We use cookies to distinguish you from other users and to provide you with a better experience on our websites. Close this message to accept cookies or find out how to manage your cookie settings.
To save content items to your account,
please confirm that you agree to abide by our usage policies.
If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your account.
Find out more about saving content to .
To save content items to your Kindle, first ensure coreplatform@cambridge.org
is added to your Approved Personal Document E-mail List under your Personal Document Settings
on the Manage Your Content and Devices page of your Amazon account. Then enter the ‘name’ part
of your Kindle email address below.
Find out more about saving to your Kindle.
Note you can select to save to either the @free.kindle.com or @kindle.com variations.
‘@free.kindle.com’ emails are free but can only be saved to your device when it is connected to wi-fi.
‘@kindle.com’ emails can be delivered even when you are not connected to wi-fi, but note that service fees apply.
We investigate a novel geometric Iwasawa theory for
${\mathbf Z}_p$
-extensions of function fields over a perfect field k of characteristic
$p>0$
by replacing the usual study of p-torsion in class groups with the study of p-torsion class group schemes. That is, if
$\cdots \to X_2 \to X_1 \to X_0$
is the tower of curves over k associated with a
${\mathbf Z}_p$
-extension of function fields totally ramified over a finite nonempty set of places, we investigate the growth of the p-torsion group scheme in the Jacobian of
$X_n$
as
$n\rightarrow \infty $
. By Dieudonné theory, this amounts to studying the first de Rham cohomology groups of
$X_n$
equipped with natural actions of Frobenius and of the Cartier operator V. We formulate and test a number of conjectures which predict striking regularity in the
$k[V]$
-module structure of the space
$M_n:=H^0(X_n, \Omega ^1_{X_n/k})$
of global regular differential forms as
$n\rightarrow \infty .$
For example, for each tower in a basic class of
${\mathbf Z}_p$
-towers, we conjecture that the dimension of the kernel of
$V^r$
on
$M_n$
is given by
$a_r p^{2n} + \lambda _r n + c_r(n)$
for all n sufficiently large, where
$a_r, \lambda _r$
are rational constants and
$c_r : {\mathbf Z}/m_r {\mathbf Z} \to {\mathbf Q}$
is a periodic function, depending on r and the tower. To provide evidence for these conjectures, we collect extensive experimental data based on new and more efficient algorithms for working with differentials on
${\mathbf Z}_p$
-towers of curves, and we prove our conjectures in the case
$p=2$
and
$r=1$
.
By analogy with the trace of an algebraic integer
$\alpha $
with conjugates
$\alpha _1=\alpha , \ldots , \alpha _d$
, we define the G-measure
$ {\mathrm {G}} (\alpha )= \sum _{i=1}^d ( |\alpha _i| + 1/ | \alpha _i | )$
and the absolute
${\mathrm G}$
-measure
${\mathrm {g}}(\alpha )={\mathrm {G}}(\alpha )/d$
. We establish an analogue of the Schur–Siegel–Smyth trace problem for totally positive algebraic integers. Then we consider the case where
$\alpha $
has all its conjugates in a sector
$| \arg z | \leq \theta $
,
$0 < \theta < 90^{\circ }$
. We compute the greatest lower bound
$c(\theta )$
of the absolute G-measure of
$\alpha $
, for
$\alpha $
belonging to
$11$
consecutive subintervals of
$]0, 90 [$
. This phenomenon appears here for the first time, conforming to a conjecture of Rhin and Smyth on the nature of the function
$c(\theta )$
. All computations are done by the method of explicit auxiliary functions.
Let
$\alpha $
be a totally positive algebraic integer of degree d, with conjugates
$\alpha _1=\alpha , \alpha _2, \ldots , \alpha _d$
. The absolute
$S_k$
-measure of
$\alpha $
is defined by
$s_k(\alpha )= d^{-1} \sum _{i=1}^{d}\alpha _i^k$
. We compute the lower bounds
$\upsilon _k$
of
$s_k(\alpha )$
for each integer in the range
$2\leq k \leq 15$
and give a conjecture on the results for integers
$k>15$
. Then we derive the lower bounds of
$s_k(\alpha )$
for all real numbers
$k>2$
. Our computation is based on an improvement in the application of the LLL algorithm and analysis of the polynomials in the explicit auxiliary functions.
