An injection of energy into the early Universe on a given characteristic length scale will result in turbulent motions primordial plasma. We calculate stochastic background gravitational radiation arising from period cosmological turbulence, using simple model isotropic Kolmogoroff turbulence produced phase transition. also derive generated by magnetic fields dynamo operating during turbulence. The resulting has maximum amplitude comparable to collision bubbles first-order transition, but at...

A stochastic magnetic field in the early universe will produce anisotropies temperature and polarization of cosmic microwave background. We derive analytic expressions for background power spectra induced by vector tensor perturbations from a power-law field. For scale-invariant smoothed over comoving scale 1 Mpc, Microwave Anisotropy Probe satellite has potential to constrain mean-field amplitude be no greater than approximately $2\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}9}...

Energy injection into the early universe can induce turbulent motions of primordial plasma, which in turn act as a source for gravitational radiation. Earlier work computed amplitude and characteristic frequency relic wave background, function total energy injected stirring scale turbulence. This paper computes spectrum radiation from stationary Kolmogoroff form acts given duration, making no other approximations. We also show that limit long wavelengths, commonly employed aeroacoustic...

In the presence of magnetic helicity, inverse transfer from small to large scales is well known in magnetohydrodynamic (MHD) turbulence and has applications astrophysics, cosmology, fusion plasmas. Using high resolution direct numerical simulations magnetically dominated self-similarly decaying MHD turbulence, we report a similar even absence helicity. We compute for first time spectral energy rates show that this about half as strong with but both cases gain at results velocity interacting...

We consider the evolution of primordial magnetic fields generated during cosmological, electroweak, or QCD phase transitions. assume that field generation can be described as an injection energy to cosmological plasma at a given scale determined by moment generation. A high Reynolds number ensures strong coupling between and fluid motions. The subsequent is governed decaying hydromagnetic turbulence. Both our numerical simulations phenomenological description allow us recover ``universal''...

We perform direct numerical simulations of magnetohydrodynamic turbulence in the early universe and numerically compute resulting stochastic background gravitational waves relic magnetic fields. These do not make simplifying assumptions earlier analytic work. If is assumed to have an energy-carrying scale that about a hundredth Hubble radius at time generation, as expected first-order phase transition, peak wave power will be mHz frequency range for signal produced electroweak scale. The...

We perform numerical simulations of decaying hydrodynamic and magnetohydrodynamic turbulence. classify our time-dependent solutions by their evolutionary tracks in parametric plots between instantaneous scaling exponents. find distinct classes evolving along specific trajectories toward points on a line self-similar solutions. These are determined the underlying physics governing individual cases, while infrared slope initial conditions plays only limited role. In helical case, even for...

We present new simulations of decaying hydromagnetic turbulence for a relativistic equation state relevant to the early universe. compare helical and nonhelical cases either with kinetically or magnetically dominated initial fields. Both kinetic magnetic helicities lead maximally fields after some time, but different temporal decay laws. are universe, although no mechanisms have yet been identified that produce helicity strengths comparable big bang nucleosynthesis limit at scales Hubble...

Scalar field ϕCDM models provide an alternative to the standard ΛCDM paradigm, while being physically better motivated. Dynamical scalar are divided into two classes: quintessence (minimally and non-minimally interacting with gravity) phantom models. These explain phenomenology of late-time dark energy. In these models, energy density pressure time-dependent functions under assumption that is described by ideal barotropic fluid model. As a consequence this, equation state parameter also...

We derive an expression for the angular power spectrum of cosmic microwave background anisotropies due to gravity waves generated by a stochastic magnetic field and compare result with current observations; we take into account non-linear nature stress energy tensor field. For almost scale invariant spectra, amplitude at galactic scales is constrained be order ${10}^{\ensuremath{-}9} \mathrm{G}.$ If assume that damped below Alfv\'en damping scale, find its ${0.1h}^{\ensuremath{-}1}...

A primordial cosmological magnetic field induces Faraday rotation of the cosmic microwave background polarization. This produces a curl-type polarization component even when unrotated possesses only gradient-type polarization, as expected from scalar density perturbations. We compute angular power spectrum arising small due to weak stochastic with power-law spectrum. The induced peaks at arc minute scales. is one few sources along tensor perturbations, gravitational lensing, and vector...

We study the effect of a helicity component primordial magnetic field on tensor part cosmic microwave background temperature anisotropies and polarization. give analytical approximations for contributions induced by helicity, discussing their amplitude spectral index in dependence power spectrum field. find that an helical creates parity odd gravity waves inducing polarization signals. However, only if is close to scale invariant its maximal, sufficiently large be observable. also discuss...

