3.10 Tesis doctorado

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Amorphous materials under stresses: understanding critical behavior
(2022) Villarroel Cortés, Carlos Javier; Düring, Gustavo; Pontificia Universidad Católica de Chile. Facultad de Física
Gran parte de los materiales que utilizamos a diario no se comportan como un sólido elástico o un fluido newtoniano cuando se les aplica deformación. Dentro de la extensa lista de estos materiales que presentan características no lineales en cantidades macroscópicas, podemos encontrar muchos alimentos que consumimos o incluso la piel humana. Comprender estos comportamientos particulares actualmente representa un desafóo importante con aplicaciones en la industria y la medicina. Para responder algunas de las preguntas que estos materiales particulares presentan hoy en día, en esta tesis, utilizando simulaciones numéricas de alto nivel, estudiamos dos fenómenos no lineales críticos, el fenómeno de “Yielding” y el fenómeno de “Strain-Stiffening”. En particular, la transición de “Yielding” se observa en materiales donde, dependiendo de la tensión aplicada, es posible pasar de un estado mecánicamente estable a uno que fluye como un líquido. En este contexto, mediante simulaciones de partículas blandas, se realiza el cálculo de los exponentes críticos que gobiernan el régimen fluido para dos escenarios de esfuerzos aplicados, y se estudia cómo las estadísticas de avalanchas pueden caracterizar el flujo. Finalmente, para el fenómeno “Strain-Stiffening”, se propone un nuevo modelo de redes semi-flexibles capaces de replicar este comportamiento, donde un sistema blando se transforma en uno rígido mediante la aplicación de una deformación. A su vez, este modelo es capaz de explicar y predecir de buena manera los exponentes críticos que gobiernan la transición.
An extensive study of models beyond the standard model
(2020) Maturana Ávila, Ivania; Díaz, Marco A.; Pontificia Universidad Católica de Chile. Instituto de Física
El presente trabajo se centró en el estudio fenomenológico de tres modelos que son extensiones del actual Modelo Estandar: El Inert Higgs Doublet Model, el Scotogenic Model and el Singlet + Triplet Scotogenic Model. La motivación de estudiar estos modelos se basa en que pueden explicar algunas de las preguntas existentes en física hoy en día; todos ellos presentan una particula que será candidato a materia oscura y los últimos dos proponen un mecanismo para dar masa a al menos dos neutrinos. En todos los modelos hemos considerado la generación de la abudancia de materia oscura en un escenario de freeze-out y la partícula candidata a materia oscura será un escalar massivo debilmente interactuante (WIMP definido por su nombre en inglés). El primer trabajo está relacionado con estudiar las principales diferencias entre el Inert Higgs Doiblet Model and el Scotogenic Model. Hemos realizado un estudio profundo de la materia oscura en ambos, investigando puntos que sobrevivan a las cotas mas fuertes en física y en los actuales experimentos y también considerando que estos resultados pueden explicar la densidad de materia oscura en el Universo en su totalidad. Estudiando una señal específica en el Compact Linear Collider (CLIC), investigamos los parámetros que contribuirán a obtener diferentes valores para la sección eficaz en ambos modelos. En el segundo trabajo, hemos reexaminado el Singlet + Triplet Scotogenic Model el cual generaliza la idea introducida en el Scotogenic model simple, haciendo su fenomenología viable y mucho mas rica. Relalizamos un estudio fenomenológico detallado de la materia oscura escalar, actualizando las cotas actuales de los experimentos. Investigamos la detección directa de dark matter y la detección indirecta vía rayos gamma. Además, realizamos un estudio en colisionadores el cual tendrá relevantes implicaciones para las futuras búsquedas a alta luminosidad del Large Hadron Collider (LHC definido por su nombre en inglés).
Aspects of quantum gravity in AdS3/CFT2
(2019) Reyes Raffo, Ignacio Andrés; Erdmenger, Johanna; Koch, Benjamin; Bañados, Máximo; Ströhmer, Raimund; Pontificia Universidad Católica de Chile. Facultad de Física
The quest for finding a unifying theory for both quantum theory and gravity lies at the heart of much of the research in high energy physics. Although recent years have witnessed spectacular experimental confirmation of our expectations from Quantum Field Theory and General Relativity, the question of unification remains as a major open problem. In this context, the perturbative aspects of quantum black holes represent arguably the best of our knowledge of how to proceed in this pursue. In this thesis we investigate certain aspects of quantum gravity in 2 + 1 dimensional anti-de Sitter space (AdS3), and its connection to Conformal field theories in 1 + 1 dimensions (CFT2), via the AdS/CFT correspondence. We study the thermodynamics properties of higher spin black holes. By focusing on the spin-4 case, we show that black holes carrying higher spin charges display a rich phase diagram in the grand canonical ensemble, including phase transitions of the Hawking-Page type, first order inter-black hole transitions, and a second order critical point. We investigate recent proposals on the connection between bulk codimension-1 volumes and computational complexity in the CFT. Using Tensor Networks we provide concrete evidence of why these bulk volumes are related to the number of gates in a quantum circuit, and exhibit their topological properties. We provide a novel formula to compute this complexity directly in terms of entanglement entropies, using techniques from Kinematic space. We then move in a slightly different direction, and study the quantum properties of black holes via de Functional Renormalisation Group prescription coming from Asymptotic safety. We avoid the arbitrary scale setting by restricting to a narrower window in parameter space, where only Newton’s coupling and the cosmological constant are allowed to vary. By one assumption on the properties of Newton’s coupling, we find black hole solutions explicitly. We explore their thermodynamical properties, and discover that very large black holes exhibit very unusual features.The quest for finding a unifying theory for both quantum theory and gravity lies at the heart of much of the research in high energy physics. Although recent years have witnessed spectacular experimental confirmation of our expectations from Quantum Field Theory and General Relativity, the question of unification remains as a major open problem. In this context, the perturbative aspects of quantum black holes represent arguably the best of our knowledge of how to proceed in this pursue. In this thesis we investigate certain aspects of quantum gravity in 2 + 1 dimensional anti-de Sitter space (AdS3), and its connection to Conformal field theories in 1 + 1 dimensions (CFT2), via the AdS/CFT correspondence. We study the thermodynamics properties of higher spin black holes. By focusing on the spin-4 case, we show that black holes carrying higher spin charges display a rich phase diagram in the grand canonical ensemble, including phase transitions of the Hawking-Page type, first order inter-black hole transitions, and a second order critical point. We investigate recent proposals on the connection between bulk codimension-1 volumes and computational complexity in the CFT. Using Tensor Networks we provide concrete evidence of why these bulk volumes are related to the number of gates in a quantum circuit, and exhibit their topological properties. We provide a novel formula to compute this complexity directly in terms of entanglement entropies, using techniques from Kinematic space. We then move in a slightly different direction, and study the quantum properties of black holes via de Functional Renormalisation Group prescription coming from Asymptotic safety. We avoid the arbitrary scale setting by restricting to a narrower window in parameter space, where only Newton’s coupling and the cosmological constant are allowed to vary. By one assumption on the properties of Newton’s coupling, we find black hole solutions explicitly. We explore their thermodynamical properties, and discover that very large black holes exhibit very unusual features.The quest for finding a unifying theory for both quantum theory and gravity lies at the heart of much of the research in high energy physics. Although recent years have witnessed spectacular experimental confirmation of our expectations from Quantum Field Theory and General Relativity, the question of unification remains as a major open problem. In this context, the perturbative aspects of quantum black holes represent arguably the best of our knowledge of how to proceed in this pursue. In this thesis we investigate certain aspects of quantum gravity in 2 + 1 dimensional anti-de Sitter space (AdS3), and its connection to Conformal field theories in 1 + 1 dimensions (CFT2), via the AdS/CFT correspondence. We study the thermodynamics properties of higher spin black holes. By focusing on the spin-4 case, we show that black holes carrying higher spin charges display a rich phase diagram in the grand canonical ensemble, including phase transitions of the Hawking-Page type, first order inter-black hole transitions, and a second order critical point. We investigate recent proposals on the connection between bulk codimension-1 volumes and computational complexity in the CFT. Using Tensor Networks we provide concrete evidence of why these bulk volumes are related to the number of gates in a quantum circuit, and exhibit their topological properties. We provide a novel formula to compute this complexity directly in terms of entanglement entropies, using techniques from Kinematic space. We then move in a slightly different direction, and study the quantum properties of black holes via de Functional Renormalisation Group prescription coming from Asymptotic safety. We avoid the arbitrary scale setting by restricting to a narrower window in parameter space, where only Newton’s coupling and the cosmological constant are allowed to vary. By one assumption on the properties of Newton’s coupling, we find black hole solutions explicitly. We explore their thermodynamical properties, and discover that very large black holes exhibit very unusual features.
