Publications de Joachim Krieger

BOUNDARY STABILIZATION OF THE FOCUSING NLKG EQUATION NEAR UNSTABLE EQUILIBRIA: RADIAL CASE

We investigate the stability and stabilization of the cubic focusing Klein–Gordon equation around static solutions on the closed ball of radius L in R3. First we show that the system is linearly unstable near the static solution u ≡ 1 for any dissipative b ...

2023

Global controllability and stabilization of the wave Maps equation from a circle to a sphere

Joachim Krieger, Shengquan Xiang

Continuing the investigations started in the recent work [12] on semi-global controllability and stabilization of the (1+1)-dimensional wave maps equation with spatial domain

S1

and target

Sk

, where semi-global refers to the

2π

-energy bound, we prov ...

2023

Probabilistic Small Data Global Well-Posedness of the Energy-Critical Maxwell-Klein-Gordon Equation

Joachim Krieger

We establish probabilistic small data global well-posedness of the energy-critical Maxwell-Klein-Gordon equation relative to the Coulomb gauge for scaling super-critical random initial data. The proof relies on an induction on frequency procedure and a mod ...

2023

Type II blow up solutions with optimal stability properties for the critical focussing nonlinear wave equation on $\R^{3+1}$

Joachim Krieger, Stefano Francesco Burzio

We show that the finite time type II blow up solutions for the energy critical nonlinear wave equation [ \Box u = -u^5 ] on

\R^{3+1}

constructed in \cite{KST}, \cite{KS1} are stable along a co-dimension one Lipschitz manifold of data perturbations in a ...

2022

Semi-global controllability of a geometric wave equation

Joachim Krieger, Shengquan Xiang

We prove the semi-global controllability and stabilization of the

(1+1)-

dimensional wave maps equation with spatial domain 𝕊1 and target

𝕊k

. First we show that damping stabilizes the system when the energy is strictly below the threshold

2π

, where ha ...

2022

Randomization improved Strichartz estimates and global well-posedness for supercritical data

Joachim Krieger

We introduce a novel data randomisation for the free wave equation which leads to the same range of Strichartz estimates as for radial data, albeit in a non-radial context. We then use these estimates to establish global wellposedness for a wave maps type ...

2021

Small data global regularity for half-wave maps in n=4 dimensions

Joachim Krieger, Anna Kiesenhofer

We prove that the half-wave maps problem on

\mathbb{R}^{4+1}

with target

S^2

is globally well-posed for smooth initial data which are small in the critical

l^1

based Besov space. This is a formal analogue of the result [17]. ...

2021

On the stability of blowup solutions for the critical corotational wave-map problem

Joachim Krieger, Shuang Miao

We show that the finite time blow up solutions for the co-rotational Wave Maps problem constructed in [7,15] are stable under suitably small perturbations within the co-rotational class, provided the scaling parameter

λ(t)=t−1−ν

is sufficiently close to ...

2020

Probabilistic small data global Well-Posedness of the energy-critical Maxwell-Klein-Gordon equation

Joachim Krieger

We establish probabilistic small data global well-posedness of the energy-critical Maxwell-Klein-Gordon equation relative to the Coulomb gauge for scaling super-critical random initial data. The proof relies on an induction on frequency procedure and a mod ...

2020

A stability theory beyond the co-rotational setting for critical wave maps blow up

Joachim Krieger, Shuang Miao

We exhibit non-equivariant perturbations of the blowup solutions constructed in [18] for energy critical wave maps into

\mathbb{S}^2

. Our admissible class of perturbations is an open set in some sufficiently smooth topology and vanishes near the light co ...

2020

Cost for a controlled linear KdV equation

Joachim Krieger, Shengquan Xiang

The controllability of the linearized KdV equation with right Neumann control is studied in the pioneering work of Rosier [25]. However, the proof is by contradiction arguments and the value of the observability constant remains unknown, though rich mathem ...

2019

On stability of type II blow up for the critical NLW on $\mathbb{R}^{3+1}$

Joachim Krieger

We show that the finite time type II blow up solutions for the energy critical nonlinear wave equation [ \Box u = -u^5 ] on

\mathbb{R}^{3+1}

constructed in [28], [27] are stable along a co-dimension three manifold of radial data perturbations in a suit ...

2018

Small data global regularity for half-wave maps

Joachim Krieger

We formulate the half-wave maps problem with target

S^2

and prove global regularity in sufficiently high spatial dimensions for a class of small critical data in Besov spaces. ...

2018

Global well-posedness for the Yang-Mills equation in 4+1 dimensions: Small energy

Joachim Krieger, Daniel Tataru

We consider the hyperbolic Yang-Mills equation on the Minkowski space

\reels^{4+1}

. Our main result asserts that this problem is globally well-posed for all initial data whose energy is sufficiently small. This solves a longstanding open problem. ...

Annal Mathematics2017

A Class Of Large Global Solutions For The Wave-Map Equation

Joachim Krieger, Elisabetta Chiodaroli

In this paper we consider the equation for equivariant wave maps from R3+1 to S-3 and we prove global in forward time existence of certain C-infinity-smooth solutions which have infinite critical Sobolev norm (H) overdot(3/4) (R-3) x (H) overdot(1/2) (R-3) ...

2017

A vector field method on the distorted Fourier side and decay for wave equations with potentials

Joachim Krieger, Roland Donninger

We study the Cauchy problem for the one-dimensional wave equation

\partial_t^2 u(t,x)-\partial_x^2 u(t,x)+V(x)u(t,x)=0.

The potential

V

is assumed to be smooth with asymptotic behavior

V(x)\sim -\tfrac14 |x|^{-2}\mbox{ as } |x|\to \infty.

...

2016

Optimal polynomial blow up range for critical wave maps

Joachim Krieger, Can Gao

We prove that the critical Wave Maps equation with target

S^2

and origin

\R^{2+1}

admits energy class blow up solutions of the form

u(t, r) = Q(\lambda(t)r) + \eps(t, r)

where

Q:\R^2\rightarrow S^2

is the ground state harmonic map and $\lambd ...

2015

Codimension one stability of the catenoid under the vanishing mean curvature flow in Minkowski space

Joachim Krieger, Roland Donninger, Willie Wai Yeung Wong

We study time-like hypersurfaces with vanishing mean curvature in the (3+1) dimensional Minkowski space, which are the hyperbolic counterparts to minimal embeddings of Riemannian manifolds. The catenoid is a stationary solution of the associated Cauchy pro ...

Duke Univ Press2015

Global Well-Posedness For The Maxwell-Klein-Gordon Equation In 4+1 Dimensions: Small Energy

Joachim Krieger, Daniel Tataru

We prove that the critical Maxwell-Klein-Gordon equation on R4+1 is globally well-posed for smooth initial data which are small in the energy norm. This reduces the problem of global regularity for large, smooth initial data to precluding concentration of ...

Duke Univ Press2015

On global regularity for systems of nonlinear wave equations with the null-condition

Joachim Krieger, Can Gao, Aparajita Dasgupta

In this note we combine a recent result by Geba [2] on the local wellposedness theory of systems of nonlinear wave equations with

Q_0

null-form structure with the classical Penrose compactification method to obtain a new small data global existence resul ...

International Press2015