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For a fixed digraph G, the Constraint Satisfaction Problem with the template G, or CSP(G) for short, is the problem of deciding whether a given input digraph H admits a homomorphism to G. The dichotomy conjecture of Feder and Vardi states that CSP(G), for any choice of G, is solvable in polynomial time or NP-complete. This paper confirms the conjecture for a class of oriented trees called special triads. As a corollary we get the smallest known example of an oriented tree (with 33 vertices) defining an NP-complete CSP(G).

A remarkable result of Moln\'ar [Proc. Amer. Math. Soc., 126 (1998), 853-861] states that automorphisms of the algebra of operators acting on a separable Hilbert space is stable under "small" perturbations. More precisely, if $\phi,\psi$ are endomorphisms of $\mathcal{B}(\mathcal{H})$ such that $\|\phi(A)-\psi(A)\, Comment: 14 pp. To appear in Proceedings of the American Mathematical Society

Let C be an Abelian group. A class X of Abelian groups is called a CE• H-class if for any groups A, B ∈ X, it follows from the existence of isomorphisms E• (A) ≅ E• (B) and Hom(C,A) ≅ Hom(C,B) that there is an isomorphism A ≅ B. In this paper, conditions are studied under which the class $$ {\mathfrak{I}}_{\mathrm{cd}}^{\mathrm{ad}} $$ of completely decomposable almost divisible Abelian groups and class $$ {\mathfrak{I}}_{\mathrm{cd}}^{\ast } $$ of completely decomposable torsion-free Abelian groups A where Ω(A) contains only incomparable types are CE• H-classes, where C is a completely decomposable torsion-free Abelian group.

A multiplication on an Abelian group G is a homomorphism μ: G ⊗ G → G. An Abelian group G with a multiplication on it is called a ring on the group G. R. A. Beaumont and D. A. Lawver have formulated the problem of studying semisimple groups. An Abelian group is said to be semisimple if there exists a semisimple associative ring on it. Semisimple groups are described in the class of vector Abelian nonmeasurable groups. It is also shown that if a set I is nonmeasurable, $$ G=\coprod_{i\in I}{A}_i $$ is a reduced vector Abelian group, and μ is a multiplication on G, then μ is determined by its restriction on the sum $$ {\displaystyle \begin{array}{c}\oplus \\ {}i\in I\end{array}}{A}_i $$ this statement is incorrect if the set I is measurable or the group G is not reduced.

We define and study approximate versions of σ-biflatness and σ-biprojectivity of a Banach algebra A where σ ∈Hom(A). We generalize the concepts pseudo amenability and pseudo contractibility via homomorphisms. We investigate their relations.

We study distinguished objects in the category $\mathcal{BL}$ of Banach lattices and lattice homomorphisms. The free Banach lattice construction introduced by de Pagter and Wickstead generates push-outs, and combining this with an old result of Kellerer on marginal measures, the amalgamation property of Banach lattices is established. This will be the key tool to prove that $L_1([0,1]^{\mathfrak{c}})$ is separably $\mathcal{BL}$-injective, as well as to give more abstract examples of Banach lattices of universal disposition for separable sublattices. Finally, an analysis of the ideals on $C(\Delta,L_1)$, which is a separably universal Banach lattice as shown by Leung, Li, Oikhberg and Tursi, allows us to conclude that separably $\mathcal{BL}$-injective Banach lattices are necessarily non-separable., Comment: third version, the main change is a proof that $L_1([0,1]^\kappa)$ is 1-separably $\mathcal{BL}$-injective for arbitrary uncountable $\kappa$, not only for $\kappa\geq \mathfrak{c}$

