The four-fermion interaction in 2+1 dimensions is nonrenormalizable in weak coupling perturbation theory. We show that this model is in fact renormalizable order by order in the 1/${\mathrm{N}}_{\mathrm{f}}$ expansion, and we find this theory a finite ultraviolet fixed point.

Consequences of matter-parity invariance on intermediate scale breaking in three-generation Calabi-Yau superstring models are discussed. It is shown that values of ${\sin }^2$${\mathrm{\theta }}_{\mathrm{W}}$ in conformity with the current experimental limits can arise in the Calabi-Yau models when the extra families and mirror families gain superheavy masses through nonrenormalizable interactions. A small number of exotic leptons with electroweak-scale masses remain and may be accessible at accelerator energies.

Several authors have noted that the forward matrix element of the axial-vector current as measured in polarized deep-inelastic electroproduction represents not only the quark contribution to the target proton spin but also the gluonic component due to the anomaly. We show that the anomalous divergence equations constrain the size of this gluonic contribution. In particular it is of such sign and magnitude that the resulting quark content of the proton spin deviates even further from the naive-quark-model expectations.

The possibility that the θ(1720) and the recently reported ζ(1480) are suitable members of a 36-dimensional multiplet of (Q${¯}^2$$Q^2$) mesons is investigated. Decay modes to two pseudoscalars and to four pseudoscalars (via virtual vector-meson pairs) are analyzed. The proposed interpretation is found to have a fair chance of being correct. Further consequences of the model concerning a narrow isoscalar at 1930 MeV and the three doubly charged exotics are presented.

We show that a classical soliton for the nonlinear Su(2) σ model in the hedgehog configuration admits a stable solution, when quantized through collective coordinates, which may be identified with the nucleon. The whole approach depends on a single, dimensional, and arbitrary constant. Numerical results seem to converge for the mass and for the right value of the weak axial-vector coupling.

To investigate the effect of vacuum polarization in the Coulomb interaction between hadrons, the relative differential cross section for elastic ${}_{}{}^{12}{}_{}{}^{}\mathrm{-}_{}^{12}{}_{}{}^{}$C scattering at ${\mathrm{E}}_{\mathrm{lab}=4\mathrm{}}$ MeV has been measured with high precision. The data are compared to theoretical calculations that take into account the contribution of the Ühling potential and other small contributions. Data and calculation agree within 1.5 standard deviations. This constitutes a test of the vacuum polarization on the 7% level.

The reaction mechanism of heavy-ion charge-exchange scattering at low and intermediate incident energies is studied theoretically. Contributions of direct charge exchange due to central and tensor isovector interactions and of charge exchange via sequential proton and neutron transfer are taken into account in one-step and two-step exact-finite-range distorted-wave Born-approximation calculations. The nuclear structure of the intermediate and final states is described within the shell model. Calculations for ${}_{}{}^{12}{}_{}{}^{}$C${(}^{12}$C, ${}_{}{}^{12}{}_{}{}^{}$N${)}^{12}$B2 indicate that direct charge exchange is safely dominant for incident energies E/A≳100 MeV.

Nuclear transport models including density- and momentum-dependent mean-field effects are compared to intranuclear-cascade models and tested on recent data on inclusive p-like cross sections for 800A-MeV La+La. We find a remarkable agreement between most model calculations but a systematic disagreement with the measured yield at 20°, possibly indicating a need for modification of nuclear transport properties at high densities.

High-resolution energy-gain spectra, in which the net projectile charge (q) is changed by one unit, have been recorded for slow (4q keV) ${\mathrm{Xe}}^{\mathrm{q}+}$-Xe (15≤q≤35) collisions. These spectra contain information about the relative importance of processes with one or more active electrons. The ratio between cross sections for transfer ionization and single-electron capture reaches a maximum around q=25 and decreases for higher q. We, tentatively, ascribe this observation to an increasing probability for radiative stabilization of doubly excited states for q>25.

We demonstrate that any first-order property can be uniquely partitioned into atomic contributions. The atomic contribution is given as a trace of the respective generalized atomic polar tensor and can be evaluated without invoking numerical integration. Partitionings of the potential energy in a model one-electron problem and of the electric charge in some molecules containing lithium atoms are used to illustrate the new formalism.

We have studied the effects of a pulsed electric field on the decay dynamics of high np, J=1 (n>30) singlet Rydberg levels of ${\mathrm{H}}_2$ We have discovered that pulsed fields of magnitudes much less than the classical value required for ionization induce a significant degree of dissociative character into levels which normally do not dissociate. This induced dissociation appears to occur during the slew of the field pulse and can be explained in terms of adiabatic passage through avoided curve crossings between the stable J=1 levels and the J=0 and 2 levels which predissociate.

