Explanipedia

Universality of Barwick’s Unfurling Construction Open

Bastiaan Cnossen, Tobias Lenz, Maxime Ramzi · 2025

Given an $\infty $-category $\mathcal{C}$ with pullbacks, its $(\infty ,2)$-category $\textbf{Span}(\mathcal{C})$ of spans has the universal property of freely adding right adjoints to morphisms in $\mathcal{C}$ satisfying a Beck–Chevalley…

Universality of span 2-categories and the construction of 6-functor formalisms Open

Bastiaan Cnossen, Tobias Lenz, Sil Linskens · 2025

Given an $\infty$-category $C$ equipped with suitable wide subcategories $I, P \subset E\subset C$, we show that the $(\infty,2)$-category $\text{S}{\scriptstyle\text{PAN}}_2(C,E)_{P,I}$ of higher (or iterated) spans defined by Haugseng ha…

Comparative Regionalism beyond Europe versus the rest Open

Tobias Lenz, Fredrik Söderbaum · 2025

What is the current state of Comparative Regionalism (CR) as a field of research? Since its inception, CR has suffered from a chasm between those who take European integration as the model for conceptualising, theorising, comparing, and de…

The Adams isomorphism revisited Open

Bastiaan Cnossen, Tobias Lenz, Sil Linskens · 2024

We establish abstract Adams isomorphisms in an arbitrary equivariantly presentable equivariantly semiadditive global category. This encompasses the well-known Adams isomorphism in equivariant stable homotopy theory, and applies more genera…

Normed equivariant ring spectra and higher Tambara functors Open

Bastiaan Cnossen, Rune Haugseng, Tobias Lenz, Sil Linskens · 2024

In this paper we extend equivariant infinite loop space theory to take into account multiplicative norms: For every finite group $G$, we construct a multiplicative refinement of the comparison between the $\infty$-categories of connective …

Parametrized (higher) semiadditivity and the universality of spans Open

Bastiaan Cnossen, Tobias Lenz, Sil Linskens · 2024

Semiadditivity of an $\infty$-category, i.e. the existence of biproducts, provides it with useful algebraic structure in the form of a canonical enrichment in commutative monoids. This ultimately comes from the fact that the $\infty$-categ…

Homotopical commutative rings and bispans Open

Bastiaan Cnossen, Rune Haugseng, Tobias Lenz, Sil Linskens · 2024

We prove that commutative semirings in a cartesian closed presentable $\infty$-category, as defined by Groth, Gepner, and Nikolaus, are equivalent to product-preserving functors from the $(2,1)$-category of bispans of finite sets. In other…

Genuine versus naïve symmetric monoidal $G$-categories Open

Tobias Lenz · 2023

We prove that through the eyes of equivariant weak equivalences the genuine symmetric monoidal G -categories of Guillou and May [Algebr. Geom. Topol. 17 (2017), no. 6, 3259–3339] are equivalent to just ordinary symmetric monoidal categorie…

The Adams isomorphism revisited Open

Bastiaan Cnossen, Tobias Lenz, Sil Linskens · 2023

We establish abstract Adams isomorphisms in an arbitrary equivariantly presentable equivariantly semiadditive global category. This encompasses the well-known Adams isomorphism in equivariant stable homotopy theory, and applies more genera…

Globalising the study of diffusion: multiple sources and the East African Community Open

Tobias Lenz, Mariel Reiss · 2023

A growing literature on diffusion shows that ideas, policies and institutions originating in the European Union shape decision-making in other regional organisations (ROs). However, a research programme which claims to examine processes of…

Expanding or defending legitimacy? Why international organizations intensify self-legitimation Open

Henning Schmidtke, Tobias Lenz · 2023

Recent decades have seen an intensification of international organizations’ (IOs) attempts to justify their authority. The existing research suggests that IO representatives have scaled up self-legitimation to defend their organizations’ l…

Simplicial $*$-modules and mild actions Open

Tobias Lenz, Anna Schröter · 2023

We develop an analogue of the theory of $*$-modules in the world of simplicial sets, based on actions of a certain simplicial monoid $E\mathcal M$ originally appearing in the construction of global algebraic $K$-theory. As our main results…

Partial parametrized presentability and the universal property of equivariant spectra Open

Bastiaan Cnossen, Tobias Lenz, Sil Linskens · 2023

We introduce a notion of partial presentability in parametrized higher category theory and investigate its interaction with the concepts of parametrized semiadditivity and stability from arXiv:2301.08240. In particular, we construct the fr…

The Legitimation of International Organizations: Introducing a New Dataset Open

Henning Schmidtke, Swantje Schirmer, Niklas Krösche, Tobias Lenz · 2023

This article introduces a new dataset on how international organizations (IOs) justify their authority. For a long time, IOs were believed to derive legitimacy from member-state consent and technocratic problem-solving capacities. Over rec…

