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Author |
Clement, G.; Fabbri, A. |
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Title |
A scenario for critical scalar field collapse in AdS(3) |
Type |
Journal Article |
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Year |
2015 |
Publication |
Classical and Quantum Gravity |
Abbreviated Journal |
Class. Quantum Gravity |
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Volume |
32 |
Issue |
9 |
Pages |
095009 - 16pp |
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Keywords |
critical collapse; exact solutions; AdS(3) |
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Abstract |
We present a family of exact solutions, depending on two parameters alpha and b (related to the scalar field strength), to the three-dimensional Einstein-scalar field equations with negative cosmological constant Lambda. For b not equal 0 these solutions reduce to the static Banados-Teitelboim-Zanelli (BTZ) family of vacuum solutions, with mass M = -alpha. For b not equal 0, the solutions become dynamical and develop a strong spacelike central singularity. The alpha < 0 solutions are black-hole like, with a global structure topologically similar to that of the BTZ black holes, and a finite effective mass. We show that the near-singularity behavior of the solutions with alpha > 0 agrees qualitatively with that observed in numerical simulations of sub-critical collapse, including the independence of the near-critical regime on the angle deficit of the spacetime. We analyze in the Lambda = 0 approximation the linear perturbations of the self-similar threshold solution, alpha = 0, and find that it has only one unstable growing mode, which qualifies it as a candidate critical solution for scalar field collapse. |
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Address  |
[Clement, Gerard] Univ Savoie, CNRS, LAPTh, F-74941 Annecy Le Vieux, France, Email: gerard.clement@lapth.cnrs.fr; |
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Iop Publishing Ltd |
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English |
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0264-9381 |
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Notes |
WOS:000353351500009 |
Approved |
no |
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Is ISI |
yes |
International Collaboration |
yes |
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Call Number |
IFIC @ pastor @ |
Serial |
2192 |
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Author |
Di Valentino, E.; Mena, O.; Pan, S.; Visinelli, L.; Yang, W.Q.; Melchiorri, A.; Mota, D.F.; Riess, A.G.; Silk, J. |
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Title |
In the realm of the Hubble tension – a review of solutions |
Type |
Journal Article |
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Year |
2021 |
Publication |
Classical and Quantum Gravity |
Abbreviated Journal |
Class. Quantum Gravity |
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Volume |
38 |
Issue |
15 |
Pages |
153001 - 110pp |
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Keywords |
cosmological parameters; cosmology; dark energy; Hubble constant |
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Abstract |
The simplest ΛCDM model provides a good fit to a large span of cosmological data but harbors large areas of phenomenology and ignorance. With the improvement of the number and the accuracy of observations, discrepancies among key cosmological parameters of the model have emerged. The most statistically significant tension is the 4 sigma to 6 sigma disagreement between predictions of the Hubble constant, H (0), made by the early time probes in concert with the 'vanilla' ΛCDM cosmological model, and a number of late time, model-independent determinations of H (0) from local measurements of distances and redshifts. The high precision and consistency of the data at both ends present strong challenges to the possible solution space and demands a hypothesis with enough rigor to explain multiple observations-whether these invoke new physics, unexpected large-scale structures or multiple, unrelated errors. A thorough review of the problem including a discussion of recent Hubble constant estimates and a summary of the proposed theoretical solutions is presented here. We include more than 1000 references, indicating that the interest in this area has grown considerably just during the last few years. We classify the many proposals to resolve the tension in these categories: early dark energy, late dark energy, dark energy models with 6 degrees of freedom and their extensions, models with extra relativistic degrees of freedom, models with extra interactions, unified cosmologies, modified gravity, inflationary models, modified recombination history, physics of the critical phenomena, and alternative proposals. Some are formally successful, improving the fit to the data in light of their additional degrees of freedom, restoring agreement within 1-2 sigma between Planck 2018, using the cosmic microwave background power spectra data, baryon acoustic oscillations, Pantheon SN data, and R20, the latest SH0ES Team Riess, et al (2021 Astrophys. J. 908 L6) measurement of the Hubble constant (H (0) = 73.2 +/- 1.3 km s(-1) Mpc(-1) at 68% confidence level). However, there are many more unsuccessful models which leave the discrepancy well above the 3 sigma disagreement level. In many cases, reduced tension comes not simply from a change in the value of H (0) but also due to an increase in its uncertainty due to degeneracy with additional physics, complicating the picture and pointing to the need for additional probes. While no specific proposal makes a strong case for being highly likely or far better than all others, solutions involving early or dynamical dark energy, neutrino interactions, interacting cosmologies, primordial magnetic fields, and modified gravity provide the best options until a better alternative comes along. |
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Address |
[Di Valentino, Eleonora] Univ Durham, Inst Particle Phys Phenomenol, Dept Phys, Durham DH1 3LE, England, Email: eleonora.di-valentino@durham.ac.uk |
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Publisher |
Iop Publishing Ltd |
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English |
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ISSN |
0264-9381 |
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Notes |
WOS:000672148200001 |
Approved |
no |
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Is ISI |
yes |
International Collaboration |
yes |
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Call Number |
IFIC @ pastor @ |
Serial |
4931 |
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Author |
Fernandez-Silvestre, D.; Foo, J.; Good, M.R.R. |
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Title |
On the duality of Schwarzschild-de Sitter spacetime and moving mirror |
Type |
Journal Article |
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Year |
2022 |
Publication |
Classical and Quantum Gravity |
Abbreviated Journal |
Class. Quantum Gravity |
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Volume |
39 |
Issue |
5 |
Pages |
055006 - 18pp |
