nils-herrmann/clean_scirepeval huggingface dataset:
The formation of entropy cores in non-radiative galaxy cluster simulations: SPH versus AMR

We simulate the formation and evolution of a massive galaxy c luster in aΛCDM Universe using three different approaches to solving the equations of h ydrodynamics in the absence of radiative cooling: one based on the ‘classic’ Smoothed Partic le Hydrodynamics (SPH) method; one based on a novel SPH algorithm with a higher order dissipa tion switch (SPHS); and one based on an adaptive mesh refinement (AMR) method. We find that SPHS and the AMR code are in excellent agreement with one another: in both, the sph rically averaged entropy profile forms a well-defined core that rapidly converges with increa sing mass and force resolution. By contrast, in agreement with previous work, SPH exhibits r ather different behaviour. At low redshift, the entropy profile shows a systematic decreas e with decreasing cluster-centric radius, converging on ever lower central entropy with incre asing resolution. At higher redshift (z ∼ 1), SPH is in better agreement with the other codes but shows mu ch poorer numerical convergence. We trace the reason for these discrepancies to a known artificial surface tension in SPH that appears at phase boundaries. At early times, the p assage of massive substructures close to the cluster centre during its violent assembly stir s and shocks the gas to build up an entropy core. At late times, the artificial surface tension c auses low entropy gas – that ought to mix with the higher entropy gas – to sink artificially to the c ntre of the cluster. We use SPHS – in which we can fully control the amount of numeri cal dissipation – to study the contribution of numerical versus physical dissip ation on the resultant entropy core. We argue that numerical dissipation is required to ensure si ngle-valued fluid quantities in converging flows. However, provided this dissipation occur s only at the resolution limit, and provided that it does not propagate errors to larger scales, its effect is benign. There is no requirement to build ‘sub-grid’ models of unresolved turbule nc for galaxy cluster simulations. We conclude that entropy cores in non-radiative simulation s f galaxy clusters are physical, resulting from entropy generation in shocked gas during the cluster assembly process. This finally puts to rest the long-standing puzzle of cluster entro py cores in AMR simulations versus their apparent absence in classic SPH simulations.
Assessing Financial Model Risk

Model risk has a huge impact on any risk measurement procedure and its quantification is therefore a crucial step. In this paper, we introduce three quantitative measures of model risk when choosing a particular reference model within a given class: the absolute measure of model risk, the relative measure of model risk and the local measure of model risk. Each of the measures has a specific purpose and so allows for flexibility. We illustrate the various notions by studying some relevant examples, so as to emphasize the practicability and tractability of our approach.
Multi-Task Policy Search

Learning policies that generalize across multiple tasks is an important and challenging research topic in reinforcement learning and robotics. Training individual policies for every single potential task is often impractical, especially for continuous task variations, requiring more principled approaches to share and transfer knowledge among similar tasks. We present a novel approach for learning a nonlinear feedback policy that generalizes across multiple tasks. The key idea is to define a parametrized policy as a function of both the state and the task, which allows learning a single policy that generalizes across multiple known and unknown tasks. Applications of our novel approach to reinforcement and imitation learning in real-robot experiments are shown.
A survey on Human Mobility and its applications

Human Mobility has attracted attentions from dierent elds of studies such as epidemic modeling, trac engineering, trac prediction and urban planning. In this survey we review major characteristics of human mobility studies including from trajectory-based studies to studies using graph and network theory. In trajectory-based studies statistical measures such as jump length distribution and radius of gyration are analyzed in order to investigate how people move in their daily life, and if it is possible to model this individual movements and make prediction based on them. Using graph in mobility studies, helps to investigate the dynamic behavior of the system, such as diusion and ow in the network and makes it easier to estimate how much one part of the network inuences another by using metrics like centrality measures. We aim to study population ow in transportation networks using mobility data to derive models and patterns, and to develop new applications in predicting phenomena such as congestion. Human Mobility studies with the new generation of mobility data provided by cellular phone networks, arise new challenges such as data storing, data representation, data analysis and computation complexity. A comparative review of dierent data types used in current tools and applications of Human Mobility studies leads us to new approaches for dealing with mentioned challenges.
Is the cosmic microwave background telling us that dark matter is weaker than weakly interacting

If moduli, or other long-lived heavy states, decay in the early universe in part into light and feebly interacting particles (such as axions), these decay products could account for the additional energy density in radiation that is suggested by recent measurements of the CMB. These moduli decays will also, however, alter the expansion history of the early universe, potentially diluting the thermal relic abundance of dark matter. If this is the case, then dark matter particles must annihilate with an even lower cross section than required in the standard thermal scenario (sigma v < 3x10^-26 cm^3/s) if they are to make up the observed density of dark matter. This possibility has significant implications for direct and indirect searches for dark matter.
Pion electroproduction and VCS at the Δ resonance region

