Lyapunov Exponent and the Solid-Fluid Phase Transition

We study changes in the chaotic properties of a many-body system undergoing a solid-fluid phase transition. To do this, we compute the temperature dependence of the largest Lyapunov exponents $\lambda_{max}$ for both two- and three-dimensional periodic systems of $N$-particles for various densities. The particles interact through a soft-core potential. The two-dimensional system exhibits an apparent second-order phase transition as indicated by a $\lambda$-shaped peak in the specific heat. The first derivative of $\lambda_{max}$ with respect to the temperature shows a peak at the same temperature. The three-dimensional system shows jumps, in both system energy and $\lambda_{max}$, at the same temperature, suggesting a first-order phase transition. Relaxation phenomena in the phase-transition region are analyzed by using the local time averages.Comment: 16 pages, REVTeX, 10 eps figures, epsfig.st

Van der Waals density-functional theory study for bulk solids with BCC, FCC, and diamond structures

Proper inclusion of van der Waals (vdW) interactions in theoretical simulations based on standard density functional theory (DFT) is crucial to describe the physics and chemistry of systems such as organic and layered materials. Many encouraging approaches have been proposed to combine vdW interactions with standard approximate DFT calculations. Despite many vdW studies, there is no consensus on the reliability of vdW methods. To help further development of vdW methods, we have assessed various vdW functionals through the calculation of structural prop- erties at equilibrium, such as lattice constants, bulk moduli, and cohesive energies, for bulk solids, including alkali, alkali-earth, and transition metals, with BCC, FCC, and diamond structures as the ground state structure. These results provide important information for the vdW-related materials research, which is essential for designing and optimizing materials systems for desired physical and chemical properties.Comment: 10 pages, 6 Figures, 3 Table

Kaon-Soliton Bound State Approach to the Pentaquark States

We show that in hidden local symmetry theory with the vector manifestation (VM), a K^+ can be bound to skyrmion to give the Theta^+ pentaquark with spin 1/2 and even parity which is consistent with large N_c counting. The vector meson K^* subject to the VM in the chiral limit plays an essential role in inducing the binding.Comment: Change of title, erroneous statements, e.g., re: interpretation of the widths, corrected, results remain unmodifie

The Inhomogeneous Phase of Dense Skyrmion Matter

It was predicted qualitatively in ref.[1] that skyrmion matter at low density is stable in an inhomogeneous phase where skyrmions condensate into lumps while the remaining space is mostly empty. The aim of this paper is to proof quantitatively this prediction. In order to construct an inhomogeneous medium we distort the original FCC crystal to produce a phase of planar structures made of skyrmions. We implement mathematically these planar structures by means of the 't Hooft instanton solution using the Atiyah-Manton ansatz. The results of our calculation of the average density and energy confirm the prediction suggesting that the phase diagram of the dense skyrmion matter is a lot more complex than a simple phase transition from the skyrmion FCC crystal lattice to the half-skyrmion CC one. Our results show that skyrmion matter shares common properties with standard nuclear matter developing a skin and leading to a binding energy equation which resembles the Weiszaecker mass formula.Comment: 8 figures, 14 page

A Geometric Model of Twisted Differential K-theory

We construct a model of even twisted differential K-theory when the underlying topological twist represents a torsion class. We use smooth U(1)-gerbes with connection as differential twists and twisted vector bundles with connection as cycles. The model we construct satisfies the axioms of Kahle and Valentino, including functoriality, naturality of twists, and the hexagon diagram. We also construct an odd twisted Chern character of a twisted vector bundle with an automorphism. In addition to our geometric model of twisted differential K-theory, we introduce a smooth variant of the Hopkins-Singer model of differential K-theory. We prove that our model is naturally isomorphic to the Hopkins-Singer model and also to the Tradler-Wilson-Zeinalian model of differential K-theory

Pyrolysis and oxidation reaction of 1,2, dichloroethylene in Ar; Ar and CH4; Ar, CH4 and O2 mixtures

The thermal reaction of trans-1,2-dichloroethylene (DCEE) in methane and oxygen mixtures in Ar bath gas has been studied in 10.5 mm I.D. tubular flow quartz reactors at I atmosphere pressure, isothermal temperature between 575°C and 1000°C, and times of 0.3 to 2.0 seconds. The thermal reaction of trans-1,2-dichloroethylene in the gas phase proceeds via unimolecular HCI elimination under the reaction condition of the present experiments. The chain branching C-Cl bond fission reaction is expected to become important at the higher temperature, competing With the HCI elimination. The decay trans- 1,2- dichloroethylene, intermediates and final product distributions varied in the absence and presence of added O2 and/or CH4. Increase in O2 concentration was observed to accelerate reagent loss in the DCEE/CH4/O2 system, especially the fuel lean and stoichiometric systems relative to the DCEE/CH4 system. Major products were C2H2, HCCCl, CH2CHCl, CH2CCl2, C6H6, CO, CO2, and HCl in the DCEE/CH4/O2 over a wide temperature range. Minor products were C2H4, CH2Cl, CH2O2, C2O2, CH3CCl3, C6H5Cl, C6H5CH3. The extensive experimental data set will be utilized for construction and validation of a mechanism consisting of elementary reactions based on thermochemical principles, Transition State Theory and Quantum Rice-Ramsperger-Kassel (QRRK) analysis