Tesis Doctorado

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Indefinite causal order towards continuous-variable quantum systems.
(Universidad de Concepción, 2025) Escandón Monardes, Jorge Ignacio Antonio; Walborn, Stephen Patrick
Indefinite causal order has attracted a growing attention during the last decade, with the quantum switch being its most prominent instance. The quantum switch has been implemented in several photonic experiments and has also provided computational advantages in several tasks. However, indefinite causal order on continuous-variable (CV) quantum systems has been barely studied. This thesis suggests that applications of indefinite causal order on CV quantum systems may offer broader advantages than using finite-dimensional quantum systems. We follow an exploratory approach comparing the performance of the quantum switch with high-dimensional and CV quantum systems in some applications to quantum computing and quantum metrology. In particular, we use Complex Hadamard matrices to introduce a generalised family of promise problems, which reduces to the known Fourier and Hadamard promise problems as limiting cases. We show that the quantum switch provides query advantage for both the continuous and discrete cases, and prove that a CV system is necessary for implementing the most general promise problem. In addition, we propose an estimation procedure for d-dimensional unitary transformations using the quantum switch. For d > 2, the unitary transformations close to the identity are estimated saturating the quantum Cram´ er-Rao bound. For d = 2, the estimation of all unitary transformations is also optimal with some prior information. We replace the unitary transformation by an arbitrary quantum channel and show that our procedure encodes the χ matrix of the channel in the output state of the control system. Although indefinite causal order does not offer metrological advantage in our proposal, it is worthy to note that an extension to the CV regime would require an infinite-dimensional control system. This inspires the introduction of the quantum switch with continuous control, which leads to new phenomena such as the accelerando/rallentando effect. We conclude that using CV systems enlarges the number of tasks benefited by indefinite causal order and exhibits new phenomena within the field.
Calibration strategies for millimeter/submillimeter observation instruments.
(Universidad de Concepción, 2025) Basoalto Salazar, Lilian de las Mercedes; Reeves Díaz, Rodrigo Andrés
Data calibration is a critical process in astronomical observations as it enables the correction of systematic errors and ensures the reliability of measurements. This aspect is particularly crucial in radio-astronomy experiments such as COMAP and LLAMA, which aim to detect faint astronomical signals with high precision. In these projects, both instrumental and observational challenges, including the perturbation of weak signals by the atmosphere and receiving systems, introduce uncertainties that must be understood and mitigated to ensure accurate results. This research focuses on developing calibration strategies for instruments in the millimeter and submillimeter bands, addressing the factors influencing data integrity. The study concentrates on two main components: the COMAP experiment and the LLAMA calibration loads. Within the framework of the LLAMA Project, a Calibration Loads sub-system for the LLAMAradio-telescope was developed and characterized. This ultra-wideband system allows the various single-pixel receivers planned for LLAMA to calibrate their intensity scales in antenna temperature using the Y-factor technique. We have developed a closed-loop temperature control system based on FPGAs, along with ACS control software, which was integrated into the LLAMA middleware to implement thermal monitoring and control for the Calibration Loads. The characterization of the loads included infrared and radiometric measurements performed on both the prototype and the final loads. Infrared measurements demonstrated thermal stability over time, with standard deviations of less than 1°C for all loads. In radiometric measurements, the calculated brightness temperatures exhibited a linear correlation with the physical temperatures evaluated between 40°C and 70°C. Discrepancies between the physical and the brightness temperatures increased with a rise in Tph. For the prototype, in which power was measured with a 93 GHz heterodyne receiver operated alongside an FPGA-based automated system, the percentage difference reached up to 1% in Kelvin scale at 70°C. In the final loads, power was manually determined using a 93 GHz direct detection receiver, the maximum difference was 5% on the Kelvin scale at 70°C, corresponding to one of the large loads. These variations are attributed to the geometric design and thermal properties of the loads. At 70◦C, the stabilization time of the brightness temperature from ambient temperature was 8 minutes for the small load and 17 and 28 minutes for the blue and red large loads, respectively. The loads remained within the allowed error margin of 1%, validating their stability and accuracy as calibration tools. In the context of the COMAP Project, a radiometric and atmospheric study for the OVRO site at COMAP frequencies was executed. The performance of the receiver was evaluated using a series of scans taken on different dates and times. The Y-factor technique was applied to determine the receiver temperature, incorporating spillover and atmospheric emission modeled with the AM radiative transfer model and MERRA-2 atmospheric database. The results showed that TRx remained stable, with 95% of the values falling between 10 and 31 K and a mean of 17.7 K. The system temperature was calculated by adapting the methodology of O’Neil [40], explicitly including the simulated sky temperature from the AM model using the MERRA-2 database. It was observed that Tsys ranged between 28 and 56 K for 95% of the data, showing dependence on PWV and the elevation angle. As expected, conditions of reduced PWV resulted in lower values of Tsys, highlighting the relevance of these factors in the accuracy of the measurements. COMAP’s sensitivity was found to vary between 146 and 260 mK for 95% of the data, with a mean of 203 mK, evaluated at a ∆ν of 2 MHz and a data sampling rate of 20 ms. The temporal stability of the data ranges between 5 and 22 seconds with a mean of 14 seconds, as evaluated through Allan variance, confirming the presence of gain fluctuations in all analyzed files. The aperture efficiency results showed a decrease with increasing frequency, ranging from 0.27 to 0.51 with a mean of 0.38, evaluated at the central frequencies of COMAP. In the observational framework of the COMAP Project, a validation study of the MERRA-2 atmospheric database model was carried out through an atmospheric analysis at the OVRO site on March 25, 2019, at 15:00 GMT. This analysis compared radiometric measurements obtained by the COMAP instrument with atmospheric simulations generated using the AM radiative transfer model based on the MERRA-2 database for the specific date and time. We determined a PWV content of 5.753 mm for that moment, calculated through vertical integration of the layered model provided by the MERRA-2 database. This value was retrieved by executing the AM radiative transfer model using the same dataset with an error of less than 1%. Additionally, we conducted a radiometric study for OVRO on March 25, 2019, between 14:18 and 14:26 UTC. We analyzed the COMAP Level-1 long skydip power data recorded at elevation angles between 30◦ and 86.5◦ during this period and estimated its atmospheric brightness temperature at different elevation angles. We compared the derived radiometric temperature with simulations from the AM radiative transfer software, based on the MERRA-2 atmospheric database model, and found strong consistency. During the data processing, we observed an excess temperature when the elevation angle decreased, which could be attributed to spillover effects. This excess temperature ranged between approximately 6 K and 8 K at an azimuthal angle of-30◦. As a key scientific outcome of this atmospheric study at the OVRO site, a zenith opacity spectrum was obtained by fitting brightness temperature data across the entire COMAP frequency range, revealing excellent agreement with simulations, with a percent error of only 4%. The same procedure was applied to a more restricted subset of skydip power data, spanning elevation angles between 40◦ and 60◦ within the same evaluated file. The percent error between the calculated and simulated zenith atmospheric opacity is only 4.4%, confirming that short skydips can effectively characterize atmospheric contributions.
