Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: A short introduction to shadows of 4-manifolds   We give a self-contained introduction to the theory of Turaev's shadows as a
tool to study 3 and 4-manifolds. The goal of the present paper twofold: on one
side it is intended to be a shortcut to a basic use of the theory of shadows,
on the other side it gives a sketchy overview of some of the recent results on
shadows. No original result is proved here and most of the details of the
proofs are not included.

24
The categories of this paper are: dg-ga
12
The categories of this paper are: nucl-th
25
The categories of this paper are: patt-sol
27
The categories of this paper are: comp-gas
6
The categories of this paper are: astro-ph
9
The categories of this paper are: nlin
30
The categories of this paper are: q-alg
26
The categories of this paper are: bayes-an
15
The categories of this paper are: nucl-ex
31
The categories of this paper are: ao-sci
0
The categories of this paper are: hep-ph
3
The categories of this paper are: physics
16
The categories of this paper are: stat
36
The categories of this paper are: cmp-lg
4
The categories of this paper are: cond-mat
32
The categories of this paper are: atom-ph