ARE THE COSMIC STRINGS SEEN AS THE DISLOCATIONS?

1991 ◽  
Vol 06 (24) ◽  
pp. 2237-2242 ◽  
Author(s):  
TAKEHIKO T. FUJISHIRO ◽  
MITSUO J. HAYASHI ◽  
SHOJI TAKESHITA
Keyword(s):  
Energy Density ◽  
Effective Action ◽  
Cosmic String ◽  
Cosmic Strings ◽  
Torsion Tensor ◽  
Space Time ◽  
Crystalline Solid ◽  
Dimensional Model ◽  
3 Dimensional ◽  
Deficit Angle

The effective action from the heterotic string compactification is studied on the manifolds with absolute parallelism. The cosmic string solutions resulting from the effective action are discussed in analogy with the dislocations in 3-dimensional crystalline solid. The cosmic string density is concluded to be given by the torsion tensor of space-time, which gives rise to a compactification at least in 1-dimensional direction in space-time. It is also shown that the contorsion tensor defines the deficit angle. We have found a stringy solution in a 6-dimensional model on M4 × T2 which coincides with that of Greene et al.,5 but the string energy density depends only on torsion, therefore independent of the space-time metric.

THE COSMIC STRINGS GENERATED FROM THE TORSION

1993 ◽  
Vol 08 (06) ◽  
pp. 491-501 ◽  
Author(s):  
TAKEHIKO T. FUJISHIRO ◽  
MITSUO J. HAYASHI ◽  
SHOJI TAKESHITA
Keyword(s):  
Cosmic Strings ◽  
Unit Length ◽  
Three Dimensional ◽  
Fine Tuning ◽  
Crystalline Solid ◽  
Dimensional Model ◽  
Einstein Theory ◽  
Maximum Value ◽  
Deficit Angle ◽  
Space Time Structure

The cosmic strings can be described naturally by torsion formalism which has a direct analogy with dislocations in three-dimensional crystalline solid. We have obtained an exact solution in a four-dimensional model on M2×T2 and may be expected to describe a space-time structure of our universe. The relation between the mass per unit length and the deficit angle are different from that of the Einstein theory, but can be made consistent since our model could reproduce its prediction. We could also obtain the maximum value of the mass per unit length µ~10−6(~1022 g/cm ) by fine tuning of a parameter, which is consistent with the recent observations.

EXACT COSMIC STRING SOLUTIONS BASED ON THE CONTINUUM THEORY OF DISLOCATIONS

1994 ◽  
Vol 09 (23) ◽  
pp. 4101-4127 ◽  
Author(s):  
TAKEHIKO T. FUJISHIRO ◽  
MITSUO J. HAYASHI ◽  
SHOJI TAKESHITA
Keyword(s):  
Exact Solution ◽  
Cosmic String ◽  
Cosmic Strings ◽  
Unit Length ◽  
Three Dimensional ◽  
Continuum Theory ◽  
Fine Tuning ◽  
Dimensional Model ◽  
Einstein Theory ◽  
Deficit Angle

The effective action from the string compactification is studied on the manifolds with absolute parallelism. The cosmic strings can be described naturally by torsion formalism which has a direct analogy with dislocations in three-dimensional crystalline solids. We have found a stringy solution in a six-dimensional model on M4 × T2 which is compatible with that of Greene et al. and a cylindrically symmetric exact solution is obtained, which are different from the exact cosmic string solutions of the Einstein theory ever proposed. We have also obtained an exact solution in a four-dimensional model on M2 × T2 which can be considered as an example of the compactification on the noncompact manifold and may be expected to describe a space–time structure of our universe. The relation between the mass per unit length and the deficit angle is different from but can be consistent with that of the Einstein theory, since our solution could reproduce its prediction with a condition. We could also obtain the maximum value of the mass per unit length μ ~ 10−6 (~ 1022 g/cm ) by fine-tuning a parameter, which is consistent with recent observations. We have discussed the cosmic strings with the deficit angle larger than 2π.

scholarly journals Possible imprints of cosmic strings in the shadows of galactic black holes

2014 ◽  
Vol 23 (07) ◽  
pp. 1450060 ◽  
Author(s):  
Vassil K. Tinchev ◽  
Stoytcho S. Yazadjiev
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Cosmic String ◽  
Cosmic Strings ◽  
Kerr Black Hole ◽  
Black Hole Spin ◽  
Deficit Angle ◽  
Spin Parameter ◽  
Shadow Cast

We examine the shadow cast by a Kerr black hole pierced by a cosmic string. The observable images depend not only on the black hole spin parameter and the angle of inclination, but also on the deficit angle yielded by the cosmic string. The dependence of the observable characteristics of the shadow on the deficit angle is explored. The imprints in the black hole shadow left by the presence of a cosmic string can serve in principle as a method for observational detection of such strings.

