 p-deficiency

For a group presentation $\mathcal{P}=⟨X\mid R⟩$ with finitely many generators and a prime number $p$, defineThis uses the unshifted convention. Identity relators have zero weight, and a divergent sum gives value $-\infty$. Some literature subtracts one instead; inequalities must be shifted accordingly. Taking roots in the free group matters: roots appearing only after passing to the quotient do not change the relator weight. The p-rank of a group bounds this quantity above, and the index-p rewriting bound for p-deficiency gives the infinitude criterion p-deficiency at least one implies infinitude.