278 research outputs found
Ground-state properties of rutile: electron-correlation effects
Electron-correlation effects on cohesive energy, lattice constant and bulk
compressibility of rutile are calculated using an ab-initio scheme. A
competition between the two groups of partially covalent Ti-O bonds is the
reason that the correlation energy does not change linearly with deviations
from the equilibrium geometry, but is dominated by quadratic terms instead. As
a consequence, the Hartree-Fock lattice constants are close to the experimental
ones, while the compressibility is strongly renormalized by electronic
correlations.Comment: 1 figure to appear in Phys. Rev.
Electronic structure and X-ray spectroscopic properties of the HfFe2Si2 compound
The valence band electronic structure of HfFe2Si2 has been established for the first time based on X-ray emission spectroscopy measurements. The band structure and X-ray emission spectra have been also obtained theoretically using the ab initio LMTO method in the non-relativistic approximation. The electron configuration of Si in the compound HfFe2Si2 can be described as . The theoretical and experimental results are in satisfactory agreement
SO(4) Symmetry of the Transfer Matrix for the One-Dimensional Hubbard Model
The SO(4) invariance of the transfer matrix for the one-dimensional Hubbard
model is clarified from the QISM (quantum inverse scattering method) point of
view. We demonstrate the SO(4) symmetry by means of the fermionic R-matrix,
which satisfy the graded Yang-Baxter relation. The transformation law of the
fermionic L-operator under the SO(4) rotation is identified with a kind of
gauge transformation, which determines the corresponding transformation of the
fermionic creation and annihilation operators under the SO(4) rotation. The
transfer matrix is confirmed to be invariant under the SO(4) rotation, which
ensures the SO(4) invariance of the conserved currents including the
Hamiltonian. Furthermore, we show that the representation of the higher
conserved currents in terms of the Clifford algebra gives manifestly SO(4)
invariant forms.Comment: 20 pages, LaTeX file using citesort.st
Cosmic Ray Extremely Distributed Observatory: a global network of detectors to probe contemporary physics mysteries
In the past few years, cosmic-rays beyond the GZK cut-off ( eV) have been detected by leading collaborations such as Pierre Auger
Observatory. Such observations raise many questions as to how such energies can
be reached and what source can possibly produce them. Although at lower
energies, mechanisms such as Fermi acceleration in supernovae front shocks seem
to be favored, top-down scenarios have been proposed to explain the existence
of ultra-high energy cosmic-rays: the decay of super-massive long-lived
particles produced in the early Universe may yield to a flux of ultra-high
energy photons. Such photons might be presently generating so called
super-preshowers, an extended cosmic-ray shower with a spatial distribution
that can be as wide as the Earth diameter. The Cosmic Ray Extremely Distributed
Observatory (CREDO) mission is to find such events by means of a network of
detectors spread around the globe. CREDO's strategy is to connect existing
detectors and create a worldwide network of cosmic-ray observatories. Moreover,
citizen-science constitutes an important pillar of our approach. By helping our
algorithms to recognize detection patterns and by using smartphones as
individual cosmic-ray detectors, non-scientists can participate in scientific
discoveries and help unravel some of the deepest mysteries in physics.Comment: excited QCD Conference, CREDO Collaboration, 7 pages, 3 figure
Strangeness nuclear physics: a critical review on selected topics
Selected topics in strangeness nuclear physics are critically reviewed. This
includes production, structure and weak decay of --Hypernuclei, the
nuclear interaction and the possible existence of bound
states in nuclei. Perspectives for future studies on these issues are also
outlined.Comment: 63 pages, 51 figures, accepted for publication on European Physical
Journal
- …