The bulge luminosity functions in the MSX infrared bands

We use an inversion technique to derive the luminosity functions of the Galactic bulge from point source counts extracted from the Midcourse Space Experiment's Point Source Catalog (version 1.2).Comment: 5 pages, 2 figures, to be published in A&

Quiescent NIR and optical counterparts to candidate black hole X-ray binaries

We present near-infrared and optical imaging of fifteen candidate black hole X-ray binaries. In addition to quiescent observations for all sources, we also observed two of these sources (IGR J17451-3022 and XTE J1818-245) in outburst. We detect the quiescent counterpart for twelve out of fifteen sources, and for the remaining three we report limiting magnitudes. The magnitudes of the detected counterparts range between $K_s$ = 17.59 and $K_s$ = 22.29 mag. We provide (limits on) the absolute magnitudes and finding charts of all sources. Of these twelve detections in quiescence, seven represent the first quiescent reported values (for MAXI J1543-564, XTE J1726-476, IGR J17451-3022, XTE J1818-245, MAXI J1828-249, MAXI J1836-194, Swift J1910.2-0546) and two detections show fainter counterparts to XTE J1752-223 and XTE J2012+381 than previously reported. We used theoretical arguments and observed trends, for instance between the outburst and quiescent X-ray luminosity and orbital period $P_{orb}$ to derive an expected trend between $\Delta K_s$ and $P_{orb}$ of $\Delta K_s \propto \log P_{orb}^{0.565}$. Comparing this to observations we find a different behaviour. We discuss possible explanations for this result.Comment: 18 pages, 6 figures. Accepted for publication in MNRA

Toward Supergravity Spectral Action

A spectral action of Euclidean supergravity is proposed. We calculate up to $a_4$, the Seeley-Dewitt coefficients in the expansion of the spectral action associated to the supergravity Dirac operator. This is possible because in simple supergravity, as in pure gravity, a well defined and mathematically consistent Dirac operator can be constructed.Comment: 10pages, no figures, matches published versio

The effect of vacancy-induced magnetism on electronic transport in armchair carbon nanotubes

The influence of local magnetic moment formation around three kinds of vacancies on the electron conduction through metallic single-wall carbon nanotubes is studied by use of the Landauer formalism within the coherent regime. The method is based on the single-band tight-binding Hamiltonian, a surface Green's function calculation, and the mean-field Hubbard model. The numerical results show that the electronic transport is spin-polarized due to the localized magnetic moments and it is strongly dependent on the geometry of the vacancies. For all kinds of vacancies, by including the effects of local magnetic moments, the electron scattering increases with respect to the nonmagnetic vacancies case and hence, the current-voltage characteristic of the system changes. In addition, a high value for the electron-spin polarization can be obtained by applying a suitable gate voltage.Comment: 6 pages, 6 figure

Continuum variational and diffusion quantum Monte Carlo calculations

This topical review describes the methodology of continuum variational and diffusion quantum Monte Carlo calculations. These stochastic methods are based on many-body wave functions and are capable of achieving very high accuracy. The algorithms are intrinsically parallel and well-suited to petascale computers, and the computational cost scales as a polynomial of the number of particles. A guide to the systems and topics which have been investigated using these methods is given. The bulk of the article is devoted to an overview of the basic quantum Monte Carlo methods, the forms and optimisation of wave functions, performing calculations within periodic boundary conditions, using pseudopotentials, excited-state calculations, sources of calculational inaccuracy, and calculating energy differences and forces