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William Cunningham, Konstantin Zuev, Dmitri Krioukov
Random geometric graphs in hyperbolic spaces explain many common structural and dynamical properties of real networks, yet they fail to predict the correct values of the exponents of power-law degree distributions observed in real networks. In that respect, random geometric graphs in asymptotically de Sitter spacetimes, such as the Lorentzian spacetime of our accelerating universe, are more attractive as their predictions are more consistent with observations in real networks. Yet another important property of hyperbolic graphs is their navigability, and it remains unclear if de Sitter graphs are as navigable as hyperbolic ones...
August 18, 2017: Scientific Reports
Ward Struyve
Loop quantum gravity is believed to eliminate singularities such as the big bang and big crunch singularity. This belief is based on studies of so-called loop quantum cosmology which concerns symmetry-reduced models of quantum gravity. In this paper, the problem of singularities is analysed in the context of the Bohmian formulation of loop quantum cosmology. In this formulation there is an actual metric in addition to the wave function, which evolves stochastically (rather than deterministically as the case of the particle evolution in non-relativistic Bohmian mechanics)...
August 15, 2017: Scientific Reports
Igor I Smolyaninov, Vera N Smolyaninova
We consider the recently suggested model of a multiverse based on a ferrofluid. When the ferrofluid is subjected to a modest external magnetic field, the nanoparticles inside the ferrofluid form small hyperbolic metamaterial domains, which from the electromagnetic standpoint behave as individual "Minkowski universes" exhibiting different "laws of physics", such as different strength of effective gravity, different versions of modified Newtonian dynamics (MOND) and different radiation lifetimes. When the ferrofluid "multiverse" is populated with atomic or molecular species, and these species are excited using an external laser source, the radiation lifetimes of atoms and molecules in these "universes" depend strongly on the individual physical properties of each "universe" via the Purcell effect...
August 14, 2017: Scientific Reports
Carlos J A P Martins
The observational evidence for the recent acceleration of the universe demonstrates that canonical theories of cosmology and particle physics are incomplete-if not incorrect-and that new physics is out there, waiting to be discovered. A key task for the next generation of laboratory and astrophysical facilities is to search for, identify and ultimately characterize this new physics. Here we highlight recent developments in tests of the stability of nature's fundamental couplings, which provide a direct handle on new physics: a detection of variations will be revolutionary, but even improved null results provide competitive constraints on a range of cosmological and particle physics paradigms...
August 14, 2017: Reports on Progress in Physics
Stephen Clucas
John Dee's Monas Hieroglyphica (1564) was a work which involved a close collaboration between its author and his "singular friend" the Antwerp printer Willem Silvius, in whose house Dee was living whilst he composed the work and saw it through the press. This article considers the reasons why Dee chose to collaborate with Silvius, and the importance of the intellectual culture - and the print trade - of the Low Countries to the development of Dee's outlook. Dee's Monas was probably the first alchemical work which focused exclusively on the diagrammatic representation of the alchemical process, combining diagrams, cosmological schemes, and various forms of tabular grid...
August 10, 2017: Ambix
Patricia Schady
Since the launch of the highly successful and ongoing Swift mission, the field of gamma-ray bursts (GRBs) has undergone a revolution. The arcsecond GRB localizations available within just a few minutes of the GRB alert has signified the continual sampling of the GRB evolution through the prompt to afterglow phases revealing unexpected flaring and plateau phases, the first detection of a kilonova coincident with a short GRB, and the identification of samples of low-luminosity, ultra-long and highly dust-extinguished GRBs...
July 2017: Royal Society Open Science
Vishwa Pal, Chene Tradonsky, Ronen Chriki, Asher A Friesem, Nir Davidson
Topological defects have been observed and studied in a wide range of systems, such as cosmology, spin systems, cold atoms, and optics, as they are quenched across a phase transition into an ordered state. These defects limit the coherence of the system and its ability to approach a fully ordered state, so revealing their origin and control is becoming an increasingly important field of research. We observe dissipative topological defects in a one-dimensional ring of phased-locked lasers, and show how their formation is related to the Kibble-Zurek mechanism and is governed in a universal manner by two competing time scales...
