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Author Magalhaes, R.B.; Ribeiro, G.P.; Lima, H.C.D.J.; Olmo, G.J.; Crispino, L.C.B.
Title Singular space-times with bounded algebraic curvature scalars Type Journal Article
Year 2024 Publication (up) Journal of Cosmology and Astroparticle Physics Abbreviated Journal J. Cosmol. Astropart. Phys.
Volume 05 Issue 5 Pages 114 - 34pp
Keywords gravity; modified gravity; Wormholes
Abstract We show that the absence of unbounded algebraic curvature invariants constructed from polynomials of the Riemann tensor cannot guarantee the absence of strong singularities. As a consequence, it is not sufficient to rely solely on the analysis of such scalars to assess the regularity of a given space-time. This conclusion follows from the analysis of incomplete geodesics within the internal region of asymmetric wormholes supported by scalar matter which arise in two distinct metric-affine gravity theories. These wormholes have bounded algebraic curvature scalars everywhere, which highlights that their finiteness does not prevent the emergence of pathologies (singularities) in the geodesic structure of space-time. By analyzing the tidal forces in the internal wormhole region, we find that the angular components are unbounded along incomplete radial time-like geodesics. The strength of the singularity is determined by the evolution of Jacobi fields along such geodesics, finding that it is of strong type, as volume elements are torn apart as the singularity is approached. Lastly, and for completeness, we consider the wormhole of the quadratic Palatini theory and present an analysis of the tidal forces in the entire space-time.
Address [Magalhaes, Renan B.; Ribeiro, Gabriel P.; Lima Jr, Haroldo C. D.; Crispino, Luis C. B.] Univ Fed Para, Programa Posgrad Fis, BR-66075110 Belem, Para, Brazil, Email: renan.magalhaes@icen.ufpa.br;
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:001265908300012 Approved no
Is ISI yes International Collaboration yes
Call Number IFIC @ pastor @ Serial 6200
Permanent link to this record
 
 
Author Lessa, L.A.; Olmo, G.J.
Title On the structure of black bounces sourced by anisotropic fluids Type Journal Article
Year 2025 Publication (up) Journal of Cosmology and Astroparticle Physics Abbreviated Journal J. Cosmol. Astropart. Phys.
Volume 03 Issue 3 Pages 019 - 18pp
Keywords Exact solutions; black holes and black hole thermodynamics in GR and beyond; GR black holes; modified gravity; Wormholes
Abstract The field equations of static, spherically symmetric geometries generated by anisotropic fluids is investigated with the aim of better understanding the relation between the matter and the emergence of minimal area throats, like in wormhole and black bounce scenarios. Imposing some simplifying restrictions on the matter, which amounts to considering nonlinear electromagnetic sources, we find analytical expressions that allow one to design the type of sought geometries. We illustrate our analysis with several examples, including an asymmetric, bounded black bounce spacetime which reproduces the standard ReissnerNordstr & ouml;m geometry on the outside all the way down to the throat.
Address [Lessa, L. A.] Univ Fed Maranhao, Programa Posgrad Fis, Campus Univ Bacanga, BR-65080805 Sao Luis, MA, Brazil, Email: leandrophys@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:001443043800001 Approved no
Is ISI yes International Collaboration yes
Call Number IFIC @ pastor @ Serial 6553
Permanent link to this record
 
