Quantum anharmonic oscillator: The airy function approach
Maiz, F., E-mail: fethimaiz@gmail.com [King Khalid University, Faculty of Science, Physics Department, PO Box 9004, Abha 61413, Asseer (Saudi Arabia); University of Cartage, Nabeul Engineering Preparatory Institute, Merazka, 8000 Nabeul (Tunisia); AlFaify, S. [King Khalid University, Faculty of Science, Physics Department, PO Box 9004, Abha 61413, Asseer (Saudi Arabia)
2014-05-15
New and simple numerical method is being reported to solve anharmonic oscillator problems. The method is setup to approach the real potential V(x) of the anharmonic oscillator system as a piecewise linear potential u(x) and to solve the Schrödinger equation of the system using the Airy function. Then, solutions continuity conditions lead to the energy quantification condition, and consequently, the energy eigenvalues. For testing purpose, the method was applied on the sextic and octic oscillators systems. The proposed method is found to be realistic, computationally simple, and having high degrees of accuracy. In addition, it can be applied to any form of potential. The results obtained by the proposed method were seen closely agreeing with results reached by other complicated methods.
Phase synchronization of two anharmonic nanomechanical oscillators.
Matheny, Matthew H; Grau, Matt; Villanueva, Luis G; Karabalin, Rassul B; Cross, M C; Roukes, Michael L
2014-01-10
We investigate the synchronization of oscillators based on anharmonic nanoelectromechanical resonators. Our experimental implementation allows unprecedented observation and control of parameters governing the dynamics of synchronization. We find close quantitative agreement between experimental data and theory describing reactively coupled Duffing resonators with fully saturated feedback gain. In the synchronized state we demonstrate a significant reduction in the phase noise of the oscillators, which is key for sensor and clock applications. Our work establishes that oscillator networks constructed from nanomechanical resonators form an ideal laboratory to study synchronization--given their high-quality factors, small footprint, and ease of cointegration with modern electronic signal processing technologies.
Observation of anharmonic Bloch oscillations.
Dreisow, Felix; Wang, Gang; Heinrich, Matthias; Keil, Robert; Tünnermann, Andreas; Nolte, Stefan; Szameit, Alexander
2011-10-15
We report on the experimental observation of Bloch oscillations of an optical wave packet in a lattice with second-order coupling. To this end, we employ zigzag waveguide arrays, in which the second-order coupling can be precisely tuned.
Living systems as coherent anharmonic oscillators
Molski, M.
2011-12-01
A model of living systems considered as coherent, time-dependent anharmonic oscillators is presented. It is based on the concept of space-like coherent states minimizing the time-energy uncertainty relation, adapted to the case of biological systems whose growth is described by the Gompertz or West-Brown-Enquist functions. The coherent states of biological growth evolve coherently in space being localized along the classical time trajectory; hence, the growth is predicted to be coherent in space. It is proven that the Gompertz function is a special solution of the space-like Horodecki-Feinberg equation for the time-dependent Morse oscillator in the dissociation state. Its eigenvalue represents the momentum of biological growth, associated with a space-like component whose properties resemble those attributed by vitalists to the life momentum or vital impulse. The physical characteristics of the life energy and momentum and their connection with the concept of zero-point momentum of vacuum are presented.
Exact and approximate expressions for the period of anharmonic oscillators
Amore, Paolo [Facultad de Ciencias, Universidad de Colima, Bernal DIaz del Castillo 340, Colima (Mexico); Fernandez, Francisco M [INIFTA (Conicet, UNLP), Blvd. 113 y 64 S/N, Sucursal 4, Casilla de Correo 16, 1900 La Plata (Argentina)
2005-07-01
In this paper, we present a straightforward systematic method for the exact and approximate calculation of integrals that appear in formulae for the period of anharmonic oscillators and other problems of interest in classical mechanics.
Linear delta expansion technique for the solution of anharmonic oscillations
P K Bera; J Datta
2007-01-01
The linear delta expansion technique has been developed for solving the differential equation of motion for symmetric and asymmetric anharmonic oscillators. We have also demonstrated the sophistication and simplicity of this new perturbation technique.
Genuine Quantum Signatures in Synchronization of Anharmonic Self-Oscillators
Lörch, Niels; Amitai, Ehud; Nunnenkamp, Andreas; Bruder, Christoph
2016-08-01
We study the synchronization of a Van der Pol self-oscillator with Kerr anharmonicity to an external drive. We demonstrate that the anharmonic, discrete energy spectrum of the quantum oscillator leads to multiple resonances in both phase locking and frequency entrainment not present in the corresponding classical system. Strong driving close to these resonances leads to nonclassical steady-state Wigner distributions. Experimental realizations of these genuine quantum signatures can be implemented with current technology.
Effective harmonic oscillator description of anharmonic molecular vibrations
Tapta Kanchan Roy; M Durga Prasad
2009-09-01
The validity of an effective harmonic oscillator approximation for anharmonic molecular vibrations is tested and compared with vibrational self consistent field and vibrational configurational interaction results. The effective harmonic oscillator is constructed variationally, by taking the trial wave function as a harmonic oscillator eigenfunction with the centroid and width parameter as variational paraeters. It is found that the effective harmonic oscillator approximation provides a description of the anharmonic eigenstates very similar to the vibrational self consistent field results. Coriolis coupling is also included in these studies.
Probing anharmonicity of a quantum oscillator in an optomechanical cavity
Latmiral, Ludovico; Armata, Federico; Genoni, Marco G.; Pikovski, Igor; Kim, M. S.
2016-05-01
We present a way of measuring with high precision the anharmonicity of a quantum oscillator coupled to an optical field via radiation pressure. Our protocol uses a sequence of pulsed interactions to perform a loop in the phase space of the mechanical oscillator, which is prepared in a thermal state. We show how the optical field acquires a phase depending on the anharmonicity. Remarkably, one only needs small initial cooling of the mechanical motion to probe even small anharmonicities. Finally, by applying tools from quantum estimation theory, we calculate the ultimate bound on the estimation precision posed by quantum mechanics and compare it with the precision obtainable with feasible measurements such as homodyne and heterodyne detection on the cavity field. In particular we demonstrate that homodyne detection is nearly optimal in the limit of a large number of photons of the field and we discuss the estimation precision of small anharmonicities in terms of its signal-to-noise ratio.
Quantum and Classical Chirps in an Anharmonic Oscillator
Shalibo, Yoni; Barth, Ido; Friedland, Lazar; Bialczack, Radoslaw; Martinis, John M; Katz, Nadav
2011-01-01
We measure the state dynamics of a tunable anharmonic quantum system, the Josephson phase circuit, under the excitation of a frequency-chirped drive. At small anharmonicity, the state evolves like a wavepacket - a characteristic response in classical oscillators; in this regime we report exponentially enhanced lifetimes of highly excited states, held by the drive. At large anharmonicity, we observe sharp steps, corresponding to the excitation of discrete energy levels. The continuous transition between the two regimes is mapped by measuring the threshold of these two effects.
Exact solutions and ladder operators for a new anharmonic oscillator
Dong Shihai [Programa de Ingenieria Molecular, Instituto Mexicano del Petroleo, Lazaro Cardenas 152, 07730 Mexico DF (Mexico)]. E-mail: dongsh2@yahoo.com; Sun Guohua [Instituto de Investigaciones en Matematicas Aplicadas y en Sistemas, UNAM, A.P. 20-726, Del. Alvaro Obregon, 01000 Mexico DF (Mexico); Lozada-Cassou, M. [Programa de Ingenieria Molecular, Instituto Mexicano del Petroleo, Lazaro Cardenas 152, 07730 Mexico DF (Mexico)
2005-06-06
In this Letter, we propose a new anharmonic oscillator and present the exact solutions of the Schrodinger equation with this oscillator. The ladder operators are established directly from the normalized radial wave functions and used to evaluate the closed expressions of matrix elements for some related functions. Some comments are made on the general calculation formula and recurrence relation for off-diagonal matrix elements. Finally, we show that this anharmonic oscillator possesses a hidden symmetry between E(r) and E(ir) by substituting r->ir.
PT-Symmetric Cubic Anharmonic Oscillator as a Physical Model
Mostafazadeh, A
2004-01-01
We perform a perturbative calculation of the physical observables, in particular pseudo-Hermitian position and momentum operators, the equivalent Hermitian Hamiltonian operator, and the classical Hamiltonian for the PT-symmetric cubic anharmonic oscillator, $ H=p^1/(2m)+\\mu^2x^2/2+i\\epsilon x^3 $. Ignoring terms of order $ \\epsilon^4 $ and higher, we show that this system describes an ordinary quartic anharmonic oscillator with a position-dependent mass and real and positive coupling constants. This observation elucidates the classical origin of the reality and positivity of the energy spectrum. We also discuss the quantum-classical correspondence for this PT-symmetric system, compute the associated conserved probability density, and comment on the issue of factor-ordering in the pseudo-Hermitian canonical quantization of the underlying classical system.
On the classical dynamics of strongly driven anharmonic oscillators
Breuer, H. P.; Dietz, K.; Holthaus, M.
1990-12-01
We investigate the dynamics of periodically driven anharmonic oscillators. In particular, we consider values of the coupling strength which are orders of magnitude higher than those required for the overlap of primary resonances. We observe a division of phase space into a regular and a stochastic region. Both regions are separated by a sharp chaos border which sets an upper limit to the stochastic heating of particles; its dependence on the coupling strength is studied. We construct perpetual adiabatic invariants governing regular motion. A bifurcation mechanism leading to the annihilation of resonances is explained.
Perfect Lattice Perturbation Theory A Study of the Anharmonic Oscillator
Bietenholz, W
1999-01-01
As an application of perfect lattice perturbation theory, we construct an O(\\lambda) perfect lattice action for the anharmonic oscillator analytically in momentum space. In coordinate space we obtain a set of 2-spin and 4-spin couplings \\propto \\lambda, which we evaluate for various masses. These couplings never involve variables separated by more than two lattice spacings. The O(\\lambda) perfect action is simulated and compared to the standard action. We discuss the improvement for the first two energy gaps \\Delta E_1, \\Delta E_2 and for the scaling quantity \\Delta E_2 / \\Delta E1 in different regimes of the interaction parameter, and of the correlation length.
A quantum anharmonic oscillator model for the stock market
Gao, Tingting; Chen, Yu
2017-02-01
A financially interpretable quantum model is proposed to study the probability distributions of the stock price return. The dynamics of a quantum particle is considered an analog of the motion of stock price. Then the probability distributions of price return can be computed from the wave functions that evolve according to Schrodinger equation. Instead of a harmonic oscillator in previous studies, a quantum anharmonic oscillator is applied to the stock in liquid market. The leptokurtic distributions of price return can be reproduced by our quantum model with the introduction of mixed-state and multi-potential. The trend following dominant market, in which the price return follows a bimodal distribution, is discussed as a specific case of the illiquid market.
Exploring Anharmonic Nuclear Dynamics and Spectroscopy Using the Kratzer Oscillator.
Toutounji, Mohamad
2011-06-14
The Kratzer oscillator is useful in modeling anharmonic molecular vibrations; therefore, its underlying theory is briefly explored in this study. The linear dipole moment time correlation function, within the Condon approximation, is analytically evaluated, and linear absorption lineshapes are calculated at different temperatures. An important integral formula of Landau and Liftshitz is, for the first time, utilized to evaluate the anharmonic Franck-Condon factor (FCF) resulting from modeling the initial and final states by Kratzer potentials. In addition, an exact closed-form expression of the FCF for the linearly displaced and shape-distorted final state energy curve, with respect to the ground state, is reported. Within the context of Mukamel formalism, nonlinear spectral/temporal lineshapes, such as hole-burning, photon echo, and pump-probe signals, may not be calculated without nonlinear response theory using the so-called "four-point dipole moment time correlation function". The above FCFs will be employed to calculate optical linear and nonlinear spectra at different temperatures utilizing a previously developed formula [Toutounji, M. J. Phys. Chem. C2010, in press], whereby a hole-burned absorption lineshape may be found using a linear dipole moment time correlation function.
The anharmonic effect study of coupled Morse oscillators for the unimolecular reaction
YAO Li; LIN Sheng-Hsien
2008-01-01
The importance of anharmonic effect in dissociation of molecular systems especially clusters has been noted. In this paper, we shall study the effect of coupled anharmonic oscillator of the standard bilinear form (SBF) Morse oscillator (MO) potential on unimolecular reaction. We shall use the systematic theoretical approach, YL method, proposed by Yao and Lin (YAO L, et. al. J Phys Chem A, 2007, 111(29): 6722-6729), which can evaluate anharmonic effects on the rate constants based on the transition state theory. In treating the anharmonic effect with the Morse oscillator potential on unimolecular reactions under collision-free conditions by using the RRKM (Rice-Ramsperger-Kassel-Marcus) theory, the in-verse Laplace transformation of the partition functions was used to obtain the total amount of state and density of state by using the first-order and the second-order approximations of the saddle-point method. To demonstrate the anharmonic effect of the SBF Morse model, we choose some model sys-tems and a real reaction as examples.
The anharmonic effect study of coupled Morse oscillators for the unimolecular reaction
2008-01-01
The importance of anharmonic effect in dissociation of molecular systems especially clusters has been noted. In this paper, we shall study the effect of coupled anharmonic oscillator of the standard bilinear form (SBF) Morse oscillator (MO) potential on unimolecular reaction. We shall use the systematic theoretical approach, YL method, proposed by Yao and Lin (YAO L, et. al. J Phys Chem A, 2007, 111(29): 6722-6729), which can evaluate anharmonic effects on the rate constants based on the transition state theory. In treating the anharmonic effect with the Morse oscillator potential on unimolecular reactions under collision-free conditions by using the RRKM (Rice-Ramsperger-Kassel-Marcus) theory, the in-verse Laplace transformation of the partition functions was used to obtain the total amount of state and density of state by using the first-order and the second-order approximations of the saddle-point method. To demonstrate the anharmonic effect of the SBF Morse model, we choose some model systems and a real reaction as examples.
The application of value distribution theory to a doubly anharmonic oscillator
Hu Juan [Department of Applied Mathematics, Zhejiang University of Technology, Hangzhou 310023 (China); Yu Guofu, E-mail: gfyu@sjtu.edu.cn [Department of Mathematics, Shanghai Jiao Tong University, Shanghai 200240 (China)
2011-07-22
The model of doubly anharmonic oscillators is first transformed into certain periodic second ordinary differential equations. A class of exact solutions for eigenfunctions and eigenvalues is obtained from Bank and Laine's theory on periodic ordinary differential equations, which is expressed in the form of the products of the polynomial and exponential functions when parameters satisfy some special relations.
Numerical experiment of anharmonic oscillators by using the symplectic scheme-shooting method
无
2002-01-01
Symplectic scheme-shooting method (SSSM) is applied to solve the energy eigenvalues of anharmonic oscillators characterized by the potentials V(x)=λx4 and V(x)=(1/2)x2+λx2α with α=2,3,4 and doubly anharmonic oscillators characterized by the potentials V(x)=(1/2)x2+λ1x4+λ2x6, and a high order symplectic scheme tailored to the "time"-dependent Hamiltonian function is presented. The numerical results illustrate that the energy eigenvalues of anharmonic oscillators with the symplectic scheme-shooting method are in good agreement with the numerical accurate ones obtained from the non-perturbative method by using an appropriately scaled basis for the expansion of each eigenfunction; and the energy eigenvalues of doubly anharmonic oscillators with the sympolectic scheme-shooting method are in good agreement with the exact ones and are better than the results obtained from the four-term asymptotic series. Therefore, the symplectic scheme-shooting method, which is very simple and is easy to grasp, is a good numerical algorithm.
Internal oscillation frequencies and anharmonic effects for the double sine-Gordon kink
Salerno, M.; Samuelsen, Mogens Rugholm
1989-01-01
A simple derivation of the small oscillation frequency around 4π-kink solutions of the double sine-Gordon equation is presented. Small corrections to these frequencies due to anharmonic effects are also numerically and analytically investigated. The analysis is based on energetic considerations...
Ulrich D. Jentschura
2009-01-01
Full Text Available The concept of a generalized nonanalytic expansion which involves nonanalytic combinations of exponentials, logarithms and powers of a coupling is introduced and its use illustrated in various areas of physics. Dispersion relations for the resonance energies of odd anharmonic oscillators are discussed, and higher-order formulas are presented for cubic and quartic potentials.
And Others; Gilmartin, Harvey
1979-01-01
Presented is a form of Hamilton's principle for classical mechanics appropriate to the study of arbitrary self-sustained vibrations in one dimension. It is applied as an approximate computational tool to the study of several examples of anharmonic oscillation. (Author/GA)
Unified Treatment of Screening Coulomb and Anharmonic Oscillator Potentials in Arbitrary Dimensions
Bülent G(o)nül; Okan (O)zer; Mehmet Ko(c)ak
2006-01-01
A mapping is obtained relating radial screened Coulomb systems with low screening parameters to radial anharmonic oscillators in N-dimensional space. Using the formalism of supersymmetric quantum mechanics, it is shown that exact solutions of these potentials exist when the parameters satisfy certain constraints.
Optomechanical self-oscillations in an anharmonic potential: engineering a nonclassical steady state
Grimm, Manuel; Bruder, Christoph; Lörch, Niels
2016-09-01
We study self-oscillations of an optomechanical system, where coherent mechanical oscillations are induced by a driven optical or microwave cavity, for the case of an anharmonic mechanical oscillator potential. A semiclassical analytical model is developed to characterize the limit cycle for large mechanical amplitudes corresponding to a weak nonlinearity. As a result, we predict conditions to achieve subpoissonian phonon statistics in the steady state, indicating classically forbidden behavior. We compare with numerical simulations and find very good agreement. Our model is quite general and can be applied to other physical systems such as trapped ions or superconducting circuits.
Energy levels of. lambda. x sup 2k anharmonic oscillators using the quantum normal form
Brajamani, S.; Mazumdar, P.S. (Manipur Univ., (India)); Chowdhury, S.K.; Sur, S. (Indian Association for the Cultivation of Science, West Bengal (India))
1991-04-01
In recent years there has been a large and important literature on the methods for studying a well-known class of single-well quantum anharmonic oscillators. These one-body Schroedinger problems have played a particularly important role in recent years as model bosonic field theories which contain only one mode. This mode is generated by the usual harmonic oscillator creation operator {alpha}. In this respect the anharmonic oscillators may be considered as the (0+1)-dimensional counterparts of more realistic quantum field theories in the physical world of (3+1)-dimensionality. The ground state and first few excited energy levels of the generalized anharmonic oscillator defined by the Hamiltonian H = {minus}d{sup 2}/dx{sup 2}+x{sup 2}+{lambda}x{sup 2k} (k = 3,4,{hor ellipsis}) have been calculated by employing the method of quantum normal form, which is the quantum mechanical analogue of the classical Birkhoff-Gustavson normal form. The present energy eigenvalues are consistent with other tabulations of the energy levels.
Özdemir, Semra Bayat; Demiralp, Metin [Computational Science and Engineering Department, Informatics Institute, Istanbul Technical University, Istanbul (Turkey)
2015-12-31
The determination of the energy states is highly studied issue in the quantum mechanics. Based on expectation values dynamics, energy states can be observed. But conditions and calculations vary depending on the created system. In this work, a symmetric exponential anharmonic oscillator is considered and development of a recursive approximation method is studied to find its ground energy state. The use of majorant values facilitates the approximate calculation of expectation values.
Perturbative analysis of the ground-state wavefunctions of the quantum anharmonic oscillators
Xie Qiongtao [Department of Physics and Key Laboratory of Low-Dimensional Quantum Structure and Quantum Control of Ministry of Education, Hunan Normal University, Changsha 410081 (China)], E-mail: xieqiongtao@yahoo.cn
2009-10-23
We investigate the perturbative expansions of the ground-state wavefunctions of the quantum anharmonic oscillators. With an appropriate change of spatial scale, the weak-coupling Schroedinger equation is transformed to an equivalent strong-coupling one. The Friedberg-Lee-Zhao method is applied to obtain the improved perturbative expansions. These perturbative expansions give a correction to the WKB results for large spatial distances, and reproduce the conventional weak-coupling results for small spatial distances.
Perturbative analysis of the ground-state wavefunctions of the quantum anharmonic oscillators
Xie, Qiong-Tao
2009-10-01
We investigate the perturbative expansions of the ground-state wavefunctions of the quantum anharmonic oscillators. With an appropriate change of spatial scale, the weak-coupling Schrödinger equation is transformed to an equivalent strong-coupling one. The Friedberg-Lee-Zhao method is applied to obtain the improved perturbative expansions. These perturbative expansions give a correction to the WKB results for large spatial distances, and reproduce the conventional weak-coupling results for small spatial distances.
An Expansion of the Free Energy of Anharmonic Oscillator Based on the Variational Result
Lu, W F; Bak, J; Kim, C K; Nahm, K; Lu, Wen-Fa; You, Sang Koo; Bak, Jino; Kim, Chul Koo; Nahm, Kyun
2002-01-01
Based on the variational result, we performed a Taylor series expansion of the free energy of an anharmonic oscillator within the functional integral formalism. The variationally extremized condition makes Cactus Feynman diagrams disappear from any higher-order diagrams, and accordingly Feynman diagrams are simplified. We obtained the analytical expression of the free energy up to the fourth order, and compared our results with exact, accurate and variational results.
Output radiation from a degenerate parametric oscillator
Tesfa, S
2007-01-01
We study the squeezing as well as the statistical properties of the output radiation from a degenerate parametric oscillator coupled to a squeezed vacuum reservoir employing the stochastic differential equations associated with the normal ordering. It is found that the degree of squeezing of the output radiation is less than the corresponding cavity radiation. However, for output radiation the correlation of the quadrature operators evaluated at different times also exhibits squeezing, which is the reason for quenching of the overall noise in one of the quadrature components of the squeezing spectrum even when the oscillator is coupled to a vacuum reservoir. Moreover, coupling the oscillator to the squeezed vacuum reservoir enhances the squeezing exponentially and it also increases the mean photon number.
Variational collocation for systems of coupled anharmonic oscillators
Amore, Paolo [Facultad de Ciencias, CUICBAS, Universidad de Colima, Bernal DIaz del Castillo 340, Colima (Mexico); Fernandez, Francisco M [INIFTA (UNLP, CCT La Plata-CONICET), Division Quimica Teorica, Diag. 113 y 64 (S/N), Sucursal 4, Casilla de Correo 16, 1900 La Plata (Argentina)
2010-04-15
By means of a collocation approach based on little sinc functions (LSF), we obtain accurate eigenvalues and eigenfunctions of the stationary Schroedinger equation for systems of coupled oscillators. Adjustable parameters introduced by means of scaling and rotation of the coordinates improve the rate of convergence of the approach. A careful comparison with the results published earlier by other authors shows the advantages of the present approach.
Degenerate parametric oscillation in quantum membrane optomechanics
Benito, Mónica; Sánchez Muñoz, Carlos; Navarrete-Benlloch, Carlos
2016-02-01
The promise of innovative applications has triggered the development of many modern technologies capable of exploiting quantum effects. But in addition to future applications, such quantum technologies have already provided us with the possibility of accessing quantum-mechanical scenarios that seemed unreachable just a few decades ago. With this spirit, in this work we show that modern optomechanical setups are mature enough to implement one of the most elusive models in the field of open system dynamics: degenerate parametric oscillation. Introduced in the eighties and motivated by its alleged implementability in nonlinear optical resonators, it rapidly became a paradigm for the study of dissipative phase transitions whose corresponding spontaneously broken symmetry is discrete. However, it was found that the intrinsic multimode nature of optical cavities makes it impossible to experimentally study the model all the way through its phase transition. In contrast, here we show that this long-awaited model can be implemented in the motion of a mechanical object dispersively coupled to the light contained in a cavity, when the latter is properly driven with multichromatic laser light. We focus on membranes as the mechanical element, showing that the main signatures of the degenerate parametric oscillation model can be studied in state-of-the-art setups, thus opening the possibility of analyzing spontaneous symmetry breaking and enhanced metrology in one of the cleanest dissipative phase transitions. In addition, the ideas put forward in this work would allow for the dissipative preparation of squeezed mechanical states.
Exact Solutions of the Klein-Gordon Equation with a New Anharmonic Oscillator Potential
ZHANG Min-Cang; WANG Zhen-Bang
2005-01-01
@@ We solve the Klein-Gordon equation with a new anharmonic oscillator potential and present the exact solutions.It is shown that under the condition of equal scalar and vector potentials, the Klein-Gordon equation could be separated into an angular equation and a radial equation. The angular solutions are the associated-Legendre polynomial and the radial solutions are expressed in terms of the confluent hypergeometric functions. Finally,the energy equation is obtained from the boundary condition satisfied by the radial wavefunctions.
Lokhov, Alexey V
2016-01-01
Data analysis of the next generation effective antineutrino mass measurement experiment KATRIN requires reliable knowledge of systematic corrections. In particular, the width of the daughter molecular ion excitation spectrum rovibrational band should be known with a better then 1% precision. Very precise ab initio quantum calculations exist, and we compare them with the well known tritium molecule parameters within the framework of a phenomenological model. The rovibrational band width with accuracy of a few percent is interpreted as a result of the zero-point atomic oscillation in the harmonic potential. The Morse interatomic potential is used to investigate the impact of anharmonic atomic oscillations. The calculated corrections cannot account for the difference between the ab initio quantum calculations and the phenomenological model.
Longitudinal, degenerate, and transversal parametric oscillation in a photorefractive media
Pedersen, H.C.; Johansen, P.M.
1996-01-01
We present a theoretical model of photorefractive parametric oscillation that covers, for the first time, to our knowledge, the occurrence of the whole spectrum of parametric processes from transversal over degenerate to longitudinal parametric oscillation. It is shown that inclusion of so......-called noneigenwaves is essential for completing the model. We report on the first experiment that shows the transition from transversal over degenerate to longitudinal parametric oscillation. The experimental observations agree well with the theoretical predictions....
Computer Simulation Study of Thermal Conduction in 1D Chains of Anharmonic Oscillators
Tejal N.Shah; P.N.Gajjar
2013-01-01
In this work thermal conduction in one-dimensional (1D) chains of anharmonic oscillators are studied using computer simulation.The temperature profile,heat flux and thermal conductivity are investigated for chain length N =100,200,400,800 and 1600.In the computer simulation anharmonicity is introduced due to Fermi-Pasta-Ulam-β (FPU-β) model For substrate interaction,an onsite potential due to Frenkel-Kontorova (FK) model has been used.Numerical simulations demonstrate that temperature gradient scales behave as N-1 linearly with the relation J =0.1765/N.For the thermal conductivity K,KN to N obey the linear relation of the type KN =0.8805N.It is shown that thermal transport is dependent on phonon-phonon interaction as well as phonon-lattice interaction.The thermal conductivity increaseslinearly with increase inanharmonicity and predicts relation κ =0.133 + 0.804β.It is also concluded that for higher value of the strength of the onsite potential system tends to a thermal insulator.
Generation of discrete superpositions of coherent states in the anharmonic oscillator model
Miranowicz, A; Kielich, S; 10.1088/0954-8998/2/3/006
2011-01-01
The problem of generating discrete superpositions of coherent states in the process of light propagation through a nonlinear Kerr medium, which is modelled by the anharmonic oscillator, is discussed. It is shown that under an appropriate choice of the length (time) of the medium the superpositions with both even and odd numbers of coherent states can appear. Analytical formulae for such superpositions with a few components are given explicitly. General rules governing the process of generating discrete superpositions of coherent states are also given. The maximum number of well distinguished states that can be obtained for a given number of initial photons is estimated. The quasiprobability distribution $Q(\\alpha,\\alpha^*,t)$ representing the superposition states is illustrated graphically, showing regular structures when the component states are well separated.
A quantum-mechanical anharmonic oscillator with a most interesting spectrum
Amore, Paolo; Fernández, Francisco M.
2017-10-01
We revisit the problem posed by an anharmonic oscillator with a potential given by a polynomial function of the coordinate of degree six that depends on a parameter λ. The ground state can be obtained exactly and its energy E0 = 1 is independent of λ. This solution is valid only for λ > 0 because the eigenfunction is not square integrable otherwise. Here we show that the perturbation series for the expectation values are Padé and Borel-Padé summable for λ > 0. When λ < 0 the spectrum exhibits an infinite number of avoided crossings at each of which the eigenfunctions undergo dramatic changes in their spatial distribution that we analyse by means of the expectation values 〈x2 〉 .
Anita Gupta; Pushpa M Rao
2008-03-01
A quadrupole ion trap consisting of electrode structures symmetric about -axis is an important tool for conducting several precision experiments. In practice the field inside the trap does not remain purely quadrupolar, and can be calculated using numerical methods. We have used boundary element method to calculate the potential inside the truncated as well as symmetrically misaligned quadrupolar ion trap. The calculated potential values are fitted to multipole expansion and the weights of multipole moments have been evaluated by minimizing the least square deviation. The higher-order multi-pole contribution in the fabricated hyperbolic electrodes due to truncation and machining imperfections is discussed. Non-linear effects arising due to the superposition of octupole moment manifest as anharmonic oscillations of trapped ions in the non-ideal Paul trap. Theoretical simulations of non-linear effects have been carried out.
Harmonic balance approach to the periodic solutions of the (an)harmonic relativistic oscillator
Belendez, Augusto [Departamento de Fisica, Ingenieria de Sistemas y Teoria de la Senal, Universidad de Alicante, Apartado 99, E-03080 Alicante (Spain)], E-mail: a.belendez@ua.es; Pascual, Carolina [Departamento de Fisica, Ingenieria de Sistemas y Teoria de la Senal, Universidad de Alicante, Apartado 99, E-03080 Alicante (Spain)
2007-11-19
The first-order harmonic balance method via the first Fourier coefficient is used to construct two approximate frequency-amplitude relations for the relativistic oscillator for which the nonlinearity (anharmonicity) is a relativistic effect due to the time line dilation along the world line. Making a change of variable, a new nonlinear differential equation is obtained and two procedures are used to approximately solve this differential equation. In the first the differential equation is rewritten in a form that does not contain a square-root expression, while in the second the differential equation is solved directly. The approximate frequency obtained using the second procedure is more accurate than the frequency obtained with the first due to the fact that, in the second procedure, application of the harmonic balance method produces an infinite set of harmonics, while in the first procedure only two harmonics are produced. Both approximate frequencies are valid for the complete range of oscillation amplitudes, and excellent agreement of the approximate frequencies with the exact one are demonstrated and discussed. The discrepancy between the first-order approximate frequency obtained by means of the second procedure and the exact frequency never exceeds 1.6%. We also obtained the approximate frequency by applying the second-order harmonic balance method and in this case the relative error is as low 0.31% for all the range of values of amplitude of oscillation A.
Isaacson, D.; Isaacson, E. L.; Paes-Leme, P. J.; Marchesin, D.
1981-01-01
Several methods for computing many eigenvalues and eigenfunctions of a single anharmonic oscillator Schroedinger operator whose potential may have one or two minima are described. One of the methods requires the solution of an ill-conditioned generalized eigenvalue problem. This method has the virtue of using a bounded amount of work to achieve a given accuracy in both the single and double well regions. Rigorous bounds are given, and it is proved that the approximations converge faster than any inverse power of the size of the matrices needed to compute them. The results of computations for the g:phi(4):1 theory are presented. These results indicate that the methods actually converge exponentially fast.
Quantum correlation in degenerate optical parametric oscillators with mutual injections
Takata, Kenta
2015-01-01
We theoretically and numerically study the quantum dynamics of two degenerate optical parametric oscillators with mutual injections. The cavity mode in the optical coupling path between the two oscillator facets is explicitly considered. Stochastic equations for the oscillators and mutual injection path based on the positive $P$ representation are derived. The system of two gradually pumped oscillators with out-of-phase mutual injections are simulated, and their quantum states are investigated. When the incoherent loss of the oscillators other than the mutual injections is small, the squeezed quadratic amplitudes $\\hat{p}$ in the oscillators are positively correlated near the oscillation threshold. It indicates finite quantum correlation, and the entanglement between the intracavity subharmonic fields. When with a small loss of the injection path, each oscillator around the phase transition point forms macroscopic superposition for a small pump noise. It suggests that the low-loss injection path works as a sq...
Low Starting Electron Beam Current in Degenerate Band Edge Oscillators
Othman, Mohamed A K; Figotin, Alexander; Capolino, Filippo
2016-01-01
We propose a new principle of operation in vacuum electron-beam-based oscillators that leads to a low beam current for starting oscillations. The principle is based on super synchronous operation of an electron beam interacting with four degenerate electromagnetic modes in a slow-wave structure (SWS). The four mode super synchronous regime is associated with a very special degeneracy condition in the dispersion diagram of a cold periodic SWS called degenerate band edge (DBE). This regime features a giant group delay in the finitelength SWS and low starting-oscillation beam current. The starting beam current is at least an order of magnitude smaller compared to a conventional backward wave oscillator (BWO) of the same length. As a representative example we consider a SWS conceived by a periodically-loaded metallic waveguide supporting a DBE, and investigate starting-oscillation conditions using Pierce theory generalized to coupled transmission lines (CTL). The proposed super synchronism regime can be straightf...
Schröder, Markus; Schreiber, Michael; Kleinekathöfer, Ulrich
2007-03-21
Several techniques to solve a hierarchical set of equations of motion for propagating a reduced density matrix coupled to a thermal bath have been developed in recent years. This is either done using the path integral technique as in the original proposal by Tanimura and Kubo [J. Phys. Soc. Jpn. 58, 101 (1998)] or by the use of stochastic fields as done by Yan et al. [Chem. Phys. Lett. 395, 216 (2004)]. Based on the latter ansatz a compact derivation of the hierarchy using a decomposition of the spectral density function is given in the present contribution. The method is applied to calculate the time evolution of the reduced density matrix describing the motion in a harmonic, an anharmonic, and two coupled oscillators where each system is coupled to a thermal bath. Calculations to several orders in the system-bath coupling with two different truncations of the hierarchy are performed. The respective density matrices are used to calculate the time evolution of various system properties and the results are compared and discussed with a special focus on the convergence with respect to the truncation scheme applied.
Bessis, N.; Bessis, G. [Laboratoire de Physique des Lasers, U.R.A. 282 du C.N.R.S., Universite Paris-Nord, avenue J. B. Clement, 93430 Villetaneuse (France)
1997-11-01
An algebraic procedure is proposed for the analytical solution of Schr{umlt o}dinger equations that can be viewed as a factorizable equation with an additional potential V(x). Once V(x) has been expanded in a series of suitable x-basis functions u=u(x), which are specific to each factorization type, the solution of the Riccati equation associated with the given equation is performed by means of an open perturbation technique, i.e., at each order of the perturbation, an additional balance u-dependent term is introduced so that the resulting equation becomes solvable. Since the unperturbed potential involves the whole given potential and since the balance term is expected to be small, improved results are expected at low orders of the perturbation, even at the zeroth order. The procedure, well adapted to the use of computer algebra, is applied to the solution of the gx{sup 4}-anharmonic oscillator equation: by means of very simple algebraic manipulations, the trend of the exact values of the energies is rather well reproduced for a large range of values of the coupling constant (g=0.002 to g=20000). {copyright} {ital 1997 American Institute of Physics.}
Bervillier, C [Laboratoire de Mathematiques et Physique Theorique, UMR 6083 (CNRS), Federation Denis Poisson, Universite Francois Rabelais, Parc de Grandmont, 37200 Tours (France)], E-mail: claude.bervillier@lmpt.univ-tours.fr
2009-12-04
The simplicity and the efficiency of a quasi-analytical method for solving nonlinear ordinary differential equations (ODE) is illustrated on the study of anharmonic oscillators (AO) with a potential V(x) = {beta}x{sup 2} + x{sup 2m} (m > 0). The method (Bervillier 2008 Nucl. Phys. B801 296) applies a priori to any ODE with two-point boundaries (one being located at infinity), the solution of which has (fixed) singularities in the complex plane of the independent variable x. A conformal mapping of a suitably chosen angular sector of the complex plane of x upon the unit disc centered at the origin makes convergent the transformed Taylor series of the generic solution so that the boundary condition at infinity can be easily imposed. In principle, this constraint, when applied on the logarithmic derivative of the wavefunction, determines the eigenvalues to an arbitrary level of accuracy. In practice, for {beta} {>=} 0 or slightly negative, the accuracy of the results obtained is astonishingly large with regard to the modest computing power used. Various aspects of the method and comparisons with some seemingly similar methods, based also on expressing the solution as a Taylor series, are shortly reviewed, presented and discussed.
A Coherent Ising Machine Based On Degenerate Optical Parametric Oscillators
Wang, Zhe; Marandi, Alireza; Wen, Kai; Byer, Robert L.; Yamamoto, Yoshihisa
2014-03-01
A degenerate optical parametric oscillator network is proposed to solve the NP-hard problem of finding a ground state of the Ising model. The underlying operating mechanism originates from the bistable output phase of each oscillator and the inherent preference of the network in selecting oscillation modes with the minimum photon decay rate. Computational experiments are performed on all instances reducible to the NP-hard MAX-CUT problems on cubic graphs of order up to 20. The numerical results reasonably suggest the effectiveness of the proposed network. This project is supported by the FIRST program of Japanese Government. Zhe Wang is also grateful for the support from Stanford Graduate Fellowship.
Dzhioev, Alan [Bogoliubov Laboratory of Theoretical Physics, Joint Institute for Nuclear Research, Dubna 141980 (Russian Federation)]. E-mail: dzhioev@thsun1.jinr.ru; Wambach, J. [Institut fuer Kernphysik, Technische Universitaet Darmstadt, D-64289 Darmstadt (Germany); Gesellschaft fuer Schwerionenforschung, D-64291 Darmstadt (Germany)]. E-mail: wambach@physik.tu-darmstadt.de; Vdovin, A. [Bogoliubov Laboratory of Theoretical Physics, Joint Institute for Nuclear Research, Dubna 141980 (Russian Federation)]. E-mail: vdovin@thsun1.jinr.ru; Aouissat, Z. [Institut fuer Kernphysik, Technische Universitaet Darmstadt, D-64289 Darmstadt (Germany)
2005-02-21
Symmetry conserving 1/N expansion method combined with the Holstein-Primakoff mapping for bosonic systems is applied to the quantum anharmonic O(N+1) oscillator model which imitates essential features of the quantum-field linear sigma model. The Holstein-Primakoff mapping earlier extended to incorporate both single- and double-boson images is used. In the leading and next-to-leading order the existence of N-Goldstone modes and the validity of the Ward identity are proved. For matrix elements of the pion-pion interaction we show the equivalence of the results obtained via a diagrammatic technique and the extended Holstein-Primakoff mapping.
Bohá\\{v}cik, J; August\\'\\{i}n, P
2013-01-01
We find the possibility of the non-perturbative an-harmonic correction to Mehler's formula for propagator of the harmonic oscillator. We evaluate the conditional Wiener measure functional integral with a term of the fourth order in the exponent by an alternative method as in the conventional perturbative approach. In contrast to the conventional perturbation theory, we expand into power series the term linear in the integration variable in the exponent. We discuss the case, when the starting point of the propagator is zero. We present the results in analytical form for positive and negative frequency.
PANAHI H; GAVABAR M MOHAMMADKAZEMI
2016-05-01
The quasiexactly solvable potential method is used to determine the energies and the corresponding exact eigenfunctions for a system of N particles with equal mass interacting via an anharmonic potential. For systems with five and seven particles, we compute the ground state and the first excited state only, and compare the spectrums with the results obtained by Ritz approximation method.
N. Al Sdran
2016-06-01
Full Text Available The numerical solutions of the time independent Schrödinger equation of different one-dimensional potentials forms are sometime achieved by the asymptotic iteration method. Its importance appears, for example, on its efficiency to describe vibrational system in quantum mechanics. In this paper, the Airy function approach and the Numerov method have been used and presented to study the oscillator anharmonic potential V(x = Ax2α + Bx2, (A>0, B<0, with (α = 2 for quadratic, (α =3 for sextic and (α =4 for octic anharmonic oscillators. The Airy function approach is based on the replacement of the real potential V(x by a piecewise-linear potential v(x, while, the Numerov method is based on the discretization of the wave function on the x-axis. The first energies levels have been calculated and the wave functions for the sextic system have been evaluated. These specific values are unlimited by the magnitude of A, B and α. It’s found that the obtained results are in good agreement with the previous results obtained by the asymptotic iteration method for α =3.
Muhammad Ashfaq Ahmad; Lin Jie; Qian Yan; Ma Zhi-Min; Ma Ai-Qun; Liu Shu-Tian
2007-01-01
This paper discusses the properties of amplitude-squared squeezing of the generalized odd-even coherent states of anharmonic oscillator in finite-dimensional Hilbert space. It demonstrates that the generalized odd coherent states do exhibit strong amplitude-squared squeezing effects in comparison with the generalized even coherent states.
Al Sdran, N.; Maiz, F.
2016-06-01
The numerical solutions of the time independent Schrödinger equation of different one-dimensional potentials forms are sometime achieved by the asymptotic iteration method. Its importance appears, for example, on its efficiency to describe vibrational system in quantum mechanics. In this paper, the Airy function approach and the Numerov method have been used and presented to study the oscillator anharmonic potential V(x) = Ax2α + Bx2, (A>0, Bdiscretization of the wave function on the x-axis. The first energies levels have been calculated and the wave functions for the sextic system have been evaluated. These specific values are unlimited by the magnitude of A, B and α. It's found that the obtained results are in good agreement with the previous results obtained by the asymptotic iteration method for α =3.
Thermalization of oscillator chains with onsite anharmonicity and comparison with kinetic theory.
Mendl, Christian B; Lu, Jianfeng; Lukkarinen, Jani
2016-12-01
We perform microscopic molecular dynamics simulations of particle chains with an onsite anharmonicity to study relaxation of spatially homogeneous states to equilibrium, and directly compare the simulations with the corresponding Boltzmann-Peierls kinetic theory. The Wigner function serves as a common interface between the microscopic and kinetic level. We demonstrate quantitative agreement after an initial transient time interval. In particular, besides energy conservation, we observe the additional quasiconservation of the phonon density, defined via an ensemble average of the related microscopic field variables and exactly conserved by the kinetic equations. On superkinetic time scales, density quasiconservation is lost while energy remains conserved, and we find evidence for eventual relaxation of the density to its canonical ensemble value. However, the precise mechanism remains unknown and is not captured by the Boltzmann-Peierls equations.
Thermalization of oscillator chains with onsite anharmonicity and comparison with kinetic theory
Mendl, Christian B.; Lu, Jianfeng; Lukkarinen, Jani
2016-12-01
We perform microscopic molecular dynamics simulations of particle chains with an onsite anharmonicity to study relaxation of spatially homogeneous states to equilibrium, and directly compare the simulations with the corresponding Boltzmann-Peierls kinetic theory. The Wigner function serves as a common interface between the microscopic and kinetic level. We demonstrate quantitative agreement after an initial transient time interval. In particular, besides energy conservation, we observe the additional quasiconservation of the phonon density, defined via an ensemble average of the related microscopic field variables and exactly conserved by the kinetic equations. On superkinetic time scales, density quasiconservation is lost while energy remains conserved, and we find evidence for eventual relaxation of the density to its canonical ensemble value. However, the precise mechanism remains unknown and is not captured by the Boltzmann-Peierls equations.
Anharmonic Oscillations of a Spring-Magnet System inside a Magnetic Coil
Ladera, Celso L.; Donoso, Guillermo
2012-01-01
We consider the nonlinear oscillations of a simple spring-magnet system that oscillates in the magnetic field of an inductive coil excited with a dc current. Using the relations for the interaction of a coil and a magnet we obtain the motion equation of the system. The relative strengths of the terms of this equation can be adjusted easily by…
Rey-Bellet, Luc; Thomas, Lawrence E.
We consider a model of heat conduction introduced in [6], which consists of a finite nonlinear chain coupled to two heat reservoirs at different temperatures. We study the low temperature asymptotic behavior of the invariant measure. We show that, in this limit, the invariant measure is characterized by a variational principle. The main technical ingredients are some control theoretic arguments to extend the Freidlin-Wentzell theory of large deviations to a class of degenerate diffusions.
Xiong, Daxing
2016-04-01
Previous studies have suggested a crossover from superdiffusive to normal heat transport in one-dimensional (1D) anharmonic oscillator systems with a double-well type interatomic interaction like V(ξ )=-{ξ2}/2+{ξ4}/4 , when the system temperature is varied. In order to better understand this unusual manner of thermal transport, here we perform a direct dynamics simulation to examine how the spreading processes of the three physical quantities, i.e. the heat, the total energy and the momentum, would depend on temperature. We find three main points that are worth noting. (i) The crossover from superdiffusive to normal heat transport is well verified from a new perspective of heat spread. (ii) The spreading of the total energy is found to be very distinct from heat diffusion, especially under some temperature regimes, energy is strongly localized, while heat can be superdiffusive. So one should take care to derive a general connection between the heat conduction and energy diffusion. (iii) In a narrow range of temperatures, the spreading of momentum implies clear unusual non-ballistic behaviors; however, such unusual transport of momentum cannot be directly related to the normal transport of heat. An analysis of phonon spectra suggests that one should also take the effects of phonon softening into account. All of these results may provide insights into establishing the connection between the macroscopic heat transport and the underlying dynamics in 1D systems.
Exact solutions of Feinberg–Horodecki equation for time-dependent anharmonic oscillator
P K Bera; Tapas Sil
2013-01-01
In this work, an alternative treatment known as Nikiforov–Uvarov (NU) method is proposed to find the exact solutions of the Feinberg–Horodecki equation for the time-dependent potentials. The present procedure is illustrated with two examples: (1) time-dependent Wei Hua oscillator, (2) time-dependent Manning–Rosen potential.
Pupasov-Maksimov, Andrey M.
2015-12-01
It is shown that fundamental solutions Kσ(x , y ; t) = of the non-stationary Schrödinger equation (Green functions, or propagators) for the rational extensions of the Harmonic oscillator Hσ =Hosc + ΔVσ are expressed in terms of elementary functions only. An algorithm to calculate explicitly Kσ for an arbitrary increasing sequence of positive integers σ is given, and compact expressions for K { 1 , 2 } and K { 2 , 3 } are presented. A generalization of Mehler's formula to the case of exceptional Hermite polynomials is given.
Anharmonic resonances with recursive delay feedback
Goldobin, Denis S., E-mail: Denis.Goldobin@gmail.com [Department of Mathematics, University of Leicester, Leicester LE1 7RH (United Kingdom); Institute of Continuous Media Mechanics, UB RAS, Perm 614013 (Russian Federation)
2011-09-12
We consider application of time-delayed feedback with infinite recursion for control of anharmonic (nonlinear) oscillators subject to noise. In contrast to the case of a single delay feedback, recursive delay feedback exhibits resonances between feedback and nonlinear harmonics, leading to a resonantly strong or weak oscillation coherence even for a small anharmonicity. Remarkably, these small-anharmonicity induced resonances can be stronger than the harmonic ones. Analytical results are confirmed numerically for van der Pol and van der Pol-Duffing oscillators. -- Highlights: → We construct general theory of noisy limit-cycle oscillators with linear feedback. → We focus on coherence and 'reliability' of oscillators. → For recursive delay feedback control the theory shows importance of anharmonicity. → Anharmonic resonances are studied both numerically and analytically.
laser development ; time dependent solutions of the master kinetic equations; electric discharge stabilization in a supersonic CO/N2 flow; and computations of vibrational pumping rates by electrons including super-elastic collisions. A description of the progress made in each of these areas is
Al Sdran, N. [King Khalid University, Faculty of Science, Physics Department P.O. Box 9004 Abha (Saudi Arabia); Najran University, Faculty of Sciences and Arts, Najran (Saudi Arabia); Maiz, F., E-mail: fethimaiz@gmail.com [King Khalid University, Faculty of Science, Physics Department P.O. Box 9004 Abha (Saudi Arabia); Thermal Process Laboratory Research and Technologies Centre of Energy, BP 95, 2050 Hammam-lif (Tunisia)
2016-06-15
The numerical solutions of the time independent Schrödinger equation of different one-dimensional potentials forms are sometime achieved by the asymptotic iteration method. Its importance appears, for example, on its efficiency to describe vibrational system in quantum mechanics. In this paper, the Airy function approach and the Numerov method have been used and presented to study the oscillator anharmonic potential V(x) = Ax{sup 2α} + Bx{sup 2}, (A>0, B<0), with (α = 2) for quadratic, (α =3) for sextic and (α =4) for octic anharmonic oscillators. The Airy function approach is based on the replacement of the real potential V(x) by a piecewise-linear potential v(x), while, the Numerov method is based on the discretization of the wave function on the x-axis. The first energies levels have been calculated and the wave functions for the sextic system have been evaluated. These specific values are unlimited by the magnitude of A, B and α. It’s found that the obtained results are in good agreement with the previous results obtained by the asymptotic iteration method for α =3.
Shubnikov-de Haas Oscillations in a Degenerate Semiconductor.
Mansfield, R.
1978-01-01
Describes an experiment, in solid-state physics, for measuring the Shubnikov-de Haas oscillations in indium antimonide. It also provides an introduction to low-temperature techniques and to cryomagnetic systems. (Author/GA)
Dual-pumped degenerate Kerr oscillator in a silicon nitride microresonator
Okawachi, Yoshitomo; Luke, Kevin; Carvalho, Daniel O; Ramelow, Sven; Farsi, Alessandro; Lipson, Michal; Gaeta, Alexander L
2015-01-01
We demonstrate a degenerate parametric oscillator in a silicon-nitride microresonator. We use two frequency-detuned pump waves to perform parametric four-wave mixing and operate in the normal group-velocity dispersion regime to produce signal and idler fields that are frequency degenerate. Our theoretical modeling shows that this regime enables generation of bimodal phase states, analogous to the \\c{hi}(2)-based degenerate OPO. Our system offers potential for realization of CMOS-chip-based coherent optical computing and an all-optical quantum random number generator.
Meng Xiang-Guo; Wang Ji-Suo; Liang Bao-Long
2013-01-01
Using thermal entangled state representation,we solve the master equation of a diffusive anharmonic oscillator (AHO) to obtain the exact time evolution formula for the density operator in the infinitive operator-sum representation.We present a new evolution formula of the Wigner function (WF) for any initial state of the diffusive AHO by converting the WF calculation into an overlap between two pure states in an enlarged Fock space.It is found that this formula is very convenient in investigating the WF's evolution of any known initial state.As applications,this formula is used to obtain the evolution of the WF for a coherent state and the evolution of the photon-number distribution of diffusive AHOs.
Fast cortical oscillation after thalamic degeneration: pivotal role of NMDA receptor.
Kyuhou, Shin-ichi; Gemba, Hisae
2007-04-27
We examined electrophysiological and molecular changes of the thalamocortical system after thalamic degeneration in Purkinje cell degeneration (pcd) mice. In pcd mice, neurons in specific thalamic nuclei including the ventral medial geniculate nucleus began to degenerate around postnatal day 50, whereas the visual thalamic nucleus and nonspecific thalamic nuclei remained almost intact. In association with the morphological changes, auditory evoked potentials in the primary auditory cortex (AC) began to decrease gradually. Fast Fourier transform analysis of spontaneous cortical field potentials revealed that fast oscillation (FO) around 25 Hz occurred in the AC but not in the visual cortex. Quantitative mRNA analysis demonstrated that expression of the N-methyl-D-aspartate (NMDA) receptor was up-regulated in the AC but not in the visual cortex. Systemic administration of an NMDA antagonist abolished the FO in the AC. These results indicate that increased NMDA activity may cause the FO in the AC of pcd mice.
Yoshitaka Haribara
2016-04-01
Full Text Available We present the operational principle of a coherent Ising machine (CIM based on a degenerate optical parametric oscillator (DOPO network. A quantum theory of CIM is formulated, and the computational ability of CIM is evaluated by numerical simulation based on c-number stochastic differential equations. We also discuss the advanced CIM with quantum measurement-feedback control and various problems which can be solved by CIM.
Kraft, Manuel; Hein, Sven M.; Lehnert, Judith; Schöll, Eckehard; Hughes, Stephen; Knorr, Andreas
2016-08-01
Quantum coherent feedback control is a measurement-free control method fully preserving quantum coherence. In this paper we show how time-delayed quantum coherent feedback can be used to control the degree of squeezing in the output field of a cavity containing a degenerate parametric oscillator. We focus on the specific situation of Pyragas-type feedback control where time-delayed signals are fed back directly into the quantum system. Our results show how time-delayed feedback can enhance or decrease the degree of squeezing as a function of time delay and feedback strength.
Feng Xiu-Qin; Shen Ke
2005-01-01
We have investigated chaotic synchronization in the generalized sense for the degenerate optical parametric oscillator (DOPO). The numerical results show that two unidirectional coupling DOPOs in chaos can be completely phase synchronization or anti-phase synchronization with a suitable coupling coefficient under which the maximum condition Lyapunov exponent (MCLE) is negative. Phase synchronization and anti-phase synchronization of chaos can be realized through positive and negative coupling. On the other hand, the different synchronization states depend on the coupling types used in the DOPO systems.
