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In [[mathematics]], a '''Severi–Brauer variety''' over a [[field (mathematics)|field]] ''K'' is an [[algebraic variety]] ''V'' which becomes [[isomorphic]] to a [[projective space]] over an [[algebraic closure]] of ''K''. The varieties are associated to [[central simple algebra]]s in such a way that the algebra splits over ''K'' if and only if the variety has a point rational over ''K''. {{harvs|txt|first=Francesco |last=Severi|authorlink=Francesco Severi|year=1932}} studied these varieties, and they are also named after [[Richard Brauer]] because of their close relation to the [[Brauer group]]. | |||
In dimension one, the Severi–Brauer varieties are [[conic section|conics]]. The corresponding central simple algebras are the [[quaternion algebra]]s. The algebra (''a'',''b'')<sub>''K''</sub> corresponds to the conic ''C''(''a'',''b'') with equation | |||
:<math>z^2 = ax^2 + by^2 \ </math> | |||
and the algebra (''a'',''b'')<sub>''K''</sub> ''splits'', that is, (''a'',''b'')<sub>''K''</sub> is isomorphic to a [[Matrix ring|matrix algebra]] over ''K'', if and only if ''C''(''a'',''b'') has a point defined over ''K'': this is in turn equivalent to ''C''(''a'',''b'') being isomorphic to the [[projective line]] over ''K''.<ref name=GS129>Gille & Szamuely (2006) p.129</ref> | |||
Such varieties are of interest not only in [[diophantine geometry]], but also in [[Galois cohomology]]. They represent (at least if ''K'' is a [[perfect field]]) Galois cohomology classes in | |||
:''H''<sup>1</sup>(''PGL''<sub>''n''</sub>) | |||
in the [[projective linear group]], where ''n'' is the [[dimension of a variety|dimension]] of ''V''. There is a [[short exact sequence]] | |||
:1 → ''GL''<sub>1</sub> → ''GL''<sub>''n''</sub> → ''PGL''<sub>''n''</sub> → 1 | |||
of [[algebraic group]]s. This implies a [[connecting homomorphism]] | |||
:''H''<sup>1</sup>(''PGL''<sub>''n''</sub>) → ''H''<sup>2</sup>(''GL''<sub>1</sub>) | |||
at the level of cohomology. Here ''H''<sup>2</sup>(''GL''<sub>''1''</sub>) is identified with the [[Brauer group]] of ''K'', while the kernel is trivial because | |||
:''H''<sup>1</sup>(''GL''<sub>''n''</sub>) = {1} | |||
by an extension of [[Hilbert's Theorem 90]].<ref name=GS26>Gille & Szamuely (2006) p.26</ref><ref>{{citation | title=An Introduction to Galois Cohomology and its Applications | volume=377 | series=London Mathematical Society Lecture Note Series | first=Grégory | last=Berhuy | publisher=[[Cambridge University Press]] | year=2010 | isbn=0-521-73866-0 | zbl=1207.12003 | page=113 }}</ref> Therefore the Severi–Brauer varieties can be faithfully represented by Brauer group elements, i.e. classes of [[central simple algebra]]s. | |||
Lichtenbaum showed that if ''X'' is a Severi–Brauer variety over ''K'' then there is an exact sequence | |||
:<math>0 \rightarrow \mathrm{Pic}(X) \rightarrow \mathbb{Z} \stackrel{\delta}{\rightarrow} \mathrm{Br}(K) \rightarrow \mathrm{Br}(K)(X) \rightarrow 0 \ . </math> | |||
Here the map δ sends 1 to the Brauer class corresponding to ''X''.<ref name="GS129"/> | |||
As a consequence, we see that if the class of ''X'' has order ''d'' in the Brauer group then there is a [[divisor class]] of degree ''d'' on ''X''. The associated [[linear system]] defines the ''d''-dimensional embedding of ''X'' over a splitting field ''L''.<ref name=GS131>Gille & Szamuely (2006) p.131</ref> | |||
==References== | |||
{{reflist}} | |||
