Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Unification of Gravity and Electromagnetism Revisited   Unification of gravity and electromagnetism based on a theory with an affine
non-symmetric connection $\Gamma^\lambda_{\mu\nu} \neq \Gamma^\lambda_{\nu\mu}$
and $\Gamma_\mu = \Gamma^\lambda_{[\mu\lambda]}\neq 0$, proposed by S. N. Bose
in 1953, is revisited in the context of modern developments in high energy
physics. It is shown that electrogravity unification can be achieved at a {\em
premetric} stage, and that this unification based on {\em projective
invariance} is broken by matter fields, opening up the possibility of a unified
theory of all forces in which gravity emerges as a classical field. The theory
predicts $\alpha_{sym} = \frac{1}{9}$ in the projective invariant limit, where
$\alpha$ is the fine structure constant

13
The categories of this paper are: quant-ph
19
The categories of this paper are: eess
36
The categories of this paper are: cmp-lg
15
The categories of this paper are: nucl-ex
33
The categories of this paper are: plasm-ph
10
The categories of this paper are: q-bio
18
The categories of this paper are: econ
9
The categories of this paper are: nlin
23
The categories of this paper are: solv-int
21
The categories of this paper are: adap-org
14
The categories of this paper are: math-ph
6
The categories of this paper are: astro-ph
25
The categories of this paper are: patt-sol
32
The categories of this paper are: atom-ph
37
The categories of this paper are: supr-con
24
The categories of this paper are: dg-ga