Nonequilibrium Phase Transitions in a Driven Sandpile Model

We construct a driven sandpile slope model and study it by numerical simulations in one dimension. The model is specified by a threshold slope \sigma_c\/, a parameter \alpha\/, governing the local current-slope relation (beyond threshold), and $j_{\rm in}$, the mean input current of sand. A nonequilibrium phase diagram is obtained in the \alpha\, -\, j_{\rm in}\/ plane. We find an infinity of phases, characterized by different mean slopes and separated by continuous or first-order boundaries, some of which we obtain analytically. Extensions to two dimensions are discussed.Comment: 11 pages, RevTeX (preprint format), 4 figures available upon requs

One step growth of GaN/SiO2 core/shell nanowire in vapor-liquid-solid route by chemical vapor deposition technique

GaN/SiO2 core/shell nanowires are grown by cobalt phthalocyanine catalyst assisted vapor-liquid-solid route, in which Si wafer coated with a mixture of gallium and indium is used as the source for Ga and Si and ammonia is used as the precursor for nitrogen and hydrogen. Gallium in the presence of indium and hydrogen, which results from the dissociation of ammonia, forms Si-Ga-In alloy at the growth temperature around 910 degree Celsius. This alloy acts as the source of Si, Ga and In. A detailed study using a variety of characterization tools reveals that these wires, which are several tens of micron long, has a diameter distribution of the core ranging from 20 to 50 nm, while the thickness of the amorphous SiO2 shell layer is about 10 nm. These wires grow along direction. It has also been observed that the average width of these wires decreases, while their density increases as the gallium proportion in the Ga-In mixture is increased.Comment: 14 pages, 4 figure

Operation of FDI caps in India and corporate control mechanisms

While India has generally been following an open door FDI policy, a few areas are still subject to caps on FDI and/or specific government approval. One of the justifications for the same is the need to retain a degree of control over the operations of the investee companies in Indian hands. Earlier this year, the government specified the methodology for calculating direct and indirect foreign equity in Indian companies in order to remove ambiguities in calculating the extent of FDI in a company. Based on empirical evidence this paper argues that percentage of shares or proportion of directors do not necessarily represent the extent of control and more direct intervention would be required if the objectives of imposing the caps are to be achieved.FDI; corporate control, veto powers, India, joint control, joint ventures, corporate governance

Enhanced conduction band density of states in intermetallic EuTSi3_3 (T=Rh, Ir)

We report on the physical properties of single crystalline EuRhSi$_3$ and polycrystalline EuIrSi$_3$, inferred from magnetisation, electrical transport, heat capacity and $^{151}$Eu M\"ossbauer spectroscopy. These previously known compounds crystallise in the tetragonal BaNiSn$_3$-type structure. The single crystal magnetisation in EuRhSi$_3$ has a strongly anisotropic behaviour at 2 K with a spin-flop field of 13 T, and we present a model of these magnetic properties which allows the exchange constants to be determined. In both compounds, specific heat shows the presence of a cascade of two close transitions near 50 K, and the $^{151}$Eu M\"ossbauer spectra demonstrate that the intermediate phase has an incommensurate amplitude modulated structure. We find anomalously large values, with respect to other members of the series, for the RKKY N\'eel temperature, for the spin-flop field (13 T), for the spin-wave gap ($\simeq$ 20-25 K) inferred from both resistivity and specific heat data, for the spin-disorder resistivity in EuRhSi$_3$ ($\simeq 35$ $\mu$Ohm.cm) and for the saturated hyperfine field (52 T). We show that all these quantities depend on the electronic density of states at the Fermi level, implying that the latter must be strongly enhanced in these two materials. EuIrSi$_3$ exhibits a giant magnetoresistance ratio, with values exceeding 600 % at 2 K in a field of 14 T.Comment: 6 pages, 8 figure

Inverse Avalanches On Abelian Sandpiles

A simple and computationally efficient way of finding inverse avalanches for Abelian sandpiles, called the inverse particle addition operator, is presented. In addition, the method is shown to be optimal in the sense that it requires the minimum amount of computation among methods of the same kind. The method is also conceptually nice because avalanche and inverse avalanche are placed in the same footing.Comment: 5 pages with no figure IASSNS-HEP-94/7

The Irreducible String and an Infinity of Additional Constants of Motion in a Deposition-Evaporation Model on a Line

We study a model of stochastic deposition-evaporation with recombination, of three species of dimers on a line. This model is a generalization of the model recently introduced by Barma {\it et. al.} (1993 {\it Phys. Rev. Lett.} {\bf 70} 1033) to $q\ge 3$ states per site. It has an infinite number of constants of motion, in addition to the infinity of conservation laws of the original model which are encoded as the conservation of the irreducible string. We determine the number of dynamically disconnected sectors and their sizes in this model exactly. Using the additional symmetry we construct a class of exact eigenvectors of the stochastic matrix. The autocorrelation function decays with different powers of $t$ in different sectors. We find that the spatial correlation function has an algebraic decay with exponent 3/2, in the sector corresponding to the initial state in which all sites are in the same state. The dynamical exponent is nontrivial in this sector, and we estimate it numerically by exact diagonalization of the stochastic matrix for small sizes. We find that in this case $z=2.39\pm0.05$.Comment: Some minor errors in the first version has been correcte