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Results for "N. K. Neilson"

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Comparison of limb-darkening laws from plane-parallel and spherically-symmetric model stellar atmospheresSep 21 2011Limb-darkening is a fundamental constraint for modeling eclipsing binary and planetary transit light curves. As observations, for example from Kepler, CoRot, and Most, become more precise then a greater understanding of limb-darkening is necessary. However, ... More
A Novel Strongly Spin-Orbit Coupled Quantum Dimer Magnet: Yb2Si2O7Oct 31 2018The quantum dimer magnet (QDM) is the canonical example of "quantum magnetism". This state consists of entangled nearest-neighbor spin dimers and often exhibits a field-induced "triplon" Bose-Einstein condensate (BEC) phase. We report on a new QDM in ... More
The occurrence of classical Cepheids in binary systemsDec 10 2014Classical Cepheids, like binary stars, are laboratories for stellar evolution and Cepheids in binary systems are especially powerful ones. About one-third of Galactic Cepheids are known to have companions and Cepheids in eclipsing binary systems have ... More
Universal Features of Terahertz Absorption in Disordered MaterialsApr 07 2006Using an analytical theory, experimental terahertz time-domain spectroscopy data and numerical evidence, we demonstrate that the frequency dependence of the absorption coupling coefficient between far-infrared photons and atomic vibrations in disordered ... More
Orbital Selective Magnetism in the Spin-Ladder Iron Selenides Ba$_{1-x}$K$_{x}$Fe$_2$Se$_3$Feb 16 2012May 16 2012Here we show that the 2.80(8) {\mu}B/Fe block antiferromagnetic order of BaFe2Se3 transforms into stripe antiferromagnetic order in KFe2Se3 with a decrease in moment to 2.1(1) {\mu}B/Fe. This reduction is larger than expected from the change in electron ... More
Laguerre-Gaussian mode sorterMar 12 2018Aug 31 2018Light's spatial properties represent an infinite state space, making it attractive for applications requiring high dimensionality, such as quantum mechanics and classical telecommunications, but also inherently spatial applications such as imaging and ... More
Full-Field, Carrier-Less, Polarization-Diversity, Direct Detection Receiver based on Phase RetrievalMar 06 2019We realize dual-polarization full-field recovery using intensity only measurements and phase retrieval techniques based on dispersive elements. 30-Gbaud QPSK waveforms are transmitted over 520-km standard single-mode fiber and equalized from the receiver ... More
Neutrinos, Cosmic Rays and the MeV BandMar 13 2019The possible association of the blazar TXS 0506+056 with a high-energy neutrino detected by IceCube holds the tantalizing potential to answer three astrophysical questions: 1. Where do high-energy neutrinos originate? 2. Where are cosmic rays produced ... More
A Multi-Moded RF Delay Line Distribution System for the Next Linear ColliderSep 17 2002The Delay Line Distribution System (DLDS) is an alternative to conventional pulse compression, which enhances the peak power of rf sources while matching the long pulse of those sources to the shorter filling time of accelerator structures. We present ... More
Revisiting the fundamental properties of Cepheid Polaris using detailed stellar evolution modelsFeb 05 2014Polaris the Cepheid has been observed for centuries, presenting surprises and changing our view of Cepheids and stellar astrophysics, in general. Specifically, understanding Polaris helps anchor the Cepheid Leavitt law, but the distance must be measured ... More
VEGA/CHARA interferometric observations of Cepheids. I. A resolved structure around the prototype classical Cepheid delta Cep in the visible spectral rangeSep 23 2016The B-W method is used to determine the distance of Cepheids and consists in combining the angular size variations of the star, as derived from infrared surface-brightness relations or interferometry, with its linear size variation, as deduced from visible ... More
Metallic Carbon Nanotubes as High-Current-Gain TransistorsFeb 01 2006Jul 04 2006Low-dimensional metallic transport is at the heart of modern high-performance transistors. While the best devices are currently based on III-V heterojunction quantum-well channels, we demonstrate that much greater performance gains reside in the unique ... More
