We extend an existing Bose-Fermi equivalence formula to two-dimensional Euclidean space-times with arbitrary compact topology. The result relates the nonchiral Dirac partition function to that of a scalar field, times a theta function. The proof is a short application of methods from complex geometry and Quillen's determinant constructions.

Classical solutions of elastic strings (i.e., strings with actions which depend on the extrinsic curvature of the world sheet) are studied to determine Regge trajectories. For open strings, our classical solutions are identical to those for the conventional Nambu-Goto action. However, for closed strings, new solutions give nonlinear trajectories that include finite-energy, static configurations.

A tensor-polarized deuteron target has been employed for the first measurements of the tensor analyzing power $T_{20}$ in $\pi d$ elastic scattering. Data at six angles were measured at pion bombarding energies of 133.8 and 150.9 MeV. The results settle a long-standing controversy over conflicting measurements of the tensor polarization $t_{20}$, and dispute evidence for dibaryon resonances predicated on one of these $t_{20}$ measurements. The data are shown to be in reasonable agreement with recent Faddeev calculations which have reduced contributions from pion absorption.

Angular correlations of the ${}_{}{}^{6,7}{}_{}{}^{}\mathrm{Li}({\pi }^{\pm },pn)$ cross sections were measured in a wide angular range at $T_{\pi }=70\mathrm{}$ MeV. The components of the two-nucleon absorption processes were extracted, and the angular distributions of the cross sections were obtained. Strong asymmetries about 90° were observed for the reactions ${}_{}{}^{6,7}{}_{}{}^{}\mathrm{Li}({\pi }^{\pm },pn)$, and the cross sections were much larger than that of ${}_{}{}^3{}_{}{}^{}\mathrm{He}$. These results show the importance of the ${\sigma }_{11}$ component in pion absorption on $T=1\mathrm{}$ nucleon pairs for $p$-shell nuclei.

A rotational band of nineteen transitions with a moment of inertia ${\mathfrak{J}}_{\mathrm{band}}^{\mathrm{}\left(2\right)\mathrm{}}$ of $84{\hslash }^2$ ${\mathrm{MeV}}^{-1\mathrm{}}$ has been observed in ${}_{}{}^{152}{}_{}{}^{}\mathrm{Dy}$. The band feeds into the oblate yrast states between ${19}^{-}$ and ${25}^{-}$ and it is proposed that the lowest member of the band has a spin of ${22}^{+}$ and thus the band extends up to $60\hslash$. It is identified as the yrast superdeformed band and its intensity accounts for the whole of the ridge structure seen previously in continuum $E_{\gamma }-E_{\gamma }$ correlations.

$\gamma$-ray angular correlations have been measured for the strongly damped reaction ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$(${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$, ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$)${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$ at ${\theta }_{\mathrm{c}.\mathrm{m}.\mathrm{}}=180\mathrm{}°$ for $E_{\mathrm{c}.\mathrm{m}.\mathrm{}}=42.7\mathrm{} \mathrm{and} 33.7$ MeV. The ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ 4.44-MeV, $J^{\pi }=2^{+}$ state is found to be produced almost exclusively in the $m=0\mathrm{}$ magnetic substate with respect to the beam axis. Comparison of singles and coincidence yields shows that the ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ comes out in its ground state most of the time (≅ 70%) resulting in the entire excitation energy ≅ 15-20 MeV appearing in ${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$. These results can be reproduced by a constrained phase-space calculation.

The excitation function for fusion of ${}_{}{}^{23}{}_{}{}^{}\mathrm{Na}$ with ${}_{}{}^{23}{}_{}{}^{}\mathrm{Na}$ was measured in the energy range $40<~E_{\mathrm{c}.\mathrm{m}.\mathrm{}}<~88.5$ MeV. Additionally, the tensor analyzing power $T_{20}$ was determined to be $T_{20}=-0.0060\mathrm{}\pm 0.0125$ at $E_{\mathrm{c}.\mathrm{m}.\mathrm{}}=85\mathrm{}$ MeV. The results are discussed in terms of an entrance-channel versus a compound-nucleus model for the observed limitation of fusion. A typical entrance-channel model, the surface-friction model, which is able to describe all fusion excitation functions leading to ${}_{}{}^{46}{}_{}{}^{}\mathrm{Ti}$, fails to reproduce the observed value of $T_{20}$. The data are consistent, on the other hand, with the compound-nucleus interpretation.

We present here analytical and numerical evidence which establishes that, for highly excited hydrogen atoms irradiated by microwaves, a large ionization peak occurs at frequencies much below those required for the conventional one-photon photoelectric effect. Indeed, we find that this ionization peak can, for suitable parameters values, be much higher than that of the usual photoelectric effect, a theoretical prediction which is currently being tested in the laboratory. A striking property of this ionization peak is that its frequency width is jointly determined by two independent effects: the classical chaotic threshold and the quantum delocalization border.

