198,343 research outputs found
Probability Calculus, Pitfalls of Intuition and Judicial Errors
No full textIn the last decades the powerful of the laboratories’ analytical results to highlight the dynamic of criminal acts has been object of an increasing attention, partly because of the enormous potentiality of the DNA test that has transformed forensic sciences. Statistics is assuming a fundamental role in forensic science, in particular to quantify the probative value of traces collected at the crime scene, or on individuals suspected to be involved in a crime, and analysed by forensic laboratories. Results of comparative analyses (comparative in the sense that some characteristics of traces recovered at the crime scene are compared to those of material originating from the suspect) are generally presented in numeric form, mostly in probability terms, and need to be carefully interpreted. Moreover, the scientific evidence collected at the
crime scene must be considered in conjunction with the bulk of informations the court possesses about the case. Judicial errors correlated to an improper use and
interpretation of probability calculus have originated a large debate about (1) how the probative value of the traces is computed, (2) how to interpret the statistical
expertise at trial, and (3) how the probative value of the scientific evidence can be combined with the other sources of information (for example, a witness statement)
in view of the court decision. Starting from a general description of the potential scenario of interest (section “The Evaluation of Scientific Evidence”), followed by
a non exhaustive overview (section “Pitfalls of Intuition”) of the possible errors of interpretation that can be originated by intuition which may be a bad substitute of
the laws of probability calculus, this paper shows (section “The Transition: Bayes’ Theorem”) how the Bayes’ theorem can represent a formidable tool to combine in a
rational way the different sources of information that may become available at trial
Il pensare dialogico nel percorso intellettuale di Hilary Putnam
No full textIl confronto di Putnam con Rosenzwig, Buber e Levinas è maturato in una monografia pubblicata nel 2008. Allo scopo di valorizzarla, propongo di leggerla alla luce di un triplice contesto. Innanzitutto, inserendola nell’itinerario speculativo di Putnam e nelle tappe che hanno seguito la sua adesione alla fede ebraica; in secondo luogo, interpretandola alla luce della proposta di Putnam in ambito di filosofia della religione; infine, mettendola in parallelo con le questioni chiave della sua (meta)filosofia. I limiti dell’interpretazione offerta da Putnam sono evidenti sotto il profilo filologico e per via di una profondità ermeneutica non esente da lacune. Anche la conoscenza dell’ambito giudaico da cui questo pensiero emerge risulta solo in parte sfruttata e, di conseguenza, le questioni su che cosa significhi realmente occuparsi di filosofia vengono affrontate senza essere sistematicamente definite. Ciò nonostante la presenza di “pensatori dialogici” nella riflessione di un autore classificato come “analitico”, rappresenta un fatto decisivo e non trascurabile nell’ambito della storia della filosofia contemporanea.Putnam's comparison with Rosenzwig, Buber and Levinas matured in a monograph published in 2008. In order to enhance it, I propose to read it in the light of a threefold context. First, by placing it in Putnam's speculative itinerary and in the stages that followed his adherence to the Jewish faith; secondly, by interpreting it in the light of Putnam's proposal in the field of philosophy of religion; finally, by placing it in parallel with the key questions of his (meta)philosophy. The limits of the interpretation offered by Putnam are evident from a philological point of view and because of a hermeneutic depth that is not free from gaps. Even the knowledge of the Jewish context from which this thought emerges is only partially exploited and, consequently, the questions on what it really means to deal with philosophy are addressed without being systematically defined. Nonetheless, the presence of "dialogical thinkers" in the reflection of an author classified as "analytic" represents a decisive and non-negligible fact in the history of contemporary philosophy
Weakly perturbed Schwarzschild lens in the strong deflection limit
