Jacobi eigenvalue algorithm: Difference between revisions
en>Rgdboer m →Description: update link |
Changed the S to S' transformation as per the definition of the Givens rotation matrix by the related wikipedia article. A clear example can be seen here: http://physics.bc.edu/MSC/430/LINEAR_EIGEN/JacobiContinued.html |
||
Line 1: | Line 1: | ||
'''Segal's Burnside ring conjecture''', or, more briefly, the '''Segal conjecture''', is a [[theorem]] in [[homotopy theory]], a branch of [[mathematics]]. The theorem relates the [[Burnside ring]] of a finite [[Group (mathematics)|group]] ''G'' to the [[stable cohomotopy]] of the [[classifying space]] ''BG''. The conjecture was made by [[Graeme Segal]] and proved by [[Gunnar Carlsson]]. {{As of|2006}}, this statement is still commonly referred to as the Segal conjecture, even though it now has the status of a theorem. | |||
==Statement of the theorem== | |||
The Segal conjecture has several different formulations, not all of which are equivalent. Here is a weak form: there exists, for every finite group ''G'', an isomorphism | |||
:<math>\varprojlim \pi_S^0(BG^{(k)}_+) \to \hat{A}(G).</math> | |||
Here, lim denotes the [[inverse limit]], π<sub>S</sub>* denotes the stable cohomotopy ring, ''B'' denotes the classifying space, the superscript ''k'' denotes the ''k''-[[CW-complex|skeleton]], and the subscript + denotes the addition of a disjoint basepoint. On the right-hand side, the hat denotes the [[topological ring#Completion|completion]] of the Burnside ring with respect to its [[augmentation ideal]]. | |||
==The Burnside ring== | |||
{{Main|Burnside ring}} | |||
The Burnside ring of a finite group ''G'' is constructed from the category of finite [[group action|''G''-sets]] as a [[Grothendieck group]]. More precisely, let ''M(G)'' be the commutative [[monoid]] of isomorphism classes of finite ''G''-sets, with addition the disjoint union of ''G''-sets and identity element the empty set (which is a ''G''-set in a unique way). Then ''A(G)'', the Grothendieck group of ''M(G)'', is an abelian group. It is in fact a [[free abelian group|free]] abelian group with basis elements represented by the ''G''-sets ''G''/''H'', where ''H'' varies over the subgroups of ''G''. (Note that ''H'' is not assumed here to be a normal subgroup of ''G'', for while ''G''/''H'' is not a group in this case, it is still a ''G''-set.) The [[ring_(mathematics)|ring]] structure on ''A(G)'' is induced by the direct product of ''G''-sets; the multiplicative identity is the (isomorphism class of any) one-point set, which becomes a ''G''-set in a unique way. | |||
The Burnside ring is the analogue of the [[representation ring]] in the category of finite sets, as opposed to the category of finite-dimensional [[vector space]]s over a [[Field (mathematics)|field]] (see [[#Motivation and interpretation|motivation]] below). It has proven to be an important tool in the [[group representation|representation theory]] of finite groups. | |||
==The classifying space== | |||
{{Main|Classifying space}} | |||
For any [[topological group]] ''G'' admitting the structure of a [[CW-complex]], one may consider the category of [[principal bundle|principal ''G''-bundles]]. One can define a [[functor]] from the category of CW-complexes to the category of sets by assigning to each CW-complex ''X'' the set of principal ''G''-bundles on ''X''. This functor descends to a functor on the homotopy category of CW-complexes, and it is natural to ask whether the functor so obtained is [[representable functor|representable]]. The answer is affirmative, and the representing object is called the classifying space of the group ''G'' and typically denoted ''BG''. If we restrict our attention to the homotopy category of CW-complexes, then ''BG'' is unique. Any CW-complex that is homotopy equivalent to ''BG'' is called a ''model'' for ''BG''. | |||
For example, if ''G'' is the group of order 2, then a model for ''BG'' is infinite-dimensional real projective space. It can be shown that if ''G'' is finite, then any CW-complex modelling ''BG'' has cells of arbitrarily large dimension. On the other hand, if ''G'' = '''Z''', the integers, then the classifying space ''BG'' is homotopy equivalent to the circle ''S''<sup>1</sup>. | |||
==Motivation and interpretation== | |||
The content of the theorem becomes somewhat clearer if it is placed in its historical context. In the theory of representations of finite groups, one can form an object ''R[G]'' called the representation ring in a way entirely analogous to the construction of the Burnside ring outlined above. The stable cohomotopy is in a sense the natural analog to complex [[K-theory]], which is denoted ''KU''*. Segal was inspired to make his conjecture after [[Michael Atiyah]] proved the existence of an isomorphism | |||
:<math>KU^0(BG) \to \hat{R}[G]</math> | |||
which is a special case of the [[Atiyah-Segal completion theorem]]. | |||
==References== | |||
*{{cite conference | |||
| author=[[Frank Adams|J.F. Adams]] | |||
| title= Graeme Segal's Burnside ring conjecture | |||
| booktitle= Proc. Topology Symp. Siegen | |||
| year= 1979}} | |||
*{{cite journal | |||
| author=G. Carlsson | |||
| title=Equivariant stable homotopy and Segal's Burnside ring conjecture | |||
| journal=Annals of Mathematics | |||
| year=1984 | |||
| volume=120 | |||
| issue=2 | |||
| pages=189–224 | |||
| doi=10.2307/2006940 | |||
| publisher=Annals of Mathematics | |||
| jstor=2006940}} | |||
[[Category:Representation theory of finite groups]] | |||
[[Category:Homotopy theory]] | |||
[[Category:Conjectures]] | |||
[[Category:Theorems in algebra]] |
Revision as of 12:51, 22 January 2014
Segal's Burnside ring conjecture, or, more briefly, the Segal conjecture, is a theorem in homotopy theory, a branch of mathematics. The theorem relates the Burnside ring of a finite group G to the stable cohomotopy of the classifying space BG. The conjecture was made by Graeme Segal and proved by Gunnar Carlsson. Template:As of, this statement is still commonly referred to as the Segal conjecture, even though it now has the status of a theorem.
