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Primordial perturbations and precision cosmology from the Cosmic Microwave Background Antony Lewis CITA, University of Toronto

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Presentation on theme: "Primordial perturbations and precision cosmology from the Cosmic Microwave Background Antony Lewis CITA, University of Toronto"— Presentation transcript:

1 Primordial perturbations and precision cosmology from the Cosmic Microwave Background Antony Lewis CITA, University of Toronto

2 Hu & White, Sci. Am., 290 44 (2004) Evolution of the universe Opaque Transparent

3 Perturbation evolution Early universe to last scattering

4 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

5 Redhead et al: astro-ph/0402359 CMB temperature power spectrum Primordial perturbations + later physics

6 Primordial Perturbations fluid at redshift < 10 9 Photons Neutrinos Baryons + electrons Cold Dark Matter Dark energy probably negligible early on

7 General regular perturbation Scalar Adiabatic (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… General regular linear primordial perturbation -isocurvature-

8 Bridle, Lewis, Weller, Efstathiou: astro-ph/0302306 Adiabatic modes What is the primordial power spectrum? Isocurvature modes Curvaton model? Gordon, Lewis: astro-ph/0212248

9 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

10 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

11 Vector and Tensor B mode spectrum Lewis: astro-ph/0403583 B-modes Non-linear scalar modes also give small B signal

12 Polarization complications E/B mixing Lensing of the CMB

13 Underlying B-modesPart-sky mix with scalar E Recovered B modes map of gravity waves Separation method Observation Lewis: astro-ph/0305545 E/B mixing and solution

14 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

15 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…

16 CMB data alone color = optical depth Samples in 6D parameter space Parameter estimation: sampling from P(parameters|data)

17 e.g. CMB+galaxy lensing +BBN prior Plot number density of samples as function of parameters CosmoMC code at Lewis, Bridle: astro-ph/0205436 Contaldi, Hoekstra, Lewis: astro-ph/0302435

18 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!

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