554,740 research outputs found
A Concurrent Logical Relation
AbstractâWe present a logical relation for showing the correctness of program transformations based on a new type-and-effect system for a concurrent extension of an ML-like language with higher-order functions, higher-order store and dynamic memory allocation. We show how to use our model to verify a number of interesting program transformations that rely on effect annotations. In particular, we prove a Parallelization Theorem, which expresses when it is sound to run two expressions in parallel instead of sequentially. The conditions are expressed solely in terms of the types and effects of the expressions. To the best of our knowledge, this is the first such result for a concurrent higher-order language with higher-order store and dynamic memory allocation. I
A Functional, Comprehensive and Extensible Multi-Platform Querying and Transformation Approach
This thesis is about a new model querying and transformation approach called FunnyQT which is realized as a set of APIs and embedded domain-specific languages (DSLs) in the JVM-based functional Lisp-dialect Clojure. Founded on a powerful model management API, FunnyQT provides querying services such as comprehensions, quantified expressions, regular path expressions, logic-based, relational model querying, and pattern matching. On the transformation side, it supports the definition of unidirectional model-to-model transformations, of in-place transformations, it supports defining bidirectional transformations, and it supports a new kind of co-evolution transformations that allow for evolving a model together with its metamodel simultaneously. Several properties make FunnyQT unique. Foremost, it is just a Clojure library, thus, FunnyQT queries and transformations are Clojure programs. However, most higher-level services are provided as task-oriented embedded DSLs which use Clojure's powerful macro-system to support the user with tailor-made language constructs important for the task at hand. Since queries and transformations are just Clojure programs, they may use any Clojure or Java library for their own purpose, e.g., they may use some templating library for defining model-to-text transformations. Conversely, like every Clojure program, FunnyQT queries and transformations compile to normal JVM byte-code and can easily be called from other JVM languages. Furthermore, FunnyQT is platform-independent and designed with extensibility in mind. By default, it supports the Eclipse Modeling Framework and JGraLab, and support for other modeling frameworks can be added with minimal effort and without having to modify the respective framework's classes or FunnyQT itself. Lastly, because FunnyQT is embedded in a functional language, it has a functional emphasis itself. Every query and every transformation compiles to a function which can be passed around, given to higher-order functions, or be parametrized with other functions
One-loop effects of extra dimensions on the WW\gamma and WWZ vertices
The one-loop contribution of the excited Kaluza-Klein (KK) modes of the
gauge group on the off-shell and vertices is
calculated in the context of a pure Yang-Mills theory in five dimensions and
its phenomenological implications discussed. The use of a gauge-fixing
procedure for the excited KK modes that is covariant under the standard gauge
transformations of the group is stressed. A gauge-fixing term and the
Faddeev-Popov ghost sector for the KK gauge modes that are separately invariant
under the standard gauge transformations of are presented. It is
shown that the one-loop contributions of the KK modes to the off-shell
and vertices are free of ultraviolet divergences and
well-behaved at high energies. It is found that for a size of the fifth
dimension of , the one-loop contribution of the KK modes to
these vertices is about one order of magnitude lower than the corresponding
standard model radiative correction. This contribution is similar to the one
estimated for new gauge bosons contributions in other contexts. Tree-level
effects on these vertices induced by operators of higher canonical dimension
are also investigated. It is found that these effects are lower than those
generated at the one-loop order by the KK gauge modes.Comment: 19 pages, 9 figures. Some typos were correcte
A transformation-driven approach to automate feedback verification results
International audienceThe integration of formal verification methods in modeling activities is a key issue to ensure the correctness of complex system design models. In this purpose, the most common approach consists in defining a translational semantics mapping the abstract syntax of the designer dedicated Domain-Specific Modeling Language (DSML) to a formal verification dedicated semantic domain in order to reuse the available powerful verification technologies. Formal verification is thus usually achieved using model transformations. However, the verification results are available in the formal domain which significantly impairs their use by the system designer which is usually not an expert of the formal technologies. In this paper, we introduce a novel approach based on Higher-Order transformations that analyze and instrument the transformation that expresses the semantics in order to produce traceability data to automatize the back propagation of verification results to the DSML end-user
