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In this paper the authors consider four questions of primary interest for the representation theory of reductive algebraic groups: (i) Donkin's Tilting Module Conjecture, (ii) the Humphreys-Verma Question, (iii) whether St r ⊗ L (λ) is a tilting module for L (λ) an irreducible representation of p r -restricted highest weight, and (iv) whether Ext G 1 1 (L (λ) , L (μ)) (− 1) is a tilting module where L (λ) and L (μ) have p -restricted highest weight. The authors establish affirmative answers to each of these questions with a new uniform bound, namely p ≥ 2 h − 4 where h is the Coxeter number. Notably, this verifies these statements for infinitely many more cases. Later in the paper, questions (i)-(iv) are considered for rank two groups where there are counterexamples (for small primes) to these questions. [ABSTRACT FROM AUTHOR]

A ring element a ∈ R is said to be of right stable range one if, for any t ∈ R , a R + t R = R implies that a + t b is a unit in R for some b ∈ R. Similarly, a ∈ R is said to be of left stable range one if R a + R t = R implies that a + b ′ t is a unit in R for some b ′ ∈ R. In the last two decades, it has often been speculated that these two notions are actually the same for any a ∈ R. In §3 of this paper, we will prove that this is indeed the case. The key to the proof of this new symmetry result is a certain "Super Jacobson's Lemma", which generalizes Jacobson's classical lemma stating that, for any a , b ∈ R , 1 − a b is a unit in R iff so is 1 − b a. Our proof for the symmetry result above has led to a new generalization of a classical determinantal identity of Sylvester, which will be published separately in [45]. In §§4-5, a detailed study is offered for stable range one ring elements that are unit-regular or nilpotent, while §6 examines the behavior of stable range one elements via their classical Peirce decompositions. The paper ends with a more concrete §7 on integral matrices of stable range one, followed by a final §8 with a few open questions. [ABSTRACT FROM AUTHOR]

In a recent paper, the author defined an operation of tensor product for a large class of 2-representations of U + , the positive half of the 2-category associated to sl 2. In this paper, we prove that the operation extends to give an operation of tensor product for 2-representations of the full 2-category U : when the inputs are 2-representations of the full U , the 2-product is also a 2-representation of the full U. As in the previous paper, the 2-product is given for a simple 2-representation L (1) and an abelian 2-representation V taken from the 2-category of algebras. This is the first construction of an operation of tensor product for higher representations of a full Lie algebra in the abelian setting. [ABSTRACT FROM AUTHOR]

Known as thin residually connected incidence geometry, hypertopes extend the framework of abstract polytopes, and can be built from Coxeter groups (not necessarily with linear diagrams). A regular hypertope is a flag-transitive hypertope. In this paper, we present infinite families of regular hypertopes of ranks 5, 6 and 7, in terms of a certain group covering approach (analogous to a method introduced by Conder and the author in an earlier paper on abstract chiral polytopes, but with wider adaptation). Although the illustrative examples within these families are derived from Coxeter groups exhibiting Y-shaped diagrams, this approach is applicable to obtaining regular hypertopes from Coxeter groups with other diagrams, such that the size of the family members grows linearly with entries of their types. [ABSTRACT FROM AUTHOR]

Let k be a field, let n ≥ 2 be a nonsquarefree integer not divisible by the characteristic of k. Assume that all roots of unity of degree n are contained in k. In the first part of the paper we consider pairs of symbol algebras over k with common slots D 1 ≃ (e , x) n ≃ (r , u) n , D 2 ≃ (e , y) n ≃ (r , v) n , exp D 1 = exp D 2 = n , and show that in general (e , x , y) n ≠ (r , u , v) n. As a consequence we prove that in general it is impossible to connect the pair { (e , x) n ; (e , y) n } and the pair { (r , u) n ; (r , v) n } by a chain of pairs of symbol algebras with a common slot and isomorphic to (D 1 ; D 2) in such a way that any two neighboring pairs in the chain are obtained from one another by a "natural" transformation. In the second part of the paper we prove that in contrast to the case n = 2 for any n divisible by 4 there exist symbol algebras D 1 , D 2 with deg ⁡ D 1 = deg ⁡ D 2 = n and exp D 1 = exp D 2 = n without common slot such that i D 1 + j D 2 is a symbol algebra of degree n for any i , j ∈ Z. [ABSTRACT FROM AUTHOR]

