We study a class of torsion-free sheaves on complex projective spaces which generalize the much studied mathematical instanton bundles. Instanton sheaves can be obtained as cohomologies of linear monads and are shown to be semistable if its rank is not too large, while semistable torsion-free sheaves satisfying certain cohomological conditions are instanton. We also study a few examples of modu...

We study the residual properties of geometric 3–manifold groups. In particular, we study conditions under which geometric 3–manifold groups are virtually residually p for a prime p, and conditions under which they are residually torsion–free nilpotent. We show that for every prime p, every geometric 3–manifold group is virtually residually p. We show that geometric 3– manifold groups are virtua...

We provide an upper bound on the `2–torsion of a free-bycyclic group, −ρ(2)(F oΦ Z), in terms of a relative train-track representative for Φ ∈ Aut(F). Our result shares features with a theorem of Lück–Schick computing the `2–torsion of the fundamental group of a 3–manifold that bers over the circle in that it shows that the `2–torsion is determined by the exponential dynamics of the monodromy. ...

between any two coordinates ( i) and ( i). Hence any choice of Γ k ij in one coordinate chart suffices to define the connection in another. Let T k ij := Γkij − Γkji be the torsion tensor of the connection. The case when torsion is zero (torsion-free) is of particular interest in geometry. In Hermann Weyl’s terms [11], the very existence of inertia systems in the Universe warrants that its line...

We will answer a question raised by Emmanuel Dror Farjoun concerning the existence of torsion-free abelian groups G such that for any ordered pair of pure elements there is a unique automorphism mapping the first element onto the second one. We will show the existence of such a group of cardinality λ for any successor cardinal λ = μ+ with μ = μ0.

A classical theorem of Fritz John allows one to describe a convex body, up to constants, as an ellipsoid. In this article we establish similar descriptions for generalized (i.e. multidimensional) arithmetic progressions in terms of proper (i.e. collision-free) generalized arithmetic progressions, in both torsion-free and torsion settings. We also obtain a similar characterization of iterated su...

We study conjugacy classes of solutions to systems of equations and inequations over torsion-free hyperbolic groups, and describe an algorithm to recognize whether or not there are finitely many conjugacy classes of solutions to such a system. The class of immutable subgroups of hyperbolic groups is introduced, which is fundamental to the study of equations in this context. We apply our results...

The residual torsion-free nilpotence of the commutator subgroup a knot group has played key role in studying bi-orderability groups. A technique developed by Mayland provides sufficient condition for to be residually-torsion-free nilpotent using work Baumslag. In this paper, we apply Mayland's several genus one pretzel knots and family with arbitrarily high genus. As result, obtain large number...

We study algebraic properties of categories of Merotopic, Nearness, and Filter Algebras. We show that the category of filter torsion free abelian groups is an epireflective subcategory of the category of filter abelian groups. The forgetful functor from the category of filter rings to filter monoids is essentially algebraic and the forgetful functor from the category of filter groups to the cat...

The author is reporting a case of torsion of gallbladder. The patient used to have episodes of intermittent torsion and there was no acute presentation. Patient was presented with abdominal swelling which was misdiagnosed as a mesenteric cyst. Distended gallbladder, free floating type, tortuous cystic artery with the mesentry were factors responsible for torsion. Gallbladder exhibited 180 degre...