Constraining the range of Yukawa gravity interaction from S2 star orbits III: improvement expectations for graviton mass bounds

Recently, the LIGO-Virgo collaboration discovered gravitational waves and in their first publication on the subject the authors also presented a graviton mass constraint as $m_g < 1.2 \times 10^{-22}$ eV (Abbott et al., 2016). In the paper we analyze a potential to reduce upper bounds for graviton mass with future observational data on trajectories of bright stars near the Galactic Center. Since gravitational potentials are different for these two cases, expressions for relativistic advance for general relativity and Yukawa potential are different functions on eccentricity and semimajor axis, it gives an opportunity to improve current estimates of graviton mass with future observational facilities. In our considerations of an improvement potential for a graviton mass estimate we adopt a conservative strategy and assume that trajectories of bright stars and their apocenter advance will be described with general relativity expressions and it gives opportunities to improve graviton mass constraints. In contrast with our previous studies, where we present current constraints on parameters of Yukawa gravity (Borka et al., 2013) and graviton mass (Zakharov et al., 2016) from observations of S2 star, in the paper we express expectations to improve current constraints for graviton mass, assuming the GR predictions about apocenter shifts will be confirmed with future observations. We concluded that if future observations of bright star orbits during around fifty years will confirm GR predictions about apocenter shifts of bright star orbits it give an opportunity to constrain a graviton mass at a level around $5 \times 10^{-23}$ eV or slightly better than current estimates obtained with LIGO observations.Comment: 16 pages, 1 Figure, 1 Table, corrected minor typo

Physical model of quantum-well infrared photodetectors

A fully quantum mechanical model for electron transport in quantum well infrared photodetectors is presented, based on a self-consistent solution of the coupled rate equations. The important macroscopic parameters like current density, responsivity and capture probability can be estimated directly from this first principles calculation. The applicability of the model was tested by comparison with experimental measurements from a GaAs/AlGaAs device, and good agreement was found. The model is general and can be applied to any other material system or QWIP design

Optically pumped intersublevel midinfrared lasers based on InAs-GaAs quantum dots

We propose an optically pumped laser based on intersublevel transitions in InAs-GaAs pyramidal self-Assembled quantum dots. A theoretical rate equations model of the laser is given in order to predict the dependence of the gain on pumping flux and temperature. The energy levels and wave functions were calculated using the 8-band k . p method where the symmetry of the pyramid was exploited to reduce the computational complexity. Carrier dynamics in the laser were modeled by taking both electron-longitudinal optical phonon and electron-longitudinal acoustic phonon interactions into account. The proposed laser emits at 14.6 μm with a gain of g ≈ 570 cm(-1) at the pumping flux Φ= 10(24) cm(-2) s(-1) and a temperature of T = 77 K. By varying the size of the investigated dots, laser emission in the spectral range 13-21 μm is predicted. In comparison to optically pumped lasers based on quantum wells, an advantage of the proposed type of laser is a lower pumping flux, due to the longer carrier lifetime in quantum dots, and also that both surface and edge emission are possible. The appropriate waveguide and cavity designs are presented, and by comparing the calculated values of the gain with the estimated losses, lasing is predicted even at room temperature for all the quantum dots investigated

Dynamics of the wakefield of a multi-petawatt, femtosecond laser pulse in a configuration with ultrarelativistic electrons

The wake field excitation in an unmagnetized plasma by a multi-petawatt, femtosecond, pancake-shaped laser pulse is described both analytically and numerically in the regime with ultrarelativistic electron jitter velocities, when the plasma electrons are almost expelled from the pulse region. This is done, for the first time, in fluid theory. A novel mathematical model is devised that does not break down for very intense pump strengths, in contrast to the standard approach that uses the laser field envelope and the ponderomotive guiding center averaging. This is accomplished by employing a three-timescale description, with the intermediate scale associated with the nonlinear phase of the electromagnetic wave and with the bending of its wave front. The evolution of the pulse and of its electrostatic wake are studied by the numerical solution in a two-dimensional geometry, with the spot diameter \geq 100 microns. It reveals that the optimum initial pulse length needs to be somewhat bigger than 1 micron (1-2 oscillations), as suggested by simple analytical local estimates, because the nonlocal plasma response tends to stretch very short pulses

Dilute magnetic semiconductor quantum-well structures for magnetic field tunable far-infrared/terahertz absorption

The design of ZnCdSe–ZnMnSe-based quantum wells is considered, in order to obtain a large shift of the peak absorption wavelength in the far infrared range, due to a giant Zeeman splitting with magnetic field, while maintaining a reasonably large value of peak absorption. A triple quantum-well structure with a suitable choice of parameters has been found to satisfy such requirements. A maximal tuning range between 14.6 and 34.7 meV is obtained, when the magnetic field varies from zero to 5 T, so the wavelength of the absorbed radiation decreases from 85.2 to 35.7 μm with absorption up to 1.25% at low temperatures. These structures might form the basis for magnetic field tunable photodetectors and quantum cascade lasers in the terahertz range

Self modulated dynamics of a relativistic charged particle beam in plasma wake field excitation

Self modulated dynamics of a relativistic charged particle beam is reviewed within the context of the theory of plasma wake field excitation. The self-consistent description of the beam dynamics is provided by coupling the Vlasov equation with a Poisson-type equation relating the plasma wake potential to the beam density. An analysis of the beam envelope self-modulation is then carried out and the criteria for the occurrence of the instability are discussed thereby.Comment: This is a 10 pages manuscript which contain 4 figures. This manuscript is recently submitted in 'Nuclear Instruments and Methods in Physics Research Section A' as a proceeding of the conference 'EAAC 2015

Evaluation of semiconductor devices for Electric and Hybrid Vehicle (EHV) ac-drive applications, volume 1

The results of evaluation of power semiconductor devices for electric hybrid vehicle ac drive applications are summarized. Three types of power devices are evaluated in the effort: high power bipolar or Darlington transistors, power MOSFETs, and asymmetric silicon control rectifiers (ASCR). The Bipolar transistors, including discrete device and Darlington devices, range from 100 A to 400 A and from 400 V to 900 V. These devices are currently used as key switching elements inverters for ac motor drive applications. Power MOSFETs, on the other hand, are much smaller in current rating. For the 400 V device, the current rating is limited to 25 A. For the main drive of an electric vehicle, device paralleling is normally needed to achieve practical power level. For other electric vehicle (EV) related applications such as battery charger circuit, however, MOSFET is advantageous to other devices because of drive circuit simplicity and high frequency capability. Asymmetrical SCR is basically a SCR device and needs commutation circuit for turn off. However, the device poses several advantages, i.e., low conduction drop and low cost

Influence of Intra-cell Traffic on the Output Power of Base Station in GSM

In this paper we analyze the influence of intracell traffic in a GSM cell on the base station output power. It is proved that intracell traffic increases this power. If offered traffic is small, the increase of output power is equal to the part of intracell traffic. When the offered traffic and, as the result, call loss increase, the increase of output power becomes less. The results of calculation are verified by the computer simulation of traffic process in the GSM cell. The calculation and the simulation consider the uniform distribution of mobile users in the cell, but the conclusions are of a general nature