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We study the following Kirchhoff type equation:−a+b∫RN|∇u|2dxΔu+u=k(x)|u|p−2u+m(x)|u|q−2u in RN,$$\begin{equation*}\begin{array}{ll} -\left(a+b\int\limits_{\mathbb{R}^{N}}|\nabla u|^{2}\mathrm{d}x\right)\Delta u+u =k(x)|u|^{p-2}u+m(x)|u|^{q-2}u~~\text{in}~~\mathbb{R}^{N}, \end{array} \end{equation*}$$whereN=3,a,b>0$ a,b \gt 0 $,1

In this paper, we study a class of fractional Schr��dinger equations involving logarithmic and critical nonlinearities on an unbounded domain, and show that such an equation with positive or sign-changing weight potentials admits at least one positive ground state solution and the associated energy is positive (or negative). By applying the Nehari manifold method and Ljusternik-Schnirelmann category, we deeply investigate how the weight potential affects the multiplicity of positive solutions, and obtain the relationship between the number of positive solutions and the category of some sets related to the weight potential., 40 pages

In this study, we consider the following quasilinear Choquard equation with singularity − Δ u + V ( x ) u − u Δ u 2 + λ ( I α ∗ ∣ u ∣ p ) ∣ u ∣ p − 2 u = K ( x ) u − γ , x ∈ R N , u > 0 , x ∈ R N , \left\{\begin{array}{ll}-\Delta u+V\left(x)u-u\Delta {u}^{2}+\lambda \left({I}_{\alpha }\ast | u{| }^{p})| u{| }^{p-2}u=K\left(x){u}^{-\gamma },\hspace{1.0em}& x\in {{\mathbb{R}}}^{N},\\ u\gt 0,\hspace{1.0em}& x\in {{\mathbb{R}}}^{N},\end{array}\right. where I α {I}_{\alpha } is a Riesz potential, 0 < α < N 0\lt \alpha \lt N , and N + α N < p < N + α N − 2 \displaystyle \frac{N+\alpha }{N}\lt p\lt \displaystyle \frac{N+\alpha }{N-2} , with λ > 0 \lambda \gt 0 . Under suitable assumption on V V and K K , we research the existence of positive solutions of the equations. Furthermore, we obtain the asymptotic behavior of solutions as λ → 0 \lambda \to 0 .

We prove the existence of ground state positive solutions for a class of semipositone p-Laplacian problems with a critical growth reaction term. The proofs are established by obtaining crucial uniform C 1,α a priori estimates and by concentration compactness arguments. Our results are new even in the semilinear case p = 2.

We analyze, from the viewpoint of positivity preservation, certain discretizations of a fundamental partial differential equation, the one-dimensional advection equation with periodic boundary condition. The full discretization is obtained by coupling a finite difference spatial semi-discretization (the second- and some higher-order centered difference schemes, or the Fourier spectral collocation method) with an arbitrary $\theta$-method in time (including the forward and backward Euler methods, and a second-order method by choosing $\theta\in [0,1]$ suitably). The full discretization generates a two-parameter family of circulant matrices $M\in\mathbb{R}^{m\times m}$, where each matrix entry is a rational function in $\theta$ and $\nu$. Here, $\nu$ denotes the CFL number, being proportional to the ratio between the temporal and spatial discretization step sizes. The entrywise non-negativity of the matrix $M$ -- which is equivalent to the positivity preservation of the fully discrete scheme -- is investigated via discrete Fourier analysis and also by solving some low-order parametric linear recursions. We find that positivity preservation of the fully discrete system is impossible if the number of spatial grid points $m$ is even. However, it turns out that positivity preservation of the fully discrete system is recovered for \emph{odd} values of $m$ provided that $\theta\ge 1/2$ and $\nu$ are chosen suitably. These results are interesting since the systems of ordinary differential equations obtained via the spatial semi-discretizations studied are \emph{not} positivity preserving.

