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Derivative Formula, Coupling Property and Strong Fellerfor S(P)DEs Driven by Levy Processes

Z. DongJoint work with: X.H. Peng, Y. L. Song, X.C. Zhang

Academy of Mathematics and Systems Sciences, Chinese Academy of Sciences

7th International Conference on Stochastic Analysis and itsApplications, Seoul national university, August 6-11, 2014

Z. Dong (AMSS CAS ) Derivative Formula, Coupling and Strong Feller 28-04-2014 1 / 42

Outline

1 Introduction: Framework and Known Results

2 Derivative formula and coupling property for SDEs

3 Derivative formula and coupling property for SPDEs

4 Strong Feller Property for SDEs driven by degenerate additive noise

5 Classical Wiener Space

Z. Dong (AMSS CAS ) Derivative Formula, Coupling and Strong Feller 28-04-2014 2 / 42

Framework

The Bismut formula (also called Bismut-Elworthy-Li formula) is afundamental tool in stochastic analysis. Let, for instance, Xt be adiffusion process on Rn generated by an elliptic differential operator andPtt≥0 be the associated Markov semigroup. The Bismut formula is oftype

∇ξPt f (x) = Ef (X xt )Mx

t , f ∈ Bb(Rn), t > 0,

where Mxt is a random variable independent of f , and ∇ξ is the directional

derivative along ξ.

Z. Dong (AMSS CAS ) Derivative Formula, Coupling and Strong Feller 28-04-2014 3 / 42

Framework

Applications of Derivative Formula:

Strong Feller properties

Heat kernel estimates

Functional inequalities · · · · · ·

Z. Dong (AMSS CAS ) Derivative Formula, Coupling and Strong Feller 28-04-2014 4 / 42

Framework

Applications of Derivative Formula:

Strong Feller properties

Heat kernel estimates

Functional inequalities · · · · · ·

Z. Dong (AMSS CAS ) Derivative Formula, Coupling and Strong Feller 28-04-2014 4 / 42

Framework

Applications of Derivative Formula:

Strong Feller properties

Heat kernel estimates

Functional inequalities

· · · · · ·

Z. Dong (AMSS CAS ) Derivative Formula, Coupling and Strong Feller 28-04-2014 4 / 42

Framework

Applications of Derivative Formula:

Strong Feller properties

Heat kernel estimates

Functional inequalities · · · · · ·

Z. Dong (AMSS CAS ) Derivative Formula, Coupling and Strong Feller 28-04-2014 4 / 42

Framework

Development:

Diffusion (jump-diffusion) case:♣ Non-degenerate Wiener processes: J.M. Bismut( Large Deviations and theMalliavin Calculus, Birkhauser, Boston, 1984), K.D. Elworthy and X.M.Li(JFA,1994), S. Peszat and J. Zabczyk(Ann.Prob,1995), A. Takeuchi(JTheor.Prob.,2010), Z.Dong and Y.C.Xie(JDE,2011), B. Xie(Poten. Ana., 2012)· · ·♣ Degenerate Wiener processes: A. Guillin and F.Y. Wang(JDE,2012), F.Y. Wang

and X.C. Zhang(JMPA,2013), · · ·

Purely jump case:♣ Non-degenerate jump processes: R.F. Bass and M. Cranston. (Ann. Probab.,1986), J.R. Norris, (Seminaire de Probabilites XXII. Lect. Notes. Math., 1988),Z.Q.Cheng(2010),F.Y. Wang(SPA, 2012), X.C. Zhang(SPA, 2012), E. Priola andJ. Zabczyk.(PTRF, 2011), J. Wang and F.Y. Wang(SPA, 2012)· · ·♣ Degenerate jump processes: Few results

Z. Dong (AMSS CAS ) Derivative Formula, Coupling and Strong Feller 28-04-2014 5 / 42

Framework

Development:

Diffusion (jump-diffusion) case:♣ Non-degenerate Wiener processes: J.M. Bismut( Large Deviations and theMalliavin Calculus, Birkhauser, Boston, 1984), K.D. Elworthy and X.M.Li(JFA,1994), S. Peszat and J. Zabczyk(Ann.Prob,1995), A. Takeuchi(JTheor.Prob.,2010), Z.Dong and Y.C.Xie(JDE,2011), B. Xie(Poten. Ana., 2012)· · ·♣ Degenerate Wiener processes: A. Guillin and F.Y. Wang(JDE,2012), F.Y. Wang

and X.C. Zhang(JMPA,2013), · · ·

Purely jump case:♣ Non-degenerate jump processes: R.F. Bass and M. Cranston. (Ann. Probab.,1986), J.R. Norris, (Seminaire de Probabilites XXII. Lect. Notes. Math., 1988),Z.Q.Cheng(2010),F.Y. Wang(SPA, 2012), X.C. Zhang(SPA, 2012), E. Priola andJ. Zabczyk.(PTRF, 2011), J. Wang and F.Y. Wang(SPA, 2012)· · ·♣ Degenerate jump processes: Few results

Z. Dong (AMSS CAS ) Derivative Formula, Coupling and Strong Feller 28-04-2014 5 / 42

Recall two Facts

Coupling Property:(Cranston, Greven.,1995,SPA)A strong Markov process on a Polish space has coupling property if andonly if

limt→∞

‖Pt(x , ·)− Pt(y , ·)‖Var = 0, x , y ∈ Rn

where Pt(x , ·) is the transition probability and ‖ · ‖Var denotes the totalvariation norm.

