catalysis cross-sections are small, depending on the grand unified scale. If cosmic strings were observed our results could help tie down the underlying gauge group.
Cosmic strings and baryon decay catalysis
Energy Technology Data Exchange (ETDEWEB)
Gregory, R.; Perkins, W.B.; Davis, A.C.; Brandenberger, R.H. (Fermi National Accelerator Lab., Batavia, IL (USA); Cambridge Univ. (UK); Brown Univ., Providence, RI (USA). Dept. of Physics)
1989-09-01
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. We review the catalysis processes both in the free quark and skyrmion pictures and discuss the implications for baryogenesis. We present a computation of the cross section for monopole catalyzed skyrmion decay using classical physics. We also discuss some effects which can screen catalysis processes. 32 refs., 1 fig.
Cosmic strings and baryon decay catalysis
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.
An Extension of Multiple Cosmic String Solution A Proposal
Hortacsu, M
1996-01-01
We extend the work done for cosmic strings and show that for a more general class of locally flat metrics the one loop calculation do not introduce any new divergences to the VEV of the energy of a scalar particle. We explicitly perform the calculation for the configuration where we have one cosmic string in the presence of a dipole made out of cosmic strings.
Warped Angle-deficit of a 5 Dimensional Cosmic String
Slagter, Reinoud Jan; Masselink, Derk
2011-01-01
We present a cosmic string on a warped five dimensional space time in Einstein-Yang-Mills theory. Four-dimensional cosmic strings show some serious problems concerning the mechanism of string smoothing related to the string mass per unit length, $G\\mu \\approx 10^{-6}$. A warped cosmic string could overcome this problem and also the superstring requirement that $G\\mu$ must be of order 1, which is far above observational bounds. Also the absence of observational evidence of axially symmetric le...
Ultrahigh-energy particles from cosmic strings
Energy Technology Data Exchange (ETDEWEB)
Bhattacharjee, P. (Chicago Univ., IL (USA). Astronomy and Astrophysics Center Fermi National Accelerator Lab., Batavia, IL (USA))
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.
Dark Energy Generated by Warped Cosmic Strings
Slagter, Reinoud Jan
2014-01-01
If we live on the weak brane in a warped 5D bulk spacetime, gravitational waves and brane fluctuations can be generated by a part of the 5D Weyl tensor and carries information of the gravitational field outside the brane. We consider the U(1) self-gravitating scalar-gauge field on the warped spacetime without bulk matter. It turns out that "branons" can be formed dynamically, due to the modified energy-momentum tensor components of the cosmic string. It turns out that the parameter $\\alpha$, i.e., the gauge-to-scalar mass, changes from a value $>1$ to a value $<1$ and the solution approaches a static global string by shedding off wave energy. It is the time-dependent part of the warp factor which triggers this extraordinary behavior.
Gravitating non-Abelian cosmic strings
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.
The minimal SUSY B - L model: simultaneous Wilson lines and string thresholds
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 . 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 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.
Superconducting Cosmic String with Propagating Torsion
Ferreira, C N; Garcia de Andrade, L C
2000-01-01
We show that it is possible to construct a consistent model describing a current-carrying cosmic string endowed with torsion. The torsion contribution to the gravitational force and geodesics of a test-particle moving around the SCCS are analyzed. In particular, we point out two interesting astrophysical phenomena in which the higher magnitude force we derived may play a critical role: the dynamics of compact objects orbiting the torsioned SCCS and accretion of matter onto it. The deficit angle associated to the SCCS can be obtained and compared with data from the Cosmic Background Explorer (COBE) satellite. We also derived a value for the torsion contribution to matter density fluctuations in the early Universe.
Gravitating non-Abelian cosmic strings
Santo, Antônio de Padua
2015-01-01
In this paper we study regular cosmic string solutions of the non-Abelian Higgs model coupled with the Einstein gravity. In order to do that, we constructed a set of coupled differential ordinary equation. Because there is no closed solution for this set of equations, we solve it numerically. The solutions that we are interested in asymptote to a flat space-time with a planar angle deficit. This model under consideration present two bosonic sectors, besides the non-Abelian gauge one, coupled minimally with the gravitational fields. The two bosonic sectors may present a direct coupling, which plays an important role on the behavior of the matter and gauge fields and also on the behavior on the geometry of the spacetime. We explicitly analyze the behaviors of the energy density and planar angle deficit as function of the energy scale where the gauge symmetry is spontaneously broken and the coupling interaction between the bosonic sectors.
Cosmic D--term Strings as Wrapped D3 Branes
Halyo, E
2004-01-01
We describe cosmic D--term strings as D3 branes wrapped on a resolved conifold. The matter content that gives rise to D--term strings is shown to describe the world--volume theory of a space--filling D3 brane transverse to the conifold which itself is a wrapped D5 brane. We show that, in this brane theory, the tension of the wrapped D3 brane mathces that of the D--term string. We argue that there is a new type of cosmic string which arises from fractional D1 branes on the world--volume of a fractional D3 brane.
Relativistic Landau Levels in the Rotating Cosmic String Spacetime
Cunha, M S; Christiansen, H R; Bezerra, V B
2016-01-01
We calculate the energy levels of a spinless massive and charged particle interacting with a stationary rotating cosmic string in a region with a static homogeneous magnetic field parallel to the string. First, we completely solve the Klein-Gordon equation in that particular spacetime, checking consistency in the non-relativistic limit and comparing with the static string case. We also solve the problem for a magnetized rotating cosmic string in order to find the Landau levels using rigid-wall boundary conditions, and discuss the possibility of these levels to be purely induced by spacetime rotation.
Scaling properties of cosmic (super)string networks
Martins, C J A P
2013-01-01
I use a combination of state-of-the-art numerical simulations and analytic modelling to discuss the scaling properties of cosmic defect networks, including superstrings. Particular attention is given to the role of extra degrees of freedom in the evolution of these networks. Compared to the 'plain vanilla' case of Goto-Nambu strings, three such extensions play important but distinct roles in the network dynamics: the presence of charges/currents on the string worldsheet, the existence of junctions, and the possibility of a hierarchy of string tensions. I also comment on insights gained from studying simpler defect networks, including Goto-Nambu strings themselves, domain walls and semilocal strings.
The bispectrum of matter perturbations from cosmic strings
Regan, Donough
2014-01-01
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 nu...
Effect of a cosmic string on spin dynamics
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.
The Flow Around a Cosmic String, Part I: Hydrodynamic Solution
Beresnyak, Andrey
2015-01-01
Cosmic strings are linear topological defects which are hypothesized to be produced during inflation. Most searches for strings have been relying on the string's lensing of background galaxies or CMB. In this paper I obtained the solution for the supersonic flow of the collisional gas past the cosmic string which has two planar shocks with shock compression ratio that depend on the angle defect of the string and its speed. The shocks result in compression and heating of the gas and, given favorable condition, particle acceleration. The gas heating and overdensity in an unusual wedge shape can be detected by observing HI line at high redshifts. The particle acceleration can occur in present-day Universe when the string crosses the hot gas contained in galaxy clusters and, since the consequences of such collision persist for cosmological timescales, could be located by looking at the unusual large-scale radio sources situated on a single spatial plane.
Wakes in Dilatonic Current-Carrying Cosmic Strings
Oliveira, A L N
2003-01-01
In this work, we present the gravitational field generated by a cosmic string carrying a timelike current in the scalar-tensor gravities. The mechanism of formation and evolution of wakes is fully investigated in this framework. We show that the inclusion of electromagnetic properties for the string induces logarithmic divergences in the accretion problem.
The Minimal SUSY $B-L$ Model: Simultaneous Wilson Lines and String Thresholds
Deen, Rehan; Purves, Austin
2016-01-01
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 ${\\mathbb Z}_{3}\\times {\\mathbb Z}_{3}$ 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 $\\left$. 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 st...
Wavelet-Bayesian inference of cosmic strings embedded in the cosmic microwave background
McEwen, J D; Peiris, H V; Wiaux, Y; Ringeval, C; Bouchet, F R
2016-01-01
Cosmic strings are a well-motivated extension to the standard cosmological model and could induce a subdominant component in the anisotropies of the cosmic microwave background (CMB), in addition to the standard inflationary component. The detection of strings, while observationally challenging, would provide a direct probe of physics at very high energy scales. We develop a new framework for cosmic string inference, constructing a Bayesian analysis in wavelet space where the string-induced CMB component has distinct statistical properties to the standard inflationary component. Our wavelet-Bayesian framework provides a principled approach to compute the posterior distribution of the string tension $G\\mu$ and the Bayesian evidence ratio comparing the string model to the standard inflationary model. Furthermore, we present a technique to recover an estimate of any string-induced CMB map embedded in observational data. Using Planck-like simulations we demonstrate the application of our framework and evaluate it...
Cosmic D-strings as Axionic D-term Strings
Blanco-Pillado, J J; Redi, M; Blanco-Pillado, Jose J.; Dvali, Gia; Redi, Michele
2005-01-01
In this work we derive non-singular BPS string solutions from an action that captures the essential features of a D-brane-anti-D-brane system compactified to four dimensions. The model we consider is a supersymmetric abelian Higgs model with a D-term potential coupled to an axion-dilaton multiplet. The strings in question are axionic D-term strings which we identify with the D-strings of type II string theory. In this picture the Higgs field represents the open string tachyon of the D-Dbar pair and the axion is dual to a Ramond Ramond form. The crucial term allowing the existence of non-singular BPS strings is the Fayet-Iliopoulos term, which is related to the tensions of the D-string and of the parent branes. Despite the presence of the axion, the strings are BPS and carry finite energy, due to the fact that the space gets very slowly decompactified away from the core, screening the long range axion field (or equivalently the theory approaches an infinitely weak 4D coupling). Within our 4D effective action w...
Search for Cosmic Strings in the COSMOS Survey
Christiansen, J L; Goldman, J; Teng, I P W; Foley, M; Smoot, G F
2010-01-01
We search the COSMOS survey for pairs of galaxies consistent with the gravitational lensing signature of a cosmic string. The COSMOS survey imaged 1.64 square degrees using the Advanced Camera for Surveys (ACS) aboard the Hubble Space Telescope (HST). Our technique includes estimates of the efficiency for finding the lensed galaxy pair. We find no evidence for cosmic strings with a mass per unit length of G\\mu/c^2 < 3.0E-7 out to redshifts greater than 0.6 at 95% confidence. This corresponds to a global limit on Omega_string<0.0017.
Cosmic Strings and the Origin of Globular Clusters
Barton, Alistair; Lin, Ling
2015-01-01
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.
Evolution of a Non-Abelian Cosmic String Network
McGraw, P N
1998-01-01
We describe a numerical simulation of the evolution of an $S_3$ cosmic string network which takes fully into account the non-commutative nature of the cosmic string fluxes and the topological obstructions which hinder strings from moving past each other or intercommuting. The influence of initial conditions, string tensions, and other parameters on the network's evolution is explored. In a broad range of regimes, the total energy density as a function of time exhibits a familiar power-law behavior, and we do not find strong support for a string-dominated cosmological scenario. However, the speed of the network's collapse (coefficient of the power law) can vary quite a bit, as can the qualitative features of the network. There is a surprisingly strong dependence on the statistical properties of the initial conditions. The results give some insight as to which processes play the most important roles in the evolution of a non-Abelian network.
Exceptional Colloquium: The Rise, Fall, and Rebirth of Cosmic Strings
CERN. Geneva
2005-01-01
In the 1980s many people were excited by the concept that cosmic strings, as relics of the Grand Unified Era, could be responsible for the formation of cosmic structure. In the 1990s the cosmic string concept steadily lost ground to the Inflationary model both as a result of the difficulty of calculations and more definitively through observations of the CMB. About the time many expected the new WMAP data to deliver the coup de grace, the concepts of cosmic strings as major physical phenomena (not so important in structure formation) has begun a renaissance. This new interest is motivated by one of the original ideas that topological defects are inevitable in symmetry breaking by the Kibble (1976) mechanism and the introduction of new ideas such as brane-cosmology/inflation and the realization that cosmic strings may be the only acceptable such defect. We find ourselves back in the business of trying to detect or limit and understand cosmic strings once again for the insight and constraints they put on p...
Cosmic Strings and Their Induced Non-Gaussianities in the Cosmic Microwave Background
Directory of Open Access Journals (Sweden)
Christophe Ringeval
2010-01-01
small fraction of the CMB angular power spectrum, cosmic strings could actually be the main source of its non-Gaussianities. In this paper, after having reviewed the basic cosmological properties of a string network, we present the signatures Nambu-Goto cosmic strings would induce in various observables ranging from the one-point function of the temperature anisotropies to the bispectrum and trispectrum. It is shown that string imprints are significantly different than those expected from the primordial type of non-Gaussianity and could therefore be easily distinguished.
Cold, warm, and composite (cool) cosmic string models
Carter, B
1994-01-01
The dynamical behaviour of a cosmic string is strongly affected by any reduction of the effective string tension $T$ below the constant value $T=m^2$ say that characterizes the simple, longitudinally Lorentz invariant, Goto Nambu string model in terms of a fixed mass scale $m$ whose magnitude depends on that of the Higgs field responsible for the existence of the string. Such a reduction occurs in the standard "hot" cosmic string model in which the effect of thermal perturbations of a simple Goto Nambu model is expressed by the formula $T^2=m^2(m^2-2\\pi\\Theta^2/3)$, where $\\Theta$ is the string temperature. A qualitatively similar though analytically more complicated tension reduction phenomenon occurs in "cold" conducting cosmic string models where the role of the temperature is played by an effective chemical potential $\\mu$ that is constructed as the magnitude of the phase $\\phi$ of a bosonic condensate of the kind whose existence was first proposed by Witten. The present article describes the construction...
Non-thermal Production of Neutralino Cold Dark Matter from Cosmic String Decays
Jeannerot, R; Brandenberger, R H
1999-01-01
We propose a mechanism of nonthermal production of a neutralino cold dark matter particle, $\\chi$, from the decay of cosmic strings which form from the spontaneous breaking of a U(1) gauge symmetry, such as $U_{B-L}(1)$, in an extension of the minimal supersymmetric standard model (MSSM). By explicit calculation, we point out that with a symmetry breaking scale $\\eta$ of around $10^8$ GeV, the decay of cosmic strings can give rise to $\\Omega_\\chi \\simeq 1$. This gives a new constraint on supersymmetric models. For example, the dark matter produced from strings will overclose the universe if $\\eta$ is near the electroweak symmetry breaking scale. To be consistent with $\\Omega_\\chi \\leq 1$, the mass of the new U(1) gauge boson must be much larger than the Fermi scale which makes it unobservable in upcoming accelerator experiments. In a supersymmetric model with an extra $U_{B-L}(1)$ symmetry, the requirement of provided neutrino masses are generated by the see-saw mechanism.
Evolution of a non-Abelian cosmic string network
Energy Technology Data Exchange (ETDEWEB)
McGraw, P. [California Institute of Technology, Pasadena, California 91125 (United States)]|[Institute of Field Physics, Department of Physics and Astronomy, University of North Carolina, Chapel Hill, North Carolina 27599 (United States)
1998-03-01
We describe a numerical simulation of the evolution of an S{sub 3} cosmic string network which takes fully into account the noncommutative nature of the cosmic string fluxes and the topological obstructions which hinder strings from moving past each other or intercommuting. The influence of initial conditions, string tensions, and other parameters on the network{close_quote}s evolution is explored. Contrary to some previous suggestions, we find no strong evidence of the {open_quotes}freezing{close_quotes} required for a string-dominated cosmological scenario. Instead, the results in a broad range of regimes are consistent with the familiar scaling law, i.e., a constant number of strings per horizon volume. The size of this number, however, can vary quite a bit, as can other overall features. There is a surprisingly strong dependence on the statistical properties of the initial conditions. We also observe a rich variety of interesting new structures, such as light string webs stretched between heavier strings, which are not seen in Abelian networks. {copyright} {ital 1998} {ital The American Physical Society}
Bosonic structure of realistic SO(10) supersymmetric cosmic strings
Allys, Erwan
2016-05-01
We study the bosonic structure of F -term Nambu-Goto cosmic strings forming in a realistic SO(10) implementation, assuming standard hybrid inflation. We describe the supersymmetric grand unified theory, and its spontaneous symmetry breaking scheme in parallel with the inflationary process. We also write the explicit tensor formulation of its scalar sector, focusing on the subrepresentations singlet under the standard model, which is sufficient to describe the string structure. We then introduce an ansatz for Abelian cosmic strings, discussing in details the hypothesis, and write down the field equations and boundary conditions. Finally, after doing a perturbative study of the model, we present and discuss the results obtained with numerical solutions of the string structure.
Light-Cone Fluctuations in the Cosmic String Spacetime
Mota, H F; Bessa, C H G; Bezerra, V B
2016-01-01
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, improving the signal and thus, making possible the detection of such quantity.
Model dependence of baryon decay enhancement by cosmic strings
Fewster, C J
1993-01-01
Cosmic strings arising from GUTs can catalyse baryon decay processes with strong interaction cross sections. We examine the mechanism by which the cross section is enhanced and find that it depends strongly on the details of the distribution of gauge fields within the string core. We propose a calculational scheme for estimating wavefunction amplification factors and also a physical understanding of the nature of the enhancement process.
New CMB constraints for Abelian Higgs cosmic strings
Lizarraga, Joanes; Daverio, David; Hindmarsh, Mark; Kunz, Martin
2016-01-01
We present cosmic microwave background (CMB) power spectra from recent numerical simulations of cosmic strings in the Abelian Higgs model and compare them to CMB power spectra measured by Planck. We obtain revised constraints on the cosmic string tension parameter $G\\mu$. For example, in the $\\Lambda$CDM model with the addition of strings and no primordial tensor perturbations, we find $G\\mu < 2.0 \\times 10^{-7}$ at 95% confidence, about 20% lower than the value obtained from previous simulations, which had 1/64 of the spatial volume. We investigate the source of the difference, showing that the main cause is an improved treatment of the string evolution across the radiation-matter transition. The increased computational volume also makes possible to simulate fully the physical equations of motion, in which the string cores shrink in comoving coordinates. This, and the larger dynamic range, changes the amplitude of the power spectra by only about 10%, demonstrating that field theory simulations of cosmic s...
Relativistic Landau levels in the rotating cosmic string spacetime
Cunha, M. S.; Muniz, C. R.; Christiansen, H. R.; Bezerra, V. B.
2016-09-01
In the spacetime induced by a rotating cosmic string we compute the energy levels of a massive spinless particle coupled covariantly to a homogeneous magnetic field parallel to the string. Afterwards, we consider the addition of a scalar potential with a Coulomb-type and a linear confining term and completely solve the Klein-Gordon equations for each configuration. Finally, assuming rigid-wall boundary conditions, we find the Landau levels when the linear defect is itself magnetized. Remarkably, our analysis reveals that the Landau quantization occurs even in the absence of gauge fields provided the string is endowed with spin.
Relativistic Landau levels in the rotating cosmic string spacetime
Energy Technology Data Exchange (ETDEWEB)
Cunha, M.S. [Universidade Estadual do Ceara, Grupo de Fisica Teorica (GFT), Fortaleza, CE (Brazil); Muniz, C.R. [Universidade Estadual do Ceara, Faculdade de Educacao, Ciencias e Letras de Iguatu, Iguatu, CE (Brazil); Christiansen, H.R. [Instituto Federal de Ciencia, Educacao e Tecnologia, IFCE Departamento de Fisica, Sobral (Brazil); Bezerra, V.B. [Universidade Federal da Paraiba-UFPB, Departamento de Fisica, Caixa Postal 5008, Joao Pessoa, PB (Brazil)
2016-09-15
In the spacetime induced by a rotating cosmic string we compute the energy levels of a massive spinless particle coupled covariantly to a homogeneous magnetic field parallel to the string. Afterwards, we consider the addition of a scalar potential with a Coulomb-type and a linear confining term and completely solve the Klein-Gordon equations for each configuration. Finally, assuming rigid-wall boundary conditions, we find the Landau levels when the linear defect is itself magnetized. Remarkably, our analysis reveals that the Landau quantization occurs even in the absence of gauge fields provided the string is endowed with spin. (orig.)
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.
Dynamical simulation of non-abelian cosmic strings
McGraw, P
1996-01-01
We describe a method for simulating the dynamics of an S_3 cosmic string network. We use a lattice Monte Carlo to generate initial conditions for the network, which subsequently is allowed to relax continuously according to a simplified model of string dynamics. The dynamics incorporates some novel features which, to our knowledge, have not been studied in previous numerical simulations: The existence of two types of string which may have different tensions, and the possibility that two non-commuting strings may intersect. Simulation of the non-commuting fluxes presents a computational challenge as it requires a rather complex gauge-fixing procedure. The flux definitions change as strings change their positions and orientations relative to each other and must be carefully updated as the network evolves. The method is described here in some detail, with results to be presented elsewhere.
A possible origin of superconducting currents in cosmic strings
Chavez, H; Chavez, Helder; Masperi, Luis
2002-01-01
The scattering and capture of right-handed neutrinos by an Abelian cosmic string in the SO(10) grand unification model are considered. The scattering cross-section of neutrinos per unit length due to the interaction with the gauge and Higgs fields of the string is much larger in its scaling regime than in the friction one because of the larger infrared cutoff of the former.The probability of capture in a zero mode of the string accompanied by the emission of a gauge or Higgs boson shows a resonant peak for neutrino momentum of the order of its mass. Considering the decrease of number of strings per unit comoving volume in the scaling epoch the cosmological consequences of the superconducting strings formed in this regime will be much smaller than those which could be produced already in the friction one.
The String and the Cosmic Bounce
Directory of Open Access Journals (Sweden)
Bozza V.
2014-04-01
Full Text Available String theory introduces a new fundamental scale (the string length that is expected to regularize the singularities of classical general relativity. In a cosmological context, the Big Bang is no longer regarded as the beginning of time, but just a transition between a Pre-Big Bang collapse phase and the current expansion. We will review old and recent attempts to build consistent bouncing cosmologies inspired to string theories, discussing their solved and unsolved problems, focussing on the observables that may distinguish them from standard inflationary scenarios.
Axions from cosmic string and wall decay
Energy Technology Data Exchange (ETDEWEB)
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.
Cosmic String Universes Embedded with Viscosity
Institute of Scientific and Technical Information of China (English)
Koijam Manihar Singh; Kangujam Priyokumar Singh
2011-01-01
We study string cosmological models with attached particles in LRS BI type space time.The dynamical and physical properties of such universes are studied,and the possibility that during the evolution of the universe the strings disappear,leaving only the particles,is also discussed.It is found that bulk viscosity plays a large role in the evolution of the universe.In these models we find critical instances of when there was a “Bounce”.The studied models are found to be of an inflationary type,and since a desirable feature of a meaningful string cosmological model is the presence of an inflationary epoch in the very early stages of evolution,our models can be thought of as realistic universes.The origin of the universe and the early stages of formation are still interesting areas of research.The concept of string theory was developed to describe the events of the early stages of the evolution of the universe.The universe can be described as a collection of extended (non point) objects.Thus,“string dust” cosmology will provide us with a model to investigate the properties related to this fact.%We study string cosmological models with attached particles in LRS BI type space time. The dynamical and physical properties of such universes are studied, and the possibility that during the evolution of the universe the strings disappear, leaving only the particles, is also discussed. It is found that bulk viscosity plays a large role in the evolution of the universe. In these models we find critical instances of when there was a "Bounce". The studied models are found to be of an inflationary type, and since a desirable feature of a meaningful string cosmological model is the presence of an inflationary epoch in the very early stages of evolution, our models can be thought of as realistic universes.
Cosmic strings in an expanding spacetime
Energy Technology Data Exchange (ETDEWEB)
Stein-Schabes, J.A.; Burd, A.B.
1988-03-15
We study string solutions in an expanding Friedmann-Robertson-Walker (FRW) spacetime. The back reaction of the string on the spacetime has been ignored so that the background stays Friedmannian throughout the evolution. By numerically integrating the field equations in both radiation- and matter-dominated eras, we discover some new oscillatory solutions. The possible damping of these oscillations is discussed. For late times the solution becomes identical to the static one.
THE FLOW AROUND A COSMIC STRING. I. HYDRODYNAMIC SOLUTION
Energy Technology Data Exchange (ETDEWEB)
Beresnyak, Andrey [Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Nordita, KTH Royal Institute of Technology and Stockholm University, SE-10691 (Sweden)
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.
New Solutions for Non-Abelian Cosmic Strings
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.
Cosmic Microwave Background and Density Fluctuations from Strings plus Inflation
Contaldi, C; Magueijo, J; Contaldi, Carlo; Hindmarsh, Mark; Magueijo, Joao
1999-01-01
In cosmological models where local cosmic strings are formed at the end of a period of inflation, the perturbations are seeded both by the defects and by the quantum fluctuations. In a subset of these models, for example those based on $D$-term inflation, the amplitudes are similar. Using our recent calculations of structure formation with cosmic strings, we point out that in a flat cosmology with zero cosmological constant and 5% baryonic component, strings plus inflation fits the observational data much better than each component individually. The large-angle CMB spectrum is mildly tilted, for Harrison-Zeldovich inflationary fluctuations. It then rises to a thick Doppler bump, covering $\\ell=200-600$, modulated by soft secondary undulations. The standard CDM anti-biasing problem is cured, giving place to a slightly biased scenario of galaxy formation.
Cosmic strings in an expanding spacetime
Energy Technology Data Exchange (ETDEWEB)
Stein-Schabes, J.A.; Burd, A.B.
1987-04-01
We investigate the stability of a static, infinitely long and straight vacuum string solution under inhomogeneous axisymmetric time-dependent perturbations. We find it to be perturbatively stable. We further extend our work by finding a string solutions in an expanding Universe. The back reaction of the string on the gravitational field has been ignored. The background is assumed to be a Friedman-Robertson-Walker (FRW) cosmology. By numerically integrating the field equations in a radiation and matter dominated models, we discover oscillatory solutions. The possible damping of these oscillations is discussed. For late times the solution becomes identical to the static one studied in the first part of the paper. 19 refs., 8 figs.
Abelian cosmic string in the extended Starobinsky model of gravity
Graça, J P Morais
2016-01-01
We analyze numerically the behaviour of the solutions corresponding to an Abelian cosmic string taking into account an extension of the Starobinsky model, where the action of general relativity is replaced by $f(R) = R - 2\\Lambda + \\eta R^2 + \\rho R^m$, with $m > 2$. As an interesting result, we find that the angular deficit which characterizes the cosmic string decreases as the parameters $\\eta$ and $\\rho$ increase. We also find that the cosmic horizon due to the presence of a cosmological constant is affected in such a way that it can grows or shrinks, depending on the vacuum expectation value of the scalar field and on the value of the cosmological constant
New solutions for non-Abelian cosmic strings
Hindmarsh, Mark; Weir, David J
2016-01-01
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 $Z_2$, 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 $Z_2$ 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 $Z_4$ 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 emb...
CMB Anisotropy due to Cosmic Strings in an Accelerated Expanding Universe
Rokni, S Y; Bordbar, M R
2013-01-01
We want to find the cosmological constant influence on cosmic microwave background (CMB) anisotropy due to cosmic strings. Considering the space-time metric of a cosmic string under the effect of a positive cosmological constant, the CMB anisotropy is studied. The result shows that a positive cosmological constant (i.e. the presence of cosmic strings in an accelerated expanding universe) weakens the anisotropy so that more strong resolution is needed to detect the corresponding influences on the CMB power spectrum.
Gravitational smoothing of kinks on cosmic string loops
Wachter, Jeremy M
2016-01-01
We analyze the effect of gravitational back reaction 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. 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 give results for the rectangular Garfinkle-Vachaspati loop.
D-term cosmic strings from N=2 Supergravity
Achúcarro, A; Esole, M; Van Proeyen, A; Van den Bergh, J; Achucarro, Ana; Bergh, Joris Van den; Celi, Alessio; Esole, Mboyo; Proeyen, Antoine Van
2006-01-01
We describe new half-BPS cosmic string solutions in N=2, d=4 supergravity coupled to one vector multiplet and one hypermultiplet. They are closely related to D-term strings in N=1 supergravity. Fields of the N=2 theory that are frozen in the solution contribute to the triplet moment map of the quaternionic isometries and leave their trace in N=1 as a constant Fayet-Iliopoulos term. The choice of U(1) gauging and of special geometry are crucial. The construction gives rise to a non-minimal Kaehler potential and can be generalized to higher dimensional quaternionic-Kaehler manifolds.
Gravitational Smoothing of Kinks on Cosmic String Loops
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.
Solution for a local straight cosmic string in the braneworld gravity
Energy Technology Data Exchange (ETDEWEB)
Abdalla, M.C.B.; Carlesso, P.F. [UNESP, Universidade Estadual Paulista, Instituto de Fisica Teorica, Rua Dr. Bento Teobaldo Ferraz 271, Bloco II, Barra-Funda, Caixa Postal 70532-2, Sao Paulo, SP (Brazil); Hoff da Silva, J.M. [UNESP, Universidade Estadual Paulista, Departamento de Fisica e Quimica, Guaratingueta, SP (Brazil)
2015-09-15
In this work we deal with the spacetime shaped by a straight cosmic string, emerging from local gauge theories, in the braneworld gravity context. We search for physical consequences of string features due to the modified gravitational scenario encoded in the projected gravitational equations. It is shown that cosmic strings in braneworld gravity may present significant differences when compared to the general relativity predictions, since its linear density is modified and the deficit angle produced by the cosmic string is attenuated. Furthermore, the existence of cosmic strings in that scenario requires a strong restriction to the braneworld tension: λ ≥ 3 x 10{sup -17}, in Planck units. (orig.)
Dynamics of cosmic strings with higher-dimensional windings
Energy Technology Data Exchange (ETDEWEB)
Yamauchi, Daisuke [Research Center for the Early Universe, School of Science, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan); Lake, Matthew J. [The Institute for Fundamental Study, “The Tah Poe Academia Institute' , Naresuan University, Phitsanulok 65000 (Thailand); Thailand Center of Excellence in Physics, Ministry of Education,Bangkok 10400 (Thailand)
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.
Cosmic microwave background experiments targeting the cosmic strings Doppler peak signal
Magueijo, J; Magueijo, Joao; Hobson, Mike
1996-01-01
We investigate which experiments are better suited to test the robust prediction that cosmic strings do not produce secondary Doppler peaks. We propose a statistic for detecting oscillations in the C^l spectrum, and study its statistical relevance given the truth of an inflationary competitor to cosmic strings. The analysis is performed for single-dish experiments and interferometers, subject to a variety of noise levels and scanning features. A high resolution of 0.2 degrees is found to be required for single-dish experiments with realistic levels of noise. Interferometers appear to be more suitable for detecting this signal.
Cosmic R-string, R-tube and vacuum instability
Energy Technology Data Exchange (ETDEWEB)
Eto, Minoru [Yamagata Univ. (Japan). Dept. of Physics; Hamada, Yuta; Kobayashi, Tatsuo [Kyoto Univ. (Japan). Dept. of Physics; Kamada, Kohei [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Ohashi, Keisuke [Osaka City Univ. (Japan). Dept. of Mathematics and Physics; Ookouchi, Yutaka [Kyoto Univ. (Japan). Dept. of Physics; Kyoto Univ. (Japan). The Hakubi Center for Advanced Research
2012-11-15
We show that a cosmic string associated with spontaneous U(1) R symmetry breaking gives a constraint for supersymmetric model building. In some models, the string can be viewed as a tube-like domain wall with a winding number interpolating a false vacuum and a true vacuum. Such string causes inhomogeneous decay of the false vacuum to the true vacuum via rapid expansion of the radius of the tube and hence its formation would be inconsistent with the present Universe. However, we demonstrate that there exist metastable solutions which do not expand rapidly. Furthermore, when the true vacua are degenerate, the structure inside the tube becomes involved. As an example, we show a ''bamboo''-like solution, which suggests a possibility observing an information of true vacua from outside of the tube through the shape and the tension of the tube.
Disruption of Cosmic String Wakes by Gaussian Fluctuations
Brandenberger, Robert H; da Cunha, Disrael C N
2015-01-01
We study the stability of cosmic string wakes against the disruption by the dominant Gaussian fluctuations which are present in cosmological models. We find that for a string tension given by $G \\mu = 10^{-7}$ wakes remain locally stable until a redshift of $z = 6$, and for a value of $G \\mu = 10^{-14}$ they are stable beyond a redshift of $z = 20$. We study a global stability criterion which shows that wakes created by strings at times after $t_{eq}$ are identifiable up to the present time, independent of the value of $G \\mu$. Taking into account our criteria it is possible to develop strategies to search for the distinctive position space signals in cosmological maps which are induced by wakes.
Cosmic R-string, R-tube and Vacuum Instability
Eto, Minoru; Kamada, Kohei; Kobayashi, Tatsuo; Ohashi, Keisuke; Ookouchi, Yutaka
2012-01-01
We show that a cosmic string associated with spontaneous $U(1)_R$ symmetry breaking gives a constraint for supersymmetric model building. In some models, the string can be viewed as a tube-like domain wall with a winding number interpolating a false vacuum and a true vacuum. Such string causes inhomogeneous decay of the false vacuum to the true vacuum via rapid expansion of the radius of the tube and hence its formation would be inconsistent with the present Universe. However, we demonstrate that there exist metastable solutions which do not expand rapidly. Furthermore, when the true vacua are degenerate, the structure inside the tube becomes involved. As an example, we show a "bamboo"-like solution, which suggests a possibility observing an information of true vacua from outside of the tube through the shape and the tension of the tube.
