Indian Institute of Technology Gandhinagar

www.iitgn.ac.in
Ahmadabad, India
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Majumder B.,Indian Institute of Technology Gandhinagar
Advances in High Energy Physics | Year: 2013

With Verlinde's recent proposal which says that gravity can be identified with an entropic force and considering the effects of generalized uncertainty principle in the black hole entropy-area relation we derive the modified equations for Newton's law of gravitation, modified Newtonian dynamics, and Einstein's general relativity. The corrections to the Newtonian potential is compared with the corrections that come from Randall-Sundrum II model and an effective field theoretical model of quantum general relativity. The effect of the generalized uncertainty principle introduces a area type correction term in the entropy-area relation whose consequences in different scenarios are discussed. © 2013 Barun Majumder.


Kumar M.,Indian Institute of Technology Gandhinagar | Gayen K.,Indian Institute of Technology Gandhinagar
Applied Energy | Year: 2011

Biobutanol will become an attractive, economic and sustainable fuel as petroleum oil leads towards expensive fuel due to diminishing oil reserves and an increase of green house gases in the atmosphere. The major challenges in biobutanol production are low butanol titer, availability of compatible feedstocks, and product inhibition. These hurdles are being resolved using several genetic engineering techniques, metabolic engineering strategies, and promising integrated continuous fermentation processes with efficient product recovery techniques (like gas stripping). Adequate success in utilizing renewable and cost-effective cellulosic materials as feedstocks has opened up novel grounds for the advancement in economic biobutanol production. In this direction, Clostridium beijerinckii is being explored as promising strain to produce biobutanol from cellulosic materials. Moreover, high biobutanol titer is being focused through genetic modifications of Clostridia and non-Clostridia organisms (e.g., Escherichia coli, Saccharomyces cerevisiae, Pseudomonas putida, and Bacillus subtilis) in both aerobic and anaerobic fermentation. Further, application of various novel genetic tools and genome sequencing of hyper-butanol-producing Clostridial organism will enhance the scope of genetic engineering for biobutanol production. Therefore, consolidation of academic and industrial research towards economic synthesis of biobutanol illustrates the possibility of substantial breakthrough in future. In this review, we focus on (i) selection of suitable bacterial strain (ii) availability of cheaper biomass to produce butanol (iii) metabolic engineering strategies of various microorganisms (iv) attempts at process development and (v) biobutanol recovery techniques that provide future direction of economical biobutanol fermentation. © 2010 Elsevier Ltd.


Sarkar S.,Indian Institute of Technology Gandhinagar | Wall A.C.,University of California at Santa Barbara
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2013

In this article we consider the second law of black holes (and other causal horizons) in theories where the gravitational action is an arbitrary function of the Lovelock densities. We show that there exists an entropy which increases locally, for linearized perturbations to regular Killing horizons. In addition to a classical increase theorem, we also prove a generalized second law for semiclassical, minimally coupled matter fields. © 2013 American Physical Society.


Garattini R.,University of Bergamo | Majumder B.,Indian Institute of Technology Gandhinagar
Nuclear Physics B | Year: 2014

In this work, we explore the possibility that quantum fluctuations induce an electric or magnetic charge or both, in the context of Gravity's Rainbow. A semi-classical approach is adopted, where the graviton one-loop contribution to a classical energy in a background spacetime is computed through a variational approach with Gaussian trial wave functionals. The energy density of the graviton one-loop contribution, in this context, acts as a source for the electric/magnetic charge. The ultraviolet (UV) divergences, which arise analyzing this procedure, are kept under control with the help of an appropriate choice of the Rainbow's functions. In this way we avoid the introduction of any regularization/renormalization scheme. A comparison with the observed data leads us to determine the size of the electron and of the magnetic monopole which appear to be of Planckian size. Both results seem to be of the same order for a Schwarzschild and a de Sitter background, respectively. Estimates on the magnetic monopole size have been done with the help of the Dirac quantization procedure. We find that the monopole radius is larger than the electron radius. Even in this case the ratio between the electric and magnetic monopole radius appears to be of the same order for both geometries. © 2014 The Authors.


Garattini R.,University of Bergamo | Majumder B.,Indian Institute of Technology Gandhinagar
Nuclear Physics B | Year: 2014

We compute the Zero Point Energy (ZPE) induced by a naked singularity with the help of a reformulation of the Wheeler-DeWitt equation. A variational approach is used for the calculation with Gaussian Trial Wave Functionals. The one loop contribution of the graviton to the ZPE is extracted keeping under control the UltraViolet divergences by means of a distorted gravitational field. Two examples of distortion are taken under consideration: Gravity's Rainbow and Noncommutative Geometry. Surprisingly, we find that the ZPE is no more singular when we approach the singularity. © 2014.


