1. Dark Energy 2007 Extra Dimensions and the Cosmological Constant Problem Cliff Burgess

2. Dark Energy 2007 Partners in Crime CC Problem: Y. Aghababaie, J. Cline, C. de Rham, H. Firouzjahi, D. Hoover, S. Parameswaran, F. Quevedo, G. Tasinato, A. Tolley, I. Zavala Phenomenology: G. Azuelos, P.-H. Beauchemin, J. Matias, F. Quevedo Cosmology: Albrecht, F. Ravndal, C. Skordis

3. Dark Energy 2007 The Plan The Cosmological Constant problem Why is it so hard? How extra dimensions might help Changing how the vacuum energy gravitates Making things concrete 6 dimensions and supersymmetry Prognosis Technical worries Observational tests

4. Dark Energy 2007 ‘Naturalness’ as an Opportunity Cosmology alone cannot distinguish amongst the various models of Dark Energy. The features required by cosmology are difficult to sensibly embed into a fundamental microscopic theory. Progress will come by combining both

5. Dark Energy 2007 The Cosmological Constant Problem Dark energy vs vacuum energy Why must the vacuum energy be large?

6. Dark Energy 2007 The Cosmological Constant Problem Dark energy vs vacuum energy Why must the vacuum energy be large? Concordance cosmology points to several types of cosmic ‘matter’:

7. Dark Energy 2007 The Cosmological Constant Problem Dark energy vs vacuum energy Why must the vacuum energy be large? w = p DE /  D   for a cosmological constant N. Wright, astro-ph/0701584

8. Dark Energy 2007 The Cosmological Constant Problem Hierarchy Problems Why Extra Dimensions? A cosmological constant is not distinguishable from a Lorentz invariant vacuum energy vs

9. Dark Energy 2007 The Cosmological Constant Problem Hierarchy Problems Why Extra Dimensions? A cosmological constant is not distinguishable* from a Lorentz invariant vacuum energy vs * in 4 dimensions…

10. Dark Energy 2007 The Cosmological Constant Problem Dark energy vs vacuum energy Why must the vacuum energy be large?

11. Dark Energy 2007 The Cosmological Constant Problem Dark energy vs vacuum energy Why must the vacuum energy be large? The observed dark energy density corresponds to a very small vacuum energy: implies

12. Dark Energy 2007 The Cosmological Constant Problem Dark energy vs vacuum energy Why must the vacuum energy be large? BUT: particles of mass m contribute  » m:

13. Dark Energy 2007 The Cosmological Constant Problem Dark energy vs vacuum energy Why must the vacuum energy be large? BUT: particles of mass m contribute  » m:

14. Dark Energy 2007 The Cosmological Constant Problem Dark energy vs vacuum energy Why must the vacuum energy be large? BUT: particles of mass m contribute  » m:

15. Dark Energy 2007 The Cosmological Constant Problem Dark energy vs vacuum energy Why must the vacuum energy be large? BUT: particles of mass m contribute  » m: Must cancel to 32 decimal places!!

16. Dark Energy 2007 The Cosmological Constant Problem Dark energy vs vacuum energy Why must the vacuum energy be large? BUT: particles of mass m contribute  » m:

17. Dark Energy 2007 The Cosmological Constant Problem Dark energy vs vacuum energy Why must the vacuum energy be large? BUT: particles of mass m contribute  » m: Must cancel to 40 decimal places!!

18. Dark Energy 2007 Technical Naturalness Given a small quantity  =  0 +  In the fundamental theory, why should  0 be small? Given that  0 is small, why does it stay small as one integrates out physics up to the scales for which  is measured?

19. Dark Energy 2007 Technical Naturalness Given a small quantity  =  0 +  In the fundamental theory, why should  0 be small? Given that  0 is small, why does it stay small as one integrates out physics up to the scales for which  is measured? This may have to wait until we know the fundamental theory.

20. Dark Energy 2007 Technical Naturalness Given a small quantity  =  0 +  In the fundamental theory, why should  0 be small? Given that  0 is small, why does it stay small as one integrates out physics up to the scales for which  is measured? This may have to wait until we know the fundamental theory. This is serious because it involves physics we think we understand…

21. Dark Energy 2007 The Cosmological Constant Problem Dark energy vs vacuum energy Why must the vacuum energy be large? Seek to change properties of low-energy particles (like the electron) so that their zero-point energy does not gravitate, even though quantum effects do gravitate in atoms! Why this? But not this?

