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La radioterapia externa constituye una de las principales técnicas de tratamiento local del cáncer en la actualidad. En este tipo de radioterapia, el haz de radiación se produce fuera del paciente. Existen diversas técnicas en función de cómo se realiza el tratamiento. Una de estas técnicas es la VMAT (Arcoterapia volumétrica de intensidad modulada). El diseño del tratamiento y el cálculo de la distribución de dosis en el paciente se realiza en el sistema de planificación que incorpora una modelización del haz de radiación a través de diferentes parámetros. Se realizará un estudio de la influencia de estos parámetros de acción que intervienen en el sistema de planificación para esta técnica de tratamiento. En particular, se llevará a cabo un análisis de la influencia en el tratamiento de un parámetro como es la velocidad límite de las láminas (MLC) cuando se trabaja con pacientes con un tumor espinal. Para estudiar dicha influencia, se elaborará en primer lugar un código que permita estudiar las conformaciones del tratamiento y complementarán estos resultados con herramientas derivadas del cálculo de la distribución de dosis absorbida como el Histograma Dosis Volumen. Finalmente, se completarán los resultados mediante la verificación de dos tratamientos con el objetivo de comprobar su viabilidad para diferentes velocidades límite.

En la actualidad existe una creciente demanda de dispositivos láser en numerosos entornos profesionales. Así, hay un gran interés por mejorar estos aparatos, obteniendo láseres cada vez más versátiles, potentes y económicos. El uso de materiales plásticos está permitiendo alcanzar muchas mejoras en las propiedades mecánicas del láser, tales como su tamaño y flexibilidad. En este trabajo se han estudiado las propiedades ópticas (absorción y fotoluminiscencia) de un nanografeno (NG) muy novedoso, concretamente un dímero de trianguleno, disperso en un polímero termoplástico (poliestireno, PS) preparado en forma de guía de ondas. Una vez determinada la presencia de emisión espontánea amplificada (ASE), indicativa de la existencia de emisión estimulada, se han fabricado láseres con realimentación distribuida (DFB) con distintas concentraciones de NG en PS. El resonador láser consiste en una red de difracción de relieve unidimensional, fabricada por litografía holográfica, en una capa de fotoresina (gelatina dicromatada) que se deposita sobre la capa activa. Los láseres han sido caracterizados y comparados con otros que utilizaban materiales parecidos al presente NG, revelando el gran potencial de este nuevo compuesto. El estudio ha revelado que este NG presenta emisión en la zona cercana al infrarrojo (NIR), así como un tiempo de vida operacional más largo que otros materiales orgánicos, siendo un compuesto muy interesante para trabajos futuros en el campo de la optoelectrónica. Además, los resultados obtenidos en el presente trabajo han contribuido a la publicación de un artículo científico, que incluye la síntesis del compuesto (Shen, Dijkstra, et al. Angew. Chem. 2023).

En este trabajo se presentará el modelo estándar, que explica las interacciones electromagnética, débil y fuerte, acompañando cada una con las reglas de Feynman correspondientes. Además, se introducirán los grupos de simetría y los grupos de Lie como herramientas matemáticas utilizadas para describir las simetrías en la física y su relación con las leyes de conservación. Estos conceptos serán fundamentales para estudiar las interacciones en detalle. En primer lugar, se abordará la interacción electromagnética, descrita por la electrodinámica cuántica e invariante bajo U(1). Se analizará el decaimiento de partículas y se presentará el modelo estándar de partículas. A continuación, se introducirá la interacción débil, invariante bajo SU(2), que es responsable de la desintegración de ciertos procesos. Se examinará la existencia de partículas mediadoras masivas asociadas a esta interacción, así como la unificación electrodébil. Se explicará cómo la ruptura espontánea de simetría y el mecanismo de Higgs permiten que estas partículas adquieran masa. Finalmente, se explorará la interacción fuerte utilizando la cromodinámica cuántica, una teoría que describe la interacción entre quarks y gluones, y que se basa en el grupo de simetría SU(3).

We present the first 3D fully coupled magneto-thermal simulations of neutron stars (including the most realistic background structure and microphysical ingredients so far) applied to a very complex initial magnetic field topology in the crust, similar to what recently obtained by proto-neutron star dynamo simulations. In such configurations, most of the energy is stored in the toroidal field, while the dipolar component is a few percent of the mean magnetic field. This initial feature is maintained during the long-term evolution (∼106 yr), since the Hall term favours a direct cascade (compensating for Ohmic dissipation) rather than a strong inverse cascade, for such an initial field topology. The surface dipolar component, responsible for the dominant electromagnetic spin-down torque, does not show any increase in time, when starting from this complex initial topology. This is at contrast with the timing properties of young pulsars and magnetars which point to higher values of the surface dipolar fields. A possibility is that the deep-seated magnetic field (currents in the core) is able to self-organize in large scales (during the collapse or in the early life of a neutron star). Alternatively, the dipolar field might be lower than is usually thought, with magnetosphere substantially contributing to the observed high spin-down, via e.g., strong winds or strong coronal magnetic loops, which can also provide a natural explanation to the tiny surface hotspots inferred from X-ray data.

Este trabajo tiene como objetivo la introducción a la teoría de las ecuaciones diferenciales estocásticas, que pueden ser vistas como una generalización de las ecuaciones diferenciales ordinarias. Para ello, daremos las bases de la teoría de probabilidad donde intervienen algunos elementos de teoría de la medida y análisis funcional. Así, se analizarán algunos conceptos básicos sobre procesos estocásticos y profundizaremos en la construcción de la Integral de Itô que será la herramienta clave para construir posteriormente algunos resultados importantes como el teorema de existencia y unicidad, que es análogo al teorema de Picard para ecuaciones diferenciales ordinarias. Dada su importancia (en la versión más general que no trataremos en este trabajo) en física, se expondrá la conocida como ecuación de Fokker-Planck. A lo largo del texto se incluirán algunos ejemplos y/o aplicaciones de estos conceptos a la física.

