1,524 research outputs found
Automated Analysis of MUTEX Algorithms with FASE
In this paper we study the liveness of several MUTEX solutions by
representing them as processes in PAFAS s, a CCS-like process algebra with a
specific operator for modelling non-blocking reading behaviours. Verification
is carried out using the tool FASE, exploiting a correspondence between
violations of the liveness property and a special kind of cycles (called
catastrophic cycles) in some transition system. We also compare our approach
with others in the literature. The aim of this paper is twofold: on the one
hand, we want to demonstrate the applicability of FASE to some concrete,
meaningful examples; on the other hand, we want to study the impact of
introducing non-blocking behaviours in modelling concurrent systems.Comment: In Proceedings GandALF 2011, arXiv:1106.081
Robustness of a bisimulation-type faster-than preorder
TACS is an extension of CCS where upper time bounds for delays can be
specified. Luettgen and Vogler defined three variants of bismulation-type
faster-than relations and showed that they all three lead to the same preorder,
demonstrating the robustness of their approach. In the present paper, the
operational semantics of TACS is extended; it is shown that two of the variants
still give the same preorder as before, underlining robustness. An explanation
is given why this result fails for the third variant. It is also shown that
another variant, which mixes old and new operational semantics, can lead to
smaller relations that prove the same preorder.Comment: Express Worksho
Smooth tensionful higher-codimensional brane worlds with bulk and brane form fields
Completely regular tensionful codimension-n brane world solutions are
discussed, where the core of the brane is chosen to be a thin codimension-(n-1)
shell in an infinite volume flat bulk, and an Einstein-Hilbert term localized
on the brane is included (Dvali-Gabadadze-Porrati models). In order to support
such localized sources we enrich the vacuum structure of the brane by the
inclusion of localized form fields. We find that phenomenological constraints
on the size of the internal core seem to impose an upper bound to the brane
tension. Finite transverse-volume smooth solutions are also discussed.Comment: 1+14 pages, 2 figures; section 2.3 improved, typos corrected and
references added. Published versio
Analysis and verification of ECA rules in intelligent environments
Intelligent Environments (IEs) are physical spaces where Information Technology (IT) and other pervasive computing technologies are combined in order to achieve specific goals for the users and the environment. IEs have the goal of enriching user experience, increasing awareness of the environment. A number of applications are currently being deployed in domains ranging from smart homes to e-health and autonomous vehicles. Quite often IE support human activities, thus essential requirements to be ensured are correctness, reliability, safety and security. In this paper we present how a set of techniques and tools that have been developed for the verification of software can be employed in the verification of IE described by means of event-condition-action rules. More precisely, we reduce the problem of verifying key properties of these rules to satisfiability and termination problems that can be addressed using state-of-the-art Satisfiability Modulo Theory (SMT) solvers and program analysers. Our approach has been implemented in a tool called vIRONy. Our approach has been validated on a number of case studies from the literature
Experimental evidence of antiproton reflection by a solid surface
We report here experimental evidence of the reflection of a large fraction of
a beam of low energy antiprotons by an aluminum wall. This derives from the
analysis of a set of annihilations of antiprotons that come to rest in rarefied
helium gas after hitting the end wall of the apparatus. A Monte Carlo
simulation of the antiproton path in aluminum indicates that the observed
reflection occurs primarily via a multiple Rutherford-style scattering on Al
nuclei, at least in the energy range 1-10 keV where the phenomenon is most
visible in the analyzed data. These results contradict the common belief
according to which the interactions between matter and antimatter are dominated
by the reciprocally destructive phenomenon of annihilation.Comment: 5 pages with 5 figure
Compton-like scattering of a scalar particle with N photons and one graviton
Tree-level scattering amplitudes for a scalar particle coupled to an arbitrary number N of photons and a single graviton are computed. We employ the worldline formalism as the main tool to compute the irreducible part of the amplitude, where all the photons and the graviton are directly attached to the scalar line, then derive a \u201ctree replacement\u201d rule to construct the reducible parts of the amplitude which involve irreducible pure N-photon two-scalar amplitudes where one photon line emits the graviton. We test our construction by verifying the on-shell gauge and diffeomorphism Ward identities, at arbitrary N
Worldline approach to noncommutative field theory
The study of the heat-trace expansion in noncommutative field theory has
shown the existence of Moyal nonlocal Seeley-DeWitt coefficients which are
related to the UV/IR mixing and manifest, in some cases, the
non-renormalizability of the theory. We show that these models can be studied
in a worldline approach implemented in phase space and arrive to a master
formula for the -point contribution to the heat-trace expansion. This
formulation could be useful in understanding some open problems in this area,
as the heat-trace expansion for the noncommutative torus or the introduction of
renormalizing terms in the action, as well as for generalizations to other
nonlocal operators.Comment: 19 pages, version
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