Let X be a finite connected poset, K a field of characteristic zero and I (X , K) the incidence algebra of X over K seen as a Lie algebra under the commutator product. In the first part of the paper we show that any 1 2 -derivation of I (X , K) decomposes into the sum of a central-valued 1 2 -derivation, an inner 1 2 -derivation and a 1 2 -derivation associated with a map σ : X < 2 → K that is constant on chains and cycles in X. In the second part of the paper we use this result to prove that any transposed Poisson structure on I (X , K) is the sum of a structure of Poisson type, a mutational structure and a structure determined by λ : X e 2 → K , where X e 2 is the set of (x , y) ∈ X 2 such that x < y is a maximal chain not contained in a cycle. [ABSTRACT FROM AUTHOR]

Let k be an algebraically closed field of characteristic 0. We study some cohomological properties of Lie subalgebras of the Witt algebra W = Der (k [ t , t − 1 ]) and the one-sided Witt algebra W ≥ − 1 = Der (k [ t ]). In the first part of the paper, we consider finite codimension subalgebras of W ≥ − 1. We compute derivations and one-dimensional extensions of such subalgebras. These correspond to Ext U (L) 1 (M , L) , where L is a subalgebra of W ≥ − 1 and M is a one-dimensional representation of L. We find that these subalgebras exhibit a kind of rigidity: their derivations and extensions are controlled by the full one-sided Witt algebra. As an application of these computations, we prove that any isomorphism between finite codimension subalgebras of W ≥ − 1 extends to an automorphism of W ≥ − 1. The second part of the paper is devoted to explaining the observed rigidity. We define a notion of "completely non-split extension" and prove that W ≥ − 1 is the universal completely non-split extension of any of its subalgebras of finite codimension. In some sense, this means that even when studying subalgebras of W ≥ − 1 as abstract Lie algebras, they remember that they are contained in W ≥ − 1. We also consider subalgebras of infinite codimension, explaining the similarities and differences between the finite and infinite codimension situations. Almost all of the results above are also true for subalgebras of the Witt algebra. We summarise results for W at the end of the paper. [ABSTRACT FROM AUTHOR]

In 1935, the introduction of the norm of a group by Reinhold Baer is a turning point in group theory. In fact, Baer proved that there is a very strong relationship between the structure of the norm and that of the whole group (see [1] , [2] , [3] , [4] , [5]). Since then, the norm has been playing a very significant roles in many aspects of group theory and its applications: it has been used in [43] to describe the connection between Hopf–Galois structures and skew braces; it has been used in [23] to describe some special types of profinite groups; and it has been fundamental in the theory of subgroup lattices of groups (see [40]). In this paper, we weaken the original definition of norm by taking into account only those subgroups that are "large" in some sense. Depending on the chosen concept of largeness, the resulting norm can have an impact on the structure of the whole group that is even greater than that of Baer's norm. This is exactly what happens with the non-polycyclic norm , and in fact, Theorem 4.17 gives a precise description of generalized soluble groups in which the non-polycyclic norm is non-Dedekind (and can be considered as the main result of the paper). Other times, the resulting norms have their own peculiar behaviour; this is the case if "large" means "infinite", "having infinite rank", "being non-Černikov", or "having cardinality m " for some given uncountable cardinal number m. [ABSTRACT FROM AUTHOR]

This article is the final one in the series of papers by the authors devoted to finite-dimensional singular (simple right-alternative with zero product in the even part) superalgebras. In previous papers, algebraically generated singular superalgebras were studied and it was proved that any such superalgebra has the structure of an extended double. In this article, we prove that any singular superalgebra is algebraically generated and, therefore, has the structure of an extended double. [ABSTRACT FROM AUTHOR]

