When it comes to synonyms for the phrase "is fixed," there are a number of options available. One possible alternative is "is set," which suggests that something has been established or arranged in a definitive way. Another option is "is determined," which implies a sense of certainty or inevitability. "Is steady" is another potential synonym, which conveys a sense of stability or consistency. Finally, "is unchanging" suggests that something remains constant or immutable, without any deviation or variation. Ultimately, the most appropriate synonym will depend on the context in which it is being used, as well as the specific nuances of meaning that the speaker or writer wishes to convey.