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2013-03-19
Stabilization of the Gear-Grimshaw system on a periodic domain
This paper is devoted to the study of a nonlinear coupled system of two Korteweg-de Vries equations in a periodic domain under the effect of an internal damping term. The system was introduced Gear and Grimshaw to model the interactions of two-dimensional, long, internal gravity waves propagation in a stratified fluid....
1303.4759v2
2013-03-26
Current-driven domain wall motion with spin Hall effect: Reduction of threshold current density
We theoretically study the current-driven domain wall motion in the presence of both the spin Hall effect and an extrinsic pinning potential. The spin Hall effect mainly affects the damping ratio of the domain wall precession in the pinning potential. When the pinning potential is not too strong, this results in a sign...
1303.6458v1
2013-03-27
Spontaneous nucleation and dynamics of kink defects in zigzag arrays of trapped ions
The spontaneous nucleation and dynamics of topological kink defects have been studied in trapped arrays of 41-43 Yb ions. The number of kinks formed as a function of quench rate across the linear-zigzag transition is measured in the under-damped regime of the inhomogeneous Kibble-Zurek theory. The experimental results ...
1303.6723v1
2013-04-11
Transport of dipolar Bose-Einstein condensates in a one-dimensional optical lattice
We show that magnetic dipolar interactions can stabilize superfluidity in atomic gases but the dipole alignment direction required to achieve this varies, depending on whether the flow is oscillatory or continuous. If a condensate is made to oscillate through a lattice, damping of the oscillations can be reduced by ali...
1304.3250v1
2013-04-12
Mechanical signaling via nonlinear wavefront propagation in a mechanically-excitable medium
Models that invoke nonlinear wavefront propagation in a chemically excitable medium are rife in the biological literature. Indeed, the idea that wavefront propagation can serve as a signaling mechanism has often been invoked to explain synchronization of developmental processes. In this paper we suggest a new kind of s...
1304.3657v1
2013-04-15
Phase-sticking in one-dimensional Josephson Junction Chains
We studied current-voltage characteristics of long one dimensional Josephson junction chains with Josephson energy much larger than charging energy, $E_J \gg E_C$. In this regime, typical IV curves of the samples consist of a supercurrent branch at low bias voltages followed by a voltage-independent chain current branc...
1304.4046v1
2013-04-18
Nonlinear dynamical systems and bistability in linearly forced isotropic turbulence
In this letter, we present an extensive study of the linearly forced isotropic turbulence. By using analytical method, we identify two parametric choices, of which they seem to be new as far as our knowledge goes. We prove that the underlying nonlinear dynamical system for linearly forced isotropic turbulence is the ge...
1304.5019v1
2013-05-17
Nonuniversal power-law spectra in turbulent systems
Turbulence is generally associated with universal power-law spectra in scale ranges without significant drive or damping. Although many examples of turbulent systems do not exhibit such an inertial range, power-law spectra may still be observed. As a simple model for such situations, a modified version of the Kuramoto-...
1305.4111v2
2013-05-25
Phonon excitation and instabilities in biased graphene nanoconstrictions
We calculate the phonons in a graphene nanoconstriction(GNC) in the presence of a high current density. The Joule-heating, current-induced forces, and coupling to electrode phonons is evaluated using first principles nonequilibrium DFT-NEGF calculations. Close to a resonance in the electronic structure we observe a str...
1305.5907v1
2013-05-28
Optical bistability in strong-coupling cavity QED with a few atoms
We present exact numerical solutions of the damped-driven Jaynes--Cummings model adapted to describe absorptive optical bistability in the limit of a few atoms strongly coupled to a high-finesse resonator. We show that the simplifying semiclassical result for many physical quantities of interest is well reproduced by t...
1305.6460v1
2013-06-16
Mapping Between Nonlinear Schödinger Equations with Real and Complex Potentials
A mapping between stationary solutions of nonlinear Sch\"odinger equations with real and complex potentials is constructed and a set of exact solutions with real energies are obtained for a large class of complex potentials. As specific examples we consider the case of the damped dynamics of a quantum harmonic oscillat...
1306.3643v1
2013-06-16
Non-determinism in the limit of nonsmooth dynamics
Discontinuous time derivatives are used to model threshold-dependent switching in such diverse applications as dry friction, electronic control, and biological growth. In a continuous flow, a discon- tinuous derivative can generate multiple outcomes from a single initial state. Here we show that well defined solution s...
1306.3648v1
2013-06-17
Uniformly exponentially stable approximations for a class of damped systems with unbounded feedbacks
In this paper we study time semi-discrete approximations of a class of exponentially stable infinite dimensional systems with unbounded feedbacks. It has recently been proved that for time semi-discrete systems, due to high frequency spurious components, the exponential decay property may be lost as the time step tends...