The Euler–Mascheroni constant
$\gamma =0.5772\ldots \!$
is the
$K={\mathbb Q}$
example of an Euler–Kronecker constant
$\gamma _K$
of a number field
$K.$
In this note, we consider the size of the
$\gamma _q=\gamma _{K_q}$
for cyclotomic fields
$K_q:={\mathbb Q}(\zeta _q).$
Assuming the Elliott–Halberstam Conjecture (EH), we prove uniformly in Q that
In other words, under EH, the
$\gamma _q /\!\log q$
in these ranges converge to the one point distribution at
$1$
. This theorem refines and extends a previous result of Ford, Luca and Moree for prime
$q.$
The proof of this result is a straightforward modification of earlier work of Fouvry under the assumption of EH.
When $p$ is an odd prime, Delbourgo observed that any Kubota–Leopoldt $p$-adic $L$-function, when multiplied by an auxiliary Euler factor, can be written as an infinite sum. We shall establish such expressions without restriction on $p$, and without the Euler factor when the character is non-trivial, by computing the periods of appropriate measures. As an application, we will reprove the Ferrero–Greenberg formula for the derivative $L_p'(0,\chi )$. We will also discuss the convergence of sum expressions in terms of elementary $p$-adic analysis, as well as their relation to Stickelberger elements; such discussions in turn give alternative proofs of the validity of sum expressions.
We prove that
$164\, 634\, 913$
is the smallest positive integer that is a sum of two rational sixth powers, but not a sum of two integer sixth powers. If
$C_{k}$
is the curve
$x^{6} + y^{6} = k$
, we use the existence of morphisms from
$C_{k}$
to elliptic curves, together with the Mordell–Weil sieve, to rule out the existence of rational points on
$C_{k}$
for various k.
Following Bridgeman, we demonstrate several families of infinite dilogarithm identities associated with Fibonacci numbers, Lucas numbers, convergents of continued fractions of even periods, and terms arising from various recurrence relations.
Let K be a number field, let A be a finite-dimensional K-algebra, let
$\operatorname {\mathrm {J}}(A)$
denote the Jacobson radical of A and let
$\Lambda $
be an
$\mathcal {O}_{K}$
-order in A. Suppose that each simple component of the semisimple K-algebra
$A/{\operatorname {\mathrm {J}}(A)}$
is isomorphic to a matrix ring over a field. Under this hypothesis on A, we give an algorithm that, given two
$\Lambda $
-lattices X and Y, determines whether X and Y are isomorphic and, if so, computes an explicit isomorphism
$X \rightarrow Y$
. This algorithm reduces the problem to standard problems in computational algebra and algorithmic algebraic number theory in polynomial time. As an application, we give an algorithm for the following long-standing problem: Given a number field K, a positive integer n and two matrices
$A,B \in \mathrm {Mat}_{n}(\mathcal {O}_{K})$
, determine whether A and B are similar over
$\mathcal {O}_{K}$
, and if so, return a matrix
$C \in \mathrm {GL}_{n}(\mathcal {O}_{K})$
such that
$B= CAC^{-1}$
. We give explicit examples that show that the implementation of the latter algorithm for
$\mathcal {O}_{K}=\mathbb {Z}$
vastly outperforms implementations of all previous algorithms, as predicted by our complexity analysis.
In [5], Chen and Yui conjectured that Gross–Zagier type formulas may also exist for Thompson series. In this work, we verify Chen and Yui’s conjecture for the cases for Thompson series
$j_{p}(\tau )$
for
$\Gamma _{0}(p)$
for p prime, and equivalently establish formulas for the prime decomposition of the resultants of two ring class polynomials associated to
$j_{p}(\tau )$
and imaginary quadratic fields and the prime decomposition of the discriminant of a ring class polynomial associated to
$j_{p}(\tau )$
and an imaginary quadratic field. Our method for tackling Chen and Yui’s conjecture on resultants can be used to give a different proof to a recent result of Yang and Yin. In addition, as an implication, we verify a conjecture recently raised by Yang, Yin, and Yu.
We consider the sum
$\sum 1/\gamma $
, where
$\gamma $
ranges over the ordinates of nontrivial zeros of the Riemann zeta-function in an interval
$(0,T]$
, and examine its behaviour as
$T \to \infty $
. We show that, after subtracting a smooth approximation
$({1}/{4\pi }) \log ^2(T/2\pi ),$
the sum tends to a limit
$H \approx -0.0171594$
, which can be expressed as an integral. We calculate H to high accuracy, using a method which has error
$O((\log T)/T^2)$
. Our results improve on earlier results by Hassani [‘Explicit approximation of the sums over the imaginary part of the non-trivial zeros of the Riemann zeta function’, Appl. Math. E-Notes16 (2016), 109–116] and other authors.
