symmetric Schrödinger operators: reality of the perturbed eigenvalues.
Parameters and solutions of linear and nonlinear oscillators.
Periodic solutions of some linear systems of differential equations.
Perturbation of an eigen-value from a dense point spectrum : a general Floquet hamiltonian
Planarizable supersymmetric quantum toboggans.
Points tournants et résonances de Stark-Wannier
Pointwise Lower and Upper Bounds for Eigenfunctions of Ordinary Differential Operators.
Pólya Operators I: Total Positivity.
Pólya Operators II: Complete Concavity.
Positive product formulas and hypergroups associated with singular Sturm-Liouville problems on a compact interval
Positive solutions and eigenvalue intervals of a nonlinear singular fourth-order boundary value problem
We consider the classical nonlinear fourth-order two-point boundary value problem In this problem, the nonlinear term contains the first and second derivatives of the unknown function, and the function may be singular at , and at , , . By introducing suitable height functions and applying the fixed point theorem on the cone, we establish several local existence theorems on positive solutions and obtain the corresponding eigenvalue intervals.
Positive solutions and eigenvalues of nonlocal boundary-value problems.
Positive solutions and nonlinear eigenvalue problems for retarded second order differential equations.
Positive solutions of two-point right focal eigenvalue problems on time scales.
Problèmes inverses pour des équations différentielles sur la droite
Problems with nonlinear boundary value conditions
The existence and multiplicity results are shown for certain types of problems with nonlinear boundary value conditions.
Properties of eigenfunctions of non-local operators
Properties of non-hermitian quantum field theories
In this paper I discuss quantum systems whose Hamiltonians are non-Hermitian but whose energy levels are all real and positive. Such theories are required to be symmetric under , but not symmetric under and separately. Recently, quantum mechanical systems having such properties have been investigated in detail. In this paper I extend the results to quantum field theories. Among the systems that I discuss are and theories. These theories all have unexpected and remarkable properties. I discuss...
Properties of solutions of quaternionic Riccati equations
In this paper we study properties of regular solutions of quaternionic Riccati equations. The obtained results we use for study of the asymptotic behavior of solutions of two first-order linear quaternionic ordinary differential equations.
Properties of the scattering map.