Seminar of Department of Theoretical Physics - Martin Krššák (27.6.2024)

27.6.2024 at 14:00, Lecture room F1/125

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Martin Krššák:
Self-excited instantons and the structure of gravitational vacuum

Abstract:
The finite Euclidean action solutions known as instantons played an important role in non-perturbative understanding of Yang-Mills theory. In 1970s, a similar idea was pioneered by Eguchi and Hanson in the case of gravity. In this talk, I will briefly comment on Eguchi Hanson construction and show why teleparallel gravity is a more suitable framework to study gravitational instantons than the standard general relativity.  Here we exploit the fact that the teleparallel action is an exterior product of torsion and excitation forms, and define new kind of self-excited solutions, where these two forms are equal to each other. These self-excited solutions bear a striking resemblance  to Yang-Mills instantons, since their action is given by a topological Nieh-Yan term, and axial torsion can be identified as a topological current, playing the role of the Chern-Simons current in Yang-Mills theory.

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