ar X iv : c on d - m at / 9 51 10 32 v 1 6 N ov 1 99 5 Space covering by growing rays

ar X iv : g r - qc / 9 51 10 48 v 1 1 6 N ov 1 99 5 Two lectures on Two - Dimensional Gravity ∗

ar X iv : c on d - m at / 9 51 10 29 v 2 1 3 N ov 1 99 5 Spin gap in CaV 4 O 9 : a large S approach Marc

We study the stability of the 4-site plaquette order in a model recently introduced by Katoh and Imada to explain the spin gap observed in CaV4O9. We show that all relevant types of order (4-site plaquette, dimerized, Néel) can be described within the framework of Schwinger boson mean field theory, and we make predictions regarding their relative stability. The results are compared to exact dia...

ar X iv : c on d - m at / 9 51 10 67 v 1 1 4 N ov 1 99 5 Excitonic Phase Transition in Electronic Systems

Although predicted theoretically excitonic phase transitions have never been observed. Recently it has been claimed that they can occur in some strongly correlated materials. We study the possibility of an excitonic transition in a two-band model and show that a true phase transition never occurs in the presence of hybridization. We suggest an

ar X iv : c on d - m at / 9 61 11 80 v 1 2 3 N ov 1 99 6 Internal Forces and the Magnetoconductivity of a Nondegenerate 2 D Electron Fluid

X iv :c on dm at /9 61 11 80 v1 2 3 N ov 1 99 6 Internal Forces and the Magnetoconductivity of a Nondegenerate 2D Electron Fluid P. Fozooni, P.J. Richardson, and M.J. Lea Department of Physics, Royal Holloway, University of London, Egham, Surrey TW20 0EX, England M.I. Dykman and C. Fang-Yen[*] (a) Department of Physics and Astronomy, Michigan State University, MI 48824 (b) Department of Physics...

ar X iv : q - a lg / 9 51 10 18 v 1 2 3 N ov 1 99 5 Unitary operator bases and q - deformed algebras

Starting from the Schwinger unitary operator bases formalism constructed out of a finite dimensional state space, the well-known q-deformed commu-tation relation is shown to emerge in a natural way, when the deformation parameter is a root of unity.