Unified tame theorem

The well-known tame theorem tells that for a given tame bocs and a positive integer n there exist finitely many minimal bocses, such that any representation of the original bocs of dimension at most n is isomorphic to the image of a representation of some minimal bocses under a certain reduction functor. In the present paper we will give an alternative statement of the tame theorem in terms of matrix problem, by constructing a unified minimal matrix problem whose indecomposable matrices cover all the canoni...     

DERIVATIVES ON NONSTORABLE RENEWABLE RESOURCES: FISH FUTURES AND OPTIONS,NOT SO FISHY AFTER ALL

Abstract We study forwards and European call options, which are written on a nonstorable renewable resource. Examples of such derivatives in form of futures on fresh catch of wild salmon for the United States and the recently created Fish Pool market in Norway, where futures on a composite of wild catch and farmed salmon are traded, will be discussed. We approach the problem of pricing these contracts from first principles, starting off by modeling the dynamics of the resource reserves, and assuming that in approximation resource extraction is managed as open access. We derive formulas for the forward price of the renewable resource as well as European call options written on it.     

Strictly wild algebras with radical square zero

It is proved that a wild algebra with radical square zero is strictly wild if and only if it has a wild hereditary algebra as its factor algebra, which, on the one hand supports one conjecture in [3], on the other hand can be used to construct many non-strictly wild algebras.     

双重约束下野生动物资源的动态均衡管理研究

野生动物资源功能用途的复合性使得其受到生物系统及经济系统双重约束,在传统生物均衡模型基础上,分别构建经济系统和生物系统的联立方程组模型,然后根据目标函数形成野生动物资源动态均衡管理的理论模型及实证应用分析,得出结论：1）野生动物资源最优种群水平不仅受种群内禀增长率和栖息环境最大承载量的影响,也受到市场价格,维持及收获的成本及税费,产品利用率以及社会平均折现率的影响.但长期来看,环境承载量是影响种群水平的最终决定性因素.2）经济系统的各项变量并不影响野生动物最优种群水平的最终结果,而只影响其趋向最终结果的路径.3）最优猎捕收获量主要取决于最优种群水平以及环境承载量和种群内禀增长率.4）麝类资源的生物系统、经济系统的各个因素的影响方向和影响力大小,并不完全和一般假设相同.     

The number of the Gabriel-Roiter measures admitting no direct predecessors over a wild quiver

A famous result by Drozd says that a finite-dimensional representation-infinite algebra is of either tame or wild representation type. But one has to make assumption on the ground field. The Gabriel-Roiter measure might be an alternative approach to extend these concepts of tame and wild to arbitrary Artin algebras. In particular, the infiniteness of the number of GR segments, i.e. sequences of Gabriel-Roiter measures which are closed under direct predecessors and successors, might relate to the wildness of Artin algebras. As the first step, we are going to study the wild quiver with three vertices, labeled by 1, 2 and 3, and one arrow from 1 to 2 and two arrows from 2 to 3. The Gabriel-Roiter submodules of the indecomposable preprojective modules and quasi-simple modules τ⁻ⁱM, i≥0 are described, where M is a Kronecker module and τ=DTr is the Auslander-Reiten translation. Based on these calculations, the existence of infinitely many GR segments will be shown. Moreover, it will be proved that there are infinitely many Gabriel-Roiter measures admitting no direct predecessors.     

野生中药材供给与稽查的不完全信息动态博弈分析

针对中药材供给中的信息不对称性,建立了三个中药材供给方与政府稽查部门之间的三个不完全信息动态博弈模型,得到了相应的子博弈精炼贝叶斯均衡解的五个结论.这五个结论合理刻画了中药材供给方与政府稽查部门的博弈行为并揭示了非法采挖野生中药材现象难以杜绝的原因.结果表明,政府对稽查行为的条件激励措施并不能有效杜绝非法采挖野生中药材现象,只有政府对所有的稽查行为实施普遍的强激励机制才可从根本上消除非法采挖野生中药材的现象.     

On wild and tame finite-dimensional Lie algebras

All finite-dimensional Lie algebras over an algebraically closed field of characteristic zero are found for which the problem of classifying finite-dimensional representations is not wild.     

On Lie Algebras with Wild Automorphisms

We exhibit a class of Lie algebras (which contains, in particular, free polynilpotent Lie algebras) that have wild automorphisms, i.e., automorphisms which are not induced by automorphisms of a free Lie algebra.     

Representation theory of the system quiver

Let A be a three-point algebra with Gabriel quiver the system quiver Q, Then, up to isomorphism and duality, A is tame if and only if A is or degenerates to a factor of a tame algebra in the tame Table T if and only if A/rad5 A is tame, and A is wild if and only if A has a wild algebra in the wild Table W as a factor if and only if A is controlled wild.     

