248,316 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
Relationships of the Genera \u3ci\u3eAcanthametropus, Analetris,\u3c/i\u3e and \u3ci\u3eSiphluriscus\u3c/i\u3e, and Re-Evaluation of Their Higher Classification (Ephemeroptera: Pisciforma)
The historical higher classification of the genera Acanthametropus Tshernova, Analetris Edmunds, and Siphluriscus Ulmer is reviewed. The first comprehensive generic description of Siphluriscus is given, and first figures of wings are provided. A cladistic analysis of adult and larval characters of Acanthametropus and Analetris. and adult characters of Siphluriscus reveal a close relationship between the former two genera, which represent a well-defined clade based on five identified synapomorphies; however, Siphluriscus, which has been classified with them in the past, does not share any apomorphies with them but instead shares apomorphies with the genera of Siphlonuridae sensu stricto. Acanthametropus and Analetris are recombined in the family Acanthametropodidae, suppressing Analetrididae; and Siphluriscus is reassigned to the family Siphlonuridae sensu stricto, although taxon rank for both of these clades is still tentative and awaits comparative cladistic analysis of the entire suborder Pisciforma. The relationship to each other of these clades also remains in doubt. Stackelbergisca Tshernova, a fossil genus formerly classified with the three extant genera apparently does not share any of the 11 apomorphies used in this study, and is placed as family incertae within the Pisciforma
Phase transition from hadronic matter to quark matter
We study the phase transition from nuclear matter to quark matter within the
SU(3) quark mean field model and NJL model. The SU(3) quark mean field model is
used to give the equation of state for nuclear matter, while the equation of
state for color superconducting quark matter is calculated within the NJL
model. It is found that at low temperature, the phase transition from nuclear
to color superconducting quark matter will take place when the density is of
order 2.5 - 5. At zero density, the quark phase will appear
when the temperature is larger than about 148 MeV. The phase transition from
nuclear matter to quark matter is always first order, whereas the transition
between color superconducting quark matter and normal quark matter is second
order.Comment: 18 pages, 11 figure
An Universal Quantum Network - Quantum CPU
An universal quantum network which can implement a general quantum computing
is proposed. In this sense, it can be called the quantum central processing
unit (QCPU). For a given quantum computing, its realization of QCPU is just its
quantum network. QCPU is standard and easy-assemble because it only has two
kinds of basic elements and two auxiliary elements. QCPU and its realizations
are scalable, that is, they can be connected together, and so they can
construct the whole quantum network to implement the general quantum algorithm
and quantum simulating procedure.Comment: 8 pages, Revised versio
Anisotropic microwave conductivity of cuprate superconductors in the presence of CuO chain induced impurities
The anisotropy in the microwave conductivity of the ortho-II
YBaCuO is studied within the kinetic energy driven
superconducting mechanism. The ortho-II YBaCuO is
characterized by a periodic alternative of filled and empty -axis CuO
chains. By considering the CuO chain induced extended anisotropy impurity
scattering, the main features of the anisotropy in the microwave conductivity
of the ortho-II YBaCuO are reproduced based on the nodal
approximation of the quasiparticle excitations and scattering processes,
including the intensity and lineshape of the energy and temperature dependence
of the -axis and -axis microwave conductivities. Our results
also confirm that the -axis CuO chain induced impurity is the main
source of the anisotropy.Comment: 6 pages, 3 figure
The NJL model and strange quark matter
The stability of strange quark matter is studied within the Nambu
Jona-Lasinio model with three different parameter sets. The model Lagrangian
contains 4-fermion (with and without vector interaction) and 6-fermion terms;
the minimum energy per baryon number as a function of the strangeness fraction
of the system is compared to the masses of hyperons having the same strangeness
fraction, and coherently calculated in the same version of the model, and for
the same parameter set. The results show that in none of the different
parameter sets strangelets are stable, and in some cases a minimum in the
energy per baryon does not even exist.Comment: 8 pages, 2 figures, reference added, typos corrected, version to
appear in Europhys. Let
The First Moments of Nucleon Generalized Parton Distributions
We extrapolate the first moments of the generalized parton distributions
using heavy baryon chiral perturbation theory. The calculation is based on the
one loop level with the finite range regularization. The description of the
lattice data is satisfactory and the extrapolated moments at physical pion mass
are consistent with the results obtained with dimensional regularization,
although the extrapolation in the momentum transfer to does show
sensitivity to form factor effects which lie outside the realm of chiral
perturbation theory. We discuss the significance of the results in the light of
modern experiments as well as QCD inspired models.Comment: 14 pages, 9 figure
Large Component QCD and Theoretical Framework of Heavy Quark Effective Field Theory
Based on a large component QCD derived directly from full QCD by integrating
over the small components of quark fields with , an
alternative quantization procedure is adopted to establish a basic theoretical
framework of heavy quark effective field theory (HQEFT) in the sense of
effective quantum field theory. The procedure concerns quantum generators of
Poincare group, Hilbert and Fock space, anticommutations and velocity
super-selection rule, propagator and Feynman rules, finite mass corrections,
trivialization of gluon couplings and renormalization of Wilson loop. The
Lorentz invariance and discrete symmetries in HQEFT are explicitly illustrated.
Some new symmetries in the infinite mass limit are discussed. Weak transition
matrix elements and masses of hadrons in HQEFT are well defined to display a
manifest spin-flavor symmetry and corrections. A simple trace
formulation approach is explicitly demonstrated by using LSZ reduction formula
in HQEFT, and shown to be very useful for parameterizing the transition form
factors via expansion. As the heavy quark and antiquark fields in HQEFT
are treated on the same footing in a fully symmetric way, the quark-antiquark
coupling terms naturally appear and play important roles for simplifying the
structure of transition matrix elements, and for understanding the concept of
`dressed heavy quark' - hadron duality. In the case that the `longitudinal' and
`transverse' residual momenta of heavy quark are at the same order of power
counting, HQEFT provides a consistent approach for systematically analyzing
heavy quark expansion in terms of . Some interesting features in
applications of HQEFT to heavy hadron systems are briefly outlined.Comment: 59 pages, RevTex, no figures, published versio
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