I’ve traveled in a lot of major US cities in the last year outside of my hometown of Boston, Mass. Most of them are experiencing gentrification as wealthy newcomers drive up the cost of housing and displace long-time residents. But there’s an additional disruptive force — a sort of globally supercharged gentrification resulting from billions of dollars in global wealth flowing into residential real estate. Across these cities, new residential luxury towers are rising up like weeds. Last month, I wrote an op-ed in the Sunday Boston Globe that has triggered some great conversations. The piece, called “Time to Tax the Swanktuaries,” describes One Dalton Place — a building under construction that I see on my daily walk. The article led to an interview on WBUR’s Radio Boston and a recent conversation on Boston Neighborhood Network with Chris Lovett.