Bunkin, S.B.; Islamov, R.S.; Konev, Y.B.; Kochetov, I.V.
1982-07-01
A technique is described for numerical analysis of kinetic processes in a system of anharmonic oscillators, based on using implicit numerical integration and replacement of derivatives by means of backward differentiation expressions. A comparison is made with calculations by the Runge--Kutta method, and it is shown that the computer time is reduced by a factor of more than 10 when the backward differentiation method is used. The influence of the natural isotopic composition of carbon monoxide molecules on the gain and lasing properties is investigated and shown to be only slight.
Large-scale Ising spin network based on degenerate optical parametric oscillators
Inagaki, Takahiro; Hamerly, Ryan; Inoue, Kyo; Yamamoto, Yoshihisa; Takesue, Hiroki
2016-01-01
Simulating a network of Ising spins with physical systems is now emerging as a promising approach for solving mathematically intractable problems. Here we report a large-scale network of artificial spins based on degenerate optical parametric oscillators (DOPO), paving the way towards a photonic Ising machine capable of solving difficult combinatorial optimization problems. We generated >10,000 time-division-multiplexed DOPOs using dual-pump four-wave mixing (FWM) in a highly nonlinear fibre (HNLF) placed in a fibre cavity. Using those DOPOs, a one-dimensional (1D) Ising model was simulated by introducing nearest-neighbour optical coupling. We observed the formation of spin domains and found that the domain size diverged near the DOPO threshold, which suggests that the DOPO network can simulate the behavior of low-temperature Ising spins.
Degenerate optomechanical parametric oscillators: cooling in the vicinity of a critical point
Degenfeld-Schonburg, Peter; Hartmann, Michael J; Navarrete-Benlloch, Carlos
2015-01-01
Degenerate optomechanical parametric oscillators are optical resonators in which a mechanical degree of freedom is coupled to a cavity mode that is nonlinearly amplified via parametric down-conversion of an external pumping laser. Below a critical pumping power the down-converted field is purely quantum-mechanical, making the theoretical description of such systems very challenging. Here we introduce a theoretical approach that is capable of describing this regime, even at the critical point itself. We find that the down-converted field can induce significant mechanical cooling and identify the process responsible of this as a "cooling by heating" mechanism. Moreover, we show that, contrary to naive expectations and semi-classical predictions, cooling is not optimal at the critical point, where the photon number is largest. Our approach opens the possibility for analyzing further hybrid dissipative quantum systems in the vicinity of critical points.
Breathers in strongly anharmonic lattices.
Rosenau, Philip; Pikovsky, Arkady
2014-02-01
We present and study a family of finite amplitude breathers on a genuinely anharmonic Klein-Gordon lattice embedded in a nonlinear site potential. The direct numerical simulations are supported by a quasilinear Schrodinger equation (QLS) derived by averaging out the fast oscillations assuming small, albeit finite, amplitude vibrations. The genuinely anharmonic interlattice forces induce breathers which are strongly localized with tails evanescing at a doubly exponential rate and are either close to a continuum, with discrete effects being suppressed, or close to an anticontinuum state, with discrete effects being enhanced. Whereas the D-QLS breathers appear to be always stable, in general there is a stability threshold which improves with spareness of the lattice.
Large-scale Ising spin network based on degenerate optical parametric oscillators
Inagaki, Takahiro; Inaba, Kensuke; Hamerly, Ryan; Inoue, Kyo; Yamamoto, Yoshihisa; Takesue, Hiroki
2016-06-01
Solving combinatorial optimization problems is becoming increasingly important in modern society, where the analysis and optimization of unprecedentedly complex systems are required. Many such problems can be mapped onto the ground-state-search problem of the Ising Hamiltonian, and simulating the Ising spins with physical systems is now emerging as a promising approach for tackling such problems. Here, we report a large-scale network of artificial spins based on degenerate optical parametric oscillators (DOPOs), paving the way towards a photonic Ising machine capable of solving difficult combinatorial optimization problems. We generate >10,000 time-division-multiplexed DOPOs using dual-pump four-wave mixing in a highly nonlinear fibre placed in a cavity. Using those DOPOs, a one-dimensional Ising model is simulated by introducing nearest-neighbour optical coupling. We observe the formation of spin domains and find that the domain size diverges near the DOPO threshold, which suggests that the DOPO network can simulate the behaviour of low-temperature Ising spins.
S Verma; C Mishra; V Kumar; M Yadav; K C Bahuguna; N S Vasan; S P Gaba
2014-02-01
This paper presents the experimental results of degenerate optical parametric generation using a high gray track resistant potassium titanyl phosphate (HGTR KTP) optical parametric oscillator (OPO). An average output power of 7 W at 10 kHz has been achieved that includes both signal and idler powers near degeneracy using 20Waverage power from a 1064 nm Nd:YVO4 pump source corresponding to an optical conversion efficiency of 35%.
Anharmonic quantum contribution to vibrational dephasing
Barik, Debashis; Ray, Deb Shankar
2004-01-01
Based on a quantum Langevin equation and its corresponding Hamiltonian within a c-number formalism we calculate the vibrational dephasing rate of a cubic oscillator. It is shown that leading order quantum correction due to anharmonicity of the potential makes a significant contribution to the rate and the frequency shift. We compare our theoretical estimates with those obtained from experiments for small diatomics $N_2$, $O_2$ and $CO$.
Enhanced Anharmonicity Under Pressure
Errea, Ion; Rousseau, Bruno; Bergara, Aitor
2012-07-01
Contradicting common sense, pressure does not monotonically harden the phonons in many systems but makes some specific modes soften at given points of the first Brilloiun zone, even inducing dynamical instabilities that drive structural phase transitions. As the harmonic part of the ionic potential becomes smaller, higher order terms turn out to be more and more important. In AlH3, for instance, anharmonicity suppresses the predicted high superconducting transition temperature at 110 GPa in agreement with experiments. Furthermore, anharmonicity stabilizes the high-pressure simple cubic phase of calcium even at zero temperature, explaining its mechanical stability. We will review the calculations performed in these two systems and show that anharmonicity can be tackled making use of perturbation theory or the so called self-consistent harmonic approximation.
Fermi-Decay Law of Bose-Einstein Condensate Trapped in an Anharmonic Potential
LIU Yuan; JIA Ya-Fei; LI Wei-Dong
2012-01-01
The Fermi-decay law of Bose-Einstein condensate, which is trapped by a cigar-shaped anharmonic trap and subjected to a weak random perturbation, is investigated by numerically calculating quantum fidelity (Loschmidt echo), to reveal the coherence loss of the condensate. We find that there are three indispensable factors, anharmonic trap, weak random perturbation and nonlinear interaction, in charging of the Fermi-decay law. The anharmonic trap creates anharmonic oscillations, and the weak random perturbation causes coherence loss by disturbing their coherent oscillations, while the nonlinear interaction enhances the loss to the Fermi-decay law. Based on the Fermi-decay law, some suggestions are presented to prolong the coherent time during coherently manipulating condensates.%The Fermi-decay law of Bose Einstein condensate,which is trapped by a cigar-shaped anharmonic trap and subjected to a weak random perturbation,is investigated by numerically calculating quantum fidelity (Loschmidt echo),to reveal the coherence loss of the condensate.We find that there are three indispensable factors,anharmonic trap,weak random perturbation and nonlinear interaction,in charging of the Fermi-decay law.The anharmonic trap creates anharmonic oscillations,and the weak random perturbation causes coherence loss by disturbing their coherent oscillations,while the nonlinear interaction enhances the loss to the Fermi-decay law.Based on the Fermi-decay law,some suggestions are presented to prolong the coherent time during coherently manipulating condensates.
Takesue, Hiroki; Inagaki, Takahiro
2016-09-15
A coherent Ising machine based on degenerate optical parametric oscillators (DOPOs) is drawing attention as a way to find a solution to the ground-state search problem of the Ising model. Here we report the generation of time-multiplexed DOPOs at a 10 GHz clock frequency. We successfully generated >50,000 DOPOs using dual-pump four-wave mixing in a highly nonlinear fiber that formed a 1 km cavity, and observed phase bifurcation of the DOPOs, which suggests that the DOPOs can be used as stable artificial spins. In addition, we demonstrated the generation of more than 1 million DOPOs by extending the cavity length to 21 km. We also confirmed that the binary numbers obtained from the DOPO phase-difference measurement passed the NIST random number test, which suggests that we can obtain unbiased artificial spins.
Cheng, Huihui; Luo, Zhengqian; Ye, Chenchun; Huang, Yizhong; Liu, Chun; Cai, Zhiping
2013-01-20
Mid-infrared fiber optical parametric oscillators (MIR FOPOs) based on the degenerate four-wave mixing (DFWM) of tellurite photonic crystal fibers (PCFs) are proposed and modeled for the first time. Using the DFWM coupled-wave equations, numerical simulations are performed to analyze the effects of tellurite PCFs, single-resonant cavity, and pump source on the MIR FOPO performances. The numerical results show that: (1) although a longer tellurite PCF can decrease the pump threshold of MIR FOPOs to a few watts only, the high conversion-efficiency of MIR idler usually requires a short-length optimum PCF with low loss; (2) compared with the single-pass DFWM configurations of the MIR fiber sources published previously, the stable oscillation of signal light in single-resonant cavity can significantly promote the MIR idler output efficiency. With a suggested tellurite PCF as parametric gain medium, the theoretical prediction indicates that such a MIR FOPO could obtain a wide MIR-tunable range and a high conversion efficiency of more than 10%.
Proudfoot, Malcolm; Rohenkohl, Gustavo; Quinn, Andrew; Colclough, Giles L.; Wuu, Joanne; Talbot, Kevin; Woolrich, Mark W.; Benatar, Michael
2016-01-01
Abstract Continuous rhythmic neuronal oscillations underpin local and regional cortical communication. The impact of the motor system neurodegenerative syndrome amyotrophic lateral sclerosis (ALS) on the neuronal oscillations subserving movement might therefore serve as a sensitive marker of disease activity. Movement preparation and execution are consistently associated with modulations to neuronal oscillation beta (15–30 Hz) power. Cortical beta‐band oscillations were measured using magnetoencephalography (MEG) during preparation for, execution, and completion of a visually cued, lateralized motor task that included movement inhibition trials. Eleven “classical” ALS patients, 9 with the primary lateral sclerosis (PLS) phenotype, and 12 asymptomatic carriers of ALS‐associated gene mutations were compared with age‐similar healthy control groups. Augmented beta desynchronization was observed in both contra‐ and ipsilateral motor cortices of ALS patients during motor preparation. Movement execution coincided with excess beta desynchronization in asymptomatic mutation carriers. Movement completion was followed by a slowed rebound of beta power in all symptomatic patients, further reflected in delayed hemispheric lateralization for beta rebound in the PLS group. This may correspond to the particular involvement of interhemispheric fibers of the corpus callosum previously demonstrated in diffusion tensor imaging studies. We conclude that the ALS spectrum is characterized by intensified cortical beta desynchronization followed by delayed rebound, concordant with a broader concept of cortical hyperexcitability, possibly through loss of inhibitory interneuronal influences. MEG may potentially detect cortical dysfunction prior to the development of overt symptoms, and thus be able to contribute to the assessment of future neuroprotective strategies. Hum Brain Mapp 38:237–254, 2017. © 2016 Wiley Periodicals, Inc. PMID:27623516
David J Margolis
Full Text Available Following photoreceptor degeneration, ON and OFF retinal ganglion cells (RGCs in the rd-1/rd-1 mouse receive rhythmic synaptic input that elicits bursts of action potentials at ∼ 10 Hz. To characterize the properties of this activity, RGCs were targeted for paired recording and morphological classification as either ON alpha, OFF alpha or non-alpha RGCs using two-photon imaging. Identified cell types exhibited rhythmic spike activity. Cross-correlation of spike trains recorded simultaneously from pairs of RGCs revealed that activity was correlated more strongly between alpha RGCs than between alpha and non-alpha cell pairs. Bursts of action potentials in alpha RGC pairs of the same type, i.e. two ON or two OFF cells, were in phase, while bursts in dissimilar alpha cell types, i.e. an ON and an OFF RGC, were 180 degrees out of phase. This result is consistent with RGC activity being driven by an input that provides correlated excitation to ON cells and inhibition to OFF cells. A2 amacrine cells were investigated as a candidate cellular mechanism and found to display 10 Hz oscillations in membrane voltage and current that persisted in the presence of antagonists of fast synaptic transmission and were eliminated by tetrodotoxin. Results support the conclusion that the rhythmic RGC activity originates in a presynaptic network of electrically coupled cells including A2s via a Na(+-channel dependent mechanism. Network activity drives out of phase oscillations in ON and OFF cone bipolar cells, entraining similar frequency fluctuations in RGC spike activity over an area of retina that migrates with changes in the spatial locus of the cellular oscillator.
Anharmonic vibrations in nuclei
Fallot, M; Andrés, M V; Catara, F; Lanza, E G; Scarpaci, J A; Chomaz, Ph.
2003-01-01
In this letter, we show that the non-linearitites of large amplitude motions in atomic nuclei induce giant quadrupole and monopole vibrations. As a consequence, the main source of anharmonicity is the coupling with configurations including one of these two giant resonances on top of any state. Two-phonon energies are often lowered by one or two MeV because of the large matrix elements with such three phonon configurations. These effects are studied in two nuclei, 40Ca and 208Pb.
A quantum parametric oscillator with trapped ions
Ding, Shiqian; Hablutzel, Roland; Loh, Huanqian; Matsukevich, Dzmitry
2015-01-01
A system of harmonic oscillators coupled via nonlinear interaction is a fundamental model in many branches of physics, from biophysics to electronics and condensed matter physics. In quantum optics, weak nonlinear interaction between light modes has enabled, for example, the preparation of squeezed states of light and generation of entangled photon pairs. While strong nonlinear interaction between the modes has been realized in circuit QED systems, achieving significant interaction strength on the level of single quanta in other physical systems remains a challenge. Here we experimentally demonstrate such interaction that is equivalent to photon up- and down-conversion using normal modes of motion in a system of two Yb ions. The nonlinearity is induced by the intrinsic anharmonicity of the Coulomb interaction between the ions and can be used to simulate fully quantum operation of a degenerate optical parametric oscillator. We exploit this interaction to directly measure the parity and Wigner functions of ion ...
Friedman, Hava Meira; Agarwalla, Bijay Kumar; Segal, Dvira
2017-03-01
We study inelastic vibration-assisted charge transfer effects in two-site molecular junctions, focusing on signatures of vibrational anharmonicity on the electrical characteristics and the thermoelectric response of the junction. We consider three types of oscillators: harmonic, anharmonic-Morse allowing bond dissociation, and harmonic-quartic, mimicking a confinement potential. Using a quantum master equation method which is perturbative in the electron-vibration interaction, we find that the (inelastic) electrical and thermal conductances can be largely affected by the nature of the vibrational potential. In contrast, the Seebeck coefficient, the thermoelectric figure-of-merit, and the thermoelectric efficiency beyond linear response conceal this information, showing a rather weak sensitivity to vibrational anharmonicity. Our work illustrates that anharmonic (many-body) effects, consequential to the current-voltage characteristics, are of little effect for the thermoelectric performance in the present model.
First-principles theories for anharmonic lattice vibrations.
Hirata, So; Keçeli, Murat; Yagi, Kiyoshi
2010-07-21
Size-extensive generalizations of the vibrational self-consistent field (VSCF), vibrational Moller-Plesset perturbation (VMP), and vibrational coupled-cluster (VCC) methods are made to anharmonic lattice vibrations of extended periodic systems on the basis of a quartic force field (QFF) in delocalized normal coordinates. Copious terms in the formalisms of VSCF that have nonphysical size dependence are identified algebraically and eliminated, leading to compact and strictly size-extensive equations. This "quartic" VSCF method (qVSCF) thus defined has no contributions from cubic force constants and alters only the transition energies of the underlying harmonic-oscillator reference from a subset of quartic force constants. It also provides a way to evaluate an anharmonic correction to the lattice structure due to cubic force constants of a certain type. The second-order VMP and VCC methods in the QFF based on the qVSCF reference are shown to account for anharmonic effects due to all cubic and quartic force constants in a size-extensive fashion. These methods can be readily extended to a higher-order truncated Taylor expansion of a potential energy surface in normal coordinates. An algebraic proof of the lack of size-extensivity in the vibrational configuration-interaction method is also presented.
Reconsidering harmonic and anharmonic coherent states: Partial differential equations approach
Toutounji, Mohamad, E-mail: Mtoutounji@uaeu.ac.ae
2015-02-15
This article presents a new approach to dealing with time dependent quantities such as autocorrelation function of harmonic and anharmonic systems using coherent states and partial differential equations. The approach that is normally used to evaluate dynamical quantities involves formidable operator algebra. That operator algebra becomes insurmountable when employing Morse oscillator coherent states. This problem becomes even more complicated in case of Morse oscillator as it tends to exhibit divergent dynamics. This approach employs linear partial differential equations, some of which may be solved exactly and analytically, thereby avoiding the cumbersome noncommutative algebra required to manipulate coherent states of Morse oscillator. Additionally, the arising integrals while using the herein presented method feature stability and high numerical efficiency. The correctness, applicability, and utility of the above approach are tested by reproducing the partition and optical autocorrelation function of the harmonic oscillator. A closed-form expression for the equilibrium canonical partition function of the Morse oscillator is derived using its coherent states and partial differential equations. Also, a nonequilibrium autocorrelation function expression for weak electron–phonon coupling in condensed systems is derived for displaced Morse oscillator in electronic state. Finally, the utility of the method is demonstrated through further simplifying the Morse oscillator partition function or autocorrelation function expressions reported by other researchers in unevaluated form of second-order derivative exponential. Comparison with exact dynamics shows identical results.
Reconsidering harmonic and anharmonic coherent states: Partial differential equations approach
Toutounji, Mohamad
2015-02-01
This article presents a new approach to dealing with time dependent quantities such as autocorrelation function of harmonic and anharmonic systems using coherent states and partial differential equations. The approach that is normally used to evaluate dynamical quantities involves formidable operator algebra. That operator algebra becomes insurmountable when employing Morse oscillator coherent states. This problem becomes even more complicated in case of Morse oscillator as it tends to exhibit divergent dynamics. This approach employs linear partial differential equations, some of which may be solved exactly and analytically, thereby avoiding the cumbersome noncommutative algebra required to manipulate coherent states of Morse oscillator. Additionally, the arising integrals while using the herein presented method feature stability and high numerical efficiency. The correctness, applicability, and utility of the above approach are tested by reproducing the partition and optical autocorrelation function of the harmonic oscillator. A closed-form expression for the equilibrium canonical partition function of the Morse oscillator is derived using its coherent states and partial differential equations. Also, a nonequilibrium autocorrelation function expression for weak electron-phonon coupling in condensed systems is derived for displaced Morse oscillator in electronic state. Finally, the utility of the method is demonstrated through further simplifying the Morse oscillator partition function or autocorrelation function expressions reported by other researchers in unevaluated form of second-order derivative exponential. Comparison with exact dynamics shows identical results.
Scleronomic Holonomic Constraints and Conservative Nonlinear Oscillators
Munoz, R.; Gonzalez-Garcia, G.; Izquierdo-De La Cruz, E.; Fernandez-Anaya, G.
2011-01-01
A bead sliding, under the sole influence of its own weight, on a rigid wire shaped in the fashion of a plane curve, will describe (generally anharmonic) oscillations around a local minimum. For given shapes, the bead will behave as a harmonic oscillator in the whole range, such as an unforced, undamped, Duffing oscillator, etc. We also present…
Optimized coordinates for anharmonic vibrational structure theories.
Yagi, Kiyoshi; Keçeli, Murat; Hirata, So
2012-11-28
A procedure to determine optimal vibrational coordinates is developed on the basis of an earlier idea of Thompson and Truhlar [J. Chem. Phys. 77, 3031 (1982)]. For a given molecule, these coordinates are defined as the unitary transform of the normal coordinates that minimizes the energy of the vibrational self-consistent-field (VSCF) method for the ground state. They are justified by the fact that VSCF in these coordinates becomes exact in two limiting cases: harmonic oscillators, where the optimized coordinates are normal, and noninteracting anharmonic oscillators, in which the optimized coordinates are localized on individual oscillators. A robust and general optimization algorithm is developed, which decomposes the transformation matrix into a product of Jacobi matrices, determines the rotation angle of each Jacobi matrix that minimizes the energy, and iterates the process until a minimum in the whole high dimension is reached. It is shown that the optimized coordinates are neither entirely localized nor entirely delocalized (or normal) in any of the molecules (the water, water dimer, and ethylene molecules) examined (apart from the aforementioned limiting cases). Rather, high-frequency stretching modes tend to be localized, whereas low-frequency skeletal vibrations remain normal. On the basis of these coordinates, we introduce two new vibrational structure methods: optimized-coordinate VSCF (oc-VSCF) and optimized-coordinate vibrational configuration interaction (oc-VCI). For the modes that become localized, oc-VSCF is found to outperform VSCF, whereas, for both classes of modes, oc-VCI exhibits much more rapid convergence than VCI with respect to the rank of excitations. We propose a rational configuration selection for oc-VCI when the optimized coordinates are localized. The use of the optimized coordinates in VCI with this configuration selection scheme reduces the mean absolute errors in the frequencies of the fundamentals and the first overtones
Alam, Mohosin; Mandal, Swapan; Wahiddin, Mohamed Ridza
2017-09-01
The essence of the rotating wave approximation (RWA) is to eliminate the non-conserving energy terms from the interaction Hamiltonian. The cost of using RWA is heavy if the frequency of the input radiation field is low (e.g. below optical region). The well known Bloch-Siegert effect is the out come of the inclusion of the terms which are normally neglected under RWA. We investigate the fluctuations of the quantum phase of the coherent light and the thermal light coupled to a nondegenerate parametric oscillator (NDPO). The Hamiltonian and hence the equations of motion involving the signal and idler modes are framed by using the strong (classical) pump condition. These differential equations are nonlinear in nature and are found coupled to each other. Without using the RWA, we obtain the analytical solutions for the signal and idler fields. These solutions are obtained up to the second orders in dimensionless coupling constants. The analytical expressions for the quantum phase fluctuation parameters due to Carruther's and Nieto are obtained in terms of the coupling constants and the initial photon numbers of the input radiation field. Moreover, we keep ourselves confined to the Pegg-Barnett formalism for measured phase operators. With and without using the RWA, we compare the quantum phase fluctuations for coherent and thermal light coupled to the NDPO. In spite of the significant departures (quantitative), the qualitative features of the phase fluctuation parameters for the input thermal light are identical for NDPO with and without RWA. On the other hand, we report some interesting results of input coherent light coupled to the NDPO which are substantially different from their RWA counterpart. In spite of the various quantum optical phenomena in a NDPO, we claim that it is the first effort where the complete analytical approach towards the solutions and hence the quantum phase fluctuations of input radiation fields coupled to it are obtained beyond rotating wave
Sokolov, V I; Shirokov, E A; Kislov, A N
2002-01-01
Paper presents the results of investigations into lattice vibrations induced by nickel impurities charged negatively as to the lattice in ZnSe:Ni, ZnO:Ni, ZnS:Ni, CdS:Ni semiconductors. To investigate into vibrations one applies a sensitive technique of field exciton-oscillation spectroscopy. One observes experimentally oscillating reiterations of the impurity exciton head line including the intensive peaks of combined repetitions up to the 8-th order. The experimental results are discussed on the basis of the model estimations of oscillations of a lattice with a charged impurity centre, as well as, on the ground of calculations for oscillations of monoatomic chain with high anharmonicity. Charged impurity centres are shown to induce new oscillations of lattice - impurity anharmonic modes
Anharmonic phonons and the isotope effect in superconductivity
Crespi, V.H.; Cohen, M.L. (Department of Physics, University of California at Berkeley, Berkeley, CA (USA) Materials Sciences Division, Lawrence Berkeley Laboratory, Berkeley, CA (USA)); Penn, D.R. (National Institute of Standards and Technology, Gaithersburg, MD (USA))
1991-06-01
Anharmonic interionic potentials are examined in an Einstein model to study the unusual isotope-effect exponents for the high-{ital T}{sub {ital c}} oxides. The mass dependences of the electron-phonon coupling constant {lambda} and the average phonon frequency {radical}{l angle}{omega}{sup 2}{r angle} are computed from weighted sums over the oscillator levels. The isotope-effect exponent is depressed below 1/2 by either a double-well potential or a potential with positive quadratic and quartic parts. Numerical solutions of Schroedinger's equation for double-well potentials produce {lambda}'s in the range 1.5--4 for a material with a vanishing isotope-effect parameter {alpha}. However, low phonon frequencies limit {ital T}{sub {ital c}} to roughly 15 K. A negative quartic perturbation to a harmonic well can increase {alpha} above 1/2. In the extreme-strong-coupling limit, {alpha} is 1/2, regardless of anharmonicity.
Direct anharmonic correction method by molecular dynamics
Liu, Zhong-Li; Li, Rui; Zhang, Xiu-Lu; Qu, Nuo; Cai, Ling-Cang
2017-04-01
The quick calculation of accurate anharmonic effects of lattice vibrations is crucial to the calculations of thermodynamic properties, the construction of the multi-phase diagram and equation of states of materials, and the theoretical designs of new materials. In this paper, we proposed a direct free energy interpolation (DFEI) method based on the temperature dependent phonon density of states (TD-PDOS) reduced from molecular dynamics simulations. Using the DFEI method, after anharmonic free energy corrections we reproduced the thermal expansion coefficients, the specific heat, the thermal pressure, the isothermal bulk modulus, and the Hugoniot P- V- T relationships of Cu easily and accurately. The extensive tests on other materials including metal, alloy, semiconductor and insulator also manifest that the DFEI method can easily uncover the rest anharmonicity that the quasi-harmonic approximation (QHA) omits. It is thus evidenced that the DFEI method is indeed a very efficient method used to conduct anharmonic effect corrections beyond QHA. More importantly it is much more straightforward and easier compared to previous anharmonic methods.
Approximation methods for the partition functions of anharmonic systems
Lew, P.; Ishida, T.
1979-07-01
The analytical approximations for the classical, quantum mechanical and reduced partition functions of the diatomic molecule oscillating internally under the influence of the Morse potential have been derived and their convergences have been tested numerically. This successful analytical method is used in the treatment of anharmonic systems. Using Schwinger perturbation method in the framework of second quantization formulism, the reduced partition function of polyatomic systems can be put into an expression which consists separately of contributions from the harmonic terms, Morse potential correction terms and interaction terms due to the off-diagonal potential coefficients. The calculated results of the reduced partition function from the approximation method on the 2-D and 3-D model systems agree well with the numerical exact calculations.
Thermodynamic properties of wadsleyite with anharmonic effect
Zhongqing Wu
2015-01-01
The thermodynamic properties of crystals can be routinely calculated by density functional theory calculations combining with quasi-harmonic approximation.Based on the method developed recently by Wu and Wentzcovitch (Phys Rev B 79:104304,2009) and Wu (Phys Rev B 81:172301,2010),we are able to further ab initio include anharmonic effect on thermodynamic properties of crystals by one additional canonical ensemble with numbers of particle,volume and temperature fixed (NVT) molecular dynamic simulations.Our study indicates that phonon-phonon interaction causes the renormalized phonon frequencies of wadsleyite decrease with temperature.This is consistent with the Raman experimental observation.The anharmonic free energy of wadsleyite is negative and its heat capacity at constant pressure can exceed the Dulong-Petit limit at high temperature.The anharmonicity still significantly affects thermodynamic properties of wadsleyite at pressure and temperature conditions correspond to the transition zone.
Anharmonicity in GaTe layered crystals
Aydinli, A. [Physics Department, Bilkent University, Ankara (Turkey); Gasanly, N.M.; Uka, A. [Physics Department, Middle East Technical University, Ankara (Turkey); Efeoglu, H. [Physics Department, Atatuerk University, Erzurum (Turkey)
2002-07-01
The temperature dependencies (10-300 K) of seven Raman-active mode frequencies in layered semiconductor gallium telluride have been measured in the frequency range from 25 to 300 cm{sup -1}. Softening and broadening of the optical phonon lines are observed with increasing temperature. Comparison between the experimental data and theories of the shift of the phonon lines during heating of the crystal showed that the experimental dependencies can be explained by contributions from thermal expansion and lattice anharmonicity. Lattice anharmonicity is determined to be due to three-phonon processes. (Abstract Copyright [2002], Wiley Periodicals, Inc.)
Mahalik, S. S.; Kundu, M.
2016-12-01
Linear resonance (LR) absorption of an intense 800 nm laser light in a nano-cluster requires a long laser pulse >100 fs when Mie-plasma frequency ( ω M ) of electrons in the expanding cluster matches the laser frequency (ω). For a short duration of the pulse, the condition for LR is not satisfied. In this case, it was shown by a model and particle-in-cell (PIC) simulations [Phys. Rev. Lett. 96, 123401 (2006)] that electrons absorb laser energy by anharmonic resonance (AHR) when the position-dependent frequency Ω [ r ( t ) ] of an electron in the self-consistent anharmonic potential of the cluster satisfies Ω [ r ( t ) ] = ω . However, AHR remains to be a debate and still obscure in multi-particle plasma simulations. Here, we identify AHR mechanism in a laser driven cluster using molecular dynamics (MD) simulations. By analyzing the trajectory of each MD electron and extracting its Ω [ r ( t ) ] in the self-generated anharmonic plasma potential, it is found that electron is outer ionized only when AHR is met. An anharmonic oscillator model, introduced here, brings out most of the features of MD electrons while passing the AHR. Thus, we not only bridge the gap between PIC simulations, analytical models, and MD calculations for the first time but also unequivocally prove that AHR process is a universal dominant collisionless mechanism of absorption in the short pulse regime or in the early time of longer pulses in clusters.
Comparative study of quantum anharmonic potentials
Amore, Paolo [Facultad de Ciencias, Universidad de Colima, Bernal Diaz del Castillo 340, Colima (Mexico)]. E-mail: paolo@ucol.mx; Aranda, Alfredo [Facultad de Ciencias, Universidad de Colima, Bernal Diaz del Castillo 340, Colima (Mexico); De Pace, Arturo [Istituto Nazionale di Fisica Nucleare, Sezione di Torino, via P. Giuria 1, I-10125 Torino (Italy); Lopez, Jorge A. [Physics Department, University of Texas at El Paso, El Paso, TX (United States)
2004-09-06
We perform a study of various anharmonic potentials using a recently developed method. We calculate both the wave functions and the energy eigenvalues for the ground and first excited states of the quartic, sextic and octic potentials with high precision, comparing the results with other techniques available in the literature.
Anharmonic Bend-Stretch Coupling in Water
Lindner, Jörg; Vöhringer, Peter; Pshenichnikov, Maxim S.; Cringus, Dan; Wiersma, Douwe A.; Corkum, Paul; Jonas, David M.; Miller, R.J. Dwayne.; Weiner, Andrew M.
2006-01-01
Following excitation of the H-O-H bending mode of water molecules in solution the stretching mode region is monitored over its entire width. The anharmonic coupling between the two modes results in a substantial change of the transient stretch absorption that decays with the bend depopulation time.
Anharmonic effects and double giant dipole resonances
Voronov, V V
2001-01-01
A brief review of recent results of the microscopic calculations to describe characteristics of the double giant dipole resonances (DGDR) is presented. A special attention is paid to a microscopic study of the anharmonic properties of the DGDR. It is found that the deviation of the energy centroid of the DGDR from the harmonic limit follows A sup - sup 1 dependence
Anharmonic phonons and high-temperature superconductivity
Crespi, V.H.; Cohen, M.L. (Department of Physics, University of California at Berkeley, and Materials Sciences Division, Lawrence Berkeley Laboratory, Berkeley, California 94720 (United States))
1993-07-01
We examine a simple model of anharmonic phonons with application to the superconducting isotope effect. Linear and quadratic electron-phonon coupling are considered for various model potentials. The results of the model calculations are compared with the high-temperature superconductors La[sub 2[minus][ital x
Shen, Tonghao; Su, Neil Qiang; Wu, Anan; Xu, Xin
2014-03-05
In this work, we first review the perturbative treatment of an oscillator with cubic anharmonicity. It is shown that there is a quantum-classical correspondence in terms of mean displacement, mean-squared displacement, and the corresponding variance in the first-order perturbation theory, provided that the amplitude of the classical oscillator is fixed at the zeroth-order energy of quantum mechanics EQM (0). This correspondence condition is realized by proposing the extended Langevin dynamics (XLD), where the key is to construct a proper driving force. It is assumed that the driving force adopts a simple harmonic form with its amplitude chosen according to EQM (0), while the driving frequency chosen as the harmonic frequency. The latter can be improved by using the natural frequency of the system in response to the potential if its anharmonicity is strong. By comparing to the accurate numeric results from discrete variable representation calculations for a set of diatomic species, it is shown that the present method is able to capture the large part of anharmonicity, being competitive with the wave function-based vibrational second-order perturbation theory, for the whole frequency range from ∼4400 cm(-1) (H2 ) to ∼160 cm(-1) (Na2 ). XLD shows a substantial improvement over the classical molecular dynamics which ceases to work for hard mode when zero-point energy effects are significant.
A uniqueness theorem for higher order anharmonic oscillators
Fournais, Soren; Sundqvist, Mikael Persson
2015-01-01
We study for alpha is an element of R, k is an element of N \\ {0} the family of self-adjoint operators -d(2)/dt(2) + (t(k+1)/k+1 - alpha)(2) in L-2(R) and show that if k is even then alpha = 0 gives the unique minimum of the lowest eigenvalue of this family of operators. Combined with earlier res...
The symmetry breaking phenomenon in anharmonic oscillator model
Mastine, Antonio Carlos; Natti, Erica Regina Takano
2010-01-01
In this article a non-perturbative time-dependent technique is used to treat the initial value problem, in Quantum Mechanics context, for a non-equilibrium self-interacting fermionic system in the presence of an external magnetic field. Particularly, in mean-field regime, we study the dynamical symmetry breaking phenomenon, identifying the physical processes associated.
Degenerate Density Perturbation Theory
Palenik, Mark C
2016-01-01
Fractional occupation numbers can be used in density functional theory to create a symmetric Kohn-Sham potential, resulting in orbitals with degenerate eigenvalues. We develop the corresponding perturbation theory and apply it to a system of $N_d$ degenerate electrons in a harmonic oscillator potential. The order-by-order expansions of both the fractional occupation numbers and unitary transformations within the degenerate subspace are determined by the requirement that a differentiable map exists connecting the initial and perturbed states. Using the X$\\alpha$ exchange-correlation (XC) functional, we find an analytic solution for the first-order density and first through third-order energies as a function of $\\alpha$, with and without a self-interaction correction. The fact that the XC Hessian is not positive definite plays an important role in the behavior of the occupation numbers.
Degenerate density perturbation theory
Palenik, Mark C.; Dunlap, Brett I.
2016-09-01
Fractional occupation numbers can be used in density functional theory to create a symmetric Kohn-Sham potential, resulting in orbitals with degenerate eigenvalues. We develop the corresponding perturbation theory and apply it to a system of Nd degenerate electrons in a harmonic oscillator potential. The order-by-order expansions of both the fractional occupation numbers and unitary transformations within the degenerate subspace are determined by the requirement that a differentiable map exists connecting the initial and perturbed states. Using the X α exchange-correlation (XC) functional, we find an analytic solution for the first-order density and first- through third-order energies as a function of α , with and without a self-interaction correction. The fact that the XC Hessian is not positive definite plays an important role in the behavior of the occupation numbers.
Anharmonic properties of potassium halide crystals
RAJU, Krishna Murti
2011-01-01
An effort has been made to obtain the anharmonic properties of potassium halides starting from primary physical parameters viz. nearest neighbor distance and hardness parameters assuming long- and short- range potentials at elevated temperatures. The elastic energy density for a deformed crystal can be expanded as power series of strains for obtaining coefficients of quadratic, cubic and quartic terms which are known as the second, third and fourth order elastic constants respectively...
Anharmonic effects and heat transport in complex systems (Invited)
Wentzcovitch, R. M.
2013-12-01
We have recently developed a hybrid strategy combining first principles molecular dynamics (MD) with vibrational normal mode analysis to obtain anharmonic frequency shifts and lifetimes of phonon quasi-particles. This approach is effective irrespective of crystal structure complexity and has been used to investigate anharmonicity in MgSiO3-perpovskite (MgPv) and cubic CaSiO3-perovskite (CaPv). The first is weakly anharmonic but has well identified temperature induced anharmonic Raman frequency shifts, while the second is strongly anharmonic. This method displays fine predictive capability by reproducing subtle measured effects in MgPv and proves to be robust and capable of handling soft phonon anharmonicity in CaPv. This strategy also facilitates calculation of anharmonic phonon dispersions throughout the Brillouin zone. Combination of analytical treatments of anharmonic free energy based on the phonon gas model (PGM) with thoroughly sampled anharmonic dispersions should improve considerably the accuracy of first-principles free energy calculations in crystalline solids at very high temperatures. This method also enables calculations of thermal conductivity, κ, using Boltzman transport equation with lifetimes calculated by MD. This is essential to predict thermodynamics properties and κ by first principles at very high temperatures. Research in collaboration with Tao Sun and Dong-Bo Zhang and supported by NSF award EAR-1019853.
Wen Hua ZHANG; Jiu Li LUO
2004-01-01
The thermokinetic behavior of the B-Z reaction system was influenced by both the chemical reaction-heat conduction coupling and the temperature undulation due to temperature controlling of heat compensation type. Quantitative research indicated that this kind of temperature fluctuation will lead to limit cycle degeneration and the periodic or quasi-periodic response behavior of the focus near a supercritical Hopf bifurcation.
Non-Gaussian wave packet dynamics in anharmonic potential: Cumulant expansion treatment
Toutounji, Mohamad
2015-03-01
This manuscript utilizes cumulant expansion as an alternative algebraic approach to evaluating integrals and solving a system of nonlinear differential equations for probing anharmonic dynamics in condensed phase systems using Morse oscillator. These integrals and differential equations become harder to solve as the anharmonicity of the system goes beyond that of Morse oscillator description. This algebraic approach becomes critically important in case of Morse oscillator as it tends to exhibit divergent dynamics and numerical uncertainties at low temperatures. The autocorrelation function is calculated algebraically and compared to the exact one for they match perfectly. It is also compared to the approximate autocorrelation function using the differential equations technique reported in Toutounji (2014) for weak and strong electron-phonon coupling cases. It is found that the present cumulant method is more efficient, and easier to use, than the exact expression. Deviation between the approximate autocorrelation function and the exact autocorrelation function starts to arise as the electron-phonon coupling strength increases. The autocorrelation function obtained using cumulants identically matches the exact autocorrelation function, thereby surpassing the approach presented in Toutounji (2014). The advantage of the present methodology is its applicability to various types of electron-phonon coupling cases. Additionally, the herein approach only uses algebraic techniques, thereby avoiding both the divergence integral and solving a set of linear first- and second-order partial differential equations as was done in previous work. Model calculations are presented to demonstrate the accuracy of the herein work.
Analytic calculations of anharmonic infrared and Raman vibrational spectra.
Cornaton, Yann; Ringholm, Magnus; Louant, Orian; Ruud, Kenneth
2016-02-07
Using a recently developed recursive scheme for the calculation of high-order geometric derivatives of frequency-dependent molecular properties [Ringholm et al., J. Comp. Chem., 2014, 35, 622], we present the first analytic calculations of anharmonic infrared (IR) and Raman spectra including anharmonicity both in the vibrational frequencies and in the IR and Raman intensities. In the case of anharmonic corrections to the Raman intensities, this involves the calculation of fifth-order energy derivatives-that is, the third-order geometric derivatives of the frequency-dependent polarizability. The approach is applicable to both Hartree-Fock and Kohn-Sham density functional theory. Using generalized vibrational perturbation theory to second order, we have calculated the anharmonic infrared and Raman spectra of the non- and partially deuterated isotopomers of nitromethane, where the inclusion of anharmonic effects introduces combination and overtone bands that are observed in the experimental spectra. For the major features of the spectra, the inclusion of anharmonicities in the calculation of the vibrational frequencies is more important than anharmonic effects in the calculated infrared and Raman intensities. Using methanimine as a trial system, we demonstrate that the analytic approach avoids errors in the calculated spectra that may arise if numerical differentiation schemes are used.
Yao, J M
2016-01-01
We discuss anharmonicity of the multi-octupole-phonon states in $^{208}$Pb based on a covariant density functional theory, by fully taking into account the interplay between the quadrupole and the octupole degrees of freedom. Our results indicate the existence of a large anharmonicity in the transition strengths, even though the excitation energies are similar to those in the harmonic limit. We also show that the quadrupole-shape fluctuation significantly enhances the fragmentation of the two-octupole-phonon states in $^{208}$Pb. Using those transition strengths as inputs to coupled channels calculations, we then discuss the fusion reaction of $^{16}$O+$^{208}$Pb at energies around the Coulomb barrier. We show that the anharmonicity of the octupole vibrational excitation considerably improves previous coupled-channels calculations in the harmonic oscillator limit, significantly reducing the height of the main peak in the fusion barrier distribution.
Eckmann, Jean-Pierre; Rey-Bellet, L; Eckmann, Jean-Pierre; Pillet, Claude-Alain; Rey-Bellet, Luc
1999-01-01
We study the statistical mechanics of a finite-dimensional non-linear Hamiltonian system (a chain of anharmonic oscillators) coupled to two heat baths (described by wave equations). Assuming that the initial conditions of the heat baths are distributed according to the Gibbs measures at two different temperatures we study the dynamics of the oscillators. Under suitable assumptions on the potential and on the coupling between the chain and the heat baths, we prove the existence of an invariant measure for any temperature difference, i.e., we prove the existence of steady states. Furthermore, if the temperature difference is sufficiently small, we prove that the invariant measure is unique and mixing. In particular, we develop new techniques for proving the existence of invariant measures for random processes on a non-compact phase space. These techniques are based on an extension of the commutator method of Hörmander used in the study of hypoelliptic differential operators.
Mckenzie, R. L.
1976-01-01
A semiclassical model of the inelastic collision between a vibrationally excited anharmonic oscillator and a structureless atom is used to predict the variation of thermally averaged vibrational-translational rate coefficients with temperature and initial-state quantum number. Multiple oscillator states are included in a numerical solution for collinear encounters. The results are compared with CO-He experimental values for both ground and excited initial states using several simplified forms of the interaction potential. The numerical model is also used as a basis for evaluating several less complete, but analytic, models. Two computationally simple analytic approximations are found that successfully reproduce the numerical rate coefficients for a wide range of molecular properties and collision partners. Their limitations are identified, and the relative rates of multiple-quantum transitions from excited states are evaluated for several molecular types.
Mckenzie, R. L.
1975-01-01
A semiclassical model of the inelastic collision between a vibrationally excited anharmonic oscillator and a structureless atom was used to predict the variation of thermally averaged vibration-translation rate coefficients with temperature and initial-state quantum number. Multiple oscillator states were included in a numerical solution for collinear encounters. The results are compared with CO-He experimental values for both ground and excited initial states using several simplified forms of the interaction potential. The numerical model was also used as a basis for evaluating several less complete but analytic models. Two computationally simple analytic approximations were found that successfully reproduced the numerical rate coefficients for a wide range of molecular properties and collision partners. Their limitations were also identified. The relative rates of multiple-quantum transitions from excited states were evaluated for several molecular types.
Scleronomic holonomic constraints and conservative nonlinear oscillators
Munoz, R; Gonzalez-Garcia, G; Izquierdo-De La Cruz, E Izquierdo-De La [Universidad Autonoma de la Ciudad de Mexico, Centro Historico, Fray Servando Teresa de Mier 92, Col Centro, Del Cuauhtemoc, Mexico DF, CP 06080 (Mexico); Fernandez-Anaya, G, E-mail: rodrigo.munoz@uacm.edu.mx, E-mail: gggharper@gmail.com, E-mail: erickidc@gmail.com, E-mail: guillermo.fernandez@uia.mx [Universidad Iberoamericana, Departamento de Fisica y Matematicas, Prolongacon Paseo de de la Reforma 880, Col Lomas de Santa Fe, Del Alvaro Obregn, Mexico DF, CP 01219 (Mexico)
2011-05-15
A bead sliding, under the sole influence of its own weight, on a rigid wire shaped in the fashion of a plane curve, will describe (generally anharmonic) oscillations around a local minimum. For given shapes, the bead will behave as a harmonic oscillator in the whole range, such as an unforced, undamped, Duffing oscillator, etc. We also present cases in which the effective potential acting on the bead is not analytical around a minimum. The small oscillation approximation cannot be applied to such pathological cases. Nonetheless, these latter instances are studied with other standard techniques.
Dynamic of cold-atom tips in anharmonic potentials
Tobias Menold
2016-10-01
Full Text Available Background: Understanding the dynamics of ultracold quantum gases in an anharmonic potential is essential for applications in the new field of cold-atom scanning probe microscopy. Therein, cold atomic ensembles are used as sensitive probe tips to investigate nanostructured surfaces and surface-near potentials, which typically cause anharmonic tip motion.Results: Besides a theoretical description of this anharmonic tip motion, we introduce a novel method for detecting the cold-atom tip dynamics in situ and real time. In agreement with theory, the first measurements show that particle interactions and anharmonic motion have a significant impact on the tip dynamics.Conclusion: Our findings will be crucial for the realization of high-sensitivity force spectroscopy with cold-atom tips and could possibly allow for the development of advanced spectroscopic techniques such as Q-control.
Ekimov, E. A.; Krivobok, V. S.; Lyapin, S. G.; Sherin, P. S.; Gavva, V. A.; Kondrin, M. V.
2017-03-01
We studied isotopically enriched nano- and microdiamonds with optically active GeV- centers synthesized at high pressures and high temperatures in nonmetallic growth systems. The influence of isotopic composition on optical properties has been thoroughly investigated by photoluminescence-excitation (PLE) and photoluminescence (PL) spectroscopy to get insight into the nature and electronic structure of this color center. We have demonstrated that the large frequency defect (difference between oscillation frequencies in the ground and excited electronic states) does bring about large discrepancy between PLE and PL spectra and comparatively high isotopic shift of the zero phonon line. Both effects seem to be rather common to split-vacancy centers (for example SiV-), where the frequency defect reaches record high values. Isotopic substitution of carbon atoms in the diamond lattice results in even larger shifts, which are only partially accounted for by a redistribution of electron density caused by the volume change of the diamond lattice. It was shown that the vibronic frequency in this case does not depend on the mass of carbon atoms. The greatest part of this isotopic shift is due to anharmonicity effects, which constitute a substantial part of vibronic frequency observed in this center. The exact physical mechanism, which leads to significant enhancement of anharmonicity on substitution of 12C to 13C, is yet to be clarified.
Alcohol dimers--how much diagonal OH anharmonicity?
Kollipost, Franz; Papendorf, Kim; Lee, Yu-Fang; Lee, Yuan-Pern; Suhm, Martin A
2014-08-14
The OH bond of methanol, ethanol and t-butyl alcohol becomes more anharmonic upon hydrogen bonding and the infrared intensity ratio between the overtone and the fundamental transition of the bridging OH stretching mode decreases drastically. FTIR spectroscopy of supersonic slit jet expansions allows to quantify these effects for isolated alcohol dimers, enabling a direct comparison to anharmonic vibrational predictions. The diagonal anharmonicity increase amounts to 15-18%, growing with increasing alkyl substitution. The overtone/fundamental IR intensity ratio, which is on the order of 0.1 or more for isolated alcohols, drops to 0.004-0.001 in the hydrogen-bonded OH group, making overtone detection very challenging. Again, alkyl substitution enhances the intensity suppression. Vibrational second order perturbation theory appears to capture these effects in a semiquantitative way. Harmonic quantum chemistry predictions for the hydrogen bond-induced OH stretching frequency shift (the widely used infrared signature of hydrogen bonding) are insufficient, and diagonal anharmonicity corrections from experiment make the agreement between theory and experiment worse. Inclusion of anharmonic cross terms between hydrogen bond modes and the OH stretching mode is thus essential, as is a high level electronic structure theory. The isolated molecule results are compared to matrix isolation data, complementing earlier studies in N2 and Ar by the more weakly interacting Ne and p-H2 matrices. Matrix effects on the hydrogen bond donor vibration are quantified.
Thermoelectricity in molecular junctions with harmonic and anharmonic modes
Bijay Kumar Agarwalla
2015-11-01
Full Text Available We study charge and energy transfer in two-site molecular electronic junctions in which electron transport is assisted by a vibrational mode. To understand the role of mode harmonicity/anharmonicity in transport behavior, we consider two limiting situations: (i the mode is assumed harmonic, (ii we truncate the mode spectrum to include only two levels, to represent an anharmonic mode. Based on the cumulant generating functions of the models, we analyze the linear-response and nonlinear performance of these junctions and demonstrate that while the electrical and thermal conductances are sensitive to whether the mode is harmonic/anharmonic, the Seebeck coefficient, the thermoelectric figure-of-merit, and the thermoelectric efficiency beyond linear response, conceal this information.
The Flux-Flux Correlation Function for Anharmonic Barriers
Goussev, Arseni; Waalkens, Holger; Wiggins, Stephen
2010-01-01
The flux-flux correlation function formalism is a standard and widely used approach for the computation of reaction rates. In this paper we introduce a method to compute the classical and quantum flux-flux correlation functions for anharmonic barriers essentially analytically through the use of the classical and quantum normal forms. In the quantum case we show that the quantum normal form reduces the computation of the flux-flux correlation function to that of an effective one dimensional anharmonic barrier. The example of the computation of the quantum flux-flux correlation function for a fourth order anharmonic barrier is worked out in detail, and we present an analytical expression for the quantum mechanical microcanonical flux-flux correlation function. We then give a discussion of the short-time and harmonic limits.
Xu, Xuefei; Papajak, Ewa; Zheng, Jingjing; Truhlar, Donald G
2012-03-28
We investigate the statistical thermodynamics and kinetics of the 1,5-hydrogen shift isomerization reaction of the 1-butoxyl radical and its reverse isomerization. The partition functions and thermodynamic functions (entropy, enthalpy, heat capacity, and Gibbs free energy) are calculated using the multi-structural torsional (MS-T) anharmonicity method including all structures for three species (reactant, product, and transition state) involved in the reaction. The calculated thermodynamic quantities have been compared to those estimated by the empirical group additivity (GA) method. The kinetics of the unimolecular isomerization reaction was investigated using multi-structural canonical variational transition state theory (MS-CVT) including both multiple-structure and torsional (MS-T) anharmonicity effects. In these calculations, multidimensional tunneling (MT) probabilities were evaluated by the small-curvature tunneling (SCT) approximation and compared to results obtained with the zero-curvature tunneling (ZCT) approximation. The high-pressure-limit rate constants for both the forward and reverse reactions are reported as calculated by MS-CVT/MT, where MT can be ZCT or SCT. Comparison with the rate constants obtained by the single-structural harmonic oscillator (SS-HO) approximation shows the importance of anharmonicity in the rate constants of these reactions, and the effect of multi-structural anharmonicity is found to be very large. Whereas the tunneling effect increases the rate constants, the MS-T anharmonicity decreases them at all temperatures. The two effects counteract each other at temperatures 385 K and 264 K for forward and reverse reactions, respectively, and tunneling dominates at lower temperatures while MS-T anharmonicity has a larger effect at higher temperatures. The multi-structural torsional anharmonicity effect reduces the final reverse reaction rate constants by a much larger factor than it does to the forward ones as a result of the
Shocks, Rarefaction Waves, and Current Fluctuations for Anharmonic Chains
Mendl, Christian B.; Spohn, Herbert
2016-10-01
The nonequilibrium dynamics of anharmonic chains is studied by imposing an initial domain-wall state, in which the two half lattices are prepared in equilibrium with distinct parameters. We analyse the Riemann problem for the corresponding Euler equations and, in specific cases, compare with molecular dynamics. Additionally, the fluctuations of time-integrated currents are investigated. In analogy with the KPZ equation, their typical fluctuations should be of size t^{1/3} and have a Tracy-Widom GUE distributed amplitude. The proper extension to anharmonic chains is explained and tested through molecular dynamics. Our results are calibrated against the stochastic LeRoux lattice gas.
Vibrational Spectra of the Azabenzenes Revisited: Anharmonic Force Fields
Boese, A D; Martin, Jan M.L.
2003-01-01
Anharmonic force fields and vibrational spectra of the azabenzene series (pyridine, pyridazine, pyrimidine, pyrazine, s-triazine, 1,2,3-triazine, 1,2,4-triazine and s-tetrazine) and benzene are obtained using density functional theory (DFT) with the B97-1 exchange-correlation functional and a triple-zeta plus double polarization (TZ2P) basis set. Overall, the fundamental frequencies computed by second-order rovibrational perturbation theory are in excellent agreement with experiment. The resolution of the presently calculated anharmonic spectra is such that they represent an extremely useful tool for the assignment and interpretation of the experimental spectra, especially where resonances are involved.
Pereira, Emmanuel; Mendonça, Mateus S.; Lemos, Humberto C. F.
