Non Thermal Relics and Alternative Theories of Gravity

Transcription

1 Non Thermal Relics and Alternative Theories of Gravity Non thermal Axion Primordial black holes WIMPZILLAs MOND Additional dimensions Motivations Mirror universes, Energy stored in the bulk Tests for additional dimensions Can this account for the Dark Energy? Dark energy models Phys Nonthermal 1

2 What can Particle Physics Offer? non baryonic dark matter exotic particles Mirror branes thermal non-thermal Light Neutrinos WIMPs Axions Wimpzillas Phys Nonthermal 2

3 Axions Invented to save QCD from strong CP violation Current experimental limits are such that if they exist, they have to be cosmologically significant Window: ev Produced out of equilibrium Theoretical discussion if Peccei Quinnn symmetry breaking occurs after inflation => global strings which radiate axions. Technically difficult to compute (Shellard Sikivie) Loss mass region may be not favored Method of detection Phys Nonthermal 3 Tunable cavity Most suitable for low mass region

4 Axion limits ev Lab Expts Red Giants (DFSZ) Red Giants (Hadronic) SN 1987A Optical photons from clusters Ω>1 uncertainty in case of PQ transition after inflation <= axion strings Phys Nonthermal 4 Potential search area

5 Axions After 2 pilot experiments missing sensitivity The US axion experiment Livermore MIT UC Berkeley/LBNL U. Florida U. Chicago/FNAL INR Moscow experiment First data analyzed, published, PRL 98 demonstrated sensitivity to KSVZ axions Currently scanning wider region R&D on DC SQUID amplifiers underway at Berkeley => proposed upgrade reaching DFZS Kyoto experiment Matsuki et al. (Rydberg atoms) Starting in narrow region but high sensitivity These experiments reach a cosmological sensitivity! Potential Problem: one decade out three mass decades allowed Phys Nonthermal 5

6 Primordial Black Holes Technically lost any information about their baryon content e.g. thermal Hawking radiation Very low mass black holes Would give rise to high energy gamma ray flashes Belyanin, A.A. and V.V. Kocharovsky, 1996, Mon. Not. R. Astr. Soc., 283, 626. Microlensing result excludes mass range between 10-7 and 10-1 solar masses Solar mass black holes? Would explain MACHOs About the mass inside the causal horizon at the quark hadron transition Appears to require fine tuning of parameters Very Massive Objects (VMO) = an early star population of at least 100 solar masses => black holes without contaminating the interstellar medium DIRBE infrared background Hauser, M.G. et al., 1998, astro-ph/ Very massive ones would disrupt galactic disks Xu, G. and J.P. Ostriker, 1994, Astrophys. J., 437, 184. Phys Nonthermal 6

7 WIMPZILLAs Gev/c 2 Gravitational production toward the end of inflation Chung,Kolb,Riotto Phys. Rev. Lett. 81 (1998) 4048, Phys Rev D 59 (1999)23501 and D 60(1999) Kuzmin and Tkachev Phys Rept 320 (1999) 199 and Phys rev D 59 (1999) Disruption of virtual pairs of particles/antiparticles (vacuum fluctuations) by fast expanding space Resulting particle density independent of the interaction strength Can be electrically charged, strongly interacting etc Evades unitarity limit Detection May be responsible for high energy cosmic rays: fine tuning of decay time? See e.g. V. Kuzmin astro-ph , Berezinski et al. Phys Rev D58 (1998) If strongly interacting, could lead to high energy t neutrino from sun/earth Alburquerque,Hui,Kolb Astro-ph/ Phys Nonthermal 7

8 Modifying Gravity An unsatisfying direction: MOND 1/r acceleration by point masses would produce flat rotation curves Modified Newtonian Dynamics Milgrom M., 1995, Astrophys. J. 455, 439. & 1997, Astrophys. J. 478, 7. Sanders, R.H., 1996, Astrophys. J. 479, 659. transition below a critical acceleration 10-8 cm/s 2 Difficulties: Inferred mass should have the same geometry of light galactic halo shapes from polar rings + x ray distribution Although it describes Tully Fisher: L V 4 CDM which requires tuning! MOND does not predict enough low surface brightness galaxy F. Van den Bosch,J. Ducanton Astro-ph/ Phys Nonthermal 8 Not a relativistic frawework! cannot account for gravitational lensing cluster observations not a coherent cosmology / structure formation but see Sanders, R.H., 1997, Astrophys. J., 480, 492

