Daniel Duverney, Takeshi Kurosawa, Iekata Shiokawa
We compute the exact irrationality exponents of certain series of rational numbers, first studied in a special case by Hone, by transforming them into suitable continued fractions.
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We prove that the formula giving the exact value of the irrationality exponent of regular continued fractions remains valid for semi-regular continued fractions satisfyiong certain conditions.
We prove that a real number a greater than or equal to 2 is the irrationality exponent of some computable real number if and only if a is the upper limit of a computable sequence of rational numbers. Thus, there are computable real numbers whose irrationality exponent is not computable.
We study how the asymptotic irrationality exponent of a given generalized continued fraction \[ \K_{n=1}^\infty \frac{a_n}{b_n}\,,\quad a_n, b_n\in \mathbb{Z}^+, \] behaves as a function of growth properties of partial coefficient sequences $(a_n)$ and $(b_n)$.
We consider Mahler functions $f(z)$ which solve the functional equation $f(z) = \frac{A(z)}{B(z)} f(z^d)$ where $\frac{A(z)}{B(z)}\in \mathbb{Q}(z)$ and $d\ge 2$ is integer. We prove that for any integer $b$ with $|b|\ge 2$ either $f(b)$ is rational or its irrationality exponent is rational. We also compute the exact value of the irrationality exponent for $f(b)$ as soon as the continued fraction for the corresponding Mahler function is known. This improves the result of Bugeaud, Han, Wei and Yao where only an upper bound for the irrationality exponent was provided.
In this paper, improving the method of Allouche \emph{et al.} \cite{APWW98}, we calculate the Hankel determinant of the regular paperfolding sequence, and prove that the Hankel determinant sequence module 2 is periodic with period 10 which answers Coon's conjecture \cite{CV12}. Then we extend Bugeaud's method \cite{Bugeaud11} to obatin the exact value of the irrationality exponent for some general transcendental numbers. Using the results above, we prove that the irrationality exponents of the regular paperfolding numbers are exactly 2.
We provide an upper bound on the efficient irrationality exponents of cubic algebraics $x$ with the minimal polynomial $x^3 - tx^2 - a$. In particular, we show that it becomes non-trivial, i.e. better than the classical bound of Liouville in the case $|t| > 19.71 a^{4/3}$. Moreover, under the condition $|t| > 86.58 a^{4/3}$, we provide an explicit lower bound on the expression $||qx||$ for all large $q\in\mathbb{Z}$. These results are based on the recently discovered continued fractions of cubic irrationals and improve the currently best-known bounds of Wakabayashi.
On the Irrationality Exponents of Mahler Numbers
本文探讨了满足特定函数方程的 Mahler 数，利用形式 Laurent 级数的连分数开发了计算其无理指数的程序，并扩展了 Badziahin 在 $C(z)=0$ 条件下的研究。
On the $b$-ary expansion of a real number whose irrationality exponent is close to 2
研究实数的$b$-进制展开的复杂性，证明当无理性指数小于2.324时，展开不能过于简单，改进了之前的结论。
In math.NT/0307308 we defined the irrationality base of an irrational number and, assuming a stronger hypothesis than the irrationality of Euler's constant, gave a conditional upper bound on its irrationality base. Here we develop the general theory of the irrationality exponent and base, giving formulas and bounds for them using continued fractions and the Fibonacci sequence. A theorem of Jarnik on Diophantine approximation yields numbers with prescribed irrationality measure. By another method we explicitly construct series with prescribed irrationality base. Many examples are given.
We introduce and study a new complexity function in combinatorics on words, which takes into account the smallest second occurrence time of a factor of an infinite word. We characterize the eventually periodic words and the Sturmian words by means of this function. Then, we establish a new result on repetitions in Sturmian words and show that it is best possible. Let $b \ge 2$ be an integer. We deduce a lower bound for the irrationality exponent of real numbers whose sequence of $b$-ary digits is a Sturmian sequence over $\{0,1,\ldots, b-1\}$ and we prove that this lower bound is best possible…
Let $ξ$ be a real irrational number. We are interested in sequences of linear forms in 1 and $ξ$, with integer coefficients, which tend to 0. Does such a sequence exist such that the linear forms are small (with given rate of decrease) and the coefficients have some given rate of growth? If these rates are essentially geometric, a necessary condition for such a sequence to exist is that the linear forms are not too small, a condition which can be expressed precisely using the irrationality exponent of $ξ$. We prove that this condition is actually sufficient, even for arbitrary rates of growth …
Exponential Sums by Irrationality Exponent
本文针对固定无理数$α$的莫比乌斯函数指数和，基于$α$的无理性指数$η$给出渐近界：$η≤5/2$时为$x^{4/5+ε}$，$η≥5/2$时为$x^{(2η-1)/2η+ε}$，扩展了Murty和Sankaranarayanan在$η=2$时的成果。
We prove that the sum of the series $\sum_{n=0}^{\infty}\, p^{v_p(n!)}$ is a $p$-adic irrational for all primes $p$, where $v_p(n!)$ denotes the exponent of the highest power of $p$ dividing $n!$.
