We briefly review an open conjecture about Higgs bundles that are semistable
with after pulling back to any curve, and prove it in the rank 2 case. We also
prove a set of inequalities holding for H-nef Higgs bundles that generalize
some of the Fulton-Lazarsfeld inequalities for numerically effective vector
bundles.Comment: 13 pages. v2: 14 pages. Some results have been strengthened and the
exposition has been reorganized. v3: minor changes, final version to appear
in Mediterranean J. Mat