Journal of Physics A: Mathematical, Nuclear and General 

About: Journal of Physics A: Mathematical, Nuclear and General is an academic journal. The journal publishes majorly in the area(s): Cosmic ray & Hamiltonian (quantum mechanics). It has an ISSN identifier of 0301-0015. Over the lifetime, 491 publications have been published receiving 5273 citations.

Solitons in nonlinear optics. I. A more accurate description of the 2π pulse in self-induced transparency

Abstract: A more accurate description of the 2 pi pulse of self-induced transparency is obtained. This is an exact solution of an approximate form of the Maxwell-Bloch equations in which only backscattering is neglected; the equations are valid at densities less than about 1018 atoms cm-3. At such densities the 2 pi sech pulse of McCall and Hahn (1967, 1969) remains a good approximate well into the picosecond range. The more accurate solution is chirped by a factor proportional to the square of the ratio of the spectral width of the pulse to its carrier wave frequency. The stability of this pulse solution and other N soliton solutions of the approximate Maxwell-Bloch equations is demonstrated.

Image reconstruction from finite numbers of projections

Abstract: Several results are obtained appertaining to the reconstruction of a two- dimensional image from a finite number of projections. Several schemes are considered for interpolating between the given data. When a trigonometrical Fourier series is used for angular interpolation then one finds, firstly, a consistency condition whereby a posteriori estimates can be made of the errors in the given data, and secondly, a basic image which contains only that information common to all physically permissible interpolation schemes. This basic image is necessarily free of misleading artefacts but it is computationally slow. Several computationally rapid interpolation schemes (based on the fast Fourier transform algorithm) are found to give good quality images, provided the given number of projections is sufficient to resolve the major details of the true image. A computational example is presented showing that a contrived image can be accurately reconstructed from a single projection.

Three-state Potts model and anomalous tricritical points

Abstract: Thirteen terms are presented of the low-temperature series for the free energy of the three-state Potts model in arbitrary external fields. Extrapolation of the series for specific heat, order parameter, and susceptibilities indicates that the transition in zero field is continuous (in contrast to the Landau prediction) with exponents alpha = alpha '=0.05+or-0.10, beta =0.10+or-0.01, gamma ' approximately=1.5+or-0.2 and gamma 'perpendicular to =1.1+or-0.1. These conclusions suggest the presence of an 'anomalous' tricritical point in the model; the associated phase diagram is discussed and contrasted with phenomenological predictions.

Intelligent spin states

Abstract: The intelligent spin states are defined as those states which satisfy the Heisenberg equality for the spin operators: Delta Jx2 Delta Jy2= mod (Jz) mod 2. The 2j+1 states which behave intelligently in each angular momentum space of spin j are found explicitly. For this purpose the Radcliffe states are used, it is shown that only the real and the pure imaginary Radcliffe states are intelligent. These intelligent states also satisfy the quartic consistency condition. The result, however, does not disagree in principle with the recent claim of Kolodziejczyk and Ryter (1974) that mod mu )= mod 0) is the only state which minimizes the uncertainty product because minimum uncertainty does not necessarily imply intelligence.

Simple derivations of generalized linear and nonlinear Langevin equations

Abstract: With the aid of a single operator identity, the derivation of the Mori generalized linear Langevin equation is simplified and a new generalized nonlinear Langevin equation is obtained. The flexibility of the method is stressed which allows the derivation of various generalized nonlinear Langevin equations that can be used as bases for devising approximation schemes such as the mode coupling scheme.