@article{22437, abstract = {Changes in rainfall amounts and patterns have been observed and are expected to continue in the near future with potentially significant ecological and societal consequences. Modelling vegetation responses to changes in rainfall is thus crucial to project water and carbon cycles in the future. In this study, we present the results of a new model‐data intercomparison project, where we tested the ability of 10 terrestrial biosphere models to reproduce the observed sensitivity of ecosystem productivity to rainfall changes at 10 sites across the globe, in nine of which, rainfall exclusion and/or irrigation experiments had been performed. The key results are as follows: (a) Inter‐model variation is generally large and model agreement varies with timescales. In severely water‐limited sites, models only agree on the interannual variability of evapotranspiration and to a smaller extent on gross primary productivity. In more mesic sites, model agreement for both water and carbon fluxes is typically higher on fine (daily–monthly) timescales and reduces on longer (seasonal–annual) scales. (b) Models on average overestimate the relationship between ecosystem productivity and mean rainfall amounts across sites (in space) and have a low capacity in reproducing the temporal (interannual) sensitivity of vegetation productivity to annual rainfall at a given site, even though observation uncertainty is comparable to inter‐model variability. (c) Most models reproduced the sign of the observed patterns in productivity changes in rainfall manipulation experiments but had a low capacity in reproducing the observed magnitude of productivity changes. Models better reproduced the observed productivity responses due to rainfall exclusion than addition. (d) All models attribute ecosystem productivity changes to the intensity of vegetation stress and peak leaf area, whereas the impact of the change in growing season length is negligible. The relative contribution of the peak leaf area and vegetation stress intensity was highly variable among models.}, author = {Paschalis, Athanasios and Fatichi, Simone and Zscheischler, Jakob and Ciais, Philippe and Bahn, Michael and Boysen, Lena and Chang, Jinfeng and De Kauwe, Martin and Estiarte, Marc and Goll, Daniel and Hanson, Paul J. and Harper, Anna B. and Hou, Enqing and Kigel, Jaime and Knapp, Alan K. and Larsen, Klaus S. and Li, Wei and Lienert, Sebastian and Luo, Yiqi and Meir, Patrick and Nabel, Julia E. M. S. and Ogaya, Romà and Parolari, Anthony J. and Peng, Changhui and Peñuelas, Josep and Pongratz, Julia and Rambal, Serge and Schmidt, Inger K. and Shi, Hao and Sternberg, Marcelo and Tian, Hanqin and Tschumi, Elisabeth and Ukkola, Anna and Vicca, Sara and Viovy, Nicolas and Wang, Ying‐Ping and Wang, Zhuonan and Williams, Karina and Wu, Donghai and Zhu, Qiuan}, issn = {1365-2486}, journal = {Global Change Biology}, number = {6}, pages = {3336--3355}, publisher = {Wiley}, title = {{Rainfall manipulation experiments as simulated by terrestrial biosphere models: Where do we stand?}}, doi = {10.1111/gcb.15024}, volume = {26}, year = {2020}, } @article{22473, abstract = {The vadose zone is a zone sensitive to environmental changes and exerts a crucial control in ecosystem functioning and even more so in cold regions considering the rapid change in seasonally frozen ground under climate warming. While the way in representing the underlying physical process of the vadose zone differs among models, the effect of such differences on ecosystem functioning and its ecohydrological response to freeze–thaw cycles are seldom reported. Here, the detailed vadose zone process model STEMMUS (Simultaneous Transfer of Energy, Mass and Momentum in Unsaturated Soil) was coupled with the ecohydrological model Tethys–Chloris (T&C) to investigate the role of influential physical processes during freeze–thaw cycles. The physical representation is increased from using T&C coupling without STEMMUS enabling the simultaneous mass and energy transfer in the soil system (liquid, vapor, ice) – and with explicit consideration of the impact of soil ice content on energy and water transfer properties – to using T&C coupling with it. We tested model performance with the aid of a comprehensive observation dataset collected at a typical meadow ecosystem on the Tibetan Plateau. Results indicated that (i) explicitly considering the frozen soil process significantly improved the soil moisture/temperature profile simulations and facilitated our understanding of the water transfer processes within the soil–plant–atmosphere continuum; (ii) the difference among various representations of vadose zone physics have an impact on the vegetation dynamics mainly at the beginning of the growing season; and (iii) models with different vadose zone physics can predict similar interannual vegetation dynamics, as well as energy, water, and carbon exchanges, at the land surface. This research highlights the important role of vadose zone physics for ecosystem functioning in cold regions and can support the development and application of future Earth system models.