Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Photon wave mechanics and position eigenvectors   One and two photon wave functions are derived by projecting the quantum state
vector onto simultaneous eigenvectors of the number operator and a recently
constructed photon position operator [Phys. Rev A 59, 954 (1999)] that couples
spin and orbital angular momentum. While only the Landau-Peierls wave function
defines a positive definite photon density, a similarity transformation to a
biorthogonal field-potential pair of positive frequency solutions of Maxwell's
equations preserves eigenvalues and expectation values. We show that this real
space description of photons is compatible with all of the usual rules of
quantum mechanics and provides a framework for understanding the relationships
amongst different forms of the photon wave function in the literature. It also
gives a quantum picture of the optical angular momentum of beams that applies
to both one photon and coherent states. According to the rules of qunatum
mechanics, this wave function gives the probability to count a photon at any
position in space.

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The categories of this paper are: hep-th
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The categories of this paper are: q-fin
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The categories of this paper are: alg-geom
5
The categories of this paper are: gr-qc
34
The categories of this paper are: chem-ph
32
The categories of this paper are: atom-ph
15
The categories of this paper are: nucl-ex
25
The categories of this paper are: patt-sol
22
The categories of this paper are: chao-dyn
8
The categories of this paper are: hep-ex
21
The categories of this paper are: adap-org
14
The categories of this paper are: math-ph
12
The categories of this paper are: nucl-th
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The categories of this paper are: nlin
26
The categories of this paper are: bayes-an
11
The categories of this paper are: hep-lat