Ignacy Sawicki Université de Genève Understanding Dark Energy

Making Sense of the Sky 18 September 2015 XXXV Physics in Collisions 2015, University of Warwick Image credit: NASA and ESA

Making Sense of the Sky 18 September 2015 XXXV Physics in Collisions 2015, University of Warwick Redshift

Ordering by redshift 18 September 2015 XXXV Physics in Collisions 2015, University of Warwick Image credit: Ivo Labbé

Use Standard Candles to Map 18 September 2015 XXXV Physics in Collisions 2015, University of Warwick

Use Standard Candles to Map 18 September 2015 XXXV Physics in Collisions 2015, University of Warwick

First Attempt at Model  Copernican Principle: here is not special Universe grossly homogeneous and isotropic  Gravity is General Relativity  Matter non-relativistic 18 September 2015 XXXV Physics in Collisions 2015, University of Warwick

First Attempt at Model: FAIL 18 September 2015 XXXV Physics in Collisions 2015, University of Warwick From D. Huterer Dimmer

18 September 2015 XXXV Physics in Collisions 2015, University of Warwick (stars 0.4%, gas 4.6%) Planck 2015

Is the Universe fooling us? 18 September 2015 XXXV Physics in Collisions 2015, University of Warwick

Is the Universe fooling us? 18 September 2015 XXXV Physics in Collisions 2015, University of Warwick Acceleration detected at 64σ

But is it actually Λ? 18 September 2015 XXXV Physics in Collisions 2015, University of Warwick Alternatives to Λ must be dynamical: search for time- and scale-dependence

ΛCDM as Null Hypothesis 18 September 2015 XXXV Physics in Collisions 2015, University of Warwick Planck 2015 Background close to ΛCDM

CMB is Gravitational Collapse 18 September 2015 XXXV Physics in Collisions 2015, University of Warwick gravitational collapse Initial conditions (inflation) Galaxy formation Vacuum in quasi-de Sitter (nearly) scale invariant Gaussian fluctuations Planck 2015

Dark Energy Changes Growth 18 September 2015 XXXV Physics in Collisions 2015, University of Warwick ΛCDM Dynamic al DE Snowmass Report 1309:5385

Use Structure to Probe Gravity/DE 18 September 2015 XXXV Physics in Collisions 2015, University of Warwick SDSS/BOSS SDSS/BOSS DR10

Redshift-Space Distortions 18 September 2015 XXXV Physics in Collisions 2015, University of Warwick Real space Redshift space Samushia et al. (2013)/BOSS Kaiser (1985)

Redshift-Space Distortions  Galaxy velocities tend to be lower than ΛCDM would imply 18 September 2015 XXXV Physics in Collisions 2015, University of Warwick Ruiz & Huterer (2014)

Weak Lensing 18 September 2015 XXXV Physics in Collisions 2015, University of Warwick

Is everything OK with ΛCDM? 18 September 2015 XXXV Physics in Collisions 2015, University of Warwick Weak Lensing (CFHTLeNS, Heymans 2012) + Distances Clusters (Planck 2013) CMB (Planck 2013) + Distances Probability Density

CMB Lensing: Smooths Peaks 18 September 2015 XXXV Physics in Collisions 2015, University of Warwick Planck: Ade et al. (2015)

The Takeaway  Dark energy is not going away  ΛCDM fits, but maybe first tensions are beginning to appear Power seems to be lacking in many probes of growth  It could well end up being other physics Massive neutrinos can have similar physics  Caveat emptor: All cosmological probes sensitive only to gravity; cannot say anything direct about composition 18 September 2015 XXXV Physics in Collisions 2015, University of Warwick

Watch this Space! 18 September 2015 XXXV Physics in Collisions 2015, University of Warwick Credit: D. Huterer

18 September 2015 XXXV Physics in Collisions 2015, University of Warwick THANK YOU!

w is not an observable 18 September 2015 XXXV Physics in Collisions 2015, University of Warwick Kunz (2007)

Scale-Dependent Growth Rate 18 September 2015 XXXV Physics in Collisions 2015, University of Warwick

BAO : SDSS vs Euclid Distance-redshift relation moves P(k) EUCLID expected SDSS today 0.7<z< <z<0.5

Measuring shear in next generation wide field cosmic shear surveys