July 7, 2017: Physical Review Letters
Dan Xie, Tianmin Shu, Sinisa Todorovic, Song-Chun Zhu
This paper presents a method for localizing functional objects and predicting human intents and trajectories in surveillance videos of public spaces, under no supervision in training. People in public spaces are expected to intentionally take shortest paths (subject to obstacles) toward certain objects (e.g. vending machine, picnic table, dumpster etc.) where they can satisfy certain needs (e.g., quench thirst). Since these objects are typically very small or heavily occluded, they cannot be inferred by their visual appearance but indirectly by their influence on people's trajectories...
July 19, 2017: IEEE Transactions on Pattern Analysis and Machine Intelligence
Xingang Chen, Yi Wang, Zhong-Zhi Xianyu
The inflationary universe can be viewed as a "cosmological collider" with an energy of the Hubble scale, producing very massive particles and recording their characteristic signals in primordial non-Gaussianities. To utilize this collider to explore any new physics at very high scales, it is a prerequisite to understand the background signals from the particle physics standard model. In this Letter we describe the standard model background of the cosmological collider.
June 30, 2017: Physical Review Letters
Volker Scheid
The history of Chinese medicine is still widely imagined in terms dictated by the discourse of modernity, that is as 'traditional' and 'Chinese.' And yet, so as to be intelligible to us moderns, it must simultaneously be framed through categories that make it comparable somehow to the 'West' and the 'modern' from which it is said to be essentially different. This is accomplished, for instance, by viewing Chinese medicine as fundamentally shaped by cosmological thinking, as focusing on process rather than matter, and as forever hampered by attachments to the past even when it tries to innovate...
June 1, 2017: History of Science; An Annual Review of Literature, Research and Teaching
Steven M Rosen
This paper carries forward the author's contribution to PBMP's previous special issue on Integral Biomathics (Rosen 2015). In the earlier paper, the crisis in contemporary theoretical physics was described and it was demonstrated that the problem can be addressed effectively only by shifting the foundations of physics from objectivist Cartesian philosophy to phenomenological philosophy. To that end, a phenomenological string theory was proposed based on qualitative topology and hypercomplex numbers. The current presentation takes this further by delving into the ancient Chinese origin of phenomenological string theory...
July 4, 2017: Progress in Biophysics and Molecular Biology
Martin Wieser
This article presents a historical analysis of the origins, rise, and demise of theories of stratification (Schichtentheorien). Following their roots in the ancient metaphysical idea of the "great chain of being," Aristotle's scala naturae, the medieval "Jacob's ladder," and Leibniz's concept of the lex continua, I argue that theories of stratification represent the modern heir to the ancient cosmological idea of a harmonious, hierarchical, and unified universe. Theories of stratification reached their heyday during the interwar period within German academia, proliferating over a vast number of disciplines and rising to special prominence within personality psychology, feeding the hope for a unitary image of the world and of human beings, their biological and mental development, their social organization and cultural creations...
June 26, 2017: History of Psychology
P E Freeman, R Izbicki, A B Lee
Photometric redshift estimation is an indispensable tool of precision cosmology. One problem that plagues the use of this tool in the era of large-scale sky surveys is that the bright galaxies that are selected for spectroscopic observation do not have properties that match those of (far more numerous) dimmer galaxies; thus, ill-designed empirical methods that produce accurate and precise redshift estimates for the former generally will not produce good estimates for the latter. In this paper, we provide a principled framework for generating conditional density estimates (i...
July 2017: Monthly Notices of the Royal Astronomical Society
Giovanni Marozzi, Giuseppe Fanizza, Enea Di Dio, Ruth Durrer
In this Letter we study the impact on cosmological parameter estimation, from present and future surveys, due to lensing corrections on cosmic microwave background temperature and polarization anisotropies beyond leading order. In particular, we show how post-Born corrections, large-scale structure effects, and the correction due to the change in the polarization direction between the emission at the source and the detection at the observer are non-negligible in the determination of the polarization spectra...
