We present analytical calculations and numerical simulations for the synchronization of oscillators interacting via a long-range power law interaction on a one-dimensional lattice. We have identified the critical value of the power law exponent αc across which a transition from a synchronized to an unsynchronized state takes place for a sufficiently strong but finite coupling strength in the large system limit. We find αc =3/2. Frequency entrainment and phase ordering are discussed as a function of α1.

Silicon undergoes a phase transition from the semiconducting diamond phase to the metallic β-Sn phase under pressure. We use quantum Monte Carlo calculations to predict the transformation pressure and compare the results to density-functional calculations employing the local-density approximation, the generalized-gradient approximations PBE, PW91, WC, AM05, PBEsol, and the hybrid functional HSE06 for the exchange-correlation functional.

Graphical processing units are now being used with dramatic effect to accelerate quantum chemistry calculations. However, early work exposed challenges involving memory bottlenecks and insufficient numerical precision. This research effort addresses those issues, proposing two new tools for accelerating matrix multiplications of arbitrary size where single-precision accuracy is not enough. © 2010, IEEE. All rights reserved.

In the high-transition-temperature (high-Tc) superconductors the pseudogap phase becomes predominant when the density of doped holes is reduced. Within this phase it has been unclear which electronic symmetries (if any) are broken, what the identity of any associated order parameter might be, and which microscopic electronic degrees of freedom are active. Here we report the determination of a quantitative order parameter representing intra-unit-cell nematicity: the breaking of rotational symmetry by the electronic structure within each CuO2 unit cell.

We present a theoretical study of the intrinsic quality factor of the fundamental flexural vibration in a carbon nanotube and its dependence on temperature, radius, length, and tension. In particular, we examine three- and four-phonon decays of the fundamental flexural mode within quantized elasticity theory.

The accuracy of the fundamental properties of the energy landscape of silicon systems obtained from density functional theory with various exchange-correlation functionals, a tight binding scheme, and force fields is studied. Depending on the application, quantum Monte Carlo or density functional theory results serve as quasiexact reference values.

Nanomechanical resonators operating in vacuum are capable of detecting and weighing single biomolecules, but their application to the life sciences has been limited by viscous forces that impede their motion in liquid environments. A promising approach to avoid this problem, encapsulating the fluid within a mechanical resonator surrounded by vacuum, has not yet been tried with resonant sensors of mass less than ∼100 ng, despite predictions that devices with smaller effective mass will have proportionally finer mass resolution.

We reconstructed the 3D Fourier intensity distribution of monodisperse prolate nanoparticles using single-shot 2D coherent diffraction patterns collected at DESY's FLASH facility when a bright, coherent, ultrafast x-ray pulse intercepted individual particles of random, unmeasured orientations. This first experimental demonstration of cryptotomography extended the expansion-maximization-compression framework to accommodate unmeasured fluctuations in photon fluence and loss of data due to saturation or background scatter.

Within a Kondo lattice, the strong hybridization between electrons localized in real space (r-space) and those delocalized in momentum-space (k-space) generates exotic electronic states called Ä€̃ heavy fermionsÄ€™. In URu 2 Si 2 these effects begin at temperatures around 55 K but they are suddenly altered by an unidentified electronic phase transition at T o = 17.5 K. Whether this is conventional ordering of the k-space states, or a change in the hybridization of the r-space states at each U atom, is unknown.