!Licia!Verde!
http://icc.ub.edu/~liciaverde
ICREA & ICC-UB Barcelona
University of Oslo, Norway
Cosmology and fundamental Physics!Some!examples!
Context • Cosmology over the past 20 years has made the
transition to precision cosmology • Cosmology has moved from a data-starved science
to a data-driven science • Cosmology has now a standard model. The
standard cosmological model only needs few parameters to describe origin composition and evolution of the Universe
• Deep links to fundamental physics (e.g.,SM, BSM) • Big difference between modeling and understanding
AIM:!!propose!some!open!ques8ons!and!s8umulate!discussion!
The!era!of!precision!cosmology:!LCDM: the standard model for cosmology
Homogenous background Perturbations
Few parameters describe the Universe composition and evolution
What s!next?!!Look!for!devia8ons!from!the!standard!model!
• Dark!energy!• Nature!of!ini8al!condi8ons:!Adiaba8city,!Gaussianity!
• Neutrino!proper8es!!• Infla8on!proper8es!• Beyond!the!standard!model!physics…!
Test physics on which it is based and beyond it
Cosmology!is!special!
We!can’t!make!experiments,!only!!observa8ons!
We only have one observable universe
We can only make observations (and only of the observable Universe) not experiments: we fit models (i.e. constrain numerical values of parameters) to the observations: Any statement is model dependent Gastrophysics and non-linearities get in the way : Different observations are more or less “trustable”, it is however somewhat a question of personal taste (think about Standard & Poor’s credit rating for countries) Results will depend on the data you (are willing to) consider. (robustness?) Not all observations are created equal ….And the Blessing
We only have one observable universe
The curse of cosmology
We can observe all there is to see
….And the Blessing
We only have one observable universe
We can observe all there is to see
And almost do
challenges!
As!the!sta8s8cal!errors!shrink…..!!!Systema8c!errors!must!be!kept!under!exquisite!control!!
There!is!no!systema8c!way!to!address!systema8c!errors!
!They!!sneak!in!from!everywhere:!!!Theory,!Astrophysics,!Observa8ons,!observables,!etc…!
From!precision!cosmology!to!accurate!cosmology!(Peebles!2002)!
Dark!maWer!
• Evidences!for!dark!maWer!come!(Only?)!from!the!sky!
• Indica8on!of!physics!BSM!
Rota8on!curves!of!galaxies!
CMB!and!perturba8ons!
Anderson et al. 2014
BAO!
P/Psmooth!
Not!forge[ng!the!bullet!cluster!
You!could!try!to!avoid!it….!!But!you!would!have!to!give!up!GR!
Neutrino!proper8es!
Neutrinos contribute at least to ~0.5% of the total matter density
Use!the!en8re!Universe!as!“detector”!!
What!is!a!neutrino!for!cosmology?!
• Behaves like radiation at T~ eV (recombination/decoupling) • Eventually (possibly) becomes non-relativistic, behaves like
matter • Small interactions (not perfect fluid) • Has a high velocity dispersion (is “HOT”)
Cosmic Neutrino Background A relict of the big bang, similar to the CMB except that the CvB decouples from matter after 2s (~ MeV) not 380,000 years
At decoupling they are still relativistic (mν
The cosmic neutrino background has been detected at >> 4 σ#
WMAP
SPT 99.7% or 0.003
Relict neutrinos influence in cosmology Primordial nucleosynthesis CMB Large-scale structure
T~ MeV
Neff
T
Neutrino mass: Physical!effects!Total mass >~1 eV become non relativistic before recombination CMB Total mass
Cosmology is the key to determine the absolute mass
upper
upper
Σ
Beware of systematics!!!!!
It would be of great value to have an internal consistency check (more later)
Σm = 0 eV Σm = 0.3 eV Σm = 1 eV
P(k)/P(k,m
ν=0)
linear theory
Neutrinos!effect!on!the!maWer!P(k)!
