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{{about|a particular structure known as a non-associative algebra|non-associativity in general|Non-associativity}} | |||
{{mergefrom|Example of a non-associative algebra|date=February 2013|discuss=Talk:Non-associative algebra#Merge example}} | |||
{{one source|date=April 2012}} | |||
A '''non-associative [[Algebra over a field|algebra]]'''{{sfn|Schafer|1966|loc=Chapter 1}} (or '''distributive algebra''') over a field (or a commutative ring) ''K'' is a ''K''-vector space (or more generally a [[Module (mathematics)|module]]{{sfn|Schafer|1966|loc=pp.1}}) ''A'' equipped with a ''K''-[[bilinear]]{{dn|date=December 2013}} map ''A'' × ''A'' → ''A'' which establishes a binary multiplication operation on ''A''. Since it is not assumed that the multiplication is associative, using parentheses to indicate the order of multiplications is necessary. For example, the expressions (''ab'')(''cd''), (''a''(''bc''))''d'' and ''a''(''b''(''cd'')) may all yield different answers. | |||
While this use of ''non-associative'' means that associativity is not assumed, it does not mean that associativity is disallowed. In other words, "non-associative" means "not necessarily associative", just as "noncommutative" means "not necessarily commutative" for [[noncommutative ring]]s. | |||
Multiplication by elements of ''A'' on the left or on the right give rise to left and right ''K''-[[linear transformation]]s of ''A'' given by | |||
<math>L_a : x \mapsto ax</math> and <math>R_a : x \mapsto xa</math>. The '''enveloping algebra''' of a non-associative algebra ''A'' is the subalgebra of the full algebra of ''K''-[[endomorphisms]] of ''A'' which is generated by the left and right multiplication maps of ''A''.{{sfn|Schafer|1966|loc=pp.14-15}} This enveloping algebra is necessarily associative, even though ''A'' may be non-associative. In a sense this makes the enveloping algebra "the smallest associative algebra containing ''A''". | |||
An algebra is ''[[unital algebra|unital]]'' or ''unitary'' if it has an [[identity element]] ''I'' with ''Ix'' = ''x'' = ''xI'' for all ''x'' in the algebra. | |||
{{Algebraic structures |Algebra}} | |||
== Algebras satisfying identities == | |||
Ring-like structures with two binary operations and no other restrictions are a broad class, one which is too general to study. For this reason, the best-known kinds of non-associative algebras satisfy [[identity (mathematics)|identities]] which simplify multiplication somewhat. These include the following identities. | |||
In the list, ''x'', ''y'' and ''z'' denote arbitrary elements of an algebra. | |||
* [[Associativity|Associative]]: (''xy'')''z'' = ''x''(''yz''). | |||
* [[Commutativity|Commutative]]: ''xy'' = ''yx''. | |||
* [[Anticommutative]]: ''xy'' = −''yx''.<ref>This is always implied by the identity ''xx'' = 0 for all ''x'', and the converse holds for fields of characteristic other than two.</ref> | |||
* [[Jacobi identity]]: (''xy'')''z'' + (''yz'')''x'' + (''zx'')''y'' = 0. | |||
* [[Jordan identity]]: (''xy'')''x''<sup>2</sup> = ''x''(''yx''<sup>2</sup>). | |||
* [[Power associative]]: For all ''x'', and any three nonnegative powers of ''x'' associate. That is if ''a'', ''b'' and ''c'' are nonnegative powers of ''x'', then ''a''(''bc'') = (''ab'')''c''. This is equivalent to saying that ''x''<sup>''m''</sup> ''x''<sup>''n''</sup> = ''x''<sup>''n+m''</sup> for all non-negative integers ''m'' and ''n''. | |||
* [[Alternative algebra|Alternative]]: (''xx'')''y'' = ''x''(''xy'') and (''yx'')''x'' = ''y''(''xx''). | |||
* [[Flexible algebra|Flexible]]:{{sfn|Okubo|1995|loc=p. 16}} ''x''(''yx'') = (''xy'')''x''. | |||
These properties are related by | |||
# ''associative'' implies ''alternative'' implies ''power associative''; | |||
# ''associative'' implies ''Jordan identity'' implies ''power associative''; | |||
# Each of the properties ''associative'', ''commutative'', ''anticommutative'', ''Jordan identity'', and ''Jacobi identity'' individually imply ''flexible''.{{sfn|Okubo|1995|loc=p. 16}} | |||
# For a field with characteristic not two, being both commutative and anticommutative implies the algebra is just {0}. | |||
== Examples == | |||
* [[Euclidean space]] '''R'''<sup>3</sup> with multiplication given by the [[vector cross product]] is an example of an algebra which is anticommutative and not associative. The cross product also satisfies the Jacobi identity. | |||
* [[Lie algebra]]s are algebras satisfying anticommutativity and the Jacobi identity. | |||
* Algebras of [[vector field]]s on a [[differentiable manifold]] (if ''K'' is '''R''' or the [[complex number]]s '''C''') or an [[algebraic variety]] (for general ''K''); | |||
