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Functional quantization for pricing derivatives

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HAL Id: inria-00070611

https://hal.inria.fr/inria-00070611

Submitted on 19 May 2006

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Functional quantization for pricing derivatives

Gilles Pagès, Jacques Printems

To cite this version:

Gilles Pagès, Jacques Printems. Functional quantization for pricing derivatives. [Research Report]

RR-5392, INRIA. 2004, pp.53. �inria-00070611�

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ISRN INRIA/RR--5392--FR+ENG

a p p o r t

d e r e c h e r c h e

Thème NUM

INSTITUT NATIONAL DE RECHERCHE EN INFORMATIQUE ET EN AUTOMATIQUE

Functional quantization for pricing derivatives.

Gilles Pagès and Jacques Printems

N° 5392

Novembre 2004

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X j™c5xzcxzymyRibp{ymibj¤xr`šU*p{ia`bPRp{cRpzibShxz›Rˆ9xz_aj™_xzcR|¼»3j™c5xWcmp{c«xzeR_b_aj¤xzc_bU`b`bj™cR

3ž›™jl´zUY|mj;eR_bjlp{cR_(5¢ˆf^5_bp{SU ¸ k3eRxzc…`šj™Ÿj™cRShxzyRymj™cR{_I¹7ˆ9xz_aUT|p{c_ap{ShUYj™c…`šU{išxz›;UTkfe9x`bj™p{cm_ 30_bUU ;1I‚@<!5' 

]3j™cR}Udpzym`šjlS5xz›3œžeRcR}`šj™pzc9xz›Rkfe9xzc…`bj™ŸIxr`šj™pzc(`šPRUp{ibU`šj™}Txz›™›µ^}p{c…‡{Uib{U_#x`¢xišx`bPRUTi¡y=pMpzi

(logN)覧išxr`šU

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θ |RUy;UcR|Rj™cm³pzcN`bPRUy9x`bP…®*j™_bUiaUT{eR›™xzibjµ`§^³pzœ7`bPRUyRiapM}UT_b_

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y=UTiœžp{ibShxzcR}UT_#œžp{i

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ibUTxz_bp{cRxzˆR›l^5_bShxz›™›Ì¹d‡xz›™emUT_*pzœ

N 30_šxI^ N10 000

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zibp{eRcm|WpzcWkfe9xcf`bj™ŸTx`šjlp{cpzœMt7j™›lˆ;Uia`F_ay9xz}UT_$xzcR|«WxeR_b_aj¤xzcyRiapM}UT_b_aUT_ ‡3j™U®UT|xz_

L2T¦¶‡zx›™eRU|WibxzcR|RpzS

‡zUT}`šp{ia_T ¥]3UT}`bj™p{c·‚hjl_7|RU‡{pz`bUT| `bp5_a`šx`šjlp{c9xzi^kfe9xzc…`šjlŸTUTia_¥xzcR|.`šPRUj™id}Tp{SyRem`šx`šjlp{c9xz› xyRyR›™jl}Ix`bj™p{cm_

3žp{cRU'¦§|RjlShUcR_bjlp{c9xz›#pzym`šjlS5xz›kfe9xzc…`šjlŸTUTia_T»U`š}5'  ]MU}`šjlp{c¬‹ |RUTxz›™_Œ®*jl`bP¬`bPRU®Uj™{P…`šU|kfe9xz|mišx`beRibU

œžpzibS(eR› E œžp{i¢`šPRU&U'ªMy;U}`~xr`šj™pzcR_

EF(X) H¦Ì‡xz›leRUT|ibxzcR|RpzS‡zUT}`šp{ia_

X ºv§c.]MU}`šjlp{c®U&j™c…‡zUT_¦

`bj™…xr`šUxŒ_by=UT}Tj™xz›F}T›™xz_b_*pzœkfe9xzc…`šjlŸTUTia_7}Txz›™›lUT|_b}Txz›™U|†ymibp3|ReR}`dkfe9xzc…`bj™ŸTUib_*®*PRj™}~P.®*j™›l›¼ˆ;U¥`bPRU´U^pzœ

