• A Banerjee

      Articles written in Pramana – Journal of Physics

    • String cosmology in Bianchi I space-time

      A Banerjee Abhik Kumar Sanyal Subenoy Chakraborty

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      Some cosmological solutions of massive strings are obtained in Bianchi I space-time following the techniques used by Letelier and Stachel. A class of solutions corresponds to string cosmology associated with/without a magnetic field and the other class consists of pure massive strings, obeying the Takabayashi equation of stateρ=(1+W)λ.

    • Spherically symmetric solutions with heat flow in general relativity

      A Banerjee S B Dutta Choudhury B K Bhui

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      Some new solutions of shear-free imperfect fluid spheres with heat flux in the radial direction are obtained. They have isotropic pressure and could be the generalizations of earlier solutions of Nariai and of Banerjee and Banerji for perfect fluid without dissipation.

    • Inflationary solutions in general scalar tensor theory of gravitation

      A Banerjee S B Dutta Choudhury N Banerjee A Sil

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      Extended inflation solution in Brans-Dicke theory given by Mathiazhagan and Johri (MJ) is shown as the unique solution only if the scale factor is assumed to be a power function of the scalar field. Only the consistent solution amongst the set of solutions given by Patra, Roy and Ray is found identical to the MJ solution. Both exponential inflation and power function inflation are studied in general scalar tensor theory where the parameter to is a function of the scalar, field. It is noted that exponential inflation is forbidden in Brans-Dicke theory wherew is a constant.

    • Even harmonics of AC susceptibility in some sintered pellets of high temperature superconductors

      A Das A Bajpai A Banerjee R Srinivasan

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      The real (χ′n) and imaginary (χ″n) parts of even harmonic susceptibility (n⩽6) are measured as a function of external DC field (Hdc) in the field increasing (H↑) and decreasing (H↑) cycle. Hysteresis is observed betweenH↑ andH↓ cycles. In theH↓ cycle, at a field,Hcomp=4·2G, bothχ′ andχ″ of all the even harmonics vanish indicating a true cancellation of fields in the intergrain region (Heff≈0) caused by the balance betweenHdc and the remanent magnetization of the grains. The position of the extrema and the zero of the various harmonics undergo a shift proportional to the remanent magnetization of the grains at that particular field.

    • Coupled dilaton and electromagnetic field in cylindrically symmetric spacetime

      A Banerjee S Chatterjee Tanwi Ghosh

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      An exact solution is obtained for coupled dilaton and electromagnetic field in a cylindrically symmetric spacetime where an axial magnetic field as well as a radial electric field both are present. Depending on the choice of the arbitrary constants our solution reduces either to dilatonic gravity with pure electric field or to that with pure magnetic field. In the first case we have a curvature singularity at a finite distance from the axis indicating the existence of the boundary of a charged cylinder which may represent the source of the electric field. For the second case we have a singularity on the axis. When the dilaton field is absent the electromagnetic field disappears in both the cases. Whereas the contrary is not true. It is further shown that light rays except for those proceeding in the radial direction are either trapped or escape to infinity depending on the magnitudes of certain constant parameters as well as on the nature of the electromagnetic field. Nature of circular geodesics is also studied in the presence of dilaton field in the cylindrically symmetric spacetime.

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