172 research outputs found
Learning From Real Springs
Many springs do not obey Hooke's Law because they are constructed to have an intrinsic tension which must be overcome before normal elongation occurs. This property, well-known to engineers, is universally neglected in elementary physics courses. In fact it can be used to enhance learning and to deepen understanding of potential energy
On a theoretical model for d-wave to mixed s- and d-wave transition in cuprate superconductors
A U(3) model proposed by Iachello for superconductivity in cuprate materials
is analyzed. The model consists of s and d pairs (approximated as bosons) in a
two-dimensional Fermi system with a surface. The transition occurs between a
phase in which the system is a condensate of one of the bosons, and a phase
which is a mixture of two types of bosons. In the current work we have
investigated the validity of the Bogoliubov approximation, and we used a
reduced Hamiltonian to determine a phase diagram, the symmetry of the phases
and the temperature dependence of the heat capacity.Comment: 8 pages, 4 figure
Beyond mean-field description of the low-lying spectrum of 16O
Starting from constrained Skyrme-mean-field calculations, the low-energy
excitation spectrum of 16O is calculated by configuration mixing of
particle-number and angular-momentum projected mean-field states in the
framework of the Generator Coordinate Method. Without any adjustable
parameters, this approach gives a very good description of those states and
their transition moments that can be described with our restriction to axially
and reflection-symmetric shapes. The structure of low-lying 0+ states is
analyzed in terms of self-consistent 0p-0h, 2p-2h, and 4p-4h Hartree-Fock
states.Comment: 15 pages LATEX, 6 figures, 3 tables, revision of sections 4 and
Augmented Lagrangian Method for Constrained Nuclear Density Functional Theory
The augmented Lagrangiam method (ALM), widely used in quantum chemistry
constrained optimization problems, is applied in the context of the nuclear
Density Functional Theory (DFT) in the self-consistent constrained Skyrme
Hartree-Fock-Bogoliubov (CHFB) variant. The ALM allows precise calculations of
multidimensional energy surfaces in the space of collective coordinates that
are needed to, e.g., determine fission pathways and saddle points; it improves
accuracy of computed derivatives with respect to collective variables that are
used to determine collective inertia; and is well adapted to supercomputer
applications.Comment: 6 pages, 3 figures; to appear in Eur. Phys. J.
Weakly-Interacting Bosons in a Trap within Approximate Second Quantization Approach
The theory of Bogoliubov is generalized for the case of a weakly-interacting
Bose-gas in harmonic trap. A set of nonlinear matrix equations is obtained to
make the diagonalization of Hamiltonian possible. Its perturbative solution is
used for the calculation of the energy and the condensate fraction of the model
system to show the applicability of the method.Comment: 6 pages, two figures .Presented at the International Symposium on
Quantum Fluids and Solids QFS2006 (Kyoto, Japan
Coexistence of the "bogolons" and the one-particle spectrum of excitations with a gap in the degenerated Bose gas
Properties of the weakly non-ideal Bose gas are considered without suggestion
on C-number representation of the creation and annihilation operators with zero
momentum. The "density-density" correlation function and the one-particle Green
function of the degenerated Bose gas are calculated on the basis of the
self-consistent Hartree-Fock approximation. It is shown that the spectrum of
the one-particle excitations possesses a gap whose value is connected with the
density of particles in the "condensate". At the same time, the pole in the
"density-density" Green function determines the phonon-roton spectrum of
excitations which exactly coincides with one discovered by Bogolyubov for the
collective excitations (the "bogolons").Comment: 8 pages, no figure
Bound-State Representation of Scattering Solutions
Journals published by the American Physical Society can be found at http://publish.aps.org
Charge- and parity-projected Hartree-Fock method for the strong tensor correlation and its application to the alpha particle
We propose a new mean-field-type framework which can treat the strong
correlation induced by the tensor force. To treat the tensor correlation we
break the charge and parity symmetries of a single-particle state and restore
these symmetries of the total system by the projection method. We perform the
charge and parity projections before variation and obtain a Hartree-Fock-like
equation, which is solved self-consistently. We apply the Hartree-Fock-like
equation to the alpha particle and find that by breaking the parity and charge
symmetries, the correlation induced by the tensor force is obtained in the
projected mean-field framework. We emphasize that the projection before the
variation is important to pick up the tensor correlation in the present
framework.Comment: 21 pages, 2 figure
Totally Microscopic Description of N-O-16 Elastic-Scattering
Journals published by the American Physical Society can be found at http://publish.aps.org
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