The immense range of colours that we see belies the relative simplicity of the system underlying colour vision. We see colours because each of the three distinct types of cone photoreceptor in our retinae is sensitive to a different range of wavelengths of light. The L, M and S cones, colloquially called red (R), green (G), and blue (B), are selective for long, middle and short wavelengths, res...

We study the Rendezvous problem for 2 autonomous mobile robots in asynchronous settings with persistent memory called light. It is well known that Rendezvous is impossible in a basic model when robots have no lights, even if the system is semi-synchronous. On the other hand, Rendezvous is possible if robots have lights of various types with a constant number of colors [9, 22]. If robots can obs...

Several features of subfitness are analyzed. Isbell’s Spatiality Theorem leads to the concept of T1-spatiality which is compared with the TD-spatiality. Subfitness is put into relation with other weak separation axioms (and with the existence of nearness), both in spaces and locales, and seeming discrepancies are explained. A new characteristic of subfitness by means of codensity is presented.