Pulsation and Mass Loss Across the HR Diagram: From OB stars to Cepheids to Red SupergiantsSep 16 2013Sep 25 2013Both pulsation and mass loss are commonly observed in stars and are important ingredients for understanding stellar evolution and structure, especially for massive stars. There is a growing body of evidence that pulsation can also drive and enhance mass ... More
A microfabricated sensor for thin dielectric layersJun 04 2007Mar 24 2008We describe a sensor for the measurement of thin dielectric layers capable of operation in a variety of environments. The sensor is obtained by microfabricating a capacitor with interleaved aluminum fingers, exposed to the dielectric to be measured. In ... More
Period change and stellar evolution of $β$ Cephei starsSep 17 2015The $\beta$ Cephei stars represent an important class of massive star pulsators probing the evolution of B-type stars and the transition from main sequence to hydrogen-shell burning evolution. By understanding $\beta$ Cep stars, we gain insights into ... More
Destabilization of the 2D conducting phase by an in-plane magnetic fieldDec 22 1998Dec 24 1998We propose a mechanism for the recently reported destabilization by an in-plane magnetic field of the conducting phase of low density electrons in 2D. We apply our self-consistent approach based on the memory function formalism to the fully spin polarized ... More
Superconductivity in correlated disordered two-dimensional electron gasOct 26 1998Oct 27 1998We calculate the dynamic effective electron-electron interaction potential for a low density disordered two-dimensional electron gas. The disordered response function is used to calculate the effective potential where the scattering rate is taken from ... More
Mixed-Valence-Driven Heavy-Fermion Behavior and Superconductivity in KNi$_2$Se$_2$Aug 16 2012Based on specific heat and magnetoresistance measurements, we report that a "heavy" electronic state exists below $T \approx$ 20 K in KNi$_2$Se$_2$, with an increased carrier mobility and enhanced effective electronic band mass, $m$* = 6$m_b$ to 18$m_b$. ... More
Convection, granulation and period jitter in classical CepheidsFeb 04 2014Analyses of recent observations of the sole classical Cepheid in the Kepler field, V1154 Cygni, found random changes of about 30 minutes in the pulsation period. These period changes challenge standard theories of pulsation and evolution because the period ... More
Central role of exchange-correlation hole in the 2D metal-insulatorJan 31 2000We show that the metal to insulator transition, whether generated by decreasing the electron density or by increasing the spin alignment, is determined by a universal functional form of the two-electron correlation function g(r). This result provides ... More
Phase diagram of the metal-insulator transition in 2D electronic systemsOct 22 1998Oct 30 1998We investigated the interdependence of the effects of disorder and carrier correlations on the metal-insulator transition in two-dimensional electronic systems. We present a quantitative metal-insulator phase diagram. Depending on the carrier density ... More
Is there a mass discrepancy in the Cepheid binary OGLE-LMC-CEP0227?Oct 30 2011Context. The Cepheid mass discrepancy, the difference between masses predicted from stellar evolution and stellar pulsation calculations, is a challenge for the understanding of stellar astrophysics. Recent models of the eclipsing binary Cepheid OGLE-LMC-CEP-0227 ... More
Magnetic order and spin dynamics in the helical magnetic system Fe$_3$PO$_4$O$_3$Jul 24 2017The 3$d$-electronic spin dynamics and the magnetic order in Fe$_3$PO$_4$O$_3$ were investigated by muon spin rotation and relaxation ($\mu$SR) and $^{57}$Fe M\"ossbauer spectroscopy. Zero-field (ZF)-$\mu$SR and $^{57}$Fe M\"ossbauer studies confirm static ... More
A xenon gas purity monitor for EXOJun 09 2011We discuss the design, operation, and calibration of two versions of a xenon gas purity monitor (GPM) developed for the EXO double beta decay program. The devices are sensitive to concentrations of oxygen well below 1 ppb at an ambient gas pressure of ... More
