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Journal articles on the topic 'Non-Perturbative Calculation'

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Author: Grafiati

Published: 10 December 2022

Last updated: 28 January 2023

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1

Verschelde, Henri. "Perturbative calculation of non-perturbative effects in quantum field theory." Physics Letters B 351, no. 1-3 (May 1995): 242–48. http://dx.doi.org/10.1016/0370-2693(95)00338-l.

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2

Pineda, A. "Next-to-leading non-perturbative calculation in heavy quarkonium." Nuclear Physics B 494, no. 1-2 (June 1997): 213–36. http://dx.doi.org/10.1016/s0550-3213(97)00175-2.

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3

Capitani, S., M. Göckeler, R. Horsley, H. Oelrich, D. Petters, P. E. L. Rakow, and G. Schierholz. "Towards a non-perturbative calculation of DIS Wilson coefficients." Nuclear Physics B - Proceedings Supplements 73, no. 1-3 (March 1999): 288–90. http://dx.doi.org/10.1016/s0920-5632(99)85050-6.

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4

Ambjørn, J., and J. Greensite. "Non-perturbative calculation of correlators in 2D quantum gravity." Physics Letters B 254, no. 1-2 (January 1991): 66–70. http://dx.doi.org/10.1016/0370-2693(91)90397-9.

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5

Hahn, Susanne, and Gerhard Stock. "Efficient calculation of time- and frequency-resolved spectra: a mixed non-perturbative/perturbative approach." Chemical Physics Letters 296, no. 1-2 (October 1998): 137–45. http://dx.doi.org/10.1016/s0009-2614(98)01003-3.

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6

Stancalie, V. "Theoretical calculation of atomic data for plasma spectroscopy." Laser and Particle Beams 27, no. 2 (April 22, 2009): 345–54. http://dx.doi.org/10.1017/s0263034609000457.

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AbstractIn the present article, a number of theoretical approximations and numerical methods, varying in complexity, are reviewed, in order to facilitate their selection for plasma diagnostic purposes. Results refer to highly charged ions, particularly in the lithium isoelectronic sequence. This article describes progress in understanding the role of laser induced degenerate state phenomenon on resonances obtained by using lasers. This type of process, implicitly included in the R-matrix Floquet calculation, contributes to some degree, to the overall behavior of the resonance profiles. The present article gives comparative results obtained from ab initio non-perturbative treatment and perturbative calculation of autoionization widths in Be-like ions. The effective oscillator strength for complex highly ionized atoms is, also, provided. Such calculations are of interest as they represent accurate benchmark data for beam emission spectroscopy, Zeff analysis, or complex atoms modeling in fusion plasma devices.

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7

Blaizot, J. P., R. Méndez-Galain, and N. Wschebor. "Non-perturbative renormalization group calculation of the scalar self-energy." European Physical Journal B 58, no. 3 (August 2007): 297–309. http://dx.doi.org/10.1140/epjb/e2007-00223-3.

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8

Shanahan, H. P., P. Boyle, C. T. H. Davies, and H. Newton. "A non-perturbative calculation of the mass of the Bc." Physics Letters B 453, no. 3-4 (May 1999): 289–94. http://dx.doi.org/10.1016/s0370-2693(99)00325-1.

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9

IGNATIUS, ROSE P., K. P. SATHEESH, V. C. KURIAKOSE, and K. BABU JOSEPH. "NON-PERTURBATIVE CALCULATION OF EFFECTIVE POTENTIAL IN SUPERSYMMETRIC LIOUVILLE MODEL." Modern Physics Letters A 05, no. 26 (October 20, 1990): 2115–25. http://dx.doi.org/10.1142/s0217732390002419.

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The Gaussian effective potential for the supersymmetric Liouville model is computed both at zero temperature and at a finite temperature. It is noted that the supersymmetric Liouville theory, just like the ordinary Liouville model, does not possess a translationally invariant ground state. The broken translational symmetry is not restored by temperature effects. The supersymmetric Liouville theory is also non-trivial.

