共查询到20条相似文献,搜索用时 15 毫秒
1.
Mohd Salmi Md. Noorani William Parry 《Bulletin of the Brazilian Mathematical Society》1992,23(1-2):137-151
We derive a Chebotarev Theorem for finite homogeneous extensions of shifts of finite type. These extensions are of the form
:X×G/H→X×G/H where
(x,gH)=(σx, α(x)gH), for some finite groupG and subgroupH. Given a σ-closed orbit τ, the periods of the
-closed orbits covering τ define a partition of the integer |G/H|. The theorem then gives us an asymptotic formula for the number of closed orbits with respect to the various partitions
of the integer |G/H|. We apply our theorem to the case of a finite extension and of an automorphism extension of shifts of finite type. We also
give a further application to ‘automorphism extensions’ of hyperbolic toral automorphisms.
Financially supported by Universiti Kebangsaan Malaysia 相似文献
2.
Letk be any field andG a finite group. Given a cohomology class α∈H
2(G,k
*), whereG acts trivially onk
*, one constructs the twisted group algebrak
αG. Unlike the group algebrakG, the twisted group algebra may be a division algebra (e.g. symbol algebras, whereG⋞Z
n×Zn). This paper has two main results: First we prove that ifD=k
α
G is a division algebra central overk (equivalentyD has a projectivek-basis) thenG is nilpotent andG’ the commutator subgroup ofG, is cyclic. Next we show that unless char(k)=0 and
, the division algebraD=k
α
G is a product of cyclic algebras. Furthermore, ifD
p is ap-primary factor ofD, thenD
p is a product of cyclic algebras where all but possibly one are symbol algebras. If char(k)=0 and
, the same result holds forD
p, p odd. Ifp=2 we show thatD
2 is a product of quaternion algebras with (possibly) a crossed product algebra (L/k,β), Gal(L/k)⋞Z
2×Z2n. 相似文献
3.
Klaus Schmidt 《Israel Journal of Mathematics》1982,41(1-2):151-153
LetG be a locally compact second countable abelian group, (X, μ) aσ-finite Lebesgue space, and (g, x) →gx a non-singular, properly ergodic action ofG on (X, μ). Let furthermore Γ be the character group ofG and let Sp(G, X) ⊂ Γ denote theL
∞-spectrum ofG on (X, μ). It has been shown in [5] that Sp(G, X) is a Borel subgroup of Γ and thatσ (Sp(G, X))<1 for every probability measureσ on Γ with lim supg→∞Re
(g)<1, where
is the Fourier transform ofσ. In this note we prove the following converse: ifσ is a probability measure on Γ with lim supg→∞Re
(g)<1 (g)=1 then there exists a non-singular, properly ergodic action ofG on (X, μ) withσ(Sp(G, X))=1. 相似文献
4.
J. S. Hwang 《数学学报(英文版)》1998,14(1):57-66
Letf(X) be an additive form defined by
wherea
i
≠0 is integer,i=1,2…,s. In 1979, Schmidt proved that if ∈>0 then there is a large constantC(k,∈) such that fors>C(k,∈) the equationf(X)=0 has a nontrivial, integer solution in σ1, σ2, …, σ3,x
1,x
2, …,x
3 satisfying
Schmidt did not estimate this constantC(k,∈) since it would be extremely large. In this paper, we prove the following result 相似文献
5.
We observe an unknown function of infinitely many variables f = f(t), t = (t1, ..., tn, ... ) ∈, [0, 1]∞, in the Gaussian white noise of level ε > 0. We suppose that in each variable there exists a 1-periodical σ-smooth extension
of the function f(t) to IR
∞. Taking a quantity σ > 0 and a positive sequence a = {ak}, we consider the set
that consists of functions f such that
. We consider the cases ak = kα and ak = exp(λk), α > 0, λ > 0. We would like to estimate a function f ∈
or to test the null hypothesis H0: f = 0 against the alternatives f ∈
, where the set
consists of functions f ∈
such that ∥f∥2 ≥ r. In the estimation problem, we obtain the asymptotics (as ε → 0) of the minimax quadratic risk. In the detection problem,
we study the sharp asymptotics of minimax separation rates f
ɛ
*
that provide distiguishability in the problems. Bibliography: 12 titles.
__________
Translated from Zapiski Nauchnykh Seminarov POMI, Vol. 328, 2005, pp. 91–113. 相似文献
6.
Let Mc = ( A0CB ) be a 2 × 2 upper triangular operator matrix acting on the Banach space X × Y. We prove that
σr(A) ∪ σr( B)= σr (Mc) ∪ W ,
where W is the union of certain of the holes in σr(Mc) which happen to be subsets of σr(A) ∩ σr(B), and σr(A), σr(B), σr(Mc) can be equal to the Browder or essential spectra of A, B, Mc, respectively. We also show that the above result isn't true for the Kato spectrum, left (right) essential spectrum and left (right) spectrum. 相似文献
σr(A) ∪ σr( B)= σr (Mc) ∪ W ,
where W is the union of certain of the holes in σr(Mc) which happen to be subsets of σr(A) ∩ σr(B), and σr(A), σr(B), σr(Mc) can be equal to the Browder or essential spectra of A, B, Mc, respectively. We also show that the above result isn't true for the Kato spectrum, left (right) essential spectrum and left (right) spectrum. 相似文献
7.
