Density dependence of resonance broadening and shadowing effects in nuclear photoabsorption

Medium effects as a function of the mass number $A$ are studied in the total photonuclear cross section from the $\Delta$-resonance region up to the region where shadowing effects are known to exist. A consistent picture is obtained by simply assuming a density dependence of the different mechanisms of resonance broadening and shadowing. The $\Delta$-mass shift is found to increase with $A$.Comment: 7 pages, LaTeX, 2 figures available from the author

Heralded gate search with genetic algorithms for quantum computation

In this paper we present genetic algorithms based search technique for the linear optics schemes, performing two-qubit quantum gates. We successfully applied this technique for finding heralded two-qubit gates and obtained the new schemes with performance parameters equal to the best currently known. The new simple metrics is introduced which enables comparison of schemes with different heralding mechanisms. The scheme performance degradation is discussed for the cases when detectors in the heralding part of the scheme are not photon-number-resolving. We propose a procedure for overcoming this drawback which allows us to restore the reliable heralding signal even with not-photon-number-resolving detectors

Feynman Diagrams and Differential Equations

We review in a pedagogical way the method of differential equations for the evaluation of D-dimensionally regulated Feynman integrals. After dealing with the general features of the technique, we discuss its application in the context of one- and two-loop corrections to the photon propagator in QED, by computing the Vacuum Polarization tensor exactly in D. Finally, we treat two cases of less trivial differential equations, respectively associated to a two-loop three-point, and a four-loop two-point integral. These two examples are the playgrounds for showing more technical aspects about: Laurent expansion of the differential equations in D (around D=4); the choice of the boundary conditions; and the link among differential and difference equations for Feynman integrals.Comment: invited review article from Int. J. Mod. Phys.

Probability-theoretic approach to modeling a respirator on chemically bound oxygen

At present, the main prospects for improving the insulating means of respiratory protection are related to the chemical method of oxygen reservation. The arguments in favor of this choice are the high density of oxygen packaging and its self-regulating supply, depending on the physical activity of the person. Usually, the working process in devices on chemically bound oxygen is modeled using mathematical physics methods that solve the so-called sorption dynamics problem. As a result, under given boundary and initial conditions, the concentration of CO2 mole-cules in the regenerative cartridge turns out to be a deterministic function of time and coordinates. However, the coordinate of the elementary act of sorption is essentially a random variable. The law of its distribution evolves as the absorbing resource of the regenerative cartridge is consumed. Taking into account the above, a probability-theoretic approach to modeling the working process of an insulating breathing apparatus based on chemically bound oxygen was developed. The approach is based on the description by probability theory methods of the random coordinate of the elementary act of chemosorption of a CO2 molecule by potassium peroxide granules and the random lifetime of this molecule in the regenerative cartridge of the respiratory apparatus. The evolution of the initial and central statistical moments of these values is es-tablished. The symmetry of their probability density with respect to the permutation of dimensionless arguments is shown, which are the time and distance from the entrance to the regenerative cartridge to the considered layer of chemisorbent. The presence of symmetry increases the speed of numerical experiments by one or two orders of magnitude. Gaussian asymptotics of the process at long times and corrections to it by inverse degrees of dispersion due to asymmetries and excesses of different orders are revealed. This further increases the speed of numerical experiments in computer simulation of the working process of an insulating respirator on chemically bound oxygen. © 2020, STC Industrial Safety CJSC. All rights reserved

Error of an arbitrary single-mode Gaussian transformation on a weighted cluster state using a cubic phase gate

In this paper, we propose two strategies for decreasing the error of arbitrary single-mode Gaussian transformations implemented using one-way quantum computation on a four-node linear cluster state. We show that it is possible to minimize the error of the arbitrary single-mode Gaussian transformation by a proper choice of the weight coefficients of the cluster state. We modify the computation scheme by adding a non-Gaussian state obtained using a cubic phase gate as one of the nodes of the cluster. This further decreases the computation error. We evaluate the efficiencies of the proposed optimization schemes comparing the probabilities of the error correction of the quantum computations with and without optimizations. We have shown that for some transformations, the error probability can be reduced by up to 900 times.Comment: 14 pages, 8 figure

Mathematical model of the fixed oxygen breathing apparatus with a circular airway scheme

The research deals with the influence of the СО2 breakthrough on the dynamic sorption activity of the regenerative cartridge of fixed oxygen breathing apparatus with a circular airway scheme. It is illustrated that the breakthrough return during breath at the later stages of the apparatus operation is essential and depending on the apparatus model or its operating regime noticeably (up to 10%) reduces its protection term

Evaluation of the resource usage efficiency increase of the fixed oxygen breathing apparatus

The research shows that the СО2 critical breakthrough time when using a heterogeneously fitted regenerative cartridge connected via the open scheme provides an understated breathing apparatus protection increase evaluation. It is better to employ the average oxygen-containing product usage along the full length of the cartridge by the time of the СО2 critical breakthrough, because the breakthrough decrease due to the dependence of the product granules diameter on the granules occurrence depth evolves in time by itself. It is shown that the suggested evaluation in terms of quantity equals the one determined by the protection term for the circular airway scheme where the СО2 breakthrough returns during breath

Mathematical model of the fixed oxygen breathing apparatus with a circular airway scheme

The research deals with the influence of the СО2 breakthrough on the dynamic sorption activity of the regenerative cartridge of fixed oxygen breathing apparatus with a circular airway scheme. It is illustrated that the breakthrough return during breath at the later stages of the apparatus operation is essential and depending on the apparatus model or its operating regime noticeably (up to 10%) reduces its protection term