Yang-Lee zeros of the Q-state Potts model in the complex magnetic-field plane

The microcanonical transfer matrix is used to study the distribution of Yang-Lee zeros of the $Q$-state Potts model in the complex magnetic-field ($x=e^{\beta h}$) plane for the first time. Finite size scaling suggests that at (and below) the critical temperature the zeros lie close to, but not on, the unit circle with the two exceptions of the critical point $x=1$ ($h=0$) itself and the zeros in the limit T=0.Comment: REVTeX, 12 pages, 5 figures, to appear in Phys. Rev. Let

Microcanonical Transfer Matrix Study of the Q-state Potts Model

The microcanonical transfer matrix is used to study the zeros of the partition function of the Q-state Potts model. Results are presented for the Yang-Lee zeros of the 3-state model, the Fisher zeros of the 3-state model in an external field $H_q<0$, and the spontaneous magnetization of the 2-state model. In addition, we are able to calculate the ground-state entropy of the 3-state model and find $s_0=0.43153(3)$ in excellent agreement with the exact value, 0.43152...Comment: 3 pages, 3 figures, LaTeX, to appear in Computer Physics Communication

Folding Mechanism of Small Proteins

Extensive Monte Carlo folding simulations for four proteins of various structural classes are carried out, using a single atomistic potential. In all cases, collapse occurs at a very early stage, and proteins fold into their native-like conformations at appropriate temperatures. The results demonstrate that the folding mechanism is controlled not only by thermodynamic factors but also by kinetic factors: The way a protein folds into its native structure, is also determined by the convergence point of early folding trajectories, which cannot be obtained by the free energy surface.Comment: 11 pages, 4 figure

Density of Yang-Lee zeros for the Ising ferromagnet

The densities of Yang-Lee zeros for the Ising ferromagnet on the $L\times L$ square lattice are evaluated from the exact grand partition functions ($L=3\sim16$). The properties of the density of Yang-Lee zeros are discussed as a function of temperature $T$ and system size $L$. The three different classes of phase transitions for the Ising ferromagnet, first-order phase transition, second-order phase transition, and Yang-Lee edge singularity, are clearly distinguished by estimating the magnetic scaling exponent $y_h$ from the densities of zeros for finite-size systems. The divergence of the density of zeros at Yang-Lee edge in high temperatures (Yang-Lee edge singularity), which has been detected only by the series expansion until now for the square-lattice Ising ferromagnet, is obtained from the finite-size data. The identification of the orders of phase transitions in small systems is also discussed using the density of Yang-Lee zeros.Comment: to appear in Physical Review

Collapse transition of a square-lattice polymer with next nearest-neighbor interaction

We study the collapse transition of a polymer on a square lattice with both nearest-neighbor and next nearest-neighbor interactions, by calculating the exact partition function zeros up to chain length 36. The transition behavior is much more pronounced than that of the model with nearest-neighbor interactions only. The crossover exponent and the transition temperature are estimated from the scaling behavior of the first zeros with increasing chain length. The results suggest that the model is of the same universality class as the usual theta point described by the model with only nearest-neighbor interaction.Comment: 14 pages, 5 figure

DP-Structure and Predication

This paper purports to derive Safir's (1987) observation (an adjunct can modify a prenominal genitive NP(PGNP) only if the nominal describes an event or process) from independently motivated principles. The acceptance of DP-structure and the classification of nominals into three types make it possible to achieve the purpose. Only the PGNP of process nominals is an argument occupying the NP-SPEC position at DS whereas the PGNP of other nominals is a modifier occupying the DP-SPEC position. This division enables us to explain why an adjectival adjunct can modify only a PGNP of the nominal with an event or process reading without any ad-hoc revision of the condition in predicate linking