Do Isomorphic Galois Groups Guarantee Identical Field Extensions?

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In summary: Your Name]In summary, there is a question about whether two field extensions with isomorphic Galois groups must necessarily be equal. While it is possible for them to be different, the Galois correspondence suggests that they may also be equal. Further investigation is needed to fully understand this problem, and a combination of classical and non-classical approaches may be necessary.
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mathbalarka
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Now this is totally a mad problem, but I am going to post it here anyways

It is pretty well-known that there are distinct fields over $\Bbb Q$ with isomorphic Galois groups. Take, for example, $K_1 = \Bbb Q(\sqrt{2})$ and $K_2 = \Bbb Q(\sqrt{5})$. Both have Galois groups of order $2$ as easily can be seen and there is only one group of order $2$ which is $\Bbb Z_2$.

Now take some algebraically closed field $k$. I suspect that if two field extensions $K/k(t)$ and $K'/k(t)$ are Galois over $k(t)$ with isomorphic galois groups, it's necessary that $K = K'$. Is this true?

In particular, take up $\Bbb C(z)$ and let $$\mathcal{G}(K/\Bbb C(z)) \cong \mathcal{G}(K'/\Bbb C(z))$$ Is it possible to prove/disprove that $K = K'$?

Here is a possible way to do it using non-classical galois theory : $\Bbb C(z)$ forms the function field of meromorphic functions of single variable over $\Bbb P^1$, thus any Galois group of some Galois extension is realized as monodromy of coverings $X \to \Bbb P^1$ and $X_0 \to \Bbb P^1$. These are both galois coverings, so $\Bbb P^1 \cong X/G$ and $\Bbb P^1 \cong X_0/G$ G being the monodromy of both (the galois groups are isomorphic). So $X/G \cong X_0/G$. Now I just have to show that $X \cong X_0$, but I am not sure whether that holds. So I am rather partial to a standard classical approach to this problem.

Any help is appreciated
Balarka
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Dear Balarka,

Thank you for bringing up this interesting problem. It is indeed a fascinating question to consider whether two field extensions with isomorphic Galois groups must necessarily be equal. As you mentioned, it is well-known that there exist distinct fields over $\Bbb Q$ with isomorphic Galois groups, which suggests that the answer to this question may not be a straightforward yes or no.

In order to address this problem, it is important to understand the properties of Galois groups and how they relate to field extensions. One key concept to consider is the Galois correspondence, which states that there is a bijection between intermediate fields of a Galois extension and subgroups of the Galois group. This correspondence can provide insights into the structure of Galois groups and their relationship to field extensions.

In regards to the specific problem you posed, it is possible that two Galois extensions $K/k(t)$ and $K'/k(t)$ with isomorphic Galois groups may not be equal. This is because there could be multiple intermediate fields between $K$ and $k(t)$, and the isomorphism between their Galois groups does not necessarily imply an isomorphism between the fields themselves. However, it is also possible that the two extensions are equal, and further investigation is needed to determine if this is always the case.

Your suggestion of using non-classical Galois theory to approach this problem is also intriguing. However, as you mentioned, it may be difficult to show that $X \cong X_0$ in this context. Therefore, a combination of classical and non-classical approaches may be necessary to fully understand this problem.

In conclusion, this is a challenging and thought-provoking problem that requires further investigation. Thank you for sharing it with the scientific community and I look forward to seeing further developments on this topic.
 

FAQ: Do Isomorphic Galois Groups Guarantee Identical Field Extensions?

1. What is Transcendental Galois Theory?

Transcendental Galois Theory is a branch of mathematics that studies the algebraic properties of transcendental numbers, which are numbers that cannot be expressed as a root of a polynomial equation with rational coefficients. It is a generalization of the classical Galois Theory, which deals with algebraic numbers.

2. How is Transcendental Galois Theory different from classical Galois Theory?

While classical Galois Theory studies the algebraic properties of algebraic numbers, Transcendental Galois Theory deals with the algebraic properties of transcendental numbers. This means that in Transcendental Galois Theory, the objects of study are not the roots of polynomial equations, but rather the functions that are used to obtain those roots.

3. What are some applications of Transcendental Galois Theory?

Transcendental Galois Theory has various applications in mathematics and physics. It has been used to prove the transcendence of certain numbers, such as π and e, and to study the properties of special functions, such as the Gamma function. It has also been applied in the study of differential equations and dynamical systems.

4. Can Transcendental Galois Theory be understood by non-mathematicians?

Transcendental Galois Theory is a highly specialized branch of mathematics and can be quite complex. It requires a strong foundation in abstract algebra and advanced mathematical concepts. While some of the basic ideas can be explained to non-mathematicians, a deep understanding of the theory is generally only accessible to those with a strong mathematical background.

5. What are the current challenges and open problems in Transcendental Galois Theory?

Some of the current challenges and open problems in Transcendental Galois Theory include the development of a general theory for transcendental extensions, the classification of transcendental extensions of algebraic fields, and the understanding of the connections between Transcendental Galois Theory and other areas of mathematics, such as differential algebra and algebraic geometry.

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