nils-herrmann/clean_scirepeval huggingface dataset:
Complex Networks

Graph theory was initiated by Euler in the eighteenth century. In mathematics, graph theory consolidated itself in the following decades and centuries. However, it was only until a little more than a decade ago that an explosion of research and applications ocurred, in what is now referred to as network science [23, 3, 17, 16]. In particular, the networks have become a central tool in the study of complex systems [2, 14, 21, 15]. The language of “nodes and edges” provided by networks has proven to be very illustrative to model elements of a system (nodes) and their interactions (edges). Having a language that describes interactions is essential for a non-reductionist science . The relevance of the study complex networks [18, 7, 4, 8] resides in the fact that so many real networks do not have a trivial topology. It follows that their properties are also not trivial, opening many research avenues.
Superlensing effect of an anisotropic metamaterial slab with near-zero dynamic mass

A metamaterial slab of anisotropic mass with one diagonal component being infinity and the other being zero is demonstrated to behave as a superlens for acoustic imaging beyond the diffraction limit. The underlying mechanism for extraordinary transmission of evanescent waves is attributed to the zero mass effect. Microstructure design for such anisotropic lens is also presented. In contrast to the anisotropic superlens based on Fabry-Perot resonant mechanism, the proposed lens operates without the limitation on lens thickness, thus more flexible in practical applications. Numerical modeling is performed to validate the proposed ideas.
Revisiting the double-binary-pulsar probe of non-dynamical Chern-Simons gravity

One of the popular modifications to the theory of general relativity is non-dynamical Chern-Simons (CS) gravity, in which the metric is coupled to an externally prescribed scalar field. Setting accurate constraints to the parameters of the theory is important owing to their implications for the scalar field and/or the underlying fundamental theory. The current best constraints rely on measurements of the periastron precession rate in the double-binary-pulsar system and place a very tight bound on the characteristic CS lengthscale k−1 cs . 3× 10−9 km. This paper considers several effects that were not accounted for when deriving this bound and lead to a substantial suppression of the predicted rate of periastron precession. It is shown, in particular, that the point mass approximation for extended test bodies does not apply in this case. The constraint to the characteristic CS lengthscale is revised to k−1 cs . 0.4 km, eight orders of magnitude weaker than what was previously found.
The map equation for link community

Community structure exists in many real-world networks and has been reported being related to several functional properties of the networks. The conventional approach was partitioning nodes into communities, while some recent studies start partitioning links instead of nodes to find overlapping communities of nodes efficiently. We extended the map equation method, which was originally developed for node communities, to find link communities in networks. This method is tested on various kinds of networks and compared with the metadata of the networks, and the results show that our method can identify the overlapping role of nodes effectively. The advantage of this method is that the node community scheme and link community scheme can be compared quantitatively by measuring the unknown information left in the networks besides the community structure. It can be used to decide quantitatively whether or not the link community scheme should be used instead of the node community scheme. Furthermore, this method can be easily extended to the directed and weighted networks since it is based on the random walk.
Evidence for dark energy from the cosmic microwave background alone using the Atacama Cosmology Telescope lensing measurements.

For the first time, measurements of the cosmic microwave background radiation (CMB) alone favor cosmologies with w = -1 dark energy over models without dark energy at a 3.2-sigma level. We demonstrate this by combining the CMB lensing deflection power spectrum from the Atacama Cosmology Telescope with temperature and polarization power spectra from the Wilkinson Microwave Anisotropy Probe. The lensing data break the geometric degeneracy of different cosmological models with similar CMB temperature power spectra. Our CMB-only measurement of the dark energy density Ω(Λ) confirms other measurements from supernovae, galaxy clusters, and baryon acoustic oscillations, and demonstrates the power of CMB lensing as a new cosmological tool.
SPECTROSCOPIC EVIDENCE FOR SN 2010ma ASSOCIATED WITH GRB 101219B

