Browsing by Subject "CONSTRAINTS"

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  • Reum, Friedemann; Goeckede, Mathias; Lavric, Jost V.; Kolle, Olaf; Zimov, Sergey; Zimov, Nikita; Pallandt, Martijn; Heimann, Martin (2019)
    Sparse data coverage in the Arctic hampers our understanding of its carbon cycle dynamics and our predictions of the fate of its vast carbon reservoirs in a changing climate. In this paper, we present accurate measurements of atmospheric carbon dioxide (CO2) and methane (CH4) dry air mole fractions at the new atmospheric carbon observation station Ambarchik, which closes a large gap in the atmospheric trace gas monitoring network in northeastern Siberia. The site, which has been operational since August 2014, is located near the delta of the Kolyma River at the coast of the Arctic Ocean. Data quality control of CO2 and CH4 measurements includes frequent calibrations traced to World Meteorological Organization (WMO) scales, employment of a novel water vapor correction, an algorithm to detect the influence of local polluters, and meteorological measurements that enable data selection. The available CO2 and CH4 record was characterized in comparison with in situ data from Barrow, Alaska. A footprint analysis reveals that the station is sensitive to signals from the East Siberian Sea, as well as the northeast Siberian tundra and taiga regions. This makes data from Ambarchik highly valuable for inverse modeling studies aimed at constraining carbon budgets within the pan-Arctic domain, as well as for regional studies focusing on Siberia and the adjacent shelf areas of the Arctic Ocean.
  • Lebedev, Oleg; Mambrini, Yann (2014)
  • Pineda-Munoz, Silvia; Jukar, Advait M.; Toth, Aniko B.; Fraser, Danielle; Du, Andrew; Barr, W. Andrew; Amatangelo, Kathryn L.; Balk, Meghan A.; Behrensmeyer, Anna K.; Blois, Jessica; Davis, Matt; Eronen, Jussi T.; Gotelli, Nicholas J.; Looy, Cindy; Miller, Joshua H.; Shupinski, Alexandria B.; Soul, Laura C.; Villasenor, Amelia; Wing, Scott; Lyons, S. Kathleen (2021)
    The late Quaternary of North America was marked by prominent ecological changes, including the end-Pleistocene megafaunal extinction, the spread of human settlements and the rise of agriculture. Here we examine the mechanistic reasons for temporal changes in mammal species association and body size during this time period. Building upon the co-occurrence results from Lyons et al. (2016) - wherein each species pair was classified as spatially aggregated, segregated or random - we examined body mass differences (BMD) between each species pair for each association type and time period (Late Pleistocene: 40 000(14)C-11 700(14)C ybp, Holocene: 11 700(14)C-50 ybp and Modern: 50-0 yr). In the Late Pleistocene and Holocene, the BMD of both aggregated and segregated species pairs was significantly smaller than the BMD of random pairs. These results are consistent with environmental filtering and competition as important drivers of community structure in both time periods. Modern assemblages showed a breakdown between BMD and co-occurrence patterns: the average BMD of aggregated, segregated and random species pairs did not differ from each other. Collectively, these results indicate that the late Quaternary mammalian extinctions not only eliminated many large-bodied species but were followed by a re-organization of communities that altered patterns of species coexistence and associated differences in body size.
  • Hassan, Badal A; Glover, Edinam K.; Luukkanen, Olavi; Kanninen, Markku; Jamnadass, Ramni (2019)
    The dryland vegetation and particularly the Acacia-Commiphora woodlands support the livelihoods of approximately 52 million rural households in the Horn of Africa. Aromatic resins are valuable non-wood forest products (NWFPs) derived from Boswellia and Commiphora species in the drylands of this region. The study seeks to answer the following main questions: “What are the ecological and livelihood roles of resin producing species, and the role that people have in either degrading or restoring these ecosystems?” “Who are the participants in frankincense and myrrh production, processing, and trade, and how do these people interact?” “What is the current and potential future economic impact of frankincense and myrrh production and trade at the household level?” “What are the barriers to enhanced economic outcomes?” The study involves the use of PRISMA method—a systematic methodology to identify, select and analyze the recent literature on aromatic resins in relation to such factors as socio-economic situation, livelihood security, value chain, climate change adaptation, ecology and sustainable development in the Horn of Africa. Systematic identification of publications was conducted using several sources, including but not limited to electronic databases for literature search. Web of Science, Social Science Citation Index and Google Scholar and various scientific journals were investigated using search terms and restrictions. A total of 991 references were retrieved, but literature only published between 2003 to 2017 was selected, which led to the use of 51 works for full-text assessment. The results indicate that of the 51 selected studies, 45% focused on ecology and sustainable management, 31% on economic contribution and livelihood security, 20% on production and value chain development, and 4% on climate change adaptation and mitigation. It could be concluded that farmers’ adoption of Boswellia and Commiphora species as economic tree crops in the Horn of Africa has a distinct role in biodiversity conservation and climate change adaptation by contributing to the sustainability of ecosystem functioning as well as improving household incomes and the rural livelihood security in general, and thereby facilitating poverty alleviation.
