790 research outputs found
Low-momentum interactions with Brown-Rho-Ericson scalings and the density dependence of the nuclear symmetry energy
We have calculated the nuclear symmetry energy up to
densities of with the effects from the Brown-Rho (BR) and
Ericson scalings for the in-medium mesons included. Using the
low-momentum interaction with and without such scalings, the equations of state
(EOS) of symmetric and asymmetric nuclear matter have been calculated using a
ring-diagarm formalism where the particle-particle-hole-hole ring diagrams are
included to all orders. The EOS for symmetric nuclear matter and neutron matter
obtained with linear BR scaling are both overly stiff compared with the
empirical constraints of Danielewicz {\it et al.} \cite{daniel02}. In contrast,
satisfactory results are obtained by either using the nonlinear Ericson scaling
or by adding a Skyrme-type three-nucleon force (TNF) to the unscaled
interaction.
Our results for obtained with the nonlinear Ericson scaling
are in good agreement with the empirical values of Tsang {\it et al.}
\cite{tsang09} and Li {\it et al.} \cite{li05}, while those with TNF are
slightly below these values. For densities below the nuclear saturation density
, the results of the above calculations are nearly equivalent to each
other and all in satisfactory agreement with the empirical values.Comment: 7 pages, 6 figure
More on nucleon-nucleon cross sections in symmetric and asymmetric matter
Following a recent work, we present numerical results for total two-nucleon
effective cross sections in isospin symmetric and asymmetric matter. The
present calculations include the additional effect of Pauli blocking of the
final states.Comment: 9 pages, no figures, 5 table
Epoxysuccinyl peptide-derived cathepsin B inhibitors: Modulating membrane permeability by conjugation with the C-terminal heptapeptide segment of penetratin
Besides its physiological role in lysosomal protein breakdown, extralysosomal cathepsin B has recently been implicated in apoptotic cell death. Highly specific irreversible cathepsin B inhibitors that are readily cellpermeant should be useful tools to elucidate the effects of cathepsin B in the cytosol. We have covalently functionalised the poorly cellpermeant epoxysuccinyl based cathepsin B inhibitor [RGlyGlyLeu(2S, 3S)tEpsLeuProOH; R=OMe] with the C-terminal heptapeptide segment of penetratin (R=εAhxArg ArgNleLysTrpLysLysNH(2)). The high inhibitory potency and selectivity for cathepsin B versus cathepsin L of the parent compound was not affected by the conjugation with the penetratin heptapeptide. The conjugate was shown to efficiently penetrate into MCF-7 cells as an active inhibitor, thereby circumventing an intracellular activation step that is required by other inhibitors, such as the prodruglike epoxysuccinyl peptides E64d and CA074Me
The relativistic self-energy in nuclear dynamics
It is a well known fact that Dirac phenomenology of nuclear forces predicts
the existence of large scalar and vector mean fields in matter. To analyse the
relativistic self-energy in a model independent way, modern high precision
nucleon-nucleon () potentials are mapped on a relativistic operator basis
using projection techniques. This allows to compare the various potentials at
the level of covariant amplitudes were a remarkable agreement is found. It
allows further to calculate the relativistic self-energy in nuclear matter in
Hartree-Fock approximation. Independent of the choice of the nucleon-nucleon
interaction large scalar and vector mean fields of several hundred MeV
magnitude are generated at tree level. In the framework of chiral EFT these
fields are dominantly generated by contact terms which occur at next-to-leading
order in the chiral expansion. Consistent with Dirac phenomenology the
corresponding low energy constants which generate the large fields are closely
connected to the spin-orbit interaction in scattering. The connection to
QCD sum rules is discussed as well.Comment: 49 pages, 13 figure
Accurate Charge-Dependent Nucleon-Nucleon Potential at Fourth Order of Chiral Perturbation Theory
We present the first nucleon-nucleon potential at
next-to-next-to-next-to-leading order (fourth order) of chiral perturbation
theory. Charge-dependence is included up to next-to-leading order of the
isospin-violation scheme. The accuracy for the reproduction of the NN data
below 290 MeV lab. energy is comparable to the one of phenomenological
high-precision potentials. Since NN potentials of order three and less are
known to be deficient in quantitative terms, the present work shows that the
fourth order is necessary and sufficient for a reliable NN potential derived
from chiral effective Lagrangians. The new potential provides a promising
starting point for exact few-body calculations and microscopic nuclear
structure theory (including chiral many-body forces derived on the same
footing).Comment: 4 pages Revtex including one figur
Predicting the single-proton/neutron potentials in asymmetric nuclear matter
We discuss the one-body potentials for protons and neutrons obtained from
Dirac-Brueckner-Hartree-Fock calculations of neutron-rich matter, in particular
their dependence upon the degree of proton/neutron asymmetry. The closely
related symmetry potential is compared with empirical information from the
isovector component of the nuclear optical potential.Comment: 9 pages, 6 figures. Minor revisions, added comments, reference
Nuclear forces from chiral EFT: The unfinished business
In spite of the great progress we have seen in recent years in the derivation
of nuclear forces from chiral effective field theory (EFT), some important
issues are still unresolved. In this contribution, we discuss the open problems
which have particular relevance for microscopic nuclear structure, namely, the
proper renormalization of chiral nuclear potentials and sub-leading many-body
forces.Comment: 16 pages, 3 figures; contribution to J. Phys. G, Special Issue, Focus
Section: Open Problems in Nuclear Structur
Recent advances in the theory of nuclear forces
After a brief historical review, we present recent progress in our
understanding of nuclear forces in terms of chiral effective field theory.Comment: 6 pages, 2 figures; talk at International Symposium on Correlations
Dynamics in Nuclei, University of Tokyo, Japan, 31 January-4 February, 200
Neutron star, -stable ring-diagram equation of state and Brown-Rho scaling
Neutron star properties, such as its mass, radius, and moment of inertia, are
calculated by solving the Tolman-Oppenheimer-Volkov (TOV) equations using the
ring-diagram equation of state (EOS) obtained from realistic low-momentum NN
interactions . Several NN potentials (CDBonn, Nijmegen, Argonne V18
and BonnA) have been employed to calculate the ring-diagram EOS where the
particle-particle hole-hole ring diagrams are summed to all orders. The proton
fractions for different radial regions of a -stable neutron star are
determined from the chemical potential conditions . The neutron star masses, radii and moments of inertia given by the
above potentials all tend to be too small compared with the accepted values.
Our results are largely improved with the inclusion of medium corrections based
on Brown-Rho scaling where the in-medium meson masses, particularly those of
, and , are slightly decreased compared with their
in-vacuum values. Representative results using such medium corrected
interactions are neutron star mass , radius km
and moment of inertia . The mass-radius trajectories
given by the above four realistic NN potentials are by and large overlapping.Comment: 12.7 pages, 13 figures, 3 table
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