Towards a warped inflationary brane scanning

We present a detailed systematics for comparing warped brane inflation with the observations, incorporating the effects of both moduli stabilization and ultraviolet bulk physics. We explicitly construct an example of the inflaton potential governing the motion of a mobile D3 brane in the entire warped deformed conifold. This allows us to precisely identify the corresponding scales of the cosmic microwave background. The effects due to bulk fluxes or localized sources are parametrized using gauge/string duality. We next perform some sample scannings to explore the parameter space of the complete potential, and first demonstrate that without the bulk effects there can be large degenerate sets of parameters with observationally consistent predictions. When the bulk perturbations are included, however, the observational predictions are generally spoiled. For them to remain consistent, the magnitudes of the bulk effects need to be highly suppressed via fine tuning.Comment: (v1) 11 pages, 2 figures, 2 tables; (v2) more clarifications and references added; (v3) 12 pages, more discussions, to appear in Physical Review

Constraints on a new alternative model to dark energy

The recent type Ia supernova data suggest that the universe is accelerating now and decelerated in recent past. This may provide the evidence that the standard Friedmann equation needs to be modified. We analyze in detail a new model in the context of modified Friedmann equation using the supernova data published by the High-$z$ Supernova Search Team and the Supernova Cosmology Project. The new model explains recent acceleration and past deceleration. Furthermore, the new model also gives a decelerated universe in the future.Comment: 12 pages, 5 figures, use ws-ijmpd, minor changes made. In the new version, a detailed derivation of the model is give

Cosmic Mach Number: A Sensitive Probe for the Growth of Structure

In this Letter, we investigate the potential power of the Cosmic Mach Number (CMN), which is the ratio between the mean velocity and the velocity dispersion of galaxies as a function of cosmic scales, to constrain cosmologies. We first measure the CMN from 5 catalogues of galaxy peculiar velocity surveys at low redshift (0.002<z<0.03), and use them to contrast cosmological models. Overall, current data is consistent with the WMAP7 LCDM model. We find that the CMN is highly sensitive to the growth of structure on scales 0.01<k<0.1 h/Mpc in Fourier space. Therefore, modified gravity models, and models with massive neutrinos, in which the structure growth generally deviates from that in the LCDM model in a scale-dependent way, can be well differentiated from the LCDM model using future CMN data.Comment: 7 pages, matches the version accepted to JCA

Sexual Bias and Household Consumption: A Semiparametic Analysis of Engel curves in Rural China

We analyze Engel curves for nuclear households in rural China. The sample includes more than 5000 nuclear families covering nineteen out of thirty Chinese provinces. We consider expenditures on food, also subdivided into several food subcategories such as cereals, or meat and fish, and other consumption categories such as alcohol and tobacco, medical, and educational goods. We use the semiparametric partially linear model. This allows for any functional form relationship between the budget shares and total expenditures, but assumes that the demographic variables enter the model in a linear way. We correct for potential endogeneity of total expenditures. Our results suggest that there are economies of scale in families' consumption expenditure patterns. We find some differences in consumption patterns which relate to differences in gender of children, which can be seen as evidence of sexual bias related to a commonly believed existing preference for boys.