346 research outputs found
Goryachev-Chaplygin, Kovalevskaya, and Brdi\v{c}ka-Eardley-Nappi-Witten pp-waves spacetimes with higher rank St\"ackel-Killing tensors
Hidden symmetries of the Goryachev-Chaplygin and Kovalevskaya gyrostats
spacetimes, as well as the Brdi\v{c}ka-Eardley-Nappi-Witten pp-waves are
studied. We find out that these spacetimes possess higher rank
St\"ackel-Killing tensors and that in the case of the pp-wave spacetimes the
symmetry group of the St\"ackel-Killing tensors is the well-known Newton-Hooke
group.Comment: 11 pages; accepted for publication in JM
The modular Dirac equation
We introduce a new equation we dubbed the modular Dirac equation to see and
reconstruct a spin 1/2 particle at the center of a nearly spacetime in
the entanglement wedge reconstruction paradigm and we study hidden symmetries
of this spacetime, too. Various properties of the Dirac modular operator are
studied: a generalized Tomita-Takesaki construction, the connection to the
Schwarzian derivative of the logarithm of the modular Dirac operator, the link
with the an allowable complex metric, the connection to regenesis, we write the
corresponding Lagrangian of the modular Dirac equation and we put in
perspective some limitations of the current bulk reconstruction in the case of
unknown couplings.Comment: 14 pages. Comments welcome
An architecture-based dependability modeling framework using AADL
For efficiency reasons, the software system designers' will is to use an
integrated set of methods and tools to describe specifications and designs, and
also to perform analyses such as dependability, schedulability and performance.
AADL (Architecture Analysis and Design Language) has proved to be efficient for
software architecture modeling. In addition, AADL was designed to accommodate
several types of analyses. This paper presents an iterative dependency-driven
approach for dependability modeling using AADL. It is illustrated on a small
example. This approach is part of a complete framework that allows the
generation of dependability analysis and evaluation models from AADL models to
support the analysis of software and system architectures, in critical
application domains
Memory Leak Analysis by Contradiction
We present a novel leak detection algorithm. To prove the absence of
a memory leak, the algorithm assumes its presence and runs a backward heap analysis to disprove this assumption. We have implemented this approach in a memory leak analysis tool and used it to analyze several routines that manipulate linked lists and trees. Because of the reverse nature of the algorithm, the analysis can locally reason about the absence of memory leaks. We have also used the tool as a scalable, but unsound leak detector for C programs. The tool has found several bugs in larger programs from the SPEC2000 suite
Software dependability modeling using an industry-standard architecture description language
Performing dependability evaluation along with other analyses at
architectural level allows both making architectural tradeoffs and predicting
the effects of architectural decisions on the dependability of an application.
This paper gives guidelines for building architectural dependability models for
software systems using the AADL (Architecture Analysis and Design Language). It
presents reusable modeling patterns for fault-tolerant applications and shows
how the presented patterns can be used in the context of a subsystem of a
real-life application
- …