}, author = {Yu, Lianyu and Fatichi, Simone and Zeng, Yijian and Su, Zhongbo}, issn = {1994-0424}, journal = {The Cryosphere}, number = {12}, pages = {4653--4673}, publisher = {Copernicus Publications}, title = {{The role of vadose zone physics in the ecohydrological response of a Tibetan meadow to freeze–thaw cycles}}, doi = {10.5194/tc-14-4653-2020}, volume = {14}, year = {2020}, } @article{22458, abstract = {Groundwater can have a critical role in sustaining the functioning of natural ecosystems during droughts, especially in dry and seasonally dry climates. However, the response to droughts of ecosystems embedded in urban areas is not well known. This study investigates how different scenarios of groundwater availability control the water balance and vegetation productivity of two urban reserves hosting native vegetation in the Melbourne metropolitan area, Australia. Using a mechanistic ecohydrological model supported by field observations, long-term simulations were run to explore the impact of groundwater flow on water, carbon, and energy fluxes under present climatic conditions, including the Millennium Drought (2001–2009), and in response to perturbations in key environmental variables (air temperature, atmospheric CO2 concentrations, and rainfall). It was found that the presence of a water table and its capillary fringe within the root depths supports ecosystem transpiration and vegetation productivity. The effects of declining groundwater were found to be more severe in predominantly sandy soils because of the lower water holding capacity, identifying that the water status of vegetation differs significantly depending on soil type. Differences in rooting strategies and groundwater availability also had a pivotal role in helping plants soften the impacts of increased air temperature (Ta) and make use of higher atmospheric CO2 concentrations. Increased Ta strongly affected evapotranspiration, enhancing the competition for water between different vegetation types. These results provide quantitative insights of how vegetation responds to groundwater depletion and climate variability, highlighting the essential role of groundwater resources in urban ecosystems characterized by seasonally dry climates.}, author = {Marchionni, V. and Daly, E. and Manoli, G. and Tapper, N. J. and Walker, J. P. and Fatichi, Simone}, issn = {1944-7973}, journal = {Water Resources Research}, number = {5}, publisher = {American Geophysical Union}, title = {{Groundwater buffers drought effects and climate variability in urban reserves}}, doi = {10.1029/2019wr026192}, volume = {56}, year = {2020}, } @article{22432, abstract = {The boreal biome accounts for approximately one third of the terrestrial carbon (C) sink. However, estimates of its individual C pools remain uncertain. Here, focusing on the southern boreal forest, we quantified the magnitude and temporal dynamics of C allocation to aboveground tree growth at a mature black spruce (Picea mariana)-dominated forest stand in Saskatchewan, Canada. We reconstructed aboveground tree biomass increments (AGBi) using a biometric approach, i.e., species-specific allometry combined with forest stand characteristics and tree ring widths collected with a C-oriented sampling design. We explored the links between boreal tree growth and ecosystem C input by comparing AGBi with eddy-covariance-derived ecosystem C fluxes from 1999 to 2015 and we synthesized our findings with a refined meta-analysis of published values of boreal forest C use efficiency (CUE). Mean AGBi at the study site was decoupled from ecosystem C input and equal to 71 ± 7 g C m–2 (1999–2015), which is only a minor fraction of gross ecosystem production (GEP; i.e., AGBi / GEP ≈ 9 %). Moreover, C allocation to AGBi remained stable over time (AGBi / GEP; –0.0001 yr–1; p-value=0.775), contrary to significant trends in GEP (+5.72 g C m–2 yr–2; p-value=0.02) and CUE (–0.0041 yr–1, p-value=0.007). CUE was estimated as 0.50 ± 0.03 at the study area and 0.41 ± 0.12 across the reviewed boreal forests. These findings highlight the importance of belowground tree C investments, together with the substantial contribution of understory, ground cover and soil to the boreal forest C balance. Our quantitative insights into the dynamics of aboveground boreal tree C allocation offer additional observational constraints for terrestrial ecosystem models that are often biased in converting C input to biomass, and can guide forest-management strategies for mitigating carbon dioxide emissions.