Dark Matter and Dark Energy

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

2. MAP WMAP Precision Cosmology

3. LCDM • 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. MatterWM~ 0.3 dynamics lensing x-ray gas cmb power spectrum simulations Wi  rirC

7. BaryonsWB h2~ 0.02 Ly-a QSO 1937-1009 Tytler Burles et al.

8. Dark matter? • Modified Newtonian dynamics

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

10. Cold Thermal Relics actual equilibrium freeze out Relative abundance T/MX WX sA-1 (independent of mass)

11. Cold Thermal Relics WX sA-1

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

13. Seeking SUSY * Assumed here to be • Hierarchy problem: • fundamental scale is Planck mass* • observe particles with mass much less than Planck mass • gauge bosons protected by gauge symmetry • fermions protected by chiral symmetry • 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?

14. Cold Thermal Relics (neutralino) • Direct detection (sS) • More than a dozen experiments • Indirect detection (sA) • Annihilation in sun, Earth, galaxy. . . neutrinos, positrons, antiprotons, g rays, . . . • Accelerator production (sP) • Tevatron, LHC, ILC

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

16. Muon Neutrinos From the Sun

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

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

19. WIMPZILLAS example of non-thermal dark matter SIZE DOES MATTER visit wimpzillas.com

20. The Vacuum of W+ W- e- quark e+ anti-quark anti particle particle Quantum Uncertainty

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

22. density perturbations from inflation gravitational waves from inflation Expanding universe particle creation 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) It’s not a bug, it’s a feature! • new application: dark matter • (Chung, Kolb, & Riotto; Kuzmin & Tkachev) • require (super)massive particle “X” • stable (or at least long lived) • initial inflationary era followed byradiation/matter

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. Wimpzilla Characteristics: • supermassive: 109 - 1019 GeV (~ 1012 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)?

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 1013 GeV = 1022 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. WIMPZILLA Decay Busca, Hooper, Kolb MX= 6  10 21 eV Auger data extra- galactic g p UHE cosmic rays mostly photons; characteristic spectrum; UHE neutrinos; lower-energy crud; clumping anisotropies

28. Dark Matter WIMP or WIMPZILLA SIZE DOES MATTER

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 Einstein-de Sitter: flat, matter-dominated model (maximum theoretical bliss) Riess et al. (2004) cosmological constant, some changing non-zero vacuum energy, or some unknown systematic effect(s) The case for L: 1) Hubble diagram dL(z) 2) subtraction

31. Subtraction dynamics lensing x-ray gas cmb power spectrum WirirC rC  3H028pG simulations WTOTAL=1 (CMB), WM=0.3,1 - 0.3 = 0.7

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

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

34. Practical Tools for Dark Energy scalar fields anthropic principle

35. How Far Will They Go? How Far Will They Go?

36. Do we “know” there is dark energy? • Assume model cosmology: • Friedmann model: H2+k/a2 = 8 G /3 • Energy (and pressure) content: =M+R++ • Input or integrate over cosmological parameters: H0, etc. • Calculate observables dL(z), dA(z),  • Compare to observations • Model cosmology fits with L, but not without L • All evidence for dark energy is indirect: observed H(z) is not • described by H(z) calculated from the Einstein-de Sitter model

37. Evolution of H(z): a Key Quantity Robertson–Walker metric Many observables based on the coordinate distance r(z) • Luminosity distance Flux = (Luminosity / 4dL2) • Angular diameter distance Angular diameter = (Physical size / dA) • Comoving number counts N/V -1(z) • Age of the universe

38. Take Sides! • Can’t hide from the data – LCDM too good to ignore • SNIa • Subtraction: 1.0 - 0.3 = 0.7 • Age • Large-scale structure • … • Dark energy (modify right-hand side of Einstein equations) • “Just” L, 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 3H2  8G rMATTER

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)-1 • Einstein & Hilbert got it wrong • Backreaction of inhomogeneities Binetruy, Deffayet, Langlois Freese & Lewis Deffayet, Dvali & Gabadadze Five-dimensional at cosmic distances Gregory, Rubakov & Sibiryakov; Dvali, Gabadadze & Porrati Gravitons metastable - leak into bulk Csaki, Erlich, Hollowood & Terning Kogan, Mouslopoulos, Papazoglou, Ross & Santiago Carroll, Duvvuri, Turner, Trodden Räsänen;Kolb, Matarrese, Notari & Riotto; Notari; Kolb, Matarrese & Riotto

40. Acceleration from inhomogeneities • Most conservative approach — nothing new • no new fields (like 10-33 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 model Inhomogeneous model We (Kolb, Matarrese, Riotto + others) think not!

42. Acceleration from inhomogeneities Cosmology  scalar field theory analogue cosmology scalar-field theory zero-mode ah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 physical effect • 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

43. Different approaches Standard approach Our approach • Model an inhomogeneous • Universe as a homogeneous • Universe model with r=hi • Zero mode [a(t) /V1/3] is the • zeromode of a homogeneous • model with r= hi • Inhomogeneities only have a • local effect on observables • Cannot account for observed • acceleration • Expansion rate of an • inhomogeneous Universe  • expansion rate of homogeneous • Universe with r=hi • Inhomogeneities modify • zero-mode [effective scale • factor is aD  VD1/3 ] • Effective scale factor has a • (global) effect on observables • Potentially can account for • acceleration without • dark energy or modified GR

44. Inhomogeneities–Cosmology • Our Universe is inhomogeneous • Can define an average density r • The expansion rate of an inhomogeneous universe of average • density r is NOT! the same as the expansion rate of a • homogeneous universe of average density r! • 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–example . • (aa is not even the expansion rate) • Could d G00 play the role of dark energy (energy conditions)? • How large could it be? . • (aa)2is not8p G 3 Kolb, Matarrese, Notari & Riotto • PerturbedFriedmann–Lemaître–Robertson–Walker model:

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 Nambu & Tanimoto (gr-qc/0507057) [also Moffet] • dust model: r = r0 a3 • spatial curvature: • k =-1 for 0 r  r0 • k= +1 forr0 r  L • “Friedmann” equation • Not to be regarded as • a realistic model L r0 open closed

48. Observational consequences • Spherical model • Inner underdense 200 Mpc region • Compensating high-density shell • Then Einstein–de Sitter • Calculate dL(z):fit SNIa data with L = 0! • Calculate Cl : first peak about right! Tomita, 2001 Alnes, Amarzguioui, Grøn astro-ph/0512006

49. Observational consequences • It’s the goal! • Eventually predict dL(z), dA(z),  w, wa , w0, • 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