Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Causal and self-dual morphisms in four complex dimensions   We define a class of maps between holomorphically embedded null curves which
generalize conformal transformations, and can be defined in any complex
dimension. In four dimensions, we can also define a similar map between
self-dual surfaces, which generalize flat $\alpha$-planes. These maps are
respectively called causal and self-dual morphisms. It is shown that there
exist an infinite class of non-trivial examples for both types of maps in four
dimensions.

37
The categories of this paper are: supr-con
10
The categories of this paper are: q-bio
32
The categories of this paper are: atom-ph
1
The categories of this paper are: cs
18
The categories of this paper are: econ
22
The categories of this paper are: chao-dyn
34
The categories of this paper are: chem-ph
4
The categories of this paper are: cond-mat
36
The categories of this paper are: cmp-lg
17
The categories of this paper are: q-fin
0
The categories of this paper are: hep-ph
8
The categories of this paper are: hep-ex
7
The categories of this paper are: hep-th
5
The categories of this paper are: gr-qc
30
The categories of this paper are: q-alg
35
The categories of this paper are: mtrl-th