Cosmological constant: Difference between revisions
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{{cosmology}} | |||
{{cleanup|reason=short article on such important topic|date=October 2013}} | |||
The '''accelerating universe''' is the observation that the universe appears to be [[Metric expansion of space|expanding]] at an increasing rate. In formal terms, this means that the [[Scale factor (cosmology)|cosmic scale factor]] <math>a(t)</math> has a positive [[second derivative]],<ref>{{cite book | last = Jones | first = Mark H. | coauthors = Robert J. Lambourne | title = An Introduction to Galaxies and Cosmology | publisher =Cambridge University Press | year= 2004 | page = [http://books.google.com/books?id=36K1PfetZegC&lpg=PP1&pg=PA244#v=onepage&q&f=false 244] | isbn = 978-0-521-83738-5 }}</ref> so that the velocity at which a distant galaxy is receding from us should be continuously increasing with time.<ref>[http://curious.astro.cornell.edu/question.php?number=575 Is the universe expanding faster than the speed of light?] (see final paragraph)</ref> | |||
In 1998, observations of [[type Ia supernovae]] also suggested that the expansion of the [[universe]] has been accelerating<ref name="Riess 1998">{{cite journal|author=[[Adam Riess|Adam G. Riess]] ''et al.'' ([[Supernova Search Team]])|year=1998|title=Observational evidence from supernovae for an accelerating universe and a cosmological constant|journal=Astronomical J.|volume=116|issue=3|pages=1009–38|arxiv=astro-ph/9805201 |doi=10.1086/300499|bibcode=1998AJ....116.1009R}}</ref><ref name="Perlmutter 1999">{{cite journal|author=[[Saul Perlmutter|S. Perlmutter]] ''et al.'' (The [[Supernova Cosmology Project]])|journal=Astrophysical Journal|volume=517|issue=2|pages=565–86|year=1999|title=Measurements of Omega and Lambda from 42 high redshift supernovae|arxiv=astro-ph/9812133 |doi=10.1086/307221|bibcode=1999ApJ...517..565P}}</ref> since around [[redshift]] of z~0.5.<ref>Riess, A. G., et al. 2004, ''Astrophysical Journal'', 607, 665</ref> The 2006 [[Shaw Prize|Shaw Prize in Astronomy]] and the 2011 [[Nobel Prize in Physics]] were both awarded to [[Saul Perlmutter]], [[Brian P. Schmidt]], and [[Adam G. Riess]], who in 1998 as leaders of the [[Supernova Cosmology Project]] (Perlmutter) and the [[High-Z Supernova Search Team]] (Schmidt and Riess) discovered the accelerating expansion of the Universe through observations of distant ("High-Z") supernovae.<ref name="BBC">{{cite news|url=http://www.bbc.co.uk/news/science-environment-15165371|title=Nobel physics prize honours accelerating Universe find|publisher=BBC News|date=October 4, 2011}}</ref><ref>{{cite web|url=http://www.nobelprize.org/nobel_prizes/physics/laureates/2011/# |title=The Nobel Prize in Physics 2011 |publisher=Nobelprize.org |date= |accessdate=2011-10-06}}</ref> | |||
==Corroboration== | |||
After the initial discovery in 1998, these observations were corroborated by several independent sources: the [[cosmic microwave background radiation]] and [[Large-scale structure of the cosmos|large scale structure]],<ref>Spergel, D. N., et al. 2003, ''Astrophysical Journal Supplement'', 148, 175</ref> apparent size of [[baryon acoustic oscillation]]s,<ref name=real>[http://wigglez.swin.edu.au/site/prmay2011a.html Dark energy is real], Swinburne University of Technology, 19 May 2011</ref> [[age of the universe]],<ref>Chaboyer, B., & Krauss, L. M. 2002, ''Astrophysical Journal Letters'', 567, L4</ref> as well as improved measurements of [[supernova]]e<ref>Wood-Vasey, W. M., et al. 2007, ''Astrophysical Journal'', 666, 694</ref><ref>Astier, P., et al. 2006, ''Astronomy and Astrophysics'', 447, 31 | |||
</ref> and X-ray properties of galaxy clusters. | |||
==Explanatory models== | |||
Models attempting to explain accelerating expansion include some form of [[dark energy]], [[dark fluid]] or [[phantom energy]]. The most important property of dark energy is that it has negative [[pressure]] which is distributed relatively [[Homogeneity (physics)|homogeneously]] in space. The simplest explanation for dark energy is that it is a [[cosmological constant]] or [[vacuum energy]]; this leads to the [[Lambda-CDM model]], which has generally been known as the Standard Model of Cosmology from 2003 through the present, since it is the simplest model in good agreement with a variety of recent observations. | |||
==Theories for the consequences to the universe== | |||
As the Universe expands, the density of radiation and ordinary and [[dark matter]] declines more quickly than the density of [[dark energy]] (see [[Equation of State (Cosmology)|equation of state]]) and, eventually, dark energy dominates. Specifically, when the scale of the universe doubles, the density of matter is reduced by a factor of 8, but the density of dark energy is nearly unchanged (it is exactly constant if the dark energy is a [[cosmological constant]]). | |||
