Coordination number: Difference between revisions
en>Dirac66 →Chemistry usage: get smaller → are smaller than the central atom |
en>Materialscientist m Reverted edits by 143.248.217.156 (talk) to last version by Materialscientist |
||
Line 1: | Line 1: | ||
In [[physics]], a '''renormalon''' (a term suggested by [[Gerardus 't Hooft|'t Hooft]]<ref>'t Hooft G, in: The whys of subnuclear physics (Erice, 1977), ed. A Zichichi, Plenum Press, New York, 1979.</ref>) is a particular source of divergence seen in perturbative approximations to quantum field theories (QFT). When a formally divergent series in a QFT is summed using [[Borel summation]], the associated [[Borel summation|Borel transform]] of the series can have singularities as a function of the complex transform parameter.<ref name=Beneke1999>{{cite journal|last=Beneke|first=M.|title=Renormalons|journal=Physics Reports|date=August 1999|volume=37|issue=1-2|pages=1-142|doi=10.1016/S0370-1573(98)00130-6|url=http://www.sciencedirect.com/science/article/pii/S0370157398001306|accessdate=20 April 2013}}</ref> The renormalon is a possible type of singularity arising in this complex ''Borel plane'', and is a counterpart of an [[instanton]] singularity. Associated with such singularities, '''renormalon''' contributions are discussed in the context of [[quantum chromodynamics]] (QCD)<ref name=Beneke1999 /> and usually have the power-like form <math>\left(\Lambda/Q\right)^p</math> as functions of the momentum <math>Q</math> (here <math>\Lambda</math> is the momentum cut-off). They are cited against the usual logarithmic effects like <math>\ln\left(\Lambda/Q\right)</math>. | |||
==Brief history== | |||
Perturbation series in quantum field theory are usually divergent as was firstly indicated by [[Freeman Dyson]].<ref>F.J.Dyson, Phys.Rev. 85, 631 (1952)</ref> According to the Lipatov method,<ref>L.N.Lipatov, Zh.Eksp.Teor.Fiz. 72, 411(1977) [Sov.Phys. JETP 45, 216 (1977)].</ref> <math>N</math>-th order contribution of perturbation theory into any quantity can be evaluated at large <math>N</math> in the saddle-point approximation for functional integrals and is determined by [[instanton]] configurations. This contribution behaves usually as <math>N!</math> in dependence on <math>N</math> and is frequently associated with approximately the same (<math>N!</math>) number of [[Feynman diagram]]s. Lautrup<ref>B.Lautrup, Phys.Lett. B 69, 109 (1977).</ref> has noted that there exist individual diagrams giving approximately the same contribution. | |||
In principle, it is possible that such diagrams are automatically taken into account in Lipatov’s calculation, because its interpretation in terms of diagrammatic technique is problematic. However, 't Hooft put forward a conjecture that Lipatov's and Lautrup's contributions are related with different types of singularities in the Borel plane, the former with instanton ones and the latter with renormalon ones. Existence of instanton singularities is beyond any doubt, while existence of renormalon ones was never proved rigorously in spite of numerous efforts. Among the essential contributions one should mention the application of the [[operator product expansion]], as was suggested by Parisi.<ref>G.Parisi, Phys.Lett. B 76, 65 (1978); Nucl.Phys. B 150, 163 (1979).</ref> | |||
Recently a proof was suggested for absence of renormalon singularities in <math>\phi^4</math> theory and a general criterion for their existence was formulated<ref>I. M. Suslov, JETP 100, 1188 (2005), http://arxiv.org/abs/hep-ph/0510142.</ref> in terms of the asymptotic behavior of the Gell-Mann - Low function <math>\beta(g)</math>. Analytical results for asymptotics of <math>\beta(g)</math> in <math>\phi^4</math> theory<ref>I. M. Suslov, JETP 107, 413 (2008), http://arxiv.org/abs/1010.4081; JETP 111, 450 (2010), http://arxiv.org/abs/1010.4317.</ref> and QED<ref>I. M. Suslov, JETP 108, 980 (2009), http://arxiv.org/abs/0804.2650.</ref> indicate the absence of renormalon singularities in these theories. | |||
==References== | |||
{{reflist|2}} | |||
[[Category:Quantum chromodynamics]] |
Revision as of 08:42, 2 December 2013
In physics, a renormalon (a term suggested by 't Hooft[1]) is a particular source of divergence seen in perturbative approximations to quantum field theories (QFT). When a formally divergent series in a QFT is summed using Borel summation, the associated Borel transform of the series can have singularities as a function of the complex transform parameter.[2] The renormalon is a possible type of singularity arising in this complex Borel plane, and is a counterpart of an instanton singularity. Associated with such singularities, renormalon contributions are discussed in the context of quantum chromodynamics (QCD)[2] and usually have the power-like form as functions of the momentum (here is the momentum cut-off). They are cited against the usual logarithmic effects like .
Brief history
Perturbation series in quantum field theory are usually divergent as was firstly indicated by Freeman Dyson.[3] According to the Lipatov method,[4] -th order contribution of perturbation theory into any quantity can be evaluated at large in the saddle-point approximation for functional integrals and is determined by instanton configurations. This contribution behaves usually as in dependence on and is frequently associated with approximately the same () number of Feynman diagrams. Lautrup[5] has noted that there exist individual diagrams giving approximately the same contribution. In principle, it is possible that such diagrams are automatically taken into account in Lipatov’s calculation, because its interpretation in terms of diagrammatic technique is problematic. However, 't Hooft put forward a conjecture that Lipatov's and Lautrup's contributions are related with different types of singularities in the Borel plane, the former with instanton ones and the latter with renormalon ones. Existence of instanton singularities is beyond any doubt, while existence of renormalon ones was never proved rigorously in spite of numerous efforts. Among the essential contributions one should mention the application of the operator product expansion, as was suggested by Parisi.[6]
Recently a proof was suggested for absence of renormalon singularities in theory and a general criterion for their existence was formulated[7] in terms of the asymptotic behavior of the Gell-Mann - Low function . Analytical results for asymptotics of in theory[8] and QED[9] indicate the absence of renormalon singularities in these theories.
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.
- ↑ 't Hooft G, in: The whys of subnuclear physics (Erice, 1977), ed. A Zichichi, Plenum Press, New York, 1979.
- ↑ 2.0 2.1 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 - ↑ F.J.Dyson, Phys.Rev. 85, 631 (1952)
- ↑ L.N.Lipatov, Zh.Eksp.Teor.Fiz. 72, 411(1977) [Sov.Phys. JETP 45, 216 (1977)].
- ↑ B.Lautrup, Phys.Lett. B 69, 109 (1977).
- ↑ G.Parisi, Phys.Lett. B 76, 65 (1978); Nucl.Phys. B 150, 163 (1979).
- ↑ I. M. Suslov, JETP 100, 1188 (2005), http://arxiv.org/abs/hep-ph/0510142.
- ↑ I. M. Suslov, JETP 107, 413 (2008), http://arxiv.org/abs/1010.4081; JETP 111, 450 (2010), http://arxiv.org/abs/1010.4317.
- ↑ I. M. Suslov, JETP 108, 980 (2009), http://arxiv.org/abs/0804.2650.