cfeRSUTiaj™}Txz›=xzyRyR›lj™}Ixr`šj™pzcR_T  ˜ PRUTc

X j™_x(«xzeR_a_bj™xzch‡zUT}`bp{iT»Mjl`b_¨xziaP3emcRUTcM¦§©FpMQ‡{UI3

K¦ L5oUªMy9xzcR_aj™p{c 3i.e.jl`b_ P CA j™cŒjlc 9cRjµ`šU|RjlShUcR_bjlp{c65$yR›™xI^M_¢x¥}TiaeR}Tj™xz›9i£p{›lUz Gs yRibp3}TU|ReRibU*jl_¢|mUT_b}ibjlˆ;U|`bpW`šxzˆReR›™x`šU

`bPRUpzym`šjlS5xz›AyRibp3|ReR}`&kfe9xzc…`šjlŸTUib_T 7u9p{i*`šPRU²ibp“®*cRj™xzc·Spz`šjlp{c`šPRU_bU`šxzˆR›lUT_7xzibUx“‡xzjl›¤xzˆm›™U¥p{c.`šPRU

®UTˆA hv§c¯]MUT}`šjlp{cM»$xw*p{S(ˆ=UTia.›lj™´UShU`šPRp3| j™_¥yRiap{y;pz_bUT|³`šp_by=UTU|¯eRy³cfeRSUTibjl}Ixz›j™c…`šU{išx`bj™p{cA 

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`bj™p{cm_¢jlcx²›™xz}~´{¦]M}~PRpz›™UT_¡SpM|mUT›CxzcR|Œ‡xzcRjl›™›¤x½#x›™›™_ojlc5xWt7U_a`bp{c5_`šp3}~P9xz_a`bj™}*‡{p{›™x`šjl›™jµ`§^Sp3|RUT›J OPRU

iaUT_aeR›l`b_7xibUkfeRjl`bUWymibp{Sj™_aj™cRR v§c†y9xia`šjl}TeR›™xziT»M®UWy;pzj™c…`*p{em``bPRU_`šiaj™´fj™cRUH}Tj™UcR}^.pzœxwdp{Sˆ;Uib

log¦ÌUª3`šibxzy=p{›¤x`bj™p{c®*PRj™}~PcfeRSUTiaj™}Ix›™›l^Œpzem`šy=UTiœžp{ibS_*Z†p{c…`bUW½#xzib›lp(_bjlS(eR›¤xr`šj™pzc5j™cˆ=pz`bPUªmxzSyR›™U_T  v§c³]3UT}`bj™p{c7Cm»;®U(p{em`b›™jlcRUx´fjlcR| pzœ

F Q¦M C ShU`šPRp3|†®*PRUibU(œžeRcm}`šjlp{c9xz›Gkfe9xzc…`šjlŸIx`bj™p{c†ˆ=UT}TpzShU_

x}p{c…`šibpz›¼‡zxibj¤xr`šU&ibxzcR|Rp{S ‡zxibj¤xˆR›™U 

(8)

" T¥"*) ! W¬ #

©FU` (H,(. | .)H) ˆ;Uhx·_aUTy9xzibxzˆR›lU5tdj™›™ˆ=UTi`W_by9xz}UxzcR|

X : (Ω,A,P) H ˆ=Ux H¦Ì‡xz›™emUT|³išxzcM¦

|mp{S ‡{UT}`šp{i†®*jl`šP |Rj™_`šiaj™ˆRem`bj™p{c

PX

|mU9cRU| p{c

H UTcR|Rp“®UT| ®*jl`bP jl`b_·²p{ibU›

σ¦ 9UT›l| Bor(H) 

O¡^3yRj™}Txz›*_bU`b`šjlcR{_5xzibU

H = R» Rd UTcR|mp•®UT| ®*jµ`šP jl`š_Œ}TxzcRp{cRjl}Ixz›dÆoeR}›™j™|mUIxzc¬cRp{iaS xzcR|

