A new blow-up condition for semi-linear edge degenerate parabolic equation with singular potentials

In this paper, we consider a class of semi-linear edge degenerate parabolic equation with singular potentials, which was proposed by Chen and Liu [Asymptotic stability and blow-up of solutions for semi-linear edge-degenerate parabolic equation with singular potentials. Discrete Contin. Dyn. Syst. 2016; 26:661–682.] in which the authors proved the solutions of the model blow up in finite time with low initial energy and critical initial energy. By constructing a new functional, we obtain a new blow-up condition, which demonstrates the possibility of finite time blow-up when the initial energy is larger than the critical initial energy.     

On a degenerate parabolic equation arising in pricing of Asian options

We study a certain one-dimensional, degenerate parabolic partial differential equation with a boundary condition which arises in pricing of Asian options. Due to degeneracy of the partial differential operator and the non-smooth boundary condition, regularity of the generalized solution of such a problem remained unclear. We prove that the generalized solution of the problem is indeed a classical solution.     

Attractors for a class of semi-linear degenerate parabolic equations

We consider degenerate parabolic equations of the form $$\left. \begin{array}{ll}\,\,\, \partial_t u = \Delta_\lambda u + f(u) \\u|_{\partial\Omega} = 0, u|_{t=0} = u_0\end{array}\right.$$ in a bounded domain ${\Omega\subset\mathbb{R}^N}$ , where Δ_λ is a subelliptic operator of the type $$\quad \Delta_\lambda:= \sum_{i=1}^{N} \partial_{x_i}(\lambda_{i}^{2} \partial_{x_i}),\qquad \lambda = (\lambda_1,\ldots, \lambda_N).$$ We prove global existence of solutions and characterize their longtime behavior. In particular, we show the existence and finite fractal dimension of the global attractor of the generated semigroup and the convergence of solutions to an equilibrium solution when time tends to infinity.     

Long-time error estimation for semi-linear parabolic equations

The long-time error estimation approach of Sun and Ewing (Dyn. Contin. Discrete Impuls. Systems Ser. B Appl. Algorithms, 9 (2002) 115–129) is applied here for the error analysis and estimation of linear and semi-linear parabolic partial differential equations. The analysis is carried out using the stability–smoothing indicator, the smoothing assumption, the moving attractor, the exact error propagation and the two-level error propagation analysis introduced by Sun and Ewing (Dyn. Contin. Discrete Impuls. Systems Ser. B Appl. Algorithms, 9 (2002) 115–129). Moreover, an inverse elliptic projection is employed here as a key technique in dealing with the spatial discretization error. The error estimates obtained are uniform in time. The results are substantiated by a complete mathematical analysis and numerical experiments.     

Semi-analytic time-marching algorithms for semi-linear parabolic equations

New time marching algorithms for numerical solution of semi-linear parabolic equations are described. They are based on the approximation method proposed by the first author. An important feature of the algorithms is that they are both explicit and stable under mild restrictions to the time step, which come from the non-linear part of the equation.     

Wave-induced perturbations in cylindrically layered smectic A liquid crystals

We consider the stability of a cylindrically layered smectic A liquid crystal sample under a sinusoidal perturbation where we allow for the decoupling between the layer normal and the director. Two forms of general anstazes are proposed: one provides exact solutions for the flow and layer undulations while the other provides series solutions for the hydrodynamic variables. Both cases provide an estimate for a stability parameter. Plots of the flow, layer undulations and pressure are provided.     

Wave-induced perturbations in cylindrically layered smectic A liquid crystals

We consider the stability of a cylindrically layered smectic A liquid crystal sample under a sinusoidal perturbation where we allow for the decoupling between the layer normal and the director. Two forms of general anstazes are proposed: one provides exact solutions for the flow and layer undulations while the other provides series solutions for the hydrodynamic variables. Both cases provide an estimate for a stability parameter. Plots of the flow, layer undulations and pressure are provided.     

Partial Sobolev spaces and anisotropic smectic liquid crystals

The partial Sobolev spaces with respect to a vector field are introduced, and are used to study minimization problems of the functionals which are degenerate in the sense that they do not have control on either the tangential part or the perpendicular part of the magnetic gradients. Based on these results we obtain the asymptotic behavior of the minimizers of the anisotropic Landau-de Gennes functional of smectic liquid crystals, as one of the anisotropy coefficients approaches to zero.     