Wagner, LV, Jimenez, 2012
Current constraints:Σ
What about real world effects? • Baryonic physics (lensing and galaxy surveys) • Bias (galaxy surveys) • redshift space (galaxy surveys)
CMB back to the rescue Lensing
T E
T E B
From Hu Okamoto 2001
CMB back to the rescue Lensing
Infancy… but promising
Planck paper XVII
Look at CMB: effects matter-radn equality and so sound horizon at decoupling -> degeneracy with ωm and H
Main effect: increasing Neff increases Silk Damping scale (for fixed θs), small phase shifts too
Hou et al 2011
H2(t) ' 8⇡G3
(⇢� + ⇢⌫) ⇢⌫ / T 4Ne↵
Any thermal background of light particles, anything affecting expansion rate
Look at BBN
Neff=3.045 Standard:
Neff around 3 to 4 Systematics!
Anisotropic stress, zeq on diffusion damping
Neff: number of effective species
Extra radiation, boosted expansion rate
See also the white paper Abazajian et al. arXiv:1204.5379,
Cosmological analyses consistently give best fit values >3.04.
“dark radiation” But analyses are NOT independent (WMAP is always in common, H0 many times in common)
Claims of non-zero neutrino mass detection since march 2013
arxiv:1307.7715
arxiv:1308.5870
arxiv:1308.3255
Cosmic!Concordance?!
Nonazero!sterile!neutrino!mass!only!favoured!due!to:!!tension!between!CMB!and!clusters!(Planck!SZ,!Xaray)!in!σ8–Ωm!plane!!!degeneracy!between!σ8!&!neutrino!mass.!!
Leistedt,!Peiris,!Verde,!2014!
Hierarchy effect on the shape of the linear matter power spectrum
Δmatmo
Δmsol Δmatmo
Δmsol NH IH
Δ# Neutrinos of different masses have different transition redshifts from relativistic to non-relativistic behavior, and their individual masses and their mass splitting change the details of the radiation-domination to matter- domination regime.!
Jimenez, Kitching, Penya-Garay, Verde, JACP2010
What would it take to measure Δ?
Cosmology is (mostly) sensitive to |Δ|
Still offers a powerful consistency check
In combination with v0ββ experiements can help answering: Are neutrinos Dirac or Majorana?
Basically: the ultimate experiment
Dirac!or!Majorana?!!!!!!!!!!hierarchy!
Jimenez, Kitching, Penya-Garay, Verde, 2010
Complementarity:!cosmology,!par8cle!physics!
Jimenez, Garay, Kitching, LV, 2010 Jimenez, Kitching, Penya-Garay, Verde, 2010, Wagner, LV, Jimenez 2012
Windows into the primordial Universe
Nucleosynthesis
Recombination 380000 yrs Atomic physics/GR
3 minutes Nuclear phyiscs
inflation 10 -30 s (?)
LHC TeV energies
GUT?
Big BANG
Infla8on!
Before!the!discovery!of!the!Higgs!!scalar!fields!in!physics!were!just!a!product!of!the!imagina8on…!!
What mechanism generated the primordial perturbations?
Inflation: Horizon problem
Flatness problem Structure Problem Accelerated expansion:
Quantum fluctuations get stretched to become classical and super-horizon
The shape of the primordial power spectrum encloses information on the shape of the inflaton potential (CMB+Large scale structure)
The energy scale of inflation is given by primordial tensor modes amplitude (CMB polarization!)
Hints!to!UV!comple8on!of!gravity?!
