arXiv subjects

S C Tiwari

Publications and source records attributed to S C Tiwari.

25 records · Page 2Linked to original sources

arXiv2007

Topological defects, geometric phases, and the angular momentum of light

Recent reports on the intriguing features of vector vortex bearing beams are analyzed using geometric phases in optics. It is argued that the spin redirection phase induced circular birefringence is the origin of topological phase singularities arising in the inhomogeneous polarization patterns. A unified picture of recent results is presented based on this proposition. Angular momentum shift within the light beam (OAM) has exact equivalence with the angular momentum holonomy associated with the geometric phase consistent with our conjecture.

quant-ph↗

arXiv2007

Thermodynamics of Spacetime and Unimodular Relativity

The black hole entropy formula applied to local Rindler horizon at each spacetime point has been used in the literature to derive the Einstein field equation as an equation of state of a thermodynamical system of spacetime. In the present paper we argue that due to the key role of causal structure and discrete spacetime in this approach the natural framework is unimodular relativity rather than general relativity. It is shown that the equation of state is trace free unimodular relativity field equation that uniquely determines only the traceless stress tensor. Recent generalization to nonequilibrium thermodynamics is shown to be equivalent to the conformally related spacetime metrics, and energy-momentum conservation is satisfied without invoking entropy production. We suggest that the cosmological constant should possess thermodynamical fluctuations, and at a deeper level the metric may have statistical origin.

gr-qc↗

arXiv2006

Topological Photon

We associate intrinsic energy equal to $hν/2$ with the spin angular momentum of photon and propose a topological model based on orbifold in space and tifold in time as topological obstructions. The model is substantiated using vector wavefield disclinations. The physical photon is suggested to be a particle like topological photon and a propagating wave such that the energy $hν$ of photon is equally divided between spin energy and translational energy corresponding to linear momentum of $hν/c$. The enigma of wave-particle duality finds natural resolution and the proposed model gives new insights into the phenomena of interference and emission of radiation.

quant-ph↗

arXiv2006

The nature of electronic charge

Advances in gauge theories and unified theories have not thrown light on the meaning of electron. The problem of the origin of electronic charge is made precise, new insights gained from Weyl space are summarized, and the origin of charge in terms of fractional spin is suggested. New perspective on the abelian Chern-Simons theory is presented to explain charge.

physics.gen-ph↗

arXiv2006

Doppler effect and frequency-shift in optics

A critical review of frequency-shift phenomena a la Doppler effect is presented. The importance of Fermi's theory of 1932 is pointed out, and it is argued that there exists a gap in our understanding of this phenomena at a fundamental level. Alternative mechanism in terms of photon number oscillations is suggested for polarization changing experiments. The physical reality of single photon is revisited, and a possible experimental scheme to test the alternative mechanism is suggested.

quant-ph↗

arXiv2004

Remarks on Aharanov-Bohm effect and geometric phase

Recently the physical mechanism for geometric phase in optics has been elucidated in terms of the angular momentum holonomy proposed in 1992. Aharonov and Kaufherr (PRL, 92, 070404, 2004) revisit the Aharonov-Bohm effect, and propose non-local exchange of a conserved, gauge invariant quantity that changes the modular momentum of the particle that is responsible for the AB phase shift. We suggest that the net angular momentum shifts proposed for GP may be analogous to the shift in the modulus momentum for the AB effect. At a single photon or electron level such non-trivial, geometric effects seem to hint at a new physics.

quant-ph↗

arXiv2004

Geometric phase in optics and angular momentum of light

Physical mechanism for the geometric phase in terms of angular momentum exchange is elucidated. It is argued that the geometric phase arising out of the cyclic changes in the tranverse mode space of the Gaussian light beams is a manifestation of the cycles in the momentum space of the light. Nonconservation of angular momentum in the spontaneous parametric down-conversion for the classical light beams is proposed to be related with the geometric phase.

quant-ph↗