Rotating black holes pierced by a cosmic string
Kubiznak, David
2015-01-01
A rotating black hole threaded by an infinitely long cosmic string is studied in the framework of the Abelian Higgs model. We show that contrary to a common belief in the presence of rotation the backreaction of the string does not induce a simple conical deficit. This leads to new distinct features of the Kerr--string system such as modified ISCO or shifted ergosphere, though these effects are most likely outside the range of observational precision. For an extremal rotating black hole, the system exhibits a first-order phase transition for the gravitational Meissner effect: small black holes exhibit a flux-expelled solution, with the gauge and scalar field remaining identically in their false vacuum state on the event horizon, whereas the horizon of large black holes is pierced by the vortex. A brief review prepared for the MG14 Proceedings.
Quantum dynamics of scalar bosons in a cosmic string background
Energy Technology Data Exchange (ETDEWEB)
Castro, Luis B. [Universidade Federal do Maranhao, Departamento de Fisica, Sao Luis, MA (Brazil)
2015-06-15
The quantum dynamics of scalar bosons embedded in the background of a cosmic string is considered. In this work, scalar bosons are described by the Duffin-Kemmer-Petiau (DKP) formalism. In particular, the effects of this topological defect in the equation of motion, energy spectrum, and DKP spinor are analyzed and discussed in detail. The exact solutions for the DKP oscillator in this background are presented in closed form. (orig.)
Search for Cosmic Strings in the GOODS Survey
Christiansen, J L; James, K A; Goldman, J; Maruyama, D; Smoot, G F
2008-01-01
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 1 (0.5) for cosmic strings to a mass per unit length limit of $G\\mu<3.0x10^{-7}$ at 95% CL. In the combined 314.9 arcmin$^2$ of the North and South survey fields this corresponds to a limit on $\\Omega_{strings}<0.0056$. Our global limit on $G\\mu$ is more than an order of magnitude lower than searches for individual strings in 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.
Fermionic condensate and the Casimir effect in cosmic string spacetime
Grigoryan, A Kh; Saharian, A A
2016-01-01
We investigate combined effects of nontrivial topology, induced by a cosmic string, and boundaries on the fermionic condensate and the vacuum expectation value (VEV) of the energy-momentum tensor for a massive fermionic field. As geometry of boundaries we consider two plates perpendicular to the string axis on which the field is constrained by the MIT bag boundary condition. By using the Abel-Plana type summation formula, the VEVs in the region between the plates are decomposed into the boundary-free and boundary-induced contributions for general case of the planar angle deficit. The boundary-induced parts in both the fermionic condensate and the energy-momentum tensor vanish on the cosmic string. Fermionic condensate is positive near the string and negative al large distances, whereas the vacuum energy density is negative everywhere. The radial stress is equal to the energy density. For a massless field, the boundary-induced contribution in the VEV of the energy-momentum tensor is different from zero in the ...
Constraints on cosmic (super)strings from the LIGO-Virgo gravitational-wave detectors
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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
2013-01-01
Cosmic string cusps produce powerful bursts of gravitational waves (GWs). These bursts provide the most promising observational signature of cosmic strings. In this letter we report stringent limits on cosmic string models obtained from the analysis of 625 days of observation with the LIGO and Virgo GW detectors. A significant fraction of the cosmic string parameter space is ruled out. This result complements and improves existing limits from searches for a stochastic background of GWs using cosmic microwave background and pulsar timing data. In particular, if the size of loops is given by gravitational back-reaction, we place upper limits on the string tension $G\\mu$ 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
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.; 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.
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.; 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.
Abelian Higgs Cosmic Strings: Small Scale Structure and Loops
Hindmarsh, Mark; Bevis, Neil
2008-01-01
Classical lattice simulations of the Abelian Higgs model are used to investigate small scale structure and loop distributions in cosmic string networks. Use of the field theory ensures that the small-scale physics is captured correctly. The results confirm analytic predictions of Polchinski & Rocha [1] for the two-point correlation function of the string tangent vector, with a power law from length scales of order the string core width up to horizon scale with evidence to suggest that the small scale structure builds up from small scales. An analysis of the size distribution of string loops gives a very low number density, of order 1 per horizon volume, in contrast with Nambu-Goto simulations. Further, our loop distribution function does not support the detailed analytic predictions for loop production derived by Dubath et al. [2]. Better agreement to our data is found with a model based on loop fragmentation [3], coupled with a constant rate of energy loss into massive radiation. Our results show a stron...
Planck 2013 results. XXV. Searches for cosmic strings and other topological defects
DEFF Research Database (Denmark)
Planck Collaboration,; Ade, P. A. R.; Aghanim, N.
2013-01-01
-Goto cosmic strings, as well as field theory strings for which radiative effects are important, thus spanning the range of theoretical uncertainty in strings models. We have added the angular power spectrum from strings to that for a simple adiabatic model, with the extra fraction defined as $f_{10......Planck data have been used to provide stringent new constraints on cosmic strings and other defects. We describe forecasts of the CMB power spectrum induced by cosmic strings, calculating these from network models and simulations using line-of-sight Boltzmann solvers. We have studied Nambu......}$ at multipole $\\ell=10$. This parameter has been added to the standard six parameter fit using COSMOMC with flat priors. For the Nambu-Goto string model, we have obtained a constraint on the string tension of $G\\mu/c^2
Gravitational back reaction on piecewise linear cosmic string loops
Wachter, Jeremy M
2016-01-01
We calculate the metric and affine connection due to a piecewise linear cosmic string loop, and the effect of gravitational back reaction for the Garfinkle-Vachaspati loop with four straight segments. As expected, back reaction reduces the size of the loop, in accord with the energy going into gravitational waves. The "square" loop whose generators lie at right angles evaporates without changing shape, but in all other cases, the kinks become less sharp and segments between kinks become curved. If the loop is close to the square case, the loop 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. In more realistic loops, the curvature of the straight segments due to gravitational back reaction may lead to cusps which did not exist in the original shape with the bending of the string concentrated at kinks.
Non-Gaussian spectra and the search for cosmic strings
Magueijo, Joao; Lewin, Alex
1997-01-01
We present a new tool for relating theory and experiment suited for non-Gaussian theories: non-Gaussian spectra. It does for non-Gaussian theories what the angular power spectrum $C_\\ell$ does for Gaussian theories. We then show how previous studies of cosmic strings have over rated their non-Gaussian signature. More realistic maps are not visually stringy. However non-Gaussian spectra will accuse their stringiness. We finally summarise the steps of an undergoing experimental project aiming a...
Is it Really Naked? On Cosmic Censorship in String Theory
Energy Technology Data Exchange (ETDEWEB)
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.
On Bianchi-I cosmic strings coupled with Maxwell ﬁelds in bimetric relativity
Indian Academy of Sciences (India)
V Mahurpawar; S D Deo
2003-10-01
Axially symmetric Bianchi-I model is studied with source cosmic cloud strings coupled with electromagnetic ﬁeld in Rosen’s bimetric theory of relativity and observed that there is no contribution from cosmic strings and Maxwell ﬁelds in this theory.
Cosmic Strings as the Source of Small-Scale Microwave Background Anisotropy
Pogosian, Levon; Wasserman, Ira; Wyman, Mark
2008-01-01
Cosmic string networks generate cosmological perturbations actively throughout the history of the universe. Thus, the string sourced anisotropy of the cosmic microwave background is not affected by Silk damping as much as the anisotropy seeded by inflation. The spectrum of perturbations generated by strings does not match the observed CMB spectrum on large angular scales (l2000) will dominate over that created by the primary inflationary perturbations. This range of angular scales in the CMB is presently being measured by a number of experiments; their results will test this prediction of cosmic string networks soon.
Gravitational backreaction on piecewise linear cosmic string loops
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.
The power spectra of CMB and density fluctuations seeded by local cosmic strings
Contaldi, C; Magueijo, J; Contaldi, Carlo; Hindmarsh, Mark; Magueijo, Joao
1999-01-01
We compute the power spectra in the cosmic microwave background and cold dark matter (CDM) fluctuations seeded by strings, using the largest string simulations performed so far to evaluate the two-point functions of their stress energy tensor. We find that local strings differ from global defects in that the scalar components of the stress-energy tensor dominate over vector and tensor components. This result has far reaching consequences. We find that cosmic strings exhibit a single Doppler peak of acceptable height at high although the CDM power spectrum in the ``standard'' cosmology (flat geometry, zero cosmological constant, 5% baryonic component) is the wrong shape to fit large scale structure data.
Evading the pulsar constraints on the cosmic string tension in supergravity inflation
Energy Technology Data Exchange (ETDEWEB)
Kamada, Kohei [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Miyamoto, Yuhei [Tokyo Univ. (Japan). Dept. of Physics; Tokyo Univ. (JP). Research Center for the Early Universe (RESCEU); Yokoyama, Jun' ichi [Tokyo Univ. (JP). Research Center for the Early Universe (RESCEU); Tokyo Univ., Kashiwa, Chiba (JP). Inst. for the Physics and Mathematics of the Universe (IPMU)
2012-04-15
The cosmic string is a useful probe of the early Universe and may give us a clue to physics at high energy scales where any artificial particle accelerators cannot reach. Although one of the most promising tools is the cosmic microwave background, the constraint from gravitational waves is becoming so stringent that one may not hope to detect its signatures in the cosmic microwave background. In this paper, we construct a scenario that contains cosmic strings observable in the cosmic microwave background while evading the constraint imposed by the recent pulsar timing data. We argue that cosmic strings with relatively large tension are allowed by delaying the onset of the scaling regime. We also show that this scenario is naturally realized in the context of chaotic inflation in supergravity, where the phase transition is governed by the Hubble induced mass.
The Battle of the Bulge: Decay of the Thin, False Cosmic String
Lee, Bum-Hoon; MacKenzie, Richard; Paranjape, M B; Yajnik, U A; Yeom, Dong-han
2013-01-01
We consider the decay of cosmic strings that are trapped in the false vacuum in a theory of scalar electrodynamics in 3+1 dimensions. We restrict our analysis to the case of thin-walled cosmic strings which occur when large magnetic flux 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 tunnelling 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 anti-soliton 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 lengt...
Searching for Cosmic Strings in CMB Anisotropy Maps using Wavelets and Curvelets
Hergt, Lukas; Brandenberger, Robert; Kacprzak, Tomasz; Refregier, Alexandre
2016-01-01
We use wavelet and curvelet transforms to extract signals of cosmic strings from cosmic microwave background (CMB) temperature anisotropy maps, and to study the limits on the cosmic string tension which various ongoing CMB temperature anisotropy experiments will be able to achieve. We construct sky maps with size and angular resolution corresponding to various experiments. These maps contain the signals of a scaling solution of long string segments with a given string tension $G \\mu$, the contribution of the dominant Gaussian primordial cosmological fluctuations, and pixel by pixel white noise with an amplitude corresponding to the instrumental noise of the various experiments. In the case that we include white noise, we find that the curvelets are more powerful than wavelets. For maps with Planck specification, we obtain bounds on the string tension comparable to what was obtained by the Planck collaboration. Experiments with better angular resolution such as the South Pole Telescope third generation (SPT-3G...
Gravitational lensing by cosmic strings: what we learn from the CSL-1 case
Sazhin, M V; Capaccioli, M; Longo, G; Paolillo, M; Covone, G; Grogin, N A; Schreier, E J
2006-01-01
Cosmic strings were postulated by Kibble in 1976 and, from a theoretical point of view, their existence finds support in modern superstring theories, both in compactification models and in theories with extended additional dimensions. Their eventual discovery would lead to significant advances in both cosmology and fundamental physics. One of the most effective ways to detect cosmic strings is through their lensing signatures which appear to be significantly different from those introduced by standard lenses (id est, compact clumps of matter). In 2003, the discovery of the peculiar object CSL-1 (Sazhin et al.2003) raised the interest of the physics community since its morphology and spectral features strongly argued in favour of it being the first case of gravitational lensing by a cosmic string. In this paper we provide a detailed description of the expected observational effects of a cosmic string and show, by means of simulations, the lensing signatures produced on background galaxies. While high angular r...
Cosmic Superstring Gravitational Lensing Phenomena: Predictions for Networks of (p,q) Strings
Shlaer, Benjamin; Wyman, Mark
2005-01-01
The unique, conical spacetime created by cosmic strings brings about distinctive gravitational lensing phenomena. The variety of these distinctive phenomena is increased when the strings have non-trivial 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 stro...
Zero modes on cosmic strings in an external magnetic field
Ferrer, F; Starkman, G D; Vachaspati, T; Ferrer, Francesc; Mathur, Harsh; Starkman, Glenn D.; Vachaspati, Tanmay
2006-01-01
A classical analysis suggests that an external magnetic field can cause trajectories of charge carriers on a superconducting domain wall or cosmic string to bend, thus expelling charge carriers with energy above the mass threshold into the bulk. We study this process by solving the Dirac equation for a fermion of mass $m_f$ and charge $e$, in the background of a domain wall and a magnetic field of strength $B$. We find that the modes of the charge carriers get shifted into the bulk, in agreement with classical expectations. However the dispersion relation for the zero modes changes dramatically -- instead of the usual linear dispersion relation, $\\omega_k =k$, the new dispersion relation is well fit by $\\omega \\approx m_f tanh(k/k_*)$ where $k_*=m_f$ for a thin wall in the weak field limit, and $k_*=eBw$ for a thick wall of width $w$. This result shows that the energy of the charge carriers on the domain wall remains below the threshold for expulsion even in the presence of an external magnetic field. If char...
Pajares, C; Vázquez, R A
2001-01-01
At high gluon or string densities, gluons' saturation or the strong interaction among strings, either forming colour ropes or giving rise to string's percolation, induces a strong suppression in the particle multiplicities produced at high energy. This suppression implies important modifications on cosmic ray shower development. In particular, it is shown that it affects the depth of maximum, the elongation rate, and the behaviour of the number of muons at energies around 10^{17}-10^{18} eV. The existing cosmic ray data point out in the same direction.
Light deflection with torsion effects caused by a spinning cosmic string
Jusufi, Kimet
2016-06-01
Using a new geometrical method introduced by Werner, we find the deflection angle in the weak limit approximation by a spinning cosmic string in the context of the Einstein-Cartan (EC) theory of gravity. We begin by adopting the String-Randers optical metric, then we apply the Gauss-Bonnet theorem to the optical geometry and derive the leading terms of the deflection angle in the equatorial plane. Calculation shows that light deflection is affected by the intrinsic spin of the cosmic string and torsion.
Light deflection with torsion effects caused by a spinning cosmic string
Energy Technology Data Exchange (ETDEWEB)
Jusufi, Kimet [State University of Tetovo, Physics Department, Tetovo (Macedonia, The Former Yugoslav Republic of)
2016-06-15
Using a new geometrical method introduced by Werner, we find the deflection angle in the weak limit approximation by a spinning cosmic string in the context of the Einstein-Cartan (EC) theory of gravity. We begin by adopting the String-Randers optical metric, then we apply the Gauss-Bonnet theorem to the optical geometry and derive the leading terms of the deflection angle in the equatorial plane. Calculation shows that light deflection is affected by the intrinsic spin of the cosmic string and torsion. (orig.)
Light Deflection with Torsion Effects Caused by a Spinning Cosmic String
Jusufi, Kimet
2016-01-01
Using a new geometrical method introduced by Werner, we find the deflection angle in the weak limit approximation by a spinning cosmic string in the context of the Einstein-Cartan (EC) theory of gravity. We begin by adopting the String-Randers optical metric, then we apply the Gauss-Bonnet theorem to the optical geometry and derive the leading terms of the deflection angle in the equatorial plane. Calculations shows that light deflection is affected by the intrinsic spin of the cosmic string and torsion.
Inflation and cosmic (super)strings: implications of their intimate relation revisited
Sakellariadou, Mairi
2013-01-01
We briefly discuss constraints on supersymmetric hybrid inflation models and examine the consistency of brane inflation models. We then address the implications for inflationary scenarios resulting from the strong constraints on the cosmic (super)string tension imposed from the most recent cosmic microwave background temperature anisotropies data.
Harmonic Gravitational Wave Spectra of Cosmic String Loops in the Galaxy
DePies, Matthew R
2009-01-01
A new candidate source of gravitational radiation is described: the nearly-perfect harmonic series from individual loops of cosmic string. It is argued that theories with light cosmic strings give rise to a population of numerous long-lived stable loops, many of which cluster gravitationally in galaxy halos along with the dark matter. Each cosmic string loop produces a spectrum of discrete frequencies in a nearly perfect harmonic series, a fundamental mode and its integer multiples. The gravitational wave signal from cosmic string loops in our Galactic halo is analyzed numerically and it is found that the for light strings, the nearest loops typically produce strong signals which stand out above confusion noise from Galactic binaries. The total population of cosmic string loops in the Milky Way also produces a broad signal that acts as a confusion noise. Both signals are enhanced by the clustering of loops gravitationally bound to the Galaxy, which significantly decreases the average distance from the solar s...
Spontaneous excitation of a static atom in a thermal bath in cosmic string spacetime
Cai, Huabing; Yu, Hongwei; Zhou, Wenting
2015-10-01
We study the average rate of change of energy for a static atom immersed in a thermal bath of electromagnetic radiation in the cosmic string spacetime and separately calculate the contributions of thermal fluctuations and radiation reaction. We find that the transition rates are crucially dependent on the atom-string distance and polarization of the atom and they in general oscillate as the atom-string distance varies. Moreover, the atomic transition rates in the cosmic string spacetime can be larger or smaller than those in Minkowski spacetime contingent upon the atomic polarization and position. In particular, when located on the string, ground-state atoms can make a transition to excited states only if they are polarizable parallel to the string, whereas ground-state atoms polarizable only perpendicular to the string are stable as if they were in a vacuum, even if they are immersed in a thermal bath. Our results suggest that the influence of a cosmic string is very similar to that of a reflecting boundary in Minkowski spacetime.
B polarization of cosmic microwave background as a tracer of strings
Seljak, U; Seljak, Uros; Slosar, Anze
2006-01-01
String models can produce successful inflationary scenarios in the context of brane collisions and in many of these models cosmic strings may also be produced. In scenarios such as KKLMMT the string contribution is naturally predicted to be well below the inflationary signal for cosmic microwave background (CMB) temperature anisotropies, in agreement with the existing limits. We find that for $B$ type polarization of CMB the situation is reversed and the dominant signal comes from vector modes generated by cosmic strings, which exceeds the gravity wave signal from both inflation and strings. The signal can be detected for a broad range of parameter space: future polarization experiments may be able to detect the string signal down to the string tension $G\\mu=10^{-9}$, although foregrounds and lensing are likely to worsen these limits. We argue that the optimal scale to search for the string signature is at $\\ell\\sim 1000$, but in models with high optical depth the signal from reionization peak at large scales...
Planck 2013 results. XXV. Searches for cosmic strings and other topological defects
Ade, P.A.R.; Armitage-Caplan, C.; Arnaud, M.; Ashdown, M.; Atrio-Barandela, F.; Aumont, J.; Baccigalupi, C.; Banday, A.J.; Barreiro, R.B.; Bartlett, J.G.; Bartolo, N.; Battaner, E.; Battye, R.; Benabed, K.; Benoit, A.; Benoit-Levy, A.; Bernard, J.P.; Bersanelli, M.; Bielewicz, P.; Bobin, J.; Bock, J.J.; Bonaldi, A.; Bonavera, L.; Bond, J.R.; Borrill, J.; Bouchet, F.R.; Bridges, M.; Bucher, M.; Burigana, C.; Butler, R.C.; Cardoso, J.F.; Catalano, A.; Challinor, A.; Chamballu, A.; Chiang, L.Y.; Chiang, H.C.; Christensen, P.R.; Church, S.; Clements, D.L.; Colombi, S.; Colombo, L.P.L.; Couchot, F.; Coulais, A.; Crill, B.P.; Curto, A.; Cuttaia, F.; Danese, L.; Davies, R.D.; Davis, R.J.; de Bernardis, P.; de Rosa, A.; de Zotti, G.; Delabrouille, J.; Delouis, J.M.; Desert, F.X.; Diego, J.M.; Dole, H.; Donzelli, S.; Dore, O.; Douspis, M.; Ducout, A.; Dunkley, J.; Dupac, X.; Efstathiou, G.; Ensslin, T.A.; Eriksen, H.K.; Fergusson, J.; Finelli, F.; Forni, O.; Frailis, M.; Franceschi, E.; Galeotta, S.; Ganga, K.; Giard, M.; Giardino, G.; Giraud-Heraud, Y.; Gonzalez-Nuevo, J.; Gorski, K.M.; Gratton, S.; Gregorio, A.; Gruppuso, A.; Hansen, F.K.; Hanson, D.; Harrison, D.; Henrot-Versille, S.; Hernandez-Monteagudo, C.; Herranz, D.; Hildebrandt, S.R.; Hivon, E.; Hobson, M.; Holmes, W.A.; Hornstrup, A.; Hovest, W.; Huffenberger, K.M.; Jaffe, T.R.; Jaffe, A.H.; Jones, W.C.; Juvela, M.; Keihanen, E.; Keskitalo, R.; Kisner, T.S.; Knoche, J.; Knox, L.; Kunz, M.; Kurki-Suonio, H.; Lagache, G.; Lahteenmaki, A.; Lamarre, J.M.; Lasenby, A.; Laureijs, R.J.; Lawrence, C.R.; Leahy, J.P.; Leonardi, R.; Lesgourgues, J.; Liguori, M.; Lilje, P.B.; Linden-Vornle, M.; Lopez-Caniego, M.; Lubin, P.M.; Macias-Perez, J.F.; Maffei, B.; Maino, D.; Mandolesi, N.; Maris, M.; Marshall, D.J.; Martin, P.G.; Martinez-Gonzalez, E.; Masi, S.; Matarrese, S.; Matthai, F.; Mazzotta, P.; McEwen, J.D.; Melchiorri, A.; Mendes, L.; Mennella, A.; Migliaccio, M.; Mitra, S.; Miville-Deschenes, M.A.; Moneti, A.; Montier, L.; Morgante, G.; Mortlock, D.; Moss, A.; Munshi, D.; Naselsky, P.; Natoli, P.; Netterfield, C.B.; Norgaard-Nielsen, H.U.; Noviello, F.; Novikov, D.; Novikov, I.; Osborne, S.; Oxborrow, C.A.; Paci, F.; Pagano, L.; Pajot, F.; Paoletti, D.; Pasian, F.; Patanchon, G.; Peiris, H.V.; Perdereau, O.; Perotto, L.; Perrotta, F.; Piacentini, F.; Piat, M.; Pierpaoli, E.; Pietrobon, D.; Plaszczynski, S.; Pointecouteau, E.; Polenta, G.; Ponthieu, N.; Popa, L.; Poutanen, T.; Pratt, G.W.; Prezeau, G.; Prunet, S.; Puget, J.L.; Rachen, J.P.; Rath, C.; Rebolo, R.; Remazeilles, M.; Renault, C.; Ricciardi, S.; Riller, T.; Ringeval, C.; Ristorcelli, I.; Rocha, G.; Rosset, C.; Roudier, G.; Rowan-Robinson, M.; Rusholme, B.; Sandri, M.; Santos, D.; Savini, G.; Scott, D.; Seiffert, M.D.; Shellard, E.P.S.; Spencer, L.D.; Starck, J.L.; Stolyarov, V.; Stompor, R.; Sudiwala, R.; Sureau, F.; Sutton, D.; Suur-Uski, A.S.; Sygnet, J.F.; Tauber, J.A.; Tavagnacco, D.; Terenzi, L.; Toffolatti, L.; Tomasi, M.; Tristram, M.; Tucci, M.; Tuovinen, J.; Valenziano, L.; Valiviita, J.; Van Tent, B.; Varis, J.; Vielva, P.; Villa, F.; Vittorio, N.; Wade, L.A.; Wandelt, B.D.; Yvon, D.; Zacchei, A.; Zonca, A.
2014-01-01
Planck data have been used to provide stringent new constraints on cosmic strings and other defects. We describe forecasts of the CMB power spectrum induced by cosmic strings, calculating these from network models and simulations using line-of-sight Boltzmann solvers. We have studied Nambu-Goto cosmic strings, as well as field theory strings for which radiative effects are important, thus spanning the range of theoretical uncertainty in strings models. We have added the angular power spectrum from strings to that for a simple adiabatic model, with the extra fraction defined as $f_{10}$ at multipole $\\ell=10$. This parameter has been added to the standard six parameter fit using COSMOMC with flat priors. For the Nambu-Goto string model, we have obtained a constraint on the string tension of $G\\mu/c^2 < 1.5 x 10^{-7}$ and $f_{10} < 0.015$ at 95% confidence that can be improved to $G\\mu/c^2 < 1.3 x 10^{-7}$ and $f_{10} < 0.010$ on inclusion of high-$\\ell$ CMB data. For the abelian-Higgs field theory ...
Spontaneous excitation of a static atom in a thermal bath in cosmic string spacetime
Cai, Huabing; Zhou, Wenting
2015-01-01
We study the average rate of change of energy for a static atom immersed in a thermal bath of electromagnetic radiation in the cosmic string spacetime and separately calculate the contributions of thermal fluctuations and radiation reaction. We find that the transition rates are crucially dependent on the atom-string distance and polarization of the atom and they in general oscillate as the atom-string distance varies. Moreover, the atomic transition rates in the cosmic string spacetime can be larger or smaller than those in Minkowski spacetime contingent upon the atomic polarization and position. In particular, when located on the string, ground-state atoms can make a transition to excited states only if they are polarizable parallel to the string, whereas ground state atoms polarizable only perpendicular to the string are stable as if they were in a vacuum, even if they are immersed in a thermal bath. Our results suggest that the influence of a cosmic string is very similar to that of a reflecting boundary ...
Searching for a Long Cosmic String through the Gravitational Lensing Effect
Shirasaki, Y.; Matsuzaki, Ei-ichi; Mizumoto, Yoshihiko; Kakimoto, Fumio; Ogio, Syoichi; Yasuda, Naoki; Tanaka, Masahiro; Yahagi, Hideki; Nagashima, Masahiro; Kosugi, George
2003-07-01
It has been suggested that cosmic strings produced at a phase transition in the early universe can be the origin of the extremely high energy cosmic rays (EHCR) observed by AGASA above 1020 eV. superheavy cosmic strings with linear mass density of 1022 g/cm can be indirectly observed through the gravitational lensing effect the distant galaxies. The lensing effect by a long straight object can be characterized by a line of double galaxies or quasars with angular separation of about 5 arcsec. We have searched for aligned double objects from the archived data taken by the Subaru Prime Fo cus Camera (Suprime-Cam). The SuprimeCam has a great advantage in observing the wide field of view (30×30 arcmin2 ) with high sensitivity (Rmethod of searching the objects lensed by cosmic strings, and present the observational result obtained by this method.
Cosmic strings with twisted magnetic flux lines and wound-strings in extra dimensions
Lake, Matthew
2012-01-01
We consider a generalization of the Nielsen-Olesen ansatz, in the abelian-Higgs model, which describes strings with twisted magnetic flux lines in the vortex core. The solution does not possess cylindrical symmetry, which leads to the existence of components of conserved momentum, both around the core-axis and along the length of the string. In addition, we consider a model of F-strings with rotating, geodesic windings in the compact space of the Klebanov-Strassler geometry and determine matching conditions which ensure energy and momentum conservation when loops chop off from the long-string network. We find that the expressions for the constants of motion, which determine the macroscopic string dynamics, can be made to coincide with those for the twisted flux line string, suggesting that extra- dimensional effects for F-strings may be mimicked by field-theoretic structure in topological defects.
First LIGO search for gravitational wave bursts from cosmic (super)strings
Abbott, B. P.; Abbott, R.; Adhikari, R.; Ajith, P.; Allen, B.; Allen, G.; Amin, R. S.; Anderson, S. B.; Anderson, W. G.; Arain, M. A.; Araya, M.; Armandula, H.; Armor, P.; Aso, Y.; Aston, S.; Aufmuth, P.; Aulbert, C.; Babak, S.; Baker, P.; Ballmer, S.; Barker, C.; Barker, D.; Barr, B.; Barriga, P.; Barsotti, L.; Barton, M. A.; Bartos, I.; Bassiri, R.; Bastarrika, M.; Behnke, B.; Benacquista, M.; Betzwieser, J.; Beyersdorf, P. T.; Bilenko, I. A.; Billingsley, G.; Biswas, R.; Black, E.; Blackburn, J. K.; Blackburn, L.; Blair, D.; Bland, B.; Bodiya, T. P.; Bogue, L.; Bork, R.; Boschi, V.; Bose, S.; Brady, P. R.; Braginsky, V. B.; Brau, J. E.; Bridges, D. O.; Brinkmann, M.; Brooks, A. F.; Brown, D. A.; Brummit, A.; Brunet, G.; Bullington, A.; Buonanno, A.; Burmeister, O.; Byer, R. L.; Cadonati, L.; Camp, J. B.; Cannizzo, J.; Cannon, K. C.; Cao, J.; Cardenas, L.; Caride, S.; Castaldi, G.; Caudill, S.; Cavaglià, M.; Cepeda, C.; Chalermsongsak, T.; Chalkley, E.; Charlton, P.; Chatterji, S.; Chelkowski, S.; Chen, Y.; Christensen, N.; Chung, C. T. Y.; Clark, D.; Clark, J.; Clayton, J. H.; Cokelaer, T.; Colacino, C. N.; Conte, R.; Cook, D.; Corbitt, T. R. C.; Cornish, N.; Coward, D.; Coyne, D. C.; Creighton, J. D. E.; Creighton, T. D.; Cruise, A. M.; Culter, R. M.; Cumming, A.; Cunningham, L.; Danilishin, S. L.; Danzmann, K.; Daudert, B.; Davies, G.; Daw, E. J.; Debra, D.; Degallaix, J.; Dergachev, V.; Desai, S.; Desalvo, R.; Dhurandhar, S.; Díaz, M.; Dietz, A.; Donovan, F.; Dooley, K. L.; Doomes, E. E.; Drever, R. W. P.; Dueck, J.; Duke, I.; Dumas, J.-C.; Dwyer, J. G.; Echols, C.; Edgar, M.; Effler, A.; Ehrens, P.; Espinoza, E.; Etzel, T.; Evans, M.; Evans, T.; Fairhurst, S.; Faltas, Y.; Fan, Y.; Fazi, D.; Fehrmann, H.; Finn, L. S.; Flasch, K.; Foley, S.; Forrest, C.; Fotopoulos, N.; Franzen, A.; Frede, M.; Frei, M.; Frei, Z.; Freise, A.; Frey, R.; Fricke, T.; Fritschel, P.; Frolov, V. V.; Fyffe, M.; Galdi, V.; Garofoli, J. A.; Gholami, I.; Giaime, J. A.; Giampanis, S.; Giardina, K. D.; Goda, K.; Goetz, E.; Goggin, L. M.; González, G.; Gorodetsky, M. L.; Goßler, S.; Gouaty, R.; Grant, A.; Gras, S.; Gray, C.; Gray, M.; Greenhalgh, R. J. S.; Gretarsson, A. M.; Grimaldi, F.; Grosso, R.; Grote, H.; Grunewald, S.; Guenther, M.; Gustafson, E. K.; Gustafson, R.; Hage, B.; Hallam, J. M.; Hammer, D.; Hammond, G. D.; Hanna, C.; Hanson, J.; Harms, J.; Harry, G. M.; Harry, I. W.; Harstad, E. D.; Haughian, K.; Hayama, K.; Heefner, J.; Heng, I. S.; Heptonstall, A.; Hewitson, M.; Hild, S.; Hirose, E.; Hoak, D.; Hodge, K. A.; Holt, K.; Hosken, D. J.; Hough, J.; Hoyland, D.; Hughey, B.; Huttner, S. H.; Ingram, D. R.; Isogai, T.; Ito, M.; Ivanov, A.; Johnson, B.; Johnson, W. W.; Jones, D. I.; Jones, G.; Jones, R.; Ju, L.; Kalmus, P.; Kalogera, V.; Kandhasamy, S.; Kanner, J.; Kasprzyk, D.; Katsavounidis, E.; Kawabe, K.; Kawamura, S.; Kawazoe, F.; Kells, W.; Keppel, D. G.; Khalaidovski, A.; Khalili, F. Y.; Khan, R.; Khazanov, E.; King, P.; Kissel, J. S.; Klimenko, S.; Kokeyama, K.; Kondrashov, V.; Kopparapu, R.; Koranda, S.; Kozak, D.; Krishnan, B.; Kumar, R.; Kwee, P.; Lam, P. K.; Landry, M.; Lantz, B.; Lazzarini, A.; Lei, H.; Lei, M.; Leindecker, N.; Leonor, I.; Li, C.; Lin, H.; Lindquist, P. E.; Littenberg, T. B.; Lockerbie, N. A.; Lodhia, D.; Longo, M.; Lormand, M.; Lu, P.; Lubiński, M.; Lucianetti, A.; Lück, H.; Machenschalk, B.; Macinnis, M.; Mageswaran, M.; Mailand, K.; Mandel, I.; Mandic, V.; Márka, S.; Márka, Z.; Markosyan, A.; Markowitz, J.; Maros, E.; Martin, I. W.; Martin, R. M.; Marx, J. N.; Mason, K.; Matichard, F.; Matone, L.; Matzner, R. A.; Mavalvala, N.; McCarthy, R.; McClelland, D. E.; McGuire, S. C.; McHugh, M.; McIntyre, G.; McKechan, D. J. A.; McKenzie, K.; Mehmet, M.; Melatos, A.; Melissinos, A. C.; Menéndez, D. F.; Mendell, G.; Mercer, R. A.; Meshkov, S.; Messenger, C.; Meyer, M. S.; Miller, J.; Minelli, J.; Mino, Y.; Mitrofanov, V. P.; Mitselmakher, G.; Mittleman, R.; Miyakawa, O.; Moe, B.; Mohanty, S. D.; Mohapatra, S. R. P.; Moreno, G.; Morioka, T.; Mors, K.; Mossavi, K.; Mowlowry, C.; Mueller, G.; Müller-Ebhardt, H.; Muhammad, D.; Mukherjee, S.; Mukhopadhyay, H.; Mullavey, A.; Munch, J.; Murray, P. G.; Myers, E.; Myers, J.; Nash, T.; Nelson, J.; Newton, G.; Nishizawa, A.; Numata, K.; O'Dell, J.; O'Reilly, B.; O'Shaughnessy, R.; Ochsner, E.; Ogin, G. H.; Ottaway, D. J.; Ottens, R. S.; Overmier, H.; Owen, B. J.; Pan, Y.; Pankow, C.; Papa, M. A.; Parameshwaraiah, V.; Patel, P.; Pedraza, M.; Penn, S.; Perreca, A.; Pierro, V.; Pinto, I. M.; Pitkin, M.; Pletsch, H. J.; Plissi, M. V.; Postiglione, F.; Principe, M.; Prix, R.; Prokhorov, L.; Punken, O.; Quetschke, V.; Raab, F. J.; Rabeling, D. S.; Radkins, H.; Raffai, P.; Raics, Z.; Rainer, N.; Rakhmanov, M.; Raymond, V.; Reed, C. M.; Reed, T.; Rehbein, H.; Reid, S.
