We present data for the temperature and magnetic-field dependence of the specific heat, magnetic susceptibility, magnetization, and electrical resistivity of ${\mathrm{U}}_{0.2}$${\mathrm{Y}}_{0.8}$${\mathrm{Pd}}_3$. The data demonstrate the scaling behavior of the thermodynamic quantities at temperatures up to 10 K and magnetic fields up to 14 T. The magnetic field scales as ${\mathit{T}}^{1.3}$. The zero-field specific heat varies with temperature as -T lnT. The magnetic field strongly affects the thermodynamics, but the magnetoresistance is very small (-2% at T=0.36 K and H=14 T). We argue that our data are inconsistent with any single-impurity interpretation. We suggest that the system has a second-order phase transition at T=0.

We have studied the low-temperature behavior of lead-alloy Josephson tunnel junctions with area S≊0.01 μ${\mathrm{m}}^2$, isolated from their electromagnetic environment by high-resistance metallic resistors inserted into the current and voltage leads. Under irradiation with microwaves frequencies, f=3.5–10 GHz, the dc differential resistance dV/dI, as a function of the dc current I, showed peaks at I=±2ef. This effect, and other observations, arises due to the periodic electrical recharging of the junction by discrete Cooper pairs, and can be explained by the ‘‘orthodox’’ theory of Bloch oscillations.

We study the effects of dilute random pins on vortex ordering and flow within a bond-diluted Josephson-junction array in a transverse magnetic field. We find evidence suggesting that the disorder drives ${\mathit{T}}_{\mathit{c}}$→0; nevertheless, the flux-flow resistivity in a dc current is reduced compared to a pure array.

The importance of the electronic spin fluctuations in the ${\mathrm{CuO}}_2$ planes in the theory of the transverse nuclear relaxation for ${\mathrm{YBa}}_2$${\mathrm{Cu}}_3$${\mathrm{O}}_7$ has been demonstrated by Pennington and Slichter. We present the predictions of a RPA-like theory for the transverse nuclear relaxation time, τ, in the superconducting state. s- and d-wave gap symmetries yield distinctively different results for ${\mathrm{\tau }}^{\mathrm{-}1}$; for an s-wave gap ${\mathrm{\tau }}^{\mathrm{-}1}$ decays rapidly below ${\mathit{T}}_{\mathit{c}}$, while for a d-wave gap it remains nearly constant. Measurements of ${\mathrm{\tau }}^{\mathrm{-}1}$ below ${\mathit{T}}_{\mathit{c}}$ could provide valuable information about the symmetry of the superconducting state. Results for the temperature dependence of ${\mathrm{\tau }}^{\mathrm{-}1}$ in the normal state are also given.

The kinetic differences of growth between standard solid-state synthesis and in situ growth by laser ablation have allowed the substitution of Ce and Tb for Y in ${\mathrm{Y}}_1$${\mathrm{Ba}}_2$${\mathrm{Cu}}_3$${\mathrm{O}}_7$ for the first time. The effects of Ce and Tb substitution on the material ${\mathit{T}}_{\mathit{c}}$ is discussed within the framework of the existing models for the Pr system. We suggest that localization of the holes by trapping may provide a suitable mechanism to account for the observed properties of the Pr and Ce substituted compounds.

We find that the linewidth and energy of an electronic excited state in a cuprate semiconductor increase linearly with increasing temperature. We model this change as due to interactions of the bound electrons with bosons in the antiferomagnetic lattice. The coupling constant between the relaxation rate and the thermal energy is of order 0.5, similar to that for free carriers in superconducting cuprates.

A novel approach to the application of high-resolution electron-energy-loss spectroscopy to polar materials is demonstrated in this Letter. By using a high-impact-energy beam and an off-specular scattering geometry, losses due to excitation of the adsorbates are observed in the 1000–4000-${\mathrm{cm}}^{\mathrm{-}1}$ range with little interference from the intense losses due to multiple surface optical phonons (Fuchs-Kliewer modes). Adsorption of water and methanol on ultrathin MgO(100) films on Mo(100) have been studied using this new approach.

We study the Hamiltonian of a two-level system interacting with a one-mode radiation field by means of the Wigner method and without using the rotating-wave approximation. We show that a phenomenon of collapses and revival, reminiscent of that exhibited by the Jaynes-Cumming model, takes place in the high coupling limit. This process appears as irreversible or virtually reversible, according to whether the semiclassical regime is chaotic or not. Thus we find a new mechanism for dissipation in the quantum domain.

In this paper we propose and test a possible varitaional principle for nonequilibrium steady states far from equilibrium where local thermodynamic equilibrium has broken down. We propose that subject to the externally imposed constraints, the rate of decrease of the volume of phase space which is accessible to the system, is a local minimum. This hypothesis reduces to the familiar principle of minimum entropy production for systems in local thermodynamic equilibrium. We provide computer-simulation data in support of our hypothesis.

A recently proposed phase-space representation for quantum mechanics provides a formal means for investigating the correspondence between classical and quantum mechanics. To explore the implications of this new representation, we introduce a numerical method for propagating an initial wave function directly in phase space. We illustrate the usefulness of the proposed method by analyzing two simple quantum-mechanical systems in phase space.

