Abstract
One of the most intriguing discoveries made by Erdös and Rényi in the course of their investigating random graphs is the so-called phase transition phenomenona, like the sudden emergence of the giant component. Since then, this kind of phenomena have been observed in many, diverse, areas of combinatorics and discrete mathematics in general. Typically, the notion of phase transition in combinatorics is related to a sudden change in the structural properties of a combinatorial construction, e.g. a (hyper)graph, arithmetic progressions e.t.c. However, it seems that the study of phase transitions goes much further. There is an empirical evidence that certain phase transition phenomena play a prominent role in the performance of algorithms for a lot of natural computational problems. That is, phase transitions are related to the, somehow elusive, notion of computational intractability. The last fifteen-twenty years, there has been serious attempts to put this relation on a mathematically rigorous basis. Our aim is to highlight some of the most central problems that arise in this endeavor.
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Notes
- 1.
As local greedy algorithms.
- 2.
The interested reader can find rapid mixing bound fro the hard-core model (weighted independent sets), too.
- 3.
The paper in [31] is for G(n, p) model for \(p=d/n\), the result for G(n, m) follow by using standard arguments.
- 4.
There are cases where the dynamics remains ergodic beyond non-reconstruction, e.g. hard-core model. In these cases the non-ergodicity is substituted by “low conductance”, which implies slow mixing.
- 5.
Since this search usually gets stuck in a local but not a global optimum, it is customary to carry out the process several times, starting from different configurations, and save the best result.
- 6.
Independent set of a graph is any subset of its vertices which do not span any edge with each other.
- 7.
Somehow the problem of computing marginals turns out to be easier than sampling.
- 8.
The algorithm in [30] is for the related G(n, p) where \(p=d/n\). result for G(n, m) follows by just using standard arguments.
- 9.
To be more precise the colour remains asymptotically random.
- 10.
This justifies the name message passing algorithm.
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Acknowledgement
Most of the material in the introduction come from discussions with Amin Coja-Oghlan. For this reason I would like to thank him.
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Efthymiou, C. (2015). Random Instances of Problems in NP – Algorithms and Statistical Physics. In: Zaroliagis, C., Pantziou, G., Kontogiannis, S. (eds) Algorithms, Probability, Networks, and Games. Lecture Notes in Computer Science(), vol 9295. Springer, Cham. https://doi.org/10.1007/978-3-319-24024-4_13
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