The higher-girth face-number conjecture for simplicial complexes

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Let Γ\Gamma be a (d−1)(d-1)-dimensional simplicial complex with nn vertices. Let fi−1(Γ)f_{i-1}(\Gamma) denote the number of (i−1)(i-1)-dimensional faces, and let gr⁡p−1(Γ)\operatorname{gr}_{p-1}(\Gamma) denote its (p−1)(p-1)-girth. For some integers p,r≥2p,r\geq 2, assume that gr⁡p−1(Γ)>2p+2r−4\operatorname{gr}_{p-1}(\Gamma)>2p+2r-4. Let ap,r,ia_{p,r,i} be the recursively defined exponents

a2,r,i=1+1/r+…+1/ri−1,a_{2,r,i}=1+1/r+\ldots+1/r^{i-1}, ap,r,p−1=p−1,a_{p,r,p-1}=p-1, ap,r,i=12ap−1,r,i−1+12ap,r,i−1+1(p≥3,i≥p).a_{p,r,i}=\frac{1}{2}a_{p-1,r,i-1}+\frac{1}{2}a_{p,r,i-1}+1\quad (p\geq 3, i\geq p).

The higher-girth face-number conjecture. There is a constant Cp,r,iC_{p,r,i} depending only on p,r,ip,r,i such that

fi−1(Γ)≤Cp,r,idi−ap,r,inap,r,i.f_{i-1}(\Gamma)\leq C_{p,r,i}d^{i-a_{p,r,i}}n^{a_{p,r,i}}.

The conjecture seeks upper bounds for face numbers from the dimension, number of vertices, and (p−1)(p-1)-girth. The recursively defined exponents increase with the relevant parameters and approach 2p−3+1/(r−1)2p-3+1/(r-1) as ii tends to infinity; the asserted bound is not established in the supplied text.

References

Primary source

Michael Goff, “Higher dimensional Moore bounds”, arXiv:0906.0763 (2009).

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