367 research outputs found
Lattice paths of slope 2/5
We analyze some enumerative and asymptotic properties of Dyck paths under a
line of slope 2/5.This answers to Knuth's problem \\#4 from his "Flajolet
lecture" during the conference "Analysis of Algorithms" (AofA'2014) in Paris in
June 2014.Our approach relies on the work of Banderier and Flajolet for
asymptotics and enumeration of directed lattice paths. A key ingredient in the
proof is the generalization of an old trick of Knuth himself (for enumerating
permutations sortable by a stack),promoted by Flajolet and others as the
"kernel method". All the corresponding generating functions are algebraic,and
they offer some new combinatorial identities, which can be also tackled in the
A=B spirit of Wilf--Zeilberger--Petkov{\v s}ek.We show how to obtain similar
results for other slopes than 2/5, an interesting case being e.g. Dyck paths
below the slope 2/3, which corresponds to the so called Duchon's club model.Comment: Robert Sedgewick and Mark Daniel Ward. Analytic Algorithmics and
Combinatorics (ANALCO)2015, Jan 2015, San Diego, United States. SIAM, 2015
Proceedings of the Twelfth Workshop on Analytic Algorithmics and
Combinatorics (ANALCO), eISBN 978-1-61197-376-1, pp.105-113, 2015, 2015
Proceedings of the Twelfth Workshop on Analytic Algorithmics and
Combinatorics (ANALCO
Generating Functions For Kernels of Digraphs (Enumeration & Asymptotics for Nim Games)
In this article, we study directed graphs (digraphs) with a coloring
constraint due to Von Neumann and related to Nim-type games. This is equivalent
to the notion of kernels of digraphs, which appears in numerous fields of
research such as game theory, complexity theory, artificial intelligence
(default logic, argumentation in multi-agent systems), 0-1 laws in monadic
second order logic, combinatorics (perfect graphs)... Kernels of digraphs lead
to numerous difficult questions (in the sense of NP-completeness,
#P-completeness). However, we show here that it is possible to use a generating
function approach to get new informations: we use technique of symbolic and
analytic combinatorics (generating functions and their singularities) in order
to get exact and asymptotic results, e.g. for the existence of a kernel in a
circuit or in a unicircuit digraph. This is a first step toward a
generatingfunctionology treatment of kernels, while using, e.g., an approach "a
la Wright". Our method could be applied to more general "local coloring
constraints" in decomposable combinatorial structures.Comment: Presented (as a poster) to the conference Formal Power Series and
Algebraic Combinatorics (Vancouver, 2004), electronic proceeding
Du Bartas et l’ars memorativa
Malgré les efforts entrepris depuis plusieurs décennies, l’oeuvre de Guillaume Salluste Du Bartas (1544-1590) est loin d’avoir livré tous ses secrets. De manière générale, son importance semble encore sous-évaluée, alors que cet auteur connut, de son vivant et jusqu’à quarante ans après sa mort, une gloire et un rayonnement exceptionnels. Afin de mieux éclairer les raisons de ce succès, cet article étudie La Sepmaine comme ressortissant à la tradition de l’ars memorativa. Le succès de ce poème à la fois didactique, apologétique et encyclopédique correspond, en effet, à la période de l’histoire occidentale où la mnémotechnie, héritée de l’Antiquité grecque, suscite un vif regain d’intérêt. Aussi l’auteur propose-t-il d’analyser tout particulièrement la place et la fonction de la mnémotechnique dans ce texte, ainsi que les divers moyens rhétoriques dont il se sert.Despite efforts undertaken in many recent decades, the work of Guillaume Salluste Du Bartas (1544-1590) has by no means revealed all its secrets. Its importance, generally speaking, still appears under-estimated, whereas there were outstanding recognition and popularity for this author during his lifetime and up to forty years after his death. To shed light on the reason for this success, this article studies the Sepmaine as issuing from the tradition of the ars memorativa. The success of this poem at once didactic, apologetic and encyclopaedic corresponds, in fact, to that period of Western history when the mnemotechnics inherited from Greek antiquity experienced a lively renewal of interest. Our purpose is therefore to analyze, very particularly, the position and function of mnemotechnics in this text, as well as the various rhetorical methods it employs
Bounded discrete walks
International audienceThis article tackles the enumeration and asymptotics of directed lattice paths (that are isomorphic to unidimensional paths) of bounded height (walks below one wall, or between two walls, for finite set of jumps). Thus, for any lattice paths, we give the generating functions of bridges ("discrete'' Brownian bridges) and reflected bridges ("discrete'' reflected Brownian bridges) of a given height. It is a new success of the "kernel method'' that the generating functions of such walks have some nice expressions as symmetric functions in terms of the roots of the kernel. These formulae also lead to fast algorithms for computing the -th Taylor coefficients of the corresponding generating functions. For a large class of walks, we give the discrete distribution of the height of bridges, and show the convergence to a Rayleigh limit law. For the family of walks consisting of a jump and many positive jumps, we give more precise bounds for the speed of convergence. We end our article with a heuristic application to bioinformatics that has a high speed-up relative to previous work
On Lattice Paths with Marked Patterns: Generating Functions and Multivariate Gaussian Distribution
International audienc
FORMULAE AND ASYMPTOTICS FOR COEFFICIENTS OF ALGEBRAIC FUNCTIONS
International audienc
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