Stability of perturbed nonlinear parabolic equations with Sturmian property

We study stability of an equilibrium f∗ of autonomous dynamical systems under asymptotically small perturbations of the equation. We show that such stability takes place if the domain of attraction of the equilibrium f∗ contains a one-parametric ordered family . In the stability analysis we need a special S-relation (a kind of “restricted partial ordering”) to be preserved relative to the family . This S-relation is inherited from the Sturmian zero set properties for linear parabolic equations. As main applications, we prove stability of the self-similar blow-up behaviour for the porous medium equation, the p-Laplacian equation and the dual porous medium equation in with nonlinear lower-order perturbations. For such one-dimensional parabolic equations the S-relation is Sturm's Theorem on the nonincrease of the number of intersections between the solutions and particular solutions with initial data in . This Sturmian property plays a key role and is true for the unperturbed PME, but is not true for perturbed equations.     

Elliptic equations with nonzero boundary conditions in weighted Sobolev spaces

We present weighted Sobolev spaces along with a trace theorem and an interpolation theorem for the spaces. Then we solve nonzero boundary value problems for elliptic equations in .     

Attractors for nonautonomous 2D Navier-Stokes equations with less regular symbols

We introduce a new class of functions satisfying normal Condition (C*), denoted by , which are translation bounded but not translation compact — in particular, which are more general than normal functions (see [S.S. Lu, H.Q. Wu, C.K. Zhong, Attractors for nonautonomous 2D Navier-Stokes equations with normal external forces, Discrete Contin. Dyn. Syst., 13 (2005) 701-719] for the definition), denoted by . Furthermore, we prove the existence of uniform attractors for 2D Navier-Stokes equations with external forces belonging to in .     

Geodesic flows, bi-Hamiltonian structure and coupled KdV type systems

We show that all the Antonowicz-Fordy type coupled KdV equations have the same symmetry group and similar bi-Hamiltonian structures. It turns out that their configuration space is , where is the Bott-Virasoro group of orientation preserving diffeomorphisms of the circle, and all these systems can be interpreted as equations of a geodesic flow with respect to L² metric on the semidirect product space .     

Stability of equilibrium of conservative systems with two degrees of freedom

This article intends to study the Liapounof's stability of an equilibrium of conservative Lagrangian systems with two degrees of freedom.We consider an open neighborhood of the origin and the Lagrangian , where of class is the potential energy with a critical point at the origin and is the kinetic energy, of class .We assume that π has a jet of order k at the origin, and this jet shows that the potential energy does not have a minimum in 0. With these hypotheses we prove that (0;0) is an unstable equilibrium according to Liapounof for the Lagrange equations of . We achieve this by proving that there is an asymptotic trajectory to the origin.     

Ill-posedness of the Navier-Stokes equations in a critical space in 3D

We prove that the Cauchy problem for the three-dimensional Navier-Stokes equations is ill-posed in in the sense that a “norm inflation” happens in finite time. More precisely, we show that initial data in the Schwartz class S that are arbitrarily small in can produce solutions arbitrarily large in after an arbitrarily short time. Such a result implies that the solution map itself is discontinuous in at the origin.     

Wave operators to a quadratic nonlinear Klein-Gordon equation in two space dimensions

We study asymptotics around the final states of solutions to the nonlinear Klein-Gordon equations with quadratic nonlinearities in two space dimensions , where . We prove that if the final states

     

Wheeled PROPs, graph complexes and the master equation

We introduce and study wheeled PROPs, an extension of the theory of PROPs which can treat traces and, in particular, solutions to the master equations which involve divergence operators. We construct a dg free wheeled PROP whose representations are in one-to-one correspondence with formal germs of SP-manifolds, key geometric objects in the theory of Batalin-Vilkovisky quantization. We also construct minimal wheeled resolutions of classical operads and as non-trivial extensions of the well-known dg operads and . Finally, we apply the above results to a computation of cohomology of a directed version of Kontsevich’s complex of ribbon graphs.     

Well-posedness and regularity of generalized Navier-Stokes equations in some critical Q-spaces

We study the well-posedness and regularity of the generalized Navier-Stokes equations with initial data in a new critical space , , which is larger than some known critical homogeneous Besov spaces. Here is a space defined as the set of all measurable functions with

     

Classification of generalized symmetries of the Yang-Mills fields with a semi-simple structure group

A complete classification of generalized (or local) symmetries of the Yang-Mills equations on four dimensional Minkowski space with a semi-simple structure group is carried out. It is shown that any generalized symmetry, up to a generalized gauge symmetry, agrees with a first order symmetry on solutions of the Yang-Mills equations. Let be the decomposition of the Lie algebra of the structure group into simple ideals. First order symmetries for -valued Yang-Mills fields are found to consist of gauge symmetries, conformal symmetries for -valued Yang-Mills fields, 1?m?n, and their images under a complex structure of .     

Attractors for non-autonomous wave equations with a new class of external forces

We introduce a new concept Condition (C*), and denote the set of all functions satisfying Condition (C*) by , which are translation bounded but not translation compact in , and we show that there are many functions satisfying Condition (C*); then, in application, we obtain the existence of uniform attractors in for non-autonomous wave equations involving mixed differential quotient terms with this new class of time dependent external forces .     

Hierarchy of Hamilton equations on Banach Lie-Poisson spaces related to restricted Grassmannian

We consider the Banach Lie-Poisson space and its complexification , where the first one of them contains the restricted Grassmannian Grres as a symplectic leaf. Using the Magri method we define an involutive family of Hamiltonians on these Banach Lie-Poisson spaces. The hierarchy of Hamilton equations given by these Hamiltonians is investigated. The operator equations of Ricatti-type are included in this hierarchy. For a few particular cases we give the explicit solutions.     

On the classification of non-normal cubic hypersurfaces

In this article we study the classification of non-normal cubic hypersurfaces over an algebraically closed field K of arbitrary characteristic. Let be an irreducible non-normal cubic hypersurface. If r≥5, then X is necessarily a cone (Remark 2.3). In view of this fact it suffices to classify irreducible non-normal cubic hypersurfaces for r≤4. We prove that there are precisely five non-normal cubic equations (resp. six non-normal cubic equations) when (resp. when is either 2 or 3), up to projective equivalence. Also we describe the normalization of X in detail.     

Infinitely many positive solutions for an elliptic problem with critical or supercritical growth

We prove that for some supercritical exponents and for some smooth domains D in RN there are infinitely many (distinct) positive solutions to the following Lane–Emden–Fowler equation: This seems to be the first result for such type of equations.