On the current status of theories of multiple spin-2 fields

by Prof. Fawad Hassan (Stockholms Universitet)

Main Auditorium (Max Planck Institute for Physics)

Main Auditorium

Max Planck Institute for Physics

Föhringer Ring 6 80805 München

Classical and quantum fields are classified in terms of their
"spin" which not only specifies their behavior under rotations, but also
determines the basic structure of their field equations. The Standard
Model (SM) describes particle physics in terms of fields of spin 0, 1/2
and 1, whereas General Relativity (GR) describes gravity in terms of a
single massless field of spin 2. Fields of higher spin may not be
describable by local field theories at all. While the SM contains fields
of a given spin in multiplets, a structure that is important for its
consistency, GR, in contrast, does not admit such enhanced
structures. Hence, a long standing question has been if GR could be
extended to contain extra spin 2 fields that could be relevant to new
physics. The main obstruction to investigating this issue has been
the difficulty in finding consistent theories of multiple spin 2
fields free of "ghost" instabilities.  Some such theories have been
found in recent years and are highly constrained by consistency
conditions.  This talk will describe the current status of theories of
two and multiple spin-2 fields commonly known as bimetric and
multimetric theories.  In particular I will focus on the structure of
ghost free bimetric and multimetric interactions, their physical
interpretation, and on the notions of space and time in such theories.

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