Treballs Finals de Grau (TFG) - Física

URI permanent per a aquesta col·leccióhttps://hdl.handle.net/2445/59725

Treballs Finals del Grau de Física de la Facultat de Físca de la Universitat de Barcelona.

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Vehicle Model Simplification for Efficient Pedestrian Impact Assessment with Human Body Models
(2026-06) Vizuete Gil, Lucía; Carmona Flores, Manuel
Finite element simulations with Human Body Models provide detailed biomechanical information for pedestrian safety assessment, but their high computational cost limits their use in iterative vehicle studies. This work investigates whether this cost can be reduced by simplifying the vehicle model without significantly altering the pedestrian response. A 2020 Nissan Rogue finite element model was coupled with THUMS Pedestrian version 4.1 and simulated using LS-DYNA. Several reduced vehicle configurations were generated by replacing selected deformable components with nodal rigid bodies, while keeping the human body model unchanged. The reduced models were compared with the full vehicle baseline using runtime, vehicle internal energy, biomechanical outputs, and ISO/CORA-based correlation scores. Simulation 3 provided the best compromise between efficiency and accuracy, reducing runtime by 35.64% while achieving the highest agreement with the baseline.
The Penrose Process
(2026-06) Villaret Ribot, Mònica; Bueno Gómez, Pablo
The Penrose process is a theoretical mechanism by which energy can be extracted from a rotating black hole. This possibility arises in the Kerr spacetime, where the existence of an ergoregion allows for asymptotic negative-energy states to exist. In this work, we study how these states allow part of the rotational energy of the black hole to be extracted when an infalling particle splits inside the ergoregion. We show that the maximum relative energy gain of the process (with respect to the infalling particle) is ΔE ≈ 0.207. The process is shown to be possible only under specific physical restrictions. The area theorem shows that this extraction cannot continue indefinitely, but only until the black hole has lost its rotational energy, while the horizon area does not decrease. The Wald and Bardeen-Press-Teukolsky inequalities further show that the process requires highly relativistic conditions: the decay products must have velocity |v| ≥ 1 2 c and relative velocity |w| ≥ 1 2 c.
ASL-based pipeline for cerebral perfusion imaging in essential tremor patients undergoing MRgFUS
(2026-06) Villalbí Tibau, Jordi; Munuera, Josep; Sala Llonch, Roser; Domínguez, Alejandro
Magnetic Resonance-guided Focused Ultrasounds (MRgFUS) has emerged as an effective minimally invasive treatment for essential tremor (ET), but its cerebral physiological effects beyond the lesioned region remain poorly understood. This work presents and evaluates a pipeline for the analysis of cerebral blood perfusion changes in ET patients treated with MRgFUS. The pipeline processes pseudo-continuous Arterial Spin Labelling (pCASL) data from 19 patients using the ExploreASL framework, incorporating quality control procedures and a Minimum Detectable Change threshold of 24% to distinguish true biological effects from measurement noise. 13 out of the 19 patients exhibited at least one significant perfusion change, yielding 49 perfusion changes exceeding the detection threshold across several regions of interest. These preliminary results suggest that MRgFUS may induce hemodynamic effects beyond the lesion, potentially related to diaschisis
A software tool for the simultaneous analysis of cortical slow waves in electrophysiological and laser-speckle hemodynamic recordings of the murine lesion model
(2026-06) Vázquez Santisteban, Abel; Sala Llonch, Roser; Sánchez-Vives, María Victoria
Cortical slow waves (< 2 Hz) can be detected from the firing of cortical neurons, and they also produce a slower change in cerebral blood flow. These two readings are usually done apart, and almost never on the same animal. We present a software tool that handles both at the same time, for the murine focal-lesion model. The tool reads a 32-channel micro-electrode-array (MEA) recording of local field potentials (LFP, Open Ephys, 5 kHz) and wide-field laser speckle contrast images of regional cerebral blood flow, pre-processed by the ICFO Medical Optics group. We describe its four signal-processing blocks: (i) zero-phase Butterworth band-pass filtering of the LFP; (ii) Up/Down state detection on a score that fuses a log-MUA estimate and a high-band variance estimate by principal-component analysis, with an Otsu threshold and a minimum-duration state cleaner; (iii) a wave-propagation block that groups channels by cross-correlation coherence with hierarchical clustering and fits a two-dimensional plane wave over the MEA geometry to get the propagation speed and direction; and (iv) a viewer that re-aligns the channels by the lags from the propagation block. The blocks are run on real LFP recordings of an anesthetized mouse, and all figures are produced by the same code used by the interface. The tool also implements a fifth block that links the electrical and the hemodynamic signals to map neurovascular coupling; it is implemented but not yet tested on real data, since we do not have a recording with both signals from the same animal yet.
