76,816 research outputs found
N K and Delta K states in the chiral SU(3) quark model
The isospin I=0 and I=1 kaon-nucleon , , , wave phase shifts are
studied in the chiral SU(3) quark model by solving the resonating group method
(RGM) equation. The calculated phase shifts for different partial waves are in
agreement with the experimental data. Furthermore, the structures of the
states with L=0, I=1 and I=2 are investigated. We find that the
interaction between and in the case of L=0, I=1 is attractive,
which is not like the situation of the system, where the -wave
interactions between and for both I=0 and I=1 are repulsive. Our
numerical results also show that when the model parameters are taken to be the
same as in our previous and scattering calculations, the
state with L=0 and I=1 is a weakly bound state with about 2 MeV binding energy,
while the one with I=2 is unbound in the present one-channel calculation.Comment: 14 pages, 6 figures. PRC70,064004(2004
The tensor structure on the representation category of the triplet algebra
We study the braided monoidal structure that the fusion product induces on
the abelian category -mod, the category of representations of
the triplet -algebra . The -algebras are a
family of vertex operator algebras that form the simplest known examples of
symmetry algebras of logarithmic conformal field theories. We formalise the
methods for computing fusion products, developed by Nahm, Gaberdiel and Kausch,
that are widely used in the physics literature and illustrate a systematic
approach to calculating fusion products in non-semi-simple representation
categories. We apply these methods to the braided monoidal structure of
-mod, previously constructed by Huang, Lepowsky and Zhang, to
prove that this braided monoidal structure is rigid. The rigidity of
-mod allows us to prove explicit formulae for the fusion product
on the set of all simple and all projective -modules, which were
first conjectured by Fuchs, Hwang, Semikhatov and Tipunin; and Gaberdiel and
Runkel.Comment: 58 pages; edit: added references and revisions according to referee
reports. Version to appear on J. Phys.
Sigma_c Dbar and Lambda_c Dbar states in a chiral quark model
The S-wave Sigma_c Dbar and Lambda_c Dbar states with isospin I=1/2 and spin
S=1/2 are dynamically investigated within the framework of a chiral constituent
quark model by solving a resonating group method (RGM) equation. The results
show that the interaction between Sigma_c and Dbar is attractive, which
consequently results in a Sigma_c Dbar bound state with the binding energy of
about 5-42 MeV, unlike the case of Lambda_c Dbar state, which has a repulsive
interaction and thus is unbound. The channel coupling effect of Sigma_c Dbar
and Lambda_c Dbar is found to be negligible due to the fact that the gap
between the Sigma_c Dbar and Lambda_c Dbar thresholds is relatively large and
the Sigma_c Dbar and Lambda_c Dbar transition interaction is weak.Comment: 7 pages,2 figures. arXiv admin note: text overlap with
arXiv:nucl-th/0606056 by other author
Markov quantum fields on a manifold
We study scalar quantum field theory on a compact manifold. The free theory
is defined in terms of functional integrals. For positive mass it is shown to
have the Markov property in the sense of Nelson. This property is used to
establish a reflection positivity result when the manifold has a reflection
symmetry. In dimension d=2 we use the Markov property to establish a sewing
operation for manifolds with boundary circles. Also in d=2 the Markov property
is proved for interacting fields.Comment: 14 pages, 1 figure, Late
Magnetoresistance in the superconducting state at the (111) LaAlO/SrTiO interface
Condensed matter systems that simultaneously exhibit superconductivity and
ferromagnetism are rare due the antagonistic relationship between conventional
spin-singlet superconductivity and ferromagnetic order. In materials in which
superconductivity and magnetic order is known to coexist (such as some
heavy-fermion materials), the superconductivity is thought to be of an
unconventional nature. Recently, the conducting gas that lives at the interface
between the perovskite band insulators LaAlO (LAO) and SrTiO (STO) has
also been shown to host both superconductivity and magnetism. Most previous
research has focused on LAO/STO samples in which the interface is in the (001)
crystal plane. Relatively little work has focused on the (111) crystal
orientation, which has hexagonal symmetry at the interface, and has been
predicted to have potentially interesting topological properties, including
unconventional superconducting pairing states. Here we report measurements of
the magnetoresistance of (111) LAO/STO heterostructures at temperatures at
which they are also superconducting. As with the (001) structures, the
magnetoresistance is hysteretic, indicating the coexistence of magnetism and
superconductivity, but in addition, we find that this magnetoresistance is
anisotropic. Such an anisotropic response is completely unexpected in the
superconducting state, and suggests that (111) LAO/STO heterostructures may
support unconventional superconductivity.Comment: 6 Pages 4 figure
Anisotropic, multi-carrier transport at the (111) LaAlO/SrTiO interface
The conducting gas that forms at the interface between LaAlO and
SrTiO has proven to be a fertile playground for a wide variety of physical
phenomena. The bulk of previous research has focused on the (001) and (110)
crystal orientations. Here we report detailed measurements of the
low-temperature electrical properties of (111) LAO/STO interface samples. We
find that the low-temperature electrical transport properties are highly
anisotropic, in that they differ significantly along two mutually orthogonal
crystal orientations at the interface. While anisotropy in the resistivity has
been reported in some (001) samples and in (110) samples, the anisotropy in the
(111) samples reported here is much stronger, and also manifests itself in the
Hall coefficient as well as the capacitance. In addition, the anisotropy is not
present at room temperature and at liquid nitrogen temperatures, but only at
liquid helium temperatures and below. The anisotropy is accentuated by exposure
to ultraviolet light, which disproportionately affects transport along one
surface crystal direction. Furthermore, analysis of the low-temperature Hall
coefficient and the capacitance as a function of back gate voltage indicates
that in addition to electrons, holes contribute to the electrical transport.Comment: 11 pages, 9 figure
Kaon-nucleon interaction in the extended chiral SU(3) quark model
The chiral SU(3) quark model is extended to include the coupling between the
quark and vector chiral fields. The one-gluon exchange (OGE) which dominantly
governs the short-range quark-quark interaction in the original chiral SU(3)
quark model is now nearly replaced by the vector-meson exchange. Using this
model, the isospin I=0 and I=1 kaon-nucleon S, P, D, F wave phase shifts are
dynamically studied by solving the resonating group method (RGM) equation.
Similar to those given by the original chiral SU(3) quark model, the calculated
results for many partial waves are consistent with the experiment, while there
is no improvement in this new approach for the P_{13} and D_{15} channels, of
which the theoretical phase shifts are too much repulsive and attractive
respectively when the laboratory momentum of the kaon meson is greater than 300
MeV.Comment: 19 pages, 16 figures. Accepted by Phys. Rev.
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