共查询到20条相似文献,搜索用时 186 毫秒
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《Nuclear Physics A》2007,781(1-2):104-121
In this work we extend the JIMWLK formalism to the two-source problem. The S-matrix for the forward scattering can be written in a double functional integral representation which involves the usual functional integral for the gluon field and the spin path integral for the external color sources. Modifications needed in the light-cone gauge are discussed. Using our source term we compute the produced gluon field and discuss the duality of the high energy evolution kernel in the pA collision. 相似文献
4.
N. P. Landsman 《Communications in Mathematical Physics》1989,125(4):643-660
Bounds for large-mass behaviour in renormalized perturbation expansions at zero temperature, which were previously obtained by Manoukian and Caswell-Kennedy in momentum space, are rederived in the parametric representation. A very simple unified proof of the BPHZ theorem and the decoupling theorem is also given. A new technique for asymptotic analysis, based on a generalized Kontorovich-Lebedev integral transform, is introduced. This method is applied to find the leading high-temperature behaviour of perturbative field theories in the imaginary-time formalism. We prove that diagrams containing nonstatic modes, which at high temperature behave like particles with a large mass, are suppressed relative to purely static diagrams. This rigorously proves a limited form of dimensional reduction at infinite temperature. 相似文献
5.
R. Kree 《Zeitschrift für Physik B Condensed Matter》1987,65(4):505-513
Starting from the Liouville-von Neumann equation for the state operator, a functional integral representation of the generating functional for time-temperature dependent Green's functions in interacting disordered quantum systems is constructed. In the framework of this method, quenched averages can be performed without introducing additional, unphysical degrees of freedom, like, e.g., in then-replica method. For interaction-free systems, the dynamical origin of the Schäfer-Wegner symmetry is pointed out. For interacting systems we derive a matrix field theory with a single matrix field, which includes all interaction effects without approximations. 相似文献
6.
Kernel polynomial representation for imaginary-time Green's functions in continuous-time quantum Monte Carlo impurity solver 下载免费PDF全文
Inspired by the recently proposed Legendre orthogonal polynomial representation for imaginary-time Green s functions G(τ),we develop an alternate and superior representation for G(τ) and implement it in the hybridization expansion continuous-time quantum Monte Carlo impurity solver.This representation is based on the kernel polynomial method,which introduces some integral kernel functions to filter the numerical fluctuations caused by the explicit truncations of polynomial expansion series and can improve the computational precision significantly.As an illustration of the new representation,we re-examine the imaginary-time Green's functions of the single-band Hubbard model in the framework of dynamical mean-field theory.The calculated results suggest that with carefully chosen integral kernel functions,whether the system is metallic or insulating,the Gibbs oscillations found in the previous Legendre orthogonal polynomial representation have been vastly suppressed and remarkable corrections to the measured Green's functions have been obtained. 相似文献
7.
Robert Graham 《Zeitschrift für Physik B Condensed Matter》1977,26(3):281-290
A method is given for the derivation of a path integral representation of the Green's function solutionP of equationsP/t=L
P,L being some Liouville operator. The method is applied to general diffusion processes.Feynman's path integral representation of the Schrödinger equation and Stratonovich's path integral representation of multivariate Markovian processes are obtained as special cases if the metric of the general diffusion process is flat. For curved phase spaces our result is a nontrivial generalization and new. New applications e.g. to quantized motion in general relativity, to transport processes in inhomogeneous systems, or to nonlinear non-equilibrium thermodynamics are made possible. We expect applications to be fruitfull in all cases where (continuous) macroscopic transport processes in Riemann geometries have to be considered. 相似文献
8.
M. Faber A. N. Ivanov N. I. Troitskaya 《International Journal of Theoretical Physics》2007,46(1):143-148
We evaluate the evolution operator Z
Reg(R
2,R
1) introduced by Diakonov and Petrov for the definition of the Wilson loop in terms of a path integral over gauge degrees of
freedom. We use the procedure suggested by Diakonov and Petrov (Physics Letters B
224 (1989) 131) and show that the evolution operator vanishes.
PACS numbers: 11.10.-z; 11.15.-q; 12.38.-t; 12.38.Aw; 12.90.+b. 相似文献
9.
The main objective of this paper was to obtain an operator realization for the bosonization of fermions in 1 + 1 dimensions, at finite, non-zero temperature T. This is achieved in the framework of the real-time formalism of Thermofield Dynamics. Formally, the results parallel those of the T = 0 case. The well-known two-dimensional Fermion–Boson correspondences at zero temperature are shown to hold also at finite temperature. To emphasize the usefulness of the operator realization for handling a large class of two-dimensional quantum field-theoretic problems, we contrast this global approach with the cumbersome calculation of the fermion-current two-point function in the imaginary-time formalism and real-time formalisms. The calculations also illustrate the very different ways in which the transmutation from Fermi–Dirac to Bose–Einstein statistics is realized. 相似文献
10.