Black hole superradiance
(2026-06) Tortosa Valero, José; Gómez Valent, Adrià
This study examines two classical mechanisms for extracting energy from rotating black holes. First, the Penrose process is analysed, and the relationship between the energy and angular momentum extracted from the black hole is derived. Second, the phenomenon of black hole superradiance is investigated for massless scalar fields in the Kerr spacetime, leading to the determination of the condition under which incident waves undergo superradiant amplification.
Chemiresistive gas sensor response based on MOFs
(2026-06) Tera Pujol, Carla de; Romano Rodríguez, Albert; Fort Grandas, Ignasi
The objective of this research is to characterize the chemiresistive gas-sensing properties of the two-dimensional Metal-Organic Framework Ni3(HHTP)2, also referred to as Ni-HHTP. Two different samples were investigated based on the ligand used to make the MOF, which correspond to different oxidation states: Ni-HHTP-red, the semi-oxidized sample, and Ni-HHTP-ox, the fully oxidized sample. Both form ohmic contacts with the electrodes and exhibit semiconducting-like transport (dR/dT < 0). An Arrhenius analysis of Ni-HHTP-ox between 21 and 104 ◦C yields an activation energy of Ea = 71 ± 5 meV, which seems to indicate an extrinsic semiconducting behavior. The material is strongly cross-sensitive to humidity, which is therefore minimized to decouple the gas response. Under low-humidity conditions, the sensors yield reproducible chemiresistive responses to CH4, CO2 and H2 at the ppm level, with sensitivities of ∼0.1–0.3 %/ppm for CH4, ∼10−3 %/ppm for CO2 and up to 1.3 · 10−2 %/ppm for H2.
Interlayer exchange coupling in Ni/Al/Py heterostructures
(2026-06) Soler Oliver, Gisela; Galceran Vercher, Regina
This study investigates the magnetic behavior of Py/Al/Ni heterostructures to evaluate the effect of the Al spacer thickness on the interlayer coupling. Hysteresis loops for sample series with 5 nm and 10 nm Py layers were measured using Magneto-Optic Kerr Effect (MOKE). The results indicate that the direct contact samples appear to be strongly coupled and switch collectively. The introduction of Al attenuates this interaction, enabling the observation of independent switching and stable antiparallel states in specific configurations. Furthermore, the increase of Py thickness has been seen to modify the interlayer coupling. However, the intrinsic magnetic anisotropy of the Py layer complicates this characterization by masking the underlying magnetic behavior. Our results highlight the importance of structural control for the development of magnetic memories such as MRAM.
Ultracold atoms in an optical lattice: One-dimensional phase diagram
(2026-06) Serralta Vidal, Judit; Guilleumas, Montserrat; Briongos-Merino, Héctor
In this project, the ground-state phase diagram of the one-dimensional Extended Bose-Hubbard Model is systematically characterized using the DMRG algorithm via the Julia ITensors library. Benchmark simulations with only on-site interactions, validate the implementation by reproducing the conventional Superfluid to Mott Insulator transition. Incorporating nearest-neighbor interactions at unit filling and employing finite-size scaling at a fixed value of the ratio between on-site interactions and tunneling strength equal to 5, we map three distinct insulating regimes. We confirm that weak nearest-neighbor interactions maintain the Mott phase, while intermediate coupling stabilizes the topological Haldane Insulator, identified by a non-local string order parameter. Finally, strong interactions drive the system into a crystalline Density Wave phase via spontaneous translational symmetry breaking.
High-Sensitivity Characterization of Magnetic Dynamics Using a Cavity Resonator
(2026-06) Segret Brau, Bernat; Costache, Marius V.
This thesis explores ferromagnetic resonance (FMR) utilizing an electromagnetic cavity as an alternative to conventional broadband coplanar waveguides. By confining the microwave field, the resonant cavity enhances sensitivity and enables high-resolution probing of magnetic dynamics. This work explores magnon-photon hybridization inside a 3D cylindrical resonant cavity, performs resonance measurements, and analyses linewidths and mode structures to refine techniques for the characterization of ferromagnetic materials. The measurements were performed sing a cylindrical microwave cavity combined with Helmholtz coils to apply a tunable external magnetic field and identify resonance conditions. Data were obtained in both weak and strong coupling regimes, allowing the extraction of relevant magnetic and coupling parameters in all cases. These findings demonstrate the suitability of cavity-based FMR techniques for the investigation of hybrid magnonic systems and their potential applications in spintronic and quantum information technologies.