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Keywords |
QFT in curved spacetime; black holes; cosmological horizons; moving mirrors |
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Abstract |
The Schwarzschild-de Sitter (SdS) metric is the simplest spacetime solution in general relativity with both a black hole event horizon and a cosmological event horizon. Since the Schwarzschild metric is the most simple solution of Einstein's equations with spherical symmetry and the de Sitter metric is the most simple solution of Einstein's equations with a positive cosmological constant, the combination in the SdS metric defines an appropriate background geometry for semi-classical investigation of Hawking radiation with respect to past and future horizons. Generally, the black hole temperature is larger than that of the cosmological horizon, so there is heat flow from the smaller black hole horizon to the larger cosmological horizon, despite questions concerning the definition of the relative temperature of the black hole without a measurement by an observer sitting in an asymptotically flat spacetime. Here we investigate the accelerating boundary correspondence of the radiation in SdS spacetime without such a problem. We have solved for the boundary dynamics, energy flux and asymptotic particle spectrum. The distribution of particles is globally non-thermal while asymptotically the radiation reaches equilibrium. |
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Address |
[Fernandez-Silvestre, Diego] Univ Valencia, CSIC, Dept Fis Teor, C Dr Moliner 50, Burjassot 46100, Spain, Email: diefer2@alumni.uv.es; |
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IOP Publishing Ltd |
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English |
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0264-9381 |
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Notes |
WOS:000754064600001 |
Approved |
no |
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Is ISI |
yes |
International Collaboration |
yes |
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Call Number |
IFIC @ pastor @ |
Serial |
5130 |
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Author |
Beltran Jimenez, J.; de Andres, D.; Delhom, A. |
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Title |
Anisotropic deformations in a class of projectively-invariant metric-affine theories of gravity |
Type |
Journal Article |
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Year |
2020 |
Publication |
Classical and Quantum Gravity |
Abbreviated Journal |
Class. Quantum Gravity |
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Volume |
37 |
Issue |
22 |
Pages |
225013 - 25pp |
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Keywords |
alternative theories of gravity; metric-affine gravity; anisotropic solutions |
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Abstract |
Among the general class of metric-affine theories of gravity, there is a special class conformed by those endowed with a projective symmetry. Perhaps the simplest manner to realise this symmetry is by constructing the action in terms of the symmetric part of the Ricci tensor. In these theories, the connection can be solved algebraically in terms of a metric that relates to the spacetime metric by means of the so-called deformation matrix that is given in terms of the matter fields. In most phenomenological applications, this deformation matrix is assumed to inherit the symmetries of the matter sector so that in the presence of an isotropic energy-momentum tensor, it respects isotropy. In this work we discuss this condition and, in particular, we show how the deformation matrix can be anisotropic even in the presence of isotropic sources due to the non-linear nature of the equations. Remarkably, we find that Eddington-inspired-Born-Infeld (EiBI) theories do not admit anisotropic deformations, but more general theories do. However, we find that the anisotropic branches of solutions are generally prone to a pathological physical behaviour. |
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Address |
[Jimenez, Jose Beltran] Univ Salamanca, Dept Fis Fundamental, E-37008 Salamanca, Spain, Email: jose.beltran@usal.es; |
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Publisher |
Iop Publishing Ltd |
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English |
Summary Language |
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Series Editor |
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ISSN |
0264-9381 |
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Notes |
WOS:000580878200001 |
Approved |
no |
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Is ISI |
yes |
International Collaboration |
no |
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Call Number |
IFIC @ pastor @ |
Serial |
4576 |
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Author |
Lledo, M.A.; Sommovigo, L. |
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Title |
Torsion formulation of gravity |
Type |
Journal Article |
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Year |
2010 |
Publication |
Classical and Quantum Gravity |
Abbreviated Journal |
Class. Quantum Gravity |
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Volume |
27 |
Issue |
6 |
Pages |
065014 - 16pp |
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Keywords |
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Abstract |
We explain precisely what it means to have a connection with torsion as a solution of the Einstein equations. While locally the theory remains the same, the new formulation allows for topologies that would have been excluded in the standard formulation of gravity. In this formulation it is possible to couple arbitrary torsion to gauge fields without breaking the gauge invariance. |
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Address |
[Lledo, M. A.; Sommovigo, L.] Univ Valencia, Dept Fis Teor, E-46100 Valencia, Spain, Email: Maria.Lledo@ific.uv.es |
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Corporate Author |
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Thesis |
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Publisher |
Iop Publishing Ltd |
Place of Publication |
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Editor |
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Language |
English |
Summary Language |
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Original Title |
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Series Editor |
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Abbreviated Series Title |
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Series Volume |
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Series Issue |
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Edition |
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ISSN |
0264-9381 |
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Conference |
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Notes |
ISI:000275120600015 |
Approved |
no |
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Is ISI |
yes |
International Collaboration |
yes |
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Call Number |
IFIC @ elepoucu @ |
Serial |
498 |
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