Imprint of f ( R ) gravity in the cosmic magnification Duniya, Didam G A; Abebe, Amare; de la Cruz-Dombriz, Álvaro ...
Monthly Notices of the Royal Astronomical Society,
02/2023, Letnik:
518, Številka:
4
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ABSTRACT
f(R) gravity is one of the simplest viable modifications to General Relativity: it passes local astrophysical tests, predicts both the early-time cosmic inflation and the late-time cosmic ...acceleration, and describes dark matter. In this paper, we probe cosmic magnification on large scales in f(R) gravity, using the well-known Hu-Sawicki model as an example. Our results indicate that at redshifts $z \, {\lt }\, 3$, values of the model exponent $n \, {\gt }\, 1$ lead to inconsistent behaviour in the evolution of the scalar perturbations. Moreover, when relativistic effects are taken into account in the large-scale analysis, our results show that as z increases, large-scale changes in the cosmic magnification angular power spectrum owing to integral values of n tend to share a similar pattern, while those of decimal values tend to share another. This feature could be searched for in the experimental data, as a potential ‘smoking gun’ for the given class of gravity models. Furthermore, we found that at $z \, {=}\, 1$ and lower, relativistic effects lead to a suppression of the cosmic magnification on large scales in f(R) gravity, relative to the concordance model; whereas, at $z \, {\gt }\, 1$, relativistic effects lead to a relative boost of the cosmic magnification. In general, relativistic effects enhance the potential of the cosmic magnification as a cosmological probe.
Dark matter candidate from torsion de la Cruz Dombriz, Álvaro; Maldonado Torralba, Francisco José; Mota, David F.
Physics letters. B,
11/2022, Letnik:
834
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The stable pseudo-scalar degree of freedom of the quadratic Poincaré Gauge theory of gravity is shown to be a suitable dark matter candidate. We find the parameter space of the theory which can ...account for all the predicted cold dark matter, and constrain such parameters with astrophysical observations.
Ghost-free higher-order theories of gravity with torsion de la Cruz-Dombriz, Álvaro; Torralba, Francisco José Maldonado; Mazumdar, Anupam
European physical journal. C, Particles and fields,
03/2021, Letnik:
81, Številka:
3
Journal Article
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In this manuscript we will present the theoretical framework of the recently proposed infinite derivative theory of gravity with a non-symmetric connection. We will explicitly derive the field ...equations at the linear level and obtain new solutions with a non-trivial form of the torsion tensor in the presence of a fermionic source, and show that these solutions are both ghost and singularity-free.
In the context of brane-world extra-dimensional theories, we compute the positron production from branon dark matter annihilations and compare with the AMS-02 data. Three different scenarios have ...been considered; the first two assume that either pulsars or dark matter may explain separately the whole positron fraction as measured by AMS-02, whereas the third one assumes that a suitable combination of these two contributions is needed. For all of them, exclusion diagrams for the brane mass and the tension of the brane, were obtained. Our analysis has been performed for a minimal, a medium and a maximum diffusion model in one extra dimension for both pseudo-Isothermal and Navarro–Frenk–White dark matter halos. Combined with previous cosmological analyses and experimental data in colliders, constraints here enable us to set further bounds on the parameter space of branons. In particular, in the case when pulsars fit the whole AMS-02 data, we have excluded mass-tension regions for masses and tensions smaller than 60.75 TeV and 8.56 TeV respectively. With regard to the scenario in which AMS-02 data are explained by a combination of dark matter and pulsars, masses and tensions smaller than 27.32 TeV and 3.85 TeV respectively turn out to be excluded. Finally, in the scenario with no pulsar contribution, a branon with a mass 38.1±0.2 TeV and a tension 4.99±0.04 TeV can fit well the experimental data.
Combined cosmological, astrophysical and numerical tests may shed some light on the viability of theories of gravity beyond Einsteinian relativity. In this letter, we present two different techniques ...providing complementary ways of testing new physics beyond the Λ CDM cosmological paradigm. First, we shall present some of the latest progress and shortcomings in the cosmographic model-independent approach for several modified gravity theories using supernovae catalogues, baryonic acoustic oscillation data and H ( z ) differential age compilations. Second, we shall show how once the Einsteinian paradigm is abandoned, the phenomenology of neutron stars changes dramatically since neutron-star masses can be much larger than their General Relativity counterparts. Consequently, the total energy available for radiating gravitational waves could be of the order of several solar masses, and thus a merger of these stars constitutes a privileged wave source. Unfortunately at the present time our persisting lack of understanding in the strong interaction sector does not allow to distinguish the alternative theories from the usual General Relativity predictions.
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