1,065 research outputs found
Commuting difference operators arising from the elliptic C_2^{(1)}-face model
We study a pair of commuting difference operators arising from the elliptic
C_2^{(1)}-face model. The operators, whose coefficients are expressed in terms
of the Jacobi's elliptic theta function, act on the space of meromorphic
functions on the weight space of the C_2 type simple Lie algebra. We show that
the space of functions spanned by the level one characters of the affine Lie
algebra sp(4,C) is invariant under the action of the difference operators.Comment: latex2e file, 19 pages, no figures; added reference
Eisenhart Lift of --Dimensional Mechanics
The Eisenhart lift is a variant of geometrization of classical mechanics with
degrees of freedom in which the equations of motion are embedded into the
geodesic equations of a Brinkmann-type metric defined on -dimensional
spacetime of Lorentzian signature. In this work, the Eisenhart lift of
-dimensional mechanics on curved background is studied. The corresponding
-dimensional metric is governed by two scalar functions which are just the
conformal factor and the potential of the original dynamical system. We derive
a conformal symmetry and a corresponding quadratic integral, associated with
the Eisenhart lift. The energy--momentum tensor is constructed which, along
with the metric, provides a solution to the Einstein equations. Uplifts of
-dimensional superintegrable models are discussed with a particular emphasis
on the issue of hidden symmetries. It is shown that for the -dimensional
Darboux--Koenigs metrics, only type I can result in Eisenhart lifts which
satisfy the weak energy condition. However, some physically viable metrics with
hidden symmetries are presented.Comment: 20 page
Bayesian inference with an adaptive proposal density for GARCH models
We perform the Bayesian inference of a GARCH model by the Metropolis-Hastings
algorithm with an adaptive proposal density. The adaptive proposal density is
assumed to be the Student's t-distribution and the distribution parameters are
evaluated by using the data sampled during the simulation. We apply the method
for the QGARCH model which is one of asymmetric GARCH models and make empirical
studies for for Nikkei 225, DAX and Hang indexes. We find that autocorrelation
times from our method are very small, thus the method is very efficient for
generating uncorrelated Monte Carlo data. The results from the QGARCH model
show that all the three indexes show the leverage effect, i.e. the volatility
is high after negative observations
The Distance to the Galactic Center Derived From Infrared Photometry of Bulge Red Clump Stars
On the basis of the near infrared observations of bulge red clump stars near
the Galactic center, we have determined the galactocentric distance to be R_0 =
7.52 +- 0.10 (stat) +- 0.35 (sys) kpc. We observed the red clump stars at |l| <
1.0 deg and 0.7 deg < |b| < 1.0 deg with the IRSF 1.4 m telescope and the
SIRIUS camera in the H and Ks bands. After extinction and population
corrections, we obtained (m - M)_0 = 14.38 +- 0.03 (stat) +- 0.10 (sys). The
statistical error is dominated by the uncertainty of the intrinsic local red
clump stars' luminosity. The systematic error is estimated to be +- 0.10
including uncertainties in extinction and population correction, zero-point of
photometry, and the fitting of the luminosity function of the red clump stars.
Our result, R_0 = 7.52 kpc, is in excellent agreement with the distance
determined geometrically with the star orbiting the massive black hole in the
Galactic center. The recent result based on the spatial distribution of
globular clusters is also consistent with our result. In addition, our study
exhibits that the distance determination to the Galactic center with the red
clump stars, even if the error of the population correction is taken into
account, can achieve an uncertainty of about 5%, which is almost the same level
as that in recent geometrical determinations.Comment: 14 pages, 4 figures, accepted by Ap
Similarity reduction of the modified Yajima-Oikawa equation
We study a similarity reduction of the modified Yajima-Oikawa hierarchy. The
hierarchy is associated with a non-standard Heisenberg subalgebra in the affine
Lie algebra of type A_2^{(1)}. The system of equations for self-similar
solutions is presented as a Hamiltonian system of degree of freedom two, and
admits a group of B\"acklund transformations isomorphic to the affine Weyl
group of type A_2^{(1)}. We show that the system is equivalent to a
two-parameter family of the fifth Painlev\'e equation.Comment: latex2e file, 18 pages, no figures; (v2)Introduction is modified.
