Cosmology as a microscope for particle physics

Project supported by the European Union and the Czech Ministry of Education, Youth and Sports for the period 01.01.2023 – 31.12.2024. Project No. MSCA Fellowship CZ FZU I - CZ.02.01.01/00/22 010/0002906

Project is hosted at CEICO --- Central European Institute for Cosmology and Fundamental Physics, which is a part of FZU --- Institute of Physics of the Czech Academy of Sciences.

Summary of the project

Some of the epochs in the history of our Universe have exhibited extreme conditions that we could hardly imagine reproducing on Earth. This proposal aims to use our knowledge of the evolution of the Universe as a tool to study the structure of matter and use cosmology as a microscope for particle physics. The current paradigm of cosmology states that all galaxies and larger structures in the Universe originate from quantum fluctuations in primordial inflation. Due to extremely rapid accelerated expansion, these fluctuations were greatly enhanced and stretched to cosmological scales. The same could have happened to fluctuations of yet unknown matter constituents we would want to look for, but also to the Higgs boson of the standard model. The objective of the first part of the proposal is to determine the influence of large infrared quantum fluctuations of the Higgs field on the vector bosons, that would otherwise be oblivious to the rapid expansion. We will compute electromagnetic correlators using techniques of non-equilibrium quantum field theory and Starobinsky's stochastic formalism. The result of this calculation will shed light on primordial magnetogenesis, and (dark) gauge bosons beyond the standard model. The second part of the proposal concerns the again accelerating late Universe. There are good reasons to consider the mysterious source of this acceleration – dark energy – to be a dynamical entity. Promising candidates for dynamical dark energy are the so-called kinetic gravity braiding models. Our objective is to embed these models into the more fundamental realm of complex scalar field dynamics, and to determine whether they allow for gauge and maybe even electromagnetic interactions. This opens up novel channels for probing dark energy throughout the history of the Universe. 

Publications

1. D. Glavan and T. Prokopec
   Tadpoles sometimes matter: One-loop corrections for spectator Higgs in inflation
   arXiv:xxxx.xxxx [gr-qc]

Dissemination

March 1, 2023

D. Glavan

Seminar at Utrecht University, Utrecht, The Netherlands

title: Even photons break de Sitter symmetry

abstract: It is commonly held that the propagator for the massless vector field in de Sitter in the general covariant gauge has to satisfy all the symmetries of the maximally symmetric background. However, this is precluded by the Ward-Takahashi identity that has gone unnoticed thus far. I will present the recent construction of the photon propagator that satisfies all the conditions of a consistently quantized theory, and that maintains all de Sitter symmetries except spatial special conformal transformations. This propagator vanishes in the infrared, opposed to previously reported solutions to just the propagator equation of motion. Even though the de Sitter breaking pertains to the gauge sector, it is important when interactions are considered. I will discuss the energy-momentum tensor as the simplest one-loop observable to demonstrate further problems arising from failing to account for the Ward-Takahashi identity and the de Sitter breaking it requires.

May 24, 2023

Talk at "Quantum Field theory in Curved Sapcetimes Workshop II", 24-25 May, Granada, Spain

title: Even photons break de Sitter symmetry

abstract: It is commonly held that the propagator for the massless vector field in de Sitter in the general covariant gauge has to satisfy all the symmetries of the maximally symmetric background. However, this is precluded by the Ward-Takahashi identity that has gone unnoticed thus far. I will present the construction of the photon propagator that satisfies all the conditions of a consistently quantized theory, and that maintains most de Sitter symmetries, but breaks spatial special conformal transformations. This propagator vanishes in the infrared, opposed to previously reported solutions to just the propagator equation of motion. Even though the de Sitter breaking pertains to the gauge sector, it is important when interactions are considered. I will discuss the energy-momentum tensor as the simplest one-loop observable to demonstrate further problems arising from not accounting for the Ward-Takahashi identity and the de Sitter breaking.