Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Degenerate spacetimes in first order gravity   We present a systematic framework to obtain the most general solutions of the
equations of motion in first order gravity theory with degenerate tetrads.
There are many possible solutions. Generically, these exhibit non-vanishing
torsion even in the absence of any matter coupling. These solutions are shown
to contain a special set of eight configurations which are associated with the
homogeneous model three-geometries of Thurston.

20
The categories of this paper are: acc-phys
17
The categories of this paper are: q-fin
33
The categories of this paper are: plasm-ph
19
The categories of this paper are: eess
31
The categories of this paper are: ao-sci
24
The categories of this paper are: dg-ga
27
The categories of this paper are: comp-gas
10
The categories of this paper are: q-bio
16
The categories of this paper are: stat
8
The categories of this paper are: hep-ex
26
The categories of this paper are: bayes-an
2
The categories of this paper are: math
34
The categories of this paper are: chem-ph
14
The categories of this paper are: math-ph
12
The categories of this paper are: nucl-th
25
The categories of this paper are: patt-sol