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(1)

Valuations on Convex Bodies and Sobolev Spaces

Monika Ludwig

Technische Universit¨at Wien

Szeged, May 2012

(2)

Valuations on Convex Bodies

Kn space of convex bodies (compact convex sets) in Rn xA, y Abelian semigroup

A function z:KnÑ xA, yis a valuation ðñ zpKq zpLq zpK YLq zpK XLq for all K,LPKn such thatK YLPKn.

Hilbert’s Third Problem:

Dehn 1902, Sydler 1965, Jessen & Thorup 1978, McMullen 1989, . . . Classification of valuations:

Blaschke 1937,Hadwiger1949, Schneider 1971, Groemer 1972, McMullen 1977, Betke & Kneser 1985, Klain 1995, L. 1999, Reitzner 1999, Alesker 1999, Fu 2006, Haberl 2006, Schuster 2006, Tsang 2010, Wannerer 2010, Abardia 2011, Bernig & Fu 2011, Parapatits 2011, . . .

(3)

Valuations on Convex Bodies

Kn space of convex bodies (compact convex sets) in Rn xA, y Abelian semigroup

A function z:KnÑ xA, y is a valuation ðñ zpKq zpLq zpK YLq zpK XLq for all K,LPKn such thatK YLPKn.

Hilbert’s Third Problem:

Dehn 1902, Sydler 1965, Jessen & Thorup 1978, McMullen 1989, . . . Classification of valuations:

Blaschke 1937,Hadwiger1949, Schneider 1971, Groemer 1972, McMullen 1977, Betke & Kneser 1985, Klain 1995, L. 1999, Reitzner 1999, Alesker 1999, Fu 2006, Haberl 2006, Schuster 2006, Tsang 2010, Wannerer 2010, Abardia 2011, Bernig & Fu 2011, Parapatits 2011, . . .

(4)

Valuations on Convex Bodies

Kn space of convex bodies (compact convex sets) in Rn xA, y Abelian semigroup

A function z:KnÑ xA, y is a valuation ðñ zpKq zpLq zpK YLq zpK XLq for all K,LPKn such thatK YLPKn.

Hilbert’s Third Problem:

Dehn 1902, Sydler 1965, Jessen & Thorup 1978, McMullen 1989, . . .

Classification of valuations:

Blaschke 1937,Hadwiger1949, Schneider 1971, Groemer 1972, McMullen 1977, Betke & Kneser 1985, Klain 1995, L. 1999, Reitzner 1999, Alesker 1999, Fu 2006, Haberl 2006, Schuster 2006, Tsang 2010, Wannerer 2010, Abardia 2011, Bernig & Fu 2011, Parapatits 2011, . . .

(5)

Valuations on Convex Bodies

Kn space of convex bodies (compact convex sets) in Rn xA, y Abelian semigroup

A function z:KnÑ xA, y is a valuation ðñ zpKq zpLq zpK YLq zpK XLq for all K,LPKn such thatK YLPKn.

Hilbert’s Third Problem:

Dehn 1902, Sydler 1965, Jessen & Thorup 1978, McMullen 1989, . . . Classification of valuations:

Blaschke 1937,Hadwiger1949, Schneider 1971, Groemer 1972, McMullen 1977, Betke & Kneser 1985, Klain 1995, L.

(6)

Hadwiger’s Classification Theorem 1952

Theorem

A functional z:KnÑ xR, yis a continuous and rigid motion invariant valuation

ðñ Dc0,c1, . . . ,cnPR such that

zpKq c0V0pKq cnVnpKq

for every K PKn.

V0pKq, . . . ,VnpKq intrinsic volumes of K

Vn n-dimensional volume

n Vn1pKq SpKq surface area

New proof by Dan Klain 1995

“Introduction to Geometric Probability” by Klain & Rota 1997

(7)

Hadwiger’s Classification Theorem 1952

Theorem

A functional z:KnÑ xR, yis a continuous and rigid motion invariant valuation

ðñ Dc0,c1, . . . ,cnPR such that

zpKq c0V0pKq cnVnpKq

for every K PKn.

V0pKq, . . . ,VnpKq intrinsic volumes of K

Vn n-dimensional volume

p q p q

(8)

Valuations on Convex Bodies

Real valued valuations z:KnÑ xR, y:

Ÿ Translation invariant, continuous: McMullen, Alesker, ...

Ÿ Rotation invariant, continuous: Alesker, ...

Ÿ SLpnqinvariant, upper semicontinuous: L. & Reitzner, ...

Tensor valued valuations z:KnÑ xTd, y:

Ÿ Vector valued: Hadwiger & Schneider, ...

Ÿ Symmetricd tensor valued: McMullen, Alesker, Hug & Schneider, ...

Body valued valuations:

Ÿ Minkowski valuations z:KnÑ xKn, y:

L., Schuster, Schneider, Wannerer, Abardia & Bernig, ...

