Ronaldo Lobato

Ronaldo Lobato
Los Andes University (Colombia) | UNIANDES · Department of Physics

Ph.D.
Working on nuclear/relativistic astrophysics, gravitation and cosmology; data mining, machine learning and big data.

About

39
Publications
2,495
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283
Citations
Introduction
My research focuses on the theoretical exploration of the properties of strongly interacting matter at ultra-high densities and temperatures, structure and evolution of compact stars, supernovae, wormholes; emission mechanisms (electromagnetic/gravitational), higher-dimensional/modified theories of gravity and noncommutative quantum theories.
Additional affiliations
November 2019 - August 2021
Texas A&M University-Commerce
Position
  • PostDoc Position
Description
  • Research in Nuclear Astrophysics: Gamma ray-bursts, rapid neutron capture process, supernova explosions, neutron star mergers, heavy element production, r-process, kilonova.
March 2017 - February 2018
International Center for Relativistic Astrophysics
Position
  • PhD Student
March 2015 - December 2019
Instituto Tecnologico de Aeronautica
Position
  • PhD Student
Education
October 2015 - February 2018
March 2015 - February 2019
March 2013 - February 2015

Publications

Publications (39)
Preprint
In this work, we investigate the equilibrium configurations of massive white dwarfs (MWD) in the context of modified gravity, namely $f(R,L_m)$ gravity, where $R$ stands for the Ricci scalar and $L_m$ is the Lagrangian matter density. We focused on the specific case $f(R,L_m) = R/2 + L_m + \sigma RL_m$, i.e., we have considered a non-minimal coupli...
Article
Full-text available
In this work, we investigate the equilibrium configurations of massive white dwarfs (MWD) in the context of modified gravity, namely f(R,Lm) gravity, where R stands for the Ricci scalar and Lm is the Lagrangian matter density. We focused on the specific case f(R,Lm)=R/2+Lm+σRLm, i.e., we have considered a non-minimal coupling between the gravity fi...
Preprint
Full-text available
The description of stellar interiors remains as a big challenge for the nuclear astrophysics community. The consolidated knowledge is restricted to density regions around the saturation of hadronic matter $\rho _{0} = 2.8\times 10^{14} {\rm\ g\ cm^{-3}}$, regimes where our nuclear models are successfully applied. As one moves towards higher densiti...
Preprint
Full-text available
Neutron stars (NS) are compact objects with strong gravitational fields, and a matter composition subject to extreme physical conditions. The properties of strongly interacting matter at ultra-high densities and temperatures impose a big challenge to our understanding and modelling tools. Some difficulties are critical, since one cannot reproduce s...
Preprint
Full-text available
Neutron stars are compact objects of large interest in the nuclear astrophysics community. The extreme conditions present in such systems impose big challenges to our current microscopic models of nuclear structure. Equation of states (EoS) are frequently derived from sophisticated quantum mechanical models, such as: relativistic, non-relativistic...
Preprint
Full-text available
This work analyses the hydrostatic equilibrium configurations of strange stars in a non-minimal geometry-matter coupling (GMC) theory of gravity. Those stars are supposed to be made of strange quark matter, whose distribution is governed by the MIT equation of state. The non-minimal GMC theory is described by the following gravitational action: f (...
Preprint
Full-text available
Neutron tunneling in neutron star crusts can release enormous amounts of energy on a short timescale. We have clarified aspects of this process occurring in the outer crust regions of neutron stars when oscillations or cataclysmic events changes the crustal ambient density. We report a time-dependent Hartree-Fock-Bogoliubov model to determine the r...
Article
Full-text available
In this work, we investigate neutron stars (NS) in f(R,Lm) theory of gravity for the case f(R,Lm)=R+Lm+σRLm, where R is the Ricci scalar and Lm the Lagrangian matter density. In the term σRLm, σ represents the coupling between the gravitational and particles fields. For the first time the hydrostatic equilibrium equations in the theory are solved c...
Preprint
Full-text available
In this work we investigate neutron stars (NS) in $f(\mathtt{R,L_m})$ theory of gravity for the case $f(\mathtt{R,L_m}) = \mathtt{R} + \mathtt{L_m} + \sigma\mathtt{R}\mathtt{L_m}$, where $\mathtt{R}$ is the Ricci scalar and $\mathtt{L_m}$ the Lagrangian matter density. In the term $\sigma\mathtt{R}\mathtt{L_m}$, $\sigma$ represents the coupling bet...
Article
Full-text available
Neutron tunneling between neutron-rich nuclei in inhomogeneous dense matter encountered in neutron star crusts can release enormous energy on a short timescale to power explosive phenomena in neutron stars. In this work, we clarify aspects of this process that can occur in the outer regions of neutron stars when oscillations or cataclysmic events i...
Article
Full-text available
The f ( R , T ) gravity is a theory whose gravitational action depends arbitrarily on the Ricci scalar, R , and the trace of the stress–energy tensor, T ; its field equations also depend on matter Lagrangian, $$\mathscr {L}_{m}$$ L m . In the modified theories of gravity where field equations depend on Lagrangian, there is no uniqueness on the Lagr...
Article
Full-text available
We study the effects of final state interactions in the non-mesonic weak decay \(\varLambda N \rightarrow nN\) (n is a neutron and N is either a neutron or a proton) of the hypernucleus \(_\varLambda ^4\)He. Using a three-body model the effects of distortion of the interaction of the emitted nucleon pair with the residual nucleus is considered. We...
Preprint
Full-text available
Neutron tunneling between neutron-rich nuclei in inhomogeneous dense matter encountered in neutron star crusts can release enormous energy on a short-timescale to power explosive phenomena in neutron stars. In this work we clarify aspects of this process that can occur in the outer regions of neutron stars when oscillations or cataclysmic events in...
Preprint
Full-text available
We study the effects of final state interactions in the non-mesonic weak decay $\Lambda N \rightarrow nN$ (n is a neutron and N is either a neutron or a proton) of the hypernucleus $_\Lambda^4$He. Using a three-body model the effects of distortion of the interaction of the emitted nucleon pair with the residual nucleus is considered. We also study...
Preprint
Full-text available
In this work we investigate neutron stars (NS) in $f(\mathcal{R,T})$ gravity for the case $R+2\lambda\mathcal{T}$, $\mathcal{R}$ is the Ricci scalar and $\mathcal{T}$ the trace of the energy-momentum tensor. The hydrostatic equilibrium equations are solved considering realistic equations of state (EsoS). The NS masses and radii obtained are subject...
