APS Northwest Section 11th Annual Meeting

The Dark Side of the Universe Van Waerbeke, Ludovic 2009-05-15

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The Dark Side of the UniverseL. Van WaerbekeAPSNW may 15th 2009PLANCK & HERSCHEL launched may 14th 2009The Big-Bang modelPower spectrum: AnknS ATknT8/An, dns/dlnkEnd of dark age: flash Re-ionisation: , z  m  ,w     b k  =nb/n Age and expansion rate: t + hLast scattering surface:  zdec, tdec, zdecPrimordial fluctuations: origin? Nature?Dark matter halos and baryon coupling:  mass and light biasing  properties b,r SDSSGalaxy distributionLarge Scale StructuresUnderstanding the content of the Universe is a bit liketrying to understand what exists at the surface ofthe Earth only from what you can “see” outer spaceEVIDENCE for DARK MATTERCornelia ParkerCold Dark Matter: An Exploded View, 1991 NGC3198Spiral galaxies rotation curvesDynamics of cluster of galaxiesAbel 1689Dark matter in clusters was “discovered” in 1933 (Zwicky) basedOn dynamical arguments and always systematically confirmed withnewer observations.Gravitational lensing as aprobe of dark matterStrong gravitational lensingWeak gravitational lensingGavazzi et a. 2007Mass versus stellar profile of early-type galaxies (from strong and weak lensing)Mass to light ratio as function of scaleDark Matter has been detected by several independent probes:-dynamical-gravitational lensing-Xray (dynamical-clusters of galaxies)-Cosmic microwave backgroundWilkinson Microwave Anisotropy ProbeMap of the photon temperaturefluctuations “released” when theUniverse was only 300000 years old.EVIDENCE for DARK ENERGY…none yet, but cosmological constant, yes!“fluids” present in the Universe: Matter (baryons and dark matter)Radiation (photons, e.g. cosmic microwave background)Unknown fluid? (with specific equation of state)Ideal gas equation of state: PV=nkBTUnknown fluid equation of state: P=weThe cosmological constant “L” has w=-1A cosmological constant is allowed by G.R.Dark energy is a cosmological constant with w not -1Effect of a cosmological constant on the UniverseMatter dominatedWith cosmological constantMatterCosmological constantCombination of the cosmic microwave background and large scale structure distributionSupernovae of type Ia are “standard candles”Supernovae dimming withRedshift consistent witha cosmological constant.Friedman 2009Combined constraints from all cosmological dataFrom WMAPThe cosmological pie w~-1Physical origin of Dark Matter…The bullet cluster: Bradac et al. 2006, Clowe et al. 2006.…not known, but…Dark Matter isDissipationless/pressurelessBlue: dark matterPink: hot gas (Xray)Dark matter cannot be made of dark compact objects(e.g. brown dwarfs) constraints from MACHODark matter cannot be baryonic anyway (constraints fromnucleosynthesis)Dark matter cannot be neutrinos only (strong mass constraintfrom CMB and LSS)Dark matter could be weakly interacting particles (WIMPS).Direct and indirect detection experiments under way.Dark matter could be no matter at all, just modified gravity,but severe observational constraints are coming…What could dark matter be and not be…How can we probe dark matter?Physical origin of Dark Energy……so far no evidence of deviation from cosmological constant…and the amplitude of DE/cosmological constant remainsone of the major issues in physics (fine tuning).WLQFT ~10120 WLcosmoUzan 2007StandardmattergmnfStandardmattergmnfStandardMatterAmgmnStandardmatterGmn(i)Ex: Quintessence, Chaplyin