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

Spin filtering implemented through Rashba and weak magnetic modulations

We present two theoretical schemes for spin filters in one-dimensional semiconductor quantum wires with spatially modulated Rashba spin-orbit coupling (SOC) as well as weak magnetic potential. For case I, the SOC is periodic and the weak magnetic potential is applied uniformly along the wire. Full spin polarizations with opposite signs are obtained within two separated energy intervals. For case II, the weak magnetic potential is periodic while the SOC is uniform. An ideal negative/positive switching effect for spin polarization is realized by tuning the strength of SOC. The roles of SOC, magnetic potential, and their coupling on the spin filtering are analyzed.Comment: 4 pages, 4 figure

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

Asymptotic behaviour of zeros of bieberbach polynomials

AbstractLet Ω be a simply-connected domain in the complex plane and let πn denote the nth-degree Bieberbach polynomial approximation to the conformal map f of Ω onto a disc. In this paper we investigate the asymptotic behaviour (as n→σ) of the zeros of πn, πn′ and also of the zeroes of certain closely related rational approximants to f. Our result show that, in each case, the distribution of the zeros is governed by the location of the singularities of the mapping function f in C⧹ω, and we present numerical examples illustrating this

Breaking scale invariance from a singular inflaton potential

In this paper we break the scale invariance of the primordial power spectrum of curvature perturbations of inflation. Introducing a singular behaviour due to spontaneous symmetry breaking in the inflaton potential, we obtain fully analytic expressions of scale dependent oscillation and a modulation in power on small scale in the primordial spectrum. And we give the associated cosmic microwave background and matter power spectra which we can observe now and discuss the signature of the scale dependence. We also address the possibility of whether some inflationary model with featured potential might mimic the predictions of the scale invariant power spectrum. We present some examples which illustrate such degeneracies.Comment: 20 pages, 9 figures; Discussion expanded and references added; Miscellaneous typos correcte