Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Null curve evolution in four-dimensional pseudo-Euclidean spaces   We define a Lie bracket on a certain set of local vector fields along a null
curve in a 4-dimensional semi-Riemannian space form. This Lie bracket will be
employed to study integrability properties of evolution equations for null
curves in a pseudo-Euclidean space. In particular, a geometric recursion
operator generating infinite many local symmetries for the null localized
induction equation is provided.

36
The categories of this paper are: cmp-lg
18
The categories of this paper are: econ
7
The categories of this paper are: hep-th
32
The categories of this paper are: atom-ph
21
The categories of this paper are: adap-org
27
The categories of this paper are: comp-gas
25
The categories of this paper are: patt-sol
12
The categories of this paper are: nucl-th
4
The categories of this paper are: cond-mat
0
The categories of this paper are: hep-ph
33
The categories of this paper are: plasm-ph
29
The categories of this paper are: funct-an
23
The categories of this paper are: solv-int
16
The categories of this paper are: stat
8
The categories of this paper are: hep-ex
26
The categories of this paper are: bayes-an