Elastic properties of plastic crystals with colossal caloric effects
(2026-06) Salvadó Fernández, Jaume; Mañosa, Lluís
Pulse/echo measurements were performed on pellets of the plastic crystals Neopentyl Glycol (NPG) and 1-Bromoadamantane (1-Br-Ad) to obtain the C11 elastic constant in the plastic and crystalline phases, and across the phase transition. The values in the plastic phase (C11 = 2.8 ± 1.5 GPa for NPG and C11 = 3.7 ± 1.5 GPa for 1-Br-Ad) are significantly lower than in the crystal phase (C11 = 8.3 ± 0.5 GPa and C11 = 4.9 ± 0.5 GPa). Furthermore, the attenuation of ultrasonic waves is larger in the plastic phase.
Study of gender bias in the Spanish film industry
(2026-06) Salceda Servitje, Maria; Cardillo, Alessio
Gender bias affects several (if not all) aspects of our lives, including the film industry. This work examines gender bias in the Spanish film industry before and after the promulgation of the 2007 gender equality law. Using the framework of complexity science, collaboration networks are built from the Sensacine database. Subsequently, their structural properties are measured and compared with those of networks obtained using a suitable null model. The empirical networks exhibit statistically significant gender homophily in both periods, with the latter decreasing significantly after 2007. Nonetheless, homophily still persists after 2007, indicating that gender-neutral collaborations had not been achieved by the end of the studied period. Therefore, we conclude that the 2007 law had a tangible but limited structural impact on gender equity in the film industry
Stochastic Volatility in a Continuous-Time Random Walk Model of Financial Markets
(2026-06) Sala Oriol, Hug; Perelló, Josep, 1974-
We develop a generalized continuous-time random walk (CTRW) formalism to describe asset price dynamics by coupling the classical Montroll-Weiss framework with stochastic volatility (SV) models, through Markovian volatility transitions. The study focuses on three primary features: (i) the derivation of a volatility-dependent Montroll-Weiss equation, (ii) the analysis of the distribution tails behaviour across time frames ranging from intraday horizons to a full trading year, and under variations of the SV parameters; and (iii) the determination of the diffusive behaviour of the price distribution through the assessment of its second-order moment.
A new |Vus| determination from kaon and tau decays
(2026-06) Sagristà Castañé, Jan; Gonzalez-Solis De La Fuente, Sergi
The determination of the CKM matrix element |Vus| provides a critical test of Standard Model’s first-row unitarity. In this work, |Vus| is extracted from leptonic and semileptonic kaon decays (Kℓ2 and Kℓ3), as well as exclusive τ → Kντ and semileptonic τ → Kπντ decays. For the semileptonic channels, phase-space integrals are evaluated using standard form-factor parameterizations. For the decay τ− → K0S π−ντ a fit to the spectrum from Belle is performed by incorporating energy-dependent Breit-Wigner resonance descriptions for the participating K∗(892) and K∗(1410) resonances. The individual extraction methods yield compatible values for |Vus| within uncertainties. Combining all determinations gives a global weighted average of |Vus| = 0.22434(29), consistent with current world averages. The corresponding unitarity test reveals a persistent deviation from unity at the 2.5σ level, indicating a lingering tension with Standard Model predictions
Quantum Teleportation of an Unknown State via a Partially Entangled Qutrit Pair
(2026-06) Sabaté Riera, Jan; Taron i Roca, Josep
Quantum teleportation allows the perfect transmission of an unknown quantum state using a shared entangled resource and a classical channel alone. In this work, we study the teleportation of three-level quantum systems, known as qutrits, using entangled three-dimensional pairs. We demonstrate teleportation under maximal entanglement, and develop two complementary probabilistic strategies to herald successful stat recovery when the resource is only partially entangled. Both approaches yield the same maximum success probability, governed entirely by the smallest component of the entangled resource. We further extend these results to quantum systems of arbitrary finite dimension, obtaining a universal closed-form expression for the maximum achievable success probability.