2009-09-01
We report on a matched-filter search for gravitational wave bursts from cosmic string cusps using LIGO data from the fourth science run (S4) which took place in February and March 2005. No gravitational waves were detected in 14.9 days of data from times when all three LIGO detectors were operating. We interpret the result in terms of a frequentist upper limit on the rate of gravitational wave bursts and use the limits on the rate to constrain the parameter space (string tension, reconnection probability, and loop sizes) of cosmic string models. Many grand unified theory-scale models (with string tension Gμ/c2≈10-6) can be ruled out at 90% confidence for reconnection probabilities p≤10-3 if loop sizes are set by gravitational back reaction.
Rotation of galaxies as a signature of cosmic strings in weak lensing surveys
Thomas, Daniel B.; Contaldi, Carlo R.; Magueijo, Joao
2009-01-01
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 or...
Relic Gravitational Waves from Cosmic Strings Updated Constraints and Opportunities for Detection
Caldwell, R R; Shellard, E P S
1996-01-01
We examine the spectrum of gravitational radiation emitted by a network of cosmic strings, with emphasis on the observational constraints and the opportunities for detection. The analysis improves over past work, as we use a phenomenological model for the radiation spectrum emitted by a cosmic string loop. This model attempts to include the effect of the gravitational back-reaction on the radiation emission by an individual loop with a high frequency cut-off in the spectrum. Comparison of the total spectrum due to a network of strings with the recently improved bound on the amplitude of a stochastic gravitational wave background, due to measurements of noise in pulsar signal arrival times, allows us to exclude a range of values of $\\mu$, the cosmic string linear mass density, for certain values of cosmic string and cosmological parameters. We find the conservative bound $G\\mu/c^2 < 5.4 (\\pm 1.1) \\times 10^{-6}$ which is consistent with all other limits. We consider variations of the standard cosmological s...
Cosmic String Helicity Constraints on Loop Configurations, and the Quantization of Baryon Number
Mendelson, T R
1999-01-01
We apply the concept of helicity from classical hydrodynamics to elucidate two problematical issues in cosmic string physics. Helicity, the space integral of the scalar product of a velocity-like field with its vorticity field (curl), can be defined for a complex scalar field in analogy with fluids. We dwell on the topological interpretation of helicity as related to the linking of field lines of the vorticity field. Earlier works failed to fully implement this interpretation for cosmic strings by missing a term connected with the linking of these lines inside the strings. As a result paradoxical conclusions were drawn: global cosmic string loops may not take on certain simple shapes, and baryon number is not quantized in integers in the presence of local cosmic strings in gauge theory. We show that both paradoxes are removed when internal contributions to helicity are properly taken into account. In particular, quantization of baryon number can be understood within a special case of the Glashow-Weinberg-Sala...
Battle of the bulge: Decay of the thin, false cosmic string
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.
Induced fermionic currents in de Sitter spacetime in the presence of a compactified cosmic string
Mohammadi, A; Saharian, A A
2014-01-01
We investigate the vacuum fermionic currents in the geometry of a compactified cosmic string on background of de Sitter 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 ...
Energy Technology Data Exchange (ETDEWEB)
Hassanabadi, H.; Hosseinpour, M. [Shahrood University of Technology, Physics Department, Shahrood (Iran, Islamic Republic of)
2016-10-15
In this paper, we study the covariant form of the non-relativistic Schroedinger-Pauli equation in the space-time generated by a cosmic string and discuss the solutions of this equation in the presence of interaction between the magnetic dipole momentum and electromagnetic field. We study the influence of the topology on this system. We obtain the solution of radial part as well as the energy levels. We consider all thermodynamic properties of a neutral particle in a magnetic cosmic string background by using an approach based on the partition function method. (orig.)
CMB and LSS Power Spectra From Local Cosmic String Seeded Struture Formation
Contaldi, C R; Magueijo, J; Contaldi, Carlo R.; Hindmarsh, Mark; Magueijo, Joao
1998-01-01
We evaluate the two point functions of the stress energy from the largest string simulations carried out so far. The two point functions are used to calculate the cosmic microwave background (CMB) and cold dark matter (CDM) power spectra from local cosmic string models for structure formation. We find that our spectra differ significantly from those previously calculated for both global and local defects. We find a higher Doppler peak at $l=400-600$ and a less severe bias problem than for global defects. Spectra were obtained for a variety of network energy-decay mechanisms.
Hassanabadi, Hassan
2016-01-01
In this paper, we study the covariant form of the non-relativistic Schrodinger-Pauli equation in the space-time generated by a cosmic string and discuss the solutions of this equation in present of interaction between the magnetic dipole momentum and electromagnetic field. We study the influence of the topology on this system. We obtain the solution of radial part as well as the energy levels. We consider all thermodynamic properties of neutral particle in magnetic cosmic string background by using an approach based on the partition function method.
Baryon inhomogeneities due to cosmic string wakes at the quark–hadron transition
Indian Academy of Sciences (India)
Biswanath Layek; Soma Sanyal; Ajit M Srivastava
2003-05-01
Baryon inhomogeneities generated during the quark–hadron transition may alter the abundances of light elements if they persist up to the time of nucleosynthesis. These inhomogeneities survive up to the nucleosynthesis epoch if they are separated by a distance of at least a few metres. In this work we present a model where large sheets of these inhomogeneities separated by a distance of a few km are formed by cosmic string wakes during the quark–hadron transition. The effect of these sheets on nucleosynthesis will also put constraints on the various cosmic string parameters.
Implications of cosmic string-induced density ﬂuctuations at the quark–hadron transition
Indian Academy of Sciences (India)
Biswanath Layek; Soma Sanyal; Ajit M Srivastava
2003-11-01
We show that cosmic strings moving through the plasma at the time of a ﬁrst-order quark–hadron transition in the early universe generate baryon inhomogeneities, which can survive till the nucleosynthesis epoch. We ﬁnd out how these inhomogeneities actually affect the calculated values of the light element abundances. Recently a wealth of observational data from various experiments have helped to reduce the uncertainties in the values of these abundances. Using these we show that it is possible to derive constraints in the presence of cosmic strings during the quark–hadron transition.
Cosmic String Loops as the Seeds of Super-Massive Black Holes
Bramberger, Sebastian F; Jreidini, Paul; Quintin, Jerome
2015-01-01
Recent discoveries of super-massive black holes at high redshifts indicate a possible tension with the standard Lambda CDM 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.
Formation of Cosmic String network from black holes: Implications from liquid crystal experiments
Srivastava, A M
2006-01-01
We present observation of large, expanding string loops forming around a heated wire tip embedded in a nematic liquid crystal sample. Loops expand due to convective stretching. This observation leads to a new insight into phenomena which could occur in the early universe. We show that local heating of plasma in the early universe by evaporating primordial black holes can lead to formation of large, expanding cosmic string loops, just as observed in the liquid crystal experiment. Intercommutation of string loops from neighboring black holes can lead to percolation, thereby forming an infinite string network. This is remarkable as such an infinite string network is thought to arise only when the entire universe undergoes phase transition.
Predicted Constraints on Cosmic String Tension from Planck and Future CMB Polarization Measurements
Foreman, Simon; Scott, Douglas
2011-01-01
We perform a Fisher matrix calculation of the predicted uncertainties on estimates of the cosmic string tension Gmu from upcoming observational data (namely, cosmic microwave background power spectra from the Planck satellite and an idealized future polarization experiment). We employ simulations that are more general than others commonly used in the literature, leaving the mean velocity of strings, correlation length of the string network, and "wiggliness" (which parametrizes smaller-scale structure along the strings) as free parameters that can be observationally measured. In a new code, StringFast, we implement a method for efficient computation of the C_l spectra induced by a network of strings, which is fast enough to be used in Markov Chain Monte Carlo analyses of future data. Performing a calculation with the string parameters left free results in projected constraints on Gmu that are larger than those obtained by fixing their values a priori, typically by a factor of ~2-7. We also find that if Gmu is ...
Cosmic strings in f(R,L{sub m}) gravity
Energy Technology Data Exchange (ETDEWEB)
Harko, Tiberiu, E-mail: t.harko@ucl.ac.uk [Department of Mathematics, University College London, Gower Street, WC1E 6BT, London (United Kingdom); Lake, Matthew J., E-mail: matthewj@nu.ac.th [The Institute for Fundamental Study, “The Tah Poe Academia Institute”, Naresuan University, 65000, Phitsanulok (Thailand); Thailand Center of Excellence in Physics, Ministry of Education, 10400, Bangkok (Thailand)
2015-02-07
We consider Kasner-type static, cylindrically symmetric interior string solutions in the f(R,L{sub m}) theory of modified gravity. The physical properties of the string are described by an anisotropic energy-momentum tensor satisfying the condition T{sub t}{sup t}=T{sub z}{sup z}; that is, the energy density of the string along the z-axis is equal to minus the string tension. As a first step in our study we obtain the gravitational field equations in the f(R,L{sub m}) theory for a general static, cylindrically symmetric metric, and then for a Kasner-type metric, in which the metric tensor components have a power law dependence on the radial coordinate r. String solutions in two particular modified gravity models are investigated in detail. The first is the so-called “exponential” modified gravity, in which the gravitational action is proportional to the exponential of the sum of the Ricci scalar and matter Lagrangian, and the second is the “self-consistent model”, obtained by explicitly determining the gravitational action from the field equations under the assumption of a power law dependent matter Lagrangian. In each case, the thermodynamic parameters of the string, as well as the precise form of the matter Lagrangian, are explicitly obtained.
Cosmic strings in f(R,L{sub m}) gravity
Energy Technology Data Exchange (ETDEWEB)
Harko, Tiberiu [University College London, Department of Mathematics, London (United Kingdom); Lake, Matthew J. [Naresuan University, The Institute for Fundamental Study, ' ' The Tah Poe Academia Institute' ' , Phitsanulok (Thailand); Ministry of Education, Thailand Center of Excellence in Physics, Bangkok (Thailand)
2015-02-01
We consider Kasner-type static, cylindrically symmetric interior string solutions in the f(R,L{sub m}) theory of modified gravity. The physical properties of the string are described by an anisotropic energy-momentum tensor satisfying the condition T{sub t}{sup t} = T{sub z}{sup z}; that is, the energy density of the string along the z-axis is equal to minus the string tension. As a first step in our study we obtain the gravitational field equations in the f(R,L{sub m}) theory for a general static, cylindrically symmetric metric, and then for a Kasner-type metric, in which the metric tensor components have a power law dependence on the radial coordinate r. String solutions in two particular modified gravity models are investigated in detail. The first is the so-called ''exponential'' modified gravity, in which the gravitational action is proportional to the exponential of the sum of the Ricci scalar and matter Lagrangian, and the second is the ''self-consistent model'', obtained by explicitly determining the gravitational action from the field equations under the assumption of a power law dependent matter Lagrangian. In each case, the thermodynamic parameters of the string, as well as the precise form of the matter Lagrangian, are explicitly obtained. (orig.)
The gravitational wave spectrum from cosmological B-L breaking
Energy Technology Data Exchange (ETDEWEB)
Buchmüller, W.; Domcke, V.; Kamada, K. [Deutsches Elektronen-Synchrotron DESY, 22607 Hamburg (Germany); Schmitz, K., E-mail: buchmuwi@mail.desy.de, E-mail: valerie.domcke@desy.de, E-mail: kohei.kamada@desy.de, E-mail: kai.schmitz@ipmu.jp [Kavli IPMU (WPI), University of Tokyo, Kashiwa 277-8583 (Japan)
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
Energy Technology Data Exchange (ETDEWEB)
Buchmueller, W.; Domcke, V.; Kamada, K. [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Schmitz, K. [Tokyo Univ., Kashiwa (Japan). Kavli IPMU (WPI)
2013-05-15
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 {Omega}{sub GW}h{sup 2}{proportional_to}10{sup -13}-10{sup -8}, much larger than the spectral amplitude predicted by inflation. Forthcoming gravitational wave detectors such as eLISA, advanced LIGO and BBO/DECIGO will reach the sensitivity needed to test the predictions from cosmological B-L breaking.
All sky CMB map from cosmic strings integrated Sachs-Wolfe effect
Ringeval, Christophe
2012-01-01
By actively distorting the Cosmic Microwave Background (CMB) over our past light cone, cosmic strings are unavoidable sources of non-Gaussianity. Developing optimal estimators able to disambiguate a string signal from the primordial type of non-Gaussianity requires calibration over synthetic full sky CMB maps, which till now had been numerically unachievable at the resolution of modern experiments. In this paper, we provide the first high resolution full sky CMB map of the temperature anisotropies induced by a network of cosmic strings since the recombination. The map has about 200 million sub-arcminute pixels in the healpix format which is the standard in use for CMB analyses (Nside=4096). This premiere required about 800,000 cpu hours; it has been generated by using a massively parallel ray tracing method piercing through a thousands of state of art Nambu-Goto cosmic string numerical simulations which pave the comoving volume between the observer and the last scattering surface. We explicitly show how this ...
CMB power spectra from cosmic strings: predictions for the Planck satellite and beyond
Bevis, Neil; Kunz, Martin; Urrestilla, Jon
2010-01-01
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 sub-orbital 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 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 > 3500. Astrophysical contributions s...
Improved calculation of the gravitational wave spectrum from kinks on infinite cosmic strings
Matsui, Yuka; Nitta, Daisuke; Kuroyanagi, Sachiko
2016-01-01
Gravitational wave observations provide unique opportunities to search for cosmic strings. One of the strongest sources of gravitational waves is discontinuities of cosmic strings, called kinks, which are generated at points of intersection. Kinks on infinite strings are known to generate a gravitational wave background over a wide range of frequencies. In this paper, we calculate the spectrum of the gravitational wave background by numerically solving the evolution equation for the distribution function of the kink sharpness. We find that the number of kinks for small sharpness is larger than the analytical estimate used in a previous work, which makes a difference in the spectral shape. Our numerical approach also helps to avoid the use of analytic approximations, and enables us to make a more precise prediction on the spectral amplitude for future gravitational wave experiments.
Lake, Matthew J
2015-01-01
The discovery of a large number of supermassive black holes at redshifts $z> 6$, when the Universe was only nine hundred million years old, has raised the fundamental question of how such massive compact objects could form in a (cosmologically) short time interval. Each of the proposed standard scenarios for black hole formation, involving rapid accretion of seed black holes, or black hole mergers, faces severe theoretical difficulties in explaining the short time formation of supermassive objects. In the present Letter, we propose an alternative scenario for the formation of supermassive black holes in the early Universe in which energy transfer from superconducting cosmic strings, piercing small seed black holes, is the main physical process leading to rapid mass increase. The increase in mass of a primordial seed black hole pierced by two antipodal strings is estimated and it is shown that this increases linearly in time. Due to the high energy transfer rate from the cosmic strings, we find that supermassi...
The Stability of D-term Cosmic Strings
Collinucci, A; Van Proeyen, A; Collinucci, Andres; Smyth, Paul; Proeyen, Antoine Van
2007-01-01
In this note, which is based on hep-th/0611111, we review the stability of the static, positive deficit angle D-term string solutions of D=4, N=1 supergravity with a constant Fayet-Iliopoulos term. We prove the semi-classical stability of this class of solutions using standard positive energy theorem techniques. In particular, we discuss how the negative deficit angle D-term string, which also solves the Killing spinor equations, violates the dominant energy condition and so is excluded from our arguments.
Isospin Invariance and the Vacuum Polarization Energy of Cosmic Strings
Weigel, H; Graham, N
2016-01-01
We corroborate the previously applied spectral approach to compute the vacuum polarization energy of string configurations in models similar to the standard model of particle physics. The central observation underlying this corroboration is the existence of a particular global isospin transformation of the string configuration. Under this transformation the single particle energies of the quantum fluctuations are invariant, while the inevitable implementation of regularization and renormalization requires operations that are not invariant. We verify numerically that all such variances eventually cancel, and that the vacuum polarization energy obtained in the spectral approach is indeed gauge invariant.
Measuring CMB non-Gaussianity as a probe of Inflation and Cosmic Strings
Regan, D M
2011-01-01
The leading candidate for the very early universe is described by a period of rapid expansion known as inflation. While the standard paradigm invokes a single slow-rolling field, many different models may be constructed which fit the current observational evidence. In this work we outline theoretical and observational studies of non-Gaussian fluctuations produced by models of inflation and by cosmic strings - topological defects that may be generated in the very early universe during a phase transition. In particular, we consider the imprint of cosmic strings on the cosmic microwave background (CMB) and describe a formalism for the measurement of general four-point correlation functions, or trispectra, using the CMB. In addition we describe the application of our methodology to non-Gaussian signals imprinted in the large scale structure of the universe. Such deviations from Gaussianity are generally expressed in terms of the so-called bispectrum and trispectrum.
Dynamics of cosmic strings with higher-dimensional windings
Yamauchi, Daisuke
2014-01-01
We consider F-strings with arbitrary configurations in the Minkowski directions of a higher-dimensional spacetime, which also wrap and spin around $S^1$ subcycles of constant radius in an arbitrary internal manifold. 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 exactly half the square of the string length lies in the large dimensions and half lies in the compact space. As examples, long straight strings and circular loops are considered in detail, and the solutions to the equations of motion, that are compatible with the tensionless condition, are presented. The critical solution is then seen to arise as a special case, in which the wavelength of the windings is equal to their circumference. Under the process of dimensional reduction, in which higher-dimensional motion is equival...
Morganson, Eric; Treu, Tommaso; Schrabback, Tim; Blandford, Roger D
2009-01-01
We have searched 4.5 square degrees of archival HST/ACS images for cosmic strings, identifying close pairs of similar, faint galaxies and selecting groups whose alignment is consistent with gravitational lensing by a long, straight string. We find no evidence for cosmic strings in five large-area HST treasury surveys (covering a total of 2.22 square degrees), or in any of 346 multi-filter guest observer images (1.18 square degrees). Assuming that simulations ccurately predict the number of cosmic strings in the universe, this non-detection allows us to place upper limits on the unitless Universal cosmic string tension of G mu/c^2 < 2.3 x 10^-6, and cosmic string density of Omega_s < 2.1 x 10^-5 at the 95% confidence level (marginalising over the other parameter in each case). We find four dubious cosmic string candidates in 318 single filter guest observer images (1.08 square degrees), which we are unable to conclusively eliminate with existing data. The confirmation of any one of these candidates as co...
Searching for a Long Cosmic String Through the Gravitational Lensing Effect
Shirasaki, Y; Mizumoto, Y; Kakimoto, F; Ogio, S; Yasuda, N; Tanaka, M; Yahagi, H; Nagashima, M; Kosugi, G; Shirasaki, Yuji; Matsuzaki, Ei-ichi; Mizumoto, Yoshihiko; Kakimoto, Fumio; Ogio, Syoichi; Yasuda, Naoki; Tanaka, Masahiro; Yahagi, Hideki; Nagashima, Masahiro; Kosugi, George
2003-01-01
It has been suggested that cosmic strings produced at a phase transition in the early universe can be the origin of the extremely high energy cosmic rays (EHCR) observed by AGASA above 10^20 eV. Superheavy cosmic strings with linear mass density of 10^22 g/cm can be indirectly observed through the gravitational lensing effect the distant galaxies. The lensing effect by a long straight object can be characterized by a line of double galaxies or quasars with angular separation of about 5 arcsec. We have searched for aligned double objects from the archived data taken by the Subaru Prime Focus Camera (Suprime-Cam). The Suprime-Cam has a great advantage in observing the wide field of view (30x30 arcmin^2) with high sensitivity (R<26 400s exposure), so it is suitable for this research. In this paper, we describe the result of simulation study for developing the method of searching the objects lensed by cosmic strings, and present the observational result obtained by this method.
Rotation of galaxies as a signature of cosmic strings in weak lensing surveys
Thomas, Daniel B; Magueijo, Joao
2009-01-01
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.
The Gravitational Wave Spectrum from Cosmological B-L Breaking
Buchmuller, Wilfried; Kamada, Kohei; Schmitz, Kai
2013-01-01
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 \\Omega_GW h^2 ~ 10^{-13} - 10^{-8}, much larger than the spectral amplitude predicted by inflation. Forthcoming gravitational wave detectors such as eL...
Formation of large-scale structure from cosmic strings and massive neutrinos
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.
Salazar-Ramírez, M.; Ojeda-Guillén, D.; Mota, R. D.
2016-09-01
We study a relativistic quantum particle in cosmic string spacetime in the presence of a magnetic field and a Coulomb-type scalar potential. It is shown that the radial part of this problem possesses the su(1 , 1) symmetry. We obtain the energy spectrum and eigenfunctions of this problem by using two algebraic methods: the Schrödinger factorization and the tilting transformation. Finally, we give the explicit form of the relativistic coherent states for this problem.
Alignment of Quasar Polarizations on Large Scales Explained by Warped Cosmic Strings
Slagter, Reinoud Jan
2016-01-01
The recently discovered alignment of quasar polarizations on very large scales could possibly explained by considering cosmic strings on a warped five dimensional spacetime. Compact objects, such as cosmic strings, could have tremendous mass in the bulk, while their warped manifestations in the brane can be consistent with general relativity in 4D. The self-gravitating cosmic string induces gravitational wavelike disturbances which could have effects felt on the brane, i.e., the massive effective 4D modes (Kaluza-Klein modes) of the perturbative 5D graviton. This effect is amplified by the time dependent part of the warp factor. Due to this warp factor, disturbances don't fade away during the expansion of the universe. From a non-linear perturbation analysis it is found that the effective Einstein 4D equations on an axially symmetric spacetime, contain a "back-reaction" term on the righthand side caused by the projected 5D Weyl tensor and can act as a dark energy term. The propagation equations to first order...
Semiclassical models for uniform-density Cosmic Strings and Relativistic Stars
Campanelli, M; Campanelli, Manuela; Lousto, Carlos O.
1996-01-01
In this paper we show how quantum corrections, although perturbatively small, may play an important role in the analysis of the existence of some classical models. This, in fact, appears to be the case of static, uniform--density models of the interior metric of cosmic strings and neutron stars. We consider the fourth order semiclassical equations and first look for perturbative solutions in the coupling constants $\\alpha$ and $\\beta$ of the quadratic curvature terms in the effective gravitational Lagrangian. We find that there is not a consistent solution; neither for strings nor for spherical stars. We then look for non--perturbative solutions and find an explicit approximate metric for the case of straight cosmic strings. We finally analyse the contribution of the non--local terms to the renormalized energy--momentum tensor and the possibility of this terms to allow for a perturbative solution. We explicitly build up a particular renormalized energy--momentum tensor to fulfill that end. These state--depend...
Non-Abelian cosmic strings in de Sitter and anti-de Sitter space
Santos, Antônio de Pádua; Bezerra de Mello, Eugênio R.
2016-09-01
In this paper we investigate the non-Abelian cosmic string in de Sitter and anti-de Sitter spacetimes. In order to do that we construct the complete set of equations of motion considering the presence of a cosmological constant. By using numerical analysis we provide the behavior of the Higgs and gauge fields and also of the metric tensor for specific values of the physical parameters of the theory. For the de Sitter case, we find the appearance of an horizon. This horizon is consequence of the presence of the cosmological constant, and its position strongly depends on the value of the gravitational coupling. In the anti-de Sitter case, we find that the system does not present horizons. In fact the new feature of this system is related with the behavior of the (00) and (z z ) components of the metric tensor. They present a strong increasing behavior for large distance from the string.
Propagation of cosmic rays through the atmosphere in the quark-gluon strings model
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.
Models for Small-Scale Structure on Cosmic Strings: II. Scaling and its stability
Vieira, J P P; Shellard, E P S
2016-01-01
We make use of the formalism described in a previous paper [Martins {\\it et al.} Phys. Rev. D90 (2014) 043518] to address general features of wiggly cosmic string evolution. In particular, we highlight the important role played by poorly understood energy loss mechanisms and propose a simple ansatz which tackles this problem in the context of an extended velocity-dependent one-scale model. We find a general procedure to determine all the scaling solutions admitted by a specific string model and study their stability, enabling a detailed comparison with future numerical simulations. A simpler comparison with previous Goto-Nambu simulations supports earlier evidence that scaling is easier to achieve in the matter era than in the radiation era. In addition, we also find that the requirement that a scaling regime be stable seems to notably constrain the allowed range of energy loss parameters.
Formation of large-scale structure from cosmic-string loops and cold dark matter
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.
Scalar bosons under the influence of noninertial effects in the cosmic string spacetime
Santos, L C N
2016-01-01
In this paper we present two different classes of solutions for the Klein-Gordon equation in the presence of a scalar potential under the influence of noninertial effects in the cosmic string spacetime. We show that noninertial effects restrict the physical region of the spacetime where the particle can be placed, and furthermore that the energy levels are shifted by these effects. In addition, we show that the presence of a Coulomb-like scalar potential allows the formation bound states when the Klein-Gordon equation is considered in this kind of spacetime.
Bursts of gravitational radiation from superconducting cosmic strings and the neutrino mass spectrum
Energy Technology Data Exchange (ETDEWEB)
Mosquera Cuesta, Herman J. [Abdus Salam International Centre for Theoretical Physics, Trieste (Italy)]|[Centro Brasileiro de Pesquisas Fisicas (CBPF), Rio de Janeiro, RJ (Brazil). Lab. de Cosmologia e Fisica Experimental de Altas Energias; Morejon Gonzalez, Danays [Pontificia Univ. Catolica do Rio de Janeiro, RJ (Brazil)
2001-02-01
Berezinsky, Hnatyk and Vilenkin showed that superconducting cosmic strings could be central engines for cosmological gamma-ray bursts and for producing the neutrino component of ultra-high energy cosmic rays. A consequence of this mechanism would be that a detectable cusp-triggered gravitational wave burst should be release simultaneously with the {gamma}-ray surge. If contemporary measurements of both {gamma} and {nu} radiation could be made for any particular source, then the cosmological time-delay between them might be useful for putting unprecedently tight bounds on the neutrino mass spectrum. Such measurements could consistently verify or rule out the model since strictly correlated behaviour is expected for the duration of the event and for the time variability of the spectra. (author)
Boumali, Abdelmalek
2016-01-01
In this paper, the problem of a two-dimensional Duffin-Petiau-Kemmer (DKP) oscillator in the presence of a coulomb potential in the cosmic string background is solved. The eigensolutions of the problem in question have been found, and the influence of the cosmic string space-time on the eigenvalues has been analyzed.
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.
Gravitating vortices, cosmic strings, and the K\\"ahler--Yang--Mills equations
Álvarez-Cónsul, Luis; García-Prada, Oscar
2015-01-01
In this work we study equations describing Abelian vortices on a Riemann surface with back reaction of the metric. The gravitating vortex equations are derived by dimensional reduction of the K\\"ahler--Yang--Mills equations on the product of the complex projective line with a Riemann surface, and inherit their moment map interpretation. Applying the general theory for the K\\"ahler--Yang--Mills equations, we give evidence of an analogue of the Donaldson--Uhlembeck--Yau Theorem for gravitating vortices --- commonly referred to as a Hitchin--Kobayashi correspondence. As a particular case of the gravitating vortex equations on $\\mathbb{P}^1$ we find the Einstein--Bogomol'nyi equations, whose solutions correspond to Nielsen--Olesen cosmic strings in the Bogomol'nyi phase. Using an existence theorem by Yisong Yang, our main result implies a Hitchin--Kobayashi correspondence for the Einstein--Bogomol'nyi equations. In particular, we prove a conjecture by Yang about the non-existence of cosmic strings on $\\mathbb{P}^...
Fermionic vacuum polarization by a magnetic tube in the cosmic string spacetime
de Sousa, M S Maior; de Mello, E R Bezerra
2016-01-01
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 condensat (FC) e 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 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 seconds are induc...
On the gravitational, dilatonic, and axionic radiative damping of cosmic strings
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.
Belich, H
2015-01-01
The behaviour of a relativistic scalar particle subject to a scalar potential under the effects of the violation of the Lorentz symmetry in the cosmic string spacetime is discussed. It is considered two possible scenarios of the Lorentz symmetry breaking in the CPT-even gauge sector of the Standard Model Extension defined by a tensor $\\left(K_{F}\\right)_{\\mu\
Gravitating Vortices, Cosmic Strings, and the Kähler-Yang-Mills Equations
Álvarez-Cónsul, Luis; Garcia-Fernandez, Mario; García-Prada, Oscar
2016-09-01
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.
Gravitating Vortices, Cosmic Strings, and the Kähler-Yang-Mills Equations
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.
Fermionic vacuum polarization by an Abelian magnetic tube in the cosmic string spacetime
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.
Energy Technology Data Exchange (ETDEWEB)
Gasparini, Maria Alice; Marshall, Phil; Treu, Tommaso; /UC, Santa Barbara; Morganson, Eric; /KIPAC, Menlo Park; 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.
Belich, H.; Bakke, K.
2016-03-01
The behavior of a relativistic scalar particle subject to a scalar potential under the effects of the violation of the Lorentz symmetry in the cosmic string space-time is discussed. It is considered two possible scenarios of the Lorentz symmetry breaking in the CPT-even gauge sector of the Standard Model Extension defined by a tensor (KF)μναβ. Then, by introducing a scalar potential as a modification of the mass term of the Klein-Gordon equation, it is shown that the Klein-Gordon equation in the cosmic string space-time is modified by the effects of the Lorentz symmetry violation backgrounds and bound state solution to the Klein-Gordon equation can be obtained.
Binétruy, Pierre; Caprini, Chiara; Dufaux, Jean-François
2012-01-01
We review the main cosmological backgrounds of gravitational waves accessible to detectors in space sensitive to the range $10^{-4}$ to $10^{-1}$ Hz, with a special emphasis on those backgrounds due to phase transitions or networks of cosmic strings. We apply this to identify the scientific potential of the NGO/eLISA mission of ESA, regarding the detectability of such cosmological backgrounds.
Scattering and bound states of a spin--1/2 neutral particle in the cosmic string spacetime
Silva, Edilberto O; Filgueiras, Cleverson
2016-01-01
In this paper the relativistic quantum dynamics of a spin-1/2 neutral particle with a magnetic moment $\\mu$ in the cosmic string spacetime is reexamined by applying the von Neumann theory of self-adjoint extensions. Contrary to previous studies where the interaction between the spin and the line of charge were neglected, here we consider its effects. This interaction gives rise to a point interaction: $\\boldsymbol{\
Topological defects in alternative theories to cosmic inflation and string cosmology
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
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Vieira, H.S., E-mail: horacio.santana.vieira@hotmail.com [Departamento de Física, Universidade Federal da Paraíba, Caixa Postal 5008, CEP 58051-970, João Pessoa, PB (Brazil); Centro de Ciências, Tecnologia e Saúde, Universidade Estadual da Paraíba, CEP 58233-000, Araruna, PB (Brazil); Bezerra, V.B., E-mail: valdir@fisica.ufpb.br [Departamento de Física, Universidade Federal da Paraíba, Caixa Postal 5008, CEP 58051-970, João Pessoa, PB (Brazil); Silva, G.V., E-mail: gislainevs@hotmail.com [Departamento de Física, Universidade Federal da Paraíba, Caixa Postal 5008, CEP 58051-970, João Pessoa, PB (Brazil)
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.
