http://hdl.handle.net/11422/15 2026-08-04T07:26:20Z http://hdl.handle.net/11422/29905 Title: Aquecimento por recuo na levitodinâmica não paraxial Author(s)/Inventor(s): Marcianesi, Lucas Bianchi Advisor: Maia Neto, Paulo Américo Abstract: Levitodynamics is a subfield of optomechanics that studies the motion and manipulation of nano- and microparticles levitated by optical forces. It is a highly active research field, standing out especially as a tool used to investigate how mesoscopic mechanical systems behave when cooled to the quantum regime. In this work, we focus on a particularly popular experiment: a levitated dielectric nanoparticle (typically a silica sphere) trapped by an optical tweezer in ultra-high vacuum. One of the main obstacles to reaching the quantum ground state is the random momentum exchange between the photons of the trapping beam and the particle, an effect known in the literature as recoil heating. Given the relevance of this problem, there are many theoretical models in the literature for the optomechanical interaction between the laser and the particle. Several of them consider only the quantum nature of the particle’s COM, but model the electromagnetic fields classically. The advantages of a fully quantum model for this problem have been explored in recent publications, an approach we adopt in this work. Another widely used premise is the paraxial approximation to describe the trapping beam; however, given the tightly focused nature of the beams used in experiments, the need to go beyond this approximation has become clear. Therefore, we use the Richards- Wolf model for the optical trapping beam, built precisely to overcome the limitations of the paraxial model. Finally, we explore how focused vector Gaussian beams can be used to minimize recoil heating. We take as an example the focusing of a beam with radial polarization and show that the heating is, indeed, reduced in this case. Publisher: Universidade Federal do Rio de Janeiro Type: Dissertação 2026-03-31T00:00:00Z http://hdl.handle.net/11422/29903 Title: A Correspondência AdS/CFT e o modelo holográfico de parede rígida anômalo para descrição de glueballs de spin ímpar e o Odderon Author(s)/Inventor(s): Santos, Renato Ribeiro dos Advisor: Boschi Filho, Henrique Abstract: This work has two main objectives. The first is to offer a conceptual introduction to the AdS/CFT correspondence, detailing the fundamental ideas that originated it and serving as an accessible guide for beginners in the subject. The second is to carry out na applied study of the Odderon using the holographic model of the anomalous rigid wall. To fulfill this dual purpose, the work is structured in two main parts. Initially, an introductory discussion on the AdS/CFT correspondence is presented. Then, the investigation of the Odderon proceeds, first using the hard wall model and subsequently incorporating the anomalous dimension of the operators on the boundary. This extension proved particularly effective, fitting previous results from the literature and producing linear Regge trajectories, which validates the proposal as a consistent improvement of the model. Publisher: Universidade Federal do Rio de Janeiro Type: Dissertação 2026-03-12T00:00:00Z http://hdl.handle.net/11422/29900 Title: Sobre o controle dos efeitos do vácuo quântico por meio de condições de contorno Author(s)/Inventor(s): Cony, João Octávio Oliveira Advisor: Souza, Carlos Farina de Abstract: In this dissertation, we trace a revision of the theory of low-energy quantum electrodynamics (QED) framework required to discuss and understand certain quantum vacuum effects. To this end, we first review classical electrodynamics and the formalism of Green dyadics, and then introduce the quantization of the electromagnetic field. Once these concepts are established, we provide a brief historical overview of QED, highlight the essential differences and similarities between the classical and quantum concepts of vacuum, and discuss some effects associated with the latter, such as the Casimir–Polder interaction, the static and dynamic Casimir effects, and the Purcell effect. A conceptual understanding of quantum vacuum effects is fundamental for establishing mechanisms to control them, which may be useful, for instance, in the design of optomechanical devices at micro- and nanometric scales. The focus of this dissertation is the control of certain vacuum effects achieved through external agents to the system, in particular via the manipulation of the boundary conditions satisfied by the radiation-field modes imposed by bodies in the vicinity of the system. We describe in great detail control mechanisms in spontaneous emission processes—namely, the Purcell effect—and in resonant energy transfer (RET), referred to throughout this work as the Andrews effect. In particular, we show that RET can be anisotropic when the atoms under consideration are placed near anisotropic planar surfaces, and we explore in detail the case in which such a surface is a phosphorene sheet, a two-dimensional material obtained from black phosphorus. In this context, we demonstrate that controlling the optical properties of phosphorene through mechanical strain can be an efficient tool for laboratory control of RET. We conclude the dissertation with some final remarks on the subject and by outlining possible perspectives and future developments stemming from this work. Publisher: Universidade Federal do Rio de Janeiro Type: Dissertação 2026-03-12T00:00:00Z http://hdl.handle.net/11422/29898 Title: Transitividade no intervalo e na reta Author(s)/Inventor(s): Pineda Reyes, Miguel Angel Advisor: Arbieto Mendoza, Alexander Eduardo Abstract: In this master's thesis, we study the concept of transitivity and other forms of mixing. We first examine these properties on an interval before extending the study to the real line. We show that the critical points and critical values ​​of a transitive map are unbounded. Furthermore, we demonstrate that, under additional hypotheses, these conditions are also sufficient. Publisher: Universidade Federal do Rio de Janeiro Type: Dissertação 2018-07-04T00:00:00Z