L2T œžp{i

œžemcR}`bj™p{c9x›ok3eRxzc…`šj™ŸTx`šjlp{c¼»GU`b}z 

"

e9xz|Ribx`šjl} (!,- 0 }TpzcR_bjl_a`š_j™c³_a`beR|m^3j™cR†`šPRUˆ;U_a`

k.k2

¦×xzyRymibpIªMj™Shx`šjlp{c

X L2H(Ω,P) ˆ…^ H¦Ì‡xz›™emUT|¯ibxzcR|RpzS ‡zUT}`bp{ib_`šxz´fj™cR°xr`Shpz_a`

N ‡xz›µ¦

emUT_T»CjlcR}T›leR|Rj™cmŒxz›™›A`bPRUj™cR|meR}TU|·kfeRUT_`šjlp{cR_d›™j™´Uxz_a^3Sym`šp`šj™}¥Uibiap{i*ˆ;p{emcR|R_T»Cibx`šU_T»9}TpzcR_a`bibeR}`šj™pzc†pzœ

cmUIxzia›l^hp{ym`šjlS5x›=kfe9xcf`bj™ŸUTib_ ¡OPRj™_œžibxzSU®p{ib´c9x`beRišxz›l›l^j™cm}T›™em|RUT_#Shxzc…^hcRp{cM¦×«Wxzem_b_bj™xzcyRiapM}UT_a_bUT_

›lj™´U¥|Rj;eR_bjlp{cR_#œžp{iU'ªmxzShym›™U-30_aUTU-;B1“‚@<F5 

©FU` x := (x1, . . . , xN) HN ˆ=UNx N¦§kfe9xzc…`šjlŸTUi xzcR| ›™U`

Projx : H → {x1, . . . , xN}

ˆ=U x yRiaprqaUT}`šj™pzc œžp{›l›™p“®*j™cR `bPRU '%(' %"08 vÌ`†ShUTxzcR_`šP9xr`†`bPRU ²pzibUT›y9xia`šjµ`šjlp{c

Projx1({xi}), i= 1, . . . , N pzœ H _šx`bj™_ RUT_

Proj−1x ({xi})⊂ {ξH | |xiξ|H = min

1jN|xjξ|H}, 1iN.

]3eR}~P°x5²p{ibU›GyRxzia`bjl`šjlp{cj™_*}Ix›™›™U|·x %('('%!5pzœ

H jlcR|ReR}UT|·ˆ…^

x OPRU((%!

x j™_pzœ`bUTc¬|RUTcRp`šUT|

Ci(x) := Projx1({xi})  &cRU|RURcRUT_Œ`šPRU /0 ³pzœ

X

jlcR|ReR}UT|.ˆ…^

x ˆ…^

Xbx := Projx(X).

3`šPRU¯UªMy;pzcRUTc…`

x ®*jl›™›pzœ `šUc ˆ=U |RibpzyRy;U| p{i·iaUTyR›™xz}TU| ˆ…^ jµ`š_†_bj™ŸU

N5.vÌ`°jl_†`šPmU ˆ;U_a`

L2(P)¦

xyRyRibpIªMj™Shx`bj™p{c

X ˆ…^ {x1, . . . , xN}¦Ì‡xz›leRUT|NibxzcR|Rp{S ‡{U}`špzib__bj™cm}TUz»¢œžp{iŒxzc…^­ibxzcR|Rp{S ‡{UT}`šp{i

X0 : Ω → {x1, . . . , xN}»

kXX0k22 = X

1iN

Z

Ci(x)(X(ω))|X(ω)X0(ω)|2HP(dω)

X

1iN

Z

Ci(x)(X(ω))|X(ω)xi|2HP(dω)

= E( min

1≤i≤N|Xxi|2H) =kXXbxk22

Vdpz`šU·`bP9x`h`šPRUibU°xziaU·jlc 9cRjµ`šUT›µ^NS5xcf^¡p{iap{cRp{j*`šU_b_aUT›™›™x`šjlp{cR_Œ®*PRj™}~P x›™›*yRibp3|ReR}U·`šPmU _šxzSU

kfe9x|Rišx`bj™}L %

kX Xbxk2

  v§c œ0xz}``šPRU·ˆ;p{emcR|9xziaj™UT_5pzœ¥`šPRU¡pzibp{cRpzj7}UT›™›l_5pzœ

xcf^¡p{iap{cRp{jF`bUT_b_aUT›l›¤x`bj™p{c.j™_d}Tp{c…`šxzj™cRU|·jlc†`šPmU_šxShU 9cRjµ`šUWeRcRj™pzc·pzœoSUT|mj¤xzc.P…^My=UTiayR›¤xcRUT_

