8,723 research outputs found
Noncommutative crossing partitions
We define and study noncommutative crossing partitions which are a
generalization of non-crossing partitions. By introducing a new cover relation
on binary trees, we show that the partially ordered set of noncommutative
crossing partitions is a graded lattice. This new lattice contains the Kreweras
lattice, the lattice of non-crossing partitions, as a sublattice. We calculate
the M\"obius function, the number of maximal chains and the number of
-chains in this new lattice by constructing an explicit -labeling on the
lattice. By use of the -labeling, we recover the classical results on the
Kreweras lattice. We characterize two endomorphism on the Kreweras lattice, the
Kreweras complement map and the involution defined by Simion and Ullman, in
terms of the maps on the noncommutative crossing partitions. We also establish
relations among three combinatorial objects: labeled -ary trees,
-chains in the lattice, and -Dyck tilings.Comment: 45 page
Random matrices, continuous circular systems and the triangular operator
We present a Hilbert space approach to the limit joint *-distributions of
complex independent Gaussian random matrices. For that purpose, we use a
suitably defined family of creation and annihilation operators living in some
direct integral of Hilbert spaces. These operators are decomposed in terms of
continuous circular systems of operators acting between the fibers of the
considered Hilbert space direct integral. In the case of square matrices with
i.i.d. entries, we obtain the circular operators of Voiculescu, whereas in the
case of upper-triangular matrices with i.i.d. entries, we obtain the triangular
operators of Dykema and Haagerup. We apply this approach to give a bijective
proof of a formula for *-moments of the triangular operator, using the
enumeration formula of Chauve, Dulucq and Rechnizter for alternating ordered
rooted trees.Comment: 26 pages, 5 figures, 1 reference added, minor change
Relations between cumulants in noncommutative probability
We express classical, free, Boolean and monotone cumulants in terms of each
other, using combinatorics of heaps, pyramids, Tutte polynomials and
permutations. We completely determine the coefficients of these formulas with
the exception of the formula for classical cumulants in terms of monotone
cumulants whose coefficients are only partially computed.Comment: 27 pages, 7 figures, AMS LaTe
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