1,939 research outputs found
Spontaneous violation of chiral symmetry in QCD vacuum is the origin of baryon masses and determines baryon magnetic moments and their other static properties
A short review is presented of the spontaneous violation of chiral symmetry
in QCD vacuum. It is demonstrated, that this phenomenon is the origin of baryon
masses in QCD. The value of nucleon mass is calculated as well as the masses of
hyperons and some baryonic resonances and expressed mainly through the values
of quark condensates -- -- the vacuum
expectation values (v.e.v.) of quark field. The concept of vacuum expectation
values induced by external fields is introduced. It is demonstrated that such
v.e.v. induced by static electromagnetic field results in quark condensate
magnetic susceptibility, which plays the main role in determination of baryon
magnetic moments. The magnetic moments of proton, neutron and hyperons are
calculated. The results of calculation of baryon octet -decay constants
are also presented.Comment: 13 pades, 5 figures. Dedicated to 85-birthday of acad. S.T.Belyaev.
To be published in Phys.At.Nucl. Few references are correcte
Chirality violating condensates in QCD and their connection with zero mode solutions of quark Dirac equations
It is demonstrated, that chirality violating condensates in massless QCD
arise entirely from zero mode solutions of Dirac equations in arbitrary gluon
fields. The model is suggested, where the zero mode solutions are the ones for
quarks, moving in the instanton field. Basing on this model were calculated the
quark condensate magnetic susceptibilities of dimensions and 5
( and ). The good considence of the values and
, obtained in this approach with ones, found from the hadronic spectrum ia
a serious argument in favour, that instantons are the only source of chirality
violating condensates in QCD. The temperature dependence of the quark
condensate is discussed. It is shown that the phase transition, corresponding
to the -dependence of the quark condensate as an order
parameter, is of the type of crossover.Comment: The talk presented of Gribov-80 Workshop, May 28-30, 2010, Trieste, 8
pages, minor change
Numerical simulation evidence of spectrum rearrangement in impure graphene
By means of numerical simulation we confirm that in graphene with point
defects a quasigap opens in the vicinity of the resonance state with increasing
impurity concentration. We prove that states inside this quasigap cannot longer
be described by a wavevector and are strongly localized. We visualize states
corresponding to the density of states maxima within the quasigap and show that
they are yielded by impurity pair clusters
The B_{s0} meson and the B_{s0}B K coupling from QCD sum rules
We evaluate the mass of the scalar meson and the coupling constant
in the vertex in the framework of QCD sum rules. We consider the
as a tetraquark state to evaluate its mass. We get m_{B_s0}=(6.04\pm
0.08) \GeV, which is bigger than predictions supposing it as a
state or a bound state with . To evaluate the coupling we use the three point correlation functions of the vertex,
considering as a normal state. The obtained coupling
constant is: g_{B_{s0} B K} =(16.3 \pm 3.2) \GeV. This number is in agreement
with light-cone QCD sum rules calculation. We have also compared the decay
width of the \BS\to BK process considering the \BS to be a state
and a molecular state. The width obtained for the molecular state is
twice as big as the width obtained for the state. Therefore, we
conclude that with the knowledge of the mass and the decay width of the \BS
meson, one can discriminate between the different theoretical proposals for its
structure.Comment: revised version to appear in Phys. Rev.
Implications of the Crystal Barrel data for meson-baryon symmetries
Making use of numerous resonances discovered by the Crystal Barrel
Collaboration we discuss some possible relations between the baryon and meson
spectra of resonances composed of the light non-strange quarks. Our goal is to
indicate new features that should be reproduced by the realistic dynamical
models describing the hadron spectrum in the sector of light quarks.Comment: Completely modified version; to appear in Mod. Phys. Lett.
Thermoelectricity in Nanowires: A Generic Model
By employing a Boltzmann transport equation and using an energy and size
dependent relaxation time () approximation (RTA), we evaluate
self-consistently the thermoelectric figure-of-merit of a quantum wire
with rectangular cross-section. The inferred shows abrupt enhancement in
comparison to its counterparts in bulk systems. Still, the estimated for
the representative BiTe nanowires and its dependence on wire parameters
deviate considerably from those predicted by the existing RTA models with a
constant . In addition, we address contribution of the higher energy
subbands to the transport phenomena, the effect of chemical potential tuning on
, and correlation of with quantum size effects (QSEs). The obtained
results are of general validity for a wide class of systems and may prove
useful in the ongoing development of the modern thermoelectric applications.Comment: 15 pages, 6 figures; Dedicated to the memory of Amirkhan Qezell
Combination Rules, Charge Symmetry, and Hall Effect in Cuprates
The rule relating the observed Hall coefficient to the spin and charge
responses of the uniform doped Mott insulator is derived. It is essential to
include the contribution of holon and spinon three-current correlations to the
effective action of the gauge field. In the vicinity of the Mott insulating
point the Hall coefficient is holon dominated and weakly temperature dependent.
In the vicinity of a point of charge conjugation symmetry the holon
contribution to the observed Hall coefficient is small: the Hall coefficient
follows the temperature dependence of the diamagnetic susceptibility with a
sign determined by the Fermi surface shape. NOTE: document prepared using
REVTEX. (3 Figs, not included, available on request from: [email protected])Comment: 8 page
Rho-meson form factors and QCD sum rules
We present predictions for rho-meson form factors obtained from the analysis
of QCD sum rules in next-to-leading order of perturbation theory. The radiative
corrections turn out to be sizeable and should be taken into account in
rigorous theoretical analysis.Comment: LaTeX file, 14 pages, 7 figure
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