Strong Feller:(Da Prato, Zabczyk, Erg.Inf.Dimen.Sys.,1995) A Markovsemigroup Pt on Bb(Rn) is strong Feller if ∀f ∈ C 2

b (Rn), one has

|Pt f (x)− Pt f (y)| ≤ C‖f ‖∞|x − y |.

Z. Dong (AMSS CAS ) Derivative Formula, Coupling and Strong Feller 28-04-2014 6 / 42

Recall two Facts

Coupling Property:(Cranston, Greven.,1995,SPA)A strong Markov process on a Polish space has coupling property if andonly if

limt→∞

‖Pt(x , ·)− Pt(y , ·)‖Var = 0, x , y ∈ Rn

where Pt(x , ·) is the transition probability and ‖ · ‖Var denotes the totalvariation norm.

Strong Feller:(Da Prato, Zabczyk, Erg.Inf.Dimen.Sys.,1995) A Markovsemigroup Pt on Bb(Rn) is strong Feller if ∀f ∈ C 2

b (Rn), one has

|Pt f (x)− Pt f (y)| ≤ C‖f ‖∞|x − y |.

Z. Dong (AMSS CAS ) Derivative Formula, Coupling and Strong Feller 28-04-2014 6 / 42

Outline

1 Introduction: Framework and Known Results

2 Derivative formula and coupling property for SDEs

3 Derivative formula and coupling property for SPDEs

4 Strong Feller Property for SDEs driven by degenerate additive noise

5 Classical Wiener Space

Z. Dong (AMSS CAS ) Derivative Formula, Coupling and Strong Feller 28-04-2014 7 / 42

Framework

Consider following semilinear SDEs:dXt = b(Xt)dt + σtdLt ,

X0 = x ,(1)

where b : Rn → Rn and σ : [0,∞)→ Rn ⊗ Rn are measurable. L is aLevy process with characteristic measure ν.

Z. Dong (AMSS CAS ) Derivative Formula, Coupling and Strong Feller 28-04-2014 8 / 42

Hypothesis

(H2.1) There exists a differentiable function ρ : Rn0 → (0,∞) satisfying

ν(dz) ≥ ν1(dz) := ρ(z)dz .

(H2.2) b ∈ C 1(Rn) with ∇b bounded and Lipschitz continuous. Andthere exists a constant β > 0 such that |σ−1

s | ≤ β for any s > 0.

(H2.3) There is a constant K > 0 such that

〈b(x)− b(y), x − y〉 ≤ −K |x − y |2

for any x , y ∈ Rn.

Z. Dong (AMSS CAS ) Derivative Formula, Coupling and Strong Feller 28-04-2014 9 / 42

Hypothesis

(H2.1) There exists a differentiable function ρ : Rn0 → (0,∞) satisfying

ν(dz) ≥ ν1(dz) := ρ(z)dz .

(H2.2) b ∈ C 1(Rn) with ∇b bounded and Lipschitz continuous. Andthere exists a constant β > 0 such that |σ−1

s | ≤ β for any s > 0.

(H2.3) There is a constant K > 0 such that

〈b(x)− b(y), x − y〉 ≤ −K |x − y |2

for any x , y ∈ Rn.

Z. Dong (AMSS CAS ) Derivative Formula, Coupling and Strong Feller 28-04-2014 9 / 42

Hypothesis

(H2.1) There exists a differentiable function ρ : Rn0 → (0,∞) satisfying

ν(dz) ≥ ν1(dz) := ρ(z)dz .

(H2.2) b ∈ C 1(Rn) with ∇b bounded and Lipschitz continuous. Andthere exists a constant β > 0 such that |σ−1

s | ≤ β for any s > 0.

(H2.3) There is a constant K > 0 such that

〈b(x)− b(y), x − y〉 ≤ −K |x − y |2

for any x , y ∈ Rn.

Z. Dong (AMSS CAS ) Derivative Formula, Coupling and Strong Feller 28-04-2014 9 / 42

Framework

Due to (H2.1), L can be decomposed into two independent parts:

Lt = L1t + L2

t ,

where L1 is purely jump process with ν1(dz). The jump measure of L1 isdenoted by N(dz , dt).

Z. Dong (AMSS CAS ) Derivative Formula, Coupling and Strong Feller 28-04-2014 10 / 42

Framework

If λ := ν1(Rn0) =∞, we aim to investigate the Bismut type formula for

Pt f (x) := Ef (X xt )

and

P1t f (x) := E

f (X x

t )I[Nt≥1]

where t ≥ 0, x ∈ Rn, f ∈ Bb(Rn),Nt := N([0, t]× Rn).

Z. Dong (AMSS CAS ) Derivative Formula, Coupling and Strong Feller 28-04-2014 11 / 42

Framework

If λ := ν1(Rn0) =∞, we aim to investigate the Bismut type formula for

Pt f (x) := Ef (X xt )

and

P1t f (x) := E

f (X x

t )I[Nt≥1]

where t ≥ 0, x ∈ Rn, f ∈ Bb(Rn),Nt := N([0, t]× Rn).

