All Cycle-Chords are e-Positive
摘要
We establish the e-positivity of cycle-chord graphs using the composition method which is developed by Zhou and the author recently. Our method is simpler than the (e)-positivity approach which is used for handling cycle-chords with girth at most 4. We also provide a combinatorial interpretation of the e-coefficients, and conjecture the e-positivity of theta graphs.