109 research outputs found

    Lattice-Induced Double-Valley Degeneracy Lifting in Magnetic Field in Graphene

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    We show that the recently discovered double-valley splitting of the low-lying Landau level(s) in the Quantum Hall Effect in graphene can be explained as perturbative orbital interaction of intra- and inter-valley microscopic orbital currents with a magnetic field. This effect is provided by the translational-non-invariant terms corresponding to graphene's crystallographic honeycomb symmetry but do not exist in the relativistic theory of massless Dirac Fermions in Quantum Electrodynamics. We discuss recent data in view of these results

    Features of seishe initiation in the water area near Poronaisk (Sakhalin Island)

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    The results of studying potential sources of seiche excitation energy in the water area near Poronaisk (Sakhalin Island) using natural measurement data in 2008–2009 are presented. Time series data with a duration of about three months were collected by two autonomous sea-level recorders at one-second sample rate. Spectral analyses of time series made possible to conclude that wave processes with periods from 2 to 7 hours can be classified as seiches. Possible seiche periods calculated by numerical methods are very close to the periods of seiches detected in the Terpeniya Bay. The calculated envelopes of wave processes showed a good coincidence of the peaks of seiches with a period of 7 hours and wind waves, which confirms the transfer of energy from atmospheric disturbances to the seven-hour seiche. Seiche period of 3.5 hours is shown to be equal to the period of tidal harmonic 4M7. Thus, the resonance pass of energy transmission from tidal harmonic to seiche was revealed taking into account high for marine waters q-factor equal to 11.9 at the period of 3.5 hours. The highest seiches at a period of 2.7 hours are observed on the 6-8 day after maximum of daily tide with a period of 24.68 hours, which is close to the period of lunar tide harmonic M1. The analyses of excitation factors of seiches with 2-hour period showed that the excitation energy, or at least a part of it, is provided by atmospheric disturbances. Thus, the increasing of seiche height occurs during the winds of southern directions in the Terpeniya Bay

    Instabilities and Bifurcations of Nonlinear Impurity Modes

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    We study the structure and stability of nonlinear impurity modes in the discrete nonlinear Schr{\"o}dinger equation with a single on-site nonlinear impurity emphasizing the effects of interplay between discreteness, nonlinearity and disorder. We show how the interaction of a nonlinear localized mode (a discrete soliton or discrete breather) with a repulsive impurity generates a family of stationary states near the impurity site, as well as examine both theoretical and numerical criteria for the transition between different localized states via a cascade of bifurcations.Comment: 8 pages, 8 figures, Phys. Rev. E in pres

    MOJAVE: Monitoring of Jets in Active Galactic Nuclei with VLBA Experiments. VIII. Faraday Rotation in Parsec-scale AGN Jets

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    We report observations of Faraday rotation measures for a sample of 191 extragalactic radio jets observed within the MOJAVE program. Multifrequency Very Long Baseline Array observations were carried out over 12 epochs in 2006 at four frequencies between 8 and 15 GHz. We detect parsec-scale Faraday rotation measures in 149 sources and find the quasars to have larger rotation measures on average than BL Lac objects. The median core rotation measures are significantly higher than in the jet components. This is especially true for quasars where we detect a significant negative correlation between the magnitude of the rotation measure and the de-projected distance from the core. We perform detailed simulations of the observational errors of total intensity, polarization, and Faraday rotation, and concentrate on the errors of transverse Faraday rotation measure gradients in unresolved jets. Our simulations show that the finite image restoring beam size has a significant effect on the observed rotation measure gradients, and spurious gradients can occur due to noise in the data if the jet is less than two beams wide in polarization. We detect significant transverse rotation measure gradients in four sources (0923+392, 1226+023, 2230+114, and 2251+158). In 1226+023 the rotation measure is for the first time seen to change sign from positive to negative over the transverse cuts, which supports the presence of a helical magnetic field in the jet. In this source we also detect variations in the jet rotation measure over a timescale of three months, which are difficult to explain with external Faraday screens and suggest internal Faraday rotation. By comparing fractional polarization changes in jet components between the four frequency bands to depolarization models, we find that an external purely random Faraday screen viewed through only a few lines of sight can explain most of our polarization observations, but in some sources, such as 1226+023 and 2251+158, internal Faraday rotation is needed

