Families of prudent self-avoiding walks

A self-avoiding walk on the square lattice is $\textit{prudent}$, if it never takes a step towards a vertex it has already visited. Préa was the first to address the enumeration of these walks, in 1997. For 4 natural classes of prudent walks, he wrote a system of recurrence relations, involving the...

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Main Author: Mireille Bousquet-Mélou
Format: Article
Language:English
Published: Discrete Mathematics & Theoretical Computer Science 2008-01-01
Series:Discrete Mathematics & Theoretical Computer Science
Subjects:
Online Access:https://dmtcs.episciences.org/3627/pdf
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author Mireille Bousquet-Mélou
author_facet Mireille Bousquet-Mélou
author_sort Mireille Bousquet-Mélou
collection DOAJ
description A self-avoiding walk on the square lattice is $\textit{prudent}$, if it never takes a step towards a vertex it has already visited. Préa was the first to address the enumeration of these walks, in 1997. For 4 natural classes of prudent walks, he wrote a system of recurrence relations, involving the length of the walks and some additional "catalytic'' parameters. The generating function of the first class is easily seen to be rational. The second class was proved to have an algebraic (quadratic) generating function by Duchi (FPSAC'05). Here, we solve exactly the third class, which turns out to be much more complex: its generating function is not algebraic, nor even $D$-finite. The fourth class ―- general prudent walks ―- still defeats us. However, we design an isotropic family of prudent walks on the triangular lattice, which we count exactly. Again, the generating function is proved to be non-$D$-finite. We also study the end-to-end distance of these walks and provide random generation procedures.
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spelling doaj.art-ba70282839fa4c9aaf6dbd8221c355702024-03-07T14:38:06ZengDiscrete Mathematics & Theoretical Computer ScienceDiscrete Mathematics & Theoretical Computer Science1365-80502008-01-01DMTCS Proceedings vol. AJ,...Proceedings10.46298/dmtcs.36273627Families of prudent self-avoiding walksMireille Bousquet-Mélou0https://orcid.org/0000-0002-2863-8300Laboratoire Bordelais de Recherche en InformatiqueA self-avoiding walk on the square lattice is $\textit{prudent}$, if it never takes a step towards a vertex it has already visited. Préa was the first to address the enumeration of these walks, in 1997. For 4 natural classes of prudent walks, he wrote a system of recurrence relations, involving the length of the walks and some additional "catalytic'' parameters. The generating function of the first class is easily seen to be rational. The second class was proved to have an algebraic (quadratic) generating function by Duchi (FPSAC'05). Here, we solve exactly the third class, which turns out to be much more complex: its generating function is not algebraic, nor even $D$-finite. The fourth class ―- general prudent walks ―- still defeats us. However, we design an isotropic family of prudent walks on the triangular lattice, which we count exactly. Again, the generating function is proved to be non-$D$-finite. We also study the end-to-end distance of these walks and provide random generation procedures.https://dmtcs.episciences.org/3627/pdfenumerationself-avoiding walks$d$-finite generating functions[math.math-co] mathematics [math]/combinatorics [math.co][info.info-dm] computer science [cs]/discrete mathematics [cs.dm]
spellingShingle Mireille Bousquet-Mélou
Families of prudent self-avoiding walks
Discrete Mathematics & Theoretical Computer Science
enumeration
self-avoiding walks
$d$-finite generating functions
[math.math-co] mathematics [math]/combinatorics [math.co]
[info.info-dm] computer science [cs]/discrete mathematics [cs.dm]
title Families of prudent self-avoiding walks
title_full Families of prudent self-avoiding walks
title_fullStr Families of prudent self-avoiding walks
title_full_unstemmed Families of prudent self-avoiding walks
title_short Families of prudent self-avoiding walks
title_sort families of prudent self avoiding walks
topic enumeration
self-avoiding walks
$d$-finite generating functions
[math.math-co] mathematics [math]/combinatorics [math.co]
[info.info-dm] computer science [cs]/discrete mathematics [cs.dm]
url https://dmtcs.episciences.org/3627/pdf
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