Gravitational waves potentially represent our only direct probe of the universe when it was less than one second old. In particular, first-order phase transitions in early can generate a stochastic background gravitational which may be detectable today. We briefly summarize physical sources radiation from and present semianalytic expressions for resulting wave spectra three distinct realistic sources: bubble collisions, turbulent plasma motions, inverse-cascade helical magnetohydrodynamic...

We study gravitational waves generated by the cosmological magnetic fields induced via bubble collisions during electroweak (EW) and QCD phase transitions. The field generation mechanisms considered here are based on use of fundamental EW minimal supersymmetric Lagrangians. spectrum is computed using a magnetohydrodynamic turbulence model. find that wave amplitude transition peaks at frequency approximately 1--2 mHz, order ${10}^{\ensuremath{-}20}--{10}^{\ensuremath{-}21}$; thus this signal...

We consider the generation of gravitational waves by primordial helical inverse-cascade magnetohydrodynamic (MHD) turbulence produced bubble collisions at electroweak phase transition. extend previous study [1] considering both currently discussed models MHD turbulence. For popular transition parameter values, generated wave spectrum is only weakly dependent on model. Compared with unmagnetized case, MHD-turbulence-generated peaks lower frequency larger amplitude and can be detected proposed...

The presence of asymmetry between fermions opposite handedness in plasmas relativistic particles can lead to exponential growth a helical magnetic field via small-scale chiral dynamo instability known as the effect. Here, we show, using dimensional arguments and numerical simulations, that this process produces through Lorentz force magnetically driven turbulence. A k^{-2} energy spectrum emerges inverse transfer over certain range wavenumbers k. total chirality (magnetic helicity plus...

We study the evolution of QCD phase transition-generated magnetic fields (MFs) in freely decaying MHD turbulence expanding universe. consider an MF generation model that starts from basic non-perturbative theory and predicts stochastic MFs with amplitude order 0.02 μG small helicity. employ direct numerical simulations to decay identify two different regimes: a "weakly helical" regime, when helicity increases during decay, "fully turbulence, maximal is reached inverse cascade develops. The...

We perform numerical simulations of gravitational waves (GWs) induced by hydrodynamic and hydromagnetic turbulent sources that might have been present at cosmological quantum chromodynamic (QCD) phase transitions. For energies about 4% the radiation energy density, typical scale such motions may a sizable fraction Hubble time. The resulting GWs are found to an $10^{-9}$ critical density in nHz range today already observed NANOGrav collaboration. This is further made possible our findings...

Cosmological magnetic fields induce temperature and polarization fluctuations in the cosmic microwave background (CMB) radiation. A cosmological field with current amplitude of order ${10}^{\ensuremath{-}9}\text{ }\text{ }\mathrm{G}$ is detectable via observations CMB anisotropies. This (with or without helicity) generates vector perturbations through vortical motions primordial plasma. paper shows that helicity induces parity-odd cross correlations between $B$-polarization $E$-...

We derive the cosmic microwave background temperature anisotropy two-point correlation function (including off-diagonal correlations) from broken spatial isotropy due to an arbitrarily oriented homogeneous cosmological magnetic field.

We study limits on a primordial magnetic field arising from cosmological data, including that big bang nucleosynthesis, cosmic microwave background polarization plane Faraday rotation limits, and large-scale structure formation. show the physically relevant quantity is value of effective field, it are independent how was generated.

A primordial magnetic field in the early universe will cause Faraday rotation of linear polarization cosmic microwave background generated via Compton scattering at surface last scattering. This induces a nonzero parity-odd (B-mode) component. The Wilkinson Microwave Anisotropy Probe 5-year data puts an upper limit on magnitude B-polarization power spectrum; assuming that signal is totally due to effect, limits comoving amplitude stochastic range from...

We estimate the degree of circular polarization for gravitational waves generated during electroweak and QCD phase transitions from kinetic magnetic helicity by bubble collisions those cosmological transitions.

Primordial magnetic fields could explain the large-scale present in Universe. Inflation and phase transitions early Universe give rise to such with unique characteristics. We investigate magneto-hydrodynamic evolution of these magnetogenesis scenarios cosmological simulations. evolve inflation-generated either as (i) uniform (homogeneous) or (ii) scale-invariant stochastic fields, transition-generated ones (iii) helical (iv) non-helical from radiation-dominated epoch. find that final...

Abstract We use direct numerical simulations of decaying primordial hydromagnetic turbulence with helicity to compute the resulting gravitational wave (GW) production and its degree circular polarization. The is sourced by magnetic fields that are either initially present or driven an electromotive force applied for a short duration, given as fraction one Hubble time. In both types simulations, we find clear dependence polarization GWs on fractional turbulent source. low frequency tail below...