Mathematical structures with name referring to a country

Question

I am looking for a list of mathematical structures (not theorems) that refer to a country or nationality.

I only know of Polish spaces and Polish groups. Does anyone have other examples?

Note: many of these can be found when looking at Olympiad contests since they often decide to name structures after the city or country where the event is hosted, but I would like examples found in the literature.

Answer 1

An answer was already given and accepted but I thought it might be cool to share this combinatorial structure; which I found in Richard Stanley's book Enumerative Combinatorics: Aztec Diamonds. Note I am taking liberty to use the word Aztec as in the Aztec empire.

Aztec diamonds were introduced by Noam Elkies, Greg Kuperberg, Michael Larsen and James Propp in 1991. The original paper can be found in the arxiv Alternating sign matrices and domino tilings. Following the paper: The Aztec diamond of order $n$ is the union of those lattice squares $[a,a + 1] \times [b,b + 1] ⊂ \mathbb{R}^{2}$ with $a,b\in Z$ that lie completely inside the tilted square $\{(x,y) : |x| + |y| \leq n + 1\}.$ Several proofs are given that show the number of domino tilings of the Aztec diamond of order $n$ is $2^{n(n+1)/2}$ a result the authors refer to as the Aztec Diamond Theorem. Apparently there is a connection between Aztec Diamonds and the square-ice-model of Lieb.

Answer 2

Another example are American puts, and American calls