We search for signatures of Lorentz and $CPT$ violations in the cosmic microwave background (CMB) temperature and polarization anisotropies by using the Wilkinson Microwave Anisotropy Probe (WMAP) and the 2003 flight of BOOMERANG (B03) data. We note that if the Lorentz and $CPT$ symmetries are broken by a Chern-Simons term in the effective Lagrangian, which couples the dual electromagnetic field strength tensor to an external four-vector, the polarization vectors of propagating CMB photons will get rotated. Using the WMAP data alone, one could put an interesting constraint on the size of such a term. Combined with the B03 data, we found that a nonzero rotation angle of the photons is mildly favored: $\Delta \alpha =-6.0\genfrac{}{}{0ex}{}{+4.0}{-4.0}\genfrac{}{}{0ex}{}{+3.9}{-3.7}\mathrm{deg}(1,2\sigma )$.

We report how a setup consisting of three gratings yields quantitative two- and three-dimensional images depicting the quantum-mechanical phase shifts of neutron de Broglie wave packets induced by the influence of macroscopic objects. Since our approach requires only a little spatial and chromatic coherence it provides a more than 2 orders of magnitude higher efficiency than existing techniques. This dramatically reduces the required measurement time for computed phase tomography and opens up the way for three-dimensional investigations of previously inaccessible quantum-mechanical phase interactions of neutrons with matter.

We propose an experiment for generating and detecting vacuum-induced dissipative motion. A high frequency mechanical resonator driven in resonance is expected to dissipate mechanical energy in quantum vacuum via photon emission. The photons are stored in a high quality electromagnetic cavity and detected through their interaction with ultracold alkali-metal atoms prepared in an inverted population of hyperfine states. Superradiant amplification of the generated photons results in a detectable radio-frequency signal temporally distinguishable from the expected background.

New scaling behavior has been both predicted and observed in the spontaneous production of fluxons in quenched $\mathrm{Nb}\mathrm{\text{−}}\mathrm{Al}/{\mathrm{Al}}_{\mathrm{ox}}/\mathrm{Nb}$ annular Josephson tunnel junctions (JTJs) as a function of the quench time, ${\tau }_Q$. The probability $f_1$ to trap a single defect during the normal-metal–superconductor phase transition clearly follows an allometric dependence on ${\tau }_Q$ with a scaling exponent $\sigma =0.5$, as predicted from the Zurek-Kibble mechanism for realistic JTJs formed by strongly coupled superconductors. This definitive experiment replaces one reported by us earlier, in which an idealized model was used that predicted $\sigma =0.25$, commensurate with the then much poorer data. Our experiment remains the only condensed matter experiment to date to have measured a scaling exponent with any reliability.

We demonstrate experimentally an optical process in which the spin angular momentum carried by a circularly polarized light beam is converted into orbital angular momentum, leading to the generation of helical modes with a wave-front helicity controlled by the input polarization. This phenomenon requires the interaction of light with matter that is both optically inhomogeneous and anisotropic. The underlying physics is also associated with the so-called Pancharatnam-Berry geometrical phases involved in any inhomogeneous transformation of the optical polarization.

Extremely high pressures ($\sim 10\mathrm{TPa}$) and temperatures ($5\times {10}^5\mathrm{K}$) have been produced using a single laser pulse (100 nJ, 800 nm, 200 fs) focused inside a sapphire crystal. The laser pulse creates an intensity over ${10}^{14}\mathrm{W}/{\mathrm{cm}}^2$ converting material within the absorbing volume of $\sim 0.2\mu {\mathrm{m}}^3$ into plasma in a few fs. A pressure of $\sim 10\mathrm{TPa}$, far exceeding the strength of any material, is created generating strong shock and rarefaction waves. This results in the formation of a nanovoid surrounded by a shell of shock-affected material inside undamaged crystal. Analysis of the size of the void and the shock-affected zone versus the deposited energy shows that the experimental results can be understood on the basis of conservation laws and be modeled by plasma hydrodynamics. Matter subjected to record heating and cooling rates of ${10}^{18}\mathrm{K}/\mathrm{s}$ can, thus, be studied in a well-controlled laboratory environment.