We report on the spectroscopic detection of supernova SN 2010ma associated with the long gamma-ray burst GRB 101219B. We observed the optical counterpart of the GRB on three nights with the X-shooter spectrograph at the Very Large Telescope. From weak absorption lines, we measure a redshift of z = 0.55. The first-epoch UV–near-infrared afterglow spectrum, taken 11.6 hr after the burst, is well fit by a power law consistent with the slope of the X-ray spectrum. The second- and third-epoch spectra (obtained 16.4 and 36.7 days after the burst), however, display clear bumps closely resembling those of the broad-lined type-Ic SN 1998bw if placed at z = 0.55. Apart from demonstrating that spectroscopic SN signatures can be observed for GRBs at these large distances, our discovery makes a step forward in establishing a general connection between GRBs and SNe. In fact, unlike most previous unambiguous GRB-associated SNe, GRB 101219B has a large gamma-ray energy (Eiso = 4.2 × 1051 erg), a bright afterglow, and obeys the “Amati” relation, thus being fully consistent with the cosmological population of GRBs.
Exploring symmetry breaking at the Dicke quantum phase transition.

We study symmetry breaking at the Dicke quantum phase transition by coupling a motional degree of freedom of a Bose-Einstein condensate to the field of an optical cavity. Using an optical heterodyne detection scheme, we observe symmetry breaking in real time and distinguish the two superradiant phases. We explore the process of symmetry breaking in the presence of a small symmetry-breaking field and study its dependence on the rate at which the critical point is crossed. Coherent switching between the two ordered phases is demonstrated.
THE CIRCULAR POLARIZATION OF SAGITTARIUS A* AT SUBMILLIMETER WAVELENGTHS

We report the first detections of circularly polarized emission at submillimeter wavelengths from the compact radio source and supermassive black hole candidate Sgr A* at a level of 1.2% ± 0.3% at 1.3 mm wavelength (230 GHz) and 1.6% ± 0.3% at 860 μm (345 GHz) with the same handedness, left circular polarization (LCP), as observed at all lower frequencies (1.4–15 GHz). The observations, taken with the Submillimeter Array in multiple epochs, also show simultaneous linear polarization (LP) at both wavelengths of about 6%. These properties differ sharply from those at wavelengths longer than 1 cm (frequencies below 30 GHz), where weak circular polarization (CP) (∼0.5%) dominates over LP, which is not detected at similar fractional limits. We describe an extensive set of tests to ensure the accuracy of our measurements. We find no CP in any other source, including the bright quasar 1924-292, which traces the same path on the sky as Sgr A* and therefore should be subject to identical systematic errors originating in the instrument frame. Since a relativistic synchrotron plasma is expected to produce little CP, the observed CP is probably generated close to the event horizon by the Faraday conversion process. We use a simple approximation to show that the phase shift associated with Faraday conversion can be nearly independent of frequency, a sufficient condition to make the handedness of CP independent of frequency. Because the size of the τ = 1 surface changes by more than an order of magnitude between 1.4 and 345 GHz, the magnetic field must be coherent over such scales to consistently produce LCP. To improve our understanding of the environment of SgrA* critical future measurements includes determining whether the Faraday rotation deviates from a λ2 dependence in wavelength and whether the circular and linear components of the flux density are correlated.
Inflation with large supergravity corrections

It is well known that large Hubble-induced supergravity corrections to the inflaton field can ruin the flatness of the potential, thus creating a tension between slow-roll inflation and supergravity. In this paper we show that it is possible to obtain a {\it cosmologically flat} direction, embedded within the minimal supersymmetric standard model, despite very large super-Hubble corrections. As an illustration, we show that a flat direction which is lifted by an $n=6$ operator matches the current cosmic microwave background data for a wide range of the Hubble parameter, $10^{5} {\rm GeV}\lesssim H_{inf}\lesssim 10^{8.5}$ GeV. Our approach can be applied to any $F$-term inflationary model.
Uncovering the Temporal Dynamics of Diffusion Networks