The Mordell-Weil groups $E(\mathbb{Q})$ of elliptic curves influence the structures of their quadratic twists $E_{-D}(\mathbb{Q})$ and the ideal class groups $\mathrm{CL}(-D)$ of imaginary quadratic fields. For appropriate $(u,v) \in \mathbb{Z}^2$, we define a family of homomorphisms $\Phi_{u,v}: E(\mathbb{Q}) \rightarrow \mathrm{CL}(-D)$ for particular negative fundamental discriminants $-D:=-D_E(u,v)$, which we use to simultaneously address questions related to lower bounds for class numbers, the structures of class groups, and ranks of quadratic twists. Specifically, given an elliptic curve $E$ of rank $r$, let $\Psi_E$ be the set of suitable fundamental discriminants $-D 0$, we show that as $X \to \infty$, we have $$\#\, \left\{-X < -D < 0: -D \in \Psi_E \right \} \, \gg_{\varepsilon} X^{\frac{1}{2}-\varepsilon}.$$ In particular, if $\ell \in \{3,5,7\}$ and $\ell \mid |E_{\mathrm{tor}}(\mathbb{Q})|$, then the number of such discriminants $-D$ for which $\ell \mid h(-D)$ is $\gg_{\varepsilon} X^{\frac{1}{2}-\varepsilon}.$ Moreover, assuming the Parity Conjecture, our results hold with the additional condition that the quadratic twist $E_{-D}$ has rank at least 2.

A relation between 𝜂-quasi-symmetric homomorphisms and K-quasiconformal mappings on n-dimensional smooth connected Riemannian manifolds has been studied. The main results of the research are presented in Theorems 2.6 and 2.7. Several conditions for the boundary behavior of 𝜂-quasi-symmetric homomorphisms between two arbitrary domains with weakly flat boundaries and compact closures, QED and uniform domains on the Riemannian manifolds, which satisfy the obtained results, were also formulated. In addition, quasiballs, c-locally connected domains, and the corresponding results were also considered.

The study of operator algebras on Hilbert spaces, and C ∗ -algebras in particular, is one of the most active areas within Functional Analysis. A natural generalization of these is to replace Hilbert spaces (which are L 2 -spaces) with L p -spaces, for p ∈ [ 1 , ∞ ) . The study of such algebras of operators is notoriously more challenging, due to the very complicated geometry of L p -spaces by comparison with Hilbert spaces. We give a modern overview of a research area whose beginnings can be traced back to the 50’s, and that has seen renewed attention in the last decade through the infusion of new techniques. The combination of these new ideas with old tools was the key to answer some long standing questions. Among others, we provide a description of all unital contractive homomorphisms between algebras of p -pseudofunctions of groups.

We show that one can recover the local Neron-Tate height of a rational point from the data of two homomorphisms of topological groups. See Theorem 1.1.

In this paper, we have discussed quotient structures of KU-algebras by using the concept of intersection soft ideals. In general, the soft sets are parameterized families of sets that are used to dealt with uncertainty. In particular, We have given the fundamental homomorphism theorem of quotient KU-algebras. A characterization of commutative quotient KU-algebras, implicative quotient KU-algebras and positive implicative quotient KU-algebras are also presented.

In this article, we introduce ideals and other special ideals on EQ-algebras, such as implicative ideals, primary ideals, prime ideals and maximal ideals. At first, we give the notion of ideal and its related properties on EQ-algebras, and give its equivalent characterizations. We discuss the relations between ideals and filters, and study the generating formula of ideals on EQ-algebras. Moreover, we study the properties of implicative ideals, primary ideals, prime ideals and maximal ideals and their relations. For example, we prove that every maximal ideal is prime and if prime ideals are implicative, then they are maximal in the EQ-algebra with the condition $ (DNP) $. Finally, we introduce the topological properties of prime ideals. We get that the set of all prime ideals is a compact $ T_{0} $ topological space. Also, we transferred the spectrum of EQ-algebras to bounded distributive lattices and given the ideal reticulation of EQ-algebras.

In this paper, we first introduce a generalized K-algebra (briefly, gK-algebra) $$(P, \cdot , \odot , e, ^{-1})$$ which is constructed on a non-symmetric polygroup $$(P, \cdot , e, ^{-1})$$ , by adjoining binary hyperoperation $$\odot $$ defined by $$x \odot y = x \cdot y^{-1}$$ , for all $$x, y \in P$$ . Then, we show that every gK-algebra associated to a canonical hypergroup is a hyper B-algebra with constant e. Finally, we define generalized gK-subalgebras, (prime) generalized gK-ideals, homomorphisms of $$(P, \cdot , \odot , e, ^{-1})$$ and quotient generalized gK-algebras.

