Effects of a small deviation from fermi statistics

By considering a generalized statistics with occupation numbers between Bose-Einstein and Fermi-Dirac statistics we study the resultant distribution when the states differ by a small factor from a Fermi-Dirac distribution. Both the Fermi energy and any level crossing phenomena are sensitive to such statistics; in particular, the electrical conductivity and the free electron heat capacity of fermions at low temperatures receive corrections due to alterations of Fermi-Dirac statistics.     

Chiral dynamics of nuclear saturation

We apply the relativistic chiral Lagrangian to the nuclear equation of state. An effective chiral power expansion scheme, which is constructed to work around nuclear saturation density, is presented. The leading and subleading terms are evaluated and are shown to provide an excellent equation of state. Our saturation mechanism is found to probe in detail the underlying pion dynamics.     

A remark on the saturation of nuclear forces in nuclear matter

The paper deals with the problem of saturation in nuclear matter, when the two-nucleon interaction is described by the soft core potentials acting in a limited number of orbital states. The potentials used belong to the class of the realistic potentials.     

Absence of the small tricritical deviation from the mean-field approximation for the isotropic-nematic phase transition

The tricritical behaviour of the isotropic-nematic phase transition is studied. The presence of two independent sixth-order terms in the free energy expansion breaks the conventional tricritical behaviour and eliminates the tricritical restriction for the deviation from the mean-field approximation.     

The tensor force in nuclear saturation

One-term separable potentials in the ³S-³D channel are constructed which fit the following low-energy nucleon-nucleon data: the triplet effective range and scattering length, deuteron binding energy and quadrupole moment. They also yield ³D₁ phase shifts which have the correct sign. These potentials differ, however, in the amount of deuteron D-state probability, P_D, which they predict, where P_D ranges from 1 % to 9 %. Binding energy calculations of infinite nuclear matter and ⁴He are performed in order to test the effect of the tensor force on nuclear saturation properties. It is found that the larger the D-state probability, the smaller the energy per particle and saturation density. Detailed comparisons with local potentials in nuclear matter are also presented.

In nuclear matter no single-particle potential in intermediate states is used; in ⁴He, , where f is varied such that the absolute value of the diagram with a single potential insertion in a particle line is minimized. It is found in ⁴He that f= 0.75 and that this result is almost independent of both the potential employed and of ω. Furthermore, for 0 f 1.5, the total energy is independent of f.     

大功率非晶态变压器磁偏饱和的预防方法

概述了非晶态材料的基本特性，深入分析了大功率非晶态变压器出现磁偏移饱和现象的原因，提出了幅值递增法，脉宽递增法和电流积分调宽法等预防磁偏饱和的方法. 关键词： 非晶态磁偏饱和 幅值递增法 脉宽递增法 电流积分调宽法     

High-density QCD and saturation of nuclear partons

We review the recent finding of the two-plateau momentum distribution of sea quarks in deep inelastic scattering off nuclei in the saturation regime. The diffractive plateau which dominates for small p measures precisely the momentum distribution of quarks in the beam photon, the rôle of the nucleus is simply to provide an opacity. The plateau for truly inelastic DIS exhibits a substantial nuclear broadening of the momentum distribution. Despite this nuclear broadening, the observed final-state and initial-state sea quark densities do coincide exactly. We emphasize how the saturated sea is generated from the nuclear-diluted Weizsäcker-Williams because of the anti-collinear splitting of gluons into sea quarks.Received: 30 September 2002, Published online: 22 October 2003PACS: 11.80.La Multiple scattering - 13.87.-a Jets in large-Q ² scattering - 24.85. + p Quarks, gluons, and QCD in nuclei and nuclear processe     

On global asymptotic stability of 2-D discrete systems with state saturation

A criterion for the global asymptotic stability of 2-D discrete systems described by the Roesser model employing state saturation nonlinearities is presented. The criterion is a less restrictive version of an earlier criterion due to Liu and Michel.     

On the radiation from small particles

The laws of equilibrium radiation within cavities and from surfaces of bodies must be recast when the cavity or body dimension is of the same order as the wavelength being considered. New formulae for the Planck function, the Wien displacement law, and the Stefan-Boltzmann law for small spherical particles are presented in this paper in terms of the three independent variables temperature, wavelength, and diameter. The most significant element of the formulation for black particles is that radiant emission, or absorption, is not permitted at wavelengths greater than √2π times the particle diameter.     

A possible quark mechanism for the saturation of nuclear matter

A nuclear matter saturation mechanism based on the quark structure of the nucleon is proposed. Nuclear matter is described by nucleons and mesons but the meson field modifies the internal quark motion and this induces a saturation mechanism. Its possible relevance for nuclear physics is studied in a schematic model where it is the only active mechanism. Though caricatural, this model provides a rather satisfactory interpretation of the nuclear matter properties.     

Positrons from supercritical fields of giant nuclear systems

During collisions of heavy nuclei with a combined chargeZ?160 the electronic 1s-state is deeply bound due to the strong Coulomb field, forZ≧173 it even enters as a resonance the lower continuum of the Dirac-Hamiltonian. In pure Rutherford scattering no qualitative indication for the filling of a dynamically createdK-hole by the spontaneous positron creation process is predicted, but the study of heavy-ion collisions with nuclear time delay due to the attractive nuclear force promises clear signatures for the decay of the vacuum. Emphasis is laid also on the quantitative influence of the electron-electron interaction and ofE0-transitions in the giant nuclear system on positron emission, the latter treated in a classical approximation. We compare our results with recent experimental data of two different groups at GSI, Darmstadt.     

On the moment of inertia of large nuclear systems with pairing forces

The moment of inertia of large nuclear systems with pairing forces was shown to be that of an irrotational flow byPrange. Following an argument due toThirring, we will give here a very simple derivation of this important result.     

On some thermodynamic effects in small molecular systems

The behavior of a gas-liquid system in a small volume has been studied. In the absence of the thermodynamic limit, the problem has been examined by methods of statistical physics. This allows the use of new mathematical methods previously applied in nuclear physics. Within the modified droplet model of a real gas sandwiched between two extended plates, an additional component of the pressure, which was previously discussed and exhibits characteristic oscillations at change in the volume, has been found. Qualitative coincidence with the previously reported molecular dynamics simulations has been found.     

QCD susceptibilities, nuclear saturation and two-pion processes

We discuss the in-medium behaviour of the QCD scalar susceptibility and of the sigma mass in a chiral relativistic theory which incorporates the scalar response of the nucleon. We also study the many-body effects in the propagation of the scalar meson in the nuclear medium arising from its coupling to two-pion states. The same modification applies to the QCD scalar susceptibility. We conclude with the nuclear physics implications for the in-medium scalar nucleon–nucleon attraction.     

On the convergence of the nuclear field theory perturbation expansion for strongly anharmonic systems

The convergence of the nuclear field theory is studied for situations in which the interaction energy between the photons is of the same order of magnitude as the correlation energy of the photons.