4,502 research outputs found
Monoid automata for displacement context-free languages
In 2007 Kambites presented an algebraic interpretation of
Chomsky-Schutzenberger theorem for context-free languages. We give an
interpretation of the corresponding theorem for the class of displacement
context-free languages which are equivalent to well-nested multiple
context-free languages. We also obtain a characterization of k-displacement
context-free languages in terms of monoid automata and show how such automata
can be simulated on two stacks. We introduce the simultaneous two-stack
automata and compare different variants of its definition. All the definitions
considered are shown to be equivalent basing on the geometric interpretation of
memory operations of these automata.Comment: Revised version for ESSLLI Student Session 2013 selected paper
Evidence for the classical integrability of the complete AdS(4) x CP(3) superstring
We construct a zero-curvature Lax connection in a sub-sector of the
superstring theory on AdS(4) x CP(3) which is not described by the
OSp(6|4)/U(3) x SO(1,3) supercoset sigma-model. In this sub-sector worldsheet
fermions associated to eight broken supersymmetries of the type IIA background
are physical fields. As such, the prescription for the construction of the Lax
connection based on the Z_4-automorphism of the isometry superalgebra OSp(6|4)
does not do the job. So, to construct the Lax connection we have used an
alternative method which nevertheless relies on the isometry of the target
superspace and kappa-symmetry of the Green-Schwarz superstring.Comment: 1+26 pages; v2: minor typos corrected, acknowledgements adde
Resonant spin-dependent electron coupling in a III-V/II-VI heterovalent double quantum well
We report on design, fabrication, and magnetooptical studies of a III-V/II-VI
hybrid structure containing a GaAs/AlGaAs/ZnSe/ZnCdMnSe double quantum well
(QW). The structure design allows one to tune the QW levels into the resonance,
thus facilitating penetration of the electron wave function from the diluted
magnetic semiconductor ZnCdMnSe QW into the nonmagnetic GaAs QW and vice versa.
Magneto-photoluminescence studies demonstrate level anticrossing and strong
intermixing resulting in a drastic renormalization of the electron effective g
factor, in perfect agreement with the energy level calculations.Comment: 4 pages, 5 Postscript figures, uses revtex
Scanning Electron Microscopy Observation of the Interaction Between the Surface Acoustic Waves and Regular Domain Structures in the LiNbO3 Crystals
This paper reports a scanning electron microscope study of the interaction between the surface acoustic waves and regular domain structures in LiNbO3 crystals. The regular domain structures in LiNbO3 crystals were formed by the method of the thermo-electric treatment after growth. We investigated two modes of interaction: the surface-acoustic-waves propagate along and across the regular domain structures. It is shown that the regular domain structures in the first case can be used as an acoustical wave-guide, because the power-flow vector of the surface acoustic waves has the direction along the domain structure. Also we observed that the surface acoustic wave inverts the voltage contrast of the image in the scanning electron microscope by π during the process of the propagation across the domain walls
Finite N Index and Angular Momentum Bound from Gravity
We exactly compute the finite N index and BPS partition functions for N=4 SYM
theory in a newly proposed maximal angular momentum limit. The new limit is not
predicted from the superconformal algebra, but naturally arises from the
supergravity dual. We show that the index does not receive any finite N
corrections while the free BPS partition function does.Comment: 14 pages, v2: minor revisions, published versio
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