An explicit Schr\"odinger picture for Aharonov's Modular Variable concept

We propose to address in a natural manner, the modular variable concept explicitly in a Schr\"odinger picture. The idea of Modular Variables was introduced in 1969 by Aharonov, Pendleton and Petersen to explain certain non-local properties of quantum mechanics. Our approach to this subject is based on Schwinger's finite quantum kinematics and it's continuous limit.Comment: 16 pages, 9 figure

An anti-Schwarzshild solution: wormholes and scalar-tensor solutions

We investigate a static solution with an hyperbolic nature, characterised by a pseudo-spherical foliation of space. This space-time metric can be perceived as an anti-Schwarzschild solution, and exhibits repulsive features. It belongs to the class of static vacuum solutions termed "a degenerate static solution of class A". In the present work we review its fundamental features, discuss the existence of generalised wormholes, and derive its extension to scalar-tensor gravity theories in general.Comment: 3 pages, contribution to the proceedings of the Spanish Relativity Meeting-ERE200

Evolving wormhole geometries within nonlinear electrodynamics

In this work, we explore the possibility of evolving (2+1) and (3+1)-dimensional wormhole spacetimes, conformally related to the respective static geometries, within the context of nonlinear electrodynamics. For the (3+1)-dimensional spacetime, it is found that the Einstein field equation imposes a contracting wormhole solution and the obedience of the weak energy condition. Nevertheless, in the presence of an electric field, the latter presents a singularity at the throat, however, for a pure magnetic field the solution is regular. For the (2+1)-dimensional case, it is also found that the physical fields are singular at the throat. Thus, taking into account the principle of finiteness, which states that a satisfactory theory should avoid physical quantities becoming infinite, one may rule out evolving (3+1)-dimensional wormhole solutions, in the presence of an electric field, and the (2+1)-dimensional case coupled to nonlinear electrodynamics.Comment: 17 pages, 1 figure; to appear in Classical and Quantum Gravity. V2: minor corrections, including a referenc

Herding and Anchoring in Macroeconomic Forecasts: The Case of the PMI

We test if analysts display multiple biases in forecasting the Institute for Supply Management’s (ISM) manufacturing Purchasing Manager’s Index (PMI). We adopt a test that does not require knowledge of the forecaster’s prior information set and is robust to rational clustering, correlated forecast errors and outliers. We find that analysts forecast the PMI poorly and display multiple biases when forecasting. In particular, forecasters anti-herd and anti-anchor. Anti-herding supports a reputation-based notion that forecasters are rewarded not only for forecast accuracy but also for being the best forecast at a single point in time. Anti-anchoring is consistent with forecasters overreacting to private information. The two biases show a strong positive correlation suggesting that the incentives that elicit anti-herding also elicit anti-anchoring behavior. Both biases result in larger absolute errors, although the effect is stronger for anti-herding

Coincidence Experiments between Interferometric and Resonant Bar Detectors

Gravitational wave coincidence experiments between bars and interferometers may be an attractive option once the new generation of full scale interferometers begins taking data. We discuss various ways in which these disparate types of data can be compared in searches for bursts (from supernovae, for example), for pulsar signals, and for a stochastic background. Comparison of broadband interferometer data with narrowband bar data is appropriate in most searches for bursts, but in many cases the results---especially null results (upper limits)---are difficult to interpret. By narrowbanding the interferometer data to the bandwidth of the bar detector, one produces data sets that may give much clearer information in certain burst searches and that are appropriate for searches for a stochastic background of gravitational waves. We suggest, in fact, that there are circumstances where searches for a stochastic background could be more efficiently performed between a bar and an interferometer than between two interferometers. We examine, in some detail, the effect of narrowbanding the interferometer data. We apply this method to a real interferometer and bar data and assess its signal-to-noise performance for different classes of gravitational wave signals

