Abstract

Abstract

We compute the flavour-changing top decays t -> ch and t -> cV (V =g ,Z)within the framework of the aligned two-Higgs-doublet models. By exploitingconstraints from flavour physics and the measured Higgs properties, weinvestigate the parameter space of the model and its impact on theassociated branching ratios. It is observed that the Higgs signal strengthin the di-photon channel imposes important restrictions on the t -> chdecay rate when the charged scalar of the model is light. We conclude thatthe rates of these flavour-changing top decays are beyondthe expected sensitivity of the future high-luminosity phase of the LHC.

Abstract

Motivated by the recent data from T2K and MINOS, which show the evidence ofa relatively large theta13 at 3 sigma level, we study the phenomenologicalimplications of the bimaximal mixing (BM), the tri-bimaximal mixing (TBM),and the democratic mixing (DC) matrices with some modifications. Using suchmixing matrices and assuming texture one-zero in the neutrino mass matriceswe have shown whether such mixing matrices satisfy normal or inverted masshierarchy, or phenomenologically viable or not. We have scrutinizedfurther implications of Democratic mixing matrix, motivated by its successin naturally accommodating the nonzero reactor mixing angle theta13. Wehave also explored the possibility of determining the mass hierarchy,octant of the atmospheric mixing angle theta23, and the CP violationdiscovery potential in the current and upcoming long-baseline experimentsT2K, NOvA and LBNE (DUNE).

Abstract

In this talk I shall try to convey to you that the interaction betweencollective excitations originating from a strongly anisotropic quantumHeisenberg ferromagnet on two dimensional lattices, can very well lead tothe formation of localized topological excitations of vortex/anti-vortextype. This happens below the Berezinskii-Kosterlitz-Thouless transitiontemperature (𝑇𝐵𝐾𝑇) when vortices andanti-vortices are immobile and remain as bound pairs. I will describe ourconstruction of quantum states of vortex like topological excitationscorresponding to spin-1/2 strongly XY- anisotropic nearest neighbourHeisenberg ferromagnet on two-dimensional lattice. The procedure involvesthe Pauli spin basis states and is carried out corresponding to bothinfinite dilute limit and finite density limit of vortex/anti-vortex. Itis found that the corresponding quantum mechanical states representingcharge 1 quantum vortices/anti-vortices can be expressed as linearcombinations of single magnon states, composite multi-magnon states andthe ground state. Detailed calculations show that these states are quantummechanically stable states of the Hamiltonian provided that the systemsize exceeds certain threshold value. I will further argue that theinteractions between different magnon modes or rather fragile magnon modescan very well generate these topological excitations. Plausibility of ourcalculations in the real magnetic systems shall also be discussed.

Abstract

Among the most interesting recent developments in the theory of nonequilibrium processes are so-called fluctuation theorems. These theorems make quantitative statements on the probability of negative entropy production in nonequilibrium systems. I will start with fluctuation theorems and its connections to large deviations. I will then describe how the large deviation function can be evaluated for the heat flow across a harmonic chain. Finally, I will show application of the results to an recent experiment.