Difference between revisions of "Hilbert Space"

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Unitary Gauge Transformations  
 
Unitary Gauge Transformations  
 
* A reason to be skeptical about assigning a physical meaning directly to the Hilbert-space ingredients: quantum theory contains a little-known form of gauge invariance  
 
* A reason to be skeptical about assigning a physical meaning directly to the Hilbert-space ingredients: quantum theory contains a little-known form of gauge invariance  
* For V (t) any time-dependent, unitary operator, the following gauge transformation leaves all empirical predictions invariant:
+
[[File:Unitary Gauge Transformations Cut.png]]
Wave functions:
 
Density matrices:
 
Observables:
 
Time-evolution
 
operators:
 
Hamiltonians:
 
  
 
==References==
 
==References==
  
 
[[Category: Physics]]
 
[[Category: Physics]]

Revision as of 22:26, 26 November 2024

Full Title

Context

  • In Quantum Mechanics the state of a physical system is represented by a vector in a Hilbert space: a complex vector space with an inner product.[1]
  • The term “Hilbert space” is often reserved for an infinite-dimensional inner product space having the property that it is complete or closed. However, the term is often used in a way that includes finite-dimensional spaces, which automatically satisfy the condition of completeness.
  • We will use Dirac notation in which the vectors in the space are denoted by |v>, called a ket, where v is some symbol which identifies the vector.
  • One could equally well use something like v. A multiple of a vector by a complex number c is written as c|v> -think of it as analogous to cv.
  • In Dirac notation the inner product of the vectors |v> with |w> is written <v|w>. This resembles the ordinary dot product ~v · ~w except that one takes a complex conjugate of the vector on the left, thus think of ~v∗· ~w.

Problems

Quantum Theory

Unitary Gauge Transformations

  • A reason to be skeptical about assigning a physical meaning directly to the Hilbert-space ingredients: quantum theory contains a little-known form of gauge invariance

Unitary Gauge Transformations Cut.png

References

  1. Robert B. Griffiths, Hilbert Space Quantum Mechanics CMU (2014-01) https://quantum.phys.cmu.edu/QCQI/qitd114.pdf