22. Dark Energy 2007 Another Naturalness Problem Dark energy vs vacuum energy Why must the vacuum energy be large?  is a constant if it is vacuum energy

23. Dark Energy 2007 Another Naturalness Problem Dark energy vs vacuum energy Why must the vacuum energy be large? More complicated time-dependence is possible

24. Dark Energy 2007 Another Naturalness Problem Dark energy vs vacuum energy Why must the vacuum energy be large? BUT: contributions to m  are of order so are too large if M > 10 -2 eV When time dependence is due to scalar field motion, the scalar field mass must be very small:

25. Dark Energy 2007 The Plan The Cosmological Constant problem Why is it so hard? How extra dimensions might help Changing how the vacuum energy gravitates Making things concrete 6 dimensions and supersymmetry Prognosis Technical worries Observational tests

26. Dark Energy 2007 How Extra Dimensions Help 4D CC vs 4D vacuum energy Branes and scales

27. Dark Energy 2007 How Extra Dimensions Help 4D CC vs 4D vacuum energy Branes and scales New Tools motivated by string theory (or condensed matter): Particles can be localized on surfaces (branes, or defects) within the extra dimensions Gravity is not similarly localized

28. Dark Energy 2007 How Extra Dimensions Help 4D CC vs 4D vacuum energy Branes and scales In higher dimensions a 4D vacuum energy, if localized in the extra dimensions, can curve the extra dimensions instead of the observed four. Arkani-Hamad et al Kachru et al, Carroll & Guica Aghababaie, et al

29. Dark Energy 2007 How Extra Dimensions Help 4D CC vs 4D vacuum energy Branes and scales Most general 4D flat solutions to chiral 6D supergravity, without matter fields. 3 nonzero gives curvature singularities at branes Gibbons, Guven & Pope

30. Dark Energy 2007 How Extra Dimensions Help 4D CC vs 4D vacuum energy Branes and scales To be useful it must be that extra dimensions can be as large as the observed Dark Energy density: ~ c/r » 10 -2 eV or r » 1  -metre This is possible! provided all known particles except gravity are trapped on a brane, since tests of Newton’s law allow r < 50  -metre Adelberger et al Arkani Hamed, Dvali, Dimopoulos

31. Dark Energy 2007 How Extra Dimensions Help 4D CC vs 4D vacuum energy Branes and scales If there are extra dimensions as large as r » 1  -metre then there can only be two of them (although others could exist if they are much smaller), or else the observed strength of gravity would require the scale of extra-dimensional physics to be smaller than m w with n extra dimensions Arkani Hamed, Dvali, Dimopoulos

32. Dark Energy 2007 How Extra Dimensions Help 4D CC vs 4D vacuum energy Branes and scales These scales are natural using standard 4D arguments.

33. Dark Energy 2007 How Extra Dimensions Help 4D CC vs 4D vacuum energy Branes and scales Only gravity gets modified over the most dangerous distance scales! Must rethink how the vacuum gravitates in 6D for these scales. SM interactions do not change at all!

34. Dark Energy 2007 The Plan The Cosmological Constant problem Why is it so hard? How extra dimensions might help Changing how the vacuum energy gravitates Making things concrete 6 dimensions and supersymmetry Prognosis Technical worries Observational tests

35. Dark Energy 2007 The SLED Proposal Suppose physics is extra-dimensional above the 10 -2 eV scale. Suppose the physics of the bulk is supersymmetric. Aghababaie, CB, Parameswaran & Quevedo

36. Dark Energy 2007 The SLED Proposal Suppose physics is extra-dimensional above the 10 -2 eV scale. Suppose the physics of the bulk is supersymmetric. Bulk supersymmetry SUSY breaks at scale M g on the branes; Trickle-down of SUSY breaking to the bulk is:

37. Dark Energy 2007 The SLED Proposal 4D graviton Particle Spectrum: 4D scalar: e  r 2 ~ const SM on brane – no partners Many KK modes in bulk

38. Dark Energy 2007 The CC Problem in 6D The 6D CC Integrate out brane physics Integrate out bulk physics Classical contribution Quantum corrections

39. Dark Energy 2007 The CC Problem in 6D The 6D CC Integrate out brane physics Integrate out bulk physics Classical contribution Quantum corrections Several 6D SUGRAs are known, including chiral and non-chiral variants. None have a 6D CC.

40. Dark Energy 2007 The CC Problem in 6D The 6D CC Integrate out brane physics Integrate out bulk physics Classical contribution Quantum corrections Several 6D SUGRAs are known, including chiral and non-chiral variants. None have a 6D CC. Nishino & Sezgin

41. Dark Energy 2007 The CC Problem in 6D The 6D CC Integrate out brane physics Integrate out bulk physics Classical contribution Quantum corrections Generates large 4D vacuum energy This energy is localized in the extra dimensions (plus higher-derivatives)

42. Dark Energy 2007 The CC Problem in 6D The 6D CC Integrate out brane physics Integrate out bulk physics Classical contribution Quantum corrections Solve classical equations in presence of branes Plug back into action

43. Dark Energy 2007 The CC Problem in 6D The 6D CC Integrate out brane physics Integrate out bulk physics Classical contribution Quantum corrections Solve classical equations in presence of branes Plug back into action

44. Dark Energy 2007 The CC Problem in 6D The 6D CC Integrate out brane physics Integrate out bulk physics Classical contribution Quantum corrections Solve classical equations in presence of branes Plug back into action Tensions cancel between brane and bulk!! Chen, Luty & Ponton

45. Dark Energy 2007 The CC Problem in 6D The 6D CC Integrate out brane physics Integrate out bulk physics Classical contribution Quantum corrections Solve classical equations in presence of branes Plug back into action Smooth parts also cancel for supersymmetric theories!! Aghababaie et al.