Preprint
Full-text available
The $f(R,T)$ gravity is a theory whose gravitational action depends arbitrarily on the Ricci scalar, $R$, and the trace of the stress-energy tensor, $T$; its field equations also depend on matter Lagrangian, $\mathcal{L}_{m}$. In the modified theories of gravity where field equations depend on Lagrangian, there is no uniqueness on the Lagrangian de...
Article
Full-text available
We analyze the influence of extra dimensions on the static equilibrium configurations and stability against radial perturbations. For this purpose, we solve stellar structure equations and radial perturbation equations, both modified for a d-dimensional spacetime (d≥4) considering that spacetime outside the object is described by a Schwarzschild-Ta...
Preprint
Full-text available
We analyze the influence of extra dimensions on the static equilibrium configurations and stability against radial perturbations. For this purpose, we solve stellar structure equations and radial perturbation equations, both modified for a $d$-dimensional spacetime ($d\geq4$) considering that spacetime outside the object is described by a Schwarzsc...
Preprint
Full-text available
In this article we study the hydrostatic equilibrium configuration of neutron stars and strange stars, whose fluid pressure is computed from the equations of state $p=\omega\rho^{5/3}$ and $p=0.28(\rho-4{\cal B})$, respectively, with $\omega$ and ${\cal B}$ being constants and $\rho$ the energy density of the fluid. We also study white dwarfs equil...
Article
Full-text available
The $f(R,T)$ gravity theory was proposed as an extension of the $f(R)$ theories, for which besides geometrical correction terms, proportional to the Ricci scalar $R$, one has also material correction terms, proportional to the trace of the energy-momentum tensor $T$. Those material extra terms prevent the energy-momentum tensor of the theory to be...
Article
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The LIGO-Virgo Collaboration has announced the detection GW170817 and associated it with GRB 1709817A observed by the Fermi satellite and with the kilonova AT 2017gfo. We compare and contrast in this article the gravitational-wave and the electromagnetic emission associated with the sources GW170817A-GRB 170817A-AT 2017gfo with the ones observed in...
Article
Full-text available
In this work we investigate white dwarfs in a modified theory of gravity, namely the $f(R,T)$ gravity, where $R$ and $T$ stand for the Ricci scalar and trace of the energy-momentum tensor, respectively. Considering the functional form $f(R,T)=R+2\lambda T$, with $\lambda$ being a constant, we obtain the hydrostatic equilibrium equation. Some physic...
Article
Full-text available
We investigate the possibility of some Soft Gamma-ray Repeaters (SGRs) and Anomalous X-ray Pulsars (AXPs) could be described as rotation-powered neutron stars (NSs). The analysis was carried out by computing the structure properties of NSs, and then we focus on giving estimates for the surface magnetic field using both realistic structure parameter...
Article
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The sources of ultra-high-energy cosmic rays ($E\gtrsim10^{19}$ eV) is still an open question in astroparticle physics and in the last years some efforts were made to understand its origin. In this work we consider white dwarf pulsars (WDPs) as possible sources of these ultra energetic particles. If some Soft Gamma Repeaters (SGRs) and Anomalous X-...
Article
Full-text available
In this work, we discuss white dwarf pulsars found recently making also reference of the possibility of some SGRs/AXPs being part of this class of pulsars. We also study the properties of very massive compact ultra magnetized white dwarfs that could be the progenitors candidates of super luminous type Ia supernovae, and also a previous stage of the...
Article
Originally proposed as a tool for teaching the general theory of relativity, wormholes are today approached in many different ways and are seeing as an efficient alternative for interstellar and time travel. Attempts to achieve observational signatures of wormholes have been growing as the subject has became more and more popular. In this article w...
Article
Full-text available
The origin of highest energy cosmic rays still remains a mystery in Astrophysics. In this work we consider the Soft Gamma Repeaters (SGRs) and Anomalous X-ray Pulsars (AXPs) as possible sources of ultra-high cosmic rays. These stars described as white dwarfs pulsars can achieved large electric potential differences in their surface and accelerate p...
Conference Paper
Full-text available
The Anomalous X-ray Pulsars (AXPs) and Soft Gamma-ray Repeaters (SGRs) are a class of pulsars understood as neutron stars (NSs) with super strong surface magnetic fields, namely B 10 14 G, and for that reason are known as Magnetars. However, in the last years some SGRs/AXPs with low surface magnetic fields B ∼ (10 12 − 10 13) G have been detected,...
Article
The Anomalous X-ray Pulsars (AXPs) and Soft Gamma-ray Repeaters (SGRs) are a class of pulsars understood as neutron stars (NSs) with super strong surface magnetic fields, namely $B\gtrsim10^{14}$ G, and for that reason are known as Magnetars. However, in the last years some SGRs/AXPs with low surface magnetic fields $B\sim(10^{12}-10^{13})$ G have...
Article
Full-text available
Recently, an alternative model based on white dwarfs pulsars has been proposed to explain a class of pulsars known as Soft Gamma Repeaters (SGR) and Anomalus X-Ray Pulsars (AXP) [6][4], usually named as magnetars. In this model the magnetized white dwarfs can have surface magnetic field B ∼ 107 — 1010G and rotate very fast with frequencies ω ∼ 1 ra...
Conference Paper
Recently, an alternative model based on white dwarfs pulsars has been proposed to explain a class of pulsars known as Soft Gamma Repeaters (SGR) and Anomalus X-Ray Pulsars (AXP) [1], usually named as magnetars. In this model, the magnetized white dwarfs can have surface magnetic field B ∼ 107 − 1010 G and rotate very fast with angular frequencies Ω...
Conference Paper
Full-text available
Noncommutative Quantum Mechanics (NCQM) still presents some open questions, such as, for instance, the study of motion in configuration spaces with boundaries, which leads to the question of how to formulate boundary value problems in this context. As usual, the behavior of the quantum state near the frontiers of the space must be consistent with t...
Thesis
Full-text available
In our study we formulate the time-dependent perturbation theory in the context of non-commutative quantum mechanics characterized by discrete time evolution. We consider a two-dimensional space-time generated by a time coordinate and a spatial coordinate satisfying a canonical commutation relation. So that the space-time, will be described by oper...

