9,045 research outputs found
Division and the Giambelli Identity
Given two polynomials f(x) and g(x), we extend the formula expressing the
remainder in terms of the roots of these two polynomials to the case where f(x)
is a Laurent polynomial. This allows us to give new expressions of a Schur
function, which generalize the Giambelli identity.Comment: 9 pages, 1 figur
The Alternative Choice of Constitutive Exons throughout Evolution
Alternative cassette exons are known to originate from two processes
exonization of intronic sequences and exon shuffling. Herein, we suggest an
additional mechanism by which constitutively spliced exons become alternative
cassette exons during evolution. We compiled a dataset of orthologous exons
from human and mouse that are constitutively spliced in one species but
alternatively spliced in the other. Examination of these exons suggests that
the common ancestors were constitutively spliced. We show that relaxation of
the 59 splice site during evolution is one of the molecular mechanisms by which
exons shift from constitutive to alternative splicing. This shift is associated
with the fixation of exonic splicing regulatory sequences (ESRs) that are
essential for exon definition and control the inclusion level only after the
transition to alternative splicing. The effect of each ESR on splicing and the
combinatorial effects between two ESRs are conserved from fish to human. Our
results uncover an evolutionary pathway that increases transcriptome diversity
by shifting exons from constitutive to alternative splicin
Analytic approach for reflected Brownian motion in the quadrant
Random walks in the quarter plane are an important object both of
combinatorics and probability theory. Of particular interest for their study,
there is an analytic approach initiated by Fayolle, Iasnogorodski and Malyshev,
and further developed by the last two authors of this note. The outcomes of
this method are explicit expressions for the generating functions of interest,
asymptotic analysis of their coefficients, etc. Although there is an important
literature on reflected Brownian motion in the quarter plane (the continuous
counterpart of quadrant random walks), an analogue of the analytic approach has
not been fully developed to that context. The aim of this note is twofold: it
is first an extended abstract of two recent articles of the authors of this
paper, which propose such an approach; we further compare various aspects of
the discrete and continuous analytic approaches.Comment: 19 pages, 5 figures. Extended abstract of the papers arXiv:1602.03054
and arXiv:1604.02918, to appear in Proceedings of the 27th International
Conference on Probabilistic, Combinatorial and Asymptotic Methods for the
Analysis of Algorithms, Krakow, Poland, 4-8 July 2016 arXiv admin note: text
overlap with arXiv:1602.0305
Partial duality of hypermaps
We introduce a collection of new operations on hypermaps, partial duality,
which include the classical Euler-Poincar\'e dualities as particular cases.
These operations generalize the partial duality for maps, or ribbon graphs,
recently discovered in a connection with knot theory. Partial duality is
different from previous studied operations of S. Wilson, G. Jones, L. James,
and A. Vince. Combinatorially hypermaps may be described in one of three ways:
as three involutions on the set of flags (-model), or as three
permutations on the set of half-edges (-model in orientable case), or
as edge 3-colored graphs. We express partial duality in each of these models.Comment: 19 pages, 16 figure
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