6,340 research outputs found
Nucleon Effective E-Mass in Neutron-Rich Matter from the Migdal-Luttinger Jump
The well-known Migdal-Luttinger theorem states that the jump of the
single-nucleon momentum distribution at the Fermi surface is equal to the
inverse of the nucleon effective E-mass. Recent experiments studying
short-range correlations (SRC) in nuclei using electron-nucleus scatterings at
the Jefferson National Laboratory (JLAB) together with model calculations
constrained significantly the Migdal-Luttinger jump at saturation density of
nuclear matter. We show that the corresponding nucleon effective E-mass is
consequently constrained to in
symmetric nuclear matter (SNM) and the E-mass of neutrons is smaller than that
of protons in neutron-rich matter. Moreover, the average depletion of the
nucleon Fermi sea increases (decreases) approximately linearly with the isospin
asymmetry according to for protons (neutrons). These results will help improve
our knowledge about the space-time non-locality of the single-nucleon potential
in neutron-rich nucleonic matter useful in both nuclear physics and
astrophysics.Comment: Discussions added. Version accepted by PL
Effects of Neutron-Proton Short-Range Correlation on the Equation of State of Dense Neutron-Rich Nucleonic Matter
The strongly isospin-dependent tensor force leads to short-range correlations
(SRC) between neutron-proton (deuteron-like) pairs much stronger than those
between proton-proton and neutron-neutron pairs. As a result of the short-range
correlations, the single-nucleon momentum distribution develops a high-momentum
tail above the Fermi surface. Because of the strongly isospin-dependent
short-range correlations, in neutron-rich matter a higher fraction of protons
will be depleted from its Fermi sea and populate above the Fermi surface
compared to neutrons. This isospin-dependent nucleon momentum distribution may
have effects on: (1) nucleon spectroscopic factors of rare isotopes, (2) the
equation of state especially the density dependence of nuclear symmetry energy,
(3) the coexistence of a proton-skin in momentum space and a neutron-skin in
coordinate space (i.e., protons move much faster than neutrons near the surface
of heavy nuclei). In this talk, we discuss these features and their possible
experimental manifestations. As an example, SRC effects on the nuclear symmetry
energy are discussed in detail using a modified Gogny-Hartree-Fock (GHF) energy
density functional (EDF) encapsulating the SRC-induced high momentum tail (HMT)
in the single-nucleon momentum distribution
Two-Loop Superstrings in Hyperelliptic Language III: the Four-Particle Amplitude
We compute explicitly the four-particle amplitude in superstring theories by
using the hyperelliptic language and the newly obtained chiral measure of
D'Hoker and Phong. Although the algebra of the intermediate steps is a little
bit involved, we obtain a quite simple expression for the four-particle
amplitude. As expected, the integrand is independent of all the insertion
points. As an application of the obtained result, we show that the perturbative
correction to the term in type II superstring theories is vanishing
point-wise in (even) moduli space at two loops.Comment: v1, LaTex file, 33 pages; v2, 34 pages, add references and minor
correction
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