If there exists an asymptotic scaling regime for spinodal decomposition in phase-separating fluids where domain sizes follow $L\sim t^n$, then, it is argued, the growth exponent $n$ is no larger than 1/2.

We present a self-consistent mean field model of the extraction of atoms from a Bose-Einstein condensate to form a cw atom laser. The model is based upon the Hartree-Fock-Bogoliubov equations within the Popov approximation, modified by the inclusion of spatially dependent source and sink terms, which lead to current flow within the condensate. The effects of this current flow are investigated for traps containing rubidium (repulsive effective interaction) and lithium (attractive interaction) atoms. The extra kinetic energy associated with this flow is shown to be able to stabilize the condensate in the attractive case against mechanical instability.

We experimentally investigate the reduction of the fringe visibility in an atom interferometer due to the storage of which-way information. We focus on the case of incomplete which-way information and use the distinguishability $D$ to quantify how much information is stored. For a given value of $D$, the fringe visibility $V$ is limited by the duality relation $D^2{+V}^2\le 1$. We have measured $D$ and $V$ independently. Combining the results, we find good agreement with the duality relation.

The dynamics of a two-level system which is coupled to an environmental sea of infinitely many spin-1/2 particles is investigated by use of the resolvent operator approach. Only at zero temperature does this spin-spin-bath model exhibit identical behavior as the more familiar spin-boson model. It is found that increasing temperature favors coherent dynamics. At high temperatures, the spin-spin-bath model for an Ohmic spectral density sustains a coherent dynamics if the dissipation coefficient $\alpha$ is sufficiently small, i.e., $\alpha <1\mathrm{}/2$; while the decoherence exhibits pure exponential decay if $\alpha >1\mathrm{}/2$.

In this paper the angle-angular momentum entropic lower bound is proved by using Tsallis-like entropies and Riesz theorem for the quantum scattering of the spinless particles. Numerical estimations of the scattering entropies, as well as an experimental test of the state-independent entropic lower bound, are obtained by using the amplitude reconstruction from the available phase shift analyses for the pion-nucleus scatterings. A standard interpretation of these results in terms of the optimal state dominance is presented. Then, it is shown that experimental pion-nucleus entropies are well described by optimal entropies and that the experimental data are consistent with the principle of minimum distance in the space of scattering states.

We distinguish two types of spatial separation exhibited by atomic trap Bose-Einstein condensates: potential separation, in which case the condensates diffuse into each other as the trap is opened adiabatically, and phase separation, in which case the separation persists in the absence of external potentials. We discuss relevant features of the dynamics and statics of the phase separation of dilute condensates.

A phase slip in the fringes of an interference pattern is an unmistakable characteristic of vorticity. We show dramatic two-dimensional simulations of interference between expanding condensate clouds with and without vorticity. In this way, vortices may be detected even when the core itself cannot be resolved.

The formation of pyramidlike structures in thin-film growth on substrates with a quadratic symmetry, e.g., $\{001\}$ surfaces, is shown to exhibit anisotropic scaling as there exist two length scales with different time dependences. Numerical results indicate that for most realizations coarsening of mounds is described by an exponent $n\simeq 1/4$. However, depending on material parameters it is shown that $n$ may lie between 0 (logarithmic coarsening) and 1/3. In contrast, growth on substrates with triangular symmetries $(\{111\}$ surfaces $)$ is dominated by a single length $\sim t^{1/3}$.

Production of Bloch waves during a rapid quench is studied by analytical and numerical methods. The density of Bloch waves decays exponentially with the quench time. It also strongly depends on temperature. Very few textures are produced for temperatures lower than a characteristic temperature proportional to the square of the magnetic field.

We consider $L$ planar random walks (or Brownian motions) of large length $t$, starting at neighboring points, and the probability $P_L\left(t\right)\sim t^{-{\zeta }_L}$ that their paths do not intersect. By a 2D quantum gravity method, i.e., a nonlinear map to an exact solution on a random surface, I establish our former conjecture that ${\zeta }_L=\frac{1}{24}({4L}^2-1\mathrm{})$. This also applies to the half plane where ${\tilde{\zeta }}_L=\frac{L}{3}(1+2L)$, as well as to nonintersection exponents of unions of paths. Mandelbrot's conjecture for the Hausdorff dimension $D_H=4/3\mathrm{}$ of the frontier of a Brownian path follows from ${\zeta }_{3/2}$.

A Comment on the Letter by Henning Struchtrup and Wolf Weiss, Phys. Rev. Lett. 80, 5048 (1998). The authors of the Letter offer a Reply.

A Reply to the Comment by V. M. Castillo and Wm. G. Hoover.

A set of collective spin states is derived for a trapped Bose-Einstein condensate in which atoms have three internal hyperfine spins. These collective states minimize the interaction energy among condensate atoms, and they are characterized by strong spin correlations. We also examine the internal dynamics of an initially spin-polarized condensate. The time scale of spin mixing is predicted.

The phase diffusion of the order parameter of trapped Bose-Einstein condensates at temperature $k_{B}T\gg ħ\overline{\omega }$ is determined, which gives the fundamental limit of the linewidth $\Delta \nu$ of an atom laser. In addition a prediction of the number fluctuations in the condensate and their correlation time ${\tau }_c$ is made and a general relation for $\Delta \nu {\tau }_c$ is derived from the fluctuation-dissipation relation.

In a major extension of our previous model [Phys. Rev. Lett. 79, 1793 (1997)] of condensate growth, we take account of the evolution of the occupations of lower trap levels, and of the full Bose-Einstein formula for the occupations of higher trap levels. We find good agreement with experiment, especially at higher temperatures. We also confirm the picture of the “kinetic” region of evolution, introduced by Kagan et al., for the time up to the initiation of the condensate. The behavior after initiation essentially follows our original growth equation, but with a substantially increased rate coefficient $W^{+}$.

A Comment on the Letter by S. Velasco et al., Phys. Rev. Lett. 78, 3241 (1997). The authors of the Letter offer a Reply.

A Reply to the Comment by Zijun Yan and Jincan Chen.

We observe strong violation of Bell's inequality in an Einstein-Podolsky-Rosen-type experiment with independent observers. Our experiment definitely implements the ideas behind the well-known work by Aspect et al. We for the first time fully enforce the condition of locality, a central assumption in the derivation of Bell's theorem. The necessary spacelike separation of the observations is achieved by sufficient physical distance between the measurement stations, by ultrafast and random setting of the analyzers, and by completely independent data registration.

We report an experiment showing that atomic diffraction at grazing incidence from an evanescent wave mirror results from polarization gradients in the evanescent wave which induce transitions among atomic internal states. The resulting grating can produce large angle coherent beam splittings. We also demonstrate atomic interference in the form of a Stückelberg oscillation in the diffraction efficiency which is very sensitive to the atom wall van der Waals potential.