We are interested in computation of locating arbitrage in-nancial markets with frictions. We consider a model with a nitenumber of nancial assets and a nitenumber of possible states of nature. We derive a negative result on computational complexity of arbitrage in the case when securities are traded in integer numbers of shares and with a maximum amount of shares that can be bought for a xed price (asin reality). When these conditions are relaxed, we show that polynomial time algorithms can be obtained by applying linear programming tech-niques. We also establish the equivalence for no-arbitrage condition & optimal consumption portfolio.

考虑连续时间金融市场的最优资产组合选择问题。在Black-Scholes 金融市场设置下，利用Roy提出的安全第一（Safety First）准则，导出了最优常数再调整资产组合投资策略的显式表达式。还将文中的结果与Markowitz均值-方差模型的最优资产组合投资策略进行了比较，并给出概念与结论的一些经济学解释和应用。

In this paper we study the optimal portfolio selection problem for assets. A doubleobjective programming model is Wrst formulated for selecting optimal portfolios of asserts with transaction costs and taxes, where short sales and borrowings are not allowed. Some properties of eYcient portfolios and the eYcient frontier to the model are then derived. Based on these results, an interactive method that requires only paired preference comparison from the investor is established for solving the optimal portfolio selection problem. A numerical example is also presented to illustrate this method.

A new minimax model on optimal portfolio selection with uncertainty of both randomness and estimation in inputs is established and the corresponding optimal portfolio is derived analytically. Based on this result, a sufficient condition for the existence and uniqueness of a nonnegative equilibrium price system under which the total demand and supply of each asset are equal is provided and an explicit formula for such a price system is obtained. Furthermore, some properties of the equilibrium are discussed.