Loss induced collective subradiant Dicke behaviour in a multiatom sample

The exact dynamics of $N$ two-level atoms coupled to a common electromagnetic bath and closely located inside a lossy cavity is reported. Stationary radiation trapping effects are found and very transparently interpreted in the context of our approach. We prove that initially injecting one excitation only in the $N$ atoms-cavity system, loss mechanisms asymptotically drive the matter sample toward a long-lived collective subradiant Dicke state. The role played by the closeness of the $N$ atoms with respect to such a cooperative behavior is brought to light and carefully discussed.Comment: 14 pages, 6 figures, submitted to EPJ

Stationary entanglement induced by dissipation

The dynamics of two two-level dipole-dipole interacting atoms coupled to a common electromagnetic bath and closely located inside a lossy cavity, is reported. Initially injecting only one excitation in the two atoms-cavity system, loss mechanisms asymptotically drive the matter sample toward a stationary maximally entangled state. The role played by the closeness of the two atoms with respect to such a cooperative behaviour is carefully discussed. Stationary radiation trapping effects are found and transparently interpreted.Comment: 1 figure, submitted to Phys. Rev. Let

On tadpoles and vacuum redefinitions in String Theory

Tadpoles accompany, in one form or another, all attempts to realize supersymmetry breaking in String Theory, making the present constructions at best incomplete. Whereas these tadpoles are typically large, a closer look at the problem from a perturbative viewpoint has the potential of illuminating at least some of its qualitative features in String Theory. A possible scheme to this effect was proposed long ago by Fischler and Susskind, but incorporating background redefinitions in string amplitudes in a systematic fashion has long proved very difficult. In the first part of this paper, drawing from field theory examples, we thus begin to explore what one can learn by working perturbatively in a ``wrong'' vacuum. While unnatural in Field Theory, this procedure presents evident advantages in String Theory, whose definition in curved backgrounds is mostly beyond reach at the present time. At the field theory level, we also identify and characterize some special choices of vacua where tadpole resummations terminate after a few contributions. In the second part we present a notable example where vacuum redefinitions can be dealt with to some extent at the full string level, providing some evidence for a new link between IIB and 0B orientifolds. We finally show that NS-NS tadpoles do not manifest themselves to lowest order in certain classes of string constructions with broken supersymmetry and parallel branes, including brane-antibrane pairs and brane supersymmetry breaking models, that therefore have UV finite threshold corrections at one loop.Comment: 51 pages, LaTeX, 7 eps figures. Typos corrected, refs added. Final version to appear in Nucl. Phys. B. Thanks to W. Mueck for very interesting correspondence. v3 was accidentally in draft forma

Potential Cost Savings from Generic Medicines - Protecting the Prescribed Minimum Benefits

Background: South Africa has followed a pro-generic policy since the introduction of the National Drug Policy in 1996. The selection processes inthe public and private sectors have, however, remained largely disconnected, and at times contradictory. Medicines provided outside of hospitals accounted for 17% of medical aid spend in 2006, up 8.8% from the previous year. Of particular concern to funders has been the expenditure on the 27 chronic conditions listed as Prescribed Minimum Benefits. The Medical Schemes Act (No 131 of 1998) provides for the definition of Prescribed Minimum Benefits, which stipulate a package of services or care a medical scheme must provide for in its benefit design. There is pressure to reconsider these requirements in order to increase the affordability of medical scheme coverage. This study assessed the potential savings that would be achievable by substituting generics for brand name (originator) medicines listed in the chronic disease algorithms set out by the Council for Medical Schemes (CMS).Methods: All medicines listed in the 25 chronic diseases algorithms made available by the CMS were identified. Brand and generic versions wereidentified in the Monthly Index of Medical Specialties (MIMS, May 2006). Single exit prices inclusive of value added tax were obtained from the website of the Pharmaceutical Blue Book and the cost per defined daily dose for one month was then calculated. Cost differentials, where available, were then identified for each medicine listed in the algorithms. Cost differentials for medicines within each algorithm were presented as the median of the difference between brand and generic medicines listed for that algorithm, and also as the median of differences between generic medicines for the same condition.Results: Three of the algorithms (diabetes insipidus, haemophilia and hypothyroidism) list medicines for which no generic equivalent was available at the time of the study. The median cost differential between brand and generic equivalents for the remaining 22 chronic conditions ranged from 19.5% (for type 1 diabetes mellitus) to 97% (for Addison’s disease). Across the entire chronic disease algorithm set, 80 medicines with generic equivalents were listed for 22 conditions. The median cost differential between brand and generic versions of these 80 medicines was 49.9% (interquartile range 32.0 to 78.5%). Of all generic medicines identified, 67.5% were more than 40% cheaper, per defined daily dose (DDD) per month, than the branded version. In 16 medicines the cost differentials between generic versions were 1% or less. Some correlation between the number of generics and the size of the cost differential was apparent (correlation coefficient 0.49). There were examples of high-cost differentials in highly competitive areas of the market.Conclusions: An argument could be made for more closely aligning the process of developing the National Essential Drugs List and the development of the CMS algorithms. By being more specific about which medicines should be covered, needless expenditure on “me-too” agents of doubtful additional benefit could be avoided. Where clinically warranted, appropriate choices could be provided. Finality in respect of the pricing of medicines needs to be achieved. This applies not only to the dispensing fee but also to the proposed benchmarking process and the proposed differential between brand and generic medicines