The study of the γ*N→Δ reaction presents the best quantitative method to explore the deviation of hadron shapes from spherical symmetry (nonspherical amplitudes). Significant non-spherical electric (E2) and Coulomb quadrupole (C2) amplitudes have been observed with good precision as a function of Q2 from photon point up to ≈ 7 (GeV/c)2. Quark model calculations for these quadrupole amplitudes are at least an order of magnitude too small and even have the wrong sign. Lattice QCD, chiral effective field theory, and dynamic model calculations which include the effects of the pion-cloud are in approximate agreement with experiment.
Semi-supervised Ranking Pursuit

We propose a novel sparse preference learning/ranking algorithm. Our algorithm approximates the true utility function by a weighted sum of basis functions using the squared loss on pairs of data points, and is a generalization of the kernel matching pursuit method. It can operate both in a supervised and a semi-supervised setting and allows efficient search for multiple, near-optimal solutions. Furthermore, we describe the extension of the algorithm suitable for combined ranking and regression tasks. In our experiments we demonstrate that the proposed algorithm outperforms several state-of-the-art learning methods when taking into account unlabeled data and performs comparably in a supervised learning scenario, while providing sparser solutions.
Entropy of a Zipfian Distributed Lexicon

This article presents the calculation of the entropy of a system with Zipfian distribution and shows that a communication system tends to present an exponent value close to one, but still greater than one, so that it might maximize entropy and hold a feasible lexicon with an increasing size. This result is in agreement with what is observed in natural languages and with the balance between the speaker and listener communication efforts. On the other hand, the entropy of the communicating source is very sensitive to the exponent value as well as the length of the observable data, making it a poor parameter to characterize the communication process.
A global mirror symmetry framework for the Landau-Ginzburg/Calabi-Yau correspondence

We show how the Landau-Ginzburg/Calabi-Yau correspondence for the quintic three-fold can be cast into a global mirror symmetry framework. Then we draw inspiration from Berglund-H\"ubsch mirror duality construction to provide an analogue conjectural picture featuring all Calabi-Yau hypersurfaces within weighted projective spaces and certain quotients by finite abelian group actions.
Improving data utility in differential privacy and k-anonymity

We deal with SDC from the computer science community perspective. The focus lies on two mainstream privacy models: k-anonymity and differential privacy. Once a privacy model has been selected, the goal is to enforce it while preserving as much data utility as possible. The main objective of this thesis is to improve the data utility in k-anonymous and differentially private data releases. k-Anonymity has several drawbacks. On the disclosure limitation side, there is a lack of protection against attribute disclosure and against informed intruders. On the data utility side, dealing with a large number of quasi-identifier attributes is problematic. We propose a relaxation of k-anonymity that deals with these issues. Differential privacy limits disclosure risk through noise addition. The Laplace distribution is commonly used for the random noise. We show that the Laplace distribution is not optimal: the same disclosure limitation guarantee can be attained by adding less noise. Optimal univariate and multivariate noises are characterized and constructed. Common mechanisms to attain differential privacy do not take into account the users’ prior knowledge; they implicitly assume zero initial knowledge about the query response. We propose a mechanism that focuses on limiting the knowledge gain over the prior knowledge. Microaggregation-based k-anonymity and differential privacy can be combined to produce microdata releases with the strong privacy guarantees of differential privacy and improved data accuracy.
Effective theory of self-interacting dark matter

We present an effective non-relativistic theory of self-interacting dark matter. We classify the long range interactions and discuss how they can be generated from quantum field theories. Generic dark sectors can generate singular potentials. We show how to consistently renormalize such potentials and apply this to the calculation of the Sommerfeld enhancement of dark matter interactions. We explore further applications of this enhancement to astrophysical probes of dark matter including the core vs. cusp problem.
Controllable quantum spin glasses with magnetic impurities embedded in quantum solids

Magnetic impurities embedded in inert solids can exhibit long coherence times and interact with one another via their intrinsic anisotropic dipolar interaction. We argue that, as a consequence of these properties, disordered ensembles of magnetic impurities provide an effective platform for realizing a controllable, tunable version of the dipolar quantum spin glass seen in LiHo_xY_(1−x)F_4. Specifically, we propose and analyze a system composed of dysprosium atoms embedded in solid helium. We describe the phase diagram of the system and discuss the realizability and detectability of the quantum spin glass and antiglass phases.
Black hole dynamics in generic spacetimes

