# Functions of a Complex Variable - MAT00024I

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• Department: Mathematics
• Module co-ordinator: Dr. Roger Colbeck
• Credit value: 10 credits
• Credit level: I
• Academic year of delivery: 2019-20

## Module will run

Occurrence Teaching cycle
A Spring Term 2019-20

## Module aims

The Core modules in the second year of mathematics programmes cover material which is essential for accessing a wide range of topics later on. Such material underpins the development of mathematics across all three of the major streams we offer through our single-subject degrees, and it is also very important for many combined programmes. As well as covering fundamental material, these modules address applications and techniques which all students will subsequently be able to draw on in various contexts.

As part of the broad aims outlined above, this module considers two important developments in calculus and analysis. First, differentiable functions of a complex variable have very many properties beyond those of the differentiable functions of real variables that were studied previously. This has applications to the expansion of functions in power series and also to the important techniques of contour integration. Second, a powerful tool both in applied mathematics and analysis is the Fourier transform, which has applications in many areas.

## Module learning outcomes

This module will extend the ideas developed about real functions to complex functions, develop the theory of holomorphic functions, and apply this theory to understand problems arising in real analysis or calculus and describe the idea and basic properties of the Fourier transform, indicating their applications in fields such as digital signal processing and differential equations.

Subject content

• Review of complex numbers.

• Limits and continuity in C. Algebra of limits. Convergence of absolutely convergent series.

• Open sets, complex differentiability, linearity, product rule, quotient rule, chain rule. Holomorphic functions, Cauchy-Riemann equations.

• Integration of complex-valued functions on a real interval: linearity, triangle inequality, Fundamental Theorem.

• Paths and path integrals. Estimation Lemma. Fundamental Theorem.

• Cauchy’s Theorem from Green’s Theorem.

• Cauchy's Integral Formulae for the function and its derivatives; the derivative of a holomorphic function is holomorphic.

Taylor’s Theorem from the integral formula, with Cauchy’s formula for the coefficients. Liouville’s Theorem. Fundamental Theorem of Algebra.

• Taylor’s formula for the Taylor coefficients.

• Term-by-term differentiation of power series.

• Isolated singularities, removable singularities and poles. Laurent series about a pole.

• The Residue Theorem.

• Example of residue calculations, to include integrals of (cos(kx))/(1+x^2) and sin(kx)/x

• Jordan's Lemma.
• Fourier Transforms. Definition and examples of the Fourier transform, including examples calculated by residue methods. Statement of the inversion theorem.
• Properties of the Fourier transform: linearity, translation, dilation, derivatives, convolutions, etc. Square-integrable functions and Plancherel’s Identity.

• Applications of Fourier transforms to (ordinary and/or partial) differential equations.

• Academic Skills: our second year Core modules continue to develop themes which start in the first year, such as the application of rigorous mathematical techniques and ideas to the development of mathematics; the power of abstraction as a way of solving many similar problems at the same time; the development and consolidation of essential skills which a mathematician needs in their toolkit and needs to be able to use without pausing for thought.

• Graduate skills: The techniques of Fourier analysis developed in this course are widely used in real-world applications (some of which the students will encounter during the module). These techniques are used by many graduates in their day-to-day work.

## Assessment

Task Length % of module mark
University - closed examination
Functions of a Complex Variable
1.5 hours 100

None

### Reassessment

Task Length % of module mark
University - closed examination
Functions of a Complex Variable
1.5 hours 100

## Module feedback

Current Department policy on feedback is available in the undergraduate student handbook. Coursework and examinations will be marked and returned in accordance with this policy.