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lots of lectures. Class is now over.
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lecture_notes/4-13/overview
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lecture_notes/4-13/overview
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Exam 2 Problem 2
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━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
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(pic) Finished the problem using the boundary conditions
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boundary conditions limit the number of possible spherical harmonics.
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Two Similar Particles
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━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
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❙a,b❭ = ❙a❭⊗❙b❭
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Exchange Operator
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──────────────────────────────────────────────────────────────────────────
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𝓟₁₂❙a,b❭ = ❙a,b❭
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𝓟₁₂(❙a❭⊗❙b❭) = ❙b❭⊗❙a❭
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If particles are indistinguishable
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𝓟₁₂❙a,b❭ = exp(iδ) ❙a,b❭ = λ ❙a,b❭
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𝓟²₁₂❙a,b❭ = λ² ❙a,b❭ = ❙a,b❭ ⇒ λ=±1
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Symmetry States
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──────────────────────────────────────────────────────────────────────────
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(pic) Two cases: symmetric, antisymmetric
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Symmetric States, λ=1
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𝓟₁₂❙a,b❭
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(pic) Constructed the exchange operator in matrix form, then found eigen states
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(pic) Showed that the exchange operator leads to the Pauli Exclusion Principle
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50
lecture_notes/4-15/Overview
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lecture_notes/4-15/Overview
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Two Spin-½ Particles
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━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
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uncoupled basis
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───────────────
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❙s₁ s₂ m₁ m₂❭
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❙+ +❭, ❙- -❭, ❙+ -❭, ❙- +❭
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coupled basis
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─────────────
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❙S Mₛ❭
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❙1 1❭, ❙1 -1❭, ❙1 0❭, ❙0 0❭
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Given the state ❙1 0❭ = 1/√2(❙+ -❭ + ❙- +❭) :
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P₁₂❙1 0❭ = ❙1 0❭ (symmetric)
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❙0 0❭ = 1/√2(❙+ -❭ - ❙- +❭) :
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P₁₂❙0 0❭ = -❙0 0❭ (antisymmetric)
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Spatial Representation
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──────────────────────────────────────────────────────────────────────────
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❙Ψ❭ = ❙Ψₛₚₐₜᵢₐₗ❭❙Ψₛₚᵢₙ❭
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Symmetric:
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❙Ψ❭ˢ = ❙Ψₛₚₐₜᵢₐₗ❭ˢ❙Ψₛₚᵢₙ❭ˢ OR ❙Ψₛₚₐₜᵢₐₗ❭ᴬ❙Ψₛₚᵢₙ❭ᴬ
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Antisymmetric:
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❙Ψ❭ᴬ = ❙Ψₛₚₐₜᵢₐₗ❭ᴬ❙Ψₛₚᵢₙ❭ˢ OR ❙Ψₛₚₐₜᵢₐₗ❭ˢ❙Ψₛₚᵢₙ❭ᴬ
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Helium Atom
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──────────────────────────────────────────────────────────────────────────
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Fermions, so overall must be antisymmetric
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Configuration Term Energy
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1s² 1s 0
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❙Ψ❭ = 1/√2 (❙a❭₁ₛ❙b❭₁ₛ + ❙b❭₁ₛ❙a❭₁ₛ)❙0 0❭
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1s²s 3s 1.46
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❙Ψ❭ = 1/√2(❙a❭₁ₛ❙b❭₁ₛ - ❙b❭₁ₛ❙a❭₁ₛ)❙1 m❭, m=-1,0,1
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1s2s 1s 1.52
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❙Ψ❭ = 1/√2 (❙a❭₁ₛ❙b❭₁ₛ + ❙b❭₁ₛ❙a❭₁ₛ)❙0 0❭
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1s2p 3pᵒ ~1.60
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❙Ψ❭ = 1√2
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1s²p 1pᵒ ~1.65
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6
lecture_notes/4-18
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lecture_notes/4-18
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∮𝐁⋅d𝐥 = B(s) sπs = μ₀[∫𝐉⋅n̂da + ε₀ d/dt ∫𝐄⋅n̂da]
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∫𝐉⋅n̂da = 0
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For capacitor:
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│𝐄│ = σ/ε₀ ⇒ B(s) 2πs = μ₀ ε₀ d/dt σ(t)/ε₀ πs²
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solutions/chap2/prob2
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solutions/chap2/prob2
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S𝓍 ≐ ħ͟⎛0 1⎞
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2⎝1 0⎠
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Diagonalize the matrix...
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First, find the characteristic equation and solve for the eigenvalues.
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S𝓍 ≐ ħ͟⎛0 1⎞
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2⎝1 0⎠
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ħ͟ ⎛-λ 1⎞
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2 ⎝ 1 -λ⎠
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λ² - ħ²/4 = 0
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λ² = ħ²/4
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λ = ±ħ/2
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So the eigenvalues are those expected for the measurement of a spin-1/2 component.
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The eigenvalue equations are
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S𝓍❙Ψ❭ = λ❙Ψ❭
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which is represented by
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ħ͟⎛0 1⎞⎛a⎞ = λ⎛a⎞
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2⎝1 0⎠⎝b⎠ ⎝b⎠
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3
solutions/chap3/prob7
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solutions/chap3/prob7
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After the first Stern-Gerlach magnet, the entire wave function will be in a single state:
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❙Ψ₁❭ = ❙S₊❭
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