Limb darkening in spherical stellar atmospheresMay 01 2011(Abridged) Context. Stellar limb darkening, I({\mu} = cos{\theta}), is an important constraint for microlensing, eclipsing binary, planetary transit, and interferometric observations, but is generally treated as a parameterized curve, such as a linear-plus-square-root ... More
Modeling Stellar Atmospheres with a Spherically Symmetric Version of the Atlas Code: Testing the Code by Comparisons to Interferometric Observations and PHOENIX ModelsAug 28 2008Sep 01 2008One of the current opportunities for stellar atmospheric modeling is the interpretation of optical interferometric data of stars. Starting from the robust, open source ATLAS atmospheric code (Kurucz, 1979), we have developed a spherically symmetric code, ... More
Spherically-symmetric model stellar atmospheres and limb darkening I: limb-darkening laws, gravity-darkening coefficients and angular diameter corrections for red giant starsMay 06 2013Model stellar atmospheres are fundamental tools for understanding stellar observations from interferometry, microlensing, eclipsing binaries and planetary transits. However, the calculations also include assumptions, such as the geometry of the model. ... More
Using Limb-Darkening to Measure the Masses of Red GiantsNov 19 2010We present a novel method for measuring the masses of evolved stars from their limb-darkening observations parameterized as a linear-plus-square-root function with two coefficients. The coefficients of the law are related to integrated moments of the ... More
Determining Parameters of Cool Giant Stars by Modeling Spectrophotometric and Interferometric Observations Using the SAtlas ProgramSep 10 2008Context: Optical interferometry is a powerful tool for observing the intensity structure and angular diameter of stars. When combined with spectroscopy and/or spectrophotometry, interferometry provides a powerful constraint for model stellar atmospheres. ... More
Convective Core Overshoot & Mass Loss in Classical Cepheids: A Solution to the Mass Discrepancy?Nov 19 2010Nov 23 2010We explore the role of mass loss and convective core overshoot in the evolution of Classical Cepheids. Stellar evolution models are computed with a recipe for pulsation-driven mass loss and it is found that mass loss alone is unable to account for the ... More
Electric field modulated topological magnetoelectric effect in Bi$_2$Se$_3$Jul 04 2018Topological insulators have been predicted to exhibit a variety of interesting phenomena including a quantized magnetoelectric response and novel spintronics effects due to spin textures on their surfaces. However, experimental observation of these phenomena ... More
CHARA/MIRC observations of two M supergiants in Perseus OB1: temperature, Bayesian modeling, and compressed sensing imagingMay 15 2014Jun 11 2014Two red supergiants of the Per OB1 association, RS Per and T Per, have been observed in H band using the MIRC instrument at the CHARA array. The data show clear evidence of departure from circular symmetry. We present here new techniques specially developed ... More
On the Enhancement of Mass Loss in Cepheids Due to Radial PulsationMar 28 2008An analytical derivation is presented for computing mass-loss rates of Cepheids by using the method of Castor, Abbott, & Klein (1975) modified to include a term for momentum input from pulsation and shocks generated in the atmosphere. Using this derivation, ... More
Metal-insulator transition in disordered 2DEG including temperature effectsOct 27 1998Oct 27 1998We calculate self-consistently the mutual dependence of electron correlations and electron-defect scattering for a two dimensional electron gas at finite temperature. We employ an STLS approach to calculate the electron correlations while the electron ... More
High Temperature Superfluidity in Double Bilayer GrapheneNov 28 2012Jan 28 2013Exciton bound states in solids between electrons and holes are predicted to form a superfluid at high temperatures. We show that by employing atomically thin crystals such as a pair of adjacent bilayer graphene sheets, equilibrium superfluidity of electron-hole ... More
A simple radionuclide-driven single-ion sourceAug 20 2010We describe a source capable of producing single barium ions through nuclear recoils in radioactive decay. The source is fabricated by electroplating 148Gd onto a silicon {\alpha}-particle detector and vapor depositing a layer of BaF2 over it. 144Sm recoils ... More
