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In [[mathematics]], the '''Littlewood conjecture''' is an [[open problem]] ({{As of|2011|lc=on}}) in [[Diophantine approximation]], proposed by [[John Edensor Littlewood]] around 1930. It states that for any two [[real number]]s α and β,
 
:<math>\liminf_{n\to\infty} \ n\,\Vert n\alpha\Vert \,\Vert n\beta\Vert = 0,</math>
 
where <math>\Vert \,\Vert</math> is here the distance to the nearest integer.
 
==Formulation and explanation==
 
This means the following: take a point (α,β) in the plane, and then consider the sequence of points
 
:(2α,2β), (3α,3β), ... .
 
For each of these consider the closest [[Lattice (group)|lattice point]], as determined by multiplying the distance to the closest line with integer x-coordinate by the distance to the closest line with integer y-coordinate. This product will certainly be at most 1/4. The conjecture makes no statement about whether this sequence of values will [[Convergence (mathematics)|converge]]; it typically does not, in fact. The conjecture states something about the [[Limit superior and limit inferior|limit inferior]], and says that there is a subsequence for which the distances decay faster than the reciprocal, i.e.
 
:o(1/''n'')
 
in the [[Big_O_notation#Little-o_notation|little-o notation]].
 
==Connection to further conjectures==
 
It is known that this would follow from a result in the [[geometry of numbers]], about the minimum on a non-zero [[lattice (group)|lattice]] point of a product of three linear forms in three real variables: the implication was shown in 1955 by [[J. W. S. Cassels]] and [[Swinnerton-Dyer]].<ref>{{cite journal | author=J.W.S. Cassels, H.P.F. Swinnerton-Dyer | title=On the product of three homogeneous linear forms and the indefinite ternary quadratic forms | journal=[[Philosophical Transactions of the Royal Society A]] | volume=248 | issue=940 | date=1955-06-23 | pages=73–96 | doi=10.1098/rsta.1955.0010 | jstor=91633 | mr = 70653 |zbl=0065.27905}}</ref> This can be formulated another way, in group-theoretic terms. There is now another conjecture, expected to hold for ''n'' ≥ 3: it is stated in terms of ''G'' = ''SL<sub>n</sub>''(''R''), Γ = ''SL<sub>n</sub>''(''Z''), and the subgroup ''D'' of ''G'' of [[diagonal matrices]].
 
'''''Conjecture''''': for any ''g'' in ''G''/Γ such that ''Dg'' is [[relatively compact]] (in ''G''/Γ), then ''Dg'' is closed.
 
This in turn is a special case of a general conjecture of [[Grigory Margulis|Margulis]] on [[Lie group]]s.
 
==Partial results==
Borel showed in 1909 that the exceptional set of real pairs (α,β) violating the statement of the conjecture is of [[Lebesgue measure]] zero.<ref name=AB444>Adamczewski & Bugeaud (2010) p.444</ref> [[Manfred Einsiedler]], [[Anatole Katok]] and [[Elon Lindenstrauss]] have shown<ref>{{cite journal | author=M. Einsiedler, A. Katok, E. Lindenstrauss | title=Invariant measures and the set of exceptions to Littlewood's conjecture | journal=[[Annals of Mathematics]] | volume=164 | issue=2 | pages=513–560 | date=2006-09-01 | doi=10.4007/annals.2006.164.513 | arxiv=math.DS/0612721 | mr = 2247967 |zbl=1109.22004}}</ref> that it must have [[Hausdorff dimension]] zero;<ref name=AB445>Adamczewski & Bugeaud (2010) p.445</ref> and in fact is a union of countably many [[Compact space|compact set]]s of [[Minkowski–Bouligand dimension|box-counting dimension]] zero. The result was proved by using measure classification theorem for diagonalizable actions of higher-rank groups, and an ''isolation theorem'' proved by Lindenstrauss and Barak Weiss.
 
