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1.
It is shown that if A?Ωn?{Jn} satisfies
nkσk(A)?(n?k+1)2 σk?1(A)
(k=1,2,…,n)
, where σk(A) denotes the sum of all kth order subpermanent of A, then Per[λJn+(1?λ)A] is strictly decreasing in the interval 0<λ<1.  相似文献   

2.
Let X and Y be Banach spaces, Y ?X, and let V be a neighborhood of zero in Y. We consider the equation G(λ, u) ≡ A(λ)u + F(λ, u) = 0, where G: [?d1, d1] × VX, G(λ, 0) = 0, and A(λ) is the Fréchet derivative of G with respect to u at (λ, 0). Furthermore, we assume that G is analytic with respect to λ and u. Bifurcation at a simple eigenvalue means that zero is a simple eigenvalue of A (0). Let μ(λ) be the simple eigenvalue of the perturbed operator A(λ) for λ near zero. Let djμ(0)j = 0, j = 0,…, m ? 1, dmμ(0)m Am ≠ 0, or μ(λ) ≡ 0. Under the nondegeneracy condition m = 1 the existence of a unique curve of solutions intersecting the trivial solution (λ, 0) at (0, 0) is well known. Furthermore the “Principle of Exchange of Stability” was established in this case. We show that in the degenerate case (m > 1) up to m bifurcating curves of solutions can exist and that at least one nontrivial curve exists if m is odd. Our approach supplies all curves of solutions near (0, 0) together with their direction of bifurcation and their linearized stability. The decisive fact is that Am is also the leading term of the bifurcation equation. A consequence is a “Generalized Principle of Exchange of Stability”, which means that adjacent solutions for the same λ have opposite stability properties in a weakened sense. For practical use we give a criterion for asymptotic stability or instability which follows from the construction of the curves of solutions themselves.  相似文献   

3.
For the variance of stationary renewal and alternating renewal processes Nn(·) the paper establishes upper and lower bounds of the form
?B1?varN8(0,x–Aλx?B2(0<x<∞)
, where λ=EN8(0,1), with constants A, B1 and B2 that depend on the first three moments of the interval distributions for the processes concerned. These results are consistent with the value of the constant A for a general stationary point process suggested by Cox in 1963 [1].  相似文献   

4.
Let C be a closed convex subset of a uniformly smooth Banach space. Let S(t) : CC be a semigroup of type ω. Then the generator A0 of S(t) has a dense domain in C. Moreover there is is an operator A such that: (i) A0 ? A and D(A) = C, (ii) A + gwI accretive, (iii) R(I + λA) ? C for λ > 0 and ωλ < 1, (iv) S(t)x = limn → ∞(I + (tn)A)?nx for every x?C.  相似文献   

5.
Let A and B be uniformly elliptic operators of orders 2m and 2n, respectively, m > n. We consider the Dirichlet problems for the equations (?2(m ? n)A + B + λ2nI)u? = f and (B + λ2nI)u = f in a bounded domain Ω in Rk with a smooth boundary ?Ω. The estimate ∥ u? ? u ∥L2(Ω) ? C? ¦ λ ¦?2n + 1(1 + ? ¦ λ ¦)?1 ∥ f ∥L2(Ω) is derived. This result extends the results of [7, 9, 10, 12, 14, 15, 18]by giving estimates up to the boundary, improving the rate of convergence in ?, using lower norms, and considering operators of higher order with variable coefficients. An application to a parabolic boundary value problem is given.  相似文献   

6.
For each t ? 0, let A(t) generate a contraction semigroup on a Banach space L. Suppose the solution of ut = ?A(t)u is given by an evolution operator V?(t, s). Conditions are given under which V?((t+s)?, s?) converges strongly as ? → 0 to a semigroup T(t) generated by the closure of A?f ≡ limT→∞(1T) ∝0TA(t)f dt.This result is applied to the following situation: Let B generate a contraction group S(t) and the closure of ?A + B generate a contraction semigroup S?(t). Conditions are given under which S(?t?) S?(t?) converges strongly to a semigroup generated by the closure of A?f ≡ limT→∞(1T) ∝ S(?t) AS(t)f dt. This work was motivated by and generalizes a result of Pinsky and Ellis for the linearized Boltzmann Equation.  相似文献   

7.
The two lowest eigenvalues E0(λ), E1(λ) of a symmetric double well tunnelling problem ?Δ + λ2V as λ → ∞ are considered and they are compared to the two lowest eigenvalues E?0(λ), E?1(λ) of ?Δ + λ2(V + W), where W is supported away from the well-bottoms of V. We determine the leading exponential splitting of various differences of the four numbers E0, E1, E?0, E?1. Related problems are discussed.  相似文献   

