The isotropic attractor solution of axion-SU(2) inflation:  universal isotropization in Bianchi type-I geometry

Wolfson, Ira; Maleknejad, Azadeh; Murata, Tomoaki; Komatsu, Eiichiro; Kobayashi, Tsutomu

doi:10.1088/1475-7516/2021/09/031

Cited by 21 publications

(12 citation statements)

References 44 publications

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“…We can obtain the (F a µν F a µν ) 2 term of Gauge-flation by integrating out the inflaton field of Chromo-natural inflation near the minimum of the potential [29,30]. Both models share similar cosmological features [31] and reach the isotropic gauge field configuration as an attractor, even if the initial configuration is highly anisotropic [32][33][34][35].…”

Section: Introductionmentioning

confidence: 99%

Axion-gauge field dynamics with backreaction

Ishiwata

Komatsu

Obata

2022

J. Cosmol. Astropart. Phys.

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Phenomenological success of inflation models with axion and SU(2) gauge fields relies crucially on control of backreaction from particle production. Most of the previous study only demanded the backreaction terms in equations of motion for axion and gauge fields be small on the basis of order-of-magnitude estimation. In this paper, we solve the equations of motion with backreaction for a wide range of parameters of the spectator axion-SU(2) model. First, we find a new slow-roll solution of the axion-SU(2) system in the absence of backreaction. Next, we obtain accurate conditions for stable slow-roll solutions in the presence of backreaction. Finally, we show that the amplitude of primordial gravitational waves sourced by the gauge fields can exceed that of quantum vacuum fluctuations in spacetime by a large factor, without backreaction spoiling slow-roll dynamics. Imposing additional constraints on the power spectra of scalar and tensor modes measured at CMB scales, we find that the sourced contribution can be more than ten times the vacuum one. Imposing further a constraint of scalar modes non-linearly sourced by tensor modes, the two contributions can still be comparable.

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Section: Introductionmentioning

confidence: 99%

Axion-gauge field dynamics with backreaction

Ishiwata

Komatsu

Obata

2022

J. Cosmol. Astropart. Phys.

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“…In the model of CNI, the gauge fields have an isotropic and attractor background solution [13][14][15], which is induced by the motion of the axion. The nonzero vacuum expectation values (VEVs) of the gauge fields induce tachyonic instabilities in the gauge field perturbations.…”

Section: Introductionmentioning

confidence: 99%

Gravitational waves detectable in laser interferometers from axion-SU(2) inflation

Fujita

Imagawa

Murai

2022

J. Cosmol. Astropart. Phys.

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Chromo-natural inflation (CNI) is an inflationary model where an axion coupled with SU(2) gauge fields acts as the inflaton. In CNI, the gauge fields have nonzero vacuum expectation values (VEVs), which results in the enhancement of gravitational waves (GWs). The original CNI is ruled out by the Planck observations due to the overproduction of GWs. In this work, we consider an inflationary model where the gauge fields acquire nonzero VEVs after the CMB modes exit the horizon. Moreover, we add to the model another field that dominates the universe and drives inflation after the axion starts to oscillate and the gauge field VEVs vanish. By performing numerical simulations, we find a parameter space where the enhanced GWs do not violate the CMB constraints and can be detected by the future GWs observations such as BBO and ET.

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“…The isotropic solution of Gauge-flation/Chromo-natural inflation is an attractor: even if spacetime geometry of the Universe was highly anisotropic initially, it approaches the isotropic solution [242][243][244] . Isotropy is broken when A a i is allowed to acquire different mass m a depending on a.…”

Section: Non-abelian Gauge Fieldmentioning

confidence: 99%

New physics from the polarised light of the cosmic microwave background

Komatsu

2022

Preprint

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Cosmology requires new physics beyond the Standard Model of elementary particles and fields. What is the fundamental physics behind dark matter and dark energy? What generated the initial fluctuations in the early Universe? Polarised light of the cosmic microwave background (CMB) may hold the key to answers. In this article, we discuss two new developments in this research area. First, if the physics behind dark matter and dark energy violates parity symmetry, their coupling to photons rotates the plane of linear polarisation as the CMB photons travel more than 13 billion years. This effect is known as 'cosmic birefringence': space filled with dark matter and dark energy behaves as if it were a birefringent material, like a crystal. A tantalising hint for such a signal has been found with the statistical significance of 3σ . Next, the period of accelerated expansion in the very early Universe, called 'cosmic inflation', produced a stochastic background of primordial gravitational waves (GW). What generated GW? The leading idea is vacuum fluctuations in spacetime, but matter fields could also produce a significant amplitude of primordial GW. Finding its origin using CMB polarisation opens a new window into the physics behind inflation. These new scientific targets may influence how data from future CMB experiments are collected, calibrated, and analysed.

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The isotropic attractor solution of axion-SU(2) inflation: universal isotropization in Bianchi type-I geometry

Cited by 21 publications

References 44 publications

Axion-gauge field dynamics with backreaction

Axion-gauge field dynamics with backreaction

Gravitational waves detectable in laser interferometers from axion-SU(2) inflation

New physics from the polarised light of the cosmic microwave background

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