Phase transition dynamics may play important roles in the evolution history of the early universe, such as its possible roles in electroweak baryogenesis and dark matter.We systematically discuss and clarify the important details of the phase transition dynamics during a strong first-order phase transition (SFOPT). We classify the SFOPT into four types: slight supercooling, mild supercooling, strong supercooling, and ultra supercooling. Using different characteristic temperatures, length scales and bubble wall velocities, the corresponding gravitational wave (GW) spectra are investigated in details. We emphasize the essential importance of using the correct characteristic temperature and length scale when the phase transition dynamics and GW spectra are calculated. Especially, for strong supercooling and ultra supercooling cases, there are obvious differences of the phase transition strength and GW spectra between the results calculated at the nucleation temperature and those derived at the percolation temperature. For ultra supercooling case, we propose a criterion to quantify whether the phase transition can terminate. Besides the model-independent discussions, we also study three representative models as concrete examples to clearly show the subtle points therein.
We study gravitational wave (GW) production in strongly supercooled cosmological phase transitions, taking particular care of models featuring a complex scalar field with a U$(1)$ symmetric potential. We perform lattice simulations of two-bubble collisions to properly model the scalar field gradients, and compute the GW spectrum sourced by them using the thin-wall approximation in many-bubble simulations. We find that in the U$(1)$ symmetric case the low-frequency spectrum is $\proptoω$ whereas for a real scalar field it is $\proptoω^3$. In both cases the spectrum decays as $ω^{-2}$ at high fr…
Strongly-coupled theories at the TeV can naturally drive a long period of supercooling in the early universe. Trapped into the deconfined phase, the universe could inflate and cool down till the temperature reaches the QCD strong scale. We show how at these low temperatures QCD effects are important and could trigger the exit from the long supercooling era. We also study the implications on relic abundances. In particular, the latent heat released at the end of supercooling could be the reason for the similarities between dark matter and baryon energy densities. The axion abundance could also …
We investigate the reach of the LIGO/Virgo/KAGRA detectors in the search for signatures of first-order phase transitions in the early Universe. Utilising data from the first three observing runs, we derive constraints on the parameters of the underlying gravitational-wave background, focusing on transitions characterised by strong supercooling. As an application of our analysis, we determine bounds on the parameter space of two representative particle physics models. We also comment on the expected reach of third-generation detectors in probing supercooled phase transitions.
If the electroweak sector of the standard model is described by classically conformal dynamics, the early Universe evolution can be substantially altered. It is already known that---contrarily to the standard model case---a first order electroweak phase transition may occur. Here we show that, depending on the model parameters, a dramatically different scenario may happen: A first-order, six massless quark QCD phase transition occurs first, which then triggers the electroweak symmetry breaking. We derive the necessary conditions for this dynamics to occur, using the specific example of the cla…
In extensions of the Standard Model with no dimensionful parameters the electroweak phase transition can be delayed to temperatures of order 100 MeV. Then the chiral phase transition of QCD can proceed with 6 massless quarks. The top-quark condensate destabilizes the Higgs potential through the Yukawa interaction, triggering the electroweak transition. Based on the symmetries of massless QCD, it has been argued that the chiral phase transition is first order. We point out that the top-Higgs Yukawa interaction is nonperturbatively large at the QCD scale, and that its effect on the chiral phase …
We study the gravitational wave (GW) production in extremely strong first order phase transitions where the latent heat density dominates the plasma energy density, $α\gtrsim 1$. In such transitions, bubbles develop extremely thin and relativistic fluid configurations, resulting in strong shock waves after collisions. We first propose a strategy to understand the GW production in such a system by separating the problem into the propagation part and the collision part. Focusing on the former, we next develop an effective theory for the propagation of the relativistic fluid shells. Using this ef…
Can the universe be matter-dominated after a supercooled first-order phase transition?