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10

Rochev, V. E. "A non-perturbative method for the calculation of Green functions." Journal of Physics A: Mathematical and General 30, no. 10 (May 21, 1997): 3671–79. http://dx.doi.org/10.1088/0305-4470/30/10/037.

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11

Loheac, Andrew C., Jens Braun, and Joaquín E. Drut. "Equation of state of non-relativistic matter from automated perturbation theory and complex Langevin." EPJ Web of Conferences 175 (2018): 03007. http://dx.doi.org/10.1051/epjconf/201817503007.

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We calculate the pressure and density of polarized non-relativistic systems of two-component fermions coupled via a contact interaction at finite temperature. For the unpolarized one-dimensional system with an attractive interaction, we perform a thirdorder lattice perturbation theory calculation and assess its convergence by comparing with hybrid Monte Carlo. In that regime, we also demonstrate agreement with real Langevin. For the repulsive unpolarized one-dimensional system, where there is a so-called complex phase problem, we present lattice perturbation theory as well as complex Langevin calculations. For our studies, we employ a Hubbard-Stratonovich transformation to decouple the interaction and automate the application of Wick’s theorem for perturbative calculations, which generates the diagrammatic expansion at any order. We find excellent agreement between the results from our perturbative calculations and stochastic studies in the weakly interacting regime. In addition, we show predictions for the strong coupling regime as well as for the polarized one-dimensional system. Finally, we show a first estimate for the equation of state in three dimensions where we focus on the polarized unitary Fermi gas.

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12

Crance, M. "Multiphoton ionisation of hydrogen. A non-perturbative calculation of strong-field effects." Journal of Physics B: Atomic, Molecular and Optical Physics 21, no. 15 (August 14, 1988): 2697–708. http://dx.doi.org/10.1088/0953-4075/21/15/015.

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13

Tellgren, E. I., A. M. Teale, J. W. Furness, K. K. Lange, U. Ekström, and T. Helgaker. "Non-perturbative calculation of molecular magnetic properties within current-density functional theory." Journal of Chemical Physics 140, no. 3 (January 21, 2014): 034101. http://dx.doi.org/10.1063/1.4861427.

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14

Verschelde, Henri, Sigurd Schelstraete, and Mark Vanderkelen. "Non-perturbative calculation of the mass-gap in the Gross-Neveu model." Zeitschrift f�r Physik C Particles and Fields 76, no. 1 (September 1, 1997): 161–73. http://dx.doi.org/10.1007/s002880050540.

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15

Li, Yang, V. A. Karmanov, P. Maris, and J. P. Vary. "Non-perturbative Calculation of the Scalar Yukawa Theory in Four-Body Truncation." Few-Body Systems 56, no. 6-9 (March 3, 2015): 495–501. http://dx.doi.org/10.1007/s00601-015-0965-0.

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16

FRIED, H. M. "A NEW, ANALYTIC, NON-PERTURBATIVE, GAUGE-INVARIANT, REALISTIC FORMULATION OF QCD." Modern Physics Letters A 28, no. 01 (January 8, 2013): 1230045. http://dx.doi.org/10.1142/s0217732312300455.

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This Brief Review presents a new, analytic, gauge-invariant, non-perturbative and rigorous approach to the calculation of QCD phenomena. In this formulation a basic distinction between the conventional description of QCD and a more "realistic" description, taking into account that asymptotic quarks exist only in bound states, is brought into focus by the evaluation of the Schwinger solution for the QCD generating functional (GF) in terms of the exact Fradkin representations of the Green's functional G0(x, y|A) and the vacuum functional L[A]. A new and simplifying output called "Effective Locality" appears, in which the interactions between quarks by the exchange of a "gluon bundle" (GB) (which "bundle" contains an infinite number of gluons, including cubic and quartic gluon interactions) display an exact locality property that reduces the several functional integrals of the formulation down to a set of ordinary integrals, susceptible to desktop-computer computation. As an example of the power of these methods we offer as a first pencil-and-paper calculation the quark–antiquark binding potential of a pion, and the corresponding three-quark binding potentials of a nucleon, obtained in a simple way from relevant eikonal scattering approximations. This example is followed by the estimation of a nucleon–nucleon binding potential to form a model deuteron, which may have relevance to the origin of the nuclear shell model and nuclear binding in general.

