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SYMMETRIES in PHYSICS

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Symmetry and Spontaneous Symmetry Break<strong>in</strong>g<br />

Po<strong>in</strong>t Groups: Simple and Double<br />

Selected Groups and Symmetries<br />

Spontaneous Symmetry Break<strong>in</strong>g<br />

Vector Fields Ψ vs Sp<strong>in</strong>or Fields Φ<br />

If the objects Ψ do not change under the rotation ˆR(2π)<br />

ˆR(2π) Ψ = +Ψ → bosons ↔ simple groups: Example T d<br />

If the objects Φ change the sign under the rotation ˆR(2π)<br />

ˆR(2π) Φ = −Φ → fermions ↔ double groups: Example T D d<br />

Remarks - Comments<br />

Objects <strong>in</strong> classical mechanics, <strong>in</strong>teger rank tensors like boson<br />

wave-functions transform under simple po<strong>in</strong>t-groups: D 2h , T d<br />

Sp<strong>in</strong>ors - the non-collective wave functions of fermions - transform<br />

under double po<strong>in</strong>t-groups: D D 2h , T D d , OD h ...<br />

Jerzy DUDEK<br />

<strong>SYMMETRIES</strong> <strong>in</strong> <strong>PHYSICS</strong>

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