Science.gov

Sample records for quantum fictitious forces

  1. Quantum mechanics in noninertial reference frames: Relativistic accelerations and fictitious forces

    NASA Astrophysics Data System (ADS)

    Klink, W. H.; Wickramasekara, S.

    2016-06-01

    One-particle systems in relativistically accelerating reference frames can be associated with a class of unitary representations of the group of arbitrary coordinate transformations, an extension of the Wigner-Bargmann definition of particles as the physical realization of unitary irreducible representations of the Poincaré group. Representations of the group of arbitrary coordinate transformations become necessary to define unitary operators implementing relativistic acceleration transformations in quantum theory because, unlike in the Galilean case, the relativistic acceleration transformations do not themselves form a group. The momentum operators that follow from these representations show how the fictitious forces in noninertial reference frames are generated in quantum theory.

  2. Fictitious Science

    ERIC Educational Resources Information Center

    Foladori, Guillermo

    2016-01-01

    Science and Technology (S&T), like Research and Development (R&D), has become a case of capital investment like any other economic sector. This has distanced R&D from social needs, to the extent that part of R&D ends up actually being fictitious, in the sense that it acquires a price on the market but never becomes part of material…

  3. Dissipative Forces and Quantum Mechanics

    ERIC Educational Resources Information Center

    Eck, John S.; Thompson, W. J.

    1977-01-01

    Shows how to include the dissipative forces of classical mechanics in quantum mechanics by the use of non-Hermetian Hamiltonians. The Ehrenfest theorem for such Hamiltonians is derived, and simple examples which show the classical correspondences are given. (MLH)

  4. Modeling the Sedimentation of Red Blood Cells in Flow under Strong External Magnetic Body Force using a Lattice Boltzmann Fictitious Domain Method

    SciTech Connect

    Shi, Xing; Lin, Guang

    2014-11-01

    To model the sedimentation of the red blood cell (RBC) in a square duct and a circular pipe, the recently developed technique derived from the lattice Boltzmann method and the distributed Lagrange multiplier/fictitious domain method (LBM-DLM/FD) is extended to employ the mesoscopic network model for simulations of the sedimentation of the RBC in flow. The flow is simulated by the lattice Boltzmann method with a strong magnetic body force, while the network model is used for modeling RBC deformation. The fluid-RBC interactions are enforced by the Lagrange multiplier. The sedimentation of the RBC in a square duct and a circular pipe is simulated, revealing the capacity of the current method for modeling the sedimentation of RBC in various flows. Numerical results illustrate that that the terminal setting velocity increases with the increment of the exerted body force. The deformation of the RBC has significant effect on the terminal setting velocity due to the change of the frontal area. The larger the exerted force is, the smaller the frontal area and the larger deformation of the RBC are.

  5. Decoherence in current induced forces: Application to adiabatic quantum motors

    NASA Astrophysics Data System (ADS)

    Fernández-Alcázar, Lucas J.; Bustos-Marún, Raúl A.; Pastawski, Horacio M.

    2015-08-01

    Current induced forces are not only related with the discrete nature of electrons but also with its quantum character. It is natural then to wonder about the effect of decoherence. Here, we develop the theory of current induced forces including dephasing processes and we apply it to study adiabatic quantum motors (AQMs). The theory is based on Büttiker's fictitious probe model, which here is reformulated for this particular case. We prove that it accomplishes the fluctuation-dissipation theorem. We also show that, in spite of decoherence, the total work performed by the current induced forces remains equal to the pumped charge per cycle times the voltage. We find that decoherence affects not only the current induced forces of the system but also its intrinsic friction and noise, modifying in a nontrivial way the efficiency of AQMs. We apply the theory to study an AQM inspired by a classical peristaltic pump where we surprisingly find that decoherence can play a crucial role by triggering its operation. Our results can help to understand how environmentally induced dephasing affects the quantum behavior of nanomechanical devices.

  6. Gravity as a quantum entanglement force

    NASA Astrophysics Data System (ADS)

    Lee, Jae-Weon; Kim, Hyeong-Chan; Lee, Jungjai

    2015-03-01

    We conjecture that total the quantum entanglement of matter and vacuum in the universe tends to increase with time, like entropy, and that an effective force is associated with this tendency. We also suggest that gravity and dark energy are types of quantum entanglement forces, similar to Verlinde's entropic force, and give holographic dark energy with an equation of state comparable to current observational data. This connection between quantum entanglement and gravity could give some new insights into the origins of gravity, dark energy, and the arrow of time.

  7. Fictitious Supercontinent Cycles

    NASA Astrophysics Data System (ADS)

    Marvin Herndon, J.

    2014-05-01

    and there is no motive force for driving supercontinent cycles. The reasonable conclusion one must draw, as in the case of epicycles, is there must exist a new and fundamentally different geoscience paradigm which obviates the problems inherent in plate tectonics and in planetesimal Earth formation and yet better explains geological features. I have disclosed a new indivisible geoscience paradigm, called Whole-Earth Decompression Dynamics (WEDD), that begins with and is the consequence of our planet's early formation as a Jupiter-like gas giant and which permits deduction of: (1) Earth's internal composition and highly-reduced oxidation state; (2) Core formation without whole-planet melting; (3) Powerful new internal energy sources, protoplanetary energy of compression and georeactor nuclear fission energy; (4) Mechanism for heat emplacement at the base of the crust; (5) Georeactor geomagnetic field generation; (6) Decompression-driven geodynamics that accounts for the myriad of observations attributed to plate tectonics without requiring physically-impossible mantle convection, and; (7) A mechanism for fold-mountain formation that does not necessarily require plate collision. The latter obviates the necessity to assume supercontinent cycles. The fundamental basis of geodynamics is this: In response to decompression-driven Earth volume increases, cracks form to increase surface area and mountain ranges characterized by folding form to accommodate changes in curvature. Resources at NuclearPlanet.com .

  8. Quantum Gravitational Force Between Polarizable Objects.

    PubMed

    Ford, L H; Hertzberg, Mark P; Karouby, J

    2016-04-15

    Since general relativity is a consistent low energy effective field theory, it is possible to compute quantum corrections to classical forces. Here we compute a quantum correction to the gravitational potential between a pair of polarizable objects. We study two distant bodies and compute a quantum force from their induced quadrupole moments due to two-graviton exchange. The effect is in close analogy to the Casimir-Polder and London-van der Waals forces between a pair of atoms from their induced dipole moments due to two photon exchange. The new effect is computed from the shift in vacuum energy of metric fluctuations due to the polarizability of the objects. We compute the potential energy at arbitrary distances compared to the wavelengths in the system, including the far and near regimes. In the far distance, or retarded, regime, the potential energy takes on a particularly simple form: V(r)=-3987ℏcG^{2}α_{1S}α_{2S}/(4πr^{11}), where α_{1S}, α_{2S} are the static gravitational quadrupole polarizabilities of each object. We provide estimates of this effect. PMID:27127955

  9. Quantum Gravitational Force Between Polarizable Objects

    NASA Astrophysics Data System (ADS)

    Hertzberg, Mark; Ford, Larry; Karouby, Johanna

    2016-03-01

    Since general relativity is a consistent low energy effective field theory, it is possible to compute quantum corrections to classical forces. Here we compute a quantum correction to the gravitational potential between a pair of polarizable objects. We study two distant bodies and compute a quantum force from their induced quadrupole moments due to two graviton exchange. The effect is in close analogy to the Casimir-Polder and London-van der Waals forces between a pair of atoms from their induced dipole moments due to two photon exchange. The new effect is computed from the shift in vacuum energy of metric fluctuations due to the polarizability of the objects. We compute the potential energy at arbitrary distances compared to the wavelengths in the system, including the far and near regimes. In the far distance, or retarded, regime, the potential energy takes on a particularly simple form: V (r) = - 3987 ℏ cG2α1 Sα2 S / (4 πr11) , where α1 S ,α2 S are the static gravitational quadrupole polarizabilities of each object. We provide estimates of this effect.

  10. Quantum Gravitational Force Between Polarizable Objects

    NASA Astrophysics Data System (ADS)

    Ford, L. H.; Hertzberg, Mark P.; Karouby, J.

    2016-04-01

    Since general relativity is a consistent low energy effective field theory, it is possible to compute quantum corrections to classical forces. Here we compute a quantum correction to the gravitational potential between a pair of polarizable objects. We study two distant bodies and compute a quantum force from their induced quadrupole moments due to two-graviton exchange. The effect is in close analogy to the Casimir-Polder and London-van der Waals forces between a pair of atoms from their induced dipole moments due to two photon exchange. The new effect is computed from the shift in vacuum energy of metric fluctuations due to the polarizability of the objects. We compute the potential energy at arbitrary distances compared to the wavelengths in the system, including the far and near regimes. In the far distance, or retarded, regime, the potential energy takes on a particularly simple form: V (r )=-3987 ℏc G2α1 Sα2 S/(4 π r11) , where α1 S , α2 S are the static gravitational quadrupole polarizabilities of each object. We provide estimates of this effect.

  11. Trapping atoms using nanoscale quantum vacuum forces

    PubMed Central

    Chang, D. E.; Sinha, K.; Taylor, J. M.; Kimble, H. J.

    2014-01-01

    Quantum vacuum forces dictate the interaction between individual atoms and dielectric surfaces at nanoscale distances. For example, their large strengths typically overwhelm externally applied forces, which makes it challenging to controllably interface cold atoms with nearby nanophotonic systems. Here we theoretically show that it is possible to tailor the vacuum forces themselves to provide strong trapping potentials. Our proposed trapping scheme takes advantage of the attractive ground-state potential and adiabatic dressing with an excited state whose potential is engineered to be resonantly enhanced and repulsive. This procedure yields a strong metastable trap, with the fraction of excited-state population scaling inversely with the quality factor of the resonance of the dielectric structure. We analyse realistic limitations to the trap lifetime and discuss possible applications that might emerge from the large trap depths and nanoscale confinement. PMID:25008119

  12. Does Bohm's Quantum Force Have a Classical Origin?

    NASA Astrophysics Data System (ADS)

    Lush, David C.

    2016-08-01

    In the de Broglie-Bohm formulation of quantum mechanics, the electron is stationary in the ground state of hydrogenic atoms, because the quantum force exactly cancels the Coulomb attraction of the electron to the nucleus. In this paper it is shown that classical electrodynamics similarly predicts the Coulomb force can be effectively canceled by part of the magnetic force that occurs between two similar particles each consisting of a point charge moving with circulatory motion at the speed of light. Supposition of such motion is the basis of the Zitterbewegung interpretation of quantum mechanics. The magnetic force between two luminally-circulating charges for separation large compared to their circulatory motions contains a radial inverse square law part with magnitude equal to the Coulomb force, sinusoidally modulated by the phase difference between the circulatory motions. When the particles have equal mass and their circulatory motions are aligned but out of phase, part of the magnetic force is equal but opposite the Coulomb force. This raises a possibility that the quantum force of Bohmian mechanics may be attributable to the magnetic force of classical electrodynamics. It is further shown that relative motion between the particles leads to modulation of the magnetic force with spatial period equal to the de Broglie wavelength.

  13. Quantum mechanical actuation of microelectromechanical systems by the Casimir force.

    PubMed

    Chan, H B; Aksyuk, V A; Kleiman, R N; Bishop, D J; Capasso, F

    2001-03-01

    The Casimir force is the attraction between uncharged metallic surfaces as a result of quantum mechanical vacuum fluctuations of the electromagnetic field. We demonstrate the Casimir effect in microelectromechanical systems using a micromachined torsional device. Attraction between a polysilicon plate and a spherical metallic surface results in a torque that rotates the plate about two thin torsional rods. The dependence of the rotation angle on the separation between the surfaces is in agreement with calculations of the Casimir force. Our results show that quantum electrodynamical effects play a significant role in such microelectromechanical systems when the separation between components is in the nanometer range. PMID:11239149

  14. Fictitious domain method for fully resolved reacting gas-solid flow simulation

    NASA Astrophysics Data System (ADS)

    Zhang, Longhui; Liu, Kai; You, Changfu

    2015-10-01

    Fully resolved simulation (FRS) for gas-solid multiphase flow considers solid objects as finite sized regions in flow fields and their behaviours are predicted by solving equations in both fluid and solid regions directly. Fixed mesh numerical methods, such as fictitious domain method, are preferred in solving FRS problems and have been widely researched. However, for reacting gas-solid flows no suitable fictitious domain numerical method has been developed. This work presents a new fictitious domain finite element method for FRS of reacting particulate flows. Low Mach number reacting flow governing equations are solved sequentially on a regular background mesh. Particles are immersed in the mesh and driven by their surface forces and torques integrated on immersed interfaces. Additional treatments on energy and surface reactions are developed. Several numerical test cases validated the method and a burning carbon particles array falling simulation proved the capability for solving moving reacting particle cluster problems.

  15. Quantum mechanical force field for water with explicit electronic polarization

    PubMed Central

    Han, Jaebeom; Mazack, Michael J. M.; Zhang, Peng; Truhlar, Donald G.; Gao, Jiali

    2013-01-01

    A quantum mechanical force field (QMFF) for water is described. Unlike traditional approaches that use quantum mechanical results and experimental data to parameterize empirical potential energy functions, the present QMFF uses a quantum mechanical framework to represent intramolecular and intermolecular interactions in an entire condensed-phase system. In particular, the internal energy terms used in molecular mechanics are replaced by a quantum mechanical formalism that naturally includes electronic polarization due to intermolecular interactions and its effects on the force constants of the intramolecular force field. As a quantum mechanical force field, both intermolecular interactions and the Hamiltonian describing the individual molecular fragments can be parameterized to strive for accuracy and computational efficiency. In this work, we introduce a polarizable molecular orbital model Hamiltonian for water and for oxygen- and hydrogen-containing compounds, whereas the electrostatic potential responsible for intermolecular interactions in the liquid and in solution is modeled by a three-point charge representation that realistically reproduces the total molecular dipole moment and the local hybridization contributions. The present QMFF for water, which is called the XP3P (explicit polarization with three-point-charge potential) model, is suitable for modeling both gas-phase clusters and liquid water. The paper demonstrates the performance of the XP3P model for water and proton clusters and the properties of the pure liquid from about 900 × 106 self-consistent-field calculations on a periodic system consisting of 267 water molecules. The unusual dipole derivative behavior of water, which is incorrectly modeled in molecular mechanics, is naturally reproduced as a result of an electronic structural treatment of chemical bonding by XP3P. We anticipate that the XP3P model will be useful for studying proton transport in solution and solid phases as well as across

  16. Quantum mechanical force field for water with explicit electronic polarization

    SciTech Connect

    Han, Jaebeom; Mazack, Michael J. M.; Zhang, Peng; Truhlar, Donald G.; Gao, Jiali

    2013-08-07

    A quantum mechanical force field (QMFF) for water is described. Unlike traditional approaches that use quantum mechanical results and experimental data to parameterize empirical potential energy functions, the present QMFF uses a quantum mechanical framework to represent intramolecular and intermolecular interactions in an entire condensed-phase system. In particular, the internal energy terms used in molecular mechanics are replaced by a quantum mechanical formalism that naturally includes electronic polarization due to intermolecular interactions and its effects on the force constants of the intramolecular force field. As a quantum mechanical force field, both intermolecular interactions and the Hamiltonian describing the individual molecular fragments can be parameterized to strive for accuracy and computational efficiency. In this work, we introduce a polarizable molecular orbital model Hamiltonian for water and for oxygen- and hydrogen-containing compounds, whereas the electrostatic potential responsible for intermolecular interactions in the liquid and in solution is modeled by a three-point charge representation that realistically reproduces the total molecular dipole moment and the local hybridization contributions. The present QMFF for water, which is called the XP3P (explicit polarization with three-point-charge potential) model, is suitable for modeling both gas-phase clusters and liquid water. The paper demonstrates the performance of the XP3P model for water and proton clusters and the properties of the pure liquid from about 900 × 10{sup 6} self-consistent-field calculations on a periodic system consisting of 267 water molecules. The unusual dipole derivative behavior of water, which is incorrectly modeled in molecular mechanics, is naturally reproduced as a result of an electronic structural treatment of chemical bonding by XP3P. We anticipate that the XP3P model will be useful for studying proton transport in solution and solid phases as well as

  17. Force law in material media, hidden momentum and quantum phases

    NASA Astrophysics Data System (ADS)

    Kholmetskii, Alexander L.; Missevitch, Oleg V.; Yarman, T.

    2016-06-01

    We address to the force law in classical electrodynamics of material media, paying attention on the force term due to time variation of hidden momentum of magnetic dipoles. We highlight that the emergence of this force component is required by the general theorem, deriving zero total momentum for any static configuration of charges/currents. At the same time, we disclose the impossibility to add this force term covariantly to the Lorentz force law in material media. We further show that the adoption of the Einstein-Laub force law does not resolve the issue, because for a small electric/magnetic dipole, the density of Einstein-Laub force integrates exactly to the same equation, like the Lorentz force with the inclusion of hidden momentum contribution. Thus, none of the available expressions for the force on a moving dipole is compatible with the relativistic transformation of force, and we support this statement with a number of particular examples. In this respect, we suggest applying the Lagrangian approach to the derivation of the force law in a magnetized/polarized medium. In the framework of this approach we obtain the novel expression for the force on a small electric/magnetic dipole, with the novel expression for its generalized momentum. The latter expression implies two novel quantum effects with non-topological phases, when an electric dipole is moving in an electric field, and when a magnetic dipole is moving in a magnetic field. These phases, in general, are not related to dynamical effects, because they are not equal to zero, when the classical force on a dipole is vanishing. The implications of the obtained results are discussed.

  18. Magnetic resonance force microscopy and a solid state quantum computer.

    SciTech Connect

    Pelekhov, D. V.; Martin, I.; Suter, A.; Reagor, D. W.; Hammel, P. C.

    2001-01-01

    A Quantum Computer (QC) is a device that utilizes the principles of Quantum Mechanics to perform computations. Such a machine would be capable of accomplishing tasks not achievable by means of any conventional digital computer, for instance factoring large numbers. Currently it appears that the QC architecture based on an array of spin quantum bits (qubits) embedded in a solid-state matrix is one of the most promising approaches to fabrication of a scalable QC. However, the fabrication and operation of a Solid State Quantum Computer (SSQC) presents very formidable challenges; primary amongst these are: (1) the characterization and control of the fabrication process of the device during its construction and (2) the readout of the computational result. Magnetic Resonance Force Microscopy (MRFM)--a novel scanning probe technique based on mechanical detection of magnetic resonance-provides an attractive means of addressing these requirements. The sensitivity of the MRFM significantly exceeds that of conventional magnetic resonance measurement methods, and it has the potential for single electron spin detection. Moreover, the MRFM is capable of true 3D subsurface imaging. These features will make MRFM an invaluable tool for the implementation of a spin-based QC. Here we present the general principles of MRFM operation, the current status of its development and indicate future directions for its improvement.

  19. The effect of gravitational tidal forces on renormalized quantum fields

    NASA Astrophysics Data System (ADS)

    Hollowood, Timothy J.; Shore, Graham M.

    2012-02-01

    The effect of gravitational tidal forces on renormalized quantum fields propagating in curved spacetime is investigated and a generalisation of the optical theorem to curved spacetime is proved. In the case of QED, the interaction of tidal forces with the vacuum polarization cloud of virtual e + e - pairs dressing the renormalized photon has been shown to produce several novel phenomena. In particular, the photon field amplitude can locally increase as well as decrease, corresponding to a negative imaginary part of the refractive index, in apparent violation of unitarity and the optical theorem. Below threshold decays into e + e - pairs may also occur. In this paper, these issues are studied from the point of view of a non-equilibrium initial-value problem, with the field evolution from an initial null surface being calculated for physically distinct initial conditions and for both scalar field theories and QED. It is shown how a generalised version of the optical theorem, valid in curved spacetime, allows a local increase in amplitude while maintaining consistency with unitarity. The picture emerges of the field being dressed and undressed as it propagates through curved spacetime, with the local gravitational tidal forces determining the degree of dressing and hence the amplitude of the renormalized quantum field. These effects are illustrated with many examples, including a description of the undressing of a photon in the vicinity of a black hole singularity.

  20. Complex Squeezing and Force Measurement Beyond the Standard Quantum Limit.

    PubMed

    Buchmann, L F; Schreppler, S; Kohler, J; Spethmann, N; Stamper-Kurn, D M

    2016-07-15

    A continuous quantum field, such as a propagating beam of light, may be characterized by a squeezing spectrum that is inhomogeneous in frequency. We point out that homodyne detectors, which are commonly employed to detect quantum squeezing, are blind to squeezing spectra in which the correlation between amplitude and phase fluctuations is complex. We find theoretically that such complex squeezing is a component of ponderomotive squeezing of light through cavity optomechanics. We propose a detection scheme called synodyne detection, which reveals complex squeezing and allows the accounting of measurement backaction. Even with the optomechanical system subject to continuous measurement, such detection allows the measurement of one component of an external force with sensitivity only limited by the mechanical oscillator's thermal occupation. PMID:27472106

  1. Complex Squeezing and Force Measurement Beyond the Standard Quantum Limit

    NASA Astrophysics Data System (ADS)

    Buchmann, L. F.; Schreppler, S.; Kohler, J.; Spethmann, N.; Stamper-Kurn, D. M.

    2016-07-01

    A continuous quantum field, such as a propagating beam of light, may be characterized by a squeezing spectrum that is inhomogeneous in frequency. We point out that homodyne detectors, which are commonly employed to detect quantum squeezing, are blind to squeezing spectra in which the correlation between amplitude and phase fluctuations is complex. We find theoretically that such complex squeezing is a component of ponderomotive squeezing of light through cavity optomechanics. We propose a detection scheme called synodyne detection, which reveals complex squeezing and allows the accounting of measurement backaction. Even with the optomechanical system subject to continuous measurement, such detection allows the measurement of one component of an external force with sensitivity only limited by the mechanical oscillator's thermal occupation.

  2. A fictitious domain approach for the simulation of dense suspensions

    NASA Astrophysics Data System (ADS)

    Gallier, Stany; Lemaire, Elisabeth; Lobry, Laurent; Peters, François

    2014-01-01

    Low Reynolds number concentrated suspensions do exhibit an intricate physics which can be partly unraveled by the use of numerical simulation. To this end, a Lagrange multiplier-free fictitious domain approach is described in this work. Unlike some methods recently proposed, the present approach is fully Eulerian and therefore does not need any transfer between the Eulerian background grid and some Lagrangian nodes attached to particles. Lubrication forces between particles play an important role in the suspension rheology and have been properly accounted for in the model. A robust and effective lubrication scheme is outlined which consists in transposing the classical approach used in Stokesian Dynamics to our present direct numerical simulation. This lubrication model has also been adapted to account for solid boundaries such as walls. Contact forces between particles are modeled using a classical Discrete Element Method (DEM), a widely used method in granular matter physics. Comprehensive validations are presented on various one-particle, two-particle or three-particle configurations in a linear shear flow as well as some O(103) and O(104) particle simulations.

  3. Efficient integration method for fictitious domain approaches

    NASA Astrophysics Data System (ADS)

    Duczek, Sascha; Gabbert, Ulrich

    2015-10-01

    In the current article, we present an efficient and accurate numerical method for the integration of the system matrices in fictitious domain approaches such as the finite cell method (FCM). In the framework of the FCM, the physical domain is embedded in a geometrically larger domain of simple shape which is discretized using a regular Cartesian grid of cells. Therefore, a spacetree-based adaptive quadrature technique is normally deployed to resolve the geometry of the structure. Depending on the complexity of the structure under investigation this method accounts for most of the computational effort. To reduce the computational costs for computing the system matrices an efficient quadrature scheme based on the divergence theorem (Gauß-Ostrogradsky theorem) is proposed. Using this theorem the dimension of the integral is reduced by one, i.e. instead of solving the integral for the whole domain only its contour needs to be considered. In the current paper, we present the general principles of the integration method and its implementation. The results to several two-dimensional benchmark problems highlight its properties. The efficiency of the proposed method is compared to conventional spacetree-based integration techniques.

  4. U-2 Spy Plane With Fictitious NASA Markings

    NASA Technical Reports Server (NTRS)

    1960-01-01

    After Francis Gary Powers was shot down over the Soviet Union during a CIA spy flight on May 1. 1960, NASA issued a press release with a cover story about a U-2 conducting weather research that may have strayed off course after the pilot reported difficulties with his oxygen equipment. To bolster the cover-up, a U-2 was quickly painted in NASA markings, with a fictitious NASA serial number, and put on display for the news media at the NASA Flight Research Center at Edwards Air Force Base on May 6, 1960. The U-2 cover story in 1956 was that it was an NACA plane to conduct high-altitude weather research. But various observers doubted this story from the beginning. Certainly the Soviets did not believe it once the aircraft began overflying their territory. The NASA cover story quickly blew up in the agency's face when both Gary Powers and aircraft wreckage were displayed by the Soviet Union, proving that it was a reconnaissance aircraft. This caused embarrassment for several top NASA officials.

  5. Transport spectroscopy of a graphene quantum dot fabricated by atomic force microscope nanolithography

    NASA Astrophysics Data System (ADS)

    Puddy, R. K.; Chua, C. J.; Buitelaar, M. R.

    2013-10-01

    We report low-temperature transport spectroscopy of a graphene quantum dot fabricated by atomic force microscope nanolithography. The excellent spatial resolution of the atomic force microscope allows us to reliably fabricate quantum dots with short constrictions of less than 15 nm in length. Transport measurements demonstrate that the device is dominated by a single quantum dot over a wide gate range. The electron spin system of the quantum dot is investigated by applying an in-plane magnetic field. The results are consistent with a Landé g-factor ˜2 but no regular spin filling sequence is observed, most likely due to disorder.

  6. Fictitious domain method for unsteady problems: Application to electromagnetic scattering

    SciTech Connect

    Collino, F.; Joly, P.; Millot, F.

    1997-12-01

    This paper investigates the use of a fictitious domain method as an alternative numerical method (compared to finite difference and finite element methods) for handling problems dealing with two-dimensional scattering by an obstacle. An example of this would be electromagnetic waves scattered from a perfectly conducting boundaries.

  7. On the spectral accuracy of a fictitious domain method for elliptic operators in multi-dimensions

    NASA Astrophysics Data System (ADS)

    Le Penven, Lionel; Buffat, Marc

    2012-10-01

    This work is a continuation of the authors efforts to develop high-order numerical methods for solving elliptic problems with complex boundaries using a fictitious domain approach. In a previous paper, a new method was proposed, based on the use of smooth forcing functions with identical shapes, mutually disjoint supports inside the fictitious domain and whose amplitudes play the role of Lagrange multipliers in relation to a discrete set of boundary constraints. For one-dimensional elliptic problems, this method shows spectral accuracy but its implementation in two dimensions seems to be limited to a fourth-order algebraic convergence rate. In this paper, a spectrally accurate formulation is presented for multi-dimensional applications. Instead of being specified locally, the forcing function is defined as a convolution of a mollifier (smooth bump function) and a Lagrange multiplier function (the amplitude of the bump). The multiplier function is then approximated by Fourier series. Using a Fourier Galerkin approximation, the spectral accuracy is demonstrated on a two-dimensional Laplacian problem and on a Stokes flow around a periodic array of cylinders. In the latter, the numerical solution achieves the same high-order accuracy as a Stokes eigenfunction expansion and is much more accurate than the solution obtained with a classical third order finite element approximation using the same number of degrees of freedom.

  8. A Lattice Boltzmann Fictitious Domain Method for Modeling Red Blood Cell Deformation and Multiple-Cell Hydrodynamic Interactions in Flow

    SciTech Connect

    Shi, Xing; Lin, Guang; Zou, Jianfeng; Fedosov, Dmitry A.

    2013-07-20

    To model red blood cell (RBC) deformation in flow, the recently developed LBM-DLM/FD method ([Shi and Lim, 2007)29], derived from the lattice Boltzmann method and the distributed Lagrange multiplier/fictitious domain methodthe fictitious domain method, is extended to employ the mesoscopic network model for simulations of red blood cell deformation. The flow is simulated by the lattice Boltzmann method with an external force, while the network model is used for modeling red blood cell deformation and the fluid-RBC interaction is enforced by the Lagrange multiplier. To validate parameters of the RBC network model, sThe stretching numerical tests on both coarse and fine meshes are performed and compared with the corresponding experimental data to validate the parameters of the RBC network model. In addition, RBC deformation in pipe flow and in shear flow is simulated, revealing the capacity of the current method for modeling RBC deformation in various flows.

  9. Casimir forces between defects in one-dimensional quantum liquids

    SciTech Connect

    Recati, A.; Fuchs, J.N.; Peca, C.S.; Zwerger, W.

    2005-08-15

    We discuss the effective interactions between two localized perturbations in one-dimensional quantum liquids. For noninteracting fermions, the interactions exhibit Friedel oscillations, giving rise to a Ruderman-Kittel-Kasuya-Yosida-type interaction familiar from impurity spins in metals. In the interacting case, at low energies, a Luttinger-liquid description applies. In the case of repulsive fermions, the Friedel oscillations of the interacting system are replaced, at long distances, by a universal Casimir-type interaction which depends only on the sound velocity and decays inversely with the separation. The Casimir-type interaction between localized perturbations embedded in a fermionic environment gives rise to a long-range coupling between quantum dots in ultracold Fermi gases, opening an alternative to couple qubits with neutral atoms. We also briefly discuss the case of bosonic quantum liquids in which the interaction between weak impurities turns out to be short ranged, decaying exponentially on the scale of the healing length.

  10. Entropic Force and its Fluctuation in Euclidean Quantum Gravity

    NASA Astrophysics Data System (ADS)

    Zhao, Yue

    In this paper, we study the idea about gravity as entropic force proposed by Verlinde. By interpreting Euclidean gravity in the language of thermodynamic quantities on holographic screen, we find the gravitational force can be calculated from the change of entropy on the screen. We show that normal gravity calculation can be reinterpreted in the language of thermodynamic variables. We also study the fluctuation of the force and find the fluctuation acting on the point-like particle can never be larger than the expectation value of the force. For a black hole in AdS space, by gauge/gravity duality, the fluctuation may be interpreted as arising from thermal fluctuation in the boundary description. And for a black hole in flat space, the ratio between fluctuation and force goes to a constant (T)/(m) at infinity.

  11. Debunking Coriolis Force Myths

    ERIC Educational Resources Information Center

    Shakur, Asif

    2014-01-01

    Much has been written and debated about the Coriolis force. Unfortunately, this has done little to demystify the paradoxes surrounding this fictitious force invoked by an observer in a rotating frame of reference. It is the purpose of this article to make another valiant attempt to slay the dragon of the Coriolis force! This will be done without…

  12. Quantum field theory of the Casimir force for graphene

    NASA Astrophysics Data System (ADS)

    Klimchitskaya, G. L.

    2016-01-01

    We present theoretical description of the Casimir interaction in graphene systems which is based on the Lifshitz theory of dispersion forces and the formalism of the polarization tensor in (2+1)-dimensional space-time. The representation for the polarization tensor of graphene allowing the analytic continuation to the whole plane of complex frequencies is given. This representation is used to obtain simple asymptotic expressions for the reflection coefficients at all Matsubara frequencies and to investigate the origin of large thermal effect in the Casimir force for graphene. The developed theory is shown to be in a good agreement with the experimental data on measuring the gradient of the Casimir force between a Au-coated sphere and a graphene-coated substrate. The possibility to observe the thermal effect for graphene due to a minor modification of the already existing experimental setup is demonstrated.