The B-L Phase Transition: Implications for Cosmology and Neutrinos
Schmitz, Kai
2013-01-01
We investigate the possibility that the hot thermal phase of the early universe is ignited in consequence of the B-L phase transition, which represents the cosmological realization of the spontaneous breaking of the Abelian gauge symmetry associated with B-L, the difference between baryon number B and lepton number L. Prior to the B-L phase transition, the universe experiences a stage of hybrid inflation. Towards the end of inflation, the false vacuum of unbroken B-L decays, which entails tachyonic preheating as well as the production of cosmic strings. The dynamics of the B-L breaking Higgs field and the B-L gauge degrees of freedom, in combination with thermal processes, generate an abundance of heavy (s)neutrinos. These (s)neutrinos decay into radiation, thereby reheating the universe, generating the baryon asymmetry of the universe and setting the stage for the thermal production of gravitinos. We study the B-L phase transition in the full supersymmetric Abelian Higgs model, for which we derive and discus...
Bianchi Type-V Bulk Viscous Cosmic String in f(R,T Gravity with Time Varying Deceleration Parameter
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Bïnaya K. Bishi
2015-01-01
Full Text Available We study the Bianchi type-V string cosmological model with bulk viscosity in f(R,T theory of gravity by considering a special form and linearly varying deceleration parameter. This is an extension of the earlier work of Naidu et al., 2013, where they have constructed the model by considering a constant deceleration parameter. Here we find that the cosmic strings do not survive in both models. In addition we study some physical and kinematical properties of both models. We observe that in one of our models these properties are identical to the model obtained by Naidu et al., 2013, and in the other model the behavior of these parameters is different.
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).
Dilaton and axion bremsstrahlung from collisions of cosmic (super)strings
Melkumova, E Y; Salehi, K
2007-01-01
We calculate dilaton and axion radiation generated in the collision of two straight initially unexcited strings and give a rough cosmological estimate of dilaton and axion densities produced via this mechanism in the early universe.
Dilaton and axion bremsstrahlung from collisions of cosmic (super)strings
Melkumova, E. Yu.; Gal'tsov, D. V.; Salehi, K.
2006-01-01
We calculate dilaton and axion radiation generated in the collision of two straight initially unexcited strings and give a rough cosmological estimate of dilaton and axion densities produced via this mechanism in the early universe.
Abbasi, R; Ackermann, M; Adams, J; Aguilar, J A; Ahlers, M; Altmann, D; Andeen, K; Auffenberg, J; Bai, X; Baker, M; Barwick, S W; Baum, V; Bay, R; Beattie, K; Beatty, J J; Bechet, S; Tjus, J Becker; Becker, K -H; Bell, M; Benabderrahmane, M L; BenZvi, S; Berdermann, J; Berghaus, P; Berley, D; Bernardini, E; Bertrand, D; Besson, D Z; Bindig, D; Bissok, M; Blaufuss, E; Blumenthal, J; Boersma, D J; Bohm, C; Bose, D; Böser, S; Botner, O; Brayeur, L; Brown, A M; Bruijn, R; Brunner, J; Buitink, S; Caballero-Mora, K S; Carson, M; Casey, J; Casier, M; Chirkin, D; Christy, B; Clevermann, F; Cohen, S; Cowen, D F; Silva, A H Cruz; Danninger, M; Daughhetee, J; Davis, J C; De Clercq, C; Descamps, F; Desiati, P; de Vries-Uiterweerd, G; DeYoung, T; Díaz-Vélez, J C; Dreyer, J; Dumm, J P; Dunkman, M; Eagan, R; Eisch, J; Ellsworth, R W; Engdegård, O; Euler, S; Evenson, P A; Fadiran, O; Fazely, A R; Fedynitch, A; Feintzeig, J; Feusels, T; Filimonov, K; Finley, C; Fischer-Wasels, T; Flis, S; Franckowiak, A; Franke, R; Frantzen, K; Fuchs, T; Gaisser, T K; Gallagher, J; Gerhardt, L; Gladstone, L; Glüsenkamp, T; Goldschmidt, A; Goodman, J A; Góra, D; Grant, D; Groß, A; Grullon, S; Gurtner, M; Ha, C; Ismail, A Haj; Hallgren, A; Halzen, F; Hanson, K; Heereman, D; Heimann, P; Heinen, D; Helbing, K; Hellauer, R; Hickford, S; Hill, G C; Hoffman, K D; Hoffmann, R; Homeier, A; Hoshina, K; Huelsnitz, W; Hulth, P O; Hultqvist, K; Hussain, S; Ishihara, A; Jacobi, E; Jacobsen, J; Japaridze, G S; Jlelati, O; Johansson, H; Kappes, A; Karg, T; Karle, A; Kiryluk, J; Kislat, F; Kläs, J; Klein, S R; Köhne, J -H; Kohnen, G; Kolanoski, H; Köpke, L; Kopper, C; Kopper, S; Koskinen, D J; Kowalski, M; Krasberg, M; Kroll, G; Kunnen, J; Kurahashi, N; Kuwabara, T; Labare, M; Laihem, K; Landsman, H; Larson, M J; Lauer, R; Lesiak-Bzdak, M; Lünemann, J; Madsen, J; Maruyama, R; Mase, K; Matis, H S; McNally, F; Meagher, K; Merck, M; Mészáros, P; Meures, T; Miarecki, S; Middell, E; Milke, N; Miller, J; Mohrmann, L; Montaruli, T; Morse, R; Movit, S M; Nahnhauer, R; Naumann, U; Nowicki, S C; Nygren, D R; Obertacke, A; Odrowski, S; Olivas, A; Olivo, M; O'Murchadha, A; Panknin, S; Paul, L; Pepper, J A; Heros, C Pérez de los; Pieloth, D; Pirk, N; Posselt, J; Price, P B; Przybylski, G T; Rädel, L; Rawlins, K; Redl, P; Resconi, E; Rhode, W; Ribordy, M; Richman, M; Riedel, B; Rodrigues, J P; Rothmaier, F; Rott, C; Ruhe, T; Rutledge, D; Ruzybayev, B; Ryckbosch, D; Saba, S M; Salameh, T; Sander, H -G; Santander, M; Sarkar, S; Schatto, K; Scheel, M; Scheriau, F; Schmidt, T; Schmitz, M; Schoenen, S; Schöneberg, S; Schönherr, L; Schönwald, A; Schukraft, A; Schulte, L; Schulz, O; Seckel, D; Seo, S H; Sestayo, Y; Seunarine, S; Smith, M W E; Soiron, M; Soldin, D; Spiczak, G M; Spiering, C; Stamatikos, M; Stanev, T; Stasik, A; Stezelberger, T; Stokstad, R G; Stößl, A; Strahler, E A; Ström, R; Sullivan, G W; Taavola, H; Taboada, I; Tamburro, A; Ter-Antonyan, S; Tilav, S; Toale, P A; Toscano, S; Usner, M; van Eijndhoven, N; van der Drift, D; Van Overloop, A; van Santen, J; Vehring, M; Voge, M; Walck, C; Waldenmaier, T; Wallraff, M; Walter, M; Wasserman, R; Weaver, Ch; Wendt, C; Westerhoff, S; Whitehorn, N; Wiebe, K; Wiebusch, C H; Williams, D R; Wissing, H; Wolf, M; Wood, T R; Woschnagg, K; Xu, C; Xu, D L; Xu, X W; Yanez, J P; Yodh, G; Yoshida, S; Zarzhitsky, P; Ziemann, J; Zilles, A; Zoll, M
2012-01-01
The mass composition of high energy cosmic rays depends on their production, acceleration, and propagation. The study of cosmic ray composition can therefore reveal hints of the origin of these particles. At the South Pole, the IceCube Neutrino Observatory is capable of measuring two components of cosmic ray air showers in coincidence: the electromagnetic component at high altitude (2835 m) using the IceTop surface array, and the muonic component above ~1 TeV using the IceCube array. This unique detector arrangement provides an opportunity for precision measurements of the cosmic ray energy spectrum and composition in the region of the knee and beyond. We present the results of a neural network analysis technique to study the cosmic ray composition and the energy spectrum from 1 PeV to 30 PeV using data recorded using the 40-string/40-station configuration of the IceCube Neutrino Observatory.
Henrot-Versillé, Sophie; Leroy, Nicolas; Plaszczynski, Stéphane; Arnaud, Nicolas; Bizouard, Marie-Anne; Cavalier, Fabien; Christensen, Nelson; Couchot, François; Franco, Samuel; Hello, Patrice; Huet, Dominique; Kasprzack, Marie; Perdereau, Olivier; Spinelli, Marta; Tristram, Matthieu
2014-01-01
The production of a primordial stochastic gravitational-wave background by processes occuring in the early Universe is expected in a broad range of models. Observing this background would open a unique window onto the Universe's evolutionary history. Probes like the Cosmic Microwave Background (CMB) or the Baryon Acoustic Oscillations (BAO) can be used to set upper limits on the stochastic gravitational-wave background energy density $\\Omega_{GW}$ for frequencies above $10^{-15}$ Hz. We perform a profile likelihood analysis of the Planck CMB temperature anisotropies and gravitational lensing data combined with WMAP low-$\\ell$ polarization, BAO, South Pole Telescope and Atacama Cosmology Telescope data. We find that $\\Omega_{GW}h_{0}^{2} < 3.8 \\times 10^{-6}$ at 95\\% confidence level for adiabatic initial conditions which improves over the previous limit by a factor 2.3. Assuming that the primordial gravitational waves have been produced by a network of cosmic strings, we have derived exclusion limits in th...
Energy Technology Data Exchange (ETDEWEB)
Lu, Jianbo; Xu, Yanfeng; Wu, Yabo [Liaoning Normal University, Department of Physics, Dalian (China)
2015-10-15
Observations indicate that most of the universal matter is invisible and the gravitational constant G(t) maybe depends on time. A theory of the variational G (VG) is explored in this paper, naturally producing the useful dark components in the universe. We utilize the following observational data: lookback time data, model-independent gamma ray bursts, growth function of matter linear perturbations, type Ia supernovae data with systematic errors, CMB, and BAO, to restrict the unified model (UM) of dark components in VG theory. Using the best-fit values of the parameters with the covariance matrix, constraints on the variation of G are ((G)/(G{sub 0})){sub z=3.5} ≅ 1.0015{sub -0.0075}{sup +0.0071} and ((G)/(G)){sub today} ≅ -0.7252{sub -2.3645}{sup +2.3645} x 10{sup -13} year{sup -1}, with small uncertainties around the constants. The limit on the equation of state of dark matter is w{sub 0dm} = 0.0072{sub -0.0170}{sup +0.0170}, assuming w{sub 0de} = -1 in the unified model, and the dark energy is w{sub 0de} = -0.9986{sub -0.0011}{sup +0.0011}, assuming w{sub 0dm} = 0 a priori. The restrictions on the UM parameters are B{sub s} = 0.7442{sub -0.0132-0.0292}{sup +0.0137+0.0262} and α =0.0002{sub -0.0209-0.0422}{sup +0.0206+0.0441} with 1σ and 2σ confidence level. In addition, the effects of a cosmic string fluid on the unified model in VG theory are investigated. In this case it is found that the Λ CDM (Ω{sub s} = 0, β = 0, and α = 0) is included in this VG-UM model at 1σ confidence level, and larger errors are given: Ω{sub s} = -0.0106{sub -0.0305-0.0509}{sup +0.0312+0.0582} (dimensionless energy density of cosmic string), ((G)/(G{sub 0})){sub z=3.5} ≅ 1.0008{sub -0.0584}{sup +0.0620}, and ((G)/(G)){sub today} ≅ -0.3496{sub -26.3135}{sup +26.3135} x 10{sup -13} year{sup -1}. (orig.)
Rotating Space Elevator: Classical and Statistical Mechanics of cosmic scale spinning strings
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.
Scattering and Bound States of a Spin-1/2 Neutral Particle in the Cosmic String Spacetime
Directory of Open Access Journals (Sweden)
Fabiano M. Andrade
2017-01-01
Full Text Available In this paper the relativistic quantum dynamics of a spin-1/2 neutral particle with a magnetic moment μ in the cosmic string spacetime is reexamined by applying the von Neumann theory of self-adjoint extensions. Contrary to previous studies where the interaction between the spin and the line of charge is neglected, here we consider its effects. This interaction gives rise to a point interaction: ∇·E=(2λ/αδ(r/r. Due to the presence of the Dirac delta function, by applying an appropriated boundary condition provided by the theory of self-adjoint extensions, irregular solutions for the Hamiltonian are allowed. We address the scattering problem obtaining the phase shift, S-matrix, and the scattering amplitude. The scattering amplitude obtained shows a dependency with energy which stems from the fact that the helicity is not conserved in this system. Examining the poles of the S-matrix we obtain an expression for the bound states. The presence of bound states for this system has not been discussed before in the literature.
Dvali, Gia; Van Proeyen, A; Dvali, Gia; Van Proeyen, Antoine
2004-01-01
We study the embedding of cosmic strings, related to the Abrikosov-Nielsen-Olesen vortex solution, into d=4, N=1 supergravity. We find that the local cosmic string solution which saturates the BPS bound of supergravity with the D-term potential for the Higgs field and with the constant Fayet--Iliopoulos term, has 1/2 of supersymmetry unbroken. We observe an interesting relation between the gravitino supersymmetry transformation, positive energy condition and the deficit angle of the cosmic string. We argue that the string solutions with the magnetic flux with F-term potential cannot be supersymmetric, which leads us to a conjecture that D1-strings of string theory in the effective 4d supergravity may be described by the D-term strings, which we study in this paper.
Gravitational Waves from Abelian Gauge Fields and Cosmic Strings at Preheating
Dufaux, Jean-Francois; Garcia-Bellido, Juan
2010-01-01
Primordial gravitational waves provide a very important stochastic background that could be detected soon with interferometric gravitational wave antennas or indirectly via the induced patterns in the polarization anisotropies of the cosmic microwave background. The detection of these waves will open a new window into the early Universe, and therefore it is important to characterize in detail all possible sources of primordial gravitational waves. In this paper we develop theoretical and numerical methods to study the production of gravitational waves from out-of-equilibrium gauge fields at preheating. We then consider models of preheating after hybrid inflation, where the symmetry breaking field is charged under a local U(1) symmetry. We analyze in detail the dynamics of the system in both momentum and configuration space, and show that gauge fields leave specific imprints in the resulting gravitational wave spectra, mainly through the appearence of new peaks at characteristic frequencies that are related to...
The B-L phase transition. Implications for cosmology and neutrinos
Energy Technology Data Exchange (ETDEWEB)
Schmitz, Kai
2012-07-15
We investigate the possibility that the hot thermal phase of the early universe is ignited in consequence of the B-L phase transition, which represents the cosmological realization of the spontaneous breaking of the Abelian gauge symmetry associated with B-L, the difference between baryon number B and lepton number L. Prior to the B-L phase transition, the universe experiences a stage of hybrid inflation. Towards the end of inflation, the false vacuum of unbroken B-L symmetry decays, which entails tachyonic preheating as well as the production of cosmic strings. Observational constraints on this scenario require the B-L phase transition to take place at the scale of grand unification. The dynamics of the B-L breaking Higgs field and the B-L gauge degrees of freedom, in combination with thermal processes, generate an abundance of heavy (s)neutrinos. These (s)neutrinos decay into radiation, thereby reheating the universe, generating the baryon asymmetry of the universe and setting the stage for the thermal production of gravitinos. The B-L phase transition along with the (s)neutrino-driven reheating process hence represents an intriguing and testable mechanism to generate the initial conditions of the hot early universe. We study the B-L phase transition in the full supersymmetric Abelian Higgs model, for which we derive and discuss the Lagrangian in arbitrary and unitary gauge. As for the subsequent reheating process, we formulate the complete set of Boltzmann equations, the solutions of which enable us to give a detailed and time-resolved description of the evolution of all particle abundances during reheating. Assuming the gravitino to be the lightest superparticle (LSP), the requirement of consistency between hybrid inflation, leptogenesis and gravitino dark matter implies relations between neutrino parameters and superparticle masses, in particular a lower bound on the gravitino mass of 10GeV. As an alternative to gravitino dark matter, we consider the case of
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.
Balanced metrics and phenomenological aspects of heterotic string compactifications
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.
Heeck, Julian
2014-01-01
The difference between baryon number B and lepton number L is the only anomaly-free global symmetry of the Standard Model, easily promoted to a local symmetry by introducing three right-handed neutrinos, which automatically make neutrinos massive. The non-observation of any (B-L)-violating processes leads us to scrutinize the case of unbroken gauged B-L; besides Dirac neutrinos, the model contains only three parameters, the gauge coupling strength g', the Stueckelberg mass $M_{Z'}$, and the kinetic mixing angle $\\chi$. The new force could manifest itself at any scale, and we collect and derive bounds on g' over the entire testable range $M_{Z'}$ = 0 - $10^{13}$ eV, also of interest for the more popular case of spontaneously broken B-L or other new light forces. We show in particular that successful Big Bang nucleosynthesis provides strong bounds for masses 10 eV < $M_{Z'}$ < 10 GeV due to resonant enhancement of the rate $\\overline{f} f \\leftrightarrow \\overline{\
On the formation of non-topological string networks
Achucarro, A; Borrill, J; Liddle, AR
1998-01-01
We review recent simulations of the formation of a particular class of non-topological defects known as semilocal strings during a phase transition. Semilocal strings have properties that are intermediate between topological cosmic strings and stable electroweak strings, and therefore the observatio
PhD Thesis: String theory in the early universe
Gwyn, Rhiannon
2009-01-01
The intersection of string theory with cosmology is unavoidable in the early universe, and its exploration may shine light on both fields. In this thesis, three papers at this intersection are presented and reviewed, with the aim of providing a thorough and pedagogical guide to their results. First, we address the longstanding problem of finding a string theory realisation 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, whose network evolution 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, giving the tension and properties of three-string junctions in these backgrounds. Finally, we examine the possibility that cosmic strings in ...
Introduction to the relativistic string theory
Barbashov, B M
1990-01-01
This book presents a systematic and detailed account of the classical and quantum theory of the relativistic string and some of its modifications. Main attention is paid to the first-quantized string theory with possible applications to the string models of hadrons as well as to the superstring approach to unifications of all the fundamental interactions in the elementary particle physics and to the "cosmic" strings. Some new aspects are provided such as the consideration of the string in an external electromagnetic field and in the space-time of constant curvature (the de Sitter universe), th
Indian Academy of Sciences (India)
C P Burgess
2004-12-01
The inflationary paradigm provides a robust description of the peculiar initial conditions which are required for the success of the hot Big Bang model of cosmology, as well as of the recent precision measurements of temperature fluctuations within the cosmic microwave background. Furthermore, the success of this description indicates that inflation is likely to be associated with physics at energies considerably higher than the weak scale, for which string theory is arguably our most promising candidate. These observations strongly motivate a detailed search for inflation within string theory, although it has (so far) proven to be a hunt for a fairly elusive quarry. This article summarizes some of the recent efforts along these lines, and draws some speculative conclusions as to what the difficulty in finding inflation might mean.
Kleman, Maurice
2011-01-01
The continuous 1D defects of an isotropic homogeneous material in an Euclidean 3D space are classified by a construction method, the Volterra process (VP). We employ the same method to classify the continuous 2D defects (which we call \\textit{cosmic forms}) of a vacuum in a 4D maximally symmetric spacetime. These defects fall into three different classes: i)- $m$-forms, akin to 3D space disclinations, related to ordinary rotations and analogous to Kibble's global cosmic strings (except that being continuous any deficit angle is allowed); ii)- $t$-forms, related to Lorentz boosts (hyperbolic rotations); iii)- $r$-forms, never been considered so far, related to null rotations. A detailed account of their metrics is presented. Their inner structure in many cases appears as a non-singular \\textit{core} separated from the outer part by a timelike hypersurface with distributional curvature and/or torsion, yielding new types of geometrical interactions with cosmic dislocations and other cosmic disclinations. Whereas...
PhD Thesis: String theory in the early universe
Gwyn, Rhiannon
2009-11-01
The intersection of string theory with cosmology is unavoidable in the early universe, and its exploration may shine light on both fields. In this thesis, three papers at this intersection are presented and reviewed, with the aim of providing a thorough and pedagogical guide to their results. First, we address the longstanding problem of finding a string theory realisation 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, whose network evolution 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, giving the tension and properties of three-string junctions in these backgrounds. Finally, we examine the possibility that cosmic strings in heterotic string theory could be responsible for generating the galactic magnetic fields that seeded those observed today.
Spontaneous B-L Breaking as the Origin of the Hot Early Universe
Buchmüller, Wilfried; Schmitz, Kai
2012-01-01
The decay of a false vacuum of unbroken B-L symmetry is an intriguing 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 yields hybrid inflation, ending in tachyonic preheating. The dynamics of the B-L breaking Higgs field and thermal processes produce an abundance of heavy neutrinos whose decays generate entropy, baryon asymmetry and gravitino dark matter. We study the phase transition for the full supersymmetric Abelian Higgs model. For the subsequent reheating process we give a detailed time-resolved description of all particle abundances. The competition of cosmic expansion and entropy production leads to an intermediate period of constant 'reheating' temperature, during which baryon asymmetry and dark matter are produced. Consistency of hybrid inflation, leptogenesis and gravitino dark matter implies relations between neutrino parameters and superparticle masses, in particular a lower bound on the gr...
Energy Technology Data Exchange (ETDEWEB)
Engquist, J. [Institute for Theoretical Physics and Spinoza Institute, Utrecht University (Netherlands); Sundell, P. [INFN, Pisa (Italy); Scuola Normale Superiore, Pisa (Italy); Tamassia, L. [Instituut voor Theoretische Fysica, Katholieke Universiteit Leuven, Celestijnenlaan 200D, 3001 Leuven (Belgium)
2007-05-15
The group theoretical structure underlying physics in anti de Sitter (AdS) spacetime is intrinsically different with respect to the flat case, due to the presence of special ultra-short representations, named singletons, that do not admit a flat space limit. The purpose of this collaboration is to exploit this feature in the study of string and brane dynamics in AdS spacetime, in particular while trying to establish a connection between String Theory in AdS backgrounds (in the tensionless limit) and Higher-Spin Gauge Theory. (orig.)
Inflection-point B -L Higgs inflation
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.
Generalised hyperbolicity in spacetimes with string-like singularities
Sanchez, Yafet Sanchez
2016-01-01
In this paper we present well-posedness results of the wave equation in $H^{1}$ for spacetimes that contain string-like singularities. These results extend a framework able to characterise gravitational singularities as obstruction to the dynamics of test fields rather than point particles. In particular, we discuss spacetimes with cosmic strings and the relation of our results to the Strong Cosmic Censorship Conjecture.
Stability of string defects in models of non-Abelian symmetry breaking
Thatcher, M J
1999-01-01
In this paper we describe a new type of topological defect, called a homilia string, which is stabilized via interactions with the string network. Using analytical and numerical techniques, we investigate the stability and dynamics of homilia strings, and their implications for cosmology. In SU(N) models of symmetry breaking, monopoles are identified with the intersection of two homilia strings. Due to repulsive forces, the homilia strings seperate, resulting in monopole annihilation. Homilia string loops cannot stabilize as vortons, which circumvents the adverse cosmological consequences of stable loops. In principle, measurments of the cosmic microwave background can distinguish between the smaller fluctuations induced by a homilia string network and those due to primordial cosmic strings.
Academic Training: String Theory for Pedestrians
2007-01-01
2006-2007 ACADEMIC TRAINING PROGRAMME LECTURE SERIES 29, 30, 31 January 2007, from 11:00 to 12:00 Main Auditorium, bldg. 500 on 29 and 30 January, TH Auditorium, Bldg 4, 3-006, on 31 January String Theory for Pedestrians B. ZWIEBACH, MIT, Cambridge, USA In this 3-lecture series I will discuss the basics of string theory, some physical applications, and the outlook for the future. I will begin with the main concepts of the classical theory and the application to the study of cosmic superstrings. Then I will turn to the quantum theory and discuss applications to the investigation of hadronic spectra and the recently discovered quark-gluon plasma. I will conclude with a sketch of string models of particle physics and showing some avenues that may lead to a complete formulation of string theory.
Probing Cosmic Superstrings with Gravitational Waves
Sousa, Lara
2016-01-01
We compute the stochastic gravitational wave background generated by cosmic superstrings using a semi-analytical 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 $G\\mu_F<3.2 \\times 10^{-9}$ 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 $G\\mu_F$. We show that the inclusion of heavier string types is required for a more accurate cha...
Highly excited strings I: Generating function
Directory of Open Access Journals (Sweden)
Dimitri P. Skliros
2017-03-01
Full Text Available 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=RD−1,1×TDcr−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.
Highly excited strings I: Generating function
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.
The Universe as a Cosmic String
Niedermann, Florian; Hofmann, Stefan; Khoury, Justin
2014-01-01
The cosmology of brane induced gravity in six infinite dimensions is investigated. It is shown that a brane with FRW 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 to solve the non-linear 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 non-vanishing energy density on the brane and super-accelerating 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 super-accelerating solutions are pote...
Self-similar motion of a Nambu-Goto string
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.
B-L assisted anomaly mediation and the radiative B-L symmetry breaking
Energy Technology Data Exchange (ETDEWEB)
Kikuchi, Tatsuru [Theory Division, KEK, Oho 1-1, Tsukuba, Ibaraki 305-0801 (Japan)], E-mail: tatsuru@post.kek.jp; Kubo, Takayuki [Theory Division, KEK, Oho 1-1, Tsukuba, Ibaraki 305-0801 (Japan); Graduate University for Advanced Studies, Oho 1-1, Tsukuba, Ibaraki 305-0801 (Japan)], E-mail: kubotaka@post.kek.jp
2008-10-30
Anomaly mediated supersymmetry breaking implemented in the minimal supersymmetric standard model (MSSM) is known to suffer from the tachyonic slepton problem leading to breakdown of electric charge conservation. We show however that when MSSM is extended to explain small neutrino masses by gauging the B-L symmetry, the slepton masses can be positive due to the Z{sup '} mediation contributions. We obtain various soft supersymmetry breaking mass spectra, which are different from those obtained in the conventional anomaly mediation scenario. Then there would be a distinct signature of this scenario at the LHC.
Ristad, E S; Ristad, Eric Sven; Yianilos, Peter N.
1996-01-01
In many applications, it is necessary to determine the similarity of two strings. A widely-used notion of string similarity is the edit distance: the minimum number of insertions, deletions, and substitutions required to transform one string into the other. In this report, we provide a stochastic model for string edit distance. Our stochastic model allows us to learn a string edit distance function from a corpus of examples. We illustrate the utility of our approach by applying it to the difficult problem of learning the pronunciation of words in conversational speech. In this application, we learn a string edit distance with one fourth the error rate of the untrained Levenshtein distance. Our approach is applicable to any string classification problem that may be solved using a similarity function against a database of labeled prototypes. Keywords: string edit distance, Levenshtein distance, stochastic transduction, syntactic pattern recognition, prototype dictionary, spelling correction, string correction, ...
String and string-inspired phenomenology
López, J L
1994-01-01
In these lectures I review the progress made over the last few years in the subject of string and string-inspired phenomenology. I take a practical approach, thereby concentrating more on explicit examples rather than on formal developments. Topics covered include: introduction to string theory the free-fermionic formulation and its general features, generic conformal field theory properties, SU(5)\\times U(1) GUT and string model-building, supersymmetry breaking, the bottom-up approach to string-inspired models, radiative electroweak symmetry breaking, the determination of the allowed parameter space of supergravity models and the experimental constraints on this class of models, and prospects for direct and indirect tests of string-inspired models. (Lectures delivered at the XXII ITEP International Winter School of Physics, Moscow, Russia, February 22 -- March 2, 1994)
Dando, O; Dando, Owen; Gregory, Ruth
1998-01-01
We examine the field equations of a self-gravitating global string in low energy superstring gravity, allowing for an arbitrary coupling of the global string to the dilaton. Massive and massless dilatons are considered. For the massive dilaton the spacetime is similar to the recently discovered non-singular time-dependent Einstein self-gravitating global string, but the massless dilaton generically gives a singular spacetime, even allowing for time-dependence. We also demonstrate a time-dependent non-singular string/anti-string configuration, in which the string pair causes a compactification of two of the spatial dimensions, albeit on a very large scale.
Closed String Amplitudes from Gauge Fixed String Field Theory
Drukker, Nadav
2002-01-01
Closed string diagrams are derived from cubic open string field theory using a gauge fixed kinetic operator. The basic idea is to use a string propagator that does not generate a boundary to the world sheet. Using this propagator and the closed string vertex, the moduli space of closed string surfaces is covered, so closed string scattering amplitudes should be reproduced. This kinetic operator could be a gauge fixed form of the string field theory action around the closed string vacuum.
Spontaneous B-L breaking as the origin of the hot early universe
Energy Technology Data Exchange (ETDEWEB)
Buchmueller, W.; Domcke, V.; Schmitz, K.
2012-03-15
The decay of a false vacuum of unbroken B-L symmetry is an intriguing 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 yields hybrid inflation, ending in tachyonic preheating. The dynamics of the B - L breaking Higgs field and thermal processes produce an abundance of heavy neutrinos whose decays generate entropy, baryon asymmetry and gravitino dark matter. We study the phase transition for the full supersymmetric Abelian Higgs model. For the subsequent reheating process we give a detailed time-resolved description of all particle abundances. The competition of cosmic expansion and entropy production leads to an intermediate period of constant 'reheating' temperature, during which baryon asymmetry and dark matter are produced. Consistency of hybrid inflation, leptogenesis and gravitino dark matter implies relations between neutrino parameters and superparticle masses, in particular a lower bound on the gravitino mass of 10 GeV.
Primordial magnetic fields from the string network
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.
Primordial magnetic fields from the string network
Horiguchi, Kouichirou; Sugiyama, Naoshi
2016-01-01
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 $a^2B(k,z)\\sim4\\times10^{-16}G\\mu/((1+z)/1000)^{4.25}(k/{\\rm Mpc}^{-1})^{3.5}$ Gauss on super-horizon scales, and $a^2B(k,z)\\sim2.4\\times10^{-17}G\\mu/((1+z)/1000)^{3.5}(k/{\\rm Mpc}^{-1})^{2.5}$ Gauss on sub-horizon scales in co-moving coordinates. This magnetic field grows up to the end of recombination, ...
Ooguri, H; Ooguri, Hirosi; Yin, Zheng
1996-01-01
These lecture notes are based on a course on string theories given by Hirosi Ooguri in the first week of TASI 96 Summer School at Boulder, Colorado. It is an introductory course designed to provide students with minimum knowledge before they attend more advanced courses on non-perturbative aspects of string theories in the School. The course consists of five lectures: 1. Bosonic String, 2. Toroidal Compactifications, 3. Superstrings, 4. Heterotic Strings, and 5. Orbifold Compactifications.
2015-10-01
UNCLASSIFIED AD-E403 689 Technical Report ARWSE-TR-14026 STD ::STRING APPEND Tom Nealis...DATES COVERED (From – To) 4. TITLE AND SUBTITLE STD ::STRING APPEND 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6...two or more strings together while developing a C++ application is a very common task. For std ::strings, there are two primary ways to achieve the
Conlon, Joseph
2016-01-01
Is string theory a fraud or one of the great scientific advances? Why do so many physicists work on string theory if it cannot be tested? This book provides insight into why such a theory, with little direct experimental support, plays such a prominent role in theoretical physics. The book gives a modern and accurate account of string theory and science, explaining what string theory is, why it is regarded as so promising, and why it is hard to test.
[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.
The series of String-Math conferences has developed into a central event on the interface between mathematics and physics related to string theory, quantum field theory and neighboring subjects. The conference will take place from July 24-28 in the main building of Hamburg university. The String-Math conference is organised by the University of Hamburg jointly with DESY Hamburg.
Cardona, Biel; Pons, Josep M
2016-01-01
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.
Bianchi type-V string cosmological models in general relativity
Indian Academy of Sciences (India)
Anil Kumar Yadav; Vineet Kumar Yadav; Lallan Yadav
2011-04-01
Bianchi type-V string cosmological models in general relativity are investigated. To get the exact solution of Einstein’s ﬁeld equations, we have taken some scale transformations used by Camci et al [Astrophys. Space Sci. 275, 391 (2001)]. It is shown that Einstein’s ﬁeld equations are solvable for any arbitrary cosmic scale function. Solutions for particular forms of cosmic scale functions are also obtained. Some physical and geometrical aspects of the models are discussed.
Dando, Owen; Gregory, Ruth
1998-07-01
We examine the field equations of a self-gravitating global string in low energy superstring gravity, allowing for an arbitrary coupling of the global string to the dilaton. Massive and massless dilatons are considered. For the massive dilaton the spacetime is similar to the recently discovered non-singular time-dependent Einstein self-gravitating global string, but the massless dilaton generically gives a singular spacetime, even allowing for time dependence. We also demonstrate a time-dependent non-singular string-antistring configuration, in which the string pair causes a compactification of two of the spatial dimensions, albeit on a very large scale.
