A geometric-probabilistic method for counting low-lying states in the Bousso-Polchinski Landscape

小真空能与在修改的Bousso-Polchinski模型中的隧道效应

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

本文提出一种简化模型，用于弦论 flux 真空中的宇宙学常数，通过IIB和F理论紧致化。该模型在薄片中产生小真空能间隔，而非薄壳。应用于Schöller-Skarke数据库中的Calabi-Yau四叠，大部分表现出10^-120量级的真空能间隔。

Consequences of moduli stabilization in the Einstein-Maxwell landscape

A toy landscape sector is introduced as a compactification of the Einstein-Maxwell model on a product of two-spheres. Features of the model include: moduli stabilization, a distribution of the effective cosmological constant of the dimensionally reduced 1+1 spacetime, which is different from the analogous distribution of the Bousso-Polchinski landscape, and the absence of the so-called "alpha-star"-problem. This problem arises when the Kachru-Kallosh-Linde-Trivedi stabilization mechanism is naively applied to the states of the Bousso-Polchinski landscape. The model also contains anthropic stat…

Probabilities in the Arkani-Hamed-Dimopolous-Kachru landscape

In a previous paper we found that in the context of the string theory ``discretuum'' proposed by Bousso and Polchinski, the cosmological constant probability distribution varies wildly. However, the successful anthropic predictions of the cosmological constant depend crucially on the assumption of a flat prior distribution. We conjectured that the staggered character of our Bousso-Polchinski distribution will arise in any landscape model which generates a dense spectrum of low-energy constants from a wide distribution of states in the parameter space of the fundamental theory. Here we calculat…

The Scales of Brane Nucleation Processes

The scales associated with Brown-Teitelboim-Bousso-Polchinski processes of brane nucleation, which result in changes of the flux parameters and the number of D-branes, are discussed in the context of type IIB models with all moduli stabilized. It is argued that such processes are unlikely to be described by effective field theory.

Counter-intuition and Scalar Masses

The Bousso-Polchinski mechanism for discretely fine-tuning the cosmological constant favors a large bare negative cosmological constant. I argue (using generalizations of results of Klebanov and Tseytlin) that a similar mechanism for fine-tuning the scalar masses to small values favors a large bare negative (i.e. tachyonic) scalar mass. I comment briefly on the related issue of the role of low energy supersymmetry in string theory.

Environmental selection of the cosmological constant and electroweak scales

We investigate whether selfish/Goldilocks Higgs models can be extended to accomodate vacua with both the right Higgs mass and cosmological constant. Through the introduction of multiple four-form fields coupled with the Higgs scalar boson we find that both the cosmological constant and the electroweak hierarchy problems can be addressed simultaneously, without inserting the relevant physical scales by hand and avoiding fine tuning. The resulting bounds on the brane charges, the only dimensionful free parameter of the theory, depend on the strength of the four-form scalar coupling and can be of…

宇宙学常数与弱引力猜想

The cosmological constant and the weak gravity conjecture

本文研究膜成核真空景观中宇宙学常数减缓条件与膜弱引力猜想的相容性，并构造满足猜想且 Minkowski 真空绝对稳定的广义 DBI Bousso-Polchinski 模型。

On Anthropic Solutions of the Cosmological Constant Problem

Motivated by recent work of Bousso and Polchinski (BP), we study theories which explain the small value of the cosmological constant using the anthropic principle. We argue that simultaneous solution of the gauge hierarchy problem is a strong constraint on any such theory. We exhibit three classes of models which satisfy these constraints. The first is a version of the BP model with precisely two large dimensions. The second involves 6-branes and antibranes wrapped on supersymmetric 3-cycles of Calabi-Yau manifolds, and the third is a version of the irrational axion model. All of them have pos…

Graceful exit from a stringy landscape via MSSM inflation

The cosmological evolution of the string landscape is expected to consist of multiple stages of old inflation with large cosmological constant ending by tunnelling. Old inflation has a well known graceful exit problem as the observable universe becomes empty, devoid of any entropy. Simultaneously, in the quest for reheating the right degrees of freedom, it is important that the final stage of inflation reheat Standard Model sector. It is known that inflation can occur naturally along a flat direction of the Minimal Supersymmetric Standard Model (MSSM), solving the reheating problem, but the in…

宇宙学常数很可能仍然为零

The cosmological constant is probably still zero

本文研究了引力与四形式耦合的四维有效场论，通过膜成核扫描宇宙学常数真空景观，确立了确保 Minkowski 真空绝对稳定及邻近真空长寿命的一般判据，在概率基础上解释了当前真空的选择并探讨了解决宇宙学常数问题的模型。