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- ItemCollider Accessible Long-Lived Inflaton Model(2025) López Fuentes, Manuel Antonio; Cottin Buracchio, Giovanna Francesca; Pontificia Universidad Católica de Chile. Instituto de FísicaThis work explores the collider phenomenology of a general single-field inflaton model featuring long-lived particle signatures and a low reheating temperature, consistent with cosmological and collider constraints. We start by reviewing the key aspects of ΛCDM and the tensions that led to the proposal of the inflationary framework, its underlying physics, and the current status of particle physics with emphasis on dark sectors and scalars which are at the interplay between cosmology and particles. Then, we present our methodology to build the exclusion regions for neutral long-lived particles at the Future Circular Collider (FCC), detailing how we use the kinematics of each simulated event to obtain a probability of detection inside a fiducial detector volume, estimating the expected number of events at the FCC-hh reference detector.Finally, we introduce our particular model, explain briefly how the inflationary physics can be applied in a future work, derive the relations among the model parameters and choose the independent variables to be {m_ϕ, θ}, the inflaton mass and its mixing angle to the Standard Model Higgs boson. We implement this model in MadGraph5 with an effective vertex for gluon-gluon Fusion, explain the code we created to directly map the LHE events into the probability of detection, and ultimately find the exclusion region for the Future Circular Collider in its hadron-hadron mode. We also discuss why the Large Hadron Collider (LHC) lacks sensitivity to this model.
- ItemDiagramas de fases magnéticos en sistemas 2D(2024) Arellano Sánchez, Felipe César; Mejia López, José Félix; Pontificia Universidad Católica de Chile. Facultad de FísicaLas redes de skyrmiones son texturas magnéticas de tipo vórtice presentes en sistemas magnéticos con una fuerte interacción de Dzyaloshinskii-Moriya (DMI), las cuales son candidatos prominentes para el desarrollo de dispositivos espintrónicos debido a su alta estabilidad y a su posible manipulabilidad.En esta tesis se desarrolló un método capaz de realizar diagramas de fases magnéticas para los estados fundamentales de monocapas hexagonales a partir de un modelo atomístico mediante el uso de simulaciones estocásticas.Se observó que en ausencia de campo magnético externo el sistema presenta una transición de fase de un estado ferromagnético a un estado de espirales de espín, mientras que al aplicar un campo magnético externo perpendicular al plano el sistema presenta una transición de fase de un estado ferromagnético a una red de skyrmiones, y posteriormente una transición continua a un régimen de tipo laberinto, hasta obtener nuevamente texturas de tipo espiral. Finalmente se discutió el efecto del campo magnético externo en el valor mínimo de la interacción DMI necesaria para producir redes de skyrmiones, así como una aproximación numérica de la curva que describe las transiciones de fases.
- ItemMás allá de la transición de strain stiffening: relación entre la densidad de estados y la velocidad no afín(2025) Roncagliolo Abarca, Emilio Gabriele; Düring, Gustavo; Pontificia Universidad Católica de Chile. Facultad de FísicaLa transición de strain stiffening se observa en una variedad de materiales, entre ellos redes proteicas estructurando células y tejidos, motivando su estudio a deformaciones bajo el punto de rigidez. A mayores esfuerzos, la exploración no es tan detallada. Esta tesis busca aportar a este vacío estudiando una deformación expansiva y observando la densidad de estados.Adicionalmente, se sabe el comportamiento crítico de la velocidad no afín es curioso: diverge desde abajo, pareciera llegar a una constante desde arriba. Esta tesis propone una explicación de esta observación mediante la relación entre la velocidad no afín y los autoestados del sistema a través de una perturbación.
- ItemCan the Core Helium Flash Synthesize Lithium and Dredge it Up?(2025) Vilaza Dallago, Sebastian Javier; Chanamé, Julio; Pontificia Universidad Católica de Chile. Instituto de AstrofísicaThe existence of lithium-rich (Li-rich) red giant stars challenges standard stellar evolution models. Although several mechanisms have been proposed, the origin of Li enrichment remains a mystery. Recent asteroseismic and spectroscopic evidence suggests that most Li-rich giants are low-mass red clump (RC) stars that have undergone the core helium (He) flash, indicating a possible connection with this event. Motivated by multi-dimensional hydrodynamical simulations, in this work I investigate whether the core He-flash in low-mass stars can trigger a proton ingestion episode (PIE) that produces lithium. Using the MESA stellar evolution code I compare standard evolution with models where a PIE is induced by implementing enhanced overshooting, in a 1.2 Msun star with subsolar metallicity ([Fe/H] = -0.3). These models show that PIEs can occur at near-solar metallicity, producing a secondary hydrogen flash followed by a dredge-up event. Although lithium and beryllium are synthesized during the PIE, which if they were dredged up they could enhance the surface Li-abundance up to a value of A(Li)~4.8, being able to explain even the most Li-rich giants, both Li and Be are destroyed before the dredge-up event, resulting in no surface enrichment. In the PIE-induced models, the post-PIE evolution diverges from standard models, with a second RGB ascent and secondary He-flash occurring before stable core He-burning. The PIE also produces substantial s-process elements via the 13C(alpha, n)16O reaction, which are dredged up to the surface, enhancing their abundance by 2–3 dex. The non-standard evolution and strong s-process enhancement contradict current observations of Li-rich red clump giants. While PIEs remain a theoretically promising mechanism for internal Li enrichment, current results do not support them as the origin of Li-rich giants. However, open questions remain before the scenario can be definitively ruled out.
- ItemRenormalization of scalar-tensor AdS gravity theories in 6D(2025) Osorio Navarro, Loreto Soledad; Araya, Ignacio ; Bañados Lira, Maximo; Pontificia Universidad Católica de Chile. Facultad de FísicaIn this work we consider a scalar-tensor gravity action in six dimensions and study its finiteness through conformal renormalization. This action comprises a purely metric sector, defined by renormalized Einstein gravity, coupled to a scalar sector derived from the Lovelock gravity scalar uplift in six dimensions. For static black holes with both conformally flat and non-conformally flat transverse sections, the renormalized action yields finite results. In conformally flat cases, finiteness is achieved solely through a topological Euler term with a specific coupling. For non-conformally flat transverse sections, an additional boundary current term with a distinct coupling is required tocancel subleading divergences. These couplings match those derived from purely metric conformal embeddings in six dimensions, validating consistency across frameworks.The results indicate that starting from renormalized Lovelock theory, one can use the scalar conformal uplift to obtain a renormalized scalar-tensor theory with a non-minimally coupled scalar, thus extending conformal renormalization as a procedure to cases with (conformally coupled) matter.