High-dimensional decoy-state quantum key distribution over 1.3 km of installed optical fiber.
(Universidad de Concepción, 2025) Sawada, Kei Braz; Moreira Lima, Gustavo de Aquino
HD-QKD(high-dimensional quantum key distribution) is an alternative to two-dimensional QKD with advantages such as higher data transmission per pulse [54] and noise tolerance [13, 66]. It has been shown that MCFs (multicore fibers) are a viable platform for performing HD-QKD through phase encoding across modes of the same fiber [10]. MCFs have also gathered attention due to their increased data transmission rates and are likely to become part of classical telecom infrastructure in the future [35, 50, 14, 51]. In this thesis we report a proof-of-concept decoy-state BB84 HD-QKDexperiment with an all-fiber setup using installed 4C-MCFs (four core multicore fibers) in a realistic environment. We introduce the theory of QKDand the motivations for decoy states as well as the security bounds for systems with different dimensions. We describe the experiment in detail, including active phase stabilization, state preparation, MCF-based technologies, channels and the detection system. We report a maximum short-range key rate of 7.8 kbit/s and a maximum secure key transmission distance of 105 km, as well as a short-range stability of over 16 hours. A comparison of our experiment with several others is provided, showing that our results are comparable to other works with similar detection technology. Wealso include two papers where we used our experimental platform for experiments simulating non-Markovian noise and implementing single setting quantum state tomography, showing the flexibility of our setup and potential for further work.
Downscaling estadístico de variables hidroclimáticas en el centro-sur de Chile: desarrollo y análisis de campos temporales mensuales y diarios en alta resolución.
(Universidad de Concepción, 2025) Alvial Vásquez, Francisco Javier; Abarca del Río, Rodrigo
A pesar de la importancia de la precipitación en el ciclo hidrológico y en diversos sectores como la agricultura, la gestión de recursos hídricos y la adaptación al cambio climático, su variabilidad física, temporal y espacial sigue representando un desafío para su simulación y proyección a escala local (Pham et al., 2021). En Chile, la interacción entre su compleja orografía, la influencia del océano Pacífico, la continentalidad y los vientos predominantes del oeste en el sur configuran un sistema climático único, lo que incrementa el desafío en la representación de esta variable (Sarricolea et al., 2017; Araya-Osses et al., 2020a; Martínez-Retureta et al., 2021). Datos meteorológicos espaciales coherentes con la información observacional son fundamentales para varios campos científicos (Parra et al., 2004; Hijmans et al., 2005; Abatzoglou, 2013; Cannon et al., 2015b; Liu XiaoMang et al., 2017; Sun et al., 2018). Sin embargo, a pesar de la existencia de numerosos conjuntos de datos de precipitación a nivel mundial, la representación de su variabilidad espacial sigue siendo una limitante, especialmente en regiones con topografía compleja. En este contexto, los productos de precipitación en alta resolución (<1 km) son preferidos, ya que permiten capturar con mayor precisión la variabilidad ambiental que puede perderse a menor resolución. Este estudio propone el desarrollo de una metodología integral de downscaling estadístico para estimar y analizar la variabilidad espacio-temporal de la precipitación en la zona centro-sur de Chile, entre las regiones de O’Higgins y Los Ríos. La investigación se organiza en dos en foques principales que corresponden a los productos generados: (a) Generación de un conjunto de datos de precipitación mensual en alta resolución (800 m) para el período 2000-2011. Es te producto se construye mediante la integración de múltiples fuentes de información: modelos numéricos regionales, datos satelitales, productos de reanálisis y observaciones in situ. Las correcciones sistemáticas aplicadas permiten reflejar de manera coherente la variabilidad climática de la región a escala mensual. (b) Desarrollo de un campo diario en alta resolución denominado DA-SDM (800 m), una metodología avanzada de downscaling estadístico específicamente diseñada para la estimación de eventos extremos diarios. Este enfoque utiliza información multifuente y considera factores orográficos y dinámicos para capturar adecuadamente estos eventos extremos, demostrando su capacidad para reproducirlos durante el período de mayo a agosto de 2006. Además, se destaca su potencial de aplicación en otras regiones con características similares. Los resultados de esta tesis proporcionan dos productos complementarios: (1) un conjunto de datos de precipitación mensual en alta resolución que captura la variabilidad climática regional; y (2) un campo diario DA-SDM que permite la evaluación detallada de eventos extremos diarios. La integración de múltiples fuentes de información y la coherencia con la realidad observacional proporcionan una base sólida para estudios hidrológicos, modelación climática y planificación de recursos hídricos.
Métodos de galerkin discontinuos para problemas de interfaz: aplicación a procesos de desalinización del agua.
