A microscopic theory of the lambda transition,II

The previously proposed finite temperature field theory of the lambda transition based on the Schwinger functional method is investigated further. A systematic method for calculating the higher-order loop terms is presented by introducing the one-loop Green's functions, which are found to be a natural finite temperature extension of the Beliaev-Hugenholtz-Pines-Gavoret-Nozières zero-temperature Green's functions. The application of the finite temperature loop expansion to the dynamical properties is presented by calculating the retarded density correlation functions at the one-loop level. The result gives a microscopic basis for the form of the dynamical structure factor recently proposed by Woods and Svensson. From a general point of view, without using any approximations or model interactions, Goldstone's theorem for the lambda transition at finite temperature is presented.     

A microscopic derivation of the classical nucleation equation

The Becker-Döring equation of classical nucleation theory is derived in the framework of spin-flip dynamics of the Ising model. The derivation is based on a microscopic analysis of droplet geometry at low temperature.     

Biophysics and the microscopic theory of helium II

Bose-Einstein condensation and solitonic propagation have recently been shown to be intimately related in biosystems. From our previous demonstration of the existence of solitons in a dilute Bose gas, we set out the basis for a full microscopic theory of He II. This is used to understand recent experiments, which are in apparent contradiction. New experiments are suggested.On leave of absence from the Department of Physics, Universidad Simon Bolivar, Caracas, Venezuela. Also at Instituto Internacional de Estudios Avanzados, Ap. 17606, Caracas 1015-A.     

A nucleation theory of cell surface capping

We propose a new theory of cell surface capping based on the principles of nucleation. When antibody interacts with cell surface molecules, the molecules initially form small aggregates called patches that later coalesce into a large aggregate called a cap. While a cap can form by patches being pulled together by action of the cell's cytoskeleton, in the case of some molecules, disruption of the cytoskeleton does not prevent cap formation. Diffusion of large aggregates on a cell surface is slow, and thus we propose that a cap can form solely through the diffusion of small aggregates containing just one or a few cell surface molecules. Here we consider the extreme case in which single molecules are mobile, but aggregates of all larger sizes are immobile. We show that a set of patches in equilibrium with a sea of free cell surface molecules can undergo a nucleation-type phase transition in which the largest patch will bind free cell surface molecules, deplete the concentration of such molecules in the sea, and thus cause the other patches to shrink in size. We therefore show that a cap can form without patches having to move, collide with each other, and aggregate.     

New theory of nucleation

New distributions are obtained in classical statistical physics; these distributions explain some old experiments.     

A bi-metric theory of gravitation. II

The bi-metric theory of gravitation proposed previously is simplified in that the auxiliary conditions are discarded, the two metric tensors being tied together only by means of the boundary conditions. Some of the properties of the field of a particle are investigated; there is no black hole, and it appears that no gravitational collapse can take place. Although the proposed theory and general relativity are at present observationally indistinguishable, some differences are pointed out which may some day be susceptible of observation. An alternative bimetric theory is considered which gives for the precession of the perihelion 5/6 of the value given by general relativity; it seems less satisfactory than the present theory from the aesthetic point of view.     

A microscopic theory of the lambda transition

Starting with a microscopic hamiltonian for a many-boson system with a hardcore interaction, the grand potential of the system, which contains the order-parameter of the lambda transition as one of the thermodynamical variables, is derived by making use of the finite temperature loop expansion. The divergence difficulty caused by the hardcore interaction is circumvented by the conventional field theoretic perturbational renormalization such that the chemical potential is renormalized instead of the conventional mass renormalization. The grand potential obtained consists of the superfluid part and the finite temperature elementary excitation part. The elementary excitation energy spectrum shows the Goldstone boson mode, namely, the photon, for the zero external field. A non-vanishing external field destroys such a Goldstone boson mode by causing an energy gap at zero momentum. The chemical potential and the critical temperature are also obtained for the weak coupling case. It is shown how the Bose-Einstein condensation is affected by the hardcore interaction.     

