Gravitational Techniwaves

TL;DR

This work analyzes gravitational waves from electroweak-scale first-order phase transitions in strongly coupled technicolor theories, focusing on Minimal Walking Technicolor (MWT) and Ultra Minimal Technicolor (UMT). Using a finite-temperature effective Lagrangian and bubble-nucleation formalism, the authors compute nucleation temperatures, transition strengths, and GW spectra from bubble collisions and turbulence. They find that MWT can realize a strong transition producing detectable GWs for instruments like BBO/LISA within a narrow parameter region, while UMT generally yields much weaker signals though it can generate a multi-peak spectrum from sequential transitions. The results suggest distinctive GW signatures as probes of strongly interacting electroweak dynamics and motivate lattice studies and extensions to explore stronger signals.

Abstract

We investigate the production and possible detection of gravitational waves stemming from the electroweak phase transition in the early universe in models of minimal walking technicolor. In particular we discuss the two possible scenarios in which one has only one electroweak phase transition and the case in which the technicolor dynamics allows for multiple phase transitions.

Figures (5)

• Figure 1: The nucleation temperature $T_*$ (left column) and the strength of the transition $\phi_*/T_*$ (right column) for MWT in the $M_H$-$M_{\Theta}$ plane for $M_A$, $M_{\rm f}=150$ GeV and $350$ GeV, as indicated in the labels. In the white regions the phase transition is either second order, very weakly first order, or does not occur at all.
• Figure 2: The parameters $\alpha$ (left column) and $\beta/H_*$ (right column), which characterize the GW production, for MWT in the $M_H$-$M_{\Theta}$ plane for $M_A$, $M_{\rm f}=150$ GeV and $350$ GeV, as indicated in the labels.
• Figure 3: The density of produced GWs $\rho_{\text{GW}}=\Omega_{\text{GW}} \text{h}^2$ in the case of the MWT as a function of the frequency (in Hz). Dashed lines represent the expected sensitivity of LISA and BBO, while solid lines represent the gravitational spectrum of bubble collision and turbulence combined. The three solid lines from thinner to thicker correspond to the gravitational spectrum with bubble collisions given, respectively, by Eqs. (\ref{['col1']}), (\ref{['col2']}), (\ref{['col3']}). The values of the parameters are given in the text.
• Figure 4: The nucleation temperature $T_*$, the strength of the phase transition $\phi_*/T_*$, the parameter $\alpha$, and the parameter $\beta/H_*$ (from top to bottom) in the $M_H$-$\Delta M_{\Pi}$ plane for the "4 transition" (left) and for the "2 transition" (right) of UMT. We fixed ETC masses at 150 GeV and used $v_2=300$ GeV.
• Figure 5: The density of produced GWs $\rho_{\text{GW}}=\Omega_{\text{GW}} \text{h}^2$ in the case of the UMT as a function of the frequency (in Hz). Dashed lines represent the expected sensitivity of LISA and BBO, while solid lines represent the gravitational spectrum of bubble collision and turbulence combined. The thin and thick solid lines correspond to the gravitational spectrum with bubble collisions given, respectively, by Eqs. (\ref{['col2']}), and (\ref{['col3']}). The spectrum from the $\sigma_4$ (electroweak) transition peaks at roughly $f=0.05$ Hz, while the spectrum from the $\sigma_2$ transition peaks around $f=0.005$ Hz. The values of the parameters are given in the text.