719 research outputs found
Euler - Heisenberg effective action and magnetoelectric effect in multilayer graphene
The low energy effective field model for the multilayer graphene (at ABC
stacking) is considered. We calculate the effective action in the presence of
constant external magnetic field (normal to the graphene sheet). We also
calculate the first two corrections to this effective action caused by the
in-plane electric field at and discuss the magnetoelectric
effect. In addition, we calculate the imaginary part of the effective action in
the presence of constant electric field and the lowest order correction to
it due to the magnetic field ().Comment: Latex, 24 pages, accepted for publication in Annals of Physic
Upper bound on the cutoff in lattice Electroweak theory
We investigate numerically lattice Weinberg - Salam model without fermions
for realistic values of the fine structure constant and the Weinberg angle. We
also analyze the data of the previous numerical investigations of lattice
Electroweak theory. We have found that moving along the line of constant
physics when the lattice spacing is decreased, one should leave the
physical Higgs phase of the theory at a certain value of . Our estimate of
the minimal value of the lattice spacing is .Comment: Latex, 21 pages, 3 figures, to appear in JHE
Quantum Versus Jahn-Teller Orbital Physics in YVO and LaVO
We argue that the large Jahn-Teller (JT) distortions in YVO and LaVO
should suppress the quantum orbital fluctuation. The unusual magnetic
properties can be well explained based on LDA+ calculations using
experimental structures, in terms of the JT orbital. The observed splitting of
the spin-wave dispersions for YVO in C-type antiferromagnetic state is
attributed to the inequivalent VO layers in the crystal structure, instead
of the ``orbital Peierls state''. Alternative stacking of -plane exchange
couplings produces the c-axis spin-wave splitting, thus the spin system is
highly three dimensional rather than quasi-one-dimensional. Similar splitting
is also predicted for LaVO, although it is weak.Comment: 4 pages, 2 tables, 2 figures, (accepted by PRL
Methyl 7,8-diacetÂoxy-11-oxo-5-(2-oxoÂpyrrolidin-1-yl)-7,9-epoxyÂcycloÂpentaÂ[4,5]pyrido[1,2-a]quinoline-10-carboxylÂate sesquihydrate
The title compound, C26H28N2O9·1.5H2O, the product of an acid-catalysed Wagner–Meerwein skeletal rearrangement, crystallizes as a sesquihydrate with the O atom of one of the two independent water molÂecules occupying a special position on a twofold axis. The organic molÂecule comprises a fused pentaÂcyclic system containing two five-membered rings (cycloÂpentane and tetraÂhydroÂfuran) and three six-membered rings (piperidinone, tetraÂhydroÂpyridine and benzene). The five-membered rings have the usual envelope conformations, and the central six-membered piperidinone and tetraÂhydroÂpyridine rings adopt boat and sofa conformations, respectively. In the crystal, there are three independent O—H⋯O hydrogen bonds, which link the organic molÂecules and water molÂecules into complex two-tier layers parallel to (001). The layers are further linked into a three-dimensional framework by attractive interÂmolecular carbonÂyl–carbonyl interÂactions
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