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1 vote
0 answers
71 views

Bias of $a^k / q$ modulo $q$?

Let $q$ be a prime. Let $0< a < q$ be an integer so that it is primitive modulo $q$. Let $k$ be a random integer up to $q-1$. Consider $$a^k = b_k + q * c_k$$ as $k$ varies modulo $q^2$. So $b_k$...
4 votes
0 answers
175 views

Intrinsic maps between complex integers modulo $p$ and integers modulo $p+2$

$\DeclareMathOperator\GF{GF}$Let $p$ and $p+2$ be twin primes. Let's assume that $-1$ is not a quadratic residue modulo $p$ (and therefore is a Q.R. modulo $p+2$). Consider the complex numbers $a+bi$ ...
0 votes
1 answer
195 views

Trying to solve for the remainder of $a^q$ modulo $q$

Let $q$ be a prime and $a$ be a number from $0$ to $q-1$ (not an equivalence class). The elements $a^q$ are exactly the elements of order $q-1$ modulo $q^2$. I'm trying to solve the equation: $$a+2*\...
3 votes
0 answers
73 views

Is the discrete logarithm equivalent to solving polynomial discrete logarithms?

Suppose we can quickly solve the discrete logarithm modulo $p$. Let's say $2$ is a generator so we can quickly find $l$ for which $2^l =h$ for any given target $h$. An interesting observation is that ...
2 votes
0 answers
145 views

What is the periodicity of $((a^n \text{ modulo } p) \text{ modulo } q)$

This feels like it should be elementary but it came up in my research and I was not able to solve it. We can ask this question for any $p$ and $q$ but,let $p$ and $q$ be primes for simplicity. The ...
3 votes
0 answers
269 views

Finding (and saturating) a sharp Babenko-Beckner inequality for finite fields

My question is a follow-up to Abdelmalek Abdesselam's recent post What makes Gaussian distributions special? Local field version? asking about various characterizations of (real-valued) Gaussian ...
2 votes
0 answers
243 views

Sums of squares in fields

Which fields $k$ have the property that any sum of squares is a square ? Are there elegant characterizations and/or classifications known for this type of field ? And what if we replace "fields" by "...
2 votes
0 answers
228 views

Satake correspondence for groups over finite field

I asked the same question in MSE, but I didn't get any answer. So I decided to post it here, too. In Langlands' program, Satake correspondence gives a correspondence between unramified ...
1 vote
0 answers
69 views

On equality of two quotients of a congruence subgroup

Related question: Non-torsion part of the abelianisation of congruence subgroups Let $A = \mathbb{F}_q[T]$ be the ring of polynomials with coefficients in a finite field, with $N$ a nonconstant ...
5 votes
2 answers
571 views

Exceptional isomorphisms between finite simple Chevalley groups

Steinberg's "Lectures on Chevalley Groups" https://math.depaul.edu/cdrupies/research/papers/chevalleygroups.pdf contain ``a complete list of isomorphisms" among the various finite simple Chevalley ...
20 votes
2 answers
2k views

Sums of powers mod p

For prime $p > 7$ with $p-1=rs$, $r>1$, $s>1$, let $A=\{x^r|x \in \mathbb{Z}_p\}$ and $B = \{x^s|x \in \mathbb{Z}_p\}$. If $g$ is a primitive root mod $p$ then $A = \{0\} \cup \{g^{ir}|0 \leq ...