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We establish the local well-posedness for a new nonlinearly dispersive wave equation and we show that the equation has solutions that exist for indefinite times as well as solutions which blowup in finite times. Furthermore, we derive an explosion criterion for the equation and we give a sharp estimate from below for the existence time of solutions with smooth initial data. | On the Cauchy problem for a nonlinearly dispersive wave equation | 11,100 |
We show that in dimensions $n \geq 6$ that one has global regularity for the Maxwell-Klein-Gordon equations in the Coulomb gauge provided that the critical Sobolev norm $\dot H^{n/2-1} \times \dot H^{n/2-2}$ of the initial data is sufficiently small. These results are analogous to those recently obtained for the high-dimensional wave map equation but unlike the wave map equation, the Coulomb gauge non-linearity cannot be iterated away directly. We shall use a different approach, proving Strichartz estimates for the covariant wave equation. This in turn will be achieved by use of Littlewood-Paley multipliers, and a global parametrix for the covariant wave equation constructed using a truncated, microlocalized Cronstrom gauge. | Global regularity for the Maxwell-Klein-Gordon equation with small
critical Sobolev norm in high dimensions | 11,101 |
We obtain solutions of the nonlinear degenerate parabolic equation \[ \frac{\partial \rho}{\partial t} = {div} \Big\{\rho \nabla c^\star [ \nabla (F^\prime(\rho)+V) ] \Big\} \] as a steepest descent of an energy with respect to a convex cost functional. The method used here is variational. It requires less uniform convexity assumption than that imposed by Alt and Luckhaus in their pioneering work \cite{luckhaus:quasilinear}. In fact, their assumption may fail in our equation. This class of problems includes the Fokker-Planck equation, the porous-medium equation, the fast diffusion equation, and the parabolic p-Laplacian equation. | Existence of solutions to degenerate parabolic equations via the
Monge-Kantorovich theory | 11,102 |
We study the asymptotic behavior of large data radial solutions to the focusing Schr\"odinger equation $i u_t + \Delta u = -|u|^2 u$ in $\R^3$, assuming globally bounded $H^1(\R^3)$ norm (i.e. no blowup in the energy space). We show that as $t \to \pm \infty$, these solutions split into the sum of three terms: a radiation term that evolves according to the linear Schr\"odinger equation, a smooth function localized near the origin, and an error that goes to zero in the $\dot H^1(\R^3)$ norm. Furthermore, the smooth function near the origin is either zero (in which case one has scattering to a free solution), or has mass and energy bounded strictly away from zero, and obeys an asymptotic Pohozaev identity. These results are consistent with the conjecture of soliton resolution. | On the asymptotic behavior of large radial data for a focusing
non-linear Schrödinger equation | 11,103 |
On demontre la convergence pour tout temps d'une approximation de l'equation de Vlasov par un systeme de particules sans regularisation du champ, ceci pour des potentiels singuliers, avec une force du type $1/|x|^{\alpha}$, pour \alpha plus petit que 1. | N particles approximation of the Vlasov equations with singular
potential | 11,104 |
Global-in-time smooth self-similar solutions to the 3D Navier-Stokes equations are constructed emanating from homogeneous of degree -1 arbitrary large initial data belonging only to the closure of the test functions in the space of uniformly-locally square-integrable functions. | Constructing regular self-similar solutions to the 3D Navier-Stokes
equations originating at singular and arbitrary large initial data | 11,105 |
The Volterra calculus is a simple and powerful pseudodifferential tool for inverting parabolic equations and it has also found many applications in geometric analysis. On the other hand, an important property in the theory of pseudodifferential operators is the asymptotic completeness, which allows us to construct parametrices modulo smoothing operators. In this paper we present new and fairly elementary proofs the asymptotic completeness of the Volterra calculus. | On the Asymptotic Completeness of the Volterra Calculus | 11,106 |
We exhibit the form of the ``radiation field,'' describing the large-scale, long-time behavior of solutions to the wave equation on a manifold with no trapped rays, as a Fourier integral operator. We work in two different geometric settings: scattering manifolds (a class which includes asymptotically Euclidean spaces) and asymptotically hyperbolic manifolds. The canonical relation of the radiation field operator is a map from the cotangent bundle of the manifold to a cotangent bundle over the boundary at infinity; it is associated to a sojourn time, or Busemann function, for geodesic rays. In non-degenerate cases, the symbol of the operator can be described explicitly in terms of the geometry of long-time geodesic flow. As a consequence of the above result, we obtain a description of the (distributional) high-frequency asymptotics of the scattering-theoretic Poisson operator, better known as the Eisenstein function in the asymptotically hyperbolic case. | The radiation field is a Fourier integral operator | 11,107 |
We construct a potential $V$ on $\RR^d$, smooth away from one pole, and a sequence of quasi-modes for the operator $-\Delta+V$, which concentrate on this pole. No smoothing effect, Strichartz estimates nor dispersive inequalities hold for the corresponding Schrodinger equation. | A Singular Critical Potential For The Schrodinger operator | 11,108 |
We prove that for any connected open set $\Omega\subset \R^n$ and for any set of matrices $K=\{A_1,A_2,A_3\}\subset M^{m\times n}$, with $m\ge n$ and rank$(A_i-A_j)=n$ for $i\neq j$, there is no non-constant solution $B\in L^{\infty}(\Omega,M^{m\times n})$, called exact solution, to the problem Div B=0 \quad \text{in} D'(\Omega,\R^m) \quad \text{and} \quad B(x)\in K \text{a.e. in} \Omega. In contrast, A. Garroni and V. Nesi \cite{GN} exhibited an example of set $K$ for which the above problem admits the so-called approximate solutions. We give further examples of this type. We also prove non-existence of exact solutions when $K$ is an arbitrary set of matrices satisfying a certain algebraic condition which is weaker than simultaneous diagonalizability. | The three divergence free matrix fields problem | 11,109 |
In this paper, we deal with a class of semilinear elliptic equation in a bounded domain $\Omega\subset\mathbb{R}^N$, $N\geq 3$, with $C\sp{1,1}$ boundary. Using a new fixed point result of the Krasnoselskii's type for the sum of two operators, an existence principle of strong solutions is proved. We give two examples where the nonlinearity can be critical. | Semilinear Elliptic Equations and Fixed Points | 11,110 |
For a class of weakly hyperbolic systems of the form D_t - A(t,x,D_x), where A(t,x,D_x) is a first-order pseudodifferential operator whose principal symbol degenerates like t^{l_*} at time t=0, for some integer l_* \geq 1, well-posedness of the Cauchy problem is proved in an adapted scale of Sobolev spaces. In addition, an upper bound for the loss of regularity that occurs when passing from the Cauchy data to the solutions is established. In examples, this upper bound turns out to be sharp. | Energy estimates for weakly hyperbolic systems of the first order | 11,111 |
Green's formulas for elliptic cone differential operators are established. This is done by an accurate description of the maximal domain of an elliptic cone differential operator and its formal adjoint, thereby utilizing the concept of a discrete asymptotic type. From this description, the singular coefficients replacing the boundary traces in classical Green's formulas are deduced. | Green's formulas for cone differential operators | 11,112 |
The nonlinear wave and Schrodinger equations on Euclidean space of any dimension, with general power nonlinearity and with both the focusing and defocusing signs, are proved to be ill-posed in the Sobolev space of index s whenever the exponent s is lower than that predicted by scaling or Galilean invariances, or when the regularity is too low to support distributional solutions. This extends previous work of the authors, which treated the one-dimensional cubic nonlinear Schrodinger equation. In the defocusing case soliton or blowup examples are unavailable, and a proof of ill-posedness requires the construction of other solutions. In earlier work this was achieved using certain long-time asymptotic behavior which occurs only for low power nonlinearities. Here we analyze instead a class of solutions for which the zero-dispersion limit provides a good approximation. | Ill-posedness for nonlinear Schrodinger and wave equations | 11,113 |
Considered herein are the family of nonlinear equations with both dispersive and dissipative homogeneous terms appended. Solutions of these equations that start with finite energia decay to zero as time goes to infinity. We present an asymptotic form which renders explicit the influence of the dissipative, dispersive and nonlinear effect in this decay. We obtain the second term in the asymptotic expansion, as time goes to infinity of the solutions of this equations and the complete asymptotic expansion, as time goes to infinity, of the linearized equations. | Asymptotic expansion for the models of nonlinear dispersive,
