A5078131843- Cosmology and Gravitation Theories
- Galaxies: Formation, Evolution, Phenomena
- Black Holes and Theoretical Physics
- Dark Matter and Cosmic Phenomena
- Stellar, planetary, and galactic studies
- Solar and Space Plasma Dynamics
- Evolutionary Game Theory and Cooperation
- Geophysics and Gravity Measurements
- Astrophysics and Star Formation Studies
- Astronomy and Astrophysical Research
- Pulsars and Gravitational Waves Research
- Advanced Thermodynamics and Statistical Mechanics
- Evolution and Genetic Dynamics
- Astro and Planetary Science
- Radio Astronomy Observations and Technology
- Relativity and Gravitational Theory
- Mathematical and Theoretical Epidemiology and Ecology Models
- Gamma-ray bursts and supernovae
- Scientific Research and Discoveries
- Particle physics theoretical and experimental studies
- Complex Systems and Time Series Analysis
- Stochastic processes and statistical mechanics
- Advanced Differential Geometry Research
- Earth Systems and Cosmic Evolution
- Complex Network Analysis Techniques
Universidade do Porto
2015-2024
Institute of Astrophysics and Space Sciences
2015-2024
Instituto Federal do Maranhão
2024
Lagrange Laboratory
2024
Observatoire de la Côte d’Azur
2024
Université Côte d'Azur
2024
Centre National de la Recherche Scientifique
2024
Centre for Astrophysics of the University of Porto
2013-2023
University of Birmingham
2019-2020
The University of Sydney
2014
The current standard model of cosmology successfully describes a variety measurements, but the nature its main ingredients, dark matter and energy, remains unknown. is medium-class mission in Cosmic Vision 2015--2025 programme European Space Agency (ESA) that will provide high-resolution optical imaging, as well near-infrared imaging spectroscopy, over about 14\,000\,deg$^2$ extragalactic sky. In addition to accurate weak lensing clustering measurements probe structure formation half age...
We study the dynamics of a homogeneous and isotropic Friedmann-Robertson-Walker universe in context Eddington-inspired Born-Infeld theory gravity. generalize earlier results, obtained radiation dominated universe, to account for evolution permeated by perfect fluid with an arbitrary equation state parameter $w$. show that bounce may occur $\ensuremath{\kappa}>0$, if $w$ is time dependent, we demonstrate it free from tensor singularities. argue cosmologies be viable alternative inflationary...
In this paper we compute stringent astrophysical and cosmological constraints on a recently proposed Eddington-inspired Born-Infeld theory of gravity. We find, using generalized version the Zel'dovich approximation, that in pressureless, cold-dark matter fluid has nonzero effective sound speed. corresponding Jeans length show it is approximately equal to fundamental ${R}_{*}={\ensuremath{\kappa}}^{1/2}{G}^{\ensuremath{-}1/2}$, where $\ensuremath{\kappa}$ only additional parameter with...
Deciphering the assembly history of Milky Way is a formidable task, which becomes possible only if one can produce high-resolution chrono-chemo-kinematical maps Galaxy. Data from large-scale astrometric and spectroscopic surveys will soon provide us with well-defined view current chemo-kinematical structure Way, but enable blurred on temporal sequence that led to present-day As demonstrated by (ongoing) exploitation data pioneering photometric missions CoRoT, Kepler, K2, asteroseismology...
We investigate the population dynamics in generalized Rock-Paper-Scissors models with an arbitrary number of species $N$. show, for first time, that spiral patterns $N$-arms may develop both odd and even $N$, particular where a bidirectional predation interaction equal strength between all is modified to include one N-cyclic predator-prey rule. While former case gives rise interface network Y-type junctions obeying scaling law $L \propto t^{1/2}$, $L$ characteristic length $t$ later can lead...
Observations of Sun-like stars over the last half-century have improved our understanding how magnetic dynamos, like that responsible for 11-year solar cycle, change with rotation, mass and age. Here we show first time metallicity can affect a stellar dynamo. Using most complete set observations cycle ever obtained star, analog HD 173701 exhibits solar-like differential rotation 7.4-year activity cycle. While duration is comparable to generated by dynamo, amplitude brightness variability...
Higher-dimensional theories have the remarkable feature of predicting a time (and hence redshift) dependence ``fundamental'' four dimensional constants on cosmological scales. In this paper, we update bounds possible variation fine structure constant $\ensuremath{\alpha}$ at big bang nucleosynthesis $(z\ensuremath{\sim}{10}^{10})$ and cosmic microwave background (CMB) $(z\ensuremath{\sim}{10}^{3}).$ Using recently released high-resolution CMB anisotropy data latest estimates primordial...
In this paper we investigate the classical non-relativistic limit of Eddington-inspired Born-Infeld theory gravity. We show that strong bounds on value only additional parameter κ, with respect to general relativity, may be obtained by requiring gravity plays a subdominant role compared electromagnetic interactions inside atomic nuclei. also discuss validity continuous fluid approximation used in and other astrophysical cosmological studies. argue although is expected valid case sufficiently...