2015-09-01
We investigate a chain of oscillators with anharmonic on-site potentials, with long range interparticle interactions, and coupled both to external and internal stochastic thermal reservoirs of Ornstein-Uhlenbeck type. We develop an integral representation, a` la Feynman-Kac, for the correlations and the heat current. We assume the approximation of discrete times in the integral formalism (together with a simplification in a subdominant part of the harmonic interaction) and develop a suitable polymer expansion for the model. In the regime of strong anharmonicity, strong harmonic pinning, and for the interparticle interaction with integrable polynomial decay, we prove the convergence of the polymer expansion uniformly in volume (number of sites and time). We also show that the two-point correlation decays in space such as the interparticle interaction. The existence of a convergent polymer expansion is of practical interest: it establishes a rigorous support for a perturbative analysis of the heat flow problem and for the computation of the thermal conductivity in related anharmonic crystals, including those with inhomogeneous potentials and long range interparticle interactions. To show the usefulness and trustworthiness of our approach, we compute the thermal conductivity of a specific anharmonic chain, and make a comparison with related numerical results presented in the literature.
Wang, Huan; Zhu, Chaoyuan; Yu, Jian-Guo; Lin, Sheng Hsien
2009-12-31
Anharmonic effects of the absorption and fluorescence spectra of pyridine molecule are studied and analyzed for the two-low lying singlet excited states S(1)((1)B(1)) and S(2)((1)B(2)). The complete active space self-consistent field (CASSCF) method is utilized to compute equilibrium geometries and all 27 vibrational normal-mode frequencies for the ground state and the two excited states. The present calculations show that the frequency differences between the ground and two excited states are small for the ten totally symmetric vibrational modes so that the displaced oscillator approximation can be used for spectrum simulations. The Franck-Condon factors within harmonic approximation basically grasp the main features of molecular spectra, but simulated 0-0 transition energy position and spectrum band shapes are not satisfactorily good for S(1)((1)B(1)) absorption and fluorescence spectra in comparison with experiment observation. As the first-order anharmonic correction added to Franck-Condon factors, both spectrum positions and band shapes can be simultaneously improved for both absorption and fluorescence spectra. It is concluded that the present anharmonic correction produces a significant dynamic shifts for spectrum positions and improves spectrum band shapes as well. The detailed structures of absorption spectrum of S(2)((1)B(2)) state observed from experiment can be also reproduced with anharmonic Franck-Condon simulation, and these were not shown in the harmonic Franck-Condon simulation with either distorted or Duschinsky effects in the literature.
Xu, Xuefei; Yu, Tao; Papajak, Ewa; Truhlar, Donald G
2012-11-01
We calculated the forward and reverse rate constants of the hydrogen abstraction reaction from carbon-2 of 2-methyl-1-propanol by hydroperoxyl radical over the temperature range 250-2400 K by using multistructural canonical variational transition state theory (MS-CVT) including both multiple-structure and torsional potential anharmonicity effects by the multistructural torsional anharmonicity (MS-T) method. In these calculations, multidimensional tunneling (MT) probabilities used to compute the tunneling transmission coefficients were evaluated by the small-curvature tunneling (SCT) approximation. Comparison with the rate constants obtained by the single-structural harmonic oscillator (SS-HO) approximation shows that multistructural anharmonicity increases the forward rate constants for all temperatures, but the reverse rate constants are reduced for temperatures lower than 430 K and increased for higher temperatures. The neglect of multistructural torsional anharmonicity would lead to errors of factors of 1.5, 8.8, and 13 at 300, 1000, and 2400 K, respectively, for the forward reaction, and would lead to errors of factors of 0.76, 3.0, and 6.0, respectively, at these temperatures for the reverse reaction.
Comparison of alternative improved perturbative methods for nonlinear oscillations
Amore, Paolo [Facultad de Ciencias, Universidad de Colima, Bernal Diaz del Castillo 340, Colima (Mexico)]. E-mail: paolo@ucol.mx; Raya, Alfredo [Facultad de Ciencias, Universidad de Colima, Bernal Diaz del Castillo 340, Colima (Mexico); Fernandez, Francisco M. [INIFTA (Conicet, UNLP), Diag. 113 y 64 S/N, Sucursal 4, Casilla de Correo 16, 1900 La Plata (Argentina)
2005-06-06
We discuss and compare two alternative perturbation approaches for the calculation of the period of nonlinear systems based on the Lindstedt-Poincare technique. As illustrative examples we choose one-dimensional anharmonic oscillators and the Van der Pol equation. Our results show that each approach is better for just one type of model considered here.
Anharmonic osillators energies via artificial perturbation method
Mustafa, O; Mustafa, Omar; Odeh, Maen
2000-01-01
A new pseudoperturbative (artificial in nature) methodical proposal [15] is used to solve for Schrodinger equation with a class of phenomenologically useful and methodically challenging anharmonice oscillator potentials V(q)=\\alpha_o q^2 + \\alpha q^4. The effect of the [4,5] Pade' approximant on the leading eigenenergy term is studied. Comparison with results from numerical (exact) and several eligible (approximation) methods is made.
Quantum unharmonic symmetrical oscillators using elliptic functions
Sanchez, A.M.; Bejarano, J.d.
1986-04-21
The authors study in the JWKB approximation the energy levels of the symmetric anharmonic oscillators V(x) Ax/sup 2/ + Bx/sup 4/ for different signs and values of A and B. Comparisons are made with published results for specific cases and with numerical calculations. An additional example is given of exact value, to add to the very rare catalogue of known examples.
Anharmonic densities of states: A general dynamics-based solution
Jellinek, Julius; Aleinikava, Darya
2016-06-01
Density of states is a fundamental physical characteristic that lies at the foundation of statistical mechanics and theoretical constructs that derive from them (e.g., kinetic rate theories, phase diagrams, and others). Even though most real physical systems are anharmonic, the vibrational density of states is customarily treated within the harmonic approximation, or with some partial, often limited, account for anharmonicity. The reason for this is that the problem of anharmonic densities of states stubbornly resisted a general and exact, yet convenient and straightforward in applications, solution. Here we formulate such a solution within both classical and quantum mechanics. It is based on actual dynamical behavior of systems as a function of energy and as observed, or monitored, on a chosen time scale, short or long. As a consequence, the resulting anharmonic densities of states are fully dynamically informed and, in general, time-dependent. As such, they lay the ground for formulation of new statistical mechanical frameworks that incorporate time and are ergodic, by construction, with respect to actual dynamical behavior of systems.
Anharmonicity and infrared bands of Polycyclic Aromatic Hydrocarbon (PAH) molecules
Petrignani, Annemieke; Maltseva, Elena; Candian, Alessandra; Mackie, Cameron; Huang, Xinchuan; Lee, Timothy J.; Tielens, Alexander; Oomens, Jos; Buma, Wybren Jan
2015-08-01
We present a systematic laboratory study of the CH stretching region in Polycyclic Aromatic Hydrocarbon (PAH) molecules of different shapes and sizes to investigate anharmonic behaviour and address the reliability of the never-validated but universally accepted scaling factors employed in astronomical PAH models. At the same time, new anharmonic theoretical quantum chemistry studies have been performed with the software program Spectro using our experimental data as benchmark. We performed mass and conformational-resolved, high-resolution spectroscopy of cold (~10K) linear and compact PAH molecules starting with naphthalene (C10H8) in the 3-µm CH stretching region. Surprisingly, the measured infrared spectra show many more strong modes than expected. Measurements of the deuterated counterparts demonstrate that these bands are the result of Fermi Resonances. First comparisons with harmonic and anharmonic DFT calculations using Gaussian 09 show that both approximations are not able to reproduce in detail the observed molecular reality. The improved anharmonic calculations performed with Spectro now include the effects of Fermi resonances and have been applied to PAHs for the first time. The analysis of the experimental data is greatly aided by these new theoretical quantum chemistry studies. Preliminary assignments are presented, aided by comparison between the observed rotational contour and the symmetry of candidate bands.
Anharmonic bend-stretch coupling in neat liquid water
Lindner, Joerg; Cringus, Dan; Pshenichnikov, Maxim S.; Voehringer, Peter
2007-01-01
Femtosecond mid-IR spectroscopy is used to study the vibrational relaxation dynamics in neat liquid water. By exciting the bending vibration and probing the stretching mode, it is possible to reliably determine the bending and librational lifetimes of water. The anharmonic coupling between the bendi
Thermodynamic scaling of relaxation: insights from anharmonic elasticity
Bernini, S.; Puosi, F.; Leporini, D.
2017-04-01
Using molecular dynamics simulations of a molecular liquid, we investigate the thermodynamic scaling (TS) of the structural relaxation time {τα} in terms of the quantity T{ρ-{γ\\text{ts}}}} , where T and ρ are the temperature and density, respectively. The liquid does not exhibit strong virial–energy correlations. We propose a method for evaluating both the characteristic exponent {{γ\\text{ts}} and the TS master curve that uses experimentally accessible quantities that characterise the anharmonic elasticity and does not use details about the microscopic interactions. In particular, we express the TS characteristic exponent {γ\\text{ts}} in terms of the lattice Grüneisen parameter {γL} and the isochoric anharmonicity {δL} . An analytic expression of the TS master curve of {τα} with {δL} as the key adjustable parameter is found. The comparison with the experimental TS master curves and the isochoric fragilities of 34 glassformers is satisfying. In a few cases, where thermodynamic data are available, we test (i) the predicted characteristic exponent {γ\\text{ts}} and (ii) the isochoric anharmonicity {δL} , as drawn by the best fit of the TS of the structural relaxation, against the available thermodynamic data. A linear relation between the isochoric fragility and the isochoric anharmonicity {δL} is found and compared favourably with the results of experiments with no adjustable parameters. A relation between the increase of the isochoric vibrational heat capacity due to anharmonicity and the isochoric fragility is derived.
[Hepatolenticular degeneration].
Zudenigo, D; Relja, M
1990-01-01
Hepatolenticular degeneration (Wilson's disease) is a hereditary disease in which metabolic disorder of copper leads to its accumulation in the liver, brain, cornea and kidneys with consequent pathologic changes in those organs. Hereditary mechanism of the disease is autosomal recessive with prevalence of 30-100 per 1,000,000 inhabitants. Etiology of this disease is not yet explained. There are two hypotheses. The first one is that it is the disorder of ceruloplasmine metabolism caused by insufficient synthesis of normal ceruloplasmine, or synthesis of functionally abnormal ceruloplasmine. The second one is: the block of copper biliar excretion which is the consequence of the liver lysosomes functional defect. Pathogenetic mechanism of disease is firstly long-term accumulation of copper in the liver, and later, when the liver depo is full, its releasing in circulation and accumulation in the brain, cornea, kidneys and bones, which causes adequate pathologic changes. Toxic activity of copper is the consequence of its activity on enzymes, particularly on those with -SH group. There are two basic clinical forms of the disease: liver disease or neurologic disease. Before puberty the liver damage is more frequent, while in adolescents and young adults neurologic form of the disease is usual. The liver disease is nonspecific and characterized by symptoms of cirrhosis and chronic aggressive hepatitis. The only specificity is hemolytic anemia which, in combination with previous symptoms, is important for diagnosis of the disease. Neurologic symptoms are the most frequent consequence of pathologic changes in the basal ganglia. In our patients the most frequent symptoms were tremor (63%); dysarthria, choreoathetosis and rigor (38%); ataxia and mental disorders (31%); dysphagia and dystonia (12%), diplopia, hypersalivation, nystagmus and Babinski's sign (6%). Among pathologic changes in other tissues and organs the most important is the finding of Kayser-Fleischer ring in the
Degenerate Neutrinos and CP Violation
Ioannisian, A N
2003-01-01
We have studied mixing and masses of three left handed Majorana neutrinos in the model, which assumes exactly degenerate neutrino masses at some "neutrino unification" scale. Such a simple theoretical ansatz naturally leads to quasidegenerate neutrinos. The neutrino mass splittings induced by renormalization effects. In the model we found that the parameters of the neutrino physics (neutrino mass spectrum, mixing angles and CP violation phases) are strongly intercorrelated to each other. From these correlations we got strong bounds on the parameters which could be checked in the oscillation experiments.
Ko, Hsin-Yu; Distasio, Robert A., Jr.; Santra, Biswajit; Car, Roberto
Molecular crystal structure prediction has posed a substantial challenge to first-principles methods and requires sophisticated electronic structure methods to determine the stabilities of nearly degenerate polymorphs. In this work, we demonstrate that the anharmonicity from van der Waals interactions is relevant to the finite-temperature structures of pyridine and pyridine-like molecular crystals. Using such an approach, we find that the equilibrium structures are well captured with classical ab initio molecular dynamics (AIMD), despite the presence of light atoms such as hydrogen. Employing path integral AIMD simulations, we demonstrate that the success of classical AIMD results from a separation of nuclear quantum effects between the intermolecular and intramolecular degrees of freedom. In this separation, the quasiclassical and anharmonic intermolecular degrees of freedom determine the equilibrium structure, while the quantum and harmonic intramolecular degrees of freedom are averaging to the correct intramolecular structure. This work has been supported by the Department of Energy under Grants No. DE-FG02-05ER46201 and DE-SC0008626.
Catalytic mechanism of LENR in quasicrystals based on localized anharmonic vibrations and phasons
Dubinko, Volodymyr; Irwin, Klee
2016-01-01
Quasicrystals (QCs) are a novel form of matter, which are neither crystalline nor amorphous. Among many surprising properties of QCs is their high catalytic activity. We propose a mechanism explaining this peculiarity based on unusual dynamics of atoms at special sites in QCs, namely, localized anharmonic vibrations (LAVs) and phasons. In the former case, one deals with a large amplitude (~ fractions of an angstrom) time-periodic oscillations of a small group of atoms around their stable positions in the lattice, known also as discrete breathers, which can be excited in regular crystals as well as in QCs. On the other hand, phasons are a specific property of QCs, which are represented by very large amplitude (~angstrom) oscillations of atoms be-tween two quasi-stable positions determined by the geometry of a QC. Large amplitude atomic motion in LAVs and phasons results in time-periodic driving of adjacent potential wells occupied by hydrogen ions (protons or deuterons) in case of hydrogenated QCs. This drivin...
Nonlinear spectroscopy of superconducting anharmonic resonators
DiVincenzo, David P
2011-01-01
We formulate a model for the steady state response of a nonlinear quantum oscillator structure, such as those used in a variety of superconducting qubit experiments, when excited by a steady, but not necessarily small, ac tone. We show that this model can be derived directly from a circuit description of some recent qubit experiments in which the state of the qubit is read out directly, without a SQUID magnetometer. The excitation profile has a rich structure depending on the detuning of the tone from the small-signal resonant frequency, on the degree of damping, and on the excitation amplitude. We explore two regions in detail: First, at high damping there is a trough in the excitation response as a function of detuning, near where the classical Duffing bifurcation occurs. This trough has been understood as a classical interference between two metastable responses with opposite phase. We use Wigner function studies to show that while this picture is roughly correct, there are also more quantum mechanical asp...
Phonon anharmonicity and negative thermal expansion in SnSe
Bansal, Dipanshu; Hong, Jiawang; Li, Chen W.; May, Andrew F.; Porter, Wallace; Hu, Michael Y.; Abernathy, Douglas L.; Delaire, Olivier
2016-08-01
The anharmonic phonon properties of SnSe in the P n m a phase were investigated with a combination of experiments and first-principles simulations. Using inelastic neutron scattering (INS) and nuclear resonant inelastic X-ray scattering (NRIXS), we have measured the phonon dispersions and density of states (DOS) and their temperature dependence, which revealed a strong, inhomogeneous shift and broadening of the spectrum on warming. First-principles simulations were performed to rationalize these measurements, and to explain the previously reported anisotropic thermal expansion, in particular the negative thermal expansion within the Sn-Se bilayers. Including the anisotropic strain dependence of the phonon free energy, in addition to the electronic ground state energy, is essential to reproduce the negative thermal expansion. From the phonon DOS obtained with INS and additional calorimetry measurements, we quantify the harmonic, dilational, and anharmonic components of the phonon entropy, heat capacity, and free energy. The origin of the anharmonic phonon thermodynamics is linked to the electronic structure.
... macular degeneration Overview By Mayo Clinic Staff Wet macular degeneration is a chronic eye disease that causes blurred vision or a blind spot in your visual field. It's generally caused by abnormal blood vessels that leak fluid or blood into ... macular degeneration is one of two types of age-related ...
Glensk, A; Grabowski, B; Hickel, T; Neugebauer, J
2015-05-15
We derive the Gibbs energy including the anharmonic contribution due to phonon-phonon interactions for an extensive set of unary fcc metals (Al, Ag, Au, Cu, Ir, Ni, Pb, Pd, Pt, Rh) by combining density-functional-theory (DFT) calculations with efficient statistical sampling approaches. We show that the anharmonicity of the macroscopic system can be traced back to the anharmonicity in local pairwise interactions. Using this insight, we derive and benchmark a highly efficient approach which allows the computation of anharmonic contributions using a few T=0 K DFT calculations only.
Anharmonicity effects in the frictionlike mode of graphite
Menéndez, C.; Lobato, A.; Abbasi-Pérez, D.; Fernández-Núñez, J.; Baonza, V. G.; Recio, J. M.
2016-04-01
Graphite is a prototypical solid lubricant demanding a thorough understanding of its low-friction behavior. The E2 g(1) Raman active vibrational mode of graphite is associated with the rigid-layer relative movement of its graphene sheets. Thus, this mode can provide a good means of exploring the low resistance of graphene layers to slip with respect to each other. To take advantage of this fact, the anharmonicity of the E2 g(1) mode has to be carefully characterized and evaluated since the atomic arrangement of carbon atoms in the ambient condition ABA stacking of graphite evidences potential asymmetry. The calculated one-dimensional energetic profile of the E2 g(1) mode reveals this local anisotropy around the energy minima and can be microscopically interpreted in terms of electron density interactions. Morse-type potentials accurately fit the energetic profiles at different interlayer separations, and provide simple analytical expressions for evaluating harmonic and anharmonic contributions to the Γ -point E2 g(1) frequency ωE2g(1 ) under a perturbative algebraic treatment. We quantify how the anharmonic contribution increases with the available energy (E ) at zero pressure, and how this contribution decreases as hydrostatic pressure (p ) or uniaxial stress is applied for a given available energy. The calculated ωE2g(1 )-p and ωE2g(1 )-E trends indicate an increasing (decreasing) of frictional forces in graphite with pressure (temperature). Our conclusions are supported by the good agreement of the calculated frequencies with existing Raman experiments under hydrostatic pressure conditions.
Stochastic many-body perturbation theory for anharmonic molecular vibrations
Hermes, Matthew R. [Department of Chemistry, University of Illinois at Urbana-Champaign, 600 South Mathews Avenue, Urbana, Illinois 61801 (United States); Hirata, So, E-mail: sohirata@illinois.edu [Department of Chemistry, University of Illinois at Urbana-Champaign, 600 South Mathews Avenue, Urbana, Illinois 61801 (United States); CREST, Japan Science and Technology Agency, 4-1-8 Honcho, Kawaguchi, Saitama 332-0012 (Japan)
2014-08-28
A new quantum Monte Carlo (QMC) method for anharmonic vibrational zero-point energies and transition frequencies is developed, which combines the diagrammatic vibrational many-body perturbation theory based on the Dyson equation with Monte Carlo integration. The infinite sums of the diagrammatic and thus size-consistent first- and second-order anharmonic corrections to the energy and self-energy are expressed as sums of a few m- or 2m-dimensional integrals of wave functions and a potential energy surface (PES) (m is the vibrational degrees of freedom). Each of these integrals is computed as the integrand (including the value of the PES) divided by the value of a judiciously chosen weight function evaluated on demand at geometries distributed randomly but according to the weight function via the Metropolis algorithm. In this way, the method completely avoids cumbersome evaluation and storage of high-order force constants necessary in the original formulation of the vibrational perturbation theory; it furthermore allows even higher-order force constants essentially up to an infinite order to be taken into account in a scalable, memory-efficient algorithm. The diagrammatic contributions to the frequency-dependent self-energies that are stochastically evaluated at discrete frequencies can be reliably interpolated, allowing the self-consistent solutions to the Dyson equation to be obtained. This method, therefore, can compute directly and stochastically the transition frequencies of fundamentals and overtones as well as their relative intensities as pole strengths, without fixed-node errors that plague some QMC. It is shown that, for an identical PES, the new method reproduces the correct deterministic values of the energies and frequencies within a few cm{sup −1} and pole strengths within a few thousandths. With the values of a PES evaluated on the fly at random geometries, the new method captures a noticeably greater proportion of anharmonic effects.
Stochastic many-body perturbation theory for anharmonic molecular vibrations.
Hermes, Matthew R; Hirata, So
2014-08-28
A new quantum Monte Carlo (QMC) method for anharmonic vibrational zero-point energies and transition frequencies is developed, which combines the diagrammatic vibrational many-body perturbation theory based on the Dyson equation with Monte Carlo integration. The infinite sums of the diagrammatic and thus size-consistent first- and second-order anharmonic corrections to the energy and self-energy are expressed as sums of a few m- or 2m-dimensional integrals of wave functions and a potential energy surface (PES) (m is the vibrational degrees of freedom). Each of these integrals is computed as the integrand (including the value of the PES) divided by the value of a judiciously chosen weight function evaluated on demand at geometries distributed randomly but according to the weight function via the Metropolis algorithm. In this way, the method completely avoids cumbersome evaluation and storage of high-order force constants necessary in the original formulation of the vibrational perturbation theory; it furthermore allows even higher-order force constants essentially up to an infinite order to be taken into account in a scalable, memory-efficient algorithm. The diagrammatic contributions to the frequency-dependent self-energies that are stochastically evaluated at discrete frequencies can be reliably interpolated, allowing the self-consistent solutions to the Dyson equation to be obtained. This method, therefore, can compute directly and stochastically the transition frequencies of fundamentals and overtones as well as their relative intensities as pole strengths, without fixed-node errors that plague some QMC. It is shown that, for an identical PES, the new method reproduces the correct deterministic values of the energies and frequencies within a few cm(-1) and pole strengths within a few thousandths. With the values of a PES evaluated on the fly at random geometries, the new method captures a noticeably greater proportion of anharmonic effects.
Origin of anomalous anharmonic lattice dynamics of lead telluride
Shiga, Takuma; Hori, Takuma; Delaire, Olivier; Shiomi, Junichiro
2015-01-01
The origin of the anomalous anharmonic lattice dynamics of lead telluride is investigated using molecular dynamics simulations with interatomic force constants (IFCs) up to quartic terms obtained from first principles. The calculations reproduce the peak asymmetry of the radial distribution functions and the double peaks of transverse optical phonon previously observed with neutron diffraction and scattering experiments. They are identified to be due to the extremely large nearest-neighbor cubic IFCs in the [100] direction. The outstanding strength of the nearest-neighbor cubic IFCs relative to the longer-range ones explains the reason why the distortion in the radial distribution function is local.
Anharmonic calculations in crystals having the diamond structure
Escamilla-Reyes, J. L.; Haro-Poniatowski, E.
1996-03-01
In this work the principal channels of decay are identified for Si, C, Ge and alpha tin. The corresponding double phonon densities of states are compu ted as well. These calculations are performed using a four parameter model developed by Wanser and Wallis [1]. Using the simplest anharmonic model : central potential nearest neighbor interactions, the phonon lifetimes are computed with the exception of alpha tin. Considering the simplicity of the employed models, a reasonable agreement with experimental results is obtain ed. [1] K. H. Wanser, R. F. Wallis, J. Phys. (Paris) 42, C6-128 (1981)
Calculation of anharmonic couplings and THz linewidths in crystalline PETN
Pereverzev, Andrey; Sewell, Thomas D.; Thompson, Donald L.
2014-03-01
We have developed a method for calculating the cubic anharmonic couplings in molecular crystals for normal modes with the zero wave vector in the framework of classical mechanics, and have applied it, combined with perturbation theory, to obtain the linewidths of all infrared absorption lines of crystalline pentaerythritol tetranitrate in the terahertz region (<100 cm-1). Contributions of the up- and down-conversion processes to the total linewidth were calculated. The computed linewidths are in qualitative agreement with experimental data and the results of molecular dynamics simulations. Quantum corrections to the linewidths in the terahertz region are shown to be negligible.
Anharmonicity and hydrogen bonding in electrooptic sucrose crystal
Szostak, M. M.; Giermańska, J.
1990-03-01
The polarized absorption spectra of the sucrose crystal in the 5300 - 7300 cm -1 region have been measured. The assignments of all the eight OH stretching overtones are proposed and their mechanical anharmonicities are estimated. The discrepancies from the oriented gas model (OGM) in the observed relative band intensities, especially of the -CH vibrations, are assumed to be connected with vibronic couplings enhanced by the helical arrangement of molecules joined by hydrogen bondings. It seems that this kind of interactions might be important for the second harmonic generation (SHG) by the sucrose crystal.
Dichromatic Langmuir waves in degenerate quantum plasma
Dubinov, A. E.; Kitayev, I. N.
2015-06-01
Langmuir waves in fully degenerate quantum plasma are considered. It is shown that, in the linear approximation, Langmuir waves are always dichromatic. The low-frequency component of the waves corresponds to classical Langmuir waves, while the high-frequency component, to free-electron quantum oscillations. The nonlinear problem on the profile of dichromatic Langmuir waves is solved. Solutions in the form of a superposition of waves and in the form of beatings of its components are obtained.
Bak, KL; Bludsky, O.; Jorgensen, P
1995-01-01
A priori theory is derived for anharmonic calculations of vibrational circular dichroism (VCD). The anharmonic VCD expression is gauge origin independent and reduce to the magnetic field perturbation theory expression in the double-harmonic approximation. The theory has been implemented using...
Anharmonicity in Light Scattering by Optical Phonons in GaAs1-xBix
Joshya, R. S.; Rajaji, V.; Narayana, Chandrabhas; Mascarenhas, Angelo; Kini, R. N.
2016-05-28
We present a Raman spectroscopic study of GaAs 1-xBix epilayers grown by molecular beam epitaxy. We have investigated the anharmonic effect on the GaAs-like longitudinal optical phonon mode (LO'GaAs) of GaAs 1-xBix for different Bi concentrations at various temperatures. The results are analyzed in terms of the anharmonic damping effect induced by thermal and compositional disorder. We have observed that the anharmonicity increases with Bi concentration in GaAs 1-xBix as evident from the increase in the anharmonicity constants. In addition, the anharmonic lifetime of the optical phonon decreases with increasing Bi concentration in GaAs 1-xBix.
Classical oscillators in the control of quantum tunneling: Numerical experiments
Kar, Susmita; Bhattacharyya, S. P.
2016-06-01
The dynamics of a classical anharmonic oscillator is exploited to control the tunneling dynamics of a quantum particle to which the classical oscillator is coupled. The mixed quantum classical problem is investigated at a mean-field like level. The anharmonic strength (λ) , particle mass (Mc) and harmonic stiffness (ωc) of the classical controller are explored as possible control parameters for the tunneling dynamics. The strength, the type of coupling between the quantum system and classical controller and the effective frequency of the controller emerge as crucial factors in shaping the nature and extent of the control. A whole spectrum of possibilities starting from enhancement, suppression to complete destruction of tunneling emerge depending on values assigned to the control parameters, the type of coupling and the control configuration used. When classical controller is replaced by a quantum controller, the control landscape becomes much simpler.
Naturalness of nearly degenerate neutrinos
Casas, J A; Ibarra, Alejandro; Navarro, I
1999-01-01
If neutrinos are to play a relevant cosmological role, they must be essentially degenerate. We study whether radiative corrections can or cannot be responsible for the small mass splittings, in agreement with all the available experimental data. We perform an exhaustive exploration of the bimaximal mixing scenario, finding that (i) the vacuum oscillations solution to the solar neutrino problem is always excluded; (ii) if the mass matrix is produced by a see-saw mechanism, there are large regions of the parameter space consistent with the large angle MSW solution, providing a natural origin for the Delta m^2_{sol} << Delta m^2_{atm} hierarchy; (iii) the bimaximal structure becomes then stable under radiative corrections. We also provide analytical expressions for the mass splittings and mixing angles and present a particularly simple see-saw ansatz consistent with all the observations.
Chaos in a double driven dissipative nonlinear oscillator.
Adamyan, H H; Manvelyan, S B; Kryuchkyan, G Y
2001-10-01
We propose an anharmonic oscillator driven by two periodic forces of different frequencies as a time-dependent model for investigating quantum dissipative chaos. Our analysis is done in the framework of the statistical ensemble of quantum trajectories in a quantum state diffusion approach. The quantum dynamical manifestations of chaotic behavior, including the emergence of chaos, properties of strange attractors, and quantum entanglement, are studied by numerical simulation of the ensemble averaged Wigner function and von Neumann entropy.
Degenerate Euler zeta function
Kim, Taekyun
2015-01-01
Recently, T. Kim considered Euler zeta function which interpolates Euler polynomials at negative integer (see [3]). In this paper, we study degenerate Euler zeta function which is holomorphic function on complex s-plane associated with degenerate Euler polynomials at negative integers.
Comment on 'Calculation of eigenfunctions in a double-well oscillator'
Fernandez, Francisco M, E-mail: fernande@quimica.unlp.edu.ar [INIFTA (UNLP, CCT La Plata-CONICET), Division Quimica Teorica, Blvd 113 S/N, Sucursal 4, Casilla de Correo 16, 1900 La Plata (Argentina)
2011-04-15
We argue that Ansaripour (2010 Phys. Scr. 82 045008) obtained not the eigenvalues and eigenfunctions of the double-well oscillator, but those for a single-well anharmonic oscillator. We show that his eigenvalues obtained by means of the Riccati-Pade method are not as accurate as the reported number of digits suggests. More precisely, Ansaripour's sequences of roots of the Hankel determinants converged to wrong limits. (comment)
Double Fourier Harmonic Balance Method for Nonlinear Oscillators by Means of Bessel Series
2014-10-16
Duffing oscillator . As an example of the results, the predicted period of a simple pendulum swinging between −90° and +90° is found to be only 0.4% larger...Eq. (42). 4.5 The Duffing oscillator with zero linear term For an anharmonic oscillator having restoring force f(x) = αx3, define ω0 = A √ α. Using...Double Fourier harmonic balance method for nonlinear oscillators by means of Bessel series T.C. Lipscombe∗1 and C.E. Mungan†2 1Catholic University of
Anharmonic effective pair potentials of gold under high pressure and high temperature
Okube, M; Ohtaka, O; Fukui, H; Katayama, Y; Utsumi, W
2002-01-01
In order to examine the effect of pressure on the anharmonicity of Au, extended x-ray absorption fine-structure spectra near the Au L sub 3 edge were measured in the temperature range from 300 to 1100 K under pressures up to 14 GPa using large-volume high-pressure devices and synchrotron radiation. The anharmonic effective pair potentials of Au, V (u) = au sup 2 + bu sup 3 , at 0.1 MPa, 6 and 14 GPa have been calculated. The pressure dependence of the thermal expansion coefficients has also been evaluated. The reliability of the anharmonic correction proposed on the basis of the Anderson scale has been discussed.
Anharmonic effects in neutron cross-section calculation for nuclei in mass range 48 [<=] A [<=] 58
Lubian, J.; Cabezas, R. (Center for Applied Studies to Nuclear Development, Havana (Cuba))
1993-08-01
In this paper, a deviation of the target nucleus wavefunction from the harmonic vibrator in the neutron scattering process by medium-mass nuclei at low energies is studied. Two forms of anharmonicities are used: anharmonicities due to the higher-order terms in the Hamiltonians and those due to the different deformation parameters, corresponding to transitions between nuclear states. For calculation of neutron cross sections, combined use of the coupled-channel method and the statistical Hauser-Feshbach-Moldauer theory is applied. It is shown that both kinds of anharmonicities introduced a correction (about 10% in some cases) to the neutron cross sections at low energies. (author).
Small perturbation of a disordered harmonic chain by a noise and an anharmonic potential
Bernardin, Cédric
2011-01-01
We study the thermal properties of a pinned disordered harmonic chain weakly perturbed by a noise and an anharmonic potential. The noise is controlled by a parameter $\\lambda \\rightarrow 0$, and the anharmonicity by a parameter $\\lambda' \\le \\lambda$. Let $\\kappa$ be the conductivity of the chain, defined through the Green-Kubo formula. Under suitable hypotheses, we show that $\\kappa = \\mathcal O (\\lambda)$ and, in the absence of anharmonic potential, that $\\kappa \\sim \\lambda$. This is in sharp contrast with the ordered chain for which $\\kappa \\sim 1/\\lambda$, and so shows the persitence of localization effects for a non-integrable dynamics.
Enthalpy of formation and anharmonic force field of diacetylene.
Simmonett, Andrew C; Schaefer, Henry F; Allen, Wesley D
2009-01-28
The enthalpy of formation of diacetylene (C4H2) is pinpointed using state-of-the-art theoretical methods, accounting for high-order electron correlation, relativistic effects, non-Born-Oppenheimer corrections, and vibrational anharmonicity. Molecular energies are determined from coupled cluster theory with single and double excitations (CCSD), perturbative triples [CCSD(T)], full triples (CCSDT), and perturbative quadruples [CCSDT(Q)], in concert with correlation-consistent basis sets (cc-pVXZ, X=D, T, Q, 5, 6) that facilitate extrapolations to the complete basis set limit. The first full quartic force field of diacetylene is determined at the highly accurate all-electron CCSD(T) level with a cc-pCVQZ basis, which includes tight functions for core correlation. Application of second-order vibrational perturbation theory to our anharmonic force field yields fundamental frequencies with a mean absolute difference of only 3.9 cm(-1) relative to the experimental band origins, without the use of any empirical scale factors. By a focal point approach, we converge on an enthalpy change for the isogyric reaction 2 H-C[triple bond]C-H-->H-C[triple bond]C-C[triple bond]C-H+H2 of (+0.03, +0.81) kcal mol(-1) at (0, 298.15) K. With the precisely established fHdegrees of acetylene, we thus obtain DeltafHdegrees(C4H2)=(109.4,109.7)+/-0.3 kcal mol(-1) at (0, 298.15) K. Previous estimates of the diacetylene enthalpy of formation range from 102 to 120 kcal mol(-1).
Gönül, B; Koçak, M; Gonul, Bulent; Ozer, Okan; Kocak, Mehmet
2001-01-01
The eigenvalues of the potentials $V(r)=\\frac{A_{1}}{r}+A_{2}+A_{3}r+A_{4}r^{2}+A_{5}r^{3}+A_{6}r^{4}$ and $V(r)=B_{1}r^{2}+B_{2}r^{4}+B_{3}r^{6}+B_{4}r^{8}+B_{5}r^{10}$ are obtained in $N$-dimensional space by the Lagrange-mesh calculations for a wide range of values of the parameters. We discuss the explicit dependence of these two potentials in higher-dimensional space. Using the formalism of supersymmetric quantum mechanics, it is shown that exact solutions of these potentials exist when the parameters satisfy certain constraints.
Anharmonic oscillators in the complex plane, $\\mathcal{PT}$-symmetry, and real eigenvalues
Shin, Kwang C
2010-01-01
For integers $m\\geq 3$ and $1\\leq\\ell\\leq m-1$, we study the eigenvalue problems $-u^{\\prime\\prime}(z)+[(-1)^{\\ell}(iz)^m-P(iz)]u(z)=\\lambda u(z)$ with the boundary conditions that $u(z)$ decays to zero as $z$ tends to infinity along the rays $\\arg z=-\\frac{\\pi}{2}\\pm \\frac{(\\ell+1)\\pi}{m+2}$ in the complex plane, where $P$ is a polynomial of degree at most $m-1$. We provide asymptotic expansions of the eigenvalues $\\lambda_{n}$. Then we show that if the eigenvalue problem is $\\mathcal{PT}$-symmetric, then the eigenvalues are all real and positive with at most finitely many exceptions. Moreover, we show that when $\\gcd(m,\\ell)=1$, the eigenvalue problem has infinitely many real eigenvalues if and only if its translation or itself is $\\mathcal{PT}$-symmetric. Also, we will prove some other interesting direct and inverse spectral results.
Maltseva, Elena; Candian, Alessandra; Mackie, Cameron J; Huang, Xinchuan; Lee, Timothy J; Tielens, Alexander G G M; Oomens, Jos; Buma, Wybren Jan
2015-01-01
We report on an experimental and theoretical investigation of the importance of anharmonicity in the 3 micron CH stretching region of Polycyclic Aromatic Hydrocarbon (PAH) molecules. We present mass-resolved, high-resolution spectra of the gas-phase cold (~4K) linear PAH molecules naphthalene, anthracene, and tetracene. The measured IR spectra show a surprisingly high number of strong vibrational bands. For naphthalene, the observed bands are well separated and limited by the rotational contour, revealing the band symmetries. Comparisons are made to the harmonic and anharmonic approaches of the widely used Gaussian software. We also present calculated spectra of these acenes using the computational program SPECTRO, providing anharmonic predictions enhanced with a Fermi-resonance treatment that utilises intensity redistribution. We demonstrate that the anharmonicity of the investigated acenes is strong, dominated by Fermi resonances between the fundamental and double combination modes, with triple combination ...
Temperature dependence of Raman-active phonons and anharmonic interactions in layered hexagonal BN
Cuscó, Ramon; Gil, Bernard; Cassabois, Guillaume; Artús, Luis
2016-10-01
We present a Raman scattering study of optical phonons in hexagonal BN for temperatures ranging from 80 to 600 K. The experiments were performed on high-quality, single-crystalline hexagonal BN platelets. The observed temperature dependence of the frequencies and linewidths of both Raman active E2 g optical phonons is analyzed in the framework of anharmonic decay theory, and possible decay channels are discussed in the light of density-functional theory calculations. With increasing temperature, the E2g high mode displays strong anharmonic interactions, with a linewidth increase that indicates an important contribution of four-phonon processes and a marked frequency downshift that can be attributed to a substantial effect of the four-phonon scattering processes (quartic anharmonicity). In contrast, the E2g low mode displays a very narrow linewidth and weak anharmonic interactions, with a frequency downshift that is primarily accounted for by the thermal expansion of the interlayer spacing.
Anharmonic Vibrational Frequency Calculations Are Not Worthwhile for Small Basis Sets.
Jacobsen, Ruth L; Johnson, Russell D; Irikura, Karl K; Kacker, Raghu N
2013-02-12
Anharmonic calculations using vibrational perturbation theory are known to provide near-spectroscopic accuracy when combined with high-level ab initio potential energy functions. However, performance with economical, popular electronic structure methods is less well characterized. We compare the accuracy of harmonic and anharmonic predictions from Hartree-Fock, second-order perturbation, and density functional theories combined with 6-31G(d) and 6-31+G(d,p) basis sets. As expected, anharmonic frequencies are closer than harmonic frequencies to experimental fundamentals. However, common practice is to correct harmonic predictions using multiplicative scaling. The surprising conclusion is that scaled anharmonic calculations are no more accurate than scaled harmonic calculations for the basis sets we used. The data used are from the Computational Chemistry Comparison and Benchmark Database (CCCBDB), maintained by the National Institute of Standards and Technology, which includes more than 3939 independent vibrations for 358 molecules.
Quantum thermal transport through anharmonic systems: A self-consistent approach
He, Dahai; Thingna, Juzar; Wang, Jian-Sheng; Li, Baowen
2016-10-01
We propose a feasible and effective approach to study quantum thermal transport through anharmonic systems. The main idea is to obtain an effective harmonic Hamiltonian for the anharmonic system by applying the self-consistent phonon theory. By using the effective harmonic Hamiltonian, we study thermal transport within the framework of the nonequilibrium Green's function method using the celebrated Caroli formula. We corroborate our quantum self-consistent approach by using the quantum master equation that can deal with anharmonicity exactly, but is limited to the weak system-bath coupling regime. Finally, in order to demonstrate its strength, we apply the quantum self-consistent approach to study thermal rectification in a weakly coupled two-segment anharmonic system.
Dabiri, Zohreh; Kazempour, Ali; Sadeghzadeh, Mohammad Ali
2016-11-01
The strength of phonon anharmonicity is investigated in the framework of the Density Functional Perturbation Theory via an applied constant electric field. In contrast to routine approaches, we have employed the electric field as an effective probe to quest after the quasi-harmonic and anharmonic effects. Two typical tetrahedral semiconductors (diamond and silicon) have been selected to test the efficiency of this approach. In this scheme the applied field is responsible for establishing the perturbation and also inducing the anharmonicity in systems. The induced polarization is a result of changing the electronic density while ions are located at their ground state coordinates or at a specified strain. Employing this method, physical quantities of the semiconductors are calculated in presence of the electron-phonon interaction directly and, phonon-phonon interaction, indirectly. The present approach, which is in good agreement with previous theoretical and experimental studies, can be introduced as a benchmark to simply investigate the anharmonicity and pertinent consequences in materials.
Raman-scattering probe of anharmonic effects in GaAs
Verma, Prabhat; Abbi, S. C.; Jain, K. P.
1995-06-01
A comparative study of anharmonic effects in various structural forms of GaAs, namely crystalline, disordered and ion-implanted, and pulse laser annealed (PLA), using temperature-dependent Raman scattering, is reported for various phonon modes over the temperature range 10-300 K. The disordered and PLA samples are found to have greater anharmonicity than crystalline GaAs. The localized vibrational mode in PLA GaAs shows shorter relaxation time than the LO-phonon mode.
Ground state properties of a Bose-Einstein condensate confined in an anharmonic external potential
Wang Deng-Long; Yan Xiao-Hong; Tang Yi
2004-01-01
In light of the interference experiment of Bose-Einstein condensates, we present an anharmonic external potential model to study ground state properties of Bose-Einstein condensates. The ground state energy and the chemical potential have been analytically obtained, which are lower than those in harmonic trap. Additionally, it is found that the anharmonic strength of the external potential has an important effect on density and velocity distributions of the ground state for the Thomas-Fermi model.
Anharmonic double-{gamma} vibrations in nuclei and their description in the interacting boson model
Garcia-Ramos, J.E.; Alonso, C.E.; Arias, J.M. [Sevilla Univ. (Spain). Departamento de Fisica Atomica, Molecular y Nuclear; Van Isacker, P. [Grand Accelerateur National d`Ions Lourds, 14 - Caen (France)
1998-07-01
Double-{gamma} vibrations in deformed nuclei are studied in the context of the interacting boson model with special reference to their anharmonic character. It is shown that large anharmonicities can be obtained with interactions that are (at least) of three-body nature between the bosons. As an example the {gamma} vibrations of the nucleus {sub 68}{sup 166}Er{sub 98} are studied in detail. (author) 28 refs.
Volpe, M.C. [Caen Univ., 14 (France)
1997-12-31
Double Giant Resonances, vibrational states in which a Giant Resonance is excited on top of another Giant Resonance, have been in the last years the object of many theories and studies. Whereas the measured energies and widths of these states agree with a theoretical predictions, the measured excitation cross sections on the other hand are almost always larger than the calculated ones. The standard theoretical approaches are based both on a harmonic approximation for the collective motion on the nucleus and on its linear response to an external field. In this work the influence of anharmonicities and non-linearities in the external field on the excitation of Double Giant Resonances are studied. First, an oscillator model and an extension of the Lipkin-Meshkow-Glick model are used to study the effects of anharmonicities and non-linearities on the excitation probabilities. The results show that these terms can influence the excitation probability of the second excited state in a significant way. Secondly, these exactly soluble schematic models are used to study some of the approximations made in microscopic calculations based on boson expansion methods and also some aspects on the time-dependent mean field approach. Finally, a microscopic calculation of the Coulomb excitation cross sections of Double Giant Resonances is presented for several nuclei. It is found that, for {sup 208} Pb, the inclusion of anharmonicities and non-linearities and the consideration of many states that play a role in the excitation process give a satisfactory agreement between calculated and observed cross sections. (author). 113 refs.
Vortices as degenerate metrics
Baptista, J M
2012-01-01
We note that the Bogomolny equation for abelian vortices is precisely the condition for invariance of the Hermitian-Einstein equation under a degenerate conformal transformation. This leads to a natural interpretation of vortices as degenerate hermitian metrics that satisfy a certain curvature equation. Using this viewpoint, we rephrase standard results about vortices and make some new observations. We note the existence of a conceptually simple, non-linear rule for superposing vortex solutions, and we describe the natural behaviour of the L^2-metric on the moduli space upon certain restrictions.
How intermixing and anharmonicity enhances interfacial thermal conductance?
Polanco, Carlos; Zhang, Jingjie; Le, Nam; Rastgarkafshgarkolaei, Rouzbeh; Norris, Pamela; Ghosh, Avik
2015-03-01
The thermal conductance at an interface, whether ballistic or diffusive, can be expressed as a product of the number of conducting channels (M) and their average transmission (T). The common expectation is that interfacial defects reduce T and thus hurt the conductance. This is however at odds with recent simulations showing that a thin intermixing layer can in fact enhance the conductance. We argue that such an enhancement occurs when the increase in number of modes outweighs the reduction in their average transmission. The new channels open as a result of (a) the random interfacial structure that relaxes the conservation rules for the transverse momentum and promotes transitions between formerly symmetry disallowed channels; and (b) inelastic scattering through phonon-phonon interactions that allow modes beyond the contact cut-off frequency to contribute to transport. We use these results to build a back of the envelope model for interfacial conductance that depends on the mixing distribution, the anharmonic strength, the phonon polarization and wavelength. Non-Equilibrium Green's Function (NEGF) as well as Molecular Dynamics (MD) simulations on Si/mixed layer/Ge, as well as simpler FCC crystals support our results. NSF-CAREER (QMHP 1028883), NSF-IDR (CBET 1134311), XSEDE (TG-DMR130123).
Nearly degenerate neutrinos, Supersymmetry and radiative corrections
Casas, J A; Ibarra, Alejandro; Navarro, I
2000-01-01
If neutrinos are to play a relevant cosmological role, they must be essentially degenerate with a mass matrix of the bimaximal mixing type. We study this scenario in the MSSM framework, finding that if neutrino masses are produced by a see-saw mechanism, the radiative corrections give rise to mass splittings and mixing angles that can accommodate the atmospheric and the (large angle MSW) solar neutrino oscillations. This provides a natural origin for the $\\Delta m^2_{sol} << \\Delta m^2_{atm}$ hierarchy. On the other hand, the vacuum oscillation solution to the solar neutrino problem is always excluded. We discuss also in the SUSY scenario other possible effects of radiative corrections involving the new neutrino Yukawa couplings, including implications for triviality limits on the Majorana mass, the infrared fixed point value of the top Yukawa coupling, and gauge coupling and bottom-tau unification.
Espinosa, Ismael; Gonzalez, Hortensia; Quiza, Jorge; Gonazalez, J. Jesus; Arroyo, Ruben; Lara, Ritaluz
1995-01-01
Oscillation of electrical activity has been found in many nervous systems, from invertebrates to vertebrates including man. There exists experimental evidence of very simple circuits with the capability of oscillation. Neurons with intrinsic oscillation have been found and also neural circuits where oscillation is a property of the network. These two types of oscillations coexist in many instances. It is nowadays hypothesized that behind synchronization and oscillation there is a system of coupled oscillators responsible for activities that range from locomotion and feature binding in vision to control of sleep and circadian rhythms. The huge knowledge that has been acquired on oscillators from the times of Lord Rayleigh has made the simulation of neural oscillators a very active endeavor. This has been enhanced with more recent physiological findings about small neural circuits by means of intracellular and extracellular recordings as well as imaging methods. The future of this interdisciplinary field looks very promising; some researchers are going into quantum mechanics with the idea of trying to provide a quantum description of the brain. In this work we describe some simulations using neuron models by means of which we form simple neural networks that have the capability of oscillation. We analyze the oscillatory activity with root locus method, cross-correlation histograms, and phase planes. In the more complicated neural network models there is the possibility of chaotic oscillatory activity and we study that by means of Lyapunov exponents. The companion paper shows an example of that kind.
Kraepelin and degeneration theory.
Hoff, Paul
2008-06-01
Emil Kraepelin's contribution to the clinical and scientific field of psychiatry is recognized world-wide. In recent years, however, there have been a number of critical remarks on his acceptance of degeneration theory in particular and on his political opinion in general, which was said to have carried "overtones of proto-fascism" by Michael Shepherd [28]. The present paper discusses the theoretical cornerstones of Kraepelinian psychiatry with regard to their relevance for Kraepelin's attitude towards degeneration theory. This theory had gained wide influence not only in scientific, but also in philosophical and political circles in the last decades of the nineteenth century. There is no doubt that Kraepelin, on the one hand, accepted and implemented degeneration theory into the debate on etiology and pathogenesis of mental disorders. On the other hand, it is not appropriate to draw a simple and direct line from early versions of degeneration theory to the crimes of psychiatrists and politicians during the rule of national socialism. What we need, is a differentiated view, since this will be the only scientific one. Much research needs to be done here in the future, and such research will surely have a significant impact not only on the historical field, but also on the continuous debate about psychiatry, neuroscience and neurophilosophy.
X-82 to Treat Age-related Macular Degeneration
2017-01-12
Age-Related Macular Degeneration (AMD); Macular Degeneration; Exudative Age-related Macular Degeneration; AMD; Macular Degeneration, Age-related, 10; Eye Diseases; Retinal Degeneration; Retinal Diseases
Atakishiyev, N.M. [Instituto de Matematicas. Universidad Nacional Autonoma de Mexico. Cuernavaca, Morelos (Mexico); Jafarov, E.I.; Nagiyev, S.M. [Institute of Physics, Azerbaijan Academy of Sciences. Baku, Azerbaijan (Azerbaijan); Wolf, K.B. [Instituto de Investigaciones en Matematicas Aplicadas y en Sistemas. Universidad Nacional Autonoma de Mexico. Cuernavaca, Morelos (Mexico)
1998-10-01
Meixner oscillators have a ground state and an energy spectrum that is equally spaced; they are a two-parameter family of models that satisfy a Hamiltonian equation with a difference operator. Meixner oscillators include as limits and particular cases the Charlier, Kravchuk and Hermite (common quantum-mechanical) harmonic oscillators. By the Sommerfeld-Watson transformation they are also related with a relativistic model of the linear harmonic oscillator, built in terms of the Meixner-Pollaczek polynomials, and their continuous weight function. We construct explicitly the corresponding coherent states with the dynamical symmetry group Sp(2,R). The reproducing kernel for the wavefunctions of these models is also found. (Author)
Maltseva, Elena; Petrignani, Annemieke; Candian, Alessandra; Mackie, Cameron J.; Huang, Xinchuan; Lee, Timothy J.; Tielens, Alexander G. G. M.; Oomens, Jos; Buma, Wybren Jan
2016-01-01
We report on an experimental and theoretical investigation of the importance of anharmonicity in the 3 micrometers CH stretching region of Polycyclic Aromatic Hydrocarbon (PAH) molecules. We present mass-resolved, high-resolution spectra of the gas-phase cold ((is) approximately 4K) linear PAH molecules naphthalene, anthracene, and tetracene. The measured IR spectra show a surprisingly high number of strong vibrational bands. For naphthalene, the observed bands are well separated and limited by the rotational contour, revealing the band symmetries. Comparisons are made to the harmonic and anharmonic approaches of the widely used Gaussian software. We also present calculated spectra of these acenes using the computational program SPECTRO, providing anharmonic predictions enhanced with a Fermi-resonance treatment that utilizes intensity redistribution. We demonstrate that the anharmonicity of the investigated acenes is strong, dominated by Fermi resonances between the fundamental and double combination modes, with triple combination bands as possible candidates to resolve remaining discrepancies. The anharmonic spectra as calculated with SPECTRO lead to predictions of the main modes that fall within 0.5% of the experimental frequencies. The implications for the Aromatic Infrared Bands, specifically the 3-m band are discussed.
On anharmonic and pressure corrections to the equilibrium isotopic constants for minerals
Polyakov, Veniamin B.
1998-09-01
Specifies of the calculations of the reduced isotopic partition function ratios (β-factor) of minerals are discussed. Comparative calculations in the framework of the fully harmonic, quasi-harmonic, and intrinsic anharmonic approximations show minor anharmonic corrections to the harmonic values of the β-factor. In the case of calcite, the difference between the fully harmonic and intrinsic anharmonic values of 10 3lnβ varies from 0.60 at 300 K to 0.37 at 1200 K and is close to typical values of the anharmonic correction in gas molecules. A new treatment for calculating isotopic effects in molar volumes of minerals and pressure effects on their β-factors is developed on the basis of the Mie-Grüneisen equation of state. There is no significant difference between the quasi-harmonic and intrinsic harmonic values of (∂lnβ/∂ P) T. For calcite, the pressure derivative of the β-factor is positive, decreases monotonically with temperature, and becomes small at T ˜ 1000 K (10 3(∂lnβ/ ∂P) T ≈ 0.1-0.15 GPa -1). These results contradict the large anharmonic and pressure effects to the β-factor of calcite calculated by Gillet et al. (1996) as well as their conclusion that the pressure correction to the β-factor of calcite is negative at higher temperatures and increases in its absolute value with increasing temperature.
