# D-particles on orientifolds and rational invariants

Journal of High Energy Physics, Jul 2017

We revisit the D0 bound state problems, of the M/IIA duality, with the Orientifolds. The cases of O4 and O8 have been studied recently, from the perspective of five-dimensional theories, while the case of O0 has been much neglected. The computation we perform for D0-O0 states boils down to the Witten indices for $\mathcal{N}=16$ O(m) and Sp(n) quantum mechanics, where we adapt and extend previous analysis by the authors. The twisted partition function Ω, obtained via localization, proves to be rational, and we establish a precise relation between Ω and the integral Witten index ℐ, by identifying continuum contributions sector by sector. The resulting Witten index shows surprisingly large numbers of threshold bound states but in a manner consistent with M-theory. We close with an exploration on how the ubiquitous rational invariants of the wall-crossing physics would generalize to theories with Orientifolds.

This is a preview of a remote PDF: https://link.springer.com/content/pdf/10.1007%2FJHEP07%282017%29046.pdf

Seung-Joo Lee, Piljin Yi. D-particles on orientifolds and rational invariants, Journal of High Energy Physics, 2017, 1-29, DOI: 10.1007/JHEP07(2017)046