Thermal contribution of unstable states

Within the framework of the Lee model, we analyze in detail the difference between the energy derivative of the phase shift and the standard spectral function of the unstable state. The fact that the model is exactly solvable allows us to demonstrate the construction of these observables from various exact Green functions. The connection to a formula due to Krein, Friedal, and Lloyd is also examined. We also directly demonstrate how the derivative of the phase shift correctly identifies the relevant interaction contributions for consistently including an unstable state in describing the thermodynamics.Comment: 11 pages, 2 figures, to be submitted to EPJ

A Markov switching model of GNP growth with duration dependence

We use a regime-switching model of real GNP growth to examine the duration dependence of business cycles. The model extends Hamilton (1989) and Durland and McCurdy (1994) and is estimated using both the postwar NIPA data and the secular data constructed by Balke-Gordon. We find that an expansion is more likely to end at a young age, that a contraction is more likely to end at an old age, that output growth slows over the course of an expansion, that a decline in output is mild at the beginning of a contraction, and that long expansions are followed by long contractions. This evidence taken together provides no support for the clustering of the whole-cycle around seven-to-ten year durations.Gross national product ; Business cycles

Local Probes for Quantum Hall Ferroelectrics and Nematics

Two-dimensional multi-valley electronic systems in which the dispersion of individual pockets has low symmetry give rise to quantum Hall ferroelectric and nematic states in the presence of strong quantising magnetic fields. We investigate local signatures of these states arising near impurities that can be probed via Scanning Tunnelling Microscopy (STM) spectroscopy. For quantum Hall ferroelectrics, we demonstrate a direct relation between the dipole moment measured at impurity bound states and the ideal bulk dipole moment obtained from the modern theory of polarisation. We also study the many-body problem with a single impurity via exact diagonalization and find that near strong impurities non-trivial excitonic state can form with specific features that can be easily identified via STM spectroscopy.Comment: Main: 5 pages, 4 figures; Supplement: 9 pages, 4 figures; published versio

Matching the Hagedorn mass spectrum with Lattice QCD results

Based on recent Lattice QCD (LQCD) results obtained at finite temperature, we discuss modeling of the hadronic phase of QCD in the framework of Hadron Resonance Gas (HRG) with discrete and continuous mass spectra. We focus on fluctuations of conserved charges, and show how a common limiting temperature can be used to constrain the Hagedorn exponential mass spectrum in different sectors of quantum number, through a matching of HRG and LQCD. For strange baryons, the extracted spectra are found to be consistent with all known and expected states listed by the Particle Data Group (PDG). The strange-mesonic sector, however, requires additional states in the intermediate mass range beyond that embodied in the database.Comment: 8 pages, 4 figures, version to appear in phys. rev.

Sugar 3D Printing: Additive Manufacturing with Molten Sugar for Investigating Molten Material Fed Printing

Recent breakthroughs in additive manufacturing of molten glass using gravity-fed mechanisms have opened a new area of research in large-scale extrusion of molten material. However, the machines and techniques used for printing molten glass are expensive and complex due to high process temperature (>1000°C). A mixture of sucrose sugar and corn syrup is proposed as an analogous substitution material for research in molten material fed three-dimensional (3D) printing. Molten sugar is optically transparent and it exhibits similar temperature–viscosity relationship and solidification properties as molten glass, but at a much lower temperature (100–150°C). A low cost, desktop size 3D printer is designed with a temperature controlled sugar reservoir made from easily obtainable parts. The process of printing with molten sugar is demonstrated with success in recreating objects with similar complexity to glass prints. The techniques described in this study can be implemented easily for future investigation of glass and other molten material fed 3D printing. The design space of the printed object can be explored, for example, minimum radii, draft angle, and optical properties. Many process parameters can be tested with this system, for example, layer height, printing speed, nozzle design, multicolor material feed, and toolpath strategy

Mean Reversion in Equilibrium Asset Prices

Recent empirical studies have found that stock returns contain substantial negative serial correlation at long horizons. We examine this finding with a series of Monte Carlo simulations in order to demonstrate that it is consistent with an equilibrium model of asset pricing. When investors display only a moderate degree of risk aversion, commonly used measures of mean reversion in stock prices calculated from actual returns data nearly always lie within a 60 percent confidence interval of the median of the Monte Carlo distributions. From this evidence, we conclude that the degree of serial correlation in the data could plausibly have been generated by our model.

Polyakov loop fluctuations and deconfinement in the limit of heavy quarks

We explore the influence of heavy quarks on the deconfinement phase transition in an effective model for gluons interacting with dynamical quarks in color SU(3). With decreasing quark mass, the strength of the explicit breaking of the Z(3) symmetry grows and the first-order transition ends in a critical endpoint. The nature of the critical endpoint is examined by studying the longitudinal and transverse fluctuations of the Polyakov loop, quantified by the corresponding susceptibilities. The longitudinal susceptibility is enhanced in the critical region, while the transverse susceptibility shows a monotonic behavior across the transition point. We investigate the dependence of the critical endpoint on the number of quark flavors at vanishing and finite quark density. Finally we confront the model results with lattice calculations and discuss a possible link between the hopping parameter and the quark mass.Comment: 8 pages, 9 figure

Strangeness fluctuations from K−πK-\pi interactions

Motivated by recent lattice QCD studies, we explore the effects of interactions on strangeness fluctuations in strongly interacting matter at finite temperature. We focus on S-wave $K\pi$ scattering and discuss the role of the $K_0^*(800)$ and $K^*(1430)$ resonances. The interaction contribution is obtained within the S-matrix formulation of thermodynamics, using the empirical $K\pi$ phase shifts as input. We find that the simplified treatment of the interactions in this channel, employed in the hadron resonance gas approach, leads to an overestimate of the strangeness fluctuations. Thus, our calculation indicates that broad resonances must be treated with caution, when modeling QCD thermodynamics in the hadronic phase.Comment: 7 pages, 4 figures, version appeared in phys. rev.

昼夜衛星画像を用いたメコン川下流域における不浸透面被覆の経年変化（2001－2012）

筑波大学 (University of Tsukuba)201