Model independent analysis of dark energy I: Supernova fitting result

The nature of dark energy is a mystery to us. This paper uses the supernova data to explore the property of dark energy by some model independent methods. We first Talyor expanded the scale factor $a(t)$ to find out the deceleration parameter $q_0<0$. This result just invokes the Robertson-Walker metric. Then we discuss several different parameterizations used in the literature. We find that $\Omega_{\rm DE0}$ is almost less than -1 at $1\sigma$ level. We also find that the transition redshift from deceleration phase to acceleration phase is $z_{\rm T}\sim 0.3$.Comment: v4: minor corrections, main results unchanged. 10 figures, use revtex, 7 pages, v5: refences updated, will appear in Class. Quantum Gra

Radiative Corrections to the Inflaton Potential as an Explanation of Suppressed Large Scale Power in Density Perturbations and the Cosmic Microwave Background

The Wilkinson Microwave Anisotropy Probe microwave background data suggest that the primordial spectrum of scalar curvature fluctuations is suppressed at small wavenumbers. We propose a UV/IR mixing effect in small-field inflationary models that can explain the observable deviation in WMAP data from the concordance model. Specifically, in inflationary models where the inflaton couples to an asymptotically free gauge theory, the radiative corrections to the effective inflaton potential can be anomalously large. This occurs for small values of the inflaton field which are of the order of the gauge theory strong coupling scale. Radiative corrections cause the inflaton potential to blow up at small values of the inflaton field. As a result, these corrections can violate the slow-roll condition at the initial stage of the inflation and suppress the production of scalar density perturbations.Comment: 20 pages, 2 figures, v2: refs added, v3: JCAP versio

Can we predict Λ\Lambda for the Non-SUSY sector of the Landscape ?

We propose a new selection criteria for predicting the most probable wavefunction of the universe that propagates on the string landscape background, by studying its dynamics from a quantum cosmology view. Previously we applied this proposal to the $SUSY$ sector of the landscape. In this work the dynamic selection criterion is applied to the investigation of the non-$SUSY$ sector.In the absence of detailed information about its structure, it is assumed that this sector has a stochastic distribution of vacua energies.The calculation of a distribution probability for the cosmological constants $\Lambda_{eff}$, obtained from the density of states $\rho$, indicates that the most probable wavefunction is peaked around universes with zero $\Lambda_{eff}$. In contrast to the {\it extended wavefunction} solutions found for the $SUSY$ sector with $N$-vacua and peaked around $\Lambda_{eff}\simeq \frac{1}{N^2}$, wavefunctions residing on the non-$SUSY$ sector exhibit {\it Anderson localization}.Although minisuperspace is a limited approach it presently provides a dynamical quantum selection rule for the most probable vacua solution from the landscape.Comment: 6 pages, 1 figur