278 research outputs found
Classification of global and blow-up sign-changing solutions of a semilinear heat equation in the subcritical fujita range:Second-order diffusion
AbstractIt is well known from the seminal paper by Fujita [22] for 1 p0there exists a class of sufficiently "small" global in time solutions. This fundamental result from the 1960-70s (see also [39] for related contributions), was a cornerstone of further active blow-up research. Nowadays, similar Fujita-type critical exponents p0, as important characteristics of stability, unstability, and blow-up of solutions, have been calculated for various nonlinear PDEs. The above blow-up conclusion does not include solutions of changing sign, so some of them may remain global even for p ≤ p0. Our goal is a thorough description of blow-up and global in time oscillatory solutions in the subcritical range in (0.1) on the basis of various analytic methods including nonlinear capacity, variational, category, fibering, and invariant manifold techniques. Two countable sets of global solutions of changing sign are shown to exist. Most of them are not radially symmetric in any dimension N ≥ 2 (previously, only radial such solutions in ℝNor in the unit ball B1⊂ℝNwere mostly studied). A countable sequence of critical exponents, at which the whole set of global solutions changes its structure, is detected:, l = 0, 1, 2, ... .. See [47, 48] for earlier interesting contributions on sign changing solutions
Eigenvalues for radially symmetric non-variational fully nonlinear operators
In this paper we present an elementary theory about the existence of
eigenvalues for fully nonlinear radially symmetric 1-homogeneous operators. A
general theory for first eigenvalues and eigenfunctions of 1-homogeneous fully
nonlinear operators exists in the framework of viscosity solutions. Here we
want to show that for the radially symmetric operators (and one dimensional) a
much simpler theory can be established, and that the complete set of
eigenvalues and eigenfuctions characterized by the number of zeroes can be
obtained
Five types of blow-up in a semilinear fourth-order reaction-diffusion equation: an analytic-numerical approach
Five types of blow-up patterns that can occur for the 4th-order semilinear
parabolic equation of reaction-diffusion type
u_t= -\Delta^2 u + |u|^{p-1} u \quad {in} \quad \ren \times (0,T), p>1,
\quad \lim_{t \to T^-}\sup_{x \in \ren} |u(x,t)|= +\iy, are discussed. For
the semilinear heat equation , various blow-up patterns
were under scrutiny since 1980s, while the case of higher-order diffusion was
studied much less, regardless a wide range of its application.Comment: 41 pages, 27 figure
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