SUSY in the sky with gravitons

Picture yourself in the wave zone of a gravitational scattering event of two massive, spinning compact bodies (black holes, neutron stars or stars). We show that this system of genuine astrophysical interest enjoys a hidden $$ \mathcal{N} $$ N = 2 supersymmetry, at least to the order of spin-squared (quadrupole) interactions in arbitrary D spacetime dimensions. Using the $$ \mathcal{N} $$ N = 2 supersymmetric worldline action, augmented by finite-size corrections for the non-Kerr black hole case, we build a quadratic-in-spin extension to the worldline quantum field theory (WQFT) formalism introduced in our previous work, and calculate the two bodies’ deflection and spin kick to sub-leading order in the post-Minkowskian expansion in Newton’s constant G. For spins aligned to the normal vector of the scattering plane we also obtain the scattering angle. All D-dimensional observables are derived from an eikonal phase given as the free energy of the WQFT that is invariant under the $$ \mathcal{N} $$ N = 2 supersymmetry transformations.

TRANSITION RADIATION OF A RELATIVISTIC ELECTRON BUNCH ON A SEMI-INFINITE METAL CYLINDER

Transition radiation of a relativistic electron bunch, which arises when it collides with the end face of a semi-infinite ideally conducting cylinder, is considered. An electron bunch moves along the axis of a semi-infinite cylin-der. Expressions for the field strength of electromagnetic radiation in the wave zone are obtained. The influence of the guiding properties of an ideally conducting cylinder on the directional diagram of the transition radiation is investigated.

Duct Attachment on Improving Breaking Wave Zone Energy Extractor Device Performance

A challenging wave energy converter design that utilized the denser energy part of the nearshore breaking wave zone to generate electricity was introduced in 2016 by Shintake. The Okinawa Institute of Science and Technology Graduate University’s project aims to take advantage of breaking wave energy to harness electricity. The 2016 version of the device consisted only of a bare turbine and power generator. Early exploration of the design recorded short periods and high impact wave pressures were experienced by the structure, with the turbine unable to harvest energy effectively. Additional structure to not only reduce incoming impact pressure but also increase the duration of water flow through the turbine was needed. These are the main reasons behind incorporating the duct attachment into the design. This paper show that the duct is capable of halving the impact pressure experienced by the turbine and can increase the energy exposure by up to 1.6 times the bare turbine configuration. Furthermore, it is also said that wave angle (β) = 40° is the critical angle, although the duct still increases wave energy exposure to the power take-off up to β = 60°.

Wave zone in the Hořava–Lifshitz theory at the kinetic-conformal point in the low energy regime

We show that in the Hořava–Lifshitz theory at the kinetic-conformal point, in the low energy regime, a wave zone for asymptotically flat fields can be consistently defined. In it, the physical degrees of freedom, the transverse traceless tensorial modes, satisfy a linear wave equation. The Newtonian contributions, among which there are terms which manifestly break the relativistic invariance, are non-trivial but do not obstruct the free propagation (radiation) of the physical degrees of freedom. For an appropriate value of the couplings of the theory, the wave equation becomes the relativistic one in agreement with the propagation of the gravitational radiation in the wave zone of General Relativity. Previously to the wave zone analysis, and in general grounds, we obtain the physical Hamiltonian of the Hořava–Lifshitz theory at the kinetic-conformal point in the constrained submanifold. We determine the canonical physical degrees of freedom in a particular coordinate system. They are well defined functions of the transverse-traceless modes of the metric and coincide with them in the wave zone and also at linearized level.

Armor Damage of Overtopped Mound Breakwaters in Depth-Limited Breaking Wave Conditions

Armor damage due to wave attack is the principal failure mode to be considered when designing conventional mound breakwaters. Armor layers of mound breakwaters are typically designed using formulas in the literature for non-overtopped mound breakwaters in non-breaking wave conditions, although overtopped mound breakwaters in the depth-induced breaking wave zone are common design conditions. In this study, 2D physical tests with an armor slope H/V = 3/2 are analyzed in order to better describe the hydraulic stability of overtopped mound breakwaters with double-layer rock, double-layer randomly-place cube and single-layer Cubipod® armors in depth-limited breaking wave conditions. Hydraulic stability formulas are derived for each armor section (front slope, crest and rear slope) and each armor layer. The front slope of overtopped double-layer rock structures is more stable than the front slope of non-overtopped mound breakwaters in breaking wave conditions. When wave attack increases, armor damage appears first on the front slope, later on the crest and, finally, on the rear side. However, once the damage begins on the crest and rear side, the progression is much faster than on the front slope, because more wave energy is dissipated through the armored crest and rear side.

TRANSITION EXCITATION OF A PERFECTLY CONDUCTING CYLINDER BY RELATIVISTIC ELECTRON BUNCHES

Transition radiation of a relativistic electron bunch, which arises when it collides with the surface of an infinite perfectly conducting cylinder, is considered. The electron bunch moves perpendicular to the cylinder surface. Expressions for the field strength of electromagnetic radiation in the wave zone are obtained and investigated.