 
Author Delhom, A.; Olmo, G.J.; Orazi, E.
Title Ricci-Based Gravity theories and their impact on Maxwell and nonlinear electromagnetic models Type Journal Article
Year 2019 Publication (up) Journal of High Energy Physics Abbreviated Journal J. High Energy Phys.
Volume 11 Issue 11 Pages 149 - 24pp
Keywords Classical Theories of Gravity; Beyond Standard Model
Abstract We extend the correspondence between metric-affine Ricci-Based Gravity the- ories and General Relativity (GR) to the case in which the matter sector is represented by linear and nonlinear electromagnetic fields. This complements previous studies focused on fluids and scalar fields. We establish the general algorithm that relates the matter fields in the GR and RBG frames and consider some applications. In particular, we find that the so-called Eddington-inspired Born-Infeld gravity theory coupled to Maxwell electromag- netism is in direct correspondence with GR coupled to Born-Infeld electromagnetism. We comment on the potential phenomenological implications of this relation.
Address [Delhom, Adria; Olmo, Gonzalo J.] Univ Valencia, Dept Fis Teor, E-46100 Valencia, Spain, Email: adria.delhom@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:000513489000001 Approved no
Is ISI yes International Collaboration yes
Call Number IFIC @ pastor @ Serial 4281
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Author Agullo, I.; Navarro-Salas, J.; Olmo, G.J.; Parker, L.
Title Acceleration radiation, transition probabilities and trans-Planckian physics Type Journal Article
Year 2010 Publication (up) New Journal of Physics Abbreviated Journal New J. Phys.
Volume 12 Issue Pages 095017 - 18pp
Keywords
Abstract An important question in the derivation of the acceleration radiation, which also arises in Hawking's derivation of black hole radiance, is the need to invoke trans-Planckian physics in describing the creation of quanta. We point out that this issue can be further clarified by reconsidering the analysis in terms of particle detectors, transition probabilities and local two-point functions. By writing down separate expressions for the spontaneous-and induced-transition probabilities of a uniformly accelerated detector, we show that the bulk of the effect comes from the natural (non-trans-Planckian) scale of the problem, which largely diminishes the importance of the trans-Planckian sector. This is so, at least, when trans-Planckian physics is defined in a Lorentz-invariant way. This analysis also suggests how one can define and estimate the role of trans-Planckian physics in the Hawking effect itself.
Address [Agullo, Ivan; Olmo, Gonzalo J.; Parker, Leonard] Univ Wisconsin, Dept Phys, Milwaukee, WI 53201 USA, Email: ivan.agullo@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 1367-2630 ISBN Medium
Area Expedition Conference
Notes ISI:000284766400006 Approved no
Is ISI yes International Collaboration yes
Call Number IFIC @ elepoucu @ Serial 318
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Author Nascimento, J.R.; Olmo, G.J.; Petrov, A.Y.; Porfirio, P.J.
Title On metric-affine bumblebee model coupled to scalar matter Type Journal Article
Year 2024 Publication (up) Nuclear Physics B Abbreviated Journal Nucl. Phys. B
Volume 1004 Issue Pages 116577 - 10pp
Keywords
Abstract We consider the coupling of the metric-affine bumblebee gravity model to scalar matter and calculate the lower -order contributions to two -point functions of bumblebee and scalar fields in the weak gravity approximation. We also obtain the one -loop effective potentials for both scalar and vector fields.
Address [Nascimento, J. R.; Petrov, A. Yu.; Porfirio, P. J.] Univ Fed Paraiba, Dept Fis, Caixa Postal 5008, BR-58051970 Joao Pessoa, PB, Brazil, Email: jroberto@fisica.ufpb.br;
Corporate Author Thesis
Publisher Elsevier Place of Publication Editor
Language English Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0550-3213 ISBN Medium
Area Expedition Conference
Notes WOS:001248177100001 Approved no
Is ISI yes International Collaboration yes
Call Number IFIC @ pastor @ Serial 6157
Permanent link to this record
 
 
Author Almeida, C.A.S.; Lima, F.C.E.; Mishra, S.S.; Olmo, G.J.; Sahoo, P.K.
Title Thick brane in mimetic-like gravity Type Journal Article
Year 2024 Publication (up) Nuclear Physics B Abbreviated Journal Nucl. Phys. B
Volume 1009 Issue Pages 116747 - 9pp
Keywords
Abstract We analyze a five-dimensional braneworld governed by a mimetic-like gravity, a plausible candidate for explaining dark matter. Within this scenario, we examine Friedmann-Lemaitre-Robertson-Walker (FLRW) branes and find that constant curvature and Minkowskian solutions are possible. We then show that the mimetic model leads to kink-like and lump-like thick brane solutions without the need for spontaneous symmetry breaking. Its stability against small perturbations is also verified.
Address [Almeida, C. A. S.; Lima, F. C. E.; Olmo, Gonzalo J.] Univ Fed Ceara UFC, Dept Fis, Campus Pici, BR-60455760 Fortaleza, CE, Brazil, Email: carlos@fisica.ufc.br;
Corporate Author Thesis
Publisher Elsevier Place of Publication Editor
Language English Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0550-3213 ISBN Medium
Area Expedition Conference
Notes WOS:001362181800001 Approved no
Is ISI yes International Collaboration yes
Call Number IFIC @ pastor @ Serial 6344
Permanent link to this record
 