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17

Tellgren, Erik I., and Heike Fliegl. "Non-perturbative treatment of molecules in linear magnetic fields: Calculation of anapole susceptibilities." Journal of Chemical Physics 139, no. 16 (October 28, 2013): 164118. http://dx.doi.org/10.1063/1.4826578.

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18

Bouchet, Freddy, Krzysztof Gawȩdzki, and Cesare Nardini. "Perturbative Calculation of Quasi-Potential in Non-equilibrium Diffusions: A Mean-Field Example." Journal of Statistical Physics 163, no. 5 (April 6, 2016): 1157–210. http://dx.doi.org/10.1007/s10955-016-1503-2.

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19

Wiecki, Paul, Yang Li, Xingbo Zhao, Pieter Maris, and James P. Vary. "Non-perturbative Calculation of the Positronium Mass Spectrum in Basis Light-Front Quantization." Few-Body Systems 56, no. 6-9 (February 15, 2015): 489–94. http://dx.doi.org/10.1007/s00601-015-0962-3.

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20

Sen, Sangita, and Erik I. Tellgren. "Non-perturbative calculation of orbital and spin effects in molecules subject to non-uniform magnetic fields." Journal of Chemical Physics 148, no. 18 (May 14, 2018): 184112. http://dx.doi.org/10.1063/1.5029431.

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21

SLAUGHTER, MILTON DEAN. "A CALCULATION OF THE MAGNETIC MOMENT OF THE Δ++." Modern Physics Letters A 08, no. 34 (November 10, 1993): 3283–90. http://dx.doi.org/10.1142/s021773239300221x.

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A fully relativistic, gauge-invariant, and non-perturbative calculation of the Δ++ magnetic moment, μΔ++, is made using equal-time commutation relations (ETCRs) and the dynamical concepts of asymptotic SU F(2) flavor symmetry and asymptotic level realization. Physical masses of the Δ and nucleon are used in this broken symmetry calculation. It is found that μΔ++=2.04μp, where μp is the proton magnetic moment. This result is very similar to that obtained by using SU(6) ⊗ O(3) symmetry or the static quark model.

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22

ESPOSITO, GIAMPIERO, ROBERTO PETTORINO, and PAOLO SCUDELLARO. "ON BOOSTED SPACE-TIMES WITH COSMOLOGICAL CONSTANT AND THEIR ULTRARELATIVISTIC LIMIT." International Journal of Geometric Methods in Modern Physics 04, no. 03 (May 2007): 361–72. http://dx.doi.org/10.1142/s0219887807002132.

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The problem of deriving a shock-wave geometry with cosmological constant by boosting a Schwarzschild-de Sitter (or anti-de Sitter) black hole is re-examined. Unlike previous works in the literature, we deal with the exact Schwarzschild-de Sitter (or anti-de Sitter) metric. In this exact calculation, where the metric does not depend linearly on the mass parameter, we find a singularity of distributional nature on a null hypersurface, which corresponds to a shock-wave geometry derived in a fully non-perturbative way. The result agrees with previous calculations, where the metric had been linearized in the mass parameter.

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23

Zhang, Pan-Pan, and Alexander Eisfeld. "Non-Perturbative Calculation of Two-Dimensional Spectra Using the Stochastic Hierarchy of Pure States." Journal of Physical Chemistry Letters 7, no. 22 (October 28, 2016): 4488–94. http://dx.doi.org/10.1021/acs.jpclett.6b02111.

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24

Giusti, L. "A high statistics lattice calculation of quark masses with a non-perturbative renormalization procedure." Nuclear Physics B - Proceedings Supplements 63, no. 1-3 (April 1998): 167–69. http://dx.doi.org/10.1016/s0920-5632(97)00710-x.

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25

MORII, MASAHIRO. "DETERMINATION OF |Vcb| AND RELATED RESULTS FROM BABAR." International Journal of Modern Physics A 20, no. 02n03 (January 30, 2005): 557–60. http://dx.doi.org/10.1142/s0217751x05021774.

