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121.
Let R be a discrete nonsingular equivalence relation on a standard probability space , and let V be an ergodic strongly asymptotically central automorphism of R. We prove that every V-invariant cocycle with values in a Polish group G takes values in an abelian subgroup of G.
The hypotheses of this result are satisfied, for example, if A is a finite set, a closed, shift-invariant subset, V is the shift, μ a shift-invariant and ergodic probability measure on X, the two-sided tail-equivalence relation on X, a shift-invariant subrelation which is μ-nonsingular, and a shift-invariant cocycle. 相似文献
122.
Summary We prove that a
d
-action by automorphisms of a compact, abelian group is Bernoulli if and only if it has completely positive entropy. The key ingredients of the proof are the extension of certain notions of asymptotic block independence from -actions to
d
-action and their equivalence with Bernoullicity, and a surprisingly close link between one of these asymptotic block independence properties for
d
-actions by automorphisms of compact, abelian groups and the product formula for valuations on global fields.Oblatum 20-X-1994 相似文献
123.
Klaus Thomsen 《Transactions of the American Mathematical Society》2004,356(9):3557-3619
The structure of a sofic shift space is investigated, and Krieger's embedding theorem and Boyle's factor theorem are generalized to a large class of sofic shifts.
124.
We consider the short-time heat content asymptotics for oblique boundary conditions. The first few coefficients in the asymptotic expansion are calculated. 相似文献
125.
This paper proposes a new geometric construction of Enriques surfaces. Its starting point are K3 surfaces with Jacobian elliptic fibration which arise from rational elliptic surfaces by a quadratic base change. The Enriques surfaces obtained in this way are characterised by elliptic fibrations with a rational curve as bisection which splits into two sections on the covering K3 surface. The construction has applications to the study of Enriques surfaces with specific automorphisms. It also allows us to answer a question of Beauville about Enriques surfaces whose Brauer groups show an exceptional behaviour. In a forthcoming paper, we will study arithmetic consequences of our construction. 相似文献
126.
Klaus Thomsen 《K-Theory》1991,4(3):245-267
We show that the homotopy groups of the group of quasi-unitaries inC
*-algebras form a homology theory on the category of allC
*-algebras which becomes topologicalK-theory when stabilized. We then show how this functorial setting, in particular the half-exactness of the involved functors, helps to calculate the homotopy groups of the group of unitaries in a series ofC
*-algebras. The calculations include the case of all AbelianC
*-algebras and allC
*-algebras of the formAB, whereA is one of the Cuntz algebras On n=2, 3, ..., an infinite dimensional simpleAF-algebra, the stable multiplier or corona algebra of a-unitalC
*-algebra, a properly infinite von Neumann algebra, or one of the projectionless simpleC
*-algebras constructed by Blackadar. 相似文献
127.
Klaus Pinn 《Complexity》1999,4(3):41-46
A number of observations are made on Hofstadter's integer sequence defined by Q(n) = Q(n − Q(n − 1)) + Q(n − Q(n − 2)), for n > 2, and Q(1) = Q(2) = 1. On short scales, the sequence looks chaotic. It turns out, however, that the Q(n) can be grouped into a sequence of generations. The k‐th generation has 2k members that have “parents” mostly in generation k − 1 and a few from generation k − 2. In this sense, the sequence becomes Fibonacci type on a logarithmic scale. The variance of S(n) = Q(n) − n/2, averaged over generations, is ≅2αk, with exponent α = 0.88(1). The probability distribution p*(x) of x = R(n) = S(n)/nα, n ≫ 1, is well defined and strongly non‐Gaussian, with tails well described by the error function erfc. The probability distribution of xm = R(n) − R(n − m) is given by pm(xm) = λm p*(xm/λm), with λm → √2 for large m. © 1999 John Wiley & Sons, Inc. 相似文献
128.
129.
130.
We consider a problem of allocating indivisible objects when agents may desire to consume more than one object and no monetary
transfers are allowed. We are interested in allocation rules that satisfy desirable properties from an economic and social
point of view. In addition to strategy-proofness and Pareto efficiency, we consider consistency and two solidarity properties
(replacement-domination and population-monotonicity). In most of the cases, these properties are satisfied only by serially
dictatorial rules.
Received: November 1999/Final version: December 2001 相似文献