Quantum corrections to the mean-field equation of state for nuclear matter are estimated in a lattice simulation of quantum hadrodynamics. In contrast with the standard coordinate-space methods used in lattice QCD, the calculations are carried out here in momentum space and on nonhypercubic (irregular) lattices. The quantum corrections to the known mean-field equation of state were found to be considerable.

Measurements of the Drell-Yan process and of charmonium and bottomonium production at CERN and Fermilab show a depletion at high Feynman x in large relative to small nuclear targets. We can attribute this depletion to energy loss of initial and final states, provided that the loss is (dE/dz${)}_{\mathrm{Drell}\mathrm{-}\mathrm{Yan}}$=4/9 (dE/dz${)}_{\mathrm{charm}}$∼1.5 GeV/fm at the highest ${\mathit{x}}_{\mathit{F}}$ measured. This small loss is magnified in the differential cross section due to the strong behavior ∼(1-x${)}^{\mathit{n}}$ of the projectile’s structure functions at large x.

The dynamics of a metastable beam of particles ‘‘injected’’ into artificially excited resonance islands in the Fermilab Tevatron is studied. Evolution of the captured beam distribution is measured by an externally detectable coherent signal. Dynamical partitions observed in the control space of amplitude and tune of a focusing modulation are consistent with an equivalent mode of an ensemble of driven gravity pendula. The model’s single parameter, the island tune ${\mathit{Q}}_{\mathit{I}}$ of small oscillations, is inferred as the central frequency of resonant detrapping under this weak drive.

We present microscopic semiclassical simulations of the femtosecond nonlinear-optical polarization (${\mathit{P}}^{\mathrm{}\left(3\right)\mathrm{}}$) of a solute in water. ${\mathit{P}}^{\mathrm{}\left(3\right)\mathrm{}}$ is dominated at short times by intermolecular vibrations that cannot be accounted for by the Bloch equations. The applicability of the Bloch, stochastic, and Brownian oscillator models to the interpretation of photon-echo and pump-probe measurements is discussed. We find that only microscopic semiclassical simulation and the Brownian oscillator model can account for the essential features of ${\mathit{P}}^{\mathrm{}\left(3\right)\mathrm{}}$.

Dislocations are important for wave-number adjustment in the almost periodic patterns found in convecting fluids and a wide variety of other physical contexts. Using a model for infinite-Prandtl-number fluids, we show that, far from onset, climbing dislocations can undergo local, finite-amplitude instabilities that lead to the formation of disclinations, bridgelike structures, sudden roll disappearance, and gliding.

The phason dispersion and the dielectric response of a ferroelectric Sm-${\mathit{C}}^{\mathrm{*}}$ liquid crystal in an external magnetic field have been measured. A magnetic-field-induced splitting of the phason branch into an acousticlike and an opticlike mode was observed, indicating a crossover between the plane-wavelike and solitonlike phason dynamics. The resulting band gap at q=0 is a direct consequence of the broken continuous helicoidal symmetry of the Sm-${\mathit{C}}^{\mathrm{*}}$ phase in a transverse magnetic field.

Simulations of diamondlike amorphous carbon formed by quenching the liquid under high pressure indicate that two distinctly different dense phases exist. The ‘‘as-quenched’’ phase is metastable and mostly fourfold coordinated. Upon annealing, it converts into a more stable structure with the majority of atoms having threefold coordination. Both structures are consistent with experimental findings. The annealed phase is clearly distinguished from the low-coordinated network of evaporated α-C.

We have performed large-scale total-energy electronic-structure calculations within the local-density approximation for the negatively charged vacancy in Si. The obtained Jahn-Teller distortion, the electronic structures, and the hyperfine coupling tensors are in good agreement with the experimental data available, indicating the validity of the one-electron theory, contrary to the prevailing picture based on model calculations.

We studied the surface diffusion of hydrogen on Ni(100) by linearly diffracting a probe laser beam from a monolayer grating of adsorbed hydrogen. In the temperature range from 110 to 161 K the Arrhenius plot shows a significant leveling off of the diffusion coefficient D(T) at around 144 K. Such a deviation from the behavior of thermally activated diffusion suggests the onset of quantum tunneling diffusion.

We consider the diffusion of a particle coupled to a surface which undergoes a structural phase transition. Using a recently developed microscopic theory of diffusion, we show that the diffusion coefficient is anomalously reduced near the transition because of the diverging value of the friction near the transition. To demonstrate this anomaly, we evaluate the diffusion coefficient for a model Hamiltonian describing an adatom on the W(100) surface which undergoes a (1×1)→c(2×2) reconstruction.

