Regular expressions with back referencing have been used in a variety of software products in common use, such as Emacs and Perl, for many years. In these products, regular expressions have been extended with a naming construct. If a subexpression is named by some variable, whenever this subexpression matches some string, that string is assigned to the variable. Later occurrences of the same va...

Spin glasses is a fascinating field, from which a variety of theoretical models and concepts were invented. As an emergent state from the random magnetic system, it defers from other statistical systems in several ways. In particular, the quenched variables prevent the system to be ergodic, and the competitive interactions gives rise to non-trivial degeneracies of the ground states as well as t...

We describe an O(n) time algorithm for computing the exact probability that two d-dimensional probabilistic point sets are linearly separable, for any fixed d ≥ 2. A probabilistic point in d-space is the usual point, but with an associated (independent) probability of existence. We also show that the d-dimensional separability problem is equivalent to a (d + 1)-dimensional convex hull membershi...

The effect of setting all T=0 two body interaction matrix elements equal to a constant (or zero) in shell model calculations (designated as < T = 0 >= 0) are investigated. Despite the apparent severity of such a procedure, one gets fairly reasonable spectra. We find that using < T = 0 >= 0 in single j shell calculations degeneracies appear e.g. the I =

We propose a new approach to calculate perturbatively the effects of a particular deformed Heisenberg algebra on an energy spectrum. We use this method to calculate the harmonic oscillator spectrum and find that the corrections are in agreement with a previous calculation. Then, we apply this approach to obtain the hydrogen atom spectrum and we find that splittings of degenerate energy levels a...

We show that triangulating a set of points with elevations such that the number of local minima of the resulting terrain is minimized is NP-hard for degenerate point sets. The same result applies when there are no degeneracies for higher-order Delaunay triangulations. Two heuristics are presented to minimize the number of local minima for higher-order Delaunay triangulations, and they are compa...