Speaker
Sebastian Garcia-Saenz
(Imperial College London)
Description
Degenerate scalar-tensor theories of gravity extend general relativity by a single degree of freedom, despite their equations of motion being higher than second order, a virtue made possible by the existence of an additional constraint that removes the would-be ghost. This constraint can however be obstructed by matter fields, even when minimally coupled to the metric. In this talk I will present this issue in detail, explaining through some illustrative examples the precise ways in which the extra degree of freedom may reappear. I will next turn to the more physically relevant case of fermionic matter, and show that spin-1/2 fermions evade these issues and can thus be consistently coupled to degenerate theories of scalar-tensor gravity.
Author
Sebastian Garcia-Saenz
(Imperial College London)
