Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: On the possibility of superluminal energy propagation in a hyperbolic
  metamaterial of metal-dielectric layers   The energy propagation of electromagnetic fields in the effective medium of a
one-dimensional photonic crystal consisting of dielectric and metallic layers
is investigated. We show that the medium behaves like Drude and Lorentz medium,
respectively, when the electric field is parallel and perpendicular to the
layers. For arbitrary time-varying electromagnetic fields in this medium, the
energy density formula is derived. We prove rigorously that the group velocity
of any propagating mode obeying the hyperbolic dispersion must be slower than
the speed of light in vacuum, taking into account the frequency dependence of
the permittivity tensor. That is, it is not possible to have superluminal
propagation in this dispersive hyperbolic medium consisting of real dielectric
and metallic material layers. The propagation velocity of a wave packet is also
studied numerically. This packet velocity is very close to the velocity of the
propagating mode having the central frequency and central wave vector of the
wave packet. When the frequency spread of the wave packet is not narrow enough,
small discrepancy between these two velocities manifests, which is caused by
the non-penetration effect of the evanescent modes. This work reveals that no
superluminal phenomenon can happen in a dispersive anisotropic metamaterial
medium made of real materials.

37
The categories of this paper are: supr-con
21
The categories of this paper are: adap-org
24
The categories of this paper are: dg-ga
29
The categories of this paper are: funct-an
8
The categories of this paper are: hep-ex
17
The categories of this paper are: q-fin
1
The categories of this paper are: cs
27
The categories of this paper are: comp-gas
23
The categories of this paper are: solv-int
30
The categories of this paper are: q-alg
16
The categories of this paper are: stat
34
The categories of this paper are: chem-ph
7
The categories of this paper are: hep-th
20
The categories of this paper are: acc-phys
10
The categories of this paper are: q-bio
0
The categories of this paper are: hep-ph