We report the results of an experimental search for double-$\beta$ decay of ${}_{}{}^{100}{}_{}{}^{}\mathrm{Mo}$. No evidence is found for the decay mode with majoron emission, yielding a half-life limit of 3.3×${10}^{20}$ yr with 90% confidence. We also obtain a lower limit for the two-neutrino mode of 3.8×${10}^{18}$ yr.

In an energy-dependent phase-shift analysis of all low-energy $\mathrm{np}$ scattering data below $T_{\mathrm{lab}}=30\mathrm{}$ MeV we reach $\frac{{\chi }^2}{N_{\mathrm{DF}}}=1.1\mathrm{}$, where $N_{\mathrm{DF}}$ is the number of degrees of freedom. In our fit we determine the $S$ matrix elements in the coupled ${}_{}{}^3{}_{}{}^{}S_1^{}{}_{}{}^{}+{}_{}{}^3{}_{}{}^{}D_1^{}{}_{}{}^{}$ channels, which allows us to compute the residue at the deuteron pole. Expressed in terms of the deuteron parameters, we find for the asymptotic normalization of the ${}_{}{}^3{}_{}{}^{}S_1^{}{}_{}{}^{}$ state $A_S=0.8838\mathrm{}\left(4\right)\mathrm{}$ ${\mathrm{fm}}^{-1/2\mathrm{}}$ and for the asymptotic $\frac{D}{S}$ ratio $\eta =0.02712\mathrm{}\left(22\right)\mathrm{}$. Compared with other determinations, there seems to be some indication for the presence of closed isobar channels and/or energy-dependent potentials in the deuteron system.

Cross sections ascribed to a multifragmentation process have been obtained from the measured fragment yields ($3\le Z_f\le 14$) in proton-xenon interactions ($1\le E_p\le 20$ GeV). The variation of the yields with both mass and bombarding energy can be understood by use of the droplet model of the liquid-gas phase transition. With increasing energy, this model indicates that multifragmentation occurs first in the mechanical-instability region, next in the supersaturated vapor, and finally in the critical region.

A novel absorption spectrometer where an absorber is placed in one beam of a parametric oscillator is described. The sensitivity is not shot-noise limited and may be enhanced by the operation of the parametric oscillator close to threshold.

Quasiresonant vibration-rotation transfer in the collision of an atom with a diatomic molecule is studies with use of classical trajectories. At high molecular rotation rates and low collision velocities the atom-diatom interaction consists of a sequence of small collisions ("collisionettes"). This leads to a nearly perfect negative correlation between the changes in the rotational and vibrational actions and very large vibrationally inelastic cross sections. This quasiresonant process shows evidence of frequency locking between the vibrator and the rotational "oscillator."

The relation between fractal dimension and intertial exponents in three-dimensional incompressible fluid turbulence is analyzed. Several polymer analogies are explained, and an application to the numerical modeling of turbulence is presented.

The full Raman scattering equations have been solved in a linear density profile in an attempt to overcome the local nature of most previous analyses. The global solution obtained elucidates the transition between absolute and convective Raman instabilities. Feedback linking backward and forward Raman scattering can result in an instability that is absolute at all scattered frequencies. Moreover, thresholds for this absolute instability are lower by a factor of 4 than those for the convective instability where backward and forward scattering are treated as independent events.

The retention of both drag and pitch-angle scattering of the energetic slowing-down-tail $\alpha \text{'}\mathrm{s}$ by the background ions can dramatically increase the radial energy flux of the $\alpha \text{'}\mathrm{s}$ in an ignited tokamak and can prevent the $\alpha$ energy from being deposited into the background plasma via electron drag. The condition that the enhanced neoclassical fluxes have negligible impact on the ignition can impose a more severe design constraint than drift loss.

We propose a generalization of the Landau theory of phase transitions which applies to reconstructive transitions. For the first time an order parameter is defined for this category of transition. This order parameter is shown to be a transcendental function of the large atomic displacements arising at the transition. The absence of a group-subgroup relationship between the symmetries of the phases is proved to be the consequence of specific displacements. The approach is introduced through examples of reconstructive transitions found in crystals of the elements.

Ga- and As-terminated GaAs(100) surfaces are studied through first-principles density-functional pseudopotential calculations of the energies of surfaces with different stoichiometries and reconstructions. We predict structural transitions as a function of Ga and As chemical potentials within an experimentally accessible range which is shown to be fixed by the bulk energies of Ga, As, and GaAs. The bulk energies are determined accurately by the ab initio calculations. The predicted surface stoichiometries are in good agreement with experimental data.

