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O. Bertolami

Publications and source records attributed to O. Bertolami.

At least 19 recordsLinked to original sources
arXiv2024

Natural Capital as a Stock Option

The unfolding climate crisis is a physical manifestation of the damage that market economy, driven by the high intensity consumption of fossil fuels, has inflicted on the Earth System and on the stability conditions that were established by a complex conjugation of natural factors during the Holoecene. The magnitude of the human activities and its predatory nature is such that it is no longer possible to consider the Earth System and the services it provides for the habitability of the planet, the so-called natural capital, as an economical externality. Thus one is left with two main choices in what concerns the sustainability of the planet's habitability: radical economic degrowth or highly efficient solutions to internalise the maintenance and the restoration of ecosystems and the services of the Earth System. It is proposed that an interesting strategy for the latter is to consider the natural capital as a stock option.

econ.GN↗
arXiv2022

Towards a Classification Scheme for the Rocky Planets based on Equilibrium Thermodynamic Considerations

A classification scheme for rocky planets is proposed, based on a description of the Earth System in terms of the Landau-Ginzburg Theory of phase transitions. Three major equilibrium states can be identified and the associated planetary states or phases are: Earth-like Holocene state; hot Venus-like state; cold Mars-like state. The scheme is based on an approach proposed to understand the Earth transition from the Holocene to the Anthropocene, driven by the impact of the human action on the Earth System. In the present work we identity the natural conditions that cause transformations on the planets forcing them into one of the states identified above. We discuss how the parameters that describe these transformations can be related with exoplanets observables. In analysing the relevant physical parameters, we were stroke by the similarities between Earth and Venus, and how likely is that the Anthropocene transition may lead to hot-house Earth scenario.

astro-ph.EP↗
arXiv2021

Comparison of Four Space Propulsion Methods for Reducing Transfer Times of Crewed Mars Mission

We assess the possibility of reducing the travel time of a crewed mission to Mars by examining four different propulsion methods and keeping the mass at departure under 2500 tonne, for a fixed architecture. We evaluated representative systems of three different state of the art technologies (chemical, nuclear thermal and electric) and one advance technology, the ``Pure Electro-Magnetic Thrust'' (PEMT) concept (proposed by Rubbia). A mission architecture mostly based on the Design Reference Architecture 5.0 is assumed in order to estimate the mass budget, that influences the performance of the propulsion system. Pareto curves of the duration of the mission and time of flight versus mass of mission are drawn. We conclude that the ion engine technology, combined with the classical chemical engine, yields the shortest mission times for this architecture with the lowest mass and that chemical propulsion alone is the best to minimise travel time. The results obtained using the PEMT suggest that it could be a more suitable solution for farther destinations than Mars.

physics.pop-ph↗
arXiv2021

Pressureless stationary solutions in a Newton-Yukawa gravity model

Non-minimally coupled curvature-matter gravity models are an interesting alternative to the Theory of General Relativity and to address the dark energy and dark matter cosmological problems. These models have complex field equations that prevent a full analytical study. Nonetheless, in a particular limit, the behavior of a matter distribution can, in these models, be described by a Schrödinger-Newton system. In nonlinear optics, the Schrödinger-Newton system can be used to tackle a wide variety of relevant situations and several numerical tools have been developed for this purpose. Interestingly, these methods can be adapted to study General Relativity problems as well as its extensions. In this work, we report the use of these numerical tools to study a particular non-minimal coupling model that introduces two new potentials, an attractive Yukawa potential and a repulsive potential proportional to the energy density. Using the imaginary-time propagation method we have shown that stationary solutions arise even at low energy density regimes.

gr-qc↗
arXiv2019

A Physical Framework for the Earth System in the Anthropocene: Towards an Accountancy System

At a time when humanity has achieved global dominance at a scale that was previously thought impossible, it might also face an existential threat due to the consequences of that overwhelming influence on our common home, the Earth System (ES). In this work we explore how Physics may help us to understand the transitions that the ES is going through and lead us to a physically motivated accounting system that allows for setting boundaries to our negative influence on the ecosystems.

