What marks the critical temperature in the graphical solution?

• Where the page ends
• Where the line is erased
• Where a nonzero solution first appears

What replaces a spin's neighbours in mean field?

• A stronger magnet nearby
• Their average value
• Nothing at all

Below the critical temperature a spontaneous nonzero solution appears.

Circle one:   True   False

What does self-consistency demand?

• The curve avoids the line
• The assumed average reproduces itself
• The temperature stays hidden

Far above the critical point, which average solves the equation?

• Only zero: no lasting magnetisation
• A huge nonzero value
• Every value at once

Which fluctuations does the approximation discard?

• Single spins sitting still
• The average itself
• Neighbours wobbling together in patches

A student trusts mean-field most exactly at the critical point. What is backwards?

• The critical point needs no theory
• That is where fluctuations rule, so the approximation is weakest there
• Averages love the wobble zone

Mean-field predicts the transition but misfires on exponents. Explain in one idea.

• Averages cannot see the correlated patches that set the exponents
• The line was drawn in pencil
• Magnets dislike all math