La gran cantidad de datos ofrecidos por el satélite Gaia en los últimos años nos ha permitido conocer magnitudes observacionales de muchas más estrellas a nuestro alrededor. Entre ellas se encuentran los movimientos propios, los cuales nos dan una visión de cómo se mueven las estrellas y, de forma global, una visión del movimiento galáctico dentro de nuestra Vía Láctea. Se sabe que los cúmulos abiertos de estrellas jóvenes tienen origen en las grandes nubes moleculares protegidas por el polvo interestelar, donde se produce la formación estelar. Estos cúmulos son trazadores excepcionales de la estructura espiral de la galaxia y estas zonas son las que nos pueden dar información más precisa sobre la propia estructura. En este trabajo nos centramos en analizar la estructura espiral y estudiar la rotación galáctica de cúmulos abiertos de estrellas jóvenes en los brazos espirales de la Vía Láctea cerca del Sol. La idea es calcular el movimiento de estas estrellas basándonos en el modelo cinemático de rotación galáctica y compararlo con los movimientos observados reales ofrecidos por Gaia. Para ello, desarrollaremos el modelo y calcularemos, con un programa hecho en python, los movimientos propios correspondientes de cúmulos jóvenes en el brazo de Perseo y en el de Sagitario. Estos valores calculados se comparan luego con los valores observacionales que ofrece Gaia. A partir de esta comparación, el primer objetivo sería ver si las estrellas o cúmulos observados tienen el movimiento o la rotación esperada según el modelo cinemático teórico. Por otro lado, también vamos a tratar con asociaciones de cúmulos estelares abiertos. Esto es, cúmulos abiertos desligados gravitacionalmente que se han creado en un mismo fenómeno de formación estelar sobre una cierta zona reducida y que conservan prácticamente los mismos movimientos propios debido a la rotación galáctica en esa zona. Conociendo este hecho y basándonos en los resultados anteriormente obtenidos, nuestro segundo objetivo

En este trabajo se expondrán las principales características que debe cumplir un agujero de gusano (o puente de Einstein-Rosen), concepto propuesto como una solución a las ecuaciones de campo de Einstein de la Relatividad General por primera vez por Albert Einstein y Nathan Rosen en 1935, para ser hipotéticamente atravesable. Además, se realizará un estudio de la naturaleza de la materia responsable de generar la estructura geométrica de un agujero de gusano de estas características, comprobando que es necesaria la existencia de lo que los físicos denominan materia exótica. Además, se abordarán temas como la violación de las Condiciones de Energía, que son restricciones referidas al contenido material considerado por la Relatividad General, en el interior de los agujeros de gusano de estas características. Finalmente, se estudiarán rudimentos de los “Warp Drives” o transporte por curvatura, haciendo especial énfasis en la solución o métrica de Alcubierre, propuesta por el físico mexicano Miguel Alcubierre en el año 1994 mientras realizaba su tesis doctoral, y sus consecuencias principales.

En este Trabajo de Fin de Grado se han analizado de manera cuantitativa una muestra de espectros ópticos de estrellas tipo OB. Las estrellas masivas tipo OB incluyen todos los tipos O y aquellas de tipo B2 o anteriores en el caso de las enanas, tipo B5 o anteriores en el caso de las gigantes, y todos los subtipos B en el caso de las supergigantes (clases de luminosidad I o II). El estudio de estas estrellas es de gran importancia para comprender mejor la estructura y evolución del Universo ya que entre sus características principales destaca que en las reacciones nucleares que tienen lugar en su interior se producen los elementos más pesados del Universo, como el hierro, y cuando estas estrellas explotan en forma de supernova expulsan estos elementos al espacio y posteriormente se incorporan en nuevas estrellas y planetas. Además, las estrellas tipo OB producen radiación ultravioleta y vientos estelares energéticos que afectan al medio interestelar y a la formación de nuevas estrellas y planetas. Los objetivos principales de este proyecto han sido determinar los parámetros estelares de una muestra de estrellas OB cuyos espectros se simularon para ser parecidos a los que obtendrá WEAVE, espectrógrafo situado en el telescopio William Herschel del observatorio del Roque de los Muchachos en España, a partir de datos existentes en la base de datos IACOB. Los resultados obtenidos permitirán conocer el grado de precisión de los parámetros que se obtengan a partir de los datos reales WEAVE, aportando un input necesario para su interpretación. Para todo ello, se ha realizado un estudio bibliográfico sobre WEAVE, los surveys asociados que implican estrellas OB y las técnicas de análisis de este tipo de estrellas. En primer lugar, se han recopilado datos fotómetricos y astrométricos de la muestra de estrellas OB seleccionada para WEAVE, haciendo uso de la herramienta TOPCAT. A partir de la base de datos IACOB, se degradó la muestra de espectros a las resoluciones de WEAVE y fi

En este trabajo se han estudiado los defectos generados por cascadas colisionales en Fe-Cr por medio de simulaciones de dinámica molecular (MD). En total, se han realizado 750 simulaciones de cascadas colisionales de energías 2 − 6 keV para una red BCC de Fe-Cr con %Cr de 0 − 15% y temperaturas de trabajo de T = 10 − 300K. Se ha utilizado un potencial que permite describir correctamente la interacción entre átomos dependiendo de la concentración de Cr, CD-EAM (Concentration-Dependent Embedded-Atom Method), en combinación con un potencial Ziegler-Biersack-Littmark (ZBL) para las colisiones de átomos energéticos a distancias interatómicas pequeñas. Para las simulaciones se ha utilizado el código de dinámica molecular LAMMPS y para observar los resultados se ha utilizado el entorno gráfico 3D OVITO, a partir del cual se ha realizado la exportación de los datos para su análisis a través de un script en Python. En este estudio se aborda la dependencia de la producción de pares de Frenkel, así como la formación de clusters de intersticiales con factores como la energía de la cascada colisional, la temperatura y el porcentaje de Cr presente en la red. Los resultados revelan un claro aumento de la formación de pares de Frenkel y clusters de intersticiales con la energía de la cascada colisional y una disminución del número de defectos con la temperatura. En cuanto a los intersticiales simples (dumbbells) se ha visto que, a pesar del aumento del % de Cr, no se observan dumbbells de tipo Cr-Cr debido a una repulsión de origen magnético entre átomos de Cr. Asimismo, el % de Cr en los defectos es claramente inferior al de la malla utilizada, lo cual estaría relacionado con la mayor energía que es necesaria para desplazar un átomo de Cr y con la repulsión de origen magnético mencionada. Además, se ha estudiado la estructura de los clusters de intersticiales y se ha observado que están compuestos de un núcleo interior formado por átomos de Fe, mientras que los átomos de Cr se ubi

