Modular Forms: Non-holomorphic Eisenstein Series E2 identity

  • Context: Graduate 
  • Thread starter Thread starter binbagsss
  • Start date Start date
  • Tags Tags
    Forms Identity Series
Click For Summary
SUMMARY

The discussion focuses on the identity involving non-holomorphic Eisenstein series, specifically the transformation properties of \( E^*_{2}(-1/t) = t^{2}E^*_{2}(t) \). The user derives that \( E^*_{2}(t) = -\frac{3}{\pi \text{Im}(t)} + E_{2}(t) \) and explores the implications of modular transformations under the group \( SL_{2}(\mathbb{Z}) \). Key equations include \( t^{-2}E_{2}(-1/t) = E_{2}(t) + \frac{12}{2\pi i t} \) and the identification of \( \text{Im}(\gamma.t) = \frac{\text{Im}(t)}{|ct+d|^2} \), which are essential for proving the weak modularity of \( E_{2}(t)^* \).

PREREQUISITES
  • Understanding of modular forms and their properties
  • Familiarity with the Eisenstein series, particularly \( E_{2}(t) \)
  • Knowledge of the modular group \( SL_{2}(\mathbb{Z}) \)
  • Basic complex analysis, specifically regarding imaginary parts and transformations
NEXT STEPS
  • Study the properties of Eisenstein series in depth, focusing on \( E_{2}(t) \)
  • Learn about modular transformations and their applications in number theory
  • Explore the implications of weak modularity in the context of modular forms
  • Investigate the role of the modular group \( SL_{2}(\mathbb{Z}) \) in the theory of modular forms
USEFUL FOR

Mathematicians, particularly those specializing in number theory, modular forms, and complex analysis, will benefit from this discussion. It is also relevant for researchers exploring the properties of Eisenstein series and their applications in various mathematical contexts.

binbagsss
Messages
1,291
Reaction score
12
Hi,

As part of showing that ##E^*_{2}(-1/t)=t^{2}E^*_{2}(t)##

where ##E^*_{2}(t)= - \frac{3}{\pi I am (t) } + E_{2}(t) ##

And since I have that ##t^{-2}E_{2}(-1/t)=E_{2}(t)+\frac{12}{2\pi i t} ##

I conclude that I need to show that ##\frac{-1}{Im(-1/t)}+\frac{2t}{i} = \frac{-t^{2}}{Im(t)} ## [1]

where ##t## inside the upper half plane
Im=imaginary

I also have the identification ##Im(\gamma.t)=\frac{Im(t)}{|ct+d | ^{2}}## [2],

where ##\gamma## is inside ##SL_{2}(Z)##, the modular group of 2x2 matrices with integer numbers and determinant 1, (apologies I'm unsure how you do a matrix in latex), with components ##\gamma_{11}=a,\gamma_{12}=b, \gamma_{21}=c, \gamma_{22}=d ## .

So this is part of a question where I am showing that ## E_{2}(t)^*## is weakly modular via showing that for the generators ##T## and ##S## the relevant identifications hold,##S## and ##T## inside ##SL_{2}(Z)##, so here, the one for ##S## being that :

##f(-1/t)=t^{k}f(t)##, ##S## is the matrix with components ##a=0,b=-1,c=1,d=0##

Now I am looking at [2] and, using ##S## as ##\gamma## that
##Im(S.t)=\frac{Im(t)}{t^{2}}##, but we also know ##S.t=-1/t## and therefore I have ##Im(-1/t)=\frac{Im(t)}{t^{2}}##, and so I have no idea how I'm going to get a ##\frac{-2t}{i}## term in [1]

Many thanks in advance.
 
Physics news on Phys.org
bump
 

Similar threads

  • · Replies 1 ·
Replies
1
Views
2K
  • · Replies 7 ·
Replies
7
Views
2K
  • · Replies 4 ·
Replies
4
Views
3K
  • · Replies 2 ·
Replies
2
Views
2K
  • · Replies 2 ·
Replies
2
Views
1K
Replies
8
Views
2K
  • · Replies 4 ·
Replies
4
Views
2K
  • · Replies 9 ·
Replies
9
Views
2K
  • · Replies 8 ·
Replies
8
Views
2K
  • · Replies 4 ·
Replies
4
Views
2K