Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Variational techniques in general relativity: A metric-affine approach
  to Kaluza's theory   A new variational principle for General Relativity, based on an action
functional $I\/(\Phi,\nabla)\/$ involving both the metric $\Phi\/$ and the
connection $\nabla\/$ as independent, \emph{unconstrained\/} degrees of freedom
is presented. The extremals of $I\/$ are seen to be pairs $\/(\Phi,\nabla)\/$
in which $\Phi\/$ is a Ricci flat metric, and $\nabla\/$ is the associated
Riemannian connection. An application to Kaluza's theory of interacting
gravitational and electromagnetic fields is discussed.

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The categories of this paper are: hep-ph
37
The categories of this paper are: supr-con
20
The categories of this paper are: acc-phys
19
The categories of this paper are: eess
26
The categories of this paper are: bayes-an
4
The categories of this paper are: cond-mat
28
The categories of this paper are: alg-geom
30
The categories of this paper are: q-alg
32
The categories of this paper are: atom-ph
3
The categories of this paper are: physics
33
The categories of this paper are: plasm-ph
22
The categories of this paper are: chao-dyn
23
The categories of this paper are: solv-int
10
The categories of this paper are: q-bio
36
The categories of this paper are: cmp-lg
21
The categories of this paper are: adap-org