Critical Phenomena and Thermodynamic Geometry of RN-AdS Black Holes

The phase transition of Reissner-Nordstr\"om black holes in $(n+1)$-dimensional anti-de Sitter spacetime is studied in details using the thermodynamic analogy between a RN-AdS black hole and a van der Waals liquid gas system. We first investigate critical phenomena of the RN-AdS black hole. The critical exponents of relevant thermodynamical quantities are evaluated. We find identical exponents for a RN-AdS black hole and a Van der Waals liquid gas system. This suggests a possible universality in the phase transitions of these systems. We finally study the thermodynamic behavior using the equilibrium thermodynamic state space geometry and find that the scalar curvature diverges exactly at the van der Waals-like critical point where the heat capacity at constant charge of the black hole diverges.Comment: 18 pages, 5 figure

The meson BcB_c annihilation to leptons and inclusive light hadrons

The annihilation of the $B_c$ meson to leptons and inclusive light hadrons is analyzed in the framework of nonrelativistic QCD (NRQCD) factorization. We find that the decay mode, which escapes from the helicity suppression, contributes a sizable fraction width. According to the analysis, the branching ratio due to the contribution from the color-singlet component of the meson $B_c$ can be of order (10^{-2}). We also estimate the contributions from the color-octet components. With the velocity scaling rule of NRQCD, we find that the color-octet contributions are sizable too, especially, in certain phase space of the annihilation they are greater than (or comparative to) the color-singlet component. A few observables relevant to the spectrum of charged lepton are suggested, that may be used as measurements on the color-octet and color-singlet components in the future $B_c$ experiments. A typical long distance contribution in the annihilation is estimated too.Comment: 26 pages, 5 figures (6 eps-files), submitted to Phys. Rev.

A Comparison of the Use of Binary Decision Trees and Neural Networks in Top Quark Detection

The use of neural networks for signal vs.~background discrimination in high-energy physics experiment has been investigated and has compared favorably with the efficiency of traditional kinematic cuts. Recent work in top quark identification produced a neural network that, for a given top quark mass, yielded a higher signal to background ratio in Monte Carlo simulation than a corresponding set of conventional cuts. In this article we discuss another pattern-recognition algorithm, the binary decision tree. We have applied a binary decision tree to top quark identification at the Tevatron and found it to be comparable in performance to the neural network. Furthermore, reservations about the "black box" nature of neural network discriminators do not apply to binary decision trees; a binary decision tree may be reduced to a set of kinematic cuts subject to conventional error analysis.Comment: 14pp. Plain TeX + mtexsis.tex (latter available through 'get mtexsis.tex'.) Two postscript files avail. by emai

The Casimir force of Quantum Spring in the (D+1)-dimensional spacetime

The Casimir effect for a massless scalar field on the helix boundary condition which is named as quantum spring is studied in our recent paper\cite{Feng}. In this paper, the Casimir effect of the quantum spring is investigated in $(D+1)$-dimensional spacetime for the massless and massive scalar fields by using the zeta function techniques. We obtain the exact results of the Casimir energy and Casimir force for any $D$, which indicate a $Z_2$ symmetry of the two space dimensions. The Casimir energy and Casimir force have different expressions for odd and even dimensional space in the massless case but in both cases the force is attractive. In the case of odd-dimensional space, the Casimir energy density can be expressed by the Bernoulli numbers, while in the even case it can be expressed by the $\zeta$-function. And we also show that the Casimir force has a maximum value which depends on the spacetime dimensions. In particular, for a massive scalar field, we found that the Casimir force varies as the mass of the field changes.Comment: 9 pages, 5 figures, v2, massive case added, refs. adde

Newton-Hooke Limit of Beltrami-de Sitter Spacetime, Principles of Galilei-Hooke's Relativity and Postulate on Newton-Hooke Universal Time

Based on the Beltrami-de Sitter spacetime, we present the Newton-Hooke model under the Newton-Hooke contraction of the $BdS$ spacetime with respect to the transformation group, algebra and geometry. It is shown that in Newton-Hooke space-time, there are inertial-type coordinate systems and inertial-type observers, which move along straight lines with uniform velocity. And they are invariant under the Newton-Hooke group. In order to determine uniquely the Newton-Hooke limit, we propose the Galilei-Hooke's relativity principle as well as the postulate on Newton-Hooke universal time. All results are readily extended to the Newton-Hooke model as a contraction of Beltrami-anti-de Sitter spacetime with negative cosmological constant.Comment: 25 pages, 3 figures; some misprints correcte

Gravity waves over topographical bottoms: Comparison with the experiment

In this paper, the propagation of water surface waves over one-dimensional periodic and random bottoms is investigated by the transfer matrix method. For the periodic bottoms, the band structure is calculated, and the results are compared to the transmission results. When the bottoms are randomized, the Anderson localization phenomenon is observed. The theory has been applied to an existing experiment (Belzons, et al., J. Fluid Mech. {\bf 186}, 530 (1988)). In general, the results are compared favorably with the experimental observation.Comment: 15 pages, 7 figure

