What is Cosmological constant: Definition and 188 Discussions

In cosmology, the cosmological constant (usually denoted by the Greek capital letter lambda: Λ), alternatively called Einstein's cosmological constant, is the energy density of space, or vacuum energy, that arises in Albert Einstein's field equations of general relativity. It is closely associated to the concept of dark energy.Einstein originally introduced the concept in 1917 to counterbalance the effects of gravity and achieve a static universe, a notion which was the accepted view at the time. Einstein abandoned the concept in 1931 after Hubble's confirmation of the expanding universe. From the 1930s until the late 1990s, most physicists assumed the cosmological constant to be equal to zero. That changed with the surprising discovery in 1998 that the expansion of the universe is accelerating, implying the possibility of a positive nonzero value for the cosmological constant.Since the 1990s, studies have shown that around 68% of the mass–energy density of the universe can be attributed to so-called dark energy. The cosmological constant Λ is the simplest possible explanation for dark energy, and is used in the current standard model of cosmology known as the ΛCDM model.
According to quantum field theory (QFT) which underlies modern particle physics, empty space is defined by the vacuum state which is a collection of quantum fields. All these quantum fields exhibit fluctuations in their ground state (lowest energy density) arising from the zero-point energy present everywhere in space. These zero-point fluctuations should act as a contribution to the cosmological constant Λ, but when calculations are performed these fluctuations give rise to an enormous vacuum energy. The discrepancy between theorized vacuum energy from quantum field theory and observed vacuum energy from cosmology is a source of major contention, with the values predicted exceeding observation by some 120 orders of magnitude, a discrepancy that has been called "the worst theoretical prediction in the history of physics". This issue is called the cosmological constant problem and it is one of the greatest mysteries in science with many physicists believing that "the vacuum holds the key to a full understanding of nature".

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  1. Z

    Question on Cosmological Constant paper

    In the paper, http://arxiv.org/pdf/1205.3365v1.pdf, page 21, the author argues that if: t →∞(1-iϵ), all the terms in equation (193) goes to zero, except the first term. Can anyone explain this to me? Thanks
  2. Chronos

    Cosmological constant from first principles

    Can the cosmological constant be derived from first principles? The answer appears to be - YES, according to this paper by Padmanabhan - 'The Physical Principle that determines the Value of the Cosmological Constant', http://arxiv.org/abs/1210.4174. This is, in part, an extension of...
  3. M

    Question about Einstein inserting the cosmological constant

    In Gravitation by MTW in section 17.3, they state (I assume it was a typo putting the cosmological constant in the center portion) Changing the symbol of the Einstein tensor and the cosmological constant to L and Ω so as not to confuse myself, I can see how with...
  4. S

    Light speed and cosmological constant

    E=mc2 gives us the cosmological constant, which later was found to be the maximum speed at which light can travel. i also understand that when accelerating particles such as they do at CERN, it requires more and more energy the faster u want to go, the mass/speed issue. so i think i understand...
  5. R

    Questions concerning Cosmological Constant

    I understand the beginning basics of what it represents but how exactly does it tie into the inflation of space and what sort of energy is in a perfect vacuum?
  6. shreyakmath

    Acceleration of a universe with -ve Cosmological Constant

    I have read this new paper by Stephen Hawking and collegues. It is very interesting to see the use of wavefunctions to show the acceleration of a universe with lambda<0 which fits in the framework of string theory and quantum mechanics. This technique bridges quantum mechanics and general...
  7. M

    Denominator in cosmological constant term in Newtonian gravity

    In General relativity: an introduction for physicists, the authors derive Newtonian gravity from the EFE, but then they also give a short statement that inserting in the cosmological constant derives down to: \vec{g}=-\nabla\Phi=-\frac{GM}{r^{2}}\hat{\vec{r}}+\frac{\Lambda...
  8. M

    General relativity, dark energy and the cosmological constant

    I see where someone listed a theory that they had https://www.physicsforums.com/showthread.php?t=49230 so going to attempt to do the same. I listed my theory at http://www.bautforum.com/showthread.php/129309-Negative-Mass-Interpretation-of-General-Relativity but they are very quiet and I would...
  9. I

