Conjecture B on curvewise bounded ramification and logarithmic conductors

Keep the hypotheses of Conjecture A: kk is perfect, X/kX/k is normal, j:UXj:U\hookrightarrow X is a kk-smooth open immersion with complement supporting an effective Cartier divisor, DD is an effective Cartier divisor supported on XUX\setminus U, and F\mathcal{F} is a smooth \ell-adic sheaf of finite rank on UU. Say that the ramification of F\mathcal F is bounded by DD if, for every CCu(U)C\in\mathrm{Cu}(U), the divisor Sw(ϕF)\mathrm{Sw}(\phi^*\mathcal F) on the normalisation Cˉ\bar C is at most ϕˉD\bar\phi^*D, and write this as Sw(F)D\mathrm{Sw}(\mathcal F)\leq D. Conjecture B. The following are equivalent:

  1. Sw(F)D\mathrm{Sw}(\mathcal F)\leq D.
  2. For every open immersion j:UXj':U\subset X' over kk such that XUX'\setminus U is a simple normal crossing divisor, and every morphism h:XXh:X'\to X extending j:UXj:U\to X, one has
Swξ(hj!F)logmξ(hD)\mathrm{Sw}_{\xi'}(h^*j_!\mathcal F)_{\mathrm{log}}\leq m_{\xi'}(h^*D)

for each generic point ξD:=XU\xi'\in D':=X'\setminus U. This gives an intrinsic logarithmic-conductor criterion equivalent to detecting bounded ramification on all curves, and is presented as a conjectural extension of the rank-one theory; the source does not specify its resolution status.

Sources & referencesView supporting material

Primary source

Ivan Barrientos, “Log ramification via curves in rank 1”, arXiv:1307.5814 (2016).

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