2,603 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
Energy transport in strongly disordered superconductors and magnets
We develop an analytical theory for quantum phase transitions driven by
disorder in magnets and superconductors. We study these transitions with a
cavity approximation which becomes exact on a Bethe lattice with large
branching number. We find two different disordered phases, characterized by
very different relaxation rates, which both exhibit strong inhomogeneities
typical of glassy physics.Comment: 4 pages, 1 figur
Structure functions for light nuclei
We discuss the nuclear EMC effect with particular emphasis on recent data for
light nuclei including 2H, 3He, 4He, 9Be, 12C and 14N. In order to verify the
consistency of available data, we calculate the \chi^2 deviation between
different data sets. We find a good agreement between the results from the NMC,
SLAC E139, and HERMES experiments. However, our analysis indicates an overall
normalization offset of about 2% in the data from the recent JLab E03-103
experiment with respect to previous data for nuclei heavier than 3He. We also
discuss the extraction of the neutron/proton structure function ratio F2n/F2p
from the nuclear ratios 3He/2H and 2H/1H. Our analysis shows that the E03-103
data on 3He/2H require a renormalization of about 3% in order to be consistent
with the F2n/F2p ratio obtained from the NMC experiment. After such a
renormalization, the 3He data from the E03-103 data and HERMES experiments are
in a good agreement. Finally, we present a detailed comparison between data and
model calculations, which include a description of the nuclear binding, Fermi
motion and off-shell corrections to the structure functions of bound proton and
neutron, as well as the nuclear pion and shadowing corrections. Overall, a good
agreement with the available data for all nuclei is obtained.Comment: 18 pages, 7 figures, 5 tables, final version published in Phys. Rev.
Thermoelectric properties of Bi2Te3 atomic quintuple thin films
Motivated by recent experimental realizations of quintuple atomic layer films
of Bi2Te3,the thermoelectric figure of merit, ZT, of the quintuple layer is
calculated and found to increase by a factor of 10 (ZT = 7.2) compared to that
of the bulk at room temperature. The large enhancement in ZT results from the
change in the distribution of the valence band density of modes brought about
by the quantum confinement in the thin film. The theoretical model uses ab
initio electronic structure calculations (VASP) with full quantum-mechanical
structure relaxation combined with a Landauer formalism for the linear-response
transport coefficients.Comment: 4 figures, submitted to AP
Enhanced thermoelectric response of hole-doped LaNiO by ab initio calculations
Thermoelectric properties of the system LaNiO have been
studied ab initio. Large Seebeck coefficient values are predicted for the
parent compound, and to some extent remain in the hole-doped metallic phase,
accompanied of an increase in the conductivity. This system, due to its layered
structure would be a suitable candidate for an improvement of its
thermoelectric figure of merit by nanostructurization in thin films, that has
already been shown to increase the electrical conductivity (). Our
calculations show that in the region around LaNiO the system has a
large thermopower at high temperatures and also a substantially increased
. Films grown with this low-doping concentration will show an optimal
relationship between thermopower and . This result is obtained for
various exchange-correlation schemes (correlated, uncorrelated and
parameter-free) that we use to analyze the electronic structure of the
hole-doped compound.Comment: 10 pages, 6 figure
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
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