* [[Jordan algebra]]s are algebras which satisfy the commutative law and the Jordan identity. | |||
* Every associative algebra gives rise to a Lie algebra by using the [[commutator]] as Lie bracket. In fact every Lie algebra can either be constructed this way, or is a subalgebra of a Lie algebra so constructed. | |||
* Every associative algebra over a field of [[characteristic (algebra)|characteristic]] other than 2 gives rise to a Jordan algebra by defining a new multiplication ''x*y'' = (1/2)(''xy'' + ''yx''). In contrast to the Lie algebra case, not every Jordan algebra can be constructed this way. Those that can are called ''special''. | |||
* [[Alternative algebra]]s are algebras satisfying the alternative property. The most important examples of alternative algebras are the [[octonions]] (an algebra over the reals), and generalizations of the octonions over other fields. All associative algebras are alternative. Up to isomorphism, the only finite-dimensional real alternative, division algebras (see below) are the reals, complexes, quaternions and octonions. | |||
* [[Power-associative algebra]]s, are those algebras satisfying the power-associative identity. Examples include all associative algebras, all alternative algebras, Jordan algebras, and the [[sedenion]]s. | |||
* The [[hyperbolic quaternion]] algebra over '''R''', which was an experimental algebra before the adoption of [[Minkowski space]] for [[special relativity]]. | |||
More classes of algebras: | |||
* [[Graded algebra]]s. These include most of the algebras of interest to [[multilinear algebra]], such as the [[tensor algebra]], [[symmetric algebra]], and [[exterior algebra]] over a given [[vector space]]. Graded algebras can be generalized to [[filtered algebra]]s. | |||
* [[Division algebra]]s, in which multiplicative inverses exist. The finite-dimensional alternative division algebras over the field of real numbers have been classified. They are the [[real number]]s (dimension 1), the [[complex number]]s (dimension 2), the [[quaternion]]s (dimension 4), and the [[octonion]]s (dimension 8). The quaternions and octonions are not commutative. Of these algebras, all are associative except for the octonions. | |||
* [[Quadratic algebra]]s, which require that ''xx'' = ''re'' + ''sx'', for some elements ''r'' and ''s'' in the ground field, and ''e'' a unit for the algebra. Examples include all finite-dimensional alternative algebras, and the algebra of real 2-by-2 matrices. Up to isomorphism the only alternative, quadratic real algebras without divisors of zero are the reals, complexes, quaternions, and octonions. | |||
* The [[Cayley–Dickson algebra]]s (where ''K'' is '''R'''), which begin with: | |||
** '''C''' (a commutative and associative algebra); | |||
** the [[quaternion]]s '''H''' (an associative algebra); | |||
** the [[octonion]]s (an [[alternative algebra]]); | |||
** the [[sedenion]]s (a [[power-associative algebra]], like all of the Cayley-Dickson algebras). | |||
* The [[Poisson algebra]]s are considered in [[geometric quantization]]. They carry two multiplications, turning them into commutative algebras and Lie algebras in different ways. | |||
*[[Genetic algebra]]s are non-associative algebras used in mathematical genetics. | |||
== See also == | |||
*[[List of algebras]] | |||
== Notes == | |||
{{reflist}} | |||
== References == | |||
* {{citation |last=Okubo |first=Susumu |title=Introduction to Octonion and Other Non-Associative Algebras in Physics |year=1995 |publisher=Cambridge University Press |ISBN=978-0-521-47215-9 |DOI=10.1017/CBO9780511524479 }} | |||
* {{citation |first=Richard D. |last=Schafer |title=An Introduction to Nonassociative Algebras |year=1995 |origyear=1966 |publisher=Dover |isbn=0-486-68813-5 |url=http://www.gutenberg.org/ebooks/25156}} | |||
[[Category:Non-associative algebras]] |
Revision as of 01:57, 16 March 2013
29 yr old Orthopaedic Surgeon Grippo from Saint-Paul, spends time with interests including model railways, top property developers in singapore developers in singapore and dolls. Finished a cruise ship experience that included passing by Runic Stones and Church. Template:Mergefrom Template:One source
A non-associative algebraTemplate:Sfn (or distributive algebra) over a field (or a commutative ring) K is a K-vector space (or more generally a moduleTemplate:Sfn) A equipped with a K-bilinearTemplate:Dn map A × A → A which establishes a binary multiplication operation on A. Since it is not assumed that the multiplication is associative, using parentheses to indicate the order of multiplications is necessary. For example, the expressions (ab)(cd), (a(bc))d and a(b(cd)) may all yield different answers.
