# On invertible 2-dimensional framed and $r$-spin topological field theories

## TL;DR

This paper classifies invertible 2D framed and r-spin topological field theories by computing homotopy groups and k-invariants of their bordism categories, revealing their algebraic and geometric structures.

## Contribution

It provides explicit computations of homotopy groups and SKK groups for 2D framed and r-spin bordism categories, advancing the classification of these topological field theories.

## Key findings

- Computed zeroth and first homotopy groups of bordism categories.
- Explicitly calculated SKK groups for stable and non-stable structures.
- Connected algebraic invariants with combinatorial models of surfaces.

## Abstract

We classify invertible 2-dimensional framed and $r$-spin topological field theories by computing the homotopy groups and the $k$-invariant of the corresponding bordism categories. The zeroth homotopy group of a bordism category is the usual Thom bordism group, the first homotopy group can be identified with a Reinhart vector field bordism group, or the so called SKK group as observed by Ebert, B\"ockstedt-Svane and Kreck-Stolz-Teichner. We present the computation of SKK groups for stable tangential structures. Then we consider non-stable examples: the 2-dimensional framed and $r$-spin SKK groups and compute them explicitly using the combinatorial model of framed and $r$-spin surfaces of Novak, Runkel and the author.

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Source: https://tomesphere.com/paper/1907.09428