On a family of q-binomial distributions

We introduce a family of q-analogues of the binomial distribution, which generalises the Stieltjes-Wigert-, Rogers-Szegö-, and Kemp-distribution. Basic properties of this family are provided and several convergence results involving the classical binomial, Poisson, discrete normal distribution, and a family of q-analogues of the Poisson distribution are established. These results generalize convergence properties of Kemp’s-distribution, and some of them are q-analogues of classical convergence properties.     

Orthogonal polynomials and laurent polynomials related to the Hahn-Extonq-Bessel function

Laurent polynomials related to the Hahn-Extonq-Bessel function, which areq-analogues of the Lommel polynomials, have been introduced by Koelink and Swarttouw. The explicit strong moment functional with respect to which the Laurentq-Lommel polynomials are orthogonal is given. The strong moment functional gives rise to two positive definite moment functionals. For the corresponding sets of orthogonal polynomials, the orthogonality measure is determined using the three-term recurrence relation as a starting point. The relation between Chebyshev polynomials of the second kind and the Laurentq-Lommel polynomials and related functions is used to obtain estimates for the latter.     

Some results for the q-Bernoulli and q-Euler polynomials

We show some results for the q-Bernoulli and q-Euler polynomials. The formulas in series of the Carlitz's q-Stirling numbers of the second kind are also considered. The q-analogues of well-known formulas are derived from these results.     

Remarks on the paper “Skew Pieri rules for Hall–Littlewood functions” by Konvalinka and Lauve

In a recent paper Konvalinka and Lauve proved several skew Pieri rules for Hall–Littlewood polynomials. In this note we show that q-analogues of these rules are encoded in a q-binomial theorem for Macdonald polynomials due to Lascoux and the author.     

Character Tables of Association Schemes Based on Attenuated Spaces

The set of subspaces of a given dimension in an attenuated space has a structure of a symmetric association scheme and this association scheme is called an association scheme based on an attenuated space. Association schemes based on attenuated spaces are generalizations of Grassmann schemes and bilinear forms schemes, and also q-analogues of nonbinary Johnson schemes. Wang, Guo, and Li computed the intersection numbers of association schemes based on attenuated spaces. The aim of this paper is to compute character tables of association schemes based on attenuated spaces using the method of Tarnanen, Aaltonen, and Goethals. Moreover, we also prove that association schemes based on attenuated spaces include as a special case the m-flat association scheme, which is defined on the set of cosets of subspaces of a constant dimension in a vector space over a finite field.     

Maximal integral point sets in affine planes over finite fields

Motivated by integral point sets in the Euclidean plane, we consider integral point sets in affine planes over finite fields. An integral point set is a set of points in the affine plane over a finite field F_q, where the formally defined squared Euclidean distance of every pair of points is a square in F_q. It turns out that integral point sets over F_q can also be characterized as affine point sets determining certain prescribed directions, which gives a relation to the work of Blokhuis. Furthermore, in one important sub-case, integral point sets can be restated as cliques in Paley graphs of square order.In this article we give new results on the automorphisms of integral point sets and classify maximal integral point sets over F_q for q≤47. Furthermore, we give two series of maximal integral point sets and prove their maximality.     

Partial q-analogues of the Pfaff/Cauchy derivative formula

The Pfaff/Cauchy derivative identities are generalizations of Leibniz formula for the nth derivative of a product of two functions. In this paper, we first derive three generalized forms of the q-Leibniz formula. The results are also partial q-analogues of the Pfaff/Cauchy derivative formulae. Then we give some applications and several q-identities are obtained.     

On small blocking sets and their linearity

We prove that a small minimal blocking set of PG(2,q) is “very close” to be a linear blocking set over some subfield GF(pe)<GF(q). This implies that (i) a similar result holds in PG(n,q) for small minimal blocking sets with respect to k-dimensional subspaces (0?k?n) and (ii) most of the intervals in the interval-theorems of Sz?nyi and Sz?nyi-Weiner are empty.     

The symmetric and unimodal expansion of Eulerian polynomials via continued fractions

This paper was motivated by a conjecture of Brändén [P. Brändén, Actions on permutations and unimodality of descent polynomials, European J. Combin. 29 (2) (2008) 514-531] about the divisibility of the coefficients in an expansion of generalized Eulerian polynomials, which implies the symmetric and unimodal property of the Eulerian numbers. We show that such a formula with the conjectured property can be derived from the combinatorial theory of continued fractions. We also discuss an analogous expansion for the corresponding formula for derangements and prove a (p,q)-analogue of the fact that the (-1)-evaluation of the enumerator polynomials of permutations (resp. derangements) by the number of excedances gives rise to tangent numbers (resp. secant numbers). The (p,q)-analogue unifies and generalizes our recent results [H. Shin, J. Zeng, The q-tangent and q-secant numbers via continued fractions, European J. Combin. 31 (7) (2010) 1689-1705] and that of Josuat-Vergès [M. Josuat-Vergés, A q-enumeration of alternating permutations, European J. Combin. 31 (7) (2010) 1892-1906].     

