ar X iv : c on d - m at / 9 50 80 80 v 2 1 7 O ct 9 5 Quantum phase transitions in spin systems and the high temperature limit of continuum quantum field theories

ar X iv : h ep - l at / 9 30 50 16 v 1 2 0 M ay 1 99 3 FUB - HEP 9 / 93 May 4 , 1993

To further improve the performance of Monte Carlo simulations of first-order phase transitions we propose to combine the multicanonical approach with multigrid techniques. We report tests of this proposition for the d-dimensional Φ4 field theory in two different situations. First, we study quantum tunneling for d = 1 in the continuum limit, and second, we investigate first-order phase transitio...

ar X iv : c on d - m at / 9 80 30 86 v 1 8 M ar 1 99 8 Nodal Liquid

We introduce and study the nodal liquid, a novel zero-temperature quantum phase obtained by quantum-disordering a d-wave superconductor. It has numerous remarkable properties which lead us to suggest it as an explanation of the pseudo-gap state in underdoped high-temperature superconductors. In the absence of impurities, these include power-law magnetic order, a T -linear spin susceptibility, n...

ar X iv : c on d - m at / 9 50 80 62 v 1 3 1 Ju l 1 99 5 QUANTUM THEORY OF LARGE SYSTEMS OF NON - RELATIVISTIC MATTER

ar X iv : c on d - m at / 9 70 11 42 21 J an 9 7 Double - layer quantum Hall antiferromagnetism at filling fraction ν = 2 / ( odd integer )

A low energy action for double-layer quantum Hall systems at filling fractions ν = 2/m (m an odd integer) is introduced. Interlayer antiferromagnetic exchange induces a phase with canted spin order, and also a spin-singlet phase. Universal properties of zero and finite temperature transitions are obtained. We compute the critical temperature at which the canted order vanishes in a KosterlitzTho...

ar X iv : c on d - m at / 9 31 00 47 v 1 2 0 O ct 1 99 3 Statistical Mechanics of Vortices in Type - II Superconductors

Thermal fluctuations and disorder play an essential role in high-Tc superconductors. After reviewing the mean-field phase diagram we describe significant modifications that result when the effects of finite temperature and disorder are incorporated. Thermal fluctuations cause the melting of the Abrikosov flux line lattice into a vortex liquid at high temperatures, and disorder produces novel gl...