Hij (xi xj|.)H = 0 3xi 6= xj

5 .]MpR»Gjlœ`šPRU|Rjl_a`šiaj™ˆReM`šj™pzc

PX

®UTj™zPf`b_cRp†P…^My=UTiayR›¤xcRUz»G`šPRUc

Xbx j™_

P¦ a.s. eRcmj™kfeRUT›µ^|RU9cRUT|A 

(9)

OPRU_aUT}p{cR|³_a`šUy pzœ¡`šPRUp{yM`šj™Sj™ŸTx`šjlp{cyRibp3}TU_b_j™_d`šp 9cm| x

N¦Ì`beRyR›lU

x HN»¼jlœ¢xcf^z»¼®*PRj™}~P Sj™cmj™Sj™ŸTU_d`bPRUŒkfe9xzc…`šjlŸIx`bj™p{c°UibibpziWp“‡zUTi

HN v§c œ0x}`p{cRUŒ}~PRU}~´f_ˆ…^ `šPmUŒ`bibj™xzcR{eR›™xziYjlcRUTkfe9x›™jl`§^

`bP9x``bPRU¥œžeRcR}`bj™p{c

QXN : (x1, . . . , xN)7→ kXXbxk2 =k min

1≤i≤N|Xxi|Hk2

jl_5©FjlyR_b}~PRjµ`šŸ†}Tp{c…`šjlcfeRp{eR_pzc

HN  ˜ PRUc N = 1» Q21(x) = E|X x|2H

j™_5x _`šibjl}`b›l^¬}Tp{c…‡zUª

œžemcR}`bj™p{c5®*Pmj™}~PiaUIxz}~PRU_jl`b_Sj™cRjlS(eRS

Var(|X|H) xr` x :=EX ºOPmUTc¼»RpzcRU&_bPmp•®*_ˆ…^hj™cR|meR}`bj™p{c pzc N 30_bUU;B1 1<Cœžp{i¡|RU`~xzjl›™_(5'»…`šP9x`

QXN xz›µ®#xI^3_iaUIxz}~PRU_#xWShjlcRj™S(emS x`_bp{SUdp{ym`šjlS5x›

N¦Ìkfe9xzc…`šjlŸTUTi

x := (x1, . . . , xN) s7_W_apMpzc¯xz_

|suppP

X| ≥ N»Gxzc…^°_aeR}~P¯p{yM`šj™Shxz›

N¦Ìk3eRxzc…`šj™ŸUTiP9xz_¥yRxzj™i®*j™_bU

|mj™_a`bj™cR}`}Tp{Sy=p{cRUTc…`b_T  OPRU ´U^@xzia{eRSUTc…`.j™_`bP9x``šPRU°œžeRcm}`šjlp{c

QXN jl_®UTxz´f›l^ ›™p“®UTi_bUShj¦ }p{c…`šjlc3emp{eR_¡p{c

HN OPRUc¼»3`bPRU*_beRymy;p{i`¡pzœAx|mj™_a`bibjlˆRem`šjlp{c(ˆ=UTjlcR

σ¦§}p{ShyRxz}`ojlc(`šPRUdtdj™›™ˆ=UTi`o_byRxz}TU

H»$jµ`j™__bUy9xzišxˆR›™U ]MpR»G›™U`

(zn)n1

|RUTcRp`šUhxzc¯U‡{UTi^f®*PRUTiaU|RUTcm_bU5_aUTkfeRUcR}TUjlc³`bPRU_beRyRy=p{i`pzœ

PX

 oOPRUTc

minHN(QXN)2 (QXN(z1, . . . , zN))2 = Z

supp(PX)