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Project (1)
Archived project
The exact conditions under which the fundamental degrees of freedom of strongly interacting matter, quarks and gluons, described by Quantum Chromodynamics (QCD), can be realized in Nature is still an open question. They certainly played a fundamental role in the very first instants of the Universe, being the quarks and gluons confined into hadrons when the temperature of the Universe dropped below 160 MeV.There are sites in the present-day Universe where the fundamental degrees of freedom of hadronic matter may still appear: the interior of super-dense stars, where the temperature can be as high as 10 bilion degrees Kelvin and the density overcomes the nuclear matter saturation density.A deeper and systematic study of systems containing compact stars may improve our understanding of the nuclear matter phase diagram. Nevertheless, giving the complexity of these stars, one can expect real advances only when applying various investigation approaches and tools, both theoretical and observational. In this research plan we propose an in-depth series of research lines aiming to increase our knowledge about compact stars and their interiors.Solid investments in space missions have been done in recent years, in particular the FERMI Gamma-ray Space Telescope, with the detection of several Gamma-ray pulsars, the ESA's INTEGRAL (INTErnational Gamma-Ray Astrophysics Laboratory) and XMM-Newton, together with CHANDRA and RXTE satellites that have revealed important astrophysical phenomena both in X- and Gamma-rays. Improvements in the understanding of the motion of matter around black holes and neutron stars are expected with the LOFT mission (Large Observatory For X-ray Timing). It will provide unprecedented information about strongly curved space-times and about matter under most extreme conditions. Facing these exciting prospects, new developments that can help explaining compact stars' phenomenology are needed. The proposal for this thematic project emerges in this scenario, joining researchers of six institutions of excellence of São Paulo State in the field of astrophysics of compact stars: ITA, IAG-USP, INPE, UFABC, UNIFESP and UFSCAR.