Doubled strings, negative strings and null waves
Blair, Chris D A
2016-01-01
We revisit the fundamental string (F1) solution in the doubled formalism. We show that the wave-like solution of double field theory (DFT) corresponding to the F1/pp-wave duality pair is more properly a solution of the DFT action coupled to a doubled sigma model action. The doubled string configuration which sources the pp-wave can be thought of as static gauge with the string oriented in a dual direction. We also discuss the DFT solution corresponding to a vibrating string, carrying both winding and momentum. We further show that the solution dual to the F1 in both time and space can be viewed as a "negative string" solution. Negative branes are closely connected to certain exotic string theories which involve unusual signatures for both spacetime and brane worldvolumes. In order to better understand this from the doubled point of view, we construct a variant of DFT suitable for describing theories in which the fundamental string has a Euclidean worldsheet, for which T-dualities appear to change the spacetim...
Interacting Strings in Matrix String Theory
Bonelli, G.
1998-01-01
It is here explained how the Green-Schwarz superstring theory arises from Matrix String Theory. This is obtained as the strong YM-coupling limit of the theory expanded around its BPS instantonic configurations, via the identification of the interacting string diagram with the spectral curve of the relevant configuration. Both the GS action and the perturbative weight $g_s^{-\\chi}$, where $\\chi$ is the Euler characteristic of the world-sheet surface and $g_s$ the string coupling, are obtained.
Galtsov, D V; Volkov, M S; Davydov, Evgeny A.; Gal'tsov, Dmitri V.; Volkov, Mikhail S.
2006-01-01
We present globally regular vortex-type solutions for a pure SU(2) Yang-Mills field coupled to gravity in 3+1 dimensions. These gravitating vortices are static, cylindrically symmetric and purely magnetic, and they support a non-zero chromo-magnetic flux through their cross section. In addition, they carry a constant non-Abelian current, and so in some sense they are analogs of the superconducting cosmic strings. They have a compact central core dominated by a longitudinal magnetic field and endowed with an approximately Melvin geometry. This magnetic field component gets color screened in the exterior part of the core, outside of which the fields approach exponentially fast those of the electrovacuum Bonnor solutions with a circular magnetic field. In the far field zone the solutions are not asymptotically flat but tend to vacuum Kasner metrics.
The energy and stability of D-term strings
Collinucci, A; Van Proeyen, A; Collinucci, Andr\\'es; Proeyen, Antoine Van; Smyth, Paul
2007-01-01
Cosmic strings derived from string theory, supergravity or any theory of choice should be stable if we hope to observe them. In this paper we consider D-term strings in D=4, N=1 supergravity with a constant Fayet-Iliopoulos term. We show that the positive deficit angle supersymmetric D-term string is non-perturbatively stable by using standard Witten-Nester techniques to prove a positive energy theorem. Particular attention is paid to the negative deficit angle D-term string, which is known to violate the dominant energy condition. Within the class of string solutions we consider, this violation implies that the negative deficit angle D-term string must have a naked pathology and therefore the positive energy theorem we prove does not apply to it. As an interesting aside, we show that the Witten-Nester charge calculates the total gravitational energy of the D-term string without the need for a cut-off, which may not have been expected.
Superconducting Electroweak Strings
Volkov, M S
2007-01-01
Classical solutions describing strings endowed with an electric charge and carrying a constant electromagnetic current are constructed within the bosonic sector of the Electroweak Theory. For any given ratio of the Higgs boson mass to W boson mass and for any Weinberg's angle, these strings comprise a family that can be parameterized by values of the current through their cross section, $I_3$, by their electric charge per unit string length, $I_0$, and by two integers. These parameters determine the electromagnetic and Z fluxes, as well as the angular momentum and momentum densities of the string. For $I_0\\to 0$ and $I_3\\to 0$ the solutions reduce to Z strings, or, for solutions with $I_0=\\pm I_3$, to the W-dressed Z strings whose existence was discussed some time ago.
Self-similar motion of a Nambu-Goto string
Igata, Takahisa; Harada, Tomohiro
2016-01-01
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 the 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-Lema\\^itre-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 t...
String Scale Cosmological Constant
Chalmers, Gordon
2006-01-01
The cosmological constant is an unexplained until now phenomena of nature that requires an explanation through string effects. The apparent discrepancy between theory and experiment is enourmous and has already been explained several times by the author including mechanisms. In this work the string theory theory of abolished string modes is documented and given perturbatively to all loop orders. The holographic underpinning is also exposed. The matching with the data of the LIGO and D0 experi...
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.
Optimal Packed String Matching
DEFF Research Database (Denmark)
Ben-Kiki, Oren; Bille, Philip; Breslauer, Dany
2011-01-01
In the packed string matching problem, each machine word accommodates – characters, thus an n-character text occupies n/– memory words. We extend the Crochemore-Perrin constantspace O(n)-time string matching algorithm to run in optimal O(n/–) time and even in real-time, achieving a factor – speedup...... over traditional algorithms that examine each character individually. Our solution can be efficiently implemented, unlike prior theoretical packed string matching work. We adapt the standard RAM model and only use its AC0 instructions (i.e., no multiplication) plus two specialized AC0 packed string...
Savvidy, G K
1998-01-01
We discuss the basic properties of the gonihedric string and the problem of its formulation in continuum. We propose a generalization of the Dirac equation and of the corresponding gamma matrices in order to describe the gonihedric string. The wave function and the Dirac matrices are infinite-dimensional. The spectrum of the theory consists of particles and antiparticles of increasing half-integer spin lying on quasilinear trajectories of different slope. Explicit formulas for the mass spectrum allow to compute the string tension and thus demonstrate the string character of the theory.
Zimmerman Jones, Andrew
2010-01-01
Making Everything Easier!. String Theory for Dummies. Learn:. The basic concepts of this controversial theory;. How string theory builds on physics concepts;. The different viewpoints in the field;. String theory's physical implications. Andrew Zimmerman Jones. Physics Guide, About.com. with Daniel Robbins, PhD in Physics. Your plain-English guide to this complex scientific theory. String theory is one of the most complicated sciences being explored today. Not to worry though! This informative guide clearly explains the basics of this hot topic, discusses the theory's hypotheses and prediction
Classically conformal radiative neutrino model with gauged B - L symmetry
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.
Kolmogorov Complexity, String Information, Panspermia and the Fermi Paradox
Gurzadyan, V G
2005-01-01
Bit strings rather than byte files can be a mode of transmission both for intelligent signals and for travels of extraterrestrial life. Kolmogorov complexity, i.e. the minimal length of a binary coded string completely defining a system, can then, due to its universality, become a key concept in the strategy of the search of extraterrestrials. Evaluating, for illustration, the Kolmogorov complexity of the human genome, one comes to an unexpected conclusion that a low complexity compressed string - analog of Noah's ark - will enable the recovery of the totality of terrestrial life. The recognition of bit strings of various complexity up to incompressible Martin-L\\"{o}f random sequences, will require a different strategy for the analysis of the cosmic signals. The Fermi paradox "Where is Everybody?" can be viewed under in the light of such information panspermia, i.e. a Universe full of traveling life streams.
Academic training : String Theory for Pedestrians
2007-01-01
LECTURE SERIES 29, 30, 31 January 2007 from 11.00 to 12.00 hrs Main Auditorium, bldg. 500 on 29 and 30 January TH Auditorium, Bldg 4, 3-006, on 31 January String Theory for Pedestrians B. ZWIEBACH/MIT, Cambridge, USA In this 3-lecture series I will discuss the basics of string theory, some physical applications, and the outlook for the future. Â I will begin with the main concepts of the classical theory and theÂ application to the study of cosmic superstrings.Â Then I will turnÂ to the quantum theory and discussÂ applications toÂ the investigation ofÂ hadronic spectra and theÂ recentlyÂ discovered quark-gluon plasma.Â Â I will concludeÂ with a sketch of string models of particle physicsÂ and showing some avenues that may lead to aÂ completeÂ formulation ofÂ string theory. Â
k-Strings as Fundamental Strings
Giataganas, Dimitrios
2015-01-01
It has been noticed that the k-string observables can be expressed in terms of the fundamental string ones. We identify a sufficient condition for a generic gravity dual background which when satisfied the mapping can be done. The condition is naturally related to a preserved quantity under the T-dualities acting on the Dp-brane describing the high representation Wilson loops. We also find the explicit relation between the observables of the heavy k-quark and the single quark states. As an application to our generic study and motivated by the fact that the anisotropic theories satisfy our condition, we compute the width of the k-string in these theories to find that the logarithmic broadening is still present, but the total result is affected by the anisotropy of the space.
de Boer, J.; de Medeiros, P.; El-Showk, S.; Sinkovics, A.
2008-01-01
We consider an open string version of the topological twist previously proposed for sigma-models with G(2) 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 submani
Probing classically conformal $B-L$ model with gravitational waves
Jinno, Ryusuke
2016-01-01
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. Especially, 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, (3) the thermal phase transition completes in almost all the patches in the universe, the gravitational wave spectrum can be as large as $\\Omega_{\\rm GW} \\sim 10^{-8}$ at the frequency $f \\sim 0.01$-$1$Hz for some model parameters, and a vast parameter region can be tested by future interferometer experiments such as eLISA, LISA, BBO and DECIGO.
2015-01-01
Welcome to String-Math 2015 at Sanya. The conference will be opened in December 31, 2015- January 4, 2016. String theory plays a central role in theoretical physics as a candidate for the quantum theory unifying gravity with other interactions. It has profound connections with broad branches of modern mathematics ever since the birth. In the last decades, the prosperous interaction, built upon the joint efforts from both mathematicians and physicists, has given rise to marvelous deep results in supersymmetric gauge theory, topological string, M-theory and duality on the physics side as well as in algebraic geometry, differential geometry, algebraic topology, representation theory and number theory on the mathematics side. The interplay is two-fold. The mathematics has provided powerful tools to fulfill the physical interconnection of ideas and clarify physical structures to understand the nature of string theory. On the other hand, ideas from string theory and quantum field theory have been a source of sign...
Non-Riemannian Cosmic Walls as Boundaries of Spinning Matter
Garcia de Andrade, L C
1998-01-01
An example is given of a plane topological defect solution of linearized Einstein-Cartan (EC) field equation representing a cosmic wall boundary of spinning matter. The source of Cartan torsion is composed of two orthogonal lines of static polarized spins bounded by the cosmic plane wall. The Kopczy\\'{n}ski- Obukhov - Tresguerres (KOT) spin fluid stress-energy current coincides with thin planar matter current in the static case. Our solution is similar to 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.
Universality and string theory
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
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.
Searching for Long Strings in CMB Maps
Perivolaropoulos, L
1998-01-01
Using analytical methods and Monte Carlo simulations, we analyze new statistics designed to detect isolated step-like discontinuities which are coherent over large areas of Cosmic Microwave Background (CMB) pixel maps. Such coherent temperature discontinuities are predicted by the Kaiser-Stebbins effect to form due to long cosmic strings present in our present horizon. The background of the coherent step-like seed is assumed to be a scale invariant Gaussian random field which could have been produced by a superposition of seeds on smaller scales and/or by inflationary quantum fluctuations. We find that the proposed statistics can detect the presense of a coherent discontinuity at a sensitivity level almost an order of magnitude better compared to more conventional statistics like the skewness or the kurtosis.
Effective String Theory Simplified
Hellerman, Simeon; Maltz, Jonathan; Swanson, Ian
2014-01-01
In this set of notes we simplify the formulation of the Poincar\\'e invariant effective string theory in D dimensions by adding an intrinsic metric and embedding its dynamics into the Polyakov formalism. We apply this formalism to classify operators order by order in the inverse physical length of the string, in a fully gauge-invariant framework. We use this classification to discuss universality and nonuniversalty of observables up to and including next-to-next-to-leading order in the long string expansion.
Energy Technology Data Exchange (ETDEWEB)
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.
Asymmetric Gepner Models III. B-L Lifting
Gato-Rivera, B
2010-01-01
In the same spirit as heterotic weight lifting, B-L lifting is a way of replacing the superfluous and ubiquitous U(1)_{B-L} with something else with the same modular properties, but different conformal weights and ground state dimensions. This method works in principle for all variants of (2,2) constructions, such as orbifolds, Calabi-Yau manifolds, free bosons and fermions and Gepner models, since it only modifies the universal SO(10) x E_8 part of the CFT. However, it can only yield chiral spectra if the ``internal" sector of the theory provides a simple current of order 5. Here we apply this new method to Gepner models. Including exceptional invariants, 86 of them have the required order 5 simple current, and 69 of these yield chiral spectra. Three family spectra occur abundantly.
Asymmetric Gepner models III. B-L lifting
Energy Technology Data Exchange (ETDEWEB)
Gato-Rivera, B. [NIKHEF Theory Group, Kruislaan 409, 1098 SJ Amsterdam (Netherlands); Instituto de Fisica Fundamental, CSIC, Serrano 123, Madrid 28006 (Spain); Schellekens, A.N., E-mail: t58@nikhef.n [NIKHEF Theory Group, Kruislaan 409, 1098 SJ Amsterdam (Netherlands); Instituto de Fisica Fundamental, CSIC, Serrano 123, Madrid 28006 (Spain); IMAPP, Radboud Universiteit, Nijmegen (Netherlands)
2011-06-21
In the same spirit as heterotic weight lifting, B-L lifting is a way of replacing the superfluous and ubiquitous U(1){sub B-L} with something else with the same modular properties, but different conformal weights and ground state dimensions. This method works in principle for all variants of (2,2) constructions, such as orbifolds, Calabi-Yau manifolds, free bosons and fermions and Gepner models, since it only modifies the universal SO(10)xE{sub 8} part of the CFT. However, it can only yield chiral spectra if the 'internal' sector of the theory provides a simple current of order 5. Here we apply this new method to Gepner models. Including exceptional invariants, 86 of them have the required order 5 simple current, and 69 of these yield chiral spectra. Three family spectra occur abundantly.
International conference on string theory
2017-01-01
The Strings 2017 conference is part of the "Strings" series of annual conferences, that bring the entire string theory community together. It will include reviews of major developments in the field, and specialized talks on specific topics. There will also be several public lectures given by conference participants, a pre-Strings school at the Technion, and a post-Strings workshop at the Weizmann Institute.
Supercritical N = 2 string theory
Hellerman, Simeon
2007-01-01
The N=2 string is examined in dimensions above the critical dimension (D=4) in a linear dilaton background. We demonstrate that string states in this background propagate in a single physical time dimension, as opposed to two such dimensions present when the dilaton gradient vanishes in D=4. We also find exact solutions describing dynamical dimensional reduction and transitions from N=2 string theory to bosonic string theory via closed-string tachyon condensation.
International conference on string theory
2016-01-01
The Strings conference is an annual event that brings the entire string theory community together. Since the 1980s, it has grown to be the largest and most important conference in the field. The aim is to review recent developments in string theory and to stimulate scientific exchanges among the participants. This is the second Strings conference organised in Beijing, after Strings 2006. Following the tradition, besides scientific talks, the conference will also include some public lectures open to a general audience.
Ménard, B
2002-01-01
I present the current status of the cosmic magnification produced by systematic amplification of background sources by large-scale structures. After introducing its principle, I focus on its interests for cosmology and underline its complementary aspect to cosmic shear and galaxy auto-correlations. I finally discuss recent investigations using higher-order statistics.
2008-01-01
String Theory supporters argue that the universe we live in has eleven dimensions, out of which three spacial dimensions and a temporal one, which define the void and the space-time environment we experience daily.
Katz, Sheldon; Klemm, Albrecht; Morrison, David R
2015-01-01
This volume contains the proceedings of the conference String-Math 2012, which was held July 16-21, 2012, at the Hausdorff Center for Mathematics, Universitat Bonn. This was the second in a series of annual large meetings devoted to the interface of mathematics and string theory. These meetings have rapidly become the flagship conferences in the field. Topics include super Riemann surfaces and their super moduli, generalized moonshine and K3 surfaces, the latest developments in supersymmetric and topological field theory, localization techniques, applications to knot theory, and many more. The contributors include many leaders in the field, such as Sergio Cecotti, Matthias Gaberdiel, Rahul Pandharipande, Albert Schwarz, Anne Taormina, Johannes Walcher, Katrin Wendland, and Edward Witten. This book will be essential reading for researchers and students in this area and for all mathematicians and string theorists who want to update themselves on developments in the math-string interface.
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 Apartado 80659, Caracas 1080A, Venezuela.
DEFF Research Database (Denmark)
Szklarczyk, Damian; Franceschini, Andrea; Wyder, Stefan;
2015-01-01
.0 of STRING covers more than 2000 organisms, which has necessitated novel, scalable algorithms for transferring interaction information between organisms. For this purpose, we have introduced hierarchical and self-consistent orthology annotations for all interacting proteins, grouping the proteins...
String theory compactifications
Graña, Mariana
2017-01-01
The lectures in this book provide graduate students and non-specialist researchers with a concise introduction to the concepts and formalism required to reduce the ten-dimensional string theories to the observable four-dimensional space-time - a procedure called string compactification. The text starts with a very brief introduction to string theory, first working out its massless spectrum and showing how the condition on the number of dimensions arises. It then dwells on the different possible internal manifolds, from the simplest to the most relevant phenomenologically, thereby showing that the most elegant description is through an extension of ordinary Riemannian geometry termed generalized geometry, which was first introduced by Hitchin. Last but not least, the authors review open problems in string phenomenology, such as the embedding of the Standard Model and obtaining de Sitter solutions.
Dijkgraaf, Robbert; Verlinde, Erik; Verlinde, Herman
1997-02-01
Via compactification on a circle, the matrix mode] of M-theory proposed by Banks et a]. suggests a concrete identification between the large N limit of two-dimensional N = 8 supersymmetric Yang-Mills theory and type IIA string theory. In this paper we collect evidence that supports this identification. We explicitly identify the perturbative string states and their interactions, and describe the appearance of D-particle and D-membrane states.
Energy Technology Data Exchange (ETDEWEB)
Dijkgraaf, R. [Amsterdam Univ. (Netherlands). Dept. of Mathematics; Verlinde, E. [TH-Division, CERN, CH-1211 Geneva 23 (Switzerland)]|[Institute for Theoretical Physics, Universtity of Utrecht, 3508 TA Utrecht (Netherlands); Verlinde, H. [Institute for Theoretical Physics, University of Amsterdam, 1018 XE Amsterdam (Netherlands)
1997-09-01
Via compactification on a circle, the matrix model of M-theory proposed by Banks et al. suggests a concrete identification between the large N limit of two-dimensional N=8 supersymmetric Yang-Mills theory and type IIA string theory. In this paper we collect evidence that supports this identification. We explicitly identify the perturbative string states and their interactions, and describe the appearance of D-particle and D-membrane states. (orig.).
Dijkgraaf, R; Verlinde, Herman L
1997-01-01
Via compactification on a circle, the matrix model of M-theory proposed by Banks et al suggests a concrete identification between the large N limit of two-dimensional N=8 supersymmetric Yang-Mills theory and type IIA string theory. In this paper we collect evidence that supports this identification. We explicitly identify the perturbative string states and their interactions, and describe the appearance of D-particle and D-membrane states.
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.
Manipulating Strings in Python
Directory of Open Access Journals (Sweden)
William J. Turkel
2012-07-01
Full Text Available This lesson is a brief introduction to string manipulation techniques in Python. Knowing how to manipulate strings plays a crucial role in most text processing tasks. If you’d like to experiment with the following lessons, you can write and execute short programs as we’ve been doing, or you can open up a Python shell / Terminal to try them out on the command line.
Itoyama, H
2016-01-01
This is a brief summary of an introductory lecture for students and scholars in general given by the author at Nambu Memorial Symposium which was held at Osaka City University on September 29, 2015. We review the invention of string theory by Professor Yoichiro Nambu following the discovery of the Veneziano amplitude. We also discuss Professor Nambu's proposal on string theory in the Schild gauge in 1976 which is related to the matrix model of Yang-Mills type.
Frampton, Paul H
2015-01-01
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, 2105.
Energy Technology Data Exchange (ETDEWEB)
Ahlén, Olof, E-mail: olof.ahlen@aei.mpg.de [Max-Planck-Institut für Gravitationsphysik (Albert-Einstein-Institut), Am Mühlenberg 1, DE-14476 Potsdam (Germany)
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.
Z'-gauge Bosons as Harbingers of Low Mass Strings
Anchordoqui, Luis A; Goldberg, Haim; Huang, Xing; Lüst, Dieter; Taylor, Tomasz R
2012-01-01
Massive Z'-gauge bosons act as excellent harbingers for string compactifications with a low string scale. In D-brane models they are associated to U(1) gauge symmetries that are either anomalous in four dimensions or exhibit a hidden higher dimensional anomaly. We discuss the possible signals of massive Z'-gauge bosons at hadron collider machines (Tevatron, LHC) in a minimal D-brane model consisting out of four stacks of D-branes. In this construction, there are two massive gauge bosons, which can be naturally associated with baryon number B and B-L (L being lepton number). Here baryon number is always anomalous in four dimensions, whereas the presence of a four-dimensional B-L anomaly depends on the U(1)-charges of the right handed neutrinos. In case B-L is anomaly free, a mass hierarchy between the two associated Z'-gauge bosons can be explained. In our phenomenological discussion about the possible discovery of massive Z'-gauge bosons, we take as a benchmark scenario the dijet plus W signal, recently obser...
Chaotic Hybrid Inflation with a Gauged B - L
Carpenter, Linda M
2014-01-01
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 $U_1(B-L)$ 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.
Ghost Structure and Closed Strings in Vacuum String Field Theory
Gaiotto, D; Sen, A; Zwiebach, B; Gaiotto, Davide; Rastelli, Leonardo; Sen, Ashoke; Zwiebach, Barton
2001-01-01
We complete the construction of vacuum string field theory by proposing a canonical choice of ghost kinetic term -- a local insertion of the ghost field at the string midpoint with an infinite normalization. This choice, supported by level expansion studies in the Siegel gauge, allows a simple analytic treatment of the ghost sector of the string field equations. As a result, solutions are just projectors, such as the sliver, of an auxiliary CFT built by combining the matter part with a twisted version of the ghost conformal theory. Level expansion experiments lead to surprising new projectors -- butterfly surface states, whose analytical expressions are obtained. With the help of a suitable open-closed string vertex we define open-string gauge invariant operators parametrized by on-shell closed string states. We use regulated vacuum string field theory to sketch how pure closed string amplitudes on surfaces without boundaries arise as correlators of such gauge invariant operators.
Perspectives on string phenomenology
Kane, Gordon; Kumar, Piyush
2015-01-01
The remarkable recent discovery of the Higgs boson at the CERN Large Hadron Collider completed the Standard Model of particle physics and has paved the way for understanding the physics which may lie beyond it. String/M theory has emerged as a broad framework for describing a plethora of diverse physical systems, which includes condensed matter systems, gravitational systems as well as elementary particle physics interactions. If string/M theory is to be considered as a candidate theory of Nature, it must contain an effectively four-dimensional universe among its solutions that is indistinguishable from our own. In these solutions, the extra dimensions of string/M Theory are “compactified” on tiny scales which are often comparable to the Planck length. String phenomenology is the branch of string/M theory that studies such solutions, relates their properties to data, and aims to answer many of the outstanding questions of particle physics beyond the Standard Model. This book contains perspectives on stri...
Haghighat, Babak; Iqbal, Amer; Kozçaz, Can; Lockhart, Guglielmo; Vafa, Cumrun
2015-03-01
M2 branes suspended between adjacent parallel M5 branes lead to light strings, the `M-strings'. In this paper we compute the elliptic genus of M-strings, twisted by maximally allowed symmetries that preserve 2 d (2, 0) supersymmetry. In a codimension one subspace of parameters this reduces to the elliptic genus of the (4, 4) supersymmetric A n-1 quiver theory in 2 d. We contrast the elliptic genus of N M-strings with the (4, 4) sigma model on the N-fold symmetric product of . For N = 1 they are the same, but for N > 1 they are close, but not identical. Instead the elliptic genus of (4, 4) N M-strings is the same as the elliptic genus of (4, 0) sigma models on the N-fold symmetric product of , but where the right-moving fermions couple to a modification of the tangent bundle. This construction arises from a dual A n-1 quiver 6 d gauge theory with U(1) gauge groups. Moreover, we compute the elliptic genus of domain walls which separate different numbers of M2 branes on the two sides of the wall.
Haghighat, Babak; Kozcaz, Can; Lockhart, Guglielmo; Vafa, Cumrun
2013-01-01
M2 branes suspended between adjacent parallel M5 branes lead to light strings, the `M-strings'. In this paper we compute the elliptic genus of M-strings, twisted by maximally allowed symmetries that preserve 2d (2,0) supersymmetry. In a codimension one subspace of parameters this reduces to the elliptic genus of the (4,4) supersymmetric A_{n-1} quiver theory in 2d. We contrast the elliptic genus of N M-strings with the (4,4) sigma model on the N-fold symmetric product of R^4. For N=1 they are the same, but for N>1 they are close, but not identical. Instead the elliptic genus of (4,4) N M-strings is the same as the elliptic genus of (4,0) sigma models on the N-fold symmetric product of R^4, but where the right-moving fermions couple to a modification of the tangent bundle. This construction arises from a dual A_{n-1} quiver 6d gauge theory with U(1) gauge groups. Moreover we compute the elliptic genus of domain walls which separate different numbers of M2 branes on the two sides of the wall.
Coulomb string tension, asymptotic string tension, and the gluon chain
Greensite, Jeff; Szczepaniak, Adam P.
2015-02-01
We compute, via numerical simulations, the nonperturbative Coulomb potential of pure SU(3) gauge theory in Coulomb gauge. We find 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.
Electromagnetic back-reaction from currents on a straight string
Wachter, Jeremy M
2014-01-01
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 back-reaction must damp this current asymptotically to nothing. We compute this back-reaction 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.
Electromagnetic backreaction from currents on a straight string
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.
De Boer, J; Hori, K; Keurentjes, A; Morgan, J; Morrison, Douglas Robert Ogston; Sethi, S K; Boer, Jan de; Dijkgraaf, Robbert; Hori, Kentaro; Keurentjes, Arjan; Morgan, John; Morrison, David R.; Sethi, Savdeep
2002-01-01
We study string compactifications with sixteen supersymmetries. The moduli space for these compactifications becomes quite intricate in lower dimensions, partly because there are many different irreducible components. We focus primarily, but not exclusively, on compactifications to seven or more dimensions. These vacua can be realized in a number ways: the perturbative constructions we study include toroidal compactifications of the heterotic/type I strings, asymmetric orbifolds, and orientifolds. In addition, we describe less conventional M and F theory compactifications on smooth spaces. The last class of vacua considered are compactifications on singular spaces with non-trivial discrete fluxes. We find a number of new components in the string moduli space. Contained in some of these components are M theory compactifications with novel kinds of ``frozen'' singularities. We are naturally led to conjecture the existence of new dualities relating spaces with different singular geometries and fluxes. As our stu...
Energy Technology Data Exchange (ETDEWEB)
Kiritsis, Elias [APC, Université Paris 7, CNRS/IN2P3, CEA/IRFU, Obs. de Paris, Sorbonne Paris Cité,Bâtiment Condorcet, F-75205, Paris Cedex 13 (UMR du CNRS 7164) (France); Theory Group, Physics Department, CERN,CH-1211, Geneva 23 (Switzerland); Crete Center for Theoretical Physics, Department of Physics, University of Crete,71003 Heraklion (Greece); Mazzanti, Liuba [Institute for Theoretical Physics and Spinoza Institute, Utrecht University,3508 TD Utrecht (Netherlands); Nitti, Francesco [APC, Université Paris 7, CNRS/IN2P3, CEA/IRFU, Obs. de Paris, Sorbonne Paris Cité,Bâtiment Condorcet, F-75205, Paris Cedex 13 (UMR du CNRS 7164) (France)
2014-02-19
We extend the holographic trailing string picture of a heavy quark to the case of a bulk geometry dual to a confining gauge theory. We compute the classical trailing confining string solution for a static as well as a uniformly moving quark. The trailing string is infinitely extended and approaches a confining horizon, situated at a critical value of the radial coordinate, along one of the space-time directions, breaking boundary rotational invariance. We compute the equations for the fluctuations around the classical solutions, which are used to obtain boundary force correlators controlling the Langevin dynamics of the quark. The imaginary part of the correlators has a non-trivial low-frequency limit, which gives rise to a viscous friction coefficient induced by the confining vacuum. The vacuum correlators are used to define finite-temperature dressed Langevin correlators with an appropriate high-frequency behavior.
Kiritsis, E; Nitti, F
2014-01-01
We extend the holographic trailing string picture of a heavy quark to the case of a bulk geometry dual to a confining gauge theory. We compute the classical trailing confining string solution for a static as well as a uniformly moving quark. The trailing string is infinitely extended and approaches a confining horizon, situated at a critical value of the radial coordinate, along one of the space-time directions, breaking boundary rotational invariance. We compute the equations for the fluctuations around the classical solutions, which are used to obtain boundary force correlators controlling the Langevin dynamics of the quark. The imaginary part of the correlators has a non-trivial low-frequency limit, which gives rise to a viscous friction coefficient induced by the confining vacuum. The vacuum correlators are used to define finite-temperature dressed Langevin correlators with an appropriate high-frequency behavior.
Matrix string partition function
Kostov, Ivan K; Kostov, Ivan K.; Vanhove, Pierre
1998-01-01
We evaluate quasiclassically the Ramond partition function of Euclidean D=10 U(N) super Yang-Mills theory reduced to a two-dimensional torus. The result can be interpreted in terms of free strings wrapping the space-time torus, as expected from the point of view of Matrix string theory. We demonstrate that, when extrapolated to the ultraviolet limit (small area of the torus), the quasiclassical expressions reproduce exactly the recently obtained expression for the partition of the completely reduced SYM theory, including the overall numerical factor. This is an evidence that our quasiclassical calculation might be exact.
Instability of colliding metastable strings
Energy Technology Data Exchange (ETDEWEB)
Hiramatsu, Takashi [Kyoto Univ. (Japan). Yukawa Inst. for Theoretical Physics; Eto, Minoru [Yamagata Univ. (Japan). Dept. of Physics; Kamada, Kohei [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Kobayashi, Tatsuo [Kyoto Univ. (Japan). Dept. of Physics; Ookouchi, Yutaka [Kyoto Univ. (Japan). Dept. of Physics; Kyoto Univ. (Japan). The Hakubi Center for Advanced Research
2013-04-15
We investigate the collision dynamics of two metastable strings which can be viewed as tube-like domain walls with winding numbers interpolating a false vacuum and a true vacuum. We find that depending on the relative angle and speed of two strings, instability of strings increases and the false vacuum is filled out by rapid expansion of the strings or of a remnant of the collision.
Bianchi type-VIh string cloud cosmological models with bulk viscosity
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
2012-07-01
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.
Cache-oblivious String Dictionaries
DEFF Research Database (Denmark)
Brodal, Gerth Stølting; Fagerberg, Rolf
2006-01-01
We present static cache-oblivious dictionary structures for strings which provide analogues of tries and suffix trees in the cache-oblivious model. Our construction takes as input either a set of strings to store, a single string for which all suffixes are to be stored, a trie, a compressed trie,...
Fast Searching in Packed Strings
DEFF Research Database (Denmark)
Bille, Philip
2009-01-01
. However, most strings are stored in a computer in a packed representation with several characters in a single word, giving us the opportunity to read multiple characters simultaneously. In this paper we study the worst-case complexity of string matching on strings given in packed representation. Let m...
Embellished String Prints. Cover Story.
Smith, Mary Ruth
1999-01-01
Focuses on a printmaking activity in which students create embellished string prints using the relief process of string glued to chip board. Explains that string prints can easily be embellished with oil pastels. Provides a description of the procedure and a list of materials and methods. (CMK)
Fast searching in packed strings
DEFF Research Database (Denmark)
Bille, Philip
2011-01-01
Given strings P and Q the (exact) string matching problem is to find all positions of substrings in Q matching P. The classical Knuth–Morris–Pratt algorithm [SIAM J. Comput. 6 (2) (1977) 323–350] solves the string matching problem in linear time which is optimal if we can only read one character ...
Dynamical String Tension in String Theory with Spacetime Weyl Invariance
Bars, Itzhak; Turok, Neil
2014-01-01
The fundamental string length, which is an essential part of string theory, explicitly breaks scale invariance. However, in field theory we demonstrated recently that the gravitational constant, which is directly related to the string length, can be promoted to a dynamical field if the standard model coupled to gravity (SM+GR) is lifted to a locally scale (Weyl) invariant theory. The higher gauge symmetry reveals previously unknown field patches whose inclusion turn the classically conformally invariant SM+GR into a geodesically complete theory with new cosmological and possibly further physical consequences. In this paper this concept is extended to string theory by showing how it can be Weyl lifted with a local scale symmetry acting on target space background fields. In this process the string tension (fundamental string length) is promoted to a dynamical field, in agreement with the parallel developments in field theory. We then propose a string theory in a geodesically complete cosmological stringy backgr...
2007-01-01
"How can the nature of basic particles be defined beyond the mechanisms presiding over their creation? Besides the standard model of particle physics - resulting from the postulations of quantum mechanics - contemporary science has pinned its hopes on the totally new unifying notion provided by the highly mathematical string theory."(2 pages)
Energy Technology Data Exchange (ETDEWEB)
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.
