Abstract

Compactifications of the Chaudhuri-Hockney-Lykken (CHL) string to eight dimensions can be characterized by embeddings of root lattices into the rank 12 momentum lattice ${\mathrm{\ensuremath{\Lambda}}}_{M}$, the so-called Mikhailov lattice. Based on these data, we devise a method to determine the global gauge group structure including all $U(1)$ factors. The key observation is that, while the physical states correspond to vectors in the momentum lattice, the gauge group topology is encoded in its dual. Interpreting a nontrivial ${\ensuremath{\pi}}_{1}(G)\ensuremath{\equiv}\mathcal{Z}$ for the non-Abelian gauge group $G$ as having gauged a $\mathcal{Z}$ 1-form symmetry, we also prove that all CHL gauge groups are free of a certain anomaly [1] that would obstruct this gauging. We verify this by explicitly computing $\mathcal{Z}$ for all 8D CHL vacua with $\mathrm{rank}(G)=10$. Since our method applies also to ${T}^{2}$ compactifications of heterotic strings, we further establish a map that determines any CHL gauge group topology from that of a ``parent'' heterotic model.

Highlights

  • Supersymmetric string compactifications on lowdimensional internal manifolds have seen a resurgence of interest within the Swampland program [2,3]

  • The key observation is that, while the physical states correspond to vectors in the momentum lattice, the gauge group topology is encoded in its dual

  • Interpreting a nontrivial π1ðGÞ ≡ Z for the non-Abelian gauge group G as having gauged a Z 1-form symmetry, we prove that all CHL gauge groups are free of a certain anomaly [1] that would obstruct this gauging

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Summary

INTRODUCTION

Supersymmetric string compactifications on lowdimensional internal manifolds have seen a resurgence of interest within the Swampland program [2,3]. Any non-Abelian gauge algebra g that can arise in an 8D CHL vacuum must have a root lattice Λgr that embeds in a specific way into ΛM Such lattice embeddings can be classified [16] in an analogous fashion as for rank 20 theories based on their heterotic realization [12], where the corresponding string momentum lattice is the rank 20 Narain lattice ΛN [17,18]. This is the dual of the character lattice ΛGc , which corresponds to the charge lattice occupied by physical states, which clearly is the momentum lattice ΛS From this perspective, the self-duality of the Narain lattice (imposed by modularity of the heterotic world sheet), together with the fact that rank 20 theories only have ADE algebras [whose (co-)root lattices Λgr 1⁄4 Λgcr agree], appear as a coincidence that makes it straightforward to compute the fundamental group Z 1⁄4 π1ðGÞ as (the torsional piece of) ΛN=Λgr , as done in [12].

GAUGE GROUPS FROM MOMENTUM LATTICES
Lattices and gauge group topology
Gauge group topology from lattice embeddings
Global gauge group structure of 8D heterotic vacua
Gauge group topology of 8D CHL vacua
Example
Absence of 1-form anomalies
G SUðNÞ Spinð4N þ 2Þ Spinð4NÞ E6 E7 SpðNÞ αG
CHL GAUGE GROUPS FROM
Finding Mikhailov inside Narain
CHL cocharacters from heterotic cocharacters
SUMMARY AND OUTLOOK

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