Z. Dong (AMSS CAS ) Derivative Formula, Coupling and Strong Feller 28-04-2014 11 / 42

L1-derivative

For T > 0, let V = V (s, z)s≤T ,z∈Rn0

be a predictable and integrableprocess. Let ε > 0, define

Nε(B × [0, t]) =

∫ t

0

∫Rn

0

IB(z + εV (s, z))N(dz , ds),

where ν(B) <∞.

Definition (Bass,1986, Ann. Prob.)

A functional Ft(N) := F (N(dz , ds)|s≤t) is called to have anL1-derivative in the direction V , if there exists an integrable randomvariable denoted by DVFt(N), such that

limε→0

E∣∣Ft(N

ε)− Ft(N)

ε− DVFt(N)

∣∣ = 0.

Z. Dong (AMSS CAS ) Derivative Formula, Coupling and Strong Feller 28-04-2014 12 / 42

L1-derivative

For T > 0, let V = V (s, z)s≤T ,z∈Rn0

be a predictable and integrableprocess. Let ε > 0, define

Nε(B × [0, t]) =

∫ t

0

∫Rn

0

IB(z + εV (s, z))N(dz , ds),

where ν(B) <∞.

Definition (Bass,1986, Ann. Prob.)

A functional Ft(N) := F (N(dz , ds)|s≤t) is called to have anL1-derivative in the direction V , if there exists an integrable randomvariable denoted by DVFt(N), such that

limε→0

E∣∣Ft(N

ε)− Ft(N)

ε− DVFt(N)

∣∣ = 0.

Z. Dong (AMSS CAS ) Derivative Formula, Coupling and Strong Feller 28-04-2014 12 / 42

Integration by Parts Formula

Denote

V =V : Ω× [0,T ]× Rn

0 → Rn∣∣∣V is predictable with V and DzV bounded,

∃U0 ⊂ Rn0 compact, s.t. SuppV ⊂ [0,T ]× U0.

Proposition 2.1(Norris,1988)

Let (H2.1) with ρ ∈ C 1(Rn0). If a functional Ft(N) has an L1-derivative

DVFt(N) for V ∈ V, then

EDVFt(N) = −EFt(N)Rt,

where

Rt =

∫ t

0

∫Rn

0

div(ρ(z)V (s, z))

ρ(z)N(dz , ds).

Z. Dong (AMSS CAS ) Derivative Formula, Coupling and Strong Feller 28-04-2014 13 / 42

Derivative formula for P1t

Let Jt be the derivative of X xt w.r.t. the initial value x .

Theorem 2.2(Dong, Song, 2013.)

Let (H2.1)-(H2.2) hold and ρ ∈ C 1(Rn) with∫Rn |∇ρ(z)|dz <∞. For

t > 0, ξ ∈ Rn and f ∈ Cb(Rn), we have

∇ξP1t f (x) = −E

f (X x

t )I[Nt≥1]

Nt

∫ t

0

∫Rn

∇ log ρ(z) · (σ−1s Jsξ)N(dz , ds)

.

Furthermore,

‖∇P1t f ‖∞ ≤

4βet‖∇b‖∞

λ(1− e−λt − e−λtλ0t)‖f ‖∞

∫Rn

|∇ρ(z)|dz .

Z. Dong (AMSS CAS ) Derivative Formula, Coupling and Strong Feller 28-04-2014 14 / 42

Theorem 2.3(Dong, Song, 2013.)

Let (H2.1)-(H2.3) hold and ρ ∈ C 1(Rn) with∫Rn |∇ρ(z)|dz <∞. Then

for t > K+λK ,

‖Pt(x , ·)− Pt(y , ·)‖Var ≤ 4β

∫Rn

|∇ρ(z)|dz |x − y |+ 2e−

KλK+λ

t .

Remark: From Theorem 2.2 or Theorem 2.3, we can not obtain the strongFeller of Pt under the condition λ <∞. The reason is that with a positiveprobability the process does not jump before a fixed time t > 0. But thecoupling property of Pt is investigated.

Z. Dong (AMSS CAS ) Derivative Formula, Coupling and Strong Feller 28-04-2014 15 / 42

Notations

Denote

Li =h : Rn → R|

∫Rn

0

|h(z)|iν1(dz) <∞, i = 1, 2;

C =h : Rn → R

∣∣∣h is differential and has compact support in Rn0

.

For h ∈ C , we define a weighted norm as

‖h‖ρ =∫

Rn0

|∇h(z)|2ν1(dz) 1

2+∫

Rn0

h2(z)|∇ log ρ(z)|2ν1(dz) 1

2.

Let C‖·‖ρ

be the closure of C under ‖ · ‖ρ. Denote

Hρ =h ∈ L1 ∩ L2

∣∣∣h ≥ 0, h ∈ C‖·‖ρ

and ∇h is bounded..

Z. Dong (AMSS CAS ) Derivative Formula, Coupling and Strong Feller 28-04-2014 16 / 42

Notations

Denote

Li =h : Rn → R|

∫Rn

0

|h(z)|iν1(dz) <∞, i = 1, 2;

C =h : Rn → R

∣∣∣h is differential and has compact support in Rn0

.

