47 research outputs found
Gamow-Teller strength distributions for double-beta-decaying nuclei within continuum-QRPA
A version of the pn-continuum-QRPA is outlined and applied to describe the
Gamow-Teller strength distributions for -decaying open-shell
nuclei. The calculation results obtained for the pairs of nuclei Cd-Sn
and Te-Xe are compared with available experimental data.Comment: 8 pages, 3 figures, To appear in the proceedings of "Nucleus-2007:
Fundamental problems of nuclear physics, atomic power engineering and nuclear
technologies" Voronezh, Russia, June 25-29, 200
Spherical convolutions on molecular graphs for protein model quality assessment
Processing information on 3D objects requires methods stable to rigid-body transformations, in particular rotations, of the input data. In image processing tasks, convolutional neural networks achieve this property using rotation-equivariant operations. However, contrary to images, graphs generally have irregular topology. This makes it challenging to define a rotation-equivariant convolution operation on these structures. In this work, we propose Spherical Graph Convolutional Network (S-GCN) that processes 3D models of proteins represented as molecular graphs. In a protein molecule, individual amino acids have common topological elements. This allows us to unambiguously associate each amino acid with a local coordinate system and construct rotation-equivariant spherical filters that operate on angular information between graph nodes. Within the framework of the protein model quality assessment problem, we demonstrate that the proposed spherical convolution method significantly improves the quality of model assessment compared to the standard message-passing approach. It is also comparable to state-of-the-art methods, as we demonstrate on Critical Assessment of Structure Prediction (CASP) benchmarks. The proposed technique operates only on geometric features of protein 3D models. This makes it universal and applicable to any other geometric-learning task where the graph structure allows constructing local coordinate systems
Improved convergence of scattering calculations in the oscillator representation
The Schr\"odinger equation for two and tree-body problems is solved for
scattering states in a hybrid representation where solutions are expanded in
the eigenstates of the harmonic oscillator in the interaction region and on a
finite difference grid in the near-- and far--field. The two representations
are coupled through a high--order asymptotic formula that takes into account
the function values and the third derivative in the classical turning points.
For various examples the convergence is analyzed for various physics problems
that use an expansion in a large number of oscillator states. The results show
significant improvement over the JM-ECS method [Bidasyuk et al, Phys. Rev. C
82, 064603 (2010)]
Novel hydrodynamic cumulation mechanism caused by quantum shell effects
The computational and theoretical analysis carried out in this article
demonstrates the existence of a nontrivial mechanism for the compression of a
submicron-sized gas bubble formed by a gas of classical ions and a gas of
degenerate electrons. This mechanism fundamentally differs from conventional
compression mechanisms. It is shown that taking into account the quantum effect
of a large spatial scale in the distribution of electrons qualitatively changes
the character of cumulative processes. Because of a large-scale electric field
caused by quantum shell effects, the compression process is characterized by
the formation of multiple shock waves. The values of gas temperature and
pressure achieved during compression occur higher by two orders of magnitude as
compared with the classical adiabatic regime. The analysis is carried out
within the framework of the following model: the dynamics of the electron
subsystem is described by equations of a quantum electron fluid, while the
hydrodynamic approximation is adopted for the ionic subsystem. The large scale
effect is taken into account by means of effective external field acting on
electrons. The theoretical analysis carried out within this approach clarifies
the nature of the cumulative process in the system under consideration; some
quantitative characteristics obtained with numerical simulation are presented.
The possibility of experimental observation of this cumulative mechanism is
analyzed. It is suggested that the manifestation of the effect can be observed
during laser compression of a system of submicron targets by measuring the
neutron yield.Comment: 49 pages, pdf onl
Microscopic Study of the
The 6Li(p, α)3He reaction important for nuclear astrophysics is studied in the framework of a microscopic approach based on a multichannel algebraic version of the resonating group model. Astrophysical S-factor for the reaction is calculated at low energies. The obtained result is compared with experimental data and other theoretical calculations
Microscopic Study of the 6Li(p, α)3He Reaction at Low Energies
The 6Li(p, α)3He reaction important for nuclear astrophysics is studied in the framework of a microscopic approach based on a multichannel algebraic version of the resonating group model. Astrophysical S-factor for the reaction is calculated at low energies. The obtained result is compared with experimental data and other theoretical calculations
The Algebra of Y-Numbers: Opportunities in Construction of Functions and Multitudes
Abstract:
This paper is devoted to the further investigation on non-associative algebra of y-numbers. The problems of divisibility, finding roots and construction of functions and multitudes are considered.Note:
Research direction:Mathematical problems and theory of numerical method