We calculate the exact frequency redshift for fields coupled to gravity in Robertson-Walker backgrounds. The exact redshift factorizes and is proportional to the naive Doppler shift times a term representing diffractive effects. These diffractive corrections can be large for field modes with wavelengths on the order of the horizon size. Implications for cosmological density perturbations are discussed.

We explore stellar cooling by nuclear axion emission, identifying those special isotopes that dominate this process for temperatures ∼${10}^7$–${10}^9$ K. We argue that such nuclear energy-loss mechanisms are distinctive because the effects track metallicity. Three observables associated with evolution of stars along the red-giant and horizontal branches are shown to impose new and restrictive constraints on axions in the hadronic window.

The atmospheric neutrino flux is measured using a 3.4-kt yr exposure of the IMB-3 detector. Single-ring events are classified as showering or nonshowering using the geometry of the Čerenkov pattern. A simulation of neutrino interactions and three models of atmospheric neutrino production are used to predict the composition of the sample. Showering-nonshowering character is strongly correlated with the flavor of the neutrino parent. In the lepton momentum range p<1500 MeV/c, we find that nonshowering events comprise [41±3±2syst]% of the total. The fraction expected is [51±5(syst)]%.

The effective Lagrangian which exhibits explicitly the transmission of the CP-violating phases induced via the electroweak gaugino masses below the scale of the spontaneous breaking of SU(2${)}_{\mathit{L}}$×${\mathrm{U}}_{\mathit{y}}$(1) electroweak gauge symmetry is deduced. The formalism is used to compute the one-loop electric dipole moment of the electron including the full set of neutralino states. Contributions of neutralinos other than the photino are found to be significant. It is shown that the current data excludes maximal CP violation in the electroweak sector except for selectron masses ≳200 GeV and photino masses ≳750 GeV.

Total cross sections for the H(${\mathrm{\pi }}^{+}$,${\mathrm{\pi }}^{+}$${\mathrm{\pi }}^{+}$)n reaction have been measured at pion kinetic energies of 180, 184, 190 and 200 MeV. The threshold value for the matrix element a(${\mathrm{\pi }}^{+}$${\mathrm{\pi }}^{+}$) and the s-wave, isospin-2, ππ scattering length ${\mathit{a}}_2^0$ were determined. The results were found to be in agreement with chiral perturbation theory and inconsistent with the model of dominance by quark loop anomalies.

The first spin-transfer observables for the πd→pp reaction have been measured at a number of energies spanning the Δ resonance in this system. These parameters correspond to ${\mathit{K}}_{\mathit{S}\mathit{L}}$ and ${\mathit{K}}_{\mathit{S}\mathit{S}}$ of the pp→dπ reaction for incident proton energies ranging from 600 to 800 MeV. Such data can provide an important constraint on the determination of the partial-wave amplitudes describing this fundamental reaction. The discrepancies between our data, theoretical predictions, and values calculated from published partial-wave amplitudes demonstrate the need for further work in this area.

Kaon production from meson-meson annihilation is enhanced significantly because of the decrease of hadron masses in hot and dense matter as a result of the restoration of chiral symmetry. We show that this can lead to enhanced kaon yield in high-energy heavy-ion collisions.

Classical dynamics of heavy-ion scattering is investigated in the case of a collision between a supposed spherical nucleus, ${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$, and a deformed one, ${}_{}{}^{24}{}_{}{}^{}\mathrm{Mg}$, at energies above the Coulomb barrier. Evidence of regular and irregular motion is found. The chaotic behavior justifies the presence of Ericson’s fluctuations observed for this reaction, while the presence of regular motion embedded in the chaotic region could be the crucial point to explain the nature of the observed isolated resonances, once the semiclassical theory is applied.

Data obtained by the associated production of Λ hypernuclei through the (${\mathrm{\pi }}^{+}$,${\mathit{K}}^{+}$) reaction are presented for a wide range of mass numbers. The special features which make this reaction useful are pointed out. The reaction is shown to be an excellent probe of Λ single-particle states, as demonstrated by the excitation of deeply bound states which are interpreted as the weak coupling of a Λ to neutron-hole states of the core. The Λ binding energies and ground-state production cross sections for ${}_{\mathrm{\Lambda }}{}^9{}_{}{}^{}\mathrm{Be}$, ${}_{\mathrm{\Lambda }}{}^{12}{}_{}{}^{}\mathrm{C}$, ${}_{\mathrm{\Lambda }}{}^{16}{}_{}{}^{}\mathrm{O}$, ${}_{\mathrm{\Lambda }}{}^{28}{}_{}{}^{}\mathrm{Si}$, ${}_{\mathrm{\Lambda }}{}^{40}{}_{}{}^{}\mathrm{Ca}$, ${}_{\mathrm{\Lambda }}{}^{51}{}_{}{}^{}\mathrm{V}$, and ${}_{\mathrm{\Lambda }}{}^{89}{}_{}{}^{}\mathrm{Y}$ are presented.