The dynamics of black hole spacetimes play a crucial role in astrophysics, high energy physics and fundamental physics. In this thesis I have investigated the dynamics of black holes in generic spacetimes by extending established numerical relativity methods to higher dimensional or non-asymptotically flat spacetimes. Additionally, I have explored BH spacetimes perturbed my massive scalar fields. By developing and further improving NR techniques I have been able to push our knowledge to new grounds.
Solar activity and transformer failures in the Greek national electric grid

We study both the short term and long term effects of solar activity on the large transformers (150 kV and 400 kV) of the Greek national electric grid.  We use data analysis and various statistical methods and models.  Contrary to common belief in PPC Greece, we see that there are considerable both short term (immediate) and long term effects of solar activity onto large transformers in a mid-latitude country like Greece. Our results can be summarised as follows: For the short term effects: During 1989–2010 there were 43 “stormy days” (namely days with for example Ap  ≥ 100) and we had 19 failures occurring during a stormy day plus or minus 3 days and 51 failures occurring during a stormy day plus or minus 7 days. All these failures can be directly related to Geomagnetically Induced Currents (GICs). Explicit cases are briefly presented. For the long term effects, again for the same period 1989–2010, we have two main results: The annual number of transformer failures seems to follow the solar activity pattern. Yet the maximum number of transformer failures occurs about half a solar cycle after the maximum of solar activity. There is statistical correlation between solar activity expressed using various newly defined long term solar activity indices and the annual number of transformer failures. These new long term solar activity indices were defined using both local (from the geomagnetic station in Greece) and global (planetary averages) geomagnetic data. Applying both linear and non-linear statistical regression we compute the regression equations and the corresponding coefficients of determination.
Effective field theory for finite systems with spontaneously broken symmetry

We extend effective field theory to the case of spontaneous symmetry breaking in genuinely finite quantum systems such as small superfluid systems, molecules or atomic nuclei, and focus on deformed nuclei. In finite superfluids, symmetry arguments alone relate the spectra of systems with different particle numbers. For systems with non-spherical intrinsic ground states such as atomic nuclei or molecules, symmetry arguments alone yield the universal features of the low-lying excitations as vibrations that are the heads of rotational bands. The low-lying excitations in deformed nuclei differ from those in molecules because of symmetry properties caused by pairing.
Network robustness of multiplex networks with interlayer degree correlations.

We study the robustness properties of multiplex networks consisting of multiple layers of distinct types of links, focusing on the role of correlations between degrees of a node in different layers. We use generating function formalism to address various notions of the network robustness relevant to multiplex networks, such as the resilience of ordinary and mutual connectivity under random or targeted node removals, as well as the biconnectivity. We found that correlated coupling can affect the structural robustness of multiplex networks in diverse fashion. For example, for maximally correlated duplex networks, all pairs of nodes in the giant component are connected via at least two independent paths and network structure is highly resilient to random failure. In contrast, anticorrelated duplex networks are on one hand robust against targeted attack on high-degree nodes, but on the other hand they can be vulnerable to random failure.
Two dimensional hydrodynamics with gauge and gravitational anomalies

We present new findings in two dimensional chiral and non-chiral hydrodynamics with gauge and gravitational anomalies. Exact constitutive relations for the stress tensor and charge current are obtained. These relations involve arbitrary constants that may be fixed by choosing appropriate boundary conditions corresponding to different vacuum states. For the chiral theory, the constitutive relations may be put in the ideal (chiral) fluid form. For the non-chiral case, the constitutive relations take the ideal fluid form only for the Boulware vacuum. Finally, we make a comparison with the derivative expansion approach.
Fast radio bursts: the last sign of supramassive neutron stars

Several fast radio bursts have been discovered recently, showing a bright, highly dispersed millisecond radio pulse. The pulses do not repeat and are not associated with a known pulsar or gamma-ray burst. The high dispersion suggests sources at cosmological distances, hence implying an extremely high radio luminosity, far larger than the power of single pulses from a pulsar.  We suggest that a fast radio burst represents the final signal of a supramassive rotating neutron star that collapses to a black hole due to magnetic braking. The neutron star is initially above the critical mass for non-rotating models and is supported by rapid rotation. As magnetic braking constantly reduces the spin, the neutron star will suddenly collapse to a black hole several thousand to million years after its birth.  We discuss several formation scenarios for supramassive neutron stars and estimate the possible observational signatures making use of the results of recent numerical general-relativistic calculations.  While the collapse will hide the stellar surface behind an event horizon, the magnetic-field lines will snap violently. This can turn an almost ordinary pulsar into a bright radio “blitzar”: Accelerated electrons from the travelling magnetic shock dissipate a significant fraction of the magnetosphere and produce a massive radio burst that is observable out to z > 0:7. Only a few percent of the neutron stars needs to be supramassive in order to explain the observed rate.  We suggest the intriguing possibility that fast radio bursts might trace the solitary and almost silent formation of stellar mass black holes at high redshifts. These bursts could be an electromagnetic complement to gravitational-wave emission and reveal a new formation and evolutionary channel for black holes and neutron stars that are not seen as gamma-ray bursts. If supramassive neutron stars are formed at birth and not by accretion, radio observations of these bursts could trace the core-collapse supernova rate throughout the universe.
Cosmic Censorship, Black Holes and Integer-spin Test Fields

