The article presents a generalization of Sherman-Morrison-Woodbury (SMW) formula for the inversion of a matrix of the form A+sum(U)k)*V(k),k=1..N).
Temperature dependent measurements of 57Fe Mossbauer spectra on CaFe2As2 single crystals in the tetragonal and collapsed tetragonal phases are reported. Clear features in the temperature dependencies of the isomer shift, relative spectra area and qua
drupole splitting are observed at the transition from the tetragonal to the collapsed tetragonal phase. From the temperature dependent isomer shift and spectral area data, an average stiffening of the phonon modes in the collapsed tetragonal phase is inferred. The quadrupole splitting increases by ~25% on cooling from room temperature to ~100 K in the tetragonal phase and is only weakly temperature dependent at low temperatures in the collapsed tetragonal phase, in agreement with the anisotropic thermal expansion in this material. In order to gain microscopic insight about these measurements we perform ab initio density functional theory calculations of the electric field gradient and the electron density of CaFe2As2 in both phases. By comparing the experimental data with the calculations we are able to fully characterize the crystal structure of the samples in the collapsed-tetragonal phase through determination of the As z-coordinate. Based on the obtained temperature dependent structural data we are able to propose charge saturation of the Fe - As bond region as the mechanism behind the stabilization of the collapsed-tetragonal phase at ambient pressure.
Refined infrared magnetotransmission experiments have been performed in magnetic fields B up to 35 T on a series of multilayer epitaxial graphene samples. Following the main optical transition involving the n=0 Landau level (LL), we observe a new abs
orption transition increasing in intensity with magnetic fields B>26 T. Our analysis shows that this is a signature of the breaking of the SU(4) symmetry of the n=0 LL. Using a quantitative model, we show that the only symmetry-breaking scheme consistent with our experiments is a charge density wave (CDW).
Using N-body simulations, we measure the power spectrum of the effective dark matter density field, which is defined through the modified Poisson equation in $f(R)$ cosmologies. We find that when compared to the conventional dark matter power spectru
m, the effective power spectrum deviates more significantly from the $Lambda$CDM model. For models with $f_{R0}=-10^{-4}$, the deviation can exceed 150% while the deviation of the conventional matter power spectrum is less than 50%. Even for models with $f_{R0}=-10^{-6}$, for which the conventional matter power spectrum is very close to the $Lambda$CDM prediction, the effective power spectrum shows sizeable deviations. Our results indicate that traditional analyses based on the dark matter density field may seriously underestimate the impact of $f(R)$ gravity on galaxy clustering. We therefore suggest the use of the effective density field in such studies. In addition, based on our findings, we also discuss several possible methods of making use of the differences between the conventional and effective dark matter power spectra in $f(R)$ gravity to discriminate the theory from the $Lambda$CDM model.
In this work we apply generalized A. Sparavigna method (use of freely available softwares (programs), e.g. http://www.sollumis.com/, http://suncalc.net/#/44.557,22.0265,13/2014.12.29/09:22, http://universimmedia.pagesperso-orange.fr/geo/loc.htm, http
://www.spectralcalc.com/solar_calculator/solar_position.php and http://www.fourmilab.ch/cgi-bin/Yourhorizon) for analysis of possible astronomical characteristics of three remarkable Giza, i.e. Cheops, Chephren and Mikerin pyramids. Concretely, we use mentioned programs for determination of the Giza plateau longitude and latitude, moments of the sunrise and sunset for any day at the Giza plateau, and, simulation of the sky horizon above Giza plateau in any moment of any day, respectively. In this way we obtain a series of the figures which unambiguously imply the following original results. Any of three remarkable Giza pyramids (Cheops, Chephren and Mikerin) holds only one characteristic edge between apex and north-west vertex of the base so that sunrise direction overlap almost exactly this edge during 28. October. (There is a small declination of the overlap date by Chephren pyramid by which overlap date is approximately 23. or 24. October.) Simultaneously, in the sunset moment for the same day, Taurus constellation (corresponding to holly bull in ancient Egypt mythology) appears at a point at the very eastern boundary of the sky horizon.
In this work we consider some old hypotheses according to which remarkable mesolithic village Lepenski Vir (9500 -- 5500 BC) at the right (nearly west) Danube riverside in the Iron gate in Serbia was an ancient (one of the oldest) Sun observatory. We
use method recently suggested by A. C. Sparavigna, concretely we use freely available software or local Sun radiation direction simulation computer programs. In this way we obtain and discuss pictures of the sunrise in the Lepenski Vir during winter and summer solstice and spring and autumn equinox in relation to position of the mountains, especially Treskavac (Trescovat) and Kukuvija at left (nearly east) Danube riverside (in Romania). While mountain Kukuvija represents really the marker for the Sun in date of the winter solstice, mountain Treskavac, in despite to usual opinions, does not represent a real marker for the Sun in date of the summer solstice. Sun rises behind Treskavac, roughly speaking, between 22.April and 1. May. It corresponds to year period when heliacal rising of the Pleiades constellation occurs, which by many ancient cultures, e.g. Celts of northern Europe, denotes very beginning of the year. All this, in common with some archeological facts (house-shrine No.47 in the Lepenski Vir holds seven signs beside hearth which would correspond to the seven Pleiades stars), opens a possibility that Lepenski Vir was an ancient Pleiades constellation observatory.
We introduce the idea of {it effective} dark matter halo catalog in $f(R)$ gravity, which is built using the {it effective} density field. Using a suite of high resolution N-body simulations, we find that the dynamical properties of halos, such as th
e distribution of density, velocity dispersion, specific angular momentum and spin, in the effective catalog of $f(R)$ gravity closely mimic those in the $Lambda$CDM model. Thus, when using effective halos, an $f(R)$ model can be viewed as a $Lambda$CDM model. This effective catalog therefore provides a convenient way for studying the baryonic physics, the galaxy halo occupation distribution and even semi-analytical galaxy formation in $f(R)$ cosmologies.
We investigate the connection between Gravitys Rainbow and Horava-Lifshitz gravity, since both theories incorporate a modification in the UltraViolet regime which improves their quantum behavior at the cost of the Lorentz invariance loss. In particul
ar, extracting the Wheeler-De Witt equations of the two theories in the case of Friedmann-Lemaitre-Robertson-Walker and spherically symmetric geometries, we establish a correspondence that bridges them.
The magnetic network observed on the solar surface harbors a sizable fraction of the total quiet Sun flux. However, its origin and maintenance are not well known. Here we investigate the contribution of internetwork magnetic fields to the network flu
x. Internetwork fields permeate the interior of supergranular cells and show large emergence rates. We use long-duration sequences of magnetograms acquired by Hinode and an automatic feature tracking algorithm to follow the evolution of network and internetwork flux elements. We find that 14% of the quiet Sun flux is in the form of internetwork fields, with little temporal variations. Internetwork elements interact with network patches and modify the flux budget of the network, either by adding flux (through merging processes) or by removing it (through cancellation events). Mergings appear to be dominant, so the net flux contribution of the internetwork is positive. The observed rate of flux transfer to the network is 1.5 x 10^24 Mx day^-1 over the entire solar surface. Thus, the internetwork supplies as much flux as is present in the network in only 9-13 hours. Taking into account that not all the transferred flux is incorporated into the network, we find that the internetwork would be able to replace the entire network flux in approximately 18-24 hours. This renders the internetwork the most important contributor to the network, challenging the view that ephemeral regions are the main source of flux in the quiet Sun. About 40% of the total internetwork flux eventually ends up in the network.