  • Beltran Almeida, Juan P.; Bernal, Nicolas; Bettoni, Dario; Rubio, Javier (2020)
    We consider an UV-protected Natural Inflation scenario involving Chern-Simonslike interactions between the inflaton and some beyond the Standard Model gauge fields. The accelerated expansion of the Universe is supported by a combination of a gravitationally-enhanced friction sensitive to the scale of inflation and quantum friction effects associated with the explosive production of gauge fluctuations. The synergy of these two velocity-restraining mechanisms allows for: i) Natural Inflation potentials involving only sub-Planckian coupling constants, ii) the generation of a dark matter component in the form of primordial black holes, and iii) a potentially observable background of chiral gravitational waves at small scales.
  • Lindholm, V.; Finoguenov, A.; Comparat, J.; Kirkpatrick, C. C.; Rykoff, E.; Clerc, N.; Collins, C.; Damsted, S.; Chitham, J. Ider; Padilla, N. (2021)
  • Kainulainen, Kimmo; Leskinen, Juuso; Nurmi, Sami; Takahashi, Tomo (2017)
    We investigate the CMB mu distortion in models where two uncorrelated sources contribute to primordial perturbations. We parameterise each source by an amplitude, tilt, running and running of the running. We perform a detailed analysis of the distribution signal as function of the model parameters, highlighting the differences compared to single-source models. As a specific example, we also investigate the mixed inflaton-curvaton scenario. We find that the mu distortion could efficiently break degeneracies of curvaton parameters especially when combined with future sensitivity of probing the tensor-to-scalar ratio r. For example, assuming bounds mu <0.5 x 10(-8) and r <0.01, the curvaton contribution should either vanish or the curvaton should dominate primordial perturbations and its slow-roll parameter eta(chi) is constrained to the interval -0.007 <eta(chi) <0.045.
  • Tuominen, Kimmo (2021)
    Possible dark matter candidates in particle physics span a mass range extending over fifty orders of magnitude. In this review, we consider the range of masses from a few keV to a few hundred TeV, which is relevant for cold particle dark matter. We will consider models where dark matter arises as weakly coupled elementary fields and models where dark matter is a composite state bound by a new strong interaction. Different production mechanisms for dark matter in these models will be described. The landscape of direct and indirect searches for dark matter and some of the resulting constraints on models will be briefly discussed.
  • Heikinheimo, Matti; Raidal, Martti; Spethmann, Christian; Veermae, Hardi (2018)
    Self-interacting dark matter (DM) has been proposed as a solution to small scale problems in cosmological structure formation, and hints of DM self scattering have been observed in mergers of galaxy clusters. One of the simplest models for self-interacting DM is a particle that is charged under dark electromagnetism, a new gauge interaction analogous to the usual electromagnetic force, but operating on the DM particle instead of the visible particles. In this case, the collisional behaviour of DM is primarily due to the formation of collisionless shocks, that should affect the distribution of DM in merging galaxy clusters. We evaluate the time and length scales of shock formation in cluster mergers, and discuss the implications for modelling charged DM in cosmological simulations.
