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Author |
Bombacigno, F.; Boudet, S.; Montani, G. |
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Title |
Generalized Ashtekar variables for Palatini f(R) models |
Type |
Journal Article |
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Year |
2021 |
Publication |
Nuclear Physics B |
Abbreviated Journal |
Nucl. Phys. B |
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Volume |
963 |
Issue |
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Pages |
115281 - 21pp |
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Abstract |
We consider special classes of Palatini f(R) theories, featured by additional Loop Quantum Gravity inspired terms, with the aim of identifying a set of modified Ashtekar canonical variables, which still preserve the SU(2) gauge structure of the standard theory. In particular, we allow for affine connection to be endowed with torsion, which turns out to depend on the additional scalar degree affecting Palatini f( R) gravity, and in this respect we successfully construct a novel Gauss constraint. We analyze the role of the additional scalar field, outlining as it acquires a dynamical character by virtue of a non vanishing Immirzi parameter, and we describe some possible effects on the area operator stemming from such a revised theoretical framework. Finally, we compare our results with earlier studies in literature, discussing differences between metric and Palatini approaches. It is worth noting how the Hamiltonian turns out to be different in the two cases. The results can be reconciled when the analysis is performed in the Einstein frame. |
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Address |
[Bombacigno, Flavio] Univ Valencia, CSIC, Ctr Mixto, Dept Fis Teor, Valencia 46100, Spain, Email: flavio.bombacigno@ext.uv.es; |
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Elsevier |
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English |
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ISSN |
0550-3213 |
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Notes |
WOS:000613579500003 |
Approved |
no |
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Is ISI |
yes |
International Collaboration |
yes |
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Call Number |
IFIC @ pastor @ |
Serial |
4706 |
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Author |
Moretti, F.; Bombacigno, F.; Montani, G. |
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Title |
Gravitational Landau damping for massive scalar modes |
Type |
Journal Article |
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Year |
2020 |
Publication |
European Physical Journal C |
Abbreviated Journal |
Eur. Phys. J. C |
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Volume |
80 |
Issue |
12 |
Pages |
1203 - 9pp |
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Abstract |
We establish the possibility of Landau damping for gravitational scalar waves which propagate in a non-collisional gas of particles. In particular, under the hypothesis of homogeneity and isotropy, we describe the medium at the equilibrium with a Juttner-Maxwell distribution, and we analytically determine the damping rate from the Vlasov equation. We find that damping occurs only if the phase velocity of the wave is subluminal throughout the propagation within the medium. Finally, we investigate relativistic media in cosmological settings by adopting numerical techniques. |
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Address |
[Moretti, Fabio; Montani, Giovanni] Sapienza Univ Rome, Phys Dept, Ple Aldo Moro 5, I-00185 Rome, Italy, Email: fabio.moretti@uniroma1.it; |
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Publisher |
Springer |
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English |
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ISSN |
1434-6044 |
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Notes |
WOS:000615196900004 |
Approved |
no |
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Is ISI |
yes |
International Collaboration |
yes |
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Call Number |
IFIC @ pastor @ |
Serial |
4707 |
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Author |
Boudet, S.; Bombacigno, F.; Montani, G.; Rinaldi, M. |
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Title |
Superentropic black hole with Immirzi hair |
Type |
Journal Article |
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Year |
2021 |
Publication |
Physical Review D |
Abbreviated Journal |
Phys. Rev. D |
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Volume |
103 |
Issue |
8 |
Pages |
084034 - 14pp |
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Abstract |
In the context of f(R) generalizations to the Hoist action, endowed with a dynamical Immirzi field, we derive an analytic solution describing asymptotically anti-de Sitter black holes with hyperbolic horizon. These exhibit a scalar hair of the second kind, which ultimately depends on the Immirzi field radial behavior. In particular, we show how the Immirzi field modifies the usual entropy law associated to the black hole. We also verify that the Immirzi field boils down to a constant value in the asymptotic region, thus restoring the standard loop quantum gravity picture. We finally prove the violation of the reverse isoperimetric inequality, resulting in the superentropic nature of the black hole, and we discuss in detail the thermodynamic stability of the solution. |
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Address |
[Boudet, Simon; Rinaldi, Massimiliano] Univ Trento, Dipartimento Fis, Via Sommar 14, I-38123 Povo, TN, Italy, Email: simon.boudet@unitn.it; |
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Publisher |
Amer Physical Soc |
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English |
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ISSN |