For the parameters accessible in current experiments, the quantum suppression of classical chaos arises from a reduction in the effective number of coupled states. A simple theory using conventional quantum methods provides a good description of the dynamics near the threshold field for classical chaos and recovers the classical, Fokker-Planck equation for large fields where many states are coupled.

Seven new electronic states of helium hydride have been observed, allowing the first determination of ionization potentials and quantum defects. From the rotational analysis and the observed intensities of the six new emission bands, the characters of the electronic states and the correlation to united atom orbitals were obtained. Thus the first clear picture of the electronic structure of this fundamental molecule is presented. Strong perturbations and interference effects between states with Δl=±1 were found. The excited HeH molecules were produced by neutralization of a fast ${\mathrm{HeH}}^{+}$ beam.

Electric birefringence studies on DNA’s of lengths N trapped in an agarose gel show a dynamic behavior which is more complex than predicted by the biased reptation theory: An ${\mathrm{N}}^3$ dependence of the two longest relaxation times is observed as expected, but a third short time, of large amplitude, varies as ${\mathrm{N}}^{1.5}$, suggesting that it is due to the Zimm-Rouse time of the chains. Moreover, the orientation under low electric field E varies as ${\mathrm{E}}^{\mathrm{-}1}$. Thus, successive elongations and retractions of the primitive path may play a major role in the separation of large DNA’s by pulsed-field gel electrophoresis.

The problem of longitudinal mode competition in free-electron lasers is addressed. It is shown that for small enough ratios of the current to output coupling coefficient many single-mode states are possible. However, the time required to reach these states becomes extremely long for typical devices. Before reaching a single-mode state the radiation field becomes relatively constant in amplitude with modulations of its phase. Finally, a simple method for reaching the stable single-mode state with maximum efficiency is suggested.

We have measured the full spectrum of the third-order optical susceptibiltiy, ${\chi }^{\mathrm{}\left(3\right)\mathrm{}}$(ω), in polyacetylene using an infrared free-electron laser. The magnitude of ${\chi }^{\mathrm{}\left(3\right)\mathrm{}}$(ω) reaches ∼${10}^{\mathrm{-}8}$ esu at 0.6 eV, the largest value of an electronic ${\chi }^{\mathrm{}\left(3\right)\mathrm{}}$(ω) inside the gap of a semiconductor. There are two peaks at 0.6 and 0.89 eV in the spectrum of ${\chi }^{\mathrm{}\left(3\right)\mathrm{}}$(ω) that are assigned to three- and two-photon resonance enhancements, respectively, implying states of opposite symmetry lie near the 1D band gap at $E_g$∼1.8 eV.

We report on a new hydrodynamic instability which occurs at the spreading edge of a thin wetting film. A drop of aqueous surfactant solution placed on a glass surface moistened with a thin layer of water spreads by propagating fingers, whose velocity and shape depend on the thickness of the ambient water layer and on the surfactant concentration. The two fluids are miscible and show negligible viscosity difference, ruling out a Saffman-Taylor instability. We propose that the Marangoni effect, which is fluid flow induced by gradients in surface tension, drives the instability.

Two laser-based diagnostics are used to determine the density (${\mathrm{n}}_{\mathrm{e}}$) and temperature (${\mathrm{T}}_{\mathrm{e}}$) of low-energy electrons confined in the negative glow of a dc helium glow discharge. Each diagnostic yields an independent relation between ${\mathrm{n}}_{\mathrm{e}}$ and ${\mathrm{T}}_{\mathrm{e}}$. From the intersection of these relations we find ${\mathrm{n}}_{\mathrm{e}}$=5×${10}^{11}$ ${\mathrm{cm}}^{\mathrm{-}3}$ and ${\mathrm{k}}_{\mathrm{B}}$${\mathrm{T}}_{\mathrm{e}}$=0.12 eV for an abnormal cathode fall of 261 V in 3.50-Torr helium.

The effect of a resistive boundary and/or a distant conducting wall on a reversed field pinch is investigated with a three-dimensional magnetohydrodynamics code. Fluctuations rise with increasing distance between the conducting wall and the plasma. The enhanced fluctuation-induced v×b electric field primarily opposes toroidal current; hence loop voltage must increase to sustain the current. This increases the helicity injection rate, which is balanced by an enhanced surface loss.

It is shown that in tokamak plasmas sustained by rf current drive, the contribution of the suprathermal rf-driven electron population to the poloidal beta (${\beta }_p$) can be substantial if the total current is comparable to the Alfvén critical current, $I_A$=(4πmcv/${\mu }_0$ec)γ. Equilibria with values of ε${\beta }_p$ up to approximately 1.3 were obtained, and no equilibrium or gross stability limits were observed.