Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Tunnelling from black holes and tunnelling into white holes   Hawking radiation is nowadays being understood as tunnelling through black
hole horizons. Here, the extension of the Hamilton-Jacobi approach to
tunnelling for non-rotating and rotating black holes in different non-singular
coordinate systems not only confirms this quantum emission from black holes but
also reveals the new phenomenon of absorption into white holes by quantum
mechanical tunnelling. The role of a boundary condition of total absorption or
emission is also clarified.

31
The categories of this paper are: ao-sci
34
The categories of this paper are: chem-ph
21
The categories of this paper are: adap-org
25
The categories of this paper are: patt-sol
20
The categories of this paper are: acc-phys
3
The categories of this paper are: physics
9
The categories of this paper are: nlin
10
The categories of this paper are: q-bio
27
The categories of this paper are: comp-gas
29
The categories of this paper are: funct-an
8
The categories of this paper are: hep-ex
19
The categories of this paper are: eess
15
The categories of this paper are: nucl-ex
0
The categories of this paper are: hep-ph
30
The categories of this paper are: q-alg
17
The categories of this paper are: q-fin