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 Why is a² + b² ≥ 2ab ?
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Category Archives: Fourier analysis
Matrix multiplication as a convolution
1. The product of two power series/polynomials is The coefficients given by is sometimes called the Cauchy product. This is a convolution. 2. Let be a finite group and be the group algebra with complex coefficients. Let be two elements … Continue reading
Posted in Analysis, Fourier analysis, Linear Algebra
Tagged convolution, matrix multiplication
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Fourier coefficients as eigenvalues/spectrum
In this post I want to make a connection between Fourier coefficients and eigenvalues/spectrum. Let me put the claim up front: If , then is not invertible with respect to the convolution product. Please feel free to jump directly to … Continue reading
Posted in Fourier analysis, Linear Algebra
Tagged fourier coefficients, linear algebra
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Arithmetic progression in some subsets of $\mathbb{Z}_N$ (Part 2)
Last time I have mentioned the idea of the proof (of theorem 2). Now I continue and give a full detail here.
Posted in Fourier analysis, Number Theory
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Arithmetic progression in some subsets of $\mathbb{Z}_N$ (Part 1)
This post is based mainly on the paper “Arithmetic progression in sumsets” by Ben Green, which talks about the length of arithmetic progressions of some special kind of subsets of , where is a sufficiently big odd prime. I will … Continue reading
Posted in Fourier analysis, Number Theory
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Fourier Analysis and Number Theory III: The Poisson summation formula as a trace formula
Yin and Yang are important concept in the Chinese philosophy. They usually describe two opposite things which are not only complement of each other but also have deep interrelationship. In mathematics, we called them duality. For example (1) primes vs … Continue reading
Posted in Fourier analysis, Number Theory
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Fourier Analysis and Number Theory II: The Poisson Summation Formula and The Functional Equation of The RiemannZeta Function
Riemann’s tenpagelong paper “Über die Anzahl der Primzahen unter einer gegebener Gröβe” has great influence on modern number theory. In the paper, he established two important properties of the Riemannzeta function (the summation is absolutely convergent for ).
Posted in Fourier analysis, Number Theory
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Fourier Analysis and Number theory I: The selfdual function e^{\pi x^2}
During a lecture at UCLA, Serge Lang asked what is the most important function in mathematics. This question is quite personal and every person certainly has his own opinion. In fact, a professor spoke out loud that the constant function … Continue reading
Posted in Fourier analysis, Number Theory
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