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Author |
Capozziello, S.; Harko, T.; Koivisto, T.S.; Lobo, F.S.N.; Olmo, G.J. |
![goto web page (via DOI) doi](img/doi.gif)
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Title |
The virial theorem and the dark matter problem in hybrid metric-Palatini gravity |
Type |
Journal Article |
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Year |
2013 |
Publication |
Journal of Cosmology and Astroparticle Physics |
Abbreviated Journal |
J. Cosmol. Astropart. Phys. |
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Volume |
07 |
Issue ![sorted by Issue field, ascending order (up)](img/sort_asc.gif) |
7 |
Pages |
024 - 19pp |
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Keywords |
modified gravity; dark matter theory; galaxy clusters |
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Abstract |
Hybrid metric-Palatini gravity is a recently proposed theory, consisting of the superposition of the metric Einstein-Hilbert Lagrangian with an f(R) term constructed a la Palatini. The theory predicts the existence of a long-range scalar field, which passes the Solar System observational constraints, even if the scalar field is very light, and modifies the cosmological and galactic dynamics. Thus, the theory opens new possibilities to approach, in the same theoretical framework, the problems of both dark energy and dark matter. In this work, we consider the generalized virial theorem in the scalar-tensor representation of the hybrid metric-Palatini gravity. More specifically, taking into account the relativistic collisionless Boltzmann equation, we show that the supplementary geometric terms in the gravitational field equations provide an effective contribution to the gravitational potential energy. We show that the total virial mass is proportional to the effective mass associated with the new terms generated by the effective scalar field, and the baryonic mass. In addition to this, we also consider astrophysical applications of the model and show that the model predicts that the mass associated to the scalar field and its effects extend beyond the virial radius of the clusters of galaxies. In the context of the galaxy cluster velocity dispersion profiles predicted by the hybrid metric-Palatini model, the generalized virial theorem can be an efficient tool in observationally testing the viability of this class of generalized gravity models. |
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Address |
[Capozziello, Salvatore] Univ Naples Federico II, Dipartimento Sci Fis, Naples, Italy, Email: capozzie@na.infn.it; |
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Publisher |
Iop Publishing Ltd |
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English |
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ISSN |
1475-7516 |
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Expedition |
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Conference |
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Notes |
WOS:000322582000025 |
Approved |
no |
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Is ISI |
yes |
International Collaboration |
yes |
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Call Number |
IFIC @ pastor @ |
Serial |
1531 |
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Permanent link to this record |
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Author |
Lobo, F.S.N.; Olmo, G.J.; Rubiera-Garcia, D. |
![goto web page (via DOI) doi](img/doi.gif)
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Title |
Semiclassical geons as solitonic black hole remnants |
Type |
Journal Article |
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Year |
2013 |
Publication |
Journal of Cosmology and Astroparticle Physics |
Abbreviated Journal |
J. Cosmol. Astropart. Phys. |
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Volume |
07 |
Issue ![sorted by Issue field, ascending order (up)](img/sort_asc.gif) |
7 |
Pages |
011 - 10pp |
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Keywords |
modified gravity; primordial black holes; Wormholes; quantum field theory on curved space |
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Abstract |
We find that the end state of black hole evaporation could be represented by non-singular and without event horizon stable solitonic remnants with masses of the order the Planck scale and up to similar to 16 units of charge. Though these objects are locally indistinguishable from spherically symmetric, massive electric (or magnetic) charges, they turn out to be sourceless geons containing a wormhole generated by the electromagnetic field. Our results are obtained by interpreting semiclassical corrections to Einstein's theory in the first-order (Palatini) formalism, which yields second-order equations and avoids the instabilities of the usual (metric) formulation of quadratic gravity. We also discuss the potential relevance of these solutions for primordial black holes and the dark matter problem. |
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Address |
[Lobo, Francisco S. N.] Univ Lisbon, Ctr Astron & Astrofis, P-1749016 Lisbon, Portugal, Email: flobo@cii.fc.ul.pt; |
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Publisher |
Iop Publishing Ltd |
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English |
Summary Language |
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Abbreviated Series Title |
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ISSN |
1475-7516 |
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Conference |
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Notes |
WOS:000322582000012 |
Approved |
no |
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Is ISI |
yes |
International Collaboration |
yes |
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Call Number |
IFIC @ pastor @ |
Serial |
1532 |
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Permanent link to this record |
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Author |
Lopez-Honorez, L.; Mena, O.; Palomares-Ruiz, S.; Vincent, A.C. |
![goto web page (via DOI) doi](img/doi.gif)
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Title |
Constraints on dark matter annihilation from CMB observations before Planck |
Type |
Journal Article |
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Year |
2013 |
Publication |
Journal of Cosmology and Astroparticle Physics |
Abbreviated Journal |
J. Cosmol. Astropart. Phys. |
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Volume |
07 |
Issue ![sorted by Issue field, ascending order (up)](img/sort_asc.gif) |
7 |
Pages |
046 - 26pp |
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Keywords |
dark matter theory; CMBR theory |
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Abstract |
We compute the bounds on the dark matter (DM) annihilation cross section using the most recent Cosmic Microwave Background measurements from WMAP9, SPT'11 and ACT'10. We consider DM with mass in the MeV-TeV range annihilating 100% into either an e(+)e(-) or a mu(+)mu(-) pair. We consider a realistic energy deposition model, which includes the dependence on the redshift, DM mass and annihilation channel. We exclude the canonical thermal relic abundance cross section (<sigma nu > = 3 x 10(-26) cm(3)s(-1)) for DM masses below 30 GeV and 15 GeV for the e(+)e(-) and mu(+)mu(-) channels, respectively. A priori, DM annihilating in halos could also modify the reionization history of the Universe at late times. We implement a realistic halo model taken from results of state-of-the-art N-body simulations and consider a mixed reionization mechanism, consisting on reionization from DM as well as from first stars. We find that the constraints on DM annihilation remain unchanged, even when large uncertainties on the halo model parameters are considered. |
