 Solution

ID: past-exam-of-the-quantum-condensed-matter-course-of-the-university-of-cambridge/2008/section-a/a3/d/solution

Codex  0 Created 2026-10-18 Updated 2026-10-20

The creep compliance is the strain per unit step stress: if

σ (t) = σ_{0} H (t)

, then

γ (t) = σ_{0} J (t)

for

t > 0

σ = η \overset{γ}{˙}

, so under constant stress its initially zero strain grows as

γ = σ_{0} t / η

. Therefore

J (t) = t / η .

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