7,441 research outputs found
Quantum Field Theory of Open Spin Networks and New Spin Foam Models
We describe how a spin-foam state sum model can be reformulated as a quantum
field theory of spin networks, such that the Feynman diagrams of that field
theory are the spin-foam amplitudes. In the case of open spin networks, we
obtain a new type of state-sum models, which we call the matter spin foam
models. In this type of state-sum models, one labels both the faces and the
edges of the dual two-complex for a manifold triangulation with the simple
objects from a tensor category. In the case of Lie groups, such a model
corresponds to a quantization of a theory whose fields are the principal bundle
connection and the sections of the associated vector bundles. We briefly
discuss the relevance of the matter spin foam models for quantum gravity and
for topological quantum field theories.Comment: 13 pages, based on the talk given at the X-th Oporto Meeting on
Geometry, Physics and Topology, Porto, September 20-24, 200
Four dimensional topological quantum field theory, Hopf categories, and the canonical bases
We propose a new mwthod of constructing 4D-TQFTs. The method uses a new type
of algebraic structure called a Hopf Category. We also outline the construction
of a family of Hopf categories related to the quantum groups, using the
canonical bases.Comment: 38 page
Thermal conductivity of heterogeneous mixtures and lunar soils
The theoretical evaluation of the effective thermal conductivity of granular materials is discussed with emphasis upon the heat transport properties of lunar soil. The following types of models are compared: probabilistic, parallel isotherm, stochastic, lunar, and a model based on nonlinear heat flow system synthesis
Cosmological Constant in LQG Vertex Amplitude
A new q-deformation of the Euclidean EPRL/FK vertex amplitude is proposed by
using the evaluation of the Vassiliev invariant associated with a 4-simplex
graph (related to two copies of quantum SU(2) group at different roots of
unity) embedded in a 3-sphere. We show that the large-j asymptotics of the
q-deformed vertex amplitude gives the Regge action with a cosmological
constant. In the end we also discuss its relation with a Chern-Simons theory on
the boundary of 4-simplex.Comment: 6 pages, 5 figures, result and presentation improve
Governance gaps in eradicating forced labor: from global to domestic supply chains
A growing body of scholarship analyzes the emergence and resilience of forced labor in developing countries within global value chains (GVCs). However, little is known about how forced labor arises within domestic supply chains concentrated within national borders, producing products for domestic consumption. We conduct one of the first studies of forced labor in domestic supply chains, through a cross-industry comparison of the regulatory gaps surrounding forced labor in the United Kingdom. We find that understanding the dynamics of forced labor in domestic supply chains requires us to conceptually modify the GVC framework to understand similarities and differences across these contexts. We conclude that addressing the governance gaps that surround forced labor will require scholars and policymakers to carefully refine their thinking about how we might design operative governance that effectively engages with local variation
EFFICACY TEST PROTOCOLS FOR EVALUATION OF ULTRASONIC RODENT REPELLENT DEVICES
Controlled laboratory and field test protocols were developed to assess the repellent efficacies of six commercially manufactured ultrasonic rodent repellent devices. The laboratory test structure (68.7 sq m) was divided into two rooms (32.5 sq m each) with a central harborage area (3.5 sq m) containing a colony of 12 wild Norway rats (Rattus norvegicus). For each test, a single ultrasonic device was attached to the far end of one room and rat activity measures (oat consumption, packet damage, photocell counts) were taken during 1-week baseline and 2-1/2-week test periods. Field test structures varied in floor area (6.5 to 197 sq m) and were of either metal or wood construction. All contained existing Norway rat, house mouse (Mus musculus), or field mouse (Peromyscus maniculatus) infestations. No rodent control was conducted at these sites other than the application of selected ultrasonic devices. Rodent activity (packet damage, food consumption, rodent tracks) was measured twice per week during three successive 3-week intervals with devices operating only during the second interval. Repeated measures analysis of variance and chi square were used to statistically evaluate the reliability of ultrasound effects
Modern slavery in business: The sad and sorry state of a non-field
“Modern slavery,” a term used to describe severe forms of labor exploitation, is beginning to spark growing interest within business and society research. As a novel phenomenon, it offers potential for innovative theoretical and empirical pathways to a range of business and management research questions. And yet, development into what we might call a “field” of modern slavery research in business and management remains significantly, and disappointingly, underdeveloped. To explore this, we elaborate on the developments to date, the potential drawbacks, and the possible future deviations that might evolve within six subdisciplinary areas of business and management. We also examine the value that nonmanagement disciplines can bring to research on modern slavery and business, examining the connections, critiques, and catalysts evident in research from political science, law, and history. These, we suggest, offer significant potential for building toward a more substantial subfield of research
4-Dimensional BF Theory as a Topological Quantum Field Theory
Starting from a Lie group G whose Lie algebra is equipped with an invariant
nondegenerate symmetric bilinear form, we show that 4-dimensional BF theory
with cosmological term gives rise to a TQFT satisfying a generalization of
Atiyah's axioms to manifolds equipped with principal G-bundle. The case G =
GL(4,R) is especially interesting because every 4-manifold is then naturally
equipped with a principal G-bundle, namely its frame bundle. In this case, the
partition function of a compact oriented 4-manifold is the exponential of its
signature, and the resulting TQFT is isomorphic to that constructed by Crane
and Yetter using a state sum model, or by Broda using a surgery presentation of
4-manifolds.Comment: 15 pages in LaTe
- …