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1.
We consider the multiparameter eigenvalue problem (Tr + ∑s = 1kλsVrs) xr = 0, xr ≠ 0, 1 ? r ? k, where Tr and Vrs are self-adjoint linear operators on Hilbert spaces Hr, the Vrs being bounded. The problem may be posed in either ⊕r = 1kHr or ⊕r = 1kHr and we develop variational approaches for both settings. We explore the rôles played in both settings by C ={λ ∈ Rk|ks=1λs(Vrsxr,xr ? 0 for some nonozero and related cones in Rk. We also compare certain geometrical conditions on C with analytical definiteness conditions already in the literature.  相似文献   

2.
In this paper we study the linked nonlinear multiparameter system
yrn(Xr) + MrYr + s=1k λs(ars(Xr) + Prs) Yr(Xr) = 0, r = l,…, k
, where xr? [ar, br], yr is subject to Sturm-Liouville boundary conditions, and the continuous functions ars satisfy ¦ A ¦ (x) = detars(xr) > 0. Conditions on the polynomial operators Mr, Prs are produced which guarantee a sequence of eigenfunctions for this problem yn(x) = Πr=1kyrn(xr), n ? 1, which form a basis in L2([a, b], ¦ A ¦). Here [a, b] = [a1, b1 × … × [ak, bk].  相似文献   

3.
Let H = ?Δ + V, where the potential V is spherically symmetric and can be decomposed as a sum of a short-range and a long-range term, V(r) = VS(r) + VL. Let λ = lim supr→∞VL(r) < ∞ (we allow λ = ? ∞) and set λ+ = max(λ, 0). Assume that for some r0, VL(r) ?C2k(r0, ∞) and that there exists δ > 0 such that (ddr)jVL(r) · (λ+ ? VL(r) + 1)?1 = O(r?jδ), j = 1,…, 2k, as r → ∞. Assume further that 1(dr¦ VL(r)¦12) = ∞ and that 2 > 1. It is shown that: (a) The restriction of H to C(Rn) is essentially self-adjoint, (b) The essential spectrum of H contains the closure of (λ, ∞). (c) The part of H over (λ, ∞) is absolutely continuous.  相似文献   

4.
Let Δ(α + β) = |Hλ2?r+1| where Hr is the complete symmetric function in (α1 + β1), (α2 + β2), …, (αn + βn). It is proved that Δ(α + β) ? Δ(α) + Δ(β). This inequality is generalised for certain symmetric functions defined by Littlewood. Let Ω(α + β) = |Qλ2?r+1staggered(α + β) (t, k1, k2, …, km)|. Then we prove that Ω(α + β) ? Ω(α) + Ω(β). Here λ1, λ2, λ3, …, λn is a partition such that λn > λn?1 > ··· > λ2 > λ1.  相似文献   

5.
We suppose that K is a countable index set and that Λ = {λk¦ k ? K} is a sequence of distinct complex numbers such that E(Λ) = {eλkt¦ λk ? Λ} forms a Riesz (strong) basis for L2[a, b], a < b. Let Σ = {σ1, σ2,…, σm} consist of m complex numbers not in Λ. Then, with p(λ) = Πk = 1m (λ ? σk), E(Σ ∪ Λ) = {eσ1t…, eσmt} ∪ {eλktp(λk)¦ k ? K} forms a Riesz (strong) bas Sobolev space Hm[a, b]. If we take σ1, σ2,…, σm to be complex numbers already in Λ, then, defining p(λ) as before, E(Λ ? Σ) = {p(λk) eλkt¦ k ? K, λk ≠ σj = 1,…, m} forms a Riesz (strong) basis for the space H?m[a, b]. We also discuss the extension of these results to “generalized exponentials” tneλkt.  相似文献   

6.
In this paper we are constructing a recurrence relation of the form
i=0rωi(k)mk+i{λ} [f] = ω(k)
for integrals (called modified moments)
mk{λ}[f]df=?11 f(x)Ck(λ)(x)dx (k = 0,1,…)
in which Ck(λ) is the k-th Gegenbauer polynomial of order λ(λ > ?12), and f is a function satisfying the differential equation
i=0n Pi(x)f(i)(x) = p(x) (?1?x?1)
of order n, where p0, p1, …, pn ? 0 are polynomials, and mkλ[p] is known for every k. We give three methods of construction of such a recurrence relation. The first of them (called Method I) is optimum in a certain sense.  相似文献   

7.
Let f(z), an analytic function with radius of convergence R (0 < R < ∞) be represented by the gap series ∑k = 0ckzλk. Set M(r) = max¦z¦ = r ¦f(z)¦, m(r) = maxk ? 0{¦ ck ¦ rλk}, v(r) = maxk ¦ ¦ ck ¦ rλk = m(r)} and define the growth constants ?, λ, T, t by
?λ=lim supr→R inf{log[Rr /(R?r)]?1log+log+M(r)}
, and if 0 < ? < ∞,
Tt=lim supr→R inf{[Rr /(R?r)]??log+M(r)}
. Then, assuming 0 < t < T < ∞, we obtain a decomposition theorem for f(z).  相似文献   