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The CKM matrix element amplitude |Vcb| was determined using the data collected by the BABAR detector. The partial branching fraction, lepton-energy moments, and hadron-mass moments were measured in inclusive semileptonic decays B→Xcℓν. A global fit to a Heavy-Quark-Expansion calculation allowed precise determination of |Vcb|, mb, mc, ℬ(B→Xcℓν) and four non-perturbative parameters.

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26

Stepanyantz, Konstantin. "Supersymmetry, quantum corrections, and the higher derivative regularization." EPJ Web of Conferences 191 (2018): 06002. http://dx.doi.org/10.1051/epjconf/201819106002.

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We investigate the structure of quantum corrections in N = 1 supersymmetric theories using the higher covariant derivative method for regularization. In particular, we discuss the non-renormalization theorem for the triple gauge-ghost vertices and its connection with the exact NSVZ β-function. Namely, using the finiteness of the triple gauge-ghost vertices we rewrite the NSVZ equation in a form of a relation between the β-function and the anomalous dimensions of the quantum gauge superfield, of the Faddeev-Popov ghosts, and of the matter superfields. We argue that it is this form that follows from the perturbative calculations, and give a simple prescription how to construct the NSVZ scheme in the non-Abelian case. These statements are confirmed by an explicit calculation of the three-loop contributions to the β-function containing Yukawa couplings. Moreover, we calculate the two-loop anomalous dimension of the ghost superfields and demonstrate that for doing this calculation it is very important that the quantum gauge superfield is renormalized non-linearly.

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27

Hayakawa, Hideaki, Kaoru Hosokawa, and Takeshi Kurimoto. "|Vub| Determination by B → Dsπ." Modern Physics Letters A 18, no. 22 (July 20, 2003): 1557–67. http://dx.doi.org/10.1142/s021773230301137x.

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We investigate [Formula: see text] decay in perturbative QCD approach which has recently been applied to B-meson decays. [Formula: see text] decay (and its charge conjugated mode) can be one of the hopeful modes to determine |Vub| since it occurs through b → u transition only. We estimate both factorizable and non-factorizable contribution, and show that the non-factorizable contribution is much less than the factorizable one. Our calculation gives [Formula: see text].

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28

Girard, Ralph, and Helmut Kr�ger. "Non-perturbative calculation of theS-matrix of the non-linear Schr�dinger model in the strong coupling regime." Zeitschrift f�r Physik C Particles and Fields 32, no. 1 (March 1986): 89–92. http://dx.doi.org/10.1007/bf01441355.

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29

Cormier, E., and P. Lambropoulos. "Optimal gauge and gauge invariance in non-perturbative time-dependent calculation of above-threshold ionization." Journal of Physics B: Atomic, Molecular and Optical Physics 29, no. 9 (May 14, 1996): 1667–80. http://dx.doi.org/10.1088/0953-4075/29/9/013.

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30

Blaizot, Jean-Paul, Andreas Ipp, and Nicolás Wschebor. "Calculation of the pressure of a hot scalar theory within the Non-Perturbative Renormalization Group." Nuclear Physics A 849, no. 1 (January 2011): 165–81. http://dx.doi.org/10.1016/j.nuclphysa.2010.10.007.

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31

Blaizot, J. P., R. Méndez Galain, and N. Wschebor. "Non-Perturbative Renormalization Group calculation of the transition temperature of the weakly interacting Bose gas." Europhysics Letters (EPL) 72, no. 5 (December 2005): 705–11. http://dx.doi.org/10.1209/epl/i2005-10318-5.

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32

Brüggemann, Ben, Pär Kjellberg, and Tõnu Pullerits. "Non-perturbative calculation of 2D spectra in heterogeneous systems: Exciton relaxation in the FMO complex." Chemical Physics Letters 444, no. 1-3 (August 2007): 192–96. http://dx.doi.org/10.1016/j.cplett.2007.07.002.

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33

BULGAC, AURBL, JOAQUIN E. DRUT, and PIOTR MAGIERSKI. "SPIN 1/2 FERMIONS IN THE UNITARY REGIME AT FINITE TEMPERATURE." International Journal of Modern Physics B 20, no. 30n31 (December 20, 2006): 5165–68. http://dx.doi.org/10.1142/s0217979206036223.

