Abstract

Existence and uniqueness for rough flows, transport and continuity equations driven by general geometric rough paths are established.

Highlights

  • We consider the transport equation, here posed (w.l.o.g.) as terminal value problem

  • Our driving vector fields will be very smooth, to compensate for the the irregularity of the noise, which we here assumed to be very rough (This trade-off is typical in rough paths and regularity structures.)

  • Throughout the paper we say geometric rough path, when we really mean weakly geometric rough path

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Summary

Introduction

We consider the transport equation, here posed (w.l.o.g.) as terminal value problem. This is,. Fd are nice enough (C1b will do) to ensure a C1 solution flow for the ODE ⎧ ⎪⎪⎨Xts,x = d fi (Xts,x )Wti ≡ f (Xt )Wt , Solving this ODE with random initial data induces a natural evolution of measures, given by the continuity - or forward equation ⎧ ⎪⎪⎨∂t ρ = d divx ( fi (x)ρt ) dWti in (0, T ) × Rn,. DiPerna–Lions [9] and Ambrsosio [1], showed that the transport problem (weak solutions) is well-posed under bounds on div b (rather than Dx b) which in turn leads to a generalized flow. Our driving vector fields will be very smooth, to compensate for the the irregularity of the noise, which we here assumed to be very rough (This trade-off is typical in rough paths and regularity structures.). Throughout the paper we say geometric rough path, when we really mean weakly geometric rough path (since we only work with this type of rough path, the difference [14] will not matter to us)

Rough paths
The shuffle algebra
Geometric rough paths
Controlled rough paths and rough integrals
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Rough differential equations
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Differentiability of the flow
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Itô’s formula for RDEs
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Rough transport equation
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Full Text
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