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Salvatore Capozziello, Mariafelicia De Laurentis, Konstantinos F Dialektopoulos
A generalized teleparallel cosmological model, [Formula: see text], containing the torsion scalar T and the teleparallel counterpart of the Gauss-Bonnet topological invariant [Formula: see text], is studied in the framework of the Noether symmetry approach. As [Formula: see text] gravity, where [Formula: see text] is the Gauss-Bonnet topological invariant and R is the Ricci curvature scalar, exhausts all the curvature information that one can construct from the Riemann tensor, in the same way, [Formula: see text] contains all the possible information directly related to the torsion tensor...
2016: European Physical Journal. C, Particles and Fields
Maggie Bartlett, Flora Bartlett
We conducted an ethnography of the faculty biscuit tin as we were interested in the lived experience of the biscuits contained within it. We used a constructivist epistemology, a social constructionist interpretive framework and a phenomenological methodology that included analysis from the perspectives of deixis and cosmology. The biscuits perceived that they were important to a selecting force and that the characteristics of one particular group had a specific value to the selector. Some enduring benefits may derive from the selection of this group, although its attractions were less immediately obvious than those of others...
December 2016: Medical Education
Oliver Davies
New data is emerging from evolutionary anthropology and the neuroscience of social cognition on our species-specific hyper-cooperation (HC). This paper attempts an integration of third-person archaeological and second-person, neuroscientific perspectives on the structure of HC, through a post-Ricoeurian development in hermeneutical phenomenology. We argue for the relatively late evolution of advanced linguistic consciousness (ALC) (Hiscock in Biological Theory 9:27-41, 2014), as a reflexive system based on the 'in-between' or 'cognitive system' as reported by Vogeley et al...
2016: Culture and Brain
V Ravi, R M Shannon, M Bailes, K Bannister, S Bhandari, N D R Bhat, S Burke-Spolaor, M Caleb, C Flynn, A Jameson, S Johnston, E F Keane, M Kerr, C Tiburzi, A V Tuntsov, H K Vedantham
Fast radio bursts (FRBs) are millisecond-duration events thought to originate beyond the Milky Way galaxy. Uncertainty surrounding the burst sources, and their propagation through intervening plasma, has limited their use as cosmological probes. We report on a mildly dispersed (dispersion measure 266.5 ± 0.1 pc cm(-3)), exceptionally intense (120 ± 30 Jy), linearly polarized, scintillating burst (FRB 150807) that we directly localize to 9 arcmin(2) Based on a low Faraday rotation (12.0 ± 0.7 rad m(-2)), we infer negligible magnetization in the circum-burst plasma and constrain the net magnetization of the cosmic web along this sightline to <21 nG, parallel to the line-of-sight...
November 17, 2016: Science
Daniel Baumann, Daniel Green, Benjamin Wallisch
Future cosmic microwave background experiments have the potential to probe the density of relativistic species at the subpercent level. This sensitivity allows light thermal relics to be detected up to arbitrarily high decoupling temperatures. Conversely, the absence of a detection would require extra light species never to have been in equilibrium with the Standard Model. In this Letter, we exploit this feature to demonstrate the sensitivity of future cosmological observations to the couplings of axions to photons, gluons, and charged fermions...
October 21, 2016: Physical Review Letters
David Garfinkle
Though the main applications of computer simulations in relativity are to astrophysical systems such as black holes and neutron stars, nonetheless there are important applications of numerical methods to the investigation of general relativity as a fundamental theory of the nature of space and time. This paper gives an overview of some of these applications. In particular we cover (i) investigations of the properties of spacetime singularities such as those that occur in the interior of black holes and in big bang cosmology...
November 7, 2016: Reports on Progress in Physics
Logan W Clark, Lei Feng, Cheng Chin
The dynamics of many-body systems spanning condensed matter, cosmology, and beyond are hypothesized to be universal when the systems cross continuous phase transitions. The universal dynamics are expected to satisfy a scaling symmetry of space and time with the crossing rate, inspired by the Kibble-Zurek mechanism. We test this symmetry based on Bose condensates in a shaken optical lattice. Shaking the lattice drives condensates across an effectively ferromagnetic quantum phase transition. After crossing the critical point, the condensates manifest delayed growth of spin fluctuations and develop antiferromagnetic spatial correlations resulting from the sub-Poisson distribution of the spacing between topological defects...
November 4, 2016: Science
S Borsanyi, Z Fodor, J Guenther, K-H Kampert, S D Katz, T Kawanai, T G Kovacs, S W Mages, A Pasztor, F Pittler, J Redondo, A Ringwald, K K Szabo
Unlike the electroweak sector of the standard model of particle physics, quantum chromodynamics (QCD) is surprisingly symmetric under time reversal. As there is no obvious reason for QCD being so symmetric, this phenomenon poses a theoretical problem, often referred to as the strong CP problem. The most attractive solution for this requires the existence of a new particle, the axion-a promising dark-matter candidate. Here we determine the axion mass using lattice QCD, assuming that these particles are the dominant component of dark matter...
