scholarly journals Dark energy in the environments of the Local Group, the M 81 group, and the CenA group: the normalized Hubble diagram

2008 ◽  
Vol 483 (2) ◽  
pp. 383-387 ◽  
Author(s):  
P. Teerikorpi ◽  
A. D. Chernin ◽  
I. D. Karachentsev ◽  
M. J. Valtonen
Keyword(s):  
Dark Energy ◽  
Local Group ◽  
Hubble Diagram

scholarly journals Observations of Type Ia Supernovae and Challenges for Cosmology

2005 ◽  
Vol 192 ◽  
pp. 525-533
Author(s):  
Weidong Li ◽  
Alexei V. Filippenko
Keyword(s):  
Dark Energy ◽  
Light Curve ◽  
Rise Time ◽  
Accelerating Universe ◽  
Type Ia Supernovae ◽  
Hubble Diagram ◽  
High Quality ◽  
Type Ia ◽  
Secondary Parameter ◽  
Ia Supernovae

SummaryObservations of Type Ia supernovae (SNe Ia) reveal correlations between their luminosities and light-curve shapes, and between their spectral sequence and photometric sequence. Assuming SNe Ia do not evolve at different redshifts, the Hubble diagram of SNe Ia may indicate an accelerating Universe, the signature of a cosmological constant or other forms of dark energy. Several studies raise concerns about the evolution of SNe Ia (e.g., the peculiarity rate, the rise time, and the color of SNe Ia at different redshifts), but all these studies suffer from the difficulties of obtaining high-quality spectroscopy and photometry for SNe Ia at high redshifts. There are also some troubling cases of SNe Ia that provide counter examples to the observed correlations, suggesting that a secondary parameter is necessary to describe the whole SN Ia family. Understanding SNe Ia both observationally and theoretically will be the key to boosting confidence in the SN Ia cosmological results.

scholarly journals The Djorgovski–Gurzadyan dark energy integral equation and the Hubble diagram

2020 ◽  
Vol 642 ◽  
pp. L9
Author(s):  
H.G. Khachatryan ◽  
A. Stepanian
Keyword(s):  
Integral Equation ◽  
Dark Energy ◽  
Cold Dark Matter ◽  
Gamma Ray ◽  
Hubble Diagram ◽  
Dark Energy Density ◽  
Cold Dark Matter Model ◽  
Matter Model ◽  
Burst Data ◽  
Dark Matter Model

We consider the observational aspects of the value of dark energy density from quantum vacuum fluctuations based initially on the Gurzadyan–Xue model. We reduce the Djorgovski–Gurzadyan integral equation to a differential equation for the co-moving horizon and then, by means of the obtained explicit form for the luminosity distance, we construct the Hubble diagram for two classes of observational samples. For supernova and gamma-ray burst data we show that this approach provides viable predictions for distances up to z ≃ 9, quantitatively at least as good as those provided by the Λ cold dark matter model. The Hubble parameter dependence H(z) of the two models also reveals mutual crossing at z = 0.4018, the interpretation of which is less evident.

scholarly journals Studying Type II supernovae as cosmological standard candles using the Dark Energy Survey

2020 ◽  
Vol 495 (4) ◽  
pp. 4860-4892 ◽  
Author(s):  
T de Jaeger ◽  
L Galbany ◽  
S González-Gaitán ◽  
R Kessler ◽  
A V Filippenko ◽  
...  
Keyword(s):  
Dark Energy ◽  
High Redshift ◽  
Cosmological Parameters ◽  
Hubble Constant ◽  
Distance Modulus ◽  
Type Ii ◽  
Hubble Diagram ◽  
Dark Energy Survey ◽  
Spectroscopic Information ◽  
Energy Survey

ABSTRACT Despite vast improvements in the measurement of the cosmological parameters, the nature of dark energy and an accurate value of the Hubble constant (H0) in the Hubble–Lemaître law remain unknown. To break the current impasse, it is necessary to develop as many independent techniques as possible, such as the use of Type II supernovae (SNe II). The goal of this paper is to demonstrate the utility of SNe II for deriving accurate extragalactic distances, which will be an asset for the next generation of telescopes where more-distant SNe II will be discovered. More specifically, we present a sample from the Dark Energy Survey Supernova Program (DES-SN) consisting of 15 SNe II with photometric and spectroscopic information spanning a redshift range up to 0.35. Combining our DES SNe with publicly available samples, and using the standard candle method (SCM), we construct the largest available Hubble diagram with SNe II in the Hubble flow (70 SNe II) and find an observed dispersion of 0.27 mag. We demonstrate that adding a colour term to the SN II standardization does not reduce the scatter in the Hubble diagram. Although SNe II are viable as distance indicators, this work points out important issues for improving their utility as independent extragalactic beacons: find new correlations, define a more standard subclass of SNe II, construct new SN II templates, and dedicate more observing time to high-redshift SNe II. Finally, for the first time, we perform simulations to estimate the redshift-dependent distance-modulus bias due to selection effects.

