303 research outputs found
"Peeling property" for linearized gravity in null coordinates
A complete description of the linearized gravitational field on a flat
background is given in terms of gauge-independent quasilocal quantities. This
is an extension of the results from gr-qc/9801068. Asymptotic spherical
quasilocal parameterization of the Weyl field and its relation with Einstein
equations is presented. The field equations are equivalent to the wave
equation. A generalization for Schwarzschild background is developed and the
axial part of gravitational field is fully analyzed. In the case of axial
degree of freedom for linearized gravitational field the corresponding
generalization of the d'Alembert operator is a Regge-Wheeler equation. Finally,
the asymptotics at null infinity is investigated and strong peeling property
for axial waves is proved.Comment: 27 page
Orthorhombic phase of LaBiNiO studied by first principles
The aim of presented first principles study of LaBiNiO
is to investigate electronic structure of orthorhombic phase Pbnm. The
calculations show that metallicity and magnetism of the system are strongly
related with hybridization between Ni 3d and O 2p. To improve the quality of
the electronic structure description of the system, especially the treatment of
correlation for the Ni 3d, we employ GGA, LDA, and GGA+U, LDA+U. The LSDA
results give good agreement with experiment. Thus, the screening effects
originating from the hybridized 3d and O 2p electrons are sufficiently strong
that they reduce the electronic correlations in the
LaBiNiO, making it a weakly correlated metal.Comment: 4 pages, 3 figures; The European Conference Physics of Magnetism
2017, submitted to Acta Physica Polonica
Energy and angular momentum of the weak gravitational waves on the Schwarzschild background -- quasilocal gauge-invariant formulation
It is shown that the axial and polar perturbations of the spherically
symmetric black hole can be described in a gauge-invariant way. The reduced
phase space describing gravitational waves outside of the horizon is described
by the gauge-invariant quantities. Both degrees of freedom fulfill generalized
scalar wave equation. For the axial degree of freedom the radial part of the
equation corresponds to the Regge-Wheeler result (Phys. Rev. 108, 1063-1069
(1957)) and for the polar one we get Zerilli result (Phys. Rev. D2, 2141-2160
(1970)), see also Chandrasekhar (The Mathematical Theory of Black
Holes,(Clarendon Press Oxford, 1983)), Moncrief (Annals of Physics 88, 323-342
(1974)) for both. An important ingredient of the analysis is the concept of
quasilocality which does duty for the separation of the angular variables in
the usual approach. Moreover, there is no need to represent perturbations by
normal modes (with time dependence ), we have fields in spacetime
and the Cauchy problem for them is well defined outside of the horizon. The
reduced symplectic structure explains the origin of the axial and polar
invariants. It allows to introduce an energy and angular momentum for the
gravitational waves which is invariant with respect to the gauge
transformations. Both generators represent quadratic approximation of the ADM
nonlinear formulae in terms of the perturbations of the Schwarzschild metric.
We also discuss the boundary-initial value problem for the linearized Einstein
equations on a Schwarzschild background outside of the horizon.Comment: 23 page
Band gap stability in Kondo insulators
We report on magnetic measurements and electronic structure investigations
of CeNiSn and CeRhSb. Both belong to the group of Kondo insulators.
