We have obtained an experimental null result for a possible composition-dependent force by a newly developed Galilean method in which we measured the acceleration difference between two objects freely falling simultaneously in a vacuum chamber. The data on two pairs of objects, an aluminum-copper pair and an aluminum-carbon pair, indicate ‖ξ‖λ<9m if baryon coupling and a simple model of the Earth is assumed.

It is shown that the presence, in the cosmic-ray spectrum, of charged particles of extragalactic origin and energies exceeding ${10}^{10}$ GeV implies that photons cannot be coupled to the gravitational field of our galaxy more strongly than relativistic charged baryons, to an accuracy of at least one part in ${10}^{14}$. This bound is based on the possible energy loss, due to Cherenkov emission, which may be induced by the galactic gravitational field if the equivalence principle is violated. No constraint is obtained, however, for the case in which the photon effective coupling to gravity is weaker than that of massive particles.

We numerically investigate collisions of cosmic strings carrying different winding numbers. We find that for strings with winding numbers ${\mathrm{n}}_1$ and ${\mathrm{n}}_2$, intercommutation occurs by peeling a string of winding number ‖${\mathrm{n}}_1$-${\mathrm{n}}_2$‖ from the string with the larger winding number. The resulting string connects the original colliding strings to form a state of three joined strings, but because of the peeling the eventual result is a reduction in the winding numbers of the network. Stable astrophysical strings with large winding number are thus unlikely to persist. All simulations have gauge/scalar-field mass ratio =2. .AE

Use of a coherent-state representation of the sphaleron allows a direct calculation of its production rate in a thermal gas of W and Higgs bosons Technical considerations permit a straightforward calculation only in the case λ/${\mathrm{g}}^2$≃1 (${\mathrm{M}}_{\mathrm{H}}$≃3${\mathrm{M}}_{\mathrm{W}}$), where λ is the Higgs-boson quartic coupling, and g is the SU(2) gauge coupling. For this case it is found that the rate is unsuppressed for temperatures T≥2.4${\mathrm{M}}_{\mathrm{W}}$(0), where ${\mathrm{M}}_{\mathrm{W}}$(0) is the zero-temperature W mass. Thus anomalous B+L violation is also unsuppressed above this temperature.

Moduli spaces for a wide class of Calabi-Yau manifolds with different numerical invariants (and thus topologically distinct) can be assembled into a connected ‘‘web’’ in which all distances are finite. This increases the plausibility of phase transitions among the corresponding superstring vacua.

We discuss the N-particle amplitude for p-adic closed bosonic strings; an effective field theory is derived and then it is shown how the space-time field equations follow from a generalized scaling property in a p-adic σ model. The closed superstring is discussed p-adically at the four-particle level, and finally a speculation is made about how nonperturbative supersymmetry breaking in the superstring might be approached using p-adics.

It is shown how a naive extension of Polyakov’s construction to the (3+1)-dimensional case leads to transmutation between bosonic and fermionic one-dimensional structures.

K factories will open the way for high-precision CP tests in $K_{\mu 3}$ decays. The standard model does not predict CP breaking in this process. We consider here the effects of nonstandard interactions mediated by vector and scalar particles and by leptoquarks. We show that, for the only experimentally measurable quantity, vector particles alone never induce CP violation, and give a general expression for the CP breaking induced by scalars and leptoquarks.

Perturbative QCD calculations of the processes pp¯→$W^{\pm }$,Z+n jets (n=1,2,3) with W→eν and Z→eē decays are presented for comparison with forthcoming Fermilab Tevatron data at √s =1.8 TeV. The W,Z+2-jet results are compared with the corresponding pp¯→WW, WZ, and ZZ electroweak cross sections.

We report the existence of narrow resonances in the positive-energy region of the diamagnetic spectrum of lithium. The level structure evolves with magnetic field in an orderly fashion. Linewidths corresponding to lifetimes greater than 3000 cyclotron periods have been observed. The regime studied is characterized by chaotic classical motion.

The linear-response matrix, L, of a composite made of two isotropic components must obey a number of compatibility relations, involving the response matrices, $L_a$ and $L_b$, of the components, but totally independent of the mixture ratio of the components and the microstructure of the composite: ${\mathrm{LL}}_a^{\mathrm{-}1}$$L_b$-$L_b$$L_a^{\mathrm{-}1}$L=0. For an anisotropic composite, the tensor elements of L must satisfy the same conditions; in this case we obtain relations that the moduli of the composite satisfy among themselves. The mere fact that the composite is made of two isotropic components imposes relations among its moduli.