We consider droplets on a substrate that grow according to a power law. When the droplets touch, they coalesce with mass conservation. It is shown by both numerical study and analytical arguments that such a system exhibits a 1/${\mathit{f}}^2$ noise even at low frequencies in the fluctuations of the substrate coverage. This type of noise is expected to be independent of the growth exponent and of the dimensionalities of the droplet and of the substrate.

Low-temperature solid-phase epitaxial regrowth of amorphous silicon (a-Si) is reported for an ion-amorphized NiSi structure. The epitaxial regrowth follows after monosilicide formation upon heating to only 425 °C, as evidenced by Rutherford backscattering and channeling measurements and transmission electron microscopy. The regrowth rate of the a-Si layer (thickness ∼600 Å) is enhanced by more than a factor of 300 compared with ordinary solid-phase epitaxy of ion-implanted a-Si. This is attributed to results from redistribution of Ni towards the a-Si/c-Si interface, as shown by secondary-ion mass spectrometry, where the presence of Ni, or Ni-silicide nuclei, enhances the solid-phase epitaxy.

The femtosecond pump-and-probe technique, with 14-fs probe pulses, was used to measure exciton dynamics utilizing the unique characteristics of II-VI CdZnTe/ZnTe quantum wells, at room temperature. We have found that the bleaching effect of ‘‘cold’’ neutral excitons on excitons is stronger than that of the same density of ‘‘cool’’ uncorrelated charged electron-hole pairs, in disagreement with predictions. We find strong evidence, however, that long-range Coulomb screening is negligible in quasi-2D quantum wells. Additionally, we have measured a very fast exciton ionization time of 110 fs.

Generation of cold excitons in GaAs quantum wells is shown to lead to enhanced condensation to the biexciton state under cw illumination. Resonant two-photon absorption to the biexciton state in the same structure is found to account for a quantum beating phenomenon involving the biexciton and exciton states in a more complex three-level system than hitherto investigated.

We present a detailed comparison between experiment and theory of the magnitude of the exchange-correlation Coulomb interaction in the collective intersubband spin-density excitation of the electron gas confined to GaAs/AlGaAs quantum wells. A widely used self-consistent-field theory in which exchange and correlation is incorporated through the local-density approximation is found to underestimate slightly the magnitude of the interaction, while a nonlocal theory involving a variational solution of the Bethe-Salpeter equation for the density-density correlation function compares well with experiment.

We present an atomistic model of light-induced defects (the Staebler-Wronski effect). The model is based in part on our observations of molecular-dynamics simulations with an ab initio code and requires a change in the charge of a well-localized state in the gap, such as a dangling bond, to nucleate a defect. The defects are formed at weak-bond sites in the network following a rearrangement caused by the change of the charge of the localized state.

Using photoionization, photoabsorption, and deexcitation spectroscopies, the dynamics of the N 1s core-hole states for ${\mathrm{N}}_2$ physisorbed on graphite has been investigated. In the photoemission spectrum only the ionic 1${\mathit{s}}^{\mathrm{-}1}$ state is observed. The Auger spectrum shows decay from both this ionic and a neutral 1${\mathit{s}}^{\mathrm{-}1}$1${\mathrm{\pi }}_{\mathit{g}}$ intermediate state created by charge transfer from the substrate. The neutralization occurs with a characteristic time ${\mathrm{\tau }}_{\mathrm{CT}}$=9×${10}^{\mathrm{-}15}$ s. The coupling with the substrate is weak, preserving the gas-phase triplet-singlet splitting of the neutral intermediate state.

The conductance of laterally confined double-barrier quantum-well resonant-tunneling heterostructures is investigated. The confinement is provided by a Schottky gate and can be varied in a continuous way, giving direct proof of the quantum-size effect. Data for dots with nominal diameters in the submicrometer range are reported. Possible evidence for a modulation of the Coulomb blockade by quantum confinement is presented.

The electronic structure of tetragonal ${\mathrm{La}}_2$${\mathrm{CuO}}_4$ is calculated in the self-interaction-corrected (SIC) local-spin-density (LSD) approximation. In contrast to LSD, the SIC-LSD approach reveals the experimentally observed antiferromagnetic and semiconducting ground state. The energy gap is 1.04 eV and of indirect charge-transfer character, and the Cu moment is 0.47${\mathrm{\mu }}_{\mathit{B}}$. The valence-band top states have about equal weight on the in-plane and out-of-plane O atoms. This region is dominated by O states not coupling to the Cu d states, but with a significant component of O states having Cu d-like symmetry.

We show that when the metal-insulation transition occurs near a superconducting state it results in a different critical behavior from that of amorphous metals or uncompensated doped semiconductors. This difference results from the enhancement of the effective electron-electron interaction caused by fluctuations to the superconducting state. This explains the recent experiments of Micklitz and co-workers on amorphous superconducting mixtures Ga-Ar and Bi-Kr.