Maltseva, Elena; Buma, Wybren Jan [University of Amsterdam, Science Park 904, 1098 XH Amsterdam (Netherlands); Petrignani, Annemieke; Candian, Alessandra; Mackie, Cameron J.; Tielens, Alexander G. G. M. [Leiden Observatory, Niels Bohrweg 2, 2333 CA Leiden (Netherlands); Huang, Xinchuan; Lee, Timothy J. [SETI Institute, 189 Bernardo Avenue, Suite 100, Mountain View, CA 94043 (United States); Oomens, Jos, E-mail: w.j.buma@uva.nl, E-mail: petrignani@strw.leidenuniv.nl [Radboud University, Toernooiveld 7, 6525 ED Nijmegen (Netherlands)
2015-11-20
We report on an experimental and theoretical investigation of the importance of anharmonicity in the 3-μm CH stretching region of polycyclic aromatic hydrocarbon (PAH) molecules. We present mass-resolved, high-resolution spectra of the gas-phase cold (∼4 K) linear PAH molecules naphthalene, anthracene, and tetracene. The measured IR spectra show a surprisingly high number of strong vibrational bands. For naphthalene, the observed bands are well separated and limited by the rotational contour, revealing the band symmetries. Comparisons are made to the harmonic and anharmonic approaches of the widely used Gaussian software. We also present calculated spectra of these acenes using the computational program SPECTRO, providing anharmonic predictions with a Fermi-resonance treatment that utilizes intensity redistribution. We demonstrate that the anharmonicity of the investigated acenes is strong, dominated by Fermi resonances between the fundamental and double combination modes, with triple combination bands as possible candidates to resolve remaining discrepancies. The anharmonic spectra as calculated with SPECTRO lead to predictions of the main bands that fall within 0.5% of the experimental frequencies. The implications for the aromatic infrared bands, specifically the 3-μm band, are discussed.
Effects of bulk and interfacial anharmonicity on thermal conductance at solid/solid interfaces
Le, Nam Q.; Polanco, Carlos A.; Rastgarkafshgarkolaei, Rouzbeh; Zhang, Jingjie; Ghosh, Avik W.; Norris, Pamela M.
2017-06-01
We present the results of classical molecular dynamics simulations to assess the relative contributions to interfacial thermal conductance from inelastic phonon processes at the interface and in the adjacent bulk materials. The simulated system is the prototypical interface between argon and "heavy argon" crystals, which enables comparison with many past computational studies. We run simulations interchanging the Lennard-Jones potential with its harmonic approximation to test the effect of anharmonicity on conductance. The results confirm that the presence of anharmonicity is correlated with increasing thermal conductance with temperature, which supports conclusions from prior experimental and theoretical work. However, in the model Ar/heavy-Ar system, anharmonic effects at the interface itself contribute a surprisingly small part of the total thermal conductance. The larger fraction of the thermal conductance at high temperatures arises from anharmonic effects away from the interface. These observations are supported by comparisons of the spectral energy density, which suggest that bulk anharmonic processes increase the interfacial conductance by thermalizing energy from modes with low transmission to modes with high transmission.
On Degenerate Partial Differential Equations
Chen, Gui-Qiang G.
2010-01-01
Some of recent developments, including recent results, ideas, techniques, and approaches, in the study of degenerate partial differential equations are surveyed and analyzed. Several examples of nonlinear degenerate, even mixed, partial differential equations, are presented, which arise naturally in some longstanding, fundamental problems in fluid mechanics and differential geometry. The solution to these fundamental problems greatly requires a deep understanding of nonlinear degenerate parti...
Hayashi, Kenta; Gotoda, Hiroshi; Okuno, Yuta; Tachibana, Shigeru; Tokyo University of Science Collaboration; Japan Aerospace Exploration Agency Collaboration
2015-11-01
We have experimentally investigated the degeneration process of combustion instability in a lean premixed gas-turbine model combustor on the basis of dynamical systems theory. Our previous study reported that with increasing the equivalence ratio, the dynamical behavior of combustion state close to lean blowout transits from stochastic fluctuations to periodic thermoacoustic combustion oscillations via low-dimensional chaotic oscillations. The further increase in the equivalence ratio gives rise to the quasi-periodic oscillations and the subsequent chaotic oscillations with small amplitudes. The route to chaotic oscillations is quantitatively shown by the use of nonlinear time series analysis involving the color recurrence plots, permutation entropy and local predictor.
Laenderyggens degeneration og radiologi
Jacobsen, Steffen; Gosvig, Kasper Kjaerulf; Sonne-Holm, Stig
2006-01-01
Low back pain (LBP) is one of the most common conditions, and at the same time one of the most complex nosological entities. The lifetime prevalence is approximately 80%, and radiological features of lumbar degeneration are almost universal in adults. The individual risk factors for LBP and signi......Low back pain (LBP) is one of the most common conditions, and at the same time one of the most complex nosological entities. The lifetime prevalence is approximately 80%, and radiological features of lumbar degeneration are almost universal in adults. The individual risk factors for LBP...... and significant relationships between radiological findings and subjective symptoms have both been notoriously difficult to identify. The lack of consensus on clinical criteria and radiological definitions has hampered the undertaking of properly executed epidemiological studies. The natural history of LBP...
Micheli, Fiorenza de [Centro de Estudios Cientificos, Arturo Prat 514, Valdivia (Chile); Instituto de Fisica, Pontificia Universidad Catolica de Valparaiso, Casilla 4059, Valparaiso (Chile); Zanelli, Jorge [Centro de Estudios Cientificos, Arturo Prat 514, Valdivia (Chile); Universidad Andres Bello, Av. Republica 440, Santiago (Chile)
2012-10-15
A degenerate dynamical system is characterized by a symplectic structure whose rank is not constant throughout phase space. Its phase space is divided into causally disconnected, nonoverlapping regions in each of which the rank of the symplectic matrix is constant, and there are no classical orbits connecting two different regions. Here the question of whether this classical disconnectedness survives quantization is addressed. Our conclusion is that in irreducible degenerate systems-in which the degeneracy cannot be eliminated by redefining variables in the action-the disconnectedness is maintained in the quantum theory: there is no quantum tunnelling across degeneracy surfaces. This shows that the degeneracy surfaces are boundaries separating distinct physical systems, not only classically, but in the quantum realm as well. The relevance of this feature for gravitation and Chern-Simons theories in higher dimensions cannot be overstated.
Role of anharmonicities and non-linearities in heavy ion collisions a microscopic approach
Lanza, E G; Catara, F; Chomaz, P; Volpe, C; Chomaz, Ph.
1996-01-01
Using a microscopic approach beyond RPA to treat anharmonicities, we mix two-phonon states among themselves and with one-phonon states. We also introduce non-linear terms in the external field. These non-linear terms and the anharmonicities are not taken into account in the "standard" multiphonon picture. Within this framework we calculate Coulomb excitation of 208Pb and 40Ca by a 208Pb nucleus at 641 and 1000MeV/A. We show with different examples the importance of the non-linearities and anharmonicities for the excitation cross section. We find an increase of 10 % for 208Pb and 20 % for 40Ca of the excitation cross section corresponding to the energy region of the double giant dipole resonance with respect to the "standard" calculation. We also find important effects in the low energy region. The predicted cross section in the DGDR region is found to be rather close to the experimental observation.
Anharmonicity effects in Cu-doped ZnO nanocombs by temperature-dependent Raman scattering
Kong, J. F.; Fan, D. H.; Shen, W. Z.
2016-09-01
Micro-Raman spectra of E 2(high) phonon mode in Cu-doped ZnO nanocombs have been presented in detail with different Cu compositions under the temperature ranging from 83 to 443 K grown by a simple catalyst-free chemical vapor deposition method. The alloy disorder effect has been investigated by analyzing the asymmetric broadening of E 2(high) phonon mode and Cu-induced localized vibration mode at room temperature. In addition, we resort to a theory model including the lattice thermal expansion and anharmonic phonon-phonon interaction, which can well describe the temperature dependence of Raman shift and linewidth of E 2(high) phonon. In combining with the theory model, we have revealed an increasing anharmonic effect on the Raman shift and linewidth behaviors with increasing Cu composition. Furthermore, it is found that the lifetime of E 2(high) phonon mode shortens with enhancing the anharmonicity.
Kashlev, Y.A., E-mail: yakashlev@yandex.ru
2017-04-15
Evolution of vibration relaxation of hydrogen atoms in metals with the close-packed lattice at high and medium temperatures is investigated based on non-equilibrium statistical thermodynamics, in that number on using the retarded two-time Green function method. In accordance with main kinetic equation – the generalized Fokker- Plank- Kolmogorov equation, anharmonism of hydrogen atoms vibration in potential wells does not make any contribution to collision effects. It influences the relaxation processes at the expense of interference of fourth order anharmonism with single-phonon scattering on impurity hydrogen atoms. Therefore, the total relaxation time of vibration energy of system metal-hydrogen is written as a product of two factors: relaxation time of system in harmonic approximation and dimensionless anharmonic attenuation of quantum hydrogen state.
Tadano, Terumasa [Department of Applied Physics, The University of Tokyo, Tokyo 113-8656 (Japan); Tsuneyuki, Shinji [Department of Physics, The University of Tokyo, Tokyo 113-0033 (Japan); Institute for Solid State Physics, The University of Tokyo, Kashiwa 277-8581 (Japan)
2015-12-31
We show a first-principles approach for analyzing anharmonic properties of lattice vibrations in solids. We firstly extract harmonic and anharmonic force constants from accurate first-principles calculations based on the density functional theory. Using the many-body perturbation theory of phonons, we then estimate the phonon scattering probability due to anharmonic phonon-phonon interactions. We show the validity of the approach by computing the lattice thermal conductivity of Si, a typical covalent semiconductor, and selected thermoelectric materials PbTe and Bi{sub 2}Te{sub 3} based on the Boltzmann transport equation. We also show that the phonon lifetime and the lattice thermal conductivity of the high-temperature phase of SrTiO{sub 3} can be estimated by employing the perturbation theory on top of the solution of the self-consistent phonon equation.
Aciksoz, E.; Bayrak, O. [Department of Physics, Akdeniz University, 07058 Antalya (Turkey); Soylu, A., E-mail: asimsoylu@gmail.com [Department of Physics, Nigde University, 51240 Nigde (Turkey)
2015-01-01
The impurity binding energy in the GaAs−Ga{sub 1−x}Al{sub x}As system is studied with an anharmonic type confinement potential by taking into account the influence of the external electric and magnetic fields within the framework of the effective mass approximation and asymptotic iteration method (AIM). The influence of the external electromagnetic fields and anharmonicity on a donor binding energy is examined systematically. It is shown that the donor binding energy is highly dependent on the external electric and magnetic fields and the confinement potential shapes. Both the electric and magnetic fields are increased, the binding energies increase for each of them. However, the behaviors of increase in the weak and strong fields’ regimes have different character a bit. Furthermore, when the more anharmonicity is considered, the binding energy of donor slightly increases as well.
Kashlev, Y. A.
2017-04-01
Evolution of vibration relaxation of hydrogen atoms in metals with the close-packed lattice at high and medium temperatures is investigated based on non-equilibrium statistical thermodynamics, in that number on using the retarded two-time Green function method. In accordance with main kinetic equation - the generalized Fokker- Plank- Kolmogorov equation, anharmonism of hydrogen atoms vibration in potential wells does not make any contribution to collision effects. It influences the relaxation processes at the expense of interference of fourth order anharmonism with single-phonon scattering on impurity hydrogen atoms. Therefore, the total relaxation time of vibration energy of system metal-hydrogen is written as a product of two factors: relaxation time of system in harmonic approximation and dimensionless anharmonic attenuation of quantum hydrogen state.
Cataracts and macular degeneration.
Shoch, D
1979-09-01
The intraocular lens restores general vision and some degree of independence and mobility to patients with dense cataracts and macular degeneration. The patient, however, must be repeatedly warned that fine central vision, particularly reading, will not be possible after the surgery. An aphakic spectacle leaves such patients a narrow band of vision when superimposed over the macular lesion, and contact lenses are too small for the patient to manage insertion without help.
Li, Fenfang; Nguyen, Dang Minh; Ohl, Claus-Dieter
2016-01-01
We report about an intriguing boiling regime occurring for small heaters embedded on the boundary in subcooled water. The microheater is realized by focusing a continuous wave laser beam to about $10\\,\\mu$m in diameter onto a 165\\,nm-thick layer of gold, which is submerged in water. After an initial vaporous explosion a single bubble oscillates continuously and repeatably at several $100\\,$kHz. The microbubble's oscillations are accompanied with bubble pinch-off leading to a stream of gaseous bubbles into the subcooled water. The self-driven bubble oscillation is explained with a thermally kicked oscillator caused by the non-spherical collapses and by surface pinning. Additionally, Marangoni stresses induce a recirculating streaming flow which transports cold liquid towards the microheater reducing diffusion of heat along the substrate and therefore stabilizing the phenomenon to many million cycles. We speculate that this oscillate boiling regime may allow to overcome the heat transfer thresholds observed dur...
Wang, Chenju; Gu, Jianbing; Kuang, Xiaoyu; Xiang, Shikai
2015-06-01
Nonlinear elastic properties of diamond-cubic silicon and germanium have not been investigated sufficiently to date. Knowledge of these properties not only can help us to understand nonlinear mechanical effects but also can assist us to have an insight into the related anharmonic properties, so we investigate the nonlinear elastic behaviour of single silicon and germanium by calculating their second- and third-order elastic constants. All the results of the elastic constants show good agreement with the available experimental data and other theoretical calculations. Such a phenomenon indicates that the present values of the elastic constants are accurate and can be used to further study the related anharmonic properties. Subsequently, the anharmonic properties such as the pressure derivatives of the second-order elastic constants, Grüneisen constants of long-wavelength acoustic modes, and ultrasonic nonlinear parameters are explored. All the anharmonic properties of silicon calculated in the present work also show good agreement with the existing experimental results; this consistency not only reveals that the calculation method of the anharmonic properties is feasible but also illuminates that the anharmonic properties obtained in the present work are reliable. For the anharmonic properties of germanium, since there are no experimental result and other theoretical data till now, we hope that the anharmonic properties of germanium first offered in this work would serve as a reference for future studies.
Wang, Chenju [Sichuan Univ., Chengdu (China). Inst. of Atomic and Molecular Physics; Institute of Fluid Physics, Sichuan (China). National Key Laboratory of Shock Wave and Detonation Physics; Gu, Jianbing [Institute of Fluid Physics, Sichuan (China). National Key Laboratory of Shock Wave and Detonation Physics; Sichuan Univ., Chengdu (China). College of Physical Science and Technology; Kuang, Xiaoyu [Sichuan Univ., Chengdu (China). Inst. of Atomic and Molecular Physics; Xiang, Shikai [Institute of Fluid Physics, Sichuan (China). National Key Laboratory of Shock Wave and Detonation Physics
2015-10-01
Nonlinear elastic properties of diamond-cubic silicon and germanium have not been investigated sufficiently to date. Knowledge of these properties not only can help us to understand nonlinear mechanical effects but also can assist us to have an insight into the related anharmonic properties, so we investigate the nonlinear elastic behaviour of single silicon and germanium by calculating their second- and third-order elastic constants. All the results of the elastic constants show good agreement with the available experimental data and other theoretical calculations. Such a phenomenon indicates that the present values of the elastic constants are accurate and can be used to further study the related anharmonic properties. Subsequently, the anharmonic properties such as the pressure derivatives of the second-order elastic constants, Grueneisen constants of long-wavelength acoustic modes, and ultrasonic nonlinear parameters are explored. All the anharmonic properties of silicon calculated in the present work also show good agreement with the existing experimental results; this consistency not only reveals that the calculation method of the anharmonic properties is feasible but also illuminates that the anharmonic properties obtained in the present work are reliable. For the anharmonic properties of germanium, since there are no experimental result and other theoretical data till now, we hope that the anharmonic properties of germanium first offered in this work would serve as a reference for future studies.
Transition from the Seniority to the Anharmonic Vibrator Regime in Nuclei
Bijker, R; Pittel, S
1996-01-01
A recent analysis of experimental energy systematics suggests that all collective nuclei fall into one of three classes -- seniority, anharmonic vibrational, or rotational -- with sharp phase transitions between them. We investigate the transition from the seniority to the anharmonic vibrator regime within a shell model framework involving a single large j-orbit. The calculations qualitatively reproduce the observed transitional behavior, both for U(5) like and O(6) like nuclei. They also confirm the preeminent role played by the neutron-proton interaction in producing the phase transition.
Anharmonic-potential-effective-charge approach for computing Raman cross sections of a gas
Kutteh, Ramzi; van Zandt, L. L.
1993-05-01
An anharmonic-potential-effective-charge approach for computing relative Raman intensities of a gas is developed. The equations of motion are set up and solved for the driven anharmonic molecular vibrations. An explicit expression for the differential polarizability tensor is derived and its properties discussed. This expression is then used within the context of Placzek's theory [Handbuch der Radiologie (Akademische Verlagsgesellschaft, Leipzig, 1934), Vol. VI] to compute the Raman cross section and depolarization ratio of a gas. The computation is carried out for the small molecules CO2, CS2, SO2, and CCl4; results are compared with experimental measurements and discussed.
Design of blade-shaped-electrode linear ion traps with reduced anharmonic contributions
Deng, K.; Che, H.; Ge, Y. P.; Xu, Z. T.; Yuan, W. H.; Zhang, J.; Lu, Z. H., E-mail: zehuanglu@mail.hust.edu.cn [MOE Key Laboratory of Fundamental Physical Quantities Measurement, School of Physics, Huazhong University of Science and Technology, 1037 Luoyu Road, Wuhan 430074 (China); Lan, Y. [MOE Key Laboratory of Fundamental Physical Quantities Measurement, School of Physics, Huazhong University of Science and Technology, 1037 Luoyu Road, Wuhan 430074 (China); Department of Physics and Astronomy, University of British Columbia, Vancouver, BC V6T 1Z1 (Canada)
2015-09-21
RF quadrupole linear Paul traps are versatile tools in quantum physics experiments. Linear Paul traps with blade-shaped electrodes have the advantages of larger solid angles for fluorescence collection. But with these kinds of traps, the existence of higher-order anharmonic terms of the trap potentials can cause large heating rate for the trapped ions. In this paper, we theoretically investigate the dependence of higher-order terms of trap potentials on the geometry of blade-shaped traps, and offer an optimized design. A modified blade electrodes trap is proposed to further reduce higher-order anharmonic terms while still retaining large fluorescence collection angle.
The influence of anharmonic phonons on the isotope effect in high-{Tc} oxides
Crespi, V.H.; Cohen, M.L.
1992-01-01
Anharmonic phonons are examined to study the unusual isotope effect exponents for the high-{Tc} oxides. Within a simple model of anharmonicity, the mass dependences of the electron-phonon coupling constant {lambda} and the phonon frequency determine the isotope effect exponent {alpha} as a function of coupling strength. A model in which the outer wells of a multiple-well potential deepen as the orthorhombic/low temperature tetragonal phase transition in La{sub 2-x}M{sub x}CuO{sub 4} is approached is consistent with some experimentally observed variations in {Tc} and {alpha}. 10 refs.
The influence of anharmonic phonons on the isotope effect in high- Tc oxides
Crespi, V.H.; Cohen, M.L.
1992-01-01
Anharmonic phonons are examined to study the unusual isotope effect exponents for the high-{Tc} oxides. Within a simple model of anharmonicity, the mass dependences of the electron-phonon coupling constant {lambda} and the phonon frequency determine the isotope effect exponent {alpha} as a function of coupling strength. A model in which the outer wells of a multiple-well potential deepen as the orthorhombic/low temperature tetragonal phase transition in La{sub 2-x}M{sub x}CuO{sub 4} is approached is consistent with some experimentally observed variations in {Tc} and {alpha}. 10 refs.
Trigonometric protocols for shortcuts to adiabatic transport of cold atoms in anharmonic traps
Li, Jing; Zhang, Qi; Chen, Xi
2017-10-01
Shortcuts to adiabaticity have been proposed to speed up the ;slow; adiabatic transport of ultracold atoms. Their realizations, using inverse engineering protocols, provide families of trajectories with appropriate boundary conditions. These trajectories can be optimized with respect to the operation time and the energy input. In this paper we propose trigonometric protocols for fast and robust atomic transport, taking into account cubic or quartic anharmonicities of the trapping potential. Numerical analysis demonstrates that this choice of the trajectory minimizes the final residual energy efficiently, and shows extraordinary robustness against anharmonic parameters. These results might be of interest for the state-of-the-art experiments on ultracold atoms and ions.
Absolute Helmholtz free energy of highly anharmonic crystals: theory vs Monte Carlo.
Yakub, Lydia; Yakub, Eugene
2012-04-14
We discuss the problem of the quantitative theoretical prediction of the absolute free energy for classical highly anharmonic solids. Helmholtz free energy of the Lennard-Jones (LJ) crystal is calculated accurately while accounting for both the anharmonicity of atomic vibrations and the pair and triple correlations in displacements of the atoms from their lattice sites. The comparison with most precise computer simulation data on sublimation and melting lines revealed that theoretical predictions are in excellent agreement with Monte Carlo simulation data in the whole range of temperatures and densities studied.
Anharmonic vibrations of the dicarbon antisite defect in 4H-SiC
Yan, F.; Devaty, R. P.; Choyke, W. J. [Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, Pennsylvania 15260 (United States); Gali, A. [Research Institute for Solid State Physics and Optics, Hungarian Academy of Sciences, P.O. Box 49, H-1525 Budapest (Hungary); Kimoto, T. [Department of Electronic Science and Engineering, Kyoto University, Katsura, Nishikyo, Kyoto 615-8510 (Japan); Ohshima, T. [Japan Atomic Energy Agency, 1233 Watanuki, Takasaki, Gunma 370-1292 (Japan); Pensl, G. [Lehrstuhl fuer Angewandte Physik, Universitaet Erlangen-Nuernberg, Staudstr. 7/A3 Erlangen (Germany)
2012-03-26
Dicarbon antisite defects were created by either electron irradiation or ion implantation into 4H-SiC. The no-phonon lines from the dicarbon antisite defect center were observed with their phonon replicas. The stretch frequencies of the defect were observed up to the fifth harmonic. The Morse potential model accounts for the anharmonicity quite well and gives a very good prediction of the vibration energies up to the fifth harmonic with an error of less than 1%. First principles calculations show that the model of a dicarbon antisite defect along with its four nearest neighboring carbon atoms can explain the observed anharmonicity.
Geometric phases for non-degenerate and degenerate mixed states
Singh, K; Basu, K; Chen, J L; Du Jiang Feng
2003-01-01
This paper focuses on the geometric phase of general mixed states under unitary evolution. Here we analyze both non-degenerate as well as degenerate states. Starting with the non-degenerate case, we show that the usual procedure of subtracting the dynamical phase from the total phase to yield the geometric phase for pure states, does not hold for mixed states. To this end, we furnish an expression for the geometric phase that is gauge invariant. The parallelity conditions are shown to be easily derivable from this expression. We also extend our formalism to states that exhibit degeneracies. Here with the holonomy taking on a non-abelian character, we provide an expression for the geometric phase that is manifestly gauge invariant. As in the case of the non-degenerate case, the form also displays the parallelity conditions clearly. Finally, we furnish explicit examples of the geometric phases for both the non-degenerate as well as degenerate mixed states.
Ultrafast Degenerate Transient Lens Spectroscopy in Semiconductor Nanosctructures
Leontyev A.V.
2015-01-01
Full Text Available We report the non-resonant excitation and probing of the nonlinear refractive index change in bulk semiconductors and semiconductor quantum dots through degenerate transient lens spectroscopy. The signal oscillates at the center laser field frequency, and the envelope of the former in quantum dots is distinctly different from the one in bulk sample. We discuss the applicability of this technique for polarization state probing in semiconductor media with femtosecond temporal resolution.
Origin of the large anharmonicity in the phonon modes of LiBH{sub 4}
Gremaud, R.; Züttel, A. [Empa, Swiss Federal Laboratories for Materials Science and Technology, Laboratory 505 (Hydrogen and Energy), Überlandstrasse 129, CH-8600 Dübendorf (Switzerland); Borgschulte, A., E-mail: andreas.borgschulte@empa.ch [Empa, Swiss Federal Laboratories for Materials Science and Technology, Laboratory 505 (Hydrogen and Energy), Überlandstrasse 129, CH-8600 Dübendorf (Switzerland); Ramirez-Cuesta, A.J.; Refson, K. [Chemical and Engineering Materials Division, Neutron Sciences Directorate, Oak Ridge National Laboratory, PO Box 2008, MS 6473 Oak Ridge (United States); Colognesi, D. [Istituto dei Sistemi Complessi – sezione di Firenze, Consiglio Nazionale delle Ricerche, via Madonna del piano 10, 50019 Sesto Fiorentino (Italy)
2013-12-12
Highlights: • IR, Raman, and INS spectroscopy data and corresponding DFT-calculations on LiBH4. • Mismatch between experiment and theory are due to anharmonicity. • Strong anharmonic effects can be expected for vibrations with high H amplitude. - Abstract: The dynamics and bonding of the complex hydride LiBH{sub 4} have been investigated by vibrational spectroscopy and density functional theory (DFT). The combination of infrared, Raman, and inelastic neutron-scattering (INS) spectroscopies on hydrided and deuterated samples reveals a complete picture of the dynamics of the BH{sub 4}{sup −} ions as well as of the lattice. Particular emphasis is laid on a comparison between experiment and theory, revealing significant discrepancy between the two approaches for vibrations with high anharmonicity, which is related to large vibrational amplitudes. The latter is typical for librational modes in molecular crystals and pseudo-ionic crystals such as complex hydrides. The presented strategy for anharmonic frequency corrections might thus be generally applicable for this kind of materials.
Probing anharmonic properties of nuclear surface vibration by heavy-ion fusion reactions
Takigawa, N; Kuyucak, S
1997-01-01
Describing fusion reactions between ^{16}O and ^{154}Dy and, between ^{16}O and ^{144}Sm by the $sd-$ and $sdf-$ interacting boson model, we show that heavy-ion fusion reactions are strongly affected by anharmonic properties of nuclear surface vibrations and nuclear shape, and thus provide a powerful method to study details of nuclear structure and dynamics.
Periodic permanent waves in an anharmonic chain with nearest-neighbour interaction
Valkering, T.P.
1978-01-01
The existence of longitudinal periodic permanent waves in a one-dimensional translationally invariant anharmonic chain with nearest-neighbour interaction is established by means of variational methods. A general expression for the energy is given in terms of the dispersion relation. The interaction
Quantum statistics and anharmonicity in the thermodynamics of spin waves in ferromagnetic metals
Wen, Haohua; Woo, C. H.
2016-09-01
The average energy needed to create a magnon is high in ferromagnetic metals due to the high-strength spin stiffness, which results in strong quantization effects that could be important even at thousands of degrees. To take into account quantum statistics at such high temperatures, the associated effects of anharmonicity of the spin vibrations must be taken into account. In addition to the complex nature of such effects, anharmonicity also affects the occupation of the density of state of the vibration states in the context of quantum statistics. Thus, an unoccupied vibration state might become occupied when its spring stiffness is substantially reduced with anharmonicity. Combined effects of quantum statistics and anharmonicity are expected. In this regard, the thermodynamics of ferromagnetic metals are investigated in this paper through the example of bcc iron between 10 and 1400 K. Theoretical analysis and spin-lattice dynamic simulations are performed, through which the physics behind the complex and dramatic temperature dependence of the thermodynamic functions of bcc iron is understood.
Local anharmonic vibrations strong correlations and superconductivity : a quantum simulation study
Frick, M.; Linden, W. von der; Morgenstern, I.; Raedt, H. de
1990-01-01
We investigate the importance of local anharmonic vibrations of the bridging oxygen in the copper oxide high-Tc materials in the context of superconductivity. For the numerical simulation we employ the projector quantum Monte Carlo method to study the ground state properties of the coupled electron-
Oscillation death in coupled oscillators
Wei ZOU; Xin-gang WANG; Qi ZHAO; Meng ZHAN
2009-01-01
We study dynamical behaviors in coupled nonlinear oscillators and find that under certain condi- tions, a whole coupled oscillator system can cease oscil- lation and transfer to a globally nonuniform stationary state [I.e., the so-called oscillation death (OD) state], and this phenomenon can be generally observed. This OD state depends on coupling strengths and is clearly differ- ent from previously studied amplitude death (AD) state, which refers to the phenomenon where the whole system is trapped into homogeneously steady state of a fixed point, which already exists but is unstable in the ab- sence of coupling. For larger systems, very rich pattern structures of global death states are observed. These Turing-like patterns may share some essential features with the classical Turing pattern.
Kuliev, I G
2002-01-01
One studied the effect of normal processes of electron-electron and phonon-phonon scattering on relaxation of quasi-particle pulse in nonequilibrium electron-phonon systems of degenerate semiconductors. One solved a system of kinetic equations for electron and phonon functions of distribution and calculated kinetic coefficients degeneration parameter. One analyzed the effect of normal processes of quasi-particle scattering on electric conductivity, thermo-emf and heat conductivity of degenerate semiconductors. One took account of redistribution of phonon pulse in N-processes of phonon-phonon scattering both inside every oscillating particle and between phonon different oscillating branches
The origin of phonon anharmonicity in MgB{sub 2} and related compounds
Boeri, L [INFM Center for Statistical Mechanics and Complexity and Dipartimento di Fisica, Universita di Roma ' La Sapienza' , Piazzale A. Moro 2, 00185 Rome (Italy); Bachelet, G B [INFM Center for Statistical Mechanics and Complexity and Dipartimento di Fisica, Universita di Roma ' La Sapienza' , Piazzale A. Moro 2, 00185 Rome (Italy); Cappelluti, E [INFM Center for Statistical Mechanics and Complexity and Dipartimento di Fisica, Universita di Roma ' La Sapienza' , Piazzale A. Moro 2, 00185 Rome (Italy); Pietronero, L [INFM Center for Statistical Mechanics and Complexity and Dipartimento di Fisica, Universita di Roma ' La Sapienza' , Piazzale A. Moro 2, 00185 Rome (Italy)
2003-02-01
The recent discovery of a superconducting transition at 39 K in MgB{sub 2} - made of alternating Mg and graphene-like B planes - has raised great interest, for both its technological and theoretical implications. It was clear since the very beginning that the properties of this material are related to an anomalous coupling between the charge carriers in the {sigma} bands - due to in-plane bonds between Boron atoms - and the phonon mode (E{sub 2g}) which involves in-plane vibrations of the B ions. Theoretical studies have thus been focused on the search for possible anomalies in the e-ph coupling: one of the first results was the discovery that the E{sub 2g} phonon is highly anharmonic, but the connection between anharmonicity and T{sub c} in this material is still a controversial point. We first present a detailed first-principles study of the E{sub 2g} phonon anharmonicity in MgB{sub 2} and analogous compounds which are not superconducting, AlB{sub 2} and graphite, and in a hypothetical hole-doped graphite (C{sup 2+}{sub 2}); we then introduce an analytical model which allows us to relate the onset of anharmonicity with the small Fermi energy of the carriers in {sigma} bands. Our study suggests a possible relation between anharmonicity and non-adiabaticity; non-adiabatic effects, which can lead to a sensible increase of T{sub c} with respect to values predicted by conventional theory, become in fact relevant when phonon frequencies are comparable to electronic energy scales.
Seifitokaldani, Ali; Gheribi, Aïmen E.; Dollé, Mickael
2016-12-01
It has been already shown that the density functional theory (DFT) combined with the quasi-harmonic approximation (QHA) overestimates the specific heat capacity (and in general the thermal properties) of fcc metals. DFT + QHA seemingly shows a large anharmonic contribution to the heat capacity. However, in this article we show that this anharmonicity has no physical origin and it is a consequence of the deviation of the QHA from the Maxwell relations. We show that one can simply avoid this overestimation by enforcing the QHA method to obey the Maxwell relations throughout the thermodynamically self-consistent (TSC) method, instead of considering non-real local anharmonic effects.
G. Bellini
2014-01-01
Full Text Available In the last decades, a very important breakthrough has been brought about in the elementary particle physics by the discovery of the phenomenon of the neutrino oscillations, which has shown neutrino properties beyond the Standard Model. But a full understanding of the various aspects of the neutrino oscillations is far to be achieved. In this paper the theoretical background of the neutrino oscillation phenomenon is described, referring in particular to the paradigmatic models. Then the various techniques and detectors which studied neutrinos from different sources are discussed, starting from the pioneering ones up to the detectors still in operation and to those in preparation. The physics results are finally presented adopting the same research path which has been crossed by this long saga. The problems not yet fixed in this field are discussed, together with the perspectives of their solutions in the near future.
Intervertebral disc degeneration in dogs
Bergknut, Niklas
2011-01-01
Back pain is common in both dogs and humans, and is often associated with intervertebral disc (IVD) degeneration. The IVDs are essential structures of the spine and degeneration can ultimately result in diseases such as IVD herniation or spinal instability. In order to design new treatments halting
LUO Xin-Lian; BAI Hua; ZHAO Lei
2008-01-01
Regardless of the formation mechanism, an exotic object, the double degenerate star (DDS), is introduced and investigated, which is composed of baryonic matter and some unknown fermion dark matter. Different from the simple white dwarfs (WDs), there is additional gravitational force provided by the unknown fermion component inside DDSs, which may strongly affect the structure and the stability of such kind of objects. Many possible and strange observational phenomena connecting with them are concisely discussed. Similar to the normal WD, this object can also experience thermonuclear explosion as type Ia supernova explosion when DDS's mass exceeds the maximum mass that can be supported by electron degeneracy pressure. However, since the total mass of baryonic matter can be much lower than that of WD at Chandrasekhar mass limit, the peak luminosity should be much dimmer than what we expect before, which may throw a slight shadow on the standard candle of SN Ia in the research of cosmology.
Nayfeh, Ali Hasan
1995-01-01
Nonlinear Oscillations is a self-contained and thorough treatment of the vigorous research that has occurred in nonlinear mechanics since 1970. The book begins with fundamental concepts and techniques of analysis and progresses through recent developments and provides an overview that abstracts and introduces main nonlinear phenomena. It treats systems having a single degree of freedom, introducing basic concepts and analytical methods, and extends concepts and methods to systems having degrees of freedom. Most of this material cannot be found in any other text. Nonlinear Oscillations uses sim
Freire, Joana G.; Cabeza, Cecilia; Marti, Arturo; Pöschel, Thorsten; Gallas, Jason A. C.
2013-06-01
The investigation of regular and irregular patterns in nonlinear oscillators is an outstanding problem in physics and in all natural sciences. In general, regularity is understood as tantamount to periodicity. However, there is now a flurry of works proving the existence of ``antiperiodicity'', an unfamiliar type of regularity. Here we report the experimental observation and numerical corroboration of antiperiodic oscillations. In contrast to the isolated solutions presently known, we report infinite hierarchies of antiperiodic waveforms that can be tuned continuously and that form wide spiral-shaped stability phases in the control parameter plane. The waveform complexity increases towards the focal point common to all spirals, a key hub interconnecting them all.
Facts about Age-Related Macular Degeneration
... Degeneration (AMD) > Facts About Age-Related Macular Degeneration Facts About Age-Related Macular Degeneration This information was ... an Eye Care Professional Last Reviewed: September 2015 Fact Sheet Blurb The National Eye Institute (NEI) is ...
Gotoda, Hiroshi; Okuno, Yuta; Hayashi, Kenta; Tachibana, Shigeru
2015-11-01
We present a detailed study on the characterization of the degeneration process in combustion instability based on dynamical systems theory. We deal with combustion instability in a lean premixed-type gas-turbine model combustor, one of the fundamentally and practically important combustion systems. The dynamic behavior of combustion instability in close proximity to lean blowout is dominated by a stochastic process and transits to periodic oscillations created by thermoacoustic combustion oscillations via chaos with increasing equivalence ratio [Chaos 21, 013124 (2011); Chaos 22, 043128 (2012)]. Thermoacoustic combustion oscillations degenerate with a further increase in the equivalence ratio, and the dynamic behavior leads to chaotic fluctuations via quasiperiodic oscillations. The concept of dynamical systems theory presented here allows us to clarify the nonlinear characteristics hidden in complex combustion dynamics.
Surpassing Fundamental Limits of Oscillators Using Nonlinear Resonators
Villanueva, L. G.; Kenig, E.; Karabalin, R. B.; Matheny, M. H.; Lifshitz, Ron; Cross, M. C.; Roukes, M. L.
2013-01-01
In its most basic form an oscillator consists of a resonator driven on resonance, through feedback, to create a periodic signal sustained by a static energy source. The generation of a stable frequency, the basic function of oscillators, is typically achieved by increasing the amplitude of motion of the resonator while remaining within its linear, harmonic regime. Contrary to this conventional paradigm, in this Letter we show that by operating the oscillator at special points in the resonator’s anharmonic regime we can overcome fundamental limitations of oscillator performance due to thermodynamic noise as well as practical limitations due to noise from the sustaining circuit. We develop a comprehensive model that accounts for the major contributions to the phase noise of the nonlinear oscillator. Using a nano-electromechanical system based oscillator, we experimentally verify the existence of a special region in the operational parameter space that enables suppressing the most significant contributions to the oscillator’s phase noise, as predicted by our model. PMID:23679770
Schirò, G.; Cupane, A.
2016-05-01
Proteins, the nano-machines of living systems, are highly dynamic molecules. The time-scale of functionally relevant motions spans over a very broad range, from femtoseconds to several seconds. In particular, the pico- to nanoseconds region is characterized by side-chain and backbone anharmonic fluctuations that are responsible for many biological tasks like ligand binding, substrate recognition and enzymatic activity. Neutron scattering on hydrated protein powders reveals two main activations of anharmonic dynamics, characterized by different onset temperature and amplitude. Here we review our work on synthetic polypeptides, native proteins, and single amino acids to identify the physical origin of the two onsets -one involving water-independent local dynamics of methyl groups and, to a minor extent, of aromatic side-chains, and the other one, known as "protein dynamical transition", concerning large scale functional protein fluctuations, most likely induced by a crossover in the structure and dynamics of hydration water connected with the second critical point hypothesis.
Zhang, Yiqi; Liu, Xing; Belić, Milivoj R; Zhong, Weiping; Wen, Feng; Zhang, Yanpeng
2015-08-15
We analytically and numerically investigate an anharmonic propagation of two-dimensional beams in a harmonic potential. We pick noncentrosymmetric beams of common interest that carry orbital angular momentum. The examples studied include superposed Bessel-Gauss (BG), Laguerre-Gauss (LG), and circular Airy (CA) beams. For the BG beams, periodic inversion, phase transition, and rotation with periodic angular velocity are demonstrated during propagation. For the LG and CA beams, periodic inversion and variable rotation are still there but not the phase transition. On the whole, the "center of mass" and the orbital angular momentum of a beam exhibit harmonic motion, but the motion of the beam intensity distribution in detail is subject to external and internal torques and forces, causing it to be anharmonic. Our results are applicable to other superpositions of finite circularly asymmetric beams.
Role of anharmonicities of nuclear vibrations in fusion reactions at subbarrier energies
Hagino, K; Kuyucak, S
1997-01-01
We discuss the effects of double octupole and quadrupole phonon excitations in $^{144}$Sm on fusion reactions between $^{16}$O and $^{144}$Sm at subbarrier energies. The effects of anharmonicities of the vibrational states are taken into account by using the $sdf$-interacting boson model. We compare the results with those in the harmonic limit to show that anharmonicities play an essential role in reproducing the experimental fusion barrier distribution. From the analysis of the high quality fusion data available for this system, we deduce negative static quadrupole moments for both the first 2$^{+}$ and 3$^{-}$ states in $^{144}$Sm. This is the first time that the sign of static quadrupole moments of phonon states in a spherical nucleus is determined from the data of subbarrier fusion reactions.
Low-temperature anharmonicity of barium titanate: A path-integral molecular-dynamics study
Geneste, Grégory; Dammak, Hichem; Hayoun, Marc; Thiercelin, Mickael
2013-01-01
We investigate the influence of quantum effects on the dielectric and piezoelectric properties of barium titanate in its (low-temperature) rhombohedral phase, and show the strongly anharmonic character of this system even at low temperature. For this purpose, we perform path-integral molecular-dynamics simulations under fixed pressure and fixed temperature, using an efficient Langevin thermostat-barostat, and an effective Hamiltonian derived from first-principles calculations. The quantum fluctuations are shown to significantly enhance the static dielectric susceptibility (≈ by a factor of 2) and the piezoelectric constants, reflecting the strong anharmonicity of this ferroelectric system even at very low temperature. The slow temperature-evolution of the dielectric properties observed below ≈100 K is attributed (i) to zero-point energy contributions and (ii) to harmonic behavior if the quantum effects are turned off.
Temperature dependence of Raman scattering and anharmonic properties in LiNbO{sub 3}
Kokanyan, Ninel; Chapron, David; Fontana, Marc D. [Universite de Lorraine, Laboratoire Materiaux Optiques, Photonique et Systemes (LMOPS), Metz (France); Supelec, Laboratoire Materiaux Optiques, Photonique et Systemes (LMOPS), Metz (France)
2014-11-15
The temperature dependence of the Raman spectrum in LiNbO{sub 3} is investigated from 100 to 700 K. The various sources of asymmetry of Raman bands and artefacts are discussed before analyzing the temperature dependence of A{sub 1} and E first-order phonon lines. The phonon frequency downshift and damping increase on heating are interpreted in terms of normal volume expansion and third- and fourth-order anharmonic potentials. Anharmonic contributions are highly anisotropic and mainly explain the temperature dependences of both frequency and damping of A{sub 1} optical vibrational modes along the ferroelectric axis. Results are consistent with Caciuc et al. (Phys Rev B 61:8806, 2000) predictions. (orig.)
Anharmonic vibrational studies of L-aspartic acid using HF and DFT calculations
Alam, Mohammad Jane; Ahmad, Shabbir
2012-10-01
The experimental and theoretical studies on the structure, molecular properties and vibrational spectra of L-aspartic acid are presented. The molecular structure, harmonic and anharmonic vibrational frequencies, molecular properties, MEP mapping, NBO analysis and electronic spectra of L-aspartic acid have been reported. Computed geometrical parameters and anharmonic frequencies of fundamental, combination and overtone transitions were found in satisfactory agreement with the experimental data. The UV-Vis spectrum of present molecule has been recorded and the electronic properties such as HOMO and LUMO energies and few low lying excited states were carried out by using time dependent density functional theory (TD-DFT) approach. Natural Bond Orbital (NBO) analysis has been performed for analyzing charge delocalization throughout the molecule. Molecular electrostatic potential map has also been used for quantitative measure of the chemical activities of various sites of the molecule.
Simplified generalized-gradient approximation and anharmonicity: Benchmark calculations on molecules
Patton, David C.; Porezag, Dirk V.; Pederson, Mark R.
1997-03-01
Recent implementational improvements of the generalized-gradient approximation (GGA) have led to a simplified version which is parametrized entirely from fundamental constants, easier to use, and possibly easier to improve. We have performed detailed calculations on the geometries, atomization energies, vibrational energies, and infrared and Raman spectra of many first- and second-row dimers as well as some polyatomic molecules. For atomization and vibrational energies, we find that the simplified version of GGA leads to results similar to the original version. We comment on the fact that GGA-induced changes of hydrogenic bonding are different than for the other atoms in the periodic table but still an improvement over the local approximations to density-functional theory. In addition to a harmonic treatment of the vibrational modes we include the contributions of anharmonicity as well. With the exception of the light hydrogen containing molecules anharmonic corrections are quite small.
Multi-photon dressing of an anharmonic superconducting many-level quantum circuit
Braumueller, Jochen; Cramer, Joel; Schloer, Steffen; Rotzinger, Hannes; Radtke, Lucas; Lukashenko, Alexander; Yang, Ping; Skacel, Sebastian; Probst, Sebastian; Weides, Martin [Karlsruhe Institute of Technology (KIT), Physikalisches Institut, 76131 Karlsruhe (Germany); Marthaler, Michael; Guo, Lingzhen [Karlsruhe Institute of Technology (KIT), Institut fuer Theoretische Festkoerperphysik, 76131 Karlsruhe (Germany); Ustinov, Alexey V. [Karlsruhe Institute of Technology (KIT), Physikalisches Institut, 76131 Karlsruhe (Germany); National University of Science and Technology MISIS, Moscow 119049 (Russian Federation)
2015-07-01
We report on the investigation of a superconducting anharmonic multi-level circuit that is coupled to a harmonic readout resonator. We observe multi-photon transitions via virtual energy levels of our system up to the fifth excited state. The back-action of these higher-order excitations on our readout device is analyzed quantitatively and demonstrated to be in accordance with theoretical expectation. By applying a strong microwave drive we achieve multi-photon dressing of our system which is dynamically coupled by a weak probe tone. The emerging higher-order Rabi sidebands and associated Autler-Townes splittings involving up to five levels of the investigated anharmonic circuit are observed. Experimental results are in good agreement with master equation simulations.
[Age related macular degeneration].
Sayen, Alexandra; Hubert, Isabelle; Berrod, Jean-Paul
2011-02-01
Age-related macular degeneration (ARMD) is a multifactorial disease caused by a combination of genetic and environmental factors. It is the first cause of blindness in patients over 50 in the western world. The disease has been traditionally classified into early and late stages with dry (atrophic) and wet (neovascular) forms: neovascular form is characterized by new blood vessels development under the macula (choroidal neovascularisation) which lead to a rapid decline of vision associated with metamorphopsia and requiring an urgent ophtalmological examination. Optical coherence tomography is now one of the most important part of the examination for diagnosis and treatment. Patient with age related maculopathy should consider taking a dietary supplement such that used in AREDS. The treatment of the wet ARMD has largely beneficied since year 2006 of anti-VEGF (vascular endothelial growth factor) molecules such as ranibizumab or bevacizumab given as repeated intravitreal injections. A systematic follow up each 4 to 8 week in required for several years. There is no effective treatment at the moment for dry AMD. For patients with binocular visual acuity under 60/200 rehabilitation includes low vision specialist, vision aids and psychological support.
System-reservoir theory with anharmonic baths: a perturbative approach
Bhadra, Chitrak; Banerjee, Dhruba
2016-04-01
In this paper we develop the formalism of a general system coupled to a reservoir (the words ‘bath’ and ‘reservoir’ will be used interchangeably) consisting of nonlinear oscillators, based on perturbation theory at the classical level, by extending the standard Zwanzig approach of elimination of bath degrees of freedom order by order in perturbation. We observe that the fluctuation dissipation relation (FDR) of the second kind in its standard form for harmonic baths gets modified due to the nonlinearity and this is manifested through higher powers of {{k}\\text{B}}T in the expression for two-time noise correlation. On the flip side, this very modification allows us to define a dressed (renormalized) system-bath coupling that depends on the temperature and the nonlinear parameters of the bath in such a way that the structure of the FDR (of the second kind) is maintained. As an aside, we also observe that the first moment of the noise arising from a nonlinear bath can be non-zero, even in the absence of any external drive, if the reservoir potential is asymmetric with respect to one of its minima, about which one builds up the perturbation theory.
Do non-relativistic neutrinos oscillate?
Akhmedov, Evgeny
2017-07-01
We study the question of whether oscillations between non-relativistic neutrinos or between relativistic and non-relativistic neutrinos are possible. The issues of neutrino production and propagation coherence and their impact on the above question are discussed in detail. It is demonstrated that no neutrino oscillations can occur when neutrinos that are non-relativistic in the laboratory frame are involved, except in a strongly mass-degenerate case. We also discuss how this analysis depends on the choice of the Lorentz frame. Our results are for the most part in agreement with Hinchliffe's rule.
Two-Dimensional Anharmonic Crystal Lattices: Solitons, Solectrons, and Electric Conduction
Velarde, Manuel G.; Ebeling, Werner; Chetverikov, Alexander P.
2011-01-01
Reported here are salient features of soliton-mediated electron transport in anharmonic crystal lattices.After recalling how an electron-soliton bound state (solectron) can be formed we comment on consequences like electron surfing on a sound wave and balistic transport, possible percolation in 2d lattices, and a novel form of electron pairing with strongly correlated electrons both in real space and momentum space.
Anharmonic effects in light scattering due to optical phonons in silicon
Balkanski, M.; Wallis, R. F.; Haro, E.
1983-08-01
Systematic measurements by light scattering of the linewidth and frequency shift of the q-->=0 optical phonon in silicon over the temperature range of 5-1400 K are presented. Both the linewidth and frequency shift exhibit a quadratic dependence on temperature at high temperatures. This indicates the necessity of including terms in the phonon proper self-energy corresponding to four-phonon anharmonic processes.
Resonant bonding driven giant phonon anharmonicity and low thermal conductivity of phosphorene
Qin, Guangzhao; Zhang, Xiaoliang; Yue, Sheng-Ying; Qin, Zhenzhen; Wang, Huimin; Han, Yang; Hu, Ming
2016-10-01
Two-dimensional (2D) phosphorene, which possesses fascinating physical and chemical properties distinctively different from other 2D materials, calls for a fundamental understanding of thermal transport properties for its rapidly growing applications in nano- and optoelectronics and thermoelectrics. However, even the basic phonon property, for example, the exact value of the lattice thermal conductivity (κ ) of phosphorene reported in the literature, can differ unacceptably by one order of magnitude. More importantly, the fundamental physics underlying its unique properties such as strong phonon anharmonicity and unusual anisotropy remains largely unknown. In this paper, based on the analysis of electronic structure and lattice dynamics from first principles, we report that the giant phonon anharmonicity in phosphorene is associated with the soft transverse optical (TO) phonon modes and arises from the long-range interactions driven by the orbital governed resonant bonding. We also provide a microscopic picture connecting the anisotropic and low κ of phosphorene to the giant directional phonon anharmonicity and long-range interactions, which are further traced back to the asymmetric resonant orbital occupations of electrons and characteristics of the hinge-like structure. The unambiguously low κ of phosphorene obtained consistently by three independent ab initio methods confirms the phonon anharmonicity to a large extent and is expected to end the confusing huge deviations in previous studies. This work further pinpoints the necessity of including van der Waals interactions to accurately describe the interatomic interactions in phosphorene. We propose in 2D material that resonant bonding leads to low thermal conductivity, despite that it is originally found in three-dimensional (3D) thermoelectric and phase-change materials. Our study offers insights into phonon transport from the view of orbital states, which would be of great significance to the design of
A method of solving simple harmonic oscillator Schroedinger equation
Maury, Juan Carlos F.
1995-01-01
A usual step in solving totally Schrodinger equation is to try first the case when dimensionless position independent variable w is large. In this case the Harmonic Oscillator equation takes the form (d(exp 2)/dw(exp 2) - w(exp 2))F = 0, and following W.K.B. method, it gives the intermediate corresponding solution F = exp(-w(exp 2)/2), which actually satisfies exactly another equation, (d(exp 2)/dw(exp 2) + 1 - w(exp 2))F = 0. We apply a different method, useful in anharmonic oscillator equations, similar to that of Rampal and Datta, and although it is slightly more complicated however it is also more general and systematic.
Hypertrophic Olivary Degeneration and Palatal or Oculopalatal Tremor
Caroline Tilikete
2017-06-01
Full Text Available Hypertrophic degeneration of the inferior olive is mainly observed in patients developing palatal tremor (PT or oculopalatal tremor (OPT. This syndrome manifests as a synchronous tremor of the palate (PT and/or eyes (OPT that may also involve other muscles from the branchial arches. It is associated with hypertrophic inferior olivary degeneration that is characterized by enlarged and vacuolated neurons, increased number and size of astrocytes, severe fibrillary gliosis, and demyelination. It appears on MRI as an increased T2/FLAIR signal intensity and enlargement of the inferior olive. There are two main conditions in which hypertrophic degeneration of the inferior olive occurs. The most frequent, studied, and reported condition is the development of PT/OPT and hypertrophic degeneration of the inferior olive in the weeks or months following a structural brainstem or cerebellar lesion. This “symptomatic” condition requires a destructive lesion in the Guillain–Mollaret pathway, which spans from the contralateral dentate nucleus via the brachium conjunctivum and the ipsilateral central tegmental tract innervating the inferior olive. The most frequent etiologies of destructive lesion are stroke (hemorrhagic more often than ischemic, brain trauma, brainstem tumors, and surgical or gamma knife treatment of brainstem cavernoma. The most accepted explanation for this symptomatic PT/OPT is that denervated olivary neurons released from inhibitory inputs enlarge and develop sustained synchronized oscillations. The cerebellum then modulates/accentuates this signal resulting in abnormal motor output in the branchial arches. In a second condition, PT/OPT and progressive cerebellar ataxia occurs in patients without structural brainstem or cerebellar lesion, other than cerebellar atrophy. This syndrome of progressive ataxia and palatal tremor may be sporadic or familial. In the familial form, where hypertrophic degeneration of the inferior olive may not
Milchev, Andrey; Markov, Ivan
1984-01-01
The behaviour of finite epitaxial islands in the periodic field of the substrate is theoretically investigated whereby the role of anharmonicity in the interatomic forces of the deposit is examined. The harmonic potential, traditionally adopted in the model of Frank and van der Merwe, is replaced by Toda and Morse potentials and sets of difference recursion equations, governing the static properties of such a system, are derived and solved numerically. Thus a new effect of substrate-induced rupture of anharmonic chains migrating on the surface, is found. It is shown that dissociation of migrating clusters is enhanced, if: (i) The substrate potential becomes increasingly modulated, (ii) the natural misfit between deposit and substrate is decreased (in absolute value), (iii) the misfit is negative, rather than positive (with the same absolute value) and (iv) the size of the cluster increases. A relation between dislocations in the chain and rupture appears to exist, suggesting dilatons (enormously stretched interatomic bonds) as the origin for destruction. The influence of anharmonicity on the equilibrium structure of the overgrowth is considered in Part II.
