Effective Superpotentials for SO/Sp with Flavor from Matrix Models

We study matrix models related to $SO/Sp$ gauge theories with flavors. We give the effective superpotentials for gauge theories with arbitrary tree level superpotential up to first instanton level. For quartic tree level superpotential we obtained exact one-cut solution. We also derive Seiberg-Witten curve for these gauge theories from matrix model argument.Comment: 17pp,2 figures, v2;refs added and to appear in MPL

Fusion and breakup in the reactions of 6,7Li and 9Be

We develop a three body classical trajectory Monte Carlo (CTMC) method to dicsuss the effect of the breakup process on heavy-ion fusion reactions induced by weakly bound nuclei. This method follows the classical trajectories of breakup fragments after the breakup takes place, and thus provides an unambiguous separation between complete and incomplete fusion cross sections. Applying this method to the fusion reaction $^{6}$Li + $^{209}$Bi, we find that there is a significant contribution to the total complete fusion cross sections from the process where all the breakup fragments are captured by the target nucleus (i.e., the breakup followed by complete fusion).Comment: 4 pages, 3 eps figures. Uses espcrc1.sty. To be published in the proceedings of the 8th international conference on clustering aspects of nuclear structure and dynamics, November 24 - 29, 2003, Nara, Japan (Nucl. Phys. A

Quiver Gauge Theory of Nonabelian Vortices and Noncommutative Instantons in Higher Dimensions

We construct explicit BPS and non-BPS solutions of the Yang-Mills equations on the noncommutative space R^{2n}_\theta x S^2 which have manifest spherical symmetry. Using SU(2)-equivariant dimensional reduction techniques, we show that the solutions imply an equivalence between instantons on R^{2n}_\theta x S^2 and nonabelian vortices on R^{2n}_\theta, which can be interpreted as a blowing-up of a chain of D0-branes on R^{2n}_\theta into a chain of spherical D2-branes on R^{2n} x S^2. The low-energy dynamics of these configurations is described by a quiver gauge theory which can be formulated in terms of new geometrical objects generalizing superconnections. This formalism enables the explicit assignment of D0-brane charges in equivariant K-theory to the instanton solutions.Comment: 45 pages, 4 figures; v2: minor correction

Growth mechanism of nanocrystals in solution: ZnO, a case study

We investigate the mechanism of growth of nanocrystals from solution using the case of ZnO. Spanning a wide range of values of the parameters, such as the temperature and the reactant concentration, that control the growth, our results establish a qualitative departure from the widely accepted diffusion controlled coarsening (Ostwald ripening) process quantified in terms of the Lifshitz-Slyozov-Wagner theory. Further, we show that these experimental observations can be qualitatively and quantitatively understood within a growth mechanism that is intermediate between the two well-defined limits of diffusion control and kinetic control.Comment: 10 pages, 4 figure

Vortex Phase Diagram of weakly pinned YBa2_2Cu3_3O7−δ_{7-\delta} for H ∥\parallel c

Vortex phase diagram in a weakly pinned crystal of YBCO for H $\parallel$ c is reviewed in the light of a recent elucidation of the process of `inverse melting' in a Bismuth cuprate system and the imaging of an interface between the ordered and the disordered regions across the peak effect in 2H-NbSe$_2$. In the given YBCO crystal, a clear distinction can be made between the second magnetization peak (SMP) and the peak effect (PE) between 65 K and 75 K. The field region between the peak fields of the SMP (H$^m_{smp}$) and the onset fields of the PE (H$^{on}_{pe}$)is not only continuously connected to the Bragg glass phase at lower fields but it is also sandwiched between the higher temperature vortex liquid phase and the lower temperature vortex glass phase. Thus, an ordered vortex state between H$^m_{smp}$ and H$^{on}_{pe}$ can get transformed to the (disordered) vortex liquid state on heating as well as to the (disordered) vortex glass state on cooling, a situation analogous to the thermal melting and the inverse melting phenomenon seen in a Bismuth cuprate.Comment: Presented in IWCC-200

