Divergence Equation Research Articles

Nonlinear divergence equation with potentials vanishing in some direction at infinity: the exponential critical case

The purpose of this article is to state some weighted Sobolev embedding involving functions that vanishing only in a direction. In this setting we prove a weighted Trudinger–Moser type inequality and as an application, we addressed the existence of solutions to a class of elliptic equation of the form −div(a(x)∇u)+V(x)u=K(x)f(u)inR2, where the nonlinearity f has exponential critical growth in sense of Trudinger–Moser.

On a field tensor for gravity and electromagnetism

We show that a three rank Lanczos type tensor field is an appropriate choice to describe relativistic electromagnetic and gravitational effects. More precisely, we identify the irreducible field-decompositions of this tensor as gravitational and electromagnetic fields. A set of divergence equations are proposed as field equations for the unified field.

A Vaporization Model for Continuous Surface Force Approaches and Subcooled Configurations

The integration of phase change phenomena through an interface is a numerical challenge that requires proper attention. Solutions to properly ensure mass and energy conservation were developed for finite difference and finite volume methods, but not for Finite Element methods. We propose a Finite Element phase change model based on an Eulerian framework with a Continuous Surface Force (CSF) approach. It handles both momentum and energy conservation at the interface for anisotropic meshes in a light an efficient way. To do so, a model based on the Level Set method is developed. A thick interface is considered to fit with the CSF approach. To properly compute the energy conservation, heat fluxes are extended through this interface thanks to the resolution of a transport equation. A dedicated pseudo compressible Navier–Stokes solver is added to compute velocity jumps with a source term at the interface in the velocity divergence equation. Several 1D and 2D benchmarks are considered with increasing complexity to highlight the performances of each feature of the framework. This stresses the capacity of the model to properly tackle phase change problems.

Blow-Up Analysis of Divergent Reaction Diffusion Equations with Weighted Functions

Blow-Up Analysis of Divergent Reaction Diffusion Equations with Weighted Functions

How Classical, Quantum-Mechanical, and Relativistic Wave and Field Equations Are Uniformly Generated by Velocity-Field Divergence Equations

How Classical, Quantum-Mechanical, and Relativistic Wave and Field Equations Are Uniformly Generated by Velocity-Field Divergence Equations

The Basic Equations under Weak Temperature Gradient Balance: Formulation, Scaling, and Types of Convectively Coupled Motions

Abstract The weak temperature gradient (WTG) approximation is extended to the basic equations on a rotating plane. The circulation is decomposed into a diabatic component that satisfies WTG balance exactly and a deviation from this balance. Scale analysis of the decomposed basic equations reveals a spectrum of motions, including unbalanced inertio-gravity waves and several systems that are in approximate WTG balance. The balanced systems include equatorial moisture modes with features reminiscent of the MJO, off-equatorial moisture modes that resemble tropical depression disturbances, “mixed systems” in which temperature and moisture play comparable roles in their thermodynamics, and moist quasigeostrophic motions. In the balanced systems the deviation from WTG balance is quasi nondivergent, in nonlinear balance, and evolves in accordance to the vorticity equation. The evolution of the strictly balanced WTG circulation is in turn described by the divergence equation. WTG balance restricts the flow to evolve in the horizontal plane by making the isobars impermeable to vorticity and divergence, even in the presence of diabatically driven vertical motions. The vorticity and divergence equations form a closed system of equations when the irrotational circulation is in WTG balance and the nondivergent circulation is in nonlinear balance. The resulting “WTG equations” may elucidate how interactions between diabatic processes and the horizontal circulation shape slowly evolving tropical motions. Significance Statement Many gaps in our understanding of tropical weather systems still exist and there are still many opportunities to improve their forecasting. We seek to further our understanding of the tropics by extending a framework known as the “weak temperature gradient approximation” to all of the equations for atmospheric flow. Doing this reveals a variety of motions whose scales are similar to observed tropical weather systems. We also show that two equations describe the evolution of slow systems: one that describes tropical thunderstorms and one for the rotating horizontal winds. The two equations may help us understand the dynamics of slowly evolving tropical systems.

