共查询到20条相似文献,搜索用时 31 毫秒
1.
《Nuclear Physics B》1986,278(3):721-737
Starting from the finite-time action formulation of the temporal gauge, we derive diagrammatic rules for the perturbative evaluation of the Yang-Mills ground state wave functional and energy to all orders. The perturbative expansions are also easily reorganized into semi-classical expansions. As an application, the ground state wave functional through first non-trivial order is explicitly computed. We also speculate on the use of gauge invariance to improve perturbation theory. 相似文献
2.
Sengupta AM Mitra PP 《Physical review. E, Statistical physics, plasmas, fluids, and related interdisciplinary topics》1999,60(3):3389-3392
The singular value decomposition is a matrix decomposition technique widely used in the analysis of multivariate data, such as complex space-time images obtained in both physical and biological systems. In this paper, we examine the distribution of singular values of low-rank matrices corrupted by additive noise. Past studies have been limited to uniform uncorrelated noise. Using diagrammatic and saddle point integration techniques, we extend these results to heterogeneous and correlated noise sources. We also provide perturbative estimates of error bars on the reconstructed low-rank matrix obtained by truncating a singular value decomposition. 相似文献
3.
《Physics letters. [Part B]》1988,203(4):425-432
Combining the Feynman-Vernon influence functional formalism with the real-time formulation of finite-temperature quantum field theories we present a general approach to relativistic quantum field theories out of thermal equilibrium. We clarify the physical meaning of the additional fields encountered in the real-time formulation of quantum statistics and outline diagrammatic rules for perturbative nonequilibrium computations. We derive a generalization of Boltzmann's equation which gives a complete characterization of relativistic nonequilibrium phenomena. 相似文献
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We show that the semiclassical approach to chaotic quantum transport in the presence of time-reversal symmetry can be described by a matrix model. In other words, we construct a matrix integral whose perturbative expansion satisfies the semiclassical diagrammatic rules for the calculation of transport statistics. One of the virtues of this approach is that it leads very naturally to the semiclassical derivation of universal predictions from random matrix theory. 相似文献
6.
In this paper we derive a diagrammatic equation for the planar sector of square non-Hermitian random matrix models. Our fundamental equation is first obtained by a graph counting argument (inspired by the Polchinski equation in quantum field theory) and subsequently derived independently by a precise saddle point analysis of the corresponding random matrix integral. We solve the equation perturbatively for a generic model and conclude by exhibiting two duality properties of the perturbative solution. 相似文献
7.
David C. Morse 《Annals of Physics》2006,321(10):2318-2389
Edwards’ functional integral approach to the statistical mechanics of polymer liquids is amenable to a diagrammatic analysis in which free energies and correlation functions are expanded as infinite sums of Feynman diagrams. This analysis is shown to lead naturally to a perturbative cluster expansion that is closely related to the Mayer cluster expansion developed for molecular liquids by Chandler and co-workers. Expansion of the functional integral representation of the grand-canonical partition function yields a perturbation theory in which all quantities of interest are expressed as functionals of a monomer-monomer pair potential, as functionals of intramolecular correlation functions of non-interacting molecules, and as functions of molecular activities. In different variants of the theory, the pair potential may be either a bare or a screened potential. A series of topological reductions yields a renormalized diagrammatic expansion in which collective correlation functions are instead expressed diagrammatically as functionals of the true single-molecule correlation functions in the interacting fluid, and as functions of molecular number density. Similar renormalized expansions are also obtained for a collective Ornstein-Zernicke direct correlation function, and for intramolecular correlation functions. A concise discussion is given of the corresponding Mayer cluster expansion, and of the relationship between the Mayer and perturbative cluster expansions for liquids of flexible molecules. The application of the perturbative cluster expansion to coarse-grained models of dense multi-component polymer liquids is discussed, and a justification is given for the use of a loop expansion. As an example, the formalism is used to derive a new expression for the wave-number dependent direct correlation function and recover known expressions for the intramolecular two-point correlation function to first-order in a renormalized loop expansion for coarse-grained models of binary homopolymer blends and diblock copolymer melts. 相似文献
8.
《Nuclear Physics B》1996,460(1):109-126
We analyse inclusive photoproduction of polarized 3P1 quarkonium in the framework of QCD. To separate non-perturbative and perturbative parts in the density matrix of the produced quarkonium we use a method, which is equivalent to the diagrammatic expansion widely used in analyzing deeply inelastic scattering. A systematic expansion in a small velocity v, with which a heavy quark moves inside the quarkonium in its rest frame, is performed for the non-perturbative parts, and they are expressed as matrix elements in non-relativistic QCD. At the leading order of v there are four matrix elements representing non-perturbative physics. The perturbative parts are calculated at the leading order of coupling constants. Some numerical results, especially numerical results for HERA, are given. 相似文献
9.
L. G. Molinari N. Manini 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,51(3):331-336
The many-body dynamics of interacting electrons in condensed matter and
quantum chemistry is often studied at the quasiparticle level, where the
perturbative diagrammatic series is partially resummed.
Based on Hedin's equations for self-energy, polarization, propagator,
effective potential, and vertex function,
dressed (skeleton) Feynman diagrams are enumerated.
Such diagram counts provide useful simple checks for extensions of the
theory for future realistic simulations. 相似文献
10.
