Miracle-dz/UniFAR-FTUs huggingface dataset:
Large-scale instability in interacting dark energy and dark matter fluids

If dark energy interacts with dark matter, this gives a new approach to the coincidence problem. But interacting dark energy models can suffer from pathologies. We consider the case where the dark energy is modelled as a fluid with constant equation of state parameter w. Non-interacting constant-w models are well behaved in the background and in the perturbed universe. But the combination of constant w and a simple interaction with dark matter leads to an instability in the dark sector perturbations at early times: the curvature perturbation blows up on super-Hubble scales. Our results underline how important it is to carefully analyse the relativistic perturbations when considering models of coupled dark energy. The instability that we find has been missed in some previous work where the perturbations were not consistently treated. The unstable mode dominates even if adiabatic initial conditions are used. The instability also arises regardless of how weak the coupling is. This non-adiabatic instability is different from previously discovered adiabatic instabilities on small scales in the strong-coupling regime.
AN UPPER BOUND TO THE SPACE DENSITY OF INTERSTELLAR COMETS

Two well-studied white dwarfs with helium-dominated atmospheres (DBs) each possess less hydrogen than carried by a single average-mass comet. Plausibly, the wind rates from these stars are low enough that most accreted hydrogen remains with the star. If so, and presuming their nominal effective temperatures, then these DBs have faced minimal impact by interstellar comets during their 50 Myr cooling age; interstellar iceballs with radii between 10 m and 2 km contain less than 1% of all interstellar oxygen. This analysis suggests that most stars do not produce comets at the rate predicted by “optimistic” scenarios for the formation of the Oort Cloud.
Fashion or Function: Examining Consumers’ Perceived Values of Mass-Customized Menswear via a Content Mining Approach

Mass customization has been used in various clothing products including T-shirts, dress shirts, jeans, sports shoes, accessories, etc. However, even though the concept of mass customization has been accepted among scholars and business practitioners, and the application of mass customization has been practiced in the fashion industry for more than two decades, the acceptance among ultimate consumers and the market of MC in the apparel industry has not taken off yet. To this end, this study intends to fill the identified gap through a content mining exploratory qualitative study using customer value theory to evaluate individual consumers’ actual customization experiences. Results identified that functional value, self-expressive value, and aesthetic value were derived from menswear customization experiences. Among them, functional value (e.g., quality, fit) is the dominant dimension of value derived from menswear customization experiences, and it determined consumers’ overall attitudes toward mass customization of menswear.
NBER WORKING PAPER SERIES DISSECTING GREEN RETURNS

Green assets delivered high returns in recent years. This performance reflects unexpectedly strong increases in environmental concerns, not high expected returns. German green bonds outperformed their higher-yielding non-green twins as the “greenium” widened, and U.S. green stocks outperformed brown as climate concerns strengthened. Despite that outperformance, we estimate lower expected returns for green stocks than for brown, consistent with theory. We estimate expected returns in two ways: ex ante, using implied costs of capital, and ex post, using realized returns purged of shocks from climate concerns and earnings. A theoretically motivated green factor explains much of value stocks' recent underperformance. Lubos Pastor University of Chicago Booth School of Business 5807 South Woodlawn Ave Chicago, IL 60637 and NBER lubos.pastor@chicagobooth.edu Robert F. Stambaugh Finance Department The Wharton School University of Pennsylvania Philadelphia, PA 19104-6367 and NBER stambaugh@wharton.upenn. edu Lucian A. Taylor Finance Department The Wharton School University of Pennsylvania 2300 Steinberg Hall Dietrich Hall 3620 Locust Walk Philadelphia, PA 19104-6367 luket@wharton.upenn. edu A data appendix is available at http://www.nber. org/data-appendix/w28940
Approximate method of free energy calculation for spin system with arbitrary connection matrix

The proposed method of the free energy calculation is based on the approximation of the energy distribution in the microcanonical ensemble by the Gaussian distribution. We hope that our approach will be effective for the systems with long-range interaction, where large coordination number q ensures the correctness of the central limit theorem application. However, the method provides good results also for systems with short-range interaction when the number q is not so large.
Percolation theory on interdependent networks based on epidemic spreading

