arXiv subjects

L. Marques

Publications and source records attributed to L. Marques.

10 recordsLinked to original sources

arXiv2026

LoKI-GM: a global model framework for plasma chemistry studies

Global (zero-dimensional or spatially averaged) models are widely employed to study complex chemistries in low-temperature plasmas (LTPs). By adopting a spatially average description of the plasma, they substantially reduce the computational cost while still providing reliable and detailed insight into the key processes taking place in the plasma. In their most general formulation, global models involve the coupled solution of a Boltzmann solver (to describe the electron kinetics) and a Chemistry solver (to describe the heavy-species kinetics). This paper presents a tutorial on the LisbOn Kinetics Global Model (LoKI-GM) framework, developed in MATLAB and available as open-source code. The framework couples the Boltzmann solver LoKI-B, which solves the space-independent form of the two-term electron Boltzmann equation for non-magnetised non-equilibrium LTPs, excited by DC/HF electric fields or time-dependent (non-oscillatory) electric fields, and the Chemistry solver LoKI-C, which solves the system of zero-dimensional rate balance equations for the main charged and neutral species in the plasma and at the surface, receiving as input the kinetic schemes for the gas/plasma/surface system under study. The inclusion of several transport models together with support for surface kinetics models are distinguishing features of LoKI-GM compared with other global chemistry models. We briefly present the formulation of LoKI-GM, including its numerical solution strategy, input/output parameters, and calculation workflow for both active discharges and afterglow plasmas. The main differences with respect to existing global models are highlighted, and the flexibility of the code for plasma chemistry studies is demonstrated through representative simulation results obtained across a range of gas discharge configurations and operating conditions.

physics.plasm-ph↗

arXiv2026

Multi-UAV Active Sensing with Information Gain-based Planning and Belief Fusion

Unmanned aerial vehicles (UAVs) are increasingly used for active sensing and information gathering in spatially distributed environments. Their performance, however, is constrained by limited flight time, sensing uncertainty, and the trade-off between spatial coverage and observation accuracy. This paper presents a real-world validation of a multi-UAV active sensing framework for probabilistic binary terrain mapping, with precision agriculture used as the application case. The environment is represented as a probabilistic belief map, where spatial dependencies are modeled through a factor-graph formulation. UAV decision making is guided by Information Gain based Informative Path Planning (IGbIPP), and the approach is compared with Random Walk and Sweep coverage path planning baselines using both synthetic terrains and real UAV-derived agricultural imagery. The study also evaluates spatial correlation weights and several probabilistic belief-fusion rules for multi-UAV information sharing. Results show that IGbIPP reduces entropy and mapping error more effectively than the baselines, while a wider field of view improves real-world coverage and map accuracy. The results further show that simple equal or biased spatial weights can be more robust than adaptive weights, and that Bayesian, log-odds, and Dempster--Shafer fusion achieve the best cooperative mapping performance. These findings highlight the importance of uncertainty-driven planning, sensing geometry, spatial modeling, and probabilistic fusion for real-world UAV-based active sensing.

cs.RO↗

arXiv2025

Milky Way disc & Bulge in situ populations: ESO white paper - Expanding horizons call

The formation and evolution of the Milky Way's disc, bar, and bulge remain fundamentally limited by the lack of a contiguous, Galaxy-wide, high-precision chemo-dynamical map. Key open questions - including the survival or destruction of the primitive discs, the origin of the bulge's multi-component structure, the role of mergers and secular processes, and the coupling between stellar chemistry, dynamics, and the Galactic potential - cannot be fully resolved with current or planned facilities. Existing spectroscopic surveys provide either high resolution for small samples or wide coverage at insufficient resolution and depth, and none can obtain homogeneous abundances, precise 3D kinematics, and reliable ages for the millions of stars required, particularly in the obscured midplane, the far side of the bar, or the outer, low-density disc. A new wide-field, massively multiplexed, large-aperture spectroscopic facility, capable of both high- and low-resolution spectroscopy over tens of thousands of square degrees, is therefore essential. Such a facility would deliver the statistical power, sensitivity, and completeness needed to reconstruct the Galaxy's assembly history, constrain its gravitational potential, and establish the Milky Way as the definitive benchmark for galaxy evolution.

astro-ph.IM↗

arXiv2025

The impact of radial migration on disk galaxy star formation histories: II. Role of bar strength, disk thickness, and merger history

Reconstructing the star formation history (SFH) of disk galaxies is central to understanding their growth and evolution, yet such estimates can be strongly biased by stellar radial migration over cosmic time. Using 186 Milky Way (MW) and Andromeda (M31) analogs from the TNG50 cosmological simulation, we compare star formation rates (SFRs) inferred from present-day stellar positions with those based on stellar birth radii to quantify the magnitude, spatial structure, and temporal evolution of migration-induced biases. We find that radial migration systematically produces artificial star formation in regions that had not yet formed stars. Notably, ~80% of galaxies exhibit outer-disk stars older than 10 Gyr, which we find to have formed at radii interior to the outer disk and to have reached their present locations via substantial outward migration. Similar effects appear in ~45% of galaxies at intermediate radii during early epochs, and in 30% of quenched inner disks within the past 4 Gyr. Migration also smooths SFHs, washing out localized bursts and suppressions by dispersing stars across neighboring radii. The strength and imprint of these distortions depend sensitively on galactic structure and evolutionary history: strong bars drive mean SFR overestimates of up to 75% in the inner disk and 150% in the outskirts; thinner, dynamically cold disks suffer average outer-disk biases up to 160%; while thick disks exhibit typical inner-disk biases up to 125%. Merger timing further modulates these patterns. Our results demonstrate that failing to account for stellar migration can lead to severe misinterpretations of when and where stars formed, with direct implications for the chemical and evolutionary histories of the MW and external galaxies.

