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Modified Gravity at Dome A

Modified Gravity at Dome A. Dark Energy & Modified Gravity. Acceleration of Universe Background level Evolution of expansion: H(a), w(a) degeneracy: DE & MG Perturbation level Evolution of inhomogeneity: G(a), G(a, k), Phi, Psi… Smoothing energy component or modified gravity?

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Modified Gravity at Dome A

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  1. Modified Gravity at Dome A

  2. Dark Energy & Modified Gravity • Acceleration of Universe • Background level • Evolution of expansion: H(a), w(a) • degeneracy: DE & MG • Perturbation level • Evolution of inhomogeneity: G(a), G(a, k), Phi, Psi… • Smoothing energy component or modified gravity? • Scalar field • F(R), DGP, TeVeS,

  3. Growth of LSS • Growth of LSS • Expansion: H(a) • consistency relation: H_growth vs. H_expansion • Metric perturbation:

  4. Growth of LSS • Modified Gravity • H(a) • Modified Poisson equation. • G_eff • Parametrization • Growth index (scale-independent)

  5. Weak Lensing • convergence power (cross) spectrum • rich information (power spectrum, cross-spectrum)‏ • photo-z error

  6. standard ruler Galaxy Survey • Spectroscopic survey • δ field • Growth factor G(z) • v field • (redshift distortion) • β~ dlnG/dlna

  7. A sensitive measure of gravity • Spectroscopic redshift surveys • Measure beta from the anisotropy • Measure galaxy bias • Obtain f Current measurements Guzzo et al. 2008 Acquaviva et al. 2008 2009 XuGuangqi-Galieo conference

  8. Type IaSupernovaes • Standard Candle • variation of SN peak L (after the standardization)‏ • photo-z error (without spectrum)‏ • z-dependent peak L (e.g. SN evolution, extinction)‏

  9. Clusters Number Count • mass of clusters are not measured directly (except for WL)‏ • SZ flux decrement, X-ray temperature, gas mass • mass selection function • complex baryon physics (hydrodynamics, galaxies formation)‏

  10. Preliminary plan • number distribution • angular density

  11. Preliminary plan • BAO • Spectroscopic survey • Photometric survey

  12. Supernovae Preliminary plan • 200 SNIa/year/deg^2 available for z<1.2 (limit for ground experiment)‏ • SN1: 50 /y/deg^2 • SN2: 100 /y/deg^2 • Systematics (Nuisance parameters): • photo-z error • N_c: # of spectra for calibration • absolute magnitude • quadratic offset

  13. Preliminary plan • Weak Lensing (same as Sun lei & Zhao Gongbo)‏

  14. Preliminary plan • Clusters Count

  15. MG at Dome A

  16. Genus of LSS • Genus • Gaussian fluctuation: • 3D (δ) • 2D (weak lensing, κ)

  17. Genus Amplitude —— Standard Ruler • Resistant against: • Bias, redshift distortion, weak nonliearity. • In GR • Invariant amplitude. • Standard ruler • In MG • Introduce new scale-dependence • time-varying • Complementaryto growth rate of matter fluctuation. • Sensitive to scale-dependent modification at sub-horizon scale.

  18. Genus of MG Fisher calculation:

  19. Testing the (generalized) Poisson Equation ? = from peculiar velocity Gravitational lensing Galaxy redshifts to recover redshift information (2D ->3D) 2009 XuGuangqi-Galieo conference

  20. EG will be measured to 1% level accuracy within two decades • Promising to detect one percent level deviation from general relativity+canonical dark energy model (if systematics can be controlled)! LCDM f(R) DGP MOND/TeVeS ZPJ et al. 2007 2009 XuGuangqi-Galieo conference

  21. One can further construct an estimator ofLensing: Φ-Ψ; Peculiar velocity: Ψ DGP dark energy with anisotropic stress • eta can be measured to 10% accuracy. • Errors in eta is larger than errors in E_G • Even so, eta can have stronger discriminating power, in some cases. • η of DGP differs significantly from that of LCDM. (EG of DGP is very close to that of LCDM.) • eta and E_G are complementary • DGP with high Omega_m MOND TeVeS ZPJ et al. 2008 SKA forecast 2009 XuGuangqi-Galieo conference

  22. Thanks

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