1306.3798v1
2013-06-19
Purifying entanglement of noisy two-qubit states via entanglement swapping
Two qubits in pure entangled states going through separate paths and interacting with their own individual environments will gradually lose their entanglement. Here we show that the entanglement change of a two-qubit state due to amplitude damping noises can be recovered by entanglement swapping. Some initial states ca...
1306.4451v4
2013-06-19
A quasi-linear spin-torque nano-oscillator via enhanced negative feedback of power fluctuations
We report an approach to improving the performance of spin torque nano-oscillators (STNOs) that utilizes power-dependent negative feedback to achieve a significantly enhanced dynamic damping. In combination with a sufficiently slow variation of frequency with power this can result in a quasi-linear STNO, with very weak...
1306.4668v1
2013-06-29
Tkachenko polarons in vortex lattices
We analyze the properties of impurities immersed in a vortex lattice formed by ultracold bosons in the mean field quantum Hall regime. In addition to the effects of a periodic lattice potential, the impurity is dressed by collective modes with parabolic dispersion (Tkachenko modes). We derive the effective polaron mode...
1307.0144v2
2013-07-01
Wigner distribution, nonclassicality and decoherence of generalized and reciprocal binomial states
There are quantum states of light that can be expressed as finite superpositions of Fock states (FSFS). We demonstrate the nonclassicality of an arbitrary FSFS by means of its phase space distributions such as the Wigner function and the $Q$-function. The decoherence of the FSFS is studied by considering the time evolu...
1307.0452v1
2013-07-25
Vector boson excitations near deconfined quantum critical points
We show that the N\'eel states of two-dimensional antiferromagnets have low energy vector boson excitations in the vicinity of deconfined quantum critical points. We compute the universal damping of these excitations arising from spin-wave emission. Detection of such a vector boson will demonstrate the existence of eme...
1307.6860v1
2013-07-29
Theoretical Study of Spin-Torque Oscillator with Perpendicularly Magnetized Free Layer
The magnetization dynamics of spin torque oscillator (STO) consisting of a perpendicularly magnetized free layer and an in-plane magnetized pinned layer was studied by solving the Landau-Lifshitz-Gilbert equation. We derived the analytical formula of the relation between the current and the oscillation frequency of the...
1307.7427v1
2013-08-06
Radiation Reaction Effects in Cascade Scattering of Intense, Tightly Focused Laser Pulses by Relativistic Electrons
Non-linear cascade scattering of intense, tightly focused laser pulses by relativistic electrons is studied numerically in the classical approximation including the radiation damping for the quantum parameter hwx-ray/E<1 and an arbitrary radiation parameter Kai. The electron energy loss, along with its side scattering ...
1308.1608v1
2013-08-07
A general method to remove the stiffness of PDEs
A new method to remove the stiffness of partial differential equations is presented. Two terms are added to the right-hand-side of the PDE : the first is a damping term and is treated implicitly, the second is of the opposite sign and is treated explicitly. A criterion for absolute stability is found and the scheme is ...
1308.1621v1
2013-08-14
Microscopic description of nuclear vibrations: Relativistic QRPA and its extensions with quasiparticle-vibration coupling
The recent extensions of the covariant energy density functional theory with the quasiparticle-vibration coupling (QVC) are reviewed. Formulation of the Quasiparticle Random Phase Approximation (QRPA) in the relativistic framework is discussed. Self-consistent extensions of the relativistic QRPA imply the QVC which is ...
1308.3164v1
2013-08-27
Actively coupled optical waveguides
We consider light propagation through a pair of nonlinear optical waveguides with absorption, placed in a medium with power gain. The active medium boosts the in-phase component of the overlapping evanescent fields of the guides, while the nonlinearity of the guides couples it to the damped out-of-phase component creat...
1308.5862v1
2013-08-27
Collective modes in the anisotropic unitary Fermi gas and the inclusion of a backflow term
We study the collective modes of the confined unitary Fermi gas under anisotropic harmonic confinement as a function of the number of atoms. We use the equations of extended superfluid hydrodynamics, which take into account a dispersive von Weizsacker-like term in the equaton of state. We also discuss the inclusion of ...
1308.5922v1
2013-09-05
Quantum speed limit of a photon under non-Markovian dynamics
Quantum speed limit (QSL) under noise has drawn considerable attention in real quantum computational processes and quantum communication. Though non-Markovian noise is proven to be able to accelerate quantum evolution for a damped Jaynes-Cummings model, in this work we show that non-Markovianity may even slow down the ...
