Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Classical trajectories in polar-asymmetric laser fields: Synchronous THz
  and XUV emission   Synchronous extreme ultraviolet (XUV) and single-cycle terahertz (THz) bursts
are generated in argon plasma induced by intense two-color femtosecond laser
pulses. Correlations between the intensity of the even and odd high-harmonics
and the THz radiation are found by studying the phase-delay between the
excitation pulses at 800 and 400 nm as well as the degree of polar asymmetry in
the incident electric field. Experiments in both the weak- and strong- polar
asymmetric regimes show remarkable agreement with a simple analytical model
based on classical electron trajectories in an arbitrary synthetic electric
field.

19
The categories of this paper are: eess
7
The categories of this paper are: hep-th
31
The categories of this paper are: ao-sci
16
The categories of this paper are: stat
35
The categories of this paper are: mtrl-th
8
The categories of this paper are: hep-ex
13
The categories of this paper are: quant-ph
36
The categories of this paper are: cmp-lg
18
The categories of this paper are: econ
37
The categories of this paper are: supr-con
23
The categories of this paper are: solv-int
29
The categories of this paper are: funct-an
17
The categories of this paper are: q-fin
20
The categories of this paper are: acc-phys
34
The categories of this paper are: chem-ph
2
The categories of this paper are: math