Let (R , m) be a Noetherian local ring, and I an R -ideal such that pd R R / I < ∞. If R / I satisfies a property P , it is natural to ask if R would also have the property P , we call this the generalized deformation problem. Our paper gives some properties that hold for the generalized deformation problems. There are two main parts in this paper. The first part is about F -singularities in the generalized deformation problems. Motivated by Aberbach's work, we show that if every maximal regular sequence on R / I is Frobenius closed, then every regular sequence on R is Frobenius closed. Moreover, under mild assumptions, Frobenius closed can be replaced by tightly closed. By these two results, we solve the generalized deformation problems for F -injectivity in the Cohen-Macaulay case and F -rationality under mild assumptions. Namely, if R is a Noetherian local ring of characteristic p , and I an R -ideal such that pd R R / I < ∞ , then if R is Cohen-Macaulay and R / I is F -injective, then R is F -injective. If R is excellent and R / I is F -rational, then R is F -rational. The second part is about some basic properties of rings in arbitrary characteristic. We prove that if R is a Noetherian local ring, I an R -ideal such that pd R R / I < ∞ , then if R / I is S k , R k + S k + 1 , normal, reduced or a domain, then so is R. [ABSTRACT FROM AUTHOR]

Since the 1974 paper by Peskine and Szpiro, liaison theory via complete intersections, and more generally via Gorenstein varieties, has become a standard tool kit in commutative algebra and algebraic geometry, allowing to compare algebraic features of linked varieties. In this paper we develop a liaison theory via quasi-Gorenstein varieties, a much broader class than Gorenstein varieties. As applications, we derive a connectedness property of quasi-Gorenstein subspace arrangements generalizing previous results by Benedetti and the first author, and we deduce the classical topological Lefschetz duality via the Stanley-Reisner correspondence. [ABSTRACT FROM AUTHOR]

A pseudo-Euclidean non-associative algebra (g , •) is a finite dimensional algebra over a field K that has a metric, i.e., a bilinear, symmetric, and non-degenerate form 〈 , 〉. The metric is considered L-invariant (resp. R-invariant) if all left multiplications (resp. right multiplications) are skew-symmetric. The metric is called associative if 〈 u • v , w 〉 = 〈 u , v • w 〉 for all u , v , w ∈ g. These three notions coincide when g is a Lie algebra and in this case g endowed with the metric is known as a quadratic Lie algebra. This paper provides a complete description of L-invariant, R-invariant, or associative pseudo-Euclidean metrics on left Leibniz algebras over a commutative field of characteristic zero. It shows that a left Leibniz algebra with an associative metric is also right Leibniz and can be obtained easily from its underlying Lie algebra, which is a quadratic Lie algebra. Additionally, it shows that at the core of a left Leibniz algebra endowed with a L-invariant or R-invariant metric, there are two Lie algebras with one quadratic and the left Leibniz algebra can be built from these Lie algebras. We derive many important results from this complete description. Finally, the paper provides a list of left Leibniz algebras with an associative metric up to dimension 6, as well as a list of left Leibniz algebras with an L-invariant metric, up to dimension 4, and R-invariant metric up to dimension 5. [ABSTRACT FROM AUTHOR]

The paper studies the lattice of subgroups of an isotropic reductive group G (R) over a commutative ring R , normalized by the elementary subgroup E (R). We prove the sandwich classification theorem for this lattice under the assumptions that the isotropic rank of G is at least 2 and the structure constants are invertible in R. The theorem asserts that the lattice splits into a disjoint union of sublattices (sandwiches) E (R , q) ⩽ ... ⩽ C (R , q) parametrized by the ideals q of R , where E (R , q) denotes the relative elementary subgroup and C (R , q) is the inverse image of the center under the natural homomorphism G (R) → G (R / q). The main ingredients of the proof are the "level computation" by the first author and the generic element method developed by the second author. [ABSTRACT FROM AUTHOR]

In this paper we introduce the galaxy of Coxeter groups (of finite rank) – an infinite dimensional, locally finite, ranked simplicial complex which captures isomorphisms between finite rank Coxeter systems. In doing so, we would like to suggest a new framework to study the isomorphism problem for Coxeter groups. We prove some structural results about this space, provide a full characterization in small ranks and propose many questions. In addition we survey known tools, results and conjectures. Along the way we show profinite rigidity of triangle Coxeter groups – a result which is possibly of independent interest. [ABSTRACT FROM AUTHOR]

In this paper we study extensions between finite-dimensional simple modules over classical Lie superalgebras gl (m | n) , osp (M | 2 n) and q m. We consider a simplified version of the extension graph which is produced from the Ext 1 -graph by identifying representations obtained by parity change and removal of the loops. We give a necessary condition for a pair of vertices to be connected and show that this condition is sufficient in most of the cases. This condition implies that the image of a finite-dimensional simple module under the Duflo-Serganova functor has indecomposable isotypical components. This yields semisimplicity of Duflo-Serganova functor for F in (gl (m | n)) and for F in (osp (M | 2 n)). [ABSTRACT FROM AUTHOR]

