2k citations · 12k across the 281 of their papers we have counts for
17 papers · 1 filter
The singularity problem and phase-space noncanonical noncommutativity
Catarina Bastos, Orfeu Bertolami, Nuno Costa Dias +1
The Wheeler-DeWitt equation arising from a Kantowski-Sachs model is considered for a Schwarzschild black hole under the assumption that the scale factors and the associated momenta…
Stability Conditions For a Noncommutative Scalar Field Coupled to Gravity via the Positive Energy Theorem
Orfeu Bertolami, Carlos A. D. Zarro
The stability requirements for a noncommutative scalar field coupled to gravity is investigated through the positive energy theorem. It is shown that for a noncommutative scalar wi…
Modified theories of gravity with non-minimal curvature-matter coupling
Orfeu Bertolami, Miguel Carvalho Sequeira
In this contribution one examines the generalization of the theories of gravity where one introduces a non-minimal coupling between curvature and matter. This model has new…
The Galileo satellite constellation and modifications to the inverse-square law for Gravitation
J. Páramos, O. Bertolami
We consider the impact of a power-law correction to the Newtonian potential, inspired by ungravity or extensions of the Standard Model, and draw conclusions on the possibili…
Stability of mass varying particle lumps
Alex E. Bernardini, O. Bertolami
The theoretical description of compact structures that share some key features with mass varying particles allows for a simple analysis of equilibrium and stability for massive ste…
Thermodynamic equilibrium conditions for mass varying particle structures
Alex E. Bernardini, O. Bertolami
The thermodynamic equilibrium conditions for compact structures composed by mass varying particles are discussed assuming that the so-called dynamical mass behaves like an addition…
Towards a Noncommutative Astrophysics
Orfeu Bertolami, Carlos A. D. Zarro
We consider astrophysical objects such as main-sequence stars, white-dwarfs and neutron stars in a noncommutative context. Noncommutativity is implemented via a deformed dispersion…
Black Holes and Phase Space Noncommutativity
C. Bastos, O. Bertolami, N. C. Dias +1
We use the solutions of the noncommutative Wheeler-De Witt equation arising from a Kantowski-Sachs cosmological model to compute thermodynamic properties of the Schwarzschild black…
Constraints on unparticle long range forces from big bang nucleosynthesis bounds on the variation of the gravitational coupling
O. Bertolami, N. M. C. Santos
We use big bang nucleosynthesis bounds on the variation of the gravitational coupling to derive constraints on the strength of the deviation from the gravitational inverse-square l…
Mimicking dark matter through a non-minimal gravitational coupling with matter
O. Bertolami, J. Paramos
In this study one resorts to the phenomenology of models endowed with a non-minimal coupling between matter and geometry, in order to develop a mechanism through which dynamics sim…
The cosmological constant problem: a user's guide
Orfeu Bertolami
We discuss the validity of general relativity at low-energy and relate the threshold below which the theory breaks down with the observed value of the cosmological constant. This s…
Astrophysical constraints on unparticle-inspired models of gravity
O. Bertolami, J. Paramos, P. Santos
We use stellar dynamics arguments to constrain the relevant parameters of ungravity inspired models. We show that resulting bounds do constrain the parameters of the theory of unpa…
Coupling dark energy with Standard Model states
M. C. Bento, A. E. Bernardini, O. Bertolami
In this contribution one examines the coupling of dark energy to the gauge fields, to neutrinos, and to the Higgs field. In the first case, one shows how a putative evolution of th…
Noncommutative Quantum Mechanics and Quantum Cosmology
Catarina Bastos, Orfeu Bertolami, Nuno Dias +1
We present a phase-space noncommutative version of quantum mechanics and apply this extension to Quantum Cosmology. We motivate this type of noncommutative algebra through the grav…
Energy Conditions and Stability in theories of gravity with non-minimal coupling to matter
Orfeu Bertolami, Miguel Carvalho Sequeira
Recently, in the context of modified theories of gravity, a new type of model has been proposed where one directly couples the scalar curvature to matter. As any model in $f…
Time and Causation
Orfeu Bertolami, Francisco S. N. Lobo
In this review paper, we consider the fundamental nature of time and causality, most particularly, in the context of the theories of special and general relativity. We also discuss…
Dark energy and the Rutherford-Soddy radiative decay law
M. C. Bento, O. Bertolami
It is shown that a putative evolution of the fundamental couplings of strong and weak interactions via coupling to dark energy through a generalized Bekenstein-type model may, for…