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In [[mathematics]], the '''Kodaira vanishing theorem''' is a basic result of [[complex manifold]] theory and complex [[algebraic geometry]], describing general conditions under which [[sheaf cohomology]] groups with indices ''q'' > 0 are automatically zero. The implications for the group with index ''q'' = 0 is usually that its dimension — the number of independent [[global section]]s — coincides with a [[holomorphic Euler characteristic]] that can be computed using the [[Hirzebruch-Riemann-Roch theorem]]. | |||
== The complex analytic case == | |||
The statement of [[Kunihiko Kodaira]]'s result is that if ''M'' is a compact [[Kähler manifold]] of complex dimension ''n'', ''L'' any [[holomorphic line bundle]] on ''M'' that is [[positive form|positive]], and ''K<sub>M</sub>'' is the [[canonical bundle|canonical line bundle]], then | |||
:::<math> H^q(M, K_M\otimes L) = 0 </math> | |||
for ''q'' > 0. Here <math>K_M\otimes L</math> stands for the [[tensor product of line bundles]]. By means of [[Serre duality]], one obtains the vanishing of other cohomology group by removing ''K''. There is a generalisation, the '''Kodaira-Nakano vanishing theorem''', in which <math>K_M\otimes L\cong\Omega^n(L)</math>, where Ω<sup>''n''</sup>(''L'') denotes the sheaf of [[Dolbeault complex|holomorphic (''n'',0)-forms]] on ''M'' with values on ''L'', is replaced by Ω<sup>''r''</sup>(''L''), the sheaf of holomorphic (r,0)-forms with values on ''L''. Then the cohomology group H<sup>''q''</sup>(''M'', Ω<sup>''r''</sup>(''L'')) vanishes whenever ''q'' + ''r'' > ''n''. | |||
== The algebraic case == | |||
The Kodaira vanishing theorem can be formulated within the language of algebraic geometry without any reference to ''transcendental'' methods such as Kähler metrics. Positivity of the line bundle ''L'' translates into the corresponding [[invertible sheaf]] being [[ample line bundle|ample]] (i.e., some tensor power gives a projective embedding). The algebraic Kodaira-Akizuki-Nakano vanishing theorem is the following statement: | |||
: If ''k'' is a [[field (mathematics)|field]] of [[characteristic (algebra)|characteristic]] zero, ''X'' is a [[smooth morphism|smooth]] and [[projective morphism|projective]] ''k''-[[Scheme (mathematics)|scheme]] of dimension ''d'', and ''L'' is an ample invertible sheaf on ''X'', then | |||
:::<math> H^q(X,L\otimes\Omega^p_{X/k}) = 0</math> for <math> p+q>d</math>, and | |||
:::<math> H^q(X,L^{\otimes-1}\otimes\Omega^p_{X/k}) = 0</math> for <math> p+q<d</math>, | |||
: where the Ω<sup>p</sup> denote the [[Sheaf (mathematics)|sheaves]] of relative (algebraic) [[differential forms]] (see [[Kähler differential]]). | |||
{{harvtxt|Raynaud|1978}} showed that this result does not always hold over fields of characteristic ''p'' > 0, and in particular fails for [[Raynaud surface]]s. | |||
Until 1987 the only known proof in characteristic zero was however based on the complex analytic proof and the [[GAGA]] comparison theorems. However, in 1987 [[Pierre Deligne]] and [[Luc Illusie]] gave a purely algebraic proof of the vanishing theorem in {{harv|Deligne|Illusie|1987}}. Their proof is based on showing that [[Hodge-de Rham spectral sequence]] for [[algebraic de Rham cohomology]] degenerates in degree 1. This is shown by lifting a corresponding more specific result from characteristic ''p'' > 0 — the positive-characteristic result does not hold without limitations but can be lifted to provide the full result. | |||
==Consequences and applications== | |||
Historically, [[Kodaira embedding theorem]] was derived with the help of the vanishing theorem. With application of Serre duality, the vanishing of various sheaf cohomology groups (usually related to the canonical line bundle) of curves and surfaces help with the classification of complex manifolds, e.g. [[Enriques–Kodaira classification]]. | |||
==See also== | |||
* [[Kawamata–Viehweg vanishing theorem]] | |||
* [[Mumford vanishing theorem]] | |||
* [[Ramanujam vanishing theorem]] | |||
==References== | |||
* {{Citation | |||
| last = Deligne | |||
| first = Pierre | |||
| last2 = Illusie | |||
| first2 = Luc | |||
| title = Relèvements modulo p<sup>2</sup> et décomposition du complexe de de Rham | |||
| journal = Inventiones Mathematicae | |||
| volume = 89 | |||
| issue = 2 | |||
