| |
Records |
Links |
|
Author |
Maso-Ferrando, A.; Sanchis-Gual, N.; Font, J.A.; Olmo, G.J. |
|
| |
Title |
Birth of baby universes from gravitational collapse in a modified-gravity scenario |
Type |
Journal Article |
| |
Year |
2023 |
Publication |
Journal of Cosmology and Astroparticle Physics |
Abbreviated Journal |
J. Cosmol. Astropart. Phys. |
|
| |
Volume  |
06 |
Issue |
6 |
Pages |
028 - 19pp |
|
| |
Keywords |
modified gravity; Wormholes |
|
| |
Abstract |
We consider equilibrium models of spherical boson stars in Palatini f (R) = R + CR2 gravity and study their collapse when perturbed. The Einstein-Klein-Gordon system is solved using a recently established correspondence in an Einstein frame representation. We find that, in that frame, the endpoint is a nonrotating black hole surrounded by a quasi -stationary cloud of scalar field. However, the dynamics in the f (R) frame is dramatically different. The innermost region of the collapsing object exhibits the formation of a finite -size, exponentially-expanding baby universe connected with the outer (parent) universe via a minimal area surface (a throat or umbilical cord). Our simulations indicate that this surface is at all times hidden inside a horizon, causally disconnecting the baby universe from observers above the horizon. The implications of our findings in other areas of gravitational physics are also discussed. |
|
| |
Address |
[Maso-Ferrando, Andreu; Olmo, Gonzalo J.] Univ Valencia, Ctr Mixto, CSIC, Dept Fis Teor, Valencia 46100, Spain, Email: andreu.maso@uv.es; |
|
| |
Corporate Author |
|
Thesis |
|
|
| |
Publisher |
IOP Publishing Ltd |
Place of Publication |
|
Editor |
|
|
| |
Language |
English |
Summary Language |
|
Original Title |
|
|
| |
Series Editor |
|
Series Title |
|
Abbreviated Series Title |
|
|
| |
Series Volume |
|
Series Issue |
|
Edition |
|
|
| |
ISSN |
1475-7516 |
ISBN |
|
Medium |
|
|
| |
Area |
|
Expedition |
|
Conference |
|
|
| |
Notes |
WOS:001025474200010 |
Approved |
no |
|
| |
Is ISI |
yes |
International Collaboration |
yes |
|
| |
Call Number |
IFIC @ pastor @ |
Serial |
5577 |
|
| Permanent link to this record |
| |
|
| |
|
Author |
Delhom, A.; Olmo, G.J.; Singh, P. |
|
| |
Title |
A diffeomorphism invariant family of metric-affine actions for loop cosmologies |
Type |
Journal Article |
| |
Year |
2023 |
Publication |
Journal of Cosmology and Astroparticle Physics |
Abbreviated Journal |
J. Cosmol. Astropart. Phys. |
|
| |
Volume |
06 |
Issue |
6 |
Pages |
059 - 21pp |
|
| |
Keywords |
quantum cosmology; modified gravity; cosmic singularity |
|
| |
Abstract |
In loop quantum cosmology (LQC) the big bang singularity is generically resolved by a big bounce. This feature holds even when modified quantization prescriptions of the Hamiltonian constraint are used such as in mLQC-I and mLQC-II. While the later describes an effective description qualitatively similar to that of standard LQC, the former describes an asymmetric evolution with an emergent Planckian de-Sitter pre-bounce phase even in the absence of a potential. We consider the potential relation of these canonically quantized non-singular models with effective actions based on a geometric description. We find a 3-parameter family of metric-affine f (R) theories which accurately approximate the effective dynamics of LQC and mLQC-II in all regimes and mLQC-I in the post-bounce phase. Two of the parameters are fixed by enforcing equivalence at the bounce, and the background evolution of the relevant observables can be fitted with only one free parameter. It is seen that the non-perturbative effects of these loop cosmologies are universally encoded by a logarithmic correction that only depends on the bounce curvature of the model. In addition, we find that the best fit value of the free parameter can be very approximately written in terms of fundamental parameters of the underlying quantum description for the three models. The values of the best fits can be written in terms of the bounce density in a simple manner, and the values for each model are related to one another by a proportionality relation involving only the Barbero-Immirzi parameter. |
