Speaker
Description
Metric teleparallelism assumes both the curvature of the affine connection and non-metricity to vanish. Within this framework it is possible to construct an action which is quadratic in torsion and parity-preserving (known as new general relativity). For decades it was thought that only two subcases of this theories would be ghost-free. One being equivalent with general relativity, and the other has strongly coupled degrees of freedom. Recently, the perturbation analysis was revisited and it has been confirmed in three independent works that there is another theory (named type 3 NGR) which is ghost-free. It also has strongly coupled degrees of freedom in Minkowski, while all degrees of freedom has been found to be ghost-free around cosmological backgrounds. The theory propagate tensor, vector, and scalar degrees of freedom, and I will demonstrate the scales for which they appear.