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The modifications induced in the standard weak-lensing formula if Newtonian gravity differs from inverse square law at large distances are studied. The possibility of putting bounds on the mass of gravitons from lensing data is explored. A bound on graviton mass, esitmated to be about 100 Mpc −1 is obtained from analysis of some recent data on gravitational… (More)

- A Yu Ignatiev, G C Joshi
- 1996

We study a novel type of extensions of the Standard Model which include a hard mass term for the U(1) gauge field and, optionally, the additional scalar multiplets spontaneously violating the electric charge conservation. Contrary to the case of abelian massive electrodynamics, in these theories the massive-ness of photon necessarily implies… (More)

- A Yu Ignatiev, G C Joshi
- 1995

We investigate in detail the problem of constructing magnetic monopole solutions within the finite-range electrodynamics (i.e., electrodynamics with non-zero photon mass, which is the simplest extension of the standard theory ; it is fully compatible with the experiment). We first analyze the classical electrodynamics with the additional terms describing… (More)

- Girish C. Joshi
- 1992

One of the important ways development takes place in mathematics is via a process of generalization. On the basis of a recent characterization of this process we propose a principle that generalizations of mathematical structures that are already part of successful physical theories serve as good guides for the development of new physical theories. The… (More)

- A K Waldron, G C Joshi
- 1992

By considering representation theory for non-associative algebras we construct the fundamental and adjoint representations of the octonion algebra. We then show how these representations by associative matrices allow a consistent octonionic gauge theory to be realized. We find that non-associativity implies the existence of new terms in the transformation… (More)

- M B Tully, G C Joshi
- 1999

Mass bounds for doubly-charged bilepton gauge bosons are derived from constraints on fermion pair production at LEP and lepton-flavour violating charged lepton decays. The limit obtained of 740 GeV for the doubly-charged bilepton does not depend on the assumption that the bilepton coupling is flavour-diagonal, unlike other bounds which have been given in… (More)

- G. C. Joshi
- 1997

Using the framework of Nambu's generalised mechanics, we obtain a new description of constrained Hamiltonian dynamics, involving the introduction of another degree of freedom in phase space, and the necessity of defining the action integral on a world sheet. We also discuss the problem of quantising Nambu mechanics.

- S. P. Brumby, G. C. Joshi
- 1996

We present some striking global consequences of a model quaternionic quantum field theory which is locally complex. We show how making the quater-nionic structure a dynamical quantity naturally leads to the prediction of cosmic strings and non-baryonic hot dark matter candidates.

- C. C. Lassig, G. C. Joshi
- 1996

The violation of the Jacobi identity by the presence of magnetic charge is accomodated by using an explicitly nonassociative theory of octonionic fields. It is found that the dynamics of this theory is simplified if the Lagrangian contains only dyonic charges, but certain problems in the constrained quanti-sation remain. The extension of these concepts to… (More)

Taking the complex nature of quantum mechanics which we observe today as a low energy effect of a broken quaternionic theory we explore the possibility that dark matter arises as a consequence of this underlying quaternionic structure to our universe. We introduce a low energy, effective, Lagrangian which incorporates the remnants of a local quaternionic… (More)