Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: No flares from Gamma-Ray Burst afterglow blast waves encountering sudden
  circumburst density change   Afterglows of gamma-ray bursts are observed to produce light curves with the
flux following power law evolution in time. However, recent observations reveal
bright flares at times on the order of minutes to days. One proposed
explanation for these flares is the interaction of a relativistic blast wave
with a circumburst density transition. In this paper, we model this type of
interaction computationally in one and two dimensions, using a relativistic
hydrodynamics code with adaptive mesh refinement called RAM, and analytically
in one dimension. We simulate a blast wave traveling in a stellar wind
environment that encounters a sudden change in density, followed by a
homogeneous medium, and compute the observed radiation using a synchrotron
model. We show that flares are not observable for an encounter with a sudden
density increase, such as a wind termination shock, nor for an encounter with a
sudden density decrease. Furthermore, by extending our analysis to two
dimensions, we are able to resolve the spreading, collimation, and edge effects
of the blast wave as it encounters the change in circumburst medium. In all
cases considered in this paper, we find that a flare will not be observed for
any of the density changes studied.

15
The categories of this paper are: nucl-ex
2
The categories of this paper are: math
5
The categories of this paper are: gr-qc
19
The categories of this paper are: eess
29
The categories of this paper are: funct-an
0
The categories of this paper are: hep-ph
7
The categories of this paper are: hep-th
20
The categories of this paper are: acc-phys
27
The categories of this paper are: comp-gas
4
The categories of this paper are: cond-mat
30
The categories of this paper are: q-alg
9
The categories of this paper are: nlin
23
The categories of this paper are: solv-int
11
The categories of this paper are: hep-lat
24
The categories of this paper are: dg-ga
28
The categories of this paper are: alg-geom