We use the distribution, and particularly the skewness, of high redshift type Ia supernovae brightnesses relative to the low redshift sample to constrain the density of macroscopic compact objects (MCOs) in the Universe. The supernova data favor dark matter made of microscopic particles (such as the lightest supersymmetric partner) over MCOs with masses between ${10}^{-2}{M}_{\odot }$ and ${10}^{10}{M}_{\odot }$ at 89% confidence. Future data will greatly improve this limit. Combined with other constraints, MCOs larger than one-tenth the mass of Earth ($\sim {10}^{-7}{M}_{\odot }$) can be eliminated as the sole constituent of dark matter.

We show that surface electromagnetic waves (SEMWs) propagating along two-dimensional (2D) interfaces separating different metamaterials can behave analogously to 3D electromagnetic waves in either usual or left-handed media, depending on the permeabilities and/or permittivities of the two materials forming the interface. We derive the conditions when SEMWs carry energy opposite to the phase velocity. In analogy to three-dimensional (3D) left-handed media, we derive both an anomalous Cherenkov emission and a reversed Doppler effect. We also predict a negative refraction at the boundary between two different interfaces, which can be useful for perfect 2D lensing.

Using laser-induced fluorescence-dip Stark spectroscopy, we performed time-resolved, direct measurements of electric-field strengths during the breakdown phase of a low-pressure, pulsed discharge in xenon. With this experimental technique we could for the first time quantitatively measure the time evolution of the driving force of the plasma breakdown process: the electric field. Moving ionization fronts were measured with submicrosecond resolution. These ionization fronts were sustained by a spatially narrow, rapidly moving region of strong electric field.

Gravitomagnetism—a motional coupling of matter analogous to the Lorentz force in electromagnetism—has observable consequences for any scenario involving differing mass currents. Examples include gyroscopes located near a rotating massive body and the interaction of two orbiting bodies. In the former case, the resulting precession of the gyroscope is often called “frame dragging” and is the principal measurement sought by the Gravity Probe-B experiment. The latter case is realized in the Earth-Moon system, and the effect has in fact been confirmed via lunar laser ranging to approximately 0.1% accuracy—better than the anticipated accuracy of the Gravity-Probe-B result. This Letter shows the connection between these seemingly disparate phenomena by employing the same gravitomagnetic term in the equation of motion to obtain both gyroscopic precession and modification of the lunar orbit.

The effects of thermal elastic fluctuations in rubbery materials are examined. It is shown that, due to their interplay with the incompressibility constraint, these fluctuations qualitatively modify the large-deformation stress-strain relation, compared to that of classical rubber elasticity. To leading order, this mechanism provides a simple and generic explanation for the peak structure of Mooney-Rivlin stress-strain relation and shows good agreement with experiments. It also leads to the prediction of a phonon correlation function that depends on the external deformation.

Stroke patterns for Purcell’s three-link swimmer are optimized. We model the swimmer as a jointed chain of three slender rods moving in an inertialess flow. The swimmer is optimized for efficiency and speed. We were able to attain swimmer designs significantly more efficient than those previously suggested by authors who only consider geometric design rather than kinematic criteria. The influence of slenderness on optimality is considered as well.

We report on the first measurement of a temperature dependence of the Casimir-Polder force. This measurement was obtained by positioning a nearly pure ${}^{87}\mathrm{Rb}$ Bose-Einstein condensate a few microns from a dielectric substrate and exciting its dipole oscillation. Changes in the collective oscillation frequency of the magnetically trapped atoms result from spatial variations in the surface-atom force. In our experiment, the dielectric substrate is heated up to 605 K, while the surrounding environment is kept near room temperature (310 K). The effect of the Casimir-Polder force is measured to be nearly 3 times larger for a 605 K substrate than for a room-temperature substrate, showing a clear temperature dependence in agreement with theory.

