Subtracting a value from a vector

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Mixing a vector and a scalar in subtraction operations is generally not valid unless they are from the same dimensional space. Subtracting a scalar from a vector, such as in the expression z - 1, requires both to be treated as elements of a compatible vector space. If z is a complex number, the scalar 1 can be interpreted as a complex number, allowing for valid operations. The discussion emphasizes the importance of understanding the vector's origin, the scalar field, and the dimensions involved in the operation. Clarifying these aspects is crucial for accurate geometric interpretation and mathematical validity.
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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