(Universidad de Concepción, 2024) Bermúdez Montiel, Isaac; Solano Palma, Manuel; Camaño Valenzuela, Jessika Pamela
The aim of this thesis is to develop continuous and discontinuous Galerkin-type discretizations applied to interface problems modelled by systems of partial differential equations (PDEs). The com plexity of these problems lies in the unknowns and their associated source terms arising from coupling interfaces, as well as the non-linearity of the equations. First, we consider a coupled Navier–Stokes/transport system inspired by the modeling of a reverse osmosis effect in water desalination processes when considering feed and permeate channels coupled through a semi-permeate membrane. The variational formulation consists of a set of equations where the velocities and concentrations, along with tensors and vector fields introduced as auxiliary unknowns, and two Lagrange multipliers, are the main unknowns of the system. The latter are introduced to deal with the trace of functions that do not have enough regularity to be restricted to the boundary. In addition, the pressures can be recovered afterwards by a postprocessing formula. As a consequence, we obtain a nonlinear Banach spaces-based mixed formulation, which has a perturbed saddle point struc ture. We analyze the continuous and discrete solvability of this problem by linearizing the perturbation term and applying the classical Banach fixed point theorem along with the Banach–Nečas–Babuška result. Regarding the discrete scheme, feasible choices of finite element subspaces that can be used include Raviart–Thomas spaces for the auxiliary tensor and vector unknowns, piecewise polynomials for the velocities and concentrations, and continuous polynomial space of lowest order for the traces, yielding stable discrete schemes. An optimal a priori error estimate is derived, and numerical results illustrating both, the performance of the scheme confirming the theoretical rates of convergence, and its applicability, are reported. Once we have established the theoretical foundations to ensure the solvability of the variational scheme, we take advantage of them to numerically address different approaches closely related to reverse osmosis processes by considering coupled Brinkman–Forchheimer/transport equations in addition to Navier–Stokes/transport equations. The cases of a single channel and coupled feed/permeate channels are covered. Thus, through diverse numerical simulations and a variety of configurations, we illustrate the capability of the method to accurately capture the behavior of saline water when passing through membrane-based reverse osmosis desalination channels. Onthe other hand, we present and analyze a hybridizable discontinuous Galerkin (HDG) method for coupling Stokes and Darcy equations, whose domains are discretized by two independent triangulations. This causes non-conformity at the intersection of the subdomains or originates a gap (unmeshed region) between them. In order to properly couple the two different discretizations and obtain a high order scheme, we propose suitable transmission conditions based on mass conservation, equilibrium of normal forces, and the Beavers–Joseph–Saffman law. Since the meshes do not necessarily coincide at the interface, we use the Transfer Path Method (TPM) to tie them. We establish the well-posedness of the method and provide error estimates where the influences of the non-conformity and the gap are explicit in the constants. Finally, numerical experiments that illustrate the performance of the method are shown.
Consequences of Torsion in Four Dimensions.
(Universidad de Concepción, 2024) Medina Medina, Perla Soledad; Anabalón Dupuy, Andrés Fernando
This thesis addresses two fundamental topics in the field of gravity. First, a reformulation of the Mimetic theory of gravity in first-order formalism for differential forms, i.e., the mimetic version of Einstein-Cartan-Kibble-Sciama (ECKS) gravity. Here we consider different possibilities on how torsion is af- fected by conformal transformations and discuss how this translates into the interpolation between two different conformal transformations of the spin con- nection, parameterized with a zero-form parameter λ. We prove that regardless of the type of transformation one chooses, in this setting torsion remains as a non-propagating field. We also discuss the conservation of the mimetic stress- energy tensor and show that the trace of the total stress-energy tensor is not null but depends on both, the value of λ and spacetime torsion. Second, the Einstein-Hilbert action is studied in the first-order formalism, considering the coupling of a scalar field to different topological invariants. The implications of this coupling on the dynamics of the gravitational field and the evolution of the early universe are analyzed. The results obtained contribute to a better understanding of gravity and its relationship with the topology of spacetime. Second, the Einstein-Hilbert action is studied in the first-order formalism, con- sidering the coupling of a scalar field to different topological invariants. The implications of these couplings on the field equations are analyzed. The re- sults obtained shed light on a theoretical framework where it could be easier to introduce couplings of scalar fields to the geometry.
Caracterización de regiones de formación estelar de alta masa: G353, L1482, y Vela.
(Universidad de Concepción, 2024) Álvarez Gutiérrez, Rodrigo Hernán; Stutz, Amelia Marie
El campo de la formación estelar a alta masa aún no es entendido del todo. Procesos tales como campos magnéticos, feedback estelar, e intrincados campos de velocidad agregan complejidad a la caracterización de estas regiones. Observatorios como ALMA, APEX, y el 30m de IRAM nos permiten acceder a escalas espaciales y espectrales pequeñas. En este contexto redujimos las observaciones de N2H+ de las 15 regiones del large program ALMA-IMF, y nos enfocamos en el análisis de la cinemática del gas denso del protocúmulo G353.41. Esta región está a una distancia de ∼ 2kpc, arraigado en un filamento de gran escala (∼ 8pc) y con una masa ∼ 2.5 × 103M⊙ en 1.3 ×1.3 pc2. Extrajimos la componente aislada de la emisión de N2H+ y ajustamos tres componentes de velocidad Gaussianas para identificar estructuras a escalas pequeñas. Identificamos varios gradientes de velocidad a escalas grandes (∼ 1pc) y pequeñas(∼0.2pc). Medimos nueve pares convergentes de gradientes de velocidad (VGs) los cuales llamamos “V-shapes” (∼ 20kms−1pc−1). Estos están en su mayoría localizados en filamentos y algunos están asociados a cores en el punto de convergencia. Interpretamos estos V-shapes como movimientos del gas hacia regiones mas densas, alimentando a los cores situados en la cercanía. Estimamos los tiempos asociados a estos V-shapes como VG−1. Estos tiempos son de alrededor de 67 kyr. Derivamos la taza de acreción de masa en estas estructuras, estando en el rango de (0.35 − 8.77) × 10−4 M⊙ yr−1. Estos movimientos del gas conlleva al colapso del filamento y la formación de nuevos cores. Sugerimos que el protocúmulo está colapsando a escalas grandes, pero la velocidad de colapso es mas lenta en comparación a solo caída libre. Por lo tanto, estos datos son consistentes con que el protocúmulo está bajo una contracción gravitatoria y rápida formación de cores dentro del mismo. Esto sugiere la formación de múltiples generaciones de estrellas a lo largo de la vida del protocúmulo. También analizamos la cinemática de las regiones L1482 south y Vela, dos sistemas masivos filamentarios dentro de 1kpc. Tanto HCO+ como C18O presentan emisión a escalas grandes, ambas con una discontinuidad en la posición del cúmulo NGC 1579. El campo de velocidad de ambos trazadores presenta múltiple gradientes de velocidad (“V-shapes”), siendo estos posibles indicadores de colapso gravitacional producto de movimientos del gas a escalas pequeñas hacia zonas mas densas. Esto también lo vemos en Vela, donde estos movimientos son a lo largo del filamento. Medimos el perfil de linea de masa de Vela y del filamento que contiene al protocúmulo G353. Vemos que el perfil de vela está ubicado en el medio de nuestro diagrama, entre estructuras en Orión, mientras que el f ilamento G353 tiene el perfil mas alto de nuestra muestra. Posiblemente las regiones ubicadas en la parte de arriba o abajo nuestro diagrama son jóvenes o presentan formación estelar muy ineficientes, y a medida que estas regiones forman estrellas, sus perfiles se mueven al medio de la distribución.
