Robert Brandenberger, Andrew M. Matheson · Modern Physics Letters A · 1987
We calculate the rate of decay of cosmic string loops into fermions and bosons, at zero and non-zero temperatures, taking the back reaction of the string on itself into account. The decay rate is controlled by the radius of curvature of the string. We find that with the exception of decays into massless scalar fields at high temperatures, the decay rate is completely negligible for cosmologically interesting string loops, when compared to gravitational energy loss.
Cited by 12
K. R. P. Sjödin · The Ninth Marcel Grossmann Meeting · 2002
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Kim, Nakwoo, Kim, Yoonbai, Kimm, Kyoungtae · arXiv (Cornell University) · 1997
Global U(1) strings with cylindrical symmetry are studied in anti-de Sitter spacetime. According as the magnitude of negative cosmological constant, they form regular global cosmic strings, extremal black cosmic strings and charged black cosmic strings, but no curvature singularity is involved. The relationship between the topological charge of a neutral global string and the black hole charge is clarified by duality transformation. Physical relevance as straight string is briefly discussed.
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Robert F. Penna · ArXiv.org · 2025
We describe a new tunneling solution for the decay of a cosmic string into a burst of gravitational waves. We find the relevant instanton and compute the tunneling rate. Locally, our solution is just an analytic continuation of the Kerr metric (but there is no black hole in our solution). An interesting feature of our result is that there is a conical singularity in the initial state but there is no singularity in the final state. This demonstrates that singularities can disappear in quantum gravity in ways that are impossible in classical gravity.
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Achucarro, A., Salmi, P., Urrestilla, J. · arXiv (Cornell University) · 2005
We report on a large scale numerical study of networks of semilocal cosmic strings in flat space in the parameter regime in which they are perturbatively stable. We find a population of segments with an exponential length distribution and indications of a scaling network without significant loop formation. Very deep in the stability regime strings of superhorizon size grow rapidly and ``percolate'' through the box. We believe these should lead at late times to a population of infinite strings similar to topologically stable strings. However, the strings are very light; scalar gradients dominate the energy density and the network has thus a global texture-like signature. As a result, the observational constraints, at least from the temperature power spectrum of the CMB, on models predicting semilocal strings, should be closer to those on global textures or monopoles, rather than on topologically stable gauged cosmic strings.
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Basilis C. Xanthopoulos · Physics Letters B · 1986
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Robert J. Scherrer, William H. Press · Physical review. D. Particles, fields, gravitation, and cosmology/Physical review. D. Particles and fields · 1989
We present the results of a numerical simulation of the fragmentation of single cosmic-string loops in flat spacetime. The analytic solution for the motion of the fragmenting loop is derived, and this solution is followed forward to determine the trajectories of the daughter loops. We find that loop fragmentation is not stochastic; the loop fragmentation probability decreases with fragmentation generation, and a universal loop fragmentation probability is not well defined. All of the loops sampled eventually reached nonintersecting trajectories. We see no evidence for fragmentation down to arbitrarily tiny loops. The final loop size distribution is approximately a lognormal distribution. The mean final loop velocity is v\ensuremath{\sim}0.6c.
Cited by 32
José J. Blanco-Pillado, Ken D. Olum, Benjamin Shlaer · Physical review. D. Particles, fields, gravitation, and cosmology/Physical review. D, Particles, fields, gravitation, and cosmology · 2015
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 backreaction, 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 cusplike 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.
Cited by 48Open access
Nakwoo Kim, Yoonbai Kim, Kyoungtae Kimm · Classical and Quantum Gravity · 1998
Global U(1) strings with cylindrical symmetry are studied in anti-de Sitter spacetime. According as the magnitude of negative cosmological constant, they form regular global cosmic strings, extremal black cosmic strings and charged black cosmic strings, but no curvature singularity is involved. The relationship between the topological charge of a neutral global string and the black hole charge is clarified by duality transformation. Physical relevance as straight string is briefly discussed.
Cited by 7Open access
José J. Blanco-Pillado, Borja Reina, Kepa Sousa et al. · Journal of Cosmology and Astroparticle Physics · 2014
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.
