1. Space Telescope Science Institute, Feb. 2006 Rocky Kolb, Fermilab & Chicago Space Telescope Science Institute, Feb. 2006 Rocky Kolb, Fermilab & Chicago (Two wildly unpopular ideas about)

2. Precision Cosmology MAP WMAP

3.  CDM Inflation-produced perturbations Baryo/leptogenesis

4. Mission accomplished … … or premature jubilation?

5. What Is Dark Matter? “In questions like this, truth is only to be had by laying together many variations of error.” -- Virginia Woolf A Room of Ones Own

6. dynamicsx-ray gaslensing Matter  M  power spectrum cmb simulations  i  i   C

7. QSO 1937-1009 Ly  Burles et al. Baryons  B h   Tytler

8. matter? matter? Modified Newtonian dynamics

9. Black holes Size challenged stars Planets Microlensing Dwarf stars brown red white Modified Newtonian dynamics Undiscovered new particle (WIMP) matter? matter?

10. Cold Thermal Relics freeze out actual equilibrium T/M X Relative abundance  X   A  (independent of mass)

11.  X   A  Cold Thermal Relics

12. freeze out actual equilibrium T/M X Relative abundance s-wave or p-wave? annihilation or scattering cross section? co-annihilation? sub-leading dependence on mass, g *, etc. targets are nuclei (spin-dependence) Not quite so clean: Cold Thermal Relics

13. Seeking SUSY Hierarchy problem: fundamental scale is Planck mass* observe particles with mass much less than Planck mass o gauge bosons protected by gauge symmetry o fermions protected by chiral symmetry o scalars (e.g., Higgs) defenseless! introduce supersymmetry to protect scalars Supersymmetric Standard Model: 105 parameters Constrained Minimal Supersymmetric Standard Model: 3 parameters: Lightest supersymmetric particle (LSP) stable: neutralino? * Assumed here to be

14. Direct detection (  S ) More than a dozen experiments Indirect detection (  A ) Annihilation in sun, Earth, galaxy... neutrinos, positrons, antiprotons,  rays,... Accelerator production (  P ) Tevatron, LHC, ILC Cold Thermal Relics (neutralino)

15. SUSY shaded areas Probing significant regions of MSSM model space Light-mass region largely ruled out Another factor of 100 may be needed Combined Soudan limits DAMA NaI/1-4 3  region ZEPLIN I EDELWEISS Cryogenic Dark Matter Search Cold Thermal Relics

16. Muon Neutrinos From the Sun

17. “For every complex natural phenomenon there is a simple, elegant, compelling, wrong explanation.” - Tommy Gold The nature of dark matter is a complex natural phenomenon. The neutralino is a simple, elegant, compelling explanation.

18. Dark Matter? neutrinos (hot dark matter) sterile neutrinos, gravitinos (warm dark matter) axions, axion clusters LKP (lightest Kaluza-Klein particle) supermassive wimpzillas solitons (Q-balls; B-balls; Odd-balls, Screw-balls….) LSP (neutralino, axino, …) (cold dark matter) axions axion clusters Mass range Noninteracting: wimpzillas Strongly interacting: B balls Interaction strength range

19. SIZEDOESMATTERSIZEDOESMATTER visit wimpzillas.com example of non-thermal dark matterWIMPZILLASWIMPZILLAS

20. TheVacuumTheVacuum ofof Quantum Uncertainty quark anti particle particle e+e+ e-e- W+W+ W-W- anti-quark

21. Disturbing the Vacuum Strong gravitational field particle production (Hawking radiation) Black Hole

22. new application: dark matter (Chung, Kolb, & Riotto; Kuzmin & Tkachev) require (super)massive particle “X” stable (or at least long lived) initial inflationary era followed by radiation/matter Arnowit, Birrell, Bunch, Davies, Deser, Ford, Fulling, Grib, Hu, Kofman, Lukash, Mostepanenko, Page, Parker, Starobinski, Unruh, Vilenkin, Wald, Zel’dovich,… first application: (Guth & Pi; Starobinski; Bardeen, Steinhardt, & Turner; Hawking; Rubakov; Fabbi & Pollack; Allen) Expanding universe particle creation Expanding universe particle creation density perturbations from inflation gravitational waves from inflation It’s not a bug, it’s a feature!