No full textWe investigate the strong deflection limit of gravitational lensing by a Schwarzschild black hole embedded in an external gravitational field. The study of this model, analogous to the Chang and Refsdal lens in the weak deflection limit, is important to evaluate the gravitational perturbations on the relativistic images that appear in proximity of supermassive black holes hosted in galactic centers. By a simple dimensional argument, we prove that the tidal effect on the light ray propagation mainly occurs in the weak field region far away from the black hole and that the external perturbation can be treated as a weak field quadrupole term. We provide a description of relativistic critical curves and caustics and discuss the inversion of the lens mapping. Relativistic caustics are shifted and acquire a finite diamond shape. Sources inside the caustics produce four sequences of relativistic images. On the other hand, retro-lensing caustics are only shifted while remaining pointlike to the lowest order
A solution to the anisotropy problem in bouncing cosmologies
No full textBouncing cosmologies are often proposed as alternatives to standard inflation for the explanation of the homogeneity and flatness of the universe. In such scenarios,the present cosmological expansion is preceded by a contraction phase. However, during the contract ion, in general the anisotropy of the universe grows and eventually lead stoachaotic mix master behavior. This would either be hard to reconcile with observations or evenlead to a singularity in stead of the bounce. In order to preserve a smooth and isotropic bounce, the source for the contraction must have a super-stiff equation of state with P/rho = w > 1. In this letter we propose a new mechanism to solve the anisotropy problem for any low-energy value of w by arguing that high energy physics leads to a modification of the equation of state,with the introduction of non-linear terms. In such a scenario, the anisotropy is strongly suppressed during the high energy phase, allowing for a graceful isotropic bounce, even when the low-energy value of w is smaller than unity
Time delay in Black Hole Gravitational Lensing as a distance estimator
No full textWe calculate the time delay between different relativistic images formed by black hole gravitational lensing in the strong field limit. For spherically symmetric black holes, it turns out that the time delay between the first two images is proportional to the minimum impact angle. Their ratio gives a very interesting and precise measure of the distance of the black hole. Moreover, using also the separation between the images and their luminosity ratio, it is possible to extract the mass of the black hole. The time delay for the black hole at the center of our Galaxy is just few minutes, but for supermassive black holes with M = 10(8) divided by 10(9)M(circle dot) in the neighbourhood of the Local Group the time delay amounts to few days, thus being measurable with a good accuracy
The M31 pixel lensing plan campaign : macho lensing and self-lensing signals
No full textA.G. was supported by NSF grant AST-1103471. M.D. is thankful to Qatar National Research Fund (QNRF), member of Qatar Foundation, for support by grant NPRP 09-476-1-078. P.J. acknowledges support by the Swiss National Science Foundation.We present the final analysis of the observational campaign carried out by the PLAN (Pixel Lensing Andromeda) collaboration to detect a dark matter signal in form of MACHOs through the microlensing effect. The campaign consists of about 1 month/year observations carried out over 4 years (2007-2010) at the 1.5 m Cassini telescope in Loiano (Astronomical Observatory of BOLOGNA, OAB) plus 10 days of data taken in 2010 at the 2 m Himalayan Chandra Telescope monitoring the central part of M31 (two fields of about 13′ × 12.′6). We establish a fully automated pipeline for the search and the characterization of microlensing flux variations. As a result, we detect three microlensing candidates. We evaluate the expected signal through a full Monte Carlo simulation of the experiment completed by an analysis of the detection efficiency of our pipeline. We consider both "self lensing" and "MACHO lensing" lens populations, given by M31 stars and dark matter halo MACHOs, in M31 and the Milky Way, respectively. The total number of events is consistent with the expected self-lensing rate. Specifically, we evaluate an expected signal of about two self-lensing events. As for MACHO lensing, for full 0.5(10-2) M☉ MACHO halos, our prediction is for about four (seven) events. The comparatively small number of expected MACHO versus self-lensing events, together with the small number statistics at our disposal, do not enable us to put strong constraints on that population. Rather, the hypothesis, suggested by a previous analysis, on the MACHO nature of OAB-07-N2, one of the microlensing candidates, translates into a sizeable lower limit for the halo mass fraction in form of the would-be MACHO population, f, of about 15% for 0.5 M☉ MACHOs.Peer reviewe
Statistica e valutazione dell'evidenza scientifica