May 26, 2017: Physical Review Letters
Gianluca Calcagni, David Rodríguez Fernández, Michele Ronco
We study static and radially symmetric black holes in the multi-fractional theories of gravity with q-derivatives and with weighted derivatives, frameworks where the spacetime dimension varies with the probed scale and geometry is characterized by at least one fundamental length [Formula: see text]. In the q-derivatives scenario, one finds a tiny shift of the event horizon. Schwarzschild black holes can present an additional ring singularity, not present in general relativity, whose radius is proportional to [Formula: see text]...
2017: European Physical Journal. C, Particles and Fields
Milan M Ćirković
There are manifold intriguing issues located within largely unexplored borderlands of bioethics, future studies (including global risk analysis), and astrobiology. Human enhancement has for quite some time been among the foci of bioethical debates, but the same cannot be said about its global, transgenerational, and even cosmological consequences. In recent years, discussions of posthuman and, in general terms, postbiological civilization(s) have slowly gained a measure of academic respect, in parallel with the renewed interest in the entire field of future studies and the great strides made in understanding of the origin and evolution of life and intelligence in their widest, cosmic context...
July 2017: Cambridge Quarterly of Healthcare Ethics: CQ: the International Journal of Healthcare Ethics Committees
E Bagnaschi, M Borsato, K Sakurai, O Buchmueller, R Cavanaugh, V Chobanova, M Citron, J C Costa, A De Roeck, M J Dolan, J R Ellis, H Flächer, S Heinemeyer, G Isidori, M Lucio, F Luo, D Martínez Santos, K A Olive, A Richards, G Weiglein
We perform a likelihood analysis of the minimal anomaly-mediated supersymmetry-breaking (mAMSB) model using constraints from cosmology and accelerator experiments. We find that either a wino-like or a Higgsino-like neutralino LSP, [Formula: see text], may provide the cold dark matter (DM), both with similar likelihoods. The upper limit on the DM density from Planck and other experiments enforces [Formula: see text] after the inclusion of Sommerfeld enhancement in its annihilations. If most of the cold DM density is provided by the [Formula: see text], the measured value of the Higgs mass favours a limited range of [Formula: see text] (and also for [Formula: see text] if [Formula: see text]) but the scalar mass [Formula: see text] is poorly constrained...
2017: European Physical Journal. C, Particles and Fields
Hironao Miyatake, Mathew S Madhavacheril, Neelima Sehgal, Anže Slosar, David N Spergel, Blake Sherwin, Alexander van Engelen
We measure the gravitational lensing shear signal around dark matter halos hosting constant mass galaxies using light sources at z∼1 (background galaxies) and at the surface of last scattering at z∼1100 (the cosmic microwave background). The galaxy shear measurement uses data from the CFHTLenS survey, and the microwave background shear measurement uses data from the Planck satellite. The ratio of shears from these cross-correlations provides a purely geometric distance measurement across the longest possible cosmological lever arm...
April 21, 2017: Physical Review Letters
T Regimbau, M Evans, N Christensen, E Katsavounidis, B Sathyaprakash, S Vitale
The merger rate of black hole binaries inferred from the detections in the first Advanced LIGO science run implies that a stochastic background produced by a cosmological population of mergers will likely mask the primordial gravitational wave background. Here we demonstrate that the next generation of ground-based detectors, such as the Einstein Telescope and Cosmic Explorer, will be able to observe binary black hole mergers throughout the Universe with sufficient efficiency that the confusion background can potentially be subtracted to observe the primordial background at the level of Ω_{GW}≃10^{-13} after 5 years of observation...
April 14, 2017: Physical Review Letters
Alberto Rorai, Joseph F Hennawi, Jose Oñorbe, Martin White, J Xavier Prochaska, Girish Kulkarni, Michael Walther, Zarija Lukić, Khee-Gan Lee
The distribution of diffuse gas in the intergalactic medium (IGM) imprints a series of hydrogen absorption lines on the spectra of distant background quasars known as the Lyman-α forest. Cosmological hydrodynamical simulations predict that IGM density fluctuations are suppressed below a characteristic scale where thermal pressure balances gravity. We measured this pressure-smoothing scale by quantifying absorption correlations in a sample of close quasar pairs. We compared our measurements to hydrodynamical simulations, where pressure smoothing is determined by the integrated thermal history of the IGM...
April 28, 2017: Science
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