23 research outputs found
Norm kernels and the closeness relation for Pauli-allowed basis functions
The norm kernel of the generator-coordinate method is shown to be a symmetric
kernel of an integral equation with eigenfunctions defined in the
Fock--Bargmann space and forming a complete set of orthonormalized states
(classified with the use of SU(3) symmetry indices) satisfying the Pauli
exclusion principle. This interpretation allows to develop a method which, even
in the presence of the SU(3) degeneracy, provides for a consistent way to
introduce additional quantum numbers for the classification of the basis
states. In order to set the asymptotic boundary conditions for the expansion
coefficients of a wave function in the SU(3) basis, a complementary basis of
functions with partial angular momenta as good quantum numbers is needed. Norm
kernels of the binary systems 6He+p, 6He+n, 6He+4He, and 8He+4He are considered
in detail.Comment: 25 pages; submitted to Few-Body System
Phenomenological three-cluster model of He
By using the method of hyperspherical functions within the appropriate for this method K_{\min} approximation, the simple three-cluster model for description of the ground state and the continuous spectrum states of \6He is developed. It is shown that many properties of \6He (its large rms radius and large values of the matrix elements of electromagnetic transitions from the ground state into the continuous spectrum) follow from the fact that the potential energy of \6He system decreases very slowly (as \rho^{-3}) and the binding energy is small
Two-neutron overlap functions for 6He from a microscopic structure model
A fully antisymmetrized microscopic model is developed for light two-neutron
halo nuclei using a hyper-spherical basis to describe halo regions. The
many-body wavefunction is optimized variationally. The model is applied to 6He
bound by semi realistic Minnesota nucleon-nucleon forces. The two-neutron
separation energy and the radius of the halo are reproduced in agreement with
experiment. Antisymmetrization effects between 4He and halo neutrons are found
to be crucial for binding of 6He. We also properly extract two-neutron overlap
functions and find that there is a significant increase of 30%-70% in their
normalization due to microscopic effects as compared to the results of
three-body models.Comment: To be published in Nucl. Phys.
FRACTURE ANALYSIS OF 20 Н3 STEEL SAMPLES AFTER TENSILE TESTS
Samples of 20Х3 steel after quenching and tempering under different regimes were studied. By means of macro analysis and scanning electron microscopy the features of the fracture surface relief of samples after tensile tests were studied.В работе исследованы образцы стали 20Х3 после закалки и отпуска по различным режимам. С помощью макроанализа и растровой электронной микроскопии изучены особенности рельефа поверхности разрушения образцов после растяжения
RESEARCH OF THE PRE-STRAIN AND ANNEALING EFFECT ON THE STRUCTURE AND MECHANICAL BEHAVIOR OF MEDIUM CARBON STEELS
The influence of pre-strain value of 2 % and subsequent low-temperature annealing at 250 °C on the structure and mechanical properties of medium carbon steels 37G2S and 37HGF.Изучено влияние предварительной деформации величиной 2 % и последующего низкотемпературного отжига при 250 оС на структуру и механические свойства среднеуглеродистых сталей 37Г2 С и 37ХГФ
A netron halo in 8He
The structure of He is investigated within a three-cluster microscopic
model. The three-cluster configuration was used to describe
the properties of the ground state of the nucleus. The obtained results
evidently indicate the existence of a neutron halo in He.Comment: 14 pages, 6 postscript figures, submitted to Phys. Atom. Nuc
Varying constants, Gravitation and Cosmology
Fundamental constants are a cornerstone of our physical laws. Any constant
varying in space and/or time would reflect the existence of an almost massless
field that couples to matter. This will induce a violation of the universality
of free fall. It is thus of utmost importance for our understanding of gravity
and of the domain of validity of general relativity to test for their
constancy. We thus detail the relations between the constants, the tests of the
local position invariance and of the universality of free fall. We then review
the main experimental and observational constraints that have been obtained
from atomic clocks, the Oklo phenomenon, Solar system observations, meteorites
dating, quasar absorption spectra, stellar physics, pulsar timing, the cosmic
microwave background and big bang nucleosynthesis. At each step we describe the
basics of each system, its dependence with respect to the constants, the known
systematic effects and the most recent constraints that have been obtained. We
then describe the main theoretical frameworks in which the low-energy constants
may actually be varying and we focus on the unification mechanisms and the
relations between the variation of different constants. To finish, we discuss
the more speculative possibility of understanding their numerical values and
the apparent fine-tuning that they confront us with.Comment: 145 pages, 10 figures, Review for Living Reviews in Relativit