We investigate the behavior of a quantum resonator coupled to a superconducting single-electron transistor (SSET) tuned to the Josephson quasiparticle resonance and show that the dynamics is similar in many ways to that found in a micromaser. Coupling to the SSET can drive the resonator into nonclassical states of self-sustained oscillation via either continuous or discontinuous transitions. Increasing the coupling further leads to a sequence of transitions and regions of multistability.

A laser-produced x-ray drive was used to shocklessly compress solid aluminum to a peak longitudinal stress of 110 GPa within 10 ns. Interface velocities versus time for multiple sample thicknesses were measured and converted to stress density ($P_x-\rho$) using an iterative Lagrangian analysis. These are the fastest shockless compression $P_x(\rho )$ results reported to date, and are stiffer than models that have been benchmarked against both static and shock-wave experiments. The present results suggest that at these short time scales there is a higher stress-dependent strength and a stiffer time-dependent inelastic response than had been expected.

Vacuum-stimulated Raman transitions are driven between two magnetic substates of a ${}^{87}\mathrm{Rb}$ atom strongly coupled to an optical cavity. A magnetic field lifts the degeneracy of these states, and the atom is alternately exposed to laser pulses of two different frequencies. This produces a stream of single photons with alternating circular polarization in a predetermined spatiotemporal mode. MHz repetition rates are possible as no recycling of the atom between photon generations is required. Photon indistinguishability is tested by time-resolved two-photon interference.

Storage and distribution of quantum information are key elements of quantum information processing and future quantum communication networks. Here, using atom-photon entanglement as the main physical resource, we experimentally demonstrate the preparation of a distant atomic quantum memory. Applying a quantum teleportation protocol on a locally prepared state of a photonic qubit, we realized this so-called remote state preparation on a single, optically trapped ${}^{87}\mathrm{Rb}$ atom. We evaluated the performance of this scheme by the full tomography of the prepared atomic state, reaching an average fidelity of 82%.

The in-plane magnetic field penetration depth (${\lambda }_{\mathrm{ab}}$) in single-crystal ${\mathrm{La}}_{1.83}{\mathrm{Sr}}_{0.17}{\mathrm{CuO}}_4$ was investigated by muon-spin rotation ($\mu \mathrm{SR}$). The temperature dependence of ${\lambda }_{\mathrm{ab}}^{-2}$ has an inflection point around 10–15 K, suggesting the presence of two superconducting gaps: a large gap (${\Delta }_1^d$) with $d$-wave and a small gap (${\Delta }_2^s$) with $s$-wave symmetry. The zero-temperature values of the gaps at ${\mu }_{0}H=0.02\mathrm{T}$ were found to be ${\Delta }_1^d(0)=8.2(1)\mathrm{meV}$ and ${\Delta }_2^s(0)=1.57(8)\mathrm{meV}$.

The magnetic coupling between single Co atoms adsorbed on a copper surface is determined by probing the Kondo resonance using low-temperature scanning tunneling spectroscopy. The Kondo resonance, which is due to magnetic correlation effects between the spin of a magnetic adatom and the conduction electrons of the substrate, is modified in a characteristic way by the coupling of the neighboring adatom spins. Increasing the interatomic distance of a Cobalt dimer from 2.56 to 8.1 Å we follow the oscillatory transition from ferromagnetic to antiferromagnetic coupling. Adding a third atom to the antiferromagnetically coupled dimer results in the formation of a collective correlated state.

Recent simulations have predicted that near jamming for collections of spherical particles, there will be a discontinuous increase in the mean contact number $Z$ at a critical volume fraction ${\varphi }_c$. Above ${\varphi }_c$, $Z$ and the pressure $P$ are predicted to increase as power laws in $\varphi -{\varphi }_c$. In experiments using photoelastic disks we corroborate a rapid increase in $Z$ at ${\varphi }_c$ and power-law behavior above ${\varphi }_c$ for $Z$ and $P$. Specifically we find a power-law increase as a function of $\varphi -{\varphi }_c$ for $Z-Z_c$ with an exponent $\beta$ around 0.5, and for $P$ with an exponent $\psi$ around 1.1. These exponents are in good agreement with simulations. We also find reasonable agreement with a recent mean-field theory for frictionless particles.

