We show that the operations of permuting columns and rows separately and independently mix a square matrix in constant time.

1. A CORRECTION Theorem 3.6 in [1] contains an error in the stated bound. As is argued above the theorem, the statistical distance to the uniform distribution decreases by a factor O ( (m/ log m)−1/2 ) = O ((log n)1/2n−1/4) for every two iterations. This implies that the bound obtained for Theorem 3.6 should read O ( n1− t−1 2 1 4 (log n) t−1 2 1 2 ) . I am grateful to Justin Holmgren for point...

We study the problem of " phantom " folding of the two-dimensional square lattice, in which the edges and diagonals of each face can be folded. The non-vanishing thermodynamic folding entropy per face s ≃ .2299(1) is estimated both analytically and numerically, by successively mapping the model onto a dense loop model, a spin model and a new 28 Vertex, 4-color model. Higher dimensional generali...