cometadata/datacite-rtg-text-other-reclassification-records huggingface dataset:
Quantum phase transitions in three-leg spin tubes
Creators: name: Charrier, D.
name: Capponi, S.
name: Oshikawa, M.
name: Pujol, P.
Publisher: name: arXiv
Year: 2010
Subjects: subject: Strongly Correlated Electrons (cond-mat.str-el)
subject: FOS: Physical sciences

description: We investigate the properties of a three-leg quantum spin tube using several techniques such as the density matrix renormalization group method, strong coupling approaches and the non linear sigma model. For integer spins S, the model proves to exhibit a particularly rich phase diagram consisting of an ensemble of 2S phase transitions. They can be accurately identified by the behavior of a non local string order parameter associated to the breaking of a hidden symmetry in the Hamiltonian. The nature of these transitions are further elucidated within the different approaches. We carry a detailed DMRG analysis in the specific cases S = 1. The numerical data confirm the existence of two Haldane phases with broken hidden symmetry separated by a trivial singlet state. The study of the gap and of the von Neumann entropy suggest a first order phase transition but at the close proximity of a tricritical point separating a gapless and a first order transition line in the phase diagram of the quantum spin tube.
description: 20 pages, 18 figures
Open Issues on the Synthesis of Evolved Stellar Populations at Ultraviolet Wavelengths
Creators: name: Chavez, Miguel
name: Bertone, Emanuele
Publisher: name: arXiv
Year: 2011
Subjects: subject: Cosmology and Nongalactic Astrophysics (astro-ph.CO)
subject: FOS: Physical sciences

description: In this paper we briefly review three topics that have motivated our (and others') investigations in recent years within the context of evolutionary population synthesis techniques. These are: The origin of the FUV up-turn in elliptical galaxies, the age-metallicity degeneracy, and the study of the mid-UV rest-frame spectra of distant red galaxies. We summarize some of our results and present a very preliminary application of a UV grid of theoretical spectra in the analysis of integrated properties of aged stellar populations. At the end, we concisely suggest how these topics can be tackled once the World Space Observatory enters into operation in the midst of this decade.
description: 8 pages, 4 figures, accepted for publication in Astrophysics & Space Science, UV Universe special issue
Threat assessment of a possible Vehicle-Born Improvised Explosive Device using DSmT
Creators: name: Dezert, Jean
name: Smarandache, Florentin
Publisher: name: arXiv
Year: 2010
Subjects: subject: Artificial Intelligence (cs.AI)
subject: FOS: Computer and information sciences

description: This paper presents the solution about the threat of a VBIED (Vehicle-Born Improvised Explosive Device) obtained with the DSmT (Dezert-Smarandache Theory). This problem has been proposed recently to the authors by Simon Maskell and John Lavery as a typical illustrative example to try to compare the different approaches for dealing with uncertainty for decision-making support. The purpose of this paper is to show in details how a solid justified solution can be obtained from DSmT approach and its fusion rules thanks to a proper modeling of the belief functions involved in this problem.
description: 26 pages
Time-resolved charge detection in graphene quantum dots
Creators: name: Guettinger, J.
name: Seif, J.
name: Stampfer, C.
name: Capelli, A.
name: Ensslin, K.
name: Ihn, T.
Publisher: name: arXiv
Year: 2011
Subjects: subject: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
subject: FOS: Physical sciences

description: We present real-time detection measurements of electron tunneling in a graphene quantum dot. By counting single electron charging events on the dot, the tunneling process in a graphene constriction and the role of localized states are studied in detail. In the regime of low charge detector bias we see only a single time-dependent process in the tunneling rate which can be modeled using a Fermi-broadened energy distribution of the carriers in the lead. We find a non-monotonic gate dependence of the tunneling coupling attributed to the formation of localized states in the constriction. Increasing the detector bias above 2 mV results in an increase of the dot-lead transition rate related to back-action of the charge detector current on the dot.
description: 8 pages, 6 figures
Key Generation in Wireless Sensor Networks Based on Frequency-selective Channels - Design, Implementation, and Analysis
Creators: name: Wilhelm, Matthias
name: Martinovic, Ivan
name: Schmitt, Jens B.
Publisher: name: arXiv
Year: 2010
Subjects: subject: Cryptography and Security (cs.CR)
subject: FOS: Computer and information sciences

description: Key management in wireless sensor networks faces several new challenges. The scale, resource limitations, and new threats such as node capture necessitate the use of an on-line key generation by the nodes themselves. However, the cost of such schemes is high since their secrecy is based on computational complexity. Recently, several research contributions justified that the wireless channel itself can be used to generate information-theoretic secure keys. By exchanging sampling messages during movement, a bit string can be derived that is only known to the involved entities. Yet, movement is not the only possibility to generate randomness. The channel response is also strongly dependent on the frequency of the transmitted signal. In our work, we introduce a protocol for key generation based on the frequency-selectivity of channel fading. The practical advantage of this approach is that we do not require node movement. Thus, the frequent case of a sensor network with static motes is supported. Furthermore, the error correction property of the protocol mitigates the effects of measurement errors and other temporal effects, giving rise to an agreement rate of over 97%. We show the applicability of our protocol by implementing it on MICAz motes, and evaluate its robustness and secrecy through experiments and analysis.
description: Submitted to IEEE Transactions on Dependable and Secure Computing
Wireless adiabatic power transfer
Creators: name: Rangelov, A. A.
name: Suchowski, H.
name: Silberberg, Y.
name: Vitanov, N. V.
Publisher: name: arXiv
Year: 2010
Subjects: subject: Quantum Physics (quant-ph)
subject: FOS: Physical sciences

