Results for "Andrii Sotnikov"

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Effects of anisotropy in simple lattice geometries on many-body properties of ultracold fermions in optical latticesMay 11 2015Nov 01 2015We study the effects of anisotropic hopping amplitudes on quantum phases of ultracold fermions in optical lattices described by the repulsive Fermi-Hubbard model. In particular, using dynamical mean-field theory (DMFT) we investigate the dimensional crossover ... More
Suppression and revival of long-range ferromagnetic order in the multiorbital Fermi-Hubbard modelFeb 08 2018By means of dynamical mean-field theory allowing for complete account of SU(2) rotational symmetry of interactions between spin-1/2 particles, we observe a strong effect of suppression of ferromagnetic order in the multiorbital Fermi-Hubbard model in ... More
Magnetic field dependence and the possibility of filtering ultraslow light pulses in atomic gases with Bose-Einstein condensatesOct 28 2010This paper studies theoretically the ultraslow light phenomenon in Bose-Einstein condensates of alkali-metal atoms. The description is based on the linear approach that is developed in the framework of the Green function formalism. It is pointed out that ... More
Perspectives of optical lattices with state-dependent tunneling in approaching quantum magnetism in the presence of the external harmonic trapping potentialSep 17 2015Feb 08 2016We study theoretically potential advantages of two-component mixtures in optical lattices with state-dependent tunneling for approaching long-range-order phases and detecting easy-axis antiferromagnetic correlations. While we do not find additional advantages ... More
Critical entropies and magnetic-phase-diagram analysis of ultracold three-component fermionic mixtures in optical latticesJun 25 2015Aug 25 2015We study theoretically many-body equilibrium magnetic phases and corresponding thermodynamic characteristics of ultracold three-component fermionic mixtures in optical lattices described by the SU(3)-symmetric single-band Hubbard model. Our analysis is ... More
Orbital magnetism of ultracold fermionic gases in a lattice: dynamical mean-field approachFeb 25 2016May 29 2016We study finite-temperature properties of ultracold four-component mixtures of alkaline-earth-like atoms in optical lattices that can be effectively described by the two-band spin-$1/2$ Hubbard model including the Hund's exchange coupling term. Our main ... More
Field-induced exciton condensation in LaCoO3Apr 07 2016Jul 27 2016Motivated by recent observation of magnetic field induced transition in LaCoO3 we study the effect of external field in systems close to instabilities towards spin-state ordering and exciton condensation. We show that, while in both cases the transition ... More
Role of temperature effects in the phenomenon of ultraslow electromagnetic pulses in Bose-Einstein condensates of alkali-metal atomsNov 17 2009We study the temperature dependence of optical properties of dilute gases of alkali-metal atoms in the state with Bose-Einstein condensates. The description is constructed in the framework of the microscopic approach that is based on the Green-functions ... More
Magnetic ordering of three-component ultracold fermionic mixtures in optical latticesFeb 14 2014Jun 03 2014We study finite-temperature magnetic phases of three-component mixtures of ultracold fermions with repulsive interactions in optical lattices with simple cubic or square geometry by means of dynamical mean-field theory (DMFT). We focus on the case of ... More
Propagation of relativistic charged particles in ultracold atomic gases with Bose-Einstein condensatesNov 23 2010Jan 15 2011We study theoretically some effects produced by a propagation of the charged particles in dilute gases of alkali-metal atoms in the state with Bose-Einstein condensates. The energy change of the high-speed (relativistic) particle that corresponds to the ... More