Este trabajo se ubica dentro del campo de estudio de materiales orientados a reactores de fusión. En él se lleva a cabo un estudio preliminar sobre el tipo de radiación generada por un reactor de fusión, su interacción con la pared y cómo abordar este problema mediante simulaciones a distintas escalas. Se examina el estado actual de las investigaciones a través de una búsqueda bibliográfica, así como los principales desafíos en este campo. A continuación, se lleva a cabo una aproximación multiescala de las interacciones plasma-pared. Por un lado, se utiliza el método BCA (binary collision approximation) a través del programa SRIM, con el objetivo de realizar un estudio preliminar para determinar los rangos de iones y el daño que causan en tres materiales comúnmente utilizados en prototipos de reactores de fusión. Además, se analizan los procesos presentes en las simulaciones de dinámica molecular mediante el uso de LAMMPS, comparando los resultados obtenidos con el método BCA.

En muchos escenarios físicos complejos, como la resolución de determinados problemas de dinámica de fluidos en contextos astrofísicos, necesitamos recurrir inevitablemente a métodos numéricos, con las limitaciones que ello comporta. A grandes escalas tenemos que el coste computacional de resolver estos problemas es muy elevado, por lo que resulta necesario buscar algún método para reducirlo, tratando de perder la menor cantidad de información posible acerca de los fenómenos físicos que están teniendo lugar. En el presente trabajo, expondremos un estudio que hemos realizado sobre un modelo sub-grid, tratando de tener en cuenta la contribución de las escalas no resueltas en las ecuaciones de evolución del sistema, aplicado a un flujo ideal incompresible con ecuación de estado genérica.

El satélite Gaia (lanzado el 19 de diciembre de 2013) ha hecho pública la mayor base de datos astrofísicos hasta la fecha, incluyendo información para cerca de 350 millones de objetos en el espacio. Proporcionando también una serie de herramientas en Python3, recopiladas en la librería denominada GaiaXPy, a través de la cual se pueden obtener tanto los espectros de las estrellas observadas (calibrados externa e internamente) como la fotometría sintética que de ellos deriva (Gaia Collaboration, Montegriffo et al. 2022), la cual será el objeto de nuestro estudio. En este trabajo se utilizará ésta última, para compararla con la fotometría ya existente en la literatura publicada de ciertos cúmulos abiertos de estrellas, con la finalidad de comprobar su buen funcionamiento así como determinar la existencia de posibles errores sistemáticos que afecten a esta aplicación en el rango óptico. Se harán 4 comparativas generales de la fotometría obtenida por el satélite Hipparcos, el telescopio Pan-STARRS y los sistemas fotométricos de Johnson (UBV) y Strömgren (uvby), con sus respectivas fotometrías sintéticas obtenidas a partir de los datos obtenidos del satélite Gaia. Tras la realización de este estudio se ha obtenido que la fotometría sintética referente al satélite Hipparcos presenta cierta dispersión en torno a los valores que se deberían simular, así como una saturación en el telescopio Pan-STARRS para estrellas de magnitudes inferiores a 14. Pese a ello, se ha encontrado que el error relativo de la fotometría sintética respecto de la real, es en todos los casos inferior al 1%, tal y como se establece en Gaia Collaboration, Montegriffo et al. 2022.

Los llamados materiales de van der Waals están constituidos por capas atómicas de material apiladas y unidas entre ellas de forma débil mediante interacciones de van der Waals. Esto permite su fácil separación por medios mecánicos y, de esta forma, pueden prepararse de forma sencilla capas delgadas de material, con espesores de incluso una sola capa (o muy pocas capas) de átomos, que se conocen como materiales bidimensionales o materiales 2D. Debido a las novedosas propiedades ópticas y optoelectrónicas que presentan estos materiales por su escaso grosor, existe un creciente interés en su estudio para aplicaciones optoelectrónicas. Especialmente, en el ámbito de los fotodetectores, donde los semiconductores convencionales, como los basados en Si o InGaAs, están limitados en aspectos como su cobertura espectral, su baja resolución y su inflexibilidad. En este trabajo se busca estudiar la fotocorriente del disulfuro de renio (ReS2) en función de la polarización de la luz incidente, con el fin de incorporarlo en dispositivos para la fotodetección de luz polarizada. Para ello, se diseñó y elaboró un montaje experimental capaz de realizar medidas eléctricas mientras se incidía a la muestra con luz polarizada. El control de esta polarización con el montaje fue exhaustivamente estudiado mediante un método propio basado en los parámetros de Stokes y el formalismo de Mueller. Con este método no solo se aseguró la validez del montaje y el posible error que este podía introducir, sino que también se confirmó su potencial para futuras medidas de reflectancia usando este mismo método. Con este montaje y con las muestras de ReS2 exfoliadas de forma mecánica, se realizaron las medidas de fotocorriente y se comprobó que existía un efecto que enmascaraba la dependencia de estas con el ángulo de polarización. Esto dio paso a un a un análisis de los distintos mecanismos que producen fotocorriente en este semiconductor, lo que llevó a demostrar que el mecanismo predominante en la fotoc

Magnons and plasmons are different collective modes, involving the spin and charge degrees of freedom, respectively. Formation of hybrid plasmon–magnon polaritons in heterostructures of plasmonic and magnetic systems faces two challenges, the small interaction of the electromagnetic field of the plasmon with the spins, and the energy mismatch, as in most systems plasmons have energies orders of magnitude larger than those of magnons. We show that graphene plasmons form polaritons with the magnons of two-dimensional ferromagnetic insulators, placed up to to half a micrometer apart, with Rabi splittings in the range of 100 GHz (dramatically larger than cavity magnonics). This is facilitated both by the small energy of graphene plasmons and the cooperative super-radiant nature of the plasmon–magnon coupling afforded by phase matching. We show that the coupling can be modulated both electrically and mechanically, and we propose a ferromagnetic resonance experiment implemented with a two-dimensional ferromagnet driven by graphene plasmons.