Boundary Lebesgue mixed-norm estimates for non-stationary Stokes systems with VMO coefficients

We consider Stokes systems with measurable coefficients and Lions-type boundary conditions. We show that, in contrast to the Dirichlet boundary conditions, local boundary mixed-norm -estimates hold for the spatial second-order derivatives of solutions, assuming the smallness of the mean oscillations of the coefficients with respect to the spatial variables in small cylinders. In the un-mixed norm case with the result is still new and provides local boundary Caccioppoli-type estimates. The main challenges in the work arise from the lack of regularity of the pressure and time derivatives of the solutions and from interaction of the boundary with the nonlocal structure of the system. To overcome these difficulties, our approach relies heavily on several newly developed regularity estimates for both divergence and non-divergence form parabolic equations with coefficients that are only measurable in the time variable and in one of the spatial variables.

Classification of Positive Solutions to a Divergent Equation on the Upper Half Space

Classification of Positive Solutions to a Divergent Equation on the Upper Half Space

Weighted Discrete Hardy Inequalities on Trees and Applications

In this paper, we study certain inequalities and a related result for weighted Sobolev spaces on Hölder-α domains, where the weights are powers of the distance to the boundary. We obtain results regarding the divergence equation’s solvability, and the improved Poincaré, the fractional Poincaré, and the Korn inequalities. The proofs are based on a local-to-global argument that involves a kind of atomic decomposition of functions and the validity of a weighted discrete Hardy-type inequality on trees. The novelty of our approach lies in the use of this weighted discrete Hardy inequality and a sufficient condition that allows us to study the weights of our interest. As a consequence, the assumptions on the weight exponents that appear in our results are weaker than those in the literature.

Estimates of the Fundamental Solution for Elliptic Equation in Divergence Form with Drift

For a linear divergent second-order elliptic equation with uniformly elliptic measurable matrix of the principal coefficients and drift, a condition on the low order coefficients is found, which guarantees the existence of classical two-sided estimates for the fundamental solution.

Improved weighted Poincaré inequalities in John domains and application to the divergence equation

We extend some results related to the Poincaré inequality and solvability of divergence obtained in [G. Acosta et al., Ann. Acad. Sci. Fenn. Math. 42 (2017)]. More precisely, we generalize to unbounded John domains the general theorem that provides a suff

CP-violating transport theory for electroweak baryogenesis with thermal corrections

We derive CP-violating transport equations for fermions for electroweak baryogenesis from the CTP-formalism including thermal corrections at the one-loop level. We consider both the VEV-insertion approximation (VIA) and the semiclassical (SC) formalism. We show that the VIA-method is based on an assumption that leads to an ill-defined source term containing a pinch singularity, whose regularisation by thermal effects leads to ambiguities including spurious ultraviolet and infrared divergences.We then carefully review the derivation of the semiclassical formalism and extend it to include thermal corrections. We present the semiclassical Boltzmann equations for thermal WKB-quasiparticles with source terms up to the second order in gradients that contain both dispersive and finite width corrections. We also show that the SC-method reproduces the current divergence equations and that a correct implementation of the Fick's law captures the semiclassical source term even with conserved total current ∂μ j μ = 0. Our results show that the VIA-source term is not just ambiguous, but that it does not exist. Finally, we show that the collisional source terms reported earlier in the semiclassical literature are also spurious, and vanish in a consistent calculation.

Achieving geometrical enhancement of fields in chiral nanoplasmonics using fractional calculus

In this paper, an analytical approach has been developed for electromagnetic field enhancement in fractal nanostructure under the quasi-static limit. A metallic fractal embedded in an unbounded, isotropic, and lossless chiral medium has been treated under this approach. In addition, the field enhancement is also noted by imposing surface plasmon resonance condition. To achieve the desired objective, Maxwell divergence equations are considered and written in an appropriate form by mean of fractional calculus.

Divergence equations and uniqueness theorem of static spacetimes with conformal scalar hair

Abstract We reexamine the Israel-type proof of the uniqueness theorem of the static spacetime outside the photon surface in the Einstein-conformal scalar system. We derive in a systematic fashion a new divergence identity which plays a key role in the proof. Our divergence identity includes three parameters, allowing us to give a new proof of the uniqueness.

