Undergrad The absolute value of the frequency in quantum mechanics

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The discussion centers on the concept that the absolute value of frequency in quantum mechanics, as stated in Bransden's Quantum Mechanics, lacks physical significance. This is because, in non-relativistic quantum mechanics and quantum field theory in flat spacetime, only energy differences hold physical meaning. The relationship E = hv highlights that absolute energy values are not meaningful, reinforcing that only energy differences matter. The clarification provided resolves the initial confusion regarding the apparent contradiction. Understanding this principle is crucial for grasping fundamental quantum mechanics concepts.
mccoy1
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I was reading Bransden's Quantum Mechanics 2nd edition, chapter 2 page 61. There,it says "It should be noted that since E =hv (v for nu), the absolute value of the frequency has no physical significance in Quantum mechanics..."
Why is that? Isn't this a contradiction?
 
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mccoy1 said:
Why is that?

Because the absolute value of the energy has no physical significance in QM (more precisely, in non-relativistic QM or in QFT in flat spacetime, where gravity is absent). Only differences in energy have physical significance.
 
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PeterDonis said:
Only differences in energy have physical significance.
I see. I got it now. Thank you PeterDonis.
 

Thread 'Two equivalent statements of time reversal symmetric Hamiltonian'

Time reversal invariant Hamiltonians must satisfy ##[H,\Theta]=0## where ##\Theta## is time reversal operator. However, in some texts (for example see Many-body Quantum Theory in Condensed Matter Physics an introduction, HENRIK BRUUS and KARSTEN FLENSBERG, Corrected version: 14 January 2016, section 7.1.4) the time reversal invariant condition is introduced as ##H=H^*##. How these two conditions are identical?
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