6 research outputs found
Um problema de extensão relacionado ao laplaciano fracionário e aplicações
No full textThe Laplacian operator positivity allows its square roots de nition and this relates
directly to the problem of harmonious extension in the superior semi-space, like
an operator that takes the condition from Dirichlet's outline to the Neumann's condition.
In this work, that was based on results developed by Ca areli and Silvestre
[8], we got similar characterization for the Fractional Laplacian Operator. In addition,
we apply the characterization reported to the sdudy of existence of non-trivial
solution of the non-linear fractional Schrodinger equation.Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPESA positividade do operador Laplaciano permite a de ni c~ao de sua raiz quadrada
e esta se relaciona diretamente ao problema de extens~ao harm^onica no semi-espa co
superior, como um operador que leva a condi c~ao de contorno de Dirichlet a condi c~ao
de Neumann. Neste trabalho, baseado nos resultados desenvolvidos por Ca arelli
e Silvestre em [8], obtemos caracteriza c~ao semelhante para o operador Laplaciano
Fracion ario. Al em disso, aplicamos a caracteriza c~ao referida ao estudo de exist^encia
de solu c~ao n~ao-trivial da equa c~ao de Schr odinger fracion aria n~ao-linear.São Cristóvão, S
CSI-RAShi: Distributed Key Generation for CSIDH
No full textWe present an honest-majority Distributed Key Generation protocol (DKG) based on Shamir’s (k, n)-threshold secret sharing in the setting of Very Hard Homogenous Spaces (VHHS). DKGs in the discrete logarithm setting use Pedersen commitments, for which there is no known analogue in the VHHS setting. As a replacement, we introduce a new primitive called piecewise verifiable proofs, which allow a prover to prove that a list of NP-statements is valid with respect to a common witness, and such that the different statements can be verified individually. Our protocol is robust and actively secure in the Quantum Random Oracle Model. For n participants, the total runtime of our protocol is 2+λ+n(1+4λ)
group action evaluations, where λ
is the underlying security parameter, and is thus independent of the threshold k. When instantiated with CSIDH-512, this amounts to approximately 4.5+18n
seconds.sponsorship: Research Council KU Leuven|C14/18/067, Research Council KU Leuven|C14/18/067, CyberSecurity Research Flanders|VR20192203, FWO|1S95620Nstatus: Publishe
CSI-RAShi: Distributed key generation for CSIDH
No full textWe present an honest-majority Distributed Key Generation protocol (DKG) based on Shamir\u27s -threshold secret sharing in the setting of Very Hard Homogenous Spaces (VHHS). DKG\u27s in the DLOG setting use Pedersen commitments, for which there is no known analogue in the VHHS setting. As a replacement, we introduce a new primitive called piecewise verifiable proofs, which allow a prover to prove that a list of NP-statements is valid with respect to a common witness, and such that the different statements can be verified individually. Our protocol is robust and actively secure in the Quantum Random Oracle Model. For participants, the total runtime of our protocol is\break group action evaluations, where is the underlying security parameter, and is thus independent of the threshold . When instantiated with CSIDH-512, this amounts to approximately seconds
Representation learning with unconditional denoising diffusion models for dynamical systems
No full textInternational audienceWe propose denoising diffusion models for data-driven representation learning of dynamical systems. In this type of generative deep learning, a neural network is trained to denoise and reverse a diffusion process, where Gaussian noise is added to states from the attractor of a dynamical system. Iteratively applied, the neural network can then map samples from isotropic Gaussian noise to the state distribution. We showcase the potential of such neural networks in proof-of-concept experiments with the Lorenz 1963 system. Trained for state generation, the neural network can produce samples that are almost indistinguishable from those on the attractor. The model has thereby learned an internal representation of the system, applicable for different tasks other than state generation. As a first task, we fine-tune the pre-trained neural network for surrogate modelling by retraining its last layer and keeping the remaining network as a fixed feature extractor. In these low-dimensional settings, such fine-tuned models perform similarly to deep neural networks trained from scratch. As a second task, we apply the pre-trained model to generate an ensemble out of a deterministic run. Diffusing the run, and then iteratively applying the neural network, conditions the state generation, which allows us to sample from the attractor in the run's neighbouring region. To control the resulting ensemble spread and Gaussianity, we tune the diffusion time and, thus, the sampled portion of the attractor. While easier to tune, this proposed ensemble sampler can outperform tuned static covariances in ensemble optimal interpolation. Therefore, these two applications show that denoising diffusion models are a promising way towards representation learning for dynamical systems
