Gruber P. Convex and Discrete Geometry

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7 Valuations 135 geometry from another is the group of transformations under which the propositions remain valid. Thus, for the purposes of integral geometry, it seems to be natural to choose the measure in such a way that it remains invariant under the corresponding group of transformation. The first reference of integral geometry and the closely related field of geometric probability, is the needle experiment of the naturalist Buffon [177]. Buffon found his formula in 1733, but it was published only in 1777. Principal contributors to this area are Cauchy, Barbier, Crofton and Czuber in the nineteenth century, Blaschke and his school, in particular his followers Santaló, Chern and Hadwiger, in the 1930s and later, and a number of contemporaries. See the collected works of Blaschke [129] and the books of Blaschke [128], Hadwiger [468], Stoka [971], Santaló [879], Ambartzumian [26], Schneider and Weil [911], Klain and Rota [587] and Beneˇs and Rataj [95]. A related, yet different, type of integral geometry deals with the Radon transform and its applications. See, e.g. Helgason [489], Gel’fand, Gindikin and Graev [368] and Palamodov [784]. In the following we state and prove the principal kinematic formula based on Hadwiger’s functional theorem. Measure on the Group of Rigid Motions Let M = M(E d ) be the group of all (proper and improper) rigid motions in E d . Since every rigid motion is a (proper or improper) rotation, i.e. an element of the orthogonal group O(d), followed by a translation, we obtain an invariant measure µ on M as follows: Take the product of the invariant measure ν on the compact group O(d), normalized such that the whole group has measure 1, with the d-dimensional Lebesgue measure. See [760]. The Principal Kinematic Formula permits us to calculate the integral � (1) χ(C ∩ mD) dµ(m), M where C, D are polyconvex bodies and χ is the Euler characteristic, see Sect. 7.1. It is due to Santaló [879] (d = 2), Blaschke [127, 128] (d = 3) and Chern and Yien [205] (general d). There exist many generalizations and extensions of it, for example the general kinematic formula which permits us to calculate the integral � Wi(C ∩ mD) dµ(m). M For convex bodies C, D the integral (1) is simply the measure of all rigid motions m such that the intersection C ∩mD is not empty. If B is a convex body which contains C, the quotient
136 Convex Bodies � χ(C ∩ mD) dµ(m) M � χ(B ∩ mD) dµ(m) M may be interpreted as the probability that a congruent copy of D which meets B also meets C. There are similar interpretations for χ replaced by the quermassintegrals Wi. Our aim is to prove the principal kinematic formula: Theorem 7.10. Let C, D ∈ L(C). Then (2) � d� χ(C ∩ mD) dµ(m) = 1 M κd i=0 � � d Wi(C) Wd−i(D). i The quermassintegrals Wi, including χ, are continuous valuations on C, see Theorem 6.13. Hence they can be extended in a unique way to valuations on L(C) by Groemer’s extension theorem. These extensions are applied in (2). Proof. We consider, first, the case C. Define a function φ : C × C → R by (3) φ(C, D) = µ �� m ∈ M : C ∩ mD �= ∅ �� = χ(C ∩ mD) dµ(m) = = � O(d) � O(d) M � � χ � C ∩ (rD+ t) � � dt dν(r) E d V (C − rD) dν(r) for C, D ∈ C, noting that {t : C ∩ (rD+ t) �= ∅}=C − rD. Since {m ∈ M : C ∩ mD �= ∅}is compact in M = O(d)×E d and thus measurable, φ is well defined. In order to apply the functional theorem of Hadwiger to φ, several properties of φ have to be shown first. The first property of φ is the following: (4) φ(C, D) = φ(D, C) for C, D ∈ C. χ is invariant with respect to rigid motions and the Haar measure µ is unimodular, that is, if in an integrand the variable m is replaced by m −1 , the integral does not change its value. See, e.g. [760], p.81. Thus (4) can be obtained as follows: � � φ(C, D) = χ(C ∩ mD) dµ(m) = χ(m −1 C ∩ D) dµ(m) M � M = χ(D ∩ m −1 � C) dµ(m) = χ(D ∩ mC) dµ(m) = φ(D, C). M M
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Grundlehren der mathematischen Wiss
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Peter M. Gruber Institute of Discre
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VI Preface theory of finite groups
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Contents Preface ..................
