There is no syntactic counterpart to
the in Japanese. Among world's languages, there are languages that do have articles and languages that do not. English and Japanese belong to the former and the latter respectively. This is a fundamental difference, and you just cannot map an article from one language to another language that does not have it.
But it you want to express a similar nuance using different syntactic components, then you can use expressions like
話題になっている depending on the context.