142 research outputs found
True ternary fission of superheavy nuclei
We found that a true ternary fission with formation of a heavy third fragment
(a new type of radioactivity) is quite possible for superheavy nuclei due to
the strong shell effects leading to a three-body clusterization with the two
doubly magic tin-like cores. The simplest way to discover this phenomenon in
the decay of excited superheavy nuclei is a detection of two tin-like clusters
with appropriate kinematics in low-energy collisions of medium mass nuclei with
actinide targets. The three-body quasi-fission process could be even more
pronounced for giant nuclear systems formed in collisions of heavy actinide
nuclei. In this case a three-body clusterization might be proved experimentally
by detection of two coincident lead-like fragments in low-energy U+U
collisions.Comment: 4 pages, 7 figure
Quasi-Continuous Symmetries of Non-Lie Type
We introduce a smooth mapping of some discrete space-time symmetries into
quasi-continuous ones. Such transformations are related with q-deformations of
the dilations of the Euclidean space and with the non-commutative space. We
work out two examples of Hamiltonian invariance under such symmetries. The
Schrodinger equation for a free particle is investigated in such a
non-commutative plane and a connection with anyonic statistics is found.Comment: 18 pages, LateX, 3 figures, Submitted Found. Phys., PACS: 03.65.Fd,
11.30.E
Transmission resonances and supercritical states in a one dimensional cusp potential
We solve the two-component Dirac equation in the presence of a spatially one
dimensional symmetric cusp potential. We compute the scattering and bound
states solutions and we derive the conditions for transmission resonances as
well as for supercriticality.Comment: 10 pages. Revtex 4. To appear in Phys Rev.
Two center multipole expansion method: application to macromolecular systems
We propose a new theoretical method for the calculation of the interaction
energy between macromolecular systems at large distances. The method provides a
linear scaling of the computing time with the system size and is considered as
an alternative to the well known fast multipole method. Its efficiency,
accuracy and applicability to macromolecular systems is analyzed and discussed
in detail.Comment: 23 pages, 7 figures, 1 tabl
Coherent radiation of an ultra-relativistic charged particle channeled in a periodically bent crystal
We suggest a new type of the undulator radiation which is generated by an
ultra-relativistic particle channeled along a periodically bent
crystallographic plane or axis. The electromagnetic radiation arises mainly due
to the bending of the particle's trajectory, which follows the shape of the
channel. The parameters of this undulator, which totally define the spectrum
and the angular distribution of the radiation (both spontaneous and
stimulated), depend on the type of the crystal and the crystallographic plane
(axis), on the type of a projectile and its energy, and on the shape of the
bent channel, and, thus, can be varied significantly by varying these
characteristics.
As an example, we consider the acoustically induced radiation (AIR) which is
generated by ultra-relativistic particles channeled in a crystal which is bent
by a transverse acoustic wave. The AIR mechanism allows to make the undulator
with the main parameters varying in wide ranges, which are inaccessible in the
undulators based on the motion of particles in the periodic magnetic fields and
also in the field of the laser radiation. The intensity of AIR can be easily
made larger than the intensity of the radiation in a linear crystal and can be
varied in a wide range by varying the frequency and the amplitude of the
acoustic wave in the crystal. A possibility to generate stimulated emission of
high-energy photons (in keV - MeV region) is also discussed.Comment: published in J. Phys. G: Nucl. Part. Phys. 24 (1998) L45-L53,
http://www.iop.or
Deuterons and space-momentum correlations in high energy nuclear collisions
Using a microscopic transport model together with a coalescence after-burner, we study the formation of deuterons in Au + Au central collisions at s = 200 AGeV . It is found that the deuteron transverse momentum distributions are strongly a ected by the nucleon space-momentum correlations, at the moment of freeze-out, which are mostly determined by the number of rescatterings. This feature is useful for studying collision dynamics at ultrarelativistic energies
Future of superheavy element research: Which nuclei could be synthesized within the next few years?
