nils-herrmann/clean_scirepeval huggingface dataset:
Birkhoff's theorem in higher derivative theories of gravity

In this paper, we present a class of higher derivative theories of gravity which admit Birkhoff's theorem. In particular, we explicitly show that in this class of theories, although generically the field equations are of fourth order, under spherical (plane or hyperbolic) symmetry, all the field equations reduce to second order and have exactly the same or similar structure to those of Lovelock theories, depending on the spacetime dimensions and the order of the Lagrangian.
Asymmetric dark matter and effective operators

In order to annihilate in the early Universe to levels well below the measured dark matter density, asymmetric dark matter must possess large couplings to the Standard Model. In this paper, we consider effective operators which allow asymmetric dark matter to annihilate into quarks. In addition to a bound from requiring sufficient annihilation, the energy scale of such operators can be constrained by limits from direct detection and monojet searches at colliders. We show that the allowed parameter space for these operators is highly constrained, leading to non-trivial requirements that any model of asymmetric dark matter must satisfy.
Anomalous scaling in the random-force-driven Burgers' equation: a Monte Carlo study

We present a new approach to determine numerically the statistical behavior of small-scale structures in hydrodynamic turbulence. Starting from the functional integral representation of the random-force-driven Burgers' equation we show that Monte Carlo simulations allow us to determine the anomalous scaling of high-order moments of velocity differences. Given the general applicability of Monte Carlo methods, this opens up the possibility of also addressing other systems relevant to the turbulence within this framework.
EXTENDED SCALING LAWS IN NUMERICAL SIMULATIONS OF MAGNETOHYDRODYNAMIC TURBULENCE

Magnetized turbulence is ubiquitous in astrophysical systems, where it notoriously spans a broad range of spatial scales. Phenomenological theories of MHD turbulence describe the self-similar dynamics of turbulent fluctuations in the inertial range of scales. Numerical simulations serve to guide and test these theories. However, the computational power that is currently available restricts the simulations to Reynolds numbers that are significantly smaller than those in astrophysical settings. In order to increase computational efficiency and, therefore, probe a larger range of scales, one often takes into account the fundamental anisotropy of field-guided MHD turbulence, with gradients being much slower in the field-parallel direction. The simulations are then optimized by employing the reduced MHD equations and relaxing the field-parallel numerical resolution. In this work we explore a different possibility. We propose that there exist certain quantities that are remarkably stable with respect to the Reynolds number. As an illustration, we study the alignment angle between the magnetic and velocity fluctuations in MHD turbulence, measured as the ratio of two specially constructed structure functions. We find that the scaling of this ratio can be extended surprisingly well into the regime of relatively low Reynolds number. However, the extended scaling easily becomes spoiled when the dissipation range in the simulations is underresolved. Thus, taking the numerical optimization methods too far can lead to spurious numerical effects and erroneous representation of the physics of MHD turbulence, which in turn can affect our ability to identify correctly the physical mechanisms that are operating in astrophysical systems.
Relating quarks and leptons without grand-unification

In combination with supersymmetry, flavor symmetry may relate quarks with leptons, even in the absence of a grand-unification group. We propose an SU(3)xSU(2)xU(1) model where both supersymmetry and the assumed A4 flavor symmetries are softly broken, reproducing well the observed fermion mass hierarchies and predicting: (i) a relation between down-type quarks and charged lepton masses, and (ii) a correlation between the Cabibbo angle in the quark sector, and the reactor angle characterizing CP violation in neutrino oscillations.
Predicted ultrafast dynamic metallization of dielectric nanofilms by strong single-cycle optical fields.

