Spherical functions and immanants

Let λ be an irreducible character of S_n corresponding to the partition (r,s) of n. Let A be a positive semidefinite Hermitian n × n matrix. Let d_λ (A) and per(A) be the immanants corresponding to λ and to the trivial character of S_n , respectively. A proof of the inequality dλ(A)≤λ(id)per(A) is given.     

An almost‐bijective proof of an asymptotic property of partitions

Let 𝒫_n be the set of all distinct ordered pairs (λ,λ_i), where λ is a partition of n and λ_i is a part size of λ. The primary result of this note is a combinatorial proof that the probability that, for a pair (λ,λ_i) chosen uniformly at random from 𝒫_n, the multiplicity of λ_i in λ is 1 tends to 1/2 as n →∞. This is inspired by work of Corteel, Pittel, Savage, and Wilf (Random Structures and Algorithms 14 (1999), 185–197). © 2007 Wiley Periodicals, Inc. Random Struct. Alg., 2007     

Multiplicity and Number of Parts in Overpartitions

The purpose of this paper is to study the parts, part sizes and multiplicities in overpartitions using combinatorics, probabilities and asymptotics. We show that the probability that a randomly chosen part size of a randomly chosen overpartition of n has multiplicity m or m + 1 approaches 1/(m(m + 1) ln 2) and that the expected multiplicity of a randomly chosen part size of a randomly chosen overpartition of n approaches ln n/(4ln 2) as n .     

Vertex coloring complete multipartite graphs from random lists of size 2

Let K_s×m be the complete multipartite graph with s parts and m vertices in each part. Assign to each vertex v of K_s×m a list L(v) of colors, by choosing each list uniformly at random from all 2-subsets of a color set C of size σ(m). In this paper we determine, for all fixed s and growing m, the asymptotic probability of the existence of a proper coloring φ, such that φ(v)∈L(v) for all v∈V(K_s×m). We show that this property exhibits a sharp threshold at σ(m)=2(s−1)m.     

Coloring complete bipartite graphs from random lists

Let K_n,n be the complete bipartite graph with n vertices in each side. For each vertex draw uniformly at random a list of size k from a base set S of size s = s(n). In this paper we estimate the asymptotic probability of the existence of a proper coloring from the random lists for all fixed values of k and growing n. We show that this property exhibits a sharp threshold for k ≥ 2 and the location of the threshold is precisely s(n) = 2n for k = 2 and approximately for k ≥ 3. © 2005 Wiley Periodicals, Inc. Random Struct. Alg., 2006     

Large Distinct Part Sizes in a Random Integer Partition

Let Y _s,n denote the number of part sizes ≧ s in a random and uniform partition of the positive integer n that are counted without multiplicity. For s = λ(6n)^1/2/π + o(n ^1/4), 0 ≦ λ < ∞, as n → ∞, we establish the weak convergence of Y _s,n to a Gaussian distribution in the form of a central limit theorem. The mean and the standard deviation are also asymptotically determined. This revised version was published online in June 2006 with corrections to the Cover Date.     

Semi-classical behaviour of the scattering phase for trapping perturbations of the laplacian

We study the influence of trapping trajectories on the semi-classical asymptotic of the scattering phase (spectral shift function), s_n(λ) associated to Schrodinger operators, if λ is a non critical energy level. Some results are known when the set of closed trajectories has Liouville measure 0 and in the case of a potential well. In this paper, for smooth and sufficiently decreasing potentials, we describe the behaviour of s_n(λ+rh) in terms of the continuity properties of a certain oscillating function Q(h,r). This function. intl.oduced by V. Petkov and G. Popov to study clustering of eigenvalues, is related to the periodic trajectories. If Q(h,r) is uniformly contiuuous in r for any h ε[0,h₀], we obtain a TVeyl type asynlptotic of s_n(λ+rh), with a second term containing Q(h,r). On the other hand, the point of discontinuity of Q(h, r) in r may give rise to a "clustering" phenomena for the scattering phase. Hence, in contrast to non-trapping case, the derivative d/dλ (s_h) can have no complete asymptotic expansion.     