46. Dark Energy 2007 The CC Problem in 6D The 6D CC Integrate out brane physics Integrate out bulk physics Classical contribution Quantum corrections Bulk is a supersymmetric theory with m sb ~ 10 -2 eV Quantum corrections can be right size in absence of m sb 2 M g 2 terms! Lifts flat direction.

47. Dark Energy 2007 The Plan The Cosmological Constant problem Why is it so hard? How extra dimensions might help Changing how the vacuum energy gravitates Making things concrete 6 dimensions and supersymmetry Prognosis Technical worries Observational tests

48. Dark Energy 2007 Prognosis Theoretical worries Observational tests

49. Dark Energy 2007 The Worries ‘Technical Naturalness’ Runaway Behaviour Stabilizing the Extra Dimensions Famous No-Go Arguments Problems with Cosmology Constraints on Light Scalars

50. Dark Energy 2007 The Worries ‘Technical Naturalness’ Runaway Behaviour Stabilizing the Extra Dimensions Famous No-Go Arguments Problems with Cosmology Constraints on Light Scalars

51. Dark Energy 2007 The Worries ‘Technical Naturalness’ Runaway Behaviour Stabilizing the Extra Dimensions Famous No-Go Arguments Problems with Cosmology Constraints on Light Scalars Classical part of the argument: What choices must be made to ensure 4D flatness? Quantum part of the argument: Are these choices stable against renormalization?

52. Dark Energy 2007 The Worries ‘Technical Naturalness’ Runaway Behaviour Stabilizing the Extra Dimensions Famous No-Go Arguments Problems with Cosmology Constraints on Light Scalars Classical part of the argument: What choices must be made to ensure 4D flatness? Now understand how 2 extra dimensions respond to presence of 2 branes having arbitrary couplings. Not all are flat in 4D, but all of those having only conical singularities are flat. (Conical singularities correspond to absence of dilaton couplings to branes) Tolley, CB, Hoover & Aghababaie Tolley, CB, de Rham & Hoover CB, Hoover & Tasinato

53. Dark Energy 2007 The Worries ‘Technical Naturalness’ Runaway Behaviour Stabilizing the Extra Dimensions Famous No-Go Arguments Problems with Cosmology Constraints on Light Scalars Quantum part of the argument: Are these choices stable against renormalization? So far so good, but not yet complete Brane loops cannot generate dilaton couplings if these are not initially present Bulk loops can generate such couplings, but are suppressed by 6D supersymmetry

54. Dark Energy 2007 The Worries ‘Technical Naturalness’ Runaway Behaviour Stabilizing the Extra Dimensions Famous No-Go Arguments Problems with Cosmology Constraints on Light Scalars

55. Dark Energy 2007 The Worries ‘Technical Naturalness’ Runaway Behaviour Stabilizing the Extra Dimensions Famous No-Go Arguments Problems with Cosmology Constraints on Light Scalars Most brane properties and initial conditions do not lead to anything like the universe we see around us. For many choices the extra dimensions implode or expand to infinite size. Albrecht, CB, Ravndal, Skordis Tolley, CB, Hoover & Aghababaie Tolley, CB, de Rham & Hoover

56. Dark Energy 2007 The Worries ‘Technical Naturalness’ Runaway Behaviour Stabilizing the Extra Dimensions Famous No-Go Arguments Problems with Cosmology Constraints on Light Scalars Most brane properties and initial conditions do not lead to anything like the universe we see around us. For many choices the extra dimensions implode or expand to infinite size. Initial condition problem: much like the Hot Big Bang, possibly understood by reference to earlier epochs of cosmology (eg: inflation) Albrecht, CB, Ravndal, Skordis Tolley, CB, Hoover & Aghababaie Tolley, CB, de Rham & Hoover

57. Dark Energy 2007 Prognosis Theoretical worries Observational tests

58. Dark Energy 2007 The Observational Tests Quintessence cosmology

59. Dark Energy 2007 The Observational Tests Quintessence cosmology Modifications to gravity

60. Dark Energy 2007 The Observational Tests Quintessence cosmology Modifications to gravity Collider physics

61. Dark Energy 2007 The Observational Tests Quintessence cosmology Modifications to gravity Collider physics SUSY broken at the TeV scale, but not the MSSM!

