D-branes on Orbifolds and Topology Change
Tomomi Muto
TL;DR
The paper investigates topology change in Calabi–Yau spaces probed by D-branes on the orbifolds $C^3/Z_n$ using toric geometry and gauged linear sigma models. It shows that for $n=11$ there are five Calabi–Yau phases connected by flop transitions, while non-geometric phases are projected out for $n=7,9,11$, and it explores the role of non-isolated singularities via explicit cases. The approach maps D-brane vacua to toric data and FI-parameter regions, providing explicit phase structures and triangulations that encode topology changes. A proposed correspondence between the a-vector data and area-$n$ triangulations suggests a general rule for which phases can occur, highlighting a D-brane–toric framework for systematic topology-changing transitions in string theory. The results contribute a concrete, computable picture of geometric transitions in brane probes and hint at a broader combinatorial classification of phases via area-$n$ lattice triangulations.
Abstract
We consider D-branes on an orbifold $C^3/Z_n$ and investigate the moduli space of the D-brane world-volume gauge theory by using toric geometry and gauged linear sigma models. For $n=11$, we find that there are five phases, which are topologically distinct and connected by flops to each other. We also verify that non-geometric phases are projected out for $n=7,9,11$ cases as expected. Resolutions of non-isolated singularities are also investigated.