1309.1391v1
2013-09-07
Optomechanical effect on the Dicke quantum phase transition and quasi-particle damping in a Bose-Einstein Condensate: A new tool to measure weak force
We make a semi-classical steady state analysis of the influence of mirror motion on the quantum phase transition for an optomechanical Dicke model in the thermodynamic limit. An additional external mechanical pump is shown to modify the critical value of atom-photon coupling needed to observe the quantum phase transiti...
1309.1838v1
2013-09-14
Dynamics of the polarization of a pinned domain wall in a magnetic nanowire
We consider the dynamics of polarization of a single domain wall in a magnetic nanowire, which is strongly pinned by impurities. In this case the equation of motion for the polarization parameter does not include any other dynamical variables and is nonlinear due to magnetic anisotropy. We calculated numerically the ma...
1309.3687v1
2013-09-28
High-efficiency GHz frequency doubling without power threshold in thin-film Ni81Fe19
We demonstrate efficient second-harmonic generation at moderate input power for thin film Ni81Fe19 undergoing ferromagnetic resonance (FMR). Powers of the generated second-harmonic are shown to be quadratic in input power, with an upconversion ratio three orders of magnitude higher than that demonstrated in ferrite. Th...
1309.7483v1
2013-09-29
Magnetic shield of PMT used in DAMPE electromagnetic calorimeter
The magnetic characteristics of photomultiplier tube R5610A-01 are studied in this paper. The experimental data shows that the gain of R5610A-01 loses about 53% when the magnetic field is 3G along its +X axis. A cylinder of one-layer permalloy strip is able to reduce the effect of 3G magnetic field on the PMT's gain to...
1309.7638v4
2013-09-30
Dynamical regimes of dissipative quantum systems
We reveal several distinct regimes of the relaxation dynamics of a small quantum system coupled to an environment within the plane of the dissipation strength and the reservoir temperature. This is achieved by discriminating between coherent dynamics with damped oscillatory behavior on all time scales, partially cohere...
1309.7860v2
2013-10-01
Graphene nanoribbon based spaser
A novel type of spaser with the net amplification of surface plasmons (SPs) in doped graphene nanoribbon is proposed. The plasmons in THz region can be generated in a dopped graphene nanoribbon due to nonradiative excitation by emitters like two level quantum dots located along a graphene nanoribbon. The minimal popula...
1310.0136v1
2013-10-02
Stochastic Schrödinger Equations for Markovian and non-Markovian cases
Firstly, the Markovian stochastic Schr\"odinger equations are presented, together with their connections with the theory of measurements in continuous time. Moreover, the stochastic evolution equations are translated into a simulation algorithm, which is illustrated by two concrete examples - the damped harmonic oscill...
1310.0644v1
2013-10-15
A new tool to study real dynamics: The Convergence Plane
In this paper, the author presents a new tool, called The Convergence Plane, that allows to study the real dynamics of iterative methods whose iterations depends on one parameter in an easy and compact way. This tool can be used, inter alia, to find the elements of a family that have good convergence properties and dis...
1310.3986v1
2013-10-27
Quantum simulation of decoherence in optical waveguide lattices
We suggest that propagation of nonclassical light in lattices of optical waveguides can provide a laboratory tool to simulate quantum decoherence phenomena with high non-Markovian features. As examples, we study decoherence of optical Schr\"{o}dinger cats in a lattice that mimics a dissipative quantum harmonic oscillat...
1310.7239v1
2013-11-05
Efficient time integration methods based on operator splitting and application to the Westervelt equation
Efficient time integration methods based on operator splitting are introduced for the Westervelt equation, a nonlinear damped wave equation that arises in nonlinear acoustics as mathematical model for the propagation of sound waves in high intensity ultrasound applications. For the first-order Lie-Trotter splitting met...
1311.1224v1
2013-11-06
A new optical field state as an output of diffusion channel when the input being number state
We theoretically propose a new optical field state which is named Laguerre-polynomial-weighted chaotic field. We show that such state can be implemented, i.e., when a number state enters into a diffusion channel, the output state is just this kind of states. We solve the master equation describing the diffusion process...
1311.1275v1
2013-11-14
Chromo-Natural Model in Anisotropic Background
In this work we study the chromo-natural inflation model in the anisotropic setup. Initiating inflation from Bianchi type-I cosmology, we analyze the system thoroughly during the slow-roll inflation, from both analytical and numerical points of view. We show that the isotropic FRW inflation is an attractor of the syste...