We predict a dynamic metallization effect where an ultrafast (single-cycle) optical pulse with a ≲1 V/Å field causes plasmonic metal-like behavior of a dielectric film with a few-nm thickness. This manifests itself in plasmonic oscillations of polarization and a significant population of the conduction band evolving on a ~1 fs time scale. These phenomena are due to a combination of both adiabatic (reversible) and diabatic (for practical purposes irreversible) pathways.
Discretisation of a stochastic continuum equation of ion-sputtered surfaces

The generalised continuum theory model of the dynamical evolution of surfaces sputtered by ion-bombardment is a noisy Kuramoto-Sivashinsky type partial differential equation. For some generic cases of sputtering parameters, existing similar equations have shed a great deal of light and therefore provided some understanding of the intricacies of evolving ion-sputtered surfaces without a direct solution of the generalised model. However, recent results have demonstrated a wider range of scaling regimes of the sputtering conditions, a large number of which have no similar existing solved models in other research fields for comparison, and whose characteristics are therefore largely unknown. In this paper, a discretisation of the generalised continuum model is performed for direct numerical simulations, the results of which are applicable to all manner of simulations required for the different possible scenarios in the dynamical evolution of sputtered surfaces. The approximation errors and implementation of the results in any such simulation are also discussed.
Default clustering in large portfolios: Typical events.

We develop a dynamic point process model of correlated default timing in a portfolio of firms, and analyze typical default profiles in the limit as the size of the pool grows. In our model, a firm defaults at a stochastic intensity that is influenced by an idiosyncratic risk process, a systematic risk process common to all firms, and past defaults. We prove a law of large numbers for the default rate in the pool, which describes the "typical" behavior of defaults.
Collaboration in social networks

The very notion of social network implies that linked individuals interact repeatedly with each other. This notion allows them not only to learn successful strategies and adapt to them, but also to condition their own behavior on the behavior of others, in a strategic forward looking manner. Game theory of repeated games shows that these circumstances are conducive to the emergence of collaboration in simple games of two players. We investigate the extension of this concept to the case where players are engaged in a local contribution game and show that rationality and credibility of threats identify a class of Nash equilibria—that we call “collaborative equilibria”—that have a precise interpretation in terms of subgraphs of the social network. For large network games, the number of such equilibria is exponentially large in the number of players. When incentives to defect are small, equilibria are supported by local structures whereas when incentives exceed a threshold they acquire a nonlocal nature, which requires a “critical mass” of more than a given fraction of the players to collaborate. Therefore, when incentives are high, an individual deviation typically causes the collapse of collaboration across the whole system. At the same time, higher incentives to defect typically support equilibria with a higher density of collaborators. The resulting picture conforms with several results in sociology and in the experimental literature on game theory, such as the prevalence of collaboration in denser groups and in the structural hubs of sparse networks.
Astronomical alignments as the cause of ~M6+ seismicity

I here demonstrate empirically my georesonator concept in which tidally induced magnification of Earth masses' resonance causes seismicity on Earth. I show that all strong (~M6+) earthquakes of 2010 occurred during Earth's long (t > 3 days) astronomical alignments within our solar system. I then show that the same holds true for all very strong (~M8+) earthquakes of the decade of 2000's. Finally, strongest (M8.6+) earthquakes of the past century are shown to have occurred during Earth's multiple long alignments, too, whereas half of the high-strongest (M9+) earthquakes occurred during Full Moon. To add robustness, I include alignments to comet C/2010 X1 (Elenin) as the only heavenly body currently in our solar system besides planets, and show that it impacted very strong seismicity since 2007. I conclude my empirical demonstration with a six-month, 100%-successful forecast of M6+ magnification, performed online in near real-time from October 2011 until April 2012, and which shows always the same, fractal pattern of intensifying-peaking-diminishing of strong earthquakes' strength during long alignments, and the absence of the pattern outside alignments. Days without killer quake can now be known exactly, amounting to several months a year of exact seismic forecast (telling with certainty there will be no strong seisms on that-and-that date). Approximate forecast of strength and timing of strong earthquakes is feasible for the rest of the year, as well as of location once the alignment starts. I thus verified my hyperresonator concept too, arrived at earlier as a mathematical-physical solution to the most general extension of georesonator. As gravity can now be expressed in terms of speed of light, hyperresonance is akin to tuning forks triggering each other at a distance, inferring the existence of aether required for propagation of mutually tuning (interfering) oscillations in Space.
Precision benchmark calculations for four particles at unitarity

