140 research outputs found
Inverse Problem for an Electrical Dipole and the Lightning Location Passive Monitoring System
We solve the problem of the locating parameters, identifying equivalent dipole electromagnetic radiation source through measured horizontal magnetic and vertical electric components at some point of the infinite conducting ground. Methods based on analysis of measured signals are suggested. The problem under consideration, like any inverse problem of mathematical physics, is ill-conditioned. The consequences of this are the high sensitivity of the algorithm to the errors in the source data and calculation errors. All these circumstances do not allow to estimate the accuracy and reliability of the results obtained with the help of single-scale algorithms. The considered problem is contained in a complex of mathematical models of the practically important problem of forecasting the development of thunderstorm foci. Lightning meteorology focuses on investigating the lightning activities in different types of convective weather systems and the relationship of lightning to the dynamic and microphysical processes in thunderstorms. With the development and application of advanced lightning detection and location technologies, lightning meteorology has been developed into an important interdisciplinary between atmospheric electricity and meteorology. This paper reviews (1) methods to identify the dipole location and (2) possibilities to analyze the pre-radiation of thunderstorm clouds by the passive methods
Stable parametric identification of vibratory diagnostics objects
A common model of vibratory diagnostics objects is the stochastic difference schemes, and theirs parametrical identification is carried out least squares and least absolute deviations techniques. It is well known that these techniques are unstable under stochastic heterogeneity of observable process, specifically, in the presence of outliers. One way to make the stable parametrical identification of vibratory diagnostics objects is implementation of generalized least absolute deviations method based on concave loss function. Obtained requirements to the loss function guaranteeing the steadiness evaluation, algorithms of identification and examples are presente
Adjoint master equation for multi-time correlators
The quantum regression theorem is a powerful tool for calculating the
muli-time correlators of operators of open quantum systems which dynamics can
be described in Markovian approximation. It enables to obtain the closed system
of equation for the multi-time correlators. However, the scope of the quantum
regression theorem is limited by a particular time order of the operators in
multi-time correlators and does not include out-of-time-ordered correlators. In
this work, we obtain an adjoint master equation for multi-time correlators that
is applicable to out-of-time-ordered correlators. We show that this equation
can be derived for various approaches to description of the dynamics of open
quantum systems, such as the global or local approach. We show that the adjoint
master equation for multi-time correlators is self-consistent. Namely, the
final equation does not depend on how the operators are grouped inside the
correlator, and it coincides with the quantum regression theorem for the
particular time ordering of the operators.Comment: 11 page
Controlling Purity, Indistinguishability and Quantum Yield of Incoherently Pumped Two-Level System by Spectral Filters
Dephasing processes significantly impact the performance of deterministic
single-photon sources. Dephasing broadens the spectral line and suppresses the
indistinguishability of the emitted photons, which is undesirable for many
applications, primarily for quantum computing. We consider a light emitted by a
two-level system with a pulsed incoherent pump in the presence of the spectral
filter. The spectral filter allows control of the second-order autocorrelation
function, indistinguishability, and quantum yield. We show that narrow spectral
filters can increase the indistinguishability of the emitted light while
undermining the quantum yield. The influence of the spectral filter on the
second-order correlation function depends on the duration of the pump. When the
pumping pulse is long compared to the lifetime of the two-level system, the
narrow spectral filters lead to a rapid increase in the second-order
autocorrelation function. In this limit, the statistics of the light from the
two-level system inherit the statistics of the incoherent pump. In the case of
the short duration of the pump pulse, it is possible to preserve single-photon
properties to some degree for the sub-lifetime width of the spectral filter.
Moreover, when the light emitted by the single-photon source is used to control
a quantum system, e.g., cavity, the single-photon properties of the light
manifest themselves differently, depending on the response time of the quantum
system. In particular, in the case of long response time, the spectral filter
with sub-lifetime width can provide the near-zero second-order autocorrelation
function
The nature and boundary of the floating phase in a dissipative Josephson junction array
We study the nature of correlations within, and the transition into, the
floating phase of dissipative Josephson junction arrays. Order parameter
correlations in this phase are long-ranged in time, but only short-ranged in
space. A perturbative RG analysis shows that, in {\it arbitrary} spatial
dimension, the transition is controlled by a continuous locus of critical fixed
points determined entirely by the \textit{local} topology of the lattice. This
may be the most natural example of a line of critical points existing in
arbitrary dimensions.Comment: Parts rewritten, typos correcte
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