2,723 research outputs found
4p states and X-Ray Spectroscopy
The 4p states in transition metals and their compounds usually play minor
roles on their physical quantities. Recent development of resonant x-ray
scattering (RXS) at the K-edge of transition metals, however, casts light on
the 4p states, because the signals on orbital and magnetic superlattice spots
are brought about by the modulation in the 4p states. The 4p states are
extending in solids and thereby sensitive to electronic states at neighboring
sites. This characteristic determines the mechanism of RXS that the intensity
on the orbital superlattice spots are mainly generated by the lattice
distortion and those on magnetic superlattice spots by the coupling of the 4p
states with the orbital polarization in the 3d states at neighboring sites.
Taking up typical examples for orbital and magnetic RXS, we demonstrate these
mechanisms on the basis of the band structure calculation. Finally, we study
the MCD spectra at the K-edge, demonstrating that the same mechanism as the
magnetic RXS is working.Comment: 9 pages, 9 figures, submitted to Physica Scripta (comment
Exploring Vacuum Structure around Identity-Based Solutions
We explore the vacuum structure in bosonic open string field theory expanded
around an identity-based solution parameterized by . Analyzing the
expanded theory using level truncation approximation up to level 20, we find
that the theory has the tachyon vacuum solution for . We also find
that, at , there exists an unstable vacuum solution in the expanded
theory and the solution is expected to be the perturbative open string vacuum.
These results reasonably support the expectation that the identity-based
solution is a trivial pure gauge configuration for , but it can be
regarded as the tachyon vacuum solution at .Comment: 12 pages, 5 figures; new numerical data up to level (20,60) included;
Contribution to the proceedings of "Second International Conference on String
Field Theory and Related Aspects" (Steklov Mathematical Institute, Moscow,
Russia, April 12-19, 2009
On zero modes of the eleven dimensional superstring
It is shown that recently pointed out by Berkovits on-shell degrees of
freedom of the D=11 superstring do not make contributions into the quantum
states spectrum of the theory. As a consequence, the spectrum coincides with
that of the D=10 type IIA superstring.Comment: 7 pages, LaTex fil
Regularization of identity based solution in string field theory
We demonstrate that an Erler-Schnabl type solution in cubic string field
theory can be naturally interpreted as a gauge invariant regularization of an
identity based solution. We consider a solution which interpolates between an
identity based solution and ordinary Erler-Schnabl one. Two gauge invariant
quantities, the classical action and the closed string tadpole, are evaluated
for finite value of the gauge parameter. It is explicitly checked that both of
them are independent of the gauge parameter.Comment: 9 pages, minor typos corrected and references adde
BRST Formulation of 4-Monopoles
A supersymmetric gauge invariant action is constructed over any 4-dimensional
Riemannian manifold describing Witten's theory of 4-monopoles. The topological
supersymmetric algebra closes off-shell. The multiplets include the auxiliary
fields and the Wess-Zumino fields in an unusual way, arising naturally from
BRST gauge fixing. A new canonical approach over Riemann manifolds is followed,
using a Morse function as an euclidean time and taking into account the BRST
boundary conditions that come from the BFV formulation. This allows a
construction of the effective action starting from gauge principles.Comment: 18 pages, Amste
Theoretical Analysis of Resonant Inelastic X-Ray Scattering Spectra in LaMnO3
We analyze the resonant inelastic x-ray scattering (RIXS) spectra at the K
edge of Mn in the antiferromagnetic insulating manganite LaMnO3. We make use of
the Keldysh-type Green-function formalism, in which the RIXS intensity is
described by a product of an incident-photon-dependent factor and a
density-density correlation function in the 3d states. We calculate the former
factor using the 4p density of states given by an ab initio band structure
calculation and the latter using a multi-orbital tight-binding model. The
ground state of the model Hamiltonian is evaluated within the Hartree-Fock
approximation. Correlation effects are treated within the random phase
approximation (RPA). We obtain the RIXS intensity in a wide range of
energy-loss 2-15 eV. The spectral shape is strongly modified by the RPA
correlation, showing good agreement with the experiments. The
incident-photon-energy dependence also agrees well with the experiments. The
present mechanism that the RIXS spectra arise from band-to-band transitions to
screen the core-hole potential is quite different from the orbiton picture
previously proposed, enabling a comprehensive understanding of the RIXS
spectra.Comment: 20 pages, 10 figures, To be published in PR
Towards a Java Subtyping Operad
The subtyping relation in Java exhibits self-similarity. The self-similarity
in Java subtyping is interesting and intricate due to the existence of wildcard
types and, accordingly, the existence of three subtyping rules for generic
types: covariant subtyping, contravariant subtyping and invariant subtyping.
