Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Momentum of superconducting electrons and the explanation of the
  Meissner effect   Momentum and energy conservation are fundamental tenets of physics, that
valid physical theories have to satisfy. In the reversible transformation
between superconducting and normal phases in the presence of a magnetic field,
the mechanical momentum of the supercurrent has to be transferred to the body
as a whole and vice versa, the kinetic energy of the supercurrent stays in the
electronic degrees of freedom, and no energy is dissipated nor entropy is
generated in the process. We argue on general grounds that to explain these
processes it is necessary that the electromagnetic field mediates the transfer
of momentum between electrons and the body as a whole, and this requires that
when the phase boundary between normal and superconducting phases is displaced,
a flow and counterflow of charge occurs in direction perpendicular to the phase
boundary. This flow and counterflow does not occur according to the
conventional BCS-London theory of superconductivity, therefore we argue that
within BCS-London theory the Meissner transition is a `forbidden transition'.
Furthermore, to explain the phase transformation in a way that is consistent
with the experimental observations requires that (i) the wavefunction $and$
charge distribution of superconducting electrons near the phase boundary extend
into the normal phase, and (ii) that the charge carriers in the normal state
have hole-like character. The conventional theory of superconductivity does not
have these physical elements, the theory of hole superconductivity does.

13
The categories of this paper are: quant-ph
28
The categories of this paper are: alg-geom
9
The categories of this paper are: nlin
19
The categories of this paper are: eess
34
The categories of this paper are: chem-ph
10
The categories of this paper are: q-bio
14
The categories of this paper are: math-ph
37
The categories of this paper are: supr-con
12
The categories of this paper are: nucl-th
35
The categories of this paper are: mtrl-th
29
The categories of this paper are: funct-an
8
The categories of this paper are: hep-ex
32
The categories of this paper are: atom-ph
7
The categories of this paper are: hep-th
0
The categories of this paper are: hep-ph
16
The categories of this paper are: stat