November 2, 2016: Nature
M Barbagallo, A Musumarra, L Cosentino, E Maugeri, S Heinitz, A Mengoni, R Dressler, D Schumann, F Käppeler, N Colonna, P Finocchiaro, M Ayranov, L Damone, N Kivel, O Aberle, S Altstadt, J Andrzejewski, L Audouin, M Bacak, J Balibrea-Correa, S Barros, V Bécares, F Bečvář, C Beinrucker, E Berthoumieux, J Billowes, D Bosnar, M Brugger, M Caamaño, M Calviani, F Calviño, D Cano-Ott, R Cardella, A Casanovas, D M Castelluccio, F Cerutti, Y H Chen, E Chiaveri, G Cortés, M A Cortés-Giraldo, S Cristallo, M Diakaki, C Domingo-Pardo, E Dupont, I Duran, B Fernandez-Dominguez, A Ferrari, P Ferreira, W Furman, S Ganesan, A García-Rios, A Gawlik, T Glodariu, K Göbel, I F Gonçalves, E González-Romero, E Griesmayer, C Guerrero, F Gunsing, H Harada, T Heftrich, J Heyse, D G Jenkins, E Jericha, T Katabuchi, P Kavrigin, A Kimura, M Kokkoris, M Krtička, E Leal-Cidoncha, J Lerendegui, C Lederer, H Leeb, S Lo Meo, S J Lonsdale, R Losito, D Macina, J Marganiec, T Martínez, C Massimi, P Mastinu, M Mastromarco, A Mazzone, E Mendoza, P M Milazzo, F Mingrone, M Mirea, S Montesano, R Nolte, A Oprea, A Pappalardo, N Patronis, A Pavlik, J Perkowski, M Piscopo, A Plompen, I Porras, J Praena, J Quesada, K Rajeev, T Rauscher, R Reifarth, A Riego-Perez, P Rout, C Rubbia, J Ryan, M Sabate-Gilarte, A Saxena, P Schillebeeckx, S Schmidt, P Sedyshev, A G Smith, A Stamatopoulos, G Tagliente, J L Tain, A Tarifeño-Saldivia, L Tassan-Got, A Tsinganis, S Valenta, G Vannini, V Variale, P Vaz, A Ventura, V Vlachoudis, R Vlastou, J Vollaire, A Wallner, S Warren, M Weigand, C Weiß, C Wolf, P J Woods, T Wright, P Žugec
The energy-dependent cross section of the ^{7}Be(n,α)^{4}He reaction, of interest for the so-called cosmological lithium problem in big bang nucleosynthesis, has been measured for the first time from 10 meV to 10 keV neutron energy. The challenges posed by the short half-life of ^{7}Be and by the low reaction cross section have been overcome at n_TOF thanks to an unprecedented combination of the extremely high luminosity and good resolution of the neutron beam in the new experimental area (EAR2) of the n_TOF facility at CERN, the availability of a sufficient amount of chemically pure ^{7}Be, and a specifically designed experimental setup...
October 7, 2016: Physical Review Letters
J T Nielsen, A Guffanti, S Sarkar
The 'standard' model of cosmology is founded on the basis that the expansion rate of the universe is accelerating at present - as was inferred originally from the Hubble diagram of Type Ia supernovae. There exists now a much bigger database of supernovae so we can perform rigorous statistical tests to check whether these 'standardisable candles' indeed indicate cosmic acceleration. Taking account of the empirical procedure by which corrections are made to their absolute magnitudes to allow for the varying shape of the light curve and extinction by dust, we find, rather surprisingly, that the data are still quite consistent with a constant rate of expansion...
October 21, 2016: Scientific Reports
Sébastien Renaux-Petel, Krzysztof Turzyński
We show the existence of a general mechanism by which heavy scalar fields can be destabilized during inflation, relying on the fact that the curvature of the field space manifold can dominate the stabilizing force from the potential and destabilize inflationary trajectories. We describe a simple and rather universal setup in which higher-order operators suppressed by a large energy scale trigger this instability. This phenomenon can prematurely end inflation, thereby leading to important observational consequences and sometimes excluding models that would otherwise perfectly fit the data...
September 30, 2016: Physical Review Letters
Grigor Aslanyan, Layne C Price, Jenni Adams, Torsten Bringmann, Hamish A Clark, Richard Easther, Geraint F Lewis, Pat Scott
Cosmological inflation generates primordial density perturbations on all scales, including those far too small to contribute to the cosmic microwave background. At these scales, isolated ultracompact minihalos of dark matter can form well before standard structure formation, if the perturbations have sufficient amplitude. Minihalos affect pulsar timing data and are potentially bright sources of gamma rays. The resulting constraints significantly extend the observable window of inflation in the presence of cold dark matter, coupling two of the key problems in modern cosmology...
