arXiv subjects

Andrey Badanin

Publications and source records attributed to Andrey Badanin.

23 records · Page 2Linked to original sources

arXiv2010

Even order periodic operators on the real line

We consider $2p\ge 4$ order differential operator on the real line with a periodic coefficients. The spectrum of this operator is absolutely continuous and is a union of spectral bands separated by gaps. We define the Lyapunov function, which is analytic on a p-sheeted Riemann surface. The Lyapunov function has real or complex branch points. We prove the following results: (1) The spectrum at high energy has multiplicity two. (2) Endpoints of all gaps are periodic (or anti-periodic) eigenvalues or real branch points. (3) The spectrum of operator has an infinite number of open gaps and there exists only a finite number of non-real branch points for some specific coefficients (the generic case). (4) The asymptotics of the periodic, anti-periodic spectrum and branch points are determined at high energy.

math-ph↗

arXiv2008

Spectral estimates for periodic fourth order operators

We consider the operator $H={d^4dt^4}+{ddt}p{ddt}+q$ with 1-periodic coefficients on the real line. The spectrum of $H$ is absolutely continuous and consists of intervals separated by gaps. We describe the spectrum of this operator in terms of the Lyapunov function, which is analytic on a two-sheeted Riemann surface. On each sheet the Lyapunov function has the standard properties of the Lyapunov function for the scalar case. We describe the spectrum of $H$ in terms of periodic, antiperiodic eigenvalues, and so-called resonances. We prove that 1) the spectrum of $H$ at high energy has multiplicity two, 2) the asymptotics of the periodic, antiperiodic eigenvalues and of the resonances are determined at high energy, 3) for some specific $p$ the spectrum of $H$ has an infinite number of gaps, 4) the spectrum of $H$ has small spectral band (near the beginner of the spectrum) with multiplicity 4 and its asymptotics are determined as $p\to 0, q=0$.

math-ph↗

arXiv2008

Magnetic Schrödinger operators on armchair nanotubes

We consider the Schrödinger operator with a periodic potential on a quasi 1D continuous periodic model of armchair nanotubes in $\R^3$ in a uniform magnetic field (with amplitude $B\in \R$), which is parallel to the axis of the nanotube. The spectrum of this operator consists of an absolutely continuous part (spectral bands separated by gaps) plus an infinite number of eigenvalues with infinite multiplicity. We describe all eigenfunctions with the same eigenvalue including compactly supported. We describe the spectrum as a function of $B$. For some specific potentials we prove an existence of gaps independent on the magnetic field. If $B\ne 0$, then there exists an infinite number of gaps $G_n$ with the length $|G_n|\to\iy$ as $n\to\iy$, and we determine the asymptotics of the gaps at high energy for fixed $B$. Moreover, we determine the asymptotics of the gaps $G_n$ as $B\to 0$ for fixed $n$.

math.SP↗

arXiv2007

Schrödinger operators on armchair nanotubes. II

We consider the Schrödinger operator with a periodic potential on quasi-1D models of armchair single-wall nanotubes. The spectrum of this operator consists of an absolutely continuous part (intervals separated by gaps) plus an infinite number of eigenvalues with infinite multiplicity. We describe the absolutely continuous spectrum of the Schrödinger operator: 1) the multiplicity, 2) endpoints of the gaps, they are given by periodic or antiperiodic eigenvalues or resonances (branch points of the Lyapunov function), 3) resonance gaps, where the Lyapunov function is non-real. We determine the asymptotics of the gaps at high energy.

math.SP↗

arXiv2007

Schrödinger operators on armchair nanotubes. I

We consider the Schrödinger operator with a periodic potential on quasi-1D models of armchair single-wall nanotubes. The spectrum of this operator consists of an absolutely continuous part (intervals separated by gaps) plus an infinite number of eigenvalues with infinite multiplicity. We describe all eigenfunctions with the same eigenvalue. We define a Lyapunov function, which is analytic on some Riemann surface. On each sheet, the Lyapunov function has the same properties as in the scalar case, but it has branch points, which we call resonances. In example we show the existence of real and complex resonances for some specific potentials.

math-ph↗