The bend elastic constant $K_3$ and the anisotropy of diamagnetic susceptibility ${\chi }_a$ of two lyotropic mixtures: potassium laurate, decanol, and water and sodium decylsulfate, decanol, and water in the nematic calamitic phase are determined. The experimental method by the action of magnetic fields in samples with and without ferrofluid. These distortions are observed in a polarizing microscope. The results of $K_3$ and ${\chi }_a$ are compared with the measurements of these parameters for a different lyotropic mixture.

Several theorems on the mechanics of gathering information are proved, and the possibility of violating the second law of thermodynamics by obtaining information is discussed in light of these theorems. Maxwell’s demon can lower the entropy of his surroundings by an amount equal to the difference between the maximum entropy of his recording device and its initial entropy, without generating a compensating entropy increase. A demon with human-scale recording devices can reduce the entropy of a gas by a negligible amount only, but the proof of the demon’s impracticability leaves open the possibility that systems highly correlated with their environment can reduce the environment’s entropy by a substantial amount without increasing entropy elsewhere. In the event that a boundary condition for the universe requires it to be in a state of low entropy when small, the correlations induced between different particle modes during the expansion phase allow the modes to behave like Maxwell’s demons during the contracting phase, reducing the entropy of the universe to a low value.

The two-species aggregation of charged monomers is investigated within a diffusion-limited-aggregate (DLA) model coupled with Coulomb drift. Regardless of the proportion of the two species, the charged, conducting aggregates are shown to be in the same universality class as the conventional DLA’s. From energy considerations, the fractal dimension $d_f$ for this class is shown to satisfy the inequality $d_f$≥d-1, in a d-dimensional space. This provides an alternative proof for the well-known causality bound of Ball and Witten [Phys. Rev. A 29, 2966 (1984)]. Energy considerations also rule out the applicability of the DLA model to the case of homopolar aggregates of real materials.

The structure of the projection-operator theory of Mori for quantum Brownian motion is reconsidered, emphasizing the nature of underlying quantum processes. Quantum-mechanical assumptions of the theory are extracted to sets of axioms. The Hilbert space scrV formed with relevant observables for quantum generalized Langevin equations (QGLE’s) includes, in general, elements that cannot be operators on state vectors of the original system. The definition of Liouville operator L, as a mapping from one operator to another, thus requires its reconstruction in scrV. The work shows that the mentioned axioms not only ensure a unified reconstruction of L (hence of QGLE’s) in systems in stationary states that may be nonequilibrium as well as equilibrium, but also extend intrinsically the domain of applicability of QGLE’s. Illustrations of the setting for these extended QGLE’s are presented by concrete examples of Hilbert spaces formed with quantum-mechanical Gaussian and non-Gaussian random variables, showing specifically the significance of a response-function-type inner product that assigns δ correlation to the quantized Gaussian white noise which is an operator-valued distributional process with Kubo-Martin-Schwinger property.

Silica particles coated with octadecyl chains and dispersed in linear alkanes (dodecane and higher alkanes) show gelation upon cooling. The structure of these gels can be characterized in terms of a fractal dimension $d_f$=2.1. Aggregation and gelation at temperatures just below the cloud point (the temperature at which phase transition occurs) have been studied by light scattering and are described in terms of the finite linear cluster size (cluster radius) ξ of the growing fractal. This size is found to increase linearly with time. The influence on $d_f$ of quench temperature, volume fraction, particle size, and solvent type is discussed.

The diffusion-limited aggregation (DLA) model of cluster growth and aggregation has been extended to include both a finite and variable diffusion length for the particle’s random walk. The new model generates a variety of different structures similar in geometry to the DLA model; however, they lack the fractal scaling indices normally expected from the DLA model. It is postulated that the DLA and Eden models of cluster growth are both limiting cases of the finite-diffusion-length model where the diffusion length approaches infinity and zero, respectively.

Classical nonlinear-response theory is applied to an ensemble of experiments performed under the same external field. If the field is time independent, the formalism simplifies, and we can derive the ‘‘Kawasaki expression’’ for the distribution function, as well as the transient correlation-function expression for the observable response. Recent computer simulations have shed new light on our understanding of the steady-state nonequilibrium distribution function: the fractal nature of the distribution causes us to reevaluate the usual mathematical tools used to describe nonequilibrium processes.