description: We propose a technique for efficient mid-range wireless power transfer between two coils, by adapting the process of adiabatic passage for a coherently driven two-state quantum system to the realm of wireless energy transfer. The proposed technique is shown to be robust to noise, resonant constraints, and other interferences that exist in the neighborhood of the coils.
description: 11 pages, 6 figures
Chern number spins of Mn acceptor magnets in GaAs
Creators: name: Strandberg, T. O.
name: Canali, C. M.
name: MacDonald, A. H.
Publisher: name: arXiv
Year: 2010
Subjects: subject: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
subject: FOS: Physical sciences

description: We determine the effective total spin $J$ of local moments formed from acceptor states bound to Mn ions in GaAs by evaluating their magnetic Chern numbers. We find that when individual Mn atoms are close to the sample surface, the total spin changes from $J = 1$ to $J = 2$, due to quenching of the acceptor orbital moment. For Mn pairs in bulk, the total $J$ depends on the pair orientation in the GaAs lattice and on the separation between the Mn atoms. We point out that Berry curvature variation as a function of local moment orientation can profoundly influence the quantum spin dynamics of these magnetic entities.
description: 4 pages, 3 figures
Electron transport and anisotropy of the upper critical magnetic field in a Ba0.68K0.32Fe2As2 single crystals
Creators: name: Gasparov, V. A.
name: Wolff-Fabris, F.
name: Sun, D. L.
name: Lin, C. T.
name: Wosnitza, J.
Publisher: name: arXiv
Year: 2010
Subjects: subject: Superconductivity (cond-mat.supr-con)
subject: FOS: Physical sciences
subject: F.2.2; I.2.7
subject: 81-05

description: Early work on the iron-arsenide compounds supported the view, that a reduced dimensionality might be a necessary prerequisite for high-Tc superconductivity. Later, however, it was found that the zero-temperature upper critical magnetic field, Hc2(0), for the 122 iron pnictides is in fact rather isotropic. Here, we report measurements of the temperature dependence of the electrical resistivity, Γ(T), in Ba0.5K0.5Fe2As2 and Ba0.68K0.32Fe2As2 single crystals in zero magnetic field and for Ba0.68K0.32Fe2As2 as well in static and pulsed magnetic fields up to 60 T. We find that the resistivity of both compounds in zero field is well described by an exponential term due to inter-sheet umklapp electron-phonon scattering between light electrons around the M point to heavy hole sheets at the Γpoint in reciprocal space. From our data, we construct an H-T phase diagram for the inter-plane (H || c) and in-plane (H || ab) directions for Ba0.68K0.32Fe2As2. Contrary to published data for underdoped 122 FeAs compounds, we find that Hc2(T) is in fact anisotropic in optimally doped samples down to low temperatures. The anisotropy parameter, γ = Habc2/Hcc2, is about 2.2 at Tc. For both field orientations we find a concave curvature of the Hc2 lines with decreasing anisotropy and saturation towards lower temperature. Taking into account Pauli spin paramagnetism we perfectly can describe Hc2(T) and its anisotropy.
description: 7 pages, 3 figures
Heavy Squarks at the LHC
Creators: name: Fan, JiJi
name: Krohn, David
name: Mosteiro, Pablo
name: Thalapillil, Arun M.
name: Wang, Lian-Tao
Publisher: name: arXiv
Year: 2011
Subjects: subject: High Energy Physics - Phenomenology (hep-ph)
subject: FOS: Physical sciences

description: The LHC, with its seven-fold increase in energy over the Tevatron, is capable of probing regions of SUSY parameter space exhibiting qualitatively new collider phenomenology. Here we investigate one such region in which first generation squarks are very heavy compared to the other superpartners. We find that the production of these squarks, which is dominantly associative, only becomes rate-limited at mSquark > 4(5) TeV for L~10(100) fb-1. However, discovery of this scenario is complicated because heavy squarks decay primarily into a jet and boosted gluino, yielding a dijet-like topology with missing energy (MET) pointing along the direction of the second hardest jet. The result is that many signal events are removed by standard jet/MET anti-alignment cuts designed to guard against jet mismeasurement errors. We suggest replacing these anti-alignment cuts with a measurement of jet substructure that can significantly extend the reach of this channel while still removing much of the background. We study a selection of benchmark points in detail, demonstrating that mSquark= 4(5) TeV first generation squarks can be discovered at the LHC with L~10(100)fb-1.
Knowledge Graph Implementation and Contextual, Graph-based Learning Path Recommendation Roadmap for the Personalized Learning Environment in the OSCAR Project
Creators: name: Weber, Christian
name: Abu-Rasheed, Hasan
Publisher: name: Zenodo
Year: 2022
Subjects: edoer
personalized learning
knowledge graph
artificial intelligence
online education

description: In the scope of OSCAR project's personalized learning environment (eDoer), student decisions about their learning paths are supported with a recommender system. The recommendation provides the user with suggestions about topics and learning materials to study, in order to gain skills that enable them to perform a corresponding job. The knowledge graph based recommender system is designed to utilize the collected data about users, jobs, skills, topics, and OERs, in which the eDoer platform is organized into, in order to predict the relations between a certain user and the skills, topics or OERs that enables them to reach their pre-defined learning goals best. The focus on the graph not only enables contextualized decisions, but also provides the structural richness to provide multi-element recommendations as learning paths. More information on the project: http://oscar-ai.eu/ Learning and mentoring platform: http://edoer.eu/
description: The OSCAR project and this deliverable was supported by the European Commission Erasmus Plus programme. Project id: 2020-1-DE01-KA203-005713
Mentoring function implementation in the personalised learning environment of the OSCAR project
Creators: name: Tavakoli, Mohammadreza
name: Faraji, Abdolali
name: Kismihók, Gábor
Publisher: name: Zenodo
Year: 2022
Subjects: edoer
online mentoring
personalised learning
learning platform
artificial intelligence

