Gravity and the Quantum: Are they Reconcilable?

General relativity and quantum mechanics are conflicting theories. The seeds of discord are the fundamental principles on which these theories are grounded. General relativity, on one hand, is based on the equivalence principle, whose strong version establishes the local equivalence between gravitation and inertia. Quantum mechanics, on the other hand, is fundamentally based on the uncertainty principle, which is essentially nonlocal in the sense that a particle does not follow one trajectory, but infinitely many trajectories, each one with a different probability. This difference precludes the existence of a quantum version of the strong equivalence principle, and consequently of a quantum version of general relativity. Furthermore, there are compelling experimental evidences that a quantum object in the presence of a gravitational field violates the weak equivalence principle. Now it so happens that, in addition to general relativity, gravitation has an alternative, though equivalent description, given by teleparallel gravity, a gauge theory for the translation group. In this theory torsion, instead of curvature, is assumed to represent the gravitational field. These two descriptions lead to the same classical results, but are conceptually different. In general relativity, curvature geometrizes the interaction, while torsion in teleparallel gravity acts as a force, similar to the Lorentz force of electrodynamics. Because of this peculiar property, teleparallel gravity describes the gravitational interaction without requiring any of the equivalence principles. The replacement of general relativity by teleparallel gravity may, in consequence, lead to a conceptual reconciliation of gravitation with quantum mechanics.Comment: 15 pages, 2 figures. Talk presented at the conference "Quantum Theory: Reconsideration of Foundations-3", June 6-11, 2005, Vaxjo University, Vaxjo, Swede

Gravitation without the equivalence principle

In the general relativistic description of gravitation, geometry replaces the concept of force. This is possible because of the universal character of free fall, and would break down in its absence. On the other hand, the teleparallel version of general relativity is a gauge theory for the translation group and, as such, describes the gravitational interaction by a force similar to the Lorentz force of electromagnetism, a non-universal interaction. Relying on this analogy it is shown that, although the geometric description of general relativity necessarily requires the existence of the equivalence principle, the teleparallel gauge approach remains a consistent theory for gravitation in its absence.Comment: Latex, 11 pages, no figures. Minor presentation changes. Version to appear in Gen. Rel. Grav. (2004

Doing without the Equivalence Principle

In Einstein's general relativity, geometry replaces the concept of force in the description of the gravitation interaction. Such an approach rests on the universality of free-fall--the weak equivalence principle--and would break down without it. On the other hand, the teleparallel version of general relativity, a gauge theory for the translation group, describes the gravitational interaction by a force similar to the Lorentz force of electromagnetism, a non-universal interaction. It is shown that, similarly to the Maxwell's description of electromagnetism, the teleparallel gauge approach provides a consistent theory for gravitation even in the absence of the weak equivalence principle.Comment: 7 pages, no figures. Talk presented at the "Tenth Marcel Grossmann Meeting", July 20 to 26, 2003, Rio de Janeiro, Brazil; to be published in the Proceedings (World Scientific, Singapore, 2005

Bilateral abducens nerve palsy due to septic thrombophlebitis.

PurposeTo report a case of septic thrombophlebitis producing bilateral abducens nerve palsy.ObservationA 65 year-old woman with recent sinus surgery experienced the onset of horizontal diplopia during treatment for bacteremia. Computer tomography of head and a neck ultrasonography showed right internal jugular vein occlusion. Ophthalmology examination was consistent with bilateral abducens nerve palsy. She was treated with systemic antibiotics and antiplatelet therapy with resolution of the internal jugular vein occlusion. The diplopia improved over a six-months.Conclusion and importanceOur patient had Lemierre syndrome with an unusual presentation. The patient was treated for septic thrombophlebitis with a resolution of her ocular symptoms

Optimal Fiscal Policy in an Economy Facing Socio-Political Instability

We present a model of optimal government policy when policy choices may exacerbate socio-political instability (SPI). We show that optimal policy that takes into account SPI transforms a standard concave growth model into a model with both a poverty trap and endogenous growth. The resulting equilibrium dynamics inherit the properties of government policies and need not be monotone. Indeed, for a broad set of conditions we demonstrate that government policy is unable to eliminate the poverty trap; when these conditions do not hold, "most" countries eventually reach a balanced growth path. The predictions of the model are tested by developing three new measures of SPI for a panel of 58 countries. Estimating optimal policies and the growth equation derived from the model reveals strong support for the theory. In particular, we show via simulations that optimal funding for public investment and the police cause a typical developing economy to expand on a quasi-linear growth path, with the baseline level of SPI determining whether growth is positive or negative.Socio-Political Instability, Endogenous Growth, Public Investment, Political Economy of Growth

Mars Atmospheric and Climatic Survey System

Before Mars can be explored by humans, its extreme climate and environment must be investigated. This can be achieved through the deployment of weather station probes capable of measuring Martian air temperature, atmospheric pressure, relative humidity, and wind speed. The Mars Atmospheric and Climatic Survey System (MACSS) aims to collect this data, allowing predictive models of global climate patterns on Mars to be developed. These models will aid NASA in providing the needed knowledge to prepare for long-term exposure to the conditions on Mars. The probes are compact and lightweight; they have been designed to withstand Mars’ harsh environment: extreme temperatures, statically-charged dust particles, a thin atmosphere, and intense solar radiation. Considerations of deployment were also made, with the size and weight of each probe allowing for them to be deployed as-needed and as accessories in future missions rather than simultaneously in a single mission. With regards to components, solar panels are to supply the probes with primary power. Data would be collected by sensors and stored on a solid-state drive. A low-gain antenna would establish communication between the probes, NASA’s Deep Space Network, and Mars’ rovers and orbiters. This data can then be evaluated on Earth, allowing models of Martian climate to be formed. In order to demonstrate the feasibility of MACSS, a mockup was designed, simulating data collection in real time with Earth-equivalent components. With continued collaboration, MACSS and its probes can be further optimized for deployment to and longevity on Mars.https://scholarscompass.vcu.edu/capstone/1202/thumbnail.jp

Firm exporting and employee benefits: first evidence from Vietnam manufacturing SMEs

This study examines linkages between the export participation of firms and employee benefits in terms of wages and employment quality. Based on a uniquely matched firmworker panel dataset for 2007 and 2009, we find evidence that export participation by firms in Vietnam has a positive impact on wages when taking into account firm characteristics alone. However, the exporter wage premium falls when both firm and worker characteristics are controlled for, and it decreases further when controlling for time-invariant unobservable factors by spell fixed effect estimation. While there are many studies on the export wage premium, the role of export participation on the quality of employment remains largely unexplored. By using a firm-level balanced panel dataset for the same period, our results suggest that export participation has a negative effect on employment quality. Nevertheless, the impact of export participation on both wages and employment quality vary greatly with respect to levels of technology