151 research outputs found
A semiparametric Bayesian approach to the analysis of financial time series with applications to value at risk estimation
Financial time series analysis deals with the understanding of data collected on financial markets. Several parametric distribution models have been entertained for describing, estimating and predicting the dynamics of financial time series. Alternatively, this article considers a Bayesian semiparametric approach. In particular, the usual parametric distributional assumptions of the GARCH-type models are relaxed by entertaining the class of location-scale mixtures of Gaussian distributions with a Dirichlet process prior on the mixing distribution, leading to a Dirichlet process mixture model. The proposed specification allows for a greater exibility in capturing both the skewness and kurtosis frequently observed in financial returns. The Bayesian model provides statistical inference with finite sample validity. Furthermore, it is also possible to obtain predictive distributions for the Value at Risk (VaR), which has become the most widely used measure of market risk for practitioners. Through a simulation study, we demonstrate the performance of the proposed semiparametric method and compare results with the ones from a normal distribution assumption. We also demonstrate the superiority of our proposed semiparametric method using real data from the Bombay Stock Exchange Index (BSE-30) and the Hang Seng Index (HSI).Bayesian estimation, Deviance information criterion, Dirichlet process mixture, Financial time series, Location-scale Gaussian mixture, Markov chain Monte Carlo
Noise-induced transition in a quantum system
We examine the noise-induced transition in a fluctuating bistable potential
of a driven quantum system in thermal equilibrium. Making use of a Wigner
canonical thermal distribution for description of the statistical properties of
the thermal bath, we explore the generic effects of quantization like vacuum
field fluctuation and tunneling in the characteristic stationary probability
distribution functions undergoing transition from unimodal to bimodal nature
and in signal-to-noise ratio characterizing the co-operative effect among the
noise processes and the weak periodic signal.Comment: To appear on Physics Letters
Noise-induced quantum transport
We analyze the problem of directed quantum transport induced by external
exponentially correlated telegraphic noise. In addition to quantum nature of
the heat bath, nonlinearity of the periodic system potential brings in quantum
contribution. We observe that quantization, in general, enhances classical
current at low temperature, while the differences become insignificant at
higher temperature. Interplay of quantum diffusion and quantum correction to
system potential is analyzed for various ranges of temperature, correlation
time and strength of external noise and asymmetry parameters. A possible
experimental realization of the observed quantum effects in a superionic
conductor placed in a random asymmetric dichotomous electric field has been
suggested.Comment: 23 pages and 5 figures. To be published in Physical Review
Noise correlation-induced splitting of Kramers' escape rate from a metastable state
A correlation between two noise processes driving the thermally activated
particles in a symmetric triple well potential, may cause a symmetry breaking
and a difference in relative stability of the two side wells with respect to
the middle one. This leads to an asymmetric localization of population and
splitting of Kramers' rate of escape from the middle well, ensuring a
preferential distribution of the products in the course of a parallel reaction
Dirichlet Process Hidden Markov Multiple Change-point Model
This paper proposes a new Bayesian multiple change-point model which is based
on the hidden Markov approach. The Dirichlet process hidden Markov model does
not require the specification of the number of change-points a priori. Hence
our model is robust to model specification in contrast to the fully parametric
Bayesian model. We propose a general Markov chain Monte Carlo algorithm which
only needs to sample the states around change-points. Simulations for a normal
mean-shift model with known and unknown variance demonstrate advantages of our
approach. Two applications, namely the coal-mining disaster data and the real
United States Gross Domestic Product growth, are provided. We detect a single
change-point for both the disaster data and US GDP growth. All the change-point
locations and posterior inferences of the two applications are in line with
existing methods.Comment: Published at http://dx.doi.org/10.1214/14-BA910 in the Bayesian
Analysis (http://projecteuclid.org/euclid.ba) by the International Society of
Bayesian Analysis (http://bayesian.org/
Semiparametric Bayesian Modeling of Multivariate Average Bioequivalence
Bioequivalence trials are usually conducted to compare two or more formulations of a drug. Simultaneous assessment of bioequivalence on multiple endpoints is called multivariate bioequivalence. Despite the fact that some tests for multivariate bioequivalence are suggested, current practice usually involves univariate bioequivalence assessments ignoring the correlations between the endpoints such as AUC and Cmax. In this paper we develop a semiparametric Bayesian test for bioequivalence under multiple endpoints. Specifically, we show how the correlation between the endpoints can be incorporated in the analysis and how this correlation affects the inference. Resulting estimates and posterior probabilities ``borrow strength\u27\u27 from one another where the amount and direction of the strength borrowed are determined by the prior correlations. The method developed is illustrated using a real data set
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