1,358 research outputs found
Invariance for multiples of the twisted canonical bundle
In this paper, we show an extension type theorem for twisted pluricanonical
sections on a family of smooth projective manifolds (the twisting line bundle
being pseudo-effective and having a prescribed multiplier ideal on the central
fiber).Comment: A Paraitre dans : Annales de l'Institut Fourier (Grenoble) 10 pages,
no figur
Threefolds with quasi-projective universal cover
We study compact K\"ahler threefolds X with infinite fundamental group whose
universal cover can be compactified. Combining techniques from -theory,
Campana's geometric orbifolds and the minimal model program we show that this
condition imposes strong restrictions on the geometry of X. In particular we
prove that if a projective threefold with infinite fundamental group has a
quasi-projective universal cover, the latter is then isomorphic to the product
of an affine space with a simply connected manifold.Comment: 26 pages, no figure. Comments are welcom
Gamma-reduction for smooth orbifolds
The aim of this short note is to show how to construct a rationnal Remmert
reduction for the universal cover of a smooth K\"ahler orbifold. Doins this, we
are led to introduce some singular K\"ahler metrics adapted to the orbifold
structure.Comment: 11 pages, no figur
Compact leaves of codimension one holomorphic foliations on projective manifolds
This article studies codimension one foliations on projective man-ifolds
having a compact leaf (free of singularities). It explores the interplay
between Ueda theory (order of flatness of the normal bundle) and the holo-nomy
representation (dynamics of the foliation in the transverse direction). We
address in particular the following problems: existence of foliation having as
a leaf a given hypersurface with topologically torsion normal bundle, global
structure of foliations having a compact leaf whose holonomy is abelian (resp.
solvable), and factorization results
Optimal all-optical switching of a microcavity resonance in the telecom range using the electronic Kerr effect
We have switched GaAs/AlAs and AlGaAs/AlAs planar microcavities that operate
in the "Original" (O) telecom band by exploiting the instantaneous electronic
Kerr effect. We observe that the resonance frequency reversibly shifts within
one picosecond. We investigate experimentally and theoretically the role of
several main parameters: the material backbone and its electronic bandgap, the
pump power, the quality factor, and the duration of the switch pulse. The
magnitude of the shift is reduced when the backbone of the central
layer has a greater electronic bandgap; pumping with photon energies
near the bandgap resonantly enhances the switched magnitude. Our model shows
that the magnitude of the resonance frequency shift depends on the pump pulse
duration and is maximized when the duration matches the cavity storage time
that is set by the quality factor. We provide the settings for the essential
parameters so that the frequency shift of the cavity resonance can be increased
to one linewidth
Decoherence processes in a current biased dc SQUID
A current bias dc SQUID behaves as an anharmonic quantum oscillator
controlled by a bias current and an applied magnetic flux. We consider here its
two level limit consisting of the two lower energy states | 0 \right> and |
1 \right>. We have measured energy relaxation times and microwave absorption
for different bias currents and fluxes in the low microwave power limit.
Decoherence times are extracted. The low frequency flux and current noise have
been measured independently by analyzing the probability of current switching
from the superconducting to the finite voltage state, as a function of applied
flux. The high frequency part of the current noise is derived from the
electromagnetic environment of the circuit. The decoherence of this quantum
circuit can be fully accounted by these current and flux noise sources.Comment: 4 pages, 4 figure
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