9,209 research outputs found
Two neutron decay of 16Be
Recently, the first example of two-neutron decay from the ground state of an
unbound nucleus, Be, was seen. Three-body methods are ideal for exactly
treating the degrees of freedom important for these decays. Using a basis
expansion over hyperspherical harmonics and the hyperspherical R-matrix method,
we construct a realistic model of Be in order to investigate its decay
mode and the role of the two-neutron interaction. The neutron-Be
interaction is constrained using shell model predictions. We obtain a ground
state for Be that is over-bound by approximately 1 MeV with a width of
approximately 0.23 MeV. This suggests, that for such systems, the three-body
force needs to be repulsive.Comment: 4 pages, 1 figure, contribution to the proceedings for the 21st
International Conference on Few Body Problems in Physics, Chicago, Illinois,
US
Reduction and construction of Poisson quasi-Nijenhuis manifolds with background
We extend the Falceto-Zambon version of Marsden-Ratiu Poisson reduction to
Poisson quasi-Nijenhuis structures with background on manifolds. We define
gauge transformations of Poisson quasi-Nijenhuis structures with background,
study some of their properties and show that they are compatible with reduction
procedure. We use gauge transformations to construct Poisson quasi-Nijenhuis
structures with background.Comment: to appear in IJGMM
Nonlocal gravity and the diffusion equation
We propose a nonlocal scalar-tensor model of gravity with pseudodifferential
operators inspired by the effective action of p-adic string and string field
theory on flat spacetime. An infinite number of derivatives act both on the
metric and scalar field sector. The system is localized via the diffusion
equation approach and its cosmology is studied. We find several exact dynamical
solutions, also in the presence of a barotropic fluid, which are stationary in
the diffusion flow. In particular, and contrary to standard general relativity,
there exist solutions with exponential and power-law scale factor also in an
open universe, as well as solutions with sudden future singularities or a
bounce. Also, from the point of view of quantum field theory, spontaneous
symmetry breaking can be naturally realized in the class of actions we
consider.Comment: 18 pages, 5 figures. v2: typos corrected, references added. Major
changes are an expansion of the discussion of homogeneous perturbations and
the inclusion of cosmological fluids in the dynamic
Effects of deformation in the three-body structure of 11Li
11Li is studied within a three-body model 9Li+n+n where the core is allowed
to be deformed and/or excite. In particular, we include reorientation couplings
and couplings between the two bound states of 9Li. Contrary to the other
examples studied within this model, we find that core excitation does not
affect the structure of 11Li significantly. Reorientation couplings of the
deformed 9Li can change the ground state of 11Li from a predominantly two
neutron s1/2^2 configuration into a p1/2^2. In addition, we see no evidence for
the existence of significant d-wave strength in its ground state, as opposed to
the prediction by shell model. A comparison with shell model is presented.Comment: 13 pages, 9 figure
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