Gravitational waves and black holes from the phase transition in models of dynamical symmetry breaking

Abstract: Theories of dynamical electroweak symmetry breaking predict a strong first order cosmological phase transition: we compute the resulting signals, primordial black holes and gravitational waves. These theories employ one SM-neutral scalar, plus some extra model-dependent particle to get the desired quantum potential out of classical scale invariance. We consider models where the extra particle is a scalar singlet, or vectors of an extended U(1) or SU(2) gauge sector. In models where the extra particle is stable, it provides a particle Dark Matter candidate with freeze-out abundance that tends to dominate over primordial black holes. These can instead be DM in models without a particle DM candidate. Gravitational waves arise at a level observable in future searches, even in regions where DM cannot be directly tested.

• The paper demonstrates that DESB models produce detectable gravitational waves and primordial black holes through vigorous first-order phase transitions.
• The paper employs detailed bubble dynamics and supercooling analysis to model phase transitions with predictions for stochastic gravitational wave backgrounds.
• The paper underscores implications for dark matter composition and future observatory prospects, bridging high-energy physics with early Universe cosmology.

Overview of "Gravitational waves and black holes from the phase transition in models of dynamical symmetry breaking"

The paper in question investigates the implications of cosmological phase transitions in theories of dynamical electroweak symmetry breaking (DESB). The work explores the production of gravitational waves (GWs) and primordial black holes (PBHs) deriving from such phase transitions, exploring various model implementations of DESB.

Theoretical Framework and Models

DESB theories augment the Standard Model (SM) with an additional scalar field, which remains neutral under the SM gauge group. This scalar interacts with extra particles, which could be either scalar singlets, vector particles of a U(1) extended gauge group, or even components of an SU(2) gauge sector. The role of these particles is crucial as they mediate the necessary quantum effects to facilitate classical scale invariance and result in symmetry breaking.

The paper formulates scenarios in which these extra particles serve as viable dark matter (DM) candidates, with the stable ones typically demanding consideration of freeze-out mechanisms. Notably, if direct particle dark matter is absent, PBHs can effectively serve as dark matter components.

Cosmological Phase Transitions

A pivotal feature of DESB models is the significance of the first-order cosmological phase transition, driven by the dynamical breaking of symmetries. The transition involves a supercooling phase, which reduces thermal energies significantly below equilibrium conditions before nucleation of bubbles commences. Bubble dynamics—expansion, collision, and percolation—are modeled meticulously, with the generation of stochastic gravitational wave backgrounds (SGWBs) being a central focus when the first-order nature of the phase transition is vigorous.

Gravitational Waves and Detection Prospects

Gravitational waves from DESB models are predicted to have distinct signatures capable of being detected by future interferometric observatories. Remarkably, these GW signals could provide empirical evidence of scenarios beyond the SM. Potential observatories, such as LISA and the Einstein Telescope, offer adequate sensitivity across frequency bands to observe these stochastic backgrounds, highlighting the feasibility of detecting GWs arising from phase transitions at electroweak scales and beyond.

Primordial Black Holes

The formation of PBHs during the late stages of supercooled phase transitions signifies regions of the Universe that failed to transition from the false to true vacuum states promptly. These PBHs, forming via multiple mechanisms, such as bubble collisions, are most pronounced under conditions of strong supercooling and intense bubble dynamics, implying a rich interplay between the phase transition properties and early Universe cosmology.

Experimental and Theoretical Implications

The models elaborated predict rich phenomenology for both GW and PBHs, paving pathways to probe early Universe physics and DM composition. On the theoretical plane, the models underscore how subtle alterations in particle content and interactions could manifest observable signatures, fundamentally connecting high-energy physics insights with cosmological phenomena.

Conclusion and Future Prospects

This paper highlights the utility of DESB models in explaining complex cosmological observations, advocating for a nuanced consideration of phase transition dynamics as potential probes for new physics. Future work will likely refine these predictions, improve simulation methods for generating SGWB, and address phenomenological constraints emerging from forthcoming observational data, thereby enhancing our understanding of the Universe’s formative processes. Future developments in AI and computation could further streamline the dynamic simulations of these cosmological phenomena, offering even more precise theoretical frameworks and predictions.