The State of the Universe: Cosmological Parameters 2002

The objective of the present paper is to investigate an almost-pseudo-Ricci symmetric FRW spacetime with a constant Ricci scalar in a dynamic cosmological term Λ(t) and equation of state (EoS) ω(t) scenario. Several cosmological parameters are calculated in this setting and thoroughly studied, which shows that the model satisfies the late-time accelerating expansion of the universe. We also examine all of the energy conditions to check our model’s self-stability.

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Physical Acceptability of the Renyi, Tsallis and Sharma-Mittal Holographic Dark Energy Models in the f(T,B) Gravity under Hubble’s Cutoff

Universe ◽

10.3390/universe7030067 ◽

2021 ◽

Vol 7 (3) ◽

pp. 67

Author(s):

Salim Harun Shekh ◽

Pedro H. R. S. Moraes ◽

Pradyumn Kumar Sahoo

Keyword(s):

Dark Energy ◽

Holographic Dark Energy ◽

Cosmological Parameters ◽

Field Equations ◽

Eos Parameter ◽

Two Fluids ◽

Gravitational Field Equations ◽

Energy Models ◽

Different Types ◽

The Universe

In the present article, we investigate the physical acceptability of the spatially homogeneous and isotropic Friedmann–Lemâitre–Robertson–Walker line element filled with two fluids, with the first being pressureless matter and the second being different types of holographic dark energy. This geometric and material content is considered within the gravitational field equations of the f(T,B) (where T is the torsion scalar and the B is the boundary term) gravity in Hubble’s cut-off. The cosmological parameters, such as the Equation of State (EoS) parameter, during the cosmic evolution, are calculated. The models are stable throughout the universe expansion. The region in which the model is presented is dependent on the real parameter δ of holographic dark energies. For all δ≥4.5, the models vary from ΛCDM era to the quintessence era.

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The State of the Universe

Physics Bulletin ◽

10.1088/0031-9112/32/2/032 ◽

1981 ◽

Vol 32 (2) ◽

pp. 50-50

Author(s):

R Hide

Keyword(s):

The State ◽

The Universe

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Standard sirens and dark sector with Gaussian process

EPJ Web of Conferences ◽

10.1051/epjconf/201816801008 ◽

2018 ◽

Vol 168 ◽

pp. 01008 ◽

Cited By ~ 1

Author(s):

Rong-Gen Cai ◽

Tao Yang

Keyword(s):

Monte Carlo ◽

Gaussian Process ◽

Gravitational Waves ◽

Binary Systems ◽

Cosmological Parameters ◽

Dark Sector ◽

Compact Binary ◽

Compact Binary Systems ◽

Process Methodology ◽

The Universe

The gravitational waves from compact binary systems are viewed as a standard siren to probe the evolution of the universe. This paper summarizes the potential and ability to use the gravitational waves to constrain the cosmological parameters and the dark sector interaction in the Gaussian process methodology. After briefly introducing the method to reconstruct the dark sector interaction by the Gaussian process, the concept of standard sirens and the analysis of reconstructing the dark sector interaction with LISA are outlined. Furthermore, we estimate the constraint ability of the gravitational waves on cosmological parameters with ET. The numerical methods we use are Gaussian process and the Markov-Chain Monte-Carlo. Finally, we also forecast the improvements of the abilities to constrain the cosmological parameters with ET and LISA combined with the Planck.

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The Cosmic Triangle: Revealing the State of the Universe

Science ◽

10.1126/science.284.5419.1481 ◽

1999 ◽

Vol 284 (5419) ◽

pp. 1481-1488 ◽

Cited By ~ 826

Author(s):

N. A. Bahcall

Keyword(s):

The State ◽

The Universe

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Long-term astrophysical processes

Global Catastrophic Risks ◽

10.1093/oso/9780198570509.003.0006 ◽

2008 ◽

Author(s):

Fred C. Adams

Keyword(s):