In this work we establish some results concerning the existence of external light rings in extremal black hole spacetimes through the Newman-Penrose formalism. Specifically, assuming flat or (anti)–de Sitter asymptotics, staticity and the null energy condition, we show that a sufficient condition for the existence of external light rings is R < 2KG, where R, the curvature scalar of the spacetime and KG, the Gaussian curvature of a spacelike two-surface, are both evaluated at the outermost event horizon, which can be endowed with spherical, hyperbolic or planar geometry. Our results are valid for any metric gravity theory where photons follow null geodesics.

Magnetic 2D materials hold promise to change the miniaturization paradigm of unidirectional photonic components. However, the integration of these materials in devices hinges on the accurate determination of the optical properties down to the monolayer limit, which is still missing. By using hyperspectral wide-field imaging at room temperature, we reveal a nonmonotonic thickness dependence of the complex optical dielectric function in the archetypal magnetic 2D material CrI3 extending across different length scales: onsetting at the mesoscale, peaking at the nanoscale, and decreasing again down to the single layer. These results portray a modification of the electronic properties of the material and align with the layer-dependent magnetism in CrI3, shedding light on the long-standing structural conundrum in this material. The unique modulation of the complex dielectric function from the monolayer up to more than 100 layers will be instrumental for understanding mesoscopic effects in layered materials and tuning light-matter interactions in magnetic 2D materials.

Two computational methods — one physics-based, and the other one deep-learning based — are proposed to enable the systematic investigation of magnetic order in moiré magnets from first principles.

We investigate two novel models of charged black holes in the framework of non-linear electrodynamics of Born–Infeld type. In particular, starting from two concrete Lagrangian densities, the corresponding metric potentials, the electric field, the Smarr formula and finally, the (scalar) quasinormal modes are computed for each model. Our findings show that although the models look very similar, their quasinormal spectra are characterized by certain differences.

In this work, we generate curved Lorentzian manifolds from a flat Minkowskian space–time, through the Gravitational Decoupling by the Minimal Geometric Deformation method interpreting the decoupling sector as a generator of curvature and matter distribution. In particular, we obtain some new wormhole geometries by imposing either physically relevant equations of state or certain physically–motivated geometric constraints. These solutions are analyzed in detail. For all these solutions, we study the associated energy conditions, the geometric behavior and construct their embedding diagrams.

Serving as the progenitors of electromagnetic and gravitational-wave transients, massive stars have received renewed interest in recent years. However, many aspects of their birth and evolution remain opaque, particularly in the context of binary interactions. The centre of our Galaxy hosts a rich cohort of very massive stars, which appear to play a prominent role in the ecology of the region. In this paper, we investigate the binary properties of the Arches cluster, which is thought to host a large number of very massive stars. A combination of multi-epoch near-IR spectroscopy and photometry was utilized to identify binaries. 13 from 36 cluster members meet our criteria to be classed as RV variable. Combining the spectroscopic data with archival radio and X-ray observations – to detect colliding wind systems – provides a lower limit to the binary fraction of ∼43 per cent; increasing to ≳50 per cent for the O-type hypergiants and WNLha. Dynamical and evolutionary masses reveal the primaries to be uniformly massive (⁠≳50M⊙⁠). Where available, orbital analysis reveals a number of short period, highly eccentric binaries, which appear to be pre-interaction systems. Such systems are X-ray luminous, with 80 per cent above an empirical bound of (Lx/Lbol) ∼ 10−7 and their orbital configurations suggest formation and evolution via a single-star channel; however, we cannot exclude a binary formation channel for a subset. Qualitative comparison to surveys of lower mass OB-type stars confirms that the trend to an extreme binary fraction (≥60 per cent) extends to the most massive stars currently forming in the local Universe.

Los materiales bidimensionales, específicamente los dicalcogenuros de metales de transición (TMDs), han despertado un gran interés en la actualidad debido a las propiedades singulares que exhiben en comparación con los materiales en su forma tridimensional. Entre estas características se destacan la fotoluminiscencia y la notable flexibilidad mecánica. La exfoliación mecánica ha sido ampliamente empleada como método de obtención de muestras de espesor atómico a partir de materiales de van der Waals en investigaciones previas. No obstante, esta técnica no es adecuada para la producción a gran escala de los TMDs. Por consiguiente, el objetivo de este estudio consiste en implementar un sistema de crecimiento por deposición química en vapor (CVD) que permita una producción más eficiente y a mayor escala de los TMDs. En primer lugar, se lleva a cabo un análisis de las propiedades generales de los TMDs semiconductores, lo cual contribuye a una mejor comprensión de su comportamiento y sus posibles aplicaciones. A continuación, se aborda de manera detallada el montaje del sistema de crecimiento por deposición química en vapor, describiendo los componentes necesarios y su funcionamiento, para posteriormente presentar el montaje implementado. Se detalla en concreto el desarrollo de un control automatizado de temperatura. Por último, se exponen los resultados obtenidos mediante este método de crecimiento, incluyendo una discusión acerca de las propiedades y características de las muestras de TMDs obtenidos, así como posibles áreas de mejora.

A lo largo de este trabajo, estudiaremos la emisión de ondas gravitacionales en estrellas de neutrones aisladas. Para ello, comenzaremos con un contexto histórico que nos permitirá conocer el origen de estas perturbaciones, así como los fenómenos que hubo detrás de la confirmación de la existencia de las estrellas de neutrones. Posteriormente, definiremos y caracterizaremos las ondas gravitacionales, con el fin de facilitar su comprensión para cuando estudiemos su generación en el seno de las estrellas de neutrones deformadas. Por último, tras haber hallado las expresiones correspondientes a la amplitud y la luminosidad de dichas ondas, analizaremos sus posibles detecciones por parte de los principales detectores interferométricos que se emplean en la actualidad.

