Droplet formation on the surface of a melt due to excitation of capillary waves by laser radiation

Abstract

This paper examines spinor structures and two-component spinor fields in in a class of spacetimes that are spacedrientable but not time-orientable. The space-oriented frames form a principal bundle acted on by the group of p r o p nononhochronous Lomtz transformations. This p u p has two double coverings, Sint and Sin-, but only Sinacts on the usual two-component spinors associated wilh Weyl neutrinos in Minkowski space Consideration is initially reshicled to Lorentzian universes-from-nothing. geometries, like antipodally identified deSiner space, that have a single spacelike boundary and a smooth meuic wilh Lorentzian signalure. Every such spacetime has a Sin+ S t " r e , but only a subclass has a Sinstructure. Inequivalent Sin+-and Sin--spinor structures correspond to members of two classes of homomorphisms from XI(=) to &, where ; i i is the orientable double covering of the spacetime m i f o l d M. For general time-nonorientable spacetimes. a similar classification is obtained of Sin' sWcNres in terms of homomorphisms from q ( E ) to & where E is the bundle of space-oriented frames of M .

Diagnostics of a Crater Growth and Plasma Jet Evolution on Laser Pulse Materials Processing

“…In the case of the processes exhibiting axial symmetry (which was true of the process we investigated) we have R ~ E 1/2 [16] and therefore V ~ E 3 ' 2 , which is in good agreement with equation (6).…”

“…In our opinion, the significant difference in the characteristic size of droplets, observed on the surface of the irradiated sample in the presence of the external electric field (independent of the direction of the field strength vector) and in the absence of the field, is a manifestation of the following mechanism of droplet formation [6]. It is known that at the surface of a liquid (including a liquid metal) the formation of gravity-capillary waves [7] is possible under the action of various perturbations.…”

“…It is known that at the surface of a liquid (including a liquid metal) the formation of gravity-capillary waves [7] is possible under the action of various perturbations. Undoubtedly, the examples of such perturbations are the spatially nonuniform evaporation of the target material due to nonuniform heating caused by nonuniform energy distribution over the focusing spot [8], the nonuniform primary plasma formation [6,9,10] caused by roughness of the irradiated sample surface [8], and, in the first place, the s1op of the molten metal initiated by each spike of laser radiation, acting on the exposed sample [2].…”

“…The radiation spot diameter with sharp edges on the sample was varied in the course of the experiments from 1 to 2 mm. From the front face of the glass wedge (5) a part (4%) of laser radiation was directed into the IMO-2N energy meter (6), whose entrance window was located in the focal plane of the lens (7). The energy of the laser pulses varied from 5 to 60 J.…”