Let X be a compact connected Riemann surface and EP a holomorphic principal P–bundle over X , where P is a parabolic subgroup of a complex reductive affine algebraic group G. If the Levi bundle associated to EP admits a holomorphic connection, and the reduction EP ⊂ EP × P G is rigid, we prove that EP admits a holomorphic connection. As an immediate consequence, we obtain a sufficient condition...

We study locally homogeneous rigid geometric structures on surfaces. We show that a locally homogeneous projective connection on a compact surface is flat. We also show that a locally homogeneous unimodular affine connection ∇ on a two dimensional torus is complete and, up to a finite cover, homogeneous. Let ∇ be a unimodular real analytic affine connection on a real analytic compact connected ...

We present a method for encoding first order proofs in SMT. Our implementation, called ChewTPTP-SMT, transforms a set of first order clauses into a propositional encoding (modulo theories) of the existence of a rigid first order connection tableau and the satisfiability of unification constraints, which is then fed to Yices. For the unification constraints, terms are represented as recursive da...

This paper gives a method to construct rigid spaces, which is similar to the method used to construct toric schemes.

Tensegrity frameworks are defined on a set of points in Rd and consist of bars, cables, and struts, which provide upper and/or lower bounds for the distance between their endpoints. The graph of the framework, in which edges are labeled as bars, cables, and struts, is called a tensegrity graph. It is said to be strongly rigid in Rd if every generic realization in Rd as a tensegrity framework is...

A direction-length framework is a pair (G, p), where G = (V ;D,L) is a ‘mixed’ graph whose edges are labeled as ‘direction’ or ‘length’ edges, and p is a map from V to R for some d. The label of an edge uv represents a direction or length constraint between p(u) and p(v). Let G be obtained from G by adding, for each length edge e of G, a direction edge with the same end vertices as e. We show t...

The topic of connections is often given only limited attention in structural analysis and design of buildings, despite the fact that they can play a critical role in the structure. It is customary practice in the U.S. for the structural engineer to design the structural members, but leave the connection details to the steel fabricator. While this practice is more efficient and pragmatic in some...

Beam column joint failure has been linked to the partial or whole collapse of reinforced structures, according information gathered during seismic reconnaissance. Under stress, a single beam only limited impact, but beam-column junction might lead structure. The resulting economic damage and human casualties are substantial. Hence, keeping from coming apart is crucial. Recent earthquakes have c...

An ideal I on a cardinal κ is called rigid if all automorphisms of P (κ)/I are trivial. An ideal is called μ-minimal if whenever G ⊆ P (κ)/I is generic and X ∈ P (μ)V [G] \ V , it follows that V [X] = V [G]. We prove that the existence of a rigid saturated μ-minimal ideal on μ+, where μ is a regular cardinal, is consistent relative to the existence of large cardinals. The existence of such an i...