Archimedean limit conjecture for sorting-network permutation matrices

Let σn\sigma^n be an nn-element uniform random sorting network, and let σGn(i,t)\sigma_G^n(i,t) be its globally rescaled particle positions. Let Arch1/2\mathfrak{Arch}_{1/2} be the probability measure on [1,1]2[-1,1]^2 with density 1/(2π1x2y2)1/(2\pi\sqrt{1-x^2-y^2}) on the unit disk, and let Archt\mathfrak{Arch}_t be the distribution of (X,Xcos(πt)+Ysin(πt))(X,X\cos(\pi t)+Y\sin(\pi t)) when (X,Y)(X,Y) has law Arch1/2\mathfrak{Arch}_{1/2}. Define

ηtn=1ni=1ndelta(σGn(i,0),σGn(i,t)).\eta_t^n=\frac1n\sum_{i=1}^ndelta(\sigma_G^n(i,0),\sigma_G^n(i,t)).

Angel–Holroyd–Romik–Virág Archimedean-limit conjecture. For every t[0,1]t\in[0,1],

ηtn\tomathfrakArcht\eta_t^n\tomathfrak{Arch}_t

in probability in the weak topology. Equivalently, for every weakly open neighbourhood OO of Archt\mathfrak{Arch}_t, P(ηtnO)1\mathbb{P}(\eta_t^n\in O)\to1 as nn\to\infty. This conjecture gives the global limiting shape of time-tt permutation matrices; the source says that subsequent work proves it.

Sources & referencesView supporting material

Primary source

Duncan Dauvergne and Bálint Virág, “Circular support in random sorting networks”, arXiv:1802.08933 (2018).

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