For h ∈ C , we define a weighted norm as

‖h‖ρ =∫

Rn0

|∇h(z)|2ν1(dz) 1

2+∫

Rn0

h2(z)|∇ log ρ(z)|2ν1(dz) 1

2.

Let C‖·‖ρ

be the closure of C under ‖ · ‖ρ. Denote

Hρ =h ∈ L1 ∩ L2

∣∣∣h ≥ 0, h ∈ C‖·‖ρ

and ∇h is bounded..

Z. Dong (AMSS CAS ) Derivative Formula, Coupling and Strong Feller 28-04-2014 16 / 42

Notations

Denote

Li =h : Rn → R|

∫Rn

0

|h(z)|iν1(dz) <∞, i = 1, 2;

C =h : Rn → R

∣∣∣h is differential and has compact support in Rn0

.

For h ∈ C , we define a weighted norm as

‖h‖ρ =∫

Rn0

|∇h(z)|2ν1(dz) 1

2+∫

Rn0

h2(z)|∇ log ρ(z)|2ν1(dz) 1

2.

Let C‖·‖ρ

be the closure of C under ‖ · ‖ρ. Denote

Hρ =h ∈ L1 ∩ L2

∣∣∣h ≥ 0, h ∈ C‖·‖ρ

and ∇h is bounded..

Z. Dong (AMSS CAS ) Derivative Formula, Coupling and Strong Feller 28-04-2014 16 / 42

Notations

Denote

Li =h : Rn → R|

∫Rn

0

|h(z)|iν1(dz) <∞, i = 1, 2;

C =h : Rn → R

∣∣∣h is differential and has compact support in Rn0

.

For h ∈ C , we define a weighted norm as

‖h‖ρ =∫

Rn0

|∇h(z)|2ν1(dz) 1

2+∫

Rn0

h2(z)|∇ log ρ(z)|2ν1(dz) 1

2.

Let C‖·‖ρ

be the closure of C under ‖ · ‖ρ. Denote

Hρ =h ∈ L1 ∩ L2

∣∣∣h ≥ 0, h ∈ C‖·‖ρ

and ∇h is bounded..

Z. Dong (AMSS CAS ) Derivative Formula, Coupling and Strong Feller 28-04-2014 16 / 42

Derivative Formula for Pt

Theorem 2.6(Dong, Song, 2013.)

Let (H2.1)-(H2.2) hold and ρ ∈ C 1(Rn0). If θ := lim inf

x→∞ν1([h≥x−1])

log x > 0 for

some h ∈ Hρ, then for t > 8(θ∧1)(1−e−1)

, ξ ∈ Rn and f ∈ Cb(Rn),

∇ξPt f (x) =− E

f (X x

t )[H−1

t

∫ t

0

∫Rn

0

〈∇(ρ(z)h(z))

ρ(z), σ−1

s Jsξ〉N(dz , ds)

+ H−2t

∫ t

0

∫Rn

0

〈∇h(z), σ−1s Jsh(z)ξ〉N(dz , ds)

],

where Ht =∫ t

0

∫Rn

0h(z)N(dz , ds).

Z. Dong (AMSS CAS ) Derivative Formula, Coupling and Strong Feller 28-04-2014 17 / 42

Derivative Formula for Pt

Continuation of Theorem 2.6

Furthermore,

‖∇Pt f ‖∞ ≤C(

1 +1

t − 8(θ∧1)(1−e−1)

)e‖∇b‖∞tβ‖f ‖∞

×∥∥ |∇(hρ)|

ρ

∥∥L2 + 2‖∇h‖∞

√‖h‖2

L2 + ‖h‖2L1

,

where C is a constant independent of t.

Remark: The condition θ > 0 can ensure Levy measure ν1 is infinite.Indeed, from Theorem 2.6 and classical approximation argument, we canderive strong Feller property of Pt when b is Lipschitz continuous.

Z. Dong (AMSS CAS ) Derivative Formula, Coupling and Strong Feller 28-04-2014 18 / 42

Derivative Formula for Pt

Continuation of Theorem 2.6

Furthermore,

‖∇Pt f ‖∞ ≤C(

1 +1

t − 8(θ∧1)(1−e−1)

)e‖∇b‖∞tβ‖f ‖∞

×∥∥ |∇(hρ)|

ρ

∥∥L2 + 2‖∇h‖∞

√‖h‖2

L2 + ‖h‖2L1

,

where C is a constant independent of t.

Remark: The condition θ > 0 can ensure Levy measure ν1 is infinite.Indeed, from Theorem 2.6 and classical approximation argument, we canderive strong Feller property of Pt when b is Lipschitz continuous.

Z. Dong (AMSS CAS ) Derivative Formula, Coupling and Strong Feller 28-04-2014 18 / 42

SDEs Driven by α-stable Process

As an example, we have

Example

Let (H2.2) hold. If ρ(z) = Cα|z|n+α with Cα > 0 and 0 < α < 2, then for

t ≥ 1 + 81−e−1 , ξ ∈ Rn and f ∈ Cb(Rn),

‖∇ξPt f ‖∞ ≤ C (n, α)‖f ‖∞|ξ|βe‖∇b‖∞t ,

where C (n, α) denotes a constant only depending on n and α.

