Subtracting a value from a vector

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Homework Help Overview

The discussion revolves around the operation of subtracting a scalar value from a vector, specifically examining the implications and interpretations of such an operation within the context of vector spaces.

Discussion Character

  • Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • Participants explore the validity of mixing scalars and vectors in subtraction, questioning the geometric interpretation of subtracting a scalar from a vector. There are inquiries about the dimensionality of the vector space and the nature of the scalar involved.

Discussion Status

Some participants have offered insights into the conditions under which scalar and vector operations can be valid, while others have raised questions about the assumptions and definitions that underpin the problem. Multiple interpretations of the operation are being considered, and the discussion is ongoing.

Contextual Notes

There are mentions of missing information regarding the vector space from which the vector originates, the scalar field in use, and the dimensionality of the vector space. These constraints are influencing the discussion and the interpretations being explored.

Aristarchus_
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Homework Statement
If we have a vector z, what does it mean to subtract a value of 1 from it? What is the geometric interpretation of this?
Relevant Equations
z-1
d
 
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What are your thoughts so far? Do you think it's okay to mix a vector and a scalar in a subtraction operation like that?
 
Aristarchus_ said:
Homework Statement:: If we have a vector z, what does it mean to subtract a value of 1 from it? What is the geometric interpretation of this?
Relevant Equations:: z-1

d
It generally makes no sense to add a scalar to a vector or to subtract a scalar from a vector. If z happens to be a complex number, then the expression ##z - 1## is treating 1 as also being a complex number (i.e., 1 + 0i), so both z and 1 are essentially vectors.
 
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Aristarchus_ said:
Homework Statement:: If we have a vector z, what does it mean to subtract a value of 1 from it? What is the geometric interpretation of this?
Relevant Equations:: z-1

d
It means that you add two numbers, ##z## and ##1.##

Explanation: You can only add vectors from the same set*). You said that ##z## is a vector. In order to add ##1## to ##z## they have to be of the same dimension*). So ##z+1## demands to be the vector addition in a one-dimensional vector space. Now, a one-dimensional vector space is isomorphic to (~ the same as) the scalar field of the vector space, whatever this is in your case. I assume the real or complex numbers. Therefore ##z+1## is the addition of two numbers, which at the same time are vectors from a one-dimensional vector space.

You see that I already had to make several guesses to answer your question at all! What was missing?
  1. Where is ##z## from? Which vector space?
  2. What scalar field do you have? Means, if you multiply a vector by a number, where is the number from?
  3. What is the dimension of the vector space?
  4. Is it a graduated vector space that allows vectors from different dimensions?
  5. Is ##1## an abbreviation, e.g. ##1=(1,\ldots,1)##?

______________
*) This is not 100% true since we can have formal sums like those in a Graßmann algebra, but as you have to ask this question, I allowed myself to make the assumption of a finite-dimensional vector space of one given dimension.
 

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