An equation for the description of volume and temperature dependences of the dynamics of supercooled liquids and polymer melts

A recently proposed expression to describe the temperature and volume dependences of the structural (or alpha) relaxation time is discussed. This equation satisfies the scaling law for the relaxation times, tau = f(TV^g), where T is temperature, V the specific volume, and g a material-dependent constant. The expression for the function f is shown to accurately fit experimental data for several glass-forming liquids and polymers over an extended range encompassing the dynamic crossover, providing a description of the dynamics with a minimal number of parameters. The results herein can be reconciled with previously found correlations of the isochoric fragility with both the isobaric fragility at atmospheric pressure and the scaling exponent g.Comment: to be published in the special edition of J. Non-Crystalline Solids honoring K.L. Nga

Quantum circuit implementation of the Hamiltonian versions of Grover's algorithm

We analyze three different quantum search algorithms, the traditional Grover's algorithm, its continuous-time analogue by Hamiltonian evolution, and finally the quantum search by local adiabatic evolution. We show that they are closely related algorithms in the sense that they all perform a rotation, at a constant angular velocity, from a uniform superposition of all states to the solution state. This make it possible to implement the last two algorithms by Hamiltonian evolution on a conventional quantum circuit, while keeping the quadratic speedup of Grover's original algorithm.Comment: 5 pages, 3 figure

Chiral perturbation theory and the 1/N_c-expansion

We briefly review the effective theory that describes the low energy properties of QCD with three light quarks and a large number of colours, N_c, and then discuss the mechanisms that forbid the Kaplan-Manohar transformation in this framework.Comment: 2 pages. Talk given at the Workshop "Chiral Dynamics 2000: Theory and Experiment", Newport News, VA, USA, July 17-22, 200

Structure and mobility of cyclohexane as a solvent for Trans-Polyisoprene

Solutions of {\it trans}$-$polyisoprene in cyclohexane are investigated in atomistic detail at different compositions at two different temperatures. We investigate the influence of polymer concentration on the dynamics of the solvent molecules and the structure of the solvation shell. The double bonds along the polymer backbone are preferentially approached by the solvent molecules. The mobility of cyclohexane molecules decreases with increasing polymer concentration at ambient conditions. The reorientation of molecules becomes more anisotropic with concentration as the polymer hinders the reorientation of the molecular plane. At elevated temperatures the influence of the polymer is weaker and the reorientation of the solvent is more isotropic. Additionally, a fast and efficient way to set up atomistic simulations is shown in detail in which the initial simulations increase in length and in the simulation time-step. The excess energy from initial overlaps is removed by resetting the velocities at regular intervals.Comment: 6 pages, 3 figure