Mondal T.,Physical Research Laboratory | Mondal T.,Indian Institute of Technology Gandhinagar | Basak T.,Physical Research Laboratory
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2015

Recently the study of anomalous gamma-ray emission in the regions surrounding the galactic center has drawn a lot of attention as it points out that the excess of ~1-3GeV gamma-ray in the low latitude is consistent with the emission expected from annihilating dark matter. The best-fit to the gamma-ray spectrum corresponds to dark matter (DM) candidate having mass in the range ~31-40GeV annihilating into bb--pair with cross-section 〈σv〉=(1.4-2.0)×10-26cm3s-1. We have shown that the Higgs-portal dark matter models in presence of scalar resonance (in the annihilation channel) are well-suited for explaining these phenomena. In addition, the parameter space of these models also satisfies constraints from the LHC Higgs searches, relic abundance and direct detection experiments. We also comment on real singlet scalar Higgs-portal DM model which is found to be incompatible with the recent analysis. © 2015 The Authors.


Hati C.,Physical Research Laboratory | Hati C.,Indian Institute of Technology Gandhinagar
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2016

We propose a possible explanation for the recent diphoton excess reported by ATLAS and CMS Collaborations at around a 750 GeV diphoton invariant mass within the framework of the E6-motivated alternative left-right symmetric model, which is capable of addressing the B decay anomalies in the flavor sector, the eejj and epTjj excesses reported by CMS in run 1 of the LHC, and high-scale leptogenesis. We find that gluon-gluon fusion can give the observed production rate of the 750 GeV resonance, ñ, through a loop of scalar leptoquarks (h(c)) with a mass below a few TeV range, while ñ can subsequently decay into a γγ final state via loops of h(c) and Ẽ(c). Interestingly, the slepton (Ẽ(c)) loop can enhance the diphoton branching ratio significantly to successfully explain the observed cross section of the diphoton signal. © 2016 American Physical Society.


Dey U.K.,Physical Research Laboratory | Mohanty S.,Physical Research Laboratory | Tomar G.,Physical Research Laboratory | Tomar G.,Indian Institute of Technology Gandhinagar
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2016

We explain the 750 GeV diphoton resonance in the context of the dark left-right symmetric model. A global symmetry in this model, stabilizes the dark matter and ensures that the scalar couples dominantly to gluons and photons. The branching fraction of the scalar to diphoton is large as a consequence of the symmetries of the theory. The benchmark values assumed to fit the diphoton signal also give the correct relic density of dark matter and muon (g - 2). A specific prediction of this model is that the dark matter has a mass of 200 GeV. © 2016 The Authors.


Majumder B.,Indian Institute of Technology Gandhinagar
General Relativity and Gravitation | Year: 2013

Here we study the effects of the Generalized Uncertainty Principle in the tunneling formalism for Hawking radiation to evaluate the quantum-corrected Hawking temperature and entropy for a Schwarzschild black hole. We compare our results with the existing results given by other candidate theories of quantum gravity. In the entropy-area relation we found some new correction terms and in the leading order we found a term which varies as ~ √Area. We also get the well known logarithmic correction in the sub-leading order. We discuss the significance of this new quantum corrected leading order term. © 2013 Springer Science+Business Media New York.


Subramanian S.V.,Harvard University | Corsi D.J.,Harvard Center for Population and Development Studies | Subramanyam M.A.,Indian Institute of Technology Gandhinagar | Smith G.D.,University of Bristol
International Journal of Epidemiology | Year: 2013

There has been an increased focus on non-communicable diseases (NCDs) in India, especially on cardiovascular diseases and associated risk factors. In this essay, we scrutinize the prevailing narrative that cardiovascular risk factors (CVRF) and cardiovascular disease (CVD) are no longer confined to the economically advantaged groups but are an increasing burden among the poor in India. We conducted a comprehensive review of studies reporting the association between socioeconomic status (SES) and CVRF, CVD, and CVD-related mortality in India. With the exception of smoking and low fruit and vegetable intake, the studies clearly suggest that CVRF/CVD is more prevalent among high SES groups in India than among the low SES groups. Although CVD-related mortality rates appear to be higher among the lower SES groups, the proportion of deaths from CVD-related causes was found to be greatest among higher SES groups. The studies on SES and CVRF/CVD also reveal a substantial discrepancy between the data presented and the authors' interpretations and conclusions, along with an unsubstantiated claim that a reversal in the positive SES-CVRF/CVD association has occurred or is occurring in India. We conclude our essay by emphasizing the need to prioritize public health policies that are focused on the health concerns of themajority of the Indian population. Resource allocation in the context of efforts to make health care in India free and universal should reflect the proportional burden of disease on different population groups if it is not to entrench inequity. © The Author 2013; all rights reserved.

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