Department of Physics

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Recently the μΔ++ was found from a fit to π+p scattering [G.L. Castro, A. Mariano, Phys. Lett. B 517 (2002) 339] 3391. This enable us to pinpoint condensate parameters more precisely in the context of QCD sum rules (QCDSR). In the octet sector, the Coleman-Glashow sum rule (CGSR) [S. Coleman, S.L. Glashow, Phys. Rev. Lett. 6 (1961) 423] is violated by the experimental μ-s. QCDSR allows us to write down two sum rules similar to the CGSR, which are obeyed by the experimental magnetic moments, whereas they rule out a specific model using the Wilson loop approach and a particular chiral quark model. It is amusing to note that the QCDSR allows us to write down the quark and gluon condensates in terms of measurables like the μ-s of the nucleons and the Σ±. © 2003 Published by Elsevier Science B.V.

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Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics

Two new sum rules for octet-baryon magnetic moments (μ) and constraints on QCD sum rules from new experimental determination of μ-s for the decuplet

The crystallization behaviour of Fe70.8Nb3.7Cu 1Al2.7Mn0.7Si13.5B7.6 alloy prepared in the form of amorphous ribbons by melt-spinning technique was studied using differential scanning calorimetry and the temperature variation in resistivity. An X-ray diffaction and transmission electron microscopy study showed the formation of α-Fe(Si, Al) and/or Fe3(Si, Al) nanoparticles after the first stage of crystallization. The activation energy for this nanophase formation was 68 kcal mol-1. The brittleness of the alloy increased with the formation of nanoparticles after heat treatment. Superior soft magnetic properties were achieved when the material was heat treated at 790 K for 15 min. The particle size at the optimum heat treatment condition for superior soft magnetic properties was found to be 6.0 ± 0. 5 nm which was less compared than for the Fe-Nb-Cu-Si-B system. The observed coercivity value at the optimum heat treatment condition was found to be 0.32 A m-1 (approximately 4 mOe). The presence of Al in the alloy reduced the particle size and the magnetic anisotropy energy of the system, which resulted in superior soft magnetic properties of the heat-treated materials.

Philosophical Magazine

Magnetic and structural behaviours of nanocrystalline Fe 70.8Nb3.7Cu1Al2.7Mn 0.7Si13.5B7.6 alloy

We consider the general problem of a single two-level atom interacting with a multimode radiation field (without the rotating-wave approximation), and additionally take the field to be coupled to a thermal reservoir. Using the method of bosonization of the spin operators in the Hamiltonian, and working in the Bargmann representation for all the boson operators, we obtain the propagator for the composite system using the techniques of functional integration, under a reasonable approximation scheme. The propagator is explicitly evaluated for a simplified version of the system with one spin and a dynamically coupled single-mode field. The results are also checked on the known problem of quantum Brownian motion.

Journal of Physics A: Mathematical and General

Propagator for a spin-Bose system with the Bose field coupled to a reservoir of harmonic oscillators

Skin vibration of ReSS and consequent resonance absorption can account for the absorption lines in the spectrum of X-ray emission from many compact stellar objects and in particular, the stars J1210-5226 and RXJ1856-3754. Observations of the X-ray spectrum of these stars is difficult to explain, if they are neutron stars.

Modern Physics Letters A

Have we observed the skin vibration of realistic strange stars (ReSS)?

X-ray bursts from compact stars are believed to be a result of Type I thermonuclear processes which are short-lived, typically ∼10 to 100 s. There are some low mass X-ray binaries, such as 4U 1820-30, 4U 1636-53, KS1731-260 and Serpens X-1, known as super bursters (SBs) which emit X-rays close to the Eddington luminosity limit for long periods of several hours. Recently, there have been reports of some long bursters (LBs), which have bursts lasting 6-25 min, whereas 4U 1735-44 has a burst period of 86 min. We suggest that these bursts from SBs and LBs may be a result of breaking and re-formation of diquark pairs, on the surface of realistic strange quark stars. We use the beta equilibrated u, d and s quark model of Dey et al. and Li et al. and allow for spin-dependent hyperfine interaction between quarks. The interaction produces pairing of specific colour-spin diquarks, leading to further lowering of energy by several MeV for each pair, on average. Diquarks are expected to break up because of the explosion and shock of the thermonuclear process. The subsequent production of copious diquark pairing may produce sufficient energy to produce the very long bursts seen in SBs or LBs. We do not claim to be able to model the complicated process fully. However, the estimated total energy liberated, 1042 erg, can be explained in our model with the calculated pair density ∼0.275 fm-3 and a surface thickness of only half a μm, if the entire surface is involved. The depth of the surface involved in the process may be only few μm if the process is restricted to a small part of the surface near the equator, as suggested by Bildsten. If SBs and LBs are surface phenomena, then recurrent super bursts, found near 4U 1636-53 by Wijnands at an interval of 4.7 yr, and the quick cooling of KS 1731-260 could be natural in this model.