A scheme for accomplishing tabletop x-ray lasing in Li-like Ne at 98 Å in an optically ionized plasma during recombination in the transient regime is presented. Saturation effects and parametric heating processes by stimulated Raman scattering are analyzed and found to allow energy efficiencies in excess of ${10}^{\mathrm{-}5}$ for a 100-fsec duration, 0.25-μm laser driver of intensity ${10}^{17}$ W/${\mathrm{cm}}^2$. Significant improvement in efficiency is indicated for shorter laser pulse lengths.

We report the first demonstration of a technique by which an optically thick medium may be rendered transparent. The transparency results from a destructive interference of two dressed states which are created by applying a temporally smooth coupling laser between a bound state of an atom and the upper state of the transition which is to be made transparent. The transmittance of an autoionizing (ultraviolet) transition in Sr is changed from exp(-20) without a coupling laser present to exp(-1) in the presence of a coupling laser.

We present two-dimensional numerical simulations of a nonlinear optical system made of a thin slice of Kerr material and a feedback mirror. The phase modulation induced on the light by the nonlinear material is transformed into amplitude modulation by propagation to the mirror and back, thus forming a feedback loop. Our simulations show that the uniform plane-wave solution deforms for sufficient pump intensity into a nonuniform pattern of hexagonal symmetry, independently of the sign of the nonlinearity, a feature which may be generic for third-order nonlinear optical systems.

We present calculations of ionization rates, trapping probabilities, and electron densities for a three-dimensional hydrogen atom in an intense, high-frequency, pulsed laser field. Under certain conditions, we find that hydrogen has a significant probability of surviving the ramp of the laser field to intensities at which ionization is strongly suppressed. We examine the dynamics of this process and discuss a method to observe it experimentally.

We report a measurement of the quantum-mechanical beam-pointing fluctuations in the output of a gain-guided, single-pass amplifier using stimulated Raman scattering. The experimental result is in reasonable agreement with a theoretical model that incorporates the effects of excess spontaneous noise associated with the transverse modes of a gain-guided amplifier.

It is suggested that the quantum uncertainty of cavity radiation is measurable via Aharonov-Bohm effects for electrons in a ring which is threaded by the magnetic cavity flux. When the electrons follow this oscillatory flux nearly adiabatically, and dissipation is negligible, the noise in the ring current should provide a quantum-nondemolition measure of the flux uncertainty. Unlike standard photodetection, such measurements should reveal the scaling of the flux uncertainty with the diamagnetic or dielectric index of the cavity medium, depending on the dimensions of the electron ring.

Coupled-channel calculations for relativistic heavy-ion collisions are performed in order to determine the electromagnetic electron-positron pair production yeild with subsequent capture of the electron into the K shell of the target. We consider heavy projectiles impinging on ${\mathrm{Pb}}^{82+}$ and ${\mathrm{U}}^{92+}$ with small impact parameters at a bombarding energy of 1.2 and 2 GeV/nucleon, respectively. The dependence of the positron yields on the charge number of the projectile exhibits a strong nonperturbative feature. The corresponding result obtained within first-order perturbation theory is exceeded by about 2 orders of magnitude.

We show that periodic dielectric composite media such as ordered colloidal suspensions exhibit enhanced dispersion forces. In an fcc structure with a full photonic band gap these forces can produce a nearly isotropic pressure on the structure due to the vacuum field fluctuations. This pressure is shown to significantly alter the phase diagram of the Kirkwood-Alder hard-sphere transition for systems with micron-size dimensions. The calculations predict that aqueous solutions of ${\mathrm{TiO}}_2$ particles of the order of 0.35 μm in diameter should be ideal of observing these effects.

The structure and dynamics of both subcritical and supercritical localized traveling-wave (LTW) convective states with different extensions and uniquely selected width are determined by numerical integration of the proper hydrodynamic field equations with realistic horizontal boundary conditions. A large-scale mean concentration current loop influences the LTW significantly. It generates a concentration distribution that hinders propagation of the LTW pulse, so that the group velocity is small but finite.

A self-induced transparency (DIT) soliton can coexist with a nonlinear Schrödinger (NLS) soliton. This mixed state is called an SIT-NLS soliton. The phase change of the new soliton is governed solely by the NLS component and the pulse delay is determined solely by the SIT component when a detuning from the resonance is zero. It is shown for the first time that a stable 2π-(N=1) SIT-NLS soliton exists and that high-order SIT/NLS solitons always split into multiple 2π-(N=1) SIT-NLS solitons.

A transmission-electron-microscope strong-beam technique is used to investigate the rigid-body translation across {110} antiphase boundaries in GaAs. The results show a translation in the 〈001〉 direction parallel to the plane of the boundary. The magnitude of the translation is determined, and the antisite bond lengths are discussed in terms of the tetrahedral radii of Ga and As. Given this knowledge of the rigid-body translation, the absolute polarity of a GaAs grain can be determined immediately from a bright-field image of the {110} antiphase boundary.