1miniN|ξzi|2HP

X(dξ)0 xz_ N → ∞

ˆ…^ `bPRU©FUTˆ=UT_a{eRU|Rp{Sj™c9xr`šUT|­}p{c…‡{Uib{UcR}TU.`šPRUp{ibUS† ¯Æ¡›leR}Tjl|9x`bj™cR·`bPRUišxr`šUpzœ7}Tp{c…‡zUTibzUTcR}U†pzœ

minHNQXN `šp“®xzib| 0 jl_Wx.S(em}~P¯Sp{ibUŒ|RUS5xzcm|Rj™cRyRiap{ˆR›lUTS.»GU‡{Uc­j™c 9cRjµ`šU|Rj™SUTcR_aj™p{cA hvÌ`WP9xz_

ˆ=UTUc}Tp{SyR›lU`šU›l^U›™eR}j™|9x`bUT|œžpzicRp{c3¦§_bjlcR{eR›™xzi

Rd¦¶‡zx›™eRU|(išxzcm|Rp{S ‡{U}`špzib_oˆ…^`bPRU#_bpr¦§}Ix›™›™U|¼xz|mp{i OPmUTp{iaUTS 30_aUTU-;ԁ<!5' 

¿fà ’ ¿

9# % '% ' "2'(', %$0

X L2+ηRd (Ω,P)

', %

η >0 ?% f #%.% % #%0'!> /%98' .%J(! ' 0 P

X

7 48%

'('8 0 %

(minRd)N(QXN)2 = min

x(Rd)NkXXbxk22 J2,d

N2/d Z

Rdfd+2d (ξ)dξ 1+2/d

+o 1

N2d

' N +.

˜ PmUTc

f 6≡ 0»C`bPRj™_^3j™U›™|R_7xh_aP9xziay·išxr`šUœžp{i`šPRUk3eRxz|Rišxr`šj™}kfe9xzc…`bj™ŸIxr`šj™pzc†Uibibpzi7_aj™cR}UW`bPRUjlc…`šUTzišxz›

jlc `šPRUiaj™{P…`YP9xzcR| _bjl|RU(jl_¥xz›l®xI^3_ 9cRjl`bUeRcR|RUi&`šPRUŒx_b_bemShym`bj™p{c°pœ¢`bPRU(`šPmUTp{iaUTS.  ˜ PRUc

f 0»

`bPRj™_dcRph›™p{cRzUTi*yRibp“‡3j™|mUT_7xh_bPRxziby ibx`šU»=xz›l`bPRp{eR{P._bem}~P°_bP9xziay·ibx`šU_Y}Ixc·ˆ=UU_a`~xˆR›™jl_bPRU|†œžp{id_bp{SU

_ay;U}Tj™xz› |Rj™_`šibjlˆRem`bj™p{cR_ 3ž_bUT›µœ¤¦§_aj™Sj™›¤xi|Rjl_a`šiaj™ˆReM`šj™pzcR_p{c·œžibxz}`šxz›F_bU`š_T»;U`b}5 *OPRU`šibemUW‡xz›leRUpœ

J2,d

®*Pmj™}~P}Tp{iaibU_by=p{cR|R_`šp(`bPRU¥eRcRjµœžp{ibS |Rjl_a`šiaj™ˆReM`šj™pzc5p“‡{Ui

[0,1]d j™_#emcR´fcRp“®*c·xz›µ`šPRpzeR{Pp{cmU¥´3cmp•®*_

`bP9x`

J2,d =d/(2πe) +o(d) 

(10)

v§c³xt7jl›™ˆ=UTia`Y_bU`b`šjlcRcRp_beR}~P³{›lp{ˆ9xz›GibU_beR›µ`PRp{›™|m_T»FU‡zUTc œžp{iW«xzeR_b_aj¤xzc°ymibp3}TUT_a_bU_T Œt7p“®U‡zUTiT»

_aj™Sj™›™xzi_bP9xziayNišx`bUT_(}TxzcNˆ;UU_a`šxzˆR›™jl_bPRU|Nj™c _ap{ShU5}Ixz_aUT_®*PRUTcNp{cmUP9xz_x {p3p3|­}Tp{c…`šiap{›pzc `šPRU

Uj™{Uc…‡zx›™eRU_#pzœ `šPRU¥}p“‡zxibj¤xcR}TU&pzy;Uišx`bp{i#pzœF`bPRUW«WxeR_b_aj¤xzcyRiapM}UT_a_T ¡OPRU¥Shxzj™cU'ªMj™_a`bj™cRiaUT_aeR›l`b_#j™c

