Tensionless String in the Notoph Background

We study the interaction between a tensionless (null) string and an antisymmetric background field B_{ab} using a 2-component spinor formalism. A geometric condition for the absence of such an interaction is formulated. We show that only one gauge-invariant degree of freedom of the field B_{ab} does not satisfy this condition. Identification of this degree of freedom with the notoph field \phi of Ogievetskii-Polubarinov-Kalb-Ramond is suggested. Application of a two-component spinor formalism allows us a reduction of the complete system of non-linear partial differential equations and constraints governing the interacting null string dynamics to a system of linear differential equations for the basis spinors of the spin-frame. We find that total effect of the interaction is contained in a single derivation coefficient which is identified with the notoph field.Comment: 15 pages, no figures, RevTeX 3.

Computation of the minimum eigenvalue for a nonlinear Sturm-Liouville problem

© 2014, Pleiades Publishing, Ltd. A condition for the existence of a minimum eigenvalue corresponding to a positive eigenfunction of the nonlinear eigenvalue problem for an ordinary differential equation is determined. The problem is approximated by a mesh scheme of the finite element method. The convergence of approximate solutions to exact ones is studied. Theoretical results are illustrated by numerical experiments for a model problem

Massless Chiral Supermultiplets of Higher Spins and the θ\theta-Twistor

Recently N. Berkovits, motivated by the supertwistor description of ${\cal N}=4 D=4$ super Yang-Mills, considered the generalization of the ${\cal N}=1 D=4$ $\theta$-twistor construction to D=10 and applied it for a compact covariant description of ${\cal N}=1 D=10$ super Yang-Mills. This supports the relevance of the $\theta$-twistor as a supersymmetric twistor alternative to the well-known supertwistor. The minimal breaking of superconformal symmetry is an inherent property of the $\theta$-twistor received from its fermionic components, described by a Grassmannian vector instead of a Grassmannian scalar in the supertwistor. The $\theta$-twistor description of the ${\cal N}=1 D=4$ massless chiral supermultiplets $(S, S + 1/2)$ with spins $S=0,1/2,1,3/2,2,...$ is considered here. The description permits to restore the auxiliary $F$ fields of the chiral supermultiplets absent in the supertwistor approach. The proposed formalism is naturally generalized to ${\cal N}=4 D=4$ and can be used for an off-shell description of the corresponding super Yang-Mills theory.Comment: 15 page

Hydrodynamic type integrable equations on a segment and a half-line

The concept of integrable boundary conditions is applied to hydrodynamic type systems. Examples of such boundary conditions for dispersionless Toda systems are obtained. The close relation of integrable boundary conditions with integrable reductions of multi-field systems is observed. The problem of consistency of boundary conditions with the Hamiltonian formulation is discussed. Examples of Hamiltonian integrable hydrodynamic type systems on a segment and a semi-line are presented

Generalized action principle and extrinsic geometry for N=1 superparticle

It is proposed the generalized action functional for N=1 superparticle in D=3,4,6 and 10 space-time dimensions. The superfield geometric approach equations describing superparticle motion in terms of extrinsic geometry of the worldline superspace are obtained on the base of the generalized action. The off-shell superdiffeomorphism invariance (in the rheonomic sense) of the superparticle generalized action is proved. It was demonstrated that the half of the fermionic and one bosonic (super)fields disappear from the generalized action in the analytical basis. Superparticle interaction with Abelian gauge theory is considered in the framework of this formulation. The geometric approach equations describing superparticle motion in Abelian background are obtained.Comment: 31 pages. Late

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Schild's Null Strings in Flat and Curved Backgrounds

Schild's null (tensionless) strings are discussed in certain flat and curved backgrounds. We find closed, stationary, null strings as natural configurations existing on the horizons of spacetimes which possess such null hypersurfaces. Examples of these are obtained in Schwarzschild and Rindler spacetimes. A dynamic null string is also identified in Rindler spacetime. Furthermore, a general prescription (with explicit examples) is outlined by means of which null string configurations can be obtained in a large class of cosmological backgrounds.Comment: RevTex 3.0, 14 Pages, no figure

(Super)twistors and (super)strings

The Lagrangian formulation of the D=4 bosonic string and superstring in terms of the (super)twistors is considered. The (super)twistor form of the equations of motion is derived and the kappa-symmetry transformation for the supertwistors is given. It is shown that the covariant kappa-symmetry gauge fixation results in the action quadratic in the (super)twistor variables.Comment: LaTeX, 17 page

Null Strings in Schwarzschild Spacetime

The null string equations of motion and constraints in the Schwarzschild spacetime are given. The solutions are those of the null geodesics of General Relativity appended by a null string constraint in which the "constants of motion" depend on the world-sheet spatial coordinate. Because of the extended nature of a string, the physical interpretation of the solutions is completely different from the point particle case. In particular, a null string is generally not propagating in a plane through the origin, although each of its individual points is. Some special solutions are obtained and their physical interpretation is given. Especially, the solution for a null string with a constant radial coordinate $r$ moving vertically from the south pole to the north pole around the photon sphere, is presented. A general discussion of classical null/tensile strings as compared to massless/massive particles is given. For instance, tensile circular solutions with a constant radial coordinate $r$ do not exist at all. The results are discussed in relation to the previous literature on the subject.Comment: 16 pages, REVTEX, no figure

Simulation of the processes of plasma modification and vacuum metallization of polymer materials by the method of molecular dynamics

The article presents the results of the development of molecular dynamics models of modifications of polypropylene (PP) material in the plasma of a radio-frequency (RF) discharge and a copper coating deposit by magnetron sputtering on the surface of a polyethylene (PE) material. The model of the RF plasma modification process describes changes in the surface layers of the PP material upon interaction with low-energy plasma ions: the nature of the breaking of covalent bonds in macromolecules, the chemical composition of sputtered particles, and changes in the ordering of the supramolecular structure. The model of the vacuum metallization process describes the processes of the introduction of metal atoms into the polymer structure, the change in the conformation of macromolecules, the formation of macroradicals with uncompensated chemical bonds, and the formation of an interfacial layer between the polymer and the metal coating