  • Schütt, Jorina Marlena; Whipp, David Michael (2020)
    Strain partitioning onto margin-parallel thrust and strike-slip faults is a common process at obliquely convergent plate margins, leading to the formation and migration of crustal slivers. The degree of strain partitioning and rate of sliver migration can be linked to several factors including the angle of convergence obliquity, the dip angle of subduction, frictional coupling between the plates and the strength of the upper plate, among others. Although these factors are known to be important, their relative influence on strain partitioning is unclear, particularly at natural margins where the factors often vary along strike. Here we use a 3-D mechanical finite-element model to investigate the relationship between continental crustal strength, the convergence obliquity angle, the subduction angle, and strain partitioning in the Northern Volcanic Zone (NVZ) of the Andes (5 degrees N-3 degrees S). In the NVZ the subduction dip and obliquity angles both vary along strike, weaknesses in the continental crust may be present in suture zones or regions of arc volcanism, and strain partitioning is only observed in some regions. Thus, it is an ideal location to gain insight in which of the factors have the largest influence on deformation and sliver formation in the upper plate. Our numerical experiments confirm that a moderately high obliquity angle is needed for partitioning and that a continental crustal weakness is also required for movement of a coherent continental sliver at rates similar to geodetic observations from the NVZ. In contrast, the subduction dip angle is only of secondary importance in controlling strain partitioning behavior. Key Points Factors influencing formation of continental slivers investigated using 3-D numerical models of finite-width oblique subduction systems Model results indicate that convergence obliquity and the presence of weak zones in the upper plate are key to formation of well-defined slivers Model predictions are in good agreement with geodetic observations of sliver motion in the Northern Volcanic Zone of the Andes
  • Enckell, Vera-Maria; Nurmi, Sami; Rasanen, Syksy; Tomberg, Eemeli (2021)
    We study Higgs inflation in the Palatini formulation with the renormalisation group improved potential in the case when loop corrections generate a feature similar to an inflection point. Assuming that there is a threshold correction for the Higgs quartic coupling lambda and the top Yukawa coupling y(t), we scan the three-dimensional parameter space formed by the two jumps and the non-minimal coupling xi .The spectral index n(s) can take any value in the observationally allowed range. The lower limit for the running is alpha (s)> -3.5 x 10(-3), and alpha (s) can be as large as the observational upper limit. Running of the running is small. The tensor-to-scalar ratio is 2.2x10(-17)< r < 2 x 10(-5). We find that slow-roll can be violated near the feature, and a possible period of ultra-slow-roll contributes to the widening of the range of CMB predictions. Nevertheless, for the simplest tree-level action, the Palatini formulation remains distinguishable from the metric formulation even when quantum corrections are taken into account, because of the small tensor-to-scalar ratio.
  • Malone, Brandon; Kangas, Kustaa; Järvisalo, Matti; Koivisto, Mikko; Myllymäki, Petri (2018)
    Various algorithms have been proposed for finding a Bayesian network structure that is guaranteed to maximize a given scoring function. Implementations of state-of-the-art algorithms, solvers, for this Bayesian network structure learning problem rely on adaptive search strategies, such as branch-and-bound and integer linear programming techniques. Thus, the time requirements of the solvers are not well characterized by simple functions of the instance size. Furthermore, no single solver dominates the others in speed. Given a problem instance, it is thus a priori unclear which solver will perform best and how fast it will solve the instance. We show that for a given solver the hardness of a problem instance can be efficiently predicted based on a collection of non-trivial features which go beyond the basic parameters of instance size. Specifically, we train and test statistical models on empirical data, based on the largest evaluation of state-of-the-art exact solvers to date. We demonstrate that we can predict the runtimes to a reasonable degree of accuracy. These predictions enable effective selection of solvers that perform well in terms of runtimes on a particular instance. Thus, this work contributes a highly efficient portfolio solver that makes use of several individual solvers.
