Trade credit: Suppliers as debt collectors and insurance providers

There are two fundamental puzzles about trade credit: why does it appearto be so expensive,and why do input suppliers engage in the business oflending money? This paper addresses and answers both questions analysingthe interaction between the financial and the industrial aspects of thesupplier-customer relationship. It examines how, in a context of limitedenforceability of contracts, suppliers may have a comparative advantageover banks in lending to their customers because they hold the extrathreat of stopping the supply of intermediate goods. Suppliers may alsoact as lenders of last resort, providing insurance against liquidityshocks that may endanger the survival of their customers. The relativelyhigh implicit interest rates of trade credit result from the existenceof default and insurance premia. The implications of the model areexamined empirically using parametric and nonparametric techniques on apanel of UK firms.

Markups, gaps and the welfare costs of business fluctuations

In this paper we present a simple theory-based measure of the variations in aggregate economic efficiency: the gap between the marginal product of labor and the household s consumption/leisure tradeoff. We show that this indicator corresponds to the inverse of the markup of price over social marginal cost, and give some evidence in support of this interpretation. We then show that, with some auxilliary assumptions our gap variable may be used to measure the efficiency costs of business fluctuations. We find that the latter costs are modest on average. However, to the extent the flexible price equilibrium is distorted,the gross efficiency losses from recessions and gains from booms may be large. Indeed, we find that the major recessions involved large efficiency losses. These results hold for reasonable parameterizations of the Frisch elasticity of labor supply, the coefficient of relative risk aversion, and steady state distortions.

Gross capital flows: Dynamics and crises

This paper analyzes the behavior of international capital flows by foreign and domestic agents,dubbed gross capital flows, over the business cycle and during financial crises. We show thatgross capital flows are very large and volatile, especially relative to net capital flows. Whenforeigners invest in a country, domestic agents invest abroad, and vice versa. Gross capital flowsare also pro-cyclical. During expansions, foreigners invest more domestically and domesticagents invest more abroad. During crises, total gross flows collapse and there is a retrenchmentin both inflows by foreigners and outflows by domestic agents. These patterns hold for differenttypes of capital flows and crises. This evidence sheds light on the sources of fluctuations drivingcapital flows and helps discriminate among existing theories. Our findings seem consistent withcrises affecting domestic and foreign agents asymmetrically, as would be the case under thepresence of sovereign risk or asymmetric information.

Banks, government bonds, and default: what do the data say?

We use data from Bankscope to analyze the holdings of public bonds by over 18,000 banks located in 185 countries and the role of these bonds in 18 sovereign debt crises over the period 1998-2012. We find that: (i) banks hold a sizeable share of their assets in government bonds (about 9% on average), particularly in less financially developed countries; (ii) during sovereign crises, banks on average increase their bondholdings by 1% of their assets, but this increase is concentrated among larger and more profitable banks, and; (iii) the correlation between a bank's holdings of public bonds and its future loans is positive in normal times, but turns negative during defaults. A 10% increase in bank bond-holdings during default is associated with a 3.2% reduction in future loans, and bonds bought in normal times account for 75% of this effect. Our results are consistent with the view that there is a liquidity benefit for banks to hold public bonds in normal times, which is critical for understanding bank fragility during sovereign crises.

Complements and substitutes in multilateral assignment markets

[cat] En aquest treball provo que, en mercats d’assignació amb més de dos costats, agents de diferents sectors poden no ser complementaris mentre que agents del mateix sector poden no ser substituts. Shapley (1962) va provar que això mai pot succeïr quan el mercat d’assignació només té dos costats. No obstant, demostro que existeixen condicions suficients que garanteixen la substitutabilitat i la complementarietat entre agents en aquests tipus de mercats. A més, provo que, quan els béns al mercat son homogenis, el resultat de Shapley (1962) es manté.

