301 citations · 2.1k across the 77 of their papers we have counts for
81 papers
Lagrangian Extensions of Newtonian Gravity constrained by Solar System tests
Pedro H. Dalprá, Júlio C. Fabris, Hermano Velten +1
We explore an extension to Newtonian gravity through a generalised Lagrangian function with the introduction of a second dynamical scalar field. Building on previous research into…
A new framework for cosmological expansion in a reformulated Newtonian-Like gravity with variable G
Felipe S. Escórcio, Júlio C. Fabris, Júnior D. Toniato +1
A Newtonian-like theory inspired by the Brans-Dicke gravitational Lagrangian has been recently proposed in Ref. arXiv:2009.04434(v4). We propose here a new variant of this theory s…
Selecting energy-momentum trace dependent gravity theories with LSS
Jonas Pinheiro da Silva, Hermano Velten
We study scalar cosmological perturbations in modified gravity theories being the trace of the energy-momentum tensor. We provide detailed equations for the matter en…
Holographic Ricci dark energy in Nonconservative Unimodular Gravity
Marcelo H. Alvarenga, Júlio C. Fabris, Hermano Velten +1
The structure of unimodular gravity (UG) is invariant to a subclass of diffeomorphism, the transverse diffeomorphism, due to the unimodular condition (). Consequen…
Spherically Symmetric Configurations in Unimodular Gravity
Júlio C. Fabris, Mahamadou Hamani Daouda, Hermano Velten
Unimodular gravity (UG) is considered, under many aspects, equivalent to General Relativity (GR), even if the theory is invariant under a more restricted diffeomorphic class of tra…
Celestial mechanics in Newtonian-like gravity with variable
Felipe S. Escórcio, Júlio C. Fabris, Júnior D. Toniato +1
A Newtonian-like theory inspired by the Brans-Dicke gravitational Lagrangian has been recently proposed in Ref. arXiv:2009.04434(v4). This work demonstrates that the modified gravi…
Fully conservative gravity and Solar System constraints
Nicolas R. Bertini, Hermano Velten
The gravity is a model whose action contains an arbitrary function of the Ricci scalar and the trace of the energy-momentum tensor . We consider the separable model…
Using cosmological perturbation theory to distinguish between General Relativity and Unimodular Gravity
Marcelo H. Alvarenga, Júlio C. Fabris, Hermano Velten
Unimodular Gravity is one of the oldest geometric gravity theory alternative to General Relativity. Essentially, it is based on the Einstein-Hilbert Lagrangian with an additional c…
Black hole lensing in Kerr-de Sitter spacetimes
Eunice Omwoyo, Humberto Belich, Júlio C. Fabris +1
We have derived analytical solutions using Jacobi elliptic functions for bound and nearly bound photon orbits in Kerr-de Sitter (KdS) and Kerr-de Sitter Revisited (RKdS) spacetimes…
Constraining the anomalous coupling of gravitational waves with double pulsar
Diego Santos de Jesus, Hermano Velten, Federico Piazza
We revisit the decay of the orbital period in binary systems that occurs due to the emission of gravitational waves in the context of modified gravity models where the coupling $G_…
Brans-Dicke unimodular gravity
Alexandre M. R. Almeida, Júlio C. Fabris, Mahamadou Hamani Daouda +3
We propose a unimodular version of the Brans-Dicke theory designed with a constrained Lagrangian formulation. The resulting field equations are traceless. The vacuum solutions in t…
Skewness as a test of dark energy perturbations
Raquel Emy Fazolo, Luca Amendola, Hermano Velten
We investigate the role played by dark energy perturbations in the skewness of large-scale matter distribution. We consider a two-fluid universe composed by matter and dark e…
Nonconservative unimodular gravity: Gravitational waves
Júlio C. Fabris, Marcelo H. Alvarenga, Mahamadou Hamani-Daouda +1
Unimodular gravity is characterized by an extra condition with respect to General Relativity: the determinant of the metric is constant. This extra condition leads to a more restri…
Nonconservative unimodular gravity: a viable cosmological scenario
Júlio C. Fabris, Marcelo H. Alvarenga, Mahamadou Hamani-Daouda +1
In this work we review the issue of imposing the conservation of the energy-momentum tensor as a necessary condition to recover the equivalence between the unimodular gravity and G…
Remarks on the black hole shadows in Kerr-de Sitter space times
Eunice Omwoyo, Humberto Belich, Júlio C. Fabris +1
This work is geared towards analysis of shadows cast by Kerr-de Sitter (KdS) and Kerr-de Sitter Revisited (RKdS) black holes. Considering observers in the vicinity of the static ra…
Stellar structure in a Newtonian theory with variable
Júlio C. Fabris, Túlio Ottoni, Júnior D. Toniato +1
A Newtonian-like theory inspired by the Brans-Dicke gravitational Lagrangian has been recently proposed. For static configurations the gravitational coupling acquires an intrinsic…
Early-time thermalization of cosmic components? A hint for solving cosmic tensions
Hermano Velten, Ingrid Costa, Winfried Zimdahl
We study an expanding two-fluid model of non-relativistic dark matter and radiation which are allowed to interact during a certain time span and to establish an approximate thermal…
To conserve, or not to conserve: A review of nonconservative theories of gravity
Hermano Velten, Thiago R. P. Caramês
Apart from the familiar structure firmly-rooted in the general relativistic field equations where the energy--momentum tensor has a null divergence i.e., it conserves, there exists…
Newtonian-like gravity with variable
Júlio C. Fabris, Tales Gomes, Júnior D. Toniato +1
We propose a Lagrangian formulation for a varying Newtonian-like theory inspired by the Brans-Dicke gravity. Rather than imposing an {\it ad hoc} dependence for the gravitation…
Skewness of matter distribution in clustering dark energy cosmologies
Hermano Velten, Raquel Emy Fazolo
We calculate the skewness (the third moment ) of matter distribution in dynamical dark energy cosmologies. We pay particular attention to the impact of dark energy perturbatio…
Is the Hubble diagram of quasars in tension with concordance cosmology?
Hermano Velten, Syrios Gomes
Recently Risaliti \& Lusso [Nature Astron. 3 (2019) 3 272] reported new measurements of the expansion rate of the Universe by constructing the Hubble diagram of 1598 quasars in the…
On (non-)dynamical dark energy
Winfried Zimdahl, Júlio Fabris, Hermano Velten +1
The current Universe is composed by a mixture of relativistic species, baryonic matter, dark matter and dark energy which evolve in a non-trivial way at perturbative level. An adva…
Modified Gravity Away from a CDM Background
Guilherme Brando, Felipe T. Falciano, Eric V. Linder +1
Within the effective field theory approach to cosmic acceleration, the background expansion can be specified separately from the gravitational modifications. We explore the impact…
On the existence of static spherically-symmetric objects in action-dependent Lagrangian theories
Julio C. Fabris, Hermano Velten, Aneta Wojnar
We study static symmetric solutions in the context of a gravitational theory based on a action-dependent Lagrangian. Such theory has been designed as a setup to implement dissipati…