Reactive PublishingMeasure-Theoretic Probability & Risk in Quant Finance provides a rigorous, trading-oriented treatment of the foundational probability structures that underpin modern derivatives pricing, systematic strategy design, and risk management. Built around the measure-theoretic framework of expectations, filtrations, and martingales, the book links abstract probability concepts directly to the dynamics of financial markets and the practical modeling of uncertainty, information, and tail risk.The text develops the machinery of sigma-algebras, conditional expectation, and stochastic processes in a way that is both mathematically precise and financially motivated. From classic martingale pricing and change of measure under risk-neutral valuation to information flow and market filtration dynamics, readers gain a production-grade understanding of how probability structures shape derivatives valuation, volatility modeling, and systematic execution. Emphasis is placed on the modeling of tail events and non-Gaussian structure, connecting theory to volatility surfaces, convexity effects, and market microstructure.Designed for quantitative analysts, traders, and risk professionals, the book bridges a crucial gap between pure mathematical probability and real-world derivatives and trading systems. Rather than treating probability as an academic prerequisite, it shows how measure-theoretic tools become operational levers for pricing, hedging, and managing complex risk exposures.Key topics covered: - Sigma-algebras, filtrations, and information flow in markets- Conditional expectation and the economics of information- Martingales, submartingales, and supermartingales in pricing- Radon-Nikodym derivatives and change of measure mechanics- Risk-neutral valuation and martingale pricing theory- Tail-risk modeling and non-Gaussian distributions- Extreme value behavior, volatility smiles, and convexity effects- Information geometry and uncertainty in systematic strategies- Practical implications for derivatives desks and risk systemsThis book serves as a definitive guide for practitioners seeking to deepen their command of probability as it is actually used in quant finance, derivatives trading, and systematic risk management.