Black holes in scale-dependent frameworks.
(2019) Rincón, Ángel; Koch, Benjamin; Pontificia Universidad Católica de Chile. Facultad de Física
In the present thesis, we investigate the scale–dependence of some well known black hole solutions in 2+1 dimensions at the level of the effective action in the presence of a cosmological constant or an electrical source. We promote the classical parameters of the theory, {G0,(· · ·)0}, to scale–dependent couplings, {Gk,(· · ·)k} and then we solve the corresponding effective Einstein field equations. To close the system of equations we impose the null energy condition. This last condition (valid in arbitrary dimension) provides a differential equation which, after solving it, allows to obtain in a simple way the specific form of the gravitational coupling. Furthermore, perfect-fluid like parameters are induced via the scale-dependent gravitational coupling. Finally, to exemplify the effect of the running of the couplings on the properties of the scale-dependent black hole solutions, we show a few concrete examples.In the present thesis, we investigate the scale–dependence of some well known black hole solutions in 2+1 dimensions at the level of the effective action in the presence of a cosmological constant or an electrical source. We promote the classical parameters of the theory, {G0,(· · ·)0}, to scale–dependent couplings, {Gk,(· · ·)k} and then we solve the corresponding effective Einstein field equations. To close the system of equations we impose the null energy condition. This last condition (valid in arbitrary dimension) provides a differential equation which, after solving it, allows to obtain in a simple way the specific form of the gravitational coupling. Furthermore, perfect-fluid like parameters are induced via the scale-dependent gravitational coupling. Finally, to exemplify the effect of the running of the couplings on the properties of the scale-dependent black hole solutions, we show a few concrete examples.In the present thesis, we investigate the scale–dependence of some well known black hole solutions in 2+1 dimensions at the level of the effective action in the presence of a cosmological constant or an electrical source. We promote the classical parameters of the theory, {G0,(· · ·)0}, to scale–dependent couplings, {Gk,(· · ·)k} and then we solve the corresponding effective Einstein field equations. To close the system of equations we impose the null energy condition. This last condition (valid in arbitrary dimension) provides a differential equation which, after solving it, allows to obtain in a simple way the specific form of the gravitational coupling. Furthermore, perfect-fluid like parameters are induced via the scale-dependent gravitational coupling. Finally, to exemplify the effect of the running of the couplings on the properties of the scale-dependent black hole solutions, we show a few concrete examples.In the present thesis, we investigate the scale–dependence of some well known black hole solutions in 2+1 dimensions at the level of the effective action in the presence of a cosmological constant or an electrical source. We promote the classical parameters of the theory, {G0,(· · ·)0}, to scale–dependent couplings, {Gk,(· · ·)k} and then we solve the corresponding effective Einstein field equations. To close the system of equations we impose the null energy condition. This last condition (valid in arbitrary dimension) provides a differential equation which, after solving it, allows to obtain in a simple way the specific form of the gravitational coupling. Furthermore, perfect-fluid like parameters are induced via the scale-dependent gravitational coupling. Finally, to exemplify the effect of the running of the couplings on the properties of the scale-dependent black hole solutions, we show a few concrete examples.
Characterization of extragalactic fast X-ray transients from X-ray archival searches
(2023) Quirola Vasquez, Jonathan Alexander; Bauer, Franz Erik; Jonker, Peter; Pontificia Universidad Católica de Chile. Instituto de Astrofísica
Extragalactic fast X-ray transients (FXTs) are non-Galactic short flashes of X-ray photons (in the narrow range of ≈0.3–10 keV) of unclear origin that last a few minutes to hours. A variety of astronomical objects and physical mechanisms have been proposed for the origin of extragalactic FXTs, such as core-collapse SNe shock breakout (SBOs), gamma-ray bursts (GRBs), and intermediate massive black holes (IMBH)-white dwarf (WD) tidal disruption events. During the last two decades, several FXTs have been detected by Chandra, XMM-Newton, and Swift-XRT, serendipitously (for instance, Soderberg et al. 2008; Bauer et al. 2017; Xue et al. 2019; Alp & Larsson 2020; Lin et al. 2022). Previously, Yang et al. (2019) developed a method that can efficiently detect single X-ray burst light curves in a single Chandra exposure, and systematically applied it to ≈19 Ms Chandra. While this method efficiently detected all past known FXTs (2), it failed to find any new FXT candidates, setting loose bounds on their space densities. The main objective of this thesis is to identify and characterize extragalactic FXTs hidden in the Chandra archive. We apply here two modified versions of the algorithm developed by Yang et al. 2019 to X-ray sources located at |b|>10 deg (i.e., 14281 Chandra observations, totaling ≈258 Ms and 857 deg 2 ) to minimize stellar flares contamination. In Chapter 2, we consider the X-ray sources of the Chandra Source Catalog 2.0 (data available until the end of 2014; CSC2). In Chapter 3, we extend our systematic search by reprocessing the Chandra data not covered by CSC2. In both instances, we adopt additional criteria to rule out strong contamination from persistent X-ray sources (analyzing further X-ray observations taken by Chandra, XMM-Newton, Swift–XRT, Einstein, and ROSAT, and considering other astronomical catalogs such as Gaia, NED, SIMBAD, VHS, DES, Pan-STARRS), in order to identify 22 FXTs (14 and 8 FXTs identified inside CSC2 and beyond it, respectively) consistent with an extragalactic origin. We rediscover all previously reported Chandra events from the literature (Jonker et al. 2013; Glennie et al. 2015; Bauer et al. 2017; Xue et al. 2019; Lin et al. 2019, 2021, 2022). The 22 FXT candidates have peak 0.3–10 keV fluxes between F X,peak ≈6×10^−14 to 2×10^−10 erg cm−2 s−1 and T 90 durations from ≈0.3 to 40 ks. The sample is split into two groups: five "nearby" FXTs that occurred within d≲100 Mpc, and 17 "distant" FXTs at d>100 Mpc. Indeed, the latter have redshifts between ≈0.3 to 2.2. Thus, the local and distant samples have associated peak X-ray luminosities of L X,peak ≈10^39 − 10^40 and 10^44 − 10^47 erg s−1, respectively. After applying completeness corrections, we calculate the first FXT X-ray luminosity function and derive event rates for the nearby and distant samples of 34.3_{−10.8}^{+13.7} and 36.9_{−8.3}^{+9.7} deg-2 yr−1, respectively, for a limiting flux of Fpeak=10^−13 erg cm−2 s−1. We compare the volumetric density rate of FXTs with well-known transient classes such as SBOs, GRBs, and TDEs, concluding that FXTs remain broadly consistent with different transients at distinct cosmic epochs. Regarding their host properties, local hosts tend to lie just below the star-forming main sequence, with many FXTs situated in or near HII regions, implying some relation to massive stars. On the other hand, distant hosts tend to be spread all over (starburst, main sequence, and green valley regions), potentially consistent with GRB and SNe hosts. Timing and spectral properties, combined with other properties such as galactic parameters and volumetric rates, might imply that we have a mix of origins related to this novel sample of FXTs. Finally, in Chapter 4 we interpret a subset of nine FXTs with plateau or fast-rise light curves in the context of an X-ray magnetar model produced after the merger of two neutron stars. The model produces good fits to the light curves of this sub-sample, and the best-fit magnetar parameters suggest a common origin. Although the interpretation is consistent with most of the observational parameters, exploring other scenarios remains a necessary future task.
