Cosmology in the Time of Dark Energy Lecture

Cosmology in the Time of Dark Energy Lecture 1 Ignacy Sawicki CEICO, Institute of Physics, CAS, Prague ceico

Rough Outline � Main assumptions in cosmology � Acceleration: how robust? � What can we know without GR? � Main aim: lay out the logic/assumptions behind what we do 20 July 2018 4 th Cosmology School, UJ

Expt. Physics vs 20 July 2018 4 th Cosmology School, UJ Cosmology

Making Sense of the Sky � 20 July 2018 4 th Cosmology School, UJ

Making Sense of the Sky 20 July 2018 4 th Cosmology School, UJ

Making Sense of the Sky Redshift 20 July 2018 4 th Cosmology School, UJ

Ordering by redshift 20 July 2018 4 th Cosmology School, UJ Image credit: Ivo Labbé

Use Standard Candles to Map 20 July 2018 4 th Cosmology School, UJ

SN Ia: Universal Objects Image credit: D. Butler 20 July 2018 4 th Cosmology School, UJ

Use Standard Candles to Map 20 July 2018 4 th Cosmology School, UJ

First Attempt at a Model � The Copernican Principle: here is not special Isotropy 20 July 2018 Homogeneity 4 th Cosmology School, UJ

First Attempt at a Model � The Copernican Principle: here is not special Isotropy Homogeneity Planck (2015) 20 July 2018 Wiggle. Z: Scrimgeur et al. (2012) 4 th Cosmology School, UJ

First Attempt at a Model � Hubble parameter 20 July 2018 4 th Cosmology School, UJ

First Attempt at a Model 2. Composition: slowly-moving or virialised objects Late universe comprises mostly nonrelativistic matter sources (dust) 20 July 2018 4 th Cosmology School, UJ

First Attempt at a Model 3. Theory of gravity: General Relativity Monica Witt 20 July 2018 4 th Cosmology School, UJ

From D. Huterer Dimmer First Attempt at Model: FAIL 20 July 2018 4 th Cosmology School, UJ

Conservation of Energy � 20 July 2018 4 th Cosmology School, UJ

How to increase distances? � 20 July 2018 4 th Cosmology School, UJ

Planck 2018 COMPOSITION OF UNIVERSE IF ΛCDM Dark Matter 26% Cosmological Constant 69% Baryons 5% (stars 0. 4%, gas 4. 6%) 20 July 2018 4 th Cosmology School, UJ

Is the Universe fooling us? � 20 July 2018 4 th Cosmology School, UJ

The FLRW Lightcone 20 July 2018 4 th Cosmology School, UJ

The inhomogeneous alternative � 20 July 2018 4 th Cosmology School, UJ

Is the Universe fooling us? Acceleration detected at 64σ 20 July 2018 4 th Cosmology School, UJ

Summary 1: Acceleration � Distances purely cosmography: � Need EM and metric � No theory of gravity � Assumption 1: sources do not evolve in time � Copernican principle: we are not in a special place � This is enough to show there is acceleration � To predict/interpret need to models � Composition: late universe is made of slowly moving stuff � Theory of gravity to link stuff to metric 20 July 2018 4 th Cosmology School, UJ

So, what is it? 20 July 2018 4 th Cosmology School, UJ

The cosmological constant � 20 July 2018 4 th Cosmology School, UJ

The cosmological constant e. g. Jerome Martin (2012) � 20 July 2018 4 th Cosmology School, UJ

Maybe it’s not stuff, but gravity? Baker, Psaltis, Skordis (2015) Binary PSR Solar System 20 July 2018 4 th Cosmology School, UJ

Tenets of Modifying Gravity � Accept Copernican Principle: universe is FRW with small fluctuations � Let go of Einstein equations: replace them with what? � Accept standard inflationary initial conditions: why is this here? 20 July 2018 4 th Cosmology School, UJ

Initial Conditions vs Transfer Fns Einstein + Boltzmann eqs Verde & Peiris (2008) Planck (2015) Einstein + Boltzmann eqs 20 July 2018 4 th Cosmology School, UJ Pratten (2016)

Tenets of Modifying Gravity � Accept Copernican Principle: universe is FRW with small fluctuations � Let go of Einstein equations: replace them with what? � Accept standard inflationary initial conditions: why is this here? 20 July 2018 4 th Cosmology School, UJ

Modify Friedmann Eq � This is not a model… 20 July 2018 4 th Cosmology School, UJ

Measure Distances: Cosmography Supernovae Image: HSR Baryon Acoustic Oscillations Image: Z. Rostomian, LBNL 20 July 2018 4 th Cosmology School, UJ

So we constrain the Eo. S. Or? Planck: Ade et al. (2013) Planck + WP w Planck + WP + BAO 20 July 2018 4 th Cosmology School, UJ

But w is not an observable � 20 July 2018 4 th Cosmology School, UJ Kunz (2007)

Andrew Liddle 20 July 2018 4 th Cosmology School, UJ

Andrew Liddle Dark Matter 20 July 2018 Dark Energy 4 th Cosmology School, UJ

Andrew Liddle 20 July 2018 Dark Matter Dark Energy Clusters Unclustered 4 th Cosmology School, UJ

Andrew Liddle 20 July 2018 Dark Matter Dark Energy Clusters Clustering 4 th Cosmology School, UJ

Distances consistent with ΛCDM Zhao et al. (2018) BOSS DR 14 20 July 2018 4 th Cosmology School, UJ

Distances consistent with ΛCDM Planck (2018) 20 July 2018 4 th Cosmology School, UJ

Measuring the Hubble rate today W. Freedman 20 July 2018 4 th Cosmology School, UJ

H 0 is not observable � 1 --5 December 2014 X Mexican School on Gravitation Marra et al. (2013)

Summary 2: c. c. and background � 20 July 2018 4 th Cosmology School, UJ