Tadano, T; Gohda, Y; Tsuneyuki, S
2014-06-04
A systematic method to calculate anharmonic force constants of crystals is presented. The method employs the direct-method approach, where anharmonic force constants are extracted from the trajectory of first-principles molecular dynamics simulations at high temperature. The method is applied to Si where accurate cubic and quartic force constants are obtained. We observe that higher-order correction is crucial to obtain accurate force constants from the trajectory with large atomic displacements. The calculated harmonic and anharmonic force constants are, then, combined with the Boltzmann transport equation (BTE) and non-equilibrium molecular dynamics (NEMD) methods in calculating the thermal conductivity. The BTE approach successfully predicts the lattice thermal conductivity of bulk Si, whereas NEMD shows considerable underestimates. To evaluate the linear extrapolation method employed in NEMD to estimate bulk values, we analyze the size dependence in NEMD based on BTE calculations. We observe strong nonlinearity in the size dependence of NEMD in Si, which can be ascribed to acoustic phonons having long mean-free-paths and carrying considerable heat. Subsequently, we also apply the whole method to a thermoelectric material Mg2Si and demonstrate the reliability of the NEMD method for systems with low thermal conductivities.
Anharmonic behavior and structural phase transition in Yb2O3
Sugandha Dogra Pandey
2013-12-01
Full Text Available The investigation of structural phase transition and anharmonic behavior of Yb2O3 has been carried out by high-pressure and temperature dependent Raman scattering studies respectively. In situ Raman studies under high pressure were carried out in a diamond anvil cell at room temperature which indicate a structural transition from cubic to hexagonal phase at and above 20.6 GPa. In the decompression cycle, Yb2O3 retained its high pressure phase. We have observed a Stark line in the Raman spectra at 337.5 cm−1 which arises from the electronic transition between 2F5/2 and 2F7/2 multiplates of Yb3+ (4f13 levels. These were followed by temperature dependent Raman studies in the range of 80–440 K, which show an unusual mode hardening with increasing temperature. The hardening of the most dominant mode (Tg + Ag was analyzed in light of the theory of anharmonic phonon-phonon interaction and thermal expansion of the lattice. Using the mode Grüneisen parameter obtained from high pressure Raman measurements; we have calculated total anharmonicity of the Tg + Ag mode from the temperature dependent Raman data.
Kamarchik, Eugene; Jasper, Ahren W.
2013-05-01
An algorithm is presented for calculating fully anharmonic vibrational state counts, state densities, and partition functions for molecules using Monte Carlo integration of classical phase space. The algorithm includes numerical evaluations of the elements of the Jacobian and is general enough to allow for sampling in arbitrary curvilinear or rectilinear coordinate systems. Invariance to the choice of coordinate system is demonstrated for vibrational state densities of methane, where we find comparable sampling efficiency when using curvilinear z-matrix and rectilinear Cartesian normal mode coordinates. In agreement with past work, we find that anharmonicity increases the vibrational state density of methane by a factor of ˜2 at its dissociation threshold. For the vinyl radical, we find a significant (˜10×) improvement in sampling efficiency when using curvilinear z-matrix coordinates relative to Cartesian normal mode coordinates. We attribute this improved efficiency, in part, to a more natural curvilinear coordinate description of the double well associated with the H2C-C-H wagging motion. The anharmonicity correction for the vinyl radical state density is ˜1.4 at its dissociation threshold. Finally, we demonstrate that with trivial parallelizations of the Monte Carlo step, tractable calculations can be made for the vinyl radical using direct ab initio potential energy surface evaluations and a composite QCISD(T)/MP2 method.
Degenerate pseudo-Riemannian metrics
Hervik, Sigbjorn; Yamamoto, Kei
2014-01-01
In this paper we study pseudo-Riemannian spaces with a degenerate curvature structure i.e. there exists a continuous family of metrics having identical polynomial curvature invariants. We approach this problem by utilising an idea coming from invariant theory. This involves the existence of a boost, the existence of this boost is assumed to extend to a neighbourhood. This approach proves to be very fruitful: It produces a class of metrics containing all known examples of degenerate metrics. To date, only Kundt and Walker metrics have been given, however, our study gives a plethora of examples showing that degenerate metrics extend beyond the Kundt and Walker examples. The approach also gives a useful criterion for a metric to be degenerate. Specifically, we use this to study the subclass of VSI and CSI metrics (i.e., spaces where polynomial curvature invariants are all vanishing or constants, respectively).
Age-Related Macular Degeneration
... version of this page please turn Javascript on. Age-related Macular Degeneration About AMD Click for more ... a leading cause of vision loss among people age 60 and older. It causes damage to the ...
Fibonacci oscillators in the Landau diamagnetism problem
Marinho, André A.; Brito, Francisco A.; Chesman, Carlos
2014-10-01
We address the issue of the Landau diamagnetism problem via q-deformed algebra of Fibonacci oscillators through its generalized sequence of two real and independent deformation parameters q1 and q2. We obtain q-deformed thermodynamic quantities such as internal energy, number of particles, magnetization and magnetic susceptibility which recover their usual form in the degenerate limit q12+q22=1.
On the degenerate phase boundaries
Ma, Y; Kuang, Z; Ma, Yongge; Liang, Canbin; Kuang, Zhiquan
1999-01-01
The structure of the phase boundary between degenerate and non-degenerate regions in Ashtekar's gravity has been studied by Bengtsson and Jacobson who conjectured that the "phase boundary" should always be null. In this paper, we reformulate the reparametrization procedure in the mapping language and distinguish a phase boundary from its image. It is shown that the image has to be null, while the nullness of the phase boundary requries more suitable criterion.
Local virial theorems and closed-orbit theory for spatial density oscillations in fermionic systems
Roccia, J; Koch, A; Murthy, M V N
2009-01-01
We investigate the particle and kinetic energy densities for a system of $N$ fermions confined in a local mean-field potential $V({\\bf r})$. For spherical harmonic oscillators in arbitrary dimensions, exact linear relations between kinetic and potential energy density, termed "local virial theorems", and some exact (integro-) differential equations for the particle density have been earlier derived. Here we use a recently developed semiclassical theory for density oscillations [J. Roccia and M. Brack, Phys. Rev. Lett. {\\bf 100}, 200408 (2008)] to generalize these theorems to arbitrary potentials and test their validity for various anharmonic potentials. We also discuss the relevance of our results for density functional theory. We show, in particular, that the Thomas-Fermi functional for a suitably defined kinetic energy density reproduces the quantum shell oscillations correctly to leading order in the oscillating parts.
Manipulating Fock states of a harmonic oscillator while preserving its linearity
Juliusson, K.; Bernon, S.; Zhou, X.; Schmitt, V.; le Sueur, H.; Bertet, P.; Vion, D.; Mirrahimi, M.; Rouchon, P.; Esteve, D.
2016-12-01
We present a scheme for controlling the quantum state of a harmonic oscillator by coupling it to an anharmonic multilevel system (MLS) with first- to second-excited-state transition on resonance with the oscillator. In this scheme, which we call ef-resonant, the spurious oscillator Kerr nonlinearity inherited from the MLS is very small, while its Fock states can still be selectively addressed via an MLS transition at a frequency that depends on the number of photons. We implement this concept in a circuit-QED setup with a microwave three-dimensional cavity (the oscillator, with frequency 6.4 GHz and quality factor QO=2 ×106 ) embedding a frequency tunable transmon qubit (the MLS). We characterize the system spectroscopically and demonstrate selective addressing of Fock states and a Kerr nonlinearity below 350 Hz. At times much longer than the transmon coherence times, a nonlinear cavity response with driving power is also observed and explained.
Thermodynamics of Anharmonic Systems: Uncoupled Mode Approximations for Molecules.
Li, Yi-Pei; Bell, Alexis T; Head-Gordon, Martin
2016-06-14
The partition functions, heat capacities, entropies, and enthalpies of selected molecules were calculated using uncoupled mode (UM) approximations, where the full-dimensional potential energy surface for internal motions was modeled as a sum of independent one-dimensional potentials for each mode. The computational cost of such approaches scales the same with molecular size as standard harmonic oscillator vibrational analysis using harmonic frequencies (HO(hf)). To compute thermodynamic properties, a computational protocol for obtaining the energy levels of each mode was established. The accuracy of the UM approximation depends strongly on how the one-dimensional potentials of each modes are defined. If the potentials are determined by the energy as a function of displacement along each normal mode (UM-N), the accuracies of the calculated thermodynamic properties are not significantly improved versus the HO(hf) model. Significant improvements can be achieved by constructing potentials for internal rotations and vibrations using the energy surfaces along the torsional coordinates and the remaining vibrational normal modes, respectively (UM-VT). For hydrogen peroxide and its isotopologs at 300 K, UM-VT captures more than 70% of the partition functions on average. By contrast, the HO(hf) model and UM-N can capture no more than 50%. For a selected test set of C2 to C8 linear and branched alkanes and species with different moieties, the enthalpies calculated using the HO(hf) model, UM-N, and UM-VT are all quite accurate comparing with reference values though the RMS errors of the HO model and UM-N are slightly higher than UM-VT. However, the accuracies in entropy calculations differ significantly between these three models. For the same test set, the RMS error of the standard entropies calculated by UM-VT is 2.18 cal mol(-1) K(-1) at 1000 K. By contrast, the RMS error obtained using the HO model and UM-N are 6.42 and 5.73 cal mol(-1) K(-1), respectively. For a test set
Wilson's disease (hepatolenticular degeneration).
Herron, B E
1976-01-01
Wilson's disease, or hepatolenticular degeneration, is a rare inherited disorder of copper metabolism which usually affects young people. Excess copper accumulates in the tissues, primarily in the liver, brain, and cornea. This copper deposition results in a wide range of hepatic and neurological symptoms, and may produce psychiatric illness. Hepatic involvement often occurs in childhood, while neurological deficits generally are detected at a later age. The disease is inherited in an autosomal recessive fashion. Ocular findings are of particular importance because the corneal copper deposition, forming the Kayser-Fleischer ring,is the only pathognomonic sign of the disease. The structure of the ring and the presence of copper have been well established. An anterior capsular deposition of copper in the lens results in a characteristic sunflower cataract in some of these patients. Other ocular abnormalities have been described but are much less common. The pathogenesis of the disease and the basic genetic defect remain obscure. It is clear that there is excess copper in the tissues, but the mechanism of its deposition is unknown. It is in some way associated with a failure to synthesize the serum copper protein ceruloplasmin normally. Another theory suggests that an abnormal protein with a high affinity for copper may bind the metal in the tissues. The diagnosis may be suggested by the clinical manifestations and confirmed by the presence of a Kayser-Fleischer ring. In the absence of these findings biochemical determinations are necessary. The most important of these are the serum ceruloplasmin, the urinary copper, and the hepatic copper concentration on biopsy. Treatment consists in the administration of the copper chelating agent, penicillamine, and the avoidance of a high copper intake. This usually results in marked clinical improvement if irreversible tissue damage has not occurred. Maintenance therapy for life is necessary in order to continue the negative
Rosensteel, George
1995-01-01
Riemann ellipsoids model rotating galaxies when the galactic velocity field is a linear function of the Cartesian coordinates of the galactic masses. In nuclear physics, the kinetic energy in the linear velocity field approximation is known as the collective kinetic energy. But, the linear approximation neglects intrinsic degrees of freedom associated with nonlinear velocity fields. To remove this limitation, the theory of symplectic dynamical symmetry is developed for classical systems. A classical phase space for a self-gravitating symplectic system is a co-adjoint orbit of the noncompact group SP(3,R). The degenerate co-adjoint orbit is the 12 dimensional homogeneous space Sp(3,R)/U(3), where the maximal compact subgroup U(3) is the symmetry group of the harmonic oscillator. The Hamiltonian equations of motion on each orbit form a Lax system X = (X,F), where X and F are elements of the symplectic Lie algebra. The elements of the matrix X are the generators of the symplectic Lie algebra, viz., the one-body collective quadratic functions of the positions and momenta of the galactic masses. The matrix F is composed from the self-gravitating potential energy, the angular velocity, and the hydostatic pressure. Solutions to the hamiltonian dynamical system on Sp(3,R)/U(3) are given by symplectic isospectral deformations. The Casimirs of Sp(3,R), equal to the traces of powers of X, are conserved quantities.
Isaacson, D.; Marchesin, D.; Paes-Leme, P. J.
1980-01-01
This paper is an expanded version of a talk given at the 1979 T.I.C.O.M. conference. It is a self-contained introduction, for applied mathematicians and numerical analysts, to quantum mechanics and quantum field theory. It also contains a brief description of the authors' numerical approach to the problems of quantum field theory, which may best be summarized by the question; Can we compute the eigenvalues and eigenfunctions of Schrodinger operators in infinitely many variables.
Amore, Paolo; Rodriguez, Martin [Facultad de Ciencias, Universidad de Colima, Bernal DIaz del Castillo 340, Colima, Colima (Mexico); Fernandez, Francisco M, E-mail: paolo.amore@gmail.com, E-mail: martinalexander.rv@gmail.com, E-mail: fernande@quimica.unlp.edu.ar [INIFTA (UNLP, CCT La Plata-CONICET), Division Quimica Teorica, Blvd 113 S/N, Sucursal 4, Casilla de Correo 16, 1900 La Plata (Argentina)
2011-04-15
We show that some of the conclusions drawn recently about the performance and convergence of the little sinc functions collocation method are misleading. To this end, we prove the convergence of the method and recalculate the ground-state energy for the Pullen-Edmonds Hamiltonian. In addition, we show the results for another nonseparable Hamiltonian operator with a somewhat more complicated potential-energy function. (comment)
Power oscillation damping controller
2012-01-01
A power oscillation damping controller is provided for a power generation device such as a wind turbine device. The power oscillation damping controller receives an oscillation indicating signal indicative of a power oscillation in an electricity network and provides an oscillation damping control...
Energy Continuity in Degenerate Density Functional Perturbation Theory
Palenik, Mark C
2016-01-01
Fractional occupation numbers can produce open-shell degeneracy in density functional theory. We develop the corresponding perturbation theory by requiring that a differentiable map connects the initial and perturbed states. The degenerate state connects to a single perturbed state which extremizes, but does not necessarily minimize or maximize, the energy with respect to occupation numbers. Using a system of three electrons in a harmonic oscillator potential, we relate the counterintuitive sign of first-order occupation numbers to eigenvalues of the electron-electron interaction Hessian.
Popovic, Zorana B.; Kim, Moonil; Rutledge, David B.
1988-01-01
Loading a two-dimensional grid with active devices offers a means of combining the power of solid-state oscillators in the microwave and millimeter-wave range. The grid structure allows a large number of negative resistance devices to be combined. This approach is attractive because the active devices do not require an external locking signal, and the combining is done in free space. In addition, the loaded grid is a planar structure amenable to monolithic integration. Measurements on a 25-MESFET grid at 9.7 GHz show power-combining and frequency-locking without an external locking signal, with an ERP of 37 W. Experimental far-field patterns agree with theoretical results obtained using reciprocity.
Uporov, S.; Bykov, V.; Estemirova, S.
2016-10-01
We present a comprehensive study of electrical and thermal conductivities, specific heat and magnetic susceptibility of rapidly crystallized Cu100-xZrx (x = 20-90) alloys. X-ray diffraction analysis has revealed that all the prepared compositions had strongly textured and distorted crystal structures. Different monoclinic and other non-equilibrium phases were detected in the case of glass-forming samples, whereas the alloys without a tendency to form glassy state show almost equilibrium phase content. Metallic type of electrical conductivity and the Kondo anomaly were observed for all the examined samples. It was found that the electrical resistance data cannot be adequately described within the standard Bloch-Grüneisen theory. We use the Debye characteristic temperature as a linear function to fit the electrical conductivity accurately. The composition dependence of the electron density of states at the Fermi level (DOS) has been extracted from room temperature magnetic susceptibility. We found that the glass-forming alloys are characterized by abnormally large values of DOS, which are comparable to those of glassy analogues. Noticeable anharmonic contribution in total specific heat has been revealed for all the studied compositions. In order to estimate the effect of anharmonicity in the system under consideration, we analyzed composition and temperature dependencies of the studied thermal characteristics related to the Grüneisen coefficient. Basing on the results obtained in this study we propose a phenomenological concept to explain abnormal behavior of physical properties of glass-forming Cu-Zr alloys within the standard solid state theory taking into account anharmonic effects.
Early Motor Fluctuations in a Patient with Striatonigral Degeneration
Yoshii, Fumihito; Moriya, Yusuke; Ohnuki, Tomohide; Takahashi, Wakoh; Ryo, Masafuchi
2016-01-01
We report a 44-year-old female with striatonigral degeneration (SND) who showed wearing-off oscillations after 4 months of levodopa treatment. The patient presented with asymmetric left-side dominant rigidity, and levodopa was effective at first. However, she began to show wearing-off oscillations of motor symptoms, which gradually worsened thereafter. Fluid-attenuated inversion recovery sequence magnetic resonance imaging (MRI) showed linear lateral putamen hyperintensities, and positron emission tomography (PET) studies using 18F-fluorodopa (FD) and 11C-N-methylspiperon (NMSP) showed a marked decrease of radioactivity in the right putamen, especially in the posterior putamen. The results of MRI and 2 PET studies with FD and NMSP were well consistent with the diagnosis of SND. PMID:28101035
Kocia, Lucas, E-mail: lkocia@fas.harvard.edu; Heller, Eric J. [Department of Chemistry and Chemical Biology, Harvard University, Cambridge, Massachusetts 02138 (United States)
2014-11-14
A simplification of the Heller-Herman-Kluk-Kay (HK) propagator is presented that does not suffer from the need for an increasing number of trajectories with dimensions of the system under study. This is accomplished by replacing HK’s uniformizing integral over all of phase space by a one-dimensional curve that is appropriately selected to lie along the fastest growing manifold of a defining trajectory. It is shown that this modification leads to eigenspectra of quantum states in weakly anharmonic systems that can outperform the comparatively computationally cheap thawed Gaussian approximation method and frequently approach the accuracy of spectra obtained with the full HK propagator.
Kocia, Lucas; Heller, Eric J.
2014-11-01
A simplification of the Heller-Herman-Kluk-Kay (HK) propagator is presented that does not suffer from the need for an increasing number of trajectories with dimensions of the system under study. This is accomplished by replacing HK's uniformizing integral over all of phase space by a one-dimensional curve that is appropriately selected to lie along the fastest growing manifold of a defining trajectory. It is shown that this modification leads to eigenspectra of quantum states in weakly anharmonic systems that can outperform the comparatively computationally cheap thawed Gaussian approximation method and frequently approach the accuracy of spectra obtained with the full HK propagator.
The TF Limit for Rapidly Rotating Bose Gases in Anharmonic Traps
Bru, J -B; Pickl, P; Yngvason, J
2007-01-01
Starting from the full many body Hamiltonian we derive the leading order energy and density asymptotics for the ground state of a dilute, rotating Bose gas in an anharmonic trap in the ` Thomas Fermi' (TF) limit when the Gross-Pitaevskii coupling parameter and/or the rotation velocity tend to infinity. Although the many-body wave function is expected to have a complicated phase, the leading order contribution to the energy can be computed by minimizing a simple functional of the density alone.
Solitons in anharmonic chains with ultra-long-range interatomic interactions
Mingaleev, S F; Mertens, F G; Mingaleev, Serge F.; Gaididei, Yuri B.; Mertens, Franz G.
2000-01-01
We study the influence of long-range interatomic interactions on the properties of supersonic pulse solitons in anharmonic chains. We show that in the case of ultra-long-range (e.g., screened Coulomb) interactions three different types of pulse solitons coexist in a certain velocity interval: one type is unstable but the two others are stable. The high-energy stable soliton is broad and can be described in the quasicontinuum approximation. But the low-energy stable soliton consists of two components, short-range and long-range ones, and can be considered as a bound state of these components.
Anharmonic Noninertial Lattice Dynamics during Ultrafast Nonthermal Melting of InSb
Zijlstra, Eeuwe S.; Walkenhorst, Jessica; Garcia, Martin E.
2008-09-01
We compute the potential energy surface of femtosecond-laser-excited InSb along the directions in which the crystal becomes soft. Using dynamical simulations the time dependence of the atomic coordinates is obtained. We find that at high excitation densities the anharmonicity of the potential energy surface becomes significant after ˜100fs. On the basis of our results we explain recent time-resolved x-ray diffraction experiments. We point out that an alternative model for ultrafast melting [A. M. Lindenberg , Science 308, 392 (2005)SCIEAS0036-807510.1126/science.1107996] is inconsistent with our calculations.
Anharmonic stabilization and band gap renormalization in the perovskite CsSnI_{3}
Patrick, Christopher; Jacobsen, Karsten Wedel; Thygesen, Kristian Sommer
2015-01-01
to rotational instabilities of the SnI6 octahedra. Here, employing self-consistent phonon theory, we show that these soft modes are stabilized at experimental conditions through anharmonic phonon-phonon interactions between the Cs ions and their iodine cages. We further calculate the renormalization...... of the electronic energies due to vibrations and find an unusual opening of the band gap, estimated as 0.24 and 0.11 eV at 500 and 300 K, which we attribute to the stretching of Sn-I bonds. Our work demonstrates the important role of temperature in accurately describing these materials....
Solutions of a generalized anharmonic oscillatory noncentral potential in higher spatial dimensions
Bai, Ya; Zhang, Min-Cang
2017-09-01
A generalized anharmonic oscillatory noncentral potential is presented and the D-dimensional Schrödinger equation for this noncentral potential is examined in hyperspherical coordinates. The Nikiforov-Uvarov (N-U) method is applied to obtain the D-dimensional energy eigenvalues and the corresponding eigenfunctions. The angular/radial wavefunction is expressed in terms of Jacobi/ Laguerre polynomials. Some special cases of this potential model including the Quesne potential and the ring-shaped non-spherical harmonic oscillatory (RNHO) potential are discussed also.
Influence of anharmonic phonon decay on self-heating in Si nanowire transistors
Rhyner, Reto, E-mail: rhyner@iis.ee.ethz.ch; Luisier, Mathieu, E-mail: mluisier@iis.ee.ethz.ch [Integrated Systems Laboratory, ETH Zürich, Gloriastr. 35, 8092 Zürich (Switzerland)
2014-08-11
Anharmonic phonon-phonon scattering is incorporated into an electro-thermal quantum transport approach based on the nonequilibrium Green's function formalism. Electron-phonon and phonon-phonon interactions are taken into account through scattering self-energies solved in the self-consistent Born approximation. While studying self-heating effects in ultra-scaled Si nanowire transistors, it is found that the phonon decay process softens the artificial accumulation of high energy phonons caused by electron relaxations close to the drain region. This leads to an increase of the device current in the ON-state and a reduction of the effective lattice temperature.
Theory of the anharmonic damping and shift of the Raman mode in silicon
Haro, E.; Balkanski, M.; Wallis, R. F.; Wanser, K. H.
1986-10-01
A theoretical investigation has been made of the damping constant and frequency shift of the Raman mode in silicon due to cubic anharmonic interactions between nearest-neighbor atoms. The normal-mode frequencies and eigenvectors for the harmonic crystal were calculated using a model containing short-range forces out to fourth neighbors and long-range nonlocal dipole interactions. The Raman-mode linewidth and frequency shift were calculated as functions of both temperature and frequency, and the results are compared with experimental data on the temperature dependences of these quantities.
Genetics Home Reference: age-related macular degeneration
... Resources (3 links) BrightFocus Foundation: Macular Degeneration Treatment Macular Degeneration Partnership: Low Vision Rehabilitation Prevent Blindness America: Age-Related Macular Degeneration (AMD) ...
Lindberg, Erik
1997-01-01
In order to obtain insight in the nature of nonlinear oscillators the eigenvalues of the linearized Jacobian of the differential equations describing the oscillator are found and displayed as functions of time. A number of oscillators are studied including Dewey's oscillator (piecewise linear...... with negative resistance), Kennedy's Colpitts-oscillator (with and without chaos) and a new 4'th order oscillator with hyper-chaos....
Oscillating Permanent Magnets.
Michaelis, M. M.; Haines, C. M.
1989-01-01
Describes several ways to partially levitate permanent magnets. Computes field line geometries and oscillation frequencies. Provides several diagrams illustrating the mechanism of the oscillation. (YP)
Gribov ambiguity and degenerate systems
Canfora, Fabrizio; Salgado-Rebolledo, Patricio; Zanelli, Jorge
2014-01-01
The relation between Gribov ambiguity and degeneracies in the symplectic structure of physical systems is analyzed. It is shown that, in finite-dimensional systems, the presence of Gribov ambiguities in regular constrained systems (those where the constraints are functionally independent) always leads to a degenerate symplectic structure upon Dirac reduction. The implications for the Gribov-Zwanziger approach to QCD are discussed.
Solar neutrinos: Oscillations or No-oscillations?
Smirnov, A Yu
2016-01-01
The Nobel prize in physics 2015 has been awarded "... for the discovery of neutrino oscillations which show that neutrinos have mass". While SuperKamiokande (SK), indeed, has discovered oscillations, SNO observed effect of the adiabatic (almost non-oscillatory) flavor conversion of neutrinos in the matter of the Sun. Oscillations are irrelevant for solar neutrinos apart from small $\
Yuksek, N. S.; Gasanly, N. M.; Ozkan, H. [Middle East Technical University, Ankara (Turkmenistan); Aydinli, A. [Bilkent University, Ankara (Turkmenistan)
2004-08-15
The temperature dependence (16 - 300 K) of unpolarized Raman spectra from TlGaS{sub 2} layered crystals was measured in the frequency range of 10 - 400 cm{sup -1}. The analysis of the experimental data showed that the temperature dependencies of the phonon frequencies and linewidths were well described by considering the contributions from thermal expansion and lattice anharmonicity. The anharmonic contribution (phonon-phonon coupling) was found to be due to three-phonon processes. The present work demonstrates that the interlayer Raman mode at 42.6 cm{sup -1} shifts toward high frequency as the temperature is raised from 16 to 300 K.
Zhang, Yongsheng; Skoug, Eric; Cain, Jeffrey; Morelli, Donald; Ozolins, Vidvuds; Wolverton, Christopher
2012-02-01
Strong anharmonicity can lead to intrinsically minimal thermal conductivity even in defect-free single crystals. In an effort to understand this behavior, we have investigated two Cu-Sb-Se ternary semiconductors, Cu3SbSe4 and Cu3SbSe3, by both experimental measurements and density functional theory (DFT) calculations. The experimental lattice thermal conductivity measurements show that while Cu3SbSe4 exhibits classical behavior, the lattice thermal conductivity in Cu3SbSe3 is anomalously low and nearly temperature independent. The vibrational properties of these two semiconductors are calculated by DFT phonon calculations within the quasi-harmonic approximation. The average of the Gr"uneisen parameters of the acoustic mode in Cu3SbSe3 is larger than that of Cu3SbSe4, which theoretically confirms that Cu3SbSe3 has a stronger lattice anharmonicity than Cu3SbSe4. Using our DFT-determined longitudinal and transverse Gr"uneisen parameters, Debye temperatures, and phonon velocities, we calculate the lattice the lattice thermal conductivity using the Debye-Callaway model (without the use of any adjustable parameters). The calculated thermal conductivity is in good agreement with the experimental measurements.
Anharmonic Vibrational Analysis for the Propadienylidene Molecule (H2C═C═C:).
Wu, Qunyan; Hao, Qiang; Wilke, Jeremiah J; Simmonett, Andrew C; Yamaguchi, Yukio; Li, Qianshu; Fang, De-Cai; Schaefer, Henry F
2010-10-12
Maier et al. found that photolysis of singlet cyclopropenylidene (1S) in a matrix yields triplet propargylene (2T), which upon further irradiation is converted to singlet propadienylidene (vinylidenecarbene, 3S). Their discovery was followed by interstellar identification of 3S by Cernicharo et al. An accurate quartic force field for propadienylidene (3S) has been determined employing the ab initio coupled-cluster (CC) with single and double excitations and perturbative triple excitations [CCSD(T)] method and the correlation-consistent core-valence quadruple-ζ (cc-pCVQZ) basis set. Utilizing vibrational second-order perturbation theory (VPT2), vibration-rotation coupling constants, rotational constants, centrifugal distortion constants, vibrational anharmonic constants, and fundamental vibrational frequencies are determined. The predicted fundamental frequencies for 3S as well as its (13)C and deuterium isotopologues are in good agreement with experimental values. The theoretical zero-point vibration corrected rotational constants B0 are consistent with experimental values within 0.3% of errors. The isotopic shifts of B0 are in close to exact agreement with experimental observations. The mean absolute deviation between theoretical anharmonic and experimental fundamental vibrational frequencies for 24 modes (excluding CH2 s-str.) is only 2.6 cm(-1). The isotopic shifts of the vibrational frequencies are also in excellent agreement with the available experimental values. However, a large discrepancy is observed for the CH2 symmetric stretch, casting doubt on the experimental assignment for this mode.
Carignano, Marcelo Andrés
2017-09-05
We present a systematic study based on first principles molecular dynamics simulations of lead iodide perovskites with three different cations, including methylammonium (MA), formamidinium (FA) and cesium. Using the high temperature perovskite structure as a reference, we investigate the instabilities that develop as the material is cooled down to 370 K. All three perovskites display anharmonicity in the motion of the iodine atoms, with the stronger effect observed for the MAPbI$_3$ and CsPbI$_3$. At high temperature, this behavior can be traced back to the reduced effective size of the Cs$^+$ and MA$^+$ cations. MAPbI$_3$ undergoes a spontaneous phase transition within our simulation model driven by the dipolar interaction between neighboring MA cations as the temperature is decreased from 450 K. The reverse transformation from tetragonal to cubic is also monitored through the large distribution of the octahedral tilting angles accompanied by an increase in the anharmonicity of the iodine atoms motion. Both MA and FA hybrid perovskites show a strong coupling between the molecular orientations and the local lattice deformations, suggesting mixed order-disorder/displacive characters of the high temperature phase transitions.
The Origin of Ultralow Thermal Conductivity in InTe: Lone-Pair-Induced Anharmonic Rattling.
Jana, Manoj K; Pal, Koushik; Waghmare, Umesh V; Biswas, Kanishka
2016-06-27
Understanding the origin of intrinsically low thermal conductivity is fundamentally important to the development of high-performance thermoelectric materials, which can convert waste-heat into electricity. Herein, we report an ultralow lattice thermal conductivity (ca. 0.4 W m(-1) K(-1) ) in mixed valent InTe (that is, In(+) In(3+) Te2 ), which exhibits an intrinsic bonding asymmetry with coexistent covalent and ionic substructures. The phonon dispersion of InTe exhibits, along with low-energy flat branches, weak instabilities associated with the rattling vibrations of In(+) atoms along the columnar ionic substructure. These weakly unstable phonons originate from the 5s(2) lone pair of the In(+) atom and are strongly anharmonic, which scatter the heat-carrying acoustic phonons through strong anharmonic phonon-phonon interactions, as evident in anomalously high mode Grüneisen parameters. A maximum thermoelectric figure of merit (z T) of about 0.9 is achieved at 600 K for the 0.3 mol % In-deficient sample, making InTe a promising material for mid-temperature thermoelectric applications.
Oscillations of Eccentric Pulsons
Christiansen, Peter Leth; Groenbech-Jensen, Niels; Lomdahl, Peter;
1997-01-01
Perturbation theory for elliptic pulsons is developed and predicts pulson and eccentricity oscillations. The pulson oscillation period is predicted qualitatively correct.......Perturbation theory for elliptic pulsons is developed and predicts pulson and eccentricity oscillations. The pulson oscillation period is predicted qualitatively correct....
Spheroidal Degeneration of the Cornea
Erdem Dinç
2011-08-01
Full Text Available A thirty-one-year-old male patient presented with bilateral epiphora and stinging sensation in the cornea. Detailed history revealed that a bilateral corneal scraping had been made regarding the initial diagnosis of fungal keratitis. His bestcorrected visual acuities were 20/20 and 20/30 in right and left eyes, respectively. Biomicroscopy showed bilateral amber colored spherules in the anterior stroma of the central cornea. The diagnosis of spheroidal corneal degeneration was established and symptomatic therapy with artificial tear drops was prescribed. Ultraviolet light is widely accepted to be the main etiological factor in the pathogenesis of spheroidal degeneration. Because of difficulties in the early stages of the diagnostic process of the disease, incorrect diagnoses can be made with inappropriate interventions. (Turk J Ophthalmol 2011; 41: 264-6
Radial keratotomy associated endothelial degeneration
Moshirfar M
2012-02-01
Full Text Available Majid Moshirfar, Andrew Ollerton, Rodmehr T Semnani, Maylon HsuJohn A Moran Eye Center, Department of Ophthalmology and Visual Sciences, University of Utah, Salt Lake City, UT, USAPurpose: To describe the presentation and clinical course of eyes with a history of radial keratotomy (RK and varying degrees of endothelial degeneration.Methods: Retrospective case series were used.Results: Thirteen eyes (seven patients were identified with clinical findings of significant guttata and a prior history of RK. The mean age of presentation for cornea evaluation was 54.3 years (range: 38–72 years, averaging 18.7 years (range: 11–33 years after RK. The presentation of guttata varied in degree from moderate to severe. Best corrected visual acuity (BCVA ranged from 20/25 to 20/80. All patients had a history of bilateral RK, except one patient who did not develop any guttata in the eye without prior RK. No patients reported a family history of Fuch’s Dystrophy. One patient underwent a penetrating keratoplasty in one eye and a Descemet’s stripping automated endothelial keratoplasty (DSAEK in the other eye.Conclusions: RK may induce a spectrum of endothelial degeneration. In elderly patients, the findings of guttata may signify comorbid Fuch’s dystrophy in which RK incisions could potentially hasten endothelial decomposition. In these select patients with stable cornea topography and prior RK, DSAEK may successfully treat RK endothelial degeneration.Keywords: radial keratotomy, RK, Descemet’s stripping automated endothelial keratoplasty, DSAEK, guttata, endothelial degeneration, Fuch’s dystrophy
Degenerating the elliptic Schlesinger system
Aminov, G. A.; Artamonov, S. B.
2013-01-01
We study various ways of degenerating the Schlesinger system on the elliptic curve with R marked points. We construct a limit procedure based on an infinite shift of the elliptic curve parameter and on shifts of the marked points. We show that using this procedure allows obtaining a nonautonomous Hamiltonian system describing the Toda chain with additional spin sl(N, ℂ) degrees of freedom.
Traveling Solitons in Long-Range Oscillator Chains
Miloshevich, George; Dauxois, Thierry; Khomeriki, Ramaz; Ruffo, Stefano
2016-01-01
We investigate the existence and propagation of solitons in a long-range extension of the quartic Fermi-Pasta-Ulam (FPU) chain of anharmonic oscillators. The coupling in the linear term decays as a power-law with an exponent greater than 1 and less than 3. We obtain an analytic perturbative expression of traveling envelope solitons by introducing a Non Linear Schrodinger (NLS) equation for the slowly varying amplitude of short wavelength modes. Due to the non analytic properties of the dispersion relation, it is crucial to develop the theory using discrete difference operators. Those properties are also the ultimate reason why kink-solitons may exist but are unstable, at variance with the short-range FPU model. We successfully compare these approximate analytic results with numerical simulations.
Radial keratotomy associated endothelial degeneration.
Moshirfar, Majid; Ollerton, Andrew; Semnani, Rodmehr T; Hsu, Maylon
2012-01-01
To describe the presentation and clinical course of eyes with a history of radial keratotomy (RK) and varying degrees of endothelial degeneration. Retrospective case series were used. Thirteen eyes (seven patients) were identified with clinical findings of significant guttata and a prior history of RK. The mean age of presentation for cornea evaluation was 54.3 years (range: 38-72 years), averaging 18.7 years (range: 11-33 years) after RK. The presentation of guttata varied in degree from moderate to severe. Best corrected visual acuity (BCVA) ranged from 20/25 to 20/80. All patients had a history of bilateral RK, except one patient who did not develop any guttata in the eye without prior RK. No patients reported a family history of Fuch's Dystrophy. One patient underwent a penetrating keratoplasty in one eye and a Descemet's stripping automated endothelial keratoplasty (DSAEK) in the other eye. RK may induce a spectrum of endothelial degeneration. In elderly patients, the findings of guttata may signify comorbid Fuch's dystrophy in which RK incisions could potentially hasten endothelial decomposition. In these select patients with stable cornea topography and prior RK, DSAEK may successfully treat RK endothelial degeneration.
Cho, Alice; Ratliff, Charles; Sampath, Alapakkam; Weiland, James
2016-01-01
Objective Here we investigate ganglion cell physiology in healthy and degenerating retina to test its influence on threshold to electrical stimulation. Approach Age-related Macular Degeneration and Retinitis Pigmentosa cause blindness via outer retinal degeneration. Inner retinal pathways that transmit visual information to the central brain remain intact, so direct electrical stimulation from prosthetic devices offers the possibility for visual restoration. Since inner retinal physiology changes during degeneration, we characterize physiological properties and responses to electrical stimulation in retinal ganglion cells of both wild type mice and the rd10 mouse model of retinal degeneration. Main results Our aggregate results support previous observations that elevated thresholds characterize diseased retinas. However, a physiology-driven classification scheme reveals distinct sub-populations of ganglion cells with thresholds either normal or strongly elevated compared to wild-type. When these populations are combined, only a weakly elevated threshold with large variance is observed. The cells with normal threshold are more depolarized at rest and exhibit periodic oscillations. Significance During degeneration, physiological changes in retinal ganglion cells affect the threshold stimulation currents required to evoke action potentials. PMID:26905177
Lee, Ching Hua; Gan, Chee Kwan
2017-07-01
Phonon-mediated thermal conductivity, which is of great technological relevance, arises due fundamentally to anharmonic scattering from interatomic potentials. Despite its prevalence, accurate first-principles calculations of thermal conductivity remain challenging, primarily due to the high computational cost of anharmonic interatomic force constant (IFC) calculations. Meanwhile, the related anharmonic phenomenon of thermal expansion is much more tractable, being computable from the Grüneisen parameters associated with phonon frequency shifts due to crystal deformations. In this work, we propose an approach for computing the largest cubic IFCs from the Grüneisen parameter data. This allows an approximate determination of the thermal conductivity via a much less expensive route. The key insight is that although the Grüneisen parameters cannot possibly contain all the information on the cubic IFCs, being derivable from spatially uniform deformations, they can still unambiguously and accurately determine the largest and most physically relevant ones. By fitting the anisotropic Grüneisen parameter data along judiciously designed deformations, we can deduce (i.e., reverse-engineer) the dominant cubic IFCs and estimate three-phonon scattering amplitudes. We illustrate our approach by explicitly computing the largest cubic IFCs and thermal conductivity of graphene, especially for its out-of-plane (flexural) modes that exhibit anomalously large anharmonic shifts and thermal conductivity contributions. Our calculations on graphene not only exhibit reasonable agreement with established density-functional theory results, but they also present a pedagogical opportunity for introducing an elegant analytic treatment of the Grüneisen parameters of generic two-band models. Our approach can be readily extended to more complicated crystalline materials with nontrivial anharmonic lattice effects.
Shao, Zhu-Lei; Feng, Zhi-Bo
2016-04-01
We propose a theoretical scheme to implement electromagnetically induced transparency (EIT) using an artificial atom of superconducting circuit. Allowed by the selection rule, two kinds of interactions between the atom and driving fields can be obtained, in which we focus on the leakage effect. In terms of dark-state mechanism in generating EIT, the leakage could destroy the EIT considerably. By removing the leakage effect in an optimized three-level atom, we consider a realization of EIT through the technique of density matrix. Furthermore, another effective way to optimize the level anharmonicity is analyzed in a dressing-state method. The scheme could provide a promising approach for experimentally improving EIT with the artificial atoms.
Anharmonic properties of Raman modes in double wall carbon nano tubes
Marquina, J. [Universidad de los Andes, Facultad de Ciencias, Centro de Estudios Avanzados en Optica, 5101 Merida (Venezuela, Bolivarian Republic of); Power, Ch.; Gonzalez, J. [Universidad de los Andes, Facultad de Ciencias, Centro de Estudios en Semiconductores, 5101 Merida (Venezuela, Bolivarian Republic of); Broto, J. M. [Universite de Toulouse, Laboratoire National des Champs Magnetiques Intenses, CNRS UPR 3228, 31400 Toulouse (France); Flahaut, E., E-mail: castella@ula.v [Universite Paul Sabatier, Laboratoire de Chimie des Materiaux Inorganiques, UMR CNRS 5085, 31062 Toulouse (France)
2011-07-01
The temperature dependence of the radial breathing modes (RB Ms) and the zone-center tangential optical phonons (G-bands) of double-walled carbon nano tubes has been investigated between 300 and 700 K using Raman scattering. As expected, with increasing temperature, the frequencies of the Raman peaks, including the RB Ms and G-bands downshift simultaneously. We show here that the temperature dependence of the RB Ms can be fitted by a simple linear dependence and different RB Ms have different frequency shifts. We observe a noticeable nonlinearity in the temperature dependence of the G-band associated with the outer semiconducting tube G+ext (s). The deviation from the linear trend is due to the contribution of the third-order anharmonic term in the lattice potential energy with a pure temperature effect. An estimated value of 1.5 for the Grueneisen parameter of the G+ext (s) band was found. (Author)
M. Durga Prasad
2002-05-01
Full Text Available Abstract: A time dependent coupled cluster approach to the calculation of Resonance Raman excitation profiles on general anharmonic surfaces is presented. The vibrational wave functions on the ground electronic surface are obtained by the coupled cluster method (CCM. It is shown that the propagation of the vibrational ground state on the upper surface is equivalent to propagation of the vacuum state by an effective hamiltonian generated by the similarity transformation of the vibrational hamiltonian of that surface by the CCM wave operator of the lower surface up to a normalization constant. This time propagation is carried out by the time-dependent coupled cluster method in a time dependent frame. Numerical studies are presented to asses the validity of the approach.
Pseudogap and anharmonic phonon behavior in Ba8Ga16Ge30: An NMR study
Sirusi, Ali A.; Ross, Joseph H.
2016-08-01
We have performed 69Ga, 71Ga, and 137Ba NMR on Ba8Ga16Ge30, a clathrate semiconductor which has been of considerable interest due to its large figure of merit for thermoelectric applications. In measurements from 4 K to 450 K, we used measurements on the two Ga nuclei to separate the magnetic and electric quadrupole hyperfine contributions and thereby gain information about the metallic and phonon behavior. The results show the presence of a pseudogap in the Ga electronic states within the conduction band, superposed upon a large Ba contribution to the conduction band. Meanwhile the phonon contributions to the Ga relaxation rates are large and increase more rapidly with temperature than typical semiconductors. These results provide evidence for enhanced anharmonicity of the propagative phonon modes over a wide range, providing experimental evidence for enhanced phonon-phonon scattering as a mechanism for the reduced thermal conductivity.
Anharmonic magnetic deformation of spherical vesicle: Field-induced tension and swelling effects
Iwamoto, Mitsumasa; Ou-Yang, Zhong-can
2013-12-01
We have derived an equation, based on Helfrich’s curvature elasticity, describing the equilibrium shape of membrane vesicles in the presence of magnetic fields. We have solved this equation with and without the constraint of constant vesicle area. For vesicles with constant area, an exact calculation using our model confirms Helfrich’s estimate (Helfrich, 1973) [20] and predicts a magnetic field induced surface tension. Without the constant area constraint, our model predicts that vesicles with positive diamagnetic susceptibility anisotropy will swell in magnetic fields. It also predicts the anharmonic magnetic deformation of self-assembled nanocapsules of bola-amphiphilic molecules and the linear birefringence observed by Manyuhina et al. (2007) [22] .
Zhou, Fei [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Nielson, Weston [Univ. of California, Los Angeles, CA (United States); Xia, Yi [Univ. of California, Los Angeles, CA (United States); Ozoliņš, Vidvuds [Univ. of California, Los Angeles, CA (United States)
2014-10-01
First-principles prediction of lattice thermal conductivity κ_{L} of strongly anharmonic crystals is a long-standing challenge in solid-state physics. Making use of recent advances in information science, we propose a systematic and rigorous approach to this problem, compressive sensing lattice dynamics. Compressive sensing is used to select the physically important terms in the lattice dynamics model and determine their values in one shot. Nonintuitively, high accuracy is achieved when the model is trained on first-principles forces in quasirandom atomic configurations. The method is demonstrated for Si, NaCl, and Cu_{12}Sb_{4}S_{13}, an earth-abundant thermoelectric with strong phonon-phonon interactions that limit the room-temperature κ_{L} to values near the amorphous limit.
Fei Xiang
1999-01-01
Harmonic potentials can be produced in cylindrical ion traps by means of dynamic orthogonalized anharmonicity compensation with use of two (or multiple) sets of compensation electrodes. One special example is for traps with multiple identical electrodes which are not only easy to construct and allow access to the center region of the trap for particle loading and releasing, laser beams, and microwaves, but also flexible in forming harmonic potential wells in many locations. The nested trap configuration and the side-by-side trap configuration are readily available in this special scheme. Analytical solutions for cylindrical traps with multiple sets of compensation potentials are presented. This work will be useful for studies involving Penning trap diagnostics, atomic and molecular interactions (including the production of antihydrogen atoms), accurate mass measurements of exotic particles, and precision measurements of the spin precession frequencies of trapped particles.
Zhou, Fei; Nielson, Weston; Xia, Yi; Ozoliņš, Vidvuds
2014-10-31
First-principles prediction of lattice thermal conductivity κ(L) of strongly anharmonic crystals is a long-standing challenge in solid-state physics. Making use of recent advances in information science, we propose a systematic and rigorous approach to this problem, compressive sensing lattice dynamics. Compressive sensing is used to select the physically important terms in the lattice dynamics model and determine their values in one shot. Nonintuitively, high accuracy is achieved when the model is trained on first-principles forces in quasirandom atomic configurations. The method is demonstrated for Si, NaCl, and Cu(12)Sb(4)S(13), an earth-abundant thermoelectric with strong phonon-phonon interactions that limit the room-temperature κ(L) to values near the amorphous limit.
Telling, Mark T F; Neylon, Cameron; Kilcoyne, Susan H; Arrighi, Valeria
2008-09-04
Quasi-elastic neutron scattering (QENS) has been used to study the deviation from Debye-law harmonic behavior in lyophilized and hydrated apoferritin, a naturally occurring, multisubunit protein. Whereas analysis of the measured mean squared displacement (msd) parameter reveals a hydration-dependent inflection above 240 K, characteristic of diffusive motion, a hydration-independent inflection is observed at 100 K. The mechanism responsible for this low-temperature anharmonic response is further investigated, via analysis of the elastic incoherent neutron scattering intensity, by applying models developed to describe side-group motion in glassy polymers. Our results suggest that the deviation from harmonic behavior is due to the onset of methyl group rotations which exhibit a broad distribution of activated processes ( E a,ave = 12.2 kJ.mol (-1), sigma = 5.0 kJ x mol (-1)). Our results are likened to those reported for other proteins.
Numerical solutions of anharmonic vibration of BaO and SrO molecules
Pramudito, Sidikrubadi; Sanjaya, Nugraha Wanda [Theoretical Physics Division, Department of Physics, Bogor Agricultural University, Jalan Meranti Kampus IPB Dramaga Bogor 16680 (Indonesia); Sumaryada, Tony, E-mail: tsumaryada@ipb.ac.id [Theoretical Physics Division, Department of Physics, Bogor Agricultural University, Jalan Meranti Kampus IPB Dramaga Bogor 16680 (Indonesia); Computational Biophysics and Molecular Modeling Research Group (CBMoRG), Department of Physics, Bogor Agricultural University, Jalan Meranti Kampus IPB Dramaga Bogor 16680 (Indonesia)
2016-03-11
The Morse potential is a potential model that is used to describe the anharmonic behavior of molecular vibration between atoms. The BaO and SrO molecules, which are two almost similar diatomic molecules, were investigated in this research. Some of their properties like the value of the dissociation energy, the energy eigenvalues of each energy level, and the profile of the wavefunctions in their correspondence vibrational states were presented in this paper. Calculation of the energy eigenvalues and plotting the wave function’s profiles were performed using Numerov method combined with the shooting method. In general we concluded that the Morse potential solved with numerical methods could accurately produce the vibrational properties and the wavefunction behavior of BaO and SrO molecules from the ground state to the higher states close to the dissociation level.
Coherent molecule formation in anharmonic potentials near confinement-induced resonances.
Sala, S; Zürn, G; Lompe, T; Wenz, A N; Murmann, S; Serwane, F; Jochim, S; Saenz, A
2013-05-17
We perform a theoretical and experimental study of a system of two ultracold atoms with tunable interaction in an elongated trapping potential. We show that the coupling of center-of-mass and relative motion due to an anharmonicity of the trapping potential leads to a coherent coupling of a state of an unbound atom pair and a molecule with a center of mass excitation. By performing the experiment with exactly two particles we exclude three-body losses and can therefore directly observe coherent molecule formation. We find quantitative agreement between our theory of inelastic confinement-induced resonances and the experimental results. This shows that the effects of center-of-mass to relative-motion coupling can have a significant impact on the physics of quantum systems near center-of-mass to relative-motion coupling resonances.
Exchange–correlation errors at harmonic and anharmonic orders: the case of bulk Cu
Shobhana Narasimhan; Stefano De Gironcoli
2003-01-01
As an aid towards improving the treatment of exchange and correlation effects in electronic structure calculations, it is desirable to have a clear picture of the errors introduced by currently popular approximate exchange–correlation functionals. We have performed ab initio density functional theory and density functional perturbation theory calculations to investigate the thermal properties of bulk Cu, using both the local density approximation (LDA) and the generalized gradient approximation (GGA). Thermal effects are treated within the quasiharmonic approximation. We find that the LDA and GGA errors for anharmonic quantities are an order of magnitude smaller than for harmonic quantities; we argue that this might be a general feature. We also obtain much closer agreement with experiment than earlier, more approximate calculations.
Elastic and anelastic properties of densified vitreous B2O3: Relaxations and anharmonicity
Carini, Giovanni, Jr.; Carini, Giuseppe; Tripodo, Gaspare; di Marco, Gaetano; Gilioli, Edmondo
2012-03-01
The elastic and anelastic properties of densified B2O3 glasses, melt quenched under pressures of 2 and 4 GPa, were investigated by measuring the sound velocity and the acoustic attenuation of longitudinal and shear ultrasonic waves in the megahertz range over the temperature interval between 8 and 300 K. Densification from 1826 to 2373 kg/m3 leads to an extraordinarily large growth of both bulk and shear moduli but leaves the Poisson's ratio nearly constant. In the glass compacted at 4 GPa, the elastic moduli become larger by a factor of five than those characterizing normal vitreous B2O3 (v-B2O3) as a consequence of modifications of the chemical bonding in the network. The thermally activated relaxations of intrinsic structural defects, which dominate the acoustic behaviors of normal glass below 150 K, giving rise to an intense attenuation peak and a corresponding steep decrease in sound velocity, are increasingly depressed by growing densification. Above 150 K, the ultrasonic velocity is mainly regulated by the vibrational anharmonicity and shows a nearly linear decrease as the temperature is increased, with a substantially smaller slope with increasing densification. Modeling the relaxation losses and the related velocity variations by an asymmetric double-well potential model that has a distribution of both the barrier potential and the asymmetry, it has been possible to separate the relaxation and the anharmonic contributions to the sound velocity. The former has been ascribed to local motions of boroxol rings formed by connected BO3 planar triangles, the basic units building up the network of v-B2O3, while the latter has been interpreted in terms of the Akhiezer mechanism concerning the “thermal vibration viscosity.”
Latyshev, A V
2016-01-01
The analytical solution of the boundary problem on behaviour (oscillations) of the electronic plasmas with arbitrary degree of degeneration of electronic gas in a slab of the conducting medium is received. The kinetic Vlasov---Boltzmann equation with integral of collisions type BGK (Bhatnagar, Gross and Krook) and Maxwell equation for electric field are applied. Mirror (reflections) boundary conditions are used.
Trapped Ion Oscillation Frequencies as Sensors for Spectroscopy
Wilfried Nörtershäuser
2010-03-01
Full Text Available The oscillation frequencies of charged particles in a Penning trap can serve as sensors for spectroscopy when additional field components are introduced to the magnetic and electric fields used for confinement. The presence of so-called “magnetic bottles” and specific electric anharmonicities creates calculable energy-dependences of the oscillation frequencies in the radiofrequency domain which may be used to detect the absorption or emission of photons both in the microwave and optical frequency domains. The precise electronic measurement of these oscillation frequencies therefore represents an optical sensor for spectroscopy. We discuss possible applications for precision laser and microwave spectroscopy and their role in the determination of magnetic moments and excited state lifetimes. Also, the trap-assisted measurement of radiative nuclear de-excitations in the X-ray domain is discussed. This way, the different applications range over more than 12 orders of magnitude in the detectable photon energies, from below μeV in the microwave domain to beyond MeV in the X-ray domain.