Some Results for Decomposition Numbers for the Hecke Algebra of Type A with q = −1

Let ? = ?_{?, ?1}(𝔖 _n ) be the Hecke algebra of the symmetric group 𝔖 _n . For partitions λ and ν with ν 2 ? regular, define the Specht module S(λ) and the irreducible module D(ν). Define d _λν = [S(λ): D(ν)] to be the composition multiplicity of D(ν) in S(λ). In this paper we compute the decomposition numbers d _λν for all partitions of the form λ = (a, c, 1 ^b ) and ν 2 ? regular.     

On random points in the unit disk

Let n be a positive integer and λ > 0 a real number. Let V_n be a set of n points in the unit disk selected uniformly and independently at random. Define G(λ, n) to be the graph with vertex set V_n, in which two vertices are adjacent if and only if their Euclidean distance is at most λ. We call this graph a unit disk random graph. Let and let X be the number of isolated points in G(λ, n). We prove that almost always X ～ n when 0 ≤ c < 1. It is known that if where ?(n) → ∞, then G(λ, n) is connected. By extending a method of Penrose, we show that under the same condition on λ, there exists a constant K such that the diameter of G(λ, n) is bounded above by K · 2/λ. Furthermore, with a new geometric construction, we show that when and c > 2.26164 …, the diameter of G(λ, n) is bounded by (4 + o(1))/λ; and we modify this construction to yield a function c(δ) > 0 such that the diameter is at most 2(1 + δ + o(1))/λ when c > c(δ). © 2005 Wiley Periodicals, Inc. Random Struct. Alg., 2006     

On the Maximal Multiplicity of Parts in a Random Integer Partition

We study the asymptotic behavior of the maximal multiplicity μ_n = μ_n(λ) of the parts in a partition λ of the positive integer n, assuming that λ is chosen uniformly at random from the set of all such partitions. We prove that πμ_n/(6n)^1/2 converges weakly to max _jX_j/j as n→∞, where X₁, X₂, … are independent and exponentially distributed random variables with common mean equal to 1.2000 Mathematics Subject Classification: Primary—05A17; Secondary—11P82, 60C05, 60F05     

Random I-colorable graphs

In this article we investigate properties of the class of all l-colorable graphs on n vertices, where l = l(n) may depend on n. Let G^l_n denote a uniformly chosen element of this class, i.e., a random l-colorable graph. For a random graph G^l_n we study in particular the property of being uniquely l-colorable. We show that not only does there exist a threshold function l = l(n) for this property, but this threshold corresponds to the chromatic number of a random graph. We also prove similar results for the class of all l-colorable graphs on n vertices with m = m(n) edges.     

How to deal with unlabeled random graphs

Let U(n,M) be a graph chosen at random from the family of all unlabeled graphs with n vertices and M edges. In the paper we study the asymptotic behavior of U(n,M) when n → ∞. In particular, we show how properties of U(n,M) could be derived from analogous properties of a labeled random graph.     

Largest 4-connected components of 3-connected planar triangulations

Let T_n be a 3-connected n-vertex planar triangulation chosen uniformly at random. Then the number of vertices in the largest 4-connected component of T_n is asymptotic to n/2 with probability tending to 1 as n → ∞. It follows that almost all 3-connected triangulations with n vertices have a cycle of length at least n/2 + o(n).     

On the maximal multiplicity of block sizes in a random set partition

We study the asymptotic behavior of the maximal multiplicity M_n = M_n(σ) of the block sizes in a set partition σ of [n] = {1,2,…,n}, assuming that σ is chosen uniformly at random from the set of all such partitions. It is known that, for large n, the blocks of a random set partition are typically of size W = W(n), with We^W = n. We show that, over subsequences {n_k}_{k ≥ 1} of the sequence of the natural numbers, , appropriately normalized, converges weakly, as k→∞, to , where Z₁ and Z₂ are independent copies of a standard normal random variable. The subsequences {n_k}_{k ≥ 1}, where the weak convergence is observed, and the quantity u depend on the fractional part f_n of the function W(n). In particular, we establish that . The behavior of the largest multiplicity M_n is in a striking contrast to the similar statistic of integer partitions of n. A heuristic explanation of this phenomenon is also given.     

