sage
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response to kanex on spontaneous symmetry breaking
可能我还是没有表述清楚我自己。
自发对称破碎在数学上是没有理解障碍的，问题在于我们是做物理，不是数学。在物理中，我们需要得到更深层的原因。
现在的情况是，我们先发现对称破碎的事实，然后purpose一个可以让对称自发破碎的phi。
也就是说，我们的因果关系是：有phi -> 对称破碎
那么 什么东西 -> 有phi？
不应认为phi存在的原因是“因为观测到了对称破碎”－－这是结果，不是原因。
举例：当问“为什么higgs场要存在”时，回答不应该是“因为观测到某些gauge boson有质量”，否则就是因果关系混乱了。
I think there are two questions
1) is it possible to do spontaneous symmetry breaking?
this is the problem people (20 years ago) usually refer to when they claim they do not undertsand spontaneous symmetry breaking. I think you and I agree that it is possible.
2) We observed spontaneous symmetry breaking in natire. How indeed it happened and why it happen this way?
This is the famous electroweak symmetry breaking problem. in this case, we know it is possible to spontaneously break electroweak symemtry, We do not know, which is probably what you want to say, how and why it happened.
Unfortunately for you, this is a very phenomenological question, :-) in the sense that we have to explain why nature is the way it is.
In this sense, we do not understand anything yet. We do not understand why Standard Model has the gauge symmetries it has. We do not understand why there is low energy gauge symmetries at all....
| 发表时间：2005-04-16, 15:29:08 |
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walk_f