5,425 research outputs found
Advection of a passive scalar field by turbulent compressible fluid: renormalization group analysis near
The field theoretic renormalization group (RG) and the operator product
expansion (OPE) are applied to the model of a density field advected by a
random turbulent velocity field. The latter is governed by the stochastic
Navier-Stokes equation for a compressible fluid. The model is considered near
the special space dimension . It is shown that various correlation
functions of the scalar field exhibit anomalous scaling behaviour in the
inertial-convective range. The scaling properties in the RG+OPE approach are
related to fixed points of the renormalization group equations. In comparison
with physically interesting case , at additional Green function
has divergences which affect the existence and stability of fixed points. From
calculations it follows that a new regime arises there and then by continuity
moves into . The corresponding anomalous exponents are identified with
scaling dimensions of certain composite fields and can be systematically
calculated as series in (the exponent, connected with random force) and
. All calculations are performed in the leading one-loop
approximation.Comment: 11pages, 6 figures, LATEX2e. arXiv admin note: substantial text
overlap with arXiv:1611.00327; text overlap with arXiv:1611.0130
Scaling Functions and Superscaling in Medium and Heavy Nuclei
The scaling function for medium and heavy nuclei with
for which the proton and neutron densities are not similar is constructed
within the coherent density fluctuation model (CDFM) as a sum of the proton and
neutron scaling functions. The latter are calculated in the cases of Ni,
Kr, Sn, and Au nuclei on the basis of the corresponding
proton and neutron density distributions which are obtained in deformed
self-consistent mean-field Skyrme HF+BCS method. The results are in a
reasonable agreement with the empirical data from the inclusive electron
scattering from nuclei showing superscaling for negative values of ,
including those smaller than -1. This is an improvement over the relativistic
Fermi gas (RFG) model predictions where becomes abruptly zero for
. It is also an improvement over the CDFM calculations made in
the past for nuclei with assuming that the neutron density is equal
to the proton one and using only the phenomenological charge density.Comment: 4 pages, 1 figure, ReVTeX, accepted for publication in Phys. Rev.
Superscaling in Nuclei: A Search for Scaling Function Beyond the Relativistic Fermi Gas Model
We construct a scaling function for inclusive electron
scattering from nuclei within the Coherent Density Fluctuation Model (CDFM).
The latter is a natural extension to finite nuclei of the Relativistic Fermi
Gas (RFG) model within which the scaling variable was
introduced by Donnelly and collaborators. The calculations show that the
high-momentum components of the nucleon momentum distribution in the CDFM and
their similarity for different nuclei lead to quantitative description of the
superscaling in nuclei. The results are in good agreement with the experimental
data for different transfer momenta showing superscaling for negative values of
, including those smaller than -1.Comment: 16 pages, 5 figures, submitted for publication to Phys. Rev.
3D Georgi-Glashow model and confining strings at zero and finite temperatures
In this review, we discuss the confining and finite-temperature properties of
the 3D SU(N) Georgi-Glashow model, and of 4D compact QED. At zero temperature,
we derive string representations of both theories, thus constructing the
SU(N)-version of Polyakov's theory of confining strings. We discuss the
geometric properties of confining strings, as well as the appearance of the
string theta-term from the field-theoretical one in 4D, and k-string tensions
at N larger than 2. In particular, we point out the relevance of negative
stiffness for stabilizing confining strings, an effect recently re-discovered
in material science. At finite temperature, we present a derivation of the
confining-string free energy and show that, at the one-loop level and for a
certain class of string models in the large-D limit, it matches that of QCD at
large N. This crucial matching is again a consequence of the negative
stiffness. In the discussion of the finite-temperature properties of the 3D
Georgi-Glashow model, in order to be closer to QCD, we mostly concentrate at
the effects produced by some extensions of the model by external matter fields,
such as dynamical fundamental quarks or photinos, in the supersymmetric
generalization of the model.Comment: 79 pages, LaTeX2e, uses ws-procs975x65.cls, no figures, minor
editorial corrections are included. To be published in the Ian Kogan Memorial
Collection "From Fields to Strings: Circumnavigating Theoretical Physics",
World Scientific, 200
Superscaling and Neutral Current Quasielastic Neutrino-Nucleus Scattering beyond the Relativistic Fermi Gas Model
The superscaling analysis is extended to include quasielastic (QE) scattering
via the weak neutral current of neutrinos and antineutrinos from nuclei. The
scaling function obtained within the coherent density fluctuation model (used
previously in calculations of QE inclusive electron and charge-changing (CC)
neutrino scattering) is applied to neutral current neutrino and antineutrino
scattering with energies of 1 GeV from C with a proton and neutron
knockout (u-channel inclusive processes). The results are compared with those
obtained using the scaling function from the relativistic Fermi gas model and
the scaling function as determined from the superscaling analysis (SuSA) of QE
electron scattering.Comment: 10 pages, 6 figures, published in Phys. Rev.
Surface properties of neutron-rich exotic nuclei: A source for studying the nuclear symmetry energy
We study the correlation between the thickness of the neutron skin in finite
nuclei and the nuclear symmetry energy for isotopic chains of even-even Ni, Sn,
and Pb nuclei in the framework of the deformed self-consistent mean-field
Skyrme HF+BCS method. The symmetry energy, the neutron pressure and the
asymmetric compressibility in finite nuclei are calculated within the coherent
density fluctuation model using the symmetry energy as a function of density
within the Brueckner energy-density functional. The mass dependence of the
nuclear symmetry energy and the neutron skin thickness are also studied
together with the role of the neutron-proton asymmetry. A correlation between
the parameters of the equation of state (symmetry energy and its density slope)
and the neutron skin is suggested in the isotopic chains of Ni, Sn, and Pb
nuclei.Comment: 13 pages, 10 figures. Accepted for publication in Phys. Rev.
Symmetry energy of deformed neutron-rich nuclei
The symmetry energy, the neutron pressure and the asymmetric compressibility
of deformed neutron-rich even-even nuclei are calculated on the examples of Kr
and Sm isotopes within the coherent density fluctuation model using the
symmetry energy as a function of density within the Brueckner energy-density
functional. The correlation between the thickness of the neutron skin and the
characteristics related with the density dependence of the nuclear symmetry
energy is investigated for isotopic chains of these nuclei in the framework of
the self-consistent Skyrme-Hartree-Fock plus BCS method. Results for an
extended chain of Pb isotopes are also presented. A remarkable difference is
found in the trend followed by the different isotopic chains: the studied
correlations reveal a smoother behavior in the Pb case than in the other cases.
We also notice that the neutron skin thickness obtained for Pb with
SLy4 force is found to be in a good agreement with recent data.Comment: 14 pages, 10 figures, 2 tables, accepted for publication in Physical
Review
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