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Stationary probability of the identity for the TASEP on a Ring
KTH, School of Engineering Sciences (SCI), Mathematics (Dept.), Mathematics (Div.).
2012 (English)Other (Other academic)
Abstract [en]

Consider the following Markov chain on permutations of length n. At each time step we choose a random position. If the letter at that position is smaller than the letter immediately to the left (cyclically) then these letters swap positions. Otherwise nothing happens, corresponding to a loop in the Markov chain. This is the circular TASEP. We compute the average proportion of time the chain spends at the identity permutation (and, in greater generality, at sorted words). This answers a conjecture by Thomas Lam.

Place, publisher, year, edition, pages
National Category
URN: urn:nbn:se:kth:diva-156857OAI: diva2:768228

QC 20141203

Available from: 2014-12-03 Created: 2014-12-03 Last updated: 2014-12-04Bibliographically approved
In thesis
1. A Markov Process on Cyclic Words
Open this publication in new window or tab >>A Markov Process on Cyclic Words
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The TASEP (totally asymmetric simple exclusion process) studied here is a Markov chain on cyclic words over the alphabet{1,2,...,n} given by at each time step sorting an adjacent pair of letters chosen uniformly at random. For example, from the word 3124 one may go to 1324, 3124, 3124, 4123 by sorting the pair 31, 12, 24, or 43.

Two words have the sametype if they are permutations of each other. If we restrict TASEP to words of some particular type m we get an ergodic Markov chain whose stationary distribution we denote by ζm. Soζm (u) is the asymptotic proportion of time spent in the state u if the chain started in some word of type m. The distribution ζ is the main object of study in this thesis. This distribution turns out to have several remarkable properties, and alternative characterizations. It has previously been studied both from physical, combinatorial, and probabilitistic viewpoints.

In the first chapter we give an extended summary of known results and results in this thesis concerning ζ. The new results are described (and proved) in detail in Papers I - IV.

The new results in Papers I and II include an explicit formula for the value ofζat sorted words and a product formula for decomposable words. We also compute some correlation functions for ζ. In Paper III we study of a generalization of TASEP to Weyl groups. In Paper IV we study a certain scaling limit of ζ, finding several interesting patterns of which we prove some. We also study an inhomogenous version of TASEP, in which different particles get sorted at different rates, which generalizes the homogenous version in several aspects. In the first chapter we compute some correlation functions for ζ

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2014. vii, 35 p.
TRITA-MAT-A, 2014:12
National Category
urn:nbn:se:kth:diva-156862 (URN)978-91-7595-357-1 (ISBN)
Public defence
2014-12-12, E3, Osquars backe 14, KTH, Stockholm, 10:00 (English)

QC 20141204

Available from: 2014-12-04 Created: 2014-12-03 Last updated: 2015-08-27Bibliographically approved

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Aas, Erik
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