Consider two phrases:
In real life, there are no superheroes.
There are no superheroes in the real world.
Are they grammatically correct? Can I say "in the real life" or "in real world"? With and without "the", what is the difference?
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The phrases are grammatically correct (and roughly interchangeable) with the original placement of "the", but are not correct (or at least not idiomatic) when you swap "the" as you suggest. This gets into the complex details of the rules for using articles in English. (There are numerous questions here that cover this topic.)
"Real life", when used in the above context, is an uncountable noun, and hence does not accept articles ("the" or "a"). But note that someone might say "Get a real life!", and in that context "real life" is countable.
It's the opposite for "real world", when functioning as a noun. It's countable (there is one and only one) and hence needs an article (and, specifically, "the"). (But, eg, in the expression "real world politics" "real world" is being used as an adjective, and the noun is "politics" -- another uncountable noun. Thus, no article.)