Quasiparticle picture of quarks near chiral transition at finite temperature

We investigate, using a chiral effective model, the quark spectrum in the critical region of the chiral transition focusing on the effect of the possible mesonic excitations in the quark-gluon plasma phase. We find that there appears a novel three-peak structure in the quark spectra. We elucidate the mechanism of the appearance of the multi-peak structure with the help of a Yukawa model with an elementary boson.Comment: 4 pages, 5 eps figures, to appear in the proceedings of International Conference on Strong & Electroweak Matter 2006, Brookhaven National Laboratory, USA, May 10-13, 200

Pedestrian vision and collision avoidance behavior: investigation of the information process space of pedestrians using an eye tracker

This study investigates the Information Process Space (IPS) of pedestrians, which has been widely used in microscopic pedestrian movement simulation models. IPS is a conceptual framework to define the spatial extent within which all objects are considered as potential obstacles for each pedestrian when computing where to move next. The particular focus of our study was identifying the size and shape of IPS by examining observed gaze patterns of pedestrians. A series of experiments was conducted in a controlled laboratory environment, in which up to 4 participants walked on a platform at their natural speed. Their gaze patterns were recorded by a head-mounted eye tracker and walking paths by laser-range-scanner–based tracking systems at the frequency of 25Hz. Our findings are threefold: pedestrians pay much more attention to ground surfaces to detect immediate potential environmental hazards than fixating on obstacles; most of their fixations fall within a cone-shape area rather than a semicircle; and the attention paid to approaching pedestrians is not as high as that paid to static obstacles. These results led to an insight that the structure of IPS should be re-examined by researching directional characteristics of pedestrians’ vision

Precursor of Color Superconductivity

We investigate possible precursory phenomena of color superconductivity at finite temperature $T$ with an effective theory of QCD. It is found that the fluctuation of the diquark pair field exists with a prominent strength even well above the critical temperature $T_c$. We show that such a fluctuaiton forms a collective mode, the corresponding pole of which approaches the origin as $T$ is lowered to $T_c$ in the complex energy plane. We discuss the possible relevance of the precursor to the observables to be detected in heavy-ion collisions.Comment: 4 pages, 5 figures, Talk presented at the XVIth International Conference on Particles and Nuclei (PANIC02), Osaka, Japan, Sep.30 - Oct.4, 2002, Uses espcrc1.st

Precursor of Color Superconductivity in Hot Quark Matter

We investigate possible precursory phenomena of color superconductivity in quark matter at finite temperature T with use of a simple Nambu-Jona-Lasinio model. It is found that the fluctuating pair field exists with a prominent strength even well above the critical temperature T_c. We show that the collective pair field has a complex energy located in the second Riemann sheet, which approaches the origin as T is lowered to T_c. We discuss the possible relevance of the precursor to the observables to be detected in heavy ion collisions.Comment: 5 pages, 3 figures, version to appear in Phys. Rev. D. Discussions are enlarged on the physical origin of the large fluctuation of the pair field and its phenomenological consequences. References are adde

Chiral and Color-superconducting Phase Transitions with Vector Interaction in a Simple Model (Addenda)

In the preceding paper(Prog.Theor.Phys.108(2002)929 or hep-ph/0207255), we have shown that the critical line of the first order chiral transition of QCD can have two endpoints. In this addendum, we elucidate the mechanism to realize the two-endpoint structure in the QCD phase diagram and argue the robustness for the appearance of such an interesting phase structure

Finite-Field Ground State of the S=1 Antiferromagnetic-Ferromagnetic Bond-Alternating Chain

We investigate the finite-field ground state of the S=1 antiferromagnetic-ferromagnetic bond-alternating chain described by the Hamiltonian {\calH}=\sum\nolimits_{\ell}\bigl\{\vecS_{2\ell-1}\cdot\vecS_{2\ell} +J\vecS_{2\ell}\cdot\vecS_{2\ell+1}\bigr\} +D\sum\nolimits_{\ell} \bigl(S_{\ell}^z)^2 -H\textstyle\sum\nolimits_\ell S_\ell^z, where \hbox{$J\leq0$} and \hbox{$-\infty<D<\infty$}. We find that two kinds of magnetization plateaux at a half of the saturation magnetization, the 1/2-plateaux, appear in the ground-state magnetization curve; one of them is of the Haldane type and the other is of the large-$D$-type. We determine the 1/2-plateau phase diagram on the $D$ versus $J$ plane, applying the twisted-boundary-condition level spectroscopy methods developed by Kitazawa and Nomura. We also calculate the ground-state magnetization curves and the magnetization phase diagrams by means of the density-matrix renormalization-group method