13,419 research outputs found
Phase Structure of Color Superconductivity
We investigate color superconductivity and chiral symmetry restoration at
finite temperature and baryon density in the frame of standard two flavor
Nambu--Jona-Lasinio model. We derive the diquark mass in RPA, discuss its
constraint on the coupling constant in the diquark channel, and find a strong
competition between the two phase transitions when the coupling constant is
large enough.Comment: Talk presented at Conference on Non-Perturbative Quantum Field
Theory: Lattice and Beyond, Guangzhou, China, Dec.16--18, 200
Turbulent shear-layer mixing: growth-rate compressibility scaling
A new shear-layer growth-rate compressibility-scaling parameter is proposed as an alternative to the total convective Mach number, Mc. This parameter derives from considerations of compressibility as a means of kinetic-to-thermal-energy conversion and can be significantly different from Mc for flows with far-from-unity free-stream-density and speed-of-sound ratios. Experimentally observed growth rates are well-represented by the new scaling
Active optical clock based on four-level quantum system
Active optical clock, a new conception of atomic clock, has been proposed
recently. In this report, we propose a scheme of active optical clock based on
four-level quantum system. The final accuracy and stability of two-level
quantum system are limited by second-order Doppler shift of thermal atomic
beam. To three-level quantum system, they are mainly limited by light shift of
pumping laser field. These limitations can be avoided effectively by applying
the scheme proposed here. Rubidium atom four-level quantum system, as a typical
example, is discussed in this paper. The population inversion between
and states can be built up at a time scale of s.
With the mechanism of active optical clock, in which the cavity mode linewidth
is much wider than that of the laser gain profile, it can output a laser with
quantum-limited linewidth narrower than 1 Hz in theory. An experimental
configuration is designed to realize this active optical clock.Comment: 5 page
Primitive Cohomology of Hopf algebras
Primitive cohomology of a Hopf algebra is defined by using a modification of
the cobar construction of the underlying coalgebra. Among many of its
applications, two classifications are presented. Firstly we classify all non
locally PI, pointed Hopf algebra domains of Gelfand-Kirillov dimension two; and
secondly we classify all pointed Hopf algebras of rank one. The first
classification extends some results of Brown, Goodearl and others in an ongoing
project to understand all Hopf algebras of low Gelfand-Kirillov dimension. The
second generalizes results of Krop-Radford and Wang-You-Chen which classified
Hopf algebras of rank one under extra hypothesis. Properties and algebraic
structures of the primitive cohomology are discussed
Effect of depreciation of the public goods in spatial public goods games
In this work, depreciated effect of the public goods is considered in the
public goods games, which is realized by rescaling the multiplication factor r
of each group as r' = r(nc/G)^beta (beat>= 0). It is assumed that each
individual enjoys the full profit of the public goods if all the players of
this group are cooperators, otherwise, the value of the public goods is reduced
to r'. It is found that compared with the original version (beta = 0),
emergence of cooperation is remarkably promoted for beta > 0, and there exit
optimal values of beta inducing the best cooperation. Moreover, the optimal
plat of beta broadens as r increases. Furthermore, effect of noise on the
evolution of cooperation is studied, it is presented that variation of
cooperator density with the noise is dependent of the value of beta and r, and
cooperation dominates over most of the range of noise at an intermediate value
of beta = 1.0. We study the initial distribution of the multiplication factor
at beta = 1.0, and find that all the distributions can be described as Gauss
distribution
Low-momentum Pion Enhancement Induced by Chiral Symmetry Restoration
The thermal and nonthermal pion production by sigma decay and its relation
with chiral symmetry restoration in a hot and dense matter are investigated.
The nonthermal decay into pions of sigma mesons which are popularly produced in
chiral symmetric phase leads to a low-momentum pion enhancement as a possible
signature of chiral phase transition at finite temperature and density.Comment: 3 pages, 2 figure
- …