Light Collection and Pulse-Shape Discrimination in Elongated Scintillator Cells for the PROSPECT Reactor Antineutrino ExperimentAug 26 2015A meter-long, 23-liter EJ-309 liquid scintillator detector has been constructed to study the light collection and pulse-shape discrimination performance of elongated scintillator cells for the PROSPECT reactor antineutrino experiment. The magnitude and ... More
Weighing Betelgeuse: Measuring the mass of alpha Orionis from stellar limb-darkeningSep 21 2011Stellar limb-darkening is an important tool for constraining the properties of a stellar atmosphere. We present a novel method for relating the fundamental stellar parameters mass and radius to limb-darkening laws using grids of spherical model stellar ... More
Representational Analysis of Extended Disorder in Atomistic Ensembles Derived from Total Scattering DataJan 20 2015Sep 02 2015With the increased availability of high intensity time-of-flight neutron and synchrotron X-ray scattering sources that can access wide ranges of momentum transfer, the pair distribution function method has become a standard analysis technique for studying ... More
Excitonic Superfluidity and Screening in Electron-Hole Bilayer SystemsAug 01 2013Feb 24 2014Superfluidity in e-h bilayers in graphene and GaAs has been predicted many times but not observed. A key problem is how to treat the screening of the Coulomb interaction for pairing. Different mean-field theories give dramatically different conclusions, ... More
Effects of density imbalance on the BCS-BEC crossover in semiconductor electron-hole bilayersOct 11 2006We study the occurrence of excitonic superfluidity in electron-hole bilayers at zero temperature. We not only identify the crossover in the phase diagram from the BCS limit of overlapping pairs to the BEC limit of non-overlapping tightly-bound pairs but ... More
Stellar Evolution with Pulsation-Driven Mass Loss: The Case of LMC CepheidsSep 21 2011The Cepheid mass discrepancy, the difference between mass estimates from stellar pulsation and stellar evolution models, is a long standing challenge for the understanding of stellar astrophysics. We discuss the current state of the mass discrepancy and ... More
SAtlas: Spherical Versions of the Atlas Stellar Atmosphere ProgramSep 10 2008Context: The current stellar atmosphere programs still cannot match some fundamental observations of the brightest stars, and with new techniques, such as optical interferometry, providing new data for these stars, additional development of stellar atmosphere ... More
Many-body electron correlations in grapheneFeb 05 2016The conduction electrons in graphene promise new opportunities to access the region of strong many-body electron-electron correlations. Extremely high quality, atomically flat two-dimensional electron sheets and quasi-one-dimensional electron nanoribbons ... More
Spherically symmetric model stellar atmospheres and limb darkening II: limb-darkening laws, gravity-darkening coefficients and angular diameter corrections for FGK dwarf starsJun 27 2013Limb darkening is a fundamental ingredient for interpreting observations of planetary transits, eclipsing binaries, optical/infrared interferometry and microlensing events. However, this modeling traditionally represents limb darkening by a simple law ... More
Using limb darkening to measure fundamental parameters of starsJul 30 2012Context. Limb darkening is an important tool for understanding stellar atmospheres, but most observations measuring limb darkening assume various parameterizations that yield no significant information about the structure of stellar atmospheres. Aims. ... More
On the Enhancement of Mass Loss in Cepheids Due to Radial Pulsation. II. The Effect of MetallicitySep 16 2008It has been observed that Cepheids in the Magellanic Clouds have lower masses for the same luminosity than those in the Milky Way. The model, from Neilson & Lester (2008), of pulsation-driven mass loss for Cepheids is applied to theoretical models of ... More
The Cepheid mass discrepancy and pulsation-driven mass lossApr 08 2011Context. A longstanding challenge for understanding classical Cepheids is the Cepheid mass discrepancy, where theoretical mass estimates using stellar evolution and stellar pulsation calculations have been found to differ by approximately 10 - 20%. Aims. ... More