In this paper we give Monk rules for Macdonald polynomials which are analogous to the Monk rules for Schubert polynomials. These formulas are similar to the formulas given by Baratta [6] , but our method of derivation is to use Cherednik's intertwiners. Deriving Monk rules by this technique addresses the relationship between the work of Baratta and the product formulas of Yip [19]. Specializations of the Monk formula's at q = 0 and/or t = 0 provide Monk rules for Iwahori-spherical polynomials and for finite and affine key polynomials. [ABSTRACT FROM AUTHOR]

The quasi-partition algebras were introduced in [10] as centralizers of the symmetric group. In this article, we give a more general definition of these algebras and give a construction of their simple modules. In addition, we introduce two new algebras, we give linear bases and show that for specializations of their parameters, these new algebras are isomorphic to centralizer algebras. We provide a generalized Bratteli diagram that illustrates how the representation theory of the three algebras discussed in this paper are related. Moreover, we give combinatorial formulas for the dimensions of the simple modules of these algebras. [ABSTRACT FROM AUTHOR]

This is a paper about c -functions and Macdonald polynomials. There are c -function formulas for E -expansions of P λ and A λ + ρ , principal specializations of P λ and E μ , for Macdonald's constant term formulas, and for the norms of Macdonald polynomials. Most of these follow from the creation formulas for Macdonald polynomials, providing alternative proofs to several results from [19]. In addition, we prove the Boson-Fermion correspondence in the Macdonald polynomial setting and the Weyl character formula for Macdonald polynomials. [ABSTRACT FROM AUTHOR]

Multiparametric quantum semigroups M q ˆ , p ˆ (n) are generalization of the one-parameter general linear semigroups M q (n) , where q ˆ = (q i j) and p ˆ = (p i j) are 2 n 2 parameters satisfying certain conditions. In this paper, we study the algebra of multiparametric Manin matrices using the R-matrix method. The systematic approach enables us to obtain several classical identities such as Muir's identities, Newton's identities, Capelli-type identities, Cauchy-Binet's identity both for determinant and permanent as well as a rigorous proof of the MacMahon master equation for the quantum algebra of multiparametric Manin matrices. Some of the generalized identities are also lifted to multiparameter q -Yangians. [ABSTRACT FROM AUTHOR]

In this paper, we study the category of modules over the Smith algebra which are free of finite rank over the unital polynomial subalgebra generated by the Cartan element h and obtain families of such simple modules of arbitrary rank. In the case of rank one we obtain a full description of the isomorphism classes, a simplicity criterion, and an algorithm to produce all composition series. We show that all such modules have finite length and describe the composition factors and their multiplicity. [ABSTRACT FROM AUTHOR]

In 1998, Georgia Benkart and Tom Roby introduced the down-up algebra A. The algebra A is associative, noncommutative, and infinite-dimensional. It is defined by two generators A , B and two relations called the down-up relations. In the present paper, we introduce the Z 3 -symmetric down-up algebra A. We define A by generators and relations. There are three generators A , B , C and any two of these satisfy the down-up relations. We describe how A is related to some familiar algebras in the literature, such as the Weyl algebra, the Lie algebras sl 2 and sl 3 , the sl 3 loop algebra, the Kac-Moody Lie algebra A 2 (1) , the q -Weyl algebra, the quantized enveloping algebra U q (sl 2) , and the quantized enveloping algebra U q (A 2 (1)). We give some open problems and conjectures. [ABSTRACT FROM AUTHOR]

Let G be a finite group and let V be a finite and faithful G -module such that V is completely reducible, possibly of mixed characteristic, or V is a G -module over a field of characteristic p with O p (G) = 1. Suppose that M is the largest orbit size in the action of G on V. It is known that the index of the commutator subgroup G ′ in G is bounded by M , that is, | G : G ′ | ≤ M. In this paper, we classify all linear group actions in which | G : G ′ | = M. It turns out that our classification is a vast generalization of a classic 1967 result by D. Passman. We also include an application of the main results to Brauer's k (B) -problem. [ABSTRACT FROM AUTHOR]

