phy-4600/lecture_notes/3-14/translation operators

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Translation Operators
Matrix mechanical expression:
T̂(a𝓍 î) ❙x,y,z❭ = ❙x+a𝓍,y,z❭
T̂(a𝓎 î) ❙x,y,z❭ = ❙x,y+a𝓎,z❭
T̂(a𝓏 î) ❙x,y,z❭ = ❙x,y,z+a𝓏
Position space form:
T(a𝓍 î) = exp(-ι p𝓍 a𝓍/ħ )
Translation operators commute since momentum operators commute.
But, [x̂ᵢ,p̂ⱼ]=ιħδᵢⱼ
T̂(𝐚) = exp(-ι p𝓍 a𝓍/ħ ) exp(-ι p𝓎 a𝓎/ħ ) exp(-ι p𝓏 a𝓏/ħ )
= exp(-ι 𝐩 𝐚/ħ )
❬r❙p̂❙Ψ❭ = ħ/ι ∇ ❬r❙Ψ❭