Orfeu Bertolami, Frederico Francisco,
Based on a dynamic systems approach to the Landau-Ginzburg model, a phase space description of the Earth System (ES) in the transition to the Anthropocene is presented. It is shown that, for a finite amount of human-driven change, there is a stable equilibrium state that is an attractor of trajectories in the system's phase space and corresponds to a Hothouse Earth scenario. Using the interaction between the components of the ES, it is argued that, through the action of the Technosphere, mitigation ...
Tópico(s): Advanced Thermodynamics and Statistical Mechanics
2019 - Institute of Physics | EPL (Europhysics Letters)
Alex E. Bernardini, Pedro Leal, Orfeu Bertolami,
A quasi-Gaussian quantum superposition of Hořava-Lifshitz (HL) stationary states is built in order to describe the transition of the quantum cosmological problem to the related classical dynamics. The obtained HL phase-space superposed Wigner function and its associated Wigner currents describe the conditions for the matching between classical and quantum phase-space trajectories. The matching quantum superposition parameter is associated to the total energy of the classical trajectory which, at ...
Tópico(s): Quantum, superfluid, helium dynamics
2018 - Institute of Physics | Journal of Cosmology and Astroparticle Physics
Catarina Cosme, João G. Rosa, Orfeu Bertolami,
We discuss the dynamics and phenomenology of an oscillating scalar field coupled to the Higgs boson that accounts for the dark matter in the Universe. The model assumes an underlying scale invariance such that the scalar field only acquires mass after the electroweak phase transition, behaving as dark radiation before the latter takes place. While for a positive coupling to the Higgs field the dark scalar is stable, for a negative coupling it acquires a vacuum expectation value after the electroweak ...
Tópico(s): Particle physics theoretical and experimental studies
2018 - Springer Nature | Journal of High Energy Physics
Catarina Cosme, João G. Rosa, Orfeu Bertolami,
We show that the present dark matter abundance can be accounted for by an oscillating scalar field that acquires both mass and a non-zero expectation value from interactions with the Higgs field. The dark matter scalar field can be sufficiently heavy during inflation, due to a non-minimal coupling to gravity, so as to avoid the generation of large isocurvature modes in the CMB anisotropies spectrum. The field begins oscillating after reheating, behaving as radiation until the electroweak phase transition ...
Tópico(s): Particle physics theoretical and experimental studies
2018 - Elsevier BV | Physics Letters B
Orfeu Bertolami, Frederico Francisco,
It is proposed, based on the Landau-Ginzburg Theory of phase transitions, that the transition of the Earth System from the stable conditions of the Holocene to the human driven condition of the Anthropocene is, actually, a phase transition, a qualitative change away from its Holocene equilibrium state. Based on this physical framework, one obtains the Anthropocene equation, the so-called Great Acceleration and shows that (i) the Earth System temperature at the future equilibrium state diverges from ...
Tópico(s): Space Science and Extraterrestrial Life
2018 - Elsevier BV | Global and Planetary Change
Orfeu Bertolami, Cláudio Gomes, Francisco S. N. Lobo,
Gravitational waves in the presence of a non-minimal curvature-matter coupling are analysed, both in the Newman–Penrose and perturbation theory formalisms. Considering a cosmological constant as a source, the non-minimally coupled matter-curvature model reduces to f(R) theories. This is in good agreement with the most recent data. Furthermore, a dark energy-like fluid is briefly considered, where the propagation equation for the tensor modes differs from the previous scenario, in that the scalar ...
Tópico(s): Advanced Differential Geometry Research
2018 - Springer Science+Business Media | The European Physical Journal C
Cláudio Gomes, João G. Rosa, Orfeu Bertolami,
We study inflationary scenarios driven by a scalar field in the presence of a non-minimal coupling between matter and curvature. We show that the Friedmann equation can be significantly modified when the energy density during inflation exceeds a critical value determined by the non-minimal coupling, which in turn may considerably modify the spectrum of primordial perturbations and the inflationary dynamics. In particular, we show that these models are characterised by a consistency relation between ...
Tópico(s): Galaxies: Formation, Evolution, Phenomena
2017 - Institute of Physics | Journal of Cosmology and Astroparticle Physics
Catarina Bastos, Alex E. Bernardini, Orfeu Bertolami, Nuno Costa Dias, João Nuno Prata,
We examine putative corrections to the Bell operator due to the noncommutativity in the phase space. Starting from a Gaussian squeezed envelope whose time evolution is driven by commutative (standard quantum mechanics) and noncommutative dynamics, respectively, we conclude that although the time-evolving covariance matrix in the noncommutative case is different from the standard case, the squeezing parameter dominates and there are no noticeable noncommutative corrections to the Bell operator. This ...
