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Search Results: 1 - 10 of 2968 matches for " Andrzej Szulkin "
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A logarithmic Schr?dinger equation with asymptotic conditions on the potential
Chao Ji,Andrzej Szulkin
Mathematics , 2015,
Abstract: In this paper we consider a class of logarithmic Schr\"{o}dinger equations with a potential which may change sign. When the potential is coercive, we obtain infinitely many solutions by adapting some arguments of the Fountain theorem, and in the case of bounded potential we obtain a ground state solution, i.e. a nontrivial solution with least possible energy. The functional corresponding to the problem is the sum of a smooth and a convex lower semicontinuous term.
Multiple solutions to logarithmic Schrodinger equations with periodic potential
Marco Squassina,Andrzej Szulkin
Mathematics , 2014,
Abstract: We study a class of logarithmic Schrodinger equations with periodic potential which come from physically relevant situations and obtain the existence of infinitely many geometrically distinct solutions.
Bifurcation from infinity for an asymptotically linear Schr?dinger equation
Wojciech Kryszewski,Andrzej Szulkin
Mathematics , 2014,
Abstract: We consider an asymptotically linear Schr\"odinger equation $-\Delta u + V(x)u = \lambda u + f(x,u), \ x\in R^N$, and show that if $\lambda_0$ is an isolated eigenvalue for the linearization at infinity, then under some additional conditions there exists a sequence $(u_n,\lambda_n)$ of solutions such that $\|u_n\|\to\infty$ and $\lambda_n\to\lambda_0$. Our results extend some recent work by Stuart. We use degree theory if the multiplicity of $\lambda_0$ is odd and Morse theory (or more specifically, Gromoll-Meyer theory) if it is not.
A concentration phenomenon for semilinear elliptic equations
Nils Ackermann,Andrzej Szulkin
Mathematics , 2012, DOI: 10.1007/s00205-012-0589-1
Abstract: For a domain $\Omega\subset\dR^N$ we consider the equation $ -\Delta u + V(x)u = Q_n(x)\abs{u}^{p-2}u$ with zero Dirichlet boundary conditions and $p\in(2,2^*)$. Here $V\ge 0$ and $Q_n$ are bounded functions that are positive in a region contained in $\Omega$ and negative outside, and such that the sets $\{Q_n>0\}$ shrink to a point $x_0\in\Omega$ as $n\to\infty$. We show that if $u_n$ is a nontrivial solution corresponding to $Q_n$, then the sequence $(u_n)$ concentrates at $x_0$ with respect to the $H^1$ and certain $L^q$-norms. We also show that if the sets $\{Q_n>0\}$ shrink to two points and $u_n$ are ground state solutions, then they concentrate at one of these points.
Multiple solutions to nonlinear Schr?dinger equations with singular electromagnetic potential
Mónica Clapp,Andrzej Szulkin
Mathematics , 2012,
Abstract: We consider the semilinear electromagnetic Schr\"{o}dinger equation (-i\nabla+A(x))^{2}u + V(x)u = |u|^{2^{\ast}-2}u, u\in D_{A,0}^{1,2}(\Omega,\mathbb{C}), where $\Omega=(\mathbb{R}^{m}\smallsetminus{0})\times\mathbb{R}^{N-m}$ with $2\leq m\leq N$, $N\geq3$, $2^{\ast}:= 2N/(N-2)$ is the critical Sobolev exponent, $V$ is a Hardy term and $A$ is a singular magnetic potential of a particular form which includes the Aharonov-Bohm potentials. Under some symmetry assumptions on $A$ we obtain multiplicity of solutions satisfying certain symmetry properties.
