Trispectrum versus Bispectrum in Single-Field Inflation

In the standard slow-roll inflationary cosmology, quantum fluctuations in a single field, the inflaton, generate approximately Gaussian primordial density perturbations. At present, the bispectrum and trispectrum of the density perturbations have not been observed and the probability distribution for these perturbations is consistent with Gaussianity. However, Planck satellite data will bring a new level of precision to bear on this issue, and it is possible that evidence for non-Gaussian effects in the primordial distribution will be discovered. One possibility is that a trispectrum will be observed without evidence for a non-zero bispectrum. It is not difficult for this to occur in inflationary models where quantum fluctuations in a field other than the inflaton contribute to the density perturbations. A natural question to ask is whether such an observation would rule out the standard scenarios. We explore this issue and find that it is possible to construct single-field models in which inflaton-generated primordial density perturbations have an observable trispectrum, but a bispectrum that is too small to be observed by the Planck satellite. However, an awkward fine tuning seems to be unavoidable.Comment: 15 pages, 3 figures; journal versio

Синтаксическая просодия и пунктуация текста художественного произведения

Изучая просодию текста художественного произведения, мы приходим к выводу о том, что арсенал устной речи несравненно богаче ее устного аналога. Экспрессивность живой речи в первую очередь реализуется с помощью таких просодических средств, как: 1) мелодика 2) темп (скорость) 3) диапазон голоса 4) паузация 5) тембр 6) громкость

Morphinanes isomères originaux isolés de Stephania zippeliana

A côté de huit aporphinoïdes, six alcaloïdes possédant une structure de morphinane ont été isolés des parties aériennes de #Stephania zippeliana$ Miq. (Ménispermacées) : quatre d'entre eux sont nouveaux : la (+)-erromangine 2, la (+)-tannagine 3, la (+)-zippeline 5 et la (+)-zippelianine 6. La (+)-isostephodeline 4 et les composés 2 et 3 sont isomères. La structure de la (+)-isostephodeline 4 a été corrigée. (Résumé d'auteur

Recaf: Java dialects as libraries

Mainstream programming languages like Java have limited support for language extensibility. Without mechanisms for syntactic abstraction, new programming styles can only be embedded in the form of libraries, limiting expressiveness. In this paper, we present Recaf, a lightweight tool for creating Java dialects; effectively extending Java with new language constructs and user defined semantics. The Recaf compiler generically transforms designated method bodies to code that is parameterized by a semantic factory (Object Algebra), defined in plain Java. The implementation of such a factory defines the desired runtime semantics. We applied our design to produce several examples from a diverse set of programming styles and two case studies: We define i) extensions for generators, asynchronous computations and asynchronous streams and ii) a Domain-Specific Language (DSL) for Parsing Expression Grammars (PEGs), in a few lines of code

Recaf: Java dialects as libraries

Mainstream programming languages like Java have limited support for language extensibility. Without mechanisms for syntactic abstraction, new programming styles can only be embedded in the form of libraries, limiting expressiveness. In this paper, we present Recaf, a lightweight tool for creating Java dialects; effectively extending Java with new language constructs and user defined semantics. The Recaf compiler generically transforms designated method bodies to code that is parameterized by a semantic factory (Object Algebra), defined in plain Java. The implementation of such a factory defines the desired runtime semantics. We applied our design to produce several examples from a diverse set of programming styles and two case studies: We define i) extensions for generators, asynchronous computations and asynchronous streams and ii) a Domain-Specific Language (DSL) for Parsing Expression Grammars (PEGs), in a few lines of code