We consider percolation on interdependent locally treelike networks, recently introduced by Buldyrev S. V. et al., Nature, 464 (2010) 1025, and demonstrate that the problem can be simplified conceptually by deleting all references to cascades of failures. Such cascades do exist, but their explicit treatment just complicates the theory —which is a straightforward extension of the usual epidemic spreading theory on a single network. Our method has the added benefits that it is directly formulated in terms of an order parameter and its modular structure can be easily extended to other problems, e.g. to any number of interdependent networks, or to networks with dependency links.
WIDE RADIO BEAMS FROM γ-RAY PULSARS

We investigate the radio and γ-ray beaming properties of normal and millisecond pulsars (MSPs) by selecting two samples from the known populations. The first, Sample G, contains pulsars which are detectable in blind searches of γ-ray data from the Fermi Large Area Telescope. The second, Sample R, contains pulsars detectable in blind radio searches which have spin-down luminosities Ė>1034 erg s−1. We analyze the fraction of the γ-ray-selected Sample G which have detectable radio pulses and the fraction of the radio-selected Sample R which have detectable γ-ray pulses. Twenty of our 35 Sample G pulsars have already observed radio pulses. This rules out low-altitude polar-cap beaming models if, as is currently believed, γ-ray beams are generated in the outer magnetosphere and are very wide. We further find that, for the highest-Ė pulsars, the radio and γ-ray beams have comparable beaming factors, i.e., the beams cover similar regions of the sky as the star rotates. For lower-Ė γ-ray emitting pulsars, the radio beams have about half of the γ-ray sky coverage. These results suggest that, for high-Ė young and MSPs, the radio emission originates in wide beams from regions high in the pulsar magnetosphere, probably close to the null-charge surface and to the γ-ray emitting regions. Furthermore, it suggests that for these high-Ė pulsars, as in the γ-ray case, features in the radio profile represent caustics in the emission beam pattern.
On the formation of planetary systems in photoevaporating transition discs

In protoplanetary discs, planetary cores must be at least 0.1 earth mass at 1 au for migration to be significant; this mass rises to 1 earth mass at 5 au. Planet formation models indicate that these cores form on million year timescales. We report here a study of the evolution of 0.1 earth mass and 1 earth mass cores, migrating from about 2 and 5 au respectively, in million year old photoevaporating discs. In such a disc, a gap opens up at around 2 au after a few million years. The inner region subsequently accrete onto the star on a smaller timescale. We find that, typically, the smallest cores form systems of non-resonant planets beyond 0.5 au with masses up to about 1.5 earth mass. In low mass discs, the same cores may evolve in situ. More massive cores form systems of a few earth masses planets. They migrate within the inner edge of the disc gap only in the most massive discs. Delivery of material to the inner parts of the disc ceases with opening of the gap. Interestingly, when the heavy cores do not migrate significantly, the type of systems that are produced resembles our solar system. This study suggests that low mm flux transition discs may not form systems of planets on short orbits but may instead harbour earth mass planets in the habitable zone.
Constraints on shear and rotation with massive galaxy clusters

A precise determination of the mass function is an important tool to verify cosmological predictions of the $\Lambda$CDM model and to infer more precisely the better model describing the evolution of the Universe. Galaxy clusters have been currently used to infer cosmological parameters, in particular the matter density parameter $\Omega_{\rm m}$, the matter power spectrum normalization $\sigma_8$ and the equation of state parameter $w_{\rm de}$ of the dark energy fluid. In this work, using data on massive galaxy clusters ($M>8\times 10^{14}~h^{-1}~M_{\odot}$) in the redshift range $0.05\lesssim z\lesssim 0.83$ we put constraints on the parameter $\alpha$ introduced within the formalism of the extended spherical collapse model to quantify deviations from sphericity due to shear and rotation. Since at the moment there is no physical model describing its functional shape, we assume it to be a logarithmic function of the cluster mass. By holding $\sigma_8$ fixed and restricting our analysis to a $\Lambda$CDM model, we find, at $1-\sigma$ confidence level, $\Omega_{\rm m}=0.284\pm0.0064$, $h=0.678\pm0.017$ and $\beta=0.0019^{+0.0008}_{-0.0015}$, where $\beta$ represents the slope of the parameter $\alpha$. This results translates into a $9\%$ decrement of the number of massive clusters with respect to a standard $\Lambda$CDM mass function, but better data are required to better constrain this quantity, since at the $2-\sigma$ and $3-\sigma$ confidence level we are only able to infer upper limits.
Weak-lensing-inferred scaling relations of galaxy clusters in the RCS2: mass-richness, mass-concentration, mass-bias, and more

