Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: A Tale of Three Equations: Breit, Eddington-Guant, and Two-Body Dirac   G.Breit's original paper of 1929 postulates the Breit equation as a
correction to an earlier defective equation due to Eddington and Gaunt,
containing a form of interaction suggested by Heisenberg and Pauli. We observe
that manifestly covariant electromagnetic Two-Body Dirac equations previously
obtained by us in the framework of Relativistic Constraint Mechanics reproduce
the spectral results of the Breit equation but through an interaction structure
that contains that of Eddington and Gaunt. By repeating for our equation the
analysis that Breit used to demonstrate the superiority of his equation to that
of Eddington and Gaunt, we show that the historically unfamiliar interaction
structures of Two-Body Dirac equations (in Breit-like form) are just what is
needed to correct the covariant Eddington Gaunt equation without resorting to
Breit's version of retardation.

24
The categories of this paper are: dg-ga
19
The categories of this paper are: eess
29
The categories of this paper are: funct-an
21
The categories of this paper are: adap-org
2
The categories of this paper are: math
8
The categories of this paper are: hep-ex
15
The categories of this paper are: nucl-ex
33
The categories of this paper are: plasm-ph
28
The categories of this paper are: alg-geom
17
The categories of this paper are: q-fin
9
The categories of this paper are: nlin
22
The categories of this paper are: chao-dyn
3
The categories of this paper are: physics
30
The categories of this paper are: q-alg
12
The categories of this paper are: nucl-th
4
The categories of this paper are: cond-mat