Dielectric and thermodynamic properties have been investigated in isotopically mixed crystals ${\mathrm{K}}_3$${\mathrm{D}}_{1\mathrm{-}\mathit{x}}$${\mathrm{H}}_{\mathit{x}}$(${\mathrm{SO}}_4$${)}_2$ with isolated hydrogen bonds interconnecting the dimeric ${\mathrm{SO}}_4^{2\mathrm{-}}$ units. The critical temperature ${\mathit{T}}_{\mathit{c}}$ for the antiferroelectric phase transition decreases with increasing proton concentration (x) and eventually the phase transition vanishes for x≥${\mathit{x}}_{\mathit{c}}$∼0.66. The x-dependent behavior of ${\mathit{T}}_{\mathit{c}}$, the dielectric constant ε(T), and the specific heat jump ΔC at ${\mathit{T}}_{\mathit{c}}$ are described by simple transverse Ising Hamiltonian. This indicates a determinative role of the proton tunneling in the phase transition and related properties.

The presence of a natural boundary in the angle complex plane of the function conjugating an area preserving map with a rotation is a signature of nonintegrability. Numerical results suggest that the boundary arises from the condensation of singularities when a real nonresonant frequency is approached by a sequence of complex resonant frequencies. For the quadratic map of the complex plane F: z’=λz+${\mathit{z}}^2$ the function conjugating the linear part of F with F has q cuts with end points on a spiral if λ=${\mathit{e}}^{2\mathrm{\pi }\mathit{i}\mathit{p}/\mathit{q}\mathrm{-}\mathrm{\alpha }}$ with α>0. When p/q tends to a (quadratic) irrational number and α→0 the points coalesce on the boundary of a circle, whose image is the Siegel disk.

We present a time-machine model in which closed timelike curves evolve, within a bounded region of space, from a well-behaved spacelike initial slice S; this slice (and the entire spacetime) is asymptotically flat and topologically trivial. In addition, this model satisfies the weak energy condition everywhere on S and up until and beyond the time slice (an achronal hypersurface) which displays the causality violation. We discuss the relation of this model to theorems by Tipler and Hawking which place constraints on time-machine solutions.

A method for interpreting discontinuities of the twist potential of vacuum stationary axisymmetric solutions of Einstein’s equations is introduced. Surface densities for the angular momentum of the source can be constructed after solving a linear partial differential equation with boundary conditions at infinity. This formalism is applied to the Kerr metric, obtaining a regularized version of the density calculated with other formalisms. The main result is that the integral defining the total angular momentum is finite for the Kerr metric.

Data taken with the CYGNUS detector between 1989 September and 1993 January have been used to search for 1 s bursts of ultrahigh-energy gamma rays from point sources at arbitrary locations in the northern sky. We find no evidence for such bursts. We set a theory-dependent upper limit on the rate-density of evaporating black holes of 8.5×${10}^5$ ${\mathrm{pc}}^{\mathrm{-}3}$ ${\mathrm{yr}}^{\mathrm{-}1}$ at the 99% C.L. When the same emission spectrum is used to recalculate previous upper limits based on direct searches, this limit is the most restrictive by nearly 2 orders of magnitude.

We have determined the strong coupling ${\mathrm{\alpha }}_{\mathit{s}}$ from measurements of jet rates in hadronic decays of ${\mathit{Z}}^0$ bosons collected by the SLD experiment at SLAC. Using six collinear and infrared safe jet algorithms we compared our data with the predictions of QCD calculated up to second order in perturbation theory, and also with resummed calculations. We find ${\mathrm{\alpha }}_{\mathit{s}}$(${\mathit{M}}_{\mathit{Z}}^2$)=0.118±0.002(stat)±0.003(syst)±0.010(theory), where the dominant uncertainty is from uncalculated higher order contributions.

We show that the J/ψ→${\mathrm{\pi }}^{+}$${\mathrm{\pi }}^{\mathrm{-}}$ decay is a reliable source of information for the electromagnetic form factor of the pion at t=${\mathit{M}}_{\mathit{J}/\mathrm{\psi }}^2$=9.6 ${\mathrm{GeV}}^2$ by using general arguments to estimate, or rather, put upper bounds on, the background processes that could spoil this extraction. We briefly comment on the significance of the resulting ${\mathit{F}}_{\mathrm{\pi }}$(${\mathit{M}}_{\mathit{J}/\mathrm{\psi }}^2$).

We report the full reconstruction of ${\mathrm{\chi }}_{\mathit{c}}$ mesons through the decay chain ${\mathrm{\chi }}_{\mathit{c}}$→J/ψ γ, J/ψ→${\mathrm{\mu }}^{+}$${\mathrm{\mu }}^{\mathrm{-}}$, using data obtained at the Collider Detector at Fermilab in 2.6±0.2 ${\mathrm{pb}}^{\mathrm{-}1}$ of p¯p collisions at √s =1.8 TeV. This exclusive ${\mathrm{\chi }}_{\mathit{c}}$ sample is used to measure the ${\mathrm{\chi }}_{\mathit{c}}$-meson production cross section times branching fractions. We obtain σ×B=3.2±0.4(stat${)}_{\mathrm{-}1.1}^{+1.2\mathrm{}}$(syst) nb for ${\mathrm{\chi }}_{\mathit{c}}$ mesons decaying to J/ψ with ${\mathit{p}}_{\mathit{T}}$>6.0 GeV/c and pseudorapidity ‖η‖<0.5. From this and the inclusive J/ψ cross section we calculate the inclusive b-quark cross section to be 12.0±4.5 μb for ${\mathit{p}}_{\mathit{T}}^{\mathit{b}}$>8.5 GeV/c and ‖${\mathit{y}}^{\mathit{b}}$‖<1.

