Departmental Doctoral Oral Examination (Thesis Title: “A study of the quantum-to-classical transition in gravity, and a study of the consequences of constraints in gauge theory path-integrals”)

Departmental Doctoral Oral Examination (Thesis Title: “A study of the quantum-to-classical transition in gravity, and a study of the consequences of constraints in gauge theory path-integrals”)

Abstract: In this thesis we discuss various aspects of low energy quantum gravity from a number of different angles. The ultimate goal we have in mind is to prepare ourselves for the upcoming wave of low-energy experiments which may test quantum gravity. In the first part of this thesis we remain within “conventional” quantum theory. We start with a study of quantum decoherence via the emission of low energy gravitational radiation. We find that after sufficiently long times this radiation can completely decohere a matter system. In studying decoherence we needed a better understanding of gauge invariance and physical states in path-integrals with prescribed boundary data. We generalize the standard Faddeev-Popov procedure to fit this purpose, and in doing so we better understand the nature of electric fields around quantum charges. The analogous work is also done in linearized quantum gravity. This language is useful for analyzing the debate around a recently proposed gravitational-entanglement experiment. We do such an analysis, and ultimately agree that these experiments indeed test conventional quantum gravity. As a tangential project we study the interactions of quarks in background gluon condensate, and show how this can cause confinement. In the second part of the thesis we study an “alternative” quantum gravity theory, the Correlated WorldLine (CWL) theory. We study the theory perturbatively, and also make use of a large-N expansion to study it non-perturbatively. We apply our results to physical systems: verifying that two-path systems experience “path-bunching” which suppresses superpositions of massive objects. We also predict a frequency band in the microhertz range where tests of CWL involving massive objects are expected to see a signature.

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2021-05-19T12:30:002021-05-19T14:30:00Departmental Doctoral Oral Examination (Thesis Title: “A study of the quantum-to-classical transition in gravity, and a study of the consequences of constraints in gauge theory path-integrals”)Event Information:
Abstract:In this thesis we discuss various aspects of low energy quantum gravity from a number of different angles. The ultimate goal we have in mind is to prepare ourselves for the upcoming wave of low-energy experiments which may test quantum gravity. In the first part of this thesis we remain within “conventional” quantum theory. We start with a study of quantum decoherence via the emission of low energy gravitational radiation. We find that after sufficiently long times this radiation can completely decohere a matter system. In studying decoherence we needed a better understanding of gauge invariance and physical states in path-integrals with prescribed boundary data. We generalize the standard Faddeev-Popov procedure to fit this purpose, and in doing so we better understand the nature of electric fields around quantum charges. The analogous work is also done in linearized quantum gravity. This language is useful for analyzing the debate around a recently proposed gravitational-entanglement experiment. We do such an analysis, and ultimately agree that these experiments indeed test conventional quantum gravity. As a tangential project we study the interactions of quarks in background gluon condensate, and show how this can cause confinement. In the second part of the thesis we study an “alternative” quantum gravity theory, the Correlated WorldLine (CWL) theory. We study the theory perturbatively, and also make use of a large-N expansion to study it non-perturbatively. We apply our results to physical systems: verifying that two-path systems experience “path-bunching” which suppresses superpositions of massive objects. We also predict a frequency band in the microhertz range where tests of CWL involving massive objects are expected to see a signature.Event Location:
via Zoom