Production of helical magnetic fields during baryogenesis

Transcription

1 Production of helical magnetic fields during baryogenesis Francesc Ferrer Washington University in Saint Louis NORDITA. June 23, 25

2 Outline Introduction: Observations of Magnetic Fields B-field production during baryogenesis One bubble Many bubbles Conclusions

3 Introduction: Observations of Magnetic Fields B-field production during baryogenesis One bubble Many bubbles Conclusions

4 Magnetic fields are ubiquitous in the Universe Starting in Large scale magnetic fields have been detected in galaxies and clusters (µg). Lyman-α systems at z 2.5 show evidence of B-fields in Faraday rotation measurements. B-fields appear to have similar magnitudes for the same type of objects regardless of location in the universe. Common primordial seeds? Important to understand formation and evolution of structure. Could provide a window to processes in the Early Universe.

5 How were these fields generated? Small field seeds get amplified via dynamo mechanisms. Seeds of astrophysical or cosmological origin? Hoyle 958 Can we fit the observed intensity and coherence length? How large should the initial seeds be for the B-fields to have enough time to grow? Is there any observational support for this idea?

6 How were these fields generated? Small field seeds get amplified via dynamo mechanisms. Seeds of astrophysical or cosmological origin? Hoyle 958 Can we fit the observed intensity and coherence length? How large should the initial seeds be for the B-fields to have enough time to grow? Is there any observational support for this idea?

7 How were these fields generated? Small field seeds get amplified via dynamo mechanisms. Seeds of astrophysical or cosmological origin? Hoyle 958 Can we fit the observed intensity and coherence length? How large should the initial seeds be for the B-fields to have enough time to grow? Is there any observational support for this idea?

8 B-fields as a window to the Early Universe Once generated, B-fields survive in the cosmological conducting plasma. There are plenty of opportunities in the early stages of the evolution of the Universe! Breaking of conformal invariance during inflation. During the QCD phase-transition. At the time of matter-genesis.

9 B-fields as a window to the Early Universe Once generated, B-fields survive in the cosmological conducting plasma. There are plenty of opportunities in the early stages of the evolution of the Universe! Breaking of conformal invariance during inflation. During the QCD phase-transition. At the time of matter-genesis.

10 Introduction: Observations of Magnetic Fields B-field production during baryogenesis One bubble Many bubbles Conclusions

11 The electroweak phase transition Vachaspati & Ng

12 B-fields and the electroweak phase-transition Once electroweak fields become massive, they leave behind the only massless field in the spectrum, the photon. At the time of the electroweak phase-transition, sphaleron processes occur that violate baryon number, CP violation is also present. A sphaleron can be seen as two linked Z-strings. The leftover magnetic field lines will be linked. Magnetic Helicity

13 Why is helicity important? h = V V d 3 x A B Discriminate astrophysical vs. cosmological seeds. Provides a window to processes in the early universe. Leptogenesis vs ew baryogenesis Relate ρ B to ρ b. Long, Sabancilar, Vachaspati, 23 For turbulent non-diffusive evolution, MHD studies show that inverse cascade increases coherence length by η 2/3.

14 Why is helicity important? h = V V d 3 x A B Discriminate astrophysical vs. cosmological seeds. Provides a window to processes in the early universe. Leptogenesis vs ew baryogenesis Relate ρb to ρ b. Long, Sabancilar, Vachaspati, 23 For turbulent non-diffusive evolution, MHD studies show that inverse cascade increases coherence length by η 2/3.

15 Evolution Kahniashvili, Tevzadze, Brandenburg & Neronov 2; Saveliev, Jedamzik & Sigl 3

16 Evolution

17 Evolution

18 Introduction: Observations of Magnetic Fields B-field production during baryogenesis One bubble Many bubbles Conclusions

19 Helicity from sphaleron decay

20 Helicity from sphaleron decay Vachaspati & Field 94

21 Helicity from sphaleron decay A = sin θ W W 3 + cos θ W Y N CS n B Sphaleron decays Phase transition h n B α B 3 r G 9 G

22 Helicity from sphaleron decay A = sin θ W W 3 + cos θ W Y N CS n B Sphaleron decays Phase transition h n B α B 3 r G 9 G

23 Helicity from sphaleron decay A = sin θ W W 3 + cos θ W Y N CS n B Sphaleron decays Phase transition h n B α B 3 r G 9 G

24 Helicity from sphaleron decay A = sin θ W W 3 + cos θ W Y N CS n B Sphaleron decays Phase transition h n B α B 3 r G 9 G

25 Helicity from sphaleron decay A = sin θ W W 3 + cos θ W Y N CS n B Sphaleron decays Phase transition h n B α B 3 r G 9 G

26 Simulations Solve classical evolution equations on the lattice. p j i Ambjorn, Askgaard, Porter & Shaposnikov 9; Rajantie, Saffin & Copeland

27 Simulations C. Copi, FF, T. Vachaspati, A. Achucarro 8

28 Helicity from sphaleron decay C. Copi, FF, T. Vachaspati, A. Achucarro 8

29 Helicity from sphaleron decay Yiyang Zahng, FF, Vachaspati

30 Helicity from sphaleron decay C. Copi, FF, T. Vachaspati, A. Achucarro 8

31 Helicity from sphaleron decay C. Copi, FF, T. Vachaspati, A. Achucarro 8 Helicity is conserved even though there is no plasma.

32 Helicity from sphaleron decay C. Copi, FF, T. Vachaspati, A. Achucarro 8 Helicity is conserved even though there is no plasma.

33 Helicity from sphaleron decay

34 Helicity from sphaleron decay -.5 helicity time Yi-Zen Chu, J. Dent, T. Vachaspati

35 Introduction: Observations of Magnetic Fields B-field production during baryogenesis One bubble Many bubbles Conclusions

36

37 The electroweak phase transition Vachaspati & Ng

38 Number of sphalerons Number of sphaleron explosions t

39 M H (r).2.5 M_H(r)..5 5 r

40 Introduction: Observations of Magnetic Fields B-field production during baryogenesis One bubble Many bubbles Conclusions

41 Conclusions Non-perturbative processes at the time of baryogenesis can give rise to cosmologicaly relevant magnetic fields. The fields have left-handed helicity, and are coherent over tens of kpc. The study of astrophysical magnetic fields provides a window to processes in the Early Universe. The detection of magnetic helicity can be linked to the epoch of matter-genesis.