M. Drzazga A. Kampf E. Müller-Hartmann H. A. Wischmann 《Zeitschrift für Physik B Condensed Matter》1989,74(1):67-74
A Ginzburg-Landau expansion for the free energy functional of the resonating valence bond state is performed for the mean field approximation (MFA) and for a functional integral approach (FIA) which includes correlations. Phase diagrams obtained in both approximations are presented. The FIA differs form the MFA in three main aspects: (i) Above the mean field transition temperature an instability exists towards the formation of degenerate singlet pair states, indicating the onset of the RVB state. (ii) The extendeds-wave phase is favoured over the extendedd-wave phase. (iii) Phase fluctuations are included, destroying off-diagonal order in the absence of holes. 相似文献
11.
We define the two dimensional Pauli operator and identify its core for magnetic fields that are regular Borel measures. The
magnetic field is generated by a scalar potential hence we bypass the usual A∈L
2
loc condition on the vector potential, which does not allow to consider such singular fields. We extend the Aharonov–Casher
theorem for magnetic fields that are measures with finite total variation and we present a counterexample in case of infinite
total variation. One of the key technical tools is a weighted L
2 estimate on a singular integral operator.
Received: 14 May 2001 / Accepted: 5 September 2001 相似文献
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C. F. Lo 《Il Nuovo Cimento D》1991,13(10):1279-1292
Summary In this paper we investigate the time evolution of a general driven time-dependent oscillator using the evolution operator
method developed by Chenget al. We obtain an exact form of the time evolution operator which, in turn, enables us to find the exact wave functions and coherent
states at any timet. Our analyses indicate that the time-dependent coherent state is equivalent to the well-known squeezed state, while the time-dependent
number state is equivalent to the displaced and squeezed number state. Besides, we also calculate the time-dependent transition
probabilities among the coherent states and number states of a simple harmonic oscillator associated with the initial HamiltonianH(0). 相似文献
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《Physics Reports》1997,278(1):1-77
We review quantum Monte Carlo methods for dealing with large shell model problems. These methods reduce the imaginary-time many-body evolution operator to a coherent superposition of one-body evolutions in fluctuating one-body fields; the resultant path integral is evaluated stochastically. We first discuss the motivation, formalism, and implementation of such Shell Model Monte Carlo (SMMC) methods. There then follows a sampler of results and insights obtained from a number of applications. These include the ground state and thermal properties of pf-shell nuclei, the thermal and rotational behavior of rare-earth and γ-soft nuclei, and the calculation of double beta-decay matrix elements. Finally, prospects for further progress in such calculations are discussed. 相似文献
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V. D. Mur B. M. Karnakov V. S. Popov 《Journal of Experimental and Theoretical Physics》1998,87(3):433-444
A relativistic version of the quasiclassical imaginary-time formalism is developed. It permits calculation of the tunneling
probability of relativistic particles through potential barriers, including barriers lacking spherical symmetry. Application
of the imaginary-time formalism to concrete problems calls for finding subbarrier trajectories which are solutions of the
classical equations of motion, but with an imaginary time (and thus cannot be realized in classical mechanics). The ionization
probability of an s level, whose binding energy can be of the order of the rest energy, under the action of electric and magnetic fields of different
configuration is calculated using the imaginary-time formalism. Besides the exponential factor, the Coulomb and pre-exponential
factors in the ionization probability are calculated. The Hamiltonian approach to the tunneling of relativistic particles
is described briefly. Scrutiny of the ionization of heavy atoms by an electric field provides an additional argument against
the existence of the “Unruh effect.”
Zh. éksp. Teor. Fiz. 114, 798–820 (September 1998) 相似文献
15.
An extension of the formalism of quantum mechanics to the case where the canonical variables are valued in a field ofp-adic numbers is considered. In particular the free particle and the harmonic oscillator are considered. In classicalp-adic mechanics we consider time as ap-adic variable and coordinates and momentum orp-adic or real. For the case ofp-adic coordinates and momentum quantum mechanics with complex amplitudes is constructed. It is shown that the Weyl representation is an adequate formulation in this case. For harmonic oscillator the evolution operator is constructed in an explicit form. For primesp of the form 4l+1 generalized vacuum states are constructed. The spectra of the evolution operator have been investigated. Thep-adic quantum mechanics is also formulated by means of probability measures over the space of generalized functions. This theory obeys an unusual property: the propagator of a massive particle has power decay at infinity, but no exponential one. 相似文献
16.