Oscillations in a simple climate–vegetation model
J. Rombouts
2015-05-01
Full Text Available We formulate and analyze a simple dynamical systems model for climate–vegetation interaction. The planet we consider consists of a large ocean and a land surface on which vegetation can grow. The temperature affects vegetation growth on land and the amount of sea ice on the ocean. Conversely, vegetation and sea ice change the albedo of the planet, which in turn changes its energy balance and hence the temperature evolution. Our highly idealized, conceptual model is governed by two nonlinear, coupled ordinary differential equations, one for global temperature, the other for vegetation cover. The model exhibits either bistability between a vegetated and a desert state or oscillatory behavior. The oscillations arise through a Hopf bifurcation off the vegetated state, when the death rate of vegetation is low enough. These oscillations are anharmonic and exhibit a sawtooth shape that is characteristic of relaxation oscillations, as well as suggestive of the sharp deglaciations of the Quaternary. Our model's behavior can be compared, on the one hand, with the bistability of even simpler, Daisyworld-style climate–vegetation models. On the other hand, it can be integrated into the hierarchy of models trying to simulate and explain oscillatory behavior in the climate system. Rigorous mathematical results are obtained that link the nature of the feedbacks with the nature and the stability of the solutions. The relevance of model results to climate variability on various timescales is discussed.
Non-degenerate 2-photon excitation in scattering medium for fluorescence microscopy
Yang, Mu-Han; Saisan, Payam A; Tian, Peifang; Ferri, Christopher G L; AnnaDevor,; Fainman, Yeshaiahu
2016-01-01
Non-degenerate 2-photon excitation (ND-2PE) of a fluorophore with two laser beams of different photon energies offers an independent degree of freedom in tuning of the photon flux for each beam. This feature takes advantage of the infrared wavelengths used in 3-photon microscopy to achieve an increased penetration depth, while preserving a relatively high degenerate 2-photon excitation (D-2PE) cross section, exceeding that achievable with 3-photon excitation. Here, using spatially and temporally aligned Ti:Sapphire laser and optical parametric oscillator beams operating at near infrared (NIR) and short-wavelength infrared (SWIR) optical frequencies, respectively, we provide a practical demonstration that the emission intensity of a fluorophore excited in the non-degenerate regime in a scattering medium is more efficient than the commonly used D-2PE.
Disc degeneration: current surgical options
C Schizas
2010-10-01
Full Text Available Chronic low back pain attributed to lumbar disc degeneration poses a serious challenge to physicians. Surgery may be indicated in selected cases following failure of appropriate conservative treatment. For decades, the only surgical option has been spinal fusion, but its results have been inconsistent. Some prospective trials show superiority over usual conservative measures while others fail to demonstrate its advantages. In an effort to improve results of fusion and to decrease the incidence of adjacent segment degeneration, total disc replacement techniques have been introduced and studied extensively. Short-term results have shown superiority over some fusion techniques. Mid-term results however tend to show that this approach yields results equivalent to those of spinal fusion. Nucleus replacement has gained some popularity initially, but evidence on its efficacy is scarce. Dynamic stabilisation, a technique involving less rigid implants than in spinal fusion and performed without the need for bone grafting, represents another surgical option. Evidence again is lacking on its superiority over other surgical strategies and conservative measures. Insertion of interspinous devices posteriorly, aiming at redistributing loads and relieving pain, has been used as an adjunct to disc removal surgery for disc herniation. To date however, there is no clear evidence on their efficacy. Minimally invasive intradiscal thermocoagulation techniques have also been tried, but evidence of their effectiveness is questioned. Surgery using novel biological solutions may be the future of discogenic pain treatment. Collaboration between clinicians and basic scientists in this multidisciplinary field will undoubtedly shape the future of treating symptomatic disc degeneration.
Regularized degenerate multi-solitons
Correa, Francisco
2016-01-01
We report complex PT-symmetric multi-soliton solutions to the Korteweg de-Vries equation that asymptotically contain one-soliton solutions, with each of them possessing the same amount of finite real energy. We demonstrate how these solutions originate from degenerate energy solutions of the Schroedinger equation. Technically this is achieved by the application of Darboux-Crum transformations involving Jordan states with suitable regularizing shifts. Alternatively they may be constructed from a limiting process within the context Hirota's direct method or on a nonlinear superposition obtained from multiple Baecklund transformations. The proposed procedure is completely generic and also applicable to other types of nonlinear integrable systems.
Radiative seesaw and degenerate neutrinos
Bajc, B; Bajc, Borut; Senjanovic, Goran
2005-01-01
The radiative see-saw mechanism of Witten generates the right-handed neutrino masses in SO(10) with the spinorial 16_H Higgs field. We study here analytically the 2nd and 3rd generations for the minimal Yukawa structure containing 10_H and 120_H Higgs representations. In the approximation of small 2nd generation masses and gauge loop domination we find the following results : (1) b-tau unification, (2) natural coexistence between large theta_l and small theta_q, (3) degenerate neutrinos.
The SU(1, 1) Perelomov number coherent states and the non-degenerate parametric amplifier
Ojeda-Guillén, D., E-mail: dojedag@ipn.mx; Granados, V. D. [Escuela Superior de Física y Matemáticas, Instituto Politécnico Nacional, Ed. 9, Unidad Profesional Adolfo López Mateos, C.P. 07738 México D. F. (Mexico); Mota, R. D. [Escuela Superior de Ingeniería Mecánica y Eléctrica, Unidad Culhuacán, Instituto Politécnico Nacional, Av. Santa Ana No. 1000, Col. San Francisco Culhuacán, Delegación Coyoacán, C.P. 04430, México D. F. (Mexico)
2014-04-15
We construct the Perelomov number coherent states for an arbitrary su(1, 1) group operation and study some of their properties. We introduce three operators which act on Perelomov number coherent states and close the su(1, 1) Lie algebra. By using the tilting transformation we apply our results to obtain the energy spectrum and eigenfunctions of the non-degenerate parametric amplifier. We show that these eigenfunctions are the Perelomov number coherent states of the two-dimensional harmonic oscillator.
Oscillator Based on Lumped Double Ladder Circuit with Band Edge Degeneracy
Oshmarin, Dmitry; Othman, Mohamed A K; Sloan, Jeff; Radfar, Mohammad; Green, Michael M; Capolino, Filippo
2016-01-01
An oscillator design based on a periodic, double ladder resonant circuit is proposed. The circuit exhibits a degenerate band edge (DBE) in the dispersion diagram of its phase-frequency eigenstates, and possesses unique resonance features associated with a high Q-factor resonance, compared to a single ladder or a conventional LC tank circuit. This oscillator is shown to have an oscillation threshold that is half that of a single LC ladder circuit having the same total quality factor, and thus is more robust than an LC oscillator in the presence of losses. It is also shown that the output and amplitude of the double-ladder oscillator is much less sensitive to the output loading compared to single-ladder oscillators. We show the analysis and design of such oscillators that potentially lead to enhancing the efficiency of RF components and sources.
Ma, Hongbin
2015-01-01
This book presents the fundamental fluid flow and heat transfer principles occurring in oscillating heat pipes and also provides updated developments and recent innovations in research and applications of heat pipes. Starting with fundamental presentation of heat pipes, the focus is on oscillating motions and its heat transfer enhancement in a two-phase heat transfer system. The book covers thermodynamic analysis, interfacial phenomenon, thin film evaporation, theoretical models of oscillating motion and heat transfer of single phase and two-phase flows, primary factors affecting oscillating motions and heat transfer, neutron imaging study of oscillating motions in an oscillating heat pipes, and nanofluid’s effect on the heat transfer performance in oscillating heat pipes. The importance of thermally-excited oscillating motion combined with phase change heat transfer to a wide variety of applications is emphasized. This book is an essential resource and learning tool for senior undergraduate, gradua...
Phenomenology of neutrino oscillations
G Rajasekaran
2000-07-01
The phenomenology of solar, atmospheric, supernova and laboratory neutrino oscillations is described. Analytical formulae for matter effects are reviewed. The results from oscillations are confronted with neutrinoless double beta decay.
Sanin, A.; Semyonov, E.
2012-01-01
Numerical integration of the non-stationary Schrödinger equation with Duffing potential depending on two coordinates has been carried out. Oscillation types and the influence of coupling between two oscillators on frequency spectra are analyzed in detail.
Macular Degeneration Prevention and Risk Factors
... Grant Terms & Conditions Patent & Intellectual Property Policy For Current Awardees FAQs Our Funding Philosophy ... Alzheimer’s Disease Research Macular Degeneration Research National Glaucoma Research ...
[Pathogenesis of age-related macular degeneration].
Kaarniranta, Kai; Seitsonen, Sanna; Paimela, Tuomas; Meri, Seppo; Immonen, Ilkka
2009-01-01
Age-related macular degeneration is a multiform disease of the macula, the region responsible for detailed central vision. In recent years, plenty of new knowledge of the pathogenesis of this disease has been obtained, and the treatment of exudative macular degeneration has greatly progressed. The number of patients with age-related macular degeneration will multiply in the following decades, because knowledge of mechanisms of development of macular degeneration that could be subject to therapeutic measures is insufficient. Central underlying factors are genetic inheritance, exposure of the retina to chronic oxidative stress and accumulation of inflammation-inducing harmful proteins into or outside of retinal cells.
Structure of Degenerate Block Algebras
Linsheng Zhu; Daoji Meng
2003-01-01
Given a non-trivial torsion-free abelian group (A,+,0), a field F of characteristic 0, and a non-degenerate bi-additive skew-symmetric map φ :A × A → F, we define a Lie algebra ∑ = ∑(A, φ) over F with basis {ex | x ∈ A\\{0}}and Lie product [ex, ey] = φ(x, y)ex+y. We show that ∑ is endowed uniquely with a non-degenerate symmetric invariant bilinear form and the derivation algebra Der ∑ of ∑ is a complete Lie algebra. We describe the double extension D(∑, T) of ∑ by T, where T is spanned by the locally finite derivations of ∑, and determine the second cohomology group H2(D(∑,T),F) using anti-derivations related to the form on D(∑, T). Finally, we compute the second Leibniz cohomology groups HL2(∑, F) and HL2(D(∑, T), F).
Neutrino Masses and Oscillations
Valle, J W F
2005-01-01
I summarize the status of three--neutrino oscillations that follow from combining the relevant world's data. The discussion includes the small parameters Delta_m-sol/Delta_m-atm and \\sin^2\\theta_{13}, which characterize the strength of CP violation in neutrino oscillations, the impact of oscillation data on the prospects for probing the absolute scale of neutrino mass in \
The colpitts oscillator family
Lindberg, Erik; Murali, K.; Tamasevicius, A.
A tutorial study of the Colpitts oscillator family defined as all oscillators based on a nonlinear amplifier and a three- terminal linear resonance circuit with one coil and two capacitors. The original patents are investigated. The eigenvalues of the linearized Jacobian for oscillators based...
Some Implications of Neutron Mirror Neutron Oscillation
Mohapatra, Rabindra N; Nussinov, S
2005-01-01
We comment on a recently discussed possibility of oscillations between neutrons and degenerate mirror neutrons in the context of mirror models for particles and forces. It has been noted by Bento and Berezhiani that if these oscillations occurred at a rate of $\\tau^{-1}_{NN'}\\sim sec^{-1}$, it would help explain putative super GKZ cosmic ray events provided the temperature of the mirror radiation is $\\sim 0.3-0.4$ times that of familiar cosmic microwave background radiation. We discuss how such oscillation time scales can be realized in mirror models and find that the simplest nonsupersymmetric model for this idea requires the existence of a low mass (30-3000 GeV) color triplet scalar or vector boson. A supersymmetric model, where this constraint can be avoided is severely constrained by the requirement of maintaining a cooler mirror sector. We also find that the reheat temperature after inflation in generic models that give fast $n-n'$ oscillation be less than about 100 GeV in order to maintain the required ...
Schwinger's oscillator method, supersymmetric quantum mechanics and massless particles
Mejía F. M.
2002-01-01
Full Text Available We consider Schwinger's method of angular momentum addition using the SU(2 algebra with both a fermionic and a bosonic oscillator. We show that the total spin states obtained are: one boson singlet state and an arbitrary number of spin-1/2 states, the later ones are energy degenerate. It means that we have in this case supersymmetric quantum mechanics and also the addition of angular momentum for massless particles. We review too the cases of two bosonic and two fermionic oscillators.
Neutrino oscillations: theory and phenomenology
Akhmedov, E.K., E-mail: akhmedov@ictp.trieste.it [Department of Theoretical Physics, Royal Institute of Technology, AlbaNova University Center, SE-106 91 Stockholm (Sweden)
2011-12-15
A brief overview of selected topics in the theory and phenomenology of neutrino oscillations is given. These include: oscillations in vacuum and in matter; phenomenology of 3-flavour neutrino oscillations; CP and T violation in neutrino oscillations in vacuum and in matter; matter effects on {nu}{sub {mu}}{r_reversible}{nu}{sub {tau}} oscillations; parametric resonance in neutrino oscillations inside the earth; oscillations below and above the MSW resonance; unsettled issues in the theory of neutrino oscillations.
Short-period intrinsic Stark GaN /AlGaN superlattice as a Bloch oscillator
Litvinov, V. I.; Manasson, A.; Pavlidis, D.
2004-07-01
We discuss the properties of AlGaN /GaN superlattice (SL) related to the feasibility of a terahertz-range oscillator. The distortion of the conduction-band profile by the polarization fields has been taken into account. We have calculated the conduction-band offset between the pseudomorphic AlGaN barrier and the GaN quantum well, the first miniband width and energy dispersion, as functions of Al content in the barrier. As the short-period SL miniband energy dispersion contains contributions from next to nearest neighbors, it causes anharmonic electron oscillations at the multiples of the fundamental Bloch frequency. The Al content and SL period that favor high-frequency oscillations have been determined.
Covariant harmonic oscillators and coupled harmonic oscillators
Han, Daesoo; Kim, Young S.; Noz, Marilyn E.
1995-01-01
It is shown that the system of two coupled harmonic oscillators shares the basic symmetry properties with the covariant harmonic oscillator formalism which provides a concise description of the basic features of relativistic hadronic features observed in high-energy laboratories. It is shown also that the coupled oscillator system has the SL(4,r) symmetry in classical mechanics, while the present formulation of quantum mechanics can accommodate only the Sp(4,r) portion of the SL(4,r) symmetry. The possible role of the SL(4,r) symmetry in quantum mechanics is discussed.
Rossi, Mariana; Ceriotti, Michele
2016-01-01
Molecular crystals often exist in multiple competing polymorphs, showing significantly different physico-chemical properties. Computational crystal structure prediction is key to interpret and guide the search for the most stable or useful form: A real challenge due to the combinatorial search space, and the complex interplay of subtle effects that work together to determine the relative stability of different structures. Here we take a comprehensive approach based on different flavors of thermodynamic integration in order to estimate all contributions to the free energies of these systems with density-functional theory, including the oft-neglected anharmonic contributions and nuclear quantum effects. We take the two main stable forms of paracetamol as a paradigmatic example. We find that anharmonic contributions, different descriptions of van der Waals interactions, and nuclear quantum effects all matter to quantitatively determine the stability of different phases. Our analysis highlights the many challenge...
Cheng Jian-zheng; Zhang De-jun; Lan Cong-qing; Ye Chao-hui
2000-01-01
Based on the cell model, the general formula for the free energy of solids is derived analytically with the lowest order anharmonic modification and correlation effect taken into account. Combining a method of summing over lattice sites, the analytic equation of state for generalized Lennard-Jones solid is derived. The calculations show that the agreement between theory and computer simulation is quite good and is significantly improved as compared with the numerical results in literature. The comparison of different effects shows the theory including all neighbors but only considering the lowest anharmonic and correlation effects may be a good and convenient approximation for practical solids. The approximation can be easily extended to the quantum case and other generalized potentials.
Phonon-state mixing in the lowest two $I^{\\pi}=2^+$ states of anharmonic vibration nuclei
Qin, Z Z
2016-01-01
The phonon-configuration mixing in $2^+_1$ and $2^+_2$ states beyond the anharmonic-vibration collectivity explains the universal correlations of $Q(2^+_1)=-Q(2^+_2)$. It also suggests another strong magnetic-moment correlation of $\\mu(2^+_1)=\\mu(2^+_2)$ for the anharmonic-vibration nuclei, which is further confirmed by our experimental-data survey. The global relation between $|Q(2^+)|$, $E_{2^+_1}$ and $E_{2^+_2}$ is analytically established according to the phonon-configuration mixing scheme, and roughly agrees with experiments. This relation may provide a convenient estimation of $|Q(2^+)|$ only with spectral input. The $N_pN_n$ scheme suggests that the phonon-configuration mixing may be driven by the neutron-proton interaction.
Nature's Autonomous Oscillators
Mayr, H. G.; Yee, J.-H.; Mayr, M.; Schnetzler, R.
2012-01-01
Nonlinearity is required to produce autonomous oscillations without external time dependent source, and an example is the pendulum clock. The escapement mechanism of the clock imparts an impulse for each swing direction, which keeps the pendulum oscillating at the resonance frequency. Among nature's observed autonomous oscillators, examples are the quasi-biennial oscillation and bimonthly oscillation of the Earth atmosphere, and the 22-year solar oscillation. The oscillations have been simulated in numerical models without external time dependent source, and in Section 2 we summarize the results. Specifically, we shall discuss the nonlinearities that are involved in generating the oscillations, and the processes that produce the periodicities. In biology, insects have flight muscles, which function autonomously with wing frequencies that far exceed the animals' neural capacity; Stretch-activation of muscle contraction is the mechanism that produces the high frequency oscillation of insect flight, discussed in Section 3. The same mechanism is also invoked to explain the functioning of the cardiac muscle. In Section 4, we present a tutorial review of the cardio-vascular system, heart anatomy, and muscle cell physiology, leading up to Starling's Law of the Heart, which supports our notion that the human heart is also a nonlinear oscillator. In Section 5, we offer a broad perspective of the tenuous links between the fluid dynamical oscillators and the human heart physiology.
Mixing Angles and Non-Degenerate Systems of Particles
Duret, Q; Duret, Quentin; Machet, Bruno
2006-01-01
Defining, in the framework of quantum field theory, their mass eigenstates through their matricial propagator, we show why the mixing matrices of non-degenerate coupled systems should not be parametrized as unitary. This is how, for leptonic binary systems, two-angles solutions with discrete values pi/4 [pi/2] and pi/2 [pi] arise when weak leptonic currents of mass eigenstates approximately satisfy the two properties of universality and vanishing of their non-diagonal neutral components. Charged weak currents are also discussed, which leads to a few remarks concerning oscillations. We argue that quarks, which cannot be defined on shell because of the confinement property, are instead more naturally endowed with unitary Cabibbo-like mixing matrices, involving a single unconstrained mixing angle. The similarity between neutrinos and neutral kaons is outlined, together with the role of the symmetry by exchange of families.
High-Order Elastic Constants and Anharmonic Properties of NaBH4: First-Principles Calculations
ZHANG Xiao-Dong; JIANG Zhen-Yi; ZHOU Bo; HOU Zhu-Feng; HOU Yu-Qing
2011-01-01
We present theoretical studies for second- and third-order elastic constants in NaBH4 based on ab initio calculations. Our calculated second-order elastic constants agree well with available experimental results. The anharmonic properties of NaBH4,such as pressure derivative of the second-order elastic constants and the Grüneisen constants for long-wavelength acoustic modeγ(q,j),are characterized using the third-order elastic constants.
Genetic association studies in lumbar disc degeneration
Eskola, Pasi J; Lemmelä, Susanna; Kjaer, Per
2012-01-01
Low back pain is associated with lumbar disc degeneration, which is mainly due to genetic predisposition. The objective of this study was to perform a systematic review to evaluate genetic association studies in lumbar disc degeneration as defined on magnetic resonance imaging (MRI) in humans....
Degenerated differential pair with controllable transconductance
Mensink, Clemens; Mensink, Clemens H.J.; Nauta, Bram
1998-01-01
A differential pair with input transistors and provided with a variable degeneration resistor. The degeneration resistor comprises a series arrangement of two branches of coupled resistors which are shunted in mutually corresponding points by respective control transistors whose gates are interconne
Regularized degenerate multi-solitons
Correa, Francisco; Fring, Andreas
2016-09-01
We report complex {P}{T} -symmetric multi-soliton solutions to the Korteweg de-Vries equation that asymptotically contain one-soliton solutions, with each of them possessing the same amount of finite real energy. We demonstrate how these solutions originate from degenerate energy solutions of the Schrödinger equation. Technically this is achieved by the application of Darboux-Crum transformations involving Jordan states with suitable regularizing shifts. Alternatively they may be constructed from a limiting process within the context Hirota's direct method or on a nonlinear superposition obtained from multiple Bäcklund transformations. The proposed procedure is completely generic and also applicable to other types of nonlinear integrable systems.
Degenerate doping of metallic anodes
Friesen, Cody A; Zeller, Robert A; Johnson, Paul B; Switzer, Elise E
2015-05-12
Embodiments of the invention relate to an electrochemical cell comprising: (i) a fuel electrode comprising a metal fuel, (ii) a positive electrode, (iii) an ionically conductive medium, and (iv) a dopant; the electrodes being operable in a discharge mode wherein the metal fuel is oxidized at the fuel electrode and the dopant increases the conductivity of the metal fuel oxidation product. In an embodiment, the oxidation product comprises an oxide of the metal fuel which is doped degenerately. In an embodiment, the positive electrode is an air electrode that absorbs gaseous oxygen, wherein during discharge mode, oxygen is reduced at the air electrode. Embodiments of the invention also relate to methods of producing an electrode comprising a metal and a doped metal oxidation product.
Martin, Jan M. L.
The quartic force fields of a number of small polyatomic molecules (specifically, rm H _2O, NH_2, NH_3, CH_4, BH_3, BeH_2, H_2CO, N_2O, CO_2, CS_2, OCS, H_2S, FNO, ClNO, and H_2CS) have been computed ab initio using large basis sets and augmented coupled cluster methods. It has been established throughout that harmonic and fundamental frequencies can consistently be reproduced to within about 10 cm^{ -1} of experimental using spdf basis sets, except in such inherently problematic cases as the umbrella motion in NH_3; such problems are solved by recomputing the harmonic frequencies with an spdf g basis set. Coupled cluster frequencies using small basis sets of spd quality agree surprisingly well with experiment (mean absolute error of 26 cm^ {-1}), but bond distances are generally seriously overestimated. Using spdf basis sets, they are consistently overestimated by 0.002 and 0.006-7 A for single and multiple bonds, respectively; for spdf g basis sets this drops to 0.001 and 0.003-4 A, respectively. Geometries and harmonic frequencies for highly polar fluorine compounds such as HF and FNO are qualitatively wrong unless special anion functions are added to the fluorine basis set. Anharmonicity, rovibrational coupling, and centrifugal distortion constants are consistently predicted well; the anharmonic portions of the computed force fields are probably more reliable than their experimental counterparts in many cases. Remaining errors in the computed geometries and harmonic frequencies are shown to be almost entirely due to a combination of core correlation and residual deficiencies in the electron correlation treatment. A 3-term correction for remaining basis set incompleteness to computed total atomization energies is proposed by the author, and is shown to result in mean absolute errors of as little as 0.5 kcal/mol for spdf g basis sets. Example applications on rm HCO^+, HOC^+, B_2C, BCN, and BNC testify to the predictive power of the methods used in this work.
Van Hung, Nguyen
2014-02-01
A pressure-dependent anharmonic correlated Einstein model is derived for extended X-ray absorption fine structure (EXAFS) Debye-Waller factors (DWFs), which are presented in terms of cumulant expansion up to the third order. The model is based on quantum thermodynamic perturbation theory and includes anharmonic effects based on empirical potentials. Explicit analytical expressions of the pressure-dependent changes in the interatomic distance, anharmonic effective potential, thermodynamic parameters, first, second, and third EXAFS cumulants, and thermal expansion coefficient have been derived. This model avoids the use of extensive full lattice dynamical calculations, yet provides good and reasonable agreement of numerical results for Cu with experimental results of X-ray diffraction (XRD) analysis and pressure-dependent EXAFS. Significant pressure effects are shown by the decrease in the pressure-induced changes in the interatomic distance, EXAFS cumulants and thermal expansion coefficient, as well as by the increase in the pressure-induced changes in the interatomic effective potential, effective spring constant, correlated Einstein frequency, and temperature.
Transversal parametric oscillation and its external stability in photorefractive sillenite crystals
Podivilov, E.V.; Pedersen, H.C.; Johansen, P.M.
1998-01-01
We develop the nonlinear theory of transversal parametric oscillation in photorefractive sillenite crystals. The theory is nonlinear in the sense that the nonlinear feedback from the parametric space-charge field waves, above threshold of their excitation, is taken into account. In this manner...... of transversal parametric oscillation is stable within certain regions of external and internal parameters. This is opposed to the degenerate case (K/2 subharmonic generation), which is unstable....
A memristor-based third-order oscillator: beyond oscillation
Talukdar, Abdul Hafiz Ibne
2012-10-06
This paper demonstrates the first third-order autonomous linear time variant circuit realization that enhances parametric oscillation through the usage of memristor in conventional oscillators. Although the output has sustained oscillation, the linear features of the conventional oscillators become time dependent. The poles oscillate in nonlinear behavior due to the oscillation of memristor resistance. The mathematical formulas as well as SPICE simulations are introduced for the memristor-based phase shift oscillator showing a great matching.
Anharmonic solution of Schrödinger time-independent equation
Ashraful Islam, Mohammed; Jamal Nazrul Islam
2011-08-01
We present here a mathematical explanation of how the Schrödinger equation for a class of harmonic oscillators possesses exact solutions. Some of the extended potentials used here are not present in the literature.
On the benefits of localized modes in anharmonic vibrational calculations for small molecules
Panek, Pawel T
2016-01-01
Anharmonic vibrational calculations can already be computationally demanding for relatively small molecules. The main bottlenecks lie in the construction of the potential energy surface and in the size of the excitation space in the vibrational configuration interaction (VCI) calculations. To address these challanges, we use localized-mode coordinates to construct potential energy surfaces and perform vibrational self-consistent field (L-VSCF) and L-VCI calculations [P. T. Panek, Ch. R. Jacob, ChemPhysChem 15, 3365 (2014)] for all vibrational modes of two prototypical test cases, the ethene and furan molecules. We find that the mutual coupling between modes is reduced when switching from normal-mode coordinates to localized-mode coordinates. When using such localized-mode coordinates, we observe a faster convergence of the $n$-mode expansion of the potential energy surface. This makes it possible to neglect higher-order contributions in the $n$-mode expansion of the potential energy surface or to approximate ...
Mackie, Cameron J., E-mail: mackie@strw.leidenuniv.nl; Candian, Alessandra; Tielens, Alexander G. G. M. [Leiden Observatory, Leiden University, P.O. Box 9513, 2300 RA Leiden (Netherlands); Huang, Xinchuan [SETI Institute, 189 Bernardo Avenue, Suite 100, Mountain View, California 94043 (United States); Maltseva, Elena; Buma, Wybren Jan [University of Amsterdam, Science Park 904, 1098 XH Amsterdam (Netherlands); Petrignani, Annemieke [Leiden Observatory, Leiden University, P.O. Box 9513, 2300 RA Leiden (Netherlands); Radboud University, FELIX Laboratory, Toernooiveld 7, 6525 ED Nijmegen (Netherlands); Oomens, Jos [Radboud University, FELIX Laboratory, Toernooiveld 7, 6525 ED Nijmegen (Netherlands); Lee, Timothy J. [NASA Ames Research Center, Moffett Field, California 94035-1000 (United States)
2015-12-14
Current efforts to characterize and study interstellar polycyclic aromatic hydrocarbons (PAHs) rely heavily on theoretically predicted infrared (IR) spectra. Generally, such studies use the scaled harmonic frequencies for band positions and double harmonic approximation for intensities of species, and then compare these calculated spectra with experimental spectra obtained under matrix isolation conditions. High-resolution gas-phase experimental spectroscopic studies have recently revealed that the double harmonic approximation is not sufficient for reliable spectra prediction. In this paper, we present the anharmonic theoretical spectra of three PAHs: naphthalene, anthracene, and tetracene, computed with a locally modified version of the SPECTRO program using Cartesian derivatives transformed from Gaussian 09 normal coordinate force constants. Proper treatments of Fermi resonances lead to an impressive improvement on the agreement between the observed and theoretical spectra, especially in the C–H stretching region. All major IR absorption features in the full-scale matrix-isolated spectra, the high-temperature gas-phase spectra, and the most recent high-resolution gas-phase spectra obtained under supersonically cooled molecular beam conditions in the CH-stretching region are assigned.
Photogeneration of superparaelectric large polarons in dielectrics with soft anharmonic T1u phonons
Nasu, Keiichiro
2003-05-01
In connection with the recent experiments on photoenhancements of the electronic conductivity and the quasistatic electric susceptibility of SrTiO3, we theoretically study global versus local parity violation of a photogenerated electron in this dielectric. The photogenerated electron, being quite itinerant in the 3d band of Ti, is assumed to couple weakly but quadratically with soft-anharmonic T1u phonons in this dielectric. The electron is also assumed to couple strongly but linearly to the breathing (A1g) type high energy phonons. We will show that these two types of electron-phonon (e-p) couplings result in two types of polarons, a “superparaelectric large polaron” with a quasiglobal parity violation, and an “off-center type self-trapped polaron” with only a local parity violation. These two states are shown to be separated by an adiabatic potential barrier, if these e-p couplings are short in their force ranges. Without the T1u phonon, these two states reduce to the well-known large polaron and the self-trapped one, both of which have even parities. We will also show that this superparaelectric large polaron enhances both the electronic conductivity and the quasistatic electric susceptibility, in qualitative agreements with the experiments.
Hydrodynamic theory of partially degenerate electron-hole fluids in semiconductors
Akbari-Moghanjoughi, M.; Eliasson, B.
2016-10-01
A quantum hydrodynamic theory for high-frequency electron-hole Langmuir and acoustic-like oscillations as well as static charge shielding effects in arbitrarily doped semiconductors is presented. The model includes kinetic corrections to the quantum statistical pressure and to the quantum Bohm potential for partially degenerate electrons and holes at finite temperatures. The holes contribute to the oscillations and screening effects in semiconductors in a similar manner as real particles. The dielectric functions are derived in the high-frequency limit for wave excitations and in the low-frequency limit for the study of static screening. The dispersion relation for the Langmuir and acoustic-like oscillations is examined for different parameters of doped silicon (Si). Some interesting properties and differences of electron hole dynamical behavior in N- and P-type Si are pointed out. Holes are also observed to enhance an attractive charge shielding effect when the semiconductor is highly acceptor-doped.
Minute-scale period oscillations of the magnetosphere
Pécseli, H. L.; Sato, H.; Børve, S.; Trulsen, J. K.
2012-04-01
Oscillations with periods on the order of 5-10 min have been observed by instrumented spacecrafts in the Earth's magnetosphere. These oscillations often follow sudden impacts related to coronal mass ejections. It is demonstrated that a simple model is capable of explaining the basic properties of these oscillations and give scaling laws for their basic characteristics in terms of the basic parameters of the problem. The period of the oscillations and their anharmonic nature, in particular, are accounted for. The model has no free adjustable numerical parameters. We use measurable quantities as inputs (such as Solar wind momentum density), and our results can be seen as an effort to predict some dynamic properties of magnetospheres on the basis of measurable steady state characteristics. A simple test of the model is found by comparing its prediction of the Earth-Magnetopause distance with observed values. The general results agree with observations. The analysis is supported by numerical simulations solving the Magneto-Hydro-Dynamic (MHD) equations in two spatial dimensions, where we let a solar wind interact with a magnetic dipole representing a magnetized Earth. Two tilt-angles of the magnetic dipole axis were considered. We observed the formation of a magnetosheath, with the magnetopause at a distance corresponding well to the analytical results. Sudden pulses in the model solar wind set the model magnetosphere into damped oscillatory motions and quantitatively good agreement with the analytical results is found. The models seem to be robust, and give good qualitative agreement with the numerical simulations for a range of parameters.
Dynamic models for magnetospheric oscillations on the minute scale
Sato, H.; Pecseli, H.; Børve, S.; Trulsen, J.
2012-12-01
Sudden pulses in the model solar wind sets the Earth's magnetosphere into damped oscillatory motions. Oscillation periods on the order of 5-10 min have been observed by instrumented spacecrafts. A simple model is capable of explaining the basic properties of these oscillations and give scaling laws for their characteristics in terms of the parameters of the problem, such as the Solar wind momentum density. The period of the oscillations, their damping and anharmonic nature are accounted for.The model has no free adjustable numerical parameters and can be seen as an effort to predict some dynamic properties of the magnetosphere on the basis of measurable steady state characteristics. A simple test of the model is found by comparing its prediction of the Earth-Magnetopause distance with observed values. The results agree well with observations. The analysis is supported by numerical simulations solving the Magneto-Hydro-Dynamic (MHD) equations in two spatial dimensions, where we let a solar wind interact with a magnetic dipole representing a magnetized Earth. Two tilt-angles of the magnetic dipole axis were considered. We observe the formation of a magnetosheath, with the magnetopause at a distance corresponding well to the analytical results. The analytical model seem to be robust, and gives good qualitative agreement with the numerical simulations for a range of parameters, also concerning oscillation periods and damping times for cases where the dynamic response to perturbations are considered. The analysis allows also for predicting the magnetic field perturbations detected on Earth due to changes in the magnetosheath current. In order to improve the model we study a conformal mapping that brings the shape of the magnetosheath model closer to observations.
Kato, Shoji
2016-01-01
This book presents the current state of research on disk oscillation theory, focusing on relativistic disks and tidally deformed disks. Since the launch of the Rossi X-ray Timing Explorer (RXTE) in 1996, many high-frequency quasiperiodic oscillations (HFQPOs) have been observed in X-ray binaries. Subsequently, similar quasi-periodic oscillations have been found in such relativistic objects as microquasars, ultra-luminous X-ray sources, and galactic nuclei. One of the most promising explanations of their origin is based on oscillations in relativistic disks, and a new field called discoseismology is currently developing. After reviewing observational aspects, the book presents the basic characteristics of disk oscillations, especially focusing on those in relativistic disks. Relativistic disks are essentially different from Newtonian disks in terms of several basic characteristics of their disk oscillations, including the radial distributions of epicyclic frequencies. In order to understand the basic processes...
A remark on the Dunne-Unsal relation in exact semi-classics
Gahramanov, Ilmar
2015-01-01
Recently, it is realized that non-perturbative instanton effects can be generated to all orders by perturbation theory around a degenerate minima via Dunne-Unsal relation in several quantum mechanical systems. In this work we verify the Dunne-Unsal relation for resonance energy levels of one-dimensional polynomial anharmonic oscillators. We show that the relation is applicable to cubic and quartic anharmonic oscillators which are genus one potentials. However for higher order (higher genus) anharmonic potentials the relation is not satisfied and is subject to a certain extension.
Remark on the Dunne-Ünsal relation in exact semiclassics
Gahramanov, Ilmar; Tezgin, Kemal
2016-03-01
Recently, it was realized that nonperturbative instanton effects can be generated to all orders by perturbation theory around a degenerate minima via the Dunne-Ünsal relation in several quantum mechanical systems. In this work we verify the Dunne-Ünsal relation for resonance energy levels of one-dimensional polynomial anharmonic oscillators. We show that the relation is applicable to cubic and quartic anharmonic oscillators which are genus-one potentials. However for higher order (higher genus) anharmonic potentials the relation is not satisfied and is subject to a certain extension.
Jenkins, Alejandro
2013-04-01
Physicists are very familiar with forced and parametric resonance, but usually not with self-oscillation, a property of certain dynamical systems that gives rise to a great variety of vibrations, both useful and destructive. In a self-oscillator, the driving force is controlled by the oscillation itself so that it acts in phase with the velocity, causing a negative damping that feeds energy into the vibration: no external rate needs to be adjusted to the resonant frequency. The famous collapse of the Tacoma Narrows bridge in 1940, often attributed by introductory physics texts to forced resonance, was actually a self-oscillation, as was the swaying of the London Millennium Footbridge in 2000. Clocks are self-oscillators, as are bowed and wind musical instruments. The heart is a “relaxation oscillator”, i.e., a non-sinusoidal self-oscillator whose period is determined by sudden, nonlinear switching at thresholds. We review the general criterion that determines whether a linear system can self-oscillate. We then describe the limiting cycles of the simplest nonlinear self-oscillators, as well as the ability of two or more coupled self-oscillators to become spontaneously synchronized (“entrained”). We characterize the operation of motors as self-oscillation and prove a theorem about their limit efficiency, of which Carnot’s theorem for heat engines appears as a special case. We briefly discuss how self-oscillation applies to servomechanisms, Cepheid variable stars, lasers, and the macroeconomic business cycle, among other applications. Our emphasis throughout is on the energetics of self-oscillation, often neglected by the literature on nonlinear dynamical systems.
Josephson quartic oscillator as a superconducting phase qubit
Zorin, Alexander [Physikalisch-Technische Bundesanstalt, 38116 Braunschweig (Germany); Chiarello, Fabio [Istituto di Fotonica e Nanotecnologie, CNR, 00156 Rome (Italy)
2010-07-01
Due to interplay between the cosine Josephson potential and parabolic magnetic-energy potential the radio-frequency SQUID with the screening parameter value {beta}{sub L} {identical_to}(2{pi}/{phi}{sub 0})LI{sub c} {approx}1 presents an oscillator circuit which energy well can dramatically change its shape. Ultimately, the magnetic flux bias of half flux quantum {phi}{sub e}={phi}{sub 0}/2 leads to the quartic polynomial shape of the well and, therefore, to significant anharmonicity of oscillations (> 30%). We show that the two lowest eigenstates in this symmetric global minimum perfectly suit for designing the qubit which is inherently insensitive to the charge variable, always biased in the optimal point and allows efficient dispersive and bifurcation-based readouts. Moreover, in the case of a double-SQUID configuration (dc SQUID instead of a single junction) the transition frequency in this Josephson phase qubit can be easy tuned within an appreciable range allowing variable qubit-qubit and qubit-resonator couplings.
Cosmological perturbations in coherent oscillating scalar field models
Cembranos, J.A.R.; Maroto, A.L.; Jareño, S.J. Núñez [Departamento de Física Teórica I, Universidad Complutense de Madrid,Avenida Complutense s/n, Madrid (Spain)
2016-03-03
The fact that fast oscillating homogeneous scalar fields behave as perfect fluids in average and their intrinsic isotropy have made these models very fruitful in cosmology. In this work we will analyse the perturbations dynamics in these theories assuming general power law potentials V(ϕ)=λ|ϕ|{sup n}/n. At leading order in the wavenumber expansion, a simple expression for the effective sound speed of perturbations is obtained c{sub eff}{sup 2}=ω=(n−2)/(n+2) with ω the effective equation of state. We also obtain the first order correction in k{sup 2}/ω{sub eff}{sup 2}, when the wavenumber k of the perturbations is much smaller than the background oscillation frequency, ω{sub eff}. For the standard massive case we have also analysed general anharmonic contributions to the effective sound speed. These results are reached through a perturbed version of the generalized virial theorem and also studying the exact system both in the super-Hubble limit, deriving the natural ansatz for δϕ; and for sub-Hubble modes, exploiting Floquet’s theorem.
Cosmological perturbations in coherent oscillating scalar field models
Cembranos, J A R; Jareño, S J Núñez
2015-01-01
The fact that fast oscillating homogeneous scalar fields behave as perfect fluids in average and their intrinsic isotropy have made these models very fruitful in cosmology. In this work we will analyse the perturbations dynamics in these theories assuming general power law potentials $V(\\phi)=\\lambda \\vert\\phi\\vert^{n}/n$. At leading order in the wavenumber expansion, a simple expression for the effective sound speed of perturbations is obtained $c_{\\text{eff}}^2 = \\omega=(n-2)/(n+2)$ with $\\omega$ the effective equation of state. We also obtain the first order correction in $k^2/\\omega_{\\text{eff}}^2$, when the wavenumber $k$ of the perturbations is much smaller than the background oscillation frequency, $\\omega_{\\text{eff}}$. For the standard massive case we have also analysed general anharmonic contributions to the effective sound speed. These results are reached through a perturbed version of the generalized virial theorem and also studying the exact system both in the super-Hubble limit, deriving the nat...
Oscillations of a highly discrete breather with a critical regime
Coquet; Remoissenet; Dinda
2000-10-01
We analyze carefully the essential features of the dynamics of a stationary discrete breather in the ultimate degree of energy localization in a nonlinear Klein-Gordon lattice with an on-site double-well potential. We demonstrate the existence of three different regimes of oscillatory motion in the breather dynamics, which are closely related to the motion of the central particle in an effective potential having two nondegenerate wells. In given parameter regions, we observe an untrapped regime, in which the central particle executes large-amplitude oscillations from one to the other side of the potential barrier. In other parameter regions, we find the trapped regime, in which the central particle oscillates in one of the two wells of the effective potential. Between these two regimes we find a critical regime in which the central particle undergoes several temporary trappings within an untrapped regime. Importantly, our study reveals that in the presence of purely anharmonic coupling forces, the breather compactifies, i.e., the energy becomes abruptly localized within the breather.
Cosmological perturbations in coherent oscillating scalar field models
Cembranos, J. A. R.; Maroto, A. L.; Jareño, S. J. Núñez
2016-03-01
The fact that fast oscillating homogeneous scalar fields behave as perfect fluids in average and their intrinsic isotropy have made these models very fruitful in cosmology. In this work we will analyse the perturbations dynamics in these theories assuming general power law potentials V( ϕ) = λ| ϕ| n /n. At leading order in the wavenumber expansion, a simple expression for the effective sound speed of perturbations is obtained c eff 2 = ω = ( n - 2)/( n + 2) with ω the effective equation of state. We also obtain the first order correction in k 2/ ω eff 2 , when the wavenumber k of the perturbations is much smaller than the background oscillation frequency, ω eff. For the standard massive case we have also analysed general anharmonic contributions to the effective sound speed. These results are reached through a perturbed version of the generalized virial theorem and also studying the exact system both in the super-Hubble limit, deriving the natural ansatz for δϕ; and for sub-Hubble modes, exploiting Floquet's theorem.
Bifurcations analysis of oscillating hypercycles.
Guillamon, Antoni; Fontich, Ernest; Sardanyés, Josep
2015-12-21
We investigate the dynamics and transitions to extinction of hypercycles governed by periodic orbits. For a large enough number of hypercycle species (n>4) the existence of a stable periodic orbit has been previously described, showing an apparent coincidence of the vanishing of the periodic orbit with the value of the replication quality factor Q where two unstable (non-zero) equilibrium points collide (named QSS). It has also been reported that, for values below QSS, the system goes to extinction. In this paper, we use a suitable Poincaré map associated to the hypercycle system to analyze the dynamics in the bistability regime, where both oscillatory dynamics and extinction are possible. The stable periodic orbit is identified, together with an unstable periodic orbit. In particular, we are able to unveil the vanishing mechanism of the oscillatory dynamics: a saddle-node bifurcation of periodic orbits as the replication quality factor, Q, undergoes a critical fidelity threshold, QPO. The identified bifurcation involves the asymptotic extinction of all hypercycle members, since the attractor placed at the origin becomes globally stable for values Qbifurcation, these extinction dynamics display a periodic remnant that provides the system with an oscillating delayed transition. Surprisingly, we found that the value of QPO is slightly higher than QSS, thus identifying a gap in the parameter space where the oscillatory dynamics has vanished while the unstable equilibrium points are still present. We also identified a degenerate bifurcation of the unstable periodic orbits for Q=1.
Modified gravitational instability of degenerate and non-degenerate dusty plasma
Jain, Shweta; Sharma, Prerana
2016-09-01
The gravitational instability of strongly coupled dusty plasma (SCDP) is studied considering degenerate and non-degenerate dusty plasma situations. The SCDP system is assumed to be composed of the electrons, ions, neutrals, and strongly coupled dust grains. First, in the high density regime, due to small interparticle distance, the electrons are considered degenerate, whereas the neutrals, dust grains, and ions are treated non-degenerate. In this case, the dynamics of inertialess electrons are managed by Fermi pressure and Bohm potential, while the inertialess ions are by only thermal pressure. Second, in the non-degenerate regime, both the electrons and ions are governed by the thermal pressure. The generalized hydrodynamic model and the normal mode analysis technique are employed to examine the low frequency waves and gravitational instability in both degenerate and non-degenerate cases. The general dispersion relation is discussed for a characteristic timescale which provides two regimes of frequency, i.e., hydrodynamic regime and kinetic regime. Analytical solutions reveal that the collisions reduce the growth rate and have a strong impact on structure formation in both degenerate and non-degenerate circumstances. Numerical estimation on the basis of observed parameters for the degenerate and non-degenerate cases is presented to show the effects of dust-neutral collisions and dust effective velocity in the presence of polarization force. The values of Jeans length and Jeans mass have been estimated for degenerate white dwarfs as Jeans length L J = 1.3 × 10 5 cm and Jeans mass M J = 0.75 × 10 - 3 M⊙ and for non-degenerate laboratory plasma Jeans length L J = 6.86 × 10 16 cm and Jeans mass M J = 0.68 × 10 10 M⊙. The stability of the SCDP system is discussed using the Routh-Hurwitz criterion.
A Monte Carlo algorithm for degenerate plasmas
Turrell, A.E., E-mail: a.turrell09@imperial.ac.uk; Sherlock, M.; Rose, S.J.
2013-09-15
A procedure for performing Monte Carlo calculations of plasmas with an arbitrary level of degeneracy is outlined. It has possible applications in inertial confinement fusion and astrophysics. Degenerate particles are initialised according to the Fermi–Dirac distribution function, and scattering is via a Pauli blocked binary collision approximation. The algorithm is tested against degenerate electron–ion equilibration, and the degenerate resistivity transport coefficient from unmagnetised first order transport theory. The code is applied to the cold fuel shell and alpha particle equilibration problem of inertial confinement fusion.
Horizon Supertranslation and Degenerate Black Hole Solution
Cai, Rong-Gen; Zhang, Yun-Long
2016-01-01
In this note we first review the degenerate vacua arising from the BMS symmetries. According to the discussion in [1] one can define BMS-analogous supertranslation and superrotation for spacetime with black hole in Gaussian null coordinates. In the leading and subleading orders of near horizon approximation, the infinitely degenerate black hole solutions are derived by considering Einstein equations with or without cosmological constant, and they are related to each other by the diffeomorphism generated by horizon supertranslation. Higher order results and degenerate Rindler horizon solutions also are given in appendices.
Genetics of frontotemporal lobar degeneration
Aswathy P
2010-10-01
Full Text Available Frontotemporal lobar degeneration (FTLD is a highly heterogenous group of progressive neurodegenerative disorders characterized by atrophy of prefrontal and anterior temporal cortices. Recently, the research in the field of FTLD has gained increased attention due to the clinical, neuropathological, and genetic heterogeneity and has increased our understanding of the disease pathogenesis. FTLD is a genetically complex disorder. It has a strong genetic basis and 50% of patients show a positive family history for FTLD. Linkage studies have revealed seven chromosomal loci and a number of genes including MAPT, PGRN, VCP, and CHMB-2B are associated with the disease. Neuropathologically, FTLD is classified into tauopathies and ubiquitinopathies. The vast majority of FTLD cases are characterized by pathological accumulation of tau or TDP-43 positive inclusions, each as an outcome of mutations in MAPT or PGRN, respectively. Identification of novel proteins involved in the pathophysiology of the disease, such as progranulin and TDP-43, may prove to be excellent biomarkers of disease progression and thereby lead to the development of better therapeutic options through pharmacogenomics. However, much more dissections into the causative pathways are needed to get a full picture of the etiology. Over the past decade, advances in research on the genetics of FTLD have revealed many pathogenic mutations leading to different clinical manifestations of the disease. This review discusses the current concepts and recent advances in our understanding of the genetics of FTLD.
Tlidi, M; Pieroux, D; Mandel, Paul
2003-09-15
We show that coupling diffraction and chromatic dispersion lead to body-centered cubic and hexagonally packed cylinders of dissipative optical crystals in a degenerate optical parametric oscillator. The stabilization of these crystals is a direct consequence of the interaction between the modulational and the quasi-neutral modes.
Vitelliform macular degeneration associated with mitochondrial myopathy.
Modi, G; Heckman, J M; Saffer, D
1992-01-01
A patient with mitochondrial myopathy is described. Examination of his fundus revealed bilateral vitelliform degeneration of the maculae. This lesion is a focal abnormality of the retinal pigment epithelium and may be a manifestation of the underlying mitochondrial disease.
Magnetic resonance imaging of intervertebral disc degeneration
Maeda, Hiroshi; Noguchi, Masao (Kitakyushu City Yahata Hospital, Fukuoka (Japan)); Kira, Hideaki; Fujiki, Hiroshi; Shimokawa, Isao; Hinoue, Kaichi
1993-02-01
The aim of this study was to correlate the degree of lumbar intervertebral disc degeneration with findings of magnetic resonance imaging (MRI). Seventeen autopsied (from 7 patients) and 21 surgical (from 20 patients) intervertebral discs were used as specimens for histopathological examination. In addition, 21 intervertebral discs were examined on T2-weighted images. Histopathological findings from both autopsied and surgical specimens were well correlated with MRI findings. In particular, T2-weighted images reflected increased collagen fibers and rupture within the fibrous ring accurately. However, when severely degenerated intervertebral discs and hernia protruding the posterior longitudinal ligament existed, histological findings were not concordant well with T2-weighted images. Morphological appearances of autopsy specimens, divided into four on T2-weighted images, were well consistent with histological degeneration. This morphological classification, as shown on T2-weighted images, could also be used in the evaluation of intervertebral disc degeneration. (N.K.).
Degenerate primer design for highly variable genomes.
Li, Kelvin; Shrivastava, Susmita; Stockwell, Timothy B
2015-01-01
The application of degenerate PCR primers towards target amplification and sequencing is a useful technique when a population of organisms under investigation is evolving rapidly, or is highly diverse. Degenerate bases in these primers are specified with ambiguity codes that represent alternative nucleotide configurations. Degenerate PCR primers allow the simultaneous amplification of a heterogeneous population by providing a mixture of PCR primers each of which anneal to an alternative genotype found in the isolated sample. However, as the number of degenerate bases specified in a pair of primers rises, the likelihood of amplifying unwanted alternative products also increases. These alternative products may confound downstream data analyses if their levels begin to obfuscate the desired PCR products. This chapter describes a set of computational methodologies that may be used to minimize the degeneracy of designed primers, while still maximizing the proportion of genotypes assayed in the targeted population.
Hyperchaotic Oscillator with Gyrators
Tamasevicius, A; Cenys, A; Mykolaitis, G.
1997-01-01
A fourth-order hyperchaotic oscillator is described. It contains a negative impedance converter, two gyratots, two capacitors and a diode. The dynamics of the oscillator is shown to be characterised by two positive Lyapunov exponents. The performance of the circuit is investigated by means...
Houdek, G
2010-01-01
In this short review on stellar convection dynamics I address the following, currently very topical, issues: (1) the surface effects of the Reynolds stresses and nonadiabaticity on solar-like pulsation frequencies, and (2) oscillation mode lifetimes of stochastically excited oscillations in red giants computed with different time-dependent convection formulations.
Dwyer, D A
2015-01-01
A concise summary of the "Oscillation at low energies" parallel session at the 2014 Neutrino Oscillation Workshop is provided. Plans to use man-made neutrinos and antineutrinos to determine the neutrino mass hierarchy, search for sterile neutrinos, and to observe coherent neutrino-nucleus scattering were discussed. Potential measurements of solar neutrinos, supernova neutrinos, and geoneutrinos are also summarized.
Hyperchaotic Oscillator with Gyrators
Tamasevicius, A; Cenys, A; Mykolaitis, G.;
1997-01-01
A fourth-order hyperchaotic oscillator is described. It contains a negative impedance converter, two gyratots, two capacitors and a diode. The dynamics of the oscillator is shown to be characterised by two positive Lyapunov exponents. The performance of the circuit is investigated by means...
Rodrigues, R. de Lima [Universidade Federal de Campina Grande (UFCG), Cuite, PB (Brazil). Centro de Tecnologia. Unidade Academica de Educacao]. E-mail: rafael@df.ufcg.edu.br; rafaelr@cbpf.br
2007-07-01
In the present work we obtain a new representation for the Dirac oscillator based on the Clifford algebra C 7. The symmetry breaking and the energy eigenvalues for our model of the Dirac oscillator are studied in the non-relativistic limit. (author)
Degenerate second order mean field games systems
Tonon, Daniela; Cardaliaguet, Pierre; Graber, Philip,; Poretta, Alessio
2014-01-01
Parallel session; International audience; We consider degenerate second order mean field games systems with a local coupling. The starting point is the idea that mean field games systems can be understood as an optimality condition for optimal control of PDEs. Developing this strategy for the degenerate second order case, we discuss the existence and uniqueness of a weak solution as well as its stability (vanishing viscosity limit). Speaker: Daniela TONON
The nature of apraxia in corticobasal degeneration.
