28,994 research outputs found
Willingness to pay and the sovereign debt contract
This paper uses a contract theory model to argue that covenants ruling debt renegotiations are important to assure the sovereign willingness to pay. The model includes the following features: first, collective action clauses, exit consents, aggregation provisions and pari passu clauses play an important role in the post default “game” of negotiations and coalitions. These covenants are represented in reduced form by the endogenous probability of refinancing a defaulted sovereign debt. Second, the model has “endogenous bad luck” because the unfavorable state of nature where default occurs depends on the level of indebtedness, which is itself an endogenous variable. Third, “vultures”, contrary to conventional wisdom, tend to improve the access of emerging economies to capital markets because they might help to rule out strategic defaults. And fourth, under special assumptions the model is able to analyze the possibility of post default discrimination between domestic and foreign bondholders.debt, default, negotiation, vultures, Shapley-values
A cluster expansion approach to renormalization group transformations
The renormalization group (RG) approach is largely responsible for the
considerable success which has been achieved in developing a quantitative
theory of phase transitions. This work treats the rigorous definition of the RG
map for classical Ising-type lattice systems in the infinite volume limit at
high temperature. A cluster expansion is used to justify the existence of the
partial derivatives of the renormalized interaction with respect to the
original interaction. This expansion is derived from the formal expressions,
but it is itself well-defined and convergent. Suppose in addition that the
original interaction is finite-range and translation-invariant. We will show
that the matrix of partial derivatives in this case displays an approximate
band property. This in turn gives an upper bound for the RG linearization.Comment: 13 page
Supersymmetric partners of the trigonometric Poschl-Teller potentials
The first and second-order supersymmetry transformations are used to generate
Hamiltonians with known spectra departing from the trigonometric Poschl-Teller
potentials. The several possibilities of manipulating the initial spectrum are
fully explored, and it is shown how to modify one or two levels, or even to
leave the spectrum unaffected. The behavior of the new potentials at the
boundaries of the domain is studied.Comment: 20 pages, 4 figure
Geometric Phases and Mielnik's Evolution Loops
The cyclic evolutions and associated geometric phases induced by
time-independent Hamiltonians are studied for the case when the evolution
operator becomes the identity (those processes are called {\it evolution
loops}). We make a detailed treatment of systems having equally-spaced energy
levels. Special emphasis is made on the potentials which have the same spectrum
as the harmonic oscillator potential (the generalized oscillator potentials)
and on their recently found coherent states.Comment: 11 pages, harvmac, 2 figures available upon request; CINVESTAV-FIS
GFMR 11/9
On Evidence-based Risk Management in Requirements Engineering
Background: The sensitivity of Requirements Engineering (RE) to the context
makes it difficult to efficiently control problems therein, thus, hampering an
effective risk management devoted to allow for early corrective or even
preventive measures. Problem: There is still little empirical knowledge about
context-specific RE phenomena which would be necessary for an effective
context- sensitive risk management in RE. Goal: We propose and validate an
evidence-based approach to assess risks in RE using cross-company data about
problems, causes and effects. Research Method: We use survey data from 228
companies and build a probabilistic network that supports the forecast of
context-specific RE phenomena. We implement this approach using spreadsheets to
support a light-weight risk assessment. Results: Our results from an initial
validation in 6 companies strengthen our confidence that the approach increases
the awareness for individual risk factors in RE, and the feedback further
allows for disseminating our approach into practice.Comment: 20 pages, submitted to 10th Software Quality Days conference, 201
Resistance to carbapenems in non-typhoidal Salmonella enterica serovars from humans, animals and food
Non-typhoidal serovars of Salmonella enterica (NTS) are a leading cause of food-borne disease in animals and humans worldwide. Like other zoonotic bacteria, NTS have the potential to act as reservoirs and vehicles for the transmission of antimicrobial drug resistance in different settings. Of particular concern is the resistance to critical “last resort” antimicrobials, such as carbapenems. In contrast to other Enterobacteriaceae (e.g., Klebsiella pneumoniae, Escherichia coli, and Enterobacter, which are major nosocomial pathogens affecting debilitated and immunocompromised patients), carbapenem resistance is still very rare in NTS. Nevertheless, it has already been detected in isolates recovered from humans, companion animals, livestock, wild animals, and food. Five carbapenemases with major clinical importance—namely KPC (Klebsiella pneumoniae carbapenemase) (class A), IMP (imipenemase), NDM (New Delhi metallo-β-lactamase), VIM (Verona integron-encoded metallo-β-lactamase) (class B), and OXA-48 (oxacillinase, class D)—have been reported in NTS. Carbapenem resistance due to the production of extended spectrum- or AmpC β-lactamases combined with porin loss has also been detected in NTS. Horizontal gene transfer of carbapenemase-encoding genes (which are frequently located on self-transferable plasmids), together with co- and cross-selective adaptations, could have been involved in the development of carbapenem resistance by NTS. Once acquired by a zoonotic bacterium, resistance can be transmitted from humans to animals and from animals to humans through the food chain. Continuous surveillance of resistance to these “last resort” antibiotics is required to establish possible links between reservoirs and to limit the bidirectional transfer of the encoding genes between S. enterica and other commensal or pathogenic bacteria
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