pinecone/core-2020-05-10-deduplication huggingface dataset:
Integrated Environment for Verifying and Running Distributed Components

International audienceThis paper targets the generation of distributed applications with safety guarantees. The proposed approach starts from graphical specification formalisms allowing the architectural and behavioral description of component systems. From this point, the user can automatically verify application properties using model-checking techniques. Finally, the specified and verified component model can be translated into executable Java code. We implement our approach in a tool suite distributed as an Eclipse plugin. This paper also illustrates our approach by modeling and verifying Peterson's leader election algorithm
Automated Model Merge by Design Space Exploration

Industrial applications of model-driven engineering to develop large and complex systems resulted in an increasing demand for collaboration features. However, use cases such as model differencing and merging have turned out to be a difficult challenge, due to (i) the graph-like nature of models, and (ii) the complexity of certain operations (e.g. hierarchy refactoring) that are common today. In the paper, we present a novel search-based automated model merge approach where rule-based design space exploration is used to search the space of solution candidates that represent conflict-free merged models. Our method also allows engineers to easily incorporate domain-specific knowledge into the merge process to provide better solutions. The merge process automatically calculates multiple merge candidates to be presented to domain experts for final selection. Furthermore, we propose to adopt a generic synthetic benchmark to carry out an initial scalability assessment for model merge with large models and large change sets
Finding Recurrent Sets with Backward Analysis and Trace Partitioning

We propose an abstract-interpretation-based analysis for recurrent sets.\ud
A recurrent set is a set of states from which the execution of a program cannot or\ud
might not (as in our case) escape. A recurrent set is a part of a program’s nontermination\ud
proof (that needs to be complemented by reachability analysis). We\ud
find recurrent sets by performing a potentially over-approximate backward analysis\ud
that produces an initial candidate. We then perform over-approximate forward\ud
analysis on the candidate to check and refine it and ensure soundness. In practice,\ud
the analysis relies on trace partitioning that predicts future paths through the\ud
program that non-terminating executions will take. Using our technique, we were\ud
able to find recurrent sets in many benchmarks found in the literature including\ud
some that, to our knowledge, cannot be handled by existing tools. In addition,\ud
we note that typically, analyses that search for recurrent sets are applied to linear\ud
under-approximations of programs or employ some form of non-approximate\ud
numeric reasoning. In contrast, our analysis uses standard abstract-interpretation\ud
techniques and is potentially applicable to a larger class of abstract domains (and\ud
therefore – programs).Post-print22nd International Conference on Tools and Algorithms for the Construction and Analysis of Systems, 2-8 April 2016, Eindhoven, The Netherlands
Approaching the Coverability Problem Continuously

The coverability problem for Petri nets plays a central role in the
verification of concurrent shared-memory programs. However, its high
EXPSPACE-complete complexity poses a challenge when encountered in real-world
instances. In this paper, we develop a new approach to this problem which is
primarily based on applying forward coverability in continuous Petri nets as a
pruning criterion inside a backward coverability framework. A cornerstone of
our approach is the efficient encoding of a recently developed polynomial-time
algorithm for reachability in continuous Petri nets into SMT. We demonstrate
the effectiveness of our approach on standard benchmarks from the literature,
which shows that our approach decides significantly more instances than any
existing tool and is in addition often much faster, in particular on large
instances.Comment: 18 pages, 4 figure
Characteristic Formulae for Session Types

© Springer-Verlag Berlin Heidelberg 2016.Subtyping is a crucial ingredient of session type theory and its applications, notably to programming language implementations. In this paper, we study effective ways to check whether a session type is a subtype of another by applying a characteristic formulae approach to the problem. Our core contribution is an algorithm to generate a modal μ-calculus formula that characterises all the supertypes (or subtypes) of a given type. Subtyping checks can then be off-loaded to model checkers, thus incidentally yielding an efficient algorithm to check safety of session types, soundly and completely. We have implemented our theory and compared its cost with other classical subtyping algorithms
Efficient Syntax-Driven Lumping of Differential Equations

We present an algorithm to compute exact aggregations of a class of systems of ordinary differential equations (ODEs). Our approach consists in an extension of Paige and Tarjan’s seminal solution to the coarsest refinement problem by encoding an ODE system into a suitable discrete-state representation. In particular, we consider a simple extension of the syntax of elementary chemical reaction networks because (i) it can express ODEs with derivatives given by polynomials of degree at most two, which are relevant in many applications in natural sciences and engineering; and (ii) we can build on two recently introduced bisimulations, which yield two complementary notions of ODE lumping. Our algorithm computes the largest bisimulations in O(r⋅s⋅logs)O(r⋅s⋅log⁡s) time, where r is the number of monomials and s is the number of variables in the ODEs. Numerical experiments on real-world models from biochemistry, electrical engineering, and structural mechanics show that our prototype is able to handle ODEs with millions of variables and monomials, providing significant model reductions
Provably weak instances of ring-LWE revisited