Agents, audiences and peers: why international organizations diversify their legitimation discourse Open

Tobias Lenz, Henning Schmidtke · 2023

In the face of public contestation, international organizations (IOs) invoke norms in their public communication to enhance relevant audiences' legitimacy beliefs. This article offers the first comprehensive analysis of what we term normat…

The origins of legitimation strategies in international organizations: agents, audiences and environments Open

Tobias Lenz, Fredrik Söderbaum · 2023

How do international organizations (IOs) claim legitimacy, and why do they do so in different ways? Confronted with contestation and critique, IOs seek to enhance audiences' beliefs in their legitimacy by justifying their governance compet…

Global model categories and topological André-Quillen cohomology Open

Tobias Lenz, Michael Stahlhauer · 2023

We introduce global model categories as a general framework to capture several phenomena in global equivariant homotopy theory. We then construct genuine stabilizations of these, generalizing the usual passage from unstable to stable globa…

Parametrized stability and the universal property of global spectra Open

Bastiaan Cnossen, Tobias Lenz, Sil Linskens · 2023

We develop a framework of parametrized semiadditivity and stability with respect to so-called atomic orbital subcategories of an indexing $\infty$-category $T$, extending work of Nardin. Specializing this framework, we introduce global $\i…

Discovering cooperation: Endogenous change in international organizations Open

Tobias Lenz, Besir Ceka, Liesbet Hooghe, Gary Marks, Alexandr Burilkov · 2022

Why do some international organizations (IO) accrete delegated authority over time while in others delegation is static or declines? We hypothesize that the dynamics of delegation are shaped by an IO’s founding contract. IOs rooted in an o…

Discovering cooperation: Endogenous change in international organizations Open

Tobias Lenz, Besir Ceka, Liesbet Hooghe, Gary Marks, Alexandr Burilkov · 2022

Why do some international organizations (IO) accrete delegated authority over time while in others delegation is static or declines? We hypothesize that the dynamics of delegation are shaped by an IO’s founding contract. IOs rooted in an o…

Genuine vs. naïve symmetric monoidal G-categories Open

Tobias Lenz · 2022

We prove that through the eyes of equivariant weak equivalences the genuine symmetric monoidal $G$-categories of Guillou and May [Algebr. Geom. Topol. 17 (2017), no. 6, 3259-3339; arXiv:1809.03017] are equivalent to just ordinary symmetric…

Global homotopy theory via spectral Mackey functors Open

Tobias Lenz · 2022

We show that Hausmann's model of global stable homotopy theory in terms of symmetric spectra is equivalent to the $\infty$-category of spectral Mackey functors in the sense of Barwick on a certain global effective Burnside category. We mor…

Categorical models of unstable G-global homotopy theory Open

Tobias Lenz · 2021

We prove that the category $\textbf{G-Cat}$ of small categories with $G$-action forms a model of unstable $G$-global homotopy theory for every discrete group $G$, generalizing Schwede's global model structure on $\textbf{Cat}$. As a conseq…

Summary Statistics Open

Tobias Lenz · 2021

How and under what conditions does the European Union (EU) shape processes of institution building in other regional organizations? This book develops and tests a theory of interorganizational diffusion in international relations that expl…

Passive European Union Influence Open

Tobias Lenz · 2021

This chapter traces the European Union’s passive influence in the establishment of the Mercosur Permanent Review Tribunal in 2004. This is an useful case to study passive EU influence because the Tribunal’s establishment constitutes an unl…

The Scope of European Union Influence Open

Tobias Lenz · 2021

This chapter examines the scope of European Union influence by combining quantitative and qualitative evidence. It argues that active and passive EU influence are likely to be discernible specifically in those regional organizations that r…

Revisiting Regional Institution Building Open

Tobias Lenz · 2021

This chapter revisits the theoretical literature on regional institution building during the last 70 years and contrasts it with the empirical literature on regional organizations. It shows that while the latter is replete with references …

Explaining the European Union’s Interorganizational Influence on Other Regional Organizations Open

Tobias Lenz · 2021

This chapter examines the European Union’s influence on other regional organizations through a statistical analysis of a dataset that contains information on the institutionalization of 36 regional organizations from 1950, or the year of t…

Interorganizational Diffusion in International Relations Open

Tobias Lenz · 2021

How and under what conditions does the European Union (EU) shape processes of institution building in other regional organizations? This book develops and tests a theory of interorganizational diffusion in international relations that expl…

The Dependent Variable ‘RO institutionalization’ Open

Tobias Lenz · 2021

Subject European Union Collection: Oxford Scholarship Online

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