Negative / Null Result ReportOpen accessPhysics and Astronomy
Broido, Anna D, Clauset, Aaron · 2019 · CU Scholar (University of Colorado Boulder)
Real-world networks are often claimed to be scale free, meaning that the fraction of nodes with degree k follows a power law k-α, a pattern with broad implications for the structure and dynamics of complex systems. However, the universality of scale-free networks remains controversial. Here, we organize different definitions of scale-free networks and construct a severe test of their empirical prevalence using state-of-the-art statistical tools applied to nearly 1000 social, biological, technological, transportation, and information networks. Across these networks, we find robust evidence that
View details →Negative / Null Result ReportOpen accessPhysics and Astronomy
Anna D. Broido, Aaron Clauset · 2019 · Nature Communications
, a pattern with broad implications for the structure and dynamics of complex systems. However, the universality of scale-free networks remains controversial. Here, we organize different definitions of scale-free networks and construct a severe test of their empirical prevalence using state-of-the-art statistical tools applied to nearly 1000 social, biological, technological, transportation, and information networks. Across these networks, we find robust evidence that strongly scale-free structure is empirically rare, while for most networks, log-normal distributions fit the data as well or be
View details →Negative / Null Result ReportOpen accessPhysics and Astronomy
The CDMS II Collaboration · 2010 · Science
Astrophysical observations indicate that dark matter constitutes most of the mass in our universe, but its nature remains unknown. Over the past decade, the Cryogenic Dark Matter Search (CDMS II) experiment has provided world-leading…
View details →Negative / Null Result ReportOpen accessPhysics and Astronomy
Kevork N. Abazajian, Manoj Kaplinghat · 2012 · Physical review. D. Particles, fields, gravitation, and cosmology/Physical review. D, Particles, fields, gravitation, and cosmology
We show the existence of a statistically significant, robust detection of a gamma-ray source in the Milky Way Galactic Center that is consistent with a spatially extended signal using about 4 years of Fermi-LAT data. The gamma-ray flux is…
View details →Negative / Null Result ReportPhysics and Astronomy
Lorenz Roth, Joachim Saur, K. D. Retherford et al. · 2013 · Science
In November and December 2012, the Hubble Space Telescope (HST) imaged Europa's ultraviolet emissions in the search for vapor plume activity. We report statistically significant coincident surpluses of hydrogen Lyman-α and oxygen OI…
View details →Negative / Null Result ReportOpen accessPhysics and Astronomy
Z. Arzoumanian, P. T. Baker, A. Brazier et al. · 2018 · The Astrophysical Journal
Abstract We search for an isotropic stochastic gravitational-wave background (GWB) in the newly released 11 year data set from the North American Nanohertz Observatory for Gravitational Waves (NANOGrav). While we find no evidence for a…
View details →Negative / Null Result ReportOpen accessPhysics and Astronomy
M. Ackermann, M. Ajello, A. Allafort et al. · 2012 · The Astrophysical Journal
Recent detections of the starburst galaxies M82 and NGC 253 by gamma-ray telescopes suggest that galaxies rapidly forming massive stars are more luminous at gamma-ray energies compared to their quiescent relatives. Building upon those…
View details →Negative / Null Result ReportOpen accessPhysics and Astronomy
Zaven Arzoumanian, P. T. Baker, Adam Brazier et al. · 2024 · Figshare
We search for an isotropic stochastic gravitational-wave background (GWB) in the newly released 11 year data set from the North American Nanohertz Observatory for Gravitational Waves (NANOGrav). While we find no evidence for a GWB, we place constraints on a population of inspiraling supermassive black hole (SMBH) binaries, a network of decaying cosmic strings, and a primordial GWB. For the first time, we find that the GWB constraints are sensitive to the solar system ephemeris (SSE) model used and that SSE errors can mimic a GWB signal. We developed an approach that bridges systematic SSE diff
View details →Negative / Null Result ReportPhysics and Astronomy
Jiawei Fan, Jiazhou Wang, Zhi Chen et al. · 2018 · Medical Physics
Purpose To develop an automated treatment planning strategy for external beam intensity‐modulated radiation therapy ( IMRT ), including a deep learning‐based three‐dimensional (3D) dose prediction and a dose distribution‐based plan…
View details →Negative / Null Result ReportOpen accessPhysics and Astronomy
M. M. Aggarwal, Z. Ahammed, A. V. Alakhverdyants et al. · 2010 · Physical Review Letters
We report the first measurements of the kurtosis ($\ensuremath{\kappa}$), skewness ($S$), and variance (${\ensuremath{\sigma}}^{2}$) of net-proton multiplicity (${N}_{p}\ensuremath{-}{N}_{\overline{p}}$) distributions at midrapidity for…
View details →Negative / Null Result ReportOpen accessPhysics and Astronomy
Michael A. Kuhn, Lynne A. Hillenbrand, Alison Sills et al. · 2019 · The Astrophysical Journal
Abstract The Gaia mission has opened a new window into the internal kinematics of young star clusters at the sub-km s −1 level, with implications for our understanding of how star clusters form and evolve. We use a sample of 28 clusters…
View details →Negative / Null Result ReportOpen accessPhysics and Astronomy
John Antoniadis, Zaven Arzoumanian, S. Babak et al. · 2021 · Monthly Notices of the Royal Astronomical Society
