Gravitational wave signatures from area metric gravity

Abstract

Area metric theories have been proposed as effective descriptions in a number of quantum gravity approaches: as continuum limit of effective spin foams, as an effective description for string theory and in the context of holography. Area metric actions allow for non-topological parity violating terms, which opens the possibility of observationally determining the Barbero-Immirzi parameter. We consider the shift symmetric version of linearized area metric theory in Lorentzian signature, which arises in particular from spin foams and modified Plebanski theory, and avoids ghost and tachyonic instabilities in the graviton sector. We discuss the gravitational wave like solutions of this theory and through an analysis of the coupling to electro-magnetism, deduce the signals in gravitational wave detectors. Using polarized light in such interferometers allows in principle to measure area metric induced birefringence. For the non-length excitations that accompany a gravitational wave this birefringence turns out to be independent of the Barbero-Immirzi parameter; the parameter is instead encoded in the polarization structure of the massive non-length waves, where it rotates the axes of the induced birefringence. Assuming Planck massive non-length excitations in the area metric the resulting signals are however extremely weak.

arXiv comment21 pages