649 research outputs found
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
Alveolar bone density measurement in risk assessment for bisphosphonate-related osteonecrosis of the jaw: response to comments by Taguchi
Financial Time Series Analysis of SV Model by Hybrid Monte Carlo
We apply the hybrid Monte Carlo (HMC) algorithm to the financial time sires
analysis of the stochastic volatility (SV) model for the first time. The HMC
algorithm is used for the Markov chain Monte Carlo (MCMC) update of volatility
variables of the SV model in the Bayesian inference. We compute parameters of
the SV model from the artificial financial data and compare the results from
the HMC algorithm with those from the Metropolis algorithm. We find that the
HMC decorrelates the volatility variables faster than the Metropolis algorithm.
We also make an empirical analysis based on the Yen/Dollar exchange rates.Comment: 8 pages, 3 figures, to be published in LNC
Renormalization group flow of SU(3) lattice gauge theory - Numerical studies in a two coupling space
We investigate the renormalization group (RG) flow of SU(3) lattice gauge
theory in a two coupling space with couplings and
corresponding to and loops respectively. Extensive
numerical calculations of the RG flow are made in the fourth quadrant of this
coupling space, i.e., and . Swendsen's factor two
blocking and the Schwinger-Dyson method are used to find an effective action
for the blocked gauge field. The resulting renormalization group flow runs
quickly towards an attractive stream which has an approximate line shape. This
is numerical evidence of a renormalized trajectory which locates close to the
two coupling space. A model flow equation which incorporates a marginal
coupling (asymptotic scaling term), an irrelevant coupling and a
non-perturbative attraction towards the strong coupling limit reproduces
qualitatively the observed features. We further examine the scaling properties
of an action which is closer to the attractive stream than the currently used
improved actions. It is found that this action shows excellent restoration of
rotational symmetry even for coarse lattices with fm.Comment: 18 pages with 9 eps figures psfig.sty, typos correcte
Lattice calculation of the lowest order hadronic contribution to the muon anomalous magnetic moment
We present a quenched lattice calculation of the lowest order (alpha^2)
hadronic contribution to the anomalous magnetic moment of the muon which arises
from the hadronic vacuum polarization. A general method is presented for
computing entirely in Euclidean space, obviating the need for the usual
dispersive treatment which relies on experimental data for e^+e^- annihilation
to hadrons. While the result is not yet of comparable accuracy to those
state-of-the-art calculations, systematic improvement of the quenched lattice
computation to this level of accuracy is straightforward and well within the
reach of present computers. Including the effects of dynamical quarks is
conceptually trivial, the computer resources required are not.Comment: 12 pages, including two figures. Added reference and footnote
Replaced with published version; minor changes asked for by referees and
minor deletions to stay within page limi
Scaling Analysis of Improved Actions for Pure SU(3) Gauge Theory
We have explored the behaviour of some improved actions based on a
nonperturbative renormalization group (RG) analysis in coupling space. We
calculate the RG flow in two-coupling space (\boneone,\bonetwo) and examine
the restoration of rotational invariance and the scaling of physical quantities
.Comment: LATTICE98(improvement
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