Using accurate calculations of the critical-to-classical crossover performed within the ${\mathrm{\phi }}^4$ theory, we show that it is possible to observe nonuniversal power laws extending over almost three decades of temperature as seems to be the case near the cloud point of micellar solutions. The possibility of a nonmonotonic crossover is quantitatively examined and confronted with measurements made near the critical point of xenon. We emphasize the difficulties of determining the mechanism responsible for the nonmonotonicity.

The origin of asymptotic freedom is clarified by a simple probabilistic argument: It is much more difficult for balls to point out the same direction than sticks and disks. This fact is used to show that the effective potentials of the two-dimensional O(N)-invariant σ models (with hierarchical kinematical energy terms) are driven into the high-temperature region by the Kadanoff-Wilson block-spin transformations, if N is larger than or equal to 3.

A dual picture between perturbative QCD and resonance production is exploited to describe nondiffractive meson pair production near threshold in γγ annihilation.

We have measured the polarization of Λ’s inclusively produced by the polarized proton beam at the Brookhaven Alternating Gradient Synchrotron at 13.3 and 18.5 GeV/c. Data were taken in the central and beam-fragmentation region with hyperon transverse momenta from 0.4 to 2.5 GeV/c. The Λ polarization parameter P is found to be large in agreement with earlier data at other energies. The analyzing power $A_N$ and spin transfer $D_{\mathrm{NN}}$ are nearly zero in the same kinematic region, as predicted by certain models of particle production.

At future high-energy accelerators, the traditional methods of studying CP nonconservation will no longer be useful. We present potential new ways to find CP nonconservation at high-energy ${\mathrm{e}}^{+}$${\mathrm{e}}^{\mathrm{-}}$ and pp¯ colliders which use jet variables in inclusive or semi-inclusive processes. These make use of asymmetries formed with beam and jet momenta. Signals are estimated in the standard model and appear to be small, but the tests could be sensitive to CP nonconservation in new interactions which become visible at higher energies.

Measurements have been made of single-neutron stripping and pickup in the system ${}_{}{}^{58}{}_{}{}^{}$Ni${+}^{208}$Pb at 10.3 and 17.4 MeV/nucleon. The complex spectra observed are found to be dominated by transfers from the valence shell of the donor to bound and unbound shells of the recipient. The data were analyzed with the distorted-wave Born approximation together with a dynamic polarization potential. The suggestion is made that the large yields seen at forward scattering angles may arise from increases in the real nuclear potential which might occur when a neutron jumps to an unoccupied major shell.

We show that dynamical symmetries other than the known U(5), SU(3), or O(6) limits of the interacting-boson model can be identified for some choices of the boson-Hamiltonian parameters. The recently discussed SO(7) symmetry is hereby completely accommodated within a boson framework. Our analysis shows that this symmetry is in fact characterized by a U(5) boson Hamiltonian accompanied by choices of transition operators which differ from the traditional choices.

A rotational band has been studied in ${}_{}{}^{132}{}_{}{}^{}\mathrm{Ce}$ to a spin above 50ħ. Lifetime measurements have resulted in a large quadrupole moment corresponding to a deformation β∼0.5. This is consistent with the moment of inertia determined from the energy-level spacing. These data are the first measurements of collectivity of discrete lines at high spin within the superdeformed second minimum.

Proton mass corrections to the Lamb shift of hydrogen of order α(Zα${)}^5$${\mathrm{m}}^2$/M are evaluated. These contributions are expected new terms beyond those given earlier for recoil effects to the self-energy of a bound electron in the external-field approximation. The new contribution of this order is -0.53 kHz, thus making the complete radiative-recoil correction of this order -2.53 kHz.

A recently proposed technique based on the Fourier transform of the spectrum is applied to the stimulated-emission pumping spectrum of acetylene at ∼26 500 ${\mathrm{cm}}^{\mathrm{-}1}$ above the vibrational ground state. Correlations on two different time scales (∼3 and ∼45 ps) were found from analysis of low-resolution (0.3 ${\mathrm{cm}}^{\mathrm{-}1}$) and high-resolution (0.05 ${\mathrm{cm}}^{\mathrm{-}1}$) spectra, respectively. Additional structure produced dynamic information on a wider (0.5–300 ps) time scale. The results show that acetylene at 26 500 ${\mathrm{cm}}^{\mathrm{-}1}$ is in the transition from the regular to the chaotic regime.