By means of spin-polarized low-energy electron microscopy, we show that the magnetic easy axis of one to three atomic-layer thick cobalt films on Ru(0001) changes its orientation twice during deposition: One-monolayer and three-monolayer thick films are magnetized in plane, while two-monolayer films are magnetized out of plane. The Curie temperatures of films thicker than one monolayer are well above room temperature. Fully relativistic calculations based on the screened Korringa-Kohn-Rostoker method demonstrate that only for two-monolayer cobalt films does the interplay between strain, surface, and interface effects lead to perpendicular magnetization.

We present a new nucleosynthesis process that we denote as the $\nu p$ process, which occurs in supernovae (and possibly gamma-ray bursts) when strong neutrino fluxes create proton-rich ejecta. In this process, antineutrino absorptions in the proton-rich environment produce neutrons that are immediately captured by neutron-deficient nuclei. This allows for the nucleosynthesis of nuclei with mass numbers $A>64$, making this process a possible candidate to explain the origin of the solar abundances of ${}^{92,94}\mathrm{Mo}$ and ${}^{96,98}\mathrm{Ru}$. This process also offers a natural explanation for the large abundance of Sr seen in a hyper-metal-poor star.

Phonon dispersion curves were obtained from inelastic x-ray and neutron scattering measurements on $\alpha$-uranium single crystals at temperatures from 298 to 573 K. Both measurements showed a softening and an abrupt loss of intensity in the longitudinal optic branch along $[00\zeta ]$ above 450 K. Above the same temperature a new dynamical mode of comparable intensity emerges along the $[01\zeta ]$ zone boundary with energy near the top of the phonon spectrum. The new mode forms without a structural transition but coincides with an anomaly in the mechanical deformation behavior. We argue that the mode is an intrinsically localized vibration and formed as a result of a strong electron-phonon interaction.

We present a detailed study of the effects of interface spin-orbit coupling on the critical field behavior of ultrathin superconducting $\mathrm{Be}/\mathrm{Au}$ bilayers. Parallel field measurements were made in bilayers with Be thicknesses in the range of $d=2–30\mathrm{nm}$ and Au coverages of 0.5 nm. Though the Au had little effect on the superconducting gap, it produced profound changes in the spin states of the system. In particular, the parallel critical field exceeded the Clogston limit by an order of magnitude in the thinnest films studied. In addition, the parallel critical field unexpectedly scaled as $H_{c\parallel }/{\Delta }_0\propto 1/d$, suggesting that the spin-orbit coupling energy was proportional to ${\Delta }_0/d^2$. Tilted field measurements showed that, contrary to recent theory, the interface spin-orbit coupling induces a large in-plane superconducting susceptibility but only a very small transverse susceptibility.

Spike-shaped structures are produced by light-driven ablation in very different contexts. Penitentes 1–4 m high are common on Andean glaciers, where their formation changes glacier dynamics and hydrology. Laser ablation can produce cones $10–100\mu \mathrm{m}$ high with a variety of proposed applications in materials science. We report the first laboratory generation of centimeter-scale snow and ice penitentes. Systematically varying conditions allows identification of the parameters controlling the formation of ablation structures. We demonstrate that penitente initiation and coarsening require cold temperatures, so that ablation leads to sublimation. Once penitentes have formed, further growth of height can occur by melting. The penitentes initially appear as small structures (3 mm high) and grow by coarsening to 1–5 cm high. Our results are an important step towards understanding ablation morphologies.

In the ear, sound waves are processed by a membrane of graded mechanical properties that resides in the fluid-filled spiral cochlea. The role of stiffness grading as a Fourier analyzer is well known, but the role of the curvature has remained elusive. Here, we report that increasing curvature redistributes wave energy density towards the cochlea’s outer wall, affecting the shape of waves propagating on the membrane, particularly in the region where low frequency sounds are processed.

