4,975 research outputs found
Overview of event-by-event analysis of high energy nuclear collisions
The event-by-event analysis of high energy nuclear collisions aims at
revealing the richness of the underlying event structures and provide unique
measures of dynamical fluctuations associated with QGP phase transition. The
major challenge in these studies is to separate the dynamical fluctuations from
the many other sources which contribute to the measured values. We present the
fluctuations in terms of event multiplicity, mean transverse momentum, elliptic
flow, source sizes, particle ratios and net charge distributions. In addition,
we discuss the effect of long range correlations, disoriented chiral
condensates and presence of jets. A brief review of various probes used for
fluctuation studies and available experimental results are presented.Comment: Invited talk at the "XIth International Workshop on Correlation and
Fluctuation in Multiparticle Production", Nov 21-24, 2006, Hangzhou, China
(19 pages
Second and higher-order quasi-normal modes in binary black hole mergers
Black hole (BH) oscillations known as quasi-normal modes (QNMs) are one of
the most important gravitational wave (GW) sources. We propose that higher
perturbative order of QNMs, generated by nonlinear gravitational interaction
near the BHs, are detectable and worth searching for in observations and
simulations of binary BH mergers. We calculate the metric perturbations to
second-order and explicitly regularize the master equation at the horizon and
spatial infinity. We find that the second-order QNMs have frequencies twice the
first-order ones and the GW amplitude is up to ~10% that of the first-order
one. The QNM frequency would also shift blueward up to ~1%. This provides a new
test of general relativity as well as a possible distance indicator.Comment: 5 pages, 1 figure, accepted for publication in PRD Rapid
Communication
Quantization of scalar perturbations in brane-world inflation
We consider a quantization of scalar perturbations about a de Sitter brane in
a 5-dimensional anti-de Sitter (AdS) bulk spacetime. We first derive the second
order action for a master variable for 5-dimensional gravitational
perturbations. For a vacuum brane, there is a continuum of normalizable
Kaluza-Klein (KK) modes with . There is also a light radion mode with
which satisfies the junction conditions for two branes, but is
non-normalizable for a single brane model. We perform the quantization of these
bulk perturbations and calculate the effective energy density of the projected
Weyl tensor on the barne. If there is a test scalar field perturbation on the
brane, the mode together with the zero-mode and an infinite ladder
of discrete tachyonic modes become normalizable in a single brane model. This
infinite ladder of discrete modes as well as the continuum of KK modes with
introduce corrections to the scalar field perturbations at first-order
in a slow-roll expansion. We derive the second order action for the
Mukhanov-Sasaki variable coupled to the bulk perturbations which is needed to
perform the quantization and determine the amplitude of scalar perturbations
generated during inflation on the brane.Comment: 14 page
Black Strings in Our World
The brane world scenario is a new approach to resolve the problem on how to
compactify the higher dimensional spacetime to our 4-dimensional world. One of
the remarkable features of this scenario is the higher dimensional effects in
classical gravitational interactions at short distances. Due to this feature,
there are black string solutions in our 4-dimensional world. In this paper,
assuming the simplest model of complex minimally coupled scalar field with the
local U(1) symmetry, we show a possibility of black-string formation by merging
processes of type I long cosmic strings in our 4-dimensional world. No fine
tuning for the parameters in the model might be necessary.Comment: 11pages, no figur
Second Order Quasi-Normal Mode of the Schwarzschild Black Hole
We formulate and calculate the second order quasi-normal modes (QNMs) of a
Schwarzschild black hole (BH). Gravitational wave (GW) from a distorted BH, so
called ringdown, is well understood as QNMs in general relativity. Since QNMs
from binary BH mergers will be detected with high signal-to-noise ratio by GW
detectors, it is also possible to detect the second perturbative order of QNMs,
generated by nonlinear gravitational interaction near the BH. In the BH
perturbation approach, we derive the master Zerilli equation for the metric
perturbation to second order and explicitly regularize it at the horizon and
spatial infinity. We numerically solve the second order Zerilli equation by
implementing the modified Leaver's continued fraction method. The second order
QNM frequencies are found to be twice the first order ones, and the GW
amplitude is up to that of the first order for the binary BH
mergers. Since the second order QNMs always exist, we can use their detections
(i) to test the nonlinearity of general relativity, in particular the no-hair
theorem, (ii) to remove fake events in the data analysis of QNM GWs and (iii)
to measure the distance to the BH.Comment: 23 pages, no figur
Infrared Spectral Energy Distribution Model for Extremely Young Galaxies
The small grain sizes produced by Type II supernova (SN II) models in young,
metal-poor galaxies make the appearance of their infrared (IR) spectral energy
distribution (SED) quite different from that of nearby, older galaxies. To
study this effect, we have developed a model for the evolution of dust content
and the IR SED of low-metallicity, extremely young galaxies based on Hirashita
et al. (2002). We find that, even in the intense ultraviolet (UV) radiation
field of very young galaxies, small silicate grains are subject to stochastic
heating resulting in a broad temperature distribution and substantial MIR
continuum emission. Larger carbonaceous grains are in thermal equilibrium at T
\simeq 50 - 100K, and they also contribute to the MIR. We present the evolution
of SEDs and IR extinction of very young, low-metallicity galaxies. The IR
extinction curve is also shown. In the first few Myrs, the emission peaks at
\lambda \sim 30-50um at later times dust self-absorption decreases the apparent
grain temperatures, shifting the bulk of the emission into the submillimetre
band. We successfully apply the model to the IR SED of a low metallicity (1/41
Z_\odot) dwarf galaxy SBS0335-052. We find the SED, optical properties and
extinction of the star forming region to be consistent with a very young and
compact starburst. We also predict the SED of another extremely low-metallicity
galaxy, I Zw 18, for future observational tests. Some prospects for future
observations are discussed.Comment: MNRAS in press, pages, 6 figures, using mn2e.cls. Abstract abridge
Constraints from Neutrinoless Double Beta Decay
We examine the constraints from the recent HEIDELBERG-MOSCOW double beta
decay experiment. It leads us to the almost degenerate or inverse hierarchy
neutrino mass scenario. In this scenario, we obtain possible upper bounds for
the Majorana CP violating phase in the lepton sector by incorporating the data
from the neutrino oscillation, the single beta decay experiments, and from the
astrophysical observation. We also predict the neutrino mass that may be
measurable in the future beta decay experiments.Comment: 10 pages, 3 figure
Open String on Symmetric Product
We develop some basic properties of the open string on the symmetric product
which is supposed to describe the open string field theory in discrete
lightcone quantization (DLCQ). After preparing the consistency conditions of
the twisted boundary conditions for Annulus/M\"obius/Klein Bottle amplitudes in
generic non-abelian orbifold, we classify the most general solutions of the
constraints when the discrete group is . We calculate the corresponding
orbifold amplitudes from two viewpoints -- from the boundary state formalism
and from the trace over the open string Hilbert space. It is shown that the
topology of the world sheet for the short string and that of the long string in
general do not coincide. For example the annulus sector for the short string
contains all the sectors (torus, annulus, Klein bottle, M\"obius strip) of the
long strings. The boundary/cross-cap states of the short strings are classified
into three categories in terms of the long string, the ordinary boundary and
the cross-cap states, and the ``joint'' state which describes the connection of
two short strings. We show that the sum of the all possible boundary conditions
is equal to the exponential of the sum of the irreducible amplitude -- one body
amplitude of long open (closed) strings. This is typical structure of DLCQ
partition function. We examined that the tadpole cancellation condition in our
language and derived the well-known gauge group .Comment: 56 pages, 11 figures, Late
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