Abstract
We discuss a novel scenario for early cosmology, when the inflationary quasi-de Sitter phase dynamically originates from the initial quantum state represented by the microcanonical density matrix. This genuine quantum effect occurs as a result of the dynamics of the topologically nontrivial sectors in a (conjectured) strongly coupled QCD-like gauge theory in expanding universe. The crucial element of our proposal is the presence in our framework of a nontrivial $\mathbb{S}^1$ which plays the dual role in construction: it defines the periodic gravitational instanton (on the gravity side) and it also defines a nontrivial gauge holonomy (on the gauge side) generating the vacuum energy. The effect is global in nature and cannot be formulated in terms of a gradient expansion in an effective local field theory. We also discuss a graceful exit from holonomy inflation due to the helical instability. The number of e-folds in the holonomy inflation framework is determined by the gauge coupling constant at the moment of inflation, and estimated as $N_{\rm infl}\sim \alpha^{-2}(H_0)\sim 10^2$. We also comment on the relation of our framework with the no-boundary and tunneling cosmological proposals and their recent criticism.
Highlights
The inflationary scenario is widely recognized as one of the most successful candidates for the description of the early Universe leading to its observable large scale structure
The majority of effective and fundamental models of this scenario are based on the assumption that matter energy density driving the quasiexponential expansion of the Universe during inflation stage is generated by local field-theoretical degrees of freedom (d.o.f.), like a scalaron field in the Starobinsky R2-gravity [1] or a scalar field inflaton ΦðxÞ with its potential VðΦÞ in chaotic and other inflationary models [2]; see textbook [3] for a general overview
As we argue below this construction provides a system with a subPlanckian energy scale such that a number of well-known and undesirable properties which always accompany the conventional inflationary scenario when a system is formulated in terms of a local field ΦðxÞ, does not even occur in our framework
Summary
The inflationary scenario is widely recognized as one of the most successful candidates for the description of the early Universe leading to its observable large scale structure. This model, which incorporates the idea of the microcanonical density matrix as the initial quantum state of the Universe [10], is conceptually very attractive because of the minimum set of assumptions underlying it and, because of a mechanism restricting the cosmological ensemble to subPlanckian energy domain and avoiding the infrared catastrophe inherent in the no-boundary wave function [11] This thermally driven cosmology [8,9] can serve as initial conditions for the observationally consistent models of R2 and Higgs inflation; see original paper [12] and the recent development [13,14] based on induced gravity aspects of the theory.
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