Following an idea close to one given by C. G. Torre (private communication), we prove that Riemannian spaces (M,g) and (M,h) that are related by a Gürses’s type (b) transforamtion [M. Gürses, Phys. Rev. Lett. 70, 367 (1993)] or, equivalently, by a Torre-Anderson generalized diffeomorphism [C. G. Torre and I. M. Anderson, Phys. Rev. Lett. 70, 3525 (1993)] are neighborhood isometric, i.e., every point x in M has a corresponding diffeomorphism φ of a neighborhood V of x onto a generally different neighborhood W of x such that ${\mathrm{\phi }}^{\mathrm{*}}$(h${\mathrm{\Vert }}_{\mathit{W}}$)=g${\mathrm{\Vert }}_{\mathit{V}}$.

We show that charged Eguchi-Hanson instantons represent a calculable, intrinsic quantum gravity breaking of the Peccei-Quinn symmetry. The size of such breaking depends sensitively on the short-distance details of a given theory, but is generically suppressed by multifermion zero modes. We also explain conditions to solve the strong-CP and the domain wall problems under such quantum gravity effects.

Long-wavelength gravitational waves can induce significant temperature anisotropy in the cosmic microwave background. Distinguishing this from anisotropy induced by energy density fluctuations is critical for testing inflationary cosmology and theories of large-scale structure formation. We describe full radiative transport calculations of the two contributions and show that they differ dramatically at angular scales below a few degrees. We show how anisotropy experiments probing large- and small-angular scales can combine to distinguish the imprint due to gravitational waves.

A black hole solution to three-dimensional general relativity with a negative cosmological constant has recently been found. We show that a slight modification of this solution yields an exact solution to string theory. This black hole is equivalent (under duality) to the previously discussed three-dimensional black string solution. Since the black string is asymptotically flat and the black hole is asymptotically anti–de Sitter, this suggests that strings are not affected by a negative cosmological constant in three dimensions.

We study the stability of small strangelets by employing a simple model of strange matter as a gas of noninteracting fermions confined in a bag. We solve the Dirac equation and populate the energy levels of the bag one quark at a time. We find that for system parameters such that strange matter is unbound in bulk, there may still exist strangelets with A<100 that are metastable. We cannot determine, however, whether the lifetime of these strangelets is sufficient to detect them in current accelerator experiments.

Triple differential cross sections ${\mathit{d}}^3$σ/${\mathit{dp}}^3$ for charged pions produced in symmetric heavy-ion collisions were measured with the KaoS magnetic spectrometer at the heavy-ion synchrotron facility SIS at GSI. The correlations between the momentum vectors of charged pions and the reaction plane in ${}_{}{}^{197}{}_{}{}^{}\mathrm{Au}$${+}^{197}$Au collisions at an incident energy of 1 GeV/nucleon were determined. We observe, for the first time, an azimuthally anisotropic distribution of pions, with enhanced emission perpendicular to the reaction plane. The anisotropy is most pronounced for pions of high transverse momentum in semicentral collisions.

A superdeformed band has been observed for the first time in an Au isotope. The reaction used was ${}_{}{}^{11}{}_{}{}^{}\mathrm{B}$ + ${}_{}{}^{186}{}_{}{}^{}\mathrm{W}$, demonstrating that very light ions can be used to populate superdeformed (SD) bands at high angular momentum. The band is assigned to ${}_{}{}^{191}{}_{}{}^{}\mathrm{Au}$. The γ-ray energies are at the quarter-point energies of the ${}_{}{}^{192}{}_{}{}^{}\mathrm{Hg}$ SD band, indicating that it is ‘‘identical’’ to that of ${}_{}{}^{192}{}_{}{}^{}$ Hg.

In a picosecond time-resolved study, Rb atoms in an electric field are excited above the classical field-ionization threshold by a laser. Part of the electron wave function is observed to return to the core before escaping over the saddle point. At energies just above the saddle point all Stark states in the wave packet contribute to the returning part. Close to the zero-field-ionization limit, only bluest Stark components are involved. Also, a wave packet is observed performing simultaneous quantum beats in the radial coordinate and angular momentum. Simple calculations reproduce the orbit times.

We have observed selection rules for the resonant excitation of swift hydrogenlike ions (Z=6,7) axially channeled in the 〈111〉 direction of a diamond lattice (silicon). The resonant excitation arises from a coherent periodic perturbation by the atoms in the bounding crystal rows. We show that the selection rules are the consequence of destructive and constructive interference in the quantum mechanical transition amplitude for excitation.

We consider two-dimensional flow stirred by a small-scale, white-in-time random noise in the zero viscosity limit. Numerical simulations show that, after a transient state, an inertial-range energy spectrum E(k)∝${\mathit{k}}^{\mathrm{-}\mathit{x}}$ with x=5/3±0.05 is established by the inverse cascade process. This range grows in time until a Bose condensate is formed at the largest scales in the system (k≊1). Prior to condensate formation the statistics of velocity differences are extremely close to Gaussian, and only after Bose condensation strong deviations from Gaussian statistics are detected at small scales. The structures responsible for this effect are identified.