description: This document describes the first version of the mentoring service for the OSCAR project . It is designed and implemented in the eDoer open, personalised learning platform, powered by Artificial Intelligence (AI). More information on the project: http://oscar-ai.eu/ Learning and mentoring platform: http://edoer.eu/
description: The OSCAR project and this deliverable was supported by the European Commission Erasmus Plus programme. Project id: 2020-1-DE01-KA203-005713
Recent news and results in the computation of NLO processes with new techniques
Creators: name: Pittau, Roberto
Publisher: name: arXiv
Year: 2011
Subjects: subject: High Energy Physics - Phenomenology (hep-ph)
subject: FOS: Physical sciences

description: I illustrate new techniques and recently obtained results in the computation of perturbative QCD processes at the NLO accuracy
description: 6 pages, 2 figures, 3 tables, contribution to the proceedings of the 10th Hellenic School on Elementary Particle Physics and Gravity, Corfu 2010
An Infrared Nebula Associated with Delta Cephei: Evidence of Mass Loss?
Creators: name: Marengo, M.
name: Evans, N. R.
name: Barmby, P.
name: Matthews, L. D.
name: Bono, G.
name: Welch, D. L.
name: Romaniello, M.
name: Huelsman, D.
name: Su, K. Y. L.
name: Fazio, G. G.
Publisher: name: arXiv
Year: 2011
Subjects: subject: Solar and Stellar Astrophysics (astro-ph.SR)
subject: FOS: Physical sciences

description: We present the discovery of an infrared nebula around the Cepheid prototype delta Cephei and its hot companion HD 213307. Large scale (~2.1x10^4 AU) nebulosity is detected at 5.8, 8.0, 24 and 70 um. Surrounding the two stars, the 5.8 and 8.0 um emission is largely attributable to Polycyclic Aromatic Hydrocarbon (PAH) emission swept from the ISM by a wind originating from delta Cephei and/or its companion. Stochastically heated small dust grains are the most likely source of the 24 and 70 um extended emission. The 70 um emission, in particular, resembles a bow shock aligned in the direction of the proper motion of delta Cephei. This discovery supports the hypothesis that delta Cephei may be currently losing mass, at a rate in the range ~ 5x10^-9 to 6x10^-8 Mo/yr.
description: Published on The Astrophysical Journal
The Fourth Gravity Test and Quintessence Matter Field
Creators: name: Liu, Molin
name: Yu, Benhai
name: Yu, Fei
name: Gui, Yuanxing
Publisher: name: arXiv
Year: 2010
Subjects: subject: General Relativity and Quantum Cosmology (gr-qc)
subject: High Energy Physics - Phenomenology (hep-ph)
subject: High Energy Physics - Theory (hep-th)
subject: FOS: Physical sciences

description: After the previous work on gravitational frequency shift, light deflection (arXiv:1003.5296) and perihelion advance (arXiv:0812.2332), we calculate carefully the fourth gravity test, i.e. radar echo delay in a central gravity field surrounded by static free quintessence matter, in this paper. Through the Lagrangian method, we find the influence of the quintessence matter on the time delay of null particle is presence by means of an additional integral term. When the quintessence field vanishes, it reduces to the usual Schwarzschild case naturally. Meanwhile, we also use the data of the Viking lander from the Mars and Cassini spacecraft to Saturn to constrain the quintessence field. For the Viking case, the field parameter $α$ is under the order of $10^{-9}$. However, $α$ is under $10^{-18}$ for the Cassini case.
description: 9 pages, 1 figure, Eur. Phys. J. C in press
Galilean quantum gravity with cosmological constant and the extended q-Heisenberg algebra
Creators: name: Papageorgiou, G
name: Schroers, B J
Publisher: name: arXiv
Year: 2010
Subjects: subject: High Energy Physics - Theory (hep-th)
subject: General Relativity and Quantum Cosmology (gr-qc)
subject: Mathematical Physics (math-ph)
subject: FOS: Physical sciences

description: We define a theory of Galilean gravity in 2+1 dimensions with cosmological constant as a Chern-Simons gauge theory of the doubly-extended Newton-Hooke group, extending our previous study of classical and quantum gravity in 2+1 dimensions in the Galilean limit. We exhibit an r-matrix which is compatible with our Chern-Simons action (in a sense to be defined) and show that the associated bi-algebra structure of the Newton-Hooke Lie algebra is that of the classical double of the extended Heisenberg algebra. We deduce that, in the quantisation of the theory according to the combinatorial quantisation programme, much of the quantum theory is determined by the quantum double of the extended q-deformed Heisenberg algebra.
description: 22 pages
Relativistic three-body recombination with the QED vacuum
Creators: name: Hu, Huayu
name: Müller, Carsten
Publisher: name: arXiv
Year: 2011
Subjects: subject: High Energy Physics - Phenomenology (hep-ph)
subject: Atomic Physics (physics.atom-ph)
subject: Plasma Physics (physics.plasm-ph)
subject: FOS: Physical sciences