In CRYPTO 2015, Elias, Lauter, Ozman and Stange described an attack on the non-dual decision version of the ring learning with errors problem (RLWE) for two special families of defining polynomials, whose construction depends on the modulus q that is being used. For particularly chosen error parameters, they managed to solve non-dual decision RLWE given 20 samples, with a success rate ranging from 10% to 80%. In this paper we show how to solve the search version for the same families and error parameters, using only 7 samples with a success rate of 100%. Moreover our attack works for every modulus q instead of the q that was used to construct the defining polynomial. The attack is based on the observation that the RLWE error distribution for these families of polynomials is very skewed in the directions of the polynomial basis. For the parameters chosen by Elias et al. the smallest errors are negligible and simple linear algebra suffices to recover the secret. But enlarging the error paremeters makes the largest errors wrap around, thereby turning the RLWE problem unsuitable for cryptographic applications. These observations also apply to dual RLWE, but do not contradict the seminal work by Lyubashevsky, Peikert and Regev
Zero-Knowledge Arguments for Lattice-Based Accumulators: Logarithmic-Size Ring Signatures and Group Signatures Without Trapdoors

International audienceAn accumulator is a function that hashes a set of inputs into a short, constant-size string while preserving the ability to efficiently prove the inclusion of a specific input element in the hashed set. It has proved useful in the design of numerous privacy-enhancing protocols, in order to handle revocation or simply prove set membership. In the lattice setting, currently known instantiations of the primitive are based on Merkle trees, which do not interact well with zero-knowledge proofs. In order to efficiently prove the membership of some element in a zero-knowledge manner, the prover has to demonstrate knowledge of a hash chain without revealing it, which is not known to be efficiently possible under well-studied hardness assumptions. In this paper, we provide an efficient method of proving such statements using involved extensions of Stern's protocol. Under the Small Integer Solution assumption, we provide zero-knowledge arguments showing possession of a hash chain. As an application, we describe new lattice-based group and ring signatures in the random oracle model. In particular, we obtain: (i) The first lattice-based ring signatures with logarithmic size in the cardinality of the ring; (ii) The first lattice-based group signature that does not require any GPV trapdoor and thus allows for a much more efficient choice of parameters
Discrete conformal maps: boundary value problems, circle domains, Fuchsian and Schottky uniformization

We discuss several extensions and applications of the theory of discretely conformally equivalent triangle meshes (two meshes are considered conformally equivalent if corresponding edge lengths are related by scale factors attached to the vertices). We extend the fundamental definitions and variational principles from triangulations to polyhedral surfaces with cyclic faces. The case of quadrilateral meshes is equivalent to the cross ratio system, which provides a link to the theory of integrable systems. The extension to cyclic polygons also brings discrete conformal maps to circle domains within the scope of the theory. We provide results of numerical experiments suggesting that discrete conformal maps converge to smooth conformal maps, with convergence rates depending on the mesh quality. We consider the Fuchsian uniformization of Riemann surfaces represented in different forms: as immersed surfaces in \mathbb {R}^{3}, as hyperelliptic curves, and as \mathbb {CP}^{1} modulo a classical Schottky group, i.e., we convert Schottky to Fuchsian uniformization. Extended examples also demonstrate a geometric characterization of hyperelliptic surfaces due to Schmutz Schaller
Constructing solutions to the Björling problem for isothermic surfaces by structure preserving discretization

In this article, we study an analog of the Björling problem for isothermic surfaces (that are a generalization of minimal surfaces): given a regular curve γ in R3 and a unit normal vector field n along γ, find an isothermic surface that contains γ, is normal to n there, and is such that the tangent vector γ′ bisects the principal directions of curvature. First, we prove that this problem is uniquely solvable locally around each point of γ, provided that γ and n are real analytic. The main result is that the solution can be obtained by constructing a family of discrete isothermic surfaces (in the sense of Bobenko and Pinkall) from data that is read off from γ, and then passing to the limit of vanishing mesh size. The proof relies on a rephrasing of the Gauss-Codazzi-system as analytic Cauchy problem and an in-depth-analysis of its discretization which is induced from the geometry of discrete isothermic surfaces. The discrete-to-continuous limit is carried out for the Christoffel and the Darboux transformations as well
A variational principle for cyclic polygons with prescribed edge lengths