| pages = 247–270 | |||
| year = 1987 | |||
| doi = 10.1007/BF01389078 }} | |||
*{{Citation | url = http://www.uni-due.de/%7Emat903/books/esvibuch.pdf|last1=Esnault | first1=Hélène | last2=Viehweg | first2=Eckart | title=Lectures on vanishing theorems | publisher=Birkhäuser Verlag | series=DMV Seminar | isbn=978-3-7643-2822-1 | id={{MathSciNet | id = 1193913}} | year=1992 | volume=20}} | |||
*[[Phillip Griffiths]] and [[Joe Harris (mathematician)|Joseph Harris]], ''Principles of Algebraic Geometry'' | |||
*{{Citation | last1=Raynaud | first1=Michel | author1-link=Michel Raynaud | title=C. P. Ramanujam---a tribute | publisher=[[Springer-Verlag]] | location=Berlin, New York | series=Tata Inst. Fund. Res. Studies in Math. | id={{MathSciNet | id = 541027}} | year=1978 | volume=8 | chapter=Contre-exemple au vanishing theorem en caractéristique p>0 | pages=273–278}} | |||
[[Category:Theorems in complex geometry]] | |||
[[Category:Topological methods of algebraic geometry]] | |||
[[Category:Theorems in algebraic geometry]] |
Revision as of 19:35, 17 January 2014
In mathematics, the Kodaira vanishing theorem is a basic result of complex manifold theory and complex algebraic geometry, describing general conditions under which sheaf cohomology groups with indices q > 0 are automatically zero. The implications for the group with index q = 0 is usually that its dimension — the number of independent global sections — coincides with a holomorphic Euler characteristic that can be computed using the Hirzebruch-Riemann-Roch theorem.
The complex analytic case
The statement of Kunihiko Kodaira's result is that if M is a compact Kähler manifold of complex dimension n, L any holomorphic line bundle on M that is positive, and KM is the canonical line bundle, then
for q > 0. Here stands for the tensor product of line bundles. By means of Serre duality, one obtains the vanishing of other cohomology group by removing K. There is a generalisation, the Kodaira-Nakano vanishing theorem, in which , where Ωn(L) denotes the sheaf of holomorphic (n,0)-forms on M with values on L, is replaced by Ωr(L), the sheaf of holomorphic (r,0)-forms with values on L. Then the cohomology group Hq(M, Ωr(L)) vanishes whenever q + r > n.
The algebraic case
The Kodaira vanishing theorem can be formulated within the language of algebraic geometry without any reference to transcendental methods such as Kähler metrics. Positivity of the line bundle L translates into the corresponding invertible sheaf being ample (i.e., some tensor power gives a projective embedding). The algebraic Kodaira-Akizuki-Nakano vanishing theorem is the following statement:
- If k is a field of characteristic zero, X is a smooth and projective k-scheme of dimension d, and L is an ample invertible sheaf on X, then
- where the Ωp denote the sheaves of relative (algebraic) differential forms (see Kähler differential).
Template:Harvtxt showed that this result does not always hold over fields of characteristic p > 0, and in particular fails for Raynaud surfaces.
Until 1987 the only known proof in characteristic zero was however based on the complex analytic proof and the GAGA comparison theorems. However, in 1987 Pierre Deligne and Luc Illusie gave a purely algebraic proof of the vanishing theorem in Template:Harv. Their proof is based on showing that Hodge-de Rham spectral sequence for algebraic de Rham cohomology degenerates in degree 1. This is shown by lifting a corresponding more specific result from characteristic p > 0 — the positive-characteristic result does not hold without limitations but can be lifted to provide the full result.
Consequences and applications
Historically, Kodaira embedding theorem was derived with the help of the vanishing theorem. With application of Serre duality, the vanishing of various sheaf cohomology groups (usually related to the canonical line bundle) of curves and surfaces help with the classification of complex manifolds, e.g. Enriques–Kodaira classification.
See also
References
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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
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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 - Phillip Griffiths and Joseph Harris, Principles of Algebraic Geometry
- 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