منابع مشابه
Quasi-sectorial contractions
We revise the notion of the quasi-sectorial contractions. Our main theorem establishes a relation between semigroups of quasi-sectorial contractions and a class of m−sectorial generators. We discuss a relevance of this kind of contractions to the theory of operator-norm approximations of strongly continuous semigroups.
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We apply a method developed by one of the authors, see [1], to localize the numerical range of quasi-sectorial contractions semigroups. Our main theorem establishes a relation between the numerical range of quasi-sectorial contraction semigroups {exp(−tS)}t≥0, and the maximal sectorial generators S. We also give a new prove of the rate O(1/n) for the operator-norm Euler formula approximation: e...
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Smooth complex Fano varieties of dimension n form a limited family, so they have only a finite number of possible topological types. However not much is known about their topological invariants in higher dimensions. In particular we consider here the second Betti number b2 of a smooth Fano variety X, which coincides with the Picard number ρX . Recall that a Del Pezzo surface S has ρS ≤ 9. Fano ...
متن کاملFixed point theorems of JS-quasi-contractions
*Correspondence: [email protected] 3Department of Mathematics, Jiangxi University of Finance and Economics, Nanchang, 330013, China Full list of author information is available at the end of the article Abstract In this paper, we introduce the concept of JS-quasi-contraction and prove some fixed point results for JS-quasi-contractions in complete metric spaces under the assumption that the ...
متن کاملOperator Holes and Extensions of Sectorial Operators and Dual Pairs of Contractions
A description of the set of m-sectorial extensions of a dual pair {A1, A2} of nonnegative operators is obtained. Some classes of nonaccretive extensions of the dual pair {A1, A2} are described too. Both problems are reduced to similar problems for a dual pair {T1, T2} of nondensely defined symmetric contractions Tj = (I−Aj)(I+Aj), j ∈ {1, 2}. In turn these problems are reduced to the investigat...
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ژورنال
عنوان ژورنال: Journal of Functional Analysis
سال: 2008
ISSN: 0022-1236
DOI: 10.1016/j.jfa.2007.10.010