In this paper, we introduce the notions of $$( \in , \in \vee q^{k}_{\delta })$$ -fuzzy soft near-ring and $$( \in , \in \vee q^{k}_{\delta })$$ -fuzzy soft ideal over a near-ring which are generalizations of $$( \in , \in \vee q_{k})$$ -fuzzy soft near-ring and $$( \in , \in \vee q_{k})$$ -fuzzy soft ideal respectively. We show that the restricted intersection (resp. extended intersection, union, “AND” operation and “OR” operation) of $$( \in , \in \vee q^{k}_{\delta })$$ -fuzzy soft near-rings (resp. ideals) is an $$( \in , \in \vee q^{k}_{\delta })$$ -fuzzy soft near-ring (resp. ideal) over a near-ring. Further, we introduce the concepts of $$( \in , \in \vee q_\delta ^{k})$$ -fuzzy soft subnear-ring and $$( \in , \in \vee q_\delta ^{k})$$ -fuzzy soft ideal of an $$( \in , \in \vee q_\delta ^{k})$$ -fuzzy soft near-ring and provide some related results. Finally, we study the image and pre-image of an $$(\in ,\in \vee q_\delta ^k)$$ -fuzzy soft near-ring (resp. ideal) over a near-ring using fuzzy soft homomorphism.

An associative ring R is called an E-ring if the canonical homomorphism R ∼= E(R+) is an isomorphism. Additive groups of E-rings are called E-groups. In other words, an Abelian group A is an E-group if and only if A ∼= End A and the endomorphism ring E(A) is commutative. In this paper, we give a survey of the main results on E-groups and E-rings and also consider some of their generalizations: E-closed groups, T -rings, A-rings, the groups admitting only commutative multiplications, etc.

Every Krull monoid has a transfer homomorphism onto a monoid of zero-sum sequences over a subset of its class group. This transfer homomorphism is a crucial tool for studying the arithmetic of Krull monoids. In the present paper, we strengthen and refine this tool for Krull monoids with finitely generated class group.

We propose an algorithm for linearizing systems of partial differential equations at constant solutions. The algorithm is based on an isomorphism constructed between the ring of linearized functions and the ring of special matrices, which makes it possible to simplify calculations in the process of linearization. The algorithm is illustrated by applying it to the quasigasdynamic system.

Let $f\,:\,C\,\longrightarrow \,D$ be a nonconstant separable morphism between irreducible smooth projective curves defined over an algebraically closed field. We say that $f$ is genuinely ramified if ${\mathcal O}_D$ is the maximal semistable subbundle of $f_*{\mathcal O}_C$ (equivalently, the induced homomorphism $f_*\,:\, \pi _1^{\textrm{et}}(C)\,\longrightarrow \, \pi _1^{\textrm{et}}(D)$ of étale fundamental groups is surjective). We prove that the pullback $f^*E\,\longrightarrow \, C$ is stable for every stable vector bundle $E$ on $D$ if and only if $f$ is genuinely ramified.

Denote a finite dimensional Hopf C*-algebra by H, and a Hopf *-subalgebra of H by H1. In this paper, we study the construction of the field algebra in Hopf spin models determined by H1 together with its symmetry. More precisely, we consider the quantum double D(H, H1) as the bicrossed product of the opposite dual $$\widehat{{H^{op}}}$$ of H and H1 with respect to the coadjoint representation, the latter acting on the former and vice versa, and under the non-trivial commutation relations between H1 and Ĥ we define the observable algebra $${{\cal A}_{{H_1}}}$$ . Then using a comodule action of D(H, H1) on $${{\cal A}_{{H_1}}}$$ , we obtain the field algebra $${{\cal F}_{{H_1}}}$$ , which is the crossed product $${{\cal A}_{{H_1}}} \rtimes D\widehat{\left({H,{H_1}} \right)}$$ , and show that the observable algebra $${{\cal A}_{{H_1}}}$$ is exactly a D(H, H1)-invariant subalgebra of $${{\cal F}_{{H_1}}}$$ . Furthermore, we prove that there exists a duality between D(H, H1) and $${{\cal A}_{{H_1}}}$$ , implemented by a *-homomorphism of D(H, H1).