dissipative, equations | 11,114 |
We study the periodic non-linear Schrodinger equations with odd integer power nonlinearities, for initial data which are assumed to be small in some negative order Sobolev space, but which may have large L^2 mass. These equations are known to be illposed in H^s for all negative s, in the sense that the solution map fails to be uniformly continuous from H^s to itself, even for short times and small norms. Here we show that these equations are even more unstable. For the cubic equation, the solution map is discontinuous from H^s to even the space of distributions. For the quintic and higher order nonlinearities, there exist pairs of solutions which are uniformly bounded in H^s, are arbitrarily close in any C^N norm at time zero, and fail to be close in the distribution topology at an arbitrarily small positive time. | Instability of the periodic nonlinear Schrodinger equation | 11,115 |
We discuss the Dirichlet problem of the quasi-linear elliptic system \begin{eqnarray*} -e^{-f(U)}div(e^{f(U)}\bigtriangledown U)+&{1/2}f'(U)|\bigtriangledown U|^2&=0, {in $\Omega$}, & U|_{\partial\Omega}&=\phi. \end{eqnarray*} Here $\Omega$ a smooth bounded domain in $R^n$, $f: R^N\to R$ is a smooth function, $U:\Omega\to R^N$ is the unknown vector-valued function, $\phi:\bar\Omega\to R^N$ is a given vector-valued $C^2$ function, $f'$ is the gradient of the function $f$ with respect to the variable $U$. Such problems arise in population dynamics and Differential Geometry. The difficulty of studying this problem is that this nonlinear elliptic system does not fit the usual growth condition in M.Giaquinta's book [G] and the natural working space $H^1\cap L^{\infty}(\Omega)$ for the corresponding Euler-Lagrange functional does not fit the usual minimization or variational argument. We use the direct method on a convex subset of $H^1\cap L^{\infty}(\Omega)$ to overcome these difficulties. Under a suitable assumption on the function $f$, we prove that there is at least one solution to this problem. We also give application of our result to the Dirichlet problem of harmonic maps into the standard sphere | Dirichlet problems of a quasi-linear elliptic system | 11,116 |
In this paper we propose some approaches for finding of pointwise estimates of a solution of the Dirichlet boundary value problem $-\Delta u \pm |u|^{q-1} u = 0 $, $|u|=k$ when $|x|=d<1$ and $|u|=0$ when $|x|=1$ where $x\in \Omega = \{x| d<|x|<1\}$. Along with these we consider the same boundary conditions for the Laplace equation and get appropriate estimates for this easier case. We indicate some way what permit to find upper and lower estimates of a solution with explicit constants in turns. | On some methods of the obtaining of a priori pointwise estimates of
Dirichlet problem solution for Emden-Fouler equation | 11,117 |
We are interested in the life span and the asymptotic behaviour of the solutions to a system governing the motion of a pressureless gas, submitted to a strong, inhomogeneous magnetic field $ \e^{-1} B(x)$, of variable amplitude but fixed direction -- this is a first step in the direction of the study of rotating Euler equations. This leads to the study of a multi--dimensional Burgers type system on the velocity field $ u_\e$, penalized by a rotating term $ \e^{-1} u_\e \wedge B(x)$. We prove that the unique, smooth solution of this Burgers system exists on a uniform time interval $ [0,T]$. We also prove that the phase of oscillation of $ u_\e$ is an order one perturbation of the phase obtained in the case of a pure rotation (with no nonlinear transport term), $ \e^{-1}B(x)t$. Finally going back to the pressureless gas system, we obtain the asymptotics of the density as $ \e$ goes to zero. | Asymptotic results for pressureless magneto--hydrodynamics | 11,118 |
We consider the initial value problem for a pseudodifferential equation with first order hyperbolic part, and an order $\gamma > 0$ dissipative term. Under an assumption, depending on an integer parameter $L \geq 2$ such that $2 \gamma < L$, we construct for this initial value problem a parametrix that is a Fourier integral operator of type $\rho = 1 - \gamma/L$. The assumption implies that where the principal symbol of the dissipative term is zero, the terms of order up to $L-1$ in its Taylor series also vanish. | Parametrix for a hyperbolic initial value problem with dissipation in
some region | 11,119 |
The asymptotic behavior of solutions of the three-dimensional Navier-Stokes equations is considered on bounded smooth domains with no-slip boundary conditions or on periodic domains. Asymptotic regularity conditions are presented to ensure that the convergence of a Leray-Hopf weak solution to its weak omega-limit set (weak in the sense of the weak topology of the space H of square-integrable divergence-free velocity fields) are achieved also in the strong topology of H. In particular, if a weak omega-limit set is bounded in the space V of velocity fields with square-integrable vorticity then the attraction to the set holds also in the strong topology of H. Corresponding results for the strong convergence towards the weak global attractor of Foias and Temam are also presented. | Asymptotic regularity conditions for the strong convergence towards weak
limit sets and weak attractors of the 3D Navier-Stokes equations | 11,120 |
We obtain an $L^4$ space-time Strichartz inequality for any smooth three-dimensional Riemannian manifold $(M,g)$ which is asymptotically conic at infinity and non-trapping, where $u$ is a solution to the Schr\"odinger equation $iu_t + {1/2} \Delta_M u = 0$. The exponent $H^{1/4}(M)$ is sharp, by scaling considerations. In particular our result covers asymptotically flat non-trapping manifolds. Our argument is based on the interaction Morawetz inequality introduced by Colliander et al., interpreted here as a positive commutator inequality for the tensor product $U(t,z',z'') := u(t,z') u(t,z'')$ of the solution with itself. We also use smoothing estimates for Schr\"odinger solutions including a new one proved here with weight $r^{-1}$ at infinity and with the gradient term involving only one angular derivative. | A Strichartz inequality for the Schroedinger equation on non-trapping
asymptotically conic manifolds | 11,121 |
The Cauchy problem for the modified KdV equation is shown to be locally well posed for data u_0 in the space \hat(H^r_s) defined by the norm ||u_0||:=||<\xi>^s \hat(u_0)||_L^r', provided 4/3 < r \le 2, s \ge 1/2 - 1/(2r). For r=2 this coincides with the best possible result on the H^s - scale due to Kenig, Ponce and Vega. The proof uses an appropriate variant of the Fourier restriction norm method and linear as well as bilinear estimates for the solutions of the Airy equation. | An improved local wellposedness result for the modified KdV equation | 11,122 |
We look for the optimal range of Lebesque exponents for which inhomogeneous Strichartz estimates are valid. We show that it is larger than the one given by admissible exponents for homogeneous estimates. We prove inhomogeneous estimates adopting the abstract setting and interpolation techniques already used by Keel and Tao for the endpoint case of the homogenenous estimates. Applications to Schrodinger equations are given, which extend previous work by Kato. | Inhomogeneous Strichartz estimates | 11,123 |
A one-way wave equation is an evolution equation in one of the space directions that describes (approximately) a wave field. The exact wave field is approximated in a high frequency, microlocal sense. Here we derive the pseudodifferential one-way wave equation for an inhomogeneous acoustic medium using a known factorization argument. We give explicitly the two highest order terms, that are necessary for approximating the solution. A wave front (singularity) whose propagation velocity has non-zero component in the special direction is correctly described. The equation can't describe singularities propagating along turning rays, i.e. rays along which the velocity component in the special direction changes sign. We show that incorrectly propagated singularities are suppressed if a suitable dissipative term is added to the equation. | A pseudodifferential equation with damping for one-way wave propagation
in inhomogeneous acoustic media | 11,124 |
We discuss the asymptotic behavior of positive solutions of the quasilinear elliptic problem $-\Delta_p u=a u^{p-1}-b(x) u^q$, $u|_{\partial \Omega}=0$ as $q \to p-1+0$ and as $q \to \infty$ via a scale argument. Here $\Delta_p$ is the $p$-Laplacian with $1<p<\infty$ and $q>p-1$. If $p=2$, such problems arise in population dynamics. Our main results generalize the results for $p=2$, but some technical difficulties arising from the nonlinear degenerate operator $-\Delta_p$ are successfully overcome. As a by-product, we can solve a free boundary problem for a nonlinear $p$-Laplacian equation. | Asymptotic behavior of positive solutions of some quasilinear elliptic
problems | 11,125 |