  13. Relaxation dispersion in MRI induced by fictitious magnetic fields.

    PubMed

    Liimatainen, Timo; Mangia, Silvia; Ling, Wen; Ellermann, Jutta; Sorce, Dennis J; Garwood, Michael; Michaeli, Shalom

    2011-04-01

    A new method entitled Relaxation Along a Fictitious Field (RAFF) was recently introduced for investigating relaxations in rotating frames of rank ≥ 2. RAFF generates a fictitious field (E) by applying frequency-swept pulses with sine and cosine amplitude and frequency modulation operating in a sub-adiabatic regime. In the present work, MRI contrast is created by varying the orientation of E, i.e. the angle ε between E and the z″ axis of the second rotating frame. When ε > 45°, the amplitude of the fictitious field E generated during RAFF is significantly larger than the RF field amplitude used for transmitting the sine/cosine pulses. Relaxation during RAFF was investigated using an invariant-trajectory approach and the Bloch-McConnell formalism. Dipole-dipole interactions between identical (like) spins and anisochronous exchange (e.g., exchange between spins with different chemical shifts) in the fast exchange regime were considered. Experimental verifications were performed in vivo in human and mouse brain. Theoretical and experimental results demonstrated that changes in ε induced a dispersion of the relaxation rate constants. The fastest relaxation was achieved at ε ≈ 56°, where the averaged contributions from transverse components during the pulse are maximal and the contribution from longitudinal components are minimal. RAFF relaxation dispersion was compared with the relaxation dispersion achieved with off-resonance spin lock T(₁ρ) experiments. As compared with the off-resonance spin lock T(₁ρ) method, a slower rotating frame relaxation rate was observed with RAFF, which under certain experimental conditions is desirable. PMID:21334231

  14. Relaxation Dispersion in MRI Induced by Fictitious Magnetic Fields

    PubMed Central

    Liimatainen, Timo; Mangia, Silvia; Ling, Wen; Ellermann, Jutta; Sorce, Dennis J.; Garwood, Michael; Michaeli, Shalom

    2011-01-01

    A new method entitled Relaxation Along a Fictitious Field (RAFF) was recently introduced for investigating relaxations in rotating frames of rank ≥ 3. RAFF generates a fictitious field (E) by applying frequency-swept pulses with sine and cosine amplitude and frequency modulation operating in a sub-adiabatic regime. In the present work, MRI contrast is created by varying the orientation of E, i.e. the angle ε between E and the z″ axis of the second rotating frame. When ε > 45°, the amplitude of the fictitious field E generated during RAFF is significantly larger than the RF field amplitude used for transmitting the sine/cosine pulses. Relaxation during RAFF was investigated using an invariant-trajectory approach and the Bloch-McConnell formalism. Dipole-dipole interactions between identical (like) spins and anisochronous exchange (e.g., exchange between spins with different chemical shifts) in the fast exchange regime were considered. Experimental verifications were performed in vivo in human and mouse brain. Theoretical and experimental results demonstrated that changes in ε induced a dispersion of the relaxation rate constants. The fastest relaxation was achieved at ε ≈ 56°, where the averaged contributions from transverse components during the pulse are maximal and the contribution from longitudinal components are minimal. RAFF relaxation dispersion was compared with the relaxation dispersion achieved with off-resonance spin lock T1ρ experiments. As compared with the off-resonance spin lock T1ρ method, a slower rotating frame relaxation rate was observed with RAFF, which under certain experimental conditions is desirable. PMID:21334231

  15. Relaxation dispersion in MRI induced by fictitious magnetic fields

    NASA Astrophysics Data System (ADS)

    Liimatainen, Timo; Mangia, Silvia; Ling, Wen; Ellermann, Jutta; Sorce, Dennis J.; Garwood, Michael; Michaeli, Shalom

    2011-04-01

    A new method entitled Relaxation Along a Fictitious Field (RAFF) was recently introduced for investigating relaxations in rotating frames of rank ⩾2. RAFF generates a fictitious field ( E) by applying frequency-swept pulses with sine and cosine amplitude and frequency modulation operating in a sub-adiabatic regime. In the present work, MRI contrast is created by varying the orientation of E, i. e. the angle ɛ between E and the z″ axis of the second rotating frame. When ɛ > 45°, the amplitude of the fictitious field E generated during RAFF is significantly larger than the RF field amplitude used for transmitting the sine/ cosine pulses. Relaxation during RAFF was investigated using an invariant-trajectory approach and the Bloch-McConnell formalism. Dipole-dipole interactions between identical (like) spins and anisochronous exchange ( e. g., exchange between spins with different chemical shifts) in the fast exchange regime were considered. Experimental verifications were performed in vivo in human and mouse brain. Theoretical and experimental results demonstrated that changes in ɛ induced a dispersion of the relaxation rate constants. The fastest relaxation was achieved at ɛ ≈ 56°, where the averaged contributions from transverse components during the pulse are maximal and the contribution from longitudinal components are minimal. RAFF relaxation dispersion was compared with the relaxation dispersion achieved with off-resonance spin lock T1ρ experiments. As compared with the off-resonance spin lock T1ρ method, a slower rotating frame relaxation rate was observed with RAFF, which under certain experimental conditions is desirable.

  16. Generalized fictitious methods for fluid-structure interactions: Analysis and simulations

    NASA Astrophysics Data System (ADS)

    Yu, Yue; Baek, Hyoungsu; Karniadakis, George Em

    2013-07-01

    We present a new fictitious pressure method for fluid-structure interaction (FSI) problems in incompressible flow by generalizing the fictitious mass and damping methods we published previously in [1]. The fictitious pressure method involves modification of the fluid solver whereas the fictitious mass and damping methods modify the structure solver. We analyze all fictitious methods for simplified problems and obtain explicit expressions for the optimal reduction factor (convergence rate index) at the FSI interface [2]. This analysis also demonstrates an apparent similarity of fictitious methods to the FSI approach based on Robin boundary conditions, which have been found to be very effective in FSI problems. We implement all methods, including the semi-implicit Robin based coupling method, in the context of spectral element discretization, which is more sensitive to temporal instabilities than low-order methods. However, the methods we present here are simple and general, and hence applicable to FSI based on any other spatial discretization. In numerical tests, we verify the selection of optimal values for the fictitious parameters for simplified problems and for vortex-induced vibrations (VIV) even at zero mass ratio ("for-ever-resonance"). We also develop an empirical a posteriori analysis for complex geometries and apply it to 3D patient-specific flexible brain arteries with aneurysms for very large deformations. We demonstrate that the fictitious pressure method enhances stability and convergence, and is comparable or better in most cases to the Robin approach or the other fictitious methods.

  17. MRI Contrast from Relaxation Along a Fictitious Field (RAFF)

    PubMed Central

    Liimatainen, Timo; Sorce, Dennis J.; O’Connell, Robert; Garwood, Michael; Michaeli, Shalom

    2016-01-01

    A new method to measure rotating frame relaxation and to create contrast for MRI is introduced. The technique exploits relaxation along a fictitious field (RAFF) generated by amplitude- and frequency-modulated irradiation in a sub-adiabatic condition. Here, RAFF is demonstrated using a radiofrequency pulse based on sine and cosine amplitude and frequency modulations of equal amplitudes, which gives rise to a stationary fictitious magnetic field in a doubly rotating frame. According to dipolar relaxation theory, the RAFF relaxation time constant (TRAFF) was found to differ from laboratory frame relaxation times (T1 and T2) and rotating frame relaxation times (T1ρ and T2ρ). This prediction was supported by experimental results obtained from human brain in vivo and three different solutions. Results from relaxation mapping in human brain demonstrated the ability to create MRI contrast based on RAFF. The value of TRAFF was found to be insensitive to the initial orientation of the magnetization vector. Finally, as compared with adiabatic pulse trains of equal durations, RAFF required less radiofrequency power and therefore can be more readily used for rotating frame relaxation studies in humans. PMID:20740665

  18. MRI contrast from relaxation along a fictitious field (RAFF).

    PubMed

    Liimatainen, Timo; Sorce, Dennis J; O'Connell, Robert; Garwood, Michael; Michaeli, Shalom

    2010-10-01

    A new method to measure rotating frame relaxation and to create contrast for MRI is introduced. The technique exploits relaxation along a fictitious field (RAFF) generated by amplitude- and frequency-modulated irradiation in a subadiabatic condition. Here, RAFF is demonstrated using a radiofrequency pulse based on sine and cosine amplitude and frequency modulations of equal amplitudes, which gives rise to a stationary fictitious magnetic field in a doubly rotating frame. According to dipolar relaxation theory, the RAFF relaxation time constant (T(RAFF)) was found to differ from laboratory frame relaxation times (T(1) and T(2)) and rotating frame relaxation times (T(1ρ) and T(2ρ)). This prediction was supported by experimental results obtained from human brain in vivo and three different solutions. Results from relaxation mapping in human brain demonstrated the ability to create MRI contrast based on RAFF. The value of T(RAFF) was found to be insensitive to the initial orientation of the magnetization vector. In the RAFF method, the useful bandwidth did not decrease as the train length increased. Finally, as compared with an adiabatic pulse train of equal duration, RAFF required less radiofrequency power and therefore can be more readily used for rotating frame relaxation studies in humans. PMID:20740665

  19. Explicit Polarization: A Quantum Mechanical Framework for Developing Next Generation Force Fields

    PubMed Central

    2015-01-01

    Conspectus Molecular mechanical force fields have been successfully used to model condensed-phase and biological systems for a half century. By means of careful parametrization, such classical force fields can be used to provide useful interpretations of experimental findings and predictions of certain properties. Yet, there is a need to further improve computational accuracy for the quantitative prediction of biomolecular interactions and to model properties that depend on the wave functions and not just the energy terms. A new strategy called explicit polarization (X-Pol) has been developed to construct the potential energy surface and wave functions for macromolecular and liquid-phase simulations on the basis of quantum mechanics rather than only using quantum mechanical results to fit analytic force fields. In this spirit, this approach is called a quantum mechanical force field (QMFF). X-Pol is a general fragment method for electronic structure calculations based on the partition of a condensed-phase or macromolecular system into subsystems (“fragments”) to achieve computational efficiency. Here, intrafragment energy and the mutual electronic polarization of interfragment interactions are treated explicitly using quantum mechanics. X-Pol can be used as a general, multilevel electronic structure model for macromolecular systems, and it can also serve as a new-generation force field. As a quantum chemical model, a variational many-body (VMB) expansion approach is used to systematically improve interfragment interactions, including exchange repulsion, charge delocalization, dispersion, and other correlation energies. As a quantum mechanical force field, these energy terms are approximated by empirical functions in the spirit of conventional molecular mechanics. This Account first reviews the formulation of X-Pol, in the full variationally correct version, in the faster embedded version, and with systematic many-body improvements. We discuss illustrative

  20. Explicit polarization: a quantum mechanical framework for developing next generation force fields.

    PubMed

    Gao, Jiali; Truhlar, Donald G; Wang, Yingjie; Mazack, Michael J M; Löffler, Patrick; Provorse, Makenzie R; Rehak, Pavel

    2014-09-16

    Conspectus Molecular mechanical force fields have been successfully used to model condensed-phase and biological systems for a half century. By means of careful parametrization, such classical force fields can be used to provide useful interpretations of experimental findings and predictions of certain properties. Yet, there is a need to further improve computational accuracy for the quantitative prediction of biomolecular interactions and to model properties that depend on the wave functions and not just the energy terms. A new strategy called explicit polarization (X-Pol) has been developed to construct the potential energy surface and wave functions for macromolecular and liquid-phase simulations on the basis of quantum mechanics rather than only using quantum mechanical results to fit analytic force fields. In this spirit, this approach is called a quantum mechanical force field (QMFF). X-Pol is a general fragment method for electronic structure calculations based on the partition of a condensed-phase or macromolecular system into subsystems ("fragments") to achieve computational efficiency. Here, intrafragment energy and the mutual electronic polarization of interfragment interactions are treated explicitly using quantum mechanics. X-Pol can be used as a general, multilevel electronic structure model for macromolecular systems, and it can also serve as a new-generation force field. As a quantum chemical model, a variational many-body (VMB) expansion approach is used to systematically improve interfragment interactions, including exchange repulsion, charge delocalization, dispersion, and other correlation energies. As a quantum mechanical force field, these energy terms are approximated by empirical functions in the spirit of conventional molecular mechanics. This Account first reviews the formulation of X-Pol, in the full variationally correct version, in the faster embedded version, and with systematic many-body improvements. We discuss illustrative examples

  1. Ideal quantum gas in an expanding cavity: nature of nonadiabatic force.

    PubMed

    Nakamura, K; Avazbaev, S K; Sobirov, Z A; Matrasulov, D U; Monnai, T

    2011-04-01

    We consider a quantum gas of noninteracting particles confined in the expanding cavity and investigate the nature of the nonadiabatic force which is generated from the gas and acts on the cavity wall. First, with use of the time-dependent canonical transformation, which transforms the expanding cavity to the nonexpanding one, we can define the force operator. Second, applying the perturbative theory, which works when the cavity wall begins to move at time origin, we find that the nonadiabatic force is quadratic in the wall velocity and thereby does not break the time-reversal symmetry, in contrast with general belief. Finally, using an assembly of the transitionless quantum states, we obtain the nonadiabatic force exactly. The exact result justifies the validity of both the definition of the force operator and the issue of the perturbative theory. The mysterious mechanism of nonadiabatic transition with the use of transitionless quantum states is also explained. The study is done for both cases of the hard- and soft-wall confinement with the time-dependent confining length. PMID:21599141

  2. Comparison of three empirical force fields for phonon calculations in CdSe quantum dots

    NASA Astrophysics Data System (ADS)

    Kelley, Anne Myers

    2016-06-01

    Three empirical interatomic force fields are parametrized using structural, elastic, and phonon dispersion data for bulk CdSe and their predictions are then compared for the structures and phonons of CdSe quantum dots having average diameters of ˜2.8 and ˜5.2 nm (˜410 and ˜2630 atoms, respectively). The three force fields include one that contains only two-body interactions (Lennard-Jones plus Coulomb), a Tersoff-type force field that contains both two-body and three-body interactions but no Coulombic terms, and a Stillinger-Weber type force field that contains Coulombic interactions plus two-body and three-body terms. While all three force fields predict nearly identical peak frequencies for the strongly Raman-active "longitudinal optical" phonon in the quantum dots, the predictions for the width of the Raman peak, the peak frequency and width of the infrared absorption peak, and the degree of disorder in the structure are very different. The three force fields also give very different predictions for the variation in phonon frequency with radial position (core versus surface). The Stillinger-Weber plus Coulomb type force field gives the best overall agreement with available experimental data.

  3. Determination of Quantum Chemistry Based Force Fields for Molecular Dynamics Simulations of Aromatic Polymers

    NASA Technical Reports Server (NTRS)

    Jaffe, Richard; Langhoff, Stephen R. (Technical Monitor)

    1995-01-01

    Ab initio quantum chemistry calculations for model molecules can be used to parameterize force fields for molecular dynamics simulations of polymers. Emphasis in our research group is on using quantum chemistry-based force fields for molecular dynamics simulations of organic polymers in the melt and glassy states, but the methodology is applicable to simulations of small molecules, multicomponent systems and solutions. Special attention is paid to deriving reliable descriptions of the non-bonded and electrostatic interactions. Several procedures have been developed for deriving and calibrating these parameters. Our force fields for aromatic polyimide simulations will be described. In this application, the intermolecular interactions are the critical factor in determining many properties of the polymer (including its color).

  4. Development of a True Transition State Force Field from Quantum Mechanical Calculations.

    PubMed

    Madarász, Ádám; Berta, Dénes; Paton, Robert S

    2016-04-12

    Transition state force fields (TSFF) treated the TS structure as an artificial minimum on the potential energy surface in the past decades. The necessary parameters were developed either manually or by the Quantum-to-molecular mechanics method (Q2MM). In contrast with these approaches, here we propose to model the TS structures as genuine saddle points at the molecular mechanics level. Different methods were tested on small model systems of general chemical reactions such as protonation, nucleophilic attack, and substitution, and the new procedure led to more accurate models than the Q2MM-type parametrization. To demonstrate the practicality of our approach, transferrable parameters have been developed for Mo-catalyzed olefin metathesis using quantum mechanical properties as reference data. Based on the proposed strategy, any force field can be extended with true transition state force field (TTSFF) parameters, and they can be readily applied in several molecular mechanics programs as well. PMID:26925858

  5. Can Real Forces Be Induced by Interference of Quantum Wavefunctions?

    NASA Astrophysics Data System (ADS)

    Kaminer, Ido; Nemirovsky, Jonathan; Rechtsman, Mikael; Bekenstein, Rivka; Segev, Mordechai

    2013-04-01

    In 1958, a revolutionary paper by Aharonov and Bohm predicted a phase difference between two parts of an electron wavefunction even when being confined to a regime with no EM field. The Aharonov-Bohm effect was groundbreaking: proving that the EM vector potential is a real physical quantity, affecting the outcome of experiments not only through the EM fields extracted from it. But is the EM potential a real necessity for an Aharonov-Bohm-type effect? Can it exist in a potential-free system such as free-space? Here, we find self-accelerating wavepackets that are solutions of the free Dirac equation, for massive/massless fermions/bosons. These accelerating Dirac particles mimic the dynamics of a free-charge moving under a ``virtual'' EM field, even though no field is acting and there is no charge: the entire dynamics is a direct result of the initial conditions. We show that such particles display an effective Aharonov-Bohm effect caused by exactly the same ``virtual'' potential that also ``causes'' the acceleration. Altogether, along the trajectory, there is no way to distinguish between a real force and the self-induced force - it is real by all measurable quantities. This proves that one can create all effects induced by EM fields by only controlling the initial conditions of a wave pattern, while the dynamics is in free-space. These phenomena can be observed in various settings: e.g., optical waves in honeycomb photonic lattices or in hyperbolic metamaterials, and matter waves in honeycomb interference structures.

  6. Force-field functor theory: classical force-fields which reproduce equilibrium quantum distributions

    PubMed Central

    Babbush, Ryan; Parkhill, John; Aspuru-Guzik, Alán

    2013-01-01

    Feynman and Hibbs were the first to variationally determine an effective potential whose associated classical canonical ensemble approximates the exact quantum partition function. We examine the existence of a map between the local potential and an effective classical potential which matches the exact quantum equilibrium density and partition function. The usefulness of such a mapping rests in its ability to readily improve Born-Oppenheimer potentials for use with classical sampling. We show that such a map is unique and must exist. To explore the feasibility of using this result to improve classical molecular mechanics, we numerically produce a map from a library of randomly generated one-dimensional potential/effective potential pairs then evaluate its performance on independent test problems. We also apply the map to simulate liquid para-hydrogen, finding that the resulting radial pair distribution functions agree well with path integral Monte Carlo simulations. The surprising accessibility and transferability of the technique suggest a quantitative route to adapting Born-Oppenheimer potentials, with a motivation similar in spirit to the powerful ideas and approximations of density functional theory. PMID:24790954

  7. Force-Field Functor Theory: Classical Force-Fields which Reproduce Equilibrium Quantum Distributions

    NASA Astrophysics Data System (ADS)

    Babbush, Ryan; Parkhill, John; Aspuru-Guzik, Alan

    2013-10-01

    Feynman and Hibbs were the first to variationally determine an effective potential whose associated classical canonical ensemble approximates the exact quantum partition function. We examine the existence of a map between the local potential and an effective classical potential which matches the exact quantum equilibrium density and partition function. The usefulness of such a mapping rests in its ability to readily improve Born-Oppenheimer potentials for use with classical sampling. We show that such a map is unique and must exist. To explore the feasibility of using this result to improve classical molecular mechanics, we numerically produce a map from a library of randomly generated one-dimensional potential/effective potential pairs then evaluate its performance on independent test problems. We also apply the map to simulate liquid para-hydrogen, finding that the resulting radial pair distribution functions agree well with path integral Monte Carlo simulations. The surprising accessibility and transferability of the technique suggest a quantitative route to adapting Born-Oppenheimer potentials, with a motivation similar in spirit to the powerful ideas and approximations of density functional theory.

  8. The Space Structure, Force Fields and Quantum Mechanics

    NASA Astrophysics Data System (ADS)

    Krasnoholovets, Volodymyr; Chung, Ding-Yu

    2006-06-01

    It is proposed that the cosmic digital code consists of 1 and 0 for an attachment space and a detachment space, respectively. The attachment space attaches to an object, while the detachment space detaches from the object. The cosmic digital code relates to the reduction of > 4D space-time into 4D space-time and the derivation of the space structure. Through the detachment space, > 4D space-time is sliced into infinitely many 4D slices surrounding the 4D core attachment space. The space structurally is a partition space, or a lattice space. The lattice space consists of repetitive units of alternative attachment space and detachment space and provides for a coherent wave function and gauge force fields, while the partition space consists of separated continuous phases of attachment space and detachment space providing the space structure for the collapse of wave function and the permanent detachment or attachment of gauge bosons. Thus, the wave function and gauge bosons become pure physical fields. The mechanism for the emergence of the space structure is varying dimension numbers, ensuring the metric for the slicing of > 4D space-time.

  9. Tuning Fano resonances by magnetic forces for electron transport through a quantum wire side coupled to a quantum ring

    NASA Astrophysics Data System (ADS)

    Szafran, B.; Poniedziałek, M. R.

    2010-08-01

    We consider electron transport in a quantum wire with a side-coupled quantum ring in a two-dimensional model that accounts for a finite width of the channels. We use the finite difference technique to solve the scattering problem as well as to determine the ring-localized states of the energy continuum. The backscattering probability exhibits Fano peaks for magnetic fields for which a ring-localized states appear at the Fermi level. We find that the width of the Fano resonances changes at high magnetic field. The width is increased (decreased) for resonant states with current circulation that produce the magnetic dipole moment that is parallel (antiparallel) to the external magnetic field. We indicate that the opposite behavior of Fano resonances due to localized states with clockwise and counterclockwise currents results from the magnetic forces which change the strength of their coupling to the channel and modify the lifetime of localized states.

  10. 16 CFR 301.11 - Fictitious or non-existing animal designations prohibited.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 16 Commercial Practices 1 2011-01-01 2011-01-01 false Fictitious or non-existing animal designations prohibited. 301.11 Section 301.11 Commercial Practices FEDERAL TRADE COMMISSION REGULATIONS UNDER SPECIFIC ACTS OF CONGRESS RULES AND REGULATIONS UNDER FUR PRODUCTS LABELING ACT Regulations § 301.11 Fictitious or non-existing animal...

  11. 16 CFR 301.11 - Fictitious or non-existing animal designations prohibited.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 16 Commercial Practices 1 2010-01-01 2010-01-01 false Fictitious or non-existing animal designations prohibited. 301.11 Section 301.11 Commercial Practices FEDERAL TRADE COMMISSION REGULATIONS UNDER SPECIFIC ACTS OF CONGRESS RULES AND REGULATIONS UNDER FUR PRODUCTS LABELING ACT Regulations § 301.11 Fictitious or non-existing animal...

  12. Fictitious Domain Methods for Fracture Models in Elasticity.

    NASA Astrophysics Data System (ADS)

    Court, S.; Bodart, O.; Cayol, V.; Koko, J.

    2014-12-01

    As surface displacements depend non linearly on sources location and shape, simplifying assumptions are generally required to reduce computation time when inverting geodetic data. We present a generic Finite Element Method designed for pressurized or sheared cracks inside a linear elastic medium. A fictitious domain method is used to take the crack into account independently of the mesh. Besides the possibility of considering heterogeneous media, the approach permits the evolution of the crack through time or more generally through iterations: The goal is to change the less things we need when the crack geometry is modified; In particular no re-meshing is required (the boundary conditions at the level of the crack are imposed by Lagrange multipliers), leading to a gain of computation time and resources with respect to classic finite element methods. This method is also robust with respect to the geometry, since we expect to observe the same behavior whatever the shape and the position of the crack. We present numerical experiments which highlight the accuracy of our method (using convergence curves), the optimality of errors, and the robustness with respect to the geometry (with computation of errors on some quantities for all kind of geometric configurations). We will also provide 2D benchmark tests. The method is then applied to Piton de la Fournaise volcano, considering a pressurized crack - inside a 3-dimensional domain - and the corresponding computation time and accuracy are compared with results from a mixed Boundary element method. In order to determine the crack geometrical characteristics, and pressure, inversions are performed combining fictitious domain computations with a near neighborhood algorithm. Performances are compared with those obtained combining a mixed boundary element method with the same inversion algorithm.

  13. Casimir force for absorbing media in an open quantum system framework: Scalar model

    SciTech Connect

    Lombardo, Fernando C.; Rubio Lopez, Adrian E.; Mazzitelli, Francisco D.

    2011-11-15

    In this article we compute the Casimir force between two finite-width mirrors at finite temperature, working in a simplified model in 1+1 dimensions. The mirrors, considered as dissipative media, are modeled by a continuous set of harmonic oscillators which in turn are coupled to an external environment at thermal equilibrium. The calculation of the Casimir force is performed in the framework of the theory of open quantum systems. It is shown that the Casimir interaction has two different contributions: the usual radiation pressure from the vacuum, which is obtained for ideal mirrors without dissipation or losses, and a Langevin force associated with the noise induced by the interaction between dielectric atoms in the slabs and the thermal bath. Both contributions to the Casimir force are needed in order to reproduce the analogous Lifshitz formula in 1+1 dimensions. We also discuss the relationship between the electromagnetic properties of the mirrors and the spectral density of the environment.

  14. Single-spin measurements for quantum computation using magnetic resonance force microscopy

    SciTech Connect

    Berman, G. P.; Borgonovi, F.; Rinkevicius, Z.; Tsifrinovich, V. I.

    2004-01-01

    The quantum theory of a singlespin measurements using a magnetic resonance force microscopy is presented. We use an oscillating cantilever-driven adiabatic reversals technique. The frequency shift of the cantilever vibrations is estimated. We show that the frequency shift causes the formation of the Schroedinger cat state for the cantilever. The interaction between the cantilever and the environment quickly destroys the coherence between the two cantilever trajectories. It is shown that using partial adiabatic reversals one can obtain a significant increase in the frequency shift. We discuss the possibility of sub-magneton spin density detection in molecules using magnetic resonance force microscopy.

  15. Competition of static magnetic and dynamic photon forces in electronic transport through a quantum dot.

    PubMed

    Rauf Abdullah, Nzar; Tang, Chi-Shung; Manolescu, Andrei; Gudmundsson, Vidar

    2016-09-21

    We investigate theoretically the balance of the static magnetic and the dynamical photon forces in the electron transport through a quantum dot in a photon cavity with a single photon mode. The quantum dot system is connected to external leads and the total system is exposed to a static perpendicular magnetic field. We explore the transport characteristics through the system by tuning the ratio, [Formula: see text], between the photon energy, [Formula: see text], and the cyclotron energy, [Formula: see text]. Enhancement in the electron transport with increasing electron-photon coupling is observed when [Formula: see text]. In this case the photon field dominates and stretches the electron charge distribution in the quantum dot, extending it towards the contact area for the leads. Suppression in the electron transport is found when [Formula: see text], as the external magnetic field causes circular confinement of the charge density around the dot. PMID:27420809

  16. Solutions to Master equations of quantum Brownian motion in a general environment with external force

    SciTech Connect

    Roura, Albert; Fleming, C H; Hu, B L

    2008-01-01

    We revisit the model of a system made up of a Brownian quantum oscillator linearly coupled to an environment made up of many quantum oscillators at finite temperature. We show that the HPZ master equation for the reduced density matrix derived earlier [B.L. Hu, J.P. Paz, Y. Zhang, Phys. Rev. D 45, 2843 (1992)] has incorrectly specified coefficients for the case of nonlocal dissipation. We rederive the QBM master equation, correctly specifying all coefficients, and determine the position uncertainty to be free of excessive cutoff sensitivity. Our coefficients and solutions are reduced entirely to contour integration for analytic spectra at arbitrary temperature, coupling strength, and cut-off. As an illustration we calculate the master equation coefficients and solve the master equation for ohmic coupling (with finite cutoff) and example supra-ohmic and sub-ohmic spectral densities. We determine the effect of an external force on the quantum oscillator and also show that our representation of the master equation and solutions naturally extends to a system of multiple oscillators bilinearly coupled to themselves and the bath in arbitrary fashion. This produces a formula for investigating the standard quantum limit which is central to addressing many theoretical issues in macroscopic quantum phenomena and experimental concerns related to low temperature precision measurements. We find that in a dissipative environment, all initial states settle down to a Gaussian density matrix whose covariance is determined by the thermal reservoir and whose mean is determined by the external force. We specify the thermal covariance for the spectral densities we explore.

  17. Parametrization of an Orbital-Based Linear-Scaling Quantum Force Field for Noncovalent Interactions

    PubMed Central

    2015-01-01

    We parametrize a linear-scaling quantum mechanical force field called mDC for the accurate reproduction of nonbonded interactions. We provide a new benchmark database of accurate ab initio interactions between sulfur-containing molecules. A variety of nonbond databases are used to compare the new mDC method with other semiempirical, molecular mechanical, ab initio, and combined semiempirical quantum mechanical/molecular mechanical methods. It is shown that the molecular mechanical force field significantly and consistently reproduces the benchmark results with greater accuracy than the semiempirical models and our mDC model produces errors twice as small as the molecular mechanical force field. The comparisons between the methods are extended to the docking of drug candidates to the Cyclin-Dependent Kinase 2 protein receptor. We correlate the protein–ligand binding energies to their experimental inhibition constants and find that the mDC produces the best correlation. Condensed phase simulation of mDC water is performed and shown to produce O–O radial distribution functions similar to TIP4P-EW. PMID:24803856

  18. Force sensing based on coherent quantum noise cancellation in a hybrid optomechanical cavity with squeezed-vacuum injection

    NASA Astrophysics Data System (ADS)

    Motazedifard, Ali; Bemani, F.; Naderi, M. H.; Roknizadeh, R.; Vitali, D.

    2016-07-01

    We propose and analyse a feasible experimental scheme for a quantum force sensor based on the elimination of backaction noise through coherent quantum noise cancellation (CQNC) in a hybrid atom-cavity optomechanical setup assisted with squeezed vacuum injection. The force detector, which allows for a continuous, broadband detection of weak forces well below the standard quantum limit (SQL), is formed by a single optical cavity simultaneously coupled to a mechanical oscillator and to an ensemble of ultracold atoms. The latter acts as a negative-mass oscillator so that atomic noise exactly cancels the backaction noise from the mechanical oscillator due to destructive quantum interference. Squeezed vacuum injection enforces this cancellation and allows sub-SQL sensitivity to be reached in a very wide frequency band, and at much lower input laser powers.

  19. Neutron matter with Quantum Monte Carlo: chiral 3N forces and static response

    DOE PAGESBeta

    Buraczynski, M.; Gandolfi, S.; Gezerlis, A.; Schwenk, A.; Tews, I.

    2016-03-01

    Neutron matter is related to the physics of neutron stars and that of neutron-rich nuclei. Moreover, Quantum Monte Carlo (QMC) methods offer a unique way of solving the many-body problem non-perturbatively, providing feedback on features of nuclear interactions and addressing scenarios that are inaccessible to other approaches. Our contribution goes over two recent accomplishments in the theory of neutron matter: a) the fusing of QMC with chiral effective field theory interactions, focusing on local chiral 3N forces, and b) the first attempt to find an ab initio solution to the problem of static response.

  20. Neutron matter with Quantum Monte Carlo: chiral 3N forces and static response

    NASA Astrophysics Data System (ADS)

    Buraczynski, M.; Gandolfi, S.; Gezerlis, A.; Schwenk, A.; Tews, I.

    2016-03-01

    Neutron matter is related to the physics of neutron stars and that of neutron-rich nuclei. Quantum Monte Carlo (QMC) methods offer a unique way of solving the many-body problem non-perturbatively, providing feedback on features of nuclear interactions and addressing scenarios that are inaccessible to other approaches. In this contribution we go over two recent accomplishments in the theory of neutron matter: a) the fusing of QMC with chiral effective field theory interactions, focusing on local chiral 3N forces, and b) the first attempt to find an ab initio solution to the problem of static response.

  1. Spectral approximation to advection-diffusion problems by the fictitious interface method

    NASA Astrophysics Data System (ADS)

    Frati, A.; Pasquarelli, F.; Quarteroni, A.

    1993-08-01

    The algorithmic aspects of the 'fictitious interface' method used in numerical approximations of convection-dominated flows are discussed. The solution algorithm presented alternates the advection-equation solution with that of the advection-diffusion equation within complementary subdomains. For the problems presently considered, spatial discretization is obtained by the spectral collocation method via Legendre-Gaussian modes. Attention is given to the the fictitious interface method's application to the Burgers equation.

