RAS_WEB (Page 4,569)

Hyperinflation. (arXiv:1705.03023v2 [hep-th] UPDATED) <a href="http://arxiv.org/find/hep-th/1/au:+Brown_A/0/1/0/all/0/1">Adam R. Brown</a> A model of cosmological inflation is proposed in which field space is a hyperbolic plane. The inflaton never slow-rolls, and instead orbits the bottom of the potential, buoyed by a centrifugal force. Though initial velocities redshift away during inflation, in negatively curved spaces angular momentum naturally starts exponentially large and remains relevant throughout. Quantum fluctuations produce perturbations that are adiabatic and approximately scale invariant; strikingly, in a certain parameter regime the perturbations can grow double-exponentially during horizon crossing. A model of cosmological inflation is proposed in which field space is a hyperbolic plane. The inflaton never slow-rolls,Read More →

Effects of a subadiabatic layer on convection and dynamos in spherical wedge simulations. (arXiv:1803.05898v2 [astro-ph.SR] UPDATED) <a href="http://arxiv.org/find/astro-ph/1/au:+Kapyla_P/0/1/0/all/0/1">Petri J. K&#xe4;pyl&#xe4;</a> (1,2,3,4,5), <a href="http://arxiv.org/find/astro-ph/1/au:+Viviani_M/0/1/0/all/0/1">Mariangela Viviani</a> (4), <a href="http://arxiv.org/find/astro-ph/1/au:+Kapyla_M/0/1/0/all/0/1">Maarit J. K&#xe4;pyl&#xe4;</a> (4,3), <a href="http://arxiv.org/find/astro-ph/1/au:+Brandenburg_A/0/1/0/all/0/1">Axel Brandenburg</a> (5,6,7,8), <a href="http://arxiv.org/find/astro-ph/1/au:+Spada_F/0/1/0/all/0/1">Federico Spada</a> (4) ((1) G&#xf6;ttingen University, (2) AIP, (3) ReSoLVE Center of Excellence, Aalto, (4) Max-Planck-Institut f&#xfc;r Sonnensystemforschung, (5) NORDITA, (6) Stockholm University, (7) JILA, (8) LASP) We consider the effect of a subadiabatic layer at the base of the convection zone on convection itself and the associated large-scale dynamos in spherical wedge geometry. We use a heat conduction prescription based on the Kramers opacity law which allows the depthRead More →

Axion Misalignment Driven to the Bottom. (arXiv:1812.11186v1 [hep-ph]) <a href="http://arxiv.org/find/hep-ph/1/au:+Co_R/0/1/0/all/0/1">Raymond T. Co</a>, <a href="http://arxiv.org/find/hep-ph/1/au:+Gonzalez_E/0/1/0/all/0/1">Eric Gonzalez</a>, <a href="http://arxiv.org/find/hep-ph/1/au:+Harigaya_K/0/1/0/all/0/1">Keisuke Harigaya</a> Several theoretical motivations point to ultralight QCD axions with large decay constants $f_a simeq mathcal{O}(10^{16}-10^{17})$ GeV, to which experimental proposals are dedicated. This regime is known to face the problem of overproduction of axion dark matter from the misalignment mechanism unless the misalignment angle $theta_{rm mis}$ is as small as $mathcal{O}(10^{-3}-10^{-4})$, which is generally considered a fine-tuning problem. We investigate a dynamical explanation for a small $theta_{rm mis}$. The axion mass arises from strong dynamics and may be sufficiently enhanced by early dynamics so as to overcomeRead More →

From ridges in the velocity distribution to wiggles in the rotation curve. (arXiv:1812.11190v1 [astro-ph.GA]) <a href="http://arxiv.org/find/astro-ph/1/au:+Martinez_Medina_L/0/1/0/all/0/1">Luis A. Martinez-Medina</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Pichardo_B/0/1/0/all/0/1">Barbara Pichardo</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Peimbert_A/0/1/0/all/0/1">Antonio Peimbert</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Valenzuela_O/0/1/0/all/0/1">Octavio Valenzuela</a> Just recently, through the Gaia Data Release 2 (DR2), we became aware of the richness in substructure contained in the kinematics of the Milky Way disk. Of particular interest is the presence of diagonal ridges covering the stellar velocity distribution, $V_{phi}-R$; as shown in some studies, it is likely that these ridges are the signature of phase mixing, of transient spiral arms, or of the central bar. Here, with a Galactic model containing both: bar and spirals, weRead More →

