Photonic molecules have been fabricated by coupling pairs of micrometer-sized semiconductor cavities via a narrow channel. The optical modes in these structures have been studied spectroscopically as a function of the coupling and the mode energies are compared to detailed calculations. These results provide a rich picture of photonic modes in these molecules.

We study several scale-independent measures of cardiac interbeat interval dynamics defined through the application of the wavelet transform. We test their performance in detecting heart disease using a database consisting of records of interbeat intervals for a group of healthy individuals and subjects with congestive heart failure. We find that scale-independent measures effectively distinguish healthy from pathologic behavior and propose a new two-variable scale-independent measure that could be clinically useful. We compare the performance of a recently proposed scale-dependent measure and find that the results depend on the database analyzed and on the analyzing wavelet.

Candidates for epitaxially stabilized structures of Fe, Co, and Ni silicides are searched by ab initio calculations. We find that the pseudomorphic phases of ${\mathrm{FeSi}}_2$ in the $C1\mathrm{}$ structure and CoSi and NiSi in the $B2\mathrm{}$ structure soften dramatically under compressive biaxial strain induced by epitaxy on a (100) substrate. This supersoft effect is reflected by zero strain energy, constant volume, and constant bond energies.

We present an analysis of atmospheric neutrino data from a 33.0 kton yr (535-day) exposure of the Super-Kamiokande detector. The data exhibit a zenith angle dependent deficit of muon neutrinos which is inconsistent with expectations based on calculations of the atmospheric neutrino flux. Experimental biases and uncertainties in the prediction of neutrino fluxes and cross sections are unable to explain our observation. The data are consistent, however, with two-flavor ${\nu }_{\mu }\leftrightarrow {\nu }_{\tau }$ oscillations with ${sin}^{2}2\theta >0.82\mathrm{}$ and $5\times {10}^{-4\mathrm{}}<\Delta m^2<6\mathrm{}\times 10^{-3\mathrm{}}\mathrm{eV}{}^2$ at 90% confidence level.

We observe the effects of noise and dissipation on dynamical localization. Our system consists of cold cesium atoms in a pulsed standing wave of light, and is an experimental realization of the $\delta$-kicked rotor. We compare the effects of amplitude noise with those of spontaneous scattering. The experimental signature in both cases is an increased growth in energy, with qualitatively similar momentum distributions.

We have discovered that the dc mass current through a superfluid ${}^3\mathrm{He}$ weak link is substantially increased when the Josephson frequency matches the resonant frequency of a coupled mechanical oscillator. The phenomenon is the result of homodyne mixing between the Josephson oscillations and the oscillating pressure field associated with the resonant system. The measured sizes of the current enhancements are in excellent agreement with calculations based on this homodyne model. Similar observations in superconducting junctions, in which microwave radiation changes the dc electronic current, were used for the first confirmation of the dynamics of the superconducting Josephson effect.

By charging a thin wire we realize a pure attractive $1/r^2$ potential of variable strength for cold neutral atoms. Scattering experiments are performed where the charged wire is placed inside a confined gas of cold lithium atoms. We observe the “falling” of atoms into the $1/r^2$ singularity which so far has been only theoretically discussed in textbooks.

We extend previous proofs that violations of the null energy condition are a generic and universal feature of traversable wormholes to completely nonsymmetric time-dependent wormholes. We show that the analysis can be phrased purely in terms of local geometry at and near the wormhole throat, and we do not have to make any technical assumptions about asymptotic flatness or other global properties. A key aspect of the analysis is the demonstration that time-dependent wormholes have two throats, one for each direction through the wormhole, and that the two throats coalesce only for the case of a static wormhole.

The structure factor $S\left(Q\right)$ and the pair distribution function $g\left(r\right)$ has been measured for liquid boron in the temperature range 2600–2000 K, extending over both the normal and supercooled liquid states. The bond length and coordination number of the first coordination shell are similar to those reported for the crystalline and amorphous solid forms, but the second and third coordination shells are broader and shifted to higher distances. The insulator-metal transition that takes place in boron upon melting is associated with a relatively small change in both volume and short-range order.

Complex photoconductive measurements of the current through a double quantum dot enable us to monitor effects of coherent electron transport in the suppression of the rabi oscillations of this “artificial molecule.” The current is induced by a new broadband millimeter wave source functioning as a heterodyne interferometer, which consists of two nonlinear transmission lines generating harmonic outputs in the range 2–400 GHz, and, being coherent, allows tracking the induced current through the sample in both magnitude and phase.

