Modified Gravity at Dome A Dark Energy Modified

Modified Gravity at Dome A

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

Growth of LSS ß Growth of LSS Þ Expansion: H(a) � Þ consistency relation: Metric perturbation: H_growth vs. H_expansion

Growth of LSS ß Modified Gravity Þ Þ H(a) Modified Poisson equation. � ß G_eff Parametrization Þ Growth index (scale-independent)

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

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

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 7 2009 Xu. Guangqi-Galieo conference

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

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

Preliminary plan number distribution angular density

Preliminary plan BAO Spectroscopic survey Photometric survey

Preliminary plan ß Supernovae 200 SNIa/year/deg^2 available for z<1. 2 (limit for ground experiment) SN 1: 50 /y/deg^2 SN 2: 100 /y/deg^2 Systematics (Nuisance parameters): photo-z error N_c: # of spectra for calibration absolute magnitude quadratic offset

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

Preliminary plan Clusters Count

MG at Dome A

Genus of LSS ß Genus Þ Gaussian fluctuation: � 3 D � 2 D (weak lensing, κ) (δ)

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

Genus of MG ß Fisher calculation:

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

• 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/Te. Ve. S ZPJ et al. 2007 2009 Xu. Guangqi-Galieo conference 20

One can further construct an estimator of Lensing: Φ-Ψ; Peculiar velocity: Ψ DGP dark energy with anisotropic stress • 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 Te. Ve. S SKA forecast • eta can be measured to 10% accuracy. ZPJ et al. 2008 21 2009 Xu. Guangqi-Galieo conference

Thanks