    ХДптОчДсĐșĐžĐč ŃˆĐŸĐș ĐČ Đ°ĐșŃƒŃˆĐ”Ń€ŃŃ‚ĐČĐ”: ĐșĐ»ĐžĐœĐžŃ‡Đ”ŃĐșОД рДĐșĐŸĐŒĐ”ĐœĐŽĐ°Ń†ĐžĐž ĐžĐ±Ń‰Đ”Ń€ĐŸŃŃĐžĐčсĐșĐŸĐč ĐŸĐ±Ń‰Đ”ŃŃ‚ĐČĐ”ĐœĐœĐŸĐč ĐŸŃ€ĐłĐ°ĐœĐžĐ·Đ°Ń†ĐžĐž Â«Đ€Đ”ĐŽĐ”Ń€Đ°Ń†ĐžŃ Đ°ĐœĐ”ŃŃ‚Đ”Đ·ĐžĐŸĐ»ĐŸĐłĐŸĐČ Đž Ń€Đ”Đ°ĐœĐžĐŒĐ°Ń‚ĐŸĐ»ĐŸĐłĐŸĐČ»

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    В ŃŃ‚Đ°Ń‚ŃŒĐ” ĐŸŃ‚Ń€Đ°Đ¶Đ”ĐœŃ‹ ĐŸŃĐœĐŸĐČĐœŃ‹Đ” ĐżĐŸĐ»ĐŸĐ¶Đ”ĐœĐžŃ ĐșĐ»ĐžĐœĐžŃ‡Đ”ŃĐșох рДĐșĐŸĐŒĐ”ĐœĐŽĐ°Ń†ĐžĐč ĐżĐŸ сДптОчДсĐșĐŸĐŒŃƒ ŃˆĐŸĐșу ĐČ аĐșŃƒŃˆĐ”Ń€ŃŃ‚ĐČĐ”, утĐČĐ”Ń€Đ¶ĐŽĐ”ĐœĐœŃ‹Ń… ĐžĐ±Ń‰Đ”Ń€ĐŸŃŃĐžĐčсĐșĐŸĐč ĐŸĐ±Ń‰Đ”ŃŃ‚ĐČĐ”ĐœĐœĐŸĐč ĐŸŃ€ĐłĐ°ĐœĐžĐ·Đ°Ń†ĐžĐ”Đč Â«Đ€Đ”ĐŽĐ”Ń€Đ°Ń†ĐžŃ Đ°ĐœĐ”ŃŃ‚Đ”Đ·ĐžĐŸĐ»ĐŸĐłĐŸĐČ ĐžÂ Ń€Đ”Đ°ĐœĐžĐŒĐ°Ń‚ĐŸĐ»ĐŸĐłĐŸĐČ» ĐČ 2022 г. АĐșŃ‚ŃƒĐ°Đ»ŃŒĐœĐŸŃŃ‚ŃŒ ĐżŃ€ĐŸĐ±Đ»Đ”ĐŒŃ‹ сĐČŃĐ·Đ°ĐœĐ° с ĐČŃ‹ŃĐŸĐșĐžĐŒĐž ĐżĐŸĐșĐ°Đ·Đ°Ń‚Đ”Đ»ŃĐŒĐž Đ»Đ”Ń‚Đ°Đ»ŃŒĐœĐŸŃŃ‚Đž ĐžÂ Đ·Đ°Đ±ĐŸĐ»Đ”ĐČĐ°Đ”ĐŒĐŸŃŃ‚Đž ĐŸŃ‚ сДпсОса О сДптОчДсĐșĐŸĐłĐŸ ŃˆĐŸĐșĐ° ĐČ аĐșŃƒŃˆĐ”Ń€ŃŃ‚ĐČĐ”. ĐŸĐŸŃĐ»Đ”ĐŽĐŸĐČĐ°Ń‚Đ”Đ»ŃŒĐœĐŸ прДЎстаĐČĐ»Đ”ĐœŃ‹ ĐŸŃĐœĐŸĐČĐœŃ‹Đ” ĐČĐŸĐżŃ€ĐŸŃŃ‹ ŃŃ‚ĐžĐŸĐ»ĐŸĐłĐžĐž, ĐżĐ°Ń‚ĐŸĐłĐ”ĐœĐ”Đ·Đ°, ĐșĐ»ĐžĐœĐžŃ‡Đ”ŃĐșĐŸĐč ĐșĐ°Ń€Ń‚ĐžĐœŃ‹, ĐŒĐ”Ń‚ĐŸĐŽĐŸĐČ Đ»Đ°Đ±ĐŸŃ€Đ°Ń‚ĐŸŃ€ĐœĐŸĐč ĐžÂ ĐžĐœŃŃ‚Ń€ŃƒĐŒĐ”ĐœŃ‚Đ°Đ»ŃŒĐœĐŸĐč ĐŽĐžĐ°ĐłĐœĐŸŃŃ‚ĐžĐșĐž, ĐŸŃĐŸĐ±Đ”ĐœĐœĐŸŃŃ‚Đž ĐżŃ€ĐžĐŒĐ”ĐœĐ”ĐœĐžŃ шĐșĐ°Đ» qSOFA, SOFA, MOEWS, SOS, MEWC, IMEWS ĐŽĐ»Ń ĐČДрОфОĐșацоо сДпсОса. Đ’Â ŃŃ‚Đ°Ń‚ŃŒĐ” прДЎстаĐČĐ»Đ”ĐœĐ° ŃŃ‚Đ°Ń€Ń‚ĐŸĐČая ĐžĐœŃ‚Đ”ĐœŃĐžĐČĐœĐ°Ń Ń‚Đ”Ń€Đ°ĐżĐžŃ (пДрĐČŃ‹Đ” 6–12 ч) Đ»Đ”Ń‡Đ”ĐœĐžŃ сДптОчДсĐșĐŸĐłĐŸ ŃˆĐŸĐșĐ° ĐČ аĐșŃƒŃˆĐ”Ń€ŃŃ‚ĐČĐ” ŃÂ ŃƒŃ‡Đ”Ń‚ĐŸĐŒ ĐŸŃĐŸĐ±Đ”ĐœĐœĐŸŃŃ‚Đ”Đč ĐŸŃ€ĐłĐ°ĐœĐžĐ·ĐŒĐ° Đ±Đ”Ń€Đ”ĐŒĐ”ĐœĐœĐŸĐč Đ¶Đ”ĐœŃ‰ĐžĐœŃ‹. ĐžĐżĐžŃĐ°ĐœĐ° ŃŃ‚Ń€Đ°Ń‚Đ”ĐłĐžŃ ĐœĐ°Đ·ĐœĐ°Ń‡Đ”ĐœĐžŃ ĐČĐ°Đ·ĐŸĐżŃ€Đ”ŃŃĐŸŃ€ĐŸĐČ (ĐœĐŸŃ€ŃĐżĐžĐœĐ”Ń„Ń€ĐžĐœ, Ń„Đ”ĐœĐžĐ»ŃŃ„Ń€ĐžĐœ, ŃĐżĐžĐœĐ”Ń„Ń€ĐžĐœ), ĐžĐœĐŸŃ‚Ń€ĐŸĐżĐœŃ‹Ń… ĐżŃ€Đ”ĐżĐ°Ń€Đ°Ń‚ĐŸĐČ (ĐŽĐŸĐ±ŃƒŃ‚Đ°ĐŒĐžĐœ), прДЎстаĐČĐ»Đ”ĐœŃ‹ Đ°ĐœŃ‚ĐžĐ±ĐžĐŸŃ‚ĐžĐșĐž ĐžÂ ĐŸĐżŃ‚ĐžĐŒĐ°Đ»ŃŒĐœŃ‹Đ” ŃŃ…Đ”ĐŒŃ‹ Đ°ĐœŃ‚ĐžĐ±Đ°ĐșŃ‚Đ”Ń€ĐžĐ°Đ»ŃŒĐœĐŸĐč тДрапОО, ĐŸŃĐŸĐ±Đ”ĐœĐœĐŸŃŃ‚Đž ĐžĐœŃ„ŃƒĐ·ĐžĐŸĐœĐœĐŸĐč о аЮъюĐČĐ°ĐœŃ‚ĐœĐŸĐč тДрапОО. ĐžĐ±ŃŃƒĐ¶ĐŽĐ”ĐœŃ‹ ĐČĐŸĐżŃ€ĐŸŃŃ‹ Ń…ĐžŃ€ŃƒŃ€ĐłĐžŃ‡Đ”ŃĐșĐŸĐłĐŸ Đ»Đ”Ń‡Đ”ĐœĐžŃ ĐŸŃ‡Đ°ĐłĐ° ĐžĐœŃ„Đ”Đșцоо ĐžÂ ĐżĐŸĐșĐ°Đ·Đ°ĐœĐžŃ ĐșÂ ĐłĐžŃŃ‚Đ”Ń€ŃĐșŃ‚ĐŸĐŒĐžĐž, а таĐșжД ĐŸŃ€ĐłĐ°ĐœĐžĐ·Đ°Ń†ĐžŃ ĐŒĐ”ĐŽĐžŃ†ĐžĐœŃĐșĐŸĐč ĐżĐŸĐŒĐŸŃ‰Đž ĐžÂ Ń€Đ”Đ°Đ±ĐžĐ»ĐžŃ‚Đ°Ń†ĐžŃ ĐżĐ°Ń†ĐžĐ”ĐœŃ‚ĐŸĐș, ĐżĐ”Ń€Đ”ĐœĐ”ŃŃˆĐžŃ… сДпсОс О сДптОчДсĐșĐžĐč ŃˆĐŸĐș. ĐžĐżĐžŃĐ°ĐœŃ‹ ĐŸŃĐœĐŸĐČĐœŃ‹Đ” ĐżŃ€ĐžĐœŃ†ĐžĐżŃ‹ ĐżŃ€ĐŸŃ„ĐžĐ»Đ°ĐșтоĐșĐž разĐČотоя сДпсОса О сДптОчДсĐșĐŸĐłĐŸ ŃˆĐŸĐșĐ° ĐČ аĐșŃƒŃˆĐ”Ń€ŃŃ‚ĐČĐ”. ĐŸŃ€Đ”ĐŽŃŃ‚Đ°ĐČĐ»Đ”ĐœŃ‹ ĐșрОтДрОО ĐșачДстĐČĐ° ĐŸĐșĐ°Đ·Đ°ĐœĐžŃ ĐŒĐ”ĐŽĐžŃ†ĐžĐœŃĐșĐŸĐč ĐżĐŸĐŒĐŸŃ‰Đž ĐżĐ°Ń†ĐžĐ”ĐœŃ‚ĐșĐ°ĐŒ с сДптОчДсĐșĐžĐŒ ŃˆĐŸĐșĐŸĐŒ ĐžÂ Đ°Đ»ĐłĐŸŃ€ĐžŃ‚ĐŒŃ‹ ĐŽĐ”ĐčстĐČĐžĐč ĐČрача про ĐŽĐžĐ°ĐłĐœĐŸŃŃ‚ĐžĐșĐ” ĐžÂ ĐžĐœŃ‚Đ”ĐœŃĐžĐČĐœĐŸĐč тДрапОО ĐżĐ°Ń†ĐžĐ”ĐœŃ‚ĐŸĐș с сДптОчДсĐșĐžĐŒ ŃˆĐŸĐșĐŸĐŒ ĐČ аĐșŃƒŃˆĐ”Ń€ŃŃ‚ĐČĐ”

