Geography on Heterotic Orbifolds

Transcription

1 Geography on Heterotic Orbifolds Hans Peter Nilles Physikalisches Institut, Universität Bonn and CERN, Geneva Based on work with S. Förste, P. Vaudrevange and A. Wingerter hep-th/ , hep-th/ StringPheno05 p.1/31

2 Outline Orbifold Compactification GUTs without GUT group Spinors of SO(10) An SO(10) Model with 3 Families Gauge group geography in extra dimensions Unification (sin 2 θ W ) Proton decay Yukawa textures and flavour symmetries Electroweak symmetry breakdown Outlook StringPheno05 p.2/31

3 Orbifold Compactification Orbifold compactifications combine the success of Calabi-Yau compactification calculability of torus compactification StringPheno05 p.3/31

4 Orbifold Compactification Orbifold compactifications combine the success of Calabi-Yau compactification calculability of torus compactification Fields can propagate Bulk (d = 10 untwisted sector) 3-Branes (d = 4 twisted sector fixed points) 5-Branes (d = 6 twisted sector fixed tori) StringPheno05 p.3/31

5 Z 3 Example StringPheno05 p.4/31

6 Z 3 Example Action of the space group on coordinates X i (θ k X) i + n α e i α, k = 0, 1, 2, i, α = 1,..., 6 Embed twist in gauge degrees of freedom X I (Θ k X) I I = 1,..., 16 StringPheno05 p.4/31

7 Results from the Z 3 Orbifold Successful model building with three families of quarks and leptons gauge group SU(3) SU(2) U(1) n doublet-triplet splitting mechanism for Yukawa suppression StringPheno05 p.5/31

8 Results from the Z 3 Orbifold Successful model building with three families of quarks and leptons gauge group SU(3) SU(2) U(1) n doublet-triplet splitting mechanism for Yukawa suppression Leads to a picture of GUTs without GUT group Incomplete gauge and Higgs multiplets Transparent geometric interpretation StringPheno05 p.5/31

9 Things to improve For models with SU(3) SU(2) U(1) gauge group, the Z 3 orbifold example is too rigid only fixed points and no fixed tori no normal grand unified picture (like SO(10)) no large string threshold corrections continuous Wilson lines too destructive value of sin 2 θ W 3/8 StringPheno05 p.6/31

10 Things to improve For models with SU(3) SU(2) U(1) gauge group, the Z 3 orbifold example is too rigid only fixed points and no fixed tori no normal grand unified picture (like SO(10)) no large string threshold corrections continuous Wilson lines too destructive value of sin 2 θ W 3/8 The only successful approach in the framework of the Z 3 orbifold might be SU(3) 3 trinification (Choi, Kim, 2003; Kim, 2004) StringPheno05 p.6/31

11 Some basic observations Gauge couplings meet at GeV in the framework of the Minimal Supersymmetric Standard Model (MSSM) StringPheno05 p.7/31

12 Some basic observations Gauge couplings meet at GeV in the framework of the Minimal Supersymmetric Standard Model (MSSM) See-saw mechanism for neutrino sector favours the interpretation of a family of quarks and leptons as a 16 dimensional spinor representation of SO(10) StringPheno05 p.7/31

13 Some basic observations Gauge couplings meet at GeV in the framework of the Minimal Supersymmetric Standard Model (MSSM) See-saw mechanism for neutrino sector favours the interpretation of a family of quarks and leptons as a 16 dimensional spinor representation of SO(10) Model building in field theoretic orbifold GUTs in 5 and 6 dimensions seems to lead to promising results StringPheno05 p.7/31

14 Some basic observations Gauge couplings meet at GeV in the framework of the Minimal Supersymmetric Standard Model (MSSM) See-saw mechanism for neutrino sector favours the interpretation of a family of quarks and leptons as a 16 dimensional spinor representation of SO(10) Model building in field theoretic orbifold GUTs in 5 and 6 dimensions seems to lead to promising results Can we incorporate this into a string theory description? StringPheno05 p.7/31

15 Five golden rules Family as spinor of SO(10) Incomplete multiplets N = 1 superymmetry in d = 4 Repetition of families from geometry Discrete symmetries of stringy origin StringPheno05 p.8/31

16 Five golden rules Family as spinor of SO(10) Incomplete multiplets N = 1 superymmetry in d = 4 Repetition of families from geometry Discrete symmetries of stringy origin Such a scheme should incorporate the successful structures of SO(10)-GUTs avoid (some of) the problems StringPheno05 p.8/31

17 Five golden rules Family as spinor of SO(10) Incomplete multiplets N = 1 superymmetry in d = 4 Repetition of families from geometry Discrete symmetries of stringy origin Such a scheme should incorporate the successful structures of SO(10)-GUTs avoid (some of) the problems We need more general constructions to identify remnants of SO(10) in string theory... StringPheno05 p.8/31

