What more can central banks reasonably do?

Once short- and long-term interest rates are zero or negative, what more can central banks do if they want to stimulate activity further? “Helicopter money” is often mentioned (where the central bank would hand out money to the population). But it is important to understand that: First, a public transfer payment financed by issuing government bonds, which the central bank then buys by creating money, is exactly the same as helicopter money; Second, in a democracy, it is for the government and parliament to decide whether to set up transfer payments to the population , and not the central bank. This reasoning also holds for the investment fund that some observers would like to see financed by money creation; Another idea is a “green monetary policy”. The central bank would give preference to buying green bonds or assets representing green loans. This would create a price distortion in favour of green financial assets, but this price distortion would be perfectly acceptable , as it would be addressing an externality (reducing greenhouse gas emissions). Expansionary monetary policy has already given rise to much less justifiable price distortions (for example between bonds and equities).