We suggest an algorithm for constructing all the isolated primary components of a given polynomial ideal. At the output, they are determined by systems of generators up to embedded components, and also as kernels of some homomorphisms. The complexity of this algorithm is subexponential in the size of the input data.

This paper shall be concerned with the notion of von-Neumann regular acts. First, the notions of semiretraction homomorphisms and fully semiretractable (FSR) S-acts are introduced and some properties of them are investigated. Finally, using semiretraction notion, we investigate locally projective and von-Neumann regular S-acts.

A hom-Lie algebroid is a vector bundle together with a Lie algebroid-like structure which is twisted by a homomorphism and a VB-hom algebroid is essentially defined as a hom-Lie algebroid object in the category of vector bundles. In this paper, we show that, there exists a correspondence between the VB-hom algebroids and two term representations up to homotopy of hom-Lie algebroid.

UDC 512.5Smith in paper [Mapping between module lattices, Int. Electron. J. Algebra, 15, 173–195 (2014)] introduced maps between the lattice of ideals of a commutative ring and the lattice of submodules of an -module i.e., and mappings.The definitions of the maps were motivated by the definition of multiplication modules.Moreover, some sufficient conditions for the maps to be a lattice homomorphisms are studied.In this work we define a class of -modules and observe the properties of the class. We give a sufficient conditions for the module and the ring such that the class is a hereditary pretorsion class.

In this paper we study graded Bourbaki ideals. It is a well-known fact that for torsionfree modules over Noetherian normal domains, Bourbaki sequences exist. We give criteria in terms of certain attached matrices for a homomorphism of modules to induce a Bourbaki sequence. Special attention is given to graded Bourbaki sequences. In the second part of the paper, we apply these results to the Koszul cycles of the residue class field and determine particular Bourbaki ideals explicitly. We also obtain in a special case the relationship between the structure of the Rees algebra of a Koszul cycle and the Rees algebra of its Bourbaki ideal., Comment: 29 pages

An algebra $$A$$ is said to be Cantor if a theorem similar to the Cantor– Bernstein– Schroder theorem holds for it; namely, if, for any algebra $$B$$ , the existence of injective homomorphisms $$A\to B$$ and $$B\to A$$ implies the isomorphism $$A\cong B$$ . Necessary and sufficient conditions for an act over a finite commutative semigroup of idempotents to be Cantor are obtained under the assumption that all connected components of this act are finite.

The paper is devoted to the normal extensions of discrete semigroups and $ * $ -homomorphisms of semigroup $ C^{*} $ -algebras. We study the normal extensions of abelian semigroups by arbitrary groups. Considering numerical semigroups, we prove that they are normal extensions of the semigroup of nonnegative integers by finite cyclic groups. On the other hand, we prove that if a semigroup is a normal extension of the semigroup of nonnegative integers by a finite cyclic group generated by a single element then this semigroup is isomorphic to a numerical semigroup. As regard a normal extension with a generating set, we consider two reduced semigroup $ C^{*} $ -algebras defined by this extension. We show that there exists an embedding of the semigroup $ C^{*} $ -algebras which is generated by an injective homomorphism of the semigroups and the natural isometric representations of these semigroups.

Recently, Wickstead investigated the long-standing problem of adding an identity to a non-unital Banach lattice algebra. In this regard, he proved that, in the category whose objects are unital Banach lattice algebras and morphisms are identity preserving algebra and lattice homomorphisms, there is no reflection for $$c_{0}$$ in which $$c_{0}$$ can be embedded as an algebra and order ideal. The main purpose of this note is to describe an alternative category in which a suitable reflection of $$c_{0}$$ can be located, producing a satisfactory lattice unitization of $$c_{0}$$ with $$c_{0}$$ as an algebra and order ideal.

If A and B are abelian varieties over a number field K such that there are non-trivial geometric homomorphisms of abelian varieties between reductions of A and B at most primes of K, then there exists a non-trivial (geometric) homomorphism from A to B defined over an algebraic closure of K.

Necessary and sufficient conditions for the exactness (in the algebraic sense) of certain sequences of bounded group homomorphisms are established.

