2004/01/26 by Lev Kofman, Johannes Martin, Marco Peloso · 73 citations
Physics and Astronomy · #Amplitude #Black Holes and Theoretical Physics #Brane #Brane cosmology #Classical mechanics #Cosmology and Gravitation Theories #Coupling (piping) #Galaxies: Formation, Evolution, Phenomena #Geometry #Observable #Physics #Quantum mechanics #Randall–Sundrum model #Scalar (mathematics) #Scalar field #Theoretical physics #astro-ph #gr-qc #hep-ph #hep-th
paper · pdf · doi:10.1103/physrevd.70.085015
published in Physical review. D. Particles, fields, gravitation, and cosmology/Physical review. D. Particles and fields 70(8) (American Physical Society) · 20 pages, 6 figures
arxiv created 2004/01/26 · openalex publication_date 2004/10/19 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
Braneworld models in extra dimensions can be tested in laboratory by the coupling of the radion to the standard model fields. The identification of the radion as a canonically normalized field involves a careful general relativity treatment: if a bulk scalar is responsible for the stabilization of the system, its fluctuations are entangled with the perturbations of the metric and they also have to be taken into account (similarly to the well-developed theory of scalar metric perturbations in 4D cosmology with a scalar field). Extracting a proper dynamical variable in a warped geometry/scalar setting is a nontrivial task, performed so far only in the limit of negligible backreaction of the scalar field on the background geometry. We perform the general calculation, diagonalizing the action up to second order in the perturbations and identifying the physical eigenmodes of the system for any amplitude of the bulk scalar. This computation allows us to derive a very simple expression for the exact coupling of the eigenmodes to the standard model fields on the brane, valid for an arbitrary background configuration. As an application, we discuss the Goldberger-Wise mechanism for the stabilization of the radion in the Randall-Sundrum--type models. The existing studies, limited to small amplitude of the bulk scalar field, are characterized by a radion mass which is significantly below the physical scale at the observable brane. We extend them beyond the small backreaction regime. For intermediate amplitudes, the radion mass approaches the electroweak scale, while its coupling to the observable brane remains nearly constant. At very high amplitudes, the radion mass instead decreases, while the coupling sharply increases. Severe experimental constraints are expected in this regime.