The Strong Connectedness conjecture for regular rings

From papers

Let Σ\Sigma be a regular ring. For points α,βSperΣ\alpha,\beta\in\operatorname{Sper}\Sigma having a common specialization, the Strong Connectedness Property requires that, for elements g1,,gsΣ(pαpβ)g_1,\dots,g_s\in\Sigma\setminus(\mathfrak p_\alpha\cup\mathfrak p_\beta) satisfying the valuation inequalities and sign condition in the source, α\alpha and β\beta lie in the same connected component of

SperΣ{g1gs=0}.\operatorname{Sper}\Sigma\setminus\{g_1\cdots g_s=0\}.

More precisely, each gig_i satisfies να(gi)να(α,β)\nu_\alpha(g_i)\leq\nu_\alpha(\langle\alpha,\beta\rangle) and νβ(gi)νβ(α,β)\nu_\beta(g_i)\leq\nu_\beta(\langle\alpha,\beta\rangle), and no gig_i changes sign between α\alpha and β\beta.

Strong Connectedness conjecture. A regular ring Σ\Sigma has the Strong Connectedness Property at every pair of points α,βSperΣ\alpha,\beta\in\operatorname{Sper}\Sigma having a common specialization.

This strengthens the ordinary connectedness framework by weakening the hypotheses on the elements to be avoided. The paper proves the strong conjecture in dimension two and uses it to obtain further cases of the Connectedness and Pierce–Birkhoff conjectures; the general statement remains open.

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Equivalent formulations 1

Other statements of this same problem, merged from separate entries. Each is equivalent to the statement above — proving any one settles them all.

  1. Strong connectedness conjecture for regular rings

    Let Σ\Sigma be a ring. The strong connectedness property is required at pairs α,βSperΣ\alpha,\beta\in\operatorname{Sper}\Sigma having a common specialization, with the defining connectedness condition imposed for such pairs. Let X\mathcal X be the class of all regular rings, and let SCP(X)SCP(\mathcal X) denote the assertion that every ring in X\mathcal X has the strong connectedness property. Strong connectedness conjecture.

    SCP(X) holds.SCP(\mathcal X)\text{ holds}.

    This is a strengthening of the connectedness conjecture. The paper’s main result proves it under a good-position hypothesis in the polynomial setting, while the general assertion for regular rings remains open.

    source: F Lucas, D. Schaub and M. Spivakovsky, “On the strong separation conjecture”, arXiv:1802.09389 (2018).

Sources & referencesView supporting material

Primary source

François Lucas, Daniel Schaub and Mark Spivakovsky, “On the Pierce-Birkhoff Conjecture”, arXiv:1207.6463 (2012).

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