The parabolic Anderson problem is the Cauchy problem for the heat equation $\partial_t u(t,z)=\Delta u(t,z)+\xi(z) u(t,z)$ on $(0,\infty)\times { \mathbb Z}^d$ with random potential $(\xi(z) \colon z\in { \mathbb Z}^d)$. We consider independent and identically distributed potential variables, such that Prob$(\xi(z)>x)$ decays polynomially as $x\uparrow\infty$. If $u$ is initially localised in the origin, i.e. if $u(0,x)=\one_0(x)$, we show that, at any large time $t$, the solution is completely localised in a single point with high probability. More precisely, we find a random process $(Z_t \colon t\ge 0)$ with values in $\Z^d$ such that $\lim_{ t \uparrow\infty} u(t,Z_t)/\sum_{ z\in\Z^d} u(t,z) =1,$ in probability. We also identify the asymptotic behaviour of $Z_t$ in terms of a weak limit theorem.
Categories: math.PR