A basic question about vectors

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    Vectors
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Discussion Overview

The discussion revolves around the definition and properties of vectors, particularly whether all vectors must satisfy the vector laws of addition and if there are exceptions to this. It explores both intuitive and abstract interpretations of vectors in different mathematical contexts.

Discussion Character

  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • Some participants assert that a vector is defined as a quantity with both magnitude and direction and must satisfy vector laws of addition.
  • Others suggest that while this definition is intuitive, it may not apply universally across all vector spaces, particularly in function vector spaces where the concept of direction becomes abstract.
  • A participant questions the classification of current, suggesting it has a directional component and inquires whether it is a vector or falls into another category.

Areas of Agreement / Disagreement

Participants express differing views on the necessity of vector laws for all vectors, with some arguing for strict adherence while others highlight exceptions in certain mathematical contexts. The classification of current remains unresolved.

Contextual Notes

The discussion includes limitations in definitions and the applicability of vector properties across different mathematical frameworks, particularly in function spaces.

mantrapad
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I've found this regular definition of vectors: A quantity which has both magnitude and direction.

On some sites, I've also found the addition: They satisfy the vector laws of addition (commutative, associative, distributive).

Is it really necessary that all vectors should satisfy all those laws? Are there any exceptions?
 
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mantrapad said:
I've found this regular definition of vectors: A quantity which has both magnitude and direction.

On some sites, I've also found the addition: They satisfy the vector laws of addition (commutative, associative, distributive).

Is it really necessary that all vectors should satisfy all those laws? Are there any exceptions?

Yes and no respectively. Otherwise it wouldn't be a vector!
There are other things that are similar to vectors, but we give them different names (like scalars and stuff).
 
mantrapad said:
I've found this regular definition of vectors: A quantity which has both magnitude and direction.

On some sites, I've also found the addition: They satisfy the vector laws of addition (commutative, associative, distributive).

Is it really necessary that all vectors should satisfy all those laws? Are there any exceptions?


The "magnitude and direction" definition is an intuitive one. They make a lot of sense for R^n, but for some vector spaces, it doesn't. There are function vector spaces, where we create rules for adding and scaling functions. For example, if f(x) = x^2 and g(x) = x + 1, then (f + g)(x) = x^2 + x + 1. But what "direction" does f, g, or f+g point? It's much more abstract!
 
Thanks for your replies and sorry about my late reply.

I was also wondering - current is neither a scalar nor a vector, right? But we say "current flows from A to B", which specifies a direction right? So it should be a vector...

And also, if it is neither, then which category does it fall in?
 

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