Parametrised loop coproduct obstruction conjecture

Let EBE\to B be a smooth fiber bundle with fiber a smooth closed manifold MM, and let f:EM×Bf:E\to M\times B be a fiberwise homotopy equivalence over BB. Suppose there are spectral operations in families, defined as morphisms of parametrised spectra, including ΔfibE\Delta_{\operatorname{fib}}^E, ΔfibB×M\Delta_{\operatorname{fib}}^{B\times M}, ΞrB\Xi_{{{r}}}^B, and ΞlB\Xi_{{{l}}}^B. Parametrised loop coproduct obstruction conjecture. An analogue of the corresponding loop coproduct formula holds:

ΔfibB×Mf!ffΔfibE=ΞrBΞlB.\Delta_{\operatorname{fib}}^{B\times M} \circ f_! - f\wedge f \circ \Delta_{\operatorname{fib}}^E = \Xi_{{{r}}}^B - \Xi_{{{l}}}^B.

This conjecture extends the obstruction formula from a single manifold to smooth fiber bundles and parametrised spectra. The source gives no evidence that it has been proved or disproved.

Sources & referencesView supporting material

Primary source

Lea Kenigsberg and Noah Porcelli, “Obstructions to homotopy invariance of loop coproduct via parametrised fixed-point theory”, arXiv:2407.13662 (2026).

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