Control of wave-particle duality via atom-field interaction in double-slit schemes
(2022) Miranda Rojas, Mario Ernesto Brayan; Orszag Posa, Miguel; Pontificia Universidad Católica de Chile. Instituto de Física
The dual nature of light and matter represents an important challenge for science. Since the origins of quantum mechanics, several theoretical and experimental works have studied the wave and corpuscular properties of photons, atoms, electrons, etc. The main model that has been considered in the development of them has been the Young's double-slit scheme, by means of which the wave nature of light was demonstrated. However, it also can be used to obtain the particle-like properties of the systems. In case of considering identical slits, this model allows to obtain total fringe visibility on a screen located at a certain distance from the double-slit, and thus, null knowledge about the path followed by the object that crosses the scheme. Therefore, the system shows a wave behavior. In order to obtain information about the path taken by the objects (photons, atoms, electrons, etc), several authors have studied the coupling of external systems to double-slit schemes, which allows to know the path followed by the particle. As a consequence, the implementation of any type of path-detector results in the loss of fringe visibility, according to the principle of complementarity postulated by Bohr. In this research, we have considered the use of double-slit schemes and atom-field interactions to control the balance between fringe visibility and which-path information. We consider field cavities which act as path-detectors and they are represented by different quantum states. Instead of photons, our schemes are crossed by atoms, whose internal levels are correlated to the paths of the schemes. Therefore, based on the peparation of both, field and atom, we can study the balance between distinguishability, visibility and the concurrence present in the system. Our results show that the wave-particle duality can be controlled by atomic and field parameters, depending on the behavior that the experimenter wishes to observe, wave-like or particle-like. Additionally, we present a model in which a classical field can control the quantum atom-field interaction. Therefore, the amplitude of the classical field can also be considered as a controlling parameter of the wave-particle duality. Finally, based on our results, we propose a theoretical model to be implemented in quantum eraser and delayed choice experiments, which nowadays arouses great interest among researchers. Our results suggest that the wave-particle duality can be controlled even at times after the atom is registered on a screen, which allows us to choose the behavior of the system, wave-like or particle-like, at any moment.
Desarrollo de hidrogeles a base de óxido de grafeno y cobre para usos en tratamiento de aguas
(2022) Acuña Porras, Camilo; Díaz, Donovan; Pontificia Universidad Católica de Chile. Instituto de Física
En el presente trabajo se modificó químicamente (grado de oxidación) y morfológicamente (tamaño de lámina) láminas de óxido de grafeno (GO) en solución sintetizado por método de Hummers modificado, además se sintetizó partículas de cobre (PCu) como refuerzo, posteriormente se crecieron hidrogeles con GO (GOH) y PCu (Cu-GOH) por vía hidrotermal. Con los hidrogeles se realizaron pruebas de adsorción de azul de metileno (AM) disuelto en agua, con el fin de determinar correlaciones entre las características químicas, estructurales y morfológicas de los hidrogeles con la capacidad y cinética de adsorción del AM como impureza del agua. La modificación química se realizó variando la cantidad del agente oxidante y el tipo de grafito de partida en la síntesis de GO. Esta modifico el grado oxidación y la distribución de grupos funcionales del GO, estudiado por espectroscopía XPS. Se encontró una reducción de los grupos funcionales oxigenados (OFG) al variar la cantidad de KMnO4, además de un punto de saturación en que el KMnO4 no influía en la química del GO. También se observó el efecto del tipo de grafito en la formación de hidrogeles, cuando se usó grafito amorfo este no se formó en contraposición a el grafito laminado donde se formó el hidrogel. La modificación morfológica consistió en un pretratamiento de sonicación a distintos intervalos de tiempo 30min, 60min, 90min, 120min, 180min y 240min en la síntesis de GO (in-situ). Y postratamiento de sonicación a distintas potencias comprendidas entre 50 y 200 W, y a tiempos de exposición de 5 y 10 minutos del GO sintetizado en solución (Post síntesis). El grado de oxidación y OFG se analizaron por los espectros de alta resolución (C1s y O1s) XPS, determinando que la sonicación del GO no presenta modificaciones significativas en la distribución de OFG y una consistencia en su grado de oxidación (relación C:O). Adicionalmente, el tamaño de lámina promedio se obtuvo por procesamiento de imágenes AFM, Para la solución de GO base encontró un valor entre 25040 - 33516 nm2 ; Para pretratamiento in-situ 57120 - 37220 nm2 ; Y post síntesis 5410 - 13620nm2 . Se observó que el tiempo de sonicación afecta el tamaño de lámina para el tratamiento in-situ como para el post síntesis. Los hidrogeles crecidos vía hidrotermal mostraron una estructura porosa (entrecruzamiento de láminas de GO) en la superficie por imágenes SEM. Químicamente se observó por los espectros de alta resolución C1s y O1s de XPS un proceso de reducción de los OFG por la síntesis hidrotermal. También la incorporación PCu afecto la morfología (interacción de láminas de GO con CuP), estructura (cambios de fases cristalinas de PCu) y química (Oxidación de PCu y reducción del GO) del hidrogel. Las pruebas de adsorción de AM se hicieron con dos concentraciones iniciales una de 1.2 mg⁄L para los hidrogeles modificados y con PCu Y de 100 mg⁄Lpara hidrogeles con la solución GO base (sin modificación morfológica y química), y condiciones de agitación y temperatura. El hidrogel con GO base y con PCu adsorben el AM eficientemente comparado a los modificados. Los hidrogeles bajo condiciones de temperatura y agitación tienen una capacidad de adsorción entre 21.99—38.45 mg⁄g. Estos hidrogeles, se analizó la cinética de adsorción mediante dos modelos, Pseudo-First Order (PFO) y Pseudo-Second Order (PSO), inicialmente la adsorción mostro que la remoción del tinte se produce por fisisorción dado los valores termodinámicos (entalpia, energía libre de Gibbs y entropía).
Dinámica de espín electrónico y nuclear en diamante
(2021) Duarte Portilla, Héctor; Maze Ríos, Jerónimo; Pontificia Universidad Católica de Chile. Instituto de Física
Durante los últimos años los centros de color o defectos ópticos en sólidos han emergido como potenciales candidatos para aplicaciones en metrología cuántica y transmisión y procesamiento de información cuántica. El modelamiento de las propiedades ópticas y de otros grados de libertad asociados a estos defectos es crucial para la implementación exitosa de estas aplicaciones o tecnologías. Muchas de estas propiedades como, por ejemplo, la coherencia de espines tanto electrónicos como nucleares, asociados a los defectos, son afectadas en gran medida por su interacción con el medio ambiente. Recientemente se ha encontrado experimentalmente que los espines nucleares aledaños pueden ser polarizados utilizando la dinámica del espín electrónico central del centro NV. La descripción y entendimiento de este fenómeno es crucial tanto para mitigar la decoherencia causados por el medio ambiente o baño de espines nucleares, como para el desarrollo de memorias nucleares y procesamiento de información ocupando espines nucleares. En esta tesis, en primer lugar, se realiza un estudio sobre evoluciones coherentes y se presenta un nuevo término no adiabático que permite entender fases acumuladas en evoluciones no adiabáticas. Logrando resolver de manera exacta la evolución no adiabática de un espín electrónico en presencia de un campo magnético oscilante. Luego se propone como utilizar las secuencias de Ramsey y Espín-ECHO sobre el centro NV para encontrar interferencia producto de una fase geométrica. Además, describimos la polarización de espines nucleares en el medio ambiente del centro de color NV bajo bombeo óptico de un espín central y radiación de microonda resonante con un espín electrónico central asociado a los centros de color NV. Se utiliza el formalismo matemático basado en la ecuación maestra para describir la dinámica del espín electrónico central en presencia de un baño radiativo fotónico y la acción de un bombeo óptico mediante un láser. Con ello se caracteriza la dinámica de polarización de espines nucleares acoplados coherentemente mediante interacción hiperfina con el espín electrónico central para varias condiciones de campo magnético externo (magnitud y orientación). Y se introduce la técnica de marco rotante y aproximación de marco rotante para caracterizar el rol de la radiación de microonda resonante con el espín electrónico central. Logramos ejemplificar cómo los acoplamientos por componente de interacción hiperfina posibilitan la polarización de espines nucleares, y como afecta o contribuye a este objetivo la magnitud de las componentes anisotrópicas de esta interacción. Se muestra además, para cuatro modelos de tasas de transición, como la tasas de cruce internos del sistema y las transiciones que no preservan espín reducen la polarización electrónica, lo que a su vez reduce la polarización nuclear. Por un lado, los resultados de esta tesis permitirán modelar evoluciones no adiabáticas, y por otro lado, muestran un camino para lograr validar el modelo de tasas de transición que mejor se ajuste al centro NV y polarizar un gran número de espines nucleares y a su vez habilitar aplicaciones en metrología como magnetometría con un bajo ruido magnético y por ende aumentando su sensibilidad.
