Bremen 2017 – scientific programme

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MP: Fachverband Theoretische und Mathematische Grundlagen der Physik

MP 12: Field Theory and Cosmology

MP 12.3: Talk

Thursday, March 16, 2017, 14:40–15:00, SFG 2010

On particle interpretation in homogeneous cosmology — •Zhirayr Avetisyan — Department of Mathematics, UCL

We work in the framework of quantum field theory in curved spacetimes. In absence of gravity - in Minkowski spacetime - the notion of an elementary particle is well-understood. Several different interpretations are possible that are naturally equivalent. In a curved spacetime, however, these interpretations become less intuitive and their equivalence on a mathematical level is not clear yet. In homogeneous cosmology the spacetime is assumed spatially homogeneous. This allows one to consider somewhat obscure generalizations of particle interpretations known to work in the flat case. One such interpretation comes from mode decomposition of a hyperbolic field equation, each mode roughly representing an elementary particle state with fixed evolution. Another particle interpretation is a reminiscent of Wigner's classification: every unitary irreducible representation of the isometry group corresponds to an elementary particle state with fixed momentum but unclear energy. We will discuss Peter-Weyl theorem from harmonic analysis and see how it may help us to achieve a mathematical identification of these two interpretations on general grounds.