8.
A single serving queueing model is studied where potential customers are discouraged at the rate λn = λqn, 0 < q < 1, n is the queue length. The serving rate is μn = μ(1 ? qn), n = 0, 1,…. The spectral function is computed and the corresponding set of orthogonal polynomials is studied in detail. The slightly more general model with λn = λqn(1 + bqn), μn = μ(1 ? qn)(1 + bqn) and the analogous orthogonal polynomials are also investigated. In both cases a method developed by Pollaczek is used which has been used very successfully to study new sets of orthogonal polynomials by Askey and Ismail.  相似文献   

9.
For a sequence A = {Ak} of finite subsets of N we introduce: δ(A) = infm?nA(m)2n, d(A) = lim infn→∞ A(n)2n, where A(m) is the number of subsets Ak ? {1, 2, …, m}.The collection of all subsets of {1, …, n} together with the operation a ∪ b, (a ∩ b), (a 1 b = a ∪ b ? a ∩ b) constitutes a finite semi-group N (semi-group N) (group N1). For N, N we prove analogues of the Erdös-Landau theorem: δ(A+B) ? δ(A)(1+(2λ)?1(1?δ(A>))), where B is a base of N of the average order λ. We prove for N, N, N1 analogues of Schnirelmann's theorem (that δ(A) + δ(B) > 1 implies δ(A + B) = 1) and the inequalities λ ? 2h, where h is the order of the base.We introduce the concept of divisibility of subsets: a|b if b is a continuation of a. We prove an analog of the Davenport-Erdös theorem: if d(A) > 0, then there exists an infinite sequence {Akr}, where Akr | Akr+1 for r = 1, 2, …. In Section 6 we consider for N∪, N∩, N1 analogues of Rohrbach inequality: 2n ? g(n) ? 2n, where g(n) = min k over the subsets {a1 < … < ak} ? {0, 1, 2, …, n}, such that every m? {0, 1, 2, …, n} can be expressed as m = ai + aj.Pour une série A = {Ak} de sous-ensembles finis de N on introduit les densités: δ(A) = infm?nA(m)2m, d(A) = lim infn→∞ A(n)2nA(m) est le nombre d'ensembles Ak ? {1, 2, …, m}. L'ensemble de toutes les parties de {1, 2, …, n} devient, pour les opérations a ∪ b, a ∩ b, a 1 b = a ∪ b ? a ∩ b, un semi-groupe fini N, N ou un groupe N1 respectivement. Pour N, N on démontre l'analogue du théorème de Erdös-Landau: δ(A + B) ? δ(A)(1 + (2λ)?1(1?δ(A))), où B est une base de N d'ordre moyen λ. On démontre pour N, N, N1 l'analogue du théorème de Schnirelmann (si δ(A) + δ(B) > 1, alors δ(A + B) = 1) et les inégalités λ ? 2h, où h est l'ordre de base. On introduit le rapport de divisibilité des enembles: a|b, si b est une continuation de a. On démontre l'analogue du théorème de Davenport-Erdös: si d(A) > 0, alors il existe une sous-série infinie {Akr}, où Akr|Akr+1, pour r = 1, 2, … . Dans le Paragraphe 6 on envisage pour N, N, N1 les analogues de l'inégalité de Rohrbach: 2n ? g(n) ? 2n, où g(n) = min k pour les ensembles {a1 < … < ak} ? {0, 1, 2, …, n} tels que pour tout m? {0, 1, 2, …, n} on a m = ai + aj.  相似文献   

10.
This paper continues the study of the inverse balayage problem for Markov chains. Let X be a Markov chain with state space A ? B2, let v be a probability measure on B2 and let M(v) consist of probability measures μ on A whose X-balayage onto B2 is v. The faces of the compact, convex set M(v) are characterized. For fixed μ?M(v) the set M(μ,v) of the measures ? of the form ?(·) = Pμ{X(S) ? ·}, where S is a randomized stopping time, is analyzed in detail. In particular, its extreme points and edge are explicitly identified. A naturally defined reversed chain X, for which v is an inverse balayage of μ, is introduced and the relation between X and X^ is studied. The question of which ? ? M(μ, v) admit a natural stopping time S? of X (not involving an independent randomization) such that ?(·) = Pμ{X(S?) ? ·}, is shown to have rather different answers in discrete and continuous time. Illustrative examples are presented.  相似文献   

11.
A series of inequalities are developed relating the spectral radius ?(A ° B) of the Schur product A ° B of two nonnegative matrices A and B with those of ?(A ° A) and ?(B ° B) yielding ?(A ° B) ? [?(A ° A)?(B ° B)]12. As a corollary it is proved that the spectral radius of the Schur powers ?r = ?(A[r]), A[r] = A ° A °?°A (r factors) satisfies (1r)log ?r is decreasing while (1r?1)log ?r is increasing, the latter provided A is a stochastic matrix. The entropy of a finite stationary Markov chain is identified with d?rdr|r=1. A number of majorization comparisons for the spectral radius of Schur powers is given.  相似文献   

