Cosmological Definition and 433 Threads

Why are the units of the Cosmological constant Lambda 1/m^2? is this just convention to make the density parameter unitless?

I’ve made several efforts to provide a simple description of how the cosmological redshift works. Each has been closer to the mark than its predecessor, and now I think I’ve got it nailed. The premise underlying the redshift is simply that a photon must travel at a local velocity of c through...

Has anybody studied this paper? http://arxiv.org/abs/0909.0212v4 Comprehensive Solution to the Cosmological Constant, Zero-Point Energy, and Quantum Gravity Problems Philip D. Mannheim (Submitted on 1 Sep 2009 (v1), last revised 7 Jan 2010 (this version, v4)) Abstract: We present a...

Are these five names cosmological constant, dark energy, vacuum density, vacuum energy, vacuum energy density names for the same thing?

Hi! This is my first post. I have a question of cosmological importance - literally and figuratively. The Standard Model is the most accepted theory of (almost) everything, yet is unable to make sense of gravity. String Theory can explain it all theoretically through quantitative...

What does this paragraph mean? I read it somewhere that a relatively newer observation renewed the concept of "cosmological constant", and it was connected with "dark energy", again, can anyone provide detailed information on that? Wasn't "cosmological constant" proved erroneous long ago...

E proposed cosmological constant to prove the universe is stationary. Some others suggested Universe is contracting, while some others suggested Universe is exanding and for either of them cosmological constant was considered responsible. Today when this is discovered universe is expanding with...

The following is from a research paper: doi:10.1088/0034-4885/68/4/R04 The structure of the world from pure numbers F J Tipler Department of Mathematics and Department of Physics, Tulane University, New Orleans, LA 70118, USA Received 21 September 2004 Published 15 March 2005 Online...

Question : How to unit transformation of Cosmological Constant? 10-47 GeV4 ===> ? eV or, x eV ===> ? GeV4 1) How compair ( X ) GeV4 with ( Y ) eV ? 2) How compair ( 10-29 g/cm3) with (Y eV)? please, easely explain to me! and, have a nice day!

I am watching a lecture by Susskind on his book The Cosmic Landscape. And he is going on about how "tuned" and unlikely it is. Largely based on work done by Weinberg. He said it was one of the biggest surprises in science and can't be ignored. How fine tuned the cosmological constant is. Is...

Can someone remind me what the difference between the Cosmological Constant (\Lambda) and Dark Energy (DE)? Doesn't DE (with w = -1) show up in the Einstein's field equations in exactly the same way as \Lambda does? (In case your an expert, I was trying to understand the conclusion of...

It's important to be able to test LQG with observations, most likely using new data on the microwave Background (CMB) collected by instruments such as the Planck spacecraft . It turned out to be impossible to derive a prediction of dispersion (energy dependent speed of light) at least so...

Hi! This is my first time on here and my first post. I don't do professional work in this field but it has been a keen interest of mine over the years. Anyway, if someone can share some insights, I would really appreciate it greatly! Given the divide between classical physics and quantum...

Apparently my recent thread on the cosmological redshift assumed more general insight into this subject than is the case. So the purpose of this thread is to help dispel some popular misconceptions about the cosmological redshift and hopefully spur a vigorous discussion. This thread is NOT...

There seems to be a difference in the way relativity views Planck length as frame dependent and the cosmological constant, an energy density?, as invariant...Any insights appreciated! There is a well known contradiction between relativity and the Planck length: Wikipedia explains the...

It is well established that the cosmological redshift causes both the wavelength and the separation of photons to increase in proportion with the increase in the cosmic scale factor a. The traditional explanation for the mechanism of the redshift is that ‘expanding space’ progressively forces...

What exactly is cosmological inflation? Just a hypothesis that the rate of expansion is increasing? What is negative-pressure vacuum energy density? If the universe is expanding faster than the speed of light, how do any photons reach us from anywhere other than our sun? Thanks in advance!

The standard model of accelerating expansion is successful in matching parameters to observation, but substantial observational problems with both CDM and MOND are now well reported in the literature. While there is no true reconciliation between general relativity and quantum mechanics, science...

can someone tell me about the cosmological constant,its significance and 'god' particle?

It is known that in result of the cosmological expansion the distances between galaxies increase according Hubble law v=H*r. Distant SNeIa show that the dark energy accelerates the expansion. I heard in a scientific popular transmission that in result of the acceleration of expansion, every...

I have read that "the cosmological constant introduces a force of repulsion between bodies. The force increases in (simple) proportion to the distance between them." Is this description accurate? Is there a classical formula of the force of the cosmological constant like that of gravitational force?

I was wondering if someone would mind talking a little about why the cosmological constant was introduced and what it actually means for the universe to collapse according to Einstein's Universe. I was reading up on Wikiepdia (not the greatest source, I know) in the Static Universe entry and it...

Homework Statement This question is a slightly customised version of Q18(a) P212 of Schutz Prove that G_{\alpha \beta} + \Lambda g_{\alpha \beta} = 8 \pi T_{\alpha \beta} in the Newtonian limit reduces to \nabla^2 \phi = 4\pi \rho + \Lambda (I found this result in another text...

I think this belongs here, while not relativistic, is is about objects moving relative to one another. Summery: This stems from the description of 'Dark Energy' in a mathamatical context to show that you can place a 'center of the universe' at any point in space, and the accelaration vector...

Hi! I have more questions. 1st. Is there any diference between Cosmological Constant and quintessence? 2nd. If there is, which is? I've only understood that cosmological constant is the energy of the vacuum but I don't know what quitessence is, so please, could somebody tell me if...

