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Let $L$ be a number field and let $E/L$ be an elliptic curve with complex multiplication by the ring of integers $\mathcal{O}_K$ of an imaginary quadratic field $K$. We use class field theory and results of Skorobogatov and Zarhin to…

Number Theory · Mathematics 2024-06-21 Rachel Newton

We show that if over some number field there exists a certain diagonal plane cubic curve that is locally solvable everywhere, but that does not have points over any cubic galois extension of the number field, then the algebraic part of the…

Number Theory · Mathematics 2007-08-22 Ronald van Luijk

We study the Brauer groups of affine surfaces that are complements of singular hyperplane sections of smooth cubic surfaces over a field $k$ of characteristic $0$. We determine the Brauer group over the algebraic closure as a Galois module…

Algebraic Geometry · Mathematics 2025-10-30 Abdulmuhsin Alfaraj

We exhibit central simple algebras over the function field of a diagonal quartic surface over the complex numbers that represent the 2-torsion part of its Brauer group. We investigate whether the 2-primary part of the Brauer group of a…

Number Theory · Mathematics 2009-11-09 Evis Ieronymou

We study the Brauer groups of regular conic bundles over elliptic curves defined over a number field $k$. We explicitly compute the Brauer group of the conic bundle when the singular fibres lie above $k$-points that are divisible by $2$ in…

Algebraic Geometry · Mathematics 2025-09-22 Abdulmuhsin Alfaraj

Let E and E' be elliptic curves over Q with complex multiplication by the ring of integers of an imaginary quadratic field K and let Y=Kum(ExE') be the minimal desingularisation of the quotient of ExE' by the action of -1. We study the…

Number Theory · Mathematics 2025-01-03 Mohamed Alaa Tawfik , Rachel Newton

We present a method for calculating the Brauer group of a surface given by a diagonal equation in the projective space. For diagonal quartic surfaces with coefficients in Q we determine the Brauer groups over Q and Q(i).

Algebraic Geometry · Mathematics 2023-05-22 Damián Gvirtz-Chen , Alexei N. Skorobogatov

Let $X$ be a K3 surface defined over a number field $k$, with principal complex multiplication by a CM field $E$. We find explicit bounds, in terms of $k$ and $E$, on the size of the transcendental Brauer group…

Number Theory · Mathematics 2025-02-14 Sebastian Monnet

Let k be a field with char(k) not 2 or 3. Let C_f be the projective curve of a binary cubic form f, and k(C_f) the function field of C_f. In this paper we explicitly describe the relative Brauer group Br(k(C_f)/k) of k(C_f) over k. When f…

Rings and Algebras · Mathematics 2010-04-07 Darrell E. Haile , Ilseop Han , Adrian R. Wadsworth

We relate the Brauer group of a Kummer surface to the Brauer group of the corresponding abelian surface. For many pairs of elliptic curves over the rational numbers we prove that the Kummer surface attached to their product has trivial…

Algebraic Geometry · Mathematics 2010-11-09 Alexei N. Skorobogatov , Yuri G. Zarhin

The distribution of degree $d$ points on curves is well understood, especially for low degrees. We refine this study to include information on the Galois group in the simplest interesting case: $d = 3$. For curves of genus at least 5, we…

Number Theory · Mathematics 2025-10-13 James Rawson

We obtain an easy sufficient condition for the Brauer group of a diagonal quartic surface D over Q to be algebraic. We also give an upper bound for the order of the quotient of the Brauer group of D by the image of the Brauer group of Q.…

Algebraic Geometry · Mathematics 2014-02-26 Evis Ieronymou , Alexei N. Skorobogatov , Yuri G. Zarhin

Let $k$ be a number field. We give an explicit bound, depending only on $[k:\mathbf{Q}]$ and the discriminant of the N\'{e}ron--Severi lattice, on the size of the Brauer group of a K3 surface $X/k$ that is geometrically isomorphic to the…

Number Theory · Mathematics 2022-08-08 Francesca Balestrieri , Alexis Johnson , Rachel Newton

We present a method to construct non-singular cubic surfaces over $\bbQ$ with a Galois invariant pair of Steiner trihedra. We start with cubic surfaces in a form generalizing that of A. Cayley and G. Salmon. For these, we develop an…

Algebraic Geometry · Mathematics 2010-06-09 Andreas-Stephan Elsenhans , Jörg Jahnel

In this paper we study the existence of rational points for the family of K3 surfaces over $\mathbb{Q}$ given by $$w^2 = A_1x_1^6 + A_2x_2^6 + A_3x_3^6.$$ When the coefficients are ordered by height, we show that the Brauer group is almost…

Number Theory · Mathematics 2023-05-22 Damián Gvirtz-Chen , Daniel Loughran , Masahiro Nakahara

We prove that the transcendental Brauer group of a K3 surface X over a finitely generated field k is finite, unless k has positive characteristic p and X is supersingular, in which case it is annihilated by p.

Algebraic Geometry · Mathematics 2025-10-03 Christopher D. Lazda , Alexei N. Skorobogatov

We derive a formula for the unramified Brauer group of a general class of rationally connected fourfolds birational to conic bundles over smooth threefolds. We produce new examples of conic bundles over P^3 where this formula applies and…

Algebraic Geometry · Mathematics 2020-08-03 Asher Auel , Christian Böhning , Hans-Christian Graf v. Bothmer , Alena Pirutka

We study K3 surfaces with complex multiplication following the classical work of Shimura on CM abelian varieties. After we translate the problem in terms of the arithmetic of the CM field and its id\`{e}les, we proceed to study some abelian…

Number Theory · Mathematics 2021-06-11 Domenico Valloni

We give explicit uniform bounds for several quantities relevant to the study of Galois representations attached to elliptic curves $E/\mathbb Q$. We consider in particular the subgroup of scalars in the image of Galois, the first Galois…

Number Theory · Mathematics 2022-10-19 Davide Lombardo , Sebastiano Tronto

This article computes the Galois groups of congruence covers arising in the context of certain hyperbolic triangle groups. As a consequence of this computation, the genera of the respective curves are deduced.

Number Theory · Mathematics 2015-03-03 Luiz Kazuo Takei
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