Lorentz covariance of optical Dirac equation and spinorial photon field

In a recent paper (2014 New J. Phys. 16 093008) Barnett discussed the so-called optical Dirac equation and referred to the involved wave function as a spinor. But as he claimed explicitly, he did not really associate that wave function with a true spinor. Here we show that if the optical Dirac equation is interpreted as the dynamical equation for the photon in conventional quantum mechanics, the wave function, called the photon field, does transform under the Lorentz transformation as a spinor. For the optical Dirac equation to be Lorentz covariant, however, a constraint on the photon field is required, which can be cast into the form of Maxwell’s divergence equations. It is found that the spinorial photon field not only satisfies the principle of locality but also has the right dimensionality as is required by conventional quantum mechanics.

Black hole gluing in de Sitter space

We construct dynamical many-black-hole spacetimes with well-controlled asymptotic behavior as solutions of the Einstein vacuum equation with positive cosmological constant. We accomplish this by gluing Schwarzschild–de Sitter or Kerr–de Sitter black hole metrics into neighborhoods of points on the future conformal boundary of de Sitter space, under certain balance conditions on the black hole parameters. We give a self-contained treatment of solving the Einstein equation directly for the metric, given the scattering data we encounter at the future conformal boundary. The main step in the construction is the solution of a linear divergence equation for trace-free symmetric 2-tensors; this is closely related to Friedrich’s analysis of scattering problems for the Einstein equation on asymptotically simple spacetimes.

Solvability in weighted Lebesgue spaces of the divergence equation with measure data

In the following paper, one studies, given a bounded, connected open set $\Omega$ $\subseteq$ R n , $\kappa$ > 0, a positive Radon measure $\mu$ 0 in $\Omega$ and a (signed) Radon measure $\mu$ on $\Omega$ satisfying $\mu$($\Omega$) = 0 and |$\mu$| $\kappa$$\mu$ 0 , the possibility of solving the equation div u = $\mu$ by a vector field u satisfying |u| $\kappa$w on $\Omega$ (where w is an integrable weight only related to the geometry of $\Omega$ and to $\mu$ 0), together with a mild boundary condition. This extends results obtained in [4] for the equation div u = f , improving them on two aspects: one works here with the divergence equation with measure data, and also construct a weight w that relies in a softer way on the geometry of $\Omega$, improving its behavior (and hence the a priori behavior of the solution we construct) substantially in some instances. The method used in this paper follows a constructive approach of Bogovskii type.

A cross-diffusive evolution system arising from biological transport networks

In this paper, we are concerned with a cross-diffusive evolution system arising from biological transport networks. We study the general regularity properties of solutions to the corresponding Dirichlet-Neumann initial-boundary value problem (DNibvp). By applying the properties of divergence equations and the Dirichlet heat semigroup, we find that DNibvp possesses a globally classical solution which is unique and uniformly bounded. Based on this uniform boundedness, we establish the existence of the steady states by means of dynamical methods. Our results demonstrate that the transient solution will stabilize to the stationary solution in infinite time with an exponential time-decay rate.

On the Solution of the Dirichlet Problem in the Half-Plane for Divergent Equations with Piecewise Smooth Coefficients

On the Solution of the Dirichlet Problem in the Half-Plane for Divergent Equations with Piecewise Smooth Coefficients

Green Functions for the Pressure of Stokes Systems

Abstract We study Green functions for the pressure of stationary Stokes systems in a (possibly unbounded) domain $\Omega \subset \mathbb{R}^d$, where $d\ge 2$. We construct the Green function when coefficients are merely measurable in one direction and have Dini mean oscillation in the other directions and $\Omega $ is such that the divergence equation is solvable there. We also establish global pointwise bounds for the Green function and its derivatives when coefficients have Dini mean oscillation and $\Omega $ has a $C^{1,\textrm{Dini}}$ boundary. Green functions for the flow velocity of Stokes systems are also considered.