PRISMA+ Cluster of Excellence（PRISMA+卓越集群）；Institut d’Astrophysique de Paris (IAP), CNRS, Sorbonne Université（巴黎天体物理学研究所，法国国家科学研究中心，索邦大学）；Institute for Astroparticle Physics (IAP), KIT（卡尔斯鲁厄理工学院亚原子物理研究所）
A strongly-coupled sector can feature a supercooled confinement transition in the early universe. We point out that, when fundamental quanta of the strong sector are swept into expanding bubbles of the confined phase, the distance between them is large compared to the confinement scale. We suggest a modelling of the subsequent dynamics and find that the flux linking the fundamental quanta deforms and stretches towards the wall, producing an enhanced number of composite states upon string fragmentation. The composite states are highly boosted in the plasma frame, which leads to additional parti…
We update predictions for the gravitational wave (GW) signal from a strongly supercooled phase transition in an illustrative classically conformal U(1)$_{B-L}$ model. We implement $\propto γ^2$ scaling of the friction on the bubble wall and update the estimates for the efficiency factors for GW production from bubble collisions and plasma-related sources. We take into account the fact that a small decay rate of the symmetry-breaking field may lead to brief matter-dominated era after the transition, as the field oscillates around its minimum before decaying. We find that a strong bubble collisi…
We derive efficiency factors for the production of gravitational waves through bubble collisions and plasma-related sources in strong phase transitions, and find the conditions under which the bubble collisions can contribute significantly to the signal. We use lattice simulations to clarify the dependence of the colliding bubbles on their initial state. We illustrate our findings in two examples, the Standard Model with an extra $|H|^6$ interaction and a classically scale-invariant $U(1)_{\rm B-L}$ extension of the Standard Model. The contribution to the GW spectrum from bubble collisions is …
We study strongly supercooled cosmological phase transitions. We perform numerical lattice simulations of two-bubble collisions and demonstrate that, depending on the scalar potential, in the collision the field can either bounce to a false vacuum or remain oscillating around the true vacuum. We study if these cases can be distinguished from their gravitational wave signals and discuss the possibility of black hole formation in the bubble collisions.
First-order phase transitions (FOPTs) are ubiquitous in physics beyond the Standard Model (SM). Recently, models with no dimensionful parameters in the tree-level action have been attracting much attention because they can predict a very strong FOPT with ultra-supercooling. In this paper, we study the cosmological signatures of such a supercooling model. As a concrete model, we consider the SM with two additional real scalars $ϕ$ and $S$, which can realize the electroweak symmetry breaking via Coleman-Weinberg mechanism. One of the additional scalars $S$ can naturally become a Dark Matter (DM)…
We investigate the properties of a stochastic gravitational wave background produced by a first-order electroweak phase transition in the regime of extreme supercooling. We study a scenario whereby the percolation temperature that signifies the completion of the transition, $T_p$, can be as low as a few MeV (nucleosynthesis temperature), while most of the true vacuum bubbles are formed much earlier at the nucleation temperature, $T_n\sim 50$ GeV. This implies that the gravitational wave spectrum is mainly produced by the collisions of large bubbles and characterised by a large amplitude and a …
Axion-CMB scenario is an interesting possibility to explain the temperature anisotropy of the cosmic microwave background (CMB) by primordial fluctuations of the QCD axion \cite{Iso:2020pzv}. In this scenario, fluctuations of radiations are generated by an energy exchange between axions and radiations, which results in the correlation between the primordial axion fluctuations and the CMB anisotropies. Consequently, the cosmological observations stringently constrain a model of the axion and the early history of the universe. In particular, we need a large energy fraction $Ω_A^{}$ of the axion …
Theoretical uncertainties in reconstructing model parameters with gravitational waves from supercooled phase transitions
Uppsala University（乌普萨拉大学）；University of Warsaw（华沙大学）；Nicolaus Copernicus Astronomical Center Polish Academy of Sciences（波兰科学院尼古拉·哥白尼天文学中心）；Université de Genève（日内瓦大学）；Karlsruhe Institute of Technology (KIT)（卡尔斯鲁厄理工学院）
We simulate the decay of isolated, spherically symmetric droplets in a cosmological phase transition. It has long been posited that such heated droplets of the metastable state could form, and they have recently been observed in 3D multi-bubble simulations. In those simulations, the droplets were associated with a reduction in the wall velocity and a decrease in the kinetic energy of the fluid, with a consequent suppression in the gravitational wave power spectrum. In the present work, we track the wall speed and kinetic energy production in isolated droplets and compare them to those found in…
