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Roger Tribe

Publications and source records attributed to Roger Tribe.

26 records · Page 2Linked to original sources
arXiv2012

Pfaffian formulae for one dimensional coalescing and annihilating systems

The paper considers instantly coalescing, or instantly annihilating, systems of one-dimensional Brownian particles on the real line. Under maximal entrance laws, the distribution of the particles at a fixed time is shown to be Pfaffian point processes closely related to the Pfaffian point process describing one dimensional distribution of real eigenvalues in the real Ginibre ensemble of random matrices. As an application, an exact large time asymptotic for the n-point density function for coalescing particles is derived.

math.PR↗
arXiv2009

A phase diagram for a stochastic reaction diffusion system

In this paper a stochastic reaction diffusion system is considered, which models the spread of a finite population reacting with a non-renewable resource in the presence of individual based noise. A two-parameter phase diagram is established to describe the large time evolution, distinguishing between certain death or possible life of the population.

math.PR↗
arXiv2007

A Feynman-Kac-type formula for the deterministic and stochastic wave equations

We establish a probabilistic representation for a wide class of linear deterministic p.d.e.s with potential term, including the wave equation in spatial dimensions 1 to 3. Our representation applies to the heat equation, where it is related to the classical Feynman-Kac formula, as well as to the telegraph and beam equations. If the potential is a (random) spatially homogeneous Gaussian noise, then this formula leads to an expression for the moments of the solution.

math.PR↗
arXiv2002

A Singular Parabolic Anderson Model

We give a new example of a measure-valued process without a density, which arises from a stochastic partial differential equation with a multiplicative noise term. This process has some unusual properties. We work with the heat equation with a random potential: u_t=Delta u+kuF. Here k>0 is a small number, and x lies in d-dimensional Euclidean space with d>2. F is a Gaussian noise which is uncorrelated in time, and whose spatial covariance equals |x-y|^(-2). The exponent 2 is critical in the following sense. For exponents less than 2, the equation has function-valued solutions, and for exponents higher than 2, we do not expect solutions to exist. This model is closely related to the parabolic Anderson model; we expect solutions to be small, except for a collection of high peaks. This phenomenon is called intermittency, and is reflected in the singular nature of our process. Solutions exist as singular measures, under suitable assumptions on the initial conditions and for sufficiently small k. We investigate various properties of the solutions, such as dimension of the support and long-time behavior. As opposed to the super-Brownian motion, which satisfies a similar equation, our process does not have compact support, nor does it die out in finite time. We use such tools as scaling, self-duality and moment formulae.

math.PR↗
arXiv2002

Hitting properties of a random string

We consider Funaki's model of a random string taking values in R^d. It is specified by the following stochastic PDE, du = u_{xx} + W, where W=W(x,t) is two-parameter white noise, also taking values in R^d. We study hitting properties, double points, and recurrence. The main difficulty is that the process has the Markov property in time, but not in space. We find: (1) The string hits points if d<6. (2) For fixed t, there are points x,y such that u(t,x)=u(t,y) iff d < 4. (3) There exist points t,x,y such that u(t,x)=u(t,y) iff d < 8. (4) There exist points s,t,x,y such that u(t,x)=u(s,y) iff d < 12. (5) The string is recurrent iff d < 7.

math.PR↗
arXiv2000

On the large time asymptotics of decaying Burgers turbulence

The decay of Burgers turbulence with compactly supported Gaussian "white noise" initial conditions is studied in the limit of vanishing viscosity and large time. Probability distribution functions and moments for both velocities and velocity differences are computed exactly, together with the "time-like" structure functions . The analysis of the answers reveals both well known features of Burgers turbulence, such as the presence of dissipative anomaly, the extreme anomalous scaling of the velocity structure functions and self similarity of the statistics of the velocity field, and new features such as the extreme anomalous scaling of the "time-like" structure functions and the non-existence of a global inertial scale due to multiscaling of the Burgers velocity field. We also observe that all the results can be recovered using the one point probability distribution function of the shock strength and discuss the implications of this fact for Burgers turbulence in general.

chao-dyn↗
arXiv1999

Uniqueness for a class of one-dimensional stochastic PDEs using moment duality

For independent nearest-neighbour bond percolation on Z^d with d >> 6, we prove that the incipient infinite cluster's two-point function and three-point function converge to those of integrated super-Brownian excursion (ISE) in the scaling limit. The proof is based on an extension of the new expansion for percolation derived in a previous paper, and involves treating the magnetic field as a complex variable. A special case of our result for the two-point function implies that the probability that the cluster of the origin consists of n sites, at the critical point, is given by a multiple of n^{-3/2}, plus an error term of order n{-3/2-ε} with ε> 0. This is a strong statement that the critical exponent δis given by δ= 2.

math.PR↗