What makes matrix mechanics matrix mechanics?

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    Matrix Mechanics
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Discussion Overview

The discussion revolves around the distinctions between matrix mechanics and wave mechanics in quantum mechanics, particularly focusing on Heisenberg's formulation and its implications in quantum chemistry. Participants explore the theoretical underpinnings, practical applications, and the conceptual differences between the Heisenberg and Schrödinger pictures.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Conceptual clarification

Main Points Raised

  • One participant notes that Heisenberg's formulation primarily dealt with matrix representations of operators and derived observables, without reference to spatially defined orbitals.
  • Another participant explains that in the Heisenberg picture, states are constant in time while operators evolve, allowing for tensorial (matrix) formulations, contrasting this with the Schrödinger picture where operators are constant and states evolve.
  • Some participants argue that the Schrödinger picture is more commonly referenced in standard quantum mechanics literature, suggesting that matrix mechanics is less prevalent in educational contexts.
  • A participant questions whether using matrix algebra in quantum chemistry, such as diagonalizing the Fock operator, constitutes matrix mechanics or if it is merely an application of Schrödinger wave mechanics.
  • Another participant asserts that quantum chemistry is fundamentally based on the Schrödinger equation, implying that using a finite basis set does not equate to matrix mechanics.
  • One participant emphasizes the physical realizability of the Heisenberg picture in experiments, while suggesting that the Schrödinger picture is less applicable unless in time-independent cases.
  • There is a challenge regarding the claim that the Schrödinger picture is rarely used, prompting a request for clarification on who holds this view.
  • A participant references historical context, mentioning Heisenberg's transition from classical to quantum mechanics and the role of matrix coefficients in describing quantum phenomena.
  • Another participant reiterates the equivalence of the Heisenberg and Schrödinger pictures, suggesting that both frameworks are valid but may be applied differently in practice.

Areas of Agreement / Disagreement

Participants express differing views on the prevalence and application of matrix mechanics versus wave mechanics, with no consensus reached on the definitions or practical implications of each approach. The discussion remains unresolved regarding the specific procedural differences that distinguish matrix mechanics from Schrödinger wave mechanics.

Contextual Notes

Participants highlight various assumptions about the applicability of the Heisenberg and Schrödinger pictures, the historical context of their development, and the implications for quantum chemistry. There are unresolved questions about the definitions and boundaries of matrix mechanics in relation to practical computational methods.

  • #31
ok there's one detail that I have ignored that may have been what you were looking for. wave mechanics failed to comply with the relativistic energy. at the time dirac solved this by introducing matrices that solved the wave equation if inserted, instead of just the single wave function. for details I recommend:http://en.wikipedia.org/wiki/Dirac_equation
the idea is that in the new tonsorial equation, the wave function must be a tensor itself, thereby introducing matrix mechanics to wave physics.
 
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  • #32
ardie said:
ok there's one detail that I have ignored that may have been what you were looking for. wave mechanics failed to comply with the relativistic energy. at the time dirac solved this by introducing matrices that solved the wave equation if inserted, instead of just the single wave function. for details I recommend:http://en.wikipedia.org/wiki/Dirac_equation
the idea is that in the new tonsorial equation, the wave function must be a tensor itself, thereby introducing matrix mechanics to wave physics.
No, this is not my question. My question is in starting from first principals looking to calculate the total energy of an atom or molecule, how would I accomplish this using "matrix mechanics" and how would I accomplish this using "wave mechanics". I know I must get the same answer regardless but they are distinct techniques. I know how I DO do this in calculations, but I don't know to which method what I do belongs or if it's some mixture of both.
 

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