Ÿ Lp Minkowski valuations z:KnÑ xKn, py: L., Haberl, Wannerer, Parapatits, ...

Ÿ Radial valuations z:KnÑ xSn,˜py: L., Haberl, ...

Ÿ Blaschke valuations z:KnÑ xKcn,#y: Haberl, ...

(9)

Valuations on Convex Bodies

Real valued valuations z:KnÑ xR, y:

Ÿ Translation invariant, continuous: McMullen, Alesker, ...

Ÿ Rotation invariant, continuous: Alesker, ...

Ÿ SLpnqinvariant, upper semicontinuous: L. & Reitzner, ...

Tensor valued valuations z:KnÑ xTd, y:

Ÿ Vector valued: Hadwiger & Schneider, ...

Ÿ Symmetricd tensor valued: McMullen, Alesker, Hug & Schneider, ...

Body valued valuations:

Ÿ Minkowski valuations z:KnÑ xKn, y:

L., Schuster, Schneider, Wannerer, Abardia & Bernig, ...

Ÿ Lp Minkowski valuations z:KnÑ xKn, py: L., Haberl, Wannerer, Parapatits, ...

Ÿ Radial valuations z:KnÑ xSn,˜py: L., Haberl, ...

Ÿ Blaschke valuations z:KnÑ xKcn,#y: Haberl, ...

(10)

Valuations on Convex Bodies

Real valued valuations z:KnÑ xR, y:

Ÿ Translation invariant, continuous: McMullen, Alesker, ...

Ÿ Rotation invariant, continuous: Alesker, ...

Ÿ SLpnqinvariant, upper semicontinuous: L. & Reitzner, ...

Tensor valued valuations z:KnÑ xTd, y:

Ÿ Vector valued: Hadwiger & Schneider, ...

Ÿ Symmetricd tensor valued: McMullen, Alesker, Hug & Schneider, ...

Body valued valuations:

Ÿ Minkowski valuations z:KnÑ xKn, y:

L., Schuster, Schneider, Wannerer, Abardia & Bernig, ...

Ÿ Lp Minkowski valuations z:KnÑ xKn, py: L., Haberl, Wannerer, Parapatits, ...

Ÿ Radial valuations z:KnÑ xSn,˜py: L., Haberl, ...

Ÿ Blaschke valuations z:KnÑ xKnc,#y: Haberl, ...

(11)

Valuations on Function Spaces

F tf :X ÑRu space of real valued functions on X f _g maxtf,gu,f ^g mintf,gu

xA, y Abelian semigroup

A function z:F Ñ xA, yis a valuation ðñ zpfq zpgq zpf _gq zpf ^gq for all f,g PF such that f _g,f ^g PF.

Birkhoff: Lattice theory1940

Valuations on Lp stars: Dan Klain (AIM 1996, 1997)

Valuations on Lp spaces: Andy Tsang (IMRN 2010, TAMS 2011+) Valuations on Orlicz spaces: Hassane Kone (2011+)

Valuations on BVpRnq: Tuo Wang (2011+)

Valuations on Sobolev spaces: L. (AIM 2011, AJM 2012, ...)

(12)

Valuations on Function Spaces

F tf :X ÑRu space of real valued functions on X f _g maxtf,gu,f ^g mintf,gu

xA, y Abelian semigroup

A function z:F Ñ xA, yis a valuation ðñ zpfq zpgq zpf _gq zpf ^gq for all f,g PF such that f _g,f ^g PF.

Birkhoff: Lattice theory1940

Valuations on Lp stars: Dan Klain (AIM 1996, 1997)

Valuations on Lp spaces: Andy Tsang (IMRN 2010, TAMS 2011+) Valuations on Orlicz spaces: Hassane Kone (2011+)

Valuations on BVpRnq: Tuo Wang (2011+)

Valuations on Sobolev spaces: L. (AIM 2011, AJM 2012, ...)

(13)

Valuations on Function Spaces

F tf :X ÑRu space of real valued functions on X f _g maxtf,gu,f ^g mintf,gu

xA, y Abelian semigroup

A function z:F Ñ xA, yis a valuation ðñ zpfq zpgq zpf _gq zpf ^gq for all f,g PF such that f _g,f ^g PF.

Birkhoff: Lattice theory1940

Valuations on Lp stars: Dan Klain (AIM 1996, 1997)

Valuations on Lp spaces: Andy Tsang (IMRN 2010, TAMS 2011+) Valuations on Orlicz spaces: Hassane Kone (2011+)

Valuations on BVpRnq: Tuo Wang (2011+)

Valuations on Sobolev spaces: L. (AIM 2011, AJM 2012, ...)

(14)

Valuations on Function Spaces

F tf :X ÑRu space of real valued functions on X f _g maxtf,gu,f ^g mintf,gu

xA, y Abelian semigroup

A function z:F Ñ xA, yis a valuation ðñ zpfq zpgq zpf _gq zpf ^gq for all f,g PF such that f _g,f ^g PF.

