1,013 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
New Two-Dimensional Integrable Quantum Models from SUSY Intertwining
Supersymmetrical intertwining relations of second order in the derivatives
are investigated for the case of supercharges with deformed hyperbolic metric
. Several classes of particular solutions of these
relations are found. The corresponding Hamiltonians do not allow the
conventional separation of variables, but they commute with symmetry operators
of fourth order in momenta. For some of these models the specific SUSY
procedure of separation of variables is applied.Comment: 18 page
Impurity effects in a two--dimensional system with Dirac spectrum
It is demonstrated that in a two--band 2D system the resonance state is
manifested close to the energy of the Dirac point in the electron spectrum for
the sufficiently large impurity perturbation. With increasing the impurity
concentration, the electron spectrum undergoes the rearrangement, which is
characterized by the opening of the broad quasi--gap in the vicinity of the
nodal point. If the critical concentration for the spectrum rearrangement is
not reached, the domain of localized states remains exponentially small
compared to the bandwidth.Comment: 4 pages, 1 figur
Metal-insulator transition in hydrogenated graphene as manifestation of quasiparticle spectrum rearrangement of anomalous type
We demonstrate that the spectrum rearrangement can be considered as a
precursor of the metal-insulator transition observed in graphene dosed with
hydrogen atoms. The Anderson-type transition is attributed to the coincidence
between the Fermi level and the mobility edge, which appearance is induced by
the spectrum rearrangement. Available experimental data are thoroughly compared
to the theoretical results for the Lifshitz impurity model
The "radiative Delta -> N gamma" decay in light cone QCD
The "g_{Delta N gamma}" coupling for the "Delta -> N gamma" decay is
calculated in framework of the light cone QCD sum rules and is found to be
g_{Delta N gamma} = (1.6 pm 0.2) GeV^(-1). Using this value of g_{Delta N
gamma} we estimate the branching ratio of the Delta^+ -> N gamma decay, which
is in a very good agreement with the experimental result.Comment: 9 pages, 1figures, LaTeX formatte
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
SUSY approach to Pauli Hamiltonians with an axial symmetry
A two-dimensional Pauli Hamiltonian describing the interaction of a neutral
spin-1/2 particle with a magnetic field having axial and second order
symmetries, is considered. After separation of variables, the one-dimensional
matrix Hamiltonian is analyzed from the point of view of supersymmetric quantum
mechanics. Attention is paid to the discrete symmetries of the Hamiltonian and
also to the Hamiltonian hierarchies generated by intertwining operators. The
spectrum is studied by means of the associated matrix shape-invariance. The
relation between the intertwining operators and the second order symmetries is
established and the full set of ladder operators that complete the dynamical
algebra is constructed.Comment: 18 pages, 3 figure
Low temperature field-effect in crystalline organic material
Molecular organic materials offer the promise of novel electronic devices but
also present challenges for understanding charge transport in narrow band
systems. Low temperature studies elucidate fundamental transport processes. We
report the lowest temperature field effect transport results on a crystalline
oligomeric organic material, rubrene. We find field effect switching with
on-off ratio up to 10^7 at temperatures down to 10 K. Gated transport shows a
factor of ~10 suppression of the thermal activation energy in 10-50 K range and
nearly temperature independent resistivity below 10 K.Comment: 5 pages, 4 figure
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