A Ginzburg-Landau Theory For Ni-Mn-Ga

(0,2) Landau-ginzburg Theory ⋆

A large class of (0,2) Calabi-Yau σ-models and Landau-Ginzburg orbifolds are shown to arise as different “phases” of supersymmetric gauge theories. We find a phenomenon in the Landau-Ginzburg phase which may enable one to understand which Calabi-Yau σ-models evade destabilization by worldsheet instantons. Examples of (0,2) LandauGinzburg vacua are analyzed in detail, and several novel features ...

Superconductivity: Ginzburg-Landau Theory

Phonon softening in Ni-Mn-Ga alloys

The TA2 phonon dispersion curves of Ni-Mn-Ga alloys with different compositions which transform to different martensitic structures have been measured over a broad temperature range covering both paramagnetic and ferromagnetic phases. The branches show an anomaly (dip) at a wave number that depends on the particular martensitic structure, and there is softening of these anomalous phonons with d...

Fluctuations in Superconductors using Landau-Ginzburg Theory

In this paper, we study the fluctuations in superconductors in the framework of Landau-Ginzurg theory. First, we review the formulation of LG theory and derive the LG equations. The we calculate the fluctuation contribution to the saddle point heat capacity, both inside and outside the immediate vicinity of the transition point. Outside the immediate vicinity, we follow the Gaussian integral ca...

Ginzburg-Landau theory of aqueous surfactant solutions

A simple two order-paraIneter Ginzburg-Landau theory for binary mixtures of water and amphiphile is introduced. The amphiphile concentration is described by a scalar, the orientational degrees of freedom of the amphiphile by a vector order parameter. Phase diagrams are calculated by minimizing the free energy functional. Several ordered lyotropic phases of lamellar, hexagonal, inverse hexagonal...