We present here the first theoretical account of the dependence of curvature elastic energies of surfactant layers on area per head group and alkyl carbon number in pure films, and on composition in mixed cases. Treating explicitly the chain conformational statistics, we show that the bending constant can be decreased by an order of magnitude upon halving of the carbon number or upon replacement of as few as one-half of the long chains by the short ones.

A new class of trial wave functions is introduced to compute variationally the ground-state energy of solid ${}_{}{}^4{}_{}{}^{}\mathrm{He}$. This wave function is symmetric under particle exchange, translationally invariant, and does not require the a priori introduction of a crystal lattice. It gives a lower energy than and has properties comparable with those given by previous calculations in which atoms are explicitly localized. The same functional form of the wave function is used to investigate the liquid phase, where a lower energy than those given by a wave function of the Jastrow form is obtained as well.

New kinds of intermediate flux states should be accessible in high-$T_c$ superconductors, in fields slightly above $H_{c1\mathrm{}}$. Flux-line wandering leads to an entangled vortex state whose statistical mechanics is isomorphic to an interacting 2D Bose superfluid with cooperative ring exchanges. In sufficiently thin samples, this "braided flux" phase transforms into a liquid of disentangled rods.

The branching ratio of core-valence transitions in x-ray absorption spectroscopy is linearly related to the expectation value of the spin-orbit operator in the valence states. This offers a direct method to determine the spin-orbit interaction in the local electronic structure of metal compounds and alloys. The method is complementary to susceptibility and paramagnetic resonance measurements because it measures a different operator and is element specific.

Spatiotemporal chaos can be produced by complicated local dynamics in a small spatial region and observed globally through a process we call information transport. Information transport can be detected by computation of an information-theoretic quantity, the time-delayed mutual information, between measurements of the system at separate spatial points.

The conditions for a macroscopic segregation of A and B in a steady-state A+B→0 reaction are studied via a finite continuum model. Segregation occurs in d=1, is marginal for d=2 (critical dimension), and is absent for d≥3. Results for infinite systems are also mentioned.

We present an analytic solution for the steady-state, subsonic accretion of a gaseous medium onto a Schwarzschild or Kerr black hole. The black hole moves at a constant velocity through the medium, which is uniform and at rest far from the hole and obeys a P=ρ adiabatic equation of state. In the case of a rotating Kerr black hole, the flow is fully three dimensional, but the accretion rate does not depend on the orientation of the hole’s spin with respect to the incident direction of the flow.

Upper limits for the time-averaged flux of air showers from the direction of Cygnus X-3 during the calendar period 2 April 1986 to 3 May 1987 are found to be 1.5×${10}^{\mathrm{-}13}$ ${\mathrm{cm}}^{\mathrm{-}2}$ ${\sec }^{\mathrm{-}1}$ for all events, and 7.6×${10}^{\mathrm{-}14}$ ${\mathrm{cm}}^{\mathrm{-}2}$ ${\sec }^{\mathrm{-}1}$ for events with no observed muons in a 44-${\mathrm{m}}^2$ muon detector. These are integral fluxes above 50 TeV on the assumption of an $E^{\mathrm{-}1}$ primary spectrum. A possible observation of a short-term signal from Cygnus X-3, with an anomalous muon content, phase correlated with the 4.8-h orbital period, with an integral flux above 50 TeV of (8.2±2.0)×${10}^{\mathrm{-}13}$ ${\mathrm{cm}}^{\mathrm{-}2}$ ${\sec }^{\mathrm{-}1}$ is also reported.

The neutrino events from the supernova SN1987A observed by the Kamiokande II and Irvine-Michigan-Brookhaven detectors are used to suggest constraints on neutrino physics. In particular, bounds on the value of the electron neutrino magnetic moment ${\mathrm{\mu }}_{\mathit{v}\mathit{e}}$≲(${10}^{\mathrm{-}12}$-${10}^{\mathrm{-}13}$)${\mathrm{\mu }}_{\mathrm{B}}$ are suggested.

The observation of a neutrino pulse from the supernova SN1987A constrains the production of light exotic particles in the proto neutron star. We derive a new bound on the axion decay constant, $f_a$≳${10}^{10}$ GeV. If right-handed (RH) neutrinos exist, the ‘‘RH Fermi constant’’ is $G_{\mathrm{RH}\lesssim {10}^{\mathrm{-}4}{G}_{\mathrm{F}}}$, 2 orders of magnitude below laboratory bounds. The Dirac mass of ${\nu }_{\mu }$ can be constrained below laboratory limits.