Abstract: The derivation and implementation of excited state gradients is reported for the approximate coupled-cluster singles and doubles model CC2 employing the resolution-of-the-identity approximation for electron repulsion integrals. The implementation is profiled for a set of examples with up to 1348 basis functions and exhibits no I/O bottlenecks. A test set of sample molecules is used to assess the performance of the CC2 model for adiabatic excitation energies, excited state structure constants and vibrational frequencies. We find very promising results, especially for adiabatic excitation energies, though the need of a single-reference ground state and a single-replacement dominated excited state puts some limits on the applicability of the method. Its reliability, however, can always be tested on grounds of diagnostic measures. As an example application, we present calculations on the π*←π excited state of trans-azobenzene.

Abstract: The relation between the distribution of work performed on a classical system by an external force switched on an arbitrary time scale and the corresponding equilibrium free energy difference is generalized to quantum systems. Using the adiabatic representation, we show that this relation holds for isolated systems as well as for systems coupled to a bath described by a master equation. A close formal analogy is established between the present "classical trajectory" picture over populations of adiabatic states and phase fluctuations (dephasing) of a quantum coherence in spectral line shapes, described by the stochastic Liouville equation.

Abstract: The saturation level of the magnetorotational instability (MRI) is investigated using three-dimensional MHD simulations. The shearing box approximation is adopted and the vertical component of gravity is ignored, so that the evolution of the MRI is followed in a small local part of the disk. We focus on the dependence of the saturation level of the stress on the gas pressure, which is a key assumption in the standard alpha disk model. From our numerical experiments it is found that there is a weak power-law relation between the saturation level of the Maxwell stress and the gas pressure in the nonlinear regime; the higher the gas pressure, the larger the stress. Although the power-law index depends slightly on the initial field geometry, the relationship between stress and gas pressure is independent of the initial field strength, and is unaffected by Ohmic dissipation if the magnetic Reynolds number is at least 10. The relationship is the same in adiabatic calculations, where pressure increases over time, and nearly-isothermal calculations, where pressure varies little with time. Our numerical results are qualitatively consistent with an idea that the saturation level of the MRI is determined by a balance between the growth of the MRI and the dissipation of the field through reconnection. The quantitative interpretation of the pressure-stress relation, however, may require advances in the theoretical understanding of non-steady magnetic reconnection.

Abstract: The effect of fluctuations in the classical control parameters on the Berry phase of a spin 1/2 interacting with an adiabatically cyclically varying magnetic field is analyzed. It is explicitly shown that in the adiabatic limit dephasing is due to fluctuations of the dynamical phase.

Abstract: The fundamentals of a quantum heat engine are derived from first principles. The study is based on the equation of motion of a minimum set of operators, which is then used to define the state of the system. The relation between the quantum framework and the thermodynamical observables is examined. A four-stroke heat engine model with a coupled two-level system as a working fluid is used to explore the fundamental relations. In the model used, the internal Hamiltonian does not commute with the external control field, which defines the two adiabatic branches. Heat is transferred to the working fluid by coupling to hot and cold reservoirs under constant field values. Explicit quantum equations of motion for the relevant observables are derived on all branches. The dynamics on the heat transfer constant field branches is solved in closed form. On the adiabats, a general numerical solution is used and compared with a particular analytic solution. These solutions are combined to construct the cycle of operation. The engine is then analyzed in terms of the frequency-entropy and entropy-temperature graphs. The irreversible nature of the engine is the result of finite heat transfer rates and frictionlike behavior due to noncommutability of the internal and external Hamiltonians.

Abstract: The basic concept of the present paper is to use a tangent line to the adiabatic pressure-volume curve as an approximation to the curve itself. First, the general characteristics of such a fluid are shown. Then in Section I a theory is developed which can be applied to flows with velocities approaching that of sound, whereas the theory of Demtchenko and Busemann only give an approximation for flows with velocities smaller than one-half of the sound velocity. This is done by a generalization of the method of approximation to the adiabatic relation by a tangent line, conceived jointly by Th. von Karman and the author. The theory is put into a form by which, knowing the incompressible flow over a body, the compressible flow over a similar body can be calculated. The theory is then applied to calculate the flow over elliptic cylinders. In Section II the work of H. Bateman is applied to this approximate adiabatic fluid and the results obtained are essentially the same as those obtained in Section I.

Abstract: Non-Abelian holonomies can be generated and detected in certain superconducting nanocircuits. Here we consider an example where the non-Abelian operations are related to the adiabatic charge dynamics of the Josephson network. We demonstrate that such a device can be applied both for adiabatic charge pumping and as an implementation of a quantum computer.