  2. Debunking Coriolis Force Myths

    NASA Astrophysics Data System (ADS)

    Shakur, Asif

    2014-11-01

    Much has been written and debated about the Coriolis force.1-8 Unfortunately, this has done little to demystify the paradoxes surrounding this fictitious force invoked by an observer in a rotating frame of reference. It is the purpose of this article to make another valiant attempt to slay the dragon of the Coriolis force! This will be done without unleashing the usual mathematical apparatus, which we believe is more of a hindrance than a help.

  3. Quantum Monte Carlo calculations of neutron matter with chiral three-body forces

    NASA Astrophysics Data System (ADS)

    Tews, I.; Gandolfi, S.; Gezerlis, A.; Schwenk, A.

    2016-02-01

    Chiral effective field theory (EFT) enables a systematic description of low-energy hadronic interactions with controlled theoretical uncertainties. For strongly interacting systems, quantum Monte Carlo (QMC) methods provide some of the most accurate solutions, but they require as input local potentials. We have recently constructed local chiral nucleon-nucleon (NN) interactions up to next-to-next-to-leading order (N2LO ). Chiral EFT naturally predicts consistent many-body forces. In this paper, we consider the leading chiral three-nucleon (3N) interactions in local form. These are included in auxiliary field diffusion Monte Carlo (AFDMC) simulations. We present results for the equation of state of neutron matter and for the energies and radii of neutron drops. In particular, we study the regulator dependence at the Hartree-Fock level and in AFDMC and find that present local regulators lead to less repulsion from 3N forces compared to the usual nonlocal regulators.

  4. A quantitative quantum-chemical analysis tool for the distribution of mechanical force in molecules

    SciTech Connect

    Stauch, Tim; Dreuw, Andreas

    2014-04-07

    The promising field of mechanochemistry suffers from a general lack of understanding of the distribution and propagation of force in a stretched molecule, which limits its applicability up to the present day. In this article, we introduce the JEDI (Judgement of Energy DIstribution) analysis, which is the first quantum chemical method that provides a quantitative understanding of the distribution of mechanical stress energy among all degrees of freedom in a molecule. The method is carried out on the basis of static or dynamic calculations under the influence of an external force and makes use of a Hessian matrix in redundant internal coordinates (bond lengths, bond angles, and dihedral angles), so that all relevant degrees of freedom of a molecule are included and mechanochemical processes can be interpreted in a chemically intuitive way. The JEDI method is characterized by its modest computational effort, with the calculation of the Hessian being the rate-determining step, and delivers, except for the harmonic approximation, exact ab initio results. We apply the JEDI analysis to several example molecules in both static quantum chemical calculations and Born-Oppenheimer Molecular Dynamics simulations in which molecules are subject to an external force, thus studying not only the distribution and the propagation of strain in mechanically deformed systems, but also gaining valuable insights into the mechanochemically induced isomerization of trans-3,4-dimethylcyclobutene to trans,trans-2,4-hexadiene. The JEDI analysis can potentially be used in the discussion of sonochemical reactions, molecular motors, mechanophores, and photoswitches as well as in the development of molecular force probes.

  5. A quantitative quantum-chemical analysis tool for the distribution of mechanical force in molecules

    NASA Astrophysics Data System (ADS)

    Stauch, Tim; Dreuw, Andreas

    2014-04-01

    The promising field of mechanochemistry suffers from a general lack of understanding of the distribution and propagation of force in a stretched molecule, which limits its applicability up to the present day. In this article, we introduce the JEDI (Judgement of Energy DIstribution) analysis, which is the first quantum chemical method that provides a quantitative understanding of the distribution of mechanical stress energy among all degrees of freedom in a molecule. The method is carried out on the basis of static or dynamic calculations under the influence of an external force and makes use of a Hessian matrix in redundant internal coordinates (bond lengths, bond angles, and dihedral angles), so that all relevant degrees of freedom of a molecule are included and mechanochemical processes can be interpreted in a chemically intuitive way. The JEDI method is characterized by its modest computational effort, with the calculation of the Hessian being the rate-determining step, and delivers, except for the harmonic approximation, exact ab initio results. We apply the JEDI analysis to several example molecules in both static quantum chemical calculations and Born-Oppenheimer Molecular Dynamics simulations in which molecules are subject to an external force, thus studying not only the distribution and the propagation of strain in mechanically deformed systems, but also gaining valuable insights into the mechanochemically induced isomerization of trans-3,4-dimethylcyclobutene to trans,trans-2,4-hexadiene. The JEDI analysis can potentially be used in the discussion of sonochemical reactions, molecular motors, mechanophores, and photoswitches as well as in the development of molecular force probes.

  6. Developing ab initio quality force fields from condensed phase quantum-mechanics/molecular-mechanics calculations through the adaptive force matching method

    NASA Astrophysics Data System (ADS)

    Akin-Ojo, Omololu; Song, Yang; Wang, Feng

    2008-08-01

    A new method called adaptive force matching (AFM) has been developed that is capable of producing high quality force fields for condensed phase simulations. This procedure involves the parametrization of force fields to reproduce ab initio forces obtained from condensed phase quantum-mechanics/molecular-mechanics (QM/MM) calculations. During the procedure, the MM part of the QM/MM is iteratively improved so as to approach ab initio quality. In this work, the AFM method has been tested to parametrize force fields for liquid water so that the resulting force fields reproduce forces calculated using the ab initio MP2 and the Kohn-Sham density functional theory with the Becke-Lee-Yang-Parr (BLYP) and Becke three-parameter LYP (B3LYP) exchange correlation functionals. The AFM force fields generated in this work are very simple to evaluate and are supported by most molecular dynamics (MD) codes. At the same time, the quality of the forces predicted by the AFM force fields rivals that of very expensive ab initio calculations and are found to successfully reproduce many experimental properties. The site-site radial distribution functions (RDFs) obtained from MD simulations using the force field generated from the BLYP functional through AFM compare favorably with the previously published RDFs from Car-Parrinello MD simulations with the same functional. Technical aspects of AFM such as the optimal QM cluster size, optimal basis set, and optimal QM method to be used with the AFM procedure are discussed in this paper.

  7. Force.

    ERIC Educational Resources Information Center

    Gamble, Reed

    1989-01-01

    Discusses pupil misconceptions concerning forces. Summarizes some of Assessment of Performance Unit's findings on meaning of (1) force, (2) force and motion in one dimension and two dimensions, and (3) Newton's second law. (YP)

  8. Quantum mechanical force field for hydrogen fluoride with explicit electronic polarization

    SciTech Connect

    Mazack, Michael J. M.; Gao, Jiali

    2014-05-28

    The explicit polarization (X-Pol) theory is a fragment-based quantum chemical method that explicitly models the internal electronic polarization and intermolecular interactions of a chemical system. X-Pol theory provides a framework to construct a quantum mechanical force field, which we have extended to liquid hydrogen fluoride (HF) in this work. The parameterization, called XPHF, is built upon the same formalism introduced for the XP3P model of liquid water, which is based on the polarized molecular orbital (PMO) semiempirical quantum chemistry method and the dipole-preserving polarization consistent point charge model. We introduce a fluorine parameter set for PMO, and find good agreement for various gas-phase results of small HF clusters compared to experiments and ab initio calculations at the M06-2X/MG3S level of theory. In addition, the XPHF model shows reasonable agreement with experiments for a variety of structural and thermodynamic properties in the liquid state, including radial distribution functions, interaction energies, diffusion coefficients, and densities at various state points.

  9. Quantum mechanical force field for hydrogen fluoride with explicit electronic polarization

    NASA Astrophysics Data System (ADS)

    Mazack, Michael J. M.; Gao, Jiali

    2014-05-01

    The explicit polarization (X-Pol) theory is a fragment-based quantum chemical method that explicitly models the internal electronic polarization and intermolecular interactions of a chemical system. X-Pol theory provides a framework to construct a quantum mechanical force field, which we have extended to liquid hydrogen fluoride (HF) in this work. The parameterization, called XPHF, is built upon the same formalism introduced for the XP3P model of liquid water, which is based on the polarized molecular orbital (PMO) semiempirical quantum chemistry method and the dipole-preserving polarization consistent point charge model. We introduce a fluorine parameter set for PMO, and find good agreement for various gas-phase results of small HF clusters compared to experiments and ab initio calculations at the M06-2X/MG3S level of theory. In addition, the XPHF model shows reasonable agreement with experiments for a variety of structural and thermodynamic properties in the liquid state, including radial distribution functions, interaction energies, diffusion coefficients, and densities at various state points.

  10. Competition of static magnetic and dynamic photon forces in electronic transport through a quantum dot

    NASA Astrophysics Data System (ADS)

    Abdullah, Nzar Rauf; Tang, Chi-Shung; Manolescu, Andrei; Gudmundsson, Vidar

    2016-09-01

    We investigate theoretically the balance of the static magnetic and the dynamical photon forces in the electron transport through a quantum dot in a photon cavity with a single photon mode. The quantum dot system is connected to external leads and the total system is exposed to a static perpendicular magnetic field. We explore the transport characteristics through the system by tuning the ratio, \\hslash {ωγ}/\\hslash {ωc} , between the photon energy, \\hslash {ωγ} , and the cyclotron energy, \\hslash {ωc} . Enhancement in the electron transport with increasing electron–photon coupling is observed when \\hslash {ωγ}/\\hslash {ωc}>1 . In this case the photon field dominates and stretches the electron charge distribution in the quantum dot, extending it towards the contact area for the leads. Suppression in the electron transport is found when \\hslash {ωγ}/\\hslash {ωc}<1 , as the external magnetic field causes circular confinement of the charge density around the dot.

  11. Quantum mechanical force field for hydrogen fluoride with explicit electronic polarization

    PubMed Central

    Mazack, Michael J. M.; Gao, Jiali

    2014-01-01

    The explicit polarization (X-Pol) theory is a fragment-based quantum chemical method that explicitly models the internal electronic polarization and intermolecular interactions of a chemical system. X-Pol theory provides a framework to construct a quantum mechanical force field, which we have extended to liquid hydrogen fluoride (HF) in this work. The parameterization, called XPHF, is built upon the same formalism introduced for the XP3P model of liquid water, which is based on the polarized molecular orbital (PMO) semiempirical quantum chemistry method and the dipole-preserving polarization consistent point charge model. We introduce a fluorine parameter set for PMO, and find good agreement for various gas-phase results of small HF clusters compared to experiments and ab initio calculations at the M06-2X/MG3S level of theory. In addition, the XPHF model shows reasonable agreement with experiments for a variety of structural and thermodynamic properties in the liquid state, including radial distribution functions, interaction energies, diffusion coefficients, and densities at various state points. PMID:24880295

  12. Influence of Force Fields and Quantum Chemistry Approach on Spectral Densities of BChl a in Solution and in FMO Proteins.

    PubMed

    Chandrasekaran, Suryanarayanan; Aghtar, Mortaza; Valleau, Stéphanie; Aspuru-Guzik, Alán; Kleinekathöfer, Ulrich

    2015-08-01

    Studies on light-harvesting (LH) systems have attracted much attention after the finding of long-lived quantum coherences in the exciton dynamics of the Fenna-Matthews-Olson (FMO) complex. In this complex, excitation energy transfer occurs between the bacteriochlorophyll a (BChl a) pigments. Two quantum mechanics/molecular mechanics (QM/MM) studies, each with a different force-field and quantum chemistry approach, reported different excitation energy distributions for the FMO complex. To understand the reasons for these differences in the predicted excitation energies, we have carried out a comparative study between the simulations using the CHARMM and AMBER force field and the Zerner intermediate neglect of differential orbital (ZINDO)/S and time-dependent density functional theory (TDDFT) quantum chemistry methods. The calculations using the CHARMM force field together with ZINDO/S or TDDFT always show a wider spread in the energy distribution compared to those using the AMBER force field. High- or low-energy tails in these energy distributions result in larger values for the spectral density at low frequencies. A detailed study on individual BChl a molecules in solution shows that without the environment, the density of states is the same for both force field sets. Including the environmental point charges, however, the excitation energy distribution gets broader and, depending on the applied methods, also asymmetric. The excitation energy distribution predicted using TDDFT together with the AMBER force field shows a symmetric, Gaussian-like distribution. PMID:26156758

  13. Force on a slow moving impurity due to thermal and quantum fluctuations in a 1D Bose-Einstein condensate

    SciTech Connect

    Roberts, David; Sykes, Andrew

    2009-01-01

    We study the drag force acting on an impurity moving through a 1D Bose-Einstein condensate in the presence of both quantum and thermal fluctuations. We are able to find exact analytical solutions of the partial differential equations to the level of the Bogoliubov approximation. At zero temperature, we find a nonzero force is exerted on the impurity at subcritical velocities, due to the scattering of quantum fluctuations. We make the following explicit assumptions: far from the impurity the system is in a quantum state given by that of a zero (or finite) temperature Bose-Einstein condensate, and the scattering process generates only causally related reflection/transmission. The results raise unanswered questions in the quantum dynamics associated with the formation of persistent currents.

  14. Refinement of sensitivity and resolution at marine CSEM survey using fictitious wave domain

    NASA Astrophysics Data System (ADS)

    Kusuda, K.; Goto, T. N.

    2015-12-01

    Marine controlled-source electromagnetic (CSEM) survey is considered as a technique in practice for the exploration of resistive hydrocarbon resources. Although CSEM could provide additional information to seismic surveys, the improvement of its resolution is one of the great issues for hydrocarbon exploration. We demonstrate the improvement of the resolution of CSEM data with our method. Recently, the interpretation of marine controlled-source electromagnetic (CSEM) data in the fictitious wave domain has been developed by analytically transforming Maxwell equations from the diffusive domain to the fictitious wave domain. However, the resolution of CSEM data in the fictitious wave domain has not been well exploited. In the present study, we conduct numerical simulations using a three dimensional resistivity model as a sub-seafloor structure including resistive anomalies such as gas hydrate by using finite-difference time-domain (FDTD) method. First, we compare the waveforms in the diffusive and fictitious wave domains. Since electromagnetic propagates like seismic wave in the fictitious wave domain, the response of anomalies are separated from other waves such as direct one and the sensitivity of anomalies becomes higher compared with the data in the diffusive domain. In order to discuss with the resolution, we have developed a gradient-based 3D full waveform inversion of CSEM data in the fictitious wave domain. From our numerical results, we conclude that a high resolution result is obtained by analyzing in the fictitious wave domain. In future work, we planned to examine applying the real observed data of marine CSEM survey.

  15. Entropy flow in quantum heat engines

    NASA Astrophysics Data System (ADS)

    Ansari, Mohammad; Nazarov, Yuli

    2015-03-01

    We evaluate Shannon and Renyi entropy flows from generic quantum heat engines (QHE) to a weakly-coupled probe environment kept in thermal equilibrium. We show the flows are determined by two quantities: heat flow and fictitious dissipation that manifest the quantum coherence in the engine. Our theory leads to novel physics in quantum heat engines.

  16. U-2 with fictitious NASA markings to support CIA cover story for pilot Gary Powers, shot down over S

    NASA Technical Reports Server (NTRS)

    1960-01-01

    After Francis Gary Powers was shot down over the Soviet Union during a CIA spy flight on 1 May 1960, NASA issued a press release with a cover story about a U-2 conducting weather research that may have strayed off course after the pilot 'reported difficulties with his oxygen equipment.' To bolster the cover-up, a U-2 was quickly painted in NASA markings, with a fictitious NASA serial number, and put on display for the news media at the NASA Flight Research Center at Edwards Air Force Base on 6 May 1960. The next day, Soviet Premier Nikita Kruschev exposed the cover-up by revealing that the pilot had been captured, and espionage equipment had been recovered from the wreckage. 7 May 1956 - NACA Director Dr. Hugh L. Dryden issues a press release stating that U-2 aircraft are conducting weather research for NACA with Air Force support from Watertown, Nevada. 22 May 1956 - A second press release is issued with cover story for U-2 aircraft operating overseas. 1 May 1960 - Francis Gary Powers is shot down near Sverdlovsk. 6 May 1960 - U-2 with fictitious NASA serial number and NASA markings is shown to news media to bolster cover story of NASA weather research flights with U-2. 7 May 1960 - Soviet Premier Kruschev announces capture and confession of Powers. 1960 - Dr. Hugh L. Dryden tells senate committee that some 200 U-2 flights carrying NASA weather instrumentation have taken place since 1956. 2 April 1971 - NASA receives two U-2C aircraft for high-altitude research.

  17. On the Potential Implications of Reports of Fictitious Drug Use for Survey Research on Juvenile Delinquency.

    PubMed

    Meldrum, Ryan Charles; Piquero, Alex R

    2015-08-01

    A variety of methodological issues have been raised over self-reports of delinquency and its correlates. In this study, we call attention to the provision of untruthful information and provide an investigation of this issue using a survey item that assesses a respondent's use of a fictitious drug in relation to reports of delinquency and traditional criminological correlates. Bivariate and multivariate analyses were conducted based on data drawn from a probability sample of middle and high school students in Florida. Results show (a) there are important differences on key criminological variables between respondents who report use of a fictitious drug and those who do not; (b) the internal consistency of a variety index of delinquency is particularly sensitive to the inclusion of respondents reporting the use of a fictitious drug; and (c) the effect size of some criminological variables on delinquency may be sensitive to controlling for reports of fictitious drug use. Overall, the inclusion of fictitious drug use items within etiological models may serve as a useful approach to further establishing the reliability and validity of information provided by survey respondents. PMID:24535948

  18. Casimir-like force arising from quantum fluctuations in a slowly moving dilute Bose-Einstein condensate.

    PubMed

    Roberts, D C; Pomeau, Y

    2005-09-30

    We calculate a force due to zero-temperature quantum fluctuations on a stationary object in a moving superfluid flow. We model the object by a localized potential varying only in the flow direction and model the flow by a three-dimensional weakly interacting Bose-Einstein condensate at zero temperature. We show that this force exists for any arbitrarily small flow velocity and discuss the implications for the stability of superfluid flow. PMID:16241666

  19. Exchange-induced relaxation in the presence of a fictitious field

    NASA Astrophysics Data System (ADS)

    Sorce, Dennis J.; Mangia, Silvia; Liimatainen, Timo; Garwood, Michael; Michaeli, Shalom

    2014-08-01

    In the present study we derive a solution for two site fast exchange-induced relaxation in the presence of a fictitious magnetic field as generated by amplitude and frequency modulated RF pulses. This solution provides a means to analyze data obtained from relaxation experiments with the method called RAFFn (Relaxation Along a Fictitious Field of rank n), in which a fictitious field is created in a coordinate frame undergoing multi-fold rotation about n axes (rank n). The RAFF2 technique is relevant to MRI relaxation methods that provide good contrast enhancement for tumor detection. The relaxation equations for n = 2 are derived for the fast exchange regime using density matrix formalism. The method of derivation can be further extended to obtain solutions for n > 2.

  20. Exchange-induced relaxation in the presence of a fictitious field.

    PubMed

    Sorce, Dennis J; Mangia, Silvia; Liimatainen, Timo; Garwood, Michael; Michaeli, Shalom

    2014-08-01

    In the present study we derive a solution for two site fast exchange-induced relaxation in the presence of a fictitious magnetic field as generated by amplitude and frequency modulated RF pulses. This solution provides a means to analyze data obtained from relaxation experiments with the method called RAFFn (Relaxation Along a Fictitious Field of rank n), in which a fictitious field is created in a coordinate frame undergoing multi-fold rotation about n axes (rank n). The RAFF2 technique is relevant to MRI relaxation methods that provide good contrast enhancement for tumor detection. The relaxation equations for n=2 are derived for the fast exchange regime using density matrix formalism. The method of derivation can be further extended to obtain solutions for n>2. PMID:24911888

  1. Exchange-Induced Relaxation in the Presence of a Fictitious Field

    PubMed Central

    Sorce, Dennis J.; Mangia, Silvia; Liimatainen, Timo; Garwood, Michael; Michaeli, Shalom

    2014-01-01

    In the present study we derive a solution for two site fast exchange-induced relaxation in the presence of a fictitious magnetic field as generated by amplitude and frequency modulated RF pulses. This solution provides a means to analyze data obtained from relaxation experiments with the method called RAFFn (Relaxation Along a Fictitious Field of rank n), in which a fictitious field is created in a coordinate frame undergoing multi-fold rotation about n axes (rank n). The RAFF2 technique is relevant to MRI relaxation methods that provide good contrast enhancement for tumor detection. The relaxation equations for n = 2 are derived for the fast exchange regime using density matrix formalism. The method of derivation can be further extended to obtain solutions for n > 2. PMID:24911888

  2. A fictitious domain method for fluid/solid coupling applied to the lithosphere/asthenosphere interaction.

    NASA Astrophysics Data System (ADS)

    Cerpa, Nestor; Hassani, Riad; Gerbault, Muriel

    2014-05-01

    A large variety of geodynamical problems can be viewed as a solid/fluid interaction problem coupling two bodies with different physics. In particular the lithosphere/asthenosphere mechanical interaction in subduction zones belongs to this kind of problem, where the solid lithosphere is embedded in the asthenospheric viscous fluid. In many fields (Industry, Civil Engineering,etc.), in which deformations of solid and fluid are "small", numerical modelers consider the exact discretization of both domains and fit as well as possible the shape of the interface between the two domains, solving the discretized physic problems by the Finite Element Method (FEM). Although, in a context of subduction, the lithosphere is submitted to large deformation, and can evolve into a complex geometry, thus leading to important deformation of the surrounding asthenosphere. To alleviate the precise meshing of complex geometries, numerical modelers have developed non-matching interface methods called Fictitious Domain Methods (FDM). The main idea of these methods is to extend the initial problem to a bigger (and simpler) domain. In our version of FDM, we determine the forces at the immersed solid boundary required to minimize (at the least square sense) the difference between fluid and solid velocities at this interface. This method is first-order accurate and the stability depends on the ratio between the fluid background mesh size and the interface discretization. We present the formulation and provide benchmarks and examples showing the potential of the method : 1) A comparison with an analytical solution of a viscous flow around a rigid body. 2) An experiment of a rigid sphere sinking in a viscous fluid (in two and three dimensional cases). 3) A comparison with an analog subduction experiment. Another presentation aims at describing the geodynamical application of this method to Andean subduction dynamics, studying cyclic slab folding on the 660 km discontinuity, and its relationship

  3. Quantum mechanics in non-inertial reference frames: Time-dependent rotations and loop prolongations

    SciTech Connect

    Klink, W.H.; Wickramasekara, S.

    2013-09-15

    This is the fourth in a series of papers on developing a formulation of quantum mechanics in non-inertial reference frames. This formulation is grounded in a class of unitary cocycle representations of what we have called the Galilean line group, the generalization of the Galilei group to include transformations amongst non-inertial reference frames. These representations show that in quantum mechanics, just as the case in classical mechanics, the transformations to accelerating reference frames give rise to fictitious forces. In previous work, we have shown that there exist representations of the Galilean line group that uphold the non-relativistic equivalence principle as well as representations that violate the equivalence principle. In these previous studies, the focus was on linear accelerations. In this paper, we undertake an extension of the formulation to include rotational accelerations. We show that the incorporation of rotational accelerations requires a class of loop prolongations of the Galilean line group and their unitary cocycle representations. We recover the centrifugal and Coriolis force effects from these loop representations. Loops are more general than groups in that their multiplication law need not be associative. Hence, our broad theoretical claim is that a Galilean quantum theory that holds in arbitrary non-inertial reference frames requires going beyond groups and group representations, the well-established framework for implementing symmetry transformations in quantum mechanics. -- Highlights: •A formulation of Galilean quantum mechanics in non-inertial reference frames is presented. •The Galilei group is generalized to infinite dimensional Galilean line group. •Loop prolongations of Galilean line group contain central extensions of Galilei group. •Unitary representations of the loops are constructed. •These representations lead to terms in the Hamiltonian corresponding to fictitious forces, including centrifugal and Coriolis

  4. On the optimal use of fictitious time in variation of parameters methods with application to BG14

    NASA Technical Reports Server (NTRS)

    Gottlieb, Robert G.

    1991-01-01

    The optimal way to use fictitious time in variation of parameter methods is presented. Setting fictitious time to zero at the end of each step is shown to cure the instability associated with some types of problems. Only some parameters are reinitialized, thereby retaining redundant information.

  5. Kinematics and dynamics in noninertial quantum frames of reference

    NASA Astrophysics Data System (ADS)

    Angelo, R. M.; Ribeiro, A. D.

    2012-11-01

    From the principle that there is no absolute description of a physical state, we advance the approach according to which one should be able to describe the physics from the perspective of a quantum particle. The kinematics seen from this frame of reference is shown to be rather unconventional. In particular, we discuss several subtleties emerging in the relative formulation of central notions, such as vector states, the classical limit, entanglement, uncertainty relations and the complementary principle. A Hamiltonian formulation is also derived which correctly encapsulates effects of fictitious forces associated with the accelerated motion of the frame. Our approach shows, therefore, how to formulate nonrelativistic quantum mechanics within noninertial reference frames which can be consistently described by the theory, with no appeal to classical elements.

  6. 16 CFR 301.11 - Fictitious or non-existing animal designations prohibited.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... designations prohibited. 301.11 Section 301.11 Commercial Practices FEDERAL TRADE COMMISSION REGULATIONS UNDER SPECIFIC ACTS OF CONGRESS RULES AND REGULATIONS UNDER FUR PRODUCTS LABELING ACT Regulations § 301.11 Fictitious or non-existing animal designations prohibited. No trade names, coined names, nor other names...

  7. 16 CFR 301.11 - Fictitious or non-existing animal designations prohibited.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... designations prohibited. 301.11 Section 301.11 Commercial Practices FEDERAL TRADE COMMISSION REGULATIONS UNDER SPECIFIC ACTS OF CONGRESS RULES AND REGULATIONS UNDER FUR PRODUCTS LABELING ACT Regulations § 301.11 Fictitious or non-existing animal designations prohibited. No trade names, coined names, nor other names...

  8. 16 CFR 301.11 - Fictitious or non-existing animal designations prohibited.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... designations prohibited. 301.11 Section 301.11 Commercial Practices FEDERAL TRADE COMMISSION REGULATIONS UNDER SPECIFIC ACTS OF CONGRESS RULES AND REGULATIONS UNDER FUR PRODUCTS LABELING ACT Regulations § 301.11 Fictitious or non-existing animal designations prohibited. No trade names, coined names, nor other names...

  9. Multipolar Ewald Methods, 2: Applications Using a Quantum Mechanical Force Field

    PubMed Central

    2015-01-01

    A fully quantum mechanical force field (QMFF) based on a modified “divide-and-conquer” (mDC) framework is applied to a series of molecular simulation applications, using a generalized Particle Mesh Ewald method extended to multipolar charge densities. Simulation results are presented for three example applications: liquid water, p-nitrophenylphosphate reactivity in solution, and crystalline N,N-dimethylglycine. Simulations of liquid water using a parametrized mDC model are compared to TIP3P and TIP4P/Ew water models and experiment. The mDC model is shown to be superior for cluster binding energies and generally comparable for bulk properties. Examination of the dissociative pathway for dephosphorylation of p-nitrophenylphosphate shows that the mDC method evaluated with the DFTB3/3OB and DFTB3/OPhyd semiempirical models bracket the experimental barrier, whereas DFTB2 and AM1/d-PhoT QM/MM simulations exhibit deficiencies in the barriers, the latter for which is related, in part, to the anomalous underestimation of the p-nitrophenylate leaving group pKa. Simulations of crystalline N,N-dimethylglycine are performed and the overall structure and atomic fluctuations are compared with the experiment and the general AMBER force field (GAFF). The QMFF, which was not parametrized for this application, was shown to be in better agreement with crystallographic data than GAFF. Our simulations highlight some of the application areas that may benefit from using new QMFFs, and they demonstrate progress toward the development of accurate QMFFs using the recently developed mDC framework. PMID:25691830

  10. Reactive Force Fields Based on Quantum Mechanics for Applications to Materials at Extreme Conditions

    NASA Astrophysics Data System (ADS)

    van Duin, Adri C. T.; Zybin, Sergey V.; Chenoweth, Kimberley; Zhang, Luzheng; Han, Si-Ping; Strachan, Alejandro; Goddard, William A.

    2006-07-01

    Understanding the response of energetic materials (EM) to thermal or shock loading at the atomistic level demands a highly accurate description of the reaction dynamics of multimillion-atom systems to capture the complex chemical and mechanical behavior involved: nonequilibrium energy/mass transfer, molecule excitation and decomposition under high strain/heat rates, formation of defects, plastic flow, and phase transitions. To enable such simulations, we developed the ReaxFF reactive force fields based on quantum mechanics (QM) calculations of reactants, products, high-energy intermediates and transition states, but using functional forms suitable for large-scale molecular dynamics simulations of chemical reactions under extreme conditions. The elements of ReaxFF are: - charge distributions change instantaneously as atomic coordinates change, - all valence interactions use bond orders derived uniquely from the bond distances which in turn describe uniquely the energies and forces, - three body (angle) and four body (torsion and inversion) terms are allowed but not required, - a general "van der Waals" term describes short range Pauli repulsion and long range dispersion interactions, which with Coulomb terms are included between all pairs of atoms (no bond or angle exclusions), - no environmental distinctions are made of atoms involving the same element; thus every carbon has the same parameters whether in diamond, graphite, benzene, porphyrin, allyl radical, HMX or TATP. ReaxFF uses the same functional form and parameters for reactive simulations in hydrocarbons, polymers, metal oxides, and metal alloys, allowing mixtures of all these systems into one simulation. We will present an overview of recent progress in ReaxFF developments, including the extension of ReaxFF to nitramine-based (nitromethane, HMX) and peroxide-based (TATP) explosives. To demonstrate the versatility and transferability of ReaxFF, we also present applications to silicone polymer poly

  11. A General Quantum Mechanically Derived Force Field (QMDFF) for Molecules and Condensed Phase Simulations.

    PubMed

    Grimme, Stefan

    2014-10-14

    A black-box type procedure is presented for the generation of molecule-specific, classical potential energy functions (force-field, FF) solely from quantum mechanically (QM) computed input data. The approach can treat covalently bound molecules and noncovalent complexes with almost arbitrary structure. The necessary QM information consists of the equilibrium structure and the corresponding Hessian matrix, atomic partial charges, and covalent bond orders. The FF fit is performed automatically without any further input and yields a specific (nontransferable) potential which very closely resembles the QM reference potential near the equilibrium. The resulting atomistic, fully flexible FF is anharmonic and allows smooth dissociation of covalent bonds into atoms. A newly proposed force-constant-bond-energy relation with little empiricism provides reasonably accurate (about 5-10% error) atomization energies for almost arbitrary diatomic and polyatomic molecules. Intra- and intermolecular noncovalent interactions are treated by using well established and accurate D3 dispersion coefficients, CM5 charges from small basis set QM calculations, and a new interatomic repulsion potential. Particular attention has been paid to the construction of the torsion potentials which are partially obtained from automatic QM-tight-binding calculations for model systems. Detailed benchmarks are presented for conformational energies, atomization energies, vibrational frequencies, gas phase structures of organic molecules, and transition metal complexes. Comparisons to results from standard FF or semiempirical methods reveal very good accuracy of the new potential. While further studies are necessary to validate the approach, the initial results suggest QMDFF as a routine tool for the computation of a wide range of properties and systems (e.g., for molecular dynamics of isolated molecules, explicit solvation, self-solvation (melting) or even for molecular crystals) in particular when standard

  12. Interviewing children about real and fictitious events: revisiting the narrative elaboration procedure.

    PubMed

    Camparo, L B; Wagner, J T; Saywitz, K J

    2001-02-01

    Elementary school children participated in a staged event. Two weeks later they were randomly assigned to three interview conditions: (a) a streamlined version of the Narrative Elaboration (NE) procedure involving training in the use of reminder cue cards, (b) exposure to reminder cue cards without training in their use (cue card control group), and (c) a standard interview including no NE training or exposure to reminder cue cards (standard-interview control group). Children in each interview condition were questioned about the staged event and a fictitious event to determine whether children trained in the streamlined NE procedure would provide more information about a staged event than would children in the two control groups and whether the NE interview would result in increased reporting of false information when questioned about a fictitious event. Results indicated that children questioned with the NE interview reported a greater amount of accurate, but not a greater amount of inaccurate, information during cue-card presentation for the staged event than did the cue-card control group. Analyses further indicated that the NE-interview group did not report significantly more false information about the fictitious event than did children in the two control groups. Large standard deviations for the NE-interview children's cue-card recall indicate that the streamlined NE procedure was useful for many children in reporting the staged event, but may have contributed to a small number of children providing false information for the fictitious event. Further research is being conducted to determine which children may be more likely to be helped and which children may be more likely to provide false information regarding a fictitious event. PMID:11276862

  13. Benchmarking density functionals for hydrogen-helium mixtures with quantum Monte Carlo: Energetics, pressures, and forces

    NASA Astrophysics Data System (ADS)

    Clay, Raymond C.; Holzmann, Markus; Ceperley, David M.; Morales, Miguel A.