A supercritical elliptic problem in a cylindrical shell
Mónica Clapp,Andrzej Szulkin
Mathematics , 2013,
Abstract: We consider the problem \[ -\Delta u=|u|^{p-2}u in \Omega, u=0 on \partial\Omega, \] where $\Omega:=\{(y,z)\in\mathbb{R}^{m+1}\times\mathbb{R}^{N-m-1}: 0
Ground states of critical and supercritical problems of Brezis-Nirenberg type
Mónica Clapp,Angela Pistoia,Andrzej Szulkin
Mathematics , 2015,
Abstract: We study the existence of symmetric ground states to the supercritical problem \[ -\Delta v=\lambda v+\left\vert v\right\vert ^{p-2}v\text{ \ in }\Omega,\qquad v=0\text{ on }\partial\Omega, \] in a domain of the form \[ \Omega=\{(y,z)\in\mathbb{R}^{k+1}\times\mathbb{R}^{N-k-1}:\left( \left\vert y\right\vert ,z\right) \in\Theta\}, \] where $\Theta$ is a bounded smooth domain such that $\overline{\Theta} \subset\left( 0,\infty\right) \times\mathbb{R}^{N-k-1},$ $1\leq k\leq N-3,$ $\lambda\in\mathbb{R},$ and $p=\frac{2(N-k)}{N-k-2}$ is the $(k+1)$-st critical exponent. We show that symmetric ground states exist for $\lambda$ in some interval to the left of each symmetric eigenvalue, and that no symmetric ground states exist in some interval $(-\infty,\lambda_{\ast})$ with $\lambda_{\ast}>0$ if $k\geq2.$ Related to this question is the existence of ground states to the anisotropic critical problem \[ -\text{div}(a(x)\nabla u)=\lambda b(x)u+c(x)\left\vert u\right\vert ^{2^{\ast }-2}u\quad\text{in}\ \Theta,\qquad u=0\quad\text{on}\ \partial\Theta, \] where $a,b,c$ are positive continuous functions on $\overline{\Theta}.$ We give a minimax characterization for the ground states of this problem, study the ground state energy level as a function of $\lambda,$ and obtain a bifurcation result for ground states.
The Environmental Dependence of Inbreeding Depression in a Wild Bird Population
Marta Szulkin, Ben C. Sheldon
PLOS ONE , 2007, DOI: 10.1371/journal.pone.0001027
Abstract: Background Inbreeding depression occurs when the offspring produced as a result of matings between relatives show reduced fitness, and is generally understood as a consequence of the elevated expression of deleterious recessive alleles. How inbreeding depression varies across environments is of importance for the evolution of inbreeding avoidance behaviour, and for understanding extinction risks in small populations. However, inbreeding-by-environment (I×E) interactions have rarely been investigated in wild populations. Methodology/Principal Findings We analysed 41 years of breeding events from a wild great tit (Parus major) population and used 11 measures of the environment to categorise environments as relatively good or poor, testing whether these measures influenced inbreeding depression. Although inbreeding always, and environmental quality often, significantly affected reproductive success, there was little evidence for statistically significant I×E interactions at the level of individual analyses. However, point estimates of the effect of the environment on inbreeding depression were sometimes considerable, and we show that variation in the magnitude of the I×E interaction across environments is consistent with the expectation that this interaction is more marked across environmental axes with a closer link to overall fitness, with the environmental dependence of inbreeding depression being elevated under such conditions. Hence, our analyses provide evidence for an environmental dependence of the inbreeding×environment interaction: effectively an I×E×E. Conclusions/Significance Overall, our analyses suggest that I×E interactions may be substantial in wild populations, when measured across relevant environmental contrasts, although their detection for single traits may require very large samples, or high rates of inbreeding.
New Nanocrystalline Matrix Materials for Sintered Diamond Tools  [PDF]
Janusz Konstanty, Andrzej Romanski
Materials Sciences and Applications (MSA) , 2012, DOI: 10.4236/msa.2012.311113
Abstract: The work presents the possibility of substitution of expensive, wear resistant Co-WC powders, that have been traditionally used in the production of sintered diamond tools, with cheap iron-base counterparts manufactured by ball milling. It has been shown that ball-milled Fe-Ni-Cu-Sn-C powders can be consolidated to a virtually pore-free condition by hot pressing at 900 ℃. The as-consolidated material has nanocrystalline structure and is characterised by a combination of high hardness, mechanical strength and excellent resistance to abrasion. Its properties can be widely modified by changing the milling conditions.
Nuclear Power for Poland  [PDF]
Andrzej G. Chmielewski
World Journal of Nuclear Science and Technology (WJNST) , 2013, DOI: 10.4236/wjnst.2013.34021

The present situation in Poland and Europe, regarding electric power generation by source, is discussed in the paper. The results of the implementation of EU competitive-low-carbon economy policy in some most developed countries in the continent, have given already good experimental data for evaluation of this strategy. Analysis of the reports provided by official sources for Germany, Denmark and Finland is a base for EU energy policy evaluation. The combustion technologies will be a main energy sources for many years from now. Therefore effects of fossil fuels and biomass combustion on the environment are presented briefly. Finally, the developments regarding Polish Nuclear Energy Programme are overviewed.

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