Noncommutative scalar field in de Sitter space–time and pair creation process

In this work, we address the process of pair creation of scalar particles in [Formula: see text] de Sitter space–time in presence of a constant electromagnetic field by applying the noncommutativity on the scalar field up to first-order in [Formula: see text]. We calculate the density of particles created in the vacuum by the mean of the Bogoliubov transformations. In contrast to a previous result, we show that noncommutativity contributes to the pair creation process. We find that the noncommutativity plays the same role of chemical potential and gives an important interest for studies at high energies.

Application of electromagnetic field in anaerobic biodigestion in batch reactors

Anaerobic digestion processes with biogas production are widely used for organic waste treatment with an emphasis on energy recovery. Some recent studies have demonstrated the influence of magnetism on microbiological activity. These indicate a possible influence on the efficiency of anaerobic digestion. Thus, technologies that act in anaerobic digestion enhancement can contribute to the improvement of treatment of organic compounds. The present study aimed to verify the influence of a constant electromagnetic field on the anaerobic digestion in anaerobic reactors fed with glucose (2 g/L) at 37 ± 2 °C. In each experiment, reactors were operated with a constant electromagnetic field of 5, 7.5, and 10 mT. The inoculum was granular sludge from an anaerobic treatment plant in a non-selective media culture. Biogas production, chemical oxygen demand (COD), and solids removal were measured during the experiment. Results showed differences in methane production of 21.5% and in COD removal of 15% in the tests with an electromagnetic field of 7.5 mT. These results signs for the viability of the application of a constant magnetic field as a biostimulation agent.

Electromagnetic instability and Schwinger effect in the Witten–Sakai–Sugimoto model with D0–D4 background

Using the Witten–Sakai–Sugimoto model in the D0–D4 background, we holographically compute the vacuum decay rate of the Schwinger effect in this model. Our calculation contains the influence of the D0-brane density which could be identified as the $$\theta $$θ angle or chiral potential in QCD. Under the strong electromagnetic fields, the instability appears due to the creation of quark–antiquark pairs and the associated decay rate can be obtained by evaluating the imaginary part of the effective Euler–Heisenberg action which is identified as the action of the probe brane with a constant electromagnetic field. In the bubble D0–D4 configuration, we find the decay rate decreases when the $$\theta $$θ angle increases since the vacuum becomes heavier in the present of the glue condensate in this system. And the decay rate matches to the result in the black D0–D4 configuration at zero temperature limit according to our calculations. In this sense, the Hawking–Page transition of this model could be consistently interpreted as the confined/deconfined phase transition. Additionally there is another instability from the D0-brane itself in this system and we suggest that this instability reflects to the vacuum decay triggered by the $$\theta $$θ angle as it is known in the $$\theta $$θ-dependent QCD.

Neutrino evolution in dense matter and electromagnetic field

Neutrino evolution in dense matter and electromagnetic field is studied within quantum-field theoretical description on the base of a modification of the Standard Model, where the neutrinos are combined in S U(3)-multiplets. A quantum wave equation for neutrino in matter and electromagnetic field is obtained. In quasi-classical approximation a general method for calculating the probabilities of different spin-flavor transitions of neutrino in constant homogeneous field and moving matter with constant polarization is developed. In two-flavor model the explicit form of the solutions is obtained in constant electromagnetic field taking into account the transition magnetic moments. The obtained spin-flavor transition probabilities are compared to the results for unpolarized moving matter.

Schwinger mechanism in electromagnetic field in de Sitter spacetime

We investigate Schwinger scalar pair production in a constant electromagnetic field in de Sitter (dS) spacetime. We obtain the pair production rate, which agrees with the Hawking radiation in the limit of zero electric field in dS. The result describes how a cosmic magnetic field affects the pair production rate. In addition, using a numerical method we study the effect of the magnetic field on the induced current. We find that in the strong electromagnetic field the current has a linear response to the electric and magnetic fields, while in the infrared regime, is inversely proportional to the electric field and leads to infrared hyperconductivity.

Research on Transient Electromagnetic Field Model of High Speed Permanent Magnet Brushless DC Motor Based on the Theory of Constant Electromagnetic Field

The development of ultra-high speed motor is the development direction of the information industry in the future, and it is also the important guarantee for the production efficiency. Objective: To study the working model of the electromagnetic field of the permanent magnet brushless DC motor in the condition of constant electromagnetic field. Methods: Based on the theory of constant electromagnetic field, the model of a high speed permanent magnet brushless DC motor is derived. Process: Combined magnetic circuit calculation method and finite element method of electromagnetic field, and then use the mathematical model to calculate the electromagnetic. Finally, by using the model simulation to verify its practicability. Conclusion: The inhibiting effect of the ring structure rotor pole and cogging torque ripple can meet the requirements of high-speed motor mechanical and electromagnetic performance, meanwhile, the motor has a good performance in this way. So, it can provide reference for the construction of the transient electromagnetic field model of high speed permanent magnet brushless DC motor in the future.

Path integral for spinning particle subjected to the constant electromagnetic field

The problem of the Dirac particle submitted to a wave [Formula: see text] of a four-dimensional constant electromagnetic tensor is solved with the path integral approach via the use of Lorentz transformation and with an adequate choice for the velocity of the mobile referential.We show that the supersymmetric action associated to the pair [Formula: see text] can be determined from that associated to the pair [Formula: see text] and from that associated to the pair [Formula: see text] following simple relations.The wave functions and the energy spectrums are thus exactly determined and tested. Special cases are considered as well.