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Gruber P. Convex and Discrete Geometry

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94 <strong>Convex</strong> Bodies<br />

The present section contains a series of important properties of mixed volumes.<br />

We start with a representation of mixed volumes by means of volumes, then consider<br />

linearity, continuity, monotony, <strong>and</strong> valuation properties <strong>and</strong>, finally, prove<br />

Minkowski’s inequalities.<br />

For more information we refer to the books of Leichtweiss [640], Burago <strong>and</strong><br />

Zalgaller [178] <strong>and</strong> Schneider [905] <strong>and</strong> the survey of Sangwine-Yager [878].<br />

A Representation of Mixed Volumes<br />

The following representation of mixed volumes gives insight into the meaning of<br />

mixed volumes. If, in a sum, a summ<strong>and</strong> has a tilde, it is to be omitted. Summation<br />

is from 1 to d, taking into account the stated restrictions.<br />

Theorem 6.7. Let C1,...,Cd ∈ C. Then<br />

(1) d ! V (C1,...,Cd) = V (C1 +···+Cd)− �<br />

V (C1 +···+�Ci1 +···+Cd)<br />

i1<br />

+ �<br />

V (C1 +···+ �Ci1 +···+ �Ci2 +···+Cd) −···<br />

i1

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