62. Dark Energy 2007 The Observational Tests Quintessence cosmology Modifications to gravity Collider physics Neutrino physics?

63. Dark Energy 2007 The Observational Tests Quintessence cosmology Modifications to gravity Collider physics Neutrino physics? And more!

64. Dark Energy 2007 Summary It is the interplay between cosmological phenomenology and microscopic constraints which will make it possible to solve the Dark Energy problem. Technical naturalness provides a crucial clue.

65. Dark Energy 2007 Summary It is the interplay between cosmological phenomenology and microscopic constraints which will make it possible to solve the Dark Energy problem. Technical naturalness provides a crucial clue. 6D brane-worlds allow progress on technical naturalness: Vacuum energy not equivalent to curved 4D Are ‘Flat’ choices stable against renormalization?

66. Dark Energy 2007 Summary It is the interplay between cosmological phenomenology and microscopic constraints which will make it possible to solve the Dark Energy problem. Technical naturalness provides a crucial clue. 6D brane-worlds allow progress on technical naturalness: Vacuum energy not equivalent to curved 4D Are ‘Flat’ choices stable against renormalization? Tuned initial conditions Much like for the Hot Big Bang Model.

67. Dark Energy 2007 Summary It is the interplay between cosmological phenomenology and microscopic constraints which will make it possible to solve the Dark Energy problem. Technical naturalness provides a crucial clue. 6D brane-worlds allow progress on technical naturalness: Vacuum energy not equivalent to curved 4D Are ‘Flat’ choices stable against renormalization? Tuned initial conditions Much like for the Hot Big Bang Model. Enormously predictive, with many observational consequences. Cosmology at Colliders! Tests of gravity…

68. Dark Energy 2007 Detailed Worries and Observations ‘Technical Naturalness’ Runaway Behaviour Stabilizing the Extra Dimensions Famous No-Go Arguments Problems with Cosmology Constraints on Light Scalars Quintessence cosmology Modifications to gravity Collider physics Neutrino physics?

69. Dark Energy 2007 Backup slides

70. Dark Energy 2007 The Worries ‘Technical Naturalness’ Runaway Behaviour Stabilizing the Extra Dimensions Famous No-Go Arguments Problems with Cosmology Constraints on Light Scalars

71. Dark Energy 2007 The Worries ‘Technical Naturalness’ Runaway Behaviour Stabilizing the Extra Dimensions Famous No-Go Arguments Problems with Cosmology Constraints on Light Scalars Classical flat direction corresponding to combination of radius and dilaton: e  r 2 = constant. Loops lift this flat direction, and in so doing give dynamics to  and r. Salam & Sezgin

72. Dark Energy 2007 The Worries ‘Technical Naturalness’ Runaway Behaviour Stabilizing the Extra Dimensions Famous No-Go Arguments Problems with Cosmology Constraints on Light Scalars Potential domination when: Canonical Variables: Kantowski & Milton Albrecht, CB, Ravndal, Skordis CB & Hoover Ghilencea, Hoover, CB & Quevedo

73. Dark Energy 2007 The Worries ‘Technical Naturalness’ Runaway Behaviour Stabilizing the Extra Dimensions Famous No-Go Arguments Problems with Cosmology Constraints on Light Scalars Potential domination when: Canonical Variables: Albrecht, CB, Ravndal, Skordis Hubble damping can allow potential domination for exponentially large r, even though r is not stabilized.

74. Dark Energy 2007 The Worries ‘Technical Naturalness’ Runaway Behaviour Stabilizing the Extra Dimensions Famous No-Go Arguments Problems with Cosmology Constraints on Light Scalars

75. Dark Energy 2007 The Worries ‘Technical Naturalness’ Runaway Behaviour Stabilizing the Extra Dimensions Famous No-Go Arguments Problems with Cosmology Constraints on Light Scalars Weinberg’s No-Go Theorem: Steven Weinberg has a general objection to self-tuning mechanisms for solving the cosmological constant problem that are based on scale invariance

76. Dark Energy 2007 The Worries ‘Technical Naturalness’ Runaway Behaviour Stabilizing the Extra Dimensions Famous No-Go Arguments Problems with Cosmology Constraints on Light Scalars Weinberg’s No-Go Theorem: Steven Weinberg has a general objection to self-tuning mechanisms for solving the cosmological constant problem that are based on scale invariance

77. Dark Energy 2007 The Worries ‘Technical Naturalness’ Runaway Behaviour Stabilizing the Extra Dimensions Famous No-Go Arguments Problems with Cosmology Constraints on Light Scalars Weinberg’s No-Go Theorem: Steven Weinberg has a general objection to self-tuning mechanisms for solving the cosmological constant problem that are based on scale invariance

78. Dark Energy 2007 The Worries ‘Technical Naturalness’ Runaway Behaviour Stabilizing the Extra Dimensions Famous No-Go Arguments Problems with Cosmology Constraints on Light Scalars Nima’s No-Go Argument: One can have a vacuum energy  4 with  greater than the cutoff, provided it is turned on adiabatically. So having extra dimensions with r ~ 1/  does not release one from having to find an intrinsically 4D mechanism.

