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Conjecture on mixed Bockstein differentials and τ-periodicity

Establish the equivalence asserted in Conjecture Type3diffs between (i) the existence of a τ^{2^n}-periodic differential d_t(τ^{2^n}x)=ρ^t z in the ℝ-motivic ρ-Bockstein spectral sequence for a τ-free class x with d_r(x)=ρ^r y where y is τ-power torsion and r<t<2^n, and (ii) the existence of the nonperiodic differential d_{t−r}(Q/ρ^{t−r} y)=γ/τ^{2^n} z in the ρ-Bockstein spectral sequence for the negative cone; moreover, deduce the predicted τ^{2^n}-extension from y to ρ^{t−r}z in Ext_ℝ(F_2/ρ^{t+1}).

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Background

The paper analyzes the ρ-Bockstein spectral sequences computing C2-equivariant Ext groups by leveraging their relationship with the better understood ℝ-motivic Bockstein spectral sequence. A key theme is translating information between the motivic (positive cone) and the negative cone parts.

In the mixed case, where the source of a motivic Bockstein differential is τ-free and the target is τ-power torsion, the authors formulate Conjecture Type3diffs to relate periodic differentials in the motivic setting to specific differentials in the negative cone. Verifying this would systematize the passage between these two parts of the spectral sequence and predict hidden τ{2n}-extensions in Ext_ℝ(F_2/ρ{t+1}).

References

Suppose that x and y are classes in \Ext_\mathbb{R} such that x is \tau-free and y is \tau-power torsion. Suppose furthermore that d_r(x)= \rhor y in the \mathbb{R}-motivic \rho-Bockstein spectral sequence and that r < t < 2n. There exists a \tau{2n}-periodic differential d_t(\tau{2n}x) = \rhot z if and only if the (nonperiodic) differential d_{t-r} \left( \frac{Q}{\rho{t-r}} y \right) = \frac{\gamma}{\tau{2n}} z

occurs in the \rho-Bockstein spectral sequence for the negative cone.

If these differentials occur, then there is a \tau{2n}-extension from y to \rho{t-r} z in \Ext_\mathbb{R} \left( \frac{\mathbb{F}_2}{\rho{t+1}} \right) that is hidden by the \rho-Bockstein spectral sequence.

C_2-Equivariant Stable Stems (2404.14627 - Guillou et al., 22 Apr 2024) in Conjecture Type3diffs, Subsection “Mixed differentials,” Section 6 (PCtoNC)