15884859
Casimir energy of a nonuniform string
The Casimir energy of a non-uniform string built up from two pieces with different speed of sound is calculated. A standard procedure of subtracting the energy of an infinite uniform string is applied, the subtraction being interpreted as the renormalization of the string tension. It is shown that in the case of a homogeneous string this method is completely equivalent to the zeta renormalization.
17711121
Boundary conditions at spatial infinity for fields in Casimir calculations
The importance of imposing proper boundary conditions for fields at spatial infinity in the Casimir calculations is elucidated.
123132132
The Model of the relativistic particle with curvature and torsion
The (2+1)-dimensional model of the relativistic particle, described by the action with a linear dependence on the curvature and torsion of a particle world trajectory, is investigated. Massive, massless and tachyonic states are shown to be generally present in the model. For all three mass sectors the solutions of classical equations of motion are constructed. Depending on the values of the model parameters, the quantization of the system leads to the unitary irreducible representations of the universal covering group of SL(2,R) of either the discrete series Dγ±, γ > 0 or the principal series Cσϑ, σ ⪖ 14, ϑ ϵ [1, 1). The quantum spectrum and the wave functions of the physical states of the system are found.
199675867
SOME RECENT RESULTS IN CALCULATION OF THE CASIMIR ENERGY AT ZERO AND FINITE TEMPERATURE
18313780
Quark mass correction to the string potential.
A consistent method for calculating the interquark potential generated by the relativistic string with massive ends is proposed. In this approach, the interquark potential in the model of the Nambu-Goto string with pointlike masses at its ends is calculated. At first the calculation is done in the one-loop approximation. For obtaining a finite result under summation over eigenfrequencies of the Nambu-Goto string with massive ends, an appropriate renormalization procedure is suggested. It is shown that in this case the L{umlt u}scher term in the string potential acquires a dependence on the quark mass which results in the reduction of the absolute value of this term. Then the interquark potential in the string model with new boundary conditions is calculated by making use of the variational estimation of the corresponding functional integral. In this case the quark mass correction results in decreasing the critical distance (deconfinement radius) in the string potential. In the framework of the developed approach, the one-loop interquark potential in the model of the relativistic string with rigidity is also calculated. {copyright} {ital 1996 The American Physical Society.}
204934704
Some recent results in calculating the Casimir energy at zero and finite temperature
The survey summarizes briefly the results obtained recently in the Casimir effect studies considering the following subjects: i) account of the material characteristics of the media and their influence on the vacuum energy (for example, dilute dielectric ball); ii) application of the spectral geometry methods for investigating the vacuum energy of quantized fields with the goal to gain some insight, specifically, in the geometrical origin of the divergences that enter the vacuum energy and to develop the relevant renormalization procedure; iii) universal method for calculating the high temperature dependence of the Casimir energy in terms of heat kernel coefficients.
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.
117764895
Physical constants and invariant charges of the U(1) x SU(3) model
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.
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.
121516467
CollectiveEλ excitations of surface character in spherical and deformed sodium clusters: vibrating potential model
The self-consistent vibrating potential model (VPM) is extended for the description ofEλ surface collective excitations in alkali metal clusters with practically any kind of static deformation. The case of spherical clusters is also covered. Any single-particle potentials and valence electron densities for which the coefficients of the multipole expansion are known can be used within the model. The strength function method incorporated into the model allows one to avoid solving the equations for every state and, as a result, simplifies the calculations drastically. The model is of a quite general character and can also be used for description of giant resonances in atomic nuclei if the Coulomb terms are neglected. The VPM is applied to calculate theE1,E2 andE3 excitations in spherical (Na8, Na20 and Na40) and deformed (Na10, Na18 and Na26) clusters.