    Galaxy expansion & cosmological constant

    Hi Astro forum... I have got something to clarify which came across my mind as I was trying to answer few problems.So without any further delay , let's start : For simplicity we will assume that dark matter doesn't influence the center of mass of galaxy A. Now let's say galaxy A has mass 'M'...
  10. S

    The quantum based calculation of the cosmological constant

    I nearly referred to it as infamous in the title. Unfair? My question is this: why did they add up the combined energy of all the fields when only the Higgs field would be active in void space (I use this term to refer to the spaces between filaments, does it have its own name or is it...
  11. J

    Cosmological constant supports MOND

    Does the cosmological constant support MOND? The equation for critical density is as follows (in terms of mass rather than density): Critical density (90.4 x e54 gm) = matter (4.1 x e54 gm) + dark matter (20.6 x e54 gm) + dark energy/cosmological constant (65.7 x e54 gm). Most estimates...
  12. B

    Why doesn't the Higgs produces a cosmological constant

    If the vacuum contains all these Higgs bosons, at expectation of <246> GeV in vacuum, why isn't there a cosmological constant, given the vacuum an energy density of 246 GeV^4 , instead we see dark energy at a few meV^4. Could just say that the graviton doesn't couple to the Higgs at all, but...
  13. Z

    Big crunch versus the Cosmological Constant

    I am no expert on cosmology. But from what I have heard, the big crunch is the scenario that will most likely happen to our universe in the (far) future. Yet the cosmological constant makes it so that our universe is currently expanding and acceleratingly so. So the question is (I know this...
  14. H

    Does Vacuum Energy Drive the Expansion of the Universe?

    So I was watching the show "Curiosity" on the Discovery channel last night. In the show, Stephen Hawking describes the birth of the Universe, and why our theory of inflation leaves no place for God. I'm not going to comment on the God thing, but Hawking said something that got me thinking...
  15. N

    Is the cosmological constant equivalent to vacuum energy?

    Wikipedia says: second paragraph here: http://en.wikipedia.org/wiki/Dark_energy Vaccum energy (density) can vary over time and space? Is that accurate? I've read the cosmological constant can vary, but not vacuum energy.
  16. K

    Variation of cosmological constant with time

    Hello, in the paper from sean carroll "the cosmological constant" we can read this: Does this variation of the cosmological constant after symetry breaking is considered as real and accepted in standard cosmology? I find very few talks about a varying cosmological constant, and it is about...
  17. Chronos

    The Value of the Cosmological Constant

    I found this new paper by John Barrow to be quite interesting: http://arxiv.org/abs/1105.3105 The Value of the Cosmological Constant Authors: John D. Barrow, Douglas J. Shaw (Submitted on 16 May 2011) Abstract: We make the cosmological constant, {\Lambda}, into a field and restrict the...
  18. P

    Is vacuum energy really identical to the cosmological constant?

    When Einstein proposed the cosmological constant, it was regarded as an arbitrary constant having no connection with flat-spacetime physics (e.g. QFT to be invented later). IMHO the effective cosmological constant, in principle, should be the sum of QFT vacuum energy and Einstein's arbitrary...
  19. D

    AdS/CFT correspondence and the cosmological constant

    Hi all, From what I understand AdS/CFT correspondence has been one of the most researched areas in string theory. I'd like to know if there has been any work done to relate this duality to the cosmological constant. As unrelated as they may sound, the expansion of space will change the...
  20. L

    Cosmological Constant: Exploring Two Different Models

    Since the discovery of an accelerating expansion in the late 1990s, the cosmological constant has been included in cosmological models for dark energy. Einstein included the cosmological constant to make the universe static. Dark energy makes the universe expand accelerating. So in the 2...
  21. C

    Cosmological Constant Problem / Vacuum Catastrophe

    By my understanding, the cosmological constant problem is that the computed vacuum energy by quantum field theory (in the form of virtual particle pairs) is far larger than the measured vacuum energy density. Would it not seem to solve the problem with dropping the proposed mass of "virtual...
  22. A

    Einstein Equation with Cosmological Constant & Variable x^u

    with the action \int (k(R- 2 \Lambda)+L_m) \sqrt{g} the Einstein equation is: R_{uv}-\frac{1}{2}R g_{uv}- \Lambda g_{uv} = k' T_{uv} How is the Einstein equation if \Lambda=\Lambda(x^u)? with x^u a coordinate
  23. I

    Two dimensional anti de Sitter space without cosmological constant?

