Search results for "Gravity"
showing 10 items of 537 documents
Mapping nonlinear gravity into General Relativity with nonlinear electrodynamics
2018
We show that families of nonlinear gravity theories formulated in a metric-affine approach and coupled to a nonlinear theory of electrodynamics can be mapped into General Relativity (GR) coupled to another nonlinear theory of electrodynamics. This allows to generate solutions of the former from those of the latter using purely algebraic transformations. This correspondence is explicitly illustrated with the Eddington-inspired Born-Infeld theory of gravity, for which we consider a family of nonlinear electrodynamics and show that, under the map, preserve their algebraic structure. For the particular case of Maxwell electrodynamics coupled to Born-Infeld gravity we find, via this corresponden…
Tourism and migration: Identifying the channels with gravity models
2020
As a result of the role played by migrants in supporting host economies, the interest in understanding the impact of migration is growing. However, the literature remains silent on the channels by which migration affects tourism. The present article aims to isolate the effect of migrant networks on tourism by exploring the role of information, travel costs, and demand for visiting friends and relatives. To this end, a theoretical framework that rests upon a structural gravity model is developed. The model allows not only a better understanding of the relationship between tourism and migration but also to overcome several empirical biases like the omission of multilateral resistance in tour…
The sensorimotor and cognitive integration of gravity.
1998
In order to demonstrate that gravity is not only a load acting locally and continuously on the body limbs, but is also used by higher levels of the nervous system as a dynamic orienting reference for the elaboration of the motor act, a review of several experiments conducted both in 1 g and 0 g are presented. During various locomotor tasks, the strategy that consists of stabilizing the head with respect to gravity illustrates one of the solutions used by the CNS to optimize the control of dynamic equilibrium. A question which remains to be solved when considering experimental results obtained in weightlessness concerns, however, the maintenance of motor schema that has evolved under normal …
Tidal gravity observations at Mt. Etna and Stromboli: Results concerning the modeled and observed tidal factors
2009
Continuous gravity observations performed in the last few years, both at Mt. Etna and Stromboli, have prompted the need to improve the tidal analysis in order to acquire the best corrected data for the detection of volcano related signals. On Mt. Etna, the sites are very close to each other and the expected tidal factor differences are negligible. It is thus useful to unify the tidal analysis results of the different data sets in a unique tidal model. This tidal model, which can be independently confirmed by a modeling of the tidal parameters based on the elastic response of the Earth to tidal forces and the computation of the ocean tides effects on gravity, is very useful for the precise t…
Fractal geometry of higher derivative gravity
2019
We determine the scaling properties of geometric operators such as lengths, areas, and volumes in models of higher derivative quantum gravity by renormalizing appropriate composite operators. We use these results to deduce the fractal dimensions of such hypersurfaces embedded in a quantum spacetime at very small distances.
Grip Force Adjustments Reflect Prediction of Dynamic Consequences in Varying Gravitoinertial Fields
2018
International audience; Humans have a remarkable ability to adjust the way they manipulate tools through a genuine regulation of grip force according to the task. However, rapid changes in the dynamical context may challenge this skill, as shown in many experimental approaches. Most experiments adopt perturbation paradigms that affect only one sensory modality. We hypothesize that very fast adaptation can occur if coherent information from multiple sensory modalities is provided to the central nervous system. Here, we test whether participants can switch between different and never experienced dynamical environments induced by centrifugation of the body. Seven participants lifted an object …
Hotel chain performance: a gravity-DEA approach
2011
Performance in business management can be measured in terms of competitiveness and efficiency. Generally speaking, competitiveness is a comparative concept of the ability of a firm, sub-sector or country to sell and supply goods and/or services in a given market, as measured by its market share. Particularly in competitive markets, efficiency plays a key role in determining this ability but it is not, by itself, sufficient. Indeed, while competitiveness has more to do with “pursuing the correct strategy” towards the conservation and/or increase of the market share, operational efficiency is mainly a measure of how well the firm, sub-sector or country under study processes inputs to achieve …
Estimating the Effect of Common Currencies on Trade: Blooming or Withering Roses?
2013
Abstract Using a gravity model and data on 182 countries worldwide, this paper estimates the effects of exchange rate volatility and currency unions on international trade for ten years spanning 1980 through 2010. We provide added confirmation and further strengthen the empirical findings in Rose (2000) prior to 1999, but we find a gradually diminishing Rose effect for the 2000-2010 period, when the Euro Zone is added to the currency union dummy. The rest of the coefficients generally comply in magnitude and sign with what is standard in the “gravity” literature. Our findings support a much stronger effect of a currency union on trade than the hypothetical effect of reducing exchange rate v…
The euro impact on trade. Long run evidence with structural breaks
2012
In this paper we present new evidence on the euro effect on trade. We use a data set containing all bilateral combinations in a panel of 26 OECD countries during the period 1967-2008. From a methodological point of view, we implement a new generation of tests that allow solving some of the problems derived from the non-stationary nature of the data. To this aim we apply panel tests that account for the presence of cross-section dependence as well as discontinuities in the non-stationary panel data. We test for cointegration between the variables using panel cointegration tests, especially the ones proposed by Banerjee and Carrióni- Silvestre (2010). We also efficiently estimate the long-run…