Conjecture on the middle-degree Bockstein and injectivity of the second Bockstein

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Let NN be an integer, let B1B_1 and B2B_2 be the differentials in the spectral sequence under consideration, and let HHiσ(A)HH_i^\sigma(\mathcal{A}) denote the twisted Hochschild homology groups. For 0≤i≤N0\leq i\leq N, write ω1(N,i)\omega_1(N,i) and ω2(N,i)\omega_2(N,i) for the indicated generators, and let f:ker⁡(B0)→HH3σ(A)f:\operatorname{ker}(B_0)\to HH_3^\sigma(\mathcal{A}) be the map appearing in the spectral sequence.

Bockstein conjecture. For NN even,

[B1(ω1(N,12N))]≠0∈HH2σ(A),[B_1(\omega_1(N,\tfrac{1}{2}N))]\neq 0\in HH_2^\sigma(\mathcal{A}),

and this class is proportional to [ω2(N,12N)][\omega_2(N,\tfrac{1}{2}N)]. For all NN, the map

B2:HH2σ(A)/im⁡(B1)⟶HH3σ(A)B_2:HH_2^\sigma(\mathcal{A})/\operatorname{im}(B_1)\longrightarrow HH_3^\sigma(\mathcal{A})

is injective. Consequently, for NN odd, the map

f:ker⁡(B0)⟶HH3σ(A)f:\operatorname{ker}(B_0)\longrightarrow HH_3^\sigma(\mathcal{A})

is zero.

These expected properties would determine the relevant differentials in the spectral sequence and hence clarify the computation of the twisted cyclic homology groups. The source explicitly states that no proof is currently available; the status of both assertions is therefore open.

References

Primary source

Tom Hadfield and Ulrich Kraehmer, “Twisted homology of quantum SL(2)”, arXiv:math/0405249 (2005).

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