General self-tuning solutions and no-go theorem

TL;DR

This paper explores brane world models with extra dimensions and self-tuning mechanisms for the cosmological constant, revealing limitations due to tachyonic modes and ghosts in the effective theory.

Contribution

It introduces new solutions with unorthodox Lagrangians that evade existing no-go theorems for self-tuning in brane models.

Findings

Classical solutions adjust the 4d cosmological constant via integration constants.

Unorthodox Lagrangians lead to effective theories with tachyons or ghosts.

Extended no-go theorems to broader classes of models.

Abstract

We consider brane world models with one extra dimension. In the bulk there is in addition to gravity a three form gauge potential or equivalently a scalar (by generalisation of electric magnetic duality). We find classical solutions for which the 4d effective cosmological constant is adjusted by choice of integration constants. No go theorems for such self-tuning mechanism are circumvented by unorthodox Lagrangians for the three form respectively the scalar. It is argued that the corresponding effective 4d theory always includes tachyonic Kaluza-Klein excitations or ghosts. Known no go theorems are extended to a general class of models with unorthodox Lagrangians.