11,714 research outputs found
Chiral phase transition at high temperature and density in the QCD-like theory
The chiral phase transition at finite temperature T and/or chemical potential
is studied using the QCD-like theory with a variational approach. The
``QCD-like theory'' means the improved ladder approximation with an infrared
cutoff in terms of a modified running coupling. The form of
Cornwall-Jackiw-Tomboulis effective potential is modified by the use of the
Schwinger-Dyson equation for generally nonzero current quark mass. We then
calculate the effective potential at finite T and/or and investigate the
phase structure in the chiral limit. We have a second-order phase transition at
MeV for and a first-order one at MeV for T=0. A
tricritical point in the T- plane is found at T=107 MeV, MeV.
The position is close to that of the random matrix model and some version of
the Nambu-Jona-Lasinio model.Comment: 10 pages, 6 figures. Accepted for publication in Physical Review
Rotor vibration caused by external excitation and rub
For turbomachinery with low natural frequencies, considerations have been recently required for rotor vibrations caused by external forces except unbalance one, such as foundation motion, seismic wave, rub and so forth. Such a forced vibration is investigated analytically and experimentally in the present paper. Vibrations in a rotor-bearing system under a harmonic excitation are analyzed by the modal technique in the case of a linear system including gyroscopic effect. For a nonlinear system a new and powerful quasi-modal technique is developed and applied to the vibration caused by rub
Constituent quark model for nuclear stopping in high energy nuclear collisions
We study the nuclear stopping in high energy nuclear collisions using the
constituent quark model. It is assumed that wounded nucleons with different
number of interacted quarks hadronize in different ways. The probabilities of
having such wounded nucleons are evaluated for proton-proton, proton-nucleus
and nucleus-nucleus collisions. After examining our model in proton-proton and
proton-nucleus collisions and fixing the hadronization functions, it is
extended to nucleus-nucleus collisions. It is used to calculate the rapidity
distribution and the rapidity shift of final state protons in nucleus-nucleus
collisions. The computed results are in good agreement with the experimental
data on ^{32}\mbox{S} +\ ^{32}\mbox{S} at AGeV and
^{208}\mbox{Pb} +\ ^{208}\mbox{Pb} at AGeV. Theoretical
predictions are also given for proton rapidity distribution in ^{197}\mbox{Au}
+\ ^{197}\mbox{Au} at AGeV (BNL-RHIC). We predict that the
nearly baryon free region will appear in the midrapidity region and the
rapidity shift is .Comment: 40 pages, 16 Postscript figures, submitted to Phys. Rev.
Multiscale expansion of the lattice potential KdV equation on functions of infinite slow-varyness order
We present a discrete multiscale expansion of the lattice potential
Korteweg-de Vries (lpKdV) equation on functions of infinite order of
slow-varyness. To do so we introduce a formal expansion of the shift operator
on many lattices holding at all orders. The lowest secularity condition from
the expansion of the lpKdV equation gives a nonlinear lattice equation,
depending on shifts of all orders, of the form of the nonlinear Schr\"odinger
(NLS) equationComment: 9 pages, submitted to Journ. Phys.
Dengue Vectors and their Spatial Distribution
The distribution of dengue vectors, Ae. aegypti and Ae. albopictus, is affected by climatic factors. In addition, since their life cycles are well adapted to the human environment, environmental changes resulting from human activity such as urbanization exert a great impact on vector distribution. The different responses of Ae. aegypti and Ae albopictus to various environments result in a difference in spatial distribution along north-south and urban-rural gradients, and between the indoors and outdoors. In the north-south gradient, climate associated with survival is an important factor in spatial distribution. In the urban-rural gradient, different distribution reflects a difference in adult niches and is modified by geographic and human factors. The direct response of the two species to the environment around houses is related to different spatial distribution indoors and outdoors. Dengue viruses circulate mainly between human and vector mosquitoes, and the vector presence is a limiting factor of transmission. Therefore, spatial distribution of dengue vectors is a significant concern in the epidemiology of the disease
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