Green-function method in the theory of ultraslow electromagnetic waves in an ideal gas with Bose-Einstein condensatesJan 16 2009We propose a microscopic approach describing the interaction of an ideal gas of hydrogenlike atoms with a weak electromagnetic field. This approach is based on the Green-function formalism and an approximate formulation of the method of second quantization ... More
Magnetic phases of mass- and population-imbalanced ultracold fermionic mixtures in optical latticesJan 08 2013May 06 2013We study magnetic phases of two-component mixtures of ultracold fermions with repulsive interactions in optical lattices in the presence of both hopping and population imbalance by means of dynamical mean-field theory (DMFT). It is shown that these mixtures ... More
Advantages of Mass-Imbalanced Ultracold Fermionic Mixtures for Approaching Quantum Magnetism in Optical LatticesMar 21 2012Aug 13 2012We study magnetic phases of two-component mixtures of ultracold fermions with repulsive interactions in optical lattices in the presence of hopping imbalance. Our analysis is based on dynamical mean-field theory (DMFT) and its real-space generalization ... More
Multi-interval Sturm-Liouville boundary-value problems with distributional potentialsAug 24 2015We study the multi-interval boundary-value Sturm-Liouville problems with distributional potentials. For the corresponding symmetric operators boundary triplets are found and the constructive descriptions of all self-adjoint, maximal dissipative and maximal ... More
Periodic Riemannian manifold with preassigned gaps in spectrum of Laplace-Beltrami operatorMay 12 2011Oct 31 2011It is known (E.L. Green (1997), O. Post (2003)) that for an arbitrary $m\in\mathbb{N}$ one can construct a periodic non-compact Riemannian manifold $M$ with at least $m$ gaps in the spectrum of the corresponding Laplace-Beltrami operator $-\Delta_M$. ... More
Periodic elliptic operators with asymptotically preassigned spectrumJan 18 2012Feb 03 2012We deal with operators in $\mathbb{R}^n$ of the form $$\mathbf{A}=-{1\over \mathbf{b}(x)}\sum\limits_{k=1}^n\ds{\partial\over\partial x_k}(\mathbf{a}(x){\partial \over\partial x_k})$$ where $\mathbf{a}(x),\mathbf{b}(x)$ are positive, bounded and periodic ... More
Miniversal deformations of pairs of symmetric formsApr 13 2011We give a miniversal deformation of each pair of symmetric matrices $(A,B)$ under congruence; that is, a normal form with minimal number of independent parameters to which all matrices $(A+E,B+E')$ close to $(A,B)$ can be reduced by congruence transformations ... More
Continuous counterparts of Poisson and binomial distributions and their propertiesMar 24 2013On the basis of integral representations of Poisson and binomial distribution functions via complete and incomplete Euler \Gamma- and B-functions, we introduce and discuss continuous counterparts of the Poisson and binomial distributions. The former turns ... More
Studies of correlations between measurements of jet observablesSep 22 2016We present a method for calculation of statistical correlations between measured jet observables in high energy collisions. The method is compared to sampling based methods used in the past. The case of measurements of jet rates in $e^+e^-$ collisions ... More
Optimal conditions for high-fidelity dispersive readout of a qubit with a photon-number-resolving detectorDec 29 2015Feb 27 2016We determine the optimal parameters for a simple and efficient scheme of dispersive readout of a qubit. Depending on the qubit state (ground or excited), the resonance of a cavity is shifted either to the red or to the blue side. Qubit state is inferred ... More
UHECRs deflections in the IRAS PSCz catalogue based models of extragalactic magnetic fieldNov 22 2006We present an investigation of the propagation of Ultra High Energy Cosmic Rays (UHECRs) in extragalactic magnetic field (EGMF). We use the IRAS PSCz catalogue in order to reconstruct EGMF taking into account power-law dependence between the magnetic ... More
