Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Optical polarization skyrmionic fields in free space   We construct optical beams in free space with robust skyrmionic structures in
their polarization fields, both in the electric spin vector for near-circular
fields and in the polarization direction for near-linear fields, and for both
Bloch (spiral) and N\'eel (hedgehog) textures. These structures are made
possible by the spin-orbit coupling of tightly-focused nonparaxial optics as
applied to higher-order Full-Poincar\'e beams, as well as by standing-wave
configurations comprising forwards- and backwards-propagating waves. Our
constructions show near-uniform circular and linear polarizations, providing a
high degree of topological protection in the absence of nonlinear interactions.

29
The categories of this paper are: funct-an
5
The categories of this paper are: gr-qc
6
The categories of this paper are: astro-ph
10
The categories of this paper are: q-bio
21
The categories of this paper are: adap-org
35
The categories of this paper are: mtrl-th
20
The categories of this paper are: acc-phys
11
The categories of this paper are: hep-lat
18
The categories of this paper are: econ
7
The categories of this paper are: hep-th
25
The categories of this paper are: patt-sol
22
The categories of this paper are: chao-dyn
32
The categories of this paper are: atom-ph
26
The categories of this paper are: bayes-an
9
The categories of this paper are: nlin
4
The categories of this paper are: cond-mat