Beyond the Daisy Chain: Running and the 3D EFT View of Supercooled Phase Transitions
PRISMA + Cluster of Excellence & Mainz Institute for Theoretical Physics, Johannes Gutenberg University（PRISMA卓越集群与美因茨理论物理研究所，约翰内斯·古腾堡大学）；Instituto de Física Teórica UAM/CSIC and Departamento de Física Teórica, Universidad Autónoma de Madrid（马德里自治大学/西班牙国家研究委员会理论物理研究所与理论物理系，马德里自治大学）；Dual CP Institute of High Energy Physics（双CP高能物理研究所）
Quasi-conformal models are an appealing scenario that can offer naturally a strongly supercooled phase transition and a period of thermal inflation in the early Universe. A crucial aspect for the viability of these models is how the Universe escapes from the supercooled state. One possibility is that thermal inflation phase ends by nucleation and percolation of true vacuum bubbles. This route is not, however, always efficient. In such case another escape mechanism, based on the growth of quantum fluctuations of the scalar field that eventually destabilize the false vacuum, becomes relevant. We…
We propose a new radion stabilization mechanism in the Randall-Sundrum spacetime, introducing a bulk ${SU(N_H)}$ gauge field which confines at a TeV scale. It turns out that the radion is stabilized by the balance between a brane tension and a pressure due to the Casimir energy of the strong ${SU(N_H)}$ gauge field. We investigate the phase transition between the Randall-Sundrum (compactified) spacetime and a de-compactified spacetime and determine the parameter regime in which eternal (old) inflation is avoided and the phase transition can be completed. In comparison to the Goldberger-Wise me…
Taking the 3-3-1 models (with $SU(3)_c \otimes SU(3)_L \otimes U(1)_Y$ gauge group) as examples, we study that a class of new physics models with extended gauge group could undergo one or several first-order phase transitions associated with the spontaneously symmetry breaking processes during the evolution of the universe, which can produce detectable phase transition gravitational wave (GW) signals at future GW experiments, such as LISA, BBO, DECIGO, SKA and aLIGO. These GW signals can provide new sources of GWs with different peak frequencies, and can be used to probe the evolution history …
In this paper we investigate a time-varying neutrino mass model, motivated by the mild tension between cosmic microwave background (CMB) measurements of the matter fluctuations and those obtained from low-redshift data. We modify the minimal case of the model proposed by Dvali and Funcke (2016) that predicts late neutrino mass generation in a post-recombination cosmic phase transition, by assuming that neutrino asymmetries allow for the presence of relic neutrinos in the late-time Universe. We show that, if the transition is supercooled, current cosmological data (including CMB temperature, po…
We study production of gravitational waves (GWs) in strongly supercooled cosmological phase transitions in gauge theories. We extract from two-bubble lattice simulations the scaling of the GW source, and use it in many-bubble simulations in the thin-wall limit to estimate the resulting GW spectrum. We find that in presence of the gauge field the GW source decays with bubble radius as $\propto R^{-3}$ after collisions. This leads to a GW spectrum that follows $Ω_{\rm GW} \propto ω^{2.3}$ at low frequencies and $Ω_{\rm GW} \propto ω^{-2.4}$ at high frequencies, marking a significant deviation fr…
Nanjing Normal University（南京师范大学）；Scuola Superiore Meridionale, Università degli studi di Napoli “Federico II”（那不勒斯费德里科二世大学南方高等学院）；INFN - Sezione di Napoli（意大利国家核物理研究所那不勒斯分部）
We study the gravitational wave spectrum from the confinement-deconfinement phase transi-tion in the holographic QCD models for both light quark and heavy quark. We obtain the gravitationalwave spectrum in the deflagration, detonation and runaway cases for different chemical potentials and duration of the phase transition. We find that the gravitational wave spectrum could be observed by EPTA/IPTA and eLISA for large chemical potential and short duartion of phase transtions.
We show that simple Two Higgs Doublet models still provide a viable explanation for the matter-antimatter asymmetry of the Universe via electroweak baryogenesis, even after taking into account the recent order-of-magnitude improvement on the electron-EDM experimental bound by the ACME Collaboration. Moreover we show that, in the region of parameter space where baryogenesis is possible, the gravitational wave spectrum generated at the end of the electroweak phase transition is within the sensitivity reach of the future space-based interferometer LISA.
The origins of matter and radiation in the universe lie in a Hot Big Bang. We present a number of well-motivated cosmologies in which the Big Bang occurs through a strong first order phase transition -- either at the end of inflation, after a period of kination ("Kination-Induced Big Bang"), or after a second period of vacuum-domination in the early universe ("Supercooled Big Bang"); we also propose a "Dark Big Bang" where only the dark matter in the Universe is created in a first-order phase transition much after inflation. In all of these scenarios, the resulting gravitational radiation can …