1311.3361v2
2013-11-27
Polynomial Stability of Semigroups Generated by Operator Matrices
In this paper we study the stability properties of strongly continuous semigroups generated by block operator matrices. We consider triangular and full operator matrices whose diagonal operator blocks generate polynomially stable semigroups. As our main results, we present conditions under which also the semigroup gene...
1311.6960v1
2013-12-02
Critical Field of Spin Torque Oscillator with Perpendicularly Magnetized Free Layer
The oscillation properties of a spin torque oscillator consisting of a perpendicularly magnetized free layer and an in-plane magnetized pinned layer are studied based on an analysis of the energy balance between spin torque and damping. The critical value of an external magnetic field applied normal to the film plane i...
1312.0300v1
2013-12-09
Spin-orbit torque opposing the Oersted torque in ultrathin Co/Pt bilayers
Current-induced torques in ultrathin Co/Pt bilayers were investigated using an electrically driven FMR technique. The angle dependence of the resonances, detected by a rectification effect as a voltage, were analysed to determine the symmetries and relative magnitudes of the spin-orbit torques. Both anti-damping (Slonc...
1312.2409v1
2013-12-10
Shifted Laplacian based multigrid preconditioners for solving indefinite Helmholtz equations
Shifted Laplacian multigrid preconditioner has become a tool du jour for solving highly indefinite Helmholtz equations. The idea is to add a complex damping to the original Helmholtz operator and then apply a multigrid processing to the resulting operator using it to precondition Krylov methods, usually Bi-CGSTAB. Not ...
1312.2880v1
2013-12-12
Fidelity of Fock-state-encoded qubits subjected to continuous variable Gaussian processes
When a harmonic oscillator is under the influence of a Gaussian process such as linear damping, parametric gain, and linear coupling to a thermal environment, its coherent states are transformed into states with Gaussian Wigner function. Qubit states can be encoded in the |0> and |1> Fock states of a quantum harmonic o...
1312.3655v1
2013-12-16
Supersonic flutter analysis of flat composite panels by unified formulation
In this paper, the linear flutter characteristics of laminated composite flat panels immersed in a supersonic flow is investigated using field consistent elements within the framework of unified formulation. The influence of the aerodynamic damping on the supersonic flutter characteristics of flat composite panels is a...
1312.4233v1
2013-12-24
Fractional Entropy Decaying and the Third Law of Thermodynamics
The quantum thermodynamic property of the fractional damping system is investigated extensively. A fractional power-law decaying entropy function is revealed which presents another evidence for the validity of the third law of thermodynamics in the quantum dissipative region. Several non-trivial characters are excavate...
1401.1425v1
2014-01-09
Universal quasinormal modes of large D black holes
We show that in the limit where the number of spacetime dimensions D grows to infinity a very large class of black holes (including non-extremal, static, asymptotically flat ones, with any number of gauge-field charges, possibly coupled to dilatons) possess a universal set of quasinormal modes whose complex frequencies...
1401.1957v1
2014-01-10
Quasi PT-symmetry in passive photonic lattices
The concept of quasi-PT symmetry in optical wave guiding system is elaborated by comparing the evolution dynamics of a PT-symmetric directional coupler and a passive directional coupler. In particular we show that in the low loss regime, apart for an overall exponentially damping factor that can be compensated via a dy...
1401.2299v3
2014-01-15
Dirac Quasinormal modes of MSW black holes
In this paper we study the Dirac quasinormal modes of an uncharged 2 + 1 black hole proposed by Mandal et. al and referred to as MSW black hole in this work. The quasi- normal mode is studied using WKB approximation method. The study shows that the imaginary part of quasinormal frequencies increases indicating that the...
1401.3496v1
2014-02-04
Mode competition and anomalous cooling in a multimode phonon laser
We study mode competition in a multimode "phonon laser" comprised of an optical cavity employing a highly reflective membrane as the output coupler. Mechanical gain is provided by the intracavity radiation pressure, to which many mechanical modes are coupled. We calculate the gain, and find that strong oscillation in o...
1402.0714v1
2014-02-11
Radiation reaction at the level of the action
The aim of this paper is to highlight a recently proposed method for the treatment of classical radiative effects, in particular radiation reaction, via effective field theory methods. We emphasize important features of the method, and in particular the doubling of fields. We apply the method to two simple systems: for...
1402.2610v2
2014-02-14
Thermodynamically self-consistent non-stochastic micromagnetic model for the ferromagnetic state
In this work, a self-consistent thermodynamic approach to micromagnetism is presented. The magnetic degrees of freedom are modeled using the Landau-Lifshitz-Baryakhtar theory, that separates the different contributions to the magnetic damping, and thereby allows them to be coupled to the electron and phonon systems in ...
