Duality and cosmological compactification of superstrings with unbroken supersymmetry

The cosmological compactification of D=10, N=1 supergravity-super-Yang-Mills theory obtained from superstring theory is studied. The constraint of unbroken N=1 supersymmetry is imposed. A duality transformation is performed on the resulting consistency conditions. The original equations as well as the transformed equations are solved numerically to obtain new configurations with a nontrivial scale factor and a dynamical dilaton. It is shown that various classes of solutions are possible, which include cosmological solutions with no initial singularity.Comment: Latex2e file, 24 pages including 10 figures as tex file

Localized structures in Kagome lattices

We investigate the existence and stability of gap vortices and multi-pole gap solitons in a Kagome lattice with a defocusing nonlinearity both in a discrete case and in a continuum one with periodic external modulation. In particular, predictions are made based on expansion around a simple and analytically tractable anti-continuum (zero coupling) limit. These predictions are then confirmed for a continuum model of an optically-induced Kagome lattice in a photorefractive crystal obtained by a continuous transformation of a honeycomb lattice

An Alternative Interpretation of Recent ARPES Measurements on TiSe2

Recently there has been a renewed interest in the charge density wave transition of TiSe2, fuelled by the possibility that this transition may be driven by the formation of an excitonic insulator or even an excitonic condensate. We show here that the recent ARPES measurements on TiSe2 can also be interpreted in terms of an alternative scenario, in which the transition is due to a combination of Jahn-Teller effects and exciton formation. The hybrid exciton-phonons which cause the CDW formation interpolate between a purely structural and a purely electronic type of transition. Above the transition temperature, the electron-phonon coupling becomes ineffective but a finite mean-field density of excitons remains and gives rise to the observed diffuse ARPES signals.Comment: 4 pages, 2 figure

Thermally Induced Local Failures in Quasi-One-Dimensional Systems: Collapse in Carbon Nanotubes, Necking in Nanowires and Opening of Bubbles in DNA

We present a general framework to explore thermally activated failures in quasi one dimensional systems. We apply it to the collapse of carbon nanotubes, the formation of bottlenecks in nanowires, both of which limit conductance, and the opening of local regions or "bubbles" of base pairs in strands of DNA that are relevant for transcription and danaturation. We predict an exponential behavior for the probability of the opening of bubbles in DNA, the average distance between flattened regions of a nanotube or necking in a nanowire as a monotonically decreasing function of temperature, and compute a temperature below which these events become extremely rare. These findings are difficult to obtain numerically, however, they could be accessible experimentally.Comment: 4 pages, 2 figures, to be submitte

String dynamics near a Kaluza-Klein black hole

The dynamics of a string near a Kaluza-Klein black hole are studied. Solutions to the classical string equations of motion are obtained using the world sheet velocity of light as an expansion parameter. The electrically and magnetically charged cases are considered separately. Solutions for string coordinates are obtained in terms of the world-sheet coordinate $\tau$. It is shown that the Kaluza-Klein radius increases/decreases with $\tau$ for electrically/magnetically charged black hole.Comment: Latex2e file with six postscript figures. Minor changes, more accurate numerical results and updated reference

Reaction-diffusion systems and nonlinear waves

The authors investigate the solution of a nonlinear reaction-diffusion equation connected with nonlinear waves. The equation discussed is more general than the one discussed recently by Manne, Hurd, and Kenkre (2000). The results are presented in a compact and elegant form in terms of Mittag-Leffler functions and generalized Mittag-Leffler functions, which are suitable for numerical computation. The importance of the derived results lies in the fact that numerous results on fractional reaction, fractional diffusion, anomalous diffusion problems, and fractional telegraph equations scattered in the literature can be derived, as special cases, of the results investigated in this article.Comment: LaTeX, 16 pages, corrected typo

Cuticular Biochemistry: Lambda-Cyhalothrin Induced Alterations in Mutant Drosophila Melanogaster

Derivatives of natural pyrethrum, synthetic pyrethroids, are well-established neurotoxins. However, they do interfere with the functioning of metabolic processes; the most important of these is chitin metabolism, a key process in the development of insects. Type II synthetic pyrethroid, lambda-cyhalothrin, when orally fed to Drosophila melanogaster revealed its efficacy in chitin synthesis modulation. Total proteins, glucosamine, N-acetylglucosamine, chitinase activity and chitin content exhibit significant changes in the final developmental stage, the adults. A reduction in chitin synthesis is suggestive of interference in polymerization process which is a must for cuticle formation. Involvement of lambda-cyhalothrin in chitin synthesis has been sought to be an additional mode of action, other than its neurotoxic nature