Spinor Decomposition of SU(2) Gauge Potential and The Spinor Structures of Chern-Simons and Chern Density

In this paper, the decomposition of SU(2) gauge potential in terms of Pauli spinors is studied. Using this decomposition, the spinor strutures of the Chern-Simons form and the Chern density are obtained. Furthermore, by these spinor structures, the knot quantum number of non-Abelian gauge theory is discussed, and the second Chern number is characterized by the Hopf indices and the Brouwer degrees of $\phi$-mapping.Comment: 11 page

Features and stability analysis of non-Schwarzschild black hole in quadratic gravity

Black holes are found to exist in gravitational theories with the presence of quadratic curvature terms and behave differently from the Schwarzschild solution. We present an exhaustive analysis for determining the quasinormal modes of a test scalar field propagating in a new class of black hole backgrounds in the case of pure Einstein-Weyl gravity. Our result shows that the field decay of quasinormal modes in such a non-Schwarzschild black hole behaves similarly to the Schwarzschild one, but the decay slope becomes much smoother due to the appearance of the Weyl tensor square in the background theory. We also analyze the frequencies of the quasinormal modes in order to characterize the properties of new back holes, and thus, if these modes can be the source of gravitational waves, the underlying theories may be testable in future gravitational wave experiments. We briefly comment on the issue of quantum (in)stability in this theory at linear order.Comment: 18 pages, 4 figures, 1 table, several references added, version published on JHE

Cold Dark Matter Isocurvature Perturbations: Cosmological Constraints and Applications

In this paper we present the constraints on cold dark matter (CDM) isocurvature contributions to the cosmological perturbations. By employing Markov Chain Monte Carlo method (MCMC), we perform a global analysis for cosmological parameters using the latest astronomical data, such as 7-year Wilkinson Microwave Anisotropy Probe (WMAP7) observations, matter power spectrum from the Sloan Digital Sky Survey (SDSS) luminous red galaxies (LRG), and "Union2" type Ia Supernovae (SNIa) sample. We find that the correlated mixture of adiabatic and isocurvature modes are mildly better fitting to the current data than the pure adiabatic ones, with the minimal $\chi^2$ given by the likelihood analysis being reduced by 3.5. We also obtain a tight limit on the fraction of the CDM isocurvature contributions, which should be less than 14.6% at 95% confidence level. With the presence of the isocurvature modes, the adiabatic spectral index becomes slightly bigger, n_s^{\rm adi}=0.972\pm0.014~(1\,\sigma), and the tilt for isocurvature spectrum could be large, namely, the best fit value is n_s^{\rm iso}=3.020. Finally, we discuss the effect on WMAP normalization priors, shift parameter R, acoustic scale l_A and z_{*}, from the CDM isocurvaure perturbation. By fitting the mixed initial condition to the combined data, we find the mean values of R, l_A and z_{*} can be changed about 2.9\sigma, 2.8\sigma and 1.5\sigma respectively, comparing with those obtained in the pure adiabatic condition.Comment: 9 pages, 5 figures, 3 tables, references adde

Exploring inbound tourists experience in Beijing, China: an online deductive approach

Purpose Beijing is becoming one of the top global destinations but the number of international tourists to the city has been declining recently. By analyzing inbound tourists experience in Beijing and identifying the relationship between the destination attributes and satisfaction, the purpose of this paper is to provide important insights into city tourism research and city destination development. Design/methodology/approach This study used an online deductive approach and collected 1,254 reviews on TripAdvisor referencing major attractions in Beijing. This study used the Leximancer software to analyze the content of the reviews and to identify the underlying relationships. Findings The results showed that international tourists’ experience in Beijing can be reflected via five aspects: attractions, city, transportation, service and people. The results further indicated that the major concern of international tourists visiting Beijing related to the service quality on site. Originality/value This study explored inbound tourists experience in Beijing using an online deductive approach. Practical implications were provided with respect to improving international tourists experience in Beijing and enhancing their satisfaction and revisiting intentions

Stability studies of ZnO and AlN thin film acoustic wave devices in acid and alkali harsh environments

Surface acoustic wave (SAW) devices based on piezoelectric thin-films such as ZnO and AlN are widely used in sensing, microfluidics and lab-on-a-chip applications. However, for many of these applications, the SAW devices will inevitably be used in acid or alkali harsh environments, which may cause their early failures. In this work, we investigated the behavior and degradation mechanisms of thin film based SAW devices in acid and alkali harsh environments. Results show that under the acid and alkali attacks, chemical reaction and corrosion of ZnO devices are very fast (usually within 45 s). During the corrosion, the crystalline orientation of the ZnO film is not changed, but its grain defects are significantly increased and the grain sizes are decreased. The velocity of ZnO-based SAW devices is decreased due to the formation of porous structures induced by the chemical reactions. Whereas an AlN thin-film based SAW device does not perform well in acid–alkali conditions, it might be able to maintain a normal performance without obvious degradation for more than ten hours in acid or alkali solutions. This work could provide guidance for the applications of both ZnO or AlN-based SAW devices in acid/alkali harsh environments

Microlensing effect of charged spherically symmetric wormhole

We systematically investigate the microlensing effect of charged spherically symmetric wormhole, where the light source is remote from the throat. Remarkably, there will be at most three images by considering the charge part. We study all situations including three images, two images, and one image, respectively. The numerical result shows that the range of total magnification is from $10^5$ to $10^{-2}$ depending on various metrics. In the case of three images, there will be two maximal values of magnification (a peak, and a gentle peak) when the contribution via mass is much less than that of charge. However, we cannot distinguish the case that forms three images or only one image as the total magnification is of order $10^5$. Finally, our theoretical investigation could shed new light on exploring the wormhole with the microlensing effect.Comment: 10 pages, 9 figure