The one-loop effective action of QED obtained by Heisenberg and Euler and by Schwinger has been expressed by an asymptotic perturbative series which is divergent. In this Letter we present a nonperturbative but convergent series of the effective action. With the convergent series we establish the existence of the manifest electric-magnetic duality in the one-loop effective action of QED. 相似文献
11.
B. Jancovici 《Molecular physics》2013,111(4):1177-1179
Many-body effects in the X1σ+ states of the hydrogen fluoride, lithium fluoride and boron fluoride molecules are investigated. Using diagrammatic perturbation theory, two, three and four-body contributions to the electronic energy are calculated to third order within the algebraic approximation. Many-body effects are found to be very significant. Two zeroth-order hamiltonians are employed and the convergence of the resulting perturbative expansions are compared. The [2/1] Padé approximants to the energy are constructed. Upper bounds to the energy are determined by evaluating the Rayleigh quotient for the first-order perturbative wavefunction. 相似文献
12.
A. Foussats E. Manavella C. Repetto O. P. Zandron O. S. Zandron 《International Journal of Theoretical Physics》1995,34(7):1037-1053
The canonical and path-integral quantization of the non-Abelian higher-derivative Chem-Simons model in three dimensions coupled to a matter field is constructed. The expression of the gauge field propagator in the momentum space for this higher-derivative model is computed. In the framework of the perturbative formalism, the diagrammatic and the Feynman rules are analyzed. Among other results, we conclude that higher-derivative terms added to the Lagrangian improve the ultraviolet behavior, rendering the model less divergent. 相似文献
13.
We review recent advances in the calculations of high-order convergent expansions for quantum many-particle systems. Calculations for ground state properties, including correlation functions and static susceptibilities, for spin models as well as for models of many fermions, such as Hubbard and Kondo models, are discussed. A historical perspective to the subject is provided. Recently important technical advances have been made in perturbative calculations of the excitation spectra of quantum many-particle systems, which enable the calculation of these spectra to high orders. The method, along with its applications, are explained. Fairly comprehensive, though simplified, algorithms for generating lists of relevant clusters, their lattice embeddings and subclusters are presented. The perturbative recursion relations and their computer implementation are also discussed in detail. A compilation is made of various series expansion studies that have been carried out for condensed matter problems. The scope and limitations of these methods are explained, and several open problems are noted. 相似文献
14.
A new perturbative approach is presented and applied to the anharmonic oscillator. Estimating the large-order behaviour by means of the Lipatov method, the new perturbation expansion turns out to be convergent for the partition function at non-zero temperature. Although the new perturbation expansion is not convergent for the ground-state energy, it nevertheless provides accurate approximations, even in situations which cannot be treated by standard perturbation techniques, like the strong coupling regime. 相似文献
15.
Hirofumi Yamada 《Zeitschrift fur Physik C Particles and Fields》1993,59(1):67-75
We study dynamical chiral symmetry breaking in massless QCD by the use of the generalized Hartree-Fock method. As the order parameter of chiral symmetry we choose the dynamical quark mass in the zero momentum limit which we call low energy quark mass. We calculate the low energy mass to the second order of diagrammatic expansion around shifted perturbative vacuum. We then show that the mass is finite and renormalization group invariant. After the improvement of the result by the method of effective charges we estimate the mass in the true vacuum under the gap and stationarity conditions and demonstrate that both of them produce non-zero mass proportional to a conventional scale, which breaks down the chiral symmetry. 相似文献
16.
R. Friedberg 《Annals of Physics》2005,316(1):44-106
We discuss a new approach to solve the low lying states of the Schroedinger equation. For a fairly large class of problems, this new approach leads to convergent iterative solutions, in contrast to perturbative series expansions. These convergent solutions include the long standing difficult problem of a quartic potential with either symmetric or asymmetric minima. 相似文献
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Summary A diagrammatic perturbative approach is adopted to derive the expression for the third-order polarization,P
(3) which originates the anti-Stokes emission in a time-resolved CARS experiment. The various contributions toP
(3) are calculated assuming that laser fields are off-resonance with respect to any electronic level of material system. The
resonant part of the polarization consists of two terms, in which the roles of the pump and probe pulses at frequency ω1 are exchanged. The global expression allows the direct calculation of the signal time profile in a transient CARS experiment
once a model is assumed for the laser pulse shape. 相似文献
19.
Mishchenko AS Nagaosa N Prokof'ev NV Sakamoto A Svistunov BV 《Physical review letters》2003,91(23):236401
We present accurate results for optical conductivity of the three dimensional Fr?hlich polaron in all coupling regimes. The systematic-error free diagrammatic quantum Monte Carlo method is employed where the Feynman graphs for the momentum-momentum correlation function in imaginary time are summed up. The real-frequency optical conductivity is obtained by the analytic continuation with stochastic optimization. We compare numerical data with available perturbative and nonperturbative approaches to the optical conductivity and show that the picture of sharp resonances due to relaxed excited states in the strong-coupling regime is "washed out" by large broadening of these states. As a result, the spectrum contains only a single-maximum broad peak with peculiar shape and a shoulder. 相似文献
20.
A theoretical analysis aimed at investigating the divergent character of perturbative series involved in the study of free-space nonparaxial propagation of vectorial optical beams is proposed. Our analysis predicts a factorial divergence for such series and provides a theoretical framework within which the results of recently published numerical experiments concerning nonparaxial propagation of vectorial Gaussian beams find a meaningful interpretation in terms of the decoding operated on such series by the Weniger transformation. 相似文献