Tópico(s): Quantum Information and Cryptography
2016 - American Physical Society | Physical review. D/Physical review. D.
Orfeu Bertolami, Catarina Cosme, João G. Rosa,
We discuss the possibility that dark matter corresponds to an oscillating scalar field coupled to the Higgs boson. We argue that the initial field amplitude should generically be of the order of the Hubble parameter during inflation, as a result of its quasi-de Sitter fluctuations. This implies that such a field may account for the present dark matter abundance for masses in the range $10^{-6} - 10^{-4}$ eV, if the tensor-to-scalar ratio is within the range of planned CMB experiments. We show that ...
Tópico(s): Particle physics theoretical and experimental studies
2016 - Elsevier BV | Physics Letters B
André G. C. Guerra, Frederico Francisco, Jaime E. Villate, Fernando Aguado Agelet, Orfeu Bertolami, Kanna Rajan,
The recent explosive growth of small satellite operations driven primarily from an academic or pedagogical need, has demonstrated the viability of commercial-off-the-shelf technologies in space. They have also leveraged and shown the need for development of compatible sensors primarily aimed for Earth observation tasks including monitoring terrestrial domains, communications and engineering tests. However, one domain that these platforms have not yet made substantial inroads into, is in the ocean ...
Tópico(s): Marine and coastal ecosystems
2016 - Elsevier BV | Acta Astronautica
Salvador Robles-Pérez, Ana Alonso-Serrano, Catarina Bastos, Orfeu Bertolami,
We examine a new multiverse scenario in which the component universes interact. We focus our attention to the process of "true" vacuum nucleation in the false vacuum within one single element of the multiverse. It is shown that the interactions lead to a collective behaviour that might lead, under specific conditions, to a pre-inflationary phase and ensued distinguishable imprints in the comic microwave background radiation.
Tópico(s): Galaxies: Formation, Evolution, Phenomena
2016 - Elsevier BV | Physics Letters B
Orfeu Bertolami, Vitor Bessa, Jorge Páramos,
We study the possibility that inflation is driven by a massive vector field with $SO(3)$ global symmetry nonminimally coupled to gravity. From an ${E}^{3}$-invariant Robertson-Walker metric we propose an Ansatz for the vector field, allowing us to study the evolution of the system. We study the behavior of the equations of motion using the methods of the theory of dynamical systems and find exponential inflationary regimes.
Tópico(s): Noncommutative and Quantum Gravity Theories
2016 - American Physical Society | Physical review. D/Physical review. D.
Produção Nacional
Catarina Bastos, Alex E. Bernardini, Orfeu Bertolami, Nuno Costa Dias, João Nuno Prata,
We revisit Ozawa's uncertainty principle (OUP) in the framework of noncommutative (NC) quantum mechanics. We derive a matrix version of OUP accommodating any NC structure in the phase-space, and compute NC corrections to lowest order for two measurement interactions, namely the Backaction Evading Quadrature Amplifier and Noiseless Quadrature Transducers. These NC corrections alter the nature of the measurement interaction, as a noiseless interaction may acquire noise, and an interaction of independent ...
Tópico(s): Advanced Operator Algebra Research
2015 - American Physical Society | Physical review. D. Particles, fields, gravitation, and cosmology/Physical review. D, Particles, fields, gravitation, and cosmology
In this work some issues in the context of Noncommutative Quantum Mechanics (NCQM) are addressed. The main focus is on finding whether symmetries present in Quantum Mechanics still hold in the phase-space noncommutative version. In particular, the issues related with gauge invariance of the electromagnetic field and the weak equivalence principle (WEP) in the context of the gravitational quantum well (GQW) are considered. The question of the Lorentz symmetry and the associated dispersion relation is ...
Tópico(s): Quantum Mechanics and Applications
2015 - Elsevier BV | Physics Letters B
Catarina Bastos, Alex E. Bernardini, Orfeu Bertolami, Nuno Costa Dias, João Nuno Prata,
In this work we derive a matrix formulation of a noise-disturbance uncertainty relation, which is akin to the Robertson-Schr\"odinger uncertainty principle. Our inequality is stronger than Ozawa's uncertainty principle and takes noise-disturbance correlations into account. Moreover, we show that, for certain types of measurement interactions, it is covariant with respect to linear symplectic transformations of the noise and disturbance operators.
