On the Space Time of a Galaxy

We present an exact solution of the averaged Einstein's field equations in the presence of two real scalar fields and a component of dust with spherical symmetry. We suggest that the space-time found provides the characteristics required by a galactic model that could explain the supermassive central object and the dark matter halo at once, since one of the fields constitutes a central oscillaton surrounded by the dust and the other scalar field distributes far from the coordinate center and can be interpreted as a halo. We show the behavior of the rotation curves all along the background. Thus, the solution could be a first approximation of a ``long exposition photograph'' of a galaxy.Comment: 8 pages REVTeX, 11 eps figure

Generation of Closed Timelike Curves with Rotating Superconductors

The spacetime metric around a rotating SuperConductive Ring (SCR) is deduced from the gravitomagnetic London moment in rotating superconductors. It is shown that theoretically it is possible to generate Closed Timelike Curves (CTC) with rotating SCRs. The possibility to use these CTC's to travel in time as initially idealized by G\"{o}del is investigated. It is shown however, that from a technology and experimental point of view these ideas are impossible to implement in the present context.Comment: 9 pages. Submitted to Classical and Quantum Gravit

Why and when social support predicts older adults’ pain-related disability

Pain-related social support has been shown to be directly associated with pain-related disability, depending on whether it promotes functional autonomy or dependence. However, previous studies mostly relied on cross-sectional methods, precluding conclusions on the temporal relationship between pain-related social support and disability. Also, research on the behavioral and psychological processes that account for such a relationship is scarce. Therefore, this study aimed at investigating the following longitudinally: (1) direct effects of social support for functional autonomy/dependence on pain-related disability, (2) mediating role of physical functioning, pain-related self-efficacy, and fear, and (3) whether pain duration and pain intensity moderate such mediating processes. A total of 168 older adults (Mage = 78.3; SDage = 8.7) participated in a 3-month prospective design, with 3 moments of measurement, with a 6-week lag between them. Participants completed the Formal Social Support for Autonomy and Dependence in Pain Inventory, the Brief Pain Inventory, the 36-SF Health Survey, behavioral tasks from the Senior Fitness Test, the Pain Self-Efficacy Questionnaire, and the Tampa Scale for Kinesiophobia. Moderated mediation analyses showed that formal social support for functional dependence (T1) predicted an increase in pain-related disability (T3), that was mediated by self-reported physical functioning (T2) and by pain-related self-efficacy (T2) at short to moderate pain duration and at low to moderate pain intensity, but not at higher levels. Findings emphasized that social support for functional dependence is a risk factor for pain-related disability and uncovered the “why” and “when” of this relationship. Implications for the design of social support interventions aiming at promoting older adults' healthy aging despite chronic pain are drawn.info:eu-repo/semantics/acceptedVersio

The forward- and the equity-premium puzzles: two symptoms of the same illness?

Using information on US domestic financial data only, we build a stochastic discountfactor—SDF— and check whether it accounts for foreign markets stylized factsthat escape consumption based models. By interpreting our SDF as the projection ofa pricing kernel from a fully specified model in the space of returns, our results indicatethat a model that accounts for the behavior of domestic assets goes a long waytoward accounting for the behavior of foreign assets prices. We address predictabilityissues associated with the forward premium puzzle by: i) using instruments that areknown to forecast excess returns in the moments restrictions associated with Eulerequations, and; ii) by pricing Lustig and Verdelhan (2007)’s foreign currency portfolios.Our results indicate that the relevant state variables that explain foreign-currencymarket asset prices are also the driving forces behind U.S. domestic assets behavior.

The Forward- and the Equity-Premium Puzzles: Two Symptoms of the Same Illness?

We build a pricing kernel using only US domestic assets data and checkwhether it accounts for foreign markets stylized facts that escape consumptionbased models. By interpreting our stochastic discount factor as the projection ofa pricing kernel from a fully specified model in the space of returns, our results indicatethat a model that accounts for the behavior of domestic assets goes a longway toward accounting for the behavior of foreign assets. We address predictabilityissues associated with the forward premium puzzle by: i) using instrumentsthat are known to forecast excess returns in the moments restrictions associatedwith Euler equations, and; ii) by pricing Lustig and Verdelhan (2007)'s foreigncurrency portfolios. Our results indicate that the relevant state variables that explainforeign-currency market asset prices are also the driving forces behind U.S.domestic assets behavior.