7,465 research outputs found
Open charm meson in nuclear matter at finite temperature beyond the zero range approximation
The properties of open charm mesons, , , and in
nuclear matter at finite temperature are studied within a self-consistent
coupled-channel approach. The interaction of the low lying pseudoscalar mesons
with the ground state baryons in the charm sector is derived from a -channel
vector-exchange model. The in-medium scattering amplitudes are obtained by
solving the Lippmann-Schwinger equation at finite temperature including Pauli
blocking effects, as well as , , and self-energies
taking their mutual influence into account. We find that the in-medium
properties of the meson are affected by the -meson self-energy through
the intermediate loops coupled to states. Similarly, dressing the
meson in the loops has an influence over the properties of
the meson.Comment: 23 pages, 9 figures, 2 table
X-ray photoelectron spectroscopy studies of non-stoichiometric superconducting NbB2+x
Polycrystalline samples of NbB2+x with nominal composition (B/Nb) = 2.0, 2.1,
2.2, 2.3, 2.4 and 2.5 were studied by X-ray photoelectron spectroscopy (XPS).
The spectra revealed Nb and B oxides on the surface of the samples, mainly B2O3
and Nb2O5. After Ar ion etching the intensity of Nb and B oxides decreased. The
Nb 3d5/2 and B 1s core levels associated with the chemical states (B/Nb) were
identified and they do not change with etching time. The Binding Energy of the
Nb 3d5/2 and B 1s core levels increase as boron content increases, suggesting a
positive chemical shift in the core levels. On the other hand, analysis of
Valence Band spectra showed that the contribution of the Nb 4d states slightly
decreased while the contribution of the B 2p(pi) states increased as the boron
content increased. As a consequence, the electronic and superconducting
properties were substantially modified, in good agreement with band-structure
calculations.Comment: 10 pages, 7 figures, 1 tabl
Lithospheric structure across the Himalayan-Tibetan orogen: a petrological and geophysical study
Abstract HKT-ISTP 2013
A
A practical guide to density matrix embedding theory in quantum chemistry
Density matrix embedding theory (DMET) provides a theoretical framework to
treat finite fragments in the presence of a surrounding molecular or bulk
environment, even when there is significant correlation or entanglement between
the two. In this work, we give a practically oriented and explicit description
of the numerical and theoretical formulation of DMET. We also describe in
detail how to perform self-consistent DMET optimizations. We explore different
embedding strategies with and without a self-consistency condition in hydrogen
rings, beryllium rings, and a sample S2 reaction. The source code
for the calculations in this work can be obtained from
\url{https://github.com/sebwouters/qc-dmet}.Comment: 41 pages, 10 figure
The Peierls substitution in an engineered lattice potential
Artificial gauge fields open new possibilities to realize quantum many-body
systems with ultracold atoms, by engineering Hamiltonians usually associated
with electronic systems. In the presence of a periodic potential, artificial
gauge fields may bring ultracold atoms closer to the quantum Hall regime. Here,
we describe a one-dimensional lattice derived purely from effective
Zeeman-shifts resulting from a combination of Raman coupling and radiofrequency
magnetic fields. In this lattice, the tunneling matrix element is generally
complex. We control both the amplitude and the phase of this tunneling
parameter, experimentally realizing the Peierls substitution for ultracold
neutral atoms.Comment: 6 pages, 5 figure
The XMM spectral catalog of SDSS optically selected Seyfert 2 galaxies
We present an X-ray spectroscopic study of optically selected (SDSS) Seyfert
2 (Sy2) galaxies. The goal is to study the obscuration of Sy2 galaxies beyond
the local universe, using good quality X-ray spectra in combination with high
S/N optical spectra for their robust classification. We analyzed all available
XMM-Newton archival observations of narrow emission line galaxies that meet the
above criteria in the redshift range 0.05<z<0.35. We initially selected narrow
line AGN using the SDSS optical spectra and the BPT classification diagram. We
further modeled and removed the stellar continuum, and we analyzed the residual
emission line spectrum to exclude any possible intermediate-type Seyferts. Our
final catalog comprises 31 Sy2 galaxies with median redshift z~0.1. X-ray
spectroscopy is performed using the available X-ray spectra from the 3XMM and
the XMMFITCAT catalogs. Implementing various indicators of obscuration, we find
seven (~23%) Compton-thick AGN. The X-ray spectroscopic Compton-thick
classification agrees with other commonly used diagnostics, such as the X-ray
to mid-IR luminosity ratio and the X-ray to [OIII] luminosity ratio. Most
importantly, we find four (~13%) unobscured Sy2 galaxies, at odds with the
simplest unification model. Their accretion rates are significantly lower than
the rest of our Sy2 sample, in agreement with previous studies that predict the
absence of the broad line region below a certain Eddington ratio threshold.Comment: 12 pages, 6 figures, accepted for publication in A&
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