The directionality of the sound generated by laser-induced liquid breakdown in water The directionality of the sound generated by laser-induced liquid breakdown in water

The directionality of the sound generated by laser-induced liq-uid breakdown in water is investigated both theoretically and experimen-tally.The theoretical analysis is based on the following model.A seriesof small spherical cavities including plasma are homogeneously distributedon a short straight line segment and every such cavity may be consideredas a point source radiating acoustic impulse.Theoretical expressions ofthe relations between the amplitude and width of acoustic impulse and thereceiving direction are given.Experimental results are in agreement withtheoretical predictions.     

Tri-meson mixing of π–η–η′ and ρ–ω–φ in the light-cone quark model

The radiative transition form factors of the pseudoscalar mesons π, η, η′ and the vector mesons ρ, ω, φ are restudied with π–η–η′ and ρ–ω–φ in the tri-meson-mixing pattern, which is described by tri-mixing matrices in the light-cone constituent quark model. The experimental transition decay widths are better reproduced with tri-meson mixing than previous results in a two-mixing-angle scenario of only two-meson η–η′ mixing and ω–φ mixing.     

Network breakdown “at the edge of chaos” in multi-agent traffic simulations

Traffic is highly influenced by network structure and human behaviour. Small changes in the human behaviour can lead to huge changes in the load of a traffic network. Current transportation models do not, and most of them cannot, research such random behaviour but always calculate a steady state. In our multi-agent transport simulation, we frequently observe seemingly random “network breakdowns”, huge traffic jams that spread over a big part of the network, making a normal traffic flow impossible. This paper describes the investigations that were performed on the results of our large-scale multi-agent transport simulations in an attempt to contribute to the better understanding of the dynamic processes in such simulations and, hopefully, better understanding and modelling of the real-world.     

Density fluctuation of the ^3He reaction-diffusion model in nonextensive statistical mechanics

In this paper the time-space correlation of density fluctuation of the 3He reaction-diffusion model is investigated where the equilibrium distribution is described by the generalized Maxwell Boltzmann distribution in the framework of Tsallis statistics. By using the density operator technique, the nonextensive pressure effect is introduced into the master equation and thus the generalized master equation is derived for the nonextensive system. This paper uses the ^3He reaction diffusion model to analyse the effect of nonextensive pressure on the fluctuation and finds that the nonextensive parameter q plays a very important role in determining the characteristics of the fluctuation waves.[第一段]     

The seesaw mechanism at TeV scale in the 3-3-1 model with right-handed neutrinos

We implement the seesaw mechanism in the 3-3-1 model with right-handed neutrinos. This will be accomplished by the introduction of a scalar sextet into the model and the spontaneous violation of lepton number. The main result of this work is that the seesaw mechanism can work already at the TeV scale with the consequence that the right-handed neutrino masses lie in the electroweak scale, in the range from MeV to tens of GeV. This window provides a great opportunity to test their appearance at current detectors, though when we contrast our results with some previous analyses concerning the detection sensitivity at LHC, we conclude that further work is needed in order to validate this search.     

Investigation of the threshold intensity versus gas pressure in the breakdown of helium by 248 nm laser radiation

An investigation of the unexpectedly strong dependence of the threshold intensity on the gas pressure in the experimental study on the breakdown of He by short laser wavelength (Turcu et al., in Opt Commun, 134:66–68, 1997) is presented. A modified electron cascade model is applied (Evans and Gamal, in J Phys D Appl Phys, 13:1447–1458, 1980). Computations revealed reasonable agreement between the calculated thresholds and the measured ones. Moreover, the calculated electron energy distribution function and its parameters proved that multiphoton ionization of ground and excited atoms is the main source for the seed electrons, which contributes to the breakdown of helium. The effect of diffusion losses over pressures <1,000 Torr elucidated the origin of the strong dependence of the threshold intensity on the gas pressure. Collisional ionization dominates only at high pressures. No evidence for recombination losses is observed for pressures up to 3,000 Torr.     

Stability of the scalar potential and symmetry breaking in the economical 3-3-1 model

A detailed study of the criteria for stability of the scalar potential and the proper electroweak symmetry breaking pattern in the economical 3-3-1 model, is presented. For the analysis we use and improve a method previously developed to study the scalar potential in the two-Higgs-doublet extension of the standard model. A new theorem related to the stability of the potential is stated. As a consequence of this study, the consistency of the economical 3-3-1 model emerges.     

The role of conformal symmetry in the Jackiw–Pi model

The Jackiw–Pi model in 2+1$2+1$ dimensions is a non-relativistic conformal field theory of charged particles with point-like self-interaction. For specific values of the interaction strengths the classical theory possesses vortex and multi-vortex solutions, which are all degenerate in energy. We compute the full set of first-order perturbative quantum corrections. Only the coupling constant g²$g^2$ requires renormalization; the fields and electric charge e are not renormalized. It is shown that in general the conformal symmetries are broken by an anomalous contribution to the conservation law, proportional to the β-function. However, the β  -function vanishes upon restricting the coupling constants to values g²=±e²$g^2=\pm e^2$, which includes the case in which vortex solutions exist. Therefore the existence of vortices also guarantees the preservation of the conformal symmetries.     

