What does it mean when a vector is barred?

Discussion in 'Physics & Math' started by kevinalm, Nov 9, 2010.

  1. kevinalm Registered Senior Member

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    I have recently been reading an introductory book on tensor analysis and came upon an unfamiliar notation. The book is pretty good at introducing new notation but this 'came out of left field'. After referring to a vector v (boldface) it suddenly uses it in an equation as a bold face v with a bold overbar. Maybe it's just a typo or perhaps it's some notation I should be familiar with, although that would be strange as I am reasonably familiar with vector analysis.

    I don't have access to the book at the moment but the equation seemed to make sense if you ignore the overbar. I'm wondering though if there is some common notational convention I'm missing.
     
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  3. phlogistician Banned Banned

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    Usually means 'Not' doesn't it? I'm out of my depth with tensors, but perhaps it's a restriction?
     
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  5. Pandaemoni Valued Senior Member

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  7. prometheus viva voce! Registered Senior Member

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    It could just be a way of distinguishing a vector v from a vector v-bar.
     
  8. Pinwheel Banned Banned

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    I've seen the bar used to describe a vector expressed in a different co-ordinate system.
     
  9. alephnull you can count on me Registered Senior Member

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    As you can tell from the replies, it's a bit ambiguous without context.

    I've seen it used to denote different coordinates (though that's usually a squigly bar) and also for conjugation, I wouldn't say either is common though, it's usually always defined if used.
     
  10. Tach Banned Banned

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    The overbar may be intended to signify 3-vector while the bold signifies 4-vector. It might also signify unit-vector. You can figure out the meaning from the context.
     
  11. kevinalm Registered Senior Member

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    Yes! The light bulb just came on. Unit vector. Thanks to all especially Tach.

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  12. prometheus viva voce! Registered Senior Member

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    Normally, a unit vector is indicated by a hat (in physics at least).
     
  13. kevinalm Registered Senior Member

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    Yeah, I am familiar with a hat signifying a unit vector. Also by a vector divided by its absolute magnitude. But I don't recall ever seeing it as an overbar. Odd. Anyway, the equation makes a lot more sense now.
     

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