# Branched Cauchy-Riemann Structures on Once-Punctured Torus Bundles

## TL;DR

This paper constructs a new CR-structure on hyperbolic once-punctured torus bundles by introducing a novel cell decomposition, enabling CR realizability and detailed analysis of holonomy and branch locus.

## Contribution

It introduces a new type of 3-cell and a corresponding cell decomposition that can be realized in CR space, providing a branched CR structure for all such bundles.

## Key findings

- Every hyperbolic once-punctured torus bundle admits a branched CR structure.
- Explicit computation of ramification orders around branch locus components.
- Analysis of holonomy representations associated with the CR structures.

## Abstract

Unlike in hyperbolic geometry, the monodromy ideal triangulation of a hyperbolic once-punctured torus bundle $M_f$ has no natural geometric realisation in Cauchy-Riemann (CR) space. By introducing a new type of $3$--cell, we construct a different cell decomposition $\mathcal{D}_f$ of $M_f$ that is always realisable in CR space. As a consequence, we show that every hyperbolic once-punctured torus bundle admits a branched CR structure, whose branch locus is the set of edges of $\mathcal{D}_f$. Furthermore, we explicitly compute the ramification order around each component of the branch locus and analyse the corresponding holonomy representations.