  • Buntin, Sebastian; Malehmir, Alireza; Koyi, Hemin; Hogdahl, Karin; Malinowski, Michal; Larsson, Sven Ake; Thybo, Hans; Juhlin, Christopher; Korja, Annakaisa; Gorszczyk, Andrzej (2019)
    Saucer-shaped intrusions of tens of meters to tens of kilometres across have been observed both from surface geological mapping and geophysical observations. However, there is only one location where they have been reported to extend c. 100 km laterally, and emplaced both in a sedimentary basin and the crystalline basement down to 12 km depth. The legacy BABEL offshore seismic data, acquired over the central Fennoscandian Shield in 1989, have been recovered and reprocessed with the main goal of focusing on this series of globally unique crustal-scale saucer-shaped intrusions present onshore and offshore below the Bothnian Sea. The intrusions (c. 1.25 Ga), emplaced in an extensional setting, are observed within both sedimentary rocks (1.5 Ga). They have oval shapes with diameters ranging 30-100 km. The reprocessed seismic data provide evidence of up-doming of the lower crust (representing the melt reservoir) below the intrusions that, in turn, are observed at different depths in addition to a steep seismically transparent zone interpreted to be a discordant feeder dyke system. Relative age constraints and correlation with onshore saucer-shaped intrusions of different size suggest that they are internally connected and fed by each other from deeper to shallower levels. We argue for a nested emplacement mechanism and against a controlling role by the overlying sedimentary basin as the saucer-shaped intrusions are emplaced in both the sedimentary rocks as well as in the underlying crystalline basement. The interplay between magma pressure and overburden pressure, as well as the, at the time, ambient stress regime, are responsible for their extensive extent and rather constant thicknesses (c. 100-300 m). Saucer-shaped intrusions may therefore be present elsewhere in the crystalline basement to the same extent as observed in this study some of which are a significant source of raw materials.
  • Euclid Collaboration; Pocino, A.; Tutusaus, I.; Gozaliasl, G.; Keihänen, E.; Kirkpatrick , C. C.; Kurki-Suonio, H.; Väliviita, J. (2021)
    Photometric redshifts (photo-zs) are one of the main ingredients in the analysis of cosmological probes. Their accuracy particularly affects the results of the analyses of galaxy clustering with photometrically selected galaxies (GC(ph)) and weak lensing. In the next decade, space missions such as Euclid will collect precise and accurate photometric measurements for millions of galaxies. These data should be complemented with upcoming ground-based observations to derive precise and accurate photo-zs. In this article we explore how the tomographic redshift binning and depth of ground-based observations will affect the cosmological constraints expected from the Euclid mission. We focus on GC(ph) and extend the study to include galaxy-galaxy lensing (GGL). We add a layer of complexity to the analysis by simulating several realistic photo-z distributions based on the Euclid Consortium Flagship simulation and using a machine learning photo-z algorithm. We then use the Fisher matrix formalism together with these galaxy samples to study the cosmological constraining power as a function of redshift binning, survey depth, and photo-z accuracy. We find that bins with an equal width in redshift provide a higher figure of merit (FoM) than equipopulated bins and that increasing the number of redshift bins from ten to 13 improves the FoM by 35% and 15% for GC(ph) and its combination with GGL, respectively. For GC(ph), an increase in the survey depth provides a higher FoM. However, when we include faint galaxies beyond the limit of the spectroscopic training data, the resulting FoM decreases because of the spurious photo-zs. When combining GC(ph) and GGL, the number density of the sample, which is set by the survey depth, is the main factor driving the variations in the FoM. Adding galaxies at faint magnitudes and high redshift increases the FoM, even when they are beyond the spectroscopic limit, since the number density increase compensates for the photo-z degradation in this case. We conclude that there is more information that can be extracted beyond the nominal ten tomographic redshift bins of Euclid and that we should be cautious when adding faint galaxies into our sample since they can degrade the cosmological constraints.
