19,996 research outputs found
Allowed charge transfers between coherent conductors driven by a time-dependent scatterer
We derive constraints on the statistics of the charge transfer between two
conductors in the model of arbitrary time-dependent instant scattering of
non-interacting fermions at zero temperature. The constraints are formulated in
terms of analytic properties of the generating function: its zeroes must lie on
the negative real axis. This result generalizes existing studies for scattering
by a time-independent scatterer under time-dependent bias voltage.Comment: 5 pages, no figures, corrected misprints and minor changes in version
Deformations of generalized calibrations and compact non-Kahler manifolds with vanishing first Chern class
We investigate the deformation theory of a class of generalized calibrations
in Riemannian manifolds for which the tangent bundle has reduced structure
group U(n), SU(n), G_2 and Spin(7). For this we use the property of the
associated calibration form to be parallel with respect to a metric connection
which may have non-vanishing torsion. In all these cases, we find that if there
is a moduli space, then it is finite dimensional.
We present various examples of generalized calibrations that include almost
hermitian manifolds with structure group U(n) or SU(n), nearly parallel G_2
manifolds and group manifolds. We find that some Hopf fibrations are
deformation families of generalized calibrations. In addition, we give
sufficient conditions for a hermitian manifold (M,g,J) to admit Chern and
Bismut connections with holonomy contained in SU(n). In particular we show that
any connected sum of copies of admits a hermitian
structure for which the restricted holonomy of a Bismut connection is contained
in SU(3).Comment: 43 pages, Latex, typos corrected, reference added in section
Non-dopplerian cosmological redshift parameters in a model of graviton-dusty universe
Possible effects are considered which would be caused by a hypothetical
superstrong interaction of photons or massive bodies with single gravitons of
the graviton background. If full cosmological redshift magnitudes are caused by
the interaction, then the luminosity distance in a flat non-expanding universe
as a function of redshift is very similar to the specific function which fits
supernova cosmology data by Riess et al. From another side, in this case every
massive body, slowly moving relatively to the background, would experience a
constant acceleration, proportional to the Hubble constant, of the same order
as a small additional acceleration of Pioneer 10, 11.Comment: 5 pages. It was presented: at SIGRAV'2000 Congress, Italy (this
version); in Proc. of the Int. Symp. "FFP 4" (9-13 Dec 2000, Hyderabad,
India), Sidharth& Altaisky, Eds., Kluwer Academic/Plenum, 2001;in Proc. of
the 4th Edoardo Amaldi Conference on GW (Perth, W. Australia, 8-13 July 2001
Factorization of quantum charge transport for non-interacting fermions
We show that the statistics of the charge transfer of non-interacting
fermions through a two-lead contact is generalized binomial, at any temperature
and for any form of the scattering matrix: an arbitrary charge-transfer process
can be decomposed into independent single-particle events. This result
generalizes previous studies of adiabatic pumping at zero temperature and of
transport induced by bias voltage.Comment: 13 pages, 3 figures, typos corrected, references adde
Comments to On the Accuracy of Lamb Shift Measurements in Hydrogen (Physica Scripta, 55 (1997) 33-40) by V. G. Pal'chikov, Yu. L. Sokolov, and V. P. Yakovlev
The work is a comments on the article of V. G. Pal'chikov, Yu. L. Sokolov,
and V. P. Yakovlev, devoted to the measurement of the Lamb shift in the
hydrogen atom and published in Physica Scripta, 55 (1997) 33-40.Comment: 4 pages; [email protected]
Improved theoretical prediction for the 2s hyperfine interval in helium ion
We consider the uncertainty of theoretical calculations for a specific
difference of the hyperfine intervals in the 1s and 2s states in a light
hydrogen-like atom. For a number of crucial radiative corrections the result
for hydrogen atom and helium ion appears as an extrapolation of the numerical
data from medium to low Z. An approach to a plausible estimation of the
uncertainty is suggested using the example of the difference
On One of the Possible Formation Mechanisms of Narrow Sporadic Ionosphere Layers
Electron density, and sounding rocket investigation of narrow sporadic ionosphere layer
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