Examples of using Functors in English and their translations into Russian
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Functors are structure-preserving maps between categories.
Hence one can consider the right derived functors of the direct image.
Left derived functors are zero on all projective objects.
Some constructions of multilinear algebra are of'mixed' variance,which prevents them from being functors.
Kamornikov, Subgroup functors and classes of finite groups, Minsk, Belarus, 2003.
Then the groups Hi(X, E)for integers i are defined as the right derived functors of the functor E↦ EX.
If F andG are contravariant functors one speaks of a duality of categories instead.
The main problem is to prove a signalizer functor theorem for nonsolvable signalizer functors.
Exact functors are functors that transform exact sequences into exact sequences.
Flatness may also be expressed using the Tor functors, the left derived functors of the tensor product.
Diagonal functors provide a way to define limits and colimits of diagrams.
If M and N are two modules over a commutative ring R(for example,two abelian groups, when R Z), Tor functors yield a family of R-modules ToriM, N.
Exact functors are convenient for algebraic calculations because they can be directly applied to presentations of objects.
Additionally, one demands that the diagram commute, which is analogous to the rule F( fg)= F( f) F( g)for ordinary functors.
In mathematics, certain functors may be derived to obtain other functors closely related to the original ones.
In practice, this fact, together with the long exact sequence property,is often used to compute the values of right derived functors.
In category theory, monoidal functors are functors between monoidal categories which preserve the monoidal structure.
One may also start with a contravariant left-exact functor F;the resulting right-derived functors are then also contravariant.
Functors often describe"natural constructions" and natural transformations then describe"natural homomorphisms" between two such constructions.
The categorical notions of universal morphisms and adjoint functors can both be expressed using representable functors.
Functors are often defined by universal properties; examples are the tensor product, the direct sum and direct product of groups or vector spaces, construction of free groups and modules, direct and inverse limits.
Much of the work in homological algebra is designed to cope with functors that fail to be exact, but in ways that can still be controlled.
The category of all small categories with functors as morphisms has the empty category, 0(with no objects and no morphisms), as initial object and the terminal category, 1(with a single object with a single identity morphism), as terminal object.
The functor category DC has all the formal properties of an exponential object;in particular the functors from E× C→ D stand in a natural one-to-one correspondence with the functors from E to DC.
Technically, to produce well-defined derivatives of F, we would have to fix an injective resolution for every object of A. This choice of injective resolutions then yields functors RiF.
The narrative function is losing its functors, its great hero, its great dangers, its great voyages, its great goal.
The operation can be realised as a class that is passed to the current node; it then queries the node'stype using RTTI and looks up the correct operation in an array of callbacks or functors.
This requires that the map of types to callbacks or functors be initialized at runtime, but offers more flexibility, speed and extensibility.
Alexander Grothendieck in lectures in Kansas defines abelian category and presheaf, andby using injective resolutions allows direct use of sheaf cohomology on all topological spaces, as derived functors.
In category theory, a branch of mathematics, the functors between two given categories form a category, where the objects are the functors and the morphisms are natural transformations between the functors. .