Cyclic Cosmology, Conformal Symmetry and the Metastability of the Higgs

Abstract: Recent measurements at the LHC suggest that the current Higgs vacuum could be metastable with a modest barrier (height 10^{10-12}{GeV})^{4}) separating it from a ground state with negative vacuum density of order the Planck scale. We note that metastability is problematic for big bang to end one cycle, bounce, and begin the next. In this paper, motivated by the approximate scaling symmetry of the standard model of particle physics and the primordial large-scale structure of the universe, we use our recent formulation of the Weyl-invariant version of the standard model coupled to gravity to track the evolution of the Higgs in a regularly bouncing cosmology. We find a band of solutions in which the Higgs field escapes from the metastable phase during each big crunch, passes through the bang into an expanding phase, and returns to the metastable vacuum, cycle after cycle after cycle. We show that, due to the effect of the Higgs, the infinitely cycling universe is geodesically complete, in contrast to inflation.

Cyclic Cosmology, Conformal Symmetry, and Higgs Metastability: An Overview

In the paper titled "Cyclic Cosmology, Conformal Symmetry and the Metastability of the Higgs", Bars, Steinhardt, and Turok propose a novel approach to addressing the metastability of the Higgs field within the context of cyclic cosmology and conformal symmetry. The research presented revolves around the implications of recent measurements at the LHC, suggesting a potential metastable Higgs vacuum, and explores how this might shape our understanding of cosmic evolution.

The fundamental hypothesis advanced in the paper is that the universe undergoes regular cycles of expansion, contraction, and bounce, driven by the dynamics of the Higgs field amidst a conformal symmetry-based framework. The Weyl-invariant version of the Standard Model coupled to gravity forms the basis for this investigation.

Key Findings

1. Metastability of the Higgs Field: The authors argue that the current Higgs vacuum may be metastable, existing through a modest barrier (height $(10^{10-12}~\mathrm{GeV})^{4}$) that separates it from a ground state with negative vacuum density. This finding raises concerns about the traditional big bang cosmology, especially regarding inflationary models, which necessitate restrictive initial conditions to accommodate inflation.
2. Cyclic Universe Model: The paper posits that a cyclic universe naturally accommodates the metastable Higgs vacuum by integrating it into the transition mechanics from a big crunch to a big bang. The cyclic model renders the universe geodesically complete, distinguishing itself from inflationary cosmologies, which are challenged by initial condition requirements for continuity.
3. Role of Conformal Symmetry: The incorporation of Weyl-invariant actions facilitates tracking the evolution of the Higgs field across cosmological cycles. Conformal symmetry is employed as a guiding principle, suggesting that fundamental physics operates under scaling invariance, simplifying the representation of cosmological dynamics.
4. Geodesical Completeness: A significant aspect of cyclic cosmology highlighted is its intrinsic geodesical completeness, contrasting with inflationary scenarios in which geodesics terminate within finite conformal time. This theoretical robustness offers a compelling narrative for the eternal continuity and past-completeness of the universe.

Implications

The research indicates profound implications for both the cosmological models and the role of Higgs physics in understanding the universe's architecture. The cyclic model provides a phenomenologically consistent framework that aligns with the observed data without necessitating unlikely initial conditions.

From a theoretical standpoint, melding conformal symmetry with cyclic dynamics presents promising directions for future inquiry, especially concerning particle physics implications at cosmological scales. Experimentally, the model may motivate targeted observations and simulations to verify cyclic patterns and the persistence of metastable states within high energy physics.

Future Directions

The exploration of cyclic cosmological models underscores the potential for advancements in understanding universal dynamics and Higgs field implications. Further investigations might refine the model and uncover novel predictions that can be empirically tested. Additionally, expanding the scope to include more diverse scalar field interactions and considering quantum corrections could uncover new facets of cosmic cycles.

Cyclic cosmology offers a rich tapestry for advancing theoretical physics independent from conventional inflationary constraints, suggesting compelling pathways for ongoing debates about the universe's initial and eventual states.