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# The Number of Optimal Matchings for Euclidean Assignment on the Line

Abstract : Abstract We consider the Random Euclidean Assignment Problem in dimension $d=1$ d = 1 , with linear cost function. In this version of the problem, in general, there is a large degeneracy of the ground state, i.e. there are many different optimal matchings (say, $\sim \exp (S_N)$ ∼ exp ( S N ) at size N ). We characterize all possible optimal matchings of a given instance of the problem, and we give a simple product formula for their number. Then, we study the probability distribution of $S_N$ S N (the zero-temperature entropy of the model), in the uniform random ensemble. We find that, for large N , $S_N \sim \frac{1}{2} N \log N + N s + {\mathcal {O}}\left( \log N \right)$ S N ∼ 1 2 N log N + N s + O log N , where s is a random variable whose distribution p ( s ) does not depend on N . We give expressions for the moments of p ( s ), both from a formulation as a Brownian process, and via singularity analysis of the generating functions associated to $S_N$ S N . The latter approach provides a combinatorial framework that allows to compute an asymptotic expansion to arbitrary order in 1/ N for the mean and the variance of $S_N$ S N .
Document type :
Journal articles

https://hal.archives-ouvertes.fr/hal-03204820
Contributor : Andrea Sportiello Connect in order to contact the contributor
Submitted on : Wednesday, April 21, 2021 - 7:15:27 PM
Last modification on : Tuesday, January 4, 2022 - 6:03:31 AM
Long-term archiving on: : Thursday, July 22, 2021 - 7:32:10 PM

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2101.04926_forHal.pdf
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### Citation

Sergio Caracciolo, Vittorio Erba, Andrea Sportiello. The Number of Optimal Matchings for Euclidean Assignment on the Line. Journal of Statistical Physics, Springer Verlag, 2021, 183 (1), ⟨10.1007/s10955-021-02741-1⟩. ⟨hal-03204820⟩

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