September 30, 2016: Physical Review Letters
Ue-Li Pen, Neil Turok
We point out a surprising consequence of the usually assumed initial conditions for cosmological perturbations. Namely, a spectrum of Gaussian, linear, adiabatic, scalar, growing mode perturbations not only creates acoustic oscillations of the kind observed on very large scales today, it also leads to the production of shocks in the radiation fluid of the very early Universe. Shocks cause departures from local thermal equilibrium as well as create vorticity and gravitational waves. For a scale-invariant spectrum and standard model physics, shocks form for temperatures 1  GeV<T<10^{7}  GeV...
September 23, 2016: Physical Review Letters
Daniela Saadeh, Stephen M Feeney, Andrew Pontzen, Hiranya V Peiris, Jason D McEwen
A fundamental assumption in the standard model of cosmology is that the Universe is isotropic on large scales. Breaking this assumption leads to a set of solutions to Einstein's field equations, known as Bianchi cosmologies, only a subset of which have ever been tested against data. For the first time, we consider all degrees of freedom in these solutions to conduct a general test of isotropy using cosmic microwave background temperature and polarization data from Planck. For the vector mode (associated with vorticity), we obtain a limit on the anisotropic expansion of (σ_{V}/H)_{0}<4...
September 23, 2016: Physical Review Letters
Anna Ijjas, Paul J Steinhardt
One of the fundamental questions of theoretical cosmology is whether the Universe can undergo a nonsingular bounce, i.e., smoothly transit from a period of contraction to a period of expansion through violation of the null energy condition (NEC) at energies well below the Planck scale and at finite values of the scale factor such that the entire evolution remains classical. A common claim has been that a nonsingular bounce either leads to ghost or gradient instabilities or a cosmological singularity. In this Letter, we consider a well-motivated class of theories based on the cubic Galileon action and present a procedure for explicitly constructing examples of a nonsingular cosmological bounce without encountering any pathologies and maintaining a subluminal sound speed for comoving curvature modes throughout the NEC violating phase...
September 16, 2016: Physical Review Letters
Emanuele Berti, Alberto Sesana, Enrico Barausse, Vitor Cardoso, Krzysztof Belczynski
We estimate the potential of present and future interferometric gravitational-wave detectors to test the Kerr nature of black holes through "gravitational spectroscopy," i.e., the measurement of multiple quasinormal mode frequencies from the remnant of a black hole merger. Using population synthesis models of the formation and evolution of stellar-mass black hole binaries, we find that Voyager-class interferometers will be necessary to perform these tests. Gravitational spectroscopy in the local Universe may become routine with the Einstein Telescope, but a 40-km facility like Cosmic Explorer is necessary to go beyond z∼3...
September 2, 2016: Physical Review Letters
Nico Hamaus, Alice Pisani, P M Sutter, Guilhem Lavaux, Stéphanie Escoffier, Benjamin D Wandelt, Jochen Weller
The Universe is mostly composed of large and relatively empty domains known as cosmic voids, whereas its matter content is predominantly distributed along their boundaries. The remaining material inside them, either dark or luminous matter, is attracted to these boundaries and causes voids to expand faster and to grow emptier over time. Using the distribution of galaxies centered on voids identified in the Sloan Digital Sky Survey and adopting minimal assumptions on the statistical motion of these galaxies, we constrain the average matter content Ω_{m}=0...
August 26, 2016: Physical Review Letters
A Trenkwalder, G Spagnolli, G Semeghini, S Coop, M Landini, P Castilho, L Pezzè, G Modugno, M Inguscio, A Smerzi, M Fattori
Symmetry-breaking quantum phase transitions play a key role in several condensed matter, cosmology and nuclear physics theoretical models1-3. Its observation in real systems is often hampered by finite temperatures and limited control of the system parameters. In this work we report for the first time the experimental observation of the full quantum phase diagram across a transition where the spatial parity symmetry is broken. Our system is made of an ultra-cold gas with tunable attractive interactions trapped in a spatially symmetric double-well potential...
September 2016: Nature Physics
Bron Taylor, Gretel Van Wieren, Bernard Daley Zaleha
Lynn White Jr.'s "The Historical Roots of Our Ecologic Crisis," which was published in Science in 1967, has played a critical role in precipitating interdisciplinary environmental studies. Although White advances a multifaceted argument, most respondents focus on his claim that the Judeo-Christian tradition, especially Christianity, has promoted anthropocentric attitudes and environmentally destructive behaviors. Decades later, some scholars argue contrarily that Christianity in particular and the world's predominant religions in general are becoming more environmentally friendly, known as the greening-of-religion hypothesis...
October 2016: Conservation Biology: the Journal of the Society for Conservation Biology
Yi-Fu Cai, Salvatore Capozziello, Mariafelicia De Laurentis, Emmanuel N Saridakis
Over recent decades, the role of torsion in gravity has been extensively investigated along the main direction of bringing gravity closer to its gauge formulation and incorporating spin in a geometric description. Here we review various torsional constructions, from teleparallel, to Einstein-Cartan, and metric-affine gauge theories, resulting in extending torsional gravity in the paradigm of f (T) gravity, where f (T) is an arbitrary function of the torsion scalar. Based on this theory, we further review the corresponding cosmological and astrophysical applications...
October 2016: Reports on Progress in Physics
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