Diluting Cosmological Constant In Infinite Volume Extra Dimensions

TL;DR

This paper proposes a braneworld model with infinite-volume extra dimensions that addresses the cosmological constant problem by altering gravity's behavior at large scales, leading to testable predictions at sub-millimeter and cosmological distances.

Contribution

It introduces a novel infinite-volume extra-dimensional framework where gravity's infrared behavior solves the cosmological constant problem without fine-tuning.

Findings

Gravity becomes higher-dimensional at super-Hubble scales.

The acceleration rate decreases with increasing vacuum energy.

Predictions include modifications of gravity at sub-millimeter and Hubble scales.

Abstract

We argue that the cosmological constant problem can be solved in a braneworld model with infinite-volume extra dimensions, avoiding no-go arguments applicable to theories that are four-dimensional in the infrared. Gravity on the brane becomes higher-dimensional at super-Hubble distances, which entails that the relation between the acceleration rate and vacuum energy density flips upside down compared to the conventional one. The acceleration rate decreases with increasing the energy density. The experimentally acceptable rate is obtained for the energy density larger than (1 TeV)$^4$. The results are stable under quantum corrections because supersymmetry is broken only on the brane and stays exact in the bulk of infinite volume extra space. Consistency of 4D gravity and cosmology on the brane requires the quantum gravity scale to be around $10^{-3}$ eV. Testable predictions emerging within this approach are: (i) simultaneous modifications of gravity at sub-millimeter and the Hubble scales; (ii) Hagedorn-type saturation in TeV energy collisions due to the Regge spectrum with the spacing equal to $10^{-3}$ eV.