Towards Realistic String Vacua From Branes At Singularities

TL;DR

This work advances a bottom-up program to realize realistic string vacua by combining D-brane models at del Pezzo singularities with LARGE volume moduli stabilisation. It analyzes explicit local quiver theories on $dP_0$ and $dP_1$ that yield three-family spectra across SM, Left-Right, Pati-Salam, and Trinification possibilities, tying Yukawa structures to local flavour symmetries. It then discusses embedding these local models into global Calabi–Yau compactifications, deriving the near-singularity EFT and exploring soft SUSY-breaking terms, including the vanishing of leading gravity- and anomaly-mediated contributions and potential subleading sources, such as twisted moduli and U(1) thresholds. A notable outcome is the prediction of hyperweak U(1) gauge bosons from D7 branes on the large cycle, with potential phenomenological implications and links to collider anomalies. The work lays a framework for fully global constructions with concrete phenomenological signatures, while identifying key open issues in complete moduli stabilisation and detailed SUSY phenomenology.

Abstract

We report on progress towards constructing string models incorporating both realistic D-brane matter content and moduli stabilisation with dynamical low-scale supersymmetry breaking. The general framework is that of local D-brane models embedded into the LARGE volume approach to moduli stabilisation. We review quiver theories on del Pezzo $n$ ($dP_n$) singularities including both D3 and D7 branes. We provide supersymmetric examples with three quark/lepton families and the gauge symmetries of the Standard, Left-Right Symmetric, Pati-Salam and Trinification models, without unwanted chiral exotics. We describe how the singularity structure leads to family symmetries governing the Yukawa couplings which may give mass hierarchies among the different generations. We outline how these models can be embedded into compact Calabi-Yau compactifications with LARGE volume moduli stabilisation, and state the minimal conditions for this to be possible. We study the general structure of soft supersymmetry breaking. At the singularity all leading order contributions to the soft terms (both gravity- and anomaly-mediation) vanish. We enumerate subleading contributions and estimate their magnitude. We also describe model-independent physical implications of this scenario. These include the masses of anomalous and non-anomalous U(1)'s and the generic existence of a new hyperweak force under which leptons and/or quarks could be charged. We propose that such a gauge boson could be responsible for the ghost muon anomaly recently found at the Tevatron's CDF detector.

Figures (8)

• Figure 1: The quiver for the $dP_0$ singularity. Dark circles correspond to fractional D3 branes wrapping only the collapsed cycles and support Standard Model gauge groups. White circles correspond to fractional D7 branes wrapping both bulk and collapsed cycles and support bulk hidden sector gauge groups. Standard Model matter arises from either $D3-D3$ or $D3-D7$ states.
• Figure 2: The quiver for the Standard Model realised at a $dP_0$ singularity.
• Figure 3: The quiver for the Left-Right symmetric model realised at a $dP_0$ singularity.
• Figure 4: The quiver diagram for the Pati-Salam models realised at a $dP_0$ singularity.
• Figure 5: Quiver diagram for the Trinification Models.