Degeneration of Tame Automorphisms of a Polynomial Ring

Recently, Edo and Poloni constructed a family of tame automorphisms of a polynomial ring in three variables which degenerates to a wild automorphism. In this note, we generalize the example by a different method.     

Wild automorphisms of varieties with Kodaira dimension 0

An automorphism σ of a projective variety X is said to be wild if σ(Y) ≠ Y for every non-empty subvariety Y \subsetneq X{Y \subsetneq X} . In [1] Z. Reichstein, D. Rogalski, and J.J. Zhang conjectured that if X is an irreducible projective variety admitting a wild automorphism then X is an abelian variety, and proved this conjecture for dim(X) ≤ 2. As a step toward answering this conjecture in higher dimensions we prove a structure theorem for projective varieties of Kodaira dimension 0 admitting wild automorphisms. This essentially reduces the Kodaira dimension 0 case to a study of Calabi-Yau varieties, which we also investigate. In support of this conjecture, we show that there are no wild automorphisms of certain Calabi-Yau varieties.     

One-Parameter Families of Modules for Tame Algebras and Bocses

Let Λ be a finite-dimensional algebra over an algebraically closed field k. We denote by mod Λ the category of finitely generated left Λ-modules. Consider the family ℱ(u) of the indecomposables M∈mod Λ such that , where is the subspace of morphisms which factorize through semisimple modules. If P,Q are projectives in mod Λ, ℱ(u)(P,Q) is the family of those modules M∈ℱ(u) such that a minimal projective presentation is of the formf_M: P→Q. We prove that if Λ is of tame representation type then each ℱ(P,Q) has only a finite number of isomorphism classes or is parametrized by μ(u,P,Q) one-parameter families. We give an upper bound for this number in terms of u,P and Q. Then we give some sufficient conditions for tame of polynomial growth type. For the proof we consider similar results for bocses. Presented by Y. Drozd Mathematics Subject Classifications (2000) 16G60, 16G70, 16G20.     

Representation type of local and two-vertex bocses

Let κ be an algebraically closed field. It has been proved by Zhang and Xu that if a bocs is of tame representation type, then the degree of the diffierential of the first solid arrow must be less than or equal to 3. We will prove in the present paper that: The bocs is still wild when the degree of the diffierential of the first arrow is equal to 3. Especially, the bocs with only one solid arrow is of tame type if and only if the degree of the diffierential of the arrow is less than or equal to 2. Moreover,...     

Semi-Continuity for Derived Categories

We prove that the number of parameters defining a complex of projective modules over an algebra is upper semi-continuous in families of algebras. The proof follows the pattern of the paper by Drozd and Greuel and rests upon universal families with projective bases. Supposing that every algebra is either derived tame or derived wild, we get that a degeneration of a derived wild algebra is also derived wild. We also discuss an apparent counter-example to the last assertion by Th. Brüstle. Presented by V. DlabMathematics Subject Classifications (2000) 16G10, 16E05.     

Complex hyperbolic Kleinian groups with limit set a wild knot

We construct quasi-Fuchsian groups acting on two-dimensional complex hyperbolic space with limit set a wild knot. Also, we study the Teichmüller space T(G) of faithful, discrete, type-preserving representations of a Fuchsian group G of the first kind with parabolic elements in complex hyperbolic space. We show that T(G) is not connected, and that the Toledo invariant does not distinguish different connected components of T(G).     

Wild tiles in ℝ<Superscript>3</Superscript> with spherical boundaries

Wildly embedded tiles in ℝ³ with spherical boundary are discussed. The construction of the topologically complicated, crumpled cube tiles is reviewed. We construct an infinite family of wildly embedded, cellular tiles with Fox-Artin-type wild points. Finally, a condition on the set of wild points on a cellular tile is given to show that certain wild cells cannot be tiles. Several observations are recorded for further investigations. __________ Translated from Fundamentalnaya i Prikladnaya Matematika, Vol. 11, No. 4, pp. 203–211, 2005.     

Wild radical square zero algebras

It is shown that a radical square zero algebra is wild, if and only if it is of Corner’s type, and it is strictly wild if and only if it is Endo-wild. This gives a negative answer to a problem posed by Simson.     

TAME TWO-POINT ALGEBRAS WITHOUT LOOPS

We determine the representation type of the algebras whose quiver has precisely two vertices and admits no loops by listing all minimal wild algebras of this form. It turns out that such an algebra A is tame if and only if A/rad³ A is tame, and in this case A degenerates to a special biserial algebra. Moreover, A is wild if and only if it is controlled wild.     

Controlled Wild Algebras

The controlled wild algebra is introduced, a covering criterionfor a finite-dimensional algebra to be controlled wild is given,and this criterion is applied to the algebras with radical squarezero, algebras with zero relations, local algebras and finitep-group algebras. 2000 Mathematical Subject Classification:16G20, 16G60.