We show that, if a building is endowed with its complete system of apartments, and if each panel is contained in at least four chambers, then the intersection of two apartments can be any convex subcomplex contained in an apartment. This combinatorial result is particularly interesting for lower dimensional convex subcomplexes of apartments, where we definitely need the assumption on the four c...

In this paper we discuss symmetrically self-dual spaces, which are simply real vector spaces with a symmetric bilinear form. Certain subsets of the space will be called q-positive, where q is the quadratic form induced by the original bilinear form. The notion of q-positivity generalizes the classical notion of the monotonicity of a subset of a product of a Banach space and its dual. Maximal q-...

Both spaces were introduced and shown to be one-dimensional but totally disconnected by Paul Erdős [9] in 1940. This result together with the obvious fact that E and Ec are homeomorphic to their squares make these spaces important examples in Dimension Theory. Both E and Ec are universal spaces for the class of almost zero-dimensional spaces; see [7, Theorem 4.15]. A subset of a space is called...

In this paper, the concepts of $L$-concave structures, concave $L$-interior operators and concave $L$-neighborhood systems are introduced. It is shown that the category of $L$-concave spaces and the category of concave $L$-interior spaces are isomorphic, and they are both isomorphic to the category of concave $L$-neighborhood systems whenever $L$ is a completely distributive lattice. Also, it i...

A Polish group G is called a group of quasi-invariance or a QI-group, if there exist a locally compact group X and a probability measure μ on X such that 1) there exists a continuous monomorphism of G to X, and 2) for each g ∈ X either g ∈ G and the shift μg is equivalent to μ or g 6∈ G and μg is orthogonal to μ. It is proved that G is a σ-compact subset of X. We show that there exists a quotie...

We prove that any standard parabolic subgroup of any Artin group is convex with respect to the standard generating set.

In the frame of fractional calculus, term convexity is primarily utilized to address several challenges in both pure and applied research. The main focus objective this review paper present Hermite–Hadamard (H-H)-type inequalities involving a variety classes convexities pertaining integral operators. Included various are classical convex functions, m-convex r-convex (α,m)-convex (α,m)-geometric...

‎For a homogeneous spaces ‎$‎G/H‎$‎, we show that the convolution on $L^1(G/H)$ is the same as convolution on $L^1(K)$, where $G$ is semidirect product of a closed subgroup $H$ and a normal subgroup $K $ of ‎$‎G‎$‎. ‎Also we prove that there exists a one to one correspondence between nondegenerat $ast$-representations of $L^1(G/H)$ and representations of ...

A Kleinian group Γ is a discrete subgroup of PSL2(C). When non-elementary, such a group possesses a unique non-empty minimal closed invariant subset ΛΓ of the Riemann sphere, called the limit set. A Kleinian group acts properly discontinuously on the complement ∆Γ of ΛΓ and so this set is called the domain of discontinuity. Such a group is said to be convex co-compact if it acts co-compactly on...

A Kleinian group Γ is a discrete subgroup of PSL2(C). When non-elementary, such a group possesses a unique non-empty minimal closed invariant subset ΛΓ of the Riemann sphere, called the limit set. A Kleinian group acts properly discontinuously on the complement ∆Γ of ΛΓ and so this set is called the domain of discontinuity. Such a group is said to be convex co-compact if it acts co-compactly on...