D.C. Khandekar

Bio: D.C. Khandekar is an academic researcher. The author has contributed to research in topics: Polymer. The author has an hindex of 1, co-authored 1 publications receiving 10 citations.

Ion/surface interaction studies with 1-3 keV/amu ions up to Th80+

Abstract: First results from a series of experiments aimed at the study of the interaction of slow very highly charged ions with conductor and insulator surfaces are reported. Charge state dependences of secondary electron, x-ray and secondary ion emission are measured. In addition, microscopic studies are performed using an ‘Atomic Force Microscope’ to investigate surface defects, produced through the stored electrostatic potential of the incident ion. The ions that have been used for these studies range from O7+ to Th80+, with low kinetic energies (generally 1–3 keV/amu). Overall, enhancement of the low energy secondary electron, sputter ion and photon emission are observed with increasing charge states. Saturation in the electron emission yield at very low velocities confirm present models for image charge acceleration effects. X-ray emission spectra are found to be consistent with the formation of so called ‘hollow’ atoms near the surface during the neutralization processes. The microscopic studies rev...

The statistical mechanics of topological polymers: a field theorist point of view

Abstract: This is a self-contained introduction to polymer physics and to the application of field theoretical techniques to the statistical mechanics of polymer systems. Of course, since polymer physics is a highly interdisciplinary subject, involving different disciplines like knot theory, field theory, statistical mechanics and some notions of bio-chemistry and chemistry, it is not possible to cover all these topics in a single review. Particular emphasis is given here to the problem of describing the fluctuations of topologically linked polymers in a solution from a microscopical point of view. Some recent advances in this direction are presented. Another purpose of this work is to serve as a guide for whoever would like to apply the methods of field theory to polymers. To ease reading, technical terms have been quoted in boldface characters at the points in which their meaning is explained.

Problems of probabilistic topology: the statistics of knots and non-commutative random walks

Abstract: This paper reviews the state of affairs in a modern branch of mathematical physics called probabilistic topology. In particular we consider the following problems: (i) we stimate the probability of trivial knot formation on a lattice using the Kauffman algebraic invariants and show the connection of this problem with the thermodynamic properties of 2D disordered Potts model; (ii) we investigate the limiting behavior of random walks in multiconnected spaces and on non-commutative groups related to knot theory. We discuss the application of the above-mentioned problems in the statistical physics of polymer chains. On the basis of non-commutative probability theory we derive some new results in the statistical physics of entangled polymer chains which unite rigorous mathematical facts with intuitive physical arguments.

Asphericity of two-dimensional closed pressurized random walks.

Abstract: This paper analyzes the size and shape of a closed, two-dimensional random walk with a pressure difference p between the inside and outside, which couples to an algebraic (signed) area This pressurized-random-walk (PRW) model is, in some respects, closely related to a computer model studied by Leibler, Singh, and Fisher [Phys Rev Lett 59, 1989 (1987)] Since all terms in the Hamiltonian are quadratic in the position-vector field r, the partition function and its derivatives can be evaluated exactly The most notable feature of the PRW model is an instability, which occurs at \ensuremath{\Vert}p\ensuremath{\Vert}=${\mathit{p}}_{\mathit{c}}$ For \ensuremath{\Vert}p\ensuremath{\Vert}${\mathit{p}}_{\mathit{c}}$, the system has a finite algebraic area and an anisotropic shape; for \ensuremath{\Vert}p\ensuremath{\Vert}\ensuremath{\ge}${\mathit{p}}_{\mathit{c}}$, the algebraic area diverges and the shape is circular The asphericity is also calculated A form of bending rigidity, also quadratic in r, is introduced into the model; however, the resulting macroscopic properties are quite different from those one might ordinarily expect This difference can be traced to the absence of a fixed link size in the model