Supporting bounded type variables also adds to the complexity of the subtyping
relation in Java and in other generic nominally-typed OO languages such as C#
and Scala. In this paper we explore defining an operad to model the
construction of the subtyping relation in Java and in similar generic
nominally-typed OO programming languages. Operads, from category theory, are
frequently used to model self-similar phenomena. The Java subtyping operad, we
hope, will shed more light on understanding the type systems of generic
nominally-typed OO languages.Comment: 13 page
X-Ray Magnetic Circular Dichroism at the K edge of Mn3GaC
We theoretically investigate the origin of the x-ray magnetic circular
dichroism (XMCD) spectra at the K edges of Mn and Ga in the ferromagnetic phase
of Mn3GaC on the basis of an ab initio calculation. Taking account of the
spin-orbit interaction in the LDA scheme, we obtain the XMCD spectra in
excellent agreement with the recent experiment. We have analyzed the origin of
each structure, and thus elucidated the mechanism of inducing the orbital
polarization in the p symmetric states. We also discuss a simple sum rule
connecting the XMCD spectra with the orbital moment in the p symmetric states.Comment: 5 pages, 5 figures, accepted for publication in Physical Review
Spin Excitations and Sum Rules in the Heisenberg Antiferromagnet
Various bounds for the energy of collective excitations in the Heisenberg
antiferromagnet are presented and discussed using the formalism of sum rules.
We show that the Feynman approximation significantly overestimates (by about
30\% in the square lattice) the spin velocity due to the non
negligible contribution of multi magnons to the energy weighted sum rule. We
also discuss a different, Goldstone type bound depending explicitly on the
order parameter (staggered magnetization). This bound is shown to be
proportional to the dispersion of classical spin wave theory with a
q-independent normalization factor. Rigorous bounds for the excitation energies
in the anisotropic Heisenberg model are also presented.Comment: 26 pages, Plain TeX including 1 PostScript figure, UTF-307-10/9
Single versus splinted short implants at sinus augmented sites: A systematic review and meta-analysis.
OBJECTIVE
This review primarily evaluated the success, survival and failure rates of implants shorter than 10 mm restored with single-unit or splinted fixed dental prostheses in maxillary sinus augmented sites.
MATERIAL AND METHODS
Two reviewers independently performed the systematic search of electronic databases, including MEDLINE, EMBASE and CENTRAL, up to September 2019 with no language restriction. A supplemental hand search consisted of screening 13 journals. The inclusion criteria were: primary studies reporting implant, prosthetic and patient-reported outcome measures (PROMs) of extra-short and short implants placed in conjunction with sinus floor elevation in partially dentate patients, restored with single- and splinted-crowns for direct comparison, with a minimal 1-year follow-up. Weighted arithmetic mean (WAM) of the implant survival was performed according to the type of prosthesis. This was confirmed by using Review Manager software to perform meta-analysis.
RESULTS
Two observational studies reporting on 106 tapered, press-fit, sintered porous-surfaced implants with a length ranging from 5 mm to 9 mm were included in this systematic review. Of these, 20 and 86 implants were restored with single and splinted prostheses, respectively. The risk ratio (RR) was 1.16 (95% CI: .31-4.30, p = .58, I² = 0%) for individually restored implants failure when compared to splinted implants, indicating that short dental implants restored with single crowns could have a 16% higher possibility of failure if compared to implants with splinted crowns. The heterogeneity value was not statistically significative (p = .58). No statistical difference in the implant survival rate of the two types of analysed prostheses was observed after WAM (p= .923). The level of evidence for the included studies ranged from low (4) to fair (2B).
CONCLUSION
Similar clinical outcomes up to a 9-year follow-up were observed in single and splinted porous-surfaced implants shorter than 10 mm located in sites with sinus lift. However, the conclusion shall be interpreted with caution due to the level of evidence and limited number of included studies included in this systematic review
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