夸克：从“永久禁闭”到“渐近自由”

物理学基本理论的建立是一个艰苦的、需要长期积累的过程，它需要动用科学家各种类型的思维方法，需要相互合作、多方探索方可取得突破．而正确的理论一旦建立，常会出人意料地把许多表面上看起来互不相干的现象联系起来，发挥理论的指导作用，带动物理学、其他自然科学乃至技术科学的发展．

Steady thermal-solutal capillary convection in a shallow annular pool with the radial temperature and concentration gradients

Using asymptotical analysis,we investigate the characteristics of the coupled thermal and solutal capillary convection with the radial temperature and solute concentration gradients in a shallow annular pool with the free surface.The pool is heated from the outer cylinder with high solutal concentration and cooled at the inner cylinder with low solutal concentration.The asymptotic solution is obtained in the core region in the limit as the aspect ratio,which is defined as the ratio of the depth to the width of the pool,goes to zero.The comparison with the previous work certifies that the asymptotic solution is right and believable.The influences of the solutal capillary force,the buoyant force,the Soret effect and the geometric parameters on the fluid flow are analyzed.

Asymptotic stability with probability one of MDOF nonlinear oscillators with fractional derivative damping

In this paper,the asymptotic stability with probability one of multi-degree-of-freedom(MDOF)nonlinear oscillators with fractional derivative damping parametrically excited by Gaussian white noises is investigated.A stochastic averaging method and the Khasminskii’s procedure are employed to evaluate the largest Lyapunov exponent,whose sign determines the stability of the system.As an example,two coupled nonlinear oscillators with fractional derivative damping is worked out to demonstrate the proposed procedure and to examine the effect of fractional order on the stochastic stability of system.In particular,the case of factional order more than 1 is studied for the first time.

A Semi-Analytical Solution to Classic Yang–Mills Equations with Both Asymptotical Freedom and Confining Features

It is well known that confinings and asymptotic freedom are properties of quantum chromo-dynamics （QCD）. But hints of these features can also be observed at purely classic levels. For this purpose we need to find solutions to the colorly-sourceful Yang-Mills equations with both confining and asymptotic freedom features. We provide such a solution in this paper which at the near-source region is of serial form, while at the far-away region is approximately expressed through simple elementary functions. From the solution, we derive out a classically non-perturbative beta function describing the running of effective coupling constant, which is linear in the couplings both in the infrared and ultraviolet region.

Quantum Gravitational Contributions to Gauge Field Theories

We revisit quantum gravitational contributions to quantum gauge field theories in the gauge condition independent Vilkovisky-DeWitt formalism based on the background field method.With the advantage of Landau-DeWitt gauge,we explicitly obtain the gauge condition independent result for the quadratically divergent gravitational corrections to gauge couplings.By employing,in a general way,a scheme-independent regularization method that can preserve both gauge invariance and original divergent behavior of integrals,we show that the resulting gauge coupling is power-law running and asymptotically free.The regularization scheme dependence is clarified by comparing with results obtained by other methods.The loop regularization scheme is found to be applicable for a consistent calculation.

Semiparametric estimation of average treatment effect through a random coefficient dummy endogenous variable model

This paper provides an estimation procedure for average treatment effect through a random coefficient dummy endogenous variable model. A leading example of the model is estimating the effect of a training program on earnings. The model is composed of two equations:an outcome equation and a decision equation.Given the linear restriction in outcome and decision equations,Chen(1999) provided a distribution-free estimation procedure under conditional symmetric error distributions. In this paper we extend Chen's estimator by relaxing the linear index into a nonparametric function,which greatly reduces the risk of model misspecification. A two-step approach is proposed:the first step uses a nonparametric regression estimator for the decision variable,and the second step uses an instrumental variables approach to estimate average treatment effect in the outcome equation. The proposed estimator is shown to be consistent and asymptotically normally distributed. Furthermore,we investigate the finite performance of our estimator by a Monte Carlo study and also use our estimator to study the return of college education in different periods of China. The estimates seem more reasonable than those of other commonly used estimators.