Cross-Lingual Word Embeddings (CLWEs) are a key component to transfer
linguistic information learnt from higher-resource settings into lower-resource
ones. Recent research in cross-lingual representation learning has focused on
offline mapping approaches due to their simplicity, computational efficacy, and
ability to work with minimal parallel resources. However, they crucially depend
on the assumption of embedding spaces being approximately isomorphic i.e.
sharing similar geometric structure, which does not hold in practice, leading
to poorer performance on low-resource and distant language pairs. In this
paper, we introduce a framework to learn CLWEs, without assuming isometry, for
low-resource pairs via joint exploitation of a related higher-resource
language. In our work, we first pre-align the low-resource and related language
embedding spaces using offline methods to mitigate the assumption of isometry.
Following this, we use joint training methods to develops CLWEs for the related
language and the target embed-ding space. Finally, we remap the pre-aligned
low-resource space and the target space to generate the final CLWEs. We show
consistent gains over current methods in both quality and degree of
isomorphism, as measured by bilingual lexicon induction (BLI) and eigenvalue
similarity respectively, across several language pairs: {Nepali, Finnish,
Romanian, Gujarati, Hungarian}-English. Lastly, our analysis also points to the
relatedness as well as the amount of related language data available as being
key factors in determining the quality of embeddings achieved.

本论文提出了一种跨语言词嵌入学习框架，其综合利用相关高资源语言，以解决低资源语言跨语言表示学习中的几何结构相似度不足的问题，并通过双语词表感应和特征值相似性等多个语言对的实验验证，在新颖性和性能上均有所提升。