Abstract We examine the contribution of electromagnetic field to the atomic spin, by adopting two different, both gauge invariant definitions of the electromagnetic angular momentum：→JI≡fd3x∈0→r×（→E×...Abstract We examine the contribution of electromagnetic field to the atomic spin, by adopting two different, both gauge invariant definitions of the electromagnetic angular momentum：→JI≡fd3x∈0→r×（→E×→B）and→JII≡fd3x（∈0→E×→A⊥＋∈0Ei→τ× A⊥i）.Notably, at the classical level, →JI gives an exactly null result while →JI gives a finite value. This suggests that Jn leads to a simpler and more reasonable picture of the atomic spin, therefore qualifies as a more appropriate definition of the electromagnetic angular momentum. Our observation gives important hint on the delicate issue of gluon contribution to the nucleon spin.展开更多
文摘Abstract We examine the contribution of electromagnetic field to the atomic spin, by adopting two different, both gauge invariant definitions of the electromagnetic angular momentum：→JI≡fd3x∈0→r×（→E×→B）and→JII≡fd3x（∈0→E×→A⊥＋∈0Ei→τ× A⊥i）.Notably, at the classical level, →JI gives an exactly null result while →JI gives a finite value. This suggests that Jn leads to a simpler and more reasonable picture of the atomic spin, therefore qualifies as a more appropriate definition of the electromagnetic angular momentum. Our observation gives important hint on the delicate issue of gluon contribution to the nucleon spin.
