M Theory Fivebrane and SQCD

Talk presented at Strings `97 in Amsterdam (June 16 - 21, 1997)Comment: 8 pages, 4 figures, latex. Talk presented at STRINGS'97, Amsterda

Excitation Spectrum of the Spin-1/2 Ferromagnetic-Antiferromagnetic Alternating Heisenberg Chain:

The natural explanation of the excitation spectrum of the spin-1 antiferromagnetic Heisenberg chain is given from the viewpoint of the spin-1/2 ferromagnetic-antiferromagnetic alternating Heisenberg chain. The energy spectrum of the latter is calculated with fixed momentum $k$ by numerical diagonalization of finite size systems. It consists of a branch of propagating triplet pair (triplet wave) and the continuum of multiple triplet waves for weak ferromagnetic coupling. As the ferromagnetic coupling increases, the triplet wave branch is absorbed in the continuum for small $k$, reproducing the characteristics of the spin-1 antiferromagnetic Heisenberg chain.Comment: 12 Pages REVTEX, Postscript file for the figures included. SKPH-94-C00

Faceting Transition in an Exactly Solvable Terrace-Ledge-Kink model

We solve exactly a Terrace-Ledge-Kink (TLK) model describing a crystal surface at a microscopic level. We show that there is a faceting transition driven either by temperature or by the chemical potential that controls the slope of the surface. In the rough phase we investigate thermal fluctuations of the surface using Conformal Field Theory.Comment: 27 pages, 18 EPS figure