We study a sample of ~10^4 galaxy clusters in the redshift range 0.2 5x10^13 h_70^-1 M_sun, discovered in the second Red-sequence Cluster Survey (RCS2). The depth and excellent image quality of the RCS2 enable us to detect the cluster-mass cross-correlation up to z~0.7. To obtain cluster masses, concentrations and halo biases, we fit a cluster halo model simultaneously to the lensing signal and to the projected density profile of red-sequence cluster members, as the latter provides tight constraints on the cluster miscentring distribution. We parametrise the mass-richness relation as M_200 = A x (N_200/20)^alpha, and find A = (15.0 +- 0.8) x 10^13 h_70^-1 M_sun and alpha = 0.73 +- 0.07 at low redshift (0.2<z<0.35). At intermediate redshift (0.35<z<0.55), we find a higher normalisation, which points at a fractional increase of the richness towards lower redshift caused by the build-up of the red-sequence. The miscentring distribution is well constrained. Only ~30% of our BCGs coincide with the peak of the dark matter distribution. The distribution of the remaining BCGs are modelled with a 2D-Gaussian, whose width increases from 0.2 to 0.4 h_70^-1 Mpc towards higher masses; the ratio of width and r_200 is constant with mass and has an average value of 0.44 +- 0.01. The mass-concentration and mass-bias relation agree fairly well with literature results at low redshift, but have a higher normalisation at higher redshifts, which may be due to selection and projection effects. The concentration of the satellite distribution decreases with mass and is correlated with the concentration of the halo.
An improved method for the identification of galaxy systems: Measuring the gravitational redshift by Dark Matter Haloes

We introduce a new method for the identification of galaxy systems in redshift surveys based on the halo model. This method is a modified version of the K-means identification algorithm developed by Yang et al (2005). We have calibrated and tested our algorithms using mock catalogs generated using the Millennium simulations (Springel et al. 2005) and applied them to the NYU-DR7 galaxy catalog (based on the SDSS datasets). Using this local sample of groups and clusters of galaxies we have measured the effect of gravitational redshift produced by their host dark matter haloes. Our results shows radial velocity decrements consistent with general relativity predictions and previous measurements by Wojtak et al (2011) in clusters of galaxies.
IONIZED REFLECTION SPECTRA FROM ACCRETION DISKS ILLUMINATED BY X-RAY PULSARS

X-ray reflection signatures are observed around multiple classes of accreting compact objects. Modeling these features yields important constraints on the physics of accretion disks, motivating the development of X-ray reflection models appropriate for a variety of systems and illumination conditions. Here, constant density ionized X-ray reflection models are presented for a disk irradiated with a very hard power-law X-ray spectrum (Γ < 1) and a variable high-energy cutoff. These models are then applied to the Suzaku data of the accreting X-ray pulsar LMC X-4, where very good fits are obtained with a highly ionized reflector responsible for both the broad Fe Kα line and the soft excess. The ionized reflector shows strong evidence for significant Doppler broadening and is redshifted by ∼104 km s−1. These features indicate that the reflecting material is associated with the complex dynamics occurring at the inner region of the magnetically truncated accretion disk. Thus, reflection studies of X-ray pulsar spectra may give important insights into the accretion physics at the magnetospheric radius.
Modelling neutral hydrogen in galaxies using cosmological hydrodynamical simulations

