On Decomposition Numbers and Branching Coefficients for Symmetric and Special Linear Groups

In this paper we find the multiplicities dim L()_– where is an arbitrary root and L() is an irreducible SL_n-module withhighest weight . We provide different bases of the correspondingweight spaces and outline some applications to the symmetricgroups. In particular we describe certain composition multiplicitiesin the modular branching rule. 1991 Mathematics Subject Classification:20C05, 20G05.     

The cohomology of the Steenrod algebra and representations of the general linear groups

Let be the algebraic transfer that maps from the coinvariants of certain -representations to the cohomology of the Steenrod algebra. This transfer was defined by W. Singer as an algebraic version of the geometrical transfer . It has been shown that the algebraic transfer is highly nontrivial, more precisely, that is an isomorphism for and that is a homomorphism of algebras.

In this paper, we first recognize the phenomenon that if we start from any degree and apply repeatedly at most times, then we get into the region in which all the iterated squaring operations are isomorphisms on the coinvariants of the -representations. As a consequence, every finite -family in the coinvariants has at most nonzero elements. Two applications are exploited.

The first main theorem is that is not an isomorphism for . Furthermore, for every 5$">, there are infinitely many degrees in which is not an isomorphism. We also show that if detects a nonzero element in certain degrees of , then it is not a monomorphism and further, for each \ell$">, is not a monomorphism in infinitely many degrees.

The second main theorem is that the elements of any -family in the cohomology of the Steenrod algebra, except at most its first elements, are either all detected or all not detected by , for every . Applications of this study to the cases and show that does not detect the three families , and , and that does not detect the family .

     

Modular Branching Rules and the Mullineux Map for Hecke Algebras of Type A

We prove the quantum version - for Hecke algebras H A_n of typeA at roots of unity - of Kleshchev's modular branching rulefor symmetric groups. This result describes the socle of therestriction of an irreducible H A_n-module to the subalgebraH A_n–1. As a consequence, we describe the quantum versionof the Mullineux involution describing the irreducible moduleobtained on twisting an irreducible module with the sign representation.1991 Mathematics Subject Classification: 20C05, 20G05.     

Solving semidefinite-quadratic-linear programs using SDPT3

 This paper discusses computational experiments with linear optimization problems involving semidefinite, quadratic, and linear cone constraints (SQLPs). Many test problems of this type are solved using a new release of SDPT3, a Matlab implementation of infeasible primal-dual path-following algorithms. The software developed by the authors uses Mehrotra-type predictor-corrector variants of interior-point methods and two types of search directions: the HKM and NT directions. A discussion of implementation details is provided and computational results on problems from the SDPLIB and DIMACS Challenge collections are reported. Received: March 19, 2001 / Accepted: January 18, 2002 Published online: October 9, 2002 Mathematics Subject Classification (2000): 90C05, 90C22     

On the Structure of Modular Categories

For a braided tensor category C and a subcategory K there isa notion of a centralizer C_C K, which is a full tensor subcategoryof C. A pre-modular tensor category is known to be modular inthe sense of Turaev if and only if the center Z₂C C_CC (not tobe confused with the center Z₁ of a tensor category, relatedto the quantum double) is trivial, that is, consists only ofmultiples of the tensor unit, and dimC 0. Here , the X_i being the simple objects. We prove several structural properties of modular categories.Our main technical tool is the following double centralizertheorem. Let C be a modular category and K a full tensor subcategoryclosed with respect to direct sums, subobjects and duals. ThenC_CC_CK = K and dim K·dim C_CK = dim C. We give several applications. (1) If C is modular and K is a full modular subcategory,then L=C_CK is also modular and C is equivalent as a ribbon categoryto the direct product: . Thus every modular category factorizes (non-uniquely, in general)into prime modular categories. We study the prime factorizationsof the categories D(G)-Mod, where G is a finite abelian group. (2) If C is a modular *-category and K is a full tensorsubcategory then dim C dim K · dim Z₂K. We give exampleswhere the bound is attained and conjecture that every pre-modularK can be embedded fully into a modular category C with dim C=dimK·dim Z₂K. (3) For every finite group G there is a braided tensor*-category C such that Z₂CRep,G and the modular closure/modularization is non-trivial. 2000 MathematicsSubject Classification 18D10.     

A globally convergent approximately active search algorithm for solving mathematical programs with linear complementarity constraints

Summary. In this paper, we propose a new algorithm for solving mathematical programs with linear complementarity constraints. The algorithm uses a method of approximately active search and introduces the idea of acceptable descent face. The main advantage of the new algorithm is that it is globally convergent without requiring strong assumptions such as nondegeneracy or linear independence condition. Numerical results are presented to show the effectiveness of the algorithm.Mathematics Subject Classification (2000): 90C30, 90C33, 65K05This research is partially supported by City University of Hong Kong under its Strategic Research Grant #7001339 and the National Natural Science Foundation of China grant # 10171108 and # 70271014     

Corrigenda: Mackey Functors And Control of Fusion

In the introduction to [3] it is mistakenly claimed that Mislin'sproof uses Carlsson's proof of Segal's Burnside ring conjecture.In fact, Mislin uses instead the work of Carlsson, Miller andLannes on Sullivan's fixed-point conjecture, and work of Dwyerand Zabrodski [1]. There is, however, a proof by Snaith [2]that depends on a version of the Segal conjecture. 2000 MathematicsSubject Classification 20J06 (primary), 20C05 (secondary).     