Axion Misalignment Driven to the Hilltop. (arXiv:1812.11192v1 [hep-ph]) <a href="http://arxiv.org/find/hep-ph/1/au:+Co_R/0/1/0/all/0/1">Raymond T. Co</a>, <a href="http://arxiv.org/find/hep-ph/1/au:+Gonzalez_E/0/1/0/all/0/1">Eric Gonzalez</a>, <a href="http://arxiv.org/find/hep-ph/1/au:+Harigaya_K/0/1/0/all/0/1">Keisuke Harigaya</a> The QCD axion serves as a well-motivated dark matter candidate and the misalignment mechanism is known to reproduce the observed abundance with a decay constant $f_a simeq mathcal{O}(10^{12})$ GeV for a misalignment angle $theta_{rm mis} simeq mathcal{O}(1)$. While $f_a ll 10^{12}$ GeV is of great experimental interest, the misalignment mechanism requires the axion to be very close to the hilltop, i.e. $theta_{rm mis} simeq pi$. This particular choice of $theta_{rm mis}$ has been understood as fine-tuning the initial condition. We offer a dynamical explanation for $theta_{rm mis}Read More →

Energy Budget and Core-Envelope Motion in Common Envelope Evolution. (arXiv:1812.11196v1 [astro-ph.SR]) <a href="http://arxiv.org/find/astro-ph/1/au:+Chamandy_L/0/1/0/all/0/1">Luke Chamandy</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Tu_Y/0/1/0/all/0/1">Yisheng Tu</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Blackman_E/0/1/0/all/0/1">Eric G. Blackman</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Carroll_Nellenback_J/0/1/0/all/0/1">Jonathan Carroll-Nellenback</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Frank_A/0/1/0/all/0/1">Adam Frank</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Liu_B/0/1/0/all/0/1">Baowei Liu</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Nordhaus_J/0/1/0/all/0/1">Jason Nordhaus</a> We analyze a 3D hydrodynamic simulation of common envelope evolution to understand how energy is transferred between various forms, leading to the partial unbinding of the envelope. We find that $13$-$14%$ of the envelope is unbound during the simulation. Virtually all of the unbinding occurs before the end of the rapid plunge-in phase, here defined to coincide with the first periastron passage. In contrast, the total envelope energy is nearly constant duringRead More →

Galaxy assembly bias of central galaxies in the Illustris simulation. (arXiv:1812.11210v1 [astro-ph.GA]) <a href="http://arxiv.org/find/astro-ph/1/au:+Xu_X/0/1/0/all/0/1">Xiaoju Xu</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Zheng_Z/0/1/0/all/0/1">Zheng Zheng</a> Galaxy assembly bias, the correlation between galaxy properties and halo properties at fixed halo mass, could be an important ingredient in halo-based modelling of galaxy clustering. We investigate the central galaxy assembly bias by studying the relation between various galaxy and halo properties in the Illustris hydrodynamic galaxy formation simulation. Galaxy stellar mass $M_{star}$ is found to have a tighter correlation with peak maximum halo circular velocity $V_{peak}$ than with halo mass $M_h$. Once the correlation with $V_{peak}$ is accounted for, $M_{star}$ has nearly no dependence onRead More →

Evaluation of Mother-Daughter Architectures for Asteroid Belt Exploration. (arXiv:1812.11243v1 [astro-ph.IM]) <a href="http://arxiv.org/find/astro-ph/1/au:+Vance_L/0/1/0/all/0/1">Leonard Dean Vance</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Asphaug_E/0/1/0/all/0/1">Erik Asphaug</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Thangavelautham_J/0/1/0/all/0/1">Jekan Thangavelautham</a> This paper examines the effectiveness of an asteroid exploration architecture comprised of multiple nanosatellite sized spacecraft deployed from a single mother ship into a heliocentric orbit in the main asteroid belt where the mothership is ideally located in region of high density. Basic mission requirements associated with a Mother-Daughter architecture are established utilizing a relatively large number (10-20) daughter spacecraft distributed from a mothership within the asteroid belt for the purpose of executing sample and return missions. A number of trade analyses are performed toRead More →