scholarly journals Weighing the Local Group in the presence of dark energy

2013 ◽  
Vol 436 (1) ◽  
pp. L45-L48 ◽  
Author(s):  
C. Partridge ◽  
O. Lahav ◽  
Y. Hoffman
Keyword(s):  
Dark Energy ◽  
Local Group

scholarly journals Problems with the Current Cosmological Paradigm

2005 ◽  
Vol 216 ◽  
pp. 398-408
Author(s):  
T. Shanks
Keyword(s):  
Dark Matter ◽  
Dark Energy ◽  
Power Spectrum ◽  
Cold Dark Matter ◽  
Hubble Diagram ◽  
Dark Energy Density ◽  
Λcdm Model ◽  
Scale Error ◽  
Standard Cosmological Model ◽  
Superstring Theories

We note that despite the apparent support for the ΛCDM model from the acoustic peaks of the CMB power spectrum and the SNIa Hubble diagram, the standard cosmological model continues to face several fundamental problems. First, the model continues to depend wholly on two pieces of undiscovered physics, namely dark energy and cold dark matter. Then, the implied dark energy density is so small that it is unstable to quantum correction and its size is fine-tuned to the almost impossible level of one part in ≈ 10102; it is also difficult to explain the coincidence between the dark energy, dark matter and baryon densities at the present day. Moreover, any model with a positive Λ also creates fundamental difficulties for superstring theories of quantum gravity. We also review the significant number of astrophysical observations which are now in contradiction with the ΛCDM model. on the grounds that the SNIa Hubble diagram is prone to evolutionary corrections and also that the CMB power spectrum may be contaminated by the effects of foreground ionised gas, we argue that the existence of such systematics could still allow more satisfactory, alternative, models to appear. We suggest that if H0 ≲ 50 kms--1Mpc--1 then a simpler, inflationary model with Ωbaryon = 1 might be allowed with no need for dark energy or cold dark matter. We note that the clear scale error between HST Cepheid and Tully-Fisher galaxy distances and also potential metallicity dependencies for both the Cepheid P-L relation and the SNIa Hubble diagram may mean that such a low value of H0 cannot yet be ruled out.

scholarly journals IS DARK ENERGY ABNORMALLY WEIGHTING?

2007 ◽  
Vol 16 (12b) ◽  
pp. 2587-2592 ◽  
Author(s):  
JEAN-MICHEL ALIMI ◽  
ANDRÉ FÜZFA
Keyword(s):  
General Relativity ◽  
Dark Energy ◽  
Time Variation ◽  
Gravitational Constant ◽  
Cosmic Acceleration ◽  
Hubble Diagram ◽  
Ordinary Matter ◽  
Gauge Interaction

We investigate the possibility that dark energy does not couple to gravitation in the same way as ordinary matter, yielding a violation of the weak and strong equivalence principles on cosmological scales. We build a transient mechanism in which gravitation is pushed away from general relativity (GR) by a Born–Infeld (BI) gauge interaction acting as an "abnormally weighting (dark) energy" (AWE). This mechanism accounts for the Hubble diagram of far-away supernovae by cosmic acceleration and time variation of the gravitational constant while accounting naturally for the present tests on GR.

scholarly journals Features in the dark energy equation of state and modulations in the Hubble diagram

2006 ◽  
Vol 74 (8) ◽  
Author(s):  
Jun-Qing Xia ◽  
Gong-Bo Zhao ◽  
Hong Li ◽  
Bo Feng ◽  
Xinmin Zhang
Keyword(s):  
Dark Energy ◽  
Equation Of State ◽  
Energy Equation ◽  
Hubble Diagram

scholarly journals A new comparison between holographic dark energy and standard $$\varLambda $$-cosmology in the context of cosmography method

2021 ◽  
Vol 81 (7) ◽  
Author(s):  
Saeed Pourojaghi ◽  
Mohammad Malekjani
Keyword(s):  
Dark Energy ◽  
Hubble Parameter ◽  
Gamma Ray ◽  
Holographic Dark Energy ◽  
Error Function ◽  
Hubble Diagram ◽  
Type Ia ◽  
Independent Technique ◽  
Model Independent ◽  
Ia Supernovae

AbstractThe cosmography method is a model-independent technique used to reconstruct the Hubble expansion of the Universe at low redshifts. In this method, using the Hubble diagrams from Type Ia Supernovae (SNIa) in Pantheon catalog, quasars and Gamma-Ray Bursts (GRB), we put observational constraints on the cosmographic parameters in holographic dark energy (HDE) and concordance $$\varLambda $$ Λ CDM models by minimizing the error function $$\chi ^2$$ χ 2 based on the statistical Markov Chain Monte Carlo (MCMC) algorithm. Then, we compare the results of the models with the results of the model-independent cosmography method. Except for the Pantheon sample, we observe that there is a big tension between standard cosmology and Hubble diagram observations, while the HDE model remains consistent in all cases. Then we use different combinations of Hubble diagram data to reconstruct the Hubble parameter of the model and compare it with the observed Hubble data. We observe that the Hubble parameter reconstructed from the model-independent cosmography method has the smallest deviation from the Hubble data and the $$\varLambda $$ Λ CDM (HDE) model has the largest (middle) deviation, especially when we keep the observational data point $$226^{+8.0}_{-0.8}$$ 226 - 0.8 + 8.0 at redshift $$z=2.36$$ z = 2.36 in the analysis. On the contrary, in the redshift $$z <1$$ z < 1 , we see that the compatibility of $$\varLambda $$ Λ CDM cosmology and observation is even better than the model independent cosmography method.

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