Holographic R\'enyi entropy in AdS3_3/LCFT2_2 correspondence

The recent study in AdS$_3$/CFT$_2$ correspondence shows that the tree level contribution and 1-loop correction of holographic R\'enyi entanglement entropy (HRE) exactly match the direct CFT computation in the large central charge limit. This allows the R\'enyi entanglement entropy to be a new window to study the AdS/CFT correspondence. In this paper we generalize the study of R\'enyi entanglement entropy in pure AdS$_3$ gravity to the massive gravity theories at the critical points. For the cosmological topological massive gravity (CTMG), the dual conformal field theory (CFT) could be a chiral conformal field theory or a logarithmic conformal field theory (LCFT), depending on the asymptotic boundary conditions imposed. In both cases, by studying the short interval expansion of the R\'enyi entanglement entropy of two disjoint intervals with small cross ratio $x$, we find that the classical and 1-loop HRE are in exact match with the CFT results, up to order $x^6$. To this order, the difference between the massless graviton and logarithmic mode can be seen clearly. Moreover, for the cosmological new massive gravity (CNMG) at critical point, which could be dual to a logarithmic CFT as well, we find the similar agreement in the CNMG/LCFT correspondence. Furthermore we read the 2-loop correction of graviton and logarithmic mode to HRE from CFT computation. It has distinct feature from the one in pure AdS$_3$ gravity.Comment: 28 pages. Typos corrected, published versio

A General Analysis of Wtb anomalous Couplings

We investigate new physics effects on the Wtb effective couplings in a model-independent manner. The new physics effects are summarized as four independent couplings $f_1^L$, $f_1^R$, $f_2^L$ and $f_2^R$. Using single-top-quark productions and W-helicity fraction measurements at the LHC and Tevatron, we perform a global fit to impose constraints on top quark effective couplings. We introduce a set of parameters $x_0$, $x_m$, $x_p$ and $x_5$ to study the correlations among Wtb effective couplings. We show that (i) improving the measurements of $\sigma_t$ and $\sigma_{tW}$ is important in constraining the correlation of $(f_1^R,f_2^R)$ and $(f_2^L,f_2^R)$; (ii) $f_1^L$ and $f_2^R$ are anti-correlated, which is sensitive to all the experiments; (iii) $f_1^R$ and $f_2^L$ are also anti-correlated, which is sensitive to the W-helicity measurements; (iv) the correlation between $f_2^L$ and $f_2^R$ is sensitive to the precision of $\sigma_t$, $\sigma_{tW}$ and $F_0$ measurements. The effective Wtb couplings are studied in three kinds of new physics models: $SU(2)_1 \times SU(2)_2 \times U(1)_X$ models, vector-like quark models and Littlest Higgs model with and without T-parity. The Wtb couplings in the left-right model and the un-unified model are sensitive to the ratio of gauge couplings when the new heavy gauge boson's mass ($M_{W'}$) is less than several hundred GeV, but the constraint is loose if $M_{W'}>1$ TeV. The Wtb couplings in vector-like quark models and the Littlest Higgs models are sensitive to the mixing angles of new heavy particles and SM particles. We also include the constraints of the oblique T-parameter and Zbb couplings which impose much tighter constraints on the mixing angles. We show that the Wtb coupling constraints become relevant if the precision of single top production cross section measurements could be reduced to 1\% relative to the SM predictions in future.Comment: Chin. Phys. C in pres

Dynamic response of overpass cable-stayed bridge due to aerodynamic effect of high-speed train

The objective of this paper is to evaluate the aerodynamic effect of the high-speed train on an overpass cable-stayed bridge completed by the rotation method. Computational fluid dynamics software Fluent was used in this numerical study. Flow field under a high-speed train has been considered as a viscous, compressible and unsteady flow. Flow model of high-speed train and bridge was established by the sliding mesh approach. Simulated train is passing 7.25 m underneath the bridge with a speed of 350 km/h and 500 km/h to obtain the time history of lifting force, resistance force and torque such that those data can be later applied to the bridge under different construction stages. Numerical results showed that larger aerodynamic response was observed when the tail of the train passed the bridge and the maximum response was observed right above the train. As for current scenario, the aerodynamic effect on such type of concrete cable-stayed bridge could be ignored but it should be checked when structure became lighter (such as steel structure)