Let $M = \mathbb{B}^2 / \Gamma$ be a smooth ball quotient of finite volume with first betti number $b_1(M)$ and let $\mathcal{E}(M) \ge 0$ be the number of cusps (i.e., topological ends) of $M$. We study the growth rates that are possible in towers of finite-sheeted coverings of $M$. In particular, $b_1$ and $\mathcal{E}$ have little to do with one another, in contrast with the well-understood cases of hyperbolic $2$- and $3$-manifolds. We also discuss growth of $b_1$ for congruence arithmetic lattices acting on $\mathbb{B}^2$ and $\mathbb{B}^3$. Along the way, we provide an explicit example of a lattice in $\mathrm{PU}(2, 1)$ admitting a homomorphism onto $\mathbb{Z}$ with finitely generated kernel. Moreover, we show that any cocompact arithmetic lattice $\Gamma \subset \mathrm{PU}(n, 1)$ of simplest type contains a finite index subgroup with this property.

Every homomorphism $\varphi: B(G) \rightarrow B(H)$ between Fourier-Stieltjes algebras on locally compact groups $G$ and $H$ is determined by a continuous mapping $\alpha: Y \rightarrow \Delta(B(G))$, where $Y$ is a set in the open coset ring of $H$ and $\Delta(B(G))$ is the Gelfand spectrum of $B(G)$ (a $*$-semigroup). We exhibit a large collection of maps $\alpha$ for which $\varphi=j_\alpha: B(G) \rightarrow B(H)$ is a completely positive/completely contractive/completely bounded homomorphism and establish converse statements in several instances. For example, we fully characterize all completely positive/completely contractive/completely bounded homomorphisms $\varphi: B(G) \rightarrow B(H)$ when $G$ is a Euclidean- or $p$-adic-motion group. In these cases, our description of the completely positive/completely contractive homomorphisms employs the notion of a "fusion map of a compatible system of homomorphisms/affine maps" and is quite different from the Fourier algebra situation.

Wang et al. introduced Lp radial Blaschke-Minkowski homomorphisms based on Schuster?s radial Blaschke-Minkowski homomorphisms. In 2018, Feng and He gave the concept of (p,q)-mixed geominimal surface area according to the Lutwak, Yang and Zhang?s (p,q)-mixed volume. In this article, associated with the (p,q)-mixed geominimal surface areas and the Lp radial Blaschke-Minkowski homomorphisms, we establish some inequalities including two Brunn-Minkowski type inequalities, a cyclic inequality and two monotonic inequalities.

In this paper, we establish the idea of fuzzy congruences on Abel-Grassmann's group (AG-group). We investigate different outcomes of fuzzy-congruences on AG-groups in detail and give some examples to illustrate the newly established results. We develop the relation between fuzzy congruence and fuzzy normal subgroup. In the end, we also provide some results of fuzzy homomorphism on AG-groups.

A new category of topological spaces with additional structures, called m-towers, is introduced. It is shown that there is a covariant functor which establishes a one-to-one correspondences between unital (resp. arbitrary) subhomogeneous C*-algebras and proper (resp. proper pointed) m-towers of finite height, and between all *-homomorphisms between two such algebras and morphisms between m-towers corresponding to these algebras., 45 pages

An extension of X by Y is a short exact sequence of quasi Banach modules and homomorphisms 0⟶Y⟶Z⟶X⟶0. When properly organized all these extensions constitute a linear space denoted by ExtB(X,Y), where B is the underlying (Banach) algebra. In this paper we "compute" the spaces of extensions for the Schatten classes when they are regarded in its natural (left) module structure over B=B(H), the algebra of all operators on the ground Hilbert space. Our main results can be summarized as follows

Let $ \pi $ be a set of primes. A group $ G $ is weakly $ \pi $ -potent if $ G $ is residually finite and, for each element $ x $ of infinite order in $ G $ , there is a positive integer $ m $ such that, for every positive $ \pi $ -integer $ n $ , there exists a homomorphism of $ G $ onto a finite group which sends $ x $ to an element of order $ mn $ . We obtain a few results about weak $ \pi $ -potency for some groups and generalized free products.

