The Dutta-multiplicity bound for short complexes

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Let (R,m)(R,\mathfrak m) be a local ring, let e(R)e(R) denote its Hilbert–Samuel multiplicity, and let FF be a short complex supported on the maximal ideal, meaning a non-exact complex of finite free RR-modules

0⟶Fdim⁡R⟶⋯⟶F1⟶F0⟶00\longrightarrow F_{\dim R}\longrightarrow\cdots\longrightarrow F_1\longrightarrow F_0\longrightarrow0

whose homology modules have finite length. In positive characteristic, let χ∞(F)\chi_\infty(F) denote its Dutta multiplicity. Dutta-multiplicity bound. Every short complex FF supported on the maximal ideal satisfies

χ∞(F)≥e(R).\chi_\infty(F)\geq e(R).

The paper proves this bound when RR is the localization at its homogeneous maximal ideal of a standard graded algebra over a field of positive characteristic. The proposed extension to arbitrary local rings remains open.

References

Primary source

Srikanth B. Iyengar, Linquan Ma and Mark E. Walker, “Multiplicities and Betti numbers in local algebra via lim Ulrich points”, arXiv:2104.10140 (2021).

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