Gelfand state

The arrangement of the seven highest weights appearing here can be altered to form an inverted pyramid, the so-called Gelfand state ... 

If the phase shifts are given as a function of the energy a unique solution can only be obtained if, in addition, the bound state energies and the normalization constants of the bound state wave function are known (Gelfand and Levitan, 1951). The explicit construction of the potential leads to a complicated solution of a Fredholm integral equation. Other procedures (Agranovich and Marchenko, 1963 Hylleraas, 1963) may be more convenient for a practical application (see Benn and Scharf, 1967, O Brien and Bernstein,... 

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