Results 21 to 30 of about 1,403 (89)
Extremal points without compactness in L1(μ)
Journal of Function Spaces, Volume 5, Issue 2, Page 199-211, 2007., 2007 We investigate the existence of extremal points and the Krein‐MIlman representation A=co̅ExtA of bounded convex subsets of L1(μ) which are only closed with respect to the topology of μ‐a.e. convergence.
Anna Martellotti, Jürgen Appell
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A note on maximal operator on ℓ{pn} and Lp(x)(ℝ)
Journal of Function Spaces, Volume 5, Issue 1, Page 49-88, 2007., 2007 We consider a discrete analogue of Hardy‐Littlewood maximal operator on the generalized Lebesque space ℓ{pn} of sequences defined on ℤ. It is known a necessary and sufficient condition P which guarantees an existence of a real number p > 1 such that the norms in the space ℓ{pn} and in the classical space ℓp are equivalent.
Aleš Nekvinda, Pankaj Jain
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Weighted norm inequalities and indices
Journal of Function Spaces, Volume 4, Issue 1, Page 43-71, 2006., 2006 We extend and simplify several classical results on weighted norm inequalities for classical operators acting on rearrangement invariant spaces using the theory of indices. As an application we obtain necessary and sufficient conditions for generalized Hardy type operators to be bounded on ?p(w), ?p,8(w), Gp(w) and Gp,8(w).
Joaquim Martín +2 more
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New classes of rearrangement‐invariant spaces appearing in extreme cases of weak interpolation
Journal of Function Spaces, Volume 4, Issue 3, Page 275-304, 2006., 2006 We study weak type interpolation for ultrasymmetric spaces L?,E i.e., having the norm ??(t)f*(t)?E˜, where ?(t) is any quasiconcave function and E˜ is arbitrary rearrangement‐invariant space with respect to the measure d t /t. When spaces L?,E are not “too close” to the endpoint spaces of interpolation (in the sense of Boyd), the optimal interpolation ...
Evgeniy Pustylnik +2 more
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Non‐equivalent greedy and almost greedy bases in lp
Journal of Function Spaces, Volume 4, Issue 1, Page 25-42, 2006., 2006 For 1 < p < 8 and p ? 2 we construct a family of mutually non‐equivalent greedy bases in lp having the cardinality of the continuum. In fact, no basis from this family is equivalent to a rearranged subsequence of any other basis thereof. We are able to extend this statement to the spaces Lp and H1.
Stephen J. Dilworth +3 more
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Modulation spaces Mp,q for 0 < p, q?8
Journal of Function Spaces, Volume 4, Issue 3, Page 329-341, 2006., 2006 The purpose of this paper is to construct modulation spaces Mp,q(Rd) for general 0 < p, q?8, which coincide with the usual modulation spaces when 1?p,q?8, and study their basic properties including their completeness. Given any g?S(Rd) such that supp g ???{?||?|?1} and ?k?Zd g (?-ak)=1, our modulation space consists of all tempered distributions f such
Masaharu Kobayashi, Hans Triebel
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Sobolev type inequalities in ultrasymmetric spaces with applications to Orlicz‐Sobolev embeddings
Journal of Function Spaces, Volume 3, Issue 2, Page 183-208, 2005., 2005 Let Dkf mean the vector composed by all partial derivatives of order k of a function f(x), x ∈ Ω ⊂ ℝn. Given a Banach function space A, we look for a possibly small space B such that ‖f‖B≤c‖|Dkf|‖A for all f∈C0k(Ω). The estimates obtained are applied to ultrasymmetric spaces A = Lφ,E, B = Lψ,E, giving some optimal (or rather sharp) relations between ...
Evgeniy Pustylnik, Lech Maligranda
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Extensions of the Hardy‐Littlewood inequalities for Schwarz symmetrization
International Journal of Mathematics and Mathematical Sciences, Volume 2004, Issue 59, Page 3129-3150, 2004., 2004 For a class of functions H:(0,∞)×ℝ+2→ℝ, including discontinuous functions of Carathéodory type, we establish that ∫ℝNH(|x|,u(x),v(x))dx≤∫ℝNH(|x|,u*(x),v*(x))dx, where u*(x) and v*(x) denote the Schwarz symmetrizations of nonnegative functions u and v.
H. Hajaiej, C. A. Stuart
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Sobolev spaces, Lebesgue points and maximal functions
, 2013 In this note we study boundedness of a large class of maximal operators in Sobolev spaces that includes the spherical maximal operator. We also study the size of the set of Lebesgue points with respect to convergence associated with such maximal ...
Hajlasz, Piotr, Liu, Zhuomin
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On the solvability of parabolic and hyperbolic problems with a boundary integral condition
International Journal of Mathematics and Mathematical Sciences, Volume 31, Issue 4, Page 201-213, 2002., 2002 We prove the existence, uniqueness, and the continuous dependence of a generalized solution upon the data of certain parabolic and hyperbolic equations with a boundary integral condition. The proof uses a functional analysis method based on a priori estimates established in nonclassical function spaces, and on the density of the range of the linear ...
Abdelfatah Bouziani
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