48,532 research outputs found
Large-N analysis of (2+1)-dimensional Thirring model
We analyze -dimensional vector-vector type four-Fermi interaction
(Thirring) model in the framework of the expansion. By solving the
Dyson-Schwinger equation in the large- limit, we show that in the
two-component formalism the fermions acquire parity-violating mass dynamically
in the range of the dimensionless coupling , . The symmetry
breaking pattern is, however, in a way to conserve the overall parity of the
theory such that the Chern-Simons term is not induced at any orders in .
turns out to be a non-perturbative UV-fixed point in . The
function is calculated to be
near the fixed point, and the UV-fixed point and the function are shown
exact in the expansion.Comment: 14 pages Latex. (Revised version: some changes have been made and
references added.) To appear in Phys. Rev. D, SNUTP 93-4
A note on color neutrality in NJL-type models
By referring to the underlying physics behind the color charge neutrality
condition in quark matter, we discuss how this condition should be properly
imposed in NJL-type models in a phenomenologically meaningful way. In
particular, we show that the standard assumption regarding the use of two color
chemical potentials, chosen in a very special way, is not justified in general.
When used uncritically, such an approach leads to wrong or unphysical
conclusions.Comment: 4 pages, no figure; v2: minor clarifications, references adde
Analysis on the evolution and governance of the biotechnology industry of China
The past twenty years have witnessed the high-speed growth of China’s biotechnology industry, and this presents an excellent opportunity to examine the changes that have taken place, especially, to carry out overall evaluation and governance analysis from the perspective of technology policies. Although China’s biotechnology industry has achieved tremendous extension both in scale and structure, the strengths it gained from basic research have been significantly weakened by commercialization. This has resulted in the comparatively limited scale of the whole industry, innovation-lacking products, poor output from research and development and scarcity of industrial resources. A large range of literature regarding China’s biotechnology industry attributes these outcomes to vague and even inappropriate governance, findings supported mainly by analyses based on the linear model of impact of government policies on industrial development. In these analyses, government, enterprises and companies as well as R&D organizations are either put on the opposite poles or in a straight line.
After examining the nature of China’s biotechnology industry, and in particular the dynamic procedures in research and development, the authors of this paper argue that besides government, enterprises and R&D organizations, a diverse array of factors should be taken into account as we tackle issues emerging in understanding the development of China’s biotechnology industry. Furthermore, these factors, human or nonhuman, should not be arranged as opposing poles or linearly connected points on a straight line. They are in fact all knitted in networks and act as both knitters and knots.
China’s biotechnology industry gains its strength to develop and evolve from these networks, thus its governance must be aimed at improving their stability and quality.
Although the main disciplinary perspectives of this research are historical and sociological (including identification of the three development stages of biotechnology in China since 1978 to present days), a large number of concepts and ideas from management studies as well as an interdisciplinary approach are also incorporated into the analysis.
The main model used in this research is Actor Network Theory, which is employed as a basic theoretical frame. From this starting point the authors attempt to make a closer examination of China’s biotechnology industry both at the level of technology research and development and at the level of commercialization. The modeling process in this research can be regarded as an attempt to explore the social construction of China’s biotechnology industry. The paper reveals how China’s biotechnology industry develops in the form of networks within the country’s social context and what kinds of relationships exist among the relevant factors; therefore, providing guiding insights for improving the governance of China’s biotechnology industry both in policy and management
Neutrino Interactions In Color-Flavor-Locked Dense Matter
At high density, diquarks could condense in the vacuum with the QCD color
spontaneously broken. Based on the observation that the symmetry breaking
pattern involved in this phenomenon is essentially the same as that of the
Pati-Salam model with broken electroweak--color SU(3) group, we determine the
relevant electroweak interactions in the color-flavor locked (CFL) phase in
high density QCD. We briefly comment on the possible implications on the
cooling of neutron stars.Comment: 13 pages. LaTeX. Talk given at the First KIAS Workshop on
Astrophysics, Seoul, May 2000; V2. references added. comments on cooling
change
Mass Terms in Effective Theories of High Density Quark Matter
We study the structure of mass terms in the effective theory for
quasi-particles in QCD at high baryon density. To next-to-leading order in the
expansion we find two types of mass terms, chirality conserving
two-fermion operators and chirality violating four-fermion operators. In the
effective chiral theory for Goldstone modes in the color-flavor-locked (CFL)
phase the former terms correspond to effective chemical potentials, while the
latter lead to Lorentz invariant mass terms. We compute the masses of Goldstone
bosons in the CFL phase, confirming earlier results by Son and Stephanov as
well as Bedaque and Sch\"afer. We show that to leading order in the coupling
constant there is no anti-particle gap contribution to the mass of
Goldstone modes, and that our results are independent of the choice of gauge.Comment: 22 pages, 4 figure
QCD phase diagram and the critical point
The recent progress in understanding the QCD phase diagram and the physics of
the QCD critical point is reviewed.Comment: 18 pages, 11 figures, for proceedings of "Finite Density QCD at
Nara", July 200
Chiral condensate and dressed Polyakov loop in the Nambu--Jona-Lasinio model
We investigate the chiral condensate and the dressed Polyakov loop or dual
chiral condensate at finite temperature and density in two-flavor
Nambu--Jona-Lasinio model. The dressed Polyakov loop is regarded as an
equivalent order parameter of deconfinement phase transition in a confining
theory. We find the behavior of dressed Polyakov loop in absence of any
confinement mechanism is quite interesting, with only quark degrees of freedom
present, it still shows an order parameter like behavior. It is found that in
the chiral limit, the critical temperature for chiral phase transition
coincides with that of the dressed Polyakov loop in the whole plane.
In the case of explicit chiral symmetry breaking, it is found that the
transition temperature for chiral restoration is smaller than that
of the dressed Polyakov loop in the low baryon density region
where the transition is a crossover. With the increase of current quark mass
the difference between the two transition temperatures is found to be
increasing. However, the two critical temperatures coincide in the high baryon
density region where the phase transition is of first order. We give an
explanation on the feature of in the case of 1st and
2nd order phase transitions, and in the case of
crossover, and expect this feature is general and can be extended to full QCD
theory. Our result might indicate that in the case of crossover, there exists a
small region where chiral symmetry is restored but the color degrees of freedom
are still confined.Comment: 7 pages, 10 figure
- …