332,042 research outputs found
The Murnaghan-Nakayama rule for k-Schur functions
We prove the Murgnaghan--Nakayama rule for -Schur functions of Lapointe
and Morse, that is, we give an explicit formula for the expansion of the
product of a power sum symmetric function and a -Schur function in terms of
-Schur functions. This is proved using the noncommutative -Schur
functions in terms of the nilCoxeter algebra introduced by Lam and the affine
analogue of noncommutative symmetric functions of Fomin and Greene.Comment: 23 pages, updated to reflect referee comments, to appear in Journal
of Combinatorial Theory, Series
Mean asymptotic behaviour of radix-rational sequences and dilation equations (Extended version)
The generating series of a radix-rational sequence is a rational formal power
series from formal language theory viewed through a fixed radix numeration
system. For each radix-rational sequence with complex values we provide an
asymptotic expansion for the sequence of its Ces\`aro means. The precision of
the asymptotic expansion depends on the joint spectral radius of the linear
representation of the sequence; the coefficients are obtained through some
dilation equations. The proofs are based on elementary linear algebra
Littlewood-Richardson Coefficients via Yang-Baxter Equation
The purpose of this paper is to present an interpretation for the
decomposition of the tensor product of two or more irreducible representations
of GL(N) in terms of a system of quantum particles. Our approach is based on a
certain scattering matrix that satisfies a Yang-Baxter type equation. The
corresponding piecewise-linear transformations of parameters give a solution to
the tetrahedron equation. These transformation maps are naturally related to
the dual canonical bases for modules over the quantum enveloping algebra
. A byproduct of our construction is an explicit description for the
cone of Kashiwara's parametrizations of dual canonical bases. This solves a
problem posed by Berenstein and Zelevinsky. We present a graphical
interpretation of the scattering matrices in terms of web functions, which are
related to honeycombs of Knutson and Tao.Comment: 24 page
Asymmetric function theory
The classical theory of symmetric functions has a central position in
algebraic combinatorics, bridging aspects of representation theory,
combinatorics, and enumerative geometry. More recently, this theory has been
fruitfully extended to the larger ring of quasisymmetric functions, with
corresponding applications. Here, we survey recent work extending this theory
further to general asymmetric polynomials.Comment: 36 pages, 8 figures, 1 table. Written for the proceedings of the
Schubert calculus conference in Guangzhou, Nov. 201
Comparator automata in quantitative verification
The notion of comparison between system runs is fundamental in formal
verification. This concept is implicitly present in the verification of
qualitative systems, and is more pronounced in the verification of quantitative
systems. In this work, we identify a novel mode of comparison in quantitative
systems: the online comparison of the aggregate values of two sequences of
quantitative weights. This notion is embodied by {\em comparator automata}
({\em comparators}, in short), a new class of automata that read two infinite
sequences of weights synchronously and relate their aggregate values.
We show that {aggregate functions} that can be represented with B\"uchi
automaton result in comparators that are finite-state and accept by the B\"uchi
condition as well. Such {\em -regular comparators} further lead to
generic algorithms for a number of well-studied problems, including the
quantitative inclusion and winning strategies in quantitative graph games with
incomplete information, as well as related non-decision problems, such as
obtaining a finite representation of all counterexamples in the quantitative
inclusion problem.
We study comparators for two aggregate functions: discounted-sum and
limit-average. We prove that the discounted-sum comparator is -regular
iff the discount-factor is an integer. Not every aggregate function, however,
has an -regular comparator. Specifically, we show that the language of
sequence-pairs for which limit-average aggregates exist is neither
-regular nor -context-free. Given this result, we introduce the
notion of {\em prefix-average} as a relaxation of limit-average aggregation,
and show that it admits -context-free comparators
Rational series and asymptotic expansion for linear homogeneous divide-and-conquer recurrences
Among all sequences that satisfy a divide-and-conquer recurrence, the
sequences that are rational with respect to a numeration system are certainly
the most immediate and most essential. Nevertheless, until recently they have
not been studied from the asymptotic standpoint. We show how a mechanical
process permits to compute their asymptotic expansion. It is based on linear
algebra, with Jordan normal form, joint spectral radius, and dilation
equations. The method is compared with the analytic number theory approach,
based on Dirichlet series and residues, and new ways to compute the Fourier
series of the periodic functions involved in the expansion are developed. The
article comes with an extended bibliography
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