Showing papers in "Physica D: Nonlinear Phenomena in 1967"

TL;DR: In this article, a relation for the variation of the energy gap (E g ) with temperature (T ) in semiconductors is proposed. And the equation satisfactorily represents the experimental data for diamond, Si, Ge, 6H-SiC, GaAs, InP and InAs.

TL;DR: In this article, the authors studied the X-Y model of a linear chain of spins in the presence of a magnetic field h along the z axis and derived an expression for the time-dependent correlation function ϱ z R (β, t) of the z -components of spins separated by an arbitrary number R of lattice sites.

TL;DR: In this article, the first-order phase transitions in magnetic fields were investigated in the case of ferromagnetic exchange (J > 0), and the behavior of the susceptibility was discussed.

TL;DR: In this article, the authors calculated the temperature correction to the Casimir effect by applying statistical mechanics to a resonant cavity at finite temperature, and compared it with the macroscopic theory of Lifshitz based on a fluctuating electromagnetic field.

TL;DR: In this paper, the magnetic properties of two antiferromagnetic manganese compounds, K2MnF4 and Rb2mNF4, were studied and the crystal structure of these compounds strongly suggests the occurrence of largely isolated quadratic layers of magnetic atoms.

TL;DR: In this article, the N -body Van der Waals interaction energy of a model crystal of point dipoles is given a closed from which, unlike the first orders of the usual perturbation development, takes into account the collective nature of dispersion forces.

TL;DR: In this article, sound velocities in liquid hexane, heptane, octane, nonane, dodecane and hexadecane have been measured in a temperature range from −20 to 200°C and at pressures up to 1400 bars using a pulse method with constant path-length.

TL;DR: In this paper, the density expansion of the diffusion coefficient D of a Lorentz gas is investigated in 2 dimensions and in 3 dimensions at the ϱ3 term, due to a logarithmically divergent integral expression for density coefficients.

TL;DR: In this paper, a Penning discharge at low pressure (P < 10-4 torr) with long anode cylinder is investigated, both theoretically and experimentally, and a classification and short description are given of the various Penning modes and corresponding characteristics are presented.

TL;DR: In this article, the authors discuss the validity of the principle of corresponding states as applied to the viscosity of simple liquids like Ar, Kr, Xe, 02, Nz, CO, CH4, CD4.

TL;DR: In this paper, a clear, covariant formulation of relativistic statistical mechanics can be constructed explicity, based on the duality between the observer's physical space-time which has the well-known Minkowski structure, and the dynamical system's phase space which has a completely different geometrical structure.

TL;DR: In this article, it was shown that the basic equations of hydrodynamics expressed in terms of a density and a velocity field follow exactly from micro-physics for a system of interacting equal particles provided the force density is not specified.

TL;DR: In this article, an account is given of the preparation of lead bromide single crystals undoped and doped with monovalent and trivalent cations and with oxygen.

TL;DR: In this paper, the influence of a magnetic field on the viscosity of polyatomic molecules at room temperature has been investigated and a description of a capillary Wheatstone bridge with a relative resolution of 2·10 −6 is given.

TL;DR: In this article, the authors extended the theoretical calculations of Kagan and Maksinov for the heat conductivity of a paramagnetic gas to the case of a nonparamagnetic gas both for heat and viscosity.

TL;DR: In this paper, the Curie-Weiss constant of CoCs3Cl5 was found to be -0.24 ± 0.02°K and the spin-lattice relaxation time was shown to obey approximately τ ∝ T-7 and to be practically field-independent.

TL;DR: In this paper, a direct method for measuring the volume change on mixing of gases at constant pressure was described for the systems N2-H2, Ar-H 2 and Ar-N2 at several concentrations between 170 and 292°K and at pressures between 3 and 100 atm.

TL;DR: In this paper, it was shown that a single equation, the master equation, correctly describes both the kinetic evolution towards equilibrium and the antikinetic evolution away from equilibrium, which explains the overwhelming predominance of irreversible behaviour in many-body systems.

TL;DR: In this article, the emission cross section of He II lines produced by electron impact (0.05-3 KeV) on helium was measured and compared with electron and proton impact for the 4686 A line.

TL;DR: In this paper, the relation between tensorial Lorentz transformations in physical space and canonical tensor transformations in phase space is examined in detail, and it is shown in particular that the Lipschitz-Liouville equation transforms the phase-space distribution function in such a way that the relevant average values computed with it, transform precisely as vectors or tensors.

TL;DR: In this article, it was shown that CoCs 3 Cl 5 and 3 Br 5 are three and two-dimensional Ising systems at very low temperatures, respectively, and the exchange constants were evaluated on basis of a proposed magnetic structure of 4 antiparallel nearest neighbours and two parallel nearest neighbours.

TL;DR: In this paper, the angular and velocity distributions of the protons obtained by passing a beam of 10 keV H 2 + ions through hydrogen or helium gases are described, and the agreement between theory and experiment indicates that this theory is essentially correct, the greatest unknown being the dependence of the excitation cross section upon the length and orientation of the H 2+ internuclear axis.

TL;DR: In this paper, a calorimeter of the flow-type was constructed with which direct measurements on the heat of mixing could be performed, and the results of the measurements were reported.

TL;DR: In this article, the propagator for the Smoluchowski equation is represented as a functional integral, and evaluated approximately by expanding this functional around the most probable path and neglecting terms of an order higher than the second in the variation.

TL;DR: In this article, the heat dissipation is derived for media in which viscous and inelastic (plastic) flows occur, where the coefficients are simple algebraic functions of the coefficients which occur in the stress-strain relation.

TL;DR: In this paper, the magnetic moment of an impure niobium sample was measured simultaneously with the heat development during variation of an external magnetic field along the axis, and the results were interpreted by means of a tentative relation in which the pinning force was assumed to be proportional to (Hc2-B), the coefficient being proportional to 1 − t4.

TL;DR: In this article, the shear viscosity of liquid argon is measured as a function of pressure ( 0.200 kg cm 2 ) and temperature (86-146°K).

TL;DR: In this article, the method of least squares employing orthonormal functions is used to determine polynomial approximations for an infinite series, which are statistically nearest to those of the infinite series and statistically "fit" the experimental data best.

TL;DR: In this article, the authors studied the effect of pseudocrossing of the two potential curves of the interacting atomic systems before and after the reaction of He+ and H+2 on the emission lines of the target atom, whose emission cross sections in many cases show a remarkable increase with decreasing impact energy.