physics.soc-ph↗
arXiv2019

Using numerical methods from nonlocal optics to simulate the dynamics of N-body systems in alternative theories of gravity

The generalized Schrödinger-Newton system of equations with both local and nonlocal nonlinearities is widely used to describe light propagating in nonlinear media under the paraxial approximation. However, its use is not limited to optical systems and can be found to describe a plethora of different physical phenomena, for example, dark matter or alternative theories for gravity. Thus, the numerical solvers developed for studying light propagating under this model can be adapted to address these other phenomena. Indeed, in this work we report the development of a solver for the HiLight simulations platform based on GPGPU supercomputing and the required adaptations for this solver to be used to test the impact of new extensions of the Theory of General Relativity in the dynamics of the systems, in particular those based on theories with non-minimal coupling between curvature and matter. This approach in the study of these new models offers a quick way to validate them since their analytical analysis is difficult. The simulation module, its performance, and some preliminary tests are presented in this paper.

gr-qc↗
arXiv2019

Towards a Physically Motivated Planetary Accounting Framework

In this work we present a physically motivated planetary Accounting Framework for the Earth System. We show that the impact of the human activity in terms of the Planetary Boundary variables can be accounted for in our Landau-Ginzburg phase transition physical formulation. We then use the interaction between climate change and ocean acidification mechanisms to exemplify the relation of the concentration and flux of substances of the Planetary Boundaries variables, as proposed by the accounting framework of Kate and Newman, with the underlying thermodynamical transformation, quantifiable by the Landau-Ginzburg inspired model. In this work we present a physically motivated planetary Accounting Framework for the Earth System. We show that the impact of the human activity in terms of the Planetary Boundary variables can be accounted for in our Landau-Ginzburg phase transition physical formulation. We then use the interaction between climate change and ocean acidification mechanisms to exemplify the relation of the concentration and flux of substances of the Planetary Boundaries variables, as proposed by the accounting framework of Kate and Newman, with the underlying thermodynamical transformation, quantifiable by the Landau-Ginzburg inspired model.

physics.ao-ph↗
arXiv2019

Ensuring Uninterrupted Power Supply to Lunar Installations Through an Organic Rankine Cycle

We propose using the temperature gradients between the Moon's surface and the soil at a certain depth to power an Organic Rankine Cycle that could supply a permanent installation, particularly at night, when solar power is not available. Our theoretical and engineering considerations show that, with existing working fluids and quite feasible technical requirements, it is possible to continuously yield $25\,{\rm kW}$ to sustain a 3 member crew.

astro-ph.IM↗
arXiv2019

Relativistic dispersion relation and putative metric structure in noncommutative phase-space

The deformation of the relativistic dispersion relation caused by noncommutative (NC) Quantum Mechanics (QM) is studied using the extended phase-space formalism. The introduction of the additional commutation relations induces Lorentz invariance violation. It is shown that this deformation does not affect the propagation speed of free massless particles. From the deformation of the dispersion relation for massless particles, gamma ray burst data is used to establish an upper bound on the noncommutative parameter, $η$, namely $\sqrtη \lesssim 10^{-12} \,\mathrm{eV/c}$. Additionally, a putative metric structure for the noncommutative phase-space is discussed.

quant-ph↗
arXiv2018

A phase-space description of the Earth System in the Anthropocene

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 strategies might arise for which the deviation of the ES temperature from the Holocene average temperature is smaller.

physics.ao-ph↗
arXiv2018

A physical framework for the Earth System, the Anthropocene Equation and the Great Acceleration