Relativistic envelopes and gamma-rays from neutron star mergers. (arXiv:1812.11247v1 [astro-ph.HE]) <a href="http://arxiv.org/find/astro-ph/1/au:+Beloborodov_A/0/1/0/all/0/1">Andrei M. Beloborodov</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Lundman_C/0/1/0/all/0/1">Christoffer Lundman</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Levin_Y/0/1/0/all/0/1">Yuri Levin</a> We suggest that neutron star mergers eject an ultra-relativistic envelope of mass $msim 10^{-7}M_odot$, which helps explain the gamma-ray burst from GW170817. One ejection mechanism is the ablation of the neutron star surface by the burst of neutrinos in the first $30,mu$s of the merger. Another, more efficient, mechanism for inflating the ultra-relativistic envelope is an internal shock in the massive ejecta from the merger. A strong shock is expected if the merger product is a magnetar, which emits a centrifugally accelerated wind. The shockRead More →

The SAMI Galaxy Survey: Exploring the gas-phase Mass-Metallicity Relation. (arXiv:1812.11263v1 [astro-ph.GA]) <a href="http://arxiv.org/find/astro-ph/1/au:+Sanchez_S/0/1/0/all/0/1">S.F. Sanchez</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Barrera_Ballesteros_J/0/1/0/all/0/1">J.K. Barrera-Ballesteros</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Lopez_Coba_C/0/1/0/all/0/1">C. Lopez-Coba</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Brough_S/0/1/0/all/0/1">S. Brough</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Bryant_J/0/1/0/all/0/1">J. J. Bryant</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Bland_Hawthorn_J/0/1/0/all/0/1">J. Bland-Hawthorn</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Croom_S/0/1/0/all/0/1">S. M. Croom</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Sande_J/0/1/0/all/0/1">J. van de Sande</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Cortese_L/0/1/0/all/0/1">L. Cortese</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Goodwin_M/0/1/0/all/0/1">M. Goodwin</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Lawrence_J/0/1/0/all/0/1">J.S. Lawrence</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Lopez_Sanchez_A/0/1/0/all/0/1">A. R. Lopez-Sanchez</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Sweet_S/0/1/0/all/0/1">S. M. Sweet</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Owers_M/0/1/0/all/0/1">M. S. Owers</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Richards_S/0/1/0/all/0/1">S. N. Richards</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Walcher_C/0/1/0/all/0/1">C. J. Walcher</a> We present a detailed exploration of the stellar mass vs. gas-phase metallicity relation (MZR) using integral field spectroscopy data obtained from ~1000 galaxies observed by the SAMI Galaxy survey. These spatially resolved spectroscopic data allow us toRead More →

Dynamical instability in non-commutative white dwarfs. (arXiv:1812.11291v1 [gr-qc]) <a href="http://arxiv.org/find/gr-qc/1/au:+Mathew_A/0/1/0/all/0/1">Arun Mathew</a>, <a href="http://arxiv.org/find/gr-qc/1/au:+Nandy_M/0/1/0/all/0/1">Malay K. Nandy</a> Newtonian gravity predicts the existence of white dwarfs with masses far exceeding the Chandrasekhar limit when the equation of state of the degenerate electron gas incorporates the effect of quantum spacetime fluctuations (via a non-commutative formulation) even when the strength of the fluctuations is taken to be very small. In this paper, we show that this Newtonian super-stability of non-commutative white dwarfs does not hold true when the gravity is treated in the general relativistic framework. Besides, we find that the Chandrasekhar limit can be reassured even for high strengthsRead More →

Chandra X-ray Observations of the Neutron Star Merger GW170817: Thermal X-Ray Emission From a Kilonova Remnant?. (arXiv:1812.11320v1 [astro-ph.HE]) <a href="http://arxiv.org/find/astro-ph/1/au:+Safi_Harb_S/0/1/0/all/0/1">Samar Safi-Harb</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Doerksen_N/0/1/0/all/0/1">Neil Doerksen</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Rogers_A/0/1/0/all/0/1">Adam Rogers</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Fryer_C/0/1/0/all/0/1">Chris L. Fryer</a> The recent discovery of the neutron star merger and multi-messenger event GW170817 (also known as kilonova GRB170817A) provides an unprecedented laboratory in which to study these mysterious objects, as well as an opportunity to test cutting-edge theories of gravity in the strong field regime. Before this event, such tests of our understanding of the nature of gravity were not possible. In this study, we analyze the X-ray observations of GW170817 obtained with NASA’s ChandraRead More →

