Physicshttps://repository.iitgn.ac.in/handle/123456789/6072018-09-19T13:46:06Z2018-09-19T13:46:06ZFermiophobic gauge boson phenomenology in 221 modelsColeppa, BaradhwajKumar, SatendraSarkar, Agnivohttps://repository.iitgn.ac.in/handle/123456789/38972018-09-11T11:26:39Z2018-08-01T00:00:00ZFermiophobic gauge boson phenomenology in 221 models
Coleppa, Baradhwaj; Kumar, Satendra; Sarkar, Agnivo
Models with extra gauge symmetry are well-motivated extensions of the Standard Model. In this paper, we study an extended gauge model with a heavy neutral gauge boson Z? which is fermiophobic. Thus, the production of such particles can occur via vector boson fusion, with subsequent decays into WW or Zh. We investigate the collider phenomenology of such Z?s in the context of both the 14 TeV LHC and the future CLIC. We find that looking at ??bb final states provides a rich opportunity to discover such new vector bosons where conventional search strategies in the dilepton channel would fail. In particular, we optimize our analysis by putting in kinematic cuts deriving model-independent values of ?�BR needed for a 5? discovery at the LHC. We then translate this into the parameter space of a specific model for illustration purpose -- our results show that fermiophobic Z?s are discoverable in the ??bb channel for wide range of parameter values.
2018-08-01T00:00:00ZOvercharging black holes and cosmic censorship in Born-Infeld gravityJana, SoumyaShaikh,RajibulSarkar, Sudiptahttps://repository.iitgn.ac.in/handle/123456789/38982018-09-11T11:26:39Z2018-08-01T00:00:00ZOvercharging black holes and cosmic censorship in Born-Infeld gravity
Jana, Soumya; Shaikh,Rajibul; Sarkar, Sudipta
The Born-Infeld gravity is a modification of the theory of general relativity inspired by the nonlinear Born-Infeld electrodynamics. The theory is described by a series of higher curvature terms added to the Einstein-Hilbert action with the parameter ?. The Born-Infeld gravity has several interesting exact neutral and charged black hole solutions. We study the problem of overcharging extremal black hole solutions of Born-Infeld gravity using a charged test particle to create naked singularity. We show that unlike general relativity, the overcharging could be possible for a charged extremal black hole in Born-Infeld gravity as long as the matter sector is described by usual Maxwell's electrodynamics. Once the matter sector is also modified in accordance to the Born-Infeld prescription with the parameter b, the overcharging is not possible as long as the parameters obey the condition 4?b2?1.
2018-08-01T00:00:00ZStochastic modeling of multiwavelength variability of the classical BL Lac object OJ 287 on timescales ranging from decades to hoursKaur, Navpreethttps://repository.iitgn.ac.in/handle/123456789/38942018-09-11T11:26:38Z2018-09-01T00:00:00ZStochastic modeling of multiwavelength variability of the classical BL Lac object OJ 287 on timescales ranging from decades to hours
Kaur, Navpreet
We present the results of our power spectral density analysis for the BL Lac object OJ\,287, utilizing the {\it Fermi}-LAT survey at high-energy ?-rays, {\it Swift}-XRT in X-rays, several ground-based telescopes and the {\it Kepler} satellite in the optical, and radio telescopes at GHz frequencies. The light curves are modeled in terms of continuous-time auto-regressive moving average (CARMA) processes. Owing to the inclusion of the {\it Kepler} data, we were able to construct \emph{for the first time} the optical variability power spectrum of a blazar without any gaps across ?6 dex in temporal frequencies. Our analysis reveals that the radio power spectra are of a colored-noise type on timescales ranging from tens of years down to months, with no evidence for breaks or other spectral features. The overall optical power spectrum is also consistent with a colored noise on the variability timescales ranging from 117 years down to hours, with no hints of any quasi-periodic oscillations. The X-ray power spectrum resembles the radio and optical power spectra on the analogous timescales ranging from tens of years down to months. Finally, the ?-ray power spectrum is noticeably different from the radio, optical, and X-ray power spectra of the source: we have detected a characteristic relaxation timescale in the {\it Fermi}-LAT data, corresponding to ?150\,days, such that on timescales longer than this, the power spectrum is consistent with uncorrelated (white) noise, while on shorter variability timescales there is correlated (colored) noise.
2018-09-01T00:00:00Zσ8 Discrepancy and its solutionsMohanty, SubhendraAnand, SampurnChaubal, PrakrutMazumdar, ArindamParashari, Priyankhttps://repository.iitgn.ac.in/handle/123456789/38902018-09-06T05:19:01Z2018-08-01T00:00:00Zσ8 Discrepancy and its solutions
Mohanty, Subhendra; Anand, Sampurn; Chaubal, Prakrut; Mazumdar, Arindam; Parashari, Priyank
In the recent past, measurements of ?8 from large scale structure observations have shown some discordance with its value obtained from Planck CMB within the ? CDM frame. This discordance naturally leads to a mismatch in the value of H0 also. Under the presumption that these discordances are not due to systematics, several attempts have been made to ameliorate the tensions. In this article, we describe the methods of determination of ?8 from large scale as well as CMB observations. We discuss that these discrepancies vanish if we consider the energy momentum tensor for an imperfect fluid which could arise due to self-interaction of dark matter or in an effective description of large scale structure. We demonstrate how the presence of viscosities in cold dark fluid on large scales ameliorate the problem elegantly than other solutions. We also estimate the neutrino mass in the viscous cosmological setup.
2018-08-01T00:00:00Z