Parallel transport

Transport of the green vector along the blue curve on the sphere. The starting point is the red dot; the movement along the curve is in the anticlockwise direction. In a few points on the curve I plotted also a basis for the tangent space to the sphere (the vector tangent to the curve and the vector normal to that).

Response of the human cones to monochromatic radiation

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Paradosso di Loschmidt

The following graph, from J. Orban and A. Bellemans, “Velocity-inversion and irreversibility in a dilute gas of hard disks,” Phys. Lett. A, vol. 24, no. 11, pp. 620–621, May 1967, illustrates the solution of Loschmidt paradox.

$$\sin(x)^2+\cos(x)^2=1$$