On the Phase Structure of the Schwinger Model with Wilson Fermions

We study the phase structure of the massive one flavour lattice Schwinger model on the basis of the finite size scaling behaviour of the partition function zeroes. At $\beta = 0$ we observe and discuss a possible discrepancy with results obtained by a different method.Comment: 3 pages (2 figures), POSTSCRIPT-file (174 KB), Contribution to Lattice 93, preprint UNIGRAZ-UTP 19-11-9

Properties of the Soliton-Lattice State in Double-Layer Quantum Hall Systems

Application of a sufficiently strong parallel magnetic field $B_\parallel > B_{c}$ produces a soliton-lattice (SL) ground state in a double-layer quantum Hall system. We calculate the ground-state properties of the SL state as a function of $B_\parallel$ for total filling factor $\nu_{T}=1$, and obtain the total energy, anisotropic SL stiffness, Kosterlitz-Thouless melting temperature, and SL magnetization. The SL magnetization might be experimentally measurable, and the magnetic susceptibility diverges as $|B_\parallel - B_{c}|^{-1}$.Comment: 4 pages LaTeX, 1 EPS figure. Proceedings of the 12th International Conference on the Electronic Properties of Two-Dimensional Electron Systems (EP2DS-12), to be published in Physica B (1998

Strong Coupling Lattice Schwinger Model on Large Spherelike Lattices

The lattice regularized Schwinger model for one fermion flavor and in the strong coupling limit is studied through its equivalent representation as a restricted 8-vertex model. The Monte Carlo simulation on lattices with torus-topology is handicapped by a severe non-ergodicity of the updating algorithm; introducing lattices with spherelike topology avoids this problem. We present a large scale study leading to the identification of a critical point with critical exponent $\nu=1$, in the universality class of the Ising model or, equivalently, the lattice model of free fermions.Comment: 16 pages + 7 figures, gzipped POSTSCRIPT fil

Bias-voltage induced phase-transition in bilayer quantum Hall ferromagnets

We consider bilayer quantum Hall systems at total filling factor $\nu=1$ in presence of a bias voltage $\Delta_v$ which leads to different filling factors in each layer. We use auxiliary field functional integral approach to study mean-field solutions and collective excitations around them. We find that at large layer separation, the collective excitations soften at a finite wave vector leading to the collapse of quasiparticle gap. Our calculations predict that as the bias voltage is increased, bilayer systems undergo a phase transition from a compressible state to a $\nu=1$ phase-coherent state {\it with charge imbalance}. We present simple analytical expressions for bias-dependent renormalized charge imbalance and pseudospin stiffness which are sensitive to the softening of collective modes.Comment: 12 pages, 5 figures. Minor changes, one reference adde

Resonance Scattering Phase Shifts in a 2-d Lattice Model

We study a simple 2-d model representing two fields with different mass and a 3-point coupling term. The phase shift in the resonating 2-particle channel is determined from the energy spectrum obtained in Monte Carlo simulations on finite lattices. Masses and wave function renormalization constants of the fields as well as mass and width of the resonance are determined and discussed. The representation of scattering states in terms of the considered operators is analysed.Comment: 24 p + 8 PS-figures, UNIGRAZ-UTP-04-05-9

Scaling Behavior of Transverse Kinetic Energy Distributions in Au+Au Collisions at sNN=200\sqrt{s_{\rm NN}}=200 GeV

With the experimental data from STAR on the centrality dependence of transverse momentum $p_T$ spectra of pions and protons in Au+Au collisions at $\sqrt{s_{NN}}=200 {\rm GeV}$, we investigate the scaling properties of transverse energy $E_T$ distributions at different centralities. In the framework of cluster formation and decay mechanism for particle production, the universal transverse energy distributions for pion and proton can be described separately but not simultaneously.Comment: 5 pages, 5 eps figures included, to be appeared in Nucl. Phys.

Lee-Yang zeroes and logarithmic corrections in the Φ44 theory

The leading mean-field critical behaviour of φ 4 4-theory is modified by multiplicative logarithmic corrections. We analyse these corrections both analytically and numerically. In particular we present a finite-size scaling theory for the Lee-Yang zeroes and temperature zeroes, both of which exhibit logarithmic corrections. On lattices from size 8 4 to 24 4, Monte-Carlo cluster methods and multi-histogram techniques are used to determine the partition function zeroes closest to the critical point. Finite-size scaling behaviour is verified and the logarithmic corrections are found to be in good agreement with our analytical predictions. 1

The zeros of the QCD partition function

We establish a relationship between the zeros of the partition function in the complex mass plane and the spectral properties of the Dirac operator in QCD. This relation is derived within the context of chiral Random Matrix Theory and applies to QCD when chiral symmetry is spontaneously broken. Further, we introduce and examine the concept of normal modes in chiral spectra. Using this formalism we study the consequences of a finite Thouless energy for the zeros of the partition function. This leads to the demonstration that certain features of the QCD partition function are universal.Comment: 13 page

Solitons in polarized double layer quantum Hall systems

A new manifestation of interlayer coherence in strongly polarized double layer quantum Hall systems with total filling factor $\nu=1$ in the presence of a small or zero tunneling is theoretically predicted. It is shown that moving (for small tunneling) and spatially localized (for zero tunneling) stable pseudospin solitons develop which could be interpreted as mobile or static charge-density excitations. The possibility of their experimental observation is also discussed.Comment: Phys. Rev. B (accepted