Paper: arXiv 2508.11649

Authors: Sergio Bianchi, Daniele Angelini, Massimiliano Frezza, Augusto Pianese

Abstract

Volatility, as a primary indicator of financial risk, forms the foundation of classical frameworks such as Markowitz’s Portfolio Theory and the Efficient Market Hypothesis (EMH). However, its conventional use rests on assumptions-most notably, the Markovian nature of price dynamics-that often fail to reflect key empirical characteristics of financial markets. Fractional stochastic volatility models expose these limitations by demonstrating that volatility alone is insufficient to capture the full structure of return dispersion. In this context, we propose pointwise regularity, measured via the Hurst-Holder exponent, as a complementary metric of financial risk. This measure quantifies local deviations from martingale behavior, enabling a more nuanced assessment of market inefficiencies and the mechanisms by which equilibrium is restored. By accounting not only for the magnitude but also for the nature of randomness, this framework bridges the conceptual divide between efficient market theory and behavioral finance.

Complexity vs Empirical Score

  • Math Complexity: 7.5/10
  • Empirical Rigor: 3.0/10
  • Quadrant: Lab Rats — theoretically deep, empirically untested

Why this score: The paper introduces advanced concepts like the Hurst-Hölder exponent and discusses fractional Brownian motion and multifractional processes, indicating high mathematical density. However, the excerpt focuses on theoretical foundations and conceptual critiques without presenting backtests, specific datasets, or implementation details for empirical validation.

Research Flowchart

  flowchart TD
  A["Research Goal: Redefine Financial Risk<br>Beyond Volatility to Ensure<br>Efficiency-Consistency"] --> B["Methodology: Introduce Pointwise Regularity<br>via Hurst-Holder Exponent"]
  B --> C{"Data Inputs:<br>Equities & Derivatives Markets"}
  C --> D["Computational Process:<br>Fractional Stochastic Volatility Modeling<br>& Efficiency Analysis"]
  D --> E["Key Finding 1: Volatility alone is<br>insufficient for risk assessment"]
  D --> F["Key Finding 2: Pointwise Regularity<br>quantifies market inefficiencies<br>and equilibrium restoration"]

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