1,699 research outputs found
CCBH-Numerics
No full textUsing gravitational wave data, CCBH-Numerics computes the probability of the existence of a single cosmologically coupled black hole with a formation mass below a specified threshold. This tool was developed alongside the paper by Amendola, Rodrigues, Kumar, and Quartin, published in MNRAS in 2024.If you use this software, please cite it using the metadata from this file
CCBH-Numerics
No full textUsing gravitational wave data, CCBH-Numerics computes the probability of the existence of a single cosmologically coupled black hole with a formation mass below a specified threshold. This tool was developed alongside the paper by Amendola, Rodrigues, Kumar, and Quartin, published in MNRAS in 2024If you use this software, please cite it as below. Please, consider also citing the corresponding MNRAS (2024) paper DOI: 10.1093/mnras/stae143
NAVanalysis
No full textNormalized Additional Velocity analysis. NAVanalysis is a code for studying the non-Baryonic or non-Newtonian contributions to galaxy rotation curves straight from a given data sample, instead of first performing individual galaxy fits. It is a fast and complementary approach to standard individual fits. It focuses on sample results of the dark-matter-profile (or modified gravity) radial dependence.If you use this software, please cite it using the metadata from this file
On Rastall gravity formulation as a and a theory
No full textRastall introduced a stress-energy tensor whose divergence is proportional to
the gradient of the Ricci scalar. This proposal leads to a change in the form
of the field equations of General Relativity, but it preserves the number of
degrees of freedom. Rastall's field equations can be either interpreted as GR
with a redefined SET, or it can imply different physical consequences inside
the matter sector. We investigate limits under which the Rastall field
equations can be directly derived from an action, in particular from two
-gravity extensions: and . We show that there
are similarities between these theories, but the Rastall SET cannot be fully
recovered from them, apart from certain particular cases here discussed. It is
remarkable that a simple, covariant and invertible redefinition of the SET, as
the one proposed by Rastall, is hard to be directly implemented in the action.Comment: 11 pages, accepted for publication in the European Physical Journal
Plu
A method for evaluating models that use galaxy rotation curves to derive the density profiles
No full textThere are some approaches, either based on General Relativity (GR) or modified gravity, that use galaxy rotation curves to derive the matter density of the corresponding galaxy, and this procedure would either indicate a partial or a complete elimination of dark matter in galaxies. Here we review these approaches, clarify the difficulties on this inverted procedure, present a method for evaluating them, and use it to test two specific approaches that are based on GR: the Cooperstock-Tieu (CT) and the Balasin-Grumiller (BG) approaches. Using this new method, we find that neither of the tested approaches can satisfactorily fit the observational data without dark matter. The CT approach results can be significantly improved if some dark matter is considered, while for the BG approach no usual dark matter halo can improve its results
Cosmological coupling of local gravitational systems
No full textWe investigate the cosmological coupling of spherical, local astrophysical systems. We derive a general formula quantifying the cosmological coupling of the Misner-Sharp mass of these objects. We show that, in the weak-field limit, the cosmological coupling is only allowed if there are pressure anisotropies. We also apply our results to galaxies, modelling them with the Navarro-Frenk-White and Einasto profiles. We show that the galactic mass can be coupled to the cosmological dynamics and examine its dependence on the scale factor of the universe
Rastall Cosmology and the ΛCDM Model
No full textRastall's theory is based on the non-conservation of the energy-momentum tensor. We show that, in this theory, if we introduce a two-fluid model, one component representing vacuum energy whereas the other pressureless matter (e.g. baryons plus cold dark matter), the cosmological scenario is the same as for the Lambda CDM model, both at background and linear perturbative levels, except for one aspect: now dark energy may cluster. We speculate that this can lead to a possibility of distinguishing the models at the non-linear perturbative level
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