Is the digamma function close to 0 for large arguments?

  • Thread starter Thread starter Judyxcheng
  • Start date Start date
  • Tags Tags
    Function
Click For Summary
SUMMARY

The digamma function, denoted as psi(x), does not approach zero for large arguments, contrary to some expectations. Instead, it diverges slowly, growing logarithmically as indicated by its integral form and recurrence relations. This conclusion is supported by mathematical resources such as MathWorld, which clarify the behavior of the digamma function at infinity. Therefore, it cannot be canceled out in limits approaching infinity.

PREREQUISITES
  • Understanding of the digamma function (psi(x))
  • Familiarity with limits and asymptotic behavior in calculus
  • Knowledge of integral forms and recurrence relations in mathematical functions
  • Basic concepts of logarithmic growth
NEXT STEPS
  • Study the integral form of the digamma function in detail
  • Research the properties of logarithmic growth in mathematical functions
  • Explore recurrence relations and their implications for function behavior
  • Examine related special functions, such as the gamma function, for further insights
USEFUL FOR

Mathematics students, researchers in mathematical analysis, and anyone studying special functions and their asymptotic properties.

Judyxcheng
Messages
1
Reaction score
0
1. The problem statement, all variables and given/known
I have taken the limit of both sides of an equation for x going toward infinity. There is a digamma (psi(x)) function on the RHS, and the limit of the term is supposed to be (at least close to) 0. Thus, the term can cancel out.

My professor said that indeed, the digamma function is supposed to be around 0 for large arguments and he wants me to justify that with the digamma function's integral form. However, when I research digamma online, it appears to slowly diverge or converge to a number larger than 0. Can someone clarify this?

Homework Equations



Integral form of digamma function, found here where it says "The digamma function satisfies": http://mathworld.wolfram.com/DigammaFunction.html
 
Physics news on Phys.org
It does not go to zero, but it grows only as fast as a logarithm, you can see that based on the recurrence relation.
 

Similar threads

  • · Replies 4 ·
Replies
4
Views
3K
  • · Replies 4 ·
Replies
4
Views
2K
  • · Replies 3 ·
Replies
3
Views
2K
  • · Replies 9 ·
Replies
9
Views
2K
  • · Replies 5 ·
Replies
5
Views
3K
Replies
10
Views
2K
Replies
8
Views
2K
Replies
4
Views
1K
  • · Replies 1 ·
Replies
1
Views
5K
  • · Replies 3 ·
Replies
3
Views
3K