Is f Holomorphic on D if and only if p_g = 0 on D?

  • Context: MHB 
  • Thread starter Thread starter Stephen88
  • Start date Start date
  • Tags Tags
    Functions
Click For Summary
SUMMARY

The discussion centers on the conditions under which a function f is holomorphic on a domain D, specifically when p_g equals zero on D. It is established that if f is holomorphic, then the conjugate partial derivative p_g must equal zero, and conversely, if p_g equals zero, then f is holomorphic. The calculations involve defining g(z) as f conjugate and utilizing the Cauchy-Riemann equations to derive these relationships. The conclusion is that f is holomorphic on D if and only if p_g = 0 on D.

PREREQUISITES
  • Understanding of holomorphic functions and their properties
  • Familiarity with Cauchy-Riemann equations
  • Knowledge of partial derivatives and conjugate variables
  • Basic concepts of complex analysis
NEXT STEPS
  • Study the Cauchy-Riemann equations in detail
  • Learn about the implications of conjugate variables in complex functions
  • Explore the properties of holomorphic functions in complex analysis
  • Investigate the applications of partial differential equations in complex variables
USEFUL FOR

Mathematicians, students of complex analysis, and anyone interested in the properties of holomorphic functions and their applications in mathematical theory.

Stephen88
Messages
60
Reaction score
0
_z=conjugate
p_g=partial diff
_p_g=conjugate pde
p_g_x=partial diff with respect to x
Suppose that f : D → C . Let g(z) : D → C be defined by
g(z) = f(_z). Calculate_p_g and p_g where _p_g=(p_g_x+i(p_g_y))/2, p_g=(p_g_x+i(p_g_y))/2;
Conclude that f is holomorphic on D if
and only if p_g = 0 on D.
I've calculated the pde and observed that I get different signs that supposed to for a regular exercise.Also there is a property that states that f is holomorphic if _p_g=0...given the nature of the function g(z) by intuition am assuming that in this case is has to be the other way around.
Any help will be great Thank you.
 
Physics news on Phys.org
StefanM said:
_z=conjugate
p_g=partial diff
_p_g=conjugate pde
p_g_x=partial diff with respect to x
Suppose that f : D → C . Let g(z) : D → C be defined by
g(z) = f(_z). Calculate_p_g and p_g where _p_g=(p_g_x+i(p_g_y))/2, p_g=(p_g_x+i(p_g_y))/2;
Conclude that f is holomorphic on D if
and only if p_g = 0 on D.
I've calculated the pde and observed that I get different signs that supposed to for a regular exercise.Also there is a property that states that f is holomorphic if _p_g=0...given the nature of the function g(z) by intuition am assuming that in this case is has to be the other way around.
Any help will be great Thank you.

The way you wrote it is a mess. I have no idea what you are asking.
Maybe you are asking the following.

Write $f(x+iy) = u(x,y) + iv(x,y)$. Then we define $f_x = \frac{\partial u}{\partial x} + i\frac{\partial v}{\partial x}$ and $f_y = \frac{\partial u}{\partial y} + i\frac{\partial v}{\partial y}$.
We also define $f_z = \frac{1}{2} \left( f_x - i f_y \right)$ and $f_{\bar z} = \frac{1}{2} \left( f_x + i f_y \right)$.

If $f$ is holomorphic on $D$ then by the substituting Cauchy-Riemann equations we get that $f_{\bar z} = 0$ (and conversely also).
All you have to do is write everything down in the definition and then substitute CR-equations to get it equal to 0.
 
I think the question should read as follows:

Suppose that $ f:\mathbb{D}\rightarrow\mathbb{C} $ is of class $\mathcal{C}^1 $. Let $ g(z):\mathbb{D}\righatrrow\mathbb{C} $ be defined by $ g(z)=f(\bar{z}) $. Calculate $ \partial g $ and $ \bar{\partial} g $. Conclude that f is holomorphic on $ \mathbb{D} $ iff $ \partial g = 0$ on $\mathbbh{D}$

where if $ z=x+iy$ and : $$ \bar{\partial} = \frac{1}{2}\left ( \frac{\partial}{\partial x}+i*\frac{\partial}{\partial y} \right ) $$

$$ \partial = \frac{1}{2}\left ( \frac{\partial}{\partial x}-i*\frac{\partial}{\partial y} \right ) $$

So that we have that f is holomorphic iff $\bar{\partial} f = 0$

To solve we write $f(z)=u(x,y)+iv(x,y)$ then $g(z)=u(x,-y)+iv(x,-y)$ and then:

$\partial g=\frac{1}{2}(g_x-ig_y)=\frac{1}{2} ((u_x+iv_x++i(u_y+iv_y))(x,-y)=\bar{\partial}f(\bar{z})$

So $\partial g=\bar{\partial} f(\bar{z})$ and so as f is holomorphic iff $\bar{\partial}f=\partial g = 0$ on $\mathbb{D}$

I think this is what is being asked for and the answer(I don't know why it won't save my edits on the first few lines I will try again latter sorry)
 
Last edited:

Similar threads

  • · Replies 0 ·
Replies
0
Views
2K
  • · Replies 5 ·
Replies
5
Views
2K
  • · Replies 2 ·
Replies
2
Views
2K
  • · Replies 3 ·
Replies
3
Views
3K
  • · Replies 4 ·
Replies
4
Views
2K
  • · Replies 8 ·
Replies
8
Views
3K
  • · Replies 4 ·
Replies
4
Views
2K
  • · Replies 2 ·
Replies
2
Views
2K
Replies
2
Views
2K
Replies
2
Views
2K