Abstract: We compare two cosmological hydrodynamic simulation codes in the context of hierarchical galaxy formation: The SPH code GADGET, and the Eulerian AMR code ENZO. Both codes represent dark matter with the N-body method, but use different gravity solvers and fundamentally different approaches to hydrodynamics. We compare the GADGET `entropy conserving' SPH formulation with two ENZO methods: The piecewise parabolic method (PPM), and the artificial viscosity-based scheme used in the ZEUS code. In this paper we focus on a comparison of cosmological simulations that follow either only dark matter, or also adiabatic baryonic gas. The dark matter-only runs agree generally quite well, provided ENZO is run with a comparatively fine root grid and a low overdensity threshold for mesh refinement, otherwise the abundance of low-mass halos is suppressed. This is due to the hierarchical particle-mesh method used to compute gravitational forces in ENZO, which tends to deliver lower force resolution than the tree algorithm of GADGET. At comparable force resolution, we find that the latter offers substantially better performance and lower memory consumption than the present gravity solver in ENZO. In simulations that include adiabatic gas dynamics, we find general agreement in the distribution functions of temperature, entropy, and density for gas of moderate to high overdensity, as found inside dark matter halos. However, there are some significant differences at lower overdensities. We argue that these discrepancies are presumably owing to differences in the shock-capturing abilities of the different methods. In particular, ZEUS hydro leads to some unphysical heating at early times in preshock regions. Overall, the GADGET hydro results are bracketed by those for ENZO/ZEUS and ENZO/PPM. (abridged)

Abstract: When gas accretes onto a black hole, at a rate either much less than or much greater than the Eddington rate, it is likely to do so in an "adiabatic" or radiatively inefficient manner. Under fluid (as opposed to MHD) conditions, the disk should become convective and evolve toward a state of marginal instability. The resulting disk structure is "gyrentropic," with convection proceeding along common surfaces of constant angular momentum, Bernoulli function and entropy, called "gyrentropes." We present a family of two-dimensional, self-similar models which describes the time-averaged disk structure. We then suppose that there is a self-similar, Newtonian torque and that the Prandtl number is large. This torque drives inflow and meridional circulation and the resulting flow is computed. Convective transport will become ineffectual near the disk surface. It is conjectured that this will lead to a large increase of entropy across a "thermal front" which we identify as the effective disk surface and the base of an outflow. The conservation of mass, momentum and energy across this thermal front permits a matching of the disk models to self-similar outflow solutions. We then demonstrate that self-similar disk solutions can be matched smoothly onto relativistic flows at small radius and thin disks at large radius. This model of adiabatic accretion is contrasted with some alternative models that have been discussed recently. The disk models developed in this paper should be useful for interpreting numerical, fluid dynamical simulations. Related principles to those described here may govern the behaviour of astrophysically relevant, magnetohydrodynamic disk models.

Abstract: We extend the full triples equation-of-motion (EOM) coupled cluster (CC) method to electron attached states. Proper factorization of the three- and four-body parts of the effective Hamiltonian makes it possible to achieve for the EA-EOM part a scaling no higher than nocc2nvir5. The method is calibrated by the evaluation of the valence vertical electron affinities for the C2 and O3 molecules for several basis sets up to 160 basis functions. For C2, EA-EOM-CCSDT gives 3.24 eV at the extrapolated basis limit, while the experimental adiabatic EA is equal to 3.27±0.008 eV. For O3 the agreement is ∼1.9 eV compared to an adiabatic value of 2.1 eV.

Abstract: In many flame simulations, simplified transport models are used to reduce computational costs. This article presents the effect of simplified transport modeling on the burning velocity of laminar premixed flames. Results obtained with the detailed transport model are compared with results obtained with a number of simplified models. Furthermore, the influence of the Soret and Dufour effects is evaluated. All the models are tested on one-dimensional adiabatic premixed flames with CH 4 /air, CH 4 /O 2 , H 2 /air, and H 2 /O 2 mixtures. Results show that the approximations may lead to large errors in the prediction of the burning velocity. For example, neglecting thermal diffusion in an H 2 /air flame may lead to an error of 10%. Furthermore, simplified mass diffusion models appear to be inaccurate, especially for the fuel/oxygen flames.

Abstract: We discuss a decoherence insensitive method to create many-particle entanglement in a spin system with controllable collective interactions and propose an implementation in an ion trap. An adiabatic change of parameters allows a transfer from separable to a large variety of entangled eigenstates. We show that the Hamiltonian can have a supersymmetry permitting an explicit construction of the ground state at all times. Of particular interest is a transition in a nondegenerate ground state with a finite energy gap since here the influence of collective as well as individual decoherence mechanisms is substantially reduced. A lower bound for the energy gap is given.

