Operator Product Expansion for Pure Spinor Superstring on AdS(5)*S(5)

The tree-level operator product expansion coefficients of the matter currents are calculated in the pure spinor formalism for type IIB superstring in the AdS(5)*S(5) background.Comment: 18 pages, no figure, corrected typos and added acknowledgement

On the Non-renormalization of the AdS Radius

We show that the relation between the 't Hooft coupling and the radius of AdS is not renormalized at one-loop in the sigma model perturbation theory. We prove this by computing the quantum effective action for the superstring on AdS_5 x S^5 and showing that it does not receive any finite alpha' corrections. We also show that the central charge of the interacting worldsheet conformal field theory vanishes at one-loop.Comment: 13 pages, harvmac. v2: refs added, version to be published on JHE

Use of National Forest Inventories to Downscale European Forest Diversity Spatial Information in Five Test Areas, Covering Different Geo-Physical and Geo-Botanical Conditions

The project ¿Use of National Forest Inventories to downscale European forest diversity spatial information in five test areas, covering different geo-physical and geo-botanical conditions¿, referred also as ¿forest downscaling¿ (JRC contract 382340 F1SC) covers one of the seven topics that have been studied in the frame of the Regulation (EC) 2152/2003 on the monitoring of forest and environmental interactions, the so-called "Forest Focus" Regulation. This study was conducted by a European consortium coordinated by the Italian Academy of Forest Sciences (Italy) and included partners from the Swedish University of Agricultural Sciences, the Institute of Forest Ecosystem Research of the Czech Republic, the German Federal Research Centre for Forestry and Forest Products, and the Swiss Federal Institute for Forest, Snow and Landscape Research. The overall supervision of the project and the processing of forest spatial pattern were done by the Joint Research Centre. This study addressed the link between field based forest biological diversity data and landscape-level forest pattern information. The former were made available from National Forest Inventories (NFIs) at plot level in five different countries; their harmonisation was implemented for the first time and benefited from outcomes of the COST Action-E43 on core biodiversity variables. For the latter, landscape level forest spatial pattern maps were automatically derived from available remote sensing based forest cover maps. The relation-ships between selected pattern and biodiversity variables available from the two different data sources were studied. Seven case studies for a total area of about 100,000 km2 were selected in five European ecological regions: one site in Germany (Atlantic zone), one in Sweden (Boreal zone), two in Czech Republic (Continental zone), one in Switzerland (Alpine zone) and two in Italy (Mediterranean zone).JRC.DDG.H.7-Land management and natural hazard

First-principles derivation of the AdS/CFT Y-systems

We provide a first-principles, perturbative derivation of the AdS5/CFT4 Y-system that has been proposed to solve the spectrum problem of N=4 SYM. The proof relies on the computation of quantum effects in the fusion of some loop operators, namely the transfer matrices. More precisely we show that the leading quantum corrections in the fusion of transfer matrices induce the correct shifts of the spectral parameter in the T-system. As intermediate steps we study UV divergences in line operators up to first order and compute the fusion of line operators up to second order for the pure spinor string in AdS5xS5. We also argue that the derivation can be easily extended to other integrable models, some of which describe string theory on AdS4, AdS3 and AdS2 spacetimes.Comment: 45 pages, 5 figures; v2: minor additions, JHEP versio

Context-dependent plant traits drive fine-scale species persistence in old-growth forests

Questions: we studied old growth beech forest vegetation in Permanent Monitoring Plots (PMPs) located in Italy, with the following questions: is species turnover the main component of the observed changes or the present species assemblages is an impoverished sub-sets of the former ones?; 2) how compositional changes are reflected by specific plant functional traits? Location: we selected 4 PMPs (50 x 50 m) of the CONECOFOR network, placed along a latitudinal and climatic gradient in Italy, from south to north: CALABRIA03, CAMPANIA04, ABRUZZO01 and VENETO20. Methods: presence/absence of herb layer species were recorded in 100 permanent micro-plots of 50 x 50 cm over 12 years (1999-2011). For all sampled species we chose a set of 8 easy-to-measure functional traits. We compared the persistence, nestedness and turnover components of compositional changes. The role of plant traits explaining species persistence were analyzed by classification and regression tree. Results: Analysis in species diversity reveal antithetical ecological phenomena due to the diversity and complexity of the 4 different forest stands. ABRUZZO01 and CALABRIA03 show a clear nestedness trends over time with persistent species in ABR01 having higher seed mass and persistent species in CALABRIA03 having scleromorphic leaves and mesoporphic leaves, with large below-ground budbank. On the other hand, VENETO20 and CAMPANIA04 exibit a significant turnover trends over the 12 years characterized by persistent species in VENETO20 having helomorphic leaves, while in CAMPANIA04 large below-ground budbank and smaller SLA were the most important traits for species survival. Conclusion: Fine-scale approach highlight different mechanisms for the maintenance of species diversity in different complex forest systems driven significantly by specific traits, influenced by context-dependent factors

