The phrase "authority on the topic" is correct and usable in written English.
It can be used to refer to someone who has extensive knowledge or expertise in a specific subject area.
Example: "Dr. Smith is considered an authority on the topic of climate change, often consulted for her insights and research."
Alternatives: "expert in the field" or "specialist on the subject".
Whatever one thinks of Debbie Wasserman Schultz, the Chair of the Democratic National Committee, we can all agree on one thing: there is no greater authority on the topic of so-called "super-delegates" to the Democratic National Convention (an event Wasserman Schultz runs) than Wasserman Schultz herself.
Last time I checked, state governments had abdicated moral authority on the topic, sponsoring lotteries and purchasing the silence of the intellectual class by earmarking a sliver of the take for art, culture and education.
Evannina, who led an investigation into the effects of Edward Snowden's disclosures of NSA surveillance of Americans, is a prominent figure of authority on the topic of leaks and unauthorized disclosure.
Trust me when I say, this play could very well last the rest of your life!" Heed her we should, since the speaker is something of an authority on the topic of duration: she is Time itself, squeezed into a black cocktail dress in the shape of an hourglass, with an elaborate cuckoo clock affixed to her head, Ziegfeld Follies-style.
There must be a single "locus of authority" on the topic within the government, he said.
In the scene, Monroe takes up the Transitivity function of "Sayer" with Ben as the Recipient: "I could have told you" and "I'm telling you man" and these clearly indicate that Monroe sees himself as the authority on the topic and qualified to tell Ben quite directly what he should be doing.
My pages on the History of Dutch Brazil and Guyana — most of them for now reproducing articles from the pen of a single author, George Edmundson (one of the most cited authorities on the topic) — trace the course of events from the initial conquests by the Dutch to their final withdrawal.
While noting that sex ratio has declined in many regions, one of the foremost authorities on the topic questions whether environmentally prevalent endocrine disrupters could ever be demonstrated to account for such broad patterns (James 1998b).
That, in so many words, was the advice recently offered by Tom Perkins, who could be considered one of the world's leading authorities on the topic.
One of the world's leading authorities on the topic, Dr. Ann McKee, told the filmmakers she thinks it's possible every athlete in pro football has CTE in one form or another, and that the condition may also affect high school and college players.
So far HRW had sent two letters to Saudi authorities on the topic and met with officials at the embassy in the US, he said, but had yet to receive "any substantial replies" to queries over the targeting of strikes and precautions taken to minimize civilian casualties.
