Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Quantum black hole without singularity   We discuss the quantization of a spherical dust shell in a rigorous manner.
Classically, the shell can collapse to form a black hole with a singularity. In
the quantum theory, we construct a well-defined self-adjoint extension for the
Hamilton operator. As a result, the evolution is unitary and the singularity is
avoided. If we represent the shell initially by a narrow wave packet, it will
first contract until it reaches the region where classically a black hole would
form, but then re-expands to infinity. In a way, the state can be interpreted
as a superposition of a black hole with a white hole.

3
The categories of this paper are: physics
21
The categories of this paper are: adap-org
6
The categories of this paper are: astro-ph
17
The categories of this paper are: q-fin
11
The categories of this paper are: hep-lat
30
The categories of this paper are: q-alg
24
The categories of this paper are: dg-ga
10
The categories of this paper are: q-bio
18
The categories of this paper are: econ
19
The categories of this paper are: eess
8
The categories of this paper are: hep-ex
31
The categories of this paper are: ao-sci
14
The categories of this paper are: math-ph
13
The categories of this paper are: quant-ph
26
The categories of this paper are: bayes-an
16
The categories of this paper are: stat