1402.3487v3
2014-02-25
Dynamics of closed ecosystems described by operators
We adopt the so--called \emph{occupation number representation}, originally used in quantum mechanics and recently adopted in the description of several classical systems, in the analysis of the dynamics of some models of closed ecosystems. In particular, we discuss two linear models, for which the solution can be foun...
1402.6214v1
2014-03-03
Logarithmic stabilization of the Euler-Bernoulli transmission plate equation with locally distributed Kelvin-Voigt damping
In this paper we will study the asymptotic behaviour of the energy decay of a transmission plate equation with locally distributed Kelvin-Voigt feedback. Precisly, we shall prove that the energy decay at least logarithmically over the time. The originality of this method comes from the fact that using a Carleman estima...
1403.0356v1
2014-03-12
Graphene Plasmonics for Terahertz to Mid-Infrared Applications
In recent years, we have seen a rapid progress in the field of graphene plasmonics, motivated by graphene's unique electrical and optical properties, tunabilty, long-lived collective excitation and their extreme light confinement. Here, we review the basic properties of graphene plasmons; their energy dispersion, local...
1403.2799v1
2014-03-12
Logarithmic stability in determining two coefficients in a dissipative wave equation. Extensions to clamped Euler-Bernoulli beam and heat equations
We are concerned with the inverse problem of determining both the potential and the damping coefficient in a dissipative wave equation from boundary measurements. We establish stability estimates of logarithmic type when the measurements are given by the operator who maps the initial condition to Neumann boundary trace...
1403.3018v2
2014-03-13
Challenges in description of heavy-ion collisions with microscopic time-dependent approaches
Important efforts have been dedicated in the past few years to describe near-barrier heavy-ion collisions with microscopic quantum theories like the time-dependent Hartree-Fock approach and some of its extensions. However, this field is still facing important challenges such as the description of cluster dynamics, the ...
1403.3246v1
2014-03-14
Optomechanical atom-cavity interaction in the sub-recoil regime
We study the optomechanical interaction of a Bose-Einstein condensate with a single longitudinal mode of an ultra-high finesse standing wave optical resonator. As a unique feature the resonator combines three extreme regimes, previously not realized together, i.e., strong cooperative coupling, cavity dominated scatteri...
1403.3545v1
2014-03-21
Steady Fock states via atomic reservoir
In this letter we present a strategy that combines the action of cavity damping mechanisms with that of an engineered atomic reservoir to drive an initial thermal distribution to a Fock equilibrium state. The same technique can be used to slice probability distributions in the Fock space, thus allowing the preparation ...
1403.5482v1
2014-03-23
Smoluchowski-Kramers approximation and large deviations for infinite dimensional gradient systems
In this paper, we explicitly calculate the quasi-potentials for the damped semilinear stochastic wave equation when the system is of gradient type. We show that in this case the infimum of the quasi-potential with respect to all possible velocities does not depend on the density of the mass and does coincide with the q...
1403.5743v1
2014-03-23
Smoluchowski-Kramers approximation and large deviations for infinite dimensional non-gradient systems with applications to the exit problem
In this paper, we study the quasi-potential for a general class of damped semilinear stochastic wave equations. We show that, as the density of the mass converges to zero, the infimum of the quasi-potential with respect to all possible velocities converges to the quasi-potential of the corresponding stochastic heat equ...
1403.5745v1
2014-03-24
L^p-tauberian theorems and L^p-rates for energy decay
We prove $L^p$-analogues of the classical tauberian theorem of Ingham and Karamata, and its variations giving rates of decay. These results are applied to derive $L^p$-decay of operator families arising in the study of the decay of energy for damped wave equations and local energy for wave equations in exterior domains...
1403.6084v2
2014-03-30
Gauge Field Turbulence as a Cause of Inflation in Chern-Simons Modified Gravity
In this paper, we study the dynamics of the Chern-Simons Inflation Model proposed by Alexander, Marciano and Spergel. According to this model, inflation begins when a fermion current interacts with a turbulent gauge field in a space larger than some critical size. This mechanism appears to work by driving energy from t...
1403.7702v1
2014-04-08
Exactly solvable model of stochastic heat engine: Optimization of power, its fluctuations and efficiency
We investigate a stochastic heat engine based on an over-damped particle diffusing on the positive real axis in an externally driven time-periodic log-harmonic potential. The periodic driving is composed of two isothermal and two adiabatic branches. Within our specific setting we verify the recent universal results reg...
1404.2030v1
2014-04-10
Dual pumped microresonator frequency combs
A study is made of the nonlinear dynamics of dual pumped microresonator Kerr frequency combs described by a driven and damped nonlinear Schr\"odinger equation, with an additional degree of freedom in the form of the modulation frequency. A truncated four wave model is derived for the pump modes and the dominant sideban...
