Weyl Invariance and Spurious Black Hole in Two-Dimensional Dilaton Gravity

TL;DR

This paper investigates how Weyl invariance in two-dimensional dilaton gravity can lead to the spurious appearance of black holes and shows that under certain symmetries, Hawking radiation is absent due to trivial conformal anomalies.

Contribution

It demonstrates that the conformal anomaly in these models can be cohomologically trivial, explaining the absence of Hawking radiation and clarifying the role of Weyl invariance.

Findings

No anomalies in Weyl invariance at the quantum level

Absence of Hawking radiation in the model due to trivial anomalies

Weyl invariance can render black holes spurious in 2D dilaton gravity

Abstract

In two-dimensional dilaton gravity theories, there may exist a global Weyl invariance which makes black hole spurious. If the global invariance and the local Weyl invariance of the matter coupling are intact at the quantum level, there is no Hawking radiation. We explicitly verify the absence of anomalies in these symmetries for the model proposed by Callan, Giddings, Harvey and Strominger. The crucial observation is that the conformal anomaly can be cohomologically trivial and so not truly anomalous in such dilaton gravity models.