Analysis of "Absolute Convergence" of $\sum_{n=2}^{\infty}\frac{1}{(lnn)^{n}}$

In summary, the conversation discusses using the geometric series and ratio test to analyze the convergence of \sum_{n=2}^{\infty}\frac{1}{(lnn)^{n}}. It is determined that when n=3, r is smaller than 1, indicating that the series converges. The conversation also highlights the importance of the series being ultimately decreasing and mentions the use of the ratio test to analyze convergence. It is noted that absolute convergence is the same as convergence for n > 1.
  • #1
rocomath
1,755
1
[tex]\sum_{n=2}^{\infty}\frac{1}{(lnn)^{n}}[/tex]

If I treat it as a geometric series, then when n=3, r is smaller than 1

[tex]\sum_{n=2}^{\infty}(\frac{1}{ln3})^3[/tex]

What matters is that it's ultimately decreasing, would that be the correct approach? Even problem, no answer!

Thanks.
 
Last edited:
Physics news on Phys.org
  • #2
What is r?
 
  • #3
Well, as for an answer I would like to say that:

When n=3, r equals

[tex]|\frac{1}{ln3}|<1[/tex]

Which is true, and so, what matters is that it is ultimately decreasing.
 
  • #4
In the ratio test r = Limn-->infinity|Ln(n+1)-(n+1)/Ln(n)-n|.

If r < 1 then the series converges.

But ultimately the ratio test is about whether you have a decreasing sequence; so I think you can use the ratio test here.

Also, for n > 1, absolute convergence is the same as convergence because Ln(n) > 0.
 
Last edited:

1. What is the concept of "absolute convergence"?

"Absolute convergence" is a term used in mathematics to describe a series that converges regardless of the order in which its terms are added. In other words, the sum of the series will always be the same, regardless of how the terms are rearranged.

2. How is "absolute convergence" determined for a series?

The "absolute convergence" of a series can be determined by taking the absolute value of each term in the series and then evaluating the sum of these absolute values. If this sum is finite, then the series is absolutely convergent.

3. What is the significance of "absolute convergence" in mathematical analysis?

"Absolute convergence" is an important concept in mathematical analysis because it guarantees that the sum of a series will be well-defined, regardless of the order in which the terms are added. This allows for more flexibility in manipulating and evaluating series, as well as making certain mathematical techniques and theorems applicable.

4. How does the series $\sum_{n=2}^{\infty}\frac{1}{(lnn)^{n}}$ exhibit "absolute convergence"?

The series $\sum_{n=2}^{\infty}\frac{1}{(lnn)^{n}}$ exhibits "absolute convergence" because the terms of the series are always positive and the series converges when the terms are taken in any order. This can be shown using the Cauchy-Hadamard criterion for series convergence.

5. Are there any applications of "absolute convergence" in real-world problems?

Yes, "absolute convergence" has applications in various real-world problems, such as in physics and engineering. For example, in electrical engineering, it is used in the analysis of alternating current circuits. In physics, it is used in the study of infinite series and their applications in thermodynamics and quantum mechanics.

Similar threads

  • Calculus and Beyond Homework Help
Replies
3
Views
402
  • Calculus and Beyond Homework Help
Replies
1
Views
232
  • Calculus and Beyond Homework Help
Replies
2
Views
703
  • Calculus and Beyond Homework Help
Replies
1
Views
330
  • Calculus and Beyond Homework Help
Replies
6
Views
366
  • Calculus and Beyond Homework Help
Replies
4
Views
286
  • Calculus and Beyond Homework Help
Replies
5
Views
1K
  • Calculus and Beyond Homework Help
Replies
4
Views
1K
  • Calculus and Beyond Homework Help
Replies
17
Views
1K
  • Calculus and Beyond Homework Help
Replies
5
Views
476
Back
Top