1404.2792v1
2014-04-11
Optimal control of a qubit in an optical cavity
We study quantum information processing by means of optimal control theory. To this end, we analyze the damped Jaynes-Cummings model, and derive optimal control protocols that minimize the heating or energy dispersion rates, and controls that drive the system at the quantum speed limit. Special emphasis is put on analy...
1404.3137v2
2014-04-13
Invariant sets and connecting orbits for nonlinear evolution equations at resonance
We study the problem of existence of orbits connecting stationary points for the nonlinear heat and strongly damped wave equations being at resonance at infinity. The main difficulty lies in the fact that the problems may have no solutions for general nonlinearity. To address this question we introduce geometrical assu...
1404.3428v2
2014-04-15
Finite time cooling in dispersively and dissipatively coupled optomechanics
The cooling performance of an optomechanical system comprising both dispersive and dissipative coupling is studied. We present a scheme to cool a mechanical resonator to its ground state in finite time by employing a chirped pulse. When the cavity damping strength increases, the phonon occupation of the resonator will ...
1404.3851v2
2014-04-22
Strong Uniform Attractors for Non-Autonomous Dissipative PDEs with non translation-compact external forces
We give a comprehensive study of strong uniform attractors of non-autonomous dissipative systems for the case where the external forces are not translation compact. We introduce several new classes of external forces which are not translation compact, but nevertheless allow to verify the attraction in a strong topology...
1404.5563v1
2014-04-26
Self-interaction model of classical point particle in one-dimension
We consider a hamiltonian system on the real line, consisting of real scalar field $\phi(x,t)$ and point particle with trajectory $y(t)$. The dynamics of this system is defined by the system of two equations: wave equation for the field, <<radiated>> by the point particle, and Newton's equation for the particle in its ...
1404.6636v1
2014-05-03
Lie Symmetry Classification and Numerical Analysis of KdV Equation with Power-law Nonlinearity
In this paper, a complete Lie symmetry analysis of the damped wave equation with time-dependent coefficients is investigated. Then the invariant solutions and the exact solutions generated from the symmetries are presented. Moreover, a Lie algebraic classifications and the optimal system are discussed. Finally, using C...
1405.0592v3
2014-05-08
Electromagnetic back-reaction from currents on a straight string
Charge carriers moving at the speed of light along a straight, superconducting cosmic string carry with them a logarithmically divergent slab of electromagnetic field energy. Thus no finite local input can induce a current that travels unimpeded to infinity. Rather, electromagnetic back-reaction must damp this current ...
1405.2097v2
2014-06-03
Improving Cooling performance of the mechanical resonator with the two-level-system defects
We study cooling performance of a realistic mechanical resonator containing defects. The normal cooling method through an optomechanical system does not work efficiently due to those defects. We show by employing periodical $\sigma_z$ pulses, we can eliminate the interaction between defects and their surrounded heat ba...
1406.0555v1
2014-06-10
Influence of Ta insertions on the magnetic properties of MgO/CoFeB/MgO films probed by ferromagnetic resonance
We show by vector network analyzer ferromagnetic resonance measurements that low Gilbert damping {\alpha} down to 0.006 can be achieved in perpendicularly magnetized MgO/CoFeB/MgO thin films with ultra-thin insertions of Ta in the CoFeB layer. While increasing the number of Ta insertions allows thicker CoFeB layers to ...
1406.2491v2
2014-06-10
Topological self-dual vacua of deformed gauge theories
We propose a deformation principle of gauge theories in three dimensions that can describe topologically stable self-dual gauge fields, i.e., vacua configurations that in spite of their masses do not deform the background geometry and are locally undetected by charged particles. We interpret these systems as describing...
1406.2727v1
2014-06-18
Photonic crystal optics in cold atomic gases
We describe propagation of light in a gas with periodic density modulation, demonstrating photonic-crystal-like refraction with negative refraction angles. We address the role of poorly defined boundaries and damping, and derive an optical analog of the quantum adiabatic theorem. For Cs atoms in an optical lattice, we ...
1406.4655v1
2014-06-20
Enhancement of quantum correlations between two particles under decoherence in finite temperature environment
Enhancing the quantum correlations in realistic quantum systems interacting with the environment of finite temperature is an important subject in quantum information processing. In this paper, we use weak measurement and measurement reversal to enhance the quantum correlations in a quantum system consisting of two part...