Algebra of Lax Connection for T-Dual Models

We study relation between T-duality and integrability. We develop the Hamiltonian formalism for principal chiral model on general group manifold and on its T-dual image. We calculate the Poisson bracket of Lax connections in T-dual model and we show that they are non-local as opposite to the Poisson brackets of Lax connection in original model. We demonstrate these calculations on two specific examples: Sigma model on S(2) and sigma model on AdS(2).Comment: 24 pages, references adde

Quantum Current Algebra for the AdS5×S5AdS_5 \times S^5 Superstring

The sigma model describing the dynamics of the superstring in the $AdS_5 \times S^5$ background can be constructed using the coset $PSU(2,2|4)/SO(4,1)\times SO(5)$. A basic set of operators in this two dimensional conformal field theory is composed by the left invariant currents. Since these currents are not (anti) holomorphic, their OPE's is not determined by symmetry principles and its computation should be performed perturbatively. Using the pure spinor sigma model for this background, we compute the one-loop correction to these OPE's. We also compute the OPE's of the left invariant currents with the energy momentum tensor at tree level and one loop.Comment: 28 pages, 12 figures, v2: typos corrected

Plant functional traits are correlated with species persistence in the herb layer of old-growth beech forests

This paper explores which traits are correlated with fine-scale (0.25 m2) species persistence patterns in the herb layer of old-growth forests. Four old-growth beech forests representing different climatic contexts (presence or absence of summer drought period) were selected along a north–south gradient in Italy. Eight surveys were conducted in each of the sites during the period spanning 1999–2011. We found that fine-scale species persistence was correlated with different sets of plant functional traits, depending on local ecological context. Seed mass was found to be as important for the fine-scale species persistence in the northern sites, while clonal and bud-bank traits were markedly correlated with the southern sites characterised by summer drought. Leaf traits appeared to correlate with species persistence in the drier and wetter sites. However, we found that different attributes, i.e. helomorphic vs scleromorphic leaves, were correlated to species persistence in the northernmost and southernmost sites, respectively. These differences appear to be dependent on local trait adaptation rather than plant phylogenetic history. Our findings suggest that the persistent species in the old-growth forests might adopt an acquisitive resource-use strategy (i.e. helomorphic leaves with high SLA) with higher seed mass in sites without summer drought, while under water-stressed conditions persistent species have a conservative resource-use strategy (i.e. scleromorphic leaves with low SLA) with an increased importance of clonal and resprouting ability

Plant functional traits are correlated with species persistence in the herb layer of old-growth beech forests

This paper explores which traits are correlated with fine-scale (0.25 m2) species persistence patterns in the herb layer of old-growth forests. Four old-growth beech forests representing different climatic contexts (presence or absence of summer drought period) were selected along a north–south gradient in Italy. Eight surveys were conducted in each of the sites during the period spanning 1999–2011. We found that fine-scale species persistence was correlated with different sets of plant functional traits, depending on local ecological context. Seed mass was found to be as important for the fine-scale species persistence in the northern sites, while clonal and bud-bank traits were markedly correlated with the southern sites characterised by summer drought. Leaf traits appeared to correlate with species persistence in the drier and wetter sites. However, we found that different attributes, i.e. helomorphic vs scleromorphic leaves, were correlated to species persistence in the northernmost and southernmost sites, respectively. These differences appear to be dependent on local trait adaptation rather than plant phylogenetic history. Our findings suggest that the persistent species in the old-growth forests might adopt an acquisitive resource-use strategy (i.e. helomorphic leaves with high SLA) with higher seed mass in sites without summer drought, while under water-stressed conditions persistent species have a conservative resource-use strategy (i.e. scleromorphic leaves with low SLA) with an increased importance of clonal and resprouting ability

The dual string sigma-model of the SU_q(3) sector

In four-dimensional N=4 super Yang-Mills (SYM) the SU(3) sub-sector spanned by purely holomorphic fields is isomorphic to the corresponding mixed one spanned by both holomorphic and antiholomorphic fields. This is no longer the case when one considers the marginally deformed N=4 SYM. The mixed SU(3) sector marginally deformed by a complex parameter beta, i.e. SU_q(3) with q=e^{2 i\pi\beta}, has been shown to be integrable at one-loop hep-th/0703150, while it is not the case for the corresponding purely holomorphic one. Moreover, the marginally deformed N=4 SYM also has a gravity dual constructed by Lunin and Maldacena in hep-th/0502086. However, the mixed SU_q(3) sector has not been studied from the supergravity point of view. Hence in this note, for the case of purely imaginary marginal $\beta$-deformations, we compute the superstring SU_q(3) \sigma-model in the fast spinning string limit and show that, for rational spinning strings, it reproduces the energy computed via Bethe equations.Comment: 20 page