The characterization of the atomic and molecular hydrogen content of high-redshift galaxies is a major observational challenge that will be addressed over the coming years with a new generation of radio telescopes. We investigate this important issue by considering the states of hydrogen across a range of structures within high-resolution cosmological hydrodynamical simulations. In addition, our simulations allow us to investigate the sensitivity of our results to numerical resolution and to sub-grid baryonic physics (especially feedback from supernovae and active galactic nuclei). We find that the most significant uncertainty in modelling the neutral hydrogen distribution arises from our need to model a self-shielding correction in moderate density regions. Future simulations incorporating radiative transfer schemes will be vital to improve on our empirical self-shielding threshold. Irrespective of the exact nature of the threshold, we find that while the atomic hydrogen mass function evolves only mildly from redshift two to zero, the molecular hydrogen mass function increases with increasing redshift, especially at the high-mass end. Interestingly, the weak evolution of the neutral hydrogen mass function is insensitive to the feedback scheme utilized, but the opposite is true for the molecular gas, which is more closely associated with the star formation in the simulations.
Equilibrium state of a trapped two-dimensional Bose gas

We study experimentally and numerically the equilibrium density profiles of a trapped two-dimensional $^{87}\mathrm{Rb}$ Bose gas and investigate the equation of state of the homogeneous system using the local density approximation. We find a clear discrepancy between in situ measurements and quantum Monte Carlo simulations, which we attribute to a nonlinear variation of the optical density of the atomic cloud with its spatial density. However, good agreement between experiment and theory is recovered for the density profiles measured after time of flight, taking advantage of their self-similarity in a two-dimensional expansion.
Blowing cold flows away: the impact of early AGN activity on the formation of a brightest cluster galaxy progenitor

Supermassive black holes (BH) are powerful sources of energy that are already in place at very early epochs of the Universe (by z=6). Using hydrodynamical simulations of the formation of a massive M_vir=5 10^11 M_sun halo by z=6 (the most massive progenitor of a cluster of M_vir=2 10^15 M_sun at z=0), we evaluate the impact of Active Galactic Nuclei (AGN) on galaxy mass content, BH self-regulation, and gas distribution inside this massive halo. We find that SN feedback has a marginal influence on the stellar structure, and no influence on the mass distribution on large scales. In contrast, AGN feedback alone is able to significantly alter the stellar-bulge mass content by quenching star formation when the BH is self-regulating, and by depleting the cold gas reservoir in the centre of the galaxy. The growth of the BH proceeds first by a rapid Eddington-limited period fed by direct cold filamentary infall. When the energy delivered by the AGN is sufficiently large to unbind the cold gas of the bulge, the accretion of gas onto the BH is maintained both by smooth gas inflow and clump migration through the galactic disc triggered by merger-induced torques. The feedback from the AGN has also a severe consequence on the baryon mass content within the halo, producing large-scale hot superwinds, able to blow away some of the cold filamentary material from the centre and reduce the baryon fraction by more than 30 per cent within the halo's virial radius. Thus in the very young universe, AGN feedback is likely to be a key process, shaping the properties of the most massive galaxies.
Bagging Propensity Weighting: A Robust method for biased PU Learning

Propensity weighting enables learning from positive and unlabeled data (PU learning) in the face of labeling bias. PU learning aims to train a binary classification model when only positive and unlabeled data is available to learn from. This problem setting arises commonly in practice. Often, PU data suffers from a labeling bias, where the labeled examples are a biased sample from the positive examples. The probability for a positive example to get selected to be labeled is called its propensity score. Weighting PU datasets using propensity scores, allows to learn an unbiased model from biased PU data. However, this method has a strong downside of being rather unstable. This paper proposes a robust method for learning from biased PU data based on bagging. We show that the proposed method remains unbiased, while it reduces the variance and hence increases robustness. Our experiments confirms this by showing that our method has lower variance and classification error than plain propensity weighting as well as another method that was proposed for variance reduction.
Importance of torsion and invariant volumes in Palatini theories of gravity

The work of G. J. O. has been supported by the Spanish Grant No. FIS2011-29813-C02-02 and the JAE-doc program of the Spanish Research Council (CSIC). D. R. -G. is financially supported by CNPq (Brazilian agency) through Grant No. 561069/2010-7, and thanks the theoretical physics group at Valencia University, where part of this work was carried out, for hospitality and partial support. The authors thank L. Fatibene and M. Francaviglia for useful discussions.
Measuring neutrino mass imprinted on the anisotropic galaxy clustering