  • Kärenlampi, Kimmo; Heinonen, Jussi S.; Kontinen, Asko; Hanski, Eero; Huhma, Hannu (2021)
    The origin of ferroan A-type granites in anorogenic tectonic settings remains a long-standing petrological puzzle. The proposed models range from extreme fractional crystallization of mantle-derived magmas to partial melting of crustal rocks, or involve combination of both. In this study, we apply whole-rock chemical and Sm-Nd isotopic compositions and thermodynamically constrained modeling (Magma Chamber Simulator, MCS) to decipher the genesis of a suite of A1-type peralkaline to peraluminous granites and associated intermediate rocks (monzodiorite-monzonite, syenite) from the southwestern margin of the Archean Karelia craton, central Finland, Fennoscandian Shield. These plutonic rocks were emplaced at ca. 2.05 Ga during an early stage of the break-up of the Karelia craton along its western margin and show trace element affinities to ocean island basalt-type magmas. The intermediate rocks show positive epsilon Nd(2050 Ma) values (+1.3 to +2.6), which are only slightly lower than the estimated contemporaneous depleted mantle value (+3.4), but much higher than average epsilon Nd(2050 Ma) of Archean TTGs (-10) in the surrounding bedrock, indicating that these rocks were essentially derived from a mantle source. The epsilon Nd(2050 Ma) values of the peralkaline and peraluminous granite samples overlap (-0.9 to +0.6 and -3.2 to +0.9, respectively) and are somewhat lower than those in the intermediate rocks, suggesting that the mafic magmas parental to granite must have assimilated some amount of older Archean continental crust during their fractionation, which is consistent with the continental crust-like trace element signatures of the granite members. The MCS modeling indicates that fractional crystallization of mantle-derived magmas can explain the major element characteristics of the intermediate rocks. The generation of the granites requires further fractional crystallization of these magmas coupled with assimilation of Archean crust. These processes took place in the middle to upper crust (-2-4 kbar, -7-15 km) and involved crystallization of large amounts of clinopyroxene, plagioclase and olivine. Our results highlight the importance of coupled FC-AFC processes in the petrogenesis of A-type magmas and support the general perception that magmas of A-type ferroan granites become more peraluminous by assimilation of crust. They further suggest that variable fractionation paths of the magmas upon the onset of assimilation may explain the broad variety of A-type felsic and intermediate igneous rocks that is often observed emplaced closely in time and space within the same igneous complex.
  • Beltran Almeida, Juan P.; Bernal, Nicolas; Rubio, Javier; Tenkanen, Tommi (2019)
    If cosmic inflation was driven by an electrically neutral scalar field stable on cosmological time scales, the field necessarily constitutes all or part of dark matter (DM). We study this possibility in a scenario where the inflaton field s resides in a hidden sector, which is coupled to the Standard Model sector through the Higgs portal lambda(hs)s(2) (HH)-H-dagger and non-minimally to gravity via xi(s)s(2)R. We study scenarios where the field s first drives inflation, then reheats the Universe, and later constitutes all DM. We consider two benchmark scenarios where the DM abundance is generated either by production during reheating or via non-thermal freeze-in. In both cases, we take into account all production channels relevant for DM in the mass range from keV to PeV scale. On the inflationary side, we compare the dynamics and the relevant observables in two different but well-motivated theories of gravity (metric and Palatini), discuss multi field effects in case both fields (s and h) were dynamical during inflation, and take into account the non-perturbative nature of particle production during reheating. We find that, depending on the initial conditions for inflation, couplings and the DM mass, the scenario works well especially for large DM masses, 10(2) GeV less than or similar to m(s) less than or similar to 10(6) GeV, although there are also small observationally allowed windows at the keV and MeV scales. We discuss how the model can be tested through astrophysical observations.
  • Enckell, Vera-Maria; Enqvist, Kari; Räsänen, Syksy; Tomberg, Eemeli (2018)
    We study inflation with the non-minimally coupled Standard Model Higgs in the case when quantum corrections generate a hilltop in the potential. We consider both the metric and the Palatini formulation of general relativity. We investigate hilltop inflation in different parts of the Higgs potential and calculate predictions for CMB observables. We run the renormalization group equations up from the electroweak scale and down from the hilltop, adding a jump in-between to account for unknown corrections in the intermediate regime. Within our approximation, no viable hilltop inflation is possible for small field values, where the non-minimal coupling has no role, nor for intermediate field values. For large field values, hilltop inflation works. We find the spectral index to be n(s)
