The high-cardinality of mean-variance portfolios is a concern in practice because it increases transaction costs and management fees. Therefore, we propose a method to resolve the cardinality problem by applying the semi-definite relaxation method to a cardinality constrained optimal tangent...

Robust portfolios reduce the uncertainty in portfolio performance. In particular, the worst-case optimization approach is based on the Markowitz model and form portfolios that are more robust compared to mean–variance portfolios. However, since the robust formulation finds a different...

For portfolio management in the real-world, it is required that a portfolio has a manageable number of assets and stable performance. However, much research has pointed out that the Markowitz model, which is a classical model in portfolio theory, forms a portfolio with many different assets that...