The dijet invariant mass distribution has been measured in the region between 140 and 1000 GeV/${\mathit{c}}^2$, in 1.8 TeV p p¯ collisions. Data collected with the Collider Detector at Fermilab show agreement with QCD calculations. A limit on quark compositeness of ${\mathrm{\Lambda }}_{\mathit{c}}$>1.3 TeV is obtained. Axigluons with masses between 240 and 640 GeV/${\mathit{c}}^2$ are excluded at 95% C.L. if we assume ten open decay channels. Model-independent limits on the production of heavy particles decaying into two jets are also presented.

We define twist-two and twist-three quark fragmentation functions in quantum chromodynamics and study their physical implications. Using this formalism we show how the nucleon’s transversity distribution can be measured in single pion inclusive electroproduction.

In a high precision experiment, Mott scattering of the ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$${+}^{108}$Pb system was measured at ${\mathit{E}}_{\mathrm{lab}}$=873.40 MeV and 1129.74 MeV with kinematic coincidences for angle pairs around ${\mathrm{\theta }}_{\mathrm{lab}}$=30°, 60° and ${\mathrm{\theta }}_{\mathrm{lab}}$=45°, 45°. The observed Mott oscillations exhibit an angular shift with respect to pure Mott scattering. A comparison with the angular shift produced by a color van der Waals force including nuclear polarizability, vacuum polarization, relativistic effects, and electronic screening provides a new upper limit for the strength of this force. Influence of atomic effects other than screening were identified for the first time.

Electromagnetic form factors for the ρπγ and ωσγ vortices, estimated from quark loop diagrams, differ considerably from the monopole form factors obtained from vector meson dominance, and significantly alter the predictions for the elastic electromagnetic form factors of the deuteron.

Relative intensities of the yrast and the first excited superdeformed bands in ${}_{}{}^{151}{}_{}{}^{}\mathrm{Tb}$ have been accurately measured, with the EUROGAM spectrometer. It is shown that he excited band depopulates at the same freqeuncy and spin as its identical band in the isotone ${}_{}{}^{152}{}_{}{}^{}\mathrm{Dy}$ whereas the yrast band deexcites at higher rotational frequency and spin even though it is much lower in excitation energy. A classification of superdeformed bands in the A∼150 mass region indicates that the decay-out mechanism is strongly affected by neutron pairing correlations and the occupancy of high-N intruder orbitals.

The photonuclear reactions ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$(γ,n${)}^{15}$O and ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$(γ,p${)}^{15}$N are simultaneously described within a coupled channels framework based on a continuum shell model formulation that includes all nonlocalities arising from antisymmetrization. This large-scale conventional many-body calculation provides a good description of the medium energy data. The inclusion of Δ(1232) degrees of freedom further, but slightly, improves the description of the available data. Complete quantitative agreement, however, is still lacking.

The characteristics of the fission step following a binary deep-inelastic interaction have been reconstructed for three-body events detected in the reaction ${}_{}{}^{100}{}_{}{}^{}\mathrm{Mo}$${+}^{100}$Mo at 18.7A MeV and ${}_{}{}^{12\mathrm{-}}{}_{}{}^{}\mathrm{Sn}$${+}^{120}$Sn at 18.4A MeV. The observed anisotropy of the in-plane angular distributions points to the fast decay of a rotating (and strongly deformed) nuclear object formed at the end of the deep-inelastic interaction. The derived time scale of the process indicates that asymmetric divisions are faster than symmetric ones.

${\mathit{K}}^{+}$-nucleus quasielastic cross sections measured for a laboratory kaon beam momentum of 705 MeV/c are presented for 3-momentum transfers of 300 and 500 MeV/c. The measured differential cross sections for C, Ca, and Pb at 500 MeV/c are used to deduce the effective number of nucleons participating in the scattering, which are compared with estimates based on the eikonal approximation. The long mean free path expected for ${\mathit{K}}^{+}$ mesons in nuclei is found. Double differential cross sections for C and Ca are compared to relativistic nuclear structure calculations.

We have studied the evolution of regular and ‘‘dark’’ radial wave packets under the influence of two coherent, temporally separated 100 fs laser pulses. The atomic states are probed by ramped-field ionization. The final state populations exhibit Ramsey oscillations with periods ranging from 2.6–1000 fs as a function of the delay between the two pulses. This time-domain bound-state interferometry reveals several new aspects of the dynamic evolution of wave packets in the presence of strong laser fields. Lowest order perturbation theory is inadequate to describe wave packet formations, even at the lowest intensities studied.

From a series of phase difference measurements by our scheme 2, in which the field at one interferometer input is phase shifted progressively in steps of 18°, we obtain the probability distribution of the phase difference. The results are in agreement with theoretical predictions based on our operational approach to the quantum phase.

We report on observations of turbulent behavior made without requiring the use of Taylor’s ‘‘frozen turbulence’’ hypothesis. Initially, a towed grid generates homogeneous turbulence of grid Reynolds number of order ${10}^5$ within a stationary channel filled with helium II. The subsequent decay in time t of the line density of quantum vortices is measured by second sound attenuation, and the associated rms vorticity ω follows the behavior expected of a classical fluid with ω∼${\mathit{t}}^{\mathrm{-}3/2}$, consistent with the notion of a coupled turbulent state of helium II. This technique also yields the time dependence of the Kolmogorov microscale.

Subpicosecond laser pulses (down to 200 fs) have been produced and measured with a free-electron laser oscillator at a wavelength around 8.5 μm. This has been achieved by running our linear accelerator in a configuration where the electron bunches acquire a quasilinear time-energy relationship while traveling on the side, rather than on the crest, of an accelerating high-frequency wave.