Chandel, India
Chandel, India

Time filter

Source Type

Rajkumar H.S.,United College | Mustoe G.E.,Western Washington University | Soibam I.,Manipur University
Ichnos:an International Journal of Plant and Animal | Year: 2015

A marine tidal delta siltstone from Gelmon locality in Northeast India preserved three crocodylian footprints and an elongate depression that appears to be a tail drag mark. Similar drag marks occur in nearby bedding surfaces. The discovery of crocodylian tracks from the basal part of Laisong Formation, Barail Group (Late Eocene–Early Oligocene age) of Manipur, India is noteworthy because of the age and the geographic location. Crocodylian tracks are rare in Cenozoic formations and they have not previously been reported from Asia. The footprints are herein named as a new ichnogenus and ichnospecies, Indosuchipes manipurensis. © 2015, Copyright © Taylor & Francis Group, LLC.


Yaiphaba N.,Manipur University | Yaiphaba N.,United College | Ningthoujam R.S.,Bhabha Atomic Research Center | Singh N.R.,Manipur University | Vatsa R.K.,Bhabha Atomic Research Center
European Journal of Inorganic Chemistry | Year: 2010

Nanoparticles of Tb3+-doped GdPO4 (Tb3+ = 0, 2, 5, 7, 10, and 20 atom-%) have been prepared at a relatively low temperature of 160 °C in ethylene glycol, medium. The particles crystallize in a monoclinic structure with an average crystallite size of 30-50 nm. From the luminescence study of Tb3+doped GdPO4, the magnetic dipole transition (5D4-→7F5) at 545 nm (green) was found to be more prominent: than the electric dipole transition (5D4-→7F6) at 484 nm (blue). Maximum luminescence intensity and lifetime was observed for 7 atom-% Tb3+. Above 7 atom-% Tb3+, a decrease in luminescence was observed. This has been attributed to a con-centration-quenching effect due to the cross-relaxation among Tb3+ ions. The highest luminescence intensity of Tb3+ was observed after excitation at: 274 nm ( 8S7/2→ 6I11/2 of Gd3+) among various excitation wavelengths (including f-f absorptions of Tb3+). This is due to an efficient transfer of energy from. Gd3+ to Tb3+ that: shows GdPO4 to be a potential host for Tb3+. These nanoparticles are found to be redispersible in water and ethanol and are incorporated into polyvinyl alcohol film homogeneously. This film showed bright green emission. © 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.


Meitei I.A.,Pettigrew College | Singh T.I.,United College | Singh K.Y.,Manipur University
International Journal of Modern Physics D | Year: 2014

Using the Hamilton-Jacobi method a study of quantum nonthermal radiation of nonstationary rotating de Sitter cosmological model is carried out. It is shown that there exist seas of positive and negative energy states in the vicinity of the cosmological event horizon and there also exists a forbidden energy gap between the two seas. The forbidden energy gap vanishes on the surface of the cosmological event horizon so that the positive and negative energy levels overlap. The width of the forbidden energy gap and the energy of the particle at the cosmological event horizon are found to depend on the cosmological constant, the rotation parameter, positions of the particle and the cosmological event horizon, angular momentum of the particle, evaporation rate and shape of the cosmological event horizon. The tunneling probability of the emitted particles constituting Hawking radiation is also deduced for stationary nonrotating de Sitter cosmological model and the standard Hawking temperature is recovered. © 2014 World Scientific Publishing Company.


Meitei I.A.,Manipur University | Meitei I.A.,Pettigrew College | Yugindro Singh K.,Manipur University | Ibungochouba Singh T.,Manipur University | And 2 more authors.
Astrophysics and Space Science | Year: 2010

The thermodynamics of the Reissner-Nordström black hole at the charge-to-mass ratio of √3/2 is studied. We show that there exists infinite discontinuity not only in the heat capacity but also in the electromagnetic potential and hence in the Gibbs free energy. Despite the existence of an infinite discontinuity in the heat capacity, it is shown that there exists no phase transition in the Reissner-Nordström black hole. The discontinuity may be merely an artefact of the change in the slope of the {pipe}Q{pipe} vs. M curve when the charge-to-mass ratio crosses √3/2. This may signify that the horizon temperature is not a well-behaved thermodynamic parameter in the black hole thermodynamics. © Springer Science+Business Media B.V. 2010.


