144 research outputs found
Nucleon QCD sum rules in nuclear matter including radiative corrections
We calculate the nucleon parameters in nuclear matter using the QCD sum rules
method. The radiative corrections to the leading operator product expansion
terms are included, with the corrections of the order \alpha_s beyond the
logarithmic approximation taken into account. The density dependence of the
influence of radiative corrections on the nucleon parameters is obtained. At
saturation density the radiative corrections increase the values of vector and
scalar self-energies by about 40 MeV, and 30 MeV correspondingly. The results
appear to be stable with respect to possible variations of the value of
\Lambda_{QCD}.Comment: 16 pages, 2 figure
Asymptotic behavior of photoionization cross section in a central field
We demonstrate that the high energy nonrelativistic asymptotic for the
photoionization cross section in a central field can be expressed in
terms of the asymptotic of the Fourier transform of the field. We show
that the cross sections drop in the same way for the fields with the Coulomb
short distance behavior. The character of the cross sections energy behavior is
related to the analytical properties of the function . The cross sections
exhibit power drop for the potentials which have singularities an the real
axis. They suffer the exponential drop if has singularities in the
complex plane.Comment: 11 page
Asymptotic behavior of photoionization cross section in a central field. Ionization of the states
We continue our studies of the high energy nonrelativistic asymptotics for
the photoionization cross section of the systems bound by a central field
. We consider the bound states with the orbital momentum . We
show, that as well as for the states the asymptotics can be obtained
without solving of the wave equations for the bound and outgoing electrons. The
asymptotics of the cross sections is expressed in terms of the asymptotics of
the Fourier transform of the field and its derivative by
employing the Lippmann--Schwinger equation. The shape of the energy dependence
of the cross sections is determined by the analytical properties of the
potential . The cross sections exhibit power drop with the increase of
the photon energy for the potentials which have singularities on the
real axis. They experience exponential drop if has poles in the complex
plane. We trace the energy dependence of the ratios of the photoionization
cross sections for and electrons from the states with the same
principle quantum number. We apply the results to the physics of fullerenes.Comment: 14 page
Holographic Meson Spectra in the Dense Medium with Chiral Condensate
We study two effects on the meson spectra by using the AdS/CFT
correspondence where the corrections from the chiral condensate and the
quark density are controlled by the gravitational backreaction of the massive
scalar field and U(1) gauge field respectively. The dual geometries with zero
and nonzero current quark masses are obtained numerically. We discuss meson
spectra and binding energy of heavy quarkonium with the subleading corrections
in the hard wall model.Comment: 16 pages, 4 figure
Equilibrium of nuclear matter in QCD sum rules
We calculate the nucleon parameters in symmetric nuclear matter employing the
QCD sum rules approach. We focus on the average energy per nucleon and study
the equilibrium states of the matter. We treat the matter as a relativistic
system of interacting nucleons. Assuming the dependence of the nucleon mass on
the light quark mass to be more important than that of nucleon
interactions we find that the contribution of the relativistic nucleons to the
scalar quark condensate can be expressed as that caused by free nucleons at
rest multiplied by the density dependent factor . We demonstrate that
there are no equilibrium states while we include only the condensates with
dimension . There are equilibrium states if we include the lowest
order radiative corrections and the condensates with . They manifest
themselves for the nucleon sigma term MeV. Including the
condensates with we find equilibrium states of nuclear matter for
MeV. In all cases the equilibrium states are due to influence of
the relativistic motion of the nucleons composing the matter on the scalar
quark condensate.Comment: 26 pages, 10 figur
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