What happens if monetary policy can create a permanent gap between the real interest rate and the neutral, equilibrium real interest rate?

It seems clear that a persistently expansionary monetary policy can keep the real interest rate below the equilibrium real interest rate (which depends on the economy’s structural characteristics, productivity growth, the savings-investment equilibrium); conversely , a persistently restrictive monetary policy could keep the real interest rate above the real equilibrium interest rate. What happens if the real interest rate is permanently lagged compared with the equilibrium real interest rate (let us assume that it is lower than the equilibrium interest rate)? In an open economy, there will be chronic excess investment over savings, where the real interest rate is lower than that which would balance savings and investment; There will normally be chronic excess debt and bubbles in price s of risky asset s as investors switch into risky assets, given the abnormally low real interest rates on risk-free bonds. We will illustrate these points with the case of the United States .