295,183 research outputs found
Liquid-gas phase transition in nuclear matter including strangeness
We apply the chiral SU(3) quark mean field model to study the properties of
strange hadronic matter at finite temperature. The liquid-gas phase transition
is studied as a function of the strangeness fraction. The pressure of the
system cannot remain constant during the phase transition, since there are two
independent conserved charges (baryon and strangeness number). In a range of
temperatures around 15 MeV (precise values depending on the model used) the
equation of state exhibits multiple bifurcates. The difference in the
strangeness fraction between the liquid and gas phases is small when they
coexist. The critical temperature of strange matter turns out to be a
non-trivial function of the strangeness fraction.Comment: 15 pages, 7 figure
QCD Evolutions of Twist-3 Chirality-Odd Operators
We study the scale dependence of twist-3 distributions defined with
chirality-odd quark-gluon operators. To derive the scale dependence we
explicitly calculate these distributions of multi-parton states instead of a
hadron. Taking one-loop corrections into account we obtain the leading
evolution kernel in the most general case. In some special cases the evolutions
are simplified. We observe that the obtained kernel in general does not get
simplified in the large- limit in contrast to the case of those twist-3
distributions defined only with chirality-odd quark operators. In the later,
the simplification is significant.Comment: 9 pages, 2 figure
H∞ controller design for networked predictive control systems based on the average dwell-time approach
This brief focuses on the problem of H∞ control for a class of networked control systems with time-varying delay in both forward and backward channels. Based on the average dwell-time method, a novel delay-compensation strategy is proposed by appropriately assigning the subsystem or designing the switching signals. Combined with this strategy, an improved predictive controller design approach in which the controller gain varies with the delay is presented to guarantee that the closed-loop system is exponentially stable with an H∞-norm bound for a class of switching signal in terms of nonlinear matrix inequalities. Furthermore, an iterative algorithm is presented to solve these nonlinear matrix inequalities to obtain a suboptimal minimum disturbance attenuation level. A numerical example illustrates the effectiveness of the proposed method
Interaction induced mergence of Dirac points in Non-Abelian optical lattices
We study the properties of an ultracold Fermi gas loaded in a square optical
lattice and subjected to an external and classical non-Abelian gauge field. We
calculate the energy spectrum of the system and show that the Dirac points in
the energy spectrum will remain quite stable under onsite interaction of
certain strength. Once the on-site interaction grows stronger than a critical
value, the Dirac points will no longer be stable and merge into a single hybrid
point. This mergence implies a quantum phase transition from a semimetallic
phase to a band insulator. The on-site interaction between ultracold fermions
could be conveniently controlled by Feshbach resonances in current experiments.
We proposed that this remarkable interaction induced mergence of Dirac points
may be observed in the ultracold fermi gas experiments
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