Resonant leptogenesis at TeV-scale and neutrinoless double beta decay. (arXiv:1812.11323v1 [hep-ph]) <a href="http://arxiv.org/find/hep-ph/1/au:+Asaka_T/0/1/0/all/0/1">Takehiko Asaka</a>, <a href="http://arxiv.org/find/hep-ph/1/au:+Yoshida_T/0/1/0/all/0/1">Takahiro Yoshida</a> We investigate a resonant leptogenesis scenario by quasi-degenerate right-handed neutrinos which have TeV-scale masses. Especially, we consider the case when two right-handed neutrinos are responsible to leptogenesis and the seesaw mechanism for active neutrino masses, and assume that the CP violation occurs only in the mixing matrix of active neutrinos. In this case the sign of the baryon asymmetry depends on the Dirac and Majorana CP phases as well as the mixing angle of the right-handed neutrinos. It is shown how the yield of the baryon asymmetry correlatesRead More →

Dust bombardment can explain the extremely elongated shape of 1I/’Oumuamua and the lack of interstellar objects. (arXiv:1812.11334v1 [astro-ph.EP]) <a href="http://arxiv.org/find/astro-ph/1/au:+Vavilov_D/0/1/0/all/0/1">Dmitrii E. Vavilov</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Medvedev_Y/0/1/0/all/0/1">Yurii D. Medvedev</a> Asteroid 1I/’Oumuamua is the first observed interstellar object. Its light-curve amplitude indicates that the object is highly elongated with an axis ratio of at least 5:1. The absence of such elongated asteroids in the Solar system, as well as the apparent lack of observed interstellar objects, are intriguing problems. Here we show that ‘Oumuamua may have originated as a slightly-elongated asteroid about $500times300$ meters in size. Surface erosion, caused by interstellar dust bombardment, subsequently increased the axis ratio. SimplyRead More →

From Dinuclear Systems to Close Binary Stars: Application to Source of Energy in the Universe. (arXiv:1812.11338v1 [astro-ph.SR]) <a href="http://arxiv.org/find/astro-ph/1/au:+Sargsyan_V/0/1/0/all/0/1">V. V. Sargsyan</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Lenske_H/0/1/0/all/0/1">H. Lenske</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Adamian_G/0/1/0/all/0/1">G. G. Adamian</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Antonenko_N/0/1/0/all/0/1">N. V. Antonenko</a> The evolution of close binary stars in mass asymmetry (transfer) coordinate is considered. The conditions for the formation of stable symmetric binary stars are analyzed. The role of symmetrization of asymmetric binary star in the transformation of potential energy into internal energy of star and the release of a large amount of energy is revealed. The evolution of close binary stars in mass asymmetry (transfer) coordinate is considered. The conditions for the formationRead More →

Prompt atmospheric neutrinos in the quark-gluon string model. (arXiv:1812.11341v1 [hep-ph]) <a href="http://arxiv.org/find/hep-ph/1/au:+Sinegovsky_S/0/1/0/all/0/1">S. I. Sinegovsky</a>, <a href="http://arxiv.org/find/hep-ph/1/au:+Sorokovikov_M/0/1/0/all/0/1">M. N. Sorokovikov</a> (Joint Institute for Nuclear Research &amp; Irkutsk State University) We calculate the atmospheric flux of prompt neutrinos, produced in decays of the charmed particles at energies beyond 1 TeV. Cross sections of the D-mesons and ${Lambda}^{+}_{c}$ baryons production in pA and $pi$A collisions are calculated in the phenomenological quark-gluon string model (QGSM) which is updated with use of the recent measurements of cross sections of the charmed meson production in the LHC experiments. A new estimate of the prompt atmospheric neutrino flux is obtained and compared withRead More →