On Higher Topological T-duality Functors
Ashwin S. Pande
TL;DR
The paper develops a higher-dimensional analogue of Bunke-Schick Topological T-duality by geometrizing P(X) through the moduli space G(X) of String Field Theory backgrounds over X. Objects are SFT backgrounds modeled as pairs (E→X, H) and morphisms are gauge transformations, organized into a category whose category of elements yields a functorial, homotopy-theoretic construction of invariants P0 and P1, with P0 recovering Bunke-Schick’s P(X) and P1 encoding mapping class group actions on background data. The framework shows Pk(X) vanishes for k≥2 in the current setting, but it provides a clear path to extend via richer gauge structures and Thomason cohomology, potentially capturing higher T-duality phenomena and connections to triples, doubled geometries, and T-folds. Physically, the approach links closed bosonic SFT massless-mode reductions to geometric moduli spaces that encode Topological T-duality, offering a new, categorially enriched perspective on dualities and their realizations in geometry and string theory.
Abstract
We use String Field Theory (SFT) to construct a higher analogue of Bunke-Schick's functor $P: \mathbf{Top}^{op} \to \mathbf{Set}$ \cite{BunkeS1} by geometrizing $P.$ We use the projection of SFT onto its massless modes \cite{SFTDiffeo} to construct the category $\C$ whose objects are pairs (which we identify with SFT backgrounds) and whose maps are morphisms of pairs (which are gauge transformations). Using $\C$ and categorical equivalence, for any $CW-$complex $X$ we define the moduli space $G(X)$ of SFT backgrounds which are pairs over $X$ up to gauge equivalence. We use the homotopy theory of the moduli space $G(X)$ to define functors on the category of $CW-$complexes $P_k:\mathbf{CW}^{op} \to \mathbf{Grpd}$ such that $P_0 \simeq P,$ $P_1$ is nontrivial and $P_k(X)$ are always trivial for $k \geq 2.$ Arrows in $P_1(X)$ are shown to be isotopy classes of maps in the mapping class group of $X$ acting on (isomorphism classes of) pairs over $X.$ We discuss applications to Topological T-duality for triples and to modelling doubled geometries and T-folds \cite{HullT}.
