| Records |
| Author |
Delhom, A.; Lobo, I.P.; Olmo, G.J.; Romero, C. |
| Title |
Conformally invariant proper time with general non-metricity |
Type |
Journal Article |
| Year |
2020 |
Publication |
European Physical Journal C |
Abbreviated Journal |
Eur. Phys. J. C |
| Volume |
80 |
Issue |
5 |
Pages |
415 - 11pp |
| Keywords |
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| Abstract |
We show that the definition of proper time for Weyl-invariant space-times given by Perlick naturally extends to spaces with arbitrary non-metricity. We then discuss the relation between this generalized proper time and the Ehlers-Pirani-Schild definition of time when there is arbitrary non-metricity. Then we show how this generalized proper time suffers from a second clock effect. Assuming that muons are a device to measure this proper time, we constrain the non-metricity tensor on Earth's surface and then elaborate on the feasibility of such assumption. |
| Address |
[Delhom, Adria] Univ Valencia, Ctr Mixto Univ Valencia, Dept Fis Teor, CSIC, Valencia 46100, Spain, Email: adria.delhom@uv.es; |
| Corporate Author |
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Thesis |
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| Publisher |
Springer |
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 |
1434-6044 |
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:000535820900011 |
Approved |
no |
| Is ISI |
yes |
International Collaboration |
yes |
Call Number  |
IFIC @ pastor @ |
Serial |
4405 |
| Permanent link to this record |
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| Author |
Olmo, G.J.; Rubiera-Garcia, D.; Wojnar, A. |
| Title |
Stellar structure models in modified theories of gravity: Lessons and challenges |
Type |
Journal Article |
| Year |
2020 |
Publication |
Physics Reports |
Abbreviated Journal |
Phys. Rep. |
| Volume |
876 |
Issue |
|
Pages |
1-75 |
| Keywords |
Stellar structure; Modified gravity; Palatini formalism; Neutron stars; Brown dwarfs; Relativistic stars; Weak field; f(R) theories; Born-Infeld theory; Horndeski theory |
| Abstract |
The understanding of stellar structure represents the crossroads of our theories of the nuclear force and the gravitational interaction under the most extreme conditions observably accessible. It provides a powerful probe of the strong field regime of General Relativity, and opens fruitful avenues for the exploration of new gravitational physics. The latter can be captured via modified theories of gravity, which modify the Einstein-Hilbert action of General Relativity and/or some of its principles. These theories typically change the Tolman-Oppenheimer-Volkoff equations of stellar's hydrostatic equilibrium, thus having a large impact on the astrophysical properties of the corresponding stars and opening a new window to constrain these theories with present and future observations of different types of stars. For relativistic stars, such as neutron stars, the uncertainty on the equation of state of matter at supranuclear densities intertwines with the new parameters coming from the modified gravity side, providing a whole new phenomenology for the typical predictions of stellar structure models, such as mass-radius relations, maximum masses, or moment of inertia. For non-relativistic stars, such as white, brown and red dwarfs, the weakening/strengthening of the gravitational force inside astrophysical bodies via the modified Newtonian (Poisson) equation may induce changes on the star's mass, radius, central density or luminosity, having an impact, for instance, in the Chandrasekhar's limit for white dwarfs, or in the minimum mass for stable hydrogen burning in high-mass brown dwarfs. This work aims to provide a broad overview of the main such results achieved in the recent literature for many such modified theories of gravity, by combining the results and constraints obtained from the analysis of relativistic and non-relativistic stars in different scenarios. Moreover, we will build a bridge between the efforts of the community working on different theories, formulations, types of stars, theoretical modelings, and observational aspects, highlighting some of the most promising opportunities in the field. |
| Address |
[Olmo, Gonzalo J.] Univ Valencia, Dept Fis Teor, Ctr Mixto, CSIC, Valencia 46100, Spain, Email: gonzalo.olmo@uv.es; |
| Corporate Author |
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Thesis |
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| Publisher |
Elsevier |
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 |
0370-1573 |
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:000570298900001 |
Approved |
no |
| Is ISI |
yes |
International Collaboration |
yes |
| Call Number |
IFIC @ pastor @ |
Serial |
4531 |
| Permanent link to this record |
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| Author |
Olmo, G.J.; Rubiera-Garcia, D. |
| Title |
Junction conditions in Palatini f(R) gravity |
Type |
Journal Article |
| Year |
2020 |
Publication |
Classical and Quantum Gravity |
Abbreviated Journal |
Class. Quantum Gravity |
| Volume |
37 |
Issue |
21 |
Pages |
215002 - 11pp |
| Keywords |
f(R) gravity; junction conditions; Palatini approach; stellar structure |
| Abstract |
