共查询到20条相似文献,搜索用时 31 毫秒
1.
We study the embeddings E : W(X(Ω), Y(Ω)) ↪ Z(Ω), where X(Ω), Y(Ω) and Z(Ω) are rearrangement–invariant Banach function spaces (BFS) defined on a generalized ridged domain Ω, and W denotes a first–order Sobolev–type space. We obtain two–sided estimates for the measure of non–compactness of E when Z(Ω) = X(Ω) and, in turn, necessary and sufficient conditions for a Poincaré–type inequality to be valid and also for E to be compact. The results are used to analyse the example of a trumpet–shaped domain Ω in Lorentz spaces. We consider the problem of determining the range of possible target spaces Z(Ω), in which case we prove that the problem is equivalent to an analogue on the generalized ridge Γ of Ω. The range of target spaces Z(Ω) is determined amongst a scale of (weighted) Lebesgue spaces for “rooms and passages” and trumpet–shaped domains. 相似文献
2.
《偏微分方程通讯》2013,38(7-8):1409-1425
3.
Lars Diening 《Mathematische Nachrichten》2004,268(1):31-43
We study the Riesz potentials Iαf on the generalized Lebesgue spaces Lp(·)(?d), where 0 < α < d and Iαf(x) ? ∫equation/tex2gif-inf-3.gif |f(y)| |x – y|α – d dy. Under the assumptions that p locally satisfies |p(x) – p(x)| ≤ C/(– ln |x – y|) and is constant outside some large ball, we prove that Iα : Lp(·)(?d) → Lp?(·)(?d), where . If p is given only on a bounded domain Ω with Lipschitz boundary we show how to extend p to on ?d such that there exists a bounded linear extension operator ? : W1,p(·)(Ω) ? (?d), while the bounds and the continuity condition of p are preserved. As an application of Riesz potentials we prove the optimal Sobolev embeddings Wk,p(·)(?d) ?Lp*(·)(Rd) with and W1,p(·)(Ω) ? Lp*(·)(Ω) for k = 1. We show compactness of the embeddings W1,p(·)(Ω) ? Lq(·)(Ω), whenever q(x) ≤ p*(x) – ε for some ε > 0. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
4.
It has been shown by Trudinger and Moser that for normalized functions u of the Sobolev space ??1, N (Ω), where Ω is a bounded domain in ?N, one has ∫Ω exp(αN|u|N/(N ? 1))dx ≤ CN, where αN is an explicit constant depending only on N, and CN is a constant depending only on N and Ω. Carleson and Chang proved that there exists a corresponding extremal function in the case that Ω is the unit ball in ?N. In this paper we give a new proof, a generalization, and a new interpretation of this result. In particular, we give an explicit sequence that is maximizing for the above integral among all normalized “concentrating sequences.” As an application, the existence of a nontrivial solution for a related elliptic equation with “Trudinger‐Moser” growth is proved. © 2002 John Wiley & Sons, Inc. 相似文献
5.
Ester Giarrusso 《Mathematische Nachrichten》2000,213(1):89-104
Given a bounded regular domain Ω in ℝN, we study existence and asymptotic behaviour of the solutions of the equation Δu + |Du|q = f(u) in Ω, which diverge on ∂Ω. We extend and complete some results contained in [4]. 相似文献
6.
M. Bildhauer M. Fuchs V. G. Osmolovskii 《Mathematical Methods in the Applied Sciences》2002,25(4):289-308
We consider the problem of minimizing 0<p<1, h∈?, σ>0, among functions u:?d?Ω→?d, u∣?Ω=0, and measurable characteristic functions χ:Ω→?. Here ?+h, ??, denote quadratic potentials defined on the space of all symmetric d×d matrices, h is the minimum energy of ?+h and ε(u) denotes the symmetric gradient of the displacement field. An equilibrium state û, χ?, of I [·,·,h, σ] is termed one‐phase if χ?≡0 or χ?≡1, two‐phase otherwise. We investigate the way in which the distribution of phases is affected by the choice of the parameters h and σ. Copyright 2002 John Wiley & Sons, Ltd. 相似文献
7.
In this article, the authors establish the conditions for the extinction of solutions, in finite time, of the fast diffusive polytropic filtration equation u t ?=?div(|?u m | p?2?u m )?+?a∫Ω u q (y,?t)dy with a, q, m?>?0, p?>?1, m(p???1)?1, in a bounded domain Ω???R N (N?>?2). More precisely speaking, it is shown that if q?>?m(p???1), any non-negative solution with small initial data vanishes in finite time, and if 0?q?m(p???1), there exists a solution which is positive in Ω for all t?>?0. For the critical case q?=?m(p???1), whether the solutions vanish in finite time or not depends on the comparison between a and μ, where μ?=?∫?Ωφ p?1(x)dx and φ is the unique positive solution of the elliptic problem ?div(|?φ| p?2?φ)?=?1, x?∈?Ω; φ(x)?=?0, x?∈??Ω. 相似文献
8.