We have studied the temporal coherence of high-order harmonics (up to the 15th order) produced by focusing 100 fs laser pulses into an argon gas jet. We measure the visibility of the interference fringes, produced when two spatially separated harmonic sources interfere in the far field, as a function of the time delay between the two sources. In general, we find long coherence times, comparable to the expected pulse durations of the harmonics. For some of the harmonics, the interference pattern exhibits two regions, with significantly different coherence times. These results are interpreted in terms of different electronic trajectories contributing to harmonic generation.

The top layer of the $\mathrm{GaAs}\left(001\right)-(2\times 4)$ surface consists of rows of As-As dimers. However, our scanning tunneling microscopy study shows that, in the initial adsorption stage, monoenergetic ${\mathrm{Br}}_2$ molecules (0.89 eV) react exclusively with the second layer Ga atoms exposed in trenches or at defects on the surface. A simple molecular orbital argument was used to explain the dynamics of forming gallium bromide species at various surface Ga sites.

We describe a new instability mechanism in free dendrite growth, which arises from electrically enhanced diffusion of polar molecules near the dendrite tip. For a small applied potential, the dendrite tip velocity increases slowly with potential, as is described by an extension of normal solvability theory. Above a threshold potential, however, capillarity is insufficient to stabilize growth. We present observations that confirm this instability, which brings about a transition from enhanced normal dendrite growth to a rapidly growing needle morphology with strongly suppressed sidebranching.

Using the Landauer formulation of transport theory, we predict that dielectric quantum wires should exhibit quantized thermal conductance at low temperatures in a ballistic phonon regime. The quantum of thermal conductance is universal, independent of the characteristics of the material, and equal to ${\pi }^2{k}_B^{2}T/3h$ where $k_B$ is the Boltzmann constant, $h$ is Planck's constant, and $T$ is the temperature. Quantized thermal conductance should be experimentally observable in suspended nanostructures adiabatically coupled to reservoirs, devices that can be realized at the present time.

Definitive evidence from a plasma wave interferometer carried on a sounding rocket is presented for the observation of counterrotating electric field structures observed at frequencies above and below the local lower hybrid resonance frequency, $f_{\mathrm{LHR}}$, of the ambient plasma. These counterrotating structures were observed within the context of a lower hybrid solitary structure (LHSS), and were found to rotate in a right-handed (left-handed) sense around the geomagnetic field at frequencies above (below) $f_{\mathrm{LHR}}$, in accord with previous predictions for and observations of electric field eigenmodes within a density depletion. The presence of a narrow band feature below $f_{\mathrm{LHR}}$ indicates the presence of trapped waves, and represents clear evidence of a bound state of lower hybrid waves in the auroral ionosphere.

We have completely determined the amplitude and phase of a quantum wave packet. The wave packet was shaped using a programmable optical pulse. Phase information comes from analysis of covariant fluctuations due to interference between the wave packet and a well-characterized reference.

In this Letter we present an experimental analysis of the acoustic transmission of a two-dimensional periodic array of rigid cylinders in air with two different geometrical configurations: square and triangular. In both configurations, and above a certain filling fraction, we observe an overlap, in the range of the audible frequencies, between the attenuation peaks measured along the two high-symmetry directions of the Brillouin zone. This effect is considered as the fingerprint of the existence of a full acoustic gap. Nevertheless, the comparison with our calculation of band structures shows that the triangular lattice has band states in that frequency range. We call them deaf bands. This contradictory result is explained by looking at the symmetry of the deaf bands; they cannot be excited by experiments of sound transmission.

Atomic force microscopy on hydrophobic microspheres in water reveals a strong attraction with a range of 20–200 nm, following an initial steep repulsion at long range. The data are consistent with a single submicroscopic bubble between the surfaces, with the attraction due to its attachment and lateral spread, and the repulsion dependent on film drainage and the electric double layer. The results provide direct experimental evidence of the existence of long-lived submicron bubbles, and of their bridging as the cause of the measured long-range attractions between macroscopic hydrophobic surfaces.

We show that stationary wave solutions of reaction-diffusion equations obey Snell's law of refraction. Refraction occurs at the interface of media where local kinetics have different reaction rates and the same steady state. In particular, we show that the apparent reflection or back refraction observed in experiments is also derived from Snell's law.

We show that gravitational radiation drives an instability in hot young rapidly rotating neutron stars. This instability occurs primarily in the $l=2\mathrm{}$ $r$-mode and will carry away most of the angular momentum of a rapidly rotating star by gravitational radiation. On the time scale needed to cool a young neutron star to about ${T=10\mathrm{}}^9\mathrm{K}$ (about one year) this instability can reduce the rotation rate of a rapidly rotating star to about $0.076{\Omega }_K$, where ${\Omega }_K$ is the Keplerian angular velocity where mass shedding occurs. In older colder neutron stars this instability is suppressed by viscous effects, allowing older stars to be spun up by accretion to larger angular velocities.