Sampling 3-colourings of regular bipartite graphs
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1. | Title | Title of document | Sampling 3-colourings of regular bipartite graphs |
2. | Creator | Author's name, affiliation, country | David J Galvin; University of Pennsylvania |
3. | Subject | Discipline(s) | |
3. | Subject | Keyword(s) | Mixing time, 3-colouring, Potts model, conductance, Glauber dynamics, discrete hypercube |
3. | Subject | Subject classification | 05C15, 82B20 |
4. | Description | Abstract | We show that if $G=(V,E)$ is a regular bipartite graph for which the expansion of subsets of a single parity of $V$ is reasonably good and which satisfies a certain local condition (that the union of the neighbourhoods of adjacent vertices does not contain too many pairwise non-adjacent vertices), and if $M$ is a Markov chain on the set of proper 3-colourings of $G$ which updates the colour of at most $c|V|$ vertices at each step and whose stationary distribution is uniform, then for $c < .22$ and $d$ sufficiently large the convergence to stationarity of $M$ is (essentially) exponential in $|V|$. In particular, if $G$ is the $d$-dimensional hypercube $Q_d$ (the graph on vertex set $\{0,1\}^d$ in which two strings are adjacent if they differ on exactly one coordinate) then the convergence to stationarity of the well-known Glauber (single-site update) dynamics is exponentially slow in $2^d/(\sqrt{d} \log d )$. A combinatorial corollary of our main result is that in a uniform 3-colouring of $Q_d$ there is an exponentially small probability (in $2^d$) that there is a colour $i$ such the proportion of vertices of the even subcube coloured $i$ differs from the proportion of the odd subcube coloured $i$ by at most .22. Our proof combines a conductance argument with combinatorial enumeration methods. |
5. | Publisher | Organizing agency, location | |
6. | Contributor | Sponsor(s) | NSF (grant DMS-0111298) |
7. | Date | (YYYY-MM-DD) | 2007-04-18 |
8. | Type | Status & genre | Peer-reviewed Article |
8. | Type | Type | |
9. | Format | File format | |
10. | Identifier | Uniform Resource Identifier | http://ejp.ejpecp.org/article/view/403 |
10. | Identifier | Digital Object Identifier | 10.1214/EJP.v12-403 |
11. | Source | Journal/conference title; vol., no. (year) | Electronic Journal of Probability; Vol 12 |
12. | Language | English=en | |
14. | Coverage | Geo-spatial location, chronological period, research sample (gender, age, etc.) | |
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