PARTICLE CREATION BY COSMIC STRINGS

1988 ◽  
Vol 03 (15) ◽  
pp. 1425-1429 ◽  
Author(s):  
VARUN SAHNI
Keyword(s):  
Gravitational Field ◽  
Energy Density ◽  
Quantum Number ◽  
Cosmic String ◽  
Cosmic Strings ◽  
Particle Creation ◽  
Number Density ◽  
Gut Scale ◽  
The Creation ◽  
Angular Quantum Number

The creation of particles by a nonstationary gravitational field during the formation of a straight, static cosmic string has been investigated and the contribution to the number density of created particles from modes with the lowest angular quantum number assessed. It is found that for GUT scale strings the energy density of created particles is many orders of magnitude smaller than the corresponding energy density of radiation at GUT times.

scholarly journals SPACE-TIME VARIABLE SUPERSTRING VACUA (CALABI-YAU COSMIC YARN)

1994 ◽  
Vol 09 (18) ◽  
pp. 3203-3227 ◽  
Author(s):  
PAUL S. GREEN ◽  
TRISTAN HÜBSCH
Keyword(s):  
Superstring Vacua ◽  
Cosmic String ◽  
Cosmic Strings ◽  
Unit Length ◽  
Finite Energy ◽  
Space Time ◽  
Topological Invariant ◽  
Time Variable ◽  
Internal Space ◽  
Lorentzian Case

In a general superstring vacuum configuration, the “internal” space (sector) varies in space-time. When this variation is nontrivial only in two spacelike dimensions, the vacuum contains static cosmic strings with finite energy per unit length and which is, up to interactions with matter, an easily computed topological invariant. The total space-time is smooth although the “internal” space is singular at the center of each cosmic string. In a similar analysis of the Wick-rotated Euclidean model, these cosmic strings acquire expected self-interactions. Also, a possibility emerges to define a global time in order to rotate back to the Lorentzian case.

scholarly journals MAGNETIC MOMENT OF ELECTRONS NEAR COSMIC STRINGS

1994 ◽  
Vol 09 (11) ◽  
pp. 1787-1795
Author(s):  
TAKUYA MAKI ◽  
KIYOSHI SHIRAISHI
Keyword(s):  
Magnetic Moment ◽  
Anomalous Magnetic Moment ◽  
Cosmic String ◽  
Quantum Correction ◽  
Cosmic Strings ◽  
Deficit Angle

We study the effect of background geometry generated by a thin cosmic string on the anomalous magnetic moment of the electron. We find that the magnitude of the quantum correction to the magnetic moment depends on the distance from the cosmic string as well as on the deficit angle.

scholarly journals SPINNING COSMIC STRINGS: A GENERAL CLASS OF SOLUTIONS

2005 ◽  
Vol 20 (13) ◽  
pp. 2821-2832 ◽  
Author(s):  
N. ÖZDEMİR
Keyword(s):  
Exact Solution ◽  
Cosmic String ◽  
General Class ◽  
Symmetry Axis ◽  
Cosmic Strings ◽  
Space Time ◽  
Closed Timelike Curves ◽  
Interior Space ◽  
Theory Of Gravity ◽  
Spin Fluid

In this work, we give a general class of solutions of the spinning cosmic string in Einstein's theory of gravity. After treating same problem in Einstein–Cartan (EC) theory of gravity, the exact solution satisfying both exterior and interior space–times representing a spin fluid moving along the symmetry axis is presented in the EC theory. The existence of closed timelike curves in this space–time are also examined.

scholarly journals Searching for gravitational-wave bursts from cosmic string cusps with the Parkes Pulsar Timing Array

2020 ◽  
Vol 501 (1) ◽  
pp. 701-712
Author(s):  
N Yonemaru ◽  
S Kuroyanagi ◽  
G Hobbs ◽  
K Takahashi ◽  
X-J Zhu ◽  
...  
Keyword(s):  
False Alarm ◽  
Gravitational Wave ◽  
Cosmic String ◽  
Cosmic Strings ◽  
False Alarm Probability ◽  
String Tension ◽  
Detection Algorithm ◽  
Pulsar Timing ◽  
Upper Limits ◽  
Pulsar Timing Array

ABSTRACT Cosmic strings are potential gravitational-wave (GW) sources that can be probed by pulsar timing arrays (PTAs). In this work we develop a detection algorithm for a GW burst from a cusp on a cosmic string, and apply it to Parkes PTA data. We find four events with a false alarm probability less than 1 per cent. However further investigation shows that all of these are likely to be spurious. As there are no convincing detections we place upper limits on the GW amplitude for different event durations. From these bounds we place limits on the cosmic string tension of Gμ ∼ 10−5, and highlight that this bound is independent from those obtained using other techniques. We discuss the physical implications of our results and the prospect of probing cosmic strings in the era of Square Kilometre Array.

The spin-zero Duffin-Kemmer-Petiau equation in a cosmic-string space-time with the Cornell interaction

2016 ◽  
Vol 31 (36) ◽  
pp. 1650191 ◽  
Author(s):  
M. de Montigny ◽  
M. Hosseinpour ◽  
H. Hassanabadi
Keyword(s):  
Gravitational Field ◽  
Coordinate System ◽  
Cosmic String ◽  
Topological Defects ◽  
Space Time ◽  
Dkp Equation

In this paper, we study the covariant Duffin-Kemmer-Petiau (DKP) equation in the cosmic-string space-time and consider the interaction of a DKP field with the gravitational field produced by topological defects in order to examine the influence of topology on this system. We solve the spin-zero DKP oscillator in the presence of the Cornell interaction with a rotating coordinate system in an exact analytical manner for nodeless and one-node states by proposing a proper ansatz solution.

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