*{{Citation | last1=Artin | first1=Michael | author1-link=Michael Artin | title=Brauer groups in ring theory and algebraic geometry (Wilrijk, 1981) | publisher=[[Springer-Verlag]] | location=Berlin, New York | others=Notes by A. Verschoren | series=Lecture Notes in Math. | isbn=978-3-540-11216-7 | doi=10.1007/BFb0092235 | mr=657430 | year=1982 | volume=917 | chapter=Brauer-Severi varieties | zbl=0536.14006 | pages=194–210}} | |||
*{{Springer|id=b/b017620|title=Brauer–Severi variety}} | |||
*{{citation | chapterurl=http://ebooks.cambridge.org/chapter.jsf?bid=CBO9780511607219&cid=CBO9780511607219A036 | pages=114–134 | title=Central Simple Algebras and Galois Cohomology | first1=Philippe | last1=Gille | first2=Tamás | last2=Szamuely | series=Cambridge Studies in Advanced Mathematics | volume=101 | publisher=[[Cambridge University Press]] | year=2006 | isbn=0-521-86103-9 | zbl=1137.12001 }} | |||
*{{citation | last=Saltman | first=David J. | title=Lectures on division algebras | series=Regional Conference Series in Mathematics | volume=94 | location=Providence, RI | publisher=[[American Mathematical Society]] | year=1999 | isbn=0-8218-0979-2 | zbl=0934.16013 }} | |||
*{{Citation | last1=Severi | first1=Francesco | title=Un nuovo campo di ricerche nella geometria sopra una superficie e sopra una varietà algebrica | language=Italian | id=Reprinted in volume 3 of his collected works | year=1932 | journal=Memorie della Reale Accademia d'Italia | volume=3 | issue=5}} | |||
==External links== | |||
*[http://www.mathcs.emory.edu/~brussel/Papers/galoisdescent.pdf Expository paper on Galois descent (PDF)] | |||
{{DEFAULTSORT:Severi-Brauer Variety}} | |||
[[Category:Algebraic varieties]] | |||
[[Category:Diophantine geometry]] | |||
[[Category:Homological algebra]] | |||
[[Category:Algebraic groups]] | |||
[[Category:Ring theory]] |
Revision as of 16:57, 7 January 2014
In mathematics, a Severi–Brauer variety over a field K is an algebraic variety V which becomes isomorphic to a projective space over an algebraic closure of K. The varieties are associated to central simple algebras in such a way that the algebra splits over K if and only if the variety has a point rational over K. Template:Harvs studied these varieties, and they are also named after Richard Brauer because of their close relation to the Brauer group.
In dimension one, the Severi–Brauer varieties are conics. The corresponding central simple algebras are the quaternion algebras. The algebra (a,b)K corresponds to the conic C(a,b) with equation
and the algebra (a,b)K splits, that is, (a,b)K is isomorphic to a matrix algebra over K, if and only if C(a,b) has a point defined over K: this is in turn equivalent to C(a,b) being isomorphic to the projective line over K.[1]
Such varieties are of interest not only in diophantine geometry, but also in Galois cohomology. They represent (at least if K is a perfect field) Galois cohomology classes in
- H1(PGLn)
in the projective linear group, where n is the dimension of V. There is a short exact sequence
- 1 → GL1 → GLn → PGLn → 1
of algebraic groups. This implies a connecting homomorphism
- H1(PGLn) → H2(GL1)
at the level of cohomology. Here H2(GL1) is identified with the Brauer group of K, while the kernel is trivial because
- H1(GLn) = {1}
by an extension of Hilbert's Theorem 90.[2][3] Therefore the Severi–Brauer varieties can be faithfully represented by Brauer group elements, i.e. classes of central simple algebras.
