The Symplectic Camel · non-squeezing

Gromov (1985): if B⁴(r) embeds symplectically in Z(R) = B²(R) × ℝ², then r ≤ R.

x₁ y₁ x₂
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Volume-preserving squeeze

4-volume kept symplectic fits the hole
y₂ = −r+r
outside the cylinder
cylinder wall, radius R
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