Some Concepts of Quantum Mechanics

Framework for QFD in 3-D Space .............................................................188 12.5 Quantum Fluid Dynamical Equations within a Density Functional Framework..................................................................................................191 12.6 Miscellaneous Aspects of the Quantum Fluid Dynamical Approach .........193 12.7 Concluding Remarks...................................................................................194 Acknowledgments..................................................................................................194 Bibliography ..........................................................................................................194 The concepts of quantum mechanics (QM) are so radically different from those of classical mechanics that soon after Schrödinger proposed the concept of quantum mechanical wavefunction, there were attempts to provide a classical interpretation of QM. In fact, the success of Madelung [1] in transforming the Schrödinger equation into a pair of hydrodynamical equations consisting of the continuity equation and an Euler type equation of hydrodynamics, giving birth to so-called quantum fluid dynamics (QFD) [2-5], in 1926, itself is testimony to the strong urge to have a classical interpretation of the strange world of QM. The concept was resurrected with full vigor more than 25 years later through the pioneering works of Bohm [6] and Takabayashi [7]. In the meantime, Wigner [8] introduced, in 1932, the concept

A. Loinger

Ernesto Benítez Rodríguez, L. M. Arévalo Aguilar

The concept of disturbance is of transcendental importance in Quantum Mechanics (QM). This key concept has been described in two different ways, the first one considering that the disturbance affects observables like x and p, as in the Heisenberg’s analysis of the measurement process and the other one takes into consideration that disturbance affects the state of the system instead. Entropic information measures have provided a path for studying disturbance in these both approaches; in fact, we found that initially it was studied by employing these entropic measures. In addition, in the last decade, there was an extensive amount of analyses and several new definitions of the disturbance concept emerged. Many crucial factors like this have inspired this concise paper which gathers the different concepts and definitions that have emerged through time for the better understanding of this topic.

F. A. Kaempffer

Karl K. Darrow

Sagar Kumar Biswal

Quantum mechanics is a relatively new branch of physics as compared to the other branches.Many of its concepts are a bit confusing, which is quite obvious, because it completely destroys the classical intuitions of physicists as well as students.But some of its concepts have a classical mechanical analogy and one such concept is the concept of expectation value of observables or operators in quantum mechanics.In a way it is related to the concept of centre of mass in classical mechanics.So, in this paper, first, a review of this concept and its correspondence with centre of mass and later the reason behind the naming of this concept is discussed in brief.