    2016-01-01

    An accurate understanding of the phase diagram of dense hydrogen and helium mixtures is a crucial component in the construction of accurate models of Jupiter, Saturn, and Jovian extrasolar planets. Though density-functional-theory-based first-principles methods have the potential to provide the accuracy and computational efficiency required for this task, recent benchmarking in hydrogen has shown that achieving this accuracy requires a judicious choice of functional, and a quantification of the errors introduced. In this work, we present a quantum Monte Carlo (QMC) -based benchmarking study of a wide range of density functionals for use in hydrogen-helium mixtures at thermodynamic conditions relevant for Jovian planets. Not only do we continue our program of benchmarking energetics and pressures, but we deploy QMC-based force estimators and use them to gain insight into how well the local liquid structure is captured by different density functionals. We find that TPSS, BLYP, and vdW-DF are the most accurate functionals by most metrics, and that the enthalpy, energy, and pressure errors are very well behaved as a function of helium concentration. Beyond this, we highlight and analyze the major error trends and relative differences exhibited by the major classes of functionals, and we estimate the magnitudes of these effects when possible.

  14. Determining polarizable force fields with electrostatic potentials from quantum mechanical linear response theory.

    PubMed

    Wang, Hao; Yang, Weitao

    2016-06-14

    We developed a new method to calculate the atomic polarizabilities by fitting to the electrostatic potentials (ESPs) obtained from quantum mechanical (QM) calculations within the linear response theory. This parallels the conventional approach of fitting atomic charges based on electrostatic potentials from the electron density. Our ESP fitting is combined with the induced dipole model under the perturbation of uniform external electric fields of all orientations. QM calculations for the linear response to the external electric fields are used as input, fully consistent with the induced dipole model, which itself is a linear response model. The orientation of the uniform external electric fields is integrated in all directions. The integration of orientation and QM linear response calculations together makes the fitting results independent of the orientations and magnitudes of the uniform external electric fields applied. Another advantage of our method is that QM calculation is only needed once, in contrast to the conventional approach, where many QM calculations are needed for many different applied electric fields. The molecular polarizabilities obtained from our method show comparable accuracy with those from fitting directly to the experimental or theoretical molecular polarizabilities. Since ESP is directly fitted, atomic polarizabilities obtained from our method are expected to reproduce the electrostatic interactions better. Our method was used to calculate both transferable atomic polarizabilities for polarizable molecular mechanics' force fields and nontransferable molecule-specific atomic polarizabilities. PMID:27305996

  15. Quantum radiation reaction force on a one-dimensional cavity with two relativistic moving mirrors

    NASA Astrophysics Data System (ADS)

    Alves, Danilo T.; Granhen, Edney R.; Pires, Wagner P.

    2010-08-01

    We consider a real massless scalar field inside a cavity with two moving mirrors in a two-dimensional spacetime, satisfying the Dirichlet boundary condition at the instantaneous position of the boundaries, for arbitrary and relativistic laws of motion. Considering vacuum as the initial field state, we obtain formulas for the exact value of the energy density of the field and the quantum force acting on the boundaries, which extend results found in previous papers [D. T. Alves, E. R. Granhen, H. O. Silva, and M. G. Lima, Phys. Rev. DPRVDAQ1550-7998 81, 025016 (2010); 10.1103/PhysRevD.81.025016L. Li and B.-Z. Li, Phys. Lett. APYLAAG0375-9601 300, 27 (2002); 10.1016/S0375-9601(02)00674-6L. Li and B.-Z. Li, Chin. Phys. Lett.CPLEEU0256-307X 19, 1061 (2002); 10.1088/0256-307X/19/8/310L. Li and B.-Z. Li, Acta Phys. Sin.WLHPAR1000-3290 52, 2762 (2003); C. K. Cole and W. C. Schieve, Phys. Rev. A 64, 023813 (2001)PLRAAN1050-294710.1103/PhysRevA.64.023813]. For the particular cases of a cavity with just one moving boundary, nonrelativistic velocities, or in the limit of infinity length of the cavity (a single mirror), our results coincide with those found in the literature.

  16. Quantum radiation reaction force on a one-dimensional cavity with two relativistic moving mirrors

    SciTech Connect

    Alves, Danilo T.; Granhen, Edney R.; Pires, Wagner P.

    2010-08-15

    We consider a real massless scalar field inside a cavity with two moving mirrors in a two-dimensional spacetime, satisfying the Dirichlet boundary condition at the instantaneous position of the boundaries, for arbitrary and relativistic laws of motion. Considering vacuum as the initial field state, we obtain formulas for the exact value of the energy density of the field and the quantum force acting on the boundaries, which extend results found in previous papers [D. T. Alves, E. R. Granhen, H. O. Silva, and M. G. Lima, Phys. Rev. D 81, 025016 (2010); L. Li and B.-Z. Li, Phys. Lett. A 300, 27 (2002); L. Li and B.-Z. Li, Chin. Phys. Lett. 19, 1061 (2002); L. Li and B.-Z. Li, Acta Phys. Sin. 52, 2762 (2003); C. K. Cole and W. C. Schieve, Phys. Rev. A 64, 023813 (2001)]. For the particular cases of a cavity with just one moving boundary, nonrelativistic velocities, or in the limit of infinity length of the cavity (a single mirror), our results coincide with those found in the literature.

  17. Analytic nuclear forces and molecular properties from full configuration interaction quantum Monte Carlo

    SciTech Connect

    Thomas, Robert E.; Overy, Catherine; Opalka, Daniel; Alavi, Ali; Knowles, Peter J.; Booth, George H.

    2015-08-07

    Unbiased stochastic sampling of the one- and two-body reduced density matrices is achieved in full configuration interaction quantum Monte Carlo with the introduction of a second, “replica” ensemble of walkers, whose population evolves in imaginary time independently from the first and which entails only modest additional computational overheads. The matrices obtained from this approach are shown to be representative of full configuration-interaction quality and hence provide a realistic opportunity to achieve high-quality results for a range of properties whose operators do not necessarily commute with the Hamiltonian. A density-matrix formulated quasi-variational energy estimator having been already proposed and investigated, the present work extends the scope of the theory to take in studies of analytic nuclear forces, molecular dipole moments, and polarisabilities, with extensive comparison to exact results where possible. These new results confirm the suitability of the sampling technique and, where sufficiently large basis sets are available, achieve close agreement with experimental values, expanding the scope of the method to new areas of investigation.

  18. Benchmarking density functionals for hydrogen-helium mixtures with quantum Monte Carlo: Energetics, pressures, and forces

    DOE PAGESBeta

    Clay, Raymond C.; Holzmann, Markus; Ceperley, David M.; Morales, Maguel A.

    2016-01-19

    An accurate understanding of the phase diagram of dense hydrogen and helium mixtures is a crucial component in the construction of accurate models of Jupiter, Saturn, and Jovian extrasolar planets. Though DFT based rst principles methods have the potential to provide the accuracy and computational e ciency required for this task, recent benchmarking in hydrogen has shown that achieving this accuracy requires a judicious choice of functional, and a quanti cation of the errors introduced. In this work, we present a quantum Monte Carlo based benchmarking study of a wide range of density functionals for use in hydrogen-helium mixtures atmore » thermodynamic conditions relevant for Jovian planets. Not only do we continue our program of benchmarking energetics and pressures, but we deploy QMC based force estimators and use them to gain insights into how well the local liquid structure is captured by di erent density functionals. We nd that TPSS, BLYP and vdW-DF are the most accurate functionals by most metrics, and that the enthalpy, energy, and pressure errors are very well behaved as a function of helium concentration. Beyond this, we highlight and analyze the major error trends and relative di erences exhibited by the major classes of functionals, and estimate the magnitudes of these e ects when possible.« less

  19. Optical and Atomic Force Microscopy Characterization of PbI2 Quantum Dots

    NASA Technical Reports Server (NTRS)

    Mu, R.; Tung, Y. S.; Ueda, A.; Henderson, D. O.

    1997-01-01

    Lead iodide (PbI2) clusters were synthesized from the chemical reaction of NaI (or KI) with Pb(NO3)2 in H2O, D2O, CH3OH, and C3H7OH media. The observation of the absorption features above 350 nm with the help of integrating sphere accessory strongly suggests the quantum dot formation of PbI2 in solution. Spectral comparison between the synthesized PbI2 clusters in solution and PbI2 nanophase by impregnation of PbI2 in four different pore-sized porous silica indicates that the PbI2 cluster size in solution is less than 2.5 nm in lateral dimension. Atomic force microscopy (AFM) measurements show that the PbL clusters deposited onto three different molecularly flat surfaces are single-layered. The measured height is 1.0 - 0.1 nm. The swollen layer thickness can be attributed to the intralayer contraction from the strong lateral interaction among PbI2 molecules, which is supported by ab initio calculation. Raman scattering measurement of LO and TO modes of PbI2 in bulk and in the confined state were also conducted in 50-150 cu cm region. The observed three bands at 74, %, 106 1/cm are assigned to TO2, LO2, and LO, mode, respectively. The relatively small red-shift in LO modes may be caused by the surface phonon polaritons of PbI2 nanophase in the porous silica.

  20. Existence of a Steady Flow of Stokes Fluid Past a Linear Elastic Structure Using Fictitious Domain

    NASA Astrophysics Data System (ADS)

    Halanay, Andrei; Murea, Cornel Marius; Tiba, Dan

    2016-06-01

    We use fictitious domain method with penalization for the Stokes equation in order to obtain approximate solutions in a fixed larger domain including the domain occupied by the structure. The coefficients of the fluid problem, excepting the penalizing term, are independent of the deformation of the structure. It is easy to check the inf-sup condition and the coercivity of the Stokes problem in the fixed domain. Subtracting the structure equations from the fictitious fluid equations in the structure domain, we obtain a weak formulation in a fixed domain, where the continuity of the stress at the interface does not appear explicitly. Existence of a solution is proved when the structure displacement is generated by a finite number of modes.

  1. Bed Partner “Gas-Lighting” as a Cause of Fictitious Sleep-Talking

    PubMed Central

    Bashford, James; Leschziner, Guy

    2015-01-01

    A case report highlighting a rare and striking, but perhaps under-recognized, cause of reported sleep-talking to a specialist sleep clinic, involving “gas-lighting” by the bed partner. Citation: Bashford J, Leschziner G. Bed partner “gas-lighting” as a cause of fictitious sleep-talking. J Clin Sleep Med 2015;11(10):1237–1238. PMID:26094915

  2. Stuck in the here and now: Construction of fictitious and future experiences following ventromedial prefrontal damage.

    PubMed

    Bertossi, Elena; Aleo, Fabio; Braghittoni, Davide; Ciaramelli, Elisa

    2016-01-29

    There is increasing interest in uncovering the cognitive and neural bases of episodic future thinking (EFT), the ability to imagine events relevant to one's own future. Recent functional neuroimaging evidence shows that the ventromedial prefrontal cortex (vmPFC) is engaged during EFT. However, vmPFC is also activated during imagination of fictitious, atemporal experiences. Therefore, its role in EFT is currently unclear. To test (1) whether vmPFC is critical for EFT, and (2) whether it supports EFT specifically, or, rather, construction of any complex experience, patients with focal lesions to vmPFC (vmPFC patients), control patients with lesions not involving vmPFC, and healthy controls were asked to imagine personal future experiences and fictitious experiences. Compared to the control groups, vmPFC patients were impaired at imagining both future and fictitious experiences, indicating a general deficit in constructing novel experiences. Unlike the control groups, however, vmPFC patients had more difficulties in imagining future compared to fictitious experiences. Exploratory correlation analyses showed that general construction deficits correlated with lesion volume in BA 11, whereas specific EFT deficits correlated with lesion volume in BA 32 and BA 10. Together, these findings indicate that vmPFC is crucial for EFT. We propose, however, that different vmPFC subregions may support different component processes of EFT: the most ventral part, BA 11, may underlie core constructive processes needed to imagine any complex experience (e.g., scene construction), whereas BA 10 and BA 32 may mediate simulation of those specific experiences that likely await us in the future. PMID:26707714

  3. Simultaneous Updating of Model and Controller Based on Fictitious Reference Iterative Tuning

    NASA Astrophysics Data System (ADS)

    Kaneko, Osamu; Miyachi, Makoto; Fujii, Takao

    In this paper, we provide a new method for updating a mathematical model of a plant and a controller, simultaneously, by using only one-shot experimental data. Here, we propose a fictitious controller which is described by the following triple: a nominal model of the plant, an initial controller designed for the nominal model, and a parameterized model of the plant. In addition, we introduce a cost function which involves the fictitious controller, the nominal model, and the actual experimental data of the closed loop with the initial controller. Then, for this very reason of the minimization of the introduced cost function, we show that utilizing the fictitious reference iterative tuning, which was proposed by the authors, enables us to obtain both a more accurate model and a more desirable controller than the nominal model and the initial controller, respectively. We also give quantitative evaluation of the difference between the nominal model and the updated one, and that between the initial controller and the updated one. Finally, we give examples in order to illustrate the validity of the proposed method.

  4. Model of a realistic InP surface quantum dot extrapolated from atomic force microscopy results

    NASA Astrophysics Data System (ADS)

    Barettin, Daniele; De Angelis, Roberta; Prosposito, Paolo; Auf der Maur, Matthias; Casalboni, Mauro; Pecchia, Alessandro

    2014-05-01

    We report on numerical simulations of a zincblende InP surface quantum dot (QD) on \\text{I}{{\\text{n}}_{0.48}}\\text{G}{{\\text{a}}_{0.52}}\\text{P} buffer. Our model is strictly based on experimental structures, since we extrapolated a three-dimensional dot directly by atomic force microscopy results. Continuum electromechanical, \\vec{k}\\;\\cdot \\;\\vec{p} bandstructure and optical calculations are presented for this realistic structure, together with benchmark calculations for a lens-shape QD with the same radius and height of the extrapolated dot. Interesting similarities and differences are shown by comparing the results obtained with the two different structures, leading to the conclusion that the use of a more realistic structure can provide significant improvements in the modeling of QDs fact, the remarkable splitting for the electron p-like levels of the extrapolated dot seems to prove that a realistic experimental structure can reproduce the right symmetry and a correct splitting usually given by atomistic calculations even within the multiband \\vec{k}\\;\\cdot \\;\\vec{p} approach. Moreover, the energy levels and the symmetry of the holes are strongly dependent on the shape of the dot. In particular, as far as we know, their wave function symmetries do not seem to resemble to any results previously obtained with simulations of zincblende ideal structures, such as lenses or truncated pyramids. The magnitude of the oscillator strengths is also strongly dependent on the shape of the dot, showing a lower intensity for the extrapolated dot, especially for the transition between the electrons and holes ground state, as a result of a relevant reduction of the wave functions overlap. We also compare an experimental photoluminescence spectrum measured on an homogeneous sample containing about 60 dots with a numerical ensemble average derived from single dot calculations. The broader energy range of the numerical spectrum motivated us to perform further

  5. Model of a realistic InP surface quantum dot extrapolated from atomic force microscopy results.

    PubMed

    Barettin, Daniele; De Angelis, Roberta; Prosposito, Paolo; Auf der Maur, Matthias; Casalboni, Mauro; Pecchia, Alessandro

    2014-05-16

    We report on numerical simulations of a zincblende InP surface quantum dot (QD) on In₀.₄₈Ga₀.₅₂ buffer. Our model is strictly based on experimental structures, since we extrapolated a three-dimensional dot directly by atomic force microscopy results. Continuum electromechanical, [Formula: see text] bandstructure and optical calculations are presented for this realistic structure, together with benchmark calculations for a lens-shape QD with the same radius and height of the extrapolated dot. Interesting similarities and differences are shown by comparing the results obtained with the two different structures, leading to the conclusion that the use of a more realistic structure can provide significant improvements in the modeling of QDs fact, the remarkable splitting for the electron p-like levels of the extrapolated dot seems to prove that a realistic experimental structure can reproduce the right symmetry and a correct splitting usually given by atomistic calculations even within the multiband [Formula: see text] approach. Moreover, the energy levels and the symmetry of the holes are strongly dependent on the shape of the dot. In particular, as far as we know, their wave function symmetries do not seem to resemble to any results previously obtained with simulations of zincblende ideal structures, such as lenses or truncated pyramids. The magnitude of the oscillator strengths is also strongly dependent on the shape of the dot, showing a lower intensity for the extrapolated dot, especially for the transition between the electrons and holes ground state, as a result of a relevant reduction of the wave functions overlap. We also compare an experimental photoluminescence spectrum measured on an homogeneous sample containing about 60 dots with a numerical ensemble average derived from single dot calculations. The broader energy range of the numerical spectrum motivated us to perform further verifications, which have clarified some aspects of the experimental

  6. Ab initio molecular dynamics with noisy and cheap quantum Monte Carlo forces: accurate calculation of vibrational frequencies

    NASA Astrophysics Data System (ADS)

    Luo, Ye; Sorella, Sandro

    2014-03-01

    We introduce a general and efficient method for the calculation of vibrational frequencies of electronic systems, ranging from molecules to solids. By performing damped molecular dynamics with ab initio forces, we show that quantum vibrational frequencies can be evaluated by diagonalizing the time averaged position-position or force-force correlation matrices, although the ionic motion is treated on the classical level within the Born-Oppenheimer approximation. The novelty of our approach is to evaluate atomic forces with QMC by means of a highly accurate and correlated variational wave function which is optimized simultaneously during the dynamics. QMC is an accurate and promising many-body technique for electronic structure calculation thanks to massively parallel computers. However, since infinite statistics is not feasible, property evaluation may be affected by large noise that is difficult to harness. Our approach controls the QMC stochastic bias systematically and gives very accurate results with moderate computational effort, namely even with noisy forces. We prove the accuracy and efficiency of our method on the water monomer[A. Zen et al., JCTC 9 (2013) 4332] and dimer. We are currently working on the challenging problem of simulating liquid water at ambient conditions.

  7. Combined friction force microscopy and quantum chemical investigation of the tribotronic response at the propylammonium nitrate-graphite interface.

    PubMed

    Li, H; Atkin, R; Page, A J

    2015-06-28

    The energetic origins of the variation in friction with potential at the propylammonium nitrate-graphite interface are revealed using friction force microscopy (FFM) in combination with quantum chemical simulations. For boundary layer lubrication, as the FFM tip slides energy is dissipated via (1) boundary layer ions and (2) expulsion of near-surface ion layers from the space between the surface and advancing tip. Simulations reveal how changing the surface potential changes the ion composition of the boundary and near surface layer, which controls energy dissipation through both pathways, and thus the friction. PMID:26027558

  8. A superconducting quantum interference device based read-out of a subattonewton force sensor operating at millikelvin temperatures

    SciTech Connect

    Usenko, O.; Vinante, A.; Wijts, G.; Oosterkamp, T. H.

    2011-03-28

    We present a scheme to measure the displacement of a nanomechanical resonator at cryogenic temperature. The technique is based on the use of a superconducting quantum interference device to detect the magnetic flux change induced by a magnetized particle attached on the end of the resonator. Unlike conventional interferometric techniques, our detection scheme does not involve direct power dissipation in the resonator, and therefore, is particularly suitable for ultralow temperature applications. We demonstrate its potential by cooling an ultrasoft silicon cantilever to a noise temperature of 25 mK, corresponding to a subattonewton thermal force noise of 0.5 aN/{radical}(Hz).

  9. Quantum Derivative Fitting and Biomolecular Force Fields: Functional Form, Coupling Terms, Charge Flux, Nonbond Anharmonicity, and Individual Dihedral Potentials.

    PubMed

    Hagler, A T

    2015-12-01

    Computer simulations are increasingly prevalent, complementing experimental studies in all fields of biophysics, chemistry, and materials. Their utility, however, is critically dependent on the validity of the underlying force fields employed. In this Perspective we review the ability of quantum mechanics, and in particular analytical ab initio derivatives, to inform on the nature of intra- and intermolecular interactions. The power inherent in the exploitation of forces and second derivatives (Hessians) to derive force fields for a variety of compound types, including inorganic, organic, and biomolecules, is explored. We discuss the use of these quantities along with QM energies and geometries to determine force constants, including nonbond and electrostatic parameters, and to assess the functional form of the energy surface. The latter includes the optimal form of out-of-plane interactions and the necessity for anharmonicity, and terms to account for coupling between internals, to adequately represent the energy of intramolecular deformations. In addition, individual second derivatives of the energy with respect to selected interaction coordinates, such as interatomic distances or individual dihedral angles, have been shown to select out for the corresponding interactions, annihilating other interactions in the potential expression. Exploitation of these quantities allows one to probe the individual interaction and explore phenomena such as, for example, anisotropy of atom-atom nonbonded interactions, charge flux, or the functional form of isolated dihedral angles, e.g., a single dihedral X-C-C-Y about a tetrahedral C-C bond. PMID:26642978

  10. Ab initio molecular dynamics with noisy forces: Validating the quantum Monte Carlo approach with benchmark calculations of molecular vibrational properties

    SciTech Connect

    Luo, Ye Sorella, Sandro; Zen, Andrea

    2014-11-21

    We present a systematic study of a recently developed ab initio simulation scheme based on molecular dynamics and quantum Monte Carlo. In this approach, a damped Langevin molecular dynamics is employed by using a statistical evaluation of the forces acting on each atom by means of quantum Monte Carlo. This allows the use of an highly correlated wave function parametrized by several variational parameters and describing quite accurately the Born-Oppenheimer energy surface, as long as these parameters are determined at the minimum energy condition. However, in a statistical method both the minimization method and the evaluation of the atomic forces are affected by the statistical noise. In this work, we study systematically the accuracy and reliability of this scheme by targeting the vibrational frequencies of simple molecules such as the water monomer, hydrogen sulfide, sulfur dioxide, ammonia, and phosphine. We show that all sources of systematic errors can be controlled and reliable frequencies can be obtained with a reasonable computational effort. This work provides convincing evidence that this molecular dynamics scheme can be safely applied also to realistic systems containing several atoms.

  11. Numerical implementation of the method of fictitious domains for elliptic equations

    NASA Astrophysics Data System (ADS)

    Temirbekov, Almas N.

    2016-08-01

    In the paper, we study the elliptical type equation with strongly changing coefficients. We are interested in studying such equation because the given type equations are yielded when we use the fictitious domain method. In this paper we suggest a special method for numerical solution of the elliptic equation with strongly changing coefficients. We have proved the theorem for the assessment of developed iteration process convergence rate. We have developed computational algorithm and numerical calculations have been done to illustrate the effectiveness of the suggested method.

  12. Quantum UV/IR relations and holographic dark energy from entropic force

    NASA Astrophysics Data System (ADS)

    Li, Miao; Wang, Yi

    2010-04-01

    We investigate the implications of the entropic force formalism proposed by Verlinde. We show that an UV/IR relation proposed by Cohen et al., as well as an uncertainty principle proposed by Hogan can be derived from the entropic force formalism. We show that applying the entropic force formalism to cosmology, there is an additional term in the Friedmann equation, which can be identified as holographic dark energy. We also propose an intuitive picture of holographic screen, which can be thought of as an improvement of Susskind's holographic screen.

  13. Introducing QMC/MMpol: Quantum Monte Carlo in Polarizable Force Fields for Excited States.

    PubMed

    Guareschi, Riccardo; Zulfikri, Habiburrahman; Daday, Csaba; Floris, Franca Maria; Amovilli, Claudio; Mennucci, Benedetta; Filippi, Claudia

    2016-04-12

    We present for the first time a quantum mechanics/molecular mechanics scheme which combines quantum Monte Carlo with the reaction field of classical polarizable dipoles (QMC/MMpol). In our approach, the optimal dipoles are self-consistently generated at the variational Monte Carlo level and then used to include environmental effects in diffusion Monte Carlo. We investigate the performance of this hybrid model in describing the vertical excitation energies of prototypical small molecules solvated in water, namely, methylenecyclopropene and s-trans acrolein. Two polarization regimes are explored where either the dipoles are optimized with respect to the ground-state solute density (polGS) or different sets of dipoles are separately brought to equilibrium with the states involved in the electronic transition (polSS). By comparing with reference supermolecular calculations where both solute and solvent are treated quantum mechanically, we find that the inclusion of the response of the environment to the excitation of the solute leads to superior results than the use of a frozen environment (point charges or polGS), in particular, when the solute-solvent coupling is dominated by electrostatic effects which are well recovered in the polSS condition. QMC/MMpol represents therefore a robust scheme to treat important environmental effects beyond static point charges, combining the accuracy of QMC with the simplicity of a classical approach. PMID:26959751

  14. Construction of high-order force-gradient algorithms for integration of motion in classical and quantum systems.

    PubMed

    Omelyan, I P; Mryglod, I M; Folk, R

    2002-08-01

    A consequent approach is proposed to construct symplectic force-gradient algorithms of arbitrarily high orders in the time step for precise integration of motion in classical and quantum mechanics simulations. Within this approach the basic algorithms are first derived up to the eighth order by direct decompositions of exponential propagators and further collected using an advanced composition scheme to obtain the algorithms of higher orders. Contrary to the scheme proposed by Chin and Kidwell [Phys. Rev. E 62, 8746 (2000)], where high-order algorithms are introduced by standard iterations of a force-gradient integrator of order four, the present method allows one to reduce the total number of expensive force and its gradient evaluations to a minimum. At the same time, the precision of the integration increases significantly, especially with increasing the order of the generated schemes. The algorithms are tested in molecular dynamics and celestial mechanics simulations. It is shown, in particular, that the efficiency of the advanced fourth-order-based algorithms is better approximately in factors 5 to 1000 for orders 4 to 12, respectively. The results corresponding to sixth- and eighth-order-based composition schemes are also presented up to the sixteenth order. For orders 14 and 16, such highly precise schemes, at considerably smaller computational costs, allow to reduce unphysical deviations in the total energy up in 100 000 times with respect to those of the standard fourth-order-based iteration approach. PMID:12241312

  15. Electrostatic force analysis, optical measurements, and structural characterization of zinc oxide colloidal quantum dots synthesized by sol-gel method

    NASA Astrophysics Data System (ADS)

    Choi, Min S.; Meshik, Xenia; Mukherjee, Souvik; Farid, Sidra; Doan, Samuel; Covnot, Leigha; Dutta, Mitra; Stroscio, Michael A.

    2015-11-01

    ZnO quantum dots (QDs) are used in a variety of applications due to several desirable characteristics, including a wide band gap, luminescence, and biocompatibility. Wurtzite ZnO QDs also exhibit a spontaneous polarization along the growth axis, leading to large electric fields. In this work, ZnO QDs around 7 nm in diameter are synthesized using the sol-gel method. Their size and structure are confirmed using photoluminescence, Raman spectroscopy, atomic force microscopy, and transmission electron microscopy. Additionally, electrostatic force microscopy (EFM) is used to measure the amplitude change in the probe which is associated with the electric field produced by ZnO immobilized by layer-by-layer synthesis technique. The measured electrostatic field of 10 8 V/m is comparable to theoretically predicted value. Additionally, the strength of the electrostatic field is shown to depend on the orientation of the QD's c-axis. These results demonstrate a unique technique of quantifying ZnO's electric force using EFM.

  16. Comparative study of donor-induced quantum dots in Si nano-channels by single-electron transport characterization and Kelvin probe force microscopy

    SciTech Connect

    Tyszka, K.; Moraru, D.; Samanta, A.; Mizuno, T.; Tabe, M.; Jabłoński, R.

    2015-06-28

    We comparatively study donor-induced quantum dots in Si nanoscale-channel transistors for a wide range of doping concentration by analysis of single-electron tunneling transport and surface potential measured by Kelvin probe force microscopy (KPFM). By correlating KPFM observations of donor-induced potential landscapes with simulations based on Thomas-Fermi approximation, it is demonstrated that single-electron tunneling transport at lowest gate voltages (for smallest coverage of screening electrons) is governed most frequently by only one dominant quantum dot, regardless of doping concentration. Doping concentration, however, primarily affects the internal structure of the quantum dot. At low concentrations, individual donors form most of the quantum dots, i.e., “donor-atom” quantum dots. In contrast, at high concentrations above metal-insulator transition, closely placed donors instead of individual donors form more complex quantum dots, i.e., “donor-cluster” quantum dots. The potential depth of these “donor-cluster” quantum dots is significantly reduced by increasing gate voltage (increasing coverage of screening electrons), leading to the occurrence of multiple competing quantum dots.

  17. Ultracold fermions in real or fictitious magnetic fields: BCS-BEC evolution and type-I-type-II transition

    SciTech Connect

    Iskin, M.; Sa de Melo, C. A. R.

    2011-04-15

    We study ultracold neutral fermion superfluids in the presence of fictitious magnetic fields, as well as charged fermion superfluids in the presence of real magnetic fields. Charged fermion superfluids undergo a phase transition from type-I to type-II superfluidity, where the magnetic properties of the superfluid change from being a perfect diamagnet without vortices to a partial diamagnet with the emergence of the Abrikosov vortex lattice. The transition from type-I to type-II superfluidity is tuned by changing the scattering parameter (interaction) for fixed density. We also find that neutral fermion superfluids such as {sup 6}Li and {sup 40}K are extreme type-II superfluids and are more robust to the penetration of a fictitious magnetic field in the BCS-BEC crossover region near unitarity, where the critical fictitious magnetic field reaches a maximum as a function of the scattering parameter (interaction).

  18. Exact solution of a quantum forced time-dependent harmonic oscillator

    NASA Technical Reports Server (NTRS)

    Yeon, Kyu Hwang; George, Thomas F.; Um, Chung IN

    1992-01-01

    The Schrodinger equation is used to exactly evaluate the propagator, wave function, energy expectation values, uncertainty values, and coherent state for a harmonic oscillator with a time dependent frequency and an external driving time dependent force. These quantities represent the solution of the classical equation of motion for the time dependent harmonic oscillator.

  19. Decoherence under many-body system-environment interactions: A stroboscopic representation based on a fictitiously homogenized interaction rate

    NASA Astrophysics Data System (ADS)

    Álvarez, Gonzalo A.; Danieli, Ernesto P.; Levstein, Patricia R.; Pastawski, Horacio M.

    2007-06-01

    An environment interacting with portions of a system leads to multiexponential interaction rates. Within the Keldysh formalism, we fictitiously homogenize the system-environment interaction yielding a uniform decay rate facilitating the evaluation of the propagators. Through an injection procedure we neutralize the fictitious interactions. This technique justifies a stroboscopic representation of the system-environment interaction which is useful for numerical implementation and converges to the natural continuous process. We apply this procedure to a fermionic two-level system and use the Jordan-Wigner transformation to solve a two-spin swapping gate in the presence of a spin environment.

  20. Decoherence induced by magnetic impurities in a quantum hall system

    SciTech Connect

    Kagalovsky, V.; Chudnovskiy, A. L.