Freidel, Laurent; Pranzetti, Daniele
2016-01-01
In this work we study canonical gravity in finite regions for which we introduce a generalisation of the Gibbons-Hawking boundary term including the Immirzi parameter. We study the canonical formulation on a spacelike hypersuface with a boundary sphere and show how the presence of this term leads to an unprecedented type of degrees of freedom coming from the restoration of the gauge and diffeomorphism symmetry at the boundary. In the presence of a loop quantum gravity state, these boundary degrees of freedom localize along a set of punctures on the boundary sphere. We demonstrate that these degrees of freedom are effectively described by auxiliary strings with a 3-dimensional internal target space attached to each puncture. We show that the string currents represent the local frame field, that the string angular momenta represent the area flux and that the string stress tensor represents the two dimensional metric on the boundary of the region of interest. Finally, we show that the commutators of these broken...
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…
Kneipp, Marco A. C.; Liebgott, Paulo J.
2016-12-01
We consider a Yang-Mills-Higgs theory with the gauge group SU (3) broken to its center Z3 by two scalar fields in the adjoint representation and obtain new Z3 strings asymptotic configurations with the gauge field and magnetic field in the direction of the step operators.
Hypermultiplets and topological strings
Rocek, M.; Vafa, C.; Vandoren, S.
2007-01-01
The c-map relates classical hypermultiplet moduli spaces in compactifications of type II strings on a Calabi-Yau threefold to vector multiplet moduli spaces via a further compactification on a circle. We give an off-shell description of the c-map in N = 2 superspace. The superspace Lagrangian for th
Kneipp, Marco A C
2016-01-01
We consider a Yang-Mills-Higgs theory with the gauge group SU(3) broken to its center Z(3) by two scalar fields in the adjoint representation and obtain new Z(3) strings asymptotic configurations with the gauge field and magnetic field in the direction of the step operators.
New Developments in String Gravity and String Cosmology.A Summary Report
Sánchez, N G
2002-01-01
New Developments in String Gravity and String Cosmology are reported: 1-String driven cosmology and its Predictions. 2-The primordial gravitational wave background in string cosmology. 3-Non-singular string cosmologies from Exact Conformal Field Theories. 4-Quantum Field Theory, String Temperature and the String Phase of de Sitter space-time, 5-Hawking Radiation in String Theory and the String Phase of Black Holes. 6-New Dual Relation between Quantum Field Theory regimes and String regimes in Curved Backgrounds, and the 'QFT/String Tango'. 7- New Coherent String States and Minimal Uncertainty Principle in WZWN models
Postmodern string theory stochastic formulation
Aurilia, A
1994-01-01
In this paper we study the dynamics of a statistical ensemble of strings, building on a recently proposed gauge theory of the string geodesic field. We show that this stochastic approach is equivalent to the Carath\\'eodory formulation of the Nambu-Goto action, supplemented by an averaging procedure over the family of classical string world-sheets which are solutions of the equation of motion. In this new framework, the string geodesic field is reinterpreted as the Gibbs current density associated with the string statistical ensemble. Next, we show that the classical field equations derived from the string gauge action, can be obtained as the semi-classical limit of the string functional wave equation. For closed strings, the wave equation itself is completely analogous to the Wheeler-DeWitt equation used in quantum cosmology. Thus, in the string case, the wave function has support on the space of all possible spatial loop configurations. Finally, we show that the string distribution induces a multi-phase, or ...
A smoothly bouncing universe from String Theory
Cheung, Yeuk-Kwan E; Li, Shuyi; Li, Yunxuan; Zhu, Yiqing
2016-01-01
We report a stable bounce universe with a scale invariant spectrum of density perturbations from a string-based model with coupled scalar and tachyon fields. This model is free of ghosts and cosmic singularity, and does not violate the null energy condition. We analyse the parameter space for a successful single bounce to arrive at a radiation dominated universe that is compatible with CMB data. We show that this bounce universe model is a viable alternative to inflation, by showing that it can naturally produce enough e-foldings--in the pre-bounce contractional phase as well in the post bounce expanding phase--to solve the flatness problem, the horizon problem and the homogeneity problem of the Big Bang theory, resulting in the observed universe of current size.
Energy Technology Data Exchange (ETDEWEB)
Svrcek, Peter; /Stanford U., Phys. Dept. /SLAC; 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
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.
Exploring String Theory Backgrounds
Williams, B P
2004-01-01
This thesis examines phenomenological and theoretical questions by exploring string theoretic backgrounds. Part I focuses on cosmology. First we propose that the induced metric along a brane moving through a curved bulk may be interpreted as the cosmology of the brane universe, providing a resolution to the apparent cosmological singularity on the brane. We then look at various decay channels of the certain meta-stable de Sitter vacua and show that there exist NS5-brane meditated decays which are much faster than decays to decompactification. Part II discusses a new class of nongeometric vacua in string theory. These backgrounds may be described locally as T2 fibrations. By enlarging the monodromy group of the fiber to include perturbative stringy duality symmetries we are able to explicitly construct nongeometric backgrounds.
Fingerprints in Compressed Strings
DEFF Research Database (Denmark)
Bille, Philip; Cording, Patrick Hagge; Gørtz, Inge Li
2013-01-01
The Karp-Rabin fingerprint of a string is a type of hash value that due to its strong properties has been used in many string algorithms. In this paper we show how to construct a data structure for a string S of size N compressed by a context-free grammar of size n that answers fingerprint queries....... That is, given indices i and j, the answer to a query is the fingerprint of the substring S[i,j]. We present the first O(n) space data structures that answer fingerprint queries without decompressing any characters. For Straight Line Programs (SLP) we get O(logN) query time, and for Linear SLPs (an SLP...... derivative that captures LZ78 compression and its variations) we get O(loglogN) query time. Hence, our data structures has the same time and space complexity as for random access in SLPs. We utilize the fingerprint data structures to solve the longest common extension problem in query time O(logNlogℓ) and O...
Thermodynamical string fragmentation
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.
Thermodynamical String Fragmentation
Fischer, Nadine
2016-01-01
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...
Barrow, John D; Barrow, John D.; Dabrowski, Mariusz P.
1998-01-01
We investigate Bianchi type IX ''Mixmaster'' universes within the framework of the low-energy tree-level effective action for string theory, which (when the ''stringy'' 2-form axion potential vanishes) is formally the same as the Brans-Dicke action with $\\omega =-1$. We show that, unlike the case of general relativity in vacuum, there is no Mixmaster chaos in these string cosmologies. In the Einstein frame an infinite sequence of chaotic oscillations of the scale factors on approach to the initial singularity is impossible, as it was in general relativistic Mixmaster universes in the presence of stiff -fluid matter (or a massless scalar field). A finite sequence of oscillations of the scale factors approximated by Kasner metrics is possible, but it always ceases when all expansion rates become positive. In the string frame the evolution through Kasner epochs changes to a new form which reflects the duality symmetry of the theory. Again, we show that chaotic oscillations must end after a finite time. The need ...
On Exceptional Instanton Strings
Del Zotto, Michele
2016-01-01
According to a recent classification of 6d (1,0) theories within F-theory there are only 5 "pure" 6d gauge theories which have a UV superconformal fixed point. The corresponding gauge groups are $SU(3),SO(8),F_4,E_6,E_7$, and $E_8$. These exceptional models have BPS strings which are also instantons for the corresponding gauge groups. For $G$ simply-laced, we determine the 2d $\\mathcal{N}=(0,4)$ worldsheet theories of such BPS instanton strings by a simple geometric engineering argument. These are given by a twisted $S^2$ compactification of the 4d $\\mathcal{N}=2$ theories of type $H_2, D_4, E_6, E_7$ and $E_8$ (and their higher rank generalizations), where the 6d instanton number is mapped to the rank of the corresponding 4d SCFT. This determines their anomaly polynomials and, via topological strings, establishes an interesting relation among the corresponding $T^2 \\times S^2$ partition functions and the Hilbert series for moduli spaces of $G$ instantons. Such relations allow to bootstrap the corresponding e...
String Theory at LHC Using Top Quarks From String Balls
Nayak, Gouranga C
2009-01-01
According to string theory, string ball is a highly excited long string which decays to standard model particles at the Hagedorn temperature with thermal spectrum. If there are extra dimensions, the string scale can be ~TeV, and we should produce string balls at CERN LHC. In this paper we study top quark production from string balls at LHC and compare with the parton fusion results at NNLO using pQCD. We find significant top quark production from string balls at LHC which is comparable to standard model NNLO results. We also find that d\\sigma/dp_T of top quarks from string balls does not decrease significantly with increase in p_T, whereas it deceases sharply in case of standard model NNLO scenario. Hence, in the absence of black hole production at LHC, an enhancement in top quark cross section and its abnormal p_T distribution can be a signature of TeV scale string physics at LHC.
Maximal unbordered factors of random strings
DEFF Research Database (Denmark)
Cording, Patrick Hagge; Knudsen, Mathias Bæk Tejs
2016-01-01
A border of a string is a non-empty prefix of the string that is also a suffix of the string, and a string is unbordered if it has no border. Loptev, Kucherov, and Starikovskaya [CPM 2015] conjectured the following: If we pick a string of length n from a fixed alphabet uniformly at random...
Brane-world cosmology with black strings
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.
Towards optimal packed string matching
DEFF Research Database (Denmark)
Ben-Kiki, Oren; Bille, Philip; Breslauer, Dany;
2014-01-01
-size string-matching instruction wssm is available in contemporary commodity processors. The other word-size maximum-suffix instruction wslm is only required during the pattern pre-processing. Benchmarks show that our solution can be efficiently implemented, unlike some prior theoretical packed string......In the packed string matching problem, it is assumed that each machine word can accommodate up to α characters, thus an n-character string occupies n/α memory words.(a) We extend the Crochemore–Perrin constant-space O(n)-time string-matching algorithm to run in optimal O(n/α) time and even in real...... matching work.(b) We also consider the complexity of the packed string matching problem in the classical word-RAM model in the absence of the specialized micro-level instructions wssm and wslm. We propose micro-level algorithms for the theoretically efficient emulation using parallel algorithms techniques...
Factorization of Chiral String Amplitudes
Huang, Yu-tin; Yuan, Ellis Ye
2016-01-01
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.
Factorization of chiral string amplitudes
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.
Quantum String Seal Is Insecure
Chau, H F
2006-01-01
A quantum string seal encodes the value of a (bit) string as a quantum state in such a way that everyone can extract a non-negligible amount of information on the string by a suitable measurement. Moreover, such measurement must disturb the quantum state and is likely to be detected by an authorized verifier. In this way, the intactness of the encoded quantum state plays the role of a wax seal in the digital world. Here I analyze the security of quantum string seal by studying the information disturbance tradeoff of a measurement. This information disturbance tradeoff analysis extends the earlier results of Bechmann-Pasquinucci et al. and Chau by concluding that all quantum string seals are insecure. Specifically, I find a way to obtain non-trivial information on the string that escapes the verifier's detection with probability at least one half.
Tachyon-Dilaton-induced Inflation as an alpha'-resummed String Background
Alexandre, Jean; Mavromatos, Nick E
2009-01-01
Within the framework of a novel functional method on the world-sheet of the string, we discuss simple but re-summed (in the Regge slope) inflationary scenarios in the context of closed Bosonic strings, living in four target-space dimensions, in the presence of non-trivial tachyon, dilaton and graviton cosmological backgrounds. The inflationary solutions are argued to guarantee the vanishing of the corresponding Weyl anomaly coefficients in a given world-sheet renormalization scheme, thereby ensuring conformal invariance of the corresponding sigma-model to all orders in the Regge slope. The key property is the requirement of "homogeneity" of the corresponding Weyl anomaly coefficients. Inflation entails appropriate relations between the dilaton and tachyon field configurations, whose form can lead to either a de Sitter vacuum, incompatible though (due to the cosmic horizons) with the perturbative string scattering amplitudes, or to cosmic space-times involving brief inflationary periods, interpolating smoothly...
Magueijo, J
1994-01-01
We propose to minimise the cosmic confusion between Gaussian and non Gaussian theories by investigating the structure in the m's for each multipole of the cosmic radiation temperature anisotropies. We prove that Gaussian theories are (nearly) the only theories which treat all the m's equally. Hence we introduce a set of invariant measures of ``m-preference'' to be seen as non-Gaussianity indicators. We then derive the distribution function for the quadrupole ``m-preference'' measure in Gaussian theories. A class of physically motivated toy non Gaussian theories is introduced as an example. We show how the quadrupole m-structure is crucial in reducing the confusion between these theories and Gaussian theories.
Bekenstein Entropy is String Entropy
Halyo, Edi
2009-01-01
We argue that Bekenstein entropy can be interpreted as the entropy of an effective string with a rescaled tension. Using the AdS/CFT correspondence we show that the Bekenstein entropy on the boundary CFT is given by the entropy of a string at the stretched horizon of the AdS black hole in the bulk. The gravitationally redshifted tension and energy of the string match those required to reproduce Bekenstein entropy.
Experimenting with string musical instruments
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.
Classical theory of radiating strings
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.
End conditions of piano strings
Ege, Kerem
2011-01-01
The end conditions of piano strings can be approximated by the input admittance at the bridge. Proper measurements of this value are therefore required. A method of validation of admittance measurements on simple structures is proposed in this paper. High resolution signal analysis performed on string's vibrations yields an estimate for the input admittance. This method is implemented on a simplified device composed of a piano string coupled to a thin steel beam.
硫化剂B-L01在IIR中的应用%Application of curative B-L01 in IIR
Institute of Scientific and Technical Information of China (English)
程继刚; 史晓东; 王飞; 司俊杰
2006-01-01
研究硫化剂B-L01在IIR中的应用效果.结果表明,采用硫化剂B-L01/树脂硫化体系的IIR硫化胶具有良好的物理性能、耐热空气和耐蒸汽老化性能;采用硫化剂B-L01/树脂硫化体系的IIR硫化胶性能可达到或超过采用树脂硫化体系的CIIR和BIIR硫化胶的水平.
Splitting strings on integrable backgrounds
Energy Technology Data Exchange (ETDEWEB)
Vicedo, Benoit
2011-05-15
We use integrability to construct the general classical splitting string solution on R x S{sup 3}. Namely, given any incoming string solution satisfying a necessary self-intersection property at some given instant in time, we use the integrability of the worldsheet {sigma}-model to construct the pair of outgoing strings resulting from a split. The solution for each outgoing string is expressed recursively through a sequence of dressing transformations, the parameters of which are determined by the solutions to Birkhoff factorization problems in an appropriate real form of the loop group of SL{sub 2}(C). (orig.)
Soft theorems from string theory
Energy Technology Data Exchange (ETDEWEB)
Di Vecchia, Paolo [The Niels Bohr Institute, University of Copenhagen (Denmark); Nordita, KTH Royal Institute of Technology and Stockholm University (Sweden); Marotta, Raffaele [Istituto Nazionale di Fisica Nucleare, Sezione di Napoli (Italy); Complesso Universitario di Monte S. Angelo, Napoli (Italy); Mojaza, Matin [Nordita, KTH Royal Institute of Technology and Stockholm University (Sweden)
2016-04-15
Soft behaviour of closed string amplitudes involving dilatons, gravitons and anti-symmetric tensors, is studied in the framework of bosonic string theory. The leading double soft limit of gluons is analysed as well, starting from scattering amplitudes computed in the open bosonic string. Field theory expressions are then obtained by sending the string tension to infinity. The presented results have been derived in the papers of Ref [1]. (copyright 2016 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)
Strings and large scale magnetohydrodynamics
Olesen, P
1995-01-01
From computer simulations of magnetohydrodynamics one knows that a turbulent plasma becomes very intermittent, with the magnetic fields concentrated in thin flux tubes. This situation looks very "string-like", so we investigate whether strings could be solutions of the magnetohydrodynamics equations in the limit of infinite conductivity. We find that the induction equation is satisfied, and we discuss the Navier-Stokes equation (without viscosity) with the Lorentz force included. We argue that the string equations (with non-universal maximum velocity) should describe the large scale motion of narrow magnetic flux tubes, because of a large reparametrization (gauge) invariance of the magnetic and electric string fields.
Split String Formalism and the Closed String Vacuum
Erler, T
2007-01-01
The split string formalism offers a simple template apon which we can build many generalizations of Schnabl's analytic solution of open string field theory. In this paper we explore two such generalizations: one which replaces the wedge state by an arbitrary function of wedge states, and another which generalizes the solution to conformal frames other than the sliver.
Non-Riemannian Cosmic Walls as Boundaries of Spinning Matter with Torsion
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.
String Field Theory Solution for Any Open String Background
Erler, Theodore
2014-01-01
We present an exact solution of open bosonic string field theory which can be used to describe any time-independent open string background. The solution generalizes an earlier construction of Kiermaier, Okawa, and Soler, and assumes the existence of boundary condition changing operators with nonsingular OPEs and vanishing conformal dimension. Our main observation is that boundary condition changing operators of this kind can describe nearly any open string background provided the background shift is accompanied by a timelike Wilson line of sufficient strength. As an application we analyze the tachyon lump describing the formation of a D$(p-1)$-brane in the string field theory of a D$p$-brane, for generic compactification radius. This not only provides a proof of Sen's second conjecture, but also gives explicit examples of higher energy solutions, confirming analytically that string field theory can "reverse" the direction of the worldsheet RG flow. We also find multiple D-brane solutions, demonstrating that s...
Axially symmetric anisotropic string cosmological models in Saez-Ballester theory of gravitation
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.
DEFF Research Database (Denmark)
Schäfer, Mirko; Greiner, Martin
Chaotic strings are coupled Tchebyscheff maps on a ring-network. With a well-specified empirical prescription they are able to explain the coupling constants of the standard model of elementary particle physics. This empirical relationship is tested further by introducing a tunable disorder to ch...... of the standard model of elementary particle physics. For the electromagnetic sector it is found that already a small disorder pushes the associated energy scale of the running coupling constant far away from the result without disorder....
Pokorski, Witold; Pokorski, Witold; Ross, Graham G.
1998-01-01
We consider the phenomenological implications of a class of compactified string theories which naturally reproduces the flavour multiplet structure of the Standard Model. The implications for gauge unification depends on which of three possibilities is realised for obtaining light Higgs multiplets. The more conventional one leads to predictions for the gauge couplings close to that of the MSSM but with an increased value of the unification scale. The other two cases offer a mechanism for bringing the prediction for the strong coupling into agreement with the measured value while still increasing the unification scale. The various possibilities lead to different expectations for the structure of the quark masses.
Energy Technology Data Exchange (ETDEWEB)
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.
Guijosa, Alberto
2016-01-01
In the nearly twenty 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 in particular, it does not presuppose knowledge of string theory.
Generalised functions and distributional curvature of cosmic strings
Clarke, C J S; Wilson, J P
1996-01-01
A new method is presented for assigning distributional curvature, in an invariant manner, to a space-time of low differentiability, using the techniques of Colombeau's `new generalised functions'. The method is applied to show that curvature of a cone is equivalent to a delta function. The same is true under small enough perturbations.
Dynamical behavior and Jacobi stability analysis of wound strings
Energy Technology Data Exchange (ETDEWEB)
Lake, Matthew J. [Naresuan University, The Institute for Fundamental Study, ' ' The Tah Poe Academia Institute' ' , Phitsanulok (Thailand); Thailand Center of Excellence in Physics, Ministry of Education, Bangkok (Thailand); Harko, Tiberiu [Babes-Bolyai University, Department of Physics, Cluj-Napoca (Romania); University College London, Department of Mathematics, London (United Kingdom)
2016-06-15
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 R{sup 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{sup 2} of constant radius 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. (orig.)
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
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…
Progress in string theory research
2016-01-01
At the first look, the String Theory seems just an interesting and non-trivial application of the quantum mechanics and the special relativity to vibrating strings. By itself, the quantization of relativistic strings does not call the attention of the particle physicist as a significant paradigm shift. However, when the string quantization is performed by applying the standard rules of the perturbative Quantum Field Theory, one discovers that the strings in certain states have the same physical properties as the gravity in the flat space-time. Chapter one of this book reviews the construction of the thermal bosonic string and D-brane in the framework of the Thermo Field Dynamics (TFD). It briefly recalls the wellknown light-cone quantization of the bosonic string in the conformal gauge in flat space-time, and gives a bird’s eye view of the fundamental concepts of the TFD. Chapter two examines a visual model inspired by string theory, on the system of interacting anyons. Chapter three investigate the late-ti...
Open string fields as matrices
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.
Open String Fields as Matrices
Kishimoto, Isao; Takahashi, Tomohiko; Takemoto, Shoko
2014-01-01
We show that the action expanded around Erler-Maccaferri's N D-branes solution describes the N+1 D-branes system where one D-brane disappears due to tachyon condensation. String fields on the multi-branes can be regarded as block matrices of a string field on a single D-brane in the same way as matrix theories.
2001-01-01
String 2 is a series of superconducting magnets that are prototypes of those which will be installed in the LHC. It was cooled down to 1.9 Kelvin on September 14th. On Thursday last week, the dipoles of String 2 were successfully taken to nominal current, 11850 A.
Arnould, M; Arnould, Marcel; Prantzos, Nikos
1999-01-01
Radionuclides with half-lives ranging from some years to billions of years presumably synthesized outside of the solar system are now recorded in ``live'' or ``fossil'' form in various types of materials, like meteorites or the galactic cosmic rays. They bring specific astrophysical messages the deciphering of which is briefly reviewed here, with special emphasis on the contribution of Dave Schramm and his collaborators to this exciting field of research. Short-lived radionuclides are also present in the Universe today, as directly testified by the gamma-ray lines emitted by the de-excitation of their daughter products. A short review of recent developments in this field is also presented.
Arnould, Marcel; Prantzos, Nikos
1999-07-01
Radionuclides with half-lives ranging from some years to billions of years presumably synthesized outside of the solar system are now recorded in "live" or "fossil" form in various types of materials, like meteorites or the galactic cosmic rays. They bring specific astrophysical messages, the deciphering of which is briefly reviewed here, with special emphasis on the contribution of Dave Schramm and his collaborators to this exciting field of research. Short-lived radionuclides are also present in the Universe today, as directly testified by the γ-ray lines emitted by the de-excitation of their daughter products. A short review of recent developments in this field is also presented.
String Mining in Bioinformatics
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 dualities and superpotential
Energy Technology Data Exchange (ETDEWEB)
Ha, Tae-Won
2010-09-15
The main objective of this thesis is the computation of the superpotential induced by D5- branes in the type IIB string theory and by five-branes in the heterotic string theory. Both superpotentials have the same functional form which is the chain integral of the holomorphic three-form. Using relative (co)homology we can unify the flux and brane superpotential. The chain integral can be seen as an example of the Abel-Jacobi map. We discuss many structures such as mixed Hodge structure which allows for the computation of Picard-Fuchs differential equations crucial for explicit computations. We blow up the Calabi-Yau threefold along the submanifold wrapped by the brane to obtain geometrically more appropriate configuration. The resulting geometry is non-Calabi-Yau and we have a canonically given divisor. This blown-up geometry makes it possible to restrict our attention to complex structure deformations. However, the direct computation is yet very difficult, thus the main tool for computation will be the lift of the brane configuration to a F-theory compactification. In F-theory, since complex structure, brane and, if present, bundlemoduli are all contained in the complex structure moduli space of the elliptic Calabi-Yau fourfold, the computation can be dramatically simplified. The heterotic/F-theory duality is extended to include the blow-up geometry and thereby used to give the blow-up geometry amore physical meaning. (orig.)
CERN. Geneva
2002-01-01
A theory with such mathematical beauty cannot be wrong: this is one of the main arguments in favour of string theory, which unifies all known physical theories of fundamental interactions in a single coherent description of the universe. But no one has ever observed strings, not even indirectly, nor the space of extra dimensions where they live. However there are good reasons to believe that the 'hidden' dimensions of string theory may be much larger than what we thought in the past and that they may be within experimental reach in the near future - together with the strings themselves. In my talk, I will give an elementary introduction of string theory and describe the main experimental predictions.Organiser(s): Jasper Kirkby / EP DivisionNote: Tea & coffee will be served at 16.00 hrs.
Basic Concepts of String Theory
Blumenhagen, Ralph; Theisen, Stefan
2013-01-01
The purpose of this book is to thoroughly prepare the reader for research in string theory. It is intended as a textbook in the sense that, starting from the basics, the material is presented in a pedagogical and self-contained fashion. The emphasis is on the world-sheet perspective of closed strings and of open strings ending on D-branes, where two-dimensional conformal field theory is the main tool. Compactifications of string theory, with and without fluxes, and string dualities are also discussed from the space-time point of view, i.e. in geometric language. End-of-chapter references have been added to guide the reader intending to pursue further studies or to start research in the topics covered by this book.
Basic concepts of string theory
Energy Technology Data Exchange (ETDEWEB)
Blumenhagen, Ralph [Max-Planck-Institut fuer Physik, Muenchen (Germany). Werner-Heisenberg-Institut; Luest, Dieter [Muenchen Univ. (Germany). Arnold-Sommerfeld Zentrum fuer Theoretische Physik; Theisen, Stefan [Albert-Einstein-Institut (Max-Planck Institut fuer Gravitationsphysik), Golm (Germany)
2013-07-01
The purpose of this book is to thoroughly prepare the reader for research in string theory. It is intended as a textbook in the sense that, starting from the basics, the material is presented in a pedagogical and self-contained fashion. The emphasis is on the world-sheet perspective of closed strings and of open strings ending on D-branes, where two-dimensional conformal field theory is the main tool. Compactifications of string theory, with and without fluxes, and string dualities are also discussed from the space-time point of view, i.e. in geometric language. End-of-chapter references have been added to guide the reader intending to pursue further studies or to start research in the topics covered by this book.
Surface operators from M -strings
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.
Poisson hierarchy of discrete strings
Energy Technology Data Exchange (ETDEWEB)
Ioannidou, Theodora, E-mail: ti3@auth.gr [Faculty of Civil Engineering, School of Engineering, Aristotle University of Thessaloniki, 54249, Thessaloniki (Greece); Niemi, Antti J., E-mail: Antti.Niemi@physics.uu.se [Department of Physics and Astronomy, Uppsala University, P.O. Box 803, S-75108, Uppsala (Sweden); Laboratoire de Mathematiques et Physique Theorique CNRS UMR 6083, Fédération Denis Poisson, Université de Tours, Parc de Grandmont, F37200, Tours (France); Department of Physics, Beijing Institute of Technology, Haidian District, Beijing 100081 (China)
2016-01-28
The Poisson geometry of a discrete string in three dimensional Euclidean space is investigated. For this the Frenet frames are converted into a spinorial representation, the discrete spinor Frenet equation is interpreted in terms of a transfer matrix formalism, and Poisson brackets are introduced in terms of the spinor components. The construction is then generalised, in a self-similar manner, into an infinite hierarchy of Poisson algebras. As an example, the classical Virasoro (Witt) algebra that determines reparametrisation diffeomorphism along a continuous string, is identified as a particular sub-algebra, in the hierarchy of the discrete string Poisson algebra. - Highlights: • Witt (classical Virasoro) algebra is derived in the case of discrete string. • Infinite dimensional hierarchy of Poisson bracket algebras is constructed for discrete strings. • Spinor representation of discrete Frenet equations is developed.
Twist Field as Three String Interaction Vertex in Light Cone String Field Theory
Kishimoto, Isao; Moriyama, Sanefumi; Teraguchi, Shunsuke
2006-01-01
It has been suggested that matrix string theory and light-cone string field theory are closely related. In this paper, we investigate the relation between the twist field, which represents string interactions in matrix string theory, and the three-string interaction vertex in light-cone string field theory carefully. We find that the three-string interaction vertex can reproduce some of the most important OPEs satisfied by the twist field.
Exact Inflationary Solution in String-Motivated Scalar Field Cosmology
Institute of Scientific and Technical Information of China (English)
王文福
2001-01-01
We present a new exact solution to Einstein's equations that describes the evolution of inflationary universe models. The inflation is driven by the evolution of a scalar field with an approximate two-loop four-dimensional string potential. In this scenario, the inflation began immediately after the epoch governed by quantum gravity and therefore there is no initial singularity. The successful inflation scenario is expected to appear only at two loop order. For a1/｜a2｜ ≥ 90, the spectral index ns of the scalar density fluctuations lies well inside the limits set by the cosmic background explorer satellite and the gravitational wave spectral index is ng≈1.
Allahverdi, Rouzbeh; Dutta, Bhaskar; Gao, Yu
2014-01-01
In this paper, we study the prospects for determining the nature of neutrinos in the context of a supersymmetric $B-L$ extension of the standard model by using dark matter indirect detection signals and bounds on $N_{\\text{eff}}$ from the cosmic microwave background data. The model contains two new dark matter candidates whose dominant annihilation channels produce more neutrinos than neutralino dark matter in the minimal supersymmetric standard model. The photon and neutrino counts may then be used to discriminate between the two models. If the dark matter comes from the B-L sector, its indirect signals and impact on the cosmic microwave background can shed light on the nature of the neutrinos. When the light neutrinos are of Majorana type, the indirect neutrino signal from the Sun and the galactic center may show a prompt neutrino box-feature, as well as an earlier cut-off in both neutrino and gamma ray energy spectra. When the light neutrinos are of Dirac type, their contribution to the effective number of...
Strings in compact cosmological spaces
Craps, Ben; Konechny, Anatoly
2013-01-01
We confront the problem of giving a fundamental definition to perturbative string theory in spacetimes with totally compact space (taken to be a torus for simplicity, though the nature of the problem is very general) and non-compact time. Due to backreaction induced by the presence of even a single string quantum, the usual formulation of perturbative string theory in a fixed classical background is infrared-divergent at all subleading orders in the string coupling, and needs to be amended. The problem can be seen as a closed string analogue of D0-brane recoil under an impact by closed strings (a situation displaying extremely similar infrared divergences). Inspired by the collective coordinate treatment of the D0-brane recoil, whereby the translational modes of the D0-brane are introduced as explicit dynamical variables in the path integral, we construct a similar formalism for the case of string-induced gravitational backreaction, in which the spatially uniform modes of the background fields on the compact ...
LHC Phenomenology for String Hunters
Anchordoqui, Luis A; Lüst, Dieter; Nawata, Satoshi; Stieberger, Stephan; Taylor, Tomasz R
2009-01-01
We consider extensions of the standard model based on open strings ending on D-branes, with gauge bosons due to strings attached to stacks of D-branes and chiral matter due to strings stretching between intersecting D-branes. Assuming that the fundamental string mass scale is in the TeV range and the theory is weakly coupled, we discuss possible signals of string physics at the Large Hadron Collider (LHC). In previous works, direct channel excitations of Regge recurrences in parton-parton scattering supplied the outstanding new signature. The present work considers the deviation from standard model expectations for the 4-fermion processes qq\\to qq and qq' \\to qq', in which the s-channel excitation of string resonances is absent. In this case, we find that Kaluza-Klein recurrences at masses somewhat less than the string scale generate effective 4-fermion contact terms which can significantly enhance the dijet R ratio above its QCD value of about 0.6. The simultaneous observation of a nearby resonant structure ...
Academic Training: String Theory
Françoise Benz
2005-01-01
2004-2005 ACADEMIC TRAINING PROGRAMME LECTURE SERIES 6, 7, 8, 9 and 10 June from 11.00 to 12.00 hrs - Auditorium, bldg. 500 on 6, 7, 8 & 10 June, TH Auditorium, bldg. 4, 3rd floor on 9 June String Theory by C. Johnson / Univ. of Southern California, USA ENSEIGNEMENT ACADEMIQUE ACADEMIC TRAINING Françoise Benz 73127 academic.training@cern.ch If you wish to participate in one of the following courses, please discuss with your supervisor and apply electronically directly from the course description pages that can be found on the Web at: http://www.cern.ch/Training/ or fill in an 'application for training' form available from your Divisional Secretariat or from your DTO (Divisional Training Officer). Applications will be accepted in the order of their receipt.
Hindmarsh, M B
1994-01-01
This work is based on a paper with Margaret James, to appear in Phys Rev D. In it we showed that the dipole moment of the sphaleron has its origin in two components: a ring of electric current circulating around the edge of the sphaleron; and also two regions of opposite magnetic charge above and below the ring. This magnetic charge has a partly topological explanation, arising from the fact that the sphaleron is axisymmetric and parity invariant. Here, I discuss the definition of the electromagnetic field and its sources in the Standard Model, comparing the one we use with the better-known one of 't Hooft. I also discuss the resemblance between the sphaleron and Nambu's ``dumb-bell'' -- a segment of Z-string which connects a monopole to an antimonopole.
String Formatting Considered Harmful for Novice Programmers
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 that 8% of all the…
Backgrounds in Boundary String Field Theory
Baumgartl, M
2009-01-01
We study the role of closed string backgrounds in boundary string field theory. Background independence requires the introduction of dual boundary fields, which are reminiscent of the doubled field formalism. We find a correspondence between closed string backgrounds and collective excitations of open strings described by vertex operators involving dual fields. Renormalization group flow, solutions and stability are discussed in an example.
