Covariant Versus Contravariant
Subscript versus superscript:
![](Images/covariant_vector.jpg)
Covariant potential vector.
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![](Images/contravariant_vector.jpg)
Contravariant potential vector.
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![](Images/Greek_indices.jpg)
Greek indexes go from 0, 1, 2, 3.
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![](Images/Roman_indices.jpg)
Roman indexes go from 1, 2, 3.
Memory aid: Co is a commie, commies are low, negative; the contras are proud, positive fighters, up against a wall.
Slide 30 believes in beliefs.