In string theory, strings are considered to be fundamental objects, meaning they are not composed of anything smaller. They are incredibly tiny, one-dimensional objects that vibrate in different modes. The tension of a string in string theory arises from its fundamental nature and the way it interacts with the spacetime around it.
The tension of a string can be thought of as a measure of its inherent energy density. Just like a stretched rubber band has tension due to the stored elastic energy within it, a string in string theory has tension associated with the energy stored in its vibrations.
According to string theory, the tension of a string is determined by the fundamental properties of spacetime. The nature of spacetime, as described by the theory, provides the framework within which the strings propagate and interact. The specific value of the string tension is determined by the dynamics of the theory and is not something that is externally assigned or derived.
In string theory, the tension of a string is related to other fundamental quantities, such as the Planck length and the string coupling constant, which determine the scale and strength of interactions in the theory. The precise relationship between these quantities depends on the particular formulation and version of string theory being considered.
It's worth noting that the tension of a string is a fundamental parameter of the theory, and it is not directly related to any observable property of macroscopic objects in our everyday experience. The strings in string theory are far smaller than any length scale we can currently probe experimentally, so their tension is not directly measurable. However, the tension of the strings does influence the behavior of particles and forces at microscopic scales, leading to the rich and intricate structure of the theory.
Overall, the tension of strings in string theory arises from the intrinsic properties of the strings themselves and their interactions with the underlying spacetime, as described by the theory.