A molecular-level theory of the phase diagram of folding proteins is developed and applied to associative memory Hamiltonian models. Equilibrium collapse, folding, and glass transitions are described with a unified variational treatment, and quantitative estimates of the capacity of recall are found.

The spectrum of neutrinos from the Sun contains large fluxes of monoenergetic neutrinos which could be observed in the next generation of solar-neutrino detectors. Such observations directly probe neutrino parameters independent of uncertainties in the standard solar model. Small neutrino mass differences, ${10}^{\mathrm{-}11}$<${\mathit{m}}_2^2$-${\mathit{m}}_1^2$<${10}^{\mathrm{-}8}$ ${\mathrm{eV}}^2$, would cause the measured flux of ${}_{}{}^7{}_{}{}^{}\mathrm{line}$ neutrinos to oscillate with a period in the range of a week up to a year. A neutrino magnetic moment comparable to the present laboratory bound would produce large distortions in the spectrum of scattered electrons.

It is shown in the context of multicritical Hermitian multimatrix models that certain salient features of nonperturbative 2D quantum gravity have a geometric interpretation in terms of algebraic curves and knots associated to the matrix models via their relation to the generalized Korteweg–de Vries hierarchy. I show that the question of unitarity in these models is linked to the singularity structure of the corresponding algebraic curves as well as to the degree of symmetry of the associated torus knots. Other characteristics of the matrix models have a geometric interpretation as well.

Braiding on a string amplitude is shown to yield a Yang-Baxter relation in which the Koba-Nielsen variables play the role of spectral parameters.

We report full QCD simulations on a ${16}^3$×4 lattice. For two degenerate flavors no finite-temperature phase transition is found for quark masses of ma=0.01 and 0.025, where a is the lattice spacing, while for three degenerate flavors a first-order transition is easily seen for ma=0.025. Nature, with nearly massless up and down quarks and one heavier strange quark, lies between these two cases. For ${\mathit{m}}_{\mathit{u},}$da=0.025 and ${\mathit{m}}_{\mathit{s}}$a=0.1 we find that ${\mathit{m}}_{\mathit{K}}$/${\mathit{m}}_{\mathrm{\rho }}$=0.46(1) and that no transition occurs, calling into question the existence of a QCD phase transition.

The conformal dimension of the Polyakov line at the deconfinement phase transition of (2+1)-dimensional SU(2) lattice gauge theory is determined numerically using two-dimensional finite-size conformal field theory. Excellent agreement with two-dimensional Ising-model values is found for both the renormalized coupling on a spatially toroidal geometry and the conformal dimensions on a finite-width strip geometry.

In supersymmetric extensions of the standard model, the neutron-electric-dipole moment is typically two or three orders of magnitude above its experimental upper bound unless the relevant CP-nonconserving phase is suppressed. This situation is highly undesirable, especially in models of radiative masses, in general, where the absence of small parameters at tree level is their raison d’être. In this paper we identify the various sources of CP nonconservation in such models and present a possible solution which also gives the observed pattern of quark masses and mixing angles.

Results on the photoproduction of 10 000 fully reconstructed charmed particles from the ${10}^8$ recorded triggers of Fermilab experiment E691 have been analyzed in the photon-gluon-fusion model. We find that the total cross section, its rise with energy, and the ${\mathit{p}}_{\mathit{T}}^2$ and ${\mathit{x}}_{\mathit{F}}$ distributions can be explained by a high mass for the charm quark (${\mathit{m}}_{\mathit{c}}$=1.${74}_{\mathrm{-}0.18}^{+0.13\mathrm{}}$ GeV/${\mathit{c}}^2$) and a soft-gluon distribution [G(x)∼(1-x${)}_{\mathit{g}}^{\mathit{n}}$, where ${\mathit{n}}_{\mathit{g}}$=7.1±2.2].

Results from a partial-wave analysis of the decay J/ψ→γ${\mathit{K}}_{\mathit{S}}^0$${\mathit{K}}^{\pm }$${\mathrm{\pi }}^{\mp }$ in the ${\mathit{K}}_{\mathit{S}}^0$${\mathit{K}}^{\pm }$${\mathrm{\pi }}^{\mp }$ invariant-mass range 1.35–1.6 GeV/${\mathit{c}}^2$ are presented. Within the isobar model, the data in this mass range are best described by a mixture of $0^{\mathrm{-}+}$ and $1^{++}$ amplitudes, corresponding to the ${\mathit{K}}^{\mathrm{*}}$K¯+c.c (P wave), ${\mathit{K}}^{\mathrm{*}}$K¯+c.c (S wave), and ${\mathit{a}}_0$(980) π (S wave) channels. These results show that η(1430) is not a ${\mathit{J}}^{\mathit{P}\mathit{C}}$=$0^{\mathrm{-}+}$ ${\mathit{a}}_0$(980)π resonance, but a mixture of overlapping states.

Spin-dependent quark and gluon distribution functions are derived in terms of light-cone correlation functions. The first moment of the gluon asymmetry Δg is shown to be related to the Chern-Simons current ${\mathit{K}}^{\mathrm{\mu }}$. Renormalization and factorization ambiguities and their implication for the ${\mathit{g}}_1$ problem are discussed.

