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Galois theory

Galois Theory – developed in the 19th century and named after the unlucky Évariste Galois, who died aged 20 following a duel – uncovers a strong relationship between the structure of groups and the structure of fields in the Fundamental Theorem of Galois Theory. This has a number of consequences, including the classification of finite fields, impossibility proofs for certain ruler-and-compass constructions, and a proof of the Fundamental Theorem of Algebra. Most famous, however, is the connection it brings between solving polynomials and group theory, culminating in the proof that there is no “quintic formula” like there is a quadratic formula.


Module code


  • Credits measure the student workload required for the successful completion of a module or qualification.
  • One credit represents about 10 hours of study over the duration of the course.
  • You are awarded credits after you have successfully completed a module.
  • For example, if you study a 60-credit module and successfully pass it, you will be awarded 60 credits.
Study level
To enable you to make international comparisons, the information provided shows how OU postgraduate modules correspond to the Framework for Higher Education Qualifications in England, Northern Ireland and Wales (FHEQ).
OU Postgraduate
Study method
Distance learning
Find out more in Why the OU?
Module cost
See Module registration
Entry requirements

Find out more about entry requirements.

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What you will study

In order to prove the Fundamental Theorem of Galois Theory and unlock its many applications, you’ll first study the fundamentals of abstract algebra. These include the study of groups, rings and fields, homomorphisms (that allow you to move between two structures) and automorphisms (that allow you to rearrange the elements within a structure in a controlled way). Some prior group theory and linear algebra is assumed in the early units, but supplementary material is available if you need to refresh your knowledge.

This module is based on readings from the set book, Galois Theory (4th edition) written by Ian Stewart, but the study materials contain additional reading both before you start the set book, and at the end.

After studying the fundamentals of algebra, you’ll learn about field extensions, which is a way of thinking about two fields, one of which is contained inside the other. Each extension comes with a set of automorphisms of the bigger field that leave the smaller one fixed. They form a group, called the Galois group, and here you will get your first glimpse of what is to come: the Fundamental Theorem of Galois Theory is about the relationship between the structure of a field extension and the structure of its Galois group.

Throughout, you’ll see how this study of groups and fields is intimately connected to the solution of polynomials. For example, a polynomial that has no solutions in the field of real numbers can always be split up into linear terms if you use the field of complex numbers. Thus, there is a relationship between field extensions and solving polynomials. You’ll learn about two properties – normality and separability – that a field extension may or may not possess, that are defined in terms of how polynomials split up in the bigger field. These two properties are the final ingredients required for you to prove the Fundamental Theorem of Galois Theory.

The last part of the module covers the applications of the Fundamental Theorem. By far the most famous is the proof that while there exists a formula to solve any quadratic equation (and also formulas to solve cubic and quartic polynomials, though these are less well known and not of much use in practice), there is no such way to solve polynomials of degree 5 or greater. You’ll see how the Fundamental Theorem can be used to translate this problem into one about group theory, which can be solved with relative ease.

Other applications include proofs for the existence or non-existence of ruler-and-compass constructions for regular polygons, a complete classification of finite fields, and at the very end, an algebraic proof of the Fundamental Theorem of Algebra.

You will learn

Successful study of this module should enhance your skills in understanding complex mathematical texts, working with abstract concepts, thinking logically and constructing logical arguments, communicating mathematical ideas clearly and succinctly, and explaining mathematical ideas to others.

Teaching and assessment

Support from your tutor

Throughout your module studies, you’ll get help and support from your assigned module tutor. They’ll help you by:

  • Marking your assignments (TMAs) and providing detailed feedback for you to improve.
  • Guiding you to additional learning resources.
  • Providing individual guidance, whether that’s for general study skills or specific module content.
  • Facilitating online discussions between your fellow students, in the dedicated module and tutor group forums.

Module tutors also run online tutorials throughout the module. Where possible, recordings of online tutorials will be made available to students. While these tutorials won’t be compulsory for you to complete the module, you’re strongly encouraged to take part. If you want to participate, you’ll likely need a headset with a microphone.