23. Inflaton mass (in principle measurable from gravitational wave background, guess ) may signal a new mass scale in nature. Other particles may exist with mass comparable to the inflaton mass. Conserved quantum numbers may render the particle stable. Superheavy Particles

24. supermassive:     GeV (~   GeV ?) abundance may depend only on mass abundance may be independent of interactions –sterile? –electrically charged? –strong interactions? –weak interactions? unstable (lifetime > age of the universe)? Wimpzilla Characteristics:

25. WIMPZILLA Footprints: Isocurvature modes:CMB, Large-scale structure Decay: Ultra High Energy Cosmic Rays Annihilate: Galactic Center, Sun Direct Detection: Bulk, Underground Searches

26. WIMPZILLA Decay X UHE cosmic rays   GeV =   eV Kuzmin & Rubakov; Birkel & Sarkar; Ellis, Gelmini, Lopez, Nanopoulos & Sarkar; Berezinsky, Kachelriess, & Vilenkin; Benakli, Ellis, & Nanopoulos; Berezinsky, Blasi, & Vilenkin; Blasi; Berezinsky & Mikhaliov; Dubovsky & Tinyakov; Medina-Tanco & Watson; Blasi & Seth; Ziaeepour; Crooks, Dunn, & Frampton

27. UHE cosmic rays mostly photons; characteristic spectrum; UHE neutrinos; lower-energy crud; clumping anisotropies WIMPZILLA Decay Busca, Hooper, Kolb M X    eV  p extra- galactic Auger data

28. WIMPZILLAor Dark Matter WIMP SIZEDOESMATTERSIZEDOESMATTER

29. What is Dark Energy? “In questions like this, truth is only to be had by laying together many variations of error.” -- Virginia Woolf A Room of Ones Own

30. High-z SNe are fainter than expected in the Einstein-deSitter model Riess et al. (2004) cosmological constant, some changing non-zero vacuum energy, or some unknown systematic effect(s) Einstein-de Sitter: flat, matter-dominated model (maximum theoretical bliss) The case for  : 1) Hubble diagram d L (z) 2) subtraction

31. dynamicsx-ray gaslensing  i   i   C  C  3H 0 2  8  G power spectrum cmb simulations  TOTAL    (CMB),  M    SubtractionSubtraction

32. High-z SNe are fainter than expected in the Einstein-deSitter model Riess et al. (2004) cosmological constant, some changing non-zero vacuum energy, or some unknown systematic effect(s) Einstein-de Sitter: flat, matter-dominated model (maximum theoretical bliss) The case for  : 1) Hubble diagram d L (z) 2) subtraction 3) age of the universe 4) structure formation

33. Illogical magnitude (what’s it related to?): Cosmo-illogical constant? Illogical timing (why now?): BBNEWKGUTREC

34. anthropic principle scalar fields Practical Tools for Dark Energy

35. How Far Will They Go?

36. Do we “know” there is dark energy? Assume model cosmology: – Friedmann model: H 2  k/a 2 =  G  /  – Energy (and pressure) content:    M   R    +  – Input or integrate over cosmological parameters: H , etc. Calculate observables d L (z), d A (z),  Compare to observations Model cosmology fits with  , but not without   All evidence for dark energy is indirect: observed H(z) is not described by H(z) calculated from the Einstein-de Sitter model

37. Age of the universe Evolution of H(z) : a Key Quantity Many observables based on the coordinate distance r(z) Luminosity distance Flux = (Luminosity /  d L  ) Angular diameter distance Angular diameter  (Physical size / d A ) Comoving number counts N / V  (z) Robertson–Walker metric

38. Take Sides! Can’t hide from the data –  CDM too good to ignore – SNIa – Subtraction:  – Age – Large - scale structure – … Dark energy (modify right-hand side of Einstein equations) – “Just” , a cosmological constant – If not constant, what drives dynamics (scalar field) Gravity (modify left-hand side of Einstein equations) – Beyond Einstein (non - GR: branes, etc.) – (Just) Einstein (GR: Back reaction of inhomogeneities) H(z) not given by Einstein–de Sitter  H    G  MATTER

39. Modifying the left-hand side Braneworld modifies Friedmann equation Phenomenological approach Gravitational force law modified at large distance Tired gravitons Gravity repulsive at distance R  Gpc n=1 KK graviton mode very light, m  ( Gpc )  Einstein & Hilbert got it wrong Backreaction of inhomogeneities Freese & Lewis Five-dimensional at cosmic distances Deffayet, Dvali & Gabadadze Gravitons metastable - leak into bulk Gregory, Rubakov & Sibiryakov; Dvali, Gabadadze & Porrati Kogan, Mouslopoulos, Papazoglou, Ross & Santiago Csaki, Erlich, Hollowood & Terning Räsänen; Kolb, Matarrese, Notari & Riotto; Notari; Kolb, Matarrese & Riotto Binetruy, Deffayet, Langlois Carroll, Duvvuri, Turner, Trodden

40. Acceleration from inhomogeneities Most conservative approach — nothing new – no new fields (like   eV mass scalars) – no extra long-range forces – no modification of general relativity – no modification of Newtonian gravity at large distances – no Lorentz violation – no extra dimensions, bulks, branes, etc. – no faith-based (anthropic) reasoning Magnitude?: calculable from observables related to  Why now?: acceleration triggered by era of non-linear structure

41. Acceleration From Inhomogeneities Homogeneous modelInhomogeneous model We (Kolb, Matarrese, Riotto + others) think not!

