1,071 research outputs found
Evangelista Torricelli (400 ani de la naştere)
No full textNumele lui s-a încetăţenit în fizică, în experienţa lui Torricelli, formula lui Torricelli, principiul lui Torricelli. În onoarea lui a fost numită şi o unitate de presiune – torr
A note on the Fermat-Torricelli point of a d-simplex
No full textThe isogonal property of the Fermat-Torricelli point for the vertex set of a d-simplex is examined. For d = 2 and 3, it is known that the property holds true if the point is in the interior of the simplex, but for d ≥ 4 an example is given, proving that the Fermat-Torricelli point is not necessarily isogonal. © Birkhäuser Verlag, Basel, 2001
The nest-holding grass goby (Zosterisessor ophiocephalus) male adjusts the spawning activity in relation to parasitic nest intrusions.
No full textThis study examines the temporal pattern of spawning behavior by the territorial (i.e. nest-holding) grass goby male, Zosterisessor ophiocephalus, in response to sneak intrusions by the small parasitic male under controlled laboratory conditions. The spawning activity of the territorial male consists of a sequence of upside-down movements on the ceiling of the nest accompanied by undulations of the body and sperm release. Five pairs of one territorial male and one parasitic male, each kept inside a large tank provided with an artificial buried nest (always occupied by the territorial male) and one small tunnel-shaped shelter (always occupied by the small male), were observed during one-female spawning taking place in the innermost part of the nest (i.e. the nest chamber). During the spawning, the presence of the small male nearby the nest openings elicited aggressive behavior and increased nest patrolling by the territorial male. In one spawn the small male never attempted to enter the nest. In four spawns the small male entered one to three times the nest chamber (sneaks), staying there from 2 to 203 s until the large male chased him away. The temporal patterning of the spawning activity by the territorial male (bouts of upside-down, U-D), and its changes following a sneak by the small male, were investigated using bout analysis and correlative tests. Results showed the length of bouts U-D did not change significantly after a sneak intrusion. whereas gap length (i.e. the period between subsequent bouts U-D) decreased significantly after each sneak intrusion. The mean duty cycle of bouts U-D tended to be positively correlated to the number of sneaker intrusions of each replicate. Results are discussed in the light of current knowledge on sperm competition among externally fertilizing teleosts
The Fermat-Torricelli problem in normed planes and spaces
No full textWe investigate the Fermat–Torricelli problem in d-dimensional real normed spaces or Minkowski spaces, mainly for d=2. Our approach is to study the Fermat–Torricelli locus in a geometric way. We present many new results, as well as give an exposition of known results that are scattered in various sources, with proofs for some of them. Together, these results can be considered to be a minitheory of the Fermat–Torricelli problem in Minkowski spaces and especially in Minkowski planes. This demonstrates that substantial results about locational problems valid for all norms can be found using a geometric approach
The internal efficiency of Index Option Markets:Tests on the Italian Market
No full textThe aim of the present paper is to provide evidence on the internal market efficiency of the Italian index option market. To this end a model-free approach is taken, whereby strategies involving only options are tested by means of a high frequency dataset covering the period 1 September – 31 December 2002. This piece of research thus completes our previous analysis (Brunetti and Torricelli(2003, 2006)), which focused on the cross-market efficiency of the same market. The results obtained further support the efficiency of one of the most important index options markets in Europe.index options;internal market efficiency; no-arbitrage; option spreads
Estimation and arbitrage opportunities for exchange rate baskets
No full textThis paper analyses short-term portfolio investment opportunities in a capital market where a currency is defined as a currency basket. In line with the mean-variance hedging approach, a self-financed optimal investment strategy is determined which minimizes the expected quadratic cost function. The successful implementation of the speculative strategy requires a precise estimate of the basket weights, which are possibly non-constant over time. To this end, an adaptive non-parametric procedure is suggested which provides satisfactory results both on simulated and real data. The optimal investment strategy is applied to the case of the Thai Baht basket whereby the weights are computed by means of the adaptive estimator. A recursive estimator, a rolling estimator and the Kalman filter, are implemented and serve as benchmark models. Results are compared with the literature. The different estimators are evaluated with profit-based criteria and the performance of the adaptive estimator turns out to be the best one.
