2,188 research outputs found
Amoebas and Instantons
We study a statistical model of random plane partitions. The statistical
model has interpretations as five-dimensional supersymmetric
SU(N) Yang-Mills on and as K\"ahler gravity on local
SU(N) geometry. At the thermodynamic limit a typical plane partition called the
limit shape dominates in the statistical model. The limit shape is linked with
a hyperelliptic curve, which is a five-dimensional version of the SU(N)
Seiberg-Witten curve. Amoebas and the Ronkin functions play intermediary roles
between the limit shape and the hyperelliptic curve. In particular, the Ronkin
function realizes an integration of thermodynamical density of the main
diagonal partitions, along one-dimensional slice of it and thereby is
interpreted as the counting function of gauge instantons. The radius of
can be identified with the inverse temperature of the statistical model. The
large radius limit of the five-dimensional Yang-Mills is the low temperature
limit of the statistical model, where the statistical model is frozen to a
ground state that is associated with the local SU(N) geometry. We also show
that the low temperature limit corresponds to a certain degeneration of amoebas
and the Ronkin functions known as tropical geometry.Comment: 58 pages, 28 figures, references adde
Constraining Physical Properties of Type IIn Supernovae through Rise Times and Peak Luminosities
We investigate the diversity in the wind density, supernova ejecta energy,
and ejecta mass in Type IIn supernovae based on their rise times and peak
luminosities. We show that the wind density and supernova ejecta properties can
be estimated independently if both the rise time and peak luminosity are
observed. The peak luminosity is mostly determined by the supernova properties
and the rise time can be used to estimate the wind density. We find that the
ejecta energy of Type IIn supernovae needs to vary by factors of 0.2-5 from the
average if their ejecta mass is similar. The diversity in the observed rise
times indicates that their wind density varies by factors of 0.2-2 from the
average. We show that Type IIn superluminous supernovae should have not only
large wind density but also large ejecta energy and/or small ejecta mass to
explain their large luminosities and the rise times at the same time. We also
note that the shock breakout does not necessarily occur in the wind even if it
is optically thick, except for the case of superluminous supernovae, and we
analyze the observational data both with and without assuming that the shock
breakout occurs in the dense wind of Type IIn supernovae.Comment: 6 pages, 2 figures, 2 tables, accepted by The Astrophysical Journal
Letter
Covariant Gravitational Equations on Brane World with Gauss-Bonnet term
We present the covariant gravitational equations to describe a
four-dimensional brane world in the case with the Gauss-Bonnet term in a bulk
spacetime, assuming that gravity is confined on the symmetric brane. It
contains some components of five-dimensional Weyl curvature ()
which describes all effects from the bulk spacetime just as in the case of the
Randall-Sundrum second model. Applying this formalism to cosmology, we derive
the generalized Friedmann equation and calculate the Weyl curvature term, which
is directly obtained from a black hole solution.Comment: 14 pages, no figur
Circumstellar and explosion properties of Type Ibn supernovae
We investigate circumstellar and explosion properties of Type Ibn supernovae
(SNe) by analyzing their bolometric light curves. Bolometric light curves of
Type Ibn SNe generally have a large contrast between peak luminosity and
late-phase luminosity, which is much larger than those of 56Ni-powered SNe.
Thus, most of them are likely powered by the interaction between SN ejecta and
dense circumstellar media. In addition, Type Ibn SNe decline much faster than
Type IIn SNe, and this indicates that the interaction in Type Ibn SNe ceases
earlier than in Type IIn SNe. Thus, we argue that Type Ibn SN progenitors
experience high mass-loss rates in a short period just before explosion, while
Type IIn SN progenitors have high mass-loss rates sustained for a long time.
Furthermore, we show that rise time and peak luminosity of Type Ibn and Type
IIn SNe are similar and thus, they have similar explosion properties and
circumstellar density. The similar circumstellar density in the two kinds of
SNe may indicate that mass-loss rates of Type Ibn SN progenitors are generally
higher than those of Type IIn as the wind velocities inferred from narrow
spectral components are generally higher in Type Ibn SNe. We also show that
56Ni mass and explosion energy of Type Ibn SNe may be smaller than those of
other stripped-envelope SNe, probably because they tend to suffer large
fallback or some of them may not even be terminal stellar explosions.Comment: 7 pages, 4 figures, 1 table, accepted by The Astrophysical Journa
Extracting information behind the veil of horizon
In AdS/CFT duality, it is often argued that information behind the event
horizon is encoded even in boundary correlators. However, its implication is
not fully understood. We study a simple model which can be analyzed explicitly.
