E-print Articles
https://repository.iitgn.ac.in/handle/123456789/615
2019-06-14T09:59:36ZOvercharging a multi black hole system and cosmic censorship
https://repository.iitgn.ac.in/handle/123456789/4429
Overcharging a multi black hole system and cosmic censorship
Mishra, Akash K.; Sarkar, Sudipta
We study the generalization of the gadenken experiment of overcharging an extremal black hole proposed by Wald in the context of a multi black hole solution. In particular, we attempt to overcharge a system of two extremal black holes via test particle absorption to produce a system involving a black hole and a naked singularity. If such a process is possible, then this would be a potential violation of the cosmic censorship hypothesis. However, we find that, analogous to Wald's result for a single charged black hole, such a test particle which can expose the singularity, would not be able to enter the horizon. This provides an interesting and non-trivial example that supports the validity of the cosmic censorship hypothesis in four-dimensional general relativity.
2019-05-01T00:00:00ZSingle photon sources with different spatial modes
https://repository.iitgn.ac.in/handle/123456789/4428
Single photon sources with different spatial modes
Lal, Nijil; Banerji, Anindya; Biswas, Ayan; Anwar, Ali; Singh, R. P.
We study the correlation properties of single photons carrying orbital angular momentum (OAM) in a Hanbury Brown and Twiss (HBT) type experiment. We have characterized single photon sources obtained by pumping a nonlinear crystal with a laser beam carrying different OAM under same experimental conditions. For heralded twisted single photons carrying OAM, we calculate g(2)(0), a measurable parameter characterizing the quality of a single photon source, and observe an increment with the OAM of the single photon.
2019-05-01T00:00:00ZConstraining a general U(1)′ inverse seesaw model from vacuum stability, dark matter and collider
https://repository.iitgn.ac.in/handle/123456789/4427
Constraining a general U(1)′ inverse seesaw model from vacuum stability, dark matter and collider
Das, Arindam; Goswami, Srubabati; K. N., Vishnudath; Nomura, Takaaki
We consider a class of gauged U(1) extensions of the Standard Model (SM), where the light neutrino masses are generated by an inverse seesaw mechanism. In addition to the three right handed neutrinos, we add three singlet fermions and demand an extra Z2 symmetry under which, the third generations of both of the neutral fermions are odd, which in turn gives us a stable dark matter candidate. We express the U(1) charges of all the fermions in terms of the U(1) charges of the standard model Higgs and the new complex scalar. We study the bounds on the parameters of the model from vacuum stability, perturbative unitarity, dark matter relic density and direct detection constraints. We also obtain the collider constraints on the Z′ mass and the U(1)′ gauge coupling. Finally we compare all the bounds on the Z′ mass versus the U(1)′ gauge coupling plane.
2019-05-01T00:00:00ZSupersolid phase of extended Bose-Hubbard model with artificial gauge field
https://repository.iitgn.ac.in/handle/123456789/4423
Supersolid phase of extended Bose-Hubbard model with artificial gauge field
Suthar, K.; Bai, Rukmani; Bandyopadhyay, Soumik; Pal, Sukla; Angom, D.
We examine the zero and finite temperature phase diagram of the extended Bose-Hubbard model on a square optical lattice. To study various quantum phases and their transitions we employ single-site and cluster Gutzwiller mean-field theory. We have observed that the Mott insulator phase vanishes above a critical value of nearest-neighbour interaction and the supersolid phase occupies a larger region in the phase diagram. We show that the presence of artificial gauge field enlarges the domain of supersolid phase. The finite temperature destroys the crystalline structure of the supersolid phase and thereby favours normal fluid to superfluid phase transition. The presence of an envelope harmonic potential demonstrates coexistence of different phases and at z kBT⩾U, the supersolidity of the system is destroyed.
2019-04-01T00:00:00Z