Birkhoff: Lattice theory1940

Valuations on Lp stars: Dan Klain (AIM 1996, 1997)

Valuations on Lp spaces: Andy Tsang (IMRN 2010, TAMS 2011+) Valuations on Orlicz spaces: Hassane Kone (2011+)

Valuations on BVpRnq: Tuo Wang (2011+)

Valuations on Sobolev spaces: L. (AIM 2011, AJM 2012, ...)

(15)

Sobolev Spaces

W1,ppRnq tf PLppRnq:|∇f| PLppRnqu p ¥1,n¥3

f _g maxtf,gu,f ^g mintf,gu W1,ppRnq lattice

xA, y Abelian semigroup

A function z:W1,ppRnq Ñ xA, yis a valuation ðñ zpfq zpgq zpf _gq zpf ^gq for all f,g PW1,ppRnq.

Question

Classification of valuations onW1,ppRnq

(16)

Sobolev Spaces

W1,ppRnq tf PLppRnq:|∇f| PLppRnqu p ¥1,n¥3

f _g maxtf,gu,f ^g mintf,gu W1,ppRnq lattice

xA, y Abelian semigroup

A function z:W1,ppRnq Ñ xA, yis a valuation ðñ zpfq zpgq zpf _gq zpf ^gq for all f,g PW1,ppRnq.

Question

Classification of valuations onW1,ppRnq

(17)

Sobolev Spaces

W1,ppRnq tf PLppRnq:|∇f| PLppRnqu p ¥1,n¥3

f _g maxtf,gu,f ^g mintf,gu W1,ppRnq lattice

xA, y Abelian semigroup

A function z:W1,ppRnq Ñ xA, yis a valuation ðñ zpfq zpgq zpf _gq zpf ^gq for all f,g PW1,ppRnq.

Question

Classification of valuations onW1,ppRnq

(18)

Sobolev Spaces

W1,ppRnq tf PLppRnq:|∇f| PLppRnqu p ¥1,n¥3

f _g maxtf,gu,f ^g mintf,gu W1,ppRnq lattice

xA, y Abelian semigroup

A function z:W1,ppRnq Ñ xA, yis a valuation ðñ zpfq zpgq zpf _gq zpf ^gq for all f,g PW1,ppRnq.

Question

Classification of valuations onW1,ppRnq

(19)

Matrix-Valued Valuations on Sobolev Spaces

W1,2pRnq tf PL2pRnq:|∇f| PL2pRnqu Mn space of symmetric nn matrices

Z:W1,2pRnq ÑMn is GLpnq contravariant ô

Zpf φq |detφ|qφtZpfqφ1 @φPGLpnq Z:W1,2pRnq ÑMn is affinely contravariantô

Z is GLpnq contravariant, translation invariant and homogeneous

(20)

Matrix-Valued Valuations on Sobolev Spaces

W1,2pRnq tf PL2pRnq:|∇f| PL2pRnqu

Mn space of symmetric nn matrices

Z:W1,2pRnq ÑMn is GLpnq contravariant ô

Zpf φq |detφ|qφtZpfqφ1 @φPGLpnq

Z:W1,2pRnq ÑMn is affinely contravariantô

Z is GLpnq contravariant, translation invariant and homogeneous

(21)

Matrix-Valued Valuations on Sobolev Spaces

W1,2pRnq tf PL2pRnq:|∇f| PL2pRnqu

Mn space of symmetric nn matrices

Z:W1,2pRnq ÑMn is GLpnq contravariant ô

Zpf φq |detφ|qφtZpfqφ1 @φPGLpnq Z:W1,2pRnq ÑMn is affinely contravariantô

Z is GLpnq contravariant, translation invariant and homogeneous

(22)

A Characterization of the Fisher Information Matrix

Theorem (L.: AIM 2011)

A function Z:W1,2pRnq Ñ xMn, yis a continuous and affinely contravariant valuation

Dc PRsuch that ðñ

Zpfq cJpf2q for every f PW1,2pRnq.

Jijpgq

»

Rn

Bloggpxq Bxi

Bloggpxq Bxj

gpxqdx

Connection between Fisher information matrix and LYZ ellipsoid (Lutwak, Yang & Zhang: DMJ 2000)

(23)

A Characterization of the Fisher Information Matrix

Theorem (L.: AIM 2011)

A function Z:W1,2pRnq Ñ xMn, yis a continuous and affinely contravariant valuation

Dc PRsuch that ðñ

Zpfq cJpf2q for every f PW1,2pRnq.