Nuclear-resonance-fluorescence spectra have been measured in the chain of ${}_{}{}^{148,150,152,154}{}_{}{}^{}\mathrm{Sm}$ isotopes. Together with supplementary information from inelastic electron scattering and other reaction studies, orbital M1 transition strengths have been deduced for a number of $1^{+}$ states located around an excitation energy of 3 MeV. The systematic study, carried out for the first time, for nuclei within a large range of the deformation parameter δ shows that the orbital M1 strength varies quadratically with δ. This result is interpreted in terms of models containing explicitly neutron and proton degrees of freedom.

We report here isovector M1 strength distributions in ${}_{}{}^{24}{}_{}{}^{}\mathrm{Mg}$ obtained in a high-resolution (e,e’) experiment at the Darmstadt Electron Linear Accelerator. The M1 strength is strongly enhanced relative to the Gamow-Teller strength for analog transitions observed in recent (p,n) and (n,p) experiments at the Indiana University Cyclotron Facility and TRIUMF. We show that this enhancement can likely be attributed to meson-exchange contributions to the spin part of the M1 operator.

The spectrum shape and the angular distribution of γ rays from highly excited and rotating ${}_{}{}^{90}{}_{}{}^{}\mathrm{Zr}$ and ${}_{}{}^{92}{}_{}{}^{}\mathrm{Mo}$ compound nuclei were measured and analyzed. The results are in good agreement with theory including both intrinsic-shape fluctuations and shape-orientation fluctuations about an equilibrium shape which changes from spherical to oblate deformed with increasing spin.

A recent macroscopic approach to the giant dipole resonances in hot rotating nuclei is extended to include the angular distributions of the γ rays emitted in the resonance decay. It provides a uniform description of thermal fluctuations in all quadrupole shape degrees of freedom within the framework of the Landau theory. In particular, the inclusion of fluctuations in the nuclear orientation with respect to the rotation axis is crucial in reproducing the observed attenuation of the angular anisotropy. The theory is applied to recent precision measurements in ${}_{}{}^{90}{}_{}{}^{}\mathrm{Zr}$ and ${}_{}{}^{92}{}_{}{}^{}\mathrm{Mo}$ and is the first to reproduce well both the observed giant-dipole-resonance cross sections and the angular anisotropies.

By increasing the Fresnel number F of a ring cavity with photorefractive gain, we show the transition between a low-F regime, where a few modes compete with a periodic alternation which becomes irregular with increasing F (chaotic itinerancy), and a high-F regime, where many modes oscillate simultaneously, giving rise to chaotic domains spatially correlated over a length much shorter than the wave-front size (spatiotemporal chaos).

The first demonstration of the combination of two powerful techniques, Fourier-transform spectroscopy and velocity modulation, for the selective detection of molecular ions, is reported. This is also the first time that velocity modulation has been observed in emission. As an application of this we also reported the experimental measurement of the ratio of the dipole moment to the vibrational transition moment of a molecular ion, ${\mathrm{ArH}}^{+}$, by the Herman-Wallis effect.

We have measured the wave number of the ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ $2^1$S-$3^1$P transition by Doppler-free spectroscopy in a metastable helium beam. The result, 19 931.924 794(45) ${\mathrm{cm}}^{\mathrm{-}1}$, represents an order-of-magnitude improvement over previous measurements and provides a sensitive test of two-electron QED effects. Our result shows an unexpectedly large deviation from theoretical prediction. We derive improved term values for a number of low-lying helium levels. All levels with n=2 show significant deviations from theory that are correlated with the size of calculted two-electron contributions to the Lamb shifts.

The electrostatic fluctuations are decorrelated in the region of a naturally occurring ${\mathbf{E}}_{\mathit{r}}$×B velocity shear close to the outermost closed flux surface of regular Ohmic TEXT discharges. The concomitant local steepening of the density profile and suppression of the fluctuations are consistent with theoretical predictions. The high-confinement mode found in other tokamaks shows, in exaggerated form, similar characteristics, and could thus be related to the same mechanism leading to a locally improved confinement.

We suggest that certain open driven systems self-organize to a critical point because their continuum diffusion limits have singularities in the diffusion constants at the critical point. We rigorously establish a continuum limit for a one-dimensional automaton that has this property, and show that certain exponents and the distribution of events are simply related to the order of the diffusion singularity. Numerically, we show that some of these results can be generalized to include a class of sandpile models that are described by a similar, but higher-order, singularity.

A new class of exactly solvable Frenkel-Kontorova models is studied. For any fixed irrational winding number w, we find examples of nonrecurrent minimum-energy configurations, the existence of which has hitherto been in doubt. Such incommensurate defects nucleate a devil’s-staircase type of ground-state phase transitions, corresponding to discontinuous transformations of cantori in the associated area-preserving maps. These minimizing cantori may have several independent orbits of gaps and are accompanied by an infinity of metastable cantori with the same w.