Miniversal deformations of pairs of skew-symmetric matrices under congruenceApr 13 2011Jun 10 2016Miniversal deformations for pairs of skew-symmetric matrices under congruence are constructed. To be precise, for each such a pair $(A,B)$ we provide a normal form with a minimal number of independent parameters to which all pairs of skew-symmetric matrices ... More
Homogenization of spectral problem on Riemannian manifold consisting of two domains connected by many tubesNov 17 2010Dec 18 2010The paper deals with the asymptotic behavior as $\eps\to 0$ of the spectrum of Laplace-Beltrami operator $\Delta\e$ on the Riemannian manifold $M\e$ ($\mathrm{\dim} M\e=N\geq 2$) depending on a small parameter $\eps>0$. $M\e$ consists of two perforated ... More
Honest confidence sets in nonparametric IV regression and other ill-posed modelsNov 09 2016This paper provides novel methods for inference in a very general class of ill-posed models in econometrics, encompassing the nonparametric instrumental regression, different functional regressions, and the deconvolution. I focus on uniform confidence ... More
A nitrogen-vacancy spin based molecular structure microscope using multiplexed projection reconstructionMay 12 2015Methods and techniques to measure and image beyond the state-of-the-art have always been influential in propelling basic science and technology. Because current technologies are venturing into nanoscopic and molecular-scale fabrication, atomic-scale measurement ... More
Regularization of binomial differential equations with singular coefficientsJun 16 2011We propose a regularization of the formal differential expression of order $m \geqslant 3$ $$ l(y) = i^my^{(m)}(t) + q(t)y(t), \,t \in (a, b), $$ applying quasi-derivatives. The distribution coefficient $q$ is supposed to have an antiderivative $Q \in ... More
Regularization of singular Sturm-Liouville equationsFeb 23 2010Jul 08 2010Paper deals with the singular Sturm-Liouville expressions $$l(y) = -(py')' + qy$$ on a finite interval with coefficients $$q = Q', \quad 1/p, Q/p, Q^2/p \in L_1,$$ where derivative of the function $Q$ is understood in the sense of distributions. Due to ... More
Input-to-state stability of nonlinear impulsive systemsDec 21 2012We prove that impulsive systems, which possess an ISS Lyapunov function, are ISS for time sequences satisfying the fixed dwell-time condition. If an ISS Lyapunov function is the exponential one, we provide a stronger result, which guarantees uniform ISS ... More
Input-to-state stability of infinite-dimensional control systemsFeb 15 2012Sep 01 2012We develop tools for investigation of input-to-state stability (ISS) of infinite-dimensional control systems. We show that for certain classes of admissible inputs the existence of an ISS-Lyapunov function implies the input-to-state stability of a system. ... More
On the spectrum of narrow Neumann waveguide with periodically distributed $δ'$ trapsMay 06 2014We analyze a family of singular Schr\"odinger operators describing a Neumann waveguide with a periodic array of singular traps of a $\delta'$ type. We show that in the limit when perpendicular size of the guide tends to zero and the $\delta'$ interactions ... More
Neumann spectral problem in a domain with very corrugated boundarySep 16 2014Jan 06 2015Let $\Omega\subset\mathbb{R}^n$ be a bounded domain. We perturb it to a domain $\Omega^\varepsilon$ attaching a family of small protuberances with "room-and-passage"-like geometry ($\varepsilon>0$ is a small parameter). Peculiar spectral properties of ... More
Gaps in the spectrum of the Neumann Laplacian generated by a system of periodically distributed trapJan 14 2013The article deals with a convergence of the spectrum of the Neumann Laplacian in a periodic unbounded domain $\Omega^\varepsilon$ depending on a small parameter $\varepsilon>0$. The domain has the form $\Omega^\varepsilon=\mathbb{R}^n\setminus S^\varepsilon$, ... More
Note on Ramsey theorem for posets with linear extensionsAug 18 2016In this note we consider a Ramsey type result for partially ordered sets. In particular, we give an alternative short proof of a theorem for a posets with multiple linear extensions recently obtained by Solecki and Zhao.
