The presence of a new singlet scalar particle $a$ can open up new decay channels for the Higgs boson, through cascades of the form $h\to 2a\to X$, possibly making discovery through standard model channels impossible. If $a$ is $CP$ odd, its decays are particularly sensitive to new physics. Quantum effects from heavy fields can naturally make $h\to 4g$ the dominant decay which is difficult to observe at hadron colliders, and is allowed by CERN LEP for $m_h>82\mathrm{GeV}$. However, there are usually associated decays, either $h\to 2g2\gamma$ or $h\to 4\gamma$, which are more promising. The decay $h\to 4\gamma$ is a clean channel that can discover both $a$ and $h$. At the CERN LHC with $300{\mathrm{fb}}^{-1}$ of luminosity, a branching ratio of order ${10}^{-4}$ is sufficient for discovery for a large range of Higgs boson masses. With total luminosity of $\sim 8{\mathrm{fb}}^{-1}$, discovery at the Fermilab Tevatron requires more than $5\times {10}^{-3}$ in branching ratio.

We show experimentally that clogging is basically a matter of the probability of the presence of particles. We describe this process as a function of the main variables of the process, namely, the ratio of particle to mesh hole size, the solid fraction, and the number of grains arriving at each mesh hole during one test, with the help of a simple model, the predictions of which are in very good agreement with our experimental data.

We present coherence-enhanced imaging, an in situ technique that uses Raman superradiance to probe the spatial coherence of an ultracold gas. Applying this technique, we identify the coherent portion of an inhomogeneous degenerate ${}^{87}\mathrm{Rb}$ gas and obtain a spatially resolved measurement of the first-order spatial correlation function. We find that the decay of spin gratings is enhanced in high density regions of a Bose-Einstein condensate, and ascribe the enhancement to collective atom-atom scattering. Further, we directly observe spatial inhomogeneities that arise generally in the course of extended-sample superradiance.

The longest relaxation time and sharpest frequency content in ferromagnetic precession is determined by the intrinsic (Gilbert) relaxation rate $G$. For many years, pure iron (Fe) has had the lowest known value of $G=57\mathrm{MHz}$ for all pure ferromagnetic metals or binary alloys. We show that an epitaxial iron alloy with vanadium (V) possesses values of $G$ which are significantly reduced to $35\pm 5\mathrm{MHz}$ at 27% V. The result can be understood as the role of spin-orbit coupling in generating relaxation, reduced through the atomic number $Z$.

Astrophysical observations (usually explained by dark matter) suggest that classical mechanics could break down when the acceleration becomes extremely small [the approach known as modified Newtonian dynamics (MOND)]. I present the first analysis of MOND manifestations in terrestrial (rather than astrophysical) settings. A new effect is reported: around each equinox date, 2 spots emerge on the Earth where static bodies experience spontaneous acceleration due to the possible violation of Newton’s second law. Preliminary estimates indicate that an experimental search for this effect can be feasible.

We demonstrate a room-temperature spin dynamo where the precession of electron spins in ferromagnets converts energy from microwaves to a bipolar current of electricity. The $\mathrm{\text{current}}/\mathrm{\text{power}}$ ratio is at least 3 orders of magnitude larger than that found previously for spin-driven currents in semiconductors. The observed bipolar nature and intriguing symmetry are fully explained by the spin rectification effect via which the nonlinear combination of spin and charge dynamics creates dc currents.

We report the generation of a beam of slow (translationally cold) KBr molecules formed by exoergic reactive collisions in counterpropagating beams of K atoms and HBr molecules. The intensity of the slow beam is estimated to $4\times {10}^{11}{\mathrm{s}}^{-1}{\mathrm{sr}}^{-1}$. The velocity distribution (density) peaks at $42.5\mathrm{m}/\mathrm{s}$ corresponding to a formal temperature of 13 K. About 7% of the molecules move at velocities between 14.2 and $20\mathrm{m}/\mathrm{s}$ and an estimated fraction of 7% is slower than $14.2\mathrm{m}/\mathrm{s}$.