18 Z 2 Z 2 Orbifold Example θ 1 θ 2 θ 3 StringPheno05 p.9/31

19 Z 2 Z 2 Orbifold Example θ 1 θ 2 θ 3 3 twisted sectors (with 16 fixed tori in each) lead to a geometrical picture of... StringPheno05 p.9/31

20 Intersecting Branes StringPheno05 p.10/31

21 Three family SO(10) toy model A 16 θ 1 A A 1 A 3 A 4 A 6 θ 2 A 3 A 5 A 2 A 6 θ 3 16 A 1 A 5 Localization of families at various fixed tori StringPheno05 p.11/31

22 Zoom on first torus... e 2 θ 1 e 1 e 2 θ 2 e 2 e 1 θ 3 e 1 Interpretation as 6-dim. model with 3 families on branes StringPheno05 p.12/31

23 second torus... e 4 θ 1 e 4 e 3 e 4 θ 2 e 3 e 3 θ families on branes, one in (6d) bulk... StringPheno05 p.13/31

24 Three family SO(10) toy model A 16 θ 1 A A 1 A 3 A 4 A 6 θ 2 A 3 A 5 A 2 A 6 θ 3 16 A 1 A 5 Localization of families at various fixed tori StringPheno05 p.14/31

25 third torus θ 1 e 6 e 6 θ 2 e 6 e 5 e 5 θ 3 e family on brane, two in (6d) bulk. StringPheno05 p.15/31

26 Model building We can easily find models with gauge group SU(3) SU(2) U(1) 3 families of quarks and leptons doublet-triplet splitting (Kobyashi, Raby, Zhang, 2004) (Förste, HPN, Vaudrevange, Wingerter, 2004) (Buchmüller, Hamaguchi, Lebedev, Ratz, 2004) (Giedt, Kane, Langacker, Nelson, 2005) StringPheno05 p.16/31

27 Model building We can easily find models with gauge group SU(3) SU(2) U(1) 3 families of quarks and leptons doublet-triplet splitting (Kobyashi, Raby, Zhang, 2004) (Förste, HPN, Vaudrevange, Wingerter, 2004) (Buchmüller, Hamaguchi, Lebedev, Ratz, 2004) (Giedt, Kane, Langacker, Nelson, 2005) Related heterotic constructions: fermionic formulation Calabi Yau compactification (talk of Faraggi) (talks of Ovrut, Honecker) StringPheno05 p.16/31

28 Model building (II) Key properties of the models depend on geometry: family symmetries texture of Yukawa couplings number of families local gauge groups on branes electroweak symmetry breakdown StringPheno05 p.17/31

29 Model building (II) Key properties of the models depend on geometry: family symmetries texture of Yukawa couplings number of families local gauge groups on branes electroweak symmetry breakdown We need to exploit these geometric properties... StringPheno05 p.17/31

30 Gauge group geography SO(10) E 6 SO(10) E 6 SO(10) E 6 E 6 E 6 SO(10) SO(10) E 6 StringPheno05 p.18/31

31 Gauge group geography SU(5) SO(10) SO(10) SO(10) SU(5) SU(5) SU(5) SU(5) SU(6) SU(2) SU(6) SU(2) SU(6) SU(2) StringPheno05 p.19/31

32 Gauge group geography: Pati-Salam SU(8) SU(6) SU(2) E 6 SU(6) SU(2) SU(4) 2 SO(10) SU(6) SU(2) E 6 SU(6) SU(2) SU(8) StringPheno05 p.20/31

33 Gauge geography: Standard Model SU(4) 2 SU(3) 2 SU(6) SU(2) SU(3) 2 SU(4) SU(2) 2 SU(4) SU(2) 2 SO(10) SU(5) SU(5) SU(6) SU(2) StringPheno05 p.21/31

34 The Memory of SO(10) SO(10) is realized in the higher dimensional theory broken in d = 4 incomplete multiplets StringPheno05 p.22/31

35 The Memory of SO(10) SO(10) is realized in the higher dimensional theory broken in d = 4 incomplete multiplets There could still be remnants of SO(10) symmetry 16 of SO(10) at some branes correct hypercharge normalization R-parity family symmetries that are very useful for realistic model building... StringPheno05 p.22/31

36 Proton decay R-parity from SO(10) memory avoids dangerous dimension-4 operators No proton decay via dimension-5 operators because of doublet-triplet splitting Avoid SO(10) brane for first family: suppressed p-decay via dimension-6 operators Thus the proton could be practically stable! StringPheno05 p.23/31

37 Unification SO(10) memory provides a reasonable value of sin 2 θ W and a unified definition of hypercharge presence of fixed tori allows for large threshold corrections at the high scale to match string and unification scale Yukawa unification from SO(10) memory for third family (on an SO(10) brane) no Yukawa unification for first and second family required StringPheno05 p.24/31