Chemical dissolution of a two-dimensional porous medium by a reactive fluid which produces fractal patterns is studied. A new model is proposed that introduces a cumulative erosion process which broadens the branches of the cluster and gives structures very similar to the experimental ones. Diffusion-limited aggregation is a limiting case of this model. An interpretation of the evolution of the injection pressure with time which yields the fractal dimension is also presented, and agrees with the experimental results.

We report the observation of synchronous energy exchange between nonrelativistic electrons and the ponderomotive (beat) force of two counterpropagating, intense, pulsed ${\mathrm{CO}}_2$ laser beams, operating at different frequencies in a stimulated Compton scattering scheme. The interaction takes place in the nonlinear (trapping) regime, and its physics is the same as in laser accelerators and efficiency-enhanced free-electron lasers with long wigglers. Two different mechanisms of enhanced energy transfer were observed—electron trapping and phase-area displacement.

Anomalous transport has been observed in heat-pulse tokamak experiments in the form of faster thermal diffusion than expected from thermal conductivity alone. The anomaly is resolved by correct treatment of time-dependent transport, coupling heat flow and plasma diffusion. The diffusion rates are exhibited as invariant eigenvalues appearing in the transport model. We show how these eigenvalues couple the basic transport processes. The thermal diffusion rate is not determined by thermal conductivity, since it is not an eigenvalue with temperature as eigenmode.

Measurements of the time evolution of the current-density distribution in ASDEX show that lower-hybrid current drive leads to broader profiles, whereby q increases from q≲1 to q>1 in the plasma central region. Simultaneously, the electron temperature is observed to peak, thus demonstrating that the lower-hybrid–driven current distribution is decoupled from the classical conductivity profile.

Ponderomotive stabilization of rigid plasma flute modes is numerically investigated by use of a variational principle, for a simple geometry, without eikonal approximation. While the near field of the studied antenna can be stabilizing, the far field has a small contribution only, because of large cancellation by quasi mode-coupling terms. The field energy for stabilization is evaluated and is a nonnegligible fraction of the plasma thermal energy. A new antenna design is proposed, and feedback stabilization is investigated. Their use drastically reduces power requirements.

We have discovered a state of superfluid turbulence in convecting dilute solutions of ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ in superfluid ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ which has many features of superfluid turbulence in straight channels. The characteristics of this state, determined by precise measurement of heat flow, are noisy temperature fluctuations and decreased thermal heat-transport efficiency relative to a ‘‘quiet’’ convecting state. There exists a ‘‘critical flow field’’ analogous to a critical velocity in pipe-flow superfluid turbulence, below which the noisy state is absent.

We determined the crossover frequency ${\mathrm{\omega }}_{\mathrm{co}}$ between phonon and fracton regimes from the study of the low-frequency inelastic light scattering in superionic borate glasses of the type (AgI${)}_{\mathit{x}}$(${\mathrm{Ag}}_2$O⋅${\mathrm{B}}_2$${\mathrm{O}}_3$${)}_{1\mathrm{-}\mathit{x}}$. The scaling of ${\mathrm{\omega }}_{\mathrm{co}}$ with the fractal characteristic length was studied by variation of the AgI concentration x. We thus obtained the diffusion coefficient scaling exponent theta and the spectral dimensionality d̃ which characterizes energy diffusion on a fractal.

An interpretation of energy-calibrated appearance-potential spectra for Ti and V reveals new correlation effects. A proposed initial-state, final-state rule is utilized to understand these and other many-body effects which arise in the x-ray, Auger-electron, and appearance-potential spectra for these metals.

A monolayer of Gd(0001) on W(110) is measured by electron-spin resonance from T=240 to 360 K in UHV. The ferromagnetic Curie temperature lies ≊20 K below the bulk Curie point. The measured temperature dependence of the static susceptibility—deduced from the ESR intensity—follows a power law χ∼${\mathrm{t}}^{\mathrm{-}\gamma }$ with γ≊1.8 for a monolayer and γ≊1.25 for an 80-Å film. This agrees well with the theoretical γ of 2D and 3D Ising systems. The experiment represents the first in situ UHV ESR with full surface analysis allowing the measurement of magnetic phase transitions on single-crystal surfaces.