Comment on some theories of state reduction

A. M. Jayannavar

David Z. Albert, Lev Vaidman A

Fred H. Thaheld

Bassi and Ghirardi have developed a new theory to address the measurement problem based upon non-linear and stochastic modifications of the Schroedinger equation, which has been given the name Quantum Mechanical Spontaneous Localization or QMSL, with one of the emphasis dealing with reduction or wavefunction collapse within the nervous system. Analysis of this portion of their theory reveals that it faces several problems.

Donald Bedford, Derek Wang

Ingram Bloch

In response to Malin's recent paper it is suggested that the important aspect of timing in relativistic descriptions of position determinations is the timing with which a pure state is converted to a mixture, rather than the timing of the mixture's reduction to a new pure state; this suggestion removes some of the subjectivism that Malin finds in quantum states. It is suggested also that viewing quantum mechanics as a branch of psychology raises more questions than it answers.

A. Holas, Marek Cinal, Norman Henry March

Two particular subjects tackled in the recent paper by Schirmer and Dreuw (SD) [J. Schirmer and A. Dreuw, Phys. Rev. A 75, 022513 (2007)] are commented on by us. By providing a convincing example, we answer positively the question posed by SD whether a local operator can be reconstructed from the knowledge of its particle-hole matrix elements (when the number of particle states exceeds one). In connection with the problem of the utmost reduction of the density-functional theory (DFT) to a solution of one equation for the density amplitude---the radical Kohn-Sham (rKS) approach---used by SD as a valuable tool to investigate the time-independent and time-dependent DFT, we demonstrate that the calculational scheme implementing the rKS formulation is rather uncompetitive with the traditional KS scheme.