Phonon-phonon coupling strengths have been derived from first-principles total energy calculations for bcc Zr. It is shown that the instability leading to the bcc-hcp first-order phase transition in Zr is overcome at high temperatures by the strong interactions between the ${\mathrm{T}}_1$ N-point phonon and other low-lying (110) ${\mathrm{T}}_1$ vibrational modes.

Heavy-ion (${\mathrm{C}}^{+}$,${\mathrm{N}}^{+}$,${\mathrm{Kr}}^{+}$)–induced low-energy electron emission (${\mathrm{E}}_{\mathrm{e}}$≤30 eV) has been measured from controlled surfaces of thin solid targets (C,Al,Cu) under ultrahigh-vacuum conditions (p≃${10}^{\mathrm{-}7}$ Pa). The angular distributions of low-energy electrons exhibit prominent structures. In each studied detail these structures agree with the predicted directed emission of ‘‘shock electrons’’ produced by the collective response of the electron plasma of the solid to the distortion of the penetrating heavy ion.

At 2 K, at low intensity, and in good quality samples, the source of the exciton-polariton dipole dephasing time (or phase coherence time) is found to be extrinsic in nature and due to dephasing elastic collisions for excitation below the A-transverse-exciton frequency, and purely intrinsic and due to quasi-elastic collisions with acoustical phonons for excitation above the longitudinal A-exciton frequency. The damping increases linearly with detuning for excitation above the A longitudinal exciton frequency.

Nuclear hyperfine structure of the anomalous muonium center (${\mathrm{Mu}}^{\mathrm{*}}$) in GaAs has been resolved in muon-spin-rotation frequency spectra and studied in detail by level-crossing-resonance spectroscopy. A comparison of the measured hyperfine parameters with the free-atom values indicates that 38% (45%) of the spin density is on one Ga (As) on the 〈111〉 symmetry axis of ${\mathrm{Mu}}^{\mathrm{*}}$ with the ratio of p to s spin density equal to about 4 (23). These results support a recently proposed model in which ${\mathrm{Mu}}^{\mathrm{*}}$ is a neutral interstitial located close to the center of a Ga—As bond.

The electronic struture of ordered ${\mathrm{Fe}}_3$Pt Invar has been studied by spin- and angle-resolved photoemission with synchrotron radiation as a function of temperature between T/${\mathrm{T}}_{\mathrm{C}}$=0.58 and 1.3. An anomalous shift of photoemission intensities in the vicinity of ${\mathrm{E}}_{\mathrm{F}}$ is found to accompany the ferromagnetic phaes transition. This is interpreted semiquantitatively as resulting from the predicted changes in the electronic structure of fcc Fe occurring with the high-spin to low-spin state transition.

For the first time, three-dimensional hysteretic phenomena for a material of moderate coercivity are accurately predicted with use of only microstructural properties as input. The theory includes magnetostatic, crystalline anisotropic, and exchange interactions as suggested by the granular structure. It is found that switching occurs by coherent rotation of individual grains for fields along the perpendicular direction and domain-wall propagation for fields along a longitudinal direction.

We demonstrate that solid-state material when microstructured on a nanometer scale leads not only to discrete electronic energy levels but to selective coupling of the electronic states via local operators due to acoustic-phonon or dipole interaction. As a result the system can be designed to allow for multistable dissipative quantum dynamics realized by only a few electronic degrees of freedom. Our model sheds some new light on the problem of fundamental constraints on information processing systems.

We analyze long-range correlations in quantum spectra within the framework of periodic-orbit theory and find excellent agreement between level clustering in quantum spectra and semiclassical predictions. The analysis demonstrates how classical chaotic motion is reflected in the spectral properties of the corresponding quantum system.

A new geometric phase factor is defined for any cyclic evolution of a quantum system. This is independent of the phase factor relating the initial and final state vectors and the Hamiltonian, for a given projection of the evolution on the projective space of rays of the Hilbert space. Some applications, including the Aharonov-Bohm effect, are considered. For the special case of adiabatic evolution, this phase factor is a gauge-invariant generalization of the one found by Berry.

A closed (bosonic) string propagating in a flat space-time where one of the dimensions is curled up into a circle has a Kramers-Wannier duality symmetry identical to that possessed by the Villain model. This is also similar to duality in string theory (in the sense of modular invariance). One is also led naturally to extend the space-time coordinate system by introducing dual coordinates. One of the consequences is that the radius of the internal manifold does not have a coordinate-independent meaning and one cannot physically distinguish between a radius R and a radius α’/R.