The unitarity limit describes interacting particles where the range of the interaction is zero and the scattering length is infinite. We present precision benchmark calculations for two-component fermions at unitarity using three different ab initio methods: Hamiltonian lattice formalism using iterated eigenvector methods, Euclidean lattice formalism with auxiliary-field projection Monte Carlo methods, and continuum diffusion Monte Carlo methods with fixed and released nodes. We have calculated the ground-state energy of the unpolarized four-particle system in a periodic cube as a dimensionless fraction of the ground-state energy for the noninteracting system. We obtain values of 0.211(2) and 0.210(2) using two different Hamiltonian lattice representations, 0.206(9) using Euclidean lattice formalism, and an upper bound of 0.212(2) from fixed-node diffusion Monte Carlo methods. Released-node calculations starting from the fixed-node result yield a decrease of less than 0.002 over a propagation of 0.4E{sub F}{sup -1} in Euclidean time, where E{sub F} is the Fermi energy. We find good agreement among all three ab initio methods.
Quantum mechanical model of the upper bounds of the cascading contribution to the second hyperpolarizability

Microscopic cascading of second-order nonlinearities between two molecules has been proposed to yield an enhanced third-order molecular nonlinear-optical response. In this contribution, we investigate the two-molecule cascaded second hyperpolarizability and show that it will never exceed the fundamental limit of a single molecule with the same number of electrons as the two-molecule system. We show the apparent divergence behavior of the cascading contribution to the second hyperpolarizability vanishes when properly taking into account the intermolecular interactions. Although cascading can never lead to a larger nonlinear-optical response than a single molecule, it provides alternative molecular design configurations for creating materials with large third-order susceptibilities that may be difficult to design into a single molecule.
Evidence for the $J^p = 1/2^+$ narrow state at 1650 MeV in the photoproduction of KLambda

We have investigated the existence of the J^p=1/2^+ narrow resonance predicted by the chiral soliton model by utilizing the kaon photoproduction process gamma + p --> K^+ + Lambda. For this purpose we have constructed two phenomenological models based on our previous effective Lagrangian model, which are able to describe kaon photoproduction from threshold up to W = 1730 MeV. By varying the mass (width) of an inserted P_{11} resonance from 1620 to 1730 MeV (0.1 to 1 MeV and 1 to 10 MeV) a number of fits has been performed in order to search for the resonance mass. Our result indicates that the most promising candidate mass (width) of this resonance is 1650 MeV (5 MeV). Although our calculation does not exclude the possibility of narrow resonances with masses of 1680, 1700 and 1720 MeV, the mass of 1650 MeV is obtained for all phenomenological models used in this investigation. Variations of the resonance width and $K\Lambda$ branching ratio are found to have a mild effect on the chi^2. The possibility that the obtained result originates from other resonance states is also discussed.
Spatially resolved kinematics of an ultracompact dwarf galaxy

We present the internal kinematics of UCD3, the brightest known ultracompact dwarf galaxy (UCD) in the Fornax cluster, making this the first UCD with spatially resolved spectroscopy. Our study is based on seeing-limited observations obtained with the ARGUS Integral Field Unit of the VLT/FLAMES spectrograph under excellent seeing conditions (0.5-0.67 arcsec FWHM).
DISCOVERY OF A LARGE STELLAR PERIPHERY AROUND THE SMALL MAGELLANIC CLOUD