12.
If A and B are C1-algebras there is, in general, a multiplicity of C1-norms on their algebraic tensor product AB, including maximal and minimal norms ν and α, respectively. A is said to be nuclear if α and ν coincide, for arbitrary B. The earliest example, due to Takesaki [11], of a nonnuclear C1-algebra was Cl1(F2), the C1-algebra generated by the left regular representation of the free group on two generators F2. It is shown here that W1-algebras, with the exception of certain finite type I's, are nonnuclear.If C1(F2) is the group C1-algebra of F2, there is a canonical homomorphism λl of C1(F2) onto Cl1(F2). The principal result of this paper is that there is a norm ζ on Cl1(F2) ⊙ Cl1(F2), distinct from α, relative to which the homomorphism λ ⊙ λl: C1(F2) ⊙ C1(F2) → Cl1(F2) ⊙ Cl1(F2) is bounded (C1(F2) ⊙ C1(F2) being endowed with the norm α). Thus quotients do not, in general, respect the norm α; a consequence of this is that the set of ideals of the α-tensor product of C1-algebras A and B may properly contain the set of product ideals {I ? B + A ? J: I ? A, J ? B}.Let A and B be C1-algebras. If A or B is a W1-algebra there are on AB certain C1-norms, defined recently by Effros and Lance [3], the definitions of which take account of normality. In the final section of the paper it is shown by example that these norms, with α and ν, can be mutually distinct.  相似文献   

13.
Asymptotic results are obtained for pA(k)(n), the kth difference of the function pA(n) which is the number of partitions of n into integers from A. Under certain restrictions on A it is shown that
PA(k+1)(n)PA(k)(n) = O(n?1/2) (n→ ∫)
thereby verifying for these A a conjecture of Bateman and Erdös.  相似文献   

14.
We study degeneration for ? → + 0 of the two-point boundary value problems
τ?±u := ?((au′)′ + bu′ + cu) ± xu′ ? κu = h, u(±1) = A ± B
, and convergence of the operators T?+ and T?? on L2(?1, 1) connected with them, T?±u := τ?±u for all
u?D(T?±, D(T?±) := {u ? L2(?1, 1) ∣ u″ ? L2(?1, 1) &; u(?1) = u(1) = O}, T0+u: = xu′
for all
u?D(TO+), D(TO+) := {u ? L2(?1, 1) ∣ xu′ ? L2(?1, 1) &; u(?1) = u(1) = O}
. Here ? is a small positive parameter, λ a complex “spectral” parameter; a, b and c are real b-functions, a(x) ? γ > 0 for all x? [?1, 1] and h is a sufficiently smooth complex function. We prove that the limits of the eigenvalues of T?+ and of T?? are the negative and nonpositive integers respectively by comparison of the general case to the special case in which a  1 and bc  0 and in which we can compute the limits exactly. We show that (T?+ ? λ)?1 converges for ? → +0 strongly to (T0+ ? λ)?1 if R e λ > ? 12. In an analogous way, we define the operator T?+, n (n ? N in the Sobolev space H0?n(? 1, 1) as a restriction of τ?+ and prove strong convergence of (T+?,n ? λ)?1 for ? → +0 in this space of distributions if R e λ > ?n ? 12. With aid of the maximum principle we infer from this that, if h?C1, the solution of τ?+u ? λu = h, u(±1) = A ± B converges for ? → +0 uniformly on [?1, ? ?] ∪ [?, 1] to the solution of xu′ ? λu = h, u(±1) = A ± B for each p > 0 and for each λ ? C if ? ?N.Finally we prove by duality that the solution of τ??u ? λu = h converges to a definite solution of the reduced equation uniformly on each compact subset of (?1, 0) ∪ (0, 1) if h is sufficiently smooth and if 1 ? ?N.  相似文献   

15.
It is shown, for n ? m ? 1, that there exist inner maps Φ: BnBm with boundary values Φ1: Bn → Bm such that σm(A) = σn1?1(A)). where σn and σm are the Haar measures on ?Bn and ?Bm, respectively, and A ? Bn is an arbitrary Borel set.  相似文献   