|
| |
Address |
[Delhom, Adria; Singh, Parampreet] Louisiana State Univ, Dept Phys & Astron, Baton Rouge, LA 70803 USA, Email: adria.delhom@gmail.com; |
|
| |
Corporate Author |
|
Thesis |
|
|
| |
Publisher |
IOP Publishing Ltd |
Place of Publication |
|
Editor |
|
|
| |
Language |
English |
Summary Language |
|
Original Title |
|
|
| |
Series Editor |
|
Series Title |
|
Abbreviated Series Title |
|
|
| |
Series Volume |
|
Series Issue |
|
Edition |
|
|
| |
ISSN |
1475-7516 |
ISBN |
|
Medium |
|
|
| |
Area |
|
Expedition |
|
Conference |
|
|
| |
Notes |
WOS:001025410500003 |
Approved |
no |
|
| |
Is ISI |
yes |
International Collaboration |
yes |
|
| |
Call Number |
IFIC @ pastor @ |
Serial |
5583 |
|
| Permanent link to this record |
| |
|
| |
|
Author |
Galli, P.; Meessen, P.; Ortin, T. |
|
| |
Title |
The Freudenthal gauge symmetry of the black holes of N=2, d=4 supergravity |
Type |
Journal Article |
| |
Year |
2013 |
Publication |
Journal of High Energy Physics |
Abbreviated Journal |
J. High Energy Phys. |
|
| |
Volume |
05 |
Issue |
5 |
Pages |
011 - 15pp |
|
| |
Keywords |
Black Holes; String Duality; Gauge Symmetry; Supergravity Models |
|
| |
Abstract |
We show that the representation of black-hole solutions in terms of the variables H-M which are harmonic functions in the supersymmetric case is non-unique due to the existence of a local symmetry in the effective action. This symmetry is a continuous (and local) generalization of the discrete Freudenthal transformations initially introduced for the black-hole charges and can be used to rewrite the physical fields of a solution in terms of entirely different-looking functions. |
|
| |
Address |
[Galli, Pietro] Univ Valencia, Dept Fis Teor, E-46100 Burjassot, Valencia, Spain, Email: Pietro.Galli@ific.uv.es; |
|
| |
Corporate Author |
|
Thesis |
|
|
| |
Publisher |
Springer |
Place of Publication |
|
Editor |
|
|
| |
Language |
English |
Summary Language |
|
Original Title |
|
|
| |
Series Editor |
|
Series Title |
|
Abbreviated Series Title |
|
|
| |
Series Volume |
|
Series Issue |
|
Edition |
|
|
| |
ISSN |
1029-8479 |
ISBN |
|
Medium |
|
|
| |
Area |
|
Expedition |
|
Conference |
|
|
| |
Notes |
WOS:000321374400011 |
Approved |
no |
|
| |
Is ISI |
yes |
International Collaboration |
no |
|
| |
Call Number |
IFIC @ pastor @ |
Serial |
1555 |
|
| Permanent link to this record |
| |
|
| |
|
Author |
Boudet, S.; Bombacigno, F.; Olmo, G.J.; Porfirio, P. |
|
| |
Title |
Quasinormal modes of Schwarzschild black holes in projective invariant Chern-Simons modified gravity |
Type |
Journal Article |
| |
Year |
2022 |
Publication |
Journal of Cosmology and Astroparticle Physics |
Abbreviated Journal |
J. Cosmol. Astropart. Phys. |
|
| |
Volume |
05 |
Issue |
5 |
Pages |
032 - 29pp |
|
| |
Keywords |
Gauss-Bonnet-Lovelock-Horndeski-Palatini etc gravity theories; Exact solutions; black holes and black hole thermodynamics in GR and beyond |
|
| |
Abstract |
We generalize the Chern-Simons modified gravity to the metric-affine case and impose projective invariance by supplementing the Pontryagin density with homothetic curvature terms which do not spoil topologicity. The latter is then broken by promoting the coupling of the Chern-Simons term to a (pseudo)-scalar field. The solutions for torsion and nonmetricity are derived perturbatively, showing that they can be iteratively obtained from the background fields. This allows us to describe the dynamics for the metric and the scalar field perturbations in a self-consistent way, and we apply the formalism to the study of quasi normal modes in a Schwarzschild black hole background. Unlike in the metric formulation of this theory, we show that the scalar field is endowed with dynamics even in the absence of its kinetic term in the action. Finally, using numerical methods we compute the quasinormal frequencies and characterize the late-time power law tails for scalar and metric perturbations, comparing the results with the outcomes of the purely metric approach. |