We generalize the classical theorem by Jarnik and Besicovitch on the irrationality exponents of real numbers and Hausdorff dimension. Let a be any real number greater than or equal to 2 and let b be any non-negative real less than or equal to 2/a. We show that there is a Cantor-like set with Hausdorff dimension equal to b such that, with respect to its uniform measure, almost all real numbers have irrationality exponent equal to a. We give an analogous result relating the irrationality exponent and the effective Hausdorff dimension of individual real numbers. We prove that there is a Cantor-li…
A new upper bound for the irrationality exponent of zeta(3)
本文通过应用Rhin-Viola定理5.1于新的积分方向，将zeta(3)的无理性指数上界改进至5.5138800，优于此前保持25年的最佳结果，并指出Rhin-Viola点并非全局最优。
A new upper bound for the irrationality exponent of $ζ(2)$
本文通过新的参数选择利用Zudilin的两个超几何构造，证明了ζ(2)的无理指数小于5.0193784，改进了已有界限，并利用算术与解析界比较验证了关键恒等式。
Continued fractions and irrationality exponents for modified Engel and Pierce series
本文研究有理数与修正 Engel 或 Pierce 级数组合生成的超越数，利用二阶非线性递推确定其连分数展开，并给出无理性指数下界及可精确计算的无穷族。
The irrationality exponent $μ(t)$ of an irrational number t, defined using the irrationality measure $1/q^μ$, distinguishes among non-Liouville numbers and is infinite for Liouville numbers. Using the irrationality measure $1/β^q$, we define the "irrationality base" $β(t)$, which distinguishes among Liouville numbers and is 1 for non-Liouville numbers. We give some properties and examples. Assuming a condition on certain linear forms in logarithms, for which we present numerical evidence supplied by P. Sebah, we prove an upper bound on the irrationality base of Euler's constant, $γ$. If $γ$ is…
We shall present effective approximations measures for certain infinite products related to $q$-exponential function. There are two main targets. First we shall prove an explicit irrationality measure result for the values of $q$-exponential function at rational points. Then, if we restrict the approximations to rational numbers of the shape $d^s/N$, we may replace Bundschuh's irrationality exponent $7/3$ by $2+\frac{1}{3+2\sqrt 3}=2.1547...$.
The irrationality exponent of an irrational number $ξ$, which measures the approximation rate of $ξ$ by rationals, is in general extremely difficult to compute explicitly, unless we know the continued fraction expansion of $ξ$. Results obtained so far are rather fragmentary, and often treated case by case. In this work, we shall unify all the known results on the subject by showing that the irrationality exponents of large classes of automatic numbers and Mahler numbers (which are transcendental) are exactly equal to $2$. Our classes contain the Thue--Morse--Mahler numbers, the sum of the reci…
Based on the structure of Fibonacci sequence, we give a new proof for the irrationality exponents of the Fibonacci real numbers. Moreover, we obtain all the irrationality exponents of the real numbers corresponding to the differences of Fibonacci sequence.
Classical and uniform exponents of multiplicative $p$-adic approximation
本文研究乘法 $p$-进逼近的无理指数，证明乘法与经典无理指数之比可任意取 $[1,2]$ 中值，并给出一致乘法指数的新上界 $(5+\sqrt{5})/2$。
We prove the new upper bound 5.095412 for the irrationality exponent of $ζ(2)=π^2/6$; the earlier record bound 5.441243 was established in 1996 by G. Rhin and C. Viola.
