1,720,958 research outputs found
Metodi algebrici per l'analisi perturbativa di equazioni stocastiche
No full textL'obiettivo di questa tesi è quello di generalizzare un approccio algebrico all'analisi perturbativa delle equazioni differenziali alle derivate parziali di tipo stocastico lungo due principali direzioni. La prima riguarda una riformulazione puramente algebrica del path integral associato ad una equazione differenziale stocastica, noto in letteratura col nome di formalismo Martin-Siggia-Rose. Ricorrendo a opportuni spazi di funzionali sulle configurazioni lisce e tramite delle mappe di deformazione, aggiriamo le ostruzioni analitiche legate ad una derivazione euristica del path integral, tenendo conto di tutte le possibili prescrizioni per la costruzione dell'integrale stocastico a livello del funzionale d'azione. Dopo aver adattato l'approccio microlocale e algebrico all'analisi perturbativa delle SPDE non lineari, sviluppato da Dappiaggi, Drago, Rinaldi e Zambotti, al caso delle SDE, mostriamo come i risultati ottenuti tramite il path integral algebrico e tramite una costruzione perturbativa dei momenti della soluzione coincidono ad ogni ordine perturbativo, nel caso puramente additivo e puramente moltiplicativo. La seconda direzione riguarda lo studio della convergenza delle serie di potenze formali che definiscono i momenti della soluzione dell'equazione di sine-Gordon stocastica tramite il nostro framework algebrico. Ispirati da recenti risultati sulla convergenza della matrice S del modello sine-Gordon sullo spaziotempo di Minkowski in 1+1 dimensioni tramite tecniche tipiche della teoria di campo algebrica, consideriamo una versione deformata del campo quantistico interagente e dei suoi prodotti. La deformazione implementa a livello algebrico l'informazione codificata dalla covarianza del processo gaussiano che risolve l'equazione di Klein-Gordon stocastica. Il risultato principale riguarda la dimostrazione della convergenza assoluta delle osservabili quantistiche deformate, una volta testate contro una configurazione di campo fissata. Dopo aver studiato il limite classico della mappa di Möller quantistica, quest'ultimo ci permette di ottenere una costruzione non perturbativa dei momenti della soluzione dell'equazione di sine-Gordon stocastica.Goal of this thesis is the generalization of an algebraic approach to the perturbative analysis of singular stochastic partial differential equations along two main directions. The first concerns a purely algebraic reformulation of the path integral measure associated to a stochastic differential equation, referred to, in the literature, as the Martin-Siggia-Rose formalism. Resorting to suitable algebras of functionals over the space of smooth configurations and via ad hoc deformation maps, we circumvent the analytical hurdles ascribed to a heuristic derivation of the path integral, while accounting for any prescription to stochastic integration at the level of the action functional. After adapting to the non-singular setting of SDEs the novel microlocal and algebraic approach to the perturbative analysis of nonlinear SPDEs proposed by Dappiaggi, Drago, Rinaldi and Zambotti, we show that the results obtained via the algebraic path integral formalism and from the perturbative construction of momenta of the solution coincide at every order in perturbation theory in the purely additive and purely multiplicative scenarios. The second direction points towards the investigation of the convergence of the formal power series defining the momenta of the solution to the stochastic sine-Gordon equation within our algebraic framework. Inspired by recent convergence results of the S-matrix of the sine-Gordon quantum field theory on the 1+1-dimensional Minkowski spacetime within the framework of algebraic quantum field theory, we consider a deformed version of the interacting quantum field and of its multilocal products. The deformation implements at the algebraic level the information on the covariance of the Gaussian process solving the stochastic linear Klein-Gordon equation. The main result concerns the proof of absolute convergence of the deformed interacting observables once evaluated on an arbitrary field configuration. Subsequently, after investigating the classical limit of the quantum Möller map, the regime for ̄h!0 yields the non-perturbative momenta of the solution to the stochastic sine-Gordon equation
On the Stochastic Sine-Gordon Model: An Interacting Field Theory Approach
Get PDFWe investigate the massive sine-Gordon model in the finite ultraviolet regime on the two-dimensional Minkowski spacetime (R^2,\eta) with an additive Gaussian white noise. In particular we construct the expectation value and the correlation functions of a solution of the underlying stochastic partial differential equation (SPDE) as a power series in the coupling constant, proving ultimately uniform convergence. This result is obtained combining an approach first devised in Dappiaggi et al. (Commun Contemp Math 24(07):2150075, 2022. arXiv:2009.07640 [math-ph]) to study SPDEs at a perturbative level with the one discussed in Bahns and Rejzner (Commun Math Phys 357(1):421, 2018. arXiv:1609.08530 [math-ph]) to construct the quantum sine-Gordon model using techniques proper of the perturbative, algebraic approach to quantum field theory (pAQFT). At a formal level the relevant expectation values are realized as the evaluation of suitably constructed functionals over C^\infty(R^2). In turn, these are elements of a distinguished algebra whose product is a deformation of the pointwise one, by means of a kernel which is a linear combination of two components. The first encompasses the information of the Feynmann propagator built out of an underlying Hadamard, quantum state, while the second encodes the correlation codified by the Gaussian white noise. In our analysis, first of all we extend the results obtained in Bahns et al. (J Math Anal Appl 526:127249, 2023. arXiv:2103.09328 [math-ph]) and Bahns and Rejzner (Commun Math Phys 357(1):421, 2018. arXiv:1609.08530 [math-ph]) proving the existence of a convergent modified version of the S-matrix and of an interacting field as elements of the underlying algebra of functionals. Subsequently we show that it is possible to remove the contribution due to the Feynmann propagator by taking a suitable s} \hbar->0^+-limit, hence obtaining the sought expectation value of the solution and of the correlation functions of the SPDE associated to the stochastic sine-Gordon model
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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