Two-Component Scaling near the Metal-Insulator Bifurcation in Two-DimensionsMar 01 2003We consider a two-component scaling picture for the resistivity of two-dimensional (2D) weakly disordered interacting electron systems at low temperature with the aim of describing both the vicinity of the bifurcation and the low resistance metallic regime ... More
HARPS-N high spectral resolution observations of Cepheids I. The Baade-Wesselink projection factor of δ Cep revisitedJan 06 2017The projection factor p is the key quantity used in the Baade-Wesselink (BW) method for distance determination; it converts radial velocities into pulsation velocities. Several methods are used to determine p, such as geometrical and hydrodynamical models ... More
Characterization of large area APDs for the EXO-200 detectorJun 13 2009EXO-200 uses 468 large area avalanche photodiodes (LAAPDs) for detection of scintillation light in an ultra-low-background liquid xenon (LXe) detector. We describe initial measurements of dark noise, gain and response to xenon scintillation light of LAAPDs ... More
Dark Matter Search Results from the Complete Exposure of the PICO-60 C$_3$F$_8$ Bubble ChamberFeb 11 2019Final results are reported from operation of the PICO-60 C$_3$F$_8$ dark matter detector, a bubble chamber filled with 52 kg of C$_3$F$_8$ located in the SNOLAB underground laboratory. The chamber was operated at thermodynamic thresholds as low as 1.2 ... More
The PROSPECT Physics ProgramDec 07 2015The Precision Reactor Oscillation and Spectrum Experiment, PROSPECT, is designed to make a precise measurement of the antineutrino spectrum from a highly-enriched uranium reactor and probe eV-scale sterile neutrinos by searching for neutrino oscillations ... More
Developing a Bubble Chamber Particle Discriminator Using Semi-Supervised LearningNov 27 2018The identification of non-signal events is a major hurdle to overcome for bubble chamber dark matter experiments such as PICO-60. The current practice of manually developing a discriminator function to eliminate background events is difficult when available ... More
Spin-down of Relativistic Stars with Phase Transitions and PSR J0537-6910Apr 23 2002Feb 07 2003Using a highly accurate numerical code, we study the spin down of rotating relativistic stars, undergoing a quark deconfinement phase transition. Such phase transitions have been suggested to yield an observable signal in the braking index of spinning-down ... More
Relativistic expansion of a magnetized fluidJan 23 2010We study semi-analytical time-dependent solutions of the relativistic magnetohydrodynamic (MHD) equations for the fields and the fluid emerging from a spherical source. We assume uniform expansion of the field and the fluid and a polytropic relation between ... More
Evolutionary Self-Energy-Loss Effects in Compact Binary Systems: Importance of Rapid Rotation and of Equation of StateSep 15 2000The spin-down of a millisecond pulsar in a compact binary system leads to self-energy losses, that cause the binary's orbital period to increase (the effect being of first post-Newtonian (1PN) order). If the pulsar's period-derivative is not exceedingly ... More
Polytropic dark matter flows illuminate dark energy and accelerated expansionNov 25 2014Currently, a large amount of data implies that the matter constituents of the cosmological dark sector might be collisional. An attractive feature of such a possibility is that, it can reconcile dark matter (DM) and dark energy (DE) in terms of a single ... More
Geodesic motions versus hydrodynamic flows in a gravitating perfect fluid: Dynamical equivalence and consequencesMay 17 1999May 18 1999Stimulated by the methods applied for the observational determination of masses in the central regions of the AGNs, we examine the conditions under which, in the interior of a gravitating perfect fluid source, the geodesic motions and the general relativistic ... More
Instanton constraints in supersymmetric gauge theories II. N=2 Yang-Mills theoryMar 15 2005The analysis in previous publications of the instanton constraints required to produce a finite action of the theory is carried out also for N=2 supersymmetric Yang-Mills theory.
