• Volume 3, Issue 1

      July 1974,   pages  1-60

    • Irreversibility and quantum measurement—The observer’s role

      Rajendra Bhandari

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      The role of the observer in physical theories in the sense of the observer’s viewpoint determining prominent features of the observed phenomena is discussed with reference to the problem of irreversibility and quantum measurement, the latter being closely related to the problem of classical behaviour of quantum systems. A completely subjective interpretation of irreversibility is proposed. It is claimed that irreversibility belongs only to phenomena as observed by a restricted observer who must project all phenomena on a restricted subset of the set of all possible states. The possibility of a completely unrestricted observer who does not see irreversibility is discussed.

    • Return current instability and its effects on beam-plasma system

      B N Goswami G S Lakhina B Buti

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      The return current induced in a plasma by a relativisitc electron beam generates a new electron-ion two-stream instability (return current instability). Although the effect of these currents on the beam-plasma e-e instability is negligible, there exists a range of wave numbers which is unstable only to return current (RC) instability and not to e-e instability. The electromagnetic waves propagating along the direction of the external magnetic field, in which the plasma is immersed, are stabilized by these currents but the e.m. waves with frequencies,ω2Ωe2ωpe2 (Ωe andωpe being cyclotron and plasma frequency for the electrons of the plasma respectively) propagating transverse to the magnetic field get destabilized. Heuristic estimates of plasma heating, due to RC instability and due to decay of ion-acoustic turbulence generated by the return current, are made. The fastest time scale on which the return current delivers energy to the plasma due to the scattering of ion-sound waves by the electrons can be ∼ωpi−1 (ωpi being the plasma frequency for the ions).

    • A generalized kerr-schild metric

      P C Vaidya P V Bhatt

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      A metricgik=ηik+iξk+2(iPk) is investigated. WhenJ=0 this reduces to the well-known Kerr metric. Conditions on the vectorpi are obtained under which a geodetic, shear-free null congruenceξi in the Minkowskian space-time (with metricηik) will continue to remain geodetic and shear-free in the Riemannian space-time ofgik. A general solution of Einstein’s equationRik=σξiξk is obtained whenpiξi=0 andξi is twist-free.

    • Creation-field theory from dimensional analysis

      Eric A Lord

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      A Lagrangian is obtained which is invariant under space-time dependent changes in the units of mass, length and time. It contains two scalar fields, one of which is effectively the Brans-Dicke scalar (varying gravitational constant), while the other can be interpreted as a creation-field.

    • Model-independent analysis of the neutral-current interaction in the inclusive neutrino reactions

      G Rajasekaran K V L Sarma

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      On the basis of some general assumptions on the deep inelastic structure functions, such as scaling and chiral symmetry we determine the values of {(HV3)2+(HA3)2}+η{(HV0)2+(HA0)2} andHV3HA3+ηHV0HA0 whereHV3,0 andHA3,0 are the four coupling constants characterizing the hadronic neutral current andη is the ratio of the isoscalar to isovector structure functions. General expressions are given for the kinematical averages 〈v〉 and 〈Q2〉 for the neutral-current reactions in terms of the coupling constants. This analysis does not depend on the validity of the quark-parton model.

    • Chiral symmetry breaking andKN sigma commutator

      S R Roy R K Roychoudhury

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      KN sigma commutator has been calculated in the framework of the (6, $$\bar 6$$)+($$\bar 6$$, 6) model. It is found that though this model could not be discarded in favour of the (3, $$\bar 3$$)+($$\bar 3$$, 3) or (8, 8) model, a very large value forKN sigma term is required to get a positive value ofπN sigma term.

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