Some typos are correcte
Model-based registration for pneumothorax deformation analysis using intraoperative cone-beam CT images
[2020 42nd Annual International Conference of the IEEE Engineering in Medicine & Biology Society (EMBC), 20-24 July 2020, Montreal, QC, Canada]Because the lung deforms during surgery because of pneumothorax, it is important to be able to track the location of a tumor. Deformation of the whole lung can be estimated using intraoperative cone-beam CT (CBCT) images. In this study, we used deformable mesh registration methods for paired CBCT images in the inflated and deflated states, and analyzed their deformation. We proposed a deformable mesh registration framework for deformations of partial organ shapes involving large deformation and rotation. Experimental results showed that the proposed methods reduced errors in point-to-point correspondence. As a result of registration using surgical clips placed on the lung surface during imaging, it was confirmed that an average error of 3.9 mm occurred in eight cases. The result of analysis showed that both tissue rotation and contraction had large effects on displacement
Numerical study of O(a) improved Wilson quark action on anisotropic lattice
The improved Wilson quark action on the anisotropic lattice is
investigated. We carry out numerical simulations in the quenched approximation
at three values of lattice spacing (--2 GeV) with the
anisotropy , where and are
the spatial and the temporal lattice spacings, respectively. The bare
anisotropy in the quark field action is numerically tuned by the
dispersion relation of mesons so that the renormalized fermionic anisotropy
coincides with that of gauge field. This calibration of bare anisotropy is
performed to the level of 1 % statistical accuracy in the quark mass region
below the charm quark mass. The systematic uncertainty in the calibration is
estimated by comparing the results from different types of dispersion
relations, which results in 3 % on our coarsest lattice and tends to vanish in
the continuum limit. In the chiral limit, there is an additional systematic
uncertainty of 1 % from the chiral extrapolation.
Taking the central value from the result of the
calibration, we compute the light hadron spectrum. Our hadron spectrum is
consistent with the result by UKQCD Collaboration on the isotropic lattice. We
also study the response of the hadron spectrum to the change of anisotropic
parameter, . We find that the change
of by 2 % induces a change of 1 % in the spectrum for physical quark
masses. Thus the systematic uncertainty on the anisotropic lattice, as well as
the statistical one, is under control.Comment: 27 pages, 25 eps figures, LaTe
Self-Consistent MHD Modeling of a Coronal Mass Ejection, Coronal Dimming, and a Giant Cusp-Shaped Arcade Formation
We performed magnetohydrodynamic simulation of coronal mass ejections (CMEs)
and associated giant arcade formations, and the results suggested new
interpretations of observations of CMEs. We performed two cases of the
simulation: with and without heat conduction. Comparing between the results of
the two cases, we found that reconnection rate in the conductive case is a
little higher than that in the adiabatic case and the temperature of the loop
top is consistent with the theoretical value predicted by the Yokoyama-Shibata
scaling law. The dynamical properties such as velocity and magnetic fields are
similar in the two cases, whereas thermal properties such as temperature and
density are very different.In both cases, slow shocks associated with magnetic
reconnectionpropagate from the reconnection region along the magnetic field
lines around the flux rope, and the shock fronts form spiral patterns. Just
outside the slow shocks, the plasma density decreased a great deal. The soft
X-ray images synthesized from the numerical results are compared with the soft
X-ray images of a giant arcade observed with the Soft X-ray Telescope aboard
{\it Yohkoh}, it is confirmed that the effect of heat conduction is significant
for the detailed comparison between simulation and observation. The comparison
between synthesized and observed soft X-ray images provides new interpretations
of various features associated with CMEs and giant arcades.Comment: 39 pages, 18 figures. Accepted for publication in the Astrophysical
Journal. The PDF file with high resplution figures can be downloaded from
http://www.kwasan.kyoto-u.ac.jp/~shiota/study/ApJ62426.preprint.pdf
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