Valuations on Convex Bodies and Sobolev Spaces
Monika Ludwig
Technische Universit¨at Wien
Szeged, May 2012
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, . . .
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, . . .
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, . . .
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.
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
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
Valuations on Convex Bodies
Real valued valuations z:KnÑ xR, y:
Translation invariant, continuous: McMullen, Alesker, ...
Rotation invariant, continuous: Alesker, ...
SLpnqinvariant, upper semicontinuous: L. & Reitzner, ...
Tensor valued valuations z:KnÑ xTd, y:
Vector valued: Hadwiger & Schneider, ...
Symmetricd tensor valued: McMullen, Alesker, Hug & Schneider, ...
Body valued valuations:
Minkowski valuations z:KnÑ xKn, y:
L., Schuster, Schneider, Wannerer, Abardia & Bernig, ...
Lp Minkowski valuations z:KnÑ xKn, py: L., Haberl, Wannerer, Parapatits, ...
Radial valuations z:KnÑ xSn,˜py: L., Haberl, ...
Blaschke valuations z:KnÑ xKcn,#y: Haberl, ...
Valuations on Convex Bodies
Real valued valuations z:KnÑ xR, y:
Translation invariant, continuous: McMullen, Alesker, ...
Rotation invariant, continuous: Alesker, ...
SLpnqinvariant, upper semicontinuous: L. & Reitzner, ...
Tensor valued valuations z:KnÑ xTd, y:
Vector valued: Hadwiger & Schneider, ...
Symmetricd tensor valued: McMullen, Alesker, Hug & Schneider, ...
Body valued valuations:
Minkowski valuations z:KnÑ xKn, y:
L., Schuster, Schneider, Wannerer, Abardia & Bernig, ...
Lp Minkowski valuations z:KnÑ xKn, py: L., Haberl, Wannerer, Parapatits, ...
Radial valuations z:KnÑ xSn,˜py: L., Haberl, ...
Blaschke valuations z:KnÑ xKcn,#y: Haberl, ...
Valuations on Convex Bodies
Real valued valuations z:KnÑ xR, y:
Translation invariant, continuous: McMullen, Alesker, ...
Rotation invariant, continuous: Alesker, ...
SLpnqinvariant, upper semicontinuous: L. & Reitzner, ...
Tensor valued valuations z:KnÑ xTd, y:
Vector valued: Hadwiger & Schneider, ...
Symmetricd tensor valued: McMullen, Alesker, Hug & Schneider, ...
Body valued valuations:
Minkowski valuations z:KnÑ xKn, y:
L., Schuster, Schneider, Wannerer, Abardia & Bernig, ...
Lp Minkowski valuations z:KnÑ xKn, py: L., Haberl, Wannerer, Parapatits, ...
Radial valuations z:KnÑ xSn,˜py: L., Haberl, ...
Blaschke valuations z:KnÑ xKnc,#y: Haberl, ...
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, ...)
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, ...)
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, ...)
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, ...)
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
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
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
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
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
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
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
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)
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)
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)
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
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
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
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
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
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
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
Origin-symmetric Convex Bodies K
ncSupport function hpK,q:RnÑR
K hpK,uq
u
hpK,uq maxtux :xPKu
hpK,u vq ¤hpK,uq hpK,vq sublinear and even
Surface area measure SpK,q:BpSn1q Ñ r0,8q
K
SpK,tuuq u
SpK, ωq
Hn1ptxPbdK :npK,xq Pωuq
npK,xq outer unit normal vector toK atx PbdK
SpK,q even measure,
not concentrated on a great sphere
Origin-symmetric Convex Bodies K
ncSupport function hpK,q:RnÑR
K hpK,uq
u
hpK,uq maxtux :xPKu
hpK,u vq ¤hpK,uq hpK,vq sublinear and even
Surface area measure SpK,q:BpSn1q Ñ r0,8q
K
SpK,tuuq u
SpK, ωq
Hn1ptxPbdK :npK,xq Pωuq
npK,xq outer unit normal vector toK atx PbdK
SpK,q even measure,
not concentrated on a great sphere
Origin-symmetric Convex Bodies K
ncSupport function hpK,q:RnÑR
K hpK,uq
u
hpK,uq maxtux :xPKu
hpK,u vq ¤hpK,uq hpK,vq sublinear and even
Surface area measure SpK,q:BpSn1q Ñ r0,8q
K
SpK,tuuq
u SpK, ωq
Hn1ptx PbdK :npK,xq Pωuq
npK,xq outer unit normal vector toK atx PbdK
SpK,q even measure,
not concentrated on a great sphere
Origin-symmetric Convex Bodies K
ncSupport function hpK,q:RnÑR
K hpK,uq
u
hpK,uq maxtux :xPKu
hpK,u vq ¤hpK,uq hpK,vq sublinear and even
Surface area measure SpK,q:BpSn1q Ñ r0,8q
SpK,tuuq
u SpK, ωq
Hn1ptx PbdK :npK,xq Pωuq
npK,xq outer unit normal vector toK
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
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
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
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
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
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
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?
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?
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.
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
»
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)
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)
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)
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)
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)
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
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.
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.
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.
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
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.
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
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+
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+
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+
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
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
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
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
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
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
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
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
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
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
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
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