The assessment of the seismic behaviour of historic residential buildings and the estimation of their possible losses in the event of an earthquake, is a must for defining strategic mitigation plans to prevent irreplaceable heritage losses. In this study an integrated performance based probabilistic risk assessment methodology is developed. An archival study and a field survey allow to identify architectural and construction characteristics of heritage residential buildings in urban areas and determine realistic structural models. These are analysed by using a limit state approach, coded in the FaMIVE method, considering different construction hypotheses, to produce capacity curves which support the identification of a discrete number of typologies representative of the entire building stock in the area. Their fragility functions are then derived using the modified N2 method. Because of the difficulty in quantifying the expected probable losses in purely economic terms, given the heritage value of these assets, losses are computed in terms of damaged floor surface area and mean damage ratio. These have been obtained through the earthquake loss estimation platform SELENA, considering different possible seismic scenarios. The procedure is applied to masonry residential buildings in Pla del Remei area of Valencia, Spain, built between the end of the 19th Century and the end of the Spanish War (1939). This neighbourhood embodies the cultural values, construction techniques and historic legacy of a new and brief era of modernity, inspired by the new urban theories and architectural styles of Eclecticism and Modernism. Despite Valencia being located in an area of low to moderate seismicity, the results show that the maximum percentage of built damaged area ranges from 5.8 to 11.6% for 475 years return period, increasing to 33.59–51.59% for 975 years return period. The high level of resolution of the study allows mapping and identifying the structures at higher risk and is

Multi-directional spin-to-charge conversion—in which spin polarizations with different orientations can be converted into a charge current in the same direction—has been demonstrated in low-symmetry materials and interfaces. This is possible because, in these systems, spin-to-charge conversion can occur in unconventional configurations in which charge current, spin current, and polarization do not need to be mutually orthogonal. Here, we explore, in the low temperature regime, the spin-to-charge conversion in heterostructures of graphene with the low-symmetry 1T' phase of MoTe2. First, we observe the emergence of charge conversion for out-of-plane spins at temperatures below 100 K. This unconventional component is allowed by the symmetries of both MoTe2 and graphene and likely arises from spin Hall effect in the spin–orbit proximitized graphene. Moreover, we examine the low-temperature evolution of non-local voltage signals arising from the charge conversion of the two in-plane spin polarizations, which have been previously observed at higher temperature. As a result, we report omni-directional spin-to-charge conversion—for all spin polarization orientations—in graphene/MoTe2 heterostructures at low temperatures.

Context. Automated analyses of Gaia astrometric data have led to the discovery of many new high-quality open cluster candidates. When a good determination of their parameters is available, these objects become excellent tools for investigating the properties of our Galaxy. Aims. We explore whether young open clusters can be readily identified from Gaia data alone by studying the properties of their Gaia colour-magnitude diagrams. We also want to compare the results of a traditional cluster analysis with those of automated methods. Methods. We selected three young open cluster candidates from the UBC catalogue, ranging from a well-populated object with a well-defined sequence to a poorly populated and poorly defined candidate. We obtained classification spectra for the brightest stars in each. We redetermined members based on EDR3 data and fitted isochrones to derive the age, distance, and reddening. Results. All three candidates are real clusters with ages below 100 Ma. UBC 103 is a moderately populous cluster, with an age around 70 Ma. At a distance of ∼3 kpc, it forms a binary cluster with nearby NGC 6683. UBC 114 is a relatively proximal (∼1.5 kpc) poorly populated cluster containing two early-B stars. UBC 587 is a dispersed and very young (≤10 Ma) cluster located at ∼3 kpc, behind the Cygnus X region, which may be a valuable tracer of the Orion arm. Conclusions. The OCfinder methodology for the identification of new open clusters is extremely effective, with even poor candidates resulting in interesting detections. The presence of an almost vertical photometric sequence in the Gaia colour-magnitude diagram is a safe way to identify young open clusters. Automated methods for the determination of cluster properties give approximate solutions, but these are still subject to difficulties. There is some evidence suggesting that artificial intelligence systems may systematically underestimate extinction, which may impact in the age determination.

This work gives a brief review of the theory behind the non-equilibrium Green’s Functions (NEGF) method for quantum transport in nanojunctions. We cover the principles of electronic transport with Landauer’s theory thought the scattering formalism, to later connect it to the Green’s functions approach and cover the main ab-initio method used to implement the theory, the Density Functional Theory (DFT). Moreover, we developed a tool to greatly boost the number and quality of quantum transport calculations. We used the tool to make a full analysis of dithia[9]helicene, a chiral molecule with two isomers, in nanojunctions of gold and platinum. This manuscript covers multiple types of junctions for the molecule, being an extensive database for dithia[9]helicene transport in nanojuntions. Also, we use new types of analysis of the spin polarization based on symmetry breaking via electrode rotations to unveil the role of the electrodes in the Chiral Induce Spin Selectivity (CISS) effect of the molecule through the Spin Orbit Coupling (SOC) of the electrodes.

Using Physics-Informed Neural Networks (PINNs) to solve a specific boundary value problem is becoming more popular as an alternative to traditional methods. However, depending on the specific problem, they could be computationally expensive and potentially less accurate. The functionality of PINNs for real-world physical problems can significantly improve if they become more flexible and adaptable. To address this, our work explores the idea of training a PINN for general boundary conditions and source terms expressed through a limited number of coefficients, introduced as additional inputs in the network. Although this process increases the dimensionality and is computationally costly, using the trained network to evaluate new general solutions is much faster. Our results indicate that PINN solutions are relatively accurate, reliable, and well-behaved. We applied this idea to the astrophysical scenario of the magnetic field evolution in the interior of a neutron star connected to a force-free magnetosphere. Solving this problem through a global simulation in the entire domain is expensive due to the elliptic solver’s needs for the exterior solution. The computational cost with a PINN was more than an order of magnitude lower than the similar case solved with a finite difference scheme, arguably at the cost of accuracy. These results pave the way for the future extension to 3D of this (or a similar) problem, where generalised boundary conditions are very costly to implement.

We introduce a classification of the radial spin textures in momentum space that emerge at the high-symmetry points in crystals characterized by nonpolar chiral point groups (D2, D3, D4, D6, T , O). Based on the symmetry constraints imposed by these point groups in a vector field, we study the general expression for the radial spin textures up to third order in momentum. Furthermore, we determine the high-symmetry points of the 45 nonpolar chiral space groups supporting a radial spin texture. These two principles are used to screen materials databases for archetypes that go beyond the basic hedgehog radial spin texture. Among the selected materials we highlight the axion insulator candidate Ta2Se8I, the material proposed for dark matter detection Ag3AuTe2, and heazlewoodite Ni3S2, a conventional metal predicted to exhibit current-induced spin polarization. We point out that the symmetry analysis proposed in this Letter is more general and extends to studying other vector properties in momentum space.

