• Volume 32, Issue 3

      March 1989,   pages  1-297

    • A satellite-borne experiment to study the fifth force

      R Cowsik N Krishnan S Unnikrishnan S N Tandon P Saraswat

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      An experiment with a satellite-borne torsion balance capable of measuring the fifth force which couples to baryon number or lepton number with a strengtr gravity and range ~ 109 cm is described.

    • A quark model based on QCD scale anomaly

      J Segar M S Sriram

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      We consider a quark model based on QCD scale anomaly in which the quarks move in the field of an effective glueball field. Hadrons correspond to solitonic bags of higher energy density in a nonperturbative sea of condensed gluons. We calculate the static properties of nucleon in this model and find that the nucleon mass is far too large (2.4–4 GeV) and the proton charge radius (0.37–0.54 fm) is low. The proton gyromagnetic ratio and gA/gv are in reasonable agreement with the experimental numbers.

    • General theory of renormalization of gauge theories in nonlinear gauges

      Satish D Joglekar

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      We discuss the general theory of renormalization of unbroken gauge theories in the nonlinear gauges in which the gauge-fixing term is of the form$$ - \frac{1}{2}\sum\limits_\alpha {f_\alpha ^2 [A] = - \frac{1}{2}} \sum\limits_\alpha {\frac{1}{{\eta _\alpha }}(\partial ^\mu A_\mu ^\alpha + \zeta _{\beta \gamma }^\alpha A_\mu ^\beta A^{\gamma \mu } )^2 } $$ We show that higher loop renormalization modifiesfα [A] to contain ghost terms of the form$$f_\alpha [A,c,\bar c] = \eta _\alpha ^{ - \frac{1}{2}} (\partial ^\mu A_\mu ^\alpha + \zeta _{\beta \gamma }^\alpha A_\mu ^\beta A^{\gamma \mu } + \tau _\gamma ^{\alpha \beta } \bar c_\beta c_\gamma )$$ and show how the corresponding ghost terms are deduced fromfα [A, c, c] uniquely. We show that the theory can be renormalized while preserving a modified form of BRS invariance by multiplicative and independent renormalizations onA, c, g, η, ζ, τ. We briefly discuss the independence of the renormalized S-matrix from η,ζ, τ.

    • Effective decoupling in some odd-A odd-Z rotational bands

      Kiran Jain A K Jain R K Sheline

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      A systematic analysis of the results of single quasiparticle-plus-rotor bandmixing calculations is presented wherein the empirically noticed characteristic effective decoupling patterns and their systematics in certain odd-A odd-Z rotational bands based onh9/2, d1/2, h11/2 andg7/2 orbitals are reproduced. The strategy adopted allows us to obtain an almost unique set of parameter values for a given decoupling pattern. The composition of wavefunctions in terms of core rotational angular momentum supports the idea of effective decoupling. These wavefunctions are then used to analyse the extent and nature of Coriolis coupling in these bands. It is found that either one or both parts of the Coriolis energies, diagonal and non-diagonal, are significant in most of the cases and the non-diagonal part is mainly responsible for the effective decoupling. These Coriolis effects prominently affect the intrabandB(M1) andB(E2) values and their variation with spin is discussed. An unusual feature in theB(M1) value of theh9/2 orbital based band is pointed out.

    • Variation of interband interaction strength in odd-A nuclei

      Kiran Jain A K Jain R K Sheline

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      Bandcrossing in 31 rotational bands of 25 different odd-A nuclei in the rare-earth region has been analysed by using a two-band mixing formalism with a constant band interaction within the framework of the effective decoupling picture. The interband interaction strengthV between the one-quasiparticle band and the three-quasiparticle band exhibits a variation with the neutron number which is not different from the oscillatory behaviour observed in even-even nuclei and does not show signs of any appreciable phase shifting as predicted by theory. However, the overall range of variation ofV is greater than that observed in even-even systems.

    • Vibrational energy transfer in a collinear HF-HF collision involving low-lying states in the presence of infrared laser beam

      Bhupat Sharma Vinod Prasad Man Mohan

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      An approximate method for the vibration-vibration (V-V) energy transfer process during collinear collisions of two HF molecules involving low-lying states in the presence of infrared laser beam using a quasi-energy approach (non-perturbative) is presented. The effect of radiation on V-V process is investigated by changing the laser field detuning and power for various values of collision velocities.

    • Theory of high temperature superconductivity in YBa2Cu3O7

      C M Srivastava

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      A theory of high temperature superconductivity in YBa2Cu3O7_δ compound has been developed on the basis of the momentum pairing of electrons through the relativistic Darwin interaction. The transport behaviour of electrons is explained in terms of a mechanism of correlated electron transfer arising from the electron-phonon coupling. A model Hamiltonian has been developed to describe the superconducting properties of the system. This gives an energy gap which is higher than the BCS value. Attempts have been made to explain the absence of isotope effect, the linear dependence of specific heat, the presence of larger temperature-independent paramagnetism in the normal phase and the softening of some of the optic phonon modes observed in this system.

    • Phonon density of states of ann-component alloy

      P Nayak

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      We have generalized the coherent potential approximation (CPA) of Tripathi and Behera to the case of ann-component alloy. It is seen that then-component CPA density of states reproduces the binary, ternary quartenary alloys etc when the appropriate limits are adopted.

    • Influence of oxygen deficiency on the thermoelectric power of Y1Ba2Cu3O7-x

      S R Jha Y S Reddy D K Suri K D Kundra R G Sharma Deepak Kumar

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      In this paper we report measurements of the thermoelectric power on a series of Y1Ba2Cu3O7-x specimens with varying amounts of oxygen deficiency obtained by changing the cooling rate of the sintered specimens. The specimens have been characterized by X-ray diffraction measurements, electric resistivity and oxygen contents. The temperature variation of the thermopower reveals a peak just before the onset of superconducting transition. We examine possible theoretical explanations of this anomaly. In particular we argue that this anomaly is associated with the pairing fluctuations in the normal state close toTc. We present some theoretical results in support of this conclusion.

    • On the formation of amorphous layers by interdiffusion in zirconium-copper system

      K Bhanumurthy G K Dey S Banerjee S K Khera M K Asundi

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      Formation of amorphous phase by solid state reaction has been observed in bulk copper-zirconium couples. Transmission electron microscopy (TEM), Auger electron spectroscopy (AES) and differential scanning calorimetry (DSC) techniques have been employed to detect and study the amorphous phase. The experimental observations have been explained with a model, which considers the breakdown of the a-zirconium lattice due to the solute enrichment beyond a certain limit where the nucleation of the amorphous phase becomes thermodynamically possible. The present-experiments convincingly show that amorphous phase can form in bulk diffusion couples made from large-grained well-annealed material and conclusively establish that the presence of crystal defects in high concentrations is not a pre-requisite for the formation of amorphous phase.

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