Fig 70 · Working principle

One signal. Three rulers.

A taller, narrower pulse can grow, hold steady and vanish—depending on how you measure it.

SIGNAL BENCH / THREE NORMSREADY
LP / 70
L1 · area1.000Range0–1
L2 · quadratic size1.000Range0–1
L∞ · peak1.000Range0–8
Support width1.0000Signal height1.000
L∞ ruler reads 1.000

The peak grows while the L2 norm stays exactly one.

Why the rulers disagree

On a unit interval, the pulse has height √n on the first1/n of its support and is zero elsewhere. The screen's fixed ranges are x0–1 and amplitude0–8. Every displayed value comes from that same idealized signal.

‖uₙ‖₁ =1/√n · ‖uₙ‖₂ =1 · ‖uₙ‖∞ =√n

The integral of u² remains one. Area falls and peak rises. L2 is the square root of that integral, rather than the energy itself. The12second sweep extends n continuously; the integer presets sample the sequence.

This illustrates concentration and the difference between function-space norms. It does not solve a PDE or establish a fluid singularity. The screen draws an idealized signal; the apparatus is not a block being compressed.

Read the MIT definitions ↗