1,276 research outputs found
The Construction of a Partially Regular Solution to the Landau-Lifshitz-Gilbert Equation in
We establish a framework to construct a global solution in the space of
finite energy to a general form of the Landau-Lifshitz-Gilbert equation in
. Our characterization yields a partially regular solution,
smooth away from a 2-dimensional locally finite Hausdorff measure set. This
construction relies on approximation by discretization, using the special
geometry to express an equivalent system whose highest order terms are linear
and the translation of the machinery of linear estimates on the fundamental
solution from the continuous setting into the discrete setting. This method is
quite general and accommodates more general geometries involving targets that
are compact smooth hypersurfaces.Comment: 43 pages, 2 figure
Superthermal photon bunching in terms of simple probability distributions
We analyze the second-order photon autocorrelation function with
respect to the photon probability distribution and discuss the generic features
of a distribution that result in superthermal photon bunching ().
Superthermal photon bunching has been reported for a number of optical
microcavity systems that exhibit processes like superradiance or mode
competition. We show that a superthermal photon number distribution cannot be
constructed from the principle of maximum entropy, if only the intensity and
the second-order autocorrelation are given. However, for bimodal systems an
unbiased superthermal distribution can be constructed from second-order
correlations and the intensities alone. Our findings suggest modeling
superthermal single-mode distributions by a mixture of a thermal and a lasing
like state and thus reveal a generic mechanism in the photon probability
distribution responsible for creating superthermal photon bunching. We relate
our general considerations to a physical system, a (single-emitter) bimodal
laser, and show that its statistics can be approximated and understood within
our proposed model. Furthermore the excellent agreement of the statistics of
the bimodal laser and our model reveal that the bimodal laser is an ideal
source of bunched photons, in the sense that it can generate statistics that
contain no other features but the superthermal bunching
Energy transfer mechanism in Gd_2(SiO_4)O:Ce scintillators
The scintillation decay of cerium-doped gadolinium oxyorthosilicate Gd_2(SiO_4)O:Ce is lengthened by the energy transfer from Gd to Ce. To investigate the role of the Gd in the scintillation processes, the Gd was partially replaced by optically inactive rare earth elements, Y and Lu, and the effective transfer rates from Gd to Ce were measured as a function of Gd and Ce concentrations using UV- and gamma-ray excitations. The data clearly indicate the dilution of the Gd by the Y and the Lu further lengthens the migration time through the Gd in the energy transfer process from Gd to Ce
Energy Transfer Mechanism In Gd_2(SiO_4)O:Ce Scintillators
The scintillation decay of cerium-doped gadolinium
oxyorthosilicate Gd_2(SiO_4)O:Ce is lengthened by the energy
transfer from Gd to Ce. To investigate the role of the Gd in
the scintillation processes, the Gd was partially replaced by
optically inactive rare earth elements, Y and Lu, and the
effective transfer rates from Gd to Ce were measured as a
function of Gd and Ce concentrations using UV- and gamma-ray
excitations. The data clearly indicate the dilution of the Gd
by the Y and the Lu further lengthens the migration time
through the Gd in the energy transfer process from Gd to Ce
Light emission mechanism of Lu_2(SiO_4)O:Ce
Lutetium oxyorthosilicate Lu_2(SiO_4)O has two crystallographically independent lutetium sites. When it is doped with Ce, the dopant Ce is assumed to occupy two different sites, and thus the existence of two activation centers is proposed. UV and gamma-ray excited spectra clearly indicate that two activation centers exist in cerium-doped lutetium oxyorthosilicate Lu_2(SiO_4)O:Ce (LSO)
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