1,200 research outputs found
Two-body correlations in Bose condensates
We formulate a method to study two-body correlations in a condensate of N
identical bosons. We use the adiabatic hyperspheric approach and assume a
Faddeev like decomposition of the wave function. We derive for a fixed
hyperradius an integro-differential equation for the angular eigenvalue and
wave function. We discuss properties of the solutions and illustrate with
numerical results. The interaction energy is for N~20 five times smaller than
that of the Gross-Pitaevskii equation
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
Two-body correlations in N-body boson systems
We formulate a method to study two-body correlations in a system of N
identical bosons interacting via central two-body potentials. We use the
adiabatic hyperspherical approach and assume a Faddeev-like decomposition of
the wave function. For a fixed hyperradius we derive variationally an optimal
integro-differential equation for hyperangular eigenvalue and wave function.
This equation reduces substantially by assuming the interaction range much
smaller than the size of the N-body system. At most one-dimensional integrals
then remain. We view a Bose-Einstein condensate pictorially as a structure in
the landscape of the potential given as a function of the one-dimensional
hyperradial coordinate. The quantum states of the condensate can be located in
one of the two potential minima. We derive and discuss properties of the
solutions and illustrate with numerical results. The correlations lower the
interaction energy substantially. The new multi-body Efimov states are
solutions independent of details of the two-body potential. We compare with
mean-field results and available experimental data.Comment: 19 pages (RevTeX4), 13 figures (latex). Journal-link:
http://pra.aps.org
Extracting the Number of Short Range Correlated Nucleon Pairs from Inclusive Electron Scattering Data
The extraction of the relative abundances of short-range correlated (SRC) nucleon pairs from inclusive electron scattering is studied using the generalized contact formalism (GCF) with several nuclear interaction models. GCF calculations can reproduce the observed scaling of the cross-section ratios for nuclei relative to deuterium at high xB and large Q2, a2 = (ĎA/A)/(Ďd/2). In the nonrelativistic instant-form formulation, the calculation is very sensitive to the model parameters and only reproduces the data using parameters that are inconsistent with ab initio many-body calculations. Using a light-cone GCF formulation significantly decreases this sensitivity and improves the agreement with ab initio calculations. The ratio of similar mass isotopes, such as 40Ca and 48Ca, should be sensitive to the nuclear asymmetry dependence of SRCs, but is found to also be sensitive to low-energy nuclear structure. Thus the empirical association of SRC pair abundances with the measured a2 values is only accurate to about 20%. Improving this will require cross-section calculations that reproduce the data while properly accounting for both nuclear structure and relativistic effects
Quantum oscillations from Fermi arcs
When a metal is subjected to strong magnetic field B nearly all measurable
quantities exhibit oscillations periodic in 1/B. Such quantum oscillations
represent a canonical probe of the defining aspect of a metal, its Fermi
surface (FS). In this study we establish a new mechanism for quantum
oscillations which requires only finite segments of a FS to exist. Oscillations
periodic in 1/B occur if the FS segments are terminated by a pairing gap. Our
results reconcile the recent breakthrough experiments showing quantum
oscillations in a cuprate superconductor YBCO, with a well-established result
of many angle resolved photoemission (ARPES) studies which consistently
indicate "Fermi arcs" -- truncated segments of a Fermi surface -- in the normal
state of the cuprates.Comment: 8 pages, 5 figure
Extracing the number of short-range corerlated nucleon pairs from inclusive electron scattering data
The extraction of the relative abundances of short-range correlated (SRC)
nucleon pairs from inclusive electron scattering is studied using the
generalized contact formalism (GCF) with several nuclear interaction models.
GCF calculations can reproduce the observed scaling of the cross-section ratios
for nuclei relative to deuterium at high- and large-,
. In the non-relativistic instant-form
formulation, the calculation is very sensitive to the model parameters and only
reproduces the data using parameters that are inconsistent with ab-initio
many-body calculations. Using a light-cone GCF formulation significantly
decreases this sensitivity and improves the agreement with ab-initio
calculations. The ratio of similar mass isotopes, such as Ca and
Ca, should be sensitive to the nuclear asymmetry dependence of SRCs, but
is found to also be sensitive to low-energy nuclear structure. Thus the
empirical association of SRC pair abundances with the measured values is
only accurate to about . Improving this will require cross-section
calculations that reproduce the data while properly accounting for both nuclear
structure and relativistic effects.Comment: Accepted for publication in Phys. Rev. C (Lett). 6 pages, 4 figures,
and online supplementary material
Structure of boson systems beyond the mean-field
We investigate systems of identical bosons with the focus on two-body
correlations. We use the hyperspherical adiabatic method and a decomposition of
the wave function in two-body amplitudes. An analytic parametrization is used
for the adiabatic effective radial potential. We discuss the structure of a
condensate for arbitrary scattering length. Stability and time scales for
various decay processes are estimated. The previously predicted Efimov-like
states are found to be very narrow. We discuss the validity conditions and
formal connections between the zero- and finite-range mean-field
approximations, Faddeev-Yakubovskii formulation, Jastrow ansatz, and the
present method. We compare numerical results from present work with mean-field
calculations and discuss qualitatively the connection with measurements.Comment: 26 pages, 6 figures, submitted to J. Phys. B. Ver. 2 is 28 pages with
modified figures and discussion
Generalized Contact Formalism Analysis of the â´He(e,eâ˛pN) Reaction
Measurements of short-range correlations in exclusive 4He (e , e Ⲡp N) reactions are analyzed using the Generalized Contact Formalism (GCF). We consider both instant-form and light-cone formulations with both the AV18 and local N2LO(1.0) nucleon-nucleon (NN) potentials. We find that kinematic distributions, such as the reconstructed pair opening angle, recoil neutron momentum distribution, and pair center of mass motion, as well as the measured missing energy, missing mass distributions, are all well reproduced by GCF calculations. The missing momentum dependence of the measured 4He (e , e Ⲡp N) /4He (e , e Ⲡp) cross-section ratios, sensitive to nature of the NN interaction at short-distacnes, are also well reproduced by GCF calculations using either interaction and formulation. This gives credence to the GCF scale-separated factorized description of the short-distance many-body nuclear wave-function
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