Inflationary predictions: or Inflation Checklist
• Spatially flat universe
• Nearly Gaussian initial perturbations
• Adiabatic initial conditions
• Power spectrum spectral index nearly scale invariant (small red tilt in many implementations) • Super-horizon perturbations
• A stochastic background of gravity waves
Simplest Inflationary Models
Flat
Adiabatic
~Scale invariant
Super-horizon
Gaussian
Small, homogeneous
Spectacular success
Consistency with Simplest Inflationary Models
• Spatially flat universe
• Nearly Gaussian initial perturbations
• Adiabatic initial conditions
• Power spectrum spectral index nearly scale invariant (small red tilt in many implementations) • Super-horizon perturbations
• A stochastic background of gravity waves
Ωtot = 1.005 ± 0.0064 (with lensing and BAO)
fNL = 2.7± 5.8
ns = 0.959 ± 0.007
Renewed confidence with Planck collaboration 2013 results
This means at better than 0.01%
Genera8on!of!CMB!polariza8on!
• Temperature!quadrupole!at!the!surface!of!last!scaWer!generates!polariza8on.!
Potential well Potential hill
From Wayne Hu!
Polariza8on!for!density!perturba8on!!
• Radial!(tangen8al)!paWern!around!hot!(cold)!spots.!
And it has been seen!
Komatsu, WMAP7yrs team (2010)
Theory prediction
Observed
Planck
Measurement
Theory prediction
Planck collaboration 2013
Cold spot Hot spot
Hot spot Cold spot
I Q I Q
Large-scale TE anti correlation
Density mode
Velocities (hot to cold)
Hot due to doppler
During decoupling
Outside the horizon quadrupole is given by velocities
Velocities are off-phase with density
Large-scale TE anti correlation
Primordial Adiabatic i.c.
Causal Seed model (Durrer
et al. 2002)
WMAP
TE data
Primordial
Isocurvature i.c.
Peiris et al 2003
Super horizon
Consistency with Simplest Inflationary Models
• Spatially flat universe
• Nearly Gaussian initial perturbations
• Adiabatic initial conditions
• Power spectrum spectral index nearly scale invariant (small red tilt in many implementations) • Super-horizon perturbations
• A stochastic background of gravity waves
Planck!polariza8on!(teasers)!plots!
Planck!collabora8on!2013!
Image from J. Rhul.
Gravity Waves… are different
Image from J. Rhul.
Gravity Waves
Polarization pattern!
E and B modes polarization
E polarization from scalar and tensor modes
B polarization only from tensor modes
Kamionkowski, Kosowsky, Stebbings 1997, Zaldarriga & Seljak 1997
“smoking gun”
Energy Scale of Inflation (Height of the potential)
Why polarization?
Shape of the inflation potential Temperature (and E-modes)
B-modes are needed! Tensor to scalar ratio, r
0.1 *
*I will mention bicep later
“Foregrounds are horrible but people are brave” (BICEP P.I.)
The challenge
Adapted from C. Pryke
Typical degree-scale brightness fluctuations (150GHz)
Ground, Telescope mount etc 3-300 K
Atmosphere 30 mK - 3 K
Galaxy 0.3-30mK
CMB T anisotropies 30µK
Lensing B modes (at arcmin) 300 nK
r=0.01 B-modes 30 nK
noise you want to reach
Planck!limits!on!r:!How!they!work!!
For!such!r!10%!of!the!TT!signal!at!low!l!comes!from!tensors!(too!much)!
For!a!LCDM!power!law!power!spectrum!!the!!probability!p(r>=bicep)=0.0033,!!according!to!Planck!data!!
BICEP!MEASUREMENT!
Extraaordinary!claim…..!Fig!adapted!from!Verde!Peiris!Jimenez!2006!
Monte Carlo simulation of the inflationary flow equations.
Why!extra!ordinary!claim?!It!implies:!
There!is!a!stochas8c!background!of!gravity!waves!as!infla8on!predicts!!We!know!the!energy!scale!of!infla8on!We!know!how!much!the!field!has!moved!if!single!field!We!have!some!hope!to!test!the!consistency!rela8on!!nt!=a!8!r!!!
Extra!ordinary!claims….!Need!extraaordinary!proofs!
does!the!frequencyadependence!of!the!signal!look!like!CMB?!
