4,115 research outputs found
Promotion on oscillating and alternating tableaux and rotation of matchings and permutations
Using Henriques' and Kamnitzer's cactus groups, Sch\"utzenberger's promotion
and evacuation operators on standard Young tableaux can be generalised in a
very natural way to operators acting on highest weight words in tensor products
of crystals.
For the crystals corresponding to the vector representations of the
symplectic groups, we show that Sundaram's map to perfect matchings intertwines
promotion and rotation of the associated chord diagrams, and evacuation and
reversal. We also exhibit a map with similar features for the crystals
corresponding to the adjoint representations of the general linear groups.
We prove these results by applying van Leeuwen's generalisation of Fomin's
local rules for jeu de taquin, connected to the action of the cactus groups by
Lenart, and variants of Fomin's growth diagrams for the Robinson-Schensted
correspondence
Increasing and Decreasing Sequences in Fillings of Moon Polyominoes
We present an adaptation of jeu de taquin and promotion for arbitrary
fillings of moon polyominoes. Using this construction we show various symmetry
properties of such fillings taking into account the lengths of longest
increasing and decreasing chains. In particular, we prove a conjecture of Jakob
Jonsson. We also relate our construction to the one recently employed by
Christian Krattenthaler, thus generalising his results.Comment: fixed typo
Some remarks on sign-balanced and maj-balanced posets
Let P be a poset with elements 1,2,...,n. We say that P is sign-balanced if
exactly half the linear extensions of P (regarded as permutations of 1,2,...,n)
are even permutations, i.e., have an even number of inversions. This concept
first arose in the work of Frank Ruskey, who was interested in the efficient
generation of all linear extensions of P. We survey a number of techniques for
showing that posets are sign-balanced, and more generally, computing their
"imbalance." There are close connections with domino tilings and, for certain
posets, a "domino generalization" of Schur functions due to Carre and Leclerc.
We also say that P is maj-balanced if exactly half the linear extensions of P
have even major index. We discuss some similarities and some differences
between sign-balanced and maj-balanced posets.Comment: 30 pages. Some inaccuracies in Section 3 have been corrected, and
Conjecture 3.6 has been adde
Estimating Fire Weather Indices via Semantic Reasoning over Wireless Sensor Network Data Streams
Wildfires are frequent, devastating events in Australia that regularly cause
significant loss of life and widespread property damage. Fire weather indices
are a widely-adopted method for measuring fire danger and they play a
significant role in issuing bushfire warnings and in anticipating demand for
bushfire management resources. Existing systems that calculate fire weather
indices are limited due to low spatial and temporal resolution. Localized
wireless sensor networks, on the other hand, gather continuous sensor data
measuring variables such as air temperature, relative humidity, rainfall and
wind speed at high resolutions. However, using wireless sensor networks to
estimate fire weather indices is a challenge due to data quality issues, lack
of standard data formats and lack of agreement on thresholds and methods for
calculating fire weather indices. Within the scope of this paper, we propose a
standardized approach to calculating Fire Weather Indices (a.k.a. fire danger
ratings) and overcome a number of the challenges by applying Semantic Web
Technologies to the processing of data streams from a wireless sensor network
deployed in the Springbrook region of South East Queensland. This paper
describes the underlying ontologies, the semantic reasoning and the Semantic
Fire Weather Index (SFWI) system that we have developed to enable domain
experts to specify and adapt rules for calculating Fire Weather Indices. We
also describe the Web-based mapping interface that we have developed, that
enables users to improve their understanding of how fire weather indices vary
over time within a particular region.Finally, we discuss our evaluation results
that indicate that the proposed system outperforms state-of-the-art techniques
in terms of accuracy, precision and query performance.Comment: 20pages, 12 figure
The oriented swap process and last passage percolation
We present new probabilistic and combinatorial identities relating three
random processes: the oriented swap process on particles, the corner growth
process, and the last passage percolation model. We prove one of the
probabilistic identities, relating a random vector of last passage percolation
times to its dual, using the duality between the Robinson-Schensted-Knuth and
Burge correspondences. A second probabilistic identity, relating those two
vectors to a vector of 'last swap times' in the oriented swap process, is
conjectural. We give a computer-assisted proof of this identity for
after first reformulating it as a purely combinatorial identity, and discuss
its relation to the Edelman-Greene correspondence. The conjectural identity
provides precise finite- and asymptotic predictions on the distribution of
the absorbing time of the oriented swap process, thus conditionally solving an
open problem posed by Angel, Holroyd and Romik.Comment: 36 pages, 6 figures. Full version of the FPSAC 2020 extended abstract
arXiv:2003.0333
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