427 research outputs found
Quantum states of electromagnetic field interacting with a classical current and their applications to radiation problems
In the beginning, the synchrotron radiation (SR) was studied by classical
methods using the Li\'{e}nard-Wiechert potentials of electric currents.
Subsequently, quantum corrections to the obtained classical formulas were
studied, considering the emission of photons arising from electronic
transitions between spectral levels, described in terms of the Dirac equation.
In this paper, we consider an intermediate approach, in which electric currents
generating the radiation are considered classically, whereas the quantum nature
of the radiation is taken into account exactly. Such an approximate approach
may be helpful in some cases, it allows one to study the one-photon and
multi-photon radiation without complicating calculations using corresponding
solutions of the Dirac equation. We construct exact quantum states of the
electromagnetic field interacting with classical currents and study their
properties. By their help, we calculate a probability of photon emission by
classical currents and obtain relatively simple formulas for the one-photon and
multi-photon radiation. Using the specific circular electric current, we
calculate the corresponding SR. We discuss a relation of obtained results with
known before, for example, with the Schott formula, with the Schwinger
calculations, with one-photon radiation of scalar particles due to transitions
between Landau levels, and with some previous results of calculating the
two-photon SR.Comment: 12 page
Electromagnetic radiation of accelerated charged particle in the framework of a semiclassical approach
We address the problem of the electromagnetic radiation produced by charge
distributions in the framework of a semiclassical approach proposed in the work
by Bagrov, Gitman, Shishmarev and Farias [J. Synchrotron Rad. (2020). 27,
902-911]. In this approach, currents, generating the radiation are considered
classically, while the quantum nature of the radiation is kept exactly. Quantum
states of the electromagnetic field are solutions of Schr\"odinger's equation
and relevant quantities to the problem are evaluated with the aid of transition
probabilities. This construction allows us to introduce the quantum transition
time in physical quantities and assess its role in radiation problems by
classical currents. We study radiated electromagnetic energies in detail and
present a definition for the rate at which radiation is emitted from sources.
In calculating the total energy and rate radiated by a pointlike charged
particle accelerated by a constant and uniform electric field, we discover that
our results are compatible with results obtained by other authors in the
framework of the classical radiation theory under an appropriate limit. We also
perform numerical and asymptotic analysis of the results.Comment: 22 pages, 3 figure
An Integrative Analysis Uncovers a New, Pseudo-Cryptic Species of Amazonian Marmoset (Primates: Callitrichidae: \u3cem\u3eMico\u3c/em\u3e) from the Arc of Deforestation
Amazonia has the richest primate fauna in the world. Nonetheless, the diversity and distribution of Amazonian primates remain little known and the scarcity of baseline data challenges their conservation. These challenges are especially acute in the Amazonian arc of deforestation, the 2500 km long southern edge of the Amazonian biome that is rapidly being deforested and converted to agricultural and pastoral landscapes. Amazonian marmosets of the genus Mico are little known endemics of this region and therefore a priority for research and conservation efforts. However, even nascent conservation efforts are hampered by taxonomic uncertainties in this group, such as the existence of a potentially new species from the Juruena–Teles Pires interfluve hidden within the M. emiliae epithet. Here we test if these marmosets belong to a distinct species using new morphological, phylogenomic, and geographic distribution data analysed within an integrative taxonomic framework. We discovered a new, pseudo-cryptic Mico species hidden within the epithet M. emiliae, here described and named after Horacio Schneider, the pioneer of molecular phylogenetics of Neotropical primates. We also clarify the distribution, evolutionary and morphological relationships of four other Mico species, bridging Linnean, Wallacean, and Darwinian shortfalls in the conservation of primates in the Amazonian arc of deforestation
Algorithm Engineering in Robust Optimization
Robust optimization is a young and emerging field of research having received
a considerable increase of interest over the last decade. In this paper, we
argue that the the algorithm engineering methodology fits very well to the
field of robust optimization and yields a rewarding new perspective on both the
current state of research and open research directions.
To this end we go through the algorithm engineering cycle of design and
analysis of concepts, development and implementation of algorithms, and
theoretical and experimental evaluation. We show that many ideas of algorithm
engineering have already been applied in publications on robust optimization.
Most work on robust optimization is devoted to analysis of the concepts and the
development of algorithms, some papers deal with the evaluation of a particular
concept in case studies, and work on comparison of concepts just starts. What
is still a drawback in many papers on robustness is the missing link to include
the results of the experiments again in the design
Neutrinos Angra experiment: commissioning and first operational measurements
The Neutrinos Angra Experiment has completed a major step by finishing the
comissioning of the detector and the data acquisition system at the
experimental site located in the Angra dos Reis nuclear power plant. The
experiment consists of a water-based detector and associated electronics, both
designed with the goal of detecting the electron antineutrinos produced by the
nuclear reactor. The detection is possible due to the Inverse Beta Decay, where
the final products in the water are photons in the UV-to-visible range of the
spectrum. The assembled detector comprises three active volumes filled with
water: (i) a cubic target detector for electron antineutrinos, covered by 32
8-inches PMTs, (ii) a lateral layer surrounding the target (veto) equipped with
4 PMTs and (iii) a third volume covering the top of both, also equipped with
4~PMTs. In the present document the main features of the detector assembly as
well as the integration of the readout electronics on-site are reported.
Finally, some operational characteristics are shown based on straightforward
analysis of the first measurements performed during the last months with the
fully working detector
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