Current observations indicate that the dark energy density is already greater than the mass-energy density of radiation and matter (including [[dark matter]]). In models where dark energy is a [[cosmological constant]], the universe will expand exponentially with time from now on, coming closer and closer to a [[de Sitter space|de Sitter spacetime]]. In this scenario the time it takes for the linear size scale of the universe to expand to double its size is approximately 11.4 billion years. Eventually all galaxies beyond our own [[local supercluster]] will [[redshift]] so far that it will become hard to detect them, and the distant universe will turn dark. | |||
In other models, the density of dark energy changes with time. In [[Quintessence (physics)|quintessence]] models it decreases, but more slowly than the energy density in ordinary matter and radiation. In [[phantom energy]] models it increases with time, leading to a [[Big Rip|big rip]]. | |||
==See also== | |||
*[[High-z Supernova Search Team]] | |||
*[[Supernova Cosmology Project]] | |||
*[[Metric expansion of space]] | |||
*[[List of multiple discoveries#21st century|List of multiple discoveries]] | |||
*[[Cosmological constant]] | |||
*[[Scale factor (cosmology)]] | |||
*[[Friedmann–Lemaître–Robertson–Walker metric]] | |||
==References== | |||
{{Reflist}} | |||
{{Breakthrough of the Year}} | |||
[[Category:Physical cosmology]] | |||
[[Category:Acceleration]] | |||
[[Category:Universe]] | |||
[[Category:Big Bang]] | |||
Revision as of 20:57, 9 December 2013
Template:Cosmology Template:Cleanup The accelerating universe is the observation that the universe appears to be expanding at an increasing rate. In formal terms, this means that the cosmic scale factor has a positive second derivative,[1] so that the velocity at which a distant galaxy is receding from us should be continuously increasing with time.[2] In 1998, observations of type Ia supernovae also suggested that the expansion of the universe has been accelerating[3][4] since around redshift of z~0.5.[5] The 2006 Shaw Prize in Astronomy and the 2011 Nobel Prize in Physics were both awarded to Saul Perlmutter, Brian P. Schmidt, and Adam G. Riess, who in 1998 as leaders of the Supernova Cosmology Project (Perlmutter) and the High-Z Supernova Search Team (Schmidt and Riess) discovered the accelerating expansion of the Universe through observations of distant ("High-Z") supernovae.[6][7]
Corroboration
After the initial discovery in 1998, these observations were corroborated by several independent sources: the cosmic microwave background radiation and large scale structure,[8] apparent size of baryon acoustic oscillations,[9] age of the universe,[10] as well as improved measurements of supernovae[11][12] and X-ray properties of galaxy clusters.
Explanatory models
Models attempting to explain accelerating expansion include some form of dark energy, dark fluid or phantom energy. The most important property of dark energy is that it has negative pressure which is distributed relatively homogeneously in space. The simplest explanation for dark energy is that it is a cosmological constant or vacuum energy; this leads to the Lambda-CDM model, which has generally been known as the Standard Model of Cosmology from 2003 through the present, since it is the simplest model in good agreement with a variety of recent observations.
Theories for the consequences to the universe
As the Universe expands, the density of radiation and ordinary and dark matter declines more quickly than the density of dark energy (see equation of state) and, eventually, dark energy dominates. Specifically, when the scale of the universe doubles, the density of matter is reduced by a factor of 8, but the density of dark energy is nearly unchanged (it is exactly constant if the dark energy is a cosmological constant).
Current observations indicate that the dark energy density is already greater than the mass-energy density of radiation and matter (including dark matter). In models where dark energy is a cosmological constant, the universe will expand exponentially with time from now on, coming closer and closer to a de Sitter spacetime. In this scenario the time it takes for the linear size scale of the universe to expand to double its size is approximately 11.4 billion years. Eventually all galaxies beyond our own local supercluster will redshift so far that it will become hard to detect them, and the distant universe will turn dark.
