Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Dynamics of Simple Cracks   Cracks are the major vehicle for material failure, and often exhibit rather
complex dynamics. The laws that govern their motion have remained an object of
constant study for nearly a century. The simplest kind of dynamic crack is a
single crack that moves along a straight line. We first briefly review current
understanding of this "simple" object. We then critically examine the
assumptions of the classic, scale-free, theory of dynamic fracture, and note
when it works and how it may fail if certain of these assumptions are relaxed.
A number of examples is provided, where the introduction of physical scales
into this scale-free theory profoundly affects both a crack's structure and the
resulting dynamics.

22
The categories of this paper are: chao-dyn
12
The categories of this paper are: nucl-th
31
The categories of this paper are: ao-sci
28
The categories of this paper are: alg-geom
13
The categories of this paper are: quant-ph
2
The categories of this paper are: math
24
The categories of this paper are: dg-ga
32
The categories of this paper are: atom-ph
20
The categories of this paper are: acc-phys
30
The categories of this paper are: q-alg
15
The categories of this paper are: nucl-ex
37
The categories of this paper are: supr-con
17
The categories of this paper are: q-fin
16
The categories of this paper are: stat
11
The categories of this paper are: hep-lat
26
The categories of this paper are: bayes-an