Finite temperature effective Lagrangian in Yang-Mills field theory

Expressions are derived for the finite temperature effective Lagrangian for particles with spin s=0 and isospin I=1/2, 1 in an external chromomagnetic field. The difference between the Lagrangians obtained and the Euler-Heisenberg Lagrangian of QED is demonstrated.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 1, pp. 78–81, January, 1985.     

Dependence of the effective masses in YbAl3 on magnetic field and disorder

The susceptibility and specific heat--and hence the effective mass--of the intermediate valence compound YbAl3 show anomalous enhancement below the Fermi liquid temperature T(coh) approximately 40 K. We show that these anomalies are suppressed by alloying in Yb1-xLuxAl3 indicating high sensitivity to lattice coherence. The de Haas-van Alphen effective masses for key branches of the Fermi surface are reduced by magnetic fields B>40 T. We argue that this reduction does not arise from 4f polarization but reflects renormalization of the quasiparticle states by the field.     

Feynman rules and S-matrix equivalence of the vilkovisky-DeWitt effective action

The reparametrization covariant background field method introduced by Honerkamp in the context of non-linear θ-models and the reparametrization invariant off-shell effective action due to Vilkovisky and DeWitt, which applies to gauge theories as well, are compared. For the latter the Feynman rules of the diagrammatic expansions beyond 1-loop order are made explicit, and the difference between the original definition of Vilkovisky and its modification by DeWitt is explained. Furthermore, within perturbation theory it is shown that the resulting S-matrix is equivalent to the usual one.     

The causality condition and the S-matrix in quantum field theory

The most general mathematical formulation is given for the concept of causality in quantum field theory. Based on it and on the Bogolyubov method, we construct the S-matrix of interacting quantized fields, being finite in each order of perturbation theory and satisfying all basic physical requirements.Siberian Medical University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 5, pp. 26–36, May, 1993.     

Existence of the S-matrix in quantum field theory in curved space-time

The existence of the S-matrix is proven for particle creation by an external gravitational field of compact support. No infrared divergences occur even for massless quantum fields; in particular, a localized gravitational field always produces a finite expected total number of particles. The results of this paper apply to both boson and fermion fields as well as to more general linear, external potential interactions.     

Creation of particles and the effective Lagrangian in the quasi-Euclidean model of the universe with an electro-magnetic field

A calculation of the number of scalar and spinor particles created in the quasi-Euclidean cosmological model with an electric field is carried out. The inverse effect of the created particles on the electric field is investigated. It is shown that for large times the creation of particles leads to a decrease of the electric field. The imaginary part of the effective action in quasi-Euclidean space with constant electric and magnetic fields is found.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 5, pp. 12–16, May, 1982.     

Dependence of physical interpretations on the choice of electromagnetic gauge

The principle of gauge invariance requires that the values of physically measurable quantities will be preserved upon changing the gauge in which electromagnetic quantities are expressed. It is emphasized here that physical interpretations do not depend only on laboratory measurables, but also upon other quantities that are altered by a gauge transformation. It is shown by a variety of simple examples that different gauges can lead to major changes in physical interpretations even though the electromagnetic fields are unaltered. The usual hypothesis that the radiation gauge (also known as the Coulomb gauge) is the “physical” gauge, in the sense that it meets the expectations of a laboratory interpretation, is supported by the various cases considered.     

The effective chiral Lagrangian from the theta term

We construct the effective chiral Lagrangian involving hadronic and electromagnetic interactions originating from the QCD term. We impose vacuum alignment at both quark and hadronic levels, including field redefinitions to eliminate pion tadpoles. We show that leading time-reversal-violating (TV) hadronic interactions are related to isospin-violating interactions that can in principle be determined from charge-symmetry-breaking experiments. We discuss the complications that arise from TV electromagnetic interactions. Some implications of the expected sizes of various pion-nucleon TV interactions are presented, and the pion-nucleon form factor is used as an example.     

