1,394,767 research outputs found
Low-Energy Heavy-Ion Reactions and the Skyrme Effective Interaction
The Skyrme effective interaction, with its multitude of parameterisations,
along with its implemen- tation using the static and time-dependent density
functional (TDHF) formalism have allowed for a range of microscopic
calculations of low-energy heavy-ion collisions. These calculations allow
variation of the effective interaction along with an interpretation of the
results of this variation informed by a comparison to experimental data.
Initial progress in implementing TDHF for heavy-ion collisions necessarily used
many approximations in the geometry or the interaction. Over the last decade or
so, the implementations have overcome all restrictions, and studies have begun
to be made where details of the effective interaction are being probed. This
review surveys these studies in low energy heavy-ion reactions, finding
significant effects on observables from the form of the spin-orbit interaction,
the use of the tensor force, and the inclusion of time-odd terms in the density
functional.Comment: submitted to Prog. Part. Nucl. Phy
Ground states of quantum kagome antiferromagnets in a magnetic field
We study the ground state properties of a quantum antiferromagnet in the
kagome lattice in the presence of a magnetic field, paying particular attention
to the stability of the plateau at magnetization 1/3 of saturation. While the
plateau is reinforced by certain deformations of the lattice, like the
introduction of structural defect lines and against an Ising anisotropy, ground
state correlations are seen to be quite different and the undistorted SU(2)
case appears to be rather special.Comment: 3 pages, 3 figures, contribution to the Japanese-French symposium on
"Quantum magnetism in spin, charge and orbital systems", Paris 1-4 October
200
Reply to the comment by Jacobs and Thorpe
Reply to a comment on "Infinite-Cluster geometry in central-force networks",
PRL 78 (1997), 1480. A discussion about the order of the rigidity percolation
transition.Comment: 1 page revTe
Cotunneling Spectroscopy in Few-Electron Quantum Dots
Few-electron quantum dots are investigated in the regime of strong tunneling
to the leads. Inelastic cotunneling is used to measure the two-electron
singlet-triplet splitting above and below a magnetic field driven
singlet-triplet transition. Evidence for a non-equilibrium two-electron
singlet-triplet Kondo effect is presented. Cotunneling allows orbital
correlations and parameters characterizing entanglement of the two-electron
singlet ground state to be extracted from dc transport.Comment: related papers available at http://marcuslab.harvard.ed
Star Clusters with Primordial Binaries: II. Dynamical Evolution of Models in a Tidal Field
[abridged] We extend our analysis of the dynamical evolution of simple star
cluster models, in order to provide comparison standards that will aid in
interpreting the results of more complex realistic simulations. We augment our
previous primordial-binary simulations by introducing a tidal field, and
starting with King models of different central concentrations. We present the
results of N-body calculations of the evolution of equal-mass models, starting
with primordial binary fractions of 0 - 100 %, and N values from 512 to 16384.
We also attempt to extrapolate some of our results to the larger number of
particles that are necessary to model globular clusters. We characterize the
steady-state `deuterium main sequence' phase in which primordial binaries are
depleted in the core in the process of `gravitationally burning'. In this phase
we find that the ratio of the core to half-mass radius, r_c/r_h, is similar to
that measured for isolated systems. In addition to the generation of energy due
to hardening and depletion of the primordial binary population, the overall
evolution of the star clusters is driven by a competing process: the tidal
disruption of the system. We find that the depletion of primordial binaries
before tidal dissolution of the system is possible only if the initial number
is below 0.05 N, in the case of a King model with W_0=7 and N=4096 (which is
one of our longest living models). We compare our findings, obtained by means
of direct N-body simulations but scaled, where possible, to larger N, with
similar studies carried out by means of Monte Carlo methods.Comment: 15 pages, 18 figures, matches MNRAS accepted version, some sections
reorganized but no major change
Open Questions in Classical Gravity
We discuss some outstanding open questions regarding the validity and
uniqueness of the standard second order Newton-Einstein classical gravitational
theory. On the observational side we discuss the degree to which the realm of
validity of Newton's Law of Gravity can actually be extended to distances much
larger than the solar system distance scales on which the law was originally
established. On the theoretical side we identify some commonly accepted but
actually still open to question assumptions which go into the formulating of
the standard second order Einstein theory in the first place. In particular, we
show that while the familiar second order Poisson gravitational equation (and
accordingly its second order covariant Einstein generalization) may be
sufficient to yield Newton's Law of Gravity they are not in fact necessary. The
standard theory thus still awaits the identification of some principle which
would then make it necessary too. We show that current observational
information does not exclusively mandate the standard theory, and that the
conformal invariant fourth order theory of gravity considered recently by
Mannheim and Kazanas is also able to meet the constraints of data, and in fact
to do so without the need for any so far unobserved non-luminous or dark
matter.Comment: UCONN-93-1, plain TeX format, 22 pages (plus 7 figures - send
requests to [email protected]). To appear in a special issue of
Foundations of Physics honoring Professor Fritz Rohrlich on the occasion of
his retirement, L. P. Horwitz and A. van der Merwe Editors, Plenum Publishing
Company, N.Y., Fall 199
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