Magnetic Fields from Phase Transitions

1. Magnetic Fields from Phase Transitions Tina Kahniashvili McWilliams Center for CosmologyCarnegie Mellon University & Abastumani Astrophysical Observatory Ilia State University Tbilisi 2015 TexPoint fonts used in EMF. Read the TexPoint manual before you delete this box.: AAAA

2. Collaboration Axel Brandenburg, NORDITA, Sweden AndriiNeronov, Geneva University, Switzerland Bharat Ratra, Kansas State University, USA Alexander Tevzadze, Tbilisi State University, Georgia TanmayVachaspati, Arizona State University, USA

3. Cosmic Magnetic Fields Earth MF Interstellar MF Galaxy MF Sun MF

4. Magnetic Helicity Solar activity: Sunspots Solar flares Coronal mass ejection Solar wind Magnetic helicity reflects mirror symmetry (parity) breaking

5. Ultra High Energy Gamma Rays Tests Neronov and Semikoz 2009 • 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 • Gamma Ray map • Blazars

6. Gamma Rays vs Magnetic Fields Tashiro, Chen, Francesc, Vachaspati 2014 Neronov and Vovk 2010

7. Cosmic Magnetic Fields Some History E. Fermi “On the origin of the cosmic radiation”, PRD, 75, 1169 (1949)

8. Known - Unknown • What we know: • The amplitude of the magnetic field • The spectral shape of the magnetic field • The correlation length scale • What we do not know: • When and how magnetic fields were generated • What were initial conditions Two Options: Cosmological and Astrophysical Scenarious

9. Why Cosmological Magnetic Fields are attractive? • Might serve as seeds for the observed fields in galaxies and clusters • Might be responsible for large scale correlated magnetic fields in the voids • Might explain some cosmological observations Are the observed magnetic fields of a primordial origin ?

10. Cosmological vs. Astrophysical MagnetogenesisMHD Simulations by Donnert et al. 2008 Ejection Primordial Z=4 Z=4 Z=0 Z=0

11. Primordial Magnetic Field Hypothesis • Inflation • Phase transitions • Supersymmetry • String Cosmology • Topological defects • Phase Transitions • Bubble collisions – first order phase transitions • QCDPT • EWPT • Causal fields • Limitation of the correlation length • Smoothed and effective fields approaches F. Hoyle in Proc. “La structure et l’evolution de l’Universe” (1958)

12. Cosmological Magnetic Fields • BBN limits: 10% of additional relativistic component • 0.1 – 1 microGauss (comoving value) • Faraday Rotation Measure • At z~2-3 microGauss • Initial picoGauss?

13. Phenomenology • If the magnetic field has been generated through a causal process in the early Universe it’s correlation length could not exceed the Hubble horizon at the moment of the generation

14. Phase Transitions Generated Magnetic Field PhenomenologyKahniashvili, Tevzadze, Brandenburg, Neronov 2012 • Non-helical field • Helical field • Helicity conservation law

15. MHD Simulations Brandenburg, Kahniashvili, Tevzadze, 2014

16. Modeling Magnetic Field

17. MHD Modeling • Coupling of the magnetic field with primordial plasma • Injection of the magnetic energy at a given scale (phase transition bubble) Kahniashvili, Brandenburg, Ratra, Tevzadze 2010

18. Magnetic Field Spectrum Kahniashvili, Tevzadze, Brandenburg, Neronov 2012 • We recover k4 spectrum at large scales for both – helical and non-helical PMF • Initial Conditions for the decay stage were prepared through forced case • The velocity field at large scales is described by white noise

21. Results Kahniashvili, Tevzadze, Brandenburg, Neronov 2012

22. Magnetic field from QCD Phase Transitions Tevzadze, Kisslinger, Brandenburg, Kahniashvili 2012

23. Magnetic Helicity Growth Tevzadze, Kisslinger, Brandenburg, Kahniashvili 2012 • The correlation length should satisfy: • Magnetic helicity grows until it reaches its maximal value

24. High Resolution MHD Simulations Brandenburg, Kahniashvili, Tevzadze 2015 • 23043meshpoints on 9216 processors • Runs A and B with magnetic Prandtl numbers = 1 and 10 • Intermediate region: Iroshnikov-Kraichnan Goldreich-Sridhar Weak-turbulence • Non-helical magnetic fields

25. Energies Cascades • Non-helical magnetic fields • Forward cascade • Helical magnetic fields • Inverse cascade We have shown the inverse transfer for non-helical fields

26. Inverse Transfer Brandenburg, Kahniashvili, Tevzadze 2014

27. Brandenburg, Kahniashvili, Tevzadze 2014

28. Brandenburg, Kahniashvili, Tevzadze 2014

29. Brandenburg, Kahniashvili, Tevzadze 2014

30. Nonhelical Magnetic Fields Decay Brandenburg, Kahniashvili, Tevzadze 2014

31. Helical Magnetic Fields Decay Brandenburg, Kahniashvili, Tevzadze 2015

32. Helical Magnetic Fields Decay Brandenburg, Kahniashvili, Tevzadze 2015 Causal fields – correlation length limitation • nB=2 or nB=0 Inverse Cascade

33. Inflation Generated Helical Magnetic Field Kahniashvili, Durrer, Brandenburgh, Tevzadze 2015 The absence of inverse cascade for Inflation generated magnetic fields

34. Helical Magnetic FieldsScaling Laws Brandenburg, Kahniashvili, Tevzadze 2015

35. Helical Magnetic Field Brandenburg, Kahniashvili, Tevzadze 2015

36. Classes of Turbulence Brandenburg & Kahniashvili, 2015

37. Conclusion • The lower bound of the extragalactic magnetic field favors a primordial (phase transitions) magnetogenesisapproach (in particular, helical magnetic fields) • The primordial magnetic field might be a plausible explanation for the galaxy magnetic field

38. Thank You