# Questions tagged [fourier-analysis]

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### Sign patterns for Fourier coefficients of Boolean functions

Given a sequence of real numbers $(a_i)$, the sign-pattern sequence $(s_i)$ is defined by $s_i = +$ if $a_i \geq 0$ and $s_i = -$ otherwise. For a boolean function $f: \{0,1\}^n \to \{0,1\}$, ...
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### Fourier spectrum of the parity of two monotone Boolean functions

This is a question that I've been pondering, on and off, for a while, and unsuccessfully. I'd be very interested in any insight regarding this conjecture. (Or rather, these conjectures.) Recall that, ...
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### relations between the degrees of a boolean function and its absolute function

Given a boolean function $f:\{0,1\}^n\rightarrow\mathbb{R}$ of degree $d$, is there any upper bound in terms of $d$ on the degree of the function $|f|$, where $|f|(x)=|f(x)|$. Here the degree of $f$ ...
78 views

### Agnostic query learning of decision trees

Gopalan, Kalai, Klivans gave an algorithm https://dl.acm.org/citation.cfm?id=1374376.1374451 for agnostically learning decision trees $h:\{0,1\}^n\to\{0,1\}$ under the uniform distribution given ...
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### Are there uses for a Fourier transform of length $n^m$ with elements of maximum size $n$?

In essence, I'm trying to get a better feel for when there is a use for FFT with small coefficients, compared to the length, assuming that we get a better runtime. I've been toying with an idea for a ...
91 views

### Period of a Multivariable Function using Quantum Computing

consider a function $$f(x_1,x_2...x_n)$$ I am told it is possible to compute the period of the function as a vector $$<l_1,l_2...l_n>$$ where each l denotes the period of the function for ...
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### Hidden subgroup problems in a tower of subgroups

Let $H$ be a hidden subgroup of $G_1$ that is indistinguishable from subgroup $H^{\prime}$ by quantum Fourier sampling. Now take a larger group $G_2$ such that it contains $G_1$. Now if I do quantum ...
Consider an arbitrary boolean function $$f: {\lbrace 0,1 \rbrace}^n \rightarrow \lbrace 0,1 \rbrace$$ which we write as: $$f(x_1, x_2 ... x_n)$$ where each $x_i$ is a boolean variable We note ...
Consider a blackbox function $$f(x): Z \rightarrow \lbrace 0,1 \rbrace$$ Which inputs an integer and outputs 0 or 1 with bit complexity n. If the period P of this function satisfies P \in O(2^{...