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Contents XI 12 Special Convex Bodie
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Contents XIII 29 Packing of Balls a
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2 Convex Functions 1 Convex Functio
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4 Convex Functions x epi f f C y Fi
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6 Convex Functions Together these i
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8 Convex Functions Theorem 1.4. Let
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10 Convex Functions z = f (x) + f
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12 Convex Functions 1.3 Convexity C
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14 Convex Functions Proof (by affin
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16 Convex Functions Minkowski’s I
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18 Convex Functions (ii) Let x > 0.
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20 Convex Functions 2 Convex Functi
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22 Convex Functions | f (z) − f (
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24 Convex Functions First-Order Dif
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26 Convex Functions Remark. More pr
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28 Convex Functions even more is tr
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30 Convex Functions G(x). The proof
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32 Convex Functions by (15), unifor
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34 Convex Functions 2.4 A Stone-Wei
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36 Convex Functions x x Fig. 2.1. S
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38 Convex Functions F is convex. Us
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40 Convex Bodies results, character
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42 Convex Bodies Convex Hulls Given
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44 Convex Bodies The next result is
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46 Convex Bodies C ∩ L ⊥ clearl
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48 Convex Bodies Suppose not. Then,
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50 Convex Bodies The Centrepoint of
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52 Convex Bodies Since G is open, w
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54 Convex Bodies in one of the two
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56 Convex Bodies or geometric infor
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58 Convex Bodies v HC (u, h(u)) (v,
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60 Convex Bodies C D Fig. 4.3. Sepa
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62 Convex Bodies For the proof of t
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64 Convex Bodies in contradiction t
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66 Convex Bodies (6) R(t) ⊆ E d i
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68 Convex Bodies 5 The Boundary of
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70 Convex Bodies for all y ∈ C an
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72 Convex Bodies the existence of s
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74 Convex Bodies where r(·) is a s
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76 Convex Bodies Hence x ∈ conv e
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78 Convex Bodies N = � � X, O Y
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80 Convex Bodies Further topics of
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82 Convex Bodies We are now ready t
Page 95 and 96: 84 Convex Bodies similarly, D j is
Page 97 and 98: 86 Convex Bodies For the proof of t
Page 99 and 100: 88 Convex Bodies The definition of
Page 101 and 102: 90 Convex Bodies If ei ∈ Pi is no
Page 103 and 104: 92 Convex Bodies Let v(·) denote (
Page 105 and 106: 94 Convex Bodies The present sectio
Page 107 and 108: 96 Convex Bodies Proposition 6.5. L
Page 109 and 110: 98 Convex Bodies Thus Second, Minko
Page 111 and 112: 100 Convex Bodies The Valuation Pro
Page 113 and 114: 102 Convex Bodies Minkowski’s the
Page 115 and 116: 104 Convex Bodies To remedy the sit
Page 117 and 118: 106 Convex Bodies Proof. Applying S
Page 119 and 120: 108 Convex Bodies Third, let C be a
Page 121 and 122: 110 Convex Bodies A Problem of Sant
Page 123 and 124: 112 Convex Bodies sets of S. Ifφ c
Page 125 and 126: 114 Convex Bodies = � (−1) |J|
Page 127 and 128: 116 Convex Bodies If P has dimensio
Page 129 and 130: 118 Convex Bodies Since, by Volland
Page 131 and 132: 120 Convex Bodies that is, V is sim
Page 133 and 134: 122 Convex Bodies Let C, D ∈ C su
Page 135 and 136: 124 Convex Bodies P Q . . . . Fig.
Page 137 and 138: 126 Convex Bodies 7.3 Characterizat
Page 139 and 140: 128 Convex Bodies and the Bi have p
Page 141 and 142: 130 Convex Bodies Since the Riemann
Page 143 and 144: 132 Convex Bodies Seventh, o v3 v2
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Page 149 and 150: 138 Convex Bodies In the following,
Page 151 and 152: 140 Convex Bodies 7.5 Hadwiger’s
Page 153 and 154: 142 Convex Bodies 8.1 The Classical
Page 155 and 156: 144 Convex Bodies C ∩ H(tC ) C D
Page 157 and 158: 146 Convex Bodies Theorem 8.4. Let
Page 159 and 160: 148 Convex Bodies In the following
Page 161 and 162: 150 Convex Bodies Integration impli
Page 163 and 164: 152 Convex Bodies As a consequence
Page 165 and 166: 154 Convex Bodies Proof. � 1 2 w(
Page 167 and 168: 156 Convex Bodies Let ϱ>0 be the m
Page 169 and 170: 158 Convex Bodies Wulff’s Theorem
Page 171 and 172: 160 Convex Bodies Third, by (8) and
Page 173 and 174: 162 Convex Bodies Since the measure
Page 175 and 176: 164 Convex Bodies An application of
Page 177 and 178: 166 Convex Bodies Since f has Lipsc
Page 179 and 180: 168 Convex Bodies Clearly, the inte
Page 181 and 182: 170 Convex Bodies Note that �st :
Page 183 and 184: 172 Convex Bodies Proposition 9.2.
