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

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In summary, if f is holomorphic on D then by substituting Cauchy-Riemann equations we get that $f_{\bar z}=0$.
  • #1
Stephen88
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_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.
 
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  • #2
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.
 
  • #3
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)
 
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FAQ: Is f Holomorphic on D if and only if p_g = 0 on D?

What are two holomorphic functions?

Two holomorphic functions are complex-valued functions that are defined and differentiable on an open subset of the complex plane. They are also known as analytic functions and can be expressed as power series.

How do you determine if a function is holomorphic?

A function is holomorphic if it satisfies the Cauchy-Riemann equations, which state that the partial derivatives of the function with respect to the real and imaginary parts must exist and be continuous. Additionally, the function must be differentiable at every point in its domain.

What is the relationship between holomorphic functions and the complex plane?

Holomorphic functions are defined and differentiable on an open subset of the complex plane. They are closely related to the concept of conformal mapping, which preserves angles and shapes on the complex plane.

Can two holomorphic functions have the same derivative?

No, two holomorphic functions cannot have the same derivative unless they are complex scalar multiples of each other. This is known as the Uniqueness Theorem for holomorphic functions.

How are holomorphic functions used in science?

Holomorphic functions are used in various fields of science, such as physics, engineering, and mathematics. They are particularly useful in complex analysis, which has applications in fluid dynamics, electrical engineering, and quantum mechanics.

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