description: Electron-positron pair annihilation into a single photon is studied when a second free electron is present. Focussing on the relativistic regime, we show that the photon emitted in the three-lepton interaction may exhibit distinct angular distributions and polarization properties. Moreover, the process can dominate over two-photon annihilation in relativistic electron-positron plasmas of few-MeV temperature. An analogy with three-body recombination of electrons with ions is drawn.
description: 5 pages, 4 figures
Reply to "Comment on Anderson Transition in Disordered Graphene"
Creators: name: Amini, M.
name: Jafari, S. A.
name: Shahbazi, F.
Publisher: name: arXiv
Year: 2010
Subjects: subject: Strongly Correlated Electrons (cond-mat.str-el)
subject: FOS: Physical sciences

description: We show that the very small numeric effects discussed in the comment by Schleede et al (arXiv:1005.0497) is not the source of mobility edge predicted in graphene in our letter [Eur. Phys. Lett., 87 (2009) 37002].
description: two pages, two figures
Far infrared properties of the rare-earth scandate DyScO3
Creators: name: Baldassarre, L.
name: Perucchi, A.
name: Lupi, S.
name: Dore, P.
Publisher: name: arXiv
Year: 2010
Subjects: subject: Materials Science (cond-mat.mtrl-sci)
subject: FOS: Physical sciences

description: We present reflectance measurements in the infrared region on a single crystal the rare earth scandate DyScO3. Measurements performed between room temperature and 10 K allow to determine the frequency of the infrared-active phonons, never investigated experimentally, and to get information on their temperature dependence. A comparison with the phonon peak frequency resulting from ab-initio computations is also provided. We finally report detailed data on the frequency dependence of the complex refractive index of DyScO3 in the terahertz region, which is important in the analysis of terahertz measurements on thin films deposited on DyScO3.
Monte Carlo simulations of the HP model (the "Ising model" of protein folding)
Creators: name: Li, Ying Wai
name: Wüst, Thomas
name: Landau, David P.
Publisher: name: arXiv
Year: 2011
Subjects: subject: Soft Condensed Matter (cond-mat.soft)
subject: Computational Physics (physics.comp-ph)
subject: Biomolecules (q-bio.BM)
subject: FOS: Physical sciences
subject: FOS: Biological sciences

description: Using Wang-Landau sampling with suitable Monte Carlo trial moves (pull moves and bond-rebridging moves combined) we have determined the density of states and thermodynamic properties for a short sequence of the HP protein model. For free chains these proteins are known to first undergo a collapse "transition" to a globule state followed by a second "transition" into a native state. When placed in the proximity of an attractive surface, there is a competition between surface adsorption and folding that leads to an intriguing sequence of "transitions". These transitions depend upon the relative interaction strengths and are largely inaccessible to "standard" Monte Carlo methods.
description: 6 pages, 6 figures. Article in press. To be published in Computer Physics Communications (2011)
Strong Coupling between On Chip Notched Ring Resonator and Nanoparticle
Creators: name: Wang, S.
name: Broderick, K.
name: Smith, H.
name: Yi, Y.
Publisher: name: arXiv
Year: 2010
Subjects: subject: Optics (physics.optics)
subject: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
subject: FOS: Physical sciences

description: We have demonstrated a new photonic structure to achieve strong optical coupling between nanoparticle and photonic molecule by utilizing a notched micro ring resonators. By creating a notch in the ring resonator and putting a nanoparticle inside the notch, large spectral shifts and splittings at nm scale can be achieved, compared to only pm scale observed by fiber tip evanescently coupled to the surface of microsphere, thereby significantly lowered the quality factor requirement for single nanoparticle detection. The ability for sorting the type of nanoparticles due to very different mode shift and splitting behavior of dielectric and metallic nanoparticles is also emphasized.
description: Accepted,
Magnetization Oscillation of a Spinor Condensate Induced by Magnetic Field Gradient
Creators: name: Zhang, Jie
name: Yang, Baoguo
name: Zhang, Yunbo
Publisher: name: arXiv
Year: 2011
Subjects: subject: Quantum Gases (cond-mat.quant-gas)
subject: Quantum Physics (quant-ph)
subject: FOS: Physical sciences

description: We study the spin mixing dynamics of ultracold spin-1 atoms in a weak non-uniform magnetic field with field gradient $G$, which can flip the spin from +1 to -1 so that the magnetization $m=ρ_{+}-ρ_{-}$ is not any more a constant. The dynamics of $m_F=0$ Zeeman component $ρ_{0}$, as well as the system magnetization $m$, are illustrated for both ferromagnetic and polar interaction cases in the mean-field theory. We find that the dynamics of system magnetization can be tuned between the Josephson-like oscillation similar to the case of double well, and the interesting self-trapping regimes, i.e. the spin mixing dynamics sustains a spontaneous magnetization. Meanwhile the dynamics of $ρ_0$ may be sufficiently suppressed for initially imbalanced number distribution in the case of polar interaction. A "beat-frequency" oscillation of the magnetization emerges in the case of balanced initial distribution for polar interaction, which vanishes for ferromagnetic interaction.
description: 6 pages, 5 figures, Phys. Rev. A accepted
Pervasive Algebras and Maximal Subalgebras
Creators: name: Gorkin, Pamela
name: O'Farrell, Anthony G.
Publisher: name: arXiv
Year: 2010
Subjects: subject: Functional Analysis (math.FA)
subject: FOS: Mathematics
subject: 46J10