The Magellanic Clouds are a local laboratory for understanding the evolution and properties of dwarf irregular galaxies. To reveal the extended structure and interaction history of the Magellanic Clouds we have undertaken a large-scale photometric and spectroscopic study of their stellar periphery (the MAgellanic Periphery Survey, MAPS). We present first MAPS results for the Small Magellanic Cloud (SMC): Washington M, T2 + DDO51 photometry reveals metal-poor red giant branch stars in the SMC that extend to large radii (∼11 kpc), are distributed nearly azimuthally symmetrically (ellipticity = 0.1), and are well fitted by an exponential profile (out to R ≈ 7.°5). An ∼6 Gyr old, [Fe/H] ≈ −1.3 main-sequence turnoff is also evident to at least R = 7.°3, and as far as 8.°4 in some directions. We find evidence for a “break” population beyond ∼8 radial scale lengths having a very shallow radial density profile that could be either a bound stellar halo or a population of extratidal stars. The distribution of the intermediate stellar component (3°≲ R ≲ 7.°5) contrasts with that of the inner stellar component (R ≲ 3°), which is both more elliptical (ϵ ≈ 0.3) and offset from the center of the intermediate component by 0.°59, although both components share a similar radial exponential scale length. This offset is likely due to a perspective effect because stars on the eastern side of the SMC are closer on average than stars on the western side. This mapping of its outer stellar structures indicates that the SMC is more complex than previously thought.
Scattering States in AdS/CFT

We show that suitably regulated multi-trace primary states in large N CFTs behave like 'in' and 'out' scattering states in the flat-space limit of AdS. Their transition matrix elements approach the exact scattering amplitudes for the bulk theory, providing a natural CFT definition of the flat space S-Matrix. We study corrections resulting from the AdS curvature and particle propagation far from the center of AdS, and show that AdS simply provides an IR regulator that disappears in the flat space limit.
Dislocation-mediated melting of one-dimensional Rydberg crystals

We consider cold Rydberg atoms in a one-dimensional optical lattice in the Mott regime with a single atom per site at zero temperature. An external laser drive with Rabi frequency {Omega} and laser detuning {Delta} creates Rydberg excitations whose dynamics is governed by an effective spin-chain model with (quasi) long-range interactions. This system possesses intrinsically a large degree of frustration resulting in a ground-state phase diagram in the ({Delta},{Omega}) plane with a rich topology. As a function of {Delta}, the Rydberg blockade effect gives rise to a series of crystalline phases commensurate with the optical lattice that form a so-called devil's staircase. The Rabi frequency {Omega}, on the other hand, creates quantum fluctuations that eventually lead to a quantum melting of the crystalline states. Upon increasing {Omega}, we find that generically a commensurate-incommensurate transition to a floating Rydberg crystal that supports gapless phonon excitations occurs first. For even larger {Omega}, dislocations within the floating Rydberg crystal start to proliferate and a second, Kosterlitz-Thouless-Nelson-Halperin-Young dislocation-mediated melting transition finally destroys the crystalline arrangement of Rydberg excitations. This latter melting transition is generic for one-dimensional Rydberg crystals and persists even in the absence of an optical lattice. The floating phase and the concomitantmore » transitions can, in principle, be detected by Bragg scattering of light.« less
Statistical mechanics of the international trade network

Analyzing real data on international trade covering the time interval 1950-2000, we show that in each year over the analyzed period the network is a typical representative of the ensemble of maximally random weighted networks, whose directed connections (bilateral trade volumes) are only characterized by the product of the trading countries' GDPs. It means that time evolution of this network may be considered as a continuous sequence of equilibrium states, i.e., a quasistatic process. This, in turn, allows one to apply the linear response theory to make (and also verify) simple predictions about the network. In particular, we show that bilateral trade fulfills a fluctuation-response theorem, which states that the average relative change in imports (exports) between two countries is a sum of the relative changes in their GDPs. Yearly changes in trade volumes prove that the theorem is valid.
Modelo An\'alogo Ac\'ustico ao Buraco Negro de Schwarzschild

