Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Cosmic Bubble Collisions   I briefly review the physics of cosmic bubble collisions in false-vacuum
eternal inflation. My purpose is to provide an introduction to the subject for
readers unfamiliar with it, focussing on recent work related to the prospects
for observing the effects of bubble collisions in cosmology. I will attempt to
explain the essential physical points as simply and concisely as possible,
leaving most technical details to the references. I make no attempt to be
comprehensive or complete. I also present a new solution to Einstein's
equations that represents a bubble universe after a collision, containing
vacuum energy and ingoing null radiation with an arbitrary density profile.

21
The categories of this paper are: adap-org
15
The categories of this paper are: nucl-ex
8
The categories of this paper are: hep-ex
24
The categories of this paper are: dg-ga
18
The categories of this paper are: econ
26
The categories of this paper are: bayes-an
35
The categories of this paper are: mtrl-th
20
The categories of this paper are: acc-phys
29
The categories of this paper are: funct-an
36
The categories of this paper are: cmp-lg
14
The categories of this paper are: math-ph
9
The categories of this paper are: nlin
25
The categories of this paper are: patt-sol
22
The categories of this paper are: chao-dyn
37
The categories of this paper are: supr-con
27
The categories of this paper are: comp-gas