[신간의 별자리x] 우리/미술, 그리고 ‘슬픔의 박물관’

We present distance measurements to 71 high redshift type Ia supernovae discovered during the first year of the 5-year Supernova Legacy Survey (SNLS). These events were detected and their multi-color light-curves measured using the MegaPrime/MegaCam instrument at the Canada-France-Hawaii Telescope (CFHT), by repeatedly imaging four one-square degree fields in four bands. Follow-up spectroscopy was performed at the VLT, Gemini and Keck telescopes to confirm the nature of the supernovae and to measure their redshift. With this data set, we have built a Hubble diagram extending to z = 1, with all distance measurements involving at least two bands. Systematic uncertainties are evaluated making use of the multiband photometry obtained at CFHT. Cosmological fits to this first year SNLS Hubble diagram give the following results: {Omega}{sub M} = 0.263 {+-} 0.042 (stat) {+-} 0.032 (sys) for a flat {Lambda}CDM model; and w = -1.023 {+-} 0.090 (stat) {+-} 0.054 (sys) for a flat cosmology with constant equation of state w when combined with the constraint from the recent Sloan Digital Sky Survey measurement of baryon acoustic oscillations.

The Supernova Legacy Survey: Measurement of Omega_m, Omega_l and w from the First Year Data Set

The universe is so much bigger than the bit we can see in our observable bubble   and we know nothing about what lies out there in the cosmos. The challenge is so  much bigger than is shown on this chart and it is evident that we really only  understand a tiny fraction of the whole cosmos.  Theories ​for Dark Energy have been around for a long time but we still have no  satisfactory explanation. None of the theories are adequate, some are clearly wrong    – an error of 10^120 is a really big miss!  Scott Dodelson of Carnegie Mellon University, one of the lead scientists behind the  Dark Energy Survey’s new map of cosmic structure says:

Dark Energy

Der speziellen Relativitatstheorie liegt folgendes Postulat zugrunde, welchem auch durch die Galilei-Newtonsche Mechanik Genuge geleistet wird: Wird ein Koordinatensystem K so gewahlt, das in bezug auf dasselbe die physikalischen Gesetze in ihrer einfachsten Form gelten, so gelten dieselben Gesetze auch in Bezug auf jedes andere Koordinatensystem K′, das relativ zu K in gleichformiger Translationsbewegung begriffen ist. Dieses Postulat nennen wir „spezielles Relativitatsprinzip“. Durch das Wort „speziell“ soll angedeutet werden, das das Prinzip auf den Fall beschrankt ist, das K′ eine gleichformige Translationsbewegung gegen K ausfuhrt, das sich aber die Gleichwertigkeit von K′ und K nicht auf den Fall ungleichformiger Bewegung von K′ gegen K erstreckt.

Die Grundlage der allgemeinen Relativitätstheorie

We present measurements of galaxy clustering from the Baryon Oscillation Spectroscopic Survey (BOSS), which is part of the Sloan Digital Sky Survey III (SDSS-III). These use the Data Release 9 (DR9) CMASS sample, which contains 264 283 massive galaxies covering 3275 square degrees with an effective redshift z = 0.57 and redshift range 0.43 < z < 0.7. Assuming a concordance ΛCDM cosmological model, this sample covers an effective volume of 2.2 Gpc, and represents the largest sample of the Universe ever surveyed at this density, n̄ ≈ 3× 10−4h−3Mpc. We measure the angle-averaged galaxy correlation function and power spectrum, including density-field reconstruction of the baryon acoustic oscillation (BAO) feature. The acoustic features are detected at a significance of 5σ in both the correlation function and power spectrum. Combining with the SDSS-II Luminous Red Galaxy Sample, the detection significance increases to 6.7σ. Fitting for the position of the acoustic features measures the distance to z = 0.57 relative to the sound horizonDV /rs = 13.67±0.22 at z = 0.57. Assuming a fiducial sound horizon of 153.19 Mpc, which matches cosmic microwave background constraints, this corresponds to a distance DV (z = 0.57) = 2094 ± 34 Mpc. At 1.7 per cent, this is the most precise distance constraint ever obtained from a galaxy survey. We place this result alongside previous BAO measurements in a cosmological distance ladder and find excellent agreement with the current supernova measurements. We use these distance measurements to constrain various cosmological models, finding continuing support for a flat Universe with a cosmological constant.

SDSS-III Baryon Oscillation Spectroscopic Survey: baryon acoustic oscillations in the data Release 9 spectroscopic galaxy sample.

We have analyzed the Barrow holographic dark energy (BHDE) in the framework of the flat FLRW Universe by considering the various estimations of Barrow exponent $\triangle$. Here we define BHDE, by applying the usual holographic principle at a cosmological system, for utilizing the Barrow entropy rather than the standard Bekenstein-Hawking. To understand the recent accelerated expansion of the universe, considering the Hubble horizon as the IR cut-off. The cosmological parameters, especially the density parameter ($\Omega_{_D}$), the equation of the state parameter ($\omega_{_D}$), energy density ($\rho_{_{D}}$) and the deceleration parameter($q$) are studied in this manuscript and found the satisfactory behaviors. Moreover, we additionally focus on the two geometric diagnostics, the statefinder $(r,s)$ and $O_{m}(z)$ to discriminant BHDE model from the $\Lambda CDM$ model. Here we determined and plotted the trajectories of evolution for statefinder $(r, s)$, $(r,q)$ and $O_{m}(z)$ diagnostic plane to understand the geometrical behavior of the BHDE model by utilizing Planck 2018 observational information. Finally, we have explored the new Barrow exponent $\triangle$, which strongly affects the dark energy equation of state that can lead it to lie in the quintessence regime, phantom regime, and exhibits the phantom-divide line during the cosmological evolution.

Barrow HDE model for statefinder diagnostic in FLRW universe

Tsallis holographic dark energy in FRW universe with time varying deceleration parameter

Statefinder hierarchy model for the Barrow holographic dark energy

In this study, we have investigated the dark energy behavior of the viscus-fluid in f(Q)-gravity in a flat, isotropic and homogeneous Friedmann–Lemaitre–Robertson–Walker (FLRW) space-time metric. W...

Dark energy nature of viscus universe in f(Q)-gravity with observational constraints

Xu et al. (Eur. Phys. J. C 79 (2019) 708) have anticipated the theory of Gravity. The modified study of f(Q,T) is elucidated here as Cosmological model. In it the action holds a role as a capriciou...

Archana Dixit

Papers

Barrow HDE model for statefinder diagnostic in FLRW universe

Tsallis holographic dark energy in FRW universe with time varying deceleration parameter

Statefinder hierarchy model for the Barrow holographic dark energy

Dark energy nature of viscus universe in f(Q)-gravity with observational constraints

The models of transit cosmology along with observational constriction in f(Q,T) gravity