The Effect of the Relative Motion of Atoms on the Frequency of the Emitted Light and the Reinterpretation of the Ives-Stilwell Experiment

We examine the process of the emission of light from an atom that is in a relative translational motion with respect to the medium at rest in which the electromagnetic excitations propagate. The effect of Lorentz contraction of the of electron orbits on the emitted frequency is incorporated in the Rydberg formula, as well as the emitter’s Doppler effect is acknowledged. The result is that the frequency of the emitted light is modified by a factor that is identical with what is called the ‘relativistic Doppler effect’. The new emission formula is applied for reinterpretation of the Ives-Stilwell experiment and shown that within the second order of approximation with respect to the speeds of the atom and the ‘absolute speed’ (Earth’s speed relative to the medium), the absolute motion does not affect the interference. The expression for the modification of the frequency involves both a first and a second-order term with respect to the speed of the atoms in the cathode tube. The latter turns out to be quantitatively the same as if the time would have changed its rate in the frame moving with the atoms. Thus, a new interpretation of the results of this famous experiment is provided without stipulating time dilation.     

Laser induced incandescence determination of the ratio of the soot absorption functions at 532 nm and 1064 nm in the nucleation zone of a low pressure premixed sooting flame

In this work, the two-excitation wavelength laser induced incandescence (LII) method has been applied in a low-pressure premixed methane/oxygen/nitrogen flame (equivalence ratio 2.32) to determine the variation of the ratio of the soot absorption functions at 532 nm and 1064 nm E(m,532 nm)/E(m,1064 nm) along the flame. This method relies on the comparison of LII signals measured upon two different excitation wavelengths (here 532 nm and 1064 nm) and with laser fluences selected in such a way that the soot particles are equally laser-heated. The comparison of the laser fluences at 532 nm and 1064 nm leads to an easy determination of E(m,532 nm)/E(m,1064 nm). The reliability of the method is demonstrated for the first time in a low pressure flame in which the soot nucleation zone can be spatially resolved and which contains soot particles acting differently with the laser fluence according to their residence time in the flame. The method is then applied to determine the profile of E(m,532 nm)/E(m,1064 nm) along the flame. A very important decrease of this ratio is observed in the region of nascent soot, while the ratio remains constant at high distance above the burner. Implication on temperature determination from spectrally resolved measurement of flame emission is studied.     

The Spectrum of the Billiard Laplacian of a Family of Random Billiards

Random billiards are billiard dynamical systems for which the reflection law giving the post-collision direction of a billiard particle as a function of the pre-collision direction is specified by a Markov (scattering) operator P. Billiards with microstructure are random billiards whose Markov operator is derived from a “microscopic surface structure” on the boundary of the billiard table. The microstructure in turn is defined in terms of what we call a billiard cellQ, the shape of which completely determines the operator P. This operator, defined on an appropriate Hilbert space, is bounded self-adjoint and, for the examples considered here, a Hilbert-Schmidt operator. A central problem in the statistical theory of such random billiards is to relate the geometric characteristics of Q and the spectrum of P. We show, for a particular family of billiard cell shapes parametrized by a scale invariant curvature K (Fig. 2), that the billiard Laplacian P−I is closely related to the ordinary spherical Laplacian, and indicate, by partly analytical and partly numerical means, how this provides asymptotic information about the spectrum of P for small values of K. It is shown, in particular, that the second moment of scattering about the incidence angle closely approximates the spectral gap of P.     

The influence of the second harmonic in the current-phase relation on the voltage-current characteristic of high TC DC SQUID

A theory for the voltage-current characteristic in high TC DC SQUIDs (Superconducting Quantum Interference Devices), which accounts for a second harmonic in the junction current-phase relation, is developed. It is shown that the small inductance DC SQUIDs can be used for the investigation of the second harmonic via its influence on the voltage-flux curve. If the second harmonic is perceptible, then for large inductance DC SQUIDs the theory can explain the substantial deviations of the experimental voltage modulation from theoretical predictions and computer simulations based on conventional sinusoidal current-phase relation. The detail comparison with the experiment is performed.     

The B-B′-U Hubbard model in the approximation of static fluctuations

Within the approximation of static fluctuations, the effect of allowing for electron transport from a given site to the second-nearest neighboring site on the energy spectrum of the two-sublattice two-dimensional Hubbard model and on the dependence of the magnetization on the system parameters is investigated. Fiz. Tverd. Tela (St. Petersburg) 41, 951–956 (June 1999)     

Fermionic perturbation theory for the statistical mechanics of the nonlinear Schrödinger model

A fermionic perturbation theory is developed for the statistical mechanics of the nonlinear Schrödinger model. The theory is based on an interacting-fermion picture of the Bethe wave function. The inner product of the Bethe wave function is explicitly evaluated, and a simple graphical representation of it is given. The basic equations obtained for the free energy agree with those of Yang and Yang. In particular, the present theory gives a clear-cut meaning to the function of Yang and Yang: It represents a fermion energy at finite temperatures.     

