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In [[particle physics]], the '''Peccei–Quinn theory''' is the best known proposal for the resolution of the [[strong CP problem]]. It was formulated by [[Roberto Peccei]] and [[Helen Quinn]]. The theory proposes that the [[Quantum chromodynamics|QCD]] [[Lagrangian]] be extended with a [[CP-violation|CP-violating]] term known as the θ parameter. Because experiments have never measured a value for θ, its value must be small or zero. | |||
Peccei–Quinn theory predicts that the θ parameter is explained by dynamic field, rather than a constant value. Because quantum fields produce particles, Peccei–Quinn theory predicts the existence of a new particle, the [[axion]]. The potential which this field carries causes it to have a [[vacuum expectation value|value]] which naturally cancels, making the θ parameter effectively zero. | |||
'''Peccei–Quinn symmetry''' is a possible additional ingredient—a global U(1) [[symmetry]] under which a complex scalar field is charged. This symmetry is [[spontaneous symmetry breaking|spontaneously broken]] by the [[VEV]] obtained by this scalar field, and the [[axion]] is the massless [[goldstone boson]] of this symmetry breaking. If the symmetry is a [[gauge symmetry]] then the axion is "eaten up" by the [[gauge boson]], meaning that the [[gauge boson]] becomes massive and the axion does not exist anymore as a physical degree of freedom (see [[Higgs mechanism]]). This is [[Particle physics phenomenology|phenomenologically]] desirable because it leaves no massless particles, which are indeed not seen experimentally. | |||
This Peccei–Quinn symmetry can't possibly be exact because it is anomalously broken by [[QCD instanton]]s. If there were a compensating term canceling the QCD anomaly breaking term, the axion becomes an exactly massless Goldstone boson and θ is no longer fixed. The effective potential for the axion is the sum of the potential above the QCD scale with the potential term induced by nonperturbative QCD effects. If the axion is fundamental, or emerges at a scale far higher than the [[QCD scale]], the dimension 5 axion coupling term <math>a \mathrm{Tr}[ F \wedge F ]</math> is suppressed by <math>1/\Lambda</math> where <math>\Lambda</math> is the scale where the axion appears. Because of this, in order for θ to be so small at the minimum of the effective potential, the bare potential has to be many orders of magnitude smaller than the instanton induced potential, compounded by the <math>\Lambda</math> factor. This requires quite a bit of adjusting for an approximate global symmetry, for which there is no current explanation. | |||
==References== | |||
* {{Cite journal | |||
|last1= Peccei | |||
|first1= Roberto D. | |||
|authorlink1= Roberto Peccei | |||
|last2= Quinn | |||
|first2= Helen R. | |||
|authorlink2= Helen Quinn | |||
|year= 1977 | |||
|title= ''CP'' Conservation in the Presence of Pseudoparticles | |||
|journal= [[Physical Review Letters]] | |||
|volume= 38 | |||
|pages= 1440 | |||
|doi= 10.1103/PhysRevLett.38.1440 | |||
|bibcode= 1977PhRvL..38.1440P | |||
|issue= 25 | |||
}} | |||
* {{Cite journal | |||
|last1= Peccei | |||
|first1= Roberto D. | |||
|authorlink1= Roberto Peccei | |||
|last2= Quinn | |||
|first2= Helen R. | |||
|authorlink2= Helen Quinn | |||
|year= 1977 | |||
|title= Constraints imposed by ''CP'' conservation in the presence of pseudoparticles | |||
|journal= [[Physical Review D]] | |||
|volume= 16 | |||
|pages= 1791 | |||
|doi= 10.1103/PhysRevD.16.1791 | |||
|bibcode= 1977PhRvD..16.1791P | |||
|issue= 6 | |||
}} | |||
{{DEFAULTSORT:Peccei-Quinn theory}} | |||
[[Category:Particle physics]] | |||
[[Category:Quantum chromodynamics]] | |||
[[Category:Anomalies in physics]] | |||
{{particle-stub}} |
Revision as of 01:53, 13 January 2014
In particle physics, the Peccei–Quinn theory is the best known proposal for the resolution of the strong CP problem. It was formulated by Roberto Peccei and Helen Quinn. The theory proposes that the QCD Lagrangian be extended with a CP-violating term known as the θ parameter. Because experiments have never measured a value for θ, its value must be small or zero.
Peccei–Quinn theory predicts that the θ parameter is explained by dynamic field, rather than a constant value. Because quantum fields produce particles, Peccei–Quinn theory predicts the existence of a new particle, the axion. The potential which this field carries causes it to have a value which naturally cancels, making the θ parameter effectively zero.
Peccei–Quinn symmetry is a possible additional ingredient—a global U(1) symmetry under which a complex scalar field is charged. This symmetry is spontaneously broken by the VEV obtained by this scalar field, and the axion is the massless goldstone boson of this symmetry breaking. If the symmetry is a gauge symmetry then the axion is "eaten up" by the gauge boson, meaning that the gauge boson becomes massive and the axion does not exist anymore as a physical degree of freedom (see Higgs mechanism). This is phenomenologically desirable because it leaves no massless particles, which are indeed not seen experimentally.
This Peccei–Quinn symmetry can't possibly be exact because it is anomalously broken by QCD instantons. If there were a compensating term canceling the QCD anomaly breaking term, the axion becomes an exactly massless Goldstone boson and θ is no longer fixed. The effective potential for the axion is the sum of the potential above the QCD scale with the potential term induced by nonperturbative QCD effects. If the axion is fundamental, or emerges at a scale far higher than the QCD scale, the dimension 5 axion coupling term is suppressed by where is the scale where the axion appears. Because of this, in order for θ to be so small at the minimum of the effective potential, the bare potential has to be many orders of magnitude smaller than the instanton induced potential, compounded by the factor. This requires quite a bit of adjusting for an approximate global symmetry, for which there is no current explanation.
References
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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