Two-dimensional melting far from equilibrium in a granular monolayer

We report an experimental investigation of the transition from a hexagonally ordered solid phase to a disordered liquid in a monolayer of vibrated spheres. The transition occurs as the intensity of the vibration amplitude is increased. Measurements of the density of dislocations and the positional and orientational correlation functions show evidence for a dislocation-mediated continuous transition from a solid phase with long-range order to a liquid with only short-range order. The results show a strong similarity to simulations of melting of hard disks in equilibrium, despite the fact that the granular monolayer is far from equilibrium due to the effects of interparticle dissipation and the vibrational forcing.Comment: 4 pages, 4 figure

Functional determinants on certain domains

Functional determinants on various domains of the sphere and flat space are presented for scalar and spinor fields.Comment: 14p, plain TeX, talk presented at the 6th Moscow Quantum Gravity Seminar, Moscow, June 12-19, 1995.(Minor errors corrected.

Dynamics of colloidal particles in ice

We use X-ray Photon Correlation Spectroscopy (XPCS) to probe the dynamics of colloidal particles in polycrystalline ice. During freezing, the dendritic ice morphology and rejection of particles from the ice created regions of high-particle-density, where some of the colloids were forced into contact and formed disordered aggregates. We find that the particles in these high density regions underwent ballistic motion coupled with both stretched and compressed exponential decays of the intensity autocorrelation function, and that the particles’ characteristic velocity increased with temperature. We explain this behavior in terms of ice grain boundary migration

Correlation functions, Bell's inequalities and the fundamental conservation laws

I derive the correlation function for a general theory of two-valued spin variables that satisfy the fundamental conservation law of angular momentum. The unique theory-independent correlation function is identical to the quantum mechanical correlation function. I prove that any theory of correlations of such discrete variables satisfying the fundamental conservation law of angular momentum violates the Bell's inequalities. Taken together with the Bell's theorem, this result has far reaching implications. No theory satisfying Einstein locality, reality in the EPR-Bell sense, and the validity of the conservation law can be constructed. Therefore, all local hidden variable theories are incompatible with fundamental symmetries and conservation laws. Bell's inequalities can be obeyed only by violating a conservation law. The implications for experiments on Bell's inequalities are obvious. The result provides new insight regarding entanglement, and its measures.Comment: LaTeX, 12pt, 11 pages, 2 figure

Clarifying interoperability: The SISO CSPI PDG standard for commercial off-the-shelf simulation package interoperability reference models

Commercial-off-the-shelf simulation packages (CSPs), visual interactive modelling environments such as Arena, Anylogic, Flexsim, Simul8, Witness, etc., are important "black box" software tools that support the development, experimentation and visualization of simulation models. They are widely used in commerce, defence, health, manufacturing and logistics. There is a growing need to link together, or to interoperate, models developed in these CSPs across computer networks. The motivation for this includes data sensitivity, difficult to move resources and speed up

Low-frequency method for magnetothermopower and Nernst effect measurements on single crystal samples at low temperatures and high magnetic fields

We describe an AC method for the measurement of the longitudinal (Sxx) and transverse (Sxy, i.e. Nernst) thermopower of mm-size single crystal samples at low temperatures (T30 T). A low-frequency (33 mHz) heating method is used to increase the resolution, and to determine the temperature gradient reliably in high magnetic fields. Samples are mounted between two thermal blocks which are heated by a sinusoidal frequency f0 with a p/2 phase difference. The phase difference between two heater currents gives a temperature gradient at 2f0. The corresponding thermopower and Nernst effect signals are extracted by using a digital signal processing method due. An important component of the method involves a superconducting link, YBa2Cu3O7+d (YBCO), which is mounted in parallel with sample to remove the background magnetothermopower of the lead wires. The method is demonstrated for the quasi two-dimensional organic conductor a-(BEDT-TTF)2KHg(SCN)4, which exhibits a complex, magnetic field dependent ground state above 22.5 T at low temperatures.Comment: 11 pages, 6 figures, 15 reference