Efecto de un plasma de radiofrecuencia dual sobre la dinámica y composición en la deposición por láser pulsado
(2021) Escalona Álvarez, Miguel Benito; Bhuyan, Heman; Pontificia Universidad Católica de Chile. Facultad de Física
En este trabajo se presentan los resultados obtenidos al combinar un sistema convencional de deposición por láser pulsado con un plasma de radiofrecuencia (RF) dual. El sistema fue utilizado para estudiar los efectos del plasma RF sobre la dinámica y composición del plasma producido por láser. Además, el sistema se utilizó para depositar películas delgadas de nitruro de titanio (TiN) y estudiar la factibilidad de obtener un control sobre el nitrógeno incorporado en el material. Mediante el análisis del plasma se evidencia que el sistema dual mejora la reactividad del plasma de nitrógeno, así como su temperatura y tasa de ionización. La temperatura y densidad alcanzadas estuvieron en un rango de 0.8 – 2.0 eV y 10^17 – 10^18 cm-3, respectivamente. Por otro lado, mediante la caracterización del TiN se observó mejoras significativas en la tasa de deposición y en la incorporación de nitrógeno en la película. Además, se observó cambios en su rugosidad y orientación cristalina, los cuales están asociados a la energía y el flujo de los iones que impactan en la superficie del sustrato. Los resultados obtenidos sugieren que la técnica desarrollada tiene un gran potencial para depositar materiales compuestos manteniendo un control en su composición y en sus propiedades.
Exploring the landscape of very special relativity
(2020) Soto Villarroel, Alex; Alfaro Solís, Jorge Luis; Pontificia Universidad Católica de Chile. Instituto de Física
In this thesis we study the Very Special Relativity (VSR) framework. In particular we put the emphasis in the QED sector. We present the basics of the Lorentz group and the subgroup SIM(2), which is the symmetry of nature in this framework instead of the full Lorentz group. This symmetry allows introducing terms like n.p/n.q, where n transforms with a phase under SIM(2) transformations. With this construction, we can explain the neutrino mass without the addition of new particles. We explore VSR in two dimensions, showing that the Lorentz group allows VSR terms. This fact shows that we can revisit QED2. We compute the photon self-energy and the axial anomaly, finding differences from the standard result. In addition, in four dimensions, we review the electron self-energy, and we discuss the importance of a prescription to regulate infrared divergencies in the VSR integrals. We present a prescription to use when we introduce a possible gauge-invariant photon mass in the electron self-energy computation. The Coulomb scattering is presented as an example of a simple process that can be computed, showing a small signal of the vector n.In this thesis we study the Very Special Relativity (VSR) framework. In particular we put the emphasis in the QED sector. We present the basics of the Lorentz group and the subgroup SIM(2), which is the symmetry of nature in this framework instead of the full Lorentz group. This symmetry allows introducing terms like n.p/n.q, where n transforms with a phase under SIM(2) transformations. With this construction, we can explain the neutrino mass without the addition of new particles. We explore VSR in two dimensions, showing that the Lorentz group allows VSR terms. This fact shows that we can revisit QED2. We compute the photon self-energy and the axial anomaly, finding differences from the standard result. In addition, in four dimensions, we review the electron self-energy, and we discuss the importance of a prescription to regulate infrared divergencies in the VSR integrals. We present a prescription to use when we introduce a possible gauge-invariant photon mass in the electron self-energy computation. The Coulomb scattering is presented as an example of a simple process that can be computed, showing a small signal of the vector n.In this thesis we study the Very Special Relativity (VSR) framework. In particular we put the emphasis in the QED sector. We present the basics of the Lorentz group and the subgroup SIM(2), which is the symmetry of nature in this framework instead of the full Lorentz group. This symmetry allows introducing terms like n.p/n.q, where n transforms with a phase under SIM(2) transformations. With this construction, we can explain the neutrino mass without the addition of new particles. We explore VSR in two dimensions, showing that the Lorentz group allows VSR terms. This fact shows that we can revisit QED2. We compute the photon self-energy and the axial anomaly, finding differences from the standard result. In addition, in four dimensions, we review the electron self-energy, and we discuss the importance of a prescription to regulate infrared divergencies in the VSR integrals. We present a prescription to use when we introduce a possible gauge-invariant photon mass in the electron self-energy computation. The Coulomb scattering is presented as an example of a simple process that can be computed, showing a small signal of the vector n.In this thesis we study the Very Special Relativity (VSR) framework. In particular we put the emphasis in the QED sector. We present the basics of the Lorentz group and the subgroup SIM(2), which is the symmetry of nature in this framework instead of the full Lorentz group. This symmetry allows introducing terms like n.p/n.q, where n transforms with a phase under SIM(2) transformations. With this construction, we can explain the neutrino mass without the addition of new particles. We explore VSR in two dimensions, showing that the Lorentz group allows VSR terms. This fact shows that we can revisit QED2. We compute the photon self-energy and the axial anomaly, finding differences from the standard result. In addition, in four dimensions, we review the electron self-energy, and we discuss the importance of a prescription to regulate infrared divergencies in the VSR integrals. We present a prescription to use when we introduce a possible gauge-invariant photon mass in the electron self-energy computation. The Coulomb scattering is presented as an example of a simple process that can be computed, showing a small signal of the vector n.In this thesis we study the Very Special Relativity (VSR) framework. In particular we put the emphasis in the QED sector. We present the basics of the Lorentz group and the subgroup SIM(2), which is the symmetry of nature in this framework instead of the full Lorentz group. This symmetry allows introducing terms like n.p/n.q, where n transforms with a phase under SIM(2) transformations. With this construction, we can explain the neutrino mass without the addition of new particles. We explore VSR in two dimensions, showing that the Lorentz group allows VSR terms. This fact shows that we can revisit QED2. We compute the photon self-energy and the axial anomaly, finding differences from the standard result. In addition, in four dimensions, we review the electron self-energy, and we discuss the importance of a prescription to regulate infrared divergencies in the VSR integrals. We present a prescription to use when we introduce a possible gauge-invariant photon mass in the electron self-energy computation. The Coulomb scattering is presented as an example of a simple process that can be computed, showing a small signal of the vector n.In this thesis we study the Very Special Relativity (VSR) framework. In particular we put the emphasis in the QED sector. We present the basics of the Lorentz group and the subgroup SIM(2), which is the symmetry of nature in this framework instead of the full Lorentz group. This symmetry allows introducing terms like n.p/n.q, where n transforms with a phase under SIM(2) transformations. With this construction, we can explain the neutrino mass without the addition of new particles. We explore VSR in two dimensions, showing that the Lorentz group allows VSR terms. This fact shows that we can revisit QED2. We compute the photon self-energy and the axial anomaly, finding differences from the standard result. In addition, in four dimensions, we review the electron self-energy, and we discuss the importance of a prescription to regulate infrared divergencies in the VSR integrals. We present a prescription to use when we introduce a possible gauge-invariant photon mass in the electron self-energy computation. The Coulomb scattering is presented as an example of a simple process that can be computed, showing a small signal of the vector n.In this thesis we study the Very Special Relativity (VSR) framework. In particular we put the emphasis in the QED sector. We present the basics of the Lorentz group and the subgroup SIM(2), which is the symmetry of nature in this framework instead of the full Lorentz group. This symmetry allows introducing terms like n.p/n.q, where n transforms with a phase under SIM(2) transformations. With this construction, we can explain the neutrino mass without the addition of new particles. We explore VSR in two dimensions, showing that the Lorentz group allows VSR terms. This fact shows that we can revisit QED2. We compute the photon self-energy and the axial anomaly, finding differences from the standard result. In addition, in four dimensions, we review the electron self-energy, and we discuss the importance of a prescription to regulate infrared divergencies in the VSR integrals. We present a prescription to use when we introduce a possible gauge-invariant photon mass in the electron self-energy computation. The Coulomb scattering is presented as an example of a simple process that can be computed, showing a small signal of the vector n.In this thesis we study the Very Special Relativity (VSR) framework. In particular we put the emphasis in the QED sector. We present the basics of the Lorentz group and the subgroup SIM(2), which is the symmetry of nature in this framework instead of the full Lorentz group. This symmetry allows introducing terms like n.p/n.q, where n transforms with a phase under SIM(2) transformations. With this construction, we can explain the neutrino mass without the addition of new particles. We explore VSR in two dimensions, showing that the Lorentz group allows VSR terms. This fact shows that we can revisit QED2. We compute the photon self-energy and the axial anomaly, finding differences from the standard result. In addition, in four dimensions, we review the electron self-energy, and we discuss the importance of a prescription to regulate infrared divergencies in the VSR integrals. We present a prescription to use when we introduce a possible gauge-invariant photon mass in the electron self-energy computation. The Coulomb scattering is presented as an example of a simple process that can be computed, showing a small signal of the vector n.In this thesis we study the Very Special Relativity (VSR) framework. In particular we put the emphasis in the QED sector. We present the basics of the Lorentz group and the subgroup SIM(2), which is the symmetry of nature in this framework instead of the full Lorentz group. This symmetry allows introducing terms like n.p/n.q, where n transforms with a phase under SIM(2) transformations. With this construction, we can explain the neutrino mass without the addition of new particles. We explore VSR in two dimensions, showing that the Lorentz group allows VSR terms. This fact shows that we can revisit QED2. We compute the photon self-energy and the axial anomaly, finding differences from the standard result. In addition, in four dimensions, we review the electron self-energy, and we discuss the importance of a prescription to regulate infrared divergencies in the VSR integrals. We present a prescription to use when we introduce a possible gauge-invariant photon mass in the electron self-energy computation. The Coulomb scattering is presented as an example of a simple process that can be computed, showing a small signal of the vector n.In this thesis we study the Very Special Relativity (VSR) framework. In particular we put the emphasis in the QED sector. We present the basics of the Lorentz group and the subgroup SIM(2), which is the symmetry of nature in this framework instead of the full Lorentz group. This symmetry allows introducing terms like n.p/n.q, where n transforms with a phase under SIM(2) transformations. With this construction, we can explain the neutrino mass without the addition of new particles. We explore VSR in two dimensions, showing that the Lorentz group allows VSR terms. This fact shows that we can revisit QED2. We compute the photon self-energy and the axial anomaly, finding differences from the standard result. In addition, in four dimensions, we review the electron self-energy, and we discuss the importance of a prescription to regulate infrared divergencies in the VSR integrals. We present a prescription to use when we introduce a possible gauge-invariant photon mass in the electron self-energy computation. The Coulomb scattering is presented as an example of a simple process that can be computed, showing a small signal of the vector n.
