String physics - Closed and open strings. Strings can be either open or closed. A closed string is a string that has no end-points, and therefore is topologically equivalent to a circle. An open string, on the otherhand, has two end-points and is topologically equivalent to a line interval. Not all string theories contain both open and closed strings. However, any theory which contains open strings must also contain closed strings as interactions betwee ...

See also:

String physics, String physics - Types of strings, String physics - Closed and open strings, String physics - Orientation

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