Who is a Jew? familiar with and willing to vouch for the Jewishness of their maternal lineage or the validity of their conversion. There have been several attempts to convene representatives of the three major movements to formulate a practical solution to this issue. To date, these have failed, though all parties concede the importance of the issue is greater than any sense of rivalry among them. Ethnic Jew is a term generally used to describe a person of Jewish parentage and background who does not necessarily actively practice Judaism, but still identifies with Judaism or other Jews culturally or fraternally, or both. The
Solution of Schrödinger equation for a step potential disappears in the context of quantum field theory. The Heaviside step potential mainly serves as an exercise in introductory quantum mechanics, as the solution requires understanding of a variety of quantum mechanical concepts: wavefunction normalization, continuity, incident/reflection/transmission amplitudes, and probabilities. A similar problem to the one considered appears in the physics of normal-metal superconductor interfaces. Quasiparticles are scattered at the pair potential which in the simplest model may be assumed to have a step-like shape. The solution of the Bogoliubov-de Gennes equation resembles that of the discussed Heaviside-step potential. In the superconductor normal-metal case this gives rise to Andreev reflection.