Copernicus observations of Betelgeuse and Antares

Copernicus observations of the M-supergiants, alpha Ori and alpha Sco, are presented. The MgII h and k resonance lines are strongly in emission in both stars. The k line is highly asymmetric in both stars but the h line is symmetric. Upper limits for several other resonance lines are given for alpha Ori. The possibility is explored that the k line asymmetry is caused by overlying resonance lines of MnI and FeI formed in the cool circumstellar gas shells around these stars. Observations of the MnI 4030-4033 A lines are used to show that circumstellar shell absorption is too weak to explain the asymmetry. It is suggested that the absorption occurs in a cool turbulent region between the base of the circumstellar shell and the top of the chromosphere

Procyon-A and Eta-Bootis: Observational Frequencies Analyzed by the Local-Wave Formalism

In the present analysis of Procyon-A and Eta-Bootis, we use the local-wave formalism which, despite its lack of precision inherent to any semi-analytical method, uses directly the model profile without any modification when calculating the acoustic mode eigenfrequencies. These two solar-like stars present steep variations toward the center due to the convective core stratification, and toward the surface due to the very thin convective zone. Based on different boundary conditions, the frequencies obtained with this formalism are different from that of the classical numerical calculation. We point out that (1) the frequencies calculated with the local-wave formalism seem to agree better with observational ones. All the frequencies detected with a good confident level including those classified as 'noise' find an identification, (2) some frequencies can be clearly identified here as indications of the core limit.Comment: SOHO 18 / GONG 2006 / HELAS I Meetin

Picosecond excitation of jet-cooled hydrogen-bonded systems: Dispersed fluorescence and time-resolved studies of methyl salicylatea

Long progressions involving frequency intervals of 180 cm^(−1) are observed in the fluoresence of MS for 3327.5 Å excitation. (AIP

Observation of intracavity absorption of molecules in supersonic beams

Intracavity absorption studies of DMT and I2 are reported at rotational and vibrational temperatures of <0.1 K and 16 K, respectively

Quasiparticle interference from different impurities on the surface of pyrochlore iridates: signatures of the Weyl phase

Weyl semimetals are gapless three-dimensional topological materials where two bands touch at an even number of points in the bulk Brillouin zone. These semimetals exhibit topologically protected surface Fermi arcs, which pairwise connect the projected bulk band touchings in the surface Brillouin zone. Here, we analyze the quasiparticle interference patterns of the Weyl phase when time-reversal symmetry is explicitly broken. We use a multi-band $d$-electron Hubbard Hamiltonian on a pyrochlore lattice, relevant for the pyrochlore iridate R$_2$Ir$_2$O$_7$ (where R is a rare earth). Using exact diagonalization, we compute the surface spectrum and quasiparticle interference (QPI) patterns for various surface terminations and impurities. We show that the spin and orbital texture of the surface states can be inferred from the absence of certain backscattering processes and from the symmetries of the QPI features for non-magnetic and magnetic impurities. Furthermore, we show that the QPI patterns of the Weyl phase in pyrochlore iridates may exhibit additional interesting features that go beyond those found previously in TaAs.Comment: 15 pages, 16 figure

Redistribution Through the Income Tax: The Vertical and Horizontal Effects of Noncompliance and Tax Evasion

This paper uses the unique Taxpayer Compliance Measurement Program (TCMP) micro data to study the equity effects of noncompliance. We access four years of TCMP data, 1979,1982,1985, and 1988. The TCMP data allows us to observe income and taxes before and after a tax audit. In order to generate a range of scalar estimates of the redistributive impact of more complete compliance we employ the family of extended Gini and concentration coefficients. We find that the vertical equity effects are very small of negative; however, there is a considerable amount of horizontal inequity generated by noncompliance and in this sense more complete auditing of tax returns could improve the fairness of the tax system

Peculiar Nature of Snake States in Graphene

We study the dynamics of the electrons in a non-uniform magnetic field applied perpendicular to a graphene sheet in the low energy limit when the excitation states can be described by a Dirac type Hamiltonian. We show that as compared to the two-dimensional electron gas (2DEG) snake states in graphene exibit peculiar properties related to the underlying dynamics of the Dirac fermions. The current carried by snake states is locally uncompensated even if the Fermi energy lies between the first non-zero energy Landau levels of the conduction and valence bands. The nature of these states is studied by calculating the current density distribution. It is shown that besides the snake states in finite samples surface states also exist.Comment: 4 pages, 5 figure

Suppression of Giant Magnetoresistance by a superconducting contact

We predict that current perpendicular to the plane (CPP) giant magnetoresistance (GMR) in a phase-coherent magnetic multilayer is suppressed when one of the contacts is superconducting. This is a consequence of a superconductivity-induced magneto-resistive (SMR) effect, whereby the conductance of the ferromagnetically aligned state is drastically reduced by superconductivity. To demonstrate this effect, we compute the GMR ratio of clean (Cu/Co)_nCu and (Cu/Co)_nPb multilayers, described by an ab-initio spd tight binding Hamiltonian. By analyzing a simpler model with two orbitals per site, we also show that the suppression survives in the presence of elastic scattering by impurities.Comment: 5 pages, 4 figures. Submitted to PR

Generalised BPS conditions

We write down two E11 invariant conditions which at low levels reproduce the known half BPS conditions for type II theories. These new conditions contain, in addition to the familiar central charges, an infinite number of further charges which are required in an underlying theory of strings and branes. We comment on the application of this work to higher derivative string corrections