Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Ultra-high energy particle collisions in a regular spacetime without
  blackholes or naked singularities   We investigate here the particle acceleration and collisions with extremely
large center of mass energies in a perfectly regular spacetime containing
neither singularity nor an event horizon. The ultra-high energy collisions of
particles near the event horizon of extremal Kerr blackhole, and also in many
other examples of extremal blackholes have been investigated and reported
recently. We studied an analogous particle acceleration process in the Kerr and
Reissner-Nordstrom spacetimes without horizon, containing naked singularities.
Further to this, we show here that the particle acceleration and collision
process is in fact independent of blackholes and naked singularities, and can
happen in a fully regular spacetime containing neither of these. We derive the
conditions on the general static spherically symmetric metric for such a
phenomena to happen. We show that in order to have ultra-high energy collisions
it is necessary for the norm of the timelike Killing vector to admit a maximum
with a vanishingly small but a negative value. This is also a condition
implying the presence of a surface with extremely large but nevertheless finite
value of the redshift or blueshift. Conditions to have ultrahigh energy
collisions and regular center imply the violation of strong energy condition
near the center while the weak energy condition is respected in the region
around the center. Thus the central region is surrounded by a dark energy
fluid. Both the energy conditions are respected at the location where the high
energy collisions take place. As a concrete example we then investigate the
acceleration process in the spacetime geometry derived by Bardeen which is
sourced by a non-liner self-gravitating magnetic monopole.

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The categories of this paper are: solv-int
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The categories of this paper are: acc-phys
34
The categories of this paper are: chem-ph
33
The categories of this paper are: plasm-ph
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The categories of this paper are: q-bio
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The categories of this paper are: dg-ga
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The categories of this paper are: supr-con
35
The categories of this paper are: mtrl-th
36
The categories of this paper are: cmp-lg
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The categories of this paper are: hep-ex
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The categories of this paper are: nucl-th
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The categories of this paper are: bayes-an
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The categories of this paper are: econ
30
The categories of this paper are: q-alg
3
The categories of this paper are: physics
4
The categories of this paper are: cond-mat