Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: UFOs -- Unidentified Figurative Objects. A Geometric Challenge   Choose a polynomial in three variables with not more than three or four
monomials of moderate degree. Take simple coefficients as 1 and -1. Then draw a
picture of the solution variety in real three space using a ray-tracing program
like POV-Ray, Surf or Spicy. Go to your colleague in the next room, show
her/him the picture and ask for a suitable equation.
  This is the theme of the article: The problem of recognizing the algebraic
definition of a geometric object, in this case a real algebraic surface. We do
not offer any answers or results. 24 surfaces are presented, each in two
different views, but without equations. The reader may try to find them -- or
consult the calendar at http://www.hh.hauser.cc, where the equations are
displayed one per day together with a short animation of the surface.

1
The categories of this paper are: cs
7
The categories of this paper are: hep-th
25
The categories of this paper are: patt-sol
35
The categories of this paper are: mtrl-th
8
The categories of this paper are: hep-ex
33
The categories of this paper are: plasm-ph
15
The categories of this paper are: nucl-ex
24
The categories of this paper are: dg-ga
32
The categories of this paper are: atom-ph
13
The categories of this paper are: quant-ph
12
The categories of this paper are: nucl-th
9
The categories of this paper are: nlin
5
The categories of this paper are: gr-qc
20
The categories of this paper are: acc-phys
28
The categories of this paper are: alg-geom
19
The categories of this paper are: eess