Jijpgq

»

Rn

Bloggpxq Bxi

Bloggpxq Bxj

gpxqdx

Connection between Fisher information matrix and LYZ ellipsoid (Lutwak, Yang & Zhang: DMJ 2000)

(24)

A Characterization of the Fisher Information Matrix

Theorem (L.: AIM 2011)

A function Z:W1,2pRnq Ñ xMn, yis a continuous and affinely contravariant valuation

Dc PRsuch that ðñ

Zpfq cJpf2q for every f PW1,2pRnq.

Jijpgq

»

Rn

Bloggpxq Bxi

Bloggpxq Bxj

gpxqdx

Connection between Fisher information matrix and LYZ ellipsoid (Lutwak, Yang & Zhang: DMJ 2000)

(25)

A Characterization of the LYZ Matrix

Theorem (L.: DMJ 2003)

A function Z:P0nÑ xM, yis a valuation such that ZpφPq |detφ|φtZpPqφ1 @φPGLpnq Dc PR such that ðñ

ZpPq cLpPq for every P PP0n.

P0n convex polytopes inRn containing the origin in their interiors

(26)

Convex-Body-Valued Valuations on Sobolev Spaces

Knc space of origin-symmetric convex bodies

z:W1,1pRnq ÑKnc is GLpnqcontravariant ô

zpf φq |detφ|qφtzpfq @φPGLpnq z:W1,1pRnq ÑKnc is affinely contravariantô

z is GLpnq contravariant, translation invariant and homogeneous z:W1,1pRnq ÑKnc is GLpnqcovariant ô

zpf φq |detφ|qφzpfq @φPGLpnq z:W1,1pRnq ÑKnc is affinely covariantô

z is GLpnq covariant, translation invariant and homogeneous

(27)

Convex-Body-Valued Valuations on Sobolev Spaces

Knc space of origin-symmetric convex bodies z:W1,1pRnq ÑKnc is GLpnq contravariant ô

zpf φq |detφ|qφtzpfq @φPGLpnq

z:W1,1pRnq ÑKnc is affinely contravariantô

z is GLpnq contravariant, translation invariant and homogeneous z:W1,1pRnq ÑKnc is GLpnqcovariant ô

zpf φq |detφ|qφzpfq @φPGLpnq z:W1,1pRnq ÑKnc is affinely covariantô

z is GLpnq covariant, translation invariant and homogeneous

(28)

Convex-Body-Valued Valuations on Sobolev Spaces

Knc space of origin-symmetric convex bodies z:W1,1pRnq ÑKnc is GLpnq contravariant ô

zpf φq |detφ|qφtzpfq @φPGLpnq z:W1,1pRnq ÑKnc is affinely contravariantô

z is GLpnq contravariant, translation invariant and homogeneous

z:W1,1pRnq ÑKnc is GLpnqcovariant ô

zpf φq |detφ|qφzpfq @φPGLpnq z:W1,1pRnq ÑKnc is affinely covariantô

z is GLpnq covariant, translation invariant and homogeneous

(29)

Convex-Body-Valued Valuations on Sobolev Spaces

Knc space of origin-symmetric convex bodies z:W1,1pRnq ÑKnc is GLpnq contravariant ô

zpf φq |detφ|qφtzpfq @φPGLpnq z:W1,1pRnq ÑKnc is affinely contravariantô

z is GLpnq contravariant, translation invariant and homogeneous z:W1,1pRnq ÑKnc is GLpnq covariant ô

zpf φq |detφ|qφzpfq @φPGLpnq

z:W1,1pRnq ÑKnc is affinely covariantô

z is GLpnq covariant, translation invariant and homogeneous

(30)

Convex-Body-Valued Valuations on Sobolev Spaces

Knc space of origin-symmetric convex bodies z:W1,1pRnq ÑKnc is GLpnq contravariant ô

zpf φq |detφ|qφtzpfq @φPGLpnq z:W1,1pRnq ÑKnc is affinely contravariantô

z is GLpnq contravariant, translation invariant and homogeneous z:W1,1pRnq ÑKnc is GLpnq covariant ô

zpf φq |detφ|qφzpfq @φPGLpnq z:W1,1pRnq ÑKnc is affinely covariantô

z is GLpnq covariant, translation invariant and homogeneous

(31)

A Characterization of the LYZ operator

Theorem (L.: AJM 2012)

An operator z:W1,1pRnq Ñ xKnc, yis a continuous and affinely contravariant valuation

Dc ¥0such that ðñ

zpfq cΠxfy for every f PW1,1pRnq.