Lichtenbaum showed that if X is a Severi–Brauer variety over K then there is an exact sequence
Here the map δ sends 1 to the Brauer class corresponding to X.[1]
As a consequence, we see that if the class of X has order d in the Brauer group then there is a divisor class of degree d on X. The associated linear system defines the d-dimensional embedding of X over a splitting field L.[4]
References
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Naturally, you will have to pay a safety deposit and that is usually one month rent for annually of the settlement. That is the place your good religion deposit will likely be taken into account and will kind part or all of your security deposit. Anticipate to have a proportionate amount deducted out of your deposit if something is discovered to be damaged if you move out. It's best to you'll want to test the inventory drawn up by the owner, which can detail all objects in the property and their condition. If you happen to fail to notice any harm not already mentioned within the inventory before transferring in, you danger having to pay for it yourself.
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Have handed an trade examination i.e Widespread Examination for House Brokers (CEHA) or Actual Property Agency (REA) examination, or equal; Exclusive brokers are extra keen to share listing information thus making certain the widest doable coverage inside the real estate community via Multiple Listings and Networking. Accepting a severe provide is simpler since your agent is totally conscious of all advertising activity related with your property. This reduces your having to check with a number of agents for some other offers. Price control is easily achieved. Paint work in good restore-discuss with your Property Marketing consultant if main works are still to be done. Softening in residential property prices proceed, led by 2.8 per cent decline within the index for Remainder of Central Region
Once you place down the one per cent choice price to carry down a non-public property, it's important to accept its situation as it is whenever you move in – faulty air-con, choked rest room and all. Get round this by asking your agent to incorporate a ultimate inspection clause within the possibility-to-buy letter. HDB flat patrons routinely take pleasure in this security net. "There's a ultimate inspection of the property two days before the completion of all HDB transactions. If the air-con is defective, you can request the seller to repair it," says Kelvin.
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To achieve the very best outcomes, you must be always updated on market situations, including past transaction information and reliable projections. You could review and examine comparable homes that are currently available in the market, especially these which have been sold or not bought up to now six months. You'll be able to see a pattern of such report by clicking here It's essential to defend yourself in opposition to unscrupulous patrons. They are often very skilled in using highly unethical and manipulative techniques to try and lure you into a lure. That you must also protect your self, your loved ones, and personal belongings as you'll be serving many strangers in your home. Sign a listing itemizing of all of the objects provided by the proprietor, together with their situation. HSR Prime Recruiter 2010 - Many property agents need to declare for the PIC grant in Singapore. However, not all of them know find out how to do the correct process for getting this PIC scheme from the IRAS. There are a number of steps that you need to do before your software can be approved.
Naturally, you will have to pay a safety deposit and that is usually one month rent for annually of the settlement. That is the place your good religion deposit will likely be taken into account and will kind part or all of your security deposit. Anticipate to have a proportionate amount deducted out of your deposit if something is discovered to be damaged if you move out. It's best to you'll want to test the inventory drawn up by the owner, which can detail all objects in the property and their condition. If you happen to fail to notice any harm not already mentioned within the inventory before transferring in, you danger having to pay for it yourself.
In case you are in search of an actual estate or Singapore property agent on-line, you simply should belief your intuition. It's because you do not know which agent is nice and which agent will not be. Carry out research on several brokers by looking out the internet. As soon as if you end up positive that a selected agent is dependable and reliable, you can choose to utilize his partnerise in finding you a home in Singapore. Most of the time, a property agent is taken into account to be good if he or she locations the contact data on his website. This may mean that the agent does not mind you calling them and asking them any questions relating to new properties in singapore in Singapore. After chatting with them you too can see them in their office after taking an appointment.
Have handed an trade examination i.e Widespread Examination for House Brokers (CEHA) or Actual Property Agency (REA) examination, or equal; Exclusive brokers are extra keen to share listing information thus making certain the widest doable coverage inside the real estate community via Multiple Listings and Networking. Accepting a severe provide is simpler since your agent is totally conscious of all advertising activity related with your property. This reduces your having to check with a number of agents for some other offers. Price control is easily achieved. Paint work in good restore-discuss with your Property Marketing consultant if main works are still to be done. Softening in residential property prices proceed, led by 2.8 per cent decline within the index for Remainder of Central Region
Once you place down the one per cent choice price to carry down a non-public property, it's important to accept its situation as it is whenever you move in – faulty air-con, choked rest room and all. Get round this by asking your agent to incorporate a ultimate inspection clause within the possibility-to-buy letter. HDB flat patrons routinely take pleasure in this security net. "There's a ultimate inspection of the property two days before the completion of all HDB transactions. If the air-con is defective, you can request the seller to repair it," says Kelvin.