Mixed Finite Element Methods for Brinkman–Forchheimer and Related Single and Coupled Models in Fluid Mechanics.
(Universidad de Concepción, 2024) Ortega Ponce, Juan Paulo; Gatica Pérez, Gabriel N.; Caucao Paillán, Sergio Andrés
The goal of this thesis is to develop, analyze, and implement new mixed finite element methods for coupled and decoupled problems that arise in the context of fluid mechanics. In particular, we focus on models describing the behavior of a fluid through porous media. Firstly, an a priori error analysis of a fully-mixed finite element method based on Banach spaces for a nonlinear coupled problem arising from the interaction between the concentration and temperature of a solute immersed in a fluid moving through a porous medium is developed. The model consists of the coupling of the stationary Brinkman-Forchheimer equations with a double diffusion phenomenon. For the mathematical analysis, a nonlinear mixed formulation for the Brinkman-Forchheimer equation is proposed, where in addition to the velocity, the velocity gradient and the pseudo-stress tensor are introduced as new unknowns. In turn, a dual-mixed formulation for the double diffusion equations is adopted using temperature/concentration gradients and Bernoulli-type vectors as additional unknowns. The solvability of this formulation is established by combining fixed-point arguments, classical results on nonlinear monotone operators, Babuška-Brezzi’s theory in Banach spaces, assumptions of sufficiently small data, and Banach’s fixed-point theorem. In particular, Raviart-Thomas spaces of order k ≥ 0 are used to approximate the pseudo-stress tensor and Bernoulli vectors, and piecewise discontinuous polynomials of degree k for the velocity, temperature, concentration fields, and their corresponding gradients. Now, an a posteriori error and computational adaptivity analysis is performed for the fully-mixed variational formulation developed for the coupling of Brinkman–Forchheimer and double-diffusion equa- tions. Here, a reliable and efficient residual-based a posteriori error estimator is derived. The reliability analysis of the proposed estimator is mainly based on the strong monotonicity and inf-sup conditions of the operators involved, along with an appropriate assumption on the data, a stable Helmholtz decom- position in non-standard Banach spaces, and local approximation properties of the Raviart-Thomas and Clément interpolants. In turn, the efficiency estimation is a consequence of standard arguments like inverse inequalities, bubble function-based localization technique, and other results available in the literature. Finally, a mixed finite element method for the nonlinear problem given by the stationary convec- tive Brinkman–Forchheimer equations with variable porosity is studied. Here, the pseudostress and the gradient of the porosity times the velocity are incorporated as additional unknowns. As a consequence, a three-field mixed variational formulation based on Banach spaces is obtained, where the aforemen- tioned variables are the main unknowns of the system along with the velocity. The resulting mixed scheme is then equivalently written as a fixed-point equation, so that Banach’s well-known theorem, combined with classical results on nonlinear monotone operators and a hypothesis of sufficiently small data, is applied to demonstrate the unique solvability of the continuous and discrete systems. For all the problems described above, several numerical experiments are provided that illustrate the good performance of the proposed methods, and that confirm the theoretical results of convergence as well as the reliability and efficiency of the respective a posteriori error estimators.
Agujeros de Gusano tipo Schwarzschild Atravesables (Traversable Schwarzschild-like Wormholes)
(Universidad de Concepción, 2024) Liempi Necul, Luis Alejandro; Oliva Zapata, Julio Eduardo
En esta tesis se aborda la construcción y análisis de soluciones de agujeros de gusano atravesables estáticos con simetría esférica. Se presenta una sutil generalización de los agujeros de gusano de Schwarzschild, introduciendo una función de forma con dependencia lineal en la coordenada radial r. Esta modificación genera agujeros de gusano cuyo espacio-tiempo asintótico no es plano, sino asintóticamente localmente plano, exhibiendo un déficit o exceso de ángulo sólido en el límite r → ∞. Se estudian dos casos principales: agujeros de gusano que conectan regiones asintóticamente no planas con déficit de ángulo sólido, cuyos diagramas de embebimiento se extienden desde la garganta hasta el infinito, y aquellos con exceso de ángulo sólido, donde los diagramas de embebimiento alcanzan un radio máximo finito y presentan densidad de energía negativa en todo el espacio. Se examina en detalle un agujero de gusano fantasma sin fuerza de marea que exhibe el primer comportamiento asintótico mencionado. La investigación profundiza en las condiciones de atravesabilidad y analiza cómo el parámetro β, asociado al déficit o exceso de ángulo sólido, influye en el movimiento de un viajero al cruzar la garganta del agujero de gusano. Además, se presenta un estudio exhaustivo del comportamiento geodésico, visualizado mediante diagramas de embebimiento tridimensional, proporcionando una comprensión más intuitiva de la geometría de estos agujeros de gusano. La segunda fase de la investigación se centra en el análisis de estabilidad de agujeros de gusano de cáscara delgada, construidos mediante la unión de agujeros de gusano no asintóticamente planos con la solución vacía de Schwarzschild. Este estudio se enfoca en cáscaras delgadas esféricamente simétricas, utilizando la función de forma lineal previamente mencionada. La estabilidad se examina empleando perturbaciones lineales alrededor de una solución estática, y se utiliza una ecuación maestra para caracterizar las regiones de equilibrio estable. El análisis considera tanto densidades de energía superficial positivas como negativas, y explorando diversas funciones de corrimiento al rojo gravitacional. Los resultados revelan que la interacción de fuerzas externas con la cáscara delgada tiene un impacto significativo en el comportamiento de las regiones estables. Notablemente, se demuestra que, bajo ciertas condiciones, la materia que soporta la cáscara delgada puede ser no exótica, cumpliendo plenamente todas las condiciones de energía.
Galactic Bulge Globular Clusters with CAPOS Survey: HP 1.
(Universidad de Concepción, 2024) Henao Ocampo, Lady Johana; Villanova, Sandro; Geisler, Douglas
Galactic Bulge Globular Clusters (BGCs) are crucial fossil relics for understanding the early formation and evolution of our galaxy. The CAPOS (Bulge Cluster APOgee Survey) project aims to study these ancient objects in detail, using the APOGEE spectrograph, which operates in the H-band infrared. This instrument provides high-resolution spectra (R ∼ 22,500) and allows for the derivation of detailed chemical abundances for over 22 species, including light elements, α- elements, iron-peak elements, and s-process elements. CAPOS has obtained high-quality data to study BGCs, employing advanced techniques to determine ages and kinematics with great precision. CAPOS I presented initial results from the ASCAP analysis, based on seven BGCs cataloged in SDSS DR16, deriving atmospheric parameters, radial velocities, and detailed abundances for up to 20 elements in 40 giant star members of these clusters. Key findings in CAPOS I include the correction of systematic correlations between metallicity and effective temperature, derivation of precise mean metallicities (ranging from [Fe/H] = −1.40 to −0.85), confirmation of slightly higher [Si/Fe] abundances in in situ main bulge clusters, clear identification of multiple populations (MPs) phenomena in each cluster, and exploration of iron-peak elements such as Mn and Ni. The project has made significant advances in characterizing specific clusters, including FSR 1758, Tonantzintla 2, NGC 6558, and HP 1. For HP 1, one of the oldest BGCs with an estimated age of 12.8 +0.9/−0.8 Gyr, abundances of Fe, C, N, O, Mg, Al, Si, S, Ca, Ti, Cr, Ni, and Ce were obtained for a sample of 10 red giant branch members using the BACCHUS package. A fundamental aspect of the study is the search for evidence of the multiple population phenomenon in HP 1 and other BGCs. The study of MPs in BGCs is crucial for understanding the formation and evolution of these ancient stellar structures and, by extension, the Galactic bulge as a whole. The complexity of this astrophysical phenomenon underscores the importance of projects like CAPOS in advancing our understanding of these fascinating objects.
Desarrollo de celdas solares sensibilizadas con colorantes naturales y co-sensibilizadas con nanopartículas de plata y puntos cuánticos.
(Universidad de Concepción, 2024) Cerda Rojas, Bayron Nath; Manidurai, Paulraj
En esta tesis se desarrollaron cuatro tipos de celdas solares sensibilizadas (Dye Sensitized Solar Cells, DSSC) y co-sensibilizadas. El primer tipo de celdas fueron las sensibilizadas con colorantes naturales de Aristotelia chilensis (AC) y Spinacia oleracia (SO), luego se desarrollaron celdas solares co-sensibilizadas con nanopartículas de plata (Ag) sintetizadas mediante síntesis verde utilizando Aristotelia chilensis como agente de reducción, el tercer tipo de celdas fueron las co-sensibilizadas con puntos cuánticos de óxido de zinc (ZnO) y finalmente se desarrollaron celdas solares sensibilizadas con colorante de Gracilaria chilensis (GC). Para el primer tipo de celdas solares de Aristotelia chilensis, se obtuvieron eficiencias de 0,1 % para el solvente de etanol, 0,105 % para el solvente de metanol y 0,044 % para el solvente de acetona. Para las celdas solares de Spinacia oleracia se obtuvieron eficiencias de 0,008 % para el solvente de etanol, 0,030 % para el solvente de metanol y 0,008 % para el solvente de acetona. Se puedo notar bajo eficiencias por las celdas construido, pero los ruta adoptados son camino verde por lo tanto baja la emisión de Carbono. Para mejorar la eficiencia y rendimiento de las celdas, el segundo tipo de celdas solares fue co-sensibilizadas con nanopartículas de plata, se obtuvieron eficiencias de 1,882 % para celdas solares solo con rutenio y de 2,240 % para una concentración molar de 0,204 mM y de 1,799 % para una concentración molar de 0,278 mM de nanopartículas de plata. También el tercer tipo de celdas solares fue co-sensibilizadas con puntos cuánticos de óxido de zinc, se obtuvieron eficiencias de 0,1 % para celdas solo de Aristotelia chilensis, de 0,12 % para celdas co-sensibilizadas con puntos cuánticos de óxido de zinc con una relación de litio de 0,25 y 0,14 % para una relación de litio de 0,67. Para celdas de rutenio se obtuvo una eficiencia de 1,29 % solo para rutenio, de 1,1% para celdas co-sensibilizadas con una relación de litio de 0,25 y 1,35 % para una relación de litio de 0,67. De cuarto tipo de celdas solares fue ensamblado con los componentes derivado del alga Gracilaria chilensis. Estos componentes fueron prestados del laboratorio de Bioquímica y Biomolecular, Universidad de Concepción. Los DSSC construidos fueron sensibilizados con las proteínas los cuales mostraron efectos por los fotones visible. Las eficiencias, transición electrónica y efecto electroquímica fue investigado. Un aumento de la eficiencia hasta 600% fue observado antes y después un proceso de funcionalización sobre el semiconductor de TiO2. En este trabajo se presenta la construcción de celdas solares de DSSC con extracto naturales y mejoramiento de sus eficiencias mediante co-sensibilización con nanopartículas de Ag. Se logro un aumento del 19 % de eficiencia con respecto a una celda sin nanopartículas de Ag. Mediante la co-sensibilización con puntos cuánticos de ZnO, se logró un aumento de la eficiencia de un 40% con respecto a una celda solo de AC y se logró un aumento de un 5% para una celda solo de rutenio. Mediante el uso de colorantes de GC, se logró aumentar la eficiencia mediante la funcionalización con APTMS en un 665% para una celda sensibilizada con aloficocianina y funcionalizada con APTMS. Mediante el desarrollo de esta tesis se logró obtener una patente para este último tipo de celdas solares titulada “Uso de pigmentos de algas chilenas para la sensibilización de fotoánodo para la construcción de celdas solares fotovoltaicas”. Varios resultados han comunicado como artículos y han presentados en congresos internacionales.
