929 research outputs found
The unrestricted Skyrme-tensor time-dependent Hartree-Fock and its application to the nuclear response from spherical to triaxial nuclei
The nuclear time-dependent Hartree-Fock model formulated in the
three-dimensional space,based on the full Skyrme energy density functional and
complemented with the tensor force,is presented for the first time. Full
self-consistency is achieved by the model. The application to the isovector
giant dipole resonance is discussed in the linear limit, ranging from spherical
nuclei (16O, 120Sn) to systems displaying axial or triaxial deformation (24Mg,
28Si, 178Os, 190W, 238U).
Particular attention is paid to the spin-dependent terms from the central
sector of the functional, recently included together with the tensor. They turn
out to be capable of producing a qualitative change on the strength
distribution in this channel. The effect on the deformation properties is also
discussed. The quantitative effects on the linear response are small and,
overall, the giant dipole energy remains unaffected.
Calculations are compared to predictions from the (quasi)-particle random
phase approximation and experimental data where available, finding good
agreement
Multiphonon Giant Resonances
A new class of giant resonances in nuclei is discussed, i.e., giant
resonances built on other giant resonances. These resonances are observed with
very large cross sections in relativistic heavy ion collisions. A great
experimental and theoretical effort is underway to understand the reaction
mechanism which leads to the excitation of these states in nuclei, as well as
the better microscopic understanding of their properties, e.g., strength,
energy centroids, widths, and anharmonicities.Comment: Postscript file with text and 11 embedded figure
Role of deformation on giant resonances within the QRPA approach and the Gogny force
Fully consistent axially-symmetric-deformed Quasi-particle Random Phase
Approximation (QRPA) calculations have been performed, in which the same Gogny
D1S effective force has been used for both the Hartree-Fock-Bogolyubov mean
field and the QRPA approaches. Giant resonances calculated in deformed
Si and Mg nuclei as well as in the spherical Si and
Mg isotopes are presented. Theoretical results for isovector-dipole and
isoscalar monopole, quadrupole, and octupole responses are presented and the
impact of the intrinsic nuclear deformation is discussed.Comment: 12 pages, 6 figures and 4 tables, accepted in PR
On the Relationship of Quantum Mechanics to Classical Electromagnetism and Classical Relativistic Mechanics
Some connections between quantum mechanics and classical physics are
explored. The Planck-Einstein and De Broglie relations, the wavefunction and
its probabilistic interpretation, the Canonical Commutation Relations and the
Maxwell--Lorentz Equation may be understood in a simple way by comparing
classical electromagnetism and the photonic description of light provided by
classical relativistic kinematics. The method used may be described as `inverse
correspondence' since quantum phenomena become apparent on considering the low
photon number density limit of classical electromagnetism. Generalisation to
massive particles leads to the Klein--Gordon and Schr\"{o}dinger Equations. The
difference between the quantum wavefunction of the photon and a classical
electromagnetic wave is discussed in some detail.Comment: 14 pages, no figures, no table
Thermodynamical Consistent Modeling and Analysis of Nematic Liquid Crystal Flows
The general Ericksen-Leslie system for the flow of nematic liquid crystals is
reconsidered in the non-isothermal case aiming for thermodynamically consistent
models. The non-isothermal model is then investigated analytically. A fairly
complete dynamic theory is developed by analyzing these systems as quasilinear
parabolic evolution equations in an -setting. First, the existence of
a unique, local strong solution is proved. It is then shown that this solution
extends to a global strong solution provided the initial data are close to an
equilibrium or the solution is eventually bounded in the natural norm of the
underlying state space. In these cases, the solution converges exponentially to
an equilibrium in the natural state manifold
Majorana: from atomic and molecular, to nuclear physics
In the centennial of Ettore Majorana's birth (1906-1938?), we re-examine some
aspects of his fundamental scientific production in atomic and molecular
physics, including a not well known short communication. There, Majorana
critically discusses Fermi's solution of the celebrated Thomas-Fermi equation
for electron screening in atoms and positive ions. We argue that some of
Majorana's seminal contributions in molecular physics already prelude to the
idea of exchange interactions (or Heisenberg-Majorana forces) in his later
workson theoretical nuclear physics. In all his papers, he tended to emphasize
the symmetries at the basis of a physical problem, as well as the limitations,
rather than the advantages, of the approximations of the method employed.Comment: to appear in Found. Phy
On the verge of Umdeutung in Minnesota: Van Vleck and the correspondence principle (Part One)
In October 1924, the Physical Review, a relatively minor journal at the time,
published a remarkable two-part paper by John H. Van Vleck, working in virtual
isolation at the University of Minnesota. Van Vleck combined advanced
techniques of classical mechanics with Bohr's correspondence principle and
Einstein's quantum theory of radiation to find quantum analogues of classical
expressions for the emission, absorption, and dispersion of radiation. For
modern readers Van Vleck's paper is much easier to follow than the famous paper
by Kramers and Heisenberg on dispersion theory, which covers similar terrain
and is widely credited to have led directly to Heisenberg's "Umdeutung" paper.
This makes Van Vleck's paper extremely valuable for the reconstruction of the
genesis of matrix mechanics. It also makes it tempting to ask why Van Vleck did
not take the next step and develop matrix mechanics himself.Comment: 82 page
On two-dimensional surface attractors and repellers on 3-manifolds
We show that if is an -diffeomorphism with a surface
two-dimensional attractor or repeller and is a
supporting surface for , then and
there is such that: 1) is a union
of disjoint tame surfaces such that every is
homeomorphic to the 2-torus . 2) the restriction of to
is conjugate to Anosov automorphism of
Biological sources and sinks of nitrous oxide and strategies to mitigate emissions
Nitrous oxide (N
2
O) is a powerful atmospheric greenhouse gas and cause of ozone layer depletion. Global emissions continue to rise. More than two-thirds of these emissions arise from bacterial and fungal denitrification and nitrification processes in soils, largely as a result of the application of nitrogenous fertilizers. This article summarizes the outcomes of an interdisciplinary meeting, ‘Nitrous oxide (N
2
O) the forgotten greenhouse gas’, held at the Kavli Royal Society International Centre, from 23 to 24 May 2011. It provides an introduction and background to the nature of the problem, and summarizes the conclusions reached regarding the biological sources and sinks of N
2
O in oceans, soils and wastewaters, and discusses the genetic regulation and molecular details of the enzymes responsible. Techniques for providing global and local N
2
O budgets are discussed. The findings of the meeting are drawn together in a review of strategies for mitigating N
2
O emissions, under three headings, namely: (i) managing soil chemistry and microbiology, (ii) engineering crop plants to fix nitrogen, and (iii) sustainable agricultural intensification.
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