Tsallis holographic dark energy in the Brans-Dicke cosmology

Using the Tsallis generalized entropy, holographic hypothesis and also considering the Hubble horizon as the IR cutoff, we build a holographic model for dark energy and study its cosmological consequences in the Brans-Dicke framework. At first, we focus on a non-interacting universe, and thereinafter, we study the results of considering a sign-changeable interaction between the dark sectors of the cosmos. Our investigations show that, compared with the flat case, the power and freedom of the model in describing the cosmic evolution is significantly increased in the presence of the curvature. The stability analysis also indicates that, independent of the universe curvature, both the interacting and non-interacting cases are classically unstable. In fact, both the classical stability criterion and an acceptable behavior for the cosmos quantities, including the deceleration and density parameters as well as the equation of state, are not simultaneously obtainable.Comment: Accepted version, Eur. Phys. J. C (2018

Convergencias y divergencias entre dos comunidades coprófagas de montaña europeas (Coleoptera, Scarabaeoidea)

We analyzed the altitudinal change in dung beetle species richness and the relative proportion of higher taxa, as well as the turnover in the type of distribution and range size of species in two mountain chains located at the two extremes of Europe (Western Rhodopes Mountains and the Iberian Central System). Both mountain ranges showed a clear substitution among higher taxa (Aphodiinae–Geotrupinae vs. Scarabaeidae) and species richness variation with the altitude was similar. We suggest that East European dung beetle assemblages are conditioned by a horizontal colonization process in which mountains had been reached in relatively recent geological time by elements coming from different latitudes. In spite of these convergences, Rhodopes dung beetle assemblages are characterized by a significantly lower proportion of narrowly distributed species and a lower relevance of Aphodiinae species in lowland places. Although these divergences can be partially attributed to the dissimilar sampling effort accomplished in both regions, we suggest that the low number on narrowly distributed species could be due to the different role of these two mountain zones as refuges during glaciar–interglaciar Pleistocene cycles. Key words: Scarabaeoidea, Dung beetles, Altitudinal variation, Rhodopes mountain range, Iberian Central System, Refuges.Compilando toda la información faunística disponible sobre los coleópteros coprófagos de dos zonas montañosas desconectadas, ubicadas a ambos extremos de Europa (los Rhodopes Occidentales y el Sistema Central Ibérico), hemos analizado el cambio altitudinal en la riqueza de especies, la modificación en la proporción relativa de los principales grupos taxonómicos implicados, así como el relevo en el tipo de distribución y el tamaño del rango geográfico de las especies implicadas. Ambas zonas de montaña muestran un patrón evidente de sustitución entre taxones de alto rango (Aphodiinae-Geotrupinae vs. Scarabaeidae) y también parecidas tasas de variación en la riqueza de especies con la altura. Sugerimos que las comunidades coprófagas del este de Europa están también condicionadas primordialmente por un proceso de colonización horizontal, en el cual las montañas serían colonizadas en periodos geológicos recientes por elementos procedentes de latitudes septentrionales. A pesar de estas convergencias, las comunidades de los Rhodopes se caracterizan por una significativa menor presencia de especies con rangos de distribución restringidos y una escasa relevancia de las especies de Aphodiinae en las zonas de menor altitud. Aunque estas divergencias pueden atribuirse parcialmente a diferencias en el esfuerzo de colecta realizado en ambas regiones, consideramos el escaso número de especies con distribución restringida estaría relacionado con el distinto papel ejercido por estas montañas como refugio durante los ciclos glaciares del Pleistoceno. Palabras clave: Scarabaeoidea, Escarabajos coprófagos, Variación altitudinal, Rhodopes, Sistema Ibérico Central, Refugios

A new special class of Petrov type D vacuum space-times in dimension five

Using extensions of the Newman-Penrose and Geroch-Held-Penrose formalisms to five dimensions, we invariantly classify all Petrov type $D$ vacuum solutions for which the Riemann tensor is isotropic in a plane orthogonal to a pair of Weyl alligned null directionsComment: 4 pages, 1 table, no figures. Contribution to the proceedings of the Spanish Relativity Meeting 2010 held in Granada (Spain