Skip to main content
September 10, 2024 past

GAPP Seminar

Davey 339

GAPP Seminar

GAPP Seminar
Tuesday, Sept. 10th at 2pm in Davey 339

Speaker: George Zahariade, Jagiellonian University (Poland)
Title: Semiclassical Backreaction in Quantum Mechanics

Abstract:
The backreaction of quantum degrees of freedom on classical backgrounds is a poorly understood topic in theoretical physics. Most often it is treated within the semiclassical approximation with the help of various ad hoc prescriptions accounting for the effect of quantum excitations on the dynamics of the background. In this talk I will focus on two popular ones: (i) the mean-field approximation whereby quantum degrees of freedom couple to the classical background via their quantum expectation values; (ii) the stochastic method whereby the fully coupled system is evolved using classical equations of motion for various randomly sampled initial conditions of the quantum degree of freedom, and a statistical average is done a posteriori. I will evaluate the performance of each method in a simple toy model against a fully quantum mechanical treatment, identify its regime of validity, and interpret the results in terms of quantum entanglement and loss of classicality of the background.

Program

Date Time Speaker Title
2024-09-10 14:00 George Zahariade Semiclassical Backreaction in Quantum Mechanics
About our wordmark
Monica Rincon Ramirez

The IGC wordmark was created by Monica Rincon Ramirez while she was a graduate student at the Institute. Monica enjoys drawing new connections between fundamental theory and observations. Her graduate work included general relativity, loop quantum gravity, and quantum fields in cosmological backgrounds; her thesis focused on effective quantum corrections to gravitational phenomena from spinfoams and applications to cosmology. She received her PhD in 2024.

The wordmark symbolizes the scope of research at the IGC. The base represents quantum gravity, evoking the quantum geometrical picture from spinfoams and loop quantum gravity — approaches studied at the Center for Fundamental Theory. The middle shows galaxies embedded in a smooth surface characteristic of spacetime in general relativity and the larger physical scales studied at the Center for Theoretical and Observational Cosmology. The top curves to an extreme representing a supermassive black hole accompanied by an energetic jet, with a binary black hole pair nearby — the high-energy phenomena studied at the Center for Multimessenger Astrophysics.