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We have performed a fully non-perturbative calculation of the thermal properties of a system of spin 1/2 fermions in 3D in the unitary regime. We have determined the critical temperature for the superfluid-normal phase transition. The thermodynamic behavior of this system presents a number of unexpected features, and we conclude that spin 1/2 fermions in the BCS-BEC crossover should be classified as a new type of superfluid.

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34

MACHADO, MAGNO V. T. "GEOMETRIC SCALING IN ULTRAHIGH ENERGY NEUTRINOS AND NONLINEAR PERTURBATIVE QCD." International Journal of Modern Physics E 20, supp01 (December 2011): 189–94. http://dx.doi.org/10.1142/s0218301311040244.

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The ultrahigh energy neutrino cross section is a crucial ingredient in the calculation of the event rate in high energy neutrino telescopes. Currently there are several approaches which predict different behaviors for its magnitude for ultrahigh energies. In this contribution is presented a summary of current predictions based on the non-linear QCD evolution equations, the so-called perturbative saturation physics. In particular, predictions are shown based on the parton saturation approaches and the consequences of geometric scaling property at high energies are discussed. The scaling property allows an analytical computation of the neutrino scattering on nucleon/nucleus at high energies, providing a theoretical parameterization.

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35

Dzhunushaliev, V. "Calculation of gluon contribution to the proton spin by using the non-perturbative quantization à la Heisenberg." Physics of Particles and Nuclei Letters 14, no. 6 (November 2017): 836–42. http://dx.doi.org/10.1134/s1547477117060152.

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36

Pixius, C., S. Celik, and M. Bartelmann. "Kinetic field theory: perturbation theory beyond first order." Journal of Cosmology and Astroparticle Physics 2022, no. 12 (December 1, 2022): 030. http://dx.doi.org/10.1088/1475-7516/2022/12/030.

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Abstract We present recent improvements in the perturbative treatment of particle interactions in Kinetic Field Theory (KFT) for inertial Zel'dovich trajectories. KFT has been developed for the systematic analytical calculation of non-linear cosmic structure formation on the basis of microscopic phase-space dynamics. We improve upon the existing treatment of the interaction operator by deriving a more rigorous treatment of phase-space trajectories of particles in an expanding universe. We then show how these results can be applied to KFT perturbation theory by calculating corrections to the late-time dark matter power spectrum at second order in the interaction operator. We find that the modified treatment of interactions w.r.t. inertial Zel'dovich trajectories improves the agreement of KFT with simulation results on intermediate scales compared to earlier results. Additionally, we illustrate that including particle interactions up to second order leads to a systematic improvement of the non-linear power spectrum compared to the first-order result.

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37

HUSAIN, VIQAR, and SEBASTIAN JAIMUNGAL. "PHASE TRANSITION IN QUANTUM GRAVITY?" Modern Physics Letters A 14, no. 16 (May 30, 1999): 1079–82. http://dx.doi.org/10.1142/s0217732399001152.

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A fundamental problem with attempting to quantize general relativity is its perturbative non-renormalizability. However, this fact does not rule out the possibility that nonperturbative effects can be computed, at least in some approximation. We outline a quantum field theory calculation, based on general relativity as the classical theory, which implies a phase transition in quantum gravity. The order parameters are composite fields derived from space–time metric functions. These are massless below a critical energy scale and become massive above it. There is a corresponding breaking of classical symmetry.

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38

da Silva, Daniel T., Mario L. L. da Silva, and Dimiter Hadjimichef. "Photon-Photon Interaction in Glueball Production." International Journal of Modern Physics: Conference Series 45 (January 2017): 1760068. http://dx.doi.org/10.1142/s2010194517600680.

