Exceptional Momenta Research Articles

Understanding Bangladesh–China Relations from ‘Win-Win Cooperation’ and ‘NOISE’ Analysis Perspectives

The study evaluates Bangladesh–China relations through the ‘win-win cooperation’ lens and concludes with a ‘NOISE’ (Needs-Opportunities-Improvements-Strengths-Exceptions) analysis. Bangladesh, a South Asian developing nation, has maintained a strategic partnership with Beijing since the establishment of their diplomatic ties. However, the relationship gained exceptional momentum after Bangladesh’s inclusion in the Belt and Road Initiative (BRI). Bangladesh’s need for growth-necessary financing and China’s massive foreign investment outlook have contributed to the growth of their economic engagements. The analysis suggests that the Bangladesh–China relationship exhibits ‘win-win cooperation’ dynamics. The study identified the significant trade gap, loan agreements, and disbursement delays, along with others, challenging the solid Bangladesh–China bilateral economic interactions. The Rohingya refugee crisis resolve and geopolitical competition among major powers are two non-bilateral issues that could potentially impact future Dhaka–Beijing relations. Overcoming the existing barriers could position Bangladesh–China relations as a model for smaller-major power bilateral relations, particularly for developing nations. It is a desk research by design. The findings of this study may provide insights to policymakers in addressing the existing barriers to meet future needs.

Solidarity with Displaced People from Ukraine in Hungary: Attitudes and Practices

AbstractThe paper explores the attitudes of Hungarian civil society in the context of the war against Ukraine, the active agents of solidarity, and the general social atmosphere associated with welcoming displaced people. Based on a population survey from the summer of 2022, the paper draws an ambivalent picture. First, it highlights the exceptional momentum and mobilising power of civil solidarity both in terms of practical involvement and expressed attitudes. At the same time, the results also reveal the limits and vulnerabilities of civil solidarity—namely, its exposure to populist political discourses which cherish or condemn moral economies of assistance according to vested interests, as well as its embeddedness in a neoliberal reliance on citizens’ individual resources (disposable time and material means), and the salient inequalities in sharing the burdens of humanitarian support. All this reflects that the consensus and relative evenness of solidarity attitudes at the time of our survey were unevenly translated into practical help, burdening those already heavily charged with care responsibilities. With this finding, we underline the importance of exploring solidarity as a complex relationship of attitudes and practices; also, we highlight the need to include the perspectives of care in inquiries of the population’s attitude towards immigrant groups and categories. Our results are drawn from the application of multi-dimensional logistic regression models based on data from a statistical survey involving 1000 respondents representative of Hungary’s adult population.

Hidden Bethe states in a partially integrable model

We present a one-dimensional multi-component model, known to be partially integrable when restricted to the subspaces made of only two components. By constructing fully anti-symmetrized bases, we find integrable excited eigenstates corresponding to the totally anti-symmetric irreducible representation of the permutation operator in the otherwise non-integrable subspaces. We establish rigorously the breakdown of integrability in those subspaces by showing explicitly the violation of the Yang-Baxter's equation. We further solve the constraints from Yang-Baxter's equation to find exceptional momenta that allows Bethe Ansatz solutions of solitonic bound states. These integrable eigenstates have distinct dynamical consequence from the embedded integrable subspaces previously known, as they do not span their separate Krylov subspaces, and a generic initial state can partly overlap with them and therefore have slow thermalization. However, this novel form of weak ergodicity breaking contrasts that of quantum many-body scars in that the integrable eigenstates involved do not have necessarily low entanglement. Our approach provides a complementary route to arrive at quantum many-body scars since, instead of solving towers of single mode excited states based on a solvable ground state in a non-integrable model, we identify the integrable eigenstates that survive in a deformation of the Hamiltonian away from its integrable point.

Newer Methods of Surgical Learning: Gifts of COVID-19 to Medical School.

BackgroundIndia has survived three waves of the COVID-19 pandemic. To adapt to the flow of life, hospitals metamorphosed into sanctums with all hands at the deck for containment of the pandemic. The training of residents in medical schools was hugely impacted during this time.MethodsVarious educational aids to improve surgical training were reviewed and assessed.ResultsAugmented, virtual and mixed reality devices, 3-D anatomy learning aids, and simulation programs were the main categories found.ConclusionThe global intelligentsia has worked at an exceptional momentum during COVID-19 to imbibe novel developments in the medical field for better surgical training. These advances are truly gifts of COVID-19 to medical school.

