Siang Cheng | Searcharxiv

arXiv2026

Complex-Valued Probability Measures and Their Applications in Information Theory

This paper introduces a comprehensive framework for complex-valued probability measures and explores their novel applications in information theory and statistical analysis. We define a complex probability measure as a phase-modulated extension of a classical probability measure. Building upon this foundation, we propose three fundamental information-theoretic quantities: complex entropy, which quantifies distribution uniformity through phase coherence; complex divergence, an asymmetric measure of dissimilarity between distributions; and the complex metric, a symmetric distance function satisfying the triangle inequality. We establish these concepts rigorously for both continuous and discrete probability distributions, proving key properties such as boundedness, continuity under total variation convergence, and clear extremal behaviors. A detailed comparative analysis with classical measures (Shannon entropy and Kullback-Leibler divergence) highlights the unique geometric and interpretive advantages of the proposed framework, particularly its sensitivity to distributional shape via a tunable phase parameter. We elucidate a profound formal analogy between the complex entropy integral and Feynman's path integral formulation of quantum mechanics, suggesting a deeper conceptual bridge. Finally, we demonstrate the practical utility of the complex metric through a detailed application in nonparametric two-sample hypothesis testing, outlining the testing procedure, advantages, limitations, and providing a conceptual simulation. This work opens new avenues for analyzing probability distributions through the lens of complex analysis and interference phenomena, with potential impacts across information theory, statistical inference, and machine learning.

cs.IT↗

arXiv2025

Efficient importance sampling for copula models

In this paper, we propose an efficient importance sampling algorithm for rare event simulation under copula models. In the algorithm, the derived optimal probability measure is based on the criterion of minimizing the variance of the importance sampling estimator within a parametric exponential tilting family. Since the copula model is defined by its marginals and a copula function, and its moment-generating function is difficult to derive, we apply the transform likelihood ratio method to first identify an alternative exponential tilting family, after which we obtain simple and explicit expressions of equations. Then, the optimal alternative probability measure can be calculated under this transformed exponential tilting family. The proposed importance sampling framework is quite general and can be implemented for many classes of copula models, including some traditional parametric copula families and a class of semiparametric copulas called regular vine copulas, from which sampling is feasible. The theoretical results of the logarithmic efficiency and bounded relative error are proved for some commonly-used copula models under the case of simple rare events. Monte Carlo experiments are conducted, in which we study the relative efficiency of the crude Monte Carlo estimator with respect to the proposed importance-sampling-based estimators, such that substantial variance reductions are obtained in comparison to the standard Monte Carlo estimators.

stat.CO↗