Tópico(s): Cold Atom Physics and Bose-Einstein Condensates
2014 - American Physical Society | Physical Review A
Produção Nacional
Catarina Bastos, Alex E. Bernardini, Orfeu Bertolami, Nuno Costa Dias, João Nuno Prata,
Ozawa's measurement-disturbance relation is generalized to a phase-space noncommutative extension of quantum mechanics. It is shown that the measurement-disturbance relations have additional terms for backaction evading quadrature amplifiers and for noiseless quadrature transducers. Several distinctive features appear as a consequence of the noncommutative extension: measurement interactions which are noiseless, and observables which are undisturbed by a measurement, or of independent intervention ...
Tópico(s): Advanced Operator Algebra Research
2014 - American Physical Society | Physical review. D. Particles, fields, gravitation, and cosmology/Physical review. D, Particles, fields, gravitation, and cosmology
Orfeu Bertolami, Cláudio Gomes,
We derive the Layzer-Irvine equation for alternative gravitational theories with non-minimal coupling between curvature and matter for an homogeneous and isotropic Universe. As an application, we study the case of Abell 586, a relaxed and spherically symmetric galaxy cluster, assuming some matter density profiles.
Tópico(s): Galaxies: Formation, Evolution, Phenomena
2014 - Institute of Physics | Journal of Cosmology and Astroparticle Physics
Orfeu Bertolami, Jorge Páramos,
In this work we study how nonminimally coupled theories of gravity modify the usual Friedmann equation, and develop two methods to treat these. The ambiguity in the form of the Lagrangian density of a perfect fluid is emphasized, and the impact of different dominant matter species is assessed. The Cosmological Constant problem is also discussed.
Tópico(s): Solar and Space Plasma Dynamics
2014 - American Physical Society | Physical review. D. Particles, fields, gravitation, and cosmology/Physical review. D, Particles, fields, gravitation, and cosmology
Orfeu Bertolami, Jorge Páramos,
In this work we study how a non-minimal coupling between matter and gravity can modify the structure of a homogeneous spherical body. The physical relevance of the adopted Lagrangian density is ascertained, with results obtained for two different choices of the latter.
Tópico(s): Relativity and Gravitational Theory
2014 - Springer Science+Business Media | General Relativity and Gravitation
Orfeu Bertolami, Jorge Páramos,
In this contribution we assess the current experimental status of special and general relativity. Particular emphasis is put on putative extensions of these theories and on how these could be detected experimentally.
Tópico(s): Relativity and Gravitational Theory
2014 - Springer International Publishing | Springer handbooks
Orfeu Bertolami, Jorge Páramos,
We examine an extension of General Relativity with an explicit non-minimal coupling between matter and curvature. The purpose of this work is to present an overview of the implications of the latter to various contexts, ranging from astrophysical matter distributions to a cosmological setting. Various results are discussed, including the impact of this non-minimal coupling on the choice of Lagrangian density, on a mechanism to mimic galactic and cluster dark matter, on the possibility of accounting ...
Tópico(s): Relativity and Gravitational Theory
2013 - World Scientific | International Journal of Geometric Methods in Modern Physics
Alex E. Bernardini, Orfeu Bertolami,
In this work we examine the effect of phase-space noncommutativity on some typically quantum properties such as quantum beating, quantum information, and decoherence. To exemplify these issues we consider the two-dimensional noncommutative quantum harmonic oscillator whose component behavior we monitor in time. This procedure allows us to determine how the noncommutative parameters are related to the missing information quantified by the linear quantum entropy and by the mutual information between ...
Tópico(s): Algebraic structures and combinatorial models
2013 - American Physical Society | Physical Review A
Catarina Bastos, Alex E. Bernardini, Orfeu Bertolami, Nuno Costa Dias, João Nuno Prata,
The entanglement criterion for continuous variable systems and the conditions under which the uncertainty relations are fulfilled are generalized to the case of a noncommutative phase space. The quantum nature and the separability of noncommutative two-mode Gaussian states are examined. It is shown that the entanglement of Gaussian states may be exclusively induced by switching on the noncommutative deformation.