A microscopic theory of binary alloy phase equilibrium

A binary alloy free energy is constructed that explicitly includes short-range order in both the internal energy and in the entropy. The internal energy is treated using the alloy Cluster-Bethe-Lattice Method and the configurational entropy is described using the Cluster Variation Method. A phase diagram for the Chromium-Tungsten system is calculated and is found to be in good agreement with experiment.     

A microscopic theory of giant electric isovector resonances

The electric multipole isovector (τ = 1) giant resonances for Δτ_z = 0, ± 1 are studied using the self-consistent HF-RPA theory.The distributions of strength, energies, the isospin compositions and other properties of the J = 0⁺, 1^?, 2⁺ resonances in the ⁴⁸Ca, ⁹⁰Zr, ¹²⁰Sn and ²⁰⁸Pb regions are calculated. Sum rules for the charge-exchange Δτ_z = ±1 excitations are derived.     

A microscopic theory of vortices in superfluid helium

It is shown that the introduction of the depletion velocity field, the vortical part of the fluid velocity, is rooted on the nature of the field operators. This result is obtained by formulating the theory of vortices in terms of the vortex coordinates. The modified Hamilton-Jacobi equation leads to a generalization of the Schrödinger equation for a particle in the presence of a vortex line. It is shown that our theory is intimately related to the microscopic theory of Bose systems developed by Nishiyama. Mention is made of the close relation between the Higgs mechanism and a gauge-wheel in superfluid helium.     

A microscopic theory of muon capture in nuclei

The muon capture rates are calculated for a series of nuclei, using the Hartree-Fock randomphase approximation, and compared with experiment. The recoil term, the binding energy of the muon and finite size effects are calculated in detail. In a schematic model, the validity of the assumption M²_V = M²_A = M²_P is studied, and found to hold reasonably well even for nuclei as heavy as ²⁰⁸Pb.     

Mean-field nucleation theory with nonlocal interactions

Mean-field nucleation theory has for a long time been successfully used to extract microscopic parameters from island density data in growth experiments. However, it produces grossly incorrect results when used to analyze weakly corrugated systems, where adsorbate interactions cannot be neglected. Here, a mean-field theory that includes nonlocal adsorbate interactions is developed and successfully tested against kinetic Monte Carlo growth simulations for a realistic adsorbate system.     

A kinetic theory of a relativistic plasma. II

A covariant formulation of the relativistic statistical mechanics of charged particles is developed on the basis of the tetradic method, which corresponds to the super-many-time formalism of Tomonaga known in quantum theory.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 5, pp. 29–31, May, 1981.     

Testing nucleation theory in two dimensions

We calculate bubble-nucleation rates for (2+1)-dimensional scalar theories at high temperature. Our approach is based on the notion of a real coarse-grained potential. The region of applicability of our method is determined through internal consistency criteria. We compare our results with data from lattice simulations. Good agreement is observed when the renormalized action of the simulated theory is known.     

Stochastic theory of metastable states and nucleation

We study on a model the role of fluctuations size in the nucleation of a first order phase transition. A bifurcation point exists between metastable and stable equilibrium solutions for a critical value of fluctuations size.     

A generalized field theory. II. Linearized field equations

A thorough examination of the generalized field theory, formulated by the same authors in a previous paper, is being carried out in the absence of feedback effects. The results obtained are found to be in complete agreement with those of linear field theories of gravity and electromagnetism. Strict functions, which serve as indicators of the strength of the two fields, are being identified. This study reveals also two interesting results: the first is the classification of tetrad vector fields used, the second is the definite appearance of a mutual interaction between gravitational and electromagnetic fields.     

On a reconsideration of classical nucleation theory

A correct account of the collective motion of a cluster does not require the Lothe-Pound correction; furthermore, this correction is shown to contradict the laws of thermodynamics.