The model is a two-dimensional scalar field propagating on the s-wave sector of
the BTZ black hole formed by the gravitational collapse of a null dust. Inside
the event horizon, we placed an artificial timelike singularity where
one-parameter family of boundary conditions is permitted. We compute two-point
correlators with two operators inserted on the boundary to see if the parameter
is reflected in the correlators. In a typical case, we give an explicit form of
the boundary correlators of an initial vacuum state and show that the parameter
can be read off from them. This does not immediately imply that the asymptotic
observer can extract the information of the singularity since one cannot
control the initial state in general. Thus, we also study whether the parameter
can be read off from the correlators for a class of initial states.Comment: 17pages, 5 figures, accepted in Physical Review
Multi-band polarization of Type IIP supernovae due to light echo from circumstellar dust
Type IIP supernovae (SNe IIP) often show relatively high continuum
polarization (\%) in the late phase. This polarization feature is
generally believed to be due to an inner aspherical core revealed in the late
phase, while this polarization feature can also be contributed by the effect of
polarized-scattered echoes by circumstellar (CS) dust around the SN. In this
paper, we propose a unique method to distinguish polarization from the SN
ejecta and from the light echo. We quantitatively examine wavelength dependence
of the polarization created by the scattered echoes for various geometries and
amounts of CS dust. It is found that the polarization in the -band has
characteristic features, i.e., the polarization emerges at an earlier phase
with higher polarization degree than that in longer wavelengths. These are due
to the rapid evolution of the -band light curve as well as higher optical
depth of dust in shorter wavelengths. Except for the band, the polarization
increases after the plateau phase, and the polarization degree is generally
higher for shorter wavelengths. These polarimetric features can be easily
distinguished from the polarization expected from an aspherical core, which
predicts almost no wavelength dependence. Moreover, we show that multi-band
polarimetric observations for SNe IIP can constrain a parameter space in the CS
dust mass and distance from the SNe. We thus encourage multi-band polarimetric
observations for SNe IIP.Comment: 12 pages, 15 figures, accepted for publication in the Astrophysical
Journa
Circumstellar Light Echo as a Possible Origin of the Polarization of Type IIP Supernovae
Type IIP supernovae (SNe IIP) are the most common class of core-collapse SNe.
They often show rapid increase of polarization degree in the late phase. This
time evolution is generally believed to originate from the emergence of an
inner aspherical core, while an effect of polarized-scattered echoes by
circumstellar (CS) dust around the SN may also substantially contribute to this
polarization feature. In this study, we examine the effects of the scatted
echoes on the SN polarization through radiative transfer simulations for
various geometry and amount of CS dust. It has been found that
asymmetrically-distributed CS dust, which is generally inferred for red
supergiants, could reproduce the observed polarization features. We have
applied our results to SNe 2004dj and 2006ov, deriving the geometry and amount
of CS dust to explain their observed polarization features in this scenario.
For both SNe, the blob-like or bipolar distribution of CS dust rather than the
disk-like distribution is favored. The derived dust mass in
the blob model (the bipolar CS dust model) for SNe 2004dj and 2006ov are M ( M) and
M ( M),
respectively. Even in the case where this process would not play a dominant
role in the observed polarization signals, this effect should in principle
contribute to it, the strength of which depends on the nature of CS dust.
Therefore, this effect must be taken into account in discussing
multi-dimensional structure of an SN explosion through polarimetric
observations.Comment: Accepted for publication in ApJ. 13 pages, 17 figure
Quasinormal modes for nonextreme Dp-branes and thermalizations of super-Yang-Mills theories
The nonextreme Dp-brane solutions in type II supergravity(in the near-horizon
limit) are expected to be dual to (p+1)-dimensional noncompact supersymmetric
Yang-Mills theories at finite temperature. We study the translationally
invariant perturbations along the branes in those backgrounds and calculate
quasinormal frequencies numerically. These frequencies should determine the
thermalization time scales in the dual Yang-Mills theories.Comment: 13 pages, 3 figures, revtex4; v2 & 3: references added, minor change
Asymptotic singular behavior of Gowdy spacetimes in string theory
We study Gowdy spacetimes in the Einstein-Maxwell-dilaton-axion
system and show by the Fuchsian algorithm that they have in general
asymptotically velocity-term dominated singularities. The families of the
corresponding solutions depend on the maximum number of arbitrary functions.
Although coupling of the dilaton field with the Maxwell and/or the axion fields
corresponds to the ``potential'' which appears in the Hamiltonian of vacuum
Bianchi IX spacetimes, our result means that the spacetimes do not become
Mixmaster necessarily.Comment: 13 pages, submitted to Class. Quantum Gra
Holographic superfluid flows with a localized repulsive potential
We investigate a holographic model of superfluid flows with an external
repulsive potential. When the strength of the potential is sufficiently weak,
we analytically construct two steady superfluid flow solutions. As the strength
of the potential is increased, the two solutions merge into a single critical
solution at a critical strength, and then disappear above the critical value,
as predicted by a saddle-node bifurcation theory. We also analyze the spectral
function of fluctuations around the solutions under a certain decoupling
approximation.Comment: 10 pages, 6 figure
- …