A Unified Construction of Two-Dimensional Pooling Designs

Following the work of Chateauneuf et al. [3], a simplified construction of a rowcolumn- front diagonal (RCF) design and a union jack design of a prime order using affine transformations is given.AMS Subject Classification: 05B30, 05C65, 60C05, 62K99.     

Bilevel programming: A survey

This paper provides an introductory survey of a class of optimization problems known as bilevel programming. We motivate this class through a simple application, and then proceed with the general formulation of bilevel programs. We consider various cases (linear, linear-quadratic, nonlinear), describe their main properties and give an overview of solution approaches.Received: April 2005, Revised: May 2005, AMS classification: 90C05, 90C11, 90C20, 90C27, 90C3D, 65K05     

Equivalence of domains arising from duality of orbits on flag manifolds

S. Gindikin and the author defined a - invariant subset of for each -orbit on every flag manifold and conjectured that the connected component of the identity would be equal to the Akhiezer-Gindikin domain if is of non-holomorphic type by computing many examples. In this paper, we first prove this conjecture for the open -orbit on an ``arbitrary' flag manifold generalizing the result of Barchini. This conjecture for closed was solved by J. A. Wolf and R. Zierau for Hermitian cases and by G. Fels and A. Huckleberry for non-Hermitian cases. We also deduce an alternative proof of this result for non-Hermitian cases.

     

Geodesic Distance in Planar Graphs: An Integrable Approach

We discuss the enumeration of planar graphs using bijections with suitably decorated trees, which allow for keeping track of the geodesic distances between faces of the graph. The corresponding generating functions obey non-linear recursion relations on the geodesic distance. These are solved by use of stationary multi-soliton tau-functions of suitable reductions of the KP hierarchy. We obtain a unified formulation of the (multi-) critical continuum limit describing large graphs with marked points at large geodesic distances, and obtain integrable differential equations for the corresponding scaling functions. This provides a continuum formulation of two-dimensional quantum gravity, in terms of the geodesic distance. 2000 Mathematics Subject Classification: Primary—05C30; Secondary—05A15, 05C05, 05C12, 68R05     

Special Points on the Product of Two Modular Curves

We prove, assuming the generalized Riemann hypothesis for imaginary quadratic fields, the following special case of a conjecture of Oort, concerning Zarsiski closures of sets of CM points in Shimura varieties. Let X be an irreducible algebraic curve in C², containing infinitely many points of which both coordinates are j-invariants of CM elliptic curves. Suppose that both projections from X to C are not constant. Then there is an integer m 1such that X is the image, under the usual map, of the modular curve Y₂0(m). The proof uses some number theory and some topological arguments.     

Hadamard Matrices Modulo p and Small Modular Hadamard Matrices

We use modular symmetric designs to study the existence of Hadamard matrices modulo certain primes. We solve the 7‐modular and 11‐modular versions of the Hadamard conjecture for all but a finite number of cases. In doing so, we state a conjectural sufficient condition for the existence of a p‐modular Hadamard matrix for all but finitely many cases. When 2 is a primitive root of a prime p, we conditionally solve this conjecture and therefore the p‐modular version of the Hadamard conjecture for all but finitely many cases when , and prove a weaker result for . Finally, we look at constraints on the existence of m‐modular Hadamard matrices when the size of the matrix is small compared to m.     

Polynomial algorithms for kernels in comparability, permutation and P 4-free graphs

In this paper, we give three polynomial algorithms which detect a kernel in comparability graphs relatively to an M-orientation, in permutation graphs and in P₄-free graphs with a normal orientation. MSC classification: 05C69, 05C85 Correspondence to: Saoula Youcef     

A Hyperelliptic Smoothness Test, II

This series of papers presents and rigorously analyzes a probabilisticalgorithm for finding small prime factors of an integer. Thealgorithm uses the Jacobian varieties of curves of genus 2 inthe same way that the elliptic curve method uses elliptic curves.This second paper in the series is concerned with the orderof the group of rational points on the Jacobian of a curve ofgenus 2 defined over a finite field. We prove a result on thedistribution of these orders. 2000 Mathematical Subject Classification:11Y05, 11G10, 11M20, 11N25.     

Redundant Integer Representations and Fast Exponentiation

In this paper two modifications to the standard square and multiply method for exponentiation are discussed. The first, using a signed-digit representation of the exponent, has been examined previously by a number of authors, and we present a new precise and simple mathematical analysis of its performance. The second, a new technique, uses a different redundant representation of the exponent, which we call a string replacement representation; the performance of this new method is analysed and compared with previously proposed methods. The techniques considered in this paper have application in the implementation of cryptographic algorithms such as RSA, where modular exponentiations of very large integers need to be calculated.     

Some Remarks on the Elliptic Harnack Inequality

Three short results are given concerning the elliptic Harnackinequality, in the context of random walks on graphs. The firstis that the elliptic Harnack inequality implies polynomial growthof the number of points in balls, and the second that the ellipticHarnack inequality is equivalent to an annulus-type Harnackinequality for Green's functions. The third result uses thelamplighter group to give a counter-example concerning the relationof coupling with the elliptic Harnack inequality. 2000 MathematicsSubject Classification 31B05 (primary), 60J35, 31C25 (secondary).     

Partition-Theoretic Interpretations of Certain Modular Equations of Schröter,Russell, and Ramanujan

We show that certain modular equations studied by Schr?oter, Russell, and Ramanujan yield elegant identities for colored partitions. Received May 3, 2006 Bruce C. Berndt: Research partially supported by grant MDA904-00-1-0015 from the National Security Agency.