We present predictions for differential cross sections for the reaction γ p → Φ p and give an outlook to which extent our calculations may be generalized to the photoproduction of J/Ψ mesons. Our results are obtained within perturbative QCD treating the proton as a quark-diquark system.

In the framework of ordered G-metric spaces, fixed points of maps that satisfy the generalized (ψ, φ)-Chatterjea type contractive conditions are obtained. The results presented in the paper generalize and extend several well known comparable results in the literature.

In a recent article, Douven and Williamson offer both (i) a rebuttal of various recent suggested sufficient conditions for rational acceptability and (ii) an alleged ‘generalization’ of this rebuttal, which, they claim, tells against a much broader class of potential suggestions. However, not only is the result mentioned in (ii) not a generalization of the findings referred to in (i), but in co...

A formula ψ(Y ) is a selector for a formula φ(Y ) in a structure M if there exists a unique Y that satisfies ψ in M and this Y also satisfies φ. A formula ψ(X,Y ) uniformizes a formula φ(X, Y ) in a structure M if for every X there exists a unique Y such that ψ(X,Y ) holds in M and for this Y , φ(X,Y ) also holds in M. In this paper we survey some fundamental algorithmic questions and recent re...

The classical interpolation theorem of Craig (cf. e.g. [ChK73]) states that if φ ⇒ ψ is a valid first order predicate logic formula, then there exists a first order formula θ built using only nonlogical symbols occurring in both φ and ψ and, possibly, equality, such that the formulas φ ⇒ θ and θ ⇒ ψ are valid too. A formula θ with this property is called an interpolant between φ and ψ. Similar ...

Let φ(x1, . . . , xh, y) = u1x1 + · · · + uhxh + vy be a linear form with nonzero integer coefficients u1, . . . , uh, v. Let A = (A1, . . . , Ah) be an h-tuple of finite sets of integers and let B be an infinite set of integers. Define the representation function associated to the form φ and the sets A and B as follows: R (φ) A,B (n) = card ({(a1, . . . , ah, b) ∈ A1 × · · · × Ah × B : φ(a1, ....

Sufficient conditions for a Lorentzian generalized quasi-Einstein manifold M,g,f,μ to be Robertson–Walker spacetime with Einstein fibers are derived. The Ricci tensor in this case gains the perfect fluid form. Likewise, it is proven that λ,n+m-Einstein M,g,w having harmonic Weyl tensor, ∇jw∇mwCjklm=0 and ∇lw∇lw<0 reduces fibers. Finally, if φ=−m∇lnw φRic-vector field on M an ψ=∇w ψRic-vector...

We have left out negation. We regard ¬φ as a shorthand for φ→ ⊥. A sequent is a pair that packages together some assumptions and a conclusion. We write Γ ` φ for the sequent whose assumptions are the finite set of formulas Γ and whose conclusion is the formula φ. We call Γ the antecedent and φ the consequent of the sequent Γ ` φ. A sequent is satisfied in a model M iff either M |= φ or for some...

A monadic formula ψ(Y) is a selector for a monadic formula φ(Y) in a structure M if ψ defines in M a unique subset P of the domain and this P also satisfies φ in M. If C is a class of structures and φ is a selector for ψ in every M ∈ C, we say φ is a selector for φ over C. For a monadic formula φ(X,Y) and ordinals α ≤ ω1 and δ < ω, we decide whether there exists a monadic formula ψ(X,Y) such th...