Author Correction: Hypervirulent Listeria monocytogenes clones’ adaptation to mammalian gut accounts for their association with dairy products
No full textInternational audienceAn amendment to this paper has been published and can be accessed via a link at the top of the paper
Objetividades y subjetividades en la investigación geográfica: una investigación filosófica sobre métodos
No full textTítol: Objectivitats i subjectivitats en la recerca geogràfica: una investigació filosòfica sobre mètodesLes qüestions epistemològiques i ontològiques estan interrelacionades en l’àmplia investigació filosòfica sobre mètodes d’investigació. En primer lloc, es mostra que les diferents perspectives teòriques sobre l’objectivitat i la subjectivitat en els mètodes de recerca són part de (i són parcials a) tres grans tradicions nacionals en la filosofia occidental. Tot seguit, es presenta una seqüència de debats en les ciències socials lligant l’epistemologia i els mètodes amb paradigmes i sintagmes científics en discòrdia d’ençà finals del segle xix. Posteriorment, es debaten crítiques específiques dirigides a la recerca etnogràfica i rural com a casos extrems de la dissonància existent entre l’investigador i la recerca. Finalment, s’ofereix un model general de caracterització del jo investigador que explicita possibles biaixos perquè es puguin adoptar estratègies per gestionar-los. En darrer lloc, aquest model és debatut en relació amb aspectes de subjectivitat que han sorgit en la mateixa recerca de l’autor en zones costaneres de l’estat de Rio de Janeiro d’ençà mitjan de la dècada de 1980, durant un període de considerable metamorfosi epistemològica en la perspectiva de l’ecologia política que ha guiat les seves recerques en aquesta zona.Epistemological and ontological issues are intertwined in the broad philosophical inquiry into research methods. First, different theoretical perspectives concerning objectivity and subjectivity in research methods are shown to be part and partial to three grand national traditions in Western philosophy. Then, a sequence of debates in the social sciences is presented tying epistemology and methods to competing scientific paradigms and syntagms from the late 19th Century onward. After this, specific critics of ethnographical and rural research are discussed as extreme cases of cultural dissonance existing between researcher and researched. Finally, a general model of characterizing the researcher self is offered which makes possible biases explicit so that one can adopt strategies for controlling them. This model is then illustrated in issues of subjectivity which arose in the author’s own research in coastal areas of Rio de Janeiro state since the mid-1980s, during a period of considerable epistemological metamorphosis in the political ecology perspective which guided investigations there.Las cuestiones epistemológicas y ontológicas están entrelazadas en la amplia indagación filosófica sobre métodos de investigación. En primer lugar, se muestra que las diferentes perspectivas teóricas sobre la objetividad y la subjetividad en los métodos de investigación son parte de (y son parciales en) tres grandes tradiciones nacionales de la filosofía occidental. A continuación, se presenta una secuencia de debates en las ciencias sociales vinculando la epistemología y los métodos con paradigmas y sintagmas científicos en discordia desde finales del siglo xix en adelante. Posteriormente, se debaten críticas específicas dirigidas ala investigación etnográfica y rural como casos extremos de la desavenencia existente entre investigador e investigado. Finalmente, se ofrece un modelo general de caracterización del yo investigador que explicita posibles sesgos con la finalidad de adoptar estrategias para gestionarlos. En último lugar, este modelo es debatido en relación con aspectos de subjetividad que han surgido en la propia investigación del autor desarrollada en áreas costeras del estado de Río de Janeiro desde mediados de la década de 1980, durante un período de considerable metamorfosis epistemológica en la perspectiva de la ecología política que ha guiado sus investigaciones en esa zona
