Magnonic Band Structure, Complete Bandgap and Collective Spin Wave Excitation in Nanoscale Two--Dimensional Magnonic Crystals

We present the observation of a complete bandgap and collective spin wave excitation in two-dimensional magnonic crystals comprised of arrays of nanoscale antidots and nanodots, respectively. Considering that the frequencies dealt with here fall in the microwave band, these findings can be used for the development of suitable magnonic metamaterials and spin wave based signal processing. We also present the application of a numerical procedure, to compute the dispersion relations of spin waves for any high symmetry direction in the first Brillouin zone. The results obtained from this procedure has been reproduced and verified by the well established plane wave method for an antidot lattice, when magnetization dynamics at antidot boundaries is pinned. The micromagnetic simulation based method can also be used to obtain iso--frequency countours of spin waves. Iso--frequency contours are analougous of the Fermi surfaces and hence, they have the potential to radicalize our understanding of spin wave dynamics. The physical origin of bands, partial and full magnonic bandgaps has been explained by plotting the spatial distribution of spin wave energy spectral density. Although, unfettered by rigid assumptions and approximations, which afflict most analytical methods used in the study of spin wave dynamics, micromagnetic simulations tend to be computationally demanding. Thus, the observation of collective spin wave excitation in the case of nanodot arrays, which can obviate the need to perform simulations may also prove to be valuable.

Evolution of Universe to the present inert phase

We assume that current state of the Universe can be described by the Inert Doublet Model, containing two scalar doublets, one of which is responsible for EWSB and masses of particles and the second one having no couplings to fermions and being responsible for dark matter. We consider possible evolutions of the Universe to this state during cooling down of the Universe after inflation. We found that in the past Universe could pass through phase states having no DM candidate. In the evolution via such states in addition to a possible EWSB phase transition (2-nd order) the Universe sustained one 1-st order phase transition or two phase transitions of the 2-nd order.

H and A Discrimination using Linear Polarization of Photons at the PLC

First realistic estimate of the usefulness of the Photon Linear Collider with linearly polarized photons as analyzer of the CP-parity of Higgs bosons is presented. MSSM Higgs bosons H and A with 300 GeV mass, for the model parameters corresponding to the so called LHC wedge region, are considered. When switching from circular to linear photon polarization a significant increase in heavy quark production background, which is no longer suppressed by helicity conservation, and decrease of the Higgs boson production cross sections by a factor of two is expected. Nevertheless, after three years of Photon Linear Collider running heavy scalar and pseudoscalar Higgs bosons in MSSM can be distinguished at a 4.5 sigma level.