55 research outputs found
The realization space of a certain conic line arrangement of degree 7 and a -equivalent Zariski pair
In this paper, we continue the study of the embedded topology of plane
algebraic curves. We study the realization space of conic line arrangements of
degree with certain fixed combinatorics and determine the number of
connected components. This is done by showing the existence of a Zariski pair
having these combinatorics, which we identified as a -equivalent Zariski
pair.Comment: 24 page
Cognitive Analytic Therapy in People with Learning Disability: An investigation into the common reciprocal roles found within this client group
Developments over the last twenty years have shown that, contrary to previous opinion, people with learning disabilities can benefit from psychotherapy (Sinason 1992; Kroese, Dagnan & Loumidia, 1997). Cognitive Analytic Therapy (CAT) has been adapted for use with a learning disability population (Ryle 2002). CAT collaboratively examines the Reciprocal Roles (RRs) a client plays in relationships. These are impacted by clientsâ experiences of the world. The aim of this research is to identify which RRs may become apparent in working with people with learning disabilities. The therapy notes of participants (n=16) who had undergone CAT were examined and analysed using content analysis. Twenty-two different RRs were found. Four common Reciprocal Roles and two common idealised Reciprocal Roles were identified. Other observations about the data are presented. The limitations and clinical implications of the study are discussed
Even-odd correlations in capacitance fluctuations of quantum dots
We investigate effects of short range interactions on the addition spectra of
quantum dots using a disordered Hubbard model. A correlation function \cS(q) is
defined on the inverse compressibility versus filling data, and computed
numerically for small lattices. Two regimes of interaction strength are
identified: the even/odd fluctuations regime typical of Fermi liquid ground
states, and a regime of structureless \cS(q) at strong interactions. We
propose to understand the latter regime in terms of magnetically correlated
localized spins.Comment: 3 pages, Revtex, Without figure
Absence of bimodal peak spacing distribution in the Coulomb blockade regime
Using exact diagonalization numerical methods, as well as analytical
arguments, we show that for the typical electron densities in chaotic and
disordered dots the peak spacing distribution is not bimodal, but rather
Gaussian. This is in agreement with the experimental observations. We attribute
this behavior to the tendency of an even number of electrons to gain on-site
interaction energy by removing the spin degeneracy. Thus, the dot is predicted
to show a non trivial electron number dependent spin polarization. Experimental
test of this hypothesis based on the spin polarization measurements are
proposed.Comment: 13 pages, 3 figures, accepted for publication in PRL - a few small
change
Magnetic Field Dependence of the Level Spacing of a Small Electron Droplet
The temperature dependence of conductance resonances is used to measure the
evolution with the magnetic field of the average level spacing
of a droplet containing electrons created by lateral confinement of a
two-dimensional electron gas in GaAs. becomes very small (eV) near two critical magnetic fields at which the symmetry of the
droplet changes and these decreases of are predicted by
Hartree-Fock (HF) for charge excitations. Between the two critical fields,
however, the largest measured eV is an order of
magnitude smaller than predicted by HF but comparable to the Zeeman splitting
at this field, which suggests that the spin degrees of freedom are important.
PACS: 73.20.Dx, 73.20.MfComment: 11 pages of text in RevTeX, 4 figures in Postscript (files in the
form of uuencoded compressed tar file
Wigner Crystalline Edges in nu < 1 Quantum Dots
We investigate the edge reconstruction phenomenon believed to occur in
quantum dots in the quantum Hall regime when the filling fraction is nu < 1.
Our approach involves the examination of large dots (< 40 electrons) using a
partial diagonalization technique in which the occupancies of the deep interior
orbitals are frozen. To interpret the results of this calculation, we evaluate
the overlap between the diagonalized ground state and a set of trial
wavefunctions which we call projected necklace (PN) states. A PN state is
simply the angular momentum projection of a maximum density droplet surrounded
by a ring of localized electrons. Our calculations reveal that PN states have
up to 99% overlap with the diagonalized ground states, and are lower in energy
than the states identified in Chamon and Wen's study of the edge
reconstruction.Comment: 8 pages, 8 figures, to be published in Phys. Rev.
Diffusion Monte Carlo study of circular quantum dots
We present ground and excited state energies obtained from Diffusion Monte
Carlo (DMC) calculations, using accurate multiconfiguration wave functions, for
electrons () confined to a circular quantum dot. We analyze the
electron-electron pair correlation functions and compare the density and
correlation energies to the predictions of local spin density approximation
theory (LSDA). The DMC estimated change in electrochemical potential as
function of the number of electrons in the dot is compared to that from LSDA
and Hartree-Fock (HF) calculations.Comment: 7 pages, 4 eps figures. To be published in Phys. Rev. B, September
15th 2000. See erratum cond-mat/030571
Pion Cloud Contribution to K+ Nucleus Scattering
A careful reanalysis is done of the contribution to nucleus
scattering from the interaction of the kaon with the virtual pion cloud. The
usual approximations made in the evaluation of the related kaon selfenergy are
shown to fail badly. We also find new interaction mechanisms which provide
appreciable corrections to the kaon selfenergy. Some of these contribute to the
imaginary part below pion creation threshold. The inclusion of these new
mechanisms in the inelastic part of the optical potential produces a
significant improvement in the differential and total nuclear cross
sections. Uncertainties remain in the dispersive part of the optical potential.Comment: 27 pages, 17 figures (not all of them included, please request them),
report UG-DFM-2/9
Coulomb Blockade Resonances in Quantum Wires
The conductance through a quantum wire of cylindrical cross section and a
weak bulge is solved exactly for two electrons within the Landauer-Buettiker
formalism. We show that this 'open' quantum dot exhibits spin-dependent Coulomb
blockade resonances resulting in two anomalous structure on the rising edge to
the first conductance plateau, one near 0.25(2e^2/h), related to a singlet
resonance, and one near 0.7(2e^2/h), related to a triplet resonance. These
resonances are generic and robust, occurring for other types of quantum wire
and surviving to temperatures of a few degrees.Comment: 5 pages, 3 postscript files with figures; uses REVTe
The antikaon nuclear potential in hot and dense matter
The antikaon optical potential in hot and dense nuclear matter is studied
within the framework of a coupled-channel self-consistent calculation taking,
as bare meson-baryon interaction, the meson-exchange potential of the J\"ulich
group. Typical conditions found in heavy-ion collisions at GSI are explored. As
in the case of zero temperature, the angular momentum components larger than
L=0 contribute significantly to the finite temperature antikaon optical
potential at finite momentum. It is found that the particular treatment of the
medium effects has a strong influence on the behavior of the antikaon potential
with temperature. Our self-consistent model, in which antikaons and pions are
dressed in the medium, gives a moderately temperature dependent antikaon
potential which remains attractive at GSI temperatures, contrary to what one
finds if only nuclear Pauli blocking effects are included.Comment: 30 pages, 8 figures, references added. Accepted for publication in
PR
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