arXiv subjects

Fuxing Li

Publications and source records attributed to Fuxing Li.

3 recordsLinked to original sources

arXiv2026

Mean field and N-agent games for optimal relative consumption-investment with jump risk and common noise

This paper studies an optimal consumption--investment problem for competitive agents in an $N$-player game and its associated mean field game. Each agent invests in an individual risky asset subject to idiosyncratic noise, common noise and downward jump risk, and the interaction among agents is induced by relative performance concerns in both consumption and terminal wealth. In the mean field limit, we characterize a deterministic mean field equilibrium in analytical form by using the stochastic maximum principle. Numerical experiments are presented to illustrate the resulting equilibrium and its financial implications. Finally, based on the obtained mean field equilibrium, we construct an approximate Nash equilibrium for the $N$-player game. This model is motivated by \cite{Merton1971} and \cite{Lacker2020}.

math.OC↗

arXiv2025

Contrastive Conditional-Unconditional Alignment for Long-tailed Diffusion Model

Training data for class-conditional image synthesis often exhibit a long-tailed distribution with limited amount of images for tail classes. Such an imbalance causes mode collapse and reduces the diversity of synthesized images for tail classes. For class-conditional diffusion models trained with imbalanced data, we aim to improve the diversity and fidelity of tail class images without compromising the quality of head class images. We propose contrastive conditional-unconditional alignment (CCUA), which comprises two synergistic loss functions. Our first loss is an Alignment Loss (AL) that aligns class-conditional generation with unconditional generation at large timesteps. Alignment loss makes the denoising process insensitive to class conditions for the initial steps, which enriches tail classes through knowledge sharing from head classes. Secondly, we diversify unconditional generation via an Unsupervised Contrastive Loss (UCL) to increase the distance/dissimilarity among synthetic images. We combine the two losses to implicitly diversify conditional generation. Our framework is easy to implement as demonstrated on both U-Net based architecture and Diffusion Transformer. Our method outperforms vanilla denoising diffusion probabilistic models, score-based diffusion model, and alternative contrastive methods for class-imbalanced image generation across various datasets, in particular ImageNet-LT with 256$\times$256 resolution.

cs.CV↗

arXiv2024

Detection of two totally eclipsing B-type binaries with extremely low mass ratios

The detection of O- and B-type stars with extremely low-mass companions is very important for understanding the formation and evolution of binary stars. However, their finding remains a challenge because the low-mass components in such systems contribute such small flux to the total. During the searching for pulsations among O- and B-type stars by using the TESS data, we found two short-period and B-type (B9) eclipsing binaries with orbital periods of 1.61613 and 2.37857 days. Photometric solutions of the two close binaries were derived by analyzing the TESS light curves with the W-D method. It is discovered that both of them are detached binaries with extremely low mass ratios of 0.067(2) for TIC 260342097 and 0.140(3) for TIC 209148631, respectively. The determined mass ratio indicates that TIC 260342097 is one of the lowest mass ratios among known B-type binary systems. We showed that the two systems have total eclipses with a broad and flat secondary minimum, suggesting that the photometric parameters could be derived reliably. The absolute parameters of the two binaries are estimated and it is found that the secondary components in the two systems are over-luminous and over-size when compared with the normal low-mass and cool main-sequence (MS) stars. These findings may imply that the two systems are composed of a B-type MS primary and a cool pre-MS secondary with orbital periods shorter than 2.5 days. They are valuable targets to test theories of binary star formation and evolution.

astro-ph.SR↗