ABSTRACT We searched for an isotropic stochastic gravitational wave background in the second data release of the International Pulsar Timing Array, a global collaboration synthesizing decadal-length pulsar-timing campaigns in North…
View details →Negative / Null Result ReportOpen accessPhysics and Astronomy
N. V. Kharchenko, А. Э. Пискунов, E. Schilbach et al. · 2013 · arXiv (Cornell University)
Although they are the main constituents of the Galactic disk population, for half of the open clusters in the Milky Way reported in the literature nothing is known except the raw position and an approximate size. The main goal of this…
View details →Negative / Null Result ReportOpen accessPhysics and Astronomy
Shao-Wen Wei, Yu-Xiao Liu · 2013 · Journal of Cosmology and Astroparticle Physics
In this paper, the shadows cast by Einstein-Maxwell-Dilaton-Axion black hole and naked singularity are studied. The shadow of a rotating black hole is found to be a dark zone covered by a deformed circle. For a fixed value of the spin a,…
View details →Negative / Null Result ReportOpen accessPhysics and Astronomy
Marko Ljubotina, Marko Žnidarič, Tomaž Prosen · 2017 · Nature Communications
Generalized hydrodynamics predicts universal ballistic transport in integrable lattice systems when prepared in generic inhomogeneous initial states. However, the ballistic contribution to transport can vanish in systems with additional discrete symmetries. Here we perform large scale numerical simulations of spin dynamics in the anisotropic Heisenberg XXZ spin 1/2 chain starting from an inhomogeneous mixed initial state which is symmetric with respect to a combination of spin reversal and spatial reflection. In the isotropic and easy-axis regimes we find non-ballistic spin transport which we
View details →Negative / Null Result ReportOpen accessPhysics and Astronomy
S. Abrahamyan, Z. Ahmed, K. Allada et al. · 2011 · Physical Review Letters
We present a search at the Jefferson Laboratory for new forces mediated by sub-GeV vector bosons with weak coupling ${\ensuremath{\alpha}}^{\ensuremath{'}}$ to electrons. Such a particle ${A}^{\ensuremath{'}}$ can be produced in…
View details →Negative / Null Result ReportOpen accessPhysics and Astronomy
Roberto Decarli, Fabian Walter, Bram P. Venemans et al. · 2018 · The Astrophysical Journal
Abstract We present a survey of the [C ii ] 158 μ m line and underlying far-infrared (FIR) dust continuum emission in a sample of 27 quasars using the Atacama Large Millimeter Array (ALMA) at resolution. The [C ii ] line was significantly…
View details →Negative / Null Result ReportOpen accessPhysics and Astronomy
Timothy D. Brandt · 2021 · The Astrophysical Journal Supplement Series
Abstract We present a cross-calibration of Hipparcos and Gaia EDR3 intended to identify astrometrically accelerating stars and to fit orbits to stars with faint, massive companions. The resulting catalog, the EDR3 edition of the…
View details →Negative / Null Result ReportOpen accessPhysics and Astronomy
Drake Deming, Heather A. Knutson, Joshua A. Kammer et al. · 2015 · The Astrophysical Journal
HAT-P-20b is a giant metal-rich exoplanet orbiting a metal-rich star. We analyze two secondary eclipses of the planet in each of the 3.6 and 4.5 m bands of Warm Spitzer. We have developed a simple, powerful, and radically different method…
View details →Negative / Null Result ReportOpen accessPhysics and Astronomy
P. Agnes, T. Alexander, A. Alton et al. · 2015 · Physics Letters B
We report the first results of DarkSide-50, a direct search for dark matter operating in the underground Laboratori Nazionali del Gran Sasso (LNGS) and searching for the rare nuclear recoils possibly induced by weakly interacting massive particles (WIMPs). The dark matter detector is a Liquid Argon Time Projection Chamber with a ( 46.4 ± 0.7 ) kg active mass, operated inside a 30 t organic liquid scintillator neutron veto, which is in turn installed at the center of a 1 kt water Cherenkov veto for the residual flux of cosmic rays. We report here the null results of a dark matter search for a (
View details →Negative / Null Result ReportOpen accessPhysics and Astronomy
Matteo Tamburini, Ф. Пегораро, A. Di Piazza et al. · 2010 · New Journal of Physics
Radiation reaction (RR) effects on the acceleration of a thin plasma foil by a superintense laser pulse in the radiation pressure dominated regime are investigated theoretically. A simple suitable approximation of the Landau-Lifshitz equation for the RR force and a novel leapfrog pusher for its inclusion in particle-in-cell simulations are provided. Simulations for both linear and circular polarization of the laser pulse are performed and compared. It is found that at intensities exceeding $10^{23} \Wcm$ the radiation reaction force strongly affects the dynamics for a linearly polarized laser
View details →Negative / Null Result ReportOpen accessPhysics and Astronomy
Simone Blasi, Vedran Brdar, Kai Schmitz · 2021 · Physical Review Letters
The North American Nanohertz Observatory for Gravitational Waves has recently reported strong evidence for a stochastic common-spectrum process affecting the pulsar timing residuals in its 12.5-year data set. We demonstrate that this process admits an interpretation in terms of a stochastic gravitational-wave background emitted by a cosmic-string network in the early Universe. We study stable Nambu-Goto strings in dependence of their tension Gμ and loop size α and show that the entire viable parameter space will be probed by an array of future experiments.