}, author = {Pappas, Christoforos and Maillet, Jason and Rakowski, Sharon and Baltzer, Jennifer L. and Barr, Alan G. and Black, T. Andrew and Fatichi, Simone and Laroque, Colin P. and Matheny, Ashley M. and Roy, Alexandre and Sonnentag, Oliver and Zha, Tianshan}, issn = {0168-1923}, journal = {Agricultural and Forest Meteorology}, publisher = {Elsevier}, title = {{Aboveground tree growth is a minor and decoupled fraction of boreal forest carbon input}}, doi = {10.1016/j.agrformet.2020.108030}, volume = {290}, year = {2020}, } @phdthesis{7896, abstract = {A search problem lies in the complexity class FNP if a solution to the given instance of the problem can be verified efficiently. The complexity class TFNP consists of all search problems in FNP that are total in the sense that a solution is guaranteed to exist. TFNP contains a host of interesting problems from fields such as algorithmic game theory, computational topology, number theory and combinatorics. Since TFNP is a semantic class, it is unlikely to have a complete problem. Instead, one studies its syntactic subclasses which are defined based on the combinatorial principle used to argue totality. Of particular interest is the subclass PPAD, which contains important problems like computing Nash equilibrium for bimatrix games and computational counterparts of several fixed-point theorems as complete. In the thesis, we undertake the study of averagecase hardness of TFNP, and in particular its subclass PPAD. Almost nothing was known about average-case hardness of PPAD before a series of recent results showed how to achieve it using a cryptographic primitive called program obfuscation. However, it is currently not known how to construct program obfuscation from standard cryptographic assumptions. Therefore, it is desirable to relax the assumption under which average-case hardness of PPAD can be shown. In the thesis we take a step in this direction. First, we show that assuming the (average-case) hardness of a numbertheoretic problem related to factoring of integers, which we call Iterated-Squaring, PPAD is hard-on-average in the random-oracle model. Then we strengthen this result to show that the average-case hardness of PPAD reduces to the (adaptive) soundness of the Fiat-Shamir Transform, a well-known technique used to compile a public-coin interactive protocol into a non-interactive one. As a corollary, we obtain average-case hardness for PPAD in the random-oracle model assuming the worst-case hardness of #SAT. Moreover, the above results can all be strengthened to obtain average-case hardness for the class CLS ⊆ PPAD. Our main technical contribution is constructing incrementally-verifiable procedures for computing Iterated-Squaring and #SAT. By incrementally-verifiable, we mean that every intermediate state of the computation includes a proof of its correctness, and the proof can be updated and verified in polynomial time. Previous constructions of such procedures relied on strong, non-standard assumptions. Instead, we introduce a technique called recursive proof-merging to obtain the same from weaker assumptions. }, author = {Kamath Hosdurg, Chethan}, issn = {2663-337X}, pages = {126}, publisher = {Institute of Science and Technology Austria}, title = {{On the average-case hardness of total search problems}}, doi = {10.15479/AT:ISTA:7896}, year = {2020}, } @article{22558, abstract = {Heavy rainfall is expected to intensify with increasing temperatures, which will likely affect rainfall spatial characteristics. The spatial variability of rainfall can affect streamflow and sediment transport volumes and peaks. Yet, the effect of climate change on the small-scale spatial structure of heavy rainfall and subsequent impacts on hydrology and geomorphology remain largely unexplored. In this study, the sensitivity of the hydro-morphological response to heavy rainfall at the small-scale resolution of minutes and hundreds of metres was investigated. A numerical experiment was conducted in which synthetic rainfall fields representing heavy rainfall events of two types, stratiform and convective, were simulated using a space-time rainfall generator model. The rainfall fields were modified to follow different spatial rainfall scenarios associated with increasing temperatures and used as inputs into a landscape evolution model. The experiment was conducted over a complex topography, a medium-sized (477 km2) Alpine catchment in central Switzerland. It was found that the responses of the streamflow and sediment yields are highly sensitive to changes in total rainfall volume and to a lesser extent to changes in local peak rainfall intensities. The results highlight that the morphological components are more sensitive to changes in rainfall spatial structure in comparison to the hydrological components. The hydro-morphological features were found to respond more to convective rainfall than stratiform rainfall because of localized runoff and erosion production. It is further shown that assuming heavy rainfall to intensify with increasing temperatures without introducing changes in the rainfall spatial structure might lead to overestimation of future climate impacts on basin hydro-morphology.