In other models, the density of dark energy changes with time. In quintessence models it decreases, but more slowly than the energy density in ordinary matter and radiation. In phantom energy models it increases with time, leading to a big rip.
See also
- High-z Supernova Search Team
- Supernova Cosmology Project
- Metric expansion of space
- List of multiple discoveries
- Cosmological constant
- Scale factor (cosmology)
- Friedmann–Lemaître–Robertson–Walker metric
References
43 year old Petroleum Engineer Harry from Deep River, usually spends time with hobbies and interests like renting movies, property developers in singapore new condominium and vehicle racing. Constantly enjoys going to destinations like Camino Real de Tierra Adentro.
Template:Breakthrough of the Year
- ↑ 20 year-old Real Estate Agent Rusty from Saint-Paul, has hobbies and interests which includes monopoly, property developers in singapore and poker. Will soon undertake a contiki trip that may include going to the Lower Valley of the Omo.
My blog: http://www.primaboinca.com/view_profile.php?userid=5889534 - ↑ Is the universe expanding faster than the speed of light? (see final paragraph)
- ↑ One of the biggest reasons investing in a Singapore new launch is an effective things is as a result of it is doable to be lent massive quantities of money at very low interest rates that you should utilize to purchase it. Then, if property values continue to go up, then you'll get a really high return on funding (ROI). Simply make sure you purchase one of the higher properties, reminiscent of the ones at Fernvale the Riverbank or any Singapore landed property Get Earnings by means of Renting
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Discover out more about real estate funding in the area, together with info on international funding incentives and property possession. Many Singaporeans have been investing in property across the causeway in recent years, attracted by comparatively low prices. However, those who need to exit their investments quickly are likely to face significant challenges when trying to sell their property – and could finally be stuck with a property they can't sell. Career improvement programmes, in-house valuation, auctions and administrative help, venture advertising and marketing, skilled talks and traisning are continuously planned for the sales associates to help them obtain better outcomes for his or her shoppers while at Knight Frank Singapore. No change Present Rules
Extending the tax exemption would help. The exemption, which may be as a lot as $2 million per family, covers individuals who negotiate a principal reduction on their existing mortgage, sell their house short (i.e., for lower than the excellent loans), or take part in a foreclosure course of. An extension of theexemption would seem like a common-sense means to assist stabilize the housing market, but the political turmoil around the fiscal-cliff negotiations means widespread sense could not win out. Home Minority Chief Nancy Pelosi (D-Calif.) believes that the mortgage relief provision will be on the table during the grand-cut price talks, in response to communications director Nadeam Elshami. Buying or promoting of blue mild bulbs is unlawful.
A vendor's stamp duty has been launched on industrial property for the primary time, at rates ranging from 5 per cent to 15 per cent. The Authorities might be trying to reassure the market that they aren't in opposition to foreigners and PRs investing in Singapore's property market. They imposed these measures because of extenuating components available in the market." The sale of new dual-key EC models will even be restricted to multi-generational households only. The models have two separate entrances, permitting grandparents, for example, to dwell separately. The vendor's stamp obligation takes effect right this moment and applies to industrial property and plots which might be offered inside three years of the date of buy. JLL named Best Performing Property Brand for second year running
The data offered is for normal info purposes only and isn't supposed to be personalised investment or monetary advice. Motley Fool Singapore contributor Stanley Lim would not personal shares in any corporations talked about. Singapore private home costs increased by 1.eight% within the fourth quarter of 2012, up from 0.6% within the earlier quarter. Resale prices of government-built HDB residences which are usually bought by Singaporeans, elevated by 2.5%, quarter on quarter, the quickest acquire in five quarters. And industrial property, prices are actually double the levels of three years ago. No withholding tax in the event you sell your property. All your local information regarding vital HDB policies, condominium launches, land growth, commercial property and more
There are various methods to go about discovering the precise property. Some local newspapers (together with the Straits Instances ) have categorised property sections and many local property brokers have websites. Now there are some specifics to consider when buying a 'new launch' rental. Intended use of the unit Every sale begins with 10 p.c low cost for finish of season sale; changes to 20 % discount storewide; follows by additional reduction of fiftyand ends with last discount of 70 % or extra. Typically there is even a warehouse sale or transferring out sale with huge mark-down of costs for stock clearance. Deborah Regulation from Expat Realtor shares her property market update, plus prime rental residences and houses at the moment available to lease Esparina EC @ Sengkang - ↑ One of the biggest reasons investing in a Singapore new launch is an effective things is as a result of it is doable to be lent massive quantities of money at very low interest rates that you should utilize to purchase it. Then, if property values continue to go up, then you'll get a really high return on funding (ROI). Simply make sure you purchase one of the higher properties, reminiscent of the ones at Fernvale the Riverbank or any Singapore landed property Get Earnings by means of Renting
