Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Pair production and optical lasers   Electron-positron pair creation in a standing wave is explored using a
parameter-free quantum kinetic equation. Field strengths and frequencies
corresponding to modern optical lasers induce a material polarisation of the
QED vacuum, which may be characterised as a plasma of e^+ e^- quasiparticle
pairs with a density of ~10^{20}cm^{-3}. The plasma vanishes almost completely
when the laser field is zero, leaving a very small residual pair density, n_r,
which is the true manifestation of vacuum decay. The average pair density per
period is proportional to the laser intensity but independent of the frequency,
\nu. The density of residual pairs also grows with laser intensity but n_r
\propto \nu^2. With optical lasers at the forefront of the current generation,
these dynamical QED vacuum effects may generate 5-10 observable two-photon
annihilation events per laser pulse.

10
The categories of this paper are: q-bio
17
The categories of this paper are: q-fin
36
The categories of this paper are: cmp-lg
19
The categories of this paper are: eess
34
The categories of this paper are: chem-ph
20
The categories of this paper are: acc-phys
30
The categories of this paper are: q-alg
14
The categories of this paper are: math-ph
1
The categories of this paper are: cs
37
The categories of this paper are: supr-con
35
The categories of this paper are: mtrl-th
4
The categories of this paper are: cond-mat
33
The categories of this paper are: plasm-ph
16
The categories of this paper are: stat
27
The categories of this paper are: comp-gas
24
The categories of this paper are: dg-ga