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Address |
[Lopez-Honorez, Laura] Vrije Univ Brussel, B-1050 Brussels, Belgium, Email: llopezho@vub.ac.be; |
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Publisher |
Iop Publishing Ltd |
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English |
Summary Language |
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ISSN |
1475-7516 |
ISBN |
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Conference |
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Notes |
WOS:000322582000047 |
Approved |
no |
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Is ISI |
yes |
International Collaboration |
yes |
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Call Number |
IFIC @ pastor @ |
Serial |
1533 |
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Permanent link to this record |
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Author |
Aristizabal Sierra, D.; Tortola, M.; Valle, J.W.F.; Vicente, A. |
![goto web page (via DOI) doi](img/doi.gif)
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Title |
Leptogenesis with a dynamical seesaw scale |
Type |
Journal Article |
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Year |
2014 |
Publication |
Journal of Cosmology and Astroparticle Physics |
Abbreviated Journal |
J. Cosmol. Astropart. Phys. |
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Volume |
07 |
Issue ![sorted by Issue field, ascending order (up)](img/sort_asc.gif) |
7 |
Pages |
052 - 20pp |
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Keywords |
leptogenesis; baryon asymmetry; particle physics – cosmology connection; neutrino theory |
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Abstract |
In the simplest type-I seesaw leptogenesis scenario right-handed neutrino annihilation processes are absent. However, in the presence of new interactions these processes are possible and can affect the resulting B – L asymmetry in an important way. A prominent example is provided by models with spontaneous lepton number violation, where the existence of new dynamical degrees of freedom can play a crucial role. In this context, we provide a model-independent discussion of the effects of right-handed neutrino annihilations. We show that in the weak washout regime, as long as the scattering processes remain slow compared with the Hubble expansion rate throughout the relevant temperature range, the efficiency can be largely enhanced, reaching in some cases maximal values. Moreover, the B – L asymmetry yield turns out to be independent upon initial conditions, in contrast to the “standard” case. On the other hand, when the annihilation processes are fast, the right-handed neutrino distribution tends to a thermal one down to low temperatures, implying a drastic suppression of the efficiency which in some cases can render the B – L generation mechanism inoperative. |
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Address |
[Sierra, D. Aristizabal; Vicente, A.] Univ Liege, IFPA, Dept Astrophys Geophys & Oceanog, B-4000 Liege, Belgium, Email: daristizabal@ulg.ac.be; |
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Corporate Author |
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Thesis |
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Publisher |
Iop Publishing Ltd |
Place of Publication |
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Language |
English |
Summary Language |
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Original Title |
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Series Editor |
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Abbreviated Series Title |
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Series Volume |
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ISSN |
1475-7516 |
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Conference |
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Notes |
WOS:000339802700053 |
Approved |
no |
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Is ISI |
yes |
International Collaboration |
yes |
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Call Number |
IFIC @ pastor @ |
Serial |
1868 |
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Permanent link to this record |
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Author |
de Salas, P.F.; Pastor, S. |
![goto web page (via DOI) doi](img/doi.gif)
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Title |
Relic neutrino decoupling with flavour oscillations revisited |
Type |
Journal Article |
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Year |
2016 |
Publication |
Journal of Cosmology and Astroparticle Physics |
Abbreviated Journal |
J. Cosmol. Astropart. Phys. |
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Volume |
07 |
Issue ![sorted by Issue field, ascending order (up)](img/sort_asc.gif) |
7 |
Pages |
051 - 18pp |
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Keywords |
cosmological neutrinos; particle physics – cosmology connection; physics of the; early universe; neutrino properties |
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Abstract |
We study the decoupling process of neutrinos in the early universe in the presence of three-flavour oscillations. The evolution of the neutrino spectra is found by solving the corresponding momentum-dependent kinetic equations for the neutrino density matrix, including for the first time the proper collision integrals for both diagonal and off-diagonal elements. This improved calculation modifies the evolution of the off-diagonal elements of the neutrino density matrix and changes the deviation from equilibrium of the frozen neutrino spectra. However, it does not vary the contribution of neutrinos to the cosmological energy density in the form of radiation, usually expressed in terms of the effective number of neutrinos, N-eff. We find a value of N-eff = 3.045, in agreement with previous theoretical calculations and consistent with the latest analysis of Planck data. This result does not depend on the ordering of neutrino masses. We also consider the effect of non-standard neutrino-electron interactions (NSI), predicted in many theoretical models where neutrinos acquire mass. For two sets of NSI parameters allowed by present data, we find that Neff can be reduced down to 3.040 or enhanced up to 3.059. |
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Address |
[de Salas, Pablo F.; Pastor, Sergio] Univ Valencia, CSIC, Inst Fis Corpuscular, Parc Cient UV,C Catedrat Jose Beltran 2, E-46980 Paterna, Valencia, Spain, Email: pabrerde@ific.uv.es; |
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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 |
1475-7516 |
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:000381830000052 |
Approved |
no |
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Is ISI |
yes |
International Collaboration |
no |
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Call Number |
IFIC @ pastor @ |
Serial |
2784 |
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Permanent link to this record |