On the physics of dissipative systems: classical dynamics and quantum dissipative adaptation

• Ano de defesa: 2024
• Autor(a) principal: Goettems, Elisa Iahn
• Tipo de documento: Tese
• Tipo de acesso: Acesso aberto
• Idioma: eng
• Instituição de defesa: Biblioteca Digitais de Teses e Dissertações da USP
• Palavras-chave em Português: Adaptação dissipativa; Asymmetric potential; Brownian motion; Dissipative adaptation; Função espectral; Movimento Browniano; Potencial assimétrico; Spectral function; Termodinâmica; Thermodynamics
• Link de acesso: https://www.teses.usp.br/teses/disponiveis/76/76134/tde-23042024-111403/

The study of dissipative systems holds significant interest in physics. This thesis aims to explore these phenomena in both classical and quantum regimes. In the first part, we utilize the system-reservoir approach to investigate the dynamics of two Brownian particles immersed in the same bath. Two methods are employed to address this problem: one with bilinear coupling and the other with nonlinear coupling between the particles and the bath. The extension of the system to include two particles with bilinear coupling yields unphysical results, such as free-particle motion for the relative coordinate and a lack of interaction between closely spaced particles. To address this issue, authors have been introduced an exponential coupling. In this work, we propose a method to reconcile both linear and nonlinear couplings. We demonstrate how to derive the same nonlinear dissipation rates starting from the bilinear Lagrangian, achieved through a modified spectral function that explicitly depends on the distance between the particles. Additionally, we implement a modified spectral function to mitigate anomalous diffusion observed in the standard nonlinear model, along with a phenomenological model describing hydrodynamic interaction between a pair of Brownian particles in a viscous fluid. In the quantum regime, we adopt the same system-reservoir approach to investigate the dissipative adaptation hypothesis proposed by Jeremy England. This hypothesis proposes a general thermodynamic mechanism that explains the self-organization of systems through the dissipation of work absorbed from an external drive. In the second part of this thesis, we explore the quantum dynamics of systems subjected to an external drive, evaluating the thermodynamic quantities of a self-organization process. To do so, we utilize a time-dependent spin-boson Hamiltonian that characterizes a particle subject to a metastable double potential with time-dependent parameters controlling the asymmetry of the wells. Our objective is to demonstrate that the asymmetric potential can localize the particle in the unstable side of the well and verify that this transition results in the highest energy absorption. In conclusion, we propose further investigations into the driven spin-boson model to establish a comprehensive theory of the systems evolution and its thermodynamic implications.