9 Additional Dimensions Motivation from string theory The 1995 Revolution: Duality: All 5 existing version of string theories + a 6th one united in M-Theory Supergravity in 10+1 dimensions Phys Nonthermal 9 Only 3+ 1 have expanded, the others stay small (Kalusa-Klein : unification of General relativity and Maxwell s electromagnetism) Achievements Natural convergence of couplings Witten Weak E&M Strong + Pre-Big Bang: start from an infinite cold universe. Instabilities where a small region gets very curved and inflates away.(gasperini+veneziano) Inflation on a platter Difficulties Many vacua? + mathematical complexity Large additional dimensions (1mm) Main idea: Gravity is so weak because it leaves in 4+n dimensions other forces Attempt to bring Planck Mass to TeV region: 1 scale instead of 2 M theory String lne

10 How can this Account for Dark Matter 2 main ideas: Mirror universes Our universe Mirror universe with which we only interact gravitationally There may be difficulties with Inflation: how do you guarantee both inflate in same way Energy stored in bulk Qualitatively, additional burden However none of these ideas are quantitative. Phys Nonthermal 10

11 Tests for Additional Dimensions Laboratory Best results so far: Adelberger s group Hoyle et al. hep-ph High degree of symmetry external influence Zero approximately Newtonian gravity Electrostatic screen between pendulum and rotor Phys Nonthermal 11 V( r) = G m m N 1 2 r ( 1+ e r / ) Cosmology constraints e.g. Hall and Smith Astro=ph equal dimensions M graviton >110 GeV/c 2 to be compatible with gamma ray background: r 2 < m! M graviton >50 GeV/c 2 not to shorten too much 1987A SN pulse

12 Vacuum Energy The problem of the vacuum fluctuations Fundamental to quantum physics: Uncertainty principle H = h k k h a + k ( a + aa + ) = h a + k a + 0 M P k3 1 2 h k dk = k 4 max ( GeV) 4 >> Λ ( ev) 4 Quantum electrodynamics: Casimir effect 2 parallel metallic plates Low k modes cannot live inside parallel plates => pressure 2 hc P = = 240 a 4 Note: also Van der Waals: 1/a 7 + orientation of micro-crystals: patch effect Vacuum pressure k a /1µm ( ) 4 N/m 2 Zero point energy! Phys Nonthermal 12 Λ 3keV/cm 3 p = Λ c N/m 2 3 Not so small: but how to cancel some of the modes hc 10 4 m Λ

13 Possible Explanations We have no clue! Deep symmetry forcing to be (approximately zero) e.g. Supersymmetry Still fails 1 2 h SUSY breaking k 3 k 0 k Coleman: quantum gravity giving very low probability to Λ 0 Large additional dimensions?? hc Λ m Arkani-Hamed,Dimopoulos,Kaloper,Sundrum Also Kachru, Silverstein Anthropic principle Weinberg Other explanations of dark energy A non relaxed field: Quintescence Tangled cosmic strings dk = k 4 max ( ev) 4 >> Λ ( ev) 4 Phys Nonthermal 13

14 Why now? Why v b DM Tracking e.g. Quintescence: density never very far. But has to cross now! Phys Nonthermal 14 Arkanami-Ahmen, Hall, Murayama conjecture Astro-ph Because M EW M M T 4 r Pl 2 Λ 2 T 3 M 2 EW M Pl T eq M EW M Pl With = =1 converge at the same point 4 Mass α=π=1 Radiation Dark energy Would explain also densities of neutrinos (see saw mechanism) Baryons generated at electroweak scale? ρ a(t) ρ With proper coefficients Mass Radiation Dark energy a(t)