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From “Precision Cosmology” to “Cosmology under revision”

Carlos Hernández-MonteagudoCentro de Estudios de Física del Cosmos de Aragón

[CEFCA]Spain, July 14th 2020

HITO y RETOS

K. Mack

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Once upon a time … not so long ago (from 1997 upto ~2018), there was, amongst cosmologists, a so-calledConcordance cosmological model upon which low redshiftand high redshift cosmological observations agreed ...

3WMAPmission

The Cosmic Microwave Background (CMB) provided an image of our universe at its childhood thatwas consistent with a flat LCDM scenario, and which wasalso consistent with cosmological observations at recentepochs …

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K. Mack

The Cosmic Microwave Background (CMB) provided an image of our universe at its childhood thatwas consistent with a flat LCDM scenario, and which wasalso consistent with cosmological observations at recentepochs …

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Silde from A. Riess (July 2019)

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Kowalski 2008

Cosmological“concordance” Model

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WMAP,2010

Planck 2018

However, when observations at either side of thehistory of the universe increased their precision,

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WMAP,2010

Planck 2018

However, when observations at either side of thehistory of the universe increased their precision,

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However, when observations at either side of thehistory of the universe increased their precision, tensions(and maybe more than tensions) have arosen:

Di Valentino+20

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The most significant sources of tensionare:

H0 measurements at low and high redshifts:

(3 – 5 σ, tension → problem, crisis?)

The amplitude of CMB lensing The amplitude of density perturbations at low redshifts (σ

8 )

(3 σ tension)

The non-flat curvature of the universe (Ωk = -0.04)

(3 σ tension)

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Measuring the universe expansion rate H0

Indirectly, using the angleprojected by the soundhorizon at recombination atz~1100 via CMBobservations, and at z~0.5via clustering measurementsof the Large Scale Structure(LSS)

Directly, by (1) usingstandard candles (SNIa),and calibrating their distancewith Cepheids in LMC,Detached Eclipsing Binaries(DEB) in LMC, galacticparallaxes, the tip of the RedGiant Branch (TRGB), or (2)gravitational lensing atintermediate redshifts (z~0.5)

V. Bonvin, for Verde, Tommaso, & Riess 2019

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Measuring the universe expansion rate H0

Pros:

Weak dependence of sound horizonon (well known) cosmologicalparameters,

Measurements based upon a modelthat is relatively simple (linear orderin perturbation theory) for CMB,mildly-non linear for LSSmeasurements

Different probes (CMB and LSS)having very different (potential)systematics yield H

0 estimates in

excellent agreement

Cons:

They are all indirect measurementsof the expansion rate that are modeldependent

Indirectly, using the angleprojected by the soundhorizon at recombination atz~1100 via CMBobservations, and at z~0.5via clustering measurementsof the Large Scale Structure(LSS)

Directly, by (1) usingstandard candles (SNIa),and calibrating their distancewith Cepheids in LMC,Detached Eclipsing Binaries(DEB) in LMC, galacticparallaxes, the tip of the RedGiant Branch (TRGB), or (2)gravitational lensing atintermediate redshifts (z~0.5)

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Measuring the universe expansion rate H0

Pros:

These are, for SNIa and SurfaceBrightness Fluctuation-basedestimates, direct measurements ofH

0 that are model independent

Lensing measurements, maser-basedH

0 measurements,, and SNIa-based

estimates, are all un-correlated,independent measurements of H

0 .

Cons: Measurements based on complex,

highly non-linear systems (Cepheids,SNIa, clusters of galaxies) whosecalibration are obtained empirically (more room for systematics)

Results from the CCHP collaborationon the TRGB significantly off fromthose of SH0ES: evidence forhidden systematics?

Indirectly, using the angleprojected by the soundhorizon at recombination atz~1100 via CMBobservations, and at z~0.5via clustering measurementsof the Large Scale Structure(LSS)

Directly, by (1) usingstandard candles (SNIa),and calibrating their distancewith Cepheids in LMC,Detached Eclipsing Binaries(DEB) in LMC, galacticparallaxes, the tip of the RedGiant Branch (TRGB), or (2)gravitational lensing atintermediate redshifts (z~0.5)

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Measuring the universe expansion rate H0

Possible solutions to this puzzle:

Systematics in CMB observations:unlikely, provided different CMBexperiments beyond Planck (like SPT,ACT) are providing very similarmeasurements of H

0

New physics! : Emerging Dark Energy(EDE), Interacting Dark Energy,Übergravity, decaying Dark Matter, Rock'n Roll models (RnR), Vacuum Dynamics, what not! – yet to be seen whether theycan satisfy, some of them (EDE, RnR)already discarded …

Systematics in the direct H0

measurements …

V. Bonvin, for Verde, Tommaso, & Riess 2019

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Measuring the universe expansion rate H0

V. Bonvin, for Verde, Tommaso, & Riess 2019

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Measuring the universe expansion rate H0

Breaking news from last

week !!

