A new semiclassical elementary particle model

A semiclassical model in which elementary particles are represented as systems of charged shells with associated quark-like quantum numbers is presented. Specifically the baryons are considered. Formulas are obtained which express baryon masses and magnetic moments in terms of model parameters which relate baryon and quark properties. Basically, the mass and moment formulas are expressions for mass ratios and magnetic moment ratios. Simple identifications for the model parameters lead to a prediction for the proton-electron mass ratio and to fairly accurate predictions for the baryon magnetic moments in units of the proton moment. The mass and moment formulas, which relate corresponding properties of different particles, are generalised such as to express relationships between the members of a sequence of particles, where such a sequence is conceived of as containing only one (normal) baryon. A specific sequence, containing the proton and electron, is proposed; various physical properties of the particles in the sequence are determined. In particular, a second prediction for the proton-electron mass ratio is obtained; the two predictions differ numerically but both agree with the measured value of the mass ratio within experimental error.     

A semiclassical model for quark jet fragmentation

A semiclassical model is presented for the way the energy of a fast quark is transformed into observable hadrons. It reproduces the features of 1+1 dimensional QED (the Schwinger model) concerning a flat rapidity distribution in the central region. It also reproduces results from phenomenological considerations, which, based upon scaling, predict that meson formation in the fragmentation region can be described by an iterative scheme, implying a set of coupled integral equations. In particular the model predicts that the probability to find a meson containing the leading quark is independent of the Feynman scaling variablez. The iterative structure corresponds to a Brownian motion with relevance both to the confinement problems and to the distribution of mass in the quark jet.     

Dynamic compression: what it is,making metallic H and magnetic fields of Uranus and Neptune

ABSTRACT

Static compression is a well-known method to achieve very high pressures in ‘cold’ (degenerate) condensed matter. Because dynamic compression is adiabatic, it achieves both high pressures and temperatures, which are tunable by choice of pressure-pulse shape. Dynamic compression uses supersonic hydrodynamic variables, which are straight forward to measure, to achieve a wide range of extreme thermodynamic states in degenerate condensed matter. Because dynamic compression developed primarily in national laboratories, it is relatively unknown to a significant portion of the high pressure community. This paper is a brief review of (i) dynamic compression itself, (ii) its application to making metallic fluid H (MFH) and (iii) implications of data generated at extreme conditions with dynamic compression for understanding the unusual magnetic fields of Uranus and Neptune, which are made primarily by convection of semiconducting and MFH. Metallic hydrogen made under dynamic and static compression is compared.     

Lenses as an atom-photon interface: A semiclassical model

Strong interaction between the light field and an atom is often achieved with cavities. Recent experiments have used a different configuration: a propagating light field is strongly focused using a system of lenses, the atom being supposed to sit at the focal position. In reality, this last condition holds only up to some approximation; in particular, at any finite temperature, the atom position fluctuates. We present a formalism that describes the focalized field and the atom sitting at an arbitrary position. As a first application, we show that thermal fluctuations do account for the extinction data reported in M. K. Tey et al., Nature Physics 4, 924 (2008).     

Non-chaotic behavior in the semiclassical Jaynes-Cummings model

The semiclassical model, describing interaction of a collection of two-level atoms with a single-mode electric field, known as the Jaynes-Cummings model, without the assumption of the rotating-wave approximation, is considered. A solution, based on an asymptotic expansion, describing small oscillations is presented. This solution also yields a relation between the coupling and detuning parameters, which is the condition for the existence of regular and chaotic behaviour. We confirmed numerically, by calculation of the Lyapunov exponent and the Fourier spectrum, that the condition is valid for both weak and strong coupling.     

The superconducting penetration depth from the semiclassical model

The semiclassical approach of Onsager and Pippard has been very successful in relating the electronic properties of a normal metal to its band structure and fermi surface. This paper extends the method to a superconductor. A generalized London equation relating the supercurrent density to the vector potential is obtained, in terms of band and fermi surface parameters and an energy gap which may be anisotropic. The results allow an interpretation of measured penetration depths directly in terms of the electronic and gap structures of the superconductor. They lead to easy physical visualization of the origin of anisotropies and other features of measured penetration depths.     

A simple,analytic solution of the semiclassical Rabi model in the red-detuned regime

We consider the semiclassical Rabi model in the large, red-detuned regime. Using the method of multiple-scales we obtain a simple, analytic, and approximate solution that describes the evolution of the system accurately for long times and for arbitrary values of the qubit-field coupling. It is used to characterize the probability to find the qubit in the excited state and the trajectory of the associated Bloch vector. Finally, we present physical situations where the results can be applied.     

