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Inflation with Planck: a survey of some "exotic" inflationary models
Cláudio Gomes, Orfeu Bertolami, João G. Rosa
We examine some inflationary models based on modifications of gravity in the light of Planck 2015 data, such as the generalised Chaplygin inspired inflation, models based in …
Equivalence between Born-Infeld tachyon and effective real scalar field theories for brane structures in warped geometry
Alex E. Bernardini, O. Bertolami
An equivalence between Born-Infeld and effective real scalar field theories for brane structures is built in some specific warped space-time scenarios. Once the equations of motion…
Wormholes and Time-Machines in Nonminimally Coupled Matter-Curvature Theories of Gravity
Orfeu Bertolami, Ricardo Zambujal Ferreira
In this work we show the existence of traversable wormhole and time-machine solutions in a modified theory of gravity where matter and curvature are nonminimally coupled. Those sol…
Noncommutative Graphene
C. Bastos, O. Bertolami, N. Dias +1
We consider a noncommutative description of graphene. This description consists of a Dirac equation for massless Dirac fermions plus noncommutative corrections, which are treated i…
Violation of the Robertson-Schrödinger uncertainty principle and non-commutative quantum mechanics
Catarina Bastos, Orfeu Bertolami, Nuno Costa Dias +1
We show that a possible violation of the Robertson-Schrödinger uncertainty principle may signal the existence of a deformation of the Heisenberg-Weyl algebra. More precisely, we pr…
Hořava-Lifshitz Quantum Cosmology
Orfeu Bertolami, Carlos A. D. Zarro
In this work, a minisuperspace model for the projectable Hořava-Lifshitz (HL) gravity without the detailed balance condition is investigated. The Wheeler-deWitt equation is derived…
Phase-Space Noncommutativity and the Dirac Equation
Orfeu Bertolami, Raquel Queiroz
We consider full phase-space noncommutativity in the Dirac equation, and find that in order to preserve gauge invariance, configuration space noncommutativity must be dropped. The…
Noncommutative Black Holes and the Singularity Problem
C. Bastos, O. Bertolami, N. C. Dias +1
A phase-space noncommutativity in the context of a Kantowski-Sachs cosmological model is considered to study the interior of a Schwarzschild black hole. Due to the divergence of th…
Non-Canonical Phase-Space Noncommutativity and the Kantowski-Sachs singularity for Black Holes
Catarina Bastos, Orfeu Bertolami, Nuno Costa Dias +1
We consider a cosmological model based upon a non-canonical noncommutative extension of the Heisenberg-Weyl algebra to address the thermodynamical stability and the singularity pro…
Entropic Gravity, Phase-Space Noncommutativity and the Equivalence Principle
Catarina Bastos, Orfeu Bertolami, Nuno Costa Dias +1
We generalize E. Verlinde's entropic gravity reasoning to a phase-space noncommutativity set-up. This allow us to impose a bound on the product of the noncommutative parameters bas…
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…
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…
Noncommutative Quantum Cosmology
C. Bastos, O. Bertolami, N. Dias +1
One presents a phase-space noncommutative extension of Quantum Cosmology in the context of a Kantowski-Sachs (KS) minisuperspace model. We obtain the Wheeler-DeWitt (WDW) equation…
Stability Conditions For a Noncommutative Scalar Field Coupled to Gravity
Orfeu Bertolami, Carlos A. D. Zarro
We consider a noncommutative scalar field with a covariantly constant noncommutative parameter in a curved space-time background. For a potential as a noncommutative polynomial it…
A new source for a braneworld cosmological constant from a modified gravity model in the bulk
Orfeu Bertolami, Carla Carvalho, Joao Laia
We show that a four-dimensional equation of state for a cosmological constant term arises from a perfect fluid in the bulk in the context of a gravity model where the scalar curvat…
Non-minimal coupling as a mechanism for spontaneous symmetry breaking on the brane
Orfeu Bertolami, Carla Carvalho
Motivated by the dimensional asymmetry characteristic of braneworlds, we populate the bulk spacetime with matter scalar fields, both real and complex, and couple them non-minimally…
Spontaneous Symmetry Breaking in the Bulk as a Localization Mechanism of Fields on the Brane
Orfeu Bertolami, Carla Carvalho
We consider real and complex scalar fields non-minimally coupled to gravity in the bulk spacetime and study their impact on the brane upon acquiring a non-vanishing vacuum expectat…
Deformation quantization of noncommutative quantum mechanics and dissipation
C. Bastos, O. Bertolami, N. C. Dias +1
We review the main features of the Weyl-Wigner formulation of noncommutative quantum mechanics. In particular, we present a -product and a Moyal bracket suitable for this th…
Weyl-Wigner Formulation of Noncommutative Quantum Mechanics
Catarina Bastos, Orfeu Bertolami, Nuno Costa Dias +1
We address the phase space formulation of a noncommutative extension of quantum mechanics in arbitrary dimension, displaying both spatial and momentum noncommutativity. By resortin…
Gravitational Quantum Well
O. Bertolami, J. G. Rosa
We discuss the implications of a model of noncommutative Quantum Mechanics where noncommutativity is extended to the phase space. We analyze how this model affects the problem of t…
Scaling of variables and the relation between noncommutative parameters in Noncommutative Quantum Mechanics
O. Bertolami, J. G. Rosa, C. M. L. de Aragão +2
We consider Noncommutative Quantum Mechanics with phase space noncommutativity. In particular, we show that a scaling of variables leaves the noncommutative algebra invariant, so t…
Noncommutative Gravitational Quantum Well
O. Bertolami, J. G. Rosa, C. M. L. de Aragão +2
We study noncommutative geometry at the Quantum Mechanics level by means of a model where noncommutativity of both configuration and momentum spaces is considered. We analyze how t…
The flight of the bumblebee: vacuum solutions of a gravity model with vector-induced spontaneous Lorentz symmetry breaking
O. Bertolami, J. Paramos
We study the vacuum solutions of a gravity model where Lorentz symmetry is spontaneously broken once a vector field acquires a vacuum expectation value. Results are presented for t…