This article concerns the existence and multiplicity of solutions for the following class of non-linear elliptic equations with variable exponents

\begin{equation*}\left\{\begin{array}{l}-\Delta u+\lambda u=f(x,u), \quad \text{in} \quad \mathbb{R}^N, \\\,u\in H^{1}(\mathbb{R}^N),\\\end{array}\right.\end{equation*}

where λ > 0, $N\geq 2$ and $f:\mathbb{R}^N \times \mathbb{R} \to \mathbb{R}$ is a function of the following types:

Type 1: The subcritical case:

\begin{equation*}f(x,t)=|t|^{p(\varepsilon x)-2}t, \quad \forall (x,t) \in \mathbb{R}^N\times \mathbb{R}, N\geq3, \end{equation*}

Type 2: The critical case:

\begin{equation*}f(x,t)=\mu|t|^{p(\varepsilon x)-2}t+|t|^{2^*-2}t, \quad \forall (x,t) \in \mathbb{R}^N\times \mathbb{R}, N\geq3, \end{equation*}

Type 3: The exponential subcritical growth case:

\begin{equation*} f(x,t)=\mu|t|^{p(\varepsilon x)-2}te^{\alpha|t|^\beta}, \quad \forall (x,t) \in \mathbb{R}^2\times \mathbb{R}, \end{equation*}

where parameterɛ > 0, α > 0, $\beta \in (0,2)$, $2^*=\frac{2N}{N-2}$ if $N \geq 3$ and $2^*=+\infty$ if N = 2. Related to the function $p:\mathbb{R}^{N}\rightarrow \mathbb{R}$, we assume that it is a continuous function with $p_{\max}, p_{\min} \in (2,2^*)$, where $p_{\max}=\displaystyle \max_{x \in \mathbb{R}^N}p(x)$ and $p_{\min}=\displaystyle \min_{x \in \mathbb{R}^N}p(x)$.

We show that for each λ > 0 the number of solutions is associated with the number of global maximum or global minimum points of p when ɛ is small enough. The proof of is based on the variational methods, Ekeland’s variational principle, Trundiger–Moser inequality, and the monotonicity of the ground state energy with respect to p. Our results extend those of Cao and Noussair (Multiplicity of positive and nodal solutions for nonlinear elliptic problem in $\mathbb{R}^{N}$. Ann. Inst. Henri Poincaré, Anal. Non Linéaire. 13 (1996), 567–588) and Ji, Wang and Wu (A monotone property of the ground state energy to the scalar field equation and applications. J. Lond. Math. Soc., II. Ser. 100 (2019), 804–824).

We establish multiplicity results for the following class of quasilinear problems P

\begin{equation*} \left\{ \begin{array}{@{}l} -\Delta_{\Phi}u=f(x,u) \quad \mbox{in} \quad \Omega, \\ u=0 \quad \mbox{on} \quad \partial \Omega, \end{array} \right. \end{equation*}

$\Delta _{\Phi }u=\text {div}(\varphi (x,|\nabla u|)\nabla u)$

$\Phi (x,t)=\int _{0}^{|t|}\varphi (x,s)s\,ds$

$\Omega \subset \mathbb {R}^{N}$

$\Omega _N$

$\Omega _p$

$\overline {\Omega _N}\cap \overline {\Omega _p}=\emptyset$

$(P)$

$-\Delta _{\Phi }$

$-\Delta _N$

$\Omega _N$

$-\Delta _p$

$\Omega _p$

$f:\Omega \times \mathbb {R}\to \mathbb {R}$

$e^{\alpha |t|^{\frac {N}{N-1}}}$

$\Omega _N$

$|t|^{p^{*}-2}t$

$\Omega _p$

$|t|$

$\alpha >0$

$p^{*}=\frac {Np}{N-p}$

$1< p< N$

$f$

$f$

$\Omega$

$(P)$

In this work we study the existence of nontrivial solution for the following class of semilinear degenerate elliptic equations

\[ -\Delta_{\gamma} u + a(z)u = f(u) \quad \mbox{in}\ \mathbb{R}^{N}, \]

$\Delta _{\gamma }$

$z:=(x,y)\in \mathbb {R}^{m}\times \mathbb {R}^{k}$

$m+k=N\geqslant 3$

$f$

$a$

$a=1$

This paper concerns with the existence of multiple solutions for a class of elliptic problems with discontinuous nonlinearity. By using dual variational methods, properties of the Nehari manifolds and Ekeland's variational principle, we show how the ‘shape’ of the graph of the function A affects the number of nontrivial solutions.