The thermodynamic role of solitons in the phase space of (super)gravity.
(Universidad de Concepción, 2024) Quijada Barrera, Constanza del Pilar; Oliva Zapata, Julio Eduardo; Anabalón Dupuy, Andrés Fernando
In this thesis we study the phase transitions between the planar charged black hole and the charged AdS soliton, which are solutions to the Einstein-AdS theory coupled to linear and non-linear electrodynamics theory. The analysis is carried out in the grand canonical ensemble. The charged planar soliton is obtained as a double analytic continuation of the charged black hole metric, which also involves analytically continuing the electric charge, therefore it appears a magnetic charge on the soliton solution which is associated with a magnetic flux along the non-cyclic planar coordinate. In the case of Einstein-Maxwell theory with negative cosmological constant, we show that there are phase transitions between both solutions depending on the values of electric potential, magnetic flux and temperature. On the other hand, when it is considered the gravitational theory coupled to a non-linear electrodynamics, we show that the phase space of the theory is very rich, containing reen trant phase transitions, as well as triple points, for small values of the coupling controlling the non-linearity of the electrodynamics Lagrangian.
Anti-de Sitter Asymptotically Rotating Black Holes and Wormholes.
(Universidad de Concepción, 2024) Narbona Olivares, Daniela Alejandra; Fierro Mondaca, Octavio Ariel
This doctoral thesis explores advanced concepts in theoretical physics, focusing on asymptotically Anti-de Sitter (AdS) rotating black holes and wormholes within the framework of Lovelock theories and New Massive Gravity (NMG). The work is divided into several key problems: • Wormhole Construction in Lovelock Theories: The thesis introduces new wormhole solutions in vacuum scenarios within Lovelock theories, particularly when coupling constants are aligned to create a unique vacuum. The study examines the effects of an integration constant on the energy content and stability of the wormholes, along with the spectrum of massive scalar probes. • Quasinormal Modes in NMG: The research investigates scalar field perturbations over asymptotically de Sitter black holes and gravitational solitons within NMG, a three-dimensional theory that extends General Relativity. The work provides exact quasinormal modes, offering insights into the stability and dynamics of these spacetimes. • Rotating Black Holes: The thesis delves into the perturbative dynamics of rotating black holes, particularly the Kerr-AdS black hole and the Black Spindle, which is obtained by applying the limit a → ℓ to the Kerr-AdS black hole. Using the Newman-Penrose formalism and Teukolsky’s master equation, the study analyzes the behavior of various fields under perturbations in rotating black hole spacetimes. Overall, this thesis contributes to the understanding of complex gravitational phenomena, including the stability of wormholes and rotating black holes, and the implications of these solutions for higher-curvature gravity theories.
Dwarf ellipticals.
(Universidad de Concepción, 2024) Urrutia Zapata, Fernanda Cecilia; Fellhauer, Michael; Kroupa, Pavel
Dwarf elliptical (dE) galaxies are at the low-luminosity end of the elliptical galaxy sequence, characterized by smaller sizes and lower luminosities compared to typical elliptical galaxies. A common method of distinguishing between a normal elliptical galaxy and a dwarf galaxy is through its absolute magnitude, with a commonly used limit of -18 mag. Below masses compared to dwarf ellipticals are found Ultra compact dwarf galaxies (UCDs). UCDs are extended objects(EOs) with high mass, typically characterized by a lower mass limit of 2×106 M⊙. Their luminosities are above the brightest known star clusters (SCs), and their effective radii range between 10 and 100 parsecs. Thus, while they are larger, brighter, and more massive than star clusters, they remain more compact than typical dwarf galaxies of comparable luminosity. In our study we investigate the possibility of dE galaxies losing their components in the tidal stripping and truncation scenario, leaving their dense central cluster on the type of orbits on which UCDs are found. I.e, a dE,N galaxy with a dense core gets partly destroyed by the gravitational forces of one or many bigger galaxies. Only the compact central part survives as UCD. It is important to test if this can be done in Lambda cold dark matter (LCDM), in where each dE galaxy has its own Navarro-Frenk-White halo with the preinfall properties as given by the theory, on how to associate a baryonic galaxy with a dark matter halo. So, in this work, our aim is to address the questions of whether the dark matter halo can be stripped, as assumed in previous studies, and whether then the stellar body of the dE galaxy can also be stripped, resulting in UCDs in the orbits where we observe them?
On the homogeneity of topological spaces.
(Universidad de Concepción, 2024) Barría Burgos, Sebastián Andrés; Martínez Ranero, Carlos
En esta tesis estudiamos la preservación de homogeneidad (y no homogeneidad) de contraejemplos universales no metrizables bajo productos e hiperespacios, con el fin de responder las siguientes preguntas: ¿Es la ω-ésima potencia del plano de Niemytzki homogénea? [Fitzpatrick Jr. and Zhou (1990), Problem 5] y ¿Es el hiperespacio de los cerrados no vacíos de la doble flecha homogéneo? [Arkhangel’skiˇi (1987), Problem II.1]. Para abordar la primera pregunta, investigamos subespacios de la ω-ésima potencia del plano de Niemytzki y la respondemos parcialmente demostrando la homogeneidad del producto entre el plano de Niemytzki y la ω-ésima potencia de un abierto básico. Como consecuencia, concluimos que el producto de la ω-ésima potencia del plano de Niemytzki con la ω-ésima potencia de un abierto básico es también homogéneo. Para responder a la segunda pregunta, analizamos hiperespacios de la doble flecha y ofrecemos una respuesta parcial probando que los espacios de uniones de a lo más una cantidad finita de intervalos cerrados, así como todos los productos simétricos excepto el primero, no son homogéneos. Como contraparte, demostramos que el segundo producto simétrico de la recta de Sorgenfrey es homogéneo. Además, logramos dar una imagen completa de cómo lucen los autohomeomorfismos de potencias finitas de la doble flecha. Mostramos que cualquier autohomeomorfismo de una potencia finita de la doble flecha es localmente (fuera de un conjunto nunca denso) un producto de encajes monótonos que van desde un intervalo abierto-cerrado de la doble flecha a esta, seguido de una permutación de las coordenadas.
