Volume 76, Issue 2

The hyperchaos and multistability of electron acoustic waves in a quantum plasma model comprising of nondegenerate cold and degenerate hot electrons and stationary ions are investigated. A six-dimensional dynamical system is constructed from the fluid equations of the model considering traveling wave transformation. The stability analysis of the system is done by finding out the equilibria in the inertia frame. It is interesting to investigate that though the novel system is conservative, it can produce hyperchaos for a set of associated parameters. We have also reported the coexistence of many hyperchaotic attractors as the system is extremely sensitive to the initials. The signature of hyperchaos and coexisting hyperchaos in a conservative quantum plasma system has never been reported before.

Multistability and chaotic scenario of arbitrary amplitude ion-acoustic waves in a quantum plasma consisting of negative ions, positive ions and electrons are investigated. The normalized basic equations are transformed to a four dimensional conservative dynamical system by introducing a travelling wave variable. Stability of the fixed points for the corresponding linearized system is briefly examined. Chaotic and quasi-periodic features of the arbitrary amplitude ion-acoustic waves are discussed using effective tools, viz. phase orientations, time series graph and graphs of Lyapunov exponents. Multistability phenomena is established with the help of phase spaces, largest Lyapunov exponents and cross-section of basins of attraction. The chaotic phenomena is further verified by 0−1 test. Results of this study can be applied in understanding dynamical phenomena of arbitrary amplitude ion-acoustic waves in quantum pair-ion plasmas.

A theoretical investigation is presented for dust-acoustic (DA), Gardner solitons (GSs), and double layers (DLs) in a magnetized cryogenic plasma system. The plasma consists of inertial negatively charged dust, Boltzmann distributed electrons, and ions, all existing in a quantizing magnetic field. The Korteweg–de Vries (KdV), a modified KdV (mKdV), and Gardner equations are derived by using the reductive perturbation method. It is found that the KdV solitons and DLs are either compressive or rarefactive depending on the plasma parameters, whereas only compressive mKdV and rarefactive GSs solitons exist. These GSs and DLs are significantly modified due to the introduction of the polarization force effect. The present results are considered to be beneficial in understanding the waves propagating at cryogenic temperatures in the experiments of the nano-electromechanical application such as cryogenic etching of silicon that leads to etched silicon and makes it highly anisotropic with a high etch rate, lower side etching, and increases the dry etch resistance of organic masks.

We have recently proposed a Lagrangian in trace dynamics at the Planck scale, for unification of gravitation, Yang–Mills fields, and fermions. Dynamical variables are described by odd-grade (fermionic) and even-grade (bosonic) Grassmann matrices. Evolution takes place in Connes time. At energies much lower than Planck scale, trace dynamics reduces to quantum field theory. In the present paper, we explain that the correct understanding of spin requires us to formulate the theory in 8-D octonionic space. The automorphisms of the octonion algebra, which belong to the smallest exceptional Lie group G 2 , replace space-time diffeomorphisms and internal gauge transformations, bringing them under a common unified fold. Building on earlier work by other researchers on division algebras, we propose the Lorentz-weak unification at the Planck scale, the symmetry group being the stabiliser group of the quaternions inside the octonions. This is one of the two maximal sub-groups of G 2 , the other one being SU (3), the element preserver group of octonions. This latter group, coupled with U (1) em , describes the electrocolour symmetry, as shown earlier by Furey. We predict a new massless spin one boson (the ‘Lorentz’ boson) which should be looked for in experiments. Our Lagrangian correctly describes three fermion generations, through three copies of the group G 2 , embedded in the exceptional Lie group F 4 . This is the unification group for the four fundamental interactions, and it also happens to be the automorphism group of the exceptional Jordan algebra. Gravitation is shown to be an emergent classical phenomenon. Although at the Planck scale, there is present a quantised version of the Lorentz symmetry, mediated by the Lorentz boson, we argue that at sub-Planck scales, the self-adjoint part of the octonionic trace dynamics bears a relationship with string theory in 11 dimensions.

Birefringence of the ferro electric liquid crystals (FLCs): (S)-(−)-2-methylbutyl 4′-(4ʺ-n-alkanoyloxybenzoyloxy) biphenyl-4-carboxylates (S-MB-nB-BC) where n  = 16 and 18 is determined experimentally using laser transmission technique. In this experimental technique, the light coming out from the laser source (of wavelength 633 nm) passes through the polarizer and analyzer via FLC sample under crossed position. Optical intensities transmitted from the sample fall on the phototransistor through the analyzer. Phototransistor is a photo detector in which the transmitted light from the analyzer is converted into the electric response and measured in terms of voltage. These voltage measurements are used to determine the birefringence values of the samples. Further, order parameter is also determined. The results are compared with image analysis technique values along with phase transition temperatures, which are in good agreement.

The perturbation formulae of the EPR gyromagnetic factors g // and g ⊥ for the lowest Kramers doublet of a 4f 1 ion in trigonal symmetry are established. By using the above perturbation formulae, the anisotropic g factors and the local structure for the trigonal Ce 3+ center in YAl 3 (BO 3 ) 4 crystal are theoretically studied. From the studies, this center is attributed to the impurity Ce 3+ occupying the trigonal prism Y 3+ site in YAl 3 (BO 3 ) 4 . The Ce 3+ –O 2− bond is found to undergo an angular variation Δθ(≈ 1.72°) related to the C 3 axis. The calculated g factors based on the above impurity angular distortion display consistence with the measured results. The anisotropic g factors and the trigonal distortion of the Ce 3+ center are analyzed with respect to the host Y 3+ site in YAl 3 (BO 3 ) 4 .

An ultraviolet curable glue (UCG)-filled microprobe Fabry–Perot fiber temperature sensor, which based on the two-beam interference principle, is proposed and fabricated. In the range of 25.7–250 °C, the average sensitivity and average linear correlation coefficient of the sensor are −41.69 pm/°C and 0.98558, respectively. Under the same temperature, the maximum fluctuation (0.56 pm) of the trough’s wavelength and the standard error (0.0023 ± 0.04%) are obtained. The proposed interferometer exhibits excellent stability and has a potential application in the field of temperature monitoring.

Tin sulphide (SnS) thin films were grown using the RF sputtering techniques. The working pressures (WP) were tuned between 0.70 and 4.00 Pa at fixed RF power of 100 W and deposition time of 2 min. X-ray diffractometry studies indicate that the films crystallized in the orthorhombic crystal structure and were single phase. The crystallite size increased up to a critical working pressure of 1.33 Pa and decreased thereafter with increased WP. Scanning electron microscopy (SEM) indicates that the films exhibit columnar grain structures. Energy dispersive spectroscopy indicates that the films are slightly Sn-rich. Transmittance and reflectance plots exhibits interference pattern, an indication that the films were of uniform thickness. Analysis from the optical data gives optical absorption coefficient ( α ) > 10 4  cm −1 , and direct energy bandgap that exhibits relative decrease with the deposition conditions. Electrical studies from Hall effect measurements indicates that the films possess p-type electrical conductivity, and carrier concentration of 10 16  cm −3 for films grown at WP of 1.33 Pa. The RF sputtered SnS thin films grown on Mo-substrates served as absorber layers to fabricate thin film hetero-junction solar cell devices in the substrate configuration with a cadmium sulphide (CdS) window partner. The best device yielded a short circuit current density of 25.94 mA/cm 2 , open circuit voltage of 0.087 V and an enhanced solar conversion efficiency of 0.60%. A world record value for RF-sputtered SnS/CdS based hetero-junction thin film solar cell devices.