Algebraic interleavings of spaces over the classifying space of the circle
Katsuhiko Kuribayashi, Takahito Naito, Shun Wakatsuki, Toshihiro Yamaguchi
TL;DR
The paper develops a Cohomology Interleaving Distance (CohI) for spaces over the classifying space $BS^1$ by transporting spaces to persistence differential graded (dg) modules via singular cochains. It proves that CohI coincides with existing interleaving distances in the homotopy-theoretic framework ($d_{HC}=d_{IHC}=d_{HI}$), enabling computation of homotopy-consistent distances through bottleneck distances on cohomology barcodes. Extending to dg $\mathbb K[u]$-modules, the authors relate CohI to barcode bottlenecks at even/odd levels and show the overall CohI distance is the maximum of two parity-based distances. They also derive cup-length bounds for spaces over $BS^1$, analyze several classes of spaces (including BV-exact and formal spaces), and provide explicit toy computations for complex projective spaces and related bundles, illustrating the practical computability and interpretability of the CohI framework in persistence and rational homotopy contexts.
Abstract
We bring spaces over the classifying space $BS^1$ of the circle group $S^1$ to persistence theory via the singular cohomology with coefficients in a field. Then, the {\it cohomology} interleaving distance (CohID) between spaces over $BS^1$ is introduced and considered in the category of persistent differential graded modules. In particular, we show that the distance coincides with the {\it interleaving distance in the homotopy category} in the sense of Lanari and Scoccola and the {\it homotopy interleaving distance} in the sense of Blumberg and Lesnick. Moreover, upper and lower bounds of the CohID are investigated with the cup-lengths of spaces over $BS^1$. As a computational example, we explicitly determine the CohID for complex projective spaces by utilizing the bottleneck distance of barcodes associated with the cohomology of the spaces.
