Deep learning is the fastest-growing method family in the archive and the one with the widest spread between its best and worst papers. The strong work uses neural networks where their inductive bias fits the problem: sequence models on limit-order-book states, deep hedging under frictions, neural calibration of pricing models, generative models for synthetic paths with measured stylized-fact fidelity. The weak work fits a large model to a short daily series and reports in-sample accuracy.

What to check when reading. Count the trials, not the layers. A credible deep-learning paper reports the number of architectures and hyperparameter settings tried, uses a fixed holdout that was never touched during tuning, compares against a tuned linear or tree baseline (not just buy-and-hold), and turns forecast accuracy into a trading or hedging result with costs. Papers that publish code and the exact data split are worth triple the ones that do not.