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arXiv · 2605.05357

Small Vacuum Energy and Tunneling in a Modified Bousso-Polchinski Model

James Halverson·Justin Khoury·Cody Long
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Abstract

We propose a simplified model for the cosmological constant in string theory flux vacua motivated by type IIB and F-theory compactifications. Relative to the Bousso-Polchinski model, small vacuum energy spacing occurs in thin wafers rather than thin shells. The model is applied to the entire Sch\"oller-Skarke database of Calabi-Yau fourfolds, which exhibit $532,600,483$ distinct sets of Hodge numbers. The overwhelming majority of those ($99.95\%$ percent for some choices of parameters) exhibit a vacuum energy spacing of~$10^{-120}$ in Planck units or smaller. Brown-Teitelboim membrane nucleation transitions can populate this landscape of flux vacua. In the thin-wall approximation, and ignoring gravitational corrections, we find that the bubble transitions are always dominated by giant leaps in flux space. The age of the universe places a bound on Calabi-Yau topology that is satisfied for the entire Sch\"oller-Skarke database.

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James Halverson, Justin Khoury, Cody Long. 2026-05-06. Small Vacuum Energy and Tunneling in a Modified Bousso-Polchinski Model. https://arxiv.org/abs/2605.05357

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