Teams of global equilibrium search algorithms for solving weighted MAXIMUM CUT problem in parallel

In this paper, we investigate the impact of communication between optimization algorithms running in parallel. In particular we focus on the weighted maximum cut (WMAXCUT) problem and compare different communication strategies between teams of GES algorithms running in parallel. The results obtained by teams encourage the development of team algorithms. They were significantly better than the algorithmic portfolio (no communication) approach and suggest that the communication between algorithms running in parallel is a promising research direction.Досліджено обмін інформацією між оптимізаційними алгоритмами, працюючими паралельно над однією задачею. Вивчалась задача про максимальний зважений розріз графа (WMAXCUT) і порівняння різних стратегій взаємодії між командами алгоритмів GES. Отримані результати свідчать про те, що обмін інформацією між алгоритмами, працюючими паралельно, є перспективним напрямом дослідження

The boson peak and the first sharp diffraction peak in (As2S3)x(GeS2)1–x glasses

The parameters of the boson peak (BP) and the first sharp diffraction peak (FSDP) in (As2S3)x(GeS2)1x glasses measured using high-resolution Raman spectroscopy and high-energy synchrotron X-ray diffraction measurements are examined as a function of x. It has been found that there is no correlation between the positions of BP and FSDP. The BP position shows a nonlinear composition behavior with a maximum at about x = 0.4, whereas the FSDP position changes virtually linearly with x. The intensities of both BP and FSDP show nonlinear composition dependences with the slope changes at x = 0.4, although there is no direct proportionality. Analysis of the partial structure factors for the glasses with x = 0.2, 0.4 and 0.6 obtained in another study has shown that the cation-cation atomic pairs of Ge–Ge, Ge–As and As–As make the largest contribution to FSDP, where the Ge–Ge and Ge–As pairs are dominant

Mixed-parity superconductivity in centrosymmetric crystals

A weak-coupling formalism for superconducting states possessing both singlet (even parity) and triplet (odd parity) components of the order parameter in centrosymmetric crystals is developed. It is shown that the quasiparticle energy spectrum may be non-degenerate even if the triplet component is unitary. The superconducting gap of a mixed-parity state may have line nodes in the strong spin-orbit coupling limit. The pseudospin carried by the superconducting electrons is calculated, from which follows a prediction of a kink anomaly in the temperature dependence of muon spin relaxation rate. The anomaly occurs at the phase boundary between the bare triplet and mixed-parity states. The stability of mixed-parity states is discussed within Ginzburg-Landau theory. The results may have immediate application to the superconducting series Pr(Os,Ru)4Sb12.Comment: 5 pages, 2 figures. Final version accepted to PR

Non-Centrosymmetric Heavy-Fermion Superconductors

In this chapter we discuss the physical properties of a particular family of non-centrosymmetric superconductors belonging to the class heavy-fermion compounds. This group includes the ferromagnet UIr and the antiferromagnets CeRhSi3, CeIrSi3, CeCoGe3, CeIrGe3 and CePt3Si, of which all but CePt3Si become superconducting only under pressure. Each of these superconductors has intriguing and interesting properties. We first analyze CePt3Si, then review CeRhSi3, CeIrSi3, CeCoGe3 and CeIrGe3, which are very similar to each other in their magnetic and electrical properties, and finally discuss UIr. For each material we discuss the crystal structure, magnetic order, occurrence of superconductivity, phase diagram, characteristic parameters, superconducting properties and pairing states. We present an overview of the similarities and differences between all these six compounds at the end.Comment: To appear in "Non-Centrosymmetric Superconductors: Introduction and Overview", Lecture Notes in Physics 847, edited by E. Bauer and M. Sigrist (Springer-Verlag, Berlin Heidelberg, 2012) Chap. 2, pp. 35-7

On the mechanisms governing gas penetration into a tokamak plasma during a massive gas injection

A new 1D radial fluid code, IMAGINE, is used to simulate the penetration of gas into a tokamak plasma during a massive gas injection (MGI). The main result is that the gas is in general strongly braked as it reaches the plasma, due to mechanisms related to charge exchange and (to a smaller extent) recombination. As a result, only a fraction of the gas penetrates into the plasma. Also, a shock wave is created in the gas which propagates away from the plasma, braking and compressing the incoming gas. Simulation results are quantitatively consistent, at least in terms of orders of magnitude, with experimental data for a D 2 MGI into a JET Ohmic plasma. Simulations of MGI into the background plasma surrounding a runaway electron beam show that if the background electron density is too high, the gas may not penetrate, suggesting a possible explanation for the recent results of Reux et al in JET (2015 Nucl. Fusion 55 093013)