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Eric Linder University of California, Berkeley Lawrence Berkeley National Lab

Seeing Darkness: The New Cosmology. Eric Linder University of California, Berkeley Lawrence Berkeley National Lab. New Frontiers. Beyond Einstein: What happens when gravity is no longer an attractive force?. Scientific American.

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Eric Linder University of California, Berkeley Lawrence Berkeley National Lab

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  1. Seeing Darkness:The New Cosmology Eric Linder University of California, Berkeley Lawrence Berkeley National Lab

  2. New Frontiers Beyond Einstein: What happens when gravity is no longer an attractive force? Scientific American Discovery(SCP,HiZ 1998):70% of the universe acts this way! Fundamentally new physics. Cosmology is the key.

  3. Cosmic Coincidence Size=2 Size=1/4 Size=1/2 Size=4 Is this mysterious dark energy the original cosmological constant , a quantum zeropoint sea? Think of the energy in  as the level of the quantum “sea”. At most times in history, matter is either drowned or dry. Dark energy Matter Today

  4. On Beyond ! We need to explore further frontiers in high energy physics, gravitation, and cosmology. New quantum physics?Does nothing weigh something?Einstein’s cosmological constant, Quintessence, M/String theory New gravitational physics? Is nowhere somewhere?Quantum gravity, supergravity, extra dimensions? We need new, highly precise data

  5. Cosmic Archaeology Supernovae: direct probe of cosmic expansion Time: 30-100% of present age of universe (When you were 12-40 years old) Cosmic matter structures: less direct probes of expansion Pattern of ripples, clumping in space, growing in time. 3D survey of galaxies and clusters - Lensing. CMB: direct probe of quantum fluctuations Time: 0.003% of the present age of the universe. (When you were 0.003% of your present age, you were 2 cells big!)

  6. Standard Candles Brightness tells us distance away (lookback time) Redshift measured tells us expansion factor (average distance between galaxies)

  7. What makes SN measurement special?Control of systematic uncertainties Each supernova is “sending” us a rich stream of information about itself. Images Nature of Dark Energy Redshift & SN Properties Spectra data analysis physics

  8. Astrophysical Uncertainties For accurate and precision cosmology, need to identify and control systematic uncertainties.

  9. Beyond Gaussian No extinction (perfect)Extinction correctionW With AV biasWith AV+RV bias Current data quality Linder & Miquel 2004 Gravitational lensing: Few hi z SN  poor PDF sampling Flux vs. magnitude bias Holz & Linder 2004 Extinction bias: One sided prior biases results Dust correction crucial; need NIR

  10. Gravitational Lensing Gravity bends light… - we can detect dark matter through its gravity, - objects are magnified and distorted, - we can view “CAT scans” of growth of structure

  11. Gravitational Lensing Lensing measures the mass of clusters of galaxies. By looking at lensing of sources at different distances (times), we measure the growth of mass. Clusters grow by swallowing more and more galaxies, more mass. Acceleration - stretching space - shuts off growth, by keeping galaxies apart. So by measuring the growth history, lensing can detect the level of acceleration, the amount of dark energy.

  12. Dark Energy – The Next Generation HDF GOODS wide 9000 the Hubble Deep Field plus 1/2 Million  HDF • Redshifts z=0-1.7 • Exploring the last 10 billion years • 70% of the age of the universe deep colorful Both optical and infrared wavelengths to see thru dust. SNAP: Supernova/Acceleration Probe

  13. Exploring Dark Energy

  14. Quintessence Scalar field  with LagrangianL = (1/2)()2 - V() . Energy density  = (1/2)  2 + V() Pressure p = (1/2)  2 - V() . Einstein gravity says gravitating mass +3p, so acceleration if equation of state ratio w = p/ < -1/3 w = (K-V) / (K+V) Potential energy dominates (slow roll): V >> K  w = -1 Kinetic energy dominates (fast roll): K >> V  w = +1 (a) ~ e3dln a [1+w(a)] ~ a-3(1+w) Dynamics important! Value and running: w, w=wa /2Equation of state model w(a) = w0+wa(1-a)

  15. Equation of State . . .    Reconstruction from EOS: (a) =  c exp{ 3 dln a [1+w(z)] } (a) = dln a H-1 sqrt{ (a) [1+w(z)] } V(a) = (1/2) (a) [1-w(z)] K(a) = (1/2)2 = (1/2) (a) [1+w(z)] But, ~ [(1+w)] ~ (1+w) HMp So if 1+w << 1,then  ~ /H << Mp. It is very hard to directly reconstruct the potential.

