2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/76599We study intersections of opposite Bruhat cells in a semisimple complex Lie group, and associated totally nonnegative varieties.45 pages, 8 figures; for color version, see http://www-math.mit.edu/~fomin/papers.htmlRepresentation TheoryAlgebraic GeometryCombinatoricsQuantum Algebra22E46; 05E15; 15A23text