Classical gravitational spin-spin interaction

I obtain an exact, axially symmetric, stationary solution of Einstein's equations for two massless spinning particles. The term representing the spin-spin interaction agrees with recently published approximate work. The spin-spin force appears to be proportional to the inverse fourth power of the coordinate distance between the particles.Comment: six pages, no figures, journal ref:accepted for Classical and Quantum Gravit

The structure of the QED-Vacuum and Electron-Positron Pair Production in Super-Intense, pulsed Laser Fields

We discuss electron-positron pair-production by super-intense, short laser pulses off the physical vacuum state locally deformed by (stripped) nuclei with large nuclear charges. Consequences of non-perturbative vacuum polarisation resulting from such a deformation are shortly broached. Production probabilities per pulse are calculated.Comment: 10 pages, 1 figure, submitted to Journal of Physics

Bound States in Sharply Bent Waveguides: Analytical and Experimental Approach

Quantum wires and electromagnetic waveguides possess common features since their physics is described by the same wave equation. We exploit this analogy to investigate experimentally with microwave waveguides and theoretically with the help of an effective potential approach the occurrence of bound states in sharply bent quantum wires. In particular, we compute the bound states, study the features of the transition from a bound to an unbound state caused by the variation of the bending angle and determine the critical bending angles at which such a transition takes place. The predictions are confirmed by calculations based on a conventional numerical method as well as experimental measurements of the spectra and electric field intensity distributions of electromagnetic waveguides

Iowan Drift Problem, Northeastern Iowa

https://ir.uiowa.edu/igs_ri/1006/thumbnail.jp

Long-run relationship between R&D investment and environmental sustainability:Evidence from the European Union member countries

The file attached to this record is the author's final peer reviewed version. The Publisher's final version can be found by following the DOI link.The researchers, environmental scientists and policymakers around the world are exerting substantial efforts to mitigate the growth of CO2 emissions to save the planet. A number of measures and initiatives, such as, energy efficiency, renewable energy technologies and emission-control are proposed in order to reduce CO2 emissions. This study examines the long-run relationship between R&D investment and environmental sustainability in a panel of 25 European Union (EU) member countries over a period of seventeen years (1998 to 2014). We use robust and reliable econometric methods to capture the interactions between R&D investment on renewable energy consumption and CO2 emissions. The findings confirm that the growth of R&D expenditures promotes renewable energy consumption and plays a significant role in reducing CO2 emissions in the sample countries. Furthermore, the findings suggest that increasing the share of renewable energy consumption in the total energy mix also reduces CO2 emissions. Given these results, we suggest that the EU policymakers provide more financial and regulatory assistance to the R&D activities, specifically in the energy sector, to ensure promoting low carbon economies in this region

Third rank Killing tensors in general relativity. The (1+1)-dimensional case

Third rank Killing tensors in (1+1)-dimensional geometries are investigated and classified. It is found that a necessary and sufficient condition for such a geometry to admit a third rank Killing tensor can always be formulated as a quadratic PDE, of order three or lower, in a Kahler type potential for the metric. This is in contrast to the case of first and second rank Killing tensors for which the integrability condition is a linear PDE. The motivation for studying higher rank Killing tensors in (1+1)-geometries, is the fact that exact solutions of the Einstein equations are often associated with a first or second rank Killing tensor symmetry in the geodesic flow formulation of the dynamics. This is in particular true for the many models of interest for which this formulation is (1+1)-dimensional, where just one additional constant of motion suffices for complete integrability. We show that new exact solutions can be found by classifying geometries admitting higher rank Killing tensors.Comment: 16 pages, LaTe

Two Kerr black holes with axisymmetric spins: An improved Newtonian model for the head-on collision and gravitational radiation

We present a semi-analytical approach to the interaction of two (originally) Kerr black holes through a head-on collision process. An expression for the rate of emission of gravitational radiation is derived from an exact solution to the Einstein's field equations. The total amount of gravitational radiation emitted in the process is calculated and compared to current numerical investigations. We find that the spin-spin interaction increases the emission of gravitational wave energy up to 0.2% of the total rest mass. We discuss also the possibility of spin-exchange between the holes.Comment: 8 pages, RevTeX, 2 figures, psbox macro include