}, author = {Peleg, Nadav and Skinner, Chris and Fatichi, Simone and Molnar, Peter}, issn = {2196-632X}, journal = {Earth Surface Dynamics}, number = {1}, pages = {17--36}, publisher = {Copernicus Publications}, title = {{Temperature effects on the spatial structure of heavy rainfall modify catchment hydro-morphological response}}, doi = {10.5194/esurf-8-17-2020}, volume = {8}, year = {2020}, } @article{22567, abstract = {Most soil hydraulic information used in Earth System Models (ESMs) is derived from pedo-transfer functions that use easy-to-measure soil attributes to estimate hydraulic parameters. This parameterization relies heavily on soil texture, but overlooks the critical role of soil structure originated by soil biophysical activity. Soil structure omission is pervasive also in sampling and measurement methods used to train pedotransfer functions. Here we show how systematic inclusion of salient soil structural features of biophysical origin affect local and global hydrologic and climatic responses. Locally, including soil structure in models significantly alters infiltration-runoff partitioning and recharge in wet and vegetated regions. Globally, the coarse spatial resolution of ESMs and their inability to simulate intense and short rainfall events mask effects of soil structure on surface fluxes and climate. Results suggest that although soil structure affects local hydrologic response, its implications on global-scale climate remains elusive in current ESMs.}, author = {Fatichi, Simone and Or, Dani and Walko, Robert and Vereecken, Harry and Young, Michael H. and Ghezzehei, Teamrat A. and Hengl, Tomislav and Kollet, Stefan and Agam, Nurit and Avissar, Roni}, issn = {2041-1723}, journal = {Nature Communications}, publisher = {Springer Nature}, title = {{Soil structure is an important omission in Earth System Models}}, doi = {10.1038/s41467-020-14411-z}, volume = {11}, year = {2020}, } @article{22565, abstract = {Solutes in rivers often come from multiple sources, notably precipitation (above) and generation from the subsurface (below). The question of which source is more influential in shaping the dynamics of solute concentration cannot be easily addressed due to the general lack of input data. An analysis of solute concentrations and their dependence on discharge across 585 catchments in nine countries leads us to hypothesize that both the timing and the vertical distribution of the solute generation are important drivers of solute export dynamics at the catchment scale. We test this hypothesis running synthetic experiments with a tracer-aided distributed hydrological model. The results reveal that the depth of solute generation is the most important control of the concentration-discharge (C-Q) relation for a number of solutes. Such relation shows that C-Q patterns of solute export vary from dilution (Ca2+, Mg2+, K+, Na+, and Cl−) to weakly enriching (dissolved organic carbon). The timing of the input imposes a signature on temporal dynamics, most evident for nutrients, and adds uncertainty in the exponent of the C-Q relation.}, author = {Botter, M. and Li, L. and Hartmann, J. and Burlando, P. and Fatichi, Simone}, issn = {1944-7973}, journal = {Water Resources Research}, number = {8}, publisher = {American Geophysical Union}, title = {{Depth of solute generation is a dominant control on concentration‐discharge relations}}, doi = {10.1029/2019wr026695}, volume = {56}, year = {2020}, } @article{179, abstract = {An asymptotic formula is established for the number of rational points of bounded anticanonical height which lie on a certain Zariski dense subset of the biprojective hypersurface x1y21+⋯+x4y24=0 in ℙ3×ℙ3. This confirms the modified Manin conjecture for this variety, in which the removal of a thin set of rational points is allowed.}, author = {Browning, Timothy D and Heath Brown, Roger}, issn = {0012-7094}, journal = {Duke Mathematical Journal}, number = {16}, pages = {3099--3165}, publisher = {Duke University Press}, title = {{Density of rational points on a quadric bundle in ℙ3×ℙ3}}, doi = {10.1215/00127094-2020-0031}, volume = {169}, year = {2020}, } @article{177, abstract = {We develop a geometric version of the circle method and use it to compute the compactly supported cohomology of the space of rational curves through a point on a smooth affine hypersurface of sufficiently low degree.