QFT it is possible to calculate the energy density of empty space. It is known to be around 10^50 orders to large. Does the calculated large cosmological constant in falsify QFT? Or does GR have to be re-done with a higher energy density

arXiv:0811.2402 [ps, pdf, other] Title: A Realistic Cosmological Model Based on Observations and Some Theory Developed Over the Last 90 Years Authors: Geoffrey Burbidge Comments: 21 pages, conference Subjects: Astrophysics (astro-ph) This meeting is entitled "A Century of Cosmology."...

Consider the vacuum solution to Einstein's equations with non-zero cosmological constant. Following Carroll, we can find the equation for the radial geodesic with the aid of killing vectors. It takes the standard form: E = T + V. But, with non-zero cosmological constant V(r) now has a term...

arXiv:0810.3022 [pdf, other] Title: Cosmological Inflation: Theory and Observations Authors: Daniel Baumann (Harvard), Hiranya V. Peiris (Cambridge) Comments: 18 pages, 12 figures. Invited review to appear in Advanced Science Letters Special Issue on Quantum Gravity, Cosmology and Black...

Homework Statement Solve for the age of the universe as a function of scale factor in a cosmology with \Omega_{M}=0.3, \Omega_{\Lambda}=0.7.Homework Equations The Attempt at a Solution (\frac{\dot{a}}{a})^2=H_0^2(0.3a^{-3}+0.7) \frac{da}{a\sqrt{0.3a^{-3}+0.7}}=H_0dt At this point, Maple seems...

It's been pointed out already at Cosmo forum that a revolution, or at least a minor insurrection, is brewing in cosmology. This paper is part of that. It comes from a different direction compared to some of the other research in nonsingular cosmology. For instance it is not specifically a Loop...

I heard there are many alternative hypoteses for cosmological redshift, e g Fred Hoyle' s variation of mass and tired light. There are other ones? Thanks.

arXiv:0808.1081 (cross-list from physics.pop-ph) [ps, pdf, other] Title: The kinematic origin of the cosmological redshift Authors: Emory F. Bunn, David W. Hogg Comments: 14 pages. Submitted to Am. J. Phys Subjects: Popular Physics (physics.pop-ph); Astrophysics (astro-ph); General...

I'm taking the liberty of revising and restating this topic which started in a separate thread. Comments are welcome. A lively debate is underway today by mainstream cosmologists as to whether the expansion of the universe implies that empty space between galaxies is also expanding. When...

This is a very technical question so I don't really expect someone to have the answer unless they have actually worked with or studied the RS models. They say that the value of the brane tensions in model 1 (which are related to the bulk cosmological constant) are such that the 4D...

The team of Francis, Barnes, James & Lewis have published several very helpful papers in recent years about the expansion of space (with their names in various orders.) I suggested in a recent thread about their Radar Ranging article that they are trending away from explaining particle...

I am new to the world of theoretical physics and was wondering if anyone can explain "vacuum energy" to me? What does it have to do with the expansion of our universe? Something about a "cosmological constant" is also involved. If someone can give me a concise and accurate version of what...

Logic of E-H action, ricci scalar, cosmological constant?? This crazy thread is mean to stimulate some reflections on the logic of Einsteins Equations. It would be interesting if those who have any ideas can join. Maybe it could be enlightning? The common way of thinking about GR is that we...

What is the force of "friction" (for want of a better word) between the two four-dimensional universes that have come together to create our three-dimensional surface (universe). As a three-dimensional analog think of two rectangular solids moving toward each other. One is moving right...

Here is a fun thing to try The Google calculator knows the values of pi, the speed of light c, Newton's G and stuff like that. So you can easily make it calculate the cosmological constant from a few familiar facts. You have to know that the usual estimate of the Hubble parameter is 71...

Hey folks, I'm writing a pop-sci article for a journal and one of the referees wants me to give the cosmological const in mks units instead of GeV. I just wanted to check with anyone in the know if the following looks correct. First, the accepted value of lambda (order of mag)...

cosmological principle states that, on large spatial scales, universe is homogeneous and isotropic. in other words, universe looks the same in every direction and that is true for every point of view. there are some challanges to this principle, but for this discussion, I will assume it is...

to those experts in the field of cosmology i was wondering if " large scale structures can be formed in stable cosmological models" or should i say that " large scale structures cannot be formed in those cosmological models that are stable with respect to gravitational or other curvature...

Hello, I am a new arrival to this forum. It was mentioned at another forum. So I came over registered and would love to see the prevailing Cosmological discussions. The post that brought me here, was this one below: Posted: Sat Jan 05, 2008 8:08 am Post subject: Physics Forum...

Is the cosmological arrow of time just a special case of the thermodynamic arrow of time, where the universe is the isolated system?

Hi everyone, If anyone could point me in the right direction with this problem I'd really appreciate it. "Show that the cosmological constant can be interpreted as a perfect fluid having an equation of state w=-1." I have a rough idea of how to do the second part of the proof: if the...

Hi everyone, If anyone could point me in the right direction with this problem I'd really appreciate it. "Show that the cosmological constant can be interpreted as a perfect fluid having an equation of state w=-1." I have a rough idea of how to do the second part of the proof: if the...

Hi everyone, If anyone could point me in the right direction with this problem I'd really appreciate it. "Show that the cosmological constant can be interpreted as a perfect fluid having an equation of state w=-1." I have a rough idea of how to do the second part of the proof: if the...

If we take Planck's constant to be a measure of quantum fluctuations, which seems natural in the world-view of https://www.physicsforums.com/showthread.php?t=204567", then it also seems natural to ask whether Planck's constant might vary over cosmological scales, just as temperature is a measure...

This is a big hole in the sky. Although you can't see it with the naked eye it actually covers almost 3 degrees of the sky, and to put that into perspective the full Moon covers about half a degree! Until recently no-one was sure how big or far away this void was but the latest calculations...