Qiss

A non-relativistic limit of twistor theory provides a non-local description of Newtonian space-times. It is argued that combining this non–locality 
with the non–locality of quantum mechanics provides a mechanism for Penrose’s proposal linking classical gravity and quantum wave function collapse.

Abstract:
The formalism of quantum theory over discrete systems is extended in two significant ways. First, tensors and traceouts are generalized, so that systems can be partitioned according to almost arbitrary logical predicates. Second, quantum evolutions are generalized to act over network configurations, in such a way that nodes be allowed to merge, split and reconnect coherently in a superposition. The hereby presented mathematical framework is anchored on solid grounds through numerous lemmas. Indeed, one might have feared that the familiar interrelations between the notions of unitarity, complete positivity, trace-preservation, non-signalling causality, locality and localizability that are standard in quantum theory be jeopardized as the partitioning of systems becomes both logical and dynamical. Such interrelations in fact carry through.
(Joint work with Amélia Durbec and Matt Wilson, reference: https://arxiv.org/abs/2110.10587

I provide a conceptually-focused presentation of `low-energy quantum gravity’ (LEQG), the effective quantum field theory obtained from general relativity and which provides a well-defined theory of quantum gravity at energies well below the Planck scale. I emphasize the extent to which some such theory is required by the abundant observational evidence in astrophysics and cosmology …

David Wallace
Pittsburg University

Quantum gravity at low energies Read More »

Don Marolf will review and summarize recent developments regarding spacetime wormholes in the gravitational path integral and their implications for the existence of a certain notion of “superselection sectors” in quantum gravity.  The existence of such sectors implies that, in certain contexts, we can think of quantum gravity as describing a statistical ensemble of theories.  …

Don Marolf
University of California Santa Barbara

Spacetime wormholes, superselection sectors, and ensembles in quantum gravity: An Overview Read More »