We prove weighted L^2 (Morawetz) estimates for the solutions of linear Schrodinger and wave equation with potentials that decay like |x|^{-2} for large x, by deducing them from estimates on the resolvent of the associated elliptic operator. We then deduce Strichartz estimates for these equations. | Strichartz estimates for the Wave and Schrodinger Equations with
Potentials of Critical Decay | 11,126 |
We present a streamlined account of recent developments in the stability theory for planar viscous shock waves, with an emphasis on applications to physical models with ``real,'' or partial viscosity. The main result is the establishment of necessary, or ``weak'', and sufficient, or ``strong'', conditions for nonlinear stability analogous to those established by Majda [Ma.1--3] in the inviscid case but (generically) separated by a codimension-one set in parameter space rather than an open set as in the inviscid case. The importance of codimension one is that transition between nonlinear stability and instability is thereby determined, lying on the boundary set between the open regions of strong stability and strong instability (the latter defined as failure of weak stability). Strong stability holds always for small-amplitude shocks of classical ``Lax'' type [PZ.1--2, FreS]; for large-amplitude shocks, however, strong instability may occur [ZS, Z.3]. | Planar stability critera for viscous shock waves of systems with real
viscosity | 11,127 |
This paper is concerned with a biharmonic equation under the Navier boundary condition with nearly critical exponent. We study the asymptotic behavior os solutions which are minimizing for the Sobolev quatient. We show that such solutions concentrate around an interior point which is a critical point of the Robin's function. Conversely, we show that for any nondegenerate critical point fo the Robin's function, the exist solutions concentrating around such a point. Finally, we prove that, in contrast with what happened in the subcritical equation, the supercritical problem has no solutions which concentrate around a point . | On a Biharmonic Equation Involving Nearly Critical Exponent | 11,128 |
In this paper we concentrate on the analysis of the critical mass blowing-up solutions for the cubic focusing Schr\"odinger equation with Dirichlet boundary conditions, posed on a plane domain. We bound the blow-up rate from below, for bounded and unbounded domains. If the blow-up occurs on the boundary, the blow-up rate is proved to grow faster than $(T-t)^{-1}$, the expected one. Moreover, we show that blow-up cannot occur on the boundary, under certain geometric conditions on the domain. | Remarks on the blow-up for the Schrödinger equation with critical mass
on a plane domain | 11,129 |
In this paper, we prove a new existence result for a variational model of crack growth in brittle materials proposed in [15]. We consider the case of $n$-dimensional finite elasticity, for an arbitrary $n\ge1$, with a quasiconvex bulk energy and with prescribed boundary deformations and applied loads, both depending on time. | Quasistatic crack growth in finite elasticity | 11,130 |
The main steps of the proof of the existence result for the quasi-static evolution of cracks in brittle materials, obtained in [7] in the vector case and for a general quasiconvex elastic energy, are presented here under the simplifying assumption that the minimizing sequences involved in the problem are uniformly bounded in $L^\infty$. | Quasi-static evolution in brittle fracture: the case of bounded
solutions | 11,131 |
The aim of these notes is to describe some recent results concerning dispersive estimates for principally normal pseudodifferential operators. The main motivation for this comes from unique continuation problems. Such estimates can be used to prove Carleman inequalities, which in turn yield unique continuation results for various partial differential operators with rough potentials. | Dispersive estimates for principally normal pseudodifferential operators | 11,132 |
It is shown that the spatial Sobolev norms of regular global solutions of the (2+1),(3+1) and (4+1)-dimensional Klein-Gordon-Schroedinger system and the (2+1) and (3+1)-dimensional Zakharov system grow at most polynomially with the bound depending on the regularity class of the data. The proof uses the Fourier restriction norm method. | Bounds in time for the Klein-Gordon-Schroedinger and the Zakharov system | 11,133 |
We perform an analysis of the size effect for quasistatic growth of fractures in linearly isotropic elastic bodies under antiplanar shear. In the framework of the variational model proposed by G.A. Francfort and J.-J. Marigo in [14], we prove that if the size of the body tends to infinity, and even if the surface energy is of cohesive form, under suitable boundary displacements the fracture propagates following the Griffith's functional. | Size effects on quasistatic growth of fractures | 11,134 |
We study the closed extensions (realizations) of differential operators subject to homogeneous boundary conditions on weighted L_p-Sobolev spaces over a manifold with boundary and conical singularities. Under natural ellipticity conditions we determine the domains of the minimal and the maximal extension. We show that both are Fredholm operators and give a formula for the relative index. | Realizations of Differential Operators on Conic Manifolds with Boundary | 11,135 |
We characterize microlocal regularity of Colombeau generalized functions by an appropriate extension of the classical notion of micro-ellipticity to pseudodifferential operators with slow scale generalized symbols. Thus we obtain an alternative, yet equivalent, way to determine generalized wave front sets, which is analogous to the original definition of the wave front set of distributions via intersections over characteristic sets. The new methods are then applied to regularity theory of generalized solutions of (pseudo-)differential equations, where we extend the general noncharacteristic regularity result for distributional solutions and consider propagation of generalized singularities for homogeneous first-order hyperbolic equations. | Microlocal analysis of generalized functions: pseudodifferential
techniques and propagation of singularities | 11,136 |
We study inverse conductivity problem for an anisotropic conductivity in $L^\infty$ in bounded and unbounded domains. Also, we give applications of the results in the case when Dirichlet-to-Neumann and Neumann-to-Dirichlet maps are given only on a part of the boundary. | Calderon's inverse problem for anisotropic conductivity in the plane | 11,137 |
We extend the Kreiss--Majda theory of stability of hyperbolic initial--boundary-value and shock problems to a class of systems, notably including the equations of magnetohydrodynamics (MHD), for which Majda's block structure condition does not hold: namely, simultaneously symmetrizable systems with characteristics of variable multiplicity, satisfying at points of variable multiplicity either a ``totally nonglancing'' or a ``nonglancing and linearly splitting'' condition. At the same time, we give a simple characterization of the block structure condition as ``geometric regularity'' of characteristics, defined as analyticity of associated eigenprojections. The totally nonglancing or nonglancing and linearly splitting conditions are generically satisfied in the simplest case of crossings of two characteristics, and likewise for our main physical examples of MHD or Maxwell equations for a crystal. Together with previous analyses of spectral stability carried out by Gardner--Kruskal and Blokhin--Trakhinin, this yields immediately a number of new results of nonlinear inviscid stability of shock waves in MHD in the cases of parallel or transverse magnetic field, and recovers the sole previous nonlinear result, obtained by Blokhin--Trakhinin by direct ``dissipative integral'' methods, of stability in the zero-magnetic field limit. Our methods apply also to the viscous case. | Hyperbolic Boundary Value Problems for Symmetric Systems with Variable
Multiplicities | 11,138 |
We consider a generalization of the Lotka-McKendrick problem describing the dynamics of an age-structured population with time-dependent vital rates. The generalization consists in allowing the initial and the boundary conditions to be derivatives of the Dirac measure. We construct a unique $\D'$-solution in the framework of intrinsic multiplication of distributions. We also investigate the regularity of this solution. | A Distributional Solution to a Hyperbolic Problem Arising in Population
Dynamics | 11,139 |
We investigate the existence and the singular structure of delta wave solutions to a semilinear strictly hyperbolic equation with strongly singular initial and boundary conditions. The boundary conditions are given in nonlocal form with a linear integral operator involved. We construct a delta wave solution as a distributional limit of solutions to the regularized system. This determines the macroscopic behavior of the corresponding generalized solution in the Colombeau algebra $\G$ of generalized functions. We represent our delta wave as a sum of a purely singular part satisfying a linear system and a regular part satisfying a nonlinear system. | Delta Waves for a Strongly Singular Initial-Boundary Hyperbolic Problem