Strictly one-dimensional theories of particle loss due to longitudinal diffusion model the loss by an absorbing boundary condition at the separatrix of the underlying unperturbed motion. Particle loss always occurs at a physical aperture and the loss is always coupled to the betatron motion. A theory of particle loss which includes the effect of betatron motion is presented. Results are compared with Monte Carlo simulations.

This paper reports that ion-neutral collisions in a magnetized plasma cause a drastic change in the dispersion relation of the shear Alfvén wave with poloidal mode number m=0, connecting to the branch of the m=+1 compressional Alfvén wave at frequencies below the ion-cyclotron frequency. An anomaly of the dispersion then appears on the refractive index curve and a wave packet in this frequency range undergoes strong amplitude damping and profile deformation. It is confirmed that the Kramers-Kronig relation holds for the dielectric function, estimated from both the measured refractive index and damping rate.

The pseudospark cathode has the remarkable property of macroscopically homogeneous electron emission at very high current density (>1 kA/${\mathrm{cm}}^2$) over a large area (some ${\mathrm{cm}}^2$). Experimental results and the model presented here provide evidence that the pseudospark microscopically utilizes explosive arc processes, as distinct from the earlier model [Phys. Rev. Lett. 60, 2371 (1988)].

Thomson scattering was used to probe the frequency and wave-number spectra of plasma waves driven in a plasma by stimulated Raman scattering (SRS). SRS was excited in exploding foil targets with a 1.06 μm wavelength laser with average intensities up to ${10}^{15}$ W/${\mathrm{cm}}^2$. The spectra show that the plasma waves are consistent with the linear SRS dispersion relation. Observed broadening of the spectrum towards smaller wave number is consistent with saturation of SRS by Langmuir decay for these conditions.

A new tight-binding-bond approach to interatomic forces in liquid aluminum–transition metal (AL-M) alloys is presented. It is shown that the bond order depends strongly on the strength of the pd hybridization in the A-M alloy, leading to nonadditive potentials with a strong preference for the formation of a pair of unlike atoms and short bond distances in the Al-M pairs. This is illustrated by studying the structural properties of liquid ${\mathrm{Al}}_{80}$${\mathrm{Ni}}_{20}$ and ${\mathrm{Al}}_{80}$${\mathrm{Mn}}_{20}$ alloys using molecular dynamics simulations and by comparing our results with the available experimental ones.

A deterministic algorithm for calculating polymer properties is presented. It is based on a variational approach where the bond and Coulomb potentials are approximated by a quadratic trial energy. The parameters which describe average atom positions and Gaussian fluctuations, are the solutions of matrix equations. By a judicious choice of parameter representations and the use of incremental matrix inversion, an efficient iterative algorithm is constructed that is several orders of magnitude faster than Monte Carlo methods. The method is explored numerically at realistic temperatures with results that agree within 5% with those of Monte Carlo calculations.

A stochastic fracture model of N ordered elements with one-sided local transfer of load is proposed and solved. The probability of total collapse is calculated as a function of the applied load and we find that, assuming Weibull-type distributions to describe the elemental strengths, in the limit of large N, the global strength of the set is proportional to (logN${)}^{\mathrm{-}1}$. To solve the model, use is made of the fact that when the length of a crack surpasses a critical value, the associated avalanche necessarily destroys the whole set. The antecedents of this model in materials science and seismology are indicated.

We calculate the full dimension (canonical plus anomalous), ${\mathit{y}}_{2\mathit{s}}$, of an infinite number of O(N) invariant operators with 2s gradients. We find that for large (ε=d-2), ${\mathrm{y}}_{2\mathrm{s}}$=2(1-s)+ε{1+[${\mathrm{s}}^2$/ (N-2)][1+O(1/s)]}+[${\mathrm{\epsilon }}^2$${\mathit{s}}^3$/(N-2${)}^2$]2/3+O(1/s)]+O(${\mathrm{\epsilon }}^3$), correct to two-loop order. Thus, in two-loop order ${\mathit{y}}_{2\mathit{s}}$ grows even more rapidly than in one-loop order. Even if ε is arbitrarily small, one can always find, to two-loop order, operators with positive full dimension by choosing s sufficiently large. We argue that the conventional analysis of this problem may be inadequate.

The spinodal decomposition and late-time domain growth in a two-dimensional binary fluid have been studied for the first time by computer simulation. The dynamical phase transition shows scaling, and evidence is found of a competition between different growth mechanisms. The scaling regime presents a time growth law with an exponent 1/2, and a subsequent crossover to a faster growth, possibly mediated by a 1/4 transient. Our results demonstrate that hydrodynamic modes play a decisive role in phase separation dynamics.

The superfluid relaxation time near the ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ λ transition is calculated using a vortex-ring theory of the phase transition. The diffusive response of the vortices is found by solving the Fokker-Planck equation, and the resulting relaxation time at low frequencies is in agreement with Landau-Khalatnikov theory and with dynamic scaling. At higher frequencies there is a deviation from the Landau-Khalatnikov form, with both the dissipation and superfluid density remaining finite at ${\mathit{T}}_{\lambda }$ as the transition broadens at finite frequency.