We introduce a family of rock-paper-scissors-type models with ${Z}_{N}$ symmetry ($N$ is the number species), and we show that it has very rich structure many completely different phases. study realizations lead to formation domains, where individuals one or more species coexist, separated by interfaces whose (average) dynamics curvature driven. This type behavior, which might be relevant for development biological complexity, leads an interface network evolution pattern similar ones several...
We compute the power spectrum of stochastic gravitational wave background generated by cosmic string networks, described velocity-dependent one-scale (VOS) model for a wide range macroscopic and microscopic parameters. The VOS model---which has been shown to provide an accurate description evolution networks---is used demonstrate that networks are unable rapidly attain scale-invariant after transition between radiation matter eras. However, in computations background, it is often assumed...
We study the nonlinear regime of unified dark energy models, using generalized Chaplygin gas cosmologies as a representative example, and introduce new parameter characterizing level small scale clustering in these scenarios. show that viable cosmologies, consistent with most recent observational constraints, may be constructed for any value by considering models sufficiently high clustering.
We revisit the problem of predominance ``weakest'' species in context Lotka-Volterra and May-Leonard formulations a spatial stochastic rock-paper-scissors model which one has its predation probability reduced by $0<{\mathcal{P}}_{w}<1$. show that, despite different population dynamics patterns, these two lead to qualitatively similar results for late time values relative abundances three (as function ${\mathcal{P}}_{w}$), as long simulation lattices are sufficiently large coexistence...
We derive a full analytical approximation to the stochastic gravitational wave background generated by loops that are produced throughout cosmological evolution of cosmic string networks. show this not only predicts amplitude radiation-era plateau exactly, but also provides good fit high-frequency cut-off and low-frequency peak decay during matter era, irrespective tension length created. then find it quantitative description across relevant frequency range.
Context. The emergence of mixed modes during the subgiant phase, whose frequencies are characterized by a fast evolution with age, can potentially enable precise determination stellar properties, key goal for future missions like PLATO. However, current modelling techniques often consider grids that lack resolution to properly account mode frequency evolution, consequently requiring use interpolation algorithms cover parameter space in between grid models when applying model-data comparison...
Grid-based modelling techniques have enabled the determination of stellar properties with great precision. The emergence mixed modes during subgiant phase, whose frequencies are characterised by a fast evolution age, can potentially enable precise properties, key goal for future missions such as PLATO. However, current often consider grids that lack resolution to properly account mode frequency evolution, consequently requiring use interpolation algorithms cover parameter space in between...
According to the von Laue condition, volume integral of proper pressure inside isolated particles with a fixed structure and finite mass vanishes in Minkowski limit general relativity. In this work, we consider simple illustrative example: non-standard static global monopoles energy, for which condition is satisfied when integrated over whole space. We demonstrate, however, that absolute value integral, calculated up distance from center monopole, generally deviates zero, deviation bounded...
We discuss the issue of toy model building for dark energy component universe. Specifically, we consider two generic models recently proposed as alternatives to quintessence models, respectively known Cardassian expansion and Chaplygin gas. show that former is entirely equivalent a class models. determine observational constraints on latter, coming from recent supernovae results shape matter power spectrum. As expected, these restrict behavior closely matches standard cosmological constant...
We perform a likelihood analysis of the recently released BOOMERanG and MAXIMA data, allowing for possibility time-varying fine-structure constant. find that in general these data prefer value \ensuremath{\alpha} was smaller past (which is agreement with measurements from quasar observations). However, there are some interesting degeneracies problem which imply strong statements about cannot be made using this method until independent accurate determinations...
We discuss the importance of including baryons in analyses unified dark matter scenarios, focusing on toy models involving a generalized Chaplygin gas. determine observational constraints this scenario coming from large-scale structure, type Ia supernovae and CMB data showing how component can bring about different behavior classical cold model with cosmological constant thus motivate further studies models. also speculate interesting new features which are likely to be important nonlinear...
We have studied the cosmological evolution of domain wall networks in two, three and four spatial dimensions using high-resolution field theory simulations. The dynamical range number our simulations is larger than previous works, but does not allow us to exclude hints deviations naively expected scale-invariant evolution. These results therefore suggest that approach linear scaling a much slower process cosmic strings, which has been previously characterized detail.
We present a detailed analysis of and future cosmic microwave background (CMB) constraints the value fine-structure constant, α. carry out more WMAP first-year data, deriving state-of-the-art on α discussing various other issues, such as possible hints for running spectral index. find, at 95 per cent confidence level, that 0.95 < αdec/α0 1.02. Setting dnS/d ln k= 0 yields 0.94 1.01 previously reported. find lower makes compatible with data. also perform thorough Fisher matrix (including both...
We introduce a new phenomenological one-scale model for the evolution of domain wall networks, and test it against high-resolution field theory numerical simulations. argue that previous estimates velocities are inaccurate, suggest more accurate method measurement. show provides an adequate approximation to key parameters characterizing network. use study possible scaling solutions discuss some their cosmological consequences.
In this work we investigate the development of stable dynamical structures along interfaces separating domains belonging to enemy partnerships, in context cyclic predator-prey models with an even number species $N \ge 8$. We use both stochastic and field theory simulations one two spatial dimensions, as well analytical arguments, describe association at mutually neutral individuals partnerships probe their role interfaces. identify interesting behaviour associated symmetric or asymmetric...