Determination of the Lagrangian of the tetrad gravitational field

By requiring correspondence with Newtonian gravitational theory and the Lorentz covariant theory of nongravitational matter and by establishing the simplest possible form of the linear approximation of the field equations, the gravitational Lagrangian of the tetrad theory of gravitation is determined uniquely. It contains two characteristic constants: Einstein's gravitational constant and the specific dimensionless “teleparallel” constant ω ≈ 1.     

Differential vertex operations in Lagrangian field theory

A general framework is derived for studying differential operations in renormalized perturbation theory. The method makes possible a simple, unified derivation of the renormalization group and Callan-Symanzik equations, as well as a direct test for broken symmetries (including broken scale invariance), without the necessity of defining currents and deriving their generalized Ward identites. A second-order differential equation of the Callan-Symanzik type is derived using similar methods.Supported in part by the U.S. Atomic Energy Commission under Contract No. AT-30-1-3829.     

Dependence of the degree of paraxiality on field correlations

A linearly polarized optical field can be obtained by filtering a stochastic field through an ideal linear polarizer. The produced field possesses a given degree of paraxiality that, as proved in the present Letter, can be affected by the correlations of the original stochastic field. An example with Gaussian beams is discussed in detail.     

Radiative corrections to the Lagrangian of the electromagnetic field

The single-loop corrections to the Lagrangian of a uniform, constant electromagnetic field are found which include the anomalous magnetic moment and electric dipole moment of the electron. The imaginary part of the effective Lagrangian, which determines the probability of electron-positron pair production is found. The asymptotic behavior of the effective action is studied for supercritical magnetic fields H » H₀ = m²/e with the dependence of the anomalous magnetic moment on H taken into account.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 3, pp. 37–42, March, 1987.     

The Dirac S-matrix in the k-plane

Expressions of the S-matrix, for the Dirac case, which are suitable for analytic continuation over the complex k-plane for a large class of potentials, fulfilling conditions (1), are derived.     

The fundamental form of a homogeneous Lagrangian in two independent variables

We construct, for a homogeneous Lagrangian of arbitrary order in two independent variables, a differential 2-form with the property that it is closed precisely when the Lagrangian is null. This is similar to the property of the ‘fundamental Lepage equivalent’ associated with first-order Lagrangians defined on jets of sections of a fibred manifold.     

Dependence of the scattering length for hydrogen atoms on effective mass

The possibility that the non-adiabatic correction to the scattering length of a pair of hydrogen atoms interacting via the ground state molecular potential, X¹Σ_g ⁺, of H₂ could be made by replacing the mass of each nucleus by a different effective mass is explored. The Born-Oppenheimer potential with adiabatic, relativistic and radiative corrections is used in calculations of the scattering lengths and the mass-dependent shifts of the rotationless vibrational levels with fixed and varying effective masses. The shifts are compared with established values and it is demonstrated that the semi-classical formula for the scattering length accounts well for the effect of changing the mass. A perturbing potential that is equivalent to a change in mass is derived and it is compared to a published local non-adiabatic potential.     

On the chiral effective meson-baryon Lagrangian at third order⋆

We show that the recently constructed complete and “minimal” third-order meson-baryon effective chiral Lagrangian can be further reduced from 84 to 78 independent operators.     

Dependence of the domain-wall velocity on the driving field in garnet films

The dependence of the domain-wall velocity on the amplitude of the driving magnetic field pulses is investigated in an iron garnet film of the (YSmCa)₃(FeGe)₅O₁₂ system with a (111) orientation. The results obtained are analyzed from the standpoint of existing theory. A maximum corresponding to the disruption of steady-state motion is observed on the dependence. Thereafter, the velocity at first decreases sharply and then increases. It is theorized that a process involving the periodic generation, propagation, and annihilation of horizontal Bloch lines occurs in the wall in this period. Data are obtained for the velocity saturation region, which confirm a previously proposed empirical formula and a theoretical model, according to which the saturation regime corresponds to a state of chaos. Fiz. Tverd. Tela (St. Petersburg) 39, 660–663 (April 1997)