We report the slowing of a supersonic beam by elastic reflection from a receding atomic mirror. We use a pulsed supersonic nozzle to generate a $511\pm 9\mathrm{m}/\mathrm{s}$ beam of helium that we slow by reflection from a $\mathrm{Si}(111)\mathrm{\text{−}}\mathrm{H}(1\times 1)$ crystal placed on the tip of a spinning rotor. We were able to reduce the velocity of helium by $246\mathrm{m}/\mathrm{s}$ and show that the temperature of the slowed beam is lower than 250 mK in the comoving frame.

We have experimentally investigated the formation of off-diagonal long-range order in a gas of ultracold atoms. A magnetically trapped atomic cloud prepared in a highly nonequilibrium state thermalizes and thereby crosses the Bose-Einstein condensation phase transition. The evolution of phase coherence between different regions of the sample is constantly monitored and information on the spatial first-order correlation function is obtained. We observe the growth of the spatial coherence and the formation of long-range order in real time and compare it to the growth of the atomic density. Moreover, we study the evolution of the momentum distribution during the nonequilibrium formation of the condensate.

The first theoretical estimate of the shear strength of a perfect crystal was given by Frenkel [Z. Phys. 37, 572 (1926)]. By assuming that two rigid atomic rows in the crystal would move over each other along a slip plane, he derived the ultimate shear strength to be about one-tenth of the shear modulus. Here we present a theoretical study showing that catastrophic failure of viscoelastic materials may occur below Frenkel’s ultimate limit as a result of thermal runaway. The thermal runaway failure mechanism exhibits progressive localization of the strain and temperature profiles in space, thereby producing a narrow region of highly deformed material, i.e., a shear band. We calculate the maximum shear strength ${\sigma }_c$ of materials and then demonstrate the relevance of this new concept for material failure known to occur at scales ranging from nanometers to kilometers.

We have demonstrated Zeeman slowing and capture of neutral ${}^{225}\mathrm{Ra}$ and ${}^{226}\mathrm{Ra}$ atoms in a magneto-optical trap. The intercombination transition ${}^{1}S_0\to {}^{3}P_1$ is the only quasicycling transition in radium and was used for laser-cooling and trapping. Repumping along the ${}^{3}D_1\to {}^{1}P_1$ transition extended the lifetime of the trap from milliseconds to seconds. Room-temperature blackbody radiation was demonstrated to provide repumping from the metastable ${}^{3}P_0$ level. We measured the isotope shift and hyperfine splittings on the ${}^{3}D_1\to {}^{1}P_1$ transition with the laser-cooled atoms, and set a limit on the lifetime of the ${}^{3}D_1$ level based on the measured blackbody repumping rate. Laser-cooled and trapped radium is an attractive system for studying fundamental symmetries.

The enigmatic stability of population oscillations within ecological systems is analyzed. The underlying mechanism is presented in the framework of two interacting species free to migrate between two spatial patches. It is shown that the combined effects of migration and noise cannot account for the stabilization. The missing ingredient is the dependence of the oscillations’ frequency upon their amplitude. A simple model of diffusively coupled oscillators allows the derivation of quantitative results, like the functional dependence of the desynchronization upon diffusion strength and frequency differences. The oscillations’ amplitude is shown to be (almost) noise independent.

Faraday waves in a cigar-shaped Bose-Einstein condensate are created. It is shown that periodically modulating the transverse confinement, and thus the nonlinear interactions in the BEC, excites small amplitude longitudinal oscillations through a parametric resonance. It is also demonstrated that even without the presence of a continuous drive, an initial transverse breathing mode excitation of the condensate leads to spontaneous pattern formation in the longitudinal direction. Finally, the effects of strongly driving the transverse breathing mode with large amplitude are investigated. In this case, impact-oscillator behavior and intriguing nonlinear dynamics, including the gradual emergence of multiple longitudinal modes, are observed.

