2,859 research outputs found

### Quark distributions in QCD sum rules: unexpected features and paradoxes

Some very unusual features of the hadron structure functions, obtained in the
generalized QCD sum rules, like the surprisingly strong difference between
longitudinally and transversally polarized $\rho$ mesons structure functions
and the strong suppression of the gluon sea in longitudinally polarized $\rho$
mesons are discussed. Also the problem of exact zero contribution of gluon
condensates to pion and longitudinally polarized $\rho$ meson quark
distributions is discussed.Comment: 9 pages, 5 fig

### Comment on "Remark on the external-field method in QCD sum rules"

It is proved, that suggested by Jin modified formalism in the external-field
method in QCD sum rules exactly coincides with the formalism used before.
Therefore, unlike the claims of ref.1, this formalism cannot improve the
predictability and reliability of external-field sum rule calculations in
comparison with those, done by the standard approach.
PACS number(s): 12.38.Lg, 11.55.HxComment: 5 pages, RevTe

### 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 -- $, ~q=u,d,s$ -- 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 $\beta$-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

### Rigorous Non-Perturbative Ornstein-Zernike Theory for Ising Ferromagnets

We rigorously derive the Ornstein-Zernike asymptotics of the pair-correlation
functions for finite-range Ising ferromagnets in any dimensions and at any
temperature above critical

### The influence of baryons on the chiral phase transition in QCD

A qualitative analysis of the chiral phase transition in QCD with two
massless quarks and non--zero baryon density is performed. It is assumed that
at zero baryonic density, $\rho=0$, the temperature phase transition is of the
second order. Due to a specific power dependence of baryon masses on the chiral
condensate the phase transition becomes of the first order at the temperature
$T=T_{\mathrm{ph}}(\rho)$ for $\rho>0$. At temperatures
$T_{\mathrm{cont}}(\rho) > T > T_{\mathrm{ph}}(\rho)$ there is a mixed phase
consisting of the quark phase (stable) and the hadron phase (unstable). At the
temperature $T = T_{\mathrm{cont}}(\rho)$ the system experiences a continuous
transition to the pure chirally symmetric phase.Comment: 5 pages, 4 figures, presented to Ian Kogan Memorial Volum

### Hyperon-nucleon coupling from QCD sum rules

The NKY coupling constant for $Y = \Lambda$ and $\Sigma$ is evaluated in a
QCD sum rule calculation. We discuss and extend the result of a previous
analysis in the $\rlap{/}{q}i\gamma_5$ structure and compare it with the result
obtained with the use of the $\gamma_5 \sigma_{\mu \nu}$ structure. We find a
huge violation of the SU(3) symmetry in the $\gamma_5 \sigma_{\mu \nu}$
structure.Comment: 4 pages, 2 figures, espcrc2.sty included. Talk presented at QCD99,
Montpellier, France (to appear in Nucl.Phys.B Proc.Suppl.

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