Trinh @ Bath

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projects_divergentphysics [2020/04/10 13:06]
trinh created
projects_divergentphysics [2020/04/10 13:11] (current)
trinh
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 V(x) = \frac{1}{2} x^2. V(x) = \frac{1}{2} x^2.
 $$ $$
-You learn that the permissible energies take discrete values like $E_n = n + 1/2$. In an effort to understand how this can be generalised, you might try to perturb the potential that you have above so that it includes a small higher-order term, like this:+You learn that the permissible energies take discrete values like $E_n = (n + 1/2)$. In an effort to understand how this can be generalised, you might try to perturb the potential that it includes a small higher-order term, like this:
 $$ $$
 V(x) = \frac{1}{2} x^2 + \lambda x^4. V(x) = \frac{1}{2} x^2 + \lambda x^4.
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 E_n = \left(n + \frac{1}{2}\right) + \lambda E_{n1} + \lambda^2 E_{n2} + \ldots = \sum_{j=0}^\infty \lambda^n E_{nj}. E_n = \left(n + \frac{1}{2}\right) + \lambda E_{n1} + \lambda^2 E_{n2} + \ldots = \sum_{j=0}^\infty \lambda^n E_{nj}.
 $$ $$
-But doing so, you quickly realise that the series is divergent. How do you assign meaning to a divergent series? Perhaps put more sensationally: how could you sum the divergent series to obtain the actual answer of the energy?  +But doing so, you quickly realise that the series is divergent and the terms in the series get very large very rapidly. How do you assign meaning to a divergent series? Perhaps put more sensationally: how could you sum the divergent series to obtain the actual answer of the energy? This problem lies at the heart of a lot of the puzzling issues about quantum theories---mainly that many of the quantities that you try to write down are divergent, and it is not clear how to extract meaning from them. 
- +
-This problem lies at the heart of a lot of the puzzling issues about quantum theories---mainly that many of the quantities that you try to write down are divergent, and it is not clear how to extract meaning from them. +
  
 This project will be about learning about some of these techniques for studying divergent series.  This project will be about learning about some of these techniques for studying divergent series.