Identification of extra neutral gauge bosons at the International Linear Collider

Heavy neutral gauge bosons, Z ^′s, are predicted by many theoretical schemes of physics beyond the Standard Model, and intensive searches for their signatures will be performed at present and future high energy colliders. It is quite possible that Z ^′s are heavy enough to lie beyond the discovery reach expected at the CERN Large Hadron Collider LHC, in which case only indirect signatures of Z ^′ exchanges may occur at future colliders, through deviations of the measured cross sections from the Standard Model predictions. We here discuss in this context the foreseeable sensitivity to Z ^′s of fermion-pair production cross sections at an e ⁺ e ^? linear collider, especially as regards the potential of distinguishing different Z ^′ models once such deviations are observed. Specifically, we assess the discovery and identification reaches on Z ^′ gauge bosons pertinent to the E ₆, LR, ALR and SSM classes of models, that should be attained at the planned International Linear Collider (ILC). With the high experimental accuracies expected at the ILC, the discovery and the identification reaches on the Z ^′ models under consideration could be increased substantially. In particular, the identification among the different models could be achieved for values of Z ^′ masses in the discovery (but beyond the identification) reach of the LHC. An important role in enhancing such reaches is played by the electron (and possibly the positron) longitudinally polarized beams. Also, although the purely leptonic processes are experimentally cleaner, the measurements of c- and b-quark pair production cross sections are found to carry important, and complementary, information on these searches.     

Review of searches for Higgs bosons and beyond the Standard Model Physics at the Tevatron

The energy frontier is currently at the Fermilab Tevatron accelerator, which collides protons and antiprotons at a center-of-mass energy of 1.96 TeV. The luminosity delivered to the CDF and DØ experiments has now surpassed the 4 fb^?1. This paper reviews the most recent direct searches for Higgs bosons and beyond-the-standard-model (BSM) physics at the Tevatron. The results reported correspond to an integrated luminosity of up to 2.5 fb^?1 of Run II data collected by the two Collaborations. Searches covered include the standard model (SM) Higgs boson (including sensitivity projections), the neutral Higgs bosons in the minimal supersymmetric extension of the standard model (MSSM), charged Higgs bosons and extended Higgs models, supersymmetric decays that conserve or violate R-parity, gauge-mediated supersymmetric breaking models, long-lived particles, leptoquarks, compositeness, extra gauge bosons, extra dimensions, and finally signature-based searches. Given the excellent performance of the collider and the continued productivity of the experiments, the Tevatron physics potential looks promising for discovery with the coming larger data sets. In particular, evidence for the SM Higgs boson could be obtained if its mass is light or near 160 GeV. The observed (expected) upper limits are currently a factor of 3.7 (3.3) higher than the expected SM Higgs boson cross section at m _H =115 GeV and 1.1 (1.6) at m _H =160 GeV at 95% C.L.     

Heavy-light meson spectroscopy and Regge trajectories in the relativistic quark model

The masses of the ground, orbitally and radially excited states of heavy-light mesons are calculated within the framework of the QCD-motivated relativistic quark model based on the quasipotential approach. Both light (q=u,d,s) and heavy (Q=c,b) quarks are treated fully relativistically without application of the heavy-quark 1/m _Q expansion. The Regge trajectories in the (M ²,J) and (M ²,n _r ) planes are investigated and their parameters are obtained. The results are in good agreement with available experimental data except for the masses of the anomalous $D^{*}_{s0}(2317)$ , D _s1(2460) and $D_{sJ}^{*}(2860)$ states.     

The Transformation Properties at the Quantum Level in Field Theories for a Gauge-Invariant System with a Higher-Order Lagrangian

Based on the configuration-space generating functional of the Green functions for the gauge-invariant system in higher-order derivatives theories, the equations of the transformation properties at the quantum level have been derived. It follows that the sufficient conditions are found which implies that there exists the conservation laws and the expressions of the quantal conserved laws are also given. Applying the results to the non-Abelian Chern-Simons higher-order derivatives theories, the quantal BRST conserved charge and other conserved charges are found, the transformation properties of the conformal transformation at the quantum level is discussed, the quantal conserved angular momentum is derived, it is pointed out that fractional spin in this system may be also preserved in quantum theories. But the connection between the symmetries and conservation laws in classical theories are not always preserved in quantum theories.     

The influence of quintessence on the motion of a binary system in cosmology

We employ the metric of Schwarzschild space surrounded by quintessential matter to study the trajectories of test masses on the motion of a binary system. The results, which are obtained through the gradually approximate approach, can be used to search for dark energy via the difference of the azimuth angle of the pericenter. The classification of the motion is discussed.