`bP9x`7«xzeR_a_bj¤xc._aU`a`šj™cmhxibUˆRibpzeR{P…`*`šp{{U`šPRUij™c`šPmU`bPRUTpzibUTS ˆ;U›™p“® 

¿fà ’ ¿

?%

H=L2T # % (Xt)t∈[0,T] 8% (%.%(% # 8., % ' 98%

9'(' (%('('2' >0

Z T 0

Var(Xt)dt <+

(a) ?% (e`)`≥1 8% ,- 8('' H % c2` := Var((X|e`)L2

T), n 1 % %-'

', %:(%

b >1 ' J 0 c2` =O(`−b) % minHN QXN =O

(logN)b21 .

(b) ?% `)`≥1 #%.% % '% %(% %"%&%(' % (& (% (% .

ΓX X "% #

!AA'(%#!"> #%#$ %

(eX` )`≥1 8% % ( %('.#!"> ,- %"%8(''I

H

% % '2', %/ %

b >1 ' >0 λ` ε0`b /"% % " ` ε0 >0 % minHN QXN ε00(logN)b21 : "%I%"

N ε00 >0 . (c) %, % λ` =cλ`b+o(`b) %

minHN QXN = cλ12b2b

2b21(b1)12 (logN)b21 +o

(logN)b21

. 3¶„M 1=5

OPRjl_W`bPRUTpzibUTS }Txzc¯ˆ=UhU'ª3`šUTcm|RUT|­ˆ…^ }TpzcR_bjl|RUTiaj™cR.`šPRU}Ixz_aUh®*PRUibU

c2` xzcR|pzi λ`

xzibU 30eRymy;Ui¦

ˆ=p{eRcm|RUT| ˆf^05ibU{eR›¤xib›l^³‡xzia^3jlcR _aUTkfeRUcR}TU_5®*jl`bP¬jlcR|RU'ª

b» b 1 30xzcR| P

`c2` < + ®*PRUc b = 15 *vÌ`7`šeRiacR_Yp{eM`7`bP9x`YœžpzidShxzc…^ 30p{cmU¦§yRxzišxzSU`bUTi 5ymibp3}TUT_a_bU_T»¼`šPmUjlcR|RUª

b jl_7}›™p{_aUT›l^iaUT›™x`šU|

`bp`šPRUŒt{›™|mUTi&iaUT{eR›™xzibjµ`§^

µ pzœ¡`šPRUŒxzymyR›™jl}Ix`bj™p{c

t 7→ Xt

œžibp{S

[0, T] jlcf`bp L2(Ω,P)±7p{cRU(‡zUTibj9UT_

`bP9x`

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(X|e`)L2

T

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i.e. `šPRU¥_akfe9xzibUWpzœ

QXN DNX(x) := E min

1≤i≤N|Xxi|2H, xHN.

¿fà ’ ¿ 4

(a) ?% x:= (x1, . . . , xN)HN 8% N 0 %2'' @!"

i6=j, xi 6=xj

# P(X∈ ∪i∂Ci(x)) = 0 3J‚M „ 5

P

X

.%""8% 8#9 /% (%!'

% DNX ' #52% %98% x !

∂DXN

∂xi

:= 2E( Ci(x)(X)(xiX)) = 2 Z

Ci(x)

(xiξ)P

X(dξ), 1iN, 30‚m Ô‚95

# !'#52% %

D(DXN) ' ( ! ' % x ' (!,- N 0% # |suppP

X| ≥ N '(' , 76 '2''98 % # '%(% : ;6 I' 0

DXN(x) = 0. 3J‚m â‹ 5

(b) 2'(', % H = R # supp(P

X) = closure((m, M)) ! R m, M R

%

#% % #

N 0% x = (x1, . . . , xN) x1 < . . . < xN !!' .%('('%!

