14,194 research outputs found
From duality to determinants for q-TASEP and ASEP
We prove duality relations for two interacting particle systems: the
-deformed totally asymmetric simple exclusion process (-TASEP) and the
asymmetric simple exclusion process (ASEP). Expectations of the duality
functionals correspond to certain joint moments of particle locations or
integrated currents, respectively. Duality implies that they solve systems of
ODEs. These systems are integrable and for particular step and half-stationary
initial data we use a nested contour integral ansatz to provide explicit
formulas for the systems' solutions, and hence also the moments. We form
Laplace transform-like generating functions of these moments and via residue
calculus we compute two different types of Fredholm determinant formulas for
such generating functions. For ASEP, the first type of formula is new and
readily lends itself to asymptotic analysis (as necessary to reprove GUE
Tracy--Widom distribution fluctuations for ASEP), while the second type of
formula is recognizable as closely related to Tracy and Widom's ASEP formula
[Comm. Math. Phys. 279 (2008) 815--844, J. Stat. Phys. 132 (2008) 291--300,
Comm. Math. Phys. 290 (2009) 129--154, J. Stat. Phys. 140 (2010) 619--634]. For
-TASEP, both formulas coincide with those computed via Borodin and Corwin's
Macdonald processes [Probab. Theory Related Fields (2014) 158 225--400]. Both
-TASEP and ASEP have limit transitions to the free energy of the continuum
directed polymer, the logarithm of the solution of the stochastic heat equation
or the Hopf--Cole solution to the Kardar--Parisi--Zhang equation. Thus,
-TASEP and ASEP are integrable discretizations of these continuum objects;
the systems of ODEs associated to their dualities are deformed discrete quantum
delta Bose gases; and the procedure through which we pass from expectations of
their duality functionals to characterizing generating functions is a rigorous
version of the replica trick in physics.Comment: Published in at http://dx.doi.org/10.1214/13-AOP868 the Annals of
Probability (http://www.imstat.org/aop/) by the Institute of Mathematical
Statistics (http://www.imstat.org
Wind farm output
The problem was to devise a simulation method for the wind speeds at a set of sites, that has the correct autocorrelation, cross-correlation and distributions. The report includes one way of doing this, using a multivariate auto-regressive system, and other comments and observations that may lead to better ways of achieving the aim
General Semiparametric Shared Frailty Model Estimation and Simulation with frailtySurv
The R package frailtySurv for simulating and fitting semi-parametric shared
frailty models is introduced. Package frailtySurv implements semi-parametric
consistent estimators for a variety of frailty distributions, including gamma,
log-normal, inverse Gaussian and power variance function, and provides
consistent estimators of the standard errors of the parameters' estimators. The
parameters' estimators are asymptotically normally distributed, and therefore
statistical inference based on the results of this package, such as hypothesis
testing and confidence intervals, can be performed using the normal
distribution. Extensive simulations demonstrate the flexibility and correct
implementation of the estimator. Two case studies performed with publicly
available datasets demonstrate applicability of the package. In the Diabetic
Retinopathy Study, the onset of blindness is clustered by patient, and in a
large hard drive failure dataset, failure times are thought to be clustered by
the hard drive manufacturer and model
Multi-channel Hybrid Access Femtocells: A Stochastic Geometric Analysis
For two-tier networks consisting of macrocells and femtocells, the channel
access mechanism can be configured to be open access, closed access, or hybrid
access. Hybrid access arises as a compromise between open and closed access
mechanisms, in which a fraction of available spectrum resource is shared to
nonsubscribers while the remaining reserved for subscribers. This paper focuses
on a hybrid access mechanism for multi-channel femtocells which employ
orthogonal spectrum access schemes. Considering a randomized channel assignment
strategy, we analyze the performance in the downlink. Using stochastic geometry
as technical tools, we model the distribution of femtocells as Poisson point
process or Neyman-Scott cluster process and derive the distributions of
signal-to-interference-plus-noise ratios, and mean achievable rates, of both
nonsubscribers and subscribers. The established expressions are amenable to
numerical evaluation, and shed key insights into the performance tradeoff
between subscribers and nonsubscribers. The analytical results are corroborated
by numerical simulations.Comment: This is the final version, which was accepted in IEEE Transactions on
Communication
Bessel bridges decomposition with varying dimension. Applications to finance
We consider a class of stochastic processes containing the classical and
well-studied class of Squared Bessel processes. Our model, however, allows the
dimension be a function of the time. We first give some classical results in a
larger context where a time-varying drift term can be added. Then in the
non-drifted case we extend many results already proven in the case of classical
Bessel processes to our context. Our deepest result is a decomposition of the
Bridge process associated to this generalized squared Bessel process, much
similar to the much celebrated result of J. Pitman and M. Yor. On a more
practical point of view, we give a methodology to compute the Laplace transform
of additive functionals of our process and the associated bridge. This permits
in particular to get directly access to the joint distribution of the value at
t of the process and its integral. We finally give some financial applications
to illustrate the panel of applications of our results
Bayes and maximum likelihood for -Wasserstein deconvolution of Laplace mixtures
We consider the problem of recovering a distribution function on the real
line from observations additively contaminated with errors following the
standard Laplace distribution. Assuming that the latent distribution is
completely unknown leads to a nonparametric deconvolution problem. We begin by
studying the rates of convergence relative to the -norm and the Hellinger
metric for the direct problem of estimating the sampling density, which is a
mixture of Laplace densities with a possibly unbounded set of locations: the
rate of convergence for the Bayes' density estimator corresponding to a
Dirichlet process prior over the space of all mixing distributions on the real
line matches, up to a logarithmic factor, with the rate
for the maximum likelihood estimator. Then, appealing to an inversion
inequality translating the -norm and the Hellinger distance between
general kernel mixtures, with a kernel density having polynomially decaying
Fourier transform, into any -Wasserstein distance, , between the
corresponding mixing distributions, provided their Laplace transforms are
finite in some neighborhood of zero, we derive the rates of convergence in the
-Wasserstein metric for the Bayes' and maximum likelihood estimators of
the mixing distribution. Merging in the -Wasserstein distance between
Bayes and maximum likelihood follows as a by-product, along with an assessment
on the stochastic order of the discrepancy between the two estimation
procedures
On the governing equations for Poisson and Skellam processes time-changed by inverse subordinators
In the paper we present the governing equations for marginal distributions of
Poisson and Skellam processes time-changed by inverse subordinators. The
equations are given in terms of convolution-type derivatives
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