3.10 Tesis doctorado

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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).
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 radiaciónde 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 preservanespín 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.
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.
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.
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.
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.
Transporte eléctrico en arreglos de nanotubos de carbono de baja cristalinidad y su utilización en dispositivos para sensado de gases
(2021) Adrián Formas, Alvaro Rodrigo; Hevia, Samuel; Pontificia Universidad Católica de Chile. Instituto de Física
Este trabajo de investigación presenta el estudio de mecanismos de transporte eléctrico en nanotubos de carbono de baja cristalinidad (LC-CNTs). Estos fueron sintetizados mediante depósito químico en fase vapor sin catalizador, utilizando una membrana autosoportada de alúmina nanoporosa como plantilla. Se proponen dos mecanismos de transporte eléctrico para explicar la conductancia eléctrica observada entre 10 K y 300 K. El mecanismo Hopping de rango variable domina en los LC-CNTs de ancho de pared menor a 0,45 nm, mientras que el mecanismo de Bloch-Grüneisen domina en los LC-CNTs de pared más gruesa (10 nm). Los LC-NTs de ancho de pared intermedio presentan ambos mecanismos coexistiendo en paralelo. Se concluyó que el ancho de la pared determina el parámetro de decaimiento espacial de los estados electrónicos, los cuales están completamente localizados en paredes delgadas y se extienden a medida que las paredes son mas anchas. Se evaluó el desempeño de estas nanoestructuras como sensores de gases resistivos. Se observó una fuerte dependencia de la respuesta resistiva al ancho de pared de los LC-CNTs. Las respuestas máximas obtenidas fueron de alrededor del 6% para C2H2 y 3% para H2 para una concentración de 50000 ppm.
Weak value amplification in an optomechanical system with mach-zehnder interferometer
(2021) Carrasco Novoa, Sergio; Orszag Posa, Miguel; Pontificia Universidad Católica de Chile. Instituto de Física
In this work an optomechanical system inside a Mach-Zehnder interferometer is studied from the perspective of the weak value amplification effect. The optomechanical system consists of a Fabry-Perot cavity with a moving mirror in the middle. Single photons are post-selected in the detector in one of the output ports of the interferometer (dark port), which allows to enlarge the displacement caused by a single photon over the moving mirror of the cavity. Since the interaction between a single photon and the mirror is weak, the amplification factor of the displacement corresponds to a weak value. By making the initial and final states of the photon quasi-orthogonal, the weak value becomes large and the radiation pressure force exerted by the photon is increased, making a single photon behave as ``many photons'' will do. The amplification effect comes, however, at the cost of the lost of data. The usefulness of weak values for parameter estimation in our setup is analysed from the perspective of the Fisher information. Although the precision of the estimation does not change either by using weak values or by implementing measurements that do not rely on post-selection, in the first scenario all the information can be put in a small amount of post-selected events, which is a verification of a well known general result in the existing literature on the subject.

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