Existence of surface smectic states of liquid crystals

The Landau–de Gennes model of liquid crystals is a functional acting on wave functions (order parameters) and vector fields (director fields). In a specific asymptotic limit of the physical parameters, we construct critical points such that the wave function (order parameter) is localized near the boundary of the domain, and we determine a sharp localization of the boundary region where the wave function concentrates. Furthermore, we compute the asymptotics of the energy of such critical points along with a boundary energy that may serve in localizing the director field. In physical terms, our results prove the existence of a surface smectic state.     

Solvability conditions for some semi-linear parabolic equations

Consider the Cauchy problem of the semi-linear parabolic equation

     

一类奇摄动半线性时滞抛物型偏微分方程的渐近解

文中讨论了一类奇摄动时滞抛物型偏微分方程的初边值问题,得到了其形式渐近展开,证明了奇摄动半线性时滞偏微分方程的极大值原理,从而得到了最大值估计及相应的Schuader估计.在此基础上,得到了柱状区域上解的存在唯一性和渐近解的一致有效性.     

半线性抛物方程的时空有限元方法

讨论半线性抛物方程的连续Galerkin时空有限元方法,利用有限元方法和有限差分方法相结合的技巧,证明了弱解的存在唯一性,给出了时间最大模,空间L~2模,即L~∞(L~2)模误差估计.并给出数值算例证明了连续时空有限元方法对于半线性抛物方程的有效性.     

Numerical analysis of semi-linear parabolic systems in diffusion–reaction problems

In this paper, we investigate problems of approximation for the solution of a system of coupled semi-linear parabolic partial differential equations that model diffusion-reaction problems in chemical engineering. Given that the solutions belong to H^s (0, ∞), we consider finite-element approximations on bounded domains (0, R(h)) such that lim_h→0[R(h)] = ∞. Optimal convergence estimates are found to depend on the asymptotic behaviour of the solution and its regularity near t = 0. In the L²-norm, they cannot exceed an order of O((;h²/t^3/4) + h²[In h]²). For that purpose, a Wheeler-type argument is also generalized to non-coercive elliptic forms. Fully discrete schemes that preserve the positivity of the solutions are also considered. Due to the singularity at t = 0, they lead to estimates of the order O(τ^1/4 + h²/t^3/4).     

The onset of layer deformations in non-chiral smectic C liquid crystals

In this paper smectic C continuum theory is used to determine, theoretically, the critical electric field strength for the onset of layer deformation in planar layers of smectic C liquid crystal. The particular sample considered is the planar layeredbookshelf geometry. The consequences of the results derived herein are discussed in relation to the measurement of the elastic constants related to layer deformations.     

A stability analysis for a semilinear parabolic partial differential equation

We consider a parabolic partial differential equation u_t = u_xx + f(u), where ? ∞ < x < + ∞ and 0 < t < + ∞. Under suitable hypotheses pertaining to f, we exhibit a class of initial data φ(x), ? ∞ < x < + ∞, for which the corresponding solutions u(x, t) approach zero as t → + ∞. This convergence is uniform with respect to x on any compact subinterval of the real axis.     

Freedericksz transitions in circular toroidal layers of smectic C liquid crystals

The aim of this paper is to consider theoretically a Freedericksztransition for concentric toroidal layers of smectic C liquidcrystal arising from a simple geometric setup, thereby extendingthe results of Atkin & Stewart [Q. Jl Mech. Appl. Math.,47, 1994] who considered spherical layers of smectic C in theusual cone and plate geometry. Application of smectic continuumtheory leads, after suitable approximations are made, to a lineargoverning equilibrium equation which is satisfied by both thetrivial solution and a variable solution involving Bessel functions.We are able to determine the critical magnitude _cH of the magneticfield H at which this variable solution exists, and a standardenergy comparison reveals that the variable solution is expectedto be more energetically favourable than the zero solution providedH > _cH. Numerical examples of critical thresholds are given,which are comparable to those in the literature for nematics.The paper ends with a discussion section and some indicationof possible future work.     

Singular solutions for semi-linear parabolic equations on nonsmooth domains

We prove the existence of positive singular solutions for the semi-linear parabolic equation on Ω=D×]0,∞[, where p>1,D is a bounded NTA-domain in Rn, n?2, and μ is in a general class of signed Radon measures on D covering the elliptic Kato class of potentials adopted by Zhang and Zhao. A new proof of the result based on a simple fixed point theorem is also given.