1,620 research outputs found
Angular distributions in decays
The differential decay rates of the processes and
close to the threshold are calculated with
the help of the optical potential. The same calculations are made
for the decays of . We use the potential which has been suggested to
fit the cross sections of scattering together with and
six pion production in annihilation close to the
threshold. The invariant mass spectra is in agreement with the
available experimental data. The anisotropy of the angular distributions, which
appears due to the tensor forces in the interaction, is predicted
close to the threshold. This anisotropy is large enough to be
investigated experimentally. Such measurements would allow one to check the
accuracy of the model of interaction.Comment: 10 pages, 8 figure
Translationally invariant nonlinear Schrodinger lattices
Persistence of stationary and traveling single-humped localized solutions in
the spatial discretizations of the nonlinear Schrodinger (NLS) equation is
addressed. The discrete NLS equation with the most general cubic polynomial
function is considered. Constraints on the nonlinear function are found from
the condition that the second-order difference equation for stationary
solutions can be reduced to the first-order difference map. The discrete NLS
equation with such an exceptional nonlinear function is shown to have a
conserved momentum but admits no standard Hamiltonian structure. It is proved
that the reduction to the first-order difference map gives a sufficient
condition for existence of translationally invariant single-humped stationary
solutions and a necessary condition for existence of single-humped traveling
solutions. Other constraints on the nonlinear function are found from the
condition that the differential advance-delay equation for traveling solutions
admits a reduction to an integrable normal form given by a third-order
differential equation. This reduction also gives a necessary condition for
existence of single-humped traveling solutions. The nonlinear function which
admits both reductions defines a two-parameter family of discrete NLS equations
which generalizes the integrable Ablowitz--Ladik lattice.Comment: 24 pages, 4 figure
Quantum renormalization group of XYZ model in a transverse magnetic field
We have studied the zero temperature phase diagram of XYZ model in the
presence of transverse magnetic field. We show that small anisotropy (0 =<
Delta <1) is not relevant to change the universality class. The phase diagram
consists of two antiferromagnetic ordering and a paramagnetic phases. We have
obtained the critical exponents, fixed points and running of coupling constants
by implementing the standard quantum renormalization group. The continuous
phase transition from antiferromagnetic (spin-flop) phase to a paramagnetic one
is in the universality class of Ising model in transverse field. Numerical
exact diagonalization has been done to justify our results. We have also
addressed on the application of our findings to the recent experiments on
Cs_2CoCl_4.Comment: 5 pages, 5 figures, new references added to the present versio
Anapole moment of an exotic nucleus
We demonstrate that there is no appreciable enhancement of the anapole moment
of Be. The effect of small energy intervals is compensated for by a
small overlap of the halo neutron wave function with core.Comment: 5 pages, LaTe
- …