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Degenerate evolution problems and Beta-type operators

Antonio Attalienti, Michele Campiti (2000)

Studia Mathematica

The present paper is concerned with the study of the differential operator Au(x):=α(x)u”(x)+β(x)u’(x) in the space C([0,1)] and of its adjoint Bv(x):=((αv)’(x)-β(x)v(x))’ in the space L 1 ( 0 , 1 ) , where α(x):=x(1-x)/2 (0≤x≤1). A careful analysis of their main properties is carried out in view of some generation results available in [6, 12, 20] and [25]. In addition, we introduce and study two different kinds of Beta-type operators as a generalization of similar operators defined in [18]. Among the corresponding...

Degree of T-equivariant maps in ℝⁿ

Joanna Janczewska, Marcin Styborski (2007)

Banach Center Publications

A special case of G-equivariant degree is defined, where G = ℤ₂, and the action is determined by an involution T : p q p q given by T(u,v) = (u,-v). The presented construction is self-contained. It is also shown that two T-equivariant gradient maps f , g : ( , S n - 1 ) ( , 0 ) are T-homotopic iff they are gradient T-homotopic. This is an equivariant generalization of the result due to Parusiński.

Degree theory for VMO maps on metric spaces

Francesco Uguzzoni, Ermanno Lanconelli (2002)

Annali della Scuola Normale Superiore di Pisa - Classe di Scienze

We construct a degree theory for Vanishing Mean Oscillation functions in metric spaces, following some ideas of Brezis & Nirenberg. The underlying sets of our metric spaces are bounded open subsets of N and their boundaries. Then, we apply our results in order to analyze the surjectivity properties of the L -harmonic extensions of VMO vector-valued functions. The operators L we are dealing with are second order linear differential operators sum of squares of vector fields satisfying the hypoellipticity...

Dense range perturbations of hypercyclic operators

Luis Bernal-Gonzalez (2002)

Colloquium Mathematicae

We show that if (Tₙ) is a hypercyclic sequence of linear operators on a locally convex space and (Sₙ) is a sequence of linear operators such that the image of each orbit under every linear functional is non-dense then the sequence (Tₙ + Sₙ) has dense range. Furthermore, it is proved that if T,S are commuting linear operators in such a way that T is hypercyclic and all orbits under S satisfy the above non-denseness property then T - S has dense range. Corresponding statements for operators and sequences...

Denseness of norm attaining mappings.

María D. Acosta (2006)

RACSAM

The Bishop-Phelps Theorem states that the set of (bounded and linear) functionals on a Banach space that attain their norms is dense in the dual. In the complex case, Lomonosov proved that there may be a closed, convex and bounded subset C of a Banach space such that the set of functionals whose maximum modulus is attained on C is not dense in the dual. This paper contains a survey of versions for operators, multilinear forms and polynomials of the Bishop-Phelps Theorem. Lindenstrauss provided examples...

Denting point in the space of operator-valued continuous maps.

Ryszard Grzaslewicz, Samir B. Hadid (1996)

Revista Matemática de la Universidad Complutense de Madrid

In a former paper we describe the geometric properties of the space of continuous functions with values in the space of operators acting on a Hilbert space. In particular we show that dent B(L(H)) = ext B(L(H)) if dim H < 8 and card K < 8 and dent B(L(H)) = 0 if dim H < 8 or card K = 8, and x-ext C(K,L(H)) = ext C(K,L(H)).

Dependence of fractional powers of elliptic operators on boundary conditions

Pavel E. Sobolevskii (1992)

Atti della Accademia Nazionale dei Lincei. Classe di Scienze Fisiche, Matematiche e Naturali. Rendiconti Lincei. Matematica e Applicazioni

The realization of an elliptic operator A under suitable boundary conditions is considered and the dependence of the square-root of A from the various conditions is studied.

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