Tópico(s): Quantum Information and Cryptography
2013 - American Physical Society | Physical review. D. Particles, fields, gravitation, and cosmology/Physical review. D, Particles, fields, gravitation, and cosmology
Orfeu Bertolami, Pedro Frazão, Jorge Páramos,
In this work, one examines how the presence of a non-minimal coupling between the spacetime curvature and matter affects the evolution of cosmological perturbations around a homogeneous and isotropic Universe and hence the formation of large-scale structure. This framework places constraints on the terms which arise due to the coupling with matter and, in particular, on the modification in the growth of matter density perturbations. One obtains approximate analytical solutions for the evolution ...
Tópico(s): Advanced Differential Geometry Research
2013 - Institute of Physics | Journal of Cosmology and Astroparticle Physics
Catarina Bastos, Orfeu Bertolami, Nuno Costa Dias, João Nuno Prata,
We consider a noncommutative description of graphene. This description consists of a Dirac equation for massless Dirac fermions plus noncommutative corrections, which are treated in the presence of an external magnetic field. We argue that, being a two-dimensional Dirac system, graphene is particularly interesting to test noncommutativity. We find that momentum noncommutativity affects the energy levels of graphene, but that it does not entail any kind of correction to the Hall conductivity.
Tópico(s): Black Holes and Theoretical Physics
2013 - World Scientific | International Journal of Modern Physics A
Orfeu Bertolami, Riccardo March, Jorge Páramos,
We extend the analysis of Chiba et al. [Phys. Rev. D 75, 124014 (2007)] of Solar System constraints on $f(R)$ gravity to a class of nonminimally coupled (NMC) theories of gravity. These generalize $f(R)$ theories by replacing the action functional of general relativity with a more general form involving two functions ${f}^{1}(R)$ and ${f}^{2}(R)$ of the Ricci scalar curvature $R$. While the function ${f}^{1}(R)$ is a nonlinear term in the action, analogous to $f(R)$ gravity, the function ${f}^{2}(R)$ yields a ...
Tópico(s): Geophysics and Gravity Measurements
2013 - American Physical Society | Physical review. D. Particles, fields, gravitation, and cosmology/Physical review. D, Particles, fields, gravitation, and cosmology
Alex E. Bernardini, Orfeu 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 for tachyon fields related to the Born–Infeld action are written as first-order equations, a simple analytical connection with a particular class of real scalar field superpotentials can be found. This equivalence leads to the conclusion that, for a certain class of superpotentials, both systems can support identical ...
Tópico(s): Noncommutative and Quantum Gravity Theories
2013 - Elsevier BV | Physics Letters B
Ana Alonso-Serrano, Catarina Bastos, Orfeu Bertolami, Salvador Robles-Pérez,
In this Letter it is studied the effects that an interaction scheme among universes can have in the values of their cosmological constants. In the case of two interacting universes, the value of the cosmological constant of one of the universes becomes very close to zero at the expense of an increasing value of the cosmological constant of the partner universe. In the more general case of a chain of N interacting universes with periodic boundary conditions, the spectrum of the Hamiltonian splits ...
Tópico(s): Cosmology and Gravitation Theories
2013 - Elsevier BV | Physics Letters B
Orfeu Bertolami, P. Carrilho, Jorge Páramos,
In this paper, we study the effects of an interaction between dark matter and dark energy through a two scalar field model with a potential $V(\phi,\chi)=e^{-\lambda\phi}P(\phi,\chi)$, where $P(\phi,\chi)$ is a polynomial. We show that the cosmic expansion dynamics of the Universe is reproduced for a large range of the bare mass of the dark matter field and that there exist solutions with transient accelerated expansion. A modification in the exponential behavior of the potential is studied, with ...
Tópico(s): Solar and Space Plasma Dynamics
2012 - American Physical Society | Physical review. D. Particles, fields, gravitation, and cosmology/Physical review. D, Particles, fields, gravitation, and cosmology
Orfeu Bertolami, Ricardo Z. Ferreira,
We obtain traversable wormhole and time machine solutions of the field equations of an alternative of gravity with non-minimally curvature-matter coupling. Our solutions exhibit a non-trivial redshift function and allow for matter that satisfy the dominant energy condition.
Tópico(s): Galaxies: Formation, Evolution, Phenomena
2012 - American Physical Society | Physical review. D. Particles, fields, gravitation, and cosmology/Physical review. D, Particles, fields, gravitation, and cosmology