3.10 Tesis doctorado
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Browsing 3.10 Tesis doctorado by Subject "510"
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- ItemAmorphous materials under stresses: understanding critical behavior(2022) Villarroel CortĂ©s, Carlos Javier; DĂŒring, Gustavo; Pontificia Universidad CatĂłlica de Chile. Facultad de FĂsicaGran parte de los materiales que utilizamos a diario no se comportan como un sĂłlido elĂĄstico o un fluido newtoniano cuando se les aplica deformaciĂłn. Dentro de la extensa lista de estos materiales que presentan caracterĂsticas no lineales en cantidades macroscĂłpicas, podemos encontrar muchos alimentos que consumimos o incluso la piel humana. Comprender estos comportamientos particulares actualmente representa un desafĂło importante con aplicaciones en la industria y la medicina. Para responder algunas de las preguntas que estos materiales particulares presentan hoy en dĂa, en esta tesis, utilizando simulaciones numĂ©ricas de alto nivel, estudiamos dos fenĂłmenos no lineales crĂticos, el fenĂłmeno de âYieldingâ y el fenĂłmeno de âStrain-Stiffeningâ. En particular, la transiciĂłn de âYieldingâ se observa en materiales donde, dependiendo de la tensiĂłn aplicada, es posible pasar de un estado mecĂĄnicamente estable a uno que fluye como un lĂquido. En este contexto, mediante simulaciones de partĂculas blandas, se realiza el cĂĄlculo de los exponentes crĂticos que gobiernan el rĂ©gimen fluido para dos escenarios de esfuerzos aplicados, y se estudia cĂłmo las estadĂsticas de avalanchas pueden caracterizar el flujo. Finalmente, para el fenĂłmeno âStrain-Stiffeningâ, se propone un nuevo modelo de redes semi-flexibles capaces de replicar este comportamiento, donde un sistema blando se transforma en uno rĂgido mediante la aplicaciĂłn de una deformaciĂłn. A su vez, este modelo es capaz de explicar y predecir de buena manera los exponentes crĂticos que gobiernan la transiciĂłn.
- ItemAspects of quantum gravity in AdS3/CFT2(2019) Reyes Raffo, Ignacio AndrĂ©s; Erdmenger, Johanna; Koch, Benjamin; Bañados, MĂĄximo; Ströhmer, Raimund; Pontificia Universidad CatĂłlica de Chile. Facultad de FĂsicaThe quest for finding a unifying theory for both quantum theory and gravity lies at the heart of much of the research in high energy physics. Although recent years have witnessed spectacular experimental confirmation of our expectations from Quantum Field Theory and General Relativity, the question of unification remains as a major open problem. In this context, the perturbative aspects of quantum black holes represent arguably the best of our knowledge of how to proceed in this pursue. In this thesis we investigate certain aspects of quantum gravity in 2 + 1 dimensional anti-de Sitter space (AdS3), and its connection to Conformal field theories in 1 + 1 dimensions (CFT2), via the AdS/CFT correspondence. We study the thermodynamics properties of higher spin black holes. By focusing on the spin-4 case, we show that black holes carrying higher spin charges display a rich phase diagram in the grand canonical ensemble, including phase transitions of the Hawking-Page type, first order inter-black hole transitions, and a second order critical point. We investigate recent proposals on the connection between bulk codimension-1 volumes and computational complexity in the CFT. Using Tensor Networks we provide concrete evidence of why these bulk volumes are related to the number of gates in a quantum circuit, and exhibit their topological properties. We provide a novel formula to compute this complexity directly in terms of entanglement entropies, using techniques from Kinematic space. We then move in a slightly different direction, and study the quantum properties of black holes via de Functional Renormalisation Group prescription coming from Asymptotic safety. We avoid the arbitrary scale setting by restricting to a narrower window in parameter space, where only Newtonâs coupling and the cosmological constant are allowed to vary. By one assumption on the properties of Newtonâs coupling, we find black hole solutions explicitly. We explore their thermodynamical properties, and discover that very large black holes exhibit very unusual features.The quest for finding a unifying theory for both quantum theory and gravity lies at the heart of much of the research in high energy physics. Although recent years