' "!&% 8

C1(x) = (−∞, x3/2], Ci(x) := (xi1/2, xi+1/2], i= 2, . . . , N 1, CN(x) = (xN1/2,+) 3J‚m Ï 5

% %

xi1/2 := xi+xi1

2 , i = 2, . . . , N P

X

' 98'.% (!69' ! 4( ! '

# f % DXN ': (%I(!69' #52%(%98% x # !!'=< %('('7 ' "!&% 8

D2(DNX)(x) =

2DXN

∂xi∂xj

(x)

1i,jN

3J‚m 95

(12)

!

2DNX

∂x2i (x) = 2 Z xi+ 1

2

xi−1 2

f(u)duxi+1xi

2 f(xi+1

2) {i≤N−1} xixi−1

2 f(xi1

2) {i≥2}, 1iN,

2DXN

∂xi∂xi−1(x) =xi xi1

2 f(xi1

2), 2iN, 2DXN

∂xi∂xi+1(x) =xi+1xi

2 f(xi+1

2), 1iN1,

# 2DXN

∂xi∂xj

(x) = 0 % '%

(c) %%('(' '(' , % H =R # P

X

'/98' .% (!69' ! >

log ( &% # f

i.e. {f >0}= (m, M)# logf '( &% (m, M) % {∇DXN = 0}={x}

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®*Pmj™}~P¯®U5iaUœžUTiW`šp ;ρ<J» ;B1•=<J vÌ`(P9x__bU‡{Uišxz›}Tp{cR_aUTkfeRUcR}TU_pzc¯ˆ=pz`šP¯`bPRUTpzibU`bj™}Txz›¢xzcR|¯cfeRSUTiaj™}Txz›

x_by=UT}`b_T uj™ia_a`jµ`*_beRz{UT_`š_*`šp`šPRU¥œžp{›l›™p“®*j™cm|RU9cRjl`bj™p{cpzœ$_a`šx`šjlp{c9xzi^{ 

¿ ‘ žÃ

N 0% xHN ' ' !" 76 # % 98&% 76 ' !% #

2'

N 0% X % #, &%(. Xbx ' !% # :' N

X

v̜ P(XCi(x))>0 œžp{iU‡zUTia^

i= 1, . . . , N»m`šPRUUk3eRx`šjlp{c

DNX(x) = 0 x›™_bp(®*iajl`bUT_

xi = E( Ci(x)(X)X)

P(XCi(x)) =E(X | {XCi(x)}), i= 1, . . . , N. 30‚m M5

½pzcR_bUk3emUTc…`š›µ^†_aj™cR}U¥`šPRU

σ¦ 9UT›l|R_*{UTcmUTišxr`šUT|.ˆ…^

Xbx xzcR| {{XCi(x)}, i= 1, . . . , N} }p{j™cm}Tj™|mU

E(X|Xbx) =Xbx. 3J‚m C95

v§c.y9xzi`šjl}TeR›™xzi

E(X) =E(Xbx) 

ƪM}TUym`7œžpzi

log¦§}p{cR}IxI‡zUWpzcRU¦Ì|Rj™SUTcR_aj™p{cRxz›;yA Ô|¼ œ× µ»Rp{ym`bj™Shxz›;kfe9xcf`bj™ŸUTi3ž_(5#xziaU¥cRpz``bPRU¥p{cR›µ^5_`~xr¦

`bj™p{cRxzia^5k3eRxzc…`šj™ŸUTia_ 3ž_bUUnoibpzy;p{_ajl`bj™p{c‹ˆ=UT›™p“® xzˆ=p{em` ¸ ¨xziaPfeRcRUTc3¦×©FpMQ‡{U{¹yRiapM|meR}`dkfe9xzc…`šjlŸTUib_(5' 

Vdpz`šU¥`šPRx`*p“®*j™cR`šp 30‚m C 5`šPRUkfe9xzc…`šjlŸIx`bj™p{cUibibpziP9xz_`šPRUc·xŒ_bjlShym›™UTiUªMyRiaUT_b_aj™p{c†_bjlcR}TU

E(|XXbx|2H |Xbx) = Xbx) +|Xbx|2H

E(|X|2H |Xbx)− |Xbx|2H

3J‚m Ôƒ95

_ap`bP9x`

kXXbxk22 = E(|X|2H)E(|Xbx|2H) =E(|X|2H) X

1iN

|xi|2P(XCi(x)).30‚m 1“Š95

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