# Local solutions to semilinear parabolic PDE with a singular nonlinearity

1. Jan 31, 2013

### doobly

Hi everyone,

I met a specific semilinear second-order PDE given by

$\frac{\partial u(x,t)}{\partial t} = {\bf A}(x,t) u(x,t) + U(x,t) u(x,t)^{-p} + A(x,t),....(1)$

$u(x,0) = b>0,$

where $p>0,\ \ (x,t) = (x_1,x_2,t)\in{\bf R}_+^2\times [0,T]$, and

${\bf A}(x,t)u = a_{11}(x,t)\frac{\partial^2 u}{\partial x_1^2} + a_{22}(x,t)\frac{\partial^2 u}{\partial x_2^2} + a_1(x,t)\frac{\partial u}{\partial x_1} + a_2(x,t)\frac{\partial u}{\partial x_2} + a_0(x,t) u$

is a uniformly elliptic differential operator, the coefficients $a_{11}(x,t)...$ are smooth enough w.r.t. (x,t)

Both U(x,t) and A(x,t) are positive for all (x,t) and which are also smooth w.r.t. (x,t).

Now I want to prove the existence and uniqueness of local solutions to (1). However, in (1), there is a singular nonlinearity $u^{-p},\ p>0$. In addition, the domain $x\in {\bf R}_+^2$ is unbounded. I appreciate that PDE experts would provide some ideas or references on it to me. Thanks again.