have witnessed spectacular experimental confirmation of our expectations from Quantum Field Theory and General Relativity, the question of unification remains as a major open problem. In this context, the perturbative aspects of quantum black holes represent arguably the best of our knowledge of how to proceed in this pursue. In this thesis we investigate certain aspects of quantum gravity in 2 + 1 dimensional anti-de Sitter space (AdS3), and its connection to Conformal field theories in 1 + 1 dimensions (CFT2), via the AdS/CFT correspondence. We study the thermodynamics properties of higher spin black holes. By focusing on the spin-4 case, we show that black holes carrying higher spin charges display a rich phase diagram in the grand canonical ensemble, including phase transitions of the Hawking-Page type, first order inter-black hole transitions, and a second order critical point. We investigate recent proposals on the connection between bulk codimension-1 volumes and computational complexity in the CFT. Using Tensor Networks we provide concrete evidence of why these bulk volumes are related to the number of gates in a quantum circuit, and exhibit their topological properties. We provide a novel formula to compute this complexity directly in terms of entanglement entropies, using techniques from Kinematic space. We then move in a slightly different direction, and study the quantum properties of black holes via de Functional Renormalisation Group prescription coming from Asymptotic safety. We avoid the arbitrary scale setting by restricting to a narrower window in parameter space, where only Newtonâs coupling and the cosmological constant are allowed to vary. By one assumption on the properties of Newtonâs coupling, we find black hole solutions explicitly. We explore their thermodynamical properties, and discover that very large black holes exhibit very unusual features.The quest for finding a unifying theory for both quantum theory and gravity lies at the heart of much of the research in high energy physics. Although recent years have witnessed spectacular experimental confirmation of our expectations from Quantum Field Theory and General Relativity, the question of unification remains as a major open problem. In this context, the perturbative aspects of quantum black holes represent arguably the best of our knowledge of how to proceed in this pursue. In this thesis we investigate certain aspects of quantum gravity in 2 + 1 dimensional anti-de Sitter space (AdS3), and its connection to Conformal field theories in 1 + 1 dimensions (CFT2), via the AdS/CFT correspondence. We study the thermodynamics properties of higher spin black holes. By focusing on the spin-4 case, we show that black holes carrying higher spin charges display a rich phase diagram in the grand canonical ensemble, including phase transitions of the Hawking-Page type, first order inter-black hole transitions, and a second order critical point. We investigate recent proposals on the connection between bulk codimension-1 volumes and computational complexity in the CFT. Using Tensor Networks we provide concrete evidence of why these bulk volumes are related to the number of gates in a quantum circuit, and exhibit their topological properties. We provide a novel formula to compute this complexity directly in terms of entanglement entropies, using techniques from Kinematic space. We then move in a slightly different direction, and study the quantum properties of black holes via de Functional Renormalisation Group prescription coming from Asymptotic safety. We avoid the arbitrary scale setting by restricting to a narrower window in parameter space, where only Newtonâs coupling and the cosmological constant are allowed to vary. By one assumption on the properties of Newtonâs coupling, we find black hole solutions explicitly. We explore their thermodynamical properties, and discover that very large black holes exhibit very unusual features.
