!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