Chapter 3: Q20P (page 118)
Show that the energy-time uncertainty principle reduces to the "your name" uncertainty principle (Problem 3.14), when the observable in question is x.
Short Answer
The energy-time uncertainty principle reduces to .
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Chapter 3: Q20P (page 118)
Show that the energy-time uncertainty principle reduces to the "your name" uncertainty principle (Problem 3.14), when the observable in question is x.
The energy-time uncertainty principle reduces to .
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(a) Write down the time-dependent "Schrödinger equation" in momentum space, for a free particle, and solve it. Answer:
(b) Find role="math" localid="1656051039815" for the traveling gaussian wave packet (Problem 2.43), and construct for this case. Also construct , and note that it is independent of time.
(c) Calculaterole="math" localid="1656051188971" androle="math" localid="1656051181044" by evaluating the appropriate integrals involving, and compare your answers to Problem 2.43.
(d) Show thatrole="math" localid="1656051421703" (where the subscript denotes the stationary gaussian), and comment on this result.
An anti-Hermitian (or skew-Hermitian) operator is equal to minus its Hermitian conjugate:
(a) Show that the expectation value of an anti-Hermitian operator is imaginary. (b) Show that the commutator of two Hermitian operators is anti-Hermitian. How about the commutator of two anti-Hermitian operators?
Let be an operator with a complete set of orthonormal eigenvectors:localid="1658131083682" (n=1,2,3,....) Show thatcan be written in terms of its spectral decomposition:
Hint: An operator is characterized by its action on all possible vectors, so what you must show is that for any vector .
Show that the energy-time uncertainty principle reduces to the "your name" uncertainty principle (Problem 3.14), when the observable in question is x.
Extended uncertainty principle.The generalized uncertainty principle (Equation 3.62) states that
where.
(a) Show that it can be strengthened to read
[3.99]
where. Hint: Keep the term in Equation 3.60
(b) Check equation 3.99 for the case(the standard uncertainty principle is trivial, in this case, since; unfortunately, the extended uncertainty principle doesn't help much either).
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