The assessment details for this module can be found in the facts box.

Residential School

This module normally includes an optional study weekend. For each day you choose to attend, you must pay an additional charge of around £60 to cover tuition and refreshments during the day. You’ll pay this charge when you book, after you’ve registered on the module. You must also pay for your travel to and from the venue and your accommodation if you need it.

Course work includes

4 Tutor-marked assignments (TMAs)
No residential school

Future availability

Galois theory (M838) starts every other year – in October.

This page describes the module that will start in October 2022.

We expect it to start for the last time in October 2034.


As a student of The Open University, you should be aware of the content of the academic regulations which are available on our Student Policies and Regulations website.

    Entry requirements

    You should have at least a second-class honours degree in a mathematics or an upper second-class honours degree with a high mathematical content.

    Normally, you should have also completed at least one of the postgraduate mathematics entry modules:

    You should have a good background in pure mathematics, with some experience in group theory and linear algebra. An adequate preparation would be our undergraduate-level modules Pure mathematics (M208) and Further pure mathematics (M303).

    All teaching is in English and your proficiency in the English language should be adequate for the level of study you wish to take. We strongly recommend that students have achieved an IELTS (International English Language Testing System) score of at least 7. To assess your English language skills in relation to your proposed studies you can visit the IELTS website.

    Preparatory work

    Additional material is provided at the module start to help you to revise the necessary group theory and linear algebra.


    Start End Fee
    - - -

    No current presentation - see Future availability

    This module is expected to start for the last time in October 2034.

    Future availability

    Galois theory (M838) starts every other year – in October.

    This page describes the module that will start in October 2022.

    We expect it to start for the last time in October 2034.

    Additional costs

    Study costs

    There may be extra costs on top of the tuition fee, such as set books, a computer and internet access.

    Study weekend

    This module has an optional study weekend. You must pay £60 for tuition and refreshments. You must also pay for your travel to and from the venue, and accommodation if you need it. Due to the ongoing pandemic, we may replace face-to-face events with online alternatives.

    Study materials

    What's included

    You’ll be provided with course notes covering the content of the module, including explanations, examples and exercises to aid your understanding of the concepts and associated skills and techniques that are contained in the set book. You’ll need to obtain your own copy of the set book.

    You’ll also have access to a module website, which includes:

    • a week-by-week study planner to help keep you on schedule
    • additional content, such as a module guide and audio and video resources.
    • copies of the printed materials
    • assessment details, instructions and guidance
    • online tutorial access
    • links to other OU websites helping you to study successfully
    • an online forum for peer-to-peer interaction and interaction with the module team.

    Computing requirements

    You'll need a desktop or laptop computer with an up-to-date version of 64-bit Windows 10 (note that Windows 7 is no longer supported) or macOS and broadband internet access.

    To join in spoken conversations in tutorials we recommend a wired headset (headphones/earphones with a built-in microphone).

    Our module websites comply with web standards and any modern browser is suitable for most activities.

    Our OU Study mobile App will operate on all current, supported, versions of Android and iOS. It's not available on Kindle.

    It's also possible to access some module materials on a mobile phone, tablet device or Chromebook, however, as you may be asked to install additional software or use certain applications, you'll also require a desktop or laptop as described above.

    Materials to buy

    Set books

    • Stewart, I.N. Galois Theory (4th edn) CRC Press £54.99 - ISBN 9781482245820 This item is Print on Demand, please allow 3 weeks for receipt following order

    If you have a disability

    Written transcripts of any audio components and Adobe Portable Document Format (PDF) versions of printed material are available. Some Adobe PDF components may not be available or fully accessible using a screen reader (and where applicable: musical notation and mathematical, scientific, and foreign language materials may be particularly difficult to read in this way). Other alternative formats of the module materials may be available in the future.

    If you have particular study requirements please tell us as soon as possible, as some of our support services may take several weeks to arrange. Visit our Disability support website to find more about what we offer.