Epidemic spreading in hyperbolic geometry
(2026-06) Rojo Mérida, Adrià; Boguñá, Marián
Epidemic spreading on complex networks is strongly influenced by the underlying network structure. In this work we simulate stochastic SIR epidemics on networks generated with the S¹H² model and compare the results with non-geometric models, including Erdős–Rényi, Barabási-Albert and Configuration model. Using distance-dependent infection rates from the H² embedding and native S¹H² coordinates, we analyse the epidemic dynamics through the variability of the recovered nodes and the spatio-temporal distribution of infection events. We find that hyperbolic networks exhibit lower epidemic thresholds than non-geometric networks, consistent with a hierarchical radial placement of hubs in the centre of the hyperbolic plane enhancing the epidemic transmissibility. The average hyperbolic distance reached by the infection follows a universal rescaled behaviour largely independent of the network topology. Furthermore, only the hyperbolic model displays an approximately coherent wavefront-like propagation through latent space, whereas non-geometric networks exhibit almost instantaneous spreading with weak distance dependence. These results show that hidden hyperbolic geometry qualitatively amplifies epidemic propagation and shapes the dynamical organisation of the spreading process.
A machine learning approach for CP asymmetry detection
(2026-06) Rodríguez Reus, Àlex; Marin Benito, Carla; Souza de Almeida, Felipe Luan
A novel model-independent approach to search for CP violation based on machine learning is presented, together with two standard approaches in the literature: the energy test and the Miranda method. The latter and the novel technique are tested using simulated D± → K∓K±π± samples of 200 pseudo-experiments generated to analyze the phase space of these decays. Results from the machine learning approach are compared against those of the Miranda method, which employs a binning scheme adapted to this specific dataset. While this binning approach is shown to be a superior detection technique for the considered dataset, potential enhancements to the machine learning strategy are suggested to achieve higher statistical significance than the Miranda method
Quantifying Non-Newtonian Reasoning in Mechanics
(2026-06) Rodríguez Calderón, Nuria; Vilà i Arbonès, Anna Maria
This thesis studies non-Newtonian reasoning in mechanics through Force Concept Inventory responses. It combines a large-scale dataset with a reduced ten-item survey administered to Physics and Engineering students in Barcelona. Answers are classified as Newtonian, Aristotelian, or residual, and are analyzed with response frequencies, Bao–Redish model analysis, and transition matrices. Overall, Aristotelian reasoning persists beyond instruction and academic level, and student responses are better described as mixed states than pure models.
Testing the performance of image deconvolution for crowded field photometry of Cepheid stars
(2026-06) Rocamora i Martorell, Ferran; Courbin, Frédéric
The systematic errors in the distance-ladder measurement of the Hubble constant (H0) have been under close scrutiny in recent years. In this work, we test a method not previously applied in this context, image deconvolution with STARRED, to examine the effects of crowding on photometry and, consequently, on the distance-ladder measurement of H0. Using simulations of crowded fields from HST images of NGC 4258, we assessed the possible bias over a range of signalto-noise ratios. The point spread function used in the simulations was extracted from another HST field, NGC 136. Ten thousand injections were performed for each crowding regime with the recovered amplitudes showing small relative errors compared with the injected amplitudes, even in low signalto-noise regimes. Our results suggest that this method is effectively unbiased within tested regimes, which could be a substantial improvement in constraining possible Cepheid photometry systematic errors.
Memristive devices for improving AI energy efficiency
(2026-06) Rivero Artalejo, Elena; Cirera Hernández, Albert; Aran Vilà, Pere
Resistive switching memories (ReRAM) are emerging devices that can exhibit both volatile and non-volatile behaviour, making them promising candidates for next-generation memory and neuromorphic computing applications. In this work, inkjet printed Ag/h-BN/Au memristive devices based on an hexagonal boron nitride dielectric, which is a two-dimensional material, are experimentally investigated. Electrical characterization is performed through current–voltage measurements, where reproducible switching between high- and low-resistance states is observed, associated with the formation and rupture of conductive filaments driven by ionic migration. Both volatile and non-volatile regimes are obtained depending on the applied electrical conditions. The role of current compliance in filament stabilization during the switching process is considered. In addition, the devices are analysed in terms of cycle-to-cycle and device-to-device variability to evaluate their reproducibility and reliability. The results highlight the stochastic nature
Analysis and diagnostics of extragalactic shock-excited regions using MUSE’s IFU spectroscopic observations
(2026-06) Riera Pintado, Maria; Kopsacheili, Maria ; Busquet Rico, Gemma
This work presents an analysis of shock-excited regions in the galaxies PGC128348 and Cartwheel based on MUSE’s IFU spectroscopic data. Applying 2D emission-line diagnostics, 27 shock-excited regions are identified in PGC128348 (12 classified as supernova remnants) and 43 in Cartwheel (all bubbles/superbubbles). Spectral analysis was used to derive gas velocity dispersions and electron densities, while shock velocities are estimated via MAPPINGS V shock models. Results show lower velocity dispersion and higher shock velocities in the outer galactic regions, reflecting the influence of local ISM density on shock evolution.

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