Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Canonical Structure of Higher Derivative Gravity in 3D   We give an explicitly gauge invariant canonical analysis of linearized
quadratic gravity theories in three dimensions for both flat and de-Sitter
backgrounds. In flat backgrounds, we also study the effects of gravitational
Chern-Simons term, and include the sources, compute the weak field limit as
well as scattering between spinning massive particles.

24
The categories of this paper are: dg-ga
25
The categories of this paper are: patt-sol
31
The categories of this paper are: ao-sci
27
The categories of this paper are: comp-gas
12
The categories of this paper are: nucl-th
33
The categories of this paper are: plasm-ph
20
The categories of this paper are: acc-phys
36
The categories of this paper are: cmp-lg
1
The categories of this paper are: cs
3
The categories of this paper are: physics
15
The categories of this paper are: nucl-ex
11
The categories of this paper are: hep-lat
9
The categories of this paper are: nlin
30
The categories of this paper are: q-alg
4
The categories of this paper are: cond-mat
22
The categories of this paper are: chao-dyn