Multipartite quantum correlations: symplectic and algebraic geometry approach

We review a geometric approach to classification and examination of quantum correlations in composite systems. Since quantum information tasks are usually achieved by manipulating spin and alike systems or, in general, systems with a finite number of energy levels, classification problems are usually treated in frames of linear algebra. We proposed to shift the attention to a geometric description. Treating consistently quantum states as points of a projective space rather than as vectors in a Hilbert space we were able to apply powerful methods of differential, symplectic and algebraic geometry to attack the problem of equivalence of states with respect to the strength of correlations, or, in other words, to classify them from this point of view. Such classifications are interpreted as identification of states with `the same correlations properties' i.e. ones that can be used for the same information purposes, or, from yet another point of view, states that can be mutually transformed one to another by specific, experimentally accessible operations. It is clear that the latter characterization answers the fundamental question `what can be transformed into what \textit{via} available means?'. Exactly such an interpretations, i.e, in terms of mutual transformability can be clearly formulated in terms of actions of specific groups on the space of states and is the starting point for the proposed methods.Comment: 29 pages, 9 figures, 2 tables, final form submitted to the journa

Novel Quaternary Dilute Magnetic Semiconductor (Ga,Mn)(Bi,As): Magnetic and Magneto-Transport Investigations

Magnetic and magneto-transport properties of thin layers of the (Ga,Mn)(Bi,As) quaternary dilute magnetic semiconductor grown by the low-temperature molecular-beam epitaxy technique on GaAs substrates have been investigated. Ferromagnetic Curie temperature and magneto-crystalline anisotropy of the layers have been examined by using magneto-optical Kerr effect magnetometry and low-temperature magneto-transport measurements. Postgrowth annealing treatment has been shown to enhance the hole concentration and Curie temperature in the layers. Significant increase in the magnitude of magnetotransport effects caused by incorporation of a small amount of Bi into the (Ga,Mn)As layers revealed in the planar Hall effect (PHE) measurements, is interpreted as a result of enhanced spin-orbit coupling in the (Ga,Mn)(Bi,As) layers. Two-state behaviour of the planar Hall resistance at zero magnetic field provides its usefulness for applications in nonvolatile memory devices.Comment: 10 pages, 3 figures, to be published in the Proceedings of ICSM-2016 conferenc

Classification of Low Dimensional Lie Super-Bialgebras

A thorough analysis of Lie super-bialgebra structures on Lie super-algebras osp(1|2) and super-e(2) is presented. Combined technique of computer algebraic computations and a subsequent identification of equivalent structures is applied. In all the cases Poisson-Lie brackets on supergroups are found. Possibility of quantizing them in order to obtain quantum groups is discussed. It turns out to be straightforward for all but one structures for super-E(2) group.Comment: 15 pages, LaTe

Source excitation strategies for obtaining impulse responses in finite difference time domain room acoustics simulation

This paper considers source excitation strategies in finite difference time domain room acoustics simulations for auralization purposes. We demonstrate that FDTD simulations can be conducted to obtain impulse responses based on unit impulse excitation, this being the shortest, simplest and most efficiently implemented signal that might be applied. Single, rather than double, precision accuracy simulations might be implemented where memory use is critical but the consequence is a remarkably increased noise floor. Hard source excitation introduces a discontinuity in the simulated acoustic field resulting in a shift of resonant modes from expected values. Additive sources do not introduce such discontinuities, but instead result in a broadband offset across the frequency spectrum. Transparent sources address both of these issues and with unit impulse excitation the calculation of the compensation filters required to implement transparency is also simplified. However, both transparent and additive source excitation demonstrate solution growth problems for a bounded space. Any of these approaches might be used if the consequences are understood and compensated for, however, for room acoustics simulation the hard source is the least favourable due to the fundamental changes it imparts on the underlying geometry. These methods are further tested through the implementation of a directional sound source based on multiple omnidirectional point sources

Valence band and core levels of Ce5Ni2Si3 crystal studied by X-ray photoemission spectroscopy

The crystal of Ce5Ni2Si3 was prepared by the Czochralski method. The X-ray photoemission spectroscopy was measured for the valence band and the core levels. Based on the Ce(3d) doublet and its satellites a small value of the hybridization parameter of the f-states with the conduction electrons ¢ = 4 meV and the f-occupancy nf close to 1 were found. X-ray photoemission spectroscopy shows that the region between 0 and 3 eV is predominated by the Ni(3d) and Ce(4f) peaks. Some features of the multiplet structure of the Ce(4f) states are also visible close to the Fermi level

The Big Occulting Steerable Satellite (BOSS)

Natural (such as lunar) occultations have long been used to study sources on small angular scales, while coronographs have been used to study high contrast sources. We propose launching the Big Occulting Steerable Satellite (BOSS), a large steerable occulting satellite to combine both of these techniques. BOSS will have several advantages over standard occulting bodies. BOSS would block all but about 4e-5 of the light at 1 micron in the region of interest around the star for planet detections. Because the occultation occurs outside the telescope, scattering inside the telescope does not degrade this performance. BOSS could be combined with a space telescope at the Earth-Sun L2 point to yield very long integration times, in excess of 3000 seconds. If placed in Earth orbit, integration times of 160--1600 seconds can be achieved from most major telescope sites for objects in over 90% of the sky. Applications for BOSS include direct imaging of planets around nearby stars. Planets separated by as little as 0.1--0.25 arcseconds from the star they orbit could be seen down to a relative intensity as little as 1e-9 around a magnitude 8 (or brighter) star. Other applications include ultra-high resolution imaging of compound sources, such as microlensed stars and quasars, down to a resolution as little as 0.1 milliarcseconds.Comment: 25pages, 4 figures, uses aaspp4, rotate, and epsfig. Submitted to the Astrophysical Journal. For more details see http://erebus.phys.cwru.edu/~boss

Effect of Misfit Strain in (Ga,Mn)(Bi,As) Epitaxial Layers on their Magnetic and Magneto-Transport Properties

Effect of misfit strain in the layers of (Ga,Mn)(Bi,As) quaternary diluted magnetic semiconductor, epitaxially grown on either GaAs substrate or (In,Ga)As buffer, on their magnetic and magneto-transport properties has been investigated. High-resolution X-ray diffraction, applied to characterize the structural quality and misfit strain in the layers, proved that the layers were fully strained to the GaAs substrate or (In,Ga)As buffer under compressive or tensile strain, respectively. Ferromagnetic Curie temperature and magnetocrystalline anisotropy of the layers have been examined by using magneto-optical Kerr effect magnetometry and low-temperature magneto-transport measurements. Post-growth annealing treatment of the layers has been shown to enhance the hole concentration and Curie temperature in the layers.Comment: 8 pages, 3 figure

Fragment formation in proton induced reactions within a BUU transport model

The formation of fragments in proton-induced reactions at low relativistic energies within a combination of a covariant dynamical transport model and a statistical approach is investigated. In particular, we discuss in detail the applicability and limitations of such a hybrid model by comparing data on fragmentation at low relativistic $SIS/GSI$-energies.Comment: Revised version accepted for publication in Phys. Lett.