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How to show that expectation value is always positive?

  1. Jun 25, 2009 #1
    1. The problem statement, all variables and given/known data
    In quantum mechanics, how to show that the expectation value is always positive?

    2. Relevant equations

    3. The attempt at a solution
  2. jcsd
  3. Jun 25, 2009 #2


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    Can you be more specific? Because as you stated it, one can easily find a counter-example (e.g. <x> for a Gaussian wavepacket centered at some x0 < 0).
  4. Jun 25, 2009 #3
    Questions just tell us to show that A+A is always self-adjoin and then show that expectation is non-negative.
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