1406.5267v2
2014-06-26
The plucked string: an example of non-normal dynamics
Motion of a single Fourier mode of the plucked string is an example of transient, free decay of coupled, damped oscillators. It shares the rarely discussed features of the generic case, e.g., possessing a complete set of non-orthogonal eigenvectors and no normal modes, but it can be analyzed and solved analytically by ...
1406.6939v2
2014-07-01
Newton methods for k-order Markov Constrained Motion Problems
This is a documentation of a framework for robot motion optimization that aims to draw on classical constrained optimization methods. With one exception the underlying algorithms are classical ones: Gauss-Newton (with adaptive step size and damping), Augmented Lagrangian, log-barrier, etc. The exception is a novel any-...
1407.0414v1
2014-07-02
On the physics of fizzing: How bubble bursting controls droplets ejection
Bubbles at a free surface surface usually burst in ejecting myriads of droplets. Focusing on the bubble bursting jet, prelude for these aerosols, we propose a simple scaling for the jet velocity and we unravel experimentally the intricate roles of bubble shape, capillary waves, gravity and liquid properties. We demonst...
1407.0560v2
2014-07-04
Metal-Dielectric-Graphene Sandwich for Surface Enhanced Raman Spectroscopy
Raman intensity of Rhodamine B (RhB) is enhanced by inserting a thin high \k{appa} dielectric layer which reduces the surface plasmon damping at the gold-graphene interface. The results indicate that the Raman intensity increases sharply by plasmonic resonance enhancement while maintaining efficient fluorescence quench...
1407.1129v1
2014-07-16
Internal Decoherence of a Gaussian Wave Packet in a Harmonic Potential
We have studied the quantum dissipative problem of a Gaussian wave packet under the influence of a harmonic potential. A phenomenological approach to dissipation is adopted in the light of the well-known model in which the environment is composed of a bath of non-interacting harmonic oscillators. As one of the effects ...
1407.4204v1
2014-07-18
Conditional Ramsey Spectroscopy with Synchronized Atoms
We investigate Ramsey spectroscopy performed on a synchronized ensemble of two-level atoms. The synchronization is induced by the collective coupling of the atoms to a heavily damped mode of an optical cavity. We show that, in principle, with this synchronized system it is possible to observe Ramsey fringes indefinitel...
1407.5132v1
2014-08-02
Damped Electromagnetic fluctuations in the early universe?
This short note considers the effects of quantum theory on the linear evolution of the magnetic fields during and after inflation. The analysis appears to show that the magnetic fields decay exponentially in the high-temperature radiation era due to a combination of ohmic dissipation and vacuum polarisation.
1408.0367v2
2014-08-05
Scalar and Electromagnetic Quasinormal modes of Extended black hole in F(R) gravity
In this paper we study the scalar and electromagnetic perturbations of an extended black hole in F(R) gravity. The quasinormal modes in two cases are evaluated and studied their behavior by plotting graphs in each case. To study the quasinormal mode, we use the third order WKB method. The present study shows that the a...
1408.0935v1
2014-08-10
Generalized Gradient Flow Equation and Its Application to Super Yang-Mills Theory
We generalize the gradient flow equation for field theories with nonlinearly realized symmetry. Applying the formalism to super Yang-Mills theory, we construct a supersymmetric extension of the gradient flow equation. It can be shown that the super gauge symmetry is preserved in the gradient flow. Furthermore, choosing...
1408.2185v3
2014-08-11
Formation of Large-Amplitude Low-Frequency Waves in Capillary Turbulence on Superfluid He-II
The results of experimental and theoretical studies of the parametric decay instability of capillary waves on the surface of superfluid helium He-II are reported. It is demonstrated that in a system of turbulent capillary waves low-frequency waves are generated along with the direct Kolmogorov-Zakharov cascade of capil...
1408.2560v1
2014-08-13
Dynamic stabilization of an optomechanical oscillator
Quantum optomechanics offers the potential to investigate quantum effects in macroscopic quantum systems in extremely well controlled experiments. In this paper we discuss one such situation, the dynamic stabilization of a mechanical system such as an inverted pendulum. The specific example that we study is a "membrane...
1408.3091v2
2014-09-15
Adaptive discontinuous Galerkin methods for non-linear diffusion-convection-reaction equations
In this work, we apply the adaptive discontinuous Galerkin (DGAFEM) method to the convection dominated non-linear, quasi-stationary diffusion-convection-reaction equations. We propose an efficient preconditioner using a matrix reordering scheme to solve the sparse linear systems iteratively arising from the discretized...
1409.4313v1
2014-09-17
Delayed-response quantum back-action in nanoelectromechanical systems
We present a semiclassical theory for the delayed response of a quantum dot (QD) to oscillations of a coupled nanomechanical resonator (NR). We prove that the back-action of the QD changes both the resonant frequency and the quality factor of the NR. An increase or decrease in the quality factor of the NR corresponds t...
