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Oded Rabinovitch
Sébastien Le Clerc (1637-1714) was the most renowned engraver of Louis XIV's France. For the history of scientific publishing, however, Le Clerc represents a telling paradox. Even though he followed a traditional route based on classic artisanal training, he also published extensively on scientific topics such as cosmology and mathematics. While contemporary scholarship usually stresses the importance of artisanal writing as a direct expression of artisanal experience and know-how, Le Clerc's publications, and specifically the work on cosmology in his Système du monde (1706-1708), go far beyond this...
October 11, 2017: British Journal for the History of Science
I Bartos, Z Haiman, Z Marka, B D Metzger, N C Stone, S Marka
The recent discovery of gravitational waves from stellar-mass binary black hole mergers by the Laser Interferometer Gravitational-wave Observatory opened the door to alternative probes of stellar and galactic evolution, cosmology and fundamental physics. Probing the origin of binary black hole mergers will be difficult due to the expected lack of electromagnetic emission and limited localization accuracy. Associations with rare host galaxy types-such as active galactic nuclei-can nevertheless be identified statistically through spatial correlation...
October 10, 2017: Nature Communications
Sebastian Bahamonde, Salvatore Capozziello, Mir Faizal, Rafael C Nunes
Even though it is not possible to differentiate general relativity from teleparallel gravity using classical experiments, it could be possible to discriminate between them by quantum gravitational effects. These effects have motivated the introduction of nonlocal deformations of general relativity, and similar effects are also expected to occur in teleparallel gravity. Here, we study nonlocal deformations of teleparallel gravity along with its cosmological solutions. We observe that nonlocal teleparallel gravity (like nonlocal general relativity) is consistent with the present cosmological data obtained by SNe Ia + BAO + CC + [Formula: see text] observations...
2017: European Physical Journal. C, Particles and Fields
Ji-An Jiang, Mamoru Doi, Keiichi Maeda, Toshikazu Shigeyama, Ken'ichi Nomoto, Naoki Yasuda, Saurabh W Jha, Masaomi Tanaka, Tomoki Morokuma, Nozomu Tominaga, Željko Ivezić, Pilar Ruiz-Lapuente, Maximilian D Stritzinger, Paolo A Mazzali, Christopher Ashall, Jeremy Mould, Dietrich Baade, Nao Suzuki, Andrew J Connolly, Ferdinando Patat, Lifan Wang, Peter Yoachim, David Jones, Hisanori Furusawa, Satoshi Miyazaki
Type Ia supernovae arise from the thermonuclear explosion of white-dwarf stars that have cores of carbon and oxygen. The uniformity of their light curves makes these supernovae powerful cosmological distance indicators, but there have long been debates about exactly how their explosion is triggered and what kind of companion stars are involved. For example, the recent detection of the early ultraviolet pulse of a peculiar, subluminous type Ia supernova has been claimed as evidence for an interaction between a red-giant or a main-sequence companion and ejecta from a white-dwarf explosion...
October 4, 2017: Nature
Francesco De Martini
The nature of the scalar field responsible for the cosmological inflation is found to be rooted in the most fundamental concept of Weyl's differential geometry: the parallel displacement of vectors in curved space-time. Within this novel geometrical scenario, the standard electroweak theory of leptons based on the SU(2) L ⊗U(1) Y as well as on the conformal groups of space-time Weyl's transformations is analysed within the framework of a general-relativistic, conformally covariant scalar-tensor theory that includes the electromagnetic and the Yang-Mills fields...
November 13, 2017: Philosophical Transactions. Series A, Mathematical, Physical, and Engineering Sciences
Shingo Hirano, Takashi Hosokawa, Naoki Yoshida, Rolf Kuiper
The origin of super-massive black holes in the early universe remains poorly understood. Gravitational collapse of a massive primordial gas cloud is a promising initial process, but theoretical studies have difficulty growing the black hole fast enough. We report numerical simulations of early black hole formation starting from realistic cosmological conditions. Supersonic gas motions left over from the Big Bang prevent early gas cloud formation until rapid gas condensation is triggered in a protogalactic halo...