Amorphization of Vortex Matter and Reentrant Peak Effect in YBa2_2Cu3_3O7−δ_{7-\delta}

The peak effect (PE) has been observed in a twinned crystal of YBa$_2$Cu$_3$O$_{7-\delta}$ for H$\parallel$c in the low field range, close to the zero field superconducting transition temperature (T$_c$(0)) . A sharp depinning transition succeeds the peak temperature T$_p$ of the PE. The PE phenomenon broadens and its internal structure smoothens out as the field is increased or decreased beyond the interval between 250 Oe and 1000 Oe. Moreover, the PE could not be observed above 10 kOe and below 20 Oe. The locus of the T$_p$(H) values shows a reentrant characteristic with a nose like feature located at T$_p$(H)/T$_c$(0)$\approx$0.99 and H$\approx$100 Oe (where the FLL constant a$_0$$\approx$penetration depth $\lambda$). The upper part of the PE curve (0.5 kOe$<$H$<$10 kOe) can be fitted to a melting scenario with the Lindemann number c$_L$$\approx$0.25. The vortex phase diagram near T$_c$(0) determined from the characteristic features of the PE in YBa$_2$Cu$_3$O$_{7-\delta}$(H$\parallel$c) bears close resemblance to that in the 2H-NbSe$_2$ system, in which a reentrant PE had been observed earlier.Comment: 15 pages and 7 figure

NiS - An unusual self-doped, nearly compensated antiferromagnetic metal

NiS, exhibiting a text-book example of a first-order transition with many unusual properties at low temperatures, has been variously described in terms of conflicting descriptions of its ground state during the past several decades. We calculate these physical properties within first-principle approaches based on the density functional theory and conclusively establish that all experimental data can be understood in terms of a rather unusual ground state of NiS that is best described as a self-doped, nearly compensated, antiferromagnetic metal, resolving the age-old controversy. We trace the origin of this novel ground state to the specific details of the crystal structure, band dispersions and a sizable Coulomb interaction strength that is still sub-critical to drive the system in to an insulating state. We also show how the specific antiferromagnetic structure is a consequence of the less-discussed 90 degree and less than 90 degree superexchange interactions built in to such crystal structures

Mass Deformations of Super Yang-Mills Theories in D= 2+1, and Super-Membranes: A Note

Mass deformations of supersymmetric Yang-Mills theories in three spacetime dimensions are considered. The gluons of the theories are made massive by the inclusion of a non-local gauge and Poincare invariant mass term due to Alexanian and Nair, while the matter fields are given standard Gaussian mass-terms. It is shown that the dimensional reduction of such mass deformed gauge theories defined on $R^3$ or $R\times T^2$ produces matrix quantum mechanics with massive spectra. In particular, all known massive matrix quantum mechanical models obtained by the deformations of dimensional reductions of minimal super Yang-Mills theories in diverse dimensions are shown also to arise from the dimensional reductions of appropriate massive Yang-Mills theories in three spacetime dimensions. Explicit formulae for the gauge theory actions are provided.Comment: 20 Page

Point-Like Graviton Scattering in Plane-Wave Matrix Model

In a plane-wave matrix model we discuss a two-body scattering of gravitons in the SO(3) symmetric space. In this case the graviton solutions are point-like in contrast to the scattering in the SO(6) symmetric space where spherical membranes are interpreted as gravitons. We concentrate on a configuration in the 1-2 plane where a graviton rotates with a constant radius and the other one elliptically rotates. Then the one-loop effective action is computed by using the background field method. As the result, we obtain the 1/r^7-type interaction potential, which strongly suggests that the scattering in the matrix model would be closely related to that in the light-front eleven-dimensional supergravity.Comment: 17 pages, 1 figure, LaTeX, v2) references adde