On the Infrared Problem for the Dressed Non-Relativistic Electron in a Magnetic Field

We consider a non-relativistic electron interacting with a classical magnetic field pointing along the $x_3$-axis and with a quantized electromagnetic field. The system is translation invariant in the $x_3$-direction and we consider the reduced Hamiltonian $H(P_3)$ associated with the total momentum $P_3$ along the $x_3$-axis. For a fixed momentum $P_3$ sufficiently small, we prove that $H(P_3)$ has a ground state in the Fock representation if and only if $E(P_3)=0$, where $P_3 mapsto E(P_3)$ is the derivative of the map $P_3 mapsto E(P_3) = inf sigma (H(P_3))$. If $E(P_3) eq 0$, we obtain the existence of a ground state in a non-Fock representation. This result holds for sufficiently small values of the coupling constant.

Inverse spectral results for Schrodinger operators on the unit interval with potentials in L^P spaces

We consider the Schrodinger operator on $[0,1]$ with potential in $L^1$. We prove that two potentials already known on $[a,1]$ ($ain(0,{1/2}]$) and having their difference in $L^p$ are equal if the number of their common eigenvalues is sufficiently large. The result here is to write down explicitly this number in terms of $p$ (and $a$) showing the role of $p$.