Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Constant angle surfaces in 4-dimensional Minkowski space   We first define a complex angle between two oriented spacelike planes in
4-dimensional Minkowski space, and then study the constant angle surfaces in
that space, i.e. the oriented spacelike surfaces whose tangent planes form a
constant complex angle with respect to a fixed spacelike plane. This notion is
the natural Lorentzian analogue of the notion of constant angle surfaces in
4-dimensional Euclidean space. We prove that these surfaces have vanishing
Gauss and normal curvatures, obtain representation formulas for the constant
angle surfaces with regular Gauss maps and construct constant angle surfaces
using PDE's methods. We then describe their invariants of second order and show
that a surface with regular Gauss map and constant angle $\psi\neq 0\ [\pi/2]$
is never complete. We finally study the special cases of surfaces with constant
angle $\pi/2\ [\pi],$ with real or pure imaginary constant angle and describe
the constant angle surfaces in hyperspheres and lightcones.

23
The categories of this paper are: solv-int
31
The categories of this paper are: ao-sci
12
The categories of this paper are: nucl-th
32
The categories of this paper are: atom-ph
14
The categories of this paper are: math-ph
20
The categories of this paper are: acc-phys
0
The categories of this paper are: hep-ph
4
The categories of this paper are: cond-mat
3
The categories of this paper are: physics
30
The categories of this paper are: q-alg
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The categories of this paper are: q-fin
36
The categories of this paper are: cmp-lg
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The categories of this paper are: nucl-ex
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The categories of this paper are: econ
10
The categories of this paper are: q-bio
24
The categories of this paper are: dg-ga