Z. Dong (AMSS CAS ) Derivative Formula, Coupling and Strong Feller 28-04-2014 19 / 42

Outline

1 Introduction: Framework and Known Results

2 Derivative formula and coupling property for SDEs

3 Derivative formula and coupling property for SPDEs

4 Strong Feller Property for SDEs driven by degenerate additive noise

5 Classical Wiener Space

Z. Dong (AMSS CAS ) Derivative Formula, Coupling and Strong Feller 28-04-2014 20 / 42

Framework

Let (H, 〈·, ·〉) be a separable Hilbert space and µ be a Gaussian measureon H with covariance operator Q.

Quasi-invariant Property:

Under the shift z 7→ z + h for any h ∈ImQ12 , µ(·+ h) and µ are mutually

absolutely continuous.

ϕ(z , h) :=µ(dz + h)

µ(dz)= exp〈h, z〉0 −

1

2〈h, h〉0, µ− a.s,

where 〈·, ·〉0 stands for the inner product induced by Q12 and equipped on

ImQ12

Z. Dong (AMSS CAS ) Derivative Formula, Coupling and Strong Feller 28-04-2014 21 / 42

Framework

Let (H, 〈·, ·〉) be a separable Hilbert space and µ be a Gaussian measureon H with covariance operator Q.

Quasi-invariant Property:

Under the shift z 7→ z + h for any h ∈ImQ12 , µ(·+ h) and µ are mutually

absolutely continuous.

ϕ(z , h) :=µ(dz + h)

µ(dz)= exp〈h, z〉0 −

1

2〈h, h〉0, µ− a.s,

where 〈·, ·〉0 stands for the inner product induced by Q12 and equipped on

ImQ12

Z. Dong (AMSS CAS ) Derivative Formula, Coupling and Strong Feller 28-04-2014 21 / 42

Framework

Consider SDEs on H:dXt = AXtdt + F (Xt)dt + dLt + dZt ,

X0 = x ,(2)

where A : D(A) ⊂ H→ H is an adjoint, unbounded and linear operatorgenerating a C0-semigroup Stt≥0 on H. L := Ltt≥0 is a Levy processon H with Levy measure ν. Z := Ztt≥0 is another square-integrableLevy process independent of L.

Z. Dong (AMSS CAS ) Derivative Formula, Coupling and Strong Feller 28-04-2014 22 / 42

Hypothesis

(H3.1) ImS(t) ⊂ ImQ holds for any t > 0.

(H3.2) F : H→ H is Frechet differentiable with ∇F bounded andLipschitz continuous.

(H3.3) A is a dissipative operator defined by

A =∑k≥1

(−γk)ek ⊗ ek , (3)

for 0 < γ1 ≤ γ2 ≤ · · · ≤ γk ≤ · · · and γk →∞ as k →∞.

Z. Dong (AMSS CAS ) Derivative Formula, Coupling and Strong Feller 28-04-2014 23 / 42

Hypothesis

(H3.1) ImS(t) ⊂ ImQ holds for any t > 0.

(H3.2) F : H→ H is Frechet differentiable with ∇F bounded andLipschitz continuous.

(H3.3) A is a dissipative operator defined by

A =∑k≥1

(−γk)ek ⊗ ek , (3)

for 0 < γ1 ≤ γ2 ≤ · · · ≤ γk ≤ · · · and γk →∞ as k →∞.

Z. Dong (AMSS CAS ) Derivative Formula, Coupling and Strong Feller 28-04-2014 23 / 42

Hypothesis

(H3.1) ImS(t) ⊂ ImQ holds for any t > 0.

(H3.2) F : H→ H is Frechet differentiable with ∇F bounded andLipschitz continuous.

(H3.3) A is a dissipative operator defined by

A =∑k≥1

(−γk)ek ⊗ ek , (3)

for 0 < γ1 ≤ γ2 ≤ · · · ≤ γk ≤ · · · and γk →∞ as k →∞.

Z. Dong (AMSS CAS ) Derivative Formula, Coupling and Strong Feller 28-04-2014 23 / 42

(H3.4) There exists a differentiable function ρ : H→ (0,∞) with ∇ρbounded and satisfying

λ :=

∫Hρ(z)µ(dz) <∞ and

∫H|z |2ρ(z)µ(dz) <∞,

such that

ν(dz) = ρ(z)µ(dz).

Z. Dong (AMSS CAS ) Derivative Formula, Coupling and Strong Feller 28-04-2014 24 / 42

Integration by Parts Formula

Set

V =V : Ω× [0,T ]→ ImQ

∣∣∣V is predictable and

∫ T

0

E|Q−1V (s)|ds <∞..

Theorem 3.1(Dong, Song, Xu 2013)

Suppose (H3.4) holds. For V ∈ V and f ∈ C 2b (H),

EDV f (Lt)

= −E

f (Lt)Mt

, t ≤ T , (4)

where Mt =∫ t

0

∫H

(〈z ,Q−1V (s)〉 + 〈∇ log ρ(z),V (s)〉

)N(dz , ds).

Z. Dong (AMSS CAS ) Derivative Formula, Coupling and Strong Feller 28-04-2014 25 / 42

Integration by Parts Formula

Set

V =V : Ω× [0,T ]→ ImQ

∣∣∣V is predictable and

∫ T

0

E|Q−1V (s)|ds <∞..