In the field of molecular electronics, especially in quantum transport experiments, determining the geometrical configurations of a single molecule trapped between two electrodes can be challenging. To address this challenge, we employed a combination of molecular dynamics (MD) simulations and electronic transport calculations based on density functional theory to determine the molecular orientation in our break-junction experiments under ambient conditions. The molecules used in this study are common solvents used in molecular electronics, such as benzene, toluene (aromatic), and cyclohexane (aliphatic). Furthermore, we introduced a novel criterion based on the normal vector of the surface formed by the cavity of these ring-shaped monocyclic hydrocarbon molecules to clearly define the orientation of the molecules with respect to the electrodes. By comparing the results obtained through MD simulations and density functional theory with experimental data, we observed that both are in good agreement. This agreement helps us to uncover the different geometrical configurations that these molecules adopt in break-junction experiments. This approach can significantly improve our understanding of molecular electronics, especially when using more complex cyclic hydrocarbons.

The absorption and emission of light in single-layer transition metal dichalcogenides are governed by the formation of excitonic quasiparticles. Strain provides a powerful technique to tune the optoelectronic properties of two-dimensional materials and thus to adjust their exciton energies. The effects of large compressive strain in the optical spectrum of two-dimensional (2D) semiconductors remain rather unexplored compared to those of tensile strain, mainly due to experimental constraints. Here, we induced large, uniform, biaxial compressive strain (∼1.2%) by cooling, down to 10 K, single-layer WS2, MoS2, WSe2, and MoSe2 deposited on polycarbonate substrates. We observed a significant strain-induced modulation of neutral exciton energies, with blue shifts up to 160 meV, larger than in any previous experiments. Our results indicate a remarkably efficient transfer of compressive strain, demonstrated by gauge factor values exceeding previous results and approaching theoretical expectations. At low temperatures, we investigated the effect of compressive strain on the resonances associated with the formation of charged excitons. In WS2, a notable reduction of gauge factors for charged compared to neutral excitons suggests an increase in their binding energy, which likely results from the effects of strain added to the influence of the polymeric substrate.

In this work, we prove that every f(R) gravity can be represented as a scale-dependent one, but not every scale-dependent gravity can be represented in the f(R) framework. Therefore, the f(R) formalism is strictly included in the scale-dependent approach. This scale-dependent representation of f(R) gravity allows for a novel approach toward both theories. In particular, we obtain a novel dynamical characterization of light rings for f(R(r)) theories and we have shown that some previous solutions of f(R) theories correspond to solutions of scale-dependent gravity. Finally, new solutions to scale-dependent gravity are identified with the help of the f(R) representation.

We provide a comprehensive theory of magnetic phases in two-dimensional triangulene crystals, using both Hubbard model and density functional theory (DFT) calculations. We consider centrosymmetric and noncentrosymmetric triangulene crystals. In all cases DFT and the mean-field Hubbard model predict the emergence of broken-symmetry antiferromagnetic (ferrimagnetic) phases for the centrosymmetric (noncentrosymmetric) crystals. This includes the special case of the [4,4]triangulene crystal, whose noninteracting energy bands feature a gap with flat valence and conduction bands. We show how the lack of contrast between the local density of states of these bands, recently measured via scanning tunneling spectroscopy, is a natural consequence of a broken-symmetry Néel state that blocks intermolecular hybridization. Using random phase approximation, we also compute the spin wave spectrum of these crystals, including the recently synthesized [4,4]triangulene crystal. The results are in excellent agreement with the predictions of a Heisenberg spin model derived from multiconfiguration calculations for the unit cell. We conclude that experimental results are compatible with an antiferromagnetically ordered phase where each triangulene retains the spin predicted for the isolated species.

We carefully develop the framework required to model the dynamical tidal response of a spinning neutron star in an inspiralling binary system, in the context of Newtonian gravity, making sure to include all relevant details and connections to the existing literature. The tidal perturbation is decomposed in terms of the normal oscillation modes, used to derive an expression for the effective Love number which is valid for any rotation rate. In contrast to previous work on the problem, our analysis highlights subtle issues relating to the orthogonality condition required for the mode-sum representation of the dynamical tide and shows how the prograde and retrograde modes combine to provide the overall tidal response. Utilising a slow-rotation expansion, we show that the dynamical tide (the effective Love number) is corrected at first order in rotation, whereas in the case of the static tide (the static Love number) the rotational corrections do not enter until second order.

Editorial on the Research Topic Seismic microzonation and risk reduction

Nanographene triangulenes with an S = 1 ground state have been used as building blocks of topological antiferromagnetic Haldane spin chains. Using inelastic electron spectroscopy, it was found that the intermolecular exchange was described by the bilinear-biquadratic Hamiltonian. Starting from a Hubbard model, we analytically derive these effective spin interactions using perturbation theory, up to fourth order. For chains with more than two units, other interactions arise that entail second neighbor linear and three-site nonlinear exchange. We discuss the extension to general S = 1 molecules and give numerical results for the strength of the nonlinear exchange for several nanographenes.

In this paper, we study the black hole spacetime structure of a model consisting of the standard Maxwell theory and a p-power-Yang-Mills term. This non-linear contribution introduces a non-Abelian charge into the global solution, resulting in a modified structure of the standard Reissner-Nordström black hole. Specifically, we focus on the model with p = 1/2, which gives rise to a new type of modified Reissner-Nordström black hole. For this class of black holes, we compute the event horizon, the innermost stable circular orbit, and the conditions to preserve the weak cosmic censorship conjecture. The latter condition sets a well-established relation between the electric and the Yang-Mills charges. As a first astrophysical implication, the accretion properties of spherical steady flows around this new modified Reissner-Nordström black hole are investigated in detail. Concretely, we compute the critical radius that establishes the condition for having stable transonic flow in terms of the local sound speed and the involved charges. Extensive numerical examples of how the Yang-Mills charge affects the accretion process of an isothermal fluid in comparison to the standard Reissner-Nordström and Schwarzschild black holes are displayed. Finally, analytical solutions in the fully relativistic regime, along with numerical computations, of the mass accretion rate for a polytropic fluid in terms of the electric and Yang-Mills charges are obtained. As a main result, the mass accretion rate efficiency is considerably improved, with respect to the standard Reissner-Nordström and Schwarzschild solutions, for negative values of the Yang-Mills charge.