79. Dark Energy 2007 The Worries ‘Technical Naturalness’ Runaway Behaviour Stabilizing the Extra Dimensions Famous No-Go Arguments Problems with Cosmology Constraints on Light Scalars Nima’s No-Go Argument: One can have a vacuum energy  4 with  greater than the cutoff, provided it is turned on adiabatically. So having extra dimensions with r ~ 1/  does not release one from having to find an intrinsically 4D mechanism. Scale invariance precludes obtaining \mu greater than the cutoff in an adiabatic way: implies

80. Dark Energy 2007 The Worries ‘Technical Naturalness’ Runaway Behaviour Stabilizing the Extra Dimensions Famous No-Go Arguments Problems with Cosmology Constraints on Light Scalars

81. Dark Energy 2007 The Worries ‘Technical Naturalness’ Runaway Behaviour Stabilizing the Extra Dimensions Famous No-Go Arguments Problems with Cosmology Constraints on Light Scalars Post BBN: Since r controls Newton’s constant, its motion between BBN and now will cause unacceptably large changes to G.

82. Dark Energy 2007 The Worries ‘Technical Naturalness’ Runaway Behaviour Stabilizing the Extra Dimensions Famous No-Go Arguments Problems with Cosmology Constraints on Light Scalars Post BBN: Since r controls Newton’s constant, its motion between BBN and now will cause unacceptably large changes to G. Even if the kinetic energy associated with r were to be as large as possible at BBN, Hubble damping keeps it from rolling dangerously far between then and now.

83. Dark Energy 2007 The Worries ‘Technical Naturalness’ Runaway Behaviour Stabilizing the Extra Dimensions Famous No-Go Arguments Problems with Cosmology Constraints on Light Scalars Post BBN: Since r controls Newton’s constant, its motion between BBN and now will cause unacceptably large changes to G. Even if the kinetic energy associated with r were to be as large as possible at BBN, Hubble damping keeps it from rolling dangerously far between then and now. log r vs log a

84. Dark Energy 2007 The Worries ‘Technical Naturalness’ Runaway Behaviour Stabilizing the Extra Dimensions Famous No-Go Arguments Problems with Cosmology Constraints on Light Scalars Pre BBN: There are strong bounds on KK modes in models with large extra dimensions from: * their later decays into photons; * their over-closing the Universe; * their light decay products being too abundant at BBN

85. Dark Energy 2007 The Worries ‘Technical Naturalness’ Runaway Behaviour Stabilizing the Extra Dimensions Famous No-Go Arguments Problems with Cosmology Constraints on Light Scalars Pre BBN: There are strong bounds on KK modes in models with large extra dimensions from: * their later decays into photons; * their over-closing the Universe; * their light decay products being too abundant at BBN Photon bounds can be evaded by having invisible channels; others are model dependent, but eventually must be addressed

86. Dark Energy 2007 The Worries ‘Technical Naturalness’ Runaway Behaviour Stabilizing the Extra Dimensions Famous No-Go Arguments Problems with Cosmology Constraints on Light Scalars

87. Dark Energy 2007 The Worries ‘Technical Naturalness’ Runaway Behaviour Stabilizing the Extra Dimensions Famous No-Go Arguments Problems with Cosmology Constraints on Light Scalars A light scalar with mass m ~ H has several generic difficulties: What protects such a small mass from large quantum corrections?

88. Dark Energy 2007 The Worries ‘Technical Naturalness’ Runaway Behaviour Stabilizing the Extra Dimensions Famous No-Go Arguments Problems with Cosmology Constraints on Light Scalars A light scalar with mass m ~ H has several generic difficulties: What protects such a small mass from large quantum corrections? Given a potential of the form V(r) = c 0 M 4 + c 1 M 2 /r 2 + c 2 /r 4 + … then c 0 = c 1 = 0 ensures both small mass and small dark energy.

89. Dark Energy 2007 The Worries ‘Technical Naturalness’ Runaway Behaviour Stabilizing the Extra Dimensions Famous No-Go Arguments Problems with Cosmology Constraints on Light Scalars A light scalar with mass m ~ H has several generic difficulties: Isn’t such a light scalar already ruled out by precision tests of GR in the solar system?