    2013-04-15

    Scattering by magnetic impurities is known to destroy coherence of electron motion in metals and semiconductors. We investigate the decoherence introduced in a single act of electron scattering by a magnetic impurity in a quantum Hall system. For this, we introduce a fictitious nonunitary scattering matrix for electrons that reproduces the exactly calculated scattering probabilities. The strength of decoherence is identified by the deviation of eigenvalues of the product from unity. Using the fictitious scattering matrix, we estimate the width of the metallic region at the quantum Hall effect inter-plateau transition and its dependence on the exchange coupling strength and the degree of polarization of magnetic impurities.

  1. An Application of Fictitious Reference Iterative Tuning to State Feedback Control

    NASA Astrophysics Data System (ADS)

    Matsui, Yoshihiro; Akamatsu, Shunichi; Kimura, Tomohiko; Nakano, Kazushi; Sakurama, Kazunori

    In this paper, an application method of Fictitious Reference Iterative Tuning (FRIT), which has been developed for controller gain tuning for single-input single-output systems, to state feedback gain tuning for single-input multivariable systems is proposed. Transient response data of a single-input multivariable plant obtained under closed-loop operation is used for model matching by the FRIT in time domain. The data is also used in frequency domain to estimate the stability and to improve the control performance of the closed-loop system with the state feedback gain tuned by the method. The method is applied to a state feedback control system for an inverted pendulum with an inertia rotor and its usefulness is illustrated through experiments.

  2. Mission analysis for the ion beam deflection of fictitious asteroid 2015 PDC

    NASA Astrophysics Data System (ADS)

    Bombardelli, Claudio; Amato, Davide; Cano, Juan Luis

    2016-01-01

    Based on a hypothetical asteroid impact scenario proposed during the 2015 IAA Planetary Defense Conference (PDC), we study the deflection of fictitious asteroid 2015 PDC starting from ephemeris data provided by the conference organizers. A realistic mission scenario is investigated that makes use of an ion beam shepherd spacecraft as a primary deflection technique. The article deals with the design of a low-thrust rendezvous trajectory to the asteroid, the estimation of the propagated covariance ellipsoid and the outcome of an ion beam slow-push deflection starting from three worst case scenarios (impacts in New Delhi, Dhaka and Tehran). Displacing the impact point towards an extremely low-populated, easy-to-evacuate region, as opposed to full deflection, is found to be a more effective mitigation approach. Mission design, technical and political aspects are discussed.

  3. A fictitious domain approach for the Stokes problem based on the extended finite element method

    NASA Astrophysics Data System (ADS)

    Court, Sébastien; Fournié, Michel; Lozinski, Alexei

    2014-01-01

    In the present work, we propose to extend to the Stokes problem a fictitious domain approach inspired by eXtended Finite Element Method and studied for Poisson problem in [Renard]. The method allows computations in domains whose boundaries do not match. A mixed finite element method is used for fluid flow. The interface between the fluid and the structure is localized by a level-set function. Dirichlet boundary conditions are taken into account using Lagrange multiplier. A stabilization term is introduced to improve the approximation of the normal trace of the Cauchy stress tensor at the interface and avoid the inf-sup condition between the spaces for velocity and the Lagrange multiplier. Convergence analysis is given and several numerical tests are performed to illustrate the capabilities of the method.

  4. Revealing energy level structure of individual quantum dots by tunneling rate measured by single-electron sensitive electrostatic force spectroscopy.

    PubMed

    Roy-Gobeil, Antoine; Miyahara, Yoichi; Grutter, Peter

    2015-04-01

    We present theoretical and experimental studies of the effect of the density of states of a quantum dot (QD) on the rate of single-electron tunneling that can be directly measured by electrostatic force microscopy (e-EFM) experiments. In e-EFM, the motion of a biased atomic force microscope cantilever tip modulates the charge state of a QD in the Coulomb blockade regime. The charge dynamics of the dot, which is detected through its back-action on the capacitavely coupled cantilever, depends on the tunneling rate of the QD to a back-electrode. The density of states of the QD can therefore be measured through its effect on the energy dependence of tunneling rate. We present experimental data on individual 5 nm colloidal gold nanoparticles that exhibit a near continuous density of state at 77 K. In contrast, our analysis of already published data on self-assembled InAs QDs at 4 K clearly reveals discrete degenerate energy levels. PMID:25761141

  5. Three-dimensional magnetic trap lattice on an atom chip with an optically induced fictitious magnetic field

    SciTech Connect

    Yan Hui

    2010-05-15

    A robust type of three-dimensional magnetic trap lattice on an atom chip combining optically induced fictitious magnetic field with microcurrent-carrying wires is proposed. Compared to the regular optical lattice, the individual trap in this three-dimensional magnetic trap lattice can be easily addressed and manipulated.

  6. An operator splitting scheme with a distributed Lagrange multiplier based fictitious domain method for wave propagation problems

    NASA Astrophysics Data System (ADS)

    Bokil, Vrushali A.; Glowinski, Roland

    2005-05-01

    We propose a novel fictitious domain method based on a distributed Lagrange multiplier technique for the solution of the time-dependent problem of scattering by an obstacle. We study discretizations that include a fully conforming approach as well as mixed finite element formulations utilizing the lowest order Nédélec edge elements (in 2D) on rectangular grids. We also present a symmetrized operator splitting scheme for the scattering problem, which decouples the operator that propagates the wave from the operator that enforces the Dirichlet condition on the boundary of an obstacle. A new perfectly matched layer (PML) model is developed to model the unbounded problem of interest. This model is based on a formulation of the wave equation as a system of first-order equations and uses a change of variables approach that has been developed to construct PML's for Maxwell's equations. We present an analysis of our fictitious domain approach for a one-dimensional wave problem. Based on calculations of reflection coefficients, we demonstrate the advantages of our fictitious domain approach over the staircase approximation of the finite difference method. We also demonstrate some important properties of the distributed multiplier approach that are not shared by a boundary multiplier fictitious domain approach for the same problem. Numerical results for two-dimensional wave problems that validate the effectiveness of the different methods are presented.

  7. Single quantum dot (QD) manipulation on nanowire using dielectrophoretic (DEP) force

    NASA Astrophysics Data System (ADS)

    Kim, J.; Lee, S. Y.; Suh, J.-K. F.; Park, J. H.; Shin, H. J.

    2011-02-01

    Au nanowires of 100 nm, 200nm and 400 nm widths with micro scale Au electrode were fabricated as electrodes to apply high electric field gradient for strong DEP force within the nanometer range. Au nanowires were fabricated on a silicon dioxide (SiO2) using lift-off process after e-beam lithography and e-beam evaporation. E-beam resister (ER) was patterned and a 50 nm thick Au layer. Photo resister (PR) was patterned to make Au microelectrode and did lift-off process. The Au nanowires with microelectrode were covered with SiO2 layer deposited with PECVD resulting in 1 um thick. Opened end of gold nanowires, the target surface for QD immobilization, were formed using etching processes. Single QD immobilization on the nanowire end-facet was accomplished through positive DEP force. Sine wave of 8 Vpp intensity and 3 MHz frequency was applied and it induced electric field of 108 V/m intensity and electric field gradient around Au nanowire to make strong positive DEP. Optical analysis confirmed the attachment of single QD on the nanowire. A single 25 nm diameter QD was manipulated on 100 nm, 200 nm and 400 nm width nanowires when 8 Vpp, 3 MHz sine wave was applied.

  8. Study of dispersion forces with quantum Monte Carlo: toward a continuum model for solvation.

    PubMed

    Amovilli, Claudio; Floris, Franca Maria

    2015-05-28

    We present a general method to compute dispersion interaction energy that, starting from London's interpretation, is based on the measure of the electronic electric field fluctuations, evaluated on electronic sampled configurations generated by quantum Monte Carlo. A damped electric field was considered in order to avoid divergence in the variance. Dispersion atom-atom C6 van der Waals coefficients were computed by coupling electric field fluctuations with static dipole polarizabilities. The dipole polarizability was evaluated at the diffusion Monte Carlo level by studying the response of the system to a constant external electric field. We extended the method to the calculation of the dispersion contribution to the free energy of solvation in the framework of the polarizable continuum model. We performed test calculations on pairs of some atomic systems. We considered He in ground and low lying excited states and Ne in the ground state and obtained a good agreement with literature data. We also made calculations on He, Ne, and F(-) in water as the solvent. Resulting dispersion contribution to the free energy of solvation shows the reliability of the method illustrated here. PMID:25535856

  9. Quantum mechanics in non-inertial reference frames: Time-dependent rotations and loop prolongations

    NASA Astrophysics Data System (ADS)

    Klink, W. H.; Wickramasekara, S.

    2013-09-01

    This is the fourth in a series of papers on developing a formulation of quantum mechanics in non-inertial reference frames. This formulation is grounded in a class of unitary cocycle representations of what we have called the Galilean line group, the generalization of the Galilei group to include transformations amongst non-inertial reference frames. These representations show that in quantum mechanics, just as the case in classical mechanics, the transformations to accelerating reference frames give rise to fictitious forces. In previous work, we have shown that there exist representations of the Galilean line group that uphold the non-relativistic equivalence principle as well as representations that violate the equivalence principle. In these previous studies, the focus was on linear accelerations. In this paper, we undertake an extension of the formulation to include rotational accelerations. We show that the incorporation of rotational accelerations requires a class of loop prolongations of the Galilean line group and their unitary cocycle representations. We recover the centrifugal and Coriolis force effects from these loop representations. Loops are more general than groups in that their multiplication law need not be associative. Hence, our broad theoretical claim is that a Galilean quantum theory that holds in arbitrary non-inertial reference frames requires going beyond groups and group representations, the well-established framework for implementing symmetry transformations in quantum mechanics.

  10. A convergence study of a new partitioned fluid-structure interaction algorithm based on fictitious mass and damping

    NASA Astrophysics Data System (ADS)

    Baek, Hyoungsu; Karniadakis, George Em

    2012-01-01

    We develop, analyze and validate a new method for simulating fluid-structure interactions (FSIs), which is based on fictitious mass and fictitious damping in the structure equation. We employ a partitioned method for the fluid and structure motions in conjunction with sub-iteration and Aitken relaxation. In particular, the use of such fictitious parameters requires sub-iterations in order to reduce the induced error in addition to the local temporal truncation error. To this end, proper levels of tolerance for terminating the sub-iteration procedure have been obtained in order to recover the formal order of temporal accuracy. For the coupled FSI problem, these fictitious terms have a significant effect, leading to better convergence rate and hence substantially smaller number of sub-iterations. Through analysis we identify the proper range of these parameters, which we then verify by corresponding numerical tests. We implement the method in the context of spectral element discretization, which is more sensitive than low-order methods to numerical instabilities arising in the explicit FSI coupling. However, the method we present here is simple and general and hence applicable to FSI based on any other discretization. We demonstrate the effectiveness of the method in applications involving 2D vortex-induced vibrations (VIV) and in 3D flexible arteries with structural density close to blood density. We also present 3D results for a patient-specific aneurysmal flow under pulsatile flow conditions examining, in particular, the sensitivity of the results on different values of the fictitious parameters.

  11. Quantum treatment of the time-dependent coupled oscillators under the action of a random force

    SciTech Connect

    Abdalla, M. Sebawe Nassar, M.M.

    2009-03-15

    In this communication we introduce the problem of time-dependent frequency converter under the action of external random force. We have assumed that the coupling parameter and the phase pump are explicitly time dependent. Using the equations of motion in the Heisenberg picture the dynamical operators are obtained, however, under a certain integrability condition. When the system is initially prepared in the even coherent states the squeezing phenomenon is discussed. The correlation function is also considered and it has been shown that the nonclassical properties are apparent and sensitive to any variation in the integrability parameter. Furthermore, the wave function in Schroedinger picture is calculated and used it to derive the wave function in the coherent states. The accurate definition of the creation and annihilation operators are also introduced and employed to diagonalize the Hamiltonian system.

  12. A variational linear-scaling framework to build practical, efficient next-generation orbital-based quantum force fields

    PubMed Central

    Giese, Timothy J.; Chen, Haoyuan; Dissanayake, Thakshila; Giambaşu, George M.; Heldenbrand, Hugh; Huang, Ming; Kuechler, Erich R.; Lee, Tai-Sung; Panteva, Maria T.; Radak, Brian K.; York, Darrin M.

    2013-01-01

    We introduce a new hybrid molecular orbital/density-functional modified divide-and-conquer (mDC) approach that allows the linear-scaling calculation of very large quantum systems. The method provides a powerful framework from which linear-scaling force fields for molecular simulations can be developed. The method is variational in the energy, and has simple, analytic gradients and essentially no break-even point with respect to the corresponding full electronic structure calculation. Furthermore, the new approach allows intermolecular forces to be properly balanced such that non-bonded interactions can be treated, in some cases, to much higher accuracy than the full calculation. The approach is illustrated using the second-order self-consistent charge density-functional tight-binding model (DFTB2). Using this model as a base Hamiltonian, the new mDC approach is applied to a series of water systems, where results show that geometries and interaction energies between water molecules are greatly improved relative to full DFTB2. In order to achieve substantial improvement in the accuracy of intermolecular binding energies and hydrogen bonded cluster geometries, it was necessary to extend the DFTB2 model to higher-order atom-centered multipoles for the second-order self-consistent intermolecular electrostatic term. Using generalized, linear-scaling electrostatic methods, timings demonstrate that the method is able to calculate a water system of 3000 atoms in less than half of a second, and systems of up to one million atoms in only a few minutes using a conventional desktop workstation. PMID:23814506

  13. Potential interstellar noble gas molecules: ArOH+ and NeOH+ rovibrational analysis from quantum chemical quartic force fields

    NASA Astrophysics Data System (ADS)

    Theis, Riley A.; Fortenberry, Ryan C.

    2016-03-01

    The discovery of ArH+ in the interstellar medium has shown that noble gas chemistry may be of more chemical significance than previously believed. The present work extends the known chemistry of small noble gas molecules to NeOH+ and ArOH+. Besides their respective neonium and argonium diatomic cation cousins, these hydroxyl cation molecules are the most stable small noble gas molecules analyzed of late. ArOH+ is once again more stable than the neon cation, but both are well-behaved enough for a complete quartic force field analysis of their rovibrational properties. The Ar-O bond in ArOH+ , for instance, is roughly three-quarters of the strength of the Ar-H bond in ArH+ highlighting the rigidity of this system. The rotational constants, geometries, and vibrational frequencies for both molecules and their various isotopologues are computed from ab initio quantum chemical theory at high-level, and it is shown that these cations may form in regions where peroxy or weakly-bound alcohols may be present. The resulting data should be of significant assistance for the laboratory or observational analysis of these potential interstellar molecules.

  14. Observing a fictitious stressful event: haematological changes, including circulating leukocyte activation.

    PubMed

    Mian, Rubina; Shelton-Rayner, Graham; Harkin, Brendan; Williams, Paul

    2003-03-01

    The aim of this study was to assess the effect of watching a psychological stressful event on the activation of leukocytes in healthy human volunteers. Blood samples were obtained from 32 healthy male and female subjects aged between 20 and 26 years before, during and after either watching an 83-minute horror film that none of the subjects had previously seen (The Texas Chainsaw Massacre, 1974) or by sitting quietly in a room (control group). Total differential cell counts, leukocyte activation as measured by the nitroblue tetrazolium (NBT) test, heart rate and blood pressure (BP) measurements were taken at defined time points. There were significant increases in peripheral circulating leukocytes, the number of activated circulating leukocytes, haemoglobin (Hb) concentration and haematocrit (Hct) in response to the stressor. These were accompanied by significant increases in heart rate, systolic and diastolic BP (P<0.05 from baseline). This is the first reported study on the effects of observing a psychologically stressful, albeit fictitious event on circulating leukocyte numbers and the state of leukocyte activation as determined by the nitrotetrazolium test. PMID:12637206

  15. Neither real nor fictitious but 'as if real'? A political ontology of the state.

    PubMed

    Hay, Colin

    2014-09-01

    The state is one of series of concepts (capitalism, patriarchy and class being others) which pose a particular kind of ontological difficulty and provoke a particular kind of ontological controversy - for it is far from self-evident that the object or entity to which they refer is in any obvious sense 'real'. In this paper I make the case for developing a distinct political ontology of the state which builds from such a reflection. In the process, I argue that the state is neither real nor fictitious, but 'as if real' - a conceptual abstraction whose value is best seen as an open analytical question. Thus understood, the state possesses no agency per se though it serves to define and construct a series of contexts within which political agency is both authorized (in the name of the state) and enacted (by those thereby authorized). The state is thus revealed as a dynamic institutional complex whose unity is at best partial, the constantly evolving outcome of unifying tendencies and dis-unifying counter-tendencies. PMID:25251140

  16. A wavelet Galerkin method employing B-spline bases for solid mechanics problems without the use of a fictitious domain

    NASA Astrophysics Data System (ADS)

    Tanaka, Satoyuki; Okada, Hiroshi; Okazawa, Shigenobu

    2012-07-01

    This study develops a wavelet Galerkin method (WGM) that uses B-spline wavelet bases for application to solid mechanics problems. A fictitious domain is often adopted to treat general boundaries in WGMs. In the analysis, the body is extended to its exterior but very low stiffness is applied to the exterior region. The stiffness matrix in the WGM becomes singular without the use of a fictitious domain. The problem arises from the lack of linear independence of the basis functions. A technique to remove basis functions that can be represented by the superposition of the other basis functions is proposed. The basis functions are automatically eliminated in the pre conditioning step. An adaptive strategy is developed using the proposed technique. The solution is refined by superposing finer wavelet functions. Numerical examples of solid mechanics problems are presented to demonstrate the multiresolution properties of the WGM.

  17. Hamiltonian flows with random-walk behaviour originating from zero-sum games and fictitious play

    NASA Astrophysics Data System (ADS)

    van Strien, Sebastian

    2011-06-01

    In this paper we introduce Hamiltonian dynamics, inspired by zero-sum games (best response and fictitious play dynamics). The Hamiltonian functions we consider are continuous and piecewise affine (and of a very simple form). It follows that the corresponding Hamiltonian vector fields are discontinuous and multi-valued. Differential equations with discontinuities along a hyperplane are often called 'Filippov systems', and there is a large literature on such systems, see for example (di Bernardo et al 2008 Theory and applications Piecewise-Smooth Dynamical Systems (Applied Mathematical Sciences vol 163) (London: Springer); Kunze 2000 Non-Smooth Dynamical Systems (Lecture Notes in Mathematics vol 1744) (Berlin: Springer); Leine and Nijmeijer 2004 Dynamics and Bifurcations of Non-smooth Mechanical Systems (Lecture Notes in Applied and Computational Mechanics vol 18) (Berlin: Springer)). The special feature of the systems we consider here is that they have discontinuities along a large number of intersecting hyperplanes. Nevertheless, somewhat surprisingly, the flow corresponding to such a vector field exists, is unique and continuous. We believe that these vector fields deserve attention, because it turns out that the resulting dynamics are rather different from those found in more classically defined Hamiltonian dynamics. The vector field is extremely simple: outside codimension-one hyperplanes it is piecewise constant and so the flow phit piecewise a translation (without stationary points). Even so, the dynamics can be rather rich and complicated as a detailed study of specific examples show (see for example theorems 7.1 and 7.2 and also (Ostrovski and van Strien 2011 Regular Chaotic Dynf. 16 129-54)). In the last two sections of the paper we give some applications to game theory, and finish with posing a version of the Palis conjecture in the context of the class of non-smooth systems studied in this paper. To Jacob Palis on his 70th birthday.

  18. Fictitious Reference Tuning of the Feed-Forward Controller in a Two-Degree-of-Freedom Control System

    NASA Astrophysics Data System (ADS)

    Kaneko, Osamu; Yamashina, Yusuke; Yamamoto, Shigeru

    In this paper, we provide a new effective tuning method to obtain the optimal parameter of the feed-forward controller in a two-degree-of-freedom (2DOF) control system for the purpose of achieving the desired response without using a mathematical model of a plant. The first author proposed “fictitious reference iterative tuning” (which is abbreviated to FRIT) as an effective method for the tuning of parameters of a controller by using only one-shot experimental data instead of using mathematical models of a plant. Here, we extend FRIT to the tuning of the feed-forward controller in a 2DOF control system and develop the off-line computation so as to be done by the least squares method. For these purposes, we introduce a new cost function consisting of the fictitious reference and the actual data (since we do not have to do iterative computation in the least squares method, we call the proposed method here as “fictitious reference tuning”). Since the new cost function is quadratically-parameterized, it is possible to analyze how far the obtained parameter is apart from the desired one. Thus, we then derive a pre-filter which is applied to the actual data so as to guarantee that the obtained parameter is close to the desired one. We also show that the proposed method is applicable to the case in which the initial experiment is performed in the conventional 1DOF control system. Finally, we illustrate experimental results in order to show the utility and the validity of the proposed method.

  19. Fictitious domains and level sets for moving boundary problems. Applications to the numerical simulation of tumor growth

    NASA Astrophysics Data System (ADS)

    Carmen Calzada, M.; Camacho, Gema; Fernández-Cara, Enrique; Marín, Mercedes

    2011-02-01

    In this work we present a new strategy for solving numerically a (relatively simple) model of tumor growth. In principle, this is devoted to describe avascular growth although, by choosing the parameters appropriately, it also permits to give an idea of the behavior after vascularization. The numerical methods rely on fictitious domain and level set techniques, with a combination of quadratic finite elements and finite differences approximations. We present a collection of numerical results that essentially coincide with others, previously obtained with other techniques.

  20. CAS22 - FORTRAN program for fast design and analysis of shock-free airfoil cascades using fictitious-gas concept

    NASA Technical Reports Server (NTRS)

    Dulikravich, D. S.; Sobieczky, H.

    1982-01-01

    A user-oriented computer program, CAS22, was developed that is applicable to aerodynamic analysis and transonic shock-free redesign of existing two-dimensional cascades of airfoils. This FORTRAN program can be used: (1) as an analysis code for full-potential, transonic, shocked or shock-free cascade flows; (2) as a design code for shock-free cascades that uses Sobieczky's fictitious-gas concept; and (3) as a shock-free design code followed automatically by the analysis in order to confirm that the newly obtained cascade shape provides for an entirely shock-free transonic flow field. A four-level boundary-conforming grid of an O type is generated. The shock-free design is performed by implementing Sobieczky's fictitious-gas concept of elliptic continuation from subsonic into supersonic flow domains. Recomputation inside each supersonic zone is performed by the method of characteristics in the rheograph plane by using isentropic gas relations. Besides converting existing cascade shapes with multiple shocked supersonic regions into shock-free cascades, CAS22 can also unchoke previously choked cascades and make them shock free.

  1. Assessment of a fictitious domain method for patient-specific biomechanical modelling of press-fit orthopaedic implantation.

    PubMed

    Kallivokas, L F; Na, S-W; Ghattas, O; Jaramaz, B

    2012-01-01

    In this article, we discuss an application of a fictitious domain method to the numerical simulation of the mechanical process induced by press-fitting cementless femoral implants in total hip replacement surgeries. Here, the primary goal is to demonstrate the feasibility of the method and its advantages over competing numerical methods for a wide range of applications for which the primary input originates from computed tomography-, magnetic resonance imaging- or other regular-grid medical imaging data. For this class of problems, the fictitious domain method is a natural choice, because it avoids the segmentation, surface reconstruction and meshing phases required by unstructured geometry-conforming simulation methods. We consider the implantation of a press-fit femoral artificial prosthesis as a prototype problem for sketching the application path of the methodology. Of concern is the assessment of the robustness and speed of the methodology, for both factors are critical if one were to consider patient-specific modelling. To this end, we report numerical results that exhibit optimal convergence rates and thus shed a favourable light on the approach. PMID:21424950

  2. Glioma cell density in a rat gene therapy model gauged by water relaxation rate along a fictitious magnetic field.

    PubMed

    Liimatainen, Timo; Sierra, Alejandra; Hanson, Timothy; Sorce, Dennis J; Ylä-Herttuala, Seppo; Garwood, Michael; Michaeli, Shalom; Gröhn, Olli

    2012-01-01

    Longitudinal and transverse rotating-frame relaxation time constants, T(1) (ρ) and T(2) (ρ) , have previously been successfully applied to detect gene therapy responses and acute stroke in animal models. Those experiments were performed with continuous-wave irradiation or with frequency-modulated pulses operating in an adiabatic regime. The technique called Relaxation Along a Fictitious Field (RAFF) is a recent extension of frequency-modulated rotating-frame relaxation methods. In RAFF, spin locking takes place along a fictitious magnetic field, and the decay rate is a function of both T(1ρ) and T(2ρ) processes. In this work, the time constant characterizing water relaxation with RAFF (T(RAFF) ) was evaluated for its utility as a marker of response to gene therapy in a rat glioma model. To investigate the sensitivity to early treatment response, we measured several rotating-frame and free-precession relaxation time constants and the water apparent diffusion coefficients, and these were compared with histological cell counts in 8 days of treated and control groups of animals. T(RAFF) was the only parameter exhibiting significant association with cell density in three different tumor regions (border, intermediate, and core tissues). These results indicate that T(RAFF) may provide a marker to identify tumors responding to treatment. PMID:21721037

  3. Glioma cell density in a rat gene therapy model gauged by water relaxation rate along a fictitious magnetic field

    PubMed Central

    Liimatainen, Timo; Sierra, Alejandra; Hanson, Timothy; Sorce, Dennis J; Ylä-Herttuala, Seppo; Garwood, Michael; Michaeli, Shalom; Gröhn, Olli

    2011-01-01

    Longitudinal and transverse rotating frame relaxation time constants, T1ρ and T2ρ, have previously been successfully applied to detect gene therapy responses and acute stroke in animal models. Those experiments were performed with continuous wave irradiation or with frequency-modulated pulses operating in an adiabatic regime. The technique called Relaxation Along a Fictitious Field (RAFF) is a recent extension of frequency-modulated rotating frame relaxation methods. In RAFF, spin-locking takes place along a fictitious magnetic field and the decay rate is a function of both T1ρ and T2ρ processes. In the present work, the time constant characterizing water relaxation with RAFF (TRAFF) was evaluated for its utility as a marker of response to gene therapy in a rat glioma model. To investigate the sensitivity to early treatment response, we measured several rotating frame and free precession relaxation time constants and the water apparent diffusion coefficients, and these were compared with histological cell counts in 8 days of treated and control groups of animals. TRAFF was the only parameter exhibiting significant association with cell density in three different tumor regions (border, intermediate, and core tissues). These results indicate that TRAFF may provide a marker to identify tumors responding to treatment. PMID:21721037

  4. Selective nanomanipulation of fluorescent polystyrene nano-beads and single quantum dots at gold nanostructures based on the AC-dielectrophoretic force

    NASA Astrophysics Data System (ADS)

    Kim, Jinsik; Hwang, Kyo Seon; Lee, Sangyoup; Park, Jung Ho; Shin, Hyun-Joon

    2015-11-01

    We introduced the selective manipulation of polystyrene (PS) nano-beads and single quantum dots (QDs) at a gold nanostructure by using the AC-dielectrophoretic (DEP) force. Manipulation in three degrees of freedom (end-facet, side, and position-selective manipulation) was accomplished in gold nanostructures between microelectrodes. A 10 μm gap between the microelectrodes, which has a 100 nm-wide nanowire and 200 nm-wide vortex nanostructures at the inside of the gap, was fabricated, and nanostructures were not connected with the electrodes. We also performed theoretical calculations to verify the selective manipulation through the floating AC-DEP force. A sufficiently high gradient of the square of the electric field (∇|E|2, ~1019 V2 m-3) was accomplished and controlled for achieving a strong attaching force of nanoparticles using the gap between microelectrodes and nanostructures as well as the rotation of structures. Fluorescent PS nano-beads and QDs were attached at the designed end facet, side, and position of nanostructures with high selectivity. A single QD attachment was also realized at gold nanostructures, and the attached QDs were verified as single using optical ``blinking'' measurements.We introduced the selective manipulation of polystyrene (PS) nano-beads and single quantum dots (QDs) at a gold nanostructure by using the AC-dielectrophoretic (DEP) force. Manipulation in three degrees of freedom (end-facet, side, and position-selective manipulation) was accomplished in gold nanostructures between microelectrodes. A 10 μm gap between the microelectrodes, which has a 100 nm-wide nanowire and 200 nm-wide vortex nanostructures at the inside of the gap, was fabricated, and nanostructures were not connected with the electrodes. We also performed theoretical calculations to verify the selective manipulation through the floating AC-DEP force. A sufficiently high gradient of the square of the electric field (∇|E|2, ~1019 V2 m-3) was accomplished and

  5. Joyce and Ulysses: integrated and user-friendly tools for the parameterization of intramolecular force fields from quantum mechanical data.

    PubMed

    Barone, Vincenzo; Cacelli, Ivo; De Mitri, Nicola; Licari, Daniele; Monti, Susanna; Prampolini, Giacomo

    2013-03-21

    The Joyce program is augmented with several new features, including the user friendly Ulysses GUI, the possibility of complete excited state parameterization and a more flexible treatment of the force field electrostatic terms. A first validation is achieved by successfully comparing results obtained with Joyce2.0 to literature ones, obtained for the same set of benchmark molecules. The parameterization protocol is also applied to two other larger molecules, namely nicotine and a coumarin based dye. In the former case, the parameterized force field is employed in molecular dynamics simulations of solvated nicotine, and the solute conformational distribution at room temperature is discussed. Force fields parameterized with Joyce2.0, for both the dye's ground and first excited electronic states, are validated through the calculation of absorption and emission vertical energies with molecular mechanics optimized structures. Finally, the newly implemented procedure to handle polarizable force fields is discussed and applied to the pyrimidine molecule as a test case. PMID:23389748

  6. Quantum criticality.

    PubMed

    Coleman, Piers; Schofield, Andrew J

    2005-01-20

    As we mark the centenary of Albert Einstein's seminal contribution to both quantum mechanics and special relativity, we approach another anniversary--that of Einstein's foundation of the quantum theory of solids. But 100 years on, the same experimental measurement that puzzled Einstein and his contemporaries is forcing us to question our understanding of how quantum matter transforms at ultra-low temperatures. PMID:15662409

  7. One Force

    NASA Astrophysics Data System (ADS)

    Kotas, Ronald R.

    2002-04-01

    There is only one entity that can extend force and couple through space; and it should be apparent that Electromagnetism is that entity. In the cases of the nuclear strong force and the nuclear weak force, this is the same fundamental Electromagnetism manifesting itself in two different ways in the nucleus. It remains the same basic Electromagnetism. On the other hand, General Relativity fails to produce force at a distance, fails the Cavendish experiment, and does not allow an apple to fall to the ground. The result shows there is only Electromagnetism that functions through physical nature providing gravity, actions in the nucleus, as well as all other physical actions universally, including Gravity and Gravitation. There are many direct proofs of this, the same proofs as in NUCLEAR QUANTUM GRAVITATION. In contrast, General Relativity plainly relies on fallacy abstract and incoherent proofs; proofs which have now been mostly disproved. In the past it was deemed necessary by some to have an "ether" to propagate Electromagnetic waves. The fallacy concept of time space needs "space distortions" in order to cause gravity. However, Electromagnetic gravity does not have this problem. Clearly there is only ONE FORCE that causes Gravity, Electromagnetism, the Nuclear Strong Force, and the Nuclear Weak Force, and that ONE FORCE is Electromagnetism.

  8. Fictitious Reference Iterative Tuning for Non-Minimum Phase Systems in the IMC Architecture: Simultaneous Attainment of Controllers and Models

    NASA Astrophysics Data System (ADS)

    Kaneko, Osamu; Nguyen, Hien Thi; Wadagaki, Yusuke; Yamamoto, Shigeru

    This paper provides a practical and meaningful application of controller parameter tuning. Here, we propose a simultaneous attainment of a desired controller and a mathematical model of a plant by utilizing the fictitious reference iterative tuning (FRIT), which is a useful method of controller parameter tuning with only one-shot experimental data, in the internal model control (IMC) architecture. Particularly, this paper focuses on systems with unstable zeros which cannot be eliminated in many applications. We explain how the utilization of the FRIT is effective for obtaining not only the desired control parameter values but also an appropriate mathematical model of the plant. In order to show the effectiveness and the validity of the proposed method, we give illustrative examples.