    Measurement of the mass difference m(D-s(+))-m(D+) at CDF II

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    We present a measurement of the mass difference m(D-s(+))-m(D+), where both the D-s(+) and D+ are reconstructed in the phipi(+) decay channel. This measurement uses 11.6 pb(-1) of data collected by CDF II using the new displaced-track trigger. The mass difference is found to be m(D-s(+))-m(D+)=99.41+/-0.38(stat)+/-0.21(syst) MeV/c(2)

    The science case and challenges of space-borne sub-millimeter interferometry

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    Ultra-high angular resolution in astronomy has always been an important vehicle for making fundamental discoveries. Recent results in direct imaging of the vicinity of the supermassive black hole in the nucleus of the radio galaxy M87 by the millimeter VLBI system Event Horizon Telescope and various pioneering results of the Space VLBI mission RadioAstron provided new momentum in high angular resolution astrophysics. In both mentioned cases, the angular resolution reached the values of about 10–20 microarcseconds (0.05–0.1 nanoradian). Further developments towards at least an order of magnitude “sharper” values, at the level of 1 microarcsecond are dictated by the needs of advanced astrophysical studies. The paper emphasis that these higher values can only be achieved by placing millimeter and submillimeter wavelength interferometric systems in space. A concept of such the system, called Terahertz Exploration and Zooming-in for Astrophysics, has been proposed in the framework of the ESA Call for White Papers for the Voyage 2050 long term plan in 2019. In the current paper we present new science objectives for such the concept based on recent results in studies of active galactic nuclei and supermassive black holes. We also discuss several approaches for addressing technological challenges of creating a millimeter/sub-millimeter wavelength interferometric system in space. In particular, we consider a novel configuration of a space-borne millimeter/sub-millimeter antenna which might resolve several bottlenecks in creating large precise mechanical structures. The paper also presents an overview of prospective space-qualified technologies of low-noise analogue front-end instrumentation for millimeter/sub-millimeter telescopes. Data handling and processing instrumentation is another key technological component of a sub-millimeter Space VLBI system. Requirements and possible implementation options for this instrumentation are described as an extrapolation of the current state-of-the-art Earth-based VLBI data transport and processing instrumentation. The paper also briefly discusses approaches to the interferometric baseline state vector determination and synchronisation and heterodyning system. The technology-oriented sections of the paper do not aim at presenting a complete set of technological solutions for sub-millimeter (terahertz) space-borne interferometers. Rather, in combination with the original ESA Voyage 2050 White Paper, it sharpens the case for the next generation microarcsecond-level imaging instruments and provides starting points for further in-depth technology trade-off studies.</p

    4MOST: Project overview and information for the First Call for Proposals

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    We introduce the 4-metre Multi-Object Spectroscopic Telescope (4MOST), a new high-multiplex, wide-field spectroscopic survey facility under development for the four-metre-class Visible and Infrared Survey Telescope for Astronomy (VISTA) at Paranal. Its key specifications are: a large field of view (FoV) of 4.2 square degrees and a high multiplex capability, with 1624 fibres feeding two low-resolution spectrographs (R=λ/Δλ∌6500R = \lambda/\Delta\lambda \sim 6500), and 812 fibres transferring light to the high-resolution spectrograph (R∌20 000R \sim 20\,000). After a description of the instrument and its expected performance, a short overview is given of its operational scheme and planned 4MOST Consortium science; these aspects are covered in more detail in other articles in this edition of The Messenger. Finally, the processes, schedules, and policies concerning the selection of ESO Community Surveys are presented, commencing with a singular opportunity to submit Letters of Intent for Public Surveys during the first five years of 4MOST operations
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