26,512 research outputs found

### An alternative understanding of mass formulas in terms of nuclear structure

A typical form of mass formula is re-explained in terms of nuclear structure.
For $N \approx Z$ nuclei, we propose to start with the shell model picture
and to consider the T=0 $2n-2p$ ($\alpha$-like) correlations as the fundamental
concept, instead of the symmetry energy.
Subsequently, the symmetry energy is described on the basis of the
$\alpha$-like superfluidity caused by the T=0 $2n-2p$ correlations, in parallel
with the pairing energy described on the basis of the pairing superfluidity.
This re-explanation gives useful insight for understanding the nuclear mass
formula. The origin of the Wigner energy is also explained in an interacting
boson model for the Cooper pairs in the $\alpha$-like superfluid vacuum. Adding
a correction term due to the T=0 $2n-2p$ correlations, which determines the T=0
base level for nuclear masses, can improve the mass formulas in practice.Comment: to be published in Prog. Theor. Phys. Vol. 113, No.

### Global features of proton-neutron interactions and symmetry energy

We study global features of proton-neutron (p-n) interactions and symmetry
energy over a wide range of nuclei, using a schematic model interaction with
four forces proposed recently.
Calculations are performed by the BCS approximation in N,Z=20-50 and
N,Z=50-82 regions. The experimental double differences of binding energies and
symmetry energy are reproduced quite well.
It is shown that the isoscalar p-n interactions with all J are indispensable
for explaining the binding energies of not only
$N\approx Z$ but also N>Z nuclei in the A=40-160 region.Comment: 15 pages, 4 figures, submitted to Phys. Lett.

### High-loop perturbative renormalization constants for Lattice QCD (III): three-loop quark currents for Iwasaki gauge action and n_f=4 Wilson fermions

This is the third of a series of papers on three-loop computation of
renormalization constants for Lattice QCD. Our main point of interest are
results for the regularization defined by Iwasaki gauge action and n_f=4 Wilson
fermions. Our results for quark bilinears renormalized according to the RI'-MOM
scheme can be compared to non-perturbative results. The latter are available
for Twisted Mass QCD: being defined in the chiral limit, renormalization
constants must be the same. We also address more general problems. In
particular, we discuss a few methodological issues connected to summing the
perturbative series such as the effectiveness of Boosted Perturbation Theory
and the disentanglement of irrelevant and finite volume contributions.
Discussing these issues we consider ont only the new results of this paper, but
also those for the regularization defined by tree-level Symanzik improved gauge
action and n_f=2 Wilson fermions, which we presented in a recent paper of ours.
We finally comment to which extent the techniques we put at work in the NSPT
context can provide a fresher look into the lattice version of the RI'-MOM
scheme.Comment: 20 pages, 4 figures, pdflatex The Section on different ways of
summing the series has been updated: a few extra informations have been
provided and a clearer notation has been introduce

### A possible mechanism to cause the quasi-biennial variability on the solar neutrino flux

It is suggested that the quasi-biennial change in the observed flux of the solar neutrinos is causally related to some non-linear process at the central core of the Sun, being associated with the charge in the central temperature. This process seems to be responsible for the physical adjustment of the internal structure of the Sun. Numerical simulation on this process is able to reproduce the quasi-biennial change in the flux of these neutrinos

### Structure of isomeric states in 66As and 67As

Strong residual correlations between neutrons and protons in N ~ Z systems
can lead to unusual structure. Using the spherical shell model, we show that a
low-excitation shape isomer can occur in the odd-odd N=Z nucleus 66As. This
extends the picture of shape coexistence beyond even-even nuclei. Furthermore,
it is demonstrated that in 66As and in the N=Z+1 nucleus 67As, a new type of
isomer, which we term j-isomer, can be formed. The underlying mechanism for the
isomerism formation is structure change in the isomeric states, which involves
either an alignment of a neutron-proton pair from the high-j intruder orbitals,
or a simultaneous occupation of these neutron and proton high-j orbitals.Comment: 11 pages, 2 figure

### Electronic structure and the Fermi surface of UTGa_{5} (T=Fe, Co, Rh)

The relativistic energy-band calculations have been carried out for
UFeGa_{5}, UCoGa_{5} and URhGa_{5} under the assumption that 5f-electrons are
itinerant. A hybridization between the U 5f state and Ga 4p state occurs in the
vicinity of the Fermi level. The Fermi surface of UCoGa_{5} is quite similar to
that of URhGa_{5}, which are all small in size and closed in topology.
UFeGa_{5} has the quasi-two-dimensional Fermi surface which looks like a
lattice structure.Comment: 2 pages, 3 figures, LT23auth.cls, elsart.cls. submitted to conference
LT2

### Superconductivity of Quasi-One-Dimensional Electrons in Strong Magnetic Field

The superconductivity of quasi-one-dimensional electrons in the magnetic
field is studied. The system is described as the one-dimensional electrons with
no frustration due to the magnetic field. The interaction is assumed to be
attractive between electrons in the nearest chains, which corresponds to the
lines of nodes of the energy gap in the absence of the magnetic field. The
effective interaction depends on the magnetic field and the transverse
momentum. As the magnetic field becomes strong, the transition temperature of
the spin-triplet superconductivity oscillates, while that of the spin-singlet
increases monotonically.Comment: 15 pages, RevTeX, 3 PostScript figures in uuencoded compressed tar
file are appende

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