Page 185 and 186: 174 Convex Bodies Proof. Let ε>0.
Page 187 and 188: 176 Convex Bodies The Brunn-Minkows
Page 189 and 190: 178 Convex Bodies 9.3 Schwarz Symme
Page 191 and 192: 180 Convex Bodies Torsional Rigidit
Page 193 and 194: 182 Convex Bodies The proof of (3)
Page 195 and 196: 184 Convex Bodies � �� 2 2
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186 Convex Bodies Theorem 9.10. Let
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188 Convex Bodies Both problems inf
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190 Convex Bodies The Area Measure
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192 Convex Bodies halfspace {z : un
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194 Convex Bodies Let σm be the di
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196 Convex Bodies Thus Minkowski’
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198 Convex Bodies Suppose now that
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200 Convex Bodies vector of St at x
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202 Convex Bodies Outer Billiards F
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204 Convex Bodies For more informat
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206 Convex Bodies with P. Thus, it
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208 Convex Bodies Note that ui ∈
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210 Convex Bodies Theorem 11.4. Let
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212 Convex Bodies the maximum of th
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214 Convex Bodies (20) mni ≥ 1 λ
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216 Convex Bodies Prove analogous r
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218 Convex Bodies Heuristic Princip
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220 Convex Bodies λC + x νC + z
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222 Convex Bodies To show that (K +
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224 Convex Bodies The integral here
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226 Convex Bodies In the following
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228 Convex Bodies The first such re
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230 Convex Bodies v o Fig. 12.3. Sy
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232 Convex Bodies What Does the Bou
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234 Convex Bodies Corollary 13.1. L
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236 Convex Bodies Hence ν = 0 and
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238 Convex Bodies geometry, see Sei
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240 Convex Bodies We distinguish th
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242 Convex Bodies by Proposition 13
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244 Convex Polytopes The material i
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246 Convex Polytopes V-Polytopes an
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248 Convex Polytopes Convex cones w
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250 Convex Polytopes Generalized Co
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252 Convex Polytopes d 2 inequaliti
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254 Convex Polytopes The Face Latti
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256 Convex Polytopes Then (6) impli
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258 Convex Polytopes P in F. For an
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260 Convex Polytopes Euler’s Poly
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262 Convex Polytopes bijection betw
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264 Convex Polytopes The Converse o
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266 Convex Polytopes (geometric) fa
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268 Convex Polytopes consists preci
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270 Convex Polytopes The Lower and
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272 Convex Polytopes A problem of S
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274 Convex Polytopes The first cond
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276 Convex Polytopes The existence
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278 Convex Polytopes For d = 3 it f
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280 Convex Polytopes 16 Volume of P
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282 Convex Polytopes by (2). Hence
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284 Convex Polytopes (12) The volum
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286 Convex Polytopes T ∩ Z, respe
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288 Convex Polytopes An Alternative
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290 Convex Polytopes P clearly can
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292 Convex Polytopes 17 Rigidity Ri
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294 Convex Polytopes Fig. 17.2. Cau
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296 Convex Polytopes Call the index
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298 Convex Polytopes of V. Fori ∈
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300 Convex Polytopes Thus (3) impli
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302 Convex Polytopes Proof. (i)⇒(
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304 Convex Polytopes For other pert
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306 Convex Polytopes where λ is a
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308 Convex Polytopes 18.3 The Isope
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310 Convex Polytopes 19 Lattice Pol
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312 Convex Polytopes Embed E d into
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314 Convex Polytopes To see this, n
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316 Convex Polytopes The Coefficien
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318 Convex Polytopes If the triangl
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320 Convex Polytopes � qP(t) = No
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322 Convex Polytopes Now, take into
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324 Convex Polytopes L � P + (n +
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326 Convex Polytopes V (S) = V .Let
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328 Convex Polytopes (7) ψ|H d = 0
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330 Convex Polytopes Theorem 19.6.
