# Fungrim entry: 03fbe8

$\chi_{q}(\ell, n) = \exp\!\left(2 \pi i \left(\frac{\left(1 - x\right) \left(1 - y\right)}{8} + \frac{a b}{{2}^{e - 2}}\right)\right)\; \text{ where } q = {2}^{e},\,L\!\left(k\right) = \begin{cases} \left(1, \log_{5}\!\left(k\right) \bmod q\right), & k \in \left\{ {5}^{i} \bmod q : i \in \mathbb{Z}_{\ge 1} \right\}\\\left(-1, \log_{5}\!\left(-k\right) \bmod q\right), & k \in \left\{ -{5}^{i} \bmod q : i \in \mathbb{Z}_{\ge 1} \right\}\\ \end{cases},\,\left(x, a\right) = L\!\left(\ell\right),\,\left(y, b\right) = L\!\left(n\right)$
Assumptions:$e \in \mathbb{Z}_{\ge 3} \,\mathbin{\operatorname{and}}\, \ell \in \{1, 2, \ldots {2}^{e} - 1\} \,\mathbin{\operatorname{and}}\, n \in \mathbb{Z} \,\mathbin{\operatorname{and}}\, \gcd\!\left(\ell, 2\right) = \gcd\!\left(n, 2\right) = 1$
TeX:
\chi_{q}(\ell, n) = \exp\!\left(2 \pi i \left(\frac{\left(1 - x\right) \left(1 - y\right)}{8} + \frac{a b}{{2}^{e - 2}}\right)\right)\; \text{ where } q = {2}^{e},\,L\!\left(k\right) = \begin{cases} \left(1, \log_{5}\!\left(k\right) \bmod q\right), & k \in \left\{ {5}^{i} \bmod q : i \in \mathbb{Z}_{\ge 1} \right\}\\\left(-1, \log_{5}\!\left(-k\right) \bmod q\right), & k \in \left\{ -{5}^{i} \bmod q : i \in \mathbb{Z}_{\ge 1} \right\}\\ \end{cases},\,\left(x, a\right) = L\!\left(\ell\right),\,\left(y, b\right) = L\!\left(n\right)

e \in \mathbb{Z}_{\ge 3} \,\mathbin{\operatorname{and}}\, \ell \in \{1, 2, \ldots {2}^{e} - 1\} \,\mathbin{\operatorname{and}}\, n \in \mathbb{Z} \,\mathbin{\operatorname{and}}\, \gcd\!\left(\ell, 2\right) = \gcd\!\left(n, 2\right) = 1
Definitions:
Fungrim symbol Notation Short description
DirichletCharacter$\chi_{q}(\ell, \cdot)$ Dirichlet character
Exp${e}^{z}$ Exponential function
ConstPi$\pi$ The constant pi (3.14...)
ConstI$i$ Imaginary unit
Pow${a}^{b}$ Power
DiscreteLog$\log_{b}\!\left(x\right) \bmod q$ Discrete logarithm
SetBuilder$\left\{ f\!\left(x\right) : P\!\left(x\right) \right\}$ Set comprehension
ZZGreaterEqual$\mathbb{Z}_{\ge n}$ Integers greater than or equal to n
ZZBetween$\{a, a + 1, \ldots b\}$ Integers between a and b inclusive
ZZ$\mathbb{Z}$ Integers
GCD$\gcd\!\left(a, b\right)$ Greatest common divisor
Source code for this entry:
Entry(ID("03fbe8"),
Formula(Where(Equal(DirichletCharacter(q, ell, n), Exp(Mul(Mul(Mul(2, ConstPi), ConstI), Add(Div(Mul(Sub(1, x), Sub(1, y)), 8), Div(Mul(a, b), Pow(2, Sub(e, 2))))))), Equal(q, Pow(2, e)), Equal(L(k), Cases(Tuple(Tuple(1, DiscreteLog(k, 5, q)), Element(k, SetBuilder(Mod(Pow(5, i), q), i, Element(i, ZZGreaterEqual(1))))), Tuple(Tuple(-1, DiscreteLog(Neg(k), 5, q)), Element(k, SetBuilder(Mod(Neg(Pow(5, i)), q), i, Element(i, ZZGreaterEqual(1))))))), Equal(Tuple(x, a), L(ell)), Equal(Tuple(y, b), L(n)))),
Variables(e, ell, n),
Assumptions(And(Element(e, ZZGreaterEqual(3)), Element(ell, ZZBetween(1, Sub(Pow(2, e), 1))), Element(n, ZZ), Equal(GCD(ell, 2), GCD(n, 2), 1))))

## Topics using this entry

Copyright (C) Fredrik Johansson and contributors. Fungrim is provided under the MIT license. The source code is on GitHub.

2019-08-17 11:32:46.829430 UTC