Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Einstein Equations from Riemann-only Gravitational Actions   Here show that, pure affine actions based solely on the Riemann curvature
tensor lead to Einstein field equations for gravitation. The matter and
radiation involved are general enough to impose no restrictions on material
dynamics or vacuum structure. This dynamical equivalence to General Relativity
can be realized via also diffeomorphism breaking.

23
The categories of this paper are: solv-int
37
The categories of this paper are: supr-con
12
The categories of this paper are: nucl-th
10
The categories of this paper are: q-bio
4
The categories of this paper are: cond-mat
26
The categories of this paper are: bayes-an
27
The categories of this paper are: comp-gas
30
The categories of this paper are: q-alg
11
The categories of this paper are: hep-lat
19
The categories of this paper are: eess
31
The categories of this paper are: ao-sci
36
The categories of this paper are: cmp-lg
25
The categories of this paper are: patt-sol
17
The categories of this paper are: q-fin
22
The categories of this paper are: chao-dyn
33
The categories of this paper are: plasm-ph