We investigate the ground states for the focusing, subcritical nonlinear Schr\"odinger equation with a point defect in dimension two, defined as the minimizers of the energy functional at fixed mass. We prove that ground states exist for every positive mass and show a logarithmic singularity at the defect. Moreover, up to a multiplication by a constant phase, they are positive, radially symmetric, and decreasing along the radial direction. In order to overcome the obstacles arising from the uncommon structure of the energy space, that complicates the application of standard rearrangement theory, we move to the study of the minimizers of the action functional on the Nehari manifold and then establish a connection with the original problem. An ad hoc result on rearrangements is given to prove qualitative features of the ground states., Comment: 28 pages. Keywords: standing waves, nonlinear Schr\"odinger, ground states, delta interaction, radially symmetric solutions, rearrangements. With respect to the previous versione, a section has been added to the Appendix and some minor revisions have been made

In this article, we establish the existence of bound state solutions for a class of quasilinear Schrödinger equations whose nonlinear term is asymptotically linear in ℝ N {\mathbb{R}^{N}} . After changing the variables, the quasilinear equation becomes a semilinear equation, whose respective associated functional is well defined in H 1 ⁢ ( ℝ N ) {H^{1}(\mathbb{R}^{N})} . The proofs are based on the Pohozaev manifold and a linking theorem.

In this paper, we study the existence of periodic and non-negative periodic solutions of the nonlinear neutral differential equation d dt x ( t ) = − a ( t ) h ( x ( t ) ) + d dt Q ( t , x ( t − τ ( t ) ) ) + G ( t , x ( t ) , x ( t − τ ( t ) ) ) . $${{\rm{d}} \over {{\rm{dt}}}}{\rm{x}}({\rm{t}}) = - {\rm{a}}\;({\rm{t}})\;{\rm{h}}\;({\rm{x}}\;({\rm{t}})) + {{\rm{d}} \over {{\rm{dt}}}}{\rm{Q}}\;({\rm{t}},\;{\rm{x}}\;({\rm{t}} - {\rm \tau} \;({\rm{t}}))) + {\rm{G}}\;({\rm{t}},\;{\rm{x}}({\rm{t}}),\;{\rm{x}}\;({\rm{t}} - {\rm \tau} \;({\rm{t}}))).$$ We invert this equation to construct a sum of a completely continuous map and a large contraction which is suitable for applying the modificatition of Krasnoselskii’s theorem. The Caratheodory condition is used for the functions Q and G.

We investigate the radial positive solutions of the Henon equation. It is known that this equation has three different types of radial solutions: the M-solutions (singular at $r=0$), the E-solutions (regular at $r=0$) and the F-solutions (whose existence begins away from $r=0$). For the M-solutions and E-solutions, by virtue of some prior estimates, we adopt a circulating iterative method, step-by-step, to derive their precise asymptotic expansions. In particular, the M-solution has an extremely plentiful structure, and its asymptotic expansions are more complicated. In contrast to previous research Bratt and Pfaffelmoser, and Gidas and Spruck, our results are more accurate.

We consider positive solutions of elliptic partial differential equations on non-compact domains of Riemannian manifolds. We establish general theorems which determine Martin compactifications and Martin kernels for a wide class of elliptic equations in skew product form, by thoroughly exploiting parabolic Martin kernels for associated parabolic equations developed in [35] and [25]. As their applications, we explicitly determine the structure of all positive solutions to a Schrödinger equation and the Martin boundary of the product of Riemannian manifolds. For their sharpness, we show that the Martin compactification of ${\mathbb R}^2$ for some Schrödinger equation is so much distorted near infinity that no product structures remain.

In this paper, we are concerned with elliptic equations with Hardy potential and critical Sobolev exponents where $2^{*}={2N}/({N-2})$ is the critical Sobolev exponent, $N\geq 3$, $0\leq \mu \lt \overline {\mu }={(N-2)^2}/{4}$, $\mathbf {\Omega }\subset \mathbb {R}^{N}$ an open bounded set. For $\lambda \in [0,\lambda _{1})$ with $\lambda _{1}$ being the first eigenvalue of the operator $-\Delta -{\mu }/{|x|^{2}}$ with zero Dirichlet boundary condition, and for $f\in H_{0}^{1}(\mathbf {\Omega })^{-1}=H^{-1}$, $f\neq 0$, we show that (\ref {eq1}) admits at least two distinct nontrivial solutions $u_{0}$ and $u_{1}$ in $H_{0}^{1}(\mathbf {\Omega })$. Furthermore, $u_{0}\geq 0$ and $u_{1}\geq 0$ whenever $f\geq 0$.