The magnetic susceptibility shows the nonmagnetic ground state for
these compounds and their alloys. The 3d X-ray photoemission spectroscopy
spectra show evidence for the mixed valence state of Ce in CeRhSb alloys, as
also seen for CeNiSn, whereas the spectra for the La substituted (Ce,La)NiSn
compounds show only evidence for a pure Ce 3+ ground state. We suggest
the presence of Kondo-hole states in (Ce,La)RhSb. The location of the pseudogap
in CeRhSb varies with the number of free electron, the valence of Ce,
and the f—d hybridization. We discuss the similar crystallographic properties
and the closed electronic structures of ZrNiSn-type semi-Heusler alloys
and CeNiSn-type Kondo insulators
Electronic structure and thermodynamic properties of RNi_{5}Sn (R = La, Ce, Pr, Nd) compounds
The electronic structure, pressure and temperature dependence of thermodynamic properties of RNi5Sn (R = La, Ce, Pr, Nd) compounds are calculated by ab initio full potential local orbital minimum-base(ver. 9 and ver. 14) method. These compounds crystallize in the hexagonal crystal structure (space group P6c/mmc, No. 194). The band calculations were performed in the scalar-relativistic mode for the exchange correlation potentials in the form: of the Perdew-Burke-Ernzerhof general gradient approximation. In this work we present the band structures of LaNi5Sn, CeNi5Sn, NdNi5Sn and PrNi5Sn compounds. The thermodynamic properties (bulk modulus, Debye temperature) are calculated in the Debye-Grüneisen model using the equation of states in the form of Birch-Murnaghan, Poirier-Tarantola and Vinet. Our results have shown that values of thermodynamic properties depend on the method of calculations
Electronic structure of CePtIn and LaPtIn compounds
The electronic structure of the ternary RPtIn (R = La, Ce) compounds, which crystallize in the hexagonal
ZrNiAl-type structure, was studied by X-ray photoelectron spectroscopy measurements and calculation using the
ab initio methods (linear mu n-tin orbital in the atomic sphere approximation, full potential linear mu n-tin
orbital, full potential linear orbital). The results showed that the valence band in these compounds is formed by
the Pt 5d and In 5s and 5p states. The band calculations with spin orbit coupling have shown that the Ce 4f
peaks consist of two peaks above the Fermi level that correspond to the Ce 4f7=2 and 4f5=2 doublet and wide peaks corresponding to the La 4f states. The analysis of Ce 3d spectra on the basis of the Gunnarsson Schönhammer model gives hybridization of 4f orbitals with the conduction electron band equal to 170 meV
Electronic structure of CePtIn and LaPtIn compounds
The electronic structure of the ternary RPtIn (R = La, Ce) compounds, which crystallize in the hexagonal
ZrNiAl-type structure, was studied by X-ray photoelectron spectroscopy measurements and calculation using the
ab initio methods (linear mu n-tin orbital in the atomic sphere approximation, full potential linear mu n-tin
orbital, full potential linear orbital). The results showed that the valence band in these compounds is formed by
the Pt 5d and In 5s and 5p states. The band calculations with spin orbit coupling have shown that the Ce 4f
peaks consist of two peaks above the Fermi level that correspond to the Ce 4f7=2 and 4f5=2 doublet and wide peaks corresponding to the La 4f states. The analysis of Ce 3d spectra on the basis of the Gunnarsson Schönhammer model gives hybridization of 4f orbitals with the conduction electron band equal to 170 meV
Conformal Yano-Killing tensor for the Kerr metric and conserved quantities
Properties of (skew-symmetric) conformal Yano--Killing tensors are reviewed.
Explicit forms of three symmetric conformal Killing tensors in Kerr spacetime
are obtained from the Yano--Killing tensor. The relation between spin-2 fields
and solutions to the Maxwell equations is used in the construction of a new
conserved quantity which is quadratic in terms of the Weyl tensor. The formula
obtained is similar to the functional obtained from the Bel--Robinson tensor
and is examined in Kerr spacetime. A new interpretation of the conserved
quantity obtained is proposed.Comment: 29 page
Uniqueness of the mass in the radiating regime
The usual approaches to the definition of energy give an ambiguous result for
the energy of fields in the radiating regime. We show that for a massless
scalar field in Minkowski space-time the definition may be rendered unambiguous
by adding the requirement that the energy cannot increase in retarded time. We
present a similar theorem for the gravitational field, proved elsewhere, which
establishes that the Trautman-Bondi energy is the unique (up to a
multiplicative factor) functional, within a natural class, which is monotonic
in time for all solutions of the vacuum Einstein equations admitting a smooth
``piece'' of conformal null infinity Scri.Comment: 8 pages, revte
Hybridization gap in some ternary f-electron and d-electron intermetallics
In this work we have discussed electronic structure, structural and magnetic properties of the CeMX-type compounds, where M is a transition metal and X is an sp element. The main goal of this presentation is to find
the influence of metal M on the coherent gap formation at the Fermi level in the Ce-Kondo insulators. We also discuss a similar semiconductor-like resistance anomaly of Fe2TiSn and CeNiSn-type Kondo insulators
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