description: A uniform algebra $A$ on its Shilov boundary $X$ is {\em maximal} if $A$ is not $C(X)$ and there is no uniform algebra properly contained between $A$ and $C(X)$. It is {\em essentially pervasive} if $A$ is dense in $C(F)$ whenever $F$ is a proper closed subset of the essential set of $A$. If $A$ is maximal, then it is essentially pervasive and proper. We explore the gap between these two concepts. We show the following: (1) If $A$ is pervasive and proper, and has a nonconstant unimodular element, then $A$ contains an infinite descending chain of pervasive subalgebras on $X$. (2) It is possible to imbed a copy of the lattice of all subsets of $\N$ into the family of pervasive subalgebras of some $C(X)$. (3) In the other direction, if $A$ is strongly logmodular, proper and pervasive, then it is maximal. (4) This fails if the word \lq strongly' is removed. We discuss further examples, involving Dirichlet algebras, $A(U)$ algebras, Douglas algebras, and subalgebras of $H^\infty(\mathbb{D})$. We develop some new results that relate pervasiveness, maximality and relative maximality to support sets of representing measures.
Accretion of a Terrestrial-Like Minor Planet by a White Dwarf
Creators: name: Melis, Carl
name: Farihi, J.
name: Dufour, P.
name: Zuckerman, B.
name: Burgasser, Adam J.
name: Bergeron, P.
name: Bochanski, J.
name: Simcoe, R.
Publisher: name: arXiv
Year: 2011
Subjects: subject: Solar and Stellar Astrophysics (astro-ph.SR)
subject: Earth and Planetary Astrophysics (astro-ph.EP)
subject: FOS: Physical sciences

description: We present optical and infrared characterization of the polluted DAZ white dwarf GALEX J193156.8+011745. Imaging and spectroscopy from the ultraviolet to the thermal infrared indicates that the white dwarf hosts excess infrared emission consistent with the presence of an orbiting dusty debris disk. In addition to the five elements previously identified, our optical echelle spectroscopy reveals chromium and manganese and enables restrictive upper limits on several other elements. Synthesis of all detections and upper limits suggests that the white dwarf has accreted a differentiated parent body. We compare the inferred bulk elemental composition of the accreted parent body to expectations for the bulk composition of an Earth-like planet stripped of its crust and mantle and find relatively good agreement. At least two processes could be important in shaping the final bulk elemental composition of rocky bodies during the late phases of stellar evolution: irradiation and interaction with the dense stellar wind.
description: 25 pages, 3 tables, 6 figures. Accepted to ApJ
Timing analysis techniques at large core distances for multi-TeV gamma ray astronomy
Creators: name: Stamatescu, V.
name: Rowell, G. P.
name: Denman, J.
name: Clay, R. W.
name: Dawson, B. R.
name: Smith, A. G. K.
name: Sudholz, T.
name: Thornton, G. J.
name: Wild, N.
Publisher: name: arXiv
Year: 2011
Subjects: subject: Instrumentation and Methods for Astrophysics (astro-ph.IM)
subject: Cosmology and Nongalactic Astrophysics (astro-ph.CO)
subject: Astrophysics of Galaxies (astro-ph.GA)
subject: High Energy Astrophysical Phenomena (astro-ph.HE)
subject: FOS: Physical sciences

description: We present an analysis technique that uses the timing information of Cherenkov images from extensive air showers (EAS). Our emphasis is on distant, or large core distance gamma-ray induced showers at multi-TeV energies. Specifically, combining pixel timing information with an improved direction reconstruction algorithm, leads to improvements in angular and core resolution as large as ~40% and ~30%, respectively, when compared with the same algorithm without the use of timing. Above 10 TeV, this results in an angular resolution approaching 0.05 degrees, together with a core resolution better than ~15 m. The off-axis post-cut gamma-ray acceptance is energy dependent and its full width at half maximum ranges from 4 degrees to 8 degrees. For shower directions that are up to ~6 degrees off-axis, the angular resolution achieved by using timing information is comparable, around 100 TeV, to the on-axis angular resolution. The telescope specifications and layout we describe here are geared towards energies above 10 TeV. However, the methods can in principle be applied to other energies, given suitable telescope parameters. The 5-telescope cell investigated in this study could initially pave the way for a larger array of sparsely spaced telescopes in an effort to push the collection area to >10 km2. These results highlight the potential of a `sparse array' approach in effectively opening up the energy range above 10 TeV.
description: Published in Astroparticle Physics
Metallic nanoparticle on micro ring resonator for bio optical detection and sensing
Creators: name: Haddadpour, Ali
name: Yi, Yasha
Publisher: name: arXiv
Year: 2010
Subjects: subject: Optics (physics.optics)
subject: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
subject: FOS: Physical sciences

description: We have investigated the unique effects of metallic nanoparticle on the ring resonator, especially multiple Au nanoparticles on the micro ring resonator with the 4-port configuration on chip. For the Au nanoparticle, because it has smaller real refractive index than air and large absorption refractive index, we found that there is a blue shift for the ring resonance wavelength, instead of red shift normally observed for dielectric nanoparticles. The drop port intensity is strongly dependent on both number and size of nanoparticles, while relatively independent on position of nanoparticles. The correlation between the penetration depth of Au and the resonance mode evanescent tail is also discussed to reveal the unique properties of Au nanoparticle to be used for detection, sensing and nano medicine.
description: Accepted
Two hard spheres in a pore: Exact Statistical Mechanics for different shaped cavities
Creators: name: Urrutia, Ignacio
Publisher: name: arXiv
Year: 2010
Subjects: subject: Statistical Mechanics (cond-mat.stat-mech)
subject: Other Condensed Matter (cond-mat.other)
subject: Mathematical Physics (math-ph)
subject: FOS: Physical sciences

