Invariants of binary forms

Popoviciu Draisma, Mihaela Ileana. Invariants of binary forms. 2014, PhD Thesis, University of Basel, Faculty of Science.


Official URL: http://edoc.unibas.ch/diss/DissB_10835


We work over the field of complex numbers. Consider the set V_n of binary forms of degree n, i.e., homogeneous polynomials of degree n in two variables. An invariant of V_n is a polynomial in the coefficients of a form in V_n whose value does not change under the action of the group of complex 2x2 matrices with determinant 1 on V_n. In 1893, Hilbert proved that the algebra of invariants of V_n is finitely generated for all n. However, finding explicit sets of generators is in general a difficult problem. They were known for binary forms of degree 8 and less than 7 since the 19th century, but for higher degrees the problem remained open. Over the last 25 years some progress was booked: generators for the invariants of binary forms of degree 7 were found by Dixmier and Lazard, and for the invariants of forms of degrees 9 and 10 by Brouwer and myself.
This thesis is organised as follows.
In Chapter 2 we introduce definitions and notation that will be used throughout this thesis. In Chapter 3 we present the computational methods that we use for finding generating invariants of binary forms. In Chapter 4 we find the generating invariants of binary forms of degree 2,3,...,10, and give explicit systems of parameters in all these cases. In Chapter 5 we review classical results regarding the invariants of several binary forms. We correct a result of Winter on the generating covariants of V_2+V_5 and results of Gundelfinger and Sylvester on the generating covariants of V_3+V_4. In Chapter 6, extending a result of Popov, we classify the modules whose algebras of invariants have homological dimension less than or equal to 15.
Advisors:Kraft, Hanspeter
Committee Members:Weyman, Jerzy
Faculties and Departments:05 Faculty of Science > Departement Mathematik und Informatik > Mathematik > Algebra (Kraft)
Item Type:Thesis
Thesis no:10835
Bibsysno:Link to catalogue
Number of Pages:212 S.
Identification Number:
Last Modified:30 Jun 2016 10:55
Deposited On:01 Jul 2014 12:58

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