Collinear versus non-collinear magnetic order in Pd atomic clusters: ab-initio calculations

We present a thorough theoretical assessment of the stability of non-collinear spin arrangements in small palladium clusters. We generally find that ferromagnetic order is always preferred, but that antiferromagnetic and non-collinear configurations of different sorts exist and compete for the first excited isomers. We also show that the ground state is insensitive to the choice of atomic configuration for the pseudopotential used and to the approximation taken for the exchange and correlation potential. Moreover, the existence and relative stability of the different excited configurations also depends weakly on the approximations employed. These results provide strong evidence on the transferability of pseudopotential and exchange and correlation functionals for palladium clusters as opposed to the situation found for the bulk phases of palladium.Comment: 5 pages, 4 figure

Playing relativistic billiards beyond graphene

The possibility of using hexagonal structures in general and graphene in particular to emulate the Dirac equation is the basis of our considerations. We show that Dirac oscillators with or without restmass can be emulated by distorting a tight binding model on a hexagonal structure. In a quest to make a toy model for such relativistic equations we first show that a hexagonal lattice of attractive potential wells would be a good candidate. First we consider the corresponding one-dimensional model giving rise to a one-dimensional Dirac oscillator, and then construct explicitly the deformations needed in the two-dimensional case. Finally we discuss, how such a model can be implemented as an electromagnetic billiard using arrays of dielectric resonators between two conducting plates that ensure evanescent modes outside the resonators for transversal electric modes, and describe an appropriate experimental setup.Comment: 23 pages, 8 figures. Submitted to NJ

Spectrum, Volume 49, Issue 3

Highlights include: An Immaculate Visit -- New iOS Update -- Hurricane Fiona marches through the Caribbean -- It’s the Great Pumpkin(Season), Charlie Brown! -- A Home Away from Home -- Order Up! Meet David Garcia, Executive Campus Chef -- Town Hall Meeting with Dr.P -- Suicide Prevention Mont

The Past, present, and future in John Greer's The Red red heart

A psychological narrative from nostalgia to optimism binds the songs in John Greer’s cycle The Red Red Heart together. In the first two songs, images of the present are viewed with fear, discomfort, and confusion while images of the past are viewed with optimistic nostalgia and longing. In the middle of the cycle, the character’s emotional responses are reversed, the past now being viewed with negativity and despair, while the present is seen as exciting, joyous, and optimistic. In the final song of the cycle, the character’s growth culminates in her cautious hope for the future. The musical setting of the character’s changing opinions and feelings towards her past, present, and future will be examined from the perspectives of tonality, climax points, formal structure, melody, expression, rhythm, and accompaniment