We study the topological properties of cohomogeneity one flat manifolds and their orbits. Among other results we prove that principal orbits of R^n are isometric to R^{n-1} or S^k(c)\times R^{n-k-1}. We show that if M has one singular orbit, it is a totally geodesic submanifold of M and if M is orientable then there is at most one singular orbit.

A group G is called co-Dedekindian if every subgroup of G is invariant under all central automorphisms of G. In this paper we give some necessary conditions for certain finite p-groups with non-cyclic abelian second centre to be co-Dedekindian. We also classify 3-generator co-Dedekindian finite p-groups which are of class 3, having non-cyclic abelian second centre with |\Omega_1(G^p)|=p.

In this paper we generalize the formula of Frobenius-Stickelberger (see (0.1) below) and the formula of Kiepert (see (0.2) below) to the genus-two case.

The purpose of this paper is to study an optimal control problem associated with the thermally coupled Navier-Stokes equations. An existence result for this problem is obtained. The most important result of this paper is the proof of the existence and regularity of a solution of the adjoint system. By defining several functions, this system (which is not a divergence free one) is replaced by a divergence free system.

In this paper BP-theory is used to give a proof that there exists a stable homotopy element in \pi _{2^{n+1} - 2}^{S}( {\tf="times-b"R}P^{\infty }) with non-zero Hurewicz image in ju-theory if and only if there exists an element of \pi _{2^{n+1} - 2}^{S}( S{\hskip1}^{0}) that is represented by a framed manifold of Arf invariant one.

An element r in a ring R is clean if r is a sum of a unit and an idempotent. Camillo and Yu showed that unit regular rings are clean and in a very surprising development Nicholson and Varadarajan showed that linear transformations on countable dimension vector spaces over division rings are clean. These rings are very far from being unit regular.

Here we note that an idempotent is just a root of g(x)=x^{2}-x. For any g(x) we say R is g(x)-clean if every r in R is a sum of a root of g(x) and a unit. We show that if V is a countable dimensional vector space and over a division ring D and g(x) is any polynomial with coefficients in <formtex>K={\text Center}D and two distinct roots in K, then {\text End}V_D is g(x)-clean.

In this paper, relative pictures are used to analyze a certain family of exponent-sum two equations over groups.

If P is a Sylow-p-subgroup of a finite p-solvable group G, we prove that G^\prime \cap \bf{N}_G(P) \subseteq {P} if and only if p divides the degree of every irreducible non-linear p-Brauer character of G. More generally if π is a set of primes containing p and G is π-separable, we give necessary and sufficient group theoretic conditions for the degree of every irreducible non-linear p-Brauer character to be divisible by some prime in π. This can also be applied to degrees of ordinary characters.

In this paper, we consider the dependence of the Dirichlet eigenvalues and eigenspaces of the Laplace operator upon perturbation of the domain of definition. We prove that the dependence of a certain eigenvalue and of the corresponding eigenspace is analytic on the set of perturbations that leave the multiplicity constant.

The paper deals with local existence, blow-up and global existence for the solutions of a wave equation with an internal nonlinear source and a nonlinear boundary damping. The typical problem studied is\cases{u_{tt}-\Delta u=|u|^{p-2}u \hfill & \rm{~}OPEN~7~in <hsp sp=0.25>[0,\rm{inf}ty )\times \Omega ,}\hfill \cr u=0 \hfill & \rm{~}OPEN~6~on <hsp sp=0.25>[0,\rm{inf}ty )\times \Gamma _0,}\hfill \cr \frac {\partial u}{\partial \nu }=-\alpha (x)|u_t|^{m-2}u_t \hfill & \rm{~}OPEN~2~on <hsp sp=0.25>[0,\rm{inf}ty )\times \Gamma _1,}\cr u(0,x)=u_0(x),u_t(0,x)=u_1(x) & \rm{~}OPEN~1~on<hsp sp=0.25>\Omega ,}\hfill }

where \Omega \subset ℝ^n (n\ge 1) is a regular and bounded domain, \partial \Omega =\Gamma _0\cup \Gamma _1, \lambda _{n-1}(\Gamma _0)>>;0, 2<>;p\le 2(n-1)/(n-2) (when n\ge 3), m>>;1, \alpha \in L^\rm{inf}ty (\Gamma _1), \alpha \ge 0, and the initial data are in the energy space. The results proved extend the potential well theory, which is well known when the nonlinear damping acts in the interior of \Omega, to this problem.

