33 research outputs found
High-temperature oxygen non-stoichiometry, conductivity and structure in strontium-rich nickelates La2-xSrxNiO4-\delta (x = 1 and 1.4)
Oxygen nonstoichiometry, electrical conductivity and thermal expansion of La2
xSrxNiO4-\delta phases with high levels of strontium substitution (1 =< x =<
1.4) have been investigated in air and oxygen atmosphere in the temperature
range 20-1050 degrees C. These phases retain the K2NiF4-type structure of
La2NiO4 (tetragonal, space group I4/mmm). The oxygen vacancy fraction was
determined independently from thermogravimetric and neutron diffraction
experiments, and is found to increase considerably on heating. The electrical
resistivity, thermal expansion and cell parameters with temperature show
peculiar variations with temperature, and differ notably from
La2NiO4\delta in this respect. These variations are tentatively correlated
with the evolution of nickel oxidation state, which crosses from a Ni3+/Ni4+ to
a Ni2+/Ni3+ equilibrium on heating
Cluster Dynamical Mean Field Theories
Cluster Dynamical Mean Field Theories are analyzed in terms of their
semiclassical limit and their causality properties, and a translation invariant
formulation of the cellular dynamical mean field theory, PCDMFT, is presented.
The semiclassical limit of the cluster methods is analyzed by applying them to
the Falikov-Kimball model in the limit of infinite Hubbard interaction U where
they map to different classical cluster schemes for the Ising model.
Furthermore the Cutkosky-t'Hooft-Veltman cutting equations are generalized and
derived for non translation invariant systems using the Schwinger-Keldysh
formalism. This provides a general setting to discuss causality properties of
cluster methods. To illustrate the method, we prove that PCDMFT is causal while
the nested cluster schemes (NCS) in general and the pair scheme in particular
are not. Constraints on further extension of these schemes are discussed.Comment: 26 page
The Lake Baikal neutrino experiment
We rewiew the present status of the Baikal Neutrino Project and present the
results of a search for high energy neutrinos with the detector intermediate
stage NT-96.Comment: 3 pages, 2 figures, to appear in the Proceedings of Sixth
International Workshop on Topics in Astroparticle and Underground Physics
(TAUP99), September 6-10, 1999, Pais, Franc
Primary CR energy spectrum and mass composition by the data of Tunka-133 array
The Cherenkov light array for the registration of extensive air showers (EAS) Tunka-133 collected data during 5 winter seasons from 2009 to 2014. The differential energy spectrum of all particles and the dependence of the average maximum depth on the energy in the range of 6 ⋅ 1015–1018 eV measured for 1540 hours of observation are presented
Primary CR energy spectrum and mass composition by the data of Tunka-133 array
The Cherenkov light array for the registration of extensive air showers (EAS) Tunka-133 collected data during 5 winter seasons from 2009 to 2014. The differential energy spectrum of all particles and the dependence of the average maximum depth on the energy in the range of 6 ⋅ 1015–1018 eV measured for 1540 hours of observation are presented