J. M. Arrieta J. W. Cholewa Tomasz Dlotko A. Rodríguez–Bernal 《Mathematische Nachrichten》2007,280(15):1643-1663
The Cauchy problem for a semilinear second order parabolic equation ut = Δu + f (x, u,?u), (t, x) ∈ ?+ × ?N , is considered within the semigroup approach in locally uniform spaces (?N ). Global solvability, dissipativeness and the existence of an attractor are established under the same assumptions as for problems in bounded domains. In particular, the condition sf (s, 0 ) < 0, |s | > s0 > 0, together with gradient's “subquadratic” growth restriction, are shown to guarantee the existence of an attractor for the above mentioned equation. This result cannot be located in the previous references devoted to reaction‐diffusion equations in the whole of ?N . (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
9.
Gregor Nickel 《Mathematische Nachrichten》2000,212(1):101-116
In this paper, we study nonautonomous Cauchy problems (NCP) {u̇(t) = A(t)u(t)u(s) = x ∈ X for a family of linear operators (A(t))t∈I on some Banach space X by means of evolution semigroups. In particular, we characterize “stability” in the so called “hyperbolic case” on the level of evolution semigroups and derive a product formula for the solutions of (NCP). Moreover, in Section 4 we connect the “hyperbolic” and the “parabolic” case by showing, that integrals ∫ts A(τ) dτ always define generators. This yields another product formula. 相似文献
10.
《Comptes Rendus de l'Academie des Sciences Series IIA Earth and Planetary Science》1998,326(6):697-702
In this paper we prove a necessary and a sufficient conditions for the existence of a positive solution of the equation (P − μW)u = 0 in Ω, where P is a critical, secondorder, linear elliptic operator which is defined on a subdomain Ω of a noncompact Riemannian manifold X. It is assumed that W ε Cδ (Ω) is a “weak” perturbation and μ < 0 is small enough. 相似文献
11.
Kernel regression estimation for continuous spatial processes 总被引:1,自引:0,他引:1
We investigate here a kernel estimate of the spatial regression function r(x) = E(Y
u | X
u = x), x ∈ ℝd, of a stationary multidimensional spatial process { Z
u = (X
u, Y
u), u ∈ ℝ
N
}. The weak and strong consistency of the estimate is shown under sufficient conditions on the mixing coefficients and the
bandwidth, when the process is observed over a rectangular domain of ℝN. Special attention is paid to achieve optimal and suroptimal strong rates of convergence. It is also shown that this suroptimal
rate is preserved by using a suitable spatial sampling scheme.
相似文献
12.
Michael Bildhauer Martin Fuchs Victor Osmolovskii 《Mathematical Methods in the Applied Sciences》2002,25(2):149-178
We consider the problem of minimizing among functions u:?d?Ω→?d, u∣?Ω=0, and measurable subsets E of Ω. Here fh+, f? denote quadratic potentials defined on Ω¯×{symmetric d×d matrices}, h is the minimum energy of fh+ and ε(u) is the symmetric gradient of the displacement field u. An equilibrium state û, Ê of J(u,E) is called one‐phase if E=?? or E=Ω, two‐phase otherwise. For two‐phase states, σ∣?E∩Ω∣ measures the effect of the separating surface, and we investigate the way in which the distribution of phases is affected by the choice of the parameters h??, σ>0. Additional results concern the smoothness of two‐phase equilibrium states and the behaviour of inf J(u,E) in the limit σ↓0. Moreover, we discuss the case of additional volume force potentials, and extend the previous results to non‐zero boundary values. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
13.
In the first part of the paper we establish the existence of a boundary trace for positive solutions of the equation ?Δu + g(x, u) = 0 in a smooth domain Ω ? ?N, for a general class of positive nonlinearities. This class includes every space independent, monotone increasing g which satisfies the Keller‐Osserman condition as well as degenerate nonlinearities gα,q of the form gα,q (x, u) = d(x, ?Ω)α |u|q?1 u, with α > ?2 and q > 1. The boundary trace is given by a positive regular Borel measure which may blow up on compact sets. In the second part we concentrate on the family of nonlinearities {gα,q}, determine the critical value of the exponent q (for fixed α > ?2) and discuss (a) positive solutions with an isolated singularity, for subcritical nonlinearities and (b) the boundary value problem for ?Δu + gα,q (x, u) = 0 with boundary data given by a positive regular Borel measure (possibly unbounded). We show that, in the subcritical case, the problem possesses a unique solution for every such measure. © 2003 Wiley Periodicals, Inc. 相似文献
14.
