Trace equality conjecture for one-dimensional graded fiber products

Let AA and BB be the graded rings and R=A×TBR=A\times_T B the graded fiber product considered above, with canonical modules ωR\omega_R and ωA,B:=ωAωB\omega_{A,B}:=\omega_A\oplus\omega_B. Assume that

dim(R)=1\dim(R)=1

and that neither AA nor BB is regular of dimension 11. Trace equality conjecture. Under these assumptions, the assertion of \autoref{aaa} holds, namely

trR(ωR)=trR(ωA,B).\operatorname{tr}_R(\omega_R)=\operatorname{tr}_R(\omega_{A,B}).

This conjecture addresses the one-dimensional case excluded from \autoref{aaa}; the surrounding discussion notes partial results for local one-dimensional Cohen--Macaulay generically Gorenstein rings when neither ring is a discrete valuation ring. Its general status is not resolved in the supplied text.

Sources & referencesView supporting material

Primary source

Shinya Kumashiro and Sora Miyashita, “Canonical traces of graded fiber products: applications to disconnected Stanley–Reisner rings”, arXiv:2506.04899 (2026).

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