No full textLa statistica sta assumendo un ruolo di grande importanza nelle scienze forensi, in particolare nella quantificazione del valore probatorio di risultati di analisi genetiche, chimiche o fisiche su indizi detti ‘scientifici’ analizzati dai laboratori di polizia scientifica o medicina legale. Si tratta di un settore per sua natura caratterizzato da forte interdisciplinarietà. I risultati delle analisi comparative di laboratorio sono presentati prevalentemente in forma di probabilità (tipicamente, probabilità che le caratteristiche di una traccia coincidano con le caratteristiche del sospetto se un’altra persona è all’origine della traccia). Il lavoro del perito presentato in sede dibattimentale deve essere non solo corretto, ma deve essere correttamente interpretato da persone con formazione prettamente non scientifica, siano essi giudici, procuratori o avvocati. La Corte, pur essendo talvolta in possesso di solidi elementi di giudizio, si trova in ogni caso ad operare in condizioni di incertezza, poiché chiamata ad esprimere un giudizio su fatti che si sono verificati nel passato. L’incertezza non può essere eliminata, ma può essere misurata attraverso le probabilità. E’ indubbio come la comprensione del calcolo delle probabilità ponga difficoltà a tutti gli indidivui, e questo è valido sia per soggetti con formazione umanistica sia per soggetti con formazione scientifica. Gli elementi di prova, scientifici e non scientifici, da considerare congiuntamente al fine di quantificare in termini probabilistici l’incertezza sul caso in esame possono essere molti, e le leggi che permettono di valutare e combinare la probabilità di eventi incerti sono sovente contrarie all’intuizione. Generalmente le persone ragionano in modo intuitivo di fronte all’incertezza, e a questo proposito esiste una consistente letteratura di casi di errori giudiziari che sono stati indotti da ragionamenti errati fondati su un utilizzo improprio del calcolo delle probabilità. Tutto questo ha originato un forte dibattito e ha posto l'attenzione su un certo numero di domande riguardanti (a) come il valore probatorio degli indizi venga calcolato, (b) il significato della statistica presentata nel rapporto peritale, (c) come questo dato debba essere gestito in collegamento con altri elementi di prova raccolti durante il procedimento e (d) come il valore probatorio debba essere gestito per poter coerentemente prendere una decisione giuridica sul caso in esame. Lo scopo di questo capitolo è capire come sia possible quantificare la forza dell’evidenza raccolta a sostegno delle ipotesi di interesse per le parti, e a tal fine verranno approfonditi i punti (b) e (c)
Scalable solutions for the Control Unit of the KM3NeT DAQ system
No full textThe neutrino telescopes of KM3NeT are being incrementally expanded, and will reach their final size in the coming years. New versions of optical modules running new versions of firmware and new instrumentation for calibration are being introduced in the originally repetitive lattice. The inner architecture and data flow of the Control Unit of the KM3NeT telescopes is described, with information about computational and architectural complexity. The current goal is to control two full blocks of the KM3NeT/ARCA detector, i.e. 4370 CLBs and 128340 photomultipliers for 230 detection units, with a single mid-range commercial server machine. The system is designed with software protections and fault tolerance for hardware failure
A general solution for scalar perturbations in bouncing cosmologies
No full textBouncing cosmologies, suggested by string/M-theory, may provide an alternative to standard inflation for accounting for the origin of inhomogeneities in our universe. The fundamental question is as regards the correct way to evolve the scalar perturbations through the bounce. In this work, we determine the evolution of perturbations and the final spectrum for an arbitrary (spatially flat) bouncing cosmology, the only assumption being that the bounce is governed by a single physical scale. In particular, we find that the spectrum of the pre-bounce growing mode of the Bardeen potential (which is scale invariant in some limit, and thus compatible with observations) survives unaltered in the post-bounce only if the comoving pressure perturbation is directly proportional to the Bardeen potential rather than its Laplacian, as for any known form of ordinary matter. If some new physics acting at the bounce justifies such a relation, then we are entitled to consider bouncing cosmologies as a real viable alternative for the generation of the observed inhomogeneities. Our treatment also includes some class of models with extra dimensions, whereas we show that bounces induced by positive spatial curvature are structurally different from all bounces in spatially flat universes, requiring a distinct analysis. © 2006 IOP Publishing Ltd
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