On Simultaneous Long-Short Stock Trading Controllers with Cross-Coupling

TL;DR

This paper introduces a novel cross-coupled control architecture for simultaneous long-short stock trading, extending the Robust Positive Expectation property to two stocks and demonstrating improved risk management when additional statistical information is available.

Contribution

The paper proposes a new cross-coupled SLS controller architecture for two stocks, deriving a closed-form expected gain expression, and proving the RPE property under various stock dynamics.

Findings

The new controller guarantees the RPE property for a large class of stock models.

Numerical simulations show reduced trading risk with additional statistical info.

The architecture outperforms independent controllers when mean and covariance bounds are used.

Abstract

The Simultaneous Long-Short(SLS) controller for trading a single stock is known to guarantee positive expected value of the resulting gain-loss function with respect to a large class of stock price dynamics. In the literature, this is known as the Robust Positive Expectation(RPE)property. An obvious way to extend this theory to the trading of two stocks is to trade each one of them using its own independent SLS controller. Motivated by the fact that such a scheme does not exploit any correlation between the two stocks, we study the case when the relative sign between the drifts of the two stocks is known. The main contributions of this paper are three-fold: First, we put forward a novel architecture in which we cross-couple two SLS controllers for the two-stock case. Second, we derive a closed-form expression for the expected value of the gain-loss function. Third, we use this closed-form expression to prove that the RPE property is guaranteed with respect to a large class of stock-price dynamics. When more information over and above the relative sign is assumed, additional benefits of the new architecture are seen. For example, when bounds or precise values for the means and covariances of the stock returns are included in the model, numerical simulations suggest that our new controller can achieve lower trading risk than a pair of decoupled SLS controllers for the same level of expected trading gain.