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1、Big-Bang Cosmology,Hitoshi Murayama 129A F2002 Semester,1,行业精制,Introduction,Brief review of standard cosmology Big-Bang Nucleosynthesis Observational evidence for Dark Matter Observational evidence for Dark Energy Particle-physics implications Baryon Asymmetry,2,行业精制,Brief review of standard cosmolo
2、gy,3,行业精制,The Isotropic Universe,4,行业精制,The Cosmological Principle,Universe highly isotropic CMBR anisotropy O(105) Unless we occupy the “center of the Universe,” it must also be homogenous Isotropy and Homogeneity maximally symmetric space Flat Euclidean space R3 Closed three-sphere S3=SO(4)/SO(3)
3、Open three-hyperbola SO(3,1)/SO(3),5,行业精制,Friedman Equation,Equation that governs expansion of the Universe k=1 (closed), k=1 (open), k=0 (flat) energy density r First law of thermodynamics: For flat Universe: Matter-dominated Universe Radiation-dominated Universe Vacuum-dominated Universe Temperatu
4、re TR1,6,行业精制,7,行业精制,Energy budget of Universe,Stars and galaxies are only 0.5% Neutrinos are 0.310% Rest of ordinary matter (electrons and protons) are 5% Dark Matter 30% Dark Energy 65% Anti-Matter 0% Higgs condensate 1062%?,8,行业精制,Cosmic Microwave Background,9,行业精制,Fossils of Hot Big Bang,When th
5、e temperature of Universe was higher than about 3000K, all atoms (mostly hydrogen and helium) were ionized. Photons scatter off unbound electrons and could not stream freely: “opaque Universe.” Photons, atoms, electrons in thermal equilibrium. Once the temperature drops below 3000K, electrons are bo
6、und to atoms and photons travel freely, “recombination.” CMBR photons from this era simply stretched by expansion R,10,行业精制,Density Fluctuation,Completely homogeneous Universe would remain homogeneous no structure Need “seed” density fluctuation From observation, it must be nearly scale-invariant (c
7、onstant in k space) Atoms also fall into gravitational potential due to the fluctuation and hence affects CMBR From COBE, we know dr/r105,11,行业精制,Structure Formation,Jeans instability of self-gravitating system causes structure to form (there is no anti-gravity to stop it!) Needs initial seed densit
8、y fluctuation Density fluctuation grows little in radiation- or vacuum-dominated Universe Density fluctuation grows linearly in matter-dominated Universe If only matter=baryons, had only time for 103 growth from 105: not enough time by now!,12,行业精制,CMBR AnisotropyProbe to Cosmology,Evolution of the
9、anisotropy in CMBR depends on the cosmological parameters: Wmatter, Wbaryon, WL, geometry of Universe Evolution: acoustic oscillation between photon and baryon fluid Characteristic distance scale due to the causal contact Yard stick at the last rescattering surface Angular scale determines geometry,
10、13,行业精制,Acoustic Peaks Probe Cosmology,Wayne Hu,Max Tegmark,14,行业精制,Polarization,Compton scattering polarizes the photon in the polarization plane,15,行业精制,Big-Bang Nucleosynthesis,16,行业精制,Thermo-Nuclear Fusionin Early Universe,Best tested theory of Early Universe Baryon-to-photon ratio hnB/ng only p
11、arameter Neutron decay-anti-decay equilibrium ends when T1MeV, they decay until they are captured in deuterium Deuterium eventually form 3He, 4He, 7Li, etc Most of neutrons end up in 4He Astronomical observations may suffer from further chemical processing in stars,17,行业精制,Data,“Crisis” the past few
12、 years Thuan-Izotov reevaluation of 4He abundance Sangalia D abundance probably false Now concordance WBh2=0.0170.004 (Thuan, Izotov) CMB+LSS now consistent WB=0.020.037 (Tegmark, Zaldarriaga. Hamilton),18,行业精制,Cosmic Microwave Background,19,行业精制,Observational evidence for Dark Matter,20,行业精制,Theore
13、tical Argumentsfor Dark Matter,Spiral galaxies made of bulge+disk: unstable as a self-gravitating system need a (near) spherical halo With only baryons as matter, structure starts forming too late: we wont exist Matter-radiation equality too late Baryon density fluctuation doesnt grow until decoupli
14、ng Need electrically neutral component,21,行业精制,Galactic Dark Matter,Observe galaxy rotation curve using Doppler shifts in 21 cm line from hyperfine splitting,22,行业精制,Galactic Dark Matter,Luminous matter (stars) Wlumh=0.0020.006 Non-luminous matter Wgal0.020.05 Only lower bound because we dont quite
15、know how far the galaxy halos extend Could in principle be baryons Jupiters? Brown dwarfs?,23,行业精制,MAssive Compact Halo Objects(MACHOs),Search for microlensing towards LMC, SMC When a “Jupiter” passes the line of sight, the background star brightens MACHO & EROS collab. Joint limit astro-ph/9803082
