Second-order scalar-tensor field theories

Şahin, Ertan Sinan
We review Horndeski’s scalar-tensor theory in this thesis. Partial differential equations that are satisfied by the Lagrangian limit its most general form. Demanding second-order field equations both for the metric and the scalar field, and choosing a four-dimensional spacetime also put restrictions on the most general form of the Lagrangian. Besides, by using similar techniques, in a four-dimensional spacetime, we find the most general form of the second-order Euler-Lagrange equations that are obtained from the Lagrangian through a variation of the metric. Finally, making use of relations between field equations and the Lagrangian, the most general form of the Lagrangian is obtained. Thus, one establishes the most general scalar-tensor theory in a four-dimensional spacetime.  
Citation Formats
E. S. Şahin, “Second-order scalar-tensor field theories,” M.S. - Master of Science, Middle East Technical University, 2017.