Rough multifactor volatility for SPX and VIX options
Rough multifactor volatility for SPX and VIX options
This paper develops a comprehensive asymptotic theory for implied volatility in multifactor rough volatility models, with applications to SPX and VIX options. The authors extend previous single-factor results to a general multifactor setting using Malliavin calculus, deriving explicit small-time limits for the ATM implied volatility level, skew, and curvature. The key technical innovation is the use of the Clark-Ocone formula to represent the underlying asset as an exponential martingale, enabling the application of asymptotic expansions even in non-Markovian rough volatility models. The results are applied to the two-factor rough Bergomi model, yielding closed-form expressions that reveal how parameters control the skew and curvature of both SPX and VIX smiles. This provides a theoretical foundation for joint calibration, showing that multifactor models can capture the different short-time behaviors of SPX and VIX implied volatilities, which single-factor models fail to do. The paper also includes detailed proofs and numerical examples demonstrating the effectiveness of the approach.
Highlights
- 1Provides explicit small-time asymptotics for ATM implied volatility level, skew, and curvature in a general class of multifactor rough volatility models.
- 2Extends previous single-factor rough volatility results to multifactor settings, enabling joint calibration of SPX and VIX options.
- 3Derives closed-form expressions for the two-factor rough Bergomi model, highlighting parameter interplay for skew and curvature.
- 4Uses Malliavin calculus and Clark-Ocone formula to handle non-Markovian rough volatility dynamics.
Methods
- MMalliavin calculus for Gaussian processes to derive Clark-Ocone representations.
- MSmall-time asymptotic expansions for implied volatility level, skew, and curvature.
- MMultifactor rough volatility modeling with fractional Brownian motion kernels.
- MNumerical analysis of the two-factor rough Bergomi model for joint SPX-VIX calibration.
Results
- RThe short-time ATM implied volatility level equals the limit of the forward volatility.
- RThe ATM skew scales as T^{H-1/2} in rough volatility models, matching empirical observations.
- RThe ATM curvature is expressed in terms of integrals of Malliavin derivatives, providing a second criterion for model selection.
- RClosed-form formulas for the two-factor rough Bergomi model show that curvature can be positive or negative depending on parameters.
- RThe multifactor framework allows decoupling of SPX and VIX smile features, improving joint calibration.
Analyze Paper
Generate insights from "Rough multifactor volatility for SPX and VIX options".