Fotodetección mediante interferometría y sintonización termomecánica de láseres.
(2017) Godoy Montecinos, Sergio Juan Pablo; Wallentowitz, Sascha; Pontificia Universidad Católica de Chile. Facultad de Física
Esta tesis esta constituida por trabajos que se pueden agrupar en dos partes. La primera es sobre usos de un montaje homodino para hacer interferometría óptica, donde se presenta una medición de anticorrelaciones entre las fotodetecciones de las salidas de un separador de haces con reflexiones internas, utilizando una fuente de luz de estado coherente, y trabajos sobre como obtener la fotoestadística de una señal óptica utilizando un sistema homodino de interferometría. En la segunda parte se presenta la construcción de un láser de cavidad externa cuya frecuencia es sintonizable por medio de un control de temperatura.
Gas adsorption properties of complex copper oxides
(2017) Rojas de la Fuente, Susana Dennis; Cabrera, Alejandro Leopoldo; Pontificia Universidad Católica de Chile. Facultad de Física
Highly epitaxial films of CuFeO2 and CuFe0.75Ga0.25O2 were grown by pulsed laserdeposition (PLD) from stoichiometric targets over Al2O3 (001) substrate undercontrolled partial pressure of oxygen as carrier gas. Resulting films were highly orientedin c-axis direction.Structural properties of samples were characterized by X-Ray Diffraction (XRD), Raman spectroscopy, X-Ray Photoelectron Spectroscopy (XPS), optical transmittance and diffuse reflectance. This characterization techniques confirmed the rhombohedral Delafossite crystal structure for both kind of samples and CuFe0.75Ga0.25O2 samples were formed by an alloy between CuFeO2 and CuGaO2 Delafossite materials. Using optical transmittance and diffuse reflectance, the optical transitions were estimated by using theTauc method. Direct optical transitions were measured at 1.28±0.02 eV and 2.20±0.05eV for pure CuFeO2 samples and for CuFe0.75Ga0.25O2 were measured at 1.50±0.04 eVand 2.30±0.09 eV, plots showed another higher transition near 3 eV but due to technical limitations this gap cannot be clearly determined. Adsorption of CO2 and H2O was studied via thermal programmed desorption technique. In both films Copper and Iron were present at the surface, and consequently formed part of the surface-gas interface. X-ray photoelectron data indicated that CO2 is adsorbed preferentially at copper sites forming a similar coordination to CuCO3. The energy for desorption of CO2 and H2O was estimated to be 1.0±0.8 eV/molecule for CuFeO2 and0.7±0.4 eV/molecule for CuFe0.75Ga0.25O2. Also, it was possible to correlate second order desorption with a CO2 reduction reaction. Copper Delafossite materials studied in this work showed some catalytic activity in good agreement with the literature. Future work in this field would involve synthesis of a wider variety of CuFe1-xGaxO2 samples in order to get a better idea of the influence ofiron substitution for gallium in the Delafossite structure. Also, for a better understanding of the relationship between adsorption properties and catalytic behavior some futurework regarding electrical and electrochemical properties is proposed
Loops in Holographic Correlators
(2023) Muñoz Sandoval, Iván Ignacio; Bañados, Máximo; Pontificia Universidad Católica de Chile. Instituto de Física
In the context of the Anti de-Sitter (AdS)/Conformal Field Theory (CFT) correspondence, we investigate the computation of holographic correlation functions for quantum fields in the bulk. Unlike the semi-classical approach, quantum computations involve Infra-Red (IR) and Ultra-Violet (UV) divergences. However, consistent with the semiclassical approximation, we find that IR infinities correspond to boundary divergences, while UV divergences correspond to the bulk. We present a systematic procedure for solving the perturbative quantum problem in the bulk. To illustrate our approach, we consider a Φ4 scalar field on a fixed AdS background and obtain the boundary correlation function in position and momentum space. In position space, we use two approximations: (i) we assume that the field is composed of the classical solution plus a quantum fluctuation, and we solve the classical part before using the holographic dictionary to obtain the quantum correction to the 2- and 4-point functions, requiring UV and IR renormalizations;(ii) using the quantum effective action, we renormalize the UV divergence from the equation of motions and then use the holographic dictionary to obtain the dual correlation function. Both formulations lead to the same conclusions and demonstrate that the bulk theory is renormalizable up to AdS7. Meanwhile, in momentum space, we use the background field method and renormalize the two-point function up to one loop, finding exact agreement with the position space computation. Finally, we provide a general set-up for obtaining the off-shell graviton bulk propagator, which is crucial for obtaining correlation functions for more realistic models.