Low values of the fusion cross sections and very short half-lives of nuclei
with Z120 put obstacles in synthesis of new elements. Different nuclear
reactions (fusion of stable and radioactive nuclei, multi-nucleon transfers and
neutron capture), which could be used for the production of new isotopes of
superheavy (SH) elements, are discussed in the paper. The gap of unknown SH
nuclei, located between the isotopes which were produced earlier in the cold
and hot fusion reactions, can be filled in fusion reactions of Ca with
available lighter isotopes of Pu, Am, and Cm. Cross sections for the production
of these nuclei are predicted to be rather large, and the corresponding
experiments can be easily performed at existing facilities. For the first time,
a narrow pathway is found to the middle of the island of stability owing to
possible -decay of SH isotopes which can be formed in ordinary fusion
reactions of stable nuclei. Multi-nucleon transfer processes at near barrier
collisions of heavy (and very heavy, U-like) ions are shown to be quite
realistic reaction mechanism allowing us to produce new neutron enriched heavy
nuclei located in the unexplored upper part of the nuclear map. Neutron capture
reactions can be also used for the production of the long-living neutron rich
SH nuclei. Strong neutron fluxes might be provided by pulsed nuclear reactors
and by nuclear explosions in laboratory conditions and by supernova explosions
in nature. All these possibilities are discussed in the paper.Comment: An Invited Plenary Talk given by Valeriy I. Zagrebaev at the 11th
International Conference on Nucleus-Nucleus Collisions (NN2012), San Antonio,
Texas, USA, May 27-June 1, 2012. To appear in the NN2012 Proceedings in
Journal of Physics: Conference Series (JPCS
Phase diagram of two-component bosons on an optical lattice
We present a theoretical analysis of the phase diagram of two--component
bosons on an optical lattice. A new formalism is developed which treats the
effective spin interactions in the Mott and superfluid phases on the same
footing. Using the new approach we chart the phase boundaries of the broken
spin symmetry states up to the Mott to superfluid transition and beyond. Near
the transition point, the magnitude of spin exchange can be very large, which
facilitates the experimental realization of spin-ordered states. We find that
spin and quantum fluctuations have a dramatic effect on the transition making
it first order in extended regions of the phase diagram. For Mott states with
even occupation we find that the competition between effective Heisenberg
exchange and spin-dependent on--site interaction leads to an additional phase
transition from a Mott insulator with no broken symmetries into a spin-ordered
insulator
Photon emission by an ultra-relativistic particle channeling in a periodically bent crystal
This paper is devoted to a detailed analysis of the new type of the undulator
radiation generated by an ultra-relativistic charged particle channeling along
a crystal plane, which is periodically bent by a transverse acoustic wave, as
well as to the conditions limiting the observation of this phenomenon. This
mechanism makes feasible the generation of electromagnetic radiation, both
spontaneous and stimulated, emitted in a wide range of the photon energies,
from X- up to gamma-rays
A New Nonlinear Liquid Drop Model. Clusters as Solitons on The Nuclear Surface
By introducing in the hydrodynamic model, i.e. in the hydrodynamic equations
and the corresponding boundary conditions, the higher order terms in the
deviation of the shape, we obtain in the second order the Korteweg de Vries
equation (KdV). The same equation is obtained by introducing in the liquid drop
model (LDM), i.e. in the kinetic, surface and Coulomb terms, the higher terms
in the second order. The KdV equation has the cnoidal waves as steady-state
solutions. These waves could describe the small anharmonic vibrations of
spherical nuclei up to the solitary waves. The solitons could describe the
preformation of clusters on the nuclear surface. We apply this nonlinear liquid
drop model to the alpha formation in heavy nuclei. We find an additional
minimum in the total energy of such systems, corresponding to the solitons as
clusters on the nuclear surface. By introducing the shell effects we choose
this minimum to be degenerated with the ground state. The spectroscopic factor
is given by the ratio of the square amplitudes in the two minima.Comment: 27 pages, LateX, 8 figures, Submitted J. Phys. G: Nucl. Part. Phys.,
PACS: 23.60.+e, 21.60.Gx, 24.30.-v, 25.70.e
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