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280
Varieties of Increasing Trees
, 1992
"... An increasing tree is a labelled rooted tree in which labels along any branch from the root go in increasing order. Under various guises, such trees have surfaced as tree representations of permutations, as data structures in computer science, and as probabilistic models in diverse applications. We ..."
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Cited by 55 (7 self)
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An increasing tree is a labelled rooted tree in which labels along any branch from the root go in increasing order. Under various guises, such trees have surfaced as tree representations of permutations, as data structures in computer science, and as probabilistic models in diverse applications. We present a unified generating function approach to the enumeration of parameters on such trees. The counting generating functions for several basic parameters are shown to be related to a simple ordinary differential equation which is non linear and autonomous. Singularity analysis applied to the intervening generating functions then permits to analyze asymptotically a number of parameters of the trees, like: root degree, number of leaves, path length, and level of nodes. In this way it is found that various models share common features: path length is O(n log n), the distributions of node levels and number of leaves are asymptotically normal, etc.
Random maps, coalescing saddles, singularity analysis, and Airy phenomena
 Random Structures & Algorithms
, 2001
"... A considerable number of asymptotic distributions arising in random combinatorics and analysis of algorithms are of the exponentialquadratic type, that is, Gaussian. We exhibit a class of "universal" phenomena that are of the exponentialcubic type, corresponding to distributions that involve the ..."
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Cited by 48 (7 self)
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A considerable number of asymptotic distributions arising in random combinatorics and analysis of algorithms are of the exponentialquadratic type, that is, Gaussian. We exhibit a class of "universal" phenomena that are of the exponentialcubic type, corresponding to distributions that involve the Airy function. In this paper, such Airy phenomena are related to the coalescence of saddle points and the confluence of singularities of generating functions. For about a dozen types of random planar maps, a common Airy distribution (equivalently, a stable law of exponent 3/2) describes the sizes of cores and of largest (multi)connected components. Consequences include the analysis and fine optimization of random generation algorithms for multiply connected planar graphs. Based on an extension of the singularity analysis framework suggested by the Airy case, the paper also presents a general classification of compositional schemas in analytic combinatorics.
Bounds On The Complex Zeros Of (Di)Chromatic Polynomials And PottsModel Partition Functions
 Chromatic Roots Are Dense In The Whole Complex Plane, Combinatorics, Probability and Computing
"... I show that there exist universal constants C(r) < ∞ such that, for all loopless graphs G of maximum degree ≤ r, the zeros (real or complex) of the chromatic polynomial PG(q) lie in the disc q  < C(r). Furthermore, C(r) ≤ 7.963907r. This result is a corollary of a more general result on the zeros ..."
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Cited by 45 (11 self)
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I show that there exist universal constants C(r) < ∞ such that, for all loopless graphs G of maximum degree ≤ r, the zeros (real or complex) of the chromatic polynomial PG(q) lie in the disc q  < C(r). Furthermore, C(r) ≤ 7.963907r. This result is a corollary of a more general result on the zeros of the Pottsmodel partition function ZG(q, {ve}) in the complex antiferromagnetic regime 1 + ve  ≤ 1. The proof is based on a transformation of the Whitney–Tutte–Fortuin–Kasteleyn representation of ZG(q, {ve}) to a polymer gas, followed by verification of the Dobrushin–Koteck´y–Preiss condition for nonvanishing of a polymermodel partition function. I also show that, for all loopless graphs G of secondlargest degree ≤ r, the zeros of PG(q) lie in the disc q  < C(r) + 1. KEY WORDS: Graph, maximum degree, secondlargest degree, chromatic polynomial,
Enumeration of Planar Constellations
 Adv. in Appl. Math
, 2000
"... The enumeration of transitive ordered factorizations of a given permutation is a combinatorial problem related to singularity theory. Let n ? 1, m ? 2, and let oe 0 be a permutation of Sn having d i cycles of length i, for i ? 1. We prove that the number of mtuples (oe 1 ; : : : ; oe m ) of permut ..."
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Cited by 43 (2 self)
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The enumeration of transitive ordered factorizations of a given permutation is a combinatorial problem related to singularity theory. Let n ? 1, m ? 2, and let oe 0 be a permutation of Sn having d i cycles of length i, for i ? 1. We prove that the number of mtuples (oe 1 ; : : : ; oe m ) of permutations of Sn such that: ffl oe 1 oe 2 \Delta \Delta \Delta oe m = oe 0 , ffl the group generated by oe 1 ; : : : ; oe m acts transitively on f1; 2; : : : ; ng, ffl P m i=0 c(oe i ) = n(m \Gamma 1) + 2, where c(oe i ) denotes the number of cycles of oe i , is m [(m \Gamma 1)n \Gamma 1]! [(m \Gamma 1)n \Gamma c(oe0 ) + 2]! Y i?1 " i / mi \Gamma 1 i !# d i : A onetoone correspondence relates these mtuples to some rooted planar maps, which we call constellations and enumerate via a bijection with some bicolored trees. For m = 2, we recover a formula of Tutte for the number of Eulerian maps. The proof extends the method applied in [21] to the latter case, and relies on the idea...
