Preheating in the Standard Model with the Higgs-Inflaton coupled to gravity (0812.4624v2)

Abstract: We study the details of preheating in an inflationary scenario in which the Standard Model Higgs, strongly non-minimally coupled to gravity, plays the role of the inflaton. We find that the Universe does not reheat immediately through perturbative decays, but rather initiate a complex process in which perturbative and non-perturbative effects are mixed. The Higgs condesate starts oscillating around the minimum of its potential, producing W and Z gauge bosons non-perturbatively, due to violation of the so-called adiabaticity condition. However, during each semi-oscillation, the created gauge bosons completely decay (perturbatively) into fermions. This way, the decay of the gauge bosons prevents the development of parametric resonance, since bosons cannot accummulate significantly at the beginning. However, the energy transferred to the decay products of the bosons is not enough to reheat the universe, so after about a hundred oscillations, the resonance effect will finally dominate over the perturbative decays. Around the same time (or slightly earlier), backreaction from the gauge bosons onto the Higgs condensate will also start to be significant. Soon afterwards, the Universe is filled with the remnant condensate of the Higgs and a non-thermal distribution of Standard Model particles which redshift as radiation, while the Higgs continues to oscillate as a pressureless fluid. We compute the distribution of energy among all the species present at backreaction. From there on until thermalization, the evolution of the system is highly non-linear and non-perturbative, and will require a careful study via numerical simulations.

• The paper demonstrates that non-perturbative gauge boson production via parametric resonance competes with perturbative decay processes during the Higgs oscillation phase.
• It employs detailed numerical simulations to capture the complex dynamics of adiabaticity violation and energy transfer from the inflaton to Standard Model particles.
• The study reveals that effective reheating and thermalization occur only after multiple oscillations, offering new insights into early universe evolution.

Analyzing Preheating Mechanisms with a Higgs-Inflaton in the Standard Model

This paper, authored by Juan García-Bellido, Daniel G. Figueroa, and Javier Rubio, undertakes a meticulous examination of preheating in an inflationary scenario where the Higgs field of the Standard Model, non-minimally coupled to gravity, acts as the inflaton. The investigation focuses on the intricate dynamics and interactions that unfold immediately after inflation, a crucial period for understanding the transition from a cold, post-inflation universe to a hot, dense state suitable for the onset of the traditional hot Big Bang cosmology.

Core Findings and Contributions

The paper opens with foundational assumptions, diverging from simpler models that often impose additional degrees of freedom by allowing the Higgs doublet to interface directly with curvature, introducing a non-minimal coupling. This leads to modifications in the Higgs sector and affects both the inflationary dynamics and the subsequent reheating phase which is pivotal for transferring inflationary energy to Standard Model particles.

Key contributions and findings of the paper include:

1. Complex Dynamics of Particle Production: The authors elucidate that preheating in this Higgs-inflaton scenario initiates a competition between non-perturbative and perturbative processes—where gauge bosons $W$ and $Z$ are produced non-perturbatively during each oscillation of the Higgs condensate but decay perturbatively into fermions.
2. Adiabaticity Violation and Parametric Resonance: As the Higgs field oscillates post-inflation, it leads to a repeated violation of the adiabaticity condition, spawning particles non-perturbatively—a phenomenon known as parametric resonance. The energy transfer involves complex feedback loops between decay products and the inflaton field, emphasizing the need for careful numerical simulations due to the nonlinear, non-perturbative system evolution before reaching a thermalized state.
3. Impact on Reheating Efficiency: Given the strong self-interaction scale and the enhanced couplings involved, the paper argues that perturbative decay initially prevents substantial energy transfer. The subsequent predominance of non-perturbative effects implies effective reheating and thermalization occur only after many oscillations, highlighting the efficiency shortfall early in preheating dominated by perturbative processes only.

Implications and Theoretical Context

By dissecting scenarios where the Higgs boson of the Standard Model itself plays the role of the inflaton, this paper provides crucial insights into potential bridges between high-energy particle physics, cosmology, and gravitational interactions. The findings suggest prospects for precision tests of inflationary scenarios that do not introduce exotic particle physics beyond the Standard Model, contingent on powerful computational modeling and potential future observations of primordial resonances or gravitational waves originating from these epochs.

The work foresees future theoretical development and computational paper avenues, including high-precision lattice computations to scrutinize the nonlinear dynamics and ultimate thermalization of the universe, linking cosmological inflation scenarios to new physics tests at collider experiments like the LHC.

In conclusion, the intricate dynamics described here elucidate the relevance of incorporating such non-minimal couplings in scalar field models and guide future paths in exploring scenarios that obviate extensions beyond the Standard Model while retaining potential for new observational insights into the universe's infancy.