The scaling properties of DNA knots of different complexities were studied by atomic force microscope. Following two different protocols DNA knots are adsorbed onto a mica surface in regimes of (i) strong binding, that induces a kinetic trapping of the three-dimensional (3D) configuration, and of (ii) weak binding, that permits (partial) relaxation on the surface. In (i) the radius of gyration of the adsorbed DNA knot scales with the 3D Flory exponent $\nu \approx 0.60$ within error. In (ii), we find $\nu \approx 0.66$, a value between the 3D and 2D ($\nu =3/4$) exponents. Evidence is also presented for the localization of knot crossings in 2D under weak adsorption conditions.

We present a theoretical study of fast-electron emission produced in ${\mathrm{H}}_2$ and ${\mathrm{H}}_2^{+}$ photoionization. We show that, when the electron wave length is comparable to the molecular size, the electron angular distributions arising from fixed-in-space molecules exhibit pronounced interference effects that critically depend on orientation and energy sharing between electrons and nuclei. In particular, for molecules oriented parallel to the polarization direction, the angular patterns reveal a complex nodal structure, while for molecules oriented perpendicularly, typical Young’s double-slit interferences are observed. These patterns change dramatically as the molecule vibrates.

We report the observation of dynamo action in the von Kármán sodium experiment, i.e., the generation of a magnetic field by a strongly turbulent swirling flow of liquid sodium. Both mean and fluctuating parts of the field are studied. The dynamo threshold corresponds to a magnetic Reynolds number $R_m\sim 30$. A mean magnetic field of the order of 40 G is observed 30% above threshold at the flow lateral boundary. The rms fluctuations are larger than the corresponding mean value for two of the components. The scaling of the mean square magnetic field is compared to a prediction previously made for high Reynolds number flows.

Invariant mass spectra of $e^{+}{e}^{-}$ pairs have been measured in 12 GeV $p+A$ reactions to detect possible in-medium modification of vector mesons. Copper and carbon targets are used to study the nuclear-size dependence of $e^{+}{e}^{-}$ invariant mass distributions. A significant excess on the low-mass side of the $\varphi$ meson peak is observed in the low $\beta \gamma (=\beta /\sqrt{1-{\beta }^2})$ region of $\varphi$ mesons ($\beta \gamma <1.25$) with copper targets. However, in the high $\beta \gamma$ region ($\beta \gamma >1.25$), spectral shapes of $\varphi$ mesons are well described by the Breit-Wigner shape when experimental effects are considered. Thus, in addition to our earlier publications on $\rho /\omega$ modification, this study has experimentally verified vector meson mass modification at normal nuclear density.

We present the first experimental discrimination between the $2e/3$ and $4e/3$ top quark electric charge scenarios, using top quark pairs ($t\overline{t}$) produced in $p\overline{p}$ collisions at $\sqrt{s}=1.96\mathrm{TeV}$ by the Fermilab Tevatron Collider. We use $370{\mathrm{pb}}^{-1}$ of data collected by the D0 experiment and select events with at least one high transverse momentum electron or muon, high transverse energy imbalance, and four or more jets. We discriminate between $b$- and $\overline{b}$-quark jets by using the charge and momenta of tracks within the jet cones. The data are consistent with the expected electric charge, $|q|=2e/3$. We exclude, at the 92% C.L., that the sample is solely due to the production of exotic quark pairs $Q\overline{Q}$ with $|q|=4e/3$. We place an upper limit on the fraction of $Q\overline{Q}$ pairs $\rho <0.80$ at the 90% C.L.

Two-dimensional images carried by optical pulses (2 ns) are delayed by up to 10 ns in a 10 cm cesium vapor cell. By interfering the delayed images with a local oscillator, the transverse phase and amplitude profiles of the images are shown to be preserved. It is further shown that delayed images can be well preserved even at very low light levels, where each pulse contains on average less than one photon.