Let A = { x ∈ ℝ 2 N + 2 : 0 < a < | x | < b } ${A=\lbrace x\in \mathbb {R}^{2N+2} : 0< a< |x| be an annulus. Consider the following singularly perturbed elliptic problem on A: - ε 2 ▵ u + | x | α u = | x | α u p ${-\varepsilon ^2{\triangle u} + |x|^{\alpha }u = |x|^{\alpha }u^p}$ in A, u > 0 in A, ∂ u ∂ ν = 0 $\frac{\partial u}{\partial \nu } = 0$ on ∂ A $\partial A$ , where 1 < p < 2 * - 1 ${1 . We shall show that there exists a positive solution u ε ${u_\varepsilon }$ concentrating on an S1 orbit as ε → 0 ${\varepsilon \rightarrow 0}$ . We prove this by reducing the problem to a lower-dimensional one and analyzing a single point concentrating solution in the lower-dimensional space. We make precise how the single peak concentration depends on the parameter α.

We demonstrate the existence of at least one positive solution to the perturbed Hammerstein integral equation \[ y(t)=\gamma _1(t)H_1\big (\varphi _1(y)\big )+\gamma _2(t)H_2\big (\varphi _2(y)\big )\] \[\qquad \qquad \qquad \quad +\lambda \int _0^1G(t,s)f\big (s,y(s)\big )\, ds,\] where certain asymptotic growth properties are imposed on the functions $f$, $H_1$ and $H_2$. Moreover, the functionals $\varphi _1$ and $\varphi _2$ are realizable as Stieltjes integrals with signed measures, which means that the nonlocal elements in the Hammerstein equation are possibly of a very general, sign-changing form. We focus here on the case where the kernel $(t,s)\mapsto G(t,s)$ is allowed to change sign and demonstrate the existence of at least one positive solution to the integral equation. As applications, we demonstrate that, by choosing $\gamma _1$ and $\gamma _2$ in particular ways, we obtain positive solutions to boundary value problems, both in the ODEs and elliptic PDEs setting, even when the Green's function is sign-changing, and, moreover, we are able to localize the range of admissible values of the parameter~$\lambda $. Finally, we also provide a result that for each $\lambda >0$ yields the existence of at least one positive solution.

A model of coupled parabolic and ordinary differential equations for a heterogeneous catalytic reaction is considered and the existence and uniqueness theorem of the classic solution is proved.

We consider the stationary Keller-Segel equation \begin{equation*} \begin{cases} -\Delta v+v=\lambda e^v, \quad v>0 \quad & \text{in }\Omega,\\ \partial_\nu v=0 &\text{on } \partial \Omega, \end{cases} \end{equation*} where $\Omega$ is a ball. In the regime $\lambda\to 0$, we study the radial bifurcations and we construct radial solutions by a gluing variational method. For any given natural positive number $n$, we build a solution having multiple layers at $r_1,\ldots,r_n$ by which we mean that the solutions concentrate on the spheres of radii $r_i$ as $\lambda\to 0$ (for all $i=1,\ldots,n$). A remarkable fact is that, in opposition to previous known results, the layers of the solutions do not accumulate to the boundary of $\Omega$ as $\lambda\to 0$. Instead they satisfy an optimal partition problem in the limit., Comment: 33 pages