description: The Partition function of two Hard Spheres in a Hard Wall Pore is studied appealing to a graph representation. The exact evaluation of the canonical partition function, and the one-body distribution function, in three different shaped pores are achieved. The analyzed simple geometries are the cuboidal, cylindrical and ellipsoidal cavities. Results have been compared with two previously studied geometries, the spherical pore and the spherical pore with a hard core. The search of common features in the analytic structure of the partition functions in terms of their length parameters and their volumes, surface area, edges length and curvatures is addressed too. A general framework for the exact thermodynamic analysis of systems with few and many particles in terms of a set of thermodynamic measures is discussed. We found that an exact thermodynamic description is feasible based in the adoption of an adequate set of measures and the search of the free energy dependence on the adopted measure set. A relation similar to the Laplace equation for the fluid-vapor interface is obtained which express the equilibrium between magnitudes that in extended systems are intensive variables. This exact description is applied to study the thermodynamic behavior of the two Hard Spheres in a Hard Wall Pore for the analyzed different geometries. We obtain analytically the external work, the pressure on the wall, the pressure in the homogeneous zone, the wall-fluid surface tension, the line tension and other similar properties.
Topics in Cubic Special Geometry
Creators: name: Bellucci, Stefano
name: Marrani, Alessio
name: Roychowdhury, Raju
Publisher: name: arXiv
Year: 2010
Subjects: subject: High Energy Physics - Theory (hep-th)
subject: FOS: Physical sciences

description: We reconsider the sub-leading quantum perturbative corrections to N=2 cubic special Kaehler geometries. Imposing the invariance under axion-shifts, all such corrections (but the imaginary constant one) can be introduced or removed through suitable, lower unitriangular symplectic transformations, dubbed Peccei-Quinn (PQ) transformations. Since PQ transformations do not belong to the d=4 U-duality group G4, in symmetric cases they generally have a non-trivial action on the unique quartic invariant polynomial I4 of the charge representation R of G4. This leads to interesting phenomena in relation to theory of extremal black hole attractors; namely, the possibility to make transitions between different charge orbits of R, with corresponding change of the supersymmetry properties of the supported attractor solutions. Furthermore, a suitable action of PQ transformations can also set I4 to zero, or vice versa it can generate a non-vanishing I4: this corresponds to transitions between "large" and "small" charge orbits, which we classify in some detail within the "special coordinates" symplectic frame. Finally, after a brief account of the action of PQ transformations on the recently established correspondence between Cayley's hyperdeterminant and elliptic curves, we derive an equivalent, alternative expression of I4, with relevant application to black hole entropy.
description: 1+39 pages
Strain modulated band gap of edge passivated armchair graphene nanoribbons
Creators: name: Peng, Xihong
name: Velasquez, Selina
Publisher: name: arXiv
Year: 2011
Subjects: subject: Computational Physics (physics.comp-ph)
subject: Materials Science (cond-mat.mtrl-sci)
subject: Quantum Physics (quant-ph)
subject: FOS: Physical sciences

description: First principles calculations were performed to study strain effects on band gap of armchair graphene nanoribbons (AGNRs)with different edge passivation, including H, O, and OH group. The band gap of the H-passivated AGNRs shows a nearly periodic zigzag variation under strain. For O and OH passivation, the zigzag patterns are significantly shifted by a modified quantum confinement due to the edges. In addition, the band gap of the O-passivated AGNRs experiences a direct-to-indirect transition with sufficient tensile strain (~5%). The indirect gap reduces to zero with further increased strain.
description: 2 tables, 4 figures
Uniform Model of Geometric Spaces
Creators: name: Popa, Alexandru
Publisher: name: arXiv
Year: 2010
Subjects: subject: Metric Geometry (math.MG)
subject: FOS: Mathematics

description: Author developed a uniform model for different spaces where distance and angle measure kinds are parameters. This model is calculus centric, but can also be used in theoretical research. It is useful in the following domains: deduction of uniform equations among geometric spaces, uniform model applied to any space, which provides an easy way to calculate distances, plane and dihedral angles of any dimension, areas and volumes as well as parallel (where applied) and orthogonal property detection, study of not yet described spaces and more.
description: published in special issue of "Acta Universitatis Apulensis", "1 Decembrie 1918" University of Alba Iulia, September 2009
Dynamic Interference Mitigation for Generalized Partially Connected Quasi-static MIMO Interference Channel
Creators: name: Ruan, Liangzhong
name: Lau, Vincent K. N.
Publisher: name: arXiv
Year: 2011
Subjects: subject: Information Theory (cs.IT)
subject: FOS: Computer and information sciences

description: Recent works on MIMO interference channels have shown that interference alignment can significantly increase the achievable degrees of freedom (DoF) of the network. However, most of these works have assumed a fully connected interference graph. In this paper, we investigate how the partial connectivity can be exploited to enhance system performance in MIMO interference networks. We propose a novel interference mitigation scheme which introduces constraints for the signal subspaces of the precoders and decorrelators to mitigate "many" interference nulling constraints at a cost of "little" freedoms in precoder and decorrelator design so as to extend the feasibility region of the interference alignment scheme. Our analysis shows that the proposed algorithm can significantly increase system DoF in symmetric partially connected MIMO interference networks. We also compare the performance of the proposed scheme with various baselines and show via simulations that the proposed algorithms could achieve significant gain in the system performance of randomly connected interference networks.
description: 30 pages, 10 figures, accepted by IEEE Transaction on Signal Processing
Operator matrices as generators of cosine operator functions
Creators: name: Mugnolo, Delio
Publisher: name: arXiv
Year: 2010
Subjects: subject: Analysis of PDEs (math.AP)
subject: FOS: Mathematics
subject: 47D05, 47H20, 35L20