Let D be a division ring, n a positive integer, and GL n (D) the general skew linear group of degree n over D. In this paper, we study the structure of a subgroup G of GL n (D) satisfying some rank conditions. Among results, we prove that if G is locally nearly radical of finite co-central rank, then G has a normal solvable subgroup N of finite co-central rank such that G / N is finite. Also, we show that G is locally generalized radical of finite rank if and only if G contains a normal solvable subgroup S of finite rank such that G / S is finite. These facts generalize some our previous results. [ABSTRACT FROM AUTHOR]

For positive integers u and v , let L u = [ 1 0 u 1 ] and R v = [ 1 v 0 1 ]. Let G u , v be the group generated by L u and R v. In a previous paper, the authors determined a characterization of matrices M = [ a b c d ] in G u , v when u , v ≥ 3 in terms of the short continued fraction representation of b / d. We extend this result to the case where u v ≥ 5. Additionally, we compute [ G u , v : G u , v ] where G u , v = { [ 1 + u v n 1 v n 2 u n 3 1 + u v n 4 ] ∈ SL 2 (Z) : (n 1 , n 2 , n 3 , n 4) ∈ Z 4 } for u , v ≥ 1 , extending a result of Chorna, Geller, and Shpilrain and solving the membership problem for G u , v with u , v ≥ 1. [ABSTRACT FROM AUTHOR]

In this paper, we present a vertex operator approach to construct and compute all complex irreducible characters of the general linear group GL n (F q). Green's theory of GL n (F q) is recovered and enhanced under the realization of the Grothendieck ring of representations R G = ⨁ n ≥ 0 R (GL n (F q)) as two isomorphic Fock spaces associated to two infinite-dimensional F -equivariant Heisenberg Lie algebras h ˆ F ‾ ˆ q and h ˆ F ‾ q , where F is the Frobenius automorphism of the algebraically closed field F ‾ q. Under this picture, the irreducible characters are realized by the Bernstein vertex operators for Schur functions, the characteristic functions of the conjugacy classes are realized by the vertex operators for the Hall-Littlewood functions, and the character table is completely given by matrix coefficients of vertex operators of these two types. One of the features of the current approach is a simpler identification of the Fock space R G as the Hall algebra of symmetric functions via vertex operator calculus, and another is that we are able to compute in general the character table, where Green's degree formula is demonstrated as an example. [ABSTRACT FROM AUTHOR]

Over fields of characteristic 2, Specht modules may decompose and there is no upper bound for the dimension of their endomorphism algebra. A classification of the (in)decomposable Specht modules and a closed formula for the dimension of their endomorphism algebra remain two important open problems in the area. In this paper, we introduce a novel description of the endomorphism algebra of the Specht modules and provide infinite families of Specht modules with one-dimensional endomorphism algebra. [ABSTRACT FROM AUTHOR]

Skew axets were first defined by McInroy and Shpectorov where they used the term of axets to classify shapes of an algebra. When they first submitted their paper, it was not known if skew axial algebras exist and now we will present such examples with axet X ′ (1 + 2). Looking at 2-generated primitive axial algebras of Monster type, we will be able to state and prove the classification of such algebras with axet X ′ (1 + 2). We will conclude by looking at larger skew axets and give a suggestion on how one could extend the classification. [ABSTRACT FROM AUTHOR]

The G -representation variety R G (Σ g) parametrizes the representations of the fundamental group π 1 (Σ g) of a closed surface into an algebraic group G. For G the groups of n × n upper triangular matrices or unipotent upper triangular matrices, we compare two methods for computing algebraic invariants of R G (Σ g). Using the geometric method initiated by González-Prieto, Logares and Muñoz, based on a Topological Quantum Field Theory (TQFT), we compute the virtual classes of R G (Σ g) in the Grothendieck ring of varieties for n = 1 , ... , 5. Introducing the notion of algebraic representatives we are able to efficiently compute the TQFT. Using the arithmetic method initiated by Hausel and Rodriguez-Villegas, we compute the E -polynomials of R G (Σ g) for n = 1 , ... , 10. For both methods, we describe how the computations can be performed algorithmically. Furthermore, we discuss how the representation varieties for the groups of unipotent upper triangular matrices are related to Higman's conjecture. The computations of this paper can be seen as positive evidence towards a generalized motivic version of the conjecture. [ABSTRACT FROM AUTHOR]

