Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: How moving cracks in brittle solids choose their path   While we fundamentally understand the dynamics of 'simple' cracks propagating
in brittle solids within perfect (homogeneous) materials, we do not understand
how paths of moving cracks are determined. We experimentally study strongly
perturbed cracks that propagate between 10-95\% of their limiting velocity
within a brittle material. These cracks are deflected by either interaction
with sparsely implanted defects or via an intrinsic oscillatory instability in
defect-free media. Dense, high-speed measurements of the strain fields
surrounding the crack tips reveal that crack paths are governed by the
direction of maximal strain energy density. This fundamentally important result
may be utilized to either direct or guide running cracks.

3
The categories of this paper are: physics
2
The categories of this paper are: math
24
The categories of this paper are: dg-ga
25
The categories of this paper are: patt-sol
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The categories of this paper are: mtrl-th
5
The categories of this paper are: gr-qc
31
The categories of this paper are: ao-sci
20
The categories of this paper are: acc-phys
33
The categories of this paper are: plasm-ph
32
The categories of this paper are: atom-ph
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The categories of this paper are: econ
23
The categories of this paper are: solv-int
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The categories of this paper are: q-bio
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The categories of this paper are: hep-th
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The categories of this paper are: cs
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The categories of this paper are: nucl-th