Geometry of unconditionally efficient portfolios formed with conditioning information: the efficient semicircle
研究发现风险-回报空间中存在一个意外的“有效半圆”，将所有条件投资组合限制在这个非双曲线的前沿上。
A surprising ‘Efficient Semicircle’ emerges in risk-return space, restricting all conditional portfolios to this unusual non-hyperbolic frontier