It has been argued that, starting with a slightly sub-extremal Kerr black hole instead of an extremal one, it is possible to overspin a black hole past the extremal limit and turn it into a naked singularity by sending test bodies, if one neglects radiative and self-force effects. In this work we show that (i) an extremal Kerr black hole can not be overspun as a result of the interaction with massless integer spin test fields (scalar, electromagnetic, or gravitational), (ii) overspinning can be achieved if we start with a nearly extremal black hole instead, and (iii) for the scalar field, the argument applies to more general black holes, and also allows use of a more general field configuration. Our analysis also neglects radiative and self-force effects.
A new introductory quantum mechanics curriculum

The Institute of Physics New Quantum Curriculum consists of freely available online learning and teaching materials (quantumphysics.iop.org) for a first course in university quantum mechanics starting from two-level systems. This approach immediately immerses students in inherently quantum-mechanical aspects by focusing on experiments that have no classical explanation. It allows from the start a discussion of the interpretive aspects of quantum mechanics and quantum information theory. This paper gives an overview of the resources available from the IOP website. The core text includes around 80 articles which are co-authored by leading experts, arranged in themes, and can be used flexibly to provide a range of alternative approaches. Many of the articles include interactive simulations with accompanying activities and problem sets that can be explored by students to enhance their understanding. Much of the linear algebra needed for this approach is included in the resource. Solutions to activities are available to instructors. The resources can be used in a variety of ways, from being supplemental to existing courses to forming a complete programme.
Quantum Entanglement of Interacting Fermions in Monte Carlo

Given a specific interacting quantum Hamiltonian in a general spatial dimension, can one access its entanglement properties, such as, the entanglement entropy corresponding to the ground state wavefunction? Even though progress has been made in addressing this question for interacting bosons and quantum spins, as yet there exist no corresponding methods for interacting fermions. Here we show that the entanglement structure of interacting fermionic Hamiltonians has a particularly simple form — the interacting reduced density matrix can be written as a sum of operators that describe free fermions. This decomposition allows one to calculate the Renyi entropies for Hamiltonians which can be simulated via Determinantal Quantum Monte Carlo, while employing the efficient techniques hitherto available only for free fermions. The method presented works for the ground state, as well as for the thermally averaged reduced density matrix.
Higgs and W boson spectrum from lattice simulations

The spectrum of energy levels is computed for all available angular momentum and parity quantum numbers in the SU(2)-Higgs model, with parameters chosen to match experimental data from the Higgs-W boson sector of the standard model. Several multi-boson states are observed, with and without linear momentum, and all are consistent with weakly-interacting Higgs and W bosons. The creation operators used in this study are gauge-invariant so, for example, the Higgs operator is quadratic rather than linear in the Lagrangian's scalar field.
A Reference for the Gravitational Hamiltonian Boundary Term

eld. It includes a boundary term which not only determines the value of the Hamiltonian, but also, via the boundary term in the variation of the Hamiltonian, the boundary conditions. The value of the Hamiltonian comes from its boundary term; it gives the quasi-local quantities: energy-momentum and angularmomentum/center-of-mass momentum. This boundary term depends not only on the dynamical variables but also on their reference values; these reference values determine the ground state|the state having vanishing quasi-local quantities. Here our concern is with how to select on the quasi-local two-boundary the reference value. To determine the \best matched" reference metric and connection values for our preferred boundary term for Einstein’s general relativity, we propose on the boundary two-surface (i) four dimensional isometric matching, and (ii) extremizing the value of the energy.
Chi-square goodness of fit tests for weighted histograms. Review and improvements

Weighted histograms are used for the estimation of probability density functions. Computer simulation is the main domain of application of this type of histogram. A review of chi-square goodness of fit tests for weighted histograms is presented in this paper. Improvements are proposed to these tests that have size more close to its nominal value. Numerical examples are presented in this paper for evaluation of tests and to demonstrate various applications of tests.