14.02.2013 Views

Gruber P. Convex and Discrete Geometry

Gruber P. Convex and Discrete Geometry

Gruber P. Convex and Discrete Geometry

SHOW MORE
SHOW LESS

You also want an ePaper? Increase the reach of your titles

YUMPU automatically turns print PDFs into web optimized ePapers that Google loves.

448 <strong>Geometry</strong> of Numbers<br />

from o, ±l1,...,±ln, onto a point outside 2D. Thus the lattice L(s) = (I + sA)L<br />

is admissible for 2D. Its determinant is given by:<br />

d � L(s) � =|det(I + sA)| d(L)<br />

⎛<br />

⎞<br />

1 + sa11 sa12 ... sa1d<br />

⎜<br />

⎟<br />

⎜ sa21 1 + sa22 ... sa2d ⎟<br />

= det ⎜<br />

⎟<br />

⎜<br />

⎝ ..............................<br />

⎟<br />

⎠ d(L)<br />

sad1 sad2 ... 1 + sadd<br />

= (1 + sa1 + s 2 a2 +···+s d ad)d(L),<br />

where a1 = �<br />

aii, a2 = �<br />

(aiiakk − aikaki).<br />

i<br />

(The expressions for a3,...,ad are not needed.) Since L is locally critical, d � L(s) � ≥<br />

d(L) for all sufficiently small |s|. Hence<br />

i

Hooray! Your file is uploaded and ready to be published.

Saved successfully!

Ooh no, something went wrong!