{"681473":{"#nid":"681473","#data":{"type":"event","title":"PhD Defense by Elyana Crowder Melnick ","body":[{"value":"\u003Cp\u003ESchool of Physics Thesis Dissertation Defense\u003Cbr\u003E\u003Cbr\u003EElyana Crowder Melnick\u0026nbsp;\u003Cbr\u003EAdvisor: Dr. Dragomir Davidovi\u0107, School of Physics, Georgia Institute of Technology\u003Cbr\u003E\u003Cbr\u003EHigher Order Perturbative Quantum Master Equations\u003Cbr\u003EDate: Friday, April 4th, 2025\u0026nbsp;\u003Cbr\u003ETime: 9:00 a.m. \u0026nbsp;\u003Cbr\u003ELocation: Howey Physics Building, Room W401\u003Cbr\u003EZoom Link: https:\/\/gatech.zoom.us\/j\/94022682974?pwd=OuagAa3ybYS1jW46LlqAKUe9FYGYHa.1\u003Cbr\u003EMeeting ID: 940 2268 2974\u003Cbr\u003EPasscode: 774314\u003Cbr\u003E\u003Cbr\u003ECommittee Members:\u003Cbr\u003EDr. Brian Kennedy, School of Physics, Georgia Institute of Technology\u003Cbr\u003EDr. Itamar Kimchi, School of Physics, Georgia Institute of Technology\u003Cbr\u003EDr. Michael Loss, School of Mathematics, Georgia Institute of Technology\u003Cbr\u003EDr. Zhu-Xi Luo, School of Physics, Georgia Institute of Technology\u003Cbr\u003E\u003Cbr\u003EAbstract:\u0026nbsp;\u003Cbr\u003EPerturbative master equations are useful for modeling how an open quantum system evolves in contrast with its isolated counterpart. The Time Convolutionless Master Equation (TCL) is exact, and the generator can be expanded in orders of the system-environment coupling strength \u03bb and account for non-Markovian dynamics while remaining a time-local equation. However, terms of the perturbative order \u03bbN Time Convolutionless equation (TCLN) past N=2, are notably difficult to compute for general systems since they require the evaluation of N\u22121 nested integrals, limiting their usability. Motivated by the necessity of the TCL4 generator to model asymptotic states to the first nonzero order in the interaction, this dissertation presents a simplified form of TCL4 where the triple integrals are reduced to a single integral over terms optimized for numeric evaluation.\u003Cbr\u003EThis simplified TCL4 generator enables the identification of infrared (frequency \u00ae zero) divergences in the long-time limit, dependent on the power-law scaling of the bath spectral density, s. For the s \u0026lt; 1 case (sub-ohmic bath), results show that though the generator converges at second order in the long-time limit, the fourth order contribution can diverge, constraining the range of validity of previous solutions. Applying the same simplification steps to the TCL6 generator, collaborative results indicate that in general the N\u22121 integrals can be reduced to \u230aN\/2\u230b\u22121. Additionally, there is a maximum N after which infrared divergences can appear for all finite s. Further analysis shows that resolving the infrared divergences through a resummed TCL master equation (rTCL) results in new inflationary terms at finite nonzero frequency. Physical interpretation of these divergences will be the focus of future study.\u003Cbr\u003E\u003Cbr\u003E\u0026nbsp;\u003C\/p\u003E","summary":"","format":"limited_html"}],"field_subtitle":"","field_summary":[{"value":"\u003Cp\u003E\u003Cstrong\u003EHigher Order Perturbative Quantum Master Equations\u003C\/strong\u003E\u003C\/p\u003E","format":"limited_html"}],"field_summary_sentence":[{"value":"Higher Order Perturbative Quantum Master Equations"}],"uid":"27707","created_gmt":"2025-03-31 18:46:42","changed_gmt":"2025-03-31 18:47:23","author":"Tatianna Richardson","boilerplate_text":"","field_publication":"","field_article_url":"","field_event_time":{"event_time_start":"2025-04-04T09:00:00-04:00","event_time_end":"2025-04-04T11:00:00-04:00","event_time_end_last":"2025-04-04T11:00:00-04:00","gmt_time_start":"2025-04-04 13:00:00","gmt_time_end":"2025-04-04 15:00:00","gmt_time_end_last":"2025-04-04 15:00:00","rrule":null,"timezone":"America\/New_York"},"location":"Howey Physics Building, Room W401","extras":[],"groups":[{"id":"221981","name":"Graduate Studies"}],"categories":[],"keywords":[{"id":"100811","name":"Phd Defense"}],"core_research_areas":[],"news_room_topics":[],"event_categories":[{"id":"1788","name":"Other\/Miscellaneous"}],"invited_audience":[{"id":"78771","name":"Public"}],"affiliations":[],"classification":[],"areas_of_expertise":[],"news_and_recent_appearances":[],"phone":[],"contact":[],"email":[],"slides":[],"orientation":[],"userdata":""}}}