Emergence String and Mass Formulas of Hadrons
Chang, Yi-Fang
2011-01-01
Assume that hadrons are formed from the emergence string. Usual string should possess two moving states: oscillation and rotation, so we propose corresponding potential and the equation of the emergence string, whose energy spectrum is namely the GMO mass formula and its modified accurate mass formula. These are some relations between the string and observable experimental data.
String matching with variable length gaps
DEFF Research Database (Denmark)
Bille, Philip; Gørtz, Inge Li; Vildhøj, Hjalte Wedel
2012-01-01
We consider string matching with variable length gaps. Given a string T and a pattern P consisting of strings separated by variable length gaps (arbitrary strings of length in a specified range), the problem is to find all ending positions of substrings in T that match P. This problem is a basic...
On the Classical String Solutions and String/Field Theory Duality
Aleksandrova, D.; Bozhilov, P.
2003-01-01
We classify almost all classical string configurations, considered in the framework of the semi-classical limit of the string/gauge theory duality. Then, we describe a procedure for obtaining the conserved quantities and the exact classical string solutions in general string theory backgrounds, when the string embedding coordinates depend non-linearly on the worldsheet time parameter.
The complexity of string partitioning
Condon, Anne; Thachuk, Chris
2012-01-01
Given a string $w$ over a finite alphabet $\\Sigma$ and an integer $K$, can $w$ be partitioned into strings of length at most $K$, such that there are no \\emph{collisions}? We refer to this question as the \\emph{string partition} problem and show it is \\NP-complete for various definitions of collision and for a number of interesting restrictions including $|\\Sigma|=2$. This establishes the hardness of an important problem in contemporary synthetic biology, namely, oligo design for gene synthesis.
Nonassociative gravity in string theory?
Energy Technology Data Exchange (ETDEWEB)
Blumenhagen, R [Max-Planck-Institut fuer Physik (Werner-Heisenberg-Institut), Foehringer Ring 6, 80805 Muenchen (Germany); Plauschinn, E, E-mail: ralph.blumenhagen@mpp.mpg.d, E-mail: e.plauschinn@uu.n [Institute for Theoretical Physics and Spinoza Institute, Utrecht University, 3508 TD Utrecht (Netherlands)
2011-01-07
In an on-shell conformal field theory approach, we find indications of a three-bracket structure for target space coordinates in general closed string backgrounds. This generalizes the appearance of noncommutative gauge theories for open strings in two-form backgrounds to a putative noncommutative/nonassociative gravity theory for closed strings probing curved backgrounds with non-vanishing three-form flux. Several aspects and consequences of the three-bracket structure are discussed and a new type of generalized uncertainty principle is proposed.
Geometry, topology, and string theory
Energy Technology Data Exchange (ETDEWEB)
Varadarajan, Uday
2003-07-10
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.
Generalised geometry for string corrections
Coimbra, André; Triendl, Hagen; Waldram, Daniel
2014-01-01
We present a general formalism for incorporating the string corrections in generalised geometry, which necessitates the extension of the generalised tangent bundle. Not only are such extensions obstructed, string symmetries and the existence of a well-defined effective action require a precise choice of the (generalised) connection. The action takes a universal form given by a generalised Lichnerowitz--Bismut theorem. As examples of this construction we discuss the corrections linear in $\\alpha'$ in heterotic strings and the absence of such corrections for type II theories.
Deforming baryons into confining strings
Hartnoll, S A; Hartnoll, Sean A.; Portugues, Ruben
2004-01-01
We find explicit probe D3-brane solutions in the infrared of the Maldacena-Nunez background. The solutions describe deformed baryon vertices: q external quarks are separated in spacetime from the remaining N-q. As the separation is taken to infinity we recover known solutions describing infinite confining strings in ${\\mathcal{N}}=1$ gauge theory. We present results for the mass of finite confining strings as a function of length. We also find probe D2-brane solutions in a confining type IIA geometry, the reduction of a G_2 holonomy M theory background. The interpretation of these solutions as deformed baryons/confining strings is not as straightforward.
Strings from large charged fields
Cardona, Carlos
2015-01-01
It has been known long time ago that the low energy dynamics of open-strings is described by non-abelian gauge theories in the same way that the low energy effective description of closed strings is governed by Einstein's gravity. In this short note, we review and comment on some examples where conversely, an effective behavior of non-abelian gauge theories in some particular limits are described by some type of extended objects like strings or branes. We constrain the discussion to a few examples sharing some similarities.
Topological partition function and string-string duality
Curio, G
1995-01-01
The evidence for string/string-duality can be extended from the matching of the vector couplings to gravitational couplings. In this note this is shown in the rank three example, the closest stringy analog of the Seiberg/Witten-setup, which is related to the Calabi-Yau WP^4_{1,1,2,2,6}(12). I provide an exact analytical verification of a relation checked by coefficient comparison to fourth order by Kaplunovsky, Louis and Theisen.
Intuitionistic Fuzzy Automaton for Approximate String Matching
Directory of Open Access Journals (Sweden)
K.M. Ravi
2014-03-01
Full Text Available This paper introduces an intuitionistic fuzzy automaton model for computing the similarity between pairs of strings. The model details the possible edit operations needed to transform any input (observed string into a target (pattern string by providing a membership and non-membership value between them. In the end, an algorithm is given for approximate string matching and the proposed model computes the similarity and dissimilarity between the pair of strings leading to better approximation.
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.
Electroweak vacuum stability in classically conformal $B-L$ extension of the Standard Model
Das, Arindam; Papapietro, Nathan
2015-01-01
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 ($Z^\\prime$ 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 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 pape...
String and Sticky Tape Experiments.
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)
Pattern recognition and string matching
Cheng, Xiuzhen
2002-01-01
The research and development of pattern recognition have proven to be of importance in science, technology, and human activity. Many useful concepts and tools from different disciplines have been employed in pattern recognition. Among them is string matching, which receives much theoretical and practical attention. String matching is also an important topic in combinatorial optimization. This book is devoted to recent advances in pattern recognition and string matching. It consists of twenty eight chapters written by different authors, addressing a broad range of topics such as those from classifica tion, matching, mining, feature selection, and applications. Each chapter is self-contained, and presents either novel methodological approaches or applications of existing theories and techniques. The aim, intent, and motivation for publishing this book is to pro vide a reference tool for the increasing number of readers who depend upon pattern recognition or string matching in some way. This includes student...
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.
Probing the String Winding Sector
Aldazabal, Gerardo; Nuñez, Carmen
2016-01-01
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 $2n$-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+antisymmetr...
Gauge Mediation in String Theory
Kawano, Teruhiko; Ooguri, Hirosi; Ookouchi, Yutaka
2007-01-01
We show that a large class of phenomenologically viable models for gauge mediation of supersymmetry breaking based on meta-stable vacua can be realized in local Calabi–Yau compactifications of string theory.
String moduli inflation. An overview
Energy Technology Data Exchange (ETDEWEB)
Cicoli, Michele [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Quevedo, Fernando [Cambridge Univ. (United Kingdom). DAMTP/CMS; Abdus Salam International Centre for Theoretical Physics, Trieste (Italy)
2011-06-15
We present an overview of inflationary models derived from string theory focusing mostly on closed string moduli as inflatons. After a detailed discussion of the {eta}-problem and different approaches to address it, we describe possible ways to obtain a de Sitter vacuum with all closed string moduli stabilised. We then look for inflationary directions and present some of the most promising scenarios where the inflatons are either the real or the imaginary part of Kaehler moduli. We pay particular attention on extracting potential observable implications, showing how most of the scenarios predict negligible gravitational waves and could therefore be ruled out by the Planck satellite. We conclude by briefly mentioning some open challenges in string cosmology beyond deriving just inflation. (orig.)
HPV 6b L1 VIRUS-LIKE PARTICLES ELICIT HUMORAL IMMUNITY IN MICE
Institute of Scientific and Technical Information of China (English)
Liu Yuehua(刘跃华); Liu Wenjun(刘文军); Liu Xiaosong(刘晓松); Ian H.Frazer
2003-01-01
Objective. To test whether intrarnuscular,intranasal, intrarectal and intravaginal administration of HPV 6b L1 virus-like particles (VLPs) could induce immune response in mice and to assess whether intra muscular and mucosal vaccination against HPV is feasible. Methods. HPV6b L1 proteins self-assembled into VLPs in Sf-9 cell in vitro. Mice were immunized on day 0 and 21 with 50 μg HPV 6b L1 VLPs intramuscularly, intranasally, intrarectally and intravagi nally respectively. Sera were collected for testing IgG titer after a further 7 days and 3 months respec tively. Results. After immunizations, all mice developed significant anti-HPV 6b L1 antibody titers in serum by 7 days after the second immunization. The titer of the serum IgG antibody against HPV 6b L1 VLPs in the intramuscularly immunized group was higher than that in the intranasally, intrarectally and intravaginally immunized groups respectively, indicating that both muscular and mucosal administration of HPV 6b L1 VLPs can stimulate a systemic HPV-specific antibody response. Sera of the mice in the in tramuscularly immunized group still maintained a high titer of the serum IgG antibody against HPV 6b L1 VLPs 3 months after the immunization. Conclusion. The results demonstrated that the HPV 6b L1 VLPs maintain strong antigenicity. Immu nization with HPV 6b L1 VLPs via intramuscular and mucosal routes, without adjuvant, can elicit spe cific antibody in sera. These findings suggest that the VLPs are able to induce protective antibodies.
Graceful Exit in String Cosmology
Brustein, Ram; Brustein, Ram; Madden, Richard
1998-01-01
The graceful exit transition from a dilaton-driven inflationary phase to a decelerated Friedmann-Robertson-Walker era requires certain classical and quantum corrections to the string effective action. Classical corrections can stabilize a high curvature string phase while the evolution is still in the weakly coupled regime, and quantum corrections can induce violation of the null energy condition, allowing evolution towards a decelerated phase.
Kim, Joonho; Lee, Kimyeong
2015-01-01
We explore 6d (1,0) superconformal field theories with SU(3) and SU(2) gauge symmetries which cascade after Higgsing to the E-string theory on a single M5 near an $E_8$ wall. Specifically, we study the 2d $\\mathcal{N}=(0,4)$ gauge theories which describe self-dual strings of these 6d theories. The self-dual strings can be also viewed as instanton string solitons of 6d Yang-Mills theories. We find the 2d anomaly-free gauge theories for self-dual strings, amending the naive ADHM gauge theories which are anomalous, and calculate their elliptic genera. While these 2d theories respect the flavor symmetry of each 6d SCFT only partially, their elliptic genera manifest the symmetry fully as these functions as BPS index are invariant in strongly coupled IR limit. Our consistent 2d (0,4) gauge theories also provide new insights on the non-linear sigma models for the instanton strings, providing novel UV completions of the small instanton singularities. Finally, we construct new 2d quiver gauge theories for the self-dua...
Tadpole Resummations in String Theory
Kitazawa, Noriaki
2008-01-01
While R-R tadpoles should be canceled for consistency, string models with broken supersymmetry generally have uncanceled NS-NS tadpoles. Their presence signals that the background does not solve the field equations, so that these models are in "wrong" vacua. In this letter we investigate, with reference to some prototype examples, whether the true values of physical quantities can be recovered resumming the NS-NS tadpoles, hence by an approach that is related to the analysis based on String Field Theory by open-closed duality. We show that, indeed, the positive classical vacuum energy of a Dp-brane of the bosonic string is exactly canceled by the negative contribution arising from tree-level tadpole resummation, in complete agreement with Sen's conjecture on open-string tachyon condensation and with the consequent analysis based on String Field Theory. We also show that the vanishing classical vacuum energy of the SO(8192) unoriented bosonic open-string theory does not receive any tree-level corrections from ...
Toward A Nonperturbative Topological String
Neitzke, A
2005-01-01
We discuss three examples of nonperturbative phenomena in the topological string. First, we consider the computation of amplitudes in N = 4 super Yang-Mills theory using the B model topological string as proposed by Witten. We give an argument suggesting that the computations using connected or disconnected D-instantons of the B model are in fact equivalent. Second, we formulate a conjecture that the squared modulus of the open topological string partition function can be defined nonperturbatively as the partition function of a mixed ensemble of BPS states in d = 4. This conjecture is an extension of a recent proposal for the closed topological string. In a particular example involving a non-compact Calabi- Yau threefold, we show that the conjecture passes some basic checks, and that the square of the open topological string amplitude has a natural interpretation in terms of 2-dimensional Yang-Mills theory, again generalizing known results for the closed string case. Third, we discuss an action for an abel...
Cosmic Censorship Conjecture in Kerr-Sen Black Hole
Gwak, Bogeun
2016-01-01
The validity of cosmic censorship conjecture for the Kerr-Sen black hole, which is a solution to the low-energy effective field theory for four-dimensional heterotic string theory, is investigated using charged particle absorption. When the black hole absorbs the particle, its charges are changed due to the conserved quantities of the particle. Changes in the black hole are constrained to the equation for the motion of the particle and are consistent with the laws of thermodynamics. Particle absorption increases the mass of the extremal Kerr-Sen black hole to more than its charges, so the black hole cannot be overcharged. Therefore, cosmic censorship conjecture is valid.
Evolution of segmented strings
Gubser, Steven S
2016-01-01
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 non-compact discrete subgroup of SL(2,R) whose structure is related to the Pell equation. A discrete version of the 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 reach...
Reproducing the observed Cosmic microwave background anisotropies with causal scaling seeds
Durrer, R.; Kunz, M.; Melchiorri, A.
2000-01-01
During the last years it has become clear that global O(N) defects and U(1) cosmic strings do not lead to the pronounced first acoustic peak in the power spectrum of anisotropies of the cosmic microwave background which has recently been observed to high accuracy. Inflationary models cannot easily accommodate the low second peak indicated by the data. Here we construct causal scaling seed models which reproduce the first and second peak. Future, more precise CMB anisotropy and polarization ex...
Non-minimal B-L inflation with observable gravity waves
Energy Technology Data Exchange (ETDEWEB)
Okada, Nobuchika, E-mail: okadan@ua.edu [Department of Physics and Astronomy, University of Alabama, Tuscaloosa, AL 35487 (United States); Rehman, Mansoor Ur, E-mail: rehman@udel.edu [Bartol Research Institute, Department of Physics and Astronomy, University of Delaware, Newark, DE 19716 (United States); Shafi, Qaisar, E-mail: shafi@bartol.udel.edu [Bartol Research Institute, Department of Physics and Astronomy, University of Delaware, Newark, DE 19716 (United States)
2011-07-27
We consider non-minimal {lambda}{phi}{sup 4} inflation in a gauged non-supersymmetric U(1){sub B-L} model containing the gravitational coupling {xi}R{Phi}{sup +}{Phi}, where R denotes the Ricci scalar and the standard model singlet inflaton field {Phi} spontaneously breaks the U(1){sub B-L} symmetry. Including radiative corrections, the predictions 0.956{<=}n{sub s}{<=}0.984 and 0.007{<=}r{<=}0.1 for the scalar spectral index and tensor to scalar ratio r lie within the current WMAP 1-{sigma} bounds. If the B-L symmetry breaking scale is of order a TeV or so, one of the three right handed neutrinos is a plausible cold dark matter candidate. Bounds on the dimensionless parameters {lambda}, {xi} and the gauge coupling g{sub B-L} are obtained.
Right-handed neutrino dark matter under the B - L gauge interaction
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.
Supersymmetric standard model from the heterotic string (II)
Energy Technology Data Exchange (ETDEWEB)
Buchmueller, W. [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Hamaguchi, K. [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany)]|[Tokyo Univ. (Japan). Dept. of Physics; Lebedev, O.; Ratz, M. [Bonn Univ. (Germany). Physikalisches Inst.
2006-06-15
We describe in detail a Z{sub 6} orbifold compactification of the heterotic E{sub 8} x E{sub 8} string which leads to the (supersymmetric) standard model gauge group and matter content. The quarks and leptons appear as three 16-plets of SO(10), two of which are localized at fixed points with local SO(10) symmetry. The model has supersymmetric vacua without exotics at low energies and is consistent with gauge coupling unification. Supersymmetry can be broken via gaugino condensation in the hidden sector. The model has large vacuum degeneracy. Certain vacua with approximate B-L symmetry have attractive phenomenological features. The top quark Yukawa coupling arises from gauge interactions and is of the order of the gauge couplings. The other Yukawa couplings are suppressed by powers of standard model singlet fields, similarly to the Froggatt-Nielsen mechanism. (Orig.)
Dynamical behavior and Jacobi stability analysis of wound strings
Lake, Matthew J
2016-01-01
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 t...
Emergence and expansion of cosmic space in BIonic system
Energy Technology Data Exchange (ETDEWEB)
Sepehri, A., E-mail: alireza.sepehri@uk.ac.ir [Faculty of Physics, Shahid Bahonar University, P.O. Box 76175, Kerman (Iran, Islamic Republic of); Rahaman, Farook, E-mail: rahaman@iucaa.ernet.in [Department of Mathematics, Jadavpur University, Kolkata 700032, West Bengal (India); Pradhan, Anirudh, E-mail: pradhan@iucaa.ernet.in [Department of Mathematics, GLA University, Mathura-281 406, U.P. (India); Sardar, Iftikar Hossain, E-mail: iftikar.spm@gmail.com [Department of Mathematics, Jadavpur University, Kolkata 700032, West Bengal (India)
2015-02-04
Recently, Padmanabhan [ (arXiv:1206.4916 [hep-th])] argued that the expansion rate of the universe can be thought of as the emergence of space as cosmic time progresses and is related to the difference between the surface degrees of freedom on the holographic horizon and the bulk degrees of freedom inside. The main question arises as to what is the origin of emergence of space in 4D universe. We answer this question in BIonic system. The BIon is a configuration in flat space of a D-brane and a parallel anti-D-brane connected by a thin shell wormhole with F-string charge. We propose a new model that allows that all degrees of freedom inside and outside the universe are controlled by the evolutions of BIon in extra dimension and tend to degrees of freedom of black F-string in string theory or black M2-brane in M-theory.
Emergence and Expansion of Cosmic Space in BIonic system
Sepehri, A; Pradhan, Anirudh; Sardar, Iftikar Hossain
2015-01-01
Recently, Padmanabhan [arXiv:1206.4916] argued that the expansion rate of the universe can be thought of as the emergence of space as cosmic time progresses and is related to the difference between the surface degrees of freedom on the holographic horizon and the bulk degrees of freedom inside. The main question arises as to what is origin of emergence of space in 4D universe? We answer to this question in BIonic system. The BIon is a configuration in flat space of a D-brane and a parallel anti-D-brane connected by a thin shell wormhole with F-string charge. We propose a new model that allows all degrees of freedom inside and outside the universe are controlled by the evolutions of BIon in extra dimension and tend to degrees of freedom of black F-string in string theory or black M2-brane in M theory.
Summing up Open String Instantons and N=1 String Amplitudes
Mayr, Peter
2002-01-01
We compute the instanton expansions of the holomorphic couplings in the effective action of certain $\\cx N=1$ supersymmetric four-dimensional open string vacua. These include the superpotential $W(\\phi)$, the gauge kinetic function $f(\\phi)$ and a series of other holomorphic couplings which are known to be related to amplitudes of topological open strings at higher world-sheet topologies. The results are in full agreement with the interpretation of the holomorphic couplings as counting functions of BPS domain walls. Similar techniques are used to compute genus one partition function for the closed topological string on Calabi--Yau 4-fold which gives rise to a theory with the same number of supercharges in two dimensions.
String Resonances at Hadron Colliders
Anchordoqui, Luis A; Dai, De-Chang; Feng, Wan-Zhe; Goldberg, Haim; Huang, Xing; Lust, Dieter; Stojkovic, Dejan; Taylor, Tomasz R
2014-01-01
[Abridged] We consider extensions of the standard model based on open strings ending on D-branes. Assuming that the fundamental string mass scale M_s is in the TeV range and that the theory is weakly coupled, we discuss possible signals of string physics at the upcoming HL-LHC run (3000 fb^{-1}) with \\sqrt{s} = 14 TeV, and at potential future pp colliders, HE-LHC and VLHC, operating at \\sqrt{s} = 33 and 100 TeV, respectively. In such D-brane constructions, the dominant contributions to full-fledged string amplitudes for all the common QCD parton subprocesses leading to dijets and \\gamma + jet are completely independent of the details of compactification, and can be evaluated in a parameter-free manner. We make use of these amplitudes evaluated near the first (n=1) and second (n=2) resonant poles to determine the discovery potential for Regge excitations of the quark, the gluon, and the color singlet living on the QCD stack. We show that for string scales as large as 7.1 TeV (6.1 TeV), lowest massive Regge exc...
Topological strings from quantum mechanics
Energy Technology Data Exchange (ETDEWEB)
Grassi, Alba; Marino, Marcos [Geneve Univ. (Switzerland). Dept. de Physique Theorique et Section de Mathematique; Hatsuda, Yasuyuki [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany). Theory Group
2014-12-15
We propose a general correspondence which associates a non-perturbative quantum-mechanical operator to a toric Calabi-Yau manifold, and we conjecture an explicit formula for its spectral determinant in terms of an M-theoretic version of the topological string free energy. As a consequence, we derive an exact quantization condition for the operator spectrum, in terms of the vanishing of a generalized θ function. The perturbative part of this quantization condition is given by the Nekrasov-Shatashvili limit of the refined topological string, but there are non-perturbative corrections determined by the conventional topological string. We analyze in detail the cases of local P{sup 2}, local P{sup 1} x P{sup 1} and local F{sub 1}. In all these cases, the predictions for the spectrum agree with the existing numerical results. We also show explicitly that our conjectured spectral determinant leads to the correct spectral traces of the corresponding operators, which are closely related to topological string theory at orbifold points. Physically, our results provide a Fermi gas picture of topological strings on toric Calabi-Yau manifolds, which is fully non-perturbative and background independent. They also suggest the existence of an underlying theory of M2 branes behind this formulation. Mathematically, our results lead to precise, surprising conjectures relating the spectral theory of functional difference operators to enumerative geometry.
Advances in String Theory in Curved Backgrounds A Synthesis Report
Sánchez, N G
2003-01-01
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 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 invariant effects;strings on plane waves, shock waves and spacetime singularities and its spectrum. New developments in string gravity and string cosmology are reported: string driven cosmology and its predictions;the primordial gravitation wave background; non-singular string cosmologies from exact conformal field theories;QFT, string temperature and the string phase of de Sitter space; the string phase of black holes;new dual relation between QFT regimes and string regimes and the 'QFT/String Tango'; new coherent string states and minimal uncertainty principle in string theory
Fernandez Tellez, A; Martinez Hernandez, M; Rodriguez Cahuantzi, M
2013-01-01
The ALICE underground cavern provides an ideal place for the detection of high energy atmospheric muons coming from cosmic ray showers. ACORDE detects cosmic ray showers by triggering the arrival of muons to the top of the ALICE magnet.
Split String Formalism and the Closed String Vacuum, II
Erler, T
2007-01-01
In this paper we reconsider a class of generalizations of Schnabl's solution of open bosonic string field theory obtained by replacing the wedge state by an arbitrary combination of wedge states. Contrary to the conclusion of our previous paper hep-th/0611200, we find that under a few modest conditions such generalizations give a sensible deformation of Schnabl's solution for the closed string vacuum--in particular, we can compute their energies and show that they reproduce the value predicted by Sen's conjecture. Though these solutions are apparently gauge equivalent, they are not in general related by midpoint preserving reparameterizations.
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.
Topological open strings on orbifolds
Bouchard, Vincent; Marino, Marcos; Pasquetti, Sara
2008-01-01
We use the remodeling approach to the B-model topological string in terms of recursion relations to study open string amplitudes at orbifold points. To this end, we clarify modular properties of the open amplitudes and rewrite them in a form that makes their transformation properties under the modular group manifest. We exemplify this procedure for the C^3/Z_3 orbifold point of local P^2, where we present results for topological string amplitudes for genus zero and up to three holes, and for the one-holed torus. These amplitudes can be understood as generating functions for either open orbifold Gromov-Witten invariants of C^3/Z_3, or correlation functions in the orbifold CFT involving insertions of both bulk and boundary operators.
Allkofer, O. C.; Grieder, P. K. F.
Contents: Cosmic rays in the atmosphere: Charged hadron data. Neutron data. Gamma-ray data. Electron data. Muon data. Data on nuclei. Data on antiparticles. Cosmic rays at sea level: Muon data. Charged hadron data.Neutron data. Electron data. Gamma-ray data. Data on nuclei. Cosmic rays underground: Muon data. Neutrino data.
Fast algorithm on string cross pattern matching
Institute of Scientific and Technical Information of China (English)
Liu Gongshen; Li Jianhua; Li Shenghong
2005-01-01
Given a set U which is consisted of strings defined on alphabet ∑ , string cross pattern matching is to find all the matches between every two strings in U. It is utilized in text processing like removing the duplication of strings.This paper presents a fast string cross pattern matching algorithm based on extracting high frequency strings. Compared with existing algorithms including single-pattern algorithms and multi-pattern matching algorithms, this algorithm is featured by both low time complexityand low space complexity. Because Chinese alphabet is large and the average length of Chinese words is much short, this algorithm is more suitable to process the text written by Chinese, especially when the size of ∑ is large and the number of strings is far more than the maximum length of strings of set U.
A versatile sensor for string motion
Waltham, C; Waltham, Chris; Kotlicki, Andrzej
2006-01-01
The full characterization of a stringed musical instrument requires measuring the motion of the strings in at least two dimensions. Traditionally this has been done using electromagnetic means or by optical transmission. However in many instruments the strings are not made of steel, nor are the strings easily accessible on both sides. In this work it is shown that string positions can be measured by inexpensive optical reflection sensors which neither require metallic strings nor obtrusive access. We have demonstrated a versatile and non-invasive technique for measuring the position of a vibrating string in a 1 mm^2 area with an accuracy of tens of microns for thin strings, and better than 0.1 mm for thick ones.
On Science, pseudoscience and String theory
Chaudhuri, Asis Kumar
2016-01-01
The article discusses the demarcation problem; how to distinguish between science and pseudoscience. It then examines the string theory under various demarcation criteria to conclude that string theory cannot be considered as science.
Planckian Axions in String Theory
Bachlechner, Thomas; Long, Cody; McAllister, Liam
2014-01-01
We argue that super-Planckian diameters of axion fundamental domains can naturally arise in Calabi-Yau compactifications of string theory. In a theory with $N$ axions $\\theta^i$, the fundamental domain is a polytope defined by the periodicities of the axions, via constraints of the form $-\\piN$ 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 t...
Strings, paths, and standard tableaux
Dasmahapatra, S
1996-01-01
For the vacuum sectors of regime-III ABF models, we observe that two sets of combinatorial objects: the strings which parametrize the row-to-row transfer matrix eigenvectors, and the paths which parametrize the corner transfer matrix eigenvectors, can both be expressed in terms of the same set of standard tableaux. Furthermore, the momenta of the strings, the energies of the paths, and the charges of the tableaux are such that there is a weight-preserving bijection between the two sets of eigenvectors, wherein the tableaux play an interpolating role. This bijection is so natural, that we conjecture that it exists in general.
Heterotic strings on homogeneous spaces
Israel, D; Orlando, D; Petropoulos, P M; Israel, Dan; Kounnas, Costas; Orlando, Domenico
2004-01-01
We construct heterotic string backgrounds corresponding to families of homogeneous spaces as exact conformal field theories. They contain left cosets of compact groups by their maximal tori supported by NS-NS 2-forms and gauge field fluxes. We give the general formalism and modular-invariant partition functions, then we consider some examples such as SU(2)/U(1) ~ S^2 (already described in a previous paper) and the SU(3)/U(1)^2 flag space. As an application we construct new supersymmetric string vacua with magnetic fluxes and a linear dilaton.
Replica trick and string winding
Prudenziati, Andrea
2016-01-01
We apply the replica trick to compute the entropy of a cylinder amplitude in string theory. We focus on the contribution from non-perturbative winding modes and impose tadpole cancellation to understand the correct prescription for integrating over moduli. Choosing the entangling surface to cut longitudinally over the whole length of the cylinder, we obtain an answer that is interpreted as the entropy of a density matrix. We recast this result in target space language, both in the open and closed string picture.
Combinatorics, observables, and String Theory
Gregori, Andrea
2011-01-01
We investigate the most general phase space of configurations, consisting of all possible ways of assigning elementary attributes, ``energies'', to elementary positions, ``cells''. We discuss how this space possesses structures that can be approximated by a quantum-relativistic physical scenario. In particular, we discuss how the Heisenberg's Uncertainty Principle and a universe with a three-dimensional space arise, and what kind of mechanics rules it. String Theory shows up as a complete representation of this structure in terms of time-dependent fields and particles. Within this context, owing to the uniqueness of the underlying mathematical structure it represents, one can also prove the uniqueness of string theory.
Finding Maximal Quasiperiodicities in Strings
DEFF Research Database (Denmark)
Brodal, Gerth Stølting; Pedersen, Christian N. S.
2000-01-01
of length n in time O(n log n) and space O(n). Our algorithm uses the suffix tree as the fundamental data structure combined with efficient methods for merging and performing multiple searches in search trees. Besides finding all maximal quasiperiodic substrings, our algorithm also marks the nodes......Apostolico and Ehrenfeucht defined the notion of a maximal quasiperiodic substring and gave an algorithm that finds all maximal quasiperiodic substrings in a string of length n in time O(n log2 n). In this paper we give an algorithm that finds all maximal quasiperiodic substrings in a string...
Bell's Inequalities, Superquantum Correlations, and String Theory
Directory of Open Access Journals (Sweden)
Lay Nam Chang
2011-01-01
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.
String Interactions in c=1 Matrix Model
De Boer, J; Verlinde, E; Yee, J T; Boer, Jan de; Sinkovics, Annamaria; Verlinde, Erik; Yee, Jung-Tay
2004-01-01
We study string interactions in the fermionic formulation of the c=1 matrix model. We give a precise nonperturbative description of the rolling tachyon state in the matrix model, and discuss S-matrix elements of the c=1 string. As a first step to study string interactions, we compute the interaction of two decaying D0-branes in terms of free fermions. This computation is compared with the string theory cylinder diagram using the rolling tachyon ZZ boundary states.
Twenty-five questions for string theorists
Energy Technology Data Exchange (ETDEWEB)
Binetruy, Pierre; /Orsay, LPT; Kane, G.L.; /Michigan U., MCTP; Lykken, Joseph D.; /Fermilab; 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.
Covariant Calculus for Effective String Theories
Dass, N. D. Hari; Matlock, Peter
2007-01-01
A covariant calculus for the construction of effective string theories is developed. Effective string theory, describing quantum string-like excitations in arbitrary dimension, has in the past been constructed using the principles of conformal field theory, but not in a systematic way. Using the freedom of choice of field definition, a particular field definition is made in a systematic way to allow an explicit construction of effective string theories with manifest exact conformal symmetry. ...
Closed string amplitudes as single-valued open string amplitudes
Energy Technology Data Exchange (ETDEWEB)
Stieberger, Stephan, E-mail: stephan.stieberger@mpp.mpg.de [Max-Planck-Institut für Physik, Werner-Heisenberg-Institut, 80805 München (Germany); Taylor, Tomasz R. [Department of Physics, Northeastern University, Boston, MA 02115 (United States)
2014-04-15
We show that the single trace heterotic N-point tree-level gauge amplitude A{sub N}{sup HET} can be obtained from the corresponding type I amplitude A{sub N}{sup I} by the single-valued (sv) projection: A{sub N}{sup HET}=sv(A{sub N}{sup I}). This projection maps multiple zeta values to single-valued multiple zeta values. The latter represent a subclass of multiple zeta values originating from single-valued multiple polylogarithms at unity. Similar relations between open and closed string amplitudes or amplitudes of different string vacua can be established. As a consequence the α{sup ′}-expansion of a closed string amplitude is dictated by that of the corresponding open string amplitude. The combination of single-valued projections, Kawai–Lewellen–Tye relations and Mellin correspondence reveal a unity of all tree-level open and closed superstring amplitudes together with the maximally supersymmetric Yang–Mills and supergravity theories.
M-strings, elliptic genera and N = 4 string amplitudes
Energy Technology Data Exchange (ETDEWEB)
Hohenegger, S. [Department of Physics, CERN - Theory Division, Geneva (Switzerland); Iqbal, A. [Department of Physics, LUMS School of Science and Engineering, Lahore (Pakistan); Department of Mathematics, LUMS School of Science and Engineering, Lahore (Pakistan)
2014-03-06
We study mass-deformed N = 2 gauge theories from various points of view. Their partition functions can be computed via three dual approaches: firstly, (p,q)-brane webs in type II string theory using Nekrasov's instanton calculus, secondly, the (refined) topological string using the topological vertex formalism and thirdly, M theory via the elliptic genus of certain M-strings configurations. We argue for a large class of theories that these approaches yield the same gauge theory partition function which we study in detail. To make their modular properties more tangible, we consider a fourth approach by connecting the partition function to the equivariant elliptic genus of C{sup 2} through a (singular) theta-transform. This form appears naturally as a specific class of one-loop scattering amplitudes in type II string theory on T{sup 2}, which we calculate explicitly. (Copyright copyright 2014 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)
Symmetries and Interactions in Matrix String Theory
Hacquebord, F.H.
