ar X iv : c on d - m at / 9 51 10 24 v 1 5 N ov 1 99 5 Dynamics of Inhomogeneous Tomonaga - Luttinger Liquid Wire

ar X iv : c on d - m at / 9 50 70 89 v 2 3 1 Ju l 1 99 5 Is there a renormalization of the 1 D conductance in Luttinger Liquid model ?

Properties of 1D transport strongly depend on the proper choice of boundary conditions. It has been frequently stated that the Luttinger Liquid (LL) conductance is renormalized by the interaction as g e 2 h. To contest this result I develop a model of 1D LL wire with the interaction switching off at the infinities. Its solution shows that there is no renormalization of the universal conductance...

ar X iv : g r - qc / 9 51 10 66 v 1 2 4 N ov 1 99 5 Scalar Field Inhomogeneous

Some exact solutions for the Einstein field equations corresponding to inhomogeneous G 2 cosmologies with an exponential-potential scalar field which generalize solutions obtained previously are considered. Several particular cases are studied and the properties related to generalized inflation and asymptotic behaviour of the models are discussed.

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