Regular nilpotent Hessenberg varieties form an important family of subvarieties of the flag variety, which are often singular and sometimes not normal varieties. Like Schubert varieties, they contain distinguished points called permutation flags. In this paper, we give a combinatorial characterization for a permutation flag of a regular nilpotent Hessenberg variety to be a singular point. We also apply this result to characterize regular nilpotent Hessenberg varieties which are normal algebraic varieties. [ABSTRACT FROM AUTHOR]

In this paper we study the Diophantine problem in Chevalley groups G π (Φ , R) , where Φ is a reduced irreducible root system of rank >1, R is an arbitrary commutative ring with 1. We establish a variant of double centralizer theorem for elementary unipotents x α (1). This theorem is valid for arbitrary commutative rings with 1. The result is principal to show that any one-parametric subgroup X α , α ∈ Φ , is Diophantine in G. Then we prove that the Diophantine problem in G π (Φ , R) is polynomial time equivalent (more precisely, Karp equivalent) to the Diophantine problem in R. This fact gives rise to a number of model-theoretic corollaries for specific types of rings. [ABSTRACT FROM AUTHOR]

In this paper, we classify simple Harish-Chandra modules over simple generalized Witt algebras. [ABSTRACT FROM AUTHOR]

The goal of this paper is to generalize a statement by Drinfeld, asserting that Yangians can be constructed as limit forms of the quantum loop algebras, to the super case. We establish a connection between quantum loop superalgebra and super Yangian of the general linear Lie superalgebra gl M | N in RTT type presentation. In particular, we derive the Poincaré-Birkhoff-Witt(PBW) theorem for the quantum loop superalgebra U q (Lgl M | N). Additionally, we investigate the application of the same argument to twisted super Yangian of the ortho-symplectic Lie superalgebra. For this purpose, we introduce the twisted quantum loop superalgebra as a one-sided coideal of U q (Lgl M | 2 n) with respect to the comultiplication. [ABSTRACT FROM AUTHOR]

For a ∈ C ⁎ there are two natural evaluation maps ev a and ev a from the affine Hecke algebra H ▵ (r) C to the Hecke algebra H (r) C. The maps ev a and ev a induce evaluation maps ev ˜ a and ev ˜ a from the affine quantum Schur algebra S ▵ (n , r) C to the quantum Schur algebra S (n , r) C , respectively. In this paper we prove that the evaluation map ev ˜ a (resp. ev ˜ a) is compatible with the evaluation map Ev a (resp. Ev (− 1) n a q n ) for quantum affine sl n. Furthermore we compute the Drinfeld polynomials associated with the simple S ▵ (n , r) C -modules which come from the simple S (n , r) C -modules via the evaluation maps ev ˜ a. Then we characterize finite-dimensional irreducible S ▵ (n , r) C -modules which are irreducible as S (n , r) C -modules for n > r. As an application, we characterize finite-dimensional irreducible modules for the affine Hecke algebra H ▵ (r) C which are irreducible as modules for the Hecke algebra H (r) C. [ABSTRACT FROM AUTHOR]

Let R be a commutative noetherian ring. In this paper, we find out close relationships between the module M being embedded in a module of projective dimension at most n and the (n + 1) -torsionfreeness of the n th syzygy of M. As an application, when R is local with residue field k , we compute the dimensions as k -vector spaces of Ext modules related to syzygies of k. [ABSTRACT FROM AUTHOR]

Let K be an algebraically closed field of characteristic p ≥ 0. Assume F , F (1) , F (2) , and (F (1)) p are the free group on n > 1 generators, the first and second derived subgroups of F , and the subgroup of F (1) generated by all p -powers, respectively. In this paper, among other results, we show that for any word w ∈ F (1) ∖ F (2) (F (1)) p , the corresponding word map w : ∏ n PSL 2 (K) → PSL 2 (K) is surjective. We show that the class of such words w contains, for instance, all (weakly) Engel words. [ABSTRACT FROM AUTHOR]

In our previous work with Grifo and Hà, we showed the stable Harbourne-Huneke containment and Chudnovsky's conjecture for the defining ideal of sufficiently many general points in P N. In this paper, we establish the conjectures for all remaining cases, and hence, give the affirmative answer to Harbourne-Huneke containment and Chudnovsky's conjecture for the general points in P N for all N. Our new technique is to develop the Cremona reduction process that provides effective lower bounds for the Waldschmidt constant of the defining ideals of generic points in projective spaces. [ABSTRACT FROM AUTHOR]

