No Arabic abstract
Let $q$ be a power of a prime $p$, let $k$ be a nontrivial divisor of $q-1$ and write $e=(q-1)/k$. We study upper bounds for cyclotomic numbers $(a,b)$ of order $e$ over the finite field $mathbb{F}_q$. A general result of our study is that $(a,b)leq 3$ for all $a,b in mathbb{Z}$ if $p> (sqrt{14})^{k/ord_k(p)}$. More conclusive results will be obtained through separate investigation of the five types of cyclotomic numbers: $(0,0), (0,a), (a,0), (a,a)$ and $(a,b)$, where $a eq b$ and $a,b in {1,dots,e-1}$. The main idea we use is to transform equations over $mathbb{F}_q$ into equations over the field of complex numbers on which we have more information. A major tool for the improvements we obtain over known results is new upper bounds on the norm of cyclotomic integers.
We look at upper bounds for the count of certain primes related to the Fermat numbers $F_n=2^{2^n}+1$ called elite primes. We first note an oversight in a result of Krizek, Luca and Somer and give the corrected, slightly weaker upper bound. We then assume the Generalized Riemann Hypothesis for Dirichlet L functions and obtain a stronger conditional upper bound.
We study Ramseys theorem for pairs and two colours in the context of the theory of $alpha$-large sets introduced by Ketonen and Solovay. We prove that any $2$-colouring of pairs from an $omega^{300n}$-large set admits an $omega^n$-large homogeneous set. We explain how a formalized version of this bound gives a more direct proof, and a strengthening, of the recent result of Patey and Yokoyama [Adv. Math. 330 (2018), 1034--1070] stating that Ramseys theorem for pairs and two colours is $forallSigma^0_2$-conservative over the axiomatic theory $mathsf{RCA}_0$ (recursive comprehension).
We study the extremal Betti numbers of the class of $t$--spread strongly stable ideals. More precisely, we determine the maximal number of admissible extremal Betti numbers for such ideals, and thereby we generalize the known results for $tin {1,2}$.
In this (mostly historical) note we show how a unified Kummer-Artin-Schreier sequence from [W], [SOS] may be recovered from the relativistic velocity addition law.
The Apery numbers $A_n$ and the Franel numbers $f_n$ are defined by $$A_n=sum_{k=0}^{n}{binom{n+k}{2k}}^2{binom{2k}{k}}^2 {rm and } f_n=sum_{k=0}^{n}{binom{n}{k}}^3(n=0, 1, cdots,).$$ In this paper, we prove three supercongruences for Apery numbers or Franel numbers conjectured by Z.-W. Sun. Let $pgeq 5$ be a prime and let $nin mathbb{Z}^{+}$. We show that begin{align} otag frac{1}{n}bigg(sum_{k=0}^{pn-1}(2k+1)A_k-psum_{k=0}^{n-1}(2k+1)A_kbigg)equiv0pmod{p^{4+3 u_p(n)}} end{align} and begin{align} otag frac{1}{n^3}bigg(sum_{k=0}^{pn-1}(2k+1)^3A_k-p^3sum_{k=0}^{n-1}(2k+1)^3A_kbigg)equiv0pmod{p^{6+3 u_p(n)}}, end{align} where $ u_p(n)$ denotes the $p$-adic order of $n$. Also, for any prime $p$ we have begin{align} otag frac{1}{n^3}bigg(sum_{k=0}^{pn-1}(3k+2)(-1)^kf_k-p^2sum_{k=0}^{n-1}(3k+2)(-1)^kf_kbigg)equiv0pmod{p^{3}}. end{align}