Transformations and BRST-Charges in 2+1 Dimensional Gravitation

Canonical transformations relating the variables of the ADM-, Ashtekar's and Witten's formulations of gravity are computed in 2+1~dimensions. Three different forms of the BRST-charge are given in the 2+1 dimensional Ashtekar formalism, two of them using Ashtekar's form of the constraints and one of them using the forms suggested by Witten. The BRST-charges are of different rank.Comment: 10 page

A topological limit of gravity admitting an SU(2) connection formulation

We study the Hamiltonian formulation of the generally covariant theory defined by the Lagrangian 4-form L=e_I e_J F^{IJ}(\omega) where e^I is a tetrad field and F^{IJ} is the curvature of a Lorentz connection \omega^{IJ}. This theory can be thought of as the limit of the Holst action for gravity for the Newton constant G goes to infinity and Immirzi parameter goes to zero, while keeping their product fixed. This theory has for a long time been conjectured to be topological. We prove this statement both in the covariant phase space formulation as well as in the standard Dirac formulation. In the time gauge, the unconstrained phase space of theory admits an SU(2) connection formulation which makes it isomorphic to the unconstrained phase space of gravity in terms of Ashtekar-Barbero variables. Among possible physical applications, we argue that the quantization of this topological theory might shed new light on the nature of the degrees of freedom that are responsible for black entropy in loop quantum gravity.Comment: Appendix added where moldels leading to boundary degrees of freedom are constructed. This version will appear in PRD

Externalities and interdependent growth: Theory and evidence

I formulate and estimate a model of externalities within countries and technological interdependence across countries. I find that external returns to scale to physical capital within countries are 8 percent; that a 10 percent increase of total factor productivity of a country's neighbors raises its total factor productivity by 6 percent; and that a 2 percent annual growth rate of labor productivity can be explained as an endogenous response to an exogenous 0.2 percent annual growth rate of total factor productivity in the steady--state.Spatial externalities, growth regressions, exogenous growth versus endogenous growth, human versus physical capital externalities

Efecto del nivel de fibra soluble y de la relación de omega-6/omega-3 sobre el consumo de agua en gazapos en cebo

El objetivo de este trabajo fue estudiar el efecto entre la fibra soluble y la relación n-6/n-3 sobre consumo de agua en gazapos tras el destete

A constitutive model for the forces of a magnetic bearing including eddy currents

A multiple magnet bearing can be developed from N individual electromagnets. The constitutive relationships for a single magnet in such a bearing is presented. Analytical expressions are developed for a magnet with poles arranged circumferencially. Maxwell's field equations are used so the model easily includes the effects of induced eddy currents due to the rotation of the journal. Eddy currents must be included in any dynamic model because they are the only speed dependent parameter and may lead to a critical speed for the bearing. The model is applicable to bearings using attraction or repulsion

Human Rights Violations After 9/11 and the Role of Constitutional Constraints

human rights, terrorism, 9/11, checks and balances, constitutions, constitutional courts

Intellectual Property Rights Protection and Imitation - An empirical examination of Japanese FDI in China -

By using the data obtained from a questionnaire survey to the Japanese firms in China this paper empirically examines the effects of the IPRs protection against local illegal imitation. No evidence has been found in the test that the patent and trademark registration, which constitutes a part of the whole IPRs protection system, has protective effect. To the contrary the results suggest that the patent and trademark registration system may play a role in facilitating local illegal imitation and may be mediate technology transfer/diffusion in China.IPR, Patent, Imitation, Technology diffusion, FDI