V. Bonvin, for Verde, Tommaso, & Riess 2019

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Measuring the universe expansion rate H0

V. Bonvin, for Verde, Tommaso, & Riess 2019

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Measuring the universe expansion rate H0

Birrer+ 2020, 2007.02941: TDCOSMO collaboration re-analyses cluster lensesaccounting for uncertainties in mass distribution in clusters

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Measuring the universe expansion rate H0

Birrer+ 2020, 2007.02941: TDCOSMO collaboration re-analyses cluster lensesaccounting for uncertainties in mass distribution in clusters

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Measuring the universe expansion rate H0

But even if wedrop clusterlensing …

V. Bonvin, for Verde, Tommaso, & Riess 2019

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Measuring the universe expansion rate H0

But even if wedrop clusterlensing …

V. Bonvin, for Verde, Tommaso, & Riess 2019

x

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Other (weaker) sources of tension … (at 2 – 3 σ)

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CMB gravitational lensing

CMB photons are deflected in their journey to the observer. This effect can beaccessed in two ways:

(Approach 1) Looking at non-Gaussianities induced by lensing on the smallestscales, using a 4-point function <T(n

1)T(n

2)T(n

3)T(n

4)>

(Approach 2) Looking at the 2-point function (<T(n1)T(n

2)> or angular power

spectra Cl = <a

l,m (a

l,m)* >): the impact of lensing-induced ray deflection

smears/softens the acousting peaks

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AL = 1 is what our theory predicts …

CMB 2-point function <al,m

al,m

* > = Cl (angular

power spectrum)

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CMB gravitational lensing

Problem: The amplitude of lensing inferred fromApproach 2 is about 15% higher than for Approach 1, at~3σ level) – It's like if lensing was more efficient atsmearing CMB acoustic peaks than predicted

CMB photons are deflected in their journey to the observer. This effect can beaccessed in two ways:

(Approach 1) Looking at non-Gaussianities induced by lensing on the smallestscales, using a 4-point function <T(n

1)T(n

2)T(n

3)T(n

4)>

(Approach 2) Looking at the 2-point function (<T(n1)T(n

2)> or angular power

spectra Cl = <a

l,m (a

l,m)* >): the impact of lensing-induced ray deflection

smears/softens the acousting peaks

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CMB gravitational lensing

Planck 2018

Problem: The amplitude of lensing inferred fromApproach 2 is about 15% higher than for Approach 1, at~3σ level) – It's like if lensing was more efficient atsmearing CMB acoustic peaks than predicted

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CMB gravitational lensing + lensing shear from KiDs & CFHTLenS

If CMB lensing were more efficient than what we predict, the 3σ tensionwith galaxy lensing shear would bealleviated

Di Valentino & Bridle 19

Problem: The amplitude of lensing inferred fromApproach 2 is about 15% higher than for Approach 1, at~3σ level) – It's like if lensing was more efficient atsmearing CMB acoustic peaks than predicted

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And finally, if we look at Planck 2018 only ...

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The universe does not seem flat, but hasstrong preference (~2σ) for being closed

instead of flat !

Di Valentino+20

Planck 2018

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The universe does not seem flat, but hasstrong preference (~2σ) for being closed

instead of flat !

This would solve the problem with the lensing amplitude/efficiencyand other internal anomalies in Planck data (low quadrupole,alignment of low l multipoles, etc)

Di Valentino+ 20

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The universe does not seem flat, but hasstrong preference (~2σ) for being closed

instead of flat !

But it falls apart with all other cosmologicalobservations at lower redshifts!

Di Valentino+20

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The universe does not seem flat, but hasstrong preference (~2σ) for being closed

instead of flat !

Can this be a fluke/result of chance??

Di Valentino+20

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The most significant sources of tensionare:

H0 measurements at low and high redshifts:

(3 – 5 σ, tension → problem, crisis ?)

The amplitude of CMB lensing The amplitude of density perturbations at low redshifts (σ

8 )

(3 σ tension)

The non-flat curvature of the universe (Ωk = -0.04)

(3 σ tension)

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Looking at the future …

CMB:

ACTPolSPTPolLiteBirdFuture ESA space CMB mission (?)

LSS:

EuclidDESIVera Rubin J-PASSphereXSKA

GWs

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Looking at the future …

CMB:

ACTPolSPTPolLiteBirdFuture ESA space CMB mission (?)

LSS:

EuclidDESIVera RubinJ-PASSphereXSKA

GWs

¡MUCHAS GRACIAS!