Central Limit Theorem for Random Strict Partitions

We consider the set of all partitions of a number n into distinct summands (the so-called strict partitions) with the uniform distribution on it and study fluctuations of a random partition near its limit shape, for large n. The use of geometrical language allows us to state the problem in terms of the limit behavior of random step functions (Young diagrams). A central limit theorem for such functions is proven. Our method essentially uses the notion of large canonical ensemble of partitions. Bibliography: 7 titles.     

Entropy for Random Partitions and Its Applications

Asymptotic properties of partitions of the unit interval are studied through the entropy for random partition

Distributions of Random Partitions and Their Applications

Assume that a random sample of size m is selected from a population containing a countable number of classes (subpopulations) of elements (individuals). A partition of the set of sample elements into (unordered) subsets, with each subset containing the elements that belong to same class, induces a random partition of the sample size m, with part sizes {Z ₁,Z ₂,...,Z _N } being positive integer-valued random variables. Alternatively, if N _j is the number of different classes that are represented in the sample by j elements, for j=1,2,...,m, then (N ₁,N ₂,...,N _m ) represents the same random partition. The joint and the marginal distributions of (N ₁,N ₂,...,N _m ), as well as the distribution of are of particular interest in statistical inference. From the inference point of view, it is desirable that all the information about the population is contained in (N ₁,N ₂,...,N _m ). This requires that no physical, genetical or other kind of significance is attached to the actual labels of the population classes. In the present paper, combinatorial, probabilistic and compound sampling models are reviewed. Also, sampling models with population classes of random weights (proportions), and in particular the Ewens and Pitman sampling models, on which many publications are devoted, are extensively presented.      

随机排列最优成组剖分的算法

本文研究随机排列的最优成组剖分问题。这一问题源于铁路列车的最优调度计划方法的设计问题。寻找切实可行的有效算法是问题的焦点。1978年这一问题被列入文献的公开问题之一。1986年许国志、陈庆华和刘继勇提出猜测:此乃NP-完全问题,即多项式时间的算法可能不会存在,除非NP=P。 本文引入一种强同构剪枝策略,以标号树形上的隐式枚举法为工具,得到了上述问题精确最优解的一个算法。其计算时间复杂度为O(n³2^n-2),其中n为随机排列中相异数字的个数。算法在给定n的条件下,     

Random Skew Plane Partitions with a Piecewise Periodic Back Wall

Random skew plane partitions of large size distributed according to an appropriately scaled Schur process develop limit shapes. In the present work, we consider the limit of large random skew plane partitions where the inner boundary approaches a piecewise linear curve with non-lattice slopes, describing the limit shape and the local fluctuations in various regions. This analysis is fairly similar to that in Okounkov and Reshetikhin (Commun Math Phys 269:571–609, 2007), but we do find some new behavior. For instance, the boundary of the limit shape is now a single smooth (not algebraic) curve, whereas the boundary in Okounkov and Reshetikhin (Commun Math Phys 269:571–609, 2007) is singular. We also observe the bead process introduced in Boutillier (Ann Probab 37(1):107–142, 2009) appearing in the asymptotics at the top of the limit shape.     

Asymptotics of the Uniform Measures on Simplices and Random Compositions and Partitions

We study the limiting behavior of uniform measures on finite-dimensional simplices as the dimension tends to infinity and a discrete analog of this problem, the limiting behavior of uniform measures on compositions. It is shown that the coordinate distribution of a typical point in a simplex, as well as the distribution of summands in a typical composition with given number of summands, is exponential. We apply these assertions to obtain a more transparent proof of our result on the limit shape of partitions with given number of summands, refine the estimate on the number of summands in partitions related to a theorem by Erds and Lehner about the asymptotic absence of repeated summands, and outline the proof of the sharpness of this estimate.     

Variational and Semigroup Methods for Waves and Diffusion in Networks

We study diffusion and wave equations in networks. Combining semigroup and variational methods we obtain well-posedness and many nice properties of the solutions in general L^p-context. Following earlier articles of other authors, we discuss how the spectrum of the generator can be connected to the structure of the network. We conclude by describing asymptotic behavior of solutions to the diffusion problem.     

Partitions and Compositions Defined by Inequalities

We consider sequences of integers (₁,..., _k) defined by a system of linear inequalities _{i j>i}a_ijj with integer coefficients. We show that when the constraints are strong enough to guarantee that all _i are nonnegative, the generating function for the integer solutions of weight n has a finite product form , where the b_i are positive integers that can be computed from the coefficients of the inequalities. The results are proved bijectively and are used to give several examples of interesting identities for integer partitions and compositions. The method can be adapted to accommodate equalities along with inequalities and can be used to obtain multivariate forms of the generating function. We show how to extend the technique to obtain the generating function when the coefficients a_i,i+1 are allowed to be rational, generalizing the case of lecture hall partitions. Our initial results were conjectured thanks to the Omega package (G.E. Andrews, P. Paule, and A. Riese, European J. Comb. 22(7) (2001), 887–904).Research supported by NSA grants MDA 904-00-1-0059 and MDA 904-01-0-0083.     

随机分析中的变分方法

In this paper, we consider the random variational inequality (its definition in the following), the methods we used belong to functional analysis.     

Radical Semigroup Rings and the Thue--Morse Semigroup

Let R be an associative ring with unit, let S be a semigroup with zero, and let RS be a contracted semigroup ring. It is proved that if RS is radical in the sense of Jacobson and if the element 1 has infinite additive order, then S is a locally finite nilsemigroup. Further, for any semigroup S, there is a semigroup T S such that the ring RT is radical in the Brown--McCoy sense. Let S be the semigroup of subwords of the sequence abbabaabbaababbab..., and let F be the two-element field. Then the ring FS is radical in the Brown--McCoy sense and semisimple in the Jacobson sense.     

Cylindric Partitions

A new object is introduced into the theory of partitions that generalizes plane partitions: cylindric partitions. We obtain the generating function for cylindric partitions of a given shape that satisfy certain row bounds as a sum of determinants of -binomial coefficients. In some special cases these determinants can be evaluated. Extending an idea of Burge (J. Combin. Theory Ser. A 63 (1993), 210-222), we count cylindric partitions in two different ways to obtain several known and new summation and transformation formulas for basic hypergeometric series for the affine root system . In particular, we provide new and elementary proofs for two basic hypergeometric summation formulas of Milne (Discrete Math. 99 (1992), 199-246).

     

Jagged Partitions

By jagged partitions we refer to an ordered collection of non-negative integers (n₁, n₂,..., n_m) with n_m≥ p for some positive integer p, further subject to some weakly decreasing conditions that prevent them for being genuine partitions. The case analyzed in greater detail here corresponds to p = 1 and the following conditions n_i≥ n_i+1−1 and n_i≥ n_i+2. A number of properties for the corresponding partition function are derived, including rather remarkable congruence relations. An interesting application of jagged partitions concerns the derivation of generating functions for enumerating partitions with special restrictions, a point that is illustrated with various examples. 2000 Mathematics Subject Classification: Primary—05A15, 05A17, 05A19     

自由单演逆半群上的核—迹算子半群

对于逆半群上的同余ρ,在它的迹类中存在最大元ρT和最小元ρt.相应地,在它的核类中有最大元ρK和最小元ρk.因此,我们在S的同余格上得到四个算子Г={T,t,K,k}.本文将给出自由单演逆半群上,由算子半群Г生成的半群,即自由单演逆半群上的核一迹算子半群.