90. Dark Energy 2007 The Worries ‘Technical Naturalness’ Runaway Behaviour Stabilizing the Extra Dimensions Famous No-Go Arguments Problems with Cosmology Constraints on Light Scalars A light scalar with mass m ~ H has several generic difficulties: Isn’t such a light scalar already ruled out by precision tests of GR in the solar system? The same logarithmic corrections which enter the potential can also appear in its matter couplings, making them field dependent and so also time-dependent as  rolls. Can arrange these to be small here & now.

91. Dark Energy 2007 The Worries ‘Technical Naturalness’ Runaway Behaviour Stabilizing the Extra Dimensions Famous No-Go Arguments Problems with Cosmology Constraints on Light Scalars A light scalar with mass m ~ H has several generic difficulties: Isn’t such a light scalar already ruled out by precision tests of GR in the solar system? The same logarithmic corrections which enter the potential can also appear in its matter couplings, making them field dependent and so also time-dependent as  rolls. Can arrange these to be small here & now.  vs log a

92. Dark Energy 2007 The Worries ‘Technical Naturalness’ Runaway Behaviour Stabilizing the Extra Dimensions Famous No-Go Arguments Problems with Cosmology Constraints on Light Scalars A light scalar with mass m ~ H has several generic difficulties: Shouldn’t there be strong bounds due to energy losses from red giant stars and supernovae? (Really a bound on LEDs and not on scalars.)

93. Dark Energy 2007 The Worries ‘Technical Naturalness’ Runaway Behaviour Stabilizing the Extra Dimensions Famous No-Go Arguments Problems with Cosmology Constraints on Light Scalars A light scalar with mass m ~ H has several generic difficulties: Shouldn’t there be strong bounds due to energy losses from red giant stars and supernovae? (Really a bound on LEDs and not on scalars.) Yes, and this is how the scale M ~ 10 TeV for gravity in the extra dimensions is obtained.

94. Dark Energy 2007 Observational Consequences Quintessence cosmology Modifications to gravity Collider physics Neutrino physics Astrophysics

95. Dark Energy 2007 Observational Consequences Quintessence cosmology Modifications to gravity Collider physics Neutrino physics Astrophysics Quantum vacuum energy lifts flat direction. Specific types of scalar interactions are predicted. Includes the Albrecht- Skordis type of potential Preliminary studies indicate it is possible to have viable cosmology: Changing G; BBN;… Albrecht, CB, Ravndal & Skordis Kainulainen & Sunhede

96. Dark Energy 2007 Quantum vacuum energy lifts flat direction. Specific types of scalar interactions are predicted. Includes the Albrecht- Skordis type of potential Preliminary studies indicate it is possible to have viable cosmology: Changing G; BBN;… Observational Consequences Quintessence cosmology Modifications to gravity Collider physics Neutrino physics Astrophysics Albrecht, CB, Ravndal & Skordis Potential domination when: Canonical Variables:

97. Dark Energy 2007 Quantum vacuum energy lifts flat direction. Specific types of scalar interactions are predicted. Includes the Albrecht- Skordis type of potential Preliminary studies indicate it is possible to have viable cosmology: Changing G; BBN;… Observational Consequences Quintessence cosmology Modifications to gravity Collider physics Neutrino physics Astrophysics Albrecht, CB, Ravndal & Skordis log  vs log a Radiation Matter Total Scalar

98. Dark Energy 2007 Quantum vacuum energy lifts flat direction. Specific types of scalar interactions are predicted. Includes the Albrecht- Skordis type of potential Preliminary studies indicate it is possible to have viable cosmology: Changing G; BBN;… Observational Consequences Quintessence cosmology Modifications to gravity Collider physics Neutrino physics Astrophysics Albrecht, CB, Ravndal & Skordis Radiation Matter Total Scalar w Parameter:  and  w vs log a   ~ 0.7 w ~ – 0.9  m ~ 0.25

99. Dark Energy 2007 Quantum vacuum energy lifts flat direction. Specific types of scalar interactions are predicted. Includes the Albrecht- Skordis type of potential Preliminary studies indicate it is possible to have viable cosmology: Changing G; BBN;… Observational Consequences Quintessence cosmology Modifications to gravity Collider physics Neutrino physics Astrophysics Albrecht, CB, Ravndal & Skordis  vs log a

100. Dark Energy 2007 Quantum vacuum energy lifts flat direction. Specific types of scalar interactions are predicted. Includes the Albrecht- Skordis type of potential Preliminary studies indicate it is possible to have viable cosmology: Changing G; BBN;… Observational Consequences Quintessence cosmology Modifications to gravity Collider physics Neutrino physics Astrophysics Albrecht, CB, Ravndal & Skordis log r vs log a

101. Dark Energy 2007 Observational Consequences Quintessence cosmology Modifications to gravity Collider physics Neutrino physics Astrophysics At small distances: Changes Newton’s Law at range r/2  ~ 1  m. At large distances Scalar-tensor theory out to distances of order H 0.