Existence theorems for the equation F(x)=\varphi (x) are proved when F is a function with “good” surjective properties and \varphi satisfies certain compactness conditions on countable subsets of the space. Also results for certain homotopic perturbations of the equation are obtained. The results lead to various fixed point theorems of Darbo type for F=id, but they are also applicable if F acts between different spaces. Also the inclusions F(x)\in \varphi (x) (resp. F(x)\subseteq \varphi (x)) for multivalued functions \varphi (resp. F and \varphi) are studied. There are some connections with the theory of 0-epi maps.

We construct three p-adic L-functions attached to the symmetric square of a modular elliptic curve. Following a calculation of Perrin-Riou for one of these functions, we compute the derivative of the p-adic L-function associated to the square of the non-unit root of Frobenius at p. This generalises Greenberg's notion of [Lscr ]-invariant to these three-dimensional Galois representions.

We study the moduli space of pluriregular threefolds of general type with K3X=8, 10, 12 and p_g(X)=5 and whose canonical map is a finite morphism onto a smooth quadric Q⊂ ℙ4[Copf].

Let T be p-hyponormal or \rm{log}-hyponormal on a Hilbert space H. Then we have XT=T^*X whenever XT^*=TX for some X \in \scriptstyle{B}(\scriptstyle{H}). This is an extension of Patel's result. Also for p-hyponormal or \rm{log}-hyponormal T^*, dominant S and any X \in \scriptstyle{B}(\scriptstyle{H}) such that XT=SX, we have XT^*=S^*T.

We discuss classes of topological groups which can be approximated by p-adic Lie groups, and varieties of Hausdorff groups generated by classes of \hboxp-adic Lie groups (for a single or multiple p). We give several characterizations of locally compact pro-p-adic Lie groups and locally compact pro-discrete groups, and prove a “pro-version” of Cartan's Theorem: whenever a locally compact group is a pro-p-adic Lie group and a pro-q-adic Lie group for distinct primes p and q, it is pro-discrete. If a locally compact group can be approximated by p-adic Lie groups for variable primes p, then it is a pro-p-adic Lie group for some prime p.

We apply a previously obtained ansatz for extremal Kähler metrics to show that if a manifold admits a Hodge metric with constant scalar curvature, then the total space of the projectivization of a line bundle with first Chern class equal to the Kähler class of the metric admits a one-parameter family of extremal Kähler metrics. This generalizes earlier constructions.

A Banach space X is said to be an {\cal M}-space if every continuous multilinear form on X is weakly sequentially continuous. We study in this paper the stability properties of the class of {\cal M}-spaces.

A sequence of solutions to the Galerkin approximation of a nonstationary magnetohydrodynamic system is proved to converge to a measure-valued solution, in the sense of R. J. DiPerna–A. J. Majda, to the three-dimensional stationary Euler equations.

Let Ea(u,v) be the extremal algebra determined by two hermitians u and v with u^2=v^2=1. We show that: Ea(u,v)={f+gu:f,g\in C(𝕋)} , where [ ] is the unit circle; Ea(u,v) is C^*-equivalent to C^*({\cal G}), where {\cal G} is the infinite dihedral group; most of the hermitian elements k of Ea(u,v) have the property that k^n is hermitian for all odd n but for no even n; any two hermitian words in {\cal G} generate an isometric copy of Ea(u,v) in Ea(u,v).

A unit speed curve \gamma =\gamma (s) in a Riemannian manifold N is called a circle if there exists a unit vector field Y(s) along \gamma and a positive constant k such that \nabla _s \gamma '(s)=k Y(s),\, \nabla _s Y(s)=-k \gamma '(s). The main purpose of this article is to investigate the fundamental relationships between circles, maximal tori in compact symmetric spaces, and immersions of finite type.