1. Observational Signatures of Primordial Turbulence
Tina Kahniashvili
Carnegie Mellon University, USA
&
Ilia State University, Georgia
PHENO2017, May 8, 2017

2. Collaborations Axel Brandenburg (NORDITA, Sweden & CU-Boulder, USA )
Nick Battaglia (Princeton University, USA)
Leonardo Campanelli (Bari University, Italy)
Ruth Durrer (Geneva University, Switzerland)
Grigol Gogoberidze (Ilia State University, Georgia)
Leonard Kisslinger (Carnegie Mellon University, USA)
Arthur Kosowsky (University of Pittsburgh, USA)
Sayan Mandal (Carnegie Mellon University, USA)
Yurii Maravin (Kansas State University, USA)
Bharat Ratra (Kansas State University, USA)
Shiv Sethi, (Raman Research Institute, India)
Alexander Tevzadze (Tbilisi State University, Georgia)
Tanmay Vachaspati (Arizona State University, USA)
Winston Yin (Oxford, USA)

3. Outlines Motivations Theory Observations Conclusions
Why primordial MHD turbulence
Theory
Magnetogenesis scenarios
Cosmological effects
Observations
Cosmic microwave background
Gravitational waves
Large scale structure
Conclusions

4. Motivations: Why Primordial MHD?
Cosmic magnetic fields
Astrophysical mechanism
Cosmological seeds
Observations
Fermi data – blazars spectra
Neronov and Vovk, Science 2010

5. MHD Simulations by Donnert et al. 2008
Ejection Primordial
Z=4
Z=4
Z=0
Z=0

6. Blazars Observations
The ultra high energy photons (gamma rays above 0.1 TeV) interact with the diffuse extragalactic background light
If the magnetic field along the path of the cascade production is strong enough to bend the pair trajectories then the cascade emission appears as an extended halo around the initial point source
Neronov & Semikoz 2009

7. Magnetogenesis Inflation Phase transitions Supersymmetry
F. Hoyle in Proc. “La structure et
l’evolution de l’Universe” (1958)
Inflation
Phase transitions
Supersymmetry
String Cosmology
Topological defects

8. Testing Very Early Universe
Magnetic field origin Red-inflation Yellow- phase transitions

9. Primordial MHD Turbulence
Primordial plasma is perfect conductor
Interaction between primordial magnetic fields and fluid (plasma)
Development of turbulence
Kahniashvili, Brandenburg, Ratra, Tevzadze 2010

10. MHD Turbulence Decay
Brandenburg, Kahniashvili, Tevzadze, 2014

11. Primordial MHD Turbulence Effects
Contribution to radiation-like energy density
BBN limits
Equality moment delay
Matter power spectrum
Jeans scale (magnetic pressure)
Density perturbations
Turbulence Decay
Cosmic microwave background
Temperature and Polarization anisotropies
Faraday rotation
Distortions
Gravitational waves
Generation from long duration sources

12. BBN and Primordial MHD Turbulence
Extra radiation like energy density less than 10% of the radiation energy density
The upper bound on the magnetic (effective) amplitude order of microGauss
To preserve the isotropy of the universe less than 10 microGauss
This field may have significant influence on gravitational instabilities
Up to 10% of thermal energy in clusters can be in the turbulent form

13. Magnetized (Turbulent) Perturbations
Gravitational perturbations
Turbulent source  
Density perturbations - scalar mode
Fast and slow magnetosound waves
Vorticity perturbations - vector mode
Alfven waves
Gravitational waves - tensor Mode

14. Magnetic Matter Power Spectrum (neglecting turbulence effects)
P(k) sensitive at k~ Mpc -1
Data:
Croft et al. 2002
Kahniashvili et al. ApJ 2013

15. Magnetic Field Upper Limits (neglecting turbulence effects)
Planck 2015 Results
POLARBEAR 2015

16. Planck Dust Polarization - Puzzle
“Perhaps the most intriguing result of Planck’s dust-polarization measurements is the observation that the power in the E-mode polarization is twice that in the B mode, as opposed to pre-Planck expectations of roughly equal dust powers in the E and B modes”
“ Although our model may be too simplistic to properly describe the nonlinear structure of interstellar magnetic fields, we find that the observed EE/BB ratio (and its scale invariance) and positive TE correlation—as well as the observed power-law index for the angular spectrum of these fluctuations—are not easily accommodated in terms of simple MHD turbulence prescriptions for the expected powers in slow, fast, and Alfvén waves”

17. Turbulence Effects
Solutions maybe in more proper accounting for turbulence (non-linear effects, decay)
Numerical modeling – coupling between the magnetic and velocity fields.
Decay of turbulence

18. Classes of MHD Turbulence
Brandenburg & Kahniashvili 2017

19. Two Classes of Initial Conditions
Magnetically dominant
Velocity dominant
Kahniashvili et al. 2010

20. Non-helical Inverse Transfer
Brandenburg, Kahniashvili, Tevzadze 2015

21. Magnetic Field Subdominant
Brandenburg, Kahniashvili, et al. 2017

22. Magnetic-Kinetic Equipartition
Brandenburg, Kahniashvili, et al. 2017

23. Cosmic Microwave Background
Polarization
Additional source from the vector (vortical) mode
Parity-odd cross correlations
Faraday rotation
POLARBEAR 2015

24. Turbulence Effects Decay Vorticity generation/amplification
Reduce the amplitude of pertubations
Vorticity generation/amplification
Additional source for B-polarization
Kahniashvili et al. 2012

25. CMB Faraday Rotation
Only scale invariant (inflationary) magnetic fields may have imprints on the CMB Faraday rotation
Causally generated magnetic fields due to the magnetic field decay are too weak to influence CMB
Kahniashvili, et al. 2014
Planck 2015 Results

26. Gravitational Waves Short duration sources
Describes gravitational waves generated through
Phase transition bubble collisions
Forced stage of hydro and MHD turbulence
Time scale is short compared to the Hubble time
Turbulence does not stop at the end of phase transitions!

27. Long-Duration Turbulence Generated Gravitational Waves
What we expect:
Additional source: kinetic or magnetic depending on initial conditions – what field (magnetic or velocity) was predominant
Substantial changes in amplitude and frequencies
Damping due to the universe expansion
Kahniashvili, Kisslinger, Stevens, 2010

28. Conclusions
Primordial turbulence is a plausible possibility to explain the presence of large-scale correlated cosmic magnetic fields
Presence of primordial turbulence can affect the large scale structure formation
Primordial turbulence can be responsible for the CMB B-polarization
Decaying primordial turbulence produces the gravitational wave signal