H. Reinhardt 《Nuclear Physics A》1982,390(1):70-116
By using the path integral approach to many-body systems, we formulate a time-dependent mean field S-matrix theory of nuclear reactions. Many-body channel eigenstates are constructed by using projection techniques. In this way the S-matrix between the channel eigenstates is expressed as a superposition of S-matrix elements between wave-packet-like states localized in space and time. A field operator representation of the interaction picture S-matrix is derived which enables one to apply the path integral approach. Applying the stationary phase approximation to the path integral representation of the interaction picture S-matrix between the localized states an asymptotically constant time-dependent mean field approximation to this S-matrix is obtained. Finally, the S-matrix between the projected channel eigenstates is obtained by evaluating the integral, arising from the projections, over the space-time positions of the localized states in the stationary phase approximation. The stationary phase conditions select those localized states from the projected channel states for which the mean field values of energy and momentum coincide with their corresponding channel eigenvalues. 相似文献
17.
Motivated by a recent use of Glauber dynamics for Monte Carlo simulations of path integral representation of quantum spin
models (Krzakala et al. in Phys. Rev. B 78(13):134428, 2008), we analyse a natural Glauber dynamics for the quantum Ising model with a transverse field on a finite graph G. We establish strict monotonicity properties of the equilibrium distribution and we extend (and improve) the censoring inequality
of Peres and Winkler to the quantum setting. Then we consider the case when G is a regular b-ary tree and prove the same fast mixing results established in Martinelli et al. (Commun. Math. Phys. 250(2):301–334, 2004) for the classical Ising model. Our main tool is an inductive relation between conditional marginals (known as the “cavity
equation”) together with sharp bounds on the operator norm of the derivative at the stable fixed point. It is here that the
main difference between the quantum and the classical case appear, as the cavity equation is formulated here in an infinite
dimensional vector space, whereas in the classical case marginals belong to a one-dimensional space. 相似文献
18.
A.-S. F. Obada A. A. Eied G. M. Abd Al-Kader 《International Journal of Theoretical Physics》2009,48(2):380-391
We investigate the evolution of the atomic quantum entropy and the atom-field entanglement in a system of a V-configuration three-level atom interacting with a single-mode field with additional forms of nonlinearities of both the field
and the intensity-dependent atom-field coupling. With the derivation of the unitary operator within the frame of the dressed
state and the exact results for the state of the system we perform a careful investigation of the temporal evolution of the
entropy. A factorization of the initial density operator is assumed, considering the field to be initially in a squeezed coherent
or binomial state. The effects of the mean photon number, detuning, Kerr-like medium and the intensity-dependent coupling
functional on the entropy are analyzed. 相似文献
19.
John R. Porter 《General Relativity and Gravitation》1981,13(6):531-539
An integral representation for the inverses of the differential operators called edth is given in the two cases of particular interest. This operator plays a large role in the study ofH spaces and of self-dual solutions to the Yang-Mills field equations in the asymptotic domain. 相似文献
20.
Renormalization-Group Method for Reduction of Evolution Equations; Invariant Manifolds and Envelopes
The renormalization group (RG) method as a powerful tool for reduction of evolution equations is formulated in terms of the notion of invariant manifolds. We start with derivation of an exact RG equation which is analogous to the Wilsonian RG equations in statistical physics and quantum field theory. It is clarified that the perturbative RG method constructs invariant manifolds successively as the initial value of evolution equations, thereby the meaning to set t0=t is naturally understood where t0 is the arbitrary initial time. We show that the integral constants in the unperturbative solution constitutes natural coordinates of the invariant manifold when the linear operator A in the evolution equation is semi-simple, i.e., diagonalizable; when A is not semi-simple and has a Jordan cell, a slight modification is necessary because the dimension of the invariant manifold is increased by the perturbation. The RG equation determines the slow motion of the would-be integral constants in the unperturbative solution on the invariant manifold. We present the mechanical procedure to construct the perturbative solutions hence the initial values with which the RG equation gives meaningful results. The underlying structure of the reduction by the RG method as formulated in the present work turns out to completely fit to the universal one elucidated by Kuramoto some years ago. We indicate that the reduction procedure of evolution equations has a good correspondence with the renormalization procedure in quantum field theory; the counter part of the universal structure of reduction elucidated by Kuramoto may be Polchinski's theorem for renormalizable field theories. We apply the method to interface dynamics such as kink–anti-kink and soliton–soliton interactions in the latter of which a linear operator having a Jordan-cell structure appears. 相似文献