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332 Convex Polytopes (15) L(nP) = L
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334 Convex Polytopes have to be sin
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336 Convex Polytopes economics, von
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338 Convex Polytopes Existence of S
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340 Convex Polytopes Description of
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342 Convex Polytopes (6) u piai xq
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344 Convex Polytopes For x ∈ Bd
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346 Convex Polytopes Rational Polyh
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348 Convex Polytopes Totally Dual I
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350 Convex Polytopes of the vectors
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Geometry of Numbers and Aspects of
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Extension to Crystallographic Group
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Relations Between Different Bases 2
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21 Lattices 359 triangle conv{o,(u,
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By definition of bi+1, Thus (6) yie
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21 Lattices 363 A similar, slightly
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21.4 Polar Lattices 21 Lattices 365
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The First Fundamental Theorem 22 Mi
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22 Minkowski’s First Fundamental
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If 22 Minkowski’s First Fundament
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22 Minkowski’s First Fundamental
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Proof. Consider the linear forms l1
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Proof. It is sufficient to consider
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Thus V (C) ≥ V (O) = 2d � �
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Given C and L, the problem arises t
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23 Successive Minima 383 as require
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24 The Minkowski-Hlawka Theorem 24
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(6) (V (J) ≈) � n�= 0 (7) J
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24 The Minkowski-Hlawka Theorem 389
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The Variance Theorem of Rogers and
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The Selection Theorem of Mahler [68
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26 The Torus Group E d /L 395 where
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Proposition 26.2. E d /L is a compa
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26 The Torus Group E d /L 399 theor
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26 The Torus Group E d /L 401 The m
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The formula to calculate the Jordan
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27 Special Problems in the Geometry
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Asymptotic Estimates 27 Special Pro
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27 Special Problems in the Geometry
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28 Basis Reduction and Polynomial A
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(ii) �b1� ≤2 1 2 (d−1) min
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28 Basis Reduction and Polynomial A
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and so 28 Basis Reduction and Polyn
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Shortest Lattice Vector Problem 28
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and therefore �x − m� 2 = �
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29 Packing of Balls and Positive Qu
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29.3 Error Correcting Codes and Bal
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30 Packing of Convex Bodies 439 The
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30 Packing of Convex Bodies 441 Nex
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Packing and Central Symmetrization
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Existence of Densest Lattice Packin
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30 Packing of Convex Bodies 447 Rem
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A Lower Estimate for the Maximum La
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Lattice Packing and Packing of Tran
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a f b o e 2D c Fig. 30.3. Disc and
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31 Covering with Convex Bodies 455
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32 Tiling with Convex Polytopes 463
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Define 32 Tiling with Convex Polyto
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33.1 Fejes Tóth’s Inequality for
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Noting that 2h 2 v − hhvv = 2π 2
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33 Optimum Quantization 485 The con
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(7) � (x, y) : x ∈ K, 0 ≤ y
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Next, we prove that (18) lim inf n
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Generalizations 33 Optimum Quantiza
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33 Optimum Quantization 493 set wit
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33 Optimum Quantization 495 In (4)
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33 Optimum Quantization 497 encoder
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34 Koebe’s Representation Theorem
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G 34 Koebe’s Representation Theor
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Di+1 34 Koebe’s Representation Th
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References 1. Achatz, H., Kleinschm
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References 515 36. Arias de Reyna,
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References 517 88. Beer, G., Topolo
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References 519 136. Bohr, H., Molle
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References 521 190. Carathéodory,
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References 523 237. Dantzig, G.B.,
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References 525 286. Edmonds, A.L.,
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References 527 337. Florian, A., Ex
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References 529 385. Goodman, J.E.,
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References 531 435. Gruber, P.M., C
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References 533 487. Heil, E., Über
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References 535 534. Hyuga, T., An e
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References 537 582. Khovanskiĭ (Ho
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References 539 632. Lazutkin, V.F.,
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References 541 684. Mani-Levitska,
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References 543 736. Minkowski, H.,
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References 545 783. Pach, J., Agarw
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References 547 835. Rickert, N.W.,
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References 549 891. Schmidt, E., Di
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References 551 941. Skubenko, B.F.,
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References 553 992. Teissier, B., V
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References 555 1042. Zassenhaus, H.
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558 INDEX Bravais classification of
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560 INDEX existence of elementary v
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562 INDEX Kneser-Macbeath theorem,
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564 INDEX rational lattice, 414 rat
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566 INDEX transference theorem of K
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568 AUTHOR INDEX Björner, 265 Blas
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570 AUTHOR INDEX Giles, J., 1 Giles
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572 AUTHOR INDEX Kuczma, 13, 17 Kü
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574 AUTHOR INDEX Pick, 316 Pisier,
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576 AUTHOR INDEX Tanemura, 464 Tarj
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578 List of Symbols sch, schL Schwa
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289. Manin: Gauge Field Theory and
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