|
| |
Address |
[Boudet, S.] Univ Trento, Dipartimento Fis, Via Sommar 14, I-38123 Povo, TN, Italy, Email: simon.boudet@unitn.it; |
|
| |
Corporate Author |
|
Thesis |
|
|
| |
Publisher |
IOP Publishing Ltd |
Place of Publication |
|
Editor |
|
|
| |
Language |
English |
Summary Language |
|
Original Title |
|
|
| |
Series Editor |
|
Series Title |
|
Abbreviated Series Title |
|
|
| |
Series Volume |
|
Series Issue |
|
Edition |
|
|
| |
ISSN |
1475-7516 |
ISBN |
|
Medium |
|
|
| |
Area |
|
Expedition |
|
Conference |
|
|
| |
Notes |
WOS:000804493000004 |
Approved |
no |
|
| |
Is ISI |
yes |
International Collaboration |
yes |
|
| |
Call Number |
IFIC @ pastor @ |
Serial |
5238 |
|
| Permanent link to this record |
| |
|
| |
|
Author |
Capozziello, S.; Harko, T.; Koivisto, T.S.; Lobo, F.S.N.; Olmo, G.J. |
|
| |
Title |
Cosmology of hybrid metric-Palatini f(X)-gravity |
Type |
Journal Article |
| |
Year |
2013 |
Publication |
Journal of Cosmology and Astroparticle Physics |
Abbreviated Journal |
J. Cosmol. Astropart. Phys. |
|
| |
Volume |
04 |
Issue |
4 |
Pages |
011 - 25pp |
|
| |
Keywords |
modified gravity; dark energy theory |
|
| |
Abstract |
A new class of modified theories of gravity, consisting of the superposition of the metric Einstein-Hilbert Lagrangian with an f(R) term constructed a la Palatini was proposed recently. The dynamically equivalent scalar-tensor representation of the model was also formulated, and it was shown that even if the scalar field is very light, the theory passes the Solar System observational constraints. Therefore the model predicts the existence of a long-range scalar field, modifying the cosmological and galactic dynamics. An explicit model that passes the local tests and leads to cosmic acceleration was also obtained. In the present work, it is shown that the theory can be also formulated in terms of the quantity X equivalent to kappa T-2 + R, where T and R are the traces of the stress-energy and Ricci tensors, respectively. The variable X represents the deviation with respect to the field equation trace of general relativity. The cosmological applications of this hybrid metric-Palatini gravitational theory are also explored, and cosmological solutions coming from the scalar-tensor representation of f(X)-gravity are presented. Criteria to obtain cosmic acceleration are discussed and the field equations are analyzed as a dynamical system. Several classes of dynamical cosmological solutions, depending on the functional form of the effective scalar field potential, describing both accelerating and decelerating Universes are explicitly obtained. Furthermore, the cosmological perturbation equations are derived and applied to uncover the nature of the propagating scalar degree of freedom and the signatures these models predict in the large-scale structure. |
|
| |
Address |
Univ Naples Federico II, Dipartimento Fis, Naples, Italy, Email: capozzie@na.infn.it; |
|
| |
Corporate Author |
|
Thesis |
|
|
| |
Publisher |
Iop Publishing Ltd |
Place of Publication |
|
Editor |
|
|
| |
Language |
English |
Summary Language |
|
Original Title |
|
|
| |
Series Editor |
|
Series Title |
|
Abbreviated Series Title |
|
|
| |
Series Volume |
|
Series Issue |
|
Edition |
|
|
| |
ISSN |
1475-7516 |
ISBN |
|
Medium |
|
|
| |
Area |
|
Expedition |
|
Conference |
|
|
| |
Notes |
WOS:000318556200011 |
Approved |
no |
|
| |
Is ISI |
yes |
International Collaboration |
yes |
|
| |
Call Number |
IFIC @ pastor @ |
Serial |
1444 |
|
| Permanent link to this record |