Pseuduscalar Heavy Quarkonium Decays With Both Relativistic and QCD Radiative Corrections

We estimate the decay rates of $\eta_c\rightarrow 2\gamma$, $\eta_c'\rightarrow 2\gamma$, and $J/\psi\rightarrow e^+ e^-$, $\psi^\prime\rightarrow e^+e^-$, by taking into account both relativistic and QCD radiative corrections. The decay amplitudes are derived in the Bethe-Salpeter formalism. The Bethe-Salpeter equation with a QCD-inspired interquark potential are used to calculate the wave functions and decay widths for these $c\bar{c}$ states. We find that the relativistic correction to the ratio $R\equiv \Gamma (\eta_c \rightarrow 2\gamma)/ \Gamma (J/ \psi \rightarrow e^+ e^-)$ is negative and tends to compensate the positive contribution from the QCD radiative correction. Our estimate gives $\Gamma(\eta_c \rightarrow 2\gamma)=(6-7) ~keV$ and $\Gamma(\eta_c^\prime \rightarrow 2\gamma)=2 ~keV$, which are smaller than their nonrelativistic values. The hadronic widths $\Gamma(\eta_c \rightarrow 2g)=(17-23) ~MeV$ and $\Gamma(\eta_c^\prime \rightarrow 2g)=(5-7)~MeV$ are then indicated accordingly to the first order QCD radiative correction, if $\alpha_s(m_c)=0.26-0.29$. The decay widths for $b\bar b$ states are also estimated. We show that when making the assmption that the quarks are on their mass shells our expressions for the decay widths will become identical with that in the NRQCD theory to the next to leading order of $v^2$ and $\alpha_s$.Comment: 14 pages LaTex (2 figures included

The Application of Micro-Raman Spectroscopy to Analysis and Identification of Minerals in Thin Section

Micro-Raman spectroscopy is a useful analytical tool for studying minerals in thin section. The advantages of this technique as a structural probe for analysis of micron-size minerals are demonstrated with a study of polymorphism of SiO2 and MgSiO3. Three polymorphs of silica, -quartz, coesite, and glass, in a thin section of Coconino sandstone were identified in situ with a Raman microprobe. The Raman spectra of these phases were compared to that measured for stishovite obtained from the same rock. Spectra of protoenstatite, orthoenstatite, and clinoenstatite, three polymorphs of MgSiO3, are consistent with their similar pyroxene chain structures but different space groups. The characteristic Raman spectra in each instance could be used for finger-printing identification of the phases and their orientations

Gluonic and leptonic decays of heavy quarkonia and the determination of αs(mc)\alpha_s(m_c) and αs(mb)\alpha_s(m_b)

QCD running coupling constant $\alpha_s(m_c)$ and $\alpha_s(m_b)$ are determined from heavy quarkonia $c\overline{c}$ and $b\overline{b}$ decays. The decay rates of $V\rightarrow 3g$ and $V\rightarrow e^+ e^-$ for $V=J/\psi$ and $\Upsilon$ are estimated by taking into account both relativistic and QCD radiative corrections. The decay amplitudes are derived in the Bethe-Salpeter formalism, and the decay rates are estimated by using the meson wavefunctions which are obtained with a QCD-inspired inter-quark potential. For the $V\rightarrow 3g$ decay we find the relativistic correction to be very large and to severely suppress the decay rate. Using the experimental values of ratio R_g\equiv \frac {\Gamma (V\longrightarrow 3g)}% {\Gamma (V\longrightarrow e^{+}e^{-})}\approx 10,~32 for $V=J/\psi, ~\Upsilon$ respectively, and the calculated widths , we find $\alpha_{s}(m_c)=0.29\pm 0.02$ and $\alpha_s(m_b)=0.20\pm 0.02$. These values for the QCD running coupling constant are substantially enhanced, as compared with the ones obtained without relativistic corrections, and are consistent with the QCD scale parameter $\Lambda_{\overline {MS}}^{(4)}$. We also find that these results are mainly due to kinematic corrections and not sensitive to the dynamical models.Comment: 15 pages in Late

Mechanisms for electron transport in atomic-scale one-dimensional wires: soliton and polaron effects

We study one-electron tunneling through atomic-scale one-dimensional wires in the presence of coherent electron-phonon (e-ph) coupling. We use a full quantum model for the e-ph interaction within the wire with open boundary conditions. We illustrate the mechanisms of transport in the context of molecular wires subject to boundary conditions imposing the presence of a soliton defect in the molecule. Competition between polarons and solitons in the coherent transport is examined. The transport mechanisms proposed are generally applicable to other one-dimensional nanoscale systems with strong e-ph coupling.Comment: 7 pages, 4 figures, accepted for publication in Europhys. Let