26,010 research outputs found
Dirac-Brueckner-Hartree-Fock calculations for isospin asymmetric nuclear matter based on improved approximation schemes
We present Dirac-Brueckner-Hartree-Fock calculations for isospin asymmetric
nuclear matter which are based on improved approximations schemes. The
potential matrix elements have been adapted for isospin asymmetric nuclear
matter in order to account for the proton-neutron mass splitting in a more
consistent way. The proton properties are particularly sensitive to this
adaption and its consequences, whereas the neutron properties remains almost
unaffected in neutron rich matter. Although at present full Brueckner
calculations are still too complex to apply to finite nuclei, these
relativistic Brueckner results can be used as a guidance to construct a density
dependent relativistic mean field theory, which can be applied to finite
nuclei. It is found that an accurate reproduction of the
Dirac-Brueckner-Hartree-Fock equation of state requires a renormalization of
these coupling functions.Comment: 34 pages, 9 figures, submitted to Eur. Phys. J.
Schnabl's L_0 Operator in the Continuous Basis
Following Schnabl's analytic solution to string field theory, we calculate
the operators for a scalar field in the
continuous basis. We find an explicit and simple expression for them
that further simplifies for their sum, which is block diagonal in this basis.
We generalize this result for the bosonized ghost sector, verify their
commutation relation and relate our expressions to wedge state representations.Comment: 1+16 pages. JHEP style. Typos correcte
Declarative Specification
Deriving formal specifications from informal requirements is extremely difficult since one has to overcome the conceptual gap between an application domain and the domain of formal specification methods. To reduce this gap we introduce application-specific specification languages, i.e., graphical and textual notations that can be unambiguously mapped to formal specifications in a logic language. We describe a number of realised approaches based on this idea, and evaluate them with respect to their domain specificity vs. generalit
Specifying Logic Programs in Controlled Natural Language
Writing specifications for computer programs is not easy since one has to
take into account the disparate conceptual worlds of the application domain and
of software development. To bridge this conceptual gap we propose controlled
natural language as a declarative and application-specific specification
language. Controlled natural language is a subset of natural language that can
be accurately and efficiently processed by a computer, but is expressive enough
to allow natural usage by non-specialists. Specifications in controlled natural
language are automatically translated into Prolog clauses, hence become formal
and executable. The translation uses a definite clause grammar (DCG) enhanced
by feature structures. Inter-text references of the specification, e.g.
anaphora, are resolved with the help of discourse representation theory (DRT).
The generated Prolog clauses are added to a knowledge base. We have implemented
a prototypical specification system that successfully processes the
specification of a simple automated teller machine.Comment: 16 pages, compressed, uuencoded Postscript, published in Proceedings
CLNLP 95, COMPULOGNET/ELSNET/EAGLES Workshop on Computational Logic for
Natural Language Processing, Edinburgh, April 3-5, 199
Schematic models for dynamic yielding of sheared colloidal glasses
The nonlinear rheological properties of dense suspensions are discussed
within simplified models, suggested by a recent first principles approach to
the model of Brownian particles in a constant-velocity-gradient solvent flow.
Shear thinning of colloidal fluids and dynamical yielding of colloidal glasses
arise from a competition between a slowing down of structural relaxation,
because of particle interactions, and enhanced decorrelation of fluctuations,
caused by the shear advection of density fluctuations. A mode coupling approach
is developed to explore the shear-induced suppression of particle caging and
the resulting speed-up of the structural relaxation.Comment: 33 pages, 10 figures; accepted for publication in Faraday Disc. 123
(2002); small numerical correction
Attempto - From Specifications in Controlled Natural Language towards Executable Specifications
Deriving formal specifications from informal requirements is difficult since
one has to take into account the disparate conceptual worlds of the application
domain and of software development. To bridge the conceptual gap we propose
controlled natural language as a textual view on formal specifications in
logic. The specification language Attempto Controlled English (ACE) is a subset
of natural language that can be accurately and efficiently processed by a
computer, but is expressive enough to allow natural usage. The Attempto system
translates specifications in ACE into discourse representation structures and
into Prolog. The resulting knowledge base can be queried in ACE for
verification, and it can be executed for simulation, prototyping and validation
of the specification.Comment: 15 pages, compressed, uuencoded Postscript, to be presented at EMISA
Workshop 'Naturlichsprachlicher Entwurf von Informationssystemen -
Grundlagen, Methoden, Werkzeuge, Anwendungen', May 28-30, 1996, Ev. Akademie
Tutzin
Attempto Controlled English (ACE)
Attempto Controlled English (ACE) allows domain specialists to interactively
formulate requirements specifications in domain concepts. ACE can be accurately
and efficiently processed by a computer, but is expressive enough to allow
natural usage. The Attempto system translates specification texts in ACE into
discourse representation structures and optionally into Prolog. Translated
specification texts are incrementally added to a knowledge base. This knowledge
base can be queried in ACE for verification, and it can be executed for
simulation, prototyping and validation of the specification.Comment: 13 pages, compressed, uuencoded Postscript, to be presented at CLAW
96, The First International Workshop on Controlled Language Applications,
Katholieke Universiteit Leuven, 26-27 March 199
Competition between glass transition and liquid-gas separation in attracting colloids
We present simulation results addressing the phenomena of colloidal gelation
induced by attractive interactions. The liquid-gas transition is prevented by
the glass arrest at high enough attraction strength, resulting in a colloidal
gel. The dynamics of the system is controlled by the glass, with little effect
of the liquid-gas transition. When the system separates in a liquid and vapor
phases, even if the denser phase enters the non-ergodic region, the vapor phase
enables the structural relaxation of the system as a whole.Comment: Proceedings of the glass conference in Pisa (September 06
Deconstructibility and the Hill lemma in Grothendieck categories
A full subcategory of a Grothendieck category is called deconstructible if it
consists of all transfinite extensions of some set of objects. This concept
provides a handy framework for structure theory and construction of
approximations for subcategories of Grothendieck categories. It also allows to
construct model structures and t-structures on categories of complexes over a
Grothendieck category. In this paper we aim to establish fundamental results on
deconstructible classes and outline how to apply these in the areas mentioned
above. This is related to recent work of Gillespie, Enochs, Estrada, Guil
Asensio, Murfet, Neeman, Prest, Trlifaj and others.Comment: 20 pages; version 2: minor changes, misprints corrected, references
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