Batalin-Vilkovisky analysis of covariant and noncovariant actions

The equivalence between the covariant and the noncovariant versions of a constrained system is shown to hold after quantization in the framework of the field-antifield formalism. Our study covers the cases of electromagnetism and Yang-Mills fields and sheds light on some aspects of the Faddeev-Popov method, for both the covariant and noncovariant approaches, which have not been fully clarified in the literature.

Uniformity Study of Amorphous and Microcrystalline Silicon Thin Films Deposited on 10cmx10cm Glass Substrate using Hot Wire CVD Technique

The scaling up of the Hot Wire Chemical Vapor Deposition (HW-CVD) technique to large deposition area can be done using a catalytic net of equal spaced parallel filaments. The large area deposition limit is defined as the limit whenever a further increment of the catalytic net area does not affect the properties of the deposited film. This is the case when a dense catalytic net is spread on a surface considerably larger than that of the film substrate. To study this limit, a system able to hold a net of twelve wires covering a surface of about 20 cm x 20 cm was used to deposit amorphous (a-Si:H) and microcrystalline (μc-Si:H) silicon over a substrate of 10 cm x 10 cm placed at a filament-substrate distance ranging from 1 to 2 cm. The uniformity of the film thickness d and optical constants, n(x, λ) and α(x,¯hω), was studied via transmission measurements. The thin film uniformity as a function of the filament-substrate distance was studied. The experimental thickness profile was compared with the theoretical result obtained solving the diffusion equations. The optimization of the filament-substrate distance allowed obtaining films with inhomogeneities lower than ±2.5% and deposition rates higher than 1 nm/s and 4.5 nm/s for (μc-Si:H) and (a-Si:H), respectively.

Batalin-Vilkovisky analysis of covariant and noncovariant actions

The equivalence between the covariant and the noncovariant versions of a constrained system is shown to hold after quantization in the framework of the field-antifield formalism. Our study covers the cases of electromagnetism and Yang-Mills fields and sheds light on some aspects of the Faddeev-Popov method, for both the covariant and noncovariant approaches, which have not been fully clarified in the literature.

Superconducting p-branes and extremal black holes

In Einstein-Maxwell theory, magnetic flux lines are "expelled" from a black hole as extremality is approached, in the sense that the component of the field strength normal to the horizon goes to zero. Thus, extremal black holes are found to exhibit the sort of ¿Meissner effect¿ which is characteristic of superconducting media. We review some of the evidence for this effect and present new evidence for it using recently found black hole solutions in string theory and Kaluza-Klein theory. We also present some new solutions, which arise naturally in string theory, which are non-superconducting extremal black holes. We present a nice geometrical interpretation of these effects derived by looking carefully at the higher dimensional configurations from which the lower dimensional black hole solutions are obtained. We show that other extremal solitonic objects in string theory (such as p-branes) can also display superconducting properties. In particular, we argue that the relativistic London equation will hold on the world volume of ¿light¿ superconducting p-branes (which are embedded in flat space), and that minimally coupled zero modes will propagate in the adS factor of the near-horizon geometries of "heavy," or gravitating, superconducting p-branes.

Complements and substitutes in multilateral assignment markets

[cat] En aquest treball provo que, en mercats d’assignació amb més de dos costats, agents de diferents sectors poden no ser complementaris mentre que agents del mateix sector poden no ser substituts. Shapley (1962) va provar que això mai pot succeïr quan el mercat d’assignació només té dos costats. No obstant, demostro que existeixen condicions suficients que garanteixen la substitutabilitat i la complementarietat entre agents en aquests tipus de mercats. A més, provo que, quan els béns al mercat son homogenis, el resultat de Shapley (1962) es manté.