102. Dark Energy 2007 Observational Consequences Quintessence cosmology Modifications to gravity Collider physics Neutrino physics Astrophysics At small distances: Changes Newton’s Law at range r/2  ~ 1  m. At large distances Scalar-tensor theory out to distances of order H 0.

103. Dark Energy 2007 Observational Consequences Quintessence cosmology Modifications to gravity Collider physics Neutrino physics Astrophysics Not the MSSM! No superpartners Bulk scale bounded by astrophysics M g ~ 10 TeV Many channels for losing energy to KK modes Scalars, fermions, vectors live in the bulk

104. Dark Energy 2007 Observational Consequences Quintessence cosmology Modifications to gravity Collider physics Neutrino physics Astrophysics Can there be observable signals if M g ~ 10 TeV? Must hit new states before E ~ M g. Eg: string and KK states have M KK < M s < M g Dimensionless couplings to bulk scalars are unsuppressed by M g

105. Dark Energy 2007 Observational Consequences Quintessence cosmology Modifications to gravity Collider physics Neutrino physics Astrophysics Not the MSSM! No superpartners Bulk scale bounded by astrophysics M g ~ 10 TeV Many channels for losing energy to KK modes Scalars, fermions, vectors live in the bulk Dimensionless coupling! O(0.1-0.001) from loops Azuelos, Beauchemin & CB

106. Dark Energy 2007 Observational Consequences Quintessence cosmology Modifications to gravity Collider physics Neutrino physics Astrophysics Not the MSSM! No superpartners Bulk scale bounded by astrophysics M g ~ 10 TeV Many channels for losing energy to KK modes Scalars, fermions, vectors live in the bulk Dimensionless coupling! O(0.1-0.001) from loops Azuelos, Beauchemin & CB Use H decay into , so search for two hard photons plus missing E T.

107. Dark Energy 2007 Observational Consequences Quintessence cosmology Modifications to gravity Collider physics Neutrino physics Astrophysics Not the MSSM! No superpartners Bulk scale bounded by astrophysics M g ~ 10 TeV Many channels for losing energy to KK modes Scalars, fermions, vectors live in the bulk Azuelos, Beauchemin & CB Standard Model backgrounds

108. Dark Energy 2007 Observational Consequences Quintessence cosmology Modifications to gravity Collider physics Neutrino physics Astrophysics Not the MSSM! No superpartners Bulk scale bounded by astrophysics M g ~ 10 TeV Many channels for losing energy to KK modes Scalars, fermions, vectors live in the bulk Azuelos, Beauchemin & CB

109. Dark Energy 2007 Observational Consequences Quintessence cosmology Modifications to gravity Collider physics Neutrino physics Astrophysics Not the MSSM! No superpartners Bulk scale bounded by astrophysics M g ~ 10 TeV Many channels for losing energy to KK modes Scalars, fermions, vectors live in the bulk Azuelos, Beauchemin & CB Significance of signal vs cut on missing E T

110. Dark Energy 2007 Observational Consequences Quintessence cosmology Modifications to gravity Collider physics Neutrino physics Astrophysics Not the MSSM! No superpartners Bulk scale bounded by astrophysics M g ~ 10 TeV Many channels for losing energy to KK modes Scalars, fermions, vectors live in the bulk Azuelos, Beauchemin & CB Possibility of missing-E T cut improves the reach of the search for Higgs through its  channel

111. Dark Energy 2007 Observational Consequences Quintessence cosmology Modifications to gravity Collider physics Neutrino physics Astrophysics SLED predicts there are 6D massless fermions in the bulk, as well as their properties Massless, chiral, etc. Masses and mixings can be chosen to agree with oscillation data. Most difficult: bounds on resonant SN oscillilations. Matias, CB

112. Dark Energy 2007 Observational Consequences Quintessence cosmology Modifications to gravity Collider physics Neutrino physics Astrophysics SLED predicts there are 6D massless fermions in the bulk, as well as their properties Massless, chiral, etc. Masses and mixings can be naturally achieved which agree with data! Sterile bounds; oscillation experiments; 6D supergravities have many bulk fermions: Gravity: (g mn,  m, B mn, ,  ) Gauge: (A m, ) Hyper: ( ,  ) Bulk couplings dictated by supersymmetry In particular: 6D fermion masses must vanish Back-reaction removes KK zero modes eg: boundary condition due to conical defect at brane position Matias, CB

113. Dark Energy 2007 Observational Consequences Quintessence cosmology Modifications to gravity Collider physics Neutrino physics Astrophysics SLED predicts there are 6D massless fermions in the bulk, as well as their properties Massless, chiral, etc. Masses and mixings can be naturally achieved which agree with data! Sterile bounds; oscillation experiments; Dimensionful coupling ~ 1/M g Matias, CB

