Baum-Dąbrowski-Hajac noncommutative Borsuk-Ulam conjectures

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Let AA be a unital C∗C^*-algebra with a free coaction δ\delta of a nontrivial compact quantum group (H,Δ)(H, \Delta). Equip the join A⊛δHA \circledast^{\delta} H with the induced free coaction δΔ\delta_\Delta. Baum-Dąbrowski-Hajac's noncommutative Borsuk-Ulam conjectures. There are no equivariant unital ∗*-homomorphisms

A→A⊛δHA \to A \circledast^{\delta} H

that are (δ,δΔ)(\delta, \delta_\Delta)-equivariant, and

H→A⊛δHH \to A \circledast^{\delta} H

that are (Δ,δΔ)(\Delta, \delta_\Delta)-equivariant. Equivalently, both the Type 1 and Type 2 conjectures in the source assert the nonexistence of the respective homomorphisms. These conjectures extend the topological formulation to coactions of compact quantum groups on possibly noncommutative C∗C^*-algebras. The source gives no resolution status for either type.

References

Primary source

Alexandru Chirvasitu and Benjamin Passer, “Invariants in Noncommutative Dynamics”, arXiv:1804.01434 (2019).

Additional references

3 papers in this index state this conjecture (2016–2018). The statement above is taken from the most recent of them; the others are arXiv:1801.00767, arXiv:1604.02173.

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