1409.4930v2
2014-09-19
Spreading in Integrable and Non--integrable Many--body Systems
We consider a finite, closed and selfbound many--body system in which a collective degree of freedom is excited. The redistribution of energy and momentum into a finite number of the non-collective degrees of freedom is referred to as spreading as opposed to damping in open systems. Spreading closely relates to thermal...
1409.5764v2
2014-09-20
Estimating the output entropy of a tensor product of two quantum channels
In this paper we find, for a class of bipartite quantum states, a nontrivial lower bound on the entropy gain resulting from the action of a tensor product of identity channel with an arbitrary channel. By means of that we then estimate (from below) the output entropy of the tensor product of dephasing channel with an a...
1409.5881v2
2014-09-24
Dissipationless Multiferroic Magnonics
We propose that the magnetoelectric effect in multiferroic insulators with coplanar antiferromagnetic spiral order, such as BiFeO$_{3}$, enables electrically controlled dissipationless magnonics. Applying an oscillating electric field in these materials with frequency as low as household frequency can activate Goldston...
1409.6900v2
2014-09-30
Mixed finite elements for global tide models
We study mixed finite element methods for the linearized rotating shallow water equations with linear drag and forcing terms. By means of a strong energy estimate for an equivalent second-order formulation for the linearized momentum, we prove long-time stability of the system without energy accumulation -- the geotryp...
1410.0045v1
2014-10-21
Coherent beam-beam experiments and implications for head-on compensation
In polarized proton operation in the Relativistic Heavy Ion Collider (RHIC) coherent beam-beam modes are routinely observed with beam transfer function measurements. These modes can become unstable under external excitation or in the presence of impedance. This becomes even more relevant in the presence of head-on comp...
1410.5623v1
2014-10-22
Optimization-based smoothing algorithm for triangle meshes over arbitrarily shaped domains
This paper describes a node relocation algorithm based on nonlinear optimization which delivers excellent results for both unstructured and structured plane triangle meshes over convex as well as non-convex domains with high curvature. The local optimization scheme is a damped Newton's method in which the gradient and ...
1410.5977v1
2014-10-23
Fully damped Mott oscillations in sub-barrier elastic scattering of identical heavy ions and the nuclear interaction
We investigate the possible disappearance of Mott oscillations in the scattering of bosonic nuclei at sub-barrier energies. This effect is universal and happens at a critical value of the Sommerfeld parameter. It is also found that the inclusion of the short-range nuclear interaction has a profound influence on this ph...
1410.6376v1
2014-11-03
Decay rates of magnetic modes below the threshold of a turbulent dynamo
We measure the decay rates of magnetic field modes in a turbulent flow of liquid sodium below the dynamo threshold.We observe that turbulent fluctuations induce energy transfers between modes with different symmetries (dipolar and quadrupolar). Using symmetry properties, we show how to measure the decay rate of each mo...
1411.0517v1
2014-11-22
On the symmetry of the Laplacian spectra of signed graphs
We study the symmetry properties of the spectra of normalized Laplacians on signed graphs. We find a new machinery that generates symmetric spectra for signed graphs, which includes bipartiteness of unsigned graphs as a special case. Moreover, we prove a fundamental connection between the symmetry of the spectrum and t...
1411.6113v1
2014-11-22
Random Attractor for Stochastic Wave Equation with Arbitrary Exponent and Additive Noise on $\mathbb{R}^n$
Asymptotic random dynamics of weak solutions for a damped stochastic wave equation with the nonlinearity of arbitrarily large exponent and the additive noise on $\mathbb{R}^n$ is investigated. The existence of a pullback random attractor is proved in a parameter region with a breakthrough in proving the pullback asympt...
1411.6139v1
2014-11-23
Dephasing of Kuramoto oscillators in kinetic regime towards a fixed asymptotically free state
We study the kinetic Kuramoto model for coupled oscillators. We prove that for any regular asymptotically free state, if the interaction is small enough, it exists a solution which is asymptotically close to it. For this class of solution the order parameter vanishes to zero, showing a behavior similar to the phenomeno...
1411.6304v1
2014-11-28
An Euler-Bernoulli beam with nonlinear damping and a nonlinear spring at the tip
We study the asymptotic behaviour for a system consisting of a clamped flexible beam that carries a tip payload, which is attached to a nonlinear damper and a nonlinear spring at its end. Characterizing the omega-limit sets of the trajectories, we give a necessary condition under which the system is asymptotically stab...
1411.7946v2