These results imply that non-trivial pairs satisfying the conjecture exist: indeed, given a real number α such that <math>\inf_{n \ge 1} n \cdot || n \alpha || > 0 </math>, it is possible to construct an explicit β such that (α,β) satisfies the conjecture.<ref name=AB446>Adamczewski & Bugeaud (2010) p.446</ref>
 
==See also==
* [[Littlewood polynomial]]
 
==References==
{{reflist}}
*{{cite book | last1=Adamczewski | first1=Boris | last2=Bugeaud | first2=Yann | chapter=8. Transcendence and diophantine approximation | editor1-last=Berthé | editor1-first=Valérie | editor2-last=Rigo | editor2-first=Michael | title=Combinatorics, automata, and number theory | location=Cambridge | publisher=[[Cambridge University Press]] | series=Encyclopedia of Mathematics and its Applications | volume=135 | pages=410–451 | year=2010 | isbn=978-0-521-51597-9 | zbl=pre05879512 }}
 
==Further reading==
* {{cite journal | author=Akshay Venkatesh | title=The work of Einsiedler, Katok, and Lindenstrauss on the Littlewood conjecture | journal=[[Bulletin of the American Mathematical Society|Bull. Amer. Math. Soc. (N.S.)]] | volume=45 | issue=1 | date=2007-10-29 | pages=117–134 | url=http://www.cims.nyu.edu/~venkatesh/research/eklexp.pdf | doi=10.1090/S0273-0979-07-01194-9 | accessdate=2011-03-27 | mr=2358379 | zbl = 1194.11075 }}
 
{{DEFAULTSORT:Littlewood Conjecture}}
[[Category:Diophantine approximation]]
[[Category:Conjectures]]

Revision as of 22:58, 11 October 2013

In mathematics, the Littlewood conjecture is an open problem (Template:As of) in Diophantine approximation, proposed by John Edensor Littlewood around 1930. It states that for any two real numbers α and β,

lim infnnnαnβ=0,

where is here the distance to the nearest integer.

Formulation and explanation

This means the following: take a point (α,β) in the plane, and then consider the sequence of points

(2α,2β), (3α,3β), ... .

For each of these consider the closest lattice point, as determined by multiplying the distance to the closest line with integer x-coordinate by the distance to the closest line with integer y-coordinate. This product will certainly be at most 1/4. The conjecture makes no statement about whether this sequence of values will converge; it typically does not, in fact. The conjecture states something about the limit inferior, and says that there is a subsequence for which the distances decay faster than the reciprocal, i.e.

o(1/n)

in the little-o notation.

Connection to further conjectures

It is known that this would follow from a result in the geometry of numbers, about the minimum on a non-zero lattice point of a product of three linear forms in three real variables: the implication was shown in 1955 by J. W. S. Cassels and Swinnerton-Dyer.[1] This can be formulated another way, in group-theoretic terms. There is now another conjecture, expected to hold for n ≥ 3: it is stated in terms of G = SLn(R), Γ = SLn(Z), and the subgroup D of G of diagonal matrices.

Conjecture: for any g in G/Γ such that Dg is relatively compact (in G/Γ), then Dg is closed.

This in turn is a special case of a general conjecture of Margulis on Lie groups.

Partial results

Borel showed in 1909 that the exceptional set of real pairs (α,β) violating the statement of the conjecture is of Lebesgue measure zero.[2] Manfred Einsiedler, Anatole Katok and Elon Lindenstrauss have shown[3] that it must have Hausdorff dimension zero;[4] and in fact is a union of countably many compact sets of box-counting dimension zero. The result was proved by using measure classification theorem for diagonalizable actions of higher-rank groups, and an isolation theorem proved by Lindenstrauss and Barak Weiss.

These results imply that non-trivial pairs satisfying the conjecture exist: indeed, given a real number α such that infn1n||nα||>0, it is possible to construct an explicit β such that (α,β) satisfies the conjecture.[5]

See also

References

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Further reading

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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

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    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

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  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
  2. Adamczewski & Bugeaud (2010) p.444
  3. 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
  4. Adamczewski & Bugeaud (2010) p.445
  5. Adamczewski & Bugeaud (2010) p.446