Coupling Quantum Matter and Gravity

Abstract

In this contribution we deal with several issues one encounters when trying to couple quantum matter to classical gravitational fields. We start with a general background discussion and then move on to two more technical sections. In the first technical part we consider the question how the Hamiltonian of a composite two-particle system in an external gravitational field can be computed in a systematic post-Newtonian setting without backreaction. This enables us to reliably estimate the consistency and completeness of less systematic and more intuitive approaches that attempt to solve this problem by adding `relativistic effects' by hand. In the second technical part we consider the question of how quantum matter may act as source for classical gravitational fields via the semiclassical Einstein equations. Statements to the effect that this approach is fundamentally inconsistent are critically reviewed.

53+6 pages (main text + references), 1 figure. Invited contribution to the forthcoming book "Modified and Quantum Gravity - From Theory to Experimental Searches on All Scales", eds. C. Lämmerzahl and C. Pfeifer. v2: Added exercises and concluding remarks; minor reformulations

References in corpus (10)

• Motional Quantum Ground State of a Levitated Nanoparticle from Room Temperature
• The Schrödinger-Newton equation as non-relativistic limit of self-gravitating Klein-Gordon and Dirac fields
• Underground test of gravity-related wave function collapse
• Some remarks on the notions of general covariance and background independence
• Measurement Analysis and Quantum Gravity
• Problems with the Newton-Schrödinger Equations
• The Lie derivative of spinor fields: theory and applications
• Ghirardi-Rimini-Weber model with massive flashes
• Geometric post-Newtonian description of massive spin-half particles in curved spacetime
• Post-Newtonian Description of Quantum Systems in Gravitational Fields

Cited by in corpus (6)

• Classical theories of gravity produce entanglement
• A coupling prescription for post-Newtonian corrections in Quantum Mechanics
• Finite Pulse-Time Effects in Long-Baseline Quantum Clock Interferometry
• Geometric post-Newtonian description of massive spin-half particles in curved spacetime
• Heisenberg dynamics of mixed quantum-classical systems
• Does Quantum Mechanics Breed Larger, More Intricate Quantum Theories? The Case for Experience-Centric Quantum Theory and the Interactome of Quantum Theories