high-energy physics vs high energy physics

high-energy physics and high energy physics both are nouns.

Word	Noun	Adjective	Verb	Adverb
high-energy physics	Yes	No	No	No
high energy physics	Yes	No	No	No

As nouns, high-energy physics and high energy physics are synonyms defined as:

high-energy physics and high energy physics: the branch of physics that studies subatomic particles and their interactions

Other synonyms of high-energy physics include particle physics.

high-energy physics (noun)	high energy physics (noun)
the branch of physics that studies subatomic particles and their interactions	the branch of physics that studies subatomic particles and their interactions