114. Dark Energy 2007 Observational Consequences Quintessence cosmology Modifications to gravity Collider physics Neutrino physics Astrophysics SLED predicts there are 6D massless fermions in the bulk, as well as their properties Massless, chiral, etc. Masses and mixings can be naturally achieved which agree with data! Sterile bounds; oscillation experiments; Dimensionful coupling ~ 1/M g SUSY keeps N massless in bulk; Natural mixing with Goldstino on branes; Chirality in extra dimensions provides natural L; Matias, CB

115. Dark Energy 2007 Observational Consequences Quintessence cosmology Modifications to gravity Collider physics Neutrino physics Astrophysics SLED predicts there are 6D massless fermions in the bulk, as well as their properties Massless, chiral, etc. Masses and mixings can be naturally achieved which agree with data! Sterile bounds; oscillation experiments; Dimensionful coupling! ~ 1/M g Matias, CB

116. Dark Energy 2007 Observational Consequences Quintessence cosmology Modifications to gravity Collider physics Neutrino physics Astrophysics SLED predicts there are 6D massless fermions in the bulk, as well as their properties Massless, chiral, etc. Masses and mixings can be naturally achieved which agree with data! Sterile bounds; oscillation experiments; t Dimensionful coupling! ~ 1/M g Constrained by bounds on sterile neutrino emission Require observed masses and large mixing. Matias, CB

117. Dark Energy 2007 Observational Consequences Quintessence cosmology Modifications to gravity Collider physics Neutrino physics Astrophysics SLED predicts there are 6D massless fermions in the bulk, as well as their properties Massless, chiral, etc. Masses and mixings can be naturally achieved which agree with data! Sterile bounds; oscillation experiments; t Dimensionful coupling! ~ 1/M g Constrained by bounds on sterile neutrino emission Require observed masses and large mixing. Bounds on sterile neutrinos easiest to satisfy if g = v < 10 -4. Degenerate perturbation theory implies massless states strongly mix even if g is small. This is a problem if there are massless KK modes. This is good for 3 observed flavours. Brane back-reaction can remove the KK zero mode for fermions. Matias, CB

118. Dark Energy 2007 Observational Consequences Quintessence cosmology Modifications to gravity Collider physics Neutrino physics Astrophysics SLED predicts there are 6D massless fermions in the bulk, as well as their properties Massless, chiral, etc. Masses and mixings can be naturally achieved which agree with data! Sterile bounds; oscillation experiments; Imagine lepton- breaking terms are suppressed. Possibly generated by loops in running to low energies from M g. Acquire desired masses and mixings with a mild hierarchy for g’/g and  ’/  Build in approximate L e – L  – L , and Z 2 symmetries. S ~ M g r Matias, CB

119. Dark Energy 2007 Observational Consequences Quintessence cosmology Modifications to gravity Collider physics Neutrino physics Astrophysics SLED predicts there are 6D massless fermions in the bulk, as well as their properties Massless, chiral, etc. Masses and mixings can be naturally achieved which agree with data! Sterile bounds; oscillation experiments; 1 massless state 2 next- lightest states have strong overlap with brane. Inverted hierarchy. Massive KK states mix weakly. Matias, CB

120. Dark Energy 2007 Observational Consequences Quintessence cosmology Modifications to gravity Collider physics Neutrino physics Astrophysics SLED predicts there are 6D massless fermions in the bulk, as well as their properties Massless, chiral, etc. Masses and mixings can be naturally achieved which agree with data! Sterile bounds; oscillation experiments; 1 massless state 2 next- lightest states have strong overlap with brane. Inverted hierarchy. Massive KK states mix weakly. Worrisome: once we choose g ~ 10 -4, good masses for the light states require:  S = k ~ 1/g Must get this from a real compactification. Matias, CB

121. Dark Energy 2007 Observational Consequences Quintessence cosmology Modifications to gravity Collider physics Neutrino physics Astrophysics SLED predicts there are 6D massless fermions in the bulk, as well as their properties Massless, chiral, etc. Masses and mixings can be naturally achieved which agree with data! Sterile bounds; oscillation experiments; Lightest 3 states can have acceptable 3- flavour mixings. Active sterile mixings can satisfy incoherent bounds provided g ~ 10 -4 or less (  i ~ g/c i ). 2 Matias, CB

122. Dark Energy 2007 Observational Consequences Quintessence cosmology Modifications to gravity Collider physics Neutrino physics Astrophysics Energy loss into extra dimensions is close to existing bounds Supernova, red-giant stars,… Scalar-tensor form for gravity may have astrophysical implications. Binary pulsars;…