We work out the junction conditions for f(R) gravity formulated in metric-affine (Palatini) spaces using a tensor distributional approach. These conditions are needed for building consistent models of gravitating bodies with an interior and exterior regions matched at some hypersurface. Some of these conditions depart from the standard Darmois-Israel ones of general relativity and from their metric f(R) counterparts. In particular, we find that the trace of the stress-energy momentum tensor in the bulk must be continuous across the matching hypersurface, though its normal derivative need not to. We illustrate the relevance of these conditions by considering the properties of stellar surfaces in polytropic models, showing that the range of equations of state with potentially pathological effects is shifted beyond the domain of physical interest. This confirms, in particular, that neutron stars and white dwarfs can be safely modelled within the Palatini f(R) framework. |
| Address |
[Olmo, Gonzalo J.] Univ Valencia, Ctr Mixto Univ Valencia, CSIC, Dept Fis Teor, Valencia 46100, Spain, Email: gonzalo.olmo@uv.es; |
| 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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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 |
0264-9381 |
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:000575326000001 |
Approved |
no |
| Is ISI |
yes |
International Collaboration |
yes |
| Call Number |
IFIC @ pastor @ |
Serial |
4555 |
| Permanent link to this record |
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| Author |
Lobo, F.S.N.; Olmo, G.J.; Orazi, E.; Rubiera-Garcia, D.; Rustam, A. |
| Title |
Structure and stability of traversable thin-shell wormholes in Palatini f(R) gravity |
Type |
Journal Article |
| Year |
2020 |
Publication |
Physical Review D |
Abbreviated Journal |
Phys. Rev. D |
| Volume |
102 |
Issue |
10 |
Pages |
104012 - 11pp |
| Keywords |
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| Abstract |
We study the structure and stability of traversable wormholes built as (spherically symmetric) thin shells in the context of Palatini f(R) gravity. Using a suitable junction formalism for these theories we find that the effective number of degrees of freedom on the shell is reduced to a single one, which fixes the equation of state to be that of massless stress-energy fields, contrary to the general relativistic and metric f(R) cases. Another major difference is that the surface energy density threading the thin shell, needed in order to sustain the wormhole, can take any sign and may even vanish, depending on the desired features of the corresponding solutions. We illustrate our results by constructing thin-shell wormholes by surgically grafting Schwarzschild space-times and show that these configurations are always linearly unstable. However, surgically joined Reissner-Nordstrom space-times allow for linearly stable, traversable thin-shell wormholes supported by a positive energy density provided that the (squared) mass-to-charge ratio, given by y = Q(2)/M-2, satisfies the constraint 1 < y < 9/8 (corresponding to overcharged Reissner-Nordstrom configurations having a photon sphere) and lies in a region bounded by specific curves defined in terms of the (dimensionless) radius of the shell x(0) = R/M. |
| Address |
[Lobo, Francisco S. N.] Univ Lisbon, Fac Ciencias, Inst Astrofis & Ciencias Espaco, Edificio C8,Campo Grande, P-1749016 Lisbon, Portugal, Email: fslobo@fc.ul.pt; |
| 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:000587286200006 |
Approved |
no |
| Is ISI |
yes |
International Collaboration |
yes |
| Call Number |
IFIC @ pastor @ |
Serial |
4596 |
| Permanent link to this record |
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| Author |
Olmo, G.J.; Orazi, E.; Rubiera-Garcia, D. |
| Title |
Multicenter solutions in Eddington-inspired Born-Infeld gravity |
Type |
Journal Article |
| Year |
2020 |
Publication |
European Physical Journal C |
Abbreviated Journal |
Eur. Phys. J. C |
| Volume |
80 |
Issue |
11 |
Pages |
1018 - 13pp |
| Keywords |
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| Abstract |
We find multicenter (Majumdar-Papapetrou type) solutions of Eddington-inspired Born-Infeld gravity coupled to electromagnetic fields governed by a Born-Infeld-like Lagrangian. We construct the general solution for an arbitrary number of centers in equilibrium and then discuss the properties of their one-particle configurations, including the existence of bounces and the regularity (geodesic completeness) of these spacetimes. Our method can be used to construct multicenter solutions in other theories of gravity. |
| Address |
[Olmo, Gonzalo J.] Univ Valencia, Dept Fis Teor, Ctr Mixto Univ Valencia, CSIC, Valencia 46100, Spain, Email: gonzalo.olmo@uv.es; |
| Corporate Author |
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Thesis |
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| Publisher |
Springer |
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 |
1434-6044 |
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:000590064800001 |
Approved |
no |
| Is ISI |
yes |
International Collaboration |
yes |
| Call Number |
IFIC @ pastor @ |
Serial |
4611 |
| Permanent link to this record |
