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Primordial perturbations and precision cosmology from the Cosmic Microwave Background Antony Lewis CITA, University of Toronto http://cosmologist.info Evolution of the universe Opaque Transparent Hu & White, Sci. Am., 290 44 (2004) Perturbation evolution Early universe to last scattering Contributions to cosmology • • • • • • • • • • Constraints on primordial perturbations Observable primordial isocurvature and vector modes (identification and predictions) CMB polarization analysis: solution to E/B mode separation problem Simulation and parameter estimation with CMB lensing Ab initio quantum gravity calculation of primordial perturbations and CMB in closed instanton model Fastest and most accurate code for calculating CMB anisotropy power spectra from initial conditions + parameters (CAMB) Methods for fast Monte Carlo parameter estimation from cosmological data (CosmoMC code) Accurate parameter constraints from CMB + other data (e.g. galaxy lensing) Evolution of dark matter and dark energy perturbations: efficient methods, numerical predictions, parameter constraints CMB signatures of primordial magnetic fields CMB temperature power spectrum Primordial perturbations + later physics Redhead et al: astro-ph/0402359 Primordial Perturbations fluid at redshift < 109 • Photons • Neutrinos • Baryons + electrons • Cold Dark Matter • Dark energy probably negligible early on General regular linear primordial perturbation General regular perturbation Scalar Adiabatic -isocurvature- (observed) Matter density Cancelling matter density (unobservable) Neutrino density (contrived) Neutrino velocity (very contrived) Vector Neutrino vorticity (very contrived) Tensor Gravitational waves + irregular modes, neutrino n-pole modes, n-Tensor modes Rebhan and Schwarz: gr-qc/9403032 + other possible components, e.g. defects, magnetic fields, exotic stuff… Adiabatic modes What is the primordial power spectrum? Bridle, Lewis, Weller, Efstathiou: astro-ph/0302306 Isocurvature modes Curvaton model? Gordon, Lewis: astro-ph/0212248 Primordial Gravitational Waves (tensor modes) • Well motivated by some inflationary models - Amplitude measures inflaton potential at horizon crossing - distinguish models of inflation • Observation would rule out other models - ekpyrotic scenario predicts exponentially small amplitude - small also in many models of inflation, esp. two field e.g. curvaton • Weakly constrained from CMB temperature anisotropy Look at CMB polarization E and B polarization • E polarization from scalar, vector and tensor modes • B polarization only from vector and tensor modes B is ‘smoking gun’ for primordial vector and tensor modes Vector and Tensor B mode spectrum Non-linear scalar modes also give small B signal B-modes Lewis: astro-ph/0403583 Polarization complications • E/B mixing • Lensing of the CMB E/B mixing and solution Underlying B-modes Part-sky mix with scalar E Observation Separation method Lewis: astro-ph/0305545 Weak lensing of the CMB Last scattering surface Inhomogeneous universe - photons deflected Observer • Lensing B-modes • Changed power spectra Lewis: PRD submitted; Challinor, Lewis: in preparation Future work • Cosmological parameters from forthcoming CMB data (Planck, Clover, etc.) + galaxy lensing etc. • Reconstruction of initial power spectrum and constraints on inflation and other models • Improved treatment of CMB lensing: lensing reconstruction, B-mode cleaning, un-lensing the temperature • Statistical methods: Monte Carlo methods for CMB map-making, polarization analysis and weak lensing • Cosmology from 21cm and galaxy weak lensing (+CMB) • Tests of new physics, string theory, etc; early universe models • New things… Parameter estimation: sampling from P(parameters|data) Samples in 6D parameter space CMB data alone color = optical depth Plot number density of samples as function of parameters e.g. CMB+galaxy lensing +BBN prior CosmoMC code at http://cosmologist.info/cosmomc Lewis, Bridle: astro-ph/0205436 Contaldi, Hoekstra, Lewis: astro-ph/0302435 Conclusions • CMB contains lots of useful information! - primordial perturbations + well understood physics (cosmological parameters) • Precision cosmology - sampling methods used to constrain many parameters with full posterior distribution • Currently no evidence for any deviations from standard near scale-invariant purely adiabatic primordial spectrum • B-mode polarization - primordial gravitational waves + vector modes: - energy scale of inflation - rule out most ekpyrotic and pure curvaton/ inhomogeneous reheating models and others • Weak lensing of CMB : - B-modes potentially confuse primordial signals - Have to account for effect on power spectra • Foregrounds, systematics, etc, may make things much more complicated!