Monthly Notices of the Royal Astronomical Society

Super bursts and long bursts as surface phenomena of compact objects

FeNbCuSiB based materials were produced in the form of ribbons by rapid solidification techniques. The crystallization, magnetic, mechanical and corrosion behaviour were studied for the prepared materials as a function of quenching rate from liquid to the solid state. Higher quench rates produced a more amorphous structure exhibiting superior soft magnetic properties with improved corrosion resistance.

Bulletin of Materials Science

Influence of quench rates on the properties of rapidly solidified FeNbCuSiB alloy

A detailed study of pulsed laser deposited ZnO and Si thin films for its applications as a medium of UV laser is presented. As such, the films are deposited using pulsed laser deposition technique using pulsed laser deposition technique using third harmonic of (355 nm) and fundamental wavelength of a Q-switched Nd:YAG laser. A steep rise in the output after the input pump energy exceeds a critical value is observed which can be taken as the lasing threshold.

IEEE International Conference on Plasma Science

Photoluminescence studies of pulsed laser deposited films

Magnetic hysteresis and magnetic Barkhausen emission (MBE) parameters have been studied for as-received and annealed Fe72Nb4.5Cu1Si13.5B9 alloys. The coercivity rapidly decreased at the initial stage of annealing, in contrast to the slow change of root-mean-square voltage of Barkhausen emissions. The amplitude of the Barkhausen emission signal reduced almost to the background noise level at an intermediate annealing temperature, at which the material exhibited superior soft magnetic properties. Pulse height distribution of the MBE signal showed the existence of a large number of small amplitude pulses at the intermediate range of annealing, an indication that the magnetization process of the system is dominated by the rotation of the magnetization vector within a small volume of nanocrystalline particles. We explain the results by a random anisotropy model, assuming the exchange coupling between the Fe80Si20 nanograins of higher magnetic moment takes place through the magnetically weaker amorphous matrix.

IEEE Transactions on Magnetics

Magnetic Barkhausen emission study in heat-treated Fe-Nb-Cu-Si-B alloy

A realistic EOS (equation of state) leads to strange stars (ReSS) which are compact in the mass-radius (M-R) plot, close to the Schwarzschild limiting line. Many of the observed stars fit in with this kind of compactness, irrespective of whether they are X-ray pulsars, bursters or soft γ repeaters or even radio pulsars. We point out that a change in the radius of a star can be small or large, when its mass is increasing and this depends on the position of a particular star on the M-R curve. We carry out a stability analysis against radial oscillations and compare with the EOS of other SS models. We find that the ReSS is stable and an M-R region can be identified to that effect.

Stability of strange stars (SS) derived from a realistic equation of state

Synthesis of emeraldine base doped with the mixed valent bridging iron oxalate complex was done in the presence of varying quantities of H2O2. Characterization of the samples was carried out using elemental analyzer, FTIR spectrophotometer, scanning electron microscopy, four probe technique and Moessbauer spectroscopy. It has been observed that the reaction conditions are such that they bring about the partial reduction of iron from the +3 state to the +2 state, resulting in the formation of monovalent bridging iron oxalate complex dopant ion with iron existing in both +2 and +3 oxidation states. H2O2 at higher concentrations during the reaction is found to influence the polymer backbone, thus affecting the conductivity of the samples. Nanosized particles of oxides of iron in +2 and +3 oxidation states are formed in the polyaniline matrix on simple chemical treatment of the doped samples with an alkali.