Relaxation of Blazar Induced Pair Beams in Cosmic VoidsAug 08 2012May 28 2013The stability properties of a low density ultra relativistic pair beam produced in the intergalactic medium by multi-TeV gamma-ray photons from blazars are analyzed. The problem is relevant for probes of magnetic field in cosmic voids through gamma-ray ... More
Evidence for strong extragalactic magnetic fields from Fermi observations of TeV blazarsJun 17 2010Magnetic fields in galaxies are produced via the amplification of seed magnetic fields of unknown nature. The seed fields, which might exist in their initial form in the intergalactic medium, were never detected. We report a lower bound $B\ge 3\times ... More
Construction of Lyapunov functions for interconnected parabolic systems: an iISS approachOct 12 2014This paper is devoted to two issues. One is to provide Lyapunov-based tools to establish integral input-to-state stability (iISS) and input-to-state stability (ISS) for some classes of nonlinear parabolic equations. The other is to provide a stability ... More
Theory for entanglement of electrons dressed with circularly polarized light in Graphene and three-dimensional topological insulatorsMay 30 2013We have formulated a theory for investigating the conditions which are required to achieve entangled states of electrons on graphene and three-dimensional (3D) topological insulators (TIs). We consider the quantum entanglement of spins by calculating ... More
An upper bound for the size of a $k$-uniform intersecting family with covering number $k$Apr 16 2016Let $r(k)$ denote the maximum number of edges in a $k$-uniform intersecting family with covering number $k$. Erd\H{o}s and Lov\'asz proved that $ \lfloor k! (e-1) \rfloor \leq r(k) \leq k^k.$ Frankl, Ota, and Tokushige improved the lower bound to $r(k) ... More
Neutrinos from Extra-Large Hadron Collider in the Milky WayDec 04 2014Jun 24 2015Neutrino telescope IceCube has recently discovered astrophysical neutrinos with energies in the TeV-PeV range. We use the data of Fermi gamma-ray telescope to demonstrate that the neutrino signal has significant contribution from the Milky Way galaxy. ... More
Microlensing constraint on the size of the gamma-ray emission region in blazar B0218+357Jul 04 2015Context. Observations of the effect of microlensing in gravitationally lensed quasars could potentially be used to study the structure of the source on distance scales down to the size of the supermassive black hole powering the quasar activity. Aims. ... More
Dwell-time conditions for robust stability of impulsive systemsFeb 15 2012Dec 21 2012We prove that impulsive systems, which possess an ISS Lyapunov function, are ISS for impulse time sequences, which satisfy the fixed dwell-time condition. If the ISS Lyapunov function is the exponential one, we provide stronger result, which guarantees ... More
Characterizations of integral input-to-state stability for bilinear systems in infinite dimensionsJun 10 2014Mar 12 2016For bilinear infinite-dimensional dynamical systems, we show the equivalence between uniform global asymptotic stability and integral input-to-state stability. We provide two proofs of this fact. One applies to general systems over Banach spaces. The ... More
Resolvent convergence of Sturm-Liouville operators with singular potentialsJan 23 2010In this paper we consider the Sturm-Liuoville operator in the Hilbert space $L_2$ with the singular complex potential of $W^{-1}_2$ and two-point boundary conditions. For this operator we give sufficient conditions for norm resolvent approximation by ... More
Multidimensional Thermoelasticity for Nonsimple Materials -- Well-Posedness and Long-Time BehaviorMay 06 2016An initial-boundary value problem for the multidimensional type III thermoelaticity for a nonsimple material with a center of symmetry is considered. In the linear case, the well-posedness with and without Kelvin-Voigt and/or frictional damping in the ... More
Gaps in the spectrum of a periodic quantum graph with periodically distributed $δ'$-type interactionsFeb 16 2015We consider a family of quantum graphs $\{(\Gamma,\mathcal{A}_\varepsilon)\}_{\varepsilon>0}$, where $\Gamma$ is a $\mathbb{Z}^n$-periodic metric graph and the periodic Hamiltonian $\mathcal{A}_\varepsilon$ is defined by the operation $-\varepsilon^{-1} ... More
Fast variability of gamma-ray emission from supermassive black hole binary OJ 287Nov 17 2010Nov 18 2010We report the discovery of fast variability of gamma-ray flares from blazar OJ 287. This blazar is known to be powered by binary system of supermassive black holes. The observed variability time scale T_var < 3-10 hr is much shorter than the light crossing ... More
High energy gamma rays from the massive black hole in the Galactic CenterAug 17 2004Accreting black holes are believed to be sites of possible particle acceleration with favorable conditions also for effective gamma-ray production. However, because of photon-photon pair production, only low energy (MeV) gamma-rays can escape these compact ... More
