FIS Tesis magíster

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Browsing FIS Tesis magíster by Subject "520"

Now showing 1 - 4 of 4
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    A search for substructures near the Galactic plane and bulge using RR Lyrae stars as tracers
    (2024) Cristi Cambiaso, Nicolas Eduardo; Catelan, Márcio; Zoccali, Manuela; Pontificia Universidad Catolica de Chile. Faculty of Physics. Institute of Astrophysics
    Usando estrellas pulsantes de tipo RR Lyrae, hacemos una búsqueda de subestructuras Galácticas ("stellar streams" y cúmulos globulares) en la región del plano Galáctico. Construimos una muestra de estrellas RR Lyrae con valores de distancia y metalicidades. Estudiamos esta muestra con un algoritmo de "clustering" para encontrar grupos de estrellas cercanas y con propiedades similares. Mediante esta búsqueda, recuperamos estructuras conocidas y encontramos posibles nuevas estructuras.
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    Evolution of Chemical Patterns During Major Mergers
    (2025) Jara Ferreira, Francisco Eduardo; Tissera, Patricia; Pontificia Universidad Católica de Chile. Instituto de Astrofísica
    El estudio de la evolución química de las galaxias es clave para comprender su formación y desarrollo, especialmente en fusiones e interacciones. Estas afectan la composición química y estructura de las galaxias al inducir flujos de gas, estallidos de formación estelar y redistribución de elementos. En esta tesis, se analizan las poblaciones estelares en 12 simulaciones no cosmológicas con el código P-Gadget3, explorando diferentes modelos de Delay Time Distribution (DTD) para supernovas tipo Ia y condiciones iniciales (galaxias aisladas con y sin barra y una fusión masiva).El análisis del plano [Fe/H]–[O/Fe] revela una doble trayectoria en las simulaciones de galaxias fusionando, con loops formados en la interacción y en episodios tardíos de formación estelar. Los modelos DTD correspondientes a SD, DD y Pritchet muestran una evolución química más dinámica, mientras que el modelo Bimodal atenúa los loops. Adicionalmente, hemos probado métodos analíticos y filogenéticos para identificar huellas químicas de fusiones masivas, encontrando diferencias claras entre galaxias aisladas y fusionadas. Estos resultados sugieren la existencia de patrones químicos característicos de galaxias que han pasado por una fusión masiva, abriendo la posibilidad de la aplicación de este análisis en observaciones y simulaciones que incluyan cosmología.
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    High-Cadence Stellar Variability Studies of Galactic RR Lyrae Stars with DECam
    (2023) Baeza Villagra, Karina; Catelan, Márcio; Pontificia Universidad Católica de Chile. Facultad de Física
    As part of the DECam Alliance for Transients (DECAT), a consortium of time- domain DECam programs, the DECam Deep Drilling Program (DDP) is being conducted at the Blanco 4m telescope, located at Cerro Tololo Inter-American Observatory, Chile. The DDP includes the DECaPS East field, situated in the Galactic bulge at coordinates (RA, DEC)(J2000) = (18:03:34, -29:32:02). We performed two nights of high-cadence, multi- band (griz) observations utilizing DECam. We obtained high-quality griz light curves for 1033 previously identified RR Lyrae stars. Subsequently, a robust Fourier decomposition analysis was con- ducted, generating well-defined, multi-band light curve templates for 143 RRab and 146 RRc stars. This process aimed to update and enhance the existing RR Lyrae star templates catalog. Therefore, our work is expected to broadly apply to the data acquired from the Vera C. Rubin Observatory’s Legacy Survey of Space and Time. Furthermore, we compared and analyzed the dependence of Fourier coef- ficients and other derived light curve parameters on the effective wavelength, providing valuable in-sights into the behavior and structure of RR Lyrae stars. Another significant contribution of this study was the construction of the Period- φ31-[Fe/H] relations, total-to-selective extinction ratios, and distances for each star in both the DECam and Sloan photometric systems. This information is crucial for investigating RR Lyrae stars and their role as tracers of Galactic structures. By combining these results, we better un- derstand the characteristics and morphology of their light curves, the chemical composition through studying their metallicities, and the spatial distribution of RR Lyrae stars within the Galactic bulge. This knowledge contributes to the overall effort of classifying and detecting variable stars.
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    Lepton universality in the MSSM with trilinear R-parity violation model
    (2024) Guirriman Alvarez, Alexis Vladimir; Díaz Gutiérrez, Marco Aurelio; Pontificia Universidad Católica de Chile. Facultad de Física
    The Standard Model (SM) of particle physics, though highly successful, fails to address several fundamental questions, including the neutrino masses origin, the nature of dark matter, among others. The recent LHCb collaboration analysis measured the ratio of branching fractions RK inB+ → K+ℓ+ℓ− decay to test lepton universality, a property predicted by the SM. This observable is particularly powerful due to the cancellation of hadronic uncertainties, making it a sensitive probe for new physics. The measured value of RK is consistent with the SM prediction, suggesting nosignificant lepton universality violation. Nevertheless, given the limitations of the SM, this thesis explores a SM extension using the MSSM+λ ′TRPV model. By incorporating all possible SUSY contributions, we aim to theoretically predict the experimental RK result, providing a novel perspective on determining the parameter space that fit with the experimental measurement. The analysis is conducted within an Effective Field Theory framework across four different scenarios for Wilson Coefficients to account for the higher energy scales associated with these particles, translating their effects to the measurable energy range. The theoretical calculation is performedusing a scan in Python, while respecting other experimental constraints regarding SUSY particles. We found that the parameter space that respect the 3σ region of the LHCb collaboration measurement is |λ′| ≲ 10−2 or m˜ ≳ 8.5 TeV. Additionally, we found that our result is independent from each scenario for Wilson Coefficients. Finally, we discovered that RK has no particular bias towards any individual λ′ijk.