- ItemDesarrollo de hidrogeles a base de Ăłxido de grafeno y cobre para usos en tratamiento de aguas(2022) Acuña Porras, Camilo; DĂaz, Donovan; Pontificia Universidad CatĂłlica de Chile. Instituto de FĂsicaEn el presente trabajo se modificĂł quĂmicamente (grado de oxidaciĂłn) y morfolĂłgicamente (tamaño de lĂĄmina) lĂĄminas de Ăłxido de grafeno (GO) en soluciĂłn sintetizado por mĂ©todo de Hummers modificado, ademĂĄs se sintetizĂł partĂculas de cobre (PCu) como refuerzo, posteriormente se crecieron hidrogeles con GO (GOH) y PCu (Cu-GOH) por vĂa hidrotermal. Con los hidrogeles se realizaron pruebas de adsorciĂłn de azul de metileno (AM) disuelto en agua, con el fin de determinar correlaciones entre las caracterĂsticas quĂmicas, estructurales y morfolĂłgicas de los hidrogeles con la capacidad y cinĂ©tica de adsorciĂłn del AM como impureza del agua. La modificaciĂłn quĂmica se realizĂł variando la cantidad del agente oxidante y el tipo de grafito de partida en la sĂntesis de GO. Esta modifico el grado oxidaciĂłn y la distribuciĂłn de grupos funcionales del GO, estudiado por espectroscopĂa XPS. Se encontrĂł una reducciĂłn de los grupos funcionales oxigenados (OFG) al variar la cantidad de KMnO4, ademĂĄs de un punto de saturaciĂłn en que el KMnO4 no influĂa en la quĂmica del GO. TambiĂ©n se observĂł el efecto del tipo de grafito en la formaciĂłn de hidrogeles, cuando se usĂł grafito amorfo este no se formĂł en contraposiciĂłn a el grafito laminado donde se formĂł el hidrogel. La modificaciĂłn morfolĂłgica consistiĂł en un pretratamiento de sonicaciĂłn a distintos intervalos de tiempo 30min, 60min, 90min, 120min, 180min y 240min en la sĂntesis de GO (in-situ). Y postratamiento de sonicaciĂłn a distintas potencias comprendidas entre 50 y 200 W, y a tiempos de exposiciĂłn de 5 y 10 minutos del GO sintetizado en soluciĂłn (Post sĂntesis). El grado de oxidaciĂłn y OFG se analizaron por los espectros de alta resoluciĂłn (C1s y O1s) XPS, determinando que la sonicaciĂłn del GO no presenta modificaciones significativas en la distribuciĂłn de OFG y una consistencia en su grado de oxidaciĂłn (relaciĂłn C:O). Adicionalmente, el tamaño de lĂĄmina promedio se obtuvo por procesamiento de imĂĄgenes AFM, Para la soluciĂłn de GO base encontrĂł un valor entre 25040 - 33516 nm2 ; Para pretratamiento in-situ 57120 - 37220 nm2 ; Y post sĂntesis 5410 - 13620nm2 . Se observĂł que el tiempo de sonicaciĂłn afecta el tamaño de lĂĄmina para el tratamiento in-situ como para el post sĂntesis. Los hidrogeles crecidos vĂa hidrotermal mostraron una estructura porosa (entrecruzamiento de lĂĄminas de GO) en la superficie por imĂĄgenes SEM. QuĂmicamente se observĂł por los espectros de alta resoluciĂłn C1s y O1s de XPS un proceso de reducciĂłn de los OFG por la sĂntesis hidrotermal. TambiĂ©n la incorporaciĂłn PCu afecto la morfologĂa (interacciĂłn de lĂĄminas de GO con CuP), estructura (cambios de fases cristalinas de PCu) y quĂmica (OxidaciĂłn de PCu y reducciĂłn del GO) del hidrogel. Las pruebas de adsorciĂłn de AM se hicieron con dos concentraciones iniciales una de 1.2 mgâL para los hidrogeles modificados y con PCu Y de 100 mgâLpara hidrogeles con la soluciĂłn GO base (sin modificaciĂłn morfolĂłgica y quĂmica), y condiciones de agitaciĂłn 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 agitaciĂłn tienen una capacidad de adsorciĂłn entre 21.99â38.45 mgâg. Estos hidrogeles, se analizĂł la cinĂ©tica de adsorciĂłn mediante dos modelos, Pseudo-First Order (PFO) y Pseudo-Second Order (PSO), inicialmente la adsorciĂłn mostro que la remociĂłn del tinte se produce por fisisorciĂłn dado los valores termodinĂĄmicos (entalpia, energĂa libre de Gibbs y entropĂa).
- ItemLoops in Holographic Correlators(2023) Muñoz Sandoval, IvĂĄn Ignacio; Bañados, MĂĄximo; Pontificia Universidad CatĂłlica de Chile. Instituto de FĂsicaIn 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 Ί4 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.
- ItemQuantum measurement transition and entanglement of trapped ions and optomechanical systems(2024) Araya Sossa, Kevin Jordan; Orszag Posa, Miguel; Pontificia Universidad CatĂłlica de Chile. Instituto de FĂsicaAlthough 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 Î that involves a system-pointer coupling by using an arbitrary measured observable A. In addition, we show that the shift in the pointerâs 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 ÏΟ 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 âmonogamy of entanglementâ in tripartite systems outside qubit-composite states, in particular, (2 â 2 â n)-dimensional systems.
- ItemTransport phenomena in nontrivial topological materials(2023) Bonilla Moreno, Daniel Alejandro; Muñoz Tavera, Enrique; Pontificia Universidad CatĂłlica de Chile. Instituto de FĂsicaIn 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.