with Integral Boundary Condition | 11,140 |
Enstrophy, half the integral of the square of vorticity, plays a role in 2D turbulence theory analogous to that played by kinetic energy in the Kolmogorov theory of 3D turbulence. It is therefore interesting to obtain a description of the way enstrophy is dissipated at high Reynolds number. In this article we explore the notions of viscous and transport enstrophy defect, which model the spatial structure of the dissipation of enstrophy. These notions were introduced by G. Eyink in an attempt to reconcile the Kraichnan-Batchelor theory of 2D turbulence with current knowledge of the properties of weak solutions of the equations of incompressible and ideal fluid motion. Three natural questions arise from Eyink's theory: (1) Existence of the enstrophy defects (2) Conditions for the equality of transport and viscous enstrophy defects (3) Conditions for the vanishing of the enstrophy defects. In [Nonlinearity, v 14 (2001) 787-802], Eyink proved a number of results related to these questions and formulated a conjecture on how to answer these problems in a physically meaningful context. In the present article we improve and extend some of Eyink's results and present a counterexample to his conjecture. | Weak solutions, renormalized solutions and enstrophy defects in 2D
turbulence | 11,141 |
We obtain global well-posedness, scattering, and global $L^{10}_{t,x}$ spacetime bounds for energy-class solutions to the quintic defocusing Schr\"odinger equation in $\R^{1+3}$, which is energy-critical. In particular, this establishes global existence of classical solutions. Our work extends the results of Bourgain and Grillakis, which handled the radial case. The method is similar in spirit to the induction-on-energy strategy of Bourgain, but we perform the induction analysis in both frequency space and physical space simultaneously, and replace the Morawetz inequality by an interaction variant. The principal advantage of the interaction Morawetz estimate is that it is not localized to the spatial origin and so is better able to handle nonradial solutions. In particular, this interaction estimate, together with an almost-conservation argument controlling the movement of $L^2$ mass in frequency space, rules out the possibility of energy concentration. | Global well-posedness and scattering for the energy-critical nonlinear
Schrödinger equation in R^3 | 11,142 |
In any dimension $n \geq 3$, we show that spherically symmetric bounded energy solutions of the defocusing energy-critical non-linear Schr\"odinger equation $i u_t + \Delta u = |u|^{\frac{4}{n-2}} u$ in $\R \times \R^n$ exist globally and scatter to free solutions; this generalizes the three and four dimensional results of Bourgain and Grillakis. Furthermore we have bounds on various spacetime norms of the solution which are of exponential type in the energy, which improves on the tower-type bounds of Bourgain. In higher dimensions $n \geq 6$ some new technical difficulties arise because of the very low power of the non-linearity. | Global well-posedness and scattering for the higher-dimensional
energy-critical non-linear Schrodinger equation for radial data | 11,143 |
We continue here with previous investigations on the global behavior of general type non-linear wave equations for a class of small, scale-invariant initial data. The method is based on the use of a new set of Strichartz estimates for the linear wave equation which incorporates extra weighted smoothness assumptions with respect to the angular variable, along with the construction of appropriate micro-local function spaces which take into account this type of additional regularity. | Global Regularity and Scattering for General Non-Linear Wave Equations
II. (4+1) Dimensional Yang--Mills Equations in the Lorentz Gauge | 11,144 |
We prove here essentially sharp linear and bilinear Strichartz type estimates for the wave equations on Minkowski space, where we assume the initial data possesses additional regularity with respect to fractional powers of the usual angular momentum operators. In this setting, the range of (q,r) exponents vastly improves over what is available for the wave equations based on translation invariant derivatives of the initial data and the dispersive inequality. Two proofs of this result are given. | Angular Regularity and Strichartz Estimates for the Wave Equation | 11,145 |
We solve here the so called division problem for wave equations with generic quadratic non-linearities in high dimensions. Specifically, we show that semilinear wave equations which can be written as systems involving quadratic derivative non-linearities are globally well posed in (6+1) and higher dimensions for all regularities greater than the scaling. This paper is the first in a series of works where we discuss the global regularity properties of general non-linear wave equations for all spatial dimensions greater than or equal to 4. | Global Regularity for General Non-Linear Wave Equations I. (6+1) and
Higher Dimensions | 11,146 |
We consider the standing wave solutions of the three dimensional semilinear Schrodinger equation with competing potential functions $V$ and $K$ and under the action of an external electromagnetic vector field $A$. We establish some necessary conditions for a sequence of such solutions to concentrate, in two different senses, around a given point. In the particular but important case of nonlinearities of power type, we prove that the spikes locate at the critical points of a smooth ground energy map independent of $A$. | On the location of spikes for the Schrodinger equation with
electromagnetic field | 11,147 |
Let P be the operator $-\Delta+V$ on R^d, where $V$ is a real potential with several inverse square singularities. The usual non-trapping type high-frequency inequality on the truncated resolvent of $P$ is shown, using semi-classical measures. This inequality implies local smoothing effect on the corresponding Schrodinger equation. | Operateur de Schrodinger avec potentiel singulier multi-polaire
(Schrodinger operator with a potential including several inverse-square
singularities) | 11,148 |
This article is devoted to incompressible Euler equations (or to Navier-Stokes equations in the vanishing viscosity limit). It describes the propagation of quasi-singularities. The underlying phenomena are consistent with the notion of a cascade of energy. | Cascade of phases in turbulent flows | 11,149 |
We study the possibility of finite-time blow-up for a two dimensional Broadwell model. In a set of rescaled variables, we prove that no self-similar blow-up solution exists, and derive some a priori bounds on the blow-up rate. In the final section, a possible blow-up scenario is discussed. | On the Blow-up for a Discrete Boltzmann Equation in the Plane | 11,150 |
Bloch equations give a quantum description of the coupling between an atom and a driving electric force. In this article, we address the asymptotics of these equations for high frequency electric fields, in a weakly coupled regime. We prove the convergence towards rate equations (i.e. linear Boltzmann equations, describing the transitions between energy levels of the atom). We give an explicit form for the transition rates. This has already been performed in [BFCD03] in the case when the energy levels are fixed, and for different classes of electric fields: quasi or almost periodic, KBM, or with continuous spectrum. Here, we extend the study to the case when energy levels are possibly almost degenerate. However, we need to restrict to quasiperiodic forcings. The techniques used stem from manipulations on the density matrix and the averaging theory for ordinary differential equations. Possibly perturbed small divisor estimates play a key role in the analysis. In the case of a finite number of energy levels, we also precisely analyze the initial time-layer in the rate aquation, as well as the long-time convergence towards equilibrium. We give hints and counterexamples in the infinite dimensional case. | From Bloch model to the rate equations II: the case of almost degenerate
energy levels | 11,151 |
The Cauchy problem for a multidimensional linear transport equation with discontinuous coefficient is investigated. Provided the coefficient satisfies a one-sided Lipschitz condition, existence, uniqueness and weak stability of solutions are obtained for either the conservative backward problem or the advective forward problem by duality. Specific uniqueness criteria are introduced for the backward conservation equation since weak solutions are not unique. A main point is the introduction of a generalized flow in the sense of partial differential equations, which is proved to have unique jacobian determinant, even though it is itself nonunique. | Uniqueness and weak stability for multi-dimensional transport equations
with one-sided Lipschitz coefficient | 11,152 |
