Pumping lemma and Ogden lemma for displacement context-free grammars

The pumping lemma and Ogden lemma offer a powerful method to prove that a particular language is not context-free. In 2008 Kanazawa proved an analogue of pumping lemma for well-nested multiple-context free languages. However, the statement of lemma is too weak for practical usage. We prove a stronger variant of pumping lemma and an analogue of Ogden lemma for this language family. We also use these statements to prove that some natural context-sensitive languages cannot be generated by tree-adjoining grammars.Comment: Shortened version accepted to DLT 2014 conferenc

On the BRST Quantization of the Massless Bosonic Particle in Twistor-Like Formulation

We study some features of bosonic particle path-integral quantization in a twistor-like approach by use of the BRST-BFV quantization prescription. In the course of the Hamiltonian analysis we observe links between various formulations of the twistor-like particle by performing a conversion of the Hamiltonian constraints of one formulation to another. A particular feature of the conversion procedure applied to turn the second-class constraints into the first-class constraints is that the simplest Lorentz-covariant way to do this is to convert a full mixed set of the initial first- and second-class constraints rather than explicitly extracting and converting only the second-class constraints. Another novel feature of the conversion procedure applied below is that in the case of the D=4 and D=6 twistor-like particle the number of new auxiliary Lorentz-covariant coordinates, which one introduces to get a system of first-class constraints in an extended phase space, exceeds the number of independent second-class constraints of the original dynamical system. We calculate the twistor-like particle propagator in D=3, 4 and 6 space-time dimensions and show, that it coincides with that of a conventional massless bosonic particle.Comment: LaTeX file, 17 page

Австрийский нейтралитет 1955 г.: МОдель для Германии или феномен холодной войны?

Introduction. The article considers the problem of solving the Austrian issue by consolidating the country’s neutrality in 1955 in the context of a possible modeling of the situation on the German issue. The consolidation of a neutral non-aligned status with Austria was the result of a broad domestic and foreign policy compromise. At the same time, the main features of the Austrian path to the neutrality of 1945–1955 are highlighted, making this one of the most well-known compromise precedents of the Cold War possible. Methods and materials. The research of the model character of the “Austrian solution” of 1955 is possible only with regard to the intertwining historical contexts in which the development of the German and Austrian issues took place from 1945 to 1949. The author uses the comparative historical method in the article while comparing historical features of the development of the German and Austrian issues between 1945 and 1955 and comparing different views and concepts of historians. The information base of the article consists of narrative and documentary sources, as well as a wide range of scientific research works of Austrian, German and Russian researchers. Analysis. The main internal reasons for the successful resolution of the Austrian issue are the existence of the pro-Western government elected in 1945, the unity of the main political forces of Austria in the matter of restoring sovereignty, and the personal role of Chancellor Julius Raab. The main international reasons are the change in the course of the USSR within the framework of the peaceful coexistence policy, as well as the reciprocal cooperation policy of the Western Allies. The author considers the problem both in historical and in historiographical perspectives. Results. The possibility of applying the “Austrian solution” to the situation with the divided Germany became the subject of a sharp historiographical dispute, which was called “Model Debate” in Austria. Two famous historians, Rolf Steininger and Michael Gehler, developed a concept confirming the model character of the Austrian solution to the situation with Germany. Most of Austrian historians tend to view the successful resolution of the Austrian issue as a single precedent, or phenomenon, of the Cold War. When comparing the situation with Germany and the attempts to model the Austrian version of it, they point to the different potential and significance of the countries for the Western Allies and the USSR, different goals of foreign policy of victorious powers in the German and Austrian issues

Worldline Superfield Actions for N=2 Superparticles

We propose doubly supersymmetric actions in terms of n=2(D-2) worldline superfields for N=2 superparticles in D=3,4 and Type IIA D=6 superspaces. These actions are obtained by dimensional reduction of superfield actions for N=1 superparticles in D=4,6 and 10, respectively. We show that in all these models geometrodynamical constraints on target superspace coordinates do not put the theory on the mass shell, so the actions constructed consistently describe the dynamics of the corresponding N=2 superparticles. We also find that in contrast to the IIA D=6 superparticle a chiral IIB D=6 superparticle, which is not obtainable by dimensional reduction from N=1, D=10, is described by superfield constraints which produce dynamical equations. This implies that for the IIB D=6 superparticle the doubly supersymmetric action does not exist in the conventional form.Comment: Latex, 20 pp. Minor corrections, acknowledgements adde