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Consumption-Investment with anticipative noise

Mathematical Finance 2026-02-10 v1

Abstract

We revisit the classical Merton consumption--investment problem when risky-asset returns are modeled by stochastic differential equations interpreted through a general α\alpha-integral, interpolating between It\^{o}, Stratonovich, and related conventions. Holding preferences and the investment opportunity set fixed, changing the noise interpretation modifies the effective drift of asset returns in a systematic way. For logarithmic utility and constant volatilities, we derive closed-form optimal policies in a market with nn risky assets: optimal consumption remains a fixed fraction of wealth, while optimal portfolio weights are shifted according to θα=V1(μr1)+αV1diag(V)1\theta_\alpha^\ast = V^{-1}(\mu-r\mathbf{1})+\alpha\,V^{-1}\operatorname{diag}(V)\mathbf{1}, where VV is the return covariance matrix and diag(V)\operatorname{diag}(V) denotes the diagonal matrix with the same diagonal as VV. In the single-asset case this reduces to θα=(μr)/σ2+α\theta_\alpha^\ast=(\mu-r)/\sigma^{2}+\alpha. We then show that genuinely state-dependent effects arise when asset volatility is driven by a stochastic factor correlated with returns. In this setting, the α\alpha-interpretation generates an additional drift correction proportional to the instantaneous covariation between factor and return noise. As a canonical example, we analyze a Heston stochastic volatility model, where the resulting optimal risky exposure depends inversely on the current variance level.

Keywords

Cite

@article{arxiv.2602.08527,
  title  = {Consumption-Investment with anticipative noise},
  author = {Mario Ayala and Benjamin Vallejo Jiménez},
  journal= {arXiv preprint arXiv:2602.08527},
  year   = {2026}
}

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21 pages