1,721,041 research outputs found
SOME PROPERTIES OF THE MOEBIUS FUNCTION IN THE SUBGROUP LATTICE OF THE ALTERNATING AND SYMMETRIC GROUPS
Full text linkWe investigate some properties of the Moebius function on the subgroup lattice of the Alternating and Symmetric groups of degree n, Alt(n) and Sym(n). The study of this function is strictly related to the study of the probabilistic zeta function of a finite or profinite group. We obtain results on two different open questions. First we prove that in all the Alternating and Symmetric groups the Moebius number of each subgroup can be bounded polinomially in terms of its index and the number of subgroups with a given index n and non trivial Moebius number grows at most polynomially in n. This result is an important step in order to prove a conjecture of A.Mann on the absolute convergency of the probabilistic series associated to a positively finitely generated profinite group. Then we consider a problem introduced by A.Mann and N.Boston: they conjectured that the existence, for a fixed value of n, of a good correspondence between the maximal subgroups of Alt(n) and Sym(n) reflects the equality between the probabilistic series of Sym(n) and the probabilistic series of the direct product of Alt(n) with a cyclic group of order 2. We prove that this conjecture holds whenever n is a prime; but it does not hold in general (for example when n=21). Even if there exists a one-to-one correspondence between maximal subgroups of Alt(n) and Sym(n) the conjecture can fail; it is the case of n=62.In questa tesi analizziamo alcune proprietà della funzione di Moebius nel reticolo dei sottogruppi dei gruppi Alterno e Simmetrico di grado n, Alt(n) and Sym(n). Lo studio di questa funzione è strettamente correlato allo studio della funzione zeta probabilistica di un gruppo finito o profinito. Otteniamo risultati riguardanti due problemi distinti. Innanzitutto dimostriamo che in ogni gruppo Alterno o Simmetrico il numero di Moebius di ogni sottogruppo può essere limitato polinomialmente nell'indice di tale sottogruppo, ed il numero di sottogruppi con un dato indice n e con numero di Moebius non nullo cresce al più polinomialmente in n. Questo risultato è un passo importante al fine di dimostrare la validità di una congettura di A.Mann riguardante la convergenza assoluta della serie probabilistica associata ad un gruppo profinito positivamente finitamente generato. In secondo luogo consideriamo un altro problema: A.Mann e N.Boston hanno congetturato che l'esistenza, per un dato valore di n, di una buona corrispondenza tra i sottogruppi massimali di Alt(n) and Sym(n) rifletta l'uguaglianza tra la serie probabilistica di Sym(n) e la serie probabilistica del prodotto diretto fra Alt(n) ed un gruppo ciclico di ordine 2. Proviamo che tale congettura vale se n è primo; ma non è vera in generale (ad esempio quando n=21). Persino se si assume l'esistenza di una corrispondenza biunivoca fra i massimali di Alt(n) e Sym(n), la congettura può non valere; è ciò che accade quando n=62
Three Essays in Macroeconometrics
Full text linkThis dissertation comprises three self-contained chapters in macroeconometrics tackling three current macroeconomic issues.
The first chapter, “Economic Policy Uncertainty in the US: Does it matter for the Euro Area", is a single-authored paper. It studies to what extent an economic policy uncertainty shock generated in the US triggers spillover effects in the Euro Area macroeconomic activity. I estimate a two-country Structural Vector Autoregressive (SVAR) model capturing the US economic policy uncertainty shock by appealing to some indicators recently proposed by Baker, Bloom and Davis (2013). The impulse responses predict a negative and statistically significant reaction of Euro area price and quantity indicators to an unexpected increase in the US policy uncertainty. The results support the view that the effects of such shock act like a demand "type" shock. Interestingly, the Euro area variables are estimated to respond strongly to US uncertainty shock than to the European counterpart. A note from this chapter has been published in the Economics Letters.
The second chapter, "Estimating Fiscal Multipliers: News from a non-linear Word", is a joint work with Giovanni Caggiano, Efrem Castelnuovo and Gabriela Nodari. We estimate the effects of a US government spending news shock on output multipliers. We deal with the issue of fiscal foresight (anticipated fiscal policy changes) by appealing to the sums of revisions of expectations on future government spending. This measure is used to add more information to a standard three-variate fiscal VAR model à la Blanchard and Perotti (2002). To study the effects of anticipated fiscal policy shocks conditionally on the state of economy (in recessions and expansions), we estimate a non-linear VAR (Smooth Transition VAR). We compute non-linear generalized impulse responses (GIRFs) à la Koop, Pesaran, and Potter (1996) to take into account the probability of smoothly switching from a regime to another due to the fiscal shock. Results show that an anticipated fiscal spending shock triggers a significant reaction of GDP. Such reaction is not significantly different between recessions and expansions. However, when we discriminate between "extreme events" (i.e., the recent great recession), we find a reaction of output significantly different among regimes. Fiscal multipliers in recessions are estimated above one and government spending news shocks are found to induce economic stabilization. This chapter is forthcoming in the Economic Journal.
The third chapter, "Opening the Red Budget Box: Real Effects of a Tax Shock in the UK", is a single-authored paper. It studies non-linear impulse responses to unanticipated tax shocks for output and its components. To do so, I estimate a non-linear version of the local projection technique developed by Jordà (2005). The identification of the tax shock is achieved by appealing to the measure of exogenous tax changes in the UK developed by Cloyne (2013). Tax shocks are found to affect UK macroeconomic variables depending when such shocks occur (in recessions or in expansions). An unexpected increase in the tax rate occurring in recessions triggers a large, persistent and negative reaction in output, consumption, investment, imports and government consumption. The results suggest that output tax multipliers are negative and above one (in absolute value) in recessions but not in expansions.The size and the sign of multipliers for most of the macroeconomic indicators above considered are also found to be state-dependent
Estimating Fiscal Multipliers: News From A Non-linear World
Full text linkWe estimate non-linear VARs to assess to what extent fiscal spending multipliers are countercyclical in the US. We deal with the issue of non-fundamentalness due to fiscal foresight by appealing to sums of revisions of expectations of fiscal expenditures. This measure of anticipated fiscal shocks is shown to carry valuable information about future dynamics of public spending. Results based on generalised impulse responses suggest that fiscal spending multipliers in recessions are greater than one, but not statistically larger than those in expansions. However, non-linearities arise when focusing on 'extreme' events, that is, deep recessions versus strong expansionary periods
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
Full text link“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
Full text linkWe 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
Full text linkWe 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
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