description: We introduce an abstract setting that allows to discuss wave equations with time-dependent boundary conditions by means of operator matrices. We show that such problems are well-posed if and only if certain perturbations of the same problems with homogeneous, time-independent boundary conditions are well-posed. As applications we discuss two wave equations in $L^p(0,1)$ and in $L^2(Ω)$ equipped with dynamical and acoustic-like boundary conditions, respectively.
New superintegrable models with position-dependent mass from Bertrand's Theorem on curved spaces
Creators: name: Ballesteros, Angel
name: Enciso, Alberto
name: Herranz, Francisco J.
name: Ragnisco, Orlando
name: Riglioni, Danilo
Publisher: name: arXiv
Year: 2010
Subjects: subject: Mathematical Physics (math-ph)
subject: Exactly Solvable and Integrable Systems (nlin.SI)
subject: FOS: Physical sciences

description: A generalized version of Bertrand's theorem on spherically symmetric curved spaces is presented. This result is based on the classification of (3+1)-dimensional (Lorentzian) Bertrand spacetimes, that gives rise to two families of Hamiltonian systems defined on certain 3-dimensional (Riemannian) spaces. These two systems are shown to be either the Kepler or the oscillator potentials on the corresponding Bertrand spaces, and both of them are maximally superintegrable. Afterwards, the relationship between such Bertrand Hamiltonians and position-dependent mass systems is explicitly established. These results are illustrated through the example of a superintegrable (nonlinear) oscillator on a Bertrand-Darboux space, whose quantization and physical features are also briefly addressed.
description: 13 pages; based in the contribution to the 28th International Colloquium on Group Theoretical Methods in Physics, Northumbria University (U.K.), 26-30th July 2010
Time evolution of high-energy emissions of low-mass stars:I. Age determination using stellar chronology with white dwarfs in wide binaries
Creators: name: Garcés, A.
name: Catalán, S.
name: Ribas, I.
Publisher: name: arXiv
Year: 2011
Subjects: subject: Solar and Stellar Astrophysics (astro-ph.SR)
subject: FOS: Physical sciences

description: Stellar ages are extremely difficult to determine and often subject to large uncertainties, especially for field low-mass stars. We plan to carry out a calibration of the decrease in high-energy emissions of low-mass GKM stars with time, and therefore precise age determination is a key ingredient. The overall goal of our research is to study the time evolution of these high-energy emissions as an essential input to studing exoplanetary atmospheres. We propose to determine stellar ages with a methodology based on wide binaries. We are interested in systems composed of a low-mass star and a white dwarf (WD), where the latter serves as a stellar chronometer for the system. We aim at obtaining reliable ages for a sample of late-type stars older than 1 Gyr. We selected a sample of wide binaries composed by a DA type WD and a GKM companion. High signal-to-noise, low-resolution spectroscopic observations were obtained for most of the WD members of the sample. Atmospheric parameters were determined by fitting the spectroscopic data to appropiate WD models. The total ages of the systems were derived by using cooling sequences, an initial-final mass relationship and evolutionary tracks, to account for the progenitor life. The spectroscopic observations have allowed us to determine ages for the binary systems using WDs as cosmochronometers. We obtained reliable ages for 27 stars between 1 and 5 Gyr, which is a range where age determination becomes difficult for field objects.
description: 10 pages, 8 figures, Accepted by A\&A 2011 March 30
Microwave-induced electron heating in the regime of radiation-induced magnetoresistance oscillations
Creators: name: Ramanayaka, A. N.
name: Mani, R. G.
name: Wegscheider, W.
Publisher: name: arXiv
Year: 2011
Subjects: subject: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
subject: FOS: Physical sciences

description: We examine the influence of microwave photoexcitation on the amplitude of Shubnikov-de Haas (SdH) oscillations in a two dimensional GaAs/AlGaAs electron system in a regime where the cyclotron frequency, $ω_{c}$, and the microwave angular frequency, $ω$, satisfy $2 ω\le ω_{c} \le 3.5 ω$. A SdH lineshape analysis indicates that increasing the incident microwave power has a weak effect on the amplitude of the SdH oscillations, in comparison to the influence of modest temperature changes on the dark-specimen SdH effect. The results indicate negligible electron heating under modest microwave photoexcitation, in good agreement with theoretical predictions.
description: 5 pages, 4 color figures
Interference and nuclear medium effects on the eta-mesic nuclear spectrum
Creators: name: Haider, Q.
name: Lon-Chang
name: Liu
Publisher: name: arXiv
Year: 2010
Subjects: subject: Nuclear Theory (nucl-th)
subject: High Energy Physics - Phenomenology (hep-ph)
subject: FOS: Physical sciences