While this use of non-associative means that associativity is not assumed, it does not mean that associativity is disallowed. In other words, "non-associative" means "not necessarily associative", just as "noncommutative" means "not necessarily commutative" for noncommutative rings.
Multiplication by elements of A on the left or on the right give rise to left and right K-linear transformations of A given by and . The enveloping algebra of a non-associative algebra A is the subalgebra of the full algebra of K-endomorphisms of A which is generated by the left and right multiplication maps of A.Template:Sfn This enveloping algebra is necessarily associative, even though A may be non-associative. In a sense this makes the enveloping algebra "the smallest associative algebra containing A".
An algebra is unital or unitary if it has an identity element I with Ix = x = xI for all x in the algebra.
Algebras satisfying identities
Ring-like structures with two binary operations and no other restrictions are a broad class, one which is too general to study. For this reason, the best-known kinds of non-associative algebras satisfy identities which simplify multiplication somewhat. These include the following identities.
In the list, x, y and z denote arbitrary elements of an algebra.
- Associative: (xy)z = x(yz).
- Commutative: xy = yx.
- Anticommutative: xy = −yx.[1]
- Jacobi identity: (xy)z + (yz)x + (zx)y = 0.
- Jordan identity: (xy)x2 = x(yx2).
- Power associative: For all x, and any three nonnegative powers of x associate. That is if a, b and c are nonnegative powers of x, then a(bc) = (ab)c. This is equivalent to saying that xm xn = xn+m for all non-negative integers m and n.
- Alternative: (xx)y = x(xy) and (yx)x = y(xx).
- Flexible:Template:Sfn x(yx) = (xy)x.
These properties are related by
- associative implies alternative implies power associative;
- associative implies Jordan identity implies power associative;
- Each of the properties associative, commutative, anticommutative, Jordan identity, and Jacobi identity individually imply flexible.Template:Sfn
- For a field with characteristic not two, being both commutative and anticommutative implies the algebra is just {0}.
Examples
- Euclidean space R3 with multiplication given by the vector cross product is an example of an algebra which is anticommutative and not associative. The cross product also satisfies the Jacobi identity.
- Lie algebras are algebras satisfying anticommutativity and the Jacobi identity.
- Algebras of vector fields on a differentiable manifold (if K is R or the complex numbers C) or an algebraic variety (for general K);
- Jordan algebras are algebras which satisfy the commutative law and the Jordan identity.
- Every associative algebra gives rise to a Lie algebra by using the commutator as Lie bracket. In fact every Lie algebra can either be constructed this way, or is a subalgebra of a Lie algebra so constructed.
- Every associative algebra over a field of characteristic other than 2 gives rise to a Jordan algebra by defining a new multiplication x*y = (1/2)(xy + yx). In contrast to the Lie algebra case, not every Jordan algebra can be constructed this way. Those that can are called special.
- Alternative algebras are algebras satisfying the alternative property. The most important examples of alternative algebras are the octonions (an algebra over the reals), and generalizations of the octonions over other fields. All associative algebras are alternative. Up to isomorphism, the only finite-dimensional real alternative, division algebras (see below) are the reals, complexes, quaternions and octonions.
- Power-associative algebras, are those algebras satisfying the power-associative identity. Examples include all associative algebras, all alternative algebras, Jordan algebras, and the sedenions.
- The hyperbolic quaternion algebra over R, which was an experimental algebra before the adoption of Minkowski space for special relativity.
More classes of algebras:
- Graded algebras. These include most of the algebras of interest to multilinear algebra, such as the tensor algebra, symmetric algebra, and exterior algebra over a given vector space. Graded algebras can be generalized to filtered algebras.
- Division algebras, in which multiplicative inverses exist. The finite-dimensional alternative division algebras over the field of real numbers have been classified. They are the real numbers (dimension 1), the complex numbers (dimension 2), the quaternions (dimension 4), and the octonions (dimension 8). The quaternions and octonions are not commutative. Of these algebras, all are associative except for the octonions.
- Quadratic algebras, which require that xx = re + sx, for some elements r and s in the ground field, and e a unit for the algebra. Examples include all finite-dimensional alternative algebras, and the algebra of real 2-by-2 matrices. Up to isomorphism the only alternative, quadratic real algebras without divisors of zero are the reals, complexes, quaternions, and octonions.
- The Cayley–Dickson algebras (where K is R), which begin with:
- C (a commutative and associative algebra);
- the quaternions H (an associative algebra);
- the octonions (an alternative algebra);
- the sedenions (a power-associative algebra, like all of the Cayley-Dickson algebras).
- The Poisson algebras are considered in geometric quantization. They carry two multiplications, turning them into commutative algebras and Lie algebras in different ways.
- Genetic algebras are non-associative algebras used in mathematical genetics.
See also
Notes
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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.
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
- ↑ This is always implied by the identity xx = 0 for all x, and the converse holds for fields of characteristic other than two.