Um fluido em movimento pode agir sobre o som da mesma forma que os espa\c{c}o-tempos curvos podem influenciar na trajet\'oria da luz na relatividade geral. Com isso, pode-se descrever a propaga\c{c}\~ao dessas ondas sonoras atrav\'es de uma m\'etrica efetiva, sob a qual elas seguir\~ao geod\'esicas nulas. Esta disserta\c{c}\~ao faz uma revis\~ao destes estudos concentrando-se em uma analogia ac\'ustica para um buraco negro de Schwarzschild, demonstrando suas vantagens e limita\c{c}\~oes quando aplicada para o estudo da teoria de Hawking. 
A fluid in moviment can act on the sound the same way that curved space-time can influence on light trajectory in the general relativity. So, one can describe the propagation these sound waves through an effective metric, under wich they will follow null geodesics. This thesis makes a review of these studies focusing in an analogy to Schwarzschild black hole using an acoustic system, showing its advantages and limitations when applied in the study of Hawking's theory.
Radiative transitions in charmonium from N-f=2 twisted mass lattice QCD

We present an exploratory study for charmonium radiative transitions: J/psi -> eta(c)gamma, chi(c0) -> J/Psi gamma, and h(c) -> eta(c)gamma using Nf = 2 twisted-mass lattice QCD gauge configurations. The single-quark vector form factors for eta(c) and chi(c0) are also determined. The simulation is performed at a lattice spacing of a = 0.067(2) fm and the lattice size is 32(3) x 64 with a pion mass of about 485 MeV. After extrapolation of lattice data at nonzero Q(2) to 0, we compare our results with previous quenched lattice results and the available experimental values.
Spin Foam Models for Quantum Gravity and semi-classical limit

The spinfoam framework is a proposal for a regularized path integral for quantum gravity. Spinfoams define quantum space-time structures describing the evolution in time of the spin network states for quantum geometry derived from Loop Quantum Gravity (LQG). The construction of this covariant approach is based on the formulation of General Relativity as a topological theory plus the so-called simplicity constraints which introduce local degrees of freedom. The simplicity constraints are essential in turning the non-physical topological theory into 4d gravity. In this PhD manuscript, an original way to impose the simplicity constraints in 4d Euclidean gravity using harmonic oscillators is proposed and new coherent states, solutions of the constraints, are given. Moreover, a consistent spinfoam model for quantum gravity has to be connected to LQG and must have the right semi-classical limit. An explicit map between the spin network states of LQG and the boundary states of spinfoam models is given connecting the canonical and the covariant approaches. Finally, new techniques to compute semiclassical asymptotic expressions for the transition amplitudes of 3d quantum gravity and to extract semi-classical information from a spinfoam model are introduced. Explicit computations based on approximation methods and on the use of recurrence relations on spinfoam amplitudes have been performed. The results are relevant to derive quantum corrections to the dynamics of the gravitational field.
Can Quantum Mechanics explain the Evolution of the Universe

This manuscript deals with a model of the evolution of an event space represented by the fundamental solution of a N-dimensional generalized Schrodinger equation for free matter. Specifically this solution can be applied to describe the 3D space evolution of the Universe in the forward direction in time. The model which is based on the presented solution is close to the well known Inflation theory, but is nonsingular, does not violate the conservation laws and is finite throughout the whole space at any moment of time. According to this model, the evolution progresses non-uniformly with a positive acceleration. Moreover, the model correctly approaches Hubble's law in the long-time limit. It is also shown that any source functions which describe substance and its physical fields set space topology of the Universe, but do not influence the general dynamics of its evolution.
Relation between 2Delta/Tc and nodes in Fe-based superconductors

We analyze the interplay between the absence or presence of the nodes in the superconducting gap along electron Fermi surfaces (FSs) in Fe-pnictides, and 2Delta/T_c along hole FSs, measured by ARPES. We solve the set of coupled gap equations for 4-band and 5-band models of Fe-pnictides and relate the presence of the nodes to 2\Delta/T_c being below a certain threshold. Using ARPES data for 2\Delta/T_c, we find that optimally doped (BaK)Fe_2As_2 and Ba(FeCo)_2As_2 and likely nodeless, but iso-valent BaFe_2(AsP)_2 likely has nodes.