Random Flights Related to the Euler-Poisson- Darboux Equation}

#### R. Garra, E. Orsingher

2016, v.22, №1, 87-110

ABSTRACT

This paper is devoted to the analysis of random motions on the line and in the space $\mathbb{R}^d$

($d>1$) performed at finite velocity and governed by a non-homogeneous

Poisson process with rate $\lambda(t)$. The explicit distributions $p(\mathbf{x},t)$ of the position of

the randomly moving particles are obtained by solving initial-value problems for the Euler-Poisson-Darboux

equation when $\lambda(t)= \alpha/t$, $\alpha >0$. We consider also the case where $\lambda(t)= \lambda \coth \lambda t$

and $\lambda(t)= \lambda \tanh\lambda t$ where some Riccati differential equations emerge and the explicit distributions

are obtained for $d=1$. We also examine planar random motions with random velocities obtained by projecting random flights in $\mathbb{R}^d$

onto the plane. Finally the case of planar motions with four orthogonal directions is considered and the corresponding

higher-order equations with time-varying coefficients obtained.

Keywords: Euler-Poisson-Darboux equation, inhomogeneous Poisson process, finite velocity random motions, telegraph process

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