16、Need non-baryonic dark matter in halo Primordial BH of M ?,24,行业精制,Dark Matter in Galaxy Clusters,Galaxies form clusters bound in a gravitational well Hydrogen gas in the well get heated, emit X-ray Can determine baryon fraction of the cluster fBh3/2=0.0560.014 Combine with the BBN Wmatterh1/2=0.380
17、.07 Agrees with SZ, virial,25,行业精制,Particle-physics implications,26,行业精制,Neutrino Dark Matter?,Now that we seem to know neutrinos are massive, cant they be dark matter? Problem: neutrinos dont clump!,27,行业精制,Cold Dark Matter,Cold Dark Matter is not moving much Gets attracted by gravity,28,行业精制,Neutr
18、ino Free Streaming,Neutrinos, on the other hand, move fast and tend to wipe out the density contrast.,29,行业精制,Particle Dark Matter,Suppose an elementary particle is the Dark Matter WIMP (Weakly Interacting Massive Particle) Stable heavy particle produced in early Universe, left-over from near-comple
19、te annihilation Electroweak scale the correct energy scale! We may produce Dark Matter in collider experiments.,30,行业精制,Particle Dark Matter,Stable, TeV-scale particle, electrically neutral, only weakly interacting No such candidate in the Standard Model Supersymmetry: (LSP) Lightest Supersymmetric
20、Particle is a superpartner of a gauge boson in most models: “bino” a perfect candidate for WIMP But there are many other possibilities (techni-baryons, gravitino, axino, invisible axion, WIMPZILLAS, etc),31,行业精制,Detection of Dark Matter,Direct detection CDMS-II, Edelweiss, DAMA, GENIUS, etc,Indirect
21、 detection SuperK, AMANDA, ICECUBE, Antares, etc,complementary techniques are getting into the interesting region of parameter space,32,行业精制,Particle Dark Matter,Stable, TeV-scale particle, electrically neutral, only weakly interacting No such candidate in the Standard Model Lightest Supersymmetric
22、Particle (LSP): superpartner of a gauge boson in most models LSP a perfect candidate for WIMP,Detect Dark Matter to see it is there. Produce Dark Matter in accelerator experiments to see what it is.,CDMS-II,33,行业精制,Observational evidence for Dark Energy,34,行业精制,Type-IA Supernovae,As bright as the ho
23、st galaxy,35,行业精制,Type-IA Supernovae,Type-IA Supernovae “standard candles” Brightness not quite standard, but correlated with the duration of the brightness curve Apparent brightness how far (“time”) Know redshift expansion since then,36,行业精制,Type-IA Supernovae,Clear indication for “cosmological con
24、stant” Can in principle be something else with negative pressure With w=p/r, Generically called “Dark Energy”,37,行业精制,Cosmic Concordance,CMBR: flat Universe W1 Cluster data etc: Wmatter0.3 SNIA: (WL2Wmatter)0.1 Good concordance among three,38,行业精制,Constraint on Dark Energy,Data consistent with cosmo
25、logical constant w=1,Dark Energy is an energy that doesnt thin much as the Universe expands!,39,行业精制,Embarrassment with Dark Energy,A nave estimate of the cosmological constant in Quantum Field Theory: rLMPl410120 times observation The worst prediction in theoretical physics! People had argued that
26、there must be some mechanism to set it zero But now it seems finite?,40,行业精制,Quintessense?,Assume that there is a mechanism to set the cosmological constant exactly zero. The reason for a seemingly finite value is that we havent gotten there yet A scalar field is slowly rolling down the potential to
27、wards zero energy But it has to be extremely light: 1042 GeV. Can we protect such a small mass against radiative corrections? It shouldnt mediate a “fifth force” either.,41,行业精制,Cosmic Coincidence Problem,Why do we see matter and cosmological constant almost equal in amount? “Why Now” problem Actual
28、ly a triple coincidence problem including the radiation If there is a fundamental reason for rL(TeV)2/MPl)4, coincidence natural,Arkani-Hamed, Hall, Kolda, HM,42,行业精制,Amusing coincidence?,The dark energy density rL(2meV)4 The Large Angle MSW solution Dm2(510meV)2 Any deep reason behind it? Again, if
29、 there is a fundamental reason for rL(TeV)2/MPl)4, and using seesaw mechanism mn(TeV)2/MPl , coincidence may not be an accident,43,行业精制,What is the Dark Energy?,We have to measure w For example with a dedicated satellite experiment,SNAP,44,行业精制,Baryogenesis,45,行业精制,Baryon AsymmetryEarly Universe,The
30、y basically have all annihilated away except a tiny difference between them,10,000,000,001,10,000,000,000,46,行业精制,Baryon AsymmetryCurrent Universe,They basically have all annihilated away except a tiny difference between them,1,us,47,行业精制,Sakharovs Conditionsfor Baryogenesis,Necessary requirements f
