3,057 research outputs found
Existence and stability of static shells for the Vlasov-Poisson System with a fixed central point mass
We consider the Vlasov-Poisson system with spherical symmetry and an exterior
potential which is induced by a point mass in the center. This system can be
used as a simple model for a newtonian galaxy surrounding a black hole. For
this system, we establish a global existence result for classical solutions
with shell-like initial data, i.e. the support of the density is bounded away
from the point mass singularity. We also prove existence and stability of
stationary solutions which describe static shells, where we use a variational
approach which was established by Y. Guo and G. Rein.Comment: 26 page
Magnetoresistance in the s-d Model with Arbitrary Impurity Spin
The magnetoresistance, the number of the localized electrons, and the s-wave
scattering phase shift at the Fermi level for the s-d model with arbitrary
impurity spin are obtained in the ground state. To obtain above results some
known exact results of the Bethe ansatz method are used. As the impurity spin S
= 1/2, our results coincide with those obtained by Ishii \textit{et al%}. The
compairsion between the theoretical and experimental magneticresistence for
impurity S = 1/2 is re-examined.Comment: 6 pages, 2 figure
Nonclassicality filters and quasiprobabilities
Necessary and sufficient conditions for the nonclassicality of bosonic
quantum states are formulated by introducing nonclassicality filters and
nonclassicality quasiprobability distributions. Regular quasiprobabilities are
constructed from characteristic functions which can be directly sampled by
balanced homodyne detection. Their negativities uncover the nonclassical
effects of general quantum states. The method is illustrated by visualizing the
nonclassical nature of a squeezed state.Comment: Significantly revised version, more emphasis on practical applicatio
On the Newtonian origin of the spin motive force in ferromagnetic atomic wires
We demonstrate numerically the existence of a spin-motive force acting on
spin-carriers when moving in a time and space dependent internal field. This is
the case of electrons in a one-dimensional wires with a precessing domain wall.
The effect can be explained solely by considering adiabatic dynamics and it is
shown to exist for both classical and quantum systems.Comment: 5 pages, 7 figures, added figure 7 and tex
Magnetic transitions induced by tunnelling electrons in individual adsorbed M-Phthalocyanine molecules (M Fe, Co)
We report on a theoretical study of magnetic transitions induced by
tunnelling electrons in individual adsorbed M-Phthalocyanine (M-Pc) molecules
where M is a metal atom: Fe-Pc on a Cu(110)(21)-O surface and Co-Pc
layers on Pb(111) islands. The magnetic transitions correspond to the change of
orientation of the spin angular momentum of the metal ion with respect to the
surroundings and possibly an applied magnetic field. The adsorbed Fe-Pc system
is studied with a Density Functional Theory (DFT) transport approach showing
that i) the magnetic structure of the Fe atom in the adsorbed Fe-Pc is quite
different from that of the free Fe atom or of other adsorbed Fe systems and ii)
that injection of electrons (holes) into the Fe atom in the adsorbed Fe-Pc
molecule dominantly involves the Fe orbital. These results fully
specify the magnetic structure of the system and the process responsible for
magnetic transitions. The dynamics of the magnetic transitions induced by
tunnelling electrons is treated in a strong-coupling approach. The Fe-Pc
treatment is extended to the Co-Pc case. The present calculations accurately
reproduce the strength of the magnetic transitions as observed by magnetic IETS
(Inelastic Electron Tunnelling Spectroscopy) experiments; in particular, the
dominance of the inelastic current in the conduction of the adsorbed M-Pc
molecule is accounted for
Defect-induced spin-glass magnetism in incommensurate spin-gap magnets
We study magnetic order induced by non-magnetic impurities in quantum
paramagnets with incommensurate host spin correlations. In contrast to the
well-studied commensurate case where the defect-induced magnetism is spatially
disordered but non-frustrated, the present problem combines strong disorder
with frustration and, consequently, leads to spin-glass order. We discuss the
crossover from strong randomness in the dilute limit to more conventional glass
behavior at larger doping, and numerically characterize the robust short-range
order inherent to the spin-glass phase. We relate our findings to magnetic
order in both BiCu2PO6 and YBa2Cu3O6.6 induced by Zn substitution.Comment: 6 pages, 5 figs, (v2) real-space RG results added; discussion
extended, (v3) final version as publishe
Hilbert space structure and positive operators
Let X be a real Banach space. We prove that the existence of an injective,
positive, symmetric and not strictly singular operator from X into its dual
implies that either X admits an equivalent Hilbertian norm or it contains a
nontrivially complemented subspace which is isomorphic to a Hilbert space. We
also treat the non-symmetric case
A Simple Proof of Inequalities of Integrals of Composite Functions
In this paper we give a simple proof of inequalities of integrals of
functions which are the composition of nonnegative continous convex functions
on a vector space and vector-valued functions in a weakly compact
subset of a Banach vector space generated by -spaces for Also, the same inequalities hold if these vector-valued functions
are in a weakly* compact subset of a Banach vector space generated by
-spaces instead
- …