  9. A direct investigation of photocharge transfer across monomolecular layer between C60 and CdS quantum dots by photoassisted conductive atomic force microscopy

    NASA Astrophysics Data System (ADS)

    Jiang, Xiaohong; Liu, He; Zhang, Xingtang; Cheng, Gang; Wang, Shujie; Du, Zuliang

    2016-04-01

    The composite assembly of C60 and CdS Quantum Dots (QDs) on ITO substrate was prepared by Langmuir-Blodgett (LB) technique using arachic acid (AA), stearic acid (SA) and octadecanyl amine (OA) as additives. Photoassisted conductive atomic force microscopy was used to make point contact current-voltage (I-V) measurements on both the CdS QDs and the composite assembly of C60/CdS. The result make it clear that the CdS, C60/CdS assemblies deposited on ITO substrate showed linear characteristics and the current increased largely under illumination comparing with that in the dark. The coherent, nonresonant tunneling mechanism was used to explain the current occurrence. It is considered that the photoinduced carriers CdS QDs tunneled through alkyl chains increased the current rapidly.

  10. Synthesis, crystal structure, vibrational spectral analysis and Z-scan studies of a new organic crystal N,N‧dimethylurea ninhydrin: A scaled quantum mechanical force field study

    NASA Astrophysics Data System (ADS)

    John, Jerin Susan; Sajan, D.; Umadevi, T.; Chaitanya, K.; Sankar, Pranitha; Philip, Reji

    2015-10-01

    A new organic material, N,N‧dimethylurea ninhydrin (3a,8a-dihydroxy-1,3-dimethyl-1,3,3a,8a-tetrahydroindeno[2,1-d]imidazole-2,8-dione) (NDUN) was synthesized. Structural details were obtained from single crystal X-ray diffraction (XRD) data. A detailed interpretation of the vibrational spectra is carried out with the aid of normal coordinate analysis following the scaled quantum mechanical force field methodology. TG/DTA and 1H NMR studies were carried out. Linear optical properties were studied from UV-Vis spectra. From the open aperture Z-scan data, it is found that the molecule shows third order nonlinear optical behaviour due to two photon absorption (2PA) mechanism.

  11. A fictitious domain method for lithosphere-asthenosphere interaction: Application to periodic slab folding in the upper mantle

    NASA Astrophysics Data System (ADS)

    Cerpa, Nestor G.; Hassani, Riad; Gerbault, Muriel; Prévost, Jean-Herve

    2014-05-01

    present a new approach for the lithosphere-asthenosphere interaction in subduction zones. The lithosphere is modeled as a Maxwell viscoelastic body sinking in the viscous asthenosphere. Both domains are discretized by the finite element method, and we use a staggered coupling method. The interaction is provided by a nonmatching interface method called the fictitious domain method. We describe a simplified formulation of this numerical technique and present 2-D examples and benchmarks. We aim at studying the effect of mantle viscosity on the cyclicity of slab folding at the 660 km depth transition zone. Such cyclicity has previously been shown to occur depending on the kinematics of both the overriding and subducting plates, in analog and numerical models that approximate the 660 km depth transition zone as an impenetrable barrier. Here we applied far-field plate velocities corresponding to those of the South-American and Nazca plates at present. Our models show that the viscosity of the asthenosphere impacts on folding cyclicity and consequently on the slab's dip as well as the stress regime of the overriding plate. Values of the mantle viscosity between 3 and 5 × 1020 Pa s are found to produce cycles similar to those reported for the Andes, which are of the order of 30-40 Myr (based on magmatism and sedimentological records). Moreover, we discuss the episodic development of horizontal subduction induced by cyclic folding and, hence, propose a new explanation for episodes of flat subduction under the South-American plate.

  12. High-temperature high-pressure phases of lithium from electron force field (eFF) quantum electron dynamics simulations

    PubMed Central

    Kim, Hyungjun; Su, Julius T.; Goddard, William A.

    2011-01-01

    We recently developed the electron force field (eFF) method for practical nonadiabatic electron dynamics simulations of materials under extreme conditions and showed that it gave an excellent description of the shock thermodynamics of hydrogen from molecules to atoms to plasma, as well as the electron dynamics of the Auger decay in diamondoids following core electron ionization. Here we apply eFF to the shock thermodynamics of lithium metal, where we find two distinct consecutive phase changes that manifest themselves as a kink in the shock Hugoniot, previously observed experimentally, but not explained. Analyzing the atomic distribution functions, we establish that the first phase transition corresponds to (i) an fcc-to-cI16 phase transition that was observed previously in diamond anvil cell experiments at low temperature and (ii) a second phase transition that corresponds to the formation of a new amorphous phase (amor) of lithium that is distinct from normal molten lithium. The amorphous phase has enhanced valence electron-nucleus interactions due to localization of electrons into interstitial locations, along with a random connectivity distribution function. This indicates that eFF can characterize and compute the relative stability of states of matter under extreme conditions (e.g., warm dense matter). PMID:21873210

  13. Time-Delayed Quantum Feedback Control

    NASA Astrophysics Data System (ADS)

    Grimsmo, Arne L.

    2015-08-01

    A theory of time-delayed coherent quantum feedback is developed. More specifically, we consider a quantum system coupled to a bosonic reservoir creating a unidirectional feedback loop. It is shown that the dynamics can be mapped onto a fictitious series of cascaded quantum systems, where the system is driven by past versions of itself. The derivation of this model relies on a tensor network representation of the system-reservoir time propagator. For concreteness, this general theory is applied to a driven two-level atom scattering into a coherent feedback loop. We demonstrate how delay effects can qualitatively change the dynamics of the atom and how quantum control can be implemented in the presence of time delays.

  14. Time-Delayed Quantum Feedback Control.

    PubMed

    Grimsmo, Arne L

    2015-08-01

    A theory of time-delayed coherent quantum feedback is developed. More specifically, we consider a quantum system coupled to a bosonic reservoir creating a unidirectional feedback loop. It is shown that the dynamics can be mapped onto a fictitious series of cascaded quantum systems, where the system is driven by past versions of itself. The derivation of this model relies on a tensor network representation of the system-reservoir time propagator. For concreteness, this general theory is applied to a driven two-level atom scattering into a coherent feedback loop. We demonstrate how delay effects can qualitatively change the dynamics of the atom and how quantum control can be implemented in the presence of time delays. PMID:26296104

  15. Extending molecular simulation time scales: Parallel in time integrations for high-level quantum chemistry and complex force representations

    NASA Astrophysics Data System (ADS)

    Bylaska, Eric J.; Weare, Jonathan Q.; Weare, John H.

    2013-08-01

    environment using very slow transmission control protocol/Internet protocol networks. Scripts written in Python that make calls to a precompiled quantum chemistry package (NWChem) are demonstrated to provide an actual speedup of 8.2 for a 2.5 ps AIMD simulation of HCl + 4H2O at the MP2/6-31G* level. Implemented in this way these algorithms can be used for long time high-level AIMD simulations at a modest cost using machines connected by very slow networks such as WiFi, or in different time zones connected by the Internet. The algorithms can also be used with programs that are already parallel. Using these algorithms, we are able to reduce the cost of a MP2/6-311++G(2d,2p) simulation that had reached its maximum possible speedup in the parallelization of the electronic structure calculation from 32 s/time step to 6.9 s/time step.

  16. Extending molecular simulation time scales: Parallel in time integrations for high-level quantum chemistry and complex force representations

    SciTech Connect

    Bylaska, Eric J.; Weare, Jonathan Q.; Weare, John H.

    2013-08-21

    written in Python that make calls to a precompiled quantum chemistry package (NWChem) are demonstrated to provide an actual speedup of 8.2 for a 2.5 ps AIMD simulation of HCl+4H2O at the MP2/6-31G* level. Implemented in this way these algorithms can be used for long time high-level AIMD simulations at a modest cost using machines connected by very slow networks such as WiFi, or in different time zones connected by the Internet. The algorithms can also be used with programs that are already parallel. By using these algorithms we are able to reduce the cost of a MP2/6-311++G(2d,2p) simulation that had reached its maximum possible speedup in the parallelization of the electronic structure calculation from 32 seconds per time step to 6.9 seconds per time step.

  17. Extending molecular simulation time scales: Parallel in time integrations for high-level quantum chemistry and complex force representations.

    PubMed

    Bylaska, Eric J; Weare, Jonathan Q; Weare, John H

    2013-08-21

    distributed computing environment using very slow transmission control protocol/Internet protocol networks. Scripts written in Python that make calls to a precompiled quantum chemistry package (NWChem) are demonstrated to provide an actual speedup of 8.2 for a 2.5 ps AIMD simulation of HCl + 4H2O at the MP2/6-31G* level. Implemented in this way these algorithms can be used for long time high-level AIMD simulations at a modest cost using machines connected by very slow networks such as WiFi, or in different time zones connected by the Internet. The algorithms can also be used with programs that are already parallel. Using these algorithms, we are able to reduce the cost of a MP2/6-311++G(2d,2p) simulation that had reached its maximum possible speedup in the parallelization of the electronic structure calculation from 32 s/time step to 6.9 s/time step. PMID:23968079

  18. Extending molecular simulation time scales: Parallel in time integrations for high-level quantum chemistry and complex force representations

    SciTech Connect

    Bylaska, Eric J.; Weare, Jonathan Q.; Weare, John H.

    2013-08-21

    to 14.3. The parallel in time algorithms can be implemented in a distributed computing environment using very slow transmission control protocol/Internet protocol networks. Scripts written in Python that make calls to a precompiled quantum chemistry package (NWChem) are demonstrated to provide an actual speedup of 8.2 for a 2.5 ps AIMD simulation of HCl + 4H{sub 2}O at the MP2/6-31G* level. Implemented in this way these algorithms can be used for long time high-level AIMD simulations at a modest cost using machines connected by very slow networks such as WiFi, or in different time zones connected by the Internet. The algorithms can also be used with programs that are already parallel. Using these algorithms, we are able to reduce the cost of a MP2/6-311++G(2d,2p) simulation that had reached its maximum possible speedup in the parallelization of the electronic structure calculation from 32 s/time step to 6.9 s/time step.

  19. Quantum radiation force on the moving mirror of a cavity, with Dirichlet and Neumann boundary conditions for a vacuum, finite temperature, and a coherent state

    SciTech Connect

    Alves, Danilo T.; Silva, Hector O.; Lima, Mateus G.; Granhen, Edney R.

    2010-01-15

    We consider a real massless scalar field inside a cavity with a moving mirror in a two-dimensional spacetime, satisfying the Dirichlet or Neumann boundary condition at the instantaneous position of the boundaries, for an arbitrary and relativistic law of motion. Considering an arbitrary initial field state, we show that the exact value of the energy density in the cavity can be obtained by tracing back a sequence of null lines, connecting the value of the energy density at the given spacetime point to a certain known value of the energy density at a point in the region where the initial field modes are not affected by the boundary motion. We obtain the particular formulas for the energy density of the field and the quantum force acting on the boundaries for a vacuum, thermal, and a coherent state. We thus generalize a previous result in literature, where this problem is approached for only one mirror. For the particular cases of vacuum and Dirichlet boundary condition, nonrelativistic velocities, or in the limit of large length of the cavity, our results coincide with those found in the literature.

  20. A semi-analytical method for near-trapped mode and fictitious frequencies of multiple scattering by an array of elliptical cylinders in water waves

    NASA Astrophysics Data System (ADS)

    Chen, Jeng-Tzong; Lee, Jia-Wei

    2013-09-01

    In this paper, we focus on the water wave scattering by an array of four elliptical cylinders. The null-field boundary integral equation method (BIEM) is used in conjunction with degenerate kernels and eigenfunctions expansion. The closed-form fundamental solution is expressed in terms of the degenerate kernel containing the Mathieu and the modified Mathieu functions in the elliptical coordinates. Boundary densities are represented by using the eigenfunction expansion. To avoid using the addition theorem to translate the Mathieu functions, the present approach can solve the water wave problem containing multiple elliptical cylinders in a semi-analytical manner by introducing the adaptive observer system. Regarding water wave problems, the phenomena of numerical instability of fictitious frequencies may appear when the BIEM/boundary element method (BEM) is used. Besides, the near-trapped mode for an array of four identical elliptical cylinders is observed in a special layout. Both physical (near-trapped mode) and mathematical (fictitious frequency) resonances simultaneously appear in the present paper for a water wave problem by an array of four identical elliptical cylinders. Two regularization techniques, the combined Helmholtz interior integral equation formulation (CHIEF) method and the Burton and Miller approach, are adopted to alleviate the numerical resonance due to fictitious frequency.

  1. A fictitious domain method for fluid/solid interaction applied to the plate folding over the 660 Km depth boundary.

    NASA Astrophysics Data System (ADS)

    Cerpa, Nestor; Hassani, Riad; Gerbault, Muriel

    2014-05-01

    A large variety of geodynamical problems involve a mechanical system where a competent body is embedded in a more deformable medium, and hence they can be viewed as belonging to the field of solid/fluid interaction.The lithosphere/asthenosphere interaction in subduction zones is among those kind of problems which are generally difficult to tackle numerically since the immersed (solid) body can be geometrically complex and the surrounding (fluid) medium can thus undergo large deformation. Our work presents a new numerical approach for the study of subduction zones. The lithosphere is modeled as a Maxwell viscoelastic body sinking in the viscous asthenosphere. Both domains are discretized by the Finite Element Method (FEM) and we use a staggered coupling method. The interaction is provided by a non-matching interface method called the Fictitious Domain Method (FDM). We have validated this method with some 2-D benchmarks and examples. Through this numerical coupling method we aim at studying the effect of mantle viscosity on the cyclicity of slab folding on the 660 km depth discontinuity approximated as an impenetrable barrier. Depending on the kinematics condition imposed to the overriding and subducting plates, analog and numerical models have previously shown that cyclicity occurs. The viscosity of the asthenosphere (taken as an isoviscous or a double viscosity-layer fluid) impacts on folding cyclicity and consequently on the slab's dip as well as the stress regime of the overriding plate. In particular, applying far-field plate velocities corresponding to those of the South-American and Nazca plates at present, (4.3 cm/yr and 2.9 cm/yr respectively), we obtain periodic slab folding which is consistent with magmatism and sedimentalogical records. These data report cycles in orogenic growth of the order of 30-40 Myrs, a period that we reproduce when the mantle viscosity ranges in between 3 and 5 x 1020 Pa.s. Moreover, we reproduce episodic development of horizontal

  2. A fictitious domain finite element method for simulations of fluid-structure interactions: The Navier-Stokes equations coupled with a moving solid

    NASA Astrophysics Data System (ADS)

    Court, Sébastien; Fournié, Michel

    2015-05-01

    The paper extends a stabilized fictitious domain finite element method initially developed for the Stokes problem to the incompressible Navier-Stokes equations coupled with a moving solid. This method presents the advantage to predict an optimal approximation of the normal stress tensor at the interface. The dynamics of the solid is governed by the Newton's laws and the interface between the fluid and the structure is materialized by a level-set which cuts the elements of the mesh. An algorithm is proposed in order to treat the time evolution of the geometry and numerical results are presented on a classical benchmark of the motion of a disk falling in a channel.

  3. The fictitious force method for efficient calculation of vibration from a tunnel embedded in a multi-layered half-space

    NASA Astrophysics Data System (ADS)

    Hussein, M. F. M.; François, S.; Schevenels, M.; Hunt, H. E. M.; Talbot, J. P.; Degrande, G.

    2014-12-01

    This paper presents an extension of the Pipe-in-Pipe (PiP) model for calculating vibrations from underground railways that allows for the incorporation of a multi-layered half-space geometry. The model is based on the assumption that the tunnel displacement is not influenced by the existence of a free surface or ground layers. The displacement at the tunnel-soil interface is calculated using a model of a tunnel embedded in a full space with soil properties corresponding to the soil in contact with the tunnel. Next, a full space model is used to determine the equivalent loads that produce the same displacements at the tunnel-soil interface. The soil displacements are calculated by multiplying these equivalent loads by Green's functions for a layered half-space. The results and the computation time of the proposed model are compared with those of an alternative coupled finite element-boundary element model that accounts for a tunnel embedded in a multi-layered half-space. While the overall response of the multi-layered half-space is well predicted, spatial shifts in the interference patterns are observed that result from the superposition of direct waves and waves reflected on the free surface and layer interfaces. The proposed model is much faster and can be run on a personal computer with much less use of memory. Therefore, it is a promising design tool to predict vibration from underground tunnels and to assess the performance of vibration countermeasures in an early design stage.

  4. QCD: Quantum Chromodynamics

    ScienceCinema

    Lincoln, Don

    2016-06-28

    The strongest force in the universe is the strong nuclear force and it governs the behavior of quarks and gluons inside protons and neutrons. The name of the theory that governs this force is quantum chromodynamics, or QCD. In this video, Fermilab?s Dr. Don Lincoln explains the intricacies of this dominant component of the Standard Model.

  5. Conspiracist ideation in Britain and Austria: evidence of a monological belief system and associations between individual psychological differences and real-world and fictitious conspiracy theories.

    PubMed

    Swami, Viren; Coles, Rebecca; Stieger, Stefan; Pietschnig, Jakob; Furnham, Adrian; Rehim, Sherry; Voracek, Martin

    2011-08-01

    Despite evidence of widespread belief in conspiracy theories, there remains a dearth of research on the individual difference correlates of conspiracist ideation. In two studies, we sought to overcome this limitation by examining correlations between conspiracist ideation and a range of individual psychological factors. In Study 1, 817 Britons indicated their agreement with conspiracist ideation concerning the July 7, 2005 (7/7), London bombings, and completed a battery of individual difference scales. Results showed that stronger belief in 7/7 conspiracy theories was predicted by stronger belief in other real-world conspiracy theories, greater exposure to conspiracist ideation, higher political cynicism, greater support for democratic principles, more negative attitudes to authority, lower self-esteem, and lower Agreeableness. In Study 2, 281 Austrians indicated their agreement with an entirely fictitious conspiracy theory and completed a battery of individual difference measures not examined in Study 1. Results showed that belief in the entirely fictitious conspiracy theory was significantly associated with stronger belief in other real-world conspiracy theories, stronger paranormal beliefs, and lower crystallized intelligence. These results are discussed in terms of the potential of identifying individual difference constellations among conspiracy theorists. PMID:21751999

  6. A 3D, fully Eulerian, VOF-based solver to study the interaction between two fluids and moving rigid bodies using the fictitious domain method

    NASA Astrophysics Data System (ADS)

    Pathak, Ashish; Raessi, Mehdi

    2016-04-01

    We present a three-dimensional (3D) and fully Eulerian approach to capturing the interaction between two fluids and moving rigid structures by using the fictitious domain and volume-of-fluid (VOF) methods. The solid bodies can have arbitrarily complex geometry and can pierce the fluid-fluid interface, forming contact lines. The three-phase interfaces are resolved and reconstructed by using a VOF-based methodology. Then, a consistent scheme is employed for transporting mass and momentum, allowing for simulations of three-phase flows of large density ratios. The Eulerian approach significantly simplifies numerical resolution of the kinematics of rigid bodies of complex geometry and with six degrees of freedom. The fluid-structure interaction (FSI) is computed using the fictitious domain method. The methodology was developed in a message passing interface (MPI) parallel framework accelerated with graphics processing units (GPUs). The computationally intensive solution of the pressure Poisson equation is ported to GPUs, while the remaining calculations are performed on CPUs. The performance and accuracy of the methodology are assessed using an array of test cases, focusing individually on the flow solver and the FSI in surface-piercing configurations. Finally, an application of the proposed methodology in simulations of the ocean wave energy converters is presented.

  7. Quantum diffusion

    SciTech Connect

    Habib, S.

    1994-10-01

    We consider a simple quantum system subjected to a classical random force. Under certain conditions it is shown that the noise-averaged Wigner function of the system follows an integro-differential stochastic Liouville equation. In the simple case of polynomial noise-couplings this equation reduces to a generalized Fokker-Planck form. With nonlinear noise injection new ``quantum diffusion`` terms rise that have no counterpart in the classical case. Two special examples that are not of a Fokker-Planck form are discussed: the first with a localized noise source and the other with a spatially modulated noise source.

  8. Quantized Casimir force.

    PubMed

    Tse, Wang-Kong; MacDonald, A H

    2012-12-01

    We investigate the Casimir effect between two-dimensional electron systems driven to the quantum Hall regime by a strong perpendicular magnetic field. In the large-separation (d) limit where retardation effects are essential, we find (i) that the Casimir force is quantized in units of 3ħcα(2)/8π(2)d(4) and (ii) that the force is repulsive for mirrors with the same type of carrier and attractive for mirrors with opposite types of carrier. The sign of the Casimir force is therefore electrically tunable in ambipolar materials such as graphene. The Casimir force is suppressed when one mirror is a charge-neutral graphene system in a filling factor ν=0 quantum Hall state. PMID:23368242

  9. Quantum optics. Gravity meets quantum physics

    SciTech Connect

    Adams, Bernhard W.

    2015-02-27

    Albert Einstein’s general theory of relativity is a classical formulation but a quantum mechanical description of gravitational forces is needed, not only to investigate the coupling of classical and quantum systems but simply to give a more complete description of our physical surroundings. In this issue of Nature Photonics, Wen-Te Liao and Sven Ahrens reveal a link between quantum and gravitational physics. They propose that in the quantum-optical effect of superradiance, the world line of electromagnetic radiation is changed by the presence of a gravitational field.

  10. LASER APPLICATIONS AND OTHER TOPICS IN QUANTUM ELECTRONICS: Properties of ponderomotive forces, proportional to , on a charged particle in an inhomogeneous electromagnetic wave

    NASA Astrophysics Data System (ADS)

    Serov, Alexander V.

    1999-02-01

    The characteristic features of the dynamics of particles crossing an inhomogeneous linearly polarised wave are investigated numerically and analytically. The initial particle velocity is perpendicular to the direction of propagation of the wave and its electric field vector. It was established that two ponderomotive forces, proportional to , act on a particle crossing the wave. One of the forces, proportional to the initial velocity of the particles, deflects the beam of particles and displaces them in the direction opposed to that of the propagation of the wave. It is found that when the length and width of the inhomogeneous wave are altered, the deflection and the displacement vary periodically. The ponderomotive force is maximal when the time taken by the particle to cross the wave corresponds to an integral number of half-periods of the particle vibrations. The second force has the same direction as the gradient force. Analytic expressions describing the forces acting on particles crossing a weakly inhomogeneous magnetic wave are obtained.

  11. Quantum Computation and Quantum Information

    NASA Astrophysics Data System (ADS)

    Nielsen, Michael A.; Chuang, Isaac L.

    2010-12-01

    Part I. Fundamental Concepts: 1. Introduction and overview; 2. Introduction to quantum mechanics; 3. Introduction to computer science; Part II. Quantum Computation: 4. Quantum circuits; 5. The quantum Fourier transform and its application; 6. Quantum search algorithms; 7. Quantum computers: physical realization; Part III. Quantum Information: 8. Quantum noise and quantum operations; 9. Distance measures for quantum information; 10. Quantum error-correction; 11. Entropy and information; 12. Quantum information theory; Appendices; References; Index.

  12. Quantum friction and fluctuation theorems

    NASA Astrophysics Data System (ADS)

    Intravaia, F.; Behunin, R. O.; Dalvit, D. A. R.

    2014-05-01

    We use general concepts of statistical mechanics to compute the quantum frictional force on an atom moving at constant velocity above a planar surface. We derive the zero-temperature frictional force using a nonequilibrium fluctuation-dissipation relation, and we show that in the large-time, steady-state regime, quantum friction scales as the cubic power of the atom's velocity. We also discuss how approaches based on Wigner-Weisskopf and quantum regression approximations fail to predict the correct steady-state zero-temperature frictional force, mainly due to the low-frequency nature of quantum friction.

  13. Quantum optics, cavity QED, and quantum optomechanics

    NASA Astrophysics Data System (ADS)

    Meystre, Pierre

    2013-05-01

    Quantum optomechanics provides a universal tool to achieve the quantum control of mechanical motion. It does that in devices spanning a vast range of parameters, with mechanical frequencies from a few Hertz to GHz, and with masses from 10-20 g to several kilos. Its underlying ideas can be traced back to the study of gravitational wave antennas, quantum optics, cavity QED and laser cooling which, when combined with the recent availability of advanced micromechanical and nanomechanical devices, opens a path to the realization of macroscopic mechanical systems that operate deep in the quantum regime. At the fundamental level this development paves the way to experiments that will lead to a more profound understanding of quantum mechanics; and from the point of view of applications, quantum optomechanical techniques will provide motion and force sensing near the fundamental limit imposed by quantum mechanics (quantum metrology) and significantly expand the toolbox of quantum information science. After a brief summary of key historical developments, the talk will give a broad overview of the current state of the art of quantum optomechanics, and comment on future prospects both in applied and in fundamental science. Work supported by NSF, ARO and the DARPA QuASAR and ORCHID programs.

  14. Quantum radiation force on a moving mirror with Dirichlet and Neumann boundary conditions for a vacuum, finite temperature, and a coherent state

    SciTech Connect

    Alves, Danilo T.; Lima, Mateus G.; Granhen, Edney R.

    2008-06-15

    We consider a real massless scalar field in a two-dimensional spacetime, satisfying Dirichlet or Neumann boundary condition at the instantaneous position of a moving boundary. For a relativistic law of motion, we show that Dirichlet and Neumann boundary conditions yield the same radiation force on a moving mirror when the initial field state is invariant under time translations. We obtain the exact formulas for the energy density of the field and the radiation force on the boundary for vacuum, thermal, coherent, and squeezed states. In the nonrelativistic limit, our results coincide with those found in the literature.

  15. Six axis force feedback input device

    NASA Technical Reports Server (NTRS)

    Ohm, Timothy (Inventor)

    1998-01-01

    The present invention is a low friction, low inertia, six-axis force feedback input device comprising an arm with double-jointed, tendon-driven revolute joints, a decoupled tendon-driven wrist, and a base with encoders and motors. The input device functions as a master robot manipulator of a microsurgical teleoperated robot system including a slave robot manipulator coupled to an amplifier chassis, which is coupled to a control chassis, which is coupled to a workstation with a graphical user interface. The amplifier chassis is coupled to the motors of the master robot manipulator and the control chassis is coupled to the encoders of the master robot manipulator. A force feedback can be applied to the input device and can be generated from the slave robot to enable a user to operate the slave robot via the input device without physically viewing the slave robot. Also, the force feedback can be generated from the workstation to represent fictitious forces to constrain the input device's control of the slave robot to be within imaginary predetermined boundaries.

  16. Tension density as counter force to the Lorentz force density

    NASA Astrophysics Data System (ADS)

    Nozaki, Hiroo; Senami, Masato; Ichikawa, Kazuhide; Tachibana, Akitomo

    2016-08-01

    It is confirmed numerically that the tension density defined in quantum field theory is the counter force to the Lorentz force density. We take benzenedithiol in a nonequilibrium steady state as an example for the numerical demonstration of the balance between these densities. While we use simply a nonequilibrium Green’s function method for a quantum conduction state instead of computations based on quantum field theory, the balance between the tension density and the Lorentz force density can be confirmed. The tension density is free from the relaxation time ansatz and defined as a local quantity. The tension density may give a novel viewpoint to the understanding of the physics of electrical conduction.

  17. Magnus forces and statistics in 2 + 1 dimensions

    SciTech Connect

    Davis, R.L. )

    1990-05-10

    Spinning vortex solutions to the abelian Higgs model, not Nielsen-Olesen solutions, are appropriate to a Ginzburg-Landau description of superconductivity. The main physical distinction is that spinning vortices experience the Magnus force while Nielsen-Olesen vortices do not. In 2 + 1 dimensional superconductivity without a Chern-Simons interaction, the effect of the Magnus force is equivalent to that of a background fictitious magnetic field. Moreover, the phase obtained an interchanging two quasi-particles is always path-dependent. When a Chern-Simons term is added there is an additional localized Magnus flux at the vortex. For point-like vortices, the Chern-Simons interaction can be seen as defining their intrinsic statistics, but in realistic cases of vortices with finite size in strong Magnus fields the quasi-particle statistics are not well-defined.

  18. Extraction of α-humulene-enriched oil from clove using ultrasound-assisted supercritical carbon dioxide extraction and studies of its fictitious solubility.

    PubMed

    Wei, Ming-Chi; Xiao, Jianbo; Yang, Yu-Chiao

    2016-11-01

    Clove buds are used as a spice and food flavoring. In this study, clove oil and α-humulene was extracted from cloves using supercritical carbon dioxide extraction with and without ultrasound assistance (USC-CO2 and SC-CO2, respectively) at different temperatures (32-50°C) and pressures (9.0-25.0MPa). The results of these extractions were compared with those of heat reflux extraction and steam distillation methods conducted in parallel. The extracts obtained using these four techniques were analyzed using gas chromatography and gas chromatography/mass spectrometry (GC/MS). The results demonstrated that the USC-CO2 extraction procedure may extract clove oil and α-humulene from clove buds with better yields and shorter extraction times than conventional extraction techniques while utilizing less severe operating parameters. Furthermore, the experimental fictitious solubility data obtained using the dynamic method were well correlated with density-based models, including the Chrastil model, the Bartle model and the Kumar and Johnston model. PMID:27211636

  19. Relaxation along a fictitious field (RAFF) and Z-spectroscopy using alternating-phase irradiation (ZAPI) in permanent focal cerebral ischemia in rat.

    PubMed

    Jokivarsi, Kimmo T; Liimatainen, Timo; Kauppinen, Risto A; Gröhn, Olli H J; Närväinen, Johanna

    2013-01-01

    Cerebral ischemia alters the molecular dynamics and content of water in brain tissue, which is reflected in NMR relaxation, diffusion and magnetization transfer (MT) parameters. In this study, the behavior of two new MRI contrasts, Relaxation Along a Fictitious Field (RAFF) and Z-spectroscopy using Alternating-Phase Irradiation (ZAPI), were quantified together with conventional relaxation parameters (T1, T2 and T1ρ) and MT ratios in acute cerebral ischemia in rat. The right middle cerebral artery was permanently occluded and quantitative MRI data was acquired sequentially for the above parameters for up to 6 hours. The following conclusions were drawn: 1) Time-dependent changes in RAFF and T1ρ relaxation are not coupled to those in MT. 2) RAFF relaxation evolves more like transverse, rather than longitudinal relaxation. 3) MT measured with ZAPI is less sensitive to ischemia than conventional MT. 4) ZAPI data suggest alterations in the T2 distribution of macromolecules in acute cerebral ischemia. It was shown that both RAFF and ZAPI provide complementary MRI information from acute ischemic brain tissue. The presented multiparametric MRI data may aid in the assessment of brain tissue status early in ischemic stroke. PMID:23874898

  20. Relaxation Along a Fictitious Field (RAFF) and Z-spectroscopy using Alternating-Phase Irradiation (ZAPI) in Permanent Focal Cerebral Ischemia in Rat

    PubMed Central

    Jokivarsi, Kimmo T.; Liimatainen, Timo; Kauppinen, Risto A.; Gröhn, Olli H. J.; Närväinen, Johanna

    2013-01-01

    Cerebral ischemia alters the molecular dynamics and content of water in brain tissue, which is reflected in NMR relaxation, diffusion and magnetization transfer (MT) parameters. In this study, the behavior of two new MRI contrasts, Relaxation Along a Fictitious Field (RAFF) and Z-spectroscopy using Alternating-Phase Irradiation (ZAPI), were quantified together with conventional relaxation parameters (T1, T2 and T1ρ) and MT ratios in acute cerebral ischemia in rat. The right middle cerebral artery was permanently occluded and quantitative MRI data was acquired sequentially for the above parameters for up to 6 hours. The following conclusions were drawn: 1) Time-dependent changes in RAFF and T1ρ relaxation are not coupled to those in MT. 2) RAFF relaxation evolves more like transverse, rather than longitudinal relaxation. 3) MT measured with ZAPI is less sensitive to ischemia than conventional MT. 4) ZAPI data suggest alterations in the T2 distribution of macromolecules in acute cerebral ischemia. It was shown that both RAFF and ZAPI provide complementary MRI information from acute ischemic brain tissue. The presented multiparametric MRI data may aid in the assessment of brain tissue status early in ischemic stroke. PMID:23874898

  1. Microphotonic Forces from Superfluid Flow

    NASA Astrophysics Data System (ADS)

    McAuslan, D. L.; Harris, G. I.; Baker, C.; Sachkou, Y.; He, X.; Sheridan, E.; Bowen, W. P.