gas,K-essence,….Ex: photon-Axion mixingEx: scalar-tensor theories, f(R),Chameleon,…Ex: Brane-induced gravity, multiDObs: CMB T(z)Obs: test of Poisson eq., variationOf constantsObs: strong field effects (BH, GW),Local tests of gravity-DE equation of state: high precision observation of intermediate redshiftuniverse (galaxy photometric and spectroscopic surveys) -> access to spaceand upcoming ground based facilitiesCopernician revolution made possible from accurate observations(Tycho+Kepler)-More theoretical investigations are absolutely necessary: None of theproposed explanations resolve the cosmological constant fine tuning problemA worry is: is there enough observational constraints available to fullycharacterize one or more of the dark energy models?Fortunately we don’t have to explain something which has not been observed yet How to probe dark energy if w is different from -1?What should you take away from this talk?Over the past 100 years, cosmology has become a solid science, based on observations and falsifiable assumptions.This lead to the astounding conclusion that 95% of the Universe is unknown dark stuff. There is undisputedevidence that something is fundamentally incomplete in t heBig Bang model.Cosmology has also turned in a big science with the need for expensive, international projects, which is exciting but could also be frustrating.  The Dar k Si de of t he Uni ver se  L. Van Waer beke  APSNW may 15 t h 2009  PLANCK & HERSCHEL launched may 14th 2009  The Bi g- Bang model • Ωm  Primordial fluctuations: origin? Nature?  • Ω λ,w •Ων  Power spectrum: AnknS ATknT  •Ωγ  σ8/An, dns/dlnk  • Ωb • Ωk • η=nb/n γ  Age and expansion rate: t + h  Last scattering surface: zdec, tdec, ∆ zdec  End of dark age: flash Re-ionisation: τ , z τ Dark matter halos and baryon coupling: mass and light biasing properties b,r  SDSS  Gal ax y di s t r i but i on  Lar ge Sc al e St r uc t ur es  er st andi ng t he c ont ent of t he Uni ver se i s a bi t l i k ng t o under s t and what exi st s at t he sur f ace of Ear t h onl y f r om what you can “ see” out er space  EVI DENCE f or DARK MATTER  Cornelia Parker Cold Dark Matter: An Exploded View, 1991  Spi r al gal axi es r ot at i on cur ves  NGC3198  Dynamics of cluster of galaxies  Abel 1689  Dark matter in clusters was “discovered” in 1933 (Zwicky) based On dynamical arguments and always systematically confirmed with newer observations.  Gr avi t at i onal l ensi ng as a pr obe of dar k mat t er  t r ong gr av i t at i onal l ens i ng  Weak gr av i t at i onal l ens i ng  Mass versus stellar profile of early-type galaxies (from strong and weak lensing)  Gavazzi et a. 2007  Mass to light ratio as function of scale  Mat t er has been det ect ed by sever al i ndependent pr - dynami cal - gr avi t at i onal l ensi ng - Xr ay ( dy nami cal - cl ust er s of gal axi es) - Cos mi c mi cr owave backgr ound  Wi l ki nson Mi c r owav e Ani s ot r opy Pr obe  Map of t he phot on t emper at ur e l uct uat i ons “ r el eas ed” when t he Uni ver se was onl y 300000 y ear s ol d.  