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Papers by Manuel O'Ryan

Research paper thumbnail of On the Similarity Group of Forms of Higher Degree

Journal of Algebra, Sep 1, 1994

Research paper thumbnail of Transfer for Kato-Milne cohomology over purely inseparable extensions

Journal of Pure and Applied Algebra, Aug 1, 2022

Research paper thumbnail of The behavior of differential forms under purely inseparable extensions

Journal of Pure and Applied Algebra, 2019

Research paper thumbnail of Hermite's Constant for Quadratic Number Fields

Experimental Mathematics, 2001

Research paper thumbnail of Cohomological kernels of mixed extensions in characteristic 2

Research paper thumbnail of On trace forms of higher degree

Linear Algebra and its Applications, Oct 1, 1996

Research paper thumbnail of Centers of higher degree forms

Linear Algebra and its Applications, Sep 1, 2003

Research paper thumbnail of Cohomological kernels of non-normal extensions in characteristic two and indecomposable division algebras of index eight

Communications in Algebra, Nov 22, 2019

Research paper thumbnail of Lenstra's Constant and Extreme Forms in Number Fields

Experimental Mathematics, 2007

Research paper thumbnail of The de Rham Witt complex, cohomological kernels and p-extensions in characteristic p

Journal of Pure and Applied Algebra, Dec 1, 2018

Research paper thumbnail of Sums of squares of linear forms

Mathematische Zeitschrift, Jun 1, 1986

Research paper thumbnail of The Automorphism Group of Certain Higher Degree Forms

arXiv (Cornell University), Mar 20, 2007

Research paper thumbnail of Automorphism Groups of Higher Degree Forms

arXiv (Cornell University), Mar 20, 2007

Research paper thumbnail of Products of higher degree forms

Linear & Multilinear Algebra, Nov 28, 2013

ABSTRACT We consider -linear () spaces of dimension over an algebraically closed field of charact... more ABSTRACT We consider -linear () spaces of dimension over an algebraically closed field of characteristic 0, whose centre (the analogue of the space of symmetric matrices of a bilinear form) is maximal, as a subalgebra of In a previous work (with S. Ryom-Hansen), we found several properties of the orthogonal group of d-linear spaces whose centre consists of powers of a single lineal map acting cyclically on the underlying vector space, called cyclic spaces. We extend those results to tensor products of cyclic spaces. In particular, we give a description of the orthogonal group of the product of two cyclic spaces.

Research paper thumbnail of Centers of higher degree trace forms

Journal of Pure and Applied Algebra, Dec 1, 2013

Research paper thumbnail of Cohomological kernels of non-normal extensions in characteristic two and indecomposable division algebras of index eight

Communications in Algebra

Abstract This article investigates the cohomological kernels of field extensions E/F in character... more Abstract This article investigates the cohomological kernels of field extensions E/F in characteristic two where separable part of E is a quadratic extension and E is quadratic or quartic and purely inseparable over Explicit generators for these kernels are described in both the normal and non-normal cases. The second part of the article gives a construction of an indecomposable division algebra D of index 8 and exponent 2 in characteristic two. The non-normal extensions E/F just considered can arise as maximal subfields of D while in the normal case such a maximal subfield will force a division algebra of exponent 2 to decompose.

Research paper thumbnail of Cohomological kernels of purely inseparable field extensions

Pacific Journal of Mathematics

Research paper thumbnail of Products of higher degree forms

Linear and Multilinear Algebra, 2013

ABSTRACT We consider -linear () spaces of dimension over an algebraically closed field of charact... more ABSTRACT We consider -linear () spaces of dimension over an algebraically closed field of characteristic 0, whose centre (the analogue of the space of symmetric matrices of a bilinear form) is maximal, as a subalgebra of In a previous work (with S. Ryom-Hansen), we found several properties of the orthogonal group of d-linear spaces whose centre consists of powers of a single lineal map acting cyclically on the underlying vector space, called cyclic spaces. We extend those results to tensor products of cyclic spaces. In particular, we give a description of the orthogonal group of the product of two cyclic spaces.

