A construction of one-dimensional affine flag-transitive linear spaces

AbstractThe finite flag-transitive linear spaces which have an insoluble automorphism group were given a precise description in [Francis Buekenhout, Anne Delandtsheer, Jean Doyen, Peter B. Kleidman, Martin W. Liebeck, Jan Saxl, Linear spaces with flag-transitive automorphism groups, Geom. Dedicata 36 (1) (1990) 89–94], and their classification has recently been completed (see [Martin W. Liebeck, The classification of finite linear spaces with flag-transitive automorphism groups of affine type, J. Combin. Theory Ser. A 84 (2) (1998) 196–235] and [Jan Saxl, On finite linear spaces with almost simple flag-transitive automorphism groups, J. Combin. Theory Ser. A 100 (2) (2002) 322–348]). However, the remaining case where the automorphism group is a subgroup of one-dimensional affine transformations has not been classified and bears a variety of known examples. Here we give a construction of new one-dimensional affine flag-transitive linear spaces via the André/Bruck–Bose construction applied to transitive line-spreads of projective space

Identität in Erzählung und im Erzählen: Versuch einer Bestimmung der Besonderheit des narrativen Diskurses für die sprachliche Verfassung von ldentität

Die Bedeutung des narrativen Diskurses für die sprachliche Verfassung von Identität wird erörtert. Dabei werden zwei Argumentationsstränge entfaltet. Zum einen wird dem Erzählen im Unterschied zu anderen Diskurstätigkeiten des alltäglichen Sprechens eine privilegierte Rolle der Ordnungsstiftung zugeschrieben. Diese gesonderte Stellung wird damit begründet, dass im Erzählen Relationen zwischen einer temporalen, einer räumlichen und einer personalen Ordnung hergestellt werden, die in anderen Diskurstätigkeiten nicht vorhanden sind. In einer Art Gegenzug wird dann jedoch diese Sonderstellung des Erzählens weitgehend relativiert und zurückgenommen, und zwar insofern, als den kontextuellen Bedingungen, unter denen erzählt wird, eine weit wesentlichere Rolle in der Sinnstiftung zukommt. Abschließend wird versucht, aus dem Verhältnis der beiden Argumentationsstränge den Begriff der Identität erzähl- und diskurstheoretisch neu zu verorten

Spreading primitive groups of diagonal type do not exist

The synchronisation hierarchy of finite permutation groups consists of classes of groups lying between 2-transitive groups and primitive groups. This includes the class of spreading groups, which are defined in terms of sets and multisets of permuted points, and which are known to be primitive of almost simple, affine or diagonal type. In this paper, we prove that in fact no spreading group of diagonal type exists. As part of our proof, we show that all non-abelian finite simple groups, other than six sporadic groups, have a transitive action in which a proper normal subgroup of a point stabiliser is supplemented by all corresponding two-point stabilisers.Comment: 10 pages. Version 2 resolves the Monster group case of Theorem 1.3, with the aid of a result drawn to our attention by Prof. Tim Burnes

Separating rank 3 graphs

We classify, up to some notoriously hard cases, the rank 3 graphs which fail to meet either the Delsarte or the Hoffman bound. As a consequence, we resolve the question of separation for the corresponding rank 3 primitive groups and give new examples of synchronising, but not $\mathbb{Q}\mathrm{I}$, groups of affine type

Enabling RTK Positioning Under Jamming: Mitigation of Carrier-Phase Distortions Induced by Blind Spatial Filtering

ew GNSS applications demand resilience against radio interference and high position accuracy. Separately, these demands can be fulfilled by multi-antenna systems using spatial filtering and carrier-phase positioning algorithms like real-time kinematic (RTK), respectively. However, combining these approaches encounters a severe issue: The spatial filtering induces a phase offset into the measured carrier phase leading to a loss of position accuracy. This paper presents a new approach to compensate for the phase offset in a blind manner, (i.e., without knowing the antenna array radiation pattern or the direction of arrival of the signals). The proposed approach is experimentally validated in two jamming scenarios. One includes a jammer with increasing power and the other includes a moving jammer. The results demonstrate that the approach successfully compensates for the phase offset and, hence, allows for the combined use of RTK positioning and spatial filtering even under jamming

Langfrist-Prognose von Performance-Indizes: Vergleich einiger Verfahren

Langfrist-Prognosen sind typischerweise problematischer als Kurzfrist-Prognosen. Im Kapitalmarktkontext ist die Sachlage jedoch umgekehrt, da verlässliche Kurzfrist-Prognosen durch Arbitrageure sofort zunichte gemacht würden. Ex ante ist der Performance-Index am Prognosehorizont eine extrem rechtsschief verteilte Zufallsvariable. Prognosen, die auf dessen Modalwert abzielen, sind daher viel zu pessimistisch. Prognosen, die auf den Erwartungswert abzielen, sind dagegen zu optimistisch. Von den drei prominenten Lagemaßen ist nur der Median in der Lage, als Basis für eine verlässliche Prognose zu dienen. Es werden einige Praktiker-Verfahren untereinander und mit einem neuen Prognoseverfahren verglichen, welches auf der erwartungstreuen Schätzung des Medians beruht. Zur Illustration der Verfahren und der resultierenden Prognosen werden Daten des DAX bis 2022 verwendet. Es zeigt sich unter anderem, dass der erwartungstreue Median-Schätzer bessere Prognosen als das beste ‚Praktiker-Verfahren‘ liefert

Developing a Spoofer Error Envelope for Tracking GNSS Signals

Global navigation satellite systems (GNSSs) are the most significant service for global positioning and timing. The high relevance and wide spread of these systems contrast with the risk for interference or even manipulations of GNSS signals. One specific threat is GNSS spoofing. A spoofer counterfeits satellite signals to mislead the receiver to an erring position/time estimation. The technological progress enabling affordable and easy-to-use spoofer hardware further increases the relevance of this threat. To maintain the integrity of the position/time information, it is mandatory to be able to assess the errors induced by spoofing. The paper at hand derives a bound of the code tracking bias in relevant spoofing scenarios extending the well-known Multipath Error Envelope. These new bounds can be used as a tool to estimate the position/time error, especially but not exclusively for receivers that are collateral damage of a spoofing attack

Point regular groups of automorphisms of generalised quadrangles

We study the point regular groups of automorphisms of some of the known generalised quadrangles. In particular we determine all point regular groups of automorphisms of the thick classical generalised quadrangles. We also construct point regular groups of automorphisms of the generalised quadrangle of order $(q-1,q+1)$ obtained by Payne derivation from the classical symplectic quadrangle $\mathsf{W}(3,q)$. For $q=p^f$ with $f\geq 2$ we obtain at least two nonisomorphic groups when $p\geq 5$ and at least three nonisomorphic groups when $p=2$ or $3$. Our groups include nonabelian 2-groups, groups of exponent 9 and nonspecial $p$-groups. We also enumerate all point regular groups of automorphisms of some small generalised quadrangles.Comment: some minor changes (including to title) after referee's comment