The well-known middle levels problem is to find a Hammiltonian cycle in the
graph induced from the binary Hamming graph
\cH_2(2k+1) by the words of
weight
k or
k+1. In this paper we define the
q-analog of the middle
levels problem. Let
n=2k+1 and let
q be a power of a prime number. Consider
the set of
(k+1)-dimensional subspaces and the set of
k-dimensional
subspaces of
\F_q^n.
... [Show full abstract] Can these subspaces be ordered in a way that for any two
adjacent subspaces X and Y, either or ? A
construction method which yields many Hamiltonian cycles for any given q and
k=2 is presented.