In this paper, we study the following Schr��dinger-Poisson system: $$ \left\{\aligned&-��u+V_��(x)u+K(x)��u=f(x,u)&\quad\text{in }\bbr^3,\\ &-����=K(x)u^2&\quad\text{in }\bbr^3,\\ &(u,��)\in\h\times\D,\endaligned\right.\eqno{(\mathcal{SP}_��)} $$ where $V_��(x)=��a(x)+b(x)$ with a positive parameter $��$, $K(x)\geq0$ and $f(x,t)$ is continuous including the power-type nonlinearity $|u|^{p-2}u$. By applying the method of penalized functions, the existence of one nontrivial solution for such system in the less-studied case $3, 17 pages

An analytical model for multicomponent systems of nonlocally interacting particles is presented. Its derivation is based on the principle of minimization of free energy under the constraint of conservation of particle number and justified by methods established in statistical mechanics. In contrast to the classical Cahn-Hilliard theory with higher order terms, the nonlocal theory leads to an evolution system of second order parabolic equations for the particle densities, weakly coupled by nonlinear and nonlocal drift terms, and state equations which involve both chemical and interaction potential differences. Applying fixed-point arguments and comparison principles we prove the existence of variational solutions in suitable Hilbert spaces for evolution systems. Moreover, using maximal regularity for nonsmooth parabolic boundary value problems in Sobolev-Morrey spaces and comparison principles, we show uniqueness, global regularity and uniform positivity of solutions under minimal assumptions on the regularity of interaction. Applying a refined version of the Łojasiewicz-Simon gradient inequality, this paves the way to the convergence of solutions to equilibrium states. We conclude our considerations with the presentation of simulation results for a phase separation process in ternary systems.

This paper deals with the existence and uniqueness of a positive continuous solution to the following singular semilinear fractional Dirichlet problem: \begin{equation*} \left( -\Delta _{\mid D}\right) ^{\frac{\alpha }{2}}u=a_{1}(x)u^{\sigma _{1}}+a_{2}(x)u^{\sigma _{2}}\text{ in }D,\text{ }\underset{x\rightarrow z\in \partial D}{\lim }\left( \delta (x)\right) ^{2-\alpha }u(x)=0, \end{equation*} where $0 < \alpha < 2,$ $\sigma _{1},\sigma _{2}\in (-1,1),$ $D$ is a bounded $C^{1,1}$-domain in $\mathbb{R}^{n},$ $n\geq 2,$ and $\delta (x)$ denotes the Euclidian distance from $x$ to the boundary of $D$. The nonnegative weight functions $a_{1}$ and $a_{2}$ are in $C_{loc}^{\gamma }(D),$ $ 0 < \gamma < 1,$ satisfying some appropriate assumptions related to Karamata regular variation theory. We also give the global behavior of such a solution.

A mathematical model of dissociative adsorption and associative desorption for diatomic molecules is generalized. The model is described by a coupled system of parabolic and ordinary differential equations. The existence and uniqueness theorem of the classical solution is proved.

In this paper, by means of the extraction of the Palais--Smale sequence in the Nehari manifold, we are concerned with the existence of multiple positive solutions of a class of the p-Laplacian equations involving concave-convex nonlinearities $$\left\{ \begin{array}{ll} -\triangle_p u+|u|^{p-2}u=a(x)|u|^{s-2}u +\lambda b(x)|u|^{r-2}u,\;\;\; x\in {\mathbb R}^N,\\ u\in W^{1,p}({\mathbb R}^N), \end{array} \right.$$ in the whole space ${\mathbb R}^N,$ where $\lambda$ is a positive constant, $1\leq r < p < s < p^*=\frac{Np}{N-p}$, and $a(x)$ and $b(x)$ are nonnegative continuous functions in ${\mathbb R}^N.$

We are concerned with a four-point boundary-value problem of the $p$-Laplacian dynamic equation on time scales where the nonlinear term contains the first-order derivatives of the dependent variable. By using Krasnosel'skii's fixed-point theorem, some new sufficient conditions are obtained for the existence of at least single or twin positive pseudo-symmetric solutions to this problem. We also establish the existence of at least triple or arbitrary odd positive pseudo-symmetric solutions to this problem by using the Avery-Peterson fixed-point theorem. As applications, two examples are given to illustrate and explain our main results.