$D^0$-$\bar{D}^0$ mixing and CP violation results from BelleNov 08 2014We report the results on $D^0$-$\bar{D}^0$ mixing in the decays of $D^0\to K^+\pi^-$ and $D^0\to K_S^0\pi^+\pi^-$, and CP violation in $D^0\to\pi^0\pi^0$ using a data sample with an integrated luminosity of about 1~ab$^{-1}$ recorded with the Belle detector, ... More
A viscous-convective instability in laminar Keplerian thin discs. II. Anelastic approximationJun 01 2015Using the anelastic approximation of linearised hydrodynamic equations, we investigate the development of axially symmetric small perturbations in thin Keplerian discs. The sixth-order dispersion equation is derived and numerically solved for different ... More
Quasi-elastic barrier distribution as a tool for investigating unstable nucleiNov 15 2004The method of fusion barrier distribution has been widely used to interpret the effect of nuclear structure on heavy-ion fusion reactions around the Coulomb barrier. We discuss a similar, but less well known, barrier distribution extracted from large-angle ... More
Effects of finite width of excited states on heavy-ion sub-barrier fusion reactionsMay 23 1998We discuss the effects of coupling of the relative motion to nuclear collective excitations which have a finite lifetime on heavy-ion fusion reactions at energies near and below the Coulomb barrier. Both spreading and escape widths are explicitly taken ... More
Challenges at the neutron star core-crust boundaryNov 28 2004Jan 10 2005This paper has been withdrawn by the authors.
Pressure, Resistance, and Current Activation of Anisotropic Compressible Hall StatesDec 08 2000Thermodynamic and electric properties of anisotropic compressible Hall states at higher Landau levels are studied using a mean field theory on the von Neumann lattice basis. It is shown that resistances agree with the recent experiments of anisotropic ... More
Effective action and collective modes in quasi-one-dimensional spin-density-wave systemsOct 21 1999Jan 26 2000We derive the effective action describing the long-wavelength low-energy collective modes of quasi-one-dimensional spin-density-wave (SDW) systems, starting from the Hubbard model within weak coupling approximation. The effective action for the spin-wave ... More
A class of exact MHD models for astrophysical jetsFeb 05 1999This paper examines a new class of exact and self-consistent MHD solutions which describe steady and axisymmetric hydromagnetic outflows from the atmosphere of a magnetized and rotating central object with possibly an orbiting accretion disk. The plasma ... More
Systematic construction of exact MHD models for astrophysical winds and jetsDec 18 1998By a systematic method we construct general classes of exact and selfconsistent axisymmetric MHD solutions describing flows which originate at the near environment of a central gravitating astrophysical object. The unifying scheme contains two large groups ... More
Lectures on supersymmetric gauge theories and electric-magnetic dualitySep 12 1995We review some of the recent work on the dynamics of four dimensional, supersymmetric gauge theories. The kinematics are largely determined by holomorphy and the dynamics are governed by duality. The results shed light on the phases of gauge theories. ... More
Duality, Monopoles, Dyons, Confinement and Oblique Confinement in Supersymmetric SO(N_c) Gauge TheoriesMar 26 1995We study supersymmetric $SO(N_c)$ gauge theories with $N_f$ flavors of quarks in the vector representation. Among the phenomena we find are dynamically generated superpotentials with physically inequivalent branches, smooth moduli spaces of vacua, confinement ... More
Investigation of the $Λ_b \rightarrow Λ\ell^+ \ell^-$ transition in universal extra dimension using form factors from full QCDNov 25 2010Dec 29 2010Using the related form factors from full QCD which recently are available, we provide a comprehensive analysis of the $\Lambda_b \rightarrow \Lambda \ell^+ \ell^-$ transition in universal extra dimension model in the presence of a single universal extra ... More
Antiferromagnetism and single-particle properties in the two-dimensional half-filled Hubbard model: Slater vs Mott-HeisenbergDec 17 2002Jun 30 2003We study antiferromagnetism and single-particle properties in the two-dimensional half-filled Hubbard model at low temperature. Collective spin fluctuations are governed by a non-linear sigma model that we derive from the Hubbard model for any value of ... More
Monte Carlo: BasicsApr 12 2001An introduction to the basics of Monte Carlo is given. The topics covered include, sample space, events, probabilities, random variables, mean, variance, covariance, characteristic function, chebyshev inequality, law of large numbers, central limit theorem ... More
An Introduction to Monte Carlo Simulation of Statistical physics ProblemApr 10 2001Dec 17 2003A brief introduction to the technique of Monte Carlo simulations in statistical physics is presented. The topics covered include statistical ensembles random and pseudo random numbers, random sampling techniques, importance sampling, Markov chain, Metropolis ... More
Leduc-Righi effect in superconductors with nontrivial density of statesAug 27 1997Sep 09 1997Increasing of electronic thermal conductivity of superconductor in the model with nontrivial density of states was considered. The electronic thermal conductivity K(T) of SC in the presence of external magnetic field was investigated. It was shown that ... More
Parallel transport along Seifert manifolds and fractional monodromySep 22 2016We show that the Euler number of a Seifert manifold can be defined in terms of parallel transport of homology cycles along this manifold. Such point of view is motivated by the study of integrable Hamiltonian systems, where parallel transport of homology ... More
Functional Dynamics II : Syntactic StructureJul 20 1999Functional dynamics, introduced in a previous paper, is analyzed, focusing on the formation of a hierarchical rule to determine the dynamics of the functional value. To study the periodic (or non-fixed) solution, the functional dynamics is separated into ... More
On classification of projective homogeneous varieties up to motivic isomorphismJul 08 2005We give a complete classification of anisotropic projective homogeneous varieties of dimension less than 6 up to motivic isomorphism. We give several criteria for anisotropic flag varieties of type A_n to have isomorphic motives.
