Use this URL to cite or link to this record in EThOS: https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.810186
Title: Computer simulation studies of frustrated spin systems
Author: Kumar, Ravinder
Awarding Body: Coventry University
Current Institution: Coventry University
Date of Award: 2019
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Abstract:
The random-field Potts model and spin-glass models are two prominent examples of NP-hard problem in statistical physics. If investigated numerically, extensive computer simulations are required to study these models. Because of the lack of efficient computational methods, the random-field Potts model has not been studied broadly yet. Here we develop an algorithm to study the random-field Potts model using a graph-cut method. It does not guarantee to find a ground state but the lowest states can be found very efficiently. We also determined the overlap of the lowest states found by the graph-cut method with the ground states found by a parallel tempering method. It is found that the lowest states found by the graph cut method have more than 80% overlap with the ground states. For the larger system sizes, the graph-cut method is much more efficient then parallel tempering method. Two-dimensional Edward-Anderson spin-glass model has been examined broadly in many previous studies. Here we focus on the phase transition of under-frustrated spin-glasses with Gaussian and bimodal couplings. There are some claims that under-frustrated two-dimensional spin-glass systems might have a spin-glass phase at finite temperatures. To study this model, we first introduce an implementation of parallel tempering and a cluster update on GPUs. The simulation results give hints that the under-frustrated spin-glass belongs to the same universality class as stochastic spin-glass and there exists no spin-glass phase at finite temperature.
Supervisor: Weigel, Martin ; Janke, Wolfhard Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID: uk.bl.ethos.810186  DOI: Not available
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