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 Spinning cosmic strings in conformal gravity

2020 ◽  
Vol 35 (05) ◽  
pp. 2050024
Author(s):  
Reinoud Jan slagter ◽  
Christopher Levi Duston
Keyword(s):  
Cosmic String ◽  
Energy Condition ◽  
Space Time ◽  
Special Choice ◽  
Mass Relation ◽  
Conformal Gravity ◽  
Field Equations ◽  
Closed Timelike Curves ◽  
The Core ◽  
Kerr Space

We investigate the space–time of a spinning cosmic string in conformal invariant gravity, where the interior consists of a gauged scalar field. We find exact solutions of the exterior of a stationary spinning cosmic string, where we write the metric as [Formula: see text], with [Formula: see text] a dilaton field which contains all the scale dependences. The “unphysical” metric [Formula: see text] is related to the [Formula: see text]-dimensional Kerr space–time. The equation for the angular momentum [Formula: see text] decouples, for the vacuum situation as well as for global strings, from the other field equations and delivers a kind of spin-mass relation. For the most realistic solution, [Formula: see text] falls off as [Formula: see text] and [Formula: see text] close to the core. The space–time is Ricci flat. The formation of closed timelike curves can be pushed to space infinity for suitable values of the parameters and the violation of the weak energy condition can be avoided. For the interior, a numerical solution is found. This solution can easily be matched at the boundary on the exterior exact solution by special choice of the parameters of the string. This example shows the power of conformal invariance to bridge the gap between general relativity and quantum field theory.

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.

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.

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 CANCELLATION OF ULTRAVIOLET DIVERGENCES FOR LOCALLY FLAT METRICS

1998 ◽  
Vol 13 (38) ◽  
pp. 3081-3090
Author(s):  
M. HORTAÇSU ◽  
N. ÖZDEMIR
Keyword(s):  
General Class ◽  
Vacuum Polarization ◽  
Cosmic Strings ◽  
Scalar Particle ◽  
Space Time ◽  
Spinor Particle ◽  
Perturbative Calculation ◽  
Massless Field ◽  
The One ◽  
Work Done

We extend the work done for cosmic strings on the perturbative calculation of vacuum polarization of a massless field in the space–time of multiple cosmic strings and show that for a more general class of locally flat metrics, the one-loop calculation does not introduce any new divergences to the vev of the energy of a scalar particle or a spinor particle.

scholarly journals Janis–Newman–Winicour and Wyman Solutions are the Same

1997 ◽  
Vol 12 (27) ◽  
pp. 4831-4835 ◽  
Author(s):  
K. S. Virbhadra
Keyword(s):  
Exact Solution ◽  
Scalar Field ◽  
Total Energy ◽  
Space Time ◽  
Massless Scalar ◽  
Spherically Symmetric ◽  
Scalar Equations

We show that the well-known most general static and spherically symmetric exact solution to the Einstein-massless scalar equations given by Wyman is the same as one found by Janis, Newman and Winicour several years ago. We obtain the energy associated with this space–time and find that the total energy for the case of the purely scalar field is zero.

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.

De la combinatoire du modèle de l'échiquier de Feynman et des fonctions spéciales

1984 ◽  
Vol 62 (7) ◽  
pp. 632-638
Author(s):  
J. G. Williams
Keyword(s):  
Exact Solution ◽  
Dirac Equation ◽  
Hypergeometric Series ◽  
Jacobi Polynomials ◽  
Dimensional Space ◽  
Space Time ◽  
Continuous Limit ◽  
Two Dimensional ◽  
Dimensional Space Time

The exact solution of the Feynman checkerboard model is given both in terms of the hypergeometric series and in terms of Jacobi polynomials. It is shown how this leads, in the continuous limit, to the Dirac equation in two-dimensional space-time.

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