Banach space-based mixed finite element methods for coupled diffusion problems and related models.
(Universidad de Concepción, 2024) Inzunza Domínguez, Cristian Andrés; Gatica Pérez, Gabriel N.; Colmenares García, Eligio Antonio; Sequeira Chavarría, Filánder de los Ángeles
In this thesis, new Banach spaces-based mixed finite element methods are explored to address coupled diffusion problems and related models in continuous mechanics. The focus is on numerical analysis and simulation of the stress-assisted diffusion problem and the chemotaxis-Navier-Stokes problem. First, we introduce and analyze mixed variational formulations based on Banach spaces for the nearly incompressible linear elasticity problem and the Stokes problem. This approach is motivated by the similarities between the variational formulations of these models with respect to those obtained for the stress-assisted diffusion problem, which will be subsequently studied. To avoid the imposition of weak symmetry on the Cauchy stress tensor, we reformulate the problems in terms of the pseudostress tensor. We apply integration by parts formulas appropriate for the Banach spaces used, resulting in continuous schemes for both models. We employ the Babuška-Brezzi theory in Banach spaces and generalize classic results to establish that the obtained formulations are well-posed within these spaces. Next, we address the system of partial differential equations describing the diffusion of a solute in an elastic material. The elasticity model, whose momentum equation includes a source term dependent on diffusion, is reformulated using the non-symmetric pseudostress tensor and the deformation of the solid as unknowns of the mixed scheme. The diffusion equation, with the diffusivity function and source term depending on the stress and strain tensor of the solid, respectively, is approached using a primal formulation with concentration as the unknown. Dirichlet boundary conditions are considered for both equations. As a natural continuation of the above, a fully-mixed approach based on Banach spaces is proposed and analyzed, generating a new finite element method for the coupled stress-assisted diffusion problem to be solved numerically. We introduce two mixed schemes for the diffusion problem, using diffusion flux as an additional variable, and for the second, we also consider the concentration gradient as an unknown.Finally, we introduce and analyze a fully-mixed method based on Banach spaces to numerically solve the stationary chemotaxis-Navier-Stokes problem. This coupled and nonlinear model represents the biological process driven by cellular movements induced by an external or internal chemical signal within an incompressible fluid. In addition to the velocity and pressure of the fluid, the velocity gradient and the Bernoulli-type stress tensor are introduced as additional variables, allowing the fluid pressure to be eliminated from the equations and calculated by post-processing after solving the system. In turn, in addition to the cellular density and the concentration of the chemical signal, the pseudostresses associated with these last variables and their corresponding gradients are introduced as additional unknowns. The resulting continuous formulation, set in a Banach framework, consists of a coupled system of three saddle point problems, each perturbed with trilinear forms dependent on the data and the unknowns of the other two problems. The continuous formulations resulting from each of the schemes are approached through a fixedpoint strategy. Therefore, the Babuška-Brezzi theory in Banach spaces allows us to establish that the operators associated with each of the problems are well-stated. In turn, the classic Banach fixed-point theorem, in conjunction with assumptions of small data, results in the existence and uniqueness of the solution at a continuous level. Then, on arbitrary finite element subspaces, we establish Galerkin schemes corresponding to each of the problems. Assuming that the mentioned subspaces are inf-sup stable, Brouwer’s theorem allows us to establish the existence of solutions at the discrete level. Additionally, for the scheme associated with the stationary chemotaxis-Navier-Stokes problem, Banach’s fixed-point theorem also allows establishing the uniqueness of such discrete solution. We obtain Céa’s estimates corresponding to each scheme, and once the finite element subspaces are particularized, the approximation properties allow us to establish the corresponding convergence rates. Finally, numerical experiments confirm these rates and illustrate the good performance of our methods.
Cinemática y dinámica de gas ionizado en el núcleo de la galaxia M87.
(Universidad de Concepción, 2023) Osorno Quiceno, Juan David; Nagar, Neil Mark
The black hole mass measurement of the galaxy M87, based on its stellar kinematics, is twice that determined via ionized gas kinematics, with the values disagreeing by more than 3σ. In order to gain insights into the reasons behind the disagreement between the measurements, it is needed to better constrain the morphology and kinematics of the ionized gas in the nuclear region. The new narrow field mode with adaptive optics integral field spectroscopic data, from the Multi Unit Spectroscopic Explorer instrument on the Very Large Telescope, covers in detail the nuclear region of the galaxy, and is used with a wide field mode data set to model the morphology and kinematics of multiple ionized gas emission lines. Moment maps and position-velocity diagrams are used to describe the ionized gas kinematics in both the large-scale and the galaxy nucleus; the position angle and inclination of the rotating disk are fixed using the program Kinemetry; simulated data cubes, across a range of black hole masses and disk inclinations, are created to obtain the best-fit model, by the parameterization of the differences of the residual (observed minus simulated) velocity maps. The results reveal complexities in the nuclear ionized gas kinematics not seen in earlier sparse and shallower spectroscopy: several ionized gas filaments, some with high flow velocities, which can be traced down into the projected sphere of influence; a partially filled biconical outflow, aligned with the jet, with radial velocities up to 400 km s−1; and a rotating ionized gas disk, with twisted velocity isophotes. The complexity of the nuclear morphology and kinematics precludes the measurement of an accurate black hole mass from the ionized gas kinematics. The fits to the subarcsecond disk inclinations from Kinemetry, and the statistics from the velocity residual maps, support a high black hole mass of about 6.0 × 109 M⊙ and low inclination disk of 25◦, rather than the previously proposed 3.5 × 109 M⊙ black hole mass with a 42◦ inclination disk.
