1,454 research outputs found
Cross-correlating the Thermal Sunyaev-Zel'dovich Effect and the Distribution of Galaxy Clusters
We present the analytical formulas, derived based on the halo model, to
compute the cross-correlation between the thermal Sunyaev-Zel'dovich (SZ)
effect and the distribution of galaxy clusters. By binning the clusters
according to their redshifts and masses, this cross-correlation, the so-called
stacked SZ signal, reveals the average SZ profile around the clusters. The
stacked SZ signal is obtainable from a joint analysis of an
arcminute-resolution cosmic microwave background (CMB) experiment and an
overlapping optical survey, which allows for detection of the SZ signals for
clusters whose masses are below the individual cluster detection threshold. We
derive the error covariance matrix for measuring the stacked SZ signal, and
then forecast for its detection from ongoing and forthcoming combined
CMB-optical surveys. We find that, over a wide range of mass and redshift, the
stacked SZ signal can be detected with a significant signal to noise ratio
(total S/N \gsim 10), whose value peaks for the clusters with intermediate
masses and redshifts. Our calculation also shows that the stacking method
allows for probing the clusters' SZ profiles over a wide range of scales, even
out to projected radii as large as the virial radius, thereby providing a
promising way to study gas physics at the outskirts of galaxy clusters.Comment: 11 pages, 6 figures, 3 tables, minor revisions reflect PRD published
versio
Heavy Right-Handed Neutrinos and Dark Matter in the CMSSM
We perform a systematic study of the effects of the type-I seesaw mechanism
on the dark matter abundance in the constrained supersymmetric standard model
(CMSSM) which includes three right-handed neutrinos (the CMSSM). For large
values of , we exploit the effects of large neutrino Yukawa
couplings on the renormalization group (RG) evolution of the up-type Higgs. In
particular, we show that the focus point scale can greatly exceed the
electroweak scale resulting in the absence of a focus point region for which
the relic density of neutralinos is within the range determined by WMAP. We
also discuss the effects of the right-handed neutrinos on the so-called funnel
region, where the relic density is controlled by s-channel annihilations
through a heavy Higgs. For small values of , we discuss the
possibility of sneutrino coannihilation regions with an emphasis on the
suppression of the left-handed slepton doublet masses due to the neutrino
Yukawa coupling. We consider two types of toy models consistent with either the
normal or inverted hierarchy of neutrino masses.Comment: 18 pages, 7 figures, references and a footnote added, typos correcte
Synthesis of magnesium ZIF-8 from Mg(BH₄)₂.
Porous Mg(2-methyl imidazolate)2 (Mg-ZIF-8) was synthesised from Mg(BH4)2 as a precursor under an Ar atmosphere. It possesses an uncommon tetrahedral Mg(2+)-N coordination geometry that is stabilised by the formation of a framework, and it exhibits a Brunauer-Emmett-Teller surface area greater than 1800 m(2) g(-1)
Positrons in Cosmic Rays from Dark Matter Annihilations for Uplifted Higgs Regions in MSSM
We point out that there are regions in the MSSM parameter space which
successfully provide a dark matter (DM) annihilation explanation for observed
positron excess (e.g. PAMELA), while still remaining in agreement with all
other data sets. Such regions (e.g. the uplifted Higgs region) can realize an
enhanced neutralino DM annihilation dominantly into leptons via a Breit-Wigner
resonance through the CP-odd Higgs channel. Such regions can give the proper
thermal relic DM abundance, and the DM annihilation products are compatible
with current antiproton and gamma ray observations. This scenario can succeed
without introducing any additional degrees of freedom beyond those already in
the MSSM.Comment: 11 pages, 9 figure
Orbital-dependent modifications of electronic structure across magneto-structural transition in BaFe2As2
Laser angle-resolved photoemission spectroscopy (ARPES) is employed to
investigate the temperature (T) dependence of the electronic structure in
BaFe2As2 across the magneto-structural transition at TN ~ 140 K. A drastic
transformation in Fermi surface (FS) shape across TN is observed, as expected
by first-principles band calculations. Polarization-dependent ARPES and band
calculations consistently indicate that the observed FSs at kz ~ pi in the
low-T antiferromagnetic (AF) state are dominated by the Fe3dzx orbital, leading
to the two-fold electronic structure. These results indicate that
magneto-structural transition in BaFe2As2 accompanies orbital-dependent
modifications in the electronic structure.Comment: 13 pages, 4 figures. accepted by Physical Review Letter
Survival of technologies: an evolutionary game approach
This paper models technology adoption as an evolutionary and asymmetric game based on a pairwise contest involving two populations, firms and consumers. First, externalities are considered only on the supply side, leading to the usual results found in the recent economic literature on the subject: path dependence, lock-in, and the possibility ofselecting inferior technology. Next externalities are introduced on the demand side, which in Leibenstein's classic paper leads to bandwagon and snob effects, and interactions between supply and demand are examined
Parameterizing the Power Spectrum: Beyond the Truncated Taylor Expansion
The power spectrum is traditionally parameterized by a truncated Taylor
series: . It is
reasonable to truncate the Taylor series if , but
it is not if . We argue that there is no good
theoretical reason to prefer , and show that current
observations are consistent with even for
. Thus, there are regions of parameter space, which are both
theoretically and observationally relevant, for which the traditional truncated
Taylor series parameterization is inconsistent, and hence it can lead to
incorrect parameter estimations. Motivated by this, we propose a simple
extension of the traditional parameterization, which uses no extra parameters,
but that, unlike the traditional approach, covers well motivated inflationary
spectra with . Our parameterization therefore covers not only
standard-slow-roll inflation models but also a much wider class of inflation
models. We use this parameterization to perform a likelihood analysis for the
cosmological parameters.Comment: References added. Typo correcte
Scale and externalities in an evolutionary game model
Este artigo discute o processo de seleção de escalas de produção em um modelo de jogo evolucionário no qual os requisitos de racionalidade são muito limitados
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