672 research outputs found
Effective Scalar Products for D-finite Symmetric Functions
Many combinatorial generating functions can be expressed as combinations of
symmetric functions, or extracted as sub-series and specializations from such
combinations. Gessel has outlined a large class of symmetric functions for
which the resulting generating functions are D-finite. We extend Gessel's work
by providing algorithms that compute differential equations these generating
functions satisfy in the case they are given as a scalar product of symmetric
functions in Gessel's class. Examples of applications to k-regular graphs and
Young tableaux with repeated entries are given. Asymptotic estimates are a
natural application of our method, which we illustrate on the same model of
Young tableaux. We also derive a seemingly new formula for the Kronecker
product of the sum of Schur functions with itself.Comment: 51 pages, full paper version of FPSAC 02 extended abstract; v2:
corrections from original submission, improved clarity; now formatted for
journal + bibliograph
Crystallization of random matrix orbits
Three operations on eigenvalues of real/complex/quaternion (corresponding to
) matrices, obtained from cutting out principal corners, adding,
and multiplying matrices can be extrapolated to general values of
through associated special functions.
We show that limit for these operations leads to the finite
free projection, additive convolution, and multiplicative convolution,
respectively.
The limit is the most transparent for cutting out the corners, where the
joint distribution of the eigenvalues of principal corners of a
uniformly-random general self-adjoint matrix with fixed eigenvalues is
known as -corners process. We show that as these
eigenvalues crystallize on the irregular lattice of all the roots of
derivatives of a single polynomial. In the second order, we observe a version
of the discrete Gaussian Free Field (dGFF) put on top of this lattice, which
provides a new explanation of why the (continuous) Gaussian Free Field governs
the global asymptotics of random matrix ensembles.Comment: 25 pages. v2: misprints corrected, to appear in IMR
An expansion formula for type A and Kronecker quantum cluster algebras
We introduce an expansion formula for elements in quantum cluster algebras associated to type A and Kronecker quivers with principal quantization. Our formula is parametrized by perfect matchings of snake graphs as in the classical case. In the Kronecker type, the coefficients are q-powers whose exponents are given by a weight function induced by the lattice of perfect matchings. As an application, we prove that a reflectional symmetry on the set of perfect matchings satisfies Stembridge's q=−1 phenomenon with respect to the weight function. Furthermore, we discuss a relation of our expansion formula to generating functions of BPS states
Explicit combinatorial interpretation of Kerov character polynomials as numbers of permutation factorizations
We find an explicit combinatorial interpretation of the coefficients of Kerov
character polynomials which express the value of normalized irreducible
characters of the symmetric groups S(n) in terms of free cumulants R_2,R_3,...
of the corresponding Young diagram. Our interpretation is based on counting
certain factorizations of a given permutation
The distribution of cycles in breakpoint graphs of signed permutations
Breakpoint graphs are ubiquitous structures in the field of genome
rearrangements. Their cycle decomposition has proved useful in computing and
bounding many measures of (dis)similarity between genomes, and studying the
distribution of those cycles is therefore critical to gaining insight on the
distributions of the genomic distances that rely on it. We extend here the work
initiated by Doignon and Labarre, who enumerated unsigned permutations whose
breakpoint graph contains cycles, to signed permutations, and prove
explicit formulas for computing the expected value and the variance of the
corresponding distributions, both in the unsigned case and in the signed case.
We also compare these distributions to those of several well-studied distances,
emphasising the cases where approximations obtained in this way stand out.
Finally, we show how our results can be used to derive simpler proofs of other
previously known results
Computer Science for Continuous Data:Survey, Vision, Theory, and Practice of a Computer Analysis System
Building on George Boole's work, Logic provides a rigorous foundation for the powerful tools in Computer Science that underlie nowadays ubiquitous processing of discrete data, such as strings or graphs. Concerning continuous data, already Alan Turing had applied "his" machines to formalize and study the processing of real numbers: an aspect of his oeuvre that we transform from theory to practice.The present essay surveys the state of the art and envisions the future of Computer Science for continuous data: natively, beyond brute-force discretization, based on and guided by and extending classical discrete Computer Science, as bridge between Pure and Applied Mathematics
- …