On a Covariant Determination of Mass Scales in Warped Backgrounds
We propose a method of determining masses in brane scenarios which is
independent of coordinate transformations. We apply our method to the scenario
of Randall and Sundrum (RS) with two branes, which provides a solution to the
hierarchy problem. The core of our proposal is the use of covariant equations
and expressing all coordinate quantities in terms of invariant distances. In
the RS model we find that massive brane fields propagate proper distances
inversely proportional to masses that are not exponentially suppressed. The
hierarchy between the gravitational and weak interactions is nevertheless
preserved on the visible brane due to suppression of gravitational interactions
on that brane. The towers of Kaluza-Klein states for bulk fields are observed
to have different spacings on different branes when all masses are measured in
units of the fundamental scale. Ratios of masses on each brane are the same in
our covariant and the standard interpretations. Since masses of brane fields
are not exponentiated, the fundamental scale of higher-dimensional gravity must
be of the order of the weak scale.Comment: 14 page
Dynamics and Control of Satellite Formations Invariant under the Zonal Harmonic Perturbation
A satellite formation operating in low-altitude orbits is subject to perturbations associated to the higher-order harmonics of the gravitational field, which cause a degradation of the formation configurations designed based on the unperturbed model of the HillâClohessyâWiltshire equations. To compensate for these effects, periodic reconfiguration maneuvers are necessary, requiring the prior allocation of a propellant mass budget and, eventually, the use of resources from the ground segment, having a non-negligible impact on the complexity and cost of the mission. Using the Hamiltonian formalism and canonical transformations, a model is developed that allows designing configurations for formation flying invariant with respect to the zonal harmonic perturbation. Jn
invariant configurations can be characterized, selecting the drift rate (or boundedness condition) and the amplitude of the oscillations, based on four parameters which can be easily converted in position and velocity components for the satellites of the formation. From this model, a guidance strategy is developed to inject a satellite approaching another spacecraft into a bounded relative trajectory about it and the optimal time for the maneuver, minimizing the total ÎV
, is identified. The effectiveness of the model and of the guidance strategy is verified on some scenarios of interest for formations operating in a sun-synchronous and a medium-inclination low Earth orbit and a medium-inclination lunar orbit
Extended Weyl Invariance in a Bimetric Model and Partial Masslessness
We revisit a particular ghost-free bimetric model which is related to both
partial masslessness (PM) and conformal gravity. Linearly, the model propagates
six instead of seven degrees of freedom not only around de Sitter but also
around flat spacetime. Nonlinearly, the equations of motion can be recast in
the form of expansions in powers of curvatures, and exhibit a remarkable amount
of structure. In this form, the equations are shown to be invariant under
scalar gauge transformations, at least up to six orders in derivatives, the
lowest order term being a Weyl scaling of the metrics. The terms at
two-derivative order reproduce the usual PM gauge transformations on de Sitter
backgrounds. At the four-derivative order, a potential obstruction that could
destroy the symmetry is shown to vanish. This in turn guarantees the gauge
invariance to at least six-orders in derivatives. This is equivalent to adding
up to 10-derivative corrections to conformal gravity. More generally, we
outline a procedure for constructing the gauge transformations order by order
as an expansion in derivatives and comment on the validity and limitations of
the procedure. We also discuss recent arguments against the existence of a PM
gauge symmetry in bimetric theory and show that, at least in their present
form, they are evaded by the model considered here. Finally, we argue that a
bimetric approach to PM theory is more promising than one based on the
existence of a fundamental PM field.Comment: Latex, 35 pages. Matches published versio
Automatically Discovering Hidden Transformation Chaining Constraints
Model transformations operate on models conforming to precisely defined
metamodels. Consequently, it often seems relatively easy to chain them: the
output of a transformation may be given as input to a second one if metamodels
match. However, this simple rule has some obvious limitations. For instance, a
transformation may only use a subset of a metamodel. Therefore, chaining
transformations appropriately requires more information. We present here an
approach that automatically discovers more detailed information about actual
chaining constraints by statically analyzing transformations. The objective is
to provide developers who decide to chain transformations with more data on
which to base their choices. This approach has been successfully applied to the
case of a library of endogenous transformations. They all have the same source
and target metamodel but have some hidden chaining constraints. In such a case,
the simple metamodel matching rule given above does not provide any useful
information
- âŠ