Phase Transition in Three-State Three-Dimensional Potts Model.

title: Tunneling and the spectrum of the Potts model.
abstract: The three-dimensional, three-state Potts model is studied as a paradigm for high-temperature quantum chromodynamics. In a high-statistics numerical simulation using a Swendson-Wang algorithm, we study cubic lattices of dimension as large as 64[sup 3] and measure correlation functions on long lattices of dimension 20[sup 2][times]120 and 30[sup 2][times]120. These correlations are controlled by the spectrum of the transfer matrix. This spectrum is studied in the vicinty of the phase transition. The analysis classifies the spectral levels according to an underlying [ital S][sub 3] symmetry. Near the phase transition the spectrum agrees nicely with a simple four-component Hamiltonian model. In the context of this model, we find that low-temperature ordered-ordered interfaces nearly always involve a disordered phase intermediate. We use a spectral method for determining the surface tension between phases.

title: Excitation energy as a basic variable to control nuclear disassembly

abstract: Thermodynamical features of Xe system is investigated as functions of temperature and freeze-out density in the frame of lattice gas model. The calculation shows different temperature dependence of physical observables at different freeze-out density. In this case, the critical temperature when the phase transition takes place depends on the freeze-out density. However, a unique critical excitation energy %and the same excitation reveals regardless of freeze-out density when the excitation energy is used as a variable instead of temperature. Moreover, the different behavior of other physical observables with temperature due to different ρf vanishes when excitation energy replaces temperature. It indicates that the excitation energy can be seen as a more basic quantity to control nuclear disassembly.

title: Symmetry-protected many-body Aharonov-Bohm effect
abstract: It is known as a purely quantum effect that a magnetic flux affects the real physics of a particle, such as the energy spectrum, even if the flux does not interfere with the particle's path\char22{}the Aharonov-Bohm effect. Here we examine an Aharonov-Bohm effect on a many-body wave function. Specifically, we study this many-body effect on the gapless edge states of a bulk gapped phase protected by a global symmetry (such as ${\mathbb{Z}}_{N}$)\char22{}the symmetry-protected topological (SPT) states. The many-body analog of spectral shifts, the twisted wave function, and the twisted boundary realization are identified in this SPT state. An explicit lattice construction of SPT edge states is derived, and a challenge of gauging its non-onsite symmetry is overcome. Agreement is found in the twisted spectrum between a numerical lattice calculation and a conformal field theory prediction.

title: A CHANDRA STUDY OF THE ROSETTE STAR-FORMING COMPLEX. II. CLUSTERS IN THE ROSETTE MOLECULAR CLOUD
abstract: We explore here the young stellar populations in the Rosette Molecular Cloud (RMC) region with high spatial resolution X-ray images from the Chandra X-ray Observatory, which are effective in locating weak-lined T Tauri stars as well as disk-bearing young stars. A total of 395 X-ray point sources are detected, 299 of which (76%) have an optical or near-infrared (NIR) counterpart identified from deep FLAMINGOS images. From X-ray and mass sensitivity limits, we infer a total population of ~1700 young stars in the survey region. Based on smoothed stellar surface density maps, we investigate the spatial distribution of the X-ray sources and define three distinctive structures and substructures within them. Structures B and C are associated with previously known embedded IR clusters, while structure A is a new X-ray-identified unobscured cluster. A high-mass protostar RMCX #89 = IRAS 06306+0437 and its associated sparse cluster are studied. The different subregions are not coeval but do not show a simple spatial-age pattern. Disk fractions vary between subregions and are generally 20% of the total stellar population inferred from the X-ray survey. The data are consistent with speculations that triggered star formation around the H II region is present in the RMC, but do not support a simple sequential triggering process through the cloud interior. While a significant fraction of young stars are located in a distributed population throughout the RMC region, it is not clear if they originated in clustered environments.

title: The sky brightness and transparency in i-band at Dome A, Antarctica
abstract: The i-band observing conditions at Dome A on the Antarctic plateau have been investigated using data acquired during 2008 with the Chinese Small Telescope ARray. The sky brightness, variations in atmospheric transparency, cloud cover, and the presence of aurorae are obtained from these images. The median sky brightness of moonless clear nights is 20.5 mag arcsec^{-2} in the SDSS $i$ band at the South Celestial Pole (which includes a contribution of about 0.06 mag from diffuse Galactic light). The median over all Moon phases in the Antarctic winter is about 19.8 mag arcsec^{-2}. There were no thick clouds in 2008. We model contributions of the Sun and the Moon to the sky background to obtain the relationship between the sky brightness and transparency. Aurorae are identified by comparing the observed sky brightness to the sky brightness expected from this model. About 2% of the images are affected by relatively strong aurorae.

title: Lattice SU(2) gauge-Higgs system in analytic treatment
abstract: The phase diagrams of SU(2) gauge-Higgs model with Higgs field of arbitrary length in the fundamental representation in four and five dimension are studied analytically. A method for determining phase transition lines is proposed. All qualitative features of the phase diagram obtained by Monte Carlo simulations are obtained analytically, and the order of phase transitions can be determined definitely.