astro-ph.GA↗

arXiv2025

The impact of radial migration on disk galaxy star formation histories I. Biases in spatially resolved estimates

Knowledge of the spatially resolved star formation history (SFH) of disk galaxies provides crucial insight into disk assembly, quenching, and chemical evolution. However, most reconstructions, both for the Milky Way and for external galaxies, implicitly assume that stars formed at their present-day radii. Using a range of zoom-in cosmological simulations, we show that stellar radial migration introduces strong and systematic biases in such SFH estimates. In the inner disk (R < h_d), early star formation is typically underestimated by 25-50% and late star formation overestimated, giving the misleading impression of prolonged, moderate activity. An exception occurs in the very central bin considered (~ 0.4h_d), which is consistently overestimated due to a net inflow of inward migrators. At intermediate radii and in the outer disk, migration drives the opposite trend: intermediate-age populations are overestimated by 100-200% as stars born in the inner disk migrate outward, whereas genuinely in-situ populations are underestimated by ~ 50% as they themselves continue to migrate. The net effect is that SFH peaks are suppressed and broadened, and the true rate of inside-out disk growth is systematically underestimated. These distortions affect all galaxies in our sample and have direct implications for interpreting spatially resolved SFHs from IFU surveys such as CALIFA and MaNGA, where present-day radii are often used as proxies for stellar birth sites. Correcting these biases will require accounting for disk mass, bar presence, disk kinematics and morphology, while recent birth-radius estimation techniques for Milky Way stars offer a promising path forward.

astro-ph.GA↗

arXiv2017

On the precise determination of the Tsallis parameters in proton - proton collisions at LHC energies

A detailed analysis is presented of the precise values of the Tsallis parameters obtained in $p-p$ collisions for identified particles, pions, kaons and protons at the LHC at three beam energies $\sqrt{s} = 0.9, 2.76$ and $7$ TeV. Interpolated data at $\sqrt{s} = $ 5.02 TeV have also been included. It is shown that the Tsallis formula provides reasonably good fits to the $p_T$ distributions in $p-p$ collisions at the LHC using three parameters $dN/dy$, $T$ and $q$. However, the parameters $T$ and $q$ depend on the particle species and are different for pions, kaons and protons. As a consequence there is no $m_T$ scaling and also no universality of the parameters for different particle species.

hep-ph↗

arXiv2015

Woods-Saxon equivalent to a double folding potential

A Woods-Saxon equivalent to a double folding potential in the surface region is obtained for the heavy-ion scattering potential. The Woods-Saxon potential has fixed geometry and was applied as a bare potential in the analysis of experimental data of several systems. A new analytical formula for the position and height of the Coulomb barrier is presented, which reproduces the results obtained using double folding potentials. This simple formula has been applied to estimate the fusion cross section above the Coulomb barrier. A comparison with experimental data is presented.

nucl-th↗

arXiv2015

Description of High-Energy pp Collisions Using Tsallis Thermodynamics: Transverse Momentum and Rapidity Distributions

A systematic analysis of transverse momentum and rapidity distributions measured in high-energy proton - proton (pp) collisions for energies ranging from 53 GeV to 7 TeV using Tsallis thermodynamics is presented. The excellent description of all transverse momentum spectra obtained in earlier analyses is confirmed and extended. All energies can be described by a single Tsallis temperature of 68 +/- 5 MeV at all beam energies and particle types investigated (43 in total). The value of the entropic index, q, shows a wider spread but is always close to q approx 1.146. These values are then used to describe the rapidity distributions using a superposition of two Tsallis fireballs along the rapidity axis. It is concluded that the hadronic system created in high-energy p - p collisions between 53 GeV and 7 TeV can be seen as obeying Tsallis thermodynamics.

hep-ph↗

arXiv2014

Measurement and analysis of the Am-243 neutron capture cross section at the n_TOF facility at CERN

Background:The design of new nuclear reactors and transmutation devices requires to reduce the present neutron cross section uncertainties of minor actinides. Purpose: Reduce the $^{243}$Am(n,$\gamma$) cross section uncertainty. Method: The $^{243}$Am(n,$\gamma$) cross section has been measured at the n_TOF facility at CERN with a BaF$_{2}$ Total Absorption Calorimeter, in the energy range between 0.7 eV and 2.5 keV. Results: The $^{243}$Am(n,$\gamma$) cross section has been successfully measured in the mentioned energy range. The resolved resonance region has been extended from 250 eV up to 400 eV. In the unresolved resonance region our results are compatible with one of the two incompatible capture data sets available below 2.5 keV. The data available in EXFOR and in the literature has been used to perform a simple analysis above 2.5 keV. Conclusions: The results of this measurement contribute to reduce the $^{243}$Am(n,$\gamma$) cross section uncertainty and suggest that this cross section is underestimated up to 25% in the neutron energy range between 50 eV and a few keV in the present evaluated data libraries.

nucl-ex↗

arXiv2012

Non-extensivity of hadronic systems

The predictions from a non-extensive self-consistent theory recently proposed are investigated. Transverse momentum ($p_T$) distribution for several hadrons obtained in $p+p$ collisions are analyzed to verify if there are evidence for a limiting effective temperature and a limiting entropic factor. In addition, the hadron-mass spectrum proposed in that theory is confronted with available data. It turns out that all $p_T$-distributions and the mass spectrum obtained in the theory are in good agreement with experiment with constant effective temperature and constant entropic factor. The results confirm that the non-extensive statistics plays an important role in the description of the termodynamics of hadronic systems, and also that the self-consistent principle holds for energies as high as those achieved in the LHC. A discussion on the best $p_T$-distirbution formula for fitting experimental data is presented.

hep-ph↗