Moscow Institute of Physics and Technology

About: Moscow Institute of Physics and Technology is a education organization based out in Dolgoprudnyy, Russia. It is known for research contribution in the topics: Laser & Large Hadron Collider. The organization has 8594 authors who have published 16968 publications receiving 246551 citations. The organization is also known as: MIPT & Moscow Institute of Physics and Technology (State University).

Divergences in maximal supersymmetric Yang-Mills theories in diverse dimensions

Abstract: The main aim of this paper is to study the scattering amplitudes in gauge field theories with maximal supersymmetry in dimensions D = 6, 8 and 10. We perform a systematic study of the leading ultraviolet divergences using the spinor helicity and on-shell momentum superspace framework. In D = 6 the first divergences start at 3 loops and we calculate them up to 5 loops, in D = 8, 10 the first divergences start at 1 loop and we calculate them up to 4 loops. The leading divergences in a given order are the polynomials of Mandelstam variables. To be on the safe side, we check our analytical calculations by numerical ones applying the alpha-representation and the dedicated routines. Then we derive an analog of the RG equations for the leading pole that allows us to get the recursive relations and construct the generating procedure to obtain the polynomials at any order of perturbation theory (PT). At last, we make an attempt to sum the PT series and derive the differential equation for the infinite sum. This equation possesses a fixed point which might be stable or unstable depending on the kinematics. Some consequences of these fixed points are discussed.

Domain Meissner state and spontaneous vortex-antivortex generation in the ferromagnetic superconductor EuFe2(As0.79P0.21)2

Abstract: The interplay between superconductivity and magnetism is one of the oldest enigmas in physics. Usually, the strong exchange field of ferromagnet suppresses singlet superconductivity via the paramagnetic effect. In EuFe2(As0.79P0.21)2, a material that becomes not only superconducting at 24.2 K but also ferromagnetic below 19 K, the coexistence of the two antagonistic phenomena becomes possible because of the unusually weak exchange field produced by the Eu subsystem. We demonstrate experimentally and theoretically that when the ferromagnetism adds to superconductivity, the Meissner state becomes spontaneously inhomogeneous, characterized by a nanometer-scale striped domain structure. At yet lower temperature and without any externally applied magnetic field, the system locally generates quantum vortex-antivortex pairs and undergoes a phase transition into a domain vortex-antivortex state characterized by much larger domains and peculiar Turing-like patterns. We develop a quantitative theory of this phenomenon and put forth a new way to realize superconducting superlattices and control the vortex motion in ferromagnetic superconductors by tuning magnetic domains—unprecedented opportunity to consider for advanced superconducting hybrids.

Accessing thermal conductivity of complex compounds by machine learning interatomic potentials

Abstract: While lattice thermal conductivity is an important parameter for many technological applications, its calculation is a time-consuming task, especially for compounds with a complex crystal structure. In this paper, we solve this problem using machine learning interatomic potentials. These potentials trained on the density functional theory results and provide an accurate description of lattice dynamics. Additionally, active learning was applied to significantly reduce the number of expensive quantum-mechanical calculations required for training and increases reliability of the potential. The ${\mathrm{CoSb}}_{3}$ skutterudite was considered as an example, and the solution of the Boltzmann transport equation for phonons was compared with the Green-Kubo method. We demonstrated that accurate and reliable potentials can be obtained by performing just a few hundred quantum-mechanical calculations. The potentials reproduce not only the vibrational spectrum, but also the lattice thermal conductivity, as calculated by various methods.

Global Modeling of Radiatively Driven Accretion of Metals from Compact Debris Disks onto White Dwarfs

Abstract: Recent infrared observations have revealed the presence of compact (radii R ?) debris disks around more than a dozen metal-rich white dwarfs (WDs), likely produced by a tidal disruption of asteroids. Accretion of high-Z material from these disks may account for the metal contamination of these WDs. It was previously shown using local calculations that the Poynting-Robertson (PR) drag acting on the dense, optically thick disk naturally drives metal accretion onto the WD at the typical rate ?g?s?1. Here we extend this local analysis by exploring the global evolution of the debris disk under the action of the PR drag for a variety of assumptions about the disk properties. We find that massive disks (mass 1020 g), which are optically thick to incident stellar radiation, inevitably give rise to metal accretion at rates . The magnitude of and its time evolution are determined predominantly by the initial pattern of the radial distribution of the debris (i.e., ring-like versus disk-like) but not by the total mass of the disk. The latter determines only the disk lifetime, which can be several Myr or longer. The evolution of an optically thick disk generically results in the development of a sharp outer edge of the disk. We also find that the low-mass ( 1020 g), optically thin disks exhibit and evolve on a characteristic timescale ~105-106 yr, independent of their total mass.