[Republic of Texas]

Is it possible to lower rates below zero?

[TigerLikesRooster]

Not in theory. However, if the going rate is lower than inflation rate, the real interest rate is essentially negative.

That is, if the current interest rate is 2% and the current inflation rate is 3%, then the interest rate is effectively negative.

[palmer]

Is it possible to lower rates below zero?

Doesn't really matter. Bernanke said in his famous paper and speech that they would work on the long term rates instead. They would print up FRNs and use them to buy 2 year T-Bills. Don't worry about theoretical helicopters, they have plenty of ways to inflate when the time comes.