Episciences.org
Not a member yet
6707 research outputs found
Sort by
All about unambiguous polynomial closure
No full textWe study a standard operator on classes of languages: unambiguous polynomialclosure. We prove that for every class C of regular languages satisfying mildproperties, the membership problem for its unambiguous polynomial closureUPol(C) reduces to the same problem for C. We also show that unambiguouspolynomial closure coincides with alternating left and right deterministicclosure. Moreover, we prove that if additionally C is finite, the separationand covering problems are decidable for UPol(C). Finally, we present anoverview of the generic logical characterizations of the classes built usingunambiguous polynomial closure
On the protected nodes in exponential recursive trees
No full textThe exponential recursive trees model several kinds of networks. At each step of growing of these trees, each node independently attracts a new node with probability p, or fails to do with probability 1 − p. Here, we investigate the number of protected nodes, total path length of protected nodes, and a mean study of the protected node profile of such trees
Du gisement à l'approvisionnement : extraction, transformation, diffusion, mise en œuvre
No full textSharp Restriction Theory
No full textThese are detailed notes for a lecture on "Sharp restriction theory" which I presented as part of my "Agregação em Matemática" in Instituto Superior Técnico, Lisboa, Portugal (9-10 February, 2023)
Properties of uniformly -connected graphs
No full textA graph on at least vertices is uniformly -connected if eachpair of its vertices is connected by and not more than independentpaths. We reinvestigate a recent constructive characterization of uniformly-connected graphs and obtain a more detailed result that relates the numberof vertices to the operations involved in constructing a respective uniformly-connected graph. Furthermore, we investigate how crossing numbers andtreewidths behave under the mentioned constructions. We demonstrate how theseresults can be utilized to study the structure and properties of uniformly-connected graphs with minimum number of vertices of minimum degree
A topological derivative-based algorithm to solve optimal control problems with control cost
No full textIn this paper, we consider optimization problems with -cost of thecontrols. Here, we take the support of the control as independent optimizationvariable. Topological derivatives of the corresponding value function withrespect to variations of the support are derived. These topological derivativesare used in a novel gradient descent algorithm with Armijo line-search. Undersuitable assumptions, the algorithm produces a minimizing sequence
Deformation and cavitation at the spherulite scale of an isotactic polypropylene
No full textEngineering stress-strain curves are generated from tensile tests on semi-crystalline thermoplastics, which may exhibit non-linearity and/or peak stress associated with striction/necking phenomenon of the specimen at the macroscopic scale. This work addresses this state of deformed specimen, on an isotactic polypropylene, where irreversible strains have led to a variable cross-sectional area along the necked region. 3D images in this region, obtained through Synchrotron Radiation Computed Tomography with two high resolutions are exploited. The best resolution (1 pixel length = 0.05 μm) allowed better understanding of the morphology of several deformed spherulites within which polar fan arrangements are clearly detailed. Thanks to the dentification of the boundaries of spherulite patterns, with a 0.7 μm resolution, the longitudinal and transverse elongations of larger numbers of spherulites are measured. The evolution of the volumetric plastic strains due to cavitation at the spherulitic scale along the necked regions is comprehensively analysed. Volume changes at this scale are highlighted, consisting of an increase in the case of void growth followed by a decrease at large strains due to the collapse of elongated voids. The effects of these results on the establishment of reliable constitutive model are discussed. It is found that accounting for plastic dilation is necessary for the accuracy of constitutive models
Solitons in 4d Wess-Zumino-Witten models -- Towards unification of integrable systems --
No full textWe construct soliton solutions of the four-dimensional Wess-Zumino-Witten(4dWZW) model in the context of a unified theory of integrable systems withrelation to the 4d/6d Chern-Simons theory. We calculate the action density ofthe solutions and find that the soliton solutions behave as the KP-typesolitons, that is, the one-soliton solution has a localized action/energydensity on a 3d hyperplane in 4-dimensions (soliton wall) and the n-solitonsolution describes n intersecting soliton walls with phase shifts. We note thatthe Ward conjecture holds mostly in the split signature (+,+,-,-). Furthermore,the 4dWZW model describes the string field theory action of the open N=2 stringtheory in the four-dimensional space-time with the split signature and henceour soliton solutions would describe a new-type of physical objects in the N=2string theory. We discuss instanton solutions in the 4dWZW model as well.Noncommutative extension and quantization of the unified theory of integrablesystems are also discussed.Comment: 19 pages, 2 figures; typos corrected, references added, version to appear in Proceedings of the OCNMP-2024 Conference: Bad Ems, 23-29 June 202
Disentangling Parallelism and Interference in Game Semantics
No full textGame semantics is a denotational semantics presenting compositionally thecomputational behaviour of various kinds of effectful programs. One of itscelebrated achievement is to have obtained full abstraction results forprogramming languages with a variety of computational effects, in a singleframework. This is known as the semantic cube or Abramsky's cube, which forsequential deterministic programs establishes a correspondence between certainconditions on strategies (''innocence'', ''well-bracketing'', ''visibility'')and the absence of matching computational effects. Outside of the sequentialdeterministic realm, there are still a wealth of game semantics-based fullabstraction results; but they no longer fit in a unified canvas. In particular,Ghica and Murawski's fully abstract model for shared state concurrency (IA)does not have a matching notion of pure parallel program-we say thatparallelism and interference (i.e. state plus semaphores) are entangled. Inthis paper we construct a causal version of Ghica and Murawski's model, alsofully abstract for IA. We provide compositional conditions parallel innocenceand sequentiality, respectively banning interference and parallelism, andleading to four full abstraction results. To our knowledge, this is the firstextension of Abramsky's semantic cube programme beyond the sequentialdeterministic world
Simply typed convertibility is TOWER-complete even for safe lambda-terms
No full textWe consider the following decision problem: given two simply typed-terms, are they -convertible? Equivalently, do they have thesame normal form? It is famously non-elementary, but the precise complexity -namely TOWER-complete - is lesser known. One goal of this short paper is topopularize this fact. Our original contribution is to show that the problem stays TOWER-completewhen the two input terms belong to Blum and Ong's safe -calculus, afragment of the simply typed -calculus arising from the study ofhigher-order recursion schemes. Previously, the best known lower bound for thissafe -convertibility problem was PSPACE-hardness. Our proof proceeds byreduction from the star-free expression equivalence problem, taking inspirationfrom the author's work with Pradic on "implicit automata in typed-calculi". These results also hold for -convertibility