In this paper, we consider the existence and non-existence of non-trivial solution to a Brezis-Nirenberg type problem with singular weights. First, we obtain a compact imbedding theorem which is an extension of the classical Rellich-Kondrachov compact imbedding theorem, and consider the corresponding eigenvalue problem. Secondly, we deduce a Pohozaev type identity and obtained a non-existence result. Thirdly, based on a generalized concentration compactness principle, we will give some abstract conditions when the functional satisfies the (PS)$_c$ condition. Finally, based on the explicit form of the extremal function, we will obtain some existence results to the problem. | The solvability of Brezis-Nirenberg type problems of singular
quasilinear elliptic equation | 11,153 |
We compute explicitely the best constants and, by solving some functional equations, we find all maximizers for homogeneous Strichartz estimates for the Schrodinger equation and for the wave equation in the cases when the Lebesgue exponent is an even integer. | Maximizers for the Strichartz inequality | 11,154 |
In this paper, using Mountain Pass Lemma and Linking Argument, we prove the existence of nontrivial weak solutions for the Dirichlet problem for the superlinear equation of Caffarelli-Kohn-Nirenberg type in the case where the parameter $\lambda\in (0, \lambda_2)$, $\lambda_2$ is the second positive eigenvalue of the quasilinear elliptic equation of Caffarelli-Kohn-Nirenberg type. | Existence results for a superlinear singular equation of
Caffarelli-Kohn-Nirenberg type | 11,155 |
In this paper, we study the existence of multiple solutions to a Caffarelli-Kohn-Nirenberg type equation with asymptotically linear term at infinity. In this case, the well-known Ambrosetti-Rabinowtz type condition doesn't hold, hence it is difficult to verify the classical (PS)$_c$ condition. To overcome this difficulty, we use an equivalent version of Cerami's condition, which allows the more general existence result. | Multiple solutions to a Caffarelli-Kohn-Nirenberg type equation with
asymptotically linear term | 11,156 |
We consider a nonlinear semi-classical Schroedinger equation for which quadratic oscillations lead to focusing at one point, described by a nonlinear scattering operator. The relevance of the nonlinearity was discussed by R. Carles, C. Fermanian-Kammerer and I. Gallagher for $L^2$-supercritical power-like nonlinearities and more general initial data. The present results concern the $L^2$-critical case, in space dimensions 1 and 2; we describe the set of non-linearizable data, which is larger, due to the scaling. As an application, we precise a result by F. Merle and L. Vega concerning finite time blow up for the critical Schroedinger equation. The proof relies on linear and nonlinear profile decompositions. | On the role of quadratic oscillations in nonlinear Schroedinger
equations II. The $L^2$-critical case | 11,157 |
A solution is developed for a convection-diffusion equation describing chemical transport with sorption, decay, and production. The problem is formulated in a finite domain where the appropriate conservation law yields Robin conditions at the ends. When the input concentration is arbitrary, the problem is underdetermined because of an unknown exit concentration. We resolve this by defining the exit concentration as a solution to a similar diffusion equation which satisfies a Dirichlet condition at the left end of the half line. This problem does not appear to have been solved in the literature, and the resulting representation should be useful for problems of practical interest. Authors of previous works on problems of this type have eliminated the unknown exit concentration by assuming a continuous concentration at the outflow boundary. This yields a well-posed problem by forcing a homogeneous Neumann exit, widely known as the Danckwerts [1] condition. We provide a solution to the Neumann problem and use it to produce an estimate which demonstrates that the Danckwerts condition implies a zero concentration at the outflow boundary, even for a long flow domain and a large time. | The convection-diffusion equation for a finite domain with time varying
boundaries | 11,158 |
We investigate the formation of singularities in a self-similar form of regular solutions of the Localized Induction Approximation (also referred as to the binormal flow). This equation appears as an approximation model for the self-induced motion of a vortex filament in an inviscid incompressible fluid. The solutions behave as 3d-logarithmic spirals at infinity. The proofs of the results are strongly based on the existing connection between the binormal flow and certain Schr\"odinger equations. | Self-binormal solutions of the Localized Induction Approximation:
Singularity formation | 11,159 |
We prove global existence of solutions to quasilinear wave equations with quadratic nonlinearities exterior to nontrapping obstacles in spatial dimensions four and higher. This generalizes a result of Shibata and Tsutsumi in spatial dimensions greater than or equal to six. The technique of proof would allow for more complicated geometries provided that an appropriate local energy decay exists for the associated linear wave equation. | Global existence for Dirichlet-wave equations with quadratic
nonlinearties in high dimensions | 11,160 |
We study properties of the semilinear elliptic equation $\Delta u = 1/u$ on domains in $R^n$, with an eye toward nonnegative singular solutions as limits of positive smooth solutions. We prove the nonexistence of such solutions in low dimensions when we also require them to be stable for the corresponding variational problem. The problem of finding singular solutions is related to the general study of singularities of minimal hypersurfaces in Euclidean space. | Stable and singular solutions of the equation $Δu = 1/u$ | 11,161 |
For $n\ge 5$ and $k\ge 4$, we show that any minimizing biharmonic map from $\Omega\subset R^n$ to $S^k$ is smooth off a closed set whose Hausdorff dimension is at most $n-5$. When $n=5$ and $k=4$, for a parameter $\lambda\in [0,1]$ we introduce a $\lambda$-relaxed energy $\H_\lambda$ for the Hessian energy for maps in $W^{2,2}(\Omega,S^4)$ so that each minimizer $u_\lambda$ of $\H_\lambda$ is also a biharmonic map. We also estabilish the existence and partial regularity of a minimizer of $\H_\lambda$ for $\lambda\in [0,1)$. | Regularity and relaxed problems of minimizing biharmonic maps into
spheres | 11,162 |
We prove that no finite time blow up can occur for nonlinear Schroedinger equations with quadratic potentials, provided that the potential has a sufficiently strong repulsive component. This is not obvious in general, since the energy associated to the linear equation is not positive. The proof relies essentially on two arguments: global in time Strichartz estimates, and a refined analysis of the linear equation, which makes it possible to use continuity arguments and to control the nonlinear effects. | Global existence results for nonlinear Schrodinger equations with
quadratic potentials | 11,163 |
The generalized Korteweg-de Vries equations are a class of Hamiltonian systems in infinite dimension derived from the KdV equation where the quadratic term is replaced by a higher order power term. These equations have two conservation laws in the energy space H^1(L^2 norm and energy). We consider in this paper the {\it critical} generalized KdV equation, which corresponds to the smallest power of the nonlinearity such that the two conservation laws do not imply a bound in H^1 uniform in time for all H^1 solutions (and thus global existence). From [15], there do exist for this equation solutions u(t) such that |u(t)|_{H^1} \to +\infty as T\uparrow T, where T\le +\infty (we call them blow-up solutions). The question is to describe, in a qualitative way, how blow up occurs. For solutions with L^2 mass close to the minimal mass allowing blow up and with decay in L^2 at the right, we prove after rescaling and translation which leave invariant the L^2 norm that the solution converges to a {\it universal} profile locally in space at the blow-up time T. From the nature of this profile, we improve the standard lower bound on the blow-up rate for finite time blow-up solutions. | Stability of blow-up profile and lower bounds for blow-up rate for the
critical generalized KdV equation | 11,164 |
We consider a simple model describing premixed combustion in the presence of fluid flow: reaction diffusion equation with passive advection and ignition type nonlinearity. Strong advection can suppress flames - a process we call quenching. A flow is called quenching if any compactly supported initial data will become extinct provided that the amplitude of the flow is chosen sufficiently large. In this paper, we provide a sharp characterization of quenching shear flows.The efficiency of quenching depends strongly on the geometry and scaling of the flow. We discuss the cases of slowly and quickly varying flows, proving analytically behavior that has been observed earlier in numerical experiments. The technique involves probabilistic and PDE estimates, in particular applications of Malliavin calculus and central limit theorem for martingales. | Quenching of combustion by shear flows | 11,165 |
