The yield curve is deeply inverted. If the economy suddenly snaps into a recession next month and the Fed is forced to aggressively cut rates, do we experience a bull steepener or a bear steepener? Walk me through the math of the spread and pitch me one derivative or fixed income trade to play it.

目前的收益率曲线严重倒挂。如果下个月经济突然陷入衰退，美联储被迫大幅降息，我们经历的是牛市陡峭（Bull Steepener）还是熊市陡峭（Bear Steepener）？给我推演一下利差的数学逻辑，并推荐一个衍生品或固收交易来押注这个情况。