Nonpropagation of tachyon on the BTZ black hole in type 0B string theory

We obtain the BTZ black hole (AdS$_3 \times$S$^3$) as a non-dilatonic solution from type 0B string theory. Analyzing the perturbation around this black hole background, we show that the tachyon is not a propagating mode.Comment: some detailed explanations are added, modified version will be appeared in Physics Letters B, 11 pages in RevTeX, no figure

Dynamical Behavior of the BTZ Black Hole

We study the dynamical behavior of the BTZ (Banados-Teitelboim-Zanelli) black hole with the low-energy string effective action. The perturbation analysis around the BTZ black hole reveals a mixing between the dilaton and other fields. Introducing the new gauge (dilaton gauge), we disentangle this mixing completely and obtain one decoupled dilaton equation. We obtain the decay rate $\Gamma$ of BTZ black hole.Comment: minor typhographical corrections, ReVTeX, 9 pages with no figure

The public and the popular media in China

The focus of this research is whether the Habermas’ ‘bourgeois public sphere’, which is characteristic of Western society, can be extended to China. My main contribution is to demonstrate that the concepts of ‘sentiment’ and ‘reason’ are central to any discussion of the public sphere in China. This is in sharp contrast to the West where rational discussion and the rule of law are the twin foundations of the classical discourse of the public sphere. China’s society is distinct from Western democracies the West in at least two fundamental ways. In the first place, the political system remains ‘communist’ with a single party controlling all of the media. As a result, the degree of freedom of thought and speech is extremely limited, and there is no obvious way in which the mass media can act directly as a forum for free and informed discussion of public policy. Secondly, whereas the rule of law is understood as a central element in Western democratic culture, it has a subordinate place in Chinese culture. These assumptions are examined through a study of the readership of the Popular Press and through text analysis. How the Popular Press engages with the general public, how the general public reads and judges media messages, and crucially whether the Popular Press could employ an indirect approach working to constitute an ‘imaginary’ public in China were the discoveries. In the end, this study concludes that while China’s cultural, political and economic system of control is the main factor leading to the restriction and dissent of the general public, a ‘reasoning’ popular public might, in time, be shaped through their reading of controversies in political and public affairs in the Popular Press

3D CFD Modeling of a Supercritical Bottom Rack Intake

Compact intake structures are used for diverting turbulent supercritical flow on steep catchments in the hinterland of the urban area of Hong Kong to an underground flood diversion system through a number of vortex dropshafts. Bottom racks are placed at the entrance of the intake to exclude debris from entering the system. The rack bars interact with the supercritical inflow and creates a highly turbulent air-water mixture. This paper presents a three-dimensional (3D) computational fluid dynamics (CFD) modeling study to predict the complex flow details and air concentration of the bottom rack intake structure, using the volume-of-fluid (VOF) technique. Numerical simulations are conducted with different inflow rates and bottom rack bar shapes. The water depth, velocity and air concentration agree well with experimental measurement. Model results show that the rack interception induces an energy loss and increase the flow depth above the rack. The rack interception also gives rise to a sheet jet beneath the rack and results in air entrainment. In the rack chamber, the flow consists of a wall jet that impinges on a spiral circulation of aerated flow, inducing significant turbulence and air entrainment. The average air concentration in the rack ranges from 20% - 50% and decreases with increasing discharge. The air concentration in the chamber appears to be little affected by the presence of bottom rack or the shape of rack

A Generalized Circle Theorem on Zeros of Partition Function at Asymmetric First Order Transitions

We present a generalized circle theorem which includes the Lee-Yang theorem for symmetric transitions as a special case. It is found that zeros of the partition function can be written in terms of discontinuities in the derivatives of the free energy. For asymmetric transitions, the locus of the zeros is tangent to the unit circle at the positive real axis in the thermodynamic limit. For finite-size systems, they lie off the unit circle if the partition functions of the two phases are added up with unequal prefactors. This conclusion is substantiated by explicit calculation of zeros of the partition function for the Blume-Capel model near and at the triple line at low temperatures.Comment: 10 pages, RevTeX. To be published in PRL. 3 Figures will be sent upon reques

ESTIMATION OF KNEE EXTENSION MOMENT CONSIDERING VELOCITY EFFECT AND MUSCLE ACTIVATION USING TENDON SLACK LENGTH OPTIMIZATION

This study presents a model to estimate knee extension moment considering muscle velocity effect and muscle activation. The muscle tendon force is very sensitive to the tendon slack length. To predict tendon slack length, exact muscle parameters of a human are needed. But it is difficult to measure all of the muscle parameters from human body. So we propose the algorithm which finds the tendon slack length of quadriceps for more accurate estimation of knee extension moment. Finally considering muscle velocity effect and muscle activation, knee extension moment is estimated. Algorithm was embodied by MATLAB optimization toolbox. And it is evaluated by using an experimental data

Absorption of fixed scalar in scattering off 4D N=4 black holes

We perform the perturbation analysis of the black holes in the 4D, N=4 supergravity. Analysis around the black holes reveals a complicated mixing between the dilaton and other fields (metric and two U(1) Maxwell fields). It turns out that considering both s-wave (l=0) and higher momentum modes (l \neq 0), the dilaton as a fixed scalar is the only propagating mode with $P=Q, h_1=h_2=0$ and $F = -G = 2\phi$. We calculate the absorption cross-section for scattering of low frequency waves of fixed scalar and U(1) Maxwell fields off the extremal black hole.Comment: 11 pages in RevTeX, no figures, minor correction is included(third version

Greybody Factors of Charged Dilaton Black Holes in 2 + 1 Dimensions

We have studied scalar perturbations of charged dilaton black holes in 2+1 dimensions. The black hole considered here is a solution to the low-energy string theory in 2+1 dimensions. The exact decay rates and the grey body factors for the massless minimally coupled scalar is computed for both the charged and the uncharged dilaton black holes. The charged and the uncharged black hole show similar behavior for grey body factors, reflection coefficients and decay rates.Comment: The equation for the potential and figure:1 are changed. The changes does not effect the result

Randall-Sundrum Gauge in the Brane World

We discuss the Randall-Sundrum (RS) choice for $h_{MN}$ in the brane-world. We begin with the de Donder gauge (transverse-tracefree) including scalar($h_{55}$), vector($h_{5\mu}$) and tensor($h_{\mu\nu}$) in five dimensions for comparison. One finds that $h_{55}=0$ and $h_{5\mu}=0$. This leads to the RS choice. It appears that the RS choice is so restrictive for the five massless states, whereas it is unique for describing the massive states. Furthermore, one can establish the stability of the RS solution with the RS choice only.Comment: corrected some typographical mistakes, 11 pages with ReVTeX, no figur