Strong competition between four-wave mixing and amplified spontaneous emission in resonant two-photon excitations is shown to generate radiation fields with strong squeezing and antibunching. The generated fields are in a new type of coherent state which is an eigenstate of the operator corresponding to the simultaneous annihilation of photons in two modes.

A new type of forward-backward asymmetry is reported for the 119-μm emission from a linear-cavity C${\mathrm{H}}_3$OH laser, near-resonantly pumped by a continuous-wave C${\mathrm{O}}_2$ laser. The observed asymmetry is related to a strong traveling-wave pump field and also saturating standing-wave-generated fields, a situation typical for most optically pumped linear-cavity gas lasers. A simple interpretation of the experimental results is given in terms of multiphoton processes involving one pump photon and several generated photons.

During tangential neutral-beam injection into the PBX tokamak, bursts of two types of instabilities are observed. One instability occurs in the frequency range 120-210 kHz and the other oscillates predominantly near the frequency of bulk plasma rotation (20-30 kHz). Both instabilities correlate with drops in neutron emission and bursts in charge-exchange neutral flux, indicating that beam ions are removed from the center of the plasma by the instabilities. The central losses are comparable to the losses induced by the fishbone instability during perpendicular injection.

A New collective mode of heat transport has been observed in superfluid helium at low temperatures and pressures. Unlike ordinary second sound, this new mode travels at essentially the acoustic-sound velocity and is characterized by the nearly collinear phonon relaxation arising from anomalous dispersion. The mode has been found to persist into the collisionless regime, $\omega \tau >1\mathrm{}$.

We report measurements of the convective conductance of ${}_{}{}^3{}_{}{}^{}\mathrm{He}$-${}_{}{}^4{}_{}{}^{}\mathrm{He}$ films near the superfluid transition. This thermal response is tested for the critical behavior observed in pure ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ films. We find that this is preserved for mixtures. The parameters $b$ and $\frac{D}{a^2}$, however, show a strong renormalization, and an unusual ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ dependence. The conductance at fixed $T-T_c$ decreases upon addition of ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ implying a decrease of the 2D correlation length. We observe a decrease in the maximum value of conductance which we attribute to a residual free-vortex density, even for $T<\mathrm{}{T}_c$.

We have measured the elastic constants of two series of glasses in the Ge-As-Se system. Each series consisted of samples whose compositions were chosen to produce an average atomic coordination ($〈r〉$) which ranged from 2 to nearly 3. Different local structures were produced by our making one series much higher in As content than the other. Despite this difference both series exhibited evidence of rigidity percolation near $〈r〉=2.4\mathrm{}$.

Bombardment of glassy ${\mathrm{Pd}}_{80}$${\mathrm{Si}}_{20}$ below 50 K with ${}_{}{}^{129}{}_{}{}^{}\mathrm{Xe}$ ions of 1.34 MeV/u leads to macroscopically visible anisotropic mass transport. It is shown that this mass transport is dominated by the energy which the projectiles transfer to the electrons of the metallic glass. Such a behavior is entirely unknown for crystalline metals. As an explanation we suggest that Coulomb explosions in the wake of the projectiles lead to a mechanical polarization of the metallic glass which then undergoes plastic flow.

A new magnetic equation of state for liquid ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ is derived. This is obtained from a model for the polarization dependence of the Landau parameters. The parameters of the model are constrained by general thermodynamic relationships and microscopic symmetries. It is shown that the non-linear field splitting of the $A$ phase in liquid ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ is consistent with this model. We propose that liquid ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ can be viewed as nearly metamagnetic.

Cell-spacing selection in directional solidification is investigated. An integral equation describing steady-state cells in the limit where the solute diffusion length is much larger than the cell spacing is derived and solved numerically by Newton's method. With surface tension and no crystalline anisotropy present the spatial periodicity of a one-dimensional array of cells with cusp singularities is found to be determined uniquely by a solvability condition. The inclusion of crystalline anisotropy has no other effect to shift the value of the selected spacing.

We show that the effect of the nonuniform environment on the static screening of the Coulomb potential causes a major change in the calculated surface energy of simple metals.

It is shown by Monte Carlo simulations that the area of an interface in two and three bulk dimensions as modeled by a discrete solid-on-solid model above the roughening transition is self-similar over a wide range of length scales. The fractal dimensions are estimated for the first time to be 2.8 ± 0.03 and 1.58 ± 0.06 for three and two dimensions, respectively. Additional Monte Carlo simulations of two-dimensional Ising lattice-gas interfaces have also been performed and are consistent with the solid-on-solid results.

We report measurements of the low-temperature thermal conductivity of diacetylene single crystals. Monomer samples show little anisotropy and display the temperature dependence of a crystalline dielectric. In polymerized samples, heat is conducted up to 60 times better parallel to the chains than perpendicular to them. Dislocations can account for this anisotropy at the lowest temperatures. Quasi one dimensionality of the polymer crystals induces anisotropy at higher temperatures and strongly suppresses anharmonic phonon interactions.