S形市场冲击函数的最优执行问题
An Optimal Execution Problem with S-shaped Market Impact Functions
摘要：
在本研究中，我们将Kato（2014）研究的具有凸市场冲击函数的最优执行问题扩展到市场冲击函数为S形的情况，即对于某些$\bar {x}_0 \geq 0$，$[0, \bar {x}_0]$上凹，$[\bar {x}_0, \infty )$上凸。研究了相应的哈密顿-雅可比-贝尔曼方程，证明了S形市场冲击下的最优执行速度等于零或大于$\bar {x}_0$ .此外，我们还提供了一些布莱克-斯科尔斯模型的例子。当市场冲击函数为S形时，对于风险中性的小股票交易者，最优策略是时间加权价策略。
英文摘要：
In this study, we extend the optimal execution problem with convex market impact function studied in Kato (2014) to the case where the market impact function is S-shaped, that is, concave on $[0, \bar {x}_0]$ and convex on $[\bar {x}_0, \infty )$ for some $\bar {x}_0 \geq 0$. We study the corresponding Hamilton-Jacobi-Bellman equation and show that the optimal execution speed under the S-shaped market impact is equal to zero or larger than $\bar {x}_0$. Moreover, we provide some examples of the Black-Scholes model. We show that the optimal strategy for a risk-neutral trader with small shares is the time-weighted average price strategy whenever the market impact function is S-shaped.
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