Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Collisions in piecewise flat gravity in 3+1 dimensions   We consider the (3+1)-dimensional locally finite gravity model proposed by 't
Hooft. In particular we revisit the problem of resolving collisions of string
defects. We provide a new geometric description of the configurations of
strings using piecewise flat manifolds, and use it to resolve a more general
class of collisions. We argue that beyond certain bounds for the
deficiency/surplus angles no resolutions may be found that satisfy the imposed
causality conditions.

19
The categories of this paper are: eess
24
The categories of this paper are: dg-ga
33
The categories of this paper are: plasm-ph
7
The categories of this paper are: hep-th
9
The categories of this paper are: nlin
0
The categories of this paper are: hep-ph
22
The categories of this paper are: chao-dyn
30
The categories of this paper are: q-alg
17
The categories of this paper are: q-fin
36
The categories of this paper are: cmp-lg
16
The categories of this paper are: stat
32
The categories of this paper are: atom-ph
10
The categories of this paper are: q-bio
20
The categories of this paper are: acc-phys
23
The categories of this paper are: solv-int
6
The categories of this paper are: astro-ph