Leiguarda, R; Lees, A J; Merello, M; STARKSTEIN, S; Marsden, C D
1994-01-01
Although apraxia is one of the most frequent signs in corticobasal degeneration, the phenomenology of this disorder has not been formally examined. Hence 10 patients with corticobasal degeneration were studied with a standardised evaluation for different types of apraxia. To minimise the confounding effects of the primary motor disorder, apraxia was assessed in the least affected limb. Whereas none of the patients showed buccofacial apraxia, seven showed deficits on tests of ideomotor apraxia...
Retinal Cell Degeneration in Animal Models
Masayuki Niwa; Hitomi Aoki; Akihiro Hirata; Hiroyuki Tomita; Green, Paul G.; Akira Hara
2016-01-01
The aim of this review is to provide an overview of various retinal cell degeneration models in animal induced by chemicals (N-methyl-d-aspartate- and CoCl2-induced), autoimmune (experimental autoimmune encephalomyelitis), mechanical stress (optic nerve crush-induced, light-induced) and ischemia (transient retinal ischemia-induced). The target regions, pathology and proposed mechanism of each model are described in a comparative fashion. Animal models of retinal cell degeneration provide insi...
Insight into structural phase transitions from the decoupled anharmonic mode approximation
Adams, Donat J.; Passerone, Daniele
2016-08-01
We develop a formalism (decoupled anharmonic mode approximation, DAMA) that allows calculation of the vibrational free energy using density functional theory even for materials which exhibit negative curvature of the potential energy surface with respect to atomic displacements. We investigate vibrational modes beyond the harmonic approximation and approximate the potential energy surface with the superposition of the accurate potential along each normal mode. We show that the free energy can stabilize crystal structures at finite temperatures which appear dynamically unstable at T = 0. The DAMA formalism is computationally fast because it avoids statistical sampling through molecular dynamics calculations, and is in principle completely ab initio. It is free of statistical uncertainties and independent of model parameters, but can give insight into the mechanism of a structural phase transition. We apply the formalism to the perovskite cryolite, and investigate the temperature-driven phase transition from the P21/n to the Immm space group. We calculate a phase transition temperature between 710 and 950 K, in fair agreement with the experimental value of 885 K. This can be related to the underestimation of the interaction of the vibrational states. We also calculate the main axes of the thermal ellipsoid and can explain the experimentally observed increase of its volume for the fluorine by 200-300% throughout the phase transition. Our calculations suggest the appearance of tunneling states in the high temperature phase. The convergence of the vibrational DOS and of the critical temperature with respect of reciprocal space sampling is investigated using the polarizable-ion model.
Elastic anharmonicity of bcc Fe and Fe-based random alloys from first-principles calculations
Li, Xiaoqing; Schönecker, Stephan; Zhao, Jijun; Vitos, Levente; Johansson, Börje
2017-01-01
We systematically investigate elastic anharmonic behavior in ferromagnetic body-centered cubic (bcc) Fe and Fe1 -xMx (M =Al , V, Cr, Co, or Ni) random alloys by means of density-functional simulations. To benchmark computational accuracy, three ab initio codes are used to obtain the complete set of second- and third-order elastic constants (TOECs) for bcc Fe. The TOECs of Fe1 -xMx alloys are studied employing the first-principles alloy theory formulated within the exact muffin-tin orbital method in combination with the coherent-potential approximation. It is found that the alloying effects on C111,C112 , and C123, which are governed by normal strains only, are more pronounced than those on C144,C166 , and C456, which involve shear strains. Remarkably, the magnitudes of all TOECs but C123 decrease upon alloying with Al, V, Cr, Co, or Ni. Using the computed TOECs, we study compositional effects on the pressure derivatives of the effective elastic constants (d Bi j/d P ), bulk (d K /d P ), and shear moduli (d G /d P ) and derive longitudinal acoustic nonlinearity parameters (β ). Our predictions show that the pressure derivatives of K and G decrease with x for all solute elements and reveal a strong correlation between the compositional trends on d K /d P and d G /d P arising from the fact that alloying predominantly alters d B11/d P . The sensitivity of d B11/d P to composition is attributed to intrinsic alloying effects as opposed to lattice parameter changes accompanying solute addition. For Fe and the considered Fe-based alloys, β along high-symmetry directions orders as β [111 ]>β [100 ]>β [110 ] , and alloying increases the directional anisotropy of β but reduces its magnitude.
De Marco, Luigi; Fournier, Joseph A.; Thämer, Martin; Carpenter, William; Tokmakoff, Andrei
2016-09-01
Water's extended hydrogen-bond network results in rich and complex dynamics on the sub-picosecond time scale. In this paper, we present a comprehensive analysis of the two-dimensional infrared (2D IR) spectrum of O-H stretching vibrations in liquid H2O and their interactions with bending and intermolecular vibrations. By exploring the dependence of the spectrum on waiting time, temperature, and laser polarization, we refine our molecular picture of water's complex ultrafast dynamics. The spectral evolution following excitation of the O-H stretching resonance reveals vibrational dynamics on the 50-300 fs time scale that are dominated by intermolecular delocalization. These O-H stretch excitons are a result of the anharmonicity of the nuclear potential energy surface that arises from the hydrogen-bonding interaction. The extent of O-H stretching excitons is characterized through 2D depolarization measurements that show spectrally dependent delocalization in agreement with theoretical predictions. Furthermore, we show that these dynamics are insensitive to temperature, indicating that the exciton dynamics alone set the important time scales in the system. Finally, we study the evolution of the O-H stretching mode, which shows highly non-adiabatic dynamics suggestive of vibrational conical intersections. We argue that the so-called heating, commonly observed within ˜1 ps in nonlinear IR spectroscopy of water, is a nonequilibrium state better described by a kinetic temperature rather than a Boltzmann distribution. Our conclusions imply that the collective nature of water vibrations should be considered in describing aqueous solvation.
Lotfipour, H.; Shahidani, S.; Roknizadeh, R.; M. H. Naderi
2016-01-01
In this paper, we theoretically investigate the displacement and momentum fluctuations spectra of the movable mirror in a standard optomechanical system driven by a finite bandwidth squeezed vacuum light accompanying a coherent laser field. Two cases in which the squeezed vacuum is generated by degenerated and non-degenerate parametric oscillators (DPO and NDPO) are considered. We find that for the case of finite bandwidth squeezed vacuum injection, the two spectra exhibit unique features, wh...
2006-01-01
The author develops a deformation theory for degenerations of complex curves; specifically, he treats deformations which induce splittings of the singular fiber of a degeneration. He constructs a deformation of the degeneration in such a way that a subdivisor is "barked" (peeled) off from the singular fiber. These "barking deformations" are related to deformations of surface singularities (in particular, cyclic quotient singularities) as well as the mapping class groups of Riemann surfaces (complex curves) via monodromies. Important applications, such as the classification of atomic degenerations, are also explained.
Disentangling neutrino oscillations
Cohen, Andrew G. [Physics Department, Boston University, Boston, MA 02215 (United States)], E-mail: cohen@bu.edu; Glashow, Sheldon L. [Physics Department, Boston University, Boston, MA 02215 (United States)], E-mail: slg@bu.edu; Ligeti, Zoltan [Ernest Orlando Lawrence Berkeley National Laboratory, University of California, Berkeley, CA 94720 (United States)], E-mail: ligeti@lbl.gov
2009-07-13
The theory underlying neutrino oscillations has been described at length in the literature. The neutrino state produced by a weak decay is usually portrayed as a linear superposition of mass eigenstates with, variously, equal energies or equal momenta. We point out that such a description is incorrect, that in fact, the neutrino is entangled with the other particle or particles emerging from the decay. We offer an analysis of oscillation phenomena involving neutrinos (applying equally well to neutral mesons) that takes entanglement into account. Thereby we present a theoretically sound proof of the universal validity of the oscillation formulae ordinarily used. In so doing, we show that the departures from exponential decay reported by the GSI experiment cannot be attributed to neutrino mixing. Furthermore, we demonstrate that the 'Moessbauer' neutrino oscillation experiment proposed by Raghavan, while technically challenging, is correctly and unambiguously describable by means of the usual oscillation formalae.
Fainman, Yeshaiahu; Yang, Mu-Han; Abashin, Maxim; Saisan, Payam; Tian, Peifang; Ferri, Christopher; Devor, Anna
2016-10-01
Non-degenerate 2-photon excitation of a fluorophore with two laser beams of different photon energies may offer independent degree of freedom in tuning of the photon flux (i.e., the power) for each beam. Wereport a practical demonstration that the emission intensity of a fluorophore excited in the non-degenerate regime in scattering medium is more efficient than the commonly used degenerate 2-photon excitation. In our experiments we use spatially and temporally aligned Ti:Sapphiremode-locked laser and optical parametric oscillator beams operating at near infrared (NIR) and short-wavelength infrared (SWIR) optical frequencies, respectively. The non-degenerate 2-photon excitation mechanism takes advantage of the infrared wavelengths used in 3-photon microscopy to achieve increased penetration depth, while preserving relatively high 2-photon excitation cross section, exceeding that achievable with the 3-photon excitation. Importantly, independent control of power for each beam implies that the flux requirement for the higher photon energy NIR beam, which experiences higher scattering in biological tissue, can be relaxed at the expense of increasing the flux of the lower photon energy SWIR beam which experiences lower scattering, thus promising deeper penetration with higher efficiency of excitation.Applications for in vivo brain imaging will be also discussed.
Carrier relaxation in (In,Ga)As quantum dots with magnetic field-induced anharmonic level structure
Kurtze, H.; Bayer, M. [Experimentelle Physik 2, TU Dortmund, D-44221 Dortmund (Germany)
2016-07-04
Sophisticated models have been worked out to explain the fast relaxation of carriers into quantum dot ground states after non-resonant excitation, overcoming the originally proposed phonon bottleneck. We apply a magnetic field along the quantum dot heterostructure growth direction to transform the confined level structure, which can be approximated by a Fock–Darwin spectrum, from a nearly equidistant level spacing at zero field to strong anharmonicity in finite fields. This changeover leaves the ground state carrier population rise time unchanged suggesting that fast relaxation is maintained upon considerable changes of the level spacing. This corroborates recent models explaining the relaxation by polaron formation in combination with quantum kinetic effects.
Sanson, Andrea, E-mail: andrea.sanson@unipd.it [Department of Physics and Astronomy, University of Padova, Padova (Italy); Giarola, Marco; Mariotto, Gino [Department of Computer Science, University of Verona, Verona (Italy); Hu, Lei; Chen, Jun; Xing, Xianran [Department of Physical Chemistry, University of Science and Technology Beijing, Beijing (China)
2016-09-01
Very recently it has been found that CaZrF{sub 6} exhibits a very large and isotropic negative thermal expansion (NTE), even greater than the current most popular NTE materials. In this work, the vibrational dynamics of CaZrF{sub 6} has been investigated by temperature-dependent Raman spectroscopy combined with ab initio calculations. As expected on the basis of the group theory for CaZrF{sub 6}, three Raman-active modes were identified: the F{sub 2g} mode peaked at about 236 cm{sup −1}, the E{sub g} mode at around 550–555 cm{sup −1}, and the A{sub g} mode peaked at about 637 cm{sup −1}. The temperature dependence of their frequencies follows an unusual trend: the F{sub 2g} mode, due to bending vibrations of fluorine atoms in the linear Ca-F-Zr chain, is hardened with increasing temperature, while the A{sub g} mode, corresponding to Ca-F-Zr bond stretching vibrations, is softened. We explain this anomalous behavior by separating implicit and explicit anharmonicity for both F{sub 2g} and A{sub g} modes. In fact, cubic anharmonicity (three-phonon processes) is observed to dominate the higher-frequency A{sub g} phonon-mode, quartic anharmonicity (four-phonon processes) is found to dominate the lower-frequency F{sub 2g} phonon-mode. As a result, the large NTE of CaZrF{sub 6} cannot be accurately predicted through the quasi-harmonic approximation. - Highlights: • A Raman and ab initio study of the lattice dynamics of CaZrF{sub 6} was performed. • All the Raman-active modes expected on the basis of the group theory were identified. • The temperature-dependence of the CaZrF{sub 6} Raman frequencies follows an unusual trend. • Explicit anharmonicity dominates for both F{sub 2g} and A{sub g} Raman modes. • The NTE of CaZrF{sub 6} cannot be accurately predicted by the quasi-harmonic approximation.
Fang, Chao; Wu, Guo-Zhen
2010-01-01
The vibrational dynamics of HOCl and HOBr between bending and OCl/OBr stretching coordinates with anharmonicity and Fermi coupling is studied with the classical dynamical potential approach. The quantal vibrational dynamics is mostly mapped out by the classical nonlinear variables such as fixed points, except for the state energies, which are quantized. This approach is global in the sense that the focus is on a set of levels instead of individual ones. The dynamics of HOBr is demonstrated to be less complicated. The localized modes along the OCl/OBr stretching coordinates are also shown to have O-Br bonds more prone to dissociation.
Kowal, Andrzej T.
2006-01-01
The equilibrium geometry of thioformamide HCSNH2 has been determined at the MP2 and CCSD (T) electron correlation levels under Cs symmetry constraints using triple-zeta basis sets up to cc-pVTZ. All optimized planar structures are true minima on the potential-energy surface and are characterized by the C-N bond length within 1.353-1.343Å, C-S distances of 1.656-1.628Å, and NCS angle between 125.7° and 125.9°. The wave number of the NH2 out-of-plane wagging mode computed in the harmonic approximation shows stronger dependence on the basis set rather than the electron correlation level and varies from 85.9cm-1 at CCSD (T)/cc-pVDZ level to 335cm-1 at MP2/aug-cc-pVTZ level. Anharmonic vibrational spectra of HCSNH2 and HCSND2 have been determined directly from the potential-energy surfaces computed at MP2 level in triple-zeta valence (TZV)(2df,2p) and TZV +(2df,2p) basis sets using vibrational self-consistent-field (VSCF) and correlation-corrected VSCF (CC-VSCF) methods. CC-VSCF wave numbers of fundamental, first overtone, and most intense combination transitions are reported for thioformamide and those of fundamentals for thioformamide-d2. The NH2 wagging (ν12) mode is strongly anharmonic and its fundamentals have been computed at 406.9cm-1[TZV(2df,2p)] and 399.5cm-1[TZV+(2df,2p)], which is remarkably close to the experimental energy of 393cm-1. Anharmonically computed fundamentals of this mode in thioformamide-d2, 299.7cm-1[TZV(2df,2p)] and 299.6cm-1[TZV+(2df,2p)], are only ˜7cm-1 higher than the transition energy (293cm-1) observed in the gas phase spectrum of HCSND2. The first overtone of the NH2 wagging mode of thioformamide (ν1202) has been calculated by CC-VSCF procedure at 830.8cm-1[TZV(2df,2p)] and 880.0cm-1[TZV+(2df,2p)], which implies "negative" (ν1202>2*ν1201) anharmonicity of this mode.
Boxing with neutrino oscillations
Wagner, D. J.; Weiler, Thomas J.
1999-06-01
We develop a characterization of neutrino oscillations based on the coefficients of the oscillating terms. These coefficients are individually observable; although they are quartic in the elements of the unitary mixing matrix, they are independent of the conventions chosen for the angle and phase parametrization of the mixing matrix. We call these reparametrization-invariant observables ``boxes'' because of their geometric relation to the mixing matrix, and because of their association with the Feynman box diagram that describes oscillations in field theory. The real parts of the boxes are the coefficients for the CP- or T-even oscillation modes, while the imaginary parts are the coefficients for the CP- or T-odd oscillation modes. Oscillation probabilities are linear in the boxes, so measurements can straightforwardly determine values for the boxes (which can then be manipulated to yield magnitudes of mixing matrix elements). We examine the effects of unitarity on the boxes and discuss the reduction of the number of boxes to a minimum basis set. For the three-generation case, we explicitly construct the basis. Using the box algebra, we show that CP violation may be inferred from measurements of neutrino flavor mixing even when the oscillatory factors have averaged. The framework presented here will facilitate general analyses of neutrino oscillations among n>=3 flavors.
Gavrilik, A M; Rebesh, A P
2010-01-01
We study the properties of sequences of the energy eigenvalues for some generalizations of q-deformed oscillators including the p,q-oscillator, the 3-, 4- and 5-parameter deformed oscillators given in the literature. It is shown that most of the considered models belong to the class of so-called Fibonacci oscillators for which any three consequtive energy levels satisfy the relation E_{n+1}=\\lambda E_n+\\rho E_{n-1} with real constants \\lambda, \\rho. On the other hand, for certain \\mu-oscillator known from 1993 we prove the fact of its non-Fibonacci nature. Possible generalizations of the three-term Fibonacci relation are discussed among which for the \\mu$-oscillator we choose, as the most adequate, the so-called quasi-Fibonacci (or local Fibonacci) property of the energy levels. The property is encoded in the three-term quasi-Fibonacci (QF) relation with non-constant, n-dependent coefficients \\lambda and \\rho. Various aspects of the QF relation are elaborated for the \\mu-oscillator and some of its extensions.
Gavrilik, A. M.; Kachurik, I. I.; Rebesh, A. P.
2010-06-01
We study the properties of the sequences of the energy eigenvalues for some generalizations of q-deformed oscillators including the p, q-oscillator, and the three-, four- and five-parameter deformed oscillators given in the literature. It is shown that most of the considered models belong to the class of so-called Fibonacci oscillators for which any three consecutive energy levels satisfy the relation En + 1 = λEn + ρEn - 1 with real constants λ, ρ. On the other hand, for a certain μ-oscillator known since 1993, we prove its non-Fibonacci nature. Possible generalizations of the three-term Fibonacci relation are discussed, among which for the μ-oscillator we choose, as the most adequate, the so-called quasi-Fibonacci (or local Fibonacci) property of the energy levels. The property is encoded in the three-term quasi-Fibonacci (QF) relation with the non-constant, n-dependent coefficients λ and ρ. Various aspects of the QF relation are elaborated for the μ-oscillator and some of its extensions.
All-Optical Quantum Random Bit Generation from Intrinsically Binary Phase of Parametric Oscillators
Marandi, Alireza; Vodopyanov, Konstantin L; Byer, Robert L
2012-01-01
True random number generators (RNGs) are desirable for applications ranging from cryptogra- phy to computer simulations. Quantum phenomena prove to be attractive for physical RNGs due to their fundamental randomness and immunity to attack [1]- [5]. Optical parametric down conversion is an essential element in most quantum optical experiments including optical squeezing [9], and generation of entangled photons [10]. In an optical parametric oscillator (OPO), photons generated through spontaneous down conversion of the pump initiate the oscillation in the absence of other inputs [11, 12]. This quantum process is the dominant effect during the oscillation build-up, leading to selection of one of the two possible phase states above threshold in a degenerate OPO [13]. Building on this, we demonstrate a novel all-optical quantum RNG in which the photodetection is not a part of the random process, and no post processing is required for the generated bit sequence. We implement a synchronously pumped twin degenerate O...
George, T F; George, Thomas F.
2000-01-01
An inversionless gain of anti-Stokes radiation above the oscillation threshold in an optically-dense far-from-degenerate double-Lambda Doppler-broadened medium accompanied by Stokes gain is predicted. The outcomes are illustrated with numerical simulations applied to sodium dimer vapor. Optical switching from absorption to gain via transparency controlled by a small variation of the medium and of the driving radiation parameters which are at a level less than one photon per molecule is shown.
Thicoipe, Sandrine; Carbonniere, Philippe; Pouchan, Claude
2014-01-01
This theoretical study provides the anharmonic vibrational wavenumbers of isolated and aqueous guanine. They were performed at the DFT B3LYP/6-31+G(d,p) level of theory using two different ways for the treatment of anharmonicity: time-independent (VPT2) and time-dependent (molecular dynamics) approaches. The wavenumbers obtained are compared to experimental data for isolated and aqueous forms: the VPT2 approach is slightly better than MD, especially for the determination of stretching and wagging (NH) motions. Finally, the structural model of solvatation used for aqueous guanine which combines an explicit solvent model with a polarizable continuum model (PCM) was validated.
Oscillating Filaments: I - Oscillation and Geometrical Fragmentation
Gritschneder, Matthias; Burkert, Andreas
2016-01-01
We study the stability of filaments in equilibrium between gravity and internal as well as external pressure using the grid based AMR-code RAMSES. A homogeneous, straight cylinder below a critical line mass is marginally stable. However, if the cylinder is bent, e.g. with a slight sinusoidal perturbation, an otherwise stable configuration starts to oscillate, is triggered into fragmentation and collapses. This previously unstudied behavior allows a filament to fragment at any given scale, as long as it has slight bends. We call this process `geometrical fragmentation'. In our realization the spacing between the cores matches the wavelength of the sinusoidal perturbation, whereas up to now, filaments were thought to be only fragmenting on the characteristical scale set by the mass-to-line ratio. Using first principles, we derive the oscillation period as well as the collapse timescale analytically. To enable a direct comparison with observations, we study the line-of-sight velocity for different inclinations. ...
Prospectives for gene therapy of retinal degenerations.
Thumann, Gabriele
2012-08-01
Retinal degenerations encompass a large number of diseases in which the retina and associated retinal pigment epithelial (RPE) cells progressively degenerate leading to severe visual disorders or blindness. Retinal degenerations can be divided into two groups, a group in which the defect has been linked to a specific gene and a second group that has a complex etiology that includes environmental and genetic influences. The first group encompasses a number of relatively rare diseases with the most prevalent being Retinitis pigmentosa that affects approximately 1 million individuals worldwide. Attempts have been made to correct the defective gene by transfecting the appropriate cells with the wild-type gene and while these attempts have been successful in animal models, human gene therapy for these inherited retinal degenerations has only begun recently and the results are promising. To the second group belong glaucoma, age-related macular degeneration (AMD) and diabetic retinopathy (DR). These retinal degenerations have a genetic component since they occur more often in families with affected probands but they are also linked to environmental factors, specifically elevated intraocular pressure, age and high blood sugar levels respectively. The economic and medical impact of these three diseases can be assessed by the number of individuals affected; AMD affects over 30 million, DR over 40 million and glaucoma over 65 million individuals worldwide. The basic defect in these diseases appears to be the relative lack of a neurogenic environment; the neovascularization that often accompanies these diseases has suggested that a decrease in pigment epithelium-derived factor (PEDF), at least in part, may be responsible for the neurodegeneration since PEDF is not only an effective neurogenic and neuroprotective agent but also a potent inhibitor of neovascularization. In the last few years inhibitors of vascularization, especially antibodies against vascular endothelial cell
Dupuis, Romain; Benoit, Magali; Tuckerman, Mark E; Méheut, Merlin
2017-07-18
Equilibrium fractionation of stable isotopes is critically important in fields ranging from chemistry, including medicinal chemistry, electrochemistry, geochemistry, and nuclear chemistry, to environmental science. The dearth of reliable estimates of equilibrium fractionation factors, from experiment or from natural observations, has created a need for accurate computational approaches. Because isotope fractionation is a purely quantum mechanical phenomenon, exact calculation of fractionation factors is nontrivial. Consequently, a severe approximation is often made, in which it is assumed that the system can be decomposed into a set of independent harmonic oscillators. Reliance on this often crude approximation is one of the primary reasons that theoretical prediction of isotope fractionation has lagged behind experiment. A class of problems for which one might expect the harmonic approximation to perform most poorly is the isotopic fractionation between solid and solution phases. In order to illustrate the errors associated with the harmonic approximation, we have considered the fractionation of Li isotopes between aqueous solution and phyllosilicate minerals, where we find that the harmonic approximation overestimates isotope fractionation factors by as much as 30% at 25 °C. Lithium is a particularly interesting species to examine, as natural lithium isotope signatures provide information about hydrothermal processes, carbon cycle, and regulation of the Earth's climate by continental alteration. Further, separation of lithium isotopes is of growing interest in the nuclear industry due to a need for pure (6)Li and (7)Li isotopes. Moving beyond the harmonic approximation entails performing exact quantum calculations, which can be achieved using the Feynman path integral formulation of quantum statistical mechanics. In the path integral approach, a system of quantum particles is represented as a set of classical-like ring-polymer chains, whose interparticle
The dissipative quantum Duffing oscillator: A comparison of Floquet-based approaches
Vierheilig, Carmen, E-mail: Carmen.Vierheilig@physik.uni-regensburg.de [Institut fuer Theoretische Physik, Universitaet Regensburg, Universitaetsstrasse 31, 93040 Regensburg (Germany); Grifoni, Milena [Institut fuer Theoretische Physik, Universitaet Regensburg, Universitaetsstrasse 31, 93040 Regensburg (Germany)
2010-10-05
We study the dissipative quantum Duffing oscillator in the deep quantum regime with two different approaches: The first is based on the exact Floquet states of the linear oscillator and the nonlinearity is treated perturbatively. It well describes the nonlinear oscillator dynamics away from resonance. The second, in contrast, is applicable at and in the vicinity of an N-photon resonance and it exploits quasi-degenerate perturbation theory for the nonlinear oscillator in Floquet space. It is perturbative both in driving and nonlinearity. A combination of both approaches yields the possibility to cover a wide range of driving frequencies. As an example we discuss the dissipative dynamics of the Duffing oscillator near and at the one-photon resonance.
Optic pathway degeneration in Japanese black cattle.
Chiba, Shiori; Funato, Shingo; Horiuchi, Noriyuki; Matsumoto, Kotaro; Inokuma, Hisashi; Furuoka, Hidefumi; Kobayashi, Yoshiyasu
2015-02-01
Degeneration of the optic pathway has been reported in various animal species including cattle. We experienced a case of bilateral optic tract degeneration characterized by severe gliosis in a Japanese black cattle without any obvious visual defects. To evaluate the significance, pathological nature and pathogenesis of the lesions, we examined the optic pathway in 60 cattle (41 Japanese black, 13 Holstein and 6 crossbreed) with or without ocular abnormalities. None of these animals had optic canal stenosis. Degenerative changes with severe gliosis in the optic pathway, which includes the optic nerve, optic chiasm and optic tract, were only observed in 8 Japanese black cattle with or without ocular abnormalities. Furthermore, strong immunoreactivity of glial fibrillary acidic protein was observed in the retinal stratum opticum and ganglion cell layer in all 5 cattle in which the optic pathway lesions could be examined. As etiological research, we also examined whether the concentrations of vitamin A and vitamin B12 or bovine viral diarrhea virus (BVDV) infection was associated with optic pathway degeneration. However, our results suggested that the observed optic pathway degeneration was probably not caused by these factors. These facts indicate the presence of optic pathway degeneration characterized by severe gliosis that has never been reported in cattle without bilateral compressive lesions in the optic pathway or bilateral severe retinal atrophy.
Synchronization of hyperchaotic oscillators
Tamasevicius, A.; Cenys, A.; Mykolaitis, G.
1997-01-01
Synchronization of chaotic oscillators is believed to have promising applications in secure communications. Hyperchaotic systems with multiple positive Lyapunov exponents (LEs) have an advantage over common chaotic systems with only one positive LE. Three different types of hyperchaotic electronic...
Neutrino anomalies without oscillations
Sandip Pakvasa
2000-01-01
I review explanations for the three neutrino anomalies (solar, atmospheric and LSND) which go beyond the `conventional' neutrino oscillations induced by mass-mixing. Several of these require non-zero neutrino masses as well.
High frequency nanotube oscillator
Peng, Haibing [Houston, TX; Zettl, Alexander K [Kensington, TX
2012-02-21
A tunable nanostructure such as a nanotube is used to make an electromechanical oscillator. The mechanically oscillating nanotube can be provided with inertial clamps in the form of metal beads. The metal beads serve to clamp the nanotube so that the fundamental resonance frequency is in the microwave range, i.e., greater than at least 1 GHz, and up to 4 GHz and beyond. An electric current can be run through the nanotube to cause the metal beads to move along the nanotube and changing the length of the intervening nanotube segments. The oscillator can operate at ambient temperature and in air without significant loss of resonance quality. The nanotube is can be fabricated in a semiconductor style process and the device can be provided with source, drain, and gate electrodes, which may be connected to appropriate circuitry for driving and measuring the oscillation. Novel driving and measuring circuits are also disclosed.
Neural Oscillators Programming Simplified
Patrick McDowell
2012-01-01
Full Text Available The neurological mechanism used for generating rhythmic patterns for functions such as swallowing, walking, and chewing has been modeled computationally by the neural oscillator. It has been widely studied by biologists to model various aspects of organisms and by computer scientists and robotics engineers as a method for controlling and coordinating the gaits of walking robots. Although there has been significant study in this area, it is difficult to find basic guidelines for programming neural oscillators. In this paper, the authors approach neural oscillators from a programmer’s point of view, providing background and examples for developing neural oscillators to generate rhythmic patterns that can be used in biological modeling and robotics applications.
Yao, X. S.; Maleki, L.
1995-01-01
We report a novel oscillator for photonic RF systems. This oscillator is capable of generating high-frequency signals up to 70 GHz in both electrical and optical domains and is a special voltage-controlled oscillator with an optical output port. It can be used to make a phase-locked loop (PLL) and perform all functions that a PLL is capable of for photonic systems. It can be synchronized to a reference source by means of optical injection locking, electrical injection locking, and PLL. It can also be self-phase locked and self-injection locked to generate a high-stability photonic RF reference. Its applications include high-frequency reference regeneration and distribution, high-gain frequency multiplication, comb-frequecy and square-wave generation, carrier recovery, and clock recovery. We anticipate that such photonic voltage-controlled oscillators (VCOs) will be as important to photonic RF systems as electrical VCOs are to electrical RF systems.
Atmospheric neutrino oscillations
Giacomelli, G; Antolini, R; Baldini, A; Barbarino, G C; Barish, B C; Battistoni, G; Becherini, Y; Bellotti, R; Bemporad, C; Bernardini, P; Bilokon, H; Bloise, C; Bower, C; Brigida, M; Cafagna, F; Campana, D; Carboni, M; Cecchini, S; Cei, F; Chiarella, V; Chiarusi, T; Choudhary, B C; Coutu, S; Cozzi, M; De Cataldo, G; Dekhissi, H; De Marzo, C; De Mitri, I; Derkauoi, J; De Vincenzi, M; Di Credico, A; Esposito, L; Forti, C; Fusco, P; Giannini, G; Giglietto, N; Giorgini, M; Grassi, M; Grillo, A; Gustavino, C; Habig, A; Hanson, K; Heinz, R; Iarocci, E; Katsavounidis, E; Katsavounidis, I; Kearns, E; Kim, H; Kumar, A; Kyriazopoulou, S; Lamanna, E; Lane, C; Levin, D S; Lipari, P; Longo, M J; Loparco, F; Maaroufi, F; Mancarella, G; Mandrioli, G; Manzoor, S; Margiotta, A; Marini, A; Martello, D; Marzari-Chiesa, A; Mazziotta, M N; Mengucci, A; Michael, D G; Monacelli, P; Montaruli, T; Monteno, M; Mufson, S; Musser, J; Nicolò, D; Nolty, R; Orth, C; Osteria, G; Palamara, O; Patera, V; Patrizii, L; Pazzi, R; Peck, C W; Perrone, L; Petrera, S; Popa, V; Rainó, A; Reynoldson, J; Ronga, F; Satriano, C; Scapparone, E; Scholberg, K; Sciubba, A; Sioli, M; Sirri, G; Sitta, M; Spinelli, P; Spinetti, M; Spurio, M; Steinberg, R; Stone, J L; Sulak, L R; Surdo, A; Tarle, G; Togo, V; Vakili, M; Walter, C W; Webb, R
2005-01-01
The latest results from the Soudan 2, MACRO and SuperKamiokande experiments on atmospheric neutrino oscillations are summarised and discussed. In particular a discussion is made on the Monte Carlo simulations used for the atmospheric neutrino flux.
Oscillations in counting statistics
Wilk, Grzegorz
2016-01-01
The very large transverse momenta and large multiplicities available in present LHC experiments on pp collisions allow a much closer look at the corresponding distributions. Some time ago we discussed a possible physical meaning of apparent log-periodic oscillations showing up in p_T distributions (suggesting that the exponent of the observed power-like behavior is complex). In this talk we concentrate on another example of oscillations, this time connected with multiplicity distributions P(N). We argue that some combinations of the experimentally measured values of P(N) (satisfying the recurrence relations used in the description of cascade-stochastic processes in quantum optics) exhibit distinct oscillatory behavior, not observed in the usual Negative Binomial Distributions used to fit data. These oscillations provide yet another example of oscillations seen in counting statistics in many different, apparently very disparate branches of physics further demonstrating the universality of this phenomenon.
Oscillating Filaments. I. Oscillation and Geometrical Fragmentation
Gritschneder, Matthias; Heigl, Stefan; Burkert, Andreas
2017-01-01
We study the stability of filaments in equilibrium between gravity and internal as well as external pressure using the grid-based AMR code RAMSES. A homogeneous, straight cylinder below a critical line mass is marginally stable. However, if the cylinder is bent, such as with a slight sinusoidal perturbation, an otherwise stable configuration starts to oscillate, is triggered into fragmentation, and collapses. This previously unstudied behavior allows a filament to fragment at any given scale, as long as it has slight bends. We call this process “geometrical fragmentation.” In our realization, the spacing between the cores matches the wavelength of the sinusoidal perturbation, whereas up to now, filaments were thought to be only fragmenting on the characteristic scale set by the mass-to-line ratio. Using first principles, we derive the oscillation period as well as the collapse timescale analytically. To enable a direct comparison with observations, we study the line-of-sight velocity for different inclinations. We show that the overall oscillation pattern can hide the infall signature of cores.
Indirect neutrino oscillations
Babu, K S; Wilczek, Frank; Pati, Jogesh C; Wilczek, Frank
1995-01-01
We show how two different scales for oscillations between e and \\mu neutrinos, characterized by different mixing angles and effective mass scales, can arise in a simple and theoretically attractive framework. One scale characterizes direct oscillations, which can accommodate the MSW approach to the solar neutrino problem, whereas the other can be considered as arising indirectly, through virtual transitions involving the \\tau neutrino with a mass \\sim 1 eV. This indirect transition allows the possibility of observable \\bar \
Kayser, Boris
2012-01-01
To complement the neutrino-physics lectures given at the 2011 International School on Astro Particle Physics devoted to Neutrino Physics and Astrophysics (ISAPP 2011; Varenna, Italy), at the 2011 European School of High Energy Physics (ESHEP 2011; Cheila Gradistei, Romania), and, in modified form, at other summer schools, we present here a written description of the physics of neutrino oscillation. This description is centered on a new way of deriving the oscillation probability. We also prov...
Ultrastable Multigigahertz Photonic Oscillator
Logan, Ronald T., Jr.
1996-01-01
Novel photonic oscillator developed to serve as ultrastable source of microwave and millimeter-wave signals. In system, oscillations generated photonically, then converted to electronic form. Includes self-mode-locked semiconductor laser producing stream of pulses, detected and fed back to laser as input. System also includes fiber-optic-delay-line discriminator, which detects fluctuations of self-mode-locking frequency and generates error signal used in negative-feedback loop to stabilize pulse-repetition frequency.
Scuflaire, R; Théado, S; Bourge, P -O; Miglio, A; Godart, M; Thoul, A; Noels, A
2007-01-01
The Liege Oscillation code can be used as a stand-alone program or as a library of subroutines that the user calls from a Fortran main program of his own to compute radial and non-radial adiabatic oscillations of stellar models. We describe the variables and the equations used by the program and the methods used to solve them. A brief account is given of the use and the output of the program.
Kiat, Jean-Michel; Baldinozzi, Gianguido; Dunlop, Muriel; Malibert, Charlotte; Dkhil, Brahim; Ménoret, Carole; Masson, Olivier; Fernandez-Diaz, Maria-Teresa
2000-10-01
We report a study of simple ABO3 type perovskites BaTiO3, PbTiO3, KNbO3, SrTiO3 and the relaxor perovskites PbSc1/2Nb1/2O3 (PSN) in their cubic phase using hard synchrotron radiation and hot neutrons. Gram-Charlier expansions of the thermal parameters have been performed and have revealed interesting features about the probability density function and the one-particle potential of the different atoms. This description is compared with other descriptions in terms of the split atom model and in terms of the rotator model. Structural trends regarding the order-disorder versus displacive character of the phase transitions have been obtained. It is concluded that SrTiO3 and BaTiO3 are quasi-harmonic systems whereas KNbO3 shows weak anharmonicity and PbTiO3 and PSN display strong anharmonic features.
Luo, Yixiu; Wang, Jiemin; Li, Yiran; Wang, Jingyang
2016-07-01
Modification of lattice thermal conductivity (κL) of a solid by means of hydrostatic pressure (P) has been a crucially interesting approach that targets a broad range of advanced materials from thermoelectrics and thermal insulators to minerals in mantle. Although it is well documented knowledge that thermal conductivity of bulk materials normally increase upon hydrostatic pressure, such positive relationship is seriously challenged when it comes to ceramics with complex crystal structure and heterogeneous chemical bonds. In this paper, we predict an abnormally negative trend dκL/dP functional theoretical calculations. The mechanism is disclosed as combined effects of slightly decreased group velocity and significantly augmented scattering of heat-carrying acoustic phonons in pressured lattice, which is originated from pressure-induced downward shift of low-lying optic and acoustic phonons. The structural origin of low-lying optic phonons as well as the induced phonon anharmonicity is also qualitatively elucidated with respect to intrinsic bonding heterogeneity of Y2Si2O7. The present results are expected to bring deeper insights for phonon engineering and modulation of thermal conductivity in complex solids with diverging structural flexibility, enormous bonding heterogeneity, and giant phonon anharmonicity.
Kolmann, Stephen J; Jordan, Meredith J T
2010-02-07
One of the largest remaining errors in thermochemical calculations is the determination of the zero-point energy (ZPE). The fully coupled, anharmonic ZPE and ground state nuclear wave function of the SSSH radical are calculated using quantum diffusion Monte Carlo on interpolated potential energy surfaces (PESs) constructed using a variety of method and basis set combinations. The ZPE of SSSH, which is approximately 29 kJ mol(-1) at the CCSD(T)/6-31G* level of theory, has a 4 kJ mol(-1) dependence on the treatment of electron correlation. The anharmonic ZPEs are consistently 0.3 kJ mol(-1) lower in energy than the harmonic ZPEs calculated at the Hartree-Fock and MP2 levels of theory, and 0.7 kJ mol(-1) lower in energy at the CCSD(T)/6-31G* level of theory. Ideally, for sub-kJ mol(-1) thermochemical accuracy, ZPEs should be calculated using correlated methods with as big a basis set as practicable. The ground state nuclear wave function of SSSH also has significant method and basis set dependence. The analysis of the nuclear wave function indicates that SSSH is localized to a single symmetry equivalent global minimum, despite having sufficient ZPE to be delocalized over both minima. As part of this work, modifications to the interpolated PES construction scheme of Collins and co-workers are presented.
Rossi, Mariana; Gasparotto, Piero; Ceriotti, Michele
2016-09-01
Molecular crystals often exist in multiple competing polymorphs, showing significantly different physicochemical properties. Computational crystal structure prediction is key to interpret and guide the search for the most stable or useful form, a real challenge due to the combinatorial search space, and the complex interplay of subtle effects that work together to determine the relative stability of different structures. Here we take a comprehensive approach based on different flavors of thermodynamic integration in order to estimate all contributions to the free energies of these systems with density-functional theory, including the oft-neglected anharmonic contributions and nuclear quantum effects. We take the two main stable forms of paracetamol as a paradigmatic example. We find that anharmonic contributions, different descriptions of van der Waals interactions, and nuclear quantum effects all matter to quantitatively determine the stability of different phases. Our analysis highlights the many challenges inherent in the development of a quantitative and predictive framework to model molecular crystals. However, it also indicates which of the components of the free energy can benefit from a cancellation of errors that can redeem the predictive power of approximate models, and suggests simple steps that could be taken to improve the reliability of ab initio crystal structure prediction.
Raman spectroscopic study of phase stability and anharmonicity in Bi{sub 12}TiO{sub 20}
Rao, Rekha, E-mail: rekhar@barc.gov.in [Solid State Physics Division, Bhabha Atomic Research Center, Mumbai 400 085 (India); Salke, Nilesh P. [Solid State Physics Division, Bhabha Atomic Research Center, Mumbai 400 085 (India); Garg, Alka B. [High Pressure and Synchrotron Radiation Physics Division, Bhabha Atomic Research Center, Mumbai 400 085 (India)
2013-05-15
Raman spectroscopic studies on lead-free piezo-electric compound Bi{sub 12}TiO{sub 20} is reported as a function of pressure upto 25 GPa at room temperature. Results indicate that the compound remains in stable crystalline phase upto 25 GPa. Temperature dependent Raman spectroscopic investigations on Bi{sub 12}TiO{sub 20} indicate that the compound is also stable at high temperatures upto 850 K. From measurements of temperature and pressure dependence of Raman mode frequencies, intrinsic anharmonic parameters are calculated for each of the Raman active modes which are useful in modeling of thermodynamic entities. The results are compared with that of analogous compound Bi{sub 12}SiO{sub 20}. Highlights: ► Raman spectroscopic study of Bi{sub 12}TiO{sub 20} is carried out at high pressure/temperature. ► This study indicates a good structural stability of Bi{sub 12}TiO{sub 20}. ► Bi{sub 12}TiO{sub 20} is an ideal system to evaluate the anharmonicity of vibrational modes.
Shulumba, Nina; Raza, Zamaan; Hellman, Olle; Janzén, Erik; Abrikosov, Igor A.; Odén, Magnus
2016-09-01
Wurtzite aluminium nitride (AlN) is a technologically important wide-band-gap semiconductor with an unusually high thermal conductivity, used in optical applications and as a heatsink substrate. Explaining many of its properties depends on an accurate description of its lattice dynamics, which have thus far only been captured in the quasiharmonic approximation. In this work, we show that anharmonic effects have a considerable impact on its phase stability and transport properties, since they are much stronger in the rocksalt phase. We construct a theoretical pressure-temperature phase diagram of AlN, demonstrating that the rocksalt phase is stabilized by increasing temperature, with respect to the wurtzite phase. We recover the thermal conductivity of the wurtzite phase (320 Wm-1K-1 under ambient conditions) and compute the hitherto unknown thermal conductivity of the rocksalt phase (81 Wm-1K-1 ). We also show that the electronic band gap decreases with temperature. These findings provide further evidence that anharmonic effects cannot be ignored in simulations of materials intended for high-temperature applications.
Jenkins, Alejandro
2011-01-01
Physicists are very familiar with forced and parametric resonance, but usually not with self-oscillation, a property of certain linear systems that gives rise to a great variety of vibrations, both useful and destructive. In a self-oscillator, the driving force is controlled by the oscillation itself so that it acts in phase with the velocity, causing a negative damping that feeds energy from the environment into the vibration: no external rate needs to be tuned to the resonant frequency. A paper from 1830 by G. B. Airy gives us the opening to introduce self-oscillation as a sort of "perpetual motion" responsible for the human voice. The famous collapse of the Tacoma Narrows bridge in 1940, often attributed by introductory physics texts to forced resonance, was actually a self-oscillation, as was the more recent swaying of the London Millenium Footbridge. Clocks are self-oscillators, as are bowed and wind musical instruments, and the heartbeat. We review the criterion that determines whether an arbitrary line...
A discussion of a homogenization procedure for a degenerate linear hyperbolic-parabolic problem
Flodén, L.; Holmbom, A.; Jonasson, P.; Lobkova, T.; Lindberg, M. Olsson; Zhang, Y.
2017-01-01
We study the homogenization of a hyperbolic-parabolic PDE with oscillations in one fast spatial scale. Moreover, the first order time derivative has a degenerate coefficient passing to infinity when ɛ→0. We obtain a local problem which is of elliptic type, while the homogenized problem is also in some sense an elliptic problem but with the limit for ɛ-1∂tuɛ as an undetermined extra source term in the right-hand side. The results are somewhat surprising and work remains to obtain a fully rigorous treatment. Hence the last section is devoted to a discussion of the reasonability of our conjecture including numerical experiments.
Phase space methods for degenerate quantum gases
Dalton, Bryan J; Barnett, Stephen M
2015-01-01
Recent experimental progress has enabled cold atomic gases to be studied at nano-kelvin temperatures, creating new states of matter where quantum degeneracy occurs - Bose-Einstein condensates and degenerate Fermi gases. Such quantum states are of macroscopic dimensions. This book presents the phase space theory approach for treating the physics of degenerate quantum gases, an approach already widely used in quantum optics. However, degenerate quantum gases involve massive bosonic and fermionic atoms, not massless photons. The book begins with a review of Fock states for systems of identical atoms, where large numbers of atoms occupy the various single particle states or modes. First, separate modes are considered, and here the quantum density operator is represented by a phase space distribution function of phase space variables which replace mode annihilation, creation operators, the dynamical equation for the density operator determines a Fokker-Planck equation for the distribution function, and measurable...
The cell stress machinery and retinal degeneration.
Athanasiou, Dimitra; Aguilà, Monica; Bevilacqua, Dalila; Novoselov, Sergey S; Parfitt, David A; Cheetham, Michael E
2013-06-27
Retinal degenerations are a group of clinically and genetically heterogeneous disorders characterised by progressive loss of vision due to neurodegeneration. The retina is a highly specialised tissue with a unique architecture and maintaining homeostasis in all the different retinal cell types is crucial for healthy vision. The retina can be exposed to a variety of environmental insults and stress, including light-induced damage, oxidative stress and inherited mutations that can lead to protein misfolding. Within retinal cells there are different mechanisms to cope with disturbances in proteostasis, such as the heat shock response, the unfolded protein response and autophagy. In this review, we discuss the multiple responses of the retina to different types of stress involved in retinal degenerations, such as retinitis pigmentosa, age-related macular degeneration and glaucoma. Understanding the mechanisms that maintain and re-establish proteostasis in the retina is important for developing new therapeutic approaches to fight blindness.
Families and degenerations of conformal field theories
Roggenkamp, D.
2004-09-01
In this work, moduli spaces of conformal field theories are investigated. In the first part, moduli spaces corresponding to current-current deformation of conformal field theories are constructed explicitly. For WZW models, they are described in detail, and sigma model realizations of the deformed WZW models are presented. The second part is devoted to the study of boundaries of moduli spaces of conformal field theories. For this purpose a notion of convergence of families of conformal field theories is introduced, which admits certain degenerated conformal field theories to occur as limits. To such a degeneration of conformal field theories, a degeneration of metric spaces together with additional geometric structures can be associated, which give rise to a geometric interpretation. Boundaries of moduli spaces of toroidal conformal field theories, orbifolds thereof and WZW models are analyzed. Furthermore, also the limit of the discrete family of Virasoro minimal models is investigated. (orig.)
Frequency of self-oscillations
Groszkowski, Janusz
2013-01-01
Frequency of Self-Oscillations covers the realm of electric oscillations that plays an important role both in the scientific and technical aspects. This book is composed of nine chapters, and begins with the introduction to the alternating currents and oscillation. The succeeding chapters deal with the free oscillations in linear isolated systems. These topics are followed by discussions on self-oscillations in linear systems. Other chapters describe the self-oscillations in non-linear systems, the influence of linear elements on frequency of oscillations, and the electro mechanical oscillato
Wessendorf, K.O.
1998-07-01
This paper describes the Active-Bridge Oscillator (ABO), a new concept in high-stability oscillator design. The ABO is ab ridge-type oscillator design that is easly to design and overcomes many of the operational and design difficulties associated with standard bridge oscillator designs. The ABO will oscillate with a very stable output amplitude over a wide range of operating conditions without the use of an automatic-level-control (ALC). A standard bridge oscillator design requires an ALC to maintain the desired amplitude of oscillation. for this and other reasons, bridge oscilaltors are not used in mainstream designs. Bridge oscillators are generally relegated to relatively low-volume, high-performance applications. The Colpitts and Pierce designs are the most popular oscillators but are typically less stable than a bridge-type oscillator.
[New aspects in age related macular degeneration].
Turlea, C
2012-01-01
Being the leading cause of blindness in modern world Age Related Macular Degeneration has beneficiated in the last decade of important progress in diagnosis, classification and the discovery of diverse factors who contribute to the etiology of this disease. Treatments have arised who can postpone the irreversible evolution of the disease and thus preserve vision. Recent findings have identified predisposing genetic factors and also inflamatory and imunological parameters that can be modified trough a good and adequate prevention and therapy This articole reviews new aspects of patology of Age Related Macular Degeneration like the role of complement in maintaining inflamation and the role of oxidative stress on different structures of the retina.
Intracavity frequency-doubled degenerate laser
Liew, Seng Fatt; Weiler, Sascha; Monjardin-Lopez, Jesus Fernando; Ramme, Mark; Redding, Brandon; Choma, Michael A; Cao, Hui
2016-01-01
We develop a green light source with low spatial coherence via intracavity frequency doubling of a solid-state degenerate laser. The second harmonic emission supports many more transverse modes than the fundamental emission, and exhibit lower spatial coherence. A strong suppression of speckle formation is demonstrated for both fundamental and second harmonic beams. Using the green emission for fluorescence excitation, we show the coherent artifacts are removed from the full-field fluorescence images. The high power, low spatial coherence and good directionality makes the green degenerate laser an attractive illumination source for parallel imaging and projection display.
Coalescence in coupled Duffing oscillators
YANG Jun-Zhong
2009-01-01
The forced Duffing oscillator has a pair of symmetrical attractors in a proper parameter regime. When a lot of Duffing oscillators are coupled linearly, the system tends to form clusters in which the neighboring oscillators fall onto the same attractor. When the coupling strength is strong, all of the oscillators fall onto one attractor. In this work, we investigate coalescence in the coupled forced Duffing oscillators. Some phenomena are found and explanations are presented.
Sang, Nguyen Anh; Thu Thuy, Do Thi; Loan, Nguyen Thi Ha; Lan, Nguyen Tri; Viet, Nguyen Ai
2017-06-01
Using the simple deformed three-level model (D3L model) proposed in our early work, we study the entanglement problem of composite bosons. Consider three first energy levels are known, we can get two energy separations, and can define the level deformation parameter δ. Using connection between q-deformed harmonic oscillator and Morse-like anharmonic potential, the deform parameter q also can be derived explicitly. Like the Einstein’s theory of special relativity, we introduce the observer e˙ects: out side observer (looking from outside the studying system) and inside observer (looking inside the studying system). Corresponding to those observers, the outside entanglement entropy and inside entanglement entropy will be defined.. Like the case of Foucault pendulum in the problem of Earth rotation, our deformation energy level investigation might be useful in prediction the environment e˙ect outside a confined box.
Dynamical Relation between Quantum Squeezing and Entanglement in Coupled Harmonic Oscillator System
Lock Yue Chew
2014-04-01
Full Text Available In this paper, we investigate into the numerical and analytical relationship between the dynamically generated quadrature squeezing and entanglement within a coupled harmonic oscillator system. The dynamical relation between these two quantum features is observed to vary monotically, such that an enhancement in entanglement is attained at a fixed squeezing for a larger coupling constant. Surprisingly, the maximum attainable values of these two quantum entities are found to consistently equal to the squeezing and entanglement of the system ground state. In addition, we demonstrate that the inclusion of a small anharmonic perturbation has the effect of modifying the squeezing versus entanglement relation into a nonunique form and also extending the maximum squeezing to a value beyond the system ground state.
Angels and Degenerates: Artistic Virtuosity and Degeneration Theory in Fin de Siècle Fiction
2015-01-01
The aim in "Angels and Degenerates: Artistic Virtuosity and Degeneration Theory in Fin de Siècle Fiction" is to complicate the popular image of the fin de siècle as uniformly pessimistic by examining the continuities between a range of novelists, as well as other late nineteenth century writers from such disparate fields as psychology and cultural criticism, as they critique degeneration theory. Some of these writers, like Thomas Hardy, H.G. Wells, and Sarah Grand, are typically read as promo...
Lutz, Oliver M. D.; Rode, Bernd M.; Bonn, Günther K.; Huck, Christian W.
2014-10-01
This paper discusses the quality and feasibility of highly correlated ab initio techniques in a vibrational self-consistent field (VSCF) approach using acetonitrile as a model system. The topical renormalized coupled-cluster technique exploiting the similarity-transformed Hamiltonian's left eigenstates (i.e. CR-CC(2,3)) is investigated alongside the well-known Hartree-Fock (HF), Møller-Plesset second-order perturbation theory (MP2) and coupled cluster (CCSD(T)) methods. The inclusion of mode triple interactions is discussed and it is found that the use of an effective core potential (ECP) serves as a viable compromise during the highly demanding task of computing such contributions, thus enabling a grid-based evaluation of three mode interaction terms with coupled cluster techniques also for larger molecules. In this context, a previously proposed reduced coupling scheme [1] is investigated, confirming the applicability of this technique to a system exhibiting a rather complex electronic structure. A combination of Ahlrichs' triple-ζ valence polarized (TZVP) basis set with Dunning's set of core-valence correlation functions is found to deliver results in good agreement with experiment while being computationally very feasible. Since CH3CN exhibits four degenerate vibrational degrees of freedom, it serves as an ideal model system for critically assessing the qualities of the degenerate second-order perturbation theory corrected (DPT2) VSCF technique. Besides fundamental vibrations, a thorough investigation of overtone transitions and combination bands is conducted by means of comparing the results to both available and newly recorded experimental data.
