Hi Marcus:
In reading the SCIAM article on Connes, there is a quote ‘"We now have to make a next step--we have to try to understand how space with fractional dimensions," which occurs in noncommutative geometry, "couples with gravitation," Connes asserts’ on page 2.
This seems to introduce fractal geometry or chaos or bifurcation theory into noncommutative geometry.
I have been noticing the peculiar repetition of the logarithmic spiral at many different gauges and scales [biology, weather, spiral galaxies] which reminds me of the Mandelbrot Set recurring initial image. Is there some relationship?
http://en.wikipedia.org/wiki/Mandelbrot_set
On page 1, I am surprised about the omission of “yaw” rotation by the author, although I agree that a different order of rotations will likely not commute.
This NASA site explains Pitch, Yaw, and Roll Systems
The orientation of the shuttle in space is defined as its attitude. This can be used to define such things as pointing the payload bay of the shuttle at the Earth or orienting the nose of the shuttle to point at a celestial object, like the sun.
Orbiter attitudes are specified using values for Pitch, Yaw, and Roll. These represent a rotation of the shuttle about the Y, Z, and X axes, respectively, to the desired orientation. However, the shuttle doesn't actually perform each rotation separately. It calculates one axis, called the eigen axis, to rotate about to get to the correct orientation.
The attitude is be expressed as Pitch/Yaw/Roll or Roll/Pitch/Yaw, however the rotation is always performed in the order described in the previous paragraph.
The pictures below show the different rotations. [NOT shown in this post]
http://liftoff.msfc.nasa.gov/academy/rocket_sci/shuttle/attitude/pyr.html
Since Penrose appears to have coined both the terms spinor and twistor, perhaps they might be related by considering one rotation as a spinoe, but a combination of three rotations as a twistor?