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Dirac海的困难

1）
Dirac's analysis of the problem of negative probabilities in Schrodinger's relativistic wave equation would seem to rule out the existence of any particle of zero spin.
 但事实上有spin-0的玻色子，因此，
it is difficult to agree that there is anything fundamentally wrong with the relativistic equation for zero spin that forced the development of the Dirac equation.

2）电子填满负能级后，由于Pauli不相容原理，正能级上的电子不会掉到负能级上。但是对于玻色子呢？Weinberg在1972年问过Dirac这个问题，Dirac当时的回答是：他认为这些玻色子是“不重要”的。但后来他承认对于玻色子
we no longer have the picture of a vacuum with negative energy states filled up.
 随着量子场论的发展，把反粒子视作空穴被认为是不必要的。如Schwinger所说：
The picture of an infinite sea of negative energy electrons is now best regarded as a historical curiosity, and forgotten.

3）
There was no reason to expect any particular value for the magnetic moment of the electron in Dirac's theory.

这些问题都会在量子场论的发展中得到解决。