}, author = {Browning, Timothy D and Sawin, Will}, journal = {Annals of Mathematics}, number = {3}, pages = {893--948}, publisher = {Princeton University}, title = {{A geometric version of the circle method}}, doi = {10.4007/annals.2020.191.3.4}, volume = {191}, year = {2020}, } @article{22520, abstract = {Increasing urbanization is likely to intensify the urban heat island effect, decrease outdoor thermal comfort, and enhance runoff generation in cities. Urban green spaces are often proposed as a mitigation strategy to counteract these adverse effects, and many recent developments of urban climate models focus on the inclusion of green and blue infrastructure to inform urban planning. However, many models still lack the ability to account for different plant types and oversimplify the interactions between the built environment, vegetation, and hydrology. In this study, we present an urban ecohydrological model, Urban Tethys-Chloris (UT&C), that combines principles of ecosystem modelling with an urban canopy scheme accounting for the biophysical and ecophysiological characteristics of roof vegetation, ground vegetation, and urban trees. UT&C is a fully coupled energy and water balance model that calculates 2 m air temperature, 2 m humidity, and surface temperatures based on the infinite urban canyon approach. It further calculates the urban hydrological fluxes in the absence of snow, including transpiration as a function of plant photosynthesis. Hence, UT&C accounts for the effects of different plant types on the urban climate and hydrology, as well as the effects of the urban environment on plant well-being and performance. UT&C performs well when compared against energy flux measurements of eddy-covariance towers located in three cities in different climates (Singapore, Melbourne, and Phoenix). A sensitivity analysis, performed as a proof of concept for the city of Singapore, shows a mean decrease in 2 m air temperature of 1.1 ∘C for fully grass-covered ground, 0.2 ∘C for high values of leaf area index (LAI), and 0.3 ∘C for high values of Vc,max (an expression of photosynthetic capacity). These reductions in temperature were combined with a simultaneous increase in relative humidity by 6.5 %, 2.1 %, and 1.6 %, for fully grass-covered ground, high values of LAI, and high values of Vc,max, respectively. Furthermore, the increase of pervious vegetated ground is able to significantly reduce surface runoff.}, author = {Meili, Naika and Manoli, Gabriele and Burlando, Paolo and Bou-Zeid, Elie and Chow, Winston T. L. and Coutts, Andrew M. and Daly, Edoardo and Nice, Kerry A. and Roth, Matthias and Tapper, Nigel J. and Velasco, Erik and Vivoni, Enrique R. and Fatichi, Simone}, issn = {1991-9603}, journal = {Geoscientific Model Development}, number = {1}, pages = {335--362}, publisher = {Copernicus Publications}, title = {{An urban ecohydrological model to quantify the effect of vegetation on urban climate and hydrology (UT&C v1.0)}}, doi = {10.5194/gmd-13-335-2020}, volume = {13}, year = {2020}, } @article{22526, abstract = {Climate change can reduce surface-water supply by enhancing evapotranspiration in forested mountains, especially during heatwaves. We investigate this ‘drought paradox’ for the European Alps using a 1,212-station database and hyper-resolution ecohydrological simulations to quantify blue (runoff) and green (evapotranspiration) water fluxes. During the 2003 heatwave, evapotranspiration in large areas over the Alps was above average despite low precipitation, amplifying the runoff deficit by 32% in the most runoff-productive areas (1,300–3,000 m above sea level). A 3 °C air temperature increase could enhance annual evapotranspiration by up to 100 mm (45 mm on average), which would reduce annual runoff at a rate similar to a 3% precipitation decrease. This suggests that green-water feedbacks—which are often poorly represented in large-scale model simulations—pose an additional threat to water resources, especially in dry summers. Despite uncertainty in the validation of the hyper-resolution ecohydrological modelling with observations, this approach permits more realistic predictions of mountain region water availability.}, author = {Mastrotheodoros, Theodoros and Pappas, Christoforos and Molnar, Peter and Burlando, Paolo and Manoli, Gabriele and Parajka, Juraj and Rigon, Riccardo and Szeles, Borbala and Bottazzi, Michele and Hadjidoukas, Panagiotis and Fatichi, Simone}, issn = {1758-6798}, journal = {Nature Climate Change}, pages = {155--161}, publisher = {Springer Nature}, title = {{More green and less blue water in the Alps during warmer summers}}, doi = {10.1038/s41558-019-0676-5}, volume = {10}, year = {2020}, } @article{22542, abstract = {Temporal dynamics of urban warming have been extensivelystudied at the diurnal scale, but the impact of background cli-mate on the observed seasonality of surface urban heat islands(SUHIs) remains largely unexplored. On seasonal time scales, theintensity of urban–rural surface temperature differences (∆Ts)exhibits distinctive hysteretic cycles whose shape and loopingdirection vary across climatic zones. These observations high-light possible delays underlying the dynamics of the coupledurban–biosphere system. However, a general argument explain-ing