The Turbulent Stress Spectrum in the Inertial and Subinertial Ranges

Brandenburg, Axel; Boldyrev, Stanislav

doi:10.3847/1538-4357/ab77bd

Cited by 22 publications

(22 citation statements)

References 27 publications

(24 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In particular the peak of the stress spectrum is to a large fraction composed of the tensor mode only. As expected from the work of Brandenburg & Boldyrev (2020), its spectrum follows a k 2 subrange to high precision.…”

Section: Energy Spectrasupporting

confidence: 65%

Simulations of helical inflationary magnetogenesis and gravitational waves

Brandenburg,

He,

Sharma

2021

Preprint

Self Cite

View full text Add to dashboard Cite

Using numerical simulations of helical inflationary magnetogenesis in a low reheating temperature scenario, we show that the magnetic energy spectrum is strongly peaked at a particular wavenumber that depends on the reheating temperature. Gravitational waves (GWs) are produced at frequencies between 3 nHz and 50 mHz for reheating temperatures between 150 MeV and 3 × 10 5 GeV, respectively. At and below the peak frequency, the stress spectrum is always found to be that of white noise. This implies a linear increase of GW energy per logarithmic wavenumber interval, instead of a cubic one, as previously thought. Both in the helical and nonhelical cases, the GW spectrum is followed by a sharp drop for frequencies above the respective peak frequency. In this magnetogenesis scenario, the presence of a helical term extends the peak of the GW spectrum and therefore also the position of the aforementioned drop toward larger frequencies compared to the case without helicity. This might make a difference in it being detectable with space interferometers. The efficiency of GW production is found to be almost the same as in the nonhelical case, and independent of the reheating temperature, provided the electromagnetic energy at the end of reheating is fixed to be a certain fraction of the radiation energy density. Also, contrary to the case without helicity, the electric energy is now less than the magnetic energy during reheating. The fractional circular polarization is found to be nearly hundred per cent in a certain range below the peak frequency range.

show abstract

Section: Energy Spectrasupporting

confidence: 65%

Simulations of helical inflationary magnetogenesis and gravitational waves

Brandenburg,

He,

Sharma

2021

Preprint

Self Cite

View full text Add to dashboard Cite

show abstract

“…1-3 show a subinertial range proportional to k or k 3/2 , which is shallower than the generic k 2 spectrum. In the present case, the subinertial range is not long enough to make strong claims, but it is useful to recall that deviations from a k 2 spectrum of the stress have been found when there are departures from Gaussianity of the underlying magnetic or velocity fields [53]. Although the departures from Gaussianity may not yet be very strong in the present simulations, it is worth noting that real astrophysical magnetic fields have much larger magnetic Reynolds numbers and may well lead to much more significant departures.…”

Section: Runmentioning

confidence: 84%

The scalar, vector, and tensor modes in gravitational wave turbulence simulations

Brandenburg,

Gogoberidze,

Kahniashvili

et al. 2021

Preprint

Self Cite

View full text Add to dashboard Cite

We study the gravitational wave (GW) signal sourced by primordial turbulence that is assumed to be present at cosmological phase transitions like the electroweak and quantum chromodynamics phase transitions. We consider various models of primordial turbulence, such as those with and without helicity, purely hydrodynamical turbulence induced by fluid motions, and magnetohydrodynamic turbulence whose energy can be dominated either by kinetic or magnetic energy, depending on the nature of the turbulence. We also study circularly polarized GWs generated by parity violating sources such as helical turbulence. Our ultimate goal is to determine the efficiency of GW production through different classes of turbulence. We find that the GW energy and strain tend to be large for acoustic or irrotational turbulence, even though its tensor mode amplitude is relatively small at most wave numbers. Only at very small wave numbers is the spectral tensor mode significant, which might explain the efficient GW production in that case.

show abstract

“…Additionally, it has been pointed out in refs. [95,97] that the spectrum of the stress becomes shallower than white noise when the turbulence field is non-Gaussian, which would lead to a shallower GW spectrum. In the case when the magnetic field is driven, the MHD evolution might indeed generate a stochastic magnetic field with deviations from a Gaussian field.…”

Section: Discussionmentioning

confidence: 99%

“…[81]. This is a consequence of the k 4 Batchelor spectrum for a Gaussian magnetic (hence, divergenceless) field, which yields a k 2 (i.e., white noise) spectrum of the magnetic stress [81,95]. The small deviations from an exact flat spectrum, which increase towards negative slopes as we decrease the value of the fractional helicity, could be due to the small number of points in wave number space when we reach the largest scales of the simulation, as well as to the oscillations over time.…”

Section: Runs With Decaying Magnetic Field At the Initial Timementioning

confidence: 99%

Polarization of gravitational waves from helical MHD turbulent sources

Pol,

Mandal,

Brandenburg

et al. 2021

Preprint

Self Cite

View full text Add to dashboard Cite

We use direct numerical simulations of decaying primordial hydromagnetic turbulence with helicity to compute the resulting gravitational wave (GW) production and its degree of circular polarization. The turbulence is sourced by magnetic fields that are either initially present or driven by an electromotive force applied for a short duration, given as a fraction of one Hubble time. In both types of simulations, we find a clear dependence of the polarization of the resulting GWs on the fractional helicity of the turbulent source. We find a low frequency tail below the spectral peak shallower than the f 3 scaling expected at super-horizon scales, in agreement with similar recent numerical simulations. This type of spectrum facilitates its observational detection with the planned Laser Interferometer Space Antenna (LISA). We show that driven magnetic fields produce GWs more efficiently than magnetic fields that are initially present, leading to larger spectral amplitudes, and to modifications of the spectral shape. In particular, we observe a sharp drop of GW energy above the spectral peak that is in agreement with the previously obtained results. The helicity does not have a huge impact on the maximum spectral amplitude in any of the two types of turbulence considered. However, the GW spectrum at wave numbers away from the peak becomes smaller for larger values of the magnetic fractional helicity. Such variations of the spectrum are most noticeable when magnetic fields are driven. The degree of circular polarization approaches zero at frequencies below the peak, and reaches its maximum at the peak. At higher frequencies, it stays finite if the magnetic field is initially present, and it approaches zero if it is driven. We predict that the spectral peak of the GW signal can be

show abstract

The Turbulent Stress Spectrum in the Inertial and Subinertial Ranges

Cited by 22 publications

References 27 publications

Simulations of helical inflationary magnetogenesis and gravitational waves

Simulations of helical inflationary magnetogenesis and gravitational waves

The scalar, vector, and tensor modes in gravitational wave turbulence simulations

Polarization of gravitational waves from helical MHD turbulent sources

Contact Info

Product

Resources

About