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world:choquet [2026/04/10 15:48]
rdouc [Krein-Milman, Choquet and Birkhoff-Von Neuman Theorems]
world:choquet [2026/04/10 15:48] (current)
rdouc [Krein-Milman, Choquet and Birkhoff-Von Neuman Theorems]
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 **Theorem (Birkhoff–Von Neumann).** Let $B_n$ be the set of bistochastic matrices (of size $n\times n$), i.e. defined by **Theorem (Birkhoff–Von Neumann).** Let $B_n$ be the set of bistochastic matrices (of size $n\times n$), i.e. defined by
 $$ $$
-B_n = \left\{ A = (a_{ij}) \in \mathcal{M}_n([0,​1]) \mid \sum_j a_{ij} = 1,\ \sum_i a_{ij} = 1 \right\}.+B_n = \left\{ A = (a_{ij}) \in \mathcal{M}_n([0,​1]) \mid \sum_{j=1}^n ​a_{ij} = 1,\ \sum_{i=1}^n ​a_{ij} = 1 \right\}.
 $$ $$
 Then $\mathrm{Extr}(B_n) = P_n$, the set of permutation matrices (i.e. matrices having exactly one $1$ in each row and each column). Then $\mathrm{Extr}(B_n) = P_n$, the set of permutation matrices (i.e. matrices having exactly one $1$ in each row and each column).
world/choquet.txt · Last modified: 2026/04/10 15:48 by rdouc