A5035656331- Rare-earth and actinide compounds
- Iron-based superconductors research
- Physics of Superconductivity and Magnetism
- Cosmology and Gravitation Theories
- Advanced Condensed Matter Physics
- Magnetic and transport properties of perovskites and related materials
- Galaxies: Formation, Evolution, Phenomena
- Magnetic Properties of Alloys
- Dark Matter and Cosmic Phenomena
- Black Holes and Theoretical Physics
- Inorganic Chemistry and Materials
- Superconductivity in MgB2 and Alloys
- High-pressure geophysics and materials
- Catalysis and Oxidation Reactions
- Radio Astronomy Observations and Technology
- Superconducting Materials and Applications
- Catalytic Processes in Materials Science
- Advanced Thermodynamics and Statistical Mechanics
- Nuclear Materials and Properties
- Geophysics and Gravity Measurements
- Mesoporous Materials and Catalysis
- Crystal Structures and Properties
- Polyoxometalates: Synthesis and Applications
- Theoretical and Computational Physics
- Intermetallics and Advanced Alloy Properties
Universidade Federal da Bahia
2014-2024
Hospital Ana Nery
2021
University of Portsmouth
2015-2020
Pontifical Catholic University of Rio de Janeiro
2004-2015
Universidade Federal do Recôncavo da Bahia
2008
Los Alamos National Laboratory
1986-2004
Centre National de la Recherche Scientifique
1995
Institut de Recherches sur la Catalyse et l'Environnement de Lyon
1994-1995
New York University
1990
Universidade Estadual de Campinas (UNICAMP)
1988
Abstract Polymer models have been used to describe non-singular quantum black holes, where the classical singularity is replaced by a transition from hole white hole. In previous letter, in context of uni-parametric model with asymptotic flat exterior metric, we fixed radius surface through identification its area gap Loop Quantum Gravity. This revealed dependence polymerisation parameter on mass, former increases as latter decreases. It also enabled extension Planck-scale holes. We...
We report the discovery of pressure-induced superconductivity, with ${T}_{c}=2\mathrm{K},$ in heavy-fermion antiferromagnet ${\mathrm{Ce}}_{2}{\mathrm{RhIn}}_{8},$ where superconductivity and magnetic order coexist over an extended pressure interval. A T-linear resistivity normal state, accessed by applied field, does not appear to derive from existence a two-dimensional quantum-critical spin-density wave.
Pressure studies of ${\mathrm{CeRh}}_{1\ensuremath{-}x}{\mathrm{Ir}}_{x}{\mathrm{In}}_{5}$ indicate two superconducting phases as a function $x$, one with ${T}_{c}\ensuremath{\geqslant}2\phantom{\rule{0.3em}{0ex}}\mathrm{K}$ for $x<0.9$ and the other ${T}_{c}<1.2\phantom{\rule{0.3em}{0ex}}\mathrm{K}$ $x>0.9$. The higher ${T}_{c}$ phase, phase 1, emerges in proximity to an antiferromagnetic quantum-critical point; whereas, Cooper pairing lower 2 is inferred arise from fluctuations yet be...
We demonstrate that creation of dark-matter particles at a constant rate implies the existence cosmological term decays linearly with Hubble rate. discuss model arises in this context and test it against observations first acoustic peak cosmic microwave background (CMB) anisotropy spectrum, diagram for supernovas type Ia (SNIa), distance scale baryonic oscillations (BAO) distribution large structures (LSS). show good concordance is obtained, albeit higher value present matter abundance than...
We investigate the observational viability of a class interacting dark energy (iDE) models in light latest observations Cosmic Microwave Background and type Ia supernovae, SH0ES measurement current expansion rate H0. Our analysis explores both assumptions non-zero spatial curvature free density, correlation between interaction parameter α H0, updates results reported [1]. The show that best-fit our joint clearly favours positive interaction, i.e., an flux from matter to energy, with α≈ 0.2,...
The oxyborates show a variety of interesting physical behavior associated with the existence low dimensional units in their crystalline structure. In this paper we present transport, x-ray, magnetic, and M\"ossbauer spectroscopy measurements homometallic ludwigites. These results give evidence charge localization reveal an unusual magnetic behavior. We observe reentrant weak ferromagnetism as well coexistence paramagnetic antiferromagnetic spins ${\mathrm{Fe}}_{3}{\mathrm{O}}_{2}{\mathrm{BO}}_{3}.$
The effects of hydrostatic pressure up to $1.11\phantom{\rule{0.3em}{0ex}}\mathrm{GPa}$ on the in-plane fluctuation conductivity $\mathrm{Y}{\mathrm{Ba}}_{2}{\mathrm{Cu}}_{3}{\mathrm{O}}_{7\ensuremath{-}d}$ are investigated. experiments focused asymptotic region closely above ${T}_{c}$ where a three-dimensional Gaussian and genuine critical regimes identified. From analysis amplitude one deduces that off-plane coherence length ${\ensuremath{\xi}}_{c}(0)$ does not change significantly with in...
