| Records |
| Author |
Bazeia, D.; Losano, L.; Menezes, R.; Olmo, G.J.; Rubiera-Garcia, D. |
| Title |
Thick brane in f(R) gravity with Palatini dynamics |
Type |
Journal Article |
| Year |
2015 |
Publication |
European Physical Journal C |
Abbreviated Journal |
Eur. Phys. J. C |
| Volume |
75 |
Issue |
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Pages |
569 - 10pp |
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| Abstract |
This work deals with modified gravity in five dimensional spacetime. We study a thick Palatini f(R) brane, that is, a braneworld scenario described by an anti-de Sitter warped geometry with a single extra dimension of infinite extent, sourced by real scalar field under the Palatini approach, where the metric and the connection are regarded as independent degrees of freedom. We consider a first-order framework which we use to provide exact solutions for the scalar field and warp factor. We also investigate a perturbative scenario such that the Palatini approach is implemented through a Lagrangian f(R)=R+ϵR^n, where the small parameter ϵ controls the deviation from the standard thick brane case. |
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no |
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yes |
International Collaboration |
yes |
| Call Number |
IFIC @ pastor @ |
Serial |
2592 |
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| Author |
Bombacigno, F.; Boudet, S.; Olmo, G.J.; Montani, G. |
| Title |
Big bounce and future time singularity resolution in Bianchi I cosmologies: The projective invariant Nieh-Yan case |
Type |
Journal Article |
| Year |
2021 |
Publication |
Physical Review D |
Abbreviated Journal |
Phys. Rev. D |
| Volume |
103 |
Issue |
12 |
Pages |
124031 |
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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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2470-0010 |
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| Notes |
WOS:000661819200005 |
Approved |
no |
| Is ISI |
yes |
International Collaboration |
yes |
| Call Number |
IFIC @ pastor @ |
Serial |
4870 |
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| Author |
Agullo, I.; Navarro-Salas, J.; Olmo, G.J.; Parker, L. |
| Title |
Hawking Radiation by Kerr Black Holes and Conformal Symmetry |
Type |
Journal Article |
| Year |
2010 |
Publication |
Physical Review Letters |
Abbreviated Journal |
Phys. Rev. Lett. |
| Volume |
105 |
Issue |
21 |
Pages |
211305 - 4pp |
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The exponential blueshift associated with the event horizon of a black hole makes conformal symmetry play a fundamental role in accounting for its thermal properties. Using a derivation based on two-point functions, we show that the full spectrum of thermal radiation of scalar particles by Kerr black holes can be explicitly derived on the basis of a conformal symmetry arising in the wave equation near the horizon. The simplicity of our approach emphasizes the depth of the connection between conformal symmetry and black hole radiance. |
| Address |
[Agullo, Ivan; Parker, Leonard] Univ Wisconsin, Dept Phys, Milwaukee, WI 53201 USA |
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Amer Physical Soc |
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English |
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0031-9007 |
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ISI:000284407400004 |
Approved |
no |
| Is ISI |
yes |
International Collaboration |
yes |
| Call Number |
IFIC @ elepoucu @ |
Serial |
322 |
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| Author |
Barragan, C.; Olmo, G.J. |
| Title |
Isotropic and anisotropic bouncing cosmologies in Palatini gravity |
Type |
Journal Article |
| Year |
2010 |
Publication |
Physical Review D |
Abbreviated Journal |
Phys. Rev. D |
| Volume |
82 |
Issue |
8 |
Pages |
084015 - 15pp |
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| Abstract |
We study isotropic and anisotropic (Bianchi I) cosmologies in Palatini f(R) and f(R, R μnu R μnu) theories of gravity with a perfect fluid and consider the existence of nonsingular bouncing solutions in the early universe. We find that all f(R) models with isotropic bouncing solutions develop shear singularities in the anisotropic case. On the contrary, the simple quadratic model R + aR(2)/R-P + R μnu R μnu/R-P exhibits regular bouncing solutions in both isotropic and anisotropic cases for a wide range of equations of state, including dust (for a<0) and radiation (for arbitrary a). It thus represents a purely gravitational solution to the big bang singularity and anisotropy problems of general relativity without the need for exotic (w>1) sources of matter/energy or extra degrees of freedom. |
| Address |
[Barragan, Carlos] Univ Autonoma Madrid, Dept Fis Teor, E-28049 Madrid, Spain, Email: gonzalo.olmo@uv.es |
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Amer Physical Soc |
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English |
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1550-7998 |
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| Notes |
ISI:000282751900002 |
Approved |
no |
| Is ISI |
yes |
International Collaboration |
yes |
| Call Number |
IFIC @ elepoucu @ |
Serial |
362 |
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| Author |
Agullo, I.; Navarro-Salas, J.; Olmo, G.J.; Parker, L. |
| Title |
Reply to "Comment on 'Insensitivity of Hawking radiation to an invariant Planck-scale cutoff' '' |
Type |
Journal Article |
| Year |
2010 |
Publication |
Physical Review D |
Abbreviated Journal |
Phys. Rev. D |
| Volume |
81 |
Issue |
10 |
Pages |
108502 - 3pp |
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| Abstract |
We clarify the relationship between the conclusions of the previous Comment of A. Helfer [A. Helfer, preceding Comment, Phys. Rev. D 81, 108501 (2010)] and that of our Brief Report [I. Agullo, J. Navarro-Salas, G. J. Olmo, and L. Parker, Phys. Rev. D 80, 047503 (2009).]. |
| Address |
[Agullo, Ivan; Olmo, Gonzalo J.; Parker, Leonard] Univ Wisconsin, Dept Phys, Milwaukee, WI 53201 USA |
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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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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 |
1550-7998 |
ISBN |
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Conference |
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| Notes |
ISI:000278146700144 |
Approved |
no |
| Is ISI |
yes |
International Collaboration |
yes |
| Call Number |
IFIC @ elepoucu @ |
Serial |
430 |
| Permanent link to this record |
