Strict local minimizer (multivariate)

In summary, the conversation is about the concept of a strict local minimizer and its existence along every line through the point (0,0). The term "minimizer" is not clearly defined and the question's wording is confusing. It is concluded that a strict local minimizer is the same as a strict local minimum and the question may need clarification from the professor.
  • #1
cateater2000
35
0
I'm stuck on this question

Show that f(x1,x2) has a strict local minimizer at t=0 along every line

{ x1=at
{ x2=bt


through (0,0).


Any hints or tips would be great thanks
 
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  • #2
What exactly do you mean by "minimizer"? I'm not familiar with that term.

At first I thought you meant "minimum" but in that case the theorem is not true.

Suppose f(x,y)= (x-1)2+ (y-1)2.

Saying that f has a strict local minimum at t= 0 on x= at, y= bt would simply mean that f has a strict local minimum at (0,0) but that is not true- the only minimum of f is at (1,1).
 
  • #3
The minimizer is the point t where the minimum is. THat's why I'm a bit confused with the question. The wording I was given in my book is a bit awkward.

I think what it means is. For every f(x1,x2) given that x1 and x2 are lines.

There is a minimum at t=0

Those that make sense?
 
  • #4
cateater2000 said:
The minimizer is the point t where the minimum is. THat's why I'm a bit confused with the question. The wording I was given in my book is a bit awkward.

I think what it means is. For every f(x1,x2) given that x1 and x2 are lines.

There is a minimum at t=0

Those that make sense?

No! In particular, the sentence "For every f(x1,x2) given that x1 and x2 are lines." makes no sense at all. x1, x2 are variables that I presume are numbers, not lines.

Aren't there some conditions on the function f(x1, x2)? The statement is certainly NOT true for general f.
 
  • #5
I think you're right. The wording of the question is not very good. A strict local minimizer is in fact the same as a strict local minimum.

I geuss I'll have to ask the prof
 

Related to Strict local minimizer (multivariate)

1. What is a strict local minimizer?

A strict local minimizer is a point in a multivariate function where the function reaches its lowest value within a specific neighborhood. This means that there is no other point nearby that has a lower value than the strict local minimizer.

2. How is a strict local minimizer different from a local minimizer?

A local minimizer is a point where the function reaches a low value, but it may not be the lowest value in its neighborhood. A strict local minimizer, on the other hand, is the lowest value in its neighborhood and there is no other point nearby with a lower value.

3. How is a strict local minimizer calculated?

A strict local minimizer can be calculated using various optimization algorithms such as gradient descent, Newton's method, or the BFGS method. These algorithms use the gradient or Hessian matrix of the function to find the point where the gradient is equal to zero, indicating a minimum.

4. Why is the concept of strict local minimizer important in optimization?

The concept of strict local minimizer is important in optimization because it helps to identify the most optimal point in a multivariate function. By finding the strict local minimizer, we can determine the best solution or set of parameters that minimizes the function and achieve the desired results.

5. Can a function have more than one strict local minimizer?

Yes, a function can have multiple strict local minimizers. This is especially common in complex and highly dimensional functions. In such cases, it is important to carefully analyze the function and choose the most appropriate optimization algorithm to find the global minimum, which is the absolute lowest value of the function.

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