Testing quantum gravity effects with latest CMB observations

Inspired by quantum gravitational physics, the approach of non-commutative (NC) phase space leads to a modified dispersion relation of gravitational waves. This feature, if applied to the very early universe, gives rise to a modified power spectrum of primordial tensor perturbations with a suppression of power on large scales. We confront this phenomenon with the BICEP2 and Planck experiments, and show that inflation with the modified dispersion relation can simultaneously fit the observations better than the standard inflationary paradigm. In particular, the numerical result implies that with the latest cosmological microwave background (CMB) observations, a quantum gravity modified power spectrum of primordial tensor modes is preferred at a statistical significance of more than $3\sigma$ compared with the minimal model. Our study indicates that the potential tension between the BICEP2 and Planck data may be resolved by quantum gravity effects.Comment: 5 pages, 2 figures, comments are welcom

Large Nonlocal Non-Gaussianity from a Curvaton Brane

We use a generalized delta N formalism to study the generation of the primordial curvature perturbation in the curvaton brane scenario inspired by stringy compactifications. We note that the non-Gaussian features, especially the trispectra, crucially depend on the decay mechanism in a general curvaton scenario. Specifically, we study the bispectra and trispectra of the curvaton brane model in detail to illustrate the importance of curvaton decay in generating nonlinear fluctuations. When the curvaton brane moves nonrelativistically during inflation, the shape of non-Gaussianity is local, but the corresponding size is different from that in the standard curvaton scenario. When the curvaton brane moves relativistically in inflationary stage, the shape of non-Gaussianity is of equilateral type.Comment: 24 pages, 2 figure

Superconducting cosmic strings as sources of cosmological fast radio bursts

In this paper we calculate the radio burst signals from three kinds of structures of superconducting cosmic strings. By taking into account the observational factors including scattering and relativistic effects, we derive the event rate of radio bursts as a function of redshift with the theoretical parameters $G\mu$ and $\mathcal{I}$ of superconducting strings. Our analyses show that cusps and kinks may have noticeable contributions to the event rate and in most cases cusps would dominate the contribution, while the kink-kink collisions tend to have secondary effects. By fitting theoretical predictions with the normalized data of fast radio bursts, we for the first time constrain the parameter space of superconducting strings and report that the parameter space of $G\mu \sim [10^{-14}, 10^{-12}]$ and $\mathcal{I} \sim [10^{-1}, 10^{2}] ~ \rm{GeV}$ fit the observation well although the statistic significance is low due to the lack of observational data. Moreover, we derive two types of best fittings, with one being dominated by cusps with a redshift $z = 1.3$, and the other dominated by kinks at the range of the maximal event rate.Comment: 13 pages, 2 figures, 1 table; references update

The Aesthetic Standard of Wen: A Comparative Study of Chinese and Western Early Artworks

A comparative study of the ancient Chinese and Western artworks over the same period (from approximately 3300 B.C. to 200 B.C) shows that the dense and rich decorative patterns on the bronze wares in China represent a strong aesthetic appreciation of patterns/embellishment, while their counterparts in the West demonstrate an aesthetic orientation rooted in science, evident in nude bodies in bronze and marble. It is argued that there was a very obvious essential difference between Chinese and Western aesthetic values, and these divergent aesthetic orientations were present at the origins of the Pre-Qin and ancient Greek arts where they have been absorbed into the foundation of each culture.Komparativna študija starodavnih kitajskih in zahodnih umetniških izdelkov iz enakega obdobja (od približno 3300 do 200 p.n.š.) razkrije, da strnjeni in bogati dekorativni vzroci na kitajskih bronastih posodah predstavljajo močno estetsko vrednotenje vzorcev oz. okrasja, medtem ko izdelki na zahodu nazorno prikažejo estetsko usmerjenost, ki izvira iz znanosti, kar je jasno razvidno iz bronastih in marmornih golih teles. Članek prikazuje, daso obstajale bistvene razlike med kitajskimi in zahodnimi estetskimi vrednotami. Tovrstna raznolika estetska vrednotenja so bila prisotna že v izvorni umetnosti obdobja pred dinastijo Qin in stare Grčije, kjer so bile kot take vsebovane v osnovanju posamičnekulture

Effect of Decoherence on the Dynamics of Bose-Einstein Condensates in a Double-well Potential

We study the dynamics of a Bose-Einstein condensate in a double-well potential in the mean-field approximation. Decoherence effects are considered by analyzing the couplings of the condensate to environments. Two kinds of coupling are taken into account. With the first kind of coupling dominated, the decoherence can enhance the self-trapping by increasing the damping of the oscillations in the dynamics, while the decoherence from the second kind of condensate-environment coupling leads to spoiling of the quantum tunneling and self-trapping.Comment: for color figures, see PR