This!is!cri8cal!!!Here:!difficult!game!to!play!!with!only!2!frequencies!(150!and!100!GHz)!one!of!them!with!high!noise!!
This!plot!!says!that!it!could!be!synchrotron!!at!2!sigma…!!more!likely,!!dust.!
Really,!we!need!more!frequencies!
Planck!
map!in!orthographic!projec8on!of!the!150!GHz!CBB"amplitudes!at!l!=!80,!computed!from!the!!Planck"353!GHz!data!,!es8mated!contamina8on!from!dust!
Planck:!The!killer!plot!
Consistency with Simplest Inflationary Models
• Spatially flat universe (generic)
• Nearly Gaussian initial perturbations
• Adiabatic initial conditions
• Power spectrum spectral index nearly scale invariant (small red tilt in many implementations) • Super-horizon perturbations (generic)
• A stochastic background of gravity waves (this is actually generic)
Gravity!and!GR!effects!!On!horizonascales!!the!Poisson!equa8on!gets!quadra8c!correc8ons:!Needs!IC!set!up!of!infla8on,!parallels!the!TE!an8acorrela8on.!
Verde & Matarrese 2009 Villa et al 2014 At a potentially detectable level!
�P
P
/ �PP
To!conclude!
…!the!maximally!boring!universe…!
The!standard!cosmological!model!has!survived!ever!more!stringent!tests!
Devia8ons!from!it!!are!even!more!constrained!
Eventually!something!will!have!to!give,!the!model!IS!incomplete!
The!point!is!how!much!smaller!would!the!observa8onal!error!bars!have!to!be!
Precision cosmology -> address fundamental physics questions!(examples: neutrinos, initial conditions…), challenging!!
“We!can’t!live!in!a!state!of!perpetual!doubt,!so!we!make!up!the!best!story!possible!and!we!live!as!if!the!story!were!true.”!
Daniel!Kahneman!about!theories!
Challenges!!(or!what!keeps!me!up!at!night)!
Essen8ally,!all!models!are!wrong!,!but!some!are!useful!(Box!and!Draper!1987)!
Cosmology!tends!to!rely!!hevily!!on!models!(both!for!“signal”!and!the!“noise”)!
What!can!be!measured!in!a!modelaindependent!way?!
In!the!era!of!precision!and!accurate!cosmology…!
There!is!no!room!for!spherical!cows!!
END!
Sta8s8cal!cosmology!
From!observa8ons!of!the!observed(observable)!Universe!!we!want!to!make!inferences!about!the!proper8es!of…!
the!en)re!Universe,!!seen!as!!an!ensamble!of!all!possible!observaed/able!Universes!
of!which!our!observed!one!is!a!random!draw!
Cosmic!variance!
No"wonder"that"many"cposmologists"are"Bayesian!"
“Fair!sample”!
Any!theore8cal!model!will!mostly!!predict!!sta)s)cal!proper)es!of!the!Universe!!
BAO!
Photons coupled to baryons
If baryons are ~1/6 of the dark matter these baryonic oscillations should leave some imprint in the dark matter distribution (gravity is the coupling)
Observe photons
See dark matter
What mechanism generated the primordial perturbations?
Horizon problem
Flatness problem The shape of the primordial power spectrum encloses information on the shape of the inflaton potential (CMB+Large scale structure) The spectrum of these perturbations will be ~ a power law: different models of inflation predict slightly different power laws, but all close to scale invariant ..
The energy scale of inflation is given by primordial tensor modes amplitude (CMB polarization!)
Inflation generates next to Gaussian perturbations: quantum fluctuations stretched to become classical by the expansion. The mechanism is similar to Hawkings radiation. (The event horizon being the complementary concept to the particle horizon…)
McMahon adapted by Peiris
The Future is Bright
Carbone et al 2011
Detailed errors depend on what assumptions about underlying cosmology one is willing to make
Σ
Forecasts for Euclid
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