This article navigates between several conceptual artworks. The first is Robert Barry’s ‘0.5 Microcurie Radiation Installation’ – an object buried somewhere in New York’s Central Park since 1969. second Walter De Maria’s ‘Lightning Field’ installation, erected Mexico 1977. two artworks are separated by eight years and 2,200 miles. former concerned with electroma...

We present a review on the accuracy of asymptotic models for the scattering problem of electromagnetic waves in domains with thin layer. These models appear as first order approximations of the electromagnetic field. They are obtained thanks to a multiscale expansion of the exact solution with respect to the thickness of the thin layer, that makes possible to replace the thin layer by approxima...

We obtain Hamilton equations for the gravitational field and demonstrate the conservation of total energy. We derive the Poisson bracket equation for a general dynamical variable.

Richard Feynman has claimed that anti-particles are nothing but particles ‘propagating backwards in time’; that time reversing a particle state always turns it into the corresponding anti-particle state. According to standard quantum field theory textbooks this is not so: time reversal does not turn particles into anti-particles. Feynman’s view is interesting because, in particular, it suggests...