Every simplicial map sends the vertices of the source of $f$ to the vertices of the target of $f$. Consequently, this determines a ring map between the ring of the source of $f$ and the ring of the target of $f$.
i1 : S = ZZ/101[a,b,c,d];
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i2 : Δ = simplexComplex(3,S)
o2 = simplicialComplex | abcd |
o2 : SimplicialComplex
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i3 : f = map(Δ,Δ,matrix{{a,b,c,d}})
o3 = | a b c d |
o3 : SimplicialMap simplicialComplex | abcd | <--- simplicialComplex | abcd |
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i4 : map f
o4 = map (S, S, {a, b, c, d})
o4 : RingMap S <-- S
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