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 on the new equilibrium state diverges from the average temperature of the Holocene as the cubic root of the human intervention, described by a parameter, $H$; (ii) the human induced departure from the Holocene can be as drastic as the ones due to natural, astronomical and geophysical causes; (iii) the susceptibility of the Earth System to human effects is much more relevant near the phase transition. The procedure to obtain numerical predictions from data is also exemplified through one of the existing proposals to account for human impact on the Earth's Holocene equilibrium.

physics.gen-ph↗
arXiv2018

Scale-invariant scalar field dark matter through the Higgs portal

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 phase transition and may decay into photon pairs, albeit with a mean lifetime much larger than the age of the Universe. We explore possible astrophysical and laboratory signatures of such a dark matter candidate in both cases, including annihilation and decay into photons, Higgs decay, photon-dark scalar oscillations and induced oscillations of fundamental constants. We find that dark matter within this scenario will be generically difficult to detect in the near future, except for the promising case of a 7 keV dark scalar decaying into photons, which naturally explains the observed galactic and extra-galactic 3.5 keV X-ray line.

hep-ph↗
arXiv2018

Scalar field dark matter with spontaneous symmetry breaking and the $3.5$ keV line

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 and afterwards as non-relativistic matter. The scalar field becomes unstable, although sufficiently long-lived to account for dark matter, due to mass mixing with the Higgs boson, decaying mainly into photon pairs for masses below the MeV scale. In particular, for a mass of $\sim 7$ keV, which is effectively the only free parameter, the model predicts a dark matter lifetime compatible with the recent galactic and extragalactic observations of a 3.5 keV X-ray line.

hep-ph↗
arXiv2018

Quantum cloning and teleportation fidelity in the noncommutative phase-space

The formulation of the no-cloning theorem in the framework of phase-space noncommutative (NC) quantum mechanics (QM) is examined, and its implications for the computation of quantum cloning probabilities and teleportation fidelity are investigated through the Weyl-Wigner formulation of QM. The principles of QM re-edited in terms of a deformed Heisenberg-Weyl algebra are shown to provide a covariant formulation for the quantum fidelity, through which the results from the no-cloning theorem for the ordinary QM can be reproduced. Besides exhibiting an explicit correspondence between standard and NC QM for Gaussian Wigner functions, our results suggest a feasible interpretation for the NC continuous variable quantum cloning given in terms of quantum teleportation protocols.

quant-ph↗
arXiv2017

Collapsing Shells and Black Holes: a quantum analysis

The quantization of a spherically symmetric null shells is performed and extended to the framework of phase-space noncommutative (NC) quantum mechanics. The encountered properties are investigated making use of the Israel junction conditions on the shell, considering that it is the boundary between two spherically symmetric spacetimes. Using this method, and considering two different Kantowski-Sachs spacetimes as a representation for the Schwarzschild spacetime, the relevant quantities on the shell are computed, such as its stress-energy tensor and the action for the whole spacetime. From the obtained action, the Wheeler-deWitt equation is deduced in order to provide the quantum framework for the system. Solutions for the wavefunction of the system are found on both the commutative and NC scenarios. It is shown that, on the commutative version, the wave function has a purely oscillatory behavior in the interior of the shell. In the NC setting, it is shown that the wavefunction vanishes at the singularity, as well as, at the event horizon of the black hole.

gr-qc↗
arXiv2016

Hyperbolic orbits of Earth flybys and effects of ungravity-inspired conservative potentials

In this work we take a critical look at the available data on the flyby anomaly and on the current limitations of attempts to develop an explanation. We aim to verify how conservative corrections to gravity could affect the hyperbolic trajectories of Earth flybys. We use ungravity-inspired potentials as illustrative examples and show how the resulting orbital simulations differ from the observed anomaly. We also get constraints on the model parameters from the observed flyby velocity shifts. The conclusion is that no kind of conservative potential can be the cause of the flyby anomaly.

gr-qc↗
arXiv2016

Inflation with a massive vector field nonminimally coupled to gravity

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 behaviour of the equations of motion using the methods of the theory of dynamical systems and find exponential inflationary regimes.

gr-qc↗