15.6.1 As the agent is an intermediary, generally, as soon as the principal and third party are introduced right into a contractual relationship, the agent drops out of the image, subject to any problems with remuneration or indemnification that he could have against the principal, and extra exceptionally, against the third occasion. Generally, agents are entitled to be indemnified for all liabilities reasonably incurred within the execution of the brokers´ authority.
To achieve the very best outcomes, you must be always updated on market situations, including past transaction information and reliable projections. You could review and examine comparable homes that are currently available in the market, especially these which have been sold or not bought up to now six months. You'll be able to see a pattern of such report by clicking here It's essential to defend yourself in opposition to unscrupulous patrons. They are often very skilled in using highly unethical and manipulative techniques to try and lure you into a lure. That you must also protect your self, your loved ones, and personal belongings as you'll be serving many strangers in your home. Sign a listing itemizing of all of the objects provided by the proprietor, together with their situation. HSR Prime Recruiter 2010 - Many property agents need to declare for the PIC grant in Singapore. However, not all of them know find out how to do the correct process for getting this PIC scheme from the IRAS. There are a number of steps that you need to do before your software can be approved.
Naturally, you will have to pay a safety deposit and that is usually one month rent for annually of the settlement. That is the place your good religion deposit will likely be taken into account and will kind part or all of your security deposit. Anticipate to have a proportionate amount deducted out of your deposit if something is discovered to be damaged if you move out. It's best to you'll want to test the inventory drawn up by the owner, which can detail all objects in the property and their condition. If you happen to fail to notice any harm not already mentioned within the inventory before transferring in, you danger having to pay for it yourself.
In case you are in search of an actual estate or Singapore property agent on-line, you simply should belief your intuition. It's because you do not know which agent is nice and which agent will not be. Carry out research on several brokers by looking out the internet. As soon as if you end up positive that a selected agent is dependable and reliable, you can choose to utilize his partnerise in finding you a home in Singapore. Most of the time, a property agent is taken into account to be good if he or she locations the contact data on his website. This may mean that the agent does not mind you calling them and asking them any questions relating to new properties in singapore in Singapore. After chatting with them you too can see them in their office after taking an appointment.
Have handed an trade examination i.e Widespread Examination for House Brokers (CEHA) or Actual Property Agency (REA) examination, or equal; Exclusive brokers are extra keen to share listing information thus making certain the widest doable coverage inside the real estate community via Multiple Listings and Networking. Accepting a severe provide is simpler since your agent is totally conscious of all advertising activity related with your property. This reduces your having to check with a number of agents for some other offers. Price control is easily achieved. Paint work in good restore-discuss with your Property Marketing consultant if main works are still to be done. Softening in residential property prices proceed, led by 2.8 per cent decline within the index for Remainder of Central Region
Once you place down the one per cent choice price to carry down a non-public property, it's important to accept its situation as it is whenever you move in – faulty air-con, choked rest room and all. Get round this by asking your agent to incorporate a ultimate inspection clause within the possibility-to-buy letter. HDB flat patrons routinely take pleasure in this security net. "There's a ultimate inspection of the property two days before the completion of all HDB transactions. If the air-con is defective, you can request the seller to repair it," says Kelvin.
15.6.1 As the agent is an intermediary, generally, as soon as the principal and third party are introduced right into a contractual relationship, the agent drops out of the image, subject to any problems with remuneration or indemnification that he could have against the principal, and extra exceptionally, against the third occasion. Generally, agents are entitled to be indemnified for all liabilities reasonably incurred within the execution of the brokers´ authority.