Research paper thumbnail of On trace forms of higher degree

Linear Algebra and its Applications, 1996

Research paper thumbnail of The automorphism group of certain higher degree forms

Journal of Pure and Applied Algebra, 2009

Research paper thumbnail of On the Similarity Group of Forms of Higher Degree

Journal of Algebra, Sep 1, 1994

Research paper thumbnail of Transfer for Kato-Milne cohomology over purely inseparable extensions

Journal of Pure and Applied Algebra, Aug 1, 2022

Research paper thumbnail of The behavior of differential forms under purely inseparable extensions

Journal of Pure and Applied Algebra, 2019

Research paper thumbnail of Hermite's Constant for Quadratic Number Fields

Experimental Mathematics, 2001

Research paper thumbnail of Cohomological kernels of mixed extensions in characteristic 2

Research paper thumbnail of On trace forms of higher degree

Linear Algebra and its Applications, Oct 1, 1996

Research paper thumbnail of Centers of higher degree forms

Linear Algebra and its Applications, Sep 1, 2003

Research paper thumbnail of Cohomological kernels of non-normal extensions in characteristic two and indecomposable division algebras of index eight

Communications in Algebra, Nov 22, 2019

Research paper thumbnail of Lenstra's Constant and Extreme Forms in Number Fields

Experimental Mathematics, 2007

Research paper thumbnail of The de Rham Witt complex, cohomological kernels and p-extensions in characteristic p

Journal of Pure and Applied Algebra, Dec 1, 2018

Research paper thumbnail of Sums of squares of linear forms

Mathematische Zeitschrift, Jun 1, 1986

Research paper thumbnail of The Automorphism Group of Certain Higher Degree Forms

arXiv (Cornell University), Mar 20, 2007

Research paper thumbnail of Automorphism Groups of Higher Degree Forms

arXiv (Cornell University), Mar 20, 2007

Research paper thumbnail of Products of higher degree forms

Linear & Multilinear Algebra, Nov 28, 2013

ABSTRACT We consider -linear () spaces of dimension over an algebraically closed field of charact... more ABSTRACT We consider -linear () spaces of dimension over an algebraically closed field of characteristic 0, whose centre (the analogue of the space of symmetric matrices of a bilinear form) is maximal, as a subalgebra of In a previous work (with S. Ryom-Hansen), we found several properties of the orthogonal group of d-linear spaces whose centre consists of powers of a single lineal map acting cyclically on the underlying vector space, called cyclic spaces. We extend those results to tensor products of cyclic spaces. In particular, we give a description of the orthogonal group of the product of two cyclic spaces.

Research paper thumbnail of Centers of higher degree trace forms

Journal of Pure and Applied Algebra, Dec 1, 2013

Research paper thumbnail of Cohomological kernels of non-normal extensions in characteristic two and indecomposable division algebras of index eight

Communications in Algebra

Abstract This article investigates the cohomological kernels of field extensions E/F in character... more Abstract This article investigates the cohomological kernels of field extensions E/F in characteristic two where separable part of E is a quadratic extension and E is quadratic or quartic and purely inseparable over Explicit generators for these kernels are described in both the normal and non-normal cases. The second part of the article gives a construction of an indecomposable division algebra D of index 8 and exponent 2 in characteristic two. The non-normal extensions E/F just considered can arise as maximal subfields of D while in the normal case such a maximal subfield will force a division algebra of exponent 2 to decompose.

Research paper thumbnail of Cohomological kernels of purely inseparable field extensions

Pacific Journal of Mathematics

Research paper thumbnail of Products of higher degree forms

Linear and Multilinear Algebra, 2013

ABSTRACT We consider -linear () spaces of dimension over an algebraically closed field of charact... more ABSTRACT We consider -linear () spaces of dimension over an algebraically closed field of characteristic 0, whose centre (the analogue of the space of symmetric matrices of a bilinear form) is maximal, as a subalgebra of In a previous work (with S. Ryom-Hansen), we found several properties of the orthogonal group of d-linear spaces whose centre consists of powers of a single lineal map acting cyclically on the underlying vector space, called cyclic spaces. We extend those results to tensor products of cyclic spaces. In particular, we give a description of the orthogonal group of the product of two cyclic spaces.

Research paper thumbnail of On trace forms of higher degree

Linear Algebra and its Applications, 1996

Research paper thumbnail of The automorphism group of certain higher degree forms

Journal of Pure and Applied Algebra, 2009

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