Theorem 3.1(Dong, Song, Xu 2013)

Suppose (H3.4) holds. For V ∈ V and f ∈ C 2b (H),

EDV f (Lt)

= −E

f (Lt)Mt

, t ≤ T , (4)

where Mt =∫ t

0

∫H

(〈z ,Q−1V (s)〉 + 〈∇ log ρ(z),V (s)〉

)N(dz , ds).

Z. Dong (AMSS CAS ) Derivative Formula, Coupling and Strong Feller 28-04-2014 25 / 42

Derivative Formula

Set

C 1b (H) =

G : H→ H

∣∣G and its first order derivatives are continuous and bounded..

Theorem 3.2(Dong, Song, Xu 2013)

Let (H3.1), (H3.2) and (H3.4) hold. If∫ t

0 ‖Q−1S(s)‖ds <∞, then for

f ∈ C 1b (H) and ξ ∈ H,

∇ξP1t f (x) = −E

f (X x

t )I[Nt≥1]

Nt

∫ t

0

∫H

(〈z ,Q−1Jsξ〉+ 〈∇ log ρ(z), Jsξ〉

)N(dz , ds)

.

Z. Dong (AMSS CAS ) Derivative Formula, Coupling and Strong Feller 28-04-2014 26 / 42

Example

Let (H3.3) hold. For 0 < δ < 12 , (−A)δ denotes the fractional power of

−A, defined by

(−A)δ =1

Γ(δ)

∫ ∞0

t−δS(t)dt,

where Γ is the Euler function. It can be proved that S(t)H ⊂ D((−A)δ),for any t > 0, and

‖(−A)δS(t)‖ ≤ Cδt−δ

for a suitable positive constant Cδ. Take Q =((−A)δ

)−1, then we have

S(t)H ⊂ ImQ. Moreover,

limt→∞

∫ t0 ‖Q

−1S(s)‖2ds

t≤ lim

t→∞

C 2δ

∫ t0 s−2δds

t= 0.

Z. Dong (AMSS CAS ) Derivative Formula, Coupling and Strong Feller 28-04-2014 27 / 42

Outline

1 Introduction: Framework and Known Results

2 Derivative formula and coupling property for SDEs

3 Derivative formula and coupling property for SPDEs

4 Strong Feller Property for SDEs driven by degenerate additive noise

5 Classical Wiener Space

Z. Dong (AMSS CAS ) Derivative Formula, Coupling and Strong Feller 28-04-2014 28 / 42

Brownian motion

W :=w : [0,∞)→ Rm|w is continuous with w0 = 0.

W is endowed with the locally uniform topology and the probabilitymeasure µW so that the coordinate process

Wt(w) := wt = (w1t , · · · ,wm

t )

is an m-dimensional Brownian motion.

Z. Dong (AMSS CAS ) Derivative Formula, Coupling and Strong Feller 28-04-2014 29 / 42

Brownian motion

W :=w : [0,∞)→ Rm|w is continuous with w0 = 0.

W is endowed with the locally uniform topology and the probabilitymeasure µW so that the coordinate process

Wt(w) := wt = (w1t , · · · ,wm

t )

is an m-dimensional Brownian motion.

Z. Dong (AMSS CAS ) Derivative Formula, Coupling and Strong Feller 28-04-2014 29 / 42

Subordinator

S :=` : R+ → Rm

+|` is cadlag with `0 = 0, each component

being increasing and purely jumping.

S is endowed with the Skorohod metric and the probability measureµS so that the coordinate process

St(`) := `t = (`1t , · · · , `mt )

is an m-dimensional Levy process with Laplace transform

EµS(e−z·St ) = exp

∫Rm

+

(e−z·u − 1)νS(du)

. (5)

Z. Dong (AMSS CAS ) Derivative Formula, Coupling and Strong Feller 28-04-2014 30 / 42

Subordinator

S :=` : R+ → Rm

+|` is cadlag with `0 = 0, each component

being increasing and purely jumping.

S is endowed with the Skorohod metric and the probability measureµS so that the coordinate process

St(`) := `t = (`1t , · · · , `mt )

is an m-dimensional Levy process with Laplace transform

EµS(e−z·St ) = exp

∫Rm

+

(e−z·u − 1)νS(du)

. (5)

Z. Dong (AMSS CAS ) Derivative Formula, Coupling and Strong Feller 28-04-2014 30 / 42

Subordinated Brownian motion

Consider the following product probability space

(Ω,F ,P) :=(W× S,B(W)×B(S), µW × µS

).

Lift Wt and St to this probability space, then Wt and St are independent,and the subordinated Brownian motion

WSt :=(W 1

S1t, · · · ,Wm

Smt

)is an m-dimensional Levy process.

Z. Dong (AMSS CAS ) Derivative Formula, Coupling and Strong Feller 28-04-2014 31 / 42

Subordinated Brownian motion

Assume

P(ω ∈ Ω : ∃j = 1, · · · ,m and ∃t > 0 such that S jt (ω) = 0) = 0, (6)

which means that St is nondegenerate along each direction.

Remark

α-stable subordinator meets this assumption.