the observed hysteretic patterns remains elusive. A coarse-grained model of SUHI coupled with a stochastic soil waterbalance is developed to demonstrate that the time lags betweenradiation forcing, air temperature, and rainfall generate a rate-dependent hysteresis, explaining the observed seasonal varia-tions of ∆Ts. If solar radiation is in phase with water availability,summer conditions cause strong SUHI intensities due to highrural evaporative cooling. Conversely, cities in seasonally dryregions where evapotranspiration is out of phase with radia-tion show a summertime oasis effect controlled by backgroundclimate and vegetation properties. These seasonal patterns ofwarming and cooling have significant implications for heat mit-igation strategies as urban green spaces can reduce ∆Ts duringsummertime, while potentially negative effects of albedo man-agement during winter are mitigated by the seasonality of solarradiation.}, author = {Manoli, Gabriele and Fatichi, Simone and Bou-Zeid, Elie and Katul, Gabriel G.}, issn = {1091-6490}, journal = {Proceedings of the National Academy of Sciences}, keywords = {Cities, Hysteresis, Seasonality, Surface temperature, Urban heat island}, number = {13}, pages = {7082--7089}, publisher = {National Academy of Sciences}, title = {{Seasonal hysteresis of surface urban heat islands}}, doi = {10.1073/pnas.1917554117}, volume = {117}, year = {2020}, } @article{14891, abstract = {We give the first mathematically rigorous justification of the local density approximation in density functional theory. We provide a quantitative estimate on the difference between the grand-canonical Levy–Lieb energy of a given density (the lowest possible energy of all quantum states having this density) and the integral over the uniform electron gas energy of this density. The error involves gradient terms and justifies the use of the local density approximation in the situation where the density is very flat on sufficiently large regions in space.}, author = {Lewin, Mathieu and Lieb, Elliott H. and Seiringer, Robert}, issn = {2578-5885}, journal = {Pure and Applied Analysis}, number = {1}, pages = {35--73}, publisher = {Mathematical Sciences Publishers}, title = {{The local density approximation in density functional theory}}, doi = {10.2140/paa.2020.2.35}, volume = {2}, year = {2020}, } @article{7388, abstract = {We give a Wong-Zakai type characterisation of the solutions of quasilinear heat equations driven by space-time white noise in 1 + 1 dimensions. In order to show that the renormalisation counterterms are local in the solution, a careful arrangement of a few hundred terms is required. The main tool in this computation is a general ‘integration by parts’ formula that provides a number of linear identities for the renormalisation constants.}, author = {Gerencser, Mate}, issn = {0294-1449}, journal = {Annales de l'Institut Henri Poincaré C}, number = {3}, pages = {663--682}, publisher = {Elsevier}, title = {{Nondivergence form quasilinear heat equations driven by space-time white noise}}, doi = {10.1016/j.anihpc.2020.01.003}, volume = {37}, year = {2020}, } @inproceedings{8536, abstract = {This work analyzes the latency of the simplified successive cancellation (SSC) decoding scheme for polar codes proposed by Alamdar-Yazdi and Kschischang. It is shown that, unlike conventional successive cancellation decoding, where latency is linear in the block length, the latency of SSC decoding is sublinear. More specifically, the latency of SSC decoding is O(N 1−1/µ ), where N is the block length and µ is the scaling exponent of the channel, which captures the speed of convergence of the rate to capacity. Numerical results demonstrate the tightness of the bound and show that most of the latency reduction arises from the parallel decoding of subcodes of rate 0 and 1.}, author = {Mondelli, Marco and Hashemi, Seyyed Ali and Cioffi, John and Goldsmith, Andrea}, booktitle = {IEEE International Symposium on Information Theory}, isbn = {9781728164328}, issn = {2157-8095}, location = {Los Angeles, CA, United States}, publisher = {IEEE}, title = {{Simplified successive cancellation decoding of polar codes has sublinear latency}}, doi = {10.1109/ISIT44484.2020.9174141}, volume = {2020-June}, year = {2020}, } @article{7651, abstract = {The growth of snail shells can be described by simple mathematical rules. Variation in a few parameters can explain much of the diversity of shell shapes seen in nature. However, empirical studies of gastropod shell shape variation typically use geometric morphometric approaches, which do not capture this growth pattern. We have developed a way to infer a set of developmentally descriptive shape parameters based on three-dimensional logarithmic helicospiral growth and using landmarks from two-dimensional shell images as input. We demonstrate the utility of this approach, and compare it to the geometric morphometric approach, using a large set of Littorina saxatilis shells in which locally adapted populations differ in shape. Our method can be modified easily to make it applicable to a wide range of shell forms, which would allow for investigations of the similarities and differences between and within many different species of gastropods.