8.
Given a set S of positive integers let ZkS(t) denote the number of k-tuples 〈m1, …, mk〉 for which mi ∈ S ? [1, t] and (m1, …, mk) = 1. Also let PkS(n) denote the probability that k integers, chosen at random from S ? [1, n], are relatively prime. It is shown that if P = {p1, …, pr} is a finite set of primes and S = {m : (m, p1pr) = 1}, then ZkS(t) = (td(S))k Πν?P(1 ? 1pk) + O(tk?1) if k ≥ 3 and Z2S(t) = (td(S))2 Πp?P(1 ? 1p2) + O(t log t) where d(S) denotes the natural density of S. From this result it follows immediately that PkS(n) → Πp?P(1 ? 1pk) = (ζ(k))?1 Πp∈P(1 ? 1pk)?1 as n → ∞. This result generalizes an earlier result of the author's where P = ? and S is then the whole set of positive integers. It is also shown that if S = {p1x1prxr : xi = 0, 1, 2,…}, then PkS(n) → 0 as n → ∞.  相似文献   

9.
If r, k are positive integers, then Tkr(n) denotes the number of k-tuples of positive integers (x1, x2, …, xk) with 1 ≤ xin and (x1, x2, …, xk)r = 1. An explicit formula for Tkr(n) is derived and it is shown that limn→∞Tkr(n)nk = 1ζ(rk).If S = {p1, p2, …, pa} is a finite set of primes, then 〈S〉 = {p1a1p2a2psas; piS and ai ≥ 0 for all i} and Tkr(S, n) denotes the number of k-tuples (x1, x3, …, xk) with 1 ≤ xin and (x1, x2, …, xk)r ∈ 〈S〉. Asymptotic formulas for Tkr(S, n) are derived and it is shown that limn→∞Tkr(S, n)nk = (p1 … pa)rkζ(rk)(p1rk ? 1) … (psrk ? 1).  相似文献   

10.
11.
Let λ1 and λN be, respectively, the greatest and smallest eigenvalues of an N×N hermitian matrix H=(hij), and x=(x1,x2,…,xN) with (x,x)=1. Then, it is known that (1) λ1?(x,Hx)?λN and (2) if, in addition, H is positive definite, 1N)21λN?(x,Hx)(x,H?1x)?1. Assuming that y=(y1,y2,…, yN) and |yi|?1, i=1,2,…,N, it is shown in this paper that these inequalities remain true if H and H?1 are, respectively, replaced by the Hadamard products M(y)1H and M(y)1H?1, where M(y) is a matrix defined by M(y)=(δij+(1?δij)yiyj. Subsequently, these results are extended to improve the spectral bounds of M(y)1H.  相似文献   

12.
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   

13.
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   

14.
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   

15.
16.
For a class of potentials including the Coulomb potential q = μr?1 with ¦ μ ¦ < 1 (1) (i.e., atomic numbers Z ? 137), the virial theorem (u, α · pu) = (u, r(?q?r)u) is shown to hold, u being an eigenfunction of the operator
Hu = TU : = (α · p + β + q)u
,
D(H) = {u ¦ u ∈ [Hloc1(R+3)]4, r?12u, TU ∈ [L2(R)3]4}
(R+3 := R?{0}). The result implies in particular that H with (1) does not have any eigenvalues embedded in the continuum. The proof uses a scale transformation.  相似文献   

17.
We study certain functionals and obtain an inverse Hölder inequality for n functions f1a1,…,fnan (fk concave, 1 dimension).We also prove a multidimensional inverse Hölder inequality for n functions f1,…,fn, where ?2fk?xi2 ? 0, i = 1,…, d, k = 1,…, n.Finally we give an inverse Minkowski inequality for concave functions.  相似文献   

18.
Let ? be defined on Tr and have an absolutely convergent Fourier series
?(〈eitj〉) = k?keik·t
. Set ∥?∥ = ∑ ¦?k¦. In this paper the problem of determining the limit of ∥?n, as n → ∞, is studied.  相似文献   

19.
Let u(x, t) be the solution of utt ? Δxu = 0 with initial conditions u(x, 0) = g(x) and ut(x, 0) = ?;(x). Consider the linear operator T: ?; → u(x, t). (Here g = 0.) We prove for t fixed the following result. Theorem 1: T is bounded in Lp if and only if ¦ p?1 ? 2?1 ¦ = (n ? 1)?1and ∥ T?; ∥LαP = ∥?;∥LPwith α = 1 ?(n ? 1) ¦ p?1 ? 2?1 ¦. Theorem 2: If the coefficients are variables in C and constant outside of some compact set we get: (a) If n = 2k the result holds for ¦ p?1 ? 2?1 ¦ < (n ? 1)?1. (b) If n = 2k ? 1, the result is valid for ¦ p?1 ? 2?1 ¦ ? (n ? 1). This result are sharp in the sense that for p such that ¦ p?1 ? 2?1 ¦ > (n ? 1)?1 we prove the existence of ?; ? LP in such a way that T?; ? LP. Several applications are given, one of them is to the study of the Klein-Gordon equation, the other to the completion of the study of the family of multipliers m(ξ) = ψ(ξ) ei¦ξ¦ ¦ ξ ¦ ?b and finally we get that the convolution against the kernel K(x) = ?(x)(1 ? ¦ x ¦)?1 is bounded in H1.  相似文献   

20.
Let g = (g1,…,gr) ≥ 0 and h = (h1,…,hr) ≥ 0, g?, h?J, be two vectors of nonnegative integers and let λ ? J, λ ≥ 0, λ ≡ 0 mod d, where d denotes g.c.d. (g1,…,gr). Define
Δ(λ)=Δ(λg,h):=min?=1rx?h?:x??0,x?∈J,?=1?x?g?
It is shown in this paper that Λ(λ) is periodic in λ with constant jump. If i? {1,…,r} is such that
detgihig?h?? (?1,…r)
then
Δ(λ)+giΔ(λ)+hi
holds true for all sufficiently large λ, λ ≡ 0 mod d.  相似文献   

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