We have determined the effect of pressure $P$ on resistance and superconducting transition temperature ${T}_{c}$ $R{\mathrm{Ba}}_{2}{\mathrm{Cu}}_{3}{\mathrm{O}}_{x}$ ($R=\mathrm{G}\mathrm{d},\phantom{\rule{0ex}{0ex}}\mathrm{E}\mathrm{r},\phantom{\rule{0ex}{0ex}}\mathrm{a}\mathrm{n}\mathrm{d}\phantom{\rule{0ex}{0ex}}\mathrm{Y}\mathrm{b}$) compare our results to those obtained high-quality $\mathrm{Y}{\mathrm{Ba}}_{2}{\mathrm{Cu}}_{3}{\mathrm{O}}_{x}$. The temperature, which is 90 K or...
Abstract In this work we consider a class of interacting vacuum corresponding to generalised Chaplygin gas (gCg) cosmology. particular analyse two different scenarios at perturbation level for the same background interaction characterised by parameter α : (i) matter that follows geodesics, homogeneous vacuum, and (ii) covariant ansatz density perturbations. latter case, show perturbations are very tiny as compared on sub-horizon scales. spite that, depending value , suppress or enhance...
Abstract Polymer models inspired by Loop Quantum Gravity (LQG) have been used to describe non-singular quantum black holes with spherical symmetry, the classical singularity replaced a transition from hole white hole. A recent model, single polymerisation parameter, leads symmetric same mass for and phases, an asymptotically flat exterior metric. The radius of surface is, however, not fixed, increasing mass. Following similar procedures, in previous paper we fixed that identifying minimal...
There is mounting observational evidence that the expansion of our Universe undergoing a late-time acceleration. Among many proposals to describe this phenomenon, cosmological constant ($\ensuremath{\Lambda}$) seems be simplest and most natural explanation. However, despite its successes, such possibility exacerbates well known $\ensuremath{\Lambda}$ problem, requiring explanation for small, but nonzero, value. In paper we consider scenario driven by varying term, in which vacuum energy...
We study cosmological perturbations in the context of an interacting dark energy model, which term decays linearly with Hubble parameter, concomitant matter production. A previous joint analysis redshift-distance relation for type Ia supernovas, barionic acoustic oscillations, and position first peak anisotropy spectrum cosmic microwave background has led to acceptable values parameters. Here we present our small perturbations, under assumption that term, therefore production, are strictly...
We investigate a spatially flat Friedmann-Lemaître-Robertson-Walker cosmology in which decaying vacuum term causes matter production at late times. Assuming decay proportional to the Hubble rate, ratio of background energy densities dark and changes with cosmic scale factor as a−3/2. The intrinsically non-adiabatic two-component perturbation dynamics this model is reduced single second-order equation. Perturbations are shown be negligible on scales that relevant for structure formation. On...
We study observational signatures of non-gravitational interactions between the dark components cosmic fluid, which can be either due to creation particles from expanding vacuum or an effect clustering a dynamical energy. In particular, we analyse class interacting models (Λ(t)CDM), characterised by parameter α, that behaves at background level like cold matter early times and tends cosmological constant in asymptotic future. Our analysis improves previous works, where only position Cosmic...
We present an investigation of the magnetic properties ludwigite ${\mathrm{Ni}}_{2}{\mathrm{FeO}}_{2}{\mathrm{BO}}_{3}$. This material is oxyborate that presents in its crystalline structure subunits form walls where transition metal ions are located. Our M\"ossbauer, ac susceptibility, and magnetization measurements show Fe Ni two independent subsystems this down to ${T}_{N}=15$ K. explain behavior terms a hierarchy interactions.
A joint analysis of the linear matter power spectrum, distance measurements from type Ia supernovae and position first peak in anisotropy spectrum cosmic microwave background indicates a cosmological, late-time dark creation at 95% confidence level.
We examine the growth of structure in three different cosmological models with interacting dark matter and vacuum energy. consider case geodesic zero sound speed, where relativistic growing mode comoving-synchronous gauge coincides Newtonian at first order $\mathrm{\ensuremath{\Lambda}}\mathrm{CDM}$. study corrections to linearly presence interactions linear rate, ${f}_{1}$, contrasting this velocity divergence, ${f}_{\mathrm{rsd}}{\ensuremath{\sigma}}_{8}$, observed through redshift-space...
The next generation of galaxy surveys will allow us to test some fundamental aspects the standard cosmological model, including assumption a minimal coupling between components dark sector. In this paper, we present Javalambre Physics Accelerated Universe Astrophysical Survey (J-PAS) forecasts on class unified models where cold matter interacts with vacuum energy, considering future observations baryon acoustic oscillations, redshift-space distortions, and power spectrum. After providing...
Effective models of quantum black holes inspired by Loop Quantum Gravity (LQG) have had success in resolving the classical singularity with polymerisation procedures and imposing LQG area gap as a minimum area. The is replaced hypersurface transition from to white holes, recent example Ashtekar, Olmedo Singh (AOS) model for Schwarzschild hole. More recently, one-parameter model, equal masses solutions, was suggested Alonso-Bardaji, Brizuela Vera (ABBV). An interesting feature their...
We present x-ray, susceptibility, and magnetization (up to 18 T) measurements in the compound ${\mathrm{MgTiOBO}}_{3}$, which forms structure known as warwickite. This is characterized by presence of ribbons along c axis where metallic ions are located. system magnetic since Ti valence state ${\mathrm{Ti}}^{3+}$ with electronic configuration 3${\mathit{d}}^{1}$. Its susceptibility has a temperature dependence, at low temperatures, given \ensuremath{\chi}(T) \ensuremath{\propto}...