The theory of optional stopping is extended from stopping sets to general adapted random sets called 'clouds' and 'anti-clouds', and a stopping theorem is proven for set-indexed martingales. An application to set-indexed survival analysis is given when the data points are indexed by sets and...

A new multivariate transformation is given, with various properties, e.g., uniqueness and convergence properties, that are similar to those of the Fourier transformation. The new transformation is particularly useful for distributions that are difficult to deal with by Fourier transformation,...

We consider the heat equation in dimension one with singular drift and inhomogeneous space-time white noise. In particular, the quadratic variation measure of the white noise is not required to be absolutely continuous w.r.t. the Lebesgue measure, neither in space nor in time. Under some...

We consider the Hopfield model of size N and with p~tN patterns, in the whole high temperature (paramagnetic) region. Our result is that the partition function has log-normal fluctuations. It is obtained by extending to the present model the method of the interpolating Brownian motions used by...

We consider an infinite system of particles characterized by their position and mass, in which coalescence occurs. Each particle endures Brownian excitation, and is subjected to the attraction of a potential. We define a stochastic process (Xt,Mt)t[greater-or-equal, slanted]0 describing the...

Given a Brownian motion (Bt)t[greater-or-equal, slanted]0 and a general target law [mu] (not necessarily centered or even in ) we show how to construct an embedding of [mu] in B. This embedding is an extension of an embedding due to Perkins, and is optimal in the sense that it simultaneously...

In (Stochastic Process. Appl. 103 (2003) 293), a pair of dynamic programming inequalities were derived for the 'separated' ergodic control problem for partially observed Markov processes, using the 'vanishing discount' argument. In this note, we strengthen these results to derive a single...

We investigate some properties of American option prices in the setting of time- and level-dependent volatility. The properties under consideration are convexity in the underlying stock price, monotonicity and continuity in the volatility and time decay. Some properties are direct consequences...

Affine term structural models (ATSM) are widely applied for pricing of bonds and interest rate derivatives but the consistency of ATSM when the short rate, r, is unbounded from below remains essentially an open question. First, the standard approach to ATSM uses the Feynman-Kac theorem which is...

Let {Zj, j[greater-or-equal, slanted]1} be a sequence of nonnegative continuous random variables. Given an arbitrary function g : [0,[infinity])--[0,[infinity]), a renewal function associated with this sequence is defined asDue to possible complexity of calculating the probabilities P{Zjb},...