Tosio Kato 《Journal d'Analyse Mathématique》1995,67(1):281-306
We consider the nonlinear Schrödinger equation (NLS) (see below) with a general “potential”F(u), for which there are in general no conservation laws. The main assumption onF(u) is a growth rateO(|u| k ) for large |u|, in addition to some smoothness depending on the problem considered. A uniqueness theorem is proved with minimal smoothness assumption onF andu, which is useful in eliminating the “auxiliary conditions” in many cases. A new local existence theorem forH S -solutions is proved using an auxiliary space of Lebesgue type (rather than Besov type); here the main assumption is thatk≤1+4/(m?2s) ifs/2,k<∞ ifs=m/2 (no assumption ifs>m/2). Moreover, a general existence theorem is proved for globalH S -solutions with small initial data, under the main additional condition thatF(u)=O(|u|1+4/m) for small |u|; in particularF(u) need not be (quasi-) homogeneous or in the critical case. The results are valid for alls≥0 ifm≤6; there are some restrictions ifm≥7 and ifF(u) isnot a polynomial inu and $\bar u$ . 相似文献
15.
This article deals with a class of nonlocal and degenerate quasilinear parabolic equation u t = f(u)(Δu + a∫Ω u(x, t)dx ? u) with homogeneous Dirichlet boundary conditions. The local existence of positive classical solutions is proved by using the method of regularization. The global existence of positive solutions and blow-up criteria are also obtained. Furthermore, it is shown that, under certain conditions, the solutions have global blow-up property. When f(s) = s p , 0 < p ≤ 1, the blow-up rate estimates are also obtained. 相似文献
16.
Thomas I Seidman 《Journal of Differential Equations》1985,60(2):151-173
We obtain a strict coercivity estimate, (generalizing that of T. I. Seidman [J. Differential Equations 19 (1975), 242–257] in considering spatial variation) for second order elliptic operators A: u ? ?▽ · γ(·, ▽u) with γ “radial in the gradient” ?γ(·, ξ) = a(·, |ξ|)ξ for ξ ? m. The estimate is then applied to obtain existence of solutions of boundary value problems: with Dirichlet conditions. 相似文献
17.
A digraph G = (V, E) is primitive if, for some positive integer k, there is a u → v walk of length k for every pair u, v of vertices of V. The minimum such k is called the exponent of G, denoted exp(G). The exponent of a vertex u ∈ V, denoted exp(u), is the least integer k such that there is a u → v walk of length k for each v ∈ V. For a set X ⊆ V, exp(X) is the least integer k such that for each v ∈ V there is a X → v walk of length k, i.e., a u → v walk of length k for some u ∈ X. Let F(G, k) : = max{exp(X) : |X| = k} and F(n, k) : = max{F(G, k) : |V| = n}, where |X| and |V| denote the number of vertices in X and V, respectively. Recently, B. Liu and Q. Li proved F(n, k) = (n − k)(n − 1) + 1 for all 1 ≤ k ≤ n − 1. In this article, for each k, 1 ≤ k ≤ n − 1, we characterize the digraphs G such that F(G, k) = F(n, k), thereby answering a question of R. Brualdi and B. Liu. We also find some new upper bounds on the (ordinary) exponent of G in terms of the maximum outdegree of G, Δ+(G) = max{d+(u) : u ∈ V}, and thus obtain a new refinement of the Wielandt bound (n − 1)2 + 1. © 1998 John Wiley & Sons, Inc. J. Graph Theory 28: 215–225, 1998 相似文献
18.
Qing Miao 《Applicable analysis》2013,92(12):1893-1905
For a given bounded domain Ω in R N with smooth boundary ?Ω, we give sufficient conditions on f so that the m-Laplacian equation △ m u = f(x, u, ?u) admits a boundary blow-up solution u ∈ W 1,p (Ω). Our main results are new and extend the results in J.V. Concalves and Angelo Roncalli [Boundary blow-up solutions for a class of elliptic equations on a bounded domain, Appl. Math. Comput. 182 (2006), pp. 13–23]. Our approach employs the method of lower–upper solution theorem, fixed point theory and weak comparison principle. 相似文献
19.
Laurent Véron 《Mathematische Zeitschrift》2013,273(1-2):1-17
If Ω is a bounded domain in ${\mathbb{R}^N}$ , we study conditions on a Radon measure μ on ?Ω for solving the equation ?Δu + e u ? 1 = 0 in Ω with u = μ on ?Ω. The conditions are expressed in terms of Orlicz capacities. 相似文献
20.
Marek Biskup 《Random Structures and Algorithms》2011,39(2):210-227
We study the asymptotic growth of the diameter of a graph obtained by adding sparse “long” edges to a square box in ${\mathbb Z}^dWe study the asymptotic growth of the diameter of a graph obtained by adding sparse “long” edges to a square box in ${\mathbb Z}^d$. We focus on the cases when an edge between x and y is added with probability decaying with the Euclidean distance as |x ? y|?s+o(1) when |x ? y| → ∞. For s ∈ (d, 2d) we show that the graph diameter for the graph reduced to a box of side L scales like (log L)Δ+o(1) where Δ?1 := log2(2d/s). In particular, the diameter grows about as fast as the typical graph distance between two vertices at distance L. We also show that a ball of radius r in the intrinsic metric on the (infinite) graph will roughly coincide with a ball of radius exp{r1/Δ+o(1)} in the Euclidean metric. © 2010 Wiley Periodicals, Inc. Random Struct. Alg., 39, 210‐227, 2011 相似文献