%0 Journal Article %T Nonlinear subelliptic Schrodinger equations with external magnetic field %A Kyril Tintarev %J Electronic Journal of Differential Equations %D 2004 %I Texas State University %X To account for an external magnetic field in a Hamiltonian of a quantum system on a manifold (modelled here by a subelliptic Dirichlet form), one replaces the the momentum operator $frac 1i d$ in the subelliptic symbol by $frac 1i d-alpha$, where $alphain TM^*$ is called a magnetic potential for the magnetic field $eta=dalpha$. We prove existence of ground state solutions (Sobolev minimizers) for nonlinear Schrodinger equation associated with such Hamiltonian on a generally, non-compact Riemannian manifold, generalizing the existence result of Esteban-Lions [5] for the nonlinear Schr dinger equation with a constant magnetic field on $mathbb{R}^N$ and the existence result of [6] for a similar problem on manifolds without a magnetic field. The counterpart of a constant magnetic field is the magnetic field, invariant with respect to a subgroup of isometries. As an example to the general statement we calculate the invariant magnetic fields in the Hamiltonians associated with the Kohn Laplacian and for the Laplace-Beltrami operator on the Heisenberg group. %K Homogeneous spaces %K magnetic field %K Schrodinger operator %K subelliptic operators %K semilinear equations %K weak convergence %K concentration compactness. %U http://ejde.math.txstate.edu/Volumes/2004/123/abstr.html