Infrared cavity quantum electrodynamics with anharmonic oscillators in nanophotonics.
(Universidad de Concepción, 2023) Arias Contreras, Mauricio Andrés; Delgado Hidalgo, Aldo Patricio; Herrera, Felipe
The characterization and manipulation of complex microscopic systems for applications in science and technology demands to have robust theoretical tools that guide the extraction of relevant information or complement such processes. In particular, condensed phase physics, which is in a blurry boundary between chemistry and quantum physics, requires several approximations due the high number of degrees of freedom present. Thereupon, achieving a satisfactory balance between a model with just the right amount of features and, hopefully, requiring low computational requirements represents a significant challenge. This is the reason why having minimal models to understand the fundamental physics of complex condensed phases, in organic or inorganic materials, particularly when subject to confined electromagnetic fields, is a valuable contribution, specially appreciated in chemical physics and quantum optics protocols. In this thesis we show an intensive exploration of the capabilities of a nonlinear mid-infrared semi empirical model for describing the coherent and incoherent dynamics of anharmonic dipoles coupled to a single harmonic mode of a cavity QED.We find that the intrinsic anharmonicity in the material spectrum is heralded to the near electric field of a nanoresonator. Depending on the classical driving intensity ratio with respect to losses, this mechanism allows for the control and modulation of the complex phase of an incident finite pulse to the resonator with respect to the scattered cavity field, which translates into a delay in the stationary temporal domain, even after the pump pulse has ended. This mechanism promises interesting applications in molecular infrared nanophotonics, where the intrinsic anharmonicities of the vibrational modes are well documented in the literature, and also because the light-matter system requires to be in weak coupling regime, increasing the prospects for its experimental realization using current nanophotonic technology. Moreover, we show that our approach is applicable to other non organic devices as intersubbands in multi-quantum wells (MQW’s), where the state–of–the–art in both material and optical parameters engineering, as well as the capability of having smaller N compared to molecular systems, promises stronger effects on the nonlinear phase modulation, which can be modified and even increased by adapted heterogeneities among the dipoles that introduce contributions from the dark manifold. We expect our model will help in the development of new infrared nanophotonic hardware for applications ranging from quantum control of materials to quantum information processing.
Numerical Methods for two types of Stochastic Differential Equations with Nonglobally Lipschitz Coefficients.
(Universidad de Concepción, 2023) Muñoz Muñoz, Mario Alejandro; Mora, Carlos; Cruz, Hugo de la
This doctoral thesis focuses on the numerical solution of Stochastic Differential Equations (SDEs) with non-globally Lipschitz coefficients. It involves two independent investigations that propose different procedures for the effective numerical simulation of these models. The first investigation centers on the numerical solution of the non-linear stochastic Schr¨odinger equation, which is a stochastic differential equation with locally Lipschitz continuous coefficients commonly used to model quantum measurement processes. We analyze the rate of weak convergence of an exponential scheme that reproduces the norm of the desired solution by using a projection onto the unit sphere. In particular, we prove that the exponential scheme converges with weak-order one, and obtain the leading order term of its weak error expansion. This justifies using the Talay-Tubaro extrapolation procedure in the numerical simulation of open quantum systems. By employing this procedure, a secondorder method for computing mean values of smooth functions of the solution is obtained. Furthermore, we prove that the exponential scheme under study has order of strong convergence 1/2, validating its application in the Multilevel Monte Carlo method. Numerical experiments involving a quantized electromagnetic field interacting with a reservoir showcase the effectiveness of the proposed methods. The second investigation introduces a new methodology for the effective pathwise numerical simulation of stochastic differential equations with non-globally Lipschitz continuous coefficients. Specifically, we focus on SDEs with linear multiplicative noise. We employ a suitable invertible continuous transformation to establish a connection between the original SDE and an auxiliary Random Differential Equation (RDE). This explicit conjugacy enables the development of new pathwise numerical schemes for the studied SDE, utilizing numerical approximations of the auxiliary RDE. In particular, we introduce two numerical methods: one based on an exponential scheme and the other based on the Heun scheme. In order to showcase the practical applicability of our approach, we implement it within a compartmental epidemic model, specifically the stochastic SVIR model. This SDE captures the dynamics of a continuous vaccination strategy in the presence of environmental noise effects. Through comparative analysis with commonly used numerical approximations, we validate the effectiveness of our proposed numerical methods for simulating epidemiological models.
Multi-dimensional entanglement generation with multi-core optical fibers.
(Universidad de Concepción, 2023) Machuca Flores, Ítalo Ignacio; Moreira Lima, Gustavo de Aquino
The common threads of my work in the Ph.D. was entanglement sources and the work and the works that served as an experimental basis are [20, 47]. Here, prove partially entangled state (PES) in quantum information protocols Bell inequality, Self-testing and Randomness certification. It was that the state with more entanglement have better performance in protocols and that nonlocality can be without additional measurements. This knowledge was used to prepare the main work of this thesis. An source of entanglement pointing to the growing in classical optics and telecommunications. In this regard, advances in multiplexing optical communications channels have also been pursued for the generation of multi-dimensional quantum states (qudits), since their use is advantageous for several quantum information tasks. One current path leading in this direction is through the use of space-division multiplexing multi-core optical fibers, which provides a new platform for efficiently controlling path-encoded qudit states. Here we report on a parametric down-conversion source of entangled qudits that is fully based on (and therefore compatible with) state-of-the-art multi-core fiber technology. The source design uses modern multi-core fiber beam splitters to prepare the pump laser beam as well as measure the generated entangled state, achieving high spectral brightness while providing a stable architecture. In addition, it can be readily used with any core geometry, which is crucial since widespread standards for multi-core fibers in telecommunications have yet to be established. Our source represents an important step towards the compatibility of quantum communications with the next-generation optical networks.

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