arXiv subjects

Andreas Klein

Publications and source records attributed to Andreas Klein.

23 records · Page 2Linked to original sources

arXiv2012

Measurement of the generalized form factors near threshold via $γ^* p \to nπ^+$ at high $Q^2$

We report the first extraction of the pion-nucleon multipoles near the production threshold for the $nπ^+$ channel at relatively high momentum transfer ($Q^2$ up to 4.2 $\rm{GeV^2}$). The dominance of the s-wave transverse multipole ($E_{0+}$), expected in this region, allowed us to access the generalized form factor $G_1$ within the light-cone sum rule (LCSR) framework as well as the axial form factor $G_A$. The data analyzed in this work were collected by the nearly $4π$ CEBAF Large Acceptance Spectrometer (CLAS) using a 5.754 $\rm{GeV}$ electron beam on a proton target. The differential cross section and the $π-N$-multipole $E_{0+}/G_D$ were measured using two different methods, the LCSR and a direct multipole fit. The results from the two methods are found to be consistent and almost $Q^2$ independent.

nucl-ex↗

arXiv2011

Symplectic Spinors, Holonomy and Maslov Index

In this note it is shown that the Maslov Index for pairs of Lagrangian Paths as introduced by Cappell, Lee and Miller appears by parallel transporting elements of (a certain complex line-subbundle of) the symplectic spinorbundle over Euclidean space, when pulled back to an (embedded) Lagrangian submanifold $L$, along closed or non-closed paths therein. In especially, the CLM-Index mod 4 determines the holonomy group of this line bundle w.r.t. the Levi-Civita-connection on $L$, hence its vanishing mod 4 is equivalent to the existence of a trivializing parallel section. Moreover, it is shown that the CLM-Index determines parallel transport in that line-bundle along arbitrary paths when compared to the parallel transport w.r.t. to the canonical flat connection of Euclidean space, if the Lagrangian tangent planes at the endpoints either coincide or are orthogonal. This is derived from a result on parallel transport of certain elements of the dual spinorbundle along closed or endpoint-transversal paths.

math.DG↗

arXiv2009

On the Number of Membranes in Unary P Systems

We consider P systems with a linear membrane structure working on objects over a unary alphabet using sets of rules resembling homomorphisms. Such a restricted variant of P systems allows for a unique minimal representation of the generated unary language and in that way for an effective solution of the equivalence problem. Moreover, we examine the descriptional complexity of unary P systems with respect to the number of membranes.

cs.FL↗

arXiv2003

Extended visual cryptography systems

Visual cryptography schemes have been introduced in 1994 by Naor and Shamir. Their idea was to encode a secret image into $n$ shadow images and to give exactly one such shadow image to each member of a group $P$ of $n$ persons. Whereas most work in recent years has been done concerning the problem of qualified and forbidden subsets of $P$ or the question of contrast optimizing, in this paper we study extended visual cryptography schemes, i.e. shared secret systems where any subset of $P$ shares its own secret.

math.CO↗

arXiv2002

The largest small polytopes

The aim of this paper is the determination of the largest $n$-dimensional polytope with $n+3$ vertices of unit diameter. This is a special case of a more general problem proposed by Graham.

math.CO↗