Ibungochouba Singh T.,United College | Ablu Meitei I.,Pettigrew College | Yugindro Singh K.,Manipur University
Astrophysics and Space Science | Year: 2013

Hawking radiation of Kerr-de Sitter black hole is investigated using Hamilton-Jacobi method. When the well-behaved Painleve coordinate system and Eddington coordinate are used, we get the correct result of Bekenstein-Hawking entropy before and after radiation but a direct computation will lead to a wrong result via Hamilton-Jacobi method. Our results show that the tunneling probability is related to the change of Bekenstein-Hawking entropy and the derived emission spectrum deviates from the pure thermal but it is consistent with underlying unitary theory. © 2013 Springer Science+Business Media Dordrecht.


Ibungochouba Singh T.,United College | Ablu Meitei I.,Pettigrew College | Yugindro Singh K.,Manipur University
Astrophysics and Space Science | Year: 2014

The entropy correction of Kerr-Newman black hole is investigated using the Hamilton-Jacobi method beyond semiclassical approximation. To get entropy correction, the inverse of the sum of square of event horizon (r +) and the square of rotational parameter a of the black hole is taken as the proportionality parameter for quantum corrections of the action I i to the semiclassical action I 0. It has been shown that as quantum effects are taken into account the corrections to the Bekenstein-Hawking entropy of the stationary black hole include a logarithmic term and an inverse area term beyond the semiclassical approximation. © 2014 Springer Science+Business Media Dordrecht.


Ibohal N.,Manipur University | Ibungochouba T.,United College
Astrophysics and Space Science | Year: 2013

Hawking's radiation effect of Klein-Gordon equation, Dirac particles and Maxwell's electromagnetic fields in the non-stationary rotating de Sitter cosmological space-time is investigated by using a new method of generalized tortoise coordinate transformation. It is found that the new transformation produces constant additional terms in the expressions of the surface gravities and the Hawking's temperatures. If the constant terms are set to zero, then the surface gravities and Hawking's temperatures will be equal to those obtained from the old generalized tortoise coordinate transformations. This shows that the new transformations are more reasonable. The Fermionic spectrum of Dirac particles displays a new spin-rotation coupling effect. © 2012 Springer Science+Business Media B.V.


Ibungochouba Singh T.,United College
Astrophysics and Space Science | Year: 2013

Hawking radiation effect of Maxwell's electromagnetic fields in the Kerr-Newman black hole space-time is investigated using two different tortoise coordinate transformations. It has been shown that the new tortoise coordinate transformation produces constant term ξ in the expression of surface gravity and Hawking temperature. If ξ is set to zero, the surface gravity and Hawking temperature will be equal to those obtained from the old tortoise coordinate transformation. This indicates that new transformation is more reliable and accurate. The black body radiant spectrum of photon displays a new spin-rotation coupling effect. © 2013 Springer Science+Business Media Dordrecht.


Ibohal N.,Manipur University | Ibungochouba T.,Manipur University | Ibungochouba T.,United College
Astrophysics and Space Science | Year: 2011

Hawking's radiation effect of Klein-Gordon scalar field, Dirac particles and Maxwell's electromagnetic field in the non-stationary rotating de Sitter cosmological space-time is investigated by using a method of generalized tortoise co-ordinates transformation. The locations and the temperatures of the cosmological horizons of the non-stationary rotating de Sitter model are derived. It is found that the locations and the temperatures of the rotating cosmological model depend not only on the time but also on the angle. The stress-energy regularization techniques are applied to the two dimensional analog of the de Sitter metrics and the calculated stress-energy tensor contains the thermal radiation effect. © 2011 Springer Science+Business Media B.V.

Loading United College collaborators
Loading United College collaborators