Statement of the theorem
The Segal conjecture has several different formulations, not all of which are equivalent. Here is a weak form: there exists, for every finite group G, an isomorphism
Here, lim denotes the inverse limit, πS* denotes the stable cohomotopy ring, B denotes the classifying space, the superscript k denotes the k-skeleton, and the subscript + denotes the addition of a disjoint basepoint. On the right-hand side, the hat denotes the completion of the Burnside ring with respect to its augmentation ideal.
The Burnside ring
Mining Engineer (Excluding Oil ) Truman from Alma, loves to spend time knotting, largest property developers in singapore developers in singapore and stamp collecting. Recently had a family visit to Urnes Stave Church.
The Burnside ring of a finite group G is constructed from the category of finite G-sets as a Grothendieck group. More precisely, let M(G) be the commutative monoid of isomorphism classes of finite G-sets, with addition the disjoint union of G-sets and identity element the empty set (which is a G-set in a unique way). Then A(G), the Grothendieck group of M(G), is an abelian group. It is in fact a free abelian group with basis elements represented by the G-sets G/H, where H varies over the subgroups of G. (Note that H is not assumed here to be a normal subgroup of G, for while G/H is not a group in this case, it is still a G-set.) The ring structure on A(G) is induced by the direct product of G-sets; the multiplicative identity is the (isomorphism class of any) one-point set, which becomes a G-set in a unique way.
The Burnside ring is the analogue of the representation ring in the category of finite sets, as opposed to the category of finite-dimensional vector spaces over a field (see motivation below). It has proven to be an important tool in the representation theory of finite groups.
The classifying space
Mining Engineer (Excluding Oil ) Truman from Alma, loves to spend time knotting, largest property developers in singapore developers in singapore and stamp collecting. Recently had a family visit to Urnes Stave Church. For any topological group G admitting the structure of a CW-complex, one may consider the category of principal G-bundles. One can define a functor from the category of CW-complexes to the category of sets by assigning to each CW-complex X the set of principal G-bundles on X. This functor descends to a functor on the homotopy category of CW-complexes, and it is natural to ask whether the functor so obtained is representable. The answer is affirmative, and the representing object is called the classifying space of the group G and typically denoted BG. If we restrict our attention to the homotopy category of CW-complexes, then BG is unique. Any CW-complex that is homotopy equivalent to BG is called a model for BG.
For example, if G is the group of order 2, then a model for BG is infinite-dimensional real projective space. It can be shown that if G is finite, then any CW-complex modelling BG has cells of arbitrarily large dimension. On the other hand, if G = Z, the integers, then the classifying space BG is homotopy equivalent to the circle S1.
Motivation and interpretation
The content of the theorem becomes somewhat clearer if it is placed in its historical context. In the theory of representations of finite groups, one can form an object R[G] called the representation ring in a way entirely analogous to the construction of the Burnside ring outlined above. The stable cohomotopy is in a sense the natural analog to complex K-theory, which is denoted KU*. Segal was inspired to make his conjecture after Michael Atiyah proved the existence of an isomorphism
which is a special case of the Atiyah-Segal completion theorem.
References
- 55 years old Systems Administrator Antony from Clarence Creek, really loves learning, PC Software and aerobics. Likes to travel and was inspired after making a journey to Historic Ensemble of the Potala Palace.
You can view that web-site... ccleaner free download - 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