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Harmonic analysis is a generalisation of Fourier analysis that studies the properties of functions. Check out this tag for abstract harmonic analysis (on abelian locally compact groups), or Euclidean harmonic analysis (eg, Littlewood-Paley theory, singular integrals). It also covers harmonic analysis on tube domains, as well as the study of eigenvalues and eigenvectors of the Laplacian on domains, manifolds and graphs.

17 votes
2 answers
4k views

Is this statement which relates the Fourier transform of a function to its singularities cor...

I am working on a problem, which would possibly relate the Fourier transform/series with the jump singularities of the function where the function itself or one of its derivatives jump. ((some kind of …
Rajesh D's user avatar
  • 698
5 votes
3 answers
1k views

Property/Relations using Fourier series/transform, which give complete information about all...

Consider a function which has only jump singularities of the form of the function itself or one of its derivatives jumping. Now let $\hat{f}(k)$ be its Fourier transform/series. We know the decay of t …
Rajesh D's user avatar
  • 698
4 votes
1 answer
486 views

What is the importance of convergence of variation of Fourier reconstruction to that of vari...

Let $f$ be a periodic function of bounded variation which jumps at a point $x_0\in\mathbb{R}$. Let $S_{N}[f]$ denote the partial Fourier sum of $f$ and let $C_{N}[f]$ denote the Cesaro partial sum. It …
Rajesh D's user avatar
  • 698
3 votes
0 answers
214 views

Is flatness of Wigner Ville Distribution of error function in Fourier Approximation possible...

For a real valued function $f(t)$ I want to check the information left, after taking a Fourier partial sum/integral. Let $\hat{f}$ be its Fourier transform and let $$e_{\omega}(t) = f(t) - \int\limits …
Rajesh D's user avatar
  • 698
2 votes
0 answers
119 views

request for any expository works in pointwise convergence of double Fourier series and espec...

Quart. J. Math. Volume 37, Issue 1, Pages 53-79 On double Fourier series, and especially those which represent the double zeta-function with real and incommensurable parameters. Hardy, G.H. I am not …
Rajesh D's user avatar
  • 698
2 votes
0 answers
194 views

Shattering with sinusoids

Let $d \geq 2$ and $K$ some positive integer. Consider distinct points $\theta_1, \ldots, \theta_K\in \mathbb{T}^d$ and (not necessarily distinct) $z_1, \ldots, z_K \in \{-1,1\}$ such that $\sum\limit …
Rajesh D's user avatar
  • 698
1 vote
0 answers
189 views

Does the Total variation of the Fourier partial sum of a bv function with jumps converge to ...

Does the total variation of the Fourier partial sum of a piecewise continuous bv function converge to the total variation of the function as $N\to\infty$. To explain briefly, Let $f$ be a periodic B …
Rajesh D's user avatar
  • 698
1 vote

Is this statement which relates the Fourier transform of a function to its singularities cor...

I would like to prove for the case of jump discontinuity of the function itself. (rather than that of one of its derivatives). Let $t_0>0$ be a point where $f$ jumps. The curve $$(X_{t_0}(s),Y_{t_0}( …
Rajesh D's user avatar
  • 698
1 vote
1 answer
194 views

A metric on the set of BV functions, is it mentioned/studied in literature?

I'd like to propose the following metric which operates on the set $M$ of all square integrable functions that are also of bounded variation, of the form $f : (0,1) \to \mathbb{R}$. Given any $x,y \in …
Rajesh D's user avatar
  • 698
1 vote
1 answer
816 views

What is the growth of sum of absolute values of Fourier coefficients

For a periodic BV function $f$ which has jump discontinuties, is there any theorem in Fourier analysis which gives like $$\sum_{k=0}^n\left|c_k\right|\sim C\log\left(n\right)$$ where $C$ is a constant …
Rajesh D's user avatar
  • 698
-1 votes
1 answer
1k views

A question about pointwise convergence of Fourier transform in $N$-dimensions

I am retreating back on this statement, after some explorations and calculation Bow to Willie and others who were skeptical on this. Main difficulty can be seen in this reference. But I must mention t …
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