On the effects of the modification of the metric in the gravitational context
(2020) Rubio, Carlos; Alfaro Solís, Jorge Luis; Pontificia Universidad Católica de Chile. Instituto de Física
This thesis consists of two parts: In the first one, simple generic extensions of isotropic Durgapal–Fuloria stars to the anisotropic domain were presented. These anisotropic solutions were obtained by guided minimal deformations over the isotropic system. When the anisotropic sector interacts in a purely gravitational manner, the conditions to decouple both sectors, by means of the minimal geometric deformation approach, were satisfied. Hence, the anisotropic field equations were isolated resulting in a more treatable set of equations. The simplicity of the equations allows one to manipulate the anisotropies that can be implemented in a systematic way to obtain different realistic models for anisotropic configurations. Later on, the observational effects of such anisotropies when measuring the surface redshift were discussed. To conclude, the consistency of the application of the method over the obtained anisotropic configurations was shown. In this manner, different anisotropic sectors can be isolated from each other and modeled in a simple and systematic way. About 70% of the Universe is Dark Energy, but there is still no consensus in the physics community on what the nature of it is. Delta Gravity (DG) is an alternative theory of gravitation that could solve this cosmological problem. DG is able to explain the SNe data successfully. In this work, we explored the cosmological fluctuations that give rise to the CMB through a hydrodynamic approximation. We calculated the gauge transformations for the metric and the perfect fluid to present the equations of the evolution of cosmological fluctuations, providing the necessary equations to solve, in a semi-analytical way, the scalar TT Power Spectrum. These equations were useful for comparing the DG theory with astronomical observations and thus, being able to restrict the DG cosmology, testing the compatibility with the CMB Planck data, which are currently in contradiction with SNe data.This thesis consists of two parts: In the first one, simple generic extensions of isotropic Durgapal–Fuloria stars to the anisotropic domain were presented. These anisotropic solutions were obtained by guided minimal deformations over the isotropic system. When the anisotropic sector interacts in a purely gravitational manner, the conditions to decouple both sectors, by means of the minimal geometric deformation approach, were satisfied. Hence, the anisotropic field equations were isolated resulting in a more treatable set of equations. The simplicity of the equations allows one to manipulate the anisotropies that can be implemented in a systematic way to obtain different realistic models for anisotropic configurations. Later on, the observational effects of such anisotropies when measuring the surface redshift were discussed. To conclude, the consistency of the application of the method over the obtained anisotropic configurations was shown. In this manner, different anisotropic sectors can be isolated from each other and modeled in a simple and systematic way. About 70% of the Universe is Dark Energy, but there is still no consensus in the physics community on what the nature of it is. Delta Gravity (DG) is an alternative theory of gravitation that could solve this cosmological problem. DG is able to explain the SNe data successfully. In this work, we explored the cosmological fluctuations that give rise to the CMB through a hydrodynamic approximation. We calculated the gauge transformations for the metric and the perfect fluid to present the equations of the evolution of cosmological fluctuations, providing the necessary equations to solve, in a semi-analytical way, the scalar TT Power Spectrum. These equations were useful for comparing the DG theory with astronomical observations and thus, being able to restrict the DG cosmology, testing the compatibility with the CMB Planck data, which are currently in contradiction with SNe data.This thesis consists of two parts: In the first one, simple generic extensions of isotropic Durgapal–Fuloria stars to the anisotropic domain were presented. These anisotropic solutions were obtained by guided minimal deformations over the isotropic system. When the anisotropic sector interacts in a purely gravitational manner, the conditions to decouple both sectors, by means of the minimal geometric deformation approach, were satisfied. Hence, the anisotropic field equations were isolated resulting in a more treatable set of equations. The simplicity of the equations allows one to manipulate the anisotropies that can be implemented in a systematic way to obtain different realistic models for anisotropic configurations. Later on, the observational effects of such anisotropies when measuring the surface redshift were discussed. To conclude, the consistency of the application of the method over the obtained anisotropic configurations was shown. In this manner, different anisotropic sectors can be isolated from each other and modeled in a simple and systematic way. About 70% of the Universe is Dark Energy, but there is still no consensus in the physics community on what the nature of it is. Delta Gravity (DG) is an alternative theory of gravitation that could solve this cosmological problem. DG is able to explain the SNe data successfully. In this work, we explored the cosmological fluctuations that give rise to the CMB through a hydrodynamic approximation. We calculated the gauge transformations for the metric and the perfect fluid to present the equations of the evolution of cosmological fluctuations, providing the necessary equations to solve, in a semi-analytical way, the scalar TT Power Spectrum. These equations were useful for comparing the DG theory with astronomical observations and thus, being able to restrict the DG cosmology, testing the compatibility with the CMB Planck data, which are currently in contradiction with SNe data.This thesis consists of two parts: In the first one, simple generic extensions of isotropic Durgapal–Fuloria stars to the anisotropic domain were presented. These anisotropic solutions were obtained by guided minimal deformations over the isotropic system. When the anisotropic sector interacts in a purely gravitational manner, the conditions to decouple both sectors, by means of the minimal geometric deformation approach, were satisfied. Hence, the anisotropic field equations were isolated resulting in a more treatable set of equations. The simplicity of the equations allows one to manipulate the anisotropies that can be implemented in a systematic way to obtain different realistic models for anisotropic configurations. Later on, the observational effects of such anisotropies when measuring the surface redshift were discussed. To conclude, the consistency of the application of the method over the obtained anisotropic configurations was shown. In this manner, different anisotropic sectors can be isolated from each other and modeled in a simple and systematic way. About 70% of the Universe is Dark Energy, but there is still no consensus in the physics community on what the nature of it is. Delta Gravity (DG) is an alternative theory of gravitation that could solve this cosmological problem. DG is able to explain the SNe data successfully. In this work, we explored the cosmological fluctuations that give rise to the CMB through a hydrodynamic approximation. We calculated the gauge transformations for the metric and the perfect fluid to present the equations of the evolution of cosmological fluctuations, providing the necessary equations to solve, in a semi-analytical way, the scalar TT Power Spectrum. These equations were useful for comparing the DG theory with astronomical observations and thus, being able to restrict the DG cosmology, testing the compatibility with the CMB Planck data, which are currently in contradiction with SNe data.This thesis consists of two parts: In the first one, simple generic extensions of isotropic Durgapal–Fuloria stars to the anisotropic domain were presented. These anisotropic solutions were obtained by guided minimal deformations over the isotropic system. When the anisotropic sector interacts in a purely gravitational manner, the conditions to decouple both sectors, by means of the minimal geometric deformation approach, were satisfied. Hence, the anisotropic field equations were isolated resulting in a more treatable set of equations. The simplicity of the equations allows one to manipulate the anisotropies that can be implemented in a systematic way to obtain different realistic models for anisotropic configurations. Later on, the observational effects of such anisotropies when measuring the surface redshift were discussed. To conclude, the consistency of the application of the method over the obtained anisotropic configurations was shown. In this manner, different anisotropic sectors can be isolated from each other and modeled in a simple and systematic way. About 70% of the Universe is Dark Energy, but there is still no consensus in the physics community on what the nature of it is. Delta Gravity (DG) is an alternative theory of gravitation that could solve this cosmological problem. DG is able to explain the SNe data successfully. In this work, we explored the cosmological fluctuations that give rise to the CMB through a hydrodynamic approximation. We calculated the gauge transformations for the metric and the perfect fluid to present the equations of the evolution of cosmological fluctuations, providing the necessary equations to solve, in a semi-analytical way, the scalar TT Power Spectrum. These equations were useful for comparing the DG theory with astronomical observations and thus, being able to restrict the DG cosmology, testing the compatibility with the CMB Planck data, which are currently in contradiction with SNe data.This thesis consists of two parts: In the first one, simple generic extensions of isotropic Durgapal–Fuloria stars to the anisotropic domain were presented. These anisotropic solutions were obtained by guided minimal deformations over the isotropic system. When the anisotropic sector interacts in a purely gravitational manner, the conditions to decouple both sectors, by means of the minimal geometric deformation approach, were satisfied. Hence, the anisotropic field equations were isolated resulting in a more treatable set of equations. The simplicity of the equations allows one to manipulate the anisotropies that can be implemented in a systematic way to obtain different realistic models for anisotropic configurations. Later on, the observational effects of such anisotropies when measuring the surface redshift were discussed. To conclude, the consistency of the application of the method over the obtained anisotropic configurations was shown. In this manner, different anisotropic sectors can be isolated from each other and modeled in a simple and systematic way. About 70% of the Universe is Dark Energy, but there is still no consensus in the physics community on what the nature of it is. Delta Gravity (DG) is an alternative theory of gravitation that could solve this cosmological problem. DG is able to explain the SNe data successfully. In this work, we explored the cosmological fluctuations that give rise to the CMB through a hydrodynamic approximation. We calculated the gauge transformations for the metric and the perfect fluid to present the equations of the evolution