A word for a group of people who believe the same scientific idea

Solution 1:

Although it is not a single word, You could say they belong to the same

school of thought
PHRASE

A particular way of thinking, especially one not followed by the speaker.
There are at least two schools of thought in contention here.

Given by Lexico.

Everyone who believes in string theory belongs to the same school of thought.

Solution 2:

Just "school" alone works, meaning a group of persons who hold the same theory or follow the same expert in certain fields such as philosophy, biology, medicine, economy, etc.

• school - A particular school of writers, artists, or thinkers is a group of them whose work, opinions, or theories are similar. ...the Chicago school of economists.

e.g. from the web:

• "The Conservative party should follow a different school: optimism."
• "The Venetian School, which arose during this thriving cultural moment, breathed fresh life into the worlds of oil painting and architecture."

Solution 3:

School, camp, group, and inclination are certainly used for Frequentists vs Bayesians (Statistics).

I don't know what the context of your question is, but also note that generally such camps or schools of thought have much woollier boundaries than ideologies can. Certainly in Mathematics, even someone who only ever uses Bayesian approaches, cannot and should not say that Frequentists are wrong - the method is established and has been tested thoroughly, even though they may struggle to see why someone would prefer that approach.

I'm no physicist, but I assume that String Theory has been tested, and so far been found to be possible. Otherwise people who prefer it as a possible solution should not be numerous enough to be referred to as a group.