16.
The composition of two Calderón-Zygmund singular integral operators is given explicitly in terms of the kernels of the operators. For φ?L1(Rn) and ε = 0 or 1 and ∝ φ = 0 if ε = 0, let Ker(φ) be the unique function on Rn + 1 homogeneous of degree ?n ? 1 of parity ε that equals φ on the hypersurface x0 = 1. Let Sing(φ, ε) denote the singular integral operator Sing(φ, ε)f(x0, x) = limδ → 0 ∝∝¦y0¦ ? δf(x0 ? y0, x ? y), Ker(φ)(y0, y) dy0 dy, which exists under suitable growth conditions on ? and φ. Then Sing(φ, ε1) Sing(ψ, ε2)f = ?2π2(∝ φ)(∝ ψ)f + Sing(A, ε1, + ε2)f, where
A(x)=limδ→0∫∫δ?|λ|?δ?1|λ+1|?1+?2n|λ|?2θ(x+λ(x?y))ψ(y)dλdy
(with notation ¦t¦0a = ¦t¦aand ¦t¦1a = ¦t¦asgn t). This result is used to show that the mapping ψA is a classical pseudo-differential operator of order zero if φ is smooth, with top-order symbol
ω0(x,?)=?πiθ(?)∫θ(x?y)sgn y·?dy if ?1=1
,
=?2θ(?)∫θ(x?y)log|y·?|dy if ?1=0
where θ(ξ) is a cut-off function. These results are generalized to singular integrals with mixed homogeneity.  相似文献   

17.
Let A = (A1 ¦ A2 ¦ ··· ¦ Ar) and B = (B1 ¦ B2 ¦ ··· ¦ Br) be column-wise partitioned matrices over complex numbers. Then an extended Kronecker product is A ⊙ B = (A1 ? B1 ¦ ··· ¦ Ar ? Br), where Ai ? Bi is the Kronecker product of Ai and Bi. Some properties of an extended Kronecker product of matrices are investigated. The properties of the solutions of the systems of linear equations whose coefficient matrices are extended Kronecker products of matrices are studied.  相似文献   

18.
This paper discusses the problem of classifying holomorphic operator functions up to equivalence. A survey is given in 41 of the main results about equivalence classes of holomorphic matrix functions and holomorphic Fredholm-operator functions. In 42, it is shown that given a holomorphic function A on a bounded domain Ω into a space of bounded linear operators between two Banach spaces, it is possible to extend the operators A(λ) (for each λ ? Ω) by an identity operator IZ in such a way that the extended operator function A(·) ⊕ IZ is equivalent on Ω to a linear function of λ, T ? λI. Other versions of this “linearization by extension” are described, including the cases of entire functions and polynomials (where Ω = C). As an application of these results, we consider the operator function equation A2(λ) Z2(λ) + Z1(λ) A1(λ) = C(λ), λ ? Ω, (1) and explicitly construct the solutions Z1 and Z2. The formulas for Z1 and Z2 seem to be new, even when A1, A2 and C are matrix polynomials. The existence of solutions of (1) makes it possible to analyze an operator function A whose spectrum decomposes into pairwise disjoint compact subsets σ1, …, σn of Ω. In this case, a suitable extension of A is equivalent on Ω to a direct sum of operator functions, A1, …, An, such that the spectrum of Ai is σi (i = 1, …, n). In the final section of the paper, we discuss the relation between local and global equivalence on Ω, and show that there exist operator functions A and B which are locally equivalent on Ω, but admit no extensions (of the sort considered in this paper) which are globally equivalent on Ω.  相似文献   

19.
Let m and vt, 0 ? t ? 2π be measures on T = [0, 2π] with m smooth. Consider the direct integral H = ⊕L2(vt) dm(t) and the operator (L?)(t, λ) = e?iλ?(t, λ) ? 2e?iλtT ?(s, x) e(s, t) dvs(x) dm(s) on H, where e(s, t) = exp ∫stTdvλ(θ) dm(λ). Let μt be the measure defined by T?(x) dμt(x) = ∫0tT ?(x) dvs dm(s) for all continuous ?, and let ?t(z) = exp[?∫ (e + z)(e ? z)?1t(gq)]. Call {vt} regular iff for all t, ¦?t(e)¦ = ¦?(e for 1 a.e.  相似文献   

20.
We prove a Szegö-type theorem for some Schrödinger operators of the form H = ?1 + V with V smooth, positive and growing like V0¦x¦k, k > 0. Namely, let πλ be the orthogonal projection of L2 onto the space of the eigenfunctions of H with eigenvalue ?λ; let A be a 0th order self-adjoint pseudo-differential operator relative to Beals-Fefferman weights ?(x, ξ) = 1, Φ(x, ξ) = (1 + ¦ξ¦2 + V(x))12 and with total symbol a(x, ξ); and let fC(R). Then
limλ→∞1rankπλtrf(πλλ)=limλ→∞1vol(H(x, ξ)?λ)H?λf(a(x, ξ))dxdξ
(assuming one limit exists).  相似文献   

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