View details →Negative / Null Result ReportOpen accessPhysics and Astronomy
M. Ajello, A. Albert, B. Anderson et al. · 2016 · Physical Review Letters
We report on the search for spectral irregularities induced by oscillations between photons and axionlike-particles (ALPs) in the γ-ray spectrum of NGC 1275, the central galaxy of the Perseus cluster. Using 6 years of Fermi Large Area…
View details →Negative / Null Result ReportOpen accessPhysics and Astronomy
Marco Gorghetto, Edward Hardy, Giovanni Villadoro · 2018 · Journal of High Energy Physics
A bstract We study the system of axion strings that forms in the early Universe if the Peccei-Quinn symmetry is restored after inflation. Using numerical simulations, we establish the existence of an asymptotic solution to which the system is attracted independently of the initial conditions. We study in detail the properties of this solution, including the average number of strings per Hubble patch, the distribution of loops and long strings, the way that different types of radiation are emitted, and the shape of the spectrum of axions produced. We find clear evidence of logarithmic violation
View details →Negative / Null Result ReportOpen accessPhysics and Astronomy
Chris Blake, I. K. Baldry, Joss Bland‐Hawthorn et al. · 2013 · Monthly Notices of the Royal Astronomical Society
We present the first application of a ‘multiple-tracer’ redshift-space distortion (RSD) analysis to an observational galaxy sample, using data from the Galaxy and Mass Assembly (GAMA) survey. Our data set is an r < 19.8 magnitude-limited…
View details →Negative / Null Result ReportOpen accessPhysics and Astronomy
Charles L. Steinhardt, Joshua S. Speagle, P. Capak et al. · 2014 · The Astrophysical Journal Letters
Using the first 50% of data collected for the Spitzer Large Area Survey with Hyper-Suprime-Cam observations on the 1.8 deg^2 Cosmological Evolution Survey we estimate the masses and star formation rates of 3398 M_* > 10^(10) M_☉…
View details →Negative / Null Result ReportOpen accessPhysics and Astronomy
C. Abel, N. J. Ayres, Ban, Giles et al. · 2017 · Repository for Publications and Research Data (ETH Zurich)
We report on a search for ultralow-mass axionlike dark matter by analyzing the ratio of the spin-precession frequencies of stored ultracold neutrons and 199Hg atoms for an axion-induced oscillating electric dipole moment of the neutron and an axion-wind spin-precession effect. No signal consistent with dark matter is observed for the axion mass range 10â24â¤maâ¤10â17 eV. Our null result sets the first laboratory constraints on the coupling of axion dark matter to gluons, which improve on astrophysical limits by up to 3 orders of magnitude, and also improves on previous laboratory constra
View details →Negative / Null Result ReportOpen accessPhysics and Astronomy
Pan Zhang, Cristopher Moore · 2014 · Proceedings of the National Academy of Sciences
Modularity is a popular measure of community structure. However, maximizing the modularity can lead to many competing partitions, with almost the same modularity, that are poorly correlated with each other. It can also produce illusory…
View details →Negative / Null Result ReportOpen accessPhysics and Astronomy
Konrad Meister, Simona Strazdaitė, Arthur L. DeVries et al. · 2014 · Proceedings of the National Academy of Sciences
We study the properties of water at the surface of an antifreeze protein with femtosecond surface sum frequency generation spectroscopy. We find clear evidence for the presence of ice-like water layers at the ice-binding site of the…
View details →Negative / Null Result ReportOpen accessPhysics and Astronomy
Ciarán Hickey, Simon Trebst · 2019 · Nature Communications
In the field of quantum magnetism, the exactly solvable Kitaev honeycomb model serves as a paradigm for the fractionalization of spin degrees of freedom and the formation of [Formula: see text] quantum spin liquids. An intense experimental search has led to the discovery of a number of spin-orbit entangled Mott insulators that realize its characteristic bond-directional interactions and, in the presence of magnetic fields, exhibit no indications of long-range order. Here, we map out the complete phase diagram of the Kitaev model in tilted magnetic fields and report the emergence of a distinct
View details →