EVI DENCE f or DARK ENERGY …none yet, but cosmological constant, yes! “ f l ui ds ” pr esent i n t he Uni ver se:  • Mat t er ( bar yons and dar k mat t er ) Radi at i on ( phot ons, e. g. cosmi c mi cr owave backgr ou • Unk nown f l ui d? ( wi t h speci f i c equat i on of st at e) I deal gas equat i on of st at e: PV=nk BT  Unk nown f l ui d equat i on of st at e: P=wε The c os mol ogi cal const ant “ Λ” has w=- 1 A c os mol ogi c al const ant i s al l owed by G. R. Dar k ener gy i s a cosmol ogi cal const ant wi t h w not  Ef f ect of a c os mol ogi cal const ant on t he Uni ver se  Mat t er domi nat ed  Wi t h cosmol ogi cal const an  Cos mol ogi cal const ant  Combi nat i on of t he cosmi c mi cr owav e backgr ound and l ar ge s cal e st r uct ur e di st r i but i on  Mat t er  Super nov ae of t ype I a ar e “ st andar d candl es”  Super novae di mmi ng wi t h Reds hi f t consi st ent wi t h a c os mol ogi cal const ant .  Fr i edman 2009  Combi ned c ons t r ai nt s f r om al l cosmol ogi cal dat a  The c os mol ogi c al pi e   w~- 1  Fr om WMAP  Phy s i c al or i gi n of Dar k Mat t er … …not known, but…  The bul l et cl us t er : Br adac et al . 2006, Cl owe et al . 2006.  Dark Matter is Dissipationless/ pressureless Blue: dark matter Pink: hot gas (Xray)  What c oul d dar k mat t er be and not be… How c an we pr obe dar k mat t er ? mat t er c annot be made of dar k compact obj ect s br own dwar f s ) c onst r ai nt s f r om MACHO  mat t er c annot be bar yoni c anyway ( const r ai nt s f r om os ynt hes i s )  mat t er c annot be neut r i nos onl y ( st r ong mass const CMB and LSS)  mat t er c oul d be weakl y i nt er act i ng par t i cl es ( WI MP and i ndi r ec t det ect i on exper i ment s under way.  mat t er c oul d be no mat t er at al l , j ust modi f i ed gr ev er e obs er v at i onal const r ai nt s ar e comi ng…  Phy s i c al or i gi n of Dar k Ener gy …  f ar no evi denc e of devi at i on f r om cosmol ogi cal cons t he ampl i t ude of DE/ cosmol ogi cal const ant r emai ns of t he maj or i s s ues i n physi cs ( f i ne t uni ng) .  ΩΛQFT ~ 1 0 1 2 0 ΩΛcosmo  Standard matter  gµν  φ  Ex: Quintessence, Chaplyin gas, K-essence,….  gµν Standard matter  φ  Ex: scalar-tensor theories, f(R), Chameleon,… Obs: test of Poisson eq., variation Of constants  Standard Matter  gµν  Aµ Ex: photon-Axion mixing Obs: CMB T(z)  Standard matter  Gµν(i)  Ex: Brane-induced gravity, multiD Obs: strong field effects (BH, GW), Local tests of gravity  Uzan 2007  How t o pr obe dar k ener gy i f w i s di f f er ent f r om - 1? - DE equat i on of s t at e: hi gh pr ec i s i on obs er v at i on of i nt er medi at e r eds hi f t uni v er s e ( gal ax y phot omet r i c and s pec t r os c opi c s ur v ey s ) - > ac c es s t o s pac e and upc omi ng gr ound bas ed f ac i l i t i es Coper ni c i an r ev ol ut i on made pos s i bl e f r om ac c ur at e obs er v at i ons ( Ty c ho+Kepl er ) - Mor e t heor et i c al i nv es t i gat i ons ar e abs ol ut el y nec es s ar y : None of t he pr opos ed ex pl anat i ons r es ol v e t he c os mol ogi c al c ons t ant f i ne t uni ng pr obl em A wor r y i s : i s t her e enough obs er v at i onal c ons t r ai nt s av ai l abl e t o f ul l y c har ac t er i z e one or mor e of t he dar k ener gy model s ?  What s houl d y ou t ak e away f r om t hi s t al  Over t he pas t 100 year s, cosmol ogy has become a sol ence, bas ed on obs er vat i ons and f al si f i abl e assumpt  hi s l ead t o t he as t oundi ng concl usi on t hat 95% of t Uni v er s e i s unk nown dar k st uf f . Ther e i s undi sput e dence t hat s omet hi ng i s f undament al l y i ncompl et e i n Bi g Bang model .  smol ogy has al s o t ur ned i n a bi g sci ence wi t h t he n ex pens i v e, i nt er nat i onal pr oj ect s, whi ch i s exci t i c oul d al so be f r ust r at i ng.  


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