No Arabic abstract
In recent work, Sun constructed two $q$-series, and he showed that their limits as $qrightarrow1$ give new derivations of the Riemann-zeta values $zeta(2)=pi^2/6$ and $zeta(4)=pi^4/90$. Goswami extended these series to an infinite family of $q$-series, which he analogously used to obtain new derivations of the evaluations of $zeta(2k)inmathbb{Q}cdotpi^{2k}$ for every positive integer $k$. Since it is well known that $Gammaleft(frac{1}{2}right)=sqrt{pi}$, it is natural to seek further specializations of these series which involve special values of the $Gamma$-function. Thanks to the theory of complex multiplication, we show that the values of these series at all CM points $tau$, where $q:=e^{2pi itau}$, are algebraic multiples of specific ratios of $Gamma$-values. In particular, classical formulas of Ramanujan allow us to explicitly evaluate these series as algebraic multiples of powers of $Gammaleft(frac{1}{4}right)^4/pi^3$ when $q=e^{-pi}$, $e^{-2pi}$.
In this paper, we use Abels summation formula to evaluate several quadratic and cubic sums of the form: [{F_N}left( {A,B;x} right) := sumlimits_{n = 1}^N {left( {A - {A_n}} right)left( {B - {B_n}} right){x^n}} ,;x in [ - 1,1]] and [Fleft( {A,B,zeta (r)} right): = sumlimits_{n = 1}^infty {left( {A - {A_n}} right)left( {B - {B_n}} right)left( {zeta left( r right) - {zeta_n}left( r right)} right)} ,] where the sequences $A_n,B_n$ are defined by the finite sums ${A_n} := sumlimits_{k = 1}^n {{a_k}} , {B_n} := sumlimits_{k = 1}^n {{b_k}} ( {a_k},{b_k} =o(n^{-p}),{mathop{Re} olimits} left( p right) > 1 $) and $A = mathop {lim }limits_{n to infty } {A_n},B = mathop {lim }limits_{n to infty } {B_n},Fleft( {A,B;x} right) = mathop {lim }limits_{n to infty } {F_n}left( {A,B;x} right)$. Namely, the sequences $A_n$ and $B_n$ are the partial sums of the convergent series $A$ and $B$, respectively. We give an explicit formula of ${F_n}left( {A,B;x} right)$ by using the method of Abels summation formula. Then we use apply it to obtain a family of identities relating harmonic numbers to multiple zeta values. Furthermore, we also evaluate several other series involving multiple zeta star values. Some interesting (known or new) consequences and illustrative examples are considered.
We study several variants of Euler sums by using the methods of contour integration and residue theorem. These variants exhibit nice properties such as closed forms, reduction, etc., like classical Euler sums. In addition, we also define a variant of multiple zeta values of level 2, and give some identities on relations between these variants of Euler sums and the variant of multiple zeta values.
We give a formula for the class number of an arbitrary CM algebraic torus over $mathbb{Q}$. This is proved based on results of Ono and Shyr. As applications, we give formulas for numbers of polarized CM abelian varieties, of connected components of unitary Shimura varieties and of certain polarized abelian varieties over finite fields. We also give a second proof of our main result.
In this paper, we consider some CM fields which we call of dihedral type and compute the Artin $L$-functions associated to all CM types of these CM fields. As a consequence of this calculation, we see that the Colmez conjecture in this case is very closely related to understanding the log derivatives of certain Hecke characters of real quadratic fields. Recall that the `abelian case of the Colmez conjecture, proved by Colmez himself, amounts to understanding the log derivatives of Hecke characters of $Q$ (cyclotomic characters). In this paper, we also prove that the Colmez conjecture holds for `unitary CM types of signature $(n-1, 1)$ and holds on average for `unitary CM types of a fixed CM number field of signature $(n-r, r)$.
For $xin (0,1)$, let $langle d_1(x),d_2(x),d_3(x),cdots rangle$ be the Engel series expansion of $x$. Denote by $lambda(x)$ the exponent of convergence of the sequence ${d_n(x)}$, namely begin{equation*} lambda(x)= infleft{s geq 0: sum_{n geq 1} d^{-s}_n(x)<inftyright}. end{equation*} It follows from ErdH{o}s, R{e}nyi and Sz{u}sz (1958) that $lambda(x) =0$ for Lebesgue almost all $xin (0,1)$. This paper is concerned with the topological and fractal properties of the level set ${xin (0,1): lambda(x) =alpha}$ for $alpha in [0,infty]$. For the topological properties, it is proved that each level set is uncountable and dense in $(0,1)$. Furthermore, the level set is of the first Baire category for $alphain [0,infty)$ but residual for $alpha =infty$. For the fractal properties, we prove that the Hausdorff dimension of the level set is as follows: [ dim_{rm H} big{x in (0,1): lambda(x) =alphabig}=dim_{rm H} big{x in (0,1): lambda(x) geqalphabig}= left{ begin{array}{ll} 1-alpha, & hbox{$0leq alphaleq1$;} 0, & hbox{$1<alpha leq infty$.} end{array} right. ]