We present an extension of the left-right-symmetric model by including extra singlet quarks and leptons, which leads to calculable ${\mathrm{W}}_{\mathrm{L}}$-${\mathrm{W}}_{\mathrm{R}}$ mixing and an ultralight Dirac mass for the neutrino. For a ${\mathrm{W}}_{\mathrm{R}}$ mass in the tera-electron-volt range, the neutrino masses can be in the right range to explain the solar neutrino puzzle via the Mikheyev-Smirnov-Wolfenstein oscillation amplification mechanism. Crucial for our results is a ‘‘see-saw’’-type mechanism for the smallness of the d-quark masses.

We deduce a lower limit on the neutron electric dipole moment in the Weinberg Ansatz for CP violation. The resulting number is comparable to the existing experimental upper limit; this Ansatz will therefore be critically tested by the next round of experiments using ultracold neutrons.

We point out the importance of the Z and box diagram to the decays B→${\mathrm{Kl}}^{+}$$l^{\mathrm{-}}$, Kνν¯. The rate for B→${\mathrm{Kl}}^{+}$$l^{\mathrm{-}}$ grows rapidly for internal quark masses >100 GeV. With three generations and 25≲$m_t$≲200 GeV the branching ratio ranges roughly from ${10}^{\mathrm{-}6}$ to ${10}^{\mathrm{-}5}$. With four generations, this rate could go up another order of magnitude. The mode B→Kνν¯ typically has a higher branching ratio, but is harder to detect experimentally. The rare B decays combined with information from K→πνν¯ studies may provide a test of the symmetry-breaking mechanism of the standard model and/or evidence for a fourth generation.

Hadron-proton total cross sections ${\sigma }_{\mathrm{hp}}^t$ and slope parameters $b_{\mathrm{hp}}$ from elastic scattering are found to be closely related. If effective radii $R_i$ are defined by $b_{\mathrm{hp}}$=$R_h^2$+$R_p^2$, we find from the data ${\sigma }_{\mathrm{hp}}^t$=${\mathrm{gR}}_h^2$$R_p^2$. This geometric factorization property, which holds for c.m. energies √s ≥15 GeV, is understood within the eikonal approach. Total cross sections ${\sigma }_{\mathrm{hp}}^t$ can be used to deduce hadronic radii of mesons and baryons.

Parity nonconservation in pp scattering has been studied by measuring the helicity dependence of the cross section, $A_z$=(${\sigma }^{+}$-${\sigma }^{-}$)/(${\sigma }^{+}$+${\sigma }^{-}$), for longitudinally polarized incident protons of 45 MeV. We found $A_z$=(-1.50±0.22)×${10}^{\mathrm{-}7}$ for the angular range 23° to 52° (laboratory). The uncertainty is the root square sum of the error of the measured asymmetry (±0.19×${10}^{\mathrm{-}7}$), the error of the applied corrections (±0.05×${10}^{\mathrm{-}7}$), and of various systematic errors (±0.09×${10}^{\mathrm{-}7}$). This is the most accurate result ever obtained on parity nonconservation in the nucleon-nucleon interaction.

A high-resolution 3s-satellite spectrum of Ar is presented, obtained at five energies between 77 and 120 eV photon energy at the positron-electron storage ring BESSY. The results are in disagreement with recent measurements by Brion et al. obtained at lower resolution but confirm earlier calculations by Smid and Hansen. This means that disagreements between photoelectron and (e,2e) experiments persist for Ar.

The monochromatized x-ray (1487-eV photon energy) excited–valence-electron spectrum of argon, down to 70 eV binding energy, is presented. More than 25 satellite lines are observed. Several of these lie above the double-ionization thresholds. The intensity of the 3$s^2$3$p^4$${(\mathrm{}}^1$D)3d ${\mathrm{}}^2$S satellite line relative to the intensity of the 3s main line is 0.186(5) which substantially differs from the earlier reported (e,2e) measurements.

An efficient procedure is developed for calculating perturbation expansions in δ=1/D, the reciprocal of the Cartesian dimensionality of space, for the ground-state energy of two-electron atoms. The method uses recursion relations between moments of the coordinate operators. Results through tenth order are presented for the helium atom. The perturbation series is divergent but Padé summation gives accurate results.

With a Biot-Savart model of vortex filaments to provide initial conditions, a finite difference scheme for the incompressible Navier-Stokes equation is used in the region of closest approach of two vortex rings. In the Navier-Stokes solution, we see that the low pressure which develops between the interacting vorticity regions causes the distortion of the initially circular vortex cross section and forces the rearrangement of vorticity on a convective time scale which is much faster than that estimated from viscous transport.

The structure of the cores of interacting vortex tubes in three-dimensional incompressible hydrodynamics has been simulated by a pseudospectral method. A fast reconnection is observed for Reynolds numbers of order 1 000. At higher Reynolds numbers, the core tends to flatten, suggesting the formation of vortex ribbons.