Abstract
We systematically study the holographic phase transition of the radion field in a five-dimensional warped model which includes a scalar potential with a power-like behavior. We consider Kaluza-Klein (KK) resonances with masses $m_{\rm KK}$ at the TeV scale or beyond. The backreaction of the radion field on the gravitational metric is taken into account by using the superpotential formalism. The confinement/deconfinement first order phase transition leads to a gravitational wave stochastic background which mainly depends on the scale $m_{\rm KK}$ and the number of colors, $N$, in the dual theory. Its power spectrum peaks at a frequency that depends on the amount of tuning required in the electroweak sector. It turns out that the present and forthcoming gravitational wave observatories can probe scenarios where the KK resonances are very heavy. Current aLIGO data already rule out vector boson KK resonances with masses in the interval $m_{\rm KK}\sim(1 - 10) \times 10^5$ TeV. Future gravitational experiments will be sensitive to resonances with masses $m_{\rm KK}\lesssim 10^5$ TeV (LISA), $10^8$ TeV (aLIGO Design) and $10^9$ TeV (ET). Finally, we also find that the Big Bang Nucleosynthesis bound in the frequency spectrum turns into a lower bound for the nucleation temperature as $T_n \gtrsim 10^{-4}\sqrt{N} \,m_{\rm KK}$.
Highlights
The Standard Model is unable to explain some experimental observations, and suffers from theoretical drawbacks
We systematically study the holographic phase transition of the radion field in a five-dimensional warped model which includes a scalar potential with a powerlike behavior
As the backreaction is an important ingredient to generate an effective potential with a stable minimum, we have conveniently used the superpotential method to analytically tackle with it
Summary
The Standard Model is unable to explain some experimental observations (e.g., dark matter, the baryon asymmetry of the universe, ...), and suffers from theoretical drawbacks (e.g., strong sensitivity to high scale physics, known as the hierarchy problem, ...). A warped extra dimension is a way of solving the hierarchy problem and relating the Planck scale MP to the low energy scale ρ, which determines the spectrum of heavy resonances and is usually considered at the TeV scale [1,2]. The answer is based on the presence of the only extra light field in the theory, the radion. This field experiences a first order phase transition, the confinement/ deconfinement transition, which generates a stochastic gravitational wave background (SGWB) detectable at the present and future interferometers [5,6,7].
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