How to solve generalised eigenvalue problems?

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Discussion Overview

The discussion centers around methods for solving generalized eigenvalue problems, particularly in the context of quantum mechanics. Participants explore both theoretical and practical aspects, including algorithm development and mathematical methods.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • One participant expresses a desire to develop their own algorithm for solving generalized eigenvalue problems to enhance their understanding of the underlying mathematics.
  • Another participant notes that solving eigenvalue problems for discrete sets is straightforward using matrix representations, as covered in introductory linear algebra and scientific computing texts.
  • In contrast, the same participant points out that continuous sets involve more complexity, typically requiring the solution of coupled partial differential equations.
  • A different participant highlights the challenges of solving the time-independent Schrödinger equation, stating that only a few cases are analytically solvable and that approximations like perturbation theory are often necessary.
  • One participant suggests consulting LAPACK for its generalized eigenvalue routines and mentions that the manual provides a description of the methods used along with an extensive bibliography.

Areas of Agreement / Disagreement

Participants express varying levels of complexity associated with solving generalized eigenvalue problems, indicating that while some aspects are straightforward, others are significantly more challenging. No consensus is reached on a singular approach or method.

Contextual Notes

Participants do not provide specific assumptions or definitions, and the discussion reflects a range of mathematical techniques and their applicability to different types of eigenvalue problems.

ngkamsengpeter
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I want to write myself a algorithm to solve generalised eigenvalue problems in quantum mechanics.I know there are a lot of library there that allow me to use it directly but i just want to write my own so that i can learn the mathematics methods that solve the problem...
I don't know how to solve the generalised eigenvalue problems without using existing library in computer...
So anyone has any reference so that i can learn the mathematical methods that solve the generalised eigen value problems??
 
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For discrete sets it is easy, e.g. for spin, then you just do a matrix representation for it and solve its eigenvalue problem, this is done in all introductory linear algebra books and scientific computing books.

For the continuous set, it is more complicated. One has to, in general, solve coupled partial differential equation, which is also outlined in any introductory book in scientific computing.

Please tell us about your background in physics, math and computing and what your aim with all this is maybe we can help you better.

cheers
 
It's not simple to solve any general eigenvalue equation, indeed, the time independent Schroedinger equation is in fact an Eigenvalue equation (for the energy-eigenvalues), and only a handful of cases are analytically solvable. A lot of the time, you need to resort to approximations, such as perturbation theory.
 
Take a look at LAPACK and see if they report the source of their algorithms for their generalized eigenvalue routines. The manual gives a description of the general method and they have an extensive bibliography at the end.
 

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