18,019 research outputs found
Rationality and Brauer group of a moduli space of framed bundles
We prove that the moduli spaces of framed bundles over a smooth projective
curve are rational. We compute the Brauer group of these moduli spaces to be
zero under some assumption on the stability parameter.Comment: 7 pages, to appear in Tbilisi Math. J; v2. reference adde
Universal Features of the Time Evolution of Evanescent Modes in a Left-Handed Perfect Lens
The time evolution of evanescent modes in Pendry's perfect lens proposal for
ideally lossless and homogeneous, left-handed materials is analyzed. We show
that time development of sub-wavelength resolution exhibits universal features,
independent of model details. This is due to the unavoidable near-degeneracy of
surface electromagnetic modes in the deep sub-wavelength region. By means of a
mechanical analog, it is shown that an intrinsic time scale (missed in
stationary studies) has to be associated with any desired lateral resolution. A
time-dependent cut-off length emerges, removing the problem of divergences
claimed to invalidate Pendry's proposal.Comment: 4 pages, 3 figures, title slightly changed, reference added, minor
correction
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