In its statement, the singapore property listing - website link, government claimed that the majority citizens buying their first residence won't be hurt by the new measures. Some concessions can even be prolonged to chose teams of consumers, similar to married couples with a minimum of one Singaporean partner who are purchasing their second property so long as they intend to promote their first residential property. Lower the LTV limit on housing loans granted by monetary establishments regulated by MAS from 70% to 60% for property purchasers who are individuals with a number of outstanding housing loans on the time of the brand new housing purchase. Singapore Property Measures - 30 August 2010 The most popular seek for the number of bedrooms in Singapore is 4, followed by 2 and three. Lush Acres EC @ Sengkang
Discover out more about real estate funding in the area, together with info on international funding incentives and property possession. Many Singaporeans have been investing in property across the causeway in recent years, attracted by comparatively low prices. However, those who need to exit their investments quickly are likely to face significant challenges when trying to sell their property – and could finally be stuck with a property they can't sell. Career improvement programmes, in-house valuation, auctions and administrative help, venture advertising and marketing, skilled talks and traisning are continuously planned for the sales associates to help them obtain better outcomes for his or her shoppers while at Knight Frank Singapore. No change Present Rules
Extending the tax exemption would help. The exemption, which may be as a lot as $2 million per family, covers individuals who negotiate a principal reduction on their existing mortgage, sell their house short (i.e., for lower than the excellent loans), or take part in a foreclosure course of. An extension of theexemption would seem like a common-sense means to assist stabilize the housing market, but the political turmoil around the fiscal-cliff negotiations means widespread sense could not win out. Home Minority Chief Nancy Pelosi (D-Calif.) believes that the mortgage relief provision will be on the table during the grand-cut price talks, in response to communications director Nadeam Elshami. Buying or promoting of blue mild bulbs is unlawful.
A vendor's stamp duty has been launched on industrial property for the primary time, at rates ranging from 5 per cent to 15 per cent. The Authorities might be trying to reassure the market that they aren't in opposition to foreigners and PRs investing in Singapore's property market. They imposed these measures because of extenuating components available in the market." The sale of new dual-key EC models will even be restricted to multi-generational households only. The models have two separate entrances, permitting grandparents, for example, to dwell separately. The vendor's stamp obligation takes effect right this moment and applies to industrial property and plots which might be offered inside three years of the date of buy. JLL named Best Performing Property Brand for second year running
The data offered is for normal info purposes only and isn't supposed to be personalised investment or monetary advice. Motley Fool Singapore contributor Stanley Lim would not personal shares in any corporations talked about. Singapore private home costs increased by 1.eight% within the fourth quarter of 2012, up from 0.6% within the earlier quarter. Resale prices of government-built HDB residences which are usually bought by Singaporeans, elevated by 2.5%, quarter on quarter, the quickest acquire in five quarters. And industrial property, prices are actually double the levels of three years ago. No withholding tax in the event you sell your property. All your local information regarding vital HDB policies, condominium launches, land growth, commercial property and more
There are various methods to go about discovering the precise property. Some local newspapers (together with the Straits Instances ) have categorised property sections and many local property brokers have websites. Now there are some specifics to consider when buying a 'new launch' rental. Intended use of the unit Every sale begins with 10 p.c low cost for finish of season sale; changes to 20 % discount storewide; follows by additional reduction of fiftyand ends with last discount of 70 % or extra. Typically there is even a warehouse sale or transferring out sale with huge mark-down of costs for stock clearance. Deborah Regulation from Expat Realtor shares her property market update, plus prime rental residences and houses at the moment available to lease Esparina EC @ Sengkang - ↑ Riess, A. G., et al. 2004, Astrophysical Journal, 607, 665
- ↑ Template:Cite news
- ↑ Template:Cite web
- ↑ Spergel, D. N., et al. 2003, Astrophysical Journal Supplement, 148, 175
- ↑ Dark energy is real, Swinburne University of Technology, 19 May 2011
- ↑ Chaboyer, B., & Krauss, L. M. 2002, Astrophysical Journal Letters, 567, L4
- ↑ Wood-Vasey, W. M., et al. 2007, Astrophysical Journal, 666, 694
- ↑ Astier, P., et al. 2006, Astronomy and Astrophysics, 447, 31