1999-01-01
This PhD-thesis reviews matrix string theory and recent developments therein. The emphasis is put on symmetries, interactions and scattering processes in the matrix model. We start with an introduction to matrix string theory and a review of the orbifold model that flows out of matrix string theory
String loop corrected hypermultiplet moduli spaces
Robles-Llana, D.; Saueressig, Frank; Vandoren, S.
2007-01-01
Using constraints from supersymmetry and string perturbation theory, we determine the string loop corrections to the hypermultiplet moduli space of type II strings compactified on a generic Calabi-Yau threefold. The corresponding quaternion-Kähler manifolds are completely encoded in terms of a singl
Architectures and representations for string transduction
Chrupala, Grzegorz
2015-01-01
String transduction problems are ubiquitous in natural language processing: they include transliteration, grapheme-to-phoneme conversion, text normalization and translation. String transduction can be reduced to the simpler problems of sequence labeling by expressing the target string as a sequence
Two-component Duality and Strings
Freund, Peter G O
2007-01-01
A phenomenologically successful two-component hadronic duality picture led to Veneziano's amplitude, the fundamental first step to string theory. This picture is briefly recalled and its two components are identified as the open strings (mesons and baryons) and closed strings (Pomeron).
String field representation of the Virasoro algebra
Mertes, Nicholas; Schnabl, Martin
2016-12-01
We construct a representation of the zero central charge Virasoro algebra using string fields in Witten's open bosonic string field theory. This construction is used to explore extensions of the KBc algebra and find novel algebraic solutions of open string field theory.
The Physics of "String Passing through Ice"
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…
String field representation of the Virasoro algebra
Mertes, Nicholas
2016-01-01
We construct a representation of the zero central charge Virasoro algebra using string fields in Witten's open bosonic string field theory. This construction is used to explore extensions of the KBc algebra and find novel algebraic solutions of open string field theory.
U(1)B-L symmetry restoration and effective neutrino species
Ishida, Hiroyuki; Takahashi, Fuminobu
2014-06-01
The U(1)B-L symmetry could be restored during inflation, since the BICEP2 results suggest a GUT-scale inflation with the Hubble parameter, Hinf≃1014 GeV, close to the U(1)B-L breaking scale. We consider a scenario in which the B-L Higgs field dominates the Universe after inflation, and mainly decays into the U(1)B-L gauge bosons, whose subsequent decays reheat the Universe. Interestingly, if one of the right-handed neutrinos is extremely light and behaves as dark radiation or hot dark matter, its abundance is determined by the B-L charge assignment and the relativistic degree of freedom in plasma. We find that ΔNeff takes discrete values between 0.188 and 0.220 in the standard model plus three right-handed neutrinos, depending on whether the decay into heavier right-handed neutrinos is kinematically accessible or not. In the fiveness U(1)5 case, we find that ΔNeff takes discrete values between 0.313 and 0.423. The tension between BICEP2 and Planck can be partially relaxed by dark radiation.
U(1)$_{B-L}$ Symmetry Restoration and Effective Neutrino Species
Ishida, Hiroyuki
2014-01-01
The U(1)$_{B-L}$ symmetry could be restored during inflation, since the BICEP2 results suggest a GUT-scale inflation with the Hubble parameter, $H_{\\rm inf} \\simeq 10^{14}$ GeV, close to the U(1)$_{B-L}$ breaking scale. If the ${B-L}$ Higgs field dominates the Universe after inflation, it can mainly decay into the U(1)$_{B-L}$ gauge bosons, whose subsequent decays reheat the Universe. Interestingly, if one (or more) of the right-handed neutrinos is extremely light and behaves as dark radiation or hot dark matter, its abundance is determined solely by the $B-L$ charge assignment and the relativistic degree of freedom in plasma. We find that $\\Delta N_{\\rm eff}$ takes discrete values between $0.188$ and $0.220$ in the standard model plus three right-handed neutrinos, depending on whether the decay into heavier right-handed neutrinos are kinematically accessible or not. In the fiveness U(1)$_{\\bf 5}$ case, we find that $\\Delta N_{\\rm eff}$ takes discrete values between $0.274$ and $0.386$. The tension between BI...
Measurement of the Anisotropy of Cosmic Ray Arrival Directions with IceCube
DEFF Research Database (Denmark)
IceCube Collaboration, The; Abbasi, R.; Abdou, Y.
2010-01-01
with 1320 digital optical sensors distributed over 22 strings at depths between 1450 and 2450 meters inside the Antarctic ice. IceCube is a neutrino detector, but the data are dominated by a large background of cosmic ray muons. Therefore, the background data are suitable for high-statistics studies...... of cosmic rays in the Southern sky. The data include 4.3 billion muons produced by downgoing cosmic ray interactions in the atmosphere; these events were reconstructed with a median angular resolution of 3 degrees and a median energy of $\\sim20$ TeV. Their arrival direction distribution exhibits...
Excess astrophysical photons from a 0.1-1 keV cosmic axion background.
Conlon, Joseph P; Marsh, M C David
2013-10-11
Primordial decays of string theory moduli at z~10(12) naturally generate a dark radiation cosmic axion background with 0.1-1 keV energies. This cosmic axion background can be detected through axion-photon conversion in astrophysical magnetic fields to give quasithermal excesses in the extreme ultraviolet and soft x-ray bands. Substantial and observable luminosities may be generated even for axion-photon couplings axion-photon conversion may explain the observed excess emission of soft x rays from galaxy clusters, and may also contribute to the diffuse unresolved cosmic x-ray background. We list a number of correlated predictions of the scenario.
A new B-L model without right-handed neutrinos
Patra, Sudhanwa; Yaguna, Carlos E
2016-01-01
We propose and study a novel extension of the Standard Model based on the B-L gauge symmetry that can account for dark matter and neutrino masses. In this model, right-handed neutrinos are absent and the gauge anomalies are canceled instead by four chiral fermions with fractional B-L charges. After the breaking of $U(1)_{B-L}$, these fermions arrange themselves into two Dirac particles, the lightest of which is automatically stable and plays the role of the dark matter. We determine the regions of the parameter space consistent with the observed dark matter density and show that they can be partially probed via direct and indirect dark matter detection or collider searches at the LHC. Neutrino masses, on the other hand, can be explained by a variant of the type-II seesaw mechanism involving one of the two scalar fields responsible for the dark matter mass.
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
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
Energy Technology Data Exchange (ETDEWEB)
Boels, Rutger H.; Hansen, Tobias [II. Institut für Theoretische Physik, Universität Hamburg,Luruper Chaussee 149, D- 22761 Hamburg (Germany)
2014-06-10
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.
Topological Strings and Integrable Hierarchies
Aganagic, M; Klemm, A D; Marino, M; Vafa, C; Aganagic, Mina; Dijkgraaf, Robbert; Klemm, Albrecht; Marino, Marcos; Vafa, Cumrun
2006-01-01
We consider the topological B-model on local Calabi-Yau geometries. We show how one can solve for the amplitudes by using W-algebra symmetries which encodes the symmetries of holomorphic diffeomorphisms of the Calabi-Yau. In the highly effective fermionic/brane formulation this leads to a free fermion description of the amplitudes. Furthermore we argue that topological strings on Calabi-Yau geometries provide a unifying picture connecting non-critical (super)strings, integrable hierarchies, and various matrix models. In particular we show how the ordinary matrix model, the double scaling limit of matrix models, and Kontsevich-like matrix model are all related and arise from studying branes in specific local Calabi-Yau three-folds. We also show how A-model topological string on P^1 and local toric threefolds (and in particular the topological vertex) can be realized and solved as B-model topological string amplitudes on a Calabi-Yau manifold.
Topological Strings and Integrable Hierarchies
Aganagic, Mina; Dijkgraaf, Robbert; Klemm, Albrecht; Mariño, Marcos; Vafa, Cumrun
2006-01-01
We consider the topological B-model on local Calabi-Yau geometries. We show how one can solve for the amplitudes by using -algebra symmetries which encode the symmetries of holomorphic diffeomorphisms of the Calabi-Yau. In the highly effective fermionic/brane formulation this leads to a free fermion description of the amplitudes. Furthermore we argue that topological strings on Calabi-Yau geometries provide a unifying picture connecting non-critical (super)strings, integrable hierarchies, and various matrix models. In particular we show how the ordinary matrix model, the double scaling limit of matrix models, and Kontsevich-like matrix model are all related and arise from studying branes in specific local Calabi-Yau three-folds. We also show how an A-model topological string on P1 and local toric threefolds (and in particular the topological vertex) can be realized and solved as B-model topological string amplitudes on a Calabi-Yau manifold.
Exotic Non-relativistic String
Casalbuoni, Roberto; Longhi, Giorgio
2007-01-01
We construct a classical non-relativistic string model in 3+1 dimensions. The model contains a spurion tensor field that is responsible for the non-commutative structure of the model. Under double dimensional reduction the model reduces to the exotic non-relativistic particle in 2+1 dimensions.
Understanding maximal repetitions in strings
Crochemore, Maxime
2008-01-01
The cornerstone of any algorithm computing all repetitions in a string of length n in O(n) time is the fact that the number of runs (or maximal repetitions) is O(n). We give a simple proof of this result. As a consequence of our approach, the stronger result concerning the linearity of the sum of exponents of all runs follows easily.
Topological Strings from Quantum Mechanics
Grassi, Alba; Marino, Marcos
2014-01-01
We propose a general correspondence which associates a non-perturbative quantum-mechanical operator to a toric Calabi-Yau manifold, and we conjecture an explicit formula for its spectral determinant in terms of an M-theoretic version of the topological string free energy. As a consequence, we derive an exact quantization condition for the operator spectrum, in terms of the vanishing of a generalized theta function. The perturbative part of this quantization condition is given by the Nekrasov-Shatashvili limit of the refined topological string, but there are non-perturbative corrections determined by the conventional topological string. We analyze in detail the cases of local P2, local P1xP1 and local F1. In all these cases, the predictions for the spectrum agree with the existing numerical results. We also show explicitly that our conjectured spectral determinant leads to the correct spectral traces of the corresponding operators, which are closely related to topological string theory at orbifold points. Phys...
Metastable Quivers in String Compactifications
Energy Technology Data Exchange (ETDEWEB)
Diaconescu, Duiliu-Emanuel; /Rutgers U., Piscataway; Donagi, Ron; /Pennsylvania U. /SLAC; Florea, Bogdan; /SLAC
2007-01-08
We propose a scenario for dynamical supersymmetry breaking in string compactifications based on geometric engineering of quiver gauge theories. In particular we show that the runaway behavior of fractional branes at del Pezzo singularities can be stabilized by a flux superpotential in compact models. Our construction relies on homological mirror symmetry for orientifolds.
DEFF Research Database (Denmark)
Szklarczyk, Damian; Morris, John H; Cook, Helen;
2016-01-01
A system-wide understanding of cellular function requires knowledge of all functional interactions between the expressed proteins. The STRING database aims to collect and integrate this information, by consolidating known and predicted protein-protein association data for a large number of organi...
Topological effects on string vacua
Loaiza-Brito, Oscar
2011-01-01
We review some topological effects on the construction of string flux-vacua. Specifically we study the effects of brane-flux transitions on the stability of D-branes on a generalized tori compactificaction, the transition that a black hole suffers in a background threaded with fluxes and the connections among some Minkowsky vacua solutions.
Precise Analysis of String Expressions
DEFF Research Database (Denmark)
Christensen, Aske Simon; Møller, Anders; Schwartzbach, Michael Ignatieff
2003-01-01
, including statically checking the syntax of dynamically generated expressions, such as SQL queries. Our analysis constructs flow graphs from class files and generates a context-free grammar with a nonterminal for each string expression. The language of this grammar is then widened into a regular language...
The Science of String Instruments
Rossing, Thomas D
2010-01-01
Many performing musicians, as well as instrument builders, are coming to realize the importance of understanding the science of musical instruments. This book explains how string instruments produce sound. It presents basic ideas in simple language, and it also translates some more sophisticated ideas in non-technical language. It should be of interest to performers, researchers, and instrument makers alike.
String effect and QCD coherence
Energy Technology Data Exchange (ETDEWEB)
Azimov, Ya.I.; Dokshitzer, Yu.L.; Khoze, V.A.; Troyan, S.I.
1985-12-19
In the framework of the idea of local parton-hadron duality we discuss the asymptotic predictions of QCD perturbation theory for angular distributions of hadron flows in the three-jet events, e/sup +/e/sup -/->qanti qg->hadrons. The coherence of soft gluon emission provides the QCD explanation of the string effect observed in experiments. (orig.).
Probing the string winding sector
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.
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.
CERN. Geneva
2014-01-01
The presence of the surrounding medium makes their dynamics dramatically different from those of ordinary string-like objects propagating in empty space, leading to quite peculiar phenomena, observed in experiments and simulations. I will argue that the effective theory provides an optimal theoretical framework to understand such phenomena, and to make precise quantitative predictions about them.
New Approaches to String Instruction.
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)
Boels, Rutger H
2014-01-01
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 Poincare invariance, unitarity and locality to that of positivity of a particular numerical sum. Interestingly, this analysis produces the main condition...
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
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.
Type Ia Supernovae and the discovery of the Cosmic Acceleration
Clocchiatti, Alejandro
2011-01-01
I present a review of the research and analysis paths that converged to make Type Ia SNe the most mature cosmological distance estimator of the present time. The narrative starts with the first works in the early decades of the 20th century and finishes with the more recent results. The review was written by a member of the High Z Supernova Search Team, the international group of astronomers that discovered Cosmic Acceleration in 1998. This result, confirmed by the Supernova Cosmology Project in 1999, received an impressive string of recognition culminating with the current Nobel prize in Physics. The review is presented thinking of physicists with a strong interest in Cosmology, who might have pondered why was that, after decades of not being able to agree upon the rate of cosmic expansion, astronomers were so quick to concur on cosmic acceleration.
ON FINITE DIFFERENCES ON A STRING PROBLEM
J. M. Mango; C. Eryenyu; S. E. Rugeihyamu
2014-01-01
This study presents an analysis of a one-Dimensional (1D) time dependent wave equation from a vibrating guitar string. We consider the transverse displacement of a plucked guitar string and the subsequent vibration motion. Guitars are known for production of great sound in form of music. An ordinary string stretched between two points and then plucked does not produce quality sound like a guitar string. A guitar string produces loud and unique sound which can be organized by the player to pro...
Charting the landscape of supercritical string theory
Hellerman, Simeon
2007-01-01
Special solutions of string theory in supercritical dimensions can interpolate in time between theories with different numbers of spacetime dimensions (via dimension quenching) and different amounts of worldsheet supersymmetry (via c-duality). 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. We describe some of these networks in detail and discuss general consistency constraints on the types of transitions that arise in this framework.
Computer Simulations of Coupled Piano Strings
Albert, Destiny L.
1997-03-01
The behavior of coupled piano strings is studied by using a finite difference scheme. The coupling of the strings produce motion in two transverse directions, parallel and perpendicular to the soundboard. The sound induced shows two decay rates, a rapid decay followed by a slow decay. These effects are in agreement with experimental results. (Weinreich, Gabriel. "The Coupled Motion of Piano Strings." Scientific American. January 1979) . Our simulations suggest that the motion of the end supports contributes to the elliptical motion of the strings. Furthermore, multiple strings contribute to the quality of the sound produced by a piano.
Growth and characterization of string ribbon
Energy Technology Data Exchange (ETDEWEB)
Hanoka, J.I. [Evergreen Solar, Inc., Waltham, MA (United States); Behnin, B.; Michel, J. [Massachusetts Inst. of Technology, Cambridge, MA (United States); Symko, M.; Sopori, B.L. [National Renewable Energy Lab., Golden, CO (United States)
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.
Ultrasensitive string-based temperature sensors
DEFF Research Database (Denmark)
Larsen, Tom; Schmid, Silvan; Gronberg, L.;
2011-01-01
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%/ degrees 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....
ON FINITE DIFFERENCES ON A STRING PROBLEM
Directory of Open Access Journals (Sweden)
J. M. Mango
2014-01-01
Full Text Available This study presents an analysis of a one-Dimensional (1D time dependent wave equation from a vibrating guitar string. We consider the transverse displacement of a plucked guitar string and the subsequent vibration motion. Guitars are known for production of great sound in form of music. An ordinary string stretched between two points and then plucked does not produce quality sound like a guitar string. A guitar string produces loud and unique sound which can be organized by the player to produce music. Where is the origin of guitar sound? Can the contribution of each part of the guitar to quality sound be accounted for, by mathematically obtaining the numerical solution to wave equation describing the vibration of the guitar string? In the present sturdy, we have solved the wave equation for a vibrating string using the finite different method and analyzed the wave forms for different values of the string variables. The results show that the amplitude (pitch or quality of the guitar wave (sound vary greatly with tension in the string, length of the string, linear density of the string and also on the material of the sound board. The approximate solution is representative; if the step width; ∂x and ∂t are small, that is <0.5.
Chemical composition of primary cosmic rays with IceCube
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.
String theory as a Lilliputian world
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.
String theory as a Lilliputian world
Ambjorn, Jan
2016-01-01
Lattice regularizations of the bosonic string allow no tachyons. 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.
String theory as a Lilliputian world
Directory of Open Access Journals (Sweden)
J. Ambjørn
2016-05-01
Full Text Available 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.
String theory as a Lilliputian world
Energy Technology Data Exchange (ETDEWEB)
Ambjørn, J., E-mail: ambjorn@nbi.dk [The Niels Bohr Institute, Copenhagen University, Blegdamsvej 17, DK-2100 Copenhagen (Denmark); IMAPP, Radboud University, Heyendaalseweg 135, 6525 AJ, Nijmegen (Netherlands); Makeenko, Y., E-mail: makeenko@nbi.dk [The Niels Bohr Institute, Copenhagen University, Blegdamsvej 17, DK-2100 Copenhagen (Denmark); Institute of Theoretical and Experimental Physics, B. Cheremushkinskaya 25, 117218 Moscow (Russian Federation)
2016-05-10
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.
Scaling behavior of regularized bosonic strings
Ambjorn, Jan
2015-01-01
We implement a proper-time UV regularisation of the Nambu-Goto string, introducing an independent metric tensor and the corresponding Lagrange multiplier, and treating them in the mean-field approximation justified for long strings and/or when the dimensions of space-time is large. We compute the regularised determinant of the 2d Laplacian for the closed string winding around a compact dimension, obtaining in this way the effective action, whose minimisation determines the energy of the string ground state in the mean-field approximation. We discuss the existence of two scaling limits when the cutoff is taken to infinity. One scaling limit reproduces the results obtained by the hypercubic regularisation of the Nambu-Goto string as well as by the use of the dynamical triangulation regularisation of the Polyakov string. The other scaling limit reproduces the results obtained by canonical quantisation of the Nambu-Goto string.
The Minimal SUSY $B-L$ Model: From the Unification Scale to the LHC
Ovrut, Burt A; Spinner, Sogee
2015-01-01
This paper introduces a random statistical scan over the high-energy initial parameter space of the minimal SUSY $B-L$ model--denoted as the $B-L$ MSSM. Each initial set of points is renormalization group evolved 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 $\\sim$125 GeV. The subspace of initial parameters that satisfies all such constraints is presented, shown to be robust and to contain a wide range of different configurations of soft supersymmetry breaking masses. The low-energy predictions of each such "valid" point - such as the sparticle mass spectrum and, in particular, the LSP - are computed and then statistically analyzed over the full subspace of valid points. Finally, the amount of fine-tuning required is quantified and compared to the MSSM computed using an identical random scan. The ...
Galactic Gamma Ray Excess and Dark Matter Phenomenology in a $U(1)_{B-L}$ Model
Biswas, Anirban; Khan, Sarif
2016-01-01
In this work, we have considered a gauged $U(1)_{\\rm B-L}$ extension of the Standard Model (SM) with three right handed neutrinos for anomaly cancellation and two additional SM singlet complex scalars with non-trivial B-L charges. One of these is used to spontaneously break the $U(1)_{\\rm B-L}$ gauge symmetry, leading to Majorana masses for the neutrinos through the standard Type I seesaw mechanism, while the other becomes the dark matter (DM) candidate in the model. We test the viability of the model to simultaneously explain the DM relic density observed in the CMB data as well as the Galactic Centre (GC) $\\gamma$-ray excess seen by Fermi-LAT. We show that for DM masses in the range 40-55 GeV and for a wide range of $U(1)_{\\rm B-L}$ gauge boson masses, one can satisfy both these constraints if the additional neutral Higgs scalar has a mass around the resonance region. In studying the dark matter phenomenology and GC excess, we have taken into account theoretical as well as experimental constraints coming fr...
Radiative Symmetry Breaking in the Supersymmetric Minimal B-L Extended Standard Model
Burell, Zachary
2016-01-01
The Standard Model (SM) of particle physics is a precise model of electroweak interactions, however there is growing tension between the SM and observations (neutrino oscillations, dark matter, dark energy, baryogenesis, among others). There is no reason to expect the validity of the ad hoc SM to remain intact at energy scales above a few TeV, thus a more fundamental theory will almost certainly be required. Motivated by these considerations, we investigate a Supersymmetric version of a natural extension of the SM, the $U(1)_{B-L}$ model, that is obtained by gauging the accidental B-L symmetry that exists in the ordinary SM. The Supersymmetric $U(1)_{B-L}$ extended SM can resolve the neutrino mass problem, the dark matter problem, the hierarchy problem, and provides a mechanism for establishing the observed baryon asymmetry of the Universe. When we include quantum corrections to the Higgs potential of the model, we find that Radiative $B-L$ symmetry breaking occurs through the interplay between large Majorana...
Galactic gamma ray excess and dark matter phenomenology in a U(1) B- L model
Biswas, Anirban; Choubey, Sandhya; Khan, Sarif
2016-08-01
In this work, we have considered a gauged U(1)B-L extension of the Standard Model (SM) with three right handed neutrinos for anomaly cancellation and two additional SM singlet complex scalars with nontrivial B-L charges. One of these is used to spontaneously break the U(1)B-L gauge symmetry, leading to Majorana masses for the neutrinos through the standard Type I seesaw mechanism, while the other becomes the dark matter (DM) candidate in the model. We test the viability of the model to simultaneously explain the DM relic density observed in the CMB data as well as the Galactic Centre (GC) γ-ray excess seen by Fermi-LAT. We show that for DM masses in the range 40-55 GeV and for a wide range of U(1)B-L gauge boson masses, one can satisfy both these constraints if the additional neutral Higgs scalar has a mass around the resonance region. In studying the dark matter phenomenology and GC excess, we have taken into account theoretical as well as experimental constraints coming from vacuum stability condition, Planck bound on DM relic density, LHC and LUX and present allowed areas in the model parameter space consistent with all relevant data, calculate the predicted gamma ray flux from the GC and discuss the related phenomenology.
Right-handed neutrino dark matter under the B-L gauge interaction
Kaneta, Kunio; Lee, Hye-Sung
2016-01-01
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 can be a sufficiently long-lived dark matter candidate, without an additional stability mechanism, 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.
Phenomenological study of $Z'$ in the minimal $B-L$ model at LHC
M., Balasubramaniam K
2016-01-01
The phenomenological study of neutral heavy gauge boson ($Z^{\\prime}_{B-L}$) of the minimal B-L extension was done on the dimuon production channel of the LHC. The study begins with the LEP-II constraints on $Z'$ searches, and the dimuon events are simulated at the parton level at the CM energies of 7 TeV and 8 TeV and studied with an integrated luminosity of 1.21 $fb^{-1}$ and 20.5 $fb^{-1}$ respectively. Later, the ATLAS detector-specific cuts unique to the Muon Pairs are imposed followed by the signal-selection-cuts on the Invariant Mass of the dimuon which restrict the events that are to be passed for Signal-Background Analysis, that are finally compared with the ATLAS data, and accounted for no experimental detection of $Z^{\\prime}_{B-L}$ boson. It has been simulated further at the CM energy of 14 TeV with an integrated luminosity of 300 $fb^{-1}$ to predict a possible discovery of this B-L neutral-heavy gauge boson with a mass corresponding to 1.5 TeV and a $Z'$ coupling strength of 0.2 based on the sig...
B-L Violating Proton Decay Modes and New Baryogenesis Scenario in SO(10)
Babu, K S
2012-01-01
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 \\to e^-K^+, e^- \\pi^+ and p \\to \
Closed String S-matrix Elements in Open String Field Theory
Garousi, M R; Garousi, Mohammad R
2005-01-01
Using the gauge invariant operators corresponding to on-shell closed string states in open string field theory, we study the tree level S-matrix element of two arbitrary closed string states, and the S-matrix element of one closed string and two open string states. By mapping the world-sheet of the amplitudes to the upper half z-plane, and by evaluating the correlators in the ghost parts, we show that the S-matrix elements are exactly identical to the corresponding disk level S-matrix elements in bosonic string theory.
Closed String S-matrix Elements in Open String Field Theory
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.
A Novel String Field Theory Solving String Theory by Liberating Left and Right Mover
Nielsen, Holger B
2012-01-01
We put forward ideas to a novel string field theory based on making some "objects" that essentially describe "liberated" left- and right- mover fields $X^{\\mu}_{L}(\\tau + \\sigma)$ and $X^{\\mu}_{R}(\\tau - \\sigma)$ on the string. The main progress is that we manage to make our novel string field theory provide the correct mass square spectrum for the string. An interesting detail is that we have to dispense of a species doubler caused by the discretization we introduced in our string field theory of the string right- and left- mover variables. We finally suggest how to obtain the Veneziano amplitude in our model.
Stanev, Todor
2010-01-01
Offers an accessible text and reference (a cosmic-ray manual) for graduate students entering the field and high-energy astrophysicists will find this an accessible cosmic-ray manual Easy to read for the general astronomer, the first part describes the standard model of cosmic rays based on our understanding of modern particle physics. Presents the acceleration scenario in some detail in supernovae explosions as well as in the passage of cosmic rays through the Galaxy. Compares experimental data in the atmosphere as well as underground are compared with theoretical models
Cosmological parameter dependence in local string theories of structure formation
Copeland, E J; Steer, D A; Magueijo, Joao
2000-01-01
We perform the most accurate study to date of the dependence on cosmological parameters of structure formation with local cosmic strings. The crucial new ingredients are the inclusion of the effects of gravitational backreaction on the evolution of the network, and the accurate evolution of the network through the radiation to matter transition. Our work re-iterates the fact that expanding Universe numerical simulations only probe a transient regime, and we incorporate our results into the unequal time correlators recently measured. We then compute the CMB and CDM fluctuations' power spectra for various values of the Hubble constant $H_0$ and baryon fraction $\\Omega_b$. We find that, whereas the dependence on $\\Omega_b$ is negligible, there is still a strong dependence on $H_0$.
The statistical physics of cosmological networks of string loops
Magueijo, J; Steer, D; Magueijo, Joao; Sandvik, Haavard; Steer, Daniele
1999-01-01
We solve numerically the Boltzmann equation describing the evolution of a cosmic string network which contains only loops. In Minkowski space time the equilibrium solution predicted by statistical mechanics is recovered, and we prove that this solution is stable to non-linear perturbations provided that their energy does not exceed the critical energy for the Hagedorn transition. In expanding Einstein - de Sitter Universes we probe the distribution of loops with length much smaller than the horizon. For these loops we discover stable scaling solutions both in the radiation and matter dominated epochs. The shape of these solutions is very different in the two eras, with much higher energy density in the radiation epoch, and a larger average loop length in the matter epoch. These results suggest that if the conditions for formation of loop networks are indeed satisfied, these could in principle be good candidates for structure formation.
Closed String Thermodynamics and a Blue Tensor Spectrum
Brandenberger, Robert H; Patil, Subodh P
2014-01-01
The BICEP-2 team has reported the detection of primordial cosmic microwave background B-mode polarization, with hints of a suppression of power at large angular scales relative to smaller scales. Provided that the B-mode polarization is due to primordial gravitational waves, this might imply a blue tilt of the primordial gravitational wave spectrum. Such a tilt would be incompatible with standard inflationary models, although it was predicted some years ago in the context of a mechanism that thermally generates the primordial perturbations through a Hagedorn phase of string cosmology. The purpose of this note is to encourage greater scrutiny of the data with priors informed by a model that is immediately falsifiable, but which \\textit{predicts} features that might be favoured by the data-- namely a blue tensor tilt with an induced and complimentary red tilt to the scalar spectrum, with a naturally large tensor to scalar ratio that relates to both.
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.
Introduction to bosonic string theory
Energy Technology Data Exchange (ETDEWEB)
Nunez, Carmen [Instituto de Astronomia y Fisica del Espacio, Buenos Aires (Argentina)], e-mail: carmen@iafe.uba.ar
2009-07-01
This is an introductory set of five lectures on bosonic string theory. The first one deals with the classical theory of bosonic strings. The second and third lectures cover quantization. Three basic quantization methods are sketched: the old covariant formalism, the light-cone gauge quantization, where the spectrum is derived and the Polyakov path integral formalism and in particular the partition function at one loop. Finally, the last lecture covers interactions, low energy effective action, the general idea of compactification and in particular toroidal compactification. The notes are based on books by Green, Schwarz and Witten, Polchinski, Lust and Theissen and Kaku and review papers by D'Hocker and Phong and O. Alvarez. (author)
Statistical Inference and String Theory
Heckman, Jonathan J
2013-01-01
In this note 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 non-linear 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 com...
Schulz, M D; Vidal, J
2016-01-01
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.
Topics in Open Topological Strings
Prudenziati, Andrea
2010-01-01
This thesis is based on some selected topics in open topological string theory which I have worked on during my Ph.D. It comprises an introductory part where I have focused on the points most needed for the later chapters, trading completeness for conciseness and clarity. Then, following [12], we discuss tadpole cancellation for topological strings where we mainly show how its implementation is needed for ensuring the same "odd" moduli decoupling encountered in the closed theory. Next we move to analyse how the open and closed effective field theories for the B model interact writing the complete Lagrangian. We first check it deriving some already known tree level amplitudes in term of target space quantities, and then we extend the recipe to new results; later we implement open closed duality from a target field theory perspective. This last subject is also analysed from a worldsheet point of view extending the analysis of [13]. Some ideas for future research are briefly reported.
Ballonet String Model of Molecules
Directory of Open Access Journals (Sweden)
Gavril NIAC
2008-06-01
Full Text Available Strings of ballonets, modelling rows of orbitals, are assembled to molecule models by crossing them properly. The ballonets at the ends of the strings of 2, 3, 4 or 5 spheres represent bonding orbitals of hydrogen with other elements like C, N or O (the proton being inside the sphere, as well as nonbonding orbitals. The ballonets between them are modelling bonding orbitals among elements other than hydrogen - except the double bond in diborane, the atomic cores laying at the junction of two or more spheres.Advantages of elastic sphere models range from self-adjusting bond angles to resistance when closing cycles like cyclopropane or modeling double bonds.Examples comprise alkanes, including platonic hydrocarbons, ethene, acetylene, and some inorganic molecules.
Polchinski, Joseph
2015-01-01
The search for a theory of quantum gravity faces two great challenges: the incredibly small scales of the Planck length and time, and the possibility that the observed constants of nature are in part the result of random processes. A priori, one might have expected these to be insuperable obstacles. However, clues from observed physics, and the discovery of string theory, raise the hope that the unification of quantum mechanics and general relativity is within reach.
String theory and cosmological singularities
Indian Academy of Sciences (India)
Sumit R Das
2007-07-01
In general relativity space-like or null singularities are common: they imply that `time' can have a beginning or end. Well-known examples are singularities inside black holes and initial or final singularities in expanding or contracting universes. In recent times, string theory is providing new perspectives of such singularities which may lead to an understanding of these in the standard framework of time evolution in quantum mechanics. In this article, we describe some of these approaches.
String networks as tropical curves
Ray, Koushik
2008-01-01
A prescription for obtaining supergravity solutions for planar (p,q)-string networks is presented, based on earlier results. It shows that networks may be looked upon as tropical curves emerging as the spine of the amoeba of a holomorphic curve in M-theory. The Kaehler potential of supergravity is identified with the corresponding Ronkin function. Implications of this identification in counting dyons is discussed.
The Damped String Problem Revisited
Gesztesy, Fritz
2010-01-01
We revisit the damped string equation on a compact interval with a variety of boundary conditions and derive an infinite sequence of trace formulas associated with it, employing methods familiar from supersymmetric quantum mechanics. We also derive completeness and Riesz basis results (with parentheses) for the associated root functions under less smoothness assumptions on the coefficients than usual, using operator theoretic methods (rather than detailed eigenvalue and root function asymptotics) only.
1994-01-01
On 6-7 December 1994, a string of powerful superconducting magnets for CERN's next particle accelerator, the Large Hadron Collider (LHC), ran successfully at 8.36 tesla for 24 hours. This magnetic field is 100 000 times that of the Earth and is required to keep beams of protons travelling on the correct circular path over 27 km at 7 TeV in the new LHC accelerator.
DEFF Research Database (Denmark)
Franceschini, A.; Simonovic, M.; Roth, A.
2013-01-01
networks covering >1100 organisms. Here, we describe the update to version 9.1 of STRING, introducing several improvements: (i) we extend the automated mining of scientific texts for interaction information, to now also include full-text articles; (ii) we entirely re-designed the algorithm for transferring...... interactions from one model organism to the other; and (iii) we provide users with statistical information on any functional enrichment observed in their networks. © The Author(s) 2012....