13,098 research outputs found
Density functional theory for fermions close to the unitary regime
We consider interacting Fermi systems close to the unitary regime and compute
the corrections to the energy density that are due to a large scattering length
and a small effective range. Our approach exploits the universality of the
density functional and determines the corrections from the analyical results
for the harmonically trapped two-body system. The corrections due to the finite
scattering length compare well with the result of Monte Carlo simulations. We
also apply our results to symmetric neutron matter.Comment: 4 pages, 2 figure
New structures in the proton-antiproton system
In the most recent measurements of the reaction
by the BABAR collaboration, new structures have been found with unknown origin.
We examine a possible relation of the most distinct peak to the recently
observed . Alternatively, we analyse possible explanations due to
the nucleon and thresholds. The latter
could explain a periodicity found in the data
Two new cremnophilous Hibbertia (Dilleniaceae) species from the Northern Territory.
Hibbertia sp. Mount Howship (C.R.Dunlop 6656) and H. sp. South Magela (K.G.Brennan 896) from the Northern Territory are formally described here as Hibbertia scopulicola T.Hammer and Hibbertia pendula T.Hammer, respectively. Their distinguishing characters and morphological affinities with species in eastern Australia are discussed. A key to the groups and species of Hibbertia in the Northern Territory is provided
Orthogonality relations for triple modes at dielectric boundary surfaces
We work out the orthogonality relations for the set of Carniglia-Mandel
triple modes which provide a set of normal modes for the source-free
electromagnetic field in a background consisting of a passive dielectric
half-space and the vacuum, respectively. Due to the inherent computational
complexity of the problem, an efficient strategy to accomplish this task is
desirable, which is presented in the paper. Furthermore, we provide all main
steps for the various proofs pertaining to different combinations of triple
modes in the orthogonality integral.Comment: 15 page
Theoretical Constraints and Systematic Effects in the Determination of the Proton Form Factors
We calculate the two-photon exchange corrections to electron-proton
scattering with nucleon and intermediate states. The results show a
dependence on the elastic nucleon and nucleon--transition form factors
used as input which leads to significant changes compared to previous
calculations. We discuss the relevance of these corrections and apply them to
the most recent and precise data set and world data from electron-proton
scattering. Using this, we show how the form factor extraction from these data
is influenced by the subsequent inclusion of physical constraints. The
determination of the proton charge radius from scattering data is shown to be
dominated by the enforcement of a realistic spectral function. Additionally,
the third Zemach moment from the resulting form factors is calculated. The
obtained radius and Zemach moment are shown to be consistent with Lamb shift
measurements in muonic hydrogen.Comment: minor changes, added references, version to appear in PR
Universal Properties of Two-Dimensional Boson Droplets
We consider a system of N nonrelativistic bosons in two dimensions,
interacting weakly via a short-range attractive potential. We show that for N
large, but below some critical value, the properties of the N-boson bound state
are universal. In particular, the ratio of the binding energies of (N+1)- and
N-boson systems, B_{N+1}/B_N, approaches a finite limit, approximately 8.567,
at large N. We also confirm previous results that the three-body system has
exactly two bound states. We find for the ground state B_3^(0) = 16.522688(1)
B_2 and for the excited state B_3^(1) = 1.2704091(1) B_2.Comment: 4 pages, 2 figures, final versio
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