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Alessia Ascanelli 《Journal of Mathematical Analysis and Applications》2008,341(1):694-706
We consider second order degenerate hyperbolic Cauchy problems, the degeneracy coming either from low regularity (less than Lipschitz continuity) of the coefficients with respect to time, or from weak hyperbolicity. In the weakly hyperbolic case, we assume an intermediate condition between effective hyperbolicity and the Levi condition. We construct the fundamental solution and study the propagation of singularities using an unified approach to these different kinds of degeneracy. 相似文献
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The purpose of this work is to prove a theorem of propagation of singularities for a class of non-real pseudo-differential operator with multiple characteristics. The main tools are L2 estimates on the time-dependent Schrödinger equation related toP. We extend here the results of [6]; we improve the results announced by the second author in [7]. The second part of this work consists in an extension of the result of [5] to complex-valued symbols. 相似文献
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Summary In this paper we consider partial differential operators of the type P(x, D)= Pm(D)+Q(x, D), where the constant coefficient principal part Pm is supposed to be hyperbolic-elliptic. We study the propagation of Gevrey singularities for solutions u of the equation P(x, D) u=f, for ultradistributions f, finding exactly to which spaces of ultradistribuiions u microlocally belongs. The results are obtained by constructing a fundamental solution for P when the lower order part Q is with constant coefficients, and a parametrix otherwise. 相似文献
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Luisa Zanghirati 《Annali di Matematica Pura ed Applicata》1984,138(1):255-265
Summary
In [4]L. Hörmander has given sufficient conditions for propagation of C
singularities for solutions of linear differential operators P with constant coefficients in terms of limit operators called «localization of P at infinity». In this paper a result (Theorem 1.2) of the same type concerning the propagation of Gevrey singularities is given. 相似文献
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We prove that one-dimensional reflectionless Schrödinger operators with spectrum a homogeneous set in the sense of Carleson, belonging to the class introduced by Sodin and Yuditskii, have purely absolutely continuous spectra. This class includes all earlier examples of reflectionless almost periodic Schrödinger operators. In addition, we construct examples of reflectionless Schrödinger operators with more general types of spectra, given by the complement of a Denjoy-Widom-type domain in C, which exhibit a singular component. 相似文献
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Jipu Ma 《Frontiers of Mathematics in China》2008,3(2):305-316
Let E and F be Banach spaces, f: U ⊂ E → F be a map of C
r
(r ⩾ 1), x
0 ∈ U, and ft (x
0) denote the FréLechet differential of f at x
0. Suppose that f′(x
0) is double split, Rank(f′(x
0)) = ∞, dimN(f′(x
0)) > 0 and codimR(f′(x
0)) s> 0. The rank theorem in advanced calculus asks to answer what properties of f ensure that f(x) is conjugate to f′(x
0) near x
0. We have proved that the conclusion of the theorem is equivalent to one kind of singularities for bounded linear operators,
i.e., x
0 is a locally fine point for f′(x) or generalized regular point of f(x); so, a complete rank theorem in advanced calculus is established, i.e., a sufficient and necessary condition such that the
conclusion of the theorem to be held is given.
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An explicit construction of all the homogeneous holomorphic Hermitian vector bundles over the unit disc D is given. It is shown that every such vector bundle is a direct sum of irreducible ones. Among these irreducible homogeneous holomorphic Hermitian vector bundles over D, the ones corresponding to operators in the Cowen–Douglas class Bn(D) are identified. The classification of homogeneous operators in Bn(D) is completed using an explicit realization of these operators. We also show how the homogeneous operators in Bn(D) split into similarity classes. 相似文献
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Cheng-qin QU 《应用数学学报(英文版)》2013,29(1):117-122
We consider the homogeneous Cantor sets which are generalization of symmetric perfect sets, and give a formula of the exact Hausdorff measures for a class of such sets. 相似文献
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Surjit Singh Khurana 《Journal of Mathematical Analysis and Applications》2009,350(1):290-293
Let X be a completely regular Hausdorff space, E Hausdorff a quasi-complete locally convex space and Cb(X,E) all E-valued bounded continuous functions on X with strict topologies βt, , . We prove that a linear continuous mapping T:Cb(X,E)→E arises from a scalar measure μ∈(Cb′(X),βz)(z=t,∞,τ) if and only if g(T(f))=0 whenever g○f=0 for any f∈Cb(X,E), g∈E′. 相似文献
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Moritz Doll 《Mathematische Nachrichten》2019,292(9):1941-1955
Let H be a self‐adjoint isotropic elliptic pseudodifferential operator of order 2. Denote by the solution of the Schrödinger equation with initial data . If u0 is compactly supported the solution is smooth for small , but not for all t. We determine the wavefront set of in terms of the wavefront set of u0 and the principal and subprincipal symbol of H. 相似文献