Time plays an essential role in the diffusion of information, influence and disease over networks. In many cases we only observe when a node copies information, makes a decision or becomes infected – but the connectivity, transmission rates between nodes and transmission sources are unknown. Inferring the underlying dynamics is of outstanding interest since it enables forecasting, influencing and retarding infections, broadly construed. To this end, we model diffusion processes as discrete networks of continuous temporal processes occurring at different rates. Given cascade data – observed infection times of nodes – we infer the edges of the global diffusion network and estimate the transmission rates of each edge that best explain the observed data. The optimization problem is convex. The model naturally (without heuristics) imposes sparse solutions and requires no parameter tuning. The problem decouples into a collection of independent smaller problems, thus scaling easily to networks on the order of hundreds of thousands of nodes. Experiments on real and synthetic data show that our algorithm both recovers the edges of diffusion networks and accurately estimates their transmission rates from cascade data.
Equilibrium strategy and population-size effects in lowest unique bid auctions.

In lowest unique bid auctions, N players bid for an item. The winner is whoever places the lowest bid, provided that it is also unique. We use a grand canonical approach to derive an analytical expression for the equilibrium distribution of strategies. We then study the properties of the solution as a function of the mean number of players, and compare them with a large data set of internet auctions. The theory agrees with the data with striking accuracy for small population-size N, while for larger N a qualitatively different distribution is observed. We interpret this result as the emergence of two different regimes, one in which adaptation is feasible and one in which it is not. Our results question the actual possibility of a large population to adapt and find the optimal strategy when participating in a collective game.
Modeling Network Evolution Using Graph Motifs

Network structures are extremely important to the study of political science. Much of the data in its subfields are naturally represented as networks. This includes trade, diplomatic and conflict relationships. The social structure of several organization is also of interest to many researchers, such as the affiliations of legislators or the relationships among terrorist. A key aspect of studying social networks is understanding the evolutionary dynamics and the mechanism by which these structures grow and change over time. While current methods are well suited to describe static features of networks, they are less capable of specifying models of change and simulating network evolution. In the following paper I present a new method for modeling network growth and evolution. This method relies on graph motifs to generate simulated network data with particular structural characteristic. This technique departs notably from current methods both in form and function. Rather than a closed-form model, or stochastic implementation from a single class of graphs, the proposed "graph motif model" provides a framework for building flexible and complex models of network evolution. The paper proceeds as follows: first a brief review of the current literature on network modeling is provided to place the graph motif model in context. Next, the graph motif model is introduced, and a simple example is provided. As a proof of concept, three classic random graph models are recovered using the graph motif modeling method: the Erdos-Renyi binomial random graph, the Watts-Strogatz "small world" model, and the Barabasi-Albert preferential attachment model. In the final section I discuss the results of these simulations and subsequent advantage and disadvantages presented by using this technique to model social networks.
TWO DISTINCT RED GIANT BRANCHES IN THE GLOBULAR CLUSTER NGC 288

We report the presence of two distinct red giant branches (RGBs) in the globular cluster NGC 288 from the narrowband calcium and Strömgren b and y photometry obtained at the CTIO 4 m Blanco telescope. The RGB of NGC 288 is clearly split into two in the hk [=(Ca − b) − (b − y)] index, while the split is not shown in the b − y color. Unlike other globular clusters with multiple populations reported thus far, the horizontal branch of NGC 288 is only mildly extended. Our stellar population models show that this and the presence of two distinct RGBs in NGC 288 can be reproduced if slightly metal-rich (Δ[m/H] ≈ 0.16) second generation stars are also enhanced in helium by small amount (ΔY ≈ 0.03) and younger by ∼1.5 Gyr. The RGB split in the hk index is most likely indicating that the second generation stars were affected by supernovae enrichment, together with the pollution of lighter elements by intermediate-mass asymptotic giant branch stars or fast-rotating massive stars. In order to confirm this, however, spectroscopy of stars in the two distinct RGB groups is urgently required.
On the nature of the extremely fast optical rebrightening of the afterglow of GRB 081029