Consider a compact symplectic sub-orbifold groupoid $\sf S$ of a compact symplectic orbifold groupoid $(\mathsf X,\omega)$. Let $\mathsf X_{\mathfrak a}$ be the weight-$\mathfrak a$ blowup of $\sf X$ along $\sf S$, and $\mathsf D_{\mathfrak a}=\mathsf{PN}_{\mathfrak a}$ be the exceptional divisor, where $\sf N$ is the normal bundle of $\sf S$ in $\sf X$. In this paper we show that the absolute orbifold Gromov--Witten theory of $\mathsf X_{\mathfrak a}$ can be effectively and uniquely reconstructed from the absolute orbifold Gromov--Witten theories of $\sf X$, $\sf S$ and $\mathsf D_{\mathfrak a}$, the natural restriction homomorphism $H^*_{\text{CR}}({\sf X})\rightarrow H^*_{\text{CR}}({\sf S})$ and the first Chern class of the tautological line bundle over $\mathsf D_{\mathfrak a}$. To achieve this we first prove similar results for the relative orbifold Gromov--Witten theories of $(\mathsf X_{\mathfrak a}|\mathsf D_{\mathfrak a})$ and $(\mathsf N_{\mathfrak a}|\mathsf D_{\mathfrak a})$. As applications of these results, we prove an orbifold version of a conjecture of Maulik--Pandharipande on the Gromov--Witten theory of blowups along complete intersections, a conjecture on the Gromov--Witten theory of root constructions and a conjecture on Leray--Hirsch result for orbifold Gromov--Witten theory of Tseng--You., Comment: 44pages; some typos fixed; comments are welcome; accepted for publication in SCIENCE CHINA Mathematics

A module M is called a D4-module if, whenever A and B are submodules of M with M = A ⊕ B and f : A → B is a homomorphism with Imf a direct summand of B, then Kerf is a direct summand of A. The class of D4-modules contains the class of D3-modules, and hence the class of semi-projective modules, and so the class of Rickart modules. In this paper we prove that, over a commutative Dedekind domain R, for an R-module M which is a direct sum of cyclic submodules, M is direct projective (equivalently, it is semi-projective) iff M is D3 iff M is D4. Also we prove that, over a prime PI-ring, for a divisible R-module X, X is direct projective (equivalently, it is Rickart) iff X ⊕ X is D4. We determine some D3-modules and D4-modules over a discrete valuation ring, as well. We give some relevant examples. We also provide several examples on D3-modules and D4-modules via quivers.

The study of pure-projectivity is accessed from an alternative point of view. Given modules M and N, M is said to be N-pure-subprojective if for every pure epimorphism $$g: B\rightarrow N$$ and homomorphism $$f : M \rightarrow N$$ , there exists a homomorphism $$h: M\rightarrow B$$ such that $$gh=f$$ . For a module M, the pure-subprojectivity domain of M is defined to be the collection of all modules N such that M is N-pure-subprojective. We obtain characterizations for various types of rings and modules, including FP-injective and FP-projective modules, von Neumann regular rings and pure-semisimple rings in terms of pure-subprojectivity domains. As pure-subprojectivity domains clearly include all pure-projective modules, a reasonable opposite to pure-projectivity in this context is obtained by considering modules whose pure-subprojectivity domain consists of only pure-projective. We refer to these modules as psp-poor. Properties of pure-subprojectivity domains and of psp-poor modules are studied.

We give asymptotics for the cumulative distribution function (CDF) for degrees of large dense random graphs sampled from a graphon. The proof is based on precise asymptotics for binomial random variables. Replacing the indicator function in the empirical CDF by a smoother function, we get general asymptotic results for functionals of homomorphism densities for partially labeled graphs with smoother functions. This general setting allows to recover recent results on asymptotics for homomorphism densities of sampled graphon., 49 pages, 3 figures

Generalized Honda formal groups are a class of formal groups, which includes all formal groups over the ring of integers of local fields weakly ramified over $${{\mathbb{Q}}_{p}}$$ . This class is the next in the chain multiplicative formal group–Lubin-Tate formal groups–Honda formal groups. The Lubin-Tate formal groups are defined by distinguished endomorphisms [π]F. Honda formal groups have distinguished homomorphisms that factor through [π]F. In this article, we prove that for generalized Honda formal groups, the composition of a sequence of distinguished homomorphisms factors through [π]F . As an application of this fact, a number of properties of πn-torsion points of the generalized Honda formal group are proved.

