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پژوهشکدهٔ ریاضیات


Seminar on Mathematical Logic سمینار منطق ریاضی




TITLE  
Graphons, Hypergraphons, and Generic Sampling


SPEAKER  
Kyle Gannon  
Peking University, China  
 


TIME  
Thursday, May 1, 2025,   14:00 - 16:00


VENUE   Lecture Hall 1, Niavaran Bldg.



SUMMARY

 

Intuitively, generic sampling is a method for sampling types over monster models of a first-order theory with respect to a Keisler measure. In practice, this involves studying countably iterated Morley products of relatively tame Keisler measures. Given such a measure, one can straightforwardly derive a corresponding Borel measure on the space of L-structures over the natural numbers. In particular, if the original monster model is a graph (respectively, a hypergraph), then generic sampling yields measures on the space of all graphs (respectively, hypergraphs) on the natural numbers.
A graphon is a symmetric measurable map from $[0,1]^{2}$ to $[0,1]$. These graph-like objects also give rise to a notion of sampling. It turns out that all Sym(N)-invariant measures on the space of graphs (over the natural numbers) are mixtures of sampling procedures arising from graphons. We remark that graphons admit a higher-arity generalization to hypergraphs, called hypergraphons, which exhibit a similar property.
We prove a representation theorem: (hyper)graphon sampling can be encoded within the framework of generic sampling. We remark that generic sampling in practice can give rise to non-Sym(N)-invariant measures and so generic sampling is strictly more general than what arises from (hyper)graphons. This is joint work with Nathanael Ackerman, Cameron Freer, James Hanson, and Rehana Patel.

Zoom room information:
https://us06web.zoom.us/j/81916335336?pwd=5zQT4lutMiBoY5Xp1pkFGtbqiaGozg.1
Meeting ID: 819 1633 5336
Passcode: 559618

 




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