23 May 2026 in SSRN Electronic Journal
Formulaic alpha synthesis has emerged as a central problem in quantitative finance, where the goal is to construct predictive signals in the form of formulaic expressions that capture asset return patterns. However, existing approaches typically overlook the non-stationarity of financial markets and fail to embed the market information appropriately, leading to brittle performance under varying market regimes. In this paper, we propose Lovas (Logic-enhanced Variational Alpha Synthesis), a novel neural–symbolic framework for robust stock prediction. Lovas integrates a symbolic regime analyzer with a neural alpha synthesizer: for a specific time step, the symbolic regime analyzer predicts the latent market regime and assigns ensemble weights for the alpha pool, while the alpha synthesizer learns specialized formulaic alphas conditioned on these regimes. Since the market regimes are hidden variables, we therefore formulate alpha synthesis as a variational inference problem and optimize it via a variational EM algorithm. This design enables Lovas to handle market regime shifts more robustly by explicitly conditioning alpha synthesis on different market categories, therefore achieving much better prediction results. Empirical results on multiple stock benchmarks demonstrate that Lovas consistently outperforms state-of-the-art alpha synthesis methods by achieving better prediction accuracy.