In this paper we describe the propagation of smooth (C^\infty) and Sobolev singularities for the wave equation on smooth manifolds with corners M equipped with a Riemannian metric g. That is, for X=MxR, P=D_t^2-\Delta_M, and u locally in H^1 solving Pu=0 with homogeneous Dirichlet or Neumann boundary conditions, we show that the wave front set of u is a union of maximally extended generalized broken bicharacteristics. This result is a smooth counterpart of Lebeau's results for the propagation of analytic singularities on real analytic manifolds with appropriately stratified boundary. Our methods rely on b-microlocal positive commutator estimates, thus providing a new proof for the propagation of singularities at hyperbolic points even if M has a smooth boundary (and no corners). | Propagation of singularities for the wave equation on manifolds with
corners | 11,166 |
In this paper we improve an earlier result by Bukhgeim and Uhlmann, by showing that in dimension larger than or equal to three, the knowledge of the Cauchy data for the Schr\"odinger equation measured on possibly very small subsets of the boundary determines uniquely the potential. We follow the general strategy of Bukhgeim and Uhlmann but use a richer set of solutions to the Dirichlet problem. | The Calderón problem with partial data | 11,167 |
In 1994 we showed that very large classes of systems of nonlinear PDEs have solutions which can be assimilated with usual measurable functions on the Euclidean domains of definition of the respective equations. Recently, the regularity of such solutions has significantly been improved by showing that they can in fact be assimilated with Hausdorff continuous functions. The method of solution of PDEs is based on the Dedekind order completion of spaces of smooth functions which are defined on the domains of the given equations. In this way, the method does not use functional analytic approaches, or any of the customary distributions, hyperfunctions, or other generalized functions. | Hausdorff continuous solutions of arbitrary continuous nonlinear PDEs
through the order completion method | 11,168 |
In this paper we consider the following two-phase obstacle-problem-like equation in the unit half-ball $\Delta u = \lambda_{+}\chi_{\{u>0\}}-\lambda_{-}\chi_{\{u<0\}}, \lambda_\pm>0$. We prove that the free boundary touches the fixed one in (uniformly) tangential fashion if the boundary data $f$ and its first and second derivatives vanish at the touch-point. | On the tangential touch between the free and the fixed boundaries for
the two-phase obstacle-like problem | 11,169 |
In this article we study some aspects of dispersive and concentration phenomena for the Schr\"odinger equation posed on hyperbolic space $\mathbb{H}^n$, in order to see if the negative curvature of the manifold gets the dynamics more stable than in the Euclidean case. It is indeed the case for the dispersive properties : we prove that the dispersion inequality is valid, in a stronger form than the one on $\mathbb{R}^n$. However, the geometry does not have enough of an effect to avoid the concentration phenomena and the picture is actually worse than expected. The critical nonlinearity power for blow-up turns out to be the same as in the euclidean case, and we prove that there are more explosive solutions for critical and supercritical nonlinearities. | The nonlinear Schrödinger equation on the hyperbolic space | 11,170 |
An explicit formula is given for a fundamental solution for a class of semielliptic operators. The fundamental solution is used to investigate properties of these operators as mappings between weighted function spaces. Necessary and sufficient conditions are given for such a mapping to be an isomorphism. Results apply, for example, to elliptic, parabolic, and generalized p-parabolic operators. | Fundamental Solutions and Mapping Properties of Semielliptic Operators | 11,171 |
In this dissertation, we study the well-posedness of the three-dimensional Lagrangian averaged Navier-Stokes (LANS-$\alpha$) equations. There are two types of LANS-$\alpha$ equations: the anisotropic version in which the fluctuation tensor is a dynamic variable that is coupled with the evolution equations for the mean velocity, and the isotropic version in which the covariance tensor is assumed to be a constant multiple of the identity matrix. We prove the global-in-time existence and uniqueness of weak solutions to the isotropic LANS-$\alpha$ equations for the case of no-slip boundary conditions. When the anisotropic LANS-$\alpha$ equations are written with the Stokes projector viscosity term, we show the local-in-time well-posedness of the anisotropic equations in the periodic box. We numerically compute strong solutions to the anisotropic equations in the laminar channel and pipe by considering steady fluid flow solutions to the Navier-Stokes equations. | Well-posedness of the three-dimensional Lagrangian averaged
Navier-Stokes equations | 11,172 |
This dissertation resolves a longstanding discussion of a mathematical problem important in contaminant hydrogeology and chemical-reaction engineering, the proper mathematical description for a miscible solute undergoing longitudinal convective-dispersive transport with production, decay, and sorption in a porous medium. Initial and input concentrations may be any continuously differentiable functions and the problem is stated for a finite domain. This domain yields a mass balance which requires Robin (i.e., third-type) boundaries, which describe a continuous flux but a discontinuous resident-concentration. The discontinuity in the resident concentration at the outflow boundary yields an underdetermined system when the exit concentration is not experimentally measured. This is resolved by defining the unknown effluent concentration from a semi-infinite problem which satisfies a Dirichlet (i.e., first-type) condition at the origin. The solution is represented in a uniformly convergent series of real variables. The large volume of antecedent literature on finite solutions for convective-dispersive transport equations grew out of the historical precedents set by Danckwerts (1953) and Wehner and Wilhelm (1956) whom made simplifying assumptions of continuous boundary concentrations. This dissertation includes the demonstration that continuous-concentration hypotheses, whether rendered as Dirichlet or homogeneous Neumann (i.e., second-type) conditions, satisfy external mass conservation yet fail to provide solutions that are internally consistent with the governing equation. | Solute Transport in a Porous Medium: A Mass-Conserving Solution for the
Convection-Dispersion Equation in a Finite Domain | 11,173 |
We prove a sharp H\"older estimate for solutions of linear two-dimensional, divergence form elliptic equations with measurable coefficients, such that the matrix of the coefficients is symmetric and has {\em unit determinant}. Our result extends some previous work by Piccinini and Spagnolo. The proof relies on a sharp Wirtinger type inequality. | A sharp Hölder estimate for elliptic equations in two variables | 11,174 |
It was shown in 1994, in Oberguggenberger & Rosinger, that very large classes of nonlinear PDEs have solutions which can be assimilated with usual measurable functions on the Euclidean domains of definition of the respective equations. In this paper the regularity of these solutions is significantly improved by showing that they can in fact be assimilated with Hausdorff continuous functions. The method of solution of PDEs is based on the Dedekind order completion of spaces of smooth functions which are defined on the domains of the given equations. | Hausdorff continuous solutions of nonlinear PDEs through the order
completion method | 11,175 |
Contrary to widespread perception, there is ever since 1994 a unified, general type independent theory for the existence of solutions for very large classes of nonlinear systems of PDEs. This solution method is based on the Dedekind order completion of suitable spaces of piece-wise smooth functions on the Euclidean domains of definition of the respective PDEs. The method can also deal with associated initial and/or boundary value problems. The solutions obtained can be assimilated with usual measurable functions or even with Hausdorff continuous functions on the respective Euclidean domains. It is important to note that the use of the order completion method does not require any monotonicity condition on the nonlinear systems of PDEs involved. One of the major advantages of the order completion method is that it eliminates the algebra based dichotomy "linear versus nonlinear" PDEs, treating both cases with equal ease. Furthermore, the order completion method does not introduce the dichotomy "monotonous versus non-monotonous" PDEs. None of the known functional analytic methods can exhibit such a performance, since in addition to topology, such methods are significantly based on algebra. | Can there be a general nonlinear PDE theory for the existence of
solutions ? | 11,176 |
