Constraints on Vector Unparticle Physics from Cosmic Censorship

Abstract

Vector unparticle couplings to standard model fields produce repulsive corrections to gravity. From a general relativistic perspective, this leads to an effective Reissner-Nordstr\"om-like metric whose "charge" is a function of the unparticle coupling constant $\lambda$, and therefore can admit naked singularities. Requiring the system to respect cosmic censorship provides a new method of constraining the value of $\lambda$. These limits are extremely loose for stellar-mass black holes, but commensurate with existing bounds for primordial black holes. In the case of theoretical low-mass black holes, the bounds on $\lambda$ are much stricter than those derived from astrophysical and accelerator phenomenology. Additional constraints on the lower limit of $\lambda$ are used to estimate the mass of the smallest possible black hole $\Mbh^{\rm min}$ that can be formed in the unparticle framework, as a function of the unparticle parameters ($\Lambda_\unp,M_\unp,\du,\dbz$).