2470-0010 |
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Expedition |
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Conference |
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Notes |
WOS:000649081100011 |
Approved |
no |
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Is ISI |
yes |
International Collaboration |
yes |
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Call Number |
IFIC @ pastor @ |
Serial |
4833 |
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Permanent link to this record |
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Author |
Bombacigno, F.; Boudet, S.; Olmo, G.J.; Montani, G. |
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Title |
Big bounce and future time singularity resolution in Bianchi I cosmologies: The projective invariant Nieh-Yan case |
Type |
Journal Article |
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Year |
2021 |
Publication |
Physical Review D |
Abbreviated Journal |
Phys. Rev. D |
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Volume |
103 |
Issue |
12 |
Pages |
124031 |
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Keywords |
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Abstract |
We extend the notion of the Nieh-Yan invariant to generic metric-affine geometries, where both torsion and nonmetricity are taken into account. Notably, we show that the properties of projective invariance and topologicity can be independently accommodated by a suitable choice of the parameters featuring this new Nieh-Yan term. We then consider a special class of modified theories of gravity able to promote the Immirzi parameter to a dynamical scalar field coupled to the Nieh-Yan form, and we discuss in more detail the dynamics of the effective scalar tensor theory stemming from such a revised theoretical framework. We focus, in particular, on cosmological Bianchi I models and we derive classical solutions where the initial singularity is safely removed in favor of a big bounce, which is ultimately driven by the nonminimal coupling with the Immirzi field. These solutions, moreover, turn out to be characterized by finite time singularities, but we show that such critical points do not spoil the geodesic completeness and wave regularity of these spacetimes. |
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Series Volume |
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Series Issue |
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ISSN |
2470-0010 |
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Expedition |
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Conference |
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Notes |
WOS:000661819200005 |
Approved |
no |
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Is ISI |
yes |
International Collaboration |
yes |
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Call Number |
IFIC @ pastor @ |
Serial |
4870 |
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Permanent link to this record |
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Author |
Magalhaes, R.B.; Maso-Ferrando, A.S.; Bombacigno, F.; Olmo, G.J.; Crispino, L.C.B. |
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Title |
Echoes from bounded universes |
Type |
Journal Article |
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Year |
2024 |
Publication |
Physical Review D |
Abbreviated Journal |
Phys. Rev. D |
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Volume |
110 |
Issue |
4 |
Pages |
044058 - 21pp |
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Keywords |
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Abstract |
We construct a general class of modified Ellis-Bronnikov wormholes, where one asymptotic Minkowski region is replaced by a bounded 2-sphere core, characterized by an asymptotic finite areal radius. We pursue an in-depth analysis of the resulting geometry, outlining that geodesic completeness is also guaranteed when the area function asymptotically shrinks to zero. Moreover, we perform an analysis of the circular orbits present in our model and conclude that stable circular orbits are allowed in the bounded region. As a consequence, a stable light ring may exist in the inner region and trapped orbits may appear within this bounded region. Such internal structure suggests that the bounded region can trap perturbations. Then, we study the evolution of scalar perturbations, bringing out how these geometric configurations can in principle affect the time-domain profiles of quasinormal modes, pointing out the distinctive features with respect to other black hole or wormhole geometries. |
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Address |
[Magalhaes, Renan B.; Crispino, Luis C. B.] Univ Fed Para, Programa Posgrad Fis, BR-66075110 Belem, PA, Brazil, Email: renan.magalhaes@icen.ufpa.br; |
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Corporate Author |
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Thesis |
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Publisher |
Amer Physical Soc |
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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Series Title |
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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 |
2470-0010 |
ISBN |
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Medium |
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Area |
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Expedition |
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Conference |
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Notes |
WOS:001306781100003 |
Approved |
no |
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Is ISI |
yes |
International Collaboration |
yes |
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Call Number |
IFIC @ pastor @ |
Serial |
6260 |
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Permanent link to this record |