Tezpur University is an Indian Central University located in Tezpur in the North Eastern state of Assam, India by an act in Parliament of India in 1994.The governor of Assam, Janaki Ballabh Patnaik is the chancellor of Tezpur University, Mihir Kanti Chaudhuri is the vice-chancellor and Amarjyoti Choudhury is the pro vice-chancellor. Wikipedia.
Borah D.,Tezpur University
Nuclear Physics B | Year: 2013
We study the possibility of generating deviations from tri-bimaximal (TBM) neutrino mixing to explain the non-zero reactor mixing angle within the framework of both type I and type II seesaw mechanisms. The type I seesaw term gives rise to the μ-τ symmetric TBM pattern of neutrino mass matrix as predicted by generic flavor symmetry models like A4 whereas the type II seesaw term gives rise to the required deviations from TBM pattern to explain the non-zero θ13. Considering extremal values of Majorana CP phases such that the neutrino mass eigenvalues have the structure (m1, -m2, m3) and (m1, m2, m3), we numerically fit the type I seesaw term by taking oscillation as well as cosmology data and then compute the predictions for neutrino parameters after the type II seesaw term is introduced. We consider a minimal structure of the type II seesaw term and check whether the predictions for neutrino parameters lie in the 3σ range. We also outline two possible flavor symmetry models to justify the minimal structure of the type II seesaw term considered in the analysis. © 2013 Elsevier B.V.
Das R.,Tezpur University
International Journal of Heat and Mass Transfer | Year: 2011
An inverse problem is solved for simultaneously estimating the convection-conduction parameter and the variable thermal conductivity parameter in a conductive-convective fin with temperature dependent thermal conductivity. Initially, the temperature field is obtained from a direct method using an analytical approach based on decomposition scheme and then using a simplex search minimization algorithm an inverse problem is solved for estimating the unknowns. The objective function to be minimized is represented by the sum of square of the error between the measured temperature field and an initially guessed value which is updated in an iterative manner. The estimation accuracy is studied for the effect of measurement errors, initial guess and number of measurement points. It is observed that although very good estimation accuracy is possible with more number of measurement points, reasonably well estimation is obtained even with fewer number of measurement points without measurement error. Subject to selection of a proper initial guess, it is seen that the number of iterations could be significantly reduced. The relative sensitiveness of the estimated parameters is studied and is observed from the present work that the estimated convection-conduction parameter contributes more to the temperature distribution than the variable conductivity parameter. © 2011 Elsevier Ltd. All rights reserved.
Majumdar K.C.,Kalyani University |
Majumdar K.C.,Tezpur University |
Mondal S.,Kalyani University
Chemical Reviews | Year: 2011
Some of the recent developments in the synthesis of fused sultams are discussed. A cascade ring-closure metathesis/isomerization and subsequent radical cyclization was utilized to generate tricyclic sultams from bisallylsulfonamides by Piva and co-workers. de Meijere and co-workers developed a facile synthesis of tricyclic sultams by cycloisomerization of 4,9-diheterododecadienyne followed by intramolecular [4 + 2]-cycloaddition. A synthesis of condensed sultams deriving from intramolecular 1,3-dipolar cycloadditions of nitrones was described by Yamamoto and co-workers. Landry and co-workers reported the synthesis of the tetracyclic N-8-quinolinyl benzenesultam, a novel nuclear factor kappa B (NF-kB) inhibitor. In 2004, Ley and co-workers developed the total synthesis of the cytotoxic antitumor natural product epothilone C by coupling of the three fragments.
Borah D.,Tezpur University
International Journal of Modern Physics A | Year: 2014
We discuss the possible origin of nonzero reactor mixing angle θ13 and Dirac CP phase δCP in the leptonic sector from a combination of type I and type II seesaw mechanisms. Type I seesaw contribution to neutrino mass matrix is of tri-bimaximal (TBM) type which gives rise to vanishing θ13 leaving the Dirac CP phase undetermined. If the Dirac neutrino mass matrix is assumed to take the diagonal charged lepton (CL) type structure, such a TBM type neutrino mass matrix originating from type I seesaw corresponds to real values of Dirac Yukawa couplings in the terms YijL̄iHNj. This makes the process of right-handed heavy neutrino decay into a light neutrino and Higgs (N → νH) CP preserving ruling out the possibility of leptogenesis. Here we consider the type II seesaw term as the common origin of nonzero θ13 and δCP by taking it as a perturbation to the leading order TBM type neutrino mass matrix. First, we numerically fit the type I seesaw term by taking oscillation as well as cosmology data and then compute the predictions for neutrino parameters after the type II seesaw term is introduced. We consider a minimal structure of the type II seesaw term and check whether the predictions for neutrino parameters lie in the 3σ range. We also compute the predictions for baryon asymmetry of the universe by considering type II seesaw term as the only source of CP violation and compare it with the latest cosmology data. © 2014 World Scientific Publishing Company.
Borah D.,Tezpur University |
Dasgupta A.,Jamia Millia Islamia University
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2015
The Fermi gamma ray space telescope data have pointed towards an excess of gamma rays with a peak around 1-3 GeV in the region surrounding the galactic center. This anomalous excess can be described well by a dark matter candidate having mass in the range 31-40 GeV annihilating into bb pairs with a cross section of (σν)≃(1.4-2.0)×10-26 cm3/s. In this work we explore the possibility of having such a dark matter candidate within the framework of a radiative neutrino mass model. The model is a simple extension of the standard model by an additional U(1)X gauge symmetry where the standard model neutrino masses arise both at tree level as well as radiatively by the anomaly free addition of one singlet fermion NR and two triplet fermions ∑1R, ∑2R with suitable Higgs scalars. The spontaneous gauge symmetry breaking is achieved in such a way which results in a residual Z2 symmetry hence providing a stable cold dark matter candidate. We show that the singlet fermionic dark matter candidate in our model can give rise to the galactic center gamma ray excess. The parameter space which simultaneously satisfies the constraints on relic density, direct detection scattering as well as collider bounds essentially corresponds to an s-wave resonance where the gauge boson mass mX is approximately twice that of dark matter mass mχ. We also discuss the compatibility of such a light fermion singlet dark matter with light neutrino mass. © 2014 The Authors.