792 research outputs found
Condition for Superradiance in Higher-dimensional Rotating Black Holes
It is shown that the superradiance modes always exist in the radiation by the
-dimensional rotating black holes. Using a Bekenstein argument the
condition for the superradiance modes is shown to be
for the scalar, electromagnetic and gravitational waves when the spacetime
background has a single angular momentum parameter about an axis on the brane,
where is a rotational frequency of the black hole and is an
azimuthal quantum number of the radiated wave.Comment: 8 pages, no figure, v2: references added, version to appear in PL
Missing energy in black hole production and decay at the Large Hadron Collider
Black holes could be produced at the Large Hadron Collider in TeV-scale
gravity scenarios. We discuss missing energy mechanisms in black hole
production and decay in large extra-dimensional models. In particular, we
examine how graviton emission into the bulk could give the black hole enough
recoil to leave the brane. Such a perturbation would cause an abrupt
termination in Hawking emission and result in large missing-energy signatures.Comment: addressed reviewer comments and updated reference
Ratio of absorption cross section for Dirac fermion to that for scalar in the higher-dimensional black hole background
The ratio of the low-energy absorption cross section for Dirac fermion to
that for minimally coupled scalar is computed when the spacetimes are various
types of the higher-dimensional Reissner-Nordstr\"{o}m black holes. It is found
that the low-energy absorption cross sections for the Dirac fermion always goes
to zero in the extremal limit regardless of the detailed geometry of the
spacetime. The physical importance of our results is discussed in the context
of the brane-world scenarios and string theories.Comment: 12 pages, no figure, V2: several references added, version to appear
in PL
Emissivities for the various Graviton Modes in the Background of the Higher-Dimensional Black Hole
The Hawking emissivities for the scalar-, vector-, and tensor-mode bulk
gravitons are computed in the full range of the graviton's energy by adopting
the analytic continuation numerically when the spacetime background is
-dimensional non-rotating black hole. The total emissivity for the
gravitons is only 5.16% of that for the spin-0 field when there is no extra
dimension. However, this ratio factor increases rapidly when the extra
dimensions exist. For example, this factor becomes 147.7%, 595.2% and 3496%
when the number of extra dimensions is 1, 2 and 6, respectively. This fact
indicates that the Hawking radiation for the graviton modes becomes more and
more significant and dominant with increasing the number of extra dimensions.Comment: 14 pages, 5 eps figures, V2: the incorrect multiplicities are
corrected. PLB versio
Proof of universality for the absorption of massive scalars by the higher-dimensional Reissner-Nordstr\"{o}m black holes
Motivated by black hole experiments as a consequence of the TeV-scale gravity
arising from modern brane-world scenarios, we study the absorption problem for
the massive scalars when the spacetime background is a -dimensional
Reissner-Nordstr\"{o}m black hole. For analytic computation we adopt the
near-extreme condition in the spacetime background. It is shown that the
low-energy absorption cross section for the s-wave case holds an universality,
{\it i.e.} the absorption cross section equals to the area of the black hole
horizon divided by a velocity parameter.Comment: 11 pages, no figure, V2: version to appear in PL
Condition for the Superradiance Modes in Higher-Dimensional Rotating Black Holes with Multiple Angular Momentum Parameters
The condition for the existence of the superradiance modes is derived for the
incident scalar, electromagnetic and gravitational waves when the spacetime
background is a higher-dimensional rotating black hole with multiple angular
momentum parameters. The final expression of the condition is , where is an angular frequency of the black
hole and, and are the energy of the incident wave and the -th
azimuthal quantum number. The physical implication of this condition in the
context of the brane-world scenarios is discussed.Comment: 11 pages, no figur
Bulk versus Brane Emissivities of Photon Fields: For the case of Higher-Dimensional Schwarzschild Phase
The emission spectra for the spin-1 photon fields are computed when the
spacetime is a -dimensional Schwarzschild phase. For the case of the
bulk emission we compute the spectra for the vector mode and scalar mode
separately. Although the emissivities for the scalar mode is larger than those
for the vector mode when is small, the emissivities for the vector mode
photon become dominant rapidly with increasing . For the case of the brane
emission the emission spectra are numerically computed by making use of the
complex potential method. Comparision of the total bulk emissivities with total
brane emissivities indicates that the effect of the field spin makes the bulk
emission to be rapidly dominant with increasing . However, the bulk-to-brane
relative emissivity per degree of freedom always remains smaller than unity.
The importance for the spin-2 graviton emission problem is discussed.Comment: 22 pages, 10 eps figures included in the text V2: mistyping is
corrected in reference and text. one more reference is added. Table is
updated. version to appear in NPB V3: REVTEX4 format (no change
Parton rescattering and screening in Au+Au collisions at RHIC
We study the microscopic dynamics of quarks and gluons in relativistic heavy
ion collisions in the framework of the Parton Cascade Model. We use lowest
order perturbative QCD cross sections with fixed lower momentum cutoff p_0. We
calculate the time-evolution of the Debye-screening mass for Au+Au collisions
at sqrt(s)=200 GeV per nucleon pair. The screening mass is used to determine a
lower limit for the allowed range of p_0. We also determine the energy density
reached through hard and semi-hard processes at RHIC, obtain a lower bound for
the rapidity density of charged hadrons produced by semihard interactions, and
analyze the extent of perturbative rescattering among partons.Comment: 6 pages, 4 figures, uses RevTeX 4.0; revised version with minor
corrections and one updated figur
Asymptotic Quasinormal Frequencies of Brane-Localized Black Hole
The asymptotic quasinormal frequencies of the brane-localized
-dimensional black hole are computed. Since the induced metric on the
brane is not an exact vacuum solution of the Einstein equation defined on the
brane, the real parts of the quasinormal frequencies do not approach
to the well-known value but approach to , where
is a number dependent on the extra dimensions. For the scalar perturbation
is reproduced when . For , however,
is smaller than . It is shown also that when ,
vanishes in the scalar perturbation. For the gravitational
perturbation it is shown that is reproduced when and . For different , however, is smaller
than . When , for example, approaches to
. Unlike the scalar perturbation
does not vanish regradless of the number of extra
dimensions.Comment: 15 pages, 1 eps figure: V2 one more reference added. The derivtaion
of the effective potential is explained in detail. Version of PL
Brane Decay of a (4+n)-Dimensional Rotating Black Hole. III: spin-1/2 particles
In this work, we have continued the study of the Hawking radiation on the
brane from a higher-dimensional rotating black hole by investigating the
emission of fermionic modes. A comprehensive analysis is performed that leads
to the particle, power and angular momentum emission rates, and sheds light on
their dependence on fundamental parameters of the theory, such as the spacetime
dimension and angular momentum of the black hole. In addition, the angular
distribution of the emitted modes, in terms of the number of particles and
energy, is thoroughly studied. Our results are valid for arbitrary values of
the energy of the emitted particles, dimension of spacetime and angular
momentum of the black hole, and complement previous results on the emission of
brane-localised scalars and gauge bosons.Comment: Latex file, JHEP style, 34 pages, 16 figures Energy range in plots
increased, minor changes, version published in JHE
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