In Zn-doped single-crystal ${\mathrm{YBa}}_2$${\mathrm{Cu}}_{3\mathrm{-}\mathit{x}}$${\mathrm{Zn}}_{\mathit{x}}$${\mathrm{O}}_{7\mathrm{-}\mathrm{\delta }}$ we show that the normal-state Hall angle varies as cot${\mathrm{\theta }}_{\mathit{H}}$=α${\mathit{T}}^2$+βx, as predicted by Anderson (T is temperature). The existence of two distinct relaxation time scales (${\mathrm{\tau }}_{\mathit{H}}$∼1/${\mathit{T}}^2$ and ${\mathrm{\tau }}_{\mathrm{tr}}$∼1/T), required by experiment, precludes all multi-band Drude-type models. A number of puzzling features of the Hall effect in the cuprates are resolved with the new analysis. We also report an improved measurement of the scattering cross section of Zn in the ${\mathrm{CuO}}_2$ planes.

The temperature dependence of the Hall effect in the normal state is a commom theme of all the cuprate superconductors and has been one of the more puzzling observations on these puzzling materials. We describe a general scheme within the Luttinger liquid theory of these two-dimensional quantum fluids which corrrelates the anomalous Hall and resistivity observations on a wide variety of both pure and doped single crystals, especially the data in the accompanying Letter of Chien, Wang, and Ong.

Measurements of the in-plane resistive transition of ${\mathrm{Bi}}_2$${\mathrm{Sr}}_2$${\mathrm{CaCu}}_2$${\mathrm{O}}_{8+\mathrm{\delta }}$ single crystals in perpendicular magnetic fields reveal that in oxygen-reduced samples a giant resistance maximum evolves with field. This is not seen in oxygenated samples with similar metallic normal resistivities. As the peak resistivity may exceed the normal resistivity, it cannot arise from ordinary vortex-motion dissipation. We propose a model where the excess resistance results from nonrigid vortex motion coupling the out-of-plane dissipation to the in-plane resistance at temperatures where pinning effects are negligible.

Experimental evidence is provided that the pinning force and the critical current density of ${\mathrm{YBa}}_2$${\mathrm{Cu}}_3$${\mathrm{O}}_{7\mathrm{-}\mathrm{\delta }}$ films can be controlled by electric fields. This novel effect is attributed to field-induced changes of the density of mobile charge carriers in the superconductor.

Ground-state populations of cationic and neutral Y, Ba, Cu, and neutral YO, BaO, and CuO are monitored by laser-induced fluorescence during laser ablation of ${\mathrm{YBa}}_2$${\mathrm{Cu}}_3$${\mathrm{O}}_{7\mathrm{-}\mathrm{\delta }}$. 193-nm photons completely dissociate CuO allowing the observation of a subsequent reaction of the Cu atom with ${\mathrm{O}}_2$ to form CuO. As a function of ${\mathrm{O}}_2$ pressure, the CuO signal increases to a maximum at approximately 120 mTorr of ${\mathrm{O}}_2$, presumably minimizing δ, and then falls to negligible levels by 400 mTorr. Ablation at 248 and 351 nm dissociates a smaller fraction of the CuO, i.e., nascent CuO is observed in the absence of ${\mathrm{O}}_2$.

The architecture of the mammalian lung has been shown to be correctly described using a fractal model with a complex dimension, related to a Cantor set with random errors, for four different species. Here we provide an interpretation of that model that has implications for biological evolution. We argue that fractals are more error tolerant than other structures and therefore have an evolutionary advantage.

Using the Faddeev equations in configuration space, we solve numerically the problem of three anyons interacting via harmonic forces. The relevance of our results to the many-anyon problem is discussed.

The low-lying quantum states of three anyons confined in a harmonic-oscillator well are obtained numerically. The interpolation of these states between the limits of noninteracting bosons to noninteracting fermions in the well is established. Particular attention is paid to the transformation of the fermionic ground state to an excited Bosonic state, and its overlap with Laughlin-Wu-type correlated states.

An exact analysis of the Ising model with infinite-range interactions in a random field and a local mean-field theory in three dimensions is carried out leading to a phase diagram with several coexistence surfaces and lines of critical points. Our results show that the phase diagram depends crucially on whether the distribution of random fields is symmetric or not. Thus, Ising-like phase transitions in a porous medium (the asymmetric case) are in a different universality class from the conventional random-field model (symmetric case).