After the launch of the Swift satellite, the gamma-ray burst (GRB) optical light-curve smoothness paradigm has been questioned thanks to the faster and better sampled optical follow-up, which has unveiled a very complex behaviour. This complexity is triggering the interest of the whole GRB community. The GROND multi-channel imager is used to study optical and near-infrared (NIR) afterglows of GRBs with unprecedented optical and near-infrared temporal and spectral resolution. The GRB 081029 has a very prominent optical rebrightening event and is an outstanding example of the application of the multi-channel imager to GRB afterglows.  Here we exploit the rich GROND multi-colour follow-up of GRB 081029 combined with XRT observations to study the nature of late-time rebrightenings that appear in the optical-NIR light-curves of some GRB afterglows.  We analyse the optical and NIR observations obtained with the seven-channel Gamma-Ray burst Optical and Near-infrared Detector (GROND) at the 2.2 m MPI/ESO telescope and the X-ray data obtained with the XRT telescope on board the Swift observatory. The multi-wavelength temporal and spectral evolution is discussed in the framework of different physical models.  The extremely steep optical and NIR rebrightening observed in GRB 081029 cannot be explained in the framework of the standard forward shock afterglow model. The absence of a contemporaneous X-ray rebrightening and the evidence of a strong spectral evolution in the optical-NIR bands during the rise suggest two separate components that dominate in the early and late-time lightcurves, respectively. The steepness of the optical rise cannot be explained even in the framework of the alternative scenarios proposed in the literature unless a late-time activity of the central engine is assumed.
GALACTIC-CENTER S STARS AS A PROSPECTIVE TEST OF THE EINSTEIN EQUIVALENCE PRINCIPLE

The S stars in the Galactic-center region are found to be on near-perfect Keplerian orbits around presumably a supermassive black hole, with periods of 15–50 yr. Since these stars reach a few percent of light speed at pericenter, various relativistic effects are expected and have been discussed in the literature. We argue that an elegant test of the Einstein equivalence principle should be possible with existing instruments, through spectroscopic monitoring of an S star concentrated during the months around pericenter, supplemented with an already-adequate astrometric determination of the inclination. In essence, the spectrum of an S star can be considered a heterogeneous ensemble of clocks in a freely falling frame, which near pericenter is moving at relativistic speeds.
Testing gravity using the environmental dependence of dark matter halos.

In this Letter, we investigate the environmental dependence of dark matter halos in theories which attempt to explain the accelerated expansion of the Universe by modifying general relativity (GR). Using high-resolution N-body simulations in f(R) gravity models which recover GR in dense environments by virtue of the chameleon mechanism, we find a significant difference, which depends on the environment, between the lensing and dynamical masses of dark matter halos. This environmental dependence of the halo properties can be used as a smoking gun to test GR observationally.
Domain wall dynamics in integrable and chaotic spin-1/2 chains.

We study the time evolution of correlation functions, spin current, and local magnetization in an isolated spin-1/2 chain initially prepared in a sharp domain wall state. The results are compared with the level of spatial delocalization of the eigenstates of the system which is measured using the inverse participation ratio. Both integrable and nonintegrable regimes are considered. Nonintegrability is introduced to the integrable Hamiltonian with nearest-neighbor couplings by adding a single-site impurity field or by adding next-nearest-neighbor couplings. A monotonic correspondence between the enhancement of the level of delocalization, spin current, and magnetization dynamics occurs in the integrable domain. This correspondence is, however, lost for chaotic models with weak Ising interactions.
On negative eigenvalues of low-dimensional Schr\"{o}dinger operators