Variability of gamma-ray emission from blazars on the black hole timescalesApr 03 2013We investigate the variability properties of blazars in the GeV band using the data of the Fermi/LAT telescope. We find that blazars exhibit variability on the scales down to the minimal timescale resolvable by Fermi, which is a function of the peak photon ... More
Spectral properties of elliptic operator with double-contrast coefficients near a hyperplaneApr 09 2014Oct 20 2015In this paper we study the asymptotic behaviour as $\varepsilon\to 0$ of the spectrum of the elliptic operator $\mathcal{A}^\varepsilon=-{1\over b^\varepsilon}\mathrm{div}(a^\varepsilon\nabla)$ posed in a bounded domain $\Omega\subset\mathbb{R}^n$ $(n ... More
Spectrum of a singularly perturbed periodic thin waveguideAug 01 2016We consider a family $\{\Omega^\varepsilon\}_{\varepsilon>0}$ of periodic domains in $\mathbb{R}^2$ with waveguide geometry and analyse spectral properties of the Neumann Laplacian $-\Delta_{\Omega^\varepsilon}$ on $\Omega^\varepsilon$. The waveguide ... More
Partial redistribution in 3D non-LTE radiative transfer in solar atmosphere modelsJun 16 2016Resonance spectral lines such as H I Ly {\alpha}, Mg II h&k, and Ca II H&K that form in the solar chromosphere are influenced by the effects of 3D radiative transfer as well as partial redistribution (PRD). So far no one has modeled these lines including ... More
What Players do with the Ball: A Physically Constrained Interaction ModelingNov 19 2015Dec 01 2015Tracking the ball is critical for video-based analysis of team sports. However, it is difficult, especially in low-resolution images, due to the small size of the ball, its speed that creates motion blur, and its often being occluded by players. In this ... More
Role Played by Surface Plasmons on Plasma Instability in Composite Layered StructuresOct 10 2014We demonstrate the engineering of a source of radiation from growing surface plasmons (charge density oscillations) in a composite nano-system. The considered hybrid nano-structure consists of a thick layer of a conducting substrate on whose surface a ... More
Quantum interference and contact effects in dangling bond loops on H-Si(100) surfacesJun 23 2015We perform electronic structure and quantum transport studies of dangling bond loops created on H-passivated Si(100) surfaces and connected to carbon nanoribbon leads. We model loops with straight and zigzag topologies as well as with varying lenght with ... More
A high-temperature expansion method for calculating paramagnetic exchange interactionsJan 13 2016The method for calculating the isotropic exchange interactions in the paramagnetic phase is proposed. It is based on the mapping of the high-temperature expansion of the spin-spin correlation function calculated for the Heisenberg model onto Hubbard Hamiltonian ... More
Scanning Gate Microscopy of Kondo Dots: Fabry-Pérot Interferences and Thermally Induced RingsMay 01 2013We study the conductance of an electron interferometer formed in a two dimensional electron gas between a nanostructured quantum contact and the charged tip of a scanning gate microscope. Measuring the conductance as a function of the tip position, thermally ... More
Decaying dark matter search with NuSTAR deep sky observationsJul 25 2016We present the results of the search for decaying dark matter with particle mass in the 6-40 keV range with NuSTAR deep observations of COSMOS and ECDFS empty sky fields. We show that main contribution to the decaying dark matter signal from the Milky ... More
Direct and inverse approximation theorems of $2π$-periodic functions by Taylor--Abel--Poisson meansSep 30 2016We obtain direct and inverse approximation theorems of $2\pi$-periodic functions by Taylor--Abel--Poisson operators in the integral metric.
Lyapunov small-gain theorems for networks of not necessarily ISS hybrid systemsOct 05 2016We prove a novel Lyapunov-based small-gain theorem for networks of $ n \geq 2 $ hybrid systems which are not necessarily input-to-state stable. This result unifies and extends several small-gain theorems for hybrid and impulsive systems proposed in the ... More
Combined analysis of charm-quark fragmentation-fraction measurementsSep 03 2015Jul 21 2016A summary of measurements of the fragmentation of charm quarks into a specific hadron is given. Measurements performed in photoproduction and deep inelastic scattering in $e^{\pm}p$, $pp$ and $e^+e^-$ collisions are compared, using up-to-date branching ... More
Triangle-free graphs with the maximum number of cyclesJan 06 2015Mar 21 2015It is shown that for $n\geq 141$, among all triangle-free graphs on $n$ vertices, the complete equibipartite graph is the unique triangle-free graph with the greatest number of cycles.
