In mathematics, Fourier analysis ( ) is the study of the way general functions may be represented or approximated by sums of simpler trigonometric functions.
 Fourier analysis grew from the study of Fourier series, and is named after Joseph Fourier, who showed that representing a function as a sum of trigonometric functions greatly simplifies the study of heat transfer.
The Collatz conjecture is a conjecture in mathematics named after Lothar Collatz.
 It concerns a sequence defined as follows: start with any positive integer "n".
 Then each term is obtained from the previous term as follows: if the previous term is even, the next term is one half the previous term.
 Otherwise, the next term is 3 times the previous term plus 1.
 The conjecture is that no matter what value of "n", the sequence will always reach 1.
Steffensen's inequality is an equation in mathematics named after Johan Frederik Steffensen.
Mark A. Pinsky (15 July 1940 – 8 December 2016) was Professor of Mathematics at Northwestern University.
 His research areas included probability theory, mathematical analysis, Fourier Analysis and wavelets.
 Pinsky earned his Ph.D at Massachusetts Institute of Technology (MIT).
In applied mathematics, Arnold diffusion is the phenomenon of instability of integrable Hamiltonian systems.
 The phenomenon is named after Vladimir Arnold who was the first to publish a result in the field in 1964.
 More precisely, Arnold diffusion refers to results asserting the existence of solutions to nearly integrable Hamiltonian systems that exhibit a significant change in the action variables.
Bakul Kayastha (Born c. 1400) was mathematician from Kamrup.
 He was specially known for his master piece in the field of mathematics named Kitabat Manjari written in 1434 and Lilavati.
A Killing vector field is a concept in mathematics named for Wilhelm Killing.
Discrete mathematics is the study of mathematical structures that are fundamentally discrete rather than continuous.
 In contrast to real numbers that have the property of varying "smoothly", the objects studied in discrete mathematics – such as integers, graphs, and statements in logic – do not vary smoothly in this way, but have distinct, separated values.
 Discrete mathematics therefore excludes topics in "continuous mathematics" such as calculus and analysis.
 Discrete objects can often be enumerated by integers.
 More formally, discrete mathematics has been characterized as the branch of mathematics dealing with countable sets (sets that have the same cardinality as subsets of the natural numbers, including rational numbers but not real numbers).
 However, there is no exact definition of the term "discrete mathematics."
 Indeed, discrete mathematics is described less by what is included than by what is excluded: continuously varying quantities and related notions.
The Hausdorff paradox is a paradox in mathematics named after Felix Hausdorff.
 It involves the sphere "S" (a 2-dimensional sphere in "R").
 It states that if a certain countable subset is removed from "S", then the remainder can be divided into three disjoint subsets "A", "B" and "C" such that "A", "B", "C" and "B" ∪ "C" are all congruent.
 In particular, it follows that on "S" there is no finitely additive measure defined on all subsets such that the measure of congruent sets is equal (because this would imply that the measure of "B" ∪ "C" is simultaneously 1/3 and 2/3 of the non-zero measure of the whole sphere).
The Pinsky phenomenon is a result in Fourier analysis, a branch of mathematics.
 This phenomenon was discovered by Mark Pinsky of Northwestern University.
 It involves the spherical inversion of the Fourier transform.

Question: The Pinsky phenomenon is a result in a branch of mathematics named after who?
Answer: Joseph Fourier