Resting-state functional heterogeneity of the right insula contributes to pain sensitivity

Previous studies have described the structure and function of the insular cortex in terms of spatially continuous gradients. Here we assess how spatial features of insular resting state functional organization correspond to individual pain sensitivity. From a previous multicenter study, we included 107 healthy participants, who underwent resting state functional MRI scans, T1-weighted scans and quantitative sensory testing on the left forearm. Thermal and mechanical pain thresholds were determined. Connectopic mapping, a technique using non-linear representations of functional organization was employed to describe functional connectivity gradients in both insulae. Partial coefficients of determination were calculated between trend surface model parameters summarizing spatial features of gradients, modal and modality-independent pain sensitivity. The dominant connectopy captured the previously reported posteroanterior shift in connectivity profiles. Spatial features of dominant connectopies in the right insula explained significant amounts of variance in thermal (R2 = 0.076; p < 0.001 and R2 = 0.031; p < 0.029) and composite pain sensitivity (R2 = 0.072; p < 0.002). The left insular gradient was not significantly associated with pain thresholds. Our results highlight the functional relevance of gradient-like insular organization in pain processing. Considering individual variations in insular connectopy might contribute to understanding neural mechanisms behind pain and improve objective brain-based characterization of individual pain sensitivity.

On Invariant Operations on a Manifold with a Linear Connection and an Orientation

We prove a theorem that describes all possible tensor-valued natural operations in the presence of a linear connection and an orientation in terms of certain linear representations of the special linear group. As an application of this result, we prove a characterization of the torsion and curvature operators as the only natural operators that satisfy the Bianchi identities.

Structured time-delay models for dynamical systems with connections to Frenet–Serret frame

Time-delay embedding and dimensionality reduction are powerful techniques for discovering effective coordinate systems to represent the dynamics of physical systems. Recently, it has been shown that models identified by dynamic mode decomposition on time-delay coordinates provide linear representations of strongly nonlinear systems, in the so-called Hankel alternative view of Koopman (HAVOK) approach. Curiously, the resulting linear model has a matrix representation that is approximately antisymmetric and tridiagonal; for chaotic systems, there is an additional forcing term in the last component. In this paper, we establish a new theoretical connection between HAVOK and the Frenet–Serret frame from differential geometry, and also develop an improved algorithm to identify more stable and accurate models from less data. In particular, we show that the sub- and super-diagonal entries of the linear model correspond to the intrinsic curvatures in the Frenet–Serret frame. Based on this connection, we modify the algorithm to promote this antisymmetric structure, even in the noisy, low-data limit. We demonstrate this improved modelling procedure on data from several nonlinear synthetic and real-world examples.

The sine extended odd Fréchet-G family of distribution with applications to complete and censored data

In this paper, we introduce the sine extended odd Fréchet-G family of distributions, obtained from two well-established families of distributions of completely different nature: the sine-G and the extended odd Fréchet-G families. A particular focus is put on a very flexible member of this family defin ed with the Nadarajah-Haghighi distribution as a baseline, called the sine extended odd Fréchet Nadarajah-Haghighi distribution. For the theoretical part, the interesting mathematical properties of the family are investigated, including asymptotes, quantile function, linear representations and moments, with application to the introduced special member. Then, the inferential aspects of the sine extended odd Fréchet Nadarajah-Haghighi model are examined. In particular, the parameters are estimated by the maximum likelihood method. Two complementary cases are distinguished: the complete data case and the right censored data case, with the development of appropriate statistical tests. A simulation study is carried out to illustrate the convergence of the obtained estimates. Applications are given for three practicaldata sets, including one having the right censored property, illustrating the applicability of the proposed model.

Curves with prescribed symmetry and associated representations of mapping class groups

Let C be a complex smooth projective algebraic curve endowed with an action of a finite group G such that the quotient curve has genus at least 3. We prove that if the G-curve C is very general for these properties, then the natural map from the group algebra $${{\mathbb {Q}}}G$$ Q G to the algebra of $${{\mathbb {Q}}}$$ Q -endomorphisms of its Jacobian is an isomorphism. We use this to obtain (topological) properties regarding certain virtual linear representations of a mapping class group. For example, we show that the connected component of the Zariski closure of such a representation often acts $${{\mathbb {Q}}}$$ Q -irreducibly in a G-isogeny space of $$H^1(C; {{\mathbb {Q}}})$$ H 1 ( C ; Q ) and with image a $${{\mathbb {Q}}}$$ Q -almost simple group.