The scalar spin chirality is a three-body physical observable that plays an outstanding role both in classical magnetism, characterizing non-co-planar spin textures, and in quantum magnetism, as an order parameter for chiral spin liquids. In quantum information, the scalar spin chirality is a witness of genuine tripartite entanglement. Here we propose an indirect measurement scheme, based on the Hadamard test, to estimate the scalar spin chirality for general quantum states. We apply our method to study chirality in two types of quantum states: generic one-magnon states of a ferromagnet, and the ground state of a model with competing symmetric and antisymmetric exchange. We show a single-shot determination of the scalar chirality is possible for chirality eigenstates, via quantum phase estimation with a single auxiliary qutrit. Our approach provides a unified theory of chirality in classical and quantum magnetism.

Energy conditions and quasinormal modes (QNMs) for scalar perturbations of regular charged black holes within the framework of General Relativity coupled to non-linear electrodynamics (NLE) are discussed. The frequencies are computed numerically adopting the WKB method, while in the eikonal limit an analytic expression for the spectra is obtained. The impact of the electric charge, the angular degree, and the overtone number on the spectra is investigated in detail. All frequencies are characterized by a negative imaginary part, and that each type of energy conditions imply a different quasinormal spectrum are found.

In this study, Physics-Informed Neural Networks (PINNs) are skilfully applied to explore a diverse range of pulsar magnetospheric models, specifically focusing on axisymmetric cases. The study successfully reproduced various axisymmetric models found in the literature, including those with non-dipolar configurations, while effectively characterizing current sheet features. Energy losses in all studied models were found to exhibit reasonable similarity, differing by no more than a factor of three from the classical dipole case. This research lays the groundwork for a reliable elliptic Partial Differential Equation solver tailored for astrophysical problems. Based on these findings, we foresee that the utilization of PINNs will become the most efficient approach in modelling three-dimensional magnetospheres. This methodology shows significant potential and facilitates an effortless generalization, contributing to the advancement of our understanding of pulsar magnetospheres.

El acuífero del Ventós es un pequeño acuífero próximo a la ciudad de Alicante cuyas aguas se destinan exclusivamente al abastecimiento de la localidad de Agost. Sus recursos subterráneos son, por tanto, de especial importancia para esta población. Puesto que estos recursos son fuertemente dependientes de la precipitación, y ante el actual escenario de cambio climático, se ha realizado un estudio con el objeto de comprobar si se han producido cambios y tendencias en la precipitación anual, así como en el número de días de lluvia, episodios lluviosos y episodios lluviosos eficaces frente a la recarga durante los últimos 44 años. Los resultados obtenidos indican que el valor de precipitación anual media es de 282 mm, y a pesar de observarse una ligera tendencia positiva, esta no es estadísticamente significativa. Tampoco la disminución del número de días y episodios lluviosos tienen significación estadística. Los episodios superiores a 20 mm, considerados eficaces frente a la recarga, no reflejan tendencia alguna, por lo que, en principio, se puede concluir que no hay evidencias de un cambio significativo en la precipitación anual sobre el acuífero del Ventós, y especialmente en lo que respecta a precipitación que genera recarga.

We propose a protocol to certify the presence of entanglement in artificial on-surface atomic and molecular spin arrays using electron spin resonance carried by scanning tunnel microscopy (ESR-STM). We first generalize the theorem that relates global spin susceptibility as an entanglement witness to the case of anisotropic Zeeman interactions, relevant for surfaces. We then propose a method to measure the spin susceptibilities of surface-spin arrays combining ESR-STM with atomic manipulation. Our calculations show that entanglement can be certified in antiferromagnetically coupled spin dimers and trimers with state-of-the-art ESR-STM magnetometry.

Perylenediimide (PDI) compounds are widely used as the active units of thin-film organic lasers. Lately, PDIs bearing two sterically hindering diphenylphenoxy groups at the 1,7-bay positions have received attention because they provide a way to red-shift the emission with respect to bay-unsubstituted PDIs, while maintaining a good amplified spontaneous emission (ASE) performance at high doping rates. Here, we report the synthesis of a series of six PDI derivatives with different aryloxy groups (PDI 6 to PDI 10) or ethoxy groups (PDI 11) at the 1,7 positions of the PDI core, together with a complete characterization of their optical properties, including absorption, photoluminescence, and ASE. We aim to stablish structure-property relationships that help designing compounds with optimized ASE performance. Film experiments were accomplished at low PDI concentrations in the film, to resemble the isolated molecule behaviour, and at a range of increasing doping rates, to investigate concentration quenching effects. Compounds PDI 10 and PDI 7, bearing substituents in the 2′ positions of the benzene ring (the one contiguous to the linking oxygen atom) attached to the 1,7 positions of the PDI core, have shown a better threshold performance, which is attributed to conformational (steric) effects. Films containing PDI 11 show dual ASE.

We study indirect exchange interactions between localized spins of magnetic impurities in spin valley coupled systems described with the Kane-Mele model. Our model captures the main ingredients of the energy bands of the 1H transition metal dichalcogenide (TMD) monolayers, such as 1H-MoS2 and 1H-NbSe2. To obtain the effective interactions, we use the exact diagonalization of the Hamiltonian, avoiding momentum cutoffs. We start by comparing the standard perturbation expansion in terms of the Kondo exchange with the exact calculation of the interaction, treating the local spins classically. We find that perturbation theory works well even beyond the regime where the relevant figure of merit, the ratio between the exchange J and the hopping t, is small. We verify that the effective indirect exchange Hamiltonian derived from perturbation theory also works in the nonperturbative regime. Additionally, we analyze the interplay between the symmetry of the different terms of the interaction (Heisenberg, Ising, and Dzyaloshinskii-Moriya), the Fermi-surface topology, and the crystallographic direction in which the impurities are placed. We show that the indirect exchange along the armchair direction is actually Heisenberg-like, due to the reflection symmetry of the crystal structure around this direction. Finally, we explore the exploitation of indirect exchange, combined with atomic manipulation, to engineer the Majumdar-Ghosh model. Our results show that TMDs provide an extremely versatile platform to engineer indirect exchange interactions.

