Burkholder–Davis–Gundy Inequalities in UMD Banach Spaces
In this paper we prove Burkholder–Davis–Gundy inequalities for a general martingale M with values in a UMD Banach space X . Assuming that M 0 = 0 , we show that the following two-sided inequality holds for all 1 ≤ p < ∞ : Here γ ( [ [ M ] ] t ) is the L 2 -norm of the unique Gaussian measure on X...
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| Vydáno v: | Communications in mathematical physics Ročník 379; číslo 2; s. 417 - 459 |
|---|---|
| Hlavní autor: | |
| Médium: | Journal Article |
| Jazyk: | angličtina |
| Vydáno: |
Berlin/Heidelberg
Springer Berlin Heidelberg
01.10.2020
Springer Nature B.V |
| Témata: | |
| ISSN: | 0010-3616, 1432-0916 |
| On-line přístup: | Získat plný text |
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| Shrnutí: | In this paper we prove Burkholder–Davis–Gundy inequalities for a general martingale
M
with values in a UMD Banach space
X
. Assuming that
M
0
=
0
, we show that the following two-sided inequality holds for all
1
≤
p
<
∞
:
Here
γ
(
[
[
M
]
]
t
)
is the
L
2
-norm of the unique Gaussian measure on
X
having
[
[
M
]
]
t
(
x
∗
,
y
∗
)
:
=
[
⟨
M
,
x
∗
⟩
,
⟨
M
,
y
∗
⟩
]
t
as its covariance bilinear form. This extends to general UMD spaces a recent result by Veraar and the author, where a pointwise version of (
⋆
) was proved for UMD Banach functions spaces
X
. We show that for continuous martingales, (
⋆
) holds for all
0
<
p
<
∞
, and that for purely discontinuous martingales the right-hand side of (
⋆
) can be expressed more explicitly in terms of the jumps of
M
. For martingales with independent increments, (
⋆
) is shown to hold more generally in reflexive Banach spaces
X
with finite cotype. In the converse direction, we show that the validity of (
⋆
) for arbitrary martingales implies the UMD property for
X
. As an application we prove various Itô isomorphisms for vector-valued stochastic integrals with respect to general martingales, which extends earlier results by van Neerven, Veraar, and Weis for vector-valued stochastic integrals with respect to a Brownian motion. We also provide Itô isomorphisms for vector-valued stochastic integrals with respect to compensated Poisson and general random measures. |
|---|---|
| Bibliografie: | ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 14 |
| ISSN: | 0010-3616 1432-0916 |
| DOI: | 10.1007/s00220-020-03845-7 |