}, author = {Larsson, J. and Westram, Anja M and Bengmark, S. and Lundh, T. and Butlin, R. K.}, issn = {1742-5662}, journal = {Journal of the Royal Society Interface}, number = {163}, publisher = {Royal Society}, title = {{A developmentally descriptive method for quantifying shape in gastropod shells}}, doi = {10.1098/rsif.2019.0721}, volume = {17}, year = {2020}, } @article{7431, abstract = {In many real-world systems, information can be transmitted in two qualitatively different ways: by copying or by transformation. Copying occurs when messages are transmitted without modification, e.g. when an offspring receives an unaltered copy of a gene from its parent. Transformation occurs when messages are modified systematically during transmission, e.g. when mutational biases occur during genetic replication. Standard information-theoretic measures do not distinguish these two modes of information transfer, although they may reflect different mechanisms and have different functional consequences. Starting from a few simple axioms, we derive a decomposition of mutual information into the information transmitted by copying versus the information transmitted by transformation. We begin with a decomposition that applies when the source and destination of the channel have the same set of messages and a notion of message identity exists. We then generalize our decomposition to other kinds of channels, which can involve different source and destination sets and broader notions of similarity. In addition, we show that copy information can be interpreted as the minimal work needed by a physical copying process, which is relevant for understanding the physics of replication. We use the proposed decomposition to explore a model of amino acid substitution rates. Our results apply to any system in which the fidelity of copying, rather than simple predictability, is of critical relevance.}, author = {Kolchinsky, Artemy and Corominas-Murtra, Bernat}, issn = {1742-5662}, journal = {Journal of the Royal Society Interface}, number = {162}, publisher = {Royal Society}, title = {{Decomposing information into copying versus transformation}}, doi = {10.1098/rsif.2019.0623}, volume = {17}, year = {2020}, } @misc{9814, abstract = {Data and mathematica notebooks for plotting figures from Language learning with communication between learners}, author = {Ibsen-Jensen, Rasmus and Tkadlec, Josef and Chatterjee, Krishnendu and Nowak, Martin}, publisher = {Royal Society}, title = {{Data and mathematica notebooks for plotting figures from language learning with communication between learners from language acquisition with communication between learners}}, doi = {10.6084/m9.figshare.5973013.v1}, year = {2020}, } @article{7563, abstract = {We introduce “state space persistence analysis” for deducing the symbolic dynamics of time series data obtained from high-dimensional chaotic attractors. To this end, we adapt a topological data analysis technique known as persistent homology for the characterization of state space projections of chaotic trajectories and periodic orbits. By comparing the shapes along a chaotic trajectory to those of the periodic orbits, state space persistence analysis quantifies the shape similarity of chaotic trajectory segments and periodic orbits. We demonstrate the method by applying it to the three-dimensional Rössler system and a 30-dimensional discretization of the Kuramoto–Sivashinsky partial differential equation in (1+1) dimensions. One way of studying chaotic attractors systematically is through their symbolic dynamics, in which one partitions the state space into qualitatively different regions and assigns a symbol to each such region.1–3 This yields a “coarse-grained” state space of the system, which can then be reduced to a Markov chain encoding all possible transitions between the states of the system. While it is possible to obtain the symbolic dynamics of low-dimensional chaotic systems with standard tools such as Poincaré maps, when applied to high-dimensional systems such as turbulent flows, these tools alone are not sufficient to determine symbolic dynamics.4,5 In this paper, we develop “state space persistence analysis” and demonstrate that it can be utilized to infer the symbolic dynamics in very high-dimensional settings.}, author = {Yalniz, Gökhan and Budanur, Nazmi B}, issn = {1089-7682}, journal = {Chaos}, number = {3}, publisher = {AIP Publishing}, title = {{Inferring symbolic dynamics of chaotic flows from persistence}}, doi = {10.1063/1.5122969}, volume = {30}, year = {2020}, }