Abstract: The magnetocaloric effect was investigated in LaFe11.7Si1.3, which undergoes a first-order transition at ∼188 K from the ferromagnetic to paramagnetic state. The magnetic entropy change upon a field increase from 0 to 5 T is as large as 29 J/kg K (212 mJ/cm3 K). The adiabatic temperature change obtained via direct measurements reaches 4 K under a field change from 0 to 1.4 T. The large values of entropy change and adiabatic temperature change confirmed the large potential of present compound LaFe11.7Si1.3 as a magnetic refrigerant in the corresponding temperature range.

Abstract: We show that temporal shape modulations (pumping) of a quantum dot in the presence of spin-orbital coupling lead to a finite dc spin current. Depending on the strength of the spin-orbit coupling, the spin current is polarized perpendicular to the plane of the two-dimensional electron gas, or has an arbitrary direction subject to mesoscopic fluctuations. We analyze the statistics of the spin and charge currents in the adiabatic limit for the full crossover from weak to strong spin-orbit coupling.

Abstract: In this paper we show how the Smoothed Particle Hydrodynamics (SPH) equations for ideal magnetohydrodynamics (MHD) can be written in conservation form with the positivity of the dissipation guaranteed. We call the resulting algorithm Smoothed Particle Magnetohydrodynamics (SPMHD). The equations appear to be accurate, robust and easy to apply and do not suffer from the instabilities known to exist previously in formulations of the SPMHD equations. In addition we formulate our MHD equations such that errors associated with non-zero divergence of the magnetic field are naturally propagated by the flow and should therefore remain small. In this and a companion paper (Price and Monaghan 2003b) we present a wide range of numerical tests in one dimension to show that the algorithm gives very good results for one dimensional flows in both adiabatic and isothermal MHD. For the one dimensional tests the field structure is either two or three dimensional. The algorithm has many astrophysical applications and is particularly suited to star formation problems.

Abstract: We theoretically investigated the dynamics of structural deformations of CO2 and its cations in near-infrared intense laser fields (∼1015 W cm-2) by using the time-dependent adiabatic state approach. To obtain “field-following” adiabatic potentials for nuclear dynamics, the electronic Hamiltonian including the interaction with the instantaneous laser electric field is diagonalized by the multiconfiguration self-consistent-field molecular orbital method. In the CO2 and CO2+ stages, ionization occurs before the field intensity becomes high enough to deform the molecule. In the CO22+ stage, simultaneous symmetric two-bond stretching occurs as well as one-bond stretching. Two-bond stretching is induced by an intense field in the lowest time-dependent adiabatic state |1〉 of CO22+, and this two-bond stretching is followed by the occurrence of a large-amplitude bending motion mainly in the second-lowest adiabatic state |2〉 nonadiabatically created at large internuclear distances by the field from |1〉. It is conc...

Abstract: In general correlated models, in addition to the usual adiabatic component with a spectral index n a d 1 there is another adiabatic component with a spectral index n a d 2 generated by entropy perturbation during inflation. We extend the analysis of a correlated mixture of adiabatic and isocurvature cosmic microwave background fluctuations of the Wilkinson Microwave Anisotropy Probe (WMAP) group, who set the two adiabatic spectral indices equal. Allowing n a d 1 and n a d 2 to vary independently we find that the WMAP data favor models where the two adiabatic components have opposite spectral tilts. Using the WMAP data only, the 2σ upper bound for the isocurvature fraction f i s o of the initial power spectrum at k 0 = 0.05 Mpc - 1 increases somewhat, e.g., from 0.76 of n a d 2 = n a d 1 models to 0.84 with a prior n i s o < 1.84 for the isocurvature spectral index.

Abstract: A nontraditional picture for primary kinetic isotope effects (KIEs) is presented for proton transfer (PT) reactions in a polar environment in the proton adiabatic regime, in which proton motion is ...

Abstract: Distortions of the electronic and molecular structures of a polarizable molecule in an inhomogeneous electrostatic potential were investigated by using perturbation theory. The second-order electronic energy correction term is directly related to the charge response kernel, which is a site representation of the nonlocal charge response susceptibility. Instead of using the sum-over-state expression for the charge response kernel, we discuss how a finite-field method using point charges can be used to calculate the charge response kernel. By invoking various levels of adiabatic approximations, four different coupled differential equations for the vibrational wave functions were obtained. From the effective vibrational potential functions thus obtained, the molecular structural distortion induced by the external electrostatic potential was shown to be calculable. We also present a discussion on how vibrational properties are affected by the presence of the electrostatic potential. The relationship between the vibrational frequency shift and molecular structural distortion, when a polarizable molecule is exposed to an electrostatic potential, was elucidated.

