Poisson-Process Topic Model for Integrating Knowledge from Pre-trained Language Models
This work addresses the limitation of traditional topic models that ignore word context, offering a flexible framework for researchers and practitioners in text analysis, though it is incremental as it builds on existing topic modeling methods.
The authors tackled the problem of topic modeling by integrating contextualized word embeddings from pre-trained language models without fine-tuning, achieving a minimax-optimal convergence rate when β ≤ 1 and demonstrating improved performance over traditional methods on several datasets.
Topic modeling is traditionally applied to word counts without accounting for the context in which words appear. Recent advancements in large language models (LLMs) offer contextualized word embeddings, which capture deeper meaning and relationships between words. We aim to leverage such embeddings to improve topic modeling. We use a pre-trained LLM to convert each document into a sequence of word embeddings. This sequence is then modeled as a Poisson point process, with its intensity measure expressed as a convex combination of $K$ base measures, each corresponding to a topic. To estimate these topics, we propose a flexible algorithm that integrates traditional topic modeling methods, enhanced by net-rounding applied before and kernel smoothing applied after. One advantage of this framework is that it treats the LLM as a black box, requiring no fine-tuning of its parameters. Another advantage is its ability to seamlessly integrate any traditional topic modeling approach as a plug-in module, without the need for modifications Assuming each topic is a $β$-Hölder smooth intensity measure on the embedded space, we establish the rate of convergence of our method. We also provide a minimax lower bound and show that the rate of our method matches with the lower bound when $β\leq 1$. Additionally, we apply our method to several datasets, providing evidence that it offers an advantage over traditional topic modeling approaches.