This page is a glossary of terms in string theory, including related areas such as supergravity, supersymmetry, and high energy physics.
Tension is energy or work per unit length. In natural units and , and hence has dimension of length/energy or length/mass. Since has the dimension of action, i.e. momentum times length, it follows that in natural units mass =1/length, and so has the unit of area. The slope of a Regge trajectory in Regge theory is the derivative of spin or angular momentum with respect to mass-squared, i.e.
Since angular momentum is moment of momentum , i.e. length times mass with , is dimensionless in natural units, and has units of or area like the inverse string tension.