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In the last years many exotic states have been identified in several colliders around the world. One of the exotic states provided in QCD is the glueball. Using a non-relativistic gluon bound-state model, we compute [Formula: see text], where [Formula: see text] is a pseudoscalar, tensor, or scalar digluon. For the starting from the amplitudes we considers the process [Formula: see text] at threshold, where the amplitudes are obtained in perturbative QCD at lowest order by deriving them from QED calculation and the [Formula: see text]s are massive constituent gluons. In this calculation the unknown parameters of the model, such as the digluon wave function, are obtained using measured values of [Formula: see text]. Our theorical results are compared with the present experimental limits for the various glueballs candidates.

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39

VACARU, SERGIU I. "TWO-CONNECTION RENORMALIZATION AND NON-HOLONOMIC GAUGE MODELS OF EINSTEIN GRAVITY." International Journal of Geometric Methods in Modern Physics 07, no. 05 (August 2010): 713–44. http://dx.doi.org/10.1142/s0219887810004531.

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A new framework for perturbative quantum gravity is proposed following the geometry of non-holonomic distributions on (pseudo)Riemannian manifolds. There are considered such distributions and adap-ted connections, also completely defined by a metric structure, when gravitational models with infinite many couplings reduce to two-loop renormalizable effective actions. We use a key result from our partner work arXiv: 0902.0911 that the classical Einstein gravity theory can be reformulated equivalently as a non-holonomic gauge model in the bundle of affine/de Sitter frames on pseudo-Riemannian space–time. It is proven that (for a class of non-holonomic constraints and splitting of the Levi–Civita connection into a "renormalizable" distinguished connection, on a base background manifold, and a gauge-like distortion tensor, in total space) a non-holonomic differential renormalization procedure for quantum gravitational fields can be elaborated. Calculation labor is reduced to one- and two-loop levels and renormalization group equations for non-holonomic configurations.

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40

SATO, MASATOSHI, and TOSHIAKI TANAKA. "ON DISAGREEMENT ABOUT NONPERTURBATIVE CORRECTIONS IN TRIPLE-WELL POTENTIAL." Modern Physics Letters A 20, no. 12 (April 20, 2005): 881–96. http://dx.doi.org/10.1142/s0217732305016993.

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We examine in detail nonperturbative corrections for low lying energies of a symmetric triple-well potential with non-equivalent vacua, for which there have been disagreement about asymptotic formulas and controversy over the validity of the dilute gas approximation. We carry out investigations from various points of view, including not only a numerical comparison of the nonperturbative corrections with the exact values but also the prediction on the large order behavior of the perturbation series, consistency with the perturbative corrections, and comparison with the WKB approximation. We show that all the results support our formulas previously obtained from the valley method calculation beyond the dilute gas approximation.

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41

MENDES, R. VILELA. "ELECTRON-POSITRON PRODUCTION IN STRONG FIELD PULSES." Modern Physics Letters A 09, no. 27 (September 7, 1994): 2493–506. http://dx.doi.org/10.1142/s0217732394002367.

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A short critical review is presented concerning the physical interpretation of electron and positron production data at the GSI accelerator in Darmstadt. The only reliable conclusions seem to be that the creation mechanism is a strong field effect and that the phenomenon is largely independent of the characteristic time of the collision. Before looking for new (exotic) physics it seems reasonable to inquire whether non-perturbative QED is fully understood. Following this motivation a rigorous but, at the same time, sufficiently explicit nonperturbative calculation scheme is developed, for QED in strong fields of short duration. The possible occurrence of correlated e+e− narrow structures is discussed in this framework.

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42

Stancalie, Viorica. "Singly Resonant Multiphoton Processes Involving Autoionizing States in the Be-like CIII Ion." Symmetry 14, no. 12 (November 30, 2022): 2528. http://dx.doi.org/10.3390/sym14122528.

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In this paper, we investigate the applicability of different theories on the intensity-dependent ionization rate for C2+ atomic targets at different laser wavelengths (frequency) and at linear polarization. We use the analytical formulas and draw conclusions, from numerical comparison with the results from ab initio ‘two-state model’ R-matrix Floquet calculation, on their correct predictions of the ionization rate. The single-photon ionization has been studied in the vicinity of the 1s2 (2Po)2pns (1Po), n = 5–12 autoionizing resonances at non-perturbative laser intensity. The results obtained from Perelomov–Popov–Terent’ev and Ammosov–Delone–Krainov models are compared in a region away from resonance where the two-state model description is not as good. To quantify the deviation between theoretical models, we analyze the ratio between different data sets as functions of the Keldysh parameter. We conclude that the results obtained with the model of Perelemov–Popov–Terent’ev are the closest to the ab initio R-matrix Floquet calculation.