On the irrationality exponent of real numbers with low complexity expansion
研究实数展开的子词复杂度与其无理数指数的关系，证明当无理数指数为2时，子词复杂度序列的极限上界不低于4/3。
Irrationality Exponents and Partial Quotient Growth in Continued Fractions
本文研究连分数展开中部分商在对数尺度下的增长率与其相对分母的上增长率之间的相互作用，确定了联合水平集的 Hausdorff 维数，推广了无理性指数与部分商增长的相关经典结果。
In the literature, we have various ways of proving irrationality of a real number. In this survey article, we shall emphasize on a particular criterion to prove irrationality. This is called nice approximation of a number by a sequence of rational numbers. This criterion of irrationality is easy to prove and is of great importance. Using it, irrationality of a large class of numbers is proved. We shall apply this method to prove irrationality of algebraic, exponential and trigonometric irrational numbers. Most of the times, explicit constructions are done of the nice sequence of rational numbe…
Irrationality exponents of logarithms of positive rational numbers
本文通过分离权重行列式论证，证明任意正有理数 r≠1 的对数的无理性指数 μ(log r)=2，并给出完整参数选择与估计，附带几何推广及有限度界。
Hausdorff dimension of intersections between the Jarník sets and Diophantine fractals
研究了Jarník集与迪奥菲内分数集合交集的Hausdorff维度，证明其为满维，并指出无理数指数大于2且部分商有界的集合维度为1。
In this paper we give a general upper bound for the irrationality exponent of algebraic Laurent series with coefficients in a finite field. Our proof is based on a method introduced in a different framework by Adamczewski and Cassaigne. It makes use of automata theory and, in our context, of a classical theorem due to Christol. We then introduce a new approach which allows us to strongly improve this general bound in many cases. As an illustration, we give few examples of algebraic Laurent series for which we are able to compute the exact value of the irrationality exponent.
Let $b \ge 2$ be an integer and $ξ$ an irrational real number. We prove that, if the irrationality exponent of $ξ$ is equal to $2$ or slightly greater than $2$, then the $b$-ary expansion of $ξ$ cannot be `too simple', in a suitable sense. Our result applies, among other classical numbers, to badly approximable numbers, non-zero rational powers of ${\mathrm e}$, and $\log (1 + \frac{1}{a})$, provided that the integer $a$ is sufficiently large. It establishes an unexpected connection between the irrationality exponent of a real number and its $b$-ary expansion.
In this paper we study the three-dimensional analogue of the relation between the irrationality exponent of a real number and the growth of its regular continued fraction partial quotients. As a multidimensional generalisation of continued fractions, we consider Klein polyhedra.
Metric results on sumsets and Cartesian products of classes of Diophantine sets
受Erdős关于刘维尔数和积结果启发，研究指定无理性指数实数类和集的度量性质，证明其和集勒贝格测度下几乎覆盖全体实数，补集豪斯多夫维数小，还拓展到笛卡尔积维数、缺数字康托尔集填充维数等问题，推广了Erdős的方法。
We present a hypergeometric construction of rational approximations to $ζ(2)$ and $ζ(3)$ which allows one to demonstrate simultaneously the irrationality of each of the zeta values, as well as to estimate from below certain linear forms in 1, $ζ(2)$ and $ζ(3)$ with rational coefficients. A new notion of (simultaneous) diophantine exponent is introduced to formalise the arithmetic structure of these specific linear forms. Finally, the properties of this newer concept are studied and linked to the classical irrationality exponent and its generalisations given recently by S. Fischler.