of cosmological fluctuations, providing the necessary equations to solve, in a semi-analytical way, the scalar TT Power Spectrum. These equations were useful for comparing the DG theory with astronomical observations and thus, being able to restrict the DG cosmology, testing the compatibility with the CMB Planck data, which are currently in contradiction with SNe data.This thesis consists of two parts: In the first one, simple generic extensions of isotropic Durgapal–Fuloria stars to the anisotropic domain were presented. These anisotropic solutions were obtained by guided minimal deformations over the isotropic system. When the anisotropic sector interacts in a purely gravitational manner, the conditions to decouple both sectors, by means of the minimal geometric deformation approach, were satisfied. Hence, the anisotropic field equations were isolated resulting in a more treatable set of equations. The simplicity of the equations allows one to manipulate the anisotropies that can be implemented in a systematic way to obtain different realistic models for anisotropic configurations. Later on, the observational effects of such anisotropies when measuring the surface redshift were discussed. To conclude, the consistency of the application of the method over the obtained anisotropic configurations was shown. In this manner, different anisotropic sectors can be isolated from each other and modeled in a simple and systematic way. About 70% of the Universe is Dark Energy, but there is still no consensus in the physics community on what the nature of it is. Delta Gravity (DG) is an alternative theory of gravitation that could solve this cosmological problem. DG is able to explain the SNe data successfully. In this work, we explored the cosmological fluctuations that give rise to the CMB through a hydrodynamic approximation. We calculated the gauge transformations for the metric and the perfect fluid to present the equations of the evolution of cosmological fluctuations, providing the necessary equations to solve, in a semi-analytical way, the scalar TT Power Spectrum. These equations were useful for comparing the DG theory with astronomical observations and thus, being able to restrict the DG cosmology, testing the compatibility with the CMB Planck data, which are currently in contradiction with SNe data.This thesis consists of two parts: In the first one, simple generic extensions of isotropic Durgapal–Fuloria stars to the anisotropic domain were presented. These anisotropic solutions were obtained by guided minimal deformations over the isotropic system. When the anisotropic sector interacts in a purely gravitational manner, the conditions to decouple both sectors, by means of the minimal geometric deformation approach, were satisfied. Hence, the anisotropic field equations were isolated resulting in a more treatable set of equations. The simplicity of the equations allows one to manipulate the anisotropies that can be implemented in a systematic way to obtain different realistic models for anisotropic configurations. Later on, the observational effects of such anisotropies when measuring the surface redshift were discussed. To conclude, the consistency of the application of the method over the obtained anisotropic configurations was shown. In this manner, different anisotropic sectors can be isolated from each other and modeled in a simple and systematic way. About 70% of the Universe is Dark Energy, but there is still no consensus in the physics community on what the nature of it is. Delta Gravity (DG) is an alternative theory of gravitation that could solve this cosmological problem. DG is able to explain the SNe data successfully. In this work, we explored the cosmological fluctuations that give rise to the CMB through a hydrodynamic approximation. We calculated the gauge transformations for the metric and the perfect fluid to present the equations of the evolution of cosmological fluctuations, providing the necessary equations to solve, in a semi-analytical way, the scalar TT Power Spectrum. These equations were useful for comparing the DG theory with astronomical observations and thus, being able to restrict the DG cosmology, testing the compatibility with the CMB Planck data, which are currently in contradiction with SNe data.This thesis consists of two parts: In the first one, simple generic extensions of isotropic Durgapal–Fuloria stars to the anisotropic domain were presented. These anisotropic solutions were obtained by guided minimal deformations over the isotropic system. When the anisotropic sector interacts in a purely gravitational manner, the conditions to decouple both sectors, by means of the minimal geometric deformation approach, were satisfied. Hence, the anisotropic field equations were isolated resulting in a more treatable set of equations. The simplicity of the equations allows one to manipulate the anisotropies that can be implemented in a systematic way to obtain different realistic models for anisotropic configurations. Later on, the observational effects of such anisotropies when measuring the surface redshift were discussed. To conclude, the consistency of the application of the method over the obtained anisotropic configurations was shown. In this manner, different anisotropic sectors can be isolated from each other and modeled in a simple and systematic way. About 70% of the Universe is Dark Energy, but there is still no consensus in the physics community on what the nature of it is. Delta Gravity (DG) is an alternative theory of gravitation that could solve this cosmological problem. DG is able to explain the SNe data successfully. In this work, we explored the cosmological fluctuations that give rise to the CMB through a hydrodynamic approximation. We calculated the gauge transformations for the metric and the perfect fluid to present the equations of the evolution of cosmological fluctuations, providing the necessary equations to solve, in a semi-analytical way, the scalar TT Power Spectrum. These equations were useful for comparing the DG theory with astronomical observations and thus, being able to restrict the DG cosmology, testing the compatibility with the CMB Planck data, which are currently in contradiction with SNe data.This thesis consists of two parts: In the first one, simple generic extensions of isotropic Durgapal–Fuloria stars to the anisotropic domain were presented. These anisotropic solutions were obtained by guided minimal deformations over the isotropic system. When the anisotropic sector interacts in a purely gravitational manner, the conditions to decouple both sectors, by means of the minimal geometric deformation approach, were satisfied. Hence, the anisotropic field equations were isolated resulting in a more treatable set of equations. The simplicity of the equations allows one to manipulate the anisotropies that can be implemented in a systematic way to obtain different realistic models for anisotropic configurations. Later on, the observational effects of such anisotropies when measuring the surface redshift were discussed. To conclude, the consistency of the application of the method over the obtained anisotropic configurations was shown. In this manner, different anisotropic sectors can be isolated from each other and modeled in a simple and systematic way. About 70% of the Universe is Dark Energy, but there is still no consensus in the physics community on what the nature of it is. Delta Gravity (DG) is an alternative theory of gravitation that could solve this cosmological problem. DG is able to explain the SNe data successfully. In this work, we explored the cosmological fluctuations that give rise to the CMB through a hydrodynamic approximation. We calculated the gauge transformations for the metric and the perfect fluid to present the equations of the evolution of cosmological fluctuations, providing the necessary equations to solve, in a semi-analytical way, the scalar TT Power Spectrum. These equations were useful for comparing the DG theory with astronomical observations and thus, being able to restrict the DG cosmology, testing the compatibility with the CMB Planck data, which are currently in contradiction with SNe data.
Parametrización y aplicación de un potencial de muchos cuerpos y transferencia de carga para Fe y FeF2
(2017) Tangarife Franco, Edwin; Mejía López, José Félix; Pontificia Universidad Católica de Chile. Facultad de Física
Las simulaciones computacionales a nivel atómico juegan un papel importante en el desarrollo, diseño y optimización de materiales, así como en la comprensión de sus propiedades estructurales, físicas y químicas. Los mejores enfoques que actualmente existen para describir las interacciones atómicas se basan en las descripciones mecánico-cuánticas, pero son computacionalmente muy costosas y su aplicación generalmente se limita a situaciones en las que el número de átomos es pequeño. Para estudiar sistemas de mayor tamaño se utilizan descripciones empíricas como el potencial COMB (carga optimizada de muchos cuerpos) que describe la interacción de átomos cargados, tomando en cuenta la posible transferencia de carga. Esto es importante principalmente en el estudio de sistemas iónicos, como los óxidos y los halogenuros, cuando se quiere investigar sus notables propiedades como catalizadores, disolventes, refrigerantes, etc. En el caso particular del Fluoruro de Hierro (FeF2), un sistema iónico antiferromagnético, ha sido usado también para la investigación básica del fenómeno de exchange bias en acoplamiento con un ferromagneto como el hierro (Fe). Este fenómeno depende fuertemente de la estructura geométrica y magnética de la interfaz generada en el acoplamiento del FeF2 y el Fe, cuya información no es fácil de obtener desde medidas experimentales. A nivel atómico este acoplamiento puede modificar la distribución de carga de las superficies de cada uno de los materiales en contacto, así como también podría tener migración de átomos de la superficie Fe a la superficie de FeF2, generando una magnetización no compensada que es necesaria para obtener el efecto de anisotropía unidireccional responsable del fenómeno de exchange bias. Por lo tanto, para simular estos sistemas a través de Monte Carlo o simulaciones de dinámica molecular, es importante considerar la transferencia de carga en el potencial de interacción utilizado para describir el sistema. En este trabajo se propone una parametrización para el potencial COMB, aplicados a sistemas compuestos por Fluoruro de Hierro y Hierro metálico (FeF2/Fe). El potencial empírico toma en cuenta los efectos de la transferencia de carga y las interacciones de muchos cuerpos dependientes del ambiente químico local que experimentan los átomos. El potencial es parametrizado pormedio de propiedades experimentales reportadas y/o calculadas desde primeros principios de las fases estables para Fe y FeF2 como: energía de disociación para moléculas de Fluor neutra F2 e ionizada F2−1, parámetros de red para el estado fundamental Fe y FeF2 y constantes elásticas. Esta parametrización es probada con simulaciones de dinámica molecular sobre estructuras macroscópicas cristalinas, superficies, nanopartículas y agregados atómicos. Principalmente se realiza un detallado estudio de la interfaz de FeF2/Fe, mostrando que existe difusión atómica desde el material antiferromagnético (FeF2) hacia el material ferromagnético (Fe). El tamaño de la interfaz obtenida es de 1.4 nm y se observa una fase amorfa que es activada por el proceso de disminución de la temperatura desde 1500K hasta 10K.