K L tx y :x PK,y PLu Minkowski sum ofK,LPKnc xy:W1,1pRnq ÑKnc,f ÞÑ xfy LYZ operator

(32)

Origin-symmetric Convex Bodies K

nc

Support function hpK,q:RnÑR

K hpK,uq

u

Ÿ hpK,uq maxtux :xPKu

Ÿ hpK,u vq ¤hpK,uq hpK,vq sublinear and even

Surface area measure SpK,q:BpSn1q Ñ r0,8q

K

SpK,tuuq u

Ÿ SpK, ωq

Hn1ptxPbdK :npK,xq Pωuq

Ÿ npK,xq outer unit normal vector toK atx PbdK

Ÿ SpK,q even measure,

not concentrated on a great sphere

(33)

Origin-symmetric Convex Bodies K

nc

Support function hpK,q:RnÑR

K hpK,uq

u

Ÿ hpK,uq maxtux :xPKu

Ÿ hpK,u vq ¤hpK,uq hpK,vq sublinear and even

Surface area measure SpK,q:BpSn1q Ñ r0,8q

K

SpK,tuuq u

Ÿ SpK, ωq

Hn1ptxPbdK :npK,xq Pωuq

Ÿ npK,xq outer unit normal vector toK atx PbdK

Ÿ SpK,q even measure,

not concentrated on a great sphere

(34)

Origin-symmetric Convex Bodies K

nc

Support function hpK,q:RnÑR

K hpK,uq

u

Ÿ hpK,uq maxtux :xPKu

Ÿ hpK,u vq ¤hpK,uq hpK,vq sublinear and even

Surface area measure SpK,q:BpSn1q Ñ r0,8q

K

SpK,tuuq

u Ÿ SpK, ωq

Hn1ptx PbdK :npK,xq Pωuq

Ÿ npK,xq outer unit normal vector toK atx PbdK

Ÿ SpK,q even measure,

not concentrated on a great sphere

(35)

Origin-symmetric Convex Bodies K

nc

Support function hpK,q:RnÑR

K hpK,uq

u

Ÿ hpK,uq maxtux :xPKu

Ÿ hpK,u vq ¤hpK,uq hpK,vq sublinear and even

Surface area measure SpK,q:BpSn1q Ñ r0,8q

SpK,tuuq

u Ÿ SpK, ωq

Hn1ptx PbdK :npK,xq Pωuq

Ÿ npK,xq outer unit normal vector toK

(36)

Projection Body, Π K , of K

uK hyperplane orthogonal tou K|uK projection of K to uK Vn1 pn1q-dimensional volume

hpΠxfy,uq

»

Rn

|u∇fpxq|dx

Definition (Minkowski 1901)

hpΠK,uq Vn1pK|uKq 1 2

»

Sn1

|uv|dSpK,vq

(37)

Projection Body, Π K , of K

uK hyperplane orthogonal tou K|uK projection of K to uK Vn1 pn1q-dimensional volume hpΠxfy,uq

»

Rn

|u∇fpxq|dx

Definition (Minkowski 1901)

hpΠK,uq V pK|uKq 1»

|uv|dSpK,vq

(38)

Sobolev Inequality

1 n

»

Rn

|∇fpxq|dx ¥vn1{nf

n{pn1q

f PW1,1pRnq tf PL1pRnq,|∇f| PL1pRnqu

|x| Euclidean norm of xPRn f

p ³

Rn|fpxq|pdx1{p

vn volume of n-dimensional unit ball

Equality for indicator functions of balls

Equivalent to Euclidean isoperimetric inequality Federer & Fleming 1960, Maz1ya 1960

(39)

Sobolev Inequality

1 n

»

Rn

|∇fpxq|dx ¥vn1{nf

n{pn1q

f PW1,1pRnq tf PL1pRnq,|∇f| PL1pRnqu

|x| Euclidean norm of xPRn f

p ³

Rn|fpxq|pdx1{p

vn volume of n-dimensional unit ball Equality for indicator functions of balls

Equivalent to Euclidean isoperimetric inequality

(40)

General Sobolev Inequality

1 n

»

Rn

}∇fpxq}Kdx ¥vn1{nf

n{pn1q

f PW1,1pRnq

Knc origin-symmetric convex bodies (compact convex sets) in Rn K PKnc with VpKq vn

K tx PRn:xy ¤1 for all y PKu polar body ofK } }L norm with unit ball L

Equality for f 1K

Equivalent to Minkowski inequality Gromov 1986

(41)

General Sobolev Inequality

1 n

»

Rn

}∇fpxq}Kdx ¥vn1{nf

n{pn1q

f PW1,1pRnq

Knc origin-symmetric convex bodies (compact convex sets) in Rn K PKnc with VpKq vn

K tx PRn:xy ¤1 for all y PKu polar body ofK } }L norm with unit ball L

Equality for f 1K

Equivalent to Minkowski inequality

(42)

Optimal Sobolev Inequality

1 n

»

Rn

}∇fpxq}Kdx ¥vn1{nf

n{pn1q

f PW1,1pRnq,VpKq vn

Question (Lutwak, Yang & Zhang 2006)

For given f PW1,1pRnq, which convex body K (of volumevn) minimizes 1

n

»

Rn

}∇fpxq}Kdx? Which norm is optimal?