Formally self-adjoint quasi-differential operators and boundary value problemsMay 08 2012Jan 04 2013We develop the machinery of boundary triplets for one-dimensional operators generated by formally self-adjoint quasi-differential expression of arbitrary order on a finite interval. The technique are then used to describe all maximal dissipative, accumulative ... More
Temperature-dependent collective effects for silicene, germanene and monolayer black phosphorusMay 27 2016We have calculated numerically electron exchange, correlation energies and dynamical polarization function for newly discovered silicene, germanene and black phosphorus (BP), consisting of puckered layers of elemental phosphorus atoms, broadening the ... More
A simple method for characterization of the magnetic field in an ion trap using Be+ ionsOct 06 2014We demonstrate a simple method for the determination of the magnetic field in an ion trap using laser-cooled Be+ ions. The method is not based on magnetic resonance and thus does not require delivering radiofrequency (RF) radiation to the trap. Instead, ... More
Approaches to the Intelligent Subject SearchApr 09 2015This article presents main results of the pilot study of approaches to the subject information search based on automated semantic processing of mass scientific and technical data. The authors focus on technology of building and qualification of search ... More
Electrically Reconfigurable Optical Metamaterial Based on Colloidal Dispersion of Metal Nano-Rods in Dielectric FluidDec 06 2009Dec 29 2009Optical metamaterials capture the imagination with breathtaking promises of nanoscale resolution in imaging and invisibility cloaking. We demonstrate an approach to construct a metamaterial in which metallic nanorods, of dimension much smaller than the ... More
Engineering semiconductor hybrids for sensingOct 14 2014The effect of screening of the coulomb interaction between two layers of two-dimensional electrons, such as in graphene, by a highly doped semiconducting substrate is investigated. We employ the random-phase approximation to calculate the dispersion equation ... More
Modeling of the Vela complex including the Vela supernova remnant, the binary system gamma2 Velorum, and the Gum nebulaNov 04 2010We study the geometry and dynamics of the Vela complex including the Vela supernova remnant (SNR), the binary system gamma2 Velorum and the Gum nebula. We show that the Vela SNR belongs to a subclass of non-Sedov adiabatic remnants in a cloudy interstellar ... More
The ZEUS long term data preservation projectJul 07 2016The ZEUS data preservation (ZEUS DP) project assures continued access to the data and documentation related to the experiment. It aims to provide the ability to continue the generation of valuable scientific results from these data in the future. This ... More
Bimeron nanoconfined designJan 24 2018We report on the stabilization of the topological bimeron excitations in confined geometries. The Monte Carlo simulations for a ferromagnet with a strong Dzyaloshinskii-Moriya interaction revealed the formation of a mixed skyrmion-bimeron phase. The vacancy ... More
Low missing mass, single- and double diffraction dissociation at the LHCNov 26 2012Low missing mass, single- and double diffraction dissociation is calculated for the LHC energies from a dual-Regge model, dominated by a Pomeron Regge pole exchange. The model reproduces the rich resonance structure in the low missing mass Mx region. ... More
Revealing Hofstadter Spectrum for Graphene in a Periodic PotentialMar 25 2014We calculate the energy bands for graphene monolayers when electrons move through a periodic electrostatic potential in the presence of a uniform perpendicular magnetic field. We clearly demonstrate the quantum fractal nature of the energy bands at reasonably ... More
Anomalous Photon-Assisted Tunneling in GrapheneJul 28 2011We investigated the Dirac electrons transmission through a potential barrier in the presence of circularly polarized light. An anomalous photon-assisted enhanced transmission is predicted and explained in a comparison with the well-known Klein paradox. ... More
Operating the Cloud from Inside OutSep 21 2013Virtual machine images and instances (VMs) in cloud computing centres are typically designed as isolation containers for applications, databases and networking functions. In order to build complex distributed applications, multiple virtual machines must ... More
