Constraint structure and Hamiltonian treatment of Nappi-Witten model

We investigate the Hamiltonian analysis of Nappi-Witten model (WZW action based on non semi simple gauge group) and find a time dependent non-commutativity by canonical quantization. Our procedure is based on constraint analysis of the model in two parts. A first class analysis is used for gauge fixing the original model following by a second class analysis in which the boundary condition are treated as Dirac constraints. We find the reduced phase space by imposing our second class constraints on the variables in an extended Fourier space

An investigation of the interrelationship between pressure and correlation in LaFeAsO under pressure

Here, we investigated the interrelationship between pressure and correlation in the LaFeAsO compound by the density functional theory method combined with the dynamical mean field theory (DFT+DMFT) method. The spectral function and the occupation number (ON) of Fe-3d orbitals at different pressures were extracted from the calculations, and the importance of the role of correlation in superconductivity in iron-based compounds was indicated. The measured ON of Fe-3d orbitals demonstrated charge transfer between them and also the crucial role of the Fe-3dxy (xy) orbital in superconductivity in these materials. A switching behavior between high and low TC through decreasing the correlation was observed in our calculations, originating from the orbital switching. This shows the significant role of the orbital degrees of freedom in iron-based superconductors

Self-equivalence 3rd order ODEs by time-fixed transformations

Let y''' = f(x, y, y', y'') be a 3rd order ODE. By Cartan equivalence method, we will study the local equivalence problem under the transformations group of time-fixed coordinates.Comment: 9 pages, accepted by "Electronic Journal Applied Sciences (http://www.mathem.pub.ro/apps)

Charge-doping-induced variation of BaFe2_2As2_2 electronic structure and the emerging physical effects

We studied the relationship between the charge doping and the correlation, and its effects on the spectral function of the BaFe$_2$As$_2$ compound in the framework of the density functional theory combined with the dynamical mean field theory (DFT+DMFT). The calculated mass enhancements showed that the electronic correlation varies systematically from weak to strong when moving from the heavily electron-doped regime to the heavily hole-doped one. Since the compound has a multi-orbital nature, the correlation is orbital-dependent and it increases as hole-doping increases. The Fe-3d$_{xy}$ (xy) orbital is much more correlated than the other orbitals, because it reaches its half-filled situation and has a narrower energy scale around the Fermi energy. Our findings can be consistently understood as the tendency of the heavily hole-doped BaFe$_2$As$_2$ compound to an orbital-selective Mott phase (OSMP). Moreover, the fact that the superconducting state of the heavily hole-doped BaFe$_2$As$_2$ is an extreme case of such a selective Mottness constrains the non-trivial role of the electronic correlation in iron-pnictide superconductors. In addition, the calculated spectral function shows a behavior that is compatible with experimental results reported for every charge-doped BaFe$_2$As$_2$ compound and clarifies the importance of the characterization of its physical effects on the material

Crystalline anisotropy induces a second antiferromagnetic phase in the absence of SDW in the heavily hydrogen-doped LaFeAsO1−x_{1-x}Hx_x (x∼0.5)(x\sim0.5 )

Electronic and magnetic properties of the heavily H-doped LaFeAsO$_{1-x}$H$_x$ $(x\sim0.5 )$ were studied in the framework of the density functional theory combined with the dynamical mean field theory (DFT+DMFT). We found a stripe-like-ordered structure of hydrogen and oxygen atoms, as a ground state, with the same configuration as the antiferromagnetic (AF) order. The new configuration could explain the existing experimental results related to the heavily H-doped LaFeAsO$_{1-x}$H$_x$, such as an in-plane electronic anisotropy and a non-uniform magnetic behavior. A significant anisotropy was observed between Fe- 3d$_{xz}$ (xz) and Fe-3d$_{yz}$ (yz) orbitals in the ground state in the absence of the pseudogap resulting from the spin density wave phase, which was found to originate from the crystalline anisotropy. Magnetic moments were not spatially uniform and were sensitive to the crystal configuration. We found that a non-uniform magnetic behavior is associated with the As-Fe-As bond angle in the structure. Our findings would clarify the importance of crystal details and orbital degrees of freedom in iron-based superconductors

Bulk Viscosity and Particle Creation in the Inflationary Cosmology

We study particle creation in the presence of bulk viscosity of cosmic fluid in the early universe within the framework of open thermodynamical systems. Since the first-order theory of non-equilibrium thermodynamics is non-causal and unstable, we try to solve the bulk viscosity equation of the cosmic fluid with particle creation through the full causal theory. By adopting an appropriate function for particle creation rate of "Creation of Cold Dark Matter" model, we obtain analytical solutions which do not suffer from the initial singularity and are in agreement with equivalent solutions of Lambda-CDM model. We constrain the free parameter of particle creation in our model based on recent Planck data. It is also found that the inflationary solution is driven by bulk viscosity with or without particle creation.Comment: 5 page

Planar infinite groups

We will determine all infinite $2$-locally finite groups as well as infinite $2$-groups with planar subgroup graph and show that infinite groups satisfying the chain conditions containing an involution do not have planar embeddings. Also, all connected outer-planar groups and outer-planar groups satisfying the chain conditions are presented. As a result, all planar groups which are direct product of connected groups are obtained.Comment: 10 pages, 3 figures, To appear in J. Group Theor

CMB and reheating constraints to \alpha-attractor inflationary models

After Planck 2013, a broad class of inflationary models called \alpha-attractors was developed which has universal observational predictions. For small values of the parameter \alpha, the models have good consistency with the recent CMB data. In this work, we first calculate analytically (and verify numerically) the predictions of these models for spectral index, n_s and tensor-to-scalar ratio, r and then using BICEP2/Keck 2015 data we impose constraints on \alpha-attractors. Then, we study the reheating in \alpha-attractors. The reheating temperature, T_{re} and the number of e-folds during reheating, N_{re} are calculated as functions of n_s. Using these results, we determine the range of free parameter \alpha for two clasees of \alpha-attractors which satisfy the constraints of recent CMB data.Comment: 13 pages, 7 figure

Surface plasmon polaritons scattering by subwavelength silicon wires

Surface plasmon polaritons scattering from 2D subwavelength silicon wires is investigated using finite difference time domain method. It is shown that coupling an incident surface plasmon polariton to inter-cavity modes of the particle can dramatically changes transmitted fields and plasmon induced forces. In particular, both transmission and optical forces are highly sensitive to the particle size that is related to the excitation of whispering gallery modes or standing-wave modes depending on the particle shape and size. This features might have potential sensing applications.Comment: 6 pages, 4 figure

A Non-minimally Coupled Potential for Inflation and Dark Energy after Planck 2015: A Comprehensive Study

In this work we introduce a new plateau-like inflationary model including a quadratic scalar potential coupled non-minimally to gravity. This potential has a dominant constant energy density at early times which can realize successful inflation. It also includes an infinitesimal non-zero term $V_0$ responsible for explaining dark energy which causing the universe to expand accelerating at the late time. We show that this model predicts small tensor-to-scalar ratio of the order of $r\approx 0.01$ which is fully consistent with Planck constraints. Using the lower and upper bounds on reheating temperature, we provide additional constraints on the non-minimal coupling parameter $\xi$ of the model. We also study the preheating stage predicted by this kind of potentials using numerical calculations.Comment: 11 pages, 5 figure