Previous calculations of two-photon absorption and emission in hydrogen have revealed frequencies at which the transition is forbidden, at least within the approximations made. Here we show that if retardation is taken into account these so-called ‘‘transparency frequencies’’ are slightly shifted, but the zero transition amplitude persists.

It is shown that our method of ‘‘successive perturbations’’ is closely related to the method of analytic continuation of perturbation series via reexpansion about a shifted origin [Silverman, Sudhindra, and Olbrich, Phys. Rev. A 30, 1554 (1984)], in that the former procedure arises from successive incremental applications of the latter. The theory is illustrated with a second-order application to the anharmonic oscillator.

The energy shift of the 1$s_{1/2}$ state in ${}_{{}_{92}{}^{238}{}_{}{}^{}}{}^{}{}_{}{}^{}\mathrm{U}$ due to virtual excitation of nuclear rotational modes is shown to be a considerable correction for atomic high-precision experiments. In contrast to this, nuclear polarization effects are of minor importance for Lamb-shift studies in ${}_{{}_{82}{}^{208}{}_{}{}^{}}{}^{}{}_{}{}^{}\mathrm{Pb}$.

We have studied the interaction of the squeezed light with the nonabsorbing nonlinear medium in the framework of the model of an anharmonic oscillator initially in a Holstein-Primakoff SU(1,1) coherent state. We have shown that the initial squeezing reappears periodically. Furthermore, due to the interaction with the nonlinear medium, the squeezing can be enhanced.

An expression is derived for the energy density of a lattice of point vortices (or other logarithmic objects) having an arbitrary number of vortices of arbitrary strengths in an arbitrary unit cell. The result is expressed in the form of a rapidly convergent series well suited for numerical evaluation. The effects of separately changing the shape and dimensions of the unit cell are shown for simple cases, and the energy of the triangular lattice is calculated as a function of slip displacement.

An improved algorithm for the calculation of correlation integrals and corresponding dimensions is introduced. The computation time is independent of both number and values of chosen embedding dimensions and therefore the algorithm should be especially useful in analyzing experimental data from high-dimensional systems.

We show that the version of the method of continued fractions presented by Staszewska [Phys. Rev. A 35, 3554 (1987)] leads to the same approximate expression for the reactance matrix as the method of continued fractions for the Green’s function of Horáček and Sasakawa [Phys. Rev. A 30, 2274 (1984)].

The relevance of the conclusions of a paper by Fan and Zaidi [Phys. Rev. A 37, 2985 (1988)] concerning the possibility of generating squeezed states of a harmonic oscillator by sudden change of its frequency is analyzed.

We disagree with the conclusions of the preceding Comment [Janszky and Yushin, Phys. Rev. A 39, 5437 (1989)]. It is shown in this Reply that a squeeze operator can also serve as the time evolution operator for a Franck-Condon transition, and that our previous interpretation is correct. It is also pointed out that the model Hamiltonian used in the preceding Comment is not appropriate for a Franck-Condon transition.

Radiative electron capture in relativistic ion-atom collisions is studied by describing the ‘‘active’’ electron in the combined field of the target and projectile. This two-center effect introduces important changes in the radiative recombination process at very high impact velocities. Estimations are given for the parameters of interest to planned measurements of electron capture from the vacuum.

We have investigated the nonlinear dynamics of a single longitudinal mode Co:${\mathrm{MgF}}_2$ laser by modulating the pump laser intensity. We measured frequency- and time-domain intensity as a function of the modulation frequency and amplitude, and observed a series of subharmonic bifurcations and chaotic behavior. The main features of this behavior are found to be displayed by the coupled nonlinear rate equations for a four-level laser with time-dependent gain.

The observation of a new critical point in liquid-crystal phase transitions is reported. Detailed tilt angle, polarization, and susceptibility measurements of a ferroelectric liquid crystal in the presence of an applied dc electric field show that a first-order transition between the polarized smectic-A phase and the ferroelectric smectic-C phase terminates at a critical point in the temperature-field plane.