RejoinderAug 19 2011Rejoinder of "Impact of Frequentist and Bayesian Methods on Survey Sampling Practice: A Selective Appraisal" by J. N. K. Rao [arXiv:1108.2356]
Parallel transport along Seifert manifolds and fractional monodromySep 22 2016Oct 02 2017The notion of fractional monodromy was introduced by Nekhoroshev, Sadovski\'{i} and Zhilinski\'{i} as a generalization of standard (`integer') monodromy in the sense of Duistermaat from torus bundles to singular torus fibrations. In the present paper ... More
Growth rate of the state vector in a generalized linear stochastic system with symmetric matrixJun 16 2017The mean growth rate of the state vector is evaluated for a generalized linear stochastic second-order system with a symmetric matrix. Diagonal entries of the matrix are assumed to be independent and exponentially distributed with different means, while ... More
Unbiased gradient estimation in queueing networks with parameter-dependent routingNov 16 2012A stochastic queueing network model with parameter-dependent service times and routing mechanism, and its related performance measures are considered. An estimate of performance measure gradient is proposed, and rather general sufficient conditions for ... More
Canonical pseudo-Kähler structures on six-dimensional nilpotent Lie groupsOct 21 2013Nov 14 2013In this paper we consider left-invariant pseudo-K\"{a}hler structures on six-dimensional nilpotent Lie algebras. The explicit expressions of the canonical complex structures are calculated, and the curvature properties of the associated pseudo-K\"{a}hler ... More
Field-induced spin-density-wave phases in TMTSF organic conductors: quantization versus non-quantizationFeb 07 2003We study the magnetic-field-induced spin-density-wave (FISDW) phases in TMTSF organic conductors in the framework of the quantized nesting model. In agreement with recent suggestions, we find that the SDW wave-vector ${\bf Q}$ deviates from its quantized ... More
Spin-density-wave instabilities in the organic conductor (TMTSF)_2ClO_4: Role of anion orderingJun 12 2001Aug 28 2001We study the spin-density-wave instabilities in the quasi-one-dimensional conductor (TMTSF)_2ClO_4. The orientational order of the anions ClO_4 doubles the unit cell and leads to the presence of two electrnic bands at the Fermi level. From the Ginzburg-Landau ... More
Mott insulator to superfluid transition in the Bose-Hubbard model: a strong-coupling approachDec 08 2004Apr 15 2005We present a strong-coupling expansion of the Bose-Hubbard model which describes both the superfluid and the Mott phases of ultracold bosonic atoms in an optical lattice. By performing two successive Hubbard-Stratonovich transformations of the intersite ... More
Physics behind the minimum of relative entropy measures for correlationsMar 08 2013Jun 17 2013The relative entropy of a correlated state and an uncorrelated reference state is a reasonable measure for the degree of correlations. A key question is however which uncorrelated state to compare to. The relative entropy becomes minimal for the uncorrelated ... More
Bi-invariant metric on symplectic diffeomorphisms groupFeb 20 2014We show the existence of a weak bi-invariant symmetric nondegenerate 2-form on the symplectic diffeomorphisms group $\mathcal{D}_\omega$ of a symplectic Riemannian manifold $(M,g,\omega)$ and study its properties. We describe the Euler's equation on a ... More
Semileptonic Transition of $Σ_b \rar Σμ^+ μ^-$ in Family Non-universal $Z^\prime$ ModelJul 17 2012Jun 26 2013Using newly available form factors obtained from light cone QCD sum rules in full theory, we study the flavor changing neutral current transition of $\Sigma_b \rar \Sigma \mu^+ \mu^-$ decay in the family non-universal $Z^\prime$ model. In particular, ... More