In a supernova core the nucleon collision rate ${\mathrm{\Gamma }}_{\mathrm{coll}}$ far exceeds oscillation frequency of neutrino or axion radiation originating from nucleon bremsstrahlung processes of the type NN→NN+νν¯ or a. Therefore, including the imaginary part of the self-energy in the effective nucleon propagator, the rate for such processes is suppressed by a factor [1+(${\mathrm{\Gamma }}_{\mathrm{coll}}$/ξT${)}^2$${]}^{\mathrm{-}1}$, where ξ is a numerical factor and T is the temperature. Previous SN 1987A bounds on axions, right-handed neutrinos, and other particles must be relaxed accordingly.

The W′ is a charged, heavy, vector boson predicted to exist by some extensions of the standard model. We have searched for the processes W′→eν and W′→μν for ${\mathrm{M}}_{\mathrm{W}\prime }$>100 GeV/${\mathrm{c}}^2$, in p¯p collisions at s=1.8 TeV, using data taken with the Collider Detector at Fermilab. The nonobservation of these processes leads to a lower limit of 520 GeV/${\mathrm{c}}^2$ (95% confidence level) on the mass of the W′, assuming standard-strength couplings to three fermion generations.

A search for the rare decays ${\mathit{K}}_{\mathit{L}}^0$→μe and ${\mathit{K}}_{\mathit{L}}^0$→ee was performed at the KEK 12-GeV Proton Synchrotron. No event was observed in the fiducial region for the decay ${\mathit{K}}_{\mathit{L}}^0$→μe. There was one event in the fiducial region for the decay ${\mathit{K}}_{\mathit{L}}^0$→ee, which was indistinguishable from the background. The upper limits on the branching ratios at 90% confidence level were B(${\mathit{K}}_{\mathit{L}}^0$→μe)<9.4×${10}^{\mathrm{-}11}$ and B(${\mathit{K}}_{\mathit{L}}^0$→ee)<1.6×${10}^{\mathrm{-}10}$.

We observed 117.8 ${\mathit{K}}_{\mathit{L}}^0$→μμ events after background subtraction of 1.2 events in an experiment to search for the deays ${\mathit{K}}_{\mathit{L}}^0$→μe and ee at the KEK 12-GeV Proton Synchrotron. Normalizing to the decay ${\mathit{K}}_{\mathit{L}}^0$→${\mathrm{\pi }}^{+}$${\mathrm{\pi }}^{\mathrm{-}}$, the branching ratio B(${\mathit{K}}_{\mathit{L}}^0$→μμ)=[7.9±0.6(stat)±0.3 (syste)]×${10}^{\mathrm{-}9}$ was obtained.

An analysis has been made of all available data near threshold for the reactions πN→ππN in terms of isospin amplitudes. The experiments for different channels are found to be consistent with each other and with the chiral-symmetry-breaking model of Olsson and Turner. The analysis yields values for the ππ scattering lengths which are in good agreement with a calculation based on the Weinberg ππ interaction corrected for the effects of the ${\mathit{f}}_0$(975) scalar meson.

Bremsstrahlung from tritium–rare-gas mixtures enclosed in low-permeability glass bulbs has been observed with a Si(Li) detector. The end point of the x-ray spectrum, 18 556(6) eV, implies a ${}_{}{}^3{}_{}{}^{}\mathrm{-}_{}^3{}_{}{}^{}$He atomic-mass difference of 18 595(6) eV.

The half-life of tritium has been measured by monitoring the decay of the x-ray bremsstrahlung emitted by gaseous mixtures of ${\mathrm{H}}_2^3$ and Xe. The result, 12.31±0.03 yr, when combined with the end-point energy measured on the same sources, yields the product (${\mathrm{G}}_{\mathrm{A}}$/${\mathrm{G}}_{\mathrm{V}}^{\prime }$)〈σ〉=2.098±0.003, where 〈σ〉 is the Gamow-Teller matrix element. Combined with a recent precise calculation of the matrix element, this value suggests that the renormalization of the axial-vector interaction can be entirely accounted for by nuclear effects in the triton. The deduced value of ${\mathrm{G}}_{\mathrm{A}}$/${\mathrm{G}}_{\mathrm{V}}^{\prime }$ constrains the neutron lifetime to lie in the range of 897±3 s.

The threshold electrodisintegration of the deuteron was measured with good energy resolution to a maximum four-momentum transfer squared of 42 ${\mathrm{fm}}^{\mathrm{-}2}$. The data are compared with meson exchange calculations that show sensitivity to the choice of exchange-current form factor, the nucleon electromagnetic form factors, and the nucleon-nucleon potential. While conventional theories can give a reasonable description of the data, comparison of the data with quark cluster calculations shows poor agreement.

The optical-absorption spectrum of ${\mathrm{Li}}_6$ has been observed by depletion spectroscopy in the 400–700-nm range. The experimetnal results are compared with theoretical spectra calculated for the three ${\mathrm{Li}}_6$ structures in competition and we have been able to unambiguously determine the most stable ${\mathrm{Li}}_6$ geometry as being the ${\mathit{C}}_{2\mathit{v}}$ tripyramidal geometry.

The static and dynamic frictional forces of single-crystal muscovite mica are measured as a function of the lattice misfit angle between the two contacting cleavage lattices at a very light load under both dry and ambient atmospheres. The frictional forces are anisotropic with respect to the lattice misfit angle, i.e., they increase (decrease) when the contacting surfaces approach being commensurate (incommensurate). The underlying mechanisms of the anisotropy are discussed in terms of the commensurability between the contacting lattices.