We define an operation on finite graphs, called co-contraction. Then we show that for any co-contraction of a finite graph , the right-angled Artin group on contains a subgroup which is isomorphic to the right-angled Artin group on . As a corollary, we exhibit a family of graphs, without any induced cycle of length at least 5, such that the right-angled Artin groups on those graphs contain hyperbolic surface groups. This gives the negative answer to a question raised by Gordon, Long and Reid.
"Co-contractions of graphs and right-angled Artin groups." Algebr. Geom. Topol. 8 (2) 849 - 868, 2008. https://doi.org/10.2140/agt.2008.8.849