    I have a spacetime which is (I think) AdS_2. The metric is, I'm trying to find the Einstein tensor, defined as, and the result is zero! I thought that, for the AdS spacetimes I needed to have a nonzero Einstein tensor which is caused by the cosmological constant. What is wrong...
  24. I

    Cosmological Constant: Dark Energy vs Gravity Ratio

    The cosmological constant has been a debated issue for a century... What if the constant is a ratio of the Force of dark energy to the force of gravity just like in a spring where the resistivity is the ratio of the force of gravity and the spring.
  25. J

    Cosmological Constant and Conservation of Energy

    The cosmological constant, or dark energy if you prefer, can be thought of as energy inherent in free space. This energy density is thought to be constant, and the volume which it occupies grows as space expands. The more this happens, the more dark energy comes to dominate the universe...
  26. nicksauce

    New Barrow paper - A New Solution of The Cosmological Constant Problems

    New Barrow paper - "A New Solution of The Cosmological Constant Problems" http://arxiv.org/abs/1007.3086 Anyone care to comment? I haven't taken too careful of a look yet, because it is late, but I'll try to write a response to it tomorrow.
  27. J

    Minimal mass from cosmological constant?

    I'm not sure in which forum this should go, but I hope this is close enough. I recently realized that the lightest neutrino could be close in mass to the fourth root of the cosmological constant and found out I'm (unsurprisingly) not the first one to think of this after some googling. The...
  28. P

    Cosmological Constant: QFT and Existence Explained

    How QFT might possibly explain existence of cosmological constant. Does it predict that vacuum stress energy tensor has on it's diagonal positive time component (density of energy) and negative spatial components (preasure=-density)?
  29. F

    Temperature of Cosmological Constant

    Is there a temperature related to the cosmological constant? As I understand it, the cosmological constant is produced by dark energy and is a form of zero point energy created by virtual particles and antiparticles being created and annihilated all the time. It seems to me that this process...
  30. A

    The cosmological constant is always dimensional less?

    the cosmological constant is always dimensional less? in the randall sundrum models the tension of our brane is T=24M^3_5 \sqrt{\frac{-\Lambda}{24M^3_5}}...the sub index of M is the number of dimension of space time and the supercript is the power. ¿whats units have the Planck scales...
  31. J

    Is the cosmological constant constant?

    In a flat, matter-dominated universe the cosmological constant is zero and the scale parameter a increases according to a two-thirds power law. In such a universe, the expansion of the universe gradually slows down (but never stops). In recent years it has been discovered (?) that the rate of...
  32. T

    Cosmological Constant: Why Lambda Units are 1/m^2

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

    Solution to the Cosmological Constant, Zero-Point Energy, P.D. Mannheim

    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...
  34. edpell

    Cosmological constant or dark energy or vaccum denisty/energy/energy density

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

    Is the Cosmological Constant the Same as Dark Energy?

    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...
  36. D

    Decaying cosmological constant

    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...
  37. I

    Unit transformation of Cosmological Constant ?

    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!
  38. F

    Susskind on the cosmological constant.

    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...
  39. B

    Difference between Dark Energy and Cosmological Constant

    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...
  40. N

    Cosmological Constant and Planck Length in relativity

    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...
  41. M

    Cosmological Constant: Significance & "God" Particle

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

    What is the force of the cosmological constant?

    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?
  43. N

    Cosmological Constant and the Colapse of the Universe

    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...
  44. P

    Cosmological Constant or Quintessence

    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...
  45. E

    Does the calculated large cosmological constant in falsify QFT?

    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
  46. L

    Vacuum solution with nonzero cosmological constant

    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...
  47. nicksauce

    Solution of Friedmann equation w/ Cosmological Constant

    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...
  48. N

    Technical question: vanishing of the cosmological constant in Randall Sundrum 1

    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...
  49. N

    How Do Vacuum Energy and the Cosmological Constant Influence Universe Expansion?

    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...
  50. Fra

    Logic of E-H action, ricci scalar, cosmological constant?

    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...
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