Moduli spaces of parabolic U(p,q)U(p,q)-Higgs bundles

Using the $L^2$-norm of the Higgs field as a Morse function, we count the number of connected components of the moduli space of parabolic $U(p,q)$-Higgs bundles over a Riemann surface with a finite number of marked points, under certain genericity conditions on the parabolic structure. This space is homeomorphic to the moduli space of representations of the fundamental group of the punctured surface in $U(p,q)$, with fixed compact holonomy classes around the marked points. We apply our results to the study of representations of the fundamental group of elliptic surfaces of general type.Comment: 46 pages, no figures. Corrected typos, added remarks. To appear in "Quarterly Journal of Mathematics

Improving agricultural production and food security under climate change conditions

[EN] Climate change represents a major challenge for food security in the coming years, as it is causing a significant reduction of crop yields worldwide, primarily due to the increase in the intensity and frequency of drought periods and the progressive salinisation of irrigated farmland. The best strategy to improve agricultural production appears to be the development of drought and salt-tolerant crop cultivars. Intensive research and promising results in recent years show that this objective will be reached soon, applying classical breeding (supported by modern molecular tools) and plant genetic transformation. In addition, domestication and commercial cultivation of stress-tolerant wild species will also help increase food production. In the meantime, other strategies will contribute, even if more modestly, to enhance stress tolerance and improve crop yields in the frame of sustainable agriculture. They could include using 'new generation' controlled-release fertilisers to optimise plant nutrition or applying a collection of unrelated substances and beneficial microorganisms with activity as 'biostimulants'. In this paper, some examples of these approaches will be discussed, with reference to recent reviews for further readingVicente, O. (2022). Improving agricultural production and food security under climate change conditions. AgroLife Scientific Journal. 11(1):241-252. https://doi.org/10.17930/AGL202212824125211

Government deficit sustainability, and monetary versus fiscal dominance: The case of Spain, 1850-2000

In this paper, we provide a test of the sustainability of the Spanish government deficit over the period 1850-2000, and examine the role played by monetary and fiscal dominance in order to get fiscal solvency. The longer than usual span of the data would allow us to obtain some more robust results on the fulfilling of the intertemporal budget constraint than in most of previous analyses. First, we analyze the relationship between primary surplus and debt, following the recent critique of Bohn (2007), and investigate the possibility of structural changes occurring along the period by means of the new approach of Kejriwal and Perron (2008). The analysis is complemented in two directions: (i) performing Granger-causality tests in order to distinguish properly between a fiscal dominant and a monetary dominant regime; and (ii) presenting the impulse-response functions of debt to innovations in the primary surplus, through the approach of Canzoneri, Cumby and Diba (2001).Fiscal policy, Sustainability, Fiscal Theory of the Price Level, Monetary dominance, Fiscal dominance.

Is the Budget Deficit Sustainable when Fiscal Policy is nonlinear? The Case of Spain, 1961-2001

In this paper we re-examine the long-run sustainability of budget deficits, when fiscal policy is conducted as a nonlinear process. Our empirical methodology makes use of recent developments on threshold cointegration that consider the possibility of a nonlinear relationship between government revenues and expenditures. The analysis is applied to the case of Spain, a country that has recently accomplished an important fiscal consolidation. Overall, our results suggest the presence of significant nonlinear effects in Spanish fiscal policy, so that fiscal authorities would cut deficits only if they are “large”, and assuring their long-run sustainability.Fiscal policy, Sustainability, Threshold cointegration.

On the sustainability of government deficits: some long-term evidence for Spain, 1850-2000

We provide a test of the sustainability of the Spanish government deficit over the period 1850-2000, from the estimation of a cointegration relationship between government expenditures and revenues derived from the intertemporal budget constraint. The longer than usual span of the data allows us to obtain more robust results on the fulfilment of the intertemporal budget constraint than most of the previous analyses. Two additional robustness checks are provided. First, we investigate the possibility of structural changes occurring along the period analyzed, using the new approach of Kejriwal and Perron (2008, 2010) to testing for multiple structural changes in cointegrated regression models. Second, we investigate whether the behaviour of fiscal authorities has been non-linear, by means of the procedure of Hansen and Seo (2002) based on a threshold cointegration model. Our results show that (i) the government deficit has been strongly sustainable in the long run, (ii) no evidence is found on any significant structural break throughout the whole period, and (iii) fiscal sustainability has been attained due to the non-linear behaviour of fiscal authorities, which have only acted on the budget deficit when it has exceeded around 4.5% of GDP.fiscal policy, sustainability, structural change, threshold cointegration, nonlinearity

Deficit sustainability and inflation in EMU: An analysis from the fiscal theory of the price level

Price determination theory typically focuses on monetary plicy, while the role of fiscal policy is ussually neglected. From a different point of view, the Fiscal Theory of Price Level takes into account monetary and fiscal policy interactions and assumes that fiscal policy may determine the price level, even if monetary authorities pursue an inflation targeting strategy. In this paper we try to test empirically whether the time path of the government budget in EMU countries would have affected price level determination. Our results point to the sustainability of fiscal policy in all the EMU countries but Finland, although no firm conclusions can be drawn about the prevalence of either monetary or fiscal dominance.Fiscal Theory of the Price Level, monetary and fiscal dominance, central bank independence, fiscal solvency, inflation

Change of regime and Phillips curve stability:The case of Spain, 1964-2002

Traditional Phillips curves relating inflation to a measure of the level of activity, and augmented to include past inflation (assumed to proxy expected inflation), have been thought to be highly unstable over time. In this paper we try to investigate, using recent econometric developments, whether such a statement can be supported over a long time period. In the empirical application, we analyze the case of Spain along the period 1964 to 2002.Structural changes, Inflation, Phillips curve

Will halophytes in Mediterranean salt marshes be able to adapt to climate change?

[EN] Mediterranean salt marshes are fragile ecosystems, highly susceptible to the effects of climate change, inhabited by a characteristic halophytic flora, which includes abundant and widely distributed `structural¿ halophytes, together with rare species of high ecological value. These plants are distributed along salinity gradients, primarily based on their relative salt tolerance; they are also adapted to the high temperatures and drought characteristic of Mediterranean summers. With periods of drought and heatwaves increasingly frequent and intense, global warming will also cause a rise in soil salinity. These changes could affect the distribution of some species, reducing their populations or even leading to the local disappearance of some taxa. Over the last years, we have investigated the salt and water stress responses of halophytes of several genera, in field studies and under greenhouse conditions. In this communication, we will present results showing that at least some of the species investigated possess mechanisms that can allow them to rapidly adapt and survive the climate change-induced alterations of the environment in their natural habitats.The initial fieldwork was funded by a grant to O. Vicente from the Spanish Ministry of Science and Innovation (Project CGL2008-00438/BOS), with contribution from the European Regional Development Fund. More recent work was partly supported by Project AICO/2017/039 from Generalitat Valenciana, granted to M. Boscaiu, and by internal funds of Universitat Politecnica de Valencia.Vicente, O.; Boscaiu, M. (2020). Will halophytes in Mediterranean salt marshes be able to adapt to climate change?. AgroLife Scientific Journal (Online). 9(2):369-376. http://hdl.handle.net/10251/166336S3693769