We provide a new proof of the elementary geometric theorem on the existence
and uniqueness of cyclic polygons with prescribed side lengths. The proof is
based on a variational principle involving the central angles of the polygon as
variables. The uniqueness follows from the concavity of the target function.
The existence proof relies on a fundamental inequality of information theory.
  We also provide proofs for the corresponding theorems of spherical and
hyperbolic geometry (and, as a byproduct, in $1+1$ spacetime). The spherical
theorem is reduced to the euclidean one. The proof of the hyperbolic theorem
treats three cases separately: Only the case of polygons inscribed in compact
circles can be reduced to the euclidean theorem. For the other two cases,
polygons inscribed in horocycles and hypercycles, we provide separate
arguments. The hypercycle case also proves the theorem for "cyclic" polygons in
$1+1$ spacetime.Comment: 18 pages, 6 figures. v2: typos corrected, final versio
Complex line bundles over simplicial complexes and their applications

Discrete vector bundles are important in Physics and recently found remarkable applications in Computer Graphics. This article approaches discrete bundles from the viewpoint of Discrete Differential Geometry, including a complete classification of discrete vector bundles over finite simplicial complexes. In particular, we obtain a discrete analogue of a theorem of André Weil on the classification of hermitian line bundles. Moreover, we associate to each discrete hermitian line bundle with curvature a unique piecewise-smooth hermitian line bundle of piecewise-constant curvature. This is then used to define a discrete Dirichlet energy which generalizes the well-known cotangent Laplace operator to discrete hermitian line bundles over Euclidean simplicial manifolds of arbitrary dimension
Black hole accretion discs

This is an introduction to models of accretion discs around black holes.
After a presentation of the non-relativistic equations describing the structure
and evolution of geometrically thin accretion discs we discuss their
steady-state solutions and compare them to observation. Next we describe in
detail the thermal-viscous disc instability model and its application to dwarf
novae for which it was designed and its X-ray irradiated-disc version which
explains the soft X--ray transients, i.e. outbursting black-hole low-mass X-ray
binaries. We then turn to the role of advection in accretion flows onto black
holes illustrating its action and importance with a toy model describing both
ADAFs and slim discs. We conclude with a presentation of the
general-relativistic formalism describing accretion discs in the Kerr
space-time.Comment: 41 pages, 11 figures, Chapter 1 in: "Astrophysics of Black Holes -
  From fundamental aspects to latest developments", Ed. Cosimo Bambi, Springer:
  Astrophysics and Space Science Library 440 (2016). Minor errors correcte
Transient Black Hole Binaries

The last two decades have seen a great improvement in our understand- ing of
the complex phenomenology observed in transient black-hole binary systems,
especially thanks to the activity of the Rossi X-Ray Timing Explorer satellite,
com- plemented by observations from many other X-ray observatories and
ground-based radio, optical and infrared facilities. Accretion alone cannot
describe accurately the intricate behavior associated with black-hole
transients and it is now clear that the role played by different kinds of
(often massive) outflows seen at different phases of the outburst evolution of
these systems is as fundamental as the one played by the accretion process
itself. The spectral-timing states originally identified in the X-rays and
fundamentally based on the observed effect of accretion, have acquired new
importance as they now allow to describe within a coherent picture the
phenomenology observed at other wave- length, where the effects of ejection
processes are most evident. With a particular focus on the phenomenology seen
in the X-ray band, we review the current state-of-the-art of our knowledge of
black hole transients, describing the accretion-ejection connection at play
during outbursts through the evolution of the observed spectral-timing
properties. Although we mainly concentrate on the ob- servational aspects of
the global X-ray transient picture, we also provide physical insight to it by
reviewing (when available) the theoretical explanations and models proposed to
explain the observed phenomenology.Comment: 37 pages, 7 figures, to be published in: "Astrophysics of Black Holes
  - From fundamental aspects to latest developments", Ed. Cosimo Bambi,
  Springer: Astrophysics and Space Science Library. arXiv admin note: text
  overlap with arXiv:0708.0148 by other author
Black hole spin: theory and observation