    2016-04-01

    In cavity optomechanics, radiation pressure and photothermal forces are widely utilized to cool and control micromechanical motion, with applications ranging from precision sensing and quantum information to fundamental science. Here, we realize an alternative approach to optical forcing based on superfluid flow and evaporation in response to optical heating. We demonstrate optical forcing of the motion of a cryogenic microtoroidal resonator at a level of 1.46 nN, roughly 1 order of magnitude larger than the radiation pressure force. We use this force to feedback cool the motion of a microtoroid mechanical mode to 137 mK. The photoconvective forces we demonstrate here provide a new tool for high bandwidth control of mechanical motion in cryogenic conditions, while the ability to apply forces remotely, combined with the persistence of flow in superfluids, offers the prospect for new applications.

  2. Insights in Quantum Dynamical Effects in the Infrared Spectroscopy of Liquid Water from a Semiclassical Study with an ab Initio-Based Flexible and Polarizable Force Field

    SciTech Connect

    Liu, Jianbo; Miller, William H.; Fanourgakis, G. S.; Xantheas, Sotiris S.; Imoto, Sho; Saito, Shinji

    2011-12-28

    The dynamical properties of liquid water play an important role in many processes in Nature. In this paper we focus on the infrared (IR) absorption spectrum of liquid water based on the linearized semiclassical initial value representation (LSC-IVR) with the local Gaussian approximation (LGA) [Liu and Miller, J. Chem. Phys. 131, 074113 (2009)] and an ab initio based, flexible, polarizable Thole-type model (TTM3-F) [Fanourgakis and Xantheas, J. Chem. Phys. 128, 074506 (2008)]. Although the LSC-IVR (LGA) gives the exact result for the isolated 3-dimensional shifted harmonic stretching model, it yields a blue-shifted peak position for the more realistic anharmonic stretching potential. By using the short time information of the LSCIVR correlation function, however, it is shown how one can obtain more accurate results for the position of the stretching peak. Due to the physical decay in the condensed phase system, the LSC-IVR (LGA) is a good and practical approximate quantum approach for the IR spectrum of liquid water. The present results offer valuable insight into future attempts to improve the accuracy of the TTM3-F potential in reproducing the IR spectrum of liquid water.

  3. Nuclear forces

    SciTech Connect

    Machleidt, R.

    2013-06-10

    These lectures present an introduction into the theory of nuclear forces. We focus mainly on the modern approach, in which the forces between nucleons emerge from low-energy QCD via chiral effective field theory.

  4. Casimir-Polder forces on moving atoms

    SciTech Connect

    Scheel, Stefan; Buhmann, Stefan Yoshi

    2009-10-15

    Polarizable atoms and molecules experience the Casimir-Polder force near magnetoelectric bodies, a force that is induced by quantum fluctuations of the electromagnetic field and the matter. Atoms and molecules in relative motion to a magnetoelectric surface experience an additional velocity-dependent force. We present a full quantum-mechanical treatment of this force and identify a generalized Doppler effect, the time delay between photon emission and reabsorption, and the Roentgen interaction as its three sources. For ground-state atoms, the force is very small and always decelerating, hence commonly known as quantum friction. For atoms and molecules in electronically excited states, on the contrary, both decelerating and accelerating forces can occur depending on the magnitude of the atomic transition frequency relative to the surface-plasmon frequency.

  5. Labor Force

    ERIC Educational Resources Information Center

    Occupational Outlook Quarterly, 2012

    2012-01-01

    The labor force is the number of people ages 16 or older who are either working or looking for work. It does not include active-duty military personnel or the institutionalized population, such as prison inmates. Determining the size of the labor force is a way of determining how big the economy can get. The size of the labor force depends on two…

  6. The molecular structures, conformations and force fields of bis(chloroimino)butanedinitrile as studied by gas-phase electron diffraction and quantum chemical calculations

    NASA Astrophysics Data System (ADS)

    Thomassen, H.; Gundersen, S.; Samdal, S.

    2009-06-01

    Quantum chemical calculations using levels up to MP2(Full)/aug-cc-pVTZ have been applied. B3LYP calculations using the 6-31G* basis set reveal that there are four conformations of bis(chloroimino)butanedinitrile. The planar anti-ZZ conformer with C2h symmetry is the most stable conformer. The non-planar EE conformer with C2 symmetry, the non-planar EZ conformer with C1 symmetry and the non-planar ZZ conformer with C2 symmetry are 16.8, 22.7, 27.2 kJ/mol, respectively, less stable than the planar anti-ZZ conformer according toB3LYP/6-31G* calculations. Calculated frequencies for the planar anti-ZZ conformer have been compared with observed frequencies, and some reassignments have been proposed. Several models have been used in the gas-phase electron diffraction analysis. The most reliable results are expected to be obtained using a dynamic model where the large amplitude motion is simulated by a harmonic angular motion using a Gaussian distribution about the central C sbnd C bond. Only the planar anti-ZZ conformer was used in the final refinements due to the high energy difference to the other conformers. The most important bond distances ( ra, Ångstrom) and bond angles (∠ α, degrees) are [GED/MP2(Full)/aug-cc-pVTZ]: rC 1sbnd C 2 = [1.509(15), 1.460], rC 2 = N 3 = [1.295(6), 1.292], rN 3sbnd Cl 5 = [1.706(5), 1.696], rC 2sbnd C 7 = [1.434(11), 1.421], rC 7tbnd N 9 = [1.165(4), 1.170], ∠C 1sbnd C 2dbnd N 3 = [114.5(11), 115.6], ∠C 2dbnd N 3sbnd Cl 5 = [115.0(4), 115.0], ∠C 1sbnd C 2sbnd C 7 = [118.8(8), 118.5], ∠C 2sbnd C 7tbnd N 9 = [178.2(15), 177.4]. The dihedral angle N 3C 2C 7N 9 is 0°, i.e. the cyano groups are bended towards the Cl atom. Error estimates from electron diffraction are given as: σr = 2.5[σ lsq2 + (0.001r) 2] ½ for bond distances and σ∠ = 2.5σ lsq for bond angles.

  7. The effect of the Earth's oblateness on predicting the shadow conditions of a distant spacecraft: Application to a fictitious lunar explorer

    NASA Astrophysics Data System (ADS)

    Song, Young-Joo; Kim, Bang-Yeop

    2016-01-01

    The effect of the Earth's oblateness on predicting the shadow events of a lunar spacecraft caused by the Earth's shadow is analyzed in this study. To ensure a reliable analysis, the proven 'line-of-intersection' method is modified and directly applied to predict the shadow conditions using a spheroidal model of the Earth and a conical shadow model. Two major lunar mission phases, namely, transfer and orbiting, are considered with corresponding fictitious initial conditions, and eclipse events are predicted and the results are compared using both spherical and spheroidal Earth models. For the lunar transfer phase, for which an Earth-bound highly elliptical orbit is assumed, not only the predicted entry and exit times of an event but also its duration are found to be more strongly shifted as the apogee altitude increases; for perigee and apogee altitudes of 1000 and 380,000 km, respectively, the maximum difference in predicted duration is found to be approximately 0.76 min for a penumbra event. For the lunar orbiting phase, for which a circular orbit around the Moon at an altitude of 100 km is assumed, a prediction difference of approximately half a minute on average and approximately one minute at maximum (e.g., 0.73 min for qumbra events, 1.03 min for penumbra events and 1.32 min for 'instantaneous' full sunlight events) can occur. The results of the present analysis highlight the importance of modeling the oblate shape of the Earth when predicting the shadow events of a distant spacecraft, and they are expected to provide numerous insights for any missions involving highly elliptical orbits around the Earth or travel to the Moon.

  8. A quantum renaissance

    NASA Astrophysics Data System (ADS)

    Aspelmeyer, Markus; Zeilinger, Anton

    2008-07-01

    Pure curiosity has been the driving force behind many groundbreaking experiments in physics. This is no better illustrated than in quantum mechanics, initially the physics of the extremely small. Since its beginnings in the 1920s and 1930s, researchers have wanted to observe the counterintuitive properties of quantum mechanics directly in the laboratory. However, because experimental technology was not sufficiently developed at the time, people like Niels Bohr, Albert Einstein, Werner Heisenberg and Erwin Schrödinger relied instead on "gedankenexperiments" (thought experiments) to investigate the quantum physics of individual particles, mainly electrons and photons.

  9. Free-energy calculation via mean-force dynamics using a logarithmic energy landscape.

    PubMed

    Morishita, Tetsuya; Itoh, Satoru G; Okumura, Hisashi; Mikami, Masuhiro

    2012-06-01

    A method for free-energy calculation based on mean-force dynamics (fictitious dynamics on a potential of mean force) is presented. The method utilizes a logarithmic form of free energy to enhance crossing barriers on a free-energy landscape, which results in efficient sampling of "rare" events. Invoking a conserved quantity in mean-force dynamics, free energy can be estimated on-the-fly without postprocessing. This means that an estimate of the free-energy profile can be locally made in contrast to the other methods based on mean-force dynamics such as metadynamics. The method is benchmarked against conventional methods and its high efficiency is demonstrated in the free-energy calculation for a glycine dipeptide molecule. PMID:23005238

  10. The molecular structure, conformation, potential to internal rotation and force field of 2,2,2-trifluoroacetamide as studied by gas electron diffraction and quantum chemical calculations

    NASA Astrophysics Data System (ADS)

    Gundersen, Snefrid; Samdal, Svein; Seip, Ragnhild; Shorokhov, Dmitry J.; Strand, Tor G.

    1998-04-01

    2,2,2-Trifluoroacetamide (TFA) has been studied by electron diffraction (ED), ab initio Hartree-Fock (HF), density functional theory (DFT), and MP2 calculations. The calculations give one conformation with one of the CF bonds anti to the CO bond and a planar NH 2 group, except for MP2/6-311 + + G∗∗, which predicts a slightly pyramidale NH 2 group. A molecular force field has been determined, and the fundamental frequencies have tentatively been assigned. The refined structural parameters were determined using constrained ED, i.e. ab initio results are included as constraints in the analysis. The structural parameters are: rg(N-H 4) = 1.040(4), rg(CO) = 1.211(2), rg(C-N) = 1.362(4), rg = 1.562(1), rg(C-F 7) = 1.347(1), ∠ αOCN = 126.5(2), ∠ αCCN = 116.3(4), ∠ αCCF 7 = 111.9(1), and ∠ αCNH 4 = 118.5(11). Bond distances are in Å and bond angles in degrees. Uncertainties are one standard deviation from least squares refinement using a diagonal weight matrix and inclusion of the uncertainty in the electron wavelength. The structural parameters have been compared with related amides. The Fourier coefficients V3 and V6 in the potential to internal rotation of the CF 3 group, V(α) = 1/2∗V 3∗(1 - cos(3∗α)) + 1/2∗V 6∗(1 - cos(6∗α)) , are determined to be 2.7(4) and - 0.7(3) kJ/mol, respectively. The syn barrier is experimentally determined to be 2.6(4) kJ/mol, which is in good agreeent with theoretical calculations.

  11. Hybrid Quantum Mechanical and Molecular Mechanics Study of the SN2 Reaction of CCl4 + OH− in Aqueous Solution: The Potential of Mean Force, Reaction Energetics, and Rate Constants

    SciTech Connect

    Wang, Ting; Yin, Hongyun; Wang, Dunyou; Valiev, Marat

    2012-02-16

    The bimolecular nucleophilic substitution reaction of CCl{sub 4} and OH{sup -} in aqueous solution was investigated on the basis of a combined quantum mechanical and molecular mechanics method. A multilayered representation approach is employed to achieve high accuracy results at the CCSD(T) level of theory. The potential of mean force calculations at the DFT level and CCSD(T) level of theory yield reaction barrier heights of 22.7 and 27.9 kcal/mol, respectively. Both the solvation effects and the solvent-induced polarization effect have significant contributions to the reaction energetics, for example, the solvation effect raises the saddle point by 10.6 kcal/mol. The calculated rate constant coefficient is 8.6 x 10{sup -28} cm{sup 3} molecule{sup -1} s{sup -1} at the standard state condition, which is about 17 orders magnitude smaller than that in the gas phase. Among the four chloromethanes (CH{sub 3}Cl, CH{sub 2}Cl{sub 2}, CHCl{sub 3}, and CCl{sub 4}), CCl{sub 4} has the lowest free energy activation barrier for the reaction with OH{sup -1} in aqueous solution, confirming the trend that substitution of Cl by H in chloromethanes diminishes the reactivity.

  12. Sizable electromagnetic forces in parallel-plate metallic cavity

    NASA Astrophysics Data System (ADS)

    Wang, S. B.; Ng, Jack; Liu, H.; Zheng, H. H.; Hang, Z. H.; Chan, C. T.

    2011-08-01

    Using a boundary element method to calculate electromagnetic fields and the Maxwell stress tensor method to compute electromagnetic forces, we investigate electromagnetic wave induced forces acting on a pair of identical metal plates that form an electromagnetic resonance cavity. Different frequency regimes are considered, from infrared frequencies with micron-scale structures down to the microwave regime, which involves millimeter-scale structures. We found that at both length scales, electromagnetic-wave-induced forces can be significantly stronger than the usual photon pressure exerted by a laser beam if the cavity is excited at resonance, although the mechanisms that underlie the strong force are different at different length scales. In the infrared frequency regime, the strong force is induced by field penetration into the metal, whereas in the microwave regime, the electromagnetic force is induced by the leakage of electric field at the edges. At both frequency scales, we compare the results we obtained for Au metal plates with fictitious perfect electric conductor plates, so as to understand the effect of field penetration. We also showed that a transmission line model can give simple expressions that can capture the essence of the physics. The effects of surface corrugation and surface roughness are also investigated, and we find that corrugation/roughness generally induces attraction between the plates.

  13. Sampling the potential energy surface of a DNA duplex damaged by a food carcinogen: Force field parameterization by ab initio quantum calculations and conformational searching using molecular mechanics computations

    NASA Astrophysics Data System (ADS)

    Wu, Xiangyang

    1999-07-01

    The heterocyclic amine 2-amino-3-methylimidazo (4, 5-f) quinoline (IQ) is one of a number of carcinogens found in barbecued meat and fish. It induces tumors in mammals and is probably involved in human carcinogenesis, because of great exposure to such food carcinogens. IQ is biochemically activated to a derivative which reacts with DNA to form a covalent adduct. This adduct may deform the DNA and consequently cause a mutation. which may initiate carcinogenesis. To understand this cancer initiating event, it is necessary to obtain atomic resolution structures of the damaged DNA. No such structures are available experimentally due to synthesis difficulties. Therefore, we employ extensive molecular mechanics and dynamics calculations for this purpose. The major IQ-DNA adduct in the specific DNA sequence d(5'G1G2C G3CCA3') - d(5'TGGCGCC3') with IQ modified at G3 is studied. The d(5'G1G2C G3CC3') sequence has recently been shown to be a hot-spot for mutations when IQ modification is at G3. Although this sequence is prone to -2 deletions via a ``slippage mechanism'' even when unmodified, a key question is why IQ increases the mutation frequency of the unmodified DNA by about 104 fold. Is there a structural feature imposed by IQ that is responsible? The molecular mechanics and dynamics program AMBER for nucleic acids with the latest force field was chosen for this work. This force field has been demonstrated to reproduce well the B-DNA structure. However, some parameters, the partial charges, bond lengths and angles, dihedral parameters of the modified residue, are not available in the AMBER database. We parameterized the force field using high level ab initio quantum calculations. We created 800 starting conformations which uniformly sampled in combination at 18° intervals three torsion angles that govern the IQ-DNA orientations, and energy minimized them. The most important structures are abnormal; the IQ damaged guanine is rotated out of its standard B

  14. Quantum speed meter based on dissipative coupling

    NASA Astrophysics Data System (ADS)

    Vyatchanin, Sergey P.; Matsko, Andrey B.

    2016-06-01

    We show that generalized dissipative optomechanical coupling enables a direct quantum measurement of speed of a free test mass. An optical detection of a weak classical mechanical force based on this interaction is proposed. The sensitivity of the force measurement can be better than the standard quantum limit.

  15. Quantum correlation via quantum coherence

    NASA Astrophysics Data System (ADS)

    Yu, Chang-shui; Zhang, Yang; Zhao, Haiqing

    2014-06-01

    Quantum correlation includes quantum entanglement and quantum discord. Both entanglement and discord have a common necessary condition—quantum coherence or quantum superposition. In this paper, we attempt to give an alternative understanding of how quantum correlation is related to quantum coherence. We divide the coherence of a quantum state into several classes and find the complete coincidence between geometric (symmetric and asymmetric) quantum discords and some particular classes of quantum coherence. We propose a revised measure for total coherence and find that this measure can lead to a symmetric version of geometric quantum correlation, which is analytic for two qubits. In particular, this measure can also arrive at a monogamy equality on the distribution of quantum coherence. Finally, we also quantify a remaining type of quantum coherence and find that for two qubits, it is directly connected with quantum nonlocality.

  16. Labor Force

    ERIC Educational Resources Information Center

    Occupational Outlook Quarterly, 2010

    2010-01-01

    The labor force is the number of people aged 16 or older who are either working or looking for work. It does not include active-duty military personnel or institutionalized people, such as prison inmates. Quantifying this total supply of labor is a way of determining how big the economy can get. Labor force participation rates vary significantly…

  17. Quantum memory Quantum memory

    NASA Astrophysics Data System (ADS)

    Le Gouët, Jean-Louis; Moiseev, Sergey

    2012-06-01

    Interaction of quantum radiation with multi-particle ensembles has sparked off intense research efforts during the past decade. Emblematic of this field is the quantum memory scheme, where a quantum state of light is mapped onto an ensemble of atoms and then recovered in its original shape. While opening new access to the basics of light-atom interaction, quantum memory also appears as a key element for information processing applications, such as linear optics quantum computation and long-distance quantum communication via quantum repeaters. Not surprisingly, it is far from trivial to practically recover a stored quantum state of light and, although impressive progress has already been accomplished, researchers are still struggling to reach this ambitious objective. This special issue provides an account of the state-of-the-art in a fast-moving research area that makes physicists, engineers and chemists work together at the forefront of their discipline, involving quantum fields and atoms in different media, magnetic resonance techniques and material science. Various strategies have been considered to store and retrieve quantum light. The explored designs belong to three main—while still overlapping—classes. In architectures derived from photon echo, information is mapped over the spectral components of inhomogeneously broadened absorption bands, such as those encountered in rare earth ion doped crystals and atomic gases in external gradient magnetic field. Protocols based on electromagnetic induced transparency also rely on resonant excitation and are ideally suited to the homogeneous absorption lines offered by laser cooled atomic clouds or ion Coulomb crystals. Finally off-resonance approaches are illustrated by Faraday and Raman processes. Coupling with an optical cavity may enhance the storage process, even for negligibly small atom number. Multiple scattering is also proposed as a way to enlarge the quantum interaction distance of light with matter. The

  18. Effect of Perturbations in the Coriolis and Centrifugal Forces on the Stability of L 4 in the Relativistic R3BP

    NASA Astrophysics Data System (ADS)

    Singh, Jagadish; Bello, Nakone

    2015-02-01

    The centrifugal and Coriolis forces do not appear as a result of physically imposed forces, but are due to a special property of a rotation. Thus, these forces are called pseudo-forces or `fictitious forces'. They are merely an artifact of the rotation of the reference frame adopted. This paper studies the motion of a test particle in the neighbourhood of the triangular point L 4 in the framework of the perturbed relativistic restricted three-body problem (R3BP) when small perturbations are conferred to the centrifugal and Coriolis forces. It is found that the position and stability of the triangular point are affected by both the relativistic factor and small perturbations in the Coriolis and centrifugal forces. As an application, the Sun-Earth system is considered.

  19. Force sensor

    DOEpatents

    Grahn, Allen R.

    1993-01-01

    A force sensor and related method for determining force components. The force sensor includes a deformable medium having a contact surface against which a force can be applied, a signal generator for generating signals that travel through the deformable medium to the contact surface, a signal receptor for receiving the signal reflected from the contact surface, a generation controller, a reception controller, and a force determination apparatus. The signal generator has one or more signal generation regions for generating the signals. The generation controller selects and activates the signal generation regions. The signal receptor has one or more signal reception regions for receiving signals and for generating detections signals in response thereto. The reception controller selects signal reception regions and detects the detection signals. The force determination apparatus measures signal transit time by timing activation and detection and, optionally, determines force components for selected cross-field intersections. The timer which times by activation and detection can be any means for measuring signal transit time. A cross-field intersection is defined by the overlap of a signal generation region and a signal reception region.

  20. Force sensor

    DOEpatents

    Grahn, A.R.

    1993-05-11

    A force sensor and related method for determining force components is described. The force sensor includes a deformable medium having a contact surface against which a force can be applied, a signal generator for generating signals that travel through the deformable medium to the contact surface, a signal receptor for receiving the signal reflected from the contact surface, a generation controller, a reception controller, and a force determination apparatus. The signal generator has one or more signal generation regions for generating the signals. The generation controller selects and activates the signal generation regions. The signal receptor has one or more signal reception regions for receiving signals and for generating detections signals in response thereto. The reception controller selects signal reception regions and detects the detection signals. The force determination apparatus measures signal transit time by timing activation and detection and, optionally, determines force components for selected cross-field intersections. The timer which times by activation and detection can be any means for measuring signal transit time. A cross-field intersection is defined by the overlap of a signal generation region and a signal reception region.

  1. Polarization effects in molecular mechanical force fields

    PubMed Central

    Cieplak, Piotr; Dupradeau, François-Yves; Duan, Yong; Wang, Junmei

    2014-01-01

    The focus here is on incorporating electronic polarization into classical molecular mechanical force fields used for macromolecular simulations. First, we briefly examine currently used molecular mechanical force fields and the current status of intermolecular forces as viewed by quantum mechanical approaches. Next, we demonstrate how some components of quantum mechanical energy are effectively incorporated into classical molecular mechanical force fields. Finally, we assess the modeling methods of one such energy component—polarization energy—and present an overview of polarizable force fields and their current applications. Incorporating polarization effects into current force fields paves the way to developing potentially more accurate, though more complex, parameterizations that can be used for more realistic molecular simulations. PMID:21828594

  2. Casimir force between integrable and chaotic pistons

    SciTech Connect

    Alvarez, Ezequiel; Mazzitelli, Francisco D.; Wisniacki, Diego A.; Monastra, Alejandro G.

    2010-11-15

    We have computed numerically the Casimir force between two identical pistons inside a very long cylinder, considering different shapes for the pistons. The pistons can be considered quantum billiards, whose spectrum determines the vacuum force. The smooth part of the spectrum fixes the force at short distances and depends only on geometric quantities like the area or perimeter of the piston. However, correcting terms to the force, coming from the oscillating part of the spectrum which is related to the classical dynamics of the billiard, could be qualitatively different for classically integrable or chaotic systems. We have performed a detailed numerical analysis of the corresponding Casimir force for pistons with regular and chaotic classical dynamics. For a family of stadium billiards, we have found that the correcting part of the Casimir force presents a sudden change in the transition from regular to chaotic geometries. This suggests that there could be signatures of quantum chaos in the Casimir effect.

  3. Polarization effects in molecular mechanical force fields.

    PubMed

    Cieplak, Piotr; Dupradeau, François-Yves; Duan, Yong; Wang, Junmei

    2009-08-19

    The focus here is on incorporating electronic polarization into classical molecular mechanical force fields used for macromolecular simulations. First, we briefly examine currently used molecular mechanical force fields and the current status of intermolecular forces as viewed by quantum mechanical approaches. Next, we demonstrate how some components of quantum mechanical energy are effectively incorporated into classical molecular mechanical force fields. Finally, we assess the modeling methods of one such energy component-polarization energy-and present an overview of polarizable force fields and their current applications. Incorporating polarization effects into current force fields paves the way to developing potentially more accurate, though more complex, parameterizations that can be used for more realistic molecular simulations. PMID:21828594

  4. Quantum simulation

    NASA Astrophysics Data System (ADS)

    Georgescu, I. M.; Ashhab, S.; Nori, Franco

    2014-01-01

    Simulating quantum mechanics is known to be a difficult computational problem, especially when dealing with large systems. However, this difficulty may be overcome by using some controllable quantum system to study another less controllable or accessible quantum system, i.e., quantum simulation. Quantum simulation promises to have applications in the study of many problems in, e.g., condensed-matter physics, high-energy physics, atomic physics, quantum chemistry, and cosmology. Quantum simulation could be implemented using quantum computers, but also with simpler, analog devices that would require less control, and therefore, would be easier to construct. A number of quantum systems such as neutral atoms, ions, polar molecules, electrons in semiconductors, superconducting circuits, nuclear spins, and photons have been proposed as quantum simulators. This review outlines the main theoretical and experimental aspects of quantum simulation and emphasizes some of the challenges and promises of this fast-growing field.

  5. Quantum Effects in Biological Systems

    NASA Astrophysics Data System (ADS)

    Roy, Sisir

    2014-07-01

    The debates about the trivial and non-trivial effects in biological systems have drawn much attention during the last decade or so. What might these non-trivial sorts of quantum effects be? There is no consensus so far among the physicists and biologists regarding the meaning of "non-trivial quantum effects". However, there is no doubt about the implications of the challenging research into quantum effects relevant to biology such as coherent excitations of biomolecules and photosynthesis, quantum tunneling of protons, van der Waals forces, ultrafast dynamics through conical intersections, and phonon-assisted electron tunneling as the basis for our sense of smell, environment assisted transport of ions and entanglement in ion channels, role of quantum vacuum in consciousness. Several authors have discussed the non-trivial quantum effects and classified them into four broad categories: (a) Quantum life principle; (b) Quantum computing in the brain; (c) Quantum computing in genetics; and (d) Quantum consciousness. First, I will review the above developments. I will then discuss in detail the ion transport in the ion channel and the relevance of quantum theory in brain function. The ion transport in the ion channel plays a key role in information processing by the brain.

  6. Multiple-state quantum Otto engine, 1D box system

    SciTech Connect

    Latifah, E.; Purwanto, A.

    2014-03-24

    Quantum heat engines produce work using quantum matter as their working substance. We studied adiabatic and isochoric processes and defined the general force according to quantum system. The processes and general force are used to evaluate a quantum Otto engine based on multiple-state of one dimensional box system and calculate the efficiency. As a result, the efficiency depends on the ratio of initial and final width of system under adiabatic processes.

  7. Quantum networks reveal quantum nonlocality.

    PubMed

    Cavalcanti, Daniel; Almeida, Mafalda L; Scarani, Valerio; Acín, Antonio

    2011-01-01

    The results of local measurements on some composite quantum systems cannot be reproduced classically. This impossibility, known as quantum nonlocality, represents a milestone in the foundations of quantum theory. Quantum nonlocality is also a valuable resource for information-processing tasks, for example, quantum communication, quantum key distribution, quantum state estimation or randomness extraction. Still, deciding whether a quantum state is nonlocal remains a challenging problem. Here, we introduce a novel approach to this question: we study the nonlocal properties of quantum states when distributed and measured in networks. We show, using our framework, how any one-way entanglement distillable state leads to nonlocal correlations and prove that quantum nonlocality is a non-additive resource, which can be activated. There exist states, local at the single-copy level, that become nonlocal when taking several copies of them. Our results imply that the nonlocality of quantum states strongly depends on the measurement context. PMID:21304513

  8. Vacuum force

    NASA Astrophysics Data System (ADS)

    Han, Yongquan

    2015-03-01

    To study on vacuum force, we must clear what is vacuum, vacuum is a space do not have any air and also ray. There is not exist an absolute the vacuum of space. The vacuum of space is relative, so that the vacuum force is relative. There is a certain that vacuum vacuum space exists. In fact, the vacuum space is relative, if the two spaces compared to the existence of relative vacuum, there must exist a vacuum force, and the direction of the vacuum force point to the vacuum region. Any object rotates and radiates. Rotate bend radiate- centripetal, gravity produced, relative gravity; non gravity is the vacuum force. Gravity is centripetal, is a trend that the objects who attracted wants to Centripetal, or have been do Centripetal movement. Any object moves, so gravity makes the object curve movement, that is to say, the radiation range curve movement must be in the gravitational objects, gravity must be existed in non vacuum region, and make the object who is in the region of do curve movement (for example: The earth moves around the sun), or final attracted in the form gravitational objects, and keep relatively static with attract object. (for example: objects on the earth moves but can't reach the first cosmic speed).

  9. Dynamics in the quantum/classical limit based on selective use of the quantum potential

    SciTech Connect

    Garashchuk, Sophya Dell’Angelo, David; Rassolov, Vitaly A.

    2014-12-21

    A classical limit of quantum dynamics can be defined by compensation of the quantum potential in the time-dependent Schrödinger equation. The quantum potential is a non-local quantity, defined in the trajectory-based form of the Schrödinger equation, due to Madelung, de Broglie, and Bohm, which formally generates the quantum-mechanical features in dynamics. Selective inclusion of the quantum potential for the degrees of freedom deemed “quantum,” defines a hybrid quantum/classical dynamics, appropriate for molecular systems comprised of light and heavy nuclei. The wavefunction is associated with all of the nuclei, and the Ehrenfest, or mean-field, averaging of the force acting on the classical degrees of freedom, typical of the mixed quantum/classical methods, is avoided. The hybrid approach is used to examine evolution of light/heavy systems in the harmonic and double-well potentials, using conventional grid-based and approximate quantum-trajectory time propagation. The approximate quantum force is defined on spatial domains, which removes unphysical coupling of the wavefunction fragments corresponding to distinct classical channels or configurations. The quantum potential, associated with the quantum particle, generates forces acting on both quantum and classical particles to describe the backreaction.

  10. Dynamics in the quantum/classical limit based on selective use of the quantum potential.

    PubMed

    Garashchuk, Sophya; Dell'Angelo, David; Rassolov, Vitaly A

    2014-12-21

    A classical limit of quantum dynamics can be defined by compensation of the quantum potential in the time-dependent Schrödinger equation. The quantum potential is a non-local quantity, defined in the trajectory-based form of the Schrödinger equation, due to Madelung, de Broglie, and Bohm, which formally generates the quantum-mechanical features in dynamics. Selective inclusion of the quantum potential for the degrees of freedom deemed "quantum," defines a hybrid quantum/classical dynamics, appropriate for molecular systems comprised of light and heavy nuclei. The wavefunction is associated with all of the nuclei, and the Ehrenfest, or mean-field, averaging of the force acting on the classical degrees of freedom, typical of the mixed quantum/classical methods, is avoided. The hybrid approach is used to examine evolution of light/heavy systems in the harmonic and double-well potentials, using conventional grid-based and approximate quantum-trajectory time propagation. The approximate quantum force is defined on spatial domains, which removes unphysical coupling of the wavefunction fragments corresponding to distinct classical channels or configurations. The quantum potential, associated with the quantum particle, generates forces acting on both quantum and classical particles to describe the backreaction. PMID:25527919

  11. Beyond the Quantum

    NASA Astrophysics Data System (ADS)

    Nieuwenhuizen, Theo M.; Mehmani, Bahar; Špička, Václav; Aghdami, Maryam J.; Khrennikov, Andrei Yu

    2007-09-01

    electrodynamics. Some quantum experiments from the point of view of Stochastic electrodynamics / V. Spicka ... [et al.]. On the ergodic behaviour of atomic systems under the action of the zero-point radiation field / L. De La Peña and A. M. Cetto. Inertia and the vacuum-view on the emergence of the inertia reaction force / A. Rueda and H. Sunahata -- pt. F. Models for the electron. Rotating Hopf-Kinks: oscillators in the sense of de Broglie / U. Enz. Kerr-Newman particles: symmetries and other properties / H.I. Arcos and J.G. Pereira. Kerr geometry beyond the quantum theory / Th. M. Nieuwenhuizen -- pt. G. Philosophical considerations. Probability in non-collapse interpretations of a quantum mechanics / D. Dieks. The Schrödinger-Park paradox about the concept of "State" in quantum statistical mechanics and quantum information theory is still open: one more reason to go beyond? / G.P. Beretta. The conjecture that local realism is possible / E. Santos -- pt. H. The round table. Round table discussion / A.M. Cetto ... [et al.].