This paper concerns the study of some bifurcation properties for the following class of Choquard-type equations: (P)

$$\left\{ {\begin{array}{*{20}{l}} { - \Delta u = \lambda f(x)\left[ {u + \left( {{I_\alpha }*f( \cdot )H(u)} \right)h(u)} \right],{\rm{ in }} \ {{\mathbb{R}}^3},}\\ {{{\lim }_{|x| \to \infty }}u(x) = 0,\quad u(x) > 0,\quad x \in {{\mathbb{R}}^3},\quad u \in {D^{1,2}}({{\mathbb{R}}^3}),} \end{array}} \right.$$

${I_\alpha }(x) = 1/|x{|^\alpha },\,\alpha \in (0,3),\,\lambda > 0,\,f:{{\mathbb{R}}^3} \to {\mathbb{R}}$

${\mathbb{R}} \to {\mathbb{R}}$

In this paper we show the existence of solution for the following class of semipositone problem P

$$\left\{\matrix{-\Delta u & = & h(x)(f(u)-a) & \hbox{in} & {\open R}^N, \cr u & \gt & 0 & \hbox{in} & {\open R}^N, \cr}\right.$$

In this paper, we study the existence and concentration phenomena of solutions for the following non-local regional Schrödinger equation

$$\begin{equation*} \left\{ \begin{array}{l} \epsilon^{2\alpha}(-\Delta)_\rho^{\alpha} u + Q(x)u = K(x)|u|^{p-1}u,\;\;\mbox{in}\;\; \mathbb{R}^n,\\ u\in H^{\alpha}(\mathbb{R}^n) \end{array} \right. \end{equation*}$$

$1<p<\frac{n+2\alpha}{n-2\alpha}$

In this paper, we study the existence of a solution for the following class of non-local problems: P

$$\eqalign{\big\{&-\Delta u=\left(\lambda f(x)-\int_{{open R}^N}K(x,y)\vert u(y)\vert ^{\gamma}\hbox{d}y\right)u\quad \mbox{in } \R^{N}, \cr &\lim_{\vert x\vert \to +\infty}u(x)=0,\quad u \gt 0 \quad \text{in } {open R}^{N},}$$

In this paper we establish the existence and multiplicity of multi-bump nodal solutions for the class of problems

where λ ∈ (0, ∞), f is a continuous function with exponential critical growth and V : ℝ2→ ℝ is a continuous function verifying some hypotheses.

We study the multiplicity and concentration behaviour of positive solutions for a quasi-linear Choquard equation

where Δp is the p-Laplacian operator, 1 < p < N, V is a continuous real function on ℝN, 0 < μ < N, F(s) is the primitive function of f(s), ε is a positive parameter and * represents the convolution between two functions. The question of the existence of semiclassical solutions for the semilinear case p = 2 has recently been posed by Ambrosetti and Malchiodi. We suppose that the potential satisfies the condition introduced by del Pino and Felmer, i.e.V has a local minimum. We prove the existence, multiplicity and concentration of solutions for the equation by the penalization method and Lyusternik–Schnirelmann theory and even show novel results for the semilinear case p = 2.

We establish the multiplicity of positive weak solutions for the quasilinear Dirichlet problem −Lpu + |u|p−2u = h(u) in Ωλ, u = 0 on ∂Ωλ, where Ωλ = λΩ, Ω is a bounded domain in ℝN, λ is a positive parameter, Lpu ≐ Δpu + Δp(u2)u and the nonlinear term h(u) has subcritical growth. We use minimax methods together with the Lyusternik–Schnirelmann category theory to get multiplicity of positive solutions.

In this paper we show existence of positive solutions for a class of quasi-linear problems with Neumann boundary conditions defined in a half-space and involving the critical exponent.

Using variational methods, we establish the existence and multiplicity of positive solutions for the following class of problems:

where λ,β∈(0,∞), q∈(1,2*−1), 2*=2N/(N−2), N≥3, V,Z:ℝN→ℝ are continuous functions verifying some hypotheses.