Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Conical Wave Propagation and Diffraction in 2D Hexagonally Packed
  Granular Lattices   Linear and nonlinear mechanisms for conical wave propagation in
two-dimensional lattices are explored in the realm of phononic crystals. As a
prototypical example, a statically compressed granular lattice of spherical
particles arranged in a hexagonal packing configuration is analyzed. Upon
identifying the dispersion relation of the underlying linear problem, the
resulting diffraction properties are considered. Analysis both via a heuristic
argument for the linear propagation of a wavepacket, as well as via asymptotic
analysis leading to the derivation of a Dirac system suggests the occurrence of
conical diffraction. This analysis is valid for strong precompression i.e.,
near the linear regime. For weak precompression, conical wave propagation is
still possible, but the resulting expanding circular wave front is of a
non-oscillatory nature, resulting from the complex interplay between the
discreteness, nonlinearity and geometry of the packing. The transition between
these two types of propagation is explored.

15
The categories of this paper are: nucl-ex
36
The categories of this paper are: cmp-lg
6
The categories of this paper are: astro-ph
28
The categories of this paper are: alg-geom
18
The categories of this paper are: econ
14
The categories of this paper are: math-ph
4
The categories of this paper are: cond-mat
32
The categories of this paper are: atom-ph
37
The categories of this paper are: supr-con
34
The categories of this paper are: chem-ph
19
The categories of this paper are: eess
33
The categories of this paper are: plasm-ph
0
The categories of this paper are: hep-ph
26
The categories of this paper are: bayes-an
12
The categories of this paper are: nucl-th
11
The categories of this paper are: hep-lat