On a Condition for the Nonexistence of W-Solutions of Nonlinear High-Order Equations with L¹ -Data

En un conjunto abierto y acotado de consideramos el problema de Dirichlet para ecuaciones no lineales de orden en la forma divergente con lados L¹ -right-hand. Se supone que , y los coeficientes de las ecuaciones admiten el radio de crecimiento con respecto a las derivadas de orden m de la función desconocida. Establecemos que bajo la condición para algn data el problema de Dirichlet correspondiente no tiene W-soluciones.In a bounded open set of we consider the Dirichlet problem for nonlinear order equations in divergence form with right-hand sides. It is supposed that , and the coefficients of the equations admit the growth of rate with respect to the derivatives of order m of unknown function. We establish that under the condition for some L¹ -data the corresponding Dirichlet problem does not have W-solutions

Mitigating Contagion Risk by ESG Investing

We study whether ESG investing may mitigate the risk of contagion among equity mutual funds. More precisely, we measure the impact of fire-sale spillover, propagating throughout the financial system, on funds ranked on ESG aspects. We compare the relative loss of capitalization experienced by high- and low-ranked funds. Contagion, which is indirect since funds are not exposed to counterparty risk, is modeled using a network structure. In cases of deleveraging from funds, fire-sale spillover propagates throughout the network because of common asset holdings among funds. We find that funds’ vulnerability to contagion decreases when the level of ESG compliance increases. Moreover, the average relative loss is lower for the high-ranked funds than for the low-ranked ones. The small-size funds mainly drive the result. Our findings indicate that contagion is less effective for high-ranked funds. From a macroeconomic perspective, ESG investing represents a new opportunity for diversification that makes the system more resilient to contagion

Simplified approach to integrate seismic retrofitting prioritization with social cost evaluation: A case study in central Italy

In the last three decades, bridge stock seismic retrofitting prioritization has become one of the cult topics for scientific discussions in the bridge management strategies. More recent methods are focusing on the evaluation of the generalized failure cost, of a specific bridge derived from direct and indirect costs induced to the users/residents of the area exposed to the seismic hazard as a consequence of bridge collapse. However, when these approaches have to be applied to large transport networks, appear still very complex and computa-tional demanding, and therefore simplified methods to evaluate the impact in terms of social cost related to the reduced efficiency of a transportation network due to potential bridge failure, are required.In this work, a simplified method for seismic retrofitting prioritization on a bridge stock is proposed, which is based on a "blended" approach considering specific fragility curves according to several bridge features and condition state, seismic inputs and generalized failure costs related to the transportation network. The effectiveness of the method has been showed on a case study of a local bridge stock placed in central Italy and the obtained results have been compared with those provided by more refined transport simulation models, on one hand, and by more traditional prioritization approaches, on the other. It is highlighted that this method can be very useful for transportation network managers with in a limited budget scenario, in case of lack of information about possible earthquake -induced impacts on a transportation network efficiency.(c) 2022 Periodical Offices of Chang'an University. Publishing services by Elsevier B.V. on behalf of KeAi Communications Co. Ltd. This is an open access article under the CC BY-NC -ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/)

An alternative 3D inversion method for magnetic anomalies with depth resolution

This paper presents a new method to invert magnetic anomaly data in a variety of non-complex contexts when a priori information about the sources is not available. The region containing magnetic sources is discretized into a set of homogeneously magnetized rectangular prisms, polarized along a common direction. The magnetization distribution is calculated by solving an underdetermined linear system, and is accomplished through the simultaneous minimization of the norm of the solution and the misfit between the observed and the calculated field. Our algorithm makes use of a dipolar approximation to compute the magnetic field of the rectangular blocks. We show how this approximation, in conjunction with other correction factors, presents numerous advantages in terms of computing speed and depth resolution, and does not affect significantly the success of the inversion. The algorithm is tested on both synthetic and real magnetic datasets