Ion cyclotron resonance in a straight magnetic field with a perpendicular gradient in field strength is analyzed using gyrokinetic theory. Propagation of the fast wave perpendicular to the equilibrium field and into the gradient is examined. The inclusion of the variation of the equilibrium magnetic field over an ion Larmor radius results in perpendicular ion cyclotron damping where previous models predict none. The effect of this damping on ion cyclotron heating of plasmas is discussed.

Measurements of neutron yield from a Z pinch formed from a solid deuterium fiber have been reported recently. The scaling of yield with applied current was a surprising $I^{10}$. Although the neutrons were believed to result from a plasma instability, no explanation for the magnitude or scaling of the yield with current was suggested. A model of a sausage, or m=0, instability has been generated which gives the observed yield to a multiplicative constant and the scaling of yield with current. It is predicted that the yield can be increased by increasing the applied current, but the model indicates that yields from this mechanism may be limited to ${10}^{12}$ unless tritium is added to the pinch.

A microinstability at a frequency equal to the second-harmonic ion cyclotron frequency was observed in the JT-60 tokamak with the injection of high-power perpendicular neutral beams. This instability appeared in a limiter configuration having relatively large clearance between the plasma surface and the wall of the vacuum vessel, but not in an outside divertor configuration. The instability was accompanied by a high-energy ion tail in the almost perpendicular direction. These experimental observations suggest that the strong anisotropy of the ion velocity distribution may be brought about by an ion banana motion localized at the outer region of the major radius, and that strong perpendicular neutral beam injection may suffer from insufficient thermalization of injected beams.

A transmission-electron-microscope technique enables direct visualization of the director field of a liquid-crystal polymer at a resolution of 30 nm. Continuum mechanics is used to describe distortions in the director field produced by a disclination, and the relative bend and splay elastic anisotropy for various polymers is measured. The elastic anisotropy varies significantly with small chemical differences. Effect of molecular weight is discussed. This technique should also yield information of disclination core structure.

Models are proposed for thick-film-coverage adsorption on a general fractal surface. The basic idea is that long-range dispersion forces dominate the thermodynamic behavior. The analysis predicts the coverage to be proportional to [ln($P_0$/P${\left)\right]}^{\left(D\mathrm{-}3\right)/3}$ where P/$P_0$ is the relative vapor pressure and D is the fractal dimension of the surface. Experimental examples for this behavior are presented. They are rough Ag surfaces, giving D=2.30. .AE

An infrared and secondary ion mass spectrometry study of H diffusion in undoped, rf-sputtered multilayered hydrogenated and deuterated amorphous silicon is reported. The results indicate that the long-range motion of atomic H is suppressed when the microvoid content exceeds a critical value associated with an initial ${\mathrm{SiH}}_2$ and ${\mathrm{SiH}}_3$ density $N_{d0}$≃7±1 at.%. The strong power-law time dependence of the diffusion constant (exponent α≃0.75±0.15) somewhat below this value of $N_{d0}$ is disucssed in relation to H migration mediated by mobile intrinsic defects, and the presence of an exponential distribution of traps for these defects and/or hydrogen.

A thermodynamic model which predicts a significant sample-size effect on the elastic properties of very thin films and small-period superlattices is presented. Compressive surface stresses cause the in-plane interatomic distances in a thin metal film to decrease as the thickness decreases. For copper films with a thickness of 0.75 nm, a 1% in-plane biaxial compressive strain is obtained which gives rise to a 50% increase in the biaxial modulus. This model also predicts a similar modulus enhancement (supermodulus effect) in multilayered thin films due to strains caused by incoherent interfacial stress.

The surface structure of ${\mathrm{SrTiO}}_3$(100) was analyzed at T=120 K by means of low-energy-electron diffraction. The best theory-experiment fit results for a surface containing domains of two different layer terminations. Both of them show a first-layer puckering with oxygen ions being pulled out of the surface by s(Ti)=0.08 Å and s(Sr)=0.16 Å combined with a relaxation of the first two layer distances. This proves the surface to be ferroelectric different from the bulk property in agreement with theoretical predictions.

We report first-principles local-density-functional pseudopotential calculations of static and dynamic electronic structure properties of crystalline 3D trans-(CH${)}_{\mathrm{x}}$. We find a broken-symmetry ground state of P$2_1$/a symmetry with in-phase dimerizations. Using a Green’s-function technique, we show that the 3D character of the electronic band-edge states strongly suppresses self-trapping, destabilizing polarons, and possibly bipolarons as well in perfectly ordered 3D trans-(CH${)}_{\mathrm{x}}$. .AE