| 您的位置：站长主页 -> 繁星客栈 -> 网友原创作品集 -> sage 文集 | December 22, 2024 |
Force Carriers
- sage -
|
I would not call gauginos gauge field. i would call them the superpatners of the gauge field, since they are not associated with the gauge transformation. changhai is absolutely right that gauge field does not have to be bosonic. the famous example is supersymmetry in which the symmetry transformation is 'fermionic'. after we make the supersymmetry into a local (gauge) symmetry, there will be ga uge field associated with such a local symmetry which is fermionic. since supersymmetry transformation mix with regular spacetime transformations, the gauge field is in the same multiplet as the graviton, it is therefore called gravitino. Since supersymmetry is the only such extension of Poincare algebra, this is so far the only example we know to have a fermionic gauge field. there is nothing new if you phrase all this in a bundle language, if you like, roughly, our space-time is generalized to a superspace. the symmetry transformation is the super-diffeomorphism. the section space is any field defined on the superspace, the fiber is generated by the super-diff. the gravitino is the connection. > 在Feynman图上，外线对应on shell的实粒子，内线对应off shell的虚粒子，后 > 者是那种产生随即又湮灭的粒子。 ------------------------------------------------------------------------ this is not exactly true. it depends what your purpose for that feyman diagram is. external line is on-shell only when the feynman diagram is used to calculate S-matrix. generically, general green's function could have off-shell external lines. a famous example is the so-called 1PI irreducible effective potential which is calculated from a loop expansion. Also, internal line could be on-shell as well. this the also famous case where the propagator has an imaginary part. |