16,697 research outputs found
Chiral SU(3) Symmetry and Strangeness
In this talk we review recent progress on the systematic evaluation of the
kaon and antikaon spectral functions in dense nuclear matter based on a chiral
SU(3) description of the low-energy pion-, kaon- and antikaon-nucleon
scattering data.Comment: 9 pages, 4 figures, invited talk given by M.F.M.L. at the SQM2001
conferenc
Kaon and antikaon properties in cold nuclear medium
We present results of a self-consistent calculation for the kaon and antikaon
spectral functions in cold nuclear matter, using as input the kaon-nucleon and
antikaon-nucleon scattering amplitudes of the vacuum. We investigate the effect
of in-medium pion dressing on the antikaon-nucleon scattering amplitudes and
antikaon spectral function. We find the influence of pion dressing to be minor
on the antikaon spectral function and limited on the hyperon resonances causing
only a small additional broadening. An exception is the \Sigma(1690). At
nuclear saturation density an attractive mass shift of about 20 MeV and width
of about 130 MeV is obtained. The kaon shows a repulsive mass increase of 36
MeV and a small width of the quasiparticle peak at saturation density.Comment: 8 pages, 4 figures, submitted to Heavy Ion Physic
Self-consistent antikaon dynamics in isospin-asymmetric nuclear medium
We investigate properties of antikaons and hyperon resonances in
isospin-asymmetric nuclear medium, using a self-consistent, covariant scheme
based on vacuum antikaon-nucleon scattering amplitude.Comment: 9 pages, 5 figures, uses budapest.sty (included);to be published in
the Proceedings of the Budapest'2002 Workshop on Quark and Hadron Dynamics,
Budapest, Hungary, 3-7 March 200
The combined approach to ontology-based data access
The use of ontologies for accessing data is one of
the most exciting new applications of description
logics in databases and other information systems.
A realistic way of realising sufficiently scalable ontology-
based data access in practice is by reduction
to querying relational databases. In this paper,
we describe the combined approach, which incorporates
the information given by the ontology into
the data and employs query rewriting to eliminate
spurious answers. We illustrate this approach for
ontologies given in the DL-Lite family of description
logics and briefly discuss the results obtained
for the EL family
Chiral symmetry, strangeness and resonances
We review the important role played by the chiral SU(3) symmetry in
predicting the properties of antikaons and hyperon resonances in cold nuclear
matter. Objects of crucial importance are the meson-baryon scattering
amplitudes obtained within the chiral coupled-channel effective field theory.
The formation of baryon resonances as implied by chiral coupled-channel
dynamics is discussed. Results for antikaon and hyperon-resonance spectral
functions are presented for isospin symmetric and asymmetric matter.Comment: invited talk presented by M.F.M.L. at the 18th Nishinomiya Yukawa
Memorial Symposium, 21 pages, 12 figure
Combined FO rewritability for conjunctive query answering in DL-Lite
Standard description logic (DL) reasoning services such as satisfiability and subsumption mainly aim to support TBox design. When the design stage is over and the TBox is used in an actual application, it is usually combined with instance data stored in an ABox, and therefore query answering becomes the most importan
On finite volume effects in the chiral extrapolation of baryon masses
We perform an analysis of the QCD lattice data on the baryon octet and
decuplet masses based on the relativistic chiral Lagrangian. The baryon self
energies are computed in a finite volume at next-to-next-to-next-to leading
order (NLO), where the dependence on the physical meson and baryon masses
is kept. The number of free parameters is reduced significantly down to 12 by
relying on large- sum rules. Altogether we describe accurately more than
220 data points from six different lattice groups, BMW, PACS-CS, HSC, LHPC,
QCDSF-UKQCD and NPLQCD. Values for all counter terms relevant at NLO are
predicted. In particular we extract a pion-nucleon sigma term of 39
MeV and a strangeness sigma term of the nucleon of MeV. The flavour SU(3) chiral limit of the baryon octet and
decuplet masses is determined with MeV and MeV.
Detailed predictions for the baryon masses as currently evaluated by the ETM
lattice QCD group are made.Comment: 44 pages, 10 figures and 6 tables - the revised manuscript contains
the results of additional fits at the N^2LO level - 4 additional figures show
the size of finite volume corrections for each lattice point - more technical
details on the evaluation of finite volume effects are give
Quark-mass dependence of baryon resonances
We study the quark-mass dependence of J^P = \frac12^- s-wave and J^P =
\frac32^- d-wave baryon resonances. Parameter-free results are obtained in
terms of the leading order chiral Lagrangian. In the 'heavy' SU(3) limit with
m_\pi =m_K \simeq 500 MeV the s-wave resonances turn into bound states forming
two octets plus a singlet representations of the SU(3) group. Similarly the
d-wave resonances turn into bound states forming an octet and a decuplet in
this limit. A contrasted result is obtained in the 'light' SU(3) limit with
m_\pi =m_K \simeq 140 MeV for which no resonances exist.Comment: 8 pages, three figures, talk presented at HYP200
Horn rewritability vs PTime query evaluation for description logic TBoxes
We study the following question: if τ is a TBox that is formulated in an expressive DL L and all CQs can be evaluated in PTime w.r.t. τ, can τ be replaced by a TBox τ' that is formulated in the Horn-fragment of L and such that for all CQs and ABoxes, the answers w.r.t. τ and τ' coincide? Our main results are that this is indeed the case when L is the set of ALCHI or ALCIF TBoxes of quantifier depth 1 (which covers the majority of such TBoxes), but not for ALCHIF and ALCQ TBoxes of depth 1
- …