Rethinking study and management of agricultural systems for policy design

There is a concern that agriculture will no longer be able to meet, on a global scale, the growing demand for food. Facing such a challenge requires new patterns of thinking in the context of complexity and sustainability sciences. This paper, focused on the social dimension of the study and management of agricultural systems, suggests that rethinking the study of agricultural systems entails analyzing them as complex socio-ecological systems, as well as considering the differing thinking patterns of diverse stakeholders. The intersubjective nature of knowledge, as studied by different philosophical schools, needs to be better integrated into the study and management of agricultural systems than it is done so far, forcing us to accept that there are no simplistic solutions, and to seek a better understanding of the social dimension of agriculture. Different agriculture related problems require different policy and institutional approaches. Finally, the intersubjective nature of knowledge asks for the visualization of different framings and the power relations taking place in the decision-making process. Rethinking management of agricultural systems implies that policy making should be shaped by different principles: learning, flexibility, adaptation, scale-matching, participation, diversity enhancement and precaution hold the promise to significantly improve current standard management procedures.

Input diffusion and the evolution of production networks

What determines which inputs are initially considered and eventually adopted in the productionof new or improved goods? Why are some inputs much more prominent than others? We modelthe evolution of input linkages as a process where new producers first search for potentially usefulinputs and then decide which ones to adopt. A new product initially draws a set of 'essentialsuppliers'. The search stage is then confined to the network neighborhood of the latter, i.e., to theinputs used by the essential suppliers. The adoption decision is driven by a tradeoff between thebenefits accruing from input variety and the costs of input adoption. This has important implicationsfor the number of forward linkages that a product (input variety) develops over time. Inputdiffusion is fostered by network centrality ? an input that is initially represented in many networkneighborhoods is subsequently more likely to be adopted. This mechanism also delivers a powerlaw distribution of forward linkages. Our predictions continue to hold when varieties are aggregatedinto sectors. We can thus test them, using detailed sectoral US input-output tables. We showthat initial network proximity of a sector in 1967 significantly increases the likelihood of adoptionthroughout the subsequent four decades. The same is true for rapid productivity growth in aninput-producing sector. Our empirical results highlight two conditions for new products to becomecentral nodes: initial network proximity to prospective adopters, and technological progress thatreduces their relative price. Semiconductors met both conditions.

Sovereign default, domestic banks and financial institutions

We present a model of sovereign debt in which, contrary to conventional wisdom, government defaultsare costly because they destroy the balance sheets of domestic banks. In our model, better financial institutionsallow banks to be more leveraged, thereby making them more vulnerable to sovereign defaults.Our predictions: government defaults should lead to declines in private credit, and these declines should belarger in countries where financial institutions are more developed and banks hold more government bonds.In these same countries, government defaults should be less likely. Using a large panel of countries, we findevidence consistent with these predictions.

Teachers' attitudes and beliefs about homosexuality

Schools play a key role in transmitting attitudes towards sexual diversity. Many studies stress the importance of teachers" and other professionals" attitudes towards gay men and/or lesbian women. This study evaluates attitudes and prejudices toward homosexuality in a sample of 254 elementary and high school teachers in Barcelona and its surrounding area. The results obtained using a scale of overt and subtle prejudice and a scale of perceived discrepancy of values indicate that discrepancy between likely behavior and personal values was significantly greater in women, those who hold religious beliefs, churchgoers and people without any gay or lesbian acquaintances. Approximately 88% of the teachers showed no type of prejudiced attitudes towards gay men and lesbian women. The experience of proximity to gay men and/or lesbian women reduces not only the discrepancy between personal values and likely behavior but also the presence of homophobic prejudice. It would be advisable to expand specific teacher training in the subject of sexual diversity in order to reduce prejudicial attitudes, thus fostering non-stereotyped knowledge of homosexuality

Beurling-Landau densities of weighted Fekete sets and correlation kernel estimates

Let $Q$ be a suitable real function on $C$. An $n$-Fekete set corresponding to $Q$ is a subset ${Z_{n1}},\dotsb, Z_{nn}}$ of $C$ which maximizes the expression $\Pi^n_i_{hold globally, and we conjecture that such global results are true for a wide range of potentials.