42. Acceleration from inhomogeneities View scale factor as zero-momentum mode of gravitational field In homogeneous/isotropic model it is the only degree of freedom Inhomogeneities: non-zero modes of gravitational field Non-zero modes interact with and modify zero-momentum mode cosmology scalar-field theory zero-mode a h   i (vev of a scalar field) non-zero modes inhomogeneities thermal/finite-density bkgd. modify a ( t ) modify h  (t) i e.g., acceleration e.g., phase transitions Cosmology  scalar field theory analogue physical effect

43. Different approaches Expansion rate of an inhomogeneous Universe  expansion rate of homogeneous Universe with   h  i Inhomogeneities modify zero-mode [effective scale factor is a D  V D  ] Effective scale factor has a (global) effect on observables Potentially can account for acceleration without dark energy or modified GR Model an inhomogeneous Universe as a homogeneous Universe model with   h  i Zero mode [ a(t ) / V  ] is the zero mode of a homogeneous model with   h  i Inhomogeneities only have a local effect on observables Cannot account for observed acceleration Standard approach Our approach

44. Inhomogeneities–CosmologyInhomogeneities–Cosmology Our Universe is inhomogeneous Can define an average density   The expansion rate of an inhomogeneous universe of average density   is NOT! the same as the expansion rate of a homogeneous universe of average density   ! Difference is a new term that enters an effective Friedmann equation — the new term need not satisfy energy conditions! We deduce dark energy because we are comparing to the wrong model universe (i.e., a homogeneous/isotropic model)

45. Inhomogeneities–exampleInhomogeneities–example ( a  a )  is not  G     Perturbed Friedmann–Lemaître–Robertson–Walker model: Kolb, Matarrese, Notari & Riotto ( a  a is not even the expansion rate) Could   G   play the role of dark energy (energy conditions)? How large could it be? 

46. Many issues: non-perturbative nature shell crossing comparison to observed LSS gauge/frame choices physical meaning of coarse graining Program: can inhomogeneities change effective zero mode? how does (does it?) affect observables? can one design an inhomogeneous universe that accelerates? could it lead to an apparent dark energy? can it be reached via evolution from usual initial conditions? does it at all resemble our universe? large perturbative terms resum to something harmless?

47. Tolman–Bondi–Lemaître open closed L r0r0 dust model:    a  spatial curvature: k   for   r  r   k  for  r    r  L “Friedmann” equation Not to be regarded as a realistic model Nambu & Tanimoto (gr-qc/0507057) [also Moffet]

48. Observational consequences Tomita, 2001 Spherical model – Inner underdense 200 Mpc region – Compensating high-density shell – Then Einstein–de Sitter Calculate d L (z): fit SN I a data with  ! Calculate C l : first peak about right! Alnes, Amarzguioui, Grøn astro-ph/0512006

49. Observational consequences It’s the goal! Eventually predict d L (z), d A (z),   w, w a, w 0,  Growth of structure in FLRW: Growth of structure in this scenario? Shear? H changes  any additional terms on r.h.s?

50. Acceleration in our local Hubble patch if the mean rarefaction factor (w.r.t. the underlying FRW model) grows fast enough to overshoot the FRW background evolution. Kolb, Matarrese, Riotto

51. DON’T KILL ROCKY Acceleration without dark energy!!!!!

52. The nature of dark energy is a complex natural phenomenon. There are no simple, elegant, compelling explanations.

53. Space Telescope Science Institute, Feb. 2006 Rocky Kolb, Fermilab & Chicago Space Telescope Science Institute, Feb. 2006 Rocky Kolb, Fermilab & Chicago (Two wildly unpopular ideas about)

54. Acceleration from inhomogeneities We assume that observables ( d A, d L, z, etc.) are modified if the effective scale factor is modified. We can only show this for unrealistic models. We must also assume that there will be no (or little) anisotropy (shear).

55. Acceleration from inhomogeneities We do not use super-Hubble modes for acceleration. We do not depend on large gravitational potentials such as black holes and neutron stars. We calculate claim the back reaction in a reference frame comoving with the matter—other frames give spurious results. We demonstrate large corrections in the gradient expansion, but the gradient expansion technique can not be used for the final answer—so we have indications (not proof) of a large effect. The basic idea is that small-scale inhomogeneities “renormalize” the large-scale properties.

56. Inhomogeneities–smoothing Matter smoothing is straightforward (particles  fluid) Space-time metric smoothing not straightforward! Consider Einstein equations on a scale where the universe is inhomogeneous and anisotropic – Smooth on some larger scale – Smoothing & evolution (the field equations) do not commute – Einstein tensor computed from smoothed metric – is not the same as the Einstein tensor computed – from the smoothed stress-energy tensor – Difference is a new term that enters an effective Friedmann – equation, new term need not satisfy energy conditions! – We deduce dark energy because we are comparing to the – wrong model universe (i.e., a homo/iso model) Ellis, Barausse, Buchert, Ellis, Kolb, Matarrese, Notari, Räsänen, Riotto, Schwarz