45 citations · 134 across the 16 of their papers we have counts for
10 papers · 1 filter
A Lagrangian formulation for Rastall gravity and a covariant formulation for unimodular gravity
Juilson A. P. Paiva, Julio C. Fabris, Vilson T. Zanchin
We propose a Lagrangian formulation for a non-conservative gravity model in which the divergence of the energy-momentum tensor in curved spacetime does not vanish. This is accompli…
Revisiting Unimodular Quantum Cosmology
Júlio C. Fabris, Luiz Filipe Guimarães, Nelson Pinto-Neto +1
The quantization of unimodular gravity in minisuperspace leads to a time evolution of states generated by the Hamiltonian, as in usual quantum mechanics. We revisit the analysis ma…
Fluid and scalar field representations in the Brans-Dicke theory: cosmological scenarios
Tiago H. B. Alves, Júlio C. Fabris, Luiz Filipe Guimarães
The Brans-Dicke scalar-tensor cosmological models are studied in both Einstein and Jordan frames, using hydrodynamical and self-interacting scalar field representations of the ener…
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…
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…
Gravitational waves from binary axionic black holes
J. A. de Freitas Pacheco, S. Carneiro, J. C. Fabris
In a recent paper we have shown that a minimally coupled, self-interacting scalar field of mass can form black holes of mass (in Planck units). If dark matter…
Non-trivial static, spherically symmetric vacuum solution in a non-conservative theory of gravity
A. M. Oliveira, H. E. S. Velten, J. C. Fabris
We analyse the vacuum static spherically symmetric space-time for a specific class of non-conservative theories of gravity based on the Rastall's theory. We obtain a new vacuum sol…
Quantum cosmology with scalar fields: self-adjointness and cosmological scenarios
C. R. Almeida, A. B. Batista, J. C. Fabris +1
We discuss the issue of unitarity in particular quantum cosmological models with scalar field. The time variable is recovered, in this context, by using the Schutz's formalism for…
An analysis of cosmological perturbations in hydrodynamical and field representations
J. C. Fabris, S. V. B. Goncalves, N. A. Tomimura
Density fluctuations of fluids with negative pressure exhibit decreasing time behaviour in the long wavelength limit, but are strongly unstable in the small wavelength limit when a…