This paper argues that curvelets provide a powerful tool for representing very general linear symmetric systems of hyperbolic differential equations. Curvelets are a recently developed multiscale system in which the elements are highly anisotropic at fine scales, with effective support shaped according to the parabolic scaling principle width ~ length^2 at fine scales. We prove that for a wide class of linear hyperbolic differential equations, the curvelet representation of the solution operator is both optimally sparse and well organized. It is sparse in the sense that the matrix entries decay nearly exponentially fast (i.e. faster than any negative polynomial), and well-organized in the sense that the very few nonnegligible entries occur near a shifted diagonal. Indeed, we actually show that the action of the wave-group on a curvelet is well-approximated by simply translating the center of the curvelet along the Hamiltonian flow--hence the diagonal shift in the curvelet epresentation. A physical interpretation of this result is that curvelets may be viewed as coherent waveforms with enough frequency localization so that they behave like waves but at the same time, with enough spatial localization so that they simultaneously behave like particles. | The Curvelet Representation of Wave Propagators is Optimally Sparse | 11,177 |
We give a necessary and sufficient condition, of geometric type, for the uniform decay of energy of solutions of the linear system of magnetoelasticity in a bounded domain with smooth boundary. A Dirichlet-type boundary condition is assumed. When the geometrical condition is not fulfilled, we show polynomial decay of the energy, for smooth initial conditions. Our strategy is to use micro-local defect measures to show suitable observability inequalities on high-frequency solutions of the Lame system. | Stabilization of the Linear System of Magnetoelasticity | 11,178 |
The concept of Hausdorff continuous interval valued functions, developed within the theory of Hausdorff approximations and originaly defined for interval valued functions of one real variable is extended to interval valued functions defined on a topological space X. The main result is that the set of all finite Hausdorff continuous functions on any topological space X is Dedekind order complete. Hence it contains the Dedekind order completion of the set C(X) of all continuous real functions defined on X as well as the Dedekind order completion of the set C_b(X) of all bounded continuous functions on X. Under some general assumptions about the topological space X the Dedekind order completions of both C(X) and C_b(X) are characterised as subsets of the set of all Hausdorff continuous functions. This solves a long outstanding open problem about the Dedekind order completion of C(X). In addition, it has major applications to the regularity of solutions of large classes of nonlinear PDEs. | Dedekind order completion of C(X) by Hausdorff continuous functions | 11,179 |
We consider the reactive Boussinesq equations in a slanted cylinder, with zero stress boundary conditions and arbitrary Rayleigh number. We show that the equations have non-planar traveling front solutions that propagate at a constant speed. We also establish uniform upper bounds on the burning rate and the flow velocity for general front-like initial data for the Cauchy problem. | Non-Planar Fronts in Boussinesq Reactive Flows | 11,180 |
The motion of an elastic solid inside of an incompressible viscous fluid is ubiquitous in nature. Mathematically, such motion is described by a PDE system that couples the parabolic and hyperbolic phases, the latter inducing a loss of regularity which has left the basic question of existence open until now. In this paper, we prove the existence and uniqueness of such motions (locally in time), when the elastic solid is the linear Kirchhoff elastic material. The solution is found using a topological fixed-point theorem that requires the analysis of a linear problem consisting of the coupling between the time-dependent Navier-Stokes equations set in Lagrangian variables and the linear equations of elastodynamics, for which we prove the existence of a unique weak solution. We then establish the regularity of the weak solution; this regularity is obtained in function spaces that scale in a hyperbolic fashion in both the fluid and solid phases. Our functional framework is optimal, and provides the a priori estimates necessary for us to employ our fixed-point procedure. | On the motion of an elastic solid inside of an incompressible viscous
fluid | 11,181 |
We prove the existence of reaction-diffusion traveling fronts in mean zero space-time periodic shear flows for nonnegative reactions including the classical KPP (Kolmogorov-Petrovsky-Piskunov) nonlinearity. For the KPP nonlinearity, the minimal front speed is characterized by a variational principle involving the principal eigenvalue of a space-time periodic parabolic operator. Analysis of the variational principle shows that adding a mean-zero space time periodic shear flow to an existing mean zero space-periodic shear flow leads to speed enhancement. Computation of KPP minimal speeds is performed based on the variational principle and a spectrally accurate discretization of the principal eigenvalue problem. It shows that the enhancement is monotone decreasing in temporal shear frequency, and that the total enhancement from pure reaction-diffusion obeys quadratic and linear laws at small and large shear amplitudes. | Existence of KPP Type Fronts in Space-Time Periodic Shear Flows and a
Study of Minimal Speeds Based on Variational Principle | 11,182 |
Through the Maximum principle we define the principal eigenvalue for a class of fully-nonlinear operators that are the non-variational equivalent of the p-Laplacian. We also obtain some a priori Holder estimates for non-negative solutions below that eigenvalue. | First eigenvalue and Maximum principle for fully nonlinear singular
operators | 11,183 |
We study the asymptotic behavior of the solution of an anisotropic, heterogeneous, linearized elasticity problem in a cylinder whose diameter $\epsilon$ tends to zero. The cylinder is assumed to be fixed (homogeneous Dirichlet boundary condition) on the whole of one of its extremities, but only on a small part (of size $\epsilon r^\epsilon$) of the second one; the Neumann boundary condition is assumed on the remainder of the boundary. We show that the result depends on $r^\epsilon$, and that there are 3 critical sizes, namely $r^\epsilon=\epsilon^3$, $r^\epsilon=\epsilon$, and $r^\epsilon=\epsilon^{1/3}$, and in total 7 different regimes. We also prove a corrector result for each behavior of $r^\epsilon$. | Asymptotic behavior of an elastic beam fixed on a small part of one of
its extremities | 11,184 |
We define and prove some properties of the semi-classical wavefront set. We also define and study semi-classical Fourier integral operators, of which we give a complete characterization. Lastly, we prove a generalization of the semi-classical Egorov's Theorem to manifolds of unequal dimensions. | Semi-Classical Wavefront Set and Fourier Integral Operators | 11,185 |
We consider scattering by general compactly supported semi-classical perturbations of the Euclidean Laplace-Beltrami operator. We show that if the suitably cut-off resolvent of the Hamiltonian quantizes a Lagrangian relation on the product cotangent bundle, the scattering amplitude quantizes the natural scattering relation. In the case when the resolvent is tempered, which is true under some non-resonance assumptions, and when we work microlocally near a non-trapped ray, our result implies that the scattering amplitude defines a semiclassical Fourier integral operator associated to the scattering relation in a neighborhood of that ray. Compared to previous work we allow this relation to have more general geometric structure. | Structure of the Semi-Classical Amplitude for General Scattering
Relations | 11,186 |
In this paper we study the Navier-Stokes equations with a Navier-type boundary condition that has been proposed as an alternative to common near wall models. The boundary condition we study, involving a linear relation between the tangential part of the velocity and the tangential part of the Cauchy stress-vector, is related to the vorticity seeding model introduced in the computational approach to turbulent flows. The presence of a point-wise non vanishing normal flux may be considered as a tool to avoid the use of phenomenological near wall models, in the boundary layer region. Furthermore, the analysis of the problem is suggested by recent advances in the study of Large Eddy Simulation. In the two dimensional case we prove existence and uniqueness of weak solutions, by using rather elementary tools, hopefully understandable also by applied people working on turbulent flows. The asymptotic behaviour of the solution, with respect to the averaging radius $\delta,$ is also studied. In particular, we prove convergence of the solutions toward the corresponding solutions of the Navier-Stokes equations with the usual no-slip boundary conditions, as the small parameter $\delta$ goes to zero. | On the existence and uniqueness of weak solutions for a vorticity
seeding model | 11,187 |
