Gal's Conjecture for Nestohedra Corresponding to Complete Bipartite Graphs

Convex polytopes have interested mathematicians since very ancient times. At present, they occupy a central place in convex geometry, combinatorics, and toric topology and demonstrate the harmony and beauty of mathematics. This paper considers the problem of describing the $f$-vectors of simple flag polytopes, that is, simple polytopes in which any set of pairwise intersecting facets has nonempty intersection. We show that for each nestohedron corresponding to a connected building set, the $h$-polynomial is a descent-generating function for some class of permutations; we also prove Gal's conjecture on the nonnegativity of $\gamma$-vectors of flag polytopes for nestohedra constructed over complete bipartite graphs.