A semiclassical theory of the laser

The kinetic equation for the density matrix is used to study the response of a laser system to a monochromatic electromagnetic standing wave. Steady-state laser operation is studied through joint solution of Maxwell's equations and the equations for the density matrix. Allowances are made for nonuniformities in the radiating medium modulated by the field and for the motion of the radiating particles. Steady-state operating conditions and oscillation thresholds for gas and solid-state lasers are compared.     

Exact periodic solutions and chaos in the semiclassical Jaynes-Cummings model

Exact periodic solutions for the semiclassical Jaynes-Cummings model without the assumption of the rotating-wave approximation are studied. They are valid for some specific values of the coupling constant, detuning parameter and the energy of the system. The behaviour of the system in the vicinity of this special solution is studied numerically. By computation of the Fourier spectrum, it is shown that the behaviour of the system changes from a non-chaotic to a chaotic one when the energy of the system increases.     

A semiclassical treatment of two-photon interaction

An analysis of two-photon interaction was carried out for a two-level system with mixed states parity. Janes-Cummings-type semiclassical equations have been derived for this model and their computer solutions have been analysed; an approximate expression for the Rabi frequency is given.     

A semiclassical interpretation of wave mechanics

The single-particle wave function =Re^iS/h has been interpreted classically: At a given point the particle momentum is S, and the relative particle density in an ensemble is R ² . It is first proposed to modify this interpretation by assuming that physical variables undergo rapid fluctuations, so that S is the average of the momentum over a short time interval. However, it appears that this is not enough. It seems necessary to assume that the density also fluctuates. The fluctuations are taken to be random and to satisfy conditions required for agreement with quantum mechanics. In some cases the fluctuating density may take on instantaneous negative values. One gets agreement with quantum mechanics for the spin correlations of two particles in a singlet state. This comes about because of the correlations between the fluctuations of the variables of the two particles, the effect of which is equivalent to an action at a distance. The relation to Bell's inequality is discussed.     

A semiclassical quantization of area-preserving maps

A semiclassical path integral formalism is developed for a class of area-preserving maps. The quasi-energy spectrum of these systems is represented as a sum over closed orbits in the manner of Gutzwiller. The method is illustrated with some numerical tests of the “standard map”.     

核子动量分布对半经典扭曲波模型计算的影响

通过单体密度矩阵的Wigner变换把相干密度涨落模型引入半经典扭曲波模型,并应用于分析在80和160MeV入射能量时⁹⁰Zr(p,p′x)反应中非弹性散射到连续态的多步直接过程.包括三步过程的双微分截面计算值与实验值有较好的符合.考察了核子动量分布对双微分截面计算的影响,并细致分析了各个核子动量区间对截面的贡献. 关键词： 双微分截面 半经典扭曲波模型 相干密度涨落模型 多步直接过程     

The inconsistency of a model for internal structure of black holes

The recent claim that a black hole can be treated as a relativistic gas of micro black holes (planckions) is shown to be physically inconsistent and in fact is grossly in error. Any deductions made about black holes from such models must therefore be treated with caution.     

A semiclassical dynamics study of the photoisomerization of methyl-substituted azobenzene

A semiclassical dynamics simulation study is reported for a trans–cis photoisomerization cycle of four azo compounds, including azobenzene, 2-methylazobenzene, 2,6-dimethylazobenzene, and 2,2′-dimethylazobenzene. For both trans?→?cis and cis?→?trans isomerization processes, each compound is excited by a 50?fs (fwhm) laser pulse with a photon energy leading to a ππ* excitation. It is found that the compound in both cases follows a rotational path from reactant to product and that the isomerization dynamics is significantly affected by substitution. The relative times for completing a trans–cis isomerization cycle for four compounds, 2,6-dimethylazobenzene?>?2,2-dimethylazobenzene and 2,6-dimethylazobenzene?>?2-methylazobenzene>?azobenzene, follow the same order as for the photoinduced formation of the surface relief grating of polymers based on these four compounds. The simulation results provide a basis for understanding the surface relief grating formation of azobenzene-based materials upon irradiation with laser beams.     

Ionization potentials and partition functions of ions in a semiclassical model

The characteristics of an isolated ion (its radius, energy, ionization potential, bound-state energy, and excitation spectrum), which appear in the chemical plasma model, are calculated via the Thomas-Fermi statistical model. The expression for the partition function of the ion excitation at a given temperature and plasma density has been derived. A comparison with the empirical results is performed.