Synonyms for the phrase "not be concerned" can help convey various degrees of disinterest, indifference, or lack of worry. Firstly, "unperturbed" implies a sense of calmness and peace of mind, suggesting a lack of concern or anxiety. Secondly, "nonchalant" suggests an attitude of indifference or casualness, indicating a lack of interest or worry. Similarly, "unbothered" conveys a state of not being bothered or affected by a particular situation. Additionally, "carefree" denotes a carefree attitude, implying a lack of concern or worry. Lastly, "untroubled" suggests a sense of ease and tranquility, indicating a lack of distress or concern. Utilizing these synonyms can offer alternative ways to express the notion of not being concerned.