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J. S. Dowker · Classical and Quantum Gravity · 1987
A string in the Einstein universe is defined by making the polar angle have period beta . The Green function of a massless scalar field is derived and the vacuum average of the energy-momentum tensor is calculated.
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Laliberté, Samuel · eScholarship@McGill (McGill) · 2020
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David N. Spergel, William H. Press, Robert J. Scherrer · Nature · 1988
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Anthony van Dalen, David N. Schramm · The Astrophysical Journal · 1988
We calculate analytically the typical peculiar velocities on scales from 10h^-1^ to 60h^-1^ Mpc with cosmic string loops as the dominant source of primordial gravitational perturbations. From this we calculate the joint probability of finding steaming velocities of at least 600 km s^-1^ on large scales and local peculiar velocities of less than 800 km s^-1^. We consider a range in the parameters of βGμ appropriate for both hot (HDM) and cold (CDM) dark matter scenarios. An {OMEGA} = 1 CDM universe is assumed with the loops randomly placed on a smooth background. It is shown how the effects can be estimated of loops breaking up and being born with a spectrum of sizes. It is found that to obtain large-scale streaming velocities of at least 600 km s^-1^ it is necessary that either a large value for βGμ or the effect of loop fissioning and production details be considerable. For CDM with Gμ = 10^-6^, β = 9, the maximum joint probability is 7% and requires the parent size spectrum to be 18 times larger than the evolved daughter spectrum. The string induced velocity spectrum is relatively flat out to scales of 2t_eq_ /a_eq_ and then drops off quickly. The flatness is a signature of string models of galaxy formation. With HDM a larger value of βGμ is necessary for galaxy formation since accretion on small scales starts later. Hence, with HDM the peculiar velocity spectrum will be larger on large scales and the flat region will extend further and lie lower relative to larger scales. A consequence of these effects is that the joint probability can be as much as 5 times larger than in the CDM scenario. If large-scale peculiar velocities greater than 600 km s^-1^ are real, then it is concluded that strings plus CDM have difficulties. The advantages of strings plus HDM in this regard will be explored in greater detail in a later paper.
Cited by 5
Joseph Polchinski · 2008
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Alexander Vilenkin · Physical review. D. Particles, fields, gravitation, and cosmology/Physical review. D. Particles and fields · 1991
Cosmic-string equations of motion are derived with the force of friction due to string-particle scattering taken into account. For strings in a Robertson-Walker space, the additional terms in the equations of motion have the same functional form as the terms due to the expansion of the Universe. As a result, a computer simulation of strings with friction would require only a trivial modification of the existing programs.
Cited by 86
Hou-Jun Mo · 1989
The reionization and the large-scale structure formation of the universe are consi-dered as results of the secondary effects of cosmic string. Primordial supermassive (～10~6M_⊙) stars and star groups M(～10~(10)M_⊙) can be formed immediately after recombinationowning to the accretions of single-string loops. The ultraviolet radiation of the starscan reionize the interstellar medium around them. The explosions of the supermassivestars sweep the interstellar medium to the shock-wave front to form mass shells of largemass and high density; the fragmentations of the mass shells lead to formations of newstars and new explosions. It is shown, when Grand Unification Theory (GUT) stringsare taken to be the seeds, the observed high ionization and large-scale cellular structureof galaxy distribution in the universe can be realized. For the usually chosen parameters,this scenario seems reasonable and imperative.
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Takashi Torii, Kengo Maeda, Makoto Narita et al. · 2001
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Davood Momeni, Sudhaker Upadhyay, Yerlan Myrzakulov et al. · Astrophysics and Space Science · 2017
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Hiramatsu, Takashi, Sendouda, Yuuiti, Takahashi, Keitaro et al. · arXiv (Cornell University) · 2013
We study the network of Type-I cosmic strings using the field-theoretic numerical simulations in the Abelian-Higgs model. For Type-I strings, the gauge field plays an important role, and thus we find that the correlation length of the strings is strongly dependent upon the parameter β, the ratio between the self-coupling constant of the scalar field and the gauge coupling constant, namely, β=λ/2e^2. In particular, if we take the cosmic expansion into account, the network becomes densest in the comoving box for a specific value of βfor β<1.
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