31、or baryogenesis: Baryon number violation CP violation Non-equilibrium G(DB0) G(DB0) Possible new consequences in Proton decay CP violation,48,行业精制,Original GUT Baryogenesis,GUT necessarily breaks B. A GUT-scale particle X decays out-of-equilibrium with direct CP violation Now direct CP violation obs
32、erved: e! But keeps BL0 “anomaly washout”,49,行业精制,Out-of-Equilibrium Decay,When in thermal equilibrium, the number density of a given particle is nem/T But once a particle is produced, they “hang out” until they decay net/t,Therefore, a long-lived particle (tMPl/m2) decay out of equilibrium,thermal,
33、actual,T=m,t=t,50,行业精制,Anomaly washout,Actually, SM violates B (but not BL). In Early Universe (T 200GeV), W/Z are massless and fluctuate in W/Z plasma Energy levels for left-handed quarks/leptons fluctuate correspon-dingly,DL=DQ=DQ=DQ=DB=1 B=L=0,51,行业精制,Two Main Directions,BL0 gets washed out at TT
34、EW174GeV Electroweak Baryogenesis (Kuzmin, Rubakov, Shaposhnikov) Start with B=L=0 First-order phase transition non-equilibrium Try to create BL0 Leptogenesis (Fukugita, Yanagida) Create L0 somehow from L-violation Anomaly partially converts L to B,52,行业精制,Electroweak Baryogenesis,53,行业精制,Electrowea
35、k Baryogenesis,Two big problems in the Standard Model First order phase transition requires mH60GeV Need new source of CP violation because J detMu Mu, Md Md/TEW12 1020 1010 Minimal Supersymmetric Standard Model First order phase transition possible if New CP violating phase e.g., (Carena, Quiros, W
36、agner), (Cline, Joyce, Kainulainen),54,行业精制,scenario,First order phase transition Different reflection probabilities for chargino species Chargino interaction with thermal bath produces an asymmetry in top quark Left-handed top quark asymmetry partially converted to lepton asymmetry via anomaly Rema
37、ining top quark asymmetry becomes baryon asymmetry,55,行业精制,parameters,Chargino mass matrix Relative phase unphysical if tanb Need fully mixed charginos M2 (Cline, Joyce, Kainulainen),56,行业精制,mass spectrum,Need with severe EDM constraints from e, n, Hg 1st, 2nd generation scalars 10 TeV To avoid LEP
38、limit on lightest Higgs boson, need left-handed scalar top TeV Light right-handed scalar top, charginos cf. Carena, Quiros, Wagner claim enough EDM constraint is weaker, but rest of phenomenology similar,57,行业精制,Signals of Electroweak Baryogenesis,O(1) enhancements to Dmd, Dms with the same phase as
39、 in the SM Bs mixing vs lattice fBs2BBs Bd mixing vs Vtd from Vub and angles Find Higgs, stop, charginos (Tevatron?) Eventually need to measure the phase in the chargino sector at LC to establish it (HM, Pierce),58,行业精制,Leptogenesis,59,行业精制,Seesaw MechanismPrerequisite for Leptogenesis,Why is neutri
40、no mass so small? Need right-handed neutrinos to generate neutrino mass, but nR SM neutral,To obtain m3(Dm2atm)1/2, mDmt, M31015GeV (GUT!) Majorana neutrinos: violate lepton number,60,行业精制,Leptogenesis,You generate Lepton Asymmetry first. L gets converted to B via EW anomaly Fukugita-Yanagida: gener
41、ate L from the direct CP violation in right-handed neutrino decay,61,行业精制,Leptogenesis,Two generations enough for CP violation because of Majorana nature (choose 1 Pilaftsis) M11010 GeV OK want supersymmetry,62,行业精制,Can we prove it experimentally?,We studied this question at Snowmass2001 (Ellis, Gav
42、ela, Kayser, HM, Chang) Unfortunately, no: it is difficult to reconstruct relevant CP-violating phases from neutrino data But: we will probably believe it if 0nbb found CP violation found in neutrino oscillation EW baryogenesis ruled out,63,行业精制,CP Violation in Neutrino Oscillation,Plans to shoot ne
43、utrino beams over thousands of kilometers to see this,CP-violation may be observed in neutrino oscillation,64,行业精制,Conclusions,Mounting evidence that non-baryonic Dark Matter and Dark Energy exist Immediately imply physics beyond the SM Dark Matter likely to be TeV-scale physics Search for Dark Matt
44、er via Collider experiment Direct Search (e.g., CDMS-II) Indirect Search via neutrinos (e.g., SuperK, ICECUBE) Dark Energy best probed by SNAP (LSST?),65,行业精制,Conclusions (cont),The origin of matter anti-matter asymmetry has two major directions: Electroweak baryogenesis leptogenesis Leptogenesis definitely gaining momentum May not be able to prove it definitively, but we hope to have enough circumstantial evidences: 0nbb , CP violation in neutrino oscillation,66,行业精制,