Radiatively stable unitarity in higher-spin models, and applications in metric-affine gravity

Abstract: The scrutiny of gravitational theories beyond Einstein-Hilbert enjoys a different standard than flat models probed at collider-level energies. Of the proposed extensions, only a subset are explicitly required to be free of ghosts. Even in such cases, only dipole ghosts are usually targeted, thus still allowing, in general, wrong-sign states to propagate. Moreover, even in rare cases where a thorough spectral analysis is performed, the stability of the resulting action under radiative corrections is uncertain. In this talk, I discuss the strong constraining power of requiring, as standard for lower-spin models, a radiatively stable ghost- and tachyon-free action for the paradigmatic scenario of metric-affine gravity. I will describe the role of non-accidental symmetries and their interplay with diffeomorphism invariance. I will also provide, in a more general way, an overview of the computational challenges on the way of the spectrum of higher-spin theories.

astrophysicscondensed mattergeneral relativity and quantum cosmologyhigh energy physicsmathematical physicsclassical physicsgeneral physics

Audience: researchers in the topic

Theoretical physics seminar @ Tartu