122920106
SUM RULES AND PION FORM FACTOR IN QCD
125654630
Pion Form-factor and {QCD} Sum Rules
125323640
{QCD} Sum Rule Analysis of the Pion Form-factor Behavior in Small $Q^2$ Region
120815334
Local Quark - Hadron Duality and Nucleon Form-factors in {QCD}
Abstract Quark-hadron duality is incorporated to estimate the non-perturbative O(α 0 S -contribution to the nucleon form factors G N E,M ( t ). For 1 t 2 the results are in satisfactory agreement with the existing data. This means that the observed dipole behaviour of G N ( t ) has nothing to do with the short distance dynamics.
120836438
Quantum gravitational effects in an isotropic universe
Effects of vacuum polarization by an external gravitational field in a system of spinor, scalar, and massive vector particles are considered in the model of conformally flat space-time. Expressions are obtained for the radiative corrections, and the part they play in gravitational theory is analyzed in the limits of weak (Vertical BarR/sup k//sub i/Vertical Bar m/sup 2/) gravitational fields. The Appendix gives expressions for the rate of spontaneous production of real particles by a strong gravitational field and the energy-momentum tensor of real particles in the ultrarelativistic limit; a law of increase of the entropy of an ultrarelativistic medium is also formulated.
118213659
Pion form factor in a scalar model
SummaryUsing as an example the simple scalar modelρ(6)3; we describe our method of analysing the bound-state form factors based on the systematic use of the alpha-representation for Feynman diagrams. The nature of «nonrenormalization group» logarithms specific for the form-factor-type problems is investigated. The summation of ladder contributions is performed in the leading-logarithm approximation.RiassuntoUsando come esempio il semplice modello scalareρ(6)3 si descrive il metodo di analizzare i fattori di forma dello stato legato basati sull’uso sistematico della rappresentazione alfa per i diagrammi di Feyman. Si studia la natura dei logaritmi del gruppo di non rinormalizzazione specifico di problemi di tipo fattore di forma. Si esegue la somma dei contributi di a gradini nell’approssimazione del logaritmo principale.РезюмеНа примере простой скалярной моделиρ(6)3 излагается метод анализа формфакторов составных систем, основанный на систематическом использовании альфа-представления фейнмановских диаграмм. Исследуется природа «неренормгрупповых» логарифмов, специфичных для задач формфакторного типа. Проведено суммирование лестничных вкладов в главном лограрифмическом приближении.
15058198
Casimir effect for a dilute dielectric ball at finite temperature
The Casimir effect at finite temperature is investigated for a dilute dielectric ball; i.e., the relevant internal and free energies are calculated. The starting point in this study is a rigorous general expression for the internal energy of a system of noninteracting oscillators in terms of the sum over the Matsubara frequencies. Summation over the angular momentum values is accomplished in a closed form by making use of the addition theorem for the relevant Bessel functions. For removing the divergences the renormalization procedure is applied that has been developed in the calculation of the corresponding Casimir energy at zero temperature. The behavior of the thermodynamic characteristics in the low and high temperature limits is investigated.
121042687
Relativistic particle with action that depends on the torsion of the world trajectory
A generalized Hamiltonian formalism is constructed for a relativistic particle with torsion in a D-dimensional spacetime. The complete set of constraints is found and separated into firstand second-class constraints. The canonical quantization of the theory is treated on this basis. For D = 3 in the sector of the theory without tachyon states, a spectral equation relating the square of the mass of a state to its spin and the parameters of the model is obtained. With increasing spin, the mass of the state decreases. Various forms of wave equation are constructed in operator form, and the particle propagator is found. The possibility of describing states with integer, half-integer, and continuous values of the spin (D = 3) in the framework of this model is demonstrated.
122347506
Singular Lagrangians with higher derivatives
The Hamiltonian formalism for systems with singular Lagrangians of the second order is constructed. A new method is proposed for obtaining the equations of motion in the phase space for theories with singular Lagrangians and the connection of the Lagrangian and Hamiltonian descriptions is traced in detail. As an example, a generalisation of the relativistic point action is considered. It involves both the length and curvature of the point trajectory in spacetime.
117621252
Exchange by the hard and soft quanta in the high energy scattering of particles
In the framework of the functional integration method in quantum field theory the method is proposed for constructing scattering amplitude of the particles which interact by means of the exchange of the infinite number of soft quanta and the finite number of hard virtual particles. In this method the form factors of the interacting particles arise in calculations of the scattering amplitude at large angles. It is in agreement with the Wu--Yang conjecture about the elastic form factor role in high energy scattering. (auth)
121857304
Generalization of the relativistic string model in the geometrical approach
We present a model of a one-dimensional extended relativistic object, whose motion is defined by the requirement that its time track in Minkowski space is a surface of the constant mean curvature H. The world surface of the relativistic string is a particular case of such surfaces, namely, a minimal surface with H=0. By differential-geometry methods the theory of the proposed object moving in three-dimensional space-time is reduced to one nonlinear equation ϕττ − ϕσσ = Hshϕ. In the theory under consideration, there naturally arises the pair of Lax's operators needed to solve this nonlinear equation by the inverse scattering method.