Opening up and control of spectral gaps of the Laplacian in periodic domainsAug 19 2013Dec 20 2014The main result of this work is as follows: for arbitrary pairwise disjoint finite intervals $(\alpha_j,\beta_j)\subset[0,\infty)$, $j=1,\dots,m$ and for arbitrary $n\geq 2$ we construct the family of periodic non-compact domains $\{\Omega^\varepsilon\subset\mathbb{R}^n\}_{\varepsilon>0}$ ... More
Coulomb Excitations for a Short Linear Chain of Metallic ShellsJan 03 2015A self-consistent-field theory is given for the electronic collective modes of a chain containing a finite number, $N$, of Coulomb-coupled spherical two-dimensional electron gases (S2DE's) arranged with their centers along a straight line, simulating ... More
Novel properties of graphene in the presence of energy gap: optics, transport and mobility studiesAug 18 2014Aug 27 2014We review the transmission of Dirac electrons through a potential barrier in the presence of circularly polarized light. A different type of transmission is demonstrated and explained. Perfect transmission for nearly head-on collision in inffnite graphene ... More
Modeling Anisotropic Plasmon Excitations in Self-Assembled FullerenesFeb 14 2014The plasmon excitations in Coulomb-coupled spherical two-dimensional electron gases (S2DEGs) reveal an interesting dependence on the displacement vector between the centers of the spheres with respect to the axis of quantization for the angular momentum ... More
Effects of periodic scattering potential on Landau quantization and ballistic transport of electrons in grapheneSep 26 2013A two-dimensional periodic array of scatterers has been introduced to a single layer of graphene in the presence of an external magnetic field perpendicular to the graphene layer. The eigenvalue equation for such a system has been solved numerically to ... More
Spectral analysis of a class of Schroedinger operators exhibiting a parameter-dependent spectral transitionOct 31 2015We analyze two-dimensional Schr\"odinger operators with the potential $|xy|^p - \lambda (x^2+y^2)^{p/(p+2)}$ where $p\ge 1$ and $\lambda\ge 0$, which exhibit an abrupt change of its spectral properties at a critical value of the coupling constant $\lambda$. ... More
Computational efficiency of staggered Wilson fermions: A first lookDec 11 2013Dec 17 2013Results on the computational efficiency of 2-flavor staggered Wilson fermions compared to usual Wilson fermions in a quenched lattice QCD simulation on $16^3\times32$ lattice at $\beta=6$ are reported. We compare the cost of inverting the Dirac matrix ... More
Stability of interconnected impulsive systems with and without time-delays using Lyapunov methodsNov 12 2010Feb 22 2012In this paper we consider input-to-state stability (ISS) of impulsive control systems with and without time-delays. We prove that if the time-delay system possesses an exponential Lyapunov-Razumikhin function or an exponential Lyapunov-Krasovskii functional, ... More
Plasmon Excitations for Encapsulated GrapheneJan 07 2016Mar 29 2016We have developed an analytical formulation to calculate the plasmon dispersion relation for a two-dimensional layer which is encapsulated within a narrow spatial gap between two bulk half-space plasmas. This is based on a solution of the inverse dielectric ... More
Temperature-dependent Plasmons and Their Damping Rates for Graphene with a Finite Energy BandgapApr 17 2015We obtained numerical and closed-form analytic expressions for finite-temperature plasmon dispersion relations for intrinsic graphene in the presence of a finite energy gap in the energy spectrum. The calculations were carried out using the random-phase ... More
Anisotropic plasmon-coupling dimerization of a pair of spherical electron gasesSep 27 2013Feb 01 2014We have discovered a novel feature in the plasmon excitations for a pair of Coulomb-coupled non- concentric spherical two-dimensional electron gases (S2DEGs). Our results show that the plasmon excitations for such pairs depend on the orientation with ... More
Photon dressed electronic states in topological insulators: Tunneling and conductanceMay 24 2012The surface bound electronic states of three-dimensional topological insulators, as well as the edge states in two-dimensional topological insulators, are investigated in the presence of a circularly polarized light. The strong coupling between electrons ... More
Fermi/LAT observations of 1ES 0229+200: implications for extragalactic magnetic fields and background lightDec 12 2011Jan 24 2012We report the observation in the GeV band of the blazar 1ES 0229+200, which over recent years has become one the primary sources used to put constraints on the Extragalactic Background Light (EBL) and Extragalactic Magnetic Field (EGMF). We derive constraints ... More