In 2006, Schuster introduced the radial Blaschke-Minkowski homomorphisms. In this article, associating with the star duality of star bodies and dual quermassintegrals, we establish Brunn-Minkowski inequalities and monotonic inequality for the radial Blaschke-Minkowski homomorphisms. In addition, we consider its Shephard-type problems and give a positive form and a negative answer, respectively.

Let $\Sigma$ be a surface with either boundary or marked points, equipped with an arbitrary framing. In this note we determine the action of the associated "framed mapping class group" on the homology of $\Sigma$ relative to its boundary (respectively marked points), describing the image as the kernel of a certain crossed homomorphism related to classical spin structures. Applying recent work of the authors, we use this to describe the monodromy action of the orbifold fundamental group of a stratum of abelian differentials on the relative periods., Comment: 18 pages. Final version, as appeared in B. Lond. Math. Soc

We would like to build Abelian groups (or R-modules) which on the one hand are quite free, say ℵω+1-free, and on the other hand are complicated in a suitable sense. We choose as our test problem one having no nontrivial homomorphism to ℤ (known classically for ℵ1-free, recently for ℵn-free). We succeed to prove the existence of even $${\aleph _{{\omega _1} \cdot n}}$$ -free ones. This requires building n-dimensional black boxes, which are quite free. This combinatorics is of self interest and we believe will be useful also for other purposes. On the other hand, modulo suitable large cardinals, we prove that it is consistent that every $${\aleph _{{\omega _1} \cdot \omega }}$$ -free Abelian group has non-trivial homomorphisms to ℤ.

We explore the extent to which constructing the inductive theory of $\mathfrak{X}$-submaximal subgroups is possible. To this end, we study the behavior of $\pi$-submaximal subgroups under homomorphisms with $\pi$-separable kernels and construct examples where such behavior is irregular.

The aim of this article is to determine entirely the Jordan automorphisms of generalized matrix rings of Morita contexts. Necessary and sufficient conditions are obtained for an $$\mathcal {R}$$ -linear map on a general Morita context to be a Jordan homomorphism. Moreover, some conditions are studied, under which, any Jordan automorphism of a general Morita context is either an automorphism or an anti-automorphism.

By a theorem of Banagl-Chriestenson, intersection spaces of depth one pseudomanifolds exhibit generalized Poincar\'{e} duality of Betti numbers, provided that certain characteristic classes of the link bundles vanish. In this paper, we show that the middle-perversity intersection space of a depth one Witt space can be completed to a rational Poincar\'{e} duality space by means of a single cell attachment, provided that a certain rational Hurewicz homomorphism associated to the link bundles is surjective. Our approach continues previous work of Klimczak covering the case of isolated singularities with simply connected links. For every singular stratum, we show that our condition on the rational Hurewicz homomorphism implies that the Banagl-Chriestenson characteristic classes of the link bundle vanish. Moreover, using Sullivan minimal models, we show that the converse implication holds at least in the case that twice the dimension of the singular stratum is bounded by the dimension of the link. As an application, we compare the signature of our rational Poincar\'{e} duality space to the Goresky-MacPherson intersection homology signature of the given Witt space. We discuss our results for a class of Witt spaces having circles as their singular strata., Comment: 32 pages

Soft set theory was introduced by Molodtsov to deal with uncertainty. In this manuscript, we commence with the notion of soft near-semirings based on soft set theory. Several associated concepts including soft subnear-semirings, idealistic soft near-semirings, soft near-semiring homomorphism and soft near-semiring anti-homomorphism are also introduced. Moreover, numerous related properties are discussed and illustrated by suitable examples. We also present the notion of chain condition along with its applications towards soft near-semirings. We conclude that applying different types of union operations on soft sets without further restrictions are possible as long as chain condition is satisfied. Few related characteristics of soft left (resp., right) near-semirings are also explored by using soft near-semiring homomorphism and soft near-semiring anti-homomorphism. Furthermore, we found that under soft near-semiring anti-homomorphism the image of soft right (left) near-semiring is a soft left (right) near-semiring. This study also bridging the link between classical near-semirings and soft sets theory.