Two-mirror Schwarzschild aplanats. Basic relations

It is shown that the theory of aplanatic two-mirror telescopes developed by Karl Schwarzschild in 1905 leads to the unified description both the prefocal and the postfocal systems. The class of surfaces in the ZEMAX optical program has been properly extended to ascertain the image quality in exact Schwarzschild aplanats. A comparison of Schwarzschild aplanats with approximate Ritchey-Chretien and Gregory-Maksutov aplanatic telescopes reveals a noticeable advantage of the former at fast focal ratio of the system.Comment: 19 page

Competition for co-operation: Roles and Realities in Russian Foreign Policy

The discursive reconstruction of Eurasia has brought about structural changes, which have strengthened Russia’s position internationally, and fortified its soft power. As such, the Eurasian project reflects Russia’s broader approach to parties including BRICS and the EU. Russia’s political elite routinely promotes specific conceptions of Russia’s international identity and role with different partners as a means to facilitate cooperation. This creates significant geographical and policy overlaps and breeds inconsistency and competition, but nonetheless contributes to Russia’s preferred low-cost, low-commitment version of co-operation. The Eurasian project therefore represents just one (albeit important) example of the Russian leadership’s conversion of ideas about the international arena into political realities. By balancing competing roles and relationships, Russia maintains a ‘multi-vector’ foreign policy that is flexible, unencumbered by restrictive alliances, and oriented towards sovereignty, great power and strength