Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Ultra high energy cosmic rays and possible signature of black strings   Ultra high energy cosmic rays (UHECRs) probably originate in extreme
conditions in which extra dimension effects might be important. In this paper
we calculate the correction in black hole accretion mechanisms due to extra
dimension effects in the static and rotating cases. A parametrization of the
external Kerr horizons in both cases is presented and analysed. We use previous
calculations of upper limits on the UHECR flux to set limits on the UHECR
production efficiency of nine sources. The upper limit on the UHECR luminosity
calculation is based on GeV-TeV gamma-ray measurements. The total luminosity
due to the accretion mechanism is compared to the upper limit on UHECRs. The
dependence of the UHECR production efficiency upper limit on black hole mass is
also presented and discussed

37
The categories of this paper are: supr-con
27
The categories of this paper are: comp-gas
17
The categories of this paper are: q-fin
21
The categories of this paper are: adap-org
15
The categories of this paper are: nucl-ex
2
The categories of this paper are: math
9
The categories of this paper are: nlin
25
The categories of this paper are: patt-sol
16
The categories of this paper are: stat
24
The categories of this paper are: dg-ga
12
The categories of this paper are: nucl-th
26
The categories of this paper are: bayes-an
22
The categories of this paper are: chao-dyn
35
The categories of this paper are: mtrl-th
20
The categories of this paper are: acc-phys
31
The categories of this paper are: ao-sci