PIRSA:17050056

Timeless cosmology with records

APA

Gomes, H. (2017). Timeless cosmology with records. Perimeter Institute. https://pirsa.org/17050056

MLA

Gomes, Henrique. Timeless cosmology with records. Perimeter Institute, May. 17, 2017, https://pirsa.org/17050056

BibTex

          @misc{ pirsa_PIRSA:17050056,
            doi = {10.48660/17050056},
            url = {https://pirsa.org/17050056},
            author = {Gomes, Henrique},
            keywords = {Quantum Gravity},
            language = {en},
            title = {Timeless cosmology with records},
            publisher = {Perimeter Institute},
            year = {2017},
            month = {may},
            note = {PIRSA:17050056 see, \url{https://pirsa.org}}
          }
          

Henrique Gomes University of Oxford

Talk Type Conference
Subject

Abstract

On the path towards quantum gravity we find friction between temporal relations in quantum mechanics (QM) (where they are fixed and field-independent), and in general relativity (where they are field-dependent and dynamic). In this talk, I will erase that distinction. I encode gravity, along with other types of interactions, in the timeless configuration space of spatial fields, with dynamics obtained through a path integral formulation. The framework demands that boundary conditions for this path integral be uniquely given. Such uniqueness arises if a reduced configuration space can be defined and if it has a profoundly asymmetric fundamental structure. These requirements place strong restrictions on the field and symmetry content of theories encompassed here. When these constraints are met, the emerging theory has no non-unitary measurement process; the Born rule is given merely by a particular volume element built from the path integral in (reduced) configuration space. Time, including space-time, emerges as an effective concept; valid for certain curves in configuration space but not assumed from the start. When some notion of time becomes available, conservation of (positive) probability currents ensues. I will show that, in the appropriate limits, a Schroedinger equation dictates the evolution of weakly coupled source fields on a classical gravitational background. Due to the asymmetry of reduced configuration space, these probabilities and currents avoid a known difficulty of standard WKB approximations for Wheeler DeWitt in minisuperspace: the selection of a unique Hamilton-Jacobi solution to serve as background. I illustrate these constructions with a simple example of a quantum gravitational theory for which the formalism is applicable, and give a formula for calculating gravitational semi-classical relative probabilities in it. Although this simple model gives the same likelihood for the evolution of all TT gravitational modes, there is evidence that a slightly more complicated model would favor modes with the smallest eigenvalues of the Laplacian and thus drive towards homogeneity.