1,721,459 research outputs found

    MOND-like fractional Laplacian theory

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    I provide a derivation of some characteristic effects of Milgrom's modified Newtonian dynamics (MOND) from a fractional version of Newton's theory based on the fractional Poisson equation. I employ the properties of the fractional Laplacian to investigate the features of the fundamental solution of the proposed model. The key difference between MOND and the fractional theory introduced here is that the latter is an inherently linear theory, featuring a characteristic length scale l, whilst the former is ultimately nonlinear in nature and it is characterized by an acceleration scale a0. Taking advantage of the Tully-Fisher relation, as the fractional order s approaches 3/2, I then connect the length scale l emerging from this modification of Newton's gravity, with the critical acceleration a0 of MOND. Finally, implications for galaxy rotation curves of a variable-order version of the model are discussed

    Domestic corpuscular inflaton

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    The aim of this paper is to provide a more precise description of the paradigm of corpuscular slow-roll inflation, which was previously introduced by Casadio et al. in [Corpuscular slow-roll inflation, Phys. Rev. D 97 (2018) 024041]. Specifically, we start by expanding the Starobinsky theory on a curved background and then infer the number and nature of the propagating degrees of freedom, both in the true inflationary phase and in a quasi-de Sitter approximation. We correctly find that the particle spectrum contains a transverse trace-free mode and a scalar one. The scalar mode displays a tachyonic nature during the slow-roll phase, due to the instability of the system, whereas it acquires the appropriate oscillatory behavior as the background approaches a critical value of the curvature. These results confirm the fact that the Einstein-Hilbert term acts as a perturbation to the quadratic one, and is responsible for driving the early Universe out of the inflationary phase, thus realizing the inflaton field in terms of pure (corpuscular) gravity

    Classicalizing gravity

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    One of the defining results of the twentieth century was the unravelling of the key feature of curvature singularities and what leads to their formation in General Relativity

    Sperimentazione di sistemi computer-assisted per la rilevazione della valutazione della didattica universitaria da parte degli studenti e dell’inserimento lavorativo e professionale dei laureati e dei diplomati

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    Il rapporto di ricerca è un'ampia descrizione dei risultati di vari esperimenti condotti in modo indipendente ma integrati l'un l'altro per raggiungere l'obiettivo di decidere al livello delle struture centrali (MIUR, CNVSU) se e come avviare in modo sistematico la valutazione della didattica via web da parte degli studenti e la valutazione con sistemi computer-assisted delle esperienze e delle riflessioni dei laureati dell'università italiana. Le conclusioni sono che bisogn aspettare qualche altro anno per avviare in modo sistematico indagini via web sulla qualità della didattica
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