Z. Dong (AMSS CAS ) Derivative Formula, Coupling and Strong Feller 28-04-2014 32 / 42

The SDE driven by subordinated Brownian motion

Consider the following SDE:

dXt = b(Xt)dt + σdWSt , X0 = x , (7)

where b : Rd → Rd is a smooth function, σ is a d ×m matrix.

Z. Dong (AMSS CAS ) Derivative Formula, Coupling and Strong Feller 28-04-2014 33 / 42

Hormander’s type condition

Hormander’s type condition at point x ∈ Rd :

∃n = n(x) ∈ N, s.t.

Rank[σ,B1(x)σ,B2(x)σ, · · · ,Bn(x)σ] = d , (8)

where B1(x) := (∇b)ij(x) = (∂jbi (x))ij , and for n ≥ 2,

Bn(x) := (b · ∇)Bn−1(x)− (∇b · Bn−1)(x).

Z. Dong (AMSS CAS ) Derivative Formula, Coupling and Strong Feller 28-04-2014 34 / 42

Strong Feller property

Theorem 4.1(Dong, Peng, Song, Zhang 2013)

Assume that

the solution to (7) globally exists

(b, σ) satisfy Hormander’s type condition (8) at each point x ∈ Rd .

Then for any t > 0, the law of Xt(x) is continuous w.r.t. variable x in thetotal variation distance. In particular, the semigroup (Pt)t>0 has thestrong Feller property, i.e., for any t > 0 and f ∈ Bb(Rd),

x 7→ Ef (Xt(x)) is continuous.

Remark

This result has been much extended to multiplicative noise by Xi ChengZhang 2013.

Z. Dong (AMSS CAS ) Derivative Formula, Coupling and Strong Feller 28-04-2014 35 / 42

Example

Stochastic oscillators:dzi (t) = ui (t)dt, i = 1, · · · , d ,dui (t) = −∂ziH(z(t), u(t))dt, i = 2, · · · , d − 1,

dui (t) = −[∂ziH(z(t), u(t)) + γiui (t)]dt +√TidW

iS it, i = 1, d ,

where d ≥ 3, γ1, γd ∈ R, T1,Td > 0, and

H(z , u) :=d∑

i=1

(1

2|ui |2 + V (zi )

)+

d−1∑i=1

U(zi+1 − zi ).

Z. Dong (AMSS CAS ) Derivative Formula, Coupling and Strong Feller 28-04-2014 36 / 42

Example

Proposition 4.2

Assume that V ,U ∈ C∞(R) are nonnegative and lim|z|→∞ V (z) =∞. If

U is strictly convex, then for any f ∈ Bb(Rd × Rd), the map

(z0, u0) 7→ Ez0,u0f (zt , ut)

is continuous.

Z. Dong (AMSS CAS ) Derivative Formula, Coupling and Strong Feller 28-04-2014 37 / 42

Outline

1 Introduction: Framework and Known Results

2 Derivative formula and coupling property for SDEs

3 Derivative formula and coupling property for SPDEs

4 Strong Feller Property for SDEs driven by degenerate additive noise

5 Classical Wiener Space

Z. Dong (AMSS CAS ) Derivative Formula, Coupling and Strong Feller 28-04-2014 38 / 42

Classical Wiener Space

Let W be the space of all continuous functions from R+ := [0,∞) toRm vanishing at starting point 0 and the Wiener measure µW so thatthe coordinate process

Wt(ω) = ωt

is a standard m-dimensional Brownian motion.

Let H ⊂W be the Cameron-Martin space. The inner product in H isdenoted by

〈h1, h2〉H :=m∑i=1

∫ ∞0

hi1(s)hi2(s)ds.

Let D be the Malliavin derivative operator.

Let Dk,p be the associated Wiener-Sobolev space with the norm

‖F‖k,p := ‖F‖p + ‖DF‖p + · · ·+ ‖DkF‖p,

Z. Dong (AMSS CAS ) Derivative Formula, Coupling and Strong Feller 28-04-2014 39 / 42

Classical Wiener Space

Let W be the space of all continuous functions from R+ := [0,∞) toRm vanishing at starting point 0 and the Wiener measure µW so thatthe coordinate process

Wt(ω) = ωt

is a standard m-dimensional Brownian motion.

Let H ⊂W be the Cameron-Martin space. The inner product in H isdenoted by

〈h1, h2〉H :=m∑i=1

∫ ∞0

hi1(s)hi2(s)ds.

Let D be the Malliavin derivative operator.

Let Dk,p be the associated Wiener-Sobolev space with the norm

‖F‖k,p := ‖F‖p + ‖DF‖p + · · ·+ ‖DkF‖p,

Z. Dong (AMSS CAS ) Derivative Formula, Coupling and Strong Feller 28-04-2014 39 / 42

Classical Wiener Space

Let W be the space of all continuous functions from R+ := [0,∞) toRm vanishing at starting point 0 and the Wiener measure µW so thatthe coordinate process

Wt(ω) = ωt

is a standard m-dimensional Brownian motion.

Let H ⊂W be the Cameron-Martin space. The inner product in H isdenoted by

〈h1, h2〉H :=m∑i=1

∫ ∞0

hi1(s)hi2(s)ds.

Let D be the Malliavin derivative operator.

