## Differential and Integral Equations

- Differential Integral Equations
- Volume 20, Number 4 (2007), 361-396.

### Nonlinear parabolic problems with a very general quadratic gradient term

A. Dall'Aglio, D. Giachetti, and S. Segura de León

#### Abstract

We study existence and regularity of distributional solutions for a class of nonlinear parabolic problems. The equations we consider have a quasi-linear diffusion operator and a lower-order term, which may grow quadratically in the gradient and may have a very fast growth (for instance, exponential) with respect to the solution. The model problem we refer to is the following \begin{equation} \begin{cases} u_t -\Delta u = \beta(u) |{\nabla} u|^2 +f(x, t), & \ \text{in}\quad \Omega\times (0, T);\\[0.1cm] u(x,t)=0, & \ \text{on}\quad \partial\Omega\times (0, T);\\[0.1cm] u(x, 0)=u_0(x), & \ \text{in}\quad \Omega; \end{cases} \tag*{(0.1)} \label{modello} \end{equation} with $\Omega \subset \mathbb R^N$ a bounded open set, $T>0$, and $\beta(u)\sim e^{|u|}$; as far as the data are concerned, we assume $\exp(\exp(|u_0|))\in L^2({\Omega})$, and $f \in X(0, T; Y({\Omega}))$, where $X, Y$ are Orlicz spaces of logarithmic and exponential type, respectively. We also study a semilinear problem having a superlinear reaction term, a problem that is linked with problem (0.1) by a change of unknown (see (1.3) below). Likewise, we deal with some other related problems, which include a gradient term and a reaction term together.

#### Article information

**Source**

Differential Integral Equations, Volume 20, Number 4 (2007), 361-396.

**Dates**

First available in Project Euclid: 20 December 2012

**Permanent link to this document**

https://projecteuclid.org/euclid.die/1356039459

**Mathematical Reviews number (MathSciNet)**

MR2307139

**Zentralblatt MATH identifier**

1212.35204

**Subjects**

Primary: 35K55: Nonlinear parabolic equations

Secondary: 35B65: Smoothness and regularity of solutions 35K20: Initial-boundary value problems for second-order parabolic equations 35K57: Reaction-diffusion equations

#### Citation

Dall'Aglio, A.; Giachetti, D.; Segura de León, S. Nonlinear parabolic problems with a very general quadratic gradient term. Differential Integral Equations 20 (2007), no. 4, 361--396. https://projecteuclid.org/euclid.die/1356039459