The paper concerns upper and lower estimates for the number of negative eigenvalues of one- and two-dimensional Schr\"{o}dinger operators and more general operators with the spectral dimensions $d\leq 2$. The classical Cwikel-Lieb-Rosenblum (CLR) upper estimates require the corresponding Markov process to be transient, and therefore the dimension to be greater than two. We obtain CLR estimates in low dimensions by transforming the underlying recurrent process into a transient one using partial annihilation. As a result, the estimates for the number of negative eigenvalues are not translation invariant and contain Bargmann type terms. We show that a classical form of CLR estimates can not be valid for operators with recurrent underlying Markov processes. We provide estimates from below which prove that the obtained results are sharp. Thirring estimates for the low-dimensional Schr\"{o}dinger operators are also studied.
Dijet Signature of Low Mass Strings in the Early LHC Data

We have examined the dijet production at the LHC as a hint to discovery of string Regge excitations of Standard Model particles. If the fundamental string mass scale is in the TeV range, the influence of string effects on the $pp$ interaction can arise as new resonances in the dijet invariant mass distribution. Near the first resonant pole we investigate the impact of the subprocesses with quark-gluon and four-gluon separately. We show that the LHC is able to probe the string mass scale $\sim$5 TeV with only 2 pb$^{-1}$ of integrated luminosity at $E_{CM}=14$ TeV.
Accelerating Expansion of the Universe

This thesis concentrates on the accelerated expansion of the Universe recently explored by measurements of redshift and luminosity-distance relations of type Ia Supernovae. We have considered a model of the universe filled with modified Chaplygin gas and barotropic fluid. The role of dynamical cosmological constant has been explored with Modified Chaplygin Gas as the background fluid. Various phenomenological models for \Lambda have been studied in presence of the gravitational constant G to be constant or time dependent. A new form of the well known Chaplygin gas model has been presented by introducing inhomogeneity in the EOS. This model explains w=-1 crossing. An interaction of this model with the scalar field has also been investigated through a phenomenological coupling function. Tachyonic field has been depicted as dark energy model to represent the present acceleration of the Universe. A mixture of the tachyonic fluid has been considered with Generalized Chaplygin Gas to show the role of the later as a dark energy candidate in presence of tachyonic matter. A model of interaction has been studied with scalar field and the inhomogeneous ideal fluid. Two forms of the ideal fluid have been analysed. A power law expansion for the scale factor has been assumed to solve the equations for the energy densities. Brans-Dicke theory has been used to investigate the possibility of obtaining cosmic acceleration. For this purpose a constant and a variable \omega (Brans-Dicke parameter) have been considered. A self-interacting potential has been introduced to show its role in the evolution of the Universe. This model has been studied in presence of barotropic fluid and Generalized Chaplygin Gas.
Collective Animal Behavior from Bayesian Estimation and Probability Matching

Animals living in groups make movement decisions that depend, among other factors, on social interactions with other group members. Our present understanding of social rules in animal collectives is mainly based on empirical fits to observations, with less emphasis in obtaining first-principles approaches that allow their derivation. Here we show that patterns of collective decisions can be derived from the basic ability of animals to make probabilistic estimations in the presence of uncertainty. We build a decision-making model with two stages: Bayesian estimation and probabilistic matching. In the first stage, each animal makes a Bayesian estimation of which behavior is best to perform taking into account personal information about the environment and social information collected by observing the behaviors of other animals. In the probability matching stage, each animal chooses a behavior with a probability equal to the Bayesian-estimated probability that this behavior is the most appropriate one. This model derives very simple rules of interaction in animal collectives that depend only on two types of reliability parameters, one that each animal assigns to the other animals and another given by the quality of the non-social information. We test our model by obtaining theoretically a rich set of observed collective patterns of decisions in three-spined sticklebacks, Gasterosteus aculeatus, a shoaling fish species. The quantitative link shown between probabilistic estimation and collective rules of behavior allows a better contact with other fields such as foraging, mate selection, neurobiology and psychology, and gives predictions for experiments directly testing the relationship between estimation and collective behavior.