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43

Denis-Alpizar, Otoniel, and Thierry Stoecklin. "Rotational relaxation of H2S by collision with He." Astronomy & Astrophysics 638 (June 2020): A31. http://dx.doi.org/10.1051/0004-6361/202037821.

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Context. The H2S molecule has been detected in several regions of the interstellar medium (ISM). The use of non-LTE models requires knowledge of accurate collisional rate coefficients of the molecules detected with the most common collider in the ISM. Aims. The main goal of this work is to study the collision of H2S with He. Methods. A grid of ab initio energies was computed at the coupled cluster level of theory including single, double, and perturbative triple excitations (CCSD(T)) and using the augmented correlation consistent polarized quadruple zeta (aug-cc-pVQZ) basis set supplemented by a set of mid-bond functions. These energies were fitted to an analytical function, which was employed to study the dynamics of the system. Close coupling calculations were performed to study the collision of H2S with He. Results. The rate coefficients determined from the close coupling calculation were compared with those of the collision with H2O+He, and large differences were found. Finally, the rate coefficients for the lower rotational de-excitation of H2S by collision with He are reported.

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44

Seke, J., A. V. Soldatov, and N. N. Bogolubov. "Novel Technique for Quantum-Mechanical Eigenstate and Eigenvalue Calculations based on Seke's Self-Consistent Projection-Operator Method." Modern Physics Letters B 11, no. 06 (March 10, 1997): 245–58. http://dx.doi.org/10.1142/s0217984997000311.

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Seke's self-consistent projection-operator method has been developed for deriving non-Markovian equations of motion for probability amplitudes of a relevant set of state vectors. This method, in a Born-like approximation, leads automatically to an Hamiltonian restricted to a subspace and thus enables the construction of effective Hamiltonians. In the present paper, in order to explain the efficiency of Seke's method in particular applications, its algebraic operator structure is analyzed and a new successive approximation technique for the calculation of eigenstates and eigenvalues of an arbitrary quantum-mechanical system is developed. Unlike most perturbative techniques, in the present case each order of the approximation determines its own effective (approximating) Hamiltonian ensuring self-consistency and formal exactness of all results in the corresponding approximation order.

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Afonso, Marco Martins, Andrea Mazzino, and Paolo Muratore-Ginanneschi. "Eddy diffusivities of inertial particles under gravity." Journal of Fluid Mechanics 694 (February 7, 2012): 426–63. http://dx.doi.org/10.1017/jfm.2011.562.

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AbstractThe large-scale/long-time transport of inertial particles of arbitrary mass density under gravity is investigated by means of a formal multiple-scale perturbative expansion in the scale-separation parameter between the carrier flow and the particle concentration field. The resulting large-scale equation for the particle concentration is determined, and is found to be diffusive with a positive definite eddy diffusivity. The calculation of the latter tensor is reduced to the resolution of an auxiliary differential problem, consisting of a coupled set of two differential equations in a $(6+ 1)$-dimensional coordinate system (three space coordinates plus three velocity coordinates plus time). Although expensive, numerical methods can be exploited to obtain the eddy diffusivity, for any desirable non-perturbative limit (e.g. arbitrary Stokes and Froude numbers). The aforementioned large-scale equation is then specialized to deal with two different relevant perturbative limits: (i) vanishing of both Stokes time and sedimenting particle velocity; (ii) vanishing Stokes time and finite sedimenting particle velocity. Both asymptotics lead to a greatly simplified auxiliary differential problem, now involving only space coordinates and thus easily tackled by standard numerical techniques. Explicit, exact expressions for the eddy diffusivities have been calculated, for both asymptotics, for the class of parallel flows, both static and time-dependent. This allows us to investigate analytically the role of gravity and inertia on the diffusion process by varying relevant features of the carrier flow, such as the form of its temporal correlation function. Our results exclude a universal role played by gravity and inertia on the diffusive behaviour: regimes of both enhanced and reduced diffusion may exist, depending on the detailed structure of the carrier flow.