Analysis of $Λ_b \rar Λ\ell^+ \ell^-$ transition in SM4 using form factors from Full QCDDec 22 2011Using the responsible form factors calculated via full QCD, we analyze the $\Lambda_{b}\rightarrow \Lambda \ell^{+}\ell^{-}$ transition in the standard model containing fourth generation quarks (SM4). We discuss effects of the presence of $t'$ fourth ... More
QCD nature of dark energy at finite temperature: cosmological implicationsJun 23 2015May 17 2016The Veneziano ghost field has been proposed as an alternative source of dark energy whose energy density is consistent with the cosmological observations. In this model, the energy density of QCD ghost field is expressed in terms of QCD degrees of freedom ... More
Antiferromagnetism and single-particle properties in the two-dimensional half-filled Hubbard model: a non-linear sigma model approachJul 10 2003Jun 07 2004We describe a low-temperature approach to the two-dimensional half-filled Hubbard model which allows us to study both antiferromagnetism and single-particle properties. This approach ignores amplitude fluctuations of the antiferromagnetic (AF) order parameter ... More
Exact non-magnetic ground state and residual entropy of S = 1/2 Heisenberg diamond spin latticesOct 19 2015Sep 30 2016Exactly solvable frustrated quantum spin models consisting of a diamond unit structure are presented. The ground states are characterized by tetramer-dimer states with a macroscopic degeneracy in a certain range of isotropic exchange interaction. The ... More
Quark and Lepton Flavor Mixings in the SU(5) Grand Unification TheoryNov 27 1998We explain the imbalance of the flavor mixing angles between the quark and the lepton sectors in the context of the SU(5) GUT with the see-saw mechanism. The quark masses and the CKM matrix elements are obtained by using, respectively, the Fritzsch and ... More
Mass transfer and magnetic braking in Sco X-1Nov 27 2015Sco X-1 is a low-mass X-ray binary (LMXB) that has one of the most precisely determined set of binary parameters such as the mass accretion rate, companions mass ratio and the orbital period. For this system, as well as for a large fraction of other well-studied ... More
Mapping from quasi-elastic scattering to fusion reactionsMar 06 2014The fusion barrier distribution has provided a nice representation for the channel coupling effects on heavy-ion fusion reactions at energies around the Coulomb barrier. Here we discuss how one can extract the same representation using the so called sum-of-differences ... More
Subbarrier fusion reactions and many-particle quantum tunnelingSep 28 2012Oct 17 2012Low energy heavy-ion fusion reactions are governed by quantum tunneling through the Coulomb barrier formed by a strong cancellation of the repulsive Coulomb force with the attractive nuclear interaction between the colliding nuclei. Extensive experimental ... More
On the Wong cross section and fusion oscillationsMar 26 2015We re-examine the well-known Wong formula for heavy-ion fusion cross sections. Although this celebrated formula yields almost exact results for single-channel calculations for relatively heavy systems such as $^{16}$O+$^{144}$Sm, it tends to overestimate ... More
Fusion at deep subbarrier energies: potential inversion revisitedNov 15 2008For a single potential barrier, the barrier penetrability can be inverted based on the WKB approximation to yield the barrier thickness. We apply this method to heavy-ion fusion reactions at energies well below the Coulomb barrier and directly determine ... More