EXPERIENCE WITH SOFTWARE WATERMARKING
, 2004
"... There are at least four U.S. patents on software watermarking, and an idea for further advancing the state of the art was presented in 1999 by Collberg and Thomborsen. The new idea is to embed a watermark in dynamic data structures, thereby protecting against many programtransformation attacks. Unti ..."
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Cited by 39 (0 self)
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There are at least four U.S. patents on software watermarking, and an idea for further advancing the state of the art was presented in 1999 by Collberg and Thomborsen. The new idea is to embed a watermark in dynamic data structures, thereby protecting against many programtransformation attacks. Until now there have been no reports on practical experience with this technique. We have implemented and experimented with a watermarking system for Java based on the ideas of Collberg and Thomborsen. Our experiments show that watermarking can be done efficiently with moderate increases in code size, execution times, and heapspace usage, while making the watermarked code resilient to a variety of programtransformation attacks. For a particular representation of watermarks, the time to retrieve a watermark is on the order of one minute per megabyte of heap space. Our implementation is not designed to resists all possible attacks; to do that it should be combined with other protection techniques such as obfuscation and tamperproofing.
New infinite families of exact sums of squares formulas, Jacobi elliptic functions, and Ramanujan’s tau function
, 1996
"... Dedicated to the memory of GianCarlo Rota who encouraged me to write this paper in the present style Abstract. In this paper we derive many infinite families of explicit exact formulas involving either squares or triangular numbers, two of which generalize Jacobi’s 4 and 8 squares identities to 4n ..."
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Cited by 35 (1 self)
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Dedicated to the memory of GianCarlo Rota who encouraged me to write this paper in the present style Abstract. In this paper we derive many infinite families of explicit exact formulas involving either squares or triangular numbers, two of which generalize Jacobi’s 4 and 8 squares identities to 4n 2 or 4n(n + 1) squares, respectively, without using cusp forms. In fact, we similarly generalize to infinite families all of Jacobi’s explicitly stated degree 2, 4, 6, 8 Lambert series expansions of classical theta functions. In addition, we extend Jacobi’s special analysis of 2 squares, 2 triangles, 6 squares, 6 triangles to 12 squares, 12 triangles, 20 squares, 20 triangles, respectively. Our 24 squares identity leads to a different formula for Ramanujan’s tau function τ(n), when n is odd. These results, depending on new expansions for powers of various products of classical theta functions, arise in the setting of Jacobi elliptic functions, associated continued fractions, regular Cfractions, Hankel or Turánian determinants, Fourier series, Lambert series, inclusion/exclusion, Laplace expansion formula for determinants, and Schur functions. The Schur function form of these infinite families of identities are analogous to the ηfunction identities of Macdonald. Moreover, the powers 4n(n + 1), 2n 2 + n, 2n 2 − n that appear in Macdonald’s work also arise at appropriate places in our analysis. A special case of our general methods yields a proof of the two Kac–Wakimoto conjectured identities involving representing
A COMBINATORIAL IDENTITY WITH APPLICATION TO CATALAN NUMBERS
, 2005
"... By a very simple argument, we prove that if l, m, n ∈ {0, 1, 2,...} then l∑ (−1) m−k ( l m − k ..."
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Cited by 33 (31 self)
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By a very simple argument, we prove that if l, m, n ∈ {0, 1, 2,...} then l∑ (−1) m−k ( l m − k
Twenty combinatorial examples of asymptotics derived from multivariate generating functions
"... Abstract. Let {ar: r ∈ Nd} be a ddimensional array of numbers for which the generating function F (z): = ∑ r arzr is meromorphic in a neighborhood of the origin. For example, F may be a rational multivariate generating function. We discuss recent results that allow the effective computation of asym ..."
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Cited by 33 (15 self)
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Abstract. Let {ar: r ∈ Nd} be a ddimensional array of numbers for which the generating function F (z): = ∑ r arzr is meromorphic in a neighborhood of the origin. For example, F may be a rational multivariate generating function. We discuss recent results that allow the effective computation of asymptotic expansions for the coefficients of F. Our purpose is to illustrate the use of these techniques on a variety of problems of combinatorial interest. The survey begins by summarizing previous work on the asymptotics of univariate and multivariate generating functions. Next we describe the Morsetheoretic underpinnings of some new asymptotic techniques. We then quote and summarize these results in such a way that only elementary analyses are needed to check hypotheses and carry out computations. The remainder of the survey focuses on combinatorial applications, such as enumeration of words with forbidden substrings, edges and cycles in graphs, polyominoes, and descents in permutations. After the individual examples, we discuss three broad classes of examples, namely, functions derived via the transfer matrix method, those derived via the kernel method, and those derived via the method of Lagrange inversion. These methods have
equations for Hurwitz numbers
"... We consider ramified coverings of P 1 with arbitrary ramification type over 0, ∞ ∈ P 1 and simple ramifications elsewhere and prove that the generating function for the numbers of such coverings is a τfunction for the Toda lattice hierarchy of Ueno and Takasaki. ..."
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Cited by 32 (3 self)
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We consider ramified coverings of P 1 with arbitrary ramification type over 0, ∞ ∈ P 1 and simple ramifications elsewhere and prove that the generating function for the numbers of such coverings is a τfunction for the Toda lattice hierarchy of Ueno and Takasaki.