398,671 research outputs found
Linear Relations of High Energy Absorption/Emission Amplitudes of D-brane
We calculate the absorption amplitudes of a closed string state at arbitrary
mass level leading to two open string states on the D-brane at high energies.
As in the case of Domain-wall scattering we studied previously, this process
contains only one kinematic variable. However, in contrast to the power-law
behavior of Domain-wall scattering, its form factor behaves as exponential
fall-off in the high energy limit. After identifying the geometric parameter of
the kinematic, we derive the linear relations (of the kinematic variable) and
ratios among the high energy amplitudes corresponding to absorption of
different closed string states for each fixed mass level by D-brane. This
result is consistent with the coexistence of the linear relations and
exponential fall-off behavior of high energy string/D-brane amplitudes.Comment: 9 pages,1 figur
Linear Relations and their Breakdown in High Energy Massive String Scatterings in Compact Spaces
We calculate high energy massive scattering amplitudes of closed bosonic
string compactified on the torus. For each fixed mass level with given
quantized and winding momenta ((m/R),(1/2)nR), we obtain infinite linear
relations among high energy scattering amplitudes of different string states.
For some kinematic regimes, we discover that linear relations with N_{R}=N_{L}
break down and, simultaneously, the amplitudes enhance to power-law behavior
instead of the usual expoential fall-off behavior at high energies. It is the
space-time T-duality symmetry that plays a role here. This result is consistent
with the coexistence of the linear relations and the softer exponential
fall-off behavior of high energy string scattering amplitudes as we pointed out
prevously. It is also reminiscent of our previous work on the power-law
behavior of high energy string/domain-wall scatterings.Comment: 18 pages, 1 figur
Comment on the Calculation of the Angular Momentum and Mass for the (Anti-) Self Dual Charged Spinning Black Hole
A recent paper [M. Kamata and T. Koikawa, Phys. Lett. {\bf B353} (1995) 196.]
claimed to obtain the charged version of the -dimensional spinning
black hole solution by assuming a (anti-) self dual condition imposed on the
electric and magnetic fields. We point out that the angular momentum and mass
diverge at spatial infinity and as a consequence the solution is unphysicalComment: 4 pages, Latex, no figures, final version to be publised in Phys.
Lett.
Scatterings of Massive String States from D-brane and Their Linear Relations at High Energies
We study scatterings of bosonic massive closed string states at arbitrary
mass levels from D-brane. We discover that all the scattering amplitudes can be
expressed in terms of the generalized hypergeometric function with special
arguments, which terminates to a finite sum and, as a result, the whole
scattering amplitudes consistently reduce to the usual beta function. For the
simple case of D-particle, we explicitly calculate high-energy limits of a
series of the above scattering amplitudes for arbitrary mass levels, and derive
infinite linear relations among them for each fixed mass level. The ratios of
these high-energy scattering amplitudes are found to be consistent with the
decoupling of high-energy zero-norm states of our previous works.Comment: 19 pages, no figure. v2:some minor corrections, refs added. v3:minor
changes and final in Nucl.Phys.
Notes on High Energy Limit of Bosonic Closed String Scattering Amplitudes
We study bosonic closed string scattering amplitudes in the high-energy
limit. We find that the methods of decoupling of high-energy zero-norm states
and the high-energy Virasoro constraints, which were adopted in the previous
works to calculate the ratios among high-energy open string scattering
amplitudes of different string states, persist for the case of closed string.
However, we clarify the previous saddle-point calculation for high-energy open
string scattering amplitudes and claim that only (t,u) channel of the
amplitudes is suitable for saddle-point calculation. We then discuss three
evidences to show that saddle-point calculation for high-energy closed string
scattering amplitudes is not reliable. By using the relation of tree-level
closed and open string scattering amplitudes of Kawai, Lewellen and Tye (KLT),
we calculate the high-energy closed string scattering amplitudes for arbitrary
mass levels. For the case of high-energy closed string four-tachyon amplitude,
our result differs from the previous one of Gross and Mende, which is NOT
consistent with KLT formula, by an oscillating factor.Comment: 14 pages, no figure. Equations and Conclusion adde
Regge Closed String Scattering and its Implication on Fixed angle Closed String Scattering
We calculate the complete closed string high energy scattering amplitudes
(HSA) in the Regge regime for arbitrary mass levels. As an application, we
deduce the complete ratios among closed string HSA in the fixed angle regime by
using Stirling number identities. These results are in contrast with the
incomplete set of closed string HSA in the fixed angle regime calculated
previously. The complete forms of the fixed angle amplitudes, and hence the
ratios, were not calculable previously without the input of zero-norm state
calculation. This is mainly due to the lack of saddle point in the fixed angle
closed string calculation.Comment: 10 pages. v2: typos correcte
A class of inflation models with non-minimal coupling
We show that the potential of the scalar field in the Einstein frame is flat
if the nonminimal coupling term is properly chosen that it satisfies the
condition (V(phi)/K^2(phi)-> constant) as phi gets large. The cosmological
implication of this theory is studied.Comment: Talk at the international Workshop on e-Science for Physics 2008
during September 8-9, 2008 at Daejeon Convention Center, Daejeon, Kore
Parkin uses the UPS to ship off dysfunctional mitochondria
Parkin is a ubiquitin E3 ligase that is implicated in familial Parkinson disease (PD). Previous studies have established its role in mitophagy, a pathway whereby dysfunctional mitochondria are targeted for autophagic degradation. We recently reported that a major function of Parkin in dysfunctional mitochondria is to activate the ubiquitin-proteasome system (UPS) for proteolysis of multiple outer membrane proteins, and that such activation of the UPS is a critical step in Parkin-mediated mitophagy. Here, we discuss the possible roles of the UPS in mitophagy and the pathogenesis of PD
High-energy String Scatterings of Compactified Open String
We calculate high-energy massive string scattering amplitudes of compactified
open string. We derive infinite linear relations, or stringy symmetries, among
soft high-energy string scattering amplitudes of different string states in the
Gross kinematic regime (GR). In addition, we systematically analyze all hard
power-law and soft exponential fall-off regimes of high-energy compactified
open string scatterings by comparing the scatterings with their 26D
noncompactified counterparts. In particular, we discover the existence of a
power-law regime at fixed angle and an exponential fall-off regime at small
angle for high-energy compactified open string scatterings. The linear
relations break down as expected in all power-law regimes. The analysis can be
extended to the high-energy scatterings of the compactified closed string,
which corrects and extends the previous results in [28] .Comment: 16 pages, 1 table. v2:typos corrected,references added. v3,v4:Eq.(26)
typos. Eq.(27) correcte
T-Duality and Spinning Solutions in 2 + 1 Gravity
Starting with the 2+1 Einstein--Maxwell--Dilaton system with a cosmological
constant and assuming two commuting Killing symmetries we derive the
corresponding --model. It is shown that, for general values of the
coupling parameters, the --duality group is , which coincides with
the group of linear coordinate transformations along the Killing orbits. This
duality, along with a suitable parameter choice, is applied to obtain some new
spinning solutions in the alternative gravity theories: Einstein--Maxwell,
Brans--Dicke and Einstein--Maxwell--Dilaton.Comment: 16 pages, LaTex with elsart.sty, no figure
- …