This paper starts from the observation that the standard arguments for compositionality are really arguments for the computability of semantics. Since computability does not entail compositionality, the question of what justifies compositionality recurs. The paper then elaborates on the idea of recursive semantics as corresponding to computable semantics. It is then shown by means of time complexity theory and with the use of term rewriting as systems of semantic computation, that syntactically unrestricted, noncompositional recursive semantics leads to computational explosion (factorial complexity). Hence, with combinatorially unrestricted syntax, semantics with tractable time complexity is compositional.
We give a new hypergeometric construction of rational approximations to ζ(4), which absorbs the earlier one from 2003 based on Bailey's 9F8 hypergeometric integrals. With the novel ingredients we are able to gain better control of the arithmetic and produce a record irrationality measure for ζ(4).
Let $f(x)=x^{6}+ax^{4}+bx^{2}+c$ be an irreducible sextic polynomial with coefficients from a field $F$ of characteristic $\neq 2$, and let $g(x)=x^{3}+ax^{2}+bx+c$. We show how to identify the conjugacy class in $S_{6}$ of the Galois group of $f$ over $F$ using only the discriminants of $f$ and $g$ and the reducibility of a related sextic polynomial. We demonstrate that our method is useful for producing one-parameter families of even sextic polynomials with a specified Galois group.
A Heron triangle is a triangle that has three rational sides $(a,b,c)$ and a rational area, whereas a perfect triangle is a Heron triangle that has three rational medians $(k,l,m)$. Finding a perfect triangle was stated as an open problem by Richard Guy [Unsolved Problems in Number Theory (Springer, New York, 1981)]. Heron triangles with two rational medians are parametrized by the eight curves $C_{1},\ldots ,C_{8}$ mentioned in Buchholz and Rathbun [‘An infinite set of heron triangles with two rational medians’, Amer. Math. Monthly104(2) (1997), 106–115; ‘Heron triangles and elliptic curves’, Bull. Aust. Math.Soc.58 (1998), 411–421] and Bácskái et al. [Symmetries of triangles with two rational medians, http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.65.6533, 2003]. In this paper, we reveal results on the curve $C_{4}$ which has the property of satisfying conditions such that six of seven parameters given by three sides, two medians and area are rational. Our aim is to perform an extensive search to prove the nonexistence of a perfect triangle arising from this curve.
A theorem of Gekeler compares the number of non-isomorphic automorphic representations associated with the space of cusp forms of weight $k$ on $\unicode[STIX]{x0393}_{0}(N)$ to a simpler function of $k$ and $N$, showing that the two are equal whenever $N$ is squarefree. We prove the converse of this theorem (with one small exception), thus providing a characterization of squarefree integers. We also establish a similar characterization of prime numbers in terms of the number of Hecke newforms of weight $k$ on $\unicode[STIX]{x0393}_{0}(N)$.
It follows that a hypothetical fast algorithm for computing the number of such automorphic representations for even a single weight $k$ would yield a fast test for whether $N$ is squarefree. We also show how to obtain bounds on the possible square divisors of a number $N$ that has been found not to be squarefree via this test, and we show how to probabilistically obtain the complete factorization of the squarefull part of $N$ from the number of such automorphic representations for two different weights. If in addition we have the number of such Hecke newforms for even a single weight $k$, then we show how to probabilistically factor $N$ entirely. All of these computations could be performed quickly in practice, given the number(s) of automorphic representations and modular forms as input.
We improve some previously known deterministic algorithms for finding integer solutions $x,y$ to the exponential equation of the form $af^{x}+bg^{y}=c$ over finite fields.
We record $\binom{42}{2}+\binom{23}{2}+\binom{13}{2}=1192$ functional identities that, apart from being amazingly amusing in themselves, find application in the derivation of Ramanujan-type formulas for $1/\unicode[STIX]{x1D70B}$ and in the computation of mathematical constants.
We use properties of the gamma function to estimate the products $\prod _{k=1}^{n}(4k-3)/4k$ and $\prod _{k=1}^{n}(4k-1)/4k$, motivated by the work of Chen and Qi [‘Completely monotonic function associated with the gamma function and proof of Wallis’ inequality’, Tamkang J. Math.36(4) (2005), 303–307] and Mortici et al. [‘Completely monotonic functions and inequalities associated to some ratio of gamma function’, Appl. Math. Comput.240 (2014), 168–174].