Abolitionism and the Back-to-Africa Movement in Britain: The Sierra Leone Experiment

The article focuses on the settlement of freed black slaves from England and Nova Scotia in Sierra Leone. As the eighteenth century drew to a close, plans were made for the “repatriation” of impoverished migrants of African descent to their “ancestral” land. Such plans were contextually defined by the abolitionist movement in Britain. Abolitionism gained exceptional momentum in the country that played a leading part in the transatlantic slave trade at that time. The movement aimed to end both the slave trade and slavery. The article investigates the activities of the Committee for the Relief of the Black Poor and especially the role of the prominent British philanthropist and abolitionist Granville Sharp (1735–1813), who made significant efforts to bring the “repatriation” plans to fruition. I argue that the Sierra Leone project was an ambivalent experiment, which should be interpreted in the light of both humanitarian compassion and imperial interests: if, at first, it was premised upon idealism and religious fervour, the desire to set foot in west Africa and to set up a colony there subsequently prevailed. For some Britons, sending impoverished free blacks to distant shores was also an opportunity to expel them from their own “white” society. In this sense, the “repatriation” of Africans was most likely to occur in the form of deportation, a form that suggests the restrictive regime of penal colonies, such as Australia.

Abolitionism and the Back-to-Africa Movement in Britain: The Sierra Leone Experiment

The article focuses on the settlement of freed black slaves from England and Nova Scotia in Sierra Leone. As the eighteenth century drew to a close, plans were made for the “repatriation” of impoverished migrants of African descent to their “ancestral” land. Such plans were contextually defined by the abolitionist movement in Britain. Abolitionism gained exceptional momentum in the country that played a leading part in the transatlantic slave trade at that time. The movement aimed to end both the slave trade and slavery. The article investigates the activities of the Committee for the Relief of the Black Poor and especially the role of the prominent British philanthropist and abolitionist Granville Sharp (1735–1813), who made significant efforts to bring the “repatriation” plans to fruition. I argue that the Sierra Leone project was an ambivalent experiment, which should be interpreted in the light of both humanitarian compassion and imperial interests: if, at first, it was premised upon idealism and religious fervour, the desire to set foot in west Africa and to set up a colony there subsequently prevailed. For some Britons, sending impoverished free blacks to distant shores was also an opportunity to expel them from their own “white” society. In this sense, the “repatriation” of Africans was most likely to occur in the form of deportation, a form that suggests the restrictive regime of penal colonies, such as Australia.

The Operator Product Expansion Converges in Massless $${\varphi_{4}^{4}}$$ φ 4 4 -Theory

It has been shown recently that the mathematical status of the operator product expansion (OPE) is better than was expected before: namely considering massive Euclidean $\varphi^4$-theory in the perturbative loop expansion, the OPE converges at any loop order when considering (as is usually done) composite operator insertions into correlation functions. In the present paper we prove the same result for the massless theory. While the short-distance properties of massive and massless theories may be expected to be similar on physical grounds, the proof in the massless case requires entirely new techniques. In our inductive construction we have to control with sufficient precision the exceptional momentum singularities of the massless correlation functions. In fact the bounds we state are expressed in terms of weight factors associated to certain tree graphs. Our proof is again based on the flow equations of the renormalisation group.

Review: The House of Light and Entropy, by Alessandra Ponte

Alessandra Ponte The House of Light and Entropy Architecture Words series, London: AA Publications, 2014, 228 pp., 33 b/w illus. £15.00, ISBN 9781907896170 In an era when global scale and New World histories steer the agendas of historical discourse, Alessandra Ponte’s insistence on looking at the specificity of places, sites, and landscapes has gained exceptional momentum. The six essays in The House of Light and Entropy span the spectrum of Ponte’s far-reaching research interests, woven into a tight fabric of critical reflections. They trace histories of the cultivation of nature, of mapping, and of media in the context of American sites that have one characteristic in common: the lawn, the sand desert, and the ice desert are vast. As landscapes conceived of as “empty,” they have repeatedly been claimed as sites of scientific and artistic testing. Recognizing the futility of hegemonic claims on these overpowering landscapes, Ponte’s narration acknowledges the volatility of any historiography of such sites, illuminating them via contrasting multiple arguments as she draws them into and out of perspective. In terms of the choreography of the six essays, the reader is left without doubt that Ponte’s interests lie far from the picturesque and from visual studies. On the contrary, what is at stake are social, cultural, and economic questions relating to the occupation of land by humans, by machines, and by media. The first subject of Ponte’s investigation is the ubiquitous suburban lawn. This essay was originally published in the catalog for the 1998 exhibition The American Lawn: The Surface of Everyday Life at the Canadian Centre for Architecture in Montreal, which Ponte cocurated with a team of seven architects.1 She points out that at the beginning of the twentieth century the concept of the “landscape garden” was replaced by that of a “natural landscape,” thereby alerting us to the idea that naturalism is a construction and preparing us to follow her further arguments. The two quotes that open …

Numerical Evaluation of One-Loop Diagrams Near Exceptional Momentum Configurations

One problem which plagues the numerical evaluation of one-loop Feynman diagrams using recursive integration by part relations is a numerical instability near exceptional momentum configurations. In this contribution we will discuss a generic solution to this problem. As an example we consider the case of forward light-by-light scattering.

