Isotropic quadratic form

2020 Mathematics Subject Classification: Primary: 15A63 [MSN][ZBL]

A quadratic form $q$ on a vector space over a field $F$ which is non-degenerate (the associated bilinear form is non-singular) but which represents zero non-trivially: there is a non-zero vector $v$ such that $q(v) = 0$.

An anisotropic quadratic form $q$ is one for which $q(v) = 0 \Rightarrow v=0$.

References

• Tsit Yuen Lam, Introduction to Quadratic Forms over Fields, Graduate Studies in Mathematics 67, American Mathematical Society (2005) ISBN 0-8218-1095-2 Zbl 1068.11023 MR2104929
• J.W. Milnor, D. Husemöller, Symmetric bilinear forms, Ergebnisse der Mathematik und ihrer Grenzgebiete 73, Springer-Verlag (1973) ISBN 0-387-06009-X Zbl 0292.10016