1. 4 ½ Problems from Modern Cosmology 4 ½ Problems from Modern Cosmology Pasquale Di Bari MAX PLANCK PROJECT REVIEW 2005 and a few solutions !

2. Pasquale Di Bari - 4 ½ Problems in Modern Cosmology Toward a Cosmological SM ? Exp. rate today: H 0 = 72 ± 7 km sec -1 Mpc -1 flat Universe: Ω 0 = 1.02 ± 0.02 Age of the Universe: t 0 =13.7 ± 0.2 Gyr 3 fluids Universe: scalar gaussian primordial perturbations  scalar index: 0.93 ± 0.03 No tensor perturbations Baryons: Ω B = 0.039 ± 0.008 (no anti matter domains) Dark Matter: Ω CDM = 0.29 ± 0.04 Dark Energy: Ω DE = 0.73 ± 0.04 w= p/ρ < -0.8 (95% c.l.)

3. Pasquale Di Bari - 4 ½ Problems in Modern Cosmology The Mass-Energy budget today

4. Pasquale Di Bari - 4 ½ Problems in Modern Cosmology 4 PROBLEMS * from COSMOLOGY: 1.Matter- anti matter asymmetry 2.Dark matter 3.Accelerating Universe 4.Inflation * ‘PROBLEM’ ´ NEED of NEW PHYSICS

5. Pasquale Di Bari - 4 ½ Problems in Modern Cosmology Matter-anti matter asymmetry Matter- anti matter domains ? Excluded ! )   = (  ±  x    À   Pre-existing ? It conflicts with inflation ! ) Dynamical generation = Baryogenesis A Standard Model Solution ?   ¿   : too low ! NEW PHYSICS IS NEEDED! CMB SMCMB

6. Pasquale Di Bari - 4 ½ Problems in Modern Cosmology Models of Baryogenesis From phase transitions: - Electroweak Baryogenesis: * in the SM * in the MSSM * ……………. Affleck-Dine: - at preheating - Q-balls - ………. From Black Hole evaporation Spontaneous Baryogenesis ………………………………… From heavy particle decays: - GUT Baryogenesis - LEPTOGENESIS

7. Pasquale Di Bari - 4 ½ Problems in Modern Cosmology Leptogenesis It is attractive for the simple reason that it relies on the only ingredient of new physics that has been already observed: neutrino masses …and on the simplest way to explain them:…and on the simplest way to explain them: the see-saw mechanism 3 light LH neutrinos: 3 light LH neutrinos: 3 heavy RH neutrinos: N 1, N 2, N 3 3 heavy RH neutrinos: N 1, N 2, N 3

8. Pasquale Di Bari - 4 ½ Problems in Modern Cosmology weak wash-out :  i  À t (T=M i ) ) N B-L =  i strong wash-out:  i  À t (T=M i ) ) N B-L =  i  i CP asymmetry If  i ≠ 0 a lepton asymmetry is generated from decays and partly converted into a baryon asym. by sphaleron processes ! N N = N N = 1 eq ii in Let us take: fin Efficiency factor :  i · 1 fin Recent results from A. Anisimov, A. Broncano, M. Plümacher non thermal Leptogenesis: one can have  i >1 (work in progress with Florian Hahn Wörnle Florian Hahn Wörnle)

9. Pasquale Di Bari - 4 ½ Problems in Modern Cosmology WEAK WASH-OUTSTRONG WASH-OUT S. Blanchet PDB & S. Blanchet z´ M 1 / T zdzd K´ t(T=M i )/ 

10. Pasquale Di Bari - 4 ½ Problems in Modern Cosmology Great advantage of strong wash-out: the final asymmetry does not depend on the initial conditions like in the weak wash-out It is remarkable that the data from neutrino mixing experiments imply K À 1 ) strong wash-out is realized ! BUT: successful thermal leptogenesis is possible only if: reh M 1, T reh & 10 9 GeV and m n. 0.1 eV N 2 - dominated scenario: lower bound on M 1 is evaded ! (but not that on T reh ) PDB ‘05 Buchmuller PDB,Plumacher ‘04

11. Pasquale Di Bari - 4 ½ Problems in Modern Cosmology Dark Matter Conceptually similar to the old problem of unseen planets: dark objects or failure of GR ? 2 famous examples: anomalous Uranus motion ) Neptune discovery anomalous Mercury motion ) discovery of GR ! What do we need today to explain Dark Matter : a new particle … … or a new description of gravity ?

12. Pasquale Di Bari - 4 ½ Problems in Modern Cosmology Particle Dark Matter SUSY DM: - neutralinos - gravitinos - sneutrinos Extra-dim’s Wimpzilla’s Sterile neutrinos …………………. It is the most popular solution with many theoretical motivations Modification of Newtonian Dynamics For accelerations a<a 0 ' 10 -8 cm s -2 usual Newton law is modified (Milgrom ’83) Relativistic tensor-vector-scalar field theory for MOND (Bekenstein ’04) However recent observations (CMB and baryon acoustic oscillation peak) would exclude it (Silk et al.’05 ; Eisenstein ’05)

13. Pasquale Di Bari - 4 ½ Problems in Modern Cosmology Accelerating Universe With Dark Energy C.C.  : why small ? - maybe SUSY breaking: - Anthropic principle (Weinberg ’87) Quintessence: A light scalar field still rolling down: w  in general Without Dark Energy modifying gravity At large distances, motivated in brane world scenarios(Dvali,Gabadadze,Porrati) without modifying gravity attempt to explain acceleration without new physics: acceleration would arise from inhomogeneities inside the horizon coincidence problem it would solve the coincidence problem but …. …..unfortunately it is unlikely to work ! Andreas Biffar & M. Plumacher Work in progress See talk of G. Veneziano at EPS-Lisboa ‘05

14. Pasquale Di Bari - 4 ½ Problems in Modern Cosmology Inflation It solves the well known problems of ‘old’ cosmology (horizon problem, flatness problem, initial conditions, spectrum of primordial perturbations…) strongly supported by CMB data but at the same time it leads to serious problems well beyond the SM: - where inflation comes from ? what is the inflaton ? - flatness of the potential - trans-Planckian scales inside the horizon - does not solve the problem of singularity (it is only shifted at earlier times) - cosmological constant problem (the large quantum vacuum energy of field theories does not gravitate today and thus we do not want it….but it is necessary for inflation !) Brandeberger See Brandeberger hep-th/0509076

15. Pasquale Di Bari - 4 ½ Problems in Modern Cosmology ½ problem: primordial Helium abundance anomaly there is a on-going debate whether this is a real problem for SBBN or just for astronomers in measuring Y p : it vaguely resembles early times of solar neutrino problem if a real problem then a solution would be a lepton asymmetry much larger than the baryon asymmetry late leptogenesis ?

16. Pasquale Di Bari - 4 ½ Problems in Modern Cosmology Cosmic connections Matter- anti matter asymmetry Neutrino masses Accelerating Universe Dark Matter Inflation

17. Pasquale Di Bari - 4 ½ Problems in Modern Cosmology Conclusions Exciting challenges from Cosmology … ….maybe rather than as ‘problems’ these should be regarded as gifts from Cosmology !