1,600 research outputs found
Di-neutron correlation in light neutron-rich nuclei
Using a three-body model with density-dependent contact interaction, we
discuss the root mean square distance between the two valence neutrons in
Li nuclues as a function of the center of mass of the neutrons relative
to the core nucleus Li. We show that the mean distance takes a pronounced
minimum around the surface of the nucleus, indicating a strong surface
di-neutron correlation. We demonstrate that the pairing correlation plays an
essential role in this behavior. We also discuss the di-neutron structure in
the He nucleus.Comment: A talk given at Franco-Japanese symposium on "New Paradigms in
Nuclear Physics", Sep. 29-Oct. 2, 2008, Paris, Franc
Atomic Bose-Fermi mixed condensates with Boson-Fermion quasi-bound cluster states
The boson-fermion atomic bound states (composite fermion) and their roles for
the phase structures are studied in a bose-fermi mixed condensate of atomic gas
in finite temperature and density. The two-body scattering equation is
formulated for a boson-fermion pair in the mixed condensate with the
Yamaguchi-type potential. By solving the equation, we evaluate the binding
energy of a composite fermion, and show that it has small T-dependence in the
physical region, because of the cancellation of the boson- and fermion-
statistical factors in the equation. We also calculate the phase structure of
the BF mixed condensate under the equilibrium B+F -> BF, and discuss the role
of the composite fermions: the competitions between the degenerate state of the
composite fermions and the Bose-Einstein condensate (BEC) of isolated bosons.
The criterion for the BEC realization is obtained from the
algebraically-derived phase diagrams at T=0.Comment: 5 pages, 3 figure
Random Phase Approximation and Extensions Applied to a Bosonic Field Theory
An application of a self-consistent version of RPA to quantum field theory
with broken symmetry is presented. Although our approach can be applied to any
bosonic field theory, we specifically study the theory in 1+1
dimensions. We show that standard RPA approach leads to an instability which
can be removed when going to a superior version,i.e. the renormalized RPA. We
present a method based on the so-called charging formula of the many electron
problem to calculate the correlation energy and the RPA effective potential.Comment: 30 pages, LaTeX file, 10 figures included, final version accepted in
EPJ
Alpha-particle condensation in nuclei
A round up of the present status of the conjecture that n alpha nuclei form
an alpha-particle condensate in excited states close to the n alpha threshold
is given. Experiments which could demonstrate the condensate character are
proposed. Possible lines of further theoretical developments are discussed.Comment: 6 page
Nuclear Pairing in the T=0 channel revisited
Recent published data on the isoscalar gap in symmetric nuclear matter using
the Paris force and the corresponding BHF single particle dispersion are
corrected leading to an extremely high proton-neutron gap of
MeV at . Arguments whether this value can be reduced due
to screening effects are discussed. A density dependent delta interaction with
cut off is adjusted so as to approximately reproduce the nuclear matter values
with the Paris force.Comment: 4 pages, 4 figure
Vertex renormalization in weak decays of Cooper pairs and cooling compact stars
At temperatures below the critical temperature of superfluid phase transition baryonic matter emits neutrinos by breaking and recombination of Cooper pairs formed in the condensate. The strong interactions in the nuclear medium modify the weak interaction vertices and the associated neutrino loss rates. We study these modifications non-perturbatively by summing infinite series of particle-hole diagrams in the S-wave superfluid neutron matter. We argue that a consistent approach requires fulfillment of the dispersion relations for the polarization tensor, which insure the unitarity of the S-matrix. The pairing and particle-hole interactions in neutron matter are described in the framework of the BCS and Fermi-liquid theories derived from microscopic interactions. The neutrino loss rates in the vector channel are enhanced compared to the rates derived from free-space weak vertices in the temperature domain close to the critical temperature, T_c, but are suppressed by factors 5-10 for temperatures below 0.5 T_c. The vertex corrected axial vector current emission is suppressed by the ratio of the baryon to the neutrino velocity squared
ON THE ROLE OF QUANTUM AND STATISTICAL EFFECTS IN THE LIQUID GAS PHASE TRANSITION OF HOT NUCLEI
The triggering of the liquid-gas phase transition in hot nuclear matter by quantum and statistical fluctuations is studied in a microscopic approach to nucleation, which is a fluid-dynamical version of the imaginary time dependent mean field theory at finite temperature
Boson-Fermion pairing in a Boson-Fermion environment
Propagation of a Boson-Fermion (B-F) pair in a B-F environment is considered.
The possibility of formation of stable strongly correlated B-F pairs, embedded
in the continuum, is pointed out. The new Fermi gas of correlated B-F pairs
shows a strongly modified Fermi surface. The interaction between like particles
is neglected in this exploratory study. Various physical situations where our
new pairing mechanism could be of importance are invoked.Comment: 8 pages, 8 figers, to be published in Phys. Rev.
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