Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Drift Lagrangian for relativistic particle in intense laser field   The Lagrangian and Hamiltonian functions describing average motion of a
relativistic particle under the action of a slightly inhomogeneous intense
laser field are obtained. In weak low-frequency background fields, such a
particle on average drifts with an effective, relativistically invariant mass,
which depends on the laser intensity. The essence of the proposed ponderomotive
formulation is presented in a physically intuitive and mathematically simple
form, yet represents a powerful tool for studying various nonlinear phenomena
caused by interaction of currently available smooth ultra-intense laser pulses
with plasmas.

8
The categories of this paper are: hep-ex
15
The categories of this paper are: nucl-ex
23
The categories of this paper are: solv-int
26
The categories of this paper are: bayes-an
9
The categories of this paper are: nlin
33
The categories of this paper are: plasm-ph
18
The categories of this paper are: econ
17
The categories of this paper are: q-fin
29
The categories of this paper are: funct-an
7
The categories of this paper are: hep-th
27
The categories of this paper are: comp-gas
1
The categories of this paper are: cs
6
The categories of this paper are: astro-ph
4
The categories of this paper are: cond-mat
21
The categories of this paper are: adap-org
14
The categories of this paper are: math-ph