221 research outputs found
Quasi-classical versus non-classical spectral asymptotics for magnetic Schroedinger operators with decreasing electric potentials
We consider the Schroedinger operator H on L^2(R^2) or L^2(R^3) with constant
magnetic field and electric potential V which typically decays at infinity
exponentially fast or has a compact support. We investigate the asymptotic
behaviour of the discrete spectrum of H near the boundary points of its
essential spectrum. If the decay of V is Gaussian or faster, this behaviour is
non-classical in the sense that it is not described by the quasi-classical
formulas known for the case where V admits a power-like decay.Comment: Corrected versio
Lifshitz Tails in Constant Magnetic Fields
We consider the 2D Landau Hamiltonian perturbed by a random alloy-type
potential, and investigate the Lifshitz tails, i.e. the asymptotic behavior of
the corresponding integrated density of states (IDS) near the edges in the
spectrum of . If a given edge coincides with a Landau level, we obtain
different asymptotic formulae for power-like, exponential sub-Gaussian, and
super-Gaussian decay of the one-site potential. If the edge is away from the
Landau levels, we impose a rational-flux assumption on the magnetic field,
consider compactly supported one-site potentials, and formulate a theorem which
is analogous to a result obtained in the case of a vanishing magnetic field
On the discrete spectrum of spin-orbit Hamiltonians with singular interactions
We give a variational proof of the existence of infinitely many bound states
below the continuous spectrum for spin-orbit Hamiltonians (including the Rashba
and Dresselhaus cases) perturbed by measure potentials thus extending the
results of J.Bruening, V.Geyler, K.Pankrashkin: J. Phys. A 40 (2007)
F113--F117.Comment: 10 pages; to appear in Russian Journal of Mathematical Physics
(memorial volume in honor of Vladimir Geyler). Results improved in this
versio
Resonances Width in Crossed Electric and Magnetic Fields
We study the spectral properties of a charged particle confined to a
two-dimensional plane and submitted to homogeneous magnetic and electric fields
and an impurity potential. We use the method of complex translations to prove
that the life-times of resonances induced by the presence of electric field are
at least Gaussian long as the electric field tends to zero.Comment: 3 figure
Cryothecomonas aestivalis sp. nov., a colourless nanoflagellate feeding on the marine centric diatomGuinardia delicatula (Cleve) Hasle
Novel techniques for alpha/beta pulse shape discrimination in Borexino
Borexino could efficiently distinguish between alpha and beta radiation in
its liquid scintillator by the characteristic time profile of their
scintillation pulse. This alpha/beta discrimination, first demonstrated at the
tonne scale in the Counting Test Facility prototype, was used throughout the
lifetime of the experiment between 2007 and 2021. With this method, alpha
events are identified and subtracted from the beta-like solar neutrino events.
This is particularly important in liquid scintillator as alpha scintillation is
quenched many-fold. In Borexino, the prominent Po-210 decay peak was a
background in the energy range of electrons scattered from Be-7 solar
neutrinos. Optimal alpha-beta discrimination was achieved with a "multi-layer
perceptron neural network", which its higher ability to leverage the timing
information of the scintillation photons detected by the photomultiplier tubes.
An event-by-event, high efficiency, stable, and uniform pulse shape
discrimination was essential in characterising the spatial distribution of
background in the detector. This benefited most Borexino measurements,
including solar neutrinos in the \pp chain and the first direct observation of
the CNO cycle in the Sun. This paper presents the key milestones in alpha/beta
discrimination in Borexino as a term of comparison for current and future large
liquid scintillator detectorsComment: 13 pages, 14 figure
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