The anisotropic galaxy clustering of large scale structure observed by the Baryon Oscillation Spectroscopic Survey Data Release 11 is analyzed to probe the sum of neutrino masses in the small mν ≲ 1 eV limit in which the early broadband shape determined before the last scattering surface is immune from the variation of mν. The signature of mν is imprinted on the altered shape of the power spectrum at later epoch, which provides an opportunity to access the non-trivial mν through the measured anisotropic correlation function in redshift space (hereafter RSD instead of Redshift Space Distortion). The non-linear RSD corrections with massive neutrinos in the quasi linear regime are approximately estimated using one-loop order terms. We suggest an approach to probe mν simultaneously with all other distance measures and coherent growth functions, exploiting this deformation of the early broadband shape of the spectrum at later epoch. If the origin of cosmic acceleration is unknown, mν is poorly determined after marginalizing over all other observables. However, we find that the measured distances and coherent growth functions are minimally affected by the presence of mild neutrino mass. Although the standard model of cosmic acceleration is assumed to be the cosmological constant, the constraint on mν is little improved. Interestingly, the measured Cosmic Microwave Background (hereafter CMB) distance to the last scattering surface sharply slices the degeneracy between the matter content and mν, and the mν is observed to be mν = 0.19+0.28−0.17 eV which is different from massless neutrino at 68% confidence.
Self-gravitating equilibrium models of dwarf galaxies and the minimum mass for star formation

Context. We constructed a series of model galaxies in rotational equilibrium consisting of gas, stars, and a fixed dark matter (DM) halo and studied how these equilibrium systems depend on the mass and form of the DM halo, gas temperature, non-thermal and rotation support against gravity, and also on the redshift of galaxy formation. For every model galaxy we found the minimum gas mass M min required to achieve a state in which star formation (SF) is allowed according to contemporary SF criteria. The obtained M min ‐MDM relations were compared against the baryon-to-DM mass relation Mb‐MDM inferred from the ΛCDM theory and WMAP4 data. Aims. Our aim is to construct realistic initial models of dwarf galaxies (DGs), which take into account the gas self-gravity and can be used as a basis to study the dynamical and chemical evolution of DGs. Methods. Rotating equilibria are found by solving numerically the steady-state momentum equation for the gas component in the combined gravitational potential of gas, stars, and DM halo using a forward substitution procedure. Results. We find that for a given MDM the value of M min depends crucially on the gas temperature Tg, gas spin parameter α ,d egree of non-thermal support σeff, and somewhat on the redshift for galaxy formation zgf. Depending on the actual values of Tg, α, σeff ,a ndzgf,
CHARACTERIZATION OF THE KOI-94 SYSTEM WITH TRANSIT TIMING VARIATION ANALYSIS: IMPLICATION FOR THE PLANET–PLANET ECLIPSE

The KOI-94 system is a closely packed, multi-transiting planetary system discovered by the Kepler space telescope. It is known as the first system that exhibited a rare event called a “planet–planet eclipse (PPE),” in which two planets partially overlap with each other in their double-transit phase. In this paper, we constrain the parameters of the KOI-94 system with an analysis of the transit timing variations (TTVs). Such constraints are independent of the radial velocity (RV) analysis recently performed by Weiss and coworkers, and valuable in examining the reliability of the parameter estimate using TTVs. We numerically fit the observed TTVs of KOI-94c, KOI-94d, and KOI-94e for their masses, eccentricities, and longitudes of periastrons, and obtain the best-fit parameters including , , , and e ≲ 0.1 for all the three planets. While these values are mostly in agreement with the RV result, the mass of KOI-94d estimated from the TTV is significantly smaller than the RV value md = 106 ± 11 M⊕. In addition, we find that the TTV of the outermost planet KOI-94e is not well reproduced in the current modeling. We also present analytic modeling of the PPE and derive a simple formula to reconstruct the mutual inclination of the two planets from the observed height, central time, and duration of the brightening caused by the PPE. Based on this model, the implication of the results of TTV analysis for the time of the next PPE is discussed.