Evangelista Torricelli, De sphaera et solidis sphaeralibus libri duo
No full textPapier, 2 parties en 1 volume, 151 pages avec figures et tableaux ; in-4L’appendice de ce traité de Torricelli, intitulé Appendix de dimensione cycloidis , constitue le premier traité imprimé sur la courbe que Mersenne qualifiait de « roulette » et que Torricelli, reprenant l’appellation que lui avait donnée Galilée, nomme « cycloïde ». L’ouvrage de Torricelli exerça une grande influence sur ses contemporains : comme il s’appuyait sur la méthode des indivisibles, c’est par son intermédiaire que Wallis prit connaissance des recherches de Cavalieri. Le traité de Torricelli a également joué un rôle essentiel dans le développement des réflexions de Pascal sur la « roulette », comme l’atteste notamment le fait qu’il lui ait emprunté la définition de la courbe donnée à la fin du premier des « Écrits sur la roulette » : « Soit une droite fixe AD, et sur cette droite un cercle DL la touchant au point D de sa circonférence. Si l’on fait avancer sur la droite DA le cercle DL par un mouvement de rotation linéaire vers A, de telle sorte qu’il touche toujours la droite DA en chacun de ses points successivement jusqu’à ce que le point D revienne à son contact, par exemple en A, alors le point D situé sur la circonférence du cercle DL décrira une ligne qui commencera par s’élever au-dessus de la droite AD, culminera en C, enfin descendra jusqu’au point A. Une telle ligne se nomme cycloïde. »téléchargeabl
The aim of the present work is to test the predictive power of the term spread in forecasting real economic growth rates and recession probabilities in Italy. According to the most recent literature, the relationship between the term spread and economic growth rates is modelled as a nonlinear one and specifically the Logistic Smooth Transition model is used, while a probit model is implemented to forecast recession probabilities. In both applications evidence supports a relevant informative content of the spread in Italy.
No full textterm structure; term spread; regime prediction
Estimation and arbitrage opportunities for exchange rate baskets
No full textThis paper analyzes short term portfolio investment opportunities in a capital market where a currency is defined as a currency basket, i.e. a linear combination of foreign currencies. In line with the mean-variance hedging approach, we determine a self-financed optimal investment strategy which minimizes an expected quadratic cost function. In order to implement such a strategy an estimate of the basket weights is required. To this end we suggest an adaptive nonparametric procedure, which, if compared with standard procedures, provides very satisfactory results both on simulated and real data. We apply the optimal investment strategy to the case of the Thai Bath basket. The basket weights are computed with the adaptive estimator. We also implement a recursive estimator, a rolling estimator and the Ka1man filter which serve as benchmark models. The different estimators are compared with profit based criteria
Call and put implied volatilities and the derivation of option implied trees
No full textStandard methodologies for the derivation of implied trees from option prices are based on the validity of the put-call parity. Muzzioli and Torricelli (2002) propose a methodology which accounts for PCP violations. Based on this latter approach the present paper advances in two main directions. First we propose a different methodology in order to imply the interval of artificial probabilities at each node of the tree. Secondly, we perform an empirical validation of the implied tree obtained, both in the sample and out of sample, by using DAX index options data set covering the period from January 4, 1999 to December 28, 2000. Numerical results are compared with one of the most used standard methodologies, i.e. Derman and Kani’s. The results suggest that the estimation proposed, by taking into account the informational content of both call and put prices, highly improves both the in-the-sample fitting and the out-of-sample performance.Binomial Method; Put-Call Parity; Choquet Pricing; Interval Tree.
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