  16. Dynamics of Quintessence ¨ ˙  + 3H = -dV()/d • Equation of motion of scalar field • driven by steepness of potential • slowed by Hubble friction • Broad categorization -- which term dominates: • field rolls but decelerates as dominates energy • field starts frozen by Hubble drag and then rolls • Freezers vs. Thawers

  17. Limits of Quintessence Distinct, narrow regions of w-w Works for: linear, quadratic, quartic, PNGB, -n,SUGRA, exponential Caldwell & Linder 2005 PRL; astro-ph/0505494 Entire “thawing” region looks like wconstant= -1±0.05. Need w experiments with  (w) ≈2(1+w).

  18. Phantoms without Ghosts 5 Ways to have w < -1 without “bad” physics: What do you mean bad? Imagine all life as you know it stopping instantaneously and every molecule in your body exploding at the speed of light.-- Ghostbusters • Vacuum metamorphosis Parker & Raval 1999: PRD 60, 063512 • Coupling: weff=w-/(3H) Turner 1985, Linder 1988, Linder 2005 • Curvature: total>1 (k>0) +   weff < -1 Linder 0508333 • Climbing field (or k-essence) Csaki, Kaloper, Terning 0507148 • Two components, e.g. brane+ Lue & Starkman 2004, CKT 2005

  19. Expansion History Observations that map out expansion history a(t), or w(a), tell us about the fundamental physics of dark energy. Alterations to Friedmann framework  w(a) Suppose we admit our ignorance: H2 = (8/3) m + H2(a) Effective equation of state: w(a) = -1 - (1/3) dln (H2) / dln a Modifications of the expansion history are equivalent to time variation w(a).Period. gravitational extensions or high energy physics

  20. Expansion History For modifications H2, define an effective scalar field with V = (3MP2/8) H2 + (MP2H02/16) [ d H2/d ln a] K = - (MP2H02/16) [ d H2/d ln a] Example:H2 = A(m)n w = -1+n Example:H2 = (8/3) [f(m) - m] w= -1 + (f-1)/[ f/m - 1 ]

  21. Revealing Physics • Time variation w(z) is a critical clue to fundamental physics. • Modifications of the expansion history = w(z). • But need an underlying theory - ? beyond Einstein gravity? • Growth history and expansion history work together. Linder 2004, Phys. Rev. D 70, 023511 cf. Lue, Scoccimarro, Starkman Phys. Rev. D 69 (2004) 124015 for braneworld perturbations

  22. Physics of Growth Growthg(a)=(/)/adepends purely on the expansion history H(z) -- andgravity theory. Expansion effects via w(z), but separate effects of gravity on growth. g(a) = exp { 0ad ln a [m(a)-1] } Linder 2005 PRD; astro-ph/0507263 Growth index= 0.55+0.05[1+w(z=1)] Works to 0.05 – 0.2%!

  23. Growth and Expansion With  as free fit parameter, we can test framework, and the origin of dark energy. Keep expansion history as w(z), growth deviation from expansion by . New paradigm: To reveal the origin of dark energy, measure w, w, and . e.g. use SN+WL.

  24. Going Nonlinear This gives a high accuracy approach to growth factor, i.e. linear mass power spectrum. Can we get high accuracy for the nonlinear power spectrum? Linder & White, Phys. Rev. D Rapid; astro-ph/0508401 • New prescription: • Normalize gtoday, i.e. scale by 8. • Match different cosmologies’ (i.e. w’s) growth at z=1.8; this determines M. • Fix h by using invariant Mh2. It works!Relative precision onPkfull to <1.5%over z=0-3. NB: fit functions were only good to ~10% -- for .

  25. Going Nonlinear Efficient generation of grid of dark energy cosmologies [w(z)] New discovery:growth  dlss So our prescription automatically “includes” CMB priors!

  26. Today’s Inflation superacceleration SNAP constraints R = (1-q)/2 Map the expansion history precisely and see the transition from acceleration todeceleration. Test the cosmology framework – alternative gravitation, higher dimensions, etc.

  27. The Next Physics The Standard Model gives us commanding knowledge about physics -- 5% of the universe (or 50% of its age). What is dark energy? Will the universe expansion accelerate forever? Does the vacuum decay? Phase transitions? How many dimensions are there? How are quantum physics and gravity unified? What is the fate of the universe? That 5% contains two fundamental forces and a zoo of elementary particles. What will we learn from the dark sector?! How can we not seek to find out?

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