In the standard paradigm, astrophysical black holes can be described solely
by their mass and angular momentum - commonly referred to as `spin' - resulting
from the process of their birth and subsequent growth via accretion. Whilst the
mass has a standard Newtonian interpretation, the spin does not, with the
effect of non-zero spin leaving an indelible imprint on the space-time closest
to the black hole. As a consequence of relativistic frame-dragging, particle
orbits are affected both in terms of stability and precession, which impacts on
the emission characteristics of accreting black holes both stellar mass in
black hole binaries (BHBs) and supermassive in active galactic nuclei (AGN).
Over the last 30 years, techniques have been developed that take into account
these changes to estimate the spin which can then be used to understand the
birth and growth of black holes and potentially the powering of powerful jets.
In this chapter we provide a broad overview of both the theoretical effects of
spin, the means by which it can be estimated and the results of ongoing
campaigns.Comment: 55 pages, 5 figures. Published in: "Astrophysics of Black Holes -
  From fundamental aspects to latest developments", Ed. Cosimo Bambi, Springer:
  Astrophysics and Space Science Library. Additional corrections mad
Descriptive complexity of graph spectra

Two graphs are co-spectral if their respective adjacency matrices have the
same multi-set of eigenvalues. A graph is said to be determined by its spectrum
if all graphs that are co-spectral with it are isomorphic to it. We consider
these properties in relation to logical definability. We show that any pair of
graphs that are elementarily equivalent with respect to the three-variable
counting first-order logic $C^3$ are co-spectral, and this is not the case with
$C^2$, nor with any number of variables if we exclude counting quantifiers. We
also show that the class of graphs that are determined by their spectra is
definable in partial fixed-point logic with counting. We relate these
properties to other algebraic and combinatorial problems.Comment: 17 page
On the formalization of some results of context-free language theory

This work describes a formalization effort, using the Coq proof assistant, of fundamental results related to the classical theory of context-free grammars and languages. These include closure properties (union, concatenation and Kleene star), grammar simplification (elimination of useless symbols, inaccessible symbols, empty rules and unit rules), the existence of a Chomsky Normal Form for context-free grammars and the Pumping Lemma for context-free languages. The result is an important set of libraries covering the main results of context-free language theory, with more than 500 lemmas and theorems fully proved and checked. This is probably the most comprehensive formalization of the classical context-free language theory in the Coq proof assistant done to the present date, and includes the important result that is the formalization of the Pumping Lemma for context-free languages.info:eu-repo/semantics/publishedVersio
Designing Massive Open Online Learning Processes: The importance of the social element

This is a pre-print for personal use only. Please refer to the Springer website for the official, published version http://www.springer.com/978-3-662-52923-2MOOCs as provision of open and online education have become phenomena in higher education that can’t be dismissed. While MOOCs might have originated in the US, the model used there does not fit well with the European take on education. In this chapter we describe an alternative more collaborative approach of MOOC design. This approach is based on a model already tested in practice and has been further elaborated and evaluated in the ECO project. The pedagogical framework is based on the notion that MOOCs should be designed to accommodate the specific context of open online education with its heterogeneity of learner needs. It differs very much from a traditional classroom approach and needs to put the learner center-stage in a social networked learning environment. We describe the characteristics of such a pedagogical framework and explain how digital inclusion, ubiquitous learning and gamification can provide affordances for active participation of learners that meet the learners’ needs. We illustrate how these aspects have been implemented in ECO sMOOCs and provide the first, positive, user evaluations of this approach.Part of the work carried out has been funded with support from the European Commission, under the ICT Policy Support Programme, as part of the Competitiveness and Innovation Framework Programme (CIP) in the ECO project under grant agreement n° 21127
On the set of periods of the 2-periodic Lyness' equation

The final publication is available at Springer via http://dx.doi.org/10.1007/978-3-662-52927-0_22We study the periodic solutions of the non-autonomous periodic Lyness’ recurrence un+2=(an+un+1)/un, where {an}n is a cycle with positive values a,b and with positive initial conditions. Among other methodological issues we give an outline of the proof of the following results: (1) If (a,b)¿(1,1), then there exists a value p0(a,b) such that for any p>p0(a,b) there exist continua of initial conditions giving rise to 2p-periodic sequences. (2) The set of minimal periods arising when (a,b)¿(0,8)2 and positive initial conditions are considered, contains all the even numbers except 4, 6, 8, 12 and 20. If a¿b, then it does not appear any odd period, except 1.Peer ReviewedPostprint (author's final draft
R&D dynamics with asymmetric efficiency

We consider an R&D investment function in a Cournot duopoly competition model inspired in the logistic equation. We study the economical effects resulting from the firms having different R&D efficiencies. We present three cases: (1) both firms are efficient and have the same degree of efficiency; (2) both firms are less efficient and have the same degree of efficiency; (3) firms are asymmetric in terms of the efficiency of their R&D investment programs. We study the myopic dynamics on the production costs obtained from investing the Nash investment equilibria.info:eu-repo/semantics/publishedVersio