We report on a thermodielectric bistability in dual frequency nematic liquid crystals (LCs) caused by the anisotropic nature of dielectric heating and director reorientation in an electric field. The bistability is a result of the positive feedback loop: director reorientation $\to$ anisotropic dielectric heating $\to$ dielectric anisotrophy $\to$ director reorientation. We demonstrate both experimentally and theoretically that two states with different temperature and director orientation, namely, a cold planar state and a hot homeotropic state coexist in a LC cell for a certain frequency and amplitude range of the applied voltage.

Can quantum-information theory shed light on black-hole evaporation? By entangling the in-fallen matter with an external system we show that the black-hole information paradox becomes more severe, even for cosmologically sized black holes. We rule out the possibility that the information about the in-fallen matter might hide in correlations between the Hawking radiation and the internal states of the black hole. As a consequence, either unitarity or Hawking’s semiclassical predictions must break down. Any resolution of the black-hole information crisis must elucidate one of these possibilities.

The Gamow-Teller strength distributions below the particle threshold in ${}^{138}\mathrm{La}$ and ${}^{180}\mathrm{Ta}$, deduced from high-resolution measurements of the (${}^3\mathrm{He},t$) reaction at 0°, allow us to evaluate the role of charged-current reactions for the production of these extremely rare nuclides in neutrino-nucleosynthesis models. The analysis suggests that essentially all ${}^{138}\mathrm{La}$ in the Universe can be made that way. Neutrino nucleosynthesis also contributes significantly to the abundance of ${}^{180}\mathrm{Ta}$ but the magnitude depends on the unknown branching ratio for population of the long-lived isomer.

Colliding ice floes are often observed to form a series of interlocking fingers. We show that this striking phenomenon is not a result of some peculiar property of ice but rather a general and robust mechanical phenomenon reproducible in the laboratory with other floating materials. We determine the theoretical relationship between the width of the resulting fingers and the material’s mechanical properties and present experimental results along with field observations to support the theory. The generality of this “finger rafting” suggests that analogous processes may be responsible for creating the large-scale structures observed at the boundaries between Earth’s convergent tectonic plates.

We show, through a refinement of the work theorem, that the average dissipation, upon perturbing a Hamiltonian system arbitrarily far out of equilibrium in a transition between two canonical equilibrium states, is exactly given by $⟨W_{\mathrm{diss}}⟩=⟨W⟩-\Delta F=kTD(\rho \parallel \tilde{\rho })=kT⟨\ln (\rho /\tilde{\rho })⟩$, where $\rho$ and $\tilde{\rho }$ are the phase-space density of the system measured at the same intermediate but otherwise arbitrary point in time, for the forward and backward process. $D(\rho \parallel \tilde{\rho })$ is the relative entropy of $\rho$ versus $\tilde{\rho }$. This result also implies general inequalities, which are significantly more accurate than the second law and include, as a special case, the celebrated Landauer principle on the dissipation involved in irreversible computations.

We demonstrate an optically active nanotube-hybrid material by functionalizing single-wall nanotubes with an azo-based chromophore. Upon UV illumination, the conjugated chromophore undergoes a cis-trans isomerization leading to a charge redistribution near the nanotube. This charge redistribution changes the local electrostatic environment, shifting the threshold voltage and increasing the conductivity of the nanotube transistor. For a $\sim 1\%–2\%$ coverage, we measure a shift in the threshold voltage of up to 1.2 V. Further, the conductance change is reversible and repeatable over long periods of time, indicating that the chromophore-functionalized nanotubes are useful for integrated nanophotodetectors.

We report the most sensitive tests to date of the assumption of local position invariance (LPI) underlying general relativity, based on a 7 yr comparison of cesium and hydrogen atomic clocks (frequency standards). The latest results place an upper limit that is over 20 times smaller than the previous most sensitive tests; this is consistent with the null shift predicted by LPI. The result is based on precise comparisons of frequencies of four hydrogen masers maintained by NIST, with four independent Cs fountain clocks—one at NIST and three in Europe—as the Sun’s gravitational potential at Earth’s surface varies due to Earth’s orbital eccentricity.