Abstract: Simple self-consistent models of galaxy groups and clusters are tested against the results of high-resolution adiabatic gasdynamical simulations. We investigate two models based on the existence of a 'universal' dark matter density profile and two versions of the beta-model. The mass distribution of relaxed clusters can be fitted by phenomenological formulae proposed in the literature. Haloes that have experienced a recent merging event are systematically less concentrated and show steeper profiles than relaxed objects near the centre. The hot X-ray emitting gas is found to be in approximate hydrostatic equilibrium with the dark matter potential, and it is well described by a polytropic equation of state. Analytic formulae for the gas density and temperature can be derived from these premises. Though able to reproduce the X-ray surface brightness, the beta-model is shown to provide a poor description of our numerical clusters. We find strong evidence of a 'universal' temperature profile that decreases by a factor of 2-3 from the centre to the virial radius, whereas baryon fraction and entropy are monotonically increasing functions. Numerical resolution and entropy conservation play a key role in the shapes of the profiles at small radii.

Abstract: 2 (V), 1 A 1 (V8), respectively, at the C 2v ground-state molecular configuration# have been studied using the equation-of-motion coupled-cluster singles and doubles method ~EOM-CCSD!. Full geometry optimizations with subsequent computation of harmonic vibrational frequencies have been performed in order to locate and characterize stationary points on the potential energy surfaces ~PES!. The latter optimization work was enabled by the availability of analytic energy gradient techniques for the EOM-CCSD approach. A major new finding is that both the 1 B2(V) and 1 A1(V8) valence states are unstable with respect to non-totally symmetric distortions at the C2v configuration. The symmetry breaking in the 1 B2(V) state involves an in-plane coordinate of b2 symmetry. The relaxation process begins on the S2 adiabatic PES and, after passing through a conical intersection of the S2 and S1 PES, continues on the S1 surface, taking the system finally to the adiabatic minimum ofS1 ( 1 A2 state!. The 1 A1(V8) valence state is found to be unstable with respect to the out-of-plane bending coordinates of b1 and a2 symmetry. The resulting relaxed molecular structures have Cs and C2 symmetry, respectively. The present findings are analyzed in terms of a linear vibronic coupling model and spectroscopic implications are discussed. © 2003 American Institute of Physics. @DOI: 10.1063/1.1578051#

Abstract: The adiabatic reaction temperature of stoichiometric Ni+Al and 3Ni+Al elemental mixtures and non-stoichiometric Ni/Al reaction systems under various initial conditions are calculated and compared with experiments. The experiments are based on the measurement of temperature–time profiles of the combustion reactions carried out in a nearly adiabatic condition. The adiabatic reaction temperature changes with the fraction of Ni with a maximum at about equal atomic ratio. The experimental results are in good agreement with the calculations.

Abstract: This is the first comprehensive study on the kinetic modeling of adiabatic decomposition of di-tert-butyl peroxide (DTBP) and its solvent mixtures. The adiabatic thermal decomposition of DTBP and its solvent mixtures was examined using an accelerating rate calorimeter under varying thermal inertia. The decomposition products were characterized using gas chromatography−total inorganic carbon analysis and gas chromatography−mass spectroscopy to elucidate the mechanistic pathways for decomposition under adiabatic conditions. Reaction models (overall stoichiometric equations) for the decomposition of neat DTBP and its mixture in various solvents have been proposed for the first time. A comprehensive kinetic analysis based on simultaneous treatment of mass and energy balances has been done using a software called BatchCAD. The activation energies for the decomposition of DTBP and its mixtures in various solvents were quite consistent. This comprehensive study has answered to many ambiguities and questions on t...

Abstract: This paper is about adiabatic transport in quantum pumps. The notion of ``energy shift'', a self-adjoint operator dual to the Wigner time delay, plays a role in our approach: It determines the current, the dissipation, the noise and the entropy currents in quantum pumps. We discuss the geometric and topological content of adiabatic transport and show that the mechanism of Thouless and Niu for quantized transport via Chern numbers cannot be realized in quantum pumps where Chern numbers necessarily vanish.

Abstract: Large eddy simulations (LESs) of aero-optical effects in a turbulent boundary layer have been carried out at two different Mach numbers (0.9 and 2.3) for two different wall boundary conditions (adiabatic and isothermal). Moreover, in the adiabatic case, LESs were performed on two different meshes. First, aerodynamic fields are proved to compare favourably with theoretical and experimental results. Once validated, the characteristics of the boundary layer allow us to obtain information concerning optical beam degradation. The density field is then used to compute the phase distortion induced by turbulent fluctuations on a coherent optical beam. The Mach number effect on the phase distortion is evaluated by means of these computations and the link between index-of-refraction fluctuations and phase distortion is discussed. Moreover, LES allows us to study optical models and the validity of their assumptions. Finally, LES is proved to be considered as a reference tool to evaluate phase distortion.