September 29, 2017: Science
Emilian Dudas, Yann Mambrini, Keith A Olive
We consider the possibility that supersymmetry is broken above the inflationary mass scale and that the only "low" energy remnant of supersymmetry is the gravitino with a mass of the order of the EeV scale. The gravitino in this class of models becomes a candidate for the dark matter of the Universe. To avoid the overproduction of gravitinos from the decays of the next-to-lightest supersymmetric particle we argue that the supersymmetric spectrum must lie above the inflationary mass scale (M_{SUSY}>10^{-5}M_{P}∼10^{13}  GeV)...
August 4, 2017: Physical Review Letters
Alan Heavens, Yabebal Fantaye, Elena Sellentin, Hans Eggers, Zafiirah Hosenie, Steve Kroon, Arrykrishna Mootoovaloo
We compute the Bayesian evidence for models considered in the main analysis of Planck cosmic microwave background data. By utilizing carefully defined nearest-neighbor distances in parameter space, we reuse the Monte Carlo Markov chains already produced for parameter inference to compute Bayes factors B for many different model-data set combinations. The standard 6-parameter flat cold dark matter model with a cosmological constant (ΛCDM) is favored over all other models considered, with curvature being mildly favored only when cosmic microwave background lensing is not included...
September 8, 2017: Physical Review Letters
Daniele Montanino, Franco Vazza, Alessandro Mirizzi, Matteo Viel
Large-scale extragalactic magnetic fields may induce conversions between very-high-energy photons and axionlike particles (ALPs), thereby shielding the photons from absorption on the extragalactic background light. However, in simplified "cell" models, used so far to represent extragalactic magnetic fields, this mechanism would be strongly suppressed by current astrophysical bounds. Here we consider a recent model of extragalactic magnetic fields obtained from large-scale cosmological simulations. Such simulated magnetic fields would have large enhancement in the filaments of matter...
September 8, 2017: Physical Review Letters
W B Houthoff, A Kurov, F Saueressig
We use a functional renormalization group equation tailored to the Arnowitt-Deser-Misner formulation of gravity to study the scale dependence of Newton's coupling and the cosmological constant on a background spacetime with topology [Formula: see text]. The resulting beta functions possess a non-trivial renormalization group fixed point, which may provide the high-energy completion of the theory through the asymptotic safety mechanism. The fixed point is robust with respect to changing the parametrization of the metric fluctuations and regulator scheme...
2017: European Physical Journal. C, Particles and Fields
Thomas Elghozi, Nick E Mavromatos, Mairi Sakellariadou
Motivated by the recent breakthrough of the detection of Gravitational Waves (GW) from coalescent black holes by the aLIGO interferometers, we study the propagation of GW in the D-material universe, which we have recently shown to be compatible with large-scale structure and inflationary phenomenology. The medium of D-particles induces an effective mass for the graviton, as a consequence of the formation of recoil-velocity field condensates due to the underlying Born-Infeld dynamics. There is a competing effect, due to a super-luminal refractive index, as a result of the gravitational energy of D-particles acting as a dark-matter component, with which propagating gravitons interact...
2017: European Physical Journal. C, Particles and Fields
S Capozziello, G Lambiase, E N Saridakis
We use Big Bang Nucleosynthesis (BBN) observational data on the primordial abundance of light elements to constrain f(T) gravity. The three most studied viable f(T) models, namely the power law, the exponential and the square-root exponential are considered, and the BBN bounds are adopted in order to extract constraints on their free parameters. For the power-law model, we find that the constraints are in agreement with those obtained using late-time cosmological data. For the exponential and the square-root exponential models, we show that for reliable regions of parameters space they always satisfy the BBN bounds...
2017: European Physical Journal. C, Particles and Fields
Stefan Rotter
No abstract text is available yet for this article.
September 13, 2017: Nature
Nicolas Langlitz
On the basis of four historical and ethnographic case studies of modeling in neuroscience laboratories, this chapter introduces a distinction between transparent and opaque models. A transparent model is a simplified representation of a real world phenomenon. If it is not patently clear, it is at least much better comprehended than its objects of representation. An opaque model, by contrast, looks at one only partially understood phenomenon to stand in for another partially understood phenomenon. Here, the model is often just as complex as its target...
2017: Progress in Brain Research
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
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