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Primordial perturbations and precision cosmology from the Cosmic Microwave Background

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).

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Primordial perturbations and precision cosmology from the Cosmic Microwave Background

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  1. Primordial perturbations and precision cosmology from the Cosmic Microwave Background Antony Lewis CITA, University of Toronto http://cosmologist.info

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

  3. Perturbation evolutionEarly 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. CMB temperature power spectrumPrimordial perturbations + later physics Redhead et al: astro-ph/0402359

  6. Primordial Perturbationsfluid at redshift < 109 • Photons • Neutrinos • Baryons + electrons • Cold Dark Matter • Dark energyprobably negligible early on

  7. General regular linear primordial perturbation -isocurvature- + 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…

  8. Adiabatic modesWhat is the primordial power spectrum? Bridle, Lewis, Weller, Efstathiou: astro-ph/0302306 Isocurvature modesCurvaton 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 Non-linear scalar modes also give small B signal B-modes Lewis: astro-ph/0403583

  12. Polarization complications • E/B mixing • Lensing of the CMB

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

  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. Parameter estimation: sampling from P(parameters|data) CMB data alonecolor = optical depth Samples in6D parameterspace

  17. Plot number density of samples as function of parameters e.g. CMB+galaxy lensing +BBN prior CosmoMC code athttp://cosmologist.info/cosmomcLewis, 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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