Mackie, Cameron J.; Candian, Alessandra; Huang, Xinchuan; Maltseva, Elena; Petrignani, Annemieke; Oomens, Jos; Mattioda, Andrew L.; Buma, Wybren Jan; Lee, Timothy J.; Tielens, Alexander G. G. M.
2016-08-01
The study of interstellar polycyclic aromatic hydrocarbons (PAHs) relies heavily on theoretically predicted infrared spectra. Most earlier studies use scaled harmonic frequencies for band positions and the double harmonic approximation for intensities. However, recent high-resolution gas-phase experimental spectroscopic studies have shown that the harmonic approximation is not sufficient to reproduce experimental results. In our previous work, we presented the anharmonic theoretical spectra of three linear PAHs, showing the importance of including anharmonicities into the theoretical calculations. In this paper, we continue this work by extending the study to include five non-linear PAHs (benz[a]anthracene, chrysene, phenanthrene, pyrene, and triphenylene), thereby allowing us to make a full assessment of how edge structure, symmetry, and size influence the effects of anharmonicities. The theoretical anharmonic spectra are compared to spectra obtained under matrix isolation low-temperature conditions, low-resolution, high-temperature gas-phase conditions, and high-resolution, low-temperature gas-phase conditions. Overall, excellent agreement is observed between the theoretical and experimental spectra although the experimental spectra show subtle but significant differences.
Atakishiyev, Natig M [Centro de Ciencias FIsicas, UNAM, Apartado Postal 48-3, 62251 Cuernavaca, Morelos (Mexico); Klimyk, Anatoliy U [Centro de Ciencias FIsicas, UNAM, Apartado Postal 48-3, 62251 Cuernavaca, Morelos (Mexico); Wolf, Kurt Bernardo [Centro de Ciencias FIsicas, UNAM, Apartado Postal 48-3, 62251 Cuernavaca, Morelos (Mexico)
2004-05-28
The finite q-oscillator is a model that obeys the dynamics of the harmonic oscillator, with the operators of position, momentum and Hamiltonian being functions of elements of the q-algebra su{sub q}(2). The spectrum of position in this discrete system, in a fixed representation j, consists of 2j + 1 'sensor'-points x{sub s} = 1/2 [2s]{sub q}, s element of {l_brace}-j, -j+1, ..., j{r_brace}, and similarly for the momentum observable. The spectrum of energies is finite and equally spaced, so the system supports coherent states. The wavefunctions involve dual q-Kravchuk polynomials, which are solutions to a finite-difference Schroedinger equation. Time evolution (times a phase) defines the fractional Fourier-q-Kravchuk transform. In the classical limit as q {yields} 1 we recover the finite oscillator Lie algebra, the N = 2j {yields} {infinity} limit returns the Macfarlane-Biedenharn q-oscillator and both limits contract the generators to the standard quantum-mechanical harmonic oscillator.
Atakishiyev, Natig M.; Klimyk, Anatoliy U.; Wolf, Kurt Bernardo
2004-05-01
The finite q-oscillator is a model that obeys the dynamics of the harmonic oscillator, with the operators of position, momentum and Hamiltonian being functions of elements of the q-algebra suq(2). The spectrum of position in this discrete system, in a fixed representation j, consists of 2j + 1 'sensor'-points x_s={\\case12}[2s]_q, s\\in\\{-j,-j+1,\\ldots,j\\} , and similarly for the momentum observable. The spectrum of energies is finite and equally spaced, so the system supports coherent states. The wavefunctions involve dual q-Kravchuk polynomials, which are solutions to a finite-difference Schrödinger equation. Time evolution (times a phase) defines the fractional Fourier-q-Kravchuk transform. In the classical limit as q rarr 1 we recover the finite oscillator Lie algebra, the N = 2j rarr infin limit returns the Macfarlane-Biedenharn q-oscillator and both limits contract the generators to the standard quantum-mechanical harmonic oscillator.
Oscillate boiling from microheaters
Li, Fenfang; Gonzalez-Avila, S. Roberto; Nguyen, Dang Minh; Ohl, Claus-Dieter
2017-01-01
We report about an intriguing boiling regime occurring for small heaters embedded on the boundary in subcooled water. The microheater is realized by focusing a continuous wave laser beam to about 10 μ m in diameter onto a 165-nm-thick layer of gold, which is submerged in water. After an initial vaporous explosion a single bubble oscillates continuously and repeatedly at several 100 kHz albeit with constant laser power input. The microbubble's oscillations are accompanied with bubble pinch-off, leading to a stream of gaseous bubbles in the subcooled water. The self-driven bubble oscillation is explained with a thermally kicked oscillator caused by surface attachment and by the nonspherical collapses. Additionally, Marangoni stresses induce a recirculating streaming flow which transports cold liquid towards the microheater, reducing diffusion of heat along the substrate and therefore stabilizing the phenomenon to many million cycles. We speculate that this oscillate boiling regime may overcome the heat transfer thresholds observed during the nucleate boiling crisis and offers a new pathway for heat transfer under microgravity conditions.
Oscillations following periodic reinforcement.
Monteiro, Tiago; Machado, Armando
2009-06-01
Three experiments examined behavior in extinction following periodic reinforcement. During the first phase of Experiment 1, four groups of pigeons were exposed to fixed interval (FI 16s or FI 48s) or variable interval (VI 16s or VI 48s) reinforcement schedules. Next, during the second phase, each session started with reinforcement trials and ended with an extinction segment. Experiment 2 was similar except that the extinction segment was considerably longer. Experiment 3 replaced the FI schedules with a peak procedure, with FI trials interspersed with non-food peak interval (PI) trials that were four times longer. One group of pigeons was exposed to FI 20s PI 80s trials, and another to FI 40s PI 160s trials. Results showed that, during the extinction segment, most pigeons trained with FI schedules, but not with VI schedules, displayed pause-peck oscillations with a period close to, but slightly greater than the FI parameter. These oscillations did not start immediately after the onset of extinction. Comparing the oscillations from Experiments 1 and 2 suggested that the alternation of reconditioning and re-extinction increases the reliability and earlier onset of the oscillations. In Experiment 3 the pigeons exhibited well-defined pause-peck cycles since the onset of extinction. These cycles had periods close to twice the value of the FI and lasted for long intervals of time. We discuss some hypotheses concerning the processes underlying behavioral oscillations following periodic reinforcement.
Oscillations in stellar superflares
Balona, L A; Kosovichev, A; Nakariakov, V M; Pugh, C E; Van Doorsselaere, T
2015-01-01
Two different mechanisms may act to induce quasi-periodic pulsations (QPP) in whole-disk observations of stellar flares. One mechanism may be magneto-hydromagnetic (MHD) forces and other processes acting on flare loops as seen in the Sun. The other mechanism may be forced local acoustic oscillations due to the high-energy particle impulse generated by the flare (known as `sunquakes' in the Sun). We analyze short-cadence Kepler data of 257 flares in 75 stars to search for QPP in the flare decay branch or post-flare oscillations which may be attributed to either of these two mechanisms. About 18 percent of stellar flares show a distinct bump in the flare decay branch of unknown origin. The bump does not seem to be a highly-damped global oscillation because the periods of the bumps derived from wavelet analysis do not correlate with any stellar parameter. We detected damped oscillations covering several cycles (QPP), in seven flares on five stars. The periods of these oscillations also do not correlate with any ...
Motor axon excitability during Wallerian degeneration
Moldovan, Mihai; Alvarez, Susana; Krarup, Christian
2008-01-01
, action potential propagation and structural integrity of the distal segment are maintained. The aim of this study was to investigate in vivo the changes in membrane function of motor axons during the 'latent' phase of Wallerian degeneration. Multiple indices of axonal excitability of the tibial nerve...
MR findings of degenerating parenchymal neurocysticercosis
Lee, Yul; Chung, Eun A; Yang, Ik; Park, Hae Jung; Chung, Soo Young [Hallym Univ. Kangnam Sungshim Hospital, Seoul (Korea, Republic of)
1996-06-01
To evaluate MR imaging findings of degenerating parenchymal neurocysticercosis and to determine the characteristics which distinguish it from other brain diseases. MR imagings of 19 patients (56 lesions) of degenerating parenchymal neurocysticercosis were retrospectively evaluated, focusing on the size and location of lesions signal intensity patterns of cyst fluid and wall, the extent of the surrounding edema and features of contrast enhancement. Degenerating parenchymal neurocysticercosis was located in gray or subcortical while matter in 89.3% of 56 lesions (50/56) ; most of these (98.2%) were smaller than 2 cm in diameter. Cyst fluid signal was hyperintense relative to CSF on T1 and proton density weighted images (92.9%). A hypointense signal rim of the cyst wall was noted in the lesions on proton density (92.9%) and T2 weighted (98.2%) images, Surrounding edema was mostly mild. Peripheral rim enhancement was noted in all lesions, and this was frequently irregular and lobulated (67.9%) with a focal defect in the enhancing rim(41.1%). Findings which could be helpful in distinguishing degenerating parencymal neurocysticercosis from other brain diseases are as follows : small, superficial lesions ; hyperintense signal of the cyst fluid on T1 and proton density weighted images ; hypointense signal of the cyst wall on proton density and T2 weighted images ; relatively mild extent of surrounding edema, and peripheral rim enhancement which is frequently irregular and lobulated with a focal defect in the enhancing rim.
Single Degenerate Progenitors of Type Ia Supernovae
Bours, Madelon; Toonen, Silvia; Nelemans, Gijs
2013-01-01
There is a general agreement that Type Ia supernovae correspond to the thermonuclear runaway of a white dwarf (WD) in a compact binary. The details of these progenitor systems are still unclear. Using the population synthesis code SeBa and several assumption for the WD retention efficiency, we estimate the delay times and supernova rates for the single degenerate scenario.
Driving and Age-Related Macular Degeneration
Owsley, Cynthia; McGwin, Gerald, Jr.
2008-01-01
This article reviews the research literature on driving and age-related macular degeneration, which is motivated by the link between driving and the quality of life of older adults and their increased collision rate. It addresses the risk of crashes, driving performance, driving difficulty, self-regulation, and interventions to enhance, safety,…
The nature of apraxia in corticobasal degeneration.
Leiguarda, R; Lees, A J; Merello, M; Starkstein, S; Marsden, C D
1994-01-01
Although apraxia is one of the most frequent signs in corticobasal degeneration, the phenomenology of this disorder has not been formally examined. Hence 10 patients with corticobasal degeneration were studied with a standardised evaluation for different types of apraxia. To minimise the confounding effects of the primary motor disorder, apraxia was assessed in the least affected limb. Whereas none of the patients showed buccofacial apraxia, seven showed deficits on tests of ideomotor apraxia and movement imitation, four on tests of sequential arm movements (all of whom had ideomotor apraxia), and three on tests of ideational apraxia (all of whom had ideomotor apraxia). Ideomotor apraxia significantly correlated with deficit in both the mini mental state examination and in a task sensitive to frontal lobe dysfunction (picture arrangement). Two of the three patients with ideomotor apraxia and ideational apraxia showed severe cognitive impairments. The alien limb behaviour was present only in patients with ideomotor apraxia. In conclusion, ideomotor apraxia is the most frequent type of apraxia in corticobasal degeneration, and may be due to dysfunction of the supplementary motor area. There is a subgroup of patients with corticobasal degeneration who have a severe apraxia (ideomotor and ideational apraxia), which correlates with global cognitive impairment, and may result from additional parietal or diffuse cortical damage. PMID:8163995
Specific heats of degenerate ideal gases
Caruso, Francisco; Oguri, Vitor; Silveira, Felipe
2017-01-01
From arguments based on Heisenberg's uncertainty principle and Pauli's exclusion principle, the molar specific heats of degenerate ideal gases at low temperatures are estimated, giving rise to values consistent with the Nerst-Planck Principle (third law of Thermodynamics). The Bose-Einstein condensation phenomenon based on the behavior of specific heat of massive and non-relativistic boson gases is also presented.
Transversal heteroclinic orbits in general degenerate cases
朱德明
1996-01-01
A geometrical method using the exponential dichotomy and the invariant manifold thoery is given to set up the criteria for the existence of transversal and tangential heterodinic orbits under the most general degenerate cases. Conclusions given here extend and contain the relevant known results.
Depression in Age-Related Macular Degeneration
Casten, Robin; Rovner, Barry
2008-01-01
Age-related macular degeneration (AMD) is a major cause of disability in the elderly, substantially degrades the quality of their lives, and is a risk factor for depression. Rates of depression in AMD are substantially greater than those found in the general population of older people, and are on par with those of other chronic and disabling…
DNA sequencing by synthesis with degenerate primers
2008-01-01
The degenerate primer-based sequencing Was developed by a synthesis method(DP-SBS)for high-throughput DNA sequencing,in which a set of degenerate primers are hybridized on the arrayed DNA templates and extended by DNA polymerase on microarrays.In this method,adifferent set of degenerate primers containing a give nnumber(n)of degenerate nucleotides at the 3'-ends were annealed to the sequenced templates that were immobilized on the solid surface.The nucleotides(n+1)on the template sequences were determined by detecting the incorporation of fluorescent labeled nucleotides.The fluorescent labeled nucleotide was incorporated into the primer in a base-specific manner after the enzymatic primer extension reactions and nine-base length were read out accurately.The main advanmge of the DP-SBS is that the method only uses very conventional biochemical reagents and avoids the complicated special chemical reagents for removing the labeled nucleotides and reactivating the primer for further extension.From the present study,it is found that the DP-SBS method is reliable,simple,and cost-effective for laboratory-sequencing a large amount of short DNA fragments.
Nonunital Spectral Triples Associated to Degenerate Metrics
Rennie, A.
We show that one can define (p,∞)-summable spectral triples using degenerate metrics on smooth manifolds. Furthermore, these triples satisfy Connes-Moscovici's discrete and finite dimension spectrum hypothesis, allowing one to use the Local Index Theorem [1] to compute the pairing with K-theory. We demonstrate this with a concrete example.
Stimulated degenerate four-wave mixing in Si nanocrystal waveguides
Manna, Santanu; Bernard, Martino; Biasi, Stefano; Ramiro Manzano, Fernando; Mancinelli, Mattia; Ghulinyan, Mher; Pucker, George; Pavesi, Lorenzo
2016-07-01
Parametric frequency conversion via four-wave mixing (FWM) in silicon nanocrystal (Si NC) waveguides is observed at 1550 nm. To investigate the role of Si NC, different types of waveguides containing Si NC in a SiO2 matrix were fabricated. Owing to the increase of the dipole oscillator strength mediated by the quantum confinement effect, the non-linear refractive index ({n}2) of Si NCs is found to be more than one order of magnitude larger than the one of bulk Si. Coupled differential equations for the degenerate FWM process taking into account the role of Si NC were numerically solved to model the experimental data. The modeling yields an effective {n}2 for Si NCs in SiO2 waveguides which is similar to the one of Si waveguides. We also measured a large signal to idler conversion bandwidth of ∼22 nm. The large non-linear refractive index is joined with a large two photon absorption coefficient which makes the use of Si NC in non-linear optical devices mostly suitable for mid-infrared applications.
Arbitrary Spin Galilean Oscillator
Hagen, C R
2014-01-01
The so-called Dirac oscillator was proposed as a modification of the free Dirac equation which reproduces many of the properties of the simple harmonic oscillator but accompanied by a strong spin-orbit coupling term. It has yet to be extended successfully to the arbitrary spin S case primarily because of the unwieldiness of general spin Lorentz invariant wave equations. It is shown here using the formalism of totally symmetric multispinors that the Dirac oscillator can, however, be made to accommodate spin by incorporating it into the framework of Galilean relativity. This is done explicitly for spin zero and spin one as special cases of the arbitrary spin result. For the general case it is shown that the coefficient of the spin-orbit term has a 1/S behavior by techniques which are virtually identical to those employed in the derivation of the g-factor carried out over four decades ago.
On Doubly Degenerate Quasilinear Parabolic Equations of Higher Order
Zhen Hai LIU
2005-01-01
We deal with the existence of periodic solutions for doubly degenerate quasilinear parabolic equations of higher order, which can degenerate, on a part of the boundary, on a segment in the interior of the domain and in time.
Quasiconformal mappings and degenerate elliptic and parabolic equations
Filippo Chiarenza
1987-11-01
Full Text Available In this paper two Harnak inequalities are proved concerning a degenerate elliptic and a degenerate parabolic equation. In both cases the weight giving the degeneracy is a power of the jacobian of a quasiconformal mapping.
Degenerate solutions obtained from several variants of factor analysis
Zijlstra, Bonne J.H.; Kiers, Henk A.L.
2002-01-01
Considerable research has been performed concerning degenerate solutions from the Parafac model. However, degenerate solutions have also been reported to occur with the shifted multiplicative model and a model for component analysis of multitrait multimethod matrices. Furthermore, we obtained
Hoeye, Gudrun Kristine
1999-07-01
We have studied radial and nonradial oscillations in neutron stars, both in a general relativistic and non-relativistic frame, for several different equilibrium models. Different equations of state were combined, and our results show that it is possible to distinguish between the models based on their oscillation periods. We have particularly focused on the p-, f-, and g-modes. We find oscillation periods of II approx. 0.1 ms for the p-modes, II approx. 0.1 - 0.8 ms for the f-modes and II approx. 10 - 400 ms for the g-modes. For high-order (l (>{sub )} 4) f-modes we were also able to derive a formula that determines II{sub l+1} from II{sub l} and II{sub l-1} to an accuracy of 0.1%. Further, for the radial f-mode we find that the oscillation period goes to infinity as the maximum mass of the star is approached. Both p-, f-, and g-modes are sensitive to changes in the central baryon number density n{sub c}, while the g-modes are also sensitive to variations in the surface temperature. The g-modes are concentrated in the surface layer, while p- and f-modes can be found in all parts of the star. The effects of general relativity were studied, and we find that these are important at high central baryon number densities, especially for the p- and f-modes. General relativistic effects can therefore not be neglected when studying oscillations in neutron stars. We have further developed an improved Cowling approximation in the non-relativistic frame, which eliminates about half of the gap in the oscillation periods that results from use of the ordinary Cowling approximation. We suggest to develop an improved Cowling approximation also in the general relativistic frame. (Author)
Nonlinear harmonic oscillators
Calogero, F [Dipartimento di Fisica, Universita di Roma ' La Sapienza' (Italy); Inozemtsev, V I [Joint Institute for Nuclear Research, Dubna (Russian Federation)
2002-12-06
The existence is noted of assemblies of an arbitrary number of complex oscillators, or equivalently, of an arbitrary even number of real oscillators, characterized by Newtonian equations of motion ('acceleration equal force') with one-body velocity-dependent linear forces and many-body velocity-independent cubic forces, all the nonsingular solutions of which are isochronous (completely periodic with the same period). As for the singular solutions, as usual they emerge, in the context of the initial-value problem, from a closed domain in phase space having lower dimensionality.
Prediction of resonant oscillation
2010-01-01
The invention relates to methods for prediction of parametric rolling of vessels. The methods are based on frequency domain and time domain information in order do set up a detector able to trigger an alarm when parametric roll is likely to occur. The methods use measurements of e.g. pitch and roll...... oscillations and compare the measured oscillations using FFT analysis of signal correlations, variance analysis of signals and other comparisons. As an example, the presence of a growing peak around a frequency that doubles the roll natural frequency indicates the possibility that parametric roll is going...
Friedel oscillations in graphene
Lawlor, J. A.; Power, S. R.; Ferreira, M.S.
2013-01-01
Symmetry breaking perturbations in an electronically conducting medium are known to produce Friedel oscillations in various physical quantities of an otherwise pristine material. Here we show in a mathematically transparent fashion that Friedel oscillations in graphene have a strong sublattice...... asymmetry. As a result, the presence of impurities and/or defects may impact the distinct graphene sublattices very differently. Furthermore, such an asymmetry can be used to explain the recent observations that nitrogen atoms and dimers are not randomly distributed in graphene but prefer to occupy one...
Krauss, L.; Wilczek, F.
1985-01-01
The theory of oscillations of solar neutrinos is developed as it applies to the electron-recoil spectrum in neutrino-electron scattering. The spectral information obtained by such measurements (as opposed to counting total event rates) is crucial for allowing observation of neutrino oscillations for masses down to 500 neV. In this regard, the effects of different masses and mixing angles, as well as such subtleties as thermal and pressure broadening, finite solar-core size, and variable indices of refraction are investigated.
Oscillation Baselining and Analysis Tool
2017-03-27
PNNL developed a new tool for oscillation analysis and baselining. This tool has been developed under a new DOE Grid Modernization Laboratory Consortium (GMLC) Project (GM0072 - “Suite of open-source applications and models for advanced synchrophasor analysis”) and it is based on the open platform for PMU analysis. The Oscillation Baselining and Analysis Tool (OBAT) performs the oscillation analysis and identifies modes of oscillations (frequency, damping, energy, and shape). The tool also does oscillation event baselining (fining correlation between oscillations characteristics and system operating conditions).
程衍富
2004-01-01
利用Kinani-Daoud方法构造了非谐振子势的Gazeau-Klauder(GK)相干态和Klaude-Perelomov(KP)相干态,表明两种相干态在非线性谐振子势下具有完全不同的形式,并对两种相干态的完备性以及各自构成的Hilbert空间进行了讨论.对相干态的Mandel Q参数的研究表明:GK相干态服从亚Poisson统计分布,KP相干态服从超Poisson统计分布.
Hermansson, Kersti; Probst, Michael M; Gajewski, Grzegorz; Mitev, Pavlin D
2009-12-28
A two-dimensional quantum-mechanical vibrational model has been used to calculate the anharmonic OH vibrational frequencies in the layered Mg(OH)(2) (brucite) crystal. The underlying potential energy surface was generated by density functional theory (DFT) calculations. The resulting OH frequencies are upshifted (blueshifted) by about +75 cm(-1) with respect to the gas-phase OH frequency (+120 cm(-1) in experiments; the discrepancy is mainly due to inadequacies in the DFT and pseudopotential models). The Raman-IR split is about 50 cm(-1), both in the calculations and in experiments. We find that the blueshift phenomenon in brucite can qualitatively be explained by a parabolalike "OH frequency versus electric field" correlation curve pertaining to an OH(-) ion exposed to an electric field. We also find that it is primarily the neighbors within the Mg(OH)(2) layer that induce the blueshift while the interlayer interaction gives a smaller (and redshifting) contribution.
Goychuk, Igor
2014-01-01
Here we generalize our previous model of molecular motors trafficking subdiffusing cargos in viscoelastic cytosol by (i) including mechanochemical coupling between cyclic conformational fluctuations of the motor protein driven by the reaction of ATP hydrolysis and its translational motion within the simplest two-state model of hand-over-hand motion of kinesin, and also (ii) by taking into account the anharmonicity of the tether between the motor and cargo (its maximally possible extension length). It is shown that the major earlier results such as occurrence of normal versus anomalous transport depending on the amplitude of binding potential, cargo size and the motor turnover frequency not only survive in this more realistic model, but the results also look very similar for the correspondingly adjusted parameters. However, this more realistic model displays a substantially larger thermodynamic efficiency due to a bidirectional mechanochemical coupling. For realistic parameters, the maximal thermodynamic effic...
Strong anharmonicity induces quantum melting of charge density wave in 2 H -NbSe2 under pressure
Leroux, Maxime; Errea, Ion; Le Tacon, Mathieu; Souliou, Sofia-Michaela; Garbarino, Gaston; Cario, Laurent; Bosak, Alexey; Mauri, Francesco; Calandra, Matteo; Rodière, Pierre
2015-10-01
The pressure and temperature dependence of the phonon dispersion of 2 H -NbSe2 is measured by inelastic x-ray scattering. A strong temperature dependent soft phonon mode, reminiscent of the charge density wave (CDW), is found to persist up to a pressure as high as 16 GPa, far above the critical pressure at which the CDW disappears at 0 K. By using ab initio calculations beyond the harmonic approximation, we obtain an accurate, quantitative description of the (P ,T ) dependence of the phonon spectrum. Our results show that the rapid destruction of the CDW under pressure is related to the zero mode vibrations—or quantum fluctuations—of the lattice renormalized by the anharmonic part of the lattice potential. The calculations also show that the low-energy longitudinal acoustic mode that drives the CDW transition barely contributes to superconductivity, explaining the insensitivity of the superconducting critical temperature to the CDW transition.
Implications of Fermionic Dark Matter on recent neutrino oscillation data
Singirala, Shivaramakrishna
2016-01-01
We investigate flavor phenomenology and dark matter in the context of scotogenic model. In this model, the neutrino masses are generated through radiative corrections at one-loop level. Considering the neutrino mixing matrix to be of tri-bimaximal form with additional perturbations to accommodate the recently observed non-zero value of reactor mixing angle $\\theta_{13}$, we obtain the relation between various neutrino oscillation parameters and the model parameters. Working in degenerate heavy neutrino mass spectrum, we obtain light neutrino masses obeying normal heirarchy and also study the relic abundance of fermionic dark matter candidate including coannihilation effects. A viable parameter space is thus obtained, consistent with neutrino oscillation data, relic abundance and various lepton flavor violating decays such as $\\ell_\\alpha\\to\\ell_\\beta\\gamma$ and $\\ell_\\alpha \\to 3 \\, \\ell_\\beta$.
A direct experimental limit on neutron -- mirror neutron oscillations
Ban, G; Naviliat-Cuncic, O; Bodek, K; Kistryn, S; Kuzniak, M; Zejma, J; Khomutov, N; Knowles, P; Rebetez, M; Weis, A; Plonka, C; Rogel, G; Quéméner, G; Rebreyend, D; Roccia, S; Tur, M; Daum, M; Henneck, R; Heule, S; Kasprzak, M; Kirch, K; Knecht, A; Mtchedlishvili, A; Zsigmond, G
2007-01-01
In case a mirror world with a copy of our ordinary particle spectrum would exist, the neutron n and its degenerate partner, the mirror neutron ${\\rm n'}$, could potentially mix and undergo ${\\rm nn'}$ oscillations. The interaction of an ordinary magnetic field with the ordinary neutron would lift the degeneracy between the mirror partners, diminish the ${\\rm n'}$-amplitude in the n-wavefunction and, thus, suppress its observability. We report an experimental comparison of ultracold neutron storage in a trap with and without superimposed magnetic field. No influence of the magnetic field is found and a limit on the oscillation time $\\tau_{\\rm nn'} > 103$ s (95% C.L.) is derived.
Oscillators and operational amplifiers
Lindberg, Erik
2005-01-01
A generalized approach to the design of oscillators using operational amplifiers as active elements is presented. A piecewise-linear model of the amplifier is used so that it make sense to investigate the eigenvalues of the Jacobian of the differential equations. The characteristic equation...
[Oscillating physiotherapy for secretolysis].
Brückner, U
2008-03-01
Assisted coughing and mechanical cough aids compensate for the weak cough flow in patients with neuromuscular diseases (NMD). In cases with preserved respiratory muscles also breathing techniques and special devices, e. g., flutter or acapella can be used for secretion mobilisation during infections of the airways. These means are summarised as oscillating physiotherapy. Their mechanisms are believed to depend on separation of the mucus from the bronchial wall by vibration, thus facilitating mucus transport from the peripheral to the central airways. In mucoviscidosis and chronic obstructive pulmonary disease their application is established, but there is a paucity of data regarding the commitment in patients with neuromuscular diseases. The effective adoption of simple oscillation physiotherapeutic interventions demands usually a sufficient force of the respiratory muscles--exceptions are the application of the percussionaire (intrapulmonary percussive ventilator, IPV) or high frequency chest wall oscillation (HFCWO). In daily practice there is evidence that patients with weak respiratory muscles are overstrained with the use of these physiotherapeutic means, or get exhausted. A general recommendation for the adoption of simple oscillating physiotherapeutic interventions cannot be made in patients with NMDs. Perhaps in the future devices such as IPV or HFCWO will prove to be more effective in NMD patients.
Jones, R. T.
1976-01-01
For acoustic tests the violin is driven laterally at the bridge by a small speaker of the type commonly found in pocket transistor radios. An audio oscillator excites the tone which is picked up by a sound level meter. Gross patterns of vibration modes are obtained by the Chladni method.
Proprioceptive evoked gamma oscillations
Arnfred, Sidse M; Hansen, Lars Kai; Parnas, Josef;
2007-01-01
A proprioceptive stimulus consisting of a weight change of a handheld load has recently been shown to elicit an evoked potential. Previously, somatosensory gamma oscillations have only been evoked by electrical stimuli. We conjectured that a natural proprioceptive stimulus also would be able...
Neutrino oscillation experiments
Camilleri, L. [European Organization for Nuclear Research, Geneva (Switzerland)
1996-11-01
Neutrino oscillation experiments ({nu}{sub {mu}}{yields}{nu}{sub e} and {nu}{sub {mu}}{yields}{nu}{sub {tau}}) currently being performed at accelerators are reviewed. Future plans for short and long base-line experiments are summarized. (author) 10 figs., 2 tabs., 29 refs.
Multiphoton coherent population oscillation
Sharypov, A V
2014-01-01
We study the bichromatic driving of a two-level system which displays long-lived coherent population oscillations (CPO). We show that under certain conditions, multiphoton parametric interaction leads to the appearance of CPO resonances at the subharmonic frequencies. In addition, in the region of the CPO resonances, there is strong parametric interaction between the weak sideband components of the electromagnetic field.
From excitability to oscillations
Postnov, D. E.; Neganova, A. Y.; Jacobsen, J. C. B.;
2013-01-01
One consequence of cell-to-cell communication is the appearance of synchronized behavior, where many cells cooperate to generate new dynamical patterns. We present a simple functional model of vasomotion based on the concept of a two-mode oscillator with dual interactions: via relatively slow...
Proprioceptive evoked gamma oscillations
Arnfred, S.M.; Hansen, Lars Kai; Parnas, J.;
2007-01-01
to evoke gamma oscillations. EEG was recorded using 64 channels in 14 healthy subjects. In each of three runs a stimulus of 100 g load increment in each hand was presented in 120 trials. Data were wavelet transformed and runs collapsed. Inter-trial phase coherence (ITPC) was computed as the best measure...
Neutrino Velocity and Neutrino Oscillations
Minakata, H
2012-01-01
We study distances of propagation and the group velocities of the muon neutrinos in the presence of mixing and oscillations assuming that Lorentz invariance holds. Oscillations lead to distortion of the $\
Microwave transistor oscillator frequency tripling
B. A. Kotserzhynskyi
2010-01-01
The frequency tripler state of the art is consided. The oscillator-frequency tripler design is now at the state of scientific research. Microwave companies release the devices of the such structure: oscillator, buffer, amplifier-tripler.
Microwave transistor oscillator frequency tripling
B. A. Kotserzhynskyi
2010-01-01
Full Text Available The frequency tripler state of the art is consided. The oscillator-frequency tripler design is now at the state of scientific research. Microwave companies release the devices of the such structure: oscillator, buffer, amplifier-tripler.
Li, Bing-Wei; Cao, Xiao-Zhi; Fu, Chenbo
2017-05-01
Many biological and chemical systems could be modeled by a population of oscillators coupled indirectly via a dynamical environment. Essentially, the environment by which the individual element communicates with each other is heterogeneous. Nevertheless, most of previous works considered the homogeneous case only. Here we investigated the dynamical behaviors in a population of spatially distributed chaotic oscillators immersed in a heterogeneous environment. Various dynamical synchronization states (such as oscillation death, phase synchronization, and complete synchronized oscillation) as well as their transitions were explored. In particular, we uncovered a non-traditional quorum sensing transition: increasing the population density leaded to a transition from oscillation death to synchronized oscillation at first, but further increasing the density resulted in degeneration from complete synchronization to phase synchronization or even from phase synchronization to desynchronization. The underlying mechanism of this finding was attributed to the dual roles played by the population density. What's more, by treating the environment as another component of the oscillator, the full system was then effectively equivalent to a locally coupled system. This fact allowed us to utilize the master stability functions approach to predict the occurrence of complete synchronization oscillation, which agreed with that from the direct numerical integration of the system. The potential candidates for the experimental realization of our model were also discussed.
Ultracompact quantum splitter of degenerate photon pairs
He, Jiakun; Casas-Bedoya, Alvaro; Zhang, Yanbing; Xiong, Chunle; Eggleton, Benjamin J
2015-01-01
Integrated sources of indistinguishable photons have attracted a lot of attention because of their applications in quantum communication and optical quantum computing. Here, we demonstrate an ultra-compact quantum splitter for degenerate single photons based on a monolithic chip incorporating Sagnac loop and a micro-ring resonator with a footprint of 0.011 mm2, generating and deterministically splitting indistinguishable photon pairs using time-reversed Hong-Ou-Mandel interference. The ring resonator provides enhanced photon generation rate, and the Sagnac loop ensures the photons travel through equal path lengths and interfere with the correct phase to enable the reversed HOM effect to take place. In the experiment, we observed a HOM dip visibility of 94.5 +- 3.3 %, indicating the photons generated by the degenerate single photon source are in a suitable state for further integration with other components for quantum applications, such as controlled-NOT gates.
Acquired hepatocerebral degeneration: A case report
Wei-Xing Chen; Ping Wang; Sen-Xiang Yan; You-Ming Li; Chao-Hui Yu; Ling-Ling Jiang
2005-01-01
AIM: Acquired hepatocerebral degeneration (AHD) is an exceptional type of hepatic encephalopathies (HE). It is characterized by neuropsychiatric and extrapyramidal symptomathology similar to that seen in hepatolenticular degeneration (Wilson's disease). In this paper, we report a case of AHD with unusual presenting features.METHODS: A 28-year-old man with AHD was described and the literature was reviewed.RESULTS: The man had a history of HBV-related liver cirrhosis. He was admitted to our hospital with apathy,dysarthria, mild consciousness impairment and extrapyramidal symptoms after hematemesis. By review of the literature,cases with AHD often did not present consciousness impairment. So our case was once diagnosed incorrectly as Wilson's disease.CONCLUSION: AHD is a rare syndrome and its variable clinical manifestations make it difficult to be diagnosed.But we believe that extensive examination and thorough understanding of the disease are beneficial to a correct diagnosis. Moreover, biocoene is effective in treating the case.
Small automorphic representations and degenerate Whittaker vectors
Gustafsson, Henrik P A; Persson, Daniel
2014-01-01
We investigate Fourier coefficients of automorphic forms on split simply-laced Lie groups G. We show that for automorphic representations of small Gelfand-Kirillov dimension the Fourier coefficients are completely determined by certain degenerate Whittaker vectors on G. Although we expect our results to hold for arbitrary simply-laced groups, we give complete proofs only for G=SL(3) and G=SL(4). This is based on a method of Ginzburg that associates Fourier coefficients of automorphic forms with nilpotent orbits of G. Our results complement and extend recent results of Miller and Sahi. We also use our formalism to calculate various local (real and p-adic) spherical vectors of minimal representations of the exceptional groups E_6, E_7, E_8 using global (adelic) degenerate Whittaker vectors, correctly reproducing existing results for such spherical vectors obtained by very different methods.
Neutrino Oscillations with Nil Mass
Floyd, Edward R.
2016-09-01
An alternative neutrino oscillation process is presented as a counterexample for which the neutrino may have nil mass consistent with the standard model. The process is developed in a quantum trajectories representation of quantum mechanics, which has a Hamilton-Jacobi foundation. This process has no need for mass differences between mass eigenstates. Flavor oscillations and ν ,bar{ν } oscillations are examined.
Immunology of age related macular degeneration
Kijlstra Aize; Yang Peizeng
2011-01-01
@@ Age-related macular degeneration(AMD)is the most important cause of blindness in persons over 55 years of age in the Western world.In view of the increasing life expectancy we can assume that the problem will increase dramatically over the coming decades unless preventive or therapeutic measures are developed.Towards this goal many groups all over the world have performed epidemiological studies to identify potential risk factors for AMD.
Degenerate spacetimes in first order gravity
Kaul, Romesh K
2016-01-01
We present a systematic framework to obtain the most general solutions of the equations of motion in first order gravity theory with degenerate tetrads. There are many possible solutions. Generically, these exhibit non-vanishing torsion even in the absence of any matter coupling. These solutions are shown to contain a special set of eight configurations which are associated with the homogeneous model three-geometries of Thurston.
Degenerate RFID Channel Modeling for Positioning Applications
A. Povalac
2012-12-01
Full Text Available This paper introduces the theory of channel modeling for positioning applications in UHF RFID. It explains basic parameters for channel characterization from both the narrowband and wideband point of view. More details are given about ranging and direction finding. Finally, several positioning scenarios are analyzed with developed channel models. All the described models use a degenerate channel, i.e. combined signal propagation from the transmitter to the tag and from the tag to the receiver.
Biomechanical study of intervertebral disc degeneration
González Guitiérrez, Ramiro Arturo
2012-01-01
Degeneration and age affect the biomechanics of the intervertebral disc, by reducing its stiffness, flexibility and shock absorption capacities against daily movement and spinal load. The biomechanical characterization of intervertebral discs is achieved by conducting mechanical testing to vertebra-disc-vertebra segments and applying axial, shear, bend and torsion loads, statically or dynamically, with load magnitudes corresponding to the physiological range. However, traditional testing does...
Biomechanical study of intervertebral disc degeneration
González Guitiérrez, Ramiro Arturo
2012-01-01
Degeneration and age affect the biomechanics of the intervertebral disc, by reducing its stiffness, flexibility and shock absorption capacities against daily movement and spinal load. The biomechanical characterization of intervertebral discs is achieved by conducting mechanical testing to vertebra-disc-vertebra segments and applying axial, shear, bend and torsion loads, statically or dynamically, with load magnitudes corresponding to the physiological range. However, traditional testing does...
Depression in Age-Related Macular Degeneration
Casten,Robin; Rovner,Barry
2008-01-01
Age-related macular degeneration (AMD) is a major cause of disability in the elderly, substantially degrades the quality of their lives, and is a risk factor for depression. Rates of depression in AMD are substantially greater than those found in the general population of older people, and are on par with those of other chronic and disabling diseases. This article discusses the effect of depression on vision-related disability in patients with AMD, suggests methods for screening for depressio...
Stem cell horizons in intervertebral disc degeneration
Joseph Ciacci
2009-01-01
Full Text Available Joseph Ciacci1, Allen Ho1,2, Christopher P Ames3, Rahul Jandial41Division of Neurosurgery, University of California, San Diego, La Jolla, California, USA; 2Del E Webb Neurosciences, Aging and Stem Cell Research Center, The Burnham Institute for Medical Research, La Jolla, California, USA; 3Department of Neurological Surgery, University of California, San Francisco, San Francisco, CA, USA; 4Division of Neurosurgery, Department of Surgery, City of Hope Cancer Center, Duarte, CA, USAAbstract: Intervertebral disc degeneration remains a pervasive and intractable disease arising from a combination of aging and stress on the back and spine. The growing field of regenerative medicine brings the promise of stem cells in the treatment of disc disease. Scientists and physicians hope to employ stem cells not only to stop, but also reverse degeneration. However, there are many important outstanding issues, including the hostile avascular, apoptotic physiological environment of the intervertebral disc, and the difficulty of obtaining mesenchymal stem cells, and directing them towards chondrocytic differentiation and integration within the nucleus pulposus of the disc. Given the recent advances in minimally invasive spine surgery, and developing body of work on stem cell manipulation and transplantation, stem cells are uniquely poised to bring about large-scale improvements in treatment and outcomes for degenerative disc disease. In this review we will first discuss the cellular and molecular factors influencing degeneration, and then examine the efficacy and difficulties of stem cell transplantation.Keywords: intervertebral disc degeneration, stem cells, disc disease, mesenchymal stem cells, stem cell transplantation
Rehabilitation Approaches in Macular Degeneration Patients
Maniglia, Marcello; Benoit R Cottereau; Soler, Vincent; Trotter, Yves
2016-01-01
Age related macular degeneration (AMD) is a visual disease that affects elderly population. It entails a progressive loss of central vision whose consequences are dramatic for the patient’s quality of life. Current rehabilitation programs are restricted to technical aids based on visual devices. They only temporarily improve specific visual functions such as reading skills. Considering the rapid increase of the aging population worldwide, it is crucial to intensify clinical research on AMD in...
Controllability of nonlinear degenerate parabolic cascade systems
Mamadou Birba
2016-08-01
Full Text Available This article studies of null controllability property of nonlinear coupled one dimensional degenerate parabolic equations. These equations form a cascade system, that is, the solution of the first equation acts as a control in the second equation and the control function acts only directly on the first equation. We prove positive null controllability results when the control and a coupling set have nonempty intersection.
Animal models of age related macular degeneration
Pennesi, Mark E.; Neuringer, Martha; Courtney, Robert J.
2012-01-01
Age related macular degeneration (AMD) is the leading cause of vision loss of those over the age of 65 in the industrialized world. The prevalence and need to develop effective treatments for AMD has lead to the development of multiple animal models. AMD is a complex and heterogeneous disease that involves the interaction of both genetic and environmental factors with the unique anatomy of the human macula. Models in mice, rats, rabbits, pigs and non-human primates have recreated many of the ...
Conceptual foundations of schizophrenia: I. Degeneration.
Barrett, R J
1998-10-01
This is the first of two papers that aim to identify some of the institutional processes of 19th century European psychiatry, and some prevailing cultural themes of that era that played a role in shaping the development of schizophrenia as a disease concept. Three areas of psychiatric history are examined: the first is concerned with the key figures who coined the concept of dementia praecox; the second with the rise of the asylum; and the third is to do with the ideology of 19th century psychiatric science and its relationship to a broader intellectual milieu. These three literatures are examined for common themes. The theme of degeneration is evident in all three literatures, and denotes both a biological process (neuro-degeneration) and a moral state (degeneracy). The idea of degeneration, a pervasive cultural theme of the 19th century, dominated psychiatric thinking long before schizophrenia was developed as a diagnostic category. It contributed to the ideational form-work that gave foundation, structure and shape to the concept of schizophrenia.
Propagation of Disturbances in Degenerate Quantum Systems
Chancellor, Nicholas
2011-01-01
Disturbances in gapless quantum many-body models are known to travel an unlimited distance throughout the system. Here, we explore this phenomenon in finite clusters with degenerate ground states. The specific model studied here is the one-dimensional J1-J2 Heisenberg Hamiltonian at and close to the Majumdar-Ghosh point. Both open and periodic boundary conditions are considered. Quenches are performed using a local magnetic field. The degenerate Majumdar-Ghosh ground state allows disturbances which carry quantum entanglement to propagate throughout the system, and thus dephase the entire system within the degenerate subspace. These disturbances can also carry polarization, but not energy, as all energy is stored locally. The local evolution of the part of the system where energy is stored drives the rest of the system through long-range entanglement. We also examine approximations for the ground state of this Hamiltonian in the strong field limit, and study how couplings away from the Majumdar-Ghosh point aff...
Visual hallucinations in patients with macular degeneration.
Holroyd, S; Rabins, P V; Finkelstein, D; Nicholson, M C; Chase, G A; Wisniewski, S C
1992-12-01
This study was undertaken to determine the prevalence of visual hallucinations in patients with macular degeneration, describe such hallucinations phenomenologically, and possibly determine factors predisposing to their development. Using a case-control design, the authors screened 100 consecutive patients with age-related macular degeneration for visual hallucinations. Each patient with visual hallucinations was matched to the next three patients without hallucinations. The patients and comparison subjects were compared in terms of scores on the Beck Depression Inventory, Eysenck Personality Questionnaire, Telephone Interview for Cognitive Status, and a structured questionnaire including demographic characteristics, family history, and medical and psychiatric history. Ophthalmologic data were obtained by chart review. Of the 100 patients, 13 experienced visual hallucinations. Four variables were significantly associated with having hallucinations: living alone, lower cognition score, history of stroke, and bilaterally worse visual acuity. Hallucinations were not associated with family or personal history of psychiatric disorder or with personality traits. In 11 (84.6%) of the 13 patients, the hallucinations had begun in association with an acute change in vision. These results indicate that visual hallucinations are prevalent among patients with macular degeneration. They appear unrelated to primary psychiatric disorder. The predisposing factors of bilaterally worse vision and living alone support an association with sensory deprivation, while history of stroke and worse cognition support a decreased cortical inhibition theory.
Kris eSingletary
2011-10-01
Full Text Available Sleep and circadian activity rhythms become irregular with age which are characterized by fragmented sleep during the night and increased daytime sleepiness. These changes lead to a reduction in the quality of life due to cognitive impairments and emotional stress. More importantly, severely disrupted sleep and circadian rhythms have been associated with an increase in disease susceptibility. Many of the same brain areas affected by neurodegenerative diseases include the sleep and wake promoting systems. Any advances in our knowledge of these sleep/wake networks are necessary to target neural areas or connections for therapy. This review will discuss research that uses molecular, behavioral, genetic and anatomical methods to further our understanding of the interaction of these systems.
Resurgence of oscillation in coupled oscillators under delayed cyclic interaction
Bera, Bidesh K.; Majhi, Soumen; Ghosh, Dibakar
2017-07-01
This paper investigates the emergence of amplitude death and revival of oscillations from the suppression states in a system of coupled dynamical units interacting through delayed cyclic mode. In order to resurrect the oscillation from amplitude death state, we introduce asymmetry and feedback parameter in the cyclic coupling forms as a result of which the death region shrinks due to higher asymmetry and lower feedback parameter values for coupled oscillatory systems. Some analytical conditions are derived for amplitude death and revival of oscillations in two coupled limit cycle oscillators and corresponding numerical simulations confirm the obtained theoretical results. We also report that the death state and revival of oscillations from quenched state are possible in the network of identical coupled oscillators. The proposed mechanism has also been examined using chaotic Lorenz oscillator.
[New drug therapy for retinal degeneration].
Ohguro, Hiroshi
2008-01-01
Retinitis pigmentosa (RP) is an inherited retinal degeneration characterized by nyctalopia, ring scotoma, and bone-spicule pigmentation of the retina. So far, no effective therapy has been found for RP. As a possible molecular etiology of RP, retina-specific gene deficits are most likely involved, but little has been identified in terms of intracellular mechanisms leading to retinal photoreceptor cell death at post-translational levels. In order to find an effective therapy for RP, we must look for underlying common mechanisms that are responsible for the development of RP, instead of designing a specific therapy for each of the RP types with different causes. Therefore, in the present study, several animal models with different causes of RP were studied, including (1)Royal College of Surgeons (RCS) rats with a deficit of retinal pigment epithelium (RPE) function caused by rhodopsin mutation; (2) P23H rats, (3) S334ter rats, (4) photo stress rats, (5) retinal degeneration (rd) mice with a deficit of phosphodiesterase(PDE) function; and (6) cancer-associated retinopathy (CAR) model rats with a deficit of recoverin-dependent photoreceptor adaptation function. In each of these models, the following assessments were made in order to elucidate common pathological mechanisms among the models: (1) retinal function assessed by electroretinogram (ERG), (2) retinal morphology, (3) retinoid analysis, (4) rhodopsin regeneration, (5) rhodopsin phosphorylation and dephosphorylation, and (6) cytosolic cGMP levels. We found that unregulated photoreceptor adaptation processes caused by an imbalance of rhodopsin phosphorylation and dephosphorylation caused retinal dysfunction leading to photoreceptor cell death. As possible candidate drugs for normalizing these retinal dysfunctions and stopping further retinal degeneration, nilvadipine, a Ca channel blocker, retinoid derivatives, and anthocyanine were chosen and tested to determine their effect on the above animal models with
Voltage-controlled photonic oscillator.
Savchenkov, A A; Ilchenko, V S; Liang, W; Eliyahu, D; Matsko, A B; Seidel, D; Maleki, L
2010-05-15
We report the development and demonstration of an X-band voltage-controlled photonic oscillator based on a whispering gallery mode resonator made of an electro-optic crystalline material. The oscillator has good spectral purity and wide, agile, linear tunability. We have modified the existing theoretical model of the opto-electronic oscillator to describe the performance of our tunable oscillator and have found a good agreement between the theoretical predictions and the measurement results. We show that the device is promising for higher-frequency applications where high-performance tunable oscillators with wide tunability do not exist.
Stable local oscillator module.
Brocato, Robert Wesley
2007-11-01
This report gives a description of the development of a Stable Local Oscillator (StaLO) multi-chip module (MCM). It is a follow-on report to SAND2006-6414, Stable Local Oscillator Microcircuit. The StaLO accepts a 100MHz input signal and produces output signals at 1.2, 3.3, and 3.6 GHz. The circuit is built as a multi-chip module (MCM), since it makes use of integrated circuit technologies in silicon and lithium niobate as well as discrete passive components. This report describes the development of an MCM-based version of the complete StaLO, fabricated on an alumina thick film hybrid substrate.
Entanglement in neutrino oscillations
Blasone, M.; Dell' Anno, F.; De Siena, S.; Illuminati, F. [Universita degli Studi di Salerno Via Ponte don Melillon, Dipt. di Matematica e Informatica, Fisciano SA (Italy); INFN Sezione di Napoli, Gruppo collegato di Salerno - Baronissi SA (Italy); Dell' Anno, F.; De Siena, S.; Illuminati, F. [CNR-INFM Coherentia - Napoli (Italy); Blasone, M. [ISI Foundation for Scientific Interchange, Torino (Italy)
2009-03-15
Flavor oscillations in elementary particle physics are related to multimode entanglement of single-particle states. We show that mode entanglement can be expressed in terms of flavor transition probabilities, and therefore that single-particle entangled states acquire a precise operational characterization in the context of particle mixing. We treat in detail the physically relevant cases of two- and three-flavor neutrino oscillations, including the effective measure of CP violation. We discuss experimental schemes for the transfer of the quantum information encoded in single-neutrino states to spatially delocalized two-flavor charged-lepton states, thus showing, at least in principle, that single-particle entangled states of neutrino mixing are legitimate physical resources for quantum information tasks. (authors)
Acoustics waves and oscillations
Sen, S.N.
2013-01-01
Parameters of acoustics presented in a logical and lucid style Physical principles discussed with mathematical formulations Importance of ultrasonic waves highlighted Dispersion of ultrasonic waves in viscous liquids explained This book presents the theory of waves and oscillations and various applications of acoustics in a logical and simple form. The physical principles have been explained with necessary mathematical formulation and supported by experimental layout wherever possible. Incorporating the classical view point all aspects of acoustic waves and oscillations have been discussed together with detailed elaboration of modern technological applications of sound. A separate chapter on ultrasonics emphasizes the importance of this branch of science in fundamental and applied research. In this edition a new chapter ''Hypersonic Velocity in Viscous Liquids as revealed from Brillouin Spectra'' has been added. The book is expected to present to its readers a comprehensive presentation of the subject matter...
Physics of Neutrino Oscillation
Mondal, Spandan
2015-01-01
The Standard Model of particle physics describes neutrinos as massless, chargeless elementary particles that come in three different flavours. However, recent experiments indicate that neutrinos not only have mass, but also have multiple mass eigenstates that are not identical to the flavour states, thereby indicating mixing. As an evidence of mixing, neutrinos have been observed to change from one flavour to another during their propagation, a phenomenon called neutrino oscillation. We have studied the reasons and derived the probabilities of neutrino flavour change, both in vacuum and in matter. We have also studied the parameters affecting this probability. We have discussed the special case of two-neutrino oscillations. Lastly, we have discussed some basic properties of neutrinos that are reflected in the previous derivations and highlighted a few relevant open problems. To begin with, we have also studied the relevant topics in introductory High Energy Physics and Quantum Mechanics to familiarize with th...
Neutrino Masses and Oscillations
CERN. Geneva. Audiovisual Unit; Treille, Daniel
2002-01-01
This course will not cover its subject in the customary way. The emphasis will be on the simple theoretical concepts (helicity, handedness, chirality, Majorana masses) which are obscure in most of the literature, and on the quantum mechanics of oscillations, that ALL books get wrong. Which, hopefully, will not deter me from discussing some of the most interesting results from the labs and from the cosmos.
Oscillations in the bispectrum
Meerburg, P Daniel
2010-01-01
There exist several models of inflation that produce primordial bispectra that contain a large number of oscillations. In this paper we discuss these models, and aim at finding a method of detecting such bispectra in the data. We explain how the recently proposed method of mode expansion of bispectra might be able to reconstruct these spectra from separable basis functions. Extracting these basis functions from the data might then lead to observational constraints on these models.
Polychromatic optical Bloch oscillations.
Longhi, Stefano
2009-07-15
Bloch oscillations (BOs) of polychromatic beams in circularly curved optical waveguide arrays are smeared out owing to the dependence of the BO spatial period on the wavelength. Here it is shown that restoring of the self-imaging property of the array and approximate BOs over relatively broad spectral ranges can be achieved by the insertion of suitable lumped phase slips uniformly applied across the array.