B. N. Pandey 《Annals of the Institute of Statistical Mathematics》1979,31(1):225-233
Summary Consider a normal population with mean μ and variance σ2. We are interested in the estimation of population variance with the help of guess value σ
0
2
and a sample of observations. In this paper, a double stage shrinkage estimator
based on the shrinkage estimatorks
1
2
+(1-k)σ
0
2
ifs
1
2
∈R and the usual estimator
ifs
1
2
∋R, whereR is some specified region, have been proposed. The expressions for bias and mean squared error have been obtained. Comparison
with the usual estimators
2 have been made. It was found that though the largest gain is obtained fork=0, we can use
with 0≦k≦1/2 even when σ2 is very close to σ
0
2 相似文献
8.
I. E. Zuber 《Vestnik St. Petersburg University: Mathematics》2010,43(3):139-142
A control of an nth-order discrete system under an external perturbation is considered. The elements of the matrix of the system are functionals
of any nature. The observation matrix is constant and has arbitrary size m × n. A control ensuring the independence of the output σ
k
on the external perturbation ψ
k
is synthesized; moreover,
$
\sigma _{k + 1} = \beta \sigma _k , 0 < \beta < 1, \sigma _k \in \mathbb{R}^m
$
\sigma _{k + 1} = \beta \sigma _k , 0 < \beta < 1, \sigma _k \in \mathbb{R}^m
相似文献
9.
V. M. Dil’nyi 《Ukrainian Mathematical Journal》2006,58(9):1425-1432
Let G ∈ H
σ
p
(ℂ+), where H
σ
p
(ℂ+) is the class of functions analytic in the half plane ℂ+ = {z: Re z > 0} and such that
10.
Let G be a finite group and let π : G → G′ be a surjective group homomorphism. Consider the cocycle deformation L = H
σ
of the Hopf algebra H = k
G
of k-valued linear functions on G, with respect to some convolution invertible 2-cocycle σ. The (normal) Hopf subalgebra corresponds to a Hopf subalgebra . Our main result is an explicit necessary and sufficient condition for the normality of L′ in L.
This work was partially supported by CONICET, Fundación Antorchas, Agencia Córdoba Ciencia, ANPCyT and Secyt (UNC). 相似文献
11.
Let M
n
= X
1 + ⋯ + X
n
be a sum of independent random variables such that X
k
⩽ 1,
and EX
k
2
= σ
k
2
for all k. Hoeffding [15, Theorem 3] proved that
12.
Yuval Z. Flicker 《Israel Journal of Mathematics》2001,122(1):61-77
The torsorP
δ=Hom⊗ (H
DR,H
σ) under the motivic Galois groupG
σ=Aut⊗
H
δ of the Tannakian category
generated by one-motives related by absolute Hodge cycles over a field κ with an embedding σ:k↪ℂ is shown to be determined by its projectionP
σ→P
σ/G
σ
0
to a Gal(
)-torsor, and by its localizationsP
σ⊕k
k
ξ at a dense subset of orderings ϕ of the field κ, provided κ has virtual cohomological dimension (vcd) one. This result is
an application of a recent local-global principle for connected linear algebraic groups over a field κ of vcd ≤1. 相似文献
13.
Wulf-Dieter Geyer 《Israel Journal of Mathematics》1978,30(4):382-396
LetK be a denumerable Hilbertian field with separable algebraic closure
and Galois group
, letw
1,...w
n be absolute values on
. Then for almost allσ ∈ G
K
n
(in the sense of Haar measure) there are no relations between the decomposition groups G
K
(ω
1
σ
1),...,G
K
(w
n
σ
n
) of the absolute valuesw
1
σ
1,...,w
n
σ
n
i.e. the subgroup of G
K
generated by these groups is the free product of these groups. 相似文献
14.
Giovanna Carnovale 《Algebras and Representation Theory》2006,9(1):99-120
We show which H
op
-cleft extensions of k for a dual quasi-triangular Hopf algebra (H, r) are H-Azumaya. The result is given in terms of bijectivity of a map defined in terms of the universal r-form r and the 2-cocycle σ, generalizing a well-known result for the commutative and co-commutative case. We illustrate the Theorem with an explicit computation for the Hopf algebras of type E(n).Presented by A. Verschoren 相似文献
15.
Zhang Lixin 《数学学报(英文版)》1998,14(1):113-124
Let {X, X
n
;n>-1} be a sequence of i.i.d.r.v.s withEX=0 andEX
2=σ2(0 < σ < ∞).
we obtain some sufficient and necessary conditions for
16.
Enrico Jabara 《Rendiconti del Circolo Matematico di Palermo》1996,45(1):84-92
LetG be a group admitting a 4-splitting automorphism (i.e. an automorphism σ such that
for everyg∈G). In this paper we prove that ifG≠1 is solvable with derived lengthd thenG′ is nilpotent of class not greater than (4
d−1−1)/3. 相似文献
17.
Summary Let
be a sequence of independent identically distributed random variables withθ
1∼G and the conditional distribution ofx
1 givenθ
1=θ given by
. HereG is unknown andF
θ(·) is known. This paper provides estimators
ofG based onx
1, …,x
n such that the random variable sup
has an asymptotic distribution asn→∞ under certain on conditionsG and for certain choices ofF
θ. A simulation model has been discussed involving the uniform distribution on (0, θ) forF
θ and an exponential distribution forG.
Research supported by the National Science Foundation under Grant #MCS77-26809. 相似文献
18.
Lutz Volkmann 《Czechoslovak Mathematical Journal》2010,60(1):77-83
Let G be a graph with vertex set V(G), and let k ⩾ 1 be an integer. A subset D ⊆ V(G) is called a k-dominating set if every vertex υ ∈ V(G)-D has at least k neighbors in D. The k-domination number γ
k
(G) of G is the minimum cardinality of a k-dominating set in G. If G is a graph with minimum degree δ(G) ⩾ k + 1, then we prove that
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