Let Dk,p be the associated Wiener-Sobolev space with the norm

‖F‖k,p := ‖F‖p + ‖DF‖p + · · ·+ ‖DkF‖p,

Z. Dong (AMSS CAS ) Derivative Formula, Coupling and Strong Feller 28-04-2014 39 / 42

Classical Wiener Space

Let W be the space of all continuous functions from R+ := [0,∞) toRm vanishing at starting point 0 and the Wiener measure µW so thatthe coordinate process

Wt(ω) = ωt

is a standard m-dimensional Brownian motion.

Let H ⊂W be the Cameron-Martin space. The inner product in H isdenoted by

〈h1, h2〉H :=m∑i=1

∫ ∞0

hi1(s)hi2(s)ds.

Let D be the Malliavin derivative operator.

Let Dk,p be the associated Wiener-Sobolev space with the norm

‖F‖k,p := ‖F‖p + ‖DF‖p + · · ·+ ‖DkF‖p,

Z. Dong (AMSS CAS ) Derivative Formula, Coupling and Strong Feller 28-04-2014 39 / 42

Strong continuity

Theorem 5.3(Dong, Peng, Song, Zhang 2013)

Let (Xλ)λ∈Λ be a family of Rd -valued Wiener functionals over W.Suppose that for some p > 1:(1) Xλ ∈ D2,p for each λ ∈ Λ, and λ 7→ ‖Xλ‖2,p is locally bounded.

(2) λ 7→ Xλ is continuous in probability, i.e., for any ε > 0 and λ0 ∈ Λ,

limλ→λ0

P(|Xλ − Xλ0 | ≥ ε) = 0.

(3) For each λ ∈ Λ, the Malliavin covariance matrix ΣXλ of Xλ is invertible

almost surely.Then the law of Xλ in Rd admits a density ρλ(x) so that λ 7→ ρλ iscontinuous in L1(Rd).

Z. Dong (AMSS CAS ) Derivative Formula, Coupling and Strong Feller 28-04-2014 40 / 42

Strong continuity

Theorem 5.3(Dong, Peng, Song, Zhang 2013)

Let (Xλ)λ∈Λ be a family of Rd -valued Wiener functionals over W.Suppose that for some p > 1:(1) Xλ ∈ D2,p for each λ ∈ Λ, and λ 7→ ‖Xλ‖2,p is locally bounded.(2) λ 7→ Xλ is continuous in probability, i.e., for any ε > 0 and λ0 ∈ Λ,

limλ→λ0

P(|Xλ − Xλ0 | ≥ ε) = 0.

(3) For each λ ∈ Λ, the Malliavin covariance matrix ΣXλ of Xλ is invertible

almost surely.Then the law of Xλ in Rd admits a density ρλ(x) so that λ 7→ ρλ iscontinuous in L1(Rd).

Z. Dong (AMSS CAS ) Derivative Formula, Coupling and Strong Feller 28-04-2014 40 / 42

Strong continuity

Theorem 5.3(Dong, Peng, Song, Zhang 2013)

Let (Xλ)λ∈Λ be a family of Rd -valued Wiener functionals over W.Suppose that for some p > 1:(1) Xλ ∈ D2,p for each λ ∈ Λ, and λ 7→ ‖Xλ‖2,p is locally bounded.(2) λ 7→ Xλ is continuous in probability, i.e., for any ε > 0 and λ0 ∈ Λ,

limλ→λ0

P(|Xλ − Xλ0 | ≥ ε) = 0.

(3) For each λ ∈ Λ, the Malliavin covariance matrix ΣXλ of Xλ is invertible

almost surely.

Then the law of Xλ in Rd admits a density ρλ(x) so that λ 7→ ρλ iscontinuous in L1(Rd).

Z. Dong (AMSS CAS ) Derivative Formula, Coupling and Strong Feller 28-04-2014 40 / 42

Strong continuity

Theorem 5.3(Dong, Peng, Song, Zhang 2013)

Let (Xλ)λ∈Λ be a family of Rd -valued Wiener functionals over W.Suppose that for some p > 1:(1) Xλ ∈ D2,p for each λ ∈ Λ, and λ 7→ ‖Xλ‖2,p is locally bounded.(2) λ 7→ Xλ is continuous in probability, i.e., for any ε > 0 and λ0 ∈ Λ,

limλ→λ0

P(|Xλ − Xλ0 | ≥ ε) = 0.

(3) For each λ ∈ Λ, the Malliavin covariance matrix ΣXλ of Xλ is invertible

almost surely.Then the law of Xλ in Rd admits a density ρλ(x) so that λ 7→ ρλ iscontinuous in L1(Rd).

Z. Dong (AMSS CAS ) Derivative Formula, Coupling and Strong Feller 28-04-2014 40 / 42

Remark

Bogachev (AMS, 2010) have already showed such a result in the first orderSobolev space W 1,p(Rd ,Rd) provided p ≥ d . Theorem 5.3 does notdepend on the dimension of space.

Z. Dong (AMSS CAS ) Derivative Formula, Coupling and Strong Feller 28-04-2014 41 / 42

Thank you !

Z. Dong (AMSS CAS ) Derivative Formula, Coupling and Strong Feller 28-04-2014 42 / 42

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