(43)

Optimal Sobolev Inequality

1 n

»

Rn

}∇fpxq}Kdx ¥vn1{nf

n{pn1q

f PW1,1pRnq,VpKq vn

Question (Lutwak, Yang & Zhang 2006)

For given f PW1,1pRnq, which convex body K (of volume vn) minimizes 1 »

}∇fpxq}Kdx?

(44)

Optimal Sobolev Body

Definition (LYZ 2006)

For f PW1,1pRnq, the optimal Sobolev body, xfy, of f is defined as the unique origin-symmetric convex body such that

»

Sn1

gpuqdSpxfy,uq

»

Rn

gp∇fpxqqdx for all even and positively 1-homogeneous functions g PCpRnq.

Theorem (LYZ 2006)

For f PW1,1pRnq, the infimum over all origin-symmetric convex bodies K of volume VpKq vn over

»

Rn

}∇fpxq}Kdx is attained if and only if K is a dilate of xfy.

(45)

Optimal Sobolev Body

Definition (LYZ 2006)

For f PW1,1pRnq, the optimal Sobolev body, xfy, of f is defined as the unique origin-symmetric convex body such that

»

Sn1

gpuqdSpxfy,uq

»

Rn

gp∇fpxqqdx

for all even and positively 1-homogeneous functions g PCpRnq. Theorem (LYZ 2006)

For f PW1,1pRnq, the infimum over all origin-symmetric convex bodies K of volume VpKq vn over

»

(46)

Affine Sobolev inequality

Theorem (Gaoyong Zhang: JDG 1999) For f PW1,1pRnq,

1 n

»

Sn1

p

»

Rn

|u∇fpxq|dxqndu¤ p vn

2vn1qn|f|nn

n1

.

Affine isoperimetric inequality H¨older’s inequalityñ

1 nvn

»

Sn1

p

»

Rn

|u∇fpxq|dxqn1

n ¤ 1

nvn

»

Sn1

»

Rn

|u∇fpxq|dx du

ñ Sobolev inequality

Left hand side is multiple ofVpΠxfyq

Extended to BVpRnq by Tuo Wang (AIM 2012)

(47)

Affine Sobolev inequality

Theorem (Gaoyong Zhang: JDG 1999) For f PW1,1pRnq,

1 n

»

Sn1

p

»

Rn

|u∇fpxq|dxqndu¤ p vn

2vn1qn|f|nn

n1

.

Affine isoperimetric inequality

H¨older’s inequalityñ 1

nvn

»

Sn1

p

»

Rn

|u∇fpxq|dxqn1

n ¤ 1

nvn

»

Sn1

»

Rn

|u∇fpxq|dx du

ñ Sobolev inequality

Left hand side is multiple ofVpΠxfyq

Extended to BVpRnq by Tuo Wang (AIM 2012)

(48)

Affine Sobolev inequality

Theorem (Gaoyong Zhang: JDG 1999) For f PW1,1pRnq,

1 n

»

Sn1

p

»

Rn

|u∇fpxq|dxqndu¤ p vn

2vn1qn|f|nn

n1

.

Affine isoperimetric inequality H¨older’s inequalityñ

1 nvn

»

Sn1

p

»

Rn

|u∇fpxq|dxqn1

n ¤ 1

nvn

»

Sn1

»

Rn

|u∇fpxq|dx du

ñ Sobolev inequality

Left hand side is multiple ofVpΠxfyq

Extended to BVpRnq by Tuo Wang (AIM 2012)

(49)

Affine Sobolev inequality

Theorem (Gaoyong Zhang: JDG 1999) For f PW1,1pRnq,

1 n

»

Sn1

p

»

Rn

|u∇fpxq|dxqndu¤ p vn

2vn1qn|f|nn

n1

.

Affine isoperimetric inequality H¨older’s inequalityñ

1 nvn

»

Sn1

p

»

Rn

|u∇fpxq|dxqn1

n ¤ 1

nvn

»

Sn1

»

Rn

|u∇fpxq|dx du

Left hand side is multiple ofVpΠxfyq

Extended to BVpRnq by Tuo Wang (AIM 2012)

(50)

Affine Sobolev inequality

Theorem (Gaoyong Zhang: JDG 1999) For f PW1,1pRnq,

1 n

»

Sn1

p

»

Rn

|u∇fpxq|dxqndu¤ p vn

2vn1qn|f|nn

n1

.

Affine isoperimetric inequality H¨older’s inequalityñ

1 nvn

»

Sn1

p

»

Rn

|u∇fpxq|dxqn1

n ¤ 1

nvn

»

Sn1

»

Rn

|u∇fpxq|dx du ñ Sobolev inequality

Left hand side is multiple ofVpΠxfyq

Extended to BVpRnq by Tuo Wang (AIM 2012)

(51)

Affine Sobolev inequality

Theorem (Gaoyong Zhang: JDG 1999) For f PW1,1pRnq,

1 n

»

Sn1

p

»

Rn

|u∇fpxq|dxqndu¤ p vn

2vn1qn|f|nn

n1

.

