# Vector Notation in Nolting Theoretical Physics 1

On pg. 60 of Nolting Theoretical Physics 1 for the definition of a vector multiplied by a scalar the book shows two little up arrows if the scalar is greater than zero and an little up arrow and then a little down arrow if the scalar is less than zero. Then again on pg. 61 for definition 1.139 there are two little up arrows (similar to particle spin notation) in between the unit vector and the vector.

What do these little pairs of arrows mean? I have never seen this notation for vectors before. Could someone please explain their semantics?

## Answers and Replies

Orodruin
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For reference, this is the excerpt of that definition:

This property is saying that ##\alpha\bf a## is parallel to (i.e., same direction as) ##\bf a## if ##\alpha > 0## and anti-parallel to (i.e., opposite direction) ##\bf a## if ##\alpha < 0##. Not mentioning this (I did not find it anywhere) seems like a serious omission by the author. In particular as the preliminaries seem to aim on defining what the student needs to know about vectors.

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Teclis and DrClaude