Local bifurcation from characteristic values with finite multiplicity and its application to axisymmetric buckled states of a thin spherical shell

The purpose of this paper is to study bifurcation points of the equation T(v) = L(λ,v) + M(λ,v), (λ,v) ? Λ × D in Banach spaces, where for any fixed λ ? Λ, T, L(λ,·) are linear mappings and M(λ,·) is a nonlinear mapping of higher order, M(λ,0) = 0 for all λ ? Λ. We assume that λ is a characteristic value of the pair (T, L) such that the mapping T – L(λ ,·) is Fredholm with nullity p and index s, p > s ? 0. We shall find some sufficient conditions to show that (λ ,0) is a bifurcation point of the above equation. The results obtained will be used to consider bifurcation points of the axisymmetric buckling of a thin spherical shell subjected to a uniform compressive force consisting of a pair of coupled non-linear ordinary differential equations of second order.     

The cycle structure of two rows in a random Latin square

Let L be chosen uniformly at random from among the latin squares of order n ≥ 4 and let r,s be arbitrary distinct rows of L. We study the distribution of σ_r,s, the permutation of the symbols of L which maps r to s. We show that for any constant c > 0, the following events hold with probability 1 ‐ o(1) as n → ∞: (i) σ_r,s has more than (log n)^1?c cycles, (ii) σ_r,s has fewer than 9 cycles, (iii) L has fewer than n^5/2 intercalates (latin subsquares of order 2). We also show that the probability that σ_r,s is an even permutation lies in an interval and the probability that it has a single cycle lies in [2n^‐2,2n^‐2/3]. Indeed, we show that almost all derangements have similar probability (within a factor of n^3/2) of occurring as σ_r,s as they do if chosen uniformly at random from among all derangements of {1,2,…,n}. We conjecture that σ_r,s shares the asymptotic distribution of a random derangement. Finally, we give computational data on the cycle structure of latin squares of orders n ≤ 11. © 2008 Wiley Periodicals, Inc. Random Struct. Alg., 2008     

Spin depolarization decay rates in α-symmetric stable fields on cubic lattices

We study the asymptotic, long-time behavior of the energy function where {X_s : 0 ≤ s < ∞} is the standard random walk on the d-dimensional lattice Z^d, 1 < α ≤ 2, and f:R⁺ → R⁺ is any nondecreasing concave function. In the special case f(x) = x, our setting represents a lattice model for the study of transverse magnetization of spins diffusing in a homogeneous, α-stable, i.i.d., random, longitudinal field {λV(x) : x ∈ Z^d} with common marginal distribution, the standard α-symmetric stable distribution; the parameter λ describes the intensity of the field. Using large-deviation techniques, we show that S_c(λ α f) = lim_t→∞ E(t; λ f) exists. Moreover, we obtain a variational formula for this decay rate S_c. Finally, we analyze the behavior S_c(λ α f) as λ → 0 when f(x) = x^β for all 1 ≥ β > 0. Consequently, several physical conjectures with respect to lattice models of transverse magnetization are resolved by setting β = 1 in our results. We show that S_c(λ, α, 1) ≈ λ^α for d ≥ 3, λ^agr;(ln 1/λ)^α−1 in d = 2, and in d = 1. © 1996 John Wiley & Sons, Inc.     

Characters of Representations for Lie Superalgebras of Type C Using Tableaux

Let  = osp(2, 2n) denote the complex Lie superalgebra of type C of rank n + 1. Let V(λ) denote the irreducible representation of  with the highest weight λ. For each finite dimensional V(λ), we describe the character of V(λ) combinatorially using the generalized osp(2, 2n)-standard tableaux of λ.     

The Smallest Parallelepiped of n Random Points and Peeling

Let n random points be given with uniform distribution in the d-dimensional unit cube [0,1]^d. The smallest parallelepiped A which includes all the n random points is dealt with. We investigate the asymptotic behavior of the volume of A as n tends to . Using a point process approach, we derive also the asymptotic behavior of the volumes of the k-th smallest parallelepipeds A _n ^(k) which are defined by iteration. Let A _n = A _n ⁽¹⁾ . Given A _n ^(k,-,1) delete the random points X _i which are on the boundary A _n ^(k,-,1) , and construct the smallest parallelepiped which includes the inner points of A _n ^(k,-,1) , this defines A _n ^(k) . This procedure is known as peeling of the parallelepiped A_n.