Affine isoperimetric inequality H¨older’s inequalityñ

1 nvn

»

Sn1

p

»

Rn

|u∇fpxq|dxqn1

n ¤ 1

nvn

»

Sn1

»

Rn

|u∇fpxq|dx du

(52)

Valuations on Sobolev Spaces

xy:W1,1pRnq ÑKnc is affinely covariant (LYZ 2006).

xy:W1,1pRnq ÑKnc is continuous. xy:W1,1pRnq Ñ xKnc,#y is a valuation.

SpK #L,q SpK,q SpL,q Blaschke addition Theorem (L. 2012)

An operator z:W1,1pRnq Ñ xKnc,#yis a continuous and affinely covariant valuation

Dc ¥0such that ðñ

zpfq cxfy for every f PW1,1pRnq.

(53)

Valuations on Sobolev Spaces

xy:W1,1pRnq ÑKnc is affinely covariant (LYZ 2006).

xy:W1,1pRnq ÑKnc is continuous.

xy:W1,1pRnq Ñ xKnc,#y is a valuation.

SpK #L,q SpK,q SpL,q Blaschke addition Theorem (L. 2012)

An operator z:W1,1pRnq Ñ xKnc,#yis a continuous and affinely covariant valuation

Dc ¥0such that ðñ

zpfq cxfy for every f PW1,1pRnq.

(54)

Valuations on Sobolev Spaces

xy:W1,1pRnq ÑKnc is affinely covariant (LYZ 2006).

xy:W1,1pRnq ÑKnc is continuous.

xy:W1,1pRnq Ñ xKnc,#y is a valuation.

SpK #L,q SpK,q SpL,q Blaschke addition

Theorem (L. 2012)

An operator z:W1,1pRnq Ñ xKnc,#yis a continuous and affinely covariant valuation

Dc ¥0such that ðñ

zpfq cxfy for every f PW1,1pRnq.

(55)

Valuations on Sobolev Spaces

xy:W1,1pRnq ÑKnc is affinely covariant (LYZ 2006).

xy:W1,1pRnq ÑKnc is continuous.

xy:W1,1pRnq Ñ xKnc,#y is a valuation.

SpK #L,q SpK,q SpL,q Blaschke addition Theorem (L. 2012)

An operator z:W1,1pRnq Ñ xKnc,#yis a continuous and affinely covariant valuation

D ¥ ðñ

(56)

Valuations on Sobolev Spaces

Πxy:W1,1pRnq ÑKcnis affinely contravariant (LYZ 2006).

Πxy:W1,1pRnq ÑKcnis continuous.

Πxy:W1,1pRnq Ñ xKnc, y is a valuation.

Theorem (L. 2012)

An operator z:W1,1pRnq Ñ xKnc, yis a continuous and affinely contravariant valuation

Dc ¥0such that ðñ

zpfq cΠxfy for every f PW1,1pRnq.

(57)

Valuations on Sobolev Spaces

Πxy:W1,1pRnq ÑKcnis affinely contravariant (LYZ 2006).

Πxy:W1,1pRnq ÑKcnis continuous.

Πxy:W1,1pRnq Ñ xKnc, y is a valuation.

Theorem (L. 2012)

An operator z:W1,1pRnq Ñ xKnc, yis a continuous and affinely contravariant valuation

Dc ¥0such that ðñ

(58)

Characterization of the Projection Body Operator

Theorem (L.: JDG 2010)

An operator Z:Kn0 Ñ xKn, yis a continuous valuation such that ZpφKq |detφ|φtZK @φPGLpnq

Dc ¥0 such that ðñ

ZpKq cΠK for every K PK0n.

Kn0 convex bodies in Rn containing the origin in their interiors

L.: AIM 2002, TAMS 2005

Schuster & Wannerer: TAMS 2012; Haberl: JEMS 2011+; Abardia & Bernig: AIM 2011; Parapatits: TAMS 2012+

(59)

Characterization of the Projection Body Operator

Theorem (L.: JDG 2010)

An operator Z:Kn0 Ñ xKn, yis a continuous valuation such that ZpφKq |detφ|φtZK @φPGLpnq

Dc ¥0 such that ðñ

ZpKq cΠK for every K PK0n.

Kn0 convex bodies in Rn containing the origin in their interiors

Schuster & Wannerer: TAMS 2012; Haberl: JEMS 2011+; Abardia & Bernig: AIM 2011; Parapatits: TAMS 2012+

(60)

Characterization of the Projection Body Operator

Theorem (L.: JDG 2010)

An operator Z:Kn0 Ñ xKn, yis a continuous valuation such that ZpφKq |detφ|φtZK @φPGLpnq

Dc ¥0 such that ðñ

ZpKq cΠK for every K PK0n.