We present an integrability criterion for discrete-time systems that is the equivalent of the Painlevé property for systems of a continuous variable. It is based on the observation that for integrable mappings the singularities that may appear are confined, i.e., they do not propagate indefinitely when one iterates the mapping. Using this novel criterion we show that there exists a family of nonautonomous integrable mappings which includes the discrete Painlevé equations by ${\mathit{P}}_{\mathrm{I}}$, recently derived in a model of two-dimensional quantum gravity, and ${\mathit{P}}_{\mathrm{II}}$, obtained as a similarity reduction of the integrable modified Korteweg–de Vries lattice. These systems possess Lax pairs, a well-known integrability feature.

We present discrete forms of the Painlevé transcendental equations ${\mathit{P}}_{\mathrm{III}}$,${\mathit{P}}_{\mathrm{IV}}$, and ${\mathit{P}}_{\mathrm{V}}$ that complement the list of the already known ${\mathit{P}}_{\mathrm{I}}$ and ${\mathit{P}}_{\mathrm{II}}$. These, most likely integrable, nonautonomous mappings go over to the usual Painlevé equations in the continuous limit, while in the autonomous limit we recover discrete system that belong to the integrable family of Quispel et al. Finally, we show that the discrete Painlevé mappings satisfy the same reduction relations as the continuous Painlevé transcendents, namely, ${\mathit{P}}_{\mathrm{V}}$→{${\mathit{P}}_{\mathrm{III}}$, ${\mathit{P}}_{\mathrm{IV}}$}→${\mathit{P}}_{\mathrm{II}}$→${\mathit{P}}_{\mathrm{I}}$.

We have examined the effects of a large gravitational field on the phenomenon of neutrino oscillations as contemplated in the Mikheyev-Smirnov-Wolfenstein mechanism. We find that the Sun’s gravitational field would amplify any small breakdown in the universality of the gravitational coupling by many orders of magnitude. A breakdown of only 1 part in ${10}^{14}$ would still make the gravitational effect comparable to the conventional weak interaction. The differing energy dependences of the two level-crossing mechanisms can therefore be used as a very sensitive tool to test the conventional universality hypothesis.

Based on the target-space modular invariance of the nonperturbative superpotential of the four-dimensional N=1 supersymmetric string vacua, we find topologically stable, stringy domain walls of nontrivial compactification modulus field configurations. They are supersymmetric solutions, thus saturating the Bogomolnyi bound. Their physical implications are discussed.

Oblique corrections from heavy fermions are studied. For certain mass ranges we find negative contributions to the S and T parameters from Majorana particles.

Photon-stimulated desorption of negatively charged ions from condensed ${\mathrm{O}}_2$ is observed in the 17–42-eV photon energy range. Two classes of photon-stimulated charge-transfer processes, i.e., resonant processes via the formation of highly excited states of the condensed molecules and nonresonant processes involving energetic photoelectrons, are considered to account for these observations.

An extensive study of the 4${\mathit{f}}_{5/2}$ photoionization in xenon is presented which allows, through the observation of the coincident ${\mathit{N}}_{5\mathrm{-}}$${\mathrm{O}}_{23}$${\mathrm{O}}_{23}$ ${}_{}{}^1{}_{}{}^{}$${\mathit{S}}_0$ Auger electron, the establishment of the first complete fragmentation pattern for two-electron emission with information on the momenta and the spin projections of both electrons.

We propose a nonlinear-interferometric scheme for generating two fermion states correlated in particle number or in wave phase. This scheme can be used for surpassing either the standard quantum limit of the number-partition noise or that of the interferometric phase sensitivity, up to a factor of the order of (total particle number${)}^{1/3}$. A possible experimental scheme in a mesoscopic system is discussed.

Atoms prepared in a coherent superposition of a ground- (or excited-) state doublet can produce a large resonant index of refraction with vanishing absorption.

We have obtained high-resolution spectra of hyperfine transitions in an excited state ${(}^1$${\mathit{D}}_2$) of ${\mathrm{Pr}}^{3+}$:${\mathrm{YAlO}}_3$ using a novel four-wave-mixing technique. Subkilohertz resolution is obtained. The hyperfine transition line shapes are determined unambiguously, revealing an interesting effect of mutual-flip interaction between the Im=±1/2> hyperfine states of the Pr ions and the host nuclear spins. The necessary conditions for obtaining laser-jitter-independent resolution in inhomogeneously broadened samples are discussed.

The viability of inertial confinement fusion depends crucially on implosion symmetry. A spherical three-dimensional hydrocode called plato has been developed to model the growth in asymmetries during an implosion. Results are presented in the deceleration phase which show indistinguishable linear growth rates, but greater nonlinear growth of the Rayleigh-Taylor instability than is found in two-dimensional cylindrical simulations. The three-dimensional enhancement of the nonlinear growth is much smaller than that found by Sakagami and Nishihara.