Heisenberg indeterminacy principle

STATISTICAL MECHANICS. One major problem of physios involves the prediction of the macroscopic properties of matter in terms of the properties of the molecules of which it is composed. According to the ideas of classical physics, this could have been accomplished by a determination of the detailed motion of each molecule and by a subsequent superposition or summation of their effects. The Heisenberg indeterminacy principle now indicates that this process is impossible, since we cannot acquire sufficient information about the initial state of the molecules. Even if this were not so, the problem would be practically insoluble because of the extremely large numbers of molecules involved in nearly all observations. Many successful predictions can be made, however, by considering only the average, or most probable, behavior of the molecules, rather than the behavior of individuals. This is the mediod used in statistical mechanics. 

This is known as the Heisenberg indeterminacy principle (also called uncertainty principle by some authors). It has to do with precision and not with accuracy. This situation has already been met in Section 1.2 when referring to the double-slit experiment. 

If two operators do not commute with each other, then the observables they represent cannot be determined simultaneously with an arbitrarily small indeterminacy. These observables are said to be incompatible (also called complementary), and are the object of the indeterminacy principle introduced in Chapter 1. We will keep to this usual expression of the Heisenberg indeterminacy principle, although, as we found in Chapter 1, this means the impossibility of preparing a state for which two incompatible properties can be determined with arbitrarily small indeterminacies. The fact that some operators do not commute with each other represents one of the main differences between classical and quantum mechanics. 

State the Heisenberg indeterminacy principle and use it to establish bounds within which the position and momentum of a particle can be known (Section 4.4, Problems 35 and 36). 

Heisenberg s principle of uncertainty (or indeterminacy) was based in the Dirac-Jordan transformation theory (see Kragh, Dirac, 44) P. A. M. Dirac, "The Physical Interpretation of the Quantum Dynamics,"... 

Q.7.13 What are the complementary observables for the Heisenberg indeterminacy or uncertainty principle How are the complementary observables related to each other ... 

Shortly after the development of VBT, an alternative model, known as MOT, was introduced by the American physicist Robert Mulliken (and others) around 1932. MOT is a delocalized bonding model, where the nuclei in the molecule are held in fixed positions at their equilibrium geometries and the Schrodinger equation is solved for the entire molecule to yield a set of MOs. In practice, it is possible to solve the Schrodinger equation exactly only for one-electron species, such as H2. Whenever more than one electron is involved, the wave equation can only yield approximate solutions because of the e/ectron correlation problem that results from Heisenberg s principle of indeterminacy. If one cannot know precisely the position and momentum of an electron, it is impossible to calculate the force field that this one electron exerts on every other electron in the molecule. As a result of this mathematical limitation, an approximation method must be used to calculate the energies of the MOs. 

The two conclusions we have reached are summarized as, and follow from, Heisenberg s Uncertainty Principle (sometimes called The Principle of Indeterminacy) that may be stated in the foiro ... 

---