There are several classical characterisations of the valuative dimension of a commutative ring. Constructive versions of this dimension have been given and proven to be equivalent to the classical notion within classical mathematics, and they can be used for the usual examples of commutative rings. To the contrary of the classical versions, the constructive versions have a clear computational content. This paper investigates the computational relationship between three possible constructive definitions of the valuative dimension of a commutative ring. In doing so, it proves these constructive versions to be equivalent within constructive mathematics. [ABSTRACT FROM AUTHOR]

Semi-standard graded rings are a generalized notion of standard graded rings. In this paper, we compare generalized notions of the Gorenstein property in semi-standard graded rings. We discuss the commonalities between standard graded rings and semi-standard graded rings, as well as elucidate distinctive phenomena present in semi-standard graded rings that are absent in standard graded rings. [ABSTRACT FROM AUTHOR]

In this paper, a symplectic structure on a Leibniz algebra is defined to be a symmetric nondegenerate bilinear form satisfying certain compatibility condition, and a phase space of a Leibniz algebra is defined to be a symplectic Leibniz algebra satisfying certain conditions. We show that a Leibniz algebra has a phase space if and only if there is a compatible Leibniz-dendriform algebra, and phase spaces of Leibniz algebras are one-to-one corresponds to Manin triples of Leibniz-dendriform algebras. Product (paracomplex) structures and complex structures on Leibniz algebras are studied in terms of decompositions of Leibniz algebras. A para-Kähler structure on a Leibniz algebra is defined to be a symplectic structure and a paracomplex structure satisfying a compatibility condition. We show that a symplectic Leibniz algebra admits a para-Kähler structure if and only if the Leibniz algebra is the direct sum of two Lagrangian subalgebras as vector spaces. A complex product structure on a Leibniz algebra consists of a complex structure and a product structure satisfying a compatibility condition. A pseudo-Kähler structure on a Leibniz algebra is defined to be a symplectic structure and a complex structure satisfying a compatibility condition. Various properties and relations of complex product structures and pseudo-Kähler structures are studied. In particular, Leibniz-dendriform algebras give rise to complex product structures and pseudo-Kähler structures naturally. [ABSTRACT FROM AUTHOR]

Let G be an infinite simple group of finite Morley rank and of Prüfer 2-rank 1 which admits a supertight automorphism α such that the fixed-point subgroup C G (α n) is pseudofinite for all integers n > 0. The main result of this paper is the identification of G with PGL 2 (K) for some algebraically closed field K of characteristic ≠2. [ABSTRACT FROM AUTHOR]

To prove that a modular variety is of general type, there are three types of obstructions: reflective, cusp and elliptic obstructions. In this paper, we give a quantitative estimate of the reflective obstructions for the unitary case. This shows in particular that the reflective obstructions are small enough in higher dimension, say greater than 138. Our result reduces the study of the Kodaira dimension of unitary modular varieties to the construction of a cusp form of small weight in a quantitative manner. As a byproduct, we formulate and partially prove the finiteness of Hermitian lattices admitting reflective modular forms, which is a unitary analog of the conjecture by Gritsenko-Nikulin in the orthogonal case. Our estimate of the reflective obstructions uses Prasad's volume formula. [ABSTRACT FROM AUTHOR]

Let U q (g) denote the rational form of the quantized enveloping algebra associated to a complex simple Lie algebra g. Let λ be a nonzero dominant integral weight of g , and let V be the corresponding type 1 finite-dimensional irreducible representation of U q (g). Starting from this data, the R -matrix formalism for quantum groups outputs a Hopf algebra U R λ (g) defined in terms of a pair of generating matrices satisfying well-known quadratic matrix relations. In this paper, we prove that this Hopf algebra admits a Chevalley–Serre type presentation which can be recovered from that of U q (g) by adding a single invertible quantum Cartan element. We simultaneously establish that U R λ (g) can be realized as a Hopf subalgebra of the tensor product of the space of Laurent polynomials in a single variable with the quantized enveloping algebra associated to the lattice generated by the weights of V. The proofs of these results are based on a detailed analysis of the homogeneous components of the matrix equations and generating matrices defining U R λ (g) , with respect to a natural grading by the root lattice of g compatible with the weight space decomposition of End (V). [ABSTRACT FROM AUTHOR]

