1,745 research outputs found
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-scannerâbased
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 pedestriansâ vision
Precursor of Color Superconductivity
We investigate possible precursory phenomena of color superconductivity at
finite temperature 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 . We show that such a fluctuaiton
forms a collective mode, the corresponding pole of which approaches the origin
as is lowered to 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{} and \hbox{}. 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--type. We determine the
1/2-plateau phase diagram on the versus 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
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