Kn0 convex bodies in Rn containing the origin in their interiors L.: AIM 2002, TAMS 2005

Schuster & Wannerer: TAMS 2012; Haberl: JEMS 2011+;

Abardia & Bernig: AIM 2011; Parapatits: TAMS 2012+

(61)

Sketch of the Proof

z:W1,1pRnq Ñ xKnc, y continuous, affinely contravariant valuations

L1,1pRnq €W1,1pRnq piecewise linear continuous functions P1,1pRnq €L1,1pRnq ‘linear elements’

P Rn

`P `P PL1,1pRnq

P PP0n

P0n convex polytopes inRn containing the origin in their interiors

(62)

Sketch of the Proof

z:W1,1pRnq Ñ xKnc, y continuous, affinely contravariant valuations

L1,1pRnq €W1,1pRnq piecewise linear continuous functions

P1,1pRnq €L1,1pRnq ‘linear elements’

P Rn

`P `P PL1,1pRnq

P PP0n

P0n convex polytopes inRn containing the origin in their interiors

(63)

Sketch of the Proof

z:W1,1pRnq Ñ xKnc, y continuous, affinely contravariant valuations

L1,1pRnq €W1,1pRnq piecewise linear continuous functions P1,1pRnq €L1,1pRnq ‘linear elements’

P Rn

`P `P PL1,1pRnq

P PP0n

P0n convex polytopes inRn containing the origin in their interiors

(64)

Sketch of the Proof, cont.

f PL1,1pRnq f

Z:P0n Ñ xKnc, y, ZpPq zp`Pq GLpnq contravariant valuation onP0n L.: JDG 2010ñ zp`Pq cΠx`Py ñ zpfq cΠxfy

(65)

Sketch of the Proof, cont.

f PL1,1pRnq f

Z:P0n Ñ xKnc, y, ZpPq zp`Pq GLpnq contravariant valuation onP0n L.: JDG 2010ñ zp`Pq cΠx`Py ñ zpfq cΠxfy

(66)

Sketch of the Proof, cont.

f PL1,1pRnq f

g

Z:P0n Ñ xKnc, y, ZpPq zp`Pq GLpnq contravariant valuation onP0n L.: JDG 2010ñ zp`Pq cΠx`Py ñ zpfq cΠxfy

(67)

Sketch of the Proof, cont.

f PL1,1pRnq f

g

`P

`P x PP1,1pRnq

Z:P0n Ñ xKnc, y, ZpPq zp`Pq GLpnq contravariant valuation onP0n L.: JDG 2010ñ zp`Pq cΠx`Py ñ zpfq cΠxfy

(68)

Sketch of the Proof, cont.

f PL1,1pRnq f

g

`P

`P x PP1,1pRnq

`Q `Q y PP1,1pRnq

Z:P0n Ñ xKnc, y, ZpPq zp`Pq GLpnq contravariant valuation onP0n L.: JDG 2010ñ zp`Pq cΠx`Py ñ zpfq cΠxfy

(69)

Sketch of the Proof, cont.

f PL1,1pRnq f

g

`P

`P x PP1,1pRnq

`Q `Q y PP1,1pRnq

f _`Q g, f ^`Q `P zpfq zp`Qq zpgq zp`Pq

Z:P0n Ñ xKnc, y, ZpPq zp`Pq GLpnq contravariant valuation onP0n L.: JDG 2010ñ zp`Pq cΠx`Py ñ zpfq cΠxfy

(70)

Sketch of the Proof, cont.

f PL1,1pRnq f

g

`P

`P x PP1,1pRnq

`Q `Q y PP1,1pRnq

f _`Q g, f ^`Q `P zpfq zp`Qq zpgq zp`Pq

Z:P0n Ñ xKnc, y, ZpPq zp`Pq GLpnq contravariant valuation onP0n

L.: JDG 2010ñ zp`Pq cΠx`Py ñ zpfq cΠxfy

(71)

Sketch of the Proof, cont.

f PL1,1pRnq f

g

`P

`P x PP1,1pRnq

`Q `Q y PP1,1pRnq

f _`Q g, f ^`Q `P zpfq zp`Qq zpgq zp`Pq

Z:P0n Ñ xKnc, y, ZpPq zp`Pq GLpnq contravariant valuation onP0n

ñ zpfq cΠxfy

(72)

Sketch of the Proof, cont.

f PL1,1pRnq f

g

`P

`P x PP1,1pRnq

`Q `Q y PP1,1pRnq

f _`Q g, f ^`Q `P zpfq zp`Qq zpgq zp`Pq

Z:P0n Ñ xKnc, y, ZpPq zp`Pq GLpnq contravariant valuation onP0n L.: JDG 2010ñ zp`Pq cΠx`Py ñ zpfq cΠxfy

(73)

Thank you !!!

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