  12. Quantum ontologies

    SciTech Connect

    Stapp, H.P.

    1988-12-01

    Quantum ontologies are conceptions of the constitution of the universe that are compatible with quantum theory. The ontological orientation is contrasted to the pragmatic orientation of science, and reasons are given for considering quantum ontologies both within science, and in broader contexts. The principal quantum ontologies are described and evaluated. Invited paper at conference: Bell's Theorem, Quantum Theory, and Conceptions of the Universe, George Mason University, October 20-21, 1988. 16 refs.

  13. Quantum Computer Games: Quantum Minesweeper

    ERIC Educational Resources Information Center

    Gordon, Michal; Gordon, Goren

    2010-01-01

    The computer game of quantum minesweeper is introduced as a quantum extension of the well-known classical minesweeper. Its main objective is to teach the unique concepts of quantum mechanics in a fun way. Quantum minesweeper demonstrates the effects of superposition, entanglement and their non-local characteristics. While in the classical…

  14. Quantum memristors

    NASA Astrophysics Data System (ADS)

    Pfeiffer, P.; Egusquiza, I. L.; di Ventra, M.; Sanz, M.; Solano, E.

    2016-07-01

    Technology based on memristors, resistors with memory whose resistance depends on the history of the crossing charges, has lately enhanced the classical paradigm of computation with neuromorphic architectures. However, in contrast to the known quantized models of passive circuit elements, such as inductors, capacitors or resistors, the design and realization of a quantum memristor is still missing. Here, we introduce the concept of a quantum memristor as a quantum dissipative device, whose decoherence mechanism is controlled by a continuous-measurement feedback scheme, which accounts for the memory. Indeed, we provide numerical simulations showing that memory effects actually persist in the quantum regime. Our quantization method, specifically designed for superconducting circuits, may be extended to other quantum platforms, allowing for memristor-type constructions in different quantum technologies. The proposed quantum memristor is then a building block for neuromorphic quantum computation and quantum simulations of non-Markovian systems.

  15. Quantum memristors.

    PubMed

    Pfeiffer, P; Egusquiza, I L; Di Ventra, M; Sanz, M; Solano, E

    2016-01-01

    Technology based on memristors, resistors with memory whose resistance depends on the history of the crossing charges, has lately enhanced the classical paradigm of computation with neuromorphic architectures. However, in contrast to the known quantized models of passive circuit elements, such as inductors, capacitors or resistors, the design and realization of a quantum memristor is still missing. Here, we introduce the concept of a quantum memristor as a quantum dissipative device, whose decoherence mechanism is controlled by a continuous-measurement feedback scheme, which accounts for the memory. Indeed, we provide numerical simulations showing that memory effects actually persist in the quantum regime. Our quantization method, specifically designed for superconducting circuits, may be extended to other quantum platforms, allowing for memristor-type constructions in different quantum technologies. The proposed quantum memristor is then a building block for neuromorphic quantum computation and quantum simulations of non-Markovian systems. PMID:27381511

  16. Quantum memristors

    PubMed Central

    Pfeiffer, P.; Egusquiza, I. L.; Di Ventra, M.; Sanz, M.; Solano, E.

    2016-01-01

    Technology based on memristors, resistors with memory whose resistance depends on the history of the crossing charges, has lately enhanced the classical paradigm of computation with neuromorphic architectures. However, in contrast to the known quantized models of passive circuit elements, such as inductors, capacitors or resistors, the design and realization of a quantum memristor is still missing. Here, we introduce the concept of a quantum memristor as a quantum dissipative device, whose decoherence mechanism is controlled by a continuous-measurement feedback scheme, which accounts for the memory. Indeed, we provide numerical simulations showing that memory effects actually persist in the quantum regime. Our quantization method, specifically designed for superconducting circuits, may be extended to other quantum platforms, allowing for memristor-type constructions in different quantum technologies. The proposed quantum memristor is then a building block for neuromorphic quantum computation and quantum simulations of non-Markovian systems. PMID:27381511

  17. Giant vacuum forces via transmission lines

    PubMed Central

    Shahmoon, Ephraim; Mazets, Igor; Kurizki, Gershon

    2014-01-01

    Quantum electromagnetic fluctuations induce forces between neutral particles, known as the van der Waals and Casimir interactions. These fundamental forces, mediated by virtual photons from the vacuum, play an important role in basic physics and chemistry and in emerging technologies involving, e.g., microelectromechanical systems or quantum information processing. Here we show that these interactions can be enhanced by many orders of magnitude upon changing the character of the mediating vacuum modes. By considering two polarizable particles in the vicinity of any standard electric transmission line, along which photons can propagate in one dimension, we find a much stronger and longer-range interaction than in free space. This enhancement may have profound implications on many-particle and bulk systems and impact the quantum technologies mentioned above. The predicted giant vacuum force is estimated to be measurable in a coplanar waveguide line. PMID:25002503

  18. Robust and efficient in situ quantum control

    NASA Astrophysics Data System (ADS)

    Ferrie, Christopher; Moussa, Osama

    2015-05-01

    Precision control of quantum systems is the driving force for both quantum technology and the probing of physics at the quantum and nanoscale levels. We propose an implementation-independent method for in situ quantum control that leverages recent advances in the direct estimation of quantum gate fidelity. Our algorithm takes account of the stochasticity of the problem, is suitable for closed-loop control, and requires only a constant number of fidelity-estimating experiments per iteration independent of the dimension of the control space. It is efficient and robust to both statistical and technical noise.

  19. Phase transitions and metastability in the distribution of the bipartite entanglement of a large quantum system

    SciTech Connect

    De Pasquale, A.; Facchi, P.; Parisi, G.; Pascazio, S.; Scardicchio, A.

    2010-05-15

    We study the distribution of the Schmidt coefficients of the reduced density matrix of a quantum system in a pure state. By applying general methods of statistical mechanics, we introduce a fictitious temperature and a partition function and translate the problem in terms of the distribution of the eigenvalues of random matrices. We investigate the appearance of two phase transitions, one at a positive temperature, associated with very entangled states, and one at a negative temperature, signaling the appearance of a significant factorization in the many-body wave function. We also focus on the presence of metastable states (related to two-dimensional quantum gravity) and study the finite size corrections to the saddle point solution.

  20. A molecular mechanics force field for lignin

    SciTech Connect

    Petridis, Loukas; Smith, Jeremy C

    2009-02-01

    A CHARMM molecular mechanics force field for lignin is derived. Parameterization is based on reproducing quantum mechanical data of model compounds. Partial atomic charges are derived using the RESP electrostatic potential fitting method supplemented by the examination of methoxybenzene:water interactions. Dihedral parameters are optimized by fitting to critical rotational potentials and bonded parameters are obtained by optimizing vibrational frequencies and normal modes. Finally, the force field is validated by performing a molecular dynamics simulation of a crystal of a lignin fragment molecule and comparing simulation-derived structural features with experimental results. Together with the existing force field for polysaccharides, this lignin force field will enable full simulations of lignocellulose.

  1. Waveguide ultrasonic force microscopy at 60 MHz

    NASA Astrophysics Data System (ADS)

    Inagaki, K.; Kolosov, O. V.; Briggs, G. A. D.; Wright, O. B.

    2000-04-01

    We present measurements using ultrasonic force microscopy at ˜60 MHz, operating in a "waveguide" mode in which the cantilever base is vibrated and flexural ultrasonic vibrations are launched down the cantilever without exciting any particular cantilever resonance. The nonlinearity of the tip-sample force-distance curve allows the conversion of a modulated ultrasonic frequency into a low frequency vibration of the cantilever, detected in a conventional atomic force microscope. Images of Ge quantum dots on a Si substrate show contrast related to elasticity and adhesion differences, and this is interpreted with the Johnson-Kendall-Roberts model of the force-distance curve.

  2. Quantum hair and quantum gravity

    SciTech Connect

    Coleman, S. ); Krauss, L.M. ); Preskill, J. ); Wilczek, F. )

    1992-01-01

    A black hole may carry quantum numbers that are not associated with massless gauge fields, contrary to the spirit of the 'no-hair' theorems. The 'quantum hair' is invisible in the classical limit, but measurable via quantum interference experiments. Quantum hair alters the temperature of the radiation emitted by a black hole. It also induces non-zero expectation values for fields outside the event horizon; these expectation values are non-perturbative in [Dirac h], and decay exponentially far from the hole. The existence of quantum hair demonstrates that a black hole can have an intricate quantum-mechanical structure that is completely missed by standard semiclassical theory.

  3. Quantum robots and quantum computers

    SciTech Connect

    Benioff, P.

    1998-07-01

    Validation of a presumably universal theory, such as quantum mechanics, requires a quantum mechanical description of systems that carry out theoretical calculations and systems that carry out experiments. The description of quantum computers is under active development. No description of systems to carry out experiments has been given. A small step in this direction is taken here by giving a description of quantum robots as mobile systems with on board quantum computers that interact with different environments. Some properties of these systems are discussed. A specific model based on the literature descriptions of quantum Turing machines is presented.

  4. Quantum Darwinism

    SciTech Connect

    Zurek, Wojciech H

    2008-01-01

    Quantum Darwinism - proliferation, in the environment, of multiple records of selected states of the system (its information-theoretic progeny) - explains how quantum fragility of individual state can lead to classical robustness of their multitude.

  5. Quantum Orbifolds

    NASA Astrophysics Data System (ADS)

    Harju, Antti J.

    2016-06-01

    This is a study of orbifold-quotients of quantum groups (quantum orbifolds {Θ } rightrightarrows Gq). These structures have been studied extensively in the case of the quantum S U 2 group. A generalized theory of quantum orbifolds over compact simple and simply connected quantum groups is developed. Associated with a quantum orbifold there is an invariant subalgebra and a crossed product algebra. For each spin quantum orbifold, there is a unitary equivalence class of Dirac spectral triples over the invariant subalgebra, and for each effective spin quantum orbifold associated with a finite group action, there is a unitary equivalence class of Dirac spectral triples over the crossed product algebra. A Hopf-equivariant Fredholm index problem is studied as an application.

  6. Quantum memristors

    DOE PAGESBeta

    Pfeiffer, P.; Egusquiza, I. L.; Di Ventra, M.; Sanz, M.; Solano, E.

    2016-07-06

    Technology based on memristors, resistors with memory whose resistance depends on the history of the crossing charges, has lately enhanced the classical paradigm of computation with neuromorphic architectures. However, in contrast to the known quantized models of passive circuit elements, such as inductors, capacitors or resistors, the design and realization of a quantum memristor is still missing. Here, we introduce the concept of a quantum memristor as a quantum dissipative device, whose decoherence mechanism is controlled by a continuous-measurement feedback scheme, which accounts for the memory. Indeed, we provide numerical simulations showing that memory effects actually persist in the quantummore » regime. Our quantization method, specifically designed for superconducting circuits, may be extended to other quantum platforms, allowing for memristor-type constructions in different quantum technologies. As a result, the proposed quantum memristor is then a building block for neuromorphic quantum computation and quantum simulations of non-Markovian systems.« less

  7. Coupled Quantum Fluctuations and Quantum Annealing

    NASA Astrophysics Data System (ADS)

    Hormozi, Layla; Kerman, Jamie

    We study the relative effectiveness of coupled quantum fluctuations, compared to single spin fluctuations, in the performance of quantum annealing. We focus on problem Hamiltonians resembling the the Sherrington-Kirkpatrick model of Ising spin glass and compare the effectiveness of different types of fluctuations by numerically calculating the relative success probabilities and residual energies in fully-connected spin systems. We find that for a small class of instances coupled fluctuations can provide improvement over single spin fluctuations and analyze the properties of the corresponding class. Disclaimer: This research was funded by ODNI, IARPA via MIT Lincoln Laboratory under Air Force Contract No. FA8721-05-C-0002. The views and conclusions contained herein are those of the authors and should not be interpreted as necessarily representing the official policies or endorsements, either expressed or implied, of ODNI, IARPA, or the US Government.

  8. Quantum frames

    NASA Astrophysics Data System (ADS)

    Brown, Matthew J.

    2014-02-01

    The framework of quantum frames can help unravel some of the interpretive difficulties i the foundation of quantum mechanics. In this paper, I begin by tracing the origins of this concept in Bohr's discussion of quantum theory and his theory of complementarity. Engaging with various interpreters and followers of Bohr, I argue that the correct account of quantum frames must be extended beyond literal space-time reference frames to frames defined by relations between a quantum system and the exosystem or external physical frame, of which measurement contexts are a particularly important example. This approach provides superior solutions to key EPR-type measurement and locality paradoxes.

  9. Quantum cheques

    NASA Astrophysics Data System (ADS)

    Moulick, Subhayan Roy; Panigrahi, Prasanta K.

    2016-06-01

    We propose the idea of a quantum cheque scheme, a cryptographic protocol in which any legitimate client of a trusted bank can issue a cheque, that cannot be counterfeited or altered in anyway, and can be verified by a bank or any of its branches. We formally define a quantum cheque and present the first unconditionally secure quantum cheque scheme and show it to be secure against any no-signalling adversary. The proposed quantum cheque scheme can been perceived as the quantum analog of Electronic Data Interchange, as an alternate for current e-Payment Gateways.

  10. Quantum cheques

    NASA Astrophysics Data System (ADS)

    Moulick, Subhayan Roy; Panigrahi, Prasanta K.

    2016-03-01

    We propose the idea of a quantum cheque scheme, a cryptographic protocol in which any legitimate client of a trusted bank can issue a cheque, that cannot be counterfeited or altered in anyway, and can be verified by a bank or any of its branches. We formally define a quantum cheque and present the first unconditionally secure quantum cheque scheme and show it to be secure against any no-signalling adversary. The proposed quantum cheque scheme can been perceived as the quantum analog of Electronic Data Interchange, as an alternate for current e-Payment Gateways.

  11. Nuclear Quantum Gravitation - The Correct Theory

    NASA Astrophysics Data System (ADS)

    Kotas, Ronald

    2016-03-01

    Nuclear Quantum Gravitation provides a clear, definitive Scientific explanation of Gravity and Gravitation. It is harmonious with Newtonian and Quantum Mechanics, and with distinct Scientific Logic. Nuclear Quantum Gravitation has 10 certain, Scientific proofs and 21 more good indications. With this theory the Physical Forces are obviously Unified. See: OBSCURANTISM ON EINSTEIN GRAVITATION? http://www.santilli- Foundation.org/inconsistencies-gravitation.php and Einstein's Theory of Relativity versus Classical Mechanics http://www.newtonphysics.on.ca/einstein/

  12. Casimir Forces On A Silicon Micromechanical Chip

    SciTech Connect

    Zou, J.; Marset, zsolt; Rodriguez, A.W.; Reid, M. T.H.; McCauley, A. P.; Kravchenko, Ivan I; Bao, Y.; Johnson, S. G.; Chan, Ho Bun

    2013-01-01

    Quantum fluctuations give rise to van der Waals and Casimir forces that dominate the interaction between electrically neutral objects at sub-micron separations. Under the trend of miniaturization, such quantum electrodynamical effects are expected to play an important role in micro- and nano-mechanical devices. Nevertheless, so far the Casimir force has been experimentally observed only in situations involving an external object manually positioned close to a micromechanical element on a silicon chip. Here, we demonstrate the Casimir effect between two silicon components on the same substrate. In addition to providing an integrated and compact platform for Casimir force measurements, this scheme also opens the possibility of tailoring the Casimir force using lithographically defined components of non-conventional shapes on a single micromechanical chip.

  13. Non-linear Langmuir waves in a warm quantum plasma

    SciTech Connect

    Dubinov, Alexander E. Kitaev, Ilya N.

    2014-10-15

    A non-linear differential equation describing the Langmuir waves in a warm quantum electron-ion plasma has been derived. Its numerical solutions of the equation show that ordinary electronic oscillations, similar to the classical oscillations, occur along with small-scale quantum Langmuir oscillations induced by the Bohm quantum force.

  14. Quantum mechanical generalization of the balistic electron wind theory

    NASA Astrophysics Data System (ADS)

    Lacina, A.

    1980-06-01

    The Fiks' quasiclassical theory of the electron wind force is quantum mechanically generalized. Within the framework of this generalization the space dependence of the electron wind force is calculated in the vicinity of an interface between two media. It is found that quantum corrections may be comparable with or even greater than corresponding quasiclassical values.

  15. Van der Waals quantum friction and fluctuation theorems

    NASA Astrophysics Data System (ADS)

    Dalvit, Diego; Intravaia, Francesco; Behunin, Ryan

    2014-03-01

    We use general concepts of statistical mechanics to compute the quantum frictional force on an atom moving at constant velocity above a planar surface. We derive the zero-temperature frictional force using a non-equilibrium fluctuation-dissipation relation, and show that in the large-time, steady-state regime quantum friction scales as the cubic power of the atom's velocity. We also discuss how approaches based on Wigner-Weisskopf and quantum regression approximations fail to predict the correct steady-state zero temperature frictional force, mainly due to the low frequency nature of quantum friction.

  16. Quantum Computing

    NASA Astrophysics Data System (ADS)

    Steffen, Matthias

    2013-03-01

    Quantum mechanics plays a crucial role in many day-to-day products, and has been successfully used to explain a wide variety of observations in Physics. While some quantum effects such as tunneling limit the degree to which modern CMOS devices can be scaled to ever reducing dimensions, others may potentially be exploited to build an entirely new computing architecture: The quantum computer. In this talk I will review several basic concepts of a quantum computer. Why quantum computing and how do we do it? What is the status of several (but not all) approaches towards building a quantum computer, including IBM's approach using superconducting qubits? And what will it take to build a functional machine? The promise is that a quantum computer could solve certain interesting computational problems such as factoring using exponentially fewer computational steps than classical systems. Although the most sophisticated modern quantum computing experiments to date do not outperform simple classical computations, it is increasingly becoming clear that small scale demonstrations with as many as 100 qubits are beginning to be within reach over the next several years. Such a demonstration would undoubtedly be a thrilling feat, and usher in a new era of controllably testing quantum mechanics or quantum computing aspects. At the minimum, future demonstrations will shed much light on what lies ahead.

  17. Quantum volume

    NASA Astrophysics Data System (ADS)

    Ryabov, V. A.

    2015-08-01

    Quantum systems in a mechanical embedding, the breathing mode of a small particles, optomechanical system, etc. are far not the full list of examples in which the volume exhibits quantum behavior. Traditional consideration suggests strain in small systems as a result of a collective movement of particles, rather than the dynamics of the volume as an independent variable. The aim of this work is to show that some problem here might be essentially simplified by introducing periodic boundary conditions. At this case, the volume is considered as the independent dynamical variable driven by the internal pressure. For this purpose, the concept of quantum volume based on Schrödinger’s equation in 𝕋3 manifold is proposed. It is used to explore several 1D model systems: An ensemble of free particles under external pressure, quantum manometer and a quantum breathing mode. In particular, the influence of the pressure of free particle on quantum oscillator is determined. It is shown also that correction to the spectrum of the breathing mode due to internal degrees of freedom is determined by the off-diagonal matrix elements of the quantum stress. The new treatment not using the “force” theorem is proposed for the quantum stress tensor. In the general case of flexible quantum 3D dynamics, quantum deformations of different type might be introduced similarly to monopole mode.

  18. Quantum games as quantum types

    NASA Astrophysics Data System (ADS)

    Delbecque, Yannick

    In this thesis, we present a new model for higher-order quantum programming languages. The proposed model is an adaptation of the probabilistic game semantics developed by Danos and Harmer [DH02]: we expand it with quantum strategies which enable one to represent quantum states and quantum operations. Some of the basic properties of these strategies are established and then used to construct denotational semantics for three quantum programming languages. The first of these languages is a formalisation of the measurement calculus proposed by Danos et al. [DKP07]. The other two are new: they are higher-order quantum programming languages. Previous attempts to define a denotational semantics for higher-order quantum programming languages have failed. We identify some of the key reasons for this and base the design of our higher-order languages on these observations. The game semantics proposed in this thesis is the first denotational semantics for a lambda-calculus equipped with quantum types and with extra operations which allow one to program quantum algorithms. The results presented validate the two different approaches used in the design of these two new higher-order languages: a first one where quantum states are used through references and a second one where they are introduced as constants in the language. The quantum strategies presented in this thesis allow one to understand the constraints that must be imposed on quantum type systems with higher-order types. The most significant constraint is the fact that abstraction over part of the tensor product of many unknown quantum states must not be allowed. Quantum strategies are a new mathematical model which describes the interaction between classical and quantum data using system-environment dialogues. The interactions between the different parts of a quantum system are described using the rich structure generated by composition of strategies. This approach has enough generality to be put in relation with other

  19. Time Domain Propagation of Quantum and Classical Systems using a Wavelet Basis Set Method

    NASA Astrophysics Data System (ADS)

    Lombardini, Richard; Nowara, Ewa; Johnson, Bruce

    2015-03-01

    The use of an orthogonal wavelet basis set (Optimized Maximum-N Generalized Coiflets) to effectively model physical systems in the time domain, in particular the electromagnetic (EM) pulse and quantum mechanical (QM) wavefunction, is examined in this work. Although past research has demonstrated the benefits of wavelet basis sets to handle computationally expensive problems due to their multiresolution properties, the overlapping supports of neighboring wavelet basis functions poses problems when dealing with boundary conditions, especially with material interfaces in the EM case. Specifically, this talk addresses this issue using the idea of derivative matching creating fictitious grid points (T.A. Driscoll and B. Fornberg), but replaces the latter element with fictitious wavelet projections in conjunction with wavelet reconstruction filters. Two-dimensional (2D) systems are analyzed, EM pulse incident on silver cylinders and the QM electron wave packet circling the proton in a hydrogen atom system (reduced to 2D), and the new wavelet method is compared to the popular finite-difference time-domain technique.

  20. A Nanocrystal Sensor for Luminescence Detection of Cellular Forces

    SciTech Connect

    Choi, Charina; Chou, Jonathan; Lutker, Katie; Werb, Zena; Alivisatos, Paul

    2011-09-29

    Quantum dots have been used as bright fluorescent tags with high photostability to probe numerous biological systems. In this work we present the tetrapod quantum dot as a dynamic, next-generation nanocrystal probe that fluorescently reports cellular forces with spatial and temporal resolution. Its small size and colloidal state suggest that the tetrapod may be further developed as a tool to measure cellular forces in vivo and with macromolecular spatial resolution.

  1. Minimal Length, Maximal Momentum and the Entropic Force Law

    NASA Astrophysics Data System (ADS)

    Nozari, Kourosh; Pedram, Pouria; Molkara, M.

    2012-04-01

    Different candidates of quantum gravity proposal such as string theory, noncommutative geometry, loop quantum gravity and doubly special relativity, all predict the existence of a minimum observable length and/or a maximal momentum which modify the standard Heisenberg uncertainty principle. In this paper, we study the effects of minimal length and maximal momentum on the entropic force law formulated recently by E. Verlinde.

  2. Quantum flywheel

    NASA Astrophysics Data System (ADS)

    Levy, Amikam; Diósi, Lajos; Kosloff, Ronnie

    2016-05-01

    In this work we present the concept of a quantum flywheel coupled to a quantum heat engine. The flywheel stores useful work in its energy levels, while additional power is extracted continuously from the device. Generally, the energy exchange between a quantum engine and a quantized work repository is accompanied by heat, which degrades the charging efficiency. Specifically when the quantum harmonic oscillator acts as a work repository, quantum and thermal fluctuations dominate the dynamics. Quantum monitoring and feedback control are applied to the flywheel in order to reach steady state and regulate its operation. To maximize the charging efficiency one needs a balance between the information gained by measuring the system and the information fed back to the system. The dynamics of the flywheel are described by a stochastic master equation that accounts for the engine, the external driving, the measurement, and the feedback operations.

  3. Quantum Groupoids

    NASA Astrophysics Data System (ADS)

    Xu, Ping

    We introduce a general notion of quantum universal enveloping algebroids (QUE algebroids), or quantum groupoids, as a unification of quantum groups and star-products. Some basic properties are studied including the twist construction and the classical limits. In particular, we show that a quantum groupoid naturally gives rise to a Lie bialgebroid as a classical limit. Conversely, we formulate a conjecture on the existence of a quantization for any Lie bialgebroid, and prove this conjecture for the special case of regular triangular Lie bialgebroids. As an application of this theory, we study the dynamical quantum groupoid , which gives an interpretation of the quantum dynamical Yang-Baxter equation in terms of Hopf algebroids.

  4. Quantifying Quantumness

    NASA Astrophysics Data System (ADS)

    Braun, Daniel; Giraud, Olivier; Braun, Peter A.

    2010-03-01

    We introduce and study a measure of ``quantumness'' of a quantum state based on its Hilbert-Schmidt distance from the set of classical states. ``Classical states'' were defined earlier as states for which a positive P-function exists, i.e. they are mixtures of coherent states [1]. We study invariance properties of the measure, upper bounds, and its relation to entanglement measures. We evaluate the quantumness of a number of physically interesting states and show that for any physical system in thermal equilibrium there is a finite critical temperature above which quantumness vanishes. We then use the measure for identifying the ``most quantum'' states. Such states are expected to be potentially most useful for quantum information theoretical applications. We find these states explicitly for low-dimensional spin-systems, and show that they possess beautiful, highly symmetric Majorana representations. [4pt] [1] Classicality of spin states, Olivier Giraud, Petr Braun, and Daniel Braun, Phys. Rev. A 78, 042112 (2008)

  5. Quantum Dots

    NASA Astrophysics Data System (ADS)

    Tartakovskii, Alexander

    2012-07-01

    Part I. Nanostructure Design and Structural Properties of Epitaxially Grown Quantum Dots and Nanowires: 1. Growth of III/V semiconductor quantum dots C. Schneider, S. Hofling and A. Forchel; 2. Single semiconductor quantum dots in nanowires: growth, optics, and devices M. E. Reimer, N. Akopian, M. Barkelid, G. Bulgarini, R. Heeres, M. Hocevar, B. J. Witek, E. Bakkers and V. Zwiller; 3. Atomic scale analysis of self-assembled quantum dots by cross-sectional scanning tunneling microscopy and atom probe tomography J. G. Keizer and P. M. Koenraad; Part II. Manipulation of Individual Quantum States in Quantum Dots Using Optical Techniques: 4. Studies of the hole spin in self-assembled quantum dots using optical techniques B. D. Gerardot and R. J. Warburton; 5. Resonance fluorescence from a single quantum dot A. N. Vamivakas, C. Matthiesen, Y. Zhao, C.-Y. Lu and M. Atature; 6. Coherent control of quantum dot excitons using ultra-fast optical techniques A. J. Ramsay and A. M. Fox; 7. Optical probing of holes in quantum dot molecules: structure, symmetry, and spin M. F. Doty and J. I. Climente; Part III. Optical Properties of Quantum Dots in Photonic Cavities and Plasmon-Coupled Dots: 8. Deterministic light-matter coupling using single quantum dots P. Senellart; 9. Quantum dots in photonic crystal cavities A. Faraon, D. Englund, I. Fushman, A. Majumdar and J. Vukovic; 10. Photon statistics in quantum dot micropillar emission M. Asmann and M. Bayer; 11. Nanoplasmonics with colloidal quantum dots V. Temnov and U. Woggon; Part IV. Quantum Dot Nano-Laboratory: Magnetic Ions and Nuclear Spins in a Dot: 12. Dynamics and optical control of an individual Mn spin in a quantum dot L. Besombes, C. Le Gall, H. Boukari and H. Mariette; 13. Optical spectroscopy of InAs/GaAs quantum dots doped with a single Mn atom O. Krebs and A. Lemaitre; 14. Nuclear spin effects in quantum dot optics B. Urbaszek, B. Eble, T. Amand and X. Marie; Part V. Electron Transport in Quantum Dots Fabricated by

  6. Dissipative quantum computing with open quantum walks

    SciTech Connect

    Sinayskiy, Ilya; Petruccione, Francesco

    2014-12-04

    An open quantum walk approach to the implementation of a dissipative quantum computing scheme is presented. The formalism is demonstrated for the example of an open quantum walk implementation of a 3 qubit quantum circuit consisting of 10 gates.

  7. Quantum ratchets for quantum communication with optical superlattices

    SciTech Connect

    Romero-Isart, Oriol; Garcia-Ripoll, Juan Jose

    2007-11-15

    We propose to use a quantum ratchet to transport quantum information in a chain of atoms trapped in an optical superlattice. The quantum ratchet is created by a continuous modulation of the optical superlattice which is periodic in time and in space. Though there is zero average force acting on the atoms, we show that indeed the ratchet effect permits atoms on even and odd sites to move along opposite directions. By loading the optical lattice with two-level bosonic atoms, this scheme permits us to perfectly transport a qubit or entangled state imprinted in one or more atoms to any desired position in the lattice. From the quantum computation point of view, the transport is achieved by a smooth concatenation of perfect swap gates. We analyze setups with noninteracting and interacting particles and in the latter case we use the tools of optimal control to design optimal modulations. We also discuss the feasibility of this method in current experiments.

  8. ForceFit: a code to fit classical force fields to ab-initio potential energy surfaces

    SciTech Connect

    Henson, Neil Jon; Waldher, Benjamin; Kuta, Jadwiga; Clark, Aurora; Clark, Aurora E

    2009-01-01

    The ForceFit program package has been developed for fitting classical force field parameters based upon a force matching algorithm to quantum mechanical gradients of configurations that span the potential energy surface of the system. The program, which runs under Unix and is written in C++, is an easy to use, nonproprietary platform that enables gradient fitting of a wide variety of functional force field forms to quantum mechanical information obtained from an array of common electronic structure codes. All aspects of the fitting process are run from a graphical user interface, from the parsing of quantum mechanical data, assembling of a potential energy surface database, setting the force field and variables to be optimized, choosing a molecular mechanics code for comparison to the reference data, and finally, the initiation of a least squares minimization algorithm. Furthermore, the code is based on a modular templated code design that enables the facile addition of new functionality to the program.

  9. Quantum computer games: quantum minesweeper

    NASA Astrophysics Data System (ADS)

    Gordon, Michal; Gordon, Goren

    2010-07-01

    The computer game of quantum minesweeper is introduced as a quantum extension of the well-known classical minesweeper. Its main objective is to teach the unique concepts of quantum mechanics in a fun way. Quantum minesweeper demonstrates the effects of superposition, entanglement and their non-local characteristics. While in the classical minesweeper the goal of the game is to discover all the mines laid out on a board without triggering them, in the quantum version there are several classical boards in superposition. The goal is to know the exact quantum state, i.e. the precise layout of all the mines in all the superposed classical boards. The player can perform three types of measurement: a classical measurement that probabilistically collapses the superposition; a quantum interaction-free measurement that can detect a mine without triggering it; and an entanglement measurement that provides non-local information. The application of the concepts taught by quantum minesweeper to one-way quantum computing are also presented.

  10. Quantum Cryptography Without Quantum Uncertainties

    NASA Astrophysics Data System (ADS)

    Durt, Thomas

    2002-06-01

    Quantum cryptography aims at transmitting a random key in such a way that the presence of a spy eavesdropping the communication would be revealed by disturbances in the transmission of the message. In standard quantum cryptography, this unavoidable disturbance is a consequence of the uncertainty principle of Heisenberg. We propose in this paper to replace quantum uncertainties by generalised, technological uncertainties, and discuss the realisability of such an idea. The proposed protocol can be considered as a simplification, but also as a generalisation of the standard quantum cryptographic protocols.