Matroids over a ring

We introduce the notion of a matroid M over a commutative ring R, assigning to every subset of the ground set an R-module according to some axioms. When R is a field, we recover matroids. When R D Z, and when R is a DVR, we get (structures which contain all the data of) quasi-arithmetic matroids, and valuated matroids, i.e. tropical linear spaces, respectively. More generally, whenever R is a Dedekind domain, we extend all the usual properties and operations holding for matroids (e.g., duality), and we explicitly describe the structure of the matroids over R. Furthermore, we compute the Tutte-Grothendieck ring of matroids over R. We also show that the Tutte quasi-polynomial of a matroid over Z can be obtained as an evaluation of the class of the matroid in the Tutte-Grothendieck ring

Routine dynamics in action: replication and transformation

Contains an Open Access chapter.This book explores central themes in the enactment and coordination of organizational routines, including replication and transfer, ecologies and interdependence, action and the generation of novelty and technology and sociomateriality.

GPM-DPR Observations on TGFs Producing Storms

Unique spaceborne measurements of the three-dimensional structure of convective clouds producing terrestrial gamma ray flashes (TGFs) were performed using both active and passive microwave sensors on board the Global Precipitation Measurement (GPM)-Core Observatory satellite, finding coherent features for nine TGF-producing storms. The delineation of cloud structure using the radar reflectivity factor shows convective cells with significant vertical development and thick layers with high ice content. Compared to other cumulonimbus clouds in the tropics, the TGFs counterparts have higher reflectivity values above 3 and 8 km altitude showing in all cases a cumulonimbus tower and the TGFs locations are very close, or coincident, to these high Z columns, where reflectivity exceeds 50dBz. Using the GPM Microwave Imager radiometer, most thunderstorms show a very strong depression of polarization corrected temperature (PCT) at channel 89GHz, indicating a strong scattering signal by ice in the upper cloud layers. At channel 166GHZ, the difference between vertical and horizontal brightness temperature signal always returns positive values, from 0.2 up to 13.7K indicating a complex structure with randomly/vertically oriented ice particles. The PCT was used to characterize the analyzed storms in terms of hydrometeor types, confirming in 7/9 cases a high likelihood of hail/graupel presence. To perform analysis on the TGFs parent flashes, radio atmospherics data from the Earth Networks Total Lightning Network lightning network were used. Waveform data indicate that all cases are intra-cloud events and TGFs typically take place during the peak of flash rate production. Finally, the analysis of the most intense event is shown

Cuts and flows of cell complexes

We study the vector spaces and integer lattices of cuts and flows associated with an arbitrary finite CW complex, and their relationships to group invariants including the critical group of a complex. Our results extend to higher dimension the theory of cuts and flows in graphs, most notably the work of Bacher, de la Harpe and Nagnibeda. We construct explicit bases for the cut and flow spaces, interpret their coefficients topologically, and give sufficient conditions for them to be integral bases of the cut and flow lattices. Second, we determine the precise relationships between the discriminant groups of the cut and flow lattices and the higher critical and cocritical groups with error terms corresponding to torsion (co)homology. As an application, we generalize a result of Kotani and Sunada to give bounds for the complexity, girth, and connectivity of a complex in terms of Hermite's constant.Comment: 30 pages. Final version, to appear in Journal of Algebraic Combinatoric

How do theories become self-fulfilling? Clarifying the process of Barnesian performativity

To explore when theories become self-fulfilling in our original paper (Marti & Gond, 2018), we first had to develop a process model of how theories become self-fulfilling. We argued that this process involves three steps: (1) new theories lead to experimentation, (2) experimentation produces anomalies, and (3) anomalies convince initially unconvinced actors to shift their practices. Our critics (i.e., D’Adderio, Glaser, & Pollock, 2019; Garud & Gehman, 2019; Shadnam, 2019) raise important issues about our process model, which is why we use this response to clarify our argument about the process of Barnesian performativity. In Section 1, we lay the groundwork for our response by explaining why Barnesian performativity is relevant to organization and management theory. In Section 2, we show that our model is in line with important insights from our critics: we show why self-fulfilling theories can be part of an “ongoing journey” (Garud & Gehman, 2019: 1), how anomalies can lead to new theories (D’Adderio et al., 2019), and why our model matters for folk theories (D’Adderio et al., 2019). In Section 3, we reflect on our process model from a philosophy of science perspective by discussing the role that “reality” plays in each step of our process model. We thereby address concerns that our process model is “positivist” (Shadnam, 2019: 1), “representational” (Garud & Gehman, 2019: 3), and “essentialist” (D’Adderio et al., 2019: 3)

We All Know How, Don’t We? On the Role of Scrum in IT-Offshoring

Part 2: Creating Value through Software DevelopmentInternational audienceOffshoring in the IT-industry involves dual interactions between a mother company and an external supplier, often viewed with an implicit perspective from the mother company. This article review general off shoring and IT offshoring literature, focusing on the proliferation of a globally available set of routines; Scrum and Agile. Two cases are studied; a small company and short process and a large mother company with a long process. The interactions of the set ups shows that global concepts like Scrum and Agile are far from a common platform. The “well known” concepts are locally shaped and the enterprises have mixed experiences

Technology and Sociomaterial Performation

Part 1: IS/IT Implementation and AppropriationInternational audienceOrganizational researchers have acknowledged that understanding the relationship between technology and organization is crucial to understanding modern organizing and organizational change [1]. There has been a significant amount of debate concerning the theoretical foundation of this relationship. Our research draws and extends Deleuze and DeLanda’s work on assemblages and Callon’s concept of performation to investigate how different sociomaterial practices are changed and stabilized after the implementation of new technology. Our findings from an in-depth study of two ambulatory clinics within a hospital system indicate that “perform-ing” of constituting, counter-performing, calibrating, and stratifying explained the process of sociomaterial change and that this process is governed by an overarching principle of “performative exigency”. Future studies on sociomateriality and change may benefit from a deeper understanding of how sociomaterial assemblages are rendered performative

Accommodating practices during episodes of disillusionment with mobile IT

This study investigates how tablet users react when technology falls short of their expectations. We deploy a data/frame model to study this process and investigate resistance-related reactions and the deployment of accommodating practices at the individual level. Analyzing user blogs that provide narratives on user interaction with tablets, we identify triggers of episodes of disillusionment and illustrate five sensemaking paths that users follow, eventually leading to one of three practices: 1) users choose to defer tasks until the situation changes, or they abandon the platform altogether; 2) they develop workarounds at different levels of proficiency; or 3) they proceed by reframing their expectations of the platform. By revealing user decision-making process during episodes of disillusionment, the findings contribute to information systems post-adoption research. At a practical level, the findings inform IT artifact and application design by offering insights on how users process discrepancies between their expectations and actual use experience