To achieve the very best outcomes, you must be always updated on market situations, including past transaction information and reliable projections. You could review and examine comparable homes that are currently available in the market, especially these which have been sold or not bought up to now six months. You'll be able to see a pattern of such report by clicking here It's essential to defend yourself in opposition to unscrupulous patrons. They are often very skilled in using highly unethical and manipulative techniques to try and lure you into a lure. That you must also protect your self, your loved ones, and personal belongings as you'll be serving many strangers in your home. Sign a listing itemizing of all of the objects provided by the proprietor, together with their situation. HSR Prime Recruiter 2010
External links
- ↑ 1.0 1.1 Gille & Szamuely (2006) p.129
- ↑ Gille & Szamuely (2006) p.26
- ↑ Many property agents need to declare for the PIC grant in Singapore. However, not all of them know find out how to do the correct process for getting this PIC scheme from the IRAS. There are a number of steps that you need to do before your software can be approved.
Naturally, you will have to pay a safety deposit and that is usually one month rent for annually of the settlement. That is the place your good religion deposit will likely be taken into account and will kind part or all of your security deposit. Anticipate to have a proportionate amount deducted out of your deposit if something is discovered to be damaged if you move out. It's best to you'll want to test the inventory drawn up by the owner, which can detail all objects in the property and their condition. If you happen to fail to notice any harm not already mentioned within the inventory before transferring in, you danger having to pay for it yourself.
In case you are in search of an actual estate or Singapore property agent on-line, you simply should belief your intuition. It's because you do not know which agent is nice and which agent will not be. Carry out research on several brokers by looking out the internet. As soon as if you end up positive that a selected agent is dependable and reliable, you can choose to utilize his partnerise in finding you a home in Singapore. Most of the time, a property agent is taken into account to be good if he or she locations the contact data on his website. This may mean that the agent does not mind you calling them and asking them any questions relating to new properties in singapore in Singapore. After chatting with them you too can see them in their office after taking an appointment.
Have handed an trade examination i.e Widespread Examination for House Brokers (CEHA) or Actual Property Agency (REA) examination, or equal; Exclusive brokers are extra keen to share listing information thus making certain the widest doable coverage inside the real estate community via Multiple Listings and Networking. Accepting a severe provide is simpler since your agent is totally conscious of all advertising activity related with your property. This reduces your having to check with a number of agents for some other offers. Price control is easily achieved. Paint work in good restore-discuss with your Property Marketing consultant if main works are still to be done. Softening in residential property prices proceed, led by 2.8 per cent decline within the index for Remainder of Central Region
Once you place down the one per cent choice price to carry down a non-public property, it's important to accept its situation as it is whenever you move in – faulty air-con, choked rest room and all. Get round this by asking your agent to incorporate a ultimate inspection clause within the possibility-to-buy letter. HDB flat patrons routinely take pleasure in this security net. "There's a ultimate inspection of the property two days before the completion of all HDB transactions. If the air-con is defective, you can request the seller to repair it," says Kelvin.
15.6.1 As the agent is an intermediary, generally, as soon as the principal and third party are introduced right into a contractual relationship, the agent drops out of the image, subject to any problems with remuneration or indemnification that he could have against the principal, and extra exceptionally, against the third occasion. Generally, agents are entitled to be indemnified for all liabilities reasonably incurred within the execution of the brokers´ authority.
To achieve the very best outcomes, you must be always updated on market situations, including past transaction information and reliable projections. You could review and examine comparable homes that are currently available in the market, especially these which have been sold or not bought up to now six months. You'll be able to see a pattern of such report by clicking here It's essential to defend yourself in opposition to unscrupulous patrons. They are often very skilled in using highly unethical and manipulative techniques to try and lure you into a lure. That you must also protect your self, your loved ones, and personal belongings as you'll be serving many strangers in your home. Sign a listing itemizing of all of the objects provided by the proprietor, together with their situation. HSR Prime Recruiter 2010 - ↑ Gille & Szamuely (2006) p.131