Random flights connecting porous medium and Euler–Poisson–Darboux equations

Random Walks and the Porous Medium Equation

R J(x − y)u(x, t)dy is the rate at which they are leaving location x to travel to all other sites. This consideration, in the absence of external sources, leads immediately to the fact that the density u satisfies equation (1.1). Throughout this note we shall assume also that J is a decreasing radial function whose support is the unit ball. Under these hypotheses we have that individuals that a...

Hamilton’s gradient estimates and Liouville theorems for porous medium equations

Lévy flights and random searches

In this work we discuss some recent contributions to the random search problem. Our analysis includes superdiffusive Lévy processes and correlated random walks in several regimes of target site density, mobility and revisitability. We present results in the context of mean-field-like and closed-form average calculations, as well as numerical simulations. We then consider random searches perform...

Lévy flights in random environments.

We consider Lévy flights characterized by the step index f in a quenched random force field. By means of a dynamic renormalization group analysis we find that the dynamic exponent z for f < 2 locks onto f , independent of dimension and independent of the presence of weak quenched disorder. The critical dimension, however, depends on the step index f for f < 2 and is given by dc = 2f − 2. For d ...

The geometry of dissipative evolution equations: the porous medium equation

We show that the porous medium equation has a gradient ow structure which is both physically and mathematically natural. In order to convince the reader that it is mathematically natural, we show the time asymptotic behavior can be easily understood in this framework. We use the intuition and the calculus of Riemannian geometry to quantify this asymptotic behavior.