Seminar Miguel Zumalacárregui

Miguel Zumalacárregui
Heidelberg University
Towards the most general scalar-tensor theories of gravity

Horndeski's theory of gravity (the most general scalar-tensor theory with second-order equations of motion) has recently attracted considerable attention as a framework to study gravitation and cosmology. I will review some features of these theories, including recent efforts to understand their cosmological signatures and the possibility of making them compatible with local gravity tests (by means of screening mechanisms). Then I will challenge the generality of Horndeski's theory as the most general, physically reasonable scalar-tensor theory by considering derivative couplings to matter. When expressed in the Jordan frame, these theories have higher derivative equations of motion but introduce no additional, ghostly degrees of freedom. Theories beyond Horndeski have unique characteristics and represent a new class of scalar-tensor theories of gravity.

Tuesday, February 17, 2015 - 12:30