arXiv subjects

Pierre A. Mandrin

Publications and source records attributed to Pierre A. Mandrin.

3 recordsLinked to original sources

arXiv2016

A non-equilibrium extension of quantum gravity

A variety of quantum gravity models (including spin foams) can be described using a path integral formulation. A path integral has a well-known statistical mechanical interpretation in connection with a canonical ensemble. In this sense, a path integral describes the thermodynamic equilibrium of a local system in a thermal bath. This interpretation is in contrast to solutions of Einstein's Equations which depart from local thermodynamical equilibrium (one example is shown explicitly). For this reason, we examine an extension of the path integral model to a (locally) non-equilibrium description. As a non-equilibrium description, we propose to use a global microcanonical ensemble with constraints. The constraints reduce the set of admissible microscopic states to be consistent with the macroscopic geometry. We also analyse the relation between the microcanonical description and a statistical approach not based on dynamical assumptions which has been proposed recently. This analysis is of interest for the test of consistency of the non-equilibrium description with general relativity and quantum field theory.

physics.gen-ph↗

arXiv2015

A non-dynamical approach for quantum gravity

By quantising the gravitational dynamics, space and time are usually forced to play fundamentally different roles. This raises the question whether physically relevent configurations could also exist which would not admit space-time-splitting. This has led to the investigation of an approach not based on quantum dynamical assumptions. The assumptions are mainly restricted to a constrained statistical concept of ordered partitions (NDA). For the time being, the continuum description is restricted in order to allow the application of the rules of differential geometry. It is verified that NDA yields equations of the same form as general relativity and quantum field theory for 3+1 dimensions and within the limits of experimental evidence. The derivations are shown in detail. First results are compared to the path integral approach to quantum gravity.

gr-qc↗

arXiv2015

An improved derivation of minimum information quantum gravity

Minimum information quantum gravity (MIQG) is a theory of quantum gravity which requires no explicit microscopic quantum structure. In this article, it is shown that the MIQG action can be derived using a more elegant and straight-forward method than in the first existence proof. The required assumptions are dramatically reduced. In particular, former assumptions referring to the existence of quantum boxes, the exact differential of the entropy variation and the role of the boundary can be omitted. Moreover, the open problem of the quantum occupation number per box is solved. Thus, the arguments in favour of MIQG become even more stringent. The remaining assumptions are 1. the principle of optimisation of the resulting per imposed degrees of freedom, 2. abstract quantum number conservation, 3. the validity of the laws of thermodynamics, 4. identification of a macroscopic parameterisation with space-time and 5. unspecific interactions. Although the requirements are reduced, all former results remain valid. In particular, all well established physics as special cases (Quantum Field Theory, QFT, and General Relativity, GR) follow and all measurable quantities may be computed.

gr-qc↗