Nonexistence of quantum black and white hole horizons in an improved dynamic approach

In this paper,we study the quantum geometric effects near the locations where classical black hole horizons used to appear in Einstein's classical theory,within the framework of an improved dynamic approach,in which the internal region of a black hole is modeled by the Kantowski-Sachs(KS)spacetime and the two polymerization parameters are functions of the phase space variables.Our detailed analysis shows that the effects are so strong that black and white hole horizons of the effective quantum theory do not exist at all and instead are replaced by transition surfaces,across which the metric coefficients and their inverses are smooth and remain finite,as are the corresponding curvatures,including the Kretschmann scalar.These surfaces always separate trapped regions from anti-trapped regions.The number of such surfaces is infinite,so the corresponding KS spacetimes become geodesically complete,and no black and white hole-like structures exist in this scheme.

On the improved dynamics approach in loop quantum black holes

In this paper,we consider the B?hmer–Vandersloot(BV)model of loop quantum black holes obtained from the improved dynamics approach.We adopt the Saini–Singh gauge,in which it was found analytically that the BV spacetime is geodesically complete.We show that black/white hole horizons do not exist in this geodesically complete spacetime.Instead,there exists only an infinite number of transition surfaces,which always separate trapped regions from anti-trapped ones.Comments on the improved dynamics approach adopted in other models of loop quantum black holes are also given.

A note on the entanglement entropy of primary fermion fields in JT gravity

In this paper we analyze and discuss 2D Jackiw-Teitelboim(JT)gravity coupled to primary fermion fields in asymptotically anti-de Sitter(AdS)spacetimes.We obtain a particular solution of the massless Dirac field outside the extremal black hole horizon and find the solution for the dilaton in JT gravity.As two dimensional JT gravity spacetime is conformally flat,we calculate the two point correlators of primary fermion fields under the Weyl transformations.The primary goal of this work is to present a standard technique,called resolvent,rather than using CFT methods.We redefine the fields in terms of the conformal factor as fermion fields and use the resolvent technique to derive the renormalized entanglement entropy for massless Dirac fields in JT gravity.