Background Radiation ◽

Cosmological Parameters ◽

Future Evolution ◽

The Future ◽

The Galaxy ◽

Microwave Background Radiation ◽

Type Ia ◽

Long Time ◽

Age Of The Universe ◽

The Universe

As we take a longer-term view of our future, a host of astrophysical processes are waiting to unfold as the Earth, the Sun, the Galaxy, and the Universe grow increasingly older. The basic astronomical parameters that describe our universe have now been measured with compelling precision. Recent observations of the cosmic microwave background radiation show that the spatial geometry of our universe is flat (Spergel et al., 2003). Independent measurements of the red-shift versus distance relation using Type Ia supernovae indicate that the universe is accelerating and apparently contains a substantial component of dark vacuum energy (Garnavich et al., 1998; Perlmutter et al., 1999; Riess et al., 1998). This newly consolidated cosmological model represents an important milestone in our understanding of the cosmos. With the cosmological parameters relatively well known, the future evolution of our universe can now be predicted with some degree of confidence (Adams and Laughlin, 1997). Our best astronomical data imply that our universe will expand forever or at least live long enough for a diverse collection of astronomical events to play themselves out. Other chapters in this book have discussed some sources of cosmic intervention that can affect life on our planet, including asteroid and comet impacts (Chapter 11, this volume) and nearby supernova explosions with their accompanying gamma-rays (Chapter 12, this volume). In the longerterm future, the chances of these types of catastrophic events will increase. In addition, taking an even longer-term view, we find that even more fantastic events could happen in our cosmological future. This chapter outlines some of the astrophysical events that can affect life, on our planet and perhaps elsewhere, over extremely long time scales, including those that vastly exceed the current age of the universe. These projections are based on our current understanding of astronomy and the laws of physics, which offer a firm and developing framework for understanding the future of the physical universe (this topic is sometimes called Physical Eschatology – see the review of ćirković, 2003). Notice that as we delve deeper into the future, the uncertainties of our projections must necessarily grow.

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Cosmological Parameters of the Universe

Astronomy, Cosmology and Fundamental Physics - Astrophysics and Space Science Library ◽

10.1007/978-94-009-0965-6_2 ◽

1989 ◽

pp. 23-40 ◽

Cited By ~ 1

Author(s):

Alan Dressler

Keyword(s):

Cosmological Parameters ◽

The Universe

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The AAO 2DF QSO Redshift Survey

Symposium - International Astronomical Union ◽

10.1017/s0074180900132504 ◽

1999 ◽

Vol 183 ◽

pp. 178-184 ◽

Cited By ~ 4

Author(s):

B.J. Boyle ◽

R.J. Smith ◽

T. Shanks ◽

S.M. Croom ◽

L. Miller

Keyword(s):

Large Scale ◽

Cosmological Parameters ◽

Large Scale Structure ◽

Scale Structure ◽

Redshift Survey ◽

The Universe

The study of large-scale structure through QSO clustering provides a potentially powerful route to determining the fundamental cosmological parameters of the Universe (see Croom & Shanks 1996). Unfortunately, previous QSO clustering studies have been limited by the relatively small sizes of homogeneous QSO catalogues that have been available. Although approximately 10,000 QSOs are now known (Veron-Cetty & Veron 1997), the largest catalogues suitable for clustering studies contain only 500–1000 QSOs (Boyle et al. 1990, Crampton et al. 1990, Hewett et al. 1994). Even combining all such suitable catalogues, the total number of QSOs which can be used for clustering studies is still only about 2000.

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Art. XX.—An Account of the Country of Sindh; with Remarks on the State of Society, the Government, Manners, and Customs of the People

Journal of the Royal Asiatic Society ◽

10.1017/s0035869x0014242x ◽

1834 ◽

Vol 1 (2) ◽

pp. 223-257 ◽

Cited By ~ 1

Author(s):

James M‘Murdo

Keyword(s):

Civil Wars ◽

The State ◽

Satisfactory Explanation ◽

The North ◽

The People ◽

River Indus ◽

The Government ◽

The Universe

The author of the Tohfat-al-Giráni states, that “the country of Sindh takes its name from Sind, the brother of Hind, the son of Noah. It is reckoned the forty-third of the sixty-one countries of the universe. The line of the second climate passes, from the north, directly through its centre; and although Sindh is situated in the five first climates, it nevertheless chiefly appertains to the second, and, consequently, lies in the region of the holy cities of Mecca and Medina.” It would be difficult to discover where the author quoted has found these grandsons of the patriarch; indeed, as is usual in such genealogies, they are probably altogether imaginary. The Hindú writings may, perhaps, afford some more satisfactory explanation of the name; but I have not been so fortunate as to meet with it. As far as I can learn from such sources, this country was called Sindhúdès, or “the country of the ocean,” alluding doubtless to the river Indus, which receives that dignified appellation in their sacred writings. The same authorities also state Sindh to have been governed by a Xhuthi, named Jayadrat'ha, who was slain in the civil wars of the Pandús; and it has, in consequence, sometimes received the name of Jayadrat'hadès, after that chieftain.

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