cosmic string
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2022 ◽  
Vol 105 (2) ◽  
Author(s):  
Guillaume Boileau ◽  
Alexander C. Jenkins ◽  
Mairi Sakellariadou ◽  
Renate Meyer ◽  
Nelson Christensen

2022 ◽  
Vol 08 (01) ◽  
pp. 85-96
Author(s):  
Gabriela Coutinho de Carvalho ◽  
Maria Emília Xavier Guimarães ◽  
Pablo Oliveira Mesquita ◽  
Joaquim Lopes Neto

2022 ◽  
Vol 2022 (01) ◽  
pp. 010
Author(s):  
S. Bellucci ◽  
W. Oliveira dos Santos ◽  
E.R. Bezerra de Mello ◽  
A.A. Saharian

Abstract We investigate topological effects of a cosmic string and compactification of a spatial dimension on the vacuum expectation value (VEV) of the energy-momentum tensor for a fermionic field in (4+1)-dimensional locally AdS spacetime. The contribution induced by the compactification is explicitly extracted by using the Abel-Plana summation formula. The mean energy-momentum tensor is diagonal and the vacuum stresses along the direction perpendicular to the AdS boundary and along the cosmic string are equal to the energy density. All the components are even periodic functions of the magnetic fluxes inside the string core and enclosed by compact dimension, with the period equal to the flux quantum. The vacuum energy density can be either positive or negative, depending on the values of the parameters and the distance from the string. The topological contributions in the VEV of the energy-momentum tensor vanish on the AdS boundary. Near the string the effects of compactification and gravitational field are weak and the leading term in the asymptotic expansion coincides with the corresponding VEV in (4+1)-dimensional Minkowski spacetime. At large distances, the decay of the cosmic string induced contribution in the vacuum energy-momentum tensor, as a function of the proper distance from the string, follows a power law. For a cosmic string in the Minkowski bulk and for massive fields the corresponding fall off is exponential. Within the framework of the AdS/CFT correspondence, the geometry for conformal field theory on the AdS boundary corresponds to the standard cosmic string in (3+1)-dimensional Minkowski spacetime compactified along its axis.


2021 ◽  
Vol 104 (12) ◽  
Author(s):  
David Maibach ◽  
Robert Brandenberger ◽  
Devin Crichton ◽  
Alexandre Refregier
Keyword(s):  

2021 ◽  
Vol 104 (12) ◽  
Author(s):  
Robert Brandenberger ◽  
Bryce Cyr ◽  
Hao Jiao

2021 ◽  
Vol 2021 ◽  
pp. 1-15
Author(s):  
Márcio M. Cunha ◽  
Edilberto O. Silva

In this manuscript, we study the relativistic quantum mechanics of an electron in external fields in the spinning cosmic string spacetime. We obtain the Dirac equation and write the first- and second-order equations from it, and then, we solve these equations for bound states. We show that there are bound state solutions for the first-order equation Dirac. For the second-order equation, we obtain the corresponding wave functions, which depend on the Kummer functions. Then, we determine the energies of the particle. We examine the behavior of the energies as a function of the physical parameters of the model, such as rotation, curvature, magnetic field, Aharonov-Bohm flux, and quantum numbers. We find that, depending on the values of these parameters, there are energy nonpermissible levels.


Universe ◽  
2021 ◽  
Vol 7 (11) ◽  
pp. 437
Author(s):  
Yi-Zen Chu ◽  
Yen-Wei Liu

Cherenkov radiation may occur whenever the source is moving faster than the waves it generates. In a radiation dominated universe, with equation-of-state w=1/3, we have recently shown that the Bardeen scalar-metric perturbations contribute to the linearized Weyl tensor in such a manner that its wavefront propagates at acoustic speed w=1/3. In this work, we explicitly compute the shape of the Bardeen Cherenkov cone and wedge generated respectively by a supersonic point mass (approximating a primordial black hole) and a straight Nambu-Goto wire (approximating a cosmic string) moving perpendicular to its length. When the black hole or cosmic string is moving at ultra-relativistic speeds, we also calculate explicitly the sudden surge of scalar-metric induced tidal forces on a pair of test particles due to the passing Cherenkov shock wave. These forces can stretch or compress, depending on the orientation of the masses relative to the shock front’s normal.


2021 ◽  
Vol 2021 (10) ◽  
Author(s):  
Stephen F. King ◽  
Silvia Pascoli ◽  
Ye-Ling Zhou ◽  
Jessica Turner

Abstract Grand Unified Theories (GUT) predict proton decay as well as the formation of cosmic strings which can generate gravitational waves. We determine which non-supersymmetric SO(10) breaking chains provide gauge unification in addition to a gravitational signal from cosmic strings. We calculate the GUT and intermediate scales for these SO(10) breaking chains by solving the renormalisation group equations at the two-loop level. This analysis predicts the GUT scale, hence the proton lifetime, in addition to the scale of cosmic string generation and thus the associated gravitational wave signal. We determine which SO(10) breaking chains survive in the event of the null results of the next generation of gravitational waves and proton decay searches and determine the correlations between proton decay and gravitational waves scales if these observables are measured.


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