Degenerate elliptic systems and applications to Ginzburg-Landau type equations,part I

This paper has three topics. In Sect. 1, we present our results on the regularity and a priori estimates for solutions ofp-harmonic systems with Hölder continuous coefficients. Such systems come up in the study of Ginzburg-Landau type functional in higher dimensions. In Sect. 2, we study a stability inequality, which, in addition to its applications in the study of Ginzburg-Landau type functional, is of independent interest. In Sects. 3 and 4, we prove that for any sequence of minimizers of the higher dimensional Ginzburg-Landau type functional, a subsequence converges strongly away from a finite number of points, generalizing some of the two dimensional results of Bethuel, Brezis, and Hélein.Partially supported by the Alfred P. Sloan Foundation Research Fellowship and NSF grant DMS-9401815.     

Degenerate elliptic equations with singular nonlinearities

The behavior of the “minimal branch” is investigated for quasilinear eigenvalue problems involving the p-Laplace operator, considered in a smooth bounded domain of , and compactness holds below a critical dimension N ^#. The nonlinearity f(u) lies in a very general class and the results we present are new even for p = 2. Due to the degeneracy of p-Laplace operator, for p ≠ 2 it is crucial to define a suitable notion of semi-stability: the functional space we introduce in the paper seems to be the natural one and yields to a spectral theory for the linearized operator. For the case p = 2, compactness is also established along unstable branches satisfying suitable spectral information. The analysis is based on a blow-up argument and stronger assumptions on the nonlinearity f(u) are required. Authors are partially supported by MIUR, project “Variational methods and nonlinear differential equations”.     

Monotonicity method applied to complex Ginzburg-Landau type equations

Global existence and smoothing effect are established for the complex Ginzburg-Landau type equation in which the real and imaginary parts of the complex coefficient are multiplied by nonlinear terms with different powers. The proof is based on monotonicity methods described by subdifferential operators. The key lies in two modified inequalities.     

Degenerate elliptic operators diagonal systems and variational integrals

Using a simple quasiconformal transformation of the independent variables it is shown how some regularity results for weak solutions of quasilinear elliptic systems generalize to several cases where the ellipticity of the principal part degenerates. Similarly it is possible to study the regularity of minima of degenerate variational integrals, as well as elliptic equations and systems in unbounded domains.     

Nonlocal fractional elliptic equations and applications

The L_p-coercive properties of a nonlocal fractional elliptic equation is studied. Particularly, it is proved that the fractional elliptic operator generated by this equation is sectorial in L_p space and also is a generator of an analytic semigroup. Moreover, by using the L_p-separability properties of the given elliptic operator the maximal regularity of the corresponding nonlocal fractional parabolic equation is established.     

Positive solutions of systems of singular Hammerstein integral equations with applications to semilinear elliptic equations in annuli

The existence of multiple positive solutions of systems of singular Hammerstein integral equations is studied, where the nonlinearities involved are allowed to have singularities in their second variables and satisfy weaker conditions involving the first eigenvalues of the corresponding linear Hammerstein integral operators. Such systems contain some mathematical models arising in science and engineering. Applications are given to the existence of multiple positive radial solutions of systems of semilinear singular elliptic equations in annuli on which, to the best of our knowledge, there has been little study.     

A monotonicity theorem and its applications to weighted elliptic equations

We study the equation w_(tt) + ?_(S~(N-1))w-μw_t-δw + h(t, ω)w~p= 0,(t, ω) ∈ R × S~(N-1), and under some conditions we prove a monotonicity theorem for its positive solutions. Applying this monotonicity theorem,we obtain a Liouville-type theorem for some nonlinear elliptic weighted singular equations. Moreover, we obtain the necessary and sufficient condition for-div(|x|~θ▽u) = |x|~lu~p, x ∈ R~N\{0} having positive solutions which are bounded near 0, which is also a positive answer to Souplet's conjecture(see Phan and Souplet(2012)) on the weighted Lane-Emden equation-?u = |x|~au~p, x ∈ R~N.     

Unrestricted lower bounds for eigenvalues for classes of elliptic equations and systems of equations with applications to problems in elasticity

Lower bounds for the eigenvalues of some elliptic equations and elliptic systems over bounded regions are obtained. The bounds are universal in that they depend only upon the volume of the region. Specific applications include the clamped plate, the buckling problem for the clamped plate and the equations of linear elasticity. Our results are consequences of extensions of the methods of Li and Yau (Comm. Mat. Phys. 88 (1983) 309–318) who obtained such results for the eigenvalues of the fixed membrane problem.     

Some degenerate elliptic systems and applications to cusped plates

We study the tension‐compression vibration of an elastic cusped plate under (all reasonable) boundary conditions at the cusped edge and given displacements at the non‐cusped edge and stresses at the upper and lower faces of the plate. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)