 
Author Barragan, C.; Olmo, G.J.
Title Isotropic and anisotropic bouncing cosmologies in Palatini gravity Type Journal Article
Year 2010 Publication (up) Physical Review D Abbreviated Journal Phys. Rev. D
Volume 82 Issue 8 Pages 084015 - 15pp
Keywords
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
Corporate Author Thesis
Publisher Amer Physical Soc Place of Publication Editor
Language English Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 1550-7998 ISBN Medium
Area Expedition Conference
Notes ISI:000282751900002 Approved no
Is ISI yes International Collaboration yes
Call Number IFIC @ elepoucu @ Serial 362
Permanent link to this record
 
 
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 (up) Physical Review D Abbreviated Journal Phys. Rev. D
Volume 81 Issue 10 Pages 108502 - 3pp
Keywords
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
Corporate Author Thesis
Publisher Amer Physical Soc Place of Publication Editor
Language English Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 1550-7998 ISBN Medium
Area Expedition Conference
Notes ISI:000278146700144 Approved no
Is ISI yes International Collaboration yes
Call Number IFIC @ elepoucu @ Serial 430
Permanent link to this record
 
 
Author Agullo, I.; Navarro-Salas, J.; Olmo, G.J.; Parker, L.
Title Revising the observable consequences of slow-roll inflation Type Journal Article
Year 2010 Publication (up) Physical Review D Abbreviated Journal Phys. Rev. D
Volume 81 Issue 4 Pages 043514 - 14pp
Keywords
Abstract We study the generation of primordial perturbations in a (single-field) slow-roll inflationary Universe. In momentum space, these (Gaussian) perturbations are characterized by a zero mean and a nonzero variance Delta(2) (k, t). However, in position space the variance diverges in the ultraviolet. The requirement of a finite variance in position space forces one to regularize Delta(2) (k, t). This can (and should) be achieved by proper renormalization in an expanding Universe in a unique way. This affects the predicted scalar and tensorial power spectra (evaluated when the modes acquire classical properties) for wavelengths that today are at observable scales. As a consequence, the imprint of slow-roll inflation on the cosmic microwave background anisotropies is significantly altered. We find a nontrivial change in the consistency condition that relates the tensor-to-scalar ratio r to the spectral indices. For instance, an exact scale-invariant tensorial power spectrum, n(t) = 0, is now compatible with a nonzero ratio r approximate to 0.12 +/- 0.06, which is forbidden by the standard prediction (r = -8n(t)). The influence of relic gravitational waves on the cosmic microwave background may soon come within the range of planned measurements, offering a nontrivial test of the new predictions.
Address [Agullo, Ivan; Olmo, Gonzalo J.; Parker, Leonard] Univ Wisconsin, Dept Phys, Milwaukee, WI 53201 USA, Email: ivan.agullo@uv.es
Corporate Author Thesis
Publisher Amer Physical Soc Place of Publication Editor
Language English Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 1550-7998 ISBN Medium
Area Expedition Conference
Notes ISI:000275898500028 Approved no
Is ISI yes International Collaboration yes
Call Number IFIC @ elepoucu @ Serial 479
Permanent link to this record
 
 
Author Olmo, G.J.; Sanchis-Alepuz, H.
Title Hamiltonian formulation of Palatini f(R) theories a la Brans-Dicke theory Type Journal Article
Year 2011 Publication (up) Physical Review D Abbreviated Journal Phys. Rev. D
Volume 83 Issue 10 Pages 104036 - 11pp
Keywords
Abstract We study the Hamiltonian formulation of f(R) theories of gravity both in metric and in Palatini formalism using their classical equivalence with Brans-Dicke theories with a nontrivial potential. The Palatini case, which corresponds to the omega = -3/2 Brans-Dicke theory, requires special attention because of new constraints associated with the scalar field, which is nondynamical. We derive, compare, and discuss the constraints and evolution equations for the omega = -3/2 and omega not equal -3/2 cases. Based on the properties of the constraint and evolution equations, we find that, contrary to certain claims in the literature, the Cauchy problem for the omega = -3/2 case is well formulated and there is no reason to believe that it is not well posed in general.
Address [Olmo, Gonzalo J.] Univ Valencia, Dept Fis Teor, E-46100 Valencia, Spain, Email: gonzalo.olmo@uv.es
Corporate Author Thesis
Publisher Amer Physical Soc Place of Publication Editor
Language English Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 1550-7998 ISBN Medium
Area Expedition Conference
Notes ISI:000290761400007 Approved no
Is ISI yes International Collaboration yes
Call Number IFIC @ elepoucu @ Serial 631
Permanent link to this record