Regularity formula for t-path ideals of unicyclic graphs

Let GG be a connected simple graph having at most one cycle CC of length mm. Let t2t\geq 2 be a natural number. Write SS for the polynomial ring associated with GG, It(G)I_t(G) for its tt-path ideal, νt(G)\nu_t(G) for the maximum number of pairwise suitable tt-paths in GG, and call GG tt-proximal when it satisfies the corresponding tt-proximity condition. Then

reg(S/It(G))={(t1)νt(G)+(reg(S/It(C))(t1)ν3(C)),if G is t-proximal,(t1)νt(G),otherwise.\operatorname{reg}(S/I_t(G))=\begin{cases} (t-1)\nu_t(G)+\left(\operatorname{reg}(S/I_t(C))-(t-1)\nu_3(C)\right), & \text{if }G\text{ is }t\text{-proximal},\\ (t-1)\nu_t(G), & \text{otherwise}. \end{cases}

Regularity conjecture for t-path ideals. The displayed formula should hold. In particular,

reg(S/It(G))=(t1)νt(G)\operatorname{reg}(S/I_t(G))=(t-1)\nu_t(G)

when GG is a tree. This conjecture is presented as a natural generalization of the paper's theorem for 33-path ideals; the supplied text gives no resolution status for the general tt-path statement.

Sources & referencesView supporting material

Primary source

Nguyen Thu Hang and Thanh Vu, “Projective dimension and regularity of 3-path ideals of unicyclic graphs”, arXiv:2402.16166 (2024).

Progress summary

Never refreshed

Nothing recorded yet. Refresh searches the literature and the public web for attempts on this problem, and writes the first summary here.

Solutions 0

No solutions have been posted yet.