Quantum measurement transition and entanglement of trapped ions and optomechanical systems
(2024) Araya Sossa, Kevin Jordan; Orszag Posa, Miguel; Pontificia Universidad Católica de Chile. Instituto de Física
Although quantum mechanics has been able to explain a wide range of physical, chemical, and even biological events with unprecedented accuracy, fundamental problems remain. For instance, the problem of quantum measurement and quantum entanglement, which are the most perplexing problems that have persisted since the foundation of quantum mechanics. Both are crucial quantum resources with broad applications in quantum information science, quantum computing and quantum optics. For this reason, this thesis is devoted to research the quantum measurement from the weakest regime to the strongest one as well as the dynamics of entanglement of different quantum systems. In this work, we study the measurement transition for a coherent-squeezed pointer state through a transition factor Γ that involves a system-pointer coupling by using an arbitrary measured observable A. In addition, we show that the shift in the pointer’s position and momentum establishes a relationship with a new value defined as the transition value, which generalizes the weak value as well as the conditional expectation value. Furthermore, a new strategy is introduced to achieve different measurement regimes by just adjusting the r and ϕξ parameters of the coherent-squeezed pointer state, opening an interesting way to test quantum mechanics foundations. Our scheme has been theoretically applied in a trapped ion illuminated by a bichromatic laser beam, with a high potential to be implemented in future experimental setups. Besides, we propose a method to regulate the quantum entanglement in the system mentioned before as well as a dispersive-hybrid system where a qubit is directly coupled to a cavity and a mechanical resonator. Entanglement can be controlled by only tuning the squeezing parameters associated with the vibrational mode. As the squeezing amplitude becomes larger, the maximal entanglement abruptly falls to zero at specific squeezing phases. For the hybrid system, it is also possible to generate entanglement for bipartitions from the qubit-cavity-resonator system after applying this strategy. Entangled qubit-cavity states are created through squeezing, even though there is no direct interaction between them. We also analyze the effect of atomic, optical, and vibrational losses on the quantum entanglement. We finally discuss our schemes to be implemented in future experimental setups and promote further studies to generalize the concept of “monogamy of entanglement” in tripartite systems outside qubit-composite states, in particular, (2 ⊗ 2 ⊗ n)-dimensional systems.
Spontaneous formation in air of DPPC Supported Lipid Bilayers (SLBs) evaporated in a solvent free process on silicon substrates
(2021) Cisternas Fruns, Marcelo Andrés; Volkmann, Ulrich; Pontificia Universidad Católica de Chile. Instituto de Física
Artificial membranes are models for biological systems and are important to gain deeper insight into biological membranes and for various applications. We introduce a dry two-step self-assembly method consisting of the high-vacuum evaporation of phospholipid molecules over silicon, followed by a subsequent annealing step in air. We evaporate dipalmitoylphosphatidylcholine (DPPC) molecules over bare silicon without the use of polymer cushions or solvents. High-resolution ellipsometry and AFM temperature-dependent measurements are performed in air to detect the characteristic phase transitions of DPPC bilayers. Complementary AFM force-spectroscopy breakthrough events are induced to detect single- and multi-bilayer formations. These combined experimental methods confirm the formation of stable non-hydrated lipid bilayers with phase transitions between gel to ripple phases at 311.5 ± 0.9 K, ripple to liquid crystalline phases at 323.8 ± 2.5 K and liquid crystalline to fluid disordered phases at 330.4 ± 0.9 K, which was consistent with such structures reported in wet environments. We find that the AFM tip induces a restructuring or intercalation of the bilayer that is strongly related to the applied tip-force. These dry supported lipid bilayers show long-term stability. These findings are relevant for the development of functional biointerfaces, specifically for fabrication of biosensors and membrane protein platforms. The observed stability is relevant in the context of lifetimes of such systems protected by bilayers in dry environments, such as e.g. SARS-CoV-2 virus.
Structure of the obscured galactic disk with pulsating variables.
(2019) Hajdu, Gergely; Catelan, Márcio; Pontificia Universidad Católica de Chile. Instituto de Astrofísica
Las estrellas variables pulsantes brillantes, tales como Cefeidas y RR-Lyras, son sondas fundamentales de la estructura de las componentes vieja y joven de la Vía Láctea. Sin embargo, el lado más alejado del disco de la Galaxia aún no ha sido mapeado usando tales variables debido a la severa extinción causada por polvo interestelar en frente de ellas. En esta tesis, las curvas de luz en infrarrojo cercano de la muestra VISTA Variables in the Vía Láctea son utilizadas para penetrar esas regiones y descubrir miles de Cefeidas o RR Lyras previamente “escondidas”. El análisis de las curvas de luz de las variables RR Lyras fue ejecutado con un algoritmo de ajuste, y sus metalicidades determinadas de siluetas de sus curvas de luz en el infrarrojo cercano usando métodos recientemente desarrollados. Estas abundancias fotométricas de metales, con sus posiciones en el disco Galáctico, apoyan las teorílas de la formación de adentro hacia fuera del disco de la Galaxia. Las Cefeidas descubiertas fueron clasificadas en los subtipos viejo (Tipo II) y nuevo (Clásicas). Una nueva ley de extinción en el infrarrojo cercano fue determinada usando Cefeidas Tipo II, utilizando su concentración en el centro Galáctico. La distribución de las Cefeidas Clásicas en el disco Galáctico sigue el pandeo Galáctico y el ensanchamiento del disco de la Galaxia en grandes radios Galactocéntricos. Un primer intento se efectuó con el fin de conectar las ubicaciones actuales de las Cefeidas Clásicas con la estructura de brazos espirales de la Vía Láctea.
The role of interacting stellar winds feeding Sagittarius A*.
(2019) Calderón Espinoza, Diego Nicolás; Cuadra, Jorge; Pontificia Universidad Católica de Chile. Instituto de Astrofísica
The central parsec of the Milky Way is among the most enigmatic regions in the entire Galaxy. The existence of the central super-massive black hole, Sgr A*, and its proximity allow us to use it as a laboratory for understanding the astrophysics of galactic nuclei, in general. Although it is well known that this is a very hostile environment due to the presence of tens ofWolf-Rayet (WR) stars with strong outflows, the recent detection of cold gas (-104 K) has challenged our understanding of the gas dynamics and thermodynamics of the region. The so-called G2 source, the dusty sources in the IRS 13E cluster, as well as the disc-like structure in the immediate vicinity of Sgr A* are examples of such cold material. In this thesis, we present a detailed study of the formation of cold gas as a potential result of the collision of the many stellar winds, which are constantly taking place. The main aims of this study are: i) testing the hypothesis of G2 being a gaseous clump formed in a massive binary system, ii) constraining the initial properties and final fate of clumps formed in unstable wind interactions, iii) establishing whether it is possible or not for the system of WR stars orbiting Sgr A* to reach and remain in a steady state between the supplying and inflowing/outflowing material. We find that the properties and dynamics of the clumps produced in the known massive binaries are not consistent with G2’s, ruling out this hypothesis. Additionally, we perform adaptive-mesh refinement hydrodynamical simulations of idealised stellar wind collisions in order to characterise the clump formation process. The results show that clumps formed through thin-shell instabilities are not massive enough to impact significantly the state of the material enclosed within the inner parsec. Finally, the simulation of the complete system of WR stars orbiting Sgr A* shows that the natural outcome of its long-term evolution is the accumulation of material at its centre. Thus, we speculate that the WR stars and their outflows could explain all the phenomenology related to the activity of Sgr A* inferred from observations without the need of invoking external agents.
Transport phenomena in nontrivial topological materials
(2023) Bonilla Moreno, Daniel Alejandro; Muñoz Tavera, Enrique; Pontificia Universidad Católica de Chile. Instituto de Física
In this Ph.D. thesis, we present our work related to electronic quantum transport in materials with nontrivial topology. The fundamental objectives of our work were as follows: Firstly, to study ballistic transport in a nano junction made of a Type I Weyl semimetal material that contains a cylindrical defect created by the application of mechanical strain. In addition to the torsion effect modeled by a pseudo-gauge field, we added an external magnetic field and the repulsive effect of the deformation produced by the mismatch of the crystal lattice. Using the appropriate Landauer ballistic formalism to describe this type of system, we calculated their transport coefficients. Secondly, to study diffusive transport using the linear response regime, of a uniform and diluted concentration of the aforementioned defects through the bulk of a Weyl semimetal slab. For this purpose, we used the standard particle scattering theory, along with Green's functions techniques and diagrammatic methods. Finally, to study the diffusive transport through a single-layer graphene sheet doped with charged impurities, and influenced by the electromagnetic coupling to a topological insulator or a semiconductor. We pursued to investigate the role played by the magneto-electric effect produced by the topological insulator in transport properties, such as electrical conductivity. Here, we also applied a combination of methods based on scattering, linear response, Green's functions, and diagrammatics. We have obtained analytical expressions for the electrical and thermal conductivities, as well as for the Seebeck coefficient. Our results demonstrate the promising nature of these novel topological materials as thermoelectrics for future applications.

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