The Gaia-ESO Survey is a public spectroscopic survey that targeted ≳105 stars covering all major components of the Milky Way from the end of 2011 to 2018, delivering its final public release in May 2022. Unlike other spectroscopic surveys, Gaia-ESO is the only survey that observed stars across all spectral types with dedicated, specialised analyses: from O (Teff ~ 30 000–52 000 K) all the way to K-M (≳3500 K). The physics throughout these stellar regimes varies significantly, which has previously prohibited any detailed comparisons between stars of significantly different types. In the final data release (internal data release 6) of the Gaia-ESO Survey, we provide the final database containing a large number of products, such as radial velocities, stellar parameters and elemental abundances, rotational velocity, and also, for example, activity and accretion indicators in young stars and membership probability in star clusters for more than 114 000 stars. The spectral analysis is coordinated by a number of working groups (WGs) within the survey, each specialised in one or more of the various stellar samples. Common targets are analysed across WGs to allow for comparisons (and calibrations) amongst instrumental setups and spectral types. Here we describe the procedures employed to ensure all survey results are placed on a common scale in order to arrive at a single set of recommended results for use by all survey collaborators. We also present some general quality and consistency checks performed on the entirety of the survey results.

Observations of individual massive stars, super-luminous supernovae, gamma-ray bursts, and gravitational wave events involving spectacular black hole mergers indicate that the low-metallicity Universe is fundamentally different from our own Galaxy. Many transient phenomena will remain enigmatic until we achieve a firm understanding of the physics and evolution of massive stars at low metallicity (Z). The Hubble Space Telescope has devoted 500 orbits to observing ∼250 massive stars at low Z in the ultraviolet (UV) with the COS and STIS spectrographs under the ULLYSES programme. The complementary X-Shooting ULLYSES (XShootU) project provides an enhanced legacy value with high-quality optical and near-infrared spectra obtained with the wide-wavelength coverage X-shooter spectrograph at ESO’s Very Large Telescope. We present an overview of the XShootU project, showing that combining ULLYSES UV and XShootU optical spectra is critical for the uniform determination of stellar parameters such as effective temperature, surface gravity, luminosity, and abundances, as well as wind properties such as mass-loss rates as a function of Z. As uncertainties in stellar and wind parameters percolate into many adjacent areas of astrophysics, the data and modelling of the XShootU project is expected to be a game changer for our physical understanding of massive stars at low Z. To be able to confidently interpret James Webb Space Telescope spectra of the first stellar generations, the individual spectra of low-Z stars need to be understood, which is exactly where XShootU can deliver.

In this work, we investigate astrophysical systems in a Newtonian regime using anisotropic matter. For this purpose, we considered that both radial and tangential pressures satisfy a generalized Chaplygin-type equation of state. Using this model, we found the Lane–Emden equation for this system and solved it numerically for several sets of parameters. Finally, we explored the mass supported by this physical system and compared it with the Chandrasekhar mass.

Conducting field surveys for exposure and seismic vulnerability evaluation is the most costly, resource-intensive task when assessing earthquake risk. During the past decade, risk analysts have been trying to alleviate this using remote sensing for building characterization. However, the use of vulnerability databases created with remote sensing had not been sufficiently validated thus far. In this paper, we have created an exposure and seismic vulnerability database in Port Prince (Haiti) using freely accessible aerial ortho-imagery and LiDAR points. We have validated this database against two reference datasets from different, independent studies. Then, we have computed an earthquake damage scenario to test whether remotely sensed data are actually valid for seismic risk evaluation. We have seen how our vulnerability database yields an accurate damage distribution with a low Mean Absolute Percentage Error of 3.78% when compared to the damage obtained with the reference vulnerability dataset. Further, we have conducted a thorough comparison of the cost that entails creating a vulnerability database using remote sensing with a traditional field survey. Twelve international experts have collaborated in the cost estimation of a typical in-field building inspection. As a result, we have found that using remote sensing techniques allows for saving up to 75% of the cost and 85% of the time. These outcomes seem to prove both, the technical and economic feasibility of remote sensing for seismic vulnerability assessment. Thus, we have proposed a 5-step approach for evaluating building vulnerability that combines both, the analysis of remotely sensed data and a reduced, targeted field survey to optimize time and cost. The final goal is to help cities reach the Sustainable Development Goal nr. 11.B to increase their resilience against disasters.

In this work we propose a correspondence between black hole entropy and a topological quantity defined for projective spaces based on the real, complex, and quaternion numbers. After interpreting Weinstein’s integer as the normalized volume of the quantum phase space, whose logarithm gives place to the area law (in the real case) and to logarithmic corrections with −1|2 and −3|2 coefficients (in the complex and quaternionic cases, respectively), the exact Bekenstein-Hawking entropy is obtained when certain equally spaced spectrum for the event horizon area is imposed. Even more, the minimal area(s) which emerge from our model, are of the form 4 log k, k∈ {2, 4, 16}, in complete agreement with previous works. Finally, the role played by global (complex and quaternionic) phases in different descriptions of black hole entropy is clarified.

We designed and built a compact device capable of measuring electronic transport in atomic-sized contacts. This experimental setup is based on the break-junction (BJ) approach. According to the samples used as electrodes, we named the instrument a Surface-Tip Break Junction. Our instrument, like a scanning tunnelling microscope in the BJ configuration, can measure the quantum transport in atoms captured by electrodes. In our case, to measure this transport, we included a homemade I–V converter, a low-cost oscilloscope, and a mobile phone that functions as a data acquisition system. Moreover, we developed a protocol to analyse the digitized data obtained from the oscilloscope. This low-cost pedagogical setup offers the possibility of implementation in undergraduate and graduate laboratories.

Electron-spin resonance carried out with scanning tunneling microscopes (ESR-STM) is a recently developed experimental technique that is attracting enormous interest on account of its potential to carry out single-spin on-surface resonance with subatomic resolution. Here we carry out a theoretical study of the role of tip-adatom interactions and provide guidelines for choosing the experimental parameters in order to optimize spin resonance measurements. We consider the case of the Fe adatom on a MgO surface and its interaction with the spin-polarized STM tip. We address three problems: first, how to optimize the tip-sample distance to cancel the effective magnetic field created by the tip on the surface spin, in order to carry out proper magnetic field sensing. Second, how to reduce the voltage dependence of the surface-spin resonance frequency, in order to minimize tip-induced decoherence due to voltage noise. Third, we propose an experimental protocol to infer the detuning angle between the applied field and the tip magnetization, which plays a crucial role in the modeling of the experimental results.