38 Yukawa textures and family symmetries Yukawa couplings depend on location of Higgs and matter fields Exponential suppression if fields at distant branes neutrino masses need some bulk mixing (one might need anti-families) GUT relations could be partially present, depending on the nature of the brane (e.g. SO(10) brane) family symmetries arise if different fields live on the same brane StringPheno05 p.25/31

39 It s a long way to go Full classification seems to be too difficult (at the moment). Work in progress: StringPheno05 p.26/31

40 It s a long way to go Full classification seems to be too difficult (at the moment). Work in progress: SO(32) classification (with SO(10) spinors) (Choi, Groot Nibbelink, Trapletti, 2004) (Ramos-Sanchez et al., 2005) StringPheno05 p.26/31

41 It s a long way to go Full classification seems to be too difficult (at the moment). Work in progress: SO(32) classification (with SO(10) spinors) (Choi, Groot Nibbelink, Trapletti, 2004) (Ramos-Sanchez et al., 2005) (partial) classification of Z 2 Z 2 and Z 2 Z 3 (Wingerter et al., 2005) StringPheno05 p.26/31

42 It s a long way to go Full classification seems to be too difficult (at the moment). Work in progress: SO(32) classification (with SO(10) spinors) (Choi, Groot Nibbelink, Trapletti, 2004) (Ramos-Sanchez et al., 2005) (partial) classification of Z 2 Z 2 and Z 2 Z 3 (Wingerter et al., 2005) smooth breakdown of gauge group (Förste, HPN, Wingerter, 2005) StringPheno05 p.26/31

43 Smooth gauge symmetry breakdown......can be achieved via continuous Wilson lines. The aim is: StringPheno05 p.27/31

44 Smooth gauge symmetry breakdown......can be achieved via continuous Wilson lines. The aim is: rank reduction electroweak symmetry breakdown breakdown of Trinification or Pati-Salam group to the Standard Model gauge group StringPheno05 p.27/31

45 Smooth gauge symmetry breakdown......can be achieved via continuous Wilson lines. The aim is: rank reduction electroweak symmetry breakdown breakdown of Trinification or Pati-Salam group to the Standard Model gauge group Continuous Wilson lines require specific embeddings of twist in the gauge group are too destructive in the Z 3 case are more promising for Z 2 twists (Ibanez, HPN, Quevedo, 1987) StringPheno05 p.27/31

46 An example We consider a model that has E 6 gauge group in the bulk of a 6d orbifold. The breakdown pattern is E 6 SO(10) U(1) via a Z 2 twist StringPheno05 p.28/31

47 An example We consider a model that has E 6 gauge group in the bulk of a 6d orbifold. The breakdown pattern is E 6 SO(10) U(1) via a Z 2 twist SO(10) SU(4) SU(2) SU(2) via a discrete (quantized) Wilson line StringPheno05 p.28/31

48 An example We consider a model that has E 6 gauge group in the bulk of a 6d orbifold. The breakdown pattern is E 6 SO(10) U(1) via a Z 2 twist SO(10) SU(4) SU(2) SU(2) via a discrete (quantized) Wilson line SU(4) SU(2) SU(2) SU(3) SU(2) U(1) via a continuous Wilson line (Förste, HPN, Wingerter, 2005) StringPheno05 p.28/31

49 Pati-Salam breakdown e 6 SO(10) U(1) Pati-Salam U(1) SU(6) SU(2) W 6 SU(5) U(1) SU(3) SU(2) U(1) 2 SU(3) SU(2) U(1) 2 SU(3) 2 U(1) SO(10) U(1) Pati-Salam U(1) W 5 SU(6) SU(2) e 5 StringPheno05 p.29/31

50 Ultraviolet Completion Such d = 6 models should find their ultraviolet completion in a consistent 10d string theory orbifold. StringPheno05 p.30/31

51 Ultraviolet Completion Such d = 6 models should find their ultraviolet completion in a consistent 10d string theory orbifold. The above breakdown chain, for example, could describe the smooth breakdown of SU(4) SU(2) SU(2) SU(3) SU(2) U(1) in model A1 of (Kobyashi, Raby, Zhang, 2004) StringPheno05 p.30/31

52 Ultraviolet Completion Such d = 6 models should find their ultraviolet completion in a consistent 10d string theory orbifold. The above breakdown chain, for example, could describe the smooth breakdown of SU(4) SU(2) SU(2) SU(3) SU(2) U(1) in model A1 of (Kobyashi, Raby, Zhang, 2004) Ultimately the mechanism should be used for the description of the Higgs mechanism of electroweak symmetry breakdown SU(3) SU(2) U(1) Y SU(3) U(1) EM in the standard model StringPheno05 p.30/31

53 Conclusion Heterotic string compactifications might lead to models that incorporate all the successful ingredients of grand unified theories, while avoiding the problematic ones. spinor representations of SO(10) geometric origin of (three) families incomplete multiplets supersymmetric unification R-parity absence of proton decay gauge-yukawa unification (partial GUT relations) discrete family symmetries StringPheno05 p.31/31