We investigate the continued fraction expansion of the infinite products $g(x) = x^{-1}\prod_{t=0}^\infty P(x^{-d^t})$ where polynomials $P(x)$ satisfy $P(0)=1$ and $°(P)<d$. We construct relations between partial quotients of $g(x)$ which can be used to get recurrent formulae for them. We provide that formulae for the cases $d=2$ and $d=3$. As an application, we prove that for $P(x) = 1+ux$ where $u$ is an arbitrary rational number except 0 and 1, and for any integer $b$ with $|b|>1$ such that $g(b)\neq0$ the irrationality exponent of $g(b)$ equals two. In the case $d=3$ we provide a partial …
Extravagance, irrationality and Diophantine approximation
该研究探讨高斯映射下测度与丢番图逼近的关系，证明部分商对数不可积的连分数混合测度下几乎所有数为刘维尔数，构造任意无理性指数的高斯不变遍历测度，并给出弱Renyi测度下的辛钦型二分法。
Let $\C{G}(z):=\sum_{n=0}^\infty z^{2^n}(1-z^{2^n})^{-1}$ denote the generating function of the ruler function, and $\C{F}(z):=\sum_{n=0}^\infty z^{2^n}(1+z^{2^n})^{-1}$; note that the special value $\C{F}(1/2)$ is the sum of the reciprocals of the Fermat numbers $F_n:=2^{2^n}+1$. The functions $\C{F}(z)$ and $\C{G}(z)$ as well as their special values have been studied by Mahler, Golomb, Schwarz, and Duverney; it is known that the numbers $\C{F}(\ga)$ and $\C{G}(\ga)$ are transcendental for all algebraic numbers $\ga$ which satisfy $0<\ga<1$. For a sequence $\mathbf{u}$, denote the Hankel matr…
Construction of subspaces with known Diophantine exponents for the last angle
本文利用数的几何方法，构造了 $\R^n$ 中能够计算最后一个角度关联丢番图指数的线性子空间，推广了实数的无理性测度。
Initial nonrepetitive complexity of regular episturmian words and their Diophantine exponents
本文提出评估正则 episturmian 词初始非重复复杂度的方法，发展广义 Ostrowski 记数系统理论，并以此刻画其丢番图指数的有限性与下界，进而发现无理指数严格大于2的新不可数超越数类。
Padé approximation for a class of hypergeometric functions and parametric geometry of numbers
本文通过形式方法构造一类超几何函数的Padé逼近，建立有效Poincaré-Perron定理，获得二项式函数值的有效无理测度，并利用参数几何证明联立逼近定理。
As a corollary of the main result of our recent paper, {\em On the rational approximation of the sum of the reciprocals of the Fermat numbers} published in this same journal, we prove that for each integer $b\geq 2$ the irrationality exponent of $\sum_{n\geqslant 0} s_2(n)/b^n$ is equal to $2$.
On several irrationality problems for Ahmes series
本文利用数学分析与概率论工具研究了单位分数级数的无理性问题，构造了双指数增长序列并推广至多级数情形，同时解决了Erdős、Straus和Stolarsky的相关猜想。
We establish a general transference principle for the irrationality measure of points with $\mathbb{Q}$-linearly independent coordinates in $\mathbb{R}^{n+1}$, for any given integer $n\geq 1$. On this basis, we recover an important inequality of Marnat and Moshchevitin which describes the spectrum of the pairs of ordinary and uniform exponents of rational approximation to those points. For points whose pair of exponents are close to the boundary in the sense that they almost realize the equality, we provide additional information about the corresponding sequence of best rational approximations…
Irrationality of rapidly converging series: a problem of Erdős and Graham
该研究证明了满足双指数增长条件的级数求和结果为无理数，并探讨了其推广形式及最优性。
Modular Forms and Numerical Explorations of Rational Approximations to $ζ(3)$
通过辅助权重二模形式重新审视Beukers对ζ(3)无理性的证明，展示其属于一个参数仿射族，并应用于其他零亏格Fricke群。
Let $p$ be a prime number and $ξ$ an irrational $p$-adic number. Its multiplicative irrationality exponent ${μ^{\times}} (ξ)$ is the supremum of the real numbers ${μ^{\times}}$ for which the inequality $$ |b ξ- a|_{p} \leq | a b |^{- {μ^{\times}} / 2} $$ has infinitely many solutions in nonzero integers $a, b$. We show that ${μ^{\times}} (ξ)$ can be expressed in terms of a new exponent of approximation attached to a sequence of rational numbers defined in terms of $ξ$. We establish that ${μ^{\times}} ({{ξ_{{\bf t}, p}}}) = 3$, where ${{ξ_{{\bf t}, p}}}$ is the $p$-adic number $1 - p - p^2 + p^…
Let $θ$ and $ρ$ be real numbers with $0 \le θ, ρ< 1$ and $θ$ irrational. We show that the Hecke-Mahler series $$ F_{θ, ρ} (z_1, z_2) = \sum_{k_1 \ge 1} \, \sum_{k_2 = 1}^{\lfloor k_1 θ+ ρ\rfloor} \, z_1^{k_1} z_2^{k_2}, $$ where $\lfloor \cdot \rfloor$ denotes the integer part function, takes transcendental values at any algebraic point $(β, α)$ with $0 < |β|, |βα^θ| < 1$. This extends earlier results of Mahler (1929) and Loxton and van der Poorten (1977), who settled the case $ρ=0$. Furthermore, for positive integers $b$ and $a$, with $b \ge 2$ and $a$ congruent to $1$ modulo $b-1$, we give t…
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