Electronic properties of closed cage nanometer-size spherical graphitic particlesJan 14 2013We investigate the localization of charged particles by the image potential of spherical shells, such as fullerene buckyballs. These "spherical image states" exist within surface potentials formed by the competition between the attractive image potential ... More
Plasmon dissipation in gapped-graphene open systems at finite temperatureOct 08 2015Numerical and closed-form analytic expressions for plasmon dispersion relations and rates of dissipation are first obtained at finite-temperatures for free-standing gapped graphene. These closed-system results are generalized to an open system with Coulomb ... More
Surface Plasmon Instability Leading to Emission of RadiationOct 28 2014We propose a new energy conversion approach from a dc electric field to a terahertz wave based on hybrid semiconductors by combining two-dimensional (2D) crystalline layers and a thick conducting material with possible applications as a source of coherent ... More
Evolution of Primordial Magnetic Fields from Phase TransitionsDec 04 2012Apr 11 2013We consider the evolution of primordial magnetic fields generated during cosmological, electroweak or QCD, phase transitions. We assume that the magnetic field generation can be described as an injection of magnetic energy to cosmological plasma at a ... More
Integrability for the Full Spectrum of Planar AdS/CFT IIFeb 25 2009Jan 29 2010Using the thermodynamical Bethe ansatz method we derive an infinite set of integral non-linear equations for the spectrum of states/operators in AdS/CFT. The Y-system conjectured in arXiv:0901.3753 for the spectrum of all operators in planar N=4 SYM theory ... More
Non-local Plasma Spectrum of Graphene Interacting with a Thick ConductorDec 22 2014Self-consistent field theory is used to obtain the non-local plasmon dispersion relation of monolayer graphene which is Coulomb-coupled to a thick conductor. We calculate numerically the undamped plasmon excitation spectrum for arbitrary wave number. ... More
Scanning Gate Microscopy of Quantum Contacts Under Parallel Magnetic Field: Beating Patterns Between Spin-Split Transmission Peaks or Channel OpeningsJul 25 2014Mar 11 2015We study the conductance $g$ of an electron interferometer created in a two dimensional electron gas between a nanostructured contact and the depletion region induced by the charged tip of a scanning gate microscope. Using non-interacting models, we study ... More
Miniversal deformations of matrices of bilinear formsApr 20 2010Dec 01 2011V.I. Arnold [Russian Math. Surveys 26 (2) (1971) 29-43] constructed a miniversal deformation of matrices under similarity; that is, a simple normal form to which not only a given square matrix A but all matrices B close to it can be reduced by similarity ... More
Electronic torsional sound in linear atomic chains: chemical energy transport at 1000 km/sFeb 17 2016Mar 17 2016We investigate entirely electronic torsional vibrational modes in linear cumulene chains. The carbon nuclei of a cumulene are positioned along the primary axis so they can participate only in transverse and longitudinal motions. However, the interatomic ... More
Tailoring single-cycle electromagnetic pulses in the 2-9 THz frequency range using DAST/SiO2 multilayer structures pumped at Ti:sapphire wavelengthAug 22 2014We present a numerical parametric study of single-cycle electromagnetic pulse generation in a DAST/SiO2 multilayer structure via collinear optical rectification of 800 nm femtosecond laser pulses. It is shown that modifications of the thicknesses of the ... More
Voltage-Controlled Nano-Scale Reconfigurable Magnonic CrystalJul 27 2016A nano-scale reconfigurable magnonic crystal is designed using voltage-controlled perpendicular magnetic anisotropy (PMA) in ferromagnetic-dielectric hetero-structures. A periodic array of gate metallic stripes is placed on top of a MgO/Co structure in ... More
Bond Model and Group Theory of Second Harmonic Generation in GaAs(001)Aug 06 2014Sep 12 2014A comprehensive analysis of second harmonic generation (SHG) in a diatomic zincblende crystal based on the Simplified Bond Hyperpolarizability Model (SBHM), Group Theory (GT) is presented. The third rank tensor between the two approaches are compared ... More
VapeTracker: Tracking Vapor Consumption to Help E-cigarette Users QuitMar 31 2016Despite current controversy over e-cigarettes as a smoking cessation aid, we present early work based on a web survey (N=249) that shows that some e-cigarette users (46.2%) want to quit altogether, and that behavioral feedback that can be tracked can ... More