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Ren, Y., and C. F. Beards. "A New Receptance-Based Perturbative Multi-Harmonic Balance Method for the Calculation of the Steady State Response of Non-Linear Systems." Journal of Sound and Vibration 172, no. 5 (May 1994): 593–604. http://dx.doi.org/10.1006/jsvi.1994.1201.

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Ren, Y. "The receptance-based perturbative multi-harmonic balance method for the calculation of the aperiodic steady state response of non-linear systems." Journal of Sound and Vibration 181, no. 2 (March 1995): 331–39. http://dx.doi.org/10.1006/jsvi.1995.0143.

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GULZARI, S., J. SWAIN, and A. WIDOM. "ASYMPTOTIC INFRARED FRACTAL STRUCTURE OF THE PROPAGATOR FOR A CHARGED FERMION." Modern Physics Letters A 21, no. 38 (December 14, 2006): 2861–71. http://dx.doi.org/10.1142/s0217732306022316.

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It is well known that the long-range nature of the Coulomb interaction makes the definition of asymptotic "in" and "out" states of charged particles problematic in quantum field theory. In particular, the notion of a simple particle pole in the vacuum charged particle propagator is untenable and should be replaced by a more complicated branch cut structure describing an electron interacting with a possibly infinite number of soft photons. Previous work suggests a Dirac propagator raised to a fractional power dependent upon the fine structure constant, however the exponent has not been calculated in a unique gauge-invariant manner. It has even been suggested that the fractal "anomalous dimension" can be removed by a gauge transformation. Here, a gauge-invariant non-perturbative calculation will be discussed yielding an unambiguous fractional exponent. The closely analogous case of soft graviton exponents is also briefly explored.

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Ghiglieri, Jacopo, and Derek Teaney. "Parton energy loss and momentum broadening at NLO in high temperature QCD plasmas." International Journal of Modern Physics E 24, no. 11 (November 2015): 1530013. http://dx.doi.org/10.1142/s0218301315300131.

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We present an overview of a perturbative-kinetic approach to jet propagation, energy loss, and momentum broadening in a high temperature quark–gluon plasma. The leading-order kinetic equations describe the interactions between energetic jet-particles and a non-abelian plasma, consisting of on-shell thermal excitations and soft gluonic fields. These interactions include [Formula: see text] scatterings, collinear bremsstrahlung, and drag and momentum diffusion. We show how the contribution from the soft gluonic fields can be factorized into a set of Wilson line correlators on the light-cone. We review recent field-theoretical developments, rooted in the causal properties of these correlators, which simplify the calculation of the appropriate Wilson lines in thermal field theory. With these simplifications lattice measurements of transverse momentum broadening have become possible, and the kinetic equations describing parton transport have been extended to next-to-leading order in the coupling [Formula: see text].

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TURCZYK, SASCHA. "HIGHER-ORDERS IN SEMILEPTONIC B-DECAYS." Modern Physics Letters A 27, no. 32 (October 11, 2012): 1230027. http://dx.doi.org/10.1142/s0217732312300273.

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In this paper, on a talk given at Lawrence Berkeley Laboratory, we discuss higher-order non-perturbative corrections in inclusive semileptonic decays of B mesons. First the generic calculation is reviewed and then we identify the relevant hadronic matrix-elements up to [Formula: see text]. For a quantitative analysis of these effects, the value of these new matrix-elements is estimated within an approximation scheme. We investigate the role of so-called "intrinsic-charm" operators in this decay, appearing first at order [Formula: see text] in the heavy-quark expansion. These operators induce an expansion infrared sensitive to the charm quark [Formula: see text]. Parametrically the power corrections complement the estimate of the potential impact of [Formula: see text] contributions, which we will explore. In this context, we draw semiquantitative conclusions for the expected scale of valence weak annihilation contribution in semileptonic B decays. Furthermore the effects on the integrated rate and on kinematic moments are then estimated up to [Formula: see text].

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