description: The missing-mass spectrum obtained in a recoil-free transfer reaction p($^{27}$Al,$^{3}$He)$π^{-}$p'X is analyzed. We find that the observed peak structure arises from the coherent contributions from two reaction processes in the energy region corresponding to a bound eta ($η$) meson. In one of the processes the intermediate $η$ is captured by the nucleus to form the $η$-mesic nucleus $^{25}$Mg$_η$. In the other process, the $η$ does not form $η$-nucleus bound state. The interference between these two processes has caused the peak of the spectrum to appear at an $η$ binding energy stronger than the actual one. Our analysis also indicates that the data are consistent with an attractive N*(1535)-nucleus interaction at energies below the $η$N threshold.
description: 12 pages, 3 figures
Splitting and Updating Hybrid Knowledge Bases (Extended Version)
Creators: name: Slota, Martin
name: Leite, João
name: Swift, Terrance
Publisher: name: arXiv
Year: 2011
Subjects: subject: Artificial Intelligence (cs.AI)
subject: FOS: Computer and information sciences

description: Over the years, nonmonotonic rules have proven to be a very expressive and useful knowledge representation paradigm. They have recently been used to complement the expressive power of Description Logics (DLs), leading to the study of integrative formal frameworks, generally referred to as hybrid knowledge bases, where both DL axioms and rules can be used to represent knowledge. The need to use these hybrid knowledge bases in dynamic domains has called for the development of update operators, which, given the substantially different way Description Logics and rules are usually updated, has turned out to be an extremely difficult task. In [SL10], a first step towards addressing this problem was taken, and an update operator for hybrid knowledge bases was proposed. Despite its significance -- not only for being the first update operator for hybrid knowledge bases in the literature, but also because it has some applications - this operator was defined for a restricted class of problems where only the ABox was allowed to change, which considerably diminished its applicability. Many applications that use hybrid knowledge bases in dynamic scenarios require both DL axioms and rules to be updated. In this paper, motivated by real world applications, we introduce an update operator for a large class of hybrid knowledge bases where both the DL component as well as the rule component are allowed to dynamically change. We introduce splitting sequences and splitting theorem for hybrid knowledge bases, use them to define a modular update semantics, investigate its basic properties, and illustrate its use on a realistic example about cargo imports.
description: 64 pages; extended version of the paper accepted for ICLP 2011
On the inner Double-Resonance Raman scattering process in bilayer graphene
Creators: name: Mafra, D. L.
name: Moujaes, E. A.
name: Nunes, R. W.
name: Pimenta, M. A.
Publisher: name: arXiv
Year: 2010
Subjects: subject: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
subject: FOS: Physical sciences

description: The dispersion of phonons and the electronic structure of graphene systems can be obtained experimentally from the double-resonance (DR) Raman features by varying the excitation laser energy. In a previous resonance Raman investigation of graphene, the electronic structure was analyzed in the framework of the Slonczewski-Weiss-McClure (SWM) model, considering the outer DR process. In this work we analyze the data considering the inner DR process, and obtain SWM parameters that are in better agreement with those obtained from other experimental techniques. This result possibly shows that there is still a fundamental open question concerning the double resonance process in graphene systems.
description: 5 pages, 3 figures
Kinetic equilibrium and relativistic thermodynamics
Creators: name: Ván, P.
Publisher: name: arXiv
Year: 2011
Subjects: subject: General Physics (physics.gen-ph)
subject: FOS: Physical sciences

description: Relativistic thermodynamics is treated from the point of view of kinetic theory. It is shown that the generalized Jüttner distribution suggested in [1] is compatible with kinetic equilibrium. The requirement of compatibility of kinetic and thermodynamic equilibrium reveals several generalizations of the Gibbs relation where the velocity field is an independent thermodynamic variable.
description: 8 pages
Analytical Solutions to the Navier-Stokes-Poisson Equations with Density-dependent Viscosity and with Pressure
Creators: name: Hei, Yeung Ling
name: Manwai, Yuen
Publisher: name: arXiv
Year: 2010
Subjects: subject: Mathematical Physics (math-ph)
subject: FOS: Physical sciences
subject: 35B44, 35C05, 35Q85, 76D05, 85A15

description: We study some particular solutions to the Navier-Stokes-Poisson equations with density-dependent viscosity and with pressure, in radial symmetry. With extension of the previous known blowup solutions for the Euler-Poisson equations / pressureless Navier-Stokes-Poisson with density-dependent viscosity, we constructed the corresponding analytical blowup solutions for the Navier-Stokes-Poisson Equations with density-dependent viscosity and with pressure.
description: 12 pages
A High-Resolution Survey of HI Absorption toward the Central 200 pc of the Galactic Center
Creators: name: Lang, Cornelia C.
name: Goss, W. Miller
name: Cyganowski, Claudia
name: Clubb, Kelsey I.
Publisher: name: arXiv
Year: 2010
Subjects: subject: Astrophysics of Galaxies (astro-ph.GA)
subject: FOS: Physical sciences

description: We present an HI absorption survey of the central 250 pc of the Galaxy. Very Large Array (VLA) observations were made at 21 cm in the DnC and CnB configurations and have a resolution of ~15"(0.6 pc at the Galactic Center (GC) distance) and a velocity resolution of ~2.5 km/s. This study provides HI data with high spatial resolution, comparable with the many high resolution observations which have been made of GC sources over the past ten years. Here we present an overview of the HI absorption toward ~40 well-known continuum sources and a detailed comparison of the ionized, atomic and molecular components of the interstellar medium for the Sgr B, Radio Arc and Sgr C regions. In these well-known regions, the atomic gas appears to be closely correlated in both velocity and distribution to the ionized and molecular gas, indicating that it resides in photo-dissociation regions related to the HII regions in the GC. Toward the majority of the radio continuum sources, HI absorption by the 3-kpc arm is detected, constraining these sources to lie beyond a 5 kpc distance in the Galaxy.
description: 59 pages, including 41 figures; accepted for publication in Astrophysical Journal Supplement Series in December 2010