We use pervaporation-based microfluidic devices to concentrate species in aqueous solutions with spatial and temporal control of the process. Using experiments and modeling, we quantitatively describe the advection-diffusion behavior of the concentration field of various solutions (electrolytes, colloids, etc.) and demonstrate the potential of these devices as universal tools for the kinetic exploration of the phases and textures that form upon concentration.

We measure the relation between convective heat flux and temperature gradient in a vertical channel filled with water, the average vertical mass flux being zero. Compared to the classical Rayleigh-Bénard case, this situation has the advantage of avoiding plates and, thus, their neighborhood, in which is usually concentrated most of the temperature gradient. Consequently, inertial processes should control the convection, with poor influence of the viscosity. This idea gives a good account of our observations, if we consider that a natural vertical length, different from the channel width, appears. Our results also suggest that heat fluxes can be deduced from velocity measurements in free convective flows. This confers to our results a wide range of applications.

Reducing skin friction is important in nature and in many technological applications. This reduction may be achieved by reducing stresses in turbulent boundary layers, for instance tailoring biomimetic rough skins. Here we take a second approach consisting of keeping the boundary layer laminar as long as possible by forcing small optimal perturbations. Because of the highly non-normal nature of the underlying linearized operator, these perturbations are highly amplified and able to modify the mean velocity profiles at leading order. We report results of wind-tunnel experiments in which we implement this concept by using suitably designed roughness elements placed on the skin to enforce nearly optimal perturbations. We show that by using this passive control technique it is possible to sensibly delay transition to turbulence.

In analogy with NMR, motion induced phase shift of pulsed ESR signals enables in principle the direct detection of electron drift velocity or electronic current, respectively. Overcoming the difficulties with additional magnetic field gradients induced by the current itself, we succeeded in demonstrating the detection of electron flow via ESR. Measuring the electron drift velocity in the organic conductor (fluoranthene)${}_2\mathrm{P}{\mathrm{F}}_6$ the microscopic Ohmic law could be observed in a current range of more than $\pm 0.25\mathrm{A}$.

We report the direct observation of a peculiar lava channel that was formed near the base of a parasitic cone during the 2001 eruption on Mount Etna. Erosive processes by flowing lava are commonly attributed to thermal erosion. However, field evidence strongly suggests that models of thermal erosion cannot explain the formation of this channel. Here, we put forward the idea that the essential erosion mechanism was abrasive wear. By applying a simple model from tribology we demonstrate that the available data agree favorably with our hypothesis. Consequently, we propose that erosional processes resembling the wear phenomena in glacial erosion are possible in a volcanic environment.

By transforming the optical fiber span into an ultralong cavity laser, we experimentally demonstrate quasilossless transmission over long (up to 75 km) distances and virtually zero signal power variation over shorter (up to 20 km) spans, opening the way for the practical implementation of integrable nonlinear systems in optical fiber. As a by-product of our technique, the longest ever laser (to the best of our knowledge) has been implemented, with a cavity length of 75 km. A simple theory of the lossless fiber span, in excellent agreement with the observed results, is presented.

We observe that the group velocity of light is reduced to an extremely low value of $0.091\mathrm{mm}/\mathrm{s}$ in a biological thin film of bacteriorhodopsin at room temperature. By exploiting unique features of a flexible photoisomerization process for coherent population oscillation, the velocity is all-optically controlled over an enormous span, from snail-paced to normal light speed, with no need of modifying the characteristics of the incident pulse. Because of the large quantum yield for the photoreaction in this biochemical system, the ultraslow light is observed even at low light levels of microwatts, indicating high energy efficiency.

The analysis of Coulomb crystallization is extended from one-component to two-component plasmas. Critical parameters for the existence of Coulomb crystals are derived for both classical and quantum crystals. In the latter case, a critical mass ratio of the two charged components is found, which is of the order of 80. Thus, holes in semiconductors with sufficiently flat valence bands are predicted to spontaneously order into a regular lattice. Such hole crystals are intimately related to ion Coulomb crystals in white dwarf and neutron stars as well as to ion crystals produced in the laboratory. A unified phase diagram of two-component Coulomb crystals is presented and is verified by first-principles computer simulations.