The time of freedom: campesino workers in Guatemala's October Revolution

The time of freedom was the name that plantation workers-campesinos-gave to Guatemala's national revolution of 1944-1954. Cindy Forster reveals the critical role played by the poor in organizing and sustaining this period of reform. Through court records, labor and agrarian ministry archives, and oral histories, Forster demonstrates how labor conflict on the plantations prepared the ground for national reforms that are usually credited to urban politicians. She focuses on two plantation zones that generated exceptional momentum: the coffee belt in the highlands around San Marcos and the United Fruit Company's banana groves near Tiquisate. Although these regions were unlike in size and complexity, language and race, popular culture and work patterns, both erupted with demands for workers' rights and economic justice shortly after the fall of Castaneda in 1944. A welcome balance to the standard top-down histories of the revolution, Forster's sophisticated analysis demonstrates how campesinos changed the course of the urban revolution. By establishing the context of grassroots mobilization, she substantially alters the conventional view of the entire revolution, and particularly the reforms enacted under President Arbenz.

Renormalizability proof for QED based on flow equations

We prove the perturbative renormalizability of Euclidean QED4 using flow equations, i.e. with the aid of the Wilson renormalization group adapted to perturbation theory. As compared toΦ 4 4 the additional difficulty to overcome is that the regularization violates gauge invariance. We prove that there exists a class of renormalization conditions such that the renormalized Green functions satisfy the QED Ward identities and such that they are infrared finite at nonexceptional momenta. We give bounds on the singular behaviour at exceptional momenta (due to the massless photon) and comment on the adaptation to the case when the fermions are also massless.

Infrared and Ultraviolet Behaviour of Effective Scalar Field Theory

We consider the infrared and ultraviolet behaviour of the effective quantum field theory of a single Z2 symmetric scalar field. In a previous paper we proved to all orders in perturbation theory the renormalizability of massive effective scalar field theory using Wilson′s exact renormalization group equation. Here we show that away from exceptional momenta the massless theory is similarly renormalizable, and we prove detailed bounds on Green′s functions as arbitrary combinations of exceptional Euclidean momenta are approached. As a corollary we also prove Weinberg′s Theorem for the massive effective theory, in the form of bounds on Green′s functions at Euclidean momenta much greater than the particle mass but below the naturalness scale of the theory.

Perturbative renormalization of massless φ 4 4 with flow equations

Perturbative renormalizability proofs in the Wilson-Polchinski renormalization group framework, based on flow equations, were so far restricted to massive theories. Here we extend them to Euclidean massless φ 4 4 . As a by-product of the proof we obtain bounds on the singularity of the Green functions at exceptional momenta in terms of the exceptionality of the latter. These bounds seem to be new and are quite sharp.

DIFFICULTIES OF AN INFRARED EXTENSION OF DIFFERENTIAL RENORMALIZATION

We investigate the possibility of generalizing the differential renormalization of D. Z. Freedman, K. Johnson and J. I. Latorre in an invariant fashion to theories with infrared divergencies via an infrared [Formula: see text] operation. Two-dimensional σ models and the four-dimensional ɸ4-theory diagrams with exceptional momenta are used as examples, while dimensional renormalization serves as a test scheme for comparison. We write the basic differential identities of the method simultaneously in co-ordinate and momentum space, introducing two scales which remove ultraviolet and infrared singularities. A consistent set of Fourier-transformation formulae is derived. However, the values for tadpole-type Feynman integrals in higher orders of perturbation theory prove to be ambiguous, depending on the order of evaluation of the subgraphs. In two dimensions, even earlier than this ambiguity manifests itself, renormalization-group calculations based on the infrared extension of differential renormalization lead to incorrect results. We conclude that the procedure of extended differential renormalization does not perform the infrared [Formula: see text] operation in a self-consistent way.

Applications of quantum field theory to statistical mechanics

Several concepts of quantum field theory in which Symanzik's work has been essential, have played a central role in statistical mechanics as well. The existence of a scaling limit near a critical point is a direct consequence of renormalization theory; scaling laws, indices and universality follow (as shown by Wilson) from the renormalization group framework, in field theory from the Callan-Symanzik equations; Symanzik's work on exceptional momenta, on the renormalization of broken symmetries, and on repeated insertions of mass operators gives important informations on the theory, for instance the possibility of calculating all the exponents at the critical temperature. Several other contributions of Symanzik, from the 1 N expansion to the Casimir effect and its relation to surface phenomena, are briefly reviewed.

Asymptotic behaviour at exceptional momenta

We develop a method for investigating the asymptotic behaviour of vertex functions at certain Minkowskian exceptional momenta. It is a direct generalization of earlier treatments of Euclidean exceptional momenta. It makes use of formal expansions in momentum space, closely related to light-cone expansions in position space. Our expansions have to be performed in those channels which carry finite total momentum squared and admit (in A4-theory) two-particle intermediate states.

Asymptotic behaviour from the exact Callan-Symanzik equations

The exact Callan-Symanzik equations written in the functional formalism are solved without dropping the mass-insertion terms. We find, from the exact solution, the asymptotic behaviour of Green functions at non-exceptional momenta without referring to Weinberg's power-counting theorem. In the case of asymptotically free theories, we also compute the non-leading asymptotic terms without using Wilson's operator product expansion. Finally, we discuss the case of exceptional momenta and study the asymptotics of theories with broken symmetry.