  • Heinonen, Aku; Kivisaari, Heli; Michallik, Radoslaw (2020)
    The occurrence of high-aluminum orthopyroxene megacrysts (HAOMs) in several massif-type Proterozoic anorthosite complexes has been used as evidence of their polybaric crystallization. Here, we report such petrographic and geochemical (XRF and EMPA) evidence from HAOMs discovered in the 1.64 Ga Ahvenisto rapakivi granite-massif-type anorthosite complex in southeastern Finland. Two different types of HAOMs were recognized: type 1 HAOMs are individual, euhedral-to-subhedral crystals, and up to 15 cm in diameter, and type 2 HAOMs occur in pegmatitic pockets closely associated with megacrystic (up to 30 cm long) plagioclase. The type 1 megacrysts in particular are surrounded by complex corona structures composed of plagioclase, low-Al orthopyroxene, iddingsite (after olivine), and sulfides. Orthopyroxene crystallization pressure estimates based on an Al-in-Opx geobarometer reveal a three-stage compositional evolution in both textural HAOM types. The Al content decreases significantly from the core regions of the HAOM (4.4-7.6 wt% Al2O3), through the rims (1.3-3.6 wt%), into the host rock (0.5-1.5 wt%). Enstatite compositions overlap, but are generally higher in the cores (En(similar to 60-70)) and rims (En(similar to 50-70)) of the HAOMs than in the host rock (En(similar to 45-60)) orthopyroxenes. The highest recorded Al abundances in the HAOM cores correspond to crystallization pressures of up to similar to 1.1 GPa (similar to 34 km depth), whereas the HAOM rims have crystallized at lower pressures (max. similar to 0.5 GPa, 20 km depth). The highest pressure estimates for the host rock orthopyroxene were similar to 0.2 GPa (<7 km depth). These observations confirm the polybaric magmatic evolution of the Ahvenisto anorthosites and suggest that the entire 1.65-1.55 Ga Fennoscandian rapakivi suite was emplaced at a relatively shallow level (<7 km depth) in the upper crust. Global comparison to similar rock types reveals remarkable similarities in the petrogenetic processes controlling HAOM composition and evolution of anorthosite parental magmas.
  • Hertzberg, Mark P.; Schiappacasse, Enrico D.; Yanagida, Tsutomu T. (2020)
    We discuss formation of dark matter (DM) mini-halos around primordial black holes (PBHs) and its implication on DM direct detection experiments, including axion searches. Motivated by LIGO observations, we consider f(DM) similar to 0.01as the fraction of DM in PBHs with masses 10M(circle dot) - 70M(circle dot). In this case, we expect the presence of dressed PBHs after Milky Way halo formation with mini-halo masses peaked around M-halo similar to(50 - 55)M-PBH. We analyze the effect of tidal forces acting on dressed PBHs within the Milky Way galaxy. In the solar neighborhood, the mini-halos are resistant against tidal disruption from the mean-field potential of the galaxy and encounters with stars, but they undergo a small level of disruption caused by disk shocking. The presence of mini-halos around LIGO-motivated PBHs today could reduce by half the local dark matter background. High-resolution simulations are encouraged. If the proposed scenario is realized, chances of direct detection of DM would decrease. (C) 2020 The Authors. Published by Elsevier B.V.
  • Pinto, C.; Fabian, A. C.; Ogorzalek, A.; Zhuravleva, I.; Werner, N.; Sanders, J.; Zhang, Y. -Y.; Gu, Liyi; de Plaa, J.; Ahoranta, J.; Finoguenov, A.; Johnstone, R.; Canning, R. E. A. (2016)
    We extend our previous study of the cool gas responsible for the emission of O VII X-ray lines in the cores of clusters and groups of galaxies. This is the coolest X-ray emitting phase and connects the 10 000 K H alpha emitting gas to the million degree phase, providing a useful tool to understand cooling in these objects. We study the location of the O VII gas and its connection to the intermediate Fe XVII and hotter O VIII phases. We use high-resolution X-ray grating spectra of elliptical galaxies with strong Fe XVII line emission and detect O VII in 11 of 24 objects. Comparing the O VII detection level and resonant scattering, which is sensitive to turbulence and temperature, suggests that O VII is preferably found in cooler objects, where the Fe XVII resonant line is suppressed due to resonant scattering, indicating subsonic turbulence. Although a larger sample of sources and further observations is needed to distinguish between effects from temperature and turbulence, our results are consistent with cooling being suppressed at high turbulence as predicted by models of active galactic nuclei feedback, gas sloshing and galactic mergers. In some objects, the O VII resonant-to-forbidden line ratio is decreased by either resonant scattering or charge exchange boosting the forbidden line, as we show for NGC 4636. Charge exchange indicates interaction between neutral and ionized gas phases. The Perseus cluster also shows a high Fe XVII forbidden-to-resonance line ratio, which can be explained with resonant scattering by low-turbulence cool gas in the line of sight.