A cosmopoietic event occurred many millennia ago.

Switching off magnetism by atomic substitution and ensuring that the electronic structure becomes two-dimensional is sufficient for topologicality to arise in such a system.

Pei-ching, the 'northern capital', has existed since about 2400 B.C., when there was a neolithic settlement on the site. Historically, it was the capital of one of the 'Warring States' in the third and fourth centuries B.C., a provincial town in Han times, lost to the northern invaders during the fourth and fifth centuries A.D., recovered by the T'ang, again held by the barbarians in the tenth to twelfth centuries. In 1215 it fell to Genghis Khan and was rebuilt as Ta-tu or T'ai-du, the 'great capital' of Kublai. This had many resemblances to later Peking, but was more regular.

There can be Keynesian and classical unemployment. Indeed there can be both at the same time: the real wage might be too high to allow full employment with existing capital stock, while at the same time aggregate demand is inadequate to take off the market what firms would wish to produce. Changes in the real wage could have demand-side and supply-side effects.