Resolvent degree is an invariant measuring the complexity of algebraic and geometric phenomena, including the complexity of finite groups. To date, the resolvent degree of a finite simple group G has only been investigated when G is a cyclic group; an alternating group; a simple factor of a Weyl group of type E 6 , E 7 , or E 8 ; or PSL (2 , F 7). In this paper, we establish upper bounds on the resolvent degrees of the sporadic groups by using the invariant theory of their projective representations. To do so, we introduce the notion of (weak) RD k ≤ d -versality, which we connect to the existence of "special points" on varieties. [ABSTRACT FROM AUTHOR]

The solubilizer of an element x of a profinite group G is the set of the elements y of G such that the subgroup of G generated by x and y is prosoluble. We propose the following conjecture: the solubilizer of x in G has positive Haar measure if and only if x centralizes 'almost all' the non-abelian chief factors of G. We reduce the proof of this conjecture to another conjecture concerning finite almost simple groups: there exists a positive c such that, for every finite simple group S and every (a , b) ∈ (Aut (S) ∖ { 1 }) × Aut (S) , the number of s is S such that 〈 a , b s 〉 is insoluble is at least c | S |. Work in progress by Fulman, Garzoni and Guralnick is leading to prove the conjecture when S is a simple group of Lie type. In this paper we prove the conjecture for alternating groups. [ABSTRACT FROM AUTHOR]

In [16] , a theory of universal extensions in abelian categories is developed; in particular, the notion of Ext 1 -universal object is presented. In the present paper, we show that an Ab3 abelian category which is Ext 1 -small satisfies the Ab4 condition if, and only if, each one of its objects is Ext 1 -universal. We use the dual of this result to construct projective effacements in Grothendieck categories. In particular, we complete the classical result of Roos on Grothendieck categories which are Ab4*, with a new proof, independent of [20]. We also give a characterization of the co- Ext 1 -universal objects of the category of torsion abelian groups. In particular, we show that such groups are the ones admitting a decomposition Q ⊕ R , in which Q is injective and R is a reduced group in which each p -component is bounded. [ABSTRACT FROM AUTHOR]

In this paper we study the classifying spaces of graph products of simplicial groups and connected Hopf algebras over a field, and show that they can be uniformly treated under the framework of polyhedral products. It turns out that these graph products are models of the loop spaces of polyhedral products over a flag complex and their homology, respectively. Certain morphisms between graph products are also considered. In the end we prove the structure theorems of such graph products in the form we need. [ABSTRACT FROM AUTHOR]

In this paper we mainly consider the notion of Drinfeld double for two weak multiplier Hopf (⁎-)algebras which are paired with each other. Then we show that the Drinfeld double is again a weak multiplier Hopf (⁎-)algebra. Furthermore, we study integrals on the Drinfeld double. Finally, we establish the correspondence between modules over a Drinfeld double D (A) and Yetter-Drinfeld modules over a weak algebraic quantum group A. [ABSTRACT FROM AUTHOR]

For a smooth affine algebra R of dimension d ≥ 3 over a field k and an invertible alternating matrix χ of rank 2 n , the group S p (χ) of invertible matrices of rank 2 n over R which are symplectic with respect to χ acts on the right on the set U m 2 n (R) of unimodular rows of length 2 n over R. In this paper, we prove that S p (χ) acts transitively on U m 2 n (R) if k is algebraically closed, d ! ∈ k × and 2 n ≥ d. [ABSTRACT FROM AUTHOR]

This paper concerns commutative plenary train algebras of rank m and their idempotents. We obtain the Peirce decomposition of these algebras having an idempotent element and the multiplication table of Peirce components when the plenary train roots are mutually different. We show that a backcrossing algebra is a plenary train algebra of rank m if and only if, it is a principal train one of rank m. For the backcrossing train algebras, we confirm a first conjecture of Juan Carlos Gutiérrez Fernández on the relation between plenary train roots and principal train roots. A second conjecture on the existence of idempotent in train algebras also obtains a positive answer in the class of backcrossing algebras. [ABSTRACT FROM AUTHOR]