8,438 research outputs found
Shape evolution and the role of intruder configurations in Hg isotopes within the interacting boson model based on a Gogny energy density functional
The interacting boson model with configuration mixing, with parameters
derived from the self-consistent mean-field calculation employing the
microscopic Gogny energy density functional, is applied to the systematic
analysis of the low-lying structure in Hg isotopes. Excitation energies,
electromagnetic transition rates, deformation properties, and ground-state
properties of the Hg nuclei are obtained by mapping the microscopic
deformation energy surface onto the equivalent IBM Hamiltonian in the boson
condensate. These results point to the overall systematic trend of the
transition from the near spherical vibrational state in lower-mass Hg nuclei
close to Hg, onset of intruder prolate configuration as well as the
manifest prolate-oblate shape coexistence around the mid-shell nucleus
Hg, weakly oblate deformed structure beyond Hg up to the
spherical vibrational structure toward the near semi-magic nucleus Hg,
as observed experimentally. The quality of the present method in the
description of the complex shape dynamics in Hg isotopes is examined.Comment: 19 pages, 14 figures, revised version including new results and
discussions, title changed, accepted for publication in Phys. Rev.
The Riccati System and a Diffusion-Type Equation
We discuss a method of constructing solution of the initial value problem for
duffusion-type equations in terms of solutions of certain Riccati and
Ermakov-type systems. A nonautonomous Burgers-type equation is also considered.Comment: 11 pages, no figure
On The Harmonic Oscillator Group
We discuss the maximum kinematical invariance group of the quantum harmonic
oscillator from a view point of the Ermakov-type system. A six parameter family
of the square integrable oscillator wave functions, which seems cannot be
obtained by the standard separation of variables, is presented as an example.
The invariance group of generalized driven harmonic oscillator is shown to be
isomorphic to the corresponding Schroedinger group of the free particle.Comment: 11 pages, no figure
The dynamics of copper intercalated molybdenum ditelluride
Layered transition metal dichalcogenides are emerging as key materials in
nanoelectronics and energy applications. Predictive models to understand their
growth, thermomechanical properties and interactions with metals are needed in
order to accelerate their incorporation into commercial products. Interatomic
potentials enable large-scale atomistic simulations at the device level, beyond
the range of applications of first principle methods. We present a ReaxFF
reactive force field to describe molybdenum ditelluride and its interactions
with copper. We optimized the force field parameters to describe the properties
of layered MoTe2 in various phases, the intercalation of Cu atoms and clusters
within its van der Waals gap, including a proper description of energetics,
charges and mechanical properties. The training set consists of an extensive
set of first principle calculations computed from density functional theory. We
use the force field to study the adhesion of a single layer MoTe2 on a Cu(111)
surface and the results are in good agreement with density functional theory,
even though such structures were not part of the training set. We characterized
the mobility of the Cu ions intercalated into MoTe2 under the presence of an
external electric fields via molecular dynamics simulations. The results show a
significant increase in drift velocity for electric fields of approximately 0.4
V/A and that mobility increases with Cu ion concentration.Comment: 21 pages, 9 Figure
Hyperbolic 3-manifolds with k-free fundamental group
The results of Culler and Shalen for 2,3 or 4-free hyperbolic 3-manifolds are
contingent on properties specific to and special about rank two subgroups of a
free group. Here we determine what construction and algebraic information is
required in order to make a geometric statement about , a closed, orientable
hyperbolic 3-manifold with -free fundamental group, for any value of
greater than four. Main results are both to show what the formulation of the
general statement should be, for which Culler and Shalen's result is a special
case, and that it is true modulo a group-theoretic conjecture. A major result
is in the case of the geometric statement. Specifically, we show that the
required group-theoretic conjecture is in fact true in this case, and so the
proposed geometric statement when is 5-free is indeed a theorem. One can
then use the existence of a point and knowledge about
resulting from this theorem to attempt to improve the known lower bound on the
volume of , which is currently 3.44.Comment: 18 page
PAH Formation in O-rich Planetary Nebulae
Polycyclic aromatic hydrocarbons (PAHs) have been observed in O-rich
planetary nebulae towards the Galactic Bulge. This combination of oxygen-rich
and carbon-rich material, known as dual-dust or mixed chemistry, is not
expected to be seen around such objects. We recently proposed that PAHs could
be formed from the photodissociation of CO in dense tori. In this work, using
VISIR/VLT, we spatially resolved the emission of the PAH bands and ionised
emission from the [SIV] line, confirming the presence of dense central tori in
all the observed O-rich objects. Furthermore, we show that for most of the
objects, PAHs are located at the outer edge of these dense/compact tori, while
the ionised material is mostly present in the inner parts of these tori,
consistent with our hypothesis for the formation of PAHs in these systems. The
presence of a dense torus has been strongly associated with the action of a
central binary star and, as such, the rich chemistry seen in these regions may
also be related to the formation of exoplanets in post-common-envelope binary
systems.Comment: 14, accepted for publication in the MNRAS Journa
Shape evolution and shape coexistence in Pt isotopes: comparing interacting boson model configuration mixing and Gogny mean-field energy surfaces
The evolution of the total energy surface and the nuclear shape in the
isotopic chain Pt are studied in the framework of the interacting
boson model, including configuration mixing. The results are compared with a
self-consistent Hartree-Fock-Bogoliubov calculation using the Gogny-D1S
interaction and a good agreement between both approaches shows up. The
evolution of the deformation parameters points towards the presence of two
different coexisting configurations in the region 176 A 186.Comment: Submitted to PR
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