Touchard–Riordan formulas, T-fractions, and Jacobi’s triple product identity

Touchard–Riordan-like formulas are certain expressions appearing in enumeration problems and as moments of orthogonal polynomials. We begin this article with a new combinatorial approach to prove such formulas, related to integer partitions. This gives a new perspective on the original result of Touchard and Riordan. But the main goal is to give a combinatorial proof of a Touchard–Riordan-like formula for q-secant numbers discovered by the first author. An interesting limit case of these objects can be directly interpreted in terms of partitions, so that we obtain a connection between the formula for q-secant numbers, and a particular case of Jacobi’s triple product identity. Building on this particular case, we obtain a “finite version” of the triple product identity. It is in the form of a finite sum which is given a combinatorial meaning, so that the triple product identity can be obtained by taking the limit. Here the proof is non-combinatorial and relies on a functional equation satisfied by a T-fraction. Then from this result on the triple product identity, we derive a whole new family of Touchard–Riordan-like formulas whose combinatorics is not yet understood. Eventually, we prove a Touchard–Riordan-like formula for a q-analog of Genocchi numbers, which is related with Jacobi’s identity for (q;q)³ rather than the triple product identity.     

Multiple q-Mahler measures and zeta functions

We introduce multiple q-Mahler measures and we calculate some specific examples, where multiple q-analogues of zeta functions appear. We study also limits as the multiple q goes to 1.     

Recent results on designs with classical parameters

We report on recent results concerning designs with the same parameters as the classical geometric designs PG _d (n, q) formed by the points and d-dimensional subspaces of the n-dimensional projective space PG(n, q) over the field GF(q) with q elements, where 1 ???d ???n?1. The corresponding case of designs with the same parameters as the classical geometric designs AG _d (n, q) formed by the points and d-dimensional subspaces of the n-dimensional affine space AG(n, q) will also be discussed, albeit in less detail.     

Operatormethoden fürq-Identitäten II:q-Laguerre-Polynome

Someq-analogues of the classical Laguerre-polynomials are studied from the point of view of umbral calculus.     

On the Gaussian q-distribution

We present a study of the Gaussian q-measure introduced by Díaz and Teruel from a probabilistic and from a combinatorial viewpoint. A main motivation for the introduction of the Gaussian q-measure is that its moments are exactly the q-analogues of the double factorial numbers. We show that the Gaussian q-measure interpolates between the uniform measure on the interval [−1,1] and the Gaussian measure on the real line.     

Permutations and words counted by consecutive patterns

Generating functions which count occurrences of consecutive sequences in a permutation or a word which matches a given pattern are studied by exploiting the combinatorics associated with symmetric functions. Our theorems take the generating function for the number of permutations which do not contain a certain pattern and give generating functions refining permutations by the both the total number of pattern matches and the number of non-overlapping pattern matches. Our methods allow us to give new proofs of several previously recorded results on this topic as well as to prove new extensions and new q-analogues of such results.     

Mixed q-analogues, lacunary polynomials and Truesdellian partial differential equations

Multiparameter families of possibly lacunary polynomials in x are constructed that have remarkably explicit (or “almost” explicit) expansions about both x=0 and x=1. They are placed in the framework of questions about mixed q-analogues with fewest terms. The properties of the most tractable of these surprisingly tractable polynomials are established with the aid of solutions to partial differential equations of a type much studied by Truesdell.     

Weyl sums over integers with affine digit restrictions

For any given integer q?2, we consider sets N of non-negative integers that are defined by affine relations between their q-adic digits (for example, the set of non-negative integers such that the number of 1's equals twice the number of 0's in the binary representation). The main goal is to prove that the sequence (αn)_n∈N is uniformly distributed modulo 1 for all irrational numbers α. The proof is based on a saddle point analysis of certain generating functions that allows us to bound the corresponding Weyl sums.     

Characterization of seminuclear sets in a finite projective plane

LetC be a set ofq + a points in the desarguesian projective plane of orderq, such that each point ofC is on exactly 1 tangent, and onea+ 1-secant (a>1). Then eitherq=a + 2 andC consists of the symmetric difference of two lines, with one further point removed from each line, orq=2a + 3 andC is projectively equivalent to the set of points {(0,1,s),(s, 0, 1),(1,s, 0): -s is not a square inGF(q)}.     

A p, q-Analogue of the Generalized Derangement Numbers

In this paper, we study the numbers D _n,k which are defined as the number of permutations σ of the symmetric group S _n such that σ has no cycles of length j for j ≤ k. In the case k = 1, D _n,1 is simply the number of derangements of an n-element set. As such, we shall call the numbers D _n,k generalized derangement numbers. Garsia and Remmel [4] defined some natural q-analogues of D _n,1, denoted by D _n,1(q), which give rise to natural q-analogues of the two classical recursions of the number of derangements. The method of Garsia and Remmel can be easily extended to give natural p, q-analogues D _n,1(p, q) which satisfy natural p, q-analogues of the two classical recursions for the number of derangements. In [4], Garsia and Remmel also suggested an approach to define q-analogues of the numbers D _n,k . In this paper, we show that their ideas can be extended to give a p, q-analogue of the generalized derangements numbers. Again there are two classical recursions for eneralized derangement numbers. However, the p, q-analogues of the two classical recursions are not as straightforward when k ≥ 2. Partially supported by NSF grant DMS 0400507.     

Colouring lines in projective space

Let V be a vector space of dimension v over a field of order q. The q-Kneser graph has the k-dimensional subspaces of V as its vertices, where two subspaces α and β are adjacent if and only if is the zero subspace. This paper is motivated by the problem of determining the chromatic numbers of these graphs. This problem is trivial when k=1 (and the graphs are complete) or when v<2k (and the graphs are empty). We establish some basic theory in the general case. Then specializing to the case k=2, we show that the chromatic number is q²+q when v=4 and (q^v-1-1)/(q-1) when v>4. In both cases we characterise the minimal colourings.