Lewis and Vogel proved that a bounded domain whose Poisson kernel is constant and whose surface measure to the boundary has at most Euclidean growth is a ball. In this paper we show that this result is stable under small perturbations. In particular a bounded domain whose Poisson kernel is smooth and close to a constant, and whose surface measure to the boundary has at most Euclidean growth is a smooth deformation of a ball. | Stability of Lewis and Vogel's result | 11,188 |
We investigate the $L^p $ asymptotic behavior $(1\le p \le \infty)$ of a perturbation of a Lax or overcompressive type shock wave solution to a system of conservation law in one dimension. The system of the equations can be strictly parabolic, or have real viscosity matrix (partially parabolic, e.g., compressible Navier--Stokes equations or equations of Magnetohydrodynamics). We use known pointwise Green function bounds for the linearized equation around the shock to show that the perturbation of such a solution can be decomposed into a part corresponding to shift in shock position or shape, a part which is the sum of diffusion waves, i.e., the solutions to a viscous Burger's equation, conserving the initial mass and convecting away from the shock profile in outgoing modes, and another part which is more rapidly decaying in $L^p$. | $L^p$ asymptotic behavior of perturbed viscous shock profiles | 11,189 |
We consider a Yamabe type problem on a family $A_\epsilon$ of annulus shaped domains of $\R^3$ which becomes "thin" as $\epsilon$ goes to zero. We show that, for any given positive constant $C$, there exists $\epsilon_0$ such that for any $\epsilon < \epsilon_0$, the problem has no solution $u_\epsilon$ whose energy is less than $C$. Such a result extends to dimension three a result previously known in higher dimensions. Although the strategy to prove this result is the same as in higher dimensions, we need a more careful and delicate blow up analysis of asymptotic profiles of solutions $u_\epsilon$ when $\epsilon$ goes to zero. | On a Yamabe Type Problem on Three Dimensional Thin Annulus | 11,190 |
We obtain the Strichartz inequalities $$ \| u \|_{L^q_t L^r_x([0,1] \times M)} \leq C \| u(0) \|_{L^2(M)}$$ for any smooth $n$-dimensional Riemannian manifold $M$ which is asymptotically conic at infinity (with either short-range or long-range metric perturbation) and non-trapping, where $u$ is a solution to the Schr\"odinger equation $iu_t + {1/2} \Delta_M u = 0$, and $2 < q, r \leq \infty$ are admissible Strichartz exponents ($\frac{2}{q} + \frac{n}{r} = \frac{n}{2}$). This corresponds with the estimates available for Euclidean space (except for the endpoint $(q,r) = (2, \frac{2n}{n-2})$ when $n > 2$). These estimates imply existence theorems for semi-linear Schr\"odinger equations on $M$, by adapting arguments from Cazenave and Weissler \cite{cwI} and Kato \cite{kato}. This result improves on our previous result in \cite{HTW}, which was an $L^4_{t,x}$ Strichartz estimate in three dimensions. It is closely related to the results of Staffilani-Tataru, Burq, Tataru, and Robbiano-Zuily, who consider the case of asymptotically flat manifolds. | Sharp Strichartz estimates on non-trapping asymptotically conic
manifolds | 11,191 |
Consider classical solutions to the parabolic reaction diffusion equation $$ &u_t =Lu+f(x,u), (x,t)\in R^n\times(0,\infty); &u(x,0) =g(x)\ge0, x\in R^n; &u\ge0, $$ where $$ L=\sum_{i,j=1}^na_{i,j}(x)\frac{\partial^2}{\partial x_i \partial x_j}+\sum_{i=1}^nb_i(x)\frac\partial{\partial x_i} $$ is a non-degenerate elliptic operator, $g\in C(R^n)$ and the reaction term $f$ converges to $-\infty$ at a super-linear rate as $u\to\infty$. We give a sharp minimal growth condition on $f$, independent of $L$, in order that there exist a universal, a priori upper bound for all solutions to the above Cauchy problem--that is, in order that there exist a finite function $M(x,t)$ on $R^n\times(0,\infty)$ such that $u(x,t)\le M(x,t)$, for all solutions to the Cauchy problem. Assuming now in addition that $f(x,0)=0$, so that $u\equiv0$ is a solution to the Cauchy problem, we show that under a similar growth condition, an intimate relationship exists between two seemingly disparate phenomena--namely, uniqueness for the Cauchy problem with initial data $g=0$ and the nonexistence of unbounded, stationary solutions to the corresponding elliptic problem. We also give a generic condition for nonexistence of nontrivial stationary solutions. | Reaction diffusion equations with super-linear absorption: universal
bounds, uniqueness for the Cauchy problem, boundedness of stationary
solutions | 11,192 |
In this paper we consider the following biharmonic equation with critical exponent $P_\epsilon$ : $\Delta^2 u= Ku^{(n+4)/(n-4)-\epsilon}, u>0$ in $\Omega$ and $u=\Delta u=0$ on $\partial\Omega$, where $\Omega$ is a domain in $R^n$, $n\geq 5$, $\epsilon$ is a small positive parameter and $K$ is smooth positive function. We construct solutions of $P_\epsilon$ which blow up and concentrate at strict local maximum of $K$ either at the boundary or in the interior of $\Omega$. We also construct solutions of $P_\epsilon$ concentrating at an interior strict local minimum of $K$. Finally, we prove a nonexistense result for the corresponding supercritical problem which is in sharp contrast with what happened for $P_\epsilon$. | Blowing up Solutions for a Biharmonic Equation with Critical
Nonlinearity | 11,193 |
We study nonlinear Schr\"odinger equations, posed on a three dimensional Riemannian manifold $M$. We prove global existence of strong $H^1$ solutions on $M=S^3$ and $M=S^2\times S^1$ as far as the nonlinearity is defocusing and sub-quintic and thus we extend the results of Ginibre-Velo and Bourgain who treated the cases of the Euclidean space $\R^3$ and the flat torus $\T^3$ respectively. The main ingredient in our argument is a new set of multilinear estimates for spherical harmonics. | Multilinear Eigenfunction Estimates And Global Existence For The Three
Dimensional Nonlinear SchrÖdinger Equations | 11,194 |
We prove existence of small amplitude, 2 pi/omega -periodic in time solutions of completely resonant nonlinear wave equations with Dirichlet boundary conditions for any frequency omega belonging to a Cantor-like set of positive measure and for a generic set of nonlinearities. The proof relies on a suitable Lyapunov-Schmidt decomposition and a variant of the Nash-Moser Implicit Function Theorem. | Bifurcation of free vibrations for completely resonant wave equations | 11,195 |
We construct positive solutions of the semilinear elliptic problem $\Delta u+ \lambda u + u^p = 0$ with Dirichet boundary conditions, in a bounded smooth domain $\Omega \subset \R^N$ $(N\geq 4)$, when the exponent $p$ is supercritical and close enough to $\frac{N+2}{N-2}$ and the parameter $\lambda\in\R$ is small enough. As $p\to \frac{N+2}{N-2}$, the solutions have multiple blow up at finitely many points which are the critical points of a function whose definition involves Green's function. Our result extends the result of Del Pino, Dolbeault and Musso \cite{DDM} when $\Omega$ is a ball and the solutions are radially symmetric. | Bubble towers for supercritical semilinear elliptic equations | 11,196 |
We study a reaction-diffusion equation in the cylinder $\Omega = \mathbb{R}\times\mathbb{T}^m$, with combustion-type reaction term without ignition temperature cutoff, and in the presence of a periodic flow. We show that if the reaction function decays as a power of $T$ larger than three as $T\to 0$ and the initial datum is small, then the flame is extinguished -- the solution quenches. If, on the other hand, the power of decay is smaller than three or initial datum is large, then quenching does not happen, and the burning region spreads linearly in time. This extends results of Aronson-Weinberger for the no-flow case. We also consider shear flows with large amplitude and show that if the reaction power-law decay is larger than three and the flow has only small plateaux (connected domains where it is constant), then any compactly supported initial datum is quenched when the flow amplitude is large enough (which is not true if the power is smaller than three or in the presence of a large plateau). This extends results of Constantin-Kiselev-Ryzhik for combustion with ignition temperature cutoff. Our work carries over to the case $\Omega = \mathbb{R}^n\times\mathbb{T}^m$, when the critical power is $1 + 2/n$, as well as to certain non-periodic flows. | Quenching and Propagation of Combustion Without Ignition Temperature
Cutoff | 11,197 |
The 1-dimensional Zakharov system is shown to have a unique global solution for data without finite energy. The proof uses the " I-method " introduced by Colliander, Keel, Staffilani, Takaoka, and Tao in connection with a refined bilinear Strichatz estimate. | Global solutions with infinite energy for the 1-dimensional Zakharov
system | 11,198 |
We study nonlinear Neumann type boundary value problems related to ergodic phenomenas. The particularity of these problems is that the ergodic constant appears in the (possibly nonlinear) Neumann boundary conditions. We provide, for bounded domains, several results on the existence, uniqueness and properties of this ergodic constant. | On the Boundary Ergodic Problem for Fully Nonlinear Equations in Bounded
Domains with General Nonlinear Neumann Boundary Conditions | 11,199 |
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