Collapse of the critical state in superconducting niobium

Giant abrupt changes in the magnetic flux distribution in niobium foils were studied by using magneto-optical visualization, thermal and magnetic measurements. Uniform flux jumps and sometimes almost total catastrophic collapse of the critical state are reported. Results are discussed in terms of thermomagnetic instability mechanism with different development scenarios.Comment: arXiv.org produced artifacts in color images (three versions were attempts to make better images). Download clean PDF and watch video-figures at: "http://cmp.ameslab.gov/supermaglab/video/Nb.html

Spiritual and moral development of the personality in modern educational space

The culture and education are viewed as areas through which the process of the personality’s full development and formation takes place. This is the way how the human being, who is capable of the implementation and development of the experience accumulated by the mankind, is formed. The article proves the fact that education involves a person in a system of socially significant values; it forms the universal behavioural patterns and promotes the assimilation of human values. Taking into account the personality’s requests and social factors, it is extremely important for modern education to find optimal conditions for the harmonization of relations between the individual and the society, man and nature. This harmonization promotes the emergence and development of all physical and spiritual powers of the human being. Features mentioned above activate a new type of world perception and a system of values, which are impossible without understanding the ways of the modern man’s spiritual culture

Tunable Holstein model with cold polar molecules

We show that an ensemble of polar molecules trapped in an optical lattice can be considered as a controllable open quantum system. The coupling between collective rotational excitations and the motion of the molecules in the lattice potential can be controlled by varying the strength and orientation of an external DC electric field as well as the intensity of the trapping laser. The system can be described by a generalized Holstein Hamiltonian with tunable parameters and can be used as a quantum simulator of excitation energy transfer and polaron phenomena. We show that the character of excitation energy transfer can be modified by tuning experimental parameters.Comment: 5 pages, 3 figures (accepted in as a Rapid Communication in Phys.Rev.A

Associated central exclusive production of charged Higgs bosons

We propose central exclusive production of a charged Higgs boson in association with a W boson as a possible signature of certain types of extended Higgs sectors. We calculate the cross section and find that the rate at the LHC could be large enough to allow observation in some models with two Higgs doublets, where the charged Higgs and at least one of the neutral scalars can be light enough. We use the two-Higgs doublet model as a prototype and consider two distinct regions of parameter space, but we also briefly discuss the prospects for the next-to-minimal supersymmetric standard model, where the charged Higgs may very well be quite light.Comment: 9 pages, 5 figures. Minor changes, references added. Version to appear in PR

A quantitative study of quasiparticle traps using the single-Cooper-pair-transistor

We use radio-frequency reflectometry to measure quasiparticle tunneling rates in the single-Cooper-pair-transistor. Devices with and without quasiparticle traps in proximity to the island are studied. A $10^2$ to $10^3$-fold reduction in the quasiparticle tunneling rate onto the island is observed in the case of quasiparticle traps. In the quasiparticle trap samples we also measure a commensurate decrease in quasiparticle tunneling rate off the island.Comment: 4 pages, 4 fig

Vacuum Photon Splitting in Lorentz-Violating Quantum Electrodynamics

Radiative corrections arising from Lorentz violation in the fermion sector induce a nonzero amplitude for vacuum photon splitting. At one loop, the on-shell amplitude acquires both CPT-even and CPT-odd contributions forbidden in conventional electrodynamics.Comment: 4 pages, minor wording changes, references added, accepted in Physical Review Letter

Rotational predissociation of extremely weakly bound atom-molecule complexes produced by Feshbach resonance association

We study the rotational predissociation of atom - molecule complexes with very small binding energy. Such complexes can be produced by Feshbach resonance association of ultracold molecules with ultracold atoms. Numerical calculations of the predissociation lifetimes based on the computation of the energy dependence of the scattering matrix elements become inaccurate when the binding energy is smaller than the energy width of the predissociating state. We derive expressions that represent accurately the predissociation lifetimes in terms of the real and imaginary parts of the scattering length and effective range for molecules in an excited rotational state. Our results show that the predissociation lifetimes are the longest when the binding energy is positive, i.e. when the predissociating state is just above the excited state threshold.Comment: 17 pages, 5 figure

FPGA Implementation of Convolutional Neural Networks with Fixed-Point Calculations

Neural network-based methods for image processing are becoming widely used in practical applications. Modern neural networks are computationally expensive and require specialized hardware, such as graphics processing units. Since such hardware is not always available in real life applications, there is a compelling need for the design of neural networks for mobile devices. Mobile neural networks typically have reduced number of parameters and require a relatively small number of arithmetic operations. However, they usually still are executed at the software level and use floating-point calculations. The use of mobile networks without further optimization may not provide sufficient performance when high processing speed is required, for example, in real-time video processing (30 frames per second). In this study, we suggest optimizations to speed up computations in order to efficiently use already trained neural networks on a mobile device. Specifically, we propose an approach for speeding up neural networks by moving computation from software to hardware and by using fixed-point calculations instead of floating-point. We propose a number of methods for neural network architecture design to improve the performance with fixed-point calculations. We also show an example of how existing datasets can be modified and adapted for the recognition task in hand. Finally, we present the design and the implementation of a floating-point gate array-based device to solve the practical problem of real-time handwritten digit classification from mobile camera video feed

On problem of polarization tomography, I

The polarization tomography problem consists of recovering a matrix function f from the fundamental matrix of the equation $D\eta/dt=\pi_{\dot\gamma}f\eta$ known for every geodesic $\gamma$ of a given Riemannian metric. Here $\pi_{\dot\gamma}$ is the orthogonal projection onto the hyperplan $\dot\gamma^{\perp}$. The problem arises in optical tomography of slightly anisotropic media. The local uniqueness theorem is proved: a $C^1$- small function f can be recovered from the data uniquely up to a natural obstruction. A partial global result is obtained in the case of the Euclidean metric on $R^3$