Generalized Odd Power Cauchy Family and Its Associated Heteroscedastic Regression Model

This study introduces a generalization of the odd power Cauchy family by adding one more shape parameter togain more flexibility modeling the complex data structures. The linear representations for the density, moments, quantile,and generating functions are derived. The model parameters are estimated employing the maximum likelihood estimationmethod. The Monte Carlo simulations are performed under different parameter settings and sample sizes for the proposedmodels. In addition, we introduce a new heteroscedastic regression model based on the special member of the proposedfamily. Three data sets are analyzed with competitive and proposed models.

Lattice regularisation and entanglement structure of the Gross-Neveu model

We construct a Hamiltonian lattice regularisation of the N-flavour Gross-Neveu model that manifestly respects the full O(2N) symmetry, preventing the appearance of any unwanted marginal perturbations to the quantum field theory. In the context of this lattice model, the dynamical mass generation is intimately related to the Coleman-Mermin-Wagner and Lieb-Schultz-Mattis theorems. In particular, the model can be interpreted as lying at the first order phase transition line between a trivial and symmetry-protected topological (SPT) phase, which explains the degeneracy of the elementary kink excitations. We show that our Hamiltonian model can be solved analytically in the large N limit, producing the correct expression for the mass gap. Furthermore, we perform extensive numerical matrix product state simulations for N = 2, thereby recovering the emergent Lorentz symmetry and the proper non-perturbative mass gap scaling in the continuum limit. Finally, our simulations also reveal how the continuum limit manifests itself in the entanglement spectrum. As expected from conformal field theory we find two conformal towers, one tower spanned by the linear representations of O(4), corresponding to the trivial phase, and the other by the projective (i.e. spinor) representations, corresponding to the SPT phase.

Using a collaborative zine to co-produce knowledge about location-based virtual reality experiences

PurposeThe purpose of this paper is to focus on a designed research methodology to distil existing research findings from an esrc/ahrc funded japan/uk network on location-based virtual reality experiences for children in order to generate new knowledge.Design/methodology/approachThe structured co-production methodology was undertaken in three stages. These were: (1) a collaborative workshop which produced a series of collage narratives, (2) collaborating with a non-human entity in the form of a digital coded tool to reconfigure the workshop responses and mediate the hierarchy of roles, (3) the co-production of a zine as a collaborative reflection method, which shared via postal service enabled a dialogue and exchange of round Robin interventions by the network members.FindingsThe analysis of the data collected in this study highlighted five themes that could be used by other researchers on a wide range of projects. These were: (1) knowing through making, (2) the importance of process, (3) beyond linear representations, (4) agency of physical materials and (5) agency of digital code.Research limitations/implicationsThe context of the study being undertaken during the first phase of the global pandemic, revealed insight into a method of co-production that was undertaken under emergency remote working conditions. The knowledge generated from this can be applied to other research contexts such as working with researchers or participants across global borders without the need to travel.Originality/valueThe research provides an innovative rethinking of co-production methods in order to generate new knowledge from multidisciplinary and multimodal research.

Postcolonial/Decolonial Critique and the Theory of International Relations

The article is devoted to the discussion of the role of postcolonial/decolonial critique and its contribution to the theory of international relations. Intersecting with multiple disciplines and area studies, the postcolonial/decolonial critique offers a broad view not only on the cultural heritage of colonialism/imperialism as such, but also on the more complex and multifaceted challenges facing international relations – the coloniality of power and geopolitics of knowledge – and conditions of their emergence. Postcolonial/decolonial approaches foster critical engagement with Eurocentric narratives in social sciences, countering teleological or linear representations of modernity. Despite its importance, postcolonial/decolonial thought penetrated the theory of international relations rather late. The two fields of intellectual quest have developed not only separately, but they have often diverged in their very epistemological constitution. Based on a review of an extensive literature, the author explores the links between the production of postcolonial knowledge and the theory of international relations. Thus, the author illuminates the problems of modern political science and international studies, on the one hand, and